阅读说明：本技术 声波器件 (Acoustic wave device ) 是由 门田道雄 田中秀治 石井良美 于 2019-10-15 设计创作，主要内容包括：公开了声波器件和相关方法。在一些实施例中,声波器件可以包括具有第一表面的石英基板,以及由LiTaO3或LiNbO3形成并且具有被配置为支持表面声波的第一表面和与石英基板的第一表面接合的第二表面的压电板。压电板的第二表面是由压电板的晶体结构取向导致的负表面。所述声波器件还可以包括叉指换能器电极,所述叉指换能器电极形成在压电板的第一表面上并且被配置为提供与所述表面声波相关联的换能器功能。(Acoustic wave devices and related methods are disclosed. In some embodiments, an acoustic wave device may include a quartz substrate having a first surface, and a piezoelectric plate formed of LiTaO3 or LiNbO3 and having a first surface configured to support a surface acoustic wave and a second surface bonded to the first surface of the quartz substrate. The second surface of the piezoelectric plate is a negative surface resulting from the orientation of the crystal structure of the piezoelectric plate. The acoustic wave device may further include an interdigital transducer electrode formed on the first surface of the piezoelectric plate and configured to provide a transducer function associated with the surface acoustic wave.)

1. An acoustic wave device comprising:

a quartz substrate, the substrate comprising a first surface;

piezoelectric plate made of LiTaO₃Or LiNbO₃Forming a piezoelectric plate having a first surface configured to support surface acoustic waves and a second surface on a quartz substrateThe first surface of the plate being bonded, the second surface being a negative surface resulting from the crystal structure orientation of the piezoelectric plate; and

an interdigital transducer electrode formed on a first surface of the piezoelectric plate and configured to provide a transducer function associated with the surface acoustic wave.

2. An acoustic wave device according to claim 1, wherein the crystal structure orientation of the piezoelectric plate comprises an euler angle (0 °,90 ° < θ <270 °,0 °).

3. An acoustic wave device according to claim 2, wherein the first surface of the quartz substrate is a front surface resulting from the crystal structure orientation of the quartz substrate.

4. An acoustic wave device according to claim 3, wherein the crystal structure orientation of the quartz substrate comprises the euler angleAngle of rotationIs provided with atThe angle psi has a value in the range 0 DEG ≦ psi<A value in the range of 180 deg..

5. An acoustic wave device as claimed in claim 4, wherein the angle isIs 0 deg..

6. An acoustic wave device according to claim 4, wherein the angle ψ is 0 °.

7. An acoustic wave device according to claim 2, wherein the first surface of the quartz substrate is a negative surface resulting from the crystal structure orientation of the quartz substrate.

8. An acoustic wave device according to claim 7, wherein the crystal structure orientation of the quartz substrate comprises an euler angleAngle of rotationIs provided with atThe angle psi has a value in the range 0 DEG ≦ psi<A value in the range of 180 deg..

9. An acoustic wave device as claimed in claim 8, wherein the angle isIs 0 deg..

10. An acoustic wave device as claimed in claim 8, wherein the angle ψ is 0 °.

11. An acoustic wave device according to claim 2, wherein the first surface of the quartz substrate is a non-polarized surface resulting from the crystal structure orientation of the quartz substrate.

12. An acoustic wave device as set forth in claim 11 wherein the crystal structure orientation of the quartz substrate comprises the euler angleOrAngle of rotationIs provided with atThe angle psi has a value in the range 0 DEG ≦ psi<A value in the range of 180 deg..

13. An acoustic wave device as claimed in claim 12, wherein the angle isHas a value of 90 deg., and the angle psi has a value of 90 deg..

14. An acoustic wave device as set forth in claim 1, wherein the piezoelectric plate is made of LiTaO₃And the quartz substrate comprises an euler angle (0 °,10 ° -80 °,0 °), (0 °,100 ° -170 °,0 °), (0 °,190 ° -260 °,0 °) or (0 °,280 ° -350 °,0 °).

15. An acoustic wave device as defined in claim 1, wherein the piezoelectric plate is made of LiNbO₃And the quartz substrate comprises an euler angle (0 °,5 ° -85 °,0 °), (0 °,95 ° -175 °,0 °), (0 °,185 ° -265 °,0 °) or (0 °,275 ° -355 °,0 °).

16. An acoustic wave device as set forth in claim 1, wherein the piezoelectric plate is made of LiTaO₃And the quartz substrate comprises an euler angle (0 °,5 ° -53 °,90 °), (0 °,127 ° -175 °,90 °), (0 °,185 ° -233 °,90 °) or (0 °,307 ° -355 °,90 °).

17. An acoustic wave device as defined in claim 1, wherein the piezoelectric plate is made of LiNbO₃And the quartz substrate comprises an euler angle (0 °,0 ° -52 °,90 °), (0 °,126 ° -180 °,90 °), (0 °,180 ° -232 °,90 °) or (0 °,306 ° -360 °,90 °).

18. An acoustic wave device as set forth in claim 1, wherein the piezoelectric plate is made of LiTaO₃Or LiNbO₃Formed and the quartz substrate comprises Euler angle (0 deg. °)0 to 360, 0 to 60 or (0, 0 to 360, 120 to 180).

19. An acoustic wave device as set forth in claim 18, wherein the piezoelectric plate is made of LiTaO₃Or LiNbO₃And the quartz substrate comprises an Euler angle (0 deg., 0 deg. -360 deg., 0 deg. -45 deg.) or (0 deg., 0 deg. -360 deg., 135 deg. -180 deg.).

20. An acoustic wave device as set forth in claim 1 further comprising a first reflector and a second reflector implemented on the first surface of the piezoelectric plate and positioned on the first and second sides of the interdigital transducer electrodes.

21. An acoustic wave device according to claim 1, wherein the piezoelectric plate has a thickness of 0.04 λ to 1.5 λ, the magnitude λ being the wavelength of said surface acoustic wave.

22. An acoustic wave device as set forth in claim 21 wherein the piezoelectric plate has a thickness of from 0.06 λ to 1.0 λ.

23. A method for fabricating an acoustic wave device, the method comprising:

forming or providing a quartz substrate having a first surface;

forming or providing a catalyst having LiTaO₃Or LiNbO₃The piezoelectric plate of (a) to include a first surface configured to support surface acoustic waves and a second surface that is a negative surface caused by the crystal structure orientation of the piezoelectric plate; and

the piezoelectric plate is coupled to the quartz substrate such that the negative surface of the piezoelectric plate is bonded to the first surface of the quartz substrate.

24. The method of claim 23, further comprising forming interdigital transducer electrodes on the first surface of the piezoelectric plate to provide a transducer function associated with surface acoustic waves.

25. The method of claim 23, wherein the crystal structure orientation of the piezoelectric plate comprises an euler angle (0 °,90 ° < θ <270 °,0 °).

26. The method of claim 25, wherein the first surface of the quartz substrate is a positive surface, a negative surface, or a non-polarized surface resulting from the crystal structure orientation of the quartz substrate.

27. The method of claim 26, wherein the first surface of the quartz substrate is a front surface and the quartz substrate comprises an euler angleAngle of rotationIs provided with atThe angle psi has a value in the range 0 DEG ≦ psi<A value in the range of 180 deg..

28. The method of claim 26, wherein the first surface of the quartz substrate is a negative surface and the quartz substrate comprises an euler angleAngle of rotationIs provided with atThe angle psi has a value in the range 0 DEG ≦ psi<A value in the range of 180 deg..

29. The method of claim 26, wherein the first surface of the quartz substrate is a non-polarized surface and the quartz substrate comprises euler anglesOrAngle of rotationIs provided with at The angle psi has a value in the range 0 DEG ≦ psi<A value in the range of 180 deg..

30. The method of claim 23, wherein forming or providing the piezoelectric plate comprises forming the piezoelectric plate after coupling the piezoelectric plate with the quartz substrate.

31. The method of claim 30, wherein coupling the piezoelectric plate to the quartz substrate and forming the piezoelectric plate comprises bonding a thick piezoelectric layer to the quartz substrate, followed by thinning the thick piezoelectric layer, thereby causing the piezoelectric plate to bond to the quartz substrate.

32. The method of claim 31, wherein de-thinning the thick piezoelectric layer comprises a polishing process.

33. The method of claim 23, wherein forming or providing the piezoelectric plate comprises forming the piezoelectric plate before coupling the piezoelectric plate with the quartz substrate.

34. The method of claim 33, wherein coupling the piezoelectric plate to the quartz substrate and forming the piezoelectric plate comprises attaching a thick piezoelectric layer to a handle substrate, then de-thinning the thick piezoelectric layer to form a negative surface of the piezoelectric plate, then bonding the negative surface of the piezoelectric plate to the quartz substrate.

35. The method of claim 34, wherein coupling the piezoelectric plate to the quartz substrate and forming the piezoelectric plate further comprises removing the handle substrate to expose the first surface of the piezoelectric plate.

36. The method of claim 35, wherein the handle substrate comprises a silicon substrate.

37. The method of claim 35, wherein attaching the thick piezoelectric layer to the handle substrate comprises bonding the thick piezoelectric layer to the handle substrate.

38. The method of claim 35, wherein de-thinning the thick piezoelectric layer comprises performing a polishing process while the thick piezoelectric layer is attached to the handle substrate.

39. The method of claim 35, wherein removing the handle substrate comprises an etching process.

40. A radio frequency filter comprising:

an input node for receiving a signal;

an output node for providing a filtered signal; and

an acoustic wave device implemented to be electrically located between an input node and an output node to generate a filtered signal, the acoustic wave device comprising a quartz substrate having a first surface and a piezoelectric plate formed of LiTaO₃Or LiNbO₃And has a first surface configured to support surface acoustic waves and a second surface bonded to the first surface of the quartz substrate, the second surface being a negative surface resulting from the crystal structure orientation of the piezoelectric plate.

41. The radio frequency filter of claim 40 further comprising first and second interdigital transducer electrodes formed on the first surface of the piezoelectric plate, the first interdigital transducer electrode being electrically connected to the input node and the second interdigital transducer electrode being electrically connected to the output node.

42. A radio frequency module, comprising:

a package substrate configured to receive a plurality of components;

radio frequency circuitry implemented on the package substrate and configured to support transmission and/or reception of signals; and

a radio frequency filter configured to provide filtering of at least some of the signals and comprising an acoustic wave device comprising a quartz substrate having a first surface and a piezoelectric plate formed of LiTaO₃Or LiNbO₃And has a first surface configured to support surface acoustic waves and a second surface bonded to the first surface of the quartz substrate, the second surface being a negative surface resulting from the crystal structure orientation of the piezoelectric plate.

43. A wireless device, comprising:

a transceiver;

an antenna; and

a wireless system implemented to be electrically located between a transceiver and an antenna, the wireless system comprising a filter configured to provide a filtering function to the wireless system, the filter comprising an acoustic wave device comprising a quartz substrate having a first surface and a piezoelectric plate formed of LiTaO₃Or LiNbO₃And has a first surface configured to support surface acoustic waves and a second surface bonded to the first surface of the quartz substrate, the second surface being a negative surface resulting from the crystal structure orientation of the piezoelectric plate.

44. A method for fabricating an acoustic wave device, the method comprising:

attaching a first surface of a piezoelectric layer to a handle substrate;

performing a thinning operation on the piezoelectric layer to expose a second surface of the piezoelectric layer attached to the handle substrate having a reduced thickness;

bonding the second surface of the piezoelectric layer of reduced thickness to the first surface of the permanent substrate; and

removing the handle substrate from the reduced thickness piezoelectric layer.

45. The method of claim 44, wherein removing the handle substrate from the reduced thickness piezoelectric layer exposes a first surface attached to the handle substrate, the first surface configured to support surface acoustic waves.

46. The method of claim 45 further comprising forming interdigital transducer electrodes on the first surface of the reduced thickness piezoelectric layer to provide a transducer function associated with surface acoustic waves.

47. A method according to claim 46 wherein the assembly of the acoustic wave device and the respective interdigital transducer electrode is one of a group of similar assemblies embodied as a wafer.

48. A method according to claim 47 further comprising dicing the wafer to provide a plurality of acoustic wave devices.

49. The method of claim 44, wherein the handle substrate comprises a silicon substrate.

50. The method of claim 44, wherein the permanent substrate comprises a quartz substrate.

51. The method of claim 44 wherein the piezoelectric layer is formed of LiTaO₃Or LiNbO₃Is formed with a crystal structure oriented such that the second surface of the piezoelectric layer of reduced thickness is a negative surface.

52. The method of claim 51, wherein the crystal structure orientation of the piezoelectric plate comprises an Euler angle (0 °,90 ° < θ <270 °,0 °).

53. The method of claim 52, wherein the first surface of the permanent substrate is a positive surface, a negative surface, or a non-polarized surface resulting from the orientation of the crystal structure of the permanent substrate.

54. The method of claim 53, wherein the first surface of the permanent substrate is a front surface and the permanent substrate comprises Euler anglesAngle of rotationIs provided with atThe angle psi has a value in the range 0 DEG ≦ psi<A value in the range of 180 deg..

55. The method of claim 53, wherein the first surface of the permanent substrate is a negative surface and the permanent substrate comprises Euler anglesAngle of rotationIs provided with atThe angle psi has a value in the range 0 DEG ≦ psi<A value in the range of 180 deg..

56. The method of claim 53, wherein the first surface of the permanent substrate is a non-polarized surface and the permanent substrate comprises EulerCornerOrAngle of rotationIs provided with at The angle psi has a value in the range 0 DEG ≦ psi<A value in the range of 180 deg..

57. A wafer assembly, comprising:

a piezoelectric layer having a first surface and a second surface;

processing a substrate, attaching a first surface of a piezoelectric layer; and

a permanent substrate attached to the second surface of the piezoelectric layer, the handle substrate being selected to be removable so as to expose the first surface of the piezoelectric layer while the piezoelectric layer is attached to the permanent substrate.

58. The wafer assembly of claim 57, wherein the handle substrate is a silicon substrate.

59. The wafer assembly of claim 57, wherein the permanent substrate is a quartz substrate.

60. The wafer assembly of claim 57, wherein the piezoelectric layer is a reduced thickness piezoelectric layer having a thick piezoelectric layer attached to the first surface of the handle wafer and without a permanent substrate that is subjected to a de-thinning operation.

61. The wafer assembly of claim 60, wherein the first surface of the piezoelectric layer is bonded to the handle substrate with a first bonding strength and the second surface of the piezoelectric layer is bonded to the permanent substrate with a second bonding strength.

62. The wafer assembly of claim 61, wherein a first bond strength between the piezoelectric layer and the handle substrate is greater than a bond strength between the piezoelectric layer and the permanent substrate, the first bond strength allowing the thinning operation to be performed without damaging the piezoelectric layer.

63. The wafer assembly of claim 62, wherein a first bond strength between the piezoelectric layer and the handle substrate is at least one order of magnitude greater than a second bond strength between the piezoelectric layer and the permanent substrate.

64. The wafer assembly of claim 57 wherein the piezoelectric layer is made of LiTaO₃Or LiNbO₃A second surface of the piezoelectric layer is formed with its crystal structure oriented such that the thickness is reduced.

65. The wafer assembly of claim 64, wherein the crystal structure orientation of the piezoelectric layer comprises an Euler angle (0 °,90 ° < θ <270 °,0 °).

66. The wafer assembly of claim 65, wherein the first surface of the permanent substrate is a positive surface, a negative surface, or a non-polarized surface resulting from the orientation of the crystal structure of the permanent substrate.

67. The wafer assembly of claim 66, wherein the first surface of the permanent substrate is a front surface and the permanent substrate comprises Euler anglesAngle of rotationIs provided with at The angle psi has a value in the range 0 DEG ≦ psi<A value in the range of 180 deg..

68. The wafer assembly of claim 66, wherein the first surface of the permanent substrate is a negative surface and the permanent substrate comprises Euler anglesAngle of rotationIs provided with at The angle psi has a value in the range 0 DEG ≦ psi<A value in the range of 180 deg..

69. The wafer assembly of claim 66, wherein the first surface of the permanent substrate is a non-polarized surface and the permanent substrate comprises Euler anglesOrAngle of rotationIs provided with atValue within the rangeThe angle psi is between 0 DEG and psi<A value in the range of 180 deg..

Technical Field

The present application relates to acoustic wave devices, such as Surface Acoustic Wave (SAW) devices.

Background

Surface Acoustic Wave (SAW) resonators typically include interdigital transducer (IDT) electrodes implemented on the surface of a piezoelectric layer. Such an electrode includes two interdigital finger groups, and in this configuration, the pitch of two adjacent fingers of the same group is substantially equivalent to the wavelength λ of the surface acoustic wave supported by the IDT electrode.

The aforementioned SAW resonators can be used as Radio Frequency (RF) filters based on wavelength λ in a number of applications. Such filters may provide a number of desirable characteristics.

Disclosure of Invention

According to some embodiments, the present application relates to an acoustic wave device comprising a quartz substrate having a first surface and a piezoelectric plate formed of LiTaO₃Or LiNbO₃And has a first surface configured to support surface acoustic waves and a second surface bonded to the first surface of the quartz substrate. The second surface is a negative surface resulting from the crystal structure orientation of the piezoelectric plate. The acoustic wave device also includes an interdigital transducer electrode formed on the first surface of the piezoelectric plate and configured to provide a transducer function associated with the surface acoustic wave.

In some embodiments, the crystal structure orientation of the piezoelectric plate may comprise the Euler angle (0 °,90 °) (Euler)<θ<270 °,0 °). In some embodiments, the first surface of the quartz substrate may be oriented by the crystal structure of the quartz substrateResulting in a front surface. The crystal structure orientation of the quartz substrate may include Euler angles Wherein the angleIs provided with atThe angle psi has a value in the range 0 DEG ≦ psi<A value in the range of 180 deg.. Angle of rotationMay have a value of, for example, 0 °. The angle ψ may have a value of, for example, 0 °.

In some embodiments, the first surface of the quartz substrate may be a negative surface resulting from the crystal structure orientation of the quartz substrate. The crystal structure orientation of the quartz substrate may include Euler anglesWherein the angleIs provided with atThe angle psi has a value in the range 0 DEG ≦ psi<A value in the range of 180 deg.. Angle of rotationMay have a value of, for example, 0 °. The angle ψ may have a value of, for example, 0 °.

In some embodiments, the first surface of the quartz substrate may be an unpolarized (unpolarized) surface resulting from the crystal structure orientation of the quartz substrate. The crystal structure orientation of the quartz substrate may include Euler angles OrWherein the angleIs provided with atThe angle psi has a value in the range 0 DEG ≦ psi<A value in the range of 180 deg.. Angle of rotationMay have a value of e.g. 90 deg., and the angle psi may have a value of e.g. 90 deg..

In some embodiments, the piezoelectric plate may be made of LiTaO₃And the quartz substrate may include an euler angle (0 °,10 ° -80 °,0 °), (0 °,100 ° -170 °,0 °), (0 °,190 ° -260 °,0 °) or (0 °,280 ° -350 °,0 °).

In some embodiments, the piezoelectric plate may be made of LiNbO₃And the quartz substrate may include an euler angle (0 °,5 ° -85 °,0 °), (0 °,95 ° -175 °,0 °), (0 °,185 ° -265 °,0 °) or (0 °,275 ° -355 °,0 °).

In some embodiments, the piezoelectric plate may be made of LiTaO₃And the quartz substrate may include euler angles (0 °,5 ° -53 °,90 °), (0 °,127 ° -175 °,90 °), (0 °,185 ° -233 °,90 °) or (0 °,307 ° -355 °,90 °).

In some embodiments, the piezoelectric plate may be made of LiNbO₃And the quartz substrate may include euler angles (0 °,0 ° -52 °,90 °), (0 °,126 ° -180 °,90 °), (0 °,180 ° -232 °,90 °) or (0 °,306 ° -360 °,90 °).

In some embodiments, the piezoelectric plate may be made of LiTaO₃Or LiNbO₃And the quartz substrate may include an Euler angle (0 deg., 0 deg. -360 deg.)0 to 60 degrees or (0, 0 to 360 degrees and 120 to 180 degrees). In some embodiments, the piezoelectric plate may be made of LiTaO₃Or LiNbO₃And the quartz substrate may include an euler angle (0 °,0 ° -360 °,0 ° -45 °) or (0 °,0 ° -360 °,135 ° -180 °).

In some embodiments, the acoustic wave device may further include a first reflector and a second reflector implemented on the first surface of the piezoelectric plate and positioned on the first side and the second side of the interdigital transducer electrodes.

In some embodiments, the thickness of the piezoelectric plate may be in the range of 0.04 λ to 1.5 λ, where the quantity λ is the wavelength of the surface acoustic wave. In some embodiments, the thickness of the piezoelectric plate may be between 0.06 λ and 1.0 λ.

In some teachings, the present application relates to a method of manufacturing an acoustic wave device. The method includes forming or providing a quartz substrate having a first surface. The method further includes forming or providing a catalyst having LiTaO₃Or LiNbO₃The piezoelectric plate of (1), to include a first surface configured to support surface acoustic waves and a second surface that is a negative surface resulting from the crystal structure orientation of the piezoelectric plate. The method also includes coupling the piezoelectric plate to the quartz substrate such that the negative surface of the piezoelectric plate is bonded to the first surface of the quartz substrate.

In some embodiments, the method may further comprise forming interdigital transducer electrodes on the first surface of the piezoelectric plate to provide transducer functionality associated with said surface acoustic wave.

In some embodiments, the crystal structure orientation of the piezoelectric plate may include euler angles (0 °,90 ° < θ <270 °,0 °). In some embodiments, the first surface of the quartz substrate may be a positive surface, a negative surface, or a non-polarized surface resulting from the crystal structure orientation of the quartz substrate.

In some embodiments, the first surface of the quartz substrate may be a front surface, and the quartz substrate may include an euler angleIs a negative surface and the quartz substrate may comprise an euler angle Or a non-polarized surface, and the quartz substrate may comprise an Euler angleOr Angle of rotationIs provided with atThe angle psi has a value in the range 0 DEG ≦ psi<A value in the range of 180 deg..

In some embodiments, the forming or providing of the piezoelectric plate may include forming the piezoelectric plate after the piezoelectric plate is coupled with the quartz substrate. The coupling of the piezoelectric plate to the quartz substrate and the forming of the piezoelectric plate may include bonding a thick piezoelectric layer to the quartz substrate, followed by thinning the thick piezoelectric layer to produce the piezoelectric plate bonded to the quartz substrate. The thinning of the thick piezoelectric layer can include a polishing process.

In some embodiments, the forming or providing of the piezoelectric plate may include forming the piezoelectric plate before the piezoelectric plate is coupled with the quartz substrate. The coupling of the piezoelectric plate to the quartz substrate and the forming of the piezoelectric plate may include attaching a thick piezoelectric layer to the handle substrate, followed by thinning the thick piezoelectric layer to form the negative surface of the piezoelectric plate, and then bonding the negative surface of the piezoelectric plate to the quartz substrate. The coupling of the piezoelectric plate to the quartz substrate and the forming of the piezoelectric plate may further include removing the handle substrate to expose the first surface of the piezoelectric plate.

In some embodiments, the processing substrate may comprise a silicon substrate. In some embodiments, attaching the thick piezoelectric layer to the handle substrate can include bonding the thick piezoelectric layer to the handle substrate. In some embodiments, the thinning of the thick piezoelectric layer can include a polishing process while the thick piezoelectric layer is attached to the handle substrate. In some embodiments, the removal of the handle substrate may include an etching process.

In several implementations, the disclosure relates to a radio frequency filter comprising an input node for receiving a signal, and an output node for providing a filtered signal. The radio frequency filter also includes an acoustic wave device implemented to be electrically located between the input node and the output node to generate a filtered signal. The acoustic wave device includes a quartz substrate having a first surface, and a piezoelectric plate made of LiTaO₃Or LiNbO₃And has a first surface configured to support surface acoustic waves and a second surface bonded to the first surface of the quartz substrate. The second surface is a negative surface resulting from the crystal structure orientation of the piezoelectric plate.

In some embodiments, the radio frequency filter may further include a first interdigital transducer electrode and a second interdigital transducer electrode formed on the first surface of the piezoelectric plate. The first interdigital transducer electrode can be electrically connected to an input node, and the second interdigital transducer electrode can be electrically connected to an output node.

In some embodiments, the present application relates to a radio frequency module including a packaging substrate (packaging substrate) configured to receive a plurality of components and radio frequency circuitry implemented on the packaging substrate and configured to support transmission and/or reception of signals. The radio frequency module further includes a radio frequency filter configured to provide filtering to at least some of the signals. The radio frequency filter includes: an acoustic wave device including a quartz substrate having a first surface and a piezoelectric plate made of LiTaO₃Or LiNbO₃Is formed andhaving a first surface configured to support surface acoustic waves and a second surface bonded to the first surface of the quartz substrate. The second surface is a negative surface resulting from the crystal structure orientation of the piezoelectric plate.

In some implementations, the invention relates to a wireless device that includes a transceiver, an antenna, and a wireless system implemented to be electrically located between the transceiver and the antenna. The wireless system includes a filter configured to provide a filtering function to the wireless system. The filter includes an acoustic wave device including a quartz substrate having a first surface and a piezoelectric plate made of LiTaO₃Or LiNbO₃And has a first surface configured to support surface acoustic waves and a second surface bonded to the first surface of the quartz substrate. The second surface is a negative surface resulting from the crystal structure orientation of the piezoelectric plate.

In some teachings, the present application relates to a method of manufacturing an acoustic wave device. The method includes attaching a first surface of a piezoelectric layer to a handle substrate, and performing a thinning operation on the piezoelectric layer to expose a second surface of the piezoelectric layer attached to the handle substrate with a reduced thickness. The method also includes bonding the second surface of the reduced thickness piezoelectric layer to the first surface of the permanent substrate and removing the handle substrate from the reduced thickness piezoelectric layer.

In some embodiments, removing the handle substrate from the reduced thickness piezoelectric layer can expose a first surface attached to the handle substrate, the first surface configured to support surface acoustic waves. The method may also include forming interdigital transducer electrodes on the first surface of the reduced thickness piezoelectric layer to provide a transducer function associated with surface acoustic waves.

In some embodiments, the assembly (assembly) formed by the acoustic wave device and the corresponding interdigital transducer electrode may be one of a group of similar assemblies implemented as a wafer. The method may further include dicing the wafer to provide a plurality of acoustic wave devices.

In some embodiments, the processing substrate may comprise a silicon substrate. In some embodiments, the permanent substrate may comprise a quartz substrate.

In some embodiments, the piezoelectric layer may be made of LiTaO₃Or LiNbO₃A second surface of the piezoelectric layer having a crystal structure oriented such that the thickness is reduced is a negative surface. The crystal structure orientation of the piezoelectric plate may include Euler angles (0 deg., 90 deg. °)<θ<270°,0°)。

In some embodiments, the first surface of the permanent substrate may be a positive surface, a negative surface, or a non-polarized surface resulting from the orientation of the crystal structure of the permanent substrate. In some embodiments, the first surface of the permanent substrate may be a front surface, and the permanent substrate may include euler anglesIs a negative surface and the permanent substrate may comprise euler anglesOr a non-polarizing surface, and the permanent substrate may comprise Euler anglesOrAngle of rotationIs provided with atThe angle psi has a value in the range 0 DEG ≦ psi<A value in the range of 180 deg..

According to some embodiments, the present application is directed to a wafer assembly including a piezoelectric layer having a first surface and a second surface. The wafer assembly also includes a handle substrate attached to the first surface of the piezoelectric layer and a permanent substrate attached to the second surface of the piezoelectric layer. The handle substrate is selected to be removable so as to expose the first surface of the piezoelectric layer when the piezoelectric layer is attached to the permanent substrate.

In some embodiments, the processing substrate may be a silicon substrate. In some embodiments, the permanent substrate may be a quartz substrate.

In some embodiments, the piezoelectric layer can be a reduced thickness piezoelectric layer resulting from a thinning operation on a thick piezoelectric layer, a first surface of which is attached to the handle wafer but without the permanent substrate. In some embodiments, the first surface of the piezoelectric layer can be bonded to the handle substrate with a first bonding strength and the second surface of the piezoelectric layer can be bonded to the permanent substrate with a second bonding strength. A first bonding strength between the piezoelectric layer and the handle substrate may be greater than a bonding strength between the piezoelectric layer and the permanent substrate, wherein the first bonding strength allows a thinning operation to be performed without damaging the piezoelectric layer. For example, a first bond strength between the piezoelectric layer and the handle substrate can be at least one order of magnitude greater than a second bond strength between the piezoelectric layer and the permanent substrate.

In some embodiments, the piezoelectric layer may be made of LiTaO₃Or LiNbO₃A second surface of the piezoelectric layer having a crystal structure oriented such that the thickness is reduced is a negative surface. The crystal structure orientation of the piezoelectric plate may include Euler angles (0 deg., 90 deg. °)<θ<270°,0°)。

In some embodiments, the first surface of the permanent substrate may be a positive surface, a negative surface, or a non-polarized surface resulting from the orientation of the crystal structure of the permanent substrate. In some embodiments, the first surface of the permanent substrate may be a front surface, and the permanent substrate may include euler anglesIs a negative surface and the permanent substrate may comprise euler anglesOr a non-polarizing surface, and the permanent substrate may comprise Euler anglesOrAngle of rotationIs provided with atThe angle psi has a value in the range 0 DEG ≦ psi<A value in the range of 180 deg..

For purposes of summarizing the present application, certain aspects, advantages, and novel features of the invention have been described herein. It is to be understood that not necessarily all such advantages may be achieved in accordance with any particular embodiment of the invention. Thus, the invention may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other advantages as may be taught or suggested herein.

Drawings

Fig. 1 illustrates an example of a conventional structure of a Surface Acoustic Wave (SAW) resonator including a structure formed at LiTaO₃(LT) or LiNbO₃An interdigital transducer (IDT) electrode on the (LN), and reflectors formed on both sides of the IDT electrode.

Fig. 2 shows an example of the structure of a SAW resonator including a combination of an LT plate or LN plate and a quartz substrate.

Fig. 3 shows an enlarged plan view alone of the IDT electrode of the SAW resonator of fig. 2.

Fig. 4 shows actually measured characteristics of a conventional SAW resonator manufactured by forming a copper (Cu) IDT electrode on a 42 ° YXLT ((euler angle of 0 °,312 °,0 °)) substrate.

Fig. 5 shows actually measured characteristics of a SAW resonator manufactured by combining a Cu electrode, a 42 ° YXLT ((euler angle of 0 °,132 °,0 °)) plate, and a 42 ° 42 ° 45 'Y90 ° X ((euler angle of 0 °,132 ° 45', 90 °)) quartz substrate.

Fig. 6A-6H show various combinations of LT or LN plates and quartz substrates.

Fig. 7A and 7B show one example of the polarization and surface charge characterization of a layer such as an LT plate or LN plate or a quartz substrate.

Fig. 8A and 8B show polarization of an example LT crystal orientation relative to a reference coordinate system.

Fig. 9A and 9B show frequency characteristics of the SAW resonator in which aluminum electrodes having a wavelength (λ) of 2 μm and a thickness of 0.08 λ are formed on a (+) surface ((euler angles of 0 °,110 °,0 °)) and a (-) surface thereof ((euler angles of 0 °,290 °,0 °)) of a Y-plate X propagation LT rotated by 20 °, respectively.

Fig. 10A and 10B show frequency characteristics of the SAW resonator in which the electrodes of fig. 9A and 9B are formed on a (+) surface ((euler angles of 0 °,132 °,0 °)) and a (-) surface thereof ((euler angles of 0 °,312 °,0 °)) of a Y-plate X propagation LT rotated by 42 °, respectively.

11A-11D show the frequency characteristics of four combinations of (+) and (-) surfaces of a 20 ° rotated Y plate X propagating LT and (+) and (-) surfaces of a 42 ° 45' Y plate 90 ° X propagating quartz.

Fig. 12A and 12B show the euler angle dependence of the bandwidth and impedance ratio of SAW resonators formed from four combinations of (+) and (-) surfaces of 20 ° rotated Y-plate X propagation LT and (+) and (-) surfaces of 35 ° Y-plate 90 ° X propagation rotated quartz to 60 ° Y-plate 90 ° X propagation.

Fig. 13A and 13B show the euler angle dependence of the bandwidth and impedance ratio of SAW resonators formed from four combinations of (+) and (-) surfaces of LT rotated toward 50 ° YX-propagation according to 10 ° X-propagation and (+) and (-) surfaces of 90 ° X-propagation quartz of a 42 ° 45' Y plate.

Fig. 14A and 14B show the euler angle dependence of the bandwidth and impedance ratio of SAW resonators formed from four combinations of (+) and (-) surfaces of 25 ° rotation Y plate X propagating LN and (+) and (-) surfaces of 35 ° Y plate 90 ° X propagating rotation quartz to 60 ° Y plate 90 ° X propagating rotation.

FIGS. 15A and 15B show the LT-thickness dependence of bandwidth and impedance ratio for a SAW resonator having a +20YXLT-/+42 deg. 45' Y90X quartz structure.

Fig. 16 shows θ dependence of the linear expansion coefficient of (0 °, θ,0 °) LT in the X direction (SAW propagation direction) and the Y direction (90 degrees from the SAW propagation direction).

Fig. 17 shows θ dependence of the linear expansion coefficient of (0 °, θ,0 °) LN in the X direction (SAW propagation direction) and the Y direction (90 degrees from the SAW propagation direction).

Fig. 18 shows θ dependence of linear expansion coefficients of (0 °, θ,0 °) quartz in the X direction and the Y direction.

Fig. 19 shows the θ dependence of the linear expansion coefficient of (0 °, θ,45 °) quartz in the X direction and the Y direction.

Fig. 20 shows the θ dependence of the linear expansion coefficient of (0 °, θ,90 °) quartz in the X direction and the Y direction.

Fig. 21 shows ψ dependence of linear expansion coefficients in the X direction and the Y direction of (0 °,126 °, ψ) quartz.

Fig. 22 shows ψ dependence of linear expansion coefficients of (0 °,132 ° 45', ψ) quartz in the X direction and the Y direction.

Fig. 23 shows ψ dependence of linear expansion coefficients of (0 °,145 °, ψ) quartz in the X direction and the Y direction.

Fig. 24A-24C illustrate one example of a process that can be used to obtain a combination of LT or LN plates and quartz substrates.

Fig. 25A-25E illustrate another example of a process that can be used to obtain a combination of LT or LN plates and quartz substrates.

Fig. 26A shows a damaged LT substrate after a heat treatment at 200 ℃ for 20 hours after the bonding process of fig. 24A-24C.

Fig. 26B shows an example in which the substrate is partially peeled due to weak bonding strength when the substrate is polished to 5 μm during the process of fig. 24A to 24C.

Fig. 27A shows the LT surface obtained after LT is bonded to a silicon substrate and the LT is polished to a thickness of 0.3 μm.

Fig. 27B shows the LT surface obtained after bonding a quartz substrate to the LT surface of the assembly of fig. 27A, and then the silicon substrate is etched by a plasma etching technique.

Fig. 28 shows the frequency characteristics of a SAW resonator manufactured by a method similar to the example of fig. 25A to 25E.

Fig. 29 illustrates that in some embodiments, multiple unit SAW resonators can be fabricated in an array, such as in wafer form.

Fig. 30 illustrates that in some embodiments, a SAW resonator having one or more of the features described herein can be implemented as part of a packaged device.

Fig. 31 illustrates that in some embodiments, the SAW resonator based packaged device of fig. 30 can be a packaged filter device.

Fig. 32 illustrates that in some embodiments, a Radio Frequency (RF) module may include components of one or more RF filters.

Fig. 33 depicts one example of a wireless device having one or more of the advantageous features described herein.

Detailed Description

The headings, if any, are provided herein for convenience only and do not necessarily affect the scope or meaning of the claimed invention.

The frequency band used for a smart phone or the like includes about 80 frequency bands close to each other, and thus a filter and a duplexer having a steep frequency characteristic are required or desired. Such filtering applications may include, for example, ladder filter structures in which resonators employing Surface Acoustic Waves (SAW) or bulk waves are arranged in steps. Therefore, a resonator having a large impedance ratio or a high Q is required or desired to realize a filter or a duplexer having a steep frequency characteristic.

Fig. 1 shows an example of a conventional structure of a Surface Acoustic Wave (SAW) resonator 10, the SAW resonator 10 including a resonator formed at LiTaO₃(LT) or LiNbO₃An interdigital transducer (IDT) electrode 12 on a (LN) substrate 18, and reflectors 14,16 formed on both sides of the IDT electrode 12.

Fig. 2 illustrates an example of a Surface Acoustic Wave (SAW) device 100 implemented as a SAW resonator. Such SAW resonators may include those made of, for example, LiTaO₃(also referred to herein as LT) or LiNbO₃(also referred to herein as LN) formed piezoelectric layer 104. Such a piezoelectric layer can include a first surface 110 (e.g., an upper surface when SAW resonator 100 is oriented as shown) and an opposing second surface. A second surface of the piezoelectric layer 104 can be attached to, for example, a quartz substrate 112.

On a first surface 110 of the piezoelectric layer 104, an interdigital transducer (IDT) electrode 102 can be implemented, as well as one or more reflector assemblies (e.g., 114, 116). Fig. 3 shows an enlarged plan view of an IDT electrode 102 of the SAW resonator 100 of fig. 2 alone. It should be understood that the IDT electrode 102 of fig. 2 and 3 may include a greater or lesser number of fingers (fingers) for the two interdigitated finger sets.

In the example of fig. 3, IDT electrodes 102 are shown as including a first set 120a of fingers 122a and a second set 120b of fingers 122b, which are arranged in interdigitated fashion. In such a configuration, the distance between two adjacent fingers of the same group (e.g., adjacent finger 122a of first group 120 a) is approximately the same as the wavelength λ of the surface acoustic wave of the associated IDT electrode 102.

In the example of fig. 3, various dimensions are shown in relation to the fingers. More specifically, each finger (122a or 122b) is shown as having a lateral width F, while a spacing G is shown as being provided between two adjacent interdigitated fingers (122a and 122 b).

It should be noted that the SAW resonator 100 of fig. 2 may be configured to provide a larger impedance ratio (e.g., about 29dB) than the conventional SAW resonator 10 of fig. 1. For example, fig. 4 shows a graph of impedance characteristics as a function of frequency for SAW resonator 10 of fig. 1, and fig. 5 shows a graph of impedance characteristics as a function of frequency for SAW resonator 100 of fig. 2. For the graph of FIG. 4, the impedance ratio (20log (Z)_a/Z_r) Is 51dB, where Z_rAnd Z_aAre respectively the resonant frequency f_rAnd antiresonance frequency f_aThe impedance value of (d). For the graph of fig. 5, the impedance ratio is 80dB, 29dB greater than that of fig. 4.

In some embodiments, the present application relates to techniques for fabricating SAW resonator 100 of fig. 2. Such techniques may allow the manufacturing process to avoid or reduce the likelihood of undesirable effects. For example, when LT or LN is bonded to a quartz substrate, damage may occur due to a difference in thermal expansion between the LT or LN and the quartz substrate during a heat treatment process performed to enhance the bonding strength. In another example, when the heat treatment is performed at a lower temperature to produce a bonded substrate in order to avoid damage, the bonding strength may be weak, and thus the LT or LN may be cracked or peeled off from the quartz substrate during the process of thinning the LT or LN plate.

In some embodiments, various apparatus, structures, and methods may be used to enhance the bonding strength by optimally or selectively combining the orientation angle of the LT or LN with the orientation angle of the quartz substrate, and/or to support the manufacturing process when the bonding is weak.

It should be noted that the bandwidth of the acoustic wave filter depends on the electromechanical coupling coefficient (coupling coefficient) of the piezoelectric substrate used in the acoustic wave filter. Thus, LiTaO with coupling coefficient necessary for filter bandwidth₃(LT) or LiNbO₃A (LN) substrate is employed.

In many applications, resonators with coupling coefficients that meet the bandwidth of the filter while having a larger impedance ratio (higher Q) are desirable. Combining thin sheet LT or LN with a quartz substrate as shown in fig. 2, as described herein, can provide a greater impedance ratio and better temperature characteristics as shown in fig. 5.

In some embodiments, optimizing or selecting the polarity of the LT or LN piezoelectric sheets and the polarity of the quartz substrate in a desired relationship can provide a wider bandwidth and a greater impedance ratio. For example, bonding a negative (-) surface of an LT or LN to a quartz substrate can provide a wider bandwidth and a larger impedance ratio than bonding a positive (+) surface of an LT or LN to a quartz substrate. Examples of such polarities are described in more detail herein.

In some embodiments, after bonding the negative surface of the LT or LN to the quartz substrate, the bonding strength may be enhanced by heat treatment. When the linear expansion coefficients in the X direction (SAW propagation direction) of LT or LN and the Y direction that is different from the X direction by 90 degrees are significantly different from those of the quartz substrate, the heat treatment after the bonding process may cause damage to the substrate. When the difference between the expansion coefficients in the X direction and the Y direction is larger, damage during heat treatment is more likely to occur. Thus, selecting the orientation of the layers being bonded may reduce the difference in expansion coefficients between the layers. It should be noted that the difference in expansion coefficient between the X direction and the Y direction can be reduced even within the same layer.

It should be noted that in some embodiments, for one or more performance characteristics, the orientation angle of the combined bonding layer is sometimes desired to be different from the orientation angle selected to address the above-described problems.

It should be noted that in some embodiments, direct bonding techniques may be difficult to apply to oxide substrates (e.g., LT and quartz). On the other hand, the LT or LN layer and the silicon (Si) layer may be directly bonded to each other, the bonding being strong enough to omit the heat treatment. Thus, in some embodiments, after the LT or LN layer is bonded to the Si layer by this direct bonding technique, the LT or LN can be thinned to a desired thickness. The polished surface of the thinned LT or LN sheet can then be bonded to the quartz substrate, and the Si layer can be etched to achieve the LT, LN sheet/quartz substrate assembly. Since the polishing process is not performed after the above process, mechanical damage related to polishing is unlikely to occur in the manufacturing process even if the bonding strength is weak to some extent.

As described above, fig. 1 shows a conventional structure of a Surface Acoustic Wave (SAW) resonator 10, the resonator 10 including an interdigital transducer (IDT) electrode 12 formed on LT or LN18 and reflectors 14,16 formed on both sides of the IDT electrode 12. Fig. 2 shows an example structure of SAW resonator 100, which includes a combination of LT or LN lamels 104 and a quartz substrate 112. IDT electrode 102 is shown formed on surface 110 of LT or LN sheet 104, and reflectors 114,116 are shown formed on both sides of IDT electrode 102.

As described above, fig. 4 shows an impedance characteristic graph as a function of frequency of the SAW resonator 10 of fig. 1, and fig. 5 shows an impedance characteristic curve as a function of frequency of the SAW resonator 100 of fig. 2. In the example of fig. 4, the IDT electrode (12 of fig. 1) is a copper (Cu) electrode formed in the SAW direction of propagation in the X direction (referred to as 42 ° YXLT ((negative plane in euler angle of 0 °,312 °,0 °)) plane on the negative plane of the Y-plate LT substrate rotated by 42 °. in this figure, the point where the impedance is the smallest is referred to as resonance impedance Zr, the corresponding frequency thereof is referred to as resonance frequency fr, the point where the impedance is the largest is referred to as anti-resonance impedance Za, the corresponding frequency thereof is referred to as anti-resonance frequency fa., bandwidth thereof is represented as (fa-fr)/fr, and the impedance ratio is represented as 20log (Za/Zr).

As described above, fig. 5 shows actually measured characteristics of a SAW resonator manufactured by combining a 42 ° YXLT (IDT is formed at 42 ° YXLT, (positive plane in euler angles of 0 °,132 °,0 °) plane) thin plate with a 42 ° 45 'Y90 ° X quartz substrate (euler angles of (0 °,132 ° 45', 90 °) propagating in a direction deviating from the X axis by 90 °). The combination of LT and quartz allows the bandwidth to be extended from 4.2% to 5.1% and the impedance ratio to be extended from 51dB to 80dB, resulting in a 29dB increase. Therefore, combining LT with a quartz substrate can significantly improve frequency characteristics.

Note that the piezoelectric body has a plus (+) polarity and a minus (-) polarity with respect to the c-axis. For example, the surface of the euler angle of the Y plate (0 °,132 °,0 °) expressed as 42 ° rotation represents the (+) surface, while the opposite, i.e. 180 ° rotation (0 °,312 °,0 °), represents the (-) surface.

Fig. 6A through 6H illustrate that in some embodiments SAW resonator 100 can have different combinations of the polarity orientation of piezoelectric layer 104 (e.g., LT or LN) and the polarity orientation of substrate 112 (e.g., quartz). In fig. 6A-6H, the piezoelectric layer 104 of each SAW resonator 100 is shown as including a first surface 103a and a second surface 103b, and the substrate 112 of the same SAW resonator is shown as including a first surface 113a and a second surface 113 b. The second surface 103b of the piezoelectric layer 104 is shown bonded to the first surface 113a of the (engage) substrate 112. Thus, for purposes of description, the second surface 103b of the piezoelectric layer 104 and the first surface 113a of the substrate 112 can be considered to be bonding surfaces, while the first surface 103a of the piezoelectric layer 104 and the second surface 113b of the substrate 112 can be considered to be non-bonding surfaces.

Fig. 6A illustrates that in some embodiments, piezoelectric layer 104 of SAW resonator 100 can be configured such that its polarity results in bonding surface 103b being a negative (-) surface, while substrate 112 of SAW resonator 100 can be configured such that its polarity results in bonding surface 113a being a positive (+) surface. In such a configuration, the non-bonding surface 103a of the piezoelectric layer 104 is a positive (+) surface, and the non-bonding surface 113b of the substrate 112 is a positive (-) surface. More detailed examples of negative (-) and positive (+) surfaces are described herein with reference to fig. 7 and 8.

Fig. 6B illustrates that in some embodiments, piezoelectric layer 104 of SAW resonator 100 can be configured such that its polarity results in bonding surface 103B being a negative (-) surface, while substrate 112 of SAW resonator 100 can be configured such that its polarity results in bonding surface 113a being a negative (-) surface. In such a configuration, the non-bonding surface 103a of the piezoelectric layer 104 is a positive (+) surface, and the non-bonding surface 113b of the substrate 112 is a positive (+) surface.

Fig. 6C illustrates that in some embodiments, piezoelectric layer 104 of SAW resonator 100 can be configured such that its polarity results in bonding surface 103b being a positive (+) surface, while substrate 112 of SAW resonator 100 can be configured such that its polarity results in bonding surface 113a being a positive (+) surface. In such a configuration, the non-bonding surface 103a of the piezoelectric layer 104 is a negative (-) surface, and the non-bonding surface 113b of the substrate 112 is a negative (-) surface.

Fig. 6D illustrates that in some embodiments, piezoelectric layer 104 of SAW resonator 100 can be configured such that its polarity results in bonding surface 103b being a positive (+) surface, while substrate 112 of SAW resonator 100 can be configured such that its polarity results in bonding surface 113a being a negative (-) surface. In such a configuration, the non-bonding surface 103a of the piezoelectric layer 104 is a negative (-) surface, and the non-bonding surface 113b of the substrate 112 is a positive (+) surface.

Fig. 6E illustrates that in some embodiments, piezoelectric layer 104 of SAW resonator 100 can be configured such that its polarity results in bonding surface 103b being a negative (-) surface, while substrate 112 of SAW resonator 100 can be configured such that its crystal orientation results in bonding surface 113a being at an euler angleOf the non-polarizing surface. In such a configuration, the non-bonding surface 103a of the piezoelectric layer 104 is a positive (+) surface.

Fig. 6F illustrates that in some embodiments, piezoelectric layer 104 of SAW resonator 100 can be configured such that its polarity results in bonding surface 103b being a negative (-) surface, while substrate 112 of SAW resonator 100 can be configured such that its crystal orientation results in bonding surface 113a being at an euler angleOf the non-polarizing surface. In such a configuration, the non-bonding surface 103a of the piezoelectric layer 104 is a positive (+) surface.

Fig. 6G illustrates that in some embodiments, piezoelectric layer 104 of SAW resonator 100 can be configured such that its polarity results in bonding surface 103b being a positive (+) surface, while substrate 112 of SAW resonator 100 can be configured such that its crystal orientation results in bonding surface 113a being at an euler angleOf the non-polarizing surface. In such a configuration, the non-bonding surface 103a of the piezoelectric layer 104 is a negative (-) surface.

Fig. 6H illustrates that in some embodiments, piezoelectric layer 104 of SAW resonator 100 can be configured such that its polarity results in bonding surface 103b being a positive (+) surface, while substrate 112 of SAW resonator 100 can be configured such that its crystal orientation results in bonding surface 113a being at an euler angleOf the non-polarizing surface. In such a configuration, the non-bonding surface 103a of the piezoelectric layer 104 is a negative (-) surface.

Fig. 7A and 7A show a body of material 105, which may be a piezoelectric layer (e.g., LT or LN layer), or a dielectric layer, such as a quartz layer. For the purpose of description, it is assumed that such a body has a planar shape between the first surface 107a and the second surface 107b, having a plane parallel to the XY plane of the rectangular coordinate system. In such a configuration, the X direction may be a propagation direction of the surface acoustic wave.

In the body 105 of fig. 7A and 7B, polarization may be present or induced, resulting in a net polarization potential difference between the first surface 107A and the second surface 107B. Such a net polarization difference may result in one type of net charge on the first surface 107a and another type of net charge on the second surface 107 b.

For example, as shown in fig. 7A, when the first surface 107A has a positive (+) polarization potential and the second surface 107b has a negative (-) polarization potential, the first surface 107A has a negative (-) charge and the second surface 107n has a positive (+) charge. Conversely, as shown in fig. 7B, when the first surface 107a has a negative (-) polarization potential and the second surface 107B has a positive (+) polarization potential, the first surface 107a has a positive (+) charge and the second surface 107n has a negative (-) charge.

For purposes of description, and unless otherwise noted, a positive (+) surface of the body 105 may correspond to a surface having a positive (+) polarization potential and a negative (-) surface of the body 105 may correspond to a surface having a negative (-) polarization potential. Thus, the positive (+) and negative (-) surfaces of the piezoelectric layer 104 and the substrate 112 of fig. 6A-6D can be understood to follow the foregoing example definitions.

It will be appreciated that the plus (+) and minus (-) surfaces of the body may be defined in other ways. For example, positive (+) and negative (-) surfaces may be defined as the charges corresponding to these surfaces. In this case, the positive (+) surface of the body may correspond to a surface having a positive (+) charge, and the negative (+) surface of the body may correspond to a surface having a negative (+) charge.

Fig. 8A illustrates an example of a unit cell 117 of the crystal structure of the body 105 of fig. 7A and 7B. Such a unit cell is shown having a crystal orientation relative to reference plane 115 parallel to the XY plane of body 105 to provide a negative (-) polarization potential to the corresponding surface of body 105. Thus, such a surface is a negative (-) surface.

It should be noted that, for example, an LT crystal (42 ° yl) having a 42 ° Y structure may represent a positive (+) ((0 °,132 °,0 °) euler angle) or negative (-) ((0 °,312 °,0 °) euler angle) plane. These two euler angle structures ((0 °,132 °,0 °) and (0 °,312 °,0 °)) provide similar frequency characteristics as described herein (e.g., with reference to fig. 10A and 10B) when only conventional LT or LN is used. However, it is easier and faster to polish (0 °,312 °,0 °) planes compared to (0 °,132 °,0 °) planes. Thus, in some embodiments, the plane for example 42 ° YXLT is a (0 °,312 °,0 °) plane.

Fig. 8B illustrates another example of a unit cell 117 of the crystal structure of the body 105 of fig. 7A and 7B. Such a unit cell is shown as having a crystal orientation relative to reference plane 115 parallel to the XY plane of body 105 to provide a positive (+) polarization potential to the corresponding surface of body 105. Thus, such a surface is a positive (+) surface.

As an example, the LT crystal having the aforementioned positive (+) surface includes euler angles (0 °,132 °,0 °). Therefore, a negative (-) surface corresponding to a negative (-) polarization potential surface of a 42 ° YX structure (42 ° YXLT) can be expressed as having euler angles (0 °,312 °,0 °). As illustrated in fig. 8A, the use of such surfaces (having euler angles (0 °,312 °,0 °)) may be preferred in some embodiments.

For purposes of description, and with reference to fig. 6 and 7, the euler angles defined for a positive (+) polarization potential surface include (0 °,90 ° < θ <270 °,0 °). Further, the euler angles defined for the negative (-) polarization potential surfaces include (0 °, -90 ° < θ <90 °,0 °). Thus, if the positive (+) and negative (-) surfaces follow the positive (+) and negative (-) polarization potential surfaces, the euler angles defined for the positive (+) surface include (0 °,90 ° < θ <270 °,0 °), and the euler angles defined for the negative (-) surface include (0 °, -90 ° < θ <90 °,0 °).

For purposes of description, it will be understood that angle α may be expressed in equivalent form as α ± n360 °, where n is an integer. For example, an euler angle (0 °,90 ° < θ <270 °,0 °) will be understood to be equivalent to (0 °, -270 ° < θ < -90 °,0 °). In another example, euler angles (0 °, -90 ° < θ <90 °,0 °) will be understood to be equivalent to (0 °,270 ° < θ <450 °,0 °).

In the case of the foregoing example definitions of positive (+) and negative (-) surfaces, table 1 summarizes the SAW resonator configuration of fig. 6A-6D, assuming that the piezoelectric layer 104 is LT, the substrate 112 is quartz, and it is believed that the euler angles correspond to the upper surfaces of the respective layers (103 a of LT layer 104, and 113a of quartz layer 112) when viewed as depicted.

TABLE 1

In the example of table 1, each quartz substrate is configured to include a positive (+) surface and a negative (-) surface corresponding to respective euler angles. It should be noted that when the polarization plane (e.g., Z-plane) of the quartz crystal is perpendicular to the surface of the SAW plane (e.g., euler angle of (90 °,90 °,90 °) or (90 °, -90 °,90 °)), the corresponding quartz substrate does not have (+) and (-) surfaces associated with the polarization plane. In some embodiments, SAW resonators utilizing such quartz substrates may be implemented.

Table 2 summarizes the SAW resonator configurations of fig. 6D-6G assuming that the piezoelectric layer 104 is LT, the substrate 112 is quartz, and that the euler angles correspond to the upper surfaces of the respective layers (103 a for LT layer 104, and 113a for quartz layer 112) when viewed as depicted.

TABLE 2

As described in greater detail herein, it should be noted that a SAW resonator having a + LT-/quartz configuration (e.g., FIG. 6E or FIG. 6F) has a higher impedance ratio than a SAW resonator having a-LT +/quartz configuration (e.g., FIG. 6G or FIG. 6H).

The bonding strength (bonding strength) of the surface combinations of LT and quartz listed in tables 1 and 2 was measured as follows. For the + LT-/+ quartz-configuration (FIG. 6A), the measured binding strength (2. gamma.) was 2.2J/m². For the + LT-/-quartz + configuration (FIG. 6B), the measured binding strength (2 γ) was 2.0J/m². For the-LT +/+ quartz-configuration (FIG. 6C), the measured binding strength (2. gamma.) was 1.8J/m². For the-LT +/-Quartz + configuration (FIG. 6D), the measured binding strength (2 γ) was 2.0 joules/m². For the + LT-/quartz configuration of FIG. 6E, the measured bond strength (2 γ) was 1.9 joules/m². For the + LT-/quartz configuration of FIG. 6F, the measured bond strength (2 γ) was 1.9 joules/m². For the-LT +/quartz configuration of FIG. 6G, the measured bond strength (2 γ) was 1.9 joules/m². For the-LT +/quartz configuration of FIG. 6H, the measured bond strength (2 γ) was 1.9 joules/m². Note that, of the eight configurations listed in tables 1 and 2, the configuration (+ LT-/+ quartz-) of fig. 6A provides the highest bonding strength (2 γ ═ 2.2 joules/m)²)。

In the foregoing measurement examples, the binding strength was expressed as 2 γ, where γ is the binding strength between two substrates as described by Tong, Q., Goesele, U., and Society, E. (1999) Semiconductor Wafer binding: Science and Technology, John Wiley & Sons, Inc., New York. Examples relating to bond strength in various manufacturing process steps are described in more detail herein.

In some embodiments, the angles used for the quartz substrates in tables 1 and 2Can haveA value in the range of 180 deg.. For example, the quartz substrate may haveOrThe configuration of (2). In some embodiments, the angle ψ for the quartz substrates in tables 1 and 2 can have 0 ° ≦ ψ<A value in the range of 180 deg.. For example, the quartz substrate may have a configuration of ψ 0 ° or ψ 90 °.

It is to be understood that the surface combinations and euler angle combinations defined in tables 1 and 2 may also be applicable to other piezoelectric layers (including LN layers) and/or other substrate layers.

It will also be understood that a positive (+) surface is also referred to herein simply as a (+) surface and that a negative (-) surface is also referred to herein simply as a (-) surface.

Fig. 9A and 9B show characteristics of the SAW resonator in which aluminum electrodes having a wavelength (λ) of 2 μm and a thickness of 0.02 λ are formed on a (+) surface ((0 °,110 °,0 °) euler angle) and a (-) surface ((0 °,290 °,0 °) euler angle) of a Y plate X rotated by 20 °, respectively, which propagates LT. Fig. 10A and 10B show the characteristics of the SAW resonator in which the same electrodes are formed on the (+) surface ((0 °,132 °,0 °) euler angle) and the (-) surface ((0 °,312 °,0 °) euler angle) of the Y-plate X propagation LT rotated by 42 °, respectively. As can be seen from these impedance characteristic curves, even if an electrode is formed on either (+) or (-) surface of the conventional LT substrate, there is substantially no difference in bandwidth, impedance ratio, resonance frequency, antiresonance frequency, spurious mode, etc. between the respective SAW resonators.

Based on the foregoing examples, it can be seen that there is no difference in impedance characteristics between the (+) and (-) surfaces of the conventional LT substrate. Therefore, in general, when a conventional LT substrate is used, the (+) plane and the (-) plane are not distinguished. However, such surfaces are typically used in conventional LT substrates because the (-) plane is easier to polish. For example, the (0 °,312 °,0 °) plane is commonly used in the conventional 42 ° YXLT example.

11-14 show various examples of characteristics associated with different combinations of LT orientation and quartz orientation. A more general form of such a combination (piezoelectric layer 104 and substrate layer 112) is shown in fig. 6A-6D.

As an example, (+) and (-) surfaces (euler angles of (0 °,110 °,0 °) and (0 °,290 °,0 °)) of a Y-plate X-propagating LT rotated by 20 ° and (+) and (-) surfaces ((0 °,132 °,45 ', 90 °) and (0 °,312 ° 45 ', 90 °)) of a 42 ° 45 ' Y-plate 90 ° X-propagating quartz were prepared so as to form four SAW resonators corresponding to the four combinations shown in fig. 6A to 6D and obtain their frequency characteristics. Fig. 11A-11D illustrate these characteristics.

Referring to fig. 6A to 6D and fig. 11A to 11D, it is noted that a combination of LT and quartz (fig. 6A) in which the LT electrode side is a (+) surface, the LT surface bonded to quartz is a (-) surface, and the bonded surface of the same LT and quartz (fig. 6B) is a (+) surface show substantially the same bandwidth and impedance ratio, see fig. 11A and 11B. It is also noted that the combination of LT and quartz (fig. 6C) in which the LT electrode side is a (-) surface, the LT surface bonded to quartz is a (+) surface, and the combination of the same LT and quartz (fig. 6D) in which the bonding surface of quartz is a (-) surface show substantially the same bandwidth and impedance ratio, see fig. 11C and 11D. However, the embodiment of fig. 11A and 11B shows a 13% increase in bandwidth and a 2dB increase in impedance ratio compared to the embodiment shown in fig. 11C and 11D. Note that the value of 13% is calculated from 6.2%/5.5% as shown in FIGS. 11A-11D.

Therefore, such a structure can lead to better characteristics when the surface to which LT is bonded is the (-) surface as shown in fig. 6A and 6B, regardless of whether quartz is the (+) surface or the (-) surface.

As another example, a (+) and a (-) surface (euler angles of (0 °,110 °,0 °) and (0 °,290 °,0 °) respectively) of a 20 ° rotated Y plate X propagating LT, and a (+) surface (euler angles (0 °,125 °,90 °) to (0 °,150 °,90 °)) of a 35 ° Y plate 90 ° X propagating quartz rotated toward a 60 ° Y plate 90 ° X propagating LT and a (-) surface (euler angles (0 °,305 °,90 °) to (0 °,330 °,90 °)) of the same quartz were made, four SAW resonators corresponding to the four combinations shown in fig. 6A to 6D were formed, and their frequency characteristics were obtained. The bandwidth and impedance ratio of these four structural combinations are shown in fig. 12A and 12B as a function of the euler angle θ of quartz. The structure of fig. 6A and 6B achieves a wider bandwidth and a larger impedance ratio than the structure of fig. 6C and 6D, throughout the quartz having any euler angle θ.

As another example, a (+) surface (euler angle (0 °,100 °,0 °) to (0 °,140 °,0 °) of LT propagating rotated toward 50 ° YX at 10 ° X and a (-) surface (euler angle (0 °,280 °,0 °) to (0 °,320 °,0 °)) of the same LT, and (+) and (-) surfaces (euler angles are (0 °,132 ° 45 ', 90 °) and (0 °,312 ° 45 ', 90 °) respectively) of quartz propagating at 90 ° X of a 42 ° 45 ' Y plate were prepared. The frequency characteristics of the SAW resonators of the four combinations shown in fig. 6A to 6D are obtained. The bandwidth and impedance ratio of these four structural combinations are shown in fig. 13A and 13B as a function of the euler angle θ of LT. The structure of fig. 6A and 6B can achieve a wider bandwidth and a larger impedance ratio than the structure of fig. 6C and 6D for LT at any euler angle.

In the various examples of fig. 11-13, the piezoelectric layer is an LT layer. Similar results can be obtained with LN as the piezoelectric layer.

For example, (+) and (-) surfaces (euler angles of (0 °,115 °,0 °) and (0 °,295 °,0 °) respectively) of 25 ° rotated Y plate X propagating LN, and (+) surfaces (euler angles (0 °,125 °,90 °) to (0 °,150 °,90 °)) and (-) surfaces (euler angles (0 °,305 °,90 °) to (0 °,330 °,90 °)) of the same quartz were made of 35 ° Y plate 90 ° X propagating rotated quartz toward 60 ° Y plate 90 ° X. The frequency characteristics of the SAW resonators of the four combinations shown in fig. 6A to 6D are obtained. The bandwidth and impedance ratio of these four structural combinations are shown in fig. 14A and 14B as a function of the euler angle theta of quartz. The structure of fig. 6A and 6B achieves a wider bandwidth and a larger impedance ratio than the structure of fig. 6C and 6D, looking at any euler angle θ of quartz. Other combinations of LN and quartz may also provide similar results to the corresponding combinations of LT and quartz described herein.

Based at least in part on the foregoing examples, when the surface of the LT or LN plate bonded to the quartz substrate is the (-) surface, using such a combination of the LT or LN plate and the quartz substrate according to the structure of fig. 6A and 6B can provide better characteristics when the LT, LN, or quartz is in any orientation.

When the plane of polarization potential of the SAW resonator is perpendicular to the quartz surface (e.g., a plane having an euler angle of (90 °,90 °,90 °) or (90 °, -90 °,90 °)), its quartz substrate does not have a (+) surface and a (-) surface with respect to the polarization direction. It should be noted that the back of this example (90 °,90 °,90 °) plane is the (90 °, -90 °,90 °) plane.

In the foregoing configuration of the quartz substrate, and referring to fig. 6E-6H and table 2, the SAW resonator (+ LT-/(90 °,90 °,90 °) quartz) of fig. 6E and the SAW resonator (+ LT-/(90 °, -90 °,90 °) quartz) of fig. 6F provide a higher impedance ratio than the SAW resonator (-LT +/(90 °,90 °,90 °) quartz) of fig. 6G and the SAW resonator (-LT +/(90 °, -90 °,90 °) quartz) of fig. 6H. Therefore, it can be seen that selecting either the (-) or (+) plane of LT or LN to bond with the quartz substrate is important to obtain a high impedance ratio regardless of whether the quartz substrate includes its own (-) and (+) planes.

FIGS. 15A and 15B show the relationship between the thickness (in wavelength λ) of a +20 ° YXLT-/+42 ° 45' Y90 ° X quartz structure, and (a) bandwidth and (B) impedance ratio, respectively. It can be seen that an impedance ratio of 70dB or more can be obtained when the LT thickness is 0.004 λ to 1.5 λ, and an impedance ratio of 73dB or more can be obtained when the LT thickness is 0.006 λ to 1 λ. Therefore, in order to obtain a larger impedance ratio, the thickness of LT or LN may be 1.5 λ or less, preferably 1 λ or less.

It is to be understood that one or more features of the present application can be applied not only to SAW resonators but also to any SAW device formed by combining LT or LN layers with a quartz substrate.

FIGS. 16 and 17 are directed to respectively: (A)0 °, θ,0 °) LT and (0 °, θ,0 °) LN show θ dependence of linear expansion coefficients of the substrate in the X direction (SAW propagation direction) and the Y direction (direction at an angle of 90 degrees to the SAW propagation direction). For both LT and LN, the linear expansion coefficient in the X direction is greater than the linear expansion coefficient in the Y direction. For both LT and LN, the difference in linear expansion coefficient between the X direction and the Y direction is larger in the vicinity of θ being 90 °. It should be noted thatCoefficient of linear expansion of interest substantially equivalent to Linear expansion coefficient of (d); therefore, in the case of the linear expansion coefficient,may be referred to herein as

Fig. 18, 19, and 20 show the θ dependence of the linear expansion coefficients in the X direction and the Y direction of the (0 °, θ,0 °) quartz substrate, the (0 °, θ,45 °) quartz substrate, and the (0 °, θ,90 °) quartz substrate, respectively. As shown in fig. 18 for (0 °, θ,0 °) quartz, the linear expansion coefficient in the X direction is larger than that in the Y direction. However, as shown in fig. 19 for (0 °, θ,45 °) quartz, the linear expansion coefficients in both directions are substantially the same, and as shown in fig. 20 for (0 °, θ,90 °) quartz, the linear expansion coefficient in the Y direction is larger than that in the X direction.

Fig. 21, 22 and 23 show ψ dependence of linear expansion coefficients in the X direction and the Y direction of a (0 °,126 °, ψ) quartz substrate, a (0 °,132 °, 45', ψ) quartz substrate, and a (0 °,145 °, ψ) quartz substrate, respectively. For any substrate with phi <45 DEG and phi <135 DEG and phi < 180 DEG, the linear expansion coefficient in the X direction is larger than that in the Y direction; for any substrate at ψ of 45 ° and 135 °, the linear expansion coefficients in both directions are substantially the same; for any substrate at 45 ° ≦ ψ <135 °, the coefficient of linear expansion in the X direction is less than the coefficient of linear expansion in the Y direction.

In some embodiments, (0 °,280 ° -330 °,0 °) (which provides the same linear expansion coefficient as (0 °,100 ° -150 °,0 °), may be used for the LT layer, taking into account a suitable coupling coefficient. Any combination of these layers with (0 °, θ,0 °) quartz layers may allow the linear expansion coefficient in the X direction to be greater than the linear expansion coefficient in the Y direction, and thus the thermally induced expansion to be greater in the X direction at any orientation angle. Therefore, the LT layer is less likely to undergo thermal cracking at any orientation angle. The difference in the linear expansion coefficient in the X direction between the two layers is about 15%; however, if such a difference is allowed even in the Y direction, the Y-direction linear expansion coefficient of the LT orientation angle (0 °,120 ° -150 °,0 °) may be about 7.10x10^-6To 13.10x10^-6And the linear expansion coefficient in the Y direction of the quartz orientation angles (0 DEG, 10 DEG to 80 DEG, 0 DEG) and (0 DEG, 100 DEG to 170 DEG, 0 DEG) is about 7.48x10^-6To 13.52x10^-6. Thus, the quartz orientation angle may allow the linear expansion coefficients of the two layers to be substantially the same.

In some embodiments, (0 °,265 ° -336 °,0 °) (which provides the same coefficient of linear expansion as (0 °,85 ° -156 °,0 °)) can be used for LN, and its combination with (0 °, θ,0 °) quartz can allow the X-direction coefficient of linear expansion to be greater than the Y-direction coefficient of linear expansion of the two layers, so that thermal expansion is greater in the X-direction at any orientation angle. The linear expansion coefficient in the Y direction for an LN orientation angle (0 deg., 85 deg. -156 deg., 0 deg.) that is equivalent in linear expansion coefficient to (0 deg., 265 deg. -336 deg., 0 deg.) is about 7.5x10^-6To 14.00x10^-6And quartz (0, 5-85, 0) and (0, 95-175, 0) have a linear expansion coefficient in the Y direction of about 7.48x10^-6To 13.71x10^-6. Accordingly, the linear expansion coefficients of LN and quartz may be substantially the same for this orientation angle.

The magnitude relation of the linear expansion coefficients in the X direction and the Y direction is inverted between (0 °, θ,0 °) LT shown in fig. 16 and (0 °, θ,90 °) quartz shown in fig. 20, and thus it may be difficult to find LT and stoneConditions for quartz bonding. However, it is preferred to use an orientation that allows the difference between the expansion coefficient of (0 °,280 ° -330 °,0 °) LT and the expansion coefficient of quartz to be as small as possible, where (0 °,280 ° -330 °,0 °) is itself the orientation normally used for LT. Such an orientation (0 °,280 ° -330 °,0 °) LT has about 16.1x10^-6And +/-40% linear expansion coefficient of about 9.66X10^-6To 22.96x10^-6Within the range of (1); and thus the orientation angle of the quartz allowing the X-direction linear expansion coefficient of the quartz to be within this range may be (0 °,0 ° -54 °,90 °) and (0 °,126 ° -180 °,90 °). On the other hand, the linear expansion coefficient of the above orientation LT is about 4.46x10 for the Y direction^-6To 13.1x10^-6Within a range of +/-40% linear expansion coefficient of about 6.24x10^-6To 18.34x10^-6(ii) a And thus the orientation angle of quartz satisfying these coefficients may be (0 °,0 ° -180 °,90 °). To this end, for an exemplary orientation (0, 100-150, 0) LT, the quartz orientation angle that allows the difference in linear expansion coefficients between LT and quartz to be within +/-40% in both the X and Y directions can be (0, 0-54, 90) to (0, 126-180, 90).

The magnitude relation of the linear expansion coefficients in the X direction and the Y direction is inverted between (0 °, θ,0 °) LN shown in fig. 17 and (0 °, θ,90 °) quartz shown in fig. 20; however, it is preferred to use an orientation that allows the difference between the expansion coefficient of (0 °,85 ° -156 °,0 °) LN and the expansion coefficient of quartz to be as small as possible, where (0 °,85 ° -156 °,0 °) is itself the orientation that is commonly used for LT. As shown in FIG. 17, the coefficient of linear expansion in the X direction of (0 °,85 ° -156 °,0 °) LN is about 15.4X10^-6Its +/-40% linear expansion coefficient in X direction is about 9.24X10^-6To 21.56x10^-6. Accordingly, the quartz corresponding to the coefficients has orientations of (0 °,0 ° -58 °,90 °) and (0 °,122 ° -180 °,90 °) as derived from fig. 20. On the other hand, the linear expansion coefficient in the Y direction of the same orientation LN is about 7.62x10^-6To 14.08x10^-6In the range of (0 DEG, 0 DEG to 180 DEG, 90 DEG) quartz has a linear expansion coefficient in the Y direction of 13.71x10^-6And the linear expansion coefficient of any orientation may be similar to that of the orientation LN described above. Thus, the (0 °,the quartz orientations between the 85 deg. -156 deg., 0 deg. LN and (0 deg., theta, 90 deg.) quartz having coefficients of linear expansion within +/-40% of each other in the X-direction and Y-direction can be (0 deg., 0 deg. -58 deg., 90 deg.) and (0 deg., 122 deg. -180 deg., 90 deg.).

Referring to fig. 21, 22 and 23, when ψ is 45 ° and 135 °, the X-direction and Y-direction linear expansion coefficients of (0 °, θ, ψ) quartz are substantially the same, and when 0 ≦ ψ <45 ° and 135 ° ≦ ψ ≦ 180 °, the X-direction linear expansion coefficient is larger than the Y-direction linear expansion coefficient. The same is true for the other θ. Thus, the X-direction linear expansion coefficient of (0 °,0 ° -180 °,0 ° -45 °) and (0 °,0 ° -180 °,135 ° -180 °) quartz is greater than the Y-direction linear expansion coefficient, similar to LT and LN described above, and is therefore the desired orientation angle for bonding. Further, as shown in fig. 21, 22 and 23, the linear expansion coefficients in the X direction and the Y direction at ψ of 30 ° to 45 ° are within +/-7% with respect to the linear expansion coefficients in the X direction and the Y direction at ψ of 45 °, and the magnitude relationship of the linear expansion coefficients in the X direction and the Y direction is reversed when ψ of 30 ° to 45 ° and ψ of 45 ° to 60 °; but still within +/-7% and sufficient bond strength can be obtained even in (0 deg., 0 deg. -180 deg., 30 deg. -60 deg.) quartz. Similarly, the X-direction and Y-direction linear expansion coefficients at ψ of 120 ° to 150 ° are also within +/-7% with respect to the X-direction and Y-direction linear expansion coefficients at ψ of 135 °, and therefore sufficient bonding strength can be obtained even in (0 °,0 ° -180 °,120 ° -150 °) quartz. Thus, (0 °,0 ° -180 °,30 ° -60 °) quartz and (0 °,0 ° -180 °,120 ° -150 °) quartz have orientation angles suitable for bonding with LT or LN, preferably, (0 °,0 ° -180 °,0 ° -45 °) and (0 °,0 ° -180 °,135 ° -180 °) quartz are more suitable orientation angles.

Fig. 24A-24C illustrate one example process that may be used to fabricate a SAW resonator having one or more of the features described herein. 25A-25E illustrate another example process that may be used to fabricate a SAW resonator having one or more of the features described herein. In both examples, LT material is used as the piezo; however, it should be understood that other materials, including LN materials, may be used.

In a first example, fig. 24A shows that in some embodiments, the manufacturing process may include process steps to form or provide an assembly 132 of a relatively thick LT plate 130 and a quartz plate 112. In some embodiments, the relatively thick LT and quartz plates may be cleaned and activated on their respective mirror sides, and these surfaces may be pressed to be bonded. Alternatively or additionally, bonding may be performed between the two plates using a thin film made of silicon (Si) or the like.

Fig. 24B shows a process step in which the thickness of the relatively thick LT plate 130 is reduced to a thinner LT plate 134 to form an assembly 136. In some embodiments, such a thinning process step may be achieved by, for example, a polishing process (such as a mechanical polishing process, a chemical mechanical process, etc.). In fig. 24B, a thinner LT plate 134 is shown to include a first surface bonded to the quartz plate 112 (e.g., by bonding), and a second surface opposite the first surface resulting from the thinning process step. In some embodiments, the thinning process step may be performed to provide a desired thickness of the thinner LT plate in a range of, for example, 0.3 to 1 μm.

Fig. 24C shows the process step of forming electrode 102 on the second surface of LT plate 134 to form assembly 138. As described herein, such electrodes may include an interdigitated arrangement of fingers 122a, 122 b.

In some embodiments, some or all of the process steps associated with fig. 24A-24C may be performed on a single unit to produce a single unit of the assembly 138, may be performed on a plurality of separate units to produce a plurality of corresponding single units of the assembly 138, or may be performed while a plurality of units are attached in an array format (e.g., wafer format) and then singulated to produce a plurality of singulated units of the assembly 138.

In a second example, fig. 25A shows that in some embodiments, the manufacturing process may include a process step of forming or providing an assembly 142 of a relatively thick LT plate 130 and a handle substrate (e.g., silicon substrate) 140. In some embodiments, the relatively thick LT plate and the silicon (Si) substrate can be cleaned and activated on their respective mirror sides, and the mirror sides of the relatively thick LT plate and the Si substrate can be directly bonded while being pressurized in a vacuum.

Fig. 25B shows the process step where the thickness of the relatively thick LT plate 130 is reduced to a thinner LT plate 144 to form an assembly 146. In some embodiments, such a thinning process step may be achieved by, for example, a polishing process (such as a mechanical polishing process, a chemical mechanical process, etc.). In fig. 25B, a thinner LT plate 144 is shown to include a first surface resulting from the de-thinning process step and a second surface opposite the first surface, which is attached to the handle substrate 140. In some embodiments, the thinning process step may be performed to provide a desired thickness of the thinner LT plate in a range of, for example, 0.3 to 1 μm.

Fig. 25C shows the process step of attaching the first surface of the LT plate 144 to the quartz plate 112 to form the assembly 148. In some embodiments, the first surface of the LT plate 144 can be directly attached (e.g., bonded) to the quartz plate 112. In some embodiments, the relatively thick LT and quartz plates may be cleaned and activated on their respective mirror sides, and these surfaces may be pressed to be bonded. In some embodiments, LT plate 144 may be bonded to quartz plate 112 so as to provide a surface combination as described in tables 1 and 2 herein, such as a surface combination of + LT-/+ quartz-or + LT-/-quartz +, or a surface combination of + LT-/quartz.

Fig. 25D shows a processing step of removing the handle substrate (140 in fig. 25C) to partially or fully expose the LT plate 144 to form the assembly 150. In some embodiments, such removal of a handle substrate (such as a silicon substrate) may be accomplished by, for example, an etching process (e.g., a plasma etching process). In some embodiments, the LT plate 144 in the assembly 150 of fig. 25D and the LT plate 144 in the assembly 148 of fig. 25C may or may not be substantially identical. For purposes of description, it will be understood that the exposed surface resulting from removing the handle substrate is similar to the second surface of LT plate 144 depicted in fig. 25B.

Fig. 25E shows the process step of forming electrode 102 on the second surface of LT plate 144 to form assembly 152. As described herein, such electrodes may include an interdigitated arrangement of fingers 122a, 122 b.

In some embodiments, some or all of the process steps associated with fig. 25A-25E may be performed on a single unit to produce a single unit of assembly 152, may be performed on a plurality of separate units to produce a plurality of corresponding single units of assembly 152, or may be performed while a plurality of units are attached in an array format (e.g., wafer format) and then singulated to produce a plurality of singulated units of assembly 152.

It should be noted that in the example manufacturing process of fig. 24A-24C, the bond strength between the quartz or glass plate and the LT or LN plate can be relatively weak, and during the polishing process, the LT plate can be peeled, cracked, etc., and thus often cannot be polished to the desired thickness. Fig. 26A shows an example of damage after heat treatment at 200 ℃ for 20 hours in order to enhance the bonding strength (in fig. 24A), and fig. 26B shows an example of LT partially peeling due to weak bonding strength when LT is polished to 5 μm.

Methods for measuring the strength of two bonded substrates and the formula for the bond strength γ can be found in Tong, Q., Goesele, U., and Society, E. (1999) Semiconductor Wafer Bonding: Science and Technology, John Wiley&Sons, inc. In various bonding techniques, the bonding force between quartz and LT is usually 1J/m²Or smaller. Similarly, the bonding force between LT and glass, LN and quartz, or LN and glass is typically 1J/m²Or smaller.

On the other hand, the bonding force between silicon other than quartz and LT or LN, sapphire, or the like is as high as 30J/m²Or higher regardless of whether heat treatment is performed at the time of or after bonding; and therefore even if polished to 0.3 μm, the LT or LN plate is highly likely not to suffer peeling or cracking. Thus, the exemplary manufacturing process of fig. 25A-25E may be preferred in a number of manufacturing applications.

Referring to FIGS. 25A-25E, when the mirror sides of LT and Si are directly bonded under vacuum pressurization, the bonding strength γ is 43J/m². The LT plate can then be polished to an exemplary thickness of 0.3 μm without flaking off or damage. One example of a polished LT surface is shown in fig. 27A. Next, the LT polishing surface and the quartz surface can be cleaned, activated, and pressurized to provide bonding. Subsequently, the Si may be etched using, for example, a plasma etch. FIG. 27B showsPhotograph of the resulting assembly (150 in fig. 25D) from LT side. The bonding strength γ between the LT plate and the quartz plate was 0.97J/m²It can provide sufficient strength for further processing to produce a SAW resonator because polishing is not required after the step of combining LT and quartz.

The resulting assembly (150 in fig. 25D) can be used and IDT electrodes can be formed on the thinned LT plate to produce a SAW resonator having one or more of the features described herein.

In some embodiments, and as described herein in fig. 6A-6H and tables 1 and 2, the bond strength between LT and quartz may vary depending on the crystal orientation of LT and/or quartz. For example, note that of the eight configurations listed in tables 1 and 2, the configuration (+ LT-/+ quartz-) of fig. 6A provides the highest bonding strength (2 γ ═ 2.2 joules/m)²Or γ is 1.1J/m²)。

Thus, it should be appreciated that in some embodiments, the example process of FIGS. 24A-24C may be implemented using, for example, + LT-/+ quartz- (FIG. 6A) or + LT-/-quartz + (FIG. 6B) when a higher bond strength between LT and quartz is desired. Preferably, the + LT-/+ quartz-configuration of FIG. 6A may be utilized if the highest bonding strength between LT and quartz is desired.

It will also be appreciated that in some embodiments, the example process of fig. 25A-25E may also be implemented with, for example, + LT-/+ quartz- (fig. 6A) or + LT-/-quartz + (fig. 6B) when a higher bond strength between LT and quartz is desired. Preferably, the + LT-/+ quartz-configuration of FIG. 6A may be utilized if the highest bonding strength between LT and quartz is desired. However, since the example process of fig. 25A-25E utilizes a processing substrate (such as a silicon substrate) as described herein, it should be understood that in some embodiments, the process of fig. 25A-25E can be implemented with any of the configurations of fig. 6A-6H and tables 1 and 2.

An example frequency characteristic of the resulting SAW resonator is shown in fig. 28. An impedance ratio of 82dB, 2dB greater than the exemplary characteristics shown in figure 5, is obtained. In addition, a 2.3GHz high frequency SAW resonator can be implemented using an LT plate having a thickness of 0.3 μm.

Therefore, by using the technique described with reference to fig. 25A to 25E, a piezoelectric plate such as an LT or LN plate can be polished to about 0.3 μm, so that a SAW device of 2GHz or more having high Q, high impedance, and better temperature characteristics can be realized. Further, in some embodiments, a bonding film may be provided between the piezoelectric sheet and the quartz. An example of such a configuration can be found in international publication number WO2018/097016, which is expressly incorporated herein by reference in its entirety.

Fig. 29 illustrates that in some embodiments, multiple SAW resonator elements may be fabricated in an array. For example, the wafer 200 may include an array of cells 100' that may be connected together to undergo processing in multiple process steps. For example, in some embodiments, an array of such cells may be bonded together as a wafer having different layers (e.g., quartz layer 112 and LT layers 130,134) while implementing all of the process steps of FIGS. 24A-24C. In another example, an array of such cells may be bonded together as a wafer having different layers (e.g., handle layer 140, LT layers 130,144, and quartz layer 112) while implementing all of the process steps of FIGS. 25A-25E.

After the process steps are completed in the wafer format described above, the array of cells 100' may be singulated to provide a plurality of SAW resonators 100. Fig. 29 depicts one such SAW resonator 100. In the example of fig. 29, a segmented SAW resonator 100 is shown as including an electrode 102 formed on a piezoelectric layer 104 (such as an LT or LN layer). Such piezoelectric layers and corresponding quartz layers can be configured as described herein to provide desired characteristics. It will be appreciated that in some embodiments, another electrode and one or more reflectors may be provided on the piezoelectric layer.

Fig. 30 illustrates that in some embodiments, a SAW resonator 100 having one or more features described herein can be implemented as part of a packaged device 300, which can include a package substrate 302 configured to receive and support one or more components including the SAW resonator 100.

Fig. 31 illustrates that in some embodiments, the SAW resonator based packaging apparatus 300 of fig. 30 can be a packaged filter device 300. Such a filter device may include a package substrate 302 adapted to receive and support a SAW resonator 100 configured to provide a filtering function, such as an RF filtering function.

Fig. 32 illustrates that in some embodiments, Radio Frequency (RF) module 400 may include components 406 of one or more RF filters. Such a filter may be a SAW resonator based filter 100, a packaged filter 300, or some combination thereof. In some embodiments, the RF module 400 of fig. 32 may also include, for example, an RF integrated circuit (RFIC)404 and an Antenna Switch Module (ASM) 408. Such a module may be, for example, a front end module configured to support wireless operation. In some embodiments, some of all of the foregoing components may be mounted on package substrate 402 and supported by package substrate 402.

In some implementations, a device and/or circuit having one or more features described herein may be included in an RF device, such as a wireless device. Such devices and/or circuits may be implemented directly in a wireless device, in a modular form as described herein, or in some combination thereof. In some embodiments, such wireless devices may include, for example, cellular telephones, smart phones, handheld wireless devices with or without phone functionality, wireless tablets, and the like.

Fig. 33 depicts an example wireless device 500 having one or more advantageous features described herein. In the case of a module having one or more features described herein, such a module may be generally depicted by dashed box 400 and may be implemented as, for example, a Front End Module (FEM). In such an example, one or more of the SAW filters described herein can be included in, for example, a filter component (e.g., duplexer 526).

Referring to fig. 33, Power Amplifiers (PAs) 520 may receive their respective RF signals from transceivers 510, and transceivers 510 may be configured and operated in a known manner to generate RF signals to be amplified and transmitted, and to process the received signals. Transceiver 510 is shown interacting with baseband subsystem 408, and baseband subsystem 408 is configured to provide conversion between data and/or voice signals appropriate for a user and RF signals appropriate for transceiver 510. The transceiver 510 may also be in communication with a power management component 506, the power management component 506 configured to manage power for operation of the wireless device 500. Such power management may also control the operation of the baseband subsystem 508 and the module 400.

The baseband subsystem 508 is shown connected to the user interface 502 to facilitate various inputs and outputs of voice and/or data provided to and received from a user. The baseband subsystem 508 may also be coupled to the memory 504, and the memory 504 may be configured to store data and/or instructions to facilitate operation of the wireless device and/or to provide storage of information for a user.

In the example wireless device 500, the outputs of the PAs 520 are shown as being routed to their respective duplexers 526. This amplified and filtered signal may be routed through antenna switch 514 to antenna 516 for transmission. In some embodiments, duplexer 526 may allow transmit and receive operations to be performed simultaneously using a common antenna (e.g., 516). In fig. 33, the received signal is shown as being routed to an "Rx" path (not shown) that may include, for example, a Low Noise Amplifier (LNA).

Unless the context clearly requires otherwise, throughout the description and the claims, the words "comprise", "comprising", and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is, it is meant to "include, but not limited to". The word "coupled," as used generally herein, means that two or more elements may be connected directly or through one or more intermediate elements. Likewise, the word "connected," as used generally herein, means that two or more elements may be connected directly or through one or more intermediate elements. Moreover, the words "herein," "above," "below," and words of similar importance, when used in this application, shall refer to the entire application, rather than to any particular portions of the application. Where the context permits, words in the above detailed description using the singular or plural form may also include the plural or singular form, respectively. The word "or" refers to a list of two or more items, which word covers all of the following interpretations of the word: any of the items in the list, all of the items in the list, and any combination of the items in the list.

The above detailed description of embodiments of the invention is not intended to be exhaustive or to limit the invention to the precise form disclosed above. While specific embodiments of, and examples for, the invention are described above for illustrative purposes, various equivalent modifications are possible within the scope of the invention, as those skilled in the relevant art will recognize. For example, while processes or blocks are presented in a given order, alternative embodiments may perform routines having steps, or employ systems having blocks, in a different order, and some processes or blocks may be deleted, moved, added, subdivided, combined, and/or modified. Each of these processes or blocks may be implemented in a variety of different ways. Further, while processes or blocks are sometimes shown as being performed in series, these processes or blocks may also be performed in parallel, or may be performed at different times.

The teachings of the invention provided herein are applicable to other systems, not necessarily the systems described above. The elements and acts of the various embodiments described above can be combined to provide further embodiments.

While certain embodiments of the present invention have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the present disclosure. Indeed, the novel methods and systems described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the methods and systems described herein may be made without departing from the spirit of the disclosure. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the disclosure.