Modified silicon dioxide sol, preparation method thereof and polishing composition

Abstract

The invention discloses modified silicon dioxide sol, a preparation method thereof and a polishing composition. According to the method, the polyether siloxane surfactant with the HLB value within the range of 8-18 is selected and matched with the cosurfactant to form the oil-in-water microemulsion, the silicon dioxide nanoparticles are generated in situ under the action of the basic catalyst, silicon hydroxyl in the surfactant is combined with the silicon dioxide nanoparticles after reaction, and surface modification of the silicon dioxide particles is achieved. By adding the modified silicon dioxide abrasive into the polishing composition, the polishing rate of silicon oxide and polycrystalline silicon can be increased, and meanwhile, defects on the surface of a polished wafer are reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of modified silica sol preparation, and specifically relates to a modified silica sol, a preparation method thereof, and a polishing composition. Background Art

[0002] Chemical mechanical polishing technology is one of the key steps in the integrated circuit manufacturing process. Its main principle is to combine the mechanical action of abrasives and the chemical action of chemical active solutions to planarize the surface of the substrate. In the polishing process of the metal layer, usually, an oxidant first forms a metal oxide with a relatively small hardness on the metal surface, and then the abrasive grinds and removes this oxide layer mechanically, generating a new metal surface that continues to be oxidized. The above process is repeated until the polishing is completed.

[0003] Currently, silica is one of the most widely used abrasives in chemical mechanical polishing. How to combine a high polishing rate with low surface defects is the main research direction of CMP polishing compositions in the future. Spherical silica abrasives have better fluidity and are more evenly stressed during polishing, which helps to reduce surface defects. The microemulsion method is one of the common methods for preparing nano-silica, but there are some significant deficiencies in traditional methods. Conventional surfactants do not bind tightly to silica particles, and subsequent demulsification and surfactant removal steps are cumbersome, increasing the preparation cost and process complexity. It may also damage the structure and properties of nano-silica, resulting in unstable product quality and uneven particle size distribution. In addition, surface modification by the microemulsion method requires multiple steps and the process is cumbersome. Therefore, it is of great practical significance to develop a preparation method of nano-silica that simplifies the process, reduces residues, and facilitates surface modification. Summary of the Invention

[0004] Aiming at the problems existing in the prior art, the present invention provides a modified silica sol, a preparation method thereof, and a polishing composition. A silanol surfactant with a specific HLB value range is selected and combined with a co-surfactant to achieve surface modification of silica particles. By adding the modified silica abrasive to the polishing composition, the polishing rates of OX silica and Poly polysilicon are increased, and at the same time, the defects and concave defects (such as Dishing) on the surface of the polished wafer are reduced.

[0005] To achieve the above invention purposes, the first aspect of the present invention provides a preparation method of a modified silica sol, including the following steps:

[0006] S1. Microemulsion preparation: First, mix a silicon-containing monomer, a surfactant, a co-surfactant, and water in a certain proportion to form an oil-in-water primary emulsion. Subsequently, perform mechanical homogenization at a rotation speed of 3000 - 9000 rpm for 30 - 120 min, and control the temperature through a cold water bath at 5 - 20 °C to obtain a nano-scale microemulsion with uniform particle size. Among them, the surfactant is selected from polyether silicone surfactants with an HLB value in the range of 8 - 18;

[0007] S2. Nanoparticle generation: Add an alkaline catalyst to the above microemulsion in a certain proportion, mix, and react at a temperature of 5 - 40 °C for 1 - 10 h, so that the oil phase in the microemulsion undergoes hydrolysis and condensation reactions under the action of the catalyst to generate silicon dioxide nanoparticles;

[0008] S3. Alcohol separation: Remove the reaction by-product alcohols through vacuum distillation at a temperature of 60 - 90 °C and a negative pressure of 70 - 98 kPa, and concentrate under reduced pressure to a solid content of 15 - 20%;

[0009] S4. Surface modification grafting: After the distillation is completed, react the reaction system at 80 - 140 °C for 1 - 24 hours, so as to graft polyether-modified groups on the surface of the silicon dioxide particles, and finally obtain a nano-scale modified silicon dioxide sol.

[0010] Further, in S1, first mix the silicon-containing monomer, the surfactant, and the co-surfactant in a certain proportion, stir at 100 - 200 rpm for 2 - 15 min to form a uniform oil-phase solution, and then add water to the above oil-phase system under continuous stirring to form an oil-in-water primary emulsion.

[0011] Further, the silicon-containing monomer is selected from at least one of methyl orthosilicate, ethyl orthosilicate, methyltrimethoxysilane, methyltriethoxysilane, or ethyltrimethoxysilane;

[0012] And / or, the surfactant is selected from XIAMETER TM OFX - 3667, VORASURF TM DC5103, or XIAMETER TM OFX - 5211;

[0013] And / or, the co-surfactant is selected from one or more of n-butanol, propylene glycol, triethanolamine, n-pentanol, isoamyl alcohol, or 1,2-pentanediol.

[0014] Further, the alkaline catalyst is selected from one or more of ammonia water, ammonium carbonate, or ethanolamine, and ethanolamine is preferred.

[0015] Further, calculated based on the total mass of the added reactants, the dosage of the silicon-containing monomer is 5-40 wt%;

[0016] and / or, the dosage of the surfactant is 1-15 wt%;

[0017] and / or, the dosage of the co-surfactant is 0.01-5 wt%;

[0018] and / or, the dosage of the basic catalyst is 0.1%-5 wt%;

[0019] Wherein, the total mass of the added reactants refers to the total mass of the silicon-containing monomer, surfactant, co-surfactant, water and basic catalyst.

[0020] Further, the mass ratio of the silicon-containing monomer to the surfactant is 1:1-10:1, preferably 1:1-5:1.

[0021] Further, the cold bath temperature range in step S1 is preferably 5-10°C.

[0022] Further, the reaction temperature in step S4 is preferably 90-110°C, and the reaction time is preferably 4-8 hours.

[0023] In the second aspect of the present invention, there is provided a modified silica sol prepared by the above-mentioned preparation method.

[0024] In the third aspect of the present invention, there is provided an application of the above-mentioned modified silica sol in a polishing composition.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] In the present invention, a polyether silicone surfactant with an HLB value in the range of 8-18 is selected and combined with a co-surfactant to form an oil-in-water microemulsion, in-situ generating silica nanoparticles. After the reaction, the silicon hydroxyl groups in the surfactant combine with the silica nanoparticles to realize surface modification of the silica particles, increasing the dispersion stability of the silica sol in the polishing composition; during the preparation process, a uniform nanoemulsion is formed by homogenization and temperature control, and the particle size distribution of the silica is narrow. By adding the modified silica abrasive to the polishing composition, the polishing rates of OX oxide and Poly polysilicon can be improved, and at the same time, the defects and concave defects (such as Dishing) on the surface of the wafer after polishing can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a scanning electron micrograph of the modified silica prepared in Example 1 of the present invention.

[0028] Figure 2Scanning electron micrograph of the modified silica prepared in Comparative Example 2 of the present invention. Detailed implementation mode

[0029] The following will combine the implementation modes of the present invention to clearly and completely describe the technical solutions in the implementation modes of the present invention. Obviously, the described implementation modes are only a part of the implementation modes of the present invention, rather than all the implementation modes. For those not specified in the examples, they are carried out according to conventional conditions or the conditions recommended by the manufacturer. For reagents or instruments without indicating the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0030] The first aspect of the present invention provides a method for preparing a modified silica sol, comprising the following steps:

[0031] S1. Microemulsion preparation: First, a silicon-containing monomer, a surfactant, a co-surfactant, and water are mixed in a certain proportion to form an oil-in-water primary emulsion. Subsequently, mechanical homogenization is carried out at a rotation speed of 3000-9000 rpm for 30-120 min, and the temperature is controlled by a cold water bath at 5-20 °C to obtain a nano-scale microemulsion with uniform particle size;

[0032] S2. Generation of nanoparticles: A basic catalyst is added to the above microemulsion in a certain proportion and mixed, and the reaction is carried out at a temperature of 5-40 °C for 1-10 h, so that the oil phase in the microemulsion undergoes hydrolysis and condensation reactions under the action of the catalyst to generate silica nanoparticles;

[0033] S3. Alcohol separation: The reaction by-product alcohols are removed by vacuum distillation at a temperature of 60-90 °C and a negative pressure of 70-98 kPa, and the solution is concentrated under reduced pressure to a solid content of 15-20%;

[0034] S4. Surface modification grafting: After the distillation is completed, the reaction system is reacted at 80-140 °C for 1-24 hours, so as to graft polyether modification groups on the surface of the silica particles, and finally a nano-scale modified silica sol is obtained.

[0035] In the examples of the present invention, a silicon-containing monomer, a surfactant, and a co-surfactant are first mixed in a certain proportion and stirred at 100-200 rpm for 2-15 min to form a uniform oil-phase solution. Then, under continuous stirring, water is added to the above oil-phase system to form an oil-in-water primary emulsion.

[0036] The present invention does not require the demulsification step of the conventional microemulsion method, reducing the complexity of the preparation process. By preparing an oil-in-water emulsion, each oil droplet encapsulated by water serves as a microreactor for fabricating nano-silica, thereby restricting the particle size of the silica. During the preparation process, high-shear homogenization at 3000 - 9000 rpm combined with low temperature (5 - 20 °C) conditions can inhibit the self-polymerization of silicon-containing monomers, forming an emulsion with a narrow particle size distribution. Additionally, by changing the structure of the surfactant, such as introducing polyether chains with different chain lengths or selecting different types of silicon sources, the surface of the silica particles can be modified, endowing the nano-silica with different properties. Moreover, the co-surfactant can be reduced to less than 1% by distillation, and the prepared modified nano-silica sol has better stability and uniformity.

[0037] Furthermore, the present invention selects surfactants with a specific HLB value in the range of 8 - 18 and combines them with co-surfactants to form an oil-in-water microemulsion, in-situ generating nano-silica particles. After the reaction, the silicon hydroxyl groups in the surfactant bind to the nano-silica particles, realizing the surface modification of the silica particles and increasing the dispersion stability of the silica sol in the polishing composition. Through surface grafting technology, the surfactant is directly chemically bonded to the surface of the silica particles, avoiding the need for an additional step of adding surfactants in traditional polishing compositions, reducing the formulation complexity and cost. The surfactant is chemically bonded to the surface of the silica particles, and the dynamic balance of the OX and Poly polishing rates can be achieved by adjusting the surface properties of the particles. Additionally, the dispersibility and wettability of the grafted silica particles are enhanced, reducing agglomeration, thereby significantly reducing surface defects (such as scratches and pits) and Dishing (local material depression).

[0038] In the examples of the present invention, the silicon-containing monomer is selected from one of methyl orthosilicate, ethyl orthosilicate, methyltrimethoxysilane, methyltriethoxysilane, and ethyltrimethoxysilane; the dosage of the silicon-containing monomer is 5 - 40 wt% of the total mass of the reactants added.

[0039] In the present invention, the total mass of the reactants added refers to the total mass of the silicon-containing monomer, surfactant, co-surfactant, water, and alkaline catalyst.

[0040] In the examples of the present invention, the surfactant is selected from polyether silicone surfactants with an HLB value in the range of 8 - 18, such as XIAMETER TM OFX-3667, VORASURF TM DC5103, XIAMETER TM OFX-5211. The dosage of the surfactant is 1 - 20 wt% of the total mass of the reactants added, preferably 1 - 15 wt%.

[0041] In an embodiment of the present invention, the co-surfactant is selected from one or more of n-butanol, propylene glycol, triethanolamine, n-pentanol, iso-pentanol, and 1,2-pentanediol, and the dosage of the co-surfactant is 0.01-5 wt% of the total mass of the added reactants.

[0042] In an embodiment of the present invention, the basic catalyst is selected from one or more of ammonia water, ammonium carbonate, or ethanolamine, and ethanolamine is preferred. The possible reason is that ethanolamine has the least impact on the conductivity in the system, the interfacial film layer between the water / oil phases fluctuates the least, and when reacting with oil-phase droplets, the surface roughness of the formed silica particles is lower, and there are fewer defect defects during polishing. The dosage of the catalyst is 0.1%-5% of the total mass of the added reactants, and the pH value of the aqueous phase during the reaction is between 8 and 10. Here, the aqueous phase refers to a mixture of water and the basic catalyst.

[0043] In an embodiment of the present invention, the mass ratio of the silicon-containing monomer to the surfactant is 1:1-10:1, preferably 1:1-5:1.

[0044] In an embodiment of the present invention, the cold bath temperature range in step S1 is preferably 5-10°C. A high temperature will cause an increase in the particle size of the emulsion droplets, and an excessively high temperature will cause the emulsion droplets to be unstable and form more abnormally shaped structural particles.

[0045] In an embodiment of the present invention, the reaction temperature in step S4 is preferably 90-110°C, and the reaction time is preferably 4-8 hours. If the reaction temperature is low and the time is too short, the grafting efficiency is insufficient, resulting in free surfactant, which will cause an increase in defect during polishing; if the temperature is kept high for too long, the condensation between hydroxyl groups increases, resulting in a decrease in the overall hydroxyl groups, thereby reducing the removal rate of silicon oxide OX.

[0046] The modified silica sol provided by the present invention can be applied in a polishing composition. The present invention also provides a chemical mechanical polishing composition, which includes water, a basic compound, a pH regulator, and the modified silica sol according to any one of the above implementation manners. The modified silica sol has good dispersibility and does not require an additional surfactant during polishing.

[0047] In an embodiment of the present invention, the basic compound is selected from at least any one of piperazine, methylpiperazine, pyrazine, pyridazine, monoethanolamine, isopropanolamine, imidazole, methylimidazole, guanidine carbonate, tetramethylguanidine, ethylenediamine, ammonium hydroxide, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide.

[0048] In an embodiment of the present invention, the pH regulator is selected from at least any one of tetrazole, imidazole, 1-methylimidazole, 2-methylimidazole, 4-methylimidazole, pyrazole, 1-methylpyrazole, 3-methylpyrazole, and 4-methylpyrazole, preferably tetrazole and imidazole. The pH regulator is used to adjust the pH value of the concentrate to prevent the dissolution of nano-silica particles due to too strong alkalinity of the concentrate. At the same time, the anions generated by its ionization or hydrolysis have a complexing effect on metal ions in the composition, etc. The preferred pH adjustment range is between 8 and 12.5.

[0049] In an embodiment of the present invention, the water is preferably ultrapure water.

[0050] The preparation method of the polishing composition of the present invention can be, for example, mixing each component known in the art. Specifically, for example, a preparation method of a polishing composition includes the step of mixing a modified silica sol, an alkaline compound, a pH regulator, and other additives.

[0051] The polishing method of the present invention includes: providing a chemical mechanical polishing pad having a polishing surface; generating dynamic contact at the interface between the chemical mechanical polishing pad and the substrate; and dispensing the chemical mechanical polishing composition of the present invention onto the polishing surface of the chemical mechanical polishing pad at or near the interface between the chemical mechanical polishing pad and the substrate; wherein at least some dielectric materials are polished off from the substrate.

[0052] The above and other advantages of the present invention can be better understood through the following examples, but the following examples are not intended to limit the scope of the present invention.

[0053] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods; unless otherwise specified, the reagents, materials, etc. used in the following examples can all be obtained from commercial sources.

[0054] <Preparation of Modified Silica Sol>

[0055] Example 1

[0056] S1. Preparation of microemulsion: Mix tetraethyl orthosilicate (235 g), surfactant XIAMETER TM OFX-3667 (50 g), and n-butanol (40 g), stir at 150 rpm for 5 min, add ultrapure water (4000 g) to form an oil-in-water primary emulsion, then perform mechanical homogenization at 5000 rpm for 90 min, and control the temperature through a cold water bath at 10 °C to obtain a nano-scale microemulsion with uniform particle size;

[0057] S2. Generation of nanoparticles: Add ammonia water (340 g) with a mass fraction of 29% to the above microemulsion, stir and react at 25 °C for 5 hours, so that tetraethyl orthosilicate undergoes hydrolysis and condensation reactions under the action of a catalyst to generate silicon dioxide nanoparticles;

[0058] S3. Separation of alcohols: Carry out vacuum distillation on the reaction system at a temperature of 85 °C and a negative pressure of 90 kPa to remove the by-product alcohols in the reaction;

[0059] S4. Surface modification grafting: After the vacuum distillation is completed, stir and react the reaction system at 90 °C for 8 h, so as to graft polyether modification groups on the surface of the silicon dioxide particles, and finally obtain the modified silicon dioxide sol B1.

[0060] Example 2

[0061] S1. Preparation of microemulsion: Mix methyltrimethoxysilane (2420 g), surfactant VORASURF TM DC 5103 (700 g), and n-butanol (25 g), stir at 200 rpm for 6 min, add ultrapure water (3900 g) to form an oil-in-water primary emulsion, then carry out mechanical homogenization at 4000 rpm for 120 min, and control the temperature through a 15 °C cold water bath to obtain a nano-scale microemulsion with uniform particle size;

[0062] S2. Generation of nanoparticles: Add ammonium carbonate aqueous solution (425 g) with a mass fraction of 20% to the above microemulsion, stir and react at 30 °C for 6 hours, so that methyltrimethoxysilane undergoes hydrolysis and condensation reactions under the action of a catalyst to generate silicon dioxide nanoparticles;

[0063] S3. Separation of alcohols: Carry out vacuum distillation on the reaction system at a temperature of 65 °C and a negative pressure of 95 kPa to remove the by-product alcohols in the reaction;

[0064] S4. Surface modification grafting: After the vacuum distillation is completed, stir and react the reaction system at 110 °C for 4 h, so as to graft polyether modification groups on the surface of the silicon dioxide particles, and finally obtain the modified silicon dioxide sol B2.

[0065] Example 3

[0066] S1. Preparation of microemulsion: Mix ethyltriethoxysilane (1600 g), surfactant XIAMETER TM OFX-5211 (300 g), n-pentanol (20 g) and 1,2-pentanediol (20 g), stir at 150 rpm for 5 min, add ultrapure water (1800 g) to form an oil-in-water primary emulsion, then carry out mechanical homogenization at 9000 rpm for 30 min, and control the temperature through a 20 °C cold water bath to obtain a nano-scale microemulsion with uniform particle size;

[0067] S2, Nanoparticle Generation: Add 29% by mass of ammonia water (260 g) to the above microemulsion, stir and react at 40 °C for 2 hours to cause hydrolysis and condensation reactions of ethyltriethoxysilane under the action of a catalyst to generate silicon dioxide nanoparticles;

[0068] S3, Alcohol Separation: Carry out vacuum distillation on the reaction system at a temperature of 70 °C and a negative pressure of 98 kPa to remove the by-product alcohols;

[0069] S4, Surface Modification Grafting: After the vacuum distillation is completed, stir and react the reaction system at 140 °C for 2 h to graft polyether modification groups on the surface of the silicon dioxide particles, and finally obtain the modified silicon dioxide sol B3.

[0070] Example 4

[0071] S1, Microemulsion Preparation: Mix methyltrimethoxysilane (490 g), surfactant XIAMETER TM OFX-5211 (490 g) and n-butanol (40 g), stir at 150 rpm for 5 min, add ultrapure water (3500 g) to form an oil-in-water primary emulsion, then carry out mechanical homogenization at 8000 rpm for 90 min, and control the temperature through a 10 °C cold water bath to obtain a nano-scale microemulsion with uniform particle size;

[0072] S2, Nanoparticle Generation: Add 29% by mass of ammonia water (340 g) to the above microemulsion, stir and react at 30 °C for 6 hours to cause hydrolysis and condensation reactions of methyltrimethoxysilane under the action of a catalyst to generate silicon dioxide nanoparticles;

[0073] S3, Alcohol Separation: Carry out vacuum distillation on the reaction system at a temperature of 80 °C and a negative pressure of 85 kPa to remove the by-product alcohols;

[0074] S4, Surface Modification Grafting: After the vacuum distillation is completed, stir and react the reaction system at 100 °C for 6 h to graft polyether modification groups on the surface of the silicon dioxide particles, and finally obtain the modified silicon dioxide sol B4.

[0075] Example 5

[0076] S1, Microemulsion Preparation: Mix methyltrimethoxysilane (1450 g), surfactant XIAMETER TMMix OFX-5211 (550 g) and n-butanol (40 g), stir at 150 rpm for 5 min, add ultrapure water (2000 g) to form an oil-in-water primary emulsion, then perform mechanical homogenization at 8000 rpm for 90 min, and control the temperature through a cold water bath at 10 °C to obtain a nano-scale microemulsion with uniform particle size;

[0077] S2. Nanoparticle generation: Add ammonia water (340 g) with a mass fraction of 29% to the above microemulsion, stir and react at 30 °C for 6 hours to cause the hydrolysis and condensation reaction of methyltrimethoxysilane under the action of a catalyst to generate silica nanoparticles;

[0078] S3. Alcohol separation: Perform vacuum distillation on the reaction system at a temperature of 80 °C and a negative pressure of 85 kPa to remove the by-product alcohols;

[0079] S4. Surface modification grafting: After the vacuum distillation is completed, stir and react the reaction system at 100 °C for 6 h to graft polyether modification groups on the surface of the silica particles, and finally obtain modified silica sol B5.

[0080] Example 6

[0081] S1. Microemulsion preparation: Mix methyltrimethoxysilane (1500 g), surfactant XIAMETER TM OFX-5211 (300 g) and n-butanol (40 g), stir at 150 rpm for 5 min, add ultrapure water (3000 g) to form an oil-in-water primary emulsion, then perform mechanical homogenization at 8000 rpm for 90 min, and control the temperature through a cold water bath at 10 °C to obtain a nano-scale microemulsion with uniform particle size;

[0082] S2. Nanoparticle generation: Add ammonia water (340 g) with a mass fraction of 29% to the above microemulsion, stir and react at 30 °C for 6 hours to cause the hydrolysis and condensation reaction of methyltrimethoxysilane under the action of a catalyst to generate silica nanoparticles;

[0083] S3. Alcohol separation: Perform vacuum distillation on the reaction system at a temperature of 80 °C and a negative pressure of 85 kPa to remove the by-product alcohols;

[0084] S4. Surface modification grafting: After the vacuum distillation is completed, stir and react the reaction system at 100 °C for 6 h to graft polyether modification groups on the surface of the silica particles, and finally obtain modified silica sol B6.

[0085] Example 7

[0086] S1. Microemulsion preparation: Mix methyltrimethoxysilane (1750 g), surfactant XIAMETERTM Mix OFX-5211 (275 g) and n-butanol (40 g), stir at 150 rpm for 5 min, add ultrapure water (2540 g) to form an oil-in-water primary emulsion, then perform mechanical homogenization at 8000 rpm for 90 min, and control the temperature through a cold water bath at 10 °C to obtain a nano-scale microemulsion with uniform particle size;

[0087] S2. Generation of nanoparticles: Add ammonia water (340 g) with a mass fraction of 29% to the above microemulsion, stir and react at 30 °C for 6 hours to cause the hydrolysis and condensation reaction of methyltrimethoxysilane under the action of a catalyst to generate silica nanoparticles;

[0088] S3. Separation of alcohols: Perform vacuum distillation on the reaction system at a temperature of 80 °C and a negative pressure of 85 kPa to remove the by-product alcohols;

[0089] S4. Surface modification grafting: After the vacuum distillation is completed, stir and react the reaction system at 100 °C for 6 h to graft polyether modification groups on the surface of the silica particles, and finally obtain modified silica sol B7.

[0090] Example 8

[0091] S1. Preparation of microemulsion: Mix methyltrimethoxysilane (2420 g), surfactant XIAMETER TM OFX-5211 (245 g) and n-butanol (40 g), stir at 150 rpm for 5 min, add ultrapure water (3000 g) to form an oil-in-water primary emulsion, then perform mechanical homogenization at 8000 rpm for 90 min, and control the temperature through a cold water bath at 10 °C to obtain a nano-scale microemulsion with uniform particle size;

[0092] S2. Generation of nanoparticles: Add ammonia water (340 g) with a mass fraction of 29% to the above microemulsion, stir and react at 30 °C for 6 hours to cause the hydrolysis and condensation reaction of methyltrimethoxysilane under the action of a catalyst to generate silica nanoparticles;

[0093] S3. Separation of alcohols: Perform vacuum distillation on the reaction system at a temperature of 80 °C and a negative pressure of 85 kPa to remove the by-product alcohols;

[0094] S4. Surface modification grafting: After the vacuum distillation is completed, stir and react the reaction system at 100 °C for 6 h to graft polyether modification groups on the surface of the silica particles, and finally obtain modified silica sol B8.

[0095] Example 9

[0096] S1. Microemulsion preparation: Mix tetraethyl orthosilicate (2420 g), surfactant XIAMETER TM OFX-3667 (700 g) and n-butanol (25 g), stir at 150 rpm for 5 min, add ultrapure water (3900 g) to form an oil-in-water primary emulsion, then perform mechanical homogenization at 8000 rpm for 90 min, and control the temperature through a cold water bath at 10 °C to obtain a nano-scale microemulsion with uniform particle size;

[0097] S2. Nanoparticle generation: Add ethanolamine with a mass fraction of 20% (425 g) to the above microemulsion, stir and react at 30 °C for 6 hours, so that tetraethyl orthosilicate undergoes hydrolysis and condensation reactions under the action of a catalyst to generate silicon dioxide nanoparticles;

[0098] S3. Alcohol separation: Perform vacuum distillation on the reaction system at a temperature of 80 °C and a negative pressure of 85 kPa to remove the by-product alcohols;

[0099] S4. Surface modification grafting: After the vacuum distillation is completed, stir and react the reaction system at 100 °C for 6 h to graft polyether-modified groups on the surface of the silicon dioxide particles, and finally obtain modified silicon dioxide sol B9.

[0100] Example 10

[0101] S1. Microemulsion preparation: Mix tetraethyl orthosilicate (2420 g), surfactant XIAMETER TM OFX-3667 (700 g) and n-butanol (25 g), stir at 150 rpm for 5 min, add ultrapure water (3900 g) to form an oil-in-water primary emulsion, then perform mechanical homogenization at 8000 rpm for 90 min, and control the temperature through a cold water bath at 10 °C to obtain a nano-scale microemulsion with uniform particle size;

[0102] S2. Nanoparticle generation: Add ammonia water with a mass fraction of 29% (425 g) to the above microemulsion, stir and react at 30 °C for 6 hours, so that tetraethyl orthosilicate undergoes hydrolysis and condensation reactions under the action of a catalyst to generate silicon dioxide nanoparticles;

[0103] S3. Alcohol separation: Perform vacuum distillation on the reaction system at a temperature of 80 °C and a negative pressure of 85 kPa to remove the by-product alcohols;

[0104] S4. Surface modification grafting: After the vacuum distillation is completed, stir and react the reaction system at 100 °C for 6 h to graft polyether-modified groups on the surface of the silicon dioxide particles, and finally obtain modified silicon dioxide sol B10.

[0105] Example 11

[0106] S1. Microemulsion preparation: Mix methyltrimethoxysilane (1450 g), surfactant XIAMETER TM OFX-5211 (550 g) and n-butanol (40 g), stir at 150 rpm for 5 min, add ultrapure water (2000 g) to form an oil-in-water primary emulsion, then perform mechanical homogenization at 8000 rpm for 90 min, and control the temperature through a cold water bath at 5 °C to obtain a nanoscale microemulsion with uniform particle size;

[0107] S2. Nanoparticle generation: Add ammonia water (340 g) with a mass fraction of 29% to the above microemulsion, stir and react at 30 °C for 6 hours, so that methyltrimethoxysilane undergoes hydrolysis and condensation reactions under the action of a catalyst to generate silica nanoparticles;

[0108] S3. Alcohol separation: Perform vacuum distillation on the reaction system at a temperature of 80 °C and a negative pressure of 85 kPa to remove the by-product alcohols;

[0109] S4. Surface modification grafting: After the vacuum distillation is completed, stir and react the reaction system at 100 °C for 6 h to graft polyether-modified groups on the surface of the silica particles, and finally obtain modified silica sol B11.

[0110] Example 12

[0111] S1. Microemulsion preparation: Mix methyltrimethoxysilane (1450 g), surfactant XIAMETER TM OFX-5211 (550 g) and n-butanol (40 g), stir at 150 rpm for 5 min, add ultrapure water (2000 g) to form an oil-in-water primary emulsion, then perform mechanical homogenization at 8000 rpm for 90 min, and control the temperature through a cold water bath at 15 °C to obtain a nanoscale microemulsion with uniform particle size;

[0112] S2. Nanoparticle generation: Add ammonia water (340 g) with a mass fraction of 29% to the above microemulsion, stir and react at 30 °C for 6 hours, so that methyltrimethoxysilane undergoes hydrolysis and condensation reactions under the action of a catalyst to generate silica nanoparticles;

[0113] S3. Alcohol separation: Perform vacuum distillation on the reaction system at a temperature of 80 °C and a negative pressure of 85 kPa to remove the by-product alcohols;

[0114] S4. Surface modification grafting: After the vacuum distillation is completed, stir and react the reaction system at 100 °C for 6 h to graft polyether-modified groups on the surface of the silica particles, and finally obtain modified silica sol B12.

[0115] Comparative Example 1

[0116] S1. Preparation of microemulsion: Mix methyltrimethoxysilane (1450 g), surfactant XIAMETER TM OFX-5211 (550 g) and n-butanol (40 g), stir at 150 rpm for 5 min, add ultrapure water (2000 g) to form an oil-in-water primary emulsion, then perform mechanical homogenization at 8000 rpm for 90 min, and control the temperature through a cold water bath at 10 °C to obtain a nano-scale microemulsion with uniform particle size;

[0117] S2. Generation of nanoparticles: Add ammonia water (340 g) with a mass fraction of 29% to the above microemulsion, stir and react at 30 °C for 6 hours to cause the hydrolysis and condensation reaction of methyltrimethoxysilane under the action of a catalyst to generate silica nanoparticles;

[0118] S3. Separation of alcohols: Perform vacuum distillation on the reaction system at a temperature of 80 °C and a negative pressure of 85 kPa to remove the by-product alcohols in the reaction to obtain modified silica sol B13.

[0119] Comparative Example 2:

[0120] Commercially available silica sol (PL-10, FuSO) (650 g, solid content of 19.5%) and surfactant XIAMETER TM OFX-3667 (50 g) are stirred evenly to obtain modified silica sol B14.

[0121] Detection method:

[0122] Solid content of silica: Take the reaction system after the separation of alcohols in step S3, place the sample in a crucible, the mass of the crucible is m0, measure the mass of the crucible and the sample as m1, where m1 - m0 is between 5 - 10 g, place the sample in an oven at 180 °C for 2 h, measure the mass of the dried sample and the crucible as m2, solid content = ((m2 - m0) / (m1 - m0)) * 100%;

[0123] Particle size: The obtained modified silica sol is detected using a Malvern Zetasizer PRO particle size analyzer;

[0124] Surface tension and silicon element content: Centrifuge the prepared modified nano-silica sol at 20000 rpm for 20 minutes to separate the abrasive and supernatant components, use a surface tension meter to detect the surface tension of the supernatant, and use ICP-MS to test the silicon element content in the supernatant.

[0125] Table 1 shows the detection results of the solid content of silica sol, the particle size of modified silica sol, and the surface tension and silicon element content of the supernatant.

[0126]

[0127] As can be seen from Table 1, the solid content of silica in Examples 1-12 and Comparative Example 1 is in the range of 15%-20%, and the average particle size of the modified silica in Examples 1-12 is in the range of 40-200 nm; the surface tension of the supernatant of Examples 1-12 is in the range of 70.6-71.8 mN / m, close to that of pure water (72 mN / m), while the surface tensions of the supernatants of Comparative Examples 1 and 2 are 42.3 and 39.8 mN / m respectively, indicating that the surfactant concentration in the supernatant of Examples 1-12 is extremely low, which shows that the surfactant in Examples 1-12 has been chemically adsorbed and fixed on the silica surface; the silicon element content in the supernatant of Examples 1-12 is 165-216 ppm, and the silicon element content in the supernatant of the comparative example is above 4500 ppm, indicating that there is very little free silicon-containing surfactant in the silica sol, further indicating that the surfactant in Examples 1-12 is chemically adsorbed and fixed on the silica surface through covalent bonds.

[0128] The obtained polishing compositions were prepared from the modified silica sols of the above Examples 1 to 12 and Comparative Examples 1 to 2 for polishing tests, and the test results are shown in Table 2.

[0129] Preparation steps of the polishing composition:

[0130] Raw material composition (by mass percentage): the modified silica sols of the above Examples 1 to 12 and Comparative Examples 1 to 2: 15%, piperazine: 0.5%, imidazole: adjusted to pH = 10, and the rest is ultrapure water.

[0131] Preparation steps: Add the modified silica sol abrasive and ultrapure water into a stirrer for stirring, then add piperazine, etc., and continue stirring, with the temperature ≤ 25°C; dropwise add imidazole until pH = 10.0 ± 0.2, and continue stirring for 30 minutes; filter through a 0.1 μm nylon filter element to remove agglomerated particles to obtain the final polishing composition, and conduct the test of the grinding rate.

[0132] Polishing process parameters: Down pressure 1.5 psi, polishing head and polishing pad rotation speeds 73 rpm / 67 rpm, polishing composition flow rate 200 mL / min, polishing pad is DH3002, and polishing disc is Blue brush.

[0133] Use a SE-VM spectroscopic ellipsometer to measure the film thickness difference before and after grinding, and calculate the grinding rate Use a surface defect scanner SP2 to detect the number of surface defects (>0.16 μm) of the polished blank wafer; use an atomic force microscope (Bruker Dimension) to measure the depth of the dish-shaped depression, with the unit of The polishing effect data are listed in Table 2.

[0134] Table 2 Polishing effects of Application Examples 1-12 and Comparative Examples 1-2 of the polishing composition of the present invention

[0135]

[0136] As can be seen from Table 2, compared with the unmodified silica used in Comparative Example 1, it can be found that when the modified silica prepared by the present invention is used as the abrasive of the polishing composition in Application Example 5, the removal rate of polysilicon is significantly higher than that of Comparative Example 1, and there is no obvious difference in the removal rate of silicon oxide. The polishing selectivity in Application Example 5 is higher than that of Comparative Example 1, and the number of defects on the wafer surface after polishing decreases significantly, while the depth of dishing in Comparative Example 1 increases significantly. This indicates that the modified silica described in the present invention can effectively inhibit the generation and expansion of dishing during the polishing of polysilicon, and can reduce the generation of surface defects of wafer silicon oxide and polysilicon during the polishing process.

[0137] Compared with the unmodified silica used in Comparative Example 2, it can be found that when the modified silica prepared by the present invention is used as the abrasive of the polishing composition in Application Example 1, the polishing selectivity in Application Example 1 is higher than that of Comparative Example 2, and the number of defects on the wafer surface after polishing decreases significantly, while the depth of dishing in Comparative Example 2 increases significantly. This indicates that the modified silica described in the present invention can effectively inhibit the generation of dishing during the polishing of polysilicon, and can reduce the generation of surface defects of wafer silicon oxide and polysilicon during the polishing process.

[0138] As can be seen from Table 2, in Application Examples 4-8, when the mass ratio of the silicon-containing monomer to the surfactant is 1:1-10:1, the removal rates of polysilicon and silicon oxide increase with the increase of the amount of the silicon-containing monomer. However, when the mass ratio of the silicon-containing monomer to the surfactant is 1:1-5:1 and the prepared modified silica is used as the abrasive of the polishing composition, the polishing selectivity increases with the increase of the amount of the silicon-containing monomer, and at the same time, the generation of polishing defects can be avoided during the polishing process.

[0139] As can be seen from Table 2, in Application Examples 2, 8, and 9, compared with ammonia water and ammonium carbonate, when the alkaline catalyst is ethanolamine and the prepared modified silica is used as the abrasive of the polishing composition, the defects and dishing defects on the wafer surface after polishing are significantly improved.

[0140] As can be seen from Table 2, in Application Examples 5, 11, and 12, in step S1 of preparing the modified silica, the cold water bath temperature is preferably 5-10°C. When the prepared modified silica is used as the abrasive of the polishing composition, the defects and dishing defects on the wafer surface after polishing are significantly improved.

[0141] Although the present invention has been described in detail above with general descriptions, specific embodiments and experiments, modifications or improvements can be made to it based on the present invention, which are obvious to those skilled in the art. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of the present invention claimed.

Claims

1. A preparation method of a modified silica sol, characterized in that, It includes the following steps: S1. Microemulsion preparation: First, a silicon-containing monomer, a surfactant, a co-surfactant, and water are mixed in a certain proportion to form an oil-in-water primary emulsion. Subsequently, mechanical homogenization is carried out at a rotation speed of 3000 - 9000 rpm for 30 - 120 min, and the temperature is controlled by a cold water bath at 5 - 20 °C to obtain a nano-scale microemulsion with uniform particle size; wherein, the surfactant is selected from polyether silicone surfactants with an HLB value in the range of 8 - 18. S2. Nanoparticle generation: A basic catalyst is added to the above microemulsion in a certain proportion and mixed. The reaction is carried out at a temperature of 5 - 40 °C for 1 - 10 h, so that the oil phase in the microemulsion undergoes hydrolysis and condensation reactions under the action of the catalyst to generate silicon dioxide nanoparticles. S3. Alcohol separation: By vacuum distillation at a temperature of 60 - 90 °C and a negative pressure of 70 - 98 kPa, the reaction by-product alcohols are removed, and the solution is concentrated under reduced pressure to a solid content of 15 - 20%. S4. Surface modification grafting: After the vacuum distillation is completed, the reaction system is reacted at 80 - 140 °C for 1 - 24 hours, so as to graft polyether-modified groups on the surface of the silicon dioxide particles, and finally a nano-scale modified silicon dioxide sol is obtained.

2. A preparation method of the modified silica sol as described in claim 1, characterized in that, In S1, first, the silicon-containing monomer, the surfactant, and the co-surfactant are mixed in a certain proportion and stirred at 100 - 200 rpm for 2 - 15 min to form a uniform oil-phase solution. Then, under continuous stirring, water is added to the above oil-phase system to form an oil-in-water primary emulsion.

3. A method for preparing the modified silica sol as described in claim 1 or 2, characterized in that, The silicon-containing monomer is selected from at least one of methyl orthosilicate, ethyl orthosilicate, methyltrimethoxysilane, methyltriethoxysilane, or ethyltrimethoxysilane. and / or, the surfactant is selected from XIAMETER of Dow TM OFX-3667, VORASURF TM DC 5103 or XIAMETER TM OFX-5211; And / or, the co-surfactant is selected from one or more of n-butanol, propylene glycol, triethanolamine, n-pentanol, iso-pentanol, or 1,2-pentanediol.

4. A method for preparing the modified silica sol as described in claim 1 or 2, characterized in that, The basic catalyst is selected from one or more of ammonia water, ammonium carbonate, or ethanolamine, and ethanolamine is preferred.

5. A method for preparing the modified silica sol as described in claim 1 or 2, characterized in that, Calculated based on the total mass of the reactants added, the dosage of the silicon-containing monomer is 5 - 40 wt%. And / or, the dosage of the surfactant is 1 - 15 wt%. And / or, the dosage of the co-surfactant is 0.01 - 5 wt%. And / or, the dosage of the basic catalyst is 0.1% - 5 wt%. Wherein, the total mass of the reactants added refers to the total mass of the silicon-containing monomer, the surfactant, the co-surfactant, water, and the basic catalyst.

6. A method for preparing the modified silica sol as described in claim 1 or 2, characterized in that, The mass ratio of the silicon-containing monomer to the surfactant is 1:1 - 10:1, preferably 1:1 - 5:

1.

7. A method for preparing the modified silica sol as described in claim 1 or 2, characterized in that, In step S1, the temperature range of the cold water bath is preferably 5 - 10 °C.

8. A method for preparing the modified silica sol as described in claim 1 or 2, characterized in that, In step S4, the reaction temperature is preferably 90 - 110 °C, and the reaction time is preferably 4 - 8 hours.

9. A modified silica sol, characterized in that, A modified silicon dioxide sol prepared by the preparation method according to any one of claims 1 - 8 above.

10. Use of a modified silicon dioxide sol as described in claim 9 in a polishing composition.

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