Gallium oxide substrate thinning method, substrate and ultra-wide bandgap semiconductor

Abstract

The application is suitable for the technical field of semiconductors, and provides a gallium oxide substrate thinning method, a substrate and an ultra-wide bandgap semiconductor. The method comprises the following steps: placing a gallium oxide substrate to be thinned in a hole pre-prepared in the center of a wafer; the size of the hole is the same as that of the gallium oxide substrate to be thinned; fixing the gallium oxide substrate to be thinned and the wafer on a carrier; sequentially performing grinding treatment and polishing treatment on the back surface of the gallium oxide substrate to be thinned and the back surface of the wafer; and taking out the gallium oxide substrate to be thinned and the wafer after the polishing treatment to obtain a thinned gallium oxide substrate. The application realizes continuous thinning of the gallium oxide substrate, and can thin the gallium oxide substrate to below 100 mu m and has a high yield.

Description

Technical Field

[0001] This application belongs to the field of semiconductor technology, and in particular relates to gallium oxide substrate thinning methods, substrates, and ultra-wide bandgap semiconductors. Background Technology

[0002] Gallium oxide (Ga2O3) is a novel ultra-wide bandgap semiconductor material. Compared to third-generation semiconductors gallium nitride (GaN) and silicon carbide (SiC), Ga2O3 exhibits an ultra-wide bandgap (~4.8 eV) and an ultra-high critical breakdown field strength (~8 MV / cm). Its Baliga figure of merit (BFOM) is 4 times that of GaN, 10 times that of SiC, and 3444 times that of Si. Under the same breakdown voltage conditions, Ga2O3-based power devices have lower on-resistance. Furthermore, high-quality Ga2O3 single-crystal substrates can be mass-produced using melting methods, including floating zone melting and guided mode methods, which will offer a cost advantage over materials such as SiC and GaN in the future. Therefore, Ga2O3 is one of the preferred materials for fabricating Schottky diodes (SBDs), field-effect transistors (MOSFETs), and other low-power, high-voltage switching and high-power applications.

[0003] Despite the numerous excellent physical properties of Ga2O3 and its relatively low-cost single-crystal growth technology, making it extremely promising for high-power electronic devices, its low thermal conductivity is a significant drawback. This makes heat dissipation a bottleneck restricting the development of Ga2O3 devices. For power devices operating under high current conditions, heat accumulation is severe, and the resulting temperature can negatively impact the device, causing its performance to deviate significantly from ideal conditions. It has been reported that the thermal conductivity of β-Ga2O3 is only 10-30 W / m³. -1 K -1 Furthermore, the thermal conductivity of β-Ga₂O₃ exhibits strong anisotropy across different crystal orientations, making it difficult to dissipate heat generated during use, resulting in a severe self-heating effect. In SBDs fabricated using β-Ga₂O₃ as the substrate material, 70% of the heat generation originates from the substrate layer, and 30% from the Schottky junction. Therefore, thinning the Ga₂O₃ substrate layer can alleviate the self-heating effect and reduce the peak temperature within the device. However, β-Ga₂O₃ crystals are hard and brittle, easily undergoing cleavage and fragmentation along a specific crystal orientation during the grinding and thinning process. Conventional thinning methods involve directly thinning the Ga₂O₃ substrate layer using chemical mechanical polishing (CMP). However, after thinning to below 500 μm, the material easily fractures from the edges, and at even thinner layers, it fractures significantly, severely reducing the material yield. Summary of the Invention

[0004] This application provides a method for thinning gallium oxide substrates, a substrate, and an ultra-wide bandgap semiconductor to achieve continuous thinning of gallium oxide substrates, which can be thinned to below 100 μm with a high yield.

[0005] This application is achieved through the following technical solution:

[0006] In a first aspect, embodiments of this application provide a method for thinning a gallium oxide substrate, comprising:

[0007] The gallium oxide substrate to be thinned is placed in a pre-made hole at the center of the wafer; the size of the hole is the same as the size of the gallium oxide substrate to be thinned.

[0008] The gallium oxide substrate and wafer to be thinned are fixed on the carrier disk.

[0009] The back side of the gallium oxide substrate to be thinned and the back side of the wafer are ground and polished in sequence.

[0010] Remove the polished gallium oxide substrate and wafer to be thinned to obtain the thinned gallium oxide substrate.

[0011] In conjunction with the first aspect, some possible implementations include, before fixing the gallium oxide substrate to be thinned and the wafer onto the carrier disk, the following steps are also included:

[0012] Photoresist is coated on the front side of the gallium oxide substrate to be thinned and the front side of the wafer to form a protective layer.

[0013] The gallium oxide substrate and wafer to be thinned are fixed on a carrier disk, including:

[0014] The gallium oxide substrate and wafer to be thinned are fixed on a quartz carrier disk through a protective layer.

[0015] In conjunction with the first aspect, in some possible implementations, the gallium oxide substrate to be thinned and the wafer are fixed to a quartz carrier disk by a protective layer, including:

[0016] Paraffin wax is coated between the photolithography layer and the carrier disk, and the paraffin wax liquid is filled in the gap between the gallium oxide substrate to be thinned and the wafer.

[0017] Raise the temperature to the melting point of the paraffin and place a flat weight vertically above the back side of the gallium oxide substrate to be thinned and the back side of the wafer.

[0018] Let it stand until it reaches room temperature, then remove the weight to complete the fixation.

[0019] In conjunction with the first aspect, in some possible implementations, the back side of the gallium oxide substrate to be thinned and the back side of the wafer are sequentially ground and polished, including:

[0020] The back side of the gallium oxide substrate to be thinned and the back side of the wafer are polished by controlling the polishing controller.

[0021] Polishing is performed on the back side of the gallium oxide substrate to be thinned after grinding and on the back side of the wafer.

[0022] Remove the polished gallium oxide substrate and wafer to be thinned to obtain the thinned gallium oxide substrate, including:

[0023] Remove the polished gallium oxide substrate and wafer to be thinned, and remove the adhering substances on the surface of the gallium oxide substrate to be thinned to obtain the thinned gallium oxide substrate; wherein, the adhering substances include paraffin wax and photoresist.

[0024] In conjunction with the first aspect, in some possible implementations, polishing is performed on the back side of the milled gallium oxide substrate to be thinned and the back side of the wafer, including:

[0025] Polishing treatment is performed on the back side of the gallium oxide substrate to be thinned and the back side of the wafer after grinding using polishing slurry and polishing pad, so that the thickness of the gallium oxide substrate to be thinned is reduced by 1-10 μm and the surface roughness is less than 1 nm.

[0026] In conjunction with the first aspect, in some possible implementations, the wafer material is sapphire, silicon, silicon carbide, or quartz.

[0027] The grinding disc of the polishing controller can be made of copper, tin, cast iron, or stainless steel.

[0028] The polishing pad can be a polyurethane polishing pad, a non-woven polishing pad, or a damping cloth polishing pad.

[0029] In conjunction with the first aspect, in some possible implementations, the back side of the gallium oxide substrate to be thinned and the back side of the wafer are polished by controlling a polishing controller, including:

[0030] Set the pressure of the polishing controller to 1-10 kg and the rotation speed to 30-300 r / min.

[0031] The back side of the gallium oxide substrate to be thinned and the back side of the wafer are ground using diamond abrasive with a particle size of 6μm until the thickness of the gallium oxide substrate to be thinned is reduced to 200-300μm and the surface roughness is less than 50nm.

[0032] The back side of the gallium oxide substrate to be thinned and the back side of the wafer were polished using diamond abrasive with a particle size of 3μm until the thickness of the gallium oxide substrate to be thinned was reduced to 100μm and the surface roughness was less than 20nm.

[0033] The back side of the gallium oxide substrate to be thinned and the back side of the wafer were polished using diamond abrasive with a particle size of 1 μm until the thickness of the gallium oxide substrate to be thinned was reduced to less than 100 μm and the surface roughness was less than 10 nm.

[0034] In conjunction with the first aspect, in some possible implementations, the thickness of the wafer is greater than or equal to the thickness of the gallium oxide substrate to be thinned; the size of the wafer is greater than the size of the gallium oxide substrate to be thinned.

[0035] Secondly, embodiments of this application provide a gallium oxide substrate obtained by the gallium oxide substrate thinning method described in any one of the first aspects.

[0036] Thirdly, embodiments of this application provide an ultra-wide bandgap semiconductor having a gallium oxide substrate as described in the third aspect.

[0037] It is understood that the beneficial effects of the second and third aspects mentioned above can be found in the relevant descriptions in the first aspect mentioned above, and will not be repeated here.

[0038] The beneficial effects of the embodiments in this application compared with the prior art are:

[0039] This application embeds a gallium oxide substrate onto a wafer for simultaneous grinding and thinning. During thinning, the gallium oxide substrate is subjected to an outward grinding force, which can cause fragmentation in the cleavage direction. The presence of the surrounding wafer provides an opposite force to the gallium oxide substrate, neutralizing the grinding force and suppressing cleavage fragmentation. This enables continuous thinning of the gallium oxide substrate to below 100 μm while maintaining a high yield.

[0040] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit this specification. Attached Figure Description

[0041] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0042] Figure 1 This is a schematic flowchart of a gallium oxide substrate thinning method provided in an embodiment of this application;

[0043] Figure 2 This is a positional diagram between a gallium oxide substrate and a wafer provided in one embodiment of this application;

[0044] Figure 3 This is a schematic diagram of fixing a gallium oxide substrate and a wafer onto a carrier disk according to an embodiment of this application;

[0045] Figure 4 This is a thinning diagram provided in one embodiment of this application. Detailed Implementation

[0046] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application may also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods have been omitted so as not to obscure the description of this application with unnecessary detail.

[0047] It should be understood that, when used in this application specification and the appended claims, the term "comprising" indicates the presence of the described features, integrals, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or a collection thereof.

[0048] It should also be understood that the term “and / or” as used in this application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0049] As used in this application specification and the appended claims, the term "if" may be interpreted, depending on the context, as "when," "once," "in response to determination," or "in response to detection." Similarly, the phrase "if determined" or "if detected [the described condition or event]" may be interpreted, depending on the context, as meaning "once determined," "in response to determination," "once detected [the described condition or event]," or "in response to detection [the described condition or event]."

[0050] Furthermore, in the description of this application and the appended claims, the terms "first," "second," "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0051] References to "one embodiment" or "some embodiments" as described in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized.

[0052] β-Ga2O3 crystals are hard and brittle crystalline materials, and are prone to cleavage and fragmentation along a specific crystal orientation during the grinding and thinning process. The conventional thinning method is to directly thin the Ga2O3 substrate layer through chemical mechanical polishing (CMP). However, after thinning to below 500 μm, it is easy to fracture from the material edge in strips, and at even thinner layers, it will fracture significantly, which will seriously reduce the material yield.

[0053] To address the aforementioned issues, this application provides a method for thinning a gallium oxide substrate. By combining the gallium oxide substrate with a wafer, the wafer applies a force in the opposite direction to the gallium oxide substrate, neutralizing the grinding force and suppressing cleavage and fragmentation of the gallium oxide. This enables continuous thinning of the gallium oxide substrate, achieving a thickness of less than 100 μm with a high yield.

[0054] Figure 1 This is a schematic flowchart of a gallium oxide substrate thinning method provided in an embodiment of this application, with reference to... Figure 1 The detailed description of the gallium oxide substrate thinning method is as follows:

[0055] Step 101: Place the gallium oxide substrate to be thinned into a pre-made hole in the center of the wafer; the size of the hole is the same as the size of the gallium oxide substrate to be thinned.

[0056] Specifically, such as Figure 2 As shown, the gallium oxide substrate can be circular, and the wafer can also be circular. In different embodiments, multiple substrates can be placed in one wafer for simultaneous thinning, improving production efficiency. Furthermore, in actual production, the shape of the wafer and the gallium oxide substrate are not limited to circular; they can also be square or other shapes.

[0057] For example, the wafer can be made of sapphire, silicon, silicon carbide, or quartz. The thickness of the wafer is greater than or equal to the thickness of the gallium oxide substrate to be thinned; the size of the wafer is greater than the size of the gallium oxide substrate to be thinned.

[0058] Specifically, ensuring that the thickness of the wafer is greater than or equal to the thickness of the gallium oxide substrate to be thinned can guarantee the stability during the thinning of the gallium oxide substrate and avoid cleavage fracture. For example, if the thickness of the gallium oxide substrate is 450 μm, and the thickness of the wafer is less than 450 μm, the gallium oxide substrate is likely to cleave fracture during thinning. Therefore, it is necessary to ensure that the thickness of the wafer is greater than or equal to the thickness of the gallium oxide substrate to be thinned.

[0059] Step 102: Fix the gallium oxide substrate and wafer to be thinned onto the carrier disk.

[0060] For example, prior to step 102, the following may also be included:

[0061] Photoresist is coated on the front side of the gallium oxide substrate to be thinned and the front side of the wafer to form a protective layer.

[0062] Specifically, the presence of photoresist ensures that no scratches are generated on the front side of the gallium oxide substrate to be thinned. If the front side of the gallium oxide substrate to be thinned is not coated with photoresist, the front side of the gallium oxide substrate to be thinned will rub against the quartz carrier during the thinning process, thus forming scratches.

[0063] Fixing the gallium oxide substrate and wafer to be thinned onto a carrier disk can include:

[0064] The gallium oxide substrate and wafer to be thinned are fixed on a quartz carrier disk through a protective layer.

[0065] For example, fixing the gallium oxide substrate and wafer to be thinned onto a quartz carrier disk using a protective layer may include:

[0066] Paraffin wax is coated between the photolithography layer and the carrier disk, and the paraffin wax liquid is filled in the gap between the gallium oxide substrate to be thinned and the wafer.

[0067] Raise the temperature to the melting point of the paraffin and place a flat weight vertically above the back side of the gallium oxide substrate to be thinned and the back side of the wafer.

[0068] Let it stand until it reaches room temperature, then remove the weight to complete the fixation.

[0069] Specifically, such as Figure 3 As shown, by placing paraffin wax and weights vertically above the back side of the gallium oxide substrate to be thinned, the front and back sides of the gallium oxide substrate to be thinned are made parallel to the horizontal plane, so that the gallium oxide substrate to be thinned is thinned uniformly and will not have one side higher than the other after thinning.

[0070] Step 103: Grinding and polishing are performed sequentially on the back side of the gallium oxide substrate to be thinned and the back side of the wafer.

[0071] For example, step 103 may include:

[0072] The back side of the gallium oxide substrate to be thinned and the back side of the wafer are polished by controlling the polishing controller.

[0073] Polishing is performed on the back side of the gallium oxide substrate to be thinned after grinding and on the back side of the wafer.

[0074] For example, the grinding disc of the polishing controller can be a copper disc, a tin disc, a cast iron disc, or a stainless steel disc.

[0075] For example, such as Figure 4 As shown, the thinning direction is as indicated by the arrow. The grinding and polishing process, which involves controlling the back side of the gallium oxide substrate to be thinned and the back side of the wafer, can include:

[0076] Set the pressure of the polishing controller to 1-10 kg and the rotation speed to 30-300 r / min.

[0077] The back side of the gallium oxide substrate to be thinned and the back side of the wafer are ground using diamond abrasive with a particle size of 6μm until the thickness of the gallium oxide substrate to be thinned is reduced to 200-300μm and the surface roughness is less than 50nm.

[0078] The back side of the gallium oxide substrate to be thinned and the back side of the wafer were polished using diamond abrasive with a particle size of 3μm until the thickness of the gallium oxide substrate to be thinned was reduced to 100μm and the surface roughness was less than 20nm.

[0079] The back side of the gallium oxide substrate to be thinned and the back side of the wafer were polished using diamond abrasive with a particle size of 1 μm until the thickness of the gallium oxide substrate to be thinned was reduced to less than 100 μm and the surface roughness was less than 10 nm.

[0080] For example, polishing the back side of the milled gallium oxide substrate to be thinned and the back side of the wafer includes:

[0081] Polishing treatment is performed on the back side of the gallium oxide substrate to be thinned and the back side of the wafer after grinding using polishing slurry and polishing pad, so that the thickness of the gallium oxide substrate to be thinned is reduced by 1-10 μm and the surface roughness is less than 1 nm.

[0082] For example, the polishing pad can be a polyurethane polishing pad, a non-woven polishing pad, or a damping cloth polishing pad.

[0083] Step 104: Remove the polished gallium oxide substrate and wafer to be thinned to obtain the thinned gallium oxide substrate.

[0084] For example, step 104 may include:

[0085] Remove the polished gallium oxide substrate and wafer to be thinned, and remove the adhering substances on the surface of the gallium oxide substrate to be thinned to obtain the thinned gallium oxide substrate; wherein, the adhering substances include paraffin wax and photoresist.

[0086] Specifically, after the thinning process is completed, a lot of residue will adhere to the surface of the gallium oxide substrate, including not only paraffin and photoresist, but also residue from the thinning process. The gallium oxide substrate that has been polished needs to be cleaned to remove the surface deposits.

[0087] The aforementioned gallium oxide substrate thinning method involves embedding a gallium oxide substrate sheet onto a wafer and performing grinding and thinning together. During thinning, the gallium oxide substrate is subjected to an outward grinding force, which can cause fragmentation in the cleavage direction. The presence of the surrounding wafer provides an opposite force to the gallium oxide substrate, neutralizing the grinding force and suppressing cleavage fragmentation. This allows for continuous thinning of the gallium oxide substrate sheet, achieving thicknesses below 100 μm while maintaining a high yield. Devices fabricated using this method exhibit excellent heat dissipation and play a crucial role in high-voltage, high-current applications of gallium oxide materials.

[0088] In some specific implementations, the process of thinning a gallium oxide substrate may include:

[0089] like Figure 2 As shown, select a Ga2O3 substrate 201 of 2-inch, 4-inch, 6-inch, or 8-inch size, with a thickness of 0-1000μm. Select a wafer 202 larger than the Ga2O3 substrate 201, with a thickness no less than that of the Ga2O3 substrate 201. Create a circular hole in the center of the wafer 202, the same size as the Ga2O3 substrate 201. Place the gallium oxide substrate 201 into the circular hole in the wafer 202.

[0090] like Figure 3 As shown, a photoresist 203 protective layer is coated on the epitaxial layer of the front side of the gallium oxide substrate 201 to protect the front side of the gallium oxide substrate 201 from damage during the grinding and thinning process. The front side of the wafer 202 is also coated with a photoresist 203 protective layer to ensure that it experiences the same stress as the gallium oxide substrate 201 during subsequent grinding and thinning. The wafer 202 can be made of materials such as sapphire, silicon, silicon carbide, or quartz.

[0091] like Figure 3As shown, a wafer 202 (face down) with a gallium oxide substrate 201 embedded in it is bonded to a quartz carrier disk 205 using paraffin wax 204 with a melting point of 100°C, and the gap between the gallium oxide substrate 201 and the wafer 202 is filled with molten paraffin wax. A flat 1-5 kg ​​weight is placed vertically above the wafer 202 with the gallium oxide substrate 201 embedded in it, and the mixture is left to stand at room temperature to ensure that the paraffin wax 204 between the quartz carrier disk 205 and the wafer 202 with the gallium oxide substrate 201 is dense and flat.

[0092] like Figure 4 As shown, the quartz carrier disk 205 is transferred to the polishing controller, with a pressure setting range of 1-10 kg; the polishing disk can be made of copper, tin, cast iron, stainless steel, etc., and the rotation speed is set to 30-300 r / min; the polishing slurry uses diamond abrasive with a particle size of 6 μm and a moderate droplet flow rate. The wafer 202 with the gallium oxide substrate 201 is polished in the direction of the dashed arrow, and can be continuously polished to reduce the thickness to 200-300 μm, with a surface roughness Ra < 50 nm.

[0093] The grinding fluid was changed to diamond abrasive with a particle size of 3μm, which can continuously grind and reduce the thickness to 100μm, with a surface roughness Ra<20nm.

[0094] The grinding fluid was changed to diamond abrasive with a particle size of 1μm, which can continuously grind and reduce the thickness to below 100μm, with a surface roughness Ra<10nm.

[0095] Using a polishing slurry and a polishing pad, the wafer 202 with the gallium oxide substrate 201 embedded is polished in the direction of the dashed arrow to further reduce the thickness of the wafer 202 with the gallium oxide substrate 201 embedded by 1-10 μm and achieve a surface roughness Ra < 1 nm. The polishing pad can be a polyurethane polishing pad, a non-woven polishing pad, or a damping cloth polishing pad, etc.

[0096] After grinding and polishing, the gallium oxide substrate 201 is removed, and the surface residues such as paraffin 204 and photoresist 203 are cleaned. The thinned gallium oxide substrate is then obtained.

[0097] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0098] This application also provides a gallium oxide substrate, obtained by the gallium oxide substrate thinning method described in any of the above claims.

[0099] This application also provides an ultra-wide bandgap semiconductor having a gallium oxide substrate as described above.

[0100] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A method for thinning a gallium oxide substrate, characterized in that, include: The gallium oxide substrate to be thinned is placed in a pre-made hole in the center of the wafer; The size of the hole is the same as the size of the gallium oxide substrate to be thinned; the thickness of the wafer is greater than or equal to the thickness of the gallium oxide substrate to be thinned; the size of the wafer is greater than the size of the gallium oxide substrate to be thinned. The gallium oxide substrate to be thinned and the wafer are fixed on a carrier disk; The back side of the gallium oxide substrate to be thinned and the back side of the wafer are sequentially ground and polished. Remove the polished gallium oxide substrate to be thinned and the wafer to obtain the thinned gallium oxide substrate; Before fixing the gallium oxide substrate to be thinned and the wafer onto the carrier disk, the method further includes: Photoresist is coated on the front side of the gallium oxide substrate to be thinned and the front side of the wafer to form a protective layer; The step of fixing the gallium oxide substrate to be thinned and the wafer onto the carrier disk includes: The gallium oxide substrate to be thinned and the wafer are fixed on a quartz carrier disk through the protective layer; The step of fixing the gallium oxide substrate to be thinned and the wafer onto the quartz carrier disk through the protective layer includes: Paraffin wax is coated between the photoresist layer and the carrier disk, and the paraffin wax liquid is filled in the gap between the gallium oxide substrate to be thinned and the wafer; Raise the temperature to the melting point of the paraffin and place a flat weight vertically above the back side of the gallium oxide substrate to be thinned and the back side of the wafer. Allow the container to stand until it reaches room temperature, then remove the weight to complete the fixation process. The sequential grinding and polishing of the back side of the gallium oxide substrate to be thinned and the back side of the wafer includes: The back side of the gallium oxide substrate to be thinned and the back side of the wafer are polished by controlling the polishing controller. The back side of the gallium oxide substrate to be thinned and the back side of the wafer are polished after grinding. The process of removing the polished gallium oxide substrate and the wafer to be thinned to obtain a thinned gallium oxide substrate includes: Remove the polished gallium oxide substrate and the wafer, and remove the adhering substances on the surface of the gallium oxide substrate to be thinned to obtain the thinned gallium oxide substrate; wherein, the adhering substances include paraffin wax and photoresist; The polishing process performed on the back side of the gallium oxide substrate to be thinned and the back side of the wafer after grinding includes: The back side of the gallium oxide substrate to be thinned and the back side of the wafer are polished using polishing slurry and polishing pad to reduce the thickness of the gallium oxide substrate to be thinned by 1-10µm and the surface roughness by less than 1nm.

2. The method for thinning a gallium oxide substrate as described in claim 1, characterized in that, The wafer is made of sapphire, silicon, silicon carbide, or quartz. The grinding disc of the grinding and polishing controller is a copper disc, a tin disc, a cast iron disc, or a stainless steel disc.

3. The method for thinning a gallium oxide substrate as described in claim 1, characterized in that, The grinding process performed on the back side of the gallium oxide substrate to be thinned and the back side of the wafer by controlling a grinding and polishing controller includes: Set the pressure of the grinding and polishing controller to 1-10 kg and the rotation speed to 30-300 r / min; The back side of the gallium oxide substrate to be thinned and the back side of the wafer are ground using diamond abrasive with a particle size of 6µm until the thickness of the gallium oxide substrate to be thinned is reduced to 200-300µm and the surface roughness is less than 50nm. The back side of the gallium oxide substrate to be thinned and the back side of the wafer are ground using diamond abrasive with a particle size of 3µm until the thickness of the gallium oxide substrate to be thinned is reduced to 100µm and the surface roughness is less than 20nm. The back side of the gallium oxide substrate to be thinned and the back side of the wafer are ground using diamond abrasive with a particle size of 1µm until the thickness of the gallium oxide substrate to be thinned is reduced to less than 100µm and the surface roughness is less than 10nm.

4. A gallium oxide substrate, characterized in that, It is obtained by the gallium oxide substrate thinning method according to any one of claims 1 to 3.

5. An ultra-wide bandgap semiconductor, characterized in that, The ultrawide bandgap semiconductor has a gallium oxide substrate as described in claim 4.

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