A colloidal silica with a rough surface, its preparation method and applications

Abstract

The present invention provides a colloidal silica with a rough surface, a preparation method and an application thereof. Using a siloxane with low metal ion impurities (≤1 ppm) as a raw material, a composite catalytic system is constructed by combining an aminopropylsilane charge regulator with a basic amino acid and a basic substance. Through amino-carboxyl condensation and silane hydrolysis, a rough spherical structure with chain-like branched protrusions on the surface is formed, solving the problems of the smooth surface of the existing silica sol abrasive, low mechanical polishing efficiency and insufficient impurity control. The colloidal silica obtained by the present invention has a rough surface, good monodispersity of particle size distribution, high purity, can effectively shorten the reaction cycle and improve the mechanical polishing efficiency.

Description

Technical Field

[0001] The invention relates to the technical field of semiconductor chemical mechanical polishing (CMP), and in particular to high-purity spherical colloidal silicon dioxide with rough surface and a preparation method thereof. Background Art

[0002] Chemical mechanical polishing (CMP) is the core technology for achieving global flattening of wafers in semiconductor manufacturing. Its performance directly depends on the morphology, purity and mechanochemical synergy of the abrasive in the grinding composition. The current mainstream CMP abrasive is mainly high-purity spherical colloidal silica, which is prepared by hydrolysis and condensation of siloxane under alkaline conditions. Although this type of abrasive has the advantages of uniform morphology and good dispersibility, its smooth surface characteristics lead to insufficient mechanical cutting force, which makes it difficult to meet the requirements of advanced processes for high polishing rates.

[0003] In the prior art, attempts to increase the polishing rate are mainly concentrated in the following two types of solutions: morphology control, giving the silica abrasive a rough surface through surface etching (such as CN112142020A) or composite polymer coating (such as US2018035512A1), but the former is prone to introduce metal ion contamination, and the latter causes a decrease in purity due to organic residues (metal impurities > 5ppm), both of which are difficult to meet semiconductor-grade purity requirements; process optimization, extending the aging time (8-12 hours) to increase the particle size, although it can slightly increase the cutting force, but leads to low production efficiency and deterioration of the particle size distribution.

[0004] In addition, the traditional process requires the use of metal catalysts (such as NaOH, etc.) to control the morphology, and the residual sodium ions in the final product often reach 2-5ppm, requiring additional purification steps, further increasing the cost. Therefore, how to give silica abrasives a controllable rough surface and shorten the preparation cycle while ensuring high purity (metal / anion ≤ 1ppm) and monodispersity (PDI ≤ 0.1) has become a technical bottleneck that needs to be broken through in the semiconductor CMP field. Summary of the invention

[0005] The purpose of the present invention is to provide a high-purity spherical colloidal silica with a rough surface and a preparation method thereof, so as to improve the mechanical cutting force of silicon abrasives during the grinding process and realize the improvement of grinding efficiency.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a method for preparing high-purity rough-surface spherical colloidal silica:

[0008] The method for preparing high-purity monodisperse spherical colloidal silica for CMP of the present application comprises the following steps:

[0009] (a) Using siloxane as a raw material, adding a charge regulator aminopropylsilane and an alcohol solvent, and mixing and stirring to form a mixed solution A; (b) Mixing an alcohol solvent, a basic amino acid, ultrapure water and a basic substance to prepare a mixed solution B; (c) Mixing solution A and solution B for reaction to prepare silica sol; (d) Subjecting the silica sol to vacuum distillation and replacing the alcohol therein with water to obtain a colloidal silica with a rough surface.

[0010] Further, the basic substance includes one or more of ammonia water, tetramethylammonium hydroxide, triethoxypropylamine, preferably ammonia water;

[0011] Further, the concentration of the basic substance in solution B is 0.1-10 wt%, preferably 0.5-5 wt%.

[0012] Further, the siloxane is selected from one or more combinations of tetramethoxysilane, tetraethoxysilane, methyltrimethoxysilane, mercaptopropyltrimethoxysilane, epoxytrimethoxysilane, mercaptopropyltriethoxysilane;

[0013] And / or, the charge regulator is selected from one or more combinations of aminopropyltrimethoxysilane or aminopropyltriethoxysilane;

[0014] And / or, the alcohol solvent includes one or more combinations of methanol, ethanol, isopropanol, butanol, isopentanol, ethylene glycol, propylene glycol, preferably one or more combinations of methanol, ethanol, isopropanol; more preferably methanol or ethanol;

[0015] And / or, the basic amino acid is selected from at least one of lysine, arginine, histidine, ornithine, citrulline, preferably lysine, arginine or a combination thereof.

[0016] Further, in step (a), the content of the charge regulator is 1-10 wt% of solution A, preferably 2-5 wt%;

[0017] And / or, in step (a), the content of the alcohol solvent is 1-50 wt% of solution A, preferably 20-30 wt%;

[0018] And / or, the concentration of the basic amino acid in solution B is 0.1-3 wt%, preferably 0.5-1 wt%;

[0019] And / or, in step (b), the concentration of the alcohol solvent in solution B is 60-90 wt%, preferably 70-80 wt%.

[0020] Further, in step (c), the mass ratio of solution A to solution B is 1:1-20, preferably 1:2-10;

[0021] And / or, the reaction temperature of solution A and solution B is 30 - 40°C, preferably 33 - 37°C;

[0022] And / or, the reaction time of solution A and solution B is 1 - 8 h, preferably 1 - 2 h;

[0023] Further, step (d) is: subjecting the silica sol to vacuum distillation for concentration, and then performing constant liquid position replacement under normal pressure. When the liquid temperature and the top temperature reach 100°C, the replacement ends, and a high-purity monodisperse silica sol with a rough surface can be obtained.

[0024] Further, the temperature range of the vacuum distillation is 40 - 80°C, and the vacuum distillation is concentrated to a solid content of 10 - 40 wt%.

[0025] The second aspect of the present invention provides a spherical colloidal silica with a rough surface, and the colloidal silica is prepared by the above method.

[0026] Further, the PDI of the colloidal silica ≤ 0.1, metal ion impurities < 1 ppm, and anion impurities ≤ 1 ppm.

[0027] The third aspect of the present invention provides a CMP polishing composition containing the above colloidal silica abrasive.

[0028] The fourth aspect of the present invention provides the application of the above colloidal silica as an abrasive in CMP mechanical polishing

[0029] In the present invention, silane hydrolyzes and condenses to form silica nanoparticles. The charge adjuster hydrolyzes and condenses with the silica nanoparticles, attaching amino functional groups to the surface of the nanoparticles, forming sites for the condensation of basic amino acids. The basic amino acids condense with the amino groups on the surface of the nanoparticles and continue to condense with amino acids to form a chain-like branched structure, forming protrusions. At the same time, silane continues to hydrolyze and condense to grow, forming nanoparticles with a rough surface. Compared with the existing high-purity CMP abrasive, the product has significant differences in morphology. In the present invention, the organic acids, inorganic bases, and methanol used can all be removed during the distillation process and no metal ion impurities are introduced. The metal ion impurities of the prepared colloidal silica < 1 ppm, and the anion impurities ≤ 1 ppm. Beneficial effects

[0030] The reaction cycle of the preparation method of the present invention is significantly shortened. Compared with the traditional process, the reaction time of the present invention can be shortened to 1 - 2 hours, and high-efficiency purification is achieved through low-temperature vacuum distillation (40 - 80°C), reducing the overall energy consumption, and being suitable for industrial continuous production.

[0031] The colloidal silica prepared by the method of the present invention has high purity. The present invention uses specific amino acids, alkaline substances, and solvents, and there is no residual metal catalyst. The total amount of metal ion impurities in the obtained colloidal silica is <1 ppm, and the total amount of anion impurities is ≤1 ppm, meeting the purity requirements in semiconductor mechanical polishing.

[0032] The colloidal silica prepared by the method of the present invention has excellent monodispersity. The particle size distribution index (PDI) of the colloidal silica prepared by the present invention is ≤0.1, thus avoiding scratch defects caused by uneven particle sizes during the polishing process.

[0033] The present invention forms a chain-like branched protrusion structure through amino-carboxyl directional condensation and silane gradient coating, thereby preparing colloidal silica with a rough surface. The polishing liquid containing the colloidal silica of the present invention has a high polishing rate in the chemical mechanical polishing of semiconductor devices, thus improving the polishing efficiency. Description of the Drawings

[0034] Figures 1 to 7 SEM images of the colloidal silica prepared in Examples 1-7 respectively;

[0035] Figure 8 SEM image of the colloidal silica in Comparative Example 1.

[0036] Figures 9 to 12 SEM images of the colloidal silica prepared in Comparative Examples 2-5. Detailed Description of the Invention

[0037] Hereinafter, the specific embodiments of the present invention will be described in detail. However, the present invention is not limited to the embodiments including the following examples and can be variously modified within the scope that can achieve the object of the invention and does not exceed the gist of the invention.

[0038] The method for preparing high-purity monodisperse spherical colloidal silica for CMP of the present invention includes the following steps:

[0039] (a) Using siloxane as a raw material, adding a charge adjuster aminopropylsilane and an alcohol solvent and mixing and stirring to form a mixed solution A; (b) Mixing an alcohol solvent, a basic amino acid, ultrapure water, and an alkaline substance to prepare a mixed solution B; (c) Mixing the solution A and the solution B for reaction to prepare a silica sol; (d) Subjecting the silica sol to vacuum distillation and replacing the alcohol inside with water to obtain a colloidal silica with a rough surface.

[0040] In the present invention, steps (a) and (b) can be carried out in any order, and can be prepared successively or simultaneously;

[0041] In step (a) of the present invention, the siloxane is any one or a combination of several of tetramethoxysilane, tetraethoxysilane, methyltrimethoxysilane, mercaptopropyltrimethoxysilane, epoxytrimethoxysilane, and mercaptopropyltriethoxysilane;

[0042] The charge control agent is selected from aminopropyltrimethoxysilane, aminopropyltriethoxysilane or a combination thereof;

[0043] In the present invention, the siloxane can be hydrolyzed and condensed to form silicon dioxide nanoparticles, and the charge control agent is simultaneously hydrolyzed and grown on the surface of the nanoparticles, grafting amino functional groups onto the surface of the nanoparticles to form sites for the condensation of basic amino acids.

[0044] In step (a) of the present invention, the total metal ion impurities in the siloxane are ≤1 ppm, and the metal ion impurities include sodium, potassium, calcium, magnesium, iron, nickel, etc.; the total anions in the siloxane are ≤1 ppm, and the anions include chloride ions, etc.

[0045] In step (a) of the present invention, the content of the charge control agent is 1-10 wt% of the mixed solution A, preferably 2-5 wt%; the content of the alcohol solvent is 1-50 wt% of the mixed solution A, preferably 20-30 wt%; the balance is siloxane. The contents in the present invention are all mass contents.

[0046] In step (b) of the present invention, the basic amino acid is selected from at least one of lysine, arginine, histidine, ornithine, and citrulline, preferably lysine, arginine or a combination thereof;

[0047] In step (b) of the present invention, the concentration of the basic amino acid in solution B is 0.1-3 wt%, preferably 0.5-1 wt%.

[0048] Basic amino acids can play a catalytic role in the preparation process, promote the hydrolysis of silanes, and do not introduce metal ion impurities. Basic amino acids generally refer to amino acids with an isoelectric point greater than 7, which can react with the charge control agent under basic conditions to form a chain-like branched structure. Therefore, the concentration of amino acids needs to be controlled within a certain range. When the amino acid concentration is too low, the amino acid grafting is insufficient, and effective surface protrusions cannot be formed, and the surface tends to be smooth. As the amino acid concentration increases, more chain-like branched structures are formed and the surface is rougher. However, when the amino acid concentration is too high, the hydrolysis of silanes is faster, the growth and nucleation of silanes are faster, and adhesion is likely to occur between particles, resulting in an increase in PDI and poor monodispersity of silicon dioxide.

[0049] Alkaline substances such as ammonia water, triethoxypropylamine, and tetramethylammonium hydroxide do not contain metal ions and meet the semiconductor-grade purity requirements; at the same time, the volatile / decomposable characteristics of alkaline substances such as ammonia water ensure that the alkali residue in the final product is ≤0.01 wt%;

[0050] In the present invention, the alcohol solvent may be selected from at least one of methanol, ethanol, isopropanol, butanol, isoamyl alcohol, ethylene glycol, propylene glycol, etc., preferably one or a combination of methanol, ethanol, and isopropanol, and more preferably methanol or ethanol.

[0051] In step (b) of the present invention, the concentration of the alcohol solvent in solution B is 60-90 wt%, preferably 70-80 wt%;

[0052] In step (b) of the present invention, the concentration of the basic substance in solution B is 0.1-10 wt%, preferably 0.5-5 wt%.

[0053] In step (b) of the present invention, the basic substance may be one or several of ammonia water, triethoxypropylamine, tetramethylammonium hydroxide, etc., preferably ammonia water. The present invention has found through research that when ammonia water is used as a catalyst, its concentration has a great influence on the surface roughness of the prepared colloidal silica. When the concentration of ammonia water is too high, it may cause amino acids to be unable to effectively participate in the condensation reaction, reducing the condensation activity of basic amino acids with amino functional groups on the charge regulator, thereby reducing the formation of branches and making the surface smooth. On the other hand, when the concentration of ammonia water is too low, the hydrolysis rate of siloxane (such as tetramethoxysilane) slows down, resulting in incomplete reaction and a longer reaction cycle. Too low a concentration of ammonia water may cause amino acids to lose the condensation activity with amino functional groups in the charge regulator and also affect the hydrolysis of siloxane.

[0054] In step (c) of the present invention, the mass ratio of the mixed solution A to solution B is 1:1-20, preferably 1:2-10.

[0055] In step (c) of the present invention, the reaction temperature of the mixed solution A and solution B is 30-40 °C, preferably 33-37 °C.

[0056] In step (c) of the present invention, the reaction time of the mixed solution A and solution B is 1-8 h, preferably 1-2 h.

[0057] In step (d) of the present invention, the temperature range of the vacuum distillation is preferably 40-80 °C.

[0058] In step (d) of the present invention, the vacuum distillation needs to be concentrated to the required solid content, preferably 10-40 wt%, to obtain a high-purity silica sol product.

[0059] Specifically, the preparation method of the high-purity monodisperse spherical colloidal silica for CMP of the present invention is as follows:

[0060] (a) Using electronic-grade tetramethoxysilane or tetraethoxysilane as raw materials, adding charge adjusters such as aminopropyltrimethoxysilane or aminopropyltriethoxysilane and an alcohol solvent, and mixing and stirring to form a mixed solution A, where the content of the charge adjuster is 2-5 wt% of the mixed solution A; the content of the alcohol solvent is 20-30 wt% of the mixed solution A, and the rest is tetramethoxysilane or tetraethoxysilane;

[0061] (b) Mixing an alcohol solvent, arginine or lysine, ultrapure water, and ammonia water to prepare a mixed solution B, where the concentration of ammonia water in solution B is 0.1-10 wt%; the concentration of amino acid in solution B is 0.5-1 wt%, the content of the alcohol solvent is 70-80 wt% of the mixed solution A, and the balance is ultrapure water;

[0062] (c) Mixing solution A and solution B in a ratio of 1:2-10 and reacting for 1-2 hours at 33-37 °C to prepare silica sol;

[0063] (d) Concentrating the silica sol under reduced pressure at 40-80 °C until the solid content is 10-40 wt%, and then performing constant liquid position replacement under normal pressure. When the liquid temperature and the top temperature reach 100 °C, the replacement ends, and high-purity monodisperse silica sol with a rough surface can be obtained.

[0064] The silica sol product prepared by the present invention has a significant difference in morphology compared with the existing high-purity CMP abrasive. In the present invention, solvents, catalysts, etc. used can all be removed during the distillation process, and metal ion impurities are not introduced. The metal ion impurities of the prepared colloidal silica are <1 ppm, and the anion impurities are ≤1 ppm.

[0065] In the examples of the present invention, to evaluate the polishing rate of the prepared colloidal silica as an abrasive, the colloidal silica was formulated into a polishing liquid composition for testing. The preparation method of the polishing liquid composition is as follows: colloidal silica abrasive: 15%, dispersant (ammonium polyacrylate, Mw = 2000-5000): 0.5%, pH regulator: adjusted to pH = 10, and the rest is water.

[0066] Preparation steps: Adding the colloidal silica abrasive and deionized water into a stirrer for stirring, then adding ammonium polyacrylate (Mw = 2000-5000), etc., continuing to stir, dropwise adding 0.1 M nitric acid at room temperature until pH = 10.0 ± 0.2, and continuing to stir for 30 minutes; filtering through a 0.1 μm nylon filter element to remove agglomerated particles to obtain the final polishing liquid. Example

[0067] In the following examples, unless otherwise specifically stated, the raw material reagents or treatment technologies used are all common commercially available raw materials or conventional treatment technologies in the art.

[0068] The raw materials used in the embodiments of the present invention are as follows:

[0069] Tetramethoxysilane (electronic grade)

[0070] Tetraethoxysilane (electronic grade)

[0071] Methanol (analytical pure)

[0072] Ethanol (analytical pure)

[0073] Lysine (analytical pure)

[0074] Arginine (analytical pure)

[0075] Ammonia water (analytical pure)

[0076] Aminopropyltrimethoxysilane (electronic grade)

[0077] Aminopropyltriethoxysilane (electronic grade)

[0078] <Testing method>

[0079] The dynamic light scattering particle size (DLS size) and PDI of colloidal silica: Measured using a Malvern laser particle size analyzer;

[0080] Metal ion impurities: Measured using an inductively coupled plasma mass spectrometer (ICP-MS);

[0081] Morphology photos of colloidal silica: Taken using a scanning electron microscope.

[0082] Abrasion rate test: Polishing an 8-inch silicon wafer (with a thermal oxide SiO 2 layer on the surface, initial thickness 1000 ± 10 nm) on a CMP polishing machine using an IC1010 porous polyurethane polishing pad: Downward pressure: 2.0 psi, polishing head rotation speed: 100 rpm, polishing plate rotation speed: 80 rpm, polishing fluid flow rate: 150 mL / min. Measuring the thickness of the film before and after polishing using an ellipsometer (nano spec Ⅱ), recording the data and measuring the film thickness (Δh, unit: angstrom) before and after 10 minutes of polishing time; Finally obtaining the abrasion rate (RR) = Δh / polishing time (angstrom / min). Example 1

[0083] Methanol and 3-aminopropyltrimethoxysilane are added to electronic-grade tetramethoxysilane. After stirring evenly, a mixed solution A is obtained. The methanol content in the mixed solution A is 30 wt%, the 3-aminopropyltrimethoxysilane content is 5 wt%, and the rest is tetramethoxysilane; ammonia water, ultrapure water, lysine, and methanol are configured into a mixed solution B. The ammonia water concentration in the configured mixed solution B is 0.5 wt%, the methanol content is 70 wt%, the lysine concentration in the mixed solution B is 0.5 wt%, and the balance is ultrapure water. The mixed solution A and the mixed solution B are reacted at a mass ratio of 1:10 at 33 °C for 2 h to generate silica sol. The silica sol is concentrated by vacuum distillation at 75 °C to 40 wt%, and then constant liquid position replacement is carried out under normal pressure. When the liquid temperature and the top temperature reach 100 °C, the replacement ends, and a high-purity monodisperse silica sol with a rough surface can be obtained. The particle size measured by a Malvern laser particle size analyzer is 69 nm, and the PDI is 0.041. Example 2

[0084] (1) Ethanol and 3-aminopropyltriethoxysilane are added to electronic-grade tetraethoxysilane. After stirring evenly, a mixed solution A is obtained. The ethanol content in the mixed solution A is 25 wt%, the 3-aminopropyltriethoxysilane content is 3 wt%, and the rest is tetraethoxysilane.

[0085] (2) Ammonia water, ultrapure water, lysine, and ethanol are configured into a mixed solution B. The ammonia water concentration in the configured mixed solution B is 2 wt%, the ethanol content is 80 wt%, the lysine concentration in the mixed solution B is 1 wt%, and the balance is ultrapure water.

[0086] (3) The mixed solution A and the mixed solution B are reacted at a mass ratio of 1:10 at 37 °C for 1 h to generate silica sol.

[0087] (4) The silica sol is concentrated by vacuum distillation at 40 °C to 10 wt%, and then constant liquid position replacement is carried out under normal pressure. When the liquid temperature and the top temperature reach 100 °C, the replacement ends, and a high-purity monodisperse silica sol with a rough surface can be obtained. The particle size measured by a Malvern laser particle size analyzer is 50 nm, and the PDI is 0.046. Example 3

[0088] (1) Ethanol and 3-aminopropyltriethoxysilane are added to electronic-grade tetraethoxysilane. After stirring evenly, a mixed solution A is obtained. The ethanol content in the mixed solution A is 25 wt%, the 3-aminopropyltriethoxysilane content is 3 wt%, and the rest is tetraethoxysilane.

[0089] (2) Prepare a mixed solution B by mixing ammonia water, ultrapure water, arginine, and ethanol. In the prepared mixed solution B, the concentration of ammonia water is 2 wt%, the content of ethanol is 75 wt%, the concentration of arginine in the mixed solution B is 0.7 wt%, and the balance is ultrapure water.

[0090] (3) React the mixed solution A and the mixed solution B at a mass ratio of 1:10 at 37 °C for 1 h to produce silica sol.

[0091] (4) Concentrate the silica sol by vacuum distillation at 40 °C to 10 wt%, and then perform constant liquid position replacement under normal pressure. When the liquid temperature and the top temperature reach 100 °C, the replacement ends, and high-purity monodisperse silica sol with a rough surface can be obtained. The particle size measured by a Malvern laser particle size analyzer is 73 nm, and the PDI is 0.073. Example 4

[0092] (1) Add methanol and aminopropyltrimethoxysilane to electronic grade tetramethoxysilane. After stirring evenly, a mixed solution A is obtained. In the mixed solution A, the content of methanol is 30 wt%, the content of aminopropyltrimethoxysilane is 4 wt%, and the rest is tetramethoxysilane.

[0093] (2) Prepare a mixed solution B by mixing ammonia water, ultrapure water, lysine, and methanol. In the prepared mixed solution B, the concentration of ammonia water is 5 wt%, the content of methanol is 70 wt%, the concentration of lysine in the mixed solution B is 0.5 wt%, and the balance is ultrapure water.

[0094] (3) React the mixed solution A and the mixed solution B at a mass ratio of 1:6 at 33 °C for 2 h to produce silica sol.

[0095] (4) Concentrate the silica sol by vacuum distillation at 80 °C to 40 wt%, and then perform constant liquid position replacement under normal pressure. When the liquid temperature and the top temperature reach 100 °C, the replacement ends, and high-purity monodisperse silica sol with a rough surface can be obtained. The particle size measured by a Malvern laser particle size analyzer is 63 nm, and the PDI is 0.052. Example 5

[0096] (1) Add methanol and aminopropyltrimethoxysilane to electronic grade tetramethoxysilane. After stirring evenly, a mixed solution A is obtained. In the mixed solution A, the content of methanol is 30 wt%, the content of aminopropyltrimethoxysilane is 5 wt%, and the rest is tetramethoxysilane.

[0097] (2) Prepare a mixed solution B by mixing ammonia water, ultrapure water, lysine, and methanol. In the prepared mixed solution B, the concentration of ammonia water is 10 wt%, the content of methanol is 70 wt%, the concentration of lysine in the mixed solution B is 0.1 wt%, and the balance is ultrapure water.

[0098] (3) Mix the mixed solution A and the mixed solution B at a mass ratio of 1:5 and react at 33 °C for 1 h to produce silica sol.

[0099] (4) Concentrate the silica sol by vacuum distillation at 75 °C to 40 wt%, then perform constant liquid position replacement under normal pressure. When the liquid temperature and the top temperature reach 100 °C, the replacement ends, and high-purity monodisperse silica sol with a rough surface can be obtained. The particle size measured by a Malvern laser particle size analyzer is 71 nm, and the PDI is 0.074. Example 6

[0100] (1) Add methanol and aminopropyltrimethoxysilane to electronic grade tetramethoxysilane. After stirring evenly, a mixed solution A is obtained. The methanol content in the mixed solution A is 20 wt%, the aminopropyltrimethoxysilane content is 1 wt%, and the rest is tetramethoxysilane.

[0101] (2) Prepare a mixed solution B with ammonia water, ultrapure water, lysine, and methanol. The ammonia water concentration in the prepared mixed solution B is 0.1 wt%, the methanol content is 70 wt%, the lysine concentration in the mixed solution B is 3 wt%, and the balance is ultrapure water.

[0102] (3) Mix the mixed solution A and the mixed solution B at a mass ratio of 1:2 and react at 33 °C for 1 h to produce silica sol.

[0103] (4) Concentrate the silica sol by vacuum distillation at 75 °C to 20 wt%, then perform constant liquid position replacement under normal pressure. When the liquid temperature and the top temperature reach 100 °C, the replacement ends, and high-purity monodisperse silica sol with a rough surface can be obtained. The particle size measured by a Malvern laser particle size analyzer is 67 nm, and the PDI is 0.081. Example 7

[0104] The preparation method is the same as that of Example 1, except that the lysine concentration in the mixed solution B during the preparation process is 5 wt%. In this preparation method, silica sol with a rough surface is obtained. The particle size measured by a Malvern laser particle size analyzer is 94 nm, and the PDI is 0.21.

[0105] Comparative Example 1

[0106] The silica sol of model PL-3 produced by Japan Fuso Corporation, see the attached Figure 8 , and a significant peanut-shaped fused particle structure can be seen, and the surface is relatively smooth.

[0107] Comparative Example 2

[0108] The preparation method was the same as that of Example 1, except that the ammonia concentration in the prepared mixed solution B was 15 wt%. The colloidal silica obtained by this preparation method had a relatively smooth surface.

[0109] Comparative Example 3

[0110] The preparation method was the same as that of Example 1, except that the ammonia concentration in the prepared mixed solution B was 0.05 wt%. The colloidal silica obtained by this preparation method had a relatively smooth surface.

[0111] Comparative Example 4

[0112] The preparation method was the same as that of Example 1, except that no amino acid was added during the preparation process. The colloidal silica obtained by this preparation method had a relatively smooth surface.

[0113] Comparative Example 5

[0114] The preparation method was the same as that of Example 1, except that the concentration of lysine in the mixed solution B during the preparation process was 0.07 wt%. The colloidal silica obtained by this preparation method had a relatively smooth surface.

[0115] Application Example

[0116] Preparation of the polishing liquid:

[0117] Raw material composition (by mass percentage): Colloidal silica abrasive prepared in Examples 1-8 or Comparative Examples 1-4 of the present invention: 15%, dispersant (ammonium polyacrylate, Mw = 2000 - 5000): 0.5%, pH regulator: adjusted to pH = 10, and the rest was water.

[0118] Preparation steps: Add the colloidal silica abrasive and deionized water into a stirrer and stir, then add ammonium polyacrylate, etc., and continue to stir, with the temperature ≤ 25°C; dropwise add 0.1M nitric acid to pH = 10.0 ± 0.2, and continue to stir for 30 minutes; filter through a 0.1μm nylon filter element to remove agglomerated particles, obtain the final polishing liquid, and conduct the test of the grinding rate

[0119] Table 1 Ion content of colloidal silica in Examples and Comparative Examples and grinding rate of the polishing liquid prepared therefrom

[0120]

[0121] See the attached specification Figures 1 - 12, the preparation method of the embodiments of the present invention can obtain colloidal silica with a rough surface. Compared with commercially available smooth colloidal silica, there is a significant improvement in the grinding rate, thereby further improving the polishing efficiency. The colloidal silica obtained in the embodiments of the present invention not only has a rough surface, but also has the advantages of monodispersity and high purity, can meet the purity requirements in the field of semiconductor polishing, and is conducive to reducing polishing defects.

[0122] It can be seen from Example 1 and Comparative Example 4 that the addition of amino acids plays a major role in the morphology control of colloidal silica. In Comparative Example 4, no amino acids are added, and a rough spherical structure with surface protrusions cannot be formed. Therefore, it can be speculated that amino acids are the key to forming colloidal silica with a rough surface. It may form protrusions by condensing basic amino acids with the amino groups on the surface of nanoparticles and then continuing to condense with amino acids to form a chain-like branched structure. At the same time, silane continues to hydrolyze and condense to grow, thus finally forming nanoparticles with a rough surface.

[0123] In Examples 2 and 3, the ammonia water concentration is not changed, and parameters such as alcohol content, amino acids, temperature, charge regulator, and siloxane are changed within a certain range. It is found that the surface roughness of the colloidal silica obtained in Examples 2 and 3 is not much different (see Appendix Figure 2 and Appendix Figure 3 ), and there is also not much change in the grinding rate. Through the test data of Examples 1-7 and Comparative Examples 2-3 of the present invention, it can be found that ammonia water, as a catalyst, its concentration has a greater impact on the surface roughness of the prepared colloidal silica. Within a certain concentration range, it is beneficial to obtain colloidal silica with a rough surface. When the ammonia water concentration is too high, it may cause amino acids to be unable to effectively participate in the condensation reaction, reduce the condensation activity of basic amino acids and the amino functional groups on the charge regulator, thereby reducing the formation of branched chains and making the surface smooth. When the ammonia water concentration is too low, the hydrolysis rate of siloxane (such as tetramethoxysilane) slows down, resulting in incomplete reaction and a longer reaction cycle. Too low ammonia water concentration may cause amino acids to lose the condensation activity with the amino functional groups in the charge regulator, and at the same time affect the hydrolysis of siloxane, forming colloidal silica with a smooth surface.

[0124] The concentration of amino acids also affects the surface roughness to a certain extent. Comparative Example 5 shows that when the amino acid concentration is too low, chain-like protrusions cannot be grafted on the surface, and thus colloidal silica with a rough surface cannot be formed. However, Example 7 shows that when the amino acid concentration is too high, amino acids accelerate the catalysis of silane hydrolysis, accelerate nucleation and growth, resulting in poor monodispersity of particles, PDI > 0.1.

Claims

1. A method for preparing colloidal silicon dioxide with a rough surface, characterized in that: The steps include: (a) Siloxane is used as a raw material, and a charge regulator aminopropylsilane and an alcohol solvent are added and mixed and stirred to form a mixed solution A; (b) The alcohol solvent, alkaline amino acid, ultrapure water and alkaline substance are mixed to prepare a mixed solution B, wherein the alkaline substance includes one or more combinations of ammonia water, tetramethylammonium hydroxide and triethoxypropylamine, and the alkaline amino acid is selected from one or more combinations of lysine, arginine, histidine and ornithine, and the concentration of the alkaline amino acid in the solution B is 0.1-3wt%, and the concentration of the alkaline substance in the solution B is 0.1-10wt%; (c) The solution A and the solution B are mixed and reacted to prepare a silica sol; (d) The silica sol is subjected to reduced pressure distillation, and water is added to replace and remove the alcohol therein to obtain a colloidal silica with a rough surface.

2. The method according to claim 1, characterized in that: The concentration of the basic amino acid in the solution B is 0.5-1 wt %.

3. The method according to claim 1, characterized in that: The concentration of the alkaline substance in the solution B is 0.5-5 wt %.

4. The method according to claim 1, characterized in that: The basic amino acid is selected from at least one of lysine and arginine.

5. The method according to any one of claims 1 to 4, characterized in that: The siloxane is selected from one or more combinations of tetramethoxysilane, tetraethoxysilane, methyltrimethoxysilane, mercaptopropyltrimethoxysilane, epoxytrimethoxysilane, and mercaptopropyltriethoxysilane; the charge regulator is selected from one or more combinations of aminopropyltrimethoxysilane and aminopropyltriethoxysilane; the alcohol solvent is selected from one or more combinations of methanol, ethanol, isopropanol, butanol, isopentanol, ethylene glycol, and propylene glycol.

6. The method according to any one of claims 1 to 4, characterized in that: In step (a), the content of the charge regulator is 1-10 wt % of solution A; the content of the alcohol solvent in step (a) is 1-50 wt % of solution A; and the content of the alcohol solvent in step (b) is 60-90 wt % of solution B.

7. The method according to any one of claims 1 to 4, characterized in that: The mass ratio of solution A to solution B is 1:1-20; the reaction temperature of solution A and solution B is 30-40°C; the reaction time of solution A and solution B is 1-8h; the temperature range of the reduced pressure distillation is 40-80°C, and the reduced pressure distillation is concentrated to a solid content of 10-40wt%.

8. A colloidal silica having a rough surface, characterized in that: The colloidal silicon dioxide is prepared according to the method for preparing colloidal silicon dioxide according to any one of claims 1 to 7.

9. A CMP polishing composition, characterized in that: Containing the colloidal silicon dioxide as claimed in claim 8.

10. Use of the colloidal silicon dioxide according to claim 8 as an abrasive in CMP chemical mechanical polishing.

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