CN114124025A - Micromechanical resonator and preparation method thereof - Google Patents
Micromechanical resonator and preparation method thereof Download PDFInfo
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- 238000002360 preparation method Methods 0.000 title abstract description 17
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 104
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 104
- 239000010703 silicon Substances 0.000 claims abstract description 104
- 239000000758 substrate Substances 0.000 claims abstract description 56
- 238000001259 photo etching Methods 0.000 claims description 52
- 238000005530 etching Methods 0.000 claims description 46
- 238000000034 method Methods 0.000 claims description 45
- 238000000059 patterning Methods 0.000 claims description 37
- 230000008569 process Effects 0.000 claims description 35
- 238000000151 deposition Methods 0.000 claims description 26
- 229910021421 monocrystalline silicon Inorganic materials 0.000 claims description 25
- 239000010409 thin film Substances 0.000 claims description 14
- 230000008859 change Effects 0.000 claims description 11
- 239000002131 composite material Substances 0.000 claims description 10
- 229910021420 polycrystalline silicon Inorganic materials 0.000 claims description 10
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 10
- 238000000605 extraction Methods 0.000 claims description 9
- 238000002161 passivation Methods 0.000 claims description 9
- XLOMVQKBTHCTTD-UHFFFAOYSA-N Zinc monoxide Chemical compound [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 0.000 claims description 8
- 238000005229 chemical vapour deposition Methods 0.000 claims description 8
- PMHQVHHXPFUNSP-UHFFFAOYSA-M copper(1+);methylsulfanylmethane;bromide Chemical compound Br[Cu].CSC PMHQVHHXPFUNSP-UHFFFAOYSA-M 0.000 claims description 8
- 238000004544 sputter deposition Methods 0.000 claims description 8
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- 238000005498 polishing Methods 0.000 claims description 6
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 5
- 229910052760 oxygen Inorganic materials 0.000 claims description 5
- 239000001301 oxygen Substances 0.000 claims description 5
- HFGPZNIAWCZYJU-UHFFFAOYSA-N lead zirconate titanate Chemical compound [O-2].[O-2].[O-2].[O-2].[O-2].[Ti+4].[Zr+4].[Pb+2] HFGPZNIAWCZYJU-UHFFFAOYSA-N 0.000 claims description 4
- 229910052451 lead zirconate titanate Inorganic materials 0.000 claims description 4
- 239000010453 quartz Substances 0.000 claims description 4
- 239000011787 zinc oxide Substances 0.000 claims description 4
- 229910000577 Silicon-germanium Inorganic materials 0.000 claims description 3
- LEVVHYCKPQWKOP-UHFFFAOYSA-N [Si].[Ge] Chemical compound [Si].[Ge] LEVVHYCKPQWKOP-UHFFFAOYSA-N 0.000 claims description 3
- 238000003384 imaging method Methods 0.000 claims description 3
- 238000010884 ion-beam technique Methods 0.000 claims description 3
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/24—Constructional features of resonators of material which is not piezoelectric, electrostrictive, or magnetostrictive
- H03H9/2405—Constructional features of resonators of material which is not piezoelectric, electrostrictive, or magnetostrictive of microelectro-mechanical resonators
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H3/00—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators
- H03H3/007—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks
- H03H3/0072—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks of microelectro-mechanical resonators or networks
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H3/00—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators
- H03H3/007—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks
- H03H3/02—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of piezoelectric or electrostrictive resonators or networks
- H03H2003/027—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of piezoelectric or electrostrictive resonators or networks the resonators or networks being of the microelectro-mechanical [MEMS] type
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- Piezo-Electric Or Mechanical Vibrators, Or Delay Or Filter Circuits (AREA)
Abstract
The invention belongs to the technical field of microelectronics, and discloses a micromechanical resonator and a preparation method thereof. The micromechanical resonator comprises a substrate silicon wafer and a resonator structure, wherein the resonator structure comprises a resonant vibrator and a supporting beam, the substrate silicon wafer is provided with a cavity structure, the resonant vibrator is suspended above the cavity structure, the resonant vibrator is connected with the substrate silicon wafer through the supporting beam, the supporting beam is connected with the boundary of the resonant vibrator, and the connecting part of the supporting beam and the resonant vibrator is of a structure with size changing in the thickness direction. The invention can effectively reduce anchor point loss and improve the Q value of the resonator.
Description
Technical Field
The invention belongs to the technical field of microelectronics, and particularly relates to a micromechanical resonator and a preparation method thereof.
Background
Micro Electro Mechanical Systems (MEMS) is a miniaturized mechanical device or system manufactured based on semiconductor micro-nano processing technology, and has the advantages of small volume, light weight, low power consumption, low price, compatibility with integrated circuit manufacturing process, and the like. The micromechanical resonator is a device mainly composed of a micromechanical structure, and the operation mode is that when the resonator is excited by an external physical signal, and the frequency of a driving signal is equal to the natural frequency of a system, the mechanical structure of the system resonates near the natural frequency, the amplitude of the system reaches the maximum, and the generated resonant signal is converted into other physical signals to be output. Since the amplitude of the micromechanical resonator is the largest at the natural frequency, the energy conversion efficiency is the highest, and the mechanical frequency selection of the micromechanical resonator is realized through mechanical vibration. In recent years, oscillators, filters, and duplexers based on micromechanical resonators have been widely used in the field of wireless communication. In addition, in the field of precision detection, the micromechanical resonator also has a wide application market.
The main performance parameters of the micromechanical resonator include a resonant frequency, a quality factor (Q value), a dynamic impedance, a frequency temperature coefficient, and the like. The Q value is a main performance parameter for measuring the energy loss condition of the micromechanical resonator, and the high Q value can improve the frequency selectivity of the micromechanical resonator, reduce the dynamic impedance and reduce the phase noise of a system, so that the frequency stability of the micromechanical resonator is improved, and the Q value is a core element for the practicability and commercialization of the high-performance micromechanical resonator.
The energy loss mechanism influencing the Q value of the micromechanical resonator mainly comprises four parts: air damping loss (Q)air) Thermoelastic loss (Q)TED) Material loss (Q)material) Anchor point loss (Q)anchor) I.e. by
The air damping loss refers to energy dissipation caused by viscous damping of air in the vibration process of the micro-mechanical resonator. Air damping losses can be eliminated by wafer level or chip level vacuum packaging methods. Material loss is due to energy loss caused by phonon-phonon and phonon-electron interactions within the material, which is negligible for an ideal single crystal silicon material. Thermoelastic losses are caused by thermal gradients generated during vibration of the resonator, which cause heat flow in the resonator material, thereby causing mechanical energy losses. The anchor point loss is an important energy loss mechanism affecting the Q value of the micromechanical resonator, and the transverse mechanical wave at resonance of the micromechanical resonator is not completely reflected back at the resonator boundary, but is transmitted to the substrate through the support structure, thereby causing energy loss. How to reduce the anchor point loss and further improve the Q value of the resonator is a problem to be solved in the field.
Disclosure of Invention
The invention aims to provide a micromechanical resonator and a preparation method thereof, so that anchor point loss is effectively reduced, and the Q value of the resonator is further improved.
The present invention provides a micromechanical resonator comprising: the resonator structure comprises a resonant vibrator and a support beam; the substrate silicon chip is provided with a cavity structure, the resonator is suspended above the cavity structure of the substrate silicon chip, and the resonator is connected with the substrate silicon chip through the supporting beam; the support beam is connected to a boundary of the resonator, and a connection portion between the support beam and the resonator has a structure in which a dimension in a thickness direction changes.
Preferably, a connection portion between the support beam and the resonator is gradually changed in a thickness direction; the upper surface of the support beam, the lower surface of the support beam, or the upper and lower surfaces of the support beam have a non-planar geometry with respect to the surface of the resonator oscillator, the non-planar geometry being a concave or convex geometry.
Preferably, the cross section of the support beam is one or any combination of more of rectangle, trapezoid, circle, ellipse and arch; the resonant vibrator is one or any combination of a plurality of rectangular plates, circular plates, elliptical plates, arched plates and polygonal plates.
Preferably, the support beams are located at the position of the vibration node, and the number of the support beams is one or more.
Preferably, the micromechanical resonator is a piezoelectric resonator, a capacitive resonator, or a piezoresistive resonator.
Preferably, the resonator is one of a single film structure, a metal-piezoelectric layer-metal composite film structure, and a metal-piezoelectric layer-monocrystalline silicon/polycrystalline silicon composite film structure; the single thin film structure is monocrystalline silicon, polycrystalline silicon or silicon germanium; the piezoelectric layer is made of one of quartz, aluminum nitride, scandium-doped aluminum nitride, zinc oxide and lead zirconate titanate.
On the other hand, the invention provides a preparation method of the micromechanical resonator, the connecting part of the supporting beam and the resonator is made by a photoetching process by utilizing a laser direct writing process or a thermal reflow process, or is made by laser or ion beam maskless etching; the micromechanical resonator is prepared by the preparation method of the micromechanical resonator.
Preferably, the prepared micromechanical resonator is a capacitive resonator, and the preparation method comprises the following steps:
step 1, etching a cavity structure on a substrate silicon wafer, and growing an oxygen embedding layer on the surface of the substrate silicon wafer;
step 4, depositing a top electrode, and photoetching and patterning the top electrode;
step 5, photoetching and patterning the upper surface of the device layer silicon to form a structure with size change of the upper surface of the device layer silicon in the thickness direction;
and 6, etching the resonator structure.
Preferably, the prepared micromechanical resonator is a piezoelectric resonator with a metal-piezoelectric layer-metal composite thin film structure, and the preparation method comprises the following steps:
step 1, etching a concave cavity on a substrate silicon wafer;
step 4, depositing a second sacrificial layer by chemical vapor deposition, and photoetching and patterning the second sacrificial layer to form a non-planar structure of the sacrificial layer;
step 5, depositing a piezoelectric layer, and photoetching and patterning the piezoelectric layer to form a structure with the size of the upper surface of the piezoelectric layer changed in the thickness direction;
step 6, etching an electrode through hole;
step 7, sputtering a top electrode, and photoetching and patterning the top electrode;
step 8, etching the release hole;
and 9, etching the first sacrificial layer and the second sacrificial layer to form a structure of which the size of the lower surface of the piezoelectric layer changes in the thickness direction and a cavity structure of the substrate silicon wafer.
Preferably, the prepared micromechanical resonator is a piezoelectric resonator with a metal-piezoelectric layer-monocrystalline silicon/polycrystalline silicon composite film structure, and the preparation method comprises the following steps:
step 1, etching a cavity structure on a substrate silicon wafer, and growing an oxygen-buried layer on the surface of the substrate silicon wafer;
step 4, photoetching and patterning the upper surface of the device layer silicon to form a structure with size change of the upper surface of the device layer silicon in the thickness direction;
step 5, depositing a piezoelectric layer, and photoetching and patterning the piezoelectric layer;
step 6, depositing a top electrode, and photoetching and patterning the top electrode;
step 7, depositing a passivation layer, and photoetching and patterning the passivation layer;
step 8, etching an upper electrode through hole and a lower electrode through hole;
step 9, depositing an extraction electrode, and photoetching and imaging the extraction electrode;
and step 10, etching the resonator structure.
One or more technical schemes provided by the invention at least have the following technical effects or advantages:
in the invention, the substrate silicon chip is provided with a cavity structure, the resonant vibrator is suspended above the cavity structure, and the resonant vibrator is connected with the substrate silicon chip through a support beam; the support beam is connected to the boundary of the resonator, and the connection portion between the support beam and the resonator has a structure in which the dimension changes in the thickness direction. The invention mainly utilizes the connection of the dimension change of the resonator oscillator and the supporting beam in the thickness direction, for example, the upper surface, the lower surface or the upper surface and the lower surface of the supporting beam have a concave or convex geometric structure relative to the surface of the resonator oscillator, thereby leading the high acoustic impedance mismatch between the resonator oscillator and the supporting beam, reducing the propagation of mechanical waves to the substrate through anchor points, effectively reducing the loss of the anchor points and further improving the Q value of the resonator.
Drawings
Fig. 1 is a three-dimensional schematic diagram of a micromechanical resonator provided in embodiment 1 of the present invention;
figure 2 is a schematic cross-sectional view of the micromechanical resonator shown in figure 1;
fig. 3 is a three-dimensional schematic diagram of a micromechanical resonator provided in embodiment 2 of the present invention;
figure 4 is a schematic cross-sectional view of the micromechanical resonator shown in figure 3;
fig. 5 is a three-dimensional schematic diagram of a micromechanical resonator provided in embodiment 3 of the present invention;
figure 6 is a schematic cross-sectional view of the micromechanical resonator shown in figure 5;
figures 7-1 through 7-4 are schematic cross-sectional shapes of several exemplary resonator structures in a micromechanical resonator;
FIG. 7-1 shows a resonator structure in which the upper and lower surfaces of the support beam are recessed with respect to the surface of the resonator, and the surface of the support beam is a curved surface;
FIG. 7-2 shows a resonator structure in which the upper and lower surfaces of the support beam have protrusions with respect to the surface of the resonator, and the surface of the support beam is a curved surface;
fig. 7-3 is a resonator structure in which the upper and lower surfaces of the support beam have depressions with respect to the surface of the resonator, and the surface portion of the support beam is a flat surface portion having an arc surface;
fig. 7-4 are resonator structures in which the upper and lower surfaces of the support beam have projections with respect to the surface of the resonator, and the surface portion of the support beam is a planar portion having an arc surface;
fig. 8 is a graph of the effect of the length of the resonator on the Q-value of a single-crystal silicon capacitive micro-mechanical resonator with different support beams when only anchor point losses are considered;
fig. 9 is a graph showing the effect of the length of the resonator on the Q value of a single-crystal silicon capacitive micro-mechanical resonator with different support beams, considering thermoelastic loss and anchor point loss.
The method comprises the following steps of 1-a substrate silicon chip, 2-a support beam and 3-a resonant vibrator;
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;
301-depressions, 302-protrusions, 303-regions of varying thickness.
Detailed Description
In order to better understand the technical solution, the technical solution will be described in detail with reference to the drawings and the specific embodiments.
In a first aspect, the present invention provides a micromechanical resonator comprising: the resonator structure comprises a resonant vibrator and a support beam; the substrate silicon chip is provided with a cavity structure, the resonator is suspended above the cavity structure of the substrate silicon chip, and the resonator is connected with the substrate silicon chip through the supporting beam; the support beam is connected to a boundary of the resonator, and a connection portion between the support beam and the resonator has a structure in which a dimension in a thickness direction changes.
The connection part of the support beam and the resonant vibrator is of a gradually-changed structure in the thickness direction; the upper surface of the support beam, the lower surface of the support beam, or the upper and lower surfaces of the support beam have a non-planar geometry with respect to the surface of the resonator oscillator, the non-planar geometry being a concave or convex geometry.
Specifically, the connection between the support beam and the resonator may be a plane, a curved surface, or a combination of a plane and a curved surface, which gradually changes in 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 geometries with respect to the surface of the resonator element.
The cross section of the support beam is one or any combination of more of rectangular, trapezoidal, circular, oval, arched and the like; the resonator is any combination of one or more of a rectangular plate, a circular plate, an elliptical plate, an arched plate and a polygonal plate, but is not limited thereto. The supporting beams are located at the positions of the vibration nodes, and the number of the supporting beams is one or more.
The micromechanical resonator is a piezoelectric resonator, a capacitive resonator or a piezoresistive resonator. The resonance oscillator is one of a single film structure, a metal-piezoelectric layer-metal composite film structure and a metal-piezoelectric layer-monocrystalline silicon/polycrystalline silicon composite film structure; the single thin film structure is monocrystalline silicon, polycrystalline silicon or silicon germanium; the piezoelectric layer is made of one of quartz, aluminum nitride, scandium-doped aluminum nitride, zinc oxide and lead zirconate titanate.
In a second aspect, the invention provides a method for manufacturing a micromechanical resonator, wherein a connecting part of a support beam and a resonator is manufactured by a photoetching process by using a laser direct writing process or a thermal reflow process, or is manufactured by laser or ion beam maskless etching; the micromechanical resonator is prepared by the preparation method of the micromechanical resonator.
(1) The prepared micromechanical resonator is a capacitive resonator, and the preparation method comprises the following steps:
step 1, etching a cavity structure on a substrate silicon wafer, and growing an oxygen embedding layer on the surface of the substrate silicon wafer;
step 4, depositing a top electrode, and photoetching and patterning the top electrode;
step 5, photoetching and patterning the upper surface of the device layer silicon to form a structure with size change of the upper surface of the device layer silicon in the thickness direction;
and 6, etching the resonator structure.
It should be noted that step 2 and step 5 may exist simultaneously, and form a structure with two thickness dimensions of the upper and lower surfaces, or only the structure with dimension variation in the thickness direction of the lower surface of the device layer silicon formed in step 2 may be left, or only the structure with dimension variation in the thickness direction of the upper surface of the device layer silicon formed in step 5 may be left.
(2) The prepared micromechanical resonator is a piezoelectric resonator with a metal-piezoelectric layer-metal composite film structure, and the preparation method comprises the following steps:
step 1, etching a concave cavity on a substrate silicon wafer;
step 4, depositing a second sacrificial layer by chemical vapor deposition, and photoetching and patterning the second sacrificial layer to form a non-planar structure of the sacrificial layer;
step 5, depositing a piezoelectric layer, and photoetching and patterning the piezoelectric layer to form a structure with the size of the upper surface of the piezoelectric layer changed in the thickness direction;
step 6, etching an electrode through hole;
step 7, sputtering a top electrode, and photoetching and patterning the top electrode;
step 8, etching the release hole;
and 9, etching the first sacrificial layer and the second sacrificial layer to form a structure of which the size of the lower surface of the piezoelectric layer changes in the thickness direction and a cavity structure of the substrate silicon wafer.
Similar to (1), the structure in which the thickness dimension of both the upper and lower surfaces varies, or the structure in which the thickness dimension of only one of the surfaces varies may be formed at the same time. The preparation method is adjusted adaptively.
(3) The prepared micro-mechanical resonator is a piezoelectric resonator with a metal-piezoelectric layer-monocrystalline silicon/polycrystalline silicon composite film structure, and the preparation method comprises the following steps:
step 1, etching a cavity structure on a substrate silicon wafer, and growing an oxygen-buried layer on the surface of the substrate silicon wafer;
step 4, photoetching and patterning the upper surface of the device layer silicon to form a structure with size change of the upper surface of the device layer silicon in the thickness direction;
step 5, depositing a piezoelectric layer, and photoetching and patterning the piezoelectric layer;
step 6, depositing a top electrode, and photoetching and patterning the top electrode;
step 7, depositing a passivation layer, and photoetching and patterning the passivation layer;
step 8, etching an upper electrode through hole and a lower electrode through hole;
step 9, depositing an extraction electrode, and photoetching and imaging the extraction electrode;
and step 10, etching the resonator structure.
Similar to (1), the structure in which the thickness dimension of both the upper and lower surfaces varies, or the structure in which the thickness dimension of only one of the surfaces varies may be formed at the same time. The preparation method is adjusted adaptively.
Several specific examples are set forth below in order to provide a better understanding of the present invention.
Example 1:
fig. 1 shows a capacitive resonator in which a resonator oscillator provided in example 1 is a single crystal silicon thin film structure.
Specifically, the micromechanical resonator comprises a substrate silicon wafer 1 and a resonator structure, wherein a cavity structure is arranged on the front surface of the substrate silicon wafer 1; the resonator structure comprises a resonator oscillator 3 and a support beam 2.
The resonator 3 is suspended above the cavity structure, and the resonator 3 is connected with the substrate silicon chip 1 through the supporting beam 2.
The supporting beam 2 is located at the boundary of the resonant vibrator 3, the thickness direction of the connecting part of the supporting beam 2 and the resonant vibrator 3 is gradually changed, and specifically, the upper surface and the lower surface of the supporting beam 2 are provided with a concave geometric structure.
The cross section of the support beam 2 is a subtraction graph of rectangular and arched Boolean operations. The supporting beams 2 are located at the positions of vibration nodes, and the number of the supporting beams 2 is two. The resonator 3 is a single thin-film structure including single crystal silicon. The resonator 3 is a rectangular plate.
Fig. 2 is a schematic cross-sectional view of the micromechanical resonator prepared in example 1, and the specific processing steps are as follows:
(1) a concave cavity is etched on the substrate silicon wafer 201 by utilizing a deep reactive ion etching process, and silicon dioxide is grown on the surface of the substrate silicon wafer as an oxygen burying layer 202 by utilizing a thermal oxidation process.
(2) The lower surface of the device layer silicon 203 is lithographically and patterned: in the photoetching step, a thermal reflow process is utilized to make the photoresist gradually slope to form a slope with a certain inclination angle, and a concave structure on the lower surface of the supporting beam is formed through a silicon etching process. In addition, the concave structure on the lower surface of the supporting beam can also be formed by adopting the conventional photoetching and monocrystalline silicon isotropic etching processes.
(3) The lower surface of the device layer silicon 203 is fused and bonded with the substrate silicon wafer 201, and the device layer silicon 203 is polished and ground to a required thickness.
(4) After depositing the top electrode 204, the top electrode 204 is lithographically and patterned.
(5) The upper surface of the device layer silicon 203 is lithographically and patterned: in the photoetching step, a thermal reflow process is utilized to make the photoresist gradually slope to form a slope with a certain inclination angle, and a concave structure on the upper surface of the supporting beam is formed through a silicon etching process. In addition, the concave structure on the upper surface of the supporting beam can also be formed by adopting the conventional photoetching and monocrystalline silicon isotropic etching processes.
(6) And etching the resonator structure by using a reactive ion etching process.
Example 2:
fig. 3 shows a piezoelectric resonator provided in embodiment 2 and having a metal-piezoelectric layer-metal composite thin film structure.
The difference from example 1 is that: the resonator 3 in embodiment 1 is a single structure including single crystal silicon, the resonator 3 is a rectangular plate, and the micromechanical resonator is a capacitive resonator. In embodiment 2, the resonator 3 is a composite thin film structure including a metal-piezoelectric layer-metal, the resonator 3 is a polygonal plate, the support beams 2 are located at vibration nodes, the number of the support beams 2 is multiple, and the resonator 3 is connected with the substrate silicon wafer 1 through the support beams 2; the micromechanical resonator is a piezoelectric resonator, and the piezoelectric layer is made of any one of quartz, aluminum nitride, scandium-doped aluminum nitride, zinc oxide and lead zirconate titanate.
Fig. 4 is a schematic cross-sectional view of the micromechanical resonator prepared in example 2, and the specific processing steps are as follows:
(1) the substrate silicon wafer 201 is etched to form a cavity by a reactive ion etching process.
(2) The first sacrificial layer is deposited by chemical vapor deposition, and the excess material is removed by a chemical mechanical polishing process.
(3) After sputtering the bottom electrode 206, the bottom electrode 206 is lithographically and patterned.
(4) After chemical vapor deposition of the second sacrificial layer, photoetching and patterning the second sacrificial layer: in the photoetching step, a thermal reflow process is utilized to make the photoresist gradually slope to form a slope with a certain inclination angle, and a sacrificial layer protruding structure is formed through an etching process.
(5) After depositing the piezoelectric layer 205, the piezoelectric layer 205 is lithographically and patterned: 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 an etching process is used to form a recessed structure on the upper surface of the piezoelectric layer 205.
(6) And etching the electrode through hole by using a reactive ion etching process.
(7) After sputtering the top electrode 204, the top electrode 204 is lithographically and patterned.
(8) Etching the release holes.
(9) And etching the first sacrificial layer and the second sacrificial layer to form a concave structure on the lower surface of the piezoelectric layer 205 and a cavity structure of the substrate silicon wafer.
Example 3:
fig. 5 shows a piezoelectric resonator provided in example 3, wherein the resonator is a metal-piezoelectric layer-single crystal silicon/polycrystalline silicon composite film structure.
The difference from example 2 is that: the resonator element 3 in embodiment 2 is a composite film structure including metal-piezoelectric layer-metal, the resonator element 3 is a polygonal plate, and the number of the support beams 2 is plural. In embodiment 3, the resonator 3 is a composite thin film structure including a metal-piezoelectric layer-single crystal silicon, the resonator 3 is a rectangular plate, the number of the support beams 2 is two, and the resonator 3 is connected to the substrate silicon wafer 1 through the support beams 2.
Fig. 6 is a schematic cross-sectional view of the micromechanical resonator prepared in example 3, and the specific processing steps are as follows:
(1) a concave cavity is etched on the substrate silicon wafer 201 by utilizing a deep reactive ion etching process, and silicon dioxide is grown on the surface of the substrate silicon wafer as an oxygen burying layer 202 by utilizing a thermal oxidation process.
(2) The lower surface of the device layer silicon 203 is lithographically and patterned: in the photoetching step, a thermal reflow process is utilized to make the photoresist gradually slope to form a slope with a certain inclination angle, and a concave structure on the lower surface of the supporting beam is formed through a silicon etching process. In addition, the concave structure on the lower surface of the supporting beam can also be formed by adopting the conventional photoetching and monocrystalline silicon isotropic etching processes.
(3) The lower surface of the device layer silicon 203 is fused and bonded with the substrate silicon wafer 201, and the device layer silicon 203 is polished and ground to a required thickness.
(4) The upper surface of the device layer silicon 203 is lithographically and patterned: in the photoetching step, a thermal reflow process is utilized to make the photoresist gradually slope to form a slope with a certain inclination angle, and a concave structure on the upper surface of the supporting beam is formed through a silicon etching process. In addition, the concave structure on the upper surface of the supporting beam can also be formed by adopting the conventional photoetching and monocrystalline silicon isotropic etching processes.
(5) After depositing the piezoelectric layer 205, the piezoelectric layer 205 is lithographically and patterned.
(6) After deposition of the top electrode 204, the top electrode 204 is lithographically and patterned.
(7) After depositing silicon dioxide as the passivation layer 207, the passivation layer 207 is lithographically patterned.
(8) And etching the upper and lower electrode through holes by using a reactive ion etching process.
(9) After the extraction electrode 208 is deposited, the extraction electrode 208 is lithographically patterned.
(10) And etching the resonator structure by using a reactive ion etching process.
Figures 7-1 through 7-4 are schematic cross-sectional shapes of several exemplary resonator structures in a micromechanical resonator. Fig. 7-1 shows a resonator structure in which the upper and lower surfaces of the support beam have depressions 301 (the thickness change region is denoted by 303) with respect to the surface of the resonator oscillator 3, and the surface of the support beam is an arc surface, and fig. 7-2 shows a resonator structure in which the upper and lower surfaces of the support beam have projections 302 with respect to the surface of the resonator oscillator 3 (the thickness change region is denoted by 303), and the surface of the support beam is an arc surface; fig. 7-3 shows a resonator structure in which the upper and lower surfaces of the support beam have a recess 301 (a thickness change region is denoted by 303) with respect to the surface of the resonator 3, and the surface portion of the support beam is a flat surface portion having an arc surface (a structure within a square dashed line frame); fig. 7-4 show a resonator structure in which the upper and lower surfaces of the support beam have projections 302 with respect to the resonator 3 (the thickness change region is denoted by 303), and the surface of the support beam is partly in the form of a flat surface and a curved surface (a structure within a square dashed line frame).
For micromechanical resonators, the main factors affecting the Q of the resonator are thermoelastic losses and anchor point losses. Wherein thermoelastic losses are related to resonator structure material type, thickness and resonator dimensions; the anchor point loss is related to the size of the resonator and the size and shape of the support beam. Fig. 8 shows the effect of the length of the resonator on the Q-value of a single-crystal silicon capacitive micromechanical resonator with different support beams, considering only the anchor point loss; fig. 9 shows the effect of the length of the resonator on the Q-value of a single-crystal silicon capacitive micro-mechanical resonator with different support beams, taking into account thermoelastic losses and anchor point losses. Wherein the recessed structure of fig. 8-9 is shown in fig. 7-1 and the raised structure is shown in fig. 7-2. For a single crystal silicon capacitive micro-mechanical resonator along the <100> crystal direction, the single crystal silicon has a thickness of 20 μm, the support beam has a length of 10 μm, and the width is 5 μm, the length of the resonator has an optimized value of 210 μm. As can be seen from fig. 8 and 9, when the resonator is optimally sized, the Q value of the resonator having the support beam with the concave structure or the convex structure is significantly improved compared to the Q value of the resonator having no concave structure or convex structure on the support beam. The size of the resonant vibrator and the size of the supporting beam are gradually changed in the thickness direction, the influence of the vibration of the resonator on the supporting beam can be reduced, further, a concave or convex geometric structure is designed on the upper surface, the lower surface or the upper surface and the lower surface of the supporting beam, high acoustic impedance mismatching between the resonant vibrator and the supporting beam is caused, when the length of the resonant vibrator is an optimized value, the mechanical amplitude of the boundary of the resonant vibrator and the supporting beam is minimum, and the outward energy dissipation of the resonator is minimum.
The micromechanical resonator and the preparation method thereof provided by the embodiment of the invention at least comprise the following technical effects:
the invention provides a micromechanical resonator capable of effectively improving Q value and a manufacturing method thereof, and the micromechanical resonator mainly utilizes that a resonant vibrator of the resonator is gradually connected with a supporting beam in the thickness direction, and the upper surface, the lower surface or the upper surface and the lower surface of the supporting beam have a concave or convex geometric structure relative to the surface of the resonant vibrator, so that high acoustic impedance mismatch exists between the resonant vibrator and the supporting beam, mechanical waves are reduced from being transmitted to a substrate through anchor points, and therefore, the anchor point loss can be effectively reduced, and the Q value of the resonator is further improved.
Finally, it should be noted that the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting, and although the present invention has been described in detail with reference to examples, it should be understood by those skilled in the art that modifications or equivalent substitutions may be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, which should be covered by the claims of the present invention.
Claims (10)
1. A micromechanical resonator, comprising: the resonator structure comprises a resonant vibrator and a support beam; the substrate silicon chip is provided with a cavity structure, the resonator is suspended above the cavity structure of the substrate silicon chip, and the resonator is connected with the substrate silicon chip through the supporting beam; the support beam is connected to a boundary of the resonator, and a connection portion between the support beam and the resonator has a structure in which a dimension in a thickness direction changes.
2. The micromechanical resonator according to claim 1, wherein a connection portion of the support beam and the resonator vibrator is a structure that is gradually changed in a thickness direction; the upper surface of the support beam, the lower surface of the support beam, or the upper and lower surfaces of the support beam have a non-planar geometry with respect to the surface of the resonator oscillator, the non-planar geometry being a concave or convex geometry.
3. The micromechanical resonator according to claim 1, wherein the cross-section of the support beam is one or any combination of rectangular, trapezoidal, circular, elliptical, and arcuate; the resonant vibrator is one or any combination of a plurality of rectangular plates, circular plates, elliptical plates, arched plates and polygonal plates.
4. A micromechanical resonator according to claim 1, characterized in that the support beams are located at vibration nodes, the number of support beams being one or more.
5. A micromechanical resonator according to claim 1, characterized in that the micromechanical resonator is a piezoelectric resonator, a capacitive resonator or a piezoresistive resonator.
6. The micromechanical resonator according to claim 1, wherein the resonator 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 monocrystalline silicon, polycrystalline silicon or silicon germanium; the piezoelectric layer is made of one of quartz, aluminum nitride, scandium-doped aluminum nitride, zinc oxide and lead zirconate titanate.
7. A method for preparing a micromechanical resonator is characterized in that a connecting part of a supporting beam and a resonator is manufactured by a photoetching process by utilizing a laser direct writing process or a thermal reflow process, or is manufactured by laser or ion beam maskless etching;
the micromechanical resonator according to any one of claims 1-6 is prepared by using the method for preparing the micromechanical resonator.
8. Method for manufacturing a micromechanical resonator according to claim 7, characterized in that the micromechanical resonator obtained is a capacitive resonator, comprising the following steps:
step 1, etching a cavity structure on a substrate silicon wafer, and growing an oxygen embedding layer on the surface of the substrate silicon wafer;
step 2, photoetching and patterning the lower surface of the device layer silicon to form a structure with the size of the lower surface of the device layer silicon changed in the thickness direction;
step 3, fusing and bonding the lower surface of the device layer silicon and the substrate silicon wafer, and polishing and grinding the device layer silicon to a required thickness;
step 4, depositing a top electrode, and photoetching and patterning the top electrode;
step 5, photoetching and patterning the upper surface of the device layer silicon to form a structure with size change of the upper surface of the device layer silicon in the thickness direction;
and 6, etching the resonator structure.
9. The method for manufacturing a micromechanical resonator according to claim 7, wherein the micromechanical resonator is a piezoelectric resonator with a metal-piezoelectric layer-metal composite thin film structure, and the method comprises the following steps:
step 1, etching a concave cavity on a substrate silicon wafer;
step 2, chemical vapor deposition of a first sacrificial layer;
step 3, sputtering a bottom electrode, and photoetching and patterning the bottom electrode;
step 4, depositing a second sacrificial layer by chemical vapor deposition, and photoetching and patterning the second sacrificial layer to form a non-planar structure of the sacrificial layer;
step 5, depositing a piezoelectric layer, and photoetching and patterning the piezoelectric layer to form a structure with the size of the upper surface of the piezoelectric layer changed in the thickness direction;
step 6, etching an electrode through hole;
step 7, sputtering a top electrode, and photoetching and patterning the top electrode;
step 8, etching the release hole;
and 9, etching the first sacrificial layer and the second sacrificial layer to form a structure of which the size of the lower surface of the piezoelectric layer changes in the thickness direction and a cavity structure of the substrate silicon wafer.
10. The method for manufacturing a micromechanical resonator according to claim 7, wherein the micromechanical resonator is a piezoelectric resonator having a metal-piezoelectric layer-single crystal silicon/polysilicon composite thin film structure, and the method comprises the following steps:
step 1, etching a cavity structure on a substrate silicon wafer, and growing an oxygen-buried layer on the surface of the substrate silicon wafer;
step 2, photoetching and patterning the lower surface of the device layer silicon to form a structure with the size of the lower surface of the device layer silicon changed in the thickness direction;
step 3, fusing and bonding the lower surface of the device layer silicon and the substrate silicon wafer, and polishing and grinding the device layer silicon to a required thickness;
step 4, photoetching and patterning the upper surface of the device layer silicon to form a structure with size change of the upper surface of the device layer silicon in the thickness direction;
step 5, depositing a piezoelectric layer, and photoetching and patterning the piezoelectric layer;
step 6, depositing a top electrode, and photoetching and patterning the top electrode;
step 7, depositing a passivation layer, and photoetching and patterning the passivation layer;
step 8, etching an upper electrode through hole and a lower electrode through hole;
step 9, depositing an extraction electrode, and photoetching and imaging the extraction electrode;
and step 10, etching the resonator structure.
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