Lamb wave resonator with high temperature stability and preparation method thereof

Abstract

The invention discloses a Lamb wave resonator with high temperature stability and a preparation method thereof, and relates to the technical field of semiconductor devices. The structure of the Lamb wave resonator comprises a first temperature compensation layer with a cavity structure, a suspended potential bottom electrode, a piezoelectric layer, a second temperature compensation layer and a top electrode from bottom to top, a plurality of groove structures are further arranged, the groove structures vertically and downwards penetrate through the top electrode and the second temperature compensation layer till the piezoelectric layer, and the top electrode is separated by the groove structures to form an interdigital shape; the surfaces of the groove structure and the top electrode are covered with passivation layers; and an Au cushion layer is arranged on the surface of the busbar of the top electrode. The temperature compensation layers are distributed at the two ends of the piezoelectric layer, the groove structure with the specific depth is arranged, and through cooperation of the temperature compensation layers and the groove structure, the electromechanical coupling coefficient of the resonator is improved while the temperature drift coefficient of the resonant frequency of the resonator is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor devices, and in particular to a Lamb wave resonator with high temperature stability and a preparation method thereof. Background Art

[0002] Resonators are core components for signal transmission and processing in the field of communications technology. With the advancement of mobile communications, fast, stable, and efficient data transmission requires resonators with high frequency, wide bandwidth, and high temperature stability. Lamb wave resonators are microelectromechanical systems (MEMS) acoustic devices based on piezoelectric materials. They achieve signal processing by exciting Lamb waves (elastic waves propagating through a plate-like structure) in a piezoelectric film. They are widely used in the field of communications technology.

[0003] The structure of a Lamb wave resonator generally consists of a piezoelectric layer, typically an AlN, LiNbO3, or AlScN thin film, whose thickness matches the wavelength to enable Lamb wave propagation. It also includes interdigitated electrodes, which are essentially metal (such as molybdenum or aluminum) electrodes arranged in an interdigitated structure. The electric field excites the piezoelectric layer to produce mechanical vibrations. Based on material classification, Lamb wave resonators include lithium niobate (LiNbO3)-based Lamb wave resonators and aluminum nitride (AlN / AlScN)-based Lamb wave resonators.

[0004] The aluminum nitride Lamb wave resonator has standing waves in the direction of the interdigital array and the thickness of the film. The resonant frequency is high and can be adjusted by the interdigital width, which meets the current development trend of MEMS resonators.

[0005] However, the electromechanical coupling coefficient of Lamb wave resonators is relatively modest, and the frequency drift caused by temperature changes will affect the effective passband range of Lamb wave filters. Therefore, the development of current communication technology has put forward the need to further improve the temperature stability of the resonant frequency of Lamb wave resonators.

[0006] The electromechanical coupling coefficient of traditional aluminum nitride (AlN / AlScN) Lamb wave resonators is moderate. Scandium (Sc) doping can increase the electromechanical coupling coefficient of the resonator, leaving more margin for temperature compensation. The traditional temperature compensation method is to add a temperature compensation layer to the resonator to increase the temperature stability of the resonant frequency. The temperature drift coefficient of the commonly used SiO2 temperature compensation layer is opposite to that of the piezoelectric layer. The temperature drift coefficient of the composite film of SiO2 and piezoelectric layer can be close to 0 ppm / °C. However, the commonly used SiO2 temperature compensation film has no piezoelectric properties, which leads to a decrease in the electromechanical coupling coefficient of the Lamb wave resonator after the temperature compensation layer is used, which in turn affects the passband width of the resonator. Summary of the Invention

[0007] To address the shortcomings of the above-mentioned prior art, the present invention provides a Lamb wave resonator with high temperature stability and a method for preparing the same, while simultaneously improving the resonant frequency and electromechanical coupling coefficient of the Lamb wave resonator. By providing a first temperature compensation layer and a second temperature compensation layer on the upper and lower sides of the piezoelectric layer, respectively, the Lamb wave resonator has a smaller frequency temperature drift coefficient; while improving the temperature performance of the resonator, the impact on the electromechanical coupling coefficient is reduced. Furthermore, a groove structure is etched between the interdigitated electrodes of the resonator to change the resonant mode of the resonator, coupling more lateral fluctuations into the main mode of the resonator, thereby increasing the temperature stability of the resonator while compensating for the negative effect of the temperature compensation material on the electromechanical coupling coefficient. This is achieved specifically through the following technologies.

[0008] A Lamb wave resonator with high temperature stability, comprising, from bottom to top, a first temperature compensation layer containing a cavity structure, a floating potential bottom electrode, a piezoelectric layer, a second temperature compensation layer, and a top electrode; the first temperature compensation layer and the second temperature compensation layer have the same thickness;

[0009] A plurality of groove structures are further provided, the groove structures vertically passing through the top electrode and the second temperature compensation layer downward to the piezoelectric layer, and the top electrode is formed into an interdigitated shape by the separation of the groove structures;

[0010] The surfaces of the groove structure and the top electrode are covered with a passivation layer; and an Au pad layer is provided on the surface of the busbar of the top electrode.

[0011] Furthermore, the depth of the groove structure is based on the bottom reaching a position 0.2-0.8 times the thickness of the piezoelectric layer.

[0012] Preferably, the depth of the groove structure is such that the bottom reaches a position 0.4 times the thickness of the piezoelectric layer.

[0013] The groove structure is generally formed by photolithography and etching. The depth of the groove structure is determined to be 0.2-0.8 times (preferably 0.4 times) the thickness of the piezoelectric layer.

[0014] Furthermore, the thickness of the first temperature compensation layer is 50-150 nm; the thickness of the second temperature compensation layer is 50-150 nm.

[0015] Furthermore, the thickness of the first temperature compensation layer is 100 nm; the thickness of the second temperature compensation layer is 100 nm.

[0016] Optionally, the first temperature compensation layer and the second temperature compensation layer are made of SiO 2 material.

[0017] Furthermore, the piezoelectric layer has a thickness of 400-1000 nm.

[0018] Furthermore, the piezoelectric layer has a thickness of 1000 nm.

[0019] Optionally, the piezoelectric layer is made of Sc 0.2 Al 0.8 Piezoelectric film composed of N material.

[0020] Furthermore, the thickness of the floating potential bottom electrode is 150-220 nm, and the thickness of the top electrode is 150-220 nm.

[0021] Furthermore, the thickness of the floating potential bottom electrode is 200 nm, and the thickness of the top electrode is 200 nm.

[0022] Optionally, the floating potential bottom electrode and / or the top electrode are made of metal Mo.

[0023] Optionally, the passivation layer may be made of aluminum nitride (AlN) material.

[0024] Optionally, the height of the cavity structure is set to 1.4 μm (1400 nm).

[0025] Optionally, the filling material of the cavity sacrificial layer is set to Si.

[0026] The resonance of the Lamb wave resonator mainly occurs in the area between the lower part of the interdigital electrode and the bottom electrode. The present invention places a first temperature compensation layer and a second temperature compensation layer of the same thickness on both sides of the piezoelectric film, forming an energy reflection structure symmetrically on both sides of the piezoelectric film, thereby reducing the temperature drift coefficient of the resonator. A groove structure is provided between the interdigital electrodes of the resonator to change the resonant mode of the resonator and improve the temperature stability of the resonator. At the same time, the resonant mode of the resonator is changed to couple more lateral fluctuations into the main mode of the resonator, thereby compensating for the negative effect of the two temperature compensation layer materials on the electromechanical coupling coefficient. The present invention changes the resonant frequency by changing the width of the interdigital fingers, and can form a series resonator and a parallel resonator, thereby building a Lamb wave resonator with good bandwidth and temperature stability.

[0027] Specifically, the temperature drift coefficients of the first and second temperature compensation layers are positive, in contrast to the negative coefficients of the piezoelectric film. This effectively compensates for temperature drift in the resonator's resonant frequency. The two temperature compensation layers reduce the rate at which the resonator's elastic modulus changes with temperature, thereby reducing the temperature drift coefficient of the resonator's resonant frequency. Since the first and second temperature compensation layers lack piezoelectricity, reducing the resonator's temperature drift coefficient also reduces the piezoelectricity of the film, thereby reducing the resonator's effective electromechanical coupling coefficient.

[0028] To address the aforementioned issues, the present invention incorporates a groove structure between the two interdigitated fingers of the Lamb wave resonator's top electrode. This groove structure divides the Lamb wave resonator plate into a structure with multiple parallel resonant units, each of which has both lateral and longitudinal free boundaries. The resonant waves formed by the lateral free boundaries have a relatively small temperature drift coefficient, and the lateral waves couple into the main mode, further reducing the resonator's temperature drift coefficient. The groove structure also reduces the parasitic capacitance between the interdigitated electrodes, increasing the Lamb wave resonator's electromechanical coupling coefficient. Therefore, while improving temperature performance, the groove structure can offset the effect of the two temperature compensation layers on the resonator's effective electromechanical coupling coefficient.

[0029] The present invention also provides a method for preparing any one of the above-mentioned Lamb wave resonators with high temperature stability, comprising the following steps:

[0030] A seed layer, a piezoelectric layer, a floating potential bottom electrode, and a first temperature compensation layer are sequentially grown on the surface of a first wafer from bottom to top, wherein a sacrificial layer is wrapped inside the first temperature compensation layer; a first bonding layer is spin-coated on the surface of the first temperature compensation layer; and a second bonding layer is spin-coated on the surface of a second wafer;

[0031] Bonding the first bonding layer on the first wafer to the second bonding layer on the second wafer, and removing the first wafer and the seed layer;

[0032] sequentially growing a second temperature compensation layer and a top electrode on the surface of the exposed piezoelectric layer from bottom to top;

[0033] A trench structure is etched, a covering passivation layer is grown on the surface of the trench structure and the top electrode, and a release hole is etched to release the material of the sacrificial layer to form a cavity structure.

[0034] In the above-mentioned Lamb wave resonator preparation method, in order to improve the growth quality of the piezoelectric layer, a thin film transfer process is adopted to manufacture the resonator. The bonding process of the piezoelectric layer transfer adopts Au-Au bonding.

[0035] Further optionally, the piezoelectric film is obtained by a wafer bonding method, and its piezoelectricity is better than that of a method of forward growth on an electrode.

[0036] Optionally, the piezoelectric layer can be formed by depositing corresponding materials on the surface of the floating potential bottom electrode by magnetron sputtering deposition.

[0037] The trench structure can be processed using the same photoresist pattern as that used for the interdigital electrodes, and the second temperature compensation layer and the piezoelectric layer are both etched using this photoresist pattern.

[0038] Specifically, the preparation method of the Lamb wave resonator is:

[0039] (1) A seed layer, a piezoelectric layer, a first temperature compensation layer and a Si sacrificial layer are sequentially grown on the first high-resistance Si wafer (the first wafer), and the first temperature compensation layer wraps the Si sacrificial layer inside. The surface is polished flat, and an Au bonding layer (the first bonding layer) is spin-coated on the surface.

[0040] In addition, a high-resistance Si wafer (second wafer) was selected, and an Au bonding layer (second bonding layer) was spin-coated on its surface.

[0041] (2) Bonding the first wafer on which the first bonding layer is spin-coated and the second wafer on which the second bonding layer is spin-coated, and removing wafer 1 so that the seed layer is exposed and located on the top of the second wafer;

[0042] (3) Remove the seed layer and grow a second temperature compensation layer and a top electrode on top of the piezoelectric layer.

[0043] (4) According to the pre-designed depth, a trapezoidal groove structure of different depths is etched; a passivation layer is grown on the surface of the top electrode and the surface of the groove structure, and a release hole is etched to release the material of the sacrificial layer to form a cavity structure, thereby obtaining a Lamb wave resonator.

[0044] The first temperature compensation layer and the second temperature compensation layer can be grown and prepared by plasma enhanced chemical vapor deposition. The two temperature compensation layers prepared have the effect of reducing the temperature drift coefficient. The first temperature compensation layer can also serve as an isolation material for the sacrificial layer.

[0045] Compared with the prior art, the present invention is beneficial in that: by providing temperature compensation layers on the upper and lower sides of the piezoelectric layer and designing a groove structure between the interdigitated fingers of the top electrode, a Lamb wave resonator with both high electromechanical coupling coefficient and high temperature stability is obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 A schematic structural diagram of a Lamb wave resonator with high temperature stability provided by the present invention.

[0047] Figure 2 This is a process flow chart of the Lamb wave resonator provided by the present invention.

[0048] Figure 3 This is the change in the main mode shape of the Lamb wave resonator prepared in Example 1.

[0049] Figure 4 This is the temperature drift curve of the Lamb wave resonator prepared in Example 1 at different temperatures.

[0050] Figure 5 This is the change in the main mode vibration shape of the resonator in comparative example 1 where the groove structure is not etched to the piezoelectric layer.

[0051] Figure 6 This is the temperature drift curve of the Lamb wave resonator prepared in Example 2 at different temperatures.

[0052] Figure 7 Temperature drift curves of the resonator prepared in Comparative Example 1 (the groove structure is not etched to the piezoelectric layer) at different temperatures.

[0053] In the figure: 10, piezoelectric layer; 11, release hole; 12, groove structure; 20, probe pad; 21, bus; 22, top electrode; 23, floating potential bottom electrode; 30, first temperature compensation layer; 31, second temperature compensation layer; 32, cavity structure. DETAILED DESCRIPTION

[0054] The technical solutions of the present invention are described clearly and completely below. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0055] The Lamb wave resonator provided by the present invention has a structure as follows Figure 1 As shown, from bottom to top, it includes a first temperature compensation layer 30 containing a cavity structure 32, a floating potential bottom electrode 23, a piezoelectric layer 10, a second temperature compensation layer 31, and a top electrode 22;

[0056] A plurality of groove structures 32 are further provided, the groove structures 32 vertically passing through the top electrode 22 and the second temperature compensation layer 31 downward to the piezoelectric layer 10 , and the top electrode 22 forms an interdigitated shape under the influence of the groove structures 12 ;

[0057] The surfaces of the groove structure 32 and the top electrode 22 are covered with a passivation layer; an Au pad layer is provided on the surface of the bus bar 21 of the top electrode 22;

[0058] A release hole 11 is further provided, and the release hole 11 is communicated with the cavity structure 32 ; the bus bar 21 is connected to the probe pad 20 .

[0059] The busbar is the conductive busbar part of the interdigital electrode (top electrode) and is a conventional component of the interdigital electrode.

[0060] The probe pad is the contact part of the lower needle of the RF probe used to test the performance of the resonator, and is used to reduce the resistance of the connecting wire of the resonator.

[0061] In some implementation cases of the present invention, the piezoelectric layer, the top electrode, and the floating potential bottom electrode are all made of commonly used materials.

[0062] Optionally, the depth of the groove structure is based on the bottom reaching a position 0.2-0.8 times the thickness of the piezoelectric layer.

[0063] Optionally, the depth of the groove structure is based on the position where the bottom reaches 0.4 times the thickness of the piezoelectric layer.

[0064] The groove structure is generally formed by photolithography and etching, and the depth of the groove structure is based on the final etching depth being 0.2-0.8 times the thickness of the piezoelectric layer.

[0065] Preferably, the depth of the groove structure is determined to be 0.4 times the thickness of the piezoelectric layer. For example, when the thickness of the piezoelectric layer is 1000 nm, the depth of the groove structure etched in the piezoelectric layer is 400 nm.

[0066] Optionally, the piezoelectric layer is made of Sc 0.2 Al 0.8 A thin film composed of N material.

[0067] Optionally, the piezoelectric layer has a thickness of 400-1000 nm, specifically 1000 nm.

[0068] Optionally, both the top electrode and the floating potential bottom electrode may be made of a thin film material composed of metal Mo.

[0069] Optionally, the thickness of the floating potential bottom electrode is 150-220 nm, and the thickness of the top electrode is 150-220 nm. Specifically, the thickness of the floating potential bottom electrode is 200 nm, and the thickness of the top electrode is 200 nm.

[0070] Optionally, the first temperature compensation layer and the second temperature compensation layer may be made of a thin film material composed of SiO2.

[0071] Optionally, the thickness of the first temperature compensation layer and the second temperature compensation layer may both be 50-150 nm, specifically 100 nm.

[0072] Optionally, the passivation layer may be made of aluminum nitride (AlN) material.

[0073] Optionally, the depth of the cavity structure (sacrificial layer) is set to 1.4 μm (1,400 nm).

[0074] In some other embodiments of the present invention, a method for preparing a Lamb wave resonator is provided, comprising the following steps:

[0075] A seed layer, a piezoelectric layer, a floating potential bottom electrode, and a first temperature compensation layer are sequentially grown on the surface of a first wafer from bottom to top, wherein a sacrificial layer is wrapped inside the first temperature compensation layer; a first bonding layer is spin-coated on the surface of the first temperature compensation layer; and a second bonding layer is spin-coated on the surface of a second wafer;

[0076] Bonding the first bonding layer on the first wafer to the second bonding layer on the second wafer, and removing the first wafer and the seed layer;

[0077] sequentially growing a second temperature compensation layer and a top electrode on the surface of the exposed piezoelectric layer from bottom to top;

[0078] A trench structure is etched, a covering passivation layer is grown on the surface of the trench structure and the top electrode, and a release hole is etched to release the material of the sacrificial layer to form a cavity structure.

[0079] In the above-mentioned method for preparing the Lamb wave resonator, optionally, in order to increase the growth quality of the piezoelectric layer, a thin film transfer process is adopted to process the resonator.

[0080] Optionally, the bonding process for transferring the piezoelectric layer adopts Au-Au bonding.

[0081] Further optionally, the piezoelectric film is obtained by a wafer bonding method, and its piezoelectricity is better than that of a method of forward growth on an electrode.

[0082] Optionally, the piezoelectric layer can be formed by depositing corresponding materials on the surface of the floating potential bottom electrode by magnetron sputtering deposition.

[0083] The trench structure can be processed using the same photoresist pattern as that used for the interdigital electrodes, and the second temperature compensation layer and the piezoelectric layer are both etched using this photoresist pattern.

[0084] Example 1

[0085] This embodiment discloses a Lamb wave resonator with high temperature stability and a method for preparing the same. The structure of the resonator is as follows: Figure 1 As shown, it mainly includes, from bottom to top, a first temperature compensation layer 30 containing a cavity structure 32, a floating potential bottom electrode 23, a piezoelectric layer (Sc 0.2 Al 0.8 N thin film) 10, a second temperature compensation layer 31, a top electrode 22; the first temperature compensation layer 30 and the second temperature compensation layer 31 have the same thickness;

[0086] A plurality of groove structures 32 are further provided, the groove structures 32 vertically passing through the top electrode 22 and the second temperature compensation layer 31 downward to the piezoelectric layer 10 , and the top electrode 22 forms an interdigitated shape under the influence of the groove structures 12 ;

[0087] The surfaces of the groove structure 32 and the top electrode 22 are covered with a passivation layer; an Au pad layer is provided on the surface of the bus bar 21 of the top electrode 22;

[0088] A release hole 11 is further provided, and the release hole 11 is communicated with the cavity structure 32 ; the bus bar 21 is connected to the probe pad 20 .

[0089] The first temperature compensation layer 30, the second temperature compensation layer 31, and the groove structure 12 collectively improve the temperature performance and electromechanical coupling performance of the Lamb wave resonator. The release hole 11 not only provides a channel for releasing the sacrificial layer, but also acts as a Lamb wave reflection structure, suppressing the divergence of the acoustic wave toward the substrate. The groove structure depth is optimized to 0.4 times the thickness of the piezoelectric film, providing sufficient lateral free boundaries to optimize the vibration mode of the Lamb wave resonator's main mode to Lamb waves in two directions while connecting multiple resonant structures in parallel.

[0090] The Lamb wave resonator provided in this embodiment is based on Figure 2 The process flow shown is used for preparation, and the specific steps are as follows.

[0091] (1) High-quality piezoelectric layer (Sc 0.2 Al 0.8 Preparation of AlN thin film): First, a seed layer composed of aluminum nitride (AlN) material is grown on the first wafer (Wafer 1).

[0092] Sc with a thickness of 1000 nm was grown on the surface of the seed layer. 0.2 Al 0.8 N film, i.e. piezoelectric layer.

[0093] A floating potential bottom electrode composed of metal Mo with a thickness of 200 nm is grown on the surface of the piezoelectric layer.

[0094] (2) A portion of the first temperature compensation layer composed of SiO2 with a thickness of 100 nm is grown on the surface of the floating potential bottom electrode.

[0095] Then, a Si sacrificial layer with a thickness of 1400 nm is grown on the surface of the first temperature compensation layer, and the Si sacrificial layer is etched into a shape matching the shape of the cavity structure through the processes of coating, exposure, development, and etching.

[0096] SiO2 continues to grow around and on the Si sacrificial layer to form the remaining first temperature compensation layer. At this point, the complete first temperature compensation layer wraps the Si sacrificial layer inside.

[0097] This structure can protect the peripheral materials of the cavity structure during the Si release process of the Si sacrificial layer.

[0098] After chemical mechanical polishing is performed on the grown first temperature compensation layer, a first bonding layer composed of Au is grown.

[0099] (3) While performing the above steps (1) and (2), a second bonding layer composed of Au is grown on the surface of the second wafer (Wafer 2).

[0100] (4) The second bonding layer on the surface of the second wafer is brought into contact with the first bonding layer on the surface of the first wafer, and bonding is performed under an environment of 300°C and 1 MPa.

[0101] (5) A combination of dry etching and wet etching is used to remove the first wafer and the seed layer, so that the piezoelectric layer is located on the top layer and exposed; a second temperature compensation layer composed of SiO2 is deposited on the surface of the piezoelectric layer; and an initial top electrode composed of metal Mo is deposited on the surface of the second temperature compensation layer.

[0102] (6) Spin-coating photoresist on the surface of the initial top electrode, etching the initial top electrode into a forked-finger-shaped top electrode, and etching a groove structure in the piezoelectric layer.

[0103] Specifically, the etching process includes etching the top electrode, etching the second temperature compensation layer, and etching the piezoelectric layer in sequence until a 400 nm thick piezoelectric layer is etched. That is, the depth of the trench structure is determined by the bottom reaching 0.4 times the thickness of the piezoelectric layer.

[0104] More specifically, an ICP etcher may be used to etch the initial top electrode and the piezoelectric layer, and a P5000 plasma etcher may be used to etch the second temperature compensation layer.

[0105] More specifically, the etching gases used to etch the initial top electrode, the second temperature compensation layer and the piezoelectric layer are Cl2, FC4 and BCl3 respectively.

[0106] (7) A passivation layer composed of aluminum nitride (AlN) is grown on the surface of the trench structure and the top electrode and patterned. A lift-off process is used to grow the Au pad layer located at the busbar.

[0107] (8) Etching release holes to release the Si film in the sacrificial layer. Specifically, xenon difluoride (XeF2) gas can be used for Si release.

[0108] Figure 3 This figure shows the changes in the main mode shape of the Lamb wave resonator of this embodiment. As can be seen from the figure, the lateral boundaries created by the trench structure promote the coupling of lateral waves into the main mode, allowing the Lamb waves introduced by the trench structure to couple waves in both the film thickness direction and the lateral direction. The trench structure can increase the effective electromechanical coupling coefficient of the Lamb wave resonator.

[0109] The impedance curves of the Lamb wave resonator at different temperatures were tested using a network analyzer and a high and low temperature probe station. Figure 4 As shown. Combined Figure 3 and Figure 4 It can be seen that the effective electromechanical coupling coefficient of the Lamb wave resonator is 5.4%, and the temperature drift coefficient is -7.2 ppm / ℃; while improving the temperature drift coefficient of the resonator, the effective electromechanical coupling coefficient of the resonator is also improved.

[0110] Example 2

[0111] Compared to Example 1, the Lamb wave resonator provided in this embodiment has substantially the same structure as that of Example 1. The difference lies in that the depth of the trench structure is modified in this embodiment. Specifically, the trench structure is etched until the bottom reaches 0.2 times the depth of the piezoelectric layer. Specifically, the trench structure is etched until a 200 nm thick piezoelectric layer is left.

[0112] The impedance curves of the Lamb wave resonator prepared in this embodiment at different temperatures are shown in FIG. Figure 6 The effective electromechanical coupling coefficient of the resonator is 3.1%, and the temperature drift coefficient is -9.3 ppm / °C.

[0113] Comparative Example 1: Resonator in which the groove structure is not etched to the piezoelectric layer

[0114] Compared with Examples 1 and 2, the preparation method of the resonator provided in this comparative example is basically the same as that in Example 1. The difference is that after completing steps (1) to (5) of Example 1, the resonator of this comparative example only etches the top electrode and the second temperature compensation layer in step (6), without etching the piezoelectric layer.

[0115] like Figure 7 As shown in the figure, it can be seen that the effective electromechanical coupling coefficient of the resonator where the trench structure is not etched to the piezoelectric layer is 2.46%, and the temperature drift coefficient is -13.2 ppm / ℃.

[0116] In summary, combined with Figure 4-7 The test results show that the temperature stability of the resonators prepared in the embodiment and comparative example gradually increases as the grooves are etched, and the electromechanical coupling coefficient gradually increases. This shows that by adopting the technical means of the present invention, by providing temperature compensation layers on the upper and lower sides of the piezoelectric layer and introducing a groove structure, the Lamb wave of the resonator couples the waves in both the thickness direction and the transverse direction of the film, thereby improving the temperature drift coefficient of the resonator while also improving the effective electromechanical coupling coefficient of the resonator.

[0117] The above specific embodiments describe the implementation of the present invention in detail, but the present invention is not limited to the specific details of the above embodiments. Within the scope of the claims and technical concept of the present invention, various simple modifications and changes can be made to the technical solution of the present invention, and these simple modifications all fall within the scope of protection of the present invention.

Claims

1. A Lamb wave resonator with high temperature stability, characterized in that: Its structure from bottom to top includes a first temperature compensation layer containing a cavity structure, a floating potential bottom electrode, a piezoelectric layer, a second temperature compensation layer, and a top electrode; the first temperature compensation layer and the second temperature compensation layer have the same thickness; A plurality of groove structures are further provided, the groove structures vertically passing through the top electrode and the second temperature compensation layer downward to the piezoelectric layer, and the top electrode forms an interdigitated shape at the separation of the groove structures; The surfaces of the groove structure and the top electrode are covered with a passivation layer; and an Au pad layer is provided on the surface of the busbar of the top electrode.

2. The Lamb wave resonator with high temperature stability according to claim 1, characterized in that The depth of the groove structure is based on the bottom reaching a position 0.2-0.8 times the thickness of the piezoelectric layer.

3. The Lamb wave resonator with high temperature stability according to claim 2, characterized in that: The depth of the groove structure is based on the position where the bottom reaches 0.4 times the thickness of the piezoelectric layer.

4. The Lamb wave resonator with high temperature stability according to claim 1, characterized in that The thickness of the first temperature compensation layer is 50-150 nm; the thickness of the second temperature compensation layer is 50-150 nm.

5. The Lamb wave resonator with high temperature stability according to claim 4, characterized in that: The thickness of the first temperature compensation layer is 100 nm; the thickness of the second temperature compensation layer is 100 nm.

6. The Lamb wave resonator with high temperature stability according to claim 1, characterized in that The thickness of the piezoelectric layer is 400-1000 nm.

7. The Lamb wave resonator with high temperature stability according to claim 6, characterized in that: The thickness of the piezoelectric layer is 1000 nm.

8. The Lamb wave resonator with high temperature stability according to claim 1, characterized in that The thickness of the floating potential bottom electrode is 150-220 nm, and the thickness of the top electrode is 150-220 nm.

9. The Lamb wave resonator with high temperature stability according to claim 8, characterized in that: The thickness of the floating potential bottom electrode is 200 nm, and the thickness of the top electrode is 200 nm.

10. A method for preparing a Lamb wave resonator with high temperature stability according to any one of claims 1 to 9, characterized in that: The following steps are involved: A seed layer, a piezoelectric layer, a floating potential bottom electrode, and a first temperature compensation layer are sequentially grown on the surface of a first wafer from bottom to top, wherein a sacrificial layer is wrapped inside the first temperature compensation layer; a first bonding layer is spin-coated on the surface of the first temperature compensation layer; and a second bonding layer is spin-coated on the surface of a second wafer; Bonding the first bonding layer on the first wafer to the second bonding layer on the second wafer, and removing the first wafer and the seed layer; sequentially growing a second temperature compensation layer and a top electrode on the surface of the exposed piezoelectric layer from bottom to top; A trench structure is etched, a covering passivation layer is grown on the surface of the trench structure and the top electrode, and a release hole is etched to release the material of the sacrificial layer to form a cavity structure.

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