Built-in power drive resonator and preparation method thereof

Abstract

The invention discloses a built-in power drive resonator and a preparation method thereof, and relates to the technical field of resonator preparation, and the method comprises the steps: preparing a patterned electrode on a silicon wafer with a silicon dioxide layer on the surface, and obtaining a silicon wafer with the patterned electrode; plating a source electrode and a drain electrode on the surface of the silicon wafer with the patterned electrode to obtain a silicon wafer with an electrode; placing the silicon wafer with the electrode in a focused ion beam system, and performing partial etching on the silicon dioxide layer by using a gallium ion etching process to form a resonant cavity so as to obtain a silicon wafer with the resonant cavity; and transferring the graphene film to the resonant cavity and the electrode, and carrying out annealing treatment to obtain the built-in power supply driven resonator. The steady-state resonance mode signal of the built-in power supply driving resonator can reach 38.7 MHz, and the quality factor can reach 268.

Description

TECHNICAL FIELD

[0001] The application relates to an in-built power supply driven resonator and a preparation method thereof, and belongs to the technical field of resonator preparation. BACKGROUND

[0002] Ga + Ion etching only plays a subtractive etching role in existing micro-nano processing, and the irradiation of gallium ions on the etched structure is usually regarded as a damage source in semiconductor device processing. The potential of gallium ions in the field of functional doping has been ignored for a long time.

[0003] How to use the reverse functionalization strategy, that is, to use Ga + In the process of FIB subtractive etching of insulating medium SiO2, the Ga + ion irradiation area forms a fixed charge center, which converts the process inherent "defects" into a controllable built-in bias field source, not only solving the problem of dependence on external DC power supply of MEMS / NEMS devices, but also reducing system noise. However, the existing research still cannot achieve this. SUMMARY

[0004] The application aims to overcome the deficiencies in the prior art, and provides an in-built power supply driven resonator and a preparation method thereof. The steady-state resonance mode signal reaches 38.7 MHz, and the quality factor reaches 268.

[0005] To achieve the above-mentioned purpose, the application adopts the following technical scheme: On the one hand, the application provides a preparation method of an in-built power supply driven resonator, comprising: preparing a patterned electrode on a silicon wafer with a silicon dioxide layer to obtain a silicon wafer with a patterned electrode; plating an electrode on the surface of the silicon wafer with a patterned electrode to obtain a silicon wafer with an electrode; placing the silicon wafer with an electrode in a focused ion beam system, and using a gallium ion etching process to partially etch the silicon dioxide layer to form a resonant cavity, thereby obtaining a silicon wafer with a resonant cavity; transferring a graphene film to the resonant cavity and the electrode of the silicon wafer with a resonant cavity, and obtaining an in-built power supply driven resonator after annealing treatment.

[0006] Further, the thickness of the silicon dioxide layer ranges from 400 to 445 nm.

[0007] Further, the preparation of the patterned electrode on the silicon wafer with a silicon dioxide layer comprises: uniformly coating an electron beam resist on the surface of the silicon dioxide layer; Exposing the electron beam photoresist by using electron beam lithography process, developing and fixing to obtain a silicon wafer with a patterned electrode; The patterned electrode comprises a photoresist covering part and a photoresist removing part, the photoresist removing part is used as a mask, and the photoresist covering part is used for plating a source electrode and a drain electrode.

[0008] Further, the plating of the source electrode and the drain electrode on the surface of the silicon wafer with the patterned electrode comprises: placing the silicon wafer with the patterned electrode in an electron beam plating machine, and plating titanium and gold from bottom to top, wherein the titanium is used as an adhesion layer, and the gold is used as the source electrode and the drain electrode; placing the silicon wafer in acetone, and then cleaning with isopropyl alcohol and drying with nitrogen to obtain the silicon wafer with the electrode.

[0009] Further, the thickness of the titanium ranges from 5 to 10 nm, and the thickness of the gold ranges from 35 to 65 nm.

[0010] Further, the plating condition parameters of the titanium include a voltage of 10 kV and a current ranging from 10 to 30 mA, and the plating condition parameters of the gold include a voltage of 10 kV and a current ranging from 140 to 200 mA, and the evaporation rate is controlled at 0.2 to 0.5 A per second.

[0011] Further, the diameter of the resonant cavity ranges from 3 to 3.2 μm, and the depth ranges from 220 to 300 nm.

[0012] Further, the process parameters of the gallium ion etching process include an acceleration voltage of 30 kV, a beam current of 200 to 300 PA, a basic dose of 200 to 300 μC / cm 2 , a positive and negative etching scanning number of 100 to 200 times, and a dose factor ranging from 0.4 to 1.2.

[0013] Further, the annealing treatment comprises heating at 300 to 400 ℃ for 2 to 4 h in an argon and hydrogen protective atmosphere.

[0014] On the other hand, the application also provides an internal power supply driven resonator prepared by the preparation method of any one of the internal power supply driven resonators.

[0015] Compared with the prior art, the application has the following beneficial effects: This invention proposes a method for fabricating a resonator with an internal power supply using gallium ion focused ion beam doping technology. This method allows for the etching of a resonant cavity onto a silicon dioxide substrate using gallium ions, and also enables the implantation of gallium ions into silicon dioxide (a wide bandgap insulator / dielectric) and their retention within the silicon dioxide lattice. These implanted gallium ions act as fixed positive charge centers within the silicon dioxide lattice, achieving the goal of constructing a stable internal bias power supply within the microelectromechanical resonator using gallium ions. This provides a novel method for fabricating resonant devices without an external DC bias voltage, opening up new application paths for functionalized doping of gallium ion focused ion beam technology and providing an on-chip integrated solution for miniaturized resonators and self-powered sensing systems. Attached Figure Description

[0016] Figure 1 This is a partial flowchart illustrating the fabrication method of a built-in power supply driven resonator in one embodiment of the present invention. Figure 2 This is a schematic diagram of the resonant cavity with a built-in power supply driving resonator in one embodiment of the present invention; Figure 3 This is an optical schematic diagram of the resonant cavity with a built-in power supply driving resonator in one embodiment of the present invention; Figure 4 This is an AFM rendering schematic diagram of the resonant cavity with a built-in power supply driving resonator in one embodiment of the present invention; Figure 5 This is a schematic diagram of the performance testing device with a built-in power supply driven resonator in one embodiment of the present invention; Figure 6 This is a schematic diagram of the resonance signal stability test of a built-in power supply driven resonator in one embodiment of the present invention; Figure 7 This is a schematic diagram of the Allen variance of the resonant signal stability of the built-in power supply driven resonator in one embodiment of the present invention; Figure 8 This is a schematic diagram of the resonance signal test of the built-in power supply driven resonator in one embodiment of the present invention. Detailed Implementation

[0017] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0018] This invention provides a method for fabricating a built-in power supply driven resonator, comprising the following steps: First, combined Figure 1 In (a) to (c), patterned electrodes are prepared on a silicon wafer with a silicon dioxide oxide layer on its surface to obtain a silicon wafer with patterned electrodes.

[0019] The thickness of the silicon dioxide oxide layer is 400~445nm, and in this embodiment, the thickness is 400nm. A layer of electron beam photoresist (PMMA 950A4) is uniformly coated on the surface of the silicon dioxide oxide layer and baked at 140~180℃ for 2 minutes after coating). Electron beam lithography is then performed (specific process parameters: 10KV accelerating current, 30 aperture, 200uC / cm). 2 Exposure (dose), development (a mixed solution of methyl isobutyl ketone and isopropanol in a 1:3 ratio, 40s), fixing (isopropanol, 30s), to obtain a silicon wafer with patterned electrodes.

[0020] The patterned electrode includes a resist-removing section and a photoresist-covering section. The resist-removing section serves as a mask, and the photoresist-covering section is used for electrode deposition.

[0021] Then, combine Figure 1 In (d), a silicon wafer with patterned electrodes is placed in an electron beam coating machine. From bottom to top, 5 nm of titanium is deposited as an adhesion layer to increase the adhesion between the silicon substrate and the electrodes. Then, 50 nm of gold is deposited as the source and drain electrodes. The process parameters for titanium plating are 10 kV voltage and 10 mA current, and the process parameters for gold plating are 10 kV voltage and 140 mA current. The evaporation rate is controlled at 0.2 A per second.

[0022] Combination Figure 1 In step (e), the silicon wafer is placed in acetone for one hour (lift-off process) to remove the photoresist on the surface of the silicon wafer and the excess titanium plated on the photoresist, leaving only the titanium in the removed part. After removing the silicon wafer, the surface is cleaned with isopropanol to remove the residual acetone and then dried with nitrogen to obtain a silicon wafer with electrodes.

[0023] In this embodiment, the silicon wafer with electrodes also needs to be characterized using an atomic force microscope to ensure that the edge burrs and roughness of the patterned electrodes meet the requirements for graphene film transfer and ohmic contact between the graphene film and the gold electrode. An image of the gold electrode under an optical microscope in this embodiment is shown below. Figure 1 As shown in (f) in the figure, the yellow part is the gold electrode.

[0024] Next, the qualified silicon wafer with electrodes was placed in a focused ion beam (FIB) system. At a distance of 10 micrometers from the titanium electrodes, a resonant cavity with a depth of 3 μm and 220 nm was etched into the silicon dioxide layer using gallium ion etching (the optimized etching parameters were: accelerating voltage 30 kV, beam current 300 Pa, and base dose 300 μC / cm). 2, the number of forward and backward etching scans is 100 times, and the dose factor is selected as 0.4, and meanwhile, a part of gallium ions can be implanted into silicon dioxide (a wide-band insulator / medium) and stay in the lattice of silicon dioxide, the implanted gallium ions act as fixed positive charge centers in the lattice of silicon dioxide, and the purpose of constructing a stable built-in bias power supply inside the micro-electromechanical resonator by the gallium ions is achieved.

[0025] The resonant cavity in the embodiment is shown in Figure 2 The resonant cavity is a circular cavity as a whole, with a diameter of 3 μm and a depth of 220 nm, and a wire groove is arranged on one side of the circular cavity. This structure is to exclude the influence of air resistance on the vibration of the graphene film during the subsequent vacuum test of the graphene resonator, so as to avoid the graphene film from collapsing in the resonant cavity after the vacuum is broken, and the device is damaged.

[0026] Finally, the target graphene film is obtained by a mechanical exfoliation method, the graphene film is transferred to the etched resonant cavity and gold electrode, and then placed in an annealing furnace under the protection of argon and hydrogen atmosphere at 300°C for 2 hours for annealing and cooling, so as to eliminate the stress between the graphene film and the silicon wafer. The graphene film becomes soft and the tuning rate increases after annealing treatment, and finally a built-in power supply driven resonator is prepared. The optical image of the built-in power supply driven resonator is shown in Figure 3 The AFM image is shown in Figure 4 , Figure 4 The yellow band with white spots in the middle is the graphene film, which can be seen to realize the transfer of the graphene film to the resonant cavity and the gold electrode.

[0027] The performance of the prepared built-in power supply driven resonator is analyzed as follows: The test device is shown in Figure 5 The built-in power supply driven resonator is placed in a vacuum cavity, a He-Ne laser emits linearly polarized light with a wavelength of 632.8 nm, the linearly polarized light is reflected by a mirror, then passes through a neutral filter to uniformly attenuate all wavelengths of light, and then passes through a single-mode polarization maintaining fiber to maintain the polarization state of the light signal stable, and then passes through a λ / 2 wave plate to adjust the energy ratio of P-polarized light and S-polarized light in the light beam. Then the light beam is reflected by the mirror again, then passes through a polarization beam splitting cube (P-polarized light is transmitted), a λ / 4 wave plate (P-polarized light is changed into circularly polarized light), and then passes through a 100x objective lens to focus on the surface of the resonator through the vacuum cavity.

[0028] The modulated reflected light passes through the objective lens, the λ / 4 wave plate (circularly polarized light is changed into S-polarized light), and the polarization beam splitting cube (S-polarized light is reflected) in turn, and then is received by a photodetector and converted into an electrical signal which is transmitted to a vector network analyzer. A white light LED and a CCD camera are used to image the reflected light to determine the test area.

[0029] The gold electrode is grounded, an AC voltage is applied to the silicon wafer (gate) of the graphene micro-cantilever beam resonator through a biasing device, and the resonance signal spectrum and resonance signal stability test spectrum of the resonator are read out by a vector network analyzer.

[0030] The resonance signal stability test spectrum is shown in Figure 6 To objectively evaluate the stability of the resonance frequency without a DC voltage source, the Allan variance statistical resonance frequency signal fluctuation in the time domain is introduced as a key indicator for evaluating stability. By analyzing the Allan variance curve, the noise type (such as white noise, flicker noise) is characterized, and the stability of the device is quantitatively evaluated, wherein the lowest point of the curve is not only a key indicator of noise source conversion, but also provides information on the optimal stability time scale of the system. Therefore, by calculating the Allan variance analysis of the fluctuation of the resonance frequency under the condition of no external DC voltage, the stability and repeatability of the resonator driven by the built-in power supply are analyzed, and the Allan variance curve is shown in Figure 7 As can be seen from the figure, the value of the Allan variance is in the order of 10 -4 , indicating that the stability of the resonator driven by the built-in power supply is high.

[0031] The resonance signal spectrum is shown in Figure 8 The orange circles in the figure are the resonance signal test data read out multiple times, and the blue peak curve is obtained by Q value fitting. From the blue peak curve, it can be seen that the steady-state resonance mode signal of the resonator driven by the built-in power supply reaches 38.7 MHz, indicating that the resonator driven by the built-in power supply reaches the MHz level, which is three orders of magnitude higher than the conventional KHz level.

[0032] The quality factor is calculated, and the calculation formula is quality factor = resonance peak / frequency difference of half width, wherein the resonance peak value is 38.7 MHz, and the frequency difference of half width is 144 KHz. The frequency difference of half width is the horizontal coordinate of the corresponding point on the right side of the half width minus the horizontal coordinate of the corresponding point on the left side of the half width in the blue peak curve. The calculated quality factor is 268, indicating that the energy loss of the resonator driven by the built-in power supply is at a low level.

[0033] The above only describes the preferred embodiments of the present application, and it should be noted that for ordinary skilled persons in the technical field, without departing from the technical principles of the present application, a number of improvements and modifications can be made, and these improvements and modifications should be considered as the protection scope of the present application.

Claims

1. A method for fabricating a resonator driven by a built-in power supply, characterized in that, include: Patterned electrodes are fabricated on a silicon wafer with a silicon dioxide layer on its surface to obtain a silicon wafer with patterned electrodes; Electrodes are deposited on the surface of a silicon wafer with patterned electrodes to obtain an electrode-bearing silicon wafer; A silicon wafer with electrodes is placed in a focused ion beam system, and a partial etching process is used to etch the silicon dioxide layer to form a resonant cavity, thus obtaining a silicon wafer with a resonant cavity. The graphene film is transferred onto the resonant cavity and electrodes of a silicon wafer with a resonant cavity, and after annealing, a resonator with a built-in power supply is obtained.

2. The method for fabricating a built-in power supply driven resonator according to claim 1, characterized in that, The thickness of the silicon dioxide layer ranges from 400 to 445 nm.

3. The method for fabricating a built-in power supply driven resonator according to claim 1, characterized in that, The process of fabricating patterned electrodes on a silicon wafer with a silicon dioxide layer on its surface to obtain a silicon wafer with patterned electrodes includes: Electron beam photoresist is uniformly coated on the surface of the silicon dioxide layer; Electron beam lithography is used to expose electron beam photoresist, followed by development and fixing to obtain a silicon wafer with patterned electrodes. The patterned electrode includes a resist-removing portion and a photoresist-covered portion. The resist-removing portion serves as a mask, and the photoresist-covered portion is used to deposit the source electrode and the drain electrode.

4. The method for fabricating a built-in power supply driven resonator according to claim 1, characterized in that, The process of depositing electrodes on the surface of a silicon wafer with patterned electrodes to obtain an electrode-bearing silicon wafer includes: A silicon wafer with patterned electrodes is placed in an electron beam coating machine and coated with titanium and gold sequentially from bottom to top. Titanium serves as the adhesion layer, and gold serves as the source electrode and drain electrode. The silicon wafer is placed in acetone, then removed, cleaned with isopropanol, and dried with nitrogen to obtain a silicon wafer with electrodes.

5. The method for fabricating a built-in power supply driven resonator according to claim 4, characterized in that, The thickness of the titanium ranges from 5 to 10 nm, and the thickness of the gold ranges from 35 to 65 nm.

6. The method for fabricating a built-in power supply driven resonator according to claim 4, characterized in that, The electroplating conditions for the titanium include a voltage of 10kV and a current range of 10~30mA, while the electroplating conditions for the gold include a voltage of 10kV and a current range of 140~200mA, with the evaporation rate controlled at 0.2~0.5A per second.

7. The method for fabricating a built-in power supply driven resonator according to claim 1, characterized in that, The diameter of the resonant cavity ranges from 3 to 3.2 μm, and the depth ranges from 220 to 300 nm.

8. The method for fabricating a built-in power supply driven resonator according to claim 1, characterized in that, The process parameters for the gallium ion etching process include an accelerating voltage of 30 kV, a beam current of 200-300 PA, and a base dose of 200-300 μC / cm. 2 The number of forward and reverse etching scans is 100 to 200, and the dose factor ranges from 0.4 to 1.

2.

9. The method for fabricating a built-in power supply driven resonator according to claim 1, characterized in that, The annealing process involves heating at 300-400°C for 2-4 hours under a protective atmosphere of argon and hydrogen.

10. A resonator driven by a built-in power supply, characterized in that, It is prepared by the method of preparing the built-in power supply driven resonator as described in any one of claims 1 to 9.

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