Silica sol with core-shell structure as well as preparation method and application of silica sol
By preparing core-shell structured silica sol, the problem of balancing polishing rate and surface quality during semiconductor device polishing was solved, achieving high polishing performance and low defect rate.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-30
- Publication Date
- 2026-04-10
AI Technical Summary
In the chemical mechanical polishing process of semiconductor devices, existing silica sols have difficulty improving surface quality while ensuring polishing rate, especially the wafer and device surface defects caused by differences in morphology and hardness.
Silica sol with a core-shell structure was prepared by forming the core at low temperature and growing the shell at high temperature. The particle morphology was controlled to ensure the ratio of spherical particles to associated particles, thus forming a core-shell structure with density differences.
While ensuring a high polishing rate, it significantly reduces defects on the wafer and device surfaces by controlling the elastic deformation of the silica sol and the particle contact area, thereby improving polishing quality.
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Figure CN121823596A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application belongs to the field of nanomaterial preparation, and particularly relates to a silica sol with a core-shell structure, a preparation method thereof, and application of the silica sol in the field of semiconductor CMP polishing. BACKGROUND
[0002] The silica sol is a colloidal substance obtained by dispersing silica particles in water or other solvents, and is widely used in the papermaking, catalyst, casting, and coating industries. In recent years, high-purity silica sol is widely used in the polishing of silicon wafers and the chemical mechanical polishing (CMP) step of semiconductor devices.
[0003] In the manufacturing process of semiconductor devices, dozens of CMP steps are involved, and different CMP processes have different requirements for abrasives, including hardness, surface silanol, purity, particle size, and morphology.
[0004] In the CMP process used in semiconductor manufacturing, the morphology and hardness of the silica sol have a great influence on the polishing rate and surface quality. For example, a silica sol with a special shape can provide a higher polishing rate than a silica sol with a spherical shape, but it will cause more defects on the surface of the wafer and device. Similarly, a silica sol with high hardness can also provide a higher polishing rate than a silica sol with low hardness, but it will cause more defects on the surface of the wafer and device. Therefore, to balance the polishing rate and surface quality, more stringent requirements are put forward for the silica sol. SUMMARY
[0005] To solve the above problems, the present application develops a silica sol with a core-shell structure, the density of the shell layer is greater than that of the core, and the particle morphology meets a specific distribution, so that it can balance the polishing rate and surface quality in CMP polishing.
[0006] Another object of the present application is to provide a preparation method of the silica sol with a core-shell structure.
[0007] Still another object of the present application is to provide the application of the silica sol with a core-shell structure in CMP.
[0008] To achieve the above objects, the present application adopts the following technical solutions.
[0009] A silica sol with a core-shell structure has the following characteristics:
[0010] (1) The silica sol has a core-shell structure of a core and a shell layer, the density of the core is less than that of the shell layer, the core is formed by reacting at a temperature T1, and the shell layer is formed by continuing to grow on the surface of the core at a temperature T2, and T1 < T2;
[0011] (2) The silica sol particles have different morphologies, wherein the number of spherical morphology particles accounts for 15-20%, the number of double-particle associated particles accounts for 30-40%, and the number of particles associated with three or more particles accounts for 40-55%.
[0012] In another aspect, the method for preparing the silica sol with core-shell structure as described above comprises the following steps:
[0013] (1) Preparation of A liquid: mixing alcohol, water, base catalyst, and morphology control agent uniformly as A liquid;
[0014] (2) Preparation of B liquid: mixing alcohol and alkoxysilane uniformly as B liquid;
[0015] (3) Dropping B liquid into A liquid, and after the dropping is completed, reacting at temperature T1 to obtain silica sol core C1;
[0016] (4) Mixing alkoxysilane and alcohol uniformly as B1 liquid;
[0017] (5) Taking silica sol core C1 as a primer liquid, increasing the reaction temperature to T2, adding B1 into C1, and constant temperature reaction to obtain finished product silica sol C2;
[0018] (6) Replacing the organic solvent in C2 with water, and concentrating to more than 20wt%, and then filtering to remove large particles to obtain the silica sol with core-shell structure.
[0019] In some specific embodiments, the alcohol in step (1), step (2), and step (4) is independently selected from one or more of methanol, ethanol, propanol, and isopropanol;
[0020] Preferably, the alcohol in step (1), step (2), and step (4) is the same alcohol; more preferably, the alcohol is the same as the alcohol produced by the hydrolysis of alkoxysilane.
[0021] In some specific embodiments, the water is ultrapure water, and the resistivity of the ultrapure water is ≥10MΩ·cm, preferably ≥18.2MΩ·cm.
[0022] In some specific embodiments, the base catalyst in step (1) is selected from at least one of alkali metal hydroxide, aqueous ammonia, organic amine, or guanidine compound; preferably, the base catalyst is aqueous ammonia or organic amine; more preferably, the alkali metal hydroxide is selected from at least one of potassium hydroxide, sodium hydroxide, and lithium hydroxide; the organic amine is selected from one or more of primary amine, secondary amine, tertiary amine, and quaternary amine; and the guanidine compound is selected from at least one of tetramethyl guanidine, trimethyl guanidine, and guanidine carbonate.
[0023] In some specific embodiments, the morphology control agent in step (1) is selected from one or more of organic acid, ammonium of organic acid, inorganic acid, ammonium of inorganic acid; preferably one or more of organic acid or ammonium of organic acid;
[0024] Preferably, the organic acid is selected from at least one of formic acid, acetic acid, citric acid, malic acid, maleic acid, quinic acid, tartaric acid, ascorbic acid, amino acid;
[0025] Preferably, the ammonium of organic acid is ammonium salt of the organic acid, selected from at least one of ammonium formate, ammonium acetate, ammonium citrate, ammonium malate, ammonium maleate, ammonium tartrate;
[0026] Preferably, the inorganic acid is selected from at least one of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid;
[0027] Preferably, the ammonium of inorganic acid is selected from at least one of ammonium chloride, ammonium sulfate, ammonium nitrate, ammonium phosphate, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, ammonium carbonate, ammonium bicarbonate.
[0028] In some specific embodiments, the mass fraction of the alcohol in A solution of step (1) is 0%-90%, the mass fraction of the water is 10%-99.5%, and the mass fraction of the base catalyst is 0.5%-5%;
[0029] Preferably, the amount of the morphology control agent is between 100 ppm and 3000 ppm, for example 100 ppm, 200 ppm, 300 ppm, 400 ppm, 500 ppm, 1000 ppm, 1500 ppm, 2000 ppm, 2500 ppm, 3000 ppm, relative to the content of the silica converted from the total alkoxysilane added.
[0030] In some specific embodiments, the alkoxysilane in step (2), step (4) is one or more of tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, preferably tetramethoxysilane;
[0031] Preferably, the volume ratio of the alcohol to the alkoxysilane in step (2) is 1:10-10:1, preferably 1:5-1:1, for example 1:5, 1:4, 1:3, 1:2, 1:1, etc.; and the molar ratio of the alkoxysilane to the water in step (1) is less than 1, preferably less than 1:4, for example 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, etc.
[0032] In some specific embodiments, the reaction temperature T1 in step (3) is between 5-40℃, preferably 20-40℃, for example 20℃, 25℃, 30℃, 35℃, 40℃;
[0033] The dropping time of solution B into solution A is 0.1 min to 40 min, preferably 0.1 min to 20 min, for example 0.1 min, 1 min, 2 min, 3 min, 4 min, 5 min, 10 min, 15 min, 20 min;
[0034] In some specific implementations, the volume ratio of alcohol to alkoxysilane in step (4) is 1:10-10:1, preferably 1:3-1:1, for example: 1:3, 1:2, 1:1;
[0035] In some specific implementations, the volume ratio of the alkoxysilane in step (4) to the alkoxysilane in step (2) is (R2 / R1). 3 Where R1 is the average particle size of silica sol core C1, and R2 is the average particle size of silica sol C2.
[0036] In some specific implementation schemes, the reaction temperature T2 in step (5) is 50-90℃, preferably 60-90℃, for example: 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, 90℃;
[0037] In step 5), the dripping time for adding B1 to C1 is 1-30h, for example, 1h, 2h, 3h, 4h, 5h, 10h, 15h, 20h, 25h, 30h.
[0038] In some specific implementations, the solvent replacement in step (6) is carried out by heating and adding water to evaporate and remove the solvent in the water, or by ultrafiltration to add ultrapure water and concentrate until the solvent content in the silica sol is reduced to below 200 ppm, preferably below 100 ppm; more preferably, the concentration in step (4) is carried out by vacuum heating concentration or ultrafiltration membrane concentration to concentrate the mass fraction of the silica sol to above 20%.
[0039] In some specific implementations, the filtration accuracy of the filter described in step (6) is 0.1μm-5μm.
[0040] On another front, the aforementioned silica sol with a core-shell structure or silica sol with a core-shell structure prepared by the aforementioned method is used in chemical mechanical polishing.
[0041] Compared with the prior art, the present invention has the following beneficial effects:
[0042] (1) This invention prepares a silica sol with a core-shell structure by controlling the reaction temperature during the preparation of silica sol (the core is formed by reaction at temperature T1, and the shell continues to grow on the surface of the core at temperature T2, and T1 < T2), so that the density of the silica sol core is less than the density of the shell, thereby allowing the silica sol to produce more elastic deformation during the polishing process.
[0043] (2) The present application controls the particle morphology of the silica sol by controlling the amount of additives during the preparation of the silica sol core, thereby preparing silica sols with different morphologies.
[0044] (3) The silica sol with a core-shell structure of the present application, which meets the characteristics that the density of the core is less than the density of the shell, and the number of spherical particles accounts for 15-20%, the number of double-particle associated particles accounts for 30%-40%, and the number of particles associated with three or more particles accounts for 40-55%, can be used in CMP while ensuring high polishing rate and surface quality. BRIEF DESCRIPTION OF DRAWINGS
[0045] Figure 1 TEM image of the silica sol prepared for Example 1 of the present application.
[0046] Figure 2 TEM image of the silica sol prepared for Comparative Example 2 of the present application.
[0047] Figure 3 TEM image of the silica sol prepared for Comparative Example 4 of the present application. DETAILED DESCRIPTION
[0048] The preparation method of the present application will be further explained by more specific examples below, but does not constitute any limitation.
[0049] Detection method:
[0050] The specific surface area S of the silica sol particles is obtained by BET specific surface area test method B , and the primary particle size is 2727 / S Bet .
[0051] The density of the silica sol is tested as follows: using a vacuum oven at 60℃ for drying, grinding into powder, and then using a true density instrument to test the true density of the silica sol particles.
[0052] The apparent morphology of the silica sol is characterized by TEM, randomly selecting a TEM field, and counting 200 particles, respectively counting the number of spherical, double-particle associated peanut-shaped and three or more particle associated irregular particles, and calculating the particle number ratio.
[0053] The polishing test method is as follows: the pH of the silica sol is adjusted to 10.0 using KOH solution, and the solid content of the silica is kept at about 8%, the polishing rate of TEOS is obtained by polishing a 300mm diameter wafer with TEOS using an Ebara CMP polisher and IC 1010 polishing pad under a pressure of 2.0 Psi, a platform rotation speed of 97 rpm and a slurry flow rate of 300ml / min. And the wafer surface defect number (LSS) is detected using KLA Surfscan SP5.
[0054] Example 1
[0055] 117.75g of methanol, 70.55g of water, 3.8g of ammonia water and 0.0242g of citric acid are mixed and stirred uniformly as A liquid, and the reaction temperature is controlled at 25°C, 5ml of methanol is mixed uniformly with 15ml of tetramethoxysilane as B liquid, the B liquid is added to A by peristaltic pump, 30min is added, after adding, continue to react for 30min, get initial silica sol C1. Take the above silica sol as the primer, the primer temperature is raised to 60°C, 45ml of tetramethoxysilane and 45ml of methanol are mixed uniformly as B1 liquid, and are added dropwise to C1 at a constant speed within 10h. After the dropwise addition is completed, continue to react at 60°C for 2h, the primary particle size of the silica sol is 45nm, and the silica sol particle density is 1.96g / cm 3 . Observed under TEM, 15% of the particles are spherical, 35% of the particles are two-particle associated, and 50% of the particles are three-particle or more associated. In the polishing performance evaluation, the polishing rate of TEOS wafer is The defect number LLS on the wafer surface is 24.
[0056] Example 2
[0057] 117.75g of methanol, 70.55g of water, 3.8g of ammonia water and 0.0242g of citric acid are mixed and stirred uniformly as A liquid, and the reaction temperature is controlled at 25°C, 5ml of methanol is mixed uniformly with 15ml of tetramethoxysilane as B liquid, the B liquid is added to A by peristaltic pump, 30min is added, after adding, continue to react for 30min, get initial silica sol C1. Take the above silica sol as the primer, the primer temperature is raised to 60°C, 45ml of tetramethoxysilane and 45ml of methanol are mixed uniformly as B1 liquid, and are added dropwise to C1 at a constant speed within 10h. After the dropwise addition is completed, continue to react at 60°C for 2h, the primary particle size of the silica sol is 45nm, and the silica sol particle density is 1.96g / cm 3. The TEM observation shows that the percentage of spherical morphology particles is 19%, the percentage of two-particle associated morphology particles is 34%, and the percentage of three-particle or more associated particles is 47%. In the polishing performance evaluation, the polishing rate of the TEOS wafer is 0. 1 1 1 nm / min, and the defect number LLS on the wafer surface is 26. wafer surface is 20.
[0058] Example 3
[0059] A solution of 117.75 g of methanol, 70.55 g of water, 3.8 g of ammonia water, and 0.0113 g of ammonium citrate was mixed and stirred uniformly as A liquid, and the reaction temperature was controlled at 40°C. A solution of 15 ml of methanol and 5 ml of tetramethoxysilane was mixed uniformly as B liquid, and the B liquid was added to the A liquid by using a peristaltic pump. The addition was completed in 20 min, and the reaction was continued for 30 min after the addition was completed. An initial silica sol Cl was obtained. The temperature of the above-mentioned silica sol was increased to 55°C as a primer liquid. A solution of 10 ml of tetramethoxysilane and 30 ml of methanol was mixed uniformly as Bl liquid, and was added dropwise to the Cl at a constant rate within 10 h. After the dropwise addition was completed, the reaction was continued for 2 h at 55°C. A silica sol was obtained, and the primary particle size of the silica sol was 26 nm, and the silica sol particle density was 1.98 g / cm3. 3 . The TEM observation shows that the percentage of spherical morphology particles is 19%, the percentage of two-particle associated morphology particles is 34%, and the percentage of three-particle or more associated particles is 47%. In the polishing performance evaluation, the polishing rate of the TEOS wafer is 0. 1 1 1 nm / min, and the defect number LLS on the wafer surface is 26. wafer surface is 20.
[0060] Example 4
[0061] A solution of 117.75 g of methanol, 70.55 g of water, 3.8 g of ammonia water, and 0.0113 g of ammonium citrate was mixed and stirred uniformly as A liquid, and the reaction temperature was controlled at 40°C. A solution of 15 ml of methanol and 5 ml of tetramethoxysilane was mixed uniformly as B liquid, and the B liquid was added to the A liquid by using a peristaltic pump. The addition was completed in 20 min, and the reaction was continued for 30 min after the addition was completed. An initial silica sol Cl was obtained. The temperature of the above-mentioned silica sol was increased to 55°C as a primer liquid. A solution of 10 ml of tetramethoxysilane and 30 ml of methanol was mixed uniformly as Bl liquid, and was added dropwise to the Cl at a constant rate within 10 h. After the dropwise addition was completed, the reaction was continued for 2 h at 55°C. A silica sol was obtained, and the primary particle size of the silica sol was 26 nm, and the silica sol particle density was 1.98 g / cm3. 3 . The TEM observation shows that the percentage of spherical morphology particles is 19%, the percentage of two-particle associated morphology particles is 34%, and the percentage of three-particle or more associated particles is 47%. In the polishing performance evaluation, the polishing rate of the TEOS wafer is 0. 1 1 1 nm / min, and the defect number LLS on the wafer surface is 26. wafer surface is 20.
[0062] Example 5
[0063] 117.75 g of methanol, 70.55 g of water, 3.8 g of ammonia water and 0.0242 g of citric acid were mixed and stirred uniformly as A liquid, and the reaction temperature was controlled at 25°C, 5 ml of methanol and 15 ml of tetramethoxysilane were mixed uniformly as B liquid, B liquid was added to A by peristaltic pump, 30 min was added, after adding, continue to react for 30 min, get initial silica sol C1. Take the above silica sol as the primer liquid, the primer liquid temperature is raised to 50°C, 45 ml of tetramethoxysilane and 45 ml of methanol are mixed uniformly as B1 liquid, and are added dropwise to C1 at a constant speed within 10 h. After the dropwise addition is completed, continue to react at 50°C for 2 h, the primary particle size of the silica sol is 45 nm, and the silica sol particle density is 1.95 g / cm 3 Under TEM observation, the proportion of spherical morphology particles is 15%, the proportion of two-particle associated morphology particles is 34%, and the proportion of three-particle and above associated particles is 51%. In the polishing performance evaluation, the polishing rate of TEOS wafer is The defect number LLS on the wafer surface is 22.
[0064] Example 6
[0065] 117.75 g of methanol, 70.55 g of water, 3.8 g of ammonia water and 0.0242 g of citric acid were mixed and stirred uniformly as A liquid, and the reaction temperature was controlled at 25°C, 5 ml of methanol and 15 ml of tetramethoxysilane were mixed uniformly as B liquid, B liquid was added to A by peristaltic pump, 30 min was added, after adding, continue to react for 30 min, get initial silica sol C1. Take the above silica sol as the primer liquid, the primer liquid temperature is raised to 50°C, 45 ml of tetramethoxysilane and 45 ml of methanol are mixed uniformly as B1 liquid, and are added dropwise to C1 at a constant speed within 10 h. After the dropwise addition is completed, continue to react at 50°C for 2 h, the primary particle size of the silica sol is 45 nm, and the silica sol particle density is 1.95 g / cm 3 Under TEM observation, the proportion of spherical morphology particles is 15%, the proportion of two-particle associated morphology particles is 34%, and the proportion of three-particle and above associated particles is 51%. In the polishing performance evaluation, the polishing rate of TEOS wafer is The defect number LLS on the wafer surface is 28.
[0066] Example 7
[0067] 117.75 g of methanol, 70.55 g of water and 3.8 g of ammonia water and 0.0242 g of acetic acid were mixed and stirred uniformly as A liquid, and the reaction temperature was controlled at 25°C, 5 ml of methanol was mixed uniformly with 15 ml of tetramethoxysilane as B liquid, and the B liquid was added to A by using a peristaltic pump, and the addition was completed in 30 min, and the reaction was continued for 30 min after the addition was completed, to obtain an initial silica sol C1. The above silica sol was taken as a primer liquid, the primer liquid temperature was raised to 60°C, 45 ml of tetramethoxysilane and 45 ml of methanol were mixed uniformly as B1 liquid, and were added dropwise to C1 at a constant speed within 10 h. After the addition was completed, the reaction was continued at 60°C for 2 h to obtain a silica sol with a primary particle size of 45 nm and a silica sol particle density of 1.96 g / cm 3 Under TEM observation, the proportion of spherical morphology particles was 15%, the proportion of two-particle associated morphology particles was 35%, and the proportion of three-particle and above associated particles was 50%. In the polishing performance evaluation, the polishing rate of the TEOS wafer was The defect number LLS on the wafer surface was 32.
[0068] Comparative Example 1
[0069] 117.75 g of methanol, 70.55 g of water and 3.8 g of ammonia water and 0.0242 g of citric acid were mixed and stirred uniformly as A liquid, and the reaction temperature was controlled at 25°C, 5 ml of methanol was mixed uniformly with 15 ml of tetramethoxysilane as B liquid, and the B liquid was added to A by using a peristaltic pump, and the addition was completed in 30 min, and the reaction was continued for 30 min after the addition was completed, to obtain an initial silica sol C1. The above silica sol was taken as a primer liquid, the primer liquid temperature was raised to 60°C, 45 ml of tetramethoxysilane and 45 ml of methanol were mixed uniformly as B1 liquid, and were added dropwise to C1 at a constant speed within 10 h, and the reaction temperature was controlled at 25°C during the period. After the addition was completed, the reaction was continued at 25°C for 2 h to obtain a silica sol with a primary particle size of 50.5 nm and a true density of 1.90 g / cm 3 Under TEM observation, the proportion of spherical morphology particles was 17%, the proportion of two-particle associated morphology particles was 35%, and the proportion of three-particle and above associated particles was 48%. In the polishing performance evaluation, the polishing rate of the TEOS wafer was The defect number LLS on the wafer surface was 20.
[0070] Comparative Example 2
[0071] 117.75 g of methanol, 70.55 g of water and 3.8 g of ammonia water were mixed and stirred uniformly as A liquid, and the reaction temperature was controlled at 25°C, 5 ml of methanol was mixed uniformly with 15 ml of tetramethoxysilane as B liquid, and the B liquid was added to A by using a peristaltic pump, and the addition was completed in 30 min, and the reaction was continued for 30 min after the addition was completed, to obtain an initial silica sol C1. The above silica sol was taken as a primer liquid, the primer liquid temperature was raised to 60°C, 45 ml of tetramethoxysilane and 45 ml of methanol were mixed uniformly as B1 liquid, and were added dropwise to C1 at a constant speed within 10 h, and after the dropwise addition was completed, the reaction was continued at 60°C for 2 h, to obtain a silica sol with a primary particle size of 45 nm, and the true density of the colloidal particles was 1.96 g / cm3. 3 Under TEM observation, the proportion of spherical morphology particles was 70%, the proportion of two-particle associated morphology particles was 30%, and the proportion of three-particle and above associated particles was 0%. In the polishing performance evaluation, the polishing rate of the TEOS wafer was The defect number LLS on the wafer surface was 21.
[0072] Comparative Example 3
[0073] 117.75 g of methanol, 70.55 g of water and 3.8 g of ammonia water were mixed and stirred uniformly as A liquid, and the reaction temperature was controlled at 25°C, 5 ml of methanol was mixed uniformly with 15 ml of tetramethoxysilane as B liquid, and the B liquid was added to A by using a peristaltic pump, and the addition was completed in 30 min, and the reaction was continued for 30 min after the addition was completed, to obtain an initial silica sol C1. The above silica sol was taken as a primer liquid, the primer liquid temperature was raised to 60°C, 45 ml of tetramethoxysilane and 45 ml of methanol were mixed uniformly as B1 liquid, and were added dropwise to C1 at a constant speed within 10 h, and after the dropwise addition was completed, the reaction was continued at 25°C for 2 h, to obtain a silica sol with a primary particle size of 50 nm, and the true density of the colloidal particles was 1.9 g / cm3. 3 Under TEM observation, the proportion of spherical morphology particles was 69%, the proportion of two-particle associated morphology particles was 31%, and the proportion of three-particle and above associated particles was 0%. In the polishing performance evaluation, the polishing rate of the TEOS wafer was The defect number LLS on the wafer surface was 19.
[0074] Comparative Example 4
[0075] Mix 117.75 g of methanol, 70.55 g of water, and 3.8 g of ammonia water and 0.0847 g of citric acid to form a mixture A, and control the reaction temperature at 25°C, mix 5 ml of methanol and 15 ml of tetramethoxysilane to form a mixture B, add the mixture B into the mixture A by using a peristaltic pump, and complete the addition in 30 min, and continue the reaction for 30 min after the addition is completed to obtain a primary silica sol C1. Take the silica sol as a primer, and increase the temperature of the primer to 60°C, mix 45 ml of tetramethoxysilane and 45 ml of methanol to form a mixture B1, and add the mixture B1 into the C1 at a constant speed drop by drop in 10 h. Continue the reaction at 60°C for 2 h after the dropwise addition is completed to obtain a silica sol with a primary particle size of 45 nm. The spherical morphology particles account for 10%, the two-particle associated morphology particles account for 30%, and the three-particle and above associated particles account for 60% under the observation of TEM. In the polishing performance evaluation, the polishing rate of the TEOS wafer is the defect number LLS of the wafer surface is 65.
[0076] The present application provides a silica sol with a core-shell structure and a preparation method thereof. The silica sol core is prepared at a relatively low temperature, so that the density is relatively small; the shell layer of the silica sol is prepared at a relatively high temperature, so that the density is relatively large. The silica sol with such a structure can produce a larger deformation in the polishing process, so that the silica sol particles have a larger contact area with the wafer surface, thereby reducing the defects on the wafer surface. The silica sol shell layer has a larger density, a larger degree of dehydration condensation between the silanol groups, and more Si-O-Si structures, which can reduce the interaction force between the silica sol particles and the wafer surface and increase the polishing rate.
[0077] As can be seen from Example 1, Example 4, and Example 5, as the reaction temperature increases, the density of the silica sol particles gradually increases, so that the density of the shell layer gradually increases, and the polishing rate also shows a trend of increase, while the defect number LSS of the wafer surface only increases slightly. Compared with Comparative Example 1, the silica sol in Comparative Example 1 is prepared at a low temperature throughout the whole process, and the overall density of the silica sol particles is lower than that in Example 1. However, the polishing rate of the silica sol in Example 1 is much higher than that in Comparative Example 1, but the defect number LSS of the wafer surface is close to that in Comparative Example 1.
[0078] Compared with Comparative Example 2, no additive is added in Comparative Example 2, and Figure 1 and Figure 2 As can be seen, the silica sol particles prepared in Comparative Example 2 have a larger proportion of spherical morphology particles and a smaller proportion of two-particle associated and three-particle and above associated morphology particles, so that the polishing rate is also much lower than that of the silica sol in Example 1. Compared with Comparative Example 4, as the content of the additive increases, the density of the silica sol particles gradually increases, so that the polishing rate gradually increases, while the defect number LSS of the wafer surface only increases slightly. Figure 3It can be seen that the proportion of associated particles of the prepared silica sol increases, and the polishing rate also increases accordingly. However, the increase of the proportion of associated particles will also result in the increase of wafer surface defects.
[0079] In comparison with the comparative examples 1, 2 and 3, the silica sol shell is prepared at low temperature, and no additive is added in the process of preparing the core. The density of the silica sol particles is reduced, and the number of associated particles is obviously reduced, so that the polishing rate is the lowest.
[0080] Although the content of the present application has been described in detail through the above preferred embodiments, it should be recognized that the above description should not be considered as a limitation of the present application. Those skilled in the art can understand that some modifications or adjustments can be made to the present application under the teaching of the present specification. These modifications or adjustments should also be within the scope defined by the claims of the present application.
Claims
1. A silica sol having a core-shell structure, characterized by, Possessing the following characteristics: (1) The silica sol has a core-shell structure of a core and a shell, wherein the density of the core is less than the density of the shell, the core is formed by reacting at a temperature T1, and the shell is formed by continuing to grow on the surface of the core at a temperature T2, and T1 (2) The silica sol particles have different morphologies, wherein the number of spherical morphology particles accounts for 15-20%, the number of double-particle associated particles accounts for 30%-40%, and the number of particles associated with three or more particles accounts for 40-55%.
2. The method of producing a silica sol having a core-shell structure according to claim 1, characterized by, Comprising the following steps: (1) Configuration of A liquid: uniformly mixing alcohol, water, base catalyst, morphology control agent as A liquid; (2) Configuration of B liquid: uniformly mixing alcohol and alkoxysilane as B liquid; (3) Drop B liquid into A liquid, after drop completion, react at temperature T1, obtain silica sol core C1; (4) Uniformly mix alkoxysilane and alcohol as B1 liquid; (5) Take silica sol core C1 as primer liquid, increase reaction temperature to T2, add B1 into C1, and constant temperature reaction, obtain finished product silica sol C2; (6) Displace organic solvent in C2 with water, and concentrate to more than 20wt%, then filter to remove large particles, obtain the silica sol with core-shell structure.
3. The preparation method according to claim 2, characterized in that, The alcohol in step (1), step (2) and step (4) is independently selected from one or more of methanol, ethanol, propanol and isopropanol; Preferably, the alcohol in step (1), step (2) and step (4) is the same alcohol. More preferably, the water is ultrapure water, and the resistivity of the ultrapure water is greater than or equal to 10 MΩ·cm, preferably greater than or equal to 18.2 MΩ·cm.
4. The preparation method according to claim 3, characterized in that, The base catalyst in step (1) is selected from at least one of alkali metal hydroxide, ammonia, organic amine or guanidine compound; Preferably, the base catalyst is ammonia or organic amine; More preferably, the alkali metal hydroxide is selected from at least one of potassium hydroxide, sodium hydroxide and lithium hydroxide; and / or The organic amine is selected from one or more of primary amine, secondary amine, tertiary amine and quaternary amine; and / or The guanidine compound is selected from at least one of tetramethyl guanidine, trimethyl guanidine and guanidine carbonate.
5. The preparation method according to claim 4, characterized in that, The morphology control agent in step (1) is selected from one or more of organic acid, ammonium salt of organic acid, inorganic acid and ammonium salt of inorganic acid; preferably one or more of organic acid or ammonium salt of organic acid; Preferably, the organic acid is selected from at least one of formic acid, acetic acid, citric acid, malic acid, maleic acid, quinine acid, tartaric acid, ascorbic acid and amino acid; and / or The ammonium salt of organic acid is an ammonium salt of the organic acid, and is selected from at least one of ammonium formate, ammonium acetate, ammonium citrate, ammonium malate, ammonium maleate and ammonium tartrate; and / or The inorganic acid is selected from at least one of hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid; and / or The ammonium salt of inorganic acid is selected from at least one of ammonium chloride, ammonium sulfate, ammonium nitrate, ammonium phosphate, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, ammonium carbonate and ammonium bicarbonate.
6. The method of any one of claims 2-5, wherein, The mass fraction of the alcohol in the A liquid of step (1) is 0%-90%, the mass fraction of the water is 10%-99.5%, and the mass fraction of the base catalyst is 0.5%-5%. Preferably, the amount of the morphology control agent is between 100 ppm and 3000 ppm relative to the content of silica converted from the total amount of alkoxysilane added.
7. The preparation method according to claim 6, characterized in that, The alkoxysilane in step (2) and step (4) is one or more of tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, preferably tetramethoxysilane; Preferably, the volume ratio of the alcohol to the alkoxysilane in step (2) is between 1:10 and 10:1, preferably between 1:5 and 1:1, and the molar ratio of the alkoxysilane to water in step (1) is less than 1, preferably less than 1:
4.
8. The preparation method according to claim 6, characterized in that, The reaction temperature T1 in step (3) is between 5 and 40℃, preferably between 20 and 40℃, and the dropping time of B liquid into A liquid is between 0.1 min and 40 min, preferably between 0.1 min and 20 min. Preferably, the volume ratio of the alcohol to the alkoxysilane in step (4) is between 1:10 and 10:1, preferably between 1:3 and 1:
1. More preferably, the volume ratio of the alkoxysilane in step (4) to the alkoxysilane in step (2) is (R2 / R1) 3 , wherein R1 is the average particle size of the silica sol glue core C1, and R2 is the average particle size of the silica sol C2.
9. The preparation method according to claim 6, characterized in that, The reaction temperature T2 in step (5) is between 50 and 90℃, preferably between 60 and 90℃, and the dropping time of B1 into C1 is between 1 and 30 h. Preferably, the solvent replacement in step (6) is performed by heating and supplementing water, evaporating the solvent in water, or by ultrafiltration, supplementing ultra-pure water and concentrating, until the content of the solvent in the silica sol is less than 200 ppm, preferably less than 100 ppm. More preferably, the concentration in step (6) is performed by vacuum heating and concentration or ultrafiltration membrane concentration, and the mass fraction of the silica sol is concentrated to more than 20%. Further preferably, the filtration precision in step (6) is between 0.1 μm and 5 μm.
10. The use of the silica sol with core-shell structure according to claim 1 or prepared by the method according to any one of claims 2-9 in chemical mechanical polishing.