A method for processing a gallium oxide hydride vapor phase epitaxy wafer

Abstract

The application provides a processing method of a gallium oxide hydride vapor phase epitaxy wafer, and belongs to the technical field of semiconductors. The processing method of the gallium oxide hydride vapor phase epitaxy wafer comprises the following steps: providing a gallium oxide hydride vapor phase epitaxy wafer; and sequentially performing back thinning, back etching, front thinning and front polishing on the gallium oxide hydride vapor phase epitaxy wafer; the back thinning uses an acidic etching liquid, and the temperature of the back thinning is 40-70 DEG C. The four-step processing procedure is adopted to prepare a gallium oxide single crystal epitaxy wafer meeting the requirements of a device. The mechanical stress generated on the wafer in the back thinning in the previous process is eliminated by back etching, the wafer surface is etched in combination with the characteristics that the gallium oxide material is not resistant to acid and alkali, the stress on the surface is removed, the wafer is prevented from being bent or even broken due to the asymmetric stress on the two surfaces of the wafer after the back thinning, and therefore the wafer with a smooth surface and uniform epitaxial layer thickness is ensured.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor, in particular to a processing method of gallium oxide hydride vapor phase epitaxy wafer. BACKGROUND

[0002] Gallium oxide is a new type of semiconductor material, which has the advantages of wide band gap, high breakdown field, high thermal conductivity and the like, and is widely used in the fields of power electronics, optoelectronics and the like. Gallium oxide HVPE (hydride vapor phase epitaxy) is mainly applied to high-power vertical devices, and can be used for vertical Schottky diodes above 3300V, and the high breakdown field strength can support the high-voltage platform of new energy vehicles.

[0003] Based on the existing gallium oxide HVPE growth technology, due to the gas flow guidance in the vapor phase growth, growth deposition will also be formed on the back surface of the wafer, which affects the uniformity of the overall wafer thickness. Due to the defects caused by the HPVE processing technology itself on the front surface of the wafer, and based on the anisotropic characteristics of gallium oxide, the growth rates on each crystal surface are inconsistent, and the rapid growth of HVPE leads to the formation of gullies or twins on the surface during the production stage, which affects the epitaxial quality.

[0004] Based on the characteristics of gallium oxide substrate in HVPE growth, the epitaxial surface needs to be processed after epitaxial growth to ensure the uniformity of the epitaxial thickness and the smoothness of the epitaxial surface, so as to meet the requirements of device application.

[0005] The related processing technology does not have a processing technology for gallium oxide single crystal substrate after HVPE growth, and the traditional technology is to use mechanical and chemical polishing. However, there are gullies and twins on the gallium oxide epitaxial surface, and based on the characteristics of gallium oxide material itself, the chemical resistance of processing on each crystal surface is significantly different. The use of traditional mechanical and chemical polishing will cause corrosion pits on the surface after processing due to the anisotropic characteristics of gallium oxide itself, and cannot prepare a wafer with smooth and undamaged surface and uniform epitaxial layer thickness. SUMMARY

[0006] Therefore, the purpose of the present application is to provide a processing method of gallium oxide hydride vapor phase epitaxy wafer. The processing method of the present application can obtain a wafer with smooth and undamaged surface and uniform epitaxial layer thickness.

[0007] In order to achieve the above-mentioned purpose of the application, the present application provides the following technical scheme:

[0008] The present application provides a processing method of gallium oxide hydride vapor phase epitaxy wafer, comprising the following steps:

[0009] Providing a gallium oxide hydride vapor phase epitaxy wafer;

[0010] The gallium oxide hydride vapor phase epitaxy wafer is sequentially subjected to back surface thinning, back surface etching, front surface thinning and front surface polishing.

[0011] The back surface thinning uses an acidic etching solution, and the temperature of the back surface thinning is 40-70℃.

[0012] Preferably, the acidic etching solution comprises a phosphoric acid solution.

[0013] Preferably, the polishing pads for the back surface thinning and the front surface thinning are not slotted.

[0014] Preferably, the back surface grinding solution used in the back surface thinning comprises water, polyethylene glycol, non-ionic emulsifier, alumina powder and polycrystalline diamond powder, the mass percentage of polyethylene glycol in the back surface grinding solution is 5-15%, the mass percentage of non-ionic emulsifier is 0.5-1%, the solid content of the powder in the back surface grinding solution is 0.3-1%, the powder comprises alumina powder and polycrystalline diamond powder, the mass ratio of the alumina powder to the polycrystalline diamond powder is 1:1-1:3, the particle size of the alumina powder is 0.2-1μm, and the particle size of the polycrystalline diamond powder is 0.2-1μm.

[0015] Preferably, the front surface grinding solution used in the front surface thinning comprises water, polyethylene glycol, non-ionic emulsifier, alumina powder and polycrystalline diamond powder, the mass percentage of polyethylene glycol in the front surface grinding solution is 5-15%, the mass percentage of non-ionic emulsifier is 0.5-1%, the solid content of the powder in the front surface grinding solution is 1-3%, the powder comprises alumina powder and polycrystalline diamond powder, the mass ratio of the alumina powder to the polycrystalline diamond powder is 1:1-1:3, the particle size of the alumina powder is 0.06-0.8μm, and the particle size of the polycrystalline diamond powder is 0.06-0.8μm.

[0016] Preferably, the high-speed grinding device used in the back surface thinning and the front surface thinning comprises, from top to bottom, a cylinder, an upper polishing head, a ceramic disc, a lower disc surface and a lower disc, and further comprises a motor connected to the lower disc, the cylinder is connected to the upper polishing head, the ceramic disc is arranged on the lower surface of the upper polishing head, and the lower disc comprises a lower disc center hole which provides the grinding solution for the lower disc surface.

[0017] Preferably, the parameters of the high-speed grinding device used in the back surface thinning and the front surface thinning independently comprise: the rotation speed of the lower disc surface is 100-300rpm, the rotation speed of the upper disc surface is 60-80% of the rotation speed of the lower disc surface, the pressure is 30-100g / cm 2 , and the flow rate of the grinding solution is 3-5mL / min.

[0018] Preferably, the back thinning removal thickness is 10-20 mu m, and the single wafer thickness difference after the back thinning is less than 1 mu m.

[0019] Preferably, the front thinning removal thickness is 2-5 mu m, and the wafer roughness after the front thinning is less than 5 nm.

[0020] Preferably, the polishing liquid used in the front polishing comprises the following components in volume percentage: 10-30% of silica colloid, 3-10% of polyethylene glycol, 0.5-5% of pH buffering agent, and the balance of water.

[0021] The application provides a processing method of a gallium oxide hydride vapor phase epitaxy wafer, comprising the following steps: providing a gallium oxide hydride vapor phase epitaxy wafer; sequentially performing back thinning, back etching, front thinning and front polishing on the gallium oxide hydride vapor phase epitaxy wafer; the back thinning uses an acidic etching liquid, and the back thinning temperature is 40-70 DEG C.

[0022] Compared with the prior art, the application has the following beneficial effects:

[0023] The application adopts a four-step processing flow, the purpose of the back thinning is to remove the growth impurities on the back surface, to guarantee the wafer flatness, the back etching is used to eliminate the mechanical stress on the wafer caused by the back thinning in the previous process, the wafer surface is etched from the back surface in combination with the characteristics that the gallium oxide material is not resistant to acid and alkali, to remove the stress on the surface, to avoid the wafer bending or even breaking caused by the asymmetric stress on the wafer after the back thinning, the purpose of the front thinning is to remove the defects on the wafer epitaxial surface, to reduce the roughness, and the purpose of the front polishing is to reduce the thickness, to further reduce the roughness.

[0024] Further, the polishing pad without slot is used to reduce the loss of the polishing liquid.

[0025] Further, the back grinding liquid and the front grinding liquid are designed according to the material characteristics of the gallium oxide, the mixed micro powder of the high-hardness materials such as the aluminum oxide powder and the polycrystalline diamond powder is used as the abrasive, to achieve the purpose of rapid cutting, the non-ionic emulsifier is added to guarantee the dispersibility of the powder in water, to avoid the damage to the wafer caused by the powder aggregation in the grinding process, and the polyethylene glycol is added as the viscosity regulator, to reduce the flowability of the grinding liquid, to guarantee the fullness of the abrasive participating in the grinding process, and to avoid the grinding liquid being quickly thrown out of the disc surface due to the centrifugal force in the high-speed grinding process.

[0026] Furthermore, in the polishing slurry of the present invention, SiO2 colloid serves as an abrasive, which is suspended in the polishing slurry and does not easily precipitate. Polyethylene glycol, as a viscosity modifier, has acid and alkali resistance properties and can be adapted to alkaline solutions. The pH slow-release agent can ensure the chemical stability of the polishing slurry during the polishing process. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of a high-speed grinding device;

[0028] Figure 2 This is a top view of the machining process during back-side thinning;

[0029] Figure 3 This is a schematic diagram of measuring wafer thickness using the 5-point measurement method;

[0030] Figure 4 This is a microscopic image of the wafer surface after removing 2 μm.

[0031] Figure 5 This is a microscopic image of the wafer surface after removing 4μm.

[0032] Figure 6 This is a microscopic image of the wafer surface after removing 5 μm.

[0033] Figure 7 The image shows the result of surface roughness detection at the first point in a 3-point / slice image.

[0034] Figure 8 The image shows the result of surface roughness detection at the second point in a 3-point / image sample.

[0035] Figure 9 The image shows the result of surface roughness detection at the third point in a 3-point / film sample.

[0036] In the diagram, 1 is the cylinder, 2 is the upper polishing head, 3 is the ceramic disk, 4 is the lower disk surface, 5 is the lower disk, 6 is the motor, 7 is the center hole of the lower disk, and 8 is the gallium oxide hydride vapor phase epitaxial wafer. Detailed Implementation

[0037] This invention provides a method for processing gallium oxide hydride vapor phase epitaxial wafers, comprising the following steps:

[0038] Gallium oxide hydride vapor phase epitaxial wafers are provided;

[0039] The gallium oxide hydride vapor phase epitaxial wafer is subjected to back-side thinning, back-side etching, front-side thinning, and front-side polishing in sequence;

[0040] The back side thinning is performed using an acidic etching solution, and the back side thinning temperature is 40~70℃.

[0041] The present application provides a gallium oxide hydride vapor phase epitaxy wafer.

[0042] Compared with the traditional processing technology, the thinning is divided into two ways, the first way is to use a solidified diamond grinding wheel to thin, which can realize rapid thinning, but is subject to material factors, the diamond grinding wheel generally uses larger particle size diamond micro powder electroplated on the grinding disc, and the surface roughness after processing can only reach the level of 20-50nm; the second way is to use a free abrasive processing way, but in order to ensure the uniformity and fullness of the disc surface abrasive, the lower disc speed is limited, so that the processing efficiency is slow, and increasing the pressure can slightly improve the processing efficiency, but will increase the pressure damage to the product, and in severe cases, it will cause the wafer to break. According to the disadvantages and advantages of the two traditional processing methods, and according to the material characteristics of gallium oxide, a new process compatible with the advantages of the two processing methods is designed.

[0043] After obtaining the gallium oxide hydride vapor phase epitaxy wafer, the gallium oxide hydride vapor phase epitaxy wafer is sequentially subjected to back thinning, back etching, front thinning and front polishing.

[0044] In the present application, the polishing pad for back thinning is preferably not slotted, which can reduce the loss of grinding liquid.

[0045] In the present application, the polishing pad is preferably white non-woven fabric, and the hardness of the polishing pad is preferably Asker 60-70.

[0046] In the present application, the back grinding liquid used for back thinning preferably comprises water, polyethylene glycol, non-ionic emulsifier, alumina powder and polycrystalline diamond powder, the mass percentage of polyethylene glycol in the back grinding liquid is preferably 5-15%, the mass percentage of non-ionic emulsifier is preferably 0.5-1%, the solid content of the powder in the back grinding liquid is preferably 1-3%, the powder comprises alumina powder and polycrystalline diamond powder, the mass ratio of the alumina powder to the polycrystalline diamond powder is preferably 1:1-1:3, the particle size of the alumina powder is preferably 0.2-1μm, and the particle size of the polycrystalline diamond powder is preferably 0.2-1μm.

[0047] In the present application, the viscosity of the back grinding liquid is preferably 10-40mpa·s, and can be 10, 18, 20, 30 or 40mpa·s, and the present application preferably adjusts the addition amount of polyethylene glycol according to the viscosity.

[0048] In the present application, the mass percentage of polyethylene glycol in the back grinding liquid can be specifically 5%, 8%, 10%, 12% or 15%, the role of the polyethylene glycol is to adjust the viscosity of the back grinding liquid, to ensure that the abrasives (including aluminum oxide powder and polycrystalline diamond powder) are in a suspended state in the back grinding liquid, and to reduce the flowability of the back grinding liquid, to ensure that the back grinding liquid does not flow quickly under the action of high centrifugal force during the back thinning grinding process.

[0049] In the present application, the polyethylene glycol is preferably polyethylene glycol-800 (PEG800).

[0050] In the present application, the mass percentage of non-ionic emulsifier in the back grinding liquid can be specifically 0.5%, 0.6%, 0.7%, 0.8%, 0.9% or 1%, due to the different molecular characteristics of the surfaces of aluminum oxide powder and polycrystalline diamond powder, agglomeration is easy to form, so that the effect cannot be achieved, the non-ionic emulsifier acts as a surfactant, adheres to the surface of the powder, and plays a dispersing role, so that the surface characteristics of the two different powders can be ensured to be consistent, and agglomeration of different abrasives in the back grinding liquid can be avoided.

[0051] In the present application, the non-ionic emulsifier is preferably an acid and alkali resistant non-ionic emulsifier, more preferably a fatty alcohol polyoxyethylene ether, and most preferably AEO-9.

[0052] In the present application, the solid content of the powder in the back grinding liquid can be specifically 0.3%, 0.5%, 0.8% or 1%, the powder includes aluminum oxide powder and polycrystalline diamond powder, the mass ratio of the aluminum oxide powder and the polycrystalline diamond powder can be specifically 1:1, 1:2 or 1:3, the particle size of the aluminum oxide powder can be specifically 0.2, 0.4, 0.6, 0.8 or 1 μm, and the particle size of the polycrystalline diamond powder can be specifically 0.2, 0.4, 0.6, 0.8 or 1 μm, the aluminum oxide powder and the polycrystalline diamond powder act as abrasives, use the high hardness of polycrystalline diamond to reduce the surface, and the hardness of aluminum oxide is slightly lower than that of diamond, which is used to improve the scratching of polycrystalline diamond powder grinding, avoiding the use of single type of traditional abrasives, which cannot eliminate the disadvantages of single abrasive, single aluminum oxide grinding, the surface quality can meet the standard, but the removal rate is slow, single diamond grinding, the removal rate is fast, but new scratches are generated, the present application selects aluminum oxide powder and polycrystalline diamond powder as abrasives.

[0053] In the present application, the back thinning preferably uses a high-speed grinding device, which preferably comprises a cylinder, an upper throwing head, a ceramic disc, a lower disc surface and a lower disc arranged in sequence from top to bottom, and preferably further comprises a motor connected with the lower disc, the cylinder is preferably connected with the upper throwing head, the ceramic disc is preferably arranged on the lower surface of the upper throwing head, and the lower disc preferably comprises a lower disc center hole which preferably provides the lower disc surface with grinding liquid. Figure 1 The structure diagram of the high-speed grinding device, wherein 1 is the cylinder, 2 is the upper throwing head, 3 is the ceramic disc, 4 is the lower disc surface, 5 is the lower disc, and 6 is the motor.

[0054] In the present application, the cylinder 1 is preferably connected with the upper throwing head 2 through an upper shaft, the ceramic disc 3 is arranged on the lower surface of the upper throwing head 2, the lower disc 4 preferably comprises a lower disc center hole which provides the lower disc surface 4 with grinding liquid, and the grinding liquid is distributed on the surface of the lower disc surface 4 by the centrifugal force of the rotation of the lower disc 5.

[0055] In the present application, the cylinder 1 provides pressurization.

[0056] In the present application, the upper shaft preferably adopts a servo-controlled autonomous speed adjustment, and the speed is preferably 5-500 rpm.

[0057] In the present application, the upper throwing head 2 is preferably a steel throwing head.

[0058] In the present application, the parallelism of the lower disc surface 4 is preferably less than 1 silk (10 μm).

[0059] In the present application, the gallium oxide hydride vapor phase epitaxial wafer is attached to the surface of the ceramic disc 3, and the back thinning is performed.

[0060] In the present application, the front surface of the gallium oxide hydride vapor phase epitaxial wafer is preferably coated with a solid wax, and then attached to the surface of the ceramic disc 3, and then flattened, and then the back thinning is performed.

[0061] In the present application, the lower disc center hole is preferably arranged at the center of the lower disc 5.

[0062] In the present application, the lower disc 5 is preferably driven to rotate by the motor 6, and the speed is autonomously adjusted, and the speed is preferably 5-500 rpm.

[0063] In the present application, the polishing pad is preferably attached to the surface of the lower disc surface 4 and used for grinding the wafer.

[0064] Figure 2The processing top view of the back thinning, wherein 7 is the center hole of the lower disc, 8 is the gallium oxide hydride vapor phase epitaxial wafer, the gallium oxide hydride vapor phase epitaxial wafer 8 is attached to the ceramic disc 3 in a ring shape, the ceramic disc 3 is vacuum adsorbed through the upper shaft, and the lower disc 4 is eccentrically rotated in the same direction, the back grinding liquid is supplied in the center hole 7 of the lower disc, and the transverse cutting force of the gallium oxide hydride vapor phase epitaxial wafer is provided through the speed difference between the upper and lower discs, so as to achieve the grinding effect.

[0065] In the application, the parameters of the high-speed grinding device during back thinning preferably include: the rotation speed of the lower disc surface is 100-300 rpm (specifically, 100, 150, 200, 220 or 300 rpm), the rotation speed of the upper disc surface is 60-80% of the rotation speed of the lower disc surface (specifically, 60%, 68%, 70% or 80%), the pressure is 30-100 g / cm 2 (30, 40, 50, 60, 70, 80, 90 or 100 g / cm 2 ) based on the wafer area of the gallium oxide hydride vapor phase epitaxial wafer, and the flow rate of the back grinding liquid is 3-5 mL / min (specifically, 3, 4 or 5 mL / min).

[0066] In the application, the lower disc surface is preferably covered with the back grinding liquid before back thinning.

[0067] In the application, the processing speed of the high-speed grinding device is preferably 0.2-0.5 μm / min, and specifically, 0.2, 0.3, 0.4 or 0.5 μm / min.

[0068] In the application, the removal thickness of back thinning is preferably 10-20 μm, and the thickness difference of a single wafer after back thinning is preferably less than 1 μm, which removes the growth impurities on the back of the gallium oxide hydride vapor phase epitaxial wafer and guarantees the flatness of the wafer.

[0069] The high-speed grinding device of the application can realize high-speed grinding, and the processing efficiency is 10-20 times that of traditional equipment, the material consumption is 1 / 10 of traditional processing, and the quality after processing can meet the target requirements, which is a mass production processing method.

[0070] In the present application, the acid etching solution comprises a phosphoric acid solution, which is preferably obtained by mixing phosphoric acid and water, the volume ratio of the phosphoric acid to water is preferably 1:3-1:5, and specifically can be 1:3, 1:4 or 1:5, the concentration of the phosphoric acid is preferably 85%-90%, and the concentration of the phosphoric acid solution can be specifically 21.25%. The back etching is used to eliminate the mechanical stress on the wafer generated in the back thinning of the previous process, and the wafer surface is etched from the back in combination with the characteristic that the gallium oxide material is not resistant to acid and alkali, so as to remove the stress on the surface and avoid the wafer bending or even breaking due to the asymmetric stress on the two surfaces of the wafer after the back thinning.

[0071] In the present application, the temperature of the back etching can be specifically 40, 50, 60 or 70℃, and the time is preferably 5-30 min, and can be specifically 5, 10, 15, 20, 25 or 30 min.

[0072] In the present application, the wafer obtained after the back thinning is preferably placed in the acid etching solution for the back etching, the wafer is taken out and washed clean after the back etching is completed, and then the wafer is unloaded.

[0073] In the specific embodiments of the present application, the wafer obtained by the back etching is unloaded from the ceramic plate in the form of heating the wafer, and is loaded into a wafer box made of PVDF material, and then the back etching is performed.

[0074] In the present application, the front grinding liquid used in the front thinning preferably comprises water, polyethylene glycol, non-ionic emulsifier, alumina powder and polycrystalline diamond powder, the mass percentage of the polyethylene glycol in the front grinding liquid is 5%-15%, the mass percentage of the non-ionic emulsifier is 0.5%-1%, the solid content of the powder in the front grinding liquid is 0.3%-1%, the powder comprises alumina powder and polycrystalline diamond powder, the mass ratio of the alumina powder to the polycrystalline diamond powder is 1:1-1:3, the particle size of the alumina powder is 0.06-0.8 μm, and the particle size of the polycrystalline diamond powder is 0.06-0.8 μm.

[0075] In the present application, the particle size of the alumina powder in the front grinding liquid is preferably 30%-80% of the particle size of the alumina powder in the back grinding liquid, and can be specifically 30%, 40%, 50%, 60%, 70% or 80%, and the particle size of the polycrystalline diamond powder in the front grinding liquid is preferably 30%-80% of the particle size of the polycrystalline diamond powder in the back grinding liquid, and can be specifically 30%, 40%, 50%, 60%, 70% or 80%. In the specific embodiments of the present application, the particle size of the alumina powder in the front grinding liquid is 0.5 μm, and the particle size of the polycrystalline diamond powder is 0.3 μm. The abrasive in the front grinding liquid of the present application adopts finer particles, which can reduce the roughness of the wafer.

[0076] In the present application, the content of polyethylene glycol, non-ionic emulsifier, alumina powder and polycrystalline diamond powder in the front side polishing liquid is preferably consistent with that in the back side polishing liquid, which will not be repeated here.

[0077] In the present application, the types of polyethylene glycol and non-ionic emulsifier in the front side polishing liquid are consistent with those in the back side polishing liquid, which will not be repeated here.

[0078] In the present application, the front side of the wafer is preferably covered with the front side polishing liquid before the front side thinning.

[0079] In the present application, the removal thickness of the front side thinning is preferably 2-5 μm, and the roughness of the wafer obtained after the front side thinning is preferably 5 nm or less, so as to remove the defects on the epitaxial surface of the wafer.

[0080] In the present application, the front side thinning is preferably performed in a high-speed grinding device, and the structure and process parameters of the high-speed grinding device are preferably consistent with those of the back side thinning, which will not be repeated here.

[0081] In the present application, the polishing pad used in the front side thinning is preferably white non-woven fabric, and the hardness of the polishing pad is preferably Asker 60-70.

[0082] In the present application, the polishing pad is preferably attached to the surface of the lower wafer 4 for grinding the wafer.

[0083] In the present application, the polishing liquid used in the front side polishing preferably comprises the following components by volume percentage: 10-30% of colloidal silica, 3-10% of polyethylene glycol, 0.5-5% of pH buffering agent, and the balance of water.

[0084] In the present application, the pH value of the polishing liquid is preferably 8.5-9.5, and can be specifically 8.5, 9 or 9.5, and the viscosity is preferably 5-15 mpa·s, and can be specifically 5, 8, 10 or 15 mpa·s.

[0085] In the present application, the volume percentage of colloidal silica in the polishing liquid can be specifically 10%, 15%, 20%, 25% or 30%, and the colloidal silica is used as an abrasive and is in a suspended state in the polishing liquid and is not easy to precipitate.

[0086] In the present application, the particle size of the colloidal silica is preferably 60-80 nm, and can be specifically 60, 65, 70, 75 or 80 nm.

[0087] In the present application, the volume percentage of polyethylene glycol in the polishing liquid can be specifically 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%, and the polyethylene glycol is used as a viscosity regulator and has the characteristics of acid and alkali resistance and can be adapted to the polishing liquid.

[0088] In the present application, the polyethylene glycol in the polishing solution is preferably polyethylene glycol-600 (PEG600).

[0089] In the present application, the volume percentage of the pH buffering agent in the polishing solution can be specifically 0.5%, 1%, 2%, 3%, 4% or 5%, which can ensure the stability of the chemical force of the polishing solution during polishing.

[0090] In the present application, the pH buffering agent is preferably AMP-95 (2-amino-2-methyl-1-propanol), which is an environmentally friendly pH buffering agent.

[0091] In the present application, the polishing pad used in the front polishing is preferably a black damping cloth, and the thickness of the black damping cloth is preferably >2mm. Since the front polishing is a high-speed processing method, the polishing solution on the lower surface is less, and the polishing pad with a thickness greater than 2mm can fully absorb the polishing solution, thereby ensuring the sufficiency of the polishing solution involved in the processing during polishing.

[0092] In the present application, the front polishing is preferably carried out in a high-speed grinding device, and the structure of the high-speed grinding device is preferably consistent with the back thinning, which will not be described here.

[0093] In the present application, the parameters of the high-speed grinding device during the front polishing preferably include: the rotation speed of the lower surface is 100-300rpm (which can be specifically 100, 150, 200, 250 or 300rpm), the rotation speed of the upper surface is 60-80% of the rotation speed of the lower surface (which can be specifically 60%, 70% or 80%), the pressure is 50-150g / cm 2 (which can be specifically 50, 70, 90, 110, 130 or 150g / cm 2 ) per wafer area, and the flow rate of the polishing solution is 5-10mL / min (which can be specifically 5, 6, 7, 8, 9 or 10mL / min).

[0094] In the present application, the lower surface is preferably covered with the polishing solution before the front polishing.

[0095] In the present application, the processing rate of the front polishing is preferably 1-3μm / h, and can be specifically 1 or 3μm / h.

[0096] In the present application, the removal thickness of the front polishing is preferably 2-4μm, and the roughness of the obtained wafer epitaxial surface is preferably 0.2nm or less.

[0097] After the processing method is adopted, the front extension layer is removed by 5-8 mu m, the remaining extension thickness is guaranteed to be 12-15 mu m, the thinning amount can be increased according to product requirements, and the gallium oxide HVPE extension wafer with different extension thickness specifications and a surface roughness of <0.5 nm (preferably <0.2 nm) can be prepared.

[0098] The technical solutions in the present application will be described clearly and completely below in combination with the embodiments in the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work belong to the protection scope of the present application.

[0099] In the embodiment of the present application, the back thinning, front thinning and front polishing are all carried out in a high-speed grinding device, and the structure of the high-speed grinding device is as shown in Figure 1 The high-speed grinding device comprises, from top to bottom, a cylinder, an upper polishing head (a steel polishing head), a ceramic disc, a lower disc surface (parallelism less than 1 silk) and a lower disc, and further comprises a motor connected with the lower disc, the cylinder is connected with the upper polishing head, the ceramic disc is arranged on the lower surface of the upper polishing head, and the lower disc comprises a lower disc center hole, and the lower disc center hole provides the lower disc surface with a grinding liquid.

[0100] Embodiment 1

[0101] The gallium oxide extension wafer (2 inches) processing method comprises the following steps:

[0102] Step one: back thinning

[0103] Process method:

[0104] (1) Incoming measurement: measure the incoming thickness of the gallium oxide extension wafer and the wafer growth surface type;

[0105] (2) Paste: after the front surface of the gallium oxide extension wafer is coated with solid wax, it is pasted on a flat ceramic disc and flattened;

[0106] (3) Prepare back grinding liquid: prepare the back grinding liquid according to Table 1, and the viscosity of the back grinding liquid is 18 mpa·s;

[0107] Table 1 Composition of back grinding liquid

[0108]

[0109] (4) Paste non-woven fabric with a hardness of Asker 60 on the lower disc surface, and the lower disc surface is covered with back grinding liquid;

[0110] (5) Put the wafer to be processed on the ceramic plate, set the lower plate speed to 220 rpm, the upper plate speed to 150 rpm, and the pressure to 100 g / cm 2 (With the wafer area of the gallium oxide hydride vapor phase epitaxial wafer), the backside polishing liquid supply flow rate is 5 mL / min; the surface existing epitaxial growth defects are removed, while the entire wafer thickness difference (TTV) is controlled within 2 μm;

[0111] According to Figure 3 Measure the wafer thickness and record the relevant data: use the 5-point measurement method to record the wafer thickness and calculate the difference, as shown in Table 2, which shows that after 3 min of processing, the surface quality and TTV meet the requirements.

[0112] Table 2 Wafer thickness results (μm) of different backside thinning processing times

[0113]

[0114] Step two: backside etching

[0115] The wafer obtained in step one is removed from the ceramic plate by heating and placed in a wafer box made of PVDF material, a phosphoric acid solution (the concentration of the phosphoric acid solution is 21.25%) is prepared according to the volume ratio of phosphoric acid to water 1:3 and heated to 70°C, the wafer box containing the wafer is placed in the phosphoric acid solution and soaked for 30 min, the wafer surface is measured by a surface detection device to determine whether it meets the specification requirements, and the results are shown in Table 3, which shows that after backside thinning processing, the surface will have mechanical processing stress, and due to the stress difference between the front and back surfaces, the wafer will be bent, and the surface micro-etching method can eliminate the mechanical stress on the surface, thereby restoring the wafer to normal.

[0116] Table 3 Test results of the wafer after backside etching (μm)

[0117]

[0118] Note: The measurement accuracy of the test results in Tables 2 and 3 is different, the measurement accuracy in Table 2 is 1 μm, and the measurement accuracy in Table 3 is 0.1 μm.

[0119] Step three: front side thinning

[0120] (1) Wafer sticking: the wafer obtained in step two is coated with solid wax on the backside and stuck to a flat ceramic plate, and then flattened;

[0121] (3) Preparation of front side polishing liquid: prepare the front side polishing liquid according to Table 4;

[0122] Table 4 Composition of front side polishing liquid

[0123]

[0124] (4) Paste the non-woven fabric with hardness of Asker 60 on the lower disc surface, and spread the front side polishing liquid on the lower disc surface;

[0125] (5) Place the wafer to be processed on the ceramic disc, set the rotation speed of the lower disc to 220 rpm, the rotation speed of the upper disc to 150 rpm, the acting pressure to 100 g / cm 2 (the wafer area obtained in step two), and the front side polishing liquid supply flow to 5 mL / min, remove the epitaxial growth defects existing on the surface, observe the surface under the microscope, so that the surface is smooth and damage-free, and ensure that the TTV control of the entire wafer is within 2 μm, Table 5 is the removal amount and surface condition of the wafer after front side thinning, Figure 4 the surface graph of the wafer under the microscope after 2 μm is removed, Figure 5 the surface graph of the wafer under the microscope after 4 μm is removed, Figure 6 the surface graph of the wafer under the microscope after 5 μm is removed, it can be seen that after 2 μm is removed, there are many defects on the wafer surface, after 4 μm is removed, the defects on the wafer surface are basically removed, and after 5 μm is removed, there are no defects on the wafer surface.

[0126] Table 5 Wafer removal thickness and surface condition results of different front side thinning processing time (μm)

[0127]

[0128] Step four: front side polishing

[0129] (1) Prepare the polishing liquid, prepare according to Table 6, and the viscosity of the prepared polishing liquid is 8 mpa·s;

[0130] Table 6 Composition of polishing liquid

[0131]

[0132] (2) Clean and wipe the ceramic disc with the wafer pasted in step three, and place it in the high-speed grinding device with the black damping cloth (thickness 3 mm) pasted on the lower disc surface, set the rotation speed of the lower disc to 150 rpm, the rotation speed of the upper disc to 120 rpm, and the acting pressure to 150 g / cm 2 (the wafer area obtained in step three), and the polishing liquid flow to 8 mL / min;

[0133] (3) Every 10 min, use a non-contact laser measuring instrument to detect the thickness change of the wafer, and the polishing removal of the wafer surface is 2 μm after the processing is completed, and the wafer is taken out for cleaning;

[0134] (4) Detect according to 3 points per piece, the detection image of 3 points per piece is as shown in Figures 7-9 .Figure 7 a result graph of detecting surface roughness at the first point in the 3-point / piece, Figure 8 a result graph of detecting surface roughness at the second point in the 3-point / piece, Figure 9 a result graph of detecting surface roughness at the third point in the 3-point / piece, and it can be seen that the surface roughness is less than 0.2 nm.

[0135] The above merely describes the preferred embodiments of the present application, and is not intended to limit the present application in any form. It should be noted that, for those skilled in the art, several improvements and refinements can be made without departing from the principles of the present application, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A processing method of a gallium oxide hydride vapor phase epitaxy wafer, characterized by, The method comprises the following steps: Providing a gallium oxide hydride vapor phase epitaxy wafer; Sequentially performing back thinning, back etching, front thinning and front polishing on the gallium oxide hydride vapor phase epitaxy wafer; The back etching uses an acidic etching solution, and the temperature of the back etching is 40-70 DEG C; the acidic etching solution is a phosphoric acid solution; The back thinning uses a back grinding liquid comprising water, polyethylene glycol, non-ionic emulsifier, alumina powder and polycrystalline diamond powder, the mass percentage of polyethylene glycol in the back grinding liquid is 5-15%, the mass percentage of non-ionic emulsifier is 0.5-1%, the solid content of the powder in the back grinding liquid is 0.3-1%, the powder comprises alumina powder and polycrystalline diamond powder, the mass ratio of the alumina powder to the polycrystalline diamond powder is 1:1-1:3, the particle size of the alumina powder is 0.2-1 μm, and the particle size of the polycrystalline diamond powder is 0.2-1 μm; The back thinning removes a thickness of 10-20 μm, and the thickness difference of the single wafer after the back thinning is less than 1 μm; The front polishing uses a polishing liquid comprising the following components in volume percentage: 10-30% of silica colloidal, 3-10% of polyethylene glycol, 0.5-5% of pH buffering agent and the balance of water.

2. The method of claim 1 wherein, The polishing pads for the back thinning and the front thinning are not slotted.

3. The method of processing according to claim 1 or 2, characterized in that, The front thinning uses a front grinding liquid comprising water, polyethylene glycol, non-ionic emulsifier, alumina powder and polycrystalline diamond powder, the mass percentage of polyethylene glycol in the front grinding liquid is 5-15%, the mass percentage of non-ionic emulsifier is 0.5-1%, the solid content of the powder in the front grinding liquid is 0.3-1%, the powder comprises alumina powder and polycrystalline diamond powder, the mass ratio of the alumina powder to the polycrystalline diamond powder is 1:1-1:3, the particle size of the alumina powder is 0.06-0.8 μm, and the particle size of the polycrystalline diamond powder is 0.06-0.8 μm.

4. The method of processing according to claim 1 or 2, wherein, The back thinning and the front thinning both use a high-speed grinding device, the high-speed grinding device comprises, from top to bottom, a cylinder, an upper polishing head, a ceramic disc, a lower disc surface and a lower disc, and further comprises a motor connected with the lower disc, the cylinder is connected with the upper polishing head, the ceramic disc is arranged on the lower surface of the upper polishing head, and the lower disc comprises a lower disc center hole which provides the lower disc surface with a grinding liquid.

5. The method of claim 4, wherein, The parameters of the high-rotation grinding device used in the back-thinning and front-thinning independently include: the rotation speed of the lower disc is 100-300 rpm, the rotation speed of the upper disc is 60-80% of the rotation speed of the lower disc, the pressure is 30-100 g / cm2 in terms of the wafer area of the gallium oxide hydride vapor phase epitaxial wafer 2 , and the flow rate of the polishing liquid is 3-5 mL / min.

6. The method of claim 1 wherein, The front thinning removes a thickness of 2-5 μm, and the roughness of the wafer obtained after the front thinning is less than 5 nm.

Images