A micromechanical resonator taking into account thermoelastic losses and a method for manufacturing the same

Abstract

The application discloses a micromechanical resonator considering thermoelastic loss and a preparation method thereof. The resonator comprises a substrate layer, a buried oxygen layer and a device layer. The substrate layer has a cavity structure. The device layer comprises a resonator oscillator suspended above the cavity structure. The structure of the resonator oscillator is distributed along a specific trajectory of <100> to <110> crystal direction. The trajectory distribution is adjusted according to the anisotropy of single crystal silicon material and the vibration characteristics of different modes, so that the profile of the resonator oscillator is a non-regular rectangular and / or circular structure. The micromechanical resonator can balance stress distribution, reduce temperature gradient caused by stress, reduce thermoelastic loss and significantly improve the Q value of the resonator without increasing the process difficulty and manufacturing cost. Q Value.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of resonators, and particularly relates to a micro-mechanical resonator considering thermoelastic loss and a preparation method thereof. BACKGROUND

[0002] Clock is a key component in digital circuits, providing frequency reference and time reference. Micro-mechanical resonators based on microelectromechanical systems (MEMS) are basic elements of clocks, which generate stable frequency signals through vibration. Resonators combined with peripheral circuits can constitute oscillators, output fixed frequency signals, and drive digital systems to run. In the current information age, micro-mechanical resonators as a kind of key micro-nano structural elements are widely used in wireless communication, sensor technology, clock system and inertial navigation fields. These applications put forward higher and higher requirements for the performance of resonators. The improvement of resonator performance is directly related to the reliability and accuracy of these application systems, especially under the background of increasing demand for high precision, high stability and low noise.

[0003] Quality factor (Q) is a key indicator to measure the performance of MEMS resonators. High Q value can reduce the dynamic impedance of resonators, reduce the phase noise of the system and improve the frequency stability of the oscillator. Therefore, improving the Q value has become one of the core goals of resonator design. The energy loss mechanisms of MEMS resonator Q value mainly include five parts: air damping loss (Q air ), thermoelastic loss (Q TED ), material loss (Q material ), anchor loss (Q anchor ) and electrical load loss (Q loaded ), that is:

[0004] ,

[0005] Reducing the thermoelastic loss of the resonator is crucial for improving the Q value of the resonator. The thermoelastic loss is closely related to the vibration frequency and mode of the resonator. High-frequency vibration usually increases the thermoelastic loss, as frequent stress and temperature changes cause more energy to be lost. Different vibration modes also cause different stress and temperature distributions, affecting the size of the thermoelastic loss. The geometry of the resonator also has an important influence on the thermoelastic loss. Complex geometry may cause stress concentration and non-uniform temperature distribution, increasing the thermoelastic loss. Optimizing the geometry of the resonator for different vibration modes can reduce stress concentration and heat conduction paths, thereby reducing the thermoelastic loss. Single crystal silicon material is one of the most common materials for MEM resonators, and its material properties depend on the orientation relative to the crystal lattice. Due to the anisotropy of the material properties of single crystal silicon, the stress distribution between the structures of different crystal orientations of the traditional resonator is uneven, resulting in a large temperature gradient, which in turn increases the thermoelastic loss. These problems limit the further improvement of the performance of the resonator, and cannot meet the increasingly stringent application requirements.

[0006] To solve these problems, a method is needed to flexibly design and adjust the structure of the resonator, balance the stress distribution of the resonator structure, reduce the temperature gradient caused by stress, and reduce the thermoelastic loss to achieve the improvement of the Q value. The present application proposes an innovative micro-mechanical resonator structure and its design method to solve the above problems. SUMMARY

[0007] The purpose of the present application is to provide a micro-mechanical resonator considering the thermoelastic loss and its preparation method. The innovation of the present application is to precisely control the geometric parameters of the resonator structure along different crystal orientations to adjust the equivalent stiffness of the resonator structure along different crystal orientations, so that the resonator achieves a more optimal stress distribution when resonating, reduces the temperature gradient, and effectively reduces the thermoelastic loss. Specifically, based on the anisotropy of the single crystal silicon material and the vibration mode of the resonator, the geometric parameters such as width, radius and thickness of the resonator structure along different crystal orientations are adjusted, and optimization methods such as finite element analysis are used to analyze the stress and thermoelastic loss of the resonator structure in detail, ensuring the accuracy and effectiveness of the design.

[0008] In summary, the present application can solve the problem of stress concentration in the resonant operation of the plate or ring structure micro-mechanical resonator through innovative structural design and adjustment method, reduce the temperature gradient caused by stress, reduce the thermoelastic loss, and significantly improve the Q value of the resonator, thereby providing higher performance and stability for the micro-mechanical resonator in various application scenarios.

[0009] To achieve the above purpose, the technical solution adopted by the present application is:

[0010] A kind of micro mechanical resonator considering thermoelastic loss, including substrate layer, and buried oxygen layer and device layer being arranged on the substrate layer, the substrate layer has cavity structure, the device layer includes resonator suspendedly arranged above the cavity structure, the structure of the resonator is distributed along the specific trajectory of <100> to <110> direction, the trajectory distribution is adjusted according to the anisotropy of single crystal silicon material and the vibration characteristics of different modes, so that the outline of the resonator is non-regular rectangular and / or circular structure;The resonator can be used alone, or form resonator array, or be used in coupling with other resonators as mechanical coupling structure.

[0011] The present micro mechanical resonator can balance stress distribution, reduce temperature gradient caused by stress, reduce thermoelastic loss and significantly improve the Q value of the resonator without increasing process difficulty and manufacturing cost by adjusting the trajectory distribution of the resonator structure along different crystal directions and changing the equivalent stiffness of the resonator structure along different crystal directions. Q

[0012] Further, the adjustment method of the trajectory distribution is suitable for various resonator structures, including ring-like or plate-like structures;The outer contour of the plate-like resonator, the inner contour and / or the outer contour of the ring-like structure are adjusted, and the inner contour and / or the outer contour are respectively contracted towards the center with different contraction amounts.

[0013] Further, when the main structure of the resonator is a circular ring or a circular plate, the inner contour and / or the outer contour of the resonator are radially contracted;When the main structure of the resonator is a square ring or a square plate, the length of the side of the inner contour and / or the outer contour changes from a straight line to a curve after contraction, and the length of the side of the outer contour is a convex curve, and the length of the side of the inner contour is a concave curve.

[0014] Further, when the structure of the resonator is used as a coupling structure to couple with other resonators, other structures are connected through support beams or anchor points, and the inner contour and / or the outer contour of the ring-like or plate-like structure of the coupling structure are also respectively contracted towards the center of the coupling structure.

[0015] Further, micro-holes or grooves are etched on the structure of the resonator along different crystal directions, and the equivalent stiffness of the resonator structure along different crystal directions is adjusted by using regional doping.

[0016] Further, the trajectory of the resonator after adjustment along different crystal directions satisfies the following conditions:

[0017] ,

[0018] wherein, is the structural parameter of the resonator, ​as a function of the structural parameters as a function of the structural parameters as a function of the structural parameters as a function of the structural parameters at least including width, radius and thickness, as a function of the structural parameters as a function of the structural parameters as a function of the structural parameters

[0019] Further, the resonator structure is a single-layer single-crystal silicon structure, or a composite thin-film structure of metal-piezoelectric layer-single-crystal silicon.

[0020] Further, the resonator structure is a single-layer single-crystal silicon structure, or a composite thin-film structure of metal-piezoelectric layer-single-crystal silicon.

[0021] A preparation method of a micro-mechanical resonator considering thermal-elastic loss, when the resonator is a single-crystal silicon single-layer structure, the preparation method is as follows:

[0022] An SOI wafer is provided, which sequentially includes a substrate layer, a buried oxygen layer and a device layer with a thickness of 5-60 µm from bottom to top;

[0023] A metal layer with a thickness of 1-2 µm is deposited on the device layer, and after a patterning process, a metal pad is formed;

[0024] The front surface of the SOI wafer is etched, the device layer is selectively etched until the etching stops on the buried oxygen layer, and the microstructure of the required resonator is formed in the device layer according to the adjusted trajectory distribution;

[0025] The back surface of the SOI wafer is etched, the substrate layer is selectively etched until the buried oxygen layer is etched, and a through hole or the cavity structure is formed in the substrate layer to expose the buried oxygen layer;

[0026] Gaseous hydrofluoric acid is introduced to corrode and release the exposed buried oxygen layer, so that the resonator is released and suspended, and a micro-mechanical resonator structure is obtained.

[0027] A preparation method of a micro-mechanical resonator considering thermal-elastic loss, when the resonator is a composite structure of metal-piezoelectric layer-single-crystal silicon, the preparation method is as follows:

[0028] An SOI wafer is provided, which sequentially includes a substrate layer, a buried oxygen layer and a device layer with a thickness of 5-60 µm from bottom to top;

[0029] Depositing a piezoelectric material with a thickness of 0.5-1 µm and an upper electrode with a thickness of 0.15-0.2 µm on the device layer, patterning the upper electrode, and then depositing a top oxide layer with a thickness greater than 0.2 µm;

[0030] Etching the top oxide layer to form an upper electrode through hole to expose the upper electrode;

[0031] Continue etching the top oxide layer and the piezoelectric material to form a lower electrode through hole, exposing the device layer;

[0032] Depositing a metal layer with a thickness of 1-2 μm in the upper electrode through hole and the lower electrode through hole, and performing patterning to form a metal pad;

[0033] Performing front etching on the top oxide layer, the piezoelectric material, and the device layer until the buried oxide layer is reached, and distributing the microstructure of the desired resonant oscillator in the device layer according to the adjusted trajectory;

[0034] Performing back etching on the substrate layer until the buried oxide layer is reached, forming a through hole or the cavity structure in the substrate layer, and exposing the buried oxide layer;

[0035] Gaseous hydrofluoric acid is introduced to corrode and release the exposed buried oxide layer, thereby releasing and suspending the resonant oscillator to obtain a micromechanical resonator structure.

[0036] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The micromechanical resonator can balance the stress distribution, reduce the temperature gradient caused by stress, reduce the thermoelastic loss, and significantly improve the mechanical properties of the micromechanical resonator by adjusting the trajectory distribution of the resonator structure along different crystal directions, thereby changing the equivalent stiffness of the resonator structure along different crystal directions without increasing the process difficulty and manufacturing cost. Q 2. The resonant oscillator has different track distributions along different crystal directions. The frequency-temperature characteristics of the resonator will be affected by the track distribution. The track distribution can be balanced and adjusted according to different application scenarios to improve the resonator. Q The influence of the value and frequency temperature characteristics; 3. The resonant oscillator is adjusted <100> to <110> After the crystal direction trajectory is distributed, its outline is no longer a regular rectangular or circular structure, and the outline has a change in curvature, which is obviously different from the circular geometric trajectory or rectangular geometric trajectory of the existing resonator. The temperature gradient on the adjusted resonant oscillator structure is significantly reduced, the vibration mode of the resonator is effectively improved, and the stress distribution inside the structure is more balanced; 4. This method has high universality and can be applied to a variety of plate or ring resonator structures. The adjusted structure can also be applied to coupling structures, can be applied to single-layer single-crystal silicon structures, and can also be applied to the structural design of multi-layer composite films. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 A three-dimensional schematic diagram of a micro-mechanical resonator considering thermoelastic loss of the application;

[0038] Figure 2 A structural schematic diagram of the resonator structure of the application showing the structure from the buried oxide layer to the device layer direction;

[0039] Figure 3 A schematic diagram of Young's modulus of monocrystalline silicon material aligned with different crystal directions;

[0040] Figure 4 A schematic diagram of the circular ring structure after adjusting the outer contour of the resonator structure of the application;

[0041] Figure 5 A schematic diagram of the circular ring structure after adjusting the inner contour of the resonator structure of the application;

[0042] Figure 6 A schematic diagram of the circular ring structure after adjusting the inner and outer contours of the resonator structure of the application;

[0043] Figure 7 A schematic diagram of the circular plate structure after adjusting the outer contour of the resonator structure of the application;

[0044] Figure 8 A schematic diagram of the square ring structure after adjusting the inner contour of the resonator structure of the application;

[0045] Figure 9 A schematic diagram of the square ring structure after adjusting the outer contour of the resonator structure of the application;

[0046] Figure 10 A schematic diagram of the square ring structure after adjusting the inner and outer contours of the resonator structure of the application;

[0047] Figure 11 A schematic diagram of the square plate structure after adjusting the outer contour of the resonator structure of the application;

[0048] Figure 12 A schematic diagram of the coupling structure of the micro-mechanical resonator structure of the application applied to the LE-RB;

[0049] Figure 13 A schematic diagram of the coupling structure of the micro-mechanical resonator structure of the application applied to the SE-RB;

[0050] Figure 14 A schematic diagram of the structure of the support beam being a straight beam of the application;

[0051] Figure 15 A schematic diagram of the structure of the support beam being a folded beam of the application;

[0052] Figure 16The support beam of the present application is a spoke beam (central anchor point) structure diagram;

[0053] Figure 17 The radial stretch modal temperature gradient and Q before and after adjustment obtained by finite element simulation TED Comparison;

[0054] Figures 18-23 The process flow chart of Example 2 is shown, wherein:

[0055] Figure 18 A customized SOI wafer is shown, including a substrate silicon wafer, a buried oxygen layer, and a device layer;

[0056] Figure 19 The process of depositing a metal on the device layer and forming a metal pad is shown;

[0057] Figure 20 The structure after front etching of the device layer is shown;

[0058] Figure 21 The structure after back etching of the substrate layer is shown;

[0059] Figure 22 After gaseous hydrofluoric acid is introduced, a micromechanical resonator structure is formed;

[0060] Figure 23 The micromechanical resonator structure of Example 2 prepared by the CSOI process flow is shown;

[0061] Figures 24-32 The process flow chart of Example 3 is shown;

[0062] Wherein: Figure 24 A customized SOI wafer is shown, including a substrate silicon wafer, a buried oxygen layer, and a device layer silicon;

[0063] Figure 25 The process of depositing a piezoelectric layer, an upper electrode, and a top oxide on the device layer is shown;

[0064] Figure 26 The process of etching the top oxide to form an upper electrode via and expose the upper electrode is shown;

[0065] Figure 27 The process of etching the top oxide and piezoelectric material to form a via for the lower electrode is shown;

[0066] Figure 28 The process of depositing a metal in the upper electrode and lower electrode via and patterning to form a metal pad is shown;

[0067] Figure 29 The structure after front etching of the top oxide, piezoelectric material, and device layer is shown;

[0068] Figure 30 The structure of back-side etching of the substrate silicon wafer is shown;

[0069] Figure 31 It was demonstrated that after the introduction of gaseous hydrofluoric acid, a micromechanical resonator structure was formed;

[0070] Figure 32 The micromechanical resonator structure of Example 3 fabricated using the CSOI process is shown;

[0071] In the figure: 1. Resonant oscillator; 2. Support beam; 3. Bias electrode; 4. Inner electrode; 5. Outer electrode; 6. Device layer; 7. Buried oxide layer; 8. Substrate layer; 9. Support sheet structure; 10. Center anchor point. DETAILED DESCRIPTION

[0072] The following will clearly and completely describe the technical solution of the present invention in conjunction with the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0073] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limiting the present invention. Furthermore, the terms "first," "second," etc., etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Example 1

[0074] like Figure 1 and 2 As shown, a micromechanical resonator considering thermoelastic loss includes a substrate layer 8, a buried oxide layer 7 and a device layer 6 arranged on the substrate layer 8, wherein the substrate layer 8 has a cavity structure, and the device layer 6 includes a resonant oscillator 1 suspended above the cavity structure, an inner electrode 4 is provided in the middle of the resonant oscillator 1, and the resonant oscillator 1 is also connected to a bias electrode 3 through a support beam 2, and an outer electrode 5 is also provided on the periphery of the resonant oscillator 1; the structure of the resonant oscillator 1 is along the <100> to <110> The track distribution of the crystal direction is adjusted so that the outline of the resonant oscillator 1 is an irregular rectangular and / or circular structure.

[0075] The micromechanical resonator can balance stress distribution, reduce temperature gradient caused by stress, reduce thermoelastic loss, and significantly improve the frequency-temperature characteristic of the resonator without increasing process difficulty and manufacturing cost by adjusting the trajectory distribution of the resonator structure along different crystal directions and changing the equivalent stiffness of the resonator structure along different crystal directions. Q

[0076] The resonator 1 has different trajectory distributions along different crystal directions, and the frequency-temperature characteristic of the resonator is affected by the trajectory distribution. Q The trajectory distribution can be balanced and adjusted according to different application scenarios to improve the frequency-temperature characteristic of the resonator.

[0077] After adjusting the trajectory distribution of the resonator 1 along the <100> to <110> crystal directions, the contour of the resonator 1 is no longer a regular rectangle (oblong or square) or a circular structure, and the contour has a curvature change, which is obviously different from the circular geometric trajectory or rectangular geometric trajectory of the existing resonator. Figure 17 As shown in the radial stretching mode and temperature gradient before and after adjustment obtained by simulating the resonator by using finite element, it can be seen that the temperature gradient on the resonator structure before adjustment of the circular ring structure resonator is greater than the temperature gradient after adjustment by using the technical solution. Q TED The vibration mode of the resonator is effectively improved, the stress distribution in the structure is more balanced,

[0078] After adjusting the trajectory distribution of the resonator 1, the shape of the electrodes inside and outside the resonator 1 is also adjusted, and the resonator adopts the structure of the inner and outer electrodes.

[0079] ​In this embodiment, the resonant oscillator is prepared in the middle of the device layer according to the pattern of track distribution, the bias electrode 3 and the external electrode 5 are respectively arranged in four symmetrical positions, the four bias electrodes 3 are distributed at 0°, 90°, 180° and 270°, and the four external electrodes 5 are distributed at 45°, 135°, 225° and 315°; the inner diameter of the cavity structure is larger than the outer diameter of the resonant oscillator 1, the cavity structure is etched out in the substrate layer, and the buried oxide layer at the corresponding position is released in the subsequent etching process, so that the resonant oscillator 1 is suspended in the substrate layer. In the state of the cavity structure, the support beam 2 on the periphery of the resonant oscillator 1 extends outside the cavity structure to the buried oxide layer 7, and then connects to the bias electrode 3. The periphery of the resonant oscillator 1 is provided with a support sheet structure 9 in the area between adjacent bias electrodes 3. The inner side of the support sheet structure 9 is arc-shaped and maintains a gap with the periphery of the resonant oscillator 1. The two straight sides and the top corners of the support sheet structure 9 are arranged on the buried oxide layer 7 and a rectangular support platform is provided at the top corner to support the external electrode 5. The support sheet structure 9 is also a structure etched on the device layer 6 to support the connection and installation of the external electrode 5. The internal electrode 4 is located in the middle area of ​​the resonant oscillator and is not directly connected to the inner periphery of the resonant oscillator. It can also be supported or connected by a support structure or an external structure.

[0080] Furthermore, the resonant oscillator 1 includes an annular main body structure, and the inner contour and / or outer contour of the annular main body structure shrinks toward the center, and the shrinkage amounts are different.

[0081] That is, the contour of the annular main structure changes from a standard circular or rectangular structure to a contour with a varying curvature, which can be adjusted based on the anisotropy of the single-crystal silicon material. When the annular main structure is a circular ring structure, multiple arc segments of its inner and / or outer contours contract radially. When the annular main structure is a square ring structure, the sides of its inner and / or outer contours contract and change from a straight line to a curved line, with the outer contour forming a convex curve and the inner contour forming a concave curve.

[0082] Specifically, taking the radial extension mode of the resonant oscillator 1 as an example, Figure 4 As shown, the traditional ring structure is a standard circle 0. According to the anisotropy of the single crystal silicon material, the structure of the adjusted resonant oscillator 1 is obviously different from the geometric trajectory of the circular resonator. The adjusted resonant oscillator 1 has four arcs indented in the radial direction. Figure 5 It shows the circular trajectory of the resonant oscillator 1 after adjusting the inner contour, and it also has four arc segments showing morphological changes. Figure 6It shows the annular trajectory of the resonant oscillator 1 after adjusting the inner and outer contours at the same time. At this time, the ring is no longer a standard circular ring, but a special-shaped ring with a varying width. The arc segments where the inner and outer contours vary are staggered, making the width of the adjusted resonant oscillator slightly larger at 0°, 90°, 180°, and 270°, which are the positions where the support beams are connected. These positions are also the vibration node positions of the resonant oscillator. Such an arrangement can improve its vibration characteristics and stress state.

[0083] Figure 7 The structure of the plate-shaped resonant oscillator after the outer contour is adjusted is shown. Figures 8 to 11 These are schematic diagrams of the square ring structure after adjusting the inner contour of the resonant oscillator, the square ring structure after adjusting the outer contour, the square ring structure after adjusting the inner and outer contours, and the square plate structure after adjusting the outer contour. It can be seen that the sides of the square ring structure are no longer straight edges, but arc-shaped edges with varying widths.

[0084] Furthermore, the periphery of the annular main structure is also connected to a mechanical coupling ring structure through the support beam or anchor point, and the inner contour and / or outer contour of the mechanical coupling ring structure also shrinks toward the center of the mechanical coupling ring structure, and the bias electrode is set at the location of the mechanical coupling ring structure.

[0085] Specifically, such as Figure 12 and Figure 13 As shown, the contour adjustment form of the mechanical coupling ring structure is basically similar to the contour adjustment form of the resonant oscillator, so that its contour is no longer a standard circle or rectangle, and electrodes are provided on the mechanical coupling ring structure.

[0086] Further, such as Figure 14 and 15 As shown, the support beam 2 is a straight beam, a T-shaped beam or a folded beam arranged at the vibration node of the resonant oscillator; Figure 16 As shown, the support beam 2 may also be a spoke beam arranged on the inner periphery of the resonant oscillator, and a central anchor point 10 is used for support at the middle intersection of the spoke beam.

[0087] Furthermore, the inner electrodes and the outer electrodes are symmetrically arranged on the periphery of the resonant oscillator, and one outer electrode is arranged between adjacent inner electrodes.

[0088] Furthermore, the resonator structure is adjusted along <100> to <110> The trajectory distribution of the crystal direction includes but is not limited to etching microholes or grooves on the structure of the resonator along different crystal directions, using regional doping to perform doping at different crystal direction positions, and adjusting the equivalent stiffness of the resonator structure in different crystal directions to balance the stress distribution and reduce thermoelastic loss.

[0089] Preferably, the single crystal silicon material is N-type or P-type heavily or super heavily doped, and the doping concentration includes but is not limited to 4.0×10 19 / cm 3 to 2.0×10 20 / cm 3 .

[0090] Preferably, the resonator structure can be used alone, or can form a resonator array or be coupled with other resonators as a mechanical coupling structure, so as to adjust the overall performance of the coupled resonators.

[0091] Preferably, the vibration modes of the resonator include but are not limited to extension mode, shear mode and combined mode.

[0092] The structure of the resonant oscillator is not limited to a specific type of resonator, including but not limited to piezoelectric, capacitive and piezoresistive resonator designs. When a piezoelectric resonator design is adopted, the device structure includes but is not limited to a composite thin film structure of metal-piezoelectric layer-single crystal silicon.

[0093] Furthermore, the trajectories of the resonant oscillator 1 in different crystal directions after adjustment satisfy the following conditions:

[0094] ,

[0095] Where, is the structural parameter of the resonant oscillator, is the vibration modal parameter, for and Function, structure parameters At least width, radius and thickness, is the Young's modulus of each crystal direction, is the trajectory parameter before adjustment, For reference Young's modulus, the Young's modulus of single crystal silicon is as follows Figure 3 shown. Example 2

[0096] A method for fabricating a micromechanical resonator that accounts for thermoelastic losses. The method is applicable to device structures, not limited to specific resonator types, including but not limited to piezoelectric, capacitive, and piezoresistive resonator designs. When a piezoelectric resonator design is employed, the device structure includes but is not limited to a composite thin-film structure of metal, piezoelectric layer, and single-crystal silicon.

[0097] When the resonator is a single-crystal silicon single-layer structure, the preparation method is as follows:

[0098] (1) If Figure 18As shown, a SOI wafer is provided, which includes, from bottom to top, a substrate layer 501 (substrate silicon wafer), a buried oxide layer, and a device layer 503 (device layer silicon) with a thickness of 5-60 μm;

[0099] (2) If Figure 19 As shown, a metal layer with a thickness of 1-2 μm is deposited on the device layer 501 and processed by a patterning process to form metal pads 504. These metal pads will be used for electrical connection in subsequent steps.

[0100] (3) If Figure 20 As shown, the front side of the SOI wafer is etched, and the device layer 503 is selectively etched until the etching stops on the buried oxide layer 502. The microstructure of the desired resonator is formed in the device layer 503 according to the adjusted trajectory. This step ensures the formation of the desired microstructure in the device layer while protecting the buried oxide layer below.

[0101] (4) If Figure 21 As shown, the back side of the SOI wafer is etched, the substrate layer 501 is selectively etched until the buried oxide layer 502 is etched, a through hole or the cavity structure is formed in the substrate layer 501, and the buried oxide layer 502 is exposed to prepare for the subsequent release process;

[0102] (5) If Figure 22 As shown, gaseous hydrofluoric acid is introduced to corrode and release the exposed buried oxide layer 502, allowing the resonant oscillator to be released and suspended, thereby obtaining a micromechanical resonator structure. Gaseous hydrofluoric acid can effectively remove the buried oxide layer, achieving the release and suspension of the device, thereby completing the resonator structure.

[0103] The above-mentioned embodiment 2 is a preparation process using SOI technology. The resonator with a single-crystal silicon single-layer structure can also be prepared using CSOI technology. The prepared resonator structure is as follows: Figure 23 shown. Example

[0104] A method for preparing a micromechanical resonator taking into account thermoelastic loss, wherein the resonator is a composite structure of metal-piezoelectric layer-single crystal silicon, the preparation method is as follows:

[0105] (1) If Figure 24 As shown, a SOI wafer is provided, which includes, from bottom to top, a substrate layer 601 (substrate silicon wafer), a buried oxide layer 602, and a device layer 603 (device layer silicon) with a thickness of 5-60 μm;

[0106] (2) If Figure 25As shown, a 0.5-1 pm thick piezoelectric material 604 (including but not limited to aluminum nitride and lead zirconate titanate, etc.) and a 0.15-0.2 pm thick upper electrode 605 (including but not limited to molybdenum) are sequentially deposited on the device layer 603, and then the upper electrode is patterned, followed by deposition of a greater than 0.2 pm thick top oxide layer 606;

[0107] (3) As shown in Figure 26 , the top oxide layer 606 is etched to form an upper electrode via, exposing the upper electrode 605;

[0108] (4) As shown in Figure 27 , the top oxide layer 606 and the piezoelectric material 604 are continuously etched to form a lower electrode via, exposing the device layer 603;

[0109] (5) As shown in Figure 28 , a 1-2 pm thick metal layer (including but not limited to aluminum) is deposited in the upper electrode via and the lower electrode via, and is patterned to form a metal pad 607;

[0110] (6) As shown in Figure 29 , the top oxide layer 606, the piezoelectric material 604, and the device layer 603 are front etched until the buried oxide layer 602, and the microstructure of the desired resonator is formed in the device layer according to the adjusted track distribution;

[0111] (7) As shown in Figure 30 , the back of the substrate layer 601 is etched until the buried oxide layer 602 is reached, forming a via or the cavity structure in the substrate layer 601, exposing the buried oxide layer 602;

[0112] (8) As shown in Figure 31 , gaseous hydrofluoric acid is introduced to etch and release the exposed buried oxide layer 602, allowing the resonator to release and suspend, obtaining a micro-mechanical resonator structure.

[0113] The above-described embodiment 3 is a preparation process using an SOI process. The metal-piezoelectric layer-single crystal silicon composite thin film structure resonator can also be prepared using a CSOI process, and the prepared resonator structure is as shown in Figure 32 .

[0114] Although embodiments of the present application have been shown and described, it is to be understood that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A micromechanical resonator considering thermoelastic loss, comprising a substrate layer, a buried oxide layer and a device layer arranged on the substrate layer, wherein the substrate layer has a cavity structure, characterized in that: The device layer includes a resonant oscillator suspended above the cavity structure, the structure of the resonant oscillator is along <100> to <110> The trajectory distribution in the crystal direction is adjusted according to the anisotropy of the single crystal silicon material and the vibration characteristics of different modes so that the outline of the resonant oscillator is an irregular rectangular and / or circular structure; the resonant oscillator is used alone, or to form a resonator array, or as a mechanical coupling structure to couple with other resonators; Microholes or grooves are etched in the resonator structure along different crystal directions, and regional doping is used to perform doping at different crystal directions to adjust the equivalent stiffness of the resonator structure in different crystal directions. The trajectory of the resonator in different crystal directions after adjustment meets the following conditions: ， Where, is the structural parameter of the resonant oscillator, is the vibration modal parameter, for and Function, structure parameters At least width, radius and thickness, is the Young's modulus of each crystal direction, is the trajectory parameter before adjustment, is the reference Young's modulus.

2. The micromechanical resonator considering thermoelastic loss according to claim 1, characterized in that: The trajectory distribution adjustment method is suitable for a variety of resonant oscillator structures, including ring-shaped or plate-shaped structures; the outer contour of the plate-shaped resonator and the inner contour and / or outer contour of the ring structure are adjusted, and the inner contour and / or outer contour are respectively contracted toward the center, and there are different contraction amounts.

3. The micromechanical resonator considering thermoelastic loss according to claim 2, characterized in that: When the main structure of the resonant oscillator is a circular ring or circular plate structure, multiple arc segments of its inner contour and / or outer contour are radially contracted; when the main structure of the resonant oscillator is a square ring or square plate structure, the side length of its inner contour and / or outer contour changes from a straight line state to a curved state after contraction, the side length of the outer contour is a convex curve, and the side length of the inner contour is a concave curve.

4. The micromechanical resonator considering thermoelastic loss according to claim 1, characterized in that: When the structure of the resonant oscillator is coupled with other resonators as a coupling structure, it is connected to other structures through support beams or anchor points, and the inner contour and / or outer contour of the annular or plate-shaped structure of the coupling structure also shrinks toward the center of the coupling structure.

5. The micromechanical resonator considering thermoelastic loss according to claim 1, characterized in that: The resonant oscillator structure is a single-layer single-crystal silicon structure, or a composite thin film structure of metal-piezoelectric layer-single-crystal silicon.

6. The micromechanical resonator considering thermoelastic loss according to claim 1, characterized in that: A support beam is provided on the periphery of the resonant oscillator. The support beam is a straight beam, a T-shaped beam or a folded beam arranged at the vibration node of the resonant oscillator, or the support beam is a spoke beam arranged on the inner periphery of the resonant oscillator.

7. A method for preparing a micromechanical resonator taking thermoelastic loss into consideration according to any one of claims 1 to 6, characterized in that: When the resonator is a single-crystal silicon single-layer structure, the preparation method is as follows: Providing an SOI wafer, wherein the SOI wafer comprises, from bottom to top, a substrate layer, a buried oxide layer, and a device layer with a thickness of 5-60 μm; Depositing a 1-2µm thick metal layer on the device layer and forming a metal pad through a patterning process; Etching the front side of the SOI wafer, selectively etching the device layer until the etching stops on the buried oxide layer, and forming a microstructure of the required resonant oscillator in the device layer according to the adjusted trajectory; Back-etching the SOI wafer, selectively etching the substrate layer until the buried oxide layer is etched, forming a through hole or the cavity structure in the substrate layer, and exposing the buried oxide layer; Gaseous hydrofluoric acid is introduced to corrode and release the exposed buried oxide layer, thereby releasing and suspending the resonant oscillator to obtain a micromechanical resonator structure.

8. A method for preparing a micromechanical resonator taking thermoelastic loss into consideration according to any one of claims 1 to 6, characterized in that: When the resonator is a composite structure of metal-piezoelectric layer-single crystal silicon, the preparation method is as follows: Providing an SOI wafer, wherein the SOI wafer comprises, from bottom to top, a substrate layer, a buried oxide layer, and a device layer with a thickness of 5-60 μm; Depositing a piezoelectric material with a thickness of 0.5-1 µm and an upper electrode with a thickness of 0.15-0.2 µm on the device layer, patterning the upper electrode, and then depositing a top oxide layer with a thickness greater than 0.2 µm; Etching the top oxide layer to form an upper electrode through hole to expose the upper electrode; Continue etching the top oxide layer and the piezoelectric material to form a lower electrode through hole, exposing the device layer; Depositing a metal layer with a thickness of 1-2 μm in the upper electrode through hole and the lower electrode through hole, and performing patterning to form a metal pad; Performing front etching on the top oxide layer, the piezoelectric material, and the device layer until the buried oxide layer is reached, and distributing the microstructure of the desired resonant oscillator in the device layer according to the adjusted trajectory; Performing back etching on the substrate layer until the buried oxide layer is reached, forming a through hole or the cavity structure in the substrate layer, and exposing the buried oxide layer; Gaseous hydrofluoric acid is introduced to corrode and release the exposed buried oxide layer, thereby releasing and suspending the resonant oscillator to obtain a micromechanical resonator structure.

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