阅读说明：本技术 弹性波装置、带通型滤波器、双工器以及多工器 (Elastic wave device, band-pass filter, duplexer, and multiplexer ) 是由 道上彰 大门克也 于 2019-10-17 设计创作，主要内容包括：提供一种能抑制由瑞利波造成的杂散的弹性波装置。弹性波装置(1)具备：压电性基板(2),包含压电体层(6),压电体层(6)包含钽酸锂；IDT电极(7),设置在压电性基板(2)上；以及一对反射器(8),设置在压电性基板(2)上的、IDT电极(7)的弹性波传播方向两侧。利用SH波作为主模,IDT电极(7)以及反射器(8)分别具有多个电极指,在将沿着与电极指延伸的方向正交的方向的长度设为宽度时,反射器(8)具有宽度不同的第1电极指(8a)和第2电极指(8b)。在反射器(8)的任意的部分中连续的4根电极指包含第1电极指(8a)以及第2电极指(8b)双方,且上述连续的4根电极指的电极指中心间距离相同。(Provided is an elastic wave device capable of suppressing stray waves caused by Rayleigh waves. An elastic wave device (1) is provided with: a piezoelectric substrate (2) including a piezoelectric layer (6), the piezoelectric layer (6) including lithium tantalate; an IDT electrode (7) provided on the piezoelectric substrate (2); and a pair of reflectors (8) provided on the piezoelectric substrate (2) on both sides in the direction of propagation of the elastic wave of the IDT electrode (7). The IDT electrode (7) and the reflector (8) each have a plurality of electrode fingers using the SH wave as a main mode, and the reflector (8) has a1 st electrode finger (8a) and a2 nd electrode finger (8b) having different widths when the length along the direction orthogonal to the direction in which the electrode fingers extend is defined as the width. The 4 continuous electrode fingers in any part of the reflector (8) include both the 1 st electrode finger (8a) and the 2 nd electrode finger (8b), and the distances between the electrode fingers of the 4 continuous electrode fingers are the same.)

1. An elastic wave device is provided with:

a piezoelectric substrate comprising a piezoelectric layer comprising lithium tantalate;

an IDT electrode provided on the piezoelectric substrate; and

a pair of reflectors provided on the piezoelectric substrate on both sides of the IDT electrode in the direction of propagation of the elastic wave,

the elastic wave device uses SH waves as a main mode,

the IDT electrode and the reflector each have a plurality of electrode fingers,

the reflector has a1 st electrode finger and a2 nd electrode finger which are different in width, where the length in a direction orthogonal to a direction in which the electrode fingers extend is defined as the width,

the 4 continuous electrode fingers in any portion of the reflector include both the 1 st electrode finger and the 2 nd electrode finger, and the distances between the electrode finger centers of the 4 continuous electrode fingers are the same.

2. The elastic wave device according to claim 1,

when the arrangement of the 4 continuous electrode fingers including the 1 st electrode finger and the 2 nd electrode finger in the reflector is set to the arrangement of 1 group of electrode fingers, the arrangement of 1 group of electrode fingers in the reflector is periodically arranged.

3. The elastic wave device according to claim 1,

when the arrangement of 3 consecutive electrode fingers including the 1 st electrode finger and the 2 nd electrode finger in the reflector is set as the arrangement of 1 group of electrode fingers, the arrangement of 1 group of electrode fingers in the reflector is periodically arranged.

4. The elastic wave device according to any one of claims 1 to 3,

the distances between the electrode finger centers of the IDT electrodes are all the same, and the distances between the electrode finger centers of the reflectors are all the same.

5. The elastic wave device according to claim 4,

the distance between the electrode finger centers of the IDT electrode is the same as the distance between the electrode finger centers of the reflectors.

6. The elastic wave device according to any one of claims 1 to 5,

the width of the electrode fingers of the IDT electrode is the same.

7. The elastic wave device according to any one of claims 1 to 6,

the piezoelectric substrate has a high acoustic velocity substrate,

the piezoelectric layer is provided directly or indirectly on the high acoustic velocity substrate,

the acoustic velocity of a bulk wave propagating through the high acoustic velocity substrate is higher than the acoustic velocity of an elastic wave propagating through the piezoelectric layer.

8. The elastic wave device according to claim 7,

the piezoelectric substrate has a low sound velocity film provided between the high sound velocity substrate and the piezoelectric body layer,

the sound velocity of the bulk wave propagating through the low sound velocity film is lower than the sound velocity of the bulk wave propagating through the piezoelectric layer.

9. The elastic wave device according to any one of claims 1 to 6,

the piezoelectric substrate has a support substrate, a high acoustic velocity film provided on the support substrate, and a low acoustic velocity film provided on the high acoustic velocity film,

the piezoelectric layer is provided on the low acoustic velocity film,

the acoustic velocity of the bulk wave propagating in the low acoustic velocity film is lower than the acoustic velocity of the bulk wave propagating in the piezoelectric layer,

the sound velocity of a bulk wave propagating through the high-sound-velocity film is higher than the sound velocity of an elastic wave propagating through the piezoelectric layer.

10. A band-pass filter is provided with:

a plurality of elastic wave resonators including a series arm resonator and a parallel arm resonator,

at least one of the plurality of elastic wave resonators is the elastic wave device according to any one of claims 1 to 9.

11. The bandpass filter of claim 10, wherein,

the band-pass filter is connected to an antenna,

the elastic wave resonator arranged closest to the antenna end among the plurality of elastic wave resonators is the elastic wave device.

12. A duplexer includes:

an antenna terminal connected to an antenna; and

a1 st bandpass filter and a2 nd bandpass filter which are connected in common to the antenna terminals and have different passbands,

at least one of the 1 st and 2 nd bandpass filters is the bandpass filter of claim 10 or 11.

13. A multiplexer includes:

an antenna terminal connected to an antenna; and

a plurality of band-pass filters commonly connected to the antenna terminals and having different pass bands,

at least one of the plurality of bandpass filters is the bandpass filter of claim 10 or 11.

Technical Field

The invention relates to an elastic wave device, a band-pass filter, a duplexer, and a multiplexer.

Background

Conventionally, elastic wave devices have been widely used in filters and the like of mobile phones. Patent document 1 listed below discloses an example of an elastic wave device. In the elastic wave device, the cut angle is 30 ° or more and 60 ° or less of LiTaO₃An IDT electrode is disposed on the membrane. Reflectors are provided on both sides of the IDT electrode in the direction of propagation of the elastic wave. The elastic wave device uses the SH wave as a main mode.

Prior art documents

Patent document

Patent document 1: international publication No. 2015/098756

Disclosure of Invention

Problems to be solved by the invention

The present inventors have focused on the problem that, in an elastic wave device using an SH wave as a main mode, a response due to a rayleigh wave, which is an unwanted wave, occurs in a frequency band around 0.75 times the resonance frequency of the main mode. When a response by a rayleigh wave occurs, there is a possibility that attenuation characteristics and reflection characteristics of the elastic wave device are deteriorated due to the response. However, the patent document 1 does not recognize such a problem, and thus cannot sufficiently suppress the stray waves due to the rayleigh waves.

An object of the present invention is to provide an elastic wave device, a bandpass filter, a duplexer, and a multiplexer, which can suppress stray waves caused by rayleigh waves.

Means for solving the problems

An elastic wave device according to the present invention includes: a piezoelectric substrate comprising a piezoelectric layer comprising lithium tantalate; an IDT electrode provided on the piezoelectric substrate; and a pair of reflectors provided on the piezoelectric substrate on both sides in an elastic wave propagation direction of the IDT electrode, wherein the elastic wave device uses SH waves as a main mode, the IDT electrode and the reflectors each have a plurality of electrode fingers, and when a length along a direction orthogonal to a direction in which the electrode fingers extend is defined as a width, the reflectors have 1 st and 2 nd electrode fingers having different widths, and 4 continuous electrode fingers in an arbitrary portion of the reflectors include both the 1 st and 2 nd electrode fingers, and distances between electrode finger centers of the 4 continuous electrode fingers are the same.

A bandpass filter according to the present invention includes a plurality of elastic wave resonators including series-arm resonators and parallel-arm resonators, and at least one of the plurality of elastic wave resonators is an elastic wave device configured according to the present invention.

A duplexer according to the present invention includes: an antenna terminal connected to an antenna; and a1 st bandpass filter and a2 nd bandpass filter which are connected in common to the antenna terminal and have different passbands, wherein at least one of the 1 st bandpass filter and the 2 nd bandpass filter is a bandpass filter configured according to the present invention.

The multiplexer according to the present invention includes: an antenna terminal connected to an antenna; and a plurality of bandpass filters that are connected in common to the antenna terminals and have different passbands, wherein at least one of the plurality of bandpass filters is a bandpass filter configured according to the present invention.

Effects of the invention

According to the present invention, it is possible to provide an elastic wave device, a band-pass filter, a duplexer, and a multiplexer that can suppress stray waves caused by rayleigh waves.

Drawings

Fig. 1 is a schematic front cross-sectional view of an elastic wave device according to embodiment 1 of the present invention.

Fig. 2 is an enlarged schematic front cross-sectional view showing the vicinity of an electrode finger of an IDT electrode in embodiment 1 of the present invention.

Fig. 3 is a schematic plan view showing part of the IDT electrode and reflectors in embodiment 1 of the present invention.

Fig. 4 is a schematic front sectional view showing an IDT electrode and a part of a reflector in embodiment 1 of the present invention.

Fig. 5 is a diagram showing the phase of the main mode and the phase of the spur in the comparative example.

Fig. 6 is a diagram showing phases of the spurs in embodiment 1 of the present invention and a comparative example.

Fig. 7 is a schematic diagram showing an example of arrangement of 1 set of electrode fingers of the reflector in the present invention.

Fig. 8 is a schematic front cross-sectional view of an elastic wave device according to modification 1 of embodiment 1 of the present invention.

Fig. 9 is a schematic front cross-sectional view of an elastic wave device according to modification 2 of embodiment 1 of the present invention.

Fig. 10 is a schematic front cross-sectional view of an elastic wave device according to modification 3 of embodiment 1 of the present invention.

Fig. 11 is a schematic front sectional view showing an IDT electrode and a part of a reflector in embodiment 2 of the present invention.

Fig. 12 is a diagram showing phases of the spurs in embodiment 2 of the present invention and a comparative example.

Fig. 13 is a schematic front sectional view showing an IDT electrode and a part of a reflector in embodiment 3 of the present invention.

Fig. 14 is a diagram showing phases of the spurs in embodiment 3 of the present invention and a comparative example.

Fig. 15 is a schematic front sectional view showing an IDT electrode and a part of a reflector in embodiment 4 of the present invention.

Fig. 16 is a diagram showing phases of the spurs in embodiment 4 of the present invention and a comparative example.

Fig. 17 is a circuit diagram of a bandpass filter according to embodiment 5 of the present invention.

Fig. 18 is a schematic circuit diagram of a duplexer according to embodiment 6 of the present invention.

Fig. 19 is a schematic diagram of a multiplexer according to embodiment 7 of the present invention.

Detailed Description

The present invention will be made clear by the following description of specific embodiments of the present invention with reference to the accompanying drawings.

Note that the embodiments described in the present specification are exemplary, and partial replacement or combination of the structures may be performed between different embodiments.

Fig. 1 is a schematic front cross-sectional view of an elastic wave device according to embodiment 1 of the present invention.

Elastic wave device 1 includes piezoelectric substrate 2. The piezoelectric substrate 2 has a support substrate 3, a high acoustic velocity film 4 provided on the support substrate 3, a low acoustic velocity film 5 provided on the high acoustic velocity film 4, and a piezoelectric layer 6 provided on the low acoustic velocity film 5. The piezoelectric layer 6 is a lithium tantalate film with a cut angle of Y-cut 55 °. The structure of the piezoelectric substrate 2 is not limited to the above-described structure, and for example, the piezoelectric substrate 2 may include only the piezoelectric layer 6. In this case, the piezoelectric substrate 2 is a lithium tantalate substrate.

An IDT electrode 7 is provided on the piezoelectric layer 6 in the piezoelectric substrate 2. The IDT electrode 7 has a plurality of electrode fingers 7 a. By applying an ac voltage to the IDT electrode 7, an elastic wave can be excited. The elastic wave device 1 uses an SH wave as a main mode. When the SH wave is used as the main mode, a spurious wave due to the rayleigh wave is generated in a frequency band around 0.75 times the resonance frequency of the main mode. In addition, for example, in the case of using SH wave as a main mode, (b) is usedθ, ψ) of the piezoelectric layer 6 is set inPreferably 60 DEG < theta < 175 DEG, -10 DEG < psi < 10 deg.

A pair of reflectors 8 and 9 are provided on both sides of the IDT electrode 7 in the piezoelectric layer 6 in the elastic wave propagation direction. Each of the reflectors 8 and 9 has a plurality of electrode fingers. In this manner, elastic wave device 1 of the present embodiment is an elastic wave resonator.

The low acoustic velocity film 5 in the piezoelectric substrate 2 is a film of a relatively low acoustic velocity. More specifically, the sound velocity of the bulk wave propagating through the low-sound-velocity film 5 is lower than the sound velocity of the bulk wave propagating through the piezoelectric layer 6. The low-acoustic-speed film 5 is made of SiO_xThe silicon oxide shown is the main component. X is any positive integer value. In the present embodiment, the low sound velocity film 5 is SiO₂And (3) a membrane. The material of the low sound velocity membrane 5 is not limited to the above-described materials, and silicon oxide, glass, silicon oxynitride, tantalum oxide, or a medium containing a compound obtained by adding fluorine, carbon, or boron to silicon oxide, which is a main component, may be used.

The high acoustic velocity membrane 4 is a relatively high acoustic velocity membrane. More specifically, the sound velocity of the bulk wave propagating through the high-sound-velocity film 4 is higher than the sound velocity of the elastic wave propagating through the piezoelectric layer 6. In the present embodiment, the high acoustic velocity film 4 is a silicon nitride film. The material of the high acoustic velocity film 4 is not limited to the above-mentioned materials, and a medium containing the above-mentioned material as a main component, such as alumina, silicon carbide, silicon nitride, silicon oxynitride, silicon, sapphire, lithium tantalate, lithium niobate, quartz, alumina, zirconia, cordierite, mullite, steatite, forsterite, magnesia, a DLC (diamond-like carbon) film, or diamond, can be used.

In the present embodiment, the support substrate 3 is a silicon substrate. The material of the support substrate 3 is not limited to the above-mentioned materials, and various ceramics such as alumina, diamond, lithium tantalate, lithium niobate, quartz, alumina, magnesia, silicon nitride, aluminum nitride, silicon carbide, zirconia, cordierite, mullite, steatite, forsterite, etc., a dielectric such as sapphire, glass, etc., a semiconductor such as gallium nitride, etc., or a resin may be used.

In the present embodiment, elastic wave device 1 includes piezoelectric substrate 2, and piezoelectric substrate 2 is a laminate in which support substrate 3, high acoustic velocity film 4, low acoustic velocity film 5, and piezoelectric layer 6 are laminated in this order. This can effectively confine the energy of the elastic wave to the piezoelectric layer 6 side.

Fig. 2 is an enlarged schematic front sectional view showing the vicinity of an electrode finger of an IDT electrode in embodiment 1.

The IDT electrode 7 includes a laminated metal film in which a1 st metal layer 7c, a2 nd metal layer 7d, and a3 rd metal layer 7e are laminated in this order from the piezoelectric substrate 2 side. The 1 st metal layer 7c is a Ti layer, the 2 nd metal layer 7d is an Al layer, and the 3 rd metal layer 7e is a Ti layer. In the present embodiment, the reflectors 8 and 9 also include the same laminated metal film as the IDT electrode 7. The material and the number of layers of the IDT electrode 7, the reflectors 8 and the reflectors 9 are not limited to the above materials and the number of layers. Alternatively, the IDT electrode 7, the reflectors 8 and 9 may include a single metal film.

Fig. 3 is a schematic plan view showing part of the IDT electrode and reflectors in embodiment 1. Fig. 4 is a schematic front sectional view showing part of the IDT electrode and reflectors in embodiment 1.

As shown in fig. 3, when the length along the direction orthogonal to the direction in which the electrode fingers extend is defined as the width of the electrode fingers, the width of the electrode fingers 7a of the IDT electrode 7 is all the same. In the IDT electrode 7, the distances between the electrode finger centers are all the same. The inter-electrode-finger center distance is a linear distance connecting the center points of the electrode fingers in the width direction with respect to the adjacent electrode fingers included in the IDT electrode 7. When the IDT electrode 7 includes a plurality of electrode fingers, the electrode fingers are the average value of the distances between the centers of the electrode fingers of the adjacent electrode fingers. The width of the electrode fingers 7a of the IDT electrode 7 is not necessarily the same, and the distance between the centers of all the electrode fingers is not necessarily the same. In the present specification, the width and the distance between the centers of the electrode fingers are the same, and include errors due to manufacturing variations.

As shown in fig. 3 and 4, the plurality of electrode fingers of the reflector 8 include a1 st electrode finger 8a and a2 nd electrode finger 8b having different widths. The 1 st electrode fingers 8a and the 2 nd electrode fingers 8b are alternately arranged. Here, when the arrangement of 4 consecutive 1-group electrode fingers including the 1 st electrode finger 8a and the 2 nd electrode finger 8b in the reflector 8 is set as the arrangement a1 of 1-group electrode fingers, the arrangement a1 of 1-group electrode fingers is periodically arranged in the reflector 8.

Here, the arrangement a1 of the 1-group electrode fingers is periodically arranged, and includes a case where the arrangement a1 of the 1-group electrode fingers is continuously arranged and a case where the arrangement a1 of the 1-group electrode fingers is periodically arranged with 1 or more electrode fingers interposed therebetween. In the present embodiment, the array a1 of 1 group of electrode fingers is continuously arranged.

The arrangement of the electrode fingers of the reflector 8 is not limited to the above arrangement, and 4 continuous electrode fingers in any portion of the reflector 8 may include both the 1 st electrode finger 8a and the 2 nd electrode finger 8 b. For example, the reflector 8 may include electrode fingers having a width other than the 1 st electrode finger 8a and the 2 nd electrode finger 8 b.

In the reflector 8, the distances between the centers of the electrode fingers are all the same. In the reflector 8, it is not always necessary that all the electrode fingers have the same center-to-center distance. The distance between the centers of the electrode fingers of 4 continuous electrode fingers including both the 1 st electrode finger 8a and the 2 nd electrode finger 8b may be the same.

The reflector 9 is configured similarly to the reflector 8. More specifically, the plurality of electrode fingers of the reflector 9 include a1 st electrode finger 9a and a2 nd electrode finger 9b having different widths. The 1 st electrode fingers 9a and the 2 nd electrode fingers 9b are alternately arranged. Thus, in the reflector 9, the arrangement a1 of 1 group of electrode fingers is periodically arranged. The arrangement a1 of 1 group of electrode fingers in the reflector 9 includes the 1 st electrode finger 9a and the 2 nd electrode finger 9 b.

The present embodiment is characterized by having the following configuration. 1) An IDT electrode 7, a reflector 8 and a reflector 9 are provided on the piezoelectric substrate 2 including the piezoelectric layer 6, and the piezoelectric layer 6 includes a lithium tantalate film using the SH wave as a main mode. 2) The 4 continuous electrode fingers in any portion of the reflector 8 include both the 1 st electrode finger 8a and the 2 nd electrode finger 8b, and the distance between the electrode finger centers of the 4 continuous electrode fingers is the same. 3) The 4 continuous electrode fingers in any portion of the reflector 9 include both the 1 st electrode finger 9a and the 2 nd electrode finger 9b, and the distance between the electrode finger centers of the 4 continuous electrode fingers is the same. With the above configuration, stray waves caused by rayleigh waves can be suppressed. This will be explained below by comparing the present embodiment with comparative examples.

A plurality of elastic wave devices having the structure of embodiment 1 were fabricated by varying the widths of the 2 nd electrode fingers of the reflector. On the other hand, an elastic wave device of a comparative example having the same configuration as that of the elastic wave device of embodiment 1 was produced, except that the widths of the electrode fingers of the reflectors were all the same.

Here, the conditions of the elastic wave device having the structure of embodiment 1 and the elastic wave device of the comparative example are as follows. The wavelength of the IDT electrode and the reflector described later is defined by the distance between the centers of the electrode fingers. When the IDT electrode is viewed in the elastic wave propagation direction, a region where adjacent electrode fingers overlap each other is defined as an intersection region of the IDT electrode, and the length of the intersection region along the direction in which the electrode fingers extend is defined as an intersection width.

Piezoelectric layer: the material is lithium tantalate (LiTaO)₃) The cutting angle is Y cutting 55 degrees, and the film thickness is 400nm

Low acoustic velocity film: the material is silicon oxide (SiO)₂) The film thickness was 400nm

A high acoustic velocity film: the material is silicon nitride (SiN), and the film thickness is 500nm

A support substrate: the material is silicon (Si)

Film thickness of each metal layer of IDT electrode: the thickness of the Ti layer was 4nm, the thickness of the Al layer was 100nm, and the thickness of the Ti layer was 4nm

Wavelength of IDT electrode: 2 μm

Intersection width of IDT electrodes: 20 μm

Logarithm and number of electrode fingers of IDT electrode: 50 pairs of 101

Width of electrode finger of IDT electrode: 0.5 μm

Film thickness of each metal layer of the reflector: the thickness of the Ti layer was 4nm, the thickness of the Al layer was 100nm, and the thickness of the Ti layer was 4nm

Wavelength of the reflector: 2 μm

Number of electrode fingers of reflector: 21 root of Chinese goldthread

Width of 1 st electrode finger: 0.5 μm

Here, as an elastic wave device having the structure of embodiment 1, elastic wave devices were manufactured in which the widths of the 2 nd electrode fingers of the reflector were set to 0.4 μm and 0.3 μm, respectively. As a comparative example, an elastic wave device was produced in which the width of the 2 nd electrode finger of the reflector was set to 0.5 μm, which was the same as the width of the 1 st electrode finger. Next, the phase of the main mode of each elastic wave device and the phase of the spurious wave due to the rayleigh wave were measured. Fig. 5 described below shows the above-described phase in the comparative example. In embodiment 1 and the comparative example having the same configuration except for the width of the 2 nd electrode finger, the resonance frequency of the main mode and the frequency of the spurious wave due to the rayleigh wave are substantially the same.

Fig. 5 is a diagram showing the phase of the main mode and the phase of the spur in the comparative example.

Arrow B in fig. 5 indicates an SH wave as a main mode, and arrow C indicates a stray caused by a rayleigh wave. It is known that the spurious radiation due to the rayleigh wave is generated in a frequency band around 0.75 times the resonance frequency of the main mode.

Fig. 6 is a diagram showing phases of the spurs in embodiment 1 and comparative example. The solid line in fig. 6 shows the result of embodiment 1 in the case where the width of the 2 nd electrode finger of the reflector is set to 0.4 μm. The one-dot chain line shows the result of embodiment 1 in the case where the width of the 2 nd electrode finger of the reflector is set to 0.3 μm. The dotted line shows the results of the comparative example.

As shown in fig. 6, it is understood that the stray waves due to the rayleigh waves in embodiment 1 shown by the solid line and the one-dot chain line are smaller than those in the comparative example shown by the broken line. Therefore, it is understood that in embodiment 1, stray waves due to rayleigh waves can be suppressed.

Further, in embodiment 1, it is understood that the stray is smaller when the width of the 2 nd electrode finger is 0.3 μm than when the width of the 2 nd electrode finger is 0.4 μm. As described above, the larger the difference between the width of the 1 st electrode finger and the width of the 2 nd electrode finger, the more the stray waves due to the rayleigh waves can be suppressed.

The rayleigh wave is a pattern of displacement per electrode finger. The rayleigh wave has a component in the depth direction and a component in the propagation direction of the elastic wave with respect to the piezoelectric layer. In embodiment 1 shown in fig. 1, 4 electrode fingers continuous in the elastic wave propagation direction in the reflector 8 include the 1 st electrode finger 8a and the 2 nd electrode finger 8b having different widths. The same applies to the reflector 9. This makes it possible to make the rayleigh wave mode asymmetric in the elastic wave propagation direction. Therefore, the stray waves caused by the rayleigh waves can be suppressed.

In embodiment 1, the arrangement a1 of 1 group of electrode fingers in the reflector 8 is an arrangement of the 1 st electrode finger 8a, the 2 nd electrode finger 8b, the 1 st electrode finger 8a, and the 2 nd electrode finger 8b in this order from the left side in fig. 3. However, the array a1 of 1 group of electrode fingers may include both the 1 st electrode finger 8a and the 2 nd electrode finger 8b, and may be any one of (a) to (n) in fig. 7. Hereinafter, an example of the arrangement a1 of 1 set of electrode fingers in fig. 7 is shown. The following arrangement is an arrangement in order from the left side in fig. 7.

(a) The 1 st electrode finger 8a, the 2 nd electrode finger 8b, the 1 st electrode finger 8a

(b) The 2 nd electrode finger 8b, the 1 st electrode finger 8a, the 2 nd electrode finger 8b

(c) The 1 st electrode finger 8a, the 2 nd electrode finger 8b, the 1 st electrode finger 8a, the 2 nd electrode finger 8b

(d) The 2 nd electrode finger 8b, the 1 st electrode finger 8a, the 2 nd electrode finger 8b, the 1 st electrode finger 8a

(e) The 1 st electrode finger 8a, the 2 nd electrode finger 8b

(f) The 2 nd electrode finger 8b, the 1 st electrode finger 8a

(g) The 1 st electrode finger 8a, the 2 nd electrode finger 8b, the 1 st electrode finger 8a

(h) No. 2 electrode finger 8b, No. 1 electrode finger 8a

(i) The 1 st electrode finger 8a, the 2 nd electrode finger 8b, the 1 st electrode finger 8a

(j) The 1 st electrode finger 8a, the 2 nd electrode finger 8b

(k) No. 2 electrode finger 8b, No. 1 electrode finger 8a, No. 2 electrode finger 8b

(1) The 1 st electrode finger 8a, the 2 nd electrode finger 8b

(m) the 2 nd electrode finger 8b, the 1 st electrode finger 8a, the 2 nd electrode finger 8b

(n) the 2 nd electrode finger 8b, the 1 st electrode finger 8a

It is preferable that the arrangement a1 of 1 group of electrode fingers in each of the reflectors 8 and 9 is periodically arranged. More preferably, 1-group electrode finger array a1 is continuously arranged as in embodiment 1. In this case, the mode of the rayleigh wave can be made more reliably asymmetric in the elastic wave propagation direction. Therefore, the stray waves caused by the rayleigh waves can be further suppressed.

The distances between the electrode finger centers are preferably the same in each of the IDT electrode 7, the reflector 8, and the reflector 9. This can suppress the dispersion of the characteristics of the main mode and also suppress the spurious radiation due to the rayleigh wave as described above.

More preferably, the distance between the electrode finger centers of the IDT electrode 7 is the same as the distance between the electrode finger centers of the reflectors 8 and 9. This makes it possible to match the wavelength of the response due to the rayleigh wave with the distance between the centers of the electrode fingers of the reflectors 8 and 9. Therefore, by making the rayleigh wave mode asymmetric as described above, the rayleigh wave can be further suppressed.

Preferably, the width of each of the electrode fingers 7a of the IDT electrode 7 is the same. In this case, it is possible to suppress the dispersion of the characteristics of the main mode and also suppress the spurious waves caused by the rayleigh wave.

However, the IDT electrode 7 is often required to have a specific capacitance. By making the width of each of the plurality of electrode fingers 7a of the IDT electrode 7 the same, a specific capacitance can be obtained while suppressing the narrowing of the gap between adjacent electrode fingers 7a in the entire IDT electrode 7. Therefore, a specific capacitance can be obtained while suppressing deterioration of surge resistance.

The piezoelectric substrate 2 of embodiment 1 is a laminate in which the support substrate 3, the high acoustic velocity film 4, the low acoustic velocity film 5, and the piezoelectric layer 6 are laminated in this order, but is not limited to this. The following describes modifications 1 to 3 of embodiment 1 having the same configuration as embodiment 1 except for the piezoelectric substrate. In the 1 st modification to the 3 rd modification as well, as in the 1 st embodiment, it is possible to suppress the stray waves caused by the rayleigh waves.

The piezoelectric substrate 14 in modification 1 shown in fig. 8 has a high sound velocity substrate 13, a low sound velocity film 5 provided on the high sound velocity substrate 13, and a piezoelectric layer 6 provided on the low sound velocity film 5. The piezoelectric layer 6 is provided indirectly on the high-sound-velocity substrate 13 via the low-sound-velocity film 5.

The high-speed substrate 13 is a relatively high-speed substrate. More specifically, the sound velocity of the bulk wave propagating through the high-sound-velocity substrate 13 is higher than the sound velocity of the elastic wave propagating through the piezoelectric layer 6. In the present embodiment, the high sound velocity substrate 13 is a silicon substrate. The material of the high-speed substrate 13 is not limited to the above-mentioned materials, and a medium containing the above-mentioned materials as a main component, such as alumina, silicon carbide, silicon nitride, silicon oxynitride, silicon, sapphire, lithium tantalate, lithium niobate, quartz, alumina, zirconia, cordierite, mullite, steatite, forsterite, magnesia, DLC, or diamond, may be used.

Since the elastic wave device of the present modification includes the piezoelectric substrate 14, and the piezoelectric substrate 14 is a laminate in which the high acoustic velocity substrate 13, the low acoustic velocity film 5, and the piezoelectric layer 6 are laminated in this order, the energy of the elastic wave can be confined to the piezoelectric layer 6 side, as in embodiment 1.

The piezoelectric substrate 15 in modification 2 shown in fig. 9 has a high sound velocity substrate 13 and a piezoelectric layer 6 provided directly on the high sound velocity substrate 13. In this modification as well, the energy of the elastic wave can be confined to the piezoelectric layer 6 side, as in embodiment 1.

The piezoelectric substrate 16 in modification 3 shown in fig. 10 is a lithium tantalate substrate including only a piezoelectric layer.

Fig. 11 is a schematic front sectional view showing part of the IDT electrode and reflectors in embodiment 2.

In the present embodiment, the arrangement a2 of 1 group of electrode fingers is different from that of embodiment 1. More specifically, the arrangement a2 of 1 set of electrode fingers is the same arrangement as (a) in fig. 7. In the reflector 28, an arrangement a2 of 1 group of electrode fingers is periodically arranged. The same applies to the reflector 29. Except for the above-described aspects, the acoustic wave device of the present embodiment has the same configuration as that of acoustic wave device 1 of embodiment 1.

Here, a plurality of elastic wave devices having the structure of the present embodiment were manufactured by varying the width of the 2 nd electrode finger of the reflector. The conditions of the elastic wave devices are the same as those of embodiment 1 shown in fig. 6 and compared with the results. On the other hand, an elastic wave device of a comparative example having the same configuration as that of the elastic wave device of the present embodiment except that the widths of the electrode fingers of the reflectors are all the same was manufactured. The comparative example to be compared with the present embodiment is the same as the comparative example to be compared with embodiment 1.

Fig. 12 is a diagram showing phases of the spurs in embodiment 2 and comparative example. The solid line in fig. 12 shows the result of embodiment 2 in the case where the width of the 2 nd electrode finger of the reflector is set to 0.4 μm. The one-dot chain line shows the result of embodiment 2 in the case where the width of the 2 nd electrode finger of the reflector is set to 0.3 μm. The dotted line shows the results of the comparative example.

As shown in fig. 12, it is understood that the stray waves due to the rayleigh waves in embodiment 2 shown by the solid line and the one-dot chain line are smaller than those in the comparative example shown by the broken line. Therefore, it is understood that in embodiment 2, spurious waves caused by rayleigh waves can be suppressed. Further, in embodiment 2, it is understood that the stray is smaller when the width of the 2 nd electrode finger is 0.3 μm than when the width of the 2 nd electrode finger is 0.4 μm. As described above, if the arrangement a2 of 1 set of electrode fingers is any one of the examples shown in fig. 7, it is possible to effectively suppress the stray waves due to the rayleigh waves.

Fig. 13 is a schematic front sectional view showing part of the IDT electrode and reflectors in embodiment 3.

The present embodiment is different from embodiment 1 in that, in the reflector 38, the arrangement a3 of 1 group of electrode fingers is an arrangement of 3 continuous electrode fingers including the 1 st electrode finger 8a and the 2 nd electrode finger 8 b. The same applies to the reflector 39. Except for the above-described aspects, the acoustic wave device of the present embodiment has the same configuration as that of acoustic wave device 1 of embodiment 1.

The arrangement a3 of the 1-group electrode fingers is an arrangement of the 1 st electrode finger 8a, the 2 nd electrode finger 8b, and the 1 st electrode finger 8a in this order from the left side in fig. 13. In the reflector 38, an arrangement a3 of 1 set of electrode fingers is periodically arranged. More specifically, in the reflector 38, the arrangement a3 of 1 group of electrode fingers is continuously arranged. The arrangement a3 of the 1-group electrode fingers is not limited to the above arrangement, and may include both the 1 st electrode finger 8a and the 2 nd electrode finger 8 b. When the arrangement a3 of 1 group of electrode fingers is an arrangement of 3 continuous electrode fingers, 4 continuous electrode fingers in any portion of the reflector 38 may include both the 1 st electrode finger 8a and the 2 nd electrode finger 8 b.

Here, a plurality of elastic wave devices having the structure of the present embodiment were manufactured by varying the width of the 2 nd electrode finger of the reflector. The conditions of the elastic wave devices are the same as those of embodiment 1 shown in fig. 6 and compared with the results. On the other hand, an elastic wave device of a comparative example having the same configuration as that of the elastic wave device of the present embodiment was produced, except that the widths of the electrode fingers of the reflectors were all the same. The comparative example to be compared with the present embodiment is the same as the comparative example to be compared with embodiment 1.

Fig. 14 is a diagram showing phases of the spurs in embodiment 3 and comparative example. The solid line in fig. 14 shows the result of embodiment 3 in the case where the width of the 2 nd electrode finger of the reflector is set to 0.4 μm. The one-dot chain line shows the result of embodiment 3 in the case where the width of the 2 nd electrode finger of the reflector is set to 0.3 μm. The dotted line shows the results of the comparative example.

As shown in fig. 14, it is understood that the stray waves due to the rayleigh waves in embodiment 3 shown by the solid line and the one-dot chain line are smaller than those in the comparative example shown by the broken line. Therefore, it is understood that in embodiment 3, stray waves due to rayleigh waves can be suppressed. Further, in embodiment 3, it is understood that the stray is smaller when the width of the 2 nd electrode finger is 0.3 μm than when the width of the 2 nd electrode finger is 0.4 μm.

The arrangement a3 of 1 group of electrode fingers is not limited to the arrangement of 3 continuous electrode fingers as in the present embodiment, or the arrangement of 4 continuous electrode fingers as in embodiment 1. As long as 4 continuous electrode fingers in any portion of the reflector 38 include both the 1 st electrode finger 8a and the 2 nd electrode finger 8b, the arrangement a3 of 1 group of electrode fingers may be an arrangement of 5 or more continuous electrode fingers.

Fig. 15 is a schematic front sectional view showing part of the IDT electrode and reflectors in embodiment 4.

The present embodiment is different from embodiment 1 in that the arrangement of 2 sets of electrode fingers is periodically arranged in the reflector 48. More specifically, in the reflector 48, the arrangement a4 of 1 group of electrode fingers and the arrangement a5 of 1 group of electrode fingers are alternately arranged. The same applies to the reflector 49. Except for the above-described aspects, the acoustic wave device of the present embodiment has the same configuration as that of acoustic wave device 1 of embodiment 1.

The arrangement a4 of the 1-group electrode fingers is the same arrangement as (d) in fig. 7. The arrangement a5 of 1 set of electrode fingers is the same arrangement as (c) in fig. 7. In the present embodiment, in the reflector 48, the arrangement of 8 continuous electrode fingers is periodically arranged by alternately arranging the arrangement a4 of 1 group of electrode fingers and the arrangement a5 of 1 group of electrode fingers. The arrangement of electrode fingers is not limited to 2 groups, and 3 or more groups may be periodically arranged in the reflector 48.

Here, a plurality of elastic wave devices having the structure of the present embodiment were manufactured by varying the width of the 2 nd electrode finger of the reflector. The conditions of the elastic wave devices are the same as those of embodiment 1 shown in fig. 6 and compared with the results. On the other hand, an elastic wave device of a comparative example having the same configuration as that of the elastic wave device of the present embodiment except that the widths of the electrode fingers of the reflectors are all the same was manufactured. The comparative example to be compared with the present embodiment is the same as the comparative example to be compared with embodiment 1.

Fig. 16 is a diagram showing phases of the spurs in embodiment 4 and comparative example. The solid line in fig. 16 shows the result of embodiment 4 in the case where the width of the 2 nd electrode finger of the reflector is set to 0.4 μm. The one-dot chain line shows the result of embodiment 4 in the case where the width of the 2 nd electrode finger of the reflector is set to 0.3 μm. The dotted line shows the results of the comparative example.

As shown in fig. 16, it is understood that the stray waves due to the rayleigh waves in embodiment 4 shown by the solid line and the one-dot chain line are smaller than those in the comparative example shown by the broken line. Therefore, it is understood that in embodiment 4, stray waves due to rayleigh waves can be suppressed. Further, in embodiment 4, it is understood that the stray is smaller when the width of the 2 nd electrode finger is 0.3 μm than when the width of the 2 nd electrode finger is 0.4 μm.

Embodiments 1 to 4 show examples of an elastic wave resonator as an elastic wave device according to the present invention. The bandpass filter, the duplexer, and the multiplexer according to the present invention will be described below.

Fig. 17 is a circuit diagram of the bandpass filter according to embodiment 5.

The bandpass filter 50 is a ladder filter having a plurality of series-arm resonators and a plurality of parallel-arm resonators. The plurality of series-arm resonators and the plurality of parallel-arm resonators are elastic wave resonators. In the present embodiment, each of the plurality of series arm resonators and the plurality of parallel arm resonators has the structure of elastic wave device 1 according to embodiment 1. At least one of the plurality of elastic wave resonators of band-pass filter 50 may have the structure of the elastic wave device according to the present invention.

The bandpass filter 50 is connected to a signal terminal 55 and an antenna terminal 56, and the antenna terminal 56 is connected to an antenna. A series-arm resonator S1, a series-arm resonator S2, a series-arm resonator S3, and a series-arm resonator S4 are connected in series with each other between the antenna terminal 56 and the signal terminal 55. A parallel-arm resonator P1 is connected between the connection point between the series-arm resonator S1 and the series-arm resonator S2 and the ground potential. A parallel-arm resonator P2 is connected between the connection point between the series-arm resonator S2 and the series-arm resonator S3 and the ground potential. A parallel-arm resonator P3 is connected between the connection point between the series-arm resonator S3 and the series-arm resonator S4 and the ground potential. In the present embodiment, the elastic wave resonator closest to the antenna end side where the antenna terminal 56 is located is the series arm resonator S1.

The circuit configuration of bandpass filter 50 is not limited to the above-described circuit configuration, and may be a series-arm resonator or a parallel-arm resonator including the configuration of the elastic wave device according to the present invention. The elastic wave resonator disposed closest to the antenna end may be a parallel arm resonator.

Each series-arm resonator and each parallel-arm resonator of bandpass filter 50 have the configuration of embodiment 1. This can suppress stray waves caused by Rayleigh waves.

When the bandpass filter is commonly connected to another filter device at the antenna terminal, there is a possibility that stray waves caused by rayleigh waves generated in the elastic wave resonator of the bandpass filter affect the other filter device. In contrast, in the present embodiment, the elastic wave resonator of band-pass filter 50 has the structure of embodiment 1. Therefore, the influence of the spurious waves caused by the rayleigh wave on the other filters connected in common can be suppressed.

Among the influences of the stray of the bandpass filter 50 on the other filter devices commonly connected to the bandpass filter 50, the influence of the stray of the elastic wave resonator disposed closest to the antenna end side is the largest. As in the present embodiment, it is preferable that the elastic wave resonator disposed closest to the antenna end side has the structure of the elastic wave device according to the present invention. This can further suppress the influence of the spurious due to the rayleigh wave on another filter device commonly connected to the bandpass filter 50.

Fig. 18 is a schematic circuit diagram of the duplexer according to embodiment 6. Fig. 18 schematically shows a2 nd bandpass filter to be described later by a block diagram.

The duplexer 60 includes an antenna terminal 56, and a1 st bandpass filter 61A and a2 nd bandpass filter 61B commonly connected to the antenna terminal 56. The 1 st bandpass filter 61A and the 2 nd bandpass filter 61B have different passbands. In the present embodiment, the 1 st bandpass filter 61A has the same configuration as the bandpass filter 50 of embodiment 4.

On the other hand, the circuit configuration of the 2 nd bandpass filter 61B is not particularly limited. The 2 nd bandpass filter 61B may be, for example, an appropriate ladder filter or a longitudinally coupled resonator type elastic wave filter. In addition, both the 1 st bandpass filter 61A and the 2 nd bandpass filter 61B may have the configuration of the bandpass filter according to the present invention.

The 1 st bandpass filter 61A of the duplexer 60 has the same configuration as that of embodiment 4. Thus, stray waves caused by rayleigh waves can be suppressed. Further, it is possible to suppress the influence of stray waves caused by rayleigh waves on the 2 nd bandpass filter 61B commonly connected to the 1 st bandpass filter 61A at the antenna terminal 56.

Fig. 19 is a schematic diagram of the multiplexer according to embodiment 7.

The multiplexer 70 includes an antenna terminal 56, and a1 st bandpass filter 61A, a2 nd bandpass filter 71B, and a3 rd bandpass filter 71C commonly connected to the antenna terminal 56. The 1 st bandpass filter 61A has the same configuration as that of embodiment 4. On the other hand, the circuit configuration of the 2 nd bandpass filter 71B and the 3 rd bandpass filter 71C is not particularly limited. The 2 nd bandpass filter 71B and the 3 rd bandpass filter 71C may have the configuration of the bandpass filter according to the present invention. The multiplexer 70 may include a filter device other than the 1 st bandpass filter 61A, the 2 nd bandpass filter 71B, and the 3 rd bandpass filter 71C connected to the antenna terminal 56.

The 1 st bandpass filter 61A of the multiplexer 70 has the same configuration as that of embodiment 4. Thus, stray waves caused by rayleigh waves can be suppressed. Further, it is possible to suppress the influence of stray waves caused by rayleigh waves on another filter device commonly connected to the 1 st bandpass filter 61A at the antenna terminal 56.

Description of the reference numerals

1: an elastic wave device;

2: a piezoelectric substrate;

3: a support substrate;

4: a high acoustic velocity membrane;

5: a low acoustic velocity membrane;

6: a piezoelectric layer;

7: an IDT electrode;

7 a: an electrode finger;

7c to 7 e: 1 st to 3 rd metal layers;

8. 9: a reflector;

8a, 9 a: the 1 st electrode finger;

8b, 9 b: the 2 nd electrode finger;

13: a high acoustic velocity substrate;

14-16: a piezoelectric substrate;

28. 29, 38, 39, 48, 49: a reflector;

50: a band-pass filter;

55: a signal terminal;

56: an antenna terminal;

60: a duplexer;

61A, 61B: a1 st band-pass filter and a2 nd band-pass filter;

70: a multiplexer;

71B, 71C: 2 nd and 3 rd bandpass filters;

P1-P3: a parallel arm resonator;

S1-S4: a series arm resonator.