MEMS resonator and composite preparation method thereof

Abstract

The present application relates to the field of resonator technology, and discloses a MEMS resonator and a composite preparation method thereof, wherein the MEMS resonator composite preparation method comprises: forming a highly doped first single crystal silicon layer as a supporting substrate; forming a piezoelectric material layer on the first single crystal silicon layer; forming a seed layer on the piezoelectric material layer at a first set rate, and epitaxially forming a main layer on the seed layer at a second set rate, wherein the seed layer and the main layer are composited to form a highly doped second single crystal silicon layer; performing deep reactive ion etching on a stacked structure layer constructed based on the first single crystal silicon layer, the piezoelectric material layer, and the second single crystal silicon layer to form a resonator body, a connecting beam, and an anchor, wherein the resonator body is suspended, and the resonator body is connected to the anchor via the connecting beam. The present application improves the electromechanical coupling efficiency and quality factor of the MEMS resonator, and ensures the temperature stability of the MEMS resonator.

Description

Technical Field

[0001] The present application relates to the technical field of resonators, and in particular to a MEMS resonator and a composite preparation method thereof. Background Art

[0002] Micro-electro-mechanical systems (MEMS) can integrate mechanical components, drive components, electronic control systems, digital processing systems, etc. into an integrated micro unit. An example of such a device is a MEMS resonator. As a type of MEMS resonator, the working principle of a piezoelectric resonator is that an electrical signal passes through electrodes to stimulate acoustic wave oscillations in the piezoelectric material, thereby achieving resonance of a specific frequency and wavelength. Piezoelectric resonators are widely used, such as for timing reference, signal filtering, mass sensing, biosensing, motion sensing, etc. With the development of electronic technology, the requirements for the size and frequency stability of piezoelectric resonators have been significantly improved.

[0003] The piezoelectric resonator body structure in the related art is a piezoelectric material-metal composite structure arranged on a silicon-based material, with the metal serving as the electrode. However, due to the excessively high thermal expansion coefficient of the metal material, which poorly matches the thermal expansion coefficient of the piezoelectric material layer, the stiffness (elastic modulus) is too high, and it is prone to hardening with use, resulting in problems such as low electromechanical coupling efficiency and low quality factor (Q value) in the piezoelectric resonator. Summary of the Invention

[0004] In view of this, the present application provides a MEMS resonator and a composite preparation method thereof to solve the above-mentioned technical problems.

[0005] In a first aspect, the embodiments of the present application disclose a composite preparation method for a MEMS resonator, comprising:

[0006] forming a highly doped first single crystal silicon layer to serve as a supporting substrate;

[0007] forming a piezoelectric material layer on the first single crystal silicon layer;

[0008] forming a seed layer on the piezoelectric material layer at a first set rate, and epitaxially forming a main layer on the seed layer at a second set rate, wherein the seed layer and the main layer are combined to form a highly doped second single crystal silicon layer;

[0009] Deep reactive ion etching is performed on a stacked structure layer constructed based on the first single crystal silicon layer, the piezoelectric material layer and the second single crystal silicon layer to form a resonator body, a connecting beam and an anchor, wherein the resonator body is suspended and the resonator body is connected to the anchor via the connecting beam.

[0010] In a possible example, forming a seed layer on the piezoelectric material layer at a first set rate, and epitaxially forming a main layer on the seed layer at a second set rate, includes:

[0011] forming the seed layer on the piezoelectric material layer in a first apparatus chamber at the first set rate;

[0012] The seed layer is transferred to a second tool chamber in an inert gas environment, and the bulk layer is epitaxially formed on the seed layer in the second tool chamber at the second set rate.

[0013] In one possible example, forming the seed layer on the piezoelectric material layer in the first device chamber at the first set rate includes:

[0014] In a set vacuum environment of a molecular beam epitaxy equipment chamber, silicon atoms are evaporated at a first set rate, phosphorus / boron doping atoms are introduced simultaneously, and a seed layer of a first set thickness is grown at a first set temperature, wherein the doping concentration of the seed layer is ≥1×10 19 cm -3 .

[0015] In a possible example, epitaxially forming the body layer on the seed layer in the second equipment chamber at the second set rate includes:

[0016] At a second set temperature in the chemical vapor deposition chamber, a main layer of a second set thickness is grown on the seed layer at the second set rate using silane of a first set flow rate as a silicon source and phosphine of a second set flow rate as a doping source.

[0017] In a possible example, the set vacuum environment is less than 10 -8 Pa, the first set rate includes 0.05-0.2 nm / s, the first set temperature includes 500-650° C., and the first set thickness includes 5-50 nm.

[0018] In a possible example, the second set temperature includes 650-850° C., the first set flow rate includes 30-100 sccm, the second set flow rate includes 3-10 sccm, the second set rate includes 0.1-1 μm / min, and the second set thickness includes 1-20 μm.

[0019] In a possible example, forming a highly doped first single crystal silicon layer includes:

[0020] A single crystal silicon substrate with a set crystal orientation and a target thickness is selected; the single crystal silicon substrate is doped by ion implantation and high temperature annealing, wherein the doping concentration range of the first single crystal silicon layer includes 1×10 18 cm -3 to 1×10 21 cm -3 , the surface roughness of the first single crystal silicon layer is ≤0.5 nm, and the resistivity of the first single crystal silicon layer is ≤0.01 Ω·cm.

[0021] In a possible example, forming a piezoelectric material layer on the first single crystal silicon layer includes:

[0022] By using a magnetron sputtering process and an aluminum target, argon and nitrogen are introduced to form an aluminum nitride layer on the first single crystal silicon layer under a set pressure environment, a third set temperature and a set power; wherein the flow ratio of the argon gas to the nitrogen gas is 1:3, and the thickness uniformity deviation of the aluminum nitride layer is ≤±5%.

[0023] In a second aspect, an embodiment of the present application discloses a MEMS resonator, which is prepared by the MEMS resonator composite preparation method of any of the above embodiments, comprising:

[0024] A resonator body, a connecting beam and an anchor, wherein the resonator body is suspended and connected to the anchor via the connecting beam; the resonator body comprises a first single crystal silicon layer, a piezoelectric material layer and a second single crystal silicon layer, wherein the first single crystal silicon layer, the piezoelectric material layer and the second single crystal silicon layer are stacked in sequence.

[0025] In a possible example, a patterned isolation groove connected to the piezoelectric material layer is provided on the second single crystal silicon layer, and a portion of the second single crystal silicon layer divided by the patterned isolation groove is a driving electrode, and another portion of the second single crystal silicon layer is a sensing electrode.

[0026] In summary, compared with the prior art, the present application discloses a MEMS resonator and a composite preparation method thereof, the MEMS resonator composite preparation method comprising: forming a highly doped first single crystal silicon layer, forming a piezoelectric material layer on the first single crystal silicon layer, forming a seed layer on the piezoelectric material layer at a first set rate, and epitaxially forming a main layer on the seed layer at a second set rate, the seed layer and the main layer are composited to form a highly doped second single crystal silicon layer, deep reactive ion etching is performed on the stacked structure layer constructed based on the first single crystal silicon layer, the piezoelectric material layer and the second single crystal silicon layer to form a resonator body, a connecting beam and an anchor, wherein the resonator body is suspended, and the resonator body is connected to the anchor via the connecting beam, that is, through the above-mentioned setting, the traditional metal electrode is replaced by the highly doped single crystal silicon layer, the thermal expansion coefficient matching with the piezoelectric material layer is optimized, and the electromechanical coupling efficiency and quality factor of the MEMS resonator are improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following is a brief introduction to the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0028] Figure 1 is a flow chart of the MEMS resonator composite preparation method of this embodiment;

[0029] Figure 2 is a schematic structural diagram of the first MEMS resonator of this embodiment;

[0030] Figure 3 is a schematic structural diagram of a second MEMS resonator of this embodiment;

[0031] Figure 4 is a schematic structural diagram of the first resonator body of this embodiment;

[0032] Figure 5 is a schematic structural diagram of a second resonator body of this embodiment;

[0033] Figure 6 is a schematic structural diagram of a third type of resonator body of this embodiment;

[0034] Figure 7 Schematic diagram of the structure of the fourth resonator body of this embodiment. DETAILED DESCRIPTION

[0035] Exemplary embodiments will be described in detail herein, with examples illustrated in the accompanying drawings. When the following description refers to the drawings, identical numbers in different figures represent identical or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments are not intended to represent all embodiments consistent with the present application. Rather, they are merely examples of apparatus and methods consistent with certain aspects of the present application, as detailed in the appended claims.

[0036] It should be noted that, in this document, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprising a ..." does not exclude the presence of other identical elements in the process, method, article or device comprising the element. In addition, components, features, and elements with the same name in different embodiments of the present application may have the same meaning or different meanings, and their specific meanings need to be determined based on their explanation in the specific embodiment or further combined with the context of the specific embodiment.

[0037] It should be understood that the specific embodiments described herein are only used to explain the present application and are not intended to limit the present application.

[0038] In the subsequent description, the use of suffixes such as "module", "component" or "unit" to represent elements is only for the purpose of facilitating the description of the present application and has no specific meaning. Therefore, "module", "component" or "unit" can be used interchangeably.

[0039] In the description of this application, it should be noted that the terms "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 the description of this application and simplify the description. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0040] The technical solutions shown in this application will be described in detail below through specific embodiments. It should be noted that the description order of the following embodiments does not limit the priority order of the embodiments.

[0041] Please refer to Figure 1 , and combined with Figures 2 to 7 The MEMS resonator composite preparation method of the embodiment of the present application includes:

[0042] S101 , forming a highly doped first single crystal silicon layer 1 to serve as a supporting substrate.

[0043] In a possible implementation of this application, reference Figure 4 , forming a highly doped first single crystal silicon layer 1, including: selecting a single crystal silicon substrate with a set crystal orientation and a target thickness; doping the single crystal silicon substrate by ion implantation and high temperature annealing.

[0044] In one example, a single crystal silicon substrate with a crystal orientation of (100) or (111) and a target thickness is preferred to take into account both the structural support strength and processing adaptability as a supporting base.

[0045] That is, dopants are introduced by ion implantation, preferably using phosphorus (n-type doping) or boron (p-type doping) as the main doping source. After the doping process, the doping atoms can be activated and the lattice defects can be restored at a set annealing temperature, thereby obtaining a first single crystal silicon layer 1 with good electrical and mechanical properties.

[0046] Of course, the dopants in the embodiment of the present application are not limited thereto, and may also include relatively high concentration dopants such as arsenic or antimony. In addition to the single crystal silicon layer, the first single crystal silicon layer 1 may also be made of other single crystal semiconductors such as single crystal germanium.

[0047] In one example, phosphorus ion implantation is preferably used for doping, and annealing is performed in a nitrogen environment at 1100° C. for 30 minutes to form an n-type doped first single crystal silicon layer 1 .

[0048] Thus, the doping concentration range of the obtained first single crystal silicon layer 1 includes 1×10 18 cm -3 to 1×10 21 cm -3 , and the resistivity of the first single crystal silicon layer 1 is ≤0.01Ω·cm, so as to ensure that it has sufficient conductivity when used as an electrode, reduce energy loss, and significantly improve the electromechanical coupling coefficient of the device.

[0049] The surface roughness of the first single crystal silicon layer 1 is ≤0.5 nm, so as to ensure good interface bonding and crystallization quality for subsequent deposition of the piezoelectric material layer.

[0050] The highly doped first single crystal silicon layer 1 thus formed can, based on its doping type, concentration and thickness setting, effectively adjust its equivalent capacitance, conductivity and the degree of matching of its thermal expansion coefficient as an electrode with the piezoelectric material layer without affecting the mechanical properties. Moreover, since the hardness of the single crystal silicon layer is stable, the attenuation is small even at high temperatures, so that the overall temperature coefficient of the resonator is small, thereby achieving higher electromechanical coupling efficiency, quality factor and temperature stability.

[0051] S102 , forming a piezoelectric material layer 2 on the first single crystal silicon layer 1 .

[0052] Preferably, the material forming the piezoelectric material layer 2 includes aluminum nitride (AlN). Aluminum nitride has excellent piezoelectric properties, good thermal conductivity, chemical stability and good compatibility with silicon substrates, and its c-axis preferred orientation structure can provide a higher piezoelectric response on a specific crystal plane.

[0053] Of course, the material forming the piezoelectric material layer 2 in the embodiment of the present application is not limited thereto, and may also include but is not limited to zinc oxide, lead zirconate titanate, lithium niobate, gallium nitride, indium nitride, scandium aluminum nitride or quartz, etc.

[0054] In a possible implementation of the present application, forming a piezoelectric material layer 2 on the first single crystal silicon layer 1 includes:

[0055] By using a magnetron sputtering process and an aluminum target, introducing argon and nitrogen, an aluminum nitride layer, namely, a piezoelectric material layer 2 is formed on the first single crystal silicon layer 1 under a set pressure environment, a third set temperature and a set power.

[0056] The flow ratio of argon to nitrogen is 1:3.

[0057] Preferably, the set pressure environment includes 3Pa, the third set temperature includes 400°C, and the set power includes 300W.

[0058] Therefore, the magnetron sputtering process uses high-purity aluminum as the target material, introduces argon and nitrogen with a flow ratio of 1:3, sets the gas pressure in the reaction chamber to 3Pa, the sputtering power to 300W, and performs sputtering deposition at a temperature of 400°C.

[0059] Based on the above settings, an aluminum nitride layer with a thickness uniformity deviation of ≤±5% and an obvious c-axis preferential orientation is formed on the first single crystal silicon layer 1. Therefore, the aluminum nitride layer with a c-axis preferential orientation can ensure that its piezoelectric constant is maximized along the thickness direction, thereby significantly improving the piezoelectric coupling efficiency under longitudinal excitation conditions, so that when an alternating voltage is applied to the resonator electrode, high-intensity shear or longitudinal wave mechanical vibration can be excited to meet the requirements of high-frequency stable oscillation.

[0060] The surface of the aluminum nitride layer with a thickness uniformity deviation of ≤±5% is flat and the grain orientation is consistent, which is conducive to the subsequent deposition of the second single crystal silicon layer and improves the overall interlayer adhesion, lattice matching and structural stability of the device.

[0061] Of course, the deposition process of this step is not limited to this. In addition to the magnetron sputtering process, it can also include metal organic chemical vapor deposition (MOCVD) or pulsed laser deposition (PLD) to form the piezoelectric material layer 2 on the first single crystal silicon layer 1.

[0062] S103 , forming a seed layer 31 on the piezoelectric material layer 2 at a first set rate, and epitaxially forming a main layer 32 on the seed layer 31 at a second set rate, the seed layer 31 and the main layer 32 are combined to form a highly doped second single crystal silicon layer 3 .

[0063] That is, the embodiment of the present application shows a method for compositely forming a highly doped second single crystal silicon layer 3 on the piezoelectric material layer 2 .

[0064] In a possible implementation of this application, reference Figure 6 , forming a seed layer 31 on the piezoelectric material layer 2 at a first set rate, and epitaxially forming a main layer 32 on the seed layer 31 at a second set rate, comprising:

[0065] A seed layer 31 is formed on the piezoelectric material layer 2 in the first equipment chamber at a first set rate; in an inert gas environment, the seed layer 31 is transferred to the second equipment chamber, and a main layer 32 is epitaxially formed on the seed layer 31 in the second equipment chamber at a second set rate.

[0066] The second single crystal silicon layer 3 is formed by the composite of the seed layer 31 and the main layer 32. The resistivity of the second single crystal silicon layer 3 is ≤0.01Ω·cm, and the seed layer 31 can provide ideal crystal orientation guidance for the main layer 32, ensuring that the entire layer is a high-quality single crystal structure. In addition, the highly doped second single crystal silicon layer 3 ensures that it has a good current response when used as a driving / sensing electrode. Based on the setting of the seed layer 31 and the main layer 32, the equivalent capacitance, conductivity and thermal expansion coefficient matching degree of the electrode as well as the piezoelectric material layer 2 can be effectively adjusted without affecting the mechanical properties. Since the hardness of the single crystal silicon layer is stable, the attenuation is small even at high temperatures, so that the overall temperature coefficient of the resonator is small, thereby having a higher electromechanical coupling efficiency, quality factor and temperature stability.

[0067] In one example, forming a seed layer 31 on a piezoelectric material layer 2 in a first device chamber at a first set rate includes:

[0068] In a set vacuum environment of a molecular beam epitaxy equipment chamber, silicon atoms are evaporated at a first set rate, phosphorus / boron doping atoms are introduced simultaneously, and a seed layer 31 of a first set thickness is grown at a first set temperature.

[0069] Optionally, set the vacuum environment to <10 -8 Pa, the first set rate includes 0.05-0.2nm / s, the first set temperature includes 500-650℃, and the first set thickness includes 5-50nm.

[0070] That is, in the molecular beam epitaxy equipment chamber <10 -8In a vacuum environment of 0.05-0.2 nm / s, silicon atoms are evaporated at a rate of 0.05-0.2 nm / s, and phosphorus / boron doping atoms are introduced simultaneously. A seed layer 31 of 5-50 nm is grown at a temperature of 500-650° C.

[0071] Therefore, the doping concentration of the seed layer 31 formed on the piezoelectric material layer 2 is ≥1×10 19 cm -3 To ensure that it has excellent electrical conductivity and provides stable current-carrying performance for subsequent epitaxy.

[0072] Preferably, the first set rate includes 0.12 nm / s, the first set temperature includes 580° C., and the first set thickness includes 32 nm.

[0073] In one example, epitaxially forming the bulk layer 32 on the seed layer 31 in the second tool chamber at a second set rate includes:

[0074] At a second set temperature in the chemical vapor deposition chamber, a main layer 32 of a second set thickness is grown on the seed layer 31 at a second set rate using silane at a first set flow rate as a silicon source and phosphine at a second set flow rate as a doping source.

[0075] Optionally, the second set temperature includes 650-850° C., the first set flow rate includes 30-100 sccm, the second set flow rate includes 3-10 sccm, the second set rate includes 0.1-1 μm / min, and the second set thickness includes 1-20 μm.

[0076] That is, at a temperature of 650-850°C in a chemical vapor deposition chamber, 30-100 sccm of silane is used as a silicon source, 3-10 sccm of phosphine is used as a doping source, and a main layer 32 with a thickness of 1-20 μm is grown on the seed layer 31 at a rate of 0.1-1 μm / min.

[0077] Preferably, the second set temperature includes 780° C., the first set flow rate includes 70 sccm, the second set flow rate includes 6 sccm, the second set rate includes 0.5 μm / min, and the second set thickness includes 15 μm.

[0078] In a possible implementation of this application, reference Figure 7 , forming a highly doped second single crystal silicon layer 3 on the piezoelectric material layer 2, and further comprising:

[0079] A buffer layer 33 is grown on the piezoelectric material layer 2 ; and a second single crystal silicon layer 3 is formed on the buffer layer 33 .

[0080] In one example, the piezoelectric material layer 2 is an aluminum nitride layer, and the growth material of the buffer layer 33 includes titanium nitride. Then, a titanium nitride layer is grown on the piezoelectric material layer 2 of aluminum nitride, and the second single crystal silicon layer 3 is formed on the titanium nitride layer.

[0081] Then, compared to directly forming the second single crystal silicon layer 3 on the aluminum nitride layer, the lattice mismatch between the single crystal silicon layer and the titanium nitride layer is low, the interface is stable, and they can be better matched, so that the process tolerance is high when preparing the highly doped single crystal silicon layer. Specifically, because the atomic arrangement in the titanium nitride crystal plane and the atomic arrangement in the aluminum nitride crystal plane have the same six-fold symmetry, and the lattice mismatch between the two is small, the titanium nitride layer can be easily formed on the aluminum nitride layer through magnetron sputtering or chemical vapor deposition process, and then the second single crystal silicon layer 3 can be directly generated on the titanium nitride layer through molecular beam epitaxy or chemical vapor deposition process.

[0082] Preferably, the thickness of the titanium nitride layer is 50-100 nm, that is, the thickness of the buffer layer 33 is 50-100 nm.

[0083] Then, the titanium nitride layer has low resistivity and can form a resonator electrode together with the second single crystal silicon layer 3. The titanium nitride layer with a smaller thickness will not affect the frequency and quality factor of the resonator, that is, it has a resonator performance close to that of the composite structure of the above-mentioned highly doped single crystal silicon layer-piezoelectric material layer stack.

[0084] Of course, in order to further increase the conductivity of the electrode, the buffer layer 33 can also be set as a metal layer, or a thin metal material layer (less than 300 nm) can be formed on the second single crystal silicon layer 3 as a guide electrode connected to the external package contact.

[0085] S104, performing deep reactive ion etching on the stacked structure layer constructed based on the first single crystal silicon layer 1, the piezoelectric material layer 2 and the second single crystal silicon layer 3 to form a resonator body 10, a connecting beam 20 and an anchor 30, wherein the resonator body 10 is suspended, and the resonator body 10 is connected to the anchor 30 via the connecting beam 20.

[0086] In one example, reference Figure 2 The stacked structure layer constructed by the first single crystal silicon layer 1, the piezoelectric material layer 2 and the second single crystal silicon layer 3 is patterned, and deep reactive ion etching is used to achieve structural separation with a high aspect ratio, thereby accurately constructing the three-dimensional structural features of the MEMS resonator, namely the resonator body 10, the connecting beam 20 and the anchor 30.

[0087] It should be noted that the resonator body 10 is composed of a first single crystal silicon layer 1, a piezoelectric material layer 2 and a second single crystal silicon layer 3 stacked together, and is released into a suspended state for mechanical resonance under the action of a driving voltage, and the cross-sectional shape of the resonator body 10 can be rectangular, circular or other regular shapes.

[0088] In order to realize the suspended arrangement of the resonator body 10 , a sacrificial layer may be released during the etching process or a groove may be opened from the back side.

[0089] Among them, the anchor 30 is used for fixing and can be directly connected to the base or substrate layer. The connecting beam 20 can be an elastic beam, of course not limited to this. A common piezoelectric resonator adopts a cantilever beam structure, a double-ended fixed beam, a bridge beam and other structures. The connecting beam 20 not only serves as a physical support, but also provides an electrical connection path, so that the single crystal silicon layer extends to the anchor 30.

[0090] The resonator body 10 and the connecting beam 20 may be integrated, and one end thereof is fixedly connected to the anchor 30 .

[0091] In combination with the aforementioned embodiments, the first single crystal silicon layer 1 of the resonator body 10 serves as the bottom electrode of the MEMS resonator, and the second single crystal silicon layer 3 serves as the top electrode of the MEMS resonator. The two together constitute an electrical-mechanical energy conversion structure through the intermediate piezoelectric material layer 2. Thus, the first single crystal silicon layer 1 and the second single crystal silicon layer 3 are electrically coupled to external packaging contacts through the connecting beam 20 and the anchor 30 to correspond to the driving electrode and the sensing electrode of the MEMS resonator, respectively, so that the MEMS resonator can receive a piezoelectric actuation driving signal and can sense a piezoelectric output signal indicating the mechanical movement of the resonant structure externally.

[0092] Furthermore, a conduction path is formed between the first single crystal silicon layer 1 and the second single crystal silicon layer 3 and the external packaging contact through the anchor 30 and the connecting beam 20. For example, the single crystal silicon layer can extend outward from the resonator body 10 and be formed on the connecting beam 20 and the anchor 30, thereby forming a conduction path on the connecting beam 20 and the anchor 30. Then, by applying a driving voltage to generate a potential on the piezoelectric material layer 2, the resonator body 10 is actuated to produce mechanical resonance.

[0093] In one example, reference Figure 5 When patterning the stacked structure layer constructed by the first single crystal silicon layer 1, the piezoelectric material layer 2 and the second single crystal silicon layer 3, the second single crystal silicon layer 3 can be patterned to form a patterned isolation groove 4 on the second single crystal silicon layer 3. Then, the part of the second single crystal silicon layer 3 divided by the patterned isolation groove 4 serves as the driving electrode, and the other part of the second single crystal silicon layer 3 serves as the sensing electrode. Under this premise, the first single crystal silicon layer 1 serves as the ground electrode.

[0094] It should be noted that the embodiment of the present application is based on the formation process design of the first single crystal silicon layer 1 and the second single crystal silicon layer 3, so that the first single crystal silicon layer 1 has a reverse polarity parabolic TCF, and the inherent parabolic TCF of the piezoelectric material layer 2 is offset by this reverse polarity parabolic TCF of the first single crystal silicon layer 1, and its first-order and second-order TCF are net TCF within the expected range (-40℃-85℃), and the net TCF is less than 50ppm, thereby ensuring that the MEMS resonator has high temperature stability, and the first single crystal silicon layer 1 and the second single crystal silicon layer 3 have few crystal defects and low mechanical loss. After being compounded with the piezoelectric material layer 2, the vibration energy loss can be significantly reduced, so that the MEMS resonator has a higher quality factor.

[0095] It can be understood that TCF refers to the Temperature Coefficient of Frequency, also known as the temperature compensation coefficient. It is a characteristic parameter used to describe the change of resonator frequency with temperature. Generally, the TCF coefficient is expressed in ppm / ℃, which means the proportion of resonator frequency change for every increase or decrease of 1 degree Celsius in temperature.

[0096] In one example, the thickness of the first single crystal silicon layer 1 ≥ the thickness of the second single crystal silicon layer 3 > the thickness of the piezoelectric material layer 2 .

[0097] In one example, the first single crystal silicon layer 1, the piezoelectric material layer 2 and the second single crystal silicon layer 3 form a symmetrical stacked structure. If the resonator structure is asymmetric, refer to Figure 3 If the resonator body 10 and the connecting beam 20 are asymmetric with respect to the X direction in the figure, then a large energy loss is likely to occur at the connection of the resonator anchor 30, which will lead to a poor quality factor of the resonator. Therefore, laser ablation can be used to adjust the various structures of the resonator to eliminate the asymmetry, thereby ensuring the quality factor of the resonator.

[0098] The embodiments of the present application further disclose a MEMS resonator, which can be prepared by the MEMS resonator composite preparation method of any of the above embodiments.

[0099] The MEMS resonator includes a resonator body 10 , a connecting beam 20 and an anchor 30 .

[0100] During the specific implementation process, the resonator body 10 is suspended, and the resonator body 10 is connected to the anchor 30 via the connecting beam 20, wherein the resonator body 10 includes a first single crystal silicon layer 1, a piezoelectric material layer 2 and a second single crystal silicon layer 3, and the first single crystal silicon layer 1, the piezoelectric material layer 2 and the second single crystal silicon layer 3 are stacked in sequence.

[0101] In a possible implementation of the present application, a patterned isolation groove 4 connected to the piezoelectric material layer 2 is provided on the second single crystal silicon layer 3, and the patterned isolation groove 4 divides a part of the second single crystal silicon layer 3 into a driving electrode, and divides another part of the second single crystal silicon layer 3 into a sensing electrode.

[0102] For other working principles and processes of the MEMS resonator of this embodiment, please refer to the description of the composite preparation method of the MEMS resonator of the aforementioned embodiment, which will not be repeated here.

[0103] The above is a detailed introduction to the MEMS resonator and its composite fabrication method provided by this application. This article uses specific examples to illustrate the principles and implementation methods of this application. It should be noted that in this application, the descriptions of each embodiment have their own focus. For parts that are not detailed or recorded in a particular embodiment, please refer to the relevant descriptions of other embodiments.

[0104] The above are only preferred embodiments of the present application and do not limit the patent scope of the present application. The various technical features of the technical solution of the present application can be arbitrarily combined. In order to make the description concise, all possible combinations of the various technical features in the above embodiments are not described. Any equivalent structure or equivalent process transformation made using the contents of the description and drawings of this application, or directly or indirectly applied in other related technical fields, as long as there is no contradiction in the combination of these technical features, are also included in the patent protection scope of the present application.

Claims

1. A composite preparation method for a MEMS resonator, characterized in that: include: forming a highly doped first single crystal silicon layer to serve as a supporting substrate; forming a piezoelectric material layer on the first single crystal silicon layer; forming a seed layer on the piezoelectric material layer at a first set rate, and epitaxially forming a main layer on the seed layer at a second set rate, wherein the seed layer and the main layer are combined to form a highly doped second single crystal silicon layer, wherein the first set rate is 0.05-0.2 nm / s and the second set rate is 0.1-1 μm / min; Deep reactive ion etching is performed on a stacked structure layer constructed based on the first single crystal silicon layer, the piezoelectric material layer and the second single crystal silicon layer to form a resonator body, a connecting beam and an anchor, wherein the resonator body is suspended and the resonator body is connected to the anchor via the connecting beam.

2. The MEMS resonator composite preparation method according to claim 1, characterized in that: The step of forming a seed layer on the piezoelectric material layer at a first set rate, and epitaxially forming a main layer on the seed layer at a second set rate, comprises: forming the seed layer on the piezoelectric material layer in a first apparatus chamber at the first set rate; The seed layer is transferred to a second tool chamber in an inert gas environment, and the bulk layer is epitaxially formed on the seed layer in the second tool chamber at the second set rate.

3. The MEMS resonator composite preparation method according to claim 2, characterized in that: The forming of the seed layer on the piezoelectric material layer in the first device chamber at the first set rate includes: In a set vacuum environment of a molecular beam epitaxy equipment chamber, silicon atoms are evaporated at a first set rate, phosphorus / boron doping atoms are introduced simultaneously, and a seed layer of a first set thickness is grown at a first set temperature, wherein the doping concentration of the seed layer is ≥1×10 19 cm -3 .

4. The MEMS resonator composite preparation method according to claim 2, characterized in that: Epitaxially forming the bulk layer on the seed layer in the second equipment chamber at the second set rate comprises: At a second set temperature in the chemical vapor deposition chamber, a main layer of a second set thickness is grown on the seed layer at the second set rate using silane of a first set flow rate as a silicon source and phosphine of a second set flow rate as a doping source.

5. The MEMS resonator composite preparation method according to claim 3, characterized in that: The vacuum environment is set to <10 -8 Pa, the first set temperature includes 500-650° C., and the first set thickness includes 5-50 nm.

6. The MEMS resonator composite preparation method according to claim 4, characterized in that: The second set temperature includes 650-850° C., the first set flow rate includes 30-100 sccm, the second set flow rate includes 3-10 sccm, and the second set thickness includes 1-20 μm.

7. The MEMS resonator composite preparation method according to claim 1, characterized in that: The forming of a highly doped first single crystal silicon layer comprises: A single crystal silicon substrate with a set crystal orientation and a target thickness is selected; the single crystal silicon substrate is doped by ion implantation and high temperature annealing, wherein the doping concentration range of the first single crystal silicon layer includes 1×10 18 cm -3 to 1×10 21 cm -3 , the surface roughness of the first single crystal silicon layer is ≤0.5 nm, and the resistivity of the first single crystal silicon layer is ≤0.01 Ω·cm.

8. The MEMS resonator composite preparation method according to claim 1, characterized in that: The forming of a piezoelectric material layer on the first single crystal silicon layer comprises: By using a magnetron sputtering process and an aluminum target, argon and nitrogen are introduced to form an aluminum nitride layer on the first single crystal silicon layer under a set pressure environment, a third set temperature and a set power; wherein the flow ratio of the argon gas to the nitrogen gas is 1:3, and the thickness uniformity deviation of the aluminum nitride layer is ≤±5%.

9. A MEMS resonator prepared by the MEMS resonator composite preparation method according to any one of claims 1 to 8, characterized in that: include: A resonator body, a connecting beam and an anchoring piece, wherein the resonator body is suspended in the air, and the resonator body is connected to the anchoring piece via the connecting beam; The resonator body includes a first single crystal silicon layer, a piezoelectric material layer and a second single crystal silicon layer, and the first single crystal silicon layer, the piezoelectric material layer and the second single crystal silicon layer are stacked in sequence.

10. The MEMS resonator according to claim 9, wherein: A patterned isolation groove connected to the piezoelectric material layer is provided on the second single crystal silicon layer. The patterned isolation groove divides a portion of the second single crystal silicon layer into a driving electrode, and divides another portion of the second single crystal silicon layer into a sensing electrode.

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