Manganese dioxide grinding fluid, preparation method and grinding method

Abstract

The invention discloses a manganese dioxide grinding liquid, a preparation method and a grinding method. The preparation method comprises the following steps: stirring and dissolving a surfactant in deionized water to obtain a dispersion liquid; manganese dioxide powder and the dispersion liquid are mixed, and manganese dioxide slurry is obtained through high-energy ball milling process treatment; adding a wetting agent and a pH buffering agent into the manganese dioxide slurry; filtering to remove large particles to obtain manganese dioxide slurry with high monodispersity; mixing an oxidizing agent with the manganese dioxide slurry obtained in the previous step, and adjusting the pH value to obtain a manganese dioxide grinding liquid; the manganese dioxide grinding fluid comprises the following components in percentage by weight: 10-20% of manganese dioxide powder, 0.2-5% of an oxidizing agent, 2-5% of a dispersing agent, 0.2-8% of a wetting agent, 0.2-2% of a pH regulator and the balance of deionized water. When the grinding fluid is used for CMP, the processing loss of a SiC substrate is reduced, and the Si surface of the SiC substrate meets the processing requirements of low roughness and no scratch under the condition of high material removal rate.

Description

Technical Field

[0001] The invention belongs to the technical field of polishing liquid, and in particular relates to a manganese dioxide polishing liquid used in a double-sided synchronous polishing process of a silicon carbide substrate, a preparation method and a polishing method. Background Art

[0002] Single-crystal SiC materials exhibit excellent electrical properties in extreme environments such as high pressure, high temperature and high radiation, making semiconductor power devices based on SiC substrates key components of equipment such as 5G communications, new energy vehicles and rail transportation. However, the processing efficiency and manufacturing cost of single-crystal SiC substrates limit the further application and promotion of SiC-based power devices in related fields. At present, chemical mechanical polishing (CMP) technology is the only technology recognized by the global integrated circuit field to achieve substrate flattening processing. In the processing of semiconductor substrates, the CMP process is mainly divided into single-sided polishing process and double-sided simultaneous polishing process.

[0003] In order to improve the processing efficiency of silicon carbide, the double-sided synchronous grinding process is often used in current industrial production to process silicon carbide substrates. However, since the production of silicon carbide devices is completed on the Si surface, the processing requirements for the Si surface of the silicon carbide substrate are much higher than those for the C surface. The grinding fluid is a key consumable in the CMP process and also plays a decisive role in the effect of CMP processing. The grinding fluid used for CMP processing of SiC substrates mainly contains components such as abrasive particles, oxidants, pH regulators, surfactants and special catalysts. At present, SiC-CMP often uses grinding fluids with aluminum oxide or silicon dioxide as abrasive particles.

[0004] When the above-mentioned polishing liquid is used for the double-sided synchronous polishing process, due to the anisotropy of the SiC crystal, the material removal rate of the C surface is much higher than that of the Si surface, and the removal rate ratio reaches about 3:1. However, in CMP, in order to remove the scratches introduced by the previous processing of the Si surface, the removal amount of the Si surface generally needs to reach 2-3um, which means that the removal amount of the C surface reaches 5-10um. Therefore, the current double-sided synchronous polishing process has the disadvantage of high processing loss.

[0005] Traditional grinding fluids also have the following disadvantages: 2 O 3 The abrasive particles have high hardness and are easy to agglomerate in aqueous solution to form large particles. During the CMP process, such abrasive particles with high hardness and large particles are easy to introduce new scratches on the substrate surface, resulting in limited processing yield of mass production of SiC substrates. 2 The abrasive grain hardness is low, SiO 2 The material removal rate when grinding SiC with abrasive slurries is low, resulting in higher processing time and cost. Summary of the invention

[0006] The purpose of the present invention is to solve the problems in the prior art and to provide a manganese dioxide polishing liquid, a preparation method and a polishing method for a double-sided synchronous polishing process of a silicon carbide substrate.

[0007] To achieve the above object, the present invention proposes a method for preparing a manganese dioxide polishing liquid for a double-sided synchronous polishing process of a silicon carbide substrate, comprising the following steps: stirring and dissolving the surfactant in deionized water to obtain a dispersion; The manganese dioxide powder and the dispersion are mixed, and subjected to a high-energy ball milling process to obtain a manganese dioxide slurry; Adding a wetting agent and a pH buffer into the manganese dioxide slurry; Filtering and removing large particles in the slurry so that the particle size of the manganese dioxide particles in the slurry does not exceed 300 nm, and obtaining a manganese dioxide slurry with high monodispersity, wherein the particle size dispersion index (PDI) value of the manganese dioxide slurry with high monodispersity is less than 0.3; The oxidant is mixed with a manganese dioxide slurry having high monodispersity, and the pH value is adjusted to 8-10.5 to obtain a manganese dioxide polishing liquid, which is composed of the following components in weight percentage: 10-20wt.% of manganese dioxide powder, 0.2-5wt.% of oxidant, 2-5wt.% of dispersant, 0.2-8wt.% of wetting agent, 0.2-2wt.% of pH adjuster, and the balance is deionized water.

[0008] Optionally, the high-energy ball milling process is carried out in a ball mill, the rotation speed of the ball mill is set to 400rpm-800rpm, the revolution speed is set to 200rpm-400rpm, the ball milling temperature is set to 30℃-40℃, and the diameter of the grinding balls in the grinding process is set to 0.6mm-1.6mm.

[0009] Optionally, the particle size of the manganese dioxide particles is in the range of 100 nm to 200 nm.

[0010] Optionally, the mass ratio of the manganese dioxide powder to the dispersion is (2-5):1.

[0011] The embodiment of the present invention also provides a manganese dioxide polishing liquid prepared by the above preparation method, wherein the manganese dioxide polishing liquid is composed of the following components in weight percentage: manganese dioxide powder 0.5-20wt.%, oxidant 0.2-5wt.%, dispersant 0.1-5wt.%, wetting agent 0.2-8wt.%, pH regulator 0.2-2wt.%, and deionized water as the balance.

[0012] Optionally, the oxidant is one or more of potassium perchlorate, potassium permanganate, potassium periodate, and potassium persulfate; the pH adjuster is one or more of potassium hydroxide, sodium hydroxide, ammonia water, tetramethylammonium hydroxide, dilute phosphoric acid, citric acid, and dilute hydrochloric acid; and the wetting agent is one or more of ethanol, hydroxyethyl cellulose, polycarboxylates, succinates, and polycarboxylic acid-type combing copolymer surfactants.

[0013] Optionally, the dispersant is a polymer surfactant, which includes at least one of a glycolipid surfactant, a lipopeptide surfactant, and a phospholipid surfactant.

[0014] The embodiment of the present invention further provides a method for synchronously polishing double sides of a silicon carbide substrate, comprising: performing synchronously polishing double sides of a silicon carbide substrate using the above-mentioned manganese dioxide polishing liquid.

[0015] Optionally, the grinding process conditions are as follows: manganese dioxide grinding liquid flow rate is 150mL / min-300mL / min, grinding disc speed is 40rpm-80rpm, grinding head speed is 40rpm-80rpm, grinding head swing is 10mm-15mm, and grinding pressure is 2.5psi-4psi.

[0016] Optionally, during the process of double-sided synchronous polishing of the silicon carbide substrate by the manganese dioxide polishing liquid, the manganese dioxide polishing liquid is continuously stirred by a mechanical stirrer and delivered to the surface of the polishing pad by a peristaltic pump, and the surface temperature of the polishing pad is 28°C-35°C during the polishing process.

[0017] The beneficial effects of the present invention are as follows: when the manganese dioxide polishing liquid prepared by the present invention is used in the double-sided synchronous polishing process of a silicon carbide substrate, the C / Si surface removal rate ratio can be reduced to below 1.5:1 without sacrificing the Si surface processing efficiency, thereby reducing the processing loss of the SiC substrate and improving the processing efficiency of the SiC substrate; after the SiC substrate is polished with the polishing liquid, the Si surface of the SiC substrate can meet the processing requirements of low roughness and no scratches under the condition of a high material removal rate, thereby meeting the use requirements of device manufacturing while reducing the processing loss and processing cost.

[0018] The features and advantages of the present invention will be described in detail through embodiments in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram comparing the grinding performance of the manganese dioxide grinding liquid according to the embodiment of the present invention and the traditional grinding liquid.

[0020] Figure 2 It is a schematic diagram of the surface roughness results of the Si surface of the substrate after the silicon carbide substrate is subjected to CMP treatment using the manganese dioxide polishing liquid according to an embodiment of the present invention.

[0021] Figure 3 It is a schematic diagram of the surface roughness of the C-surface of the substrate after the silicon carbide substrate is subjected to CMP treatment using the manganese dioxide polishing liquid according to an embodiment of the present invention. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application.

[0023] The present invention is described in detail below in conjunction with the accompanying drawings.

[0024] This embodiment provides a method for preparing a manganese dioxide polishing liquid for a double-sided synchronous polishing process of a silicon carbide substrate, comprising the following steps: stirring and dissolving the surfactant in deionized water to obtain a dispersion; The manganese dioxide powder and the dispersion are mixed and subjected to a high-energy ball milling process to obtain a manganese dioxide slurry; Under high-speed mechanical stirring conditions, a wetting agent and a pH buffer are added to the manganese dioxide slurry; Filtering and removing large particles in the slurry so that the particle size of the manganese dioxide particles in the slurry does not exceed 300 nm, and obtaining a manganese dioxide slurry with high monodispersity, wherein the particle size dispersion index (PDI) value of the manganese dioxide slurry with high monodispersity is less than 0.1; The oxidant is mixed with the manganese dioxide slurry having high monodispersity, and the pH value is adjusted to 8-10.5 to obtain the manganese dioxide grinding liquid.

[0025] Among them, the high-energy ball milling process is carried out in a ball mill, the rotation speed of the ball mill is set to 400rpm-800rpm, the revolution speed is 200rpm-400rpm, the ball milling temperature is 30℃-40℃, and the diameter of the grinding balls in the grinding process is 0.6mm-1.6mm, so that the particle size dispersion index PDI value of the manganese dioxide slurry with high monodispersity is less than 0.3.

[0026] Preferably, the particle size dispersity index PDI value of the manganese dioxide slurry is less than 0.1. Under high-energy ball milling treatment with process parameters, a manganese dioxide slurry with a uniform particle size distribution in the range of 100nm-200nm can be obtained, so that when the grinding liquid is used for grinding silicon carbide substrates, the surface damage of the substrate can be removed uniformly, which is beneficial to shorten the silicon surface processing time, improve the processing yield, and reduce processing losses and processing costs.

[0027] The pH of the manganese dioxide polishing liquid is 8-10.5, which is less corrosive to the equipment and is conducive to reducing the equipment maintenance cost. The hardness of the manganese dioxide particles is relatively low, which greatly reduces the risk of scratches introduced by the polishing liquid of the present invention in the subsequent CMP process.

[0028] As an implementation manner of this embodiment, the grinding balls are zirconium balls, and the diameter of the grinding balls is 0.6 mm-0.8 mm and / or 1.4 mm-1.6 mm.

[0029] In this embodiment, the oxidant is one or more of potassium perchlorate, potassium permanganate, potassium periodate, and potassium persulfate; the pH adjuster is one or more of potassium hydroxide, sodium hydroxide, ammonia water, tetramethylammonium hydroxide, dilute phosphoric acid, citric acid, and dilute hydrochloric acid; the wetting agent is one or more of ethanol, hydroxyethyl cellulose, polycarboxylates, succinates, and polycarboxylic acid type comb copolymer surfactants.

[0030] In this embodiment, the dispersant is a polymer surfactant, which includes at least one of a glycolipid surfactant, a lipopeptide surfactant, and a phospholipid surfactant. The selection of the above dispersant can meet the environmental protection requirements while meeting the grinding requirements, and is conducive to the waste liquid treatment of the grinding liquid.

[0031] As an implementation mode of this embodiment, the mass ratio of manganese dioxide powder to dispersion liquid is (2-5):1, and the particle size dispersion index PDI value of the manganese dioxide slurry is less than 0.3.

[0032] The embodiment of the present invention also proposes a manganese dioxide polishing liquid, which is used for the double-sided synchronous polishing process of the silicon carbide substrate. It is prepared according to the preparation method of the above-mentioned manganese dioxide polishing liquid. The manganese dioxide polishing liquid is composed of the following components in weight percentage: manganese dioxide powder 10-20wt.%, oxidant 0.2-5wt.%, dispersant 2-5wt.%, wetting agent 0.2-8wt.%, pH adjuster 0.2-2wt.%, and deionized water as the balance. Using the above-mentioned manganese dioxide polishing liquid, the silicon carbide substrate is polished on both sides simultaneously, and the polishing rate ratio of the C surface and the Si surface is less than 1.7.

[0033] Table 1 shows the manganese dioxide concentration, oxidant concentration content in the manganese dioxide polishing liquid of each embodiment, and the C-surface and Si-surface polishing rates when applied to the polishing of silicon carbide substrates as follows: Table 1

[0034] In this embodiment, the grinding process conditions set when the manganese dioxide grinding liquid is used for double-sided synchronous grinding of the silicon carbide substrate are as follows: the grinding liquid flow rate is 150mL / min-300mL / min, the grinding disk speed is 40rpm-80rpm, the grinding head speed is 40rpm-80rpm, the grinding head swing is 10mm-15mm, and the grinding pressure is 2.5psi-4psi.

[0035] During the double-sided synchronous grinding of the silicon carbide substrate by manganese dioxide grinding liquid, the manganese dioxide grinding liquid is stirred continuously by a mechanical stirrer, and the manganese dioxide particles do not agglomerate to form large particles, and are transported to the surface of the grinding pad by a peristaltic pump. During the grinding process, the surface temperature of the grinding pad is 28℃-35℃. During the grinding process, the staff adjusts the inlet flow rate and temperature of the manganese dioxide grinding liquid according to the size and rotation speed of the grinding disc to ensure that the grinding liquid on the surface of the grinding pad is evenly distributed and the manganese dioxide particles are not easily agglomerated.

[0036] 1. Test on the influence of different grinding fluids on the grinding performance of silicon carbide liner Fifteen identical silicon carbide substrates with a diameter of 150 mm were selected and divided into three groups. The three groups of silicon carbide substrates were subjected to double-sided synchronous grinding under the same grinding process conditions using 15% manganese dioxide grinding liquid, traditional aluminum oxide grinding liquid and silicon dioxide grinding liquid. The grinding process conditions are as follows: grinding liquid flow rate is 150 mL / min-300 mL / min, grinding disc speed is 40 rpm-80 rpm, grinding head speed is 40 rpm-80 rpm, grinding head swing is 10 mm-15 mm, grinding pressure is 2.5 psi-4 psi, and grinding temperature is 28°C-35°C. The material removal rates of the Si surface and C surface of the silicon carbide substrates after grinding were collected, and the average value of each group was taken. The specific test results are shown in Figure 2. Figure 1 shown.

[0037] Depend on Figure 1 It can be seen that under the same grinding conditions, the removal rate ratios of the C-surface and Si-surface of the silicon carbide substrate by the manganese dioxide grinding liquid, the aluminum oxide grinding liquid and the silicon dioxide grinding liquid are 1.33, 3.09 and 2.17 respectively. Although the removal rate of the C-surface and Si-surface of the silicon carbide substrate by the silicon dioxide grinding liquid is also about 2, the grinding rate of the silicon dioxide grinding liquid is small. The manganese dioxide grinding liquid of the present invention can reduce the processing loss of the C-surface without sacrificing the material removal rate of the Si-surface. In the double-sided grinding process, when the Si-surface meets the use requirements of the power device manufacturing, the processing loss of the C-surface is as small as possible, thereby reducing the processing loss and processing cost.

[0038] 2. Test on the influence of the grinding fluid of the present invention on the surface quality of the silicon carbide liner after grinding A silicon carbide substrate with a diameter of 150 mm was taken, and the silicon carbide substrate was subjected to double-sided synchronous grinding with the manganese dioxide grinding liquid of the present invention. The grinding process conditions were as follows: the grinding liquid flow rate was 150 mL / min-300 mL / min, the grinding disc speed was 40 rpm-80 rpm, the grinding head speed was 40 rpm-80 rpm, the grinding head swing was 10 mm-15 mm, the grinding pressure was 2.5 psi-4 psi, and the grinding temperature was 28° C.-35° C. The roughness of the Si surface and the C surface of the silicon carbide substrate after grinding, and the surface scratches of the Si surface were respectively detected by an atomic force microscope and a wafer surface analyzer. The detection results are as follows: Figures 2 to 3 shown.

[0039] Depend on Figure 2 It can be seen that the surface roughness of the Si surface of the silicon carbide substrate after grinding is less than 0.1 nm, with an average of 0.08 nm.

[0040] Depend on Figure 3 It can be seen that the surface roughness of the C surface of the silicon carbide substrate after grinding is less than 0.3 nm, and the average is 0.14 nm.

[0041] It can be seen that the surface of the silicon carbide substrate after grinding reaches the global flatness requirement of atomic-level smoothness. After the SiC substrate is ground with the grinding liquid, the Si surface of the SiC substrate reaches the processing requirements of low roughness and no scratches.

[0042] The above embodiments are intended to illustrate the present invention, not to limit the present invention. Any solution that is a simple transformation of the present invention belongs to the protection scope of the present invention.

Claims

1. A method for preparing a manganese dioxide polishing liquid for a double-sided synchronous polishing process of a silicon carbide substrate, characterized in that: It includes the following steps: stirring and dissolving the surfactant in deionized water to obtain a dispersion; The manganese dioxide powder and the dispersion are mixed, and subjected to a high-energy ball milling process to obtain a manganese dioxide slurry; Adding a wetting agent and a pH buffer into the manganese dioxide slurry; Filtering and removing large particles in the slurry so that the particle size of the manganese dioxide particles in the slurry does not exceed 300 nm, and obtaining a manganese dioxide slurry with high monodispersity, wherein the particle size dispersion index (PDI) value of the manganese dioxide slurry with high monodispersity is less than 0.3; The oxidant is mixed with a manganese dioxide slurry having high monodispersity, and the pH value is adjusted to 8-10.5 to obtain a manganese dioxide polishing liquid, which is composed of the following components in weight percentage: 10-20wt.% of manganese dioxide powder, 0.2-5wt.% of oxidant, 2-5wt.% of dispersant, 0.2-8wt.% of wetting agent, 0.2-2wt.% of pH adjuster, and the balance is deionized water.

2. The method for preparing a manganese dioxide polishing liquid for a double-sided simultaneous polishing process of a silicon carbide substrate according to claim 1, characterized in that: The high-energy ball milling process is carried out in a ball milling jar, the rotation speed of the ball milling jar is set to 400rpm-800rpm, the revolution speed is set to 200rpm-400rpm, the ball milling temperature is set to 30℃-40℃, and the diameter of the grinding balls in the grinding process is set to 0.6mm-1.6mm.

3. The method for preparing a manganese dioxide polishing liquid for a double-sided simultaneous polishing process of a silicon carbide substrate according to claim 1, characterized in that: The particle size of the manganese dioxide particles ranges from 100 nm to 200 nm, and the particle size dispersion index (PDI) value of the manganese dioxide slurry with high monodispersity is less than 0.

1.

4. The method for preparing a manganese dioxide polishing liquid for a double-sided simultaneous polishing process of a silicon carbide substrate according to claim 1, characterized in that: The mass ratio of the manganese dioxide powder to the dispersion is (2-5):

1.

5. A manganese dioxide polishing liquid prepared according to the method for preparing a manganese dioxide polishing liquid for a double-sided simultaneous polishing process of a silicon carbide substrate according to any one of claims 1 to 4, characterized in that: The manganese dioxide polishing liquid is composed of the following components in weight percentage: 10-20wt.% of manganese dioxide powder, 0.2-5wt.% of oxidant, 2-5wt.% of dispersant, 0.2-8wt.% of wetting agent, 0.2-2wt.% of pH regulator, and the balance of deionized water.

6. The manganese dioxide polishing liquid as claimed in claim 5, characterized in that: The oxidant is one or more of potassium perchlorate, potassium permanganate, potassium periodate, and potassium persulfate; the pH adjuster is one or more of potassium hydroxide, sodium hydroxide, ammonia water, tetramethylammonium hydroxide, dilute phosphoric acid, citric acid, and dilute hydrochloric acid; and the wetting agent is one or more of ethanol, hydroxyethyl cellulose, polycarboxylates, succinates, and polycarboxylic acid type comb copolymer active agents.

7. The manganese dioxide polishing liquid as claimed in claim 5, characterized in that: The dispersant is a high molecular surfactant, and the high molecular surfactant includes at least one of a glycolipid surfactant, a lipopeptide surfactant, and a phospholipid surfactant.

8. A method for synchronously polishing double sides of a silicon carbide substrate, characterized in that: include: The silicon carbide substrate is polished on both sides simultaneously using the manganese dioxide polishing liquid described in claim 5.

9. The method for simultaneous double-sided polishing of a silicon carbide substrate according to claim 8, wherein: The grinding process conditions are as follows: manganese dioxide grinding liquid flow rate is 150mL / min-300mL / min, grinding disc speed is 40rpm-80rpm, grinding head speed is 40rpm-80rpm, grinding head swing is 10mm-15mm, and grinding pressure is 2.5psi-4psi.

10. The method for simultaneous double-sided polishing of a silicon carbide substrate according to claim 9, wherein: During the double-sided synchronous polishing of the silicon carbide substrate by the manganese dioxide polishing liquid, the manganese dioxide polishing liquid is continuously stirred by a mechanical stirrer and transported to the surface of the polishing pad by a peristaltic pump. During the polishing process, the surface temperature of the polishing pad is 28°C-35°C.

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