TPobS Lamb wave resonator with symmetrical structure in thickness direction and preparation method of TPobS Lamb wave resonator

Abstract

The invention provides a silicon upper and lower piezoelectric film lamb wave resonator with a symmetrical structure in the thickness direction and a preparation method of the lamb wave resonator, and belongs to the technical field of micro electro mechanical systems. A resonance area of the resonator comprises a bottom interdigital electrode, a bottom piezoelectric layer, a resonance silicon layer, a top piezoelectric layer and a top interdigital electrode from bottom to top. The resonance silicon layer is grounded through the metal electrode disc, and meanwhile, an alternating current signal with a certain frequency is applied to the two interdigital electrode pairs, so that the resonator generates resonance. According to the resonator, the excited A1 or S1 mode can be determined by controlling the phases of the metal electrodes at the same upper and lower positions. When electric signals with the same amplitude and the same phase are applied to the metal electrodes at the same positions up and down, the resonator can excite a stray-free A1 mode, and when electric signals with the same amplitude and the opposite phase are applied to the metal electrodes at the same positions up and down, the resonator can excite a stray-free S1 mode.

Description

Technical Field

[0001] The present invention belongs to the field of micro-electro-mechanical systems (MEMS) technology, and in particular relates to a piezoelectric thin film Lamb wave resonator on silicon having a symmetrical structure in the thickness direction and a preparation method thereof. Background Art

[0002] Acoustic resonators based on the piezoelectric effect can form acoustic filters, which are one of the most core components in current RF front-end modules. The mainstream ones on the market include surface acoustic wave resonators and bulk acoustic wave resonators. The operating frequency of the surface acoustic wave resonator is determined by the spacing between the interdigitated electrodes. Affected by the processing accuracy, the operating frequency is generally below 3GHz. The operating frequency of the bulk acoustic wave resonator is determined by the thickness of the piezoelectric film. It can operate at a higher frequency, but it is difficult to prepare multiple resonators with different resonant frequencies on the same chip.

[0003] Lamb wave resonator is an emerging piezoelectric micro-electromechanical system acoustic resonator with advantages such as high quality factor, appropriate electromechanical coupling coefficient, low loss and small size. Lamb wave resonator uses a similar interdigital electrode structure to surface acoustic wave resonator to achieve acoustic wave excitation. The resonant frequency is determined by the electrode spacing. At the same time, the production of Lamb wave resonator can utilize the existing mature bulk acoustic wave technology platform. Therefore, Lamb wave resonator has the characteristics of both surface acoustic wave resonator (SAW) and bulk acoustic wave resonator (BAW). Because the same resonator can excite multiple Lamb wave modes at the same time, using Lamb wave as the working mode is conducive to the frequency expansion of acoustic wave devices and the miniaturization of devices.

[0004] The traditional thin piezoelectric film on silicon (TPoS) Lamb wave resonator adopts a metal electrode layer-piezoelectric film functional layer-silicon acoustic cavity layer structure from top to bottom in the thickness direction, which is an asymmetric structure. The problem with this structure is that it is difficult to effectively excite the first-order Lamb wave (A1 and S1) vibration mode or there are often many stray interference signals near the resonant frequency of the excited first-order Lamb wave mode, which seriously limits the application space and development prospects of TPoS resonators in the field of high-performance resonant sensing. Summary of the invention

[0005] In view of the above problems, the present invention provides a novel thin piezoelectric film on and below silicon (TPobS) Lamb wave resonator and a preparation method thereof. The structural resonator can effectively excite high-frequency Lamb waves to achieve a spectrum-free effect.

[0006] To achieve the above object, the present invention adopts the following technical solution:

[0007] A new type of resonator that can effectively excite high-frequency Lamb waves and achieve spectrum without spurious. The resonator body is composed of a bottom electrode, a piezoelectric layer, a resonant silicon layer, a piezoelectric layer, and a top electrode from bottom to top. The bottom of the resonator body is suspended, and a silicon substrate and an oxide layer are provided at the bottom of the non-resonant area to play a supporting role. The bottom electrode and the top electrode are both interdigitated electrodes, and the upper and lower piezoelectric layers and the resonant silicon layer are provided with two through holes in the non-resonant area. The two electrode pairs of the top interdigitated electrode are connected to the corresponding interdigitated electrodes at the bottom through the corresponding through holes. The specific structure is as follows:

[0008] A TPobS Lamb wave resonator having a symmetrical structure in the thickness direction, wherein the upper and lower structures of the resonator are symmetrical, including a resonant region and a non-resonant region; the structure of the resonant region is, from bottom to top along the thickness direction, a bottom interdigital electrode 2, a bottom piezoelectric layer 5, a resonant silicon layer 6, a top piezoelectric layer 4, and a top interdigital electrode 1;

[0009] The non-resonant region is located around the resonant region, and includes a resonant silicon layer 6, silicon dioxide 9, a grounded metal electrode disk 10, a metal electrode disk 12, and an etching window 11; the resonant silicon layer of the resonant region and the non-resonant region are the same plane layer;

[0010] The grounded metal electrode disk 10 is located on the upper surface of the resonant silicon layer 6 in the non-resonant region, and the silicon resonator in the resonant region is grounded through the grounded metal electrode disk;

[0011] There are four metal electrode disks 12, two of which are respectively distributed on the upper and lower surfaces of the resonant silicon layer in the non-resonant region. The two metal electrode disks located on the upper surface are respectively connected to the top first interdigital electrode 101 and the top second interdigital electrode 102; the two metal electrode disks located on the lower surface are respectively connected to the bottom first interdigital electrode 201 and the bottom second interdigital electrode 202; the contact surfaces of the two metal electrode disks 12 located on the upper surface and the resonant silicon layer 6 are isolated by silicon dioxide 9, so that the metal electrode disks 12 are not in contact with the resonant silicon layer 6;

[0012] The etched windows 11 are located on both sides of the resonance region and are parallel to the electrode strips of the interdigitated electrodes;

[0013] The metal electrode disk on the upper surface and the metal electrode disk on the lower surface are relatively overlapped in position. The resonant silicon layer in the non-resonant zone has two through holes located at the positions of the metal electrode disks. The side walls of the through holes have silicon dioxide 9 that serves as an insulator. The through holes are filled with metal electrodes to connect the upper and lower metal electrode disks located at the same position.

[0014] The top interdigital electrode 1 comprises a top first interdigital electrode 101 and a top second interdigital electrode 102, wherein the interdigital electrodes are N parallel electrode strips, the electrode strips of the top first interdigital electrode 101 are connected via the same bus bar, the electrode strips of the top second interdigital electrode 102 are connected via the same bus bar, and the same electrical signal is applied to the interdigital electrodes connected via the same bus bar; the electrode strips of the top first interdigital electrode 101 and the top second interdigital electrode 102 are arranged in parallel and spaced apart, and signals are applied respectively via different metal electrode disks;

[0015] The bottom interdigitated electrode includes a bottom first interdigitated electrode 201 and a bottom second interdigitated electrode 202, the electrode strips of the bottom first interdigitated electrode 201 and the bottom second interdigitated electrode 202 are arranged in parallel and spaced apart, the bottom first interdigitated electrode 201 is connected by the same bus bar, the bottom second interdigitated electrode 202 is connected by the same bus bar, and signals are applied through different metal electrode disks respectively.

[0016] When the top first interdigital electrode 101 and the bottom second interdigital electrode 202 of the resonator are connected through a through hole to form an interdigital electrode pair, and the top second interdigital electrode 102 and the bottom first interdigital electrode 201 are connected through a through hole to form an interdigital electrode pair, voltages with the same amplitude and opposite phases are applied to the two interdigital electrode pairs, and the resonant silicon layer is grounded, the S1 mode is excited;

[0017] When the top first interdigitated electrode 101 and the bottom second interdigitated electrode 201 of the resonator are connected through a through hole to form an interdigitated electrode pair, and the top second interdigitated electrode 102 and the bottom second interdigitated electrode 202 are connected through a through hole to form an interdigitated electrode pair, voltages with the same amplitude and opposite phases are applied to the two interdigitated electrode pairs, and the resonant silicon layer is grounded, the A1 mode is excited.

[0018] Furthermore, the metal electrode disk, the top interdigital electrodes and the bottom interdigital electrodes are made of the same metal material, specifically aluminum, copper, gold, nickel or lead, and the top interdigital electrodes and the bottom interdigital electrodes have the same thickness.

[0019] Furthermore, the material of the top piezoelectric layer 4 and the bottom piezoelectric layer 5 is the same material, specifically aluminum nitride, lead zirconate titanate, zinc oxide, lithium niobate, lithium tantalate, and the thickness is 0.5 μm to 1.5 μm.

[0020] Furthermore, the material of the resonant silicon layer 6 is doped silicon, and the thickness is 5 μm to 50 μm.

[0021] Furthermore, there are four grounding metal electrode disks 10, which are located on both sides of the two metal electrode disks on the upper surface of the resonant silicon layer.

[0022] Furthermore, there is a piezoelectric layer 4 between the resonant silicon layer and the silicon dioxide 9 ; there is a piezoelectric layer 5 between the metal electrode disk 12 located on the lower surface of the resonant silicon layer 6 and the resonant silicon layer 6 .

[0023] The present invention also provides a method for preparing a TPobS Lamb wave resonator having a symmetrical structure in the thickness direction, comprising the following steps:

[0024] S1: obtaining a supporting substrate, including a bottom supporting silicon layer 8 and an isolation oxide layer 7 on its upper surface;

[0025] S2: preparing a bottom interdigital electrode 2 and two metal electrode disks located on both sides of the bottom interdigital electrode on the upper surface of the isolation oxide layer 7 by a metal film sputtering process and a lift-off process;

[0026] S3: growing silicon nitride 3 in the gap region between the interdigital electrodes at the bottom of the resonance region by using a photolithography process and chemical vapor deposition, so that the thickness of the silicon nitride is the same as the thickness of the interdigital electrodes at the bottom;

[0027] S4: Depositing a bottom piezoelectric layer 5 on the upper surface of the silicon nitride and the bottom interdigital electrodes and the corresponding area of ​​the metal electrode 12 by using a photolithography process and a sputtering technique.

[0028] S5: using photolithography and chemical vapor deposition to deposit a resonant silicon layer 6 .

[0029] S6: depositing a top piezoelectric layer 4 on the resonant silicon layer by using a photolithography process and a sputtering technique, wherein the top piezoelectric layer and the bottom piezoelectric layer are located in the same region;

[0030] S7: depositing a layer of silicon dioxide 9 on the sidewall of the through hole by using a sidewall coating process, and then depositing a layer of silicon dioxide 9 on the resonant silicon layer in the area corresponding to the metal electrode 12 by using a photolithography process and a sputtering process;

[0031] S8: Filling the through hole with a metal electrode using a conductor filling process;

[0032] S9: preparing a top interdigital electrode 1 and two top metal electrode disks and a ground metal electrode disk by a metal thin film sputtering process and a lift-off process;

[0033] S10: etching the bottom silicon and silicon dioxide layers of the resonance region by plasma etching or wet etching process;

[0034] S11: using hydrofluoric acid or plasma etching process to remove the silicon nitride between the bottom interdigital electrodes, and finally obtaining the Lamb wave resonator.

[0035] After adopting the above technical solution, the present invention has the following beneficial effects:

[0036] 1. The present invention proposes a silicon upper and lower piezoelectric film (TPobS) Lamb wave resonator which can effectively excite high-frequency Lamb waves and achieve a spurious-free spectrum. Compared with the traditional piezoelectric film on silicon structure (TPoS), the resonator has an additional layer of piezoelectric film and bottom electrode at the bottom. By applying AC signals with the same or different phases to the upper and lower symmetrical electrodes and grounding the middle resonant silicon layer, the upper and lower piezoelectric layers and the middle resonant silicon layer can produce relatively symmetrical strains, which can effectively excite A1 and S1 modes and is suitable for applications in high-frequency fields.

[0037] 2. The silicon upper and lower piezoelectric thin film (TPobS) Lamb wave resonator proposed in the present invention can control the excited Lamb wave mode by controlling the phase of the upper and lower symmetrical electrodes, and simultaneously achieve a spurious-free spectrum, the same phase, which can excite the spurious-free A1 mode, and the anti-phase, which can excite the spurious-free S1 mode. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 A three-dimensional structural diagram of a silicon top-bottom piezoelectric film (TPobS) Lamb wave resonator proposed in Example 1 of the present invention;

[0039] Figure 2 is a top view of the TPobS Lamb wave resonator of Example 1;

[0040] Figure 3 A bottom view of the TPobS Lamb wave resonator of Example 1;

[0041] Figure 4 for Figure 1 A-A' section view;

[0042] Figure 5 for Figure 1 Middle B-B' cross section;

[0043] Figure 6 Schematic diagram of the electric field direction inside the piezoelectric film when the Lamb wave resonator of the silicon top and bottom piezoelectric film (TPobS) proposed in Example 1 of the present invention excites the A1 mode;

[0044] Figure 7 Schematic diagram of the electric field direction inside the piezoelectric film when the Lamb wave resonator of silicon top and bottom piezoelectric film (TPobS) proposed in Example 1 of the present invention excites the S1 mode;

[0045] Figure 8 This is a cross-sectional diagram of the simulated displacement distribution of Example 1 of the present invention when it resonates in the A1 mode;

[0046] Fig. 9 This is a cross-sectional diagram of the simulated displacement distribution of Example 1 of the present invention when it resonates in the S1 mode;

[0047] Fig.10This is a frequency domain diagram of the simulated admittance when the A1 mode is excited in Example 1 of the present invention;

[0048] Fig.11 This is a frequency domain diagram of the simulated admittance when the S1 mode is excited in Example 1 of the present invention;

[0049] Fig.12 It is a cross-sectional schematic diagram of the steps of the preparation method in Example 2 of the present invention;

[0050] Reference numerals:

[0051] 1. Top interdigitated electrode; 2. Bottom interdigitated electrode; 101 is connected to the top interdigitated electrode of the same signal, i.e., the top first interdigitated electrode; 102 is connected to another top interdigitated electrode of the same signal, i.e., the top second interdigitated electrode; 201 is connected to the bottom interdigitated electrode of the same signal, i.e., the bottom first interdigitated electrode; 202 is connected to another bottom interdigitated electrode of the same signal, i.e., the bottom second interdigitated electrode; 3. Silicon nitride 4. Top piezoelectric layer; 5. Bottom piezoelectric layer; 6. Resonant silicon layer; 7. Silicon dioxide layer; 8. Support silicon layer; 9. Isolation oxide layer 10. Grounded metal electrode disk; 11. Etching window; 12. Metal electrode disk. DETAILED DESCRIPTION

[0052] Hereinafter, the term "include" or "may include" used in various embodiments of the present invention indicates the presence of the invented function, operation or element, and does not limit the addition of one or more functions, operations or elements. In addition, as used in various embodiments of the present invention, the terms "include", "have" and their cognates are intended only to indicate specific features, numbers, steps, operations, elements, components or combinations of the foregoing items, and should not be understood as first excluding the presence of one or more other features, numbers, steps, operations, elements, components or combinations of the foregoing items or the possibility of adding one or more features, numbers, steps, operations, elements, components or combinations of the foregoing items.

[0053] In various embodiments of the present invention, the expression "or" or "at least one of A or / and B" includes any combination or all combinations of the words listed at the same time. For example, the expression "A or B" or "at least one of A or / and B" may include A, may include B, or may include both A and B.

[0054] The expressions (such as "first", "second", etc.) used in various embodiments of the present invention may modify the various constituent elements in various embodiments, but may not limit the corresponding constituent elements. For example, the above expressions do not limit the order and / or importance of the elements. The above expressions are only used for the purpose of distinguishing an element from other elements. For example, the first user device and the second user device indicate different user devices, although both are user devices. For example, without departing from the scope of various embodiments of the present invention, the first element may be referred to as the second element, and similarly, the second element may also be referred to as the first element.

[0055] It should be noted that if it is described that one component element is “connected” to another component element, the first component element may be directly connected to the second component element, and a third component element may be “connected” between the first component element and the second component element. Conversely, when one component element is “directly connected” to another component element, it can be understood that there is no third component element between the first component element and the second component element.

[0056] The terms used in various embodiments of the present invention are only used for the purpose of describing specific embodiments and are not intended to limit various embodiments of the present invention. As used herein, the singular form is intended to also include the plural form, unless the context clearly indicates otherwise. Unless otherwise limited, all terms used here (including technical terms and scientific terms) have the same meaning as the meaning generally understood by those of ordinary skill in the art to which the various embodiments of the present invention belong. The terms (such as the terms defined in the dictionary generally used) will be interpreted as having the same meaning as the contextual meaning in the relevant technical field and will not be interpreted as having an idealized meaning or an overly formal meaning, unless clearly defined in various embodiments of the present invention.

[0057] In order to make the purpose, technical scheme and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments and the accompanying drawings. The exemplary embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention. The technical scheme of the present invention is described in detail below in conjunction with the accompanying drawings.

[0058] Example 1

[0059] The traditional Lamb wave resonator of thin piezoelectric film on silicon (TPoS) is a metal electrode layer-piezoelectric film functional layer-silicon acoustic cavity layer structure from top to bottom in the thickness direction. The resonant silicon layer is grounded through the upper metal electrode disk, and the metal finger electrodes apply voltages of the same amplitude and opposite phase through the metal electrode disks to excite the resonance of the resonator. However, because the structure is asymmetric from top to bottom, it is difficult to effectively excite the first-order Lamb wave (A1 and S1) mode, and there are many nearby strays. Therefore, in order to solve this problem, this example proposes a Lamb wave resonator of piezoelectric film on silicon (TPobS) that can effectively excite high-frequency Lamb waves and achieve a spurious-free spectrum. The mode of the excited first-order Lamb wave can be controlled by controlling the phase of the voltage applied by the finger electrodes.

[0060] The three-dimensional diagram of the Lamb wave resonator of the silicon top and bottom piezoelectric film (TPobS) proposed in this embodiment is shown in Figure 1 As shown, Figure 2 This is its top view. Figure 3 This is its bottom view. The resonator has symmetrical upper and lower structures. The thickness direction of the resonant part is as follows from bottom to top. Figure 4 As shown, it is composed of bottom interdigital electrode 2, bottom piezoelectric layer 5, resonant silicon layer 6, top piezoelectric layer 4, and top interdigital electrode 1. The non-resonant region is located around the resonant region, including resonant silicon layer 6, silicon dioxide 9, grounded metal electrode disk 10, metal electrode disk 12, and etched window 11;

[0061] The top interdigital electrode 1 includes a top first interdigital electrode 101 and a top second interdigital electrode 102, wherein the interdigital electrodes are N parallel electrode strips, the top first interdigital electrode 101 is connected through the same bus bar, and the top second interdigital electrode 102 is connected through the same bus bar, and the same electrical signal can be applied to the interdigital electrodes connected through the same bus bar; the electrode strips of the top first interdigital electrode 101 and the top second interdigital electrode 102 are arranged in parallel and spaced apart, and signals are applied through different metal electrode disks respectively; similarly, the bottom interdigital electrode includes a bottom first interdigital electrode 201 and a bottom second interdigital electrode 202, and its structure is the same as that of the top interdigital electrode. The materials of the top interdigital electrode and the bottom interdigital electrode can be metals such as aluminum, copper, gold, nickel or lead, and have the same thickness.

[0062] The top piezoelectric layer 4 and the bottom piezoelectric layer 5 are made of the same material, which may be aluminum nitride, lead zirconate titanate, zinc oxide, lithium niobate, lithium tantalate, with a thickness of 0.5 μm to 1.5 μm, and the thickness of the resonant silicon layer 6 is 5 μm to 50 μm.

[0063] There are four grounded metal electrode disks 10, which are located on the upper surface of the resonant silicon layer in the non-resonant region. The silicon resonator in the resonant region is grounded through the metal disk, so that the device can achieve resonance.

[0064] There are four metal electrode disks 12, two of which are distributed on the upper and lower surfaces of the resonant silicon layer in the non-resonant zone. The two metal electrode disks located on the upper surface are respectively connected to the top first interdigitated electrode 101 and the top second interdigitated electrode 102; the two metal electrode disks located on the lower surface are respectively connected to the bottom first interdigitated electrode 201 and the bottom second interdigitated electrode 202; the metal electrode disk 12 located on the upper surface of the resonant silicon layer 6 is isolated from the resonant silicon layer 6 by silicon dioxide 9, so that the metal electrode disk 12 does not contact the resonant silicon layer 6.

[0065] Furthermore, there is a top piezoelectric layer 4 between the resonant silicon layer and the silicon dioxide 9 ; and there is a bottom piezoelectric layer 5 between the metal electrode disk 12 located on the lower surface of the resonant silicon layer 6 and the resonant silicon layer 6 .

[0066] The etched windows 11 play a role in reflecting sound waves, so that the device can achieve a better resonance effect; the etched windows 11 are located on both sides of the resonance region and are parallel to the electrode strips of the interdigital electrodes.

[0067] The metal electrode disk on the upper surface is relatively overlapped with the metal electrode disk on the lower surface. The resonant silicon layer in the non-resonant region has two through holes, located at the location of the metal electrode disk. The side walls of the through holes have silicon dioxide 9 for insulation. The through holes are filled with electrodes to connect the upper and lower metal electrode disks at the same position. The cross-sectional view at the through holes is shown in FIG. Figure 5 shown.

[0068] There are two ways to connect the interdigital electrodes of the resonator. One is that the top interdigital electrodes and the bottom interdigital electrodes at corresponding upper and lower positions are connected through the same through hole (which can excite the A1 mode), and the other is that the top interdigital electrodes and the bottom interdigital electrodes at non-corresponding upper and lower positions are connected through the same through hole (which can excite the S1 mode). The excited first-order Lamb wave mode can be controlled by controlling different electrode connection methods.

[0069] Specifically, when the top first interdigital electrode 101 and the bottom second interdigital electrode 202 of the resonator are connected through a through hole to form an interdigital electrode pair, and the top second interdigital electrode 102 and the bottom first interdigital electrode 201 are connected through a through hole to form an interdigital electrode pair, voltages with the same amplitude and opposite phases are applied to the two interdigital electrode pairs, and the resonant silicon layer is grounded, a spurious S1 mode can be excited, and the simulated frequency domain admittance diagram is as follows: Fig.11 As shown in Figure 2, the electric field under this excitation mode is shown in Figure 2. Figure 6 , the displacement diagram of S1 mode is shown in Fig. 9 .

[0070] When the top first interdigital electrode 101 and the bottom first interdigital electrode 201 of the resonator are connected through a through hole to form an interdigital electrode pair, and the top second interdigital electrode 102 and the bottom second interdigital electrode 202 are connected through a through hole to form an interdigital electrode pair, when voltages with the same amplitude and opposite phases are applied to the two interdigital electrode pairs, and the resonant silicon layer is grounded, the A1 mode without spurious can be excited. The simulated frequency domain admittance diagram is shown in Fig.10 The electric field under this excitation mode is shown in Figure 7 , the displacement diagram of mode A1 is shown in Figure 8 .

[0071] Example 2

[0072] This embodiment proposes a method for preparing the above-mentioned silicon top and bottom piezoelectric film (TPobS) Lamb wave resonator, the cross-sectional view of which is shown in FIG. Fig.12 As shown, the specific steps include:

[0073] S1: obtaining a supporting substrate, including a bottom supporting silicon layer 8 and an isolation oxide layer 7 on its upper surface;

[0074] S2: preparing the bottom interdigital electrode 2 and two metal electrode disks located on both sides of the bottom interdigital electrode on the upper surface of the isolation oxide layer 7 by a metal film sputtering process and a lift-off process;

[0075] S3: growing silicon nitride 3 in the gap region between the interdigital electrodes at the bottom of the resonance region by using a photolithography process and chemical vapor deposition (CVD), so that the thickness of the silicon nitride is the same as the thickness of the bottom interdigital electrodes, that is, the silicon nitride and the bottom interdigital electrodes are at the same surface height;

[0076] S4: Depositing a bottom piezoelectric layer 5 on the upper surface of the silicon nitride and the bottom interdigital electrode and the corresponding area of ​​the metal electrode disk 12 by using a photolithography process and a sputtering technique.

[0077] S5: using photolithography and chemical vapor deposition to deposit a resonant silicon layer 6;

[0078] S6: depositing a top piezoelectric layer 4 on the resonant silicon layer by using a photolithography process and a sputtering technique, wherein the pattern of the top piezoelectric layer is the same as the pattern of the bottom piezoelectric layer, that is, the positions are the same;

[0079] S7: using a sidewall coating process (HDPCVD) to deposit a layer of silicon dioxide 9 on the sidewall of the through hole to play an insulating role; then using a photolithography process and a sputtering process to deposit a layer of silicon dioxide 9 on the resonant silicon layer in the corresponding area of ​​the metal electrode disk 12;

[0080] S8: filling the through hole with a metal electrode by a conductor filling process, so that the bottom metal electrode disk and the top metal electrode disk located at upper and lower relative positions are connected;

[0081] S9: preparing a top interdigital electrode 1, a top metal electrode disk and a ground metal electrode disk by a metal film sputtering process and a lift-off process;

[0082] S10: using plasma etching or wet etching process to remove the bottom support silicon layer 8 and the isolation oxide layer 7 of the resonance region;

[0083] S11: using hydrofluoric acid or plasma etching process (mixed gas of carbon tetrafluoride, sulfur hexafluoride, chlorine, hydrofluoric acid and ammonia) to remove silicon nitride between the bottom interdigital electrodes, and finally obtaining the Lamb wave resonator.

[0084] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A TPobS Lamb wave resonator having a symmetrical structure in the thickness direction, comprising a resonant region and a non-resonant region, characterized in that: The resonator has symmetrical upper and lower structures, and the structure of the resonance region is, from bottom to top along the thickness direction, a bottom interdigital electrode (2), a bottom piezoelectric layer (5), a resonant silicon layer (6), a top piezoelectric layer (4), and a top interdigital electrode (1); The non-resonant region is located around the resonant region and includes a resonant silicon layer (6), silicon dioxide (9), a grounded metal electrode disk (10), a metal electrode disk (12), and an etching window (11); the resonant silicon layer of the resonant region and the non-resonant region are in the same plane layer; A grounded metal electrode disk (10) is located on the upper surface of the resonant silicon layer (6) in the non-resonant region, and the silicon resonator in the resonant region is grounded through the grounded metal electrode disk; There are four metal electrode disks (12), two of which are respectively distributed on the upper and lower surfaces of the resonant silicon layer in the non-resonant region; the two metal electrode disks located on the upper surface are respectively connected to the top first interdigital electrode (101) and the top second interdigital electrode (102); the two metal electrode disks located on the lower surface are respectively connected to the bottom first interdigital electrode (201) and the bottom second interdigital electrode (202); the contact surfaces of the two metal electrode disks (12) located on the upper surface and the resonant silicon layer (6) are isolated by silicon dioxide (9), so that the metal electrode disks (12) and the resonant silicon layer (6) are not in contact; The etched windows (11) are located on both sides of the resonance region and are parallel to the electrode strips of the interdigitated electrodes; The metal electrode disk located on the upper surface and the metal electrode disk located on the lower surface are relatively overlapped in position. The resonant silicon layer in the non-resonant region has two through holes located at the positions of the metal electrode disks. The side walls of the through holes have silicon dioxide (9) for insulation. The through holes are filled with metal electrodes to connect the upper and lower metal electrode disks located at the same position.

2. The TPobS Lamb wave resonator having a symmetrical structure in the thickness direction according to claim 1, characterized in that: The top interdigital electrode (1) comprises a top first interdigital electrode (101) and a top second interdigital electrode (102), wherein the interdigital electrodes are N parallel electrode strips, the electrode strips of the top first interdigital electrode (101) are connected via the same bus bar, the electrode strips of the top second interdigital electrode (102) are connected via the same bus bar, and the same electrical signal is applied to the interdigital electrodes connected via the same bus bar; the electrode strips of the top first interdigital electrode (101) and the top second interdigital electrode (102) are arranged in parallel and spaced apart, and signals are applied respectively via different metal electrode disks; The bottom interdigital electrodes include a bottom first interdigital electrode (201) and a bottom second interdigital electrode (202), the electrode strips of the bottom first interdigital electrode (201) and the second interdigital electrode (202) are arranged in parallel and spaced apart, the bottom first interdigital electrodes (201) are connected via the same bus bar, the bottom second interdigital electrodes (202) are connected via the same bus bar, and signals are applied via different metal electrode disks respectively.

3. The TPobS Lamb wave resonator having a symmetrical structure in the thickness direction according to claim 2, characterized in that: When the top first interdigital electrode (101) and the bottom second interdigital electrode (202) of the resonator are connected through a through hole to form an interdigital electrode pair, and the top second interdigital electrode (102) and the bottom first interdigital electrode (201) are connected through a through hole to form an interdigital electrode pair, voltages with the same amplitude and opposite phases are applied to the two interdigital electrode pairs, and the resonant silicon layer is grounded, the S1 mode is excited; When the top first interdigital electrode (101) and the bottom first interdigital electrode (201) of the resonator are connected through a through hole to form an interdigital electrode pair, and the top second interdigital electrode (102) and the bottom second interdigital electrode (202) are connected through a through hole to form an interdigital electrode pair, voltages with the same amplitude and opposite phases are applied to the two interdigital electrode pairs, and the resonant silicon layer is grounded, the A1 mode is excited.

4. The TPobS Lamb wave resonator having a symmetrical structure in the thickness direction according to claim 3, characterized in that: The metal electrode disk, the top interdigital electrodes and the bottom interdigital electrodes are made of the same metal material, specifically aluminum, copper, gold, nickel or lead, and the top interdigital electrodes and the bottom interdigital electrodes have the same thickness.

5. The TPobS Lamb wave resonator having a symmetrical structure in the thickness direction according to claim 4, characterized in that: The material of the top piezoelectric layer (4) and the bottom piezoelectric layer (5) is the same material, specifically aluminum nitride, lead zirconate titanate, zinc oxide, lithium niobate, lithium tantalate, and the thickness is 0.5 μm to 1.5 μm.

6. The TPobS Lamb wave resonator having a symmetrical structure in the thickness direction according to claim 5, characterized in that: The material of the resonant silicon layer (6) is doped silicon, and the thickness is 5 μm to 50 μm.

7. The TPobS Lamb wave resonator having a symmetrical structure in the thickness direction according to claim 6, characterized in that: There are four grounding metal electrode disks (10), which are located on both sides of the two metal electrode disks on the upper surface of the resonant silicon layer.

8. The TPobS Lamb wave resonator having a symmetrical structure in the thickness direction according to claim 7, characterized in that: There is also a top piezoelectric layer (4) between the resonant silicon layer and the silicon dioxide (9); there is also a bottom piezoelectric layer (5) between the metal electrode disk (12) located on the lower surface of the resonant silicon layer (6) and the resonant silicon layer (6).

9. A method for preparing a TPobS Lamb wave resonator having a symmetrical structure in the thickness direction, used for preparing the resonator as claimed in any one of claims 1 to 8, characterized in that: The following steps are involved: S1: obtaining a supporting substrate, including a bottom supporting silicon layer (8) and an isolation oxide layer (7) on its upper surface; S2: preparing a bottom interdigital electrode (2) and two metal electrode disks located on both sides of the bottom interdigital electrode on the upper surface of the isolation oxide layer 7 by a metal film sputtering process and a lift-off process; S3: growing silicon nitride 3 in the gap region between the interdigital electrodes at the bottom of the resonance region by using a photolithography process and chemical vapor deposition, so that the thickness of the silicon nitride is the same as the thickness of the interdigital electrodes at the bottom; S4: Depositing a bottom piezoelectric layer (5) on the upper surface of silicon nitride and the bottom interdigital electrode and the corresponding area of ​​the metal electrode 12 by using photolithography and sputtering technology. S5: using photolithography and chemical vapor deposition to deposit a resonant silicon layer (6). S6: depositing a top piezoelectric layer (4) on the resonant silicon layer by using a photolithography process and a sputtering technique, wherein the top piezoelectric layer and the bottom piezoelectric layer are located in the same region; S7: depositing a layer of silicon dioxide (9) on the side wall of the through hole by using a side wall coating process, and then depositing a layer of silicon dioxide (9) on the piezoelectric layer in the corresponding area of ​​the metal electrode disk (12) by using a photolithography process and a sputtering process; S8: Filling the through hole with a metal electrode using a conductor filling process; S9: preparing a top interdigital electrode (1) and two top metal electrode disks and a ground metal electrode disk by a metal thin film sputtering process and a lift-off process; S10: etching the bottom silicon and silicon dioxide layers of the resonance region by plasma etching or wet etching process; S11: using hydrofluoric acid or plasma etching process to remove the silicon nitride between the bottom interdigital electrodes, and finally obtaining the Lamb wave resonator.

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