Resonator, filter and molding method with function of suppressing heterogeneous mode ripples

Abstract

The invention discloses a resonator, a filter and a forming method with the function of suppressing heterogeneous mode ripples. The resonator, the filter and the forming method comprise an upper interdigital region and a lower interdigital region. Both the upper interdigital region and the lower interdigital region comprise a plurality of interdigital bars arranged side by side at intervals and a bus bar region arranged at one end of the interdigital bars and connected to all the interdigital bars. The plurality of interdigital bars in the upper interdigital region and the plurality of interdigital bars in the lower interdigital region are arranged in an interdigital and cross arrangement. Both the upper interdigital region and the lower interdigital region are divided into functional areas D. The functional areas D are provided with a metal compound film layer obtained based on a chemical reaction. The resonator, the filter and the forming method with the function of suppressing heterogeneous mode ripples achieve the function of optimizing and attenuating heterogeneous mode propagation by changing the reflection characteristics of the functional areas.

Description

Technical Field

[0001] The present invention relates to the technical field of SAW resonators / filters, and in particular to a resonator, a filter and a molding method capable of suppressing heterogeneous mode ripples. Background Art

[0002] With the advancement of SAW resonator / filter technology, high Q, high isolation, and low loss performance resonators / filters have been widely studied, especially filter devices based on composite film substrates (bonded substrates / multilayer film substrates) and LiNbO3 piezoelectric thin films. However, products based on composite film substrates and LiNbO3 piezoelectric thin film manufacturing technology will cause serious heterogeneous mode ripples.

[0003] like Fig.14 As shown in the figure, in the comparative form of the product under the prior art, the heterogeneous mode ripples shown by arrows R1 to R5 appear between the resonant frequency and the anti-resonant frequency. Disadvantages: The SAW surface acoustic wave product of the product realized by the semiconductor process based on the composite film substrate and the LiNbO3 piezoelectric film manufacturing technology will have strong heterogeneous mode ripples when the sound wave propagates in the typical interdigital structure ( Fig.14 R1~R5), which leads to uneven filter band, unstable performance and large insertion loss fluctuation. Summary of the invention

[0004] Based on the technical problems existing in the background technology, the present invention proposes a resonator, a filter and a molding method with the function of suppressing heterogeneous mode ripples, and optimizes the attenuation of heterogeneous mode propagation in the passband by changing the reflection characteristics of the functional area.

[0005] The resonator with the function of suppressing heterogeneous mode ripples proposed by the present invention comprises a wafer substrate and an interdigitated metal layer arranged in sequence from bottom to top, wherein the interdigitated metal layer comprises an upper interdigitated region and a lower interdigitated region, each of which comprises a plurality of interdigitated bars arranged side by side at intervals and a bus bar region arranged at one end of the interdigitated bars and connected to all the interdigitated bars, the plurality of interdigitated bars in the upper interdigitated region and the plurality of interdigitated bars in the lower interdigitated region are arranged in an interdigitated and crossed manner, the upper interdigitated region and the lower interdigitated region are divided into functional regions D, and the upper part of the interdigitated bars in the functional region D is covered with a metal compound film layer based on a chemical reaction.

[0006] Furthermore, the functional area D is extended along the arrangement direction of the interdigitated strips, and the functional area D covers all or part of the ends of the interdigitated strips in the upper interdigitated area or the lower interdigitated area.

[0007] Furthermore, the width of the functional area D is 0.3λ-0.6λ, the thickness of the metal compound film layer is 1%λ~3%λ, λ represents the wavelength of sound waves propagating in the piezoelectric crystal, and the density of the metal compound in the metal compound film layer needs to be greater than the density of the interdigitated metal.

[0008] The filter with the function of suppressing heterogeneous mode ripples comprises a housing and a resonator arranged in the housing, wherein the resonator is the resonator as described above.

[0009] Furthermore, the interdigitated metal layer is arranged on the wafer substrate, and the upper interdigitated area and the lower interdigitated area are divided into functional areas C. The upper part of the interdigitated strips in the functional area C is covered with a metal compound film layer based on chemical reaction, and the upper part of the wafer substrate in the functional area C is subjected to substrate etching to obtain an etching area.

[0010] Furthermore, the functional area C is extended along the arrangement direction of the interdigitated strips, the etching area is arranged in the gap position between the interdigitated strips in the upper interdigitated area and the interdigitated strips in the lower interdigitated area, and the functional area C does not cover the ends of the interdigitated strips.

[0011] A method for forming a resonator with the function of suppressing heterogeneous mode ripples comprises the following steps:

[0012] The structure composed of the wafer substrate and the interdigitated metal layer is divided into functional areas to obtain functional area C and functional area D;

[0013] Injecting gaseous / liquid / solid reactants onto the interdigitated metal layer by ion implantation, etching sputtering reaction, and reactive ion beam polishing techniques;

[0014] The interdigitated strips in the interdigitated metal layer located in the functional area D react chemically with the injected reactants to obtain metal compounds, and the obtained metal compounds will cover the interdigitated strips undergoing the chemical reaction to form a metal compound film layer;

[0015] When the thickness of the metal compound film layer is 1%λ to 3%λ, the injection of reactants is stopped, and the setting of the metal compound film layer is completed.

[0016] Furthermore, the interdigitated strips located in the functional area C react chemically with the injected reactants to obtain metal compounds, and the obtained metal compounds will cover the interdigitated strips undergoing the chemical reaction to form a metal compound film layer;

[0017] The wafer substrate in the functional area C is etched by etching and sputtering reaction to obtain an etched area, and the etched area is arranged at the relative gap position between the interdigital strips in the upper interdigital area and the interdigital strips in the lower interdigital area.

[0018] The advantages of the resonator, filter and molding method with the function of suppressing heterogeneous mode ripples provided by the present invention are: the resonator, filter and molding method with the function of suppressing heterogeneous mode ripples provided in the structure of the present invention carry out a chemical reaction on the divided functional area D to obtain a metal compound film layer, and the density of the metal compound in the metal compound film layer needs to be greater than the density of the metal of the interdigitated strips, so as to change the metal film material properties of the specific area and the reflection characteristics of the functional area, so as to achieve the effect of optimizing the attenuation of heterogeneous mode ripple propagation, so that the filter has a flat band, stable performance, and small insertion loss fluctuation, and can complete the design of various interdigitated electrode structures, and the process flow is simple, saving production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a structural schematic diagram of the present invention;

[0020] Figure 2 A schematic diagram of a chemical reaction between a reactant and the interdigitated strips of the interdigitated metal layer;

[0021] Figure 3 It is a simplified top view of the resonator;

[0022] Figure 4 Schematic diagram of the structure of the metal compound in the top region of the IDT electrode finger formed after the functional region D is treated by chemical reaction;

[0023] Figure 5 is a schematic diagram of the structure of a multilayer film substrate;

[0024] Figure 6 is a schematic diagram of the structure of the bonding substrate;

[0025] Figure 7 It is a schematic diagram of the structure of the LiNbO3 piezoelectric substrate;

[0026] Figure 8 It is a schematic diagram of the structure of functional areas C and D after processing;

[0027] Fig. 9 for Figure 8 A top view of

[0028] Fig.10 It is a schematic diagram of the structure of the multilayer thin film substrate after etching the functional area C;

[0029] Fig.11 It is a schematic diagram of the structure of the bonding substrate after etching the functional area C;

[0030] Fig.12 Schematic diagram of the structure of the LiNbO3 piezoelectric substrate after etching the functional area C;

[0031] Fig.13Schematic diagram of the acoustic wave shape of the resonator in this embodiment;

[0032] Fig.14 It is a schematic diagram of the sound wave morphology with existing heterogeneous mode ripples;

[0033] Fig.15 Schematic diagram of the structure of the metal compound film layer covered on the functional area E based on chemical reaction;

[0034] Among them, 1-upper interdigitated region, 2-lower interdigitated region, 3-interdigitated bar, 4-bus bar region, 5-metal compound film layer, 6-wafer substrate, 7-interdigitated metal layer, 8-etching region, 61-substrate, 62-piezoelectric layer, 63-high resistance film, 64-functional layer, 65-LiNbO3 piezoelectric layer. DETAILED DESCRIPTION

[0035] Below, the technical solution of the present invention is described in detail through specific embodiments. Many specific details are set forth in the following description to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific implementation disclosed below.

[0036] like Figures 1 to 15 As shown, a finger structure proposed in the present invention includes an upper finger region 1 and a lower finger region 2, each of which includes a plurality of finger bars 3 arranged side by side at intervals and a bus bar region 4 arranged at one end of the finger bars 3 and connected to all the finger bars 3, the plurality of finger bars 3 in the upper finger region 1 and the plurality of finger bars 3 in the lower finger region 2 are arranged alternately, the upper finger region 1 and the lower finger region 2 are divided into functional regions D, the upper part of the finger bars 3 in the functional region D is covered with a metal compound film layer 5 based on a chemical reaction.

[0037] Comparative forms of products under existing technologies, such as Fig.14 As shown in the figure, the heterogeneous mode ripples indicated by arrows R1 to R5 appear between the resonant frequency and the anti-resonant frequency. It can be clearly seen from the figure that the prior art has serious heterogeneous mode ripples. In this embodiment, the upper interdigital region 1 and the lower interdigital region 2 are divided into functional areas, and a chemical reaction is performed on the divided functional area D to obtain a metal compound film layer 5. The density of the metal compound in the metal compound film layer 5 needs to be greater than the density of the metal of the interdigital strip 3. Therefore, by changing the material properties of the metal film in a specific area, the reflection characteristics of the functional area are changed, and the following is obtained. Fig.13 The acoustic wave diagram shown achieves the effect of optimizing the attenuation of heterogeneous mode propagation, making the filter band flat, the performance stable, and the insertion loss fluctuation small. It can complete the design of various interdigital electrode structures, and the process flow is simple, saving production costs.

[0038] According to the formula: the propagation speed of the medium V = λ × f0, that is, the wave speed V is equal to the product of the wavelength λ and the vibration frequency f0. It can be seen that for the sound waves propagating in the piezoelectric crystal with a specified tangent (same tangent, same propagation speed), at different device operating frequencies, the wavelengths caused by different frequencies will also be different. The design of the filter device is different according to different operating frequency requirements, using different λ. Therefore, the material parameters below are proportional to λ, that is, inversely proportional to the operating frequency.

[0039] Specifically, Figure 3 and 4 As shown, functional area D (including functional area D1 and functional area D2) is the IDT electrode finger reaction area. The electrode film material in the reaction area is processed into a metal compound through chemical reaction technology. The density of the metal compound film layer must be greater than the metal electrode film layer of the finger strip 3, and at the same time greater than the density of other metal electrode film layers.

[0040] In this embodiment, the functional area D is extended along the arrangement direction of the interdigitated strips 3, and the functional area D covers all or part of the ends of the interdigitated strips 3 in the upper interdigitated area 1 or the lower interdigitated area 2; since the upper interdigitated area 1 or the lower interdigitated area 2 is relatively spaced and crossed, the functional area D includes the functional area D1 and the functional area D2, wherein the functional area D1 is located at the end of the interdigitated strip 3 in the lower interdigitated area 2 and covers the end of the interdigitated strip 3, and the functional area D2 is located at the end of the interdigitated strip 3 in the upper interdigitated area 1 and covers the end of the interdigitated strip 3. Due to the crossing of the interdigitated strips 3 in the upper interdigitated area 1 and the lower interdigitated area 2, both the functional area D1 and the functional area D2 partially cover the interdigitated strips 3 in the upper interdigitated area 1 and the lower interdigitated area 2, and it is not ruled out that the chemical reaction area is located in the functional area E, and the functional area E is the IDT electrode interdigitation.

[0041] The film thickness of the interdigitated strip 3 is preferably (5%λ~12%λ) (the actual process is approximately: 0.01um~0.85um); the film thickness of the metal compound film layer 5 is preferably (1%λ~3%λ) (the actual process is approximately: 0.01um~0.06um); the width of the functional area D (metal compound area) is preferably (0.3λ-0.6λ).

[0042] In this embodiment, a resonator with the function of suppressing heterogeneous mode ripples is disclosed, including a wafer substrate 6 and an interdigitated metal layer 7 arranged in sequence from bottom to top, and the interdigitated metal layer 7 is the interdigitated structure mentioned above.

[0043] After the resonator is formed based on the interdigitated metal layer 7, wherein the interdigitated metal layer 7 is arranged on the wafer substrate 6, functional areas are divided on the structure composed of the interdigitated metal layer 7 and the wafer substrate 6, and are divided into functional areas A, functional areas B, functional areas C, functional areas D and functional areas E, wherein functional area A corresponds to the bus bar area 4, functional area B corresponds to the virtual finger electrode, functional area C corresponds to the GAP, functional area D corresponds to the IDT electrode reaction area, and functional area E corresponds to the IDT electrode interdigitated finger.

[0044] When a chemical reaction is carried out on the functional area D, a corresponding chemical reaction is also carried out on the functional area C, specifically: the upper part of the interdigitated strips 3 in the functional area C is covered with a metal compound film layer 5 based on a chemical reaction, and the upper part of the wafer substrate 6 in the functional area C is subjected to substrate etching to obtain an etching area 8, and the functional area C is extended along the arrangement direction of the interdigitated strips 3, and the etching area 8 is arranged in the relative gap position between the interdigitated strips 3 in the upper interdigitated area 1 and the interdigitated strips 3 in the lower interdigitated area 2, and the functional area C does not cover the end of the interdigitated strips 3.

[0045] In this embodiment, the wafer substrate 6 is preferably a composite substrate and a LiNbO3 piezoelectric substrate, wherein the composite substrate is preferably a bonding substrate and a multilayer thin film substrate. In the bonding substrate, the wafer substrate 6 is composed of a backing substrate 61 and a piezoelectric layer 62, and the piezoelectric layer 62 is arranged on the backing substrate 61; in the multilayer thin film substrate, the wafer substrate 6 includes a backing substrate 61, a high-resistance film 63, a functional layer 64 and a piezoelectric layer 62 arranged in sequence from bottom to top; in the LiNbO3 piezoelectric substrate, the wafer substrate 6 includes a LiNbO3 piezoelectric layer 65.

[0046] The etched area 8 at the functional area C is formed on the piezoelectric layer 62. In appearance, the piezoelectric layer 62 is etched into an uneven structure, which can effectively change the reflection characteristics of the functional area, thereby achieving the effect of optimizing the attenuation of heterogeneous mode propagation.

[0047] For the piezoelectric layer 62, the elastic wave propagation direction It is determined by the Euler angles (Φ, θ, ψ) of the piezoelectric single crystal, preferably (35-60) degree YX-cut LiTaO3, and the thickness is preferably (0.2λ~0.5λ100nm~4000nm).

[0048] For the substrate 61, high-resistance silicon (Si) is preferred, and the resistivity is preferably above 100Ωcm, more preferably above 1000Ωcm, and further preferably above 4000Ωcm. The preferred crystal phase is (001) / (100) / (010), the preferred crystal plane is (100) / (110) / (111), and the thickness is greater than 100um; for the high-resistance film 63, polycrystalline silicon (Poly-Si) is preferred, and the thickness is (100nm~1000nm); for the functional layer 64, SiO2 is preferred, and the thickness is (0.2λ~0.6λ100nm~4500nm).

[0049] For LiNbO3 piezoelectric substrate, the Euler angles ( The cutting angle of LiNbO3 in the expression is Piezoelectric material with ψ=0±10°, θ=38±10°; or Piezoelectric material with ψ=0±10°, θ=-85±15°; or ψ=0±10°、θ=131±15°or The piezoelectric material has an angle of θ = -90 ± 10° and a thickness of more than 100 um.

[0050] As an embodiment

[0051] Piezoelectric film: YX-cut LiTaO3 film with a cutting angle of 42°;

[0052] IDT electrode interdigitation (functional region E) cross width = 20λ, dummy electrode is 2λ single side, Gap (functional regions C1 and C2) is 1um. λ = 2μm, λ is the wavelength determined by the electrode interdigitation distance; duty cycle in IDT electrode interdigitation (functional region E) = 0.3~0.7, IDT electrode interdigitation (functional region E) film thickness = 8%λ, metal compound film thickness = 2%λ, LiTaO3 film thickness = 0.2λ~0.5λ, silicon dioxide film thickness constituting the bonding material layer = 0.2λ~0.6λ.

[0053] In addition, this embodiment discloses a filter having the function of suppressing heterogeneous mode ripples in a passband, comprising a housing and a resonator disposed in the housing, wherein the resonator is the resonator as described above.

[0054] In this embodiment, a method for forming a resonator having the function of suppressing heterogeneous mode ripples is disclosed, comprising the following steps:

[0055] S1, dividing the structure composed of the wafer substrate 6 and the interdigitated metal layer 7 into functional areas to obtain functional areas C and functional areas D;

[0056] S2, injecting gaseous / liquid / solid reactants onto the interdigitated metal layer 7 by ion implantation, etching sputtering reaction, and reactive ion beam polishing technology;

[0057] The gas may be O2 / CF4 / NF3 / Ar / N2 / CHF3, etc., the liquid may be HF / HCl / H2SO4 / CeO2, etc., and the solid may be SiO2, etc. The injection flow rate of these reactants may affect the rate of the chemical reaction. In the specific use process, the reaction rate of the reactants may be controlled by controlling the injection flow rate of the reactants.

[0058] S3, the interdigitated strips 3 in the interdigitated metal layer 7 located in the functional area D react chemically with the injected reactant to obtain a metal compound, and the obtained metal compound will cover the interdigitated strips 3 undergoing the chemical reaction to form a metal compound film layer 5; the interdigitated strips 3 located in the functional area C react chemically with the injected reactant to obtain a metal compound, and the obtained metal compound will cover the interdigitated strips 3 undergoing the chemical reaction to form a metal compound film layer 5;

[0059] The wafer substrate 6 in the functional area C is etched by etching sputtering reaction to obtain an etched area 8, and the etched area 8 is arranged at the gap position between the interdigital strips 3 in the upper interdigital area 1 and the interdigital strips 3 in the lower interdigital area 2;

[0060] S4. When the thickness of the metal compound film layer 5 is 1%λ to 3%λ, the injection of reactants is stopped, and the setting of the metal compound film layer 5 is completed.

[0061] Through steps S1 to S4, a specific structure is treated by chemical reaction to change the properties of the metal film material, thereby changing the reflection characteristics of the functional area to achieve the effect of suppressing the propagation of the heterogeneous mode, and obtaining the following Fig.13 The curve results shown are similar to those shown in Fig.14 By comparing with the existing resonators with heterogeneous mode ripples, it can be clearly seen that this embodiment has a higher suppression effect on heterogeneous mode ripples. Compared with the existing process, it meets the optimization of various structures of the device, the performance is significantly improved, the process flow is simple, and the cost is low.

[0062] It should be noted that the functional area C (including C1 and C2) and the functional area D (including D1 and D2) in this embodiment are not limited to the above-mentioned range. The metal compound film layer 5 obtained by the chemical reaction between the above-mentioned reactants and the interdigitated strips 3 can also occur in the functional area E, for example Fig.15 As shown, a reaction area is set by dividing the functional area E into a U-shape, in which the reactants chemically react with the interdigitated strips 3 to obtain a metal compound film layer 5. By changing the material properties of the metal film in the reaction area, the reflection properties of the functional area are changed, thereby achieving the effect of optimizing the attenuation of heterogeneous mode propagation.

[0063] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A resonator having the function of suppressing heterogeneous mode ripples, characterized in that: A wafer substrate (6) and an interdigitated metal layer (7) are arranged in sequence from bottom to top, the interdigitated metal layer (7) comprising an upper interdigitated region (1) and a lower interdigitated region (2), the upper interdigitated region (1) and the lower interdigitated region (2) both comprising a plurality of interdigitated strips (3) arranged in parallel at intervals and arranged at one end of the interdigitated strips (3) and connected to all the interdigitated strips (3), the plurality of interdigitated strips (3) of the upper interdigitated region (1) and the plurality of interdigitated strips (3) of the lower interdigitated region (2) are arranged in an interdigitated and cross-arranged manner, the upper interdigitated region (1) and the lower interdigitated region (2) are divided into functional regions D, the upper part of the interdigitated strips (3) in the functional region D is covered with a metal compound film layer (5) based on a chemical reaction; The specific method of forming the resonator is as follows: Dividing the structure composed of the wafer substrate (6) and the interdigitated metal layer (7) into functional areas to obtain a functional area C and a functional area D; Injecting gaseous / liquid / solid reactants onto the interdigitated metal layer (7) by ion implantation, etching sputtering reaction, reactive ion beam polishing or other techniques; The interdigitated strips (3) in the interdigitated metal layer (7) located in the functional area D undergo a chemical reaction with the injected reactant to obtain a metal compound, and the obtained metal compound will cover the interdigitated strips (3) undergoing the chemical reaction to form a metal compound film layer (5); When the thickness of the metal compound film layer (5) is 1%λ~3%λ, the injection of the reactant is stopped, and the setting of the metal compound film layer (5) is completed, and λ represents the wavelength of the sound wave propagating in the piezoelectric crystal.

2. The resonator having the function of suppressing heterogeneous mode ripples according to claim 1 is characterized in that: The functional area D is extended along the arrangement direction of the interdigitated strips (3), and the functional area D covers all or part of the ends of the interdigitated strips (3) in the upper interdigitated area (1) or the lower interdigitated area (2).

3. The resonator having the function of suppressing heterogeneous mode ripples according to claim 1 is characterized in that: The width of the functional area D is 0.3λ-0.6λ, and the density of the metal compound in the metal compound film layer (5) is greater than the density of the metal in the interdigitated strips (3).

4. The resonator with the function of suppressing heterogeneous mode ripples according to claim 1 is characterized in that: The upper interdigitated region (1) and the lower interdigitated region (2) are both divided into functional regions C, the upper portion of the interdigitated strips (3) in the functional region C is covered with a metal compound film layer (5) based on a chemical reaction, and the upper portion of the wafer substrate (6) in the functional region C is subjected to substrate etching to obtain an etching region (8).

5. The resonator having the function of suppressing heterogeneous mode ripples according to claim 4 is characterized in that: The functional area C is arranged to extend along the arrangement direction of the interdigitated strips (3), the etching area (8) is arranged at the gap position between the interdigitated strips (3) in the upper interdigitated area (1) and the interdigitated strips (3) in the lower interdigitated area (2), and the functional area C does not cover the end of the interdigitated strips (3).

6. A filter having the function of suppressing heterogeneous mode ripples, characterized in that: The invention comprises a shell and a resonator arranged in the shell, wherein the resonator is the resonator according to any one of claims 1 to 5.

7. The resonator according to claim 1, characterized in that The interdigitated strips (3) located in the functional area C undergo a chemical reaction with the injected reactant to obtain a metal compound, and the obtained metal compound will cover the interdigitated strips (3) undergoing the chemical reaction to form a metal compound film layer (5); The wafer substrate (6) located in the functional area C is etched by etching the substrate through a sputtering reaction to obtain an etched area (8), wherein the etched area (8) is arranged at a relative gap position between the interdigitated strips (3) in the upper interdigitated area (1) and the interdigitated strips (3) in the lower interdigitated area (2).

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