A single-crystal β-Ga2O3 MSM detector and its fabrication method

Abstract

This invention discloses a single-crystal β-Ga2O3 MSM detector and its fabrication method, comprising the following steps: processing a groove on a single-crystal β-Ga2O3 substrate using laser-assisted water jet processing technology to form a three-dimensional morphology; performing wet etching on the processed single-crystal β-Ga2O3 substrate using HF solution to remove processing damage; performing Au evaporation on the surface of the processed single-crystal β-Ga2O3 substrate to cover the surface of the single-crystal β-Ga2O3 substrate with an Au thin film; and grinding the surface of the deposited single-crystal β-Ga2O3 substrate to remove the Au thin film on the unprocessed surface, retaining the Au thin film in the groove, thus obtaining the detector.

Description

Technical Field

[0001] This invention belongs to the field of laser composite microfabrication technology, specifically relating to a single-crystal β-Ga2O3MSM detector and its fabrication method. Background Technology

[0002] The statements herein provide only background information in relation to this invention and do not necessarily constitute prior art.

[0003] Gallium oxide (β-Ga₂O₃), as a new generation of oxide semiconductor material, possesses advantages such as an ultra-wide bandgap, high breakdown electric field strength, high ultraviolet transmittance, and stable physicochemical properties. Gallium oxide has an absorption cutoff edge of 240–280 nm, located in the solar-blind ultraviolet band, and exhibits good transmittance in the ultraviolet to visible light region, making it an excellent material for solar-blind detectors. However, because gallium oxide is a hard and brittle material that is easily dissociated, it is prone to defects such as scratches, dissociation pits, and abrasive embedding during precision machining. Furthermore, the poor thermal conductivity and large anisotropy of gallium oxide single crystals make them susceptible to microcracks during laser processing. This significantly restricts the application and development of gallium oxide single crystals.

[0004] The current method for fabricating β-Ga₂O₃ MSM detectors involves photolithography on β-Ga₂O₃ thin films. However, for single-crystal β-Ga₂O₃ substrates, photolithography cannot fully utilize the advantages of single-crystal β-Ga₂O₃ substrates (photolithography fabrication of MSM detectors involves two-dimensional processing on the substrate surface, which is suitable for β-Ga₂O₃ thin film substrates. Single-crystal substrates, on the other hand, can have three-dimensional morphologies fabricated on their surface using etching and laser processing, thereby increasing the ohmic contact area between the metal and β-Ga₂O₃). Therefore, it is necessary to fabricate three-dimensional morphologies on single-crystal β-Ga₂O₃ substrates. Currently, the main processing method for gallium oxide single crystals is wet etching. Although it is not as resistant to chemical corrosion as sapphire (Al2O3), β-Ga2O3 is still difficult to wet etch. In sputtered Ga2O3 films deposited at substrate temperatures of 400-1000℃, the etching rate of gallium oxide grown at 400℃ is about 490nm / s, while the etching rate of films grown at 1000℃ is only about 0.196nm / s. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the purpose of this invention is to provide a single-crystal β-Ga2O3MSM detector and its fabrication method.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0007] In a first aspect, the present invention provides a method for fabricating a single-crystal β-Ga2O3 MSM detector, comprising the following steps:

[0008] A three-dimensional morphology was formed by processing a groove on a single-crystal β-Ga2O3 substrate using laser-assisted waterjet processing technology.

[0009] The processed single-crystal β-Ga2O3 substrate was wet-etched using HF solution to remove processing damage;

[0010] Au was deposited on the surface of the treated single-crystal β-Ga2O3 substrate to cover the surface of the single-crystal β-Ga2O3 substrate with an Au thin film.

[0011] The surface of the vapor-deposited single-crystal β-Ga2O3 substrate is ground to remove the Au film on the unprocessed surface, while retaining the Au film in the tank, thus obtaining the desired product.

[0012] In some embodiments, the groove is an inverted trapezoidal groove.

[0013] In some embodiments, in laser-assisted waterjet processing technology, the pulse width of the nanosecond laser is 10–350 ns, the pulse repetition frequency is 20–1000 kHz, the scanning speed is 1–16 mm / s, and the waterjet pressure is 4–16 MPa.

[0014] Preferably, the water jet pressure is 5-10 MPa.

[0015] Preferably, the wavelength of the nanosecond laser is 1064 nm.

[0016] More preferably, the laser single pulse energy is 0.02 to 0.1 mJ, and the focal plane height is -0.1 to 0.1 mm.

[0017] Preferably, in the laser-assisted waterjet processing technology, the waterjet nozzle-target distance is 0.3–1.4 mm, the waterjet offset distance is 0.3–0.7 mm, and the waterjet impact angle is 39°–51°.

[0018] The water jet gradually diverges as the target distance increases. If the target distance is too large, the quality of the water jet impacting the workpiece surface is poor, and the water layer formed on the workpiece surface is unstable. This will cause instability of the laser after passing through the water layer, thus affecting the processing quality. If the target distance is too small, the impact of the water jet on the workpiece is greater. At the same time, the minimum target distance is limited to 0.3mm due to the nozzle shape.

[0019] The stress generated on the workpiece surface by the impact force of the water jet can be decomposed into wall compressive stress and wall shear stress. Among them, wall shear stress is the influencing factor for material removal. If the angle is too large, the wall shear stress is small, and the material cannot be removed. If the angle is too small, the wall shear stress is large, and the material will undergo large-area brittle peeling during processing, resulting in poor processing quality.

[0020] In some embodiments, the concentration of the HF solution used for wet etching is 47%–49%, the etching temperature is 5–25°C, and the etching time is 8–15 min.

[0021] The reaction mechanism of wet etching of β-Ga2O3 in HF solution is as follows:

[0022] Ga2O3 + 6HF → 2GaF3 + 3H2O.

[0023] In some embodiments, the grinding slurry used is an Al2O3 grinding slurry with a thickness of 1 to 2.5 μm, and the grinding disc is a relatively soft lead grinding disc.

[0024] Secondly, the present invention provides a three-dimensional single-crystal β-Ga2O3MSM detector, which is prepared by the aforementioned preparation method.

[0025] The beneficial effects achieved by one or more embodiments of the present invention described above are as follows:

[0026] The material removal mechanism of laser-assisted waterjet processing technology is different from that of laser processing. Laser processing uses high temperature to vaporize the material, while in laser-assisted waterjet processing, the laser only heats and softens the material. After softening, the material is removed by the impact of high-pressure water jet, which greatly reduces the recast layer and thermal cracks, and has the advantage of less processing damage.

[0027] The cross-shaped trapezoidal grooves provide more contact area for the Au thin film, enabling a larger ohmic contact between the electrode and the single-crystal β-Ga2O3 substrate, thereby improving the sensitivity of the MSM-type solar-blind detector and reducing the size of the detector.

[0028] This invention combines laser-assisted waterjet processing and wet etching. Laser-assisted waterjet processing can efficiently rough the three-dimensional morphology, while wet etching can remove processing damage and reduce surface roughness. Attached Figure Description

[0029] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0030] Figure 1This is a schematic diagram of the surface structure of the fabricated single-crystal β-Ga2O3 MSM detector;

[0031] Figure 2 This is a flowchart of the fabrication process for a single-crystal β-Ga2O3 MSM detector in an embodiment of the present invention. (a) is the single-crystal β-Ga2O3 substrate to be processed, (b) is a schematic diagram of the MSM detector structure after laser-assisted water jet processing and wet etching, (c) is a schematic diagram of the substrate surface covered with an Au thin film after evaporation, and (d) is a schematic diagram of the MSM detector prepared after grinding and polishing.

[0032] Figure 3 This is a surface morphology diagram of single-crystal β-Ga2O3 processed by laser-assisted water jet in Example 1, where B is a magnified view of A. Detailed Implementation

[0033] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0034] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0035] Example 1

[0036] like Figure 2 As shown, the fabrication method of a single-crystal β-Ga2O3 MSM detector includes the following steps:

[0037] 1) Laser-assisted waterjet processing for fabricating inverted trapezoidal cross-groove structures

[0038] The process uses a nanosecond laser with a wavelength of 1064nm, a laser pulse width of 30ns, and a pulse frequency of 315KHz.

[0039] (1) Ultrasonic cleaning of single-crystal β-Ga2O3 substrate, and mounting it on a laser-assisted water jet transparent worktable;

[0040] (2) Focus the equipment until the laser focal plane height is 0mm. Adjust the relative position of the laser and the water jet, with the water jet angle at 45°, the jet offset distance at 0.5mm, and the water jet nozzle-target distance at 0.6mm;

[0041] (3) Set the laser parameters: pulse width 30ns, pulse frequency 315KHz, average laser power 20W, scanning speed 1mm / s, processing times 1, and lateral offset distance 10μm.

[0042] (4) Adjust the water jet pressure to 6MPa;

[0043] (5) Run the machining program to process the MSM structure. The depth of the processed inverted trapezoidal groove is 15-25 μm and the width is 50-60 μm. The morphology of the laser-assisted waterjet processed single crystal β-Ga2O3 is shown in the figure. Figure 3 As shown.

[0044] 2) Wet etching was performed on the processed single-crystal β-Ga2O3;

[0045] The etching solution used in the process is HF solution with a concentration of 47% to 49% and an etching temperature of 5 to 25°C.

[0046] (1) Clean the single-crystal β-Ga2O3 substrate and place it in a beaker;

[0047] (2) Prepare an HF solution with a concentration of 49%;

[0048] (3) Pour the HF solution into a beaker until it submerges the substrate, and react at room temperature (20°C) for 10 min;

[0049] (4) Remove the substrate and clean it.

[0050] 3) Evaporation deposition of single-crystal β-Ga2O3

[0051] (1) The processed single-crystal β-Ga2O3 substrate is mounted on the evaporation worktable;

[0052] (2) A nano-scale Au thin film was deposited on the surface of a single-crystal β-Ga2O3 substrate;

[0053] (3) Remove the substrate.

[0054] 4) Grinding single-crystal β-Ga2O3

[0055] The grinding slurry used in the process is 1μm Al2O3, and the grinding disc is a relatively soft lead grinding disc.

[0056] (1) Mount the single crystal β-Ga2O3 substrate on the grinding table;

[0057] (2) Install the lead grinding disc and spray it with 1μm Al2O3 grinding liquid;

[0058] (3) Start the equipment to perform grinding;

[0059] (4) After grinding for a period of time, remove the single crystal β-Ga2O3 substrate and observe under a microscope whether the Au film on the micro-machined surface has been completely removed. If it has not been completely removed, continue grinding until it is completely removed.

[0060] (5) Clean the single-crystal β-Ga2O3MSM detector to obtain the final product.

[0061] Example 2

[0062] The fabrication method of a single-crystal β-Ga2O3 MSM detector includes the following steps:

[0063] 1) Laser-assisted waterjet processing to prepare inverted trapezoidal cross groove structure.

[0064] The process uses a nanosecond laser with a wavelength of 1064nm, a laser pulse width of 20ns, and a pulse frequency of 490KHz.

[0065] (1) Ultrasonic cleaning of single-crystal β-Ga2O3 substrate, and mounting it on a laser-assisted water jet transparent worktable;

[0066] (2) Focus the equipment until the laser focal plane height is -0.1mm. Adjust the relative position of the laser and the water jet, with the water jet angle at 45°, the jet offset distance at 0.5mm, and the water jet nozzle-target distance at 0.6mm;

[0067] (3) Set the laser parameters: pulse width 20ns, pulse frequency 490KHz, average laser power 25W, scanning speed 1mm / s, number of processing times 2, and lateral offset distance 15μm.

[0068] (4) Adjust the water jet pressure to 6MPa;

[0069] (5) Run the machining program to process the MSM structure. The depth of the inverted trapezoidal groove after machining is 20-30 μm and the width is 60-70 μm.

[0070] 2) Wet etching is performed on the processed single-crystal β-Ga2O3.

[0071] The etching solution used in the process is HF solution with a concentration of 47% to 49% and an etching temperature of 5 to 25°C.

[0072] (1) Clean the single-crystal β-Ga2O3 substrate and place it in a beaker;

[0073] (2) Prepare an HF solution with a concentration of 47%;

[0074] (3) Pour the HF solution into a beaker until it submerges the substrate, and react at room temperature (25°C) for 10 min;

[0075] (4) Remove the substrate and clean it.

[0076] 3) Evaporation deposition of single-crystal β-Ga2O3

[0077] (1) The processed single-crystal β-Ga2O3 substrate is mounted on the evaporation worktable;

[0078] (2) A nano-scale Au thin film was deposited on the surface of a single-crystal β-Ga2O3 substrate;

[0079] (3) Remove the substrate.

[0080] 4) Grinding single-crystal β-Ga2O3

[0081] The grinding slurry used in the process is 1μm Al2O3, and the grinding disc is a relatively soft lead grinding disc.

[0082] (1) Mount the single crystal β-Ga2O3 substrate on the grinding table;

[0083] (2) Install the lead grinding disc and spray it with 1μm Al2O3 grinding liquid;

[0084] (3) Start the equipment to perform grinding;

[0085] (4) After grinding for a period of time, remove the single crystal β-Ga2O3 substrate and observe under a microscope whether the Au film on the micro-machined surface has been completely removed. If it has not been completely removed, continue grinding until it is completely removed.

[0086] (5) Clean the single-crystal β-Ga2O3MSM detector to obtain the final product.

[0087] Example 3

[0088] The fabrication method of a single-crystal β-Ga2O3 MSM detector includes the following steps:

[0089] 1) Laser-assisted waterjet processing to prepare inverted trapezoidal cross groove structure.

[0090] The process uses a nanosecond laser with a wavelength of 1064nm, a laser pulse width of 10ns, and a pulse frequency of 1000KHz.

[0091] (1) Ultrasonic cleaning of single-crystal β-Ga2O3 substrate, and mounting it on a laser-assisted water jet transparent worktable;

[0092] (2) Focus the equipment until the laser focal plane height is 0.1mm. Adjust the relative position of the laser and the water jet, with the water jet angle at 45°, the jet offset distance at 0.5mm, and the water jet nozzle-target distance at 0.6mm;

[0093] (3) Set the laser parameters: pulse width 10ns, pulse frequency 1000KHz, average laser power 30W, scanning speed 1mm / s, number of processing times 3, and lateral offset distance 10μm.

[0094] (4) Adjust the water jet pressure to 6MPa;

[0095] (5) Run the machining program to process the MSM structure. The depth of the inverted trapezoidal groove after machining is 10-15 μm and the width is 50-60 μm.

[0096] 2) Wet etching is performed on the processed single-crystal β-Ga2O3.

[0097] The etching solution used in the process is HF solution with a concentration of 47% to 49% and an etching temperature of 5 to 25°C.

[0098] (1) Clean the single-crystal β-Ga2O3 substrate and place it in a beaker;

[0099] (2) Prepare an HF solution with a concentration of 47%;

[0100] (3) Pour the HF solution into a beaker until it submerges the substrate, and react at room temperature (15°C) for 10 min;

[0101] (4) Remove the substrate and clean it.

[0102] 3) Evaporation deposition of single-crystal β-Ga2O3

[0103] (1) The processed single-crystal β-Ga2O3 substrate is mounted on the evaporation worktable;

[0104] (2) A nano-scale Au thin film was deposited on the surface of a single-crystal β-Ga2O3 substrate;

[0105] (3) Remove the substrate.

[0106] 4) Grinding single-crystal β-Ga2O3

[0107] The grinding slurry used in the process is 1μm Al2O3, and the grinding disc is a relatively soft lead grinding disc.

[0108] (1) Mount the single crystal β-Ga2O3 substrate on the grinding table;

[0109] (2) Install the lead grinding disc and spray it with 1μm Al2O3 grinding liquid;

[0110] (3) Start the equipment to perform grinding;

[0111] (4) After grinding for a period of time, remove the single crystal β-Ga2O3 substrate and observe under a microscope whether the Au film on the micro-machined surface has been completely removed. If it has not been completely removed, continue grinding until it is completely removed.

[0112] (5) Clean the single-crystal β-Ga2O3MSM detector to obtain the final product.

[0113] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for fabricating a single-crystal β-Ga₂O₃ MSM detector, characterized in that: Includes the following steps: A three-dimensional morphology was formed by processing a groove on a single-crystal β-Ga2O3 substrate using laser-assisted waterjet processing technology. The processed single-crystal β-Ga2O3 substrate was wet-etched using HF solution to remove processing damage; Au was deposited on the surface of the treated single-crystal β-Ga2O3 substrate to cover the surface of the single-crystal β-Ga2O3 substrate with an Au thin film. The surface of the vapor-deposited single-crystal β-Ga2O3 substrate is ground to remove the Au film on the unprocessed surface, while retaining the Au film in the tank to obtain the desired product. In laser-assisted waterjet processing technology, the pulse width of the nanosecond laser is 10~350ns, the pulse repetition frequency is 315KHz, 490KHz or 1000KHz, the scanning speed is 1~16mm / s, and the waterjet pressure is 4~16MPa. The laser single-pulse energy is 0.02~0.1mJ, and the focal plane height is -0.1~0.1mm; The concentration of the HF solution used in wet etching is 47%~49%; The wet etching temperature is 5~25℃, and the etching time is 8-15min; The groove is an inverted trapezoidal cross groove; The average laser power is 20W, 25W, or 30W; The processing times are 1, 2, or 3; The lateral offset distance is 10μm or 15μm.

2. The method for fabricating a single-crystal β-Ga₂O₃ MSM detector according to claim 1, characterized in that: The wavelength of a nanosecond laser is 1064 nm.

3. The method for fabricating a single-crystal β-Ga2O3 MSM detector according to claim 1, characterized in that: In laser-assisted waterjet processing technology, the waterjet nozzle-target distance is 0.3~1.4mm, the waterjet offset distance is 0.3~0.7mm, and the waterjet impact angle is 39°~51°.

4. The method for fabricating a single-crystal β-Ga2O3 MSM detector according to claim 1, characterized in that: The grinding process uses an Al2O3 grinding slurry with a thickness of 1~2.5μm, and the grinding disc is a relatively soft lead grinding disc.

5. A three-dimensional single-crystal β-Ga₂O₃ MSM detector, characterized in that: It is prepared by any one of the preparation methods described in claims 1-4.

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