A grinding cloth and its preparation method

Abstract

The present invention discloses a polishing cloth, which comprises an elastic composite layer prepared by impregnating a fiber substrate twice with a foaming material; the foaming material comprises a primary impregnating slurry and a secondary impregnating slurry, the reaction raw materials of the primary impregnating slurry include 5-40 wt% of diisocyanate, 40-60 wt% of polyolefin polyol, 20-40 wt% of polyester polyol, 1-5 wt% of aliphatic polyol, the secondary impregnating slurry comprises a prepolymer and a polyamine compound, and the reaction raw materials of the prepolymer include 10-25 wt% of diisocyanate, 60-70 wt% of polyolefin polyol, 10-20 wt% of aliphatic polyol or alicyclic polyol. The present invention uses a two-time impregnation process to maintain the performance of the above elastic composite layer, can improve the uniformity of double-sided polishing of silicon wafers, improve the planarization effect of chemical mechanical polishing, and effectively solve the problem of edge collapse of silicon wafer grinding.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical mechanical planarization. More specifically, the present invention relates to an abrasive cloth and a preparation method thereof. Background Art

[0002] A silicon wafer is a substrate for manufacturing electrical components such as integrated circuits commonly referred to. Usually, a single-crystalline silicon ingot is cut into thin slices with a thickness of 0.015 to 0.025 inches, and then the thin slices are ground to make them flat, and then chemically etched. After etching, the thin slices are processed by a process called polishing in the industry. The device used for polishing is similar to the device used for grinding. During the polishing process, the thin slice is fixed on a polishing machine and then rubbed against one or more porous materials adhered to a rotating grinding plate. During the polishing process, the porous matrix material is always saturated with an alkaline suspension containing silica microparticles. The alkaline suspension (slurry) reacts chemically with the silicon atoms on the surface of the thin slice to form a reaction product that is slightly softer than the underlying silicon. Once this reaction product is formed on the surface of the thin slice, further reaction is inhibited. During the polishing process, this reaction product is continuously ground off, exposing the newly exposed silicon to the action of the slurry.

[0003] During the polishing process of semiconductor silicon wafers, it can be mainly divided into double-sided polishing, edge polishing, and final polishing. Among them, the double-sided polishing process is the main process affecting the flatness of the wafer. During the double-sided polishing process, the warping of the edge will affect the flatness of the wafer to varying degrees. Controlling the edge warping of the wafer during the CMP process can be achieved by adjusting the physical and chemical properties of the abrasive cloth.

[0004] Rodel, Inc. in the United States has disclosed a porous polishing pad composed of a sheet-like fiber substrate and a thermoplastic polyurethane resin. Compared with a hard thermosetting polishing pad, this polishing pad can reduce the scratching of the silicon wafer surface while maintaining a relatively high grinding rate, achieving a relatively ideal flatness. However, using this type of polishing pad will cause wafer edge collapse.

[0005] Chinese Patent CN1565048A has also disclosed a polishing pad with organic fibers exposed on the surface. This technology improves the planarization efficiency of the object to be polished and reduces the occurrence probability of polishing damage by regulating the length and distribution of the soft fibers on the polishing surface of the polishing pad. However, at a lower polishing pressure, the flatness of the wafer surface is poor, and the grinding rate uniformity is not good.

[0006] In order to comprehensively solve the technical problems such as low flatness, poor grinding uniformity, and wafer edge collapse of the polishing pad made of polyurethane resin attached with sheet-like fibers in silicon wafer polishing, the inventors of the present invention have conducted repeated in-depth studies. Summary of the Invention

[0007] One object of the present invention is to solve at least the above problems and provide at least the advantages described hereinafter.

[0008] Another object of the present invention is to provide a polishing cloth. It is found that under the condition of two impregnations, the water absorption rate of the elastic composite layer maintained for 6 hours is not more than 15 wt%, and the hardness of the elastic composite layer is 70-85A, the density is 0.3-0.6 g / cm 3 , and the compression ratio is 0-5%, which can improve the uniformity of double-sided polishing of silicon wafers, improve the planarization effect of chemical mechanical polishing, and effectively solve the problem of edge collapse during silicon wafer grinding.

[0009] To achieve these objects and other advantages according to the present invention, a polishing cloth is provided, which includes an elastic composite layer obtained by impregnating a fiber substrate twice in a foaming material; the foaming material includes a primary impregnation slurry and a secondary impregnation slurry. The reaction raw materials of the primary impregnation slurry include 5-40 wt% of diisocyanate, 40-60 wt% of polyolefin polyol, 20-40 wt% of polyester polyol, and 1-5 wt% of aliphatic polyol. The reaction raw materials of the secondary impregnation slurry include a prepolymer and a polyamine compound. The reaction raw materials of the prepolymer include 10-25 wt% of diisocyanate, 60-70 wt% of polyolefin polyol, and 10-20 wt% of aliphatic polyol or alicyclic polyol.

[0010] Specifically, the water absorption rate of the elastic composite layer for 6 hours is not more than 15%, the hardness of the elastic composite layer is 70-85A, the density of the elastic composite layer is 0.3-0.6 g / cm 3 , and the compression ratio of the elastic composite layer is 0-5%.

[0011] Preferably, the molar ratio of the prepolymer to the polyamine compound is (1.0-1.3):1.0.

[0012] Preferably, the primary impregnation slurry further includes 1-5 wt% of sorbitan fatty acid ester.

[0013] Preferably, the molecular weight (Mn) of the polyolefin polyol is 1800-3000.

[0014] Preferably, the density of the fiber substrate is 0.10-0.30 g / cm 3 , and the thickness is 0.1-10 mm.

[0015] Preferably, the water absorption rate of the elastic composite layer at pH 7.0 for 6 hours is greater than the water absorption rate at pH 10.0, and preferably the difference is between 0.6-1.1%.

[0016] The present invention provides a method for preparing an abrasive cloth, comprising the following steps:

[0017] S1. Immerse a fiber substrate in a DMF solution containing a primary impregnation slurry, immerse it in a coagulation bath for solidification and molding, wash it with water, and dry it to obtain a primary impregnated fiber substrate;

[0018] S2. After sanding the surface of the primary impregnated fiber substrate, immerse it again in an organic solution of a secondary impregnation slurry, and dry it at 90-130 °C for 80-150 min to obtain an elastic composite layer;

[0019] S3. Cut, hot press, double-sided sand, apply a double-sided adhesive film containing a PET film, blank, and grooving to the elastic composite layer to obtain an abrasive cloth.

[0020] Preferably, in the DMF solution in step S1, the primary impregnation slurry accounts for 6-8 wt%; the reaction raw materials of the primary impregnation slurry include 5-40 wt% of diisocyanate, 40-60 wt% of polyolefin polyol, 20-40 wt% of polyester polyol, and 1-5 wt% of aliphatic polyol;

[0021] Preferably, the primary impregnation slurry further includes 1-5 wt% of sorbitan fatty acid ester;

[0022] The coagulation bath in step S1 uses a DMF aqueous solution with 20 wt% of DMF.

[0023] Preferably, in step S2, the organic solution is a tetrahydrofuran / ethyl methyl ketone solution, the foaming material accounts for 20-30 wt% in the organic solution, and the mass ratio of tetrahydrofuran to ethyl methyl ketone is 80:20;

[0024] The secondary impregnation slurry includes a prepolymer and a polyamine compound with a molar ratio of (1.0-1.3):1, and the reaction raw materials of the prepolymer include 10-25 wt% of diisocyanate, 60-70 wt% of polyolefin polyol, and 10-20 wt% of aliphatic polyol.

[0025] The present invention has at least the following beneficial effects:

[0026] 1. The present invention adopts a secondary impregnation process, maintaining the water absorption rate of the elastic composite layer not greater than 15 wt% for 6 hours, and the hardness of the elastic composite layer is 70-85A, the density is 0.3-0.6 g / cm 3 , and the compression ratio is 0-5%, which can improve the stability of the grinding rate and the grinding uniformity, and avoid the collapse of the silicon wafer edge;

[0027] 2. Using sorbitan fatty acid ester in the primary impregnation slurry can improve the surface roughness of the abrasive cloth;

[0028] 3. Using poly-cis-4-cyclopentene-1,3-diol in the primary impregnation slurry can reduce the number of scratches on the wafer surface;

[0029] 4. Adding an alicyclic diol structure to the secondary impregnation slurry can increase the hardness of the polishing cloth;

[0030] 5. The water absorption rate of the elastic composite layer of the present invention at pH 7.0 for 6 hours is greater than that at pH 10.0, enabling it to have a better polishing effect when using an alkaline polishing solution. Preferably, the difference is between 0.6% and 1.1%, which can increase the grinding rate of the polishing cloth.

[0031] Other advantages, objectives, and features of the present invention will be partially reflected by the following description and partially understood by those skilled in the art through the research and practice of the present invention. Brief Description of the Drawings

[0032] Figure 1 It is a schematic structural diagram of a polishing pad according to one embodiment of the present invention;

[0033] Figure 2 It is a schematic diagram after the statistical normalization of the silicon wafer thickness of Example 1 and Comparative Example 5 in one embodiment of the present invention. Detailed Embodiments

[0034] The first aspect of the present invention provides a polishing cloth, which includes an elastic composite layer, an adhesive layer, a resin film layer, and a release film layer arranged from top to bottom, as Figure 1 shown, for grinding unprocessed bare silicon wafers.

[0035] In the embodiments of the present invention, to improve the grinding uniformity and avoid silicon wafer edge collapse, the water absorption rate range of the elastic composite layer is controlled in the embodiments of the present invention, so that the water absorption rate of the elastic composite layer for 6 hours is not greater than 15 wt%, preferably not greater than 13 wt%, more preferably not greater than 12 wt%, and the hardness of the elastic composite layer is 70-85A, and the density of the elastic composite layer is 0.3-0.6 g / cm 3 , preferably 0.3-0.5 g / cm 3 , more preferably 0.3-0.4 g / cm 3 , and the compression ratio of the elastic composite layer is 0-5%.

[0036] In the embodiments of the present invention, the polishing pad of the present invention includes a fiber substrate impregnated twice in a foaming material to prepare an elastic composite layer. The foaming material includes a primary impregnation slurry and a secondary impregnation slurry.

[0037] In an embodiment of the present invention, the reaction raw materials of the primary impregnation slurry include 5-40 wt% of diisocyanate, 40-60 wt% of polyolefin polyol, 20-40 wt% of polyester polyol, and 1-5 wt% of aliphatic polyol. Preferably, the primary impregnation slurry further includes 1-5 wt% of sorbitan fatty acid ester. After adding sorbitan fatty acid ester, the surface roughness of the abrasive cloth can be improved.

[0038] The secondary impregnation slurry includes a prepolymer and a polyamine compound with a molar ratio of (1.0-1.3):1. The reaction raw materials of the prepolymer include 10-25 wt% of diisocyanate, 60-70 wt% of polyolefin polyol, and 10-20 wt% of aliphatic polyol.

[0039] Examples of the diisocyanate compound having two isocyanate groups in the molecule include: m-phenylene diisocyanate, p-phenylene diisocyanate, 2,6-toluene diisocyanate (2,6-TDI), 2,4-toluene diisocyanate (2,4-TDI), naphthalene-1,4-diisocyanate, diphenylmethane-4,4'-diisocyanate (MDI), 4,4'-methylene-bis(cyclohexyl isocyanate) (hydrogenated MDI), 3,3'-dimethoxy-4,4'-biphenyl diisocyanate, 3,3'-dimethyl diphenylmethane-4,4'-diisocyanate, benzene dimethyl-1,4-diisocyanate, 4,4'-diphenylpropane diisocyanate, trimethylene diisocyanate, hexamethylene diisocyanate, propylene-1,2-diisocyanate, butylene-1,2-diisocyanate, cyclohexylene-1,2-diisocyanate, cyclohexylene-1,4-diisocyanate, p-phenylene diisothiocyanate, benzene dimethyl-1,4-diisothiocyanate, ethylene diisothiocyanate, etc. These polyisocyanate compounds can be used alone or in combination of multiple polyisocyanate compounds.

[0040] As the diisocyanate compound having two isocyanate groups, preferably 2,4-TDI and MDI, more preferably 2,4-TDI.

[0041] In an embodiment of the present invention, the polyolefin polyol is any one or more of polyisoprene polyol, polybutadiene polyol, hydroxy-terminated polybutadiene-acrylonitrile, hydroxy-terminated styrene-butadiene liquid rubber, hydrogenated hydroxy-terminated polybutadiene, and poly-cis-4-cyclopentene-1,3-diol. In an embodiment of the present invention, the molecular weight (Mn) of the polyolefin polyol is 1800-3000. Preferably, the number average molecular weight of the polyolefin polyol is 1,800 to 2,500 and the hydroxyl value of the polyolefin polyol is 40 KOH mg / g to 55 KOH mg / g.

[0042] The preparation method of the above-mentioned poly-cis-4-cyclopentene-1,3-diol is as follows: using cis-4-cyclopentene-1,3-diol as the raw material, adding a composite alkaline catalyst of potassium borate and potassium hydroxide with a mass ratio of 50:50, and the dosage of the composite alkaline catalyst accounts for 0.1-1% of the total weight of the reaction system. Heat up to 80-130 °C and control the pressure at 0.5 MPa to prepare poly-cis-4-cyclopentene-1,3-diol. Using poly-cis-4-cyclopentene-1,3-diol in the primary impregnation slurry can reduce the number of scratches on the wafer surface.

[0043] In the embodiments of the present invention, the polyester polyol is selected from one or a combination of two or more polyester polyols with an average functionality of 2, specifically including ethylene glycol adipate, butylene glycol adipate, hexanediol adipate, ethylene glycol-butylene glycol adipate, diethylene glycol adipate, neopentyl glycol adipate, polycaprolactone, polycarbonate, or a combination of two or more of them.

[0044] In the embodiments of the present invention, a polyester polyol with a molecular weight range of 1000-3000 is selected. When the molecular weight is too low, the hardness and elastic modulus of the polyurethane resin are relatively high, lacking sufficient elasticity, with poor buffering performance, becoming a brittle polymer. The polishing pad made of this polyurethane resin becomes too hard, easily causing scratches on the wafer surface, and is not preferred in terms of the polishing pad life due to easier wear. On the other hand, when the molecular weight is too high, the polyurethane resin becomes too soft, with too low hardness and elastic modulus, and the planarization characteristics of the obtained polishing pad are poor.

[0045] In the embodiments of the present invention, examples of the aliphatic polyol compound used in the synthesis of the isocyanate group-containing compound in the primary impregnation slurry and the secondary impregnation slurry include diol compounds such as ethylene glycol and butylene glycol. As the aliphatic polyol structure of the secondary impregnation slurry, an alicyclic diol structure is preferred. Examples of the alicyclic diol structure include 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, and spiro diol. The alicyclic diol component preferably has 5 to 20 carbon atoms in its alicyclic group. Adding the alicyclic diol structure can increase the hardness of the abrasive cloth.

[0046] In the embodiments of the present invention, the polyamine compound refers to a compound having two or more amino groups in the molecule. The polyamine compound functions as a chain extender, reacting with a part of the above-mentioned polyisocyanate compound to form a hard segment, and binding to the main chain end side of a part of the above-mentioned isocyanate group-containing compound (soft segment part), thereby further extending the polymer chain. Thereby, a polyurethane resin having a block copolymer of a hard segment and a soft segment is generated.

[0047] The polyamine compound can be an aliphatic or aromatic polyamine compound, especially a diamine compound. For example, ethylenediamine, propylenediamine, hexamethylenediamine, isophoronediamine, dicyclohexylmethane-4,4'-diamine, 3,3'-dichloro-4,4'-diaminodiphenylmethane (methylene bis-o-chloroaniline) (hereinafter abbreviated as MOCA), polyamine compounds having the same structure as MOCA, etc. can be cited. In addition, the polyamine compound can have a hydroxyl group. Such amine compounds include, for example, 2-hydroxyethyl ethylenediamine, 2-hydroxyethyl propylenediamine, di-2-hydroxyethyl ethylenediamine, di-2-hydroxyethyl propylenediamine, 2-hydroxypropyl ethylenediamine, di-2-hydroxypropyl ethylenediamine, etc.

[0048] The polyamine compound is preferably a diamine compound, more preferably MOCA, diaminodiphenylmethane, or diaminodiphenylsulfone, and particularly preferably MOCA.

[0049] For the fiber substrate, as long as it can be used as the substrate of the abrasive cloth, there is no particular limitation, and it can be a known substance. The fiber substrate is in sheet form. The fiber substrate can be a non-woven fabric formed by interweaving fibers, or a fabric, or a knitted fabric. From the viewpoint of more effectively and reliably exerting the effects of the present invention, a non-woven fabric is preferred. The method of interweaving fibers when obtaining the non-woven fabric is not particularly limited. For example, it can be a needling method, or a hydroentangling method, heat bonding, chemical bonding, stitch-bonding, or steam jetting method. In addition, as the fiber material of the sheet-like fiber substrate, it can be either a natural fiber or a synthetic fiber. For example, natural fibers such as cotton and hemp, and synthetic fibers such as polyethylene terephthalate (PET), other polyesters, polyamides, polyurethanes, polypropylenes, polyethylenes, and (meth)acrylic resin fibers can be cited. Among them, materials selected from polyesters, polyamides, polypropylenes, polyethylenes, and (meth)acrylic resins are preferred. The fiber materials can be used alone or in combination of two or more.

[0050] The density of the fiber substrate is preferably 0.10 g / cm 3 ~0.30 g / cm 3 and more preferably 0.12 g / cm 3 ~0.22 g / cm 3 . By making its density above the above lower limit value, the foaming material can be further uniformly formed and held. In addition, by making its density below the above upper limit value, the impregnation process of the foaming material becomes easier, and more foaming material can be held.

[0051] The adhesive layer is used for bonding between the elastic composite layer and the resin film layer. The adhesive layer may include a hot-melt adhesive and a pressure-sensitive adhesive. The hot-melt adhesive may be at least one selected from the group consisting of polyurethane resin, polyester resin, ethylene-vinyl acetate resin, polyamide resin, and polyolefin resin, and the pressure-sensitive adhesive is PSA.

[0052] The resin film layer is a polyester film, a PET film. Since the resin film layer of the abrasive cloth is a layer attached to the polishing machine table and has adhesiveness, it is not convenient to place. Therefore, to facilitate the placement of the abrasive cloth, a release film layer is adhered to one side of the resin film layer, and the material of the release film layer is a release film.

[0053] In an embodiment of the present invention, there is a difference in the water absorption rate of the elastic composite layer at pH 7.0 and pH 10.0 at 6 hours. Preferably, the difference is between 0.6 and 1.1%, more preferably between 0.6 and 1.0%, and even more preferably between 0.6 and 0.9%. There is a difference in the 6-hour water absorption rate of the elastic composite layer at pH 7.0 and pH 10.0. When using an alkaline polishing solution, the grinding rate of the silicon wafer can be increased. If the difference in the water absorption rate at the above two pH values is less than 0.6%, then when grinding the silicon wafer using an alkaline polishing solution, there is no difference or a small difference in the water absorption rate, which has little effect on the grinding rate of the silicon wafer. If the difference in the water absorption rate at the above two pH values is greater than 1.1%, then when grinding the silicon wafer, since the polishing slurry accumulates more at the edge of the silicon wafer and the grinding rate is high, it is easy to cause the problem of edge collapse of the silicon wafer.

[0054] The second aspect of the present invention provides a method for preparing an abrasive cloth, including the following steps:

[0055] S1. Immerse the fiber substrate in a DMF solution containing a primary impregnation slurry, immerse it in a coagulation bath for solidification molding, wash with water, and dry to obtain a primary impregnated fiber substrate;

[0056] S2. After sanding the surface of the primary impregnated fiber substrate, impregnate it again in an organic solution of a secondary impregnation slurry, and dry it at 90 - 130 °C for 80 - 150 min to obtain an elastic composite layer;

[0057] S3. Cut, hot-press, double-side sand the elastic composite layer, apply a double-sided adhesive film containing a PET film, punch, and groove to obtain the abrasive cloth. The hot-press is to bond the elastic composite layer and the resin film layer, and the resin film layer and the elastic composite layer are bonded using an adhesive layer.

[0058] In the DMF solution of step S1, the primary impregnation slurry accounts for 6 - 8 wt%, and the reaction raw materials of the primary impregnation slurry include 5 - 40 wt% of diisocyanate, 40 - 60 wt% of polyolefin polyol, 20 - 40 wt% of polyester polyol, and 1 - 5 wt% of aliphatic polyol;

[0059] Preferably, the primary impregnation slurry further comprises 1-5 wt% of sorbitan fatty acid ester;

[0060] In step S1, the coagulation bath is a DMF aqueous solution with 20 wt% of DMF.

[0061] In step S2, the organic solution is a tetrahydrofuran / methyl ethyl ketone solution. The secondary impregnation slurry accounts for 20-30 wt% in the organic solution, and the mass ratio of tetrahydrofuran to methyl ethyl ketone is 80:20. The secondary impregnation slurry comprises a prepolymer and a polyamine compound with a molar ratio of (1.0-1.3):1. The reaction raw materials of the prepolymer include 10-25 wt% of diisocyanate, 60-70 wt% of polyolefin polyol, and 10-20 wt% of aliphatic polyol.

[0062] The following further describes the present invention in detail with reference to embodiments, so that those skilled in the art can implement it according to the description in the specification.

[0063] It should be noted that, unless otherwise specified, the experimental methods in the following embodiments are all conventional methods, and the reagents and materials, unless otherwise specified, can all be obtained from commercial channels.

[0064] <Example 1>

[0065] Configuration of the primary impregnation slurry: Appropriately weigh and mix 20 wt% of 2,4-toluene diisocyanate, 50 wt% of polybutadiene polyol (Mn = 2000), 25 wt% of polybutylene adipate, and 5 wt% of ethylene glycol;

[0066] Configuration of the secondary impregnation slurry: At room temperature (25 °C), 2,4-toluene diisocyanate is fed into the polymerization reactor at one time. The stirring speed in the reactor is controlled at 250 ± 20 rpm, and the temperature is raised to 55 °C. Then, hydroxyl-terminated polybutadiene (GI2000, Mn = 2000) is gradually added. This process is carried out by dropping with a peristaltic pump, and the material temperature is controlled within 80 °C. After the dropping is completed, the temperature is lowered to 40 °C, and butanediol is also added to the reactor in a dropping manner. Keep the temperature at 80 °C and stir for 3 hours, then discharge to obtain the prepolymer. The mass ratio of 2,4-toluene diisocyanate, hydroxyl-terminated polybutadiene, and butanediol is 15:65:20. During the secondary impregnation, dicyclohexylmethane-4,4'-diamine is added. The molar ratio of the above prepolymer to dicyclohexylmethane-4,4'-diamine is 1:1, and the molar amount of the prepolymer is calculated using the theoretical average molecular weight.

[0067] Manufacture of the abrasive cloth:

[0068] S1. Immerse the fibrous substrate in a DMF solution containing the above-configured primary impregnating slurry. The proportion of the primary impregnating slurry in the DMF solution is 6-8 wt%. After impregnation, immerse it in a coagulation bath for coagulation molding for 30 minutes. The coagulation bath uses an aqueous solution with 20 wt% DMF. After coagulation molding, wash with water to displace the DMF solvent in the fibrous substrate, and then dry to obtain the primary impregnated fibrous substrate.

[0069] S2. After sanding the surface of the primary impregnated fibrous substrate, impregnate it again in a secondary impregnating slurry with a molar ratio of prepolymer to dicyclohexylmethane-4,4'-diamine of 1:1. The proportion of the secondary impregnating slurry in the tetrahydrofuran / ethyl methyl ketone solution is 20-30 wt%. Dry it at 90-130 °C for 80-150 minutes to obtain the elastic composite layer.

[0070] S3. Cut the elastic composite layer according to the size, perform hot pressing at a hot pressing temperature of 110 °C for 180 s, sand both sides, apply a resin film layer containing a release film, and then perform blanking and grooving to obtain the abrasive cloth.

[0071] The preparation methods of the primary impregnating slurry and the secondary impregnating slurry in Examples 2-9 and Comparative Examples 1-3 below are the same as those in Example 1. The preparation methods of the abrasive cloths in Examples 2-9 and Comparative Examples 1-3 are also the same as those in Example 1. Among them, the difference is that the mass proportions of the raw material types of the primary impregnating slurry and the secondary impregnating slurry are different from those in Example 1. The remaining steps in Comparative Example 4 are the same as those in Example 1, except that after coating the secondary impregnating slurry on the primary impregnated fibrous substrate, it is dried to prepare the elastic composite layer. Comparative Example 5 is a commercially available abrasive cloth Suba 600, manufactured by DuPont Company, USA. The grinding thickness normalization of Example 1 and Comparative Example 5 is as Figure 2 shown.

[0072] To clearly express the types and mass proportions of the primary impregnating slurry and the secondary impregnating slurry in Examples 1-9 and Comparative Examples 1-5, they are shown in Table 1 below.

[0073] Table 1

[0074]

[0075]

[0076] <Evaluation of the abrasive cloth>

[0077] 1. Evaluation of water absorption

[0078] Sample preparation: Punch the elastic composite layers of Examples 1-9 and Comparative Examples 1-4 and the abrasive cloth of Comparative Example 5 with the back adhesive layer removed into 4-cm diameter circular pieces using a mold, with 5 pieces in each group.

[0079] Experimental conditions: room temperature, 25 °C; ultrapure water, prepared into ultrapure water with pH = 7.0 and pH = 10.0 respectively;

[0080] Weigh the test wafers of each experimental group as m 0 ; Immerse them in aqueous solutions with pH = 7.0 and pH = 10.0, take them out after 6 hours, wipe them with lint-free paper to absorb the water stains on the surface of the samples, and weigh them as m t ;

[0081] Water absorption rate S(%) = (m t - m 0 ) / m 0 * 100

[0082] 2. Evaluation of grinding rate and stability

[0083] For the polishing cloths of Examples 1-9 and Comparative Examples 1-5, the polished wafer is a 12-inch Si wafer, the polishing liquid is a diluted solution (30 times) of Fujimi 3108, the flow rate is 1 L / min, the dresser is a white brush diamond disc, the pressure is 7 lbf, the polishing head pressure is 2.5 psi, the platen speed is 97 rpm, the carrier speed is 91 rpm, and the polishing time is 45 s.

[0084] For the 100th ground wafer, measure the grinding rate, grinding non-uniformity and defect density;

[0085] The grinding rate is calculated by measuring the grinding removal amount at different positions of the wafer within a certain polishing time, and the measuring tool is NanoSpec II;

[0086] The grinding rate non-uniformity (Nu) is calculated by NanoSpec II;

[0087] The defect density is the number of scratches measured on each wafer, and the instrument used is the KLA-Tencor SP2 analyzer.

[0088] 3. Determination of hardness

[0089] For the polishing cloths of Examples 1-9 and Comparative Examples 1-5, it is determined according to ASTM D 2240.

[0090] 4. Determination of density

[0091] For the polishing cloths of Examples 1-9 and Comparative Examples 1-5, it is determined according to ASTM D 1622-2003.

[0092] 5. Evaluation of compression ratio

[0093] Using a cylindrical indenter with a diameter of 5 mm, a load was applied to the abrasive cloths (sample size: diameter 7 mm) of Examples 1 to 9 and Comparative Examples 1 to 5 at 25 °C on a TMA manufactured by Mac Science, and T1 (μm) and T2 (μm) were measured.

[0094] Compression ratio (%) = [(T1 - T2) / T1] × 100

[0095] Among them, T1 represents the thickness of the thin plate after applying a stress of 30 kPa (300 g / cm 2 ) and maintaining it for 60 s, and T2 represents the thickness of the thin plate after applying a stress of 180 kPa to the thin plate in state T1 and maintaining it for 60 s.

[0096] 6. Surface roughness

[0097] Using white light interferometry, an arbitrary diameter of the circle was taken for each group of samples, and the surface roughness was measured at the Center / Middle / Edge parts respectively. The measuring equipment was a Bruker Contour GTX three-dimensional optical profiler.

[0098] The measurement results of the above evaluations are shown in Table 2.

[0099] Table 2

[0100]

[0101] As can be seen from Table 2, by adopting the secondary impregnation process, good grinding rate stability and uniformity can be achieved, and wafer edge collapse can be avoided;

[0102] When the difference in water absorption rate maintained at pH = 7.0 and pH = 10.0 for 6 hours is maintained between 0.6% and 1.1%, the grinding rate can be increased;

[0103] As can be seen from Example 4, using poly-cis-4-cyclopentene-1,3-diol in the primary impregnation slurry can further reduce the number of grinding scratches on the abrasive cloth;

[0104] As can be seen from Example 5, using sorbitan fatty acid ester in the primary impregnation slurry can improve the surface roughness of the abrasive cloth;

[0105] As can be seen from Examples 8 and 9, adding an alicyclic diol structure to the secondary impregnation slurry can increase the hardness of the abrasive cloth.

[0106] 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 embodiments. It can be fully applied to various fields suitable for the present invention. For those skilled in the art, additional modifications can be easily made. Therefore, without departing from the general concept defined by the claims and the equivalent scope, the present invention is not limited to the specific details and the embodiments shown and described herein.

Claims

1. A polishing cloth, characterized in that: The invention relates to an elastic composite layer prepared by impregnating a fiber substrate twice with a foaming material; the foaming material comprises a primary impregnation slurry and a secondary impregnation slurry, the reaction raw materials of the primary impregnation slurry comprise 5-40wt% of diisocyanate, 40-60wt% of polyolefin polyol, 20-40wt% of polyester polyol, and 1-5wt% of aliphatic polyol, the reaction raw materials of the secondary impregnation slurry comprise a prepolymer and a polyamine compound, the reaction raw materials of the prepolymer comprise 10-25wt% of diisocyanate, 60-70wt% of polyolefin polyol, and 10-20wt% of aliphatic polyol or alicyclic polyol; The difference between the water absorption rate of the elastic composite layer at pH 7.0 and the water absorption rate at pH 10.0 after 6 hours is between 0.6% and 1.1%.

2. The polishing cloth according to claim 1, wherein The water absorption rate of the elastic composite layer in 6 hours is not more than 15%, the hardness of the elastic composite layer is 70-85A, and the density of the elastic composite layer is 0.3-0.6g / cm 3 The compression ratio of the elastic composite layer is 0-5%.

3. The polishing cloth according to claim 1, wherein The molar ratio of the prepolymer to the polyamine compound is (1.0-1.3):1.

0.

4. The polishing cloth according to claim 1, wherein The primary impregnation slurry also includes 1-5 wt% of sorbitan fatty acid ester.

5. The polishing cloth according to claim 1, wherein The molecular weight (Mn) of the polyolefin polyol is 1800-3000.

6. The polishing cloth according to claim 1, wherein The density of the fiber substrate is 0.10 to 0.30 g / cm 3 , thickness is 0.1~10mm.

7. The method for preparing the polishing cloth according to claim 1, characterized in that: The following steps are involved: S1, impregnating the fiber substrate in a DMF solution containing a primary impregnation slurry, immersing the fiber substrate in a coagulation bath for coagulation, washing with water, and drying to obtain a primary impregnation fiber substrate; S2, grinding the surface of the primary impregnated fiber substrate, impregnating it again in the organic solution of the secondary impregnation slurry, and drying it at 90-130° C. for 80-150 min to obtain an elastic composite layer; S3, cutting the elastic composite layer, applying with hot pressing, double-sided grinding, punching, and notching to obtain the grinding cloth.

8. The method for preparing the polishing cloth according to claim 7, characterized in that: The primary impregnation slurry accounts for 6-8wt% in the DMF solution of step S1; The reaction raw materials of the primary impregnation slurry include 5-40 wt% of diisocyanate, 40-60 wt% of polyolefin polyol, 20-40 wt% of polyester polyol, and 1-5 wt% of aliphatic polyol.

9. The method for preparing the polishing cloth according to claim 7, characterized in that: The organic solution in step S2 is a tetrahydrofuran / methyl ethyl ketone solution, and the secondary impregnation slurry accounts for 20-30 wt % of the organic solution; The secondary impregnation slurry comprises a prepolymer and a polyamine compound in a molar ratio of (1.0-1.3):1, and the reaction raw materials of the prepolymer comprise 10-25wt% of diisocyanate, 60-70wt% of polyolefin polyol, and 10-20wt% of aliphatic polyol.

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