Treatment method for bonding surface of silicon carbide substrate and application of treatment method

Abstract

The invention belongs to the technical field of semiconductor processing. The invention provides a treatment method of a bonding surface of a silicon carbide substrate and application of the treatment method, and the treatment method uses a combined polishing solution to perform chemical mechanical polishing on the bonding surface of the silicon carbide substrate, the combined polishing solution comprises a polishing solution A containing nanocrystalline cellulose as an oxidizing agent and a polishing solution B containing bacterial cellulase as a catalyst, through cooperation of the polishing solution A and the polishing solution B, in the polishing process, the nanocrystalline cellulose is subjected to enzymolysis to release hydroxyl free radicals, oxidation reaction is conducted on the hydroxyl free radicals and silicon carbide to generate a surface modification layer, and the surface modification layer is formed. Therefore, the surface hardness is reduced, the polishing rate is improved, finally the atomic-scale flatness of the bonding surface of the silicon carbide substrate is improved, the bonding surface quality of the silicon carbide substrate is effectively improved, and the bonding quality of the composite substrate obtained through bonding is effectively improved.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor processing, and relates to a method for processing a bonding surface of a silicon carbide substrate and a use thereof. Background Art

[0002] Silicon carbide is a wide bandgap semiconductor material with the advantages of high temperature resistance, high voltage resistance, high frequency, high power, radiation resistance and high efficiency, which makes it occupy an important position in the fields of radio frequency, new energy vehicles, etc. It has been widely used in radar systems, satellite communications, wireless base stations and other equipment, and has become an ideal choice for core components such as drive motor controllers and on-board chargers.

[0003] In order to further leverage the advantages of silicon carbide materials and reduce production costs, researchers have begun to explore technical solutions for bonding silicon carbide substrates with other homogeneous or heterogeneous materials to form composite substrates. This composite substrate can not only retain the original high-performance characteristics of silicon carbide materials, but also achieve performance complementarity through the combination of different materials and broaden the scope of application. For example, bonding a silicon carbide substrate to a silicon (Si) substrate can utilize the mature processing technology of silicon materials to reduce device manufacturing costs; bonding with other wide bandgap semiconductor materials such as gallium nitride (GaN) can improve the integration and reliability of the device while maintaining high-frequency and high-power performance.

[0004] Bonding technology is one of the key steps to achieve composite substrates, and its core is to ensure that the bonding surface is flat at the atomic level. For silicon carbide materials, this requirement is particularly strict. First of all, the hardness of silicon carbide material itself is extremely high (Mohs hardness is about 9.25), which makes it difficult for traditional mechanical polishing process to meet the high flatness requirements required for bonding. Secondly, even single-crystal silicon carbide may have microscopic defects on its surface, such as dislocations, voids, etc., which will directly affect the bonding quality. For polycrystalline silicon carbide materials, due to the orientation differences between different grains, it becomes more difficult to control the flatness of the bonding surface.

[0005] There are many methods used to improve the bonding quality of silicon carbide materials, such as chemical mechanical polishing (CMP). The CMP process involves a combination of chemical action and mechanical grinding. The uneven parts of the material surface are removed through the synergistic effect of chemical reagents (polishing liquid) and mechanical grinding (polishing pad). The polishing liquid is a crucial component in the CMP process, and its composition and ratio directly affect the polishing effect. Typical polishing liquids are mainly composed of abrasives, acids, alkalis or other corrosive agents, and deionized water. Parameters such as the selection of abrasives and their particle size distribution, the type and concentration of chemical reagents, and the pH value of the polishing liquid will affect the polishing efficiency and surface quality.

[0006] Therefore, the development of new polishing liquids and CMP polishing schemes is of great significance for improving and optimizing the bonding quality of polycrystalline silicon carbide materials. Summary of the invention

[0007] In view of the problems existing in the prior art, the purpose of the present invention is to provide a method for treating the bonding surface of a silicon carbide substrate and its use. The treatment method uses a combined polishing liquid to perform chemical mechanical polishing on the bonding surface of the silicon carbide substrate. The combined polishing liquid includes a polishing liquid A containing nanocrystalline cellulose as an oxidant and a polishing liquid B containing bacterial cellulase as a catalyst. Through the coordination of the polishing liquid A and the polishing liquid B, during the polishing process, the nanocrystalline cellulose releases hydroxyl radicals through enzymatic hydrolysis, and undergoes an oxidation reaction with silicon carbide to generate a surface modification layer, thereby reducing the surface hardness, increasing the polishing rate, and ultimately improving the atomic-level flatness of the bonding surface of the silicon carbide substrate, effectively improving the bonding surface quality of the silicon carbide substrate, and effectively improving the bonding quality of the composite substrate obtained by bonding.

[0008] To achieve this object, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a method for processing a bonding surface of a silicon carbide substrate, the processing method comprising: using a combined polishing liquid to chemically mechanically polish the bonding surface of the silicon carbide substrate;

[0010] The combined polishing liquid comprises independent polishing liquid A and polishing liquid B; the polishing liquid A comprises an oxidant, a pH regulator and an abrasive, and the polishing liquid B comprises a catalyst; the oxidant comprises nanocrystalline cellulose, and the catalyst comprises bacterial cellulase.

[0011] In the present invention, in order to balance the chemical and mechanical effects of the substrate during the polishing process, nanocrystalline cellulose is used as an oxidant and mixed with an abrasive (such as silicon oxide and / or cerium oxide, etc.), so that during the polishing process, the nanocrystalline cellulose body can be enzymatically hydrolyzed by a catalyst to release hydroxyl radicals. The released hydroxyl radicals play a leading role in the chemical modification process, while the abrasive part with high hardness and small particle size plays a leading role in the mechanical effect, thereby obtaining a better polishing effect.

[0012] Specifically, in the present invention, the nanocrystalline cellulose is a nanoscale cellulose crystal (or cellulose nanocrystal, abbreviated as CNCs) extracted from natural fibers. Cellulose is a linear polysaccharide composed of many D-glucose groups (1-5 rings) connected by 1-4, β-type linkages. Its simple molecular formula is (C6H 10 O5) n, where n represents the degree of polymerization group. Nanocrystalline cellulose can be enzymatically hydrolyzed to form hydroxyl radicals OH*, which react with the (polycrystalline) silicon carbide substrate (wafer) to undergo oxidation reaction (SiC+4OH*+3O2→2SiO3 2- +4H + +2CO 2 ) to generate a surface modification layer.

[0013] The catalyst bacterial cellulase is usually composed of a variety of enzymes, including exo-β-glucanase, endo-β-glucanase and β-glucosidase. These enzymes work synergistically and produce an enzymatic reaction with the nanocrystalline cellulose under the condition of pH 6.0-8.0 to convert the insoluble nanocrystalline cellulose into soluble sugars. In the enzymatic hydrolysis process, it mainly includes the process of three main types of enzymes reacting: exo-β-glucanase starts from the end of the cellulose chain and gradually releases cellobiose or glucose monomers; endo-β-glucanase acts on the inside of the cellulose chain, randomly cuts β-1,4-glycosidic bonds, and produces new chain ends; β-glucosidase further hydrolyzes cellobiose into glucose. When these glycosidic bonds are broken, free hydroxyl groups are formed.

[0014] When nanocrystalline cellulose is enzymatically hydrolyzed to produce hydroxyl radicals, it directly decomposes silicon carbide into soluble 2SiO3 2- When the surface hardness is effectively reduced, the mechanical action of the abrasive can make it easier and faster to remove, thus effectively improving the polishing rate.

[0015] The following are preferred technical solutions of the present invention, but are not intended to be limitations of the technical solutions provided by the present invention. Through the following technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.

[0016] As a preferred technical solution of the present invention, taking the mass of the polishing liquid A as 100%, the mass of the oxidant is ≤10%, for example, it can be 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2% or 1%; the mass of the abrasive is ≤6%, for example, it can be 6%, 5%, 4%, 3%, 2% or 1%; the mass of the solvent of the polishing liquid A is ≥83%, for example, it can be 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97% or 98%, etc.

[0017] Preferably, based on the mass of the polishing liquid B as 100%, the mass of the catalyst is ≤10%, for example, it can be 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2% or 1%, etc., preferably 7% to 9%, and the mass of the solvent of the polishing liquid B is ≥90%, for example, it can be 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or 99%, etc.

[0018] Preferably, the pH value of the polishing liquid A is 6-8, for example, it can be 6, 6.2, 6.4, 6.6, 6.8, 7.2, 7.4, 7.6, 7.8 or 8.

[0019] As a preferred technical solution of the present invention, the abrasive comprises silicon oxide and / or cerium oxide.

[0020] Preferably, the pH adjuster comprises potassium hydroxide and / or hydrogen peroxide.

[0021] Preferably, the solvent of the polishing liquid A and the polishing liquid B includes water.

[0022] Preferably, the particle size of the oxidant is 30 to 100 nm, for example, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm or 100 nm, etc., preferably 60 to 80 nm.

[0023] Preferably, the particle size of the oxidizing agent is larger than the particle size of the abrasive.

[0024] Preferably, the particle size of the abrasive is 30-60 nm, for example, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm or 60 nm.

[0025] As a preferred technical solution of the present invention, the polishing liquid A also includes a dispersant.

[0026] Preferably, the dispersant comprises sodium polyacrylate.

[0027] Preferably, based on the mass of the polishing liquid A as 100%, the mass of the dispersant is ≤1%, for example, 1%, 0.95%, 0.9%, 0.85%, 0.8%, 0.75%, 0.7%, 0.65%, 0.6%, 0.55%, 0.5%, 0.45%, 0.4%, 0.35%, 0.3%, 0.25%, 0.2%, 0.15% or 0.1%, etc.

[0028] In the present invention, the dispersant sodium polyacrylate can reduce the interfacial tension between liquid and liquid and solid and liquid, effectively disperse the abrasive particles in the polishing liquid, and keep them evenly distributed. Sodium polyacrylate has a thickening effect, which can increase the viscosity of the polishing liquid and improve the stability of the polishing liquid.

[0029] As a preferred technical solution of the present invention, the preparation method of the combined polishing liquid comprises:

[0030] The oxidant is mixed with the solvent, a pH adjuster is added to adjust to the target pH value, and then an abrasive is added for ball milling. The suspension is filtered to obtain a suspension, and the suspension is mixed with the solvent to adjust to the target concentration to obtain a polishing liquid A; the catalyst is weighed and dissolved in the solvent and magnetically stirred to obtain the polishing liquid B.

[0031] In the present invention, the polishing liquid A is preferably ball-milled during preparation so that the pressure and friction generated by the ball milling pre-treat the nanocrystalline cellulose. This pre-treatment process helps to destroy the crystalline structure of cellulose, making it easier to enzymatically hydrolyze in subsequent polishing applications.

[0032] As a preferred technical solution of the present invention, the ball milling media includes zirconium beads.

[0033] Preferably, the ball-to-material mass ratio of the ball mill is (2-4):1, such as 2:1, 2.5:1, 3:1, 3.5:1 or 4:1.

[0034] Preferably, the rotation speed of the ball mill is 600-800 rpm, for example, 600 rpm, 650 rpm, 700 rpm, 750 rpm or 800 rpm.

[0035] Preferably, the ball milling time is 3 to 5 h, such as 3 h, 3.5 h, 4 h, 4.5 h or 5 h.

[0036] Preferably, the filtration pore size is 80-100 μm, for example, 80 μm, 83 μm, 85 μm, 88 μm, 90 μm, 93 μm, 95 μm, 98 μm or 100 μm.

[0037] As a preferred technical solution of the present invention, the process of chemical mechanical polishing includes:

[0038] A polishing head and a polishing disk facing each other are provided, wherein a polishing pad is arranged on the polishing disk; a silicon carbide substrate is fixed to the polishing head so that the bonding surface of the silicon carbide substrate faces the polishing pad, and polishing liquid A starts to pre-flow and is evenly distributed on the surface of the polishing pad; the polishing head is controlled to carry the silicon carbide substrate to move until the bonding surface contacts the polishing pad, and polishing liquid B starts to flow out and mix with the polishing liquid A to start polishing processing, and the polishing head is controlled to carry the silicon carbide substrate and the polishing pad to perform relative rotation and / or translation motion until the polishing processing is completed.

[0039] The method for processing the bonding surface of the silicon carbide substrate using the combined polishing liquid of the present invention belongs to a one-step polishing method. By setting appropriate polishing parameters, the polishing mode of rough polishing + fine polishing in the traditional polishing process is simplified, the polishing process steps are shortened, the polishing efficiency is improved, and the mass production requirements can be better met.

[0040] As a preferred technical solution of the present invention, during the chemical mechanical polishing process, the flow rate of the polishing liquid A is 50-400 mL / min, for example, 50 mL / min, 80 mL / min, 100 mL / min, 120 mL / min, 150 mL / min, 180 mL / min, 200 mL / min, 230 mL / min, 250 mL / min, 280 mL / min, 300 mL / min, 330 mL / min, 350 mL / min, 380 mL / min or 400 mL / min, etc., preferably 150-200 mL / min.

[0041] Preferably, the flow rate of the polishing liquid B is 50-400 mL / min, for example, 50 mL / min, 80 mL / min, 100 mL / min, 120 mL / min, 150 mL / min, 180 mL / min, 200 mL / min, 230 mL / min, 250 mL / min, 280 mL / min, 300 mL / min, 320 mL / min, 350 mL / min, 380 mL / min or 400 mL / min, etc., preferably 100-150 mL / min.

[0042] Preferably, the flow ratio of the polishing liquid A to the polishing liquid B is (1.2-1.8):1, for example, 1.2:1, 1.25:1, 1.3:1, 1.35:1, 1.4:1, 1.45:1, 1.5:1, 1.55:1, 1.6:1, 1.65:1, 1.7:1, 1.75:1 or 1.8:1, etc., preferably 1.42-1.64:1, and more preferably 1.5:1.

[0043] Preferably, the polishing pad comprises polyurethane and / or nonwoven fabric; preferably polyurethane.

[0044] Preferably, the polishing pressure is 2 to 10 psi, such as 2 psi, 3 psi, 4 psi, 5 psi, 6 psi, 7 psi, 8 psi, 9 psi or 10 psi, etc., preferably 3 to 6 psi.

[0045] Preferably, the rotation speed of the polishing head relative to the polishing pad during the polishing process is 40-120 rpm, for example, 40 rpm, 50 rpm, 60 rpm, 70 rpm, 80 rpm, 90 rpm, 100 rpm, 110 rpm or 120 rpm, etc., preferably 80-110 rpm.

[0046] Preferably, the polishing rate of the polishing process is ≥4 μm / h, for example, it can be 4 μm / h, 4.1 μm / h, 4.12 μm / h, 4.15 μm / h, 4.18 μm / h, 4.2 μm / h, 4.21 μm / h, 4.23 μm / h or 4.25 μm / h.

[0047] Preferably, the polishing process makes the roughness Ra value of the bonding surface of the silicon carbide substrate less than 0.2 nm, for example, it can be 0.19 nm, 0.185 nm, 0.18 nm, 0.175 nm, 0.17 nm, 0.165 nm or 0.16 nm, etc., preferably ≤0.1 nm.

[0048] Preferably, the polishing time is 2 to 30 min, for example, 2 min, 5 min, 8 min, 10 min, 13 min, 15 min, 18 min, 20 min, 23 min, 25 min, 28 min or 30 min.

[0049] It should be noted that the present invention does not exhaustively list all point values ​​within the above numerical range, but is not limited to the listed values, and other unlisted values ​​within the above numerical range are also applicable.

[0050] In a second aspect, the present invention provides a silicon carbide substrate, which is obtained using the processing method described in the first aspect.

[0051] In a third aspect, the present invention provides a composite substrate, wherein the composite substrate comprises the silicon carbide substrate described in the second aspect.

[0052] Compared with the prior art solutions, the present invention has at least the following beneficial effects:

[0053] The present invention uses a specific combined polishing liquid to perform chemical mechanical polishing on the bonding surface of the silicon carbide substrate, and uses a polishing liquid A containing nanocrystalline cellulose as an oxidant and a polishing liquid B containing bacterial cellulase as a catalyst to form a combined polishing liquid. By using the polishing liquid A and the polishing liquid B simultaneously during the polishing process, the nanocrystalline cellulose is enzymatically hydrolyzed to release hydroxyl radicals, and the hydroxyl radicals react with silicon carbide to generate a surface modification layer, thereby reducing the surface hardness and improving the polishing rate. The polishing rate is ≥4μm / h, and the surface roughness of the substrate after polishing is low, Ra<0.2nm, and there is no scratch under the AFM field of view, which effectively solves the problem of low polishing removal rate of polycrystalline silicon carbide wafers and scratches on the surface of the wafer after polishing in the prior art, and finally improves the atomic-level flatness of the bonding surface of the silicon carbide substrate, effectively improves the bonding surface quality of the silicon carbide substrate, and effectively improves the bonding quality of the composite substrate obtained by bonding. And the key raw materials of the combined polishing liquid of the present invention belong to biomass materials, which are green and pollution-free, and more energy-saving and environmentally friendly.

[0054] The method for processing the bonding surface of the silicon carbide substrate using the combined polishing liquid of the present invention belongs to a one-step polishing method. By setting appropriate polishing parameters, the polishing mode of the rough polishing + fine polishing of the traditional polishing process is simplified, the polishing process steps are shortened, the polishing efficiency is improved, and the mass production requirements can be better met. With the cooperation of the combined polishing liquid, the removal rate of the polishing of the bonding surface of the silicon carbide substrate can be improved, and a silicon carbide surface with low roughness and no scratches can be obtained, taking into account the surface quality and removal rate of the silicon carbide substrate after polishing, and is particularly suitable for polishing and bonding pre-treatment of polycrystalline silicon carbide materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 is an AFM test image of the polished silicon carbide substrate obtained in Example 1;

[0056] Figure 2 This is an infrared light scanning image of the bonding interface of the composite substrate made using the polished silicon carbide substrate obtained in Example 1 in Application Example 1;

[0057] Figure 3 Schematic diagram of a chemical mechanical polishing device used in the method for processing the bonding surface of a silicon carbide substrate in Example 1; in the figure: 1-polishing head, 2-silicon carbide substrate, 3-polishing pad, 4-first liquid supply device, 5-second liquid supply device, 6-polishing disk;

[0058] Figure 4 It is a schematic flow chart of a method for preparing a composite substrate of Application Example 1. DETAILED DESCRIPTION

[0059] The technical solution of the present invention is further illustrated below through specific implementation methods.

[0060] It should be clear to those skilled in the art that the embodiments are only intended to help understand the present invention and should not be considered as specific limitations of the present invention.

[0061] Example 1

[0062] This embodiment provides a method for processing a bonding surface of a silicon carbide substrate. Figure 3 As shown, the treatment method is carried out in a chemical mechanical polishing device, which includes at least one set of rotating polishing head 1, a rotatable polishing disc 6 relative thereto, a polishing pad 3 is arranged on the polishing disc 6, and the polishing pad 3 is polyurethane; it also includes two sets of liquid supply devices, namely a first liquid supply device 4 and a second liquid supply device 5 for supplying polishing liquid A and polishing liquid B to the polishing pad 3 of the polishing disc 6 respectively, and also includes a control system for automatically controlling the polishing head 2, the polishing disc 6 and the liquid supply device;

[0063] The processing method comprises:

[0064] (1) Prepare the combined polishing liquid:

[0065] The combined polishing liquid includes independent polishing liquid A and polishing liquid B; based on the mass of the polishing liquid A being 100%, the polishing liquid A includes 5% of oxidant nanocrystalline cellulose (particle size 70nm), 3% of abrasive cerium oxide (particle size 50nm), 0.7% of dispersant sodium polyacrylate, pH adjuster potassium hydroxide and solvent water; the pH adjuster makes the pH value of the polishing liquid A be 7; based on the mass of the polishing liquid B being 100%, the polishing liquid B includes 8% of catalyst bacterial cellulase and 92% of solvent water, and the bacterial cellulase includes exo-β-glucanase, endo-β-glucanase and β-glucosidase.

[0066] The preparation method of the combined polishing liquid comprises:

[0067] An oxidant is weighed and added to deionized water and magnetically stirred. The pH value is adjusted to a target pH value using a pH adjuster and then magnetically stirred for 10 minutes. Then, an abrasive, a dispersant and a grinding ball are added and ball-milled in a nylon jar for 4 hours. The mixture is filtered through a filter with a pore size of 90 μm to separate the grinding balls and the suspension. A certain amount of deionized water is poured into the obtained suspension to dilute and adjust to a target concentration to obtain the polishing liquid A. A catalyst is weighed and dissolved in deionized water and magnetically stirred to obtain the polishing liquid B.

[0068] (2) Chemical mechanical polishing using the combined polishing liquid:

[0069] Specifically, a silicon carbide substrate is fixed on the polishing head, and the silicon carbide substrate is a polycrystalline silicon carbide wafer produced in the same batch; the bonding surface of the silicon carbide substrate is directed toward the polishing pad, and polishing liquid A starts to pre-flow and is evenly distributed on the surface of the polishing pad; the polishing head is controlled to carry the silicon carbide substrate to move until the bonding surface contacts the polishing pad, and polishing liquid B starts to flow out and mix with the polishing liquid A to react, and the polishing process is started; the polishing head is controlled to carry the silicon carbide substrate and the polishing pad to perform relative rotation and / or translation movement, the flow rate of the polishing liquid A is controlled to be 150 mL / min, the flow rate of the polishing liquid B is controlled to be 100 mL / min, the pressure applied by the polishing head to the polishing pad is 5 psi, the rotation speed of the polishing head relative to the polishing pad is 80 rpm, and the polishing process is performed for 20 minutes to obtain a polished silicon carbide substrate.

[0070] Example 2

[0071] The present embodiment provides a method for treating the bonding surface of a silicon carbide substrate. In step (1) of the treatment method, the mass proportion of the oxidant nanocrystalline cellulose in the polishing liquid A of the combined polishing liquid is adjusted from 5% to 1%, and only the mass proportion of the solvent water is adaptively adjusted to keep the mass proportions of other components unchanged. Except for the above, other conditions are exactly the same as those in Example 1.

[0072] Example 3

[0073] The present embodiment provides a method for treating the bonding surface of a silicon carbide substrate. In step (1) of the treatment method, the mass proportion of the oxidant nanocrystalline cellulose in the polishing liquid A of the combined polishing liquid is adjusted from 5% to 10%, and only the mass proportion of the solvent water is adaptively adjusted to keep the mass proportions of other components unchanged. Except for the above, other conditions are exactly the same as those in Example 1.

[0074] Example 4

[0075] The present embodiment provides a method for treating the bonding surface of a silicon carbide substrate. In step (1) of the treatment method, the mass proportion of the oxidant nanocrystalline cellulose in the polishing liquid A of the combined polishing liquid is adjusted from 5% to 13%, and only the mass proportion of the solvent water is adaptively adjusted to keep the mass proportions of other components unchanged. Except for the above, other conditions are exactly the same as those in Example 1.

[0076] Example 5

[0077] This embodiment provides a method for treating the bonding surface of a silicon carbide substrate. In step (1) of the treatment method, the particle size of the oxidant nanocrystalline cellulose in the polishing liquid A of the combined polishing liquid is adjusted from 70 nm to 30 nm. Except for the above, other conditions are exactly the same as those in Example 1.

[0078] Example 6

[0079] This embodiment provides a method for treating the bonding surface of a silicon carbide substrate. In step (1) of the treatment method, the particle size of the oxidant nanocrystalline cellulose in the polishing liquid A of the combined polishing liquid is adjusted from 70 nm to 50 nm. Except for the above, other conditions are exactly the same as those in Example 1.

[0080] Example 7

[0081] This embodiment provides a method for treating the bonding surface of a silicon carbide substrate. In step (1) of the treatment method, the particle size of the oxidant nanocrystalline cellulose in the polishing liquid A of the combined polishing liquid is adjusted from 70 nm to 80 nm. Except for the above, other conditions are exactly the same as those in Example 1.

[0082] Example 8

[0083] This embodiment provides a method for treating the bonding surface of a silicon carbide substrate. In step (1) of the treatment method, the particle size of the oxidant nanocrystalline cellulose in the polishing liquid A of the combined polishing liquid is adjusted from 70 nm to 100 nm. Except for the above, other conditions are exactly the same as those in Example 1.

[0084] Example 9

[0085] The present embodiment provides a method for treating the bonding surface of a silicon carbide substrate. In step (1) of the treatment method, the amount of the pH regulator of the polishing liquid A of the combined polishing liquid is adjusted so that the pH value of the polishing liquid A is adjusted from 7 to 5, and only the amount of solvent water is adaptively adjusted to keep the mass proportion of other components unchanged. Except for the above, other conditions are exactly the same as those in Example 1.

[0086] Example 10

[0087] The present embodiment provides a method for treating the bonding surface of a silicon carbide substrate. In step (1) of the treatment method, the amount of the pH regulator of the polishing liquid A of the combined polishing liquid is adjusted so that the pH value of the polishing liquid A is adjusted from 7 to 6, and only the amount of solvent water is adaptively adjusted to keep the mass proportion of other components unchanged. Except for the above, other conditions are exactly the same as those in Example 1.

[0088] Embodiment 11

[0089] The present embodiment provides a method for treating the bonding surface of a silicon carbide substrate. In step (1) of the treatment method, the amount of the pH regulator of the polishing liquid A of the combined polishing liquid is adjusted so that the pH value of the polishing liquid A is adjusted from 7 to 8, and only the amount of solvent water is adaptively adjusted to keep the mass proportion of other components unchanged. Except for the above, other conditions are exactly the same as those in Example 1.

[0090] Example 12

[0091] The present embodiment provides a method for treating the bonding surface of a silicon carbide substrate. In step (1) of the treatment method, the amount of the pH regulator of the polishing liquid A of the combined polishing liquid is adjusted so that the pH value of the polishing liquid A is adjusted from 7 to 9, and only the amount of solvent water is adaptively adjusted to keep the mass proportion of other components unchanged. Except for the above, other conditions are exactly the same as those in Example 1.

[0092] Embodiment 13

[0093] The present embodiment provides a method for treating the bonding surface of a silicon carbide substrate. In step (1) of the treatment method, the mass proportion of the catalyst bacterial cellulase in the polishing liquid B of the combined polishing liquid is adjusted from 8% to 1%, and only the mass proportion of the solvent water is adaptively adjusted to keep the mass proportions of other components unchanged. Except for the above, other conditions are exactly the same as those in Example 1.

[0094] Embodiment 14

[0095] The present embodiment provides a method for treating the bonding surface of a silicon carbide substrate. In step (1) of the treatment method, the mass proportion of the catalyst bacterial cellulase in the polishing liquid B of the combined polishing liquid is adjusted from 8% to 5%, and only the mass proportion of the solvent water is adaptively adjusted to keep the mass proportions of other components unchanged. Except for the above, other conditions are exactly the same as those in Example 1.

[0096] Embodiment 15

[0097] The present embodiment provides a method for treating the bonding surface of a silicon carbide substrate. In step (1) of the treatment method, the mass proportion of the catalyst bacterial cellulase in the polishing liquid B of the combined polishing liquid is adjusted from 8% to 10%, and only the mass proportion of the solvent water is adaptively adjusted to keep the mass proportions of other components unchanged. Except for the above, other conditions are exactly the same as those in Example 1.

[0098] Example 16

[0099] The present embodiment provides a method for treating the bonding surface of a silicon carbide substrate. In step (1) of the treatment method, the mass proportion of the catalyst bacterial cellulase in the polishing liquid B of the combined polishing liquid is adjusted from 8% to 13%, and only the mass proportion of the solvent water is adaptively adjusted to keep the mass proportions of other components unchanged. Except for the above, other conditions are exactly the same as those in Example 1.

[0100] Example 17-Example 32

[0101] Example 17 to Example 32 respectively provide a method for processing the bonding surface of a silicon carbide substrate, wherein the processing method uses the combined polishing liquid provided in Example 1 to adjust at least one of the flow rate of polishing liquid A, the flow rate of polishing liquid B, the pressure, rotation speed and time of the polishing process, as shown in Table 2. Except for the above, other conditions are exactly the same as those in Example 1.

[0102] Comparative Example 1

[0103] This comparative example provides a method for treating the bonding surface of a silicon carbide substrate. In step (1) of the treatment method, the polishing liquid A of Example 1 is used, and the polishing liquid B does not contain a catalyst but only contains deionized water. Except for the above, other conditions are exactly the same as those of Example 1.

[0104] Characterization and Testing:

[0105] During the polishing process of Examples 1-32 and Comparative Example 1, the polishing rate was monitored. The weighing method was used to calculate the polishing rate (Pre-Post) by the difference in the weight of the substrate before and after polishing, that is, the polishing rate RR = (m1-m2) / p / S / t, where m1 and m2 are the weights of the silicon carbide substrate before and after polishing, respectively, in g, and p is the density of silicon carbide, p = 3.2 g / cm 3 , t is the polishing time, unit is s, S is the surface area of ​​the polished silicon carbide sample, unit is cm 2 The results are shown in Table 1 and Table 2.

[0106] At the same time, the polished surface (bonding surface) of the obtained polished silicon carbide substrate is tested for surface roughness using an atomic force microscope. Figure 1 1 is an AFM test image of the polished silicon carbide substrate obtained in Example 1. It can be seen that the surface has no scratches and has a smooth atomic-level surface morphology. Other results are shown in Tables 1 and 2.

[0107] Table 1

[0108]

[0109] It can be seen from Table 1 that when CMP processing is performed on silicon carbide substrates, a balance needs to be achieved between chemical oxidation and mechanical grinding. Strong oxidation will cause severe surface corrosion, and pits will appear, affecting the surface quality of silicon carbide. Strong mechanical action will cause scratches on the silicon carbide substrate, affecting the surface roughness.

[0110] Table 2

[0111]

[0112]

[0113] It can be seen from Table 2 that when the silicon carbide substrate is CMP processed, the flow rate of polishing liquid A and B increases, which accelerates the oxidation reaction and increases the polishing rate accordingly. Strong oxidation causes serious surface corrosion, and pits appear, affecting the surface quality of silicon carbide. Strong mechanical action causes scratches on the silicon carbide substrate, affecting the surface roughness.

[0114] Application Example 1

[0115] This application example provides a composite substrate and a method for preparing the same. Figure 4 As shown, the preparation method comprises:

[0116] Prepare a first substrate and a second substrate to be bonded, wherein the first substrate is the processed silicon carbide substrate obtained in Example 1 or Comparative Example 1; the second substrate is a high-quality silicon carbide substrate sheet; then bond the first substrate and the cleaned second substrate together by surface activation bonding at room temperature, the bonding temperature is 20 to 40° C., the absolute vacuum is less than 10 Pa, and the bonding strength is >1.5 J / m 2 , and obtain a composite substrate.

[0117] Figure 2 This is an infrared light scanning image of the bonding interface of a composite substrate prepared using the polished silicon carbide substrate obtained in Example 1 in Application Example 1. It can be seen from the figure that the polished surface of the silicon carbide substrate polished in the manner of Example 1 is of good quality, and there are no voids (i.e., no unbonded areas) at the bonding interface of the formed composite substrate. If there are voids, bubbles will appear in the scanning image, indicating that bonding is not successful at the bubbles.

[0118] The bonding strength of the bonded substrate was tested using a tensile testing machine, and the results are shown in Table 3.

[0119] Table 3

[0120]

[0121] As can be seen from the above, the present invention uses a specific combination of polishing liquids to perform chemical mechanical polishing on the bonding surface of the silicon carbide substrate, and uses a polishing liquid A containing nanocrystalline cellulose as an oxidant and a polishing liquid B containing bacterial cellulase as a catalyst to form a combined polishing liquid. By using polishing liquid A and polishing liquid B simultaneously during the polishing process, the nanocrystalline cellulose is enzymatically hydrolyzed to release hydroxyl radicals, and the hydroxyl radicals react with silicon carbide to form a surface modification layer, thereby reducing the surface hardness and improving the polishing rate. The polishing rate is ≥4μm / h, and the surface roughness of the substrate after polishing is low, Ra<0.2nm, and there are no scratches under the AFM field of view, which effectively solves the problem of low polishing removal rate of polycrystalline silicon carbide wafers and scratches on the surface of the wafer after polishing in the prior art, and finally improves the atomic-level flatness of the bonding surface of the silicon carbide substrate, effectively improves the bonding surface quality of the silicon carbide substrate, and effectively improves the bonding quality of the composite substrate obtained by bonding. And the key raw materials of the combined polishing liquid of the present invention belong to biomass materials, which are green and pollution-free, and more energy-saving and environmentally friendly.

[0122] The present invention illustrates the detailed process equipment and process flow of the present invention through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned detailed process equipment and process flow, that is, it does not mean that the present invention must rely on the above-mentioned detailed process equipment and process flow to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of various raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0123] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0124] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0125] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A method for processing a bonding surface of a silicon carbide substrate, characterized in that: The processing method comprises: using a combination polishing liquid to chemically and mechanically polish the bonding surface of the silicon carbide substrate; The combined polishing liquid comprises independent polishing liquid A and polishing liquid B; the polishing liquid A comprises an oxidant, a pH regulator and an abrasive, and the polishing liquid B comprises a catalyst; the oxidant comprises nanocrystalline cellulose, and the catalyst comprises bacterial cellulase.

2. The method for processing the bonding surface of a silicon carbide substrate according to claim 1, characterized in that: Taking the mass of the polishing liquid A as 100%, the mass of the oxidant is ≤10%, the mass of the abrasive is ≤6%, and the mass of the solvent of the polishing liquid A is ≥83%; Preferably, based on the mass of the polishing liquid B being 100%, the mass of the catalyst is ≤10%, preferably 7% to 9%, and the mass of the solvent of the polishing liquid B is ≥90%; Preferably, the pH value of the polishing liquid A is 6-8.

3. The method for processing the bonding surface of a silicon carbide substrate according to claim 1 or 2, characterized in that: The bacterial cellulase comprises exo-β-glucanase, endo-β-glucanase and β-glucosidase; Preferably, the abrasive comprises silicon oxide and / or cerium oxide; Preferably, the pH adjuster comprises potassium hydroxide and / or hydrogen peroxide; Preferably, the solvent of the polishing liquid A and the polishing liquid B includes water; Preferably, the particle size of the oxidant is 30 to 100 nm, preferably 60 to 80 nm; Preferably, the particle size of the oxidant is larger than the particle size of the abrasive; Preferably, the particle size of the abrasive is 30-60 nm.

4. The method for processing the bonding surface of a silicon carbide substrate according to any one of claims 1 to 3, characterized in that: The polishing liquid A also includes a dispersant; Preferably, the dispersant comprises sodium polyacrylate; Preferably, based on the mass of the polishing liquid A being 100%, the mass of the dispersant is ≤1%.

5. The method for processing the bonding surface of a silicon carbide substrate according to any one of claims 1 to 4, characterized in that: The preparation method of the combined polishing liquid comprises: The oxidant is mixed with the solvent, a pH adjuster is added to adjust to the target pH value, and then an abrasive is added for ball milling. The suspension is filtered to obtain a suspension, and the suspension is mixed with the solvent to adjust to the target concentration to obtain a polishing liquid A; the catalyst is weighed and dissolved in the solvent and magnetically stirred to obtain the polishing liquid B.

6. The method for processing the bonding surface of a silicon carbide substrate according to claim 5, characterized in that: The ball milling media of the ball milling includes zirconium beads; Preferably, the ball-to-material mass ratio of the ball mill is (2-4):1; Preferably, the rotation speed of the ball mill is 600-800 rpm; Preferably, the ball milling time is 3 to 5 hours; Preferably, the pore size of the filter is 80-100 μm.

7. The method for processing the bonding surface of a silicon carbide substrate according to any one of claims 1 to 6, characterized in that: The chemical mechanical polishing process includes: A polishing head and a polishing disk facing each other are provided, wherein a polishing pad is arranged on the polishing disk; a silicon carbide substrate is fixed to the polishing head so that the bonding surface of the silicon carbide substrate faces the polishing pad, and polishing liquid A starts to pre-flow and is evenly distributed on the surface of the polishing pad; the polishing head is controlled to carry the silicon carbide substrate to move until the bonding surface contacts the polishing pad, and polishing liquid B starts to flow out and mix with the polishing liquid A to start polishing processing, and the polishing head is controlled to carry the silicon carbide substrate and the polishing pad to perform relative rotation and / or translation motion until the polishing processing is completed.

8. The method for processing the bonding surface of a silicon carbide substrate according to claim 7, characterized in that: During the chemical mechanical polishing process, the flow rate of the polishing liquid A is 50 to 400 mL / min, preferably 150 to 200 mL / min; Preferably, the flow rate of the polishing liquid B is 50 to 400 mL / min, preferably 100 to 150 mL / min; Preferably, the flow ratio of the polishing liquid A to the polishing liquid B is (1.2-1.8):1, preferably 1.5:1; Preferably, the polishing pad comprises polyurethane and / or nonwoven fabric; preferably polyurethane; Preferably, the polishing pressure is 2 to 10 psi, preferably 3 to 6 psi; Preferably, the rotation speed of the polishing head relative to the polishing pad during the polishing process is 40 to 120 rpm, preferably 80 to 110 rpm; Preferably, the polishing rate of the polishing process is ≥4 μm / h; Preferably, the polishing process makes the roughness Ra value of the bonding surface of the silicon carbide substrate less than 0.2 nm, preferably ≤ 0.1 nm; Preferably, the polishing process takes 2 to 30 minutes.

9. A silicon carbide substrate, characterized in that: Obtained by the treatment method described in any one of claims 1 to 8.

10. A composite substrate, characterized in that: Comprising the silicon carbide substrate according to claim 9.

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