Sol gel silica with low dispersity and controllable particle size and synthesis method thereof

Abstract

The application discloses a sol silica with controllable particle size and low dispersity and a synthesis method, and adopts a seed pre-preparation method, wherein part of organosilanes is added into an alkaline aqueous solution containing polyols and a particle size stabilizer, the seed is pre-prepared by stirring, and then the rest of the organosilanes is continuously added to prepare the sol silica. The sol silica prepared by the method has controllable particle size, low dispersity and excellent stability, can be used in an etching solution to improve the selectivity ratio of Si3N4 / SiO2, thereby improving the manufacturing layer number of the guarantee; meanwhile, the sol silica with high particle size prepared by the method can be used in a CMP abrasive, thereby significantly improving the polishing performance and effectively enriching the market of domestic semiconductor polishing materials.

Description

Technical Field

[0001] This invention belongs to the field of electronic chemicals technology, specifically relating to a sol-gel silica with controllable particle size and low dispersion, and its synthesis method. Background Technology

[0002] Sol-gel silica is a colloidal sol with near-spherical particles and a negative charge. Its aggregation and kinetic stability are conferred by three main factors: zeta potential, Brownian motion, and sufficient solvent barrier. The colloidal particles are metastable and always have a tendency to spontaneously aggregate. When any one of the three factors is weakened, they will automatically aggregate, forming a gel or sediment. Sol-gel silica has a large adsorption capacity and specific surface area, exhibiting good adhesion, temperature resistance, wear resistance, and light transmittance. It also possesses high dispersibility, making it a good dispersant, preservative, flocculant, and coolant. With technological advancements, sol-gel silica can also be used for etching semiconductor materials and as a CMP abrasive.

[0003] From early MLC to today's QLC technology, memory technology has been rapidly iterating and evolving. The maximum capacity of memory chips has increased from KB to TB, and memory density has become a crucial factor that memory chip design companies are vying to surpass. Higher memory density requires greater etching and a higher selectivity ratio between Si3N4 and silicon dioxide. To improve the memory density of information technology devices, some semiconductor companies have designed shallow trench isolation (STI) technology to manufacture semiconductors at extreme scales with zero leakage current. In this process, a solid-phase silicon nitride (Si3N4) layer acts as a mask during partial silicon dioxide (SiO2) deposition. This deposition forms a vertically stacked structure consisting of hundreds of alternating layers of Si3N4 and silicon dioxide atoms. The Si3N4 mask must be removed at the end of the process, typically through thermochemical etching. Therefore, selective and complete etching of Si3N4 onto silicon dioxide is a critical step in manufacturing high-performance semiconductor devices using STI technology.

[0004] Typically, selectivity is defined as the ratio between the etching rates of Si3N4 and silicon dioxide. However, selective etching is quite challenging due to the marginal difference in the preferential chemical affinity of conventional etchants for the two silicon materials. Furthermore, both materials are chemically inert at standard temperatures and pressures. In contemporary methods, etching is performed under two distinct conditions: dry etching and wet etching. Dry etching physically removes material through ion bombardment. It is known to produce high-resolution etching due to the anisotropy and negligible tendency of undercutting. However, low selectivity is detrimental to thin films because ions randomly attack the surface, even damaging the substrate. On the other hand, wet etching exhibits higher selectivity than dry etching, causes less damage to the substrate, and is more suitable for large-scale production. Therefore, wet etching is commonly used in various commercial manufacturing technologies.

[0005] Studies have found that adding sol-silica to concentrated phosphoric acid at 140-160℃ provides a high selectivity. However, commercially available sol-silica has a uniform particle size, causing the selectivity of the phosphoric acid etching solution to vary with particle size, affecting etching results. Furthermore, each batch of sol-silica needs to be used within six months, otherwise precipitation will occur, reducing its content and leading to etching failure. In addition, each batch of sol-silica produced by the same company will differ from batch to batch, requiring retesting and adjustment of the amount added to achieve the desired selectivity.

[0006] Chemical mechanical polishing (CMP) is a technology that combines mechanical grinding and chemical etching. It uses the grinding action of ultrafine particles and the chemical etching action of slurry to form a smooth surface on the surface of the medium being polished (such as single crystal silicon wafers, oxide films on integrated circuits, metal films, etc.). It overcomes the disadvantages of traditional chemical polishing, such as slow polishing speed and easy to cause polishing haze, as well as the disadvantages of mechanical polishing, such as easy to cause mechanical damage and low polishing precision. It has now become the dominant technology in the semiconductor processing industry.

[0007] Abrasives are the main component of CMP slurry, playing two roles in the CMP process: (1) acting as the implementer of mechanical action, performing mechanical grinding; and (2) transporting materials, not only transferring fresh slurry between the polishing pad and the material being polished, but also carrying reactants away from the material surface, exposing the new surface of the material for further reaction and removal. When selecting abrasives, priority should be given to those with good dispersibility, good fluidity, moderate hardness, and easy cleaning.

[0008] Currently, commonly used abrasives in CMP processes include sol-gel silica, cerium dioxide, and alumina. Cerium dioxide offers advantages such as fast polishing speed, low hardness, and good stability. However, most cerium dioxide used is mechanically ground, resulting in large particle size dispersion and high viscosity. Furthermore, its high-low selectivity during polishing is relatively poor, and it is also quite expensive. Alumina, due to its high hardness, easily scratches the surface of soft workpieces, making it unsuitable for polishing softer materials. Sol-gel silica, with particle sizes ranging from 1-100 nm, possesses a large specific surface area, high dispersibility, and excellent permeability, resulting in minimal damage to the polished workpiece surface. Additionally, silica's hardness is similar to that of silicon wafers, making it commonly used for polishing semiconductor silicon wafers. In summary, sol-gel silica offers advantages such as controllable particle size, moderate hardness, low viscosity, low adhesion, and easy cleaning after polishing.

[0009] The current international polishing slurry market is trending towards fragmentation, with a significant shortage of domestically produced materials. There is considerable room for development in the domestic CMP materials market. However, silica polishing slurries suffer from poor particle size controllability, low dispersion, short shelf life, and poor batch stability, requiring further improvement. Today, advanced manufacturing processes necessitate customized polishing pads to meet specific requirements. Specialization and customization of polishing slurries will present opportunities for emerging domestic manufacturers. Silica polishing slurries can be modified based on the characteristics of the workpiece, adjusting properties such as particle size, hardness, and pH to better meet diverse application needs. Therefore, the application prospects of silica polishing slurries in the field of chemical mechanical polishing are very broad.

[0010] Currently, sol-crystal produced using traditional processes suffers from uneven particle size and high dispersion when reducing its particle size. Furthermore, the batch stability of sol-crystal produced by different companies is poor, with inconsistent particle size and dispersion between batches. As a result, even with the development of semiconductor etching and CMP abrasive applications, a significant amount of time still needs to be spent screening for the same type of sol-crystal with suitable particle size and low dispersion. This leads to a substantial waste of human and material resources and significantly reduces production efficiency, thereby limiting the further development of semiconductor and CMP technologies. Summary of the Invention

[0011] To address the aforementioned technical problems, this invention provides a sol-gel silica with controllable particle size and low dispersion, and a method for its synthesis. The prepared sol-gel silica can improve the selectivity ratio of silicon nitride to silicon dioxide, as well as its durability in CMP abrasives.

[0012] To achieve the above objectives, the present invention provides a sol-gel silica with controllable particle size and low dispersion, wherein the sol-gel silica comprises the following raw materials in the following mass percentages: 10-30% organosilane, 0.3-3% alkaline substance, 0.1-1% particle size stabilizer, 0.01-0.2% polyol, and the balance being deionized water.

[0013] Preferably, the organosilane is any one of methyltrimethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, methyltriethoxysilane, tetraethyl orthosilicate, aminopropyltriethoxysilane, cyanoethyltriethoxysilane, and mercaptoethyltriethoxysilane.

[0014] Preferably, the alkaline substance is any one of sodium hydroxide solution, potassium hydroxide solution, tetramethylammonium hydroxide solution, ethylenediamine solution, triethylamine solution, ammonia solution, diethanolamine solution, and triethanolamine solution, with a mass concentration of 10%-28%; more preferably, it is any one of 10% sodium hydroxide, 10% potassium hydroxide, 25% tetramethylammonium hydroxide, 20% ethylenediamine, 20% triethylamine, 28% ammonia solution, 25% diethanolamine, and 25% triethanolamine.

[0015] Preferably, the particle size stabilizer is any one of OP-10, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, polyethylene glycol, and fatty alcohol polyoxyethylene ether.

[0016] Preferably, the polyol is any one of diethylene glycol, diethylene glycol monohydrate, glycerol, ethylene glycol, isopropanol, and pentaerythritol.

[0017] This invention also provides a method for synthesizing sol-gel silica with controllable particle size and low dispersion, comprising the following steps:

[0018] (1) Preparation of mother liquor: Add ammonia to deionized water to adjust the pH to 11-12.5, then add polyol and particle size stabilizer in proportion, mix evenly to obtain mother liquor;

[0019] (2) Seed preparation: Add organosilane dropwise to the mother liquor while stirring and heating. After the addition is completed, keep warm for 3 hours to obtain seed liquor;

[0020] (3) Secondary addition: Add the remaining organosilane to the seed liquid and keep the solution pH > 8. After the addition is complete, keep it warm for 3 hours to obtain sol silica.

[0021] Preferably, the organosilane added in step (2) accounts for 10-50% of the total organosilane.

[0022] Preferably, the dropping rate in steps (2) and (3) is 1-5 mL / min, the stirring speed is 50-1750 rpm / min, and the temperature is 60-70℃.

[0023] This invention also provides an application of sol-gel silica with controllable particle size and low dispersion in semiconductor processing technology.

[0024] Preferably, the semiconductor processing technology is semiconductor etching technology or semiconductor polishing technology.

[0025] The beneficial effects of this invention are as follows:

[0026] 1. Select organosilanes containing hydrophilic groups and / or branched hydrolytic groups as the main raw materials to control the particle size of the prepared sol silica. When preparing sol silica with a particle size range of 10-50 nm, select organosilanes with more hydrophilic groups or only branched hydrolytic groups; when preparing sol silica with a particle size range of 50-100 nm, select organosilanes with more branched hydrolytic groups and some hydrophilic groups; when preparing sol silica with a particle size range of 100-200 nm, select organosilanes with fewer branched hydrolytic groups and a small amount of hydrophilic groups to control the particle size of the sol silica.

[0027] 2. The organosilane is divided into two parts. 10-50% of the total mass of organosilane is added dropwise to the mother liquor containing polyol and particle size dispersant. Monodisperse sol-silica is prepared first using the seed pre-preparation method as a seed. Then, the remaining organosilane is added dropwise to the solution to allow the seeds to grow synchronously on the seeds, thereby preparing sol-silica with controllable particle size and low dispersion.

[0028] 3. Alkaline compounds are used in the preparation process. On the one hand, they can enhance the alkalinity of the solution, and on the other hand, they can reduce the anisotropy in the synthesis process and reduce the particle size of sol silica. Alkaline solutions are added as needed to adjust the sol silica to obtain the required particle size.

[0029] 4. Introducing a particle size stabilizer into the raw materials greatly improves the stability of sol-silica in water, increasing the absolute value of the ZETA potential from 11 to 61.25, resulting in excellent particle stability.

[0030] 5. With the addition of polyols and the increase in the amount of polyols, the dispersibility of the prepared sol-silica gradually improved, and the particle size was stabilized within the required range. The measured PDI < 0.1 indicates that the particle size of the prepared sol-silica is relatively concentrated. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the structure containing silicon nitride and silicon dioxide thin films in Example 2. In the figure, A is a schematic diagram of the structure before etching, and B is a schematic diagram of the ideal etching effect.

[0032] Figure 2 The figures show a comparison of the number of etched silicon nitride and silicon dioxide thin films after etching with different etching solutions in Example 2 and Comparative Example 1. In the figures, A is the SEM image of the etching after adding sol-gel silicon dioxide to the etching solution in Example 2, and B is the SEM image of the etching after not adding sol-gel silicon dioxide to the etching solution in Comparative Example 1.

[0033] Figure 3The figures show the ZETA potential diagrams of sol-gel silica prepared in Example 9 and Comparative Example 2, where A represents Comparative Example 2 and B represents Example 9.

[0034] Figure 4 The figures show silicon wafers before and after polishing in Example 10. In the figure, A represents the wafer before polishing and B represents the wafer after polishing. Detailed Implementation

[0035] The technical solution of the present invention will be further explained and described below with reference to the accompanying drawings and specific embodiments. It is worth noting that the following embodiments are only preferred embodiments of the present invention and should not be construed as limiting the present invention. The scope of protection of the present invention should be determined by the contents of the claims. Modifications and substitutions made by those skilled in the art to the technical solution of the present invention without creative effort all fall within the scope of protection of the present invention.

[0036] Example 1

[0037] A sol-gel silica with a particle size of 10 nm was synthesized, and the specific synthesis method is as follows:

[0038] Raw materials: Methyltrimethoxysilane, possessing three excellent hydrolytic groups—methoxy groups—can rapidly hydrolyze to form hydrophilic compounds, with a mass content of 13.5%; ammonia (mass concentration of 28%) content not exceeding 0.35%; sodium dodecyl sulfate content of 0.12%; diethylene glycol content of 0.05%; the remainder being deionized water.

[0039] (1) Preparation of mother liquor: Add ammonia to 3000mL of deionized water, adjust the pH to 12, then add 0.12% diethylene glycol and 0.5% polyethylene glycol (PEG), and stir evenly to obtain the mother liquor;

[0040] (2) Seed preparation: 3% methyltrimethoxysilane was added dropwise to the mother liquor at a rate of 1.5 mL / min using a peristaltic pump. The mixture was stirred with a φ100 mm polytetrafluoroethylene stirring paddle at a stirring speed of 750 rpm. At the same time, the solution was heated to 65℃. After the addition of methyltrimethoxysilane, the pH of the solution was measured to be 9 (if the pH is lower than 9, ammonia water needs to be added to adjust the pH to 9; if the pH is higher than 9, some silane is added dropwise until the pH is 9). The solution was kept warm for 3 hours to obtain the seed liquid.

[0041] (3) Secondary addition: The remaining 10.5% methyltrimethoxysilane was added to the seed solution at a rate of 3 mL / min. During the reaction, ammonia was added to keep the solution pH > 8. After the addition was completed, the solution was kept warm for 3 h to obtain sol silica.

[0042] Example 2

[0043] Etching experiments were conducted on thin films containing silicon nitride and silicon dioxide using phosphoric acid and the sol-gel silica prepared in Example 1. The structure of the thin film containing silicon nitride and silicon dioxide is as follows: Figure 1 As shown in Figure A, its ideal etching effect is as follows: Figure 1 As shown in B, the specific steps of the etching experiment are as follows:

[0044] (1) Cut the film containing silicon nitride and silicon oxide into regular squares with a size of 2*2cm, then place them in a 200:1 DHF solution for 30s to remove the oxide layer on the surface, and then place them in an 88% phosphoric acid solution at 165℃ for 10min.

[0045] (2) The silicon nitride and silicon dioxide in the thin film were measured by an ellipsometry polarimeter. The initial thickness of silicon nitride and silicon dioxide was calculated by model fitting. The average value of four points was taken for each film.

[0046] (3) Preparation of etching solution: 1% (mass percentage) of the sol-silica prepared in Example 1 was added to 100g of phosphoric acid solution with a mass concentration of 85.5% and mixed evenly to obtain etching solution; at the same time, only the 85.5% phosphoric acid solution was used as etching solution for etching.

[0047] (4) Place the thin film containing silicon nitride and silicon dioxide into the etching solution and etch at 145°C for 5 min (30 min for silicon oxide wafers), then clean it and blow it dry with nitrogen.

[0048] (5) Use an ellipsometry to test the spectra of silicon nitride and silicon dioxide respectively (keep the test points consistent with those before etching), fit the data, calculate and take the average value to obtain the thickness of silicon nitride and silicon dioxide, and calculate the etching rate of silicon nitride and silicon dioxide.

[0049] The results showed that using a phosphoric acid solution with added sol-silica as the etching solution, the etching rate of silicon nitride could reach [a certain percentage]. The etching rate of silicon oxide is The selection ratio is as high as 1650 ( Figure 2 A).

[0050] Comparative Example 1

[0051] The method and steps are the same as in Example 2, except that the etching solution is replaced with 100g of 85.5% phosphoric acid solution to etch the thin film containing silicon nitride and silicon oxide. The etching rate of the etching solution on silicon nitride can reach [missing information]. The etching rate of silicon oxide is The selection ratio was only 64 ( Figure 2 B).

[0052] Example 3

[0053] A sol-gel silica with a particle size of 10 nm was synthesized, and the specific synthesis method is as follows:

[0054] Raw materials: Dimethyldimethoxysilane with a mass content of 11.8%, ethylenediamine (mass concentration of 20%) with a mass content of 0.82%, OP-10 with a mass content of 0.33%, ethylene glycol with a mass content of 0.03%, and the remainder being deionized water.

[0055] (1) Preparation of mother liquor: Add ethylenediamine to 3000 mL of deionized water to adjust the pH to 12, then add 0.03% ethylene glycol and 0.33% OP-10, and mix well to obtain the mother liquor:

[0056] (2) Seed preparation: 3% dimethyldimethoxysilane was added dropwise to the mother liquor at a rate of 1.5 mL / min using a peristaltic pump. The mixture was stirred with a φ100 mm polytetrafluoroethylene stirring paddle at a stirring speed of 1000 rpm. At the same time, the solution was heated to 65℃. After the addition of dimethyldimethoxysilane was completed, the pH of the solution was measured to be 9. The solution was kept warm for 3 hours to obtain the seed liquid.

[0057] (3) Secondary addition: The remaining 8.8% dimethyldimethoxysilane was added to the seed solution at a rate of 3 mL / min. The pH was measured during the reaction and kept at pH > 8. After the addition was completed, the solution was kept warm for 3 h to obtain sol silica.

[0058] Example 4

[0059] A sol-gel silica with a particle size of 10 nm was synthesized, and the specific synthesis method is as follows:

[0060] Raw materials: 13.5% dimethyldimethoxysilane, 2.58% ammonia (28% by mass), 0.15% sodium dodecylbenzenesulfonate, 0.15% diethylene glycol, and the remainder is deionized water.

[0061] (1) Preparation of mother liquor: Add ammonia to 3000 mL of deionized water to adjust the pH to 12, then add 0.15% diethylene glycol and 0.15% sodium dodecylbenzenesulfonate, and mix well to obtain the mother liquor:

[0062] (2) Seed preparation: 3% dimethyldimethoxysilane was added dropwise to the mother liquor at a rate of 1.2 mL / min using a peristaltic pump. The mixture was stirred with a φ100 mm polytetrafluoroethylene stirring paddle at a stirring speed of 900 rpm. At the same time, the solution was heated to 65℃. After the addition of dimethyldimethoxysilane was completed, the pH of the solution was measured to be 9. The solution was kept warm for 3 hours to obtain the seed liquid.

[0063] (3) Secondary addition: The remaining 10.5% dimethyldimethoxysilane was added to the seed solution at a rate of 3 mL / min. The pH was measured during the reaction and kept at pH > 8. After the addition was completed, the solution was kept warm for 3 h to obtain sol silica.

[0064] Example 5

[0065] A sol-gel silica with a particle size of 10 nm was synthesized, and the specific synthesis method is as follows:

[0066] Raw materials: Tetraethyl orthosilicate with a mass content of 13.5%, sodium hydroxide (mass concentration of 10%) with a mass concentration not exceeding 2.24%, fatty alcohol polyoxyethylene ether with a mass content of 0.12%, diethylene glycol with a mass content of 0.10%, and the remainder being deionized water.

[0067] (1) Preparation of mother liquor: Add ammonia to 3000 mL of deionized water to adjust the pH to 12.5, then add 0.10% diethylene glycol and 0.12% sodium dodecyl sulfate, and mix well to obtain the mother liquor:

[0068] (2) Seed preparation: 3% tetraethyl orthosilicate was added dropwise to the mother liquor at a rate of 1.0 mL / min using a peristaltic pump. The mixture was stirred with a φ100 mm polytetrafluoroethylene stirring paddle at a stirring speed of 850 rpm. At the same time, the solution was heated to 65°C. After the addition of tetraethyl orthosilicate was completed, the pH of the solution was measured to be 9. The solution was kept warm for 3 hours to obtain the seed liquid.

[0069] (3) Secondary addition: The remaining 10.5% tetraethyl orthosilicate was added to the seed solution at a rate of 3 mL / min. The pH was measured during the reaction. Sodium hydroxide was added to keep the pH > 8. After the addition was completed, the solution was kept warm for 3 h to obtain sol silica.

[0070] Example 6

[0071] A sol-gel silica with a particle size of 50 nm was synthesized, and the specific synthesis method is as follows:

[0072] Raw materials: aminopropyltriethoxysilane with a mass content of 13.5%, ammonia (mass concentration of 28%) with a mass content of 1.65%, sodium dodecyl sulfate with a mass content of 0.12%, glycerol with a mass content of 0.15%, and the remainder being deionized water.

[0073] (1) Preparation of mother liquor: Add ammonia to 3000 mL of deionized water to adjust the pH to 12.5, then add 0.15% ethylene glycol and 0.12% sodium dodecyl sulfate, and mix well to obtain the mother liquor:

[0074] (2) Seed preparation: In the mother liquor, aminopropyltriethoxysilane was added dropwise at a rate of 2.0 mL / min using a peristaltic pump. The mixture was stirred with a φ100 mm polytetrafluoroethylene stirring paddle at a stirring speed of 550 rpm. At the same time, the solution was heated to 65℃. After the addition of aminopropyltriethoxysilane was completed, the pH of the solution was measured to be 9. The solution was kept warm for 3 hours to obtain the seed liquid.

[0075] (3) Secondary addition: The remaining 10.5% aminopropyltriethoxysilane was added to the seed solution at a rate of 3 mL / min. The pH was measured during the reaction and kept at pH > 8. After the addition was completed, the solution was kept warm for 3 h to obtain sol silica.

[0076] Example 7

[0077] A sol-gel silica with a particle size of 80 nm was synthesized, and the specific synthesis method is as follows:

[0078] Raw materials: mercaptoethyltriethoxysilane with a mass content of 13.5%, tetramethylammonium hydroxide (mass concentration of 25%) with a mass content of 1.35%, sodium dodecyl sulfate with a mass content of 0.12%, diethylene glycol with a mass content of 0.15%, and the remainder being deionized water.

[0079] (1) Preparation of mother liquor: Add ammonia to 3000 mL of deionized water, adjust the pH to 12.5, then add 0.12% diethylene glycol and 0.32% sodium dodecyl sulfate, mix well to obtain mother liquor;

[0080] (2) Seed preparation: 3% mercaptoethyltriethoxysilane was added dropwise to the mother liquor at a rate of 2.5 mL / min using a peristaltic pump. The mixture was stirred with a φ100 mm polytetrafluoroethylene stirring paddle at a stirring speed of 450 rpm. At the same time, the solution was heated to 65℃. After the addition of mercaptoethyltriethoxysilane was completed, the pH of the solution was measured to be 9. The solution was kept warm for 3 h to obtain the seed liquid.

[0081] (3) Secondary addition: The remaining 10.5% mercaptoethyltriethoxysilane was added to the seed solution at a rate of 3 mL / min. The pH was measured during the reaction and kept at pH > 8. After the addition was completed, the solution was kept warm for 3 h to obtain sol silica.

[0082] Example 8

[0083] A sol-gel silica with a particle size of 120 nm was synthesized, and the specific synthesis method is as follows:

[0084] Raw materials: Tetraethyl orthosilicate (25.5% by mass), diethanolamine (25% by mass) (0.89%), sodium dodecyl sulfate (0.12%), isopropanol (0.15%), and the remainder is deionized water.

[0085] (1) Preparation of mother liquor: Add diethanolamine to 3000 mL of deionized water, adjust the pH to 12.5, then add 0.12% diethylene glycol and 0.18% sodium dodecylbenzenesulfonate, mix well to obtain mother liquor;

[0086] (2) Seed preparation: 10% tetraethyl orthosilicate was added dropwise to the mother liquor at a rate of 2.0 mL / min using a peristaltic pump. The mixture was stirred with a φ100 mm polytetrafluoroethylene stirring paddle at a stirring speed of 450 rpm. At the same time, the solution was heated to 65°C. After the addition of tetraethyl orthosilicate was completed, the pH of the solution was measured to be 9. The solution was kept warm for 3 hours to obtain the seed liquid.

[0087] (3) Secondary addition: The remaining 15.5% tetraethyl orthosilicate was added to the seed solution at a rate of 3 mL / min. The pH was measured during the reaction and kept at pH > 8. After the addition was completed, the solution was kept warm for 3 h to obtain sol silica.

[0088] Example 9

[0089] A sol-gel silica with a particle size of 120 nm was synthesized, and the specific synthesis method is as follows:

[0090] Raw materials: tetraethyl orthosilicate (mass content) 23.5%, triethylamine (mass concentration) 0.94%, sodium dodecyl sulfate 0.12%, pentaerythritol 0.15%, and the remainder is deionized water.

[0091] (1) Preparation of mother liquor: Add triethylamine to 3000 mL of deionized water, adjust the pH to 12.5, then add 0.12% pentaerythritol and 0.12% sodium dodecyl sulfate, mix well to obtain mother liquor;

[0092] (2) Seed preparation: 8% tetraethyl orthosilicate was added dropwise to the mother liquor at a rate of 1.5 mL / min using a peristaltic pump. The mixture was stirred with a φ100 mm polytetrafluoroethylene stirring paddle at a stirring speed of 750 rpm. At the same time, the solution was heated to 65°C. After the addition of tetraethyl orthosilicate was completed, the pH of the solution was measured to be 9. The solution was kept warm for 3 hours to obtain the seed liquid.

[0093] (3) Secondary addition: The remaining 15.5% tetraethyl orthosilicate was added to the seed solution at a rate of 3 mL / min. The pH was measured during the reaction and kept at pH > 8. After the addition was completed, the solution was kept warm for 3 h to obtain sol silica.

[0094] Comparative Example 2

[0095] The synthesis method for sol-gel silica without the use of polyols is as follows:

[0096] Raw materials: Tetraethyl orthosilicate (mass content) 23.5%, triethylamine (mass concentration) 0.94%, sodium dodecyl sulfate 0.12%, and the remainder is deionized water.

[0097] (1) Preparation of mother liquor: Add triethylamine to 3000 mL of deionized water, adjust the pH to 12, then add 0.12% sodium dodecyl sulfate and mix well to obtain the mother liquor;

[0098] (2) Seed preparation: 8% tetraethyl orthosilicate was added dropwise to the mother liquor at a rate of 1.5 mL / min using a peristaltic pump. The mixture was stirred with a φ100 mm polytetrafluoroethylene stirring paddle at a stirring speed of 750 rpm. At the same time, the solution was heated to 65°C. After the addition of tetraethyl orthosilicate was completed, the pH of the solution was measured to be 9. The solution was kept warm for 3 hours to obtain the seed liquid.

[0099] (3) Secondary addition: The remaining 15.5% tetraethyl orthosilicate was added to the seed solution at a rate of 3 mL / min. The pH was measured during the reaction and kept at pH > 8. After the addition was completed, the solution was kept warm for 3 h to obtain sol silica.

[0100] Comparative Example 3

[0101] The specific method for synthesizing sol-gel silica without using particle size stabilizers is as follows:

[0102] Raw materials: Tetraethyl orthosilicate (mass content) 23.5%, triethylamine (mass concentration) 0.94%, pentaerythritol 0.15%, and the remainder is deionized water.

[0103] (1) Preparation of mother liquor: Add triethylamine to 3000 mL of deionized water, adjust the pH to 12, then add 0.12% pentaerythritol, mix well to obtain mother liquor;

[0104] (2) Seed preparation: 8% tetraethyl orthosilicate was added dropwise to the mother liquor at a rate of 1.5 mL / min using a peristaltic pump. The mixture was stirred with a φ100 mm polytetrafluoroethylene stirring paddle at a stirring speed of 750 rpm. At the same time, the solution was heated to 65°C. After the addition of tetraethyl orthosilicate was completed, the pH of the solution was measured to be 9. The solution was kept warm for 3 hours to obtain the seed liquid.

[0105] (3) Secondary addition: The remaining 15.5% tetraethyl orthosilicate was added to the seed solution at a rate of 3 mL / min. The pH was measured during the reaction and kept at pH > 8. After the addition was completed, the solution was kept warm for 3 h to obtain sol silica.

[0106] Comparative Example 4

[0107] Sol-gel silica was synthesized using only organosilanes and alkaline substances. The specific synthesis method is as follows:

[0108] Raw materials: Tetraethyl orthosilicate with a mass content of 23.5%, the remainder being deionized water.

[0109] (1) Preparation of mother liquor: Add triethylamine (25% by mass) to 3000 mL of deionized water and adjust the pH to 12;

[0110] (2) Seed preparation: 8% tetraethyl orthosilicate was added dropwise to the mother liquor at a rate of 1.5 mL / min using a peristaltic pump. The mixture was stirred with a φ100 mm polytetrafluoroethylene stirring paddle at a stirring speed of 750 rpm. At the same time, the solution was heated to 65°C. After the addition of tetraethyl orthosilicate was completed, the pH of the solution was measured to be 9. The solution was kept warm for 3 hours to obtain the seed liquid.

[0111] (3) Secondary addition: The remaining 15.5% tetraethyl orthosilicate was added to the seed solution at a rate of 3 mL / min. The pH was measured during the reaction and kept at pH > 8. After the addition was completed, the solution was kept warm for 3 h to obtain sol silica.

[0112] Comparative Example 5

[0113] The synthesis method for sol-gel silica without using a seed pre-preparation method is as follows:

[0114] Raw materials: Tetraethyl orthosilicate (mass content) 23.5%, triethylamine (mass concentration 25%) 0.94%, sodium dodecyl sulfate 0.12%, pentaerythritol 0.15%, and the remainder is deionized water.

[0115] (1) Preparation of mother liquor: Add triethylamine to 3000 mL of deionized water, adjust the pH to 12, then add 0.12% pentaerythritol and 0.12% sodium dodecyl sulfate, mix well to obtain mother liquor;

[0116] (2) In the mother liquor, 23.5% tetraethyl orthosilicate was added dropwise at a rate of 1.5 mL / min using a peristaltic pump. The mixture was stirred with a φ100 mm polytetrafluoroethylene stirring paddle at a stirring speed of 750 rpm. At the same time, the solution was heated to 65 °C. The pH was measured during the reaction and kept at pH > 8. After the addition was completed, the mixture was kept at this temperature for 3 h to obtain sol silica.

[0117] Result detection:

[0118] The sol-gel silica prepared in Examples 1 and 3-9 were subjected to particle size testing, ZETA potential testing, silicon nitride to silica selectivity ratio testing, roughness testing after CMP polishing, and dispersibility testing, respectively. The results are shown in Table 1.

[0119] Table 1. Particle size dispersibility and ZETA potential of sol-gel silica

[0120] Controlling particle size / nm Measured particle size / nm PDI ZETA potential / mV Example 1 10 10.3 0.068 63.5 Example 3 10 10.7 0.046 67.5 Example 4 10 10.1 0.049 62.3 Example 5 10 10.1 0.092 61.4 Example 6 50 59 0.034 63.3 Example 7 80 80.4 0.024 74.2 Example 8 120 120.5 0.087 70.4 Example 9 120 125 0.075 84.09 Comparative Example 2 120 135.6 0.523 50.26 Comparative Example 3 120 149.7 0.781 13.4 Comparative Example 4 120 152.3 0.827 0.6 Comparative Example 5 120 Gel precipitation — —

[0121] The results showed that, compared with the comparative example, the silane raw material, particle size control agent, dispersant, and alkaline substance selected by this method yielded a PDI < 0.1 and a ZETA potential > 61 (an absolute ZETA potential > 61 indicates an absolutely stable substance that can be stored for more than one year without sedimentation; the ZETA potential of Comparative Example 2 was 50.26). Figure 3 A), the ZETA potential in Example 9 was 84.09 (A). Figure 3 B)) Sol-gel silica, which meets the experimental setup for particle size control.

[0122] Example 10: Application of Sol-gel Silica in CMP

[0123] The sol-gel silica with a particle size of 120 nm prepared in Example 9 was used to prepare a solution for application in the CMP process. The specific steps are as follows:

[0124] (1) Fix the rough silicon wafer on the polishing head, apply a certain pressure to the polishing head to make it fully contact the polishing pad, and the polishing head and polishing pad rotate at a certain speed and direction under the drive of the motor.

[0125] (2) Preparation of polishing solution: The sol-silica prepared in Examples 6-9 was mixed with the self-made additives to prepare the polishing solution;

[0126] (3) The polishing liquid is dripped onto the polishing pad at a certain flow rate through the liquid addition system of the polishing machine. Under the action of centrifugal force, it is evenly distributed on the entire polishing pad. The chemical reagents in the polishing liquid will oxidize the substrate material to be polished, generating a relatively soft oxide film layer. Then, the oxide film layer is removed by mechanical friction. In this way, through repeated oxidation film formation-mechanical removal process, effective polishing is achieved.

[0127] (4) After polishing, the polished workpiece is cleaned to prepare a material with an ultra-fine surface. The roughness of the silicon wafer before and after polishing is measured by a profilometer, and the stability of the polishing solution is determined by measuring the ZETA potential.

[0128] Roughness results are as follows Figure 4 As shown, before polishing, the arithmetic mean deviation (Ra) of the rough silicon wafer profile is 10.6 nm. Figure 4 A), after polishing, Ra is 0.8 nm ( Figure 4 B) Smooth surface.

Claims

1. A method for synthesizing sol-gel silica with controllable particle size and low dispersion, characterized in that: Includes the following steps: (1) Preparation of mother liquor: Add ammonia to deionized water to adjust the pH to 11-12.5, then add polyol and particle size stabilizer in proportion, mix evenly to obtain mother liquor; (2) Seed preparation: Add organosilane dropwise to the mother liquor while stirring and heating. After the addition is completed, keep warm for 3 hours to obtain seed liquid; (3) Secondary addition: Add the remaining organosilane to the seed liquid and keep the solution pH > 8. After the addition is complete, keep it warm for 3 hours to obtain sol silica. The sol-gel silica comprises the following raw materials in the following mass percentages: 10-30% organosilane, 0.3-3% alkaline substances, 0.1-1% particle size stabilizer, 0.01-0.2% polyol, and the balance being deionized water; The polyol is any one of diethylene glycol, diethylene glycol monohydrate, glycerol, ethylene glycol, isopropanol, and pentaerythritol.

2. The method for synthesizing sol-gel silica with controllable particle size and low dispersion according to claim 1, characterized in that: The organosilane is any one of methyltrimethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, methyltriethoxysilane, tetraethyl orthosilicate, aminopropyltriethoxysilane, cyanoethyltriethoxysilane, and mercaptoethyltriethoxysilane.

3. The method for synthesizing sol-gel silica with controllable particle size and low dispersion according to claim 1, characterized in that: The alkaline substance is any one of sodium hydroxide solution, potassium hydroxide solution, tetramethylammonium hydroxide solution, ethylenediamine solution, triethylamine solution, ammonia solution, diethanolamine solution, and triethanolamine solution, and the mass concentration of the alkaline substance is 10%-28%.

4. The method for synthesizing sol-gel silica with controllable particle size and low dispersion according to claim 1, characterized in that: The particle size stabilizer is any one of OP-10, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, polyethylene glycol, and fatty alcohol polyoxyethylene ether.

5. The synthesis method according to claim 1, characterized in that: The organosilane added in step (2) accounts for 10-50% of the total organosilane.

6. The synthesis method according to claim 1, characterized in that: The dropping rate described in steps (2) and (3) is 1-5 mL / min, the stirring speed is 50-1750 rpm / min, and the temperature is 60-70℃.

7. The application of sol-gel silica synthesized by the method for synthesizing sol-gel silica with controllable particle size and low dispersion as described in any one of claims 1-6 in semiconductor processing technology.

8. The application according to claim 7, characterized in that: The semiconductor processing technology is semiconductor etching technology or semiconductor polishing technology.

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