Soft chemical mechanical polishing pad as well as preparation method and application thereof

Abstract

The invention discloses a preparation method of a soft chemical mechanical polishing pad, the chemical mechanical polishing pad and application of the chemical mechanical polishing pad. The polishing layer of the chemical mechanical polishing pad is prepared by reacting an isocyanate prepolymer, polymer microspheres serving as filler and a bi-component curing agent formed by combining high-functionality polyol polyether and an amine curing agent. The density of the prepared polishing layer ranges from 0.6 g / cm < 3 > to 0.9 g / cm < 3 >, the Shore A hardness ranges from 50 A to 80 A, and the polishing layer has the remarkable advantage of being low in scratch.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical mechanical polishing pads, and in particular, to a soft chemical mechanical polishing pad, a preparation method thereof, and an application thereof. Background Art

[0002] In the manufacture of integrated circuits and other electronic devices, multiple layers of conductive media, semiconductors, and dielectric materials are deposited on the surface of a wafer, and are partially or selectively removed from the surface of the semiconductor wafer. Thin layers of conductive media, semiconductors, and dielectric materials can be deposited using a variety of deposition techniques. Common deposition techniques in modern wafer processing include physical vapor deposition (PVD, also known as sputtering), chemical vapor deposition (CVD), plasma enhanced chemical vapor deposition (PECVD), and electrochemical deposition (ECD), etc. Common removal techniques include wet and dry etching, etc.

[0003] As the sequential deposition and removal of wafer stack material layers progresses, the uppermost surface of the wafer becomes uneven. Since subsequent semiconductor processing (e.g., lithography, metallization, etc.) requires the wafer to have a flat surface, wafer planarization is needed.

[0004] Planarization can be used to remove unwanted surface topographies and surface defects, such as rough surfaces, agglomerated materials, lattice damage, scratches, and contamination layers or materials. In addition, in the damascene process, deposition materials are used to fill recessed areas created by patterned etching, but the filling step cannot be very precise, and overfilling may occur. Therefore, materials outside the recessed areas need to be removed.

[0005] Chemical mechanical planarization or chemical mechanical polishing (CMP) is a commonly used technique for planarizing or polishing workpieces such as semiconductor wafers and for removing excess materials in the damascene process. In traditional CMP, a wafer carrier or polishing head is mounted on a carrier assembly. The polishing head holds the wafer and positions the wafer in contact with the polishing surface of the polishing pad, and the polishing pad is mounted on a workbench or platen within a CMP device. The carrier assembly can provide a controllable pressure between the wafer and the polishing pad. At the same time, a slurry or other polishing medium is dispensed onto the polishing pad and is drawn into the gap between the wafer and the polishing layer. To achieve polishing, the polishing pad and the wafer generally rotate relative to each other. When the polishing pad rotates under the wafer, the wafer traverses a typical annular polishing track or polishing area, where the surface of the wafer directly faces the polishing layer. The wafer surface is polished and made planar by the chemical and mechanical action of the polishing surface and the polishing medium (e.g., slurry) on the surface.

[0006] The interaction between the polishing layer, the polishing medium, and the wafer surface during the CMP process has been the subject of increasing research and analysis, and the development of the polishing pad is a key point among them.

[0007] As early as in 1993, H.F. Reinhardt et al. proposed in Patent CN 1059219C a method of casting polyurethane mixed with microspheres into a block and cutting this block into several thin polishing pads. This has proven to be a feasible method for preparing porous polishing pads. Since CMP began as a key process in semiconductor manufacturing, most of the development of polishing pads has been similar, involving tests of many different porous and non-porous polymer materials and the mechanical properties of these materials. Most of the designs of the polishing surface or layer focus on providing various microstructures for these layers, or patterns of void regions and solid regions, as well as macrostructures, or arrangements of surface perforations or grooves, which are claimed to improve the polishing rate, improve polishing uniformity, or reduce polishing defects (scratches, pits, delaminated regions, and other surface or subsurface damages).

[0008] In subsequent patents such as CN100540225C, CN105382680B, CN107553313B, etc., the vast majority of the prepared polishing pads have a hardness greater than 40D. As semiconductor devices become increasingly complex, with finer features and more metal layers at the same time, this trend requires polishing to not only have a fast speed and improve efficiency, but also have lower scratches (polishing defects). The latter may cause open circuits or short circuits in the conductive metal layer, which will result in a significant reduction in the yield. Therefore, it is necessary to prepare a softer polishing pad that reduces polishing defects (such as micro-scratches or chatter marks). Summary of the Invention

[0009] The object of the present invention is to provide a method for preparing a soft chemical mechanical polishing pad, wherein the polishing layer of the polishing pad is a soft polyurethane porous material with a thickness of about 2 mm, which is very soft and elastic.

[0010] Another object of the present invention is to provide such a soft chemical mechanical polishing pad and its application.

[0011] To achieve the above-mentioned invention objects, the present invention adopts the following technical solutions:

[0012] A method for preparing a soft chemical mechanical polishing pad, wherein the polishing layer of the chemical mechanical polishing pad is made from an isocyanate prepolymer containing polymer microspheres and a curing agent as raw materials, and wherein the curing agent is a two-component curing agent comprising a diamine curing agent and a polyfunctional polyether polyol.

[0013] In some specific embodiments, the isocyanate prepolymer is an isocyanate prepolymer formed by reacting raw material components including TDI-80, 4,4'-dicyclohexylmethane diisocyanate (HMDI), polybutylene glycol (PTMG), and diethylene glycol (DEG); preferably, based on the total mass of each raw material component, TDI-80 accounts for 25-35%; HMDI accounts for 10-15%; PTMG accounts for 45-55%; DEG accounts for 10-15%.

[0014] In some specific embodiments, the unreacted isocyanate groups (NCO) in the isocyanate prepolymer account for 8.0-9.5% of the total mass of the isocyanate prepolymer.

[0015] In some specific embodiments, the curing agent includes: 10-40 wt% of a diamine curing agent, preferably selected from at least one of 3,3'-dichloro-4,4'-diaminodiphenylmethane (MOCA), 4,4'-bis(sec-butylamino)diphenylmethane and its isomers; and 60-90% of a polyfunctional polyether polyol, preferably a polyether polyol with a hydroxyl value of 400-1000 mg KOH / g and a functionality of 2-6.

[0016] In some specific embodiments, the stoichiometric ratio of the active hydrogen in the curing agent to the unreacted isocyanate groups in the isocyanate prepolymer is 0.85-1.05:1, preferably 0.85-0.95:1.

[0017] In some specific embodiments, the density of the polymer microspheres is 0.010-0.10 g / cm 3 , preferably 0.060-0.080 g / cm 3 ; preferably, the polymer microspheres are treated by air flow screening, and the particle size D50 of the treated polymer microspheres is 10-30 μm, and the particle size span Span is less than 1.2.

[0018] In some specific embodiments, the addition amount of the polymer microspheres is 0.1-10 wt%, preferably 1-5 wt%, of the mass of the polyurethane "cake" made from the isocyanate prepolymer containing polymer microspheres and the curing agent.

[0019] In some specific embodiments, a polyurethane "cake" is made from the isocyanate prepolymer containing polymer microspheres and the curing agent, cut into thin slices by a slicing machine, punched into discs of a certain size, and then surface grooved to form a groove pattern, and a buffer layer and a back glue are attached to finally obtain a soft chemical mechanical polishing pad.

[0020] On the other hand, for the soft chemical mechanical polishing pad prepared by the foregoing preparation method, preferably, the density of the polishing layer of the polishing pad is 0.6-0.9 g / cm3 The Shore A hardness is 50 - 80A, preferably 50 - 70A.

[0021] On the other hand, the application of the soft chemical mechanical polishing pad prepared by the foregoing preparation method in the chemical mechanical polishing of optical materials, semiconductor materials, metal materials, especially in silica, copper, tungsten, etc.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The soft chemical mechanical polishing pad prepared by the method of the present invention has significant advantages for materials or processes with high Partical sensitivity without sacrificing its polishing efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a scanning electron microscope photograph of impurity-containing polymer microspheres used in an embodiment of the present invention.

[0025] Figure 2 It is a schematic diagram of the eccentric circle pattern on the surface of the polishing pad of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] In order to better understand the technical solution of the present invention, the following embodiments will further illustrate the method provided by the present invention. However, the present invention is not limited to the listed embodiments, and should also include any other known changes within the scope of the claims of the present invention.

[0027] The flexible polyurethane chemical mechanical polishing pad for polishing semiconductor substrates of the present invention is composed of a multi-layer structure, which from top to bottom are a polishing layer, a buffer layer, and a support layer at the bottom. Among them, the top polishing layer is a soft polyurethane porous material with a thickness of about 2 mm, which is very soft and elastic. The buffer layer is made of foam, and a PET film as the support layer is attached to the bottom. The three components are bonded together by double-sided tape or hot melt adhesive to form the polishing pad.

[0028] The preparation process of the soft chemical mechanical polishing pad of the present invention uses an isocyanate prepolymer containing polymer microspheres and a curing agent as the main raw materials, mixes them in the stirring cavity of a casting machine, casts and vulcanizes to obtain a polyurethane "Cake", and then slices, punches, and forms a groove pattern on the surface, and bonds the buffer layer and the back glue to obtain a polyurethane polishing pad.

[0029] The isocyanate prepolymer is mainly prepared from aromatic isocyanates and aliphatic isocyanates, in combination with polymer polyols and small molecule chain extenders. The aromatic isocyanates include 2,4-dinitrotoluene, 2,6-dinitrotoluene, 2,4'-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, p-phenylene diisocyanate, benzylidene diisocyanate, 3,3'-dimethyl-4,4'-biphenyl diisocyanate, triphenylmethane triisocyanate, 4,4',4''-thiotri-phenyl phosphate triisocyanate, 3,3'-dimethyl-4,4'-diphenylmethane diisocyanate, etc. and their mixtures. The aliphatic isocyanates mainly include 4,4'-dicyclohexylmethane diisocyanate, cyclohexane dimethylene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, etc. and their mixtures. Preferably, the mass fraction of the aliphatic isocyanate in the prepolymer is at least 10%, and the mass fraction of the aromatic isocyanate component in the prepolymer is at least 26%. On the one hand, the aliphatic isocyanate can significantly reduce the reaction heat release rate and the maximum reaction heat release temperature. On the other hand, it can extend the gel time of the reaction between the isocyanate prepolymer and the curing agent.

[0030] The polymer polyols used for chain extension in the prepolymer are mainly divided into polyether polyols, polyester polyols and other oligomer polyols. The polyester polyols are selected from alkyd polyester polyols, polycaprolactone polyols (PCL), polycarbonate polyols, (PCDL), etc. and their mixtures. The polyether polyols include polyoxypropylene polyols, polytetrahydrofuran polyols (PTMG), copolymer polyethers, etc. and their mixtures. The small molecule chain extenders can be selected from diamines or small molecule polyols and alkanolamines, including 1,4-butanediol, ethylene glycol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, methylpropanediol, diethylene glycol, diethylene glycol monomethyl ether, dipropylene glycol, tripropylene glycol, butylethylpropanediol, diethylpentanediol, 3-methyl-1,5-pentanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-ethyl-1,3-hexanediol, 1,4-cyclohexanediol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, trimethylolpropane, glycerol, ethanolamine, etc. Considering various aspects such as the strength, dynamic mechanical properties, low temperature resistance, and hydrolysis resistance of the polishing pad, the optimal choice is PTMG and diethylene glycol and their blends.

[0031] Examples of suitable prepolymers within this range include: AdipreneTM L325, Adiprene LF600D, LF700D, LF750D, LF751D, LF753D, LF800A, LF900A, LF930AL, LF950A, etc. from Chemtura. Preferably, when the isocyanate prepolymer polyol is selected as PTMG and diethylene glycol, the isocyanate prepolymer has an unreacted NCO of 8.0 - 9.5% by weight.

[0032] In some preferred embodiments, the isocyanate prepolymer is formed by reacting raw material components including TDI - 80, 4,4'-dicyclohexylmethane diisocyanate (HMDI), poly(tetramethylene glycol) (PTMG), and diethylene glycol (DEG). Preferably, TDI - 80 accounts for 25 - 35% of the total mass of the raw material components, such as 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, etc.; HMDI accounts for 10 - 15%, such as 10%, 11%, 12%, 13%, 14%, 15%, etc.; PTMG accounts for 45 - 55%, such as 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, etc.; DEG accounts for 10 - 15%, such as 10%, 11%, 12%, 13%, 14%, 15%, etc. At the end point of the synthesis of the prepolymer, the unreacted isocyanate groups (NCO) account for 8.0 - 9.5% of the total mass of the prepolymer, such as 8%, 8.5%, 9%, 9.5%, etc. Among them, the method for judging the end point can refer to the prior art, and the present invention has no restrictions.

[0033] The polyurethane polishing pad is used in a solid state, and the mechanical properties exhibited under various external forces are the most important indicators of its use performance. The mechanical properties mainly depend on the regularity of the chemical structure, the intermolecular force, and the flexibility between macromolecules, that is, they depend on the crystallization tendency of the polyurethane, such as large molecular polarity, regular structure, and no side chain branches. However, during the polishing process, not only the strength of the material but also the elasticity of the polyurethane need to be considered, which requires finding a balance between the two at the use temperature. When selecting a curing agent, special care is needed.

[0034] In the present invention, the curing agent is a two-component curing agent, specifically a two-component curing agent containing a diamine curing agent and a polyfunctional polyether polyol. This two-component curing agent has more controllable heat release, longer pot life, better flexibility and elongation at break compared to the reaction of diamine curing agents and polyether polyamines.

[0035] The technical solution of the present invention uses a blend of diamines and polyfunctional polyether polyols as the curing agent. Among them, the diamine curing agents include 3,3'-dichloro-4,4'-diaminodiphenylmethane (MOCA), 3,5-dimethylthiotoluenediamine, 3,5-diethyltoluenediamine, 4,4'-methylenebis(2-chloro-2,6-diethylaniline) (MCDEA), 4,4'-methylenebisaniline (MDEA), 4,4'-methylenebis(2-isopropyl-6-methyl)aniline, 4,4'-methylenebis(2-methyl-6-diethylaniline), 4,4'-methylenebis(2-ethylaniline), propanediamine bis(4-aminobenzoate), 4,4'-bis(sec-butylamino)diphenylmethane, 1,4-bis(sec-butylamino)benzene, isobutyl 3,5-diamino-4-chlorobenzoate, 2,4-diamino-3,5-dimethylthiochlorobenzene, toluenediamine, 2,4-diamino-3-methylthio-5-propyltoluene, 4,4'-diaminodicyclohexylmethane, trimethylethylenediamine, 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane, and quinidine diamine. More preferably, 3,3'-dichloro-4,4'-diaminodiphenylmethane (MOCA) and 4,4'-bis(sec-butylamino)diphenylmethane and their isomers are selected, and they account for 10-40 wt% of the total mass of the curing agent.

[0036] The preferably used polyfunctional polyether for forming the curing agent has 2-6 hydroxyl groups per molecule, and its hydroxyl value is 400-1000 mg KOH / g, accounting for 60-90 wt% of the entire curing agent system. It includes polyoxypropylene triol with glycerol, trimethylolpropane, ethanolamine, diethanolamine, triethanolamine, etc. as initiators; polyether tetrol with ethylenediamine, pentaerythritol, toluenediamine, methylenedianiline as initiators, and polyether pentol prepared by ring-opening polymerization of diethylenetriamine or xylitol with propylene oxide as the initiator; and hexahydroxy polyether obtained with sorbitol, mannitol, sucrose, diethylenetriamine, triethylenetetramine, etc. as initiators. Examples of commercially available polyhydroxy polyol curing agents include polyols from Dow Chemical Company Polyether from Arch Chemicals, Inc. in the United States, Actcol series polyethers from Mitsui Chemicals, Japan, and polyfunctional polyethers produced by many companies such as Shandong Bluestar Dongda Chemical Co., Ltd., the polyurethane division of Shanghai Gaojiao Petrochemical Company, Nanjing Hongbao Li, and Hebei Yadong in China.

[0037] Taking Hebei Yadong as an example, the following table lists various preferred high-molecular-weight polyol curing agents.

[0038]

[0039] In a preferred embodiment, the curing agent comprises: 10-40 wt% of a diamine curing agent, such as 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt% of a diamine curing agent, preferably selected from at least any one of 3,3'-dichloro-4,4'-diaminodiphenylmethane (MOCA), 3,5-dimethylthiotoluenediamine, 3,5-diethyltoluenediamine, 4,4'-methylenebis(2-chloro-2,6-diethylaniline) (MCDEA), 4,4'-methylenebisaniline (MDEA), 4,4'-methylenebis(2-isopropyl-6-methyl)aniline, 4,4'-methylenebis(2-methyl-6-diethylaniline), 4,4'-methylenebis(2-ethylaniline), propanediamine bis(4-aminobenzoate), 4,4'-bis(sec-butylamino)diphenylmethane, 1,4-bis(sec-butylamino)benzene, isobutyl 3,5-diamino-4-chlorobenzoate, 2,4-diamino-3,5-dimethylthiochlorobenzene, toluenediamine, 2,4-diamino-3-methylthio-5-propyltoluene, 4,4'-diaminodicyclohexylmethane, trimethylethylenediamine, 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane, and quinidine diamine, more preferably selected from at least any one of 3,3'-dichloro-4,4'-diaminodiphenylmethane (MOCA) and 4,4'-bis(sec-butylamino)diphenylmethane and its isomers; and 60-90% of a polyfunctional polyether polyol, such as 60%, 70%, 80%, 90% of a polyfunctional polyether polyol, the polyfunctional polyether polyol being initiated with a polyhydroxy, primary amino group-containing compound or an alkanolamine, and polymerized by ring-opening homopolymerization or copolymerization using an epoxide such as ethylene oxide and propylene oxide; preferably a polyether polyol having a functionality of 2-6, such as 2, 3, 4, 5, 6, and a hydroxyl value of 400-1000 mg KOH / g, such as a hydroxyl value of 400 mg KOH / g, 500 mg KOH / g, 600 mg KOH / g, 700 mg KOH / g, 800 mg KOH / g, 900 mg KOH / g, 1000 mg KOH / g, etc.

[0040] In the present invention, in addition to controlling the mass fraction of unreacted NCO, it is also required that the stoichiometric ratio of active hydrogen (such as NH2, OH, etc.) in the curing agent to the unreacted isocyanate in the isocyanate prepolymer is 0.85-1.05, such as 0.85, 0.9, 0.95, 1, 1.05, etc., and preferably 0.85-0.95 for the polyurethane polishing pad to have the best effect.

[0041] In the present invention, the polymer microspheres used are composed of a polymer shell and internal gas. The constituent materials of the polymer shell include at least one of polyacrylonitrile, polyethylene, polypropylene, polydecaneamide, polycaprolactam, poly(decamethylene sebacate), poly(decane-1,10-dicarboxylic acid ethylene ester), poly(dodecane-1,10-dicarboxylic acid ethylene ester), poly(ethylene adipate), polyoctanamide, polyaluminum chloride, polyacrylamide, polyaminophenol, polyaramide, polysulfone, poly(butadiene-acrylonitrile), poly(butylene terephthalate), polycarbonate, poly(cyclohexanedimethanol terephthalate), diallyl isophthalate, diallyl terephthalate, polyether ester fiber, polyethylene glycol, polyethylene oxide, poly(ethylene oxide), polyethylene naphthalate, polyvinylidene fluoride, polyvinylidene chloride, isobutyronitrile, etc. The most preferred are polyvinylidene chloride and polyacrylonitrile shells, or polyacrylonitrile / methacrylonitrile shells. The hollow part of the microspheres is air, nitrogen, carbon dioxide, argon, neon, ethane, butane, etc. The most preferred is isobutane gas. The preparation method of the microspheres can refer to the prior art and is not particularly limited. They can also be directly purchased externally, such as the expanded microspheres of AkzoNobel. The qualified microsphere products are preferably WANHUA Vesmody E620.

[0042] In the present invention, the polymer microspheres are preferably treated by air classification, and their density ranges from 0.010 to 0.10 g / cm 3 , such as 0.010 g / cm 3 , 0.020 g / cm 3 , 0.030 g / cm 3 , 0.040 g / cm 3 , 0.050 g / cm 3 , 0.060 g / cm 3 , 0.070 g / cm 3 , 0.080 g / cm 3 , 0.090 g / cm 3 , 0.10 g / cm 3 etc. After screening, the unnecessary components in the microspheres are: 1) impurities in the microsphere manufacturing process, including metal particles, etc.; 2) parts with relatively low density in the microspheres, including parts with significantly larger size and thinner shells after excessive expansion of the microspheres; 3) parts with relatively high density in the microspheres, including damaged microsphere shells during the expansion process inside the microspheres and irregular agglomerated lumps formed by microsphere aggregation. All or part of the above components are screened out to improve the uniformity of the polymer microspheres. Preferably, the density of the screened microspheres is controlled at 0.060 - 0.080 g / cm 3, the D50 of the processed polymer microspheres is mainly distributed in the range of 10 - 30 μm, such as 15 μm, 20 μm, 25 μm, 30 μm, etc., and the particle size span Span is less than 1.2, such as 1.15, 1.1, 1.05, etc. (D50 is the median particle size; Span = (D90 - D10) / D50, where D10 and D90 are the particle sizes corresponding to the cumulative volume distribution reaching 10% and 90% respectively, that is, the particles with particle sizes less than D10 and D90 account for 10% and 90% of the total volume respectively).

[0043] The particle size of the polymer microspheres used as fillers is, for example, 10 - 100 μm, the addition amount of the microspheres is 0.1 - 10 wt%, preferably 1 - 5 wt%, and the density is 0.010 - 0.10 g / cm 3 , in order to maintain a high porosity while effectively reducing the defects in the polishing process and reducing the occurrence of defects during the dispersion and casting processes, the microspheres used as fillers are specially treated microspheres with a uniform particle size distribution. After screening, the particle sizes are generally distributed in the range of 10 - 30 μm, and the mass fraction accounts for 0.1 - 4 wt%, and the density is controlled at 0.06 - 0.08 g / cm 3 .

[0044] In the method for preparing the polishing layer of the chemical mechanical polishing pad of the present invention, the prepolymer mixed with microspheres and the curing agent are mixed and cast by a stirring head. After curing, the cake is sliced and sanded, and the thickness of the polishing layer is 2.03 μm, and the density is 0.6 - 0.9 g / cm 3 , the Shore A hardness is 50 - 80 A, preferably 50 - 70 A. Then, through surface grooving and punching, an eccentric circular groove pattern is formed, and the buffer layer and the back glue are attached, and finally a low-defect polyurethane polishing pad is obtained.

[0045] In a specific embodiment, a soft polyurethane chemical mechanical polishing pad, the composition of its polishing layer is composed of an isocyanate prepolymer mainly based on TDI - 80 / HMDI / PTMG / DEG, a curing agent mixed with 3,3'-dichloro - 4,4'-diaminodiphenylmethane (MOCA) and a polyfunctional polyether, and polymer microspheres used as fillers.

[0046] The present invention controls the density of the polyurethane polishing pad by controlling the addition amount of the microspheres. The density of the polishing pad is preferably 0.6 - 0.9 g / cm 3 , the Shore A hardness is 50 - 80 A, preferably 50 - 70 A.

[0047] The polishing pad of the present invention including the aforementioned polishing layer is suitable for polishing the surface of silicon wafers, and is also applicable to polishing inorganic materials in semiconductor substrates, such as copper, silicon dioxide, tungsten, etc.; and organic materials, such as polyimide, etc.

[0048] The present invention will be further described below through specific embodiments. The embodiments of the present invention are only for the description of the present invention and do not limit the scope of the present invention.

[0049] Unless otherwise specified, the polishing pads of the embodiments and comparative examples of the present invention can be prepared by the following method:

[0050] (1) Sieving treatment of polymer microspheres

[0051] Use Expancel from Nouryon @ Microspheres 461DE20d70, Figure 1 which are polymer microspheres containing impurities (microsphere skins and agglomerated irregular lumps). The expanded polymer microspheres are added to the hopper of the air sieve through a peristaltic pump. After starting the equipment, the microspheres pass through the screw conveyor system, are mixed with the air flow, atomized and then enter the mesh cylinder. Under the dual action of the rotation of the mesh cylinder and the wind, the microspheres penetrate through a 200-mesh 316L stainless steel filter screen and enter the discharge port, while the materials that cannot pass through the net, such as metal impurities, burst skins in the microspheres, and large-sized microspheres or microsphere lumps, are discharged from the impurity discharge port along the wall of the mesh cylinder.

[0052] The density of the sieved microspheres was measured using an automatic gas displacement true density meter ACCUPYC II 1345, and the particle size change of the microspheres was measured using a laser particle size distribution analyzer Bettersize 2600. See Table 1 below.

[0053] Table 1

[0054]

[0055] From the data in the table, it can be seen that the particle size distribution of the sieved microspheres is significantly narrowed, and large-sized impurity particles are filtered out, resulting in an increase in the median particle size of the sieved microspheres.

[0056] (2) Table 2 lists the polishing layers of nine embodiments of the present invention and two comparative examples. The microspheres used in the embodiments and comparative examples are all selected from Expancel @ Microspheres 461DE20d70 after sieving. The unreacted isocyanate NCO of the used isocyanate prepolymer is 8.95 - 9.35 wt%, and the curing agents are 3,3'-dichloro-4,4'-diaminodiphenylmethane (MOCA), YD-403 from Yadong Company, and amino-terminated polypropylene oxide ether D-230 from Huntsman Company, USA. The molar ratio of the amine group of the curing agent to the unreacted NCO of the isocyanate prepolymer is measured according to 0.9. Expancel @The addition amount of microspheres 461DE20d70 accounts for 2-5 wt% of the mass of polyurethane. Sieved or unsieved microspheres with different mass fractions are respectively mixed into the prepolymer, and then poured into a mold with a diameter of 680 mm through a casting head at 1700 r / min to form a polyurethane Cake with a height of about 10 cm. The polyurethane Cake is transferred to an oven at 106 °C for 16 h. After curing is completed, the temperature is lowered to room temperature, and the Cake is taken out from the mold in the oven and cut into slices with a thickness of 80 mil at room temperature. During the slicing process, incomplete slices on the surface layer are discarded, and the thickness of the slices is measured.

[0057] Table 2

[0058]

[0059]

[0060] Comparative Examples 1-3 and Examples 1-9 are respectively qualified groove-free polishing layer materials with no defects in appearance and a thickness of about 2.03 mm after casting and slicing. Then, their physical properties are measured, and the performance is shown in Table 3. The density data shown in the table is measured according to GB4472-84; the recorded Shore D hardness data is measured according to ISO 7619D; the recorded Shore A hardness data is measured according to ISO 7619A, and the tensile modulus, elongation at break, and fracture toughness data are measured according to GB / T528-2009.

[0061] Table 3

[0062]

[0063]

[0064] The difference between Examples 1 and 2 of the present invention and Comparative Example 1 is that the curing agent is MCOA mixed with YD-403, and the addition amount of Example 2 is more than that of Example 1. At the same density, as the addition amount of YD-403 increases, its hardness decreases. The same is true for the other examples. Comparing Examples 1-9 with the corresponding Comparative Example 1 and Comparative Example 2, the hardness of the polishing layer cast with the mixed curing agent is between the two. Without considering the microspheres, by adjusting the addition amount, the hardness, tensile modulus, elongation at break, and fracture toughness of the polishing layer can be controlled. The ratio of microspheres to the curing agent jointly affects the physical properties of the polishing layer.

[0065] Examples 1-9 are different from Comparative Example 3 in that the curing agent selected in the examples is a combination of MOCA and polyether polyol, while Comparative Example 3 is a combination of MOCA and polyether polyamine. From the perspective of the approximate NCO step reaction, when comparing Example 8 with Comparative Example 3 in terms of the curing agent component, using polyether polyol is more conducive to reducing the hardness of the polishing layer, and at the same time has a higher tensile modulus, elongation at break, and fracture toughness.

[0066] Table 3 shows that the wafers of the examples and comparative examples applicable to wafer surface planarization of the present invention are die-cut after lamination, and then the surface is patterned in the form of an eccentric circle. The polishing pad adopts the design scheme of an eccentric circle as Figure 2 shown, including a polishing layer having a plurality of geometric centers instead of a common geometric center, and having a plurality of offset circular grooves. Each radial groove is spaced a certain distance from its nearest or adjacent one or more radial grooves, but the distances are not the same. For example, the spacing increases in the half or hemisphere of the polishing layer that is farthest from the off-center eccentric circle, and decreases in the half that is closest to the geometric center. Specifically, the polishing layer includes a complete and continuous outermost peripheral groove. The groove has a depth of 0.80 mm, and the polishing layer is laminated with SUBA IV (DOW) to obtain a polishing pad with a diameter of 300 mm.

[0067] (3) Polishing conditions: The polishing pressure is 1.5 psi for all, the rotational speeds of the polishing platen and the polishing head are 87 / 93 rpm, the polishing liquid is CuSlurry (diluted 11 times, pH 6-7), the polishing pad dressing wheel is 3M A165, and the flow rate of the polishing liquid is 250 ml / min. The polishing machines are all E460E / 12 type 300 mm chemical mechanical planarization systems.

[0068] The stopwatch timing method is used to count the service life of the polishing pad. The Four Dimensions four-point detector (333A) is used to measure the thickness of 81 test points on the copper film, and the average difference is calculated based on the measurement results before and after polishing to determine the copper polishing rate (RR), and the surface non-uniformity (N.U. = Std / Avg) is calculated based on the standard deviation of the measurement rates of 81 points. The Dektak 150 profilometer is used to test the flatness of the wafer from the edge to the center using the probe profiling technique. Two mutually perpendicular radii are selected for testing, and the scratch size and quantity are counted.

[0069] The polishing test results of each example and comparative example are shown in Table 4:

[0070] Table 4

[0071]

[0072]

[0073] To meet the requirements of the efficient and high-speed development of integrated circuits and the subsequent deposition process in IC manufacturing, the requirements for the surface of Cu wafers after Cu CMP process are the copper polishing rate inconsistency ≤ 5%, number of scratches (max <0.09μm) < 20, and polishing life ≥ 24h.

[0074] From the polishing experiment results, it can be seen that when comparing Comparative Example 1 and Comparative Example 2, each has its own advantages. Among them, Comparative Example 1 has a fast polishing rate RR and a higher polishing life, but it performs poorly in terms of the number of scratches and inconsistency. On the contrary, Comparative Example 2 has a lower hardness, better number of scratches and inconsistency, but lacks a good polishing rate and polishing life. When comparing Examples 1 - 8 of the chemical mechanical polishing pad provided by the present invention with Comparative Examples 1 and 2, it is obvious that after curing with two mixed curing agent components, the comprehensive performance of the polishing pad is better than that of using a single curing agent.

[0075] Combined with the above table, it can be found that the difference between Examples 1, 2, 3, 4 and Comparative Example 1 is that they are mixed with YD - 403. The addition amount of YD - 403 in Example 2 is more than that in Example 1. As the addition amount of YD - 403 increases, its hardness decreases. Comparing the results after polishing, it is found that the polishing rates RR of Examples 1 and 2 are slightly lower than that of Comparative Example 1. At the same time, the inconsistency, number of scratches and polishing life also decrease accordingly, indicating that hardness affects the polishing rate and the influence factor is positively correlated. In addition, too fast polishing speed, in turn, affects the inconsistency, number of scratches and polishing life. In addition, Examples 5 and 6 also show the same rule when compared with Comparative Example 2. Examples 5 and 6 have a polishing rate close to that of Comparative Example 3, but are significantly better than Comparative Example 3 in terms of the number of scratches and inconsistency.

[0076] Among them, the inconsistency, number of scratches, polishing rate and polishing life of the surfaces after polishing of Examples 6 - 8 meet the process requirements. At the same time, they have a good polishing rate and polishing life, and there is a significant reduction in inconsistency and number of scratches. It further proves the improvement in the formula, reduces the defect degree of the polishing pad, effectively improves the utilization rate of the polishing liquid and the flatness of the surface after polishing. It is possible to modify the performance of the polishing pad while reducing the scratch rate, which helps to further improve the performance of the polishing pad.

[0077] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the method of the present invention, several improvements and supplements can still be made, and these improvements and supplements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a soft chemical mechanical polishing pad, characterized in that, The polishing layer of the chemical mechanical polishing pad is made from an isocyanate prepolymer containing polymer microspheres and a curing agent, wherein the curing agent is a two-component curing agent comprising a diamine curing agent and a polyfunctional polyether polyol.

2. The preparation method according to claim 1, characterized in that, The isocyanate prepolymer is an isocyanate prepolymer formed by reacting raw material components including TDI-80, 4,4'-dicyclohexylmethane diisocyanate (HMDI), polybutylene glycol (PTMG), and diethylene glycol (DEG); preferably, based on the total mass of each raw material component, TDI-80 accounts for 25-35%; HMDI accounts for 10-15%; PTMG accounts for 45-55%; DEG accounts for 10-15%.

3. The preparation method according to claim 1 or 2, characterized in that, The unreacted isocyanate groups (NCO) in the isocyanate prepolymer account for 8.0-9.5% of the total mass of the isocyanate prepolymer.

4. The preparation method according to claim 1, wherein The curing agent contains: 10-40 wt% of a diamine curing agent, and 60-90% of a polyfunctional polyether polyol, preferably a polyether polyol with a hydroxyl value of 400-1000 mg KOH / g and a functionality of 2-6; Preferably, the diamine curing agent is selected from at least one of 3,3'-dichloro-4,4'-diaminodiphenylmethane (MOCA), 3,5-dimethylthiotoluenediamine, 3,5-diethyltoluenediamine, 4,4'-methylenebis(2-chloro-2,6-diethylaniline) (MCDEA), 4,4'-methylenebisaniline (MDEA), 4,4'-methylenebis(2-isopropyl-6-methyl)aniline, 4,4'-methylenebis(2-methyl-6-diethylaniline), 4,4'-methylenebis(2-ethylaniline), propanediamine bis(4-aminobenzoate), 4,4'-bis(sec-butylamino)diphenylmethane, 1,4-bis(sec-butylamino)benzene, isobutyl 3,5-diamino-4-chlorobenzoate, 2,4-diamino-3,5-dimethylthiochlorobenzene, toluenediamine, 2,4-diamino-3-methylthio-5-propyltoluene, 4,4'-diaminodicyclohexylmethane, trimethylethylenediamine, 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane, and quinenediamine, more preferably selected from at least one of 3,3'-dichloro-4,4'-diaminodiphenylmethane (MOCA) and 4,4'-bis(sec-butylamino)diphenylmethane and its isomers.

5. The preparation method according to any one of claims 1 to 4, characterized in that, The stoichiometric ratio of the active hydrogen in the curing agent to the unreacted isocyanate groups in the isocyanate prepolymer is 0.85-1.05:1, preferably 0.85-0.95:

1.

6. The preparation method according to any one of claims 1 to 5, characterized in that, The density of the polymer microspheres is 0.010 - 0.10 g / cm 3 , preferably 0.060 - 0.080 g / cm 3 ; Preferably, the polymer microspheres are treated by air flow screening, and the particle size D50 of the treated polymer microspheres is 10 - 30 μm, and the particle size span Span is less than 1.

2.

7. The preparation method according to any one of claims 1 to 6, characterized in that, A polyurethane "cake" is made from an isocyanate prepolymer containing polymer microspheres and a curing agent, sliced into thin slices by a slicing machine, punched, and surface patterned to form a groove pattern, and then bonded to a buffer layer and a back glue to obtain a soft chemical mechanical polishing pad.

8. The preparation method according to claim 7, characterized in that, The addition amount of the polymer microspheres is 0.1-10 wt% of the mass of the polyurethane "cake" made, preferably 1-5 wt%.

9. The soft chemical mechanical polishing pad prepared by the preparation method according to any one of claims 1 to 8, preferably, the density of the polishing layer of the polishing pad is 0.6-0.9 g / cm 3 , the Shore A hardness is 50-80 A, preferably 50-70 A.

10. Use of the soft chemical mechanical polishing pad prepared by the preparation method according to any one of claims 1 to 8 or the soft chemical mechanical polishing pad according to claim 9 in optical materials, semiconductor materials, metal materials, especially in chemical mechanical polishing of silica, copper and tungsten.

Images