High-frequency acoustic wave resonator and manufacturing method therefor

Abstract

A high-frequency acoustic wave resonator and a manufacturing method therefor, relating to the field of microelectronic devices. The high-frequency acoustic wave resonator comprises a support substrate (1), a piezoelectric film (2) and interdigital transducers (3) which are sequentially stacked from bottom to top. The sound velocity of the support substrate (1) is not less than 5000 m / s; a target mode of the high-frequency acoustic wave resonator is a quasi-bulk wave mode generated by longitudinal electric field excitation; the thickness of each interdigital transducer (3) is inversely proportional to the material density of the interdigital transducer (3); the sound velocity in the target mode is less than the sound velocity of the support substrate (1). On the basis of a heterogeneous integrated substrate, the structure of the acoustic wave resonator is simplified, and the ohmic loss is reduced and the electromechanical coupling coefficient in a high-order mode is improved.

Description

A high-frequency acoustic wave resonator and its preparation method Technical Field

[0001] The present invention relates to the field of microelectronic devices, and in particular to a high-frequency acoustic wave resonator and a preparation method thereof. Background Art

[0002] The modern communications industry is facing increasingly stringent requirements for signal quality, and competition for communication spectrum resources is intensifying. Low loss, wide bandwidth, tunability, and temperature stability have become universal goals in the communications industry. Acoustic resonators, due to their small size, wide bandwidth, and high Q factor, are currently widely used in the communications field. Acoustic resonators include surface acoustic wave (SAW) resonators and bulk acoustic wave (BAW) resonators.

[0003] In the related art, since the resonant frequency of a BAW resonator is inversely proportional to the thickness of the device, the frequency of the resonator is usually increased by reducing the thickness of the piezoelectric film. However, as the frequency increases, the suspended piezoelectric film gradually becomes thinner, the structure becomes more fragile, and heat dissipation becomes more difficult. And usually, the first-order plate wave mode is excited by the structure of the top interdigitated electrode and the suspended bottom electrode to meet the high-frequency requirements. However, for single-crystal piezoelectric materials, it is very difficult to form a patterned suspended bottom electrode, and the electrode width is small at high frequencies, resulting in large ohmic losses. Therefore, how to simplify the resonator structure, reduce ohmic losses, and make the resonator have a larger electromechanical coupling coefficient becomes the key to achieving high-performance high-frequency applications.

[0004] Summary of the Invention

[0005] To solve the above technical problems, the present application discloses, on one hand, a high-frequency acoustic wave resonator, which includes a supporting substrate, a piezoelectric film, and an interdigital transducer stacked sequentially from bottom to top;

[0006] Among them, the sound velocity of the supporting substrate is not less than 5000 meters per second; the target mode of the high-frequency acoustic wave resonator is a quasi-bulk wave mode generated by longitudinal electric field excitation; the thickness of the interdigital transducer is inversely proportional to the material density of the interdigital transducer; and the sound velocity of the target mode is less than the sound velocity of the supporting substrate.

[0007] In a feasible embodiment, the product of the period of the IDT and the frequency of the target mode is greater than or equal to 80% of the sound velocity of the supporting substrate and less than the sound velocity of the supporting substrate.

[0008] In a feasible embodiment, the quasi-bulk wave mode includes a horizontal shear wave mode, a Lamb wave mode, and a first-order and higher-order modes of a Rayleigh mode.

[0009] In a feasible embodiment, the thickness of the IDT is a product of a preset value and a thickness of a reference IDT;

[0010] The preset value is a ratio of the material density of the reference IDT to the material density of the IDT;

[0011] When the material of the reference IDT is pure aluminum or an alloy with an aluminum content exceeding 95%, the thickness of the reference IDT is greater than or equal to 15% of the wavelength of the high-frequency acoustic wave resonator.

[0012] In a feasible embodiment, when the material of the IDT is aluminum, the material of the piezoelectric film is X-cut lithium niobate, and the material of the supporting substrate is 6H-silicon carbide, the thickness of the IDT is 0.2 times the wavelength.

[0013] In a feasible embodiment, when the material of the IDT is aluminum, the material of the piezoelectric film is X-cut lithium niobate, and the material of the supporting substrate is sapphire, the thickness of the IDT is 0.18 to 0.19 times the wavelength.

[0014] In a feasible embodiment, when the material of the IDT is aluminum, the material of the piezoelectric film is X-cut lithium tantalate, and the material of the supporting substrate is sapphire, the thickness of the IDT is 0.19 to 0.2 times the wavelength.

[0015] In a feasible embodiment, the piezoelectric film includes at least one of lithium niobate, lithium tantalate, potassium niobate, aluminum nitride, scandium-doped aluminum nitride, zinc oxide, lead zirconate titanate, or lead magnesium niobate-lead titanate crystal.

[0016] In a feasible embodiment, the IDT is any one of a single-layer metal film, a multi-layer metal film, and a composite film composed of metal and non-metal.

[0017] In another aspect, the present application further discloses a method for preparing a high-frequency acoustic wave resonator, which comprises:

[0018] Providing a support substrate with a piezoelectric film on the top layer; the speed of sound of the support substrate is not less than 5000 m / s;

[0019] An IDT is fabricated on a piezoelectric film; the thickness of the IDT is inversely proportional to the material density of the IDT; the target mode of the high-frequency acoustic wave resonator is a quasi-bulk wave mode generated by longitudinal electric field excitation; and the sound velocity of the target mode is less than the sound velocity of the supporting substrate.

[0020] By adopting the above technical solution, the high-frequency acoustic wave resonator provided by this application has the following beneficial effects:

[0021] The high-frequency acoustic wave resonator includes a supporting substrate, a piezoelectric film and an interdigital transducer stacked in sequence from bottom to top; wherein the sound velocity of the supporting substrate is not less than 5000 m / s; the target mode of the high-frequency acoustic wave resonator is a quasi-bulk wave mode generated by longitudinal electric field excitation; the thickness of the interdigital transducer is inversely proportional to the material density of the interdigital transducer; the sound velocity of the target mode is less than the sound velocity of the supporting substrate. In this way, the electromechanical coupling coefficient of the first-order mode can be effectively reduced, and the electromechanical coupling coefficient of the high-order mode can be improved. By setting the sound velocity of the high-order mode to be lower than the sound velocity of the supporting substrate, the sound wave can be prevented from leaking to the supporting substrate, so that the sound wave energy is confined to the substrate surface. At the same time, the setting of the thickness of the interdigital transducer means lower ohmic loss, which is very important for high-frequency resonators with small wavelengths and small electrode widths, and the high-frequency acoustic wave resonator also has the advantage of simple structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0023] FIG1 is a schematic structural diagram of a high-frequency acoustic wave resonator provided in an embodiment of the present application;

[0024] FIG2 is a simulated admittance curve corresponding to different thicknesses of IDTs provided in an embodiment of the present application;

[0025] Figure 3 is the vibration mode diagram corresponding to the S1 mode in Figure 2;

[0026] FIG4 is a simulated admittance curve corresponding to the first high-frequency acoustic wave resonator provided in an embodiment of the present application;

[0027] FIG5 is a mode shape diagram corresponding to the target mode in FIG4 ;

[0028] FIG6 is a simulated admittance curve corresponding to the second high-frequency acoustic wave resonator provided in an embodiment of the present application;

[0029] FIG7 is a mode shape diagram corresponding to the target mode in FIG6 ;

[0030] FIG8 is a simulated admittance curve corresponding to the third high-frequency acoustic wave resonator provided in an embodiment of the present application;

[0031] FIG9 is a simulated admittance curve corresponding to the fourth high-frequency acoustic wave resonator provided in an embodiment of the present application;

[0032] Figure 10 is the mode shape diagram corresponding to the target mode in Figure 8;

[0033] FIG11 is a mode shape diagram corresponding to the target mode in FIG9 ;

[0034] FIG12 is a schematic flow chart of a method for preparing a high-frequency acoustic wave resonator provided in an embodiment of the present application.

[0035] The following is a supplementary description of the accompanying drawings:

[0036] 1-support substrate; 2-piezoelectric film; 3-interdigital transducer. DETAILED DESCRIPTION

[0037] The following will be combined with the accompanying drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making any creative work are within the scope of protection of this application.

[0038] References to "one embodiment" or "embodiment" herein refer to specific features, structures, or characteristics that may be included in at least one implementation of the present application. Throughout the description of this application, it should be understood that the terms "upper," "lower," "top," and "bottom," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely for ease of description and simplification. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation, and are therefore not to be construed as limiting the present application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly specifying the number of the technical features indicated. Thus, a feature designated "first" or "second" may explicitly or implicitly include one or more of such features. Furthermore, the terms "first," "second," etc. are used to distinguish similar objects and are not necessarily used to describe a specific order or sequential sequence. It should be understood that such terms are interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than that illustrated or described herein.

[0039] For the purpose of the following detailed description, it should be understood that the present invention may adopt various alternative variations and step sequences, unless expressly provided otherwise. In addition, except in any operating examples, or when otherwise indicated, all numerals representing the amount of the components used in the specification and claims should be understood to be modified by the term "about" in all cases. Therefore, unless otherwise indicated, the numerical parameters set forth in the following specification and the appended claims are approximate values ​​that vary according to the desired performance to be obtained by the present invention. At least, it is not intended to limit the application of the doctrine of equivalents to the scope of the claims, and each numerical parameter should at least be interpreted according to the number of reported significant figures and by applying ordinary rounding techniques.

[0040] Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values ​​set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements.

[0041] When a numerical range is disclosed herein, the above range is considered to be continuous and includes the minimum and maximum values ​​of the range, as well as every value between such minimum and maximum values. Further, when a range refers to an integer, every integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe a feature or characteristic, the ranges can be merged. In other words, unless otherwise indicated, all ranges disclosed herein should be understood to include any and all subranges included therein. For example, a specified range from "1 to 10" should be considered to include any and all subranges between a minimum of 1 and a maximum of 10. Exemplary subranges of the range 1 to 10 include, but are not limited to, 1 to 6.1, 3.5 to 7.8, 5.5 to 10, etc.

[0042] The frequency of an acoustic wave resonator is primarily determined by the thickness of the piezoelectric film, the velocity of the bulk acoustic wave of the piezoelectric material, and the load. Therefore, the general structure of a resonator is a substrate, a suspended bottom electrode, a piezoelectric film, and a top electrode, arranged in order from bottom to top. The top electrode and the suspended bottom electrode structure are used to excite the first-order plate wave mode to meet high-frequency requirements. However, for single-crystal piezoelectric materials, forming a patterned suspended bottom electrode is very difficult, and the electrode width is small at high frequencies, resulting in large ohmic losses. The frequency can also be increased by reducing the thickness of the piezoelectric film, but this approach makes the suspended piezoelectric film structure fragile and has poor heat dissipation. This makes simplifying the resonator structure, reducing ohmic losses, and ensuring that the resonator has a large electromechanical coupling coefficient the key to achieving high-performance high-frequency applications. To this end, referring to FIG1 , the present application provides a high-frequency acoustic wave resonator comprising a supporting substrate 1, a piezoelectric film 2, and an interdigital transducer 3 stacked in sequence from bottom to top; wherein the acoustic velocity of the supporting substrate 1 is not less than 5000 m / s; the target mode of the high-frequency acoustic wave resonator is a quasi-bulk wave mode generated by longitudinal electric field excitation; the thickness of the interdigital transducer 3 is inversely proportional to the material density of the interdigital transducer 3; and the acoustic velocity of the target mode is less than the acoustic velocity of the supporting substrate 1. Since the resonator has no bottom electrode, the parasitic capacitance and parasitic modes caused by the bottom electrode are effectively avoided, simplifying the acoustic wave resonator structure, reducing ohmic losses, and improving the electromechanical coupling coefficient of high-order modes, enabling better application in high-frequency and high-performance applications.

[0043] In one feasible embodiment, the product of the period of the IDT 3 and the frequency of the target mode (i.e., the acoustic velocity of the target mode) is greater than or equal to 80% of the acoustic velocity of the supporting substrate 1, and less than the acoustic velocity of the supporting substrate 1. This prevents leakage of acoustic wave energy to the supporting substrate 1, improves the electromechanical coupling coefficient of high-order plate waves, and reduces the electromechanical coupling coefficient of low-order modes, thereby reducing ohmic losses and improving power handling.

[0044] The IDT 3 includes a first bus bar and a second bus bar facing each other; the first bus bar is provided with a plurality of first electrodes spaced apart; the second bus bar is provided with a plurality of second electrodes spaced apart, and the plurality of first electrodes and the plurality of second electrodes are arranged in an interlaced and spaced manner to form interdigitated electrodes; optionally, the distance between adjacent second electrodes is equal to the distance between adjacent first electrodes. Optionally, the period of the IDT 3 is the spacing distance between the centers of adjacent first electrodes among the plurality of first electrodes, or the spacing distance between the centers of adjacent second electrodes among the plurality of second electrodes.

[0045] In a feasible embodiment, the quasi-bulk wave modes include first-order and higher-order modes of horizontal shear wave modes, Lamb wave modes and Rayleigh modes, such as first-order symmetric Lamb wave (S1), higher-order mode of first-order horizontal shear wave (SH1), first-order antisymmetric Lamb wave (A1) and first-order Rayleigh mode (Sezawa).

[0046] In a feasible embodiment, the thickness of the IDT 3 is the product of a preset value and the thickness of the reference IDT; the preset value is the ratio of the material density of the reference IDT to the material density of the IDT 3; when the material of the reference IDT is pure aluminum or an alloy with an aluminum content exceeding 95%, the thickness of the reference IDT is greater than or equal to 15% of the wavelength of the high-frequency acoustic wave resonator. Specifically, assuming that the material of the reference IDT is pure aluminum or an alloy with an aluminum content exceeding 95%, the thickness d of the IDT 3 is ≥ (ρ0 / ρ1)×0.15λ, where ρ0 is the material density of the reference IDT, ρ1 is the material density of the IDT 3 in this application, and λ is the wavelength of the high-frequency acoustic wave resonator; for example, when the material of the IDT is platinum, ρ0 / ρ1 is 1 / 8, and the required thickness can be set to 1 / 4 times the thickness of the reference IDT. When the IDT is made of copper and the ratio ρ0 / ρ1 is 1 / 3.3, the required thickness can be set to half the thickness of the reference IDT. This IDT thickness setting results in lower ohmic losses, which is crucial for high-frequency resonators with short wavelengths and narrow electrode widths. Furthermore, these high-frequency acoustic resonators have the advantage of a simple structure.

[0047] In one feasible embodiment, when the IDT 3 is made of aluminum, the piezoelectric film 2 is made of X-cut lithium niobate, and the supporting substrate 1 is made of 6H-silicon carbide, the thickness of the IDT 3 is 0.2 times the wavelength. In another feasible embodiment, when the IDT 3 is made of aluminum, the piezoelectric film 2 is made of X-cut lithium niobate, and the supporting substrate 1 is made of sapphire, the thickness of the IDT 3 is 0.18 to 0.19 times the wavelength. In another feasible embodiment, when the IDT 3 is made of aluminum, the piezoelectric film 2 is made of X-cut lithium tantalate, and the supporting substrate 1 is made of sapphire, the thickness of the IDT 3 is 0.19 to 0.2 times the wavelength. This allows the resulting resonator to have a simple structure, i.e., no bottom electrode is required, lower ohmic loss, and prevent acoustic wave leakage to the supporting substrate, confining the acoustic wave energy to the substrate surface.

[0048] In a feasible embodiment, the piezoelectric film 2 is at least one of lithium niobate, lithium tantalate, potassium niobate, aluminum nitride, scandium-doped aluminum nitride, zinc oxide, lead zirconate titanate, or lead magnesium niobate-lead titanate crystal.

[0049] In a feasible embodiment, the IDT 3 is any one of a single-layer metal film, a multi-layer metal film, and a composite film composed of metal and non-metal. Optionally, the material of the metal film can be any one of pure metal, alloy, and doped non-metallic elements.

[0050] In order to facilitate understanding of the technical solution of the present application and illustrate the beneficial effects of the present application, specific embodiments will be described below.

[0051] Example 1

[0052] An acoustic wave resonator having the structure shown in Figure 1 is provided. Please refer to Figures 2 and 3. Figure 2 shows the simulated admittance curves corresponding to different IDT thicknesses; Figure 3 shows the mode shape diagram corresponding to the S1 mode in Figure 2. The piezoelectric film 2 of the acoustic wave resonator is an X-cut lithium niobate film with Euler angles of (30, 90, -90). The supporting substrate 1 is 6H-silicon carbide. The IDT 3 is made of aluminum. The target mode is a high-order plate wave mode. The wavelength of the resonator is 1.6 microns. Among them, curve a in Figure 2 corresponds to the simulated admittance curve when the thickness of the IDT 3 is 80 nanometers. It can be seen that when the thickness of the IDT 3 is 80 nanometers, the modes include S0 and SH1. Through further comparison, it can be seen that the admittance ratio of the S0 mode is about 90 dB, while the admittance ratio of the SH1 mode is about 40 dB. Therefore, the S0 mode is the strongest when the thickness of the IDT 3 is 80 nanometers. Under the action of the high sound velocity of 6H-silicon carbide, the sound velocity of the S0 mode reaches 7544 m / s. Curve b in Figure 2 corresponds to the simulated admittance curve when the thickness of the IDT 3 is 160 nanometers. It can be seen that when the thickness of the IDT 3 reaches 160 nm, the SH1 mode is the strongest. At this time, the sound velocity of the S0 mode decreases and the electromechanical coupling coefficient decreases significantly. Coupled with the existence of the SH1 mode at a nearby frequency, the S0 mode is no longer suitable as the target mode. This shows that the S0 mode is only suitable as a target mode when the IDT 3 is thin. However, a thinner IDT 3 means greater ohmic loss, which limits the quality factor of the resonator. The SH1 mode cannot be used as a target mode because its resonant frequency is close to that of S0. When the thickness is further increased to 240 nm, new high-order plate wave modes appear. As shown in curve c in FIG2 , which corresponds to the simulated admittance curve when the thickness of the IDT 3 is 240 nm, the target mode at this time is the S1 mode, and its vibration shape is shown in FIG3 . The S1 mode is mainly excited by the longitudinal electric field, and a large amount of its vibration energy enters the IDT 3. At this time, the resonant cavity is composed of the piezoelectric film 2 and the IDT 3. Curve d in FIG2 corresponds to the simulated admittance curve when the thickness of the IDT 3 is 320 nm. It can be seen that when the thickness of the IDT 3 reaches 320 nm, the thickness of the IDT 3 reaches 0.2 times the wavelength, and the SH1 and S0 modes are greatly weakened and far away from the target mode S1. The high-order plate waves excited at this time are expected to be used in high-performance high-frequency filters. The sound velocity is as high as 8576 m / s, which is higher than the target mode S0 when the thickness of the IDT 3 is 80 nm. Under the conditions of existing photolithography technology, the frequency requirements of all frequency bands below 7 GHz can be easily met.

[0053] It is understandable that the above example only illustrates the case where the material of the IDT 3 is aluminum. In fact, if the material of the IDT 3 is a metal material such as gold, silver, platinum or an alloy, since its material density is higher than that of aluminum, the thickness of the IDT 3 corresponding to the target mode generated by the high-order plate wave mode is smaller than that of aluminum. For example, when the thickness of aluminum is set to be greater than 0.15 times the wavelength, the aluminum is replaced with gold, and the thickness of the IDT 3 can be set to 0.05 times the wavelength. The thick electrode in this application refers to the thickness of the electrode of the same material relative to the existing commonly set thickness.

[0054] From the analysis of FIG. 2 above, it can be understood that the thick electrode solution provided by the present application helps reduce ohmic losses, improve power capacity, and facilitate the realization of a resonator with a high quality factor. This high-order mode is mainly excited by the longitudinal electric field, but a large electromechanical coupling coefficient is obtained by only utilizing the longitudinal electric field component provided by the top interdigital transducer 3. Therefore, no bottom electrode is required, and the structure is very simple. Therefore, the process of this high-order plate wave resonator is very simple, and it has the characteristics of high sound velocity and low ohmic loss, which is suitable for realizing high-frequency, high-performance acoustic wave resonators.

[0055] Example 2

[0056] Please refer to Figures 4 and 5. Figure 4 shows the simulated admittance curve corresponding to the first high-frequency acoustic wave resonator, while Figure 5 shows the mode shape diagram corresponding to the target mode in Figure 4. The piezoelectric film 2 of this acoustic wave resonator is an X-cut lithium niobate film with Euler angles of (30, 90, -90). The supporting substrate 1 is sapphire with Euler angles of (44.5, 125, 0). The IDT 3 is made of aluminum with a thickness of 230 nanometers, which is 0.184 times the wavelength. The wavelength of this resonator is 1.25 microns. As can be seen from Figure 4, this high-frequency acoustic wave resonator not only achieves a resonant frequency close to 5 GHz, but also has an electromechanical coupling coefficient of 14.1%, which is sufficient to meet the requirements of some high-frequency bands. As can be seen from Figure 5, its target mode is the S1 mode, and a considerable portion of its vibration energy enters the IDT 3. At this time, the resonant cavity is composed of the piezoelectric film 2 and the IDT 3, further verifying its high electromechanical coupling coefficient.

[0057] Example 3

[0058] Please refer to Figures 6 and 7. Figure 6 shows the simulated admittance curve corresponding to the second high-frequency acoustic wave resonator, while Figure 7 shows the mode shape diagram corresponding to the target mode in Figure 6. The piezoelectric film 2 of this acoustic wave resonator is made of X-cut lithium tantalate with Euler angles of (30, 90, -90). The supporting substrate 1 is sapphire with Euler angles of (44.5, 125, 0). The IDT 3 is made of aluminum with a thickness of 230 nanometers, which is 0.192 times the wavelength. The wavelength of this resonator is 1.2 microns. As can be seen from Figure 4, this high-frequency acoustic wave resonator not only achieves a resonant frequency close to 5 GHz, but also has an electromechanical coupling coefficient of 5.9%, which is comparable to that of an aluminum nitride-based FBAR. As can be seen from Figure 5, its target mode is the S1 mode, and a large amount of vibration energy enters the IDT 3. At this time, the resonant cavity is composed of the piezoelectric film 2 and the IDT 3, further verifying its high electromechanical coupling coefficient.

[0059] Example 4

[0060] The piezoelectric film 2 of the acoustic wave resonator is Y36-cut lithium niobate, the Euler angle of lithium niobate is (0, 54, 0), the supporting substrate 1 is sapphire, the Euler angle of sapphire is (48, 125, 0), the material of the interdigital transducer 3 is aluminum, and the thickness is 260 nanometers, which reaches 0.186 times the wavelength; assuming that the wavelength of the resonator is 1.4 microns; as can be seen from Figure 8, the high-frequency acoustic wave resonator not only achieves a resonant frequency close to 4.5 GHz, but also has an electromechanical coupling coefficient of 13.1%, and its target mode is the first-order Rayleigh mode (Sezawa mode). When the electrode material is platinum electrode, the required electrode thickness is reduced, and the platinum electrode thickness is 0.046 times the wavelength. The corresponding simulated admittance curve and target mode vibration shape diagram are shown in Figure 9. The frequency is basically consistent with Figure 9, and the electromechanical coupling coefficient is 11.6%. It can be seen from the vibration mode diagrams corresponding to the target modes in Figures 8 and 9 (as shown in Figures 10 and 11) that the target mode is the first-order Rayleigh mode (Sezawa), and a large amount of vibration energy enters the IDT 3. At this time, the resonant cavity is composed of the piezoelectric film 2 and the IDT 3, which further verifies that it has a high electromechanical coupling coefficient.

[0061] Example 5

[0062] Referring to FIG. 12 , the present application also discloses a method for preparing a high-frequency acoustic wave resonator, which includes:

[0063] S1201: Provide a supporting substrate 1 with a piezoelectric film 2 on the top layer; the sound velocity of the supporting substrate 1 is not less than 5000 m / s.

[0064] Optionally, the supporting substrate 1 with a piezoelectric film 2 on the top layer in step S1201 can be prepared by an ion implantation and stripping process, a bonding and grinding process or a thin film growth process; wherein, the ion implantation and stripping process can specifically be, first providing a piezoelectric wafer; performing ion implantation on the piezoelectric wafer from the implantation surface, thereby forming a defect layer in the middle of the piezoelectric wafer, and then bonding it to the supporting substrate 1 through the implantation surface, and then performing annealing and stripping and polishing along the defect layer to obtain a supporting substrate 1 with a piezoelectric film 2 on the top layer; the bonding and grinding process can specifically be, directly bonding the piezoelectric wafer to the supporting substrate 1, and then grinding the piezoelectric wafer until the required thickness is reached; the thin film growth process can specifically be, directly epitaxially growing the piezoelectric film 2 on the supporting substrate 1.

[0065] S1202: Prepare an IDT 3 on the piezoelectric film 2; the thickness of the IDT 3 is inversely proportional to the material density of the IDT 3; the target mode of the high-frequency acoustic wave resonator is a quasi-bulk wave mode generated by longitudinal electric field excitation; the sound velocity of the target mode is less than the sound velocity of the supporting substrate 1.

[0066] In step S1202 , a metal electrode layer may be formed on the piezoelectric film 2 by sputtering or deposition process, and then patterned by photolithography process to obtain the interdigital transducer 3 .

[0067] The above description is merely an optional embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A high frequency acoustic wave resonator, It is characterized in that It includes a supporting substrate, a piezoelectric film and an interdigital transducer which are stacked in sequence from bottom to top; Among them, the sound velocity of the supporting substrate is not less than 5000 meters per second; the target mode of the high-frequency acoustic wave resonator is a quasi-bulk wave mode generated by longitudinal electric field excitation; the thickness of the interdigital transducer is inversely proportional to the material density of the interdigital transducer; and the sound velocity of the target mode is less than the sound velocity of the supporting substrate.

2. The high-frequency acoustic wave resonator according to claim 1, It is characterized in that The product of the period of the IDT and the frequency of the target mode is greater than or equal to 80% of the sound velocity of the support substrate and less than the sound velocity of the support substrate.

3. The high-frequency acoustic wave resonator according to claim 1, It is characterized in that The thickness of the IDT is the product of a preset value and the thickness of a reference IDT; The preset value is a ratio of the material density of the reference IDT to the material density of the IDT; When the material of the reference IDT is pure aluminum or an alloy with an aluminum content exceeding 95%, the thickness of the reference IDT is greater than or equal to 15% of the wavelength of the high-frequency acoustic wave resonator.

4. The high-frequency acoustic wave resonator according to claim 1, It is characterized in that The quasi-bulk wave modes include horizontal shear wave modes, Lamb wave modes, and first-order and higher-order modes of Rayleigh modes.

5. The high-frequency acoustic wave resonator according to claim 4, It is characterized in that When the material of the IDT is aluminum, the material of the piezoelectric film is X-cut lithium niobate, and the material of the supporting substrate is 6H-silicon carbide, the thickness of the IDT is 0.2 times the wavelength.

6. The high-frequency acoustic wave resonator according to claim 4, It is characterized in that When the material of the IDT is aluminum, the material of the piezoelectric film is X-cut lithium niobate, and the material of the supporting substrate is sapphire, the thickness of the IDT is 0.18 to 0.19 times the wavelength.

7. The high-frequency acoustic wave resonator according to claim 4, It is characterized in that When the material of the IDT is aluminum, the material of the piezoelectric film is X-cut lithium tantalate, and the material of the supporting substrate is sapphire, the thickness of the IDT is 0.19 to 0.2 times the wavelength.

8. The high-frequency acoustic wave resonator according to claim 1, It is characterized in that The piezoelectric film includes at least one of lithium niobate, lithium tantalate, potassium niobate, aluminum nitride, scandium-doped aluminum nitride, zinc oxide, lead zirconate titanate, or lead magnesium niobate-lead titanate crystal.

9. The high-frequency acoustic wave resonator according to claim 1, It is characterized in that The interdigital transducer is any one of a single-layer metal film, a multi-layer metal film, and a composite film composed of metal and non-metal.

10. A method for preparing a high-frequency acoustic wave resonator, It is characterized in that include: Providing a support substrate with a piezoelectric film on the top layer; the sound velocity of the support substrate is not less than 5000 m / s; An interdigital transducer is prepared on the piezoelectric film; the thickness of the interdigital transducer is inversely proportional to the material density of the interdigital transducer; the target mode of the high-frequency acoustic wave resonator is a quasi-bulk wave mode generated by longitudinal electric field excitation; the sound velocity of the target mode is less than the sound velocity of the supporting substrate.

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