A micromechanical resonator and a method for manufacturing the same

Abstract

The present invention belongs to the field of microelectronic technology, and discloses a micromechanical resonator and a preparation method thereof. The micromechanical resonator comprises a substrate silicon wafer and a resonator structure, the resonator structure comprises a resonant oscillator and a support beam, the substrate silicon wafer has a cavity structure, the resonant oscillator is suspended above the cavity structure, the resonant oscillator is connected to the substrate silicon wafer through a support beam, the support beam is connected to the boundary of the resonant oscillator, and the connection part between the support beam and the resonant oscillator is a structure with a size change in the thickness direction. The present invention can effectively reduce anchor point loss and improve the Q value of the resonator.

Description

Technical Field

[0001] The present invention belongs to the field of microelectronic technology, and more specifically, relates to a micromechanical resonator and a preparation method thereof. Background Art

[0002] Microelectromechanical Systems (MEMS) are miniaturized mechanical devices or systems manufactured based on semiconductor micro-nano processing technology. They have the advantages of small size, light weight, low power consumption, low price, and compatibility with integrated circuit manufacturing processes. A micromechanical resonator is a device with a micromechanical structure as its main body. Its working method is that when the resonator is stimulated by an external physical signal, when the frequency of the driving signal is equal to the natural frequency of the system, the mechanical structure of the system will resonate near its natural frequency, the system amplitude will reach the maximum, and the generated resonant signal will be converted into other physical signal outputs. Since the amplitude of the micromechanical resonator at the natural frequency is the largest and the energy conversion efficiency is the highest, the microresonator realizes mechanical frequency selection through mechanical vibration. In recent years, oscillators, filters, and duplexers based on micromechanical resonators have been widely used in the field of wireless communications. In addition, in the field of precision detection, micromechanical resonators also have a broad application market.

[0003] The main performance parameters of micromechanical resonators include resonant frequency, quality factor (Q value), dynamic impedance, and frequency temperature coefficient. Q value is the main performance parameter used to measure the energy loss of micromechanical resonators. High Q value can improve the frequency selectivity of micromechanical resonators, reduce dynamic impedance, and reduce the phase noise of the system, thereby improving the frequency stability of micromechanical resonators. It is the core element for the practical application and commercialization of high-performance micromechanical resonators.

[0004] There are four main energy loss mechanisms that affect the Q value of micromechanical resonators: air damping loss (Q air ), thermoelastic loss (Q TED ), material loss (Q material ), anchor loss (Q anchor ),Right now

[0005]

[0006] Among them, air damping loss refers to the energy dissipation caused by the viscous damping of air during the vibration of the micromechanical resonator. Air damping loss can be eliminated by wafer-level or chip-level vacuum packaging methods. Material loss is the energy loss caused by the phonon-phonon and phonon-electron interactions inside the material. For ideal single-crystal silicon materials, the material loss is negligible. Thermoelastic loss is caused by the thermal gradient generated during the vibration of the resonator. The thermal gradient causes heat flow in the resonator material, causing mechanical energy loss. Anchor point loss is an important energy loss mechanism that affects the Q value of the micromechanical resonator. When the micromechanical resonator resonates, the transverse mechanical wave is not completely reflected back at the boundary of the resonator, but is transmitted to the substrate through the supporting structure, causing energy loss. How to reduce anchor point loss and thus improve the Q value of the resonator is a problem that needs to be solved in this field. Summary of the invention

[0007] The object of the present invention is to provide a micromechanical resonator and a method for preparing the same, so as to effectively reduce the anchor point loss and thereby improve the Q value of the resonator.

[0008] The present invention provides a micromechanical resonator, comprising: a substrate silicon wafer and a resonator structure, wherein the resonator structure comprises a resonant oscillator and a support beam; the substrate silicon wafer has a cavity structure, the resonant oscillator is suspended above the cavity structure of the substrate silicon wafer, and the resonant oscillator is connected to the substrate silicon wafer through the support beam; the support beam is connected to the boundary of the resonant oscillator, and the connection portion between the support beam and the resonant oscillator is a structure with a size varying in a thickness direction.

[0009] Preferably, the connecting portion between the support beam and the resonant oscillator is a gradual structure in the thickness direction; the upper surface of the support beam, the lower surface of the support beam, or the upper surface and the lower surface of the support beam have a non-planar geometric structure relative to the surface of the resonant oscillator, and the non-planar geometric structure is a concave or convex geometric structure.

[0010] Preferably, the cross-section of the support beam is any combination of one or more of rectangular, trapezoidal, circular, elliptical, and arched shapes; the resonant oscillator is any combination of one or more of rectangular plates, circular plates, elliptical plates, arched plates, and polygonal plates.

[0011] Preferably, the support beam is located at the vibration node, and the number of the support beam is one or more.

[0012] Preferably, the micromechanical resonator is a piezoelectric resonator, a capacitive resonator or a piezoresistive resonator.

[0013] Preferably, the resonant oscillator is one of a single thin film structure, a composite thin film structure of metal-piezoelectric layer-metal, and a composite thin film junction of metal-piezoelectric layer-single crystal silicon / polycrystalline silicon; the single thin film structure is single crystal silicon, polycrystalline silicon or silicon germanium; the material of the piezoelectric layer is one of quartz, aluminum nitride, scandium-doped aluminum nitride, zinc oxide, and lead zirconate titanate.

[0014] On the other hand, the present invention provides a method for preparing a micromechanical resonator, wherein the connecting portion between the support beam and the resonant oscillator is made by a photolithography process using a laser direct writing process or a thermal reflow process, or is made by maskless etching using a laser or ion beam; the above-mentioned micromechanical resonator is prepared by using the method for preparing the micromechanical resonator.

[0015] Preferably, the prepared micromechanical resonator is a capacitive resonator, and the preparation method comprises the following steps:

[0016] Step 1, etching a cavity structure on a substrate silicon wafer, and growing a buried oxide layer on the surface of the substrate silicon wafer;

[0017] Step 2, photolithography and patterning the lower surface of the device layer silicon to form a structure in which the lower surface of the device layer silicon has a varying size in the thickness direction;

[0018] Step 3, melt-bonding the lower surface of the device layer silicon to the substrate silicon wafer, and polishing and grinding the device layer silicon to a desired thickness;

[0019] Step 4, depositing a top electrode, photolithography and patterning the top electrode;

[0020] Step 5, photolithography and patterning the upper surface of the device layer silicon to form a structure in which the upper surface of the device layer silicon has a varying size in the thickness direction;

[0021] Step 6: Etch out the resonator structure.

[0022] Preferably, the prepared micromechanical resonator is a piezoelectric resonator of a metal-piezoelectric layer-metal composite film structure, and the preparation method comprises the following steps:

[0023] Step 1, etching a cavity on a substrate silicon wafer;

[0024] Step 2, chemical vapor deposition of a first sacrificial layer;

[0025] Step 3, sputtering a bottom electrode, and photolithography and patterning the bottom electrode;

[0026] Step 4, chemical vapor deposition of a second sacrificial layer, photolithography and patterning of the second sacrificial layer, to form a non-planar structure of the sacrificial layer;

[0027] Step 5, depositing a piezoelectric layer, photolithography and patterning the piezoelectric layer, and forming a structure in which the size of the upper surface of the piezoelectric layer changes in the thickness direction;

[0028] Step 6, etching electrode through holes;

[0029] Step 7, sputtering a top electrode, photolithography and patterning the top electrode;

[0030] Step 8, etching release holes;

[0031] Step 9: Etching the first sacrificial layer and the second sacrificial layer to form a structure in which the lower surface of the piezoelectric layer has a varying size in the thickness direction and a cavity structure of the substrate silicon wafer.

[0032] Preferably, the prepared micromechanical resonator is a piezoelectric resonator of a metal-piezoelectric layer-single crystal silicon / polycrystalline silicon composite thin film structure, and the preparation method comprises the following steps:

[0033] Step 1, etching a cavity structure on a substrate silicon wafer, and growing a buried oxide layer on the surface of the substrate silicon wafer;

[0034] Step 2, photolithography and patterning the lower surface of the device layer silicon to form a structure in which the lower surface of the device layer silicon has a varying size in the thickness direction;

[0035] Step 3, melt-bonding the lower surface of the device layer silicon to the substrate silicon wafer, and polishing and grinding the device layer silicon to a desired thickness;

[0036] Step 4, photolithography and patterning the upper surface of the device layer silicon to form a structure in which the upper surface of the device layer silicon has a varying size in the thickness direction;

[0037] Step 5, depositing a piezoelectric layer, photolithography and patterning the piezoelectric layer;

[0038] Step 6: depositing a top electrode, photolithography and patterning the top electrode;

[0039] Step 7, depositing a passivation layer, photolithography and patterning the passivation layer;

[0040] Step 8, etching the upper and lower electrode through holes;

[0041] Step 9, depositing an extraction electrode, photolithography and patterning the extraction electrode;

[0042] Step 10: Etch out the resonator structure.

[0043] One or more technical solutions provided in the present invention have at least the following technical effects or advantages:

[0044] In the invention, the substrate silicon wafer has a cavity structure, the resonant oscillator is suspended above the cavity structure, and the resonant oscillator is connected to the substrate silicon wafer through a support beam; the support beam is connected to the boundary of the resonant oscillator, and the connection part between the support beam and the resonant oscillator is a structure with size changes in the thickness direction. The present invention mainly utilizes the connection between the resonant oscillator of the resonator and the support beam with size changes in the thickness direction, for example, the upper surface, the lower surface, or the upper and lower surfaces of the support beam have a concave or convex geometric structure relative to the surface of the resonant oscillator, so that there is a high acoustic impedance mismatch between the resonant oscillator and the support beam, reducing the propagation of mechanical waves through the anchor point to the substrate, thereby effectively reducing the anchor point loss, thereby improving the Q value of the resonator. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 A three-dimensional schematic diagram of a micromechanical resonator provided in Example 1 of the present invention;

[0046] Figure 2 for Figure 1 A schematic cross-sectional view of a micromechanical resonator is shown;

[0047] Figure 3 A three-dimensional schematic diagram of a micromechanical resonator provided in Example 2 of the present invention;

[0048] Figure 4 for Figure 3 A schematic cross-sectional view of a micromechanical resonator is shown;

[0049] Figure 5 A three-dimensional schematic diagram of a micromechanical resonator provided in Example 3 of the present invention;

[0050] Figure 6 for Figure 5 A schematic cross-sectional view of a micromechanical resonator is shown;

[0051] Figure 7-1 to Figure 7-4 Schematic diagrams of cross-sectional shapes of several typical resonator structures in micromechanical resonators;

[0052] Figure 7-1 The upper and lower surfaces of the support beam have a resonator structure that is concave relative to the surface of the resonant vibrator, and the surface of the support beam is a curved surface;

[0053] Figure 7-2 The upper and lower surfaces of the support beam have a resonator structure with protrusions relative to the surface of the resonant vibrator, and the surface of the support beam is a curved surface;

[0054] Figure 7-3 The upper and lower surfaces of the support beam have a resonator structure that is concave relative to the surface of the resonant vibrator, and the surface of the support beam is partially flat and partially curved;

[0055] Figure 7-4The upper and lower surfaces of the support beam have a resonator structure with protrusions relative to the surface of the resonant vibrator, and the surface of the support beam is partially flat and partially curved;

[0056] Figure 8 The effect of the length of the resonator on the Q value of the single-crystal silicon capacitive micromechanical resonator with different support beams when only the anchor point loss is considered;

[0057] Fig. 9 The effect of the length of the resonator on the Q value of single-crystal silicon capacitive micromechanical resonators with different support beams when considering thermoelastic loss and anchor point loss.

[0058] Among them, 1-substrate silicon wafer, 2-support beam, 3-resonant oscillator;

[0059] 201-substrate silicon wafer, 202-buried oxide layer, 203-device layer silicon, 204-top electrode, 205-piezoelectric layer, 206-bottom electrode, 207-passivation layer, 208-extraction electrode;

[0060] 301-depression, 302-protrusion, 303-thickness variation area. DETAILED DESCRIPTION

[0061] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0062] In a first aspect, the present invention provides a micromechanical resonator, comprising: a substrate silicon wafer and a resonator structure, wherein the resonator structure includes a resonant oscillator and a support beam; the substrate silicon wafer has a cavity structure, the resonant oscillator is suspended above the cavity structure of the substrate silicon wafer, and the resonant oscillator is connected to the substrate silicon wafer through the support beam; the support beam is connected to a boundary of the resonant oscillator, and the connection portion between the support beam and the resonant oscillator is a structure whose size changes in the thickness direction.

[0063] The connecting portion between the support beam and the resonant oscillator is a gradual structure in the thickness direction; the upper surface of the support beam, the lower surface of the support beam, or the upper surface and the lower surface of the support beam have a non-planar geometric structure relative to the surface of the resonant oscillator, and the non-planar geometric structure is a concave or convex geometric structure.

[0064] Specifically, the connection between the support beam and the resonant vibrator can be a plane, a curved surface, or a combination of a plane and a curved surface that changes gradually along the thickness direction. For example, the upper surface, the lower surface, or the upper and lower surfaces of the support beam have one or more concave or convex geometric structures relative to the surface of the resonant vibrator.

[0065] The cross section of the support beam is any combination of one or more of the shapes of rectangle, trapezoid, circle, ellipse, arch, etc.; the resonant vibrator is any combination of one or more of the shapes of rectangle, circle, ellipse, arch, polygon, but not limited thereto. The support beam is located at the position of the vibration node, and the number of the support beam is one or more.

[0066] The micromechanical resonator is a piezoelectric resonator, a capacitive resonator or a piezoresistive resonator. The resonant oscillator is one of a single film structure, a composite film structure of metal-piezoelectric layer-metal, and a composite film junction of metal-piezoelectric layer-single crystal silicon / polycrystalline silicon; the single film structure is single crystal silicon, polycrystalline silicon or silicon germanium; the material of the piezoelectric layer is one of quartz, aluminum nitride, scandium-doped aluminum nitride, zinc oxide, and lead zirconate titanate.

[0067] In a second aspect, the present invention provides a method for preparing a micromechanical resonator, wherein the connecting portion between the support beam and the resonant oscillator is made by a photolithography process using a laser direct writing process or a thermal reflow process, or is made by maskless etching using a laser or ion beam; the above-mentioned micromechanical resonator is prepared by using the method for preparing the micromechanical resonator.

[0068] (1) The prepared micromechanical resonator is a capacitive resonator, and the preparation method comprises the following steps:

[0069] Step 1, etching a cavity structure on a substrate silicon wafer, and growing a buried oxide layer on the surface of the substrate silicon wafer;

[0070] Step 2, photolithography and patterning the lower surface of the device layer silicon to form a structure in which the lower surface of the device layer silicon has a varying size in the thickness direction;

[0071] Step 3, melt-bonding the lower surface of the device layer silicon to the substrate silicon wafer, and polishing and grinding the device layer silicon to a desired thickness;

[0072] Step 4, depositing a top electrode, photolithography and patterning the top electrode;

[0073] Step 5, photolithography and patterning the upper surface of the device layer silicon to form a structure in which the upper surface of the device layer silicon has a varying size in the thickness direction;

[0074] Step 6: Etch out the resonator structure.

[0075] It should be noted that step 2 and step 5 may exist simultaneously to form a structure with two thickness dimensions varying on the upper and lower surfaces, or only step 2 may be retained to form a structure with a dimension varying in the thickness direction on the lower surface of the device layer silicon, or only step 5 may be retained to form a structure with a dimension varying in the thickness direction on the upper surface of the device layer silicon.

[0076] (2) The prepared micromechanical resonator is a piezoelectric resonator of a metal-piezoelectric layer-metal composite film structure, and the preparation method comprises the following steps:

[0077] Step 1, etching a cavity on a substrate silicon wafer;

[0078] Step 2, chemical vapor deposition of a first sacrificial layer;

[0079] Step 3, sputtering a bottom electrode, and photolithography and patterning the bottom electrode;

[0080] Step 4, chemical vapor deposition of a second sacrificial layer, photolithography and patterning of the second sacrificial layer, to form a non-planar structure of the sacrificial layer;

[0081] Step 5, depositing a piezoelectric layer, photolithography and patterning the piezoelectric layer, and forming a structure in which the size of the upper surface of the piezoelectric layer changes in the thickness direction;

[0082] Step 6, etching electrode through holes;

[0083] Step 7, sputtering a top electrode, photolithography and patterning the top electrode;

[0084] Step 8, etching release holes;

[0085] Step 9: Etching the first sacrificial layer and the second sacrificial layer to form a structure in which the lower surface of the piezoelectric layer has a varying size in the thickness direction and a cavity structure of the substrate silicon wafer.

[0086] Similar to (1), the structure with thickness variation on both the upper and lower surfaces can be formed simultaneously, or the structure with thickness variation on only one of the surfaces can be formed. The preparation method can be adjusted adaptively.

[0087] (3) The prepared micromechanical resonator is a piezoelectric resonator of a metal-piezoelectric layer-single crystal silicon / polycrystalline silicon composite thin film structure, and the preparation method comprises the following steps:

[0088] Step 1, etching a cavity structure on a substrate silicon wafer, and growing a buried oxide layer on the surface of the substrate silicon wafer;

[0089] Step 2, photolithography and patterning the lower surface of the device layer silicon to form a structure in which the lower surface of the device layer silicon has a varying size in the thickness direction;

[0090] Step 3, melt-bonding the lower surface of the device layer silicon to the substrate silicon wafer, and polishing and grinding the device layer silicon to a desired thickness;

[0091] Step 4, photolithography and patterning the upper surface of the device layer silicon to form a structure in which the upper surface of the device layer silicon has a varying size in the thickness direction;

[0092] Step 5, depositing a piezoelectric layer, photolithography and patterning the piezoelectric layer;

[0093] Step 6: depositing a top electrode, photolithography and patterning the top electrode;

[0094] Step 7, depositing a passivation layer, photolithography and patterning the passivation layer;

[0095] Step 8, etching the upper and lower electrode through holes;

[0096] Step 9, depositing an extraction electrode, photolithography and patterning the extraction electrode;

[0097] Step 10: Etch out the resonator structure.

[0098] Similar to (1), the structure with thickness variation on both the upper and lower surfaces can be formed simultaneously, or the structure with thickness variation on only one of the surfaces can be formed. The preparation method can be adjusted adaptively.

[0099] Several specific embodiments are given below to facilitate a better understanding of the present invention.

[0100] Embodiment 1:

[0101] Figure 1 It is shown that the resonant oscillator provided in Example 1 is a capacitive resonator with a single crystal silicon thin film structure.

[0102] Specifically, a micromechanical resonator includes a substrate silicon wafer 1 and a resonator structure, wherein a cavity structure is arranged on the front side of the substrate silicon wafer 1; the resonator structure includes a resonant oscillator 3 and a support beam 2.

[0103] The resonant oscillator 3 is suspended above the cavity structure, and the resonant oscillator 3 is connected to the substrate silicon wafer 1 through the support beam 2 .

[0104] The support beam 2 is located at the boundary of the resonant oscillator 3 , and the thickness direction of the support beam 2 and the resonant oscillator 3 at the connection is gradually changed, specifically, the upper and lower surfaces of the support beam 2 have a concave geometric structure.

[0105] The cross section of the support beam 2 is a Boolean operation subtraction figure of a rectangle and an arc. The support beam 2 is located at the position of the vibration node, and the number of the support beams 2 is two. The resonant oscillator 3 is a single thin film structure including single crystal silicon. The resonant oscillator 3 is a rectangular plate.

[0106] Figure 2 This is a schematic cross-sectional view of a micromechanical resonator prepared in Example 1. The specific processing steps are as follows:

[0107] (1) A cavity is etched on the substrate silicon wafer 201 using a deep reactive ion etching process, and silicon dioxide is grown on the surface of the substrate silicon wafer as a buried oxide layer 202 using a thermal oxidation process.

[0108] (2) Photolithography and patterning the lower surface of the device layer silicon 203: In the photolithography step, a thermal reflow process is used to gently slope the photoresist to form a slope with a certain inclination angle, and a silicon etching process is used to form a concave structure on the lower surface of the support beam. In addition, conventional photolithography and single crystal silicon isotropic etching processes can also be used to form a concave structure on the lower surface of the support beam.

[0109] (3) The lower surface of the device layer silicon 203 is melt-bonded to the substrate silicon wafer 201, and the device layer silicon 203 is polished and ground to a desired thickness.

[0110] (4) After depositing the top electrode 204, the top electrode 204 is photolithographically patterned.

[0111] (5) Photolithography and patterning the upper surface of the device layer silicon 203: In the photolithography step, a thermal reflow process is used to gently slope the photoresist to form a slope with a certain inclination angle, and a silicon etching process is used to form a concave structure on the upper surface of the support beam. In addition, conventional photolithography and single crystal silicon isotropic etching processes can also be used to form a concave structure on the upper surface of the support beam.

[0112] (6) The resonator structure is etched out using reactive ion etching technology.

[0113] Embodiment 2:

[0114] Figure 3 It is shown that the resonant oscillator provided in Example 2 is a piezoelectric resonator with a metal-piezoelectric layer-metal composite film structure.

[0115] The difference from Example 1 is that: the resonant vibrator 3 in Example 1 is a single structure including single crystal silicon, the resonant vibrator 3 is a rectangular plate, and the micromechanical resonator is a capacitive resonator. In Example 2, the resonant vibrator 3 is a composite thin film structure including metal-piezoelectric layer-metal, the resonant vibrator 3 is a polygonal plate, the support beam 2 is located at the position of the vibration node, the number of the support beams 2 is multiple, and the resonant vibrator 3 is connected to the substrate silicon wafer 1 through the support beam 2; the micromechanical resonator is a piezoelectric resonator, and the material of the piezoelectric layer is any one of quartz, aluminum nitride, scandium-doped aluminum nitride, zinc oxide, and lead zirconate titanate.

[0116] Figure 4 This is a schematic cross-sectional view of a micromechanical resonator prepared in Example 2. The specific processing steps are as follows:

[0117] (1) A cavity is etched on the substrate silicon wafer 201 using a reactive ion etching process.

[0118] (2) Chemical vapor deposition of a first sacrificial layer and removal of excess material using a chemical mechanical polishing process.

[0119] (3) After sputtering the bottom electrode 206, the bottom electrode 206 is photolithographically patterned.

[0120] (4) After chemical vapor deposition of the second sacrificial layer, the second sacrificial layer is photolithographically patterned: in the photolithographic step, a thermal reflow process is used to gently slope the photoresist to form a slope with a certain inclination angle, and a sacrificial layer protrusion structure is formed through an etching process.

[0121] (5) After the piezoelectric layer 205 is deposited, the piezoelectric layer 205 is patterned by photolithography: in the photolithography step, a thermal reflow process is used to gently slope the photoresist to form a slope with a certain inclination angle, and a concave structure is formed on the upper surface of the piezoelectric layer 205 by an etching process.

[0122] (6) Etch electrode through holes using reactive ion etching technology.

[0123] (7) After sputtering the top electrode 204, the top electrode 204 is photolithographically patterned.

[0124] (8) Etching release holes.

[0125] (9) Etching the first sacrificial layer and the second sacrificial layer to form a recessed structure on the lower surface of the piezoelectric layer 205 and a cavity structure of the substrate silicon wafer.

[0126] Embodiment 3:

[0127] Figure 5 It is shown that the resonant oscillator provided in Example 3 is a piezoelectric resonator with a metal-piezoelectric layer-single crystal silicon / polycrystalline silicon composite thin film structure.

[0128] The difference from Example 2 is that the resonant oscillator 3 in Example 2 is a composite thin film structure including metal-piezoelectric layer-metal, the resonant oscillator 3 is a polygonal plate, and the number of support beams 2 is multiple. In Example 3, the resonant oscillator 3 is a composite thin film structure including metal-piezoelectric layer-single crystal silicon, the resonant oscillator 3 is a rectangular plate, the number of support beams 2 is two, and the resonant oscillator 3 is connected to the substrate silicon wafer 1 through the support beams 2.

[0129] Figure 6 This is a schematic cross-sectional view of a micromechanical resonator prepared in Example 3. The specific processing steps are as follows:

[0130] (1) A cavity is etched on the substrate silicon wafer 201 using a deep reactive ion etching process, and silicon dioxide is grown on the surface of the substrate silicon wafer as a buried oxide layer 202 using a thermal oxidation process.

[0131] (2) Photolithography and patterning the lower surface of the device layer silicon 203: In the photolithography step, a thermal reflow process is used to gently slope the photoresist to form a slope with a certain inclination angle, and a silicon etching process is used to form a concave structure on the lower surface of the support beam. In addition, conventional photolithography and single crystal silicon isotropic etching processes can also be used to form a concave structure on the lower surface of the support beam.

[0132] (3) The lower surface of the device layer silicon 203 is melt-bonded to the substrate silicon wafer 201, and the device layer silicon 203 is polished and ground to a desired thickness.

[0133] (4) Photolithography and patterning the upper surface of the device layer silicon 203: In the photolithography step, a thermal reflow process is used to gently slope the photoresist to form a slope with a certain inclination angle, and a silicon etching process is used to form a concave structure on the upper surface of the support beam. In addition, conventional photolithography and single crystal silicon isotropic etching processes can also be used to form a concave structure on the upper surface of the support beam.

[0134] (5) After the piezoelectric layer 205 is deposited, the piezoelectric layer 205 is photolithographically patterned.

[0135] (6) After depositing the top electrode 204, the top electrode 204 is photolithographically patterned.

[0136] (7) After depositing silicon dioxide as the passivation layer 207 , the passivation layer 207 is photolithographically processed and patterned.

[0137] (8) Use reactive ion etching technology to etch the upper and lower electrode through holes.

[0138] (9) After the extraction electrode 208 is deposited, the extraction electrode 208 is photolithographically patterned.

[0139] (10) The resonator structure is etched out using a reactive ion etching process.

[0140] Figure 7-1 to Figure 7-4 Figure 1 is a schematic diagram of the cross-sectional shape of several typical resonator structures in micromechanical resonators. Figure 7-1 The upper and lower surfaces of the support beam have a resonator structure with a depression 301 relative to the surface of the resonant vibrator 3 (the thickness variation area is marked as 303), and the surface of the support beam is a curved surface. Figure 7-2 The resonator structure has protrusions 302 on the upper and lower surfaces of the support beam relative to the surface of the resonant vibrator 3 (the thickness variation area is marked as 303), and the surface of the support beam is a curved surface; Figure 7-3 The resonator structure has a depression 301 on the upper and lower surfaces of the support beam relative to the surface of the resonant oscillator 3 (the thickness variation region is denoted as 303), and the surface part of the support beam is a plane surface and the part is a curved surface (the structure in the square dotted frame); Figure 7-4The resonator structure has protrusions 302 on the upper and lower surfaces of the support beam relative to the resonant oscillator 3 (the thickness change area is marked as 303), and the surface of the support beam is partially flat and partially curved (the structure in the square dotted box).

[0141] For micromechanical resonators, the main factors affecting the resonator Q value are thermoelastic loss and anchor loss. Thermoelastic loss is related to the type and thickness of the resonator structure material and the size of the resonator; anchor loss is related to the size of the resonator and the size and shape of the support beam. Figure 8 The influence of the length of the resonator on the Q value of the single crystal silicon capacitive micromechanical resonator with different support beams is given when only the anchor point loss is considered. Fig. 9 The influence of the length of the resonator on the Q value of the single crystal silicon capacitive micromechanical resonator with different support beams is given when considering the thermoelastic loss and anchor loss. Figures 8 to 9 The concave structure in Figure 7-1 As shown, the raised structure is Figure 7-2 As shown. <100> For a single-crystal silicon capacitive micromechanical resonator with a crystal orientation, the thickness of the single-crystal silicon is 20μm, the length of the support beam is 10μm, and the width is 5μm, the optimized value of the length of the resonant oscillator is 210μm. Figure 8 , Fig. 9 It can be seen that when the resonant vibrator is of the optimal size, the Q value of the resonator with a concave or convex structure of the support beam is significantly improved compared to the Q value of the resonator with a support beam without a concave or convex structure. The resonant vibrator is connected to the support beam with a gradual change in size in the thickness direction, which can reduce the impact of the resonator vibration on the support beam. Further, by designing a concave or convex geometric structure on the upper surface, lower surface, or upper and lower surfaces of the support beam, a high acoustic impedance mismatch is caused between the resonant vibrator and the support beam. When the length of the resonant vibrator is the optimized value, the mechanical amplitude at the boundary between the resonant vibrator and the support beam is the smallest, and the energy dissipation of the resonator outward is the smallest.

[0142] A micromechanical resonator and a method for manufacturing the same provided by an embodiment of the present invention include at least the following technical effects:

[0143] The present invention provides a micromechanical resonator capable of effectively improving the Q value and a manufacturing method thereof. The present invention mainly utilizes that a resonant oscillator of the resonator is gradually connected to a support beam in the thickness direction, and the upper surface, the lower surface or the upper and lower surfaces of the support beam have a concave or convex geometric structure relative to the surface of the resonant oscillator, so that a high acoustic impedance mismatch exists between the resonant oscillator and the support beam, reducing the propagation of mechanical waves through an anchor point to a substrate, thereby effectively reducing the anchor point loss and further improving the Q value of the resonator.

[0144] Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A micromechanical resonator, characterized in that: include: A substrate silicon wafer and a resonator structure, wherein the resonator structure comprises a resonant vibrator and a support beam; The substrate silicon wafer has a cavity structure, the resonant oscillator is suspended above the cavity structure of the substrate silicon wafer, and the resonant oscillator is connected to the substrate silicon wafer through the support beam; the support beam is connected to the boundary of the resonant oscillator, and the connection part between the support beam and the resonant oscillator is a structure with a size change in the thickness direction; The connecting portion between the support beam and the resonant vibrator is a gradually changing structure in the thickness direction; the upper surface of the support beam, the lower surface of the support beam, or the upper surface and the lower surface of the support beam have a non-planar geometric structure relative to the surface of the resonant vibrator, and the non-planar geometric structure is a concave or convex geometric structure; The cross section of the support beam is any combination of one or more of a rectangular, trapezoidal, circular, elliptical, and arched; the resonant vibrator is any combination of one or more of a rectangular plate, a circular plate, an elliptical plate, an arched plate, and a polygonal plate; The support beam is located at the position of the vibration node, and the number of the support beam is one or more; The micromechanical resonator is a piezoelectric resonator, a capacitive resonator or a piezoresistive resonator; The resonant oscillator is one of a single thin film structure, a metal-piezoelectric layer-metal composite thin film structure, and a metal-piezoelectric layer-single crystal silicon / polycrystalline silicon composite thin film junction; the single thin film structure is single crystal silicon, polycrystalline silicon or silicon germanium; the material of the piezoelectric layer is one of quartz, aluminum nitride, scandium-doped aluminum nitride, zinc oxide, and lead zirconate titanate.

2. A method for preparing a micromechanical resonator, characterized in that: The connection part between the support beam and the resonant oscillator is made by a photolithography process using a laser direct writing process or a thermal reflow process, or is made by maskless etching using a laser or ion beam; The micromechanical resonator as claimed in claim 1 is prepared by adopting the preparation method of the micromechanical resonator; The prepared micromechanical resonator is a capacitive resonator, a piezoelectric resonator of a metal-piezoelectric layer-metal composite film structure, or a piezoelectric resonator of a metal-piezoelectric layer-single crystal silicon / polycrystalline silicon composite film structure; When the prepared micromechanical resonator is a capacitive resonator, the preparation method comprises the following steps: Step 1, etching a cavity structure on a substrate silicon wafer, and growing a buried oxide layer on the surface of the substrate silicon wafer; Step 2, photolithography and patterning the lower surface of the device layer silicon to form a structure in which the lower surface of the device layer silicon has a varying size in the thickness direction; Step 3, melt-bonding the lower surface of the device layer silicon to the substrate silicon wafer, and polishing and grinding the device layer silicon to a desired thickness; Step 4, depositing a top electrode, photolithography and patterning the top electrode; Step 5, photolithography and patterning the upper surface of the device layer silicon to form a structure in which the upper surface of the device layer silicon has a varying size in the thickness direction; Step 6: Etch out the resonator structure.

3. The method for preparing a micromechanical resonator according to claim 2, characterized in that: When the prepared micromechanical resonator is a piezoelectric resonator of a metal-piezoelectric layer-metal composite film structure, the preparation method comprises the following steps: Step 1, etching a cavity on a substrate silicon wafer; Step 2, chemical vapor deposition of a first sacrificial layer; Step 3, sputtering a bottom electrode, and photolithography and patterning the bottom electrode; Step 4, chemical vapor deposition of a second sacrificial layer, photolithography and patterning of the second sacrificial layer, to form a non-planar structure of the sacrificial layer; Step 5, depositing a piezoelectric layer, photolithography and patterning the piezoelectric layer, and forming a structure in which the size of the upper surface of the piezoelectric layer changes in the thickness direction; Step 6, etching electrode through holes; Step 7, sputtering a top electrode, photolithography and patterning the top electrode; Step 8, etching release holes; Step 9: Etching the first sacrificial layer and the second sacrificial layer to form a structure in which the lower surface of the piezoelectric layer has a varying size in the thickness direction and a cavity structure of the substrate silicon wafer.

4. The method for preparing a micromechanical resonator according to claim 2, characterized in that: When the prepared micromechanical resonator is a piezoelectric resonator of a metal-piezoelectric layer-single crystal silicon / polycrystalline silicon composite thin film structure, the preparation method comprises the following steps: Step 1, etching a cavity structure on a substrate silicon wafer, and growing a buried oxide layer on the surface of the substrate silicon wafer; Step 2, photolithography and patterning the lower surface of the device layer silicon to form a structure in which the lower surface of the device layer silicon has a varying size in the thickness direction; Step 3, melt-bonding the lower surface of the device layer silicon to the substrate silicon wafer, and polishing and grinding the device layer silicon to a desired thickness; Step 4, photolithography and patterning the upper surface of the device layer silicon to form a structure in which the upper surface of the device layer silicon has a varying size in the thickness direction; Step 5, depositing a piezoelectric layer, photolithography and patterning the piezoelectric layer; Step 6, depositing a top electrode, photolithography and patterning the top electrode; Step 7, depositing a passivation layer, photolithography and patterning the passivation layer; Step 8, etching the upper and lower electrode through holes; Step 9, depositing an extraction electrode, photolithography and patterning the extraction electrode; Step 10: Etch out the resonator structure.

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