CN109702639B - SiC single crystal wafer grinding and polishing method - Google Patents
SiC single crystal wafer grinding and polishing method Download PDFInfo
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Abstract
A SiC single crystal wafer grinding and polishing method comprises the steps of grinding a SiC cutting wafer to obtain a pre-polished wafer and polishing the pre-polished wafer to obtain a SiC single crystal wafer, wherein in the grinding process, the water-based grinding fluid for grinding is obtained by pre-grinding the SiC cutting wafer by using initial grinding fluid and meeting a first condition; during the polishing process, the water-based polishing solution for polishing is obtained by pre-polishing the pre-polished wafer and satisfying the second condition. The SiC single crystal wafer prepared by the method can obviously reduce the damage and scratches on the surface of the SiC single crystal wafer, and the high-quality SiC single crystal wafer is obtained.
Description
Technical Field
The application belongs to the technical field of super-precision surface grinding and polishing, and particularly relates to a SiC single crystal wafer grinding and polishing method.
Background
Silicon carbide single crystal is one of the most important third-generation semiconductor materials, and is widely applied to the fields of power electronics, radio frequency devices, photoelectronic devices and the like because of the excellent properties of large forbidden bandwidth, high saturated electron mobility, strong breakdown field, high thermal conductivity and the like. When used as an epitaxial thin film substrate, epitaxial growth is highly substrate-dependent, and a small defect on the substrate also destroys the periodicity of the surface of the silicon carbide single crystal, spreads and spreads on the thin film, and seriously affects the film quality. Even when used as a seed, the bulk single crystal material grown is severely affected by the substrate and all defects on the surface of the substrate are typically replicated as is into the new epitaxial material.
In order to obtain high quality thin films and bulk single crystals, polishing methods are mainly used at present. Chenopodium et al propose to polish wafers by hydrogen, but this method does little to the deep scratches left during mechanical polishing. In addition, lingueming et al propose that the wafer is subjected to plasma etching after being ground, and the method utilizes plasma to bombard the surface of the silicon carbide to remove the damaged layer formed in the grinding process, and the method has high removal rate, but often introduces new damage and defects while removing the damaged layer.
CN101161800A discloses an aqueous suspension grinding fluid, which is prepared by uniformly dispersing silicon carbide powder or/and diamond powder with the fineness of more than or equal to 1200 meshes by taking water as a matrix under the action of an anionic surfactant. When the particle fineness of the hard material is more than or equal to 5000 meshes, the hard material is the polishing solution. 1-15% of anionic surfactant, 20-50% of silicon carbide powder or/and diamond powder and the balance of water in the suspension. The suspension liquid takes water as a substrate, the viscosity is adjustable, namely the cutting speed is variable, the cutting efficiency is improved, and the application range is wide. The cutting and polishing device is suitable for cutting and polishing hard materials and crystal materials. The application only uses the polishing liquid for polishing, but the optimal polishing state of the polishing liquid is not studied, so that the polishing effect cannot reach the optimal effect.
CN103013345A discloses an oily diamond grinding fluid and a preparation method thereof, wherein the grinding fluid comprises the following components: diamond micropowder, surfactant, dispersant, pH value regulator, wetting agent and oil, wherein the weight ratio (wt.) of each component is as follows: diamond micro powder: 0.001% -10%; surfactant (b): 0.001% -20%; dispersing agent: 0 to 20 percent; pH value regulator: 0 to 10 percent; wetting agent: 0 to 10 percent; the balance being oil. The polishing solution is mainly applied to the grinding and polishing of the surfaces of silicon carbide wafers, LED sapphire substrate sheets, ceramics, optical fibers, molds, semiconductor compound wafers and the like. The grinding liquid provided by the invention can greatly improve the polishing efficiency, has good dispersion performance, can keep a uniform and stable state for a long time, has high product smoothness and good polishing effect after being polished, does not contain components harmful to human bodies, is easy to clean and is beneficial to environmental protection. The application only discloses the components of the polishing slurry and does not study how to achieve the optimal polishing state when the polishing slurry is used.
CN102337082A discloses a chemical mechanical polishing solution for silicon carbide substrate, which comprises the following components in percentage by weight as shown below: 1-50 wt% of an abrasive; 0.01 to 8 wt% of a chelating agent; 0.01 to 10 wt% of a surfactant; 0.01 to 10 wt% of a dispersant; 0.1 to 20 wt% of an oxidizing agent; the balance being deionized water. The polishing solution has small damage to the surface of the silicon carbide substrate; the roughness value of the silicon carbide substrate is low, and the roughness Ra value can be less than 0.5 nm; the surface of the substrate has no defects of scratches and corrosion pits; the removal rate is high, and the cleaning is easy; does not corrode processing equipment and pollute the environment; the raw materials are cheap and low in cost; is easy to store. The polishing solution is mainly used for chemical mechanical polishing of silicon carbide crystals for substrates. The application discloses the composition of the polishing solution, but does not explore how the polishing solution is treated to achieve the best use condition.
In CN106349948A, a method for preparing a nano polishing solution is disclosed, which comprises the following steps: uniformly mixing silicon carbide micro powder, water and a dispersing agent according to a mass ratio to obtain a mixture, and then placing the mixture into a sand mill for circular crushing until the particle size of a solid material in the mixture is nano-scale to obtain nano-silicon carbide slurry; secondly, adding water for dilution to obtain a nano silicon carbide suspension; and thirdly, adding a chelating agent, a lubricant, a preservative and a pH regulator, and uniformly stirring to obtain the nano polishing solution. The nano polishing solution prepared by the invention is aqueous, and has the advantages of environmental protection, quick polishing and heat dissipation, strong diluting capability, low cost and the like. The application discloses a method for preparing the polishing solution, but does not explore how the polishing solution can be used optimally during the use process.
In the prior art, the research on the polishing solution mostly focuses on the composition, the proportion and the preparation method of the polishing solution, but neglects how the polishing solution can achieve the best use effect in the use process. Which is often the key to determining the quality of the SiC single wafer after polishing.
Content of application
In order to solve the problems, the application provides a method for grinding and polishing a SiC single crystal wafer, which comprises the steps of grinding a SiC cutting wafer to obtain a pre-polished wafer and polishing the pre-polished wafer to obtain the SiC single crystal wafer in sequence, wherein in the grinding process, the water-based grinding fluid for grinding is obtained by pre-grinding the SiC cutting wafer by using initial grinding fluid and meeting a first condition; during the polishing process, the water-based polishing solution for polishing is obtained by pre-polishing the pre-polished wafer and performing post-treatment meeting a second condition.
After the initial grinding fluid is prepared, because the initial grinding fluid contains different particles, the particle diameters of the particles are different, the mutual matching degree among the particles is not good, and the particles have edges and corners in a micro angle and are not smooth, the SiC cutting slice ground by the grinding fluid can leave different damaged scratches on the surface of the SiC cutting slice after the grinding is just started The stability is better. The water-based grinding fluid has better compatibility of components such as the grinding material, the lubricant and the like. Because different molecules such as abrasive, dispersing agent, polymerization inhibitor, stabilizer and the like exist in the polishing solution, on one hand, the surface of the abrasive cannot be ensured to be smooth, if the surface of the SiC monocrystal wafer is not smooth, the surface of the SiC monocrystal wafer can be damaged or scratched when the SiC monocrystal wafer is subjected to fine polishing treatment, and on the other hand, the quality of the SiC monocrystal wafer is influenced, and on the other hand, the abrasive in the polishing solution can be agglomerated, so that the polishing solution cannot uniformly perform fine polishing treatment on the SiC monocrystal wafer in an initial use state, and a good fine polishing effect cannot be achieved; on the other hand, other auxiliary components added into the polishing solution cannot be matched well in the initial use state, the matching among particles is not in place, and the optimal fine polishing effect cannot be achieved. According to the method, the initial polishing solution is prepared, the SiC single crystal wafer is not subjected to fine polishing treatment immediately, but the initial polishing solution is firstly placed in a polishing device to perform rough polishing treatment on the SiC single crystal wafer or a material with the same hardness as the SiC single crystal wafer, so that the purpose of the treatment is to perform rough polishing treatment on the SiC single crystal wafer on one hand, and damage or scratches on the surface of the original SiC single crystal wafer are reduced; on the other hand, through rough polishing treatment, the surfaces of the grinding particles in the initial polishing solution are smoother and smoother, and the particles are more uniformly and stably dispersed and have higher matching degree; but also can increase the content of solid components in the polishing solution and improve the polishing effect. When the initial polishing solution is subjected to rough polishing treatment to reach the first condition, impurity removal is carried out on the initial polishing solution to obtain the water-based polishing solution, and the rough polishing treatment can also be carried out on the initial polishing solution by using a material with the same hardness as the SiC single wafer.
Preferably, the initial grinding fluid comprises the following raw materials in parts by weight: 0.5-1.2 parts of polymerization inhibitor; 2-4 parts of a dispersing agent; 0.5-1.5 parts of powder lubricant; 15-25 parts of abrasive; the initial polishing solution comprises the following raw materials in parts by weight: 0.1-0.3 part of polymerization inhibitor, 0.2-0.5 part of dispersant, 20-40 parts of stabilizer and 10-20 parts of abrasive.
Preferably, the polymerization inhibitor comprises one or more of benzoquinone, aniline, benzenediol, sodium carboxymethylcellulose, polymaleic acid, polyamino acid, sodium polyacrylate, phosphonic acid carboxylic acid, glycerol and propylene glycol, and the mixture ratio of the two or more is arbitrary.
Preferably, the dispersing agent comprises one or more than two of water glass, sodium tripolyphosphate, sodium hexametaphosphate, sodium pyrophosphate, triethylhexyl phosphoric acid, sodium dodecyl sulfate, methylpentanol, polyacrylamide, Guel gum and polyethylene glycol fatty acid ester, and the mixture ratio of the two or more than two is arbitrary.
Preferably, the powder lubricant is one or a mixture of more than two of graphite, hexagonal boron nitride, niobium diselenide and molybdenum disulfide, and the mixture ratio of the two or more is arbitrary.
Preferably, the powder lubricant has a median particle diameter of 5 to 10 μm; the stabilizer comprises one or more than two of ethanol, propanol, isopropanol, butanol, isobutanol, ethylene glycol, glycerol, glucose, gluconic acid, fructose, mannose and maltose, and the mixture ratio of the two or more than two is arbitrary.
Preferably, the abrasive is a high-hardness powder material, the median particle size of the high-hardness powder material in the grinding fluid is 10-15 μm, and the median particle size of the high-hardness powder material in the polishing fluid is 0.5-5 μm.
Preferably, the high-hardness powder material contains at least diamond.
Preferably, the high-hardness powder material further comprises one or a mixture of two or more of cubic boron nitride, boron carbide and aluminum oxide, and the mixture ratio of the two or more is arbitrary.
Preferably, the first condition is that the thickness of the SiC cutting slice removed after grinding is 1/3-2/3 of the target thickness; the second condition is that the service time of the initial polishing solution is not less than 140h, and filtering treatment is carried out; preferably, the filtration treatment is performed under conditions that the polishing solution is passed through a filtration membrane at one or more times, the pore size of the filtration membrane being in the range of 0.5 to 1 μm.
This application can bring following beneficial effect: the initial grinding liquid is ground to obtain water-based grinding liquid, the SiC single crystal wafer is ground and processed on two sides by the water-based grinding liquid, the damage and scratch generated on the surface of the wafer are few, the degree is low, the influence on the subsequent processing procedures is low, and the polishing efficiency is improved; meanwhile, the grinding liquid is uniform in dispersion, stable in state, high in removal rate of processed SiC single crystal wafers, recyclable and long in service life of grinding materials; the effect of finely polishing the SiC single crystal wafer by the water-based polishing solution obtained by carrying out rough polishing pretreatment on the polishing solution reaches the optimal state; after the SiC single crystal wafer is precisely polished by the water-based polishing solution prepared by the method, the damage and scratches on the surface of the SiC single crystal wafer can be obviously reduced, and the high-quality SiC single crystal wafer can be obtained.
Detailed Description
Example 1: preparing an initial grinding fluid:
the preparation method of the initial grinding fluid comprises the following steps:
s1, mixing deionized water and 0.5-1.5 parts of powder lubricant, and uniformly stirring to obtain a mixed solution;
s2, adding 15-25 parts of grinding materials into the mixed solution, and uniformly stirring to obtain intermediate liquid;
s3, adding 0.5-1.2 parts of polymerization inhibitor and 2-4 parts of dispersant into the intermediate liquid, and uniformly stirring to obtain the initial grinding liquid.
Example 2: grinding the initial grinding fluid to obtain a water-based grinding fluid:
grinding the SiC cutting slice on a grinding machine by using the initial grinding fluid prepared in the embodiment 1, and removing the thickness of 1/3-2/3 to obtain water-based grinding fluid; the grinding process comprises the steps of setting the upper disc at 15rpm and the lower disc at 18rpm, and setting the pressure at 100g/cm2The feed liquid supply flow rate was 800mL/min, and the time was 2 hours.
Specific examples are as follows:
in the above table, "-" means that the substance is not contained or that the condition is not satisfied
The composition of each sample is shown in the following table:
in the above table, the polymerization inhibitor includes: one or more than two of benzoquinone, aniline, benzenediol, sodium carboxymethylcellulose, polymaleic acid, polyamino acid, sodium polyacrylate, phosphonic acid carboxylic acid, glycerol and propylene glycol are mixed, and the mixture ratio of the two or more than two is arbitrary; the dispersant comprises: one or more than two of water glass, sodium tripolyphosphate, sodium hexametaphosphate, sodium pyrophosphate, triethylhexyl phosphoric acid, sodium dodecyl sulfate, methyl amyl alcohol, polyacrylamide, Guergel gum and polyethylene glycol fatty acid ester are mixed, and the mixture ratio of the two or more than two is arbitrary; the powder lubricant is one or more than two of graphite, hexagonal boron nitride, niobium diselenide and molybdenum disulfide which are mixed in any proportion; the grinding material is one or the mixture of more than two of diamond, cubic boron nitride, boron carbide and alumina, and the mixture ratio of the two is arbitrary.
Example 3: the step of grinding the single SiC wafer using the water-based grinding fluid in example 2:
s1, using a water-based grinding fluid on a grinding machine to continuously grind the SiC single crystal wafer ground in the embodiment 2, wherein the grinding processing technology comprises the steps of upper disc rotating speed of 15rpm, lower disc rotating speed of 18rpm and pressure of 100g/cm2The feed liquid supply flow rate was 800mL/min, and the time was 2 hours.
And S2, continuously using the grinding fluid ground by the S1 to grind the new cutting blade, wherein the process adopts the processing process in the S1, the grinding time is 4 hours, and the target thickness is achieved.
Example 4: characterization of
The same SiC single crystal wafer was polished by the polishing process in example 3 using the initial polishing slurry prepared in example 1, and the same SiC single crystal wafer was polished by the polishing process in example 3 using the water-based polishing slurry prepared in example 2, and the stability of the polishing slurry, the removal rate of the SiC single crystal wafer, and the surface roughness were comparatively tested, wherein the stability of the polishing slurry was tested by: and (3) standing the prepared grinding fluid for 3 days, and observing whether the grinding fluid has layering and coagulation phenomena, wherein the grinding fluid has poor stability if the layering and coagulation phenomena occur, and the grinding fluid has good stability if the layering or coagulation phenomena do not occur.
According to the experimental results, the following results are obtained: comparison of the experimental results according to comparative example 1 and example 3 gives: the reason why the removal rate is reduced when the SiC single crystal wafer is ground and the surface of the SiC single crystal wafer is rougher after grinding is that the smaller the content of the polymerization inhibitor, the particles in the grinding fluid agglomerate to different degrees, the SiC single crystal wafer cannot be uniformly ground when being in contact with the particles in the grinding fluid, and the contact area is reduced.
According to the comparison of the experimental results of comparative example 2 and example 2, the reason why the removal rate is decreased when the SiC single crystal wafer is polished due to too small content of the dispersant and the surface of the SiC single crystal wafer is rougher after polishing is also because the particles in the polishing liquid are not uniformly dispersed and the SiC single crystal wafer is not uniformly polished when contacting with the particles in the polishing liquid, and the contact area is decreased.
According to the comparison of the experimental results of comparative example 3 and example 4, when the amount of the powder lubricant is too small, the surface of the SiC single crystal wafer after grinding becomes rougher, because when the amount of the powder lubricant is too small, the powder lubricant cannot perform a lubricating and buffering function well during grinding, and the abrasive causes damage and scratches on the surface of the SiC single crystal wafer during grinding.
According to the comparison of the experimental results of the comparative example 4 and the example 2, the particle size of the powder lubricant is too large, the removal rate of the SiC single crystal wafer is reduced during grinding, and the surface of the SiC single crystal wafer is rougher after grinding, because the particle size of the powder lubricant is too large, the powder lubricant cannot be in uniform contact with the SiC single crystal wafer, and the powder lubricant cannot be matched with the grinding material, so that the powder lubricant cannot play a good lubricating and buffering role.
According to the comparison of the experimental results of the comparative example 5 and the example 2, the removal rate of the SiC single crystal wafer is reduced when the content of the abrasive is too small; according to the comparison of the experimental results of the comparative example 6 and the example 2, the removal rate of the SiC single crystal wafer is reduced when the grain size of the abrasive is too large, because the grinding efficiency is reduced when the grain size of the abrasive is too large; from the comparison of the experimental results of comparative example 7 and example 5, it is understood that the removal efficiency of the SiC single crystal wafer is slightly improved but the surface roughness is decreased because the grain size of the abrasive is small, the contact area with the SiC single crystal wafer is larger, and the degree of damage and scratch to the surface of the SiC single crystal wafer is deeper.
The experimental results according to example 3 and example 6 compared give: the shorter the time for polishing the initial polishing liquid is within a certain range, the lower the removal rate of the SiC single crystal wafer during polishing, and the rougher the surface of the SiC single crystal wafer after polishing. The experimental results according to example 7 and example 5 compared give: and grinding the SiC single crystal wafer, wherein the smaller the ratio of the removal thickness to the target thickness is in a certain range, the lower the removal rate of the SiC single crystal wafer during grinding is, and the rougher the surface of the SiC single crystal wafer after grinding is.
According to the experimental results, the following results are obtained: the stability of the water-based grinding fluid is better than that of the initial grinding fluid, which shows that after the initial grinding fluid is ground, the particles in the grinding fluid are dispersed more uniformly, the dispersibility is improved, the grinding fluid is more stable, and the phenomenon of agglomeration, sedimentation or layering is not easy to occur.
According to the experimental results, the following results are obtained: the same SiC single crystal wafer is ground under the same grinding conditions and grinding process, the initial grinding fluid is used for directly grinding and the initial grinding fluid is ground to obtain the water-based grinding fluid, compared with the grinding of the SiC single crystal wafer by the water-based grinding fluid, the SiC single crystal wafer obtained by the water-based grinding fluid has higher removal rate and smaller surface roughness, the grinding efficiency is higher when the initial grinding fluid is firstly ground and then the material is ground, the surface of the obtained SiC single crystal wafer is smoother and has higher quality, and the reason is that: on one hand, after grinding treatment, the particle dispersibility of the grinding fluid is stronger, which is beneficial to grinding; on the other hand, the surface of the particles in the initial grinding liquid is not smooth, and after grinding treatment, the surface of the grinding particles in the grinding liquid is smoother, so that damage or scratches on the surface of the SiC single crystal wafer can be reduced; on the other hand, through grinding treatment, the matching degree between the powder lubricant and the grinding material in the grinding fluid is improved, and the lubricating effect of the powder lubricant is also improved.
Example 5: the preparation method of the initial polishing solution comprises the following steps:
s1, mixing deionized water and 10-20 parts of grinding materials, and uniformly stirring to obtain a mixed solution;
s2, adding 0.1-0.3 part of polymerization inhibitor, 0.2-0.5 part of dispersant and 20-40 parts of stabilizer into the intermediate liquid, and uniformly stirring to obtain the initial polishing solution.
Example 6: the method for pre-treating the initial polishing solution to obtain the water-based polishing solution comprises the following steps:
s1, ultrasonic cleaning is carried out on the pre-polished wafer, wherein the cleaning agent comprises one or more of hydrochloric acid, nitric acid, sulfuric acid and hydrofluoric acid, the cleaning condition is cleaning for 20min, and the cleaning temperature is controlled at 50 +/-5 ℃.
S2, using the initial polishing solution prepared in the embodiment 1, roughly polishing the grinded SiC single crystal wafer or the material with the same hardness as the SiC single crystal wafer on a double-sided polishing machine, wherein the primary rough polishing process of the SiC single crystal wafer or the material with the same hardness as the SiC single crystal wafer comprises the steps of upper disc rotating speed of 16-20rpm, lower disc rotating speed of 20-30rpm and pressure of 35MPa, and if the rough polishing object is the SiC single crystal wafer, the rough polishing can be completed by controlling the processing time to be 4-6 h.
And S3, after the initial polishing solution is subjected to rough polishing for more than 140 hours, filtering the pretreated water-based polishing solution to obtain the water-based polishing solution, wherein the filtering condition is that the polishing solution passes through a filter membrane once or for many times, and the aperture range of the filter membrane is 0.5-1 μm. . The sample numbers used were set in correspondence with example 2.
Specific examples are as follows:
the composition of each sample is shown in the following table:
in the above table, the polymerization inhibitor includes: one or more than two of benzoquinone, aniline, benzenediol, sodium carboxymethylcellulose, polymaleic acid, polyamino acid, sodium polyacrylate, phosphonic acid carboxylic acid, glycerol and propylene glycol are mixed, and the mixture ratio of the two or more than two is arbitrary; the dispersant comprises: one or more than two of water glass, sodium tripolyphosphate, sodium hexametaphosphate, sodium pyrophosphate, triethylhexyl phosphoric acid, sodium dodecyl sulfate, methyl amyl alcohol, polyacrylamide, Guergel gum and polyethylene glycol fatty acid ester are mixed, and the mixture ratio of the two or more than two is arbitrary; the stabilizer comprises one or more than two of ethanol, propanol, isopropanol, butanol, isobutanol, ethylene glycol, glycerol, glucose, gluconic acid, fructose, mannose and maltose, and the mixture ratio of the two or more than two is arbitrary; the grinding material is one or the mixture of more than two of diamond, cubic boron nitride, boron carbide and alumina, and the mixture ratio of the two is arbitrary.
Example 7: the procedure of fine polishing a pre-polished wafer using the water-based polishing liquid of example 6 was as follows:
s1, carrying out ultrasonic cleaning on the pre-polished wafer which is numbered 1-4 in the example 2 and subjected to rough polishing in the example 1-5 under the cleaning condition of 20min at the cleaning temperature of 50 +/-5 ℃.
S2, inputting the water-based polishing solution obtained in the embodiment 2 into another special polishing machine for fine polishing, and performing fine polishing on the pre-polished wafer cleaned in the step 1 by adopting a fine polishing process, wherein the fine polishing process comprises an upper disc rotating speed of 12rpm, a lower disc rotating speed of 17rpm, a pressure of 30MPa and a time of 1.5 h.
Example 8: characterization of
According to the comparison of the experimental results of the comparative example 1 and the example 3, the fact that the removal rate is reduced when the SiC single crystal wafer is polished due to the low content of the polymerization inhibitor, and the surface of the polished SiC single crystal wafer is rougher is also known, because the particles in the polishing solution are agglomerated to different degrees due to the low content of the polymerization inhibitor, the SiC single crystal wafer cannot be uniformly polished when being contacted with the particles in the polishing solution, and the contact area is reduced.
From comparison of the experimental results of comparative example 2 and example 2, it is understood that the reason why the removal rate is decreased when the SiC single crystal wafer is polished due to a small content of the dispersant, the surface of the SiC single crystal wafer after polishing is rougher, and the contact area is decreased because the particles in the polishing liquid are not uniformly dispersed and the SiC single crystal wafer is not uniformly polished when contacting the particles in the polishing liquid.
From the experimental results of comparative example 3 and example 3, it is understood that the removal rate is decreased when the SiC single wafer is polished due to a small content of the stabilizer, the surface of the SiC single wafer is rougher after polishing, and unstable phenomena such as delamination and coagulation of the abrasive may occur during polishing of the SiC single wafer due to an unstable state of the polishing liquid, and the SiC single wafer cannot be stably polished.
From the experimental results of comparative example 4 and example 2, it is understood that the amount of the abrasive is reduced and the removal rate of the SiC single crystal wafer is lowered when polished.
According to the experimental results of comparative example 5 and example 1, when the grinding time is less than 140h, the initial polishing solution is not optimized to the use condition.
According to the experimental results, the following results are obtained: the same polishing conditions and the same polishing process are used for polishing the same SiC single crystal wafer, the initial polishing solution is used for directly polishing, the initial polishing solution is used for roughly polishing to obtain the water-based polishing solution, compared with the step of polishing the SiC single crystal wafer by using the water-based polishing solution, the SiC single crystal wafer obtained by using the water-based polishing solution has higher removal rate and smaller surface roughness, the reason that the initial polishing solution is firstly roughly polished and then the material is polished is fully explained, the polishing efficiency is higher, the surface of the obtained SiC single crystal wafer is smoother, and the quality is higher, is that: on one hand, after rough polishing treatment, the particle dispersibility of the polishing solution is stronger, which is beneficial to polishing; on the other hand, the surface of the particles in the initial polishing solution is not smooth, and after rough polishing treatment, the surface of the abrasive particles in the polishing solution is smoother, which is beneficial to reducing the damage or scratch generated on the surface of the SiC single crystal wafer; on the other hand, through rough polishing treatment, the matching degree of all components in the polishing solution is improved.
According to the experimental results, the following results are obtained: the stability of the water-based polishing solution is better than that of the initial polishing solution, which shows that after the initial polishing solution is polished, the particles in the polishing solution are dispersed more uniformly, the dispersibility is improved, the polishing solution is more stable, and the phenomenon of agglomeration, sedimentation or layering is not easy to occur.
The embodiments in the present specification are described in a progressive manner, and the same and similar parts among the embodiments are referred to each other, and each embodiment focuses on the differences from the other embodiments. In particular, for the system embodiment, since it is substantially similar to the method embodiment, the description is simple, and for the relevant points, reference may be made to the partial description of the method embodiment.
The above description is only an example of the present application and is not intended to limit the present application. Various modifications and changes may occur to those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.
Claims (9)
1. A SiC single crystal wafer grinding and polishing method comprises the steps of grinding a SiC cutting wafer in sequence to obtain a pre-polished wafer and polishing the pre-polished wafer to obtain the SiC single crystal wafer, and is characterized in that: in the grinding process, the water-based grinding fluid for grinding is obtained by pre-grinding the SiC cutting slice by using the initial grinding fluid and meeting a first condition; in the polishing process, the water-based polishing solution for polishing is obtained by pre-polishing a pre-polished wafer by using an initial polishing solution and performing post-treatment when a second condition is met;
the initial grinding fluid comprises the following raw materials in parts by weight: 0.5-1.2 parts of polymerization inhibitor; 2-4 parts of a dispersing agent; 0.5-1.5 parts of powder lubricant; 15-25 parts of abrasive; the initial polishing solution comprises the following raw materials in parts by weight: 0.1-0.3 part of polymerization inhibitor, 0.2-0.5 part of dispersant, 20-40 parts of stabilizer and 10-20 parts of abrasive;
the first condition is that the thickness of the SiC cutting slice removed after grinding is 1/3-2/3 of the target thickness; and the second condition is that the service time of the initial polishing solution is not less than 140h, and the filtering treatment is carried out.
2. The SiC single crystal wafer polishing method according to claim 1, characterized in that: the polymerization inhibitor comprises one or more than two of benzoquinone, aniline, benzenediol, sodium carboxymethylcellulose, polymaleic acid, polyamino acid, sodium polyacrylate, phosphonic acid carboxylic acid, glycerol and propylene glycol, and the mixture ratio of the two or more than two is arbitrary.
3. The SiC single crystal wafer polishing method according to claim 1, characterized in that: the dispersing agent comprises one or more than two of water glass, sodium tripolyphosphate, sodium hexametaphosphate, sodium pyrophosphate, triethylhexyl phosphoric acid, sodium dodecyl sulfate, methylpentanol, polyacrylamide, Guel gum and polyethylene glycol fatty acid ester, and the mixture ratio of the two or more than two is arbitrary.
4. The SiC single crystal wafer polishing method according to claim 1, characterized in that: the powder lubricant is one or more than two of graphite, hexagonal boron nitride, niobium diselenide and molybdenum disulfide which are mixed in any proportion; the median particle size of the powder lubricant is 5-10 μm; the stabilizer comprises one or more than two of ethanol, propanol, isopropanol, butanol, isobutanol, ethylene glycol, glycerol, glucose, gluconic acid, fructose, mannose and maltose, and the mixture ratio of the two or more than two is arbitrary.
5. The SiC single crystal wafer polishing method according to claim 1, characterized in that: putting the pre-polished wafer into a cleaning solution for ultrasonic auxiliary cleaning before pre-polishing; putting the pre-polished wafer obtained by pre-polishing into a cleaning solution for ultrasonic auxiliary cleaning before polishing; the cleaning solution is one or more of the following solutes: hydrochloric acid, nitric acid, sulfuric acid and hydrofluoric acid, and the mixture ratio of more than two of the above components is arbitrary.
6. The SiC single crystal wafer polishing method according to claim 1, characterized in that: the abrasive is a high-hardness powder material, the median particle size of the high-hardness powder material in the grinding liquid is 10-15 mu m, and the median particle size of the high-hardness powder material in the polishing liquid is 0.5-5 mu m.
7. The SiC single crystal wafer polishing method according to claim 6, characterized in that: the high-hardness powder material contains at least diamond.
8. The SiC single crystal wafer polishing method according to claim 7, characterized in that: the high-hardness powder material also comprises one or more than two of cubic boron nitride, boron carbide and aluminum oxide, and the mixture ratio of the two or more than two is arbitrary.
9. The SiC single crystal wafer polishing method according to claim 1, characterized in that: the filtering treatment condition is that the polishing solution passes through the filter membrane once or for many times, and the aperture range of the filter membrane is 0.5-1 μm.
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| CN201910001876.0A CN109702639B (en) | 2019-01-02 | 2019-01-02 | SiC single crystal wafer grinding and polishing method |
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| CN109702639B true CN109702639B (en) | 2021-02-19 |
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