阅读说明：本技术 一种高频大宽带低插损高性能声表面波谐振器及制造方法 (High-frequency large-broadband low-insertion-loss high-performance surface acoustic wave resonator and manufacturing method thereof ) 是由 李红浪 许欣 柯亚兵 于 2020-12-18 设计创作，主要内容包括：本发明涉及一种高频大宽带低插损高性能声表面波谐振器及制造方法。本发明的声表面波谐振器包括：高声速材料衬底层和形成于其上的单晶LGS低声速材料层共同组成的布拉格反射层,单晶42°YX LiNbO-3高声速材料压电层,以及设在高声速材料压电层上且全部埋入其中的电极,其中所单晶LGS低声速材料层欧拉角为(0°,90°,90°),厚度为0.1λ；高声速材料压电层的厚度为0.5λ；电极厚度180nm、宽度0.25λ、间距0.25λ、占空比0.5、沿孔径长度10λ。其中,λ是电极激发的声波波长。本发明的声表面波谐振器具有高频大带宽低插损无杂散且TCF值低的特征。(The invention relates to a high-frequency large-broadband low-insertion-loss high-performance surface acoustic wave resonator and a manufacturing method thereof. The surface acoustic wave resonator of the present invention includes: a Bragg reflector layer consisting of a substrate layer of high acoustic velocity material and a layer of single-crystal LGS low acoustic velocity material formed thereon, the single crystal 42 ° YX LiNbO 3 The high-sound-velocity material piezoelectric layer and the electrodes are arranged on the high-sound-velocity material piezoelectric layer and are completely embedded into the high-sound-velocity material piezoelectric layer, wherein the Euler angle of the single-crystal LGS low-sound-velocity material layer is (0 degrees, 90 degrees and 90 degrees), and the thickness of the single-crystal LGS low-sound-velocity material layer is 0.1 lambda; the thickness of the piezoelectric layer made of the high-acoustic-speed material is 0.5 lambda; the electrode thickness is 180nm, width 0.25 lambda, spacing 0.25 lambda, duty cycle 0.5, and length along the aperture 10 lambda. Where λ is the wavelength of the acoustic wave excited by the electrodes.The surface acoustic wave resonator has the characteristics of high frequency, large bandwidth, low insertion loss, no stray and low TCF value.)

1. A surface acoustic wave resonator comprising:

the Bragg reflection layer is formed by a high-acoustic-velocity material substrate layer and an LGS low-acoustic-velocity material layer formed on the high-acoustic-velocity material substrate layer, wherein the LGS low-acoustic-velocity material layer is made of a single-crystal LGS, the Euler angle is (0 degrees, 90 degrees and 90 degrees), and the thickness of the LGS low-acoustic-velocity material layer is 0.1 lambda;

a single crystal 42 DEG YX LiNbO formed over the LGS low acoustic velocity material layer₃A piezoelectric layer of high acoustic velocity material having a thickness of 0.5 λ; and

the electrode is arranged on the piezoelectric layer of the high-sound-velocity material, and the electrode is completely embedded into the piezoelectric layer of the high-sound-velocity material;

where λ is the wavelength of the acoustic wave excited by the electrode.

2. A surface acoustic wave resonator as set forth in claim 1, further comprising more layers of alternately stacked bragg reflection layers formed of a high-sound-velocity-material substrate layer and LGS low-sound-velocity-material layers, the piezoelectric layer of high-sound-velocity-material being formed on the uppermost LGS low-sound-velocity-material layer.

3. A surface acoustic wave resonator as set forth in claim 2, wherein the number of bragg reflection layer layers is n, and n is an integer of 2 to 10.

4. The surface acoustic wave resonator according to claim 1, wherein the high acoustic velocity material of the high acoustic velocity material substrate layer is at least one selected from Si, SiN, SiON, 3C-SiC, diamond, W, 4H-SiC, or 6H-SiC, and has a thickness of 5 λ, and the LGS low acoustic velocity material layer is plated on the high acoustic velocity material substrate layer by using one of PECVD, CVD, MOCVD, and MBE.

5. A surface acoustic wave resonator according to claim 1, wherein said electrode is an IDT electrode composed of one of Ti, Al, Cu, Au, Pt, Ag, Pd and Ni, or an alloy thereof, or a laminate thereof.

6. A surface acoustic wave resonator as set forth in claim 5, wherein the width of the electrodes and the spacing between the electrodes are each 0.25 λ, the thickness is 180nm, the length along the aperture is 10 λ, and the number of pairs of electrode fingers is 1000 pairs.

7. A surface acoustic wave resonator as set forth in claim 5, wherein a duty ratio of said electrode is 0.5.

8. A method for manufacturing a surface acoustic wave resonator, comprising:

providing a substrate layer of a high acoustic velocity material;

plating an LGS low sound velocity material layer on the high sound velocity material substrate layer, wherein the Euler angle of the LGS low sound velocity material layer is (0 degrees, 90 degrees and 90 degrees), and the thickness of the LGS low sound velocity material layer is 0.1 lambda;

formation of single crystal 42 ° YX LiNbO over LGS low acoustic velocity material layer₃A piezoelectric layer of high acoustic velocity material, said single crystal 42 ° YX LiNbO₃The thickness of the piezoelectric layer made of the high-acoustic-speed material is 0.5 lambda; and

in the single crystal 42 degree YX LiNbO₃Electrodes are formed on the piezoelectric layer of the high-speed acoustic material, the width of each electrode and the distance between the electrodes are both 0.25 lambda, the duty ratio of the electrodes is 0.5, the thickness is 180nm, the length along the aperture is 10 lambda, the number of pairs of electrode fingers is 1000 pairs,

where λ is the wavelength of the acoustic wave excited by the electrode.

9. The method of claim 8, wherein the LGS low acoustic velocity material layer is plated on the high acoustic velocity material substrate layer with a thickness of 5 λ by one of PECVD, CVD, MOCVD, and MBE.

10. The method of claim 8, wherein the electrode is an IDT electrode composed of one of Ti, Al, Cu, Au, Pt, Ag, Pd and Ni, or an alloy thereof, or a laminate thereof.

Technical Field

The invention relates to the field of mobile communication, in particular to a high-frequency large-broadband low-insertion-loss high-performance surface acoustic wave resonator in a radio frequency front end of a mobile phone and a manufacturing method thereof.

Background

The radio frequency front end of the mobile equipment is a functional area between a radio frequency transceiver and an antenna, and consists of devices such as a power amplifier, an antenna switch, a filter, a duplexer, a low noise amplifier and the like. In the 5G era, the demand for data transmission speed is increasing. To support sufficient data transmission rates within a limited bandwidth, higher demands are placed on various capabilities of the radio frequency front end of the mobile device.

In order to realize high bandwidth, the number of channels of the carrier aggregation technology must be increased, which also means that the number of frequency bands that the mobile phone needs to support is continuously increased, and since each frequency band needs to have its own filter, the number of filters in the rf front-end module is increasing, and the design of the filter becomes more challenging.

Surface Acoustic Wave (SAW), Bulk Acoustic Wave (BAW), and thin film bulk acoustic wave (FBAR) are three major mainstream technologies in the field of current mobile device filters. The low frequency and the middle frequency band mainly use a SAW filter. Its technology has evolved from Normal-SAW, TC-SAW, and further to IHP-SAW, as well as future XBAR technologies.

IHP-SAW filters are a major development trend in the SAW filter industry at present, with their excellent temperature compensation performance and low insertion loss, comparable to or even exceeding that of part of BAW and FBAR filters.

The IHP-SAW technology is realized by adopting a hybrid technology of a multilayer reflecting gate structure similar to a SAW device + SMR-BAW device and adopting a mode of alternately stacking high acoustic impedance and low acoustic impedance. TCF (temperature Coefficient of frequency) is mostly adopted as the low acoustic impedance material, such as silicon dioxide; the high acoustic impedance layer is usually made of a material with a low temperature coefficient, such as SiN, W, etc. The mixed structure technology not only simplifies the single-side processing technology of the SAW device, but also endows the SMR-BAW device with the characteristic of low energy leakage.

The IHP-SAW filter has three advantages that:

1. a high Q value;

2. low frequency Temperature Coefficient (TCF);

3. and (4) good heat dissipation performance.

The filter adopts a multilayer reflection grating structure of SMR-BAW, so that more surface acoustic wave energy can be focused on the surface of the substrate, thereby reducing the loss of acoustic waves in the transmission process and improving the Q value of a device. The high Q (Qmax-3000, traditional SAW Qmax-1000) characteristics make it have high out-of-band rejection, steep passband edge roll-off, and high isolation. The TCF of the IHP-SAW can reach less than or equal to-20 ppm/DEG C, the further optimized design can reach 0 ppm/DEG C, and the TCF of the TC-SAW with lithium niobate as the piezoelectric layer is-20 to-25 ppm/DEG C.

On the other hand, however, the conventional IHP-SAW filter has the following problems:

firstly, the working frequency is about 3.5GHz, and the high-frequency requirement of 5G communication can not be met (generally, the working frequency is more than 5G);

two, k thereof_t ²Less than or equal to 14 percent, and can not meet the requirement of 5G communication large bandwidth.

Therefore, a high-frequency, large-bandwidth, low-insertion-loss, high-performance surface acoustic wave resonator is now in demand.

Disclosure of Invention

This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter; nor is it intended to be used as an aid in determining or limiting the scope of the claimed subject matter.

The high-frequency high-performance surface acoustic wave resonator adopts the silicon carbide single crystal substrate as the substrate, has high sound velocity, and has the advantages of high crystal quality, good consistency and the like compared with a diamond self-supporting substrate and a diamond-like film; using single crystal LiNbO₃As a piezoelectric material; the low acoustic impedance layer is made of LGS material (lanthanum gallium silicate), and the electromechanical coupling coefficient of LGS crystal is 17% and is about quartz (SiO)₂) 2-3 times of the quartz crystal, but has the same temperature stability as quartz. The Euler angle of the LGS material is (0 degrees, 90 degrees and 90 degrees), the TCF is the largest, and the temperature compensation effect is the largest.

The surface acoustic wave resonator of the present invention comprises: at least one bragg reflector layer, a piezoelectric layer of high acoustic velocity material, and electrodes.

The Bragg reflector layer is composed of a high acoustic velocity material substrate layer and an LGS low acoustic velocity material layer formed on the high acoustic velocity material substrate layer. Wherein the substrate layer is made of high sound velocity material selected from at least one of Si, SiN, SiON, 3C-SiC, diamond, W, 4H-SiC or 6H-SiC, and the thickness of the substrate layer made of the high sound velocity material is 5 lambda; the LGS low-sound-velocity material layer is made of single-crystal LGS, the Euler angle is (0 degrees, 90 degrees and 90 degrees), and the thickness of the LGS low-sound-velocity material layer is 0.1 lambda; the number of bragg reflective layers may be 1-10. The LGS low-sound-velocity material layer is plated on the high-sound-velocity material substrate layer in one of PECVD, CVD, MOCVD and MBE.

The piezoelectric layer of the high-acoustic-velocity material is made of single crystal 42-degree YX LiNbO₃And is formed on the uppermost LGS low acoustic velocity material layer to have a thickness of 0.5 λ.

The electrode is an IDT electrode and is composed of one of Ti, Al, Cu, Au, Pt, Ag, Pd and Ni, an alloy thereof, or a laminate thereof. The electrodes are disposed on the high acoustic velocity material piezoelectric layer and are all embedded in the high acoustic velocity material piezoelectric layer. The width of the electrodes and the distance between the electrodes are both 0.25 lambda, the thickness is 180nm, the length along the aperture is 10 lambda, the number of pairs of electrode fingers is 1000 pairs, and the duty ratio of the electrodes is 0.5.

Where λ is the wavelength of the acoustic wave excited by the electrodes.

The method for manufacturing a surface acoustic wave resonator of the present invention includes: providing a substrate layer of a high sound velocity material with a thickness of 5 lambda; plating an LGS low-sound-velocity material layer on the high-sound-velocity material substrate layer in one of PECVD, CVD, MOCVD and MBE modes, wherein the Euler angle of the LGS low-sound-velocity material layer is (0 DEG, 90 DEG and 90 DEG), and the thickness of the LGS low-sound-velocity material layer is 0.1 lambda; formation of single crystal 42 ° YX LiNbO over LGS low acoustic velocity material layer₃Piezoelectric layer of high acoustic velocity material, single crystal 42 ° YX LiNbO₃The thickness of the piezoelectric layer made of the high-acoustic-speed material is 0.5 lambda; and in single crystal 42 ° YX LiNbO₃The IDT electrode formed on the piezoelectric layer of the high-speed acoustic material is composed of one of Ti, Al, Cu, Au, Pt, Ag, Pd and Ni, or an alloy or a laminated body thereof, the width of the electrode and the distance between the electrodes are both 0.25 lambda, the duty ratio of the electrode is 0.5, the thickness is 180nm, the length along the aperture is 10 lambda, and the number of pairs of electrode fingers is 1000 pairs, wherein lambda is the acoustic wave wavelength excited by the electrode.

These and other features and advantages will become apparent upon reading the following detailed description and upon reference to the accompanying drawings. It is to be understood that both the foregoing general description and the following detailed description are explanatory only and are not restrictive of aspects as claimed.

Drawings

The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which specific embodiments of the invention are shown. The flowchart and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods and computer program products according to embodiments of the present application. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the application. Also, like reference numerals are used to refer to like parts throughout the drawings. The drawings are only schematic and are not to be construed as limiting the actual dimensional proportions.

Figure 1 is a schematic diagram of a resonator according to the present invention;

FIG. 2 is a schematic diagram of a Bragg reflector of a resonator according to the present invention;

fig. 3 is a schematic structural diagram of an IHP resonator with n-layer bragg reflector according to the present invention;

figure 4 is a schematic diagram of the structural parameters of a resonator according to the invention;

FIG. 5 is a graph showing the change of TCF value with Euler angle at room temperature of LGS;

FIG. 6 shows K at room temperature of LGS_t ²Schematic plot of the variation with euler angle;

fig. 7 is an admittance diagram of a resonator having a 1-layer bragg reflector layer according to the present invention;

fig. 8 is an admittance diagram of a resonator having a 2-layer bragg reflector layer according to the present invention;

fig. 9 is an admittance diagram of a resonator having a 3-layer bragg reflector layer according to the present invention;

fig. 10 is a process flow diagram of a method of manufacturing a resonator according to the present invention.

Detailed Description

The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which specific embodiments of the invention are shown. Various advantages and benefits of the present invention will become apparent to those of ordinary skill in the art upon reading the following detailed description of the specific embodiments. It should be understood, however, that the present invention may be embodied in various forms and should not be limited to the embodiments set forth herein. The following embodiments are provided so that the invention may be more fully understood. Unless otherwise defined, technical or scientific terms used herein shall have the ordinary meaning as understood by those of skill in the art to which this application belongs.

Fig. 1 is a schematic view of a resonator according to the present invention, and fig. 4 is a structural parameter schematic view thereof. Described below in conjunction with fig. 1 and 4.

As can be seen from the figure, the resonator comprises a substrate layer 101, a low acoustic velocity layer 102, a piezoelectric layer 103 and an electrode 104.

The substrate layer 101 of the resonator of the present invention is made of a high acoustic velocity material having high acoustic impedance, and may be made of Si, SiN, SiON, 3C-SiC, diamond, W, 4H-SiC, or 6H-SiC, and has a thickness of 5 λ (λ is the wavelength of an acoustic wave excited by an electrode finger, and λ is 1 μm).

The material of the piezoelectric layer 103 is single crystal 42 ° YX LiNbO₃The piezoelectric layer thickness is 0.5 λ.

The piezoelectric layer is provided with electrodes 104, the width of each electrode is the same as the distance between the electrodes, the width of each electrode is 0.25 lambda, the thickness of each electrode is 180nm, the length len of each electrode along the aperture is 10 lambda, and the number of pairs of electrode fingers is 1000 pairs. The duty cycle of the electrodes was 0.5. The electrodes are preferably completely embedded in the piezoelectric layer as shown. The electrode is an interdigital transducer (IDT) electrode and is composed of metal or alloy such as Ti, Al, Cu, Au, Pt, Ag, Pd, Ni, etc., or a laminate of these metals or alloys, and has an electromechanical coupling coefficient k²＝(π²/8)(fp²-fs²)/fs²Wherein fs is the resonance frequency and fp is the antiresonance frequency.

A layer of the LGS low acoustic velocity layer 102 is interposed between the piezoelectric layer 103 and the high acoustic velocity substrate layer 101. LGS is a low acoustic impedance material (single crystal LGS), has the sound velocity of 2350-2850m/s and has weak piezoelectric characteristics. The LGS has different TCFs according to different tangential directions, and the Euler angle of the LGS low-acoustic-speed material layer of the resonator of the invention is preferably(0 °,90 °,90 °). LGS with positive temperature coefficient of frequency and single crystal 42 DEG YX LiNbO with negative temperature coefficient of frequency₃Superposition may reduce the TCF value of the device.

The LGS layer has a thickness of 0.1 lambda and can be formed by plating an LGS layer on a substrate layer of a high-sound-velocity material in a PECVD (plasma enhanced chemical vapor deposition), CVD (chemical vapor deposition), MOCVD (metal organic chemical vapor deposition), MBE (molecular beam epitaxy) mode and the like.

Fig. 2 is a schematic diagram of one bragg reflector layer 210 in the resonator of fig. 1 and 4, which is composed of a substrate layer 101 of high acoustic velocity and an LGS layer 102 of low acoustic velocity. The Bragg reflection layer is composed of two layers with different sound velocities (different acoustic impedances), sound waves can be reflected on an interface between different layers of acoustic impedances, and the reflection layer reflects the sound waves leaked to the substrate, so that the sound waves are prevented from being leaked from the direction of the substrate, and the Q value of the device is greatly improved.

Fig. 3 is a schematic diagram of a resonator structure in which the bragg reflector layer is n layers according to the present invention. n may preferably be 2-10 layers, alternately stacked by substrate layers of high sound velocity material and low sound velocity layers (LGS layers), the number of which can be selected by those skilled in the art according to design needs.

Fig. 5 is a graph showing changes in TCF value with euler angle (0 °,90 °, Φ) in the Y-cut direction at room temperature (T ═ 25 ℃).

As can be seen from the figure, the TCF value of the LGS varies with the crystal tangent, and varies from 38 ppm/deg.c to-8 ppm/deg.c as Φ increases, and when Φ is 80-100, the TCF is 38 ppm/deg.c, which is the maximum value of the positive frequency temperature coefficient; when Φ is 0 or 180, TCF-8 ppm/deg.c, the TCF value does not vary linearly with the Φ value. The Euler angle (0 degree, 90 degree and 90 degree) is selected, at the moment, the TCF is the largest, and the temperature compensation effect is the largest.

FIG. 6 shows the K at room temperature (T25 ℃ C.) for LGS_t ²Schematic representation of the variation with euler angle (0 °,90 °, Φ) in Y-cut direction.

As can be seen from the figure, K of LGS_t ²The K of the LGS varies with the crystal tangent and increases with phi_t ²The value varies between 0.02% and 0.035%, when Φ is 90, k_t ²0.02% by weight, k_t ²Minimum value, at which LGS piezoelectricity is minimum; when phi is 180，k_t ²0.35% or k_t ²Minimum value, where the LGS piezoelectricity is maximum. The euler angles (0 °,90 °,90 °) are selected for the present invention, where the LGS has the lowest piezoelectricity and the introduced stray is also the lowest.

Fig. 7 is an admittance diagram of a resonator having a 1-layer bragg reflector layer according to the present invention.

As can be seen, the sound velocity V is 4961m/s, fs is 4.659GHz, fp is 5.263GHz, and f₀＝4.961GHz，k²34.03%, relative bandwidth 12.96%, Q1938.8, high Q, and no spurs. FOM ═ k²Q and FOM are comprehensive indexes of the resonator, the FOM value of normal saw and tc-saw is smaller than 100, the FOM value of IHP saw and Fbar is smaller than 200, the resonator with FOM value larger than 200 is very rare, and the FOM is 695.8.

Fig. 8 is an admittance diagram of a resonator having a 2-layer bragg reflector layer according to the present invention.

As can be seen, the sound velocity V is 4959m/s, fs is 4.662GHz, fp is 5.256GHz, and f₀＝4.959GHz，k²33.41%, relative bandwidth 12.74%, Q1651.6, high Q, and no spurs, FOM 551.8.

Fig. 9 is an admittance diagram of a resonator having a 3-layer bragg reflector layer according to the present invention.

As can be seen from the figure, the sound velocity V is 4875m/s, fs is 4.601GHz, fp is 5.149GHz, and f₀＝4.875GHz，k²31.11%, relative bandwidth 11.91%, Q2093, high Q, and no spurs, FOM 651.1.

Fig. 10 is a process flow diagram of a method of manufacturing a resonator according to the present invention.

In step 1001, a high acoustic velocity material substrate layer is provided.

The high acoustic velocity material having high acoustic impedance may be Si, SiN, SiON, 3C-SiC, diamond, W, 4H-SiC or 6H-SiC, and the substrate layer has a thickness of 5 λ (λ is the wavelength of the acoustic wave excited by the electrode fingers, λ ═ 1 μm).

At step 1002, an LGS low acoustic velocity material layer (single crystal LGS) is plated on a high acoustic velocity material substrate layer by PECVD, CVD, MOCVD, MBE, or the like.

The Euler angle of the LGS low-sound-velocity material layer is (0 DEG, 90 DEG); the thickness of the LGS layer was 0.1 λ.

The substrate layer of the high sound velocity material and the LGS layer of the low sound velocity material formed in the previous step together form a Bragg reflection layer. The person skilled in the art can choose a multilayer bragg reflector layer (which may preferably be 2-10 layers) according to the design needs. When the number n of layers is two or more, the process returns to step 1001 after the end step 1002 to form another bragg reflector layer. The process is cycled until n bragg reflective layers are formed.

At step 1003, single crystal 42 ° YX LiNbO is formed over the uppermost LGS low acoustic velocity material layer₃The piezoelectric layer of the high sound velocity material is 0.5 lambda thick.

At step 1004, LiNbO is grown at 42 ° on a single crystal₃IDT electrodes are formed on the piezoelectric layer of the high acoustic velocity material. The IDT electrode is made of a metal or alloy such as Ti, Al, Cu, Au, Pt, Ag, Pd, and Ni, or a laminate of these metals or alloys. The duty cycle of the electrodes was 0.5. The electrode width and the spacing between the electrodes were the same and were 0.25 λ, the electrode thickness was 180nm, the electrode length along the aperture len ═ 10 λ, and the electrode finger pairs were 1000 pairs.

The piezoelectric layer of the resonator adopts single crystal 42 degrees YX LiNbO₃The low sound velocity layer uses the characteristic that the piezoelectric property of the LGS changes with the tangential direction, and uses the LGS of euler angle (0 °,90 °,90 °). Both layers have piezoelectricity, with an electrode thickness of 180nm, a width of 0.25 lambda, a duty cycle of 0.5, and a length along the aperture of 10 lambda. Thereby obtaining the surface acoustic wave resonator with high frequency, large bandwidth, low insertion loss and no stray.

The method utilizes the characteristic that the frequency temperature coefficient of LGS changes with the tangential direction to adjust the 42-degree YX LiNbO of the single crystal₃The thickness of the piezoelectric layer and the LGS layer reduces the TCF value of the resonator.

The above embodiments are only used for illustrating the technical solutions of the present application, and not for limiting the same; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; such modifications and substitutions do not depart from the spirit and scope of the present disclosure, and the present disclosure should be construed as being covered by the claims and the specification.