CMP slurry composition for polishing wafer surface and preparation method thereof

Abstract

The invention provides a CMP slurry composition for polishing the surface of a wafer. The CMP slurry composition comprises the following components: a solvent; 0.5 to 20 w% of multi-layer composite abrasive particles; the multi-layer grinding material comprises a nano silicon dioxide inner core, an aluminum oxide connecting layer and nano diamond particles distributed on the periphery of the aluminum oxide connecting layer, rapid polishing can be carried out in the earlier stage of polishing through the multi-layer composite grinding particles, in the middle stage of polishing, the diamond particles gradually fall off from the periphery of the aluminum oxide connecting layer, the diameter of the grinding particles is reduced, and the diamond particles are evenly distributed on the periphery of the aluminum oxide connecting layer; and in the later stage of polishing, the falling diamond particles and the silicon dioxide-aluminum oxide structure particles act synergistically to further polish the surface of the wafer, so that the damage to the surface of the wafer is avoided, and the rapid damage-free polishing of the wafer is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical mechanical polishing, and specifically to a CMP slurry composition for polishing the surface of a wafer and a preparation method thereof. Background Art

[0002] A wafer refers to a single crystal silicon chip used in the production of silicon semiconductor integrated circuits and is the carrier for manufacturing integrated circuits. A smooth and undamaged wafer surface is the basis for subsequent applications. CMP treatment of the wafer surface is a commonly used polishing method at present. By polishing multiple times, the surface damage of the wafer is greatly reduced, and the flatness of the wafer surface is improved.

[0003] However, when using large-particle abrasives with high hardness during CMP, it is extremely easy to leave damage on the surface and subsurface of the wafer, affecting the subsequent use of the wafer. Although using small-particle abrasives can reduce damage, the polishing speed is greatly reduced, the pre-treatment time of the wafer is prolonged, and the labor and equipment costs are increased. Therefore, there is an urgent need to develop a new slurry to reduce the surface / subsurface damage of the wafer while ensuring the polishing rate, so as to reduce the processing cost of the wafer. Summary of the Invention

[0004] (I) Technical Problems to be Solved

[0005] In view of the deficiencies of the prior art, the present invention provides a CMP slurry composition for polishing the surface of a wafer and a preparation method thereof to solve the problems raised in the above background art.

[0006] (II) Technical Solutions

[0007] To achieve the above object, the present invention is achieved through the following technical solutions: A CMP slurry composition for polishing the surface of a wafer, comprising the following components: a solvent; 0.5-20 w% of multi-layer composite abrasives based on the mass of the solvent; 0.01-5 w% of a dispersant based on the mass of the solvent, wherein:

[0008] The pH of the solvent is 6-8, and the solvent is deionized water or an aqueous solution of at least one of acetic acid, sodium acetate, lactic acid, and glycolic acid;

[0009] The multi-layer abrasive comprises a nano-silica core, an alumina connecting layer, and nano-diamond particles distributed on the periphery of the alumina connecting layer;

[0010] The dispersant is one or more of sodium polyacrylate, polyvinyl alcohol, and polyethylene glycol.

[0011] As a further preference, the D50 of the multi-layer composite abrasive is 50-200 nm.

[0012] A method for manufacturing a CMP slurry composition for polishing the surface of a wafer, which is used to manufacture a CMP slurry composition for polishing the surface of a wafer, includes the following steps:

[0013] ① Prepare multi-layer composite abrasive grains;

[0014] ② Put the solvent into the reactor, and simultaneously put the multi-layer composite abrasive grains and the dispersant into the solvent, stir and mix at 500 - 800 r / min for 20 min to obtain the CMP slurry composition;

[0015] Wherein the viscosity of the CMP slurry composition (20 °C) < 18 cps, and the density is 1.03 - 1.15 g / cm 3 .

[0016] As a further preference, the preparation steps of the multi-layer composite abrasive grains include:

[0017] ① Configure an aluminum salt solution, add silica sol and an alkaline precipitant to the aluminum salt solution to form a reaction solution, transfer the reaction solution to a reaction kettle and seal it, and carry out a hydrothermal reaction at 200 °C for 3 h to obtain a solid-liquid mixture;

[0018] Wherein the concentration of the aluminum salt is 0.5 - 1 mol / L, and the molar ratio of aluminum:silicon:alkaline precipitant is 1:10 - 20:5 - 10;

[0019] ② Filter, wash, and dry the solid-liquid mixture in step ① to obtain a silicon dioxide core with loose alumina wrapped on the outside, intermediate product A;

[0020] ③ Take a reaction container with a fixed shape, fill nano-diamond powder at the bottom, lay intermediate product A flat on the upper layer of the nano-diamond powder, then fill nano-diamond powder again to cover the intermediate product, and then calcine at 800 - 1000 °C for 2 hours, cool to room temperature with the furnace, and separate the nano-diamond powder through a cyclone separator to obtain multi-layer composite abrasive grains.

[0021] As a further preference, the aluminum salt is one or more of aluminum chloride, aluminum sulfate, aluminum nitrate, aluminum silicate, and aluminum sulfide.

[0022] As a further preference, the particle size distribution range of the sol particles in the silica sol is 30 - 100 nm.

[0023] As a further preference, the precipitant is one or more of urea, ammonium bicarbonate, and ammonium carbonate.

[0024] As a further preference, the D50 of the nano-diamond powder is 5 - 15 nm, and the mass ratio of the nano-diamond powder to intermediate product A is 5 - 20:1.

[0025] (III) Beneficial effects

[0026] The present invention provides a CMP slurry composition for polishing the surface of a wafer and a preparation method, having the following beneficial effects:

[0027] The multi-layer composite abrasive grains of the present invention include a silica core, an alumina connecting layer, and diamond particles distributed on the alumina connecting layer. In the early stage of polishing, the diamond particles distributed on the outermost side quickly polish the surface of the wafer. Due to the high hardness of diamond and its distribution on the periphery of the alumina connecting layer, which increases its distribution diameter and at the same time increases the diameter of the abrasive grains, the polishing efficiency is greatly improved. At the same time, the small diameter of the diamond particles themselves and the small contact area with the wafer can greatly reduce the generation of subsurface damage. In the middle stage of polishing, the diamond particles gradually fall off from the periphery of the alumina connecting layer, and the diameter of the abrasive grains decreases. At this time, the outer wall of the alumina connecting layer is used to polish the surface of the wafer, ensuring the polishing efficiency while avoiding subsurface damage. In the late stage of polishing, the fallen diamond particles and the silica-alumina structure particles act synergistically to further polish the surface of the wafer, avoiding damage to the wafer surface;

[0028] At the same time, the dispersant contained in the slurry composition prevents the slurry from stratifying and precipitating, and can re-disperse the diamond particles during the polishing process, avoiding particle agglomeration and affecting the polishing effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the preparation process of the slurry composition of the present invention;

[0030] Figure 2 It is a schematic diagram of the structure of the multi-layer composite abrasive grains of the present invention;

[0031] Figure 3 It is a schematic diagram of the calcination distribution of intermediate product A of the present invention.

[0032] Among them: 1 silica core, 2 alumina connecting layer, 3 diamond particles, 4 nano-diamond powder, 5 intermediate product A, 6 calcination container. DETAILED DESCRIPTION OF THE INVENTION

[0033] In the present invention, unless otherwise clearly defined and limited, the first feature being "on" or "under" the second feature may include the first and second features being in direct contact, or may include the first and second features not being in direct contact but being in contact through other features therebetween. Moreover, the first feature being "above", "over" and "on" the second feature includes the first feature being directly above and obliquely above the second feature, or merely indicating that the first feature has a higher horizontal height than the second feature. The first feature being "under", "beneath" and "under" the second feature includes the first feature being directly below and obliquely below the second feature, or merely indicating that the first feature has a lower horizontal height than the second feature.

[0034] The following disclosure provides many different embodiments or examples for implementing different structures of the present invention. To simplify the disclosure of the present invention, the components and settings of specific examples are described below. Of course, they are only examples and are not intended to limit the present invention. In addition, the present invention may repeat reference numerals and / or reference letters in different examples. Such repetition is for the purpose of simplification and clarity, and does not itself indicate the relationship between the various embodiments and / or settings discussed. In addition, the present invention provides examples of various specific processes and materials, but those of ordinary skill in the art can be aware of the application of other processes and / or the use of other materials.

[0035] On the one hand, the present invention provides a CMP slurry composition for polishing the surface of a wafer, comprising the following components: a solvent; 0.5-20 w% of multi-layer composite abrasive grains based on the mass of the solvent; 0.01-5 w% of a dispersant based on the mass of the solvent, wherein:

[0036] The pH of the solvent is 6-8, and the solvent is deionized water or an aqueous solution of at least one of acetic acid, sodium acetate, lactic acid, glycolic acid, and sodium glycolate;

[0037] The multi-layer abrasive includes a nano-silica core, an alumina connecting layer, and nano-diamond particles distributed on the periphery of the alumina connecting layer;

[0038] The dispersant is one or more of sodium polyacrylate, polyvinyl alcohol, and polyethylene glycol.

[0039] Specifically, deionized water can be directly used as the slurry solvent, or one or more of acetic acid, sodium acetate, lactic acid, glycolic acid, and sodium glycolate can be selected according to the actual polishing environment to configure a weakly alkaline or weakly acidic solvent system.

[0040] Furthermore, the D50 of the multi-layer composite abrasive grains is 50-200 nm.

[0041] Specifically, if the particle size of the multi-layer composite abrasive grains is too small, the polishing speed is slow; if the particle size is too large, irreversible damage will be caused to the surface of the wafer.

[0042] On the other hand, this embodiment also provides a manufacturing method of a CMP slurry composition for polishing the surface of a wafer, which is used to manufacture the above-mentioned CMP slurry, and includes the following steps:

[0043] ① Prepare multi-layer composite abrasive grains;

[0044] ② Put the solvent into the reactor, and put the multi-layer composite abrasive grains and the dispersant into the solvent at the same time, stir and mix at 500-800 r / min for 20 min to obtain the CMP slurry composition;

[0045] Wherein the viscosity of the CMP slurry composition (20 °C) < 18 cps, and the density is 1.03 - 1.15 g / cm 3 .

[0046] Wherein the preparation steps of the multi-layer composite abrasive grains include:

[0047] ① Prepare an aluminum salt solution, add silica sol and an alkaline precipitant to the aluminum salt solution to form a reaction solution, transfer the reaction solution to a reaction kettle and seal it, and perform a hydrothermal reaction at 200 °C for 3 h to obtain a solid-liquid mixture;

[0048] Wherein the aluminum salt concentration is 0.5 - 1 mol / L, and the molar ratio of aluminum:silicon:alkaline precipitant is 1:10 - 20:5 - 10;

[0049] ② Filter, wash, and dry the solid-liquid mixture in step ① to obtain a silica core, and an intermediate product A with loose alumina wrapped on the outside;

[0050] Specifically, after filtering the solid-liquid mixture, wash it with alcohol, and then wash it with deionized water until the washing liquid is neutral. Place the washed product in a drying oven and dry it under vacuum at 60 °C for 6 h.

[0051] ③ Take a reaction container with a fixed shape, fill nano-diamond powder at the bottom, spread the intermediate product A on top of the nano-diamond powder, then fill nano-diamond powder again to cover the intermediate product, and then calcine it at 800 - 1000 °C for 2 hours, and cool it to room temperature with the furnace. Separate the nano-diamond powder through a cyclone separator to obtain multi-layer composite abrasive grains.

[0052] Furthermore, the particle size distribution range of the sol particles in the silica sol is 30 - 100 nm, and the D50 of the nano-diamond powder is 5 - 15 nm.

[0053] As Figure 1 shown, the multi-layer composite abrasive grains include a silica core 1, an alumina connection layer 2, and diamond particles 3 distributed on the periphery.

[0054] Specifically, silica is used as the abrasive core, and its original particle size plays a decisive role in the final particle size of the multi-layer composite abrasive grains. If the silica particle size is too small, the final product is difficult to achieve the purpose of rapid polishing. If the silica particle size is too large, the particle size of the multi-layer composite abrasive grains is too large, which will cause irreversible damage to the wafer surface during polishing; if the particle size of the diamond particles 3 is too large, it will affect the uniformity of their distribution on the surface of the alumina connection layer 2. If the particle size of the diamond particles 3 is too small, they will completely enter the pores of the alumina connection layer 2 and cannot effectively increase the particle size of the intermediate product A to improve the polishing efficiency.

[0055] Further, the aluminum salt is one or more of aluminum chloride, aluminum sulfate, aluminum nitrate, aluminum silicate, and aluminum sulfide, which is input as an aluminum source; silica sol is input into the aluminum salt solution as the core. At the same time, silica sol has good solubility in water, reducing the agglomeration of silicon particles; the precipitant is one or more of urea, ammonium bicarbonate, and ammonium carbonate, which reacts with the acidic aluminum salt solution to deposit alumina and wrap it outside the silica, forming an alumina connection layer.

[0056] Furthermore, the mass ratio of the nano-diamond powder to the intermediate product A is 5 - 20:1.

[0057] As Figure 2 shown, the intermediate product A 5 is buried in the nano-diamond powder 4, and the thickness of the nano-diamond powder 4 above and below the intermediate product A remains the same.

[0058] Specifically, when the mass ratio of the nano-diamond powder to the intermediate product A is too small, the nano-diamond powder cannot effectively cover the surface of the intermediate product A, affecting the loading amount of diamond on the periphery of the subsequent alumina connection layer. However, when there is too much nano-diamond powder, it will cause caking due to its own gravity and the interaction between powders during calcination, and cannot effectively enter the pores of alumina.

[0059] It can be understood that the intermediate product A is composed of a silica core and loose alumina wrapped outside. When the intermediate product A is buried in the diamond powder, diamond particles will enter the pores outside the alumina. After high-temperature calcination, the crystallinity of the loose alumina increases, and the crystal form changes to partially confine the diamond particles inside the voids, thus forming a multi-layer composite abrasive of a silica core, an alumina connection layer, and diamond particles distributed in the alumina connection layer. Since the diamond particles are partially embedded, they will loosen and fall off as the polishing time increases during polishing. After the diamond falls off, the particle size of the multi-layer composite abrasive decreases, and then by cooperating with the fallen diamond particles, the effects of rough polishing first and then fine polishing are achieved.

[0060] To further understand the present invention, the CMP slurry composition provided by the present invention will be described below in conjunction with embodiments. The protection scope of the present invention is not limited by the following embodiments.

[0061] Example 1

[0062] 8.102 g of aluminum silicate was put into 100 ml of deionized water to prepare an aluminum salt solution. 14 g of silica sol (silicon particle size is 100 nm) and 15 g of urea were added in sequence, and after dispersion, a reaction solution was formed. Then the reaction solution was transferred to a reaction kettle and sealed, and hydrothermal reaction was carried out at 200 °C for 3 h. The obtained solid-liquid mixture was filtered, washed three times with ethanol and deionized water in sequence, and then placed in a drying oven and vacuum dried at 60 °C for 6 h to obtain the intermediate product A. The mass of the intermediate product A was weighed and recorded as x;

[0063] Weigh 5x of diamond powder with a D50 of 5 nm. Take diamond powder with a mass fraction of 50% and lay it in a square crucible. After laying the intermediate product A flat on top of the nano-diamond powder, lay the remaining diamond powder flat and fill it on top of the intermediate product A. Place it in a muffle furnace and calcine it at 800 °C for 2 h. After cooling to room temperature with the furnace, take out the reactants and separate the nano-diamond powder by a cyclone separator to obtain multi-layer composite abrasive grains;

[0064] Weigh 0.5 g of the above multi-layer composite abrasive grains and 0.01 g of sodium polyacrylate and put them into 100 ml of deionized water. Stir and mix at 500 r / min for 20 min to obtain a CMP slurry composition.

[0065] Example 2

[0066] Put 16.205 g of aluminum silicate into 100 ml of deionized water to prepare an aluminum salt solution. Sequentially add silica sol containing 24 g of silicon (silicon particle size is 100 nm) and 19.75 g of urea. After dispersion, a reaction solution is formed. Transfer this reaction solution to a reaction kettle and seal it. Carry out hydrothermal reaction at 200 °C for 3 h to obtain a solid-liquid mixture. Filter it, wash it three times with ethanol and deionized water in sequence, and then place it in a drying oven and vacuum dry it at 60 °C for 6 h to obtain the intermediate product A. Weigh the mass of the intermediate product A and record it as x;

[0067] Weigh 5x of diamond powder with a D50 of 5 nm. Take diamond powder with a mass fraction of 50% and lay it in a square crucible. After laying the intermediate product A flat on top of the nano-diamond powder, lay the remaining diamond powder flat and fill it on top of the intermediate product A. Place it in a muffle furnace and calcine it at 900 °C for 2 h. After cooling to room temperature with the furnace, take out the reactants and separate the nano-diamond powder by a cyclone separator to obtain multi-layer composite abrasive grains;

[0068] Weigh 0.5 g of the above multi-layer composite abrasive grains and 0.01 g of polyvinyl alcohol and put them into 100 ml of deionized water. Stir and mix at 500 r / min for 20 min to obtain a CMP slurry composition.

[0069] Example 3

[0070] Put 6.675 g of aluminum chloride into 100 ml of deionized water to prepare an aluminum salt solution. Sequentially add silica sol containing 7 g of silicon (silicon particle size is 100 nm) and 11.85 g of ammonium bicarbonate. After dispersion, a reaction solution is formed. Transfer this reaction solution to a reaction kettle and seal it. Carry out hydrothermal reaction at 200 °C for 3 h to obtain a solid-liquid mixture. Filter it, wash it three times with ethanol and deionized water in sequence, and then place it in a drying oven and vacuum dry it at 60 °C for 6 h to obtain the intermediate product A. Weigh the mass of the intermediate product A and record it as x;

[0071] Weigh 5x of nanodiamond powder with a D50 of 10 nm. Take diamond powder with a mass fraction of 50% and lay it in a square crucible. After laying intermediate product A flat on top of the nanodiamond powder, lay the remaining diamond powder flat and fill it on top of intermediate product A. Place it in a muffle furnace and calcine at 1000 °C for 2 h. After cooling to room temperature with the furnace, take out the reactants and separate the nanodiamond powder by a cyclone separator to obtain multi-layer composite abrasive grains;

[0072] Weigh 0.5 g of the above multi-layer composite abrasive grains and 0.01 g of polyvinyl alcohol respectively and put them into 100 ml of deionized water. Stir and mix at 500 r / min for 20 min to obtain a CMP slurry composition.

[0073] Example 4

[0074] Except that the mass of the nanodiamond powder is 10 times that of intermediate product A, the rest of the process is the same as that of Example 3.

[0075] Example 5

[0076] Except that the mass of the nanodiamond powder is 20 times that of intermediate product A, the rest of the process is the same as that of Example 3.

[0077] Example 6

[0078] Put 17.1 g of aluminum sulfate into 100 ml of deionized water to prepare an aluminum salt solution. Add a silica sol containing 9.5 g of silicon (silicon particle size is 70 nm) and 9 g of urea in sequence, disperse to form a reaction solution, and transfer the reaction solution to a reaction kettle and seal it. Carry out hydrothermal reaction at 200 °C for 3 h to obtain a solid-liquid mixture. Filter it, wash it three times with ethanol and deionized water in sequence, and then place it in a drying oven and vacuum dry at 60 °C for 6 h to obtain intermediate product A. Weigh the mass of intermediate product A and record it as x;

[0079] Weigh 10x of nanodiamond powder with a D50 of 15 nm. Take diamond powder with a mass fraction of 50% and lay it in a square crucible. After laying intermediate product A flat on top of the nanodiamond powder, lay the remaining diamond powder flat and fill it on top of intermediate product A. Place it in a muffle furnace and calcine at 1000 °C for 2 h. After cooling to room temperature with the furnace, take out the reactants and separate the nanodiamond powder by a cyclone separator to obtain multi-layer composite abrasive grains;

[0080] Weigh 10 g of the above multi-layer composite abrasive grains and 2.5 g of polyethylene glycol respectively and put them into 100 ml of deionized water. Stir and mix at 650 r / min for 20 min to obtain a CMP slurry composition.

[0081] Example 7

[0082] 34.2 g of aluminum sulfate was put into 100 ml of deionized water to prepare an aluminum salt solution. A silica sol containing 14 g of silicon (silicon particle size is 30 nm) and 15 g of urea were added successively. After dispersion, a reaction solution was formed, and this reaction solution was transferred to a reaction kettle and sealed. Hydrothermal reaction was carried out at 200 °C for 3 h to obtain a solid-liquid mixture. After filtration, it was washed three times with ethanol and deionized water successively, and then placed in a drying oven for vacuum drying at 60 °C for 6 h to obtain intermediate product A. The mass of intermediate product A was weighed and recorded as x;

[0083] 15x of nano-diamond powder with a D50 of 15 nm was weighed. Diamond powder with a mass fraction of 50% was laid in a square crucible. After intermediate product A was laid flat on the upper layer of the nano-diamond powder, the remaining diamond powder was laid flat and filled on the upper layer of intermediate product A. It was placed in a muffle furnace and calcined at 1000 °C for 2 h. After cooling to room temperature with the furnace, the reactants were taken out, and the nano-diamond powder was separated by a cyclone separator to obtain multi-layer composite abrasive grains;

[0084] 20 g of the above multi-layer composite abrasive grains and 5 g of polyethylene glycol were weighed and put into 100 ml of sodium acetate aqueous solution with a pH of 8, and stirred and mixed at 800 r / min for 20 min to obtain a CMP slurry composition.

[0085] Example 8

[0086] 34.2 g of aluminum sulfate was put into 100 ml of deionized water to prepare an aluminum salt solution. A silica sol containing 14 g of silicon (silicon particle size is 30 nm) and 15 g of urea were added successively. After dispersion, a reaction solution was formed, and this reaction solution was transferred to a reaction kettle and sealed. Hydrothermal reaction was carried out at 200 °C for 3 h to obtain a solid-liquid mixture. After filtration, it was washed three times with ethanol and deionized water successively, and then placed in a drying oven for vacuum drying at 60 °C for 6 h to obtain intermediate product A. The mass of intermediate product A was weighed and recorded as x;

[0087] 15x of nano-diamond powder with a D50 of 15 nm was weighed. Diamond powder with a mass fraction of 50% was laid in a square crucible. After intermediate product A was laid flat on the upper layer of the nano-diamond powder, the remaining diamond powder was laid flat and filled on the upper layer of intermediate product A. It was placed in a muffle furnace and calcined at 1000 °C for 2 h. After cooling to room temperature with the furnace, the reactants were taken out, and the nano-diamond powder was separated by a cyclone separator to obtain multi-layer composite abrasive grains;

[0088] 20 g of the above multi-layer composite abrasive grains and 5 g of polyethylene glycol were weighed and put into 100 ml of lactic acid aqueous solution with a pH of 6, and stirred and mixed at 800 r / min for 20 min to obtain a CMP slurry composition.

[0089] Comparative Example 1

[0090] Replace the silica sol in Example 6 with a silica sol having a particle size distribution of less than 10 nm, and keep the other conditions unchanged to prepare a CMP slurry.

[0091] Comparative Example 2

[0092] Replace the silica sol in Example 6 with a silica sol having a particle size distribution greater than 200 nm, and keep the other conditions unchanged to prepare a CMP slurry.

[0093] Comparative Example 3

[0094] Replace the diamond powder in Example 6 with diamond powder having a D50 of 3 nm, and keep the other conditions unchanged to prepare a CMP slurry.

[0095] Comparative Example 4

[0096] Replace the diamond powder in Example 6 with diamond powder having a D50 of 50 nm, and keep the other conditions unchanged to prepare a CMP slurry.

[0097] Comparative Example 5

[0098] Except that the mass of the nanodiamond powder is equal to that of the intermediate product A, the other process steps are the same as in Example 6 to prepare a CMP slurry.

[0099] Comparative Example 6

[0100] Except that the mass of the nanodiamond powder is 30 times that of the intermediate product, the other process steps are the same as in Example 6 to prepare a CMP slurry.

[0101] Comparative Example 7

[0102] Put 17.1 g of aluminum sulfate into 100 ml of deionized water to prepare an aluminum salt solution. Sequentially add 9.5 g of silica sol (silicon particle size is 70 nm) containing silicon and 9 g of urea, disperse to form a reaction solution, and transfer the reaction solution to a reaction kettle and seal it. Carry out a hydrothermal reaction at 200 °C for 3 h to obtain a solid-liquid mixture. Filter it, wash it three times with ethanol and deionized water in sequence, and then place it in a drying oven for vacuum drying at 60 °C for 6 h to obtain intermediate product A;

[0103] Put the intermediate product A into a muffle furnace and calcine it at 1000 °C for 2 h. After cooling to room temperature with the furnace, obtain composite abrasive grains;

[0104] Weigh 10 g of the above composite abrasive grains and 2.5 g of polyethylene glycol and put them into 100 ml of deionized water, stir and mix at 700 r / min for 20 min to obtain a CMP slurry.

[0105] Test Example:

[0106] Collect the multi-layer composite abrasive grains prepared in Examples 1-7 and Comparative Examples 1-7, and use a laser particle size analyzer to test the particle size. The test results are shown in Table 1.

[0107] For Examples 1-7 and Comparative Examples 1-7, the micro-Vickers hardness of the prepared multi-layer composite abrasive grains was tested by a micro-Vickers hardness tester. Five points were taken for each group of samples for testing, and the average value obtained was the micro-Vickers hardness of the group of samples. The test results are shown in Table 1.

[0108] The slurries of Example 6 and Comparative Examples 1-7 were taken, and CMP tests were carried out using single-crystalline silicon as the substrate. The material removal rate index MRR within a fixed time was measured, and the polished workpiece was visually inspected to determine whether there were scratches. The test results are shown in Table 1.

[0109] The slurries after testing in Example 6, Comparative Example 3 and Comparative Example 4 were collected, washed three times with deionized water and filtered, and vacuum dried at 60 °C for 6 hours. The multi-layer composite abrasive grains prepared in Example 6, Comparative Example 3 and Comparative Example 4 were used as the control group, and C element detection was carried out by EDS. The detection results are shown in Table 2.

[0110] The CMP slurries prepared in Examples 1-8 were taken, and their viscosities were tested by a viscometer, and the slurry density was calculated by measuring the volume and weight. The detection results are shown in Table 3.

[0111] Table 1 is the test statistical table of each example and comparative example

[0112]

[0113] In Table 1, by comparing the D50 values of Examples 1-7 and Comparative Examples 1-2, it can be seen that the particle size of silica plays a dominant role in the final particle size of the composite abrasive; by comparing the data of Example 6 and Comparative Examples 4-7, it can be seen that when the diamond particles are too large, or the mass ratio of diamond particles to the intermediate product is too large, it is difficult to be loaded into the pores of the intermediate product A. The former is because the particle size is larger than the particle size of most pores, and the latter is because of its own gravity and agglomeration occurs during calcination. At the same time, when the diamond microparticles are too small and completely enter the pores, although the hardness of the multi-layer composite abrasive grains is improved to a certain extent, the particle size of the composite abrasive grains cannot be effectively increased. And when the mass ratio of diamond particles to the intermediate product is too small, the outer load of the alumina connection layer is too small, affecting the polishing effect.

[0114] Table 2 Detection table of C content before and after using multi-layer composite abrasive grains

[0115]

[0116] From the change in the content of element C before and after Example 6 in Table 2, it can be seen that when the particle size of diamond particles is 5 - 15 nm, during calcination, they are loaded on the periphery of the alumina connection layer and fall off during the polishing process. Therefore, before and after polishing, the content of element C in the abrasive grains drops sharply. From the change in the content of element C before and after Comparative Examples 3 and 4, it can be seen that when the particle size of diamond particles is too small, the diamond particles enter the interior of the alumina connection layer and remain unchanged during the polishing process. When the particle size of diamond particles is too large, it is difficult to be loaded on the alumina connection layer. Combining the relevant data of Comparative Example 4 in Table 1, a very small number of diamonds loaded on the alumina connection layer will cause subsurface damage to the wafer surface.

[0117]

[0118] Table 3 Viscosity and Density of CMP Slurry

[0119] In summary, when the nano - diamond particles are too small, they will enter the pores inside the alumina transition layer, while when the nano - diamond particles are too large, they cannot enter the alumina pores to form a load. When the D50 of diamond particles is between 5 - 15 nm, effective loading can be carried out on the periphery of the alumina transition layer, that is, part of the diamond particles enter the pores of the intermediate product A. After calcination, the alumina transforms into a crystal form with higher crystallinity, which will fix the diamond particles in the pores. Since part of the diamond is exposed outside the alumina connection layer, the particle size of the multi - layer composite abrasive grains increases. At the same time, the diamond exposed outside polishes the wafer surface in the early stage of polishing, improving the polishing rate. Since only part of the diamond is confined in the alumina connection layer, as the polishing progresses, the diamond particles become loose and fall off from the surface of the alumina connection layer, making the particle size of the multi - layer composite abrasive grains decrease. At the same time, the fallen diamond particles cooperate with the composite abrasive, making the polishing process change from rough polishing to fine polishing.

[0120] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A CMP slurry composition for polishing a wafer surface, characterized in that: The invention comprises the following components: a solvent; Based on the mass of the solvent, the multilayer composite abrasive is 0.5-20 wt%; based on the mass of the solvent, the dispersant is 0.01-5 wt%, of which: The pH of the solvent is 6-8, and the solvent is deionized water or an aqueous solution of at least one of acetic acid, sodium acetate, lactic acid, and glycolic acid; The multilayer abrasive comprises a nano silicon dioxide core, an aluminum oxide connecting layer, and nano diamond particles distributed on the periphery of the aluminum oxide connecting layer; The dispersant is one or more of sodium polyacrylate, polypropylene alcohol and polyethylene glycol.

2. The CMP slurry composition for polishing a wafer surface according to claim 1, characterized in that: The multi-layer composite abrasive grains have a D50 of 50-200 nm.

3. A method for preparing a CMP slurry composition for polishing a wafer surface, for preparing the CMP slurry composition for polishing a wafer surface according to any one of claims 1 to 2, characterized in that: The following steps are involved: ①Preparation of multi-layer composite abrasive; ② Adding a solvent into a reactor, adding the multi-layer composite abrasive and the dispersant into the solvent at the same time, stirring and mixing at 500-800 r / min for 20 minutes to obtain a CMP slurry composition; The CMP slurry composition has a viscosity (20°C) of <18 cps and a density of 1.03-1.15 g / cm 3 .

4. The method for preparing a CMP slurry composition for polishing a wafer surface according to claim 3, characterized in that: The preparation steps of the multi-layer composite abrasive grains include: ① Prepare an aluminum salt solution, add silica sol and alkaline precipitant into the aluminum salt solution to form a reaction solution, transfer the reaction solution to a reactor, seal it, and perform hydrothermal reaction at 200°C for 3h to obtain a solid-liquid mixture; The aluminum salt concentration is 0.5-1 mol / L, and the molar ratio of aluminum:silicon:alkaline precipitant is 1:5-10:3-5; ② Filtering, washing and drying the solid-liquid mixture in step ① to obtain an intermediate product A having a silicon dioxide core and loose aluminum oxide wrapped around the core; ③ Take a reaction container of fixed shape, fill the bottom with nano-diamond powder, spread the intermediate product A on the upper layer of the nano-diamond powder, fill it with nano-diamond powder again to cover the intermediate product, then calcine at 800-1000°C for 2 hours, cool to room temperature with the furnace, separate the nano-diamond powder through a cyclone separator, and obtain a multi-layer composite abrasive.

5. The method for preparing a CMP slurry composition for polishing a wafer surface according to claim 4, characterized in that: The aluminum salt is one or more of aluminum chloride, aluminum sulfate, aluminum nitrate, aluminum silicate, and aluminum sulfide.

6. The method for preparing a CMP slurry composition for polishing a wafer surface according to claim 4, characterized in that: The particle size distribution range of the sol particles in the silica sol is 30-100 nm.

7. The method for preparing a CMP slurry composition for polishing a wafer surface according to claim 4, characterized in that: The precipitant is one or more of urea, ammonium bicarbonate and ammonium carbonate.

8. The method for preparing a CMP slurry composition for polishing a wafer surface according to claim 4, characterized in that: The nano-diamond powder D50 is 5-15 nm, and the mass ratio of the nano-diamond powder to the intermediate product A is 5-20:1.

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