A method for chemical polishing of a silicon wafer

Abstract

The present application relates to the field of silicon wafer processing, and particularly relates to a chemical polishing method of a silicon wafer, which comprises the following steps: (S.1) coating a layer of liquid sacrificial agent on the surface of the silicon wafer; (S.2) solidifying the sacrificial agent after natural flow leveling, so as to form a sacrificial layer on the surface of the silicon wafer, which can be corroded by a polishing liquid; (S.3) placing the obtained silicon wafer with the sacrificial layer on the surface into the polishing liquid to perform chemical polishing; (S.4) cleaning the silicon wafer after the polishing is completed to obtain a polished silicon wafer. By forming a sacrificial layer on the surface of the silicon wafer, the silicon wafer can be gradually and sequentially chemically corroded and polished from the highest point to the lowest point on the surface during the chemical polishing process, so as to finally form a polished surface with a consistent surface depth and smoothness, and the problem that the corrosion depth of the silicon wafer surface is difficult to control in the traditional chemical polishing method is effectively solved, thereby facilitating the control of the final polishing effect.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of silicon wafer processing, in particular to a chemical polishing method of silicon wafer. BACKGROUND

[0002] At present, the silicon wafer used in the two fields of semiconductor and photovoltaic will be polished in the production process. The existing silicon wafer polishing step is usually divided into three types: mechanical polishing, chemical polishing and chemical mechanical polishing (CMP).

[0003] Among them, the chemical polishing is to use chemical reagent to carry out chemical corrosion polishing on the surface of the silicon wafer, which includes liquid phase, gas phase corrosion, electrolytic polishing, etc. The chemical polishing can carry out small area flattening and polishing of irregular surface. The conventional chemical polishing is to directly immerse the polishing surface to be polished into the polishing liquid. Since the corrosion components in the polishing liquid will corrode the highest point (the most convex point) and the lowest point (the most concave point) of the surface of the silicon wafer at the same time, and the corrosion process is usually longitudinal reaction, it is easy to corrode the deep layer of the silicon wafer, so the peak-valley difference of the surface of the silicon wafer after chemical polishing is still large, and the weight loss of the silicon wafer in the polishing process is large.

[0004] For example, the application number CN201310602911.7 is a kind of single crystal silicon wafer polishing method, solar cell and its manufacturing method. The polishing method is to place the back surface of the single crystal silicon wafer for making back field in the polishing liquid, and the front surface is placed outside the polishing liquid for chemical polishing. By polishing the back surface of the texturing structure, the flatness of the back field of the silicon wafer cell is increased, the reflection of long wave band light in the single crystal silicon back surface in the solar spectrum is increased, the texturing area of the back surface of the silicon wafer and the surface defect state density of the back surface of the silicon wafer are reduced, and the recombination rate of the back surface of the silicon wafer is reduced. The light passing through the silicon wafer is more reflected back to the inside of the silicon wafer, the probability of exciting electron-hole pairs is increased, the open circuit voltage, short circuit current and photoelectric conversion efficiency of the solar cell are improved, and the manufacturing cost is reduced. SUMMARY

[0005] The present application is to overcome the defect that the chemical polishing method in the prior art has great difficulty in depth control of the surface of the silicon wafer, resulting in low surface flatness. Therefore, a chemical polishing method of silicon wafer is provided, which can effectively improve the surface flatness of the silicon wafer after chemical polishing.

[0006] In order to achieve the above-mentioned application purpose, the present application is realized by the following technical scheme:

[0007] A chemical polishing method of silicon wafer, comprising the following steps:

[0008] (S.1) coating a layer of liquid sacrificial agent on the surface of the silicon wafer;

[0009] (S.2) solidifying the sacrificial agent after natural flow leveling, thereby forming a sacrificial layer on the surface of the silicon wafer that can be corroded by the polishing liquid; (S.3) placing the obtained silicon wafer with the sacrificial layer on the surface into the polishing liquid to perform chemical polishing;

[0010] (S.4) cleaning the silicon wafer after the polishing to obtain a polished silicon wafer.

[0011] The conventional chemical polishing is directly immersing the polishing surface to be polished into the polishing liquid. Since the corrosion component in the polishing liquid corrodes the highest point (the most convex point) and the lowest point (the most concave point) on the surface of the silicon wafer at the same time, and the corrosion process is usually longitudinal reaction, it is easy to corrode the deep layer of the silicon wafer, thus the peak-valley difference of the surface of the silicon wafer after the chemical polishing is still large, and the weight loss of the silicon wafer during the polishing is large, and the principle diagram is shown as Figure 1

[0012] The chemical polishing method of the silicon wafer in the present application is obviously different from the conventional chemical polishing method. Before immersing the silicon wafer into the polishing liquid, a sacrificial layer is coated on the surface of the silicon wafer, which can fill the area between the highest point on the surface of the silicon wafer and the lowest point on the surface of the silicon wafer. Since the sacrificial layer can also react with the polishing liquid, the silicon wafer can be gradually corroded from the highest point to the lowest point during the polishing process, and finally a polished surface with uniform surface depth and smoothness is formed, thus effectively solving the problem that the corrosion depth of the conventional chemical polishing method is difficult to control. At the same time, since the surface of the silicon wafer is protected by the sacrificial layer, the chemical corrosion polishing only starts from the highest point on the surface of the silicon wafer during the polishing process, and the polishing step can be ended when the chemical corrosion polishing reaches the lowest point on the surface of the silicon wafer, thus effectively overcoming the problem of excessive weight loss caused by the polishing.

[0013] As a preferred embodiment, the sacrificial agent comprises a curable organic polysiloxane material.

[0014] The polysiloxane material can effectively react with the conventional concentrated alkali type polishing liquid and the hydrogen fluoride type polishing liquid, thus the corrosion speed of the low point on the surface of the silicon wafer can be controlled, the low point on the surface of the silicon wafer can be protected before the high point on the surface of the silicon wafer is corroded, and the peak-valley difference between the high point on the surface of the silicon wafer and the low point on the surface of the silicon wafer can be greatly reduced, i.e. the flatness of the surface of the silicon wafer is greatly improved.

[0015] As a preferred embodiment, the curable organic polysiloxane material is any one of a thermally cured silicone material, a light cured silicone material, and a moisture cured silicone material.

[0016] As a further preferred embodiment, the thermally cured silicone material can be selected from a condensation type silicone material or an addition type silicone material.

[0017] ​As a preference, the sacrificial agent further comprises a corrosion rate control agent.

[0018] Since there is a gap between the reaction rate of the sacrificial layer and the acid or base in the polishing solution and the reaction rate of the silicon wafer and the acid or base, it is necessary to control the reaction rate of the sacrificial layer to be close to the reaction rate of the silicon wafer, so as to facilitate the control of the final polishing effect.

[0019] As a preference, the corrosion rate control agent is polysiloxane.

[0020] Polysiloxane is prone to decomposition under acid or base conditions, thereby increasing the corrosion rate of the sacrificial layer, so that the etching rate of the sacrificial layer matches the silicon wafer.

[0021] As a further preference, the polysiloxane comprises any one or a combination of alkoxyl, hydroxyl, carboxyl, silicon hydride, vinyl, propylene, acrylic, acetyl, and epoxy groups.

[0022] Polysiloxane is a compound containing -B-O-Si- bonds in the molecule, and the combination of any one or more of alkoxyl, hydroxyl, carboxyl, silicon hydride, vinyl, propylene, acrylic, acetyl, and epoxy groups in polysiloxane helps it to participate in the curing reaction with the sacrificial agent.

[0023] As a preference, the addition amount of the polysiloxane is 2% to 15% of the mass of the curable organopolysiloxane-based material.

[0024] The content of polysiloxane has a significant relationship with the reaction rate of the sacrificial layer and the acid or base in the polishing solution. Under general conditions, the higher the content of polysiloxane, the faster the corrosion rate of the sacrificial layer by the acid or base. Through experiments, the addition amount of polysiloxane is between 2% and 15%, that is, the corrosion rate of the sacrificial layer can be effectively controlled to be the same as the corrosion rate of the silicon wafer, and too much or too little will cause the etching rates of the two to be mismatched.

[0025] As a preference, the polysiloxane is obtained by hydrolytic polycondensation of boric acid and alkoxysilane or chlorosilane.

[0026] As a preference, the polysiloxane is obtained by reacting dimethyl chlorosilane with hydroxyethyl acrylate to obtain a dimethyl silane compound containing an acrylic structure, and then condensing the dimethyl silane compound with an equimolar amount of trimethyl borate under the catalysis of tris(pentafluorophenyl)borate.

[0027] As a preference, the polishing solution is an alkali solution or a hydrofluoric acid solution.

[0028] As a further preference, 10 to 30 g of alkali, 1 to 5 g of surfactant, 0 to 10 g of oxidant, and 0 to 5 g of auxiliary additive are included in every 1 L of the alkali solution.

[0029] As further preferred, the base in the base solution is any one or a combination of sodium hydroxide, potassium hydroxide, cesium hydroxide, lithium hydroxide, rubidium hydroxide, sodium methoxide, sodium ethoxide, potassium ethoxide, sodium tert-butoxide, and a quaternary ammonium base.

[0030] As further preferred, the oxidizing agent in the base solution is any one or a combination of hydrogen peroxide and sodium nitrate.

[0031] As further preferred, the auxiliary additive in the base solution is any one or a combination of sodium fluoride, ammonium fluoride, and sodium phosphate.

[0032] As further preferred, the hydrofluoric acid solution can comprise, by weight, 10-20 parts of 40% hydrofluoric acid, 5-7 parts of 60% nitric acid, 1-1.5 parts of glacial acetic acid, 0-5 parts of tartaric acid, and 0-10 parts of a surfactant per 1 L of the hydrofluoric acid solution.

[0033] As preferred, the polishing temperature in the step (S.3) is 30-85°C, and the polishing time is 1.5-3 min.

[0034] Therefore, the present application has the following advantages: by forming a sacrificial layer on the surface of the silicon wafer, the silicon wafer can be gradually and sequentially subjected to chemical etching polishing from the highest point to the lowest point on the surface during chemical polishing, and a polished surface with a uniform surface depth and smoothness is finally formed, effectively solving the problem that the etching depth of the silicon wafer surface is difficult to control in the conventional chemical polishing method, thereby facilitating the control of the final polishing effect. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 is a schematic diagram of the conventional chemical polishing method.

[0036] Figure 2 is a schematic diagram of the chemical polishing method of the silicon wafer provided by the present application.

[0037] Figure 3 is a tower base diagram of the polished silicon wafer in Example 1.

[0038] Figure 4 is a reflectivity diagram of the polished silicon wafer in Example 1.

[0039] Figure 5 is a tower base diagram of the polished silicon wafer in Example 2.

[0040] Figure 6 is a reflectivity diagram of the polished silicon wafer in Example 2.

[0041] Figure 7 is a tower base diagram of the polished silicon wafer in Example 3.

[0042] Figure 8 Figure 4 is a reflectance plot of the polished silicon wafer of Example 3.

[0043] Figure 9 Figure 5 is a Tauc plot of the polished silicon wafer of Example 3.

[0044] Figure 10 Figure 6 is a reflectance plot of the polished silicon wafer of Example 3.

[0045] Figure 11 Figure 7 is a Tauc plot of the polished silicon wafer of Example 4.

[0046] Figure 12 Figure 8 is a reflectance plot of the polished silicon wafer of Example 4.

[0047] Figure 13 Figure 9 is a Tauc plot of the polished silicon wafer of Example 5.

[0048] Figure 14 Figure 10 is a reflectance plot of the polished silicon wafer of Example 5.

[0049] Figure 15 Figure 5 is a Tauc plot of the polished silicon wafer of Example 3. DETAILED DESCRIPTION

[0050] The present application will be further described with reference to the following examples. Persons skilled in the art will be able to implement the present application based on the description and examples. Furthermore, the examples of the present application described in the following description are generally only exemplary and explanatory for the present application and are not intended to be limiting of the present application in all aspects. Therefore, it will be appreciated that all modifications, equivalents and alternatives falling within the scope of the present application are included in the present application.

[0051] General Examples

[0052] As shown in Figure 1 is a flow chart of the polishing process of the present application. The present application provides a chemical polishing method of a silicon wafer, which comprises the following steps: Figure 2 (S.1) coating a liquid sacrificial agent on the surface of the silicon wafer;

[0053] (S.2) solidifying the sacrificial agent after natural flow leveling, thereby forming a sacrificial layer on the surface of the silicon wafer, which can be corroded by the polishing liquid;

[0054] (S.3) placing the obtained silicon wafer with the sacrificial layer on the surface into the polishing liquid for chemical polishing;

[0055] (S.4) cleaning the silicon wafer after polishing to obtain a polished silicon wafer.

[0056] Since the effective component in the polishing liquid is concentrated alkali or hydrofluoric acid, the sacrificial agent in the present application is preferably a material that can react with conventional alkali and hydrofluoric acid. Preferably, the sacrificial agent includes a curable organopolysiloxane material. The curable organopolysiloxane material can simultaneously react with alkali and hydrofluoric acid, and thus is corroded and polished.

[0057] Since the sacrificial agent is required to fill the protrusions and recesses of the silicon wafer, the sacrificial agent in the present application is required to be a liquid silicone material with viscosity within a certain range. In some embodiments, a curable organopolysiloxane material with average viscosity (cSt) of 10-30000 is usually selected. When the viscosity is too low, the thickness of the sacrificial layer is small, and the protrusions and recesses of the silicon wafer cannot be quickly filled. When the viscosity is too high, the protrusions and recesses of the silicon wafer cannot be quickly filled, and bubbles are easily generated in the thin film and are difficult to remove.

[0058] In some embodiments, the curable organopolysiloxane material is any one of a thermally curable silicone material, a light curable silicone material, and a moisture curable silicone material.

[0059] Further, the thermally curable silicone material can be a condensation type silicone material or an addition type silicone material.

[0060] Specifically, the condensation type silicone material can be an organosilicon material containing an alkoxy group in the molecule, such as an alkoxy group-containing methyl-phenyl silicone resin, an MQ resin, or a hyperbranched polysiloxane polyester and composition.

[0061] For example, tetraalkoxysilane (e.g., tetraethoxysilane), trialkoxysilane (e.g., methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, or phenyltrimethoxysilane), dialkoxysilane (e.g., dimethyldimethoxysilane, dimethyldiethoxysilane, methylphenyldimethoxysilane, methylethyldiethoxysilane, or methylvinyl dimethoxysilane), and a blocking agent (hexamethyldisiloxane, hexaphenyl disiloxane, tetramethyldivinyl dimethoxysilane, or tetramethyldimethoxysilane) are catalytically hydrolyzed in hydrochloric acid to obtain a polymer. The polymer itself can undergo crosslinking reaction at high temperature to cure the sacrificial layer, or the polymer is mixed with other crosslinking agents (e.g., organotin) to quickly cure at high temperature.

[0062] The condensation type silicone material can also be a ketoxime group-containing ketoxime group-containing polysiloxane or a peroxide type polysiloxane or a composition containing components thereof.

[0063] The addition type silicone material is a resin or a combination thereof which is cured by a hydrosilylation reaction within the molecule or the combination. For example, a silicone oil or a silicone resin containing a silicon-hydrogen structure can be used to react with a silicone oil or a silicone resin containing a vinyl structure in the presence of a platinum catalyst to form a film by a hydrosilylation reaction.

[0064] The photo-curable silicone material can use a silicone compound containing a photosensitive group within the molecule, such as a silicone compound or a combination thereof containing a vinyl group, a propenyl group, an acrylic group, a methacrylic group, an acetyl group, or an epoxy group. The silicone compound or the combination thereof is mixed with a photo-initiator and then cured under ultraviolet light to form the sacrificial layer.

[0065] The moisture-curable silicone material is similar to the heat-curable silicone material in terms of the raw material components. A silicone material or a ketoxime polysiloxane containing an alkoxy group within the molecule or the combination can be used, and an organotin crosslinking agent can be added to ensure rapid curing.

[0066] Since the reaction rate of the wafer with the active components in the polishing solution is usually different from the reaction rate of the organic silicone material with the active components in the polishing solution, and the reaction rate of the organic silicone material with the active components in the polishing solution is usually slower, in some embodiments, a certain amount of etching rate control agent is added to the sacrificial agent to balance the reaction rates of the wafer and the sacrificial layer. The etching rate control agent can be a polyborosiloxane which is easily decomposed under acid or base conditions to increase the etching rate of the sacrificial layer so that the etching rate of the sacrificial layer matches the etching rate of the wafer.

[0067] The polyborosiloxane is a compound containing a -B-O-Si- bond in the molecule. In some embodiments, the polyborosiloxane contains an alkoxy group, a hydroxyl group, a carboxyl group, a silicon-hydrogen group, a vinyl group, a propenyl group, an acrylic group, an acetyl group, an epoxy group, or the like to participate in the curing reaction with the sacrificial agent.

[0068] In addition, the content of the polyborosiloxane has a significant relationship with the reaction rate of the sacrificial layer with the acid or the base. Under normal conditions, the higher the content of the polyborosiloxane, the faster the etching rate of the sacrificial layer under the acid or the base. Through experiments, the addition amount of the polyborosiloxane is between 2% and 15% to effectively control the etching rate of the sacrificial layer to be the same as the etching rate of the wafer. Too much or too little will cause the etching rates of the sacrificial layer and the wafer to be mismatched.

[0069] The polishing solution in the present application is an alkaline solution or a hydrofluoric acid solution.

[0070] The base in the base solution is any one or a combination of sodium hydroxide, potassium hydroxide, cesium hydroxide, lithium hydroxide, rubidium hydroxide, sodium methoxide, sodium ethoxide, potassium ethoxide, sodium tert-butoxide, and quaternary ammonium base. Further preferably, the quaternary ammonium base is any one or a combination of tetramethylammonium hydroxide, trimethylethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetramethylammonium fluoride, hexamethonium hydroxide, and benzyltrimethylammonium hydroxide. Generally, 10-30 g of base, 1-5 g of surfactant, 0-10 g of oxidant, and 0-5 g of auxiliary additive are included in 1 L of the base solution. Further preferably, the oxidant in the base solution is any one or a combination of hydrogen peroxide and sodium nitrate. Further preferably, the auxiliary additive in the base solution is any one or a combination of sodium fluoride, ammonium fluoride, and sodium phosphate.

[0071] The main effective component in the hydrofluoric acid solution is hydrofluoric acid, and a certain amount of nitric acid, tartaric acid, glacial acetic acid, and surfactant can also be included. Generally, 10-20 parts of 40% hydrofluoric acid, 5-7 parts of 60% nitric acid, 1-1.5 parts of glacial acetic acid, 0-5 parts of tartaric acid, and 0-10 parts of surfactant are included in 1 L of the hydrofluoric acid solution. Specific embodiments

[0073] Example 1

[0074] As shown in Figure 2 A chemical polishing method of a silicon wafer includes the following steps:

[0075] (S.1) coating a layer of liquid sacrificial agent on the surface of the silicon wafer;

[0076] (S.2) curing the sacrificial agent after natural flow leveling to form a sacrificial layer on the surface of the silicon wafer, which can be corroded by the polishing liquid;

[0077] (S.4) cleaning the silicon wafer after polishing to obtain a polished silicon wafer.

[0078] The sacrificial agent is composed of 8 wt% of polyborosiloxane and the rest of thermally cured silicone resin. The sacrificial agent is cured by heating at 120°C for 5 min.

[0079] The polyborosiloxane is obtained by hydrolytic polycondensation of 5 parts of boric acid, 18 parts of phenyltrimethoxysilane, 25 parts of dimethyldiethoxysilane, and 10 parts of hexamethyldisiloxane under the catalysis of acid clay.

[0080] The thermally cured silicone resin is an MQ resin obtained by hydrolytic polycondensation of 50 parts of tetraethoxysilane and 10 parts of hexamethyldisiloxane under the catalysis of hydrochloric acid.

[0081] The polishing liquid is an alkaline solution containing 15 g of sodium hydroxide, 2 g of sodium octadecyl sulfonate, 5 g of hydrogen peroxide, and 3 g of ammonium fluoride per 1 L of the alkaline solution. The polishing temperature of the silicon wafer is 75°C, and the polishing time is 3 min. The pyramid pattern of the polished silicon wafer in this example is shown in FIG. 2. The reflectivity of the polished silicon wafer in this example is shown in FIG. 3. Figure 3 Figure 4

[0082] Example 2

[0083] The difference between this example and Example 1 is that:

[0084] The sacrificial agent is composed of 2 wt% of polyborosiloxane and the balance of thermally cured silicone resin.

[0085] The polyborosiloxane is obtained by hydrolytic polycondensation of 5 parts of boric acid, 25 parts of dimethyldichlorosilane, 20 parts of diphenyldichlorosilane, and 2 parts of phenyltrichlorosilane.

[0086] The thermally cured silicone resin is prepared from 15 parts of phenyltrimethoxysilane, 25 parts of dimethyldiethoxysilane, and 10 parts of hexamethyldisiloxane under the catalysis of acid clay.

[0087] After 0.05% of dibutyltin dilaurate is added to the mixture of the polyborosiloxane and the thermally cured silicone resin, the sacrificial agent is cured by heating at 105°C for 3 min.

[0088] The polishing liquid is an alkaline solution containing 30 g of sodium hydroxide, 5 g of sodium octadecyl sulfonate, and 1 g of ammonium fluoride per 1 L of the alkaline solution. The polishing temperature of the silicon wafer is 85°C, and the polishing time is 2 min. The other conditions are the same as in Example 1. The pyramid pattern of the polished silicon wafer in this example is shown in FIG. 6. The reflectivity of the polished silicon wafer in this example is shown in FIG. 7. Figure 5 Figure 6

[0089] Example 3

[0090] The difference between this example and Example 1 is that:

[0091] The sacrificial agent is composed of 15 wt% of polyborosiloxane containing an acrylic group, 1% of a photoinitiator 1173, and the balance of a photocured silicone resin.

[0092] The polyborosiloxane containing an acrylic group is prepared by the following method: 0.5 mol of dimethylchlorosilane is reacted with 0.5 mol of hydroxyethyl acrylate to obtain a dimethylsilane compound containing an acrylic structure, and the dimethylsilane compound is condensed with an equimolar amount of trimethyl borate under the catalysis of tris(pentafluorophenyl)borate to obtain the polyborosiloxane containing an acrylic group. ​​​​

[0093] The photocuring silicone resin is obtained by mixing and hydrolyzing 10 parts of tetraethoxysilane, 50 parts of dimethyldimethoxysilane, 10 parts of γ-methacryloxypropyltrimethoxysilane and 20 parts of phenyltrimethoxysilane.

[0094] The polyborosiloxane containing acrylic groups, the photocuring silicone resin and the photoinitiator 1173 are irradiated under ultraviolet light for 30 seconds, and the curing is completed. The other conditions are the same as in Example 1. The tower base pattern of the polished silicon wafer in this example is shown in Figure 7 The reflectivity of the polished silicon wafer in this example is shown in Figure 8

[0095] Example 4

[0096] The difference between this example and Example 1 is that:

[0097] The sacrificial agent is composed of 15 wt% of the polyborosiloxane containing acrylic groups, 1% of the photoinitiator 1173 and the rest of the photocuring silicone resin.

[0098] The polyborosiloxane containing acrylic groups is prepared by reacting 1.5 mol of dimethylchlorosilane with 0.5 mol of boric acid to obtain a borosiloxane compound containing silicon-hydrogen structure, and condensing the borosiloxane compound with pentaerythritol triacrylate under the catalysis of tris(pentafluorophenyl)borate to obtain the polyborosiloxane containing acrylic groups.

[0099] The photocuring silicone resin is obtained by mixing and hydrolyzing 10 parts of tetraethoxysilane, 50 parts of dimethyldimethoxysilane, 10 parts of γ-methacryloxypropyltrimethoxysilane and 20 parts of phenyltrimethoxysilane.

[0100] The polyborosiloxane containing acrylic groups, the photocuring silicone resin and the photoinitiator 1173 are irradiated under ultraviolet light for 30 seconds, and the curing is completed.

[0101] The polishing solution is an alkali solution containing 10 g of sodium hydroxide, 1 g of sodium octadecyl sulfonate, 10 g of hydrogen peroxide and 5 g of sodium fluoride per 1 L of the alkali solution. The polishing temperature of the silicon wafer is 85°C, and the polishing time is 1.5 minutes. The other conditions are the same as in Example 1.

[0102] Example 5

[0103] As shown in Figure 2 A method for chemically polishing a silicon wafer, comprising the following steps:

[0104] (S.1) coating a layer of liquid sacrificial agent on the surface of the silicon wafer;

[0105] ​(S.2) solidifying the sacrificial agent after natural flow leveling, thereby forming a sacrificial layer on the surface of the silicon wafer which can be corroded by the polishing liquid; (S.3) placing the silicon wafer with the sacrificial layer on the surface into the polishing liquid to perform chemical polishing;

[0106] (S.4) cleaning the silicon wafer after polishing to obtain a polished silicon wafer.

[0107] The sacrificial agent is composed of 15wt% of polyborosiloxane, 1% of photoinitiator 1173 and the rest of photo-curable silicone resin.

[0108] The polyborosiloxane is prepared by the following method: reacting 1.5 mol of dimethylchlorosilane with 0.5 mol of boric acid to obtain a borosiloxane compound containing a silicon-hydrogen structure, and condensing the borosiloxane compound with pentaerythritol triacrylate under the catalysis of tris(pentafluorophenyl)borate to obtain polyborosiloxane containing acryl groups.

[0109] The photo-curable silicone resin is obtained by mixing and hydrolyzing 10 parts of tetraethoxysilane, 50 parts of dimethyldimethoxysilane, 10 parts of γ-methacryloyloxypropyltrimethoxysilane and 20 parts of phenyltrimethoxysilane.

[0110] The polyborosiloxane containing acryl groups, the photo-curable silicone resin and the photoinitiator 1173 are irradiated under ultraviolet light for 30 seconds, and the solidification is completed.

[0111] The polishing liquid is a hydrofluoric acid solution, and the composition of 1 L of the hydrofluoric acid solution is as follows: 15 parts of 40% hydrofluoric acid, 5 parts of 60% nitric acid, 1 part of glacial acetic acid, 3 parts of tartaric acid and 5 parts of sodium octadecyl benzene sulfonate. The polishing temperature of the silicon wafer is 30°C, and the polishing time is 3 minutes. The silicon wafer after polishing in this embodiment is shown in FIG. 2. Figure 15

[0112] Example 6

[0113] The difference between this embodiment and Example 5 is that:

[0114] The polishing liquid is a hydrofluoric acid solution, and the composition of 1 L of the hydrofluoric acid solution is modified as follows: 20 parts of 40% hydrofluoric acid, 7 parts of 60% nitric acid and 1.5 parts of glacial acetic acid. The polishing time of the silicon wafer is replaced with 1.5 minutes. The others are the same as in Example 5.

[0115] Example 7

[0116] The difference between this embodiment and Example 5 is that:

[0117] ​The polishing liquid is a hydrofluoric acid solution, and the composition of each 1 L of the hydrofluoric acid solution is modified as follows: 10 parts of 40% hydrofluoric acid, 5 parts of 60% nitric acid, 1 part of glacial acetic acid, 5 parts of tartaric acid, and 10 parts of sodium octadecyl benzene sulfonate. The polishing time of the silicon wafer is replaced by 160 s. The others are the same as in Example 5.

[0118] Example 8

[0119] The difference between this example and Example 1 is that:

[0120] In the mixture of polyborosiloxane and MQ resin, 1% of dibutyltin dilaurate is added, and then it is placed at room temperature for 15 h to solidify into a film. The others are the same as in Example 1.

[0121] Comparative Example 1

[0122] The difference between this comparative example and Example 1 is that:

[0123] In this comparative example, the silicon wafer with no sacrificial agent coated on the surface is placed in a polishing liquid for chemical polishing. After polishing, the silicon wafer is cleaned to obtain a polished silicon wafer. The polishing liquid is an alkali solution containing 15 g of sodium hydroxide, 2 g of sodium octadecyl sulfonate, 5 g of hydrogen peroxide, and 3 g of ammonium fluoride in each 1 L of the alkali solution. The others are the same as in Example 1. The wafer map of the polished silicon wafer in this comparative example is shown in Figure 9 . The reflectivity of the polished silicon wafer in this comparative example is shown in Figure 10 .

[0124] Comparative Example 2

[0125] The difference between this comparative example and Example 5 is that:

[0126] In this comparative example, the silicon wafer with no sacrificial agent coated on the surface is placed in a polishing liquid for chemical polishing. After polishing, the silicon wafer is cleaned to obtain a polished silicon wafer. The polishing liquid is a hydrofluoric acid solution, and the composition of each 1 L of the hydrofluoric acid solution is as follows: 15 parts of 40% hydrofluoric acid, 5 parts of 60% nitric acid, 1 part of glacial acetic acid, 3 parts of tartaric acid, and 5 parts of sodium octadecyl benzene sulfonate. The others are the same as in Example 5.

[0127] Comparative Example 3

[0128] The difference between this comparative example and Example 1 is that:

[0129] The sacrificial agent is composed of 1 wt% of polyborosiloxane and the rest of thermally cured silicone resin. The others are the same as in Example 1. The wafer map of the polished silicon wafer in this comparative example is shown in Figure 11 . The reflectivity of the polished silicon wafer in this comparative example is shown in Figure 12 .

[0130] Comparative Example 4

[0131] The difference between this comparative example and Example 1 is as follows:

[0132] The sacrificial agent consists of 20 wt% polyborosiloxane and the remainder is thermosetting silicone resin. Everything else is the same as in Example 1. The polished silicon wafer tower base diagram in this comparative example is shown below. Figure 13 As shown. The reflectivity of the polished silicon wafer in this comparative example is as follows. Figure 14 As shown.

[0133] Comparative Example 5

[0134] The difference between this comparative example and Example 5 is as follows:

[0135] The sacrificial agent consists of 1 wt% polyborosiloxane and the remainder is photocurable silicone resin. Everything else is the same as in Example 5.

[0136] Comparative Example 6

[0137] The difference between this comparative example and Example 5 is as follows:

[0138] The sacrificial agent consists of 20 wt% polyborosiloxane and the remainder is photocurable silicone resin. Everything else is the same as in Example 5.

[0139] The silicon wafers were chemically polished according to the polishing methods in Examples 1-8 and Comparative Examples 1-6, respectively. The weight reduction of the silicon wafers after polishing and the changes in reflectivity before and after polishing are shown in Table 1 below.

[0140] Table 1

[0141] Group Reflectance before polishing (%) Reflectance after polishing (%) Weight loss (g) Example 1 10.412 45.890 0.211 Example 2 10.415 45.586 0.215 Example 3 10.417 45.510 0.221 Example 4 10.419 45.515 0.219 Example 5 10.432 45.352 0.232 Example 6 10.435 45.364 0.234 Example 7 10.433 45.376 0.237 Example 8 10.434 45.391 0.235 Comparative Example 1 10.420 39.542 0.412 Comparative Example 2 10.431 39.534 0.453 Comparative Example 3 10.421 42.147 0.321 Comparative Example 4 10.423 43.732 0.325 Comparative Example 5 10.436 40.763 0.353 Comparative Example 6 10.438 41.483 0.357 .

[0142] From Table 1 and Figures 3 to 8 , Figure 15 Analysis revealed that, under the same weight reduction conditions (approximately 0.2g), silicon wafers polished in an alkaline solution exhibited larger base dimensions (11.37–13.65 μm), more regular base shapes, fewer missing corners, flatter surfaces, and fewer black cores. Furthermore, the wafers showed a uniform and clean appearance, free of air bubbles and dirt residue. The polished wafers also exhibited higher reflectivity, exceeding 45%. In contrast, silicon wafers polished in a hydrofluoric acid solution (Example 5) displayed a caterpillar-like surface structure, with more corrosion pits and less flatness compared to those polished in the alkaline solution.

[0143] From Table 1 and Figures 3 to 4 , Figures 9 to 14From the above analysis, it can be seen that when the silicon wafer without coating the surface with the sacrificial agent is placed in the polishing solution composed of the alkali solution to perform chemical polishing (Comparative Example 1), the weight loss of the polished silicon wafer is relatively large, and the size of the silicon wafer is relatively small, and there are a small amount of obvious black cores. When the concentration of the polysiloxane added in the sacrificial agent is too low (less than 2%) (Comparative Example 3), it can be found that the size of the silicon wafer after polishing in the polishing solution composed of the alkali solution is too small. When the concentration of the polysiloxane added in the sacrificial agent is too high (more than 15%) (Comparative Example 4), it can be observed that the size of the silicon wafer after polishing in the polishing solution composed of the alkali solution is relatively large (close to Examples 1-3), but the line mark is relatively obvious, and the treatment effect at the line mark is poor.

[0144] The above only describes the preferred embodiments and principles of the present application in detail. For those skilled in the art, the specific implementation manner can be changed according to the idea provided by the present application, and these changes should be considered as the protection scope of the present application.

Claims

1. A method for chemical polishing of a silicon wafer, characterized by, The method comprises the following steps: (S.1) coating a layer of liquid sacrificial agent on the surface of a silicon wafer; (S.2) curing the sacrificial agent after natural flow leveling, thereby forming a sacrificial layer on the surface of the silicon wafer, which can be corroded by a polishing liquid; the sacrificial agent comprises a curable organopolysiloxane material, which is any one of a thermally curable silicone material, a light curable silicone material, and a moisture curable silicone material; the sacrificial agent further comprises a corrosion rate control agent, which is a polyborosiloxane, and the addition amount of the polyborosiloxane is 2% to 15% of the mass of the curable organopolysiloxane material; (S.3) placing the obtained silicon wafer with a sacrificial layer on the surface into a polishing liquid for chemical polishing; (S.4) cleaning the silicon wafer after polishing, thereby obtaining a polished silicon wafer.

2. The chemical polishing method of a silicon wafer according to claim 1, characterized in that the polyborosiloxane is obtained by hydrolytic polycondensation of boric acid and alkoxysilane or chlorosilane.

3. The chemical polishing method of a silicon wafer according to claim 1, characterized in that the polyborosiloxane is obtained by reacting dimethyl chlorosilane with hydroxyethyl acrylate to obtain a dimethyl silane compound containing an acrylic acid structure, and then condensing the dimethyl silane compound with equimolar trimethyl borate under the catalysis of tris(pentafluorophenyl)boric acid ester.

4. The chemical polishing method of a silicon wafer according to claim 1, characterized in that the polishing liquid is an alkali solution or a hydrofluoric acid solution.

5. The chemical polishing method of a silicon wafer according to claim 1, characterized in that the polishing temperature in step (S.3) is 30 to 85°C, and the polishing time is 1.5 to 3 minutes. ​ ​ ​ ​

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