CN110311642B - Micro-electromechanical resonator integrated with phonon crystal matrix and processing method thereof - Google Patents
Micro-electromechanical resonator integrated with phonon crystal matrix and processing method thereof Download PDFInfo
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- 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
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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
- H03H9/02—Details
- H03H9/02244—Details of microelectro-mechanical resonators
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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
- H03H9/02—Details
- H03H9/02244—Details of microelectro-mechanical resonators
- H03H9/02433—Means for compensation or elimination of undesired effects
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- H—ELECTRICITY
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- H03H9/24—Constructional features of resonators of material which is not piezoelectric, electrostrictive, or magnetostrictive
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- H—ELECTRICITY
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- H03H9/02—Details
- H03H9/02244—Details of microelectro-mechanical resonators
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Abstract
The invention discloses a micro-electromechanical resonator integrating a phonon crystal matrix and a processing method thereof, wherein the micro-electromechanical resonator comprises a supporting table, an external input electrode, an external output electrode, an external ground electrode, a supporting beam, a resonator body and the phonon crystal matrix, wherein the external input electrode, the external output electrode, the external ground electrode, the supporting beam and the phonon crystal matrix are positioned on the supporting table; the external input electrode and the external output electrode are symmetrically arranged at two sides of the top end of the supporting table, and external ground electrodes are symmetrically arranged at two sides of the external input electrode and the external output electrode; the resonator is suspended at the center of the top end of the supporting table through the fixation of the two supporting beams, phonon crystal matrixes are symmetrically placed on the two sides of the resonator, and the interdigital electrodes on the resonator are electrically connected with the external input electrode and the external output electrode through corresponding metal wires; the photonic crystal matrix has 3 x 12 unit cells and a full band gap with frequencies ranging from 127MHz to 216 MHz. The invention solves the problems of larger anchor point loss, lower quality factor and low stability of the existing micro-electromechanical resonator in practical application.
Description
Technical Field
The invention belongs to the technical field of radio frequency micro-electromechanical systems, and particularly relates to a micro-electromechanical resonator integrated with a phonon crystal matrix and a design of a processing method thereof.
Background
Microelectromechanical Systems (MEMS) technology is an emerging technology that is rapidly evolving and has a broad application prospect in a new generation of highly integrated wireless communication systems. For a radio communication system, a front-end transceiver circuit processes a radio frequency signal, the size of the circuit is matched with the wavelength of the signal, an acoustic device manufactured by adopting a MEMS technology is an important means for realizing the miniaturization of the radio frequency front-end, and the wavelength of the acoustic wave is far smaller than that of a traditional radio frequency device for the signal with the same frequency because the propagation speed of the acoustic wave in a medium (for example, the wave speed in the air is about 340 m/s) is far smaller than that of an electromagnetic wave (for example, the wave speed in the air is about 299,792,458 m/s).
At present, more acoustic resonators are studied and mainly divided into two major categories, namely a surface acoustic wave SAW (Surface Acoustic Wave) device and a bulk acoustic wave BAW (Bulk Acoustic Wave) device. The main advantages of SAW are: the processing technology is relatively simple and mature, and the electromechanical coupling coefficient is high; the disadvantage is the low power capability, which makes it difficult to integrate on-chip with Complementary Metal Oxide Semiconductor (CMOS) circuits. BAWs differ most in comparison to SAW devices in that the acoustic waves propagate inside the device rather than on the surface, so that the energy of the acoustic waves can be confined in the substrate and kept acoustically isolated from the outside, so that typically the quality factor (Q) of a BAW device will be better than a SAW device. Existing BAW resonators have a large number of acoustic waves propagating through the support beam to the substrate during the electromechanical conversion process, creating a significant energy loss, known as anchor point loss. The quality factor (Q) of a resonator is defined as the ratio of the energy stored by the resonator to the energy lost, and the anchor loss significantly reduces the Q of the device, thereby severely limiting the practical application of BAW resonators, since high Q can improve the detection resolution of the sensor, reduce the bandwidth of the filter, and improve the phase noise of the oscillator.
Many methods of increasing the Q value by reducing the anchor loss have been proposed today, and among them, the use of phonon crystals is a very effective method. Phonon crystals are proposed according to the concept of photonic crystals, when an elastic wave propagates in a periodic elastic medium, it is affected by the periodic structure, forming a special band structure, which is called an acoustic band gap, in which the propagation of the elastic wave is suppressed, and outside the band gap, no loss occurs. Thus, by utilizing this property of the photonic crystal, the acoustic wave propagating to the substrate through the support beam can be reduced to a great extent, thereby reducing the anchor loss of the resonator.
The existing method for improving the Q value by utilizing the phonon crystal is mainly divided into two types, one is to place the phonon crystal with a one-dimensional structure at the supporting beam, and the other is to place the phonon crystal with a two-dimensional structure at the anchor point at the tail end of the supporting beam. The two methods have the problems of poor mechanical structure stability of the resonator and poor energy loss inhibition effect, and still cannot well improve the Q value of the resonator.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a micro-electromechanical resonator integrated with a phonon crystal matrix and a processing method thereof, and the two-dimensional phonon crystal matrix is placed at two sides of a resonator body, so that sound energy is trapped in the middle part of the resonator body, and sound waves dissipated to a supporting table through a supporting beam are reduced, thereby effectively reducing anchor point loss of the resonator, improving quality factor of the resonator, and realizing high Q value and miniaturization without increasing the size of the whole resonator, and promoting the practical application of the MEMS resonator.
The technical scheme of the invention is as follows: a micro-electromechanical resonator integrating a phonon crystal matrix comprises a supporting table, an external input electrode, an external output electrode, an external ground electrode, a supporting beam, a resonator body and the phonon crystal matrix, wherein the external input electrode, the external output electrode, the external ground electrode, the supporting beam and the phonon crystal matrix are arranged on the supporting table; the external input electrode and the external output electrode are symmetrically arranged at two sides of the top end of the supporting table, and external ground electrodes are symmetrically arranged at two sides of the external input electrode and the external output electrode; the resonator is fixedly suspended at the center of the top end of the supporting table through two supporting beams, phonon crystal matrixes are symmetrically placed on two sides of the resonator, and interdigital electrodes on the resonator are respectively and electrically connected with the external input electrode and the external output electrode through corresponding metal wires; each phonon crystal matrix has 3 x 12 unit cells, which are symmetrically placed on both sides of the resonator body.
Further, the supporting table comprises a silicon substrate, a first buried oxide layer and back lining bottom silicon which are sequentially arranged from top to bottom, and the resonator, the external input electrode, the external output electrode, the external ground electrode, the supporting beam and the phonon crystal matrix are all arranged at the top end of the silicon substrate.
Further, the contact parts of the external input electrode and the external output electrode with the silicon substrate are respectively provided with a second buried oxide layer.
Further, the resonator body comprises an input metal electrode film, an output metal electrode film and a piezoelectric film, wherein the input metal electrode film is electrically connected with an external input electrode through a metal wire, the output metal electrode film is electrically connected with an external output electrode through a metal wire, and the piezoelectric film is arranged at the contact parts of the input metal electrode film and the output metal electrode film and the silicon substrate.
Further, the backing bottom silicon is made of silicon with the thickness of 400 mu m, the silicon substrate is made of p-type doped low-resistance silicon with the thickness of 10 mu m; the first buried oxide layer and the second buried oxide layer are both made of silicon dioxide, and the thickness of the first buried oxide layer and the second buried oxide layer is 1 mu m; the input metal electrode film and the output metal electrode film are made of aluminum and chromium doped materials, and comprise a metal aluminum film layer and a metal chromium film layer which are sequentially arranged, wherein the thickness of the metal aluminum film layer is 1 mu m, and the thickness of the metal chromium film layer is 0.02 mu m; the piezoelectric film is made of aluminum nitride and has a thickness of 0.5 μm.
The invention also provides a processing method of the micro-electromechanical resonator integrated with the phonon crystal matrix, which comprises the following steps:
s1, sequentially setting back substrate silicon, a first buried oxide layer and a silicon substrate from bottom to top to obtain a supporting table.
S2, doping phosphorus at symmetrical positions of the two sides of the top end of the silicon substrate to form a conductive layer, and obtaining four external ground electrodes.
S3, performing thermal oxidation and photoetching heating on the middle positions of the external ground electrodes on the two sides of the top end of the silicon substrate to obtain a second buried oxide layer.
And S4, setting a piezoelectric film at the central position of the silicon substrate, acquiring an input metal electrode film and an output metal electrode film through deposition, and acquiring corresponding metal wires, transduction electrodes and bonding pads through photoetching.
And S5, etching the two sides of the resonator at the top end of the silicon substrate to obtain a phonon crystal matrix structure.
S6, arranging a protective layer at the top end of the silicon substrate.
And S7, etching the supporting table to obtain a resonator structure with a phonon crystal matrix on the suspended resonator body.
S8, releasing the protective layer and removing the surface silicon oxide layer, and processing to obtain the micro-electromechanical resonator with the photonic crystal matrix integrated on the resonator body.
Further, the transduction electrode in step S4 includes an external input electrode and an external output electrode at the top ends of the second buried oxide layers on both sides; the corresponding metal wire is the connecting wire of the resonant body and the corresponding transduction electrode, and the metal wire is arranged at the top end of the supporting beam.
Further, the specific method for etching in step S5 is as follows: the silicon substrate is etched using a DRIE etching method and the first buried oxide layer at the bottom of the silicon substrate is etched using a RIE etching method.
Further, the protective layer in step S6 is a polyimide layer, and is used as a front end protective layer during bottom trench etching, for protecting the resonator, the external input electrode, the external output electrode, the external ground electrode and the photonic crystal matrix structure at the top end of the support table.
Further, in step S7, the specific method for performing the etching operation on the support table includes: and deep etching the supporting table by using a DRIE etching method to form a groove, and deep etching the first buried oxide layer at the bottom of the silicon substrate by using an RIE etching method to obtain the resonator structure with the phonon crystal matrix on the suspended resonator.
The beneficial effects of the invention are as follows:
(1) The micro-electromechanical resonator integrating the phonon crystal matrix on the resonator body can effectively prevent the dissipation of sound wave energy, so that the displacement on the peripheral substrate is obviously reduced or even eliminated, thereby greatly reducing the anchor point loss of the resonator and improving the quality factor of the resonator.
(2) According to the invention, the problems that in the prior art, in order to reduce anchor point loss of the resonator, a supporting beam or an anchor point area is provided with a phonon crystal, so that the size of the resonator is increased, the mechanical strength is reduced, and the resonator is easy to damage are avoided; the invention integrates the phonon crystal matrix on the resonator body, which not only has higher quality factor than the traditional design, but also improves the reliability of the resonator.
Drawings
FIG. 1 is a schematic diagram of a micro-electromechanical resonator with integrated photonic crystal matrix according to an embodiment of the present invention;
FIG. 2 is a schematic view of an electrode and a support table according to a first embodiment of the present invention;
fig. 3 is a schematic diagram of a resonator structure according to a first embodiment of the present invention;
FIG. 4 is a schematic view of a photonic crystal structure according to an embodiment of the present invention;
FIG. 5 is a diagram showing a band gap structure of a photonic crystal according to an embodiment of the present invention;
FIG. 6 is a schematic diagram showing output performance of a resonator according to a first embodiment of the present invention;
fig. 7 is a flowchart of a processing method of a microelectromechanical resonator according to a second embodiment of the invention.
Reference numerals illustrate: 1. a support table; 11. a silicon substrate; 12. a first buried oxide layer; 13. a back substrate silicon; 2. externally connecting an input electrode; 21. a second buried oxide layer; 3. externally connecting an output electrode; 4. an external ground electrode; 5. a support beam; 6. a resonator body; 61. inputting a metal electrode film; 62. outputting a metal electrode film; 63. a piezoelectric film; 7. a phonon crystal matrix.
Detailed Description
Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It is to be understood that the embodiments shown and described in the drawings are merely illustrative of the principles and spirit of the invention and are not intended to limit the scope of the invention.
Embodiment one:
the embodiment of the invention provides a micro-electromechanical resonator integrated with a photonic crystal matrix, which is shown in fig. 1, and comprises a supporting table 1, an external input electrode 2, an external output electrode 3, an external ground electrode 4, a supporting beam 5, a resonator body 6 and a photonic crystal matrix 7, wherein the external input electrode 2, the external ground electrode 4, the supporting beam 5, the resonator body 6 and the photonic crystal matrix 7 are arranged on the supporting table 1. The external input electrode 2 and the external output electrode 3 are symmetrically arranged at two sides of the top end of the supporting table 1, and external ground electrodes 4 are symmetrically arranged at two sides of the external input electrode 2 and the external output electrode 3. The resonant body 6 is fixedly suspended at the center of the top end of the supporting table 1 through two supporting beams 5, phonon crystal matrixes 7 are symmetrically placed on two sides of the resonant body, interdigital electrodes on the resonant body 6 are respectively and electrically connected with the external input electrode 2 and the external output electrode 3 through corresponding metal wires, and the metal wires are arranged at the top ends of the supporting beams 5. Each photonic crystal matrix 7 has 3 x 12 unit cells, which are symmetrically placed on both sides of the resonator body 6.
In the embodiment of the present invention, as shown in fig. 2, the support table 1 includes a silicon substrate 11, a first buried oxide layer 12 and a backing silicon 13 sequentially disposed from top to bottom, the resonator 6, the external input electrode 2, the external output electrode 3, the external ground electrode 4, the support beam 5 and the photonic crystal matrix 7 are all disposed at the top end of the silicon substrate 11, and the photonic crystal matrix 7 is disposed at two sides of the resonator 6. The photonic crystal matrix 7 effectively blocks acoustic energy dissipated from the resonator body 6 and thereby reduces the propagation of acoustic energy through the support beam 5 into the silicon substrate 11.
In the embodiment of the present invention, as shown in fig. 2, the contact portions of the external input electrode 2 and the external output electrode 3 with the silicon substrate 11 are both provided with the second buried oxide layer 21. The second buried oxide layer 21 serves to isolate the input electrode 2 and the output electrode 3 from the silicon substrate 11, which is a ground electrode, and to avoid a short circuit in the electrical connection.
In the embodiment of the present invention, as shown in fig. 3, the resonator 6 includes an input metal electrode film 61, an output metal electrode film 62 and a piezoelectric film 63, where the input metal electrode film 61 is electrically connected to the external input electrode 2 through a metal wire, the output metal electrode film 62 is electrically connected to the external output electrode 3 through a metal wire, the piezoelectric film 63 is disposed at the contact portions of the input metal electrode film 61 and the output metal electrode film 62 with the silicon substrate 11, so as to form a sandwich structure of metal electrode film-piezoelectric film-silicon substrate, the input metal electrode film 61 is electrically connected to the input external electrode 2, so as to convert electric energy into sound waves based on the inverse piezoelectric effect to form resonance, and the output metal electrode film 62 is electrically connected to the output external electrode 3, so as to convert generated sound wave signals into electric signals based on the positive piezoelectric effect to output.
In the embodiment of the present invention, the material of the back substrate silicon 13 is silicon, the thickness thereof is 400 μm, the material of the silicon substrate 11 is p-type doped low-resistance silicon with <100> crystal orientation, and the thickness thereof is 10 μm. The p-doped low-resistance silicon is used as a signal grounding layer to be directly and electrically communicated with the external ground electrode 5, and the length direction of the resonance block is aligned with the <110> crystal orientation of the wafer. The first buried oxide layer 12 and the second buried oxide layer 21 are both made of silicon dioxide, and each has a thickness of 1 μm. The materials of the input metal electrode film 61 and the output metal electrode film 62 are aluminum and chromium doped materials, and the materials comprise a metal aluminum film layer and a metal chromium film layer which are sequentially arranged, wherein the thickness of the metal aluminum film layer is 1 mu m, and the thickness of the metal chromium film layer is 0.02 mu m. The piezoelectric film 63 is made of aluminum nitride and has a thickness of 0.5 μm.
The working principle and the working process of the micro-electromechanical resonator provided by the embodiment of the invention are as follows: the piezoelectric bulk acoustic wave resonator on the silicon utilizes the piezoelectric property of the piezoelectric layer material to convert electric energy into acoustic energy, in order to generate resonance of acoustic waves, most of the acoustic waves need to be limited in a piezoelectric resonance stack formed by a metal electrode film, a piezoelectric film and a silicon substrate, according to a transmission line theory, when the load is infinity or zero, the incident waves generate total reflection, in the embodiment of the invention, the upper surface of the piezoelectric resonance stack is interfaced with air, the acoustic impedance of the air is approximately equal to zero, a good acoustic wave limiting boundary can be naturally formed, the lower surface of the piezoelectric resonance stack is suspended because the lower surface of the piezoelectric resonance stack is arranged on a supporting table to form a lower surface acoustic wave limiting boundary, therefore, acoustic waves are reflected between the two interfaces to form standing wave oscillation, and the acoustic wave loss is minimum at the moment and is converted into electric energy by inverse piezoelectric effect.
The first order modal center frequency of a thin film piezoelectric bulk acoustic resonator on silicon can be defined by equation (1):
wherein f is the resonant frequency, W is the width of the silicon substrate, E eff Young's modulus, ρ, equivalent to a resonator eff Is the equivalent mass density of the resonator.
The quality factor (Q) of a thin film piezoelectric bulk acoustic resonator on silicon can be defined by equation (2):
wherein Q is the quality factor, Q i For each energy loss of the resonator, the most important factor determining the quality factor is Q related to anchor loss anc ∈Q i The method comprises the steps of carrying out a first treatment on the surface of the i is the resonator energy loss variable. It can thus be seen that: reducing anchor loss can effectively improve the quality factor of the device.
The photonic crystal matrix 7 used in the embodiment of the present invention is shown in fig. 4, symmetrically placed on both sides of the resonator body 6, and each matrix is formed of 3×12 photonic crystal unit cells, wherein each unit cell is square, and the size is shown in fig. 4. The band gap structure of the photonic crystal can prevent the propagation of sound waves, and the band gap structure diagram shown in fig. 5 can be obtained by calculating the irreducible brillouin zone of the triangular area in fig. 4, wherein the band gap structure diagram has a complete band gap ranging from 127MHz to 216MHz, so long as the working frequency of the resonator is in the band gap, the photonic crystal matrix can effectively reduce the sound wave energy dissipated from the resonator body to propagate into the substrate through the supporting beam, thereby reducing anchor point loss and improving the quality factor.
The transmission characteristics of the mems resonator designed in the embodiment of the present invention are shown in fig. 6, and the electrical performance of the mems resonator is characterized by S11 (return loss) and S21 (insertion loss) parameters, where the unloaded Q value at the resonance frequency point 141.4Mhz is 53442, the insertion loss is 0.53dB, and the return loss is 12.8dB.
Embodiment two:
the embodiment of the invention provides a processing method of a micro-electromechanical resonator integrated with a phonon crystal matrix, which is shown in fig. 7 and comprises the following steps S1-S8:
s1, sequentially arranging 400 mu m backing bottom silicon, 1 mu m first buried oxide layer and 10 mu m silicon substrate from bottom to top to obtain a supporting table.
S2, doping phosphorus at symmetrical positions of the two sides of the top end of the silicon substrate to form a conductive layer, and obtaining four external ground electrodes.
S3, performing thermal oxidation and photoetching heating on the middle positions of the external ground electrodes on the two sides of the top end of the silicon substrate to obtain a second buried oxide layer with the thickness of 1 mu m.
And S4, setting a piezoelectric film at the central position of the silicon substrate, acquiring an input metal electrode film and an output metal electrode film through deposition, and acquiring corresponding metal wires, transduction electrodes and bonding pads through photoetching.
In the embodiment of the invention, the transduction electrode comprises an external input electrode and an external output electrode which are positioned at the top ends of the second buried oxide layers at two sides; the corresponding metal wire is the connecting wire of the resonant body and the corresponding transduction electrode, and the metal wire is arranged at the top end of the supporting beam.
And S5, etching the two sides of the resonator at the top end of the silicon substrate to obtain a phonon crystal matrix structure.
In the embodiment of the invention, the specific method for etching comprises the following steps: the silicon substrate is etched using a DRIE etching method and the first buried oxide layer at the bottom of the silicon substrate is etched using a RIE etching method.
S6, arranging a protective layer at the top end of the silicon substrate.
In the embodiment of the invention, the protective layer is a polyimide layer and is used as a front end protective layer in bottom groove etching and used for protecting a resonator, an external input electrode, an external output electrode, an external ground electrode and a phonon crystal matrix structure which are positioned at the top end of the supporting table.
And S7, etching the supporting table to obtain a resonator structure with a phonon crystal matrix on the suspended resonator body.
In the embodiment of the invention, the specific method for carrying out etching operation on the supporting table comprises the following steps: and according to the multistage vibration reduction outer frame structure, a DRIE etching method is used for deeply etching the supporting table to form a groove, and an RIE etching method is used for deeply etching the first buried oxide layer at the bottom of the silicon substrate to obtain a resonator structure with a phonon crystal matrix on the suspended resonator.
S8, releasing the protective layer and removing the surface silicon oxide layer, and processing to obtain the micro-electromechanical resonator with the photonic crystal matrix integrated on the resonator body.
The micro-electromechanical resonator processed by the embodiment of the invention effectively reduces the anchor point loss of the bulk acoustic wave resonator, improves the quality factor and the reliability of the device, and solves the problems of larger anchor point loss, difficult improvement of the quality factor and low reliability in the prior art.
Those of ordinary skill in the art will recognize that the embodiments described herein are for the purpose of aiding the reader in understanding the principles of the present invention and should be understood that the scope of the invention is not limited to such specific statements and embodiments. Those of ordinary skill in the art can make various other specific modifications and combinations from the teachings of the present disclosure without departing from the spirit thereof, and such modifications and combinations remain within the scope of the present disclosure.
Claims (10)
1. The micro-electromechanical resonator integrated with the photonic crystal matrix is characterized by comprising a supporting table (1), an external input electrode (2), an external output electrode (3), an external ground electrode (4), a supporting beam (5), a resonator body (6) and the photonic crystal matrix (7), wherein the external input electrode (2), the external output electrode (3), the external ground electrode (4) and the supporting beam are arranged on the supporting table (1);
the external input electrode (2) and the external output electrode (3) are symmetrically arranged on two sides of the top end of the supporting table (1), and external ground electrodes (4) are symmetrically arranged on two sides of the external input electrode (2) and the external output electrode (3);
the resonant body (6) is fixedly suspended at the center of the top end of the supporting table (1) through two supporting beams (5), a phonon crystal matrix (7) is symmetrically arranged on two sides of the resonant body, and interdigital electrodes on the resonant body (6) are respectively electrically connected with the external input electrode (2) and the external output electrode (3) through corresponding metal wires;
each of said photonic crystal matrices (7) has 3 x 12 unit cells, which are symmetrically placed on both sides of the resonator body (6);
each unit cell is square, the side length of the unit cell is 20 mu m, the thickness of the outer wall of the unit cell is 1 mu m, the radius of a semicircle bulge in the unit cell is 6 mu m, and the phonon crystal matrix (7) has a band gap structure of 127MHz to 216 MHz.
2. The microelectromechanical resonator of claim 1, characterized in that the support table (1) comprises a silicon substrate (11), a first buried oxide layer (12) and a backing bottom silicon (13) sequentially arranged from top to bottom, and the resonator body (6), the external input electrode (2), the external output electrode (3), the external ground electrode (4), the support beam (5) and the photonic crystal matrix (7) are all arranged on top of the silicon substrate (11).
3. Microelectromechanical resonator of claim 2, characterized in that the contact portions of the external input electrode (2) and the external output electrode (3) with the silicon substrate (11) are both provided with a second buried oxide layer (21).
4. A microelectromechanical resonator of claim 3, characterized in that the resonator body (6) comprises an input metal electrode film (61), an output metal electrode film (62) and a piezoelectric film (63), the input metal electrode film (61) is electrically connected to the external input electrode (2) through a metal wire, the output metal electrode film (62) is electrically connected to the external output electrode (3) through a metal wire, and the contact portions of the input metal electrode film (61) and the output metal electrode film (62) with the silicon substrate (11) are both provided with the piezoelectric film (63).
5. The microelectromechanical resonator of claim 4, characterized in that the backing silicon (13) is silicon with a thickness of 400 μm, and the silicon substrate (11) is p-doped low-resistance silicon with a thickness of 10 μm;
the first buried oxide layer (12) and the second buried oxide layer (21) are made of silicon dioxide, and the thickness of the first buried oxide layer and the second buried oxide layer is 1 mu m;
the input metal electrode film (61) and the output metal electrode film (62) are made of aluminum and chromium doped materials, and comprise a metal aluminum film layer and a metal chromium film layer which are sequentially arranged, wherein the thickness of the metal aluminum film layer is 1 mu m, and the thickness of the metal chromium film layer is 0.02 mu m;
the piezoelectric film (63) is made of aluminum nitride, and has a thickness of 0.5 μm.
6. A method of fabricating a microelectromechanical resonator integrated with a photonic crystal matrix, comprising the steps of:
s1, sequentially arranging back substrate silicon, a first buried oxide layer and a silicon substrate from bottom to top to obtain a supporting table;
s2, doping phosphorus at symmetrical positions of the two sides of the top end of the silicon substrate to form a conductive layer, and obtaining four external ground electrodes;
s3, performing thermal oxidation and photoetching heating on the middle positions of the external ground electrodes on the two sides of the top end of the silicon substrate to obtain a second buried oxide layer;
s4, arranging a piezoelectric film at the central position of the silicon substrate, acquiring an input metal electrode film and an output metal electrode film through deposition, and acquiring corresponding metal wires, transduction electrodes and bonding pads through photoetching;
s5, etching two sides of the resonator at the top end of the silicon substrate to obtain a phonon crystal matrix structure;
s6, arranging a protective layer at the top end of the silicon substrate;
s7, etching the supporting table to obtain a resonator structure with a phonon crystal matrix on the suspended resonator body;
s8, releasing the protective layer and removing the surface silicon oxide layer, and processing to obtain the micro-electromechanical resonator with the photonic crystal matrix integrated on the resonator body.
7. The method according to claim 6, wherein in the step S4, the transduction electrode includes an external input electrode and an external output electrode on top of the second buried oxide layers on both sides; the corresponding metal wire is a connecting wire of the resonant body and the corresponding transduction electrode, and the metal wire is arranged at the top end of the supporting beam.
8. The processing method according to claim 6, wherein the specific method for performing etching in step S5 is as follows: the silicon substrate is etched using a DRIE etching method and the first buried oxide layer at the bottom of the silicon substrate is etched using a RIE etching method.
9. The method according to claim 6, wherein in the step S6, the protective layer is a polyimide layer, and is used as a front protective layer during bottom trench etching, for protecting the resonator, the external input electrode, the external output electrode, the external ground electrode, and the photonic crystal matrix structure located at the top of the support table.
10. The processing method according to claim 6, wherein in step S7, the specific method for performing the etching operation on the support table is as follows: and deep etching the supporting table by using a DRIE etching method to form a groove, and deep etching the first buried oxide layer at the bottom of the silicon substrate by using an RIE etching method to obtain the resonator structure with the phonon crystal matrix on the suspended resonator.
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| CN112073024B (en) * | 2020-09-14 | 2023-10-20 | 电子科技大学 | Differential input-output MEMS resonator and processing method thereof |
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| CN113507276A (en) * | 2021-06-22 | 2021-10-15 | 电子科技大学 | Phonon lattice plate micro-electromechanical resonator of cell-like topological structure and processing method |
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