A GaN optomechanical microdisk accelerometer and its fabrication method

Abstract

This invention discloses a GaN optomechanical microdisk accelerometer and its fabrication method. The sensor includes a silicon substrate layer. A first support portion, a second support portion, and a third support portion are integrally connected on the bottom support layer of the silicon substrate layer. A first nitride disk, a second nitride disk, and a third nitride disk are respectively disposed at the upper ends of the first, second, and third support portions. An integrally connected suspended beam is disposed between the first and second nitride disks. The third nitride disk is located between the first and second nitride disks. The suspended beam, the first nitride disk, the second nitride disk, and the third nitride disk are all composed of aluminum nitride layers and gallium nitride layers disposed vertically. The GaN optomechanical microdisk accelerometer and its fabrication method provided by this invention can avoid interference from electrical noise, resulting in higher sensitivity and resolution, and a larger measurement range for the accelerometer.

Description

Technical Field

[0001] This invention relates to a GaN optomechanical microdisk accelerometer and its fabrication method, belonging to the field of optical accelerometer technology. Background Technology

[0002] An accelerometer is a sensor used to measure acceleration caused by the Earth's gravity or the motion of an object. It converts acceleration into an easily measurable and analyzable output signal. Accelerometers are one of the core components of inertial navigation systems and have wide applications in aerospace, aviation, and military fields.

[0003] Optical accelerometers offer advantages such as miniaturization, low cost, high sensitivity, and avoidance of electromagnetic noise accumulation. They combine the strengths of optical measurement and silicon-based microfabrication. Based on optical principles, the displacement of a sensitive mass under acceleration causes changes in optical properties such as interference and diffraction. Acceleration is measured by monitoring these optical parameters. Because optical methods offer high displacement measurement accuracy and are immune to circuit noise, optical accelerometers possess extremely high sensitivity and resolution. Optical accelerometers have proven to provide superior displacement resolution and strong resistance to electromagnetic interference. However, current silicon photonic optical accelerometers primarily use silicon or silicon nitride materials as sensing components. Since these materials themselves do not emit light, the entire system requires an additional light source, hindering miniaturization and making high-density optoelectronic integration difficult.

[0004] Furthermore, the structure of a traditional micromechanical accelerometer consists of a sensitive mass, a flexible arm, a potentiometer, a spring, a damper, and a housing. Its principle is that when acceleration is input, the sensitive mass deflects under inertial force, generating stress on the flexible arm, causing a change in the potentiometer's resistance. The magnitude of acceleration is measured by detecting the electrical signal. This approach has the following drawbacks: susceptibility to electrical noise interference, relatively low sensitivity and resolution, and a small measurement range. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the defects of the prior art and provide a GaN optomechanical microdisk accelerometer and its preparation method, which can reduce the interference of electrical noise and has higher sensitivity, resolution and range of accelerometer.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0007] A GaN optomechanical microdisk accelerometer includes a silicon substrate layer. The silicon substrate layer includes a bottom support layer. A first support portion, a second support portion, and a third support portion are integrally connected to the bottom support layer. A first nitride disk, a second nitride disk, and a third nitride disk are respectively disposed at the upper ends of the first support portion, the second support portion, and the third support portion. An integrally connected suspended beam is disposed between the first nitride disk and the second nitride disk. The third nitride disk is located between the first nitride disk and the second nitride disk. The suspended beam, the first nitride disk, the second nitride disk, and the third nitride disk are all composed of aluminum nitride layers and gallium nitride layers disposed vertically.

[0008] The diameters of the first nitride disk, the second nitride disk, and the third nitride disk are 40 μm.

[0009] The thickness of the gallium nitride layer is 2 μm.

[0010] The suspended connecting beam is 100μm long and 5μm wide.

[0011] The distance between the third nitride disk and the suspended connecting beam is 200-300 nm.

[0012] A method for fabricating a GaN optomechanical microdisk accelerometer includes the following steps:

[0013] After cleaning, the silicon substrate nitride epitaxial wafer is dried with a nitrogen gun. The silicon substrate nitride includes a silicon substrate layer, an aluminum nitride layer and a gallium nitride layer from bottom to top. Then, a photoresist layer is spin-coated on the epitaxial wafer using a spin coater.

[0014] Using optical lithography, a patterned structure of a suspended connecting beam, a first nitride disk, a second nitride disk, and a third nitride disk is defined on a photoresist layer;

[0015] Using III-V group inductively coupled plasma etching technology, gallium nitride and aluminum nitride layers are etched downwards with an etching solution according to the defined pattern structure, until the upper surface of the silicon substrate is etched. Finally, acetone solution is used to remove the residual photoresist.

[0016] An isotropic wet etching technique is used to etch the silicon substrate layer from the bottom using an etching solution to form a first support, a second support, and a third support.

[0017] The spin coating speed of the photoresist layer is 3000-4500 rpm, the spin coating time is 40-50 seconds, and the photoresist layer thickness is 1-1.5 μm.

[0018] The etching solution is a mixture of hydrofluoric acid and dilute nitric acid in a ratio of 1:1 to 1:10.

[0019] The beneficial effects of this invention are as follows: This invention provides a GaN optomechanical microdisk accelerometer and its fabrication method, which is prepared using nitride materials. As a representative of group III nitride wide bandgap semiconductors, nitrides have significant performance advantages compared to the previous two generations of semiconductors. They possess properties such as a wide direct bandgap, strong atomic bonds, high thermal conductivity, good chemical stability (almost unaffected by any acid corrosion), and strong radiation resistance. The gallium nitride active microcavity emits its own light and is coupled with the sensing component beam to obtain a resonant frequency. Acceleration is sensed through the frequency difference, which avoids interference from electrical noise. Due to the gain characteristics of the microcavity, the microcavity laser linewidth is narrower, and the high-sensitivity mechanical strain of the beam ensures high resolution and high sensitivity of the accelerometer. The small structural size of this invention is more conducive to realizing an on-chip accelerometer. Attached Figure Description

[0020] Figure 1 This is a side view of the GaN optomechanical microdisk accelerometer of the present invention.

[0021] Figure 2 This is a top view of the GaN optomechanical microdisk accelerometer sensor of the present invention.

[0022] Figure 3 This is a process flow diagram of the GaN optomechanical microdisk accelerometer fabrication method of the present invention;

[0023] The reference numerals in the figure are as follows: 1-Silicon substrate layer; 2-Aluminum nitride layer; 3-Gallium nitride layer; 4-Suspended connecting beam; 5-First nitride disk; 6-Second nitride disk; 7-Third nitride disk; 11-Bottom support layer; 12-First support part; 13-Second support part; 14-Third support part. Detailed Implementation

[0024] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to illustrate the technical solution of the present invention more clearly, and should not be used to limit the scope of protection of the present invention.

[0025] like Figure 1 and Figure 2 As shown, this invention discloses a GaN optomechanical microdisk accelerometer. The device uses a silicon-based nitride epitaxial wafer as a carrier and includes a silicon substrate layer 1, an aluminum nitride layer 2, and a gallium nitride layer 3. The silicon substrate layer 1 is a silicon-based material, and the gallium nitride layer 3 has a thickness of 2 μm. In this invention, GaN, as a third-generation semiconductor, exhibits stable physical properties, corrosion resistance, and high-temperature resistance, enabling it to withstand extreme environments of high temperature, strong acids, and strong alkalis. Importantly, it possesses excellent optical and mechanical properties. This invention combines the optical and mechanical properties of GaN.

[0026] The silicon substrate 1 includes a bottom support layer 11, on which an integrally connected first support portion 12, second support portion 13, and third support portion 14 are formed. A first nitride disk 5, a second nitride disk 6, and a third nitride disk 7 are respectively disposed at the upper ends of the first support portion 12, the second support portion 13, and the third support portion 14. The diameters of the first nitride disk 5, the second nitride disk 6, and the third nitride disk 7 are 40 μm. The nitride disk microcavity structure is supported below by the support portion of the silicon substrate 1, thus suspending the nitride disk microcavity structure.

[0027] A suspended connecting beam 4, integrally connected to the first nitride disk 5 and the second nitride disk 6, is provided. The suspended connecting beam 4 has a length of 100 μm and a width of 5 μm. A third nitride disk 7 is located between the first nitride disk 5 and the second nitride disk 6, close to the suspended connecting beam 4, with a distance of 200–300 nm between the third nitride disk 7 and the suspended connecting beam 4. The suspended connecting beam 4, the first nitride disk 5, the second nitride disk 6, and the third nitride disk 7 are all composed of an aluminum nitride layer 2 and a gallium nitride layer 3 disposed vertically.

[0028] The working principle of this invention is as follows: When an acceleration load is applied, the suspended connecting beam 4 of the GaN optomechanical microdisk accelerometer undergoes mechanical strain, causing it to vibrate and drive the third gallium nitride disk 7 to resonate. The magnitude of the acceleration is sensed by detecting the resonant frequency difference of the overall structure of the GaN optomechanical microdisk accelerometer when acceleration is applied and unloaded.

[0029] like Figure 3 As shown, this invention also discloses a method for fabricating a GaN optomechanical microdisk accelerometer, comprising the following steps:

[0030] Step 1: The silicon substrate nitride epitaxial wafer is ultrasonically cleaned once with acetone, anhydrous ethanol, and deionized water, and then dried with a nitrogen gun. The silicon substrate nitride consists of a silicon substrate layer 1, an aluminum nitride layer 2, and a gallium nitride layer 3 from bottom to top. Then, a photoresist layer is spin-coated onto the epitaxial wafer (the surface of the gallium nitride layer 3) using a spin coater. The spin-coating speed is 3000–4500 rpm, the spin-coating time is 40–50 seconds, and the photoresist layer thickness is 1–1.5 μm.

[0031] Step two, using optical lithography, define as follows on the photoresist layer: Figure 1 and Figure 2 The graphic structure of the suspended connecting beam 4, the first nitride disk 5, the second nitride disk 6, and the third nitride disk 7 shown is based on the MA6 lithography machine.

[0032] Step 3: Using III-V group inductively coupled plasma etching technology, gallium nitride layer 3 and aluminum nitride layer 2 are etched downwards using an etching solution according to the defined pattern structure. The etching solution is a mixture of hydrofluoric acid and dilute nitric acid in a ratio of 1:1 to 1:10. The etching is carried out until the upper surface of silicon substrate layer 1, thereby transferring the defined pattern structure downwards into the nitride layer of the epitaxial wafer. Finally, residual photoresist is removed with acetone solution.

[0033] Step four: Using isotropic wet etching technology, an etching solution is used to etch the silicon substrate layer 1 from the bottom of the GaN optomechanical microdisk accelerometer microcavity structure. The etching solution is a mixed solution of hydrofluoric acid and dilute nitric acid in a ratio of 1:1 to 1:10, forming the first support part 12, the second support part 13 and the third support part 14, thus obtaining a suspended GaN optomechanical microdisk accelerometer microcavity structure supported by silicon pillars.

[0034] The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A GaN optomechanical microdisk acceleration sensor, characterized by: The application relates to a silicon substrate layer (1) comprising a bottom support layer (11), wherein a first support part (12), a second support part (13) and a third support part (14) are integrally arranged on the bottom support layer (11), the upper ends of the first support part (12), the second support part (13) and the third support part (14) are respectively provided with a first nitride disc (5), a second nitride disc (6) and a third nitride disc (7), a suspension connecting beam (4) is integrally arranged between the first nitride disc (5) and the second nitride disc (6), the third nitride disc (7) is located between the first nitride disc (5) and the second nitride disc (6), the suspension connecting beam (4), the first nitride disc (5), the second nitride disc (6) and the third nitride disc (7) are all composed of an upper and lower aluminum nitride layer (2) and a gallium nitride layer (3), and the distance between the third nitride disc (7) and the suspension connecting beam (4) is 200-300 nm.

2. The GaN optomechanical microdisk acceleration sensor of claim 1, wherein: The diameters of the first nitride disc (5), the second nitride disc (6) and the third nitride disc (7) are 40 mu m.

3. The GaN optomechanical microdisk acceleration sensor of claim 1, wherein: The thickness of the gallium nitride layer (3) is 2 mu m.

4. The GaN optomechanical microdisk acceleration sensor of claim 1, wherein: The length of the suspension connecting beam (4) is 100 mu m, and the width is 5 mu m.

5. A method for fabricating the GaN optomechanical microdisk acceleration sensor according to any one of claims 1 to 4, characterized in that: The application comprises the following steps: After cleaning, the silicon substrate nitride epitaxial wafer is dried by using a nitrogen gun, wherein the silicon substrate nitride comprises a silicon substrate layer (1), an aluminum nitride layer (2) and a gallium nitride layer (3) from bottom to top, then a photoresist layer is spin-coated on the epitaxial wafer by using a spin coater; An optical lithography technology is adopted to define the pattern structure of the suspension connecting beam (4), the first nitride disc (5), the second nitride disc (6) and the third nitride disc (7) on the photoresist layer; A III-V group inductive coupling plasma etching technology is adopted to etch the gallium nitride layer (3) and the aluminum nitride layer (2) downwards according to the defined pattern structure, the etching is performed until the upper surface of the silicon substrate layer (1), and finally the residual photoresist is removed by using an acetone solution; An isotropic wet etching technology is adopted to etch the silicon substrate layer (1) from the bottom by using an etching solution, so as to form the first support part (12), the second support part (13) and the third support part (14).

6. The method for fabricating a GaN optomechanical microdisk accelerometer according to claim 5, characterized in that: The spin-coating rotating speed of the photoresist layer is 3000-4500 revolutions per minute, the spin-coating time is 40-50 seconds, and the thickness of the photoresist layer is 1-1.5 mu m.

7. The method of claim 5, wherein the GaN micromechanical optical disk acceleration sensor is prepared by the steps of: The etching solution is a mixed solution of hydrofluoric acid and dilute nitric acid with a ratio of 1:1-1:

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