Cmp slurry composition for wafer surface polishing and method of preparation

Abstract

The application provides a preparation method of a CMP slurry composition for polishing a wafer surface, and comprises the following components: a solvent; 0.5-20 w% of multilayer composite abrasive grains; and 0.01-5 w% of a dispersing agent, wherein the multilayer abrasive grains comprise a nanosilica core, an alumina connecting layer, and nanodiamond particles distributed on the periphery of the alumina connecting layer. In the early polishing stage, the multilayer composite abrasive grains can be used for rapid polishing. In the middle polishing stage, the diamond particles gradually fall off from the periphery of the alumina connecting layer, the diameter of the abrasive grains is reduced, and the subsurface damage is avoided. In the late polishing stage, the fallen diamond particles and the silicon-alumina structure particles synergistically polish the wafer surface, the wafer surface damage is avoided, and thus the wafer rapid non-damage polishing is realized.

Description

Technical Field

[0001] The invention relates to the technical field of chemical mechanical polishing, in particular to a method for preparing a CMP slurry composition for polishing a wafer surface. Background Art

[0002] Wafer refers to the single crystal silicon chip used in the production of silicon semiconductor integrated circuits. It is the carrier used in the production of integrated circuits. A smooth and damage-free wafer surface is the basis for subsequent applications. CMP treatment of the wafer surface is currently a commonly used polishing method. Through multiple polishing, the surface damage of the wafer is greatly reduced and the surface flatness of the wafer is improved.

[0003] However, using large, hard abrasives during CMP can easily leave damage on the wafer surface and subsurface, affecting subsequent wafer use. While using small abrasives can reduce damage, they significantly reduce polishing speed, extending wafer pre-processing time and increasing labor and equipment costs. Therefore, there is an urgent need to develop a new slurry that can reduce wafer surface and subsurface damage while maintaining the polishing rate, thereby reducing wafer processing costs. Summary of the Invention

[0004] (1) Technical problems solved

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

[0006] (2) Technical solution

[0007] To achieve the above objectives, the present invention is implemented through the following technical solutions: A CMP slurry composition for polishing a wafer surface, comprising the following components: a solvent; 0.5-20 wt% of multilayer composite abrasive particles based on the mass of the solvent; and 0.01-5 wt% 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 multilayer composite abrasive grains include a nano-silicon dioxide core, an aluminum oxide connecting layer, and nano-diamond particles distributed on the periphery of the aluminum oxide connecting layer;

[0010] The dispersant is one or more of sodium polyacrylate, polypropylene 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 preparing a CMP slurry composition for polishing a wafer surface, comprising the following steps:

[0013] ①Preparation of multi-layer composite abrasive;

[0014] ② Add the solvent into the reactor, add the multi-layer composite abrasive and the dispersant into the solvent at the same time, and stir and mix at 500-800 r / min for 20 minutes to obtain a CMP slurry composition;

[0015] The CMP slurry composition has a viscosity (20°C) of less than 18 cps and a density of 1.03-1.15 g / cm 3 .

[0016] As a further preferred embodiment, the steps of preparing the multilayer composite abrasive include:

[0017] ① Prepare an aluminum salt solution, add silica sol and alkaline precipitant to the aluminum salt solution to form a reaction solution, transfer the reaction solution to a reactor, seal it, and hydrothermally react at 200°C for 3 hours to obtain a solid-liquid mixture;

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

[0019] 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 outside;

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

[0021] As further preferred, 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 further preferred, the precipitant is one or more of urea, ammonium bicarbonate, and ammonium carbonate.

[0024] As a further preference, 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.

[0025] (3) Beneficial effects

[0026] The present invention provides a method for preparing a CMP slurry composition for polishing a wafer surface, which has the following beneficial effects:

[0027] The multilayer composite abrasive of the present invention comprises a silica core, an alumina connecting layer, and diamond particles distributed in the alumina connecting layer. In the early stage of polishing, the diamond particles distributed on the outermost side quickly polish the wafer surface. Since the diamond has high hardness and is distributed on the periphery of the alumina connecting layer, its distribution diameter is increased, and the diameter of the abrasive particles is also increased, thereby greatly improving the polishing efficiency. At the same time, the diamond particles themselves have a small diameter and a small contact area with the wafer, which can greatly reduce the generation of sub-surface damage. In the middle stage of polishing, the diamond particles gradually fall off from the periphery of the alumina connecting layer, and the abrasive particle diameter decreases. At this time, the wafer surface is polished through the outer wall of the alumina connecting layer, thereby ensuring the polishing efficiency and avoiding sub-surface damage. In the late stage of polishing, the detached diamond particles synergistically act with the silica-alumina structure particles to further polish the wafer surface, thereby avoiding wafer surface damage.

[0028] At the same time, the dispersant contained in the slurry composition prevents the slurry from stratification and precipitation, and can perform secondary dispersion of the diamond particles during the polishing process to prevent particle agglomeration and affect the polishing effect. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0030] Figure 2 Schematic diagram of the multi-layer composite abrasive structure of the present invention;

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

[0032] Including: 1 silicon dioxide core, 2 aluminum oxide connecting layer, 3 diamond particles, 4 nano diamond powder, 5 intermediate product A, 6 calcination container. DETAILED DESCRIPTION

[0033] In the present invention, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Furthermore, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly below or obliquely below the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0034] The disclosure below provides many different embodiments or examples for realizing different structures of the present invention. In order to simplify the disclosure of the present invention, the components and settings of specific examples are described below. Of course, they are merely examples and are not intended to limit the present invention. In addition, the present invention may repeat reference numbers and / or reference letters in different examples. Such repetition is for the purpose of simplicity and clarity and does not in 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 skilled in the art will recognize the application of other processes and / or the use of other materials.

[0035] In one aspect, the present invention provides a CMP slurry composition for polishing a wafer surface, comprising the following components: a solvent; 0.5-20 wt% of multilayer composite abrasive particles based on the mass of the solvent; and 0.01-5 wt% 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 multilayer composite abrasive grains include a nano-silicon dioxide core, an aluminum oxide connecting layer, and nano-diamond particles distributed on the periphery of the aluminum oxide connecting layer;

[0038] The dispersant is one or more of sodium polyacrylate, polypropylene 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 prepare a weak alkaline or weak acidic solvent system.

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

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

[0042] On the other hand, this embodiment also provides a method for preparing a CMP slurry composition for polishing a wafer surface, which is used to prepare the above-mentioned CMP slurry, comprising the following steps:

[0043] ①Preparation of multi-layer composite abrasive;

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

[0045] The CMP slurry composition has a viscosity (20°C) of less than 18 cps and a density of 1.03-1.15 g / cm 3 .

[0046] The steps for preparing the multilayer composite abrasive include:

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

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

[0049] 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 outside;

[0050] Specifically, the solid-liquid mixture was filtered, washed with alcohol, and then washed with deionized water until the washing liquid was neutral. The washed product was placed in a drying oven at 60° C. and vacuum dried for 6 h.

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

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

[0053] like Figure 1 As shown, the multi-layer composite abrasive comprises a silicon dioxide core 1, an aluminum oxide connecting layer 2 and diamond particles 3 distributed on the periphery.

[0054] Specifically, the original particle size of silica as the abrasive core plays a decisive role in the final particle size of the multi-layer composite abrasive. If the silica particle size is too small, the final product will be difficult to achieve the purpose of rapid polishing. If the silica particle size is too large, the multi-layer composite abrasive particle size will be too large, which will cause irreversible damage to the wafer surface during polishing. If the diamond particle size 3 is too large, it will affect the uniformity of its distribution on the surface of the alumina connecting layer 2. If the diamond particle size is too small, it will completely enter the pores of the alumina connecting 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 used as an aluminum source; the silica sol is used as a core to be put into the aluminum salt solution, and the silica sol has good solubility in water, thereby reducing the agglomeration of silicon particles; and the precipitating agent is one or more of urea, ammonium bicarbonate, and ammonium carbonate, which reacts with the acidic aluminum salt solution to make the alumina deposited and wrapped outside the silica to form an alumina connecting layer.

[0056] Still further, the mass ratio of the nanodiamond powder to the intermediate product A is 5-20:1.

[0057] As shown in FIG. 1, the intermediate product A 5 is buried in the nanodiamond powder 4, and the thickness of the nanodiamond powder 4 on the upper and lower layers of the intermediate product A is kept consistent. Figure 2

[0058] Specifically, when the mass ratio of the nanodiamond powder to the intermediate product A is too small, the nanodiamond powder cannot effectively cover the surface of the intermediate product A, which affects the loading amount of the diamond on the periphery of the alumina connecting layer. However, when the nanodiamond powder is too much, the nanodiamond powder will be cemented due to its own gravity and the interaction between the powders during calcination, and thus cannot effectively enter the pores of the 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, the diamond particles will enter the pores on the periphery of the alumina. After high-temperature calcination, the crystallinity of the loose alumina increases, the crystal form changes, and part of the diamond particles are limited in the interstices, thereby forming a multi-layer composite abrasive material composed of the silica core, the alumina connecting layer, and the diamond particles distributed in the alumina connecting layer. Since the diamond particles are partially embedded, the diamond particles will be loosened and then fall off with the increase of the polishing time during polishing. After the diamond particles fall off, the particle size of the multi-layer composite abrasive material is reduced, and the multi-layer composite abrasive material is combined with the fallen diamond particles to achieve the effect of rough polishing first and then fine polishing.

[0060] In order to further understand the present application, the CMP slurry composition provided by the present application is described below in conjunction with examples, and the protection scope of the present application is not limited by the following examples.

[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 containing 14 g of silicon (the particle size of the silicon was 100 nm) and 15 g of urea were sequentially added, and after dispersion, a reaction liquid was formed. The reaction liquid was transferred to a reaction kettle for sealing, and hydrothermal reaction was carried out at 200℃ for 3 h. The obtained solid-liquid mixture was filtered, washed with ethanol and deionized water three times in sequence, and then placed in a drying box for vacuum drying at 60℃ for 6 h to obtain an intermediate product A. The mass of the intermediate product A was weighed and recorded as x. ​

[0063] Weigh 5x diamond powder with a D50 of 5nm, take 50% of the diamond powder by mass and spread it in a square crucible, spread the intermediate product A on the upper layer of the nano-diamond powder, and then spread the remaining diamond powder on the upper layer of the intermediate product A. Place it in a muffle furnace and calcine it at 800℃ for 2h. After cooling to room temperature with the furnace, take out the reactants and separate the nano-diamond powder through a cyclone separator to obtain a multi-layer composite abrasive.

[0064] 0.5 g of the multi-layer composite abrasive and 0.01 g of sodium polyacrylate were weighed and added into 100 ml of deionized water, and stirred at 500 r / min for 20 min to obtain a CMP slurry composition.

[0065] Example 2

[0066] 16.205 g of aluminum silicate was added to 100 ml of deionized water to prepare an aluminum salt solution, and a silica sol containing 24 g of silicon (silicon particle size of 100 nm) and 19.75 g of urea were added in sequence and dispersed to form a reaction solution. The reaction solution was transferred to a reactor, sealed, and subjected to hydrothermal reaction at 200°C for 3 h. The obtained solid-liquid mixture was filtered, washed three times with ethanol and deionized water, and then dried in a drying oven at 60°C under vacuum for 6 h to obtain an intermediate product A. The mass of the intermediate product A was weighed and recorded as x.

[0067] Weigh 5x diamond powder with a D50 of 5nm, take 50% of the diamond powder by mass and spread it in a square crucible, spread the intermediate product A on the upper layer of the nano-diamond powder, and then spread the remaining diamond powder on the upper layer of the intermediate product A. Place it in a muffle furnace and calcine it at 900℃ for 2h. After cooling to room temperature with the furnace, take out the reactants and separate the nano-diamond powder through a cyclone separator to obtain a multi-layer composite abrasive.

[0068] 0.5 g of the multi-layer composite abrasive and 0.01 g of polypropylene alcohol were weighed and added into 100 ml of deionized water, and stirred at 500 r / min for 20 min to obtain a CMP slurry composition.

[0069] Example 3

[0070] 6.675 g of aluminum chloride was added to 100 ml of deionized water to prepare an aluminum salt solution, and silica sol containing 7 g of silicon (silicon particle size of 100 nm) and 11.85 g of ammonium bicarbonate were added in sequence. After dispersion, a reaction solution was formed. The reaction solution was transferred to a reactor, sealed, and hydrothermally reacted at 200°C for 3 h. The obtained solid-liquid mixture was filtered, washed three times with ethanol and deionized water, and then dried in a drying oven at 60°C under vacuum for 6 h to obtain an intermediate product A. The mass of the intermediate product A was weighed and recorded as x.

[0071] Weigh 5x nanodiamond powder with a D50 of 10nm, take 50% of the diamond powder by mass and spread it in a square crucible, spread the intermediate product A on the top of the nanodiamond powder, and then spread the remaining diamond powder on the top of the intermediate product A. Place it in a muffle furnace and calcine it at 1000℃ for 2h. After cooling to room temperature with the furnace, take out the reactants and separate the nanodiamond powder through a cyclone separator to obtain a multilayer composite abrasive.

[0072] 0.5 g of the multi-layer composite abrasive and 0.01 g of polypropylene alcohol were weighed and added into 100 ml of deionized water, and stirred at 500 r / min for 20 min to obtain a CMP slurry composition.

[0073] Example 4

[0074] Except that the mass of the nano-diamond powder is 10 times that of the 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 nano-diamond powder is 20 times that of the intermediate product A, the rest of the process is the same as that of Example 3.

[0077] Example 6

[0078] 17.1 g of aluminum sulfate was added to 100 ml of deionized water to prepare an aluminum salt solution. Silica sol containing 9.5 g of silicon (silicon particle size of 70 nm) and 9 g of urea were added in sequence and dispersed to form a reaction solution. The reaction solution was transferred to a reactor, sealed, and subjected to hydrothermal reaction at 200°C for 3 h. The obtained solid-liquid mixture was filtered, washed three times with ethanol and deionized water, and then dried in a drying oven at 60°C under vacuum for 6 h to obtain an intermediate product A. The mass of the intermediate product A was weighed and recorded as x.

[0079] Weigh 10x nanodiamond powder with a D50 of 15nm, take 50% of the diamond powder by mass and spread it in a square crucible, spread the intermediate product A on the top of the nanodiamond powder, and then spread the remaining diamond powder on the top of the intermediate product A. Place it in a muffle furnace and calcine it at 1000℃ for 2h. After cooling to room temperature with the furnace, take out the reactants and separate the nanodiamond powder through a cyclone separator to obtain a multilayer composite abrasive.

[0080] 10 g of the multi-layer composite abrasive and 2.5 g of polyethylene glycol were weighed separately and added into 100 ml of deionized water, and stirred at 650 r / min for 20 min to obtain a CMP slurry composition.

[0081] Example 7

[0082] 34.2 g of aluminum sulfate was added to 100 ml of deionized water to prepare an aluminum salt solution, and a silica sol containing 14 g of silicon (silicon particle size of 30 nm) and 15 g of urea were added in sequence. After dispersion, a reaction solution was formed. The reaction solution was transferred to a reactor, sealed, and hydrothermally reacted at 200°C for 3 h. The obtained solid-liquid mixture was filtered, washed three times with ethanol and deionized water, and then dried in a drying oven at 60°C under vacuum for 6 h to obtain an intermediate product A. The mass of the intermediate product A was weighed and recorded as x.

[0083] Weigh 15x nanodiamond powder with a D50 of 15 nm, take 50% of the diamond powder by mass and spread it in a square crucible, spread the intermediate product A on the top of the nanodiamond powder, and then spread the remaining diamond powder on the top of the intermediate product A. Place it in a muffle furnace and calcine it at 1000°C for 2 hours. After cooling to room temperature with the furnace, take out the reactants and separate the nanodiamond powder through a cyclone separator to obtain a multilayer composite abrasive.

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

[0085] Example 8

[0086] 34.2 g of aluminum sulfate was added to 100 ml of deionized water to prepare an aluminum salt solution, and a silica sol containing 14 g of silicon (silicon particle size of 30 nm) and 15 g of urea were added in sequence. After dispersion, a reaction solution was formed. The reaction solution was transferred to a reactor, sealed, and hydrothermally reacted at 200°C for 3 h. The obtained solid-liquid mixture was filtered, washed three times with ethanol and deionized water, and then dried in a drying oven at 60°C under vacuum for 6 h to obtain an intermediate product A. The mass of the intermediate product A was weighed and recorded as x.

[0087] Weigh 15x nanodiamond powder with a D50 of 15 nm, take 50% of the diamond powder by mass and spread it in a square crucible, spread the intermediate product A on the top of the nanodiamond powder, and then spread the remaining diamond powder on the top of the intermediate product A. Place it in a muffle furnace and calcine it at 1000°C for 2 hours. After cooling to room temperature with the furnace, take out the reactants and separate the nanodiamond powder through a cyclone separator to obtain a multilayer composite abrasive.

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

[0089] Comparative Example 1

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

[0091] Comparative Example 2

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

[0093] Comparative Example 3

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

[0095] Comparative Example 4

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

[0097] Comparative Example 5

[0098] Except that the mass of the nano-diamond powder is equal to that of the intermediate product A, the rest of the process is the same as that of Example 6 to prepare the CMP slurry.

[0099] Comparative Example 6

[0100] Except that the mass of the nano-diamond powder is 30 times that of the intermediate product, the rest of the process is the same as that of Example 6 to prepare the CMP slurry.

[0101] Comparative Example 7

[0102] 17.1 g of aluminum sulfate was added to 100 ml of deionized water to prepare an aluminum salt solution, and silica sol containing 9.5 g of silicon (silicon particle size of 70 nm) and 9 g of urea were added in sequence. After dispersion, a reaction solution was formed. The reaction solution was transferred to a reactor, sealed, and hydrothermally reacted at 200°C for 3 hours. The obtained solid-liquid mixture was filtered, washed three times with ethanol and deionized water, and then dried in a drying oven at 60°C under vacuum for 6 hours to obtain intermediate product A.

[0103] The intermediate product A was calcined at 1000°C for 2 h in a muffle furnace and then cooled to room temperature to obtain composite abrasive particles.

[0104] 10 g of the composite abrasive and 2.5 g of polyethylene glycol were weighed respectively, added into 100 ml of deionized water, and stirred at 700 r / min for 20 min to obtain a CMP slurry.

[0105] Test example:

[0106] The multilayer composite abrasive particles prepared in Examples 1-7 and Comparative Examples 1-7 were collected and the particle size was tested using a laser particle size analyzer. The test results are shown in Table 1.

[0107] The multilayer composite abrasive prepared in Examples 1-7 and Comparative Examples 1-7 was tested for micro Vickers hardness using a micro Vickers hardness tester. Five points were taken from each group of samples for testing, and the average value 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 used to perform CMP tests on single crystal silicon substrates. 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 slurry after testing in Example 6, Comparative Example 3 and Comparative Example 4 was collected, washed three times with deionized water and filtered, and vacuum dried at 60°C for 6 hours. The multilayer composite abrasive prepared in Comparative Example 3 and Comparative Example 4 of Example 6 was used as a control group, and the C element was detected by EDS. The test results are shown in Table 2.

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

[0111] Table 1 is a test statistics table of each embodiment and comparative example

[0112] Multilayer composite abrasive D50 (nm) <![CDATA[显微维氏硬度(kg / mm 2 )]]> <![CDATA[MRR(mm 3 / s)]]> scratches Example 1 191.3 738 \ \ Example 2 177.4 776 \ \ Example 3 149.2 799 \ \ Example 4 163.9 819 \ \ Example 5 167.1 843 \ \ Example 6 98.5 837 417 No scratches Example 7 54.7 851 \ \ Comparative Example 1 20.4 476 314 Minor surface scratches, no subsurface scratches Comparative Example 2 263.5 847 429 Obvious surface scratches Minor subsurface scratches Comparative Example 3 94.8 781 384 Obvious surface scratches Comparative Example 4 99.6 859 432 Obvious subsurface scratches Comparative Example 5 98.7 724 405 Obvious surface scratches Comparative Example 6 97.9 703 393 Obvious surface scratches Comparative Example 7 96.5 697 379 Obvious surface scratches

[0113] In Table 1, by comparing the D50 values ​​of Examples 1-7 and Comparative Examples 1-2, it can be seen that the silica particle size 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 the diamond particles are too large, or the mass ratio of diamond particles to the intermediate product is too large, and it is difficult to load them in 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 hardened during the calcination process due to its own gravity. At the same time, the diamond particles are too small and completely enter the pores. Although the hardness of the multi-layer composite abrasive is improved to a certain extent, the particle size of the composite abrasive is not effectively increased. If the mass ratio of diamond particles to the intermediate product is too small, the peripheral load of the alumina connecting layer is too small, which affects the polishing effect.

[0114] Table 2 C content test table of multi-layer composite abrasive before and after use

[0115] Abrasive C content before use % Abrasive C content after use % Example 6 16.82 3.72 Comparative Example 3 17.43 16.98 Comparative Example 4 2.39 1.97

[0116] In Table 2, the changes in the C content before and after Example 6 show that when the diamond particle size is 5-15 nm, it is loaded on the periphery of the alumina connecting layer during calcination and falls off during polishing. Therefore, the C element in the abrasive particles drops sharply before and after polishing. From the changes in the C content before and after Comparative Examples 3 and 4, it can be seen that when the diamond particle size is too small, the diamond particles enter the interior of the alumina connecting layer and remain unchanged during the polishing process. When the diamond particle size is large, it is difficult to load on the alumina connecting layer. Combined with the relevant data of Comparative Example 4 in Table 1, a very small amount of diamond loaded on the alumina connecting layer will cause sub-surface damage to the wafer surface.

[0117] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Viscosity / cps 3.2 3.3 3.2 2.9 3.4 12.1 16.9 17.6 <![CDATA[密度(g / cm 3 )]]> 1.05 1.064 1.059 1.057 1.061 1.098 1.143 1.147

[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 of 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 diamond particles D50 are between 5-15nm, they can be effectively loaded on the periphery of the alumina transition layer, that is, some diamond particles enter the pores of the intermediate product A. After calcination, the alumina transforms to a crystal form with higher crystallinity, which will fix the diamond particles in the pores. Since the diamond is partially exposed outside the alumina connecting layer, the particle size of the multi-layer composite abrasive is increased. At the same time, the diamond exposed to the outside polishes the wafer surface in the early stage of polishing, thereby increasing the polishing rate. Since only part of the diamond is confined in the alumina connecting layer, as the polishing proceeds, the diamond particles loosen and fall off from the surface of the alumina connecting layer, reducing the particle size of the multi-layer composite abrasive. At the same time, the fallen diamond particles cooperate with the composite abrasive, so that the polishing process is transformed from rough polishing to fine polishing.

[0120] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a CMP slurry composition for polishing a wafer surface, characterized in that: The invention comprises the following components: a solvent; The multilayer composite abrasive comprises 0.5-20 wt% of the solvent mass; and the dispersant comprises 0.01-5 wt% of the solvent mass, wherein: 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 composite abrasive comprises a nano-silica core, an alumina connecting layer, and nano-diamond particles distributed around the alumina connecting layer; and the dispersant is one or more of sodium polyacrylate, polypropylene alcohol, and polyethylene glycol. The following steps are involved: (1) Preparing multi-layer composite abrasive particles; the steps of preparing the multi-layer composite abrasive particles include: 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 reactor, seal it, and hydrothermally react at 200°C for 3 hours to obtain a solid-liquid mixture, wherein the particle size distribution range of the sol particles in the silica sol is 30-100 nm; The aluminum salt concentration is 0.5-1 mol / L, and the aluminum:silicon:alkaline precipitant molar ratio 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 outside; ③ Take a fixed-shape reaction vessel, fill the bottom with nano-diamond powder, and spread the intermediate product A on the top layer of the nano-diamond powder, then fill it with nano-diamond powder again to cover the intermediate product, then calcine at 800-1000°C for 2 hours, cool it to room temperature with the furnace, and separate the nano-diamond powder through a cyclone separator to obtain a multi-layer composite abrasive, wherein the nano-diamond powder D50 is 5-15nm, and the mass ratio of the nano-diamond powder to the intermediate product A is 5-20:1; (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 of less than 18 cps at 20° C. and a density of 1.03-1.15 g / cm 3 .

2. The method for preparing a CMP slurry composition for polishing a wafer surface according to claim 1, wherein: The D50 of the multi-layer composite abrasive is 50-200 nm.

3. The method for preparing a CMP slurry composition for polishing a wafer surface according to claim 1, wherein: The aluminum salt is one or more of aluminum chloride, aluminum sulfate, aluminum nitrate, aluminum silicate, and aluminum sulfide.

4. The method for preparing a CMP slurry composition for polishing a wafer surface according to claim 1, wherein: The precipitant is one or more of urea, ammonium bicarbonate, and ammonium carbonate.

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