Spherical silicon dioxide particle, silica sol containing spherical silicon dioxide particle and application of spherical silicon dioxide particle in polishing solution
By introducing amino or sulfonic acid groups onto the surface of silica nanoparticles, the instability of silica sol under acidic conditions is solved, achieving long-term stability and high-efficiency polishing performance under acidic conditions.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- DALIAN INSTITUTE OF CHEMICAL PHYSICS CHINESE ACADEMY OF SCIENCES
- Filing Date
- 2025-12-26
- Publication Date
- 2026-05-12
AI Technical Summary
Existing silica nanoparticles tend to agglomerate under acidic conditions, leading to instability in silica sol and affecting the efficiency of the chemical mechanical polishing process and product quality.
Introducing amino or sulfonic acid groups onto the surface of silica nanoparticles allows them to carry a charge under acidic conditions, forming an electric double layer, thereby maintaining a stable silica sol under acidic conditions.
This achieves long-term stability of silica sol under acidic conditions, reduces metal ion contamination, and improves the efficiency of the polishing process and product yield.
Smart Images
Figure CN122010123A_ABST
Abstract
Description
Technical Field
[0001] This application relates to a spherical silica particle, a silica sol containing the particle, and its application in a polishing slurry, belonging to the field of materials technology. Background Technology
[0002] The development of modern semiconductor processing technology has led to the continuous shrinking of the size of very large-scale integrated circuits (VLSI) and the continuous increase in the density of components and metal interconnects on wafers. This has resulted in increasingly stringent requirements for global planarization of wafers. Chemical Mechanical Polishing (CMP), pioneered in the 1980s as the only means of global wafer planarization, works on the principle of using a combination of chemical etching and mechanical friction to remove material from the wafer to achieve global planarization. Specifically, the wafer is fixed and pressed onto a polyurethane polishing pad. While a polishing slurry is injected into the pad, the wafer and pad are rotated in the same direction, creating friction that removes material. During this process, nanoparticles in the polishing slurry contact and interact with the wafer, softening the wafer surface; subsequently, a physical-mechanical interaction removes the softened layer. This process is repeated to achieve global planarization.
[0003] After the components and circuits of each layer of a very large-scale integrated circuit are deposited on the wafer surface, planarization is required before subsequent photolithography, deposition, and etching processes can proceed. Therefore, chemical mechanical polishing (CMP) is one of the key processes in chip manufacturing.
[0004] In theory, chemical mechanical polishing (CMP) produces a smooth, scratch-free surface. If high-hardness abrasive particles are used in the polishing slurry, although the material removal rate is increased, scratches will be left on the material surface. If softer abrasive particles are used, the material removal rate decreases, and the CMP process takes longer.
[0005] Amorphous silica nanoparticles are relatively soft, thus effectively controlling scratches formed on the wafer surface during chemical mechanical polishing (CMP). Simultaneously, the hydroxyl groups on the surface of the silica nanoparticles react chemically with the material during polishing, accelerating the removal of material from the wafer surface and saving polishing time. Therefore, silica nanoparticles are widely used in the industry as slurry particles for wafer polishing.
[0006] Silica nanoparticles can be obtained by the gaseous method (reaction of silicon chloride with water vapor), the water glass method (sodium silicate solution per cation exchange resin), and the Stöber method (hydrolysis and condensation of organosilanes under the action of ammonia). Gas-phase silica particles have a wide particle size distribution and uneven shape, which can cause extensive scratches on the wafer surface when used for chemical mechanical polishing (CMP). The water glass method can produce silica nanoparticles with a narrower particle size distribution and more uniform shape, but some metal ions may remain, affecting the post-polishing cleaning process. Furthermore, the production process is more complex, time-consuming, and difficult to control. Therefore, silica nanoparticles obtained by the Stöber method are used as nanoparticles for CMP. Silica nanoparticles can disperse in water to form a sol. This sol is relatively stable under alkaline conditions and can be stored for a long time without changing its basic physicochemical form. Under acidic conditions, silica sols are prone to agglomeration and even sedimentation. Some products can only maintain stability for a few hours before sedimentation. Part of the reason for this phenomenon is that the surface of silica nanoparticles consists almost entirely of hydroxyl groups. Under alkaline conditions, hydroxyl groups can ionize to release protons, becoming negatively charged and forming an electric double layer on the surface of the nanoparticles. This creates repulsion between the particles, stabilizing the sol. Under acidic conditions, hydroxyl groups cannot ionize to release protons, the electric double layer cannot form, and there is no electrostatic repulsion between the particles, making them prone to agglomeration and sedimentation. Summary of the Invention
[0007] To solve the above-mentioned technical problems, this application introduces new chemical groups, such as amino or sulfonic acid groups, onto the surface of nano-silica particles, so that the particles can still carry charges and form an electric double layer under acidic conditions, thereby ensuring that the sol formed by the particles and water can remain stable under acidic conditions.
[0008] According to one aspect of this application, spherical silica particles are provided, which are characterized by large particle size, uniform distribution and low metal content, and are suitable for chemical mechanical polishing processes in the chip manufacturing field.
[0009] The average particle size of the spherical silica particles is selected from any value in the range of 20~200nm, and the polydispersity index (PDI) of the spherical silica particles is ≤0.10.
[0010] Preferably, the average particle size of the spherical silica particles is selected from any value in the range of 60~120nm, and the polydispersity index (PDI) of the spherical silica particles is 0.01≤PDI≤0.10.
[0011] According to another aspect of this application, a silica sol is provided that can maintain system stability for a long time under acidic conditions, and is suitable for chemical mechanical polishing processes in the chip manufacturing field.
[0012] The silica sol contains the aforementioned spherical silica particles; The spherical silica particles have a mass percentage of 1-10% in the silica sol.
[0013] Optionally, the mass percentage of the spherical silica particles in the silica sol is any value from 1%, 1.5%, 2%, 2.5%, 2.84%, 3.0%, 3.5%, 3.91%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or any range of both.
[0014] Preferably, the spherical silica particles have a mass percentage content of 2% to 4% in the silica sol.
[0015] The spherical silica particles in the silica sol contain amino and / or sulfonic acid groups on their surface.
[0016] According to another aspect of this application, a method for preparing the silica sol is provided, wherein only instruments and equipment that do not contain metal elements are used in the preparation process, thereby avoiding contamination of the wafer by metal ions.
[0017] The method for preparing the silica sol includes the following steps: a) A solution containing an organosilane is added to a solution containing an organic amine to obtain a mixture; b) The mixture is aged, centrifuged, washed, and the pH value is adjusted to acidic to obtain the silica sol.
[0018] Preferably, the solution containing the organic amine in step a) is composed of an organic amine, an alcohol solvent, and water; the organic amine is selected from at least one of the alkanolamine compounds.
[0019] The solution containing organic amines has a pH of 9.5 to 12.5 at 298 K.
[0020] Preferably, the organic amine is selected from at least one of ethanolamine, 1,2-propanediolamine, 1,3-propanediolamine, diethanolamine, triethanolamine, and isopropanolamine.
[0021] Preferably, the alcohol solvent is selected from at least one of methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, 2-butanol, and tert-butanol.
[0022] Preferably, the volume ratio of the organic amine, alcohol solvent, and water is (5~30):(300~500):(10~100).
[0023] More preferably, the volume ratio of the organic amine, alcohol solvent, and water is (10~20):(300~500):(40~60).
[0024] Preferably, the solution containing organosilane is an anhydrous alcohol solution of organosilane, obtained by dissolving organosilane in an anhydrous alcohol solvent.
[0025] Preferably, the organosilane is selected from at least one of tetramethoxysilane, tetraethoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, 3-aminopropyltrimethoxysilane, and 3-mercaptopropyltrimethoxysilane.
[0026] More preferably, the organosilane is a composition of at least one selected from tetramethoxysilane, tetraethoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane, and propyltrimethoxysilane, together with 3-aminopropyltrimethoxysilane and / or 3-mercaptopropyltrimethoxysilane.
[0027] The anhydrous alcohol solvent is selected from at least one of anhydrous methanol, anhydrous ethanol, anhydrous n-propanol, anhydrous isopropanol, anhydrous n-butanol, anhydrous isobutanol, anhydrous 2-butanol, and anhydrous tert-butanol.
[0028] Preferably, the concentration of the organosilane in the solution containing the organosilane is 1 mol / L to 10 mol / L.
[0029] Preferably, the concentration of the organosilane in the solution containing the organosilane is any value from 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, 6 mol / L, 7 mol / L, 8 mol / L, 9 mol / L, 10 mol / L, or any range between the two.
[0030] When the organosilane is a composition of at least one of tetramethoxysilane, tetraethoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane, and propyltrimethoxysilane with 3-aminopropyltrimethoxysilane and / or 3-mercaptopropyltrimethoxysilane, the molar ratio of at least one of tetramethoxysilane, tetraethoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane, and propyltrimethoxysilane to (3-aminopropyltrimethoxysilane and / or 3-mercaptopropyltrimethoxysilane) is 10 to 40:1, preferably 20 to 30:1, and more preferably 21.75 to 27.24:1.
[0031] Preferably, step a) involves stirring the solution containing the organic amine at 15-65°C for at least 30 minutes; maintaining the temperature and stirring, and then adding the solution containing the organosilane dropwise. The dripping time is 30 min to 600 min; The stirring speed is 200~1000 rpm; The volume ratio of the solution containing organosilane to the solution containing organic amine is 0.05~0.5:1.
[0032] More preferably, step a) involves stirring the solution containing the organic amine at 35-55°C for at least 0.5-1.5 hours; maintaining the temperature and stirring, and then adding the solution containing the organosilane dropwise. The dripping time is 5-7 hours; The stirring rate is 600~1000 rpm; The volume ratio of the solution containing organosilane to the solution containing organic amine is 0.11~0.16:1.
[0033] Preferably, the aging temperature in step b) is 15~65℃, and the aging time is 2~48h; The washing process involves adding deionized ultrasonic washing to the gel obtained by centrifugation, followed by centrifugation again.
[0034] More preferably, the aging temperature in step b) is 35~55℃, and the aging time is 12~48h.
[0035] When the organosilane contains 3-mercaptopropyltrimethoxysilane, step b) further includes the following steps between centrifugation and washing: Add hydrogen peroxide and heat under reflux for at least 6 hours.
[0036] According to another aspect of this application, a polishing fluid is provided, comprising at least one of the spherical silica particles, the silica sol, and the silica sol prepared according to the method.
[0037] The polishing solution contains the spherical silica particles, organic acid, and water.
[0038] The polishing slurry contains 1% to 10% by mass of spherical silica particles. The pH range of the polishing solution is 3.0~5.5.
[0039] Preferably, the mass content of spherical silica particles in the polishing liquid is 3-5%.
[0040] Preferably, the pH range of the polishing solution is 3.0 to 5.0.
[0041] Preferably, the polishing solution is composed of the silica sol, water, citric acid, and ammonium citrate.
[0042] The beneficial effects of this application include, but are not limited to: (1) By introducing new groups onto the surface of nano-silica particles, they can carry charges even under acidic conditions, thereby making the chemical mechanical polishing slurry composed of these particles and water highly stable under acidic conditions.
[0043] (2) By eliminating the introduction of metal ions into the chemical mechanical polishing slurry during the production process, the metal content of the chemical mechanical polishing slurry is reduced, the purity is improved, and the adsorption of metal ions during the polishing process is improved, thereby increasing the product yield. Attached Figure Description
[0044] Figure 1 This is a SEM image of spherical silica particles in acidic silica sol G1#, with a scale bar of 100 nm.
[0045] Figure 2 This is a SEM image of spherical silica particles in acidic silica sol G2#, with a scale bar of 100 nm.
[0046] Figure 3 This is a SEM image of silica particles in the comparative silica sol DG1#, with a scale bar of 100 nm.
[0047] Figure 4 This is a comparison chart of the polishing rates of polishing slurry samples M(3%)1#, M(3%)2#, and DM(3%)1#; wherein Example 1 corresponds to polishing slurry sample M(3%)1#, Example 2 corresponds to polishing slurry sample M(3%)2#, and Comparative Example 1 corresponds to polishing slurry sample DM(3%)1#. Detailed Implementation
[0048] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.
[0049] Unless otherwise specified, all raw materials and reagents used in this application are commercially purchased and used directly without processing. The instruments and equipment used adopt the manufacturer's recommended scheme and parameters.
[0050] In this embodiment, the particle size of the sample was measured using a Malvern Zetasizer Nano ZS90 nanometer laser particle size analyzer.
[0051] The morphology of the samples was observed using a JSM-7800F scanning electron microscope.
[0052] Example 1: Preparation of Acidic Silica Sol G1# Mix 15 ml of ethanolamine, 400 ml of methanol, and 50 ml of water to prepare an alkaline solution. Incubate at 45°C with stirring at 800 rpm for one hour. Add dropwise 50 ml of a methanol solution containing a mixture of tetramethoxysilane and 3-aminopropyltrimethoxysilane (3-aminopropyltrimethoxysilane mass percentage 5%, molar ratio of organosilane to anhydrous methanol 1:0.2) to the alkaline solution after incubation. The dropwise addition process takes 6 hours. Stop stirring and maintain the temperature for at least 12 hours to obtain a crude product. Centrifuge the crude product to obtain a gel and supernatant. Add water to the gel and sonicate for 2 hours, then centrifuge again to obtain a gel and supernatant. Repeat this process. Add water to the gel and sonicate for 2 hours to obtain a gel and supernatant. Add water to the resulting gel and sonicate for another 2 hours to obtain a silica sol, denoted as G1#. The concentration of G1# is not critical and can be adjusted by changing the amount of water added.
[0053] Example 2 Preparation of Acidic Silica Sol G2# Mix 15 ml of ethanolamine, 400 ml of methanol, and 50 ml of water to prepare an alkaline solution. Incubate at 45°C with stirring at 800 rpm for one hour. Add 75 ml of a methanol solution containing a mixture of tetramethoxysilane and 3-mercaptopropyltrimethoxysilane (3-mercaptopropyltrimethoxysilane comprising 5% of the total silane, and a molar ratio of organosilane to anhydrous methanol of 1:2) dropwise to the alkaline solution over 6 hours. Stop stirring and maintain the temperature for at least 12 hours to obtain a crude product. Centrifuge the crude product to obtain a gel and supernatant. Add water to the gel and sonicate for 2 hours, then centrifuge again to obtain a gel and supernatant. Repeat this process. Add water to the gel, sonicate for 2 hours, then centrifuge again to obtain a gel and supernatant. Add water to the gel, sonicate for 2 hours, then add 10 mL of water. Reflux the gel with 30% hydrogen peroxide at 80°C for 12 hours, then centrifuge to obtain a gel and supernatant. Add water to the gel, sonicate for 2 hours, then centrifuge again to obtain a gel and supernatant. Repeat this process. Add water to the resulting gel and sonicate for another 2 hours to obtain a silica sol, denoted as G2#. The concentration of G2# is not critical and can be adjusted by changing the amount of water added.
[0054] Comparative Example 1: Preparation of Silica Sol DG1# Mix 15 ml of ethanolamine, 400 ml of methanol, and 50 ml of water to form an alkaline solution, and incubate at 45°C and 800 rpm for one hour. Add 50 ml of tetramethoxysilane dropwise to the alkaline solution after incubation for 30 minutes, and then age for another 2 hours to obtain a crude product. Add water to the crude product and distill until all the methanol in the sol is evaporated, yielding nano-silica gel, denoted as DG1#. The concentration of DG1# is not critical and can be adjusted by changing the amount of water added.
[0055] Example 3 Particle size characterization of acidic silica sols G1#, G2# and silica sol GD1# The particle sizes of acidic silica sols G1# and G2# and the comparative silica sol DG1# were characterized, and the results are as follows: The average particle size of the acidic silica sol G1# particles is 106.6 nm, and the PDI is 0.044.
[0056] The average particle size of the acidic silica sol G2# particles is 85.7 nm, and the PDI is 0.065.
[0057] The average particle size of the silica sol D1# particles is 62.3 nm, and the PDI is 0.041.
[0058] Acidic silica sols G1#, G2#, and DG1# were dropped onto copper mesh and dried, respectively. The morphology of the spherical silica particles contained within them was then characterized. (See details below.) Figures 1 to 3 SEM images.
[0059] As shown in the figure, the spherical silica particles in acidic silica sols G1# and G2# have a uniform particle size distribution and good dispersion, with no aggregation between particles. In contrast, the silica particles in the comparative silica sol DG1# exhibit more agglomeration.
[0060] Example 4: Stability Comparison of Acidic Silica Sol Take silica sols G1#, G2# and DG1# respectively and mix them with water to prepare silica sols containing about 2% silica. Adjust the pH to 3.5 with citric acid and ammonium citrate.
[0061] The results showed that the pH of G1# and G2# was adjusted to 3.5, and the system remained uniform and stable throughout the process. During the pH adjustment process of DG1#, the sol color changed and the particles agglomerated when the pH was <4.
[0062] Subsequent experiments showed that G1# and G2# remained stable for over 6 months at pH 3.5, with no significant change in particle size. DG1# immediately aggregated under acidic conditions, indicating that the amino or sulfonic acid groups on the particle surface stabilized the silica sol under acidic conditions, extending the product's shelf life.
[0063] Example 5: Preparation of polishing slurry and testing of polishing performance The preparation method of the polishing slurry is as follows: Silica sols G1#, G2#, and DG1# were diluted with water, and then ammonium citrate was added to adjust the pH to pH=4, respectively, to obtain silica sols with a silica particle mass percentage of 3%, with the remainder being water, citric acid, and ammonium citrate. The resulting polishing solutions were designated as polishing solutions M(3%)1#, M(3%)2#, and DM(3%)1#, respectively.
[0064] The preparation methods and steps are the same as those for M(3%)1#, M(3%)2# and DM(3%)1#, except that the mass percentage of silica particles in the polishing solution is 4%, and the resulting polishing solutions are respectively denoted as polishing solutions M(4%)1#, M(4%)2# and DM(4%)1#.
[0065] The preparation method and steps are the same as those of M(3%)1#, M(3%)2# and DM(3%)1#, except that the mass percentage of silica particles in the polishing solution is 5%, and the resulting polishing solutions are respectively denoted as polishing solution M(5%)1#, M(5%)2# and DM(5%)1#.
[0066] The performance testing methods and results of the polishing slurry are as follows: The polishing equipment used was a Bruker UMT-TriboLab polishing machine, and the polishing pads were polyurethane polishing pads (Sub 400 & IC1000) provided by DOWE Electronic Materials (USA). During the experiment, the pressure was 2 Psi, the rotary table speed was 60 rpm, the rotor speed was 65 rpm, the polishing time was 1 min, and the flow rate was 80 mL / min. The wafer being polished was a 4-inch silicon wafer.
[0067] The performance of polishing slurry samples M(3%)1#, M(3%)2#, DM(3%)1#, M(4%)1#, M(4%)2#, DM(4%)1#, M(5%)1#, M(5%)2#, and DM(5%)1# was tested respectively. The results showed that, compared with DM(3%)1#, DM(4%)1#, and DM(5%)1#, the polishing performance of polishing slurry samples M(3%)1#, M(3%)2#, M(4%)1#, M(4%)2#, M(5%)1#, and M(5%)2# using the technical solution of this application was not significantly reduced.
[0068] Taking polishing slurry samples M(3%)1#, M(3%)2#, and DM(3%)1# as typical examples, their polishing rates are compared to... Figure 4 As shown in the figure, the acidic polishing slurries M(3%)1# and M(3%)2#, which improve stability by introducing functional groups onto the nanoparticles of silica sol, do not show a significant decrease in polishing performance compared to the ordinary silica sol polishing slurry DM(3%)1#.
[0069] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.
Claims
1. A type of spherical silica particles, characterized in that, The average particle size of the spherical silica particles is selected from any value in the range of 20~200nm, and the polydispersity index (PDI) of the spherical silica particles is ≤0.
10.
2. The spherical silica particles according to claim 1, characterized in that, The average particle size of the spherical silica particles is selected from any value in the range of 60~120nm, and the polydispersity index (PDI) of the spherical silica particles is 0.01≤PDI≤0.
10.
3. A silica sol, characterized in that, Contains the spherical silica particles as described in claim 1 or 2; The spherical silica particles have a mass percentage of 1-10% in the silica sol.
4. The method for preparing the silica sol according to claim 3, characterized in that, Includes the following steps: a) A solution containing an organosilane is added to a solution containing an organic amine to obtain a mixture; b) The mixture is aged, centrifuged, washed, and the pH value is adjusted to acidic to obtain the silica sol.
5. The method according to claim 4, characterized in that, The solution containing organic amine described in step a) consists of organic amine, alcohol solvent, and water; The organic amine is selected from at least one of the alcohol amine compounds; The solution containing organic amines has a pH of 9.5–12.5 at 298 K; Preferably, the organic amine is selected from at least one of ethanolamine, 1,2-propanediolamine, 1,3-propanediolamine, diethanolamine, triethanolamine, and isopropanolamine; Preferably, the alcohol solvent is selected from at least one of methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, 2-butanol, and tert-butanol.
6. The method according to claim 4, characterized in that, The solution containing organosilane is an anhydrous alcoholic solution of organosilane; The organosilane is selected from at least one of tetramethoxysilane, tetraethoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, 3-aminopropyltrimethoxysilane, and 3-mercaptopropyltrimethoxysilane; Preferably, the organosilane is a composition of at least one selected from tetramethoxysilane, tetraethoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane, and propyltrimethoxysilane, combined with 3-aminopropyltrimethoxysilane and / or 3-mercaptopropyltrimethoxysilane. Preferably, the concentration of the organosilane in the solution containing the organosilane is 1 mol / L to 10 mol / L.
7. The method according to claim 4, characterized in that, Step a) involves stirring the solution containing the organic amine at 15-65°C for at least 30 minutes; while maintaining the temperature and stirring, adding the solution containing the organosilane dropwise. The dripping time is 30 min to 600 min; The stirring speed is 200~1000 rpm; The volume ratio of the solution containing organosilane to the solution containing organic amine is 0.05~0.5:
1.
8. The method according to claim 4, characterized in that, The aging temperature in step b) is 15~65℃, and the aging time is 2~48h; The washing process involves adding deionized ultrasonic washing to the gel obtained by centrifugation, followed by centrifugation again.
9. The method according to claim 6, characterized in that, When the organosilane contains 3-mercaptopropyltrimethoxysilane, step b) further includes the following steps between centrifugation and washing: Add hydrogen peroxide and heat under reflux for at least 6 hours.
10. A polishing liquid, characterized in that, It contains at least one of the spherical silica particles according to claim 1 or 2, the silica sol according to claim 3, and the silica sol prepared by the method according to any one of claims 4 to 9.