A preparation method of wide-distribution large-particle silica sol, silica sol and application thereof

Abstract

The present invention discloses a preparation method of a wide-distribution large-particle silica sol, silica sol and its application. The present invention discloses a preparation method of a wide-distribution large-particle silica sol, firstly dripping a first organosilicon solution into a 30-50nm inorganic silicon seed solution for reaction, then dripping a second organosilicon solution thereto for reaction, and preparing a silica sol with a particle size of 20-140nm; the ratio of the silicon content in the inorganic silicon seed solution to the first organosilicon solution is 1:(1.2-2.0), and the ratio of the silicon content in the inorganic silicon seed solution to the second organosilicon solution is 1:(2.1-2.8). The present invention first drips the organosilicon solution slowly into the inorganic silicon seed, grows the seed by hydrolysis, and then adds the organosilicon solution at a faster dripping rate, and the whole process maintains a constant liquid level. The polishing liquid prepared by the wide-distribution large-particle silica sol prepared by the present invention can well take into account the requirements of high removal rate and low defectivity.

Description

Technical Field

[0001] The present invention relates to the technical field of new materials, and more specifically, to a preparation method of a widely distributed large-particle silica sol, the silica sol and its application. Background Art

[0002] Chemical Mechanical Polishing (CMP) technology is known as the only technology that can achieve global flattening of the wafer surface in integrated circuit (IC) manufacturing in today's era. The effect of chemical mechanical polishing directly affects the final quality and yield of the chip. The concept of chemical mechanical polishing was proposed by Walsh et al. in 1965. It was first used to manufacture high-quality glass surfaces, such as military telescopes. In 1986, IBM first applied this technology to the metal mechanical polishing process. With the continuous advancement of IC manufacturing technology nodes and the introduction of low-k dielectric materials, the traditional CMP process will damage the low-k dielectric material due to the high polishing pressure. Therefore, the CMP process began to develop in the direction of low pressure and low abrasive, and was successfully applied to the IC manufacturing process, gradually growing into an indispensable key technology in the IC manufacturing process.

[0003] Silica sol is a dispersion formed by amorphous silicon dioxide particles dispersed in water (also known as silicic acid solution). The silica sol currently prepared in industry contains nano-silica particles with a particle size of 5-100 nm. A series of products with different properties and uses are prepared based on the particle size. 2 It has good stability and dispersibility, will not introduce metal cation pollution, its hardness is close to that of elemental silicon, and it causes fewer scratches and scratches on the base material. It is suitable for polishing soft metals, silicon and other materials. It is the most widely used polishing liquid, but its material removal rate is relatively low. By studying the effect of silica sol particle size on the polishing effect of silicon wafers, it was found that as the particle size increases, MRR (removal rate) first increases and then decreases, while Ra (surface roughness) first decreases and then increases. Analysis shows that: when the particle size is small, chemical corrosion plays a leading role; as the particle size increases, the mechanical effect is strengthened. As the particle size continues to increase beyond a certain range, the mechanical effect exceeds the chemical effect, resulting in local scratches on the material surface, reducing the polishing quality. Therefore, it is of great significance to prepare a polishing liquid that takes into account both removal rate and low defectivity. Summary of the invention

[0004] An object of the present invention is to solve at least the above problems and to provide at least the advantages which will be described hereinafter.

[0005] Another object of the present invention is to provide a method for preparing a widely distributed large-particle silica sol. When the semiconductor material polishing liquid prepared by the present invention is polished, the large-particle silica sol and the small-particle silica sol cooperate with each other to increase the friction coefficient and strengthen the chemical activity, thereby effectively improving the polishing efficiency. It has been verified in practice that the polishing liquid prepared by the silica sol of the present invention can increase the polishing rate and significantly reduce the generation of scratches during the polishing process, effectively ensuring the polishing quality.

[0006] In order to achieve these purposes and other advantages according to the present invention, the first aspect of the present invention provides a method for preparing a wide-distribution large-particle silica sol, firstly, a first organic silicon solution is added dropwise to a 30-50nm inorganic silicon seed solution for reaction, and then a second organic silicon solution is added dropwise thereto for reaction to prepare a silica sol with a particle size of 20-140nm; the silicon content ratio of the inorganic silicon seed solution to the first organic silicon solution is 1:(1.2-2.0), and the silicon content ratio of the inorganic silicon seed solution to the second organic silicon solution is 1:(2.1-2.8).

[0007] Preferably, the solid content of the first organosilicon solution is 5-8 wt %, and the solid content of the second organosilicon solution is 9-12 wt %.

[0008] Preferably, the ratio of the dropping speed of the first organosilicon solution to its volume is (0.001-0.002) mL / min:1 mL, and the ratio of the dropping speed of the second organosilicon solution to its volume is (0.005-0.007) mL / min:1 mL.

[0009] Preferably, the dispersion coefficient of the silica sol is 1.303-1.398, and the difference between the D90 particle size and the D10 particle size of the silica sol is 66-90 nm.

[0010] Preferably, the first organosilicon solution and the second organosilicon solution respectively contain one or both of tetramethyl orthosilicate and tetraethyl orthosilicate.

[0011] Preferably, the reaction liquid level is kept constant throughout the reaction process, the pH of the reaction is maintained between 9.5 and 10.5, and the reaction temperature is 90 to 120°C.

[0012] Preferably, the inorganic silicon seed solution is prepared by adding active silicic acid having a pH of 2.0 to 3.0 to an inorganic alkaline solution at a rate of 5 to 10 mL / min.

[0013] Preferably, the preparation method of the active silicate is: dilute concentrated water glass with ultrapure water to a solution with a silicon dioxide content of 4-8wt%, stir evenly and then add to a strong acid cation exchange resin for cation exchange to obtain active silicate with a pH of 2.0-3.0.

[0014] The second aspect of the present invention provides a broad distribution large particle size silica sol, including a silica sol prepared by a broad distribution large particle size preparation method.

[0015] A third aspect of the present invention provides an application of a widely distributed large-particle silica sol in a polishing liquid.

[0016] The present invention has at least the following beneficial effects:

[0017] By adding an inorganic silicon seed solution with organosilicon acid, controlling the ratio of the first organosilicon solution and the second organosilicon solution to the inorganic silicon seed solution, and controlling the content or the dropping speed of the first organosilicon solution and the second organosilicon solution, the upper limit of the silica sol particle size can be broken, the degree of dispersion of the particle size can be increased, and a silica sol with a wider particle size can be obtained, thereby effectively improving the polishing rate and reducing scratches generated during the polishing process.

[0018] Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a scanning electron microscope image of Example 3 of the present invention. DETAILED DESCRIPTION

[0020] In order to better understand the technical solution of the present invention, the present invention is described in detail below.

[0021] The first aspect of the present invention provides a method for preparing a silica sol with a wide distribution and large particle size, comprising the following steps:

[0022] Step (1): Preparation of active silicic acid solution

[0023] The concentrated water glass is diluted with ultrapure water to a solution with a silica content of 4-8wt%, stirred evenly, and then added to a strong acid cation exchange resin for cation exchange to obtain active silica with a pH of 3.0-4.0. The solid content of silica is adjusted to 4-8wt% with ultrapure water, and the pH is adjusted to 2.0-3.0 with sulfuric acid.

[0024] In an embodiment of the present invention, the content of silicon dioxide is measured by molybdate photometry. The mass content of silicon dioxide will affect the ion exchange process. Active silicic acid with different solid contents can affect the particle size distribution of silica sol and the morphology of silicon dioxide particles in silica sol.

[0025] In an embodiment of the present invention, concentrated water glass is diluted to a silicon dioxide content of 4-8wt% before cation exchange. The cation exchange resin is regenerated, and the strong acidic cationic resin can be selected from polybenzenesulfonic acid type resin. Active silica is relatively stable under acidic conditions, and the pH of the active silica solution is generally adjusted between 2.0 and 3.0.

[0026] The ultrapure water used above has a resistivity of ≥10 MΩ·cm, preferably 12.5 MΩ·cm. The ultrapure water used below has the same resistivity requirement as the ultrapure water used in this embodiment.

[0027] Step (2): Preparation of silicon seed solution

[0028] The inorganic silicon seed solution is prepared by adding active silicic acid with a pH of 2.0 to 3.0 to an inorganic alkaline solution at a rate of 5 to 10 mL / min for growth.

[0029] In an embodiment of the present invention, the solid content in the inorganic silicon seed solution is determined by a drying method. The sample is placed in an oven and dried at 180°C for 30 minutes. The difference between the mass of the dried sample and the initial mass is calculated to calculate the solid content. The solid content in the inorganic silicon seed solution is silicon dioxide. The solid content in the inorganic silicon seed solution of the present invention is substantially the same as the solid content of silicon dioxide in the active silicic acid in step (1).

[0030] In an embodiment of the present invention, the inorganic alkali solution is a mixed aqueous solution of one or more of potassium silicate, sodium silicate, potassium hydroxide and sodium hydroxide. The content of the inorganic alkali in the inorganic alkali solution is 0.1-2wt%, preferably 1wt%.

[0031] In an embodiment of the present invention, when preparing the silicon seed solution, the inorganic alkali solution is first placed in a reaction container, heated to 90-100° C., and then active silicic acid is added dropwise thereto. After the active silicic acid is added dropwise, the temperature is kept for 0.5-2 hours, and then naturally cooled to room temperature. The volume ratio of the inorganic alkali solution to the active silicic acid is 1:(40-50).

[0032] In an embodiment of the present invention, the particle size of the particles in the silicon seed solution is between 30 and 50 nm. Only when the particle size of the particles in the silicon seed solution is between 30 and 50 nm can silica sol particles of 20 to 140 nm be prepared. If the maximum value of the particle size exceeds the distribution range, the silica sol particles with large particle size will be more; if the minimum value of the particle size is less than the range, the silica sol particles with the maximum threshold value of the particle size range cannot be obtained.

[0033] Step (3): Preparation of large-particle silica sol

[0034] The silicon seed solution prepared in step (2) is taken as the mother liquor, stirred and heated to boiling, and then the first organosilicon solution is added dropwise to the reaction system. At the same time, water is condensed from the reaction system to maintain a constant liquid level. At the same time, 0.1-2 wt% of an inorganic base solution is added dropwise to keep the pH value of the entire system at 9.5-10.5.

[0035] In an embodiment of the present invention, the ratio of silicon content in the inorganic silicon seed solution to that in the first organic silicon solution is 1:(1.2-2.0).

[0036] In a preferred embodiment of the present invention, the solid content of the first organosilicon solution is preferably 5-8 wt %. The first organosilicon solution comprises one or both of tetramethyl orthosilicate and tetraethyl orthosilicate, and the first organosilicon solution is an ethanol solution.

[0037] In a preferred embodiment of the present invention, the dripping speed of the first organosilicon solution increases or decreases in proportion to the volume of the first organosilicon solution; as the volume of the first organosilicon solution increases, the dripping speed of the first organosilicon solution increases accordingly; as the volume of the first organosilicon solution decreases, the dripping speed of the first organosilicon solution decreases accordingly. The specific relationship between the dripping speed of the first organosilicon solution and the volume of the first organosilicon solution is: the ratio of the dripping speed of the first organosilicon solution to the volume of the first organosilicon solution is (0.001~0.002)mL / min:1mL. At this speed, the silica sol can effectively grow to obtain silica sol particles with a larger particle size.

[0038] In an embodiment of the present invention, the inorganic alkali solution is a mixed aqueous solution of one or more of potassium silicate, sodium silicate, potassium hydroxide and sodium hydroxide. The content of the inorganic alkali in the inorganic alkali solution is 0.1-2wt%, preferably 1wt%.

[0039] It should be noted that the pH value of the entire system of the reaction needs to be maintained at 9.5 to 10.5. When the pH in the system is close to the maximum value, the dropping speed of the inorganic alkali solution is accelerated, and when the pH in the system is close to the minimum value, the dropping speed of the inorganic alkali solution is slowed down. The inorganic alkali solution is preferably added dropwise at a speed of 0.1 to 5 mL / min. The inorganic alkali solution can be added dropwise using a peristaltic pump or other methods capable of controlling the dropping speed.

[0040] Step (4): Preparation of wide distribution large particle size silica sol

[0041] After the step (3) is completed, the second organosilicon solution is added to the reaction system, and water is condensed from the reaction system to maintain a constant liquid level. At the same time, 0.1-2 wt% of an inorganic base solution is added to keep the pH value of the entire system at 9.5-10.5. After the second organosilicon solution is added, the temperature is kept at 2-4 hours, and the solution is naturally cooled to room temperature to obtain a widely distributed large-particle silica sol.

[0042] In an embodiment of the present invention, the ratio of silicon content in the inorganic silicon seed solution to that in the second organic silicon solution is 1:(2.1-2.8).

[0043] In a preferred embodiment of the present invention, the solid content of the second organosilicon solution is preferably 9-12wt%. Using a second organosilicon solution with a higher solid content than the first organosilicon solution can accelerate the growth of silica sol particles and promote the generation of new crystal seeds. The second organosilicon solution contains one or two of tetramethyl orthosilicate and tetraethyl orthosilicate, and the second organosilicon solution is an ethanol solution.

[0044] In a preferred embodiment of the present invention, the dripping speed of the second organosilicon solution increases or decreases in proportion to the volume of the second organosilicon solution; as the volume of the second organosilicon solution increases, the dripping speed of the second organosilicon solution increases accordingly; as the volume of the second organosilicon solution decreases, the dripping speed of the second organosilicon solution decreases accordingly. The specific relationship between the dripping speed of the second organosilicon solution and the volume of the second organosilicon solution is: the ratio of the dripping speed of the second organosilicon solution to its volume is (0.005~0.007)mL / min:1mL. Using a faster dripping speed than the first organosilicon sol can make the silica sol particles have better sphericity and faster growth rate, promote the generation of new crystal seeds, and thus increase the wide distribution effect of the silica sol particles.

[0045] In the embodiment of the present invention, the pH value of the whole system is maintained at 9.5-10.5. When the pH value of the reaction system is lower than 9.5, the surface charge of the particles may be low, which may lead to easy aggregation and premature gelation of the silica sol particles. The pH value of the reaction system is maintained between 9.5-10.5, so that the alkaline environment provides sufficient OH - Ions make the particle surface negatively charged, and the stability of silica sol is maintained by electrostatic repulsion. When the pH of the reaction system is greater than 10.5, more metal cations are introduced due to the addition of more inorganic alkaline solution, which is not conducive to the stable formation of silica sol.

[0046] In an embodiment of the present invention, the liquid level is maintained constant. In the later stage of the reaction, the solid content in the reaction system will gradually increase, the growth will be faster, the morphology will be more rounded, and the silica sol particle size distribution will be relatively wider.

[0047] A second aspect of the present invention provides a silica sol with a wide distribution and large particle size, wherein the particle size of the silica sol is between 20 and 140 nm.

[0048] In the embodiment of the present invention, the particle size range of the width distribution can only be obtained by dripping inorganic silicon seeds with organosilicon, and the particle size range of the width distribution can only be obtained by dripping organosilicon solutions with different solid contents at different rates. In the present invention, the ratio of the silicon content in the inorganic silicon seed solution to the first organosilicon solution is 1:(1.2~2.0), and the ratio of the silicon content in the inorganic silicon seed solution to the second organosilicon solution is 1:(2.1~2.8). The present invention uses organosilicon acid to drip inorganic silicon seed solution, and controls the ratio of the first organosilicon solution and the second organosilicon solution to the inorganic silicon seed solution, which can break the upper limit of the silica sol particle size, obtain a silica sol with a wider particle size, and effectively improve the polishing rate.

[0049] In an embodiment of the present invention, the difference between the D90 particle size and the D10 particle size of the silica sol is between 66 and 90 nm, indicating that the wide distribution of large-particle silica sol is relatively dispersed between the two end values ​​of the threshold range of 20 to 140 nm. It is preferably between 70 and 88 nm, preferably between 72 and 88 nm, and more preferably between 76 and 88 nm. The present invention controls the difference between the D90 particle size and the D10 particle size of the silica sol between 66 and 90 nm, which can further improve the polishing rate and reduce the scratches generated during the polishing process.

[0050] In the embodiment of the present invention, PDI represents the dispersion coefficient, which represents the degree of dispersion of the normal distribution. The larger the PDI value, the wider the distribution of abrasives of different particle sizes in the silica sol; the smaller the PDI value, the narrower the distribution of silica sol particles. The dispersion coefficient of the silica sol described in the present invention is 1.303-1.398, indicating that the particle size distribution of the silica sol particles obtained by the above preparation method is relatively wide.

[0051] The third aspect of the present invention provides an application of a widely distributed large-particle silica sol in a polishing liquid. The polishing liquid provided by the present invention has the beneficial effect of increasing the removal rate and the flattening processing efficiency in the chemical mechanical polishing process of polishing a copper wafer, and can also reduce the occurrence of local scratches on the surface.

[0052] The present invention is further described in detail below in conjunction with embodiments so that those skilled in the art can implement the invention with reference to the description.

[0053] It should be noted that the experimental methods described in the following embodiments are conventional methods unless otherwise specified, and the reagents and materials can be obtained from commercial channels unless otherwise specified.

[0054] <Example 1>

[0055] Step (1): Preparation of active silicic acid

[0056] Concentrated sodium silicate (Na 2 SiO 3 ) is diluted with ultrapure water to a concentration of silica (SiO 2 ) content is 5wt%, and after being fully stirred, it is passed through a strong acid cationic resin exchange column to obtain active silicic acid. The solid content of silicon dioxide in the treated active silicic acid is 5.4wt%, and the pH is 3.1. Ultrapure water is used to adjust the solid content of silicon dioxide to 4wt%, and 15wt% sulfuric acid is used to adjust the pH of the active silicic acid to 2.5.

[0057] Step (2): Preparation of silicon seed solution

[0058] 60 mL of 2 wt% solid potassium silicate solution was placed in a reactor, heated to 100°C, and kept warm for 1 hour while stirring. Subsequently, 2700 mL of active silicate in step (1) was added dropwise to the reactor at a rate of 5 mL / min. After the addition of active silicate, the solution was kept warm for 2 hours and cooled naturally to room temperature to obtain a monodisperse spherical silicon seed solution with a particle size of 30-40 nm.

[0059] Step (3): Preparation of large-particle silica sol

[0060] Take 500 mL of the silicon seed solution in step (2) in a reactor, stir and heat to 100°C, then take 1000 mL of 10 wt% ethanol solution of methyl orthosilicate (TMOS) (first organic silicon solution) and drop it into the reactor at a rate of 1 mL / min, and add 1 wt% KOH solution at the same time, maintain the pH at 9.5-10.5, condense water while dropping methyl orthosilicate (TMOS), and maintain the liquid level constant. The ratio of silicon content in the inorganic silicon seed solution to that in the first organic silicon solution is about 1:1.974.

[0061] Step (4): Preparation of wide distribution large particle size silica sol

[0062] After the step (3) is completed, 1000 mL of 14 wt% ethanol solution of methyl orthosilicate (TMOS) (the second organosilicon solution) is added to the reactor at a rate of 5 mL / min, and 1 wt% KOH solution is added at the same time to maintain the pH at 9.5-10.5 and the reaction temperature at 100°C. While the methyl orthosilicate (TMOS) is being added, water is condensed to maintain a constant liquid level. After the addition of methyl orthosilicate (TMOS) is completed, the solution is kept warm for 2 hours and cooled naturally to room temperature to obtain a widely distributed large-particle silica sol. The particle size distribution is within 25-125 nm, and the PDI coefficient is 1.252. The ratio of the silicon content in the inorganic silicon seed solution to that in the second organosilicon solution is approximately 1:2.763.

[0063] <Example 2>

[0064] Step (1): Preparation of active silicic acid

[0065] Concentrated sodium silicate (Na 2 SiO 3 ) is diluted with ultrapure water to a concentration of silica (SiO 2 ) content is 5wt%, and after being fully stirred, it is passed through a strong acid cationic resin exchange column to obtain active silicic acid. The solid content of silicon dioxide in the treated active silicic acid is 5.4wt%, and the pH is 3.1. Ultrapure water is used to adjust the solid content of silicon dioxide to 4wt%, and 15wt% sulfuric acid is used to adjust the pH of the active silicic acid to 2.5.

[0066] Step (2): Preparation of silicon seed solution

[0067] 60 mL of 2 wt% solid potassium silicate solution was placed in a reactor, heated to 100°C, and kept warm for 1 hour while stirring. Subsequently, 2700 mL of active silicate in step (1) was added dropwise to the reactor at a rate of 5 mL / min. After the addition of active silicate, the solution was kept warm for 2 hours and cooled naturally to room temperature to obtain a monodisperse spherical silica sol with a particle size of 30-40 nm.

[0068] Step (3): Preparation of large-particle silica sol

[0069] 500 mL of the silicon seed solution in step (2) was placed in a reaction kettle, stirred and heated to 100°C, and then 1000 mL of 8 wt% methyl orthosilicate (TMOS) ethanol solution (first organic silicon solution) was added dropwise to the reaction kettle at a rate of 2.5 mL / min, and 1 wt% KOH solution was added at the same time, maintaining the pH at 9.5-10.5, and condensing water while adding methyl orthosilicate (TMOS) to maintain a constant liquid level. The ratio of the silicon content in the inorganic silicon seed solution to that in the first organic silicon solution is approximately 1:1.579.

[0070] Step (4): Preparation of wide distribution large particle size silica sol

[0071] After the step (3) is completed, 1000 mL of 12 wt% ethanol solution of methyl orthosilicate (TMOS) (the second organosilicon solution) is added to the reactor at a rate of 4 mL / min, and 1 wt% KOH solution is added at the same time to maintain the pH at 9.5-10.5 and the reaction temperature at 100°C. While the methyl orthosilicate (TMOS) is being added, water is condensed to maintain a constant liquid level. After the addition of methyl orthosilicate (TMOS) is completed, the solution is kept warm for 2 hours and cooled naturally to room temperature to obtain a widely distributed large-particle silica sol. The particle size distribution is within 35-128 nm, and the PDI coefficient is 1.279. The ratio of the silicon content in the inorganic silicon seed solution to that in the second organosilicon solution is approximately 1:2.368.

[0072] <Example 3>

[0073] Step (1): Preparation of active silicic acid solution

[0074] Concentrated sodium silicate (Na 2 SiO 3 ) is diluted with ultrapure water to a concentration of silica (SiO 2 ) content is 5wt%, and after being fully stirred, it is passed through a strong acid cationic resin exchange column to obtain active silicic acid. The solid content of silicon dioxide in the treated active silicic acid is 5.4wt%, and the pH is 3.1. Ultrapure water is used to adjust the solid content of silicon dioxide to 5wt%, and 15wt% sulfuric acid is used to adjust the pH of the active silicic acid to 2.5.

[0075] Step (2): Preparation of silicon seed solution

[0076] 60 mL of 2 wt% solid potassium silicate solution was placed in a reactor, heated to 100°C, and kept warm for 1 hour while stirring. Subsequently, 2700 mL of active silicate in step (1) was added dropwise to the reactor at a rate of 5 mL / min. After the addition of active silicate, the solution was kept warm for 2 hours and cooled naturally to room temperature to obtain a monodisperse spherical silica sol with a particle size of 30-40 nm.

[0077] Step (3): Preparation of large-particle silica sol

[0078] Take 500 mL of the silicon seed solution in step (2) in a reactor, stir and heat to 100°C, then take 1000 mL of 8 wt% methyl orthosilicate (TMOS) ethanol solution (first organic silicon solution) and drop it into the reactor at a rate of 1.5 mL / min, and add 1 wt% KOH solution at the same time, maintain the pH at 9.5-10.5, condense water while dropping methyl orthosilicate (TMOS), and maintain the liquid level constant. The ratio of silicon content in the inorganic silicon seed solution to that in the first organic silicon solution is about 1:1.263.

[0079] Step (4): Preparation of wide distribution large particle size silica sol

[0080] After the step (3) is completed, 1500 mL of 10 wt% ethanol solution of tetraethyl orthosilicate (TEOS) (the second organosilicon solution) is added to the reactor at a rate of 8 mL / min, and 1 wt% KOH solution is added at the same time to maintain the pH at 9.5-10.5 and the reaction temperature at 100°C. While the tetraethyl orthosilicate (TEOS) is being added, water is condensed to maintain a constant liquid level. After the addition of tetraethyl orthosilicate (TEOS) is completed, the mixture is kept warm for 2 hours and cooled naturally to room temperature to obtain a widely distributed large-particle silica sol. The particle size distribution is within the range of 25 to 135 nm, and the PDI coefficient is 1.352. Among them, the ratio of the silicon content in the inorganic silicon seed solution to that in the second organosilicon solution is approximately 1:2.368. The scanning electron microscope image is shown in the figure below Figure 1 shown.

[0081] <Example 4>

[0082] Step (1): Preparation of active silicic acid

[0083] Concentrated sodium silicate (Na 2 SiO 3 ) is diluted with ultrapure water to a concentration of silica (SiO 2 ) content is 5wt%, and after being fully stirred, it is passed through a strong acid cationic resin exchange column to obtain active silicic acid. The solid content of silicon dioxide in the treated active silicic acid is 5.4wt%, and the pH is 3.1. Ultrapure water is used to adjust the solid content of silicon dioxide to 4wt%, and 15wt% sulfuric acid is used to adjust the pH of the active silicic acid to 2.5.

[0084] Step (2): Preparation of silicon seed solution

[0085] 60 mL of 2 wt% solid potassium silicate solution was placed in a reactor, heated to 100°C, and kept warm for 1 hour while stirring. Subsequently, 2700 mL of active silicate in step (1) was added dropwise to the reactor at a rate of 5 mL / min. After the addition of active silicate, the solution was kept warm for 2 hours and cooled naturally to room temperature to obtain a monodisperse spherical silicon seed solution with a particle size of 30-40 nm.

[0086] Step (3): Preparation of large-particle silica sol

[0087] 500 mL of the silicon seed solution in step (2) was placed in a reaction kettle, stirred and heated to 100°C, and then 1250 mL of a 6 wt% ethanol solution of methyl orthosilicate (TMOS) (the first organosilicon solution) was added dropwise to the reaction kettle at a rate of 1.25 mL / min, and 1 wt% KOH solution was added dropwise at the same time, maintaining the pH at 9.5-10.5, and condensing water while adding methyl orthosilicate (TMOS) to maintain a constant liquid level. The ratio of the silicon content in the inorganic silicon seed solution to that in the first organosilicon solution was approximately 1:1.480.

[0088] Step (4): Preparation of wide distribution large particle size silica sol

[0089] After the step (3) is completed, 1250 mL of 10 wt% ethanol solution of methyl orthosilicate (TMOS) (the second organosilicon solution) is added to the reactor at a rate of 7.5 mL / min, and 1 wt% KOH solution is added at the same time to maintain the pH at 9.5-10.5 and the reaction temperature at 100°C. While the methyl orthosilicate (TMOS) is being added, water is condensed to maintain a constant liquid level. After the addition of methyl orthosilicate (TMOS) is completed, the mixture is kept warm for 2 hours and cooled naturally to room temperature to obtain a widely distributed large-particle silica sol. The particle size distribution is within 20-138 nm, and the PDI coefficient is 1.359. The ratio of the silicon content in the inorganic silicon seed solution to that in the second organosilicon solution is approximately 1:2.467.

[0090] <Example 5>

[0091] Step (1): Preparation of active silicic acid

[0092] Concentrated sodium silicate (Na 2 SiO 3 ) is diluted with ultrapure water to a concentration of silica (SiO 2 ) content is 8wt%, and after being fully stirred, it is passed through a strong acid cationic resin exchange column to obtain active silicic acid. The solid content of silicon dioxide in the treated active silicic acid is 8.7wt%, and the pH is 3.2. The solid content of silicon dioxide is adjusted to 6wt% using ultrapure water, and the pH is adjusted to 2.5 using 15wt% sulfuric acid.

[0093] Step (2): Preparation of silicon seed solution

[0094] 60 mL of 2 wt% solid potassium silicate solution was placed in a reactor, heated to 100°C, and kept warm for 1 hour while stirring. Subsequently, 2700 mL of active silicate in step (1) was added dropwise to the reactor at a rate of 5 mL / min. After the addition of active silicate, the solution was kept warm for 2 hours and cooled naturally to room temperature to obtain a monodisperse spherical silicon seed solution with a particle size of 40-50 nm.

[0095] Step (3): Preparation of large-particle silica sol

[0096] Take 500 mL of the silicon seed solution in step (2) in a reactor, stir and heat to 100°C, then take 1500 mL of 8 wt% methyl orthosilicate (TMOS) ethanol solution (first organic silicon solution) and add it dropwise to the reactor at a rate of 1.5 mL / min, and add 1 wt% KOH solution at the same time, maintain the pH at 9.5-10.5, condense water while adding methyl orthosilicate (TMOS), and maintain the liquid level constant. The ratio of the silicon content in the inorganic silicon seed solution to the first organic silicon solution is about 1:1.579.

[0097] Step (4): Preparation of wide distribution large particle size silica sol

[0098] After the step (3) is completed, 1400 mL of 12 wt% ethanol solution of methyl orthosilicate (TMOS) (the second organosilicon solution) is added to the reactor at a rate of 7.5 mL / min, and 1 wt% KOH solution is added at the same time to maintain the pH at 9.5-10.5 and the reaction temperature at 100°C. While the methyl orthosilicate (TMOS) is being added, water is condensed to maintain a constant liquid level. After the addition of methyl orthosilicate (TMOS) is completed, the mixture is kept warm for 2 hours and cooled naturally to room temperature to obtain a widely distributed large-particle silica sol. The particle size distribution is within the range of 25-140 nm, and the PDI coefficient is 1.348. The ratio of the silicon content in the inorganic silicon seed solution to that in the second organosilicon solution is approximately 1:2.210.

[0099] <Comparative Example 1>

[0100] The preparation of active silicate in step (1) and the preparation of silicon seed solution in step (2) are the same as in Example 1, except that 500 mL of silicon seed solution in step (2) is placed in a reactor, stirred and heated to 100°C, and then 2000 mL of active silicate in step (1) is added dropwise to the reactor at a rate of 2 mL / min, and 1 wt% KOH solution is added at the same time, the pH is maintained at 9.5-10.5, and water is condensed while the active silicate is added dropwise, and the liquid level is maintained constant to prepare silica sol. The silica sol particle size distribution is within 25-95 nm, and the PDI coefficient is 1.226.

[0101] <Comparative Example 2>

[0102] The preparation of active silicate in step (1) and the preparation of silicon seed solution in step (2) are the same as those in Example 1, except that in step (3): 500 mL of the silicon seed solution in step (2) is placed in a reaction kettle, stirred and heated to 100° C., then 1000 mL of the active silicate in step (1) is added dropwise to the reaction kettle at a rate of 1 mL / min, and 1 wt % KOH solution is added at the same time to maintain the pH at 9.5-10.5. While the active silicate is being added dropwise, water is condensed to maintain a constant liquid level.

[0103] Step (4): After the step (3) is completed, 1000 mL of 10 wt% active silicate is added to the reactor at a rate of 5 mL / min, and 1 wt% KOH solution is added at the same time, the pH is maintained at 9.5-10.5, and the reaction temperature is maintained at 100°C. While the active silicate is being added, water is condensed to maintain a constant liquid level. After the addition is completed, the temperature is kept constant for 2 hours, and the silica sol is naturally cooled to room temperature to obtain the silica sol. The particle size distribution of the silica sol is within 25-104 nm, and the PDI coefficient is 1.249.

[0104] <Comparative Example 3>

[0105] The preparation of active silicic acid in step (1) and the preparation of silicon seed solution in step (2) are the same as in Example 1, except that in step (3): 500 mL of the silicon seed solution in step (2) is placed in a reactor, stirred and heated to 100°C, then 2000 mL of 8 wt% ethanol solution of methyl orthosilicate (TMOS) is added dropwise to the reactor at a rate of 1 mL / min, and 1 wt% KOH solution is added at the same time, the pH is maintained at 9.5-10.5, and water is condensed while methyl orthosilicate (TMOS) is added dropwise to maintain a constant liquid level. The particle size distribution is within 25-98 nm, and the PDI coefficient is 1.238.

[0106] <Comparative Example 4>

[0107] The preparation of active silicic acid in step (1) and the preparation of silicon seed solution in step (2) are the same as those in Example 1, except that in step (3): 500 mL of the silicon seed solution in step (2) is placed in a reaction kettle, stirred and heated to 100° C., then 500 mL of 8 wt % ethanol solution of methyl orthosilicate (TMOS) is added dropwise to the reaction kettle at a rate of 1 mL / min, and 1 wt % KOH solution is added at the same time to maintain the pH at 9.5-10.5. While methyl orthosilicate (TMOS) is added dropwise, water is condensed to maintain a constant liquid level.

[0108] Step (4): After the step (3) is completed, 1000 mL of 8 wt% ethanol solution of methyl orthosilicate (TMOS) is added to the reactor at a rate of 5 mL / min, and 1 wt% KOH solution is added at the same time, the pH is maintained at 9.5-10.5, and the reaction temperature is maintained at 100°C. While the methyl orthosilicate (TMOS) is added, water is condensed to maintain a constant liquid level. After the addition of methyl orthosilicate (TMOS) is completed, the temperature is kept constant for 2 hours, and it is naturally cooled to room temperature to obtain a widely distributed large-particle silica sol. The particle size distribution is within 25~105nm, and the PDI coefficient is 1.252.

[0109] The polishing liquids prepared from the silica sols of Examples 1 to 5 and Comparative Examples 1 to 4 were tested. The test results are shown in Table 1.

[0110] Preparation of polishing liquid: The solid content of the silica sol prepared in Examples 1 to 5 and Comparative Examples 1 to 4 was adjusted to 10 wt %, and 140 g of the silica sol in Examples 1 to 5 and Comparative Examples 1 to 4, 4 g of polyvinyl pyrrolidone, 0.5 g of benzotriazole inhibitor, 1 g of phosphoric acid, 3 g of citric acid, 8 g of hydrogen peroxide, and 840 g of water were taken and mixed to prepare the polishing liquid.

[0111] Polishing liquid grinding rate measurement: the polishing machine is an Ebara machine, the polishing wafer is a silicon wafer loaded with Cu, the polishing pad is a Fujibo pad (H800), the polishing liquid is the polishing liquid prepared from the silica sol of Examples 1 to 5 and Comparative Examples 1 to 4, the flow rate is 150 mL / min, the dresser is a 3M A165P diamond disk, the pressure is 6 lbf, the platen speed is 73 rpm, the carrier speed is 67 rpm, and the polishing head pressure is 1.5 psi. Under the above test conditions, the sample wafer is ground, and the Cu removal rate is calculated from the wear loss, and the unit is (Å / min).

[0112] Defectivity test method: Defectivity is the measurement of the number of defects on the wafer. The instrument used is KLA-Tencor SP2 analyzer, which records the average number of defects in 10 wafers.

[0113] Table 1

[0114] serial number Particle size range / nm PDI D90 / nm D10 / nm (D90-D10) / nm Cu polishing rate / (Å / min) Defects / pcs Example 1 25~125 1.252 116.3 49.2 67.1 8012 109 Example 2 35~128 1.279 118.2 51.3 66.9 7954 114 Example 3 25~135 1.352 123.5 44.9 78.6 8965 87 Example 4 20~138 1.359 122.8 38.6 84.2 8746 92 Example 5 25~140 1.348 124.7 39.5 85.2 8759 83 Comparative Example 1 25~95 1.226 87.2 43.6 43.6 6368 215 Comparative Example 2 25~104 1.249 90.1 35.2 54.9 6952 232 Comparative Example 3 25~98 1.238 88.3 32.2 56.1 7034 183 Comparative Example 4 25~105 1.252 91.2 34.5 56.7 7328 168

[0115] As can be seen from Table 1, the polishing liquids prepared from the silica sols of Examples 1 to 5 have the effects of increasing the grinding speed and reducing grinding defects, especially the polishing liquids prepared from the silica sols of Examples 3 to 5.

[0116] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation modes. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and the embodiments shown and described herein.

Claims

1. A method for preparing a wide-distribution large-particle silica sol, characterized in that: First, a first organic silicon solution is added dropwise to a 30-50 nm inorganic silicon seed solution for reaction, and then a second organic silicon solution is added dropwise thereto for reaction to prepare a silica sol with a particle size of 20-140 nm; the silicon content ratio of the inorganic silicon seed solution to the first organic silicon solution is 1:(1.2-2.0), and the silicon content ratio of the inorganic silicon seed solution to the second organic silicon solution is 1:(2.1-2.8); The ratio of the droplet velocity of the first organosilicon solution to its volume is (0.001-0.002) mL / min:1 mL, and the ratio of the droplet velocity of the second organosilicon solution to its volume is (0.005-0.007) mL / min:1 mL; The first organosilicon solution and the second organosilicon solution respectively contain one or both of tetramethyl orthosilicate and tetraethyl orthosilicate.

2. The method for preparing a silica sol with a wide distribution and large particle size according to claim 1, characterized in that: The solid content of the first organosilicon solution is 5-8 wt %, and the solid content of the second organosilicon solution is 9-12 wt %.

3. The method for preparing a silica sol with a wide distribution and large particle size according to claim 1, characterized in that: The dispersion coefficient of the silica sol is 1.303-1.398, and the difference between the D90 particle size and the D10 particle size of the silica sol is 66-90 nm.

4. The method for preparing a silica sol with a wide distribution and large particle size according to claim 1, characterized in that: The reaction liquid level is kept constant throughout the entire reaction process, the reaction pH is maintained between 9.5 and 10.5, and the reaction temperature is 90 to 120°C.

5. The method for preparing a silica sol with a wide distribution and large particle size according to claim 1, characterized in that: The inorganic silicon seed solution is prepared by adding active silicic acid with a pH of 2.0 to 3.0 to an inorganic alkaline solution at a rate of 5 to 10 mL / min.

6. The method for preparing a silica sol with a wide distribution and large particle size according to claim 5, characterized in that: The preparation method of the active silicate is as follows: concentrated water glass is diluted with ultrapure water to a solution with a silicon dioxide content of 4-8 wt%, and after being stirred evenly, the solution is added into a strong acid cation exchange resin for cation exchange to obtain active silicate with a pH of 2.0-3.

0.

7. A silica sol with wide distribution and large particle size, characterized in that: The silica sol is prepared by the method for preparing the wide-distribution large-particle silica sol according to any one of claims 1 to 6.

8. Use of the widely distributed large-particle silica sol as claimed in claim 7 in a polishing liquid.

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