CN117118390B

CN117118390B - elastic wave filter

Info

Publication number: CN117118390B
Application number: CN202310957678.8A
Authority: CN
Inventors: 许志斌; 王为标; 俞振一; 傅肃磊; 毕玉梅; 刘平
Original assignee: Wuxi Haoda Electronic Co ltd
Current assignee: Wuxi Haoda Electronic Co ltd
Priority date: 2023-08-01
Filing date: 2023-08-01
Publication date: 2024-02-13
Anticipated expiration: 2043-08-01
Also published as: CN117118390A

Abstract

The application relates to an elastic wave filter capable of improving out-of-band suppression level and reducing process difficulty, and relates to the field of elastic wave filters. The first electrode finger and the second electrode finger are overlapped with each other along the elastic wave propagation direction, and the first electrode finger and the second electrode finger are arranged as interdigital transducer crossing areas, and the interdigital transducer crossing areas are at least partially arranged on the non-piezoelectric material film. Under such circumstances, the present application provides an elastic wave filter based on a piezoelectric composite substrate of a piezoelectric thin film and a non-piezoelectric substrate, which has a better out-of-band rejection level and lower process difficulty than the IHP type elastic wave filter in the prior art.

Description

Elastic wave filter

Technical Field

The application relates to the technical field of elastic wave filters, in particular to an elastic wave filter capable of improving out-of-band rejection level and reducing process difficulty.

Background

The elastic wave device has the characteristics of low cost, small volume, multiple functions and the like, and is widely applied to the fields of radar, communication, navigation and the like. The most commonly used elastic wave devices in mobile phone and base station communication include an elastic wave filter, an elastic wave duplexer and an elastic wave multiplexer, which are formed by combining a plurality of elastic wave filters. In any type of elastic wave filter, a thin film pattern of a conductive material is provided on a piezoelectric functional material to determine a plurality of interdigital transducers and a plurality of sections of conductive traces for realizing electrical connection between the interdigital transducers, and band pass characteristics are obtained by utilizing frequency characteristics of a conversion function of an electric signal of the interdigital transducer into an elastic wave.

In the prior art, an elastic wave filter (IHP type elastic wave filter) based on a piezoelectric composite substrate has gained a great deal of attention due to the high Q value performance, and as a common knowledge, we often increase the rectangular degree of the IHP type elastic wave filter by adding an interdigital transducer. However, the added interdigital transducer in the common IHP type elastic wave filter reduces the out-of-band inhibition of the filter due to the resonance effect of the interdigital transducer, the performance of the filter is deteriorated, and the period of the added interdigital transducer is often smaller than that of other interdigital transducers, which causes great process difficulty and is unfavorable for the processing and preparation of the elastic wave filter.

Disclosure of Invention

It is an object of the present application to provide an elastic wave filter with a better out-of-band rejection level and lower process difficulty to solve the above-mentioned problems of the prior art.

In order to achieve the above purpose, the technical scheme adopted in the application is as follows:

in a first aspect, the present application provides an elastic wave filter comprising:

a piezoelectric multilayer substrate including at least a piezoelectric thin film, a non-piezoelectric material thin film, and a non-piezoelectric substrate; and

a conductive material thin film pattern provided on the piezoelectric multilayer substrate, the conductive material thin film pattern being formed with a plurality of interdigital transducers including a plurality of first electrode fingers and a plurality of second electrode fingers which are inserted alternately with each other, and a first bus bar and a second bus bar which are opposed to each other in an extending direction of the first electrode fingers and the second electrode finger fingers;

the region where the first electrode fingers and the second electrode fingers overlap each other in the elastic wave propagation direction is set as an interdigital transducer crossing region, and the interdigital transducer crossing region is at least partially arranged on the non-piezoelectric material film.

In one possible implementation, the interdigital transducer crossover region is disposed at least partially over the piezoelectric film.

In one possible implementation, the piezoelectric film is a lithium tantalate film or a lithium niobate film.

In one possible implementation, the non-piezoelectric substrate includes:

a support substrate disposed directly below the piezoelectric film; or (b)

A low acoustic speed material film disposed directly under the piezoelectric film, and a support substrate disposed directly under the low acoustic speed material film; or (b)

The piezoelectric thin film comprises a low sound velocity material film directly arranged below the piezoelectric thin film, a capture material layer directly arranged below the low sound velocity material film, and a support substrate directly arranged below the capture material layer.

In one possible implementation, the thin film of non-piezoelectric material is formed from one or more combinations of non-piezoelectric property materials.

In one possible implementation, the acoustic velocity of the bulk wave propagating in the low acoustic velocity material film is lower than the acoustic velocity of the bulk wave propagating in the piezoelectric film;

the acoustic velocity of the bulk wave propagating in the support substrate is higher than the acoustic velocity of the bulk wave propagating in the piezoelectric film.

In one possible implementation, the trapping material layer is formed of one or more combinations of amorphous silicon, polysilicon, amorphous germanium, and polycrystalline germanium.

In one possible implementation, the conductive material thin film pattern includes a first conductive material thin film pattern and a second conductive material thin film pattern partially overlapping the first conductive material thin film pattern, the second conductive material thin film pattern having a different pattern and film thickness from the first conductive material thin film pattern.

In a second aspect, the present application provides a method for preparing an elastic wave filter, the method being applicable to an elastic wave filter as described in any one of the above, the method comprising:

s1, preparing a non-piezoelectric substrate;

s2, preparing a piezoelectric film on the non-piezoelectric substrate;

s3, removing the unnecessary part of the piezoelectric film by adopting an MEMS process to expose the non-piezoelectric substrate;

s4, depositing a non-piezoelectric material film on the structure of the step S3 by adopting an MEMS process, and processing the non-piezoelectric material film by adopting a chemical mechanical polishing process, so that the non-piezoelectric material film is filled in the area of the non-piezoelectric substrate exposed in the step S3, and the piezoelectric film which is not removed in the step S3 is re-exposed;

s5, preparing a first conductive material film pattern on the structure of the step S4 by adopting an MEMS process;

s6, preparing a second conductive material film pattern on the structure of the step S5 by adopting an MEMS process, wherein the second conductive material film pattern is provided with a thickening pattern aiming at the bus bar.

In a third aspect, the present application provides a multiplexer comprising:

an antenna terminal connected to the antenna; and

a plurality of filter means commonly connected to said antenna terminals, at least one of said filter means being an elastic wave filter as described in any one of the above.

The beneficial effects that this application provided technical scheme brought include at least:

by setting the region where the first electrode finger and the second electrode finger overlap each other in the elastic wave propagation direction as the interdigital transducer intersecting region, the interdigital transducer intersecting region is provided at least partially over the thin film of non-piezoelectric material. Under such circumstances, the present application provides an elastic wave filter (IHP-type elastic wave filter) based on a piezoelectric composite substrate of a piezoelectric thin film and a non-piezoelectric substrate, which has a better out-of-band rejection level and lower process difficulty than the IHP-type elastic wave filter in the prior art.

Drawings

The accompanying drawings are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate the application and together with the embodiments of the application, and not constitute a limitation to the application. In the drawings:

FIG. 1 (a) shows a schematic top view of a conventional IHP-type acoustic wave filter 100;

FIG. 1 (b) shows a schematic cross-sectional view of A-A' of FIG. 1 (a);

fig. 2 (a) shows a schematic top view of an acoustic wave filter 200 according to an embodiment of the present disclosure;

FIG. 2 (B) shows a schematic cross-sectional view B-B' of FIG. 2 (a);

FIG. 3 shows a schematic view of the intersection region of an interdigital transducer;

fig. 4 (a) shows a schematic diagram of the topology of a conventional IHP-type acoustic wave filter 100;

fig. 4 (b) shows a schematic topology of an acoustic wave filter 200 according to an embodiment of the present application;

fig. 5 shows a graph of insertion loss versus frequency for a conventional IHP-type elastic wave filter 100 and 200;

FIG. 6 (a) is a schematic top view of an interdigital transducer C1 of a conventional IHP-type acoustic wave filter 100;

fig. 6 (b) is a schematic top view of an interdigital transducer C2 in an acoustic wave filter 200 according to an embodiment of the present application;

FIG. 6 (C) shows a schematic cross-sectional view of C-C' of FIG. 6 (a);

FIG. 6 (D) shows a schematic cross-sectional view of D-D' of FIG. 6 (b);

FIG. 7 shows an admittance magnitude-frequency plot for interdigital transducer C1 from FIG. 6 (a) and interdigital transducer C2 from FIG. 6 (b);

fig. 8 shows a flowchart of a method for manufacturing an elastic wave filter according to a second embodiment of the present application.

Detailed Description

The following description of the embodiments of the present application will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all, of the embodiments of the present application. All other embodiments, which can be made by one of ordinary skill in the art without undue burden from the present disclosure, are within the scope of the present disclosure.

Wherein like parts are designated by like reference numerals. It should be noted that the words "front", "rear", "left", "right", "upper" and "lower" used in the following description refer to directions in drawings of the present specification, and the words "bottom" and "top", "inner" and "outer" refer to directions toward or away from, respectively, a specific component. Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature. In the description of the present specification, the meaning of "plurality" is two or more.

The present application is further described below with reference to the drawings and examples.

First, a brief description will be given of the elastic wave filter 100 provided in the prior art:

fig. 1 (a) shows a schematic top view of a conventional IHP-type acoustic wave filter 100, and fig. 1 (b) shows a schematic cross-sectional view of A-A' of fig. 1 (a). The direction parallel to the x-axis in the coordinate system in fig. 1 is defined as the elastic wave propagation direction, the direction parallel to the y-axis in the coordinate system in fig. 1 is defined as the electrode finger extending direction, and the direction parallel to the z-axis in the coordinate system in fig. 1 is defined as the height direction of the elastic wave filter 100.

In detail, the IHP elastic wave filter 100 includes a non-piezoelectric substrate, a piezoelectric thin film 101 disposed on the non-piezoelectric substrate, and a conductive material thin film pattern disposed on at least one of the non-piezoelectric substrate and the piezoelectric thin film 101.

In the present embodiment, the piezoelectric film 101 is implemented as a 170 ° YX-lithium niobate film having a thickness of 600 nm.

Specifically, a non-piezoelectric substrate is provided below the piezoelectric thin film 101, and includes, from top to bottom, a low acoustic velocity material film 102, a trapping material layer 103, and a support substrate 104. A low acoustic velocity material film 102 is located below the piezoelectric film 101, and the acoustic velocity of bulk waves propagating in the low acoustic velocity material film 102 is higher than that of bulk waves propagating in the piezoelectric film 101The sound velocity of the propagating bulk wave is low; the low acoustic velocity material film 102 is realized as SiO with a thickness of 500nm ₂ (silicon dioxide) film. The trapping material layer 103 is located below the low acoustic velocity material film 102, and the trapping material layer 103 is implemented as a polysilicon film having a thickness of 1 μm. The support substrate 104 is located below the trapping material layer 103, and the acoustic velocity of bulk waves propagating in the support substrate 104 is higher than that of bulk waves propagating in the piezoelectric thin film 101, and the support substrate 104 is implemented as a Si (silicon) substrate having a thickness of 250 μm.

In addition, a conductive material film pattern is provided above the piezoelectric film 101, specifically, all patterns within a dotted rectangular frame of the piezoelectric film 101 in fig. 1 (a). The conductive material film pattern includes a plurality of interdigital transducers (S1, S2, S3, S4, P1, P2, P3, P4, C1), a signal input pad 106, a signal output pad 107, a ground pad (108, 109), and a plurality of segments of conductive traces (110, 111, 112, 113, 114, 115, 116, 117).

Further, as shown in fig. 1 (a), each interdigital transducer (S1, S2, S3, S4, P1, P2, P3, P4, C1) has a plurality of first electrode fingers and a plurality of second electrode fingers interleaved with each other, and a first bus bar and a second bus bar are opposed to each other in the extending direction of the first electrode fingers and the second electrode fingers; the plurality of first electrode fingers have two groups of end portions, one group of end portions are electrically connected with the first bus bar, and the other group of end portions are opposite to the second bus bar with a gap; the plurality of second electrode fingers have two sets of end portions, one set of end portions being electrically connected to the second bus bar, and the other set of end portions being opposed to the first bus bar with a gap therebetween. The plurality of first electrode fingers and the plurality of second electrode fingers include two sub-layers respectively laminated of a titanium material film and an aluminum material film. The titanium material film sub-layer is directly positioned on the piezoelectric film 101, and the thickness of the titanium material film sub-layer is 5nm; the aluminum material film sub-layer is directly positioned on the titanium material film sub-layer, and the thickness of the aluminum material film sub-layer is 220nm.

Not shown in fig. 1 (a), one reflective gate electrode is provided on each of both sides of each interdigital transducer (S1, S2, S3, S4, P1, P2, P3, P4, C1) in the propagation direction of the elastic wave. Each of the reflective gate electrodes includes a plurality of reflective gate electrode fingers, and third and fourth bus bars opposing each other in an extending direction of the plurality of reflective gate electrode fingers, one set of ends of the plurality of reflective gate electrode fingers being directly connected to the third bus bar, and the other set of ends being directly connected to the fourth bus bar.

Referring to fig. 1 (b), it can be seen that the piezoelectric film 101 is disposed over the entire area of the low acoustic velocity material film 102.

In fact, the piezoelectric film 101 is present in the entire area in fig. 1 (a), i.e., the plurality of interdigital transducers (S1, S2, S3, S4, P1, P2, P3, P4, C1), the signal input pad 106, the signal output pad 107, the ground pad (108, 109), the multi-segment conductive trace (110, 111, 112, 113, 114, 115, 116, 117), and the area therebetween, all exist the piezoelectric film 101.

Similarly, one reflective gate electrode is provided on each of the interdigital transducers (S1, S2, S3, S4, P1, P2, P3, P4, C1) on both sides in the elastic wave propagation direction, and a plurality of reflective gate electrodes are omitted from fig. 1 (b).

Fig. 4 (a) shows a schematic diagram of the topology of a conventional IHP-type elastic wave filter 100, in which the interdigital transducers (S1, S2, S3, S4) are interdigital transducers connected in series, the interdigital transducers (P1, P2, P3, P4) are interdigital transducers connected in parallel, the interdigital transducer C1 is an interdigital capacitor with no lower piezoelectric film missing, and the interdigital transducer C1 can be regarded as a resonator similar to the interdigital transducers (S1, S2, S3, S4, P1, P2, P3, P4) due to the existence of the piezoelectric effect, but the interdigital transducer C1 only plays a role of the capacitor.

To more clearly show the partial structure of the interdigital transducer C1, fig. 6 (a) shows a schematic top view of the interdigital transducer C1 in the conventional IHP-type elastic wave filter 100, and fig. 6 (C) shows a schematic cross-sectional view of C-C' of fig. 6 (a). The direction parallel to the x-axis in the coordinate system in fig. 6 is defined as the elastic wave propagation direction, the direction parallel to the y-axis in the coordinate system in fig. 6 is defined as the electrode finger extending direction, and the direction parallel to the z-axis in the coordinate system in fig. 6 is defined as the height direction of the interdigital transducer C1. It should be noted that the interdigital transducer C1 in fig. 6 (a) and 6 (C) is a part of the elastic wave filter 100 in fig. 1, and its parameters remain the same as those in fig. 1.

Embodiment one:

fig. 2 (a) shows a schematic top view of an elastic wave filter 200 according to an embodiment of the present application, and fig. 2 (B) shows a schematic cross-sectional view of B-B' of fig. 2 (a). The direction parallel to the x-axis in the coordinate system in fig. 2 is defined as the elastic wave propagation direction, the direction parallel to the y-axis in the coordinate system in fig. 2 is defined as the electrode finger extending direction, and the direction parallel to the z-axis in the coordinate system in fig. 2 is defined as the height direction of the elastic wave filter 200.

In detail, the elastic wave filter 200 includes a non-piezoelectric substrate, a piezoelectric thin film 201a provided in a large area on the non-piezoelectric substrate, and a conductive material thin film pattern provided on at least one of the non-piezoelectric material thin film 201b and the piezoelectric thin film 201 a.

It should be noted that the structural distinguishing technical features of the elastic wave filter 200 from the elastic wave filter 100 described above include: as shown in fig. 2 (a), there is a piezoelectric film 201a in most areas on the non-piezoelectric substrate, but a non-piezoelectric material film 201b in the crossover area 218 of the interdigital transducer C2; the absence of piezoelectric film in crossover region 218 can be more clearly seen in the corresponding region of fig. 2 (b). And the interdigital transducer C2 in the second embodiment is wider than the electrode fingers of the interdigital transducer C1 in the prior art. As shown in fig. 3, a region where the first electrode finger and the second electrode finger overlap each other as viewed in the elastic wave propagation direction is defined as an interdigital transducer intersection region.

In the present embodiment, the non-piezoelectric material film 201b is implemented as a 600nm silicon dioxide film. The piezoelectric film 201a is implemented as a 170 ° YX-lithium niobate film having a thickness of 600 nm.

Further, as shown in fig. 2 (a), a non-piezoelectric substrate is provided below the piezoelectric thin film 201a, and includes, from top to bottom, a low acoustic velocity material film 202, a trapping material layer 203, and a support substrate 204. The low acoustic velocity material film 202 is located below the piezoelectric film 201a, and acoustic velocity of bulk waves propagating in the low acoustic velocity material film 202 is lower than acoustic velocity of bulk waves propagating in the piezoelectric film 201 a; the low sound velocity material film202 is realized as SiO with the thickness of 500nm ₂ (silicon dioxide) film. The trapping material layer 203 is located below the low acoustic velocity material film 202, and the trapping material layer 203 is implemented as a polysilicon film having a thickness of 1 μm. The support substrate 204 is located below the trapping material layer 203, and the acoustic velocity of bulk waves propagating in the support substrate 204 is higher than that of bulk waves propagating in the piezoelectric thin film 201a, and the support substrate 204 is implemented as a Si (silicon) substrate with a thickness of 250 μm.

In addition, a conductive material thin film pattern is provided above the piezoelectric functional thin film 201, specifically, all patterns within a dotted rectangular frame of the piezoelectric functional thin film 201 in fig. 2 (a). The conductive material film pattern includes a plurality of interdigital transducers (S1, S2, S3, S4, P1, P2, P3, P4, C2), a signal input pad 206, a signal output pad 207, a ground pad (208, 209), and a plurality of segments of conductive traces (210, 211, 212, 213, 214, 215, 216, 217).

Further, as shown in fig. 2 (a), each of the interdigital transducers (S1, S2, S3, S4, P1, P2, P3, P4, C2) has a plurality of first electrode fingers and a plurality of second electrode fingers interleaved with each other, and a first bus bar and a second bus bar are opposed to each other in the extending directions of the first electrode fingers and the second electrode fingers; the plurality of first electrode fingers have two groups of end portions, one group of end portions are electrically connected with the first bus bar, and the other group of end portions are opposite to the second bus bar with a gap; the plurality of second electrode fingers have two sets of end portions, one set of end portions being electrically connected to the second bus bar, and the other set of end portions being opposed to the first bus bar with a gap therebetween. The plurality of first electrode fingers and the plurality of second electrode fingers include two sub-layers respectively laminated of a titanium material film and an aluminum material film. The titanium material film sub-layer is directly positioned on the piezoelectric film 101, and the thickness of the titanium material film sub-layer is 5nm; the aluminum material film sub-layer is directly positioned on the titanium material film sub-layer, and the thickness of the aluminum material film sub-layer is 220nm.

Not shown in fig. 2 (a), one reflective gate electrode is provided on each of both sides of each interdigital transducer (S1, S2, S3, S4, P1, P2, P3, P4) in the propagation direction of the elastic wave. Each of the reflective gate electrodes includes a plurality of reflective gate electrode fingers, and a fifth bus bar and a sixth bus bar that are opposite to each other in an extending direction of the plurality of reflective gate electrode fingers, one set of ends of the plurality of reflective gate electrode fingers being directly connected to the fifth bus bar, and the other set of ends being directly connected to the sixth bus bar. The reflective gate electrode of interdigital transducer C2 can be present or absent.

Referring to fig. 2 (b), it can be seen that the piezoelectric film 201 is disposed over the entire area of the low acoustic velocity material film 202.

In fact, the piezoelectric functional film 201 exists in the entire area in fig. 2 (a), i.e., the plurality of interdigital transducers (S1, S2, S3, S4, P1, P2, P3, P4, C2), the signal input pad 206, the signal output pad 207, the ground pad (208, 209), the multi-segment conductive trace (210, 211, 212, 213, 214, 215, 216, 217), and the area therebetween, all exist the piezoelectric functional film 201.

Similarly, one reflective gate electrode is provided on each of both sides of each interdigital transducer (S1, S2, S3, S4, P1, P2, P3, P4, C2) in the elastic wave propagation direction, and a plurality of reflective gate electrodes are omitted in fig. 2 (b).

As shown in fig. 4 (b), the schematic topological structure of the elastic wave filter 200 provided in the first embodiment of the present application is shown, the interdigital transducers (S1, S2, S3, S4) are interdigital transducers connected in series, the interdigital transducers (P1, P2, P3, P4) are interdigital transducers connected in parallel, the piezoelectric film below the interdigital transducer C2 is absent, and the capacitance value of the interdigital transducer is not changed with the change of frequency due to the absence of the piezoelectric effect, so that the interdigital transducer C2 can be imagined as a plate capacitor with a constant capacitance value, i.e., an interdigital capacitor.

To more clearly show the partial structure of the interdigital transducer C2, fig. 6 (b) shows a schematic top view of the interdigital transducer C2 in the elastic wave filter 200 according to the first embodiment of the present application, and fig. 6 (D) shows a schematic cross-sectional view D-D' of fig. 6 (b). The direction parallel to the x-axis in the coordinate system in fig. 6 is defined as the elastic wave propagation direction, the direction parallel to the y-axis in the coordinate system in fig. 6 is defined as the electrode finger extending direction, and the direction parallel to the z-axis in the coordinate system in fig. 6 is defined as the height direction of the interdigital transducer C2. It should be noted that the interdigital transducer C2 in fig. 6 (b) and 6 (d) is a part of the elastic wave filter 200 in fig. 2, and its parameters remain the same as those in fig. 2.

And (3) effect verification:

fig. 5 shows a graph of insertion loss versus frequency for a known IHP-type elastic wave filter 100 and elastic wave filter 200. Wherein the dashed line is the insertion loss-frequency curve of the IHP elastic wave filter 100, and the solid line is the insertion loss-frequency curve of the elastic wave filter 200 according to the first embodiment.

It can be seen that the interdigital transducer C1 in the elastic wave filter 100 is placed on the piezoelectric film 101, and due to its resonant response, a larger spurious mode is generated in the elastic wave filter 100 at around 800MHz, which will deteriorate the out-of-band rejection of the filter; in contrast, the interdigital transducer C2 in the elastic wave filter 200 is placed on the non-piezoelectric material film 201b, so that no piezoelectric effect causes the electric signal to be converted into a mechanical signal and resonate, thereby being capable of suppressing spurious modes generated by the elastic wave filter 100 at about 800MHz, which can raise the out-of-band suppression level of the filter. By contrast, the out-of-band rejection of the elastic wave filter 200 at around 800MHz is improved by about 10dB over the elastic wave filter 100.

Fig. 7 shows an admittance amplitude-frequency plot for the interdigital transducer C1 of fig. 6 (a) and the interdigital transducer C2 of fig. 6 (b). Wherein the broken line is the admittance magnitude-frequency curve of the interdigital transducer C1 in fig. 6 (a), and the solid line is the admittance magnitude-frequency curve of the interdigital transducer C2 in fig. 6 (b).

It can be seen that, as analyzed in fig. 5, the interdigital transducer C1 in the elastic wave filter 100 generates a large impedance change at around 800MHz due to the resonance effect, and this large impedance change is also a main cause of attenuation of the out-of-band rejection of the elastic wave filter 100. By contrast, the interdigital transducer C2 of the elastic wave filter 200, because of being placed on the non-piezoelectric material film 201b, does not generate impedance change due to resonance effect, and its admittance amplitude-frequency curve is smooth and flat, so that the out-of-band rejection of the elastic wave filter 200 can be improved compared with the elastic wave filter 100.

Next, the following description is made regarding the principle of reducing the process difficulty, which is the beneficial effects that can be achieved in the present application:

according to the above effect verification, the resonant frequency (fig. 6) of the interdigital transducer C1 in fig. 1 (a) and 1 (b) is far greater than the center frequency of the conventional IHP-type elastic wave filter 100, so, in order to meet this frequency requirement, the line width of the interdigital transducer C1 is often smaller than the line width of the interdigital transducers (S1, S2, S3, S4, P1, P2, P3, P4), which clearly increases the difficulty in manufacturing the conventional IHP-type elastic wave filter 100 in the MEMS process.

However, since the interdigital transducer C2 in fig. 2 (a) and 2 (b) does not generate resonance, only the capacitance value is required to meet the design requirement, so the line width of the interdigital transducer C2 is not required to be smaller than that of the interdigital transducers (S1, S2, S3, S4, P1, P2, P3, P4), and the capacitance thereof can be realized by adjusting the number of electrodes of the interdigital capacitor and the relative dielectric constant of the dielectric functional film 201b, thereby being capable of reducing the difficulty in manufacturing the conventional IHP-type elastic wave filter 100 in the MEMS process.

Embodiment two:

fig. 8 is a flowchart of a method for manufacturing an elastic wave filter according to a third embodiment of the present application, where the method is applicable to the elastic wave filter described in the first embodiment, and the method includes:

step S1, preparing a non-piezoelectric substrate;

s2, preparing a piezoelectric film on a non-piezoelectric substrate;

s3, removing unnecessary parts of the piezoelectric film by adopting an MEMS process to expose the non-piezoelectric substrate;

step S4, depositing a non-piezoelectric material film on the structure of the step S3 by adopting an MEMS process, and processing the non-piezoelectric material film by adopting a chemical mechanical polishing (Chemical Mechanical Polishing, CMP) process, so that the non-piezoelectric material film is filled in the area of the non-piezoelectric substrate exposed in the step S3, and the non-removed piezoelectric film in the step S3 is re-exposed;

and S6, preparing a second conductive material film pattern on the structure of the step S5 by adopting an MEMS process, wherein the second conductive material film pattern is provided with a thickening pattern aiming at the bus bar.

In summary, the present application sets the region where the first electrode finger and the second electrode finger overlap each other in the elastic wave propagation direction as the interdigital transducer intersection region, and the interdigital transducer intersection region is at least partially disposed on the non-piezoelectric material film. Under such circumstances, the present application provides an elastic wave filter (IHP-type elastic wave filter) based on a piezoelectric composite substrate of a piezoelectric thin film and a non-piezoelectric substrate, which has a better out-of-band rejection level and lower process difficulty than the IHP-type elastic wave filter in the prior art.

In the embodiments disclosed herein, the terms "mounted," "connected," "secured," and the like are to be construed broadly, and for example, "connected" may be a fixed connection, a removable connection, or an integral connection; "coupled" may be directly coupled or indirectly coupled through intermediaries. The specific meaning of the above terms in the embodiments of the present disclosure will be understood by those of ordinary skill in the art according to the specific circumstances.

The foregoing is merely a preferred embodiment of the present application, and it should be noted that: it will be apparent to those skilled in the art that numerous modifications and variations can be made thereto without departing from the principles of the present application, and such modifications and variations are to be regarded as being within the scope of the application.

Claims

1. An elastic wave filter, comprising:

2. An elastic wave filter according to claim 1, characterized in that:

the interdigital transducer intersection region is at least partially disposed on the piezoelectric film.

3. An elastic wave filter according to claim 1, characterized in that:

the piezoelectric film is a lithium tantalate film or a lithium niobate film.

4. An elastic wave filter according to claim 1, characterized in that:

the non-piezoelectric substrate includes:

a support substrate disposed directly below the piezoelectric film; or (b)

5. An elastic wave filter according to claim 1, characterized in that:

the thin film of non-piezoelectric material is formed from one or more combinations of non-piezoelectric materials.

6. The acoustic wave filter according to claim 4, wherein:

the sound velocity of bulk waves propagating in the low sound velocity material film is lower than that of bulk waves propagating in the piezoelectric film;

7. The acoustic wave filter according to claim 4, wherein:

the trapping material layer is formed by one or more of amorphous silicon, polycrystalline silicon, amorphous germanium and polycrystalline germanium.

8. An elastic wave filter according to claim 1, characterized in that:

the conductive material thin film pattern includes a first conductive material thin film pattern and a second conductive material thin film pattern partially overlapping the first conductive material thin film pattern, the second conductive material thin film pattern having a different pattern and film thickness from the first conductive material thin film pattern.

9. A method of manufacturing an elastic wave filter, the method being applied to the elastic wave filter according to any one of claims 1 to 8, the method comprising:

s1, preparing a non-piezoelectric substrate;

s2, preparing a piezoelectric film on the non-piezoelectric substrate;

10. A multiplexer, comprising:

an antenna terminal connected to the antenna; and

a plurality of filter means commonly connected to said antenna terminals, at least one of said filter means being an elastic wave filter as claimed in any one of claims 1 to 8.