A polishing pad substrate and a preparation method thereof

Abstract

The present invention relates to a polishing pad substrate and a preparation method thereof. The polishing pad substrate is obtained by reacting the following raw materials: polyester polyol, polyether polyol, isocyanate, chain extender, inorganic filler, catalyst, surfactant, and diluent. The present invention also provides a preparation method of the polishing pad substrate, which specifically includes the following steps: (1) Preparation of the first polymer: The polyester polyol and the polyether polyol react with the isocyanate under the action of the catalyst to form a hydroxyl-terminated prepolymer; (2) Preparation of the second polymer: A chain extender, isocyanate, and diluent are added to the first polymer to control the molecular weight of the polymer; (3) Preparation of the foaming slurry: The second polymer is mixed evenly with the inorganic filler, surfactant, and diluent; (4) Polyurethane foaming: The foaming slurry is degassed under vacuum, coated on a polyethylene terephthalate (PET) substrate, placed in a curing solution to shape the pores, and then washed with water and dried to obtain a polishing pad substrate with a pore structure. In the present invention, the molecular weight of the polymer is precisely controlled, the distribution is concentrated, and the synthesis conditions are mild and the process is stable. The polishing pad prepared by using it can improve the wafer grinding removal rate, reduce defects, and extend the service life.

Description

Technical Field

[0001] The present invention belongs to the technical field of polishing in chemical mechanical planarization, and particularly relates to a polishing pad substrate and a preparation method thereof. Background Art

[0002] Chemical mechanical polishing technology is one of the key technologies in the process of semiconductor wafer processing, and is widely used in the planarization process of various stages of wafer production. The polishing pad is an important part of chemical mechanical polishing. Different types of bladder holes and interconnected grooves exist on the surface of the polishing pad, which has the function of storing and uniformly transporting the polishing liquid, enhancing the grinding effect, and at the same time can timely discharge the debris generated during the grinding process, reducing the defect rate of the wafer surface.

[0003] Polyurethane (TPU) has a unique soft-hard segment inlaid structure. Polyester or polyether polyols endow TPU with certain flexibility, elasticity and good low-temperature performance. Isocyanates and small molecule diols endow TPU with certain hardness and strength, and have good mechanical properties and corrosion resistance. Therefore, it is widely used as an excellent polishing material in the field of semiconductor fine polishing.

[0004] At present, most of the CMP fine polishing pads used by domestic semiconductor manufacturers are imported. The domestic polyurethane-based polymer substrates have disadvantages such as wide molecular weight distribution, poor mechanical properties, and large surface roughness. At the same time, the prepared polishing pads have disadvantages such as low removal rate, high defect rate, and short service life. Summary of the Invention

[0005] In order to solve the problems of the currently required polyurethane resin for polishing pads, such as wide molecular weight distribution, poor mechanical properties, large surface roughness, and the prepared polishing pads having low removal rate, high defect rate, and short service life, a polishing pad substrate and a preparation method thereof are provided. The polishing pad substrate of the present invention has high molecular weight, narrow distribution, low surface roughness, good mechanical and mechanical properties, and at the same time has the advantages of high removal rate, low defect rate, and long service life.

[0006] In order to achieve the above object, the present invention is realized through the following technical solutions:

[0007] A polishing pad substrate and a preparation method thereof, comprising the following steps:

[0008] 1. Preparation of the first polymer: Polyester polyol and polyether polyol react with isocyanate under the action of a catalyst to form a hydroxyl-terminated prepolymer, control the isocyanate index R1 = 0.75 - 0.95, add a diluent, and control the viscosity to 4000 - 6000 mPa·s;

[0009] 2. Preparation of the second polymer: Add a chain extender, isocyanate and diluent to the first polymer, control the total isocyanate index R = 0.98 - 1.05, monitor the polymer molecular weight to reach 60,000 - 100,000 g / mol, add a capping agent, and control the viscosity to 120,000 - 180,000 mPa·s;

[0010] 3. Preparation of the foaming slurry: Mix the second polymer, inorganic filler, surfactant and diluent evenly, and control the viscosity to 3,000 - 15,000 mPa·s;

[0011] 4. Polyurethane foaming: After vacuum degassing the foaming slurry, coat it on the PET substrate, place it in the curing solution to shape the pores, and obtain the polishing pad substrate with a pore structure after washing and drying.

[0012] Further, the polyester polyol includes one or more combinations of polyethylene adipate, polybutylene adipate, polyhexylene adipate, polyethylene - butylene adipate, diethylene adipate, neopentyl glycol adipate, polycaprolactone, polycarbonate; the polyether polyol includes one or more combinations of polytetrahydrofuran, polypropylene oxide, polyethylene oxide, polypropylene oxide - ethylene oxide copolymer.

[0013] Further, the functionality f of the polyester polyol is 2, and the number - average molecular weight is 1,000 - 3,000 g / mol; the functionality f of the polyether polyol is 2 - 3, and the number - average molecular weight is 500 - 3,000 g / mol; the molar ratio of the polyester polyol to the polyether polyol is 3:1.

[0014] Further, the isocyanate includes aromatic isocyanate and aliphatic isocyanate; the aromatic isocyanate includes one or more combinations of 2,4 - toluene diisocyanate, 2,6 - toluene diisocyanate, 2,2’ - diphenylmethane diisocyanate, 2,4’ - diphenylmethane diisocyanate, diphenylmethane - 4,4’ - diisocyanate, 1,5 - naphthalene diisocyanate, p - phenylene diisocyanate, m - phenylene diisocyanate; the aliphatic isocyanate includes one or more combinations of 1,4 - cyclohexane diisocyanate, 4,4’ - dicyclohexylmethane diisocyanate, isophorone diisocyanate, norbornane diisocyanate.

[0015] Further, two - component isocyanate is used in the preparation of the first polymer, and one - component isocyanate is used in the preparation of the second polymer.

[0016] Further, the catalyst is 1,4-diazabicyclo[2.2.2]octane or dibutyltin dilaurate, the diluent is N,N-dimethylformamide, and the chain extender includes one or more combinations of ethylene glycol, propylene glycol, butylene glycol, 1,4-cyclohexanediol, and pure water; the end-capping agent is methanol or di-n-butylamine.

[0017] Further, the inorganic filler includes one or more combinations of carbon black, silica, calcium carbonate, cerium oxide, and iron oxide, and the particle size range is 30 to 100 nm; the surfactants used include one or more combinations of nonionic surfactants and anionic surfactants.

[0018] Further, the curing solution is an aqueous solution of N,N-dimethylformamide with a concentration of 2% to 25%; preferably, the concentration of N,N-dimethylformamide is 5% to 15%.

[0019] Beneficial effects:

[0020] 1. By using a two-component alcohol hydroxyl donor to adjust the soft / hard segment ratio, the resin has both flexibility and rigidity, optimizes the mechanical properties, and has better polishing performance.

[0021] 2. Through a stepwise polymerization method, a hydroxyl-terminated first polymer is reacted with isocyanate and a small molecule chain extender to obtain a multi-block copolymerized polyurethane resin. The molecular structure is reasonably designed, the resin has a more regular soft / hard segment distribution, good homogeneity, a more concentrated molecular weight distribution, and an extended service life.

[0022] 3. By controlling the diluent ratio, the polymerization reaction is more mild and controllable, which is beneficial to commercial scale-up production.

[0023] 4. By adjusting the types and contents of the inorganic filler and the surfactant, the polishing pad has a lower surface roughness and good myogenicity, a more uniform cell pore distribution, and more uniform pore diameters, which is beneficial to improving the grinding removal rate of the wafer surface and reducing the defect rate. Description of the drawings

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings described below are only a part of the embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0025] Figure 1 It is a process flow chart for preparing the polishing pad substrate.

[0026] Figure 2 It is an SEM image of the polishing pad substrate of Example 1. Specific embodiments

[0027] The embodiments of the present invention will be described in detail below in conjunction with examples. However, those skilled in the art will understand that the following examples are only used to illustrate the present invention rather than to limit the scope of the invention. For specific conditions not specified in the examples, they are carried out under conventional conditions or the recommended conditions of the manufacturer. For reagents or instruments without indicating the manufacturer, they can all be obtained as conventional products through commercial sales or purchases.

[0028] The polishing pad substrate of the present invention and its preparation method include the following steps:

[0029] 1. Preparation of the first polymer: Polyester polyol and polyether polyol are dehydrated to control the water content ≤ 150 ppm; then, under the action of a catalyst, they react with isocyanate to form a hydroxyl-terminated prepolymer. The reaction temperature is 60 - 100 °C; the reaction time is 2 - 5 h, the reaction pressure is atmospheric pressure, and the isocyanate index R1 = 0.75 - 0.95, where R1 is the molar ratio of isocyanate groups to hydroxyl groups in the first polymer system. A diluent is added to control the viscosity to 4000 - 6000 mPa·s;

[0030] 2. Preparation of the second polymer: A chain extender, isocyanate, and diluent are added to the first polymer. The reaction temperature is 60 - 100 °C, the reaction pressure is atmospheric pressure, and the total isocyanate index R = 0.98 - 1.05, where R is the molar ratio of total isocyanate groups to total hydroxyl groups in the system. The molecular weight of the polymer is monitored to reach 60000 - 100000 g / mol, and a capping agent is added to control the viscosity to 120000 - 180000 mPa·s;

[0031] 3. Preparation of the foaming slurry: The second polymer is mixed evenly with inorganic fillers, surfactants, and diluents. In the foaming slurry, there are 30 - 80 parts by mass of the second polymer, 1 - 8 parts by mass of inorganic fillers, 4 - 10 parts by mass of surfactants, and 20 - 70 parts by mass of diluents, and the viscosity is controlled to 3000 - 15000 mPa·s;

[0032] 4. Polyurethane foaming: After the foaming slurry is vacuum degassed, it is coated on a polyethylene terephthalate (PET) substrate and placed in an aqueous solution of N,N - dimethylformamide with different concentrations. It is cured for 30 min to fix the cell structure, and after washing with water and drying for 12 h, a polishing pad substrate with different cell structures is obtained.

[0033] Polyester polyol

[0034] In 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 but not limited to one or a combination of two or more of polyethylene adipate, polybutylene adipate, polyhexylene adipate, polyethylene glycol - butylene glycol adipate, diethylene glycol adipate, neopentyl glycol adipate, polycaprolactone, and polycarbonate.

[0035] In 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 from 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, resulting in poor planarization characteristics of the polishing pad.

[0036] Polyether polyol

[0037] In the present invention, the polyether polyol is selected from one or a combination of two or more polyether polyols with an average functionality of 2 - 3, specifically including but not limited to one or a combination of two or more of polytetrahydrofuran, polypropylene oxide, polyethylene oxide, and polypropylene oxide - ethylene oxide copolymer.

[0038] In the present invention, a polyether polyol with an average functionality of 2 - 3 is selected. By adjusting the average functionality of the polyether polyol, the cross - linking degree of the product is controlled, thereby obtaining polishing pad substrates with different hardnesses and elasticities. Specifically, when using a polyether polyol with an average functionality greater than 3, the hardness of the polyurethane substrate is too high, easily causing scratches on the workpiece, and cannot meet the requirements of fine polishing of the wafer surface; when using a polyether polyol with an average functionality less than 2, the polyurethane substrate is too soft, making it difficult to meet the required planar uniformity of the workpiece to be polished.

[0039] In the present invention, for controlling the hardness and resilience of the polishing pad substrate, regulating the ratio of soft and hard segments of the polyurethane molecular chain, and improving the removal rate of the polishing pad while reducing the surface defect rate of the workpiece after polishing, a combination of polyester polyol and polyether polyol is selected. Specifically, the molar ratio of polyester polyol to polyether polyol is 3:1.

[0040] Isocyanate

[0041] In the present invention, the isocyanate includes but is not limited to one or a combination of aromatic isocyanates or aliphatic isocyanates.

[0042] Aromatic isocyanates include, but are not limited to, one or a combination of more than one of 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 2,2'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, p-phenylene diisocyanate, and m-phenylene diisocyanate.

[0043] Aliphatic isocyanates include, but are not limited to, one or a combination of more than one of 1,4-cyclohexane diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, isophorone diisocyanate, and norbornane diisocyanate.

[0044] In the present invention, for considerations of reactivity and the use characteristics of the polishing pad, preferably, a two-component isocyanate is used in the preparation of the first polymer, and a one-component isocyanate is used in the preparation of the second polymer.

[0045] Particularly preferably, in the preparation process of the first polymer, a combination of 2,4-toluene diisocyanate and diphenylmethane-4,4'-diisocyanate is selected, and the molar ratio is 15:1 to 25:1; in the preparation process of the second polymer, 2,4-toluene diisocyanate or diphenylmethane-4,4'-diisocyanate is selected.

[0046] In the present invention, in order to obtain a polishing pad with desired polishing characteristics, the isocyanate index in the reaction process, that is, the molar ratio of isocyanate groups to hydroxyl groups in the system, is controlled. Among them, in the preparation of the first polymer, the isocyanate index R1 = 0.75 to 0.95. When R1 is greater than 0.95, it is difficult to generate a hydroxyl-terminated polyurethane prepolymer. When R1 is lower than 0.75, it is difficult to obtain a molecular chain structure with a pre-designed soft and hard block distribution. In the preparation of the second polymer, the total isocyanate index R = 0.98 to 1.05. When the total isocyanate index is outside the above range, it will cause the number-average molecular weight of the resin to be too large or too small, resulting in the inability to obtain the required resilience, hardness, and good muscle-forming properties, and reducing the polishing characteristics of the substrate.

[0047] Catalyst

[0048] In the present invention, the catalyst includes, but is not limited to, one or a combination of more than one of tertiary amine catalysts or organometallic catalysts. Among them, the tertiary amine catalysts include, but are not limited to, one or a combination of more than one of 1,4-diazabicyclo[2.2.2]octane, N,N-dimethylcyclohexylamine, benzyldimethylamine, triethylenediamine, and tetramethylbutanediamine. The organometallic catalysts include, but are not limited to, one or a combination of more than one of dibutyltin dilaurate, stannous octoate, dibutyltin bis(dodecyl sulfide), and dibutyltin diacetate.

[0049] The function of the catalyst in the present invention is to selectively accelerate the polymerization reaction.

[0050] Diluent

[0051] In the present invention, the diluent includes, but is not limited to, one or a combination of more of N,N-dimethylformamide, methyl ethyl ketone, cyclohexanone, tetrahydrofuran, dioxane polyurethane.

[0052] The function of the diluent in the present invention is to fully dissolve the polyurethane resin, making the polymerization reaction milder and more controllable, facilitating precise control of the molecular weight, and being more suitable for commercial scale-up production.

[0053] Chain extender

[0054] In the present invention, the chain extender includes, but is not limited to, one or a combination of more of ethylene glycol, propylene glycol, 1,4-butanediol, 1,4-cyclohexanediol, pure water, 1,6-hexanediol, glycerol, trimethylolpropane, diethylene glycol, triethylene glycol, neopentyl glycol, sorbitol, diethylaminoethanol.

[0055] Preferably, the chain extender includes, but is not limited to, one or a combination of more of ethylene glycol, propylene glycol, 1,4-butanediol, 1,4-cyclohexanediol, pure water.

[0056] The function of the chain extender in the present invention is to make the molecular structure of the polyurethane resin more uniform and the molecular weight higher, which is beneficial to improving the service life of the polishing pad and suppressing uneven polishing characteristics.

[0057] Inorganic filler

[0058] In the present invention, the inorganic filler includes, but is not limited to, one or a combination of more of carbon black, silica, calcium carbonate, cerium oxide, iron oxide, wherein the particle size range of the inorganic filler is 30 - 100 nm.

[0059] The function of the inorganic filler in the present invention is to improve the surface roughness, mechanical strength, enhance the polishing ability and reduce the cost.

[0060] Surfactant

[0061] In the present invention, the surfactant includes, but is not limited to, one or a combination of more of non-ionic surfactants, anionic surfactants.

[0062] The function of the surfactant in the present invention is to finely adjust the pore size and porosity of the polyurethane resin. Its plasticizing effect can reduce the problem of mechanical property degradation caused by the generation of irregular sponge-like pores and intramolecular crystallites, and reduce the surface defect rate of the workpiece after polishing.

[0063] Curing liquid

[0064] In the present invention, the curing liquid is a mixed liquid of DMF and water, wherein the concentration of DMF is 2% - 25%, preferably, the concentration of DMF is 5% - 15%.

[0065] In the present invention, the role of the curing liquid is to cause the polyurethane foaming slurry to undergo phase inversion and solidify into a film. By regulating the concentration of DMF, the pore shape and size of the foam can be controlled, forming a uniform and regularly arranged pore structure, which is beneficial to the storage of the polishing liquid and the departure of the particles during the polishing process, and further improves the removal rate of the polishing pad obtained.

[0066] Examples

[0067] To facilitate the understanding of the present invention, the following examples are listed. Those skilled in the art should understand that the examples are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0068] Explanation of the reference numerals in the examples:

[0069] AA / BG: Polybutylene adipate;

[0070] AA / EG: Polyethylene adipate;

[0071] AA / HG: Polyhexylene adipate;

[0072] PTMG: Polytetrahydrofuran;

[0073] PPG: Polypropylene oxide;

[0074] PEG: Polyethylene oxide;

[0075] MDI: Diphenylmethane - 4,4'-diisocyanate;

[0076] TDI: 2,4-Toluene diisocyanate;

[0077] DMF: N,N-Dimethylformamide;

[0078] The above raw materials are all commercially available bulk industrial products, and the manufacturers include BASF, Wanhua Chemical, Asahi Kasei Chemicals, Huafeng, etc.

[0079] The following are the methods for measuring the physical and chemical parameters and the calculation methods for other parameters:

[0080] Isocyanate index

[0081] The isocyanate index is the molar ratio of isocyanate groups to hydroxyl groups in the system and is calculated according to the following formula:

[0082]

[0083] Where: n is the molar amount of the substance, f is the functionality, PES is the polyester polyol, PEM is the polyether polyol, and PEX is the chain extender.

[0084] Molecular weight and polydispersity test

[0085] Refer to the national standard GB / T 27843-2011; Gel Permeation Chromatograph model: Agilent 1260 InfinityII.

[0086] Elastic modulus test

[0087] Refer to the national standard GB / T 1040.3-2006; Universal testing machine model: AGX-V2.

[0088] Glass transition temperature test

[0089] Refer to the national standard GB / T 19466.2-2004; DSC test instrument model: NEXTA DSC600.

[0090] Myogenicity test

[0091] Calculate according to the following formula:

[0092] Myogenicity K = H1 / H2 Formula 2

[0093] Where H1 is the thickness of the sample after drying, and H2 is the coating thickness of the sample.

[0094] Pore size and porosity test

[0095] Pore size: Take a picture of the sample using a scanning electron microscope, and scale the largest cell pore according to the magnification ratio, which is the pore size data of the sample;

[0096] Porosity test: Use the software Image Pro Plus 6.0 to process the scanning electron microscope images obtained by shooting, and calculate according to the following formula:

[0097] Porosity = S*N / 7741940.81 Formula 3

[0098] Where S is the average pore area, N is the number of pores within a certain area. The analysis method of the scanning electron microscope refers to the industry standard JY / T 0584-2020; Scanning electron microscope model: JEOL JSM-6510.

[0099] Surface roughness test

[0100] Refer to the national standard GB / T 14234-93; 3D optical profiler model: Gontour GT X.

[0101] Polishing layer density test

[0102] Calculate according to the following formula:

[0103] S.G = m / v = m / (3.14*R^2*h) Formula 4

[0104] Where m is the weight of the polishing layer, R is the radius of the polishing layer, and h is the thickness of the polishing layer.

[0105] Hardness test

[0106] Refer to national standard GB / T531-1999, equipment model TIME5430 A.

[0107] Polishing pad wear evaluation

[0108] The sample was cut into an 8-inch standard circle and attached to the polishing machine (polishing machine model UNIPOL-802). A disk (weight 3.7 kg) was placed on the sample. The speed was 130 n / min and the polishing time was 20 min. The mass change before and after polishing was recorded and calculated according to the following formula:

[0109] Wear amount = m1 - m2 Formula 5

[0110] Where m1 is the mass before polishing and m2 is the mass after polishing.

[0111] Removal rate evaluation

[0112] A four-probe film thickness meter (NAPSON Crestest / RG3000) was used to record the removal rate during the polishing process and calculate the average value.

[0113] Defect evaluation

[0114] The defects on the polished substrate after polishing are obtained using KLA-Tencor The SP2 defect inspection system is used for inspection, and the defect size is: 0.16μm; ○○ indicates almost no defect, ○ indicates very few defects, × indicates a few defects, ×× indicates a relatively large number of defects, and ××× indicates a large number of defects.

[0115] Polishing pad service life evaluation

[0116] The polishing pads in the embodiments and comparative examples were used in wafer planarization polishing tests, and their maximum service life was recorded.

[0117] Example 1

[0118] (1) Preparation of the first polymer: Heat the polyester polyol and polyether polyol to 140 °C, evacuate to -0.1 MPa until no liquid is discharged, and measure the water content < 150 ppm; Add the measured materials of AA / BG (f = 2, Mn = 2000): AA / EG (f = 2, Mn = 2000): PTMG (f = 2, Mn = 1000): PPG (f = 3, Mn = 3000) = 1.4:1.6:0.8:0.2 according to the molar ratio into the reaction kettle, mix evenly, then add MDI, TDI (MDI:TDI = 18:1) and 1,4-diazabicyclo[2.2.2]octane accounting for 0.1% of the total mass of the materials to carry out the catalytic reaction, control the isocyanate index R1 = 0.80, the reaction temperature is 85 °C, seal and react at atmospheric pressure for 3 h, then add DMF for dilution, and measure the viscosity of 4300 mPa·s.

[0119] (2) Preparation of the second polymer: Add ethylene glycol, MDI and DMF into the first polymer, control the total isocyanate index R = 1.02, and react at 85 °C under atmospheric pressure; Detect the molecular weight every 2 h. When the molecular weight of the polymer reaches 70000 g / moL, add the capping agent methanol to terminate the reaction, and measure the viscosity of 145000 mPa·s.

[0120] (3) Preparation of the foaming slurry: Mix the second polymer (45 parts), inorganic filler (3 parts), surfactant (4 parts of polyether-modified polysiloxane and 2 parts of sodium dioctyl sulfosuccinate) and DMF (46 parts) evenly, and measure the viscosity of 8000 mPa·s.

[0121] (4) Polyurethane foaming: After the foaming slurry is vacuum degassed, it is coated on the PET substrate, placed in a curing solution containing 12% DMF for 30 min, then washed with pure water for 12 h and dried to obtain a polishing pad substrate with a uniform cell structure.

[0122] The physical property indexes and performance parameters of the polishing pad substrate prepared in Example 1 are shown in Table 1.

[0123] Example 2

[0124] (1) Preparation of the first polymer: Heat the polyester polyol and polyether polyol to 140 °C, evacuate to -0.1 MPa until no liquid is discharged, and measure the water content < 150 ppm; Add the measured materials of AA / BG (f = 2, Mn = 2000): AA / HG (f = 2, Mn = 2000): PTMG (f = 2, Mn = 1000): PPG (f = 3, Mn = 2500) = 1.7:1.3:0.9:0.1 according to the molar ratio into the reaction kettle, after mixing evenly, add isocyanate (MDI: TDI = 23:1) and 1,4-diazabicyclo[2.2.2]octane accounting for 0.1% of the total mass of the materials to carry out the catalytic reaction, control the isocyanate index R1 = 0.90, the reaction temperature is 85 °C, react under normal pressure and seal for 2 h, then add DMF for dilution, and measure the viscosity to be 5400 mPa·s.

[0125] (2) Preparation of the second polymer: Add ethylene glycol, MDI and DMF into the first polymer, control the total isocyanate index R = 1.03, and react at 80 °C under normal pressure; Detect the molecular weight every 2 h. When the molecular weight of the polymer reaches 85000 g / mol, add the capping agent methanol to terminate the reaction, and measure the viscosity to be 163000 mPa·s.

[0126] (3) Preparation of the foaming slurry: Mix the second polymer (37 parts), inorganic filler (5 parts), surfactant (5 parts of polyether-modified polysiloxane) and DMF (53 parts) evenly, and measure the viscosity to be 9000 mPa·s.

[0127] (4) Polyurethane foaming: After the foaming slurry is vacuum degassed, it is coated on the PET substrate, placed in a curing solution containing 15% DMF for 30 min, then washed with pure water for 12 h and dried to obtain a polishing pad substrate with a uniform cell structure.

[0128] The physical property indexes and performance parameters of the polishing pad substrate prepared in Example 2 are shown in Table 1.

[0129] Example 3

[0130] (1) Preparation of the first polymer: Heat the polyester polyol and polyether polyol to 140 °C, evacuate to -0.1 MPa until no liquid is discharged, and measure the moisture content < 150 ppm; Add the metered materials of AA / HG (f = 2, Mn = 2000): AA / EG (f = 2, Mn = 2000): PTMG (f = 2, Mn = 1000): PEG (f = 3, Mn = 3000) = 1.6:1.4:0.7:0.3 according to the molar ratio into the reaction kettle, mix evenly, then add isocyanate (MDI:TDI = 17:1) and 1,4-diazabicyclo[2.2.2]octane accounting for 0.1% of the total mass of the materials to carry out the catalytic reaction, control the isocyanate index R1 = 0.80, the reaction temperature is 75 °C, react at normal pressure for 4 h, then add DMF for dilution, and measure the viscosity to be 4750 mPa·s.

[0131] (2) Preparation of the second polymer: Add butanediol, MDI and DMF into the first polymer, control the total isocyanate index R = 1.025, and react at 80 °C under normal pressure; Detect the molecular weight every 2 h. When the molecular weight of the polymer reaches 70000 g / mol, add the terminator dibutylamine to terminate the reaction, and measure the viscosity to be 158000 mPa·s.

[0132] (3) Preparation of the foaming slurry: Mix the second polymer (60 parts), inorganic filler (2 parts), surfactant (8 parts of sodium dioctyl sulfosuccinate) and DMF (30 parts) evenly, and measure the viscosity to be 10300 mPa·s.

[0133] (4) Polyurethane foaming: After the slurry is vacuum degassed, coat it on the PET substrate, place it in the curing solution containing 8% DMF for 30 min, then wash it with pure water for 12 h and dry it to obtain a polishing pad substrate with a uniform cell structure.

[0134] The physical property indexes and performance parameters of the polishing pad substrate prepared in Example 3 are shown in Table 1.

[0135] Example 4

[0136] (1) Preparation of the first polymer: Heat the polyester polyol and polyether polyol to 140 °C, evacuate to -0.1 MPa until no liquid is discharged, and measure the water content < 150 ppm; Add the metered materials of AA / HG (f = 2, Mn = 2000): AA / EG (f = 2, Mn = 2000): PPG (f = 2, Mn = 1000): PEG (f = 3, Mn = 3000) = 1.5:1.5:0.8:0.2 according to the molar ratio into the reaction kettle, mix evenly, then add isocyanate (MDI:TDI = 25:1) and 1,4-diazabicyclo[2.2.2]octane accounting for 0.1% of the total mass of the materials to carry out the catalytic reaction. Control the isocyanate index R1 = 0.90, the reaction temperature is 90 °C, and react at normal pressure for 2 h, then add DMF for dilution, and measure the viscosity to be 5400 mPa·s.

[0137] (2) Preparation of the second polymer: Add butanediol, MDI and DMF to the first polymer, control the total isocyanate index R = 1.035, and react at 75 °C under normal pressure; Detect the molecular weight every 2 h. When the molecular weight of the polymer reaches 85000 g / mol, add the end-capping agent di-n-butylamine to terminate the reaction, and measure the viscosity to be 161000 mPa·s.

[0138] (3) Preparation of the foaming slurry: Mix the second polymer (50 parts), inorganic filler (3 parts), surfactants (5 parts of polyether-modified polysiloxane and 3 parts of sodium dioctyl sulfosuccinate) and DMF (39 parts) evenly, and measure the viscosity to be 8400 mPa·s.

[0139] (4) Polyurethane foaming: After the slurry is vacuum degassed, it is coated on the PET substrate, placed in a curing solution containing 10% DMF for 30 min, then washed with pure water for 12 h and dried to obtain a polishing pad substrate with a uniform cell structure.

[0140] The physical property indexes and performance parameters of the polishing pad substrate prepared in Example 4 are shown in Table 1.

[0141] Comparative example

[0142] Heat the polyester and polyether polyols to 140 °C, evacuate to -0.1 MPa until no liquid is discharged, and measure the water content < 150 ppm. Add all the materials at one time according to the formula in Example 1, react at 85 °C throughout the process, and add methanol to terminate the reaction when the molecular weight reaches 70000 g / mol.

[0143] The forming process is the same as that in Example 1.

[0144] The physical property indexes and performance parameters of the polishing pad substrate prepared in the comparative example are shown in Table 1.

[0145] Table 1

[0146]

[0147]

[0148] Performance of the examples compared to that of the comparative examples:

[0149] 1. Under the condition of the same molecular weight (number-average molecular weight of 70,000 - 80,000), the polydispersity is smaller (2.23 < 2.78), and the molecular weight distribution is more concentrated;

[0150] 2. The resin has a greater elastic modulus, less wear amount, better wear resistance, and a longer service life;

[0151] 3. The myogenicity is significantly better, and the cell pore distribution is more uniform;

[0152] 4. The surface roughness is lower, and the number of defects on the wafer surface after planarization is less.

[0153] It should be noted that according to the above explanations and elaborations in the specification, those skilled in the art to which the present invention pertains can also make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some equivalent modifications and changes to the present invention should also be within the scope of protection of the claims of the present invention. In addition, although this specification uses some specific terms, these terms are only for convenience of description and do not constitute any limitation to the invention.

Claims

1. A preparation method of a polishing pad substrate, characterized in that, It includes the following steps: (1) Preparation of the first polymer: Polyester polyol and polyether polyol react with isocyanate under the action of a catalyst to form a hydroxyl-terminated prepolymer. Control the isocyanate index R1 = 0.75 - 0.95, add a diluent, and control the viscosity to be 4000 - 6000 mPa·s; (2) Preparation of the second polymer: Add a chain extender, isocyanate, and diluent to the first polymer. Control the total isocyanate index R = 0.98 - 1.05, monitor that the polymer molecular weight reaches 60000 - 100000 g / mol, add a capping agent, and control the viscosity to be 120000 - 180000 mPa·s; (3) Preparation of the foaming slurry: Mix the second polymer evenly with inorganic fillers, surfactants, and diluents, and control the viscosity to be 3000 - 15000 mPa·s; (4) Polyurethane foaming: After vacuum degassing the foaming slurry, coat it on a polyethylene terephthalate (PET) substrate, place it in a curing liquid to shape the pores, and obtain a polishing pad substrate with a pore structure after washing and drying; The polyether polyol includes one or more combinations of polytetrahydrofuran, polypropylene oxide, polyethylene oxide, and polypropylene oxide - ethylene oxide copolymer. The functionality f of the polyether polyol is 2 - 3. The polyester polyol includes one or more combinations of polyethylene adipate, polybutylene adipate, polyhexylene adipate, ethylene - butylene adipate, diethylene adipate, neopentyl glycol adipate, polycaprolactone, and polycarbonate. The functionality f of the polyester polyol is 2, and the number average molecular weight is 1000 - 3000 g / mol. The number average molecular weight of the polyether polyol is 500 - 3000 g / mol. The molar ratio of polyester polyol to polyether polyol is 3:1; In the preparation of the first polymer, a combination of 2,4 - toluene diisocyanate and diphenylmethane - 4,4'-diisocyanate is selected, and the molar ratio is 1:15 - 1:

25. In the preparation of the second polymer, 2,4 - toluene diisocyanate or diphenylmethane - 4,4'-diisocyanate is selected.

2. The preparation method of the polishing pad substrate according to claim 1, wherein: The catalyst is 1,4 - diazabicyclo[2.2.2]octane or dibutyltin dilaurate. The diluent is N,N - dimethylformamide. The chain extender includes one or more combinations of ethylene glycol, propylene glycol, 1,4 - butanediol, 1,4 - cyclohexanediol, and pure water. The capping agent is methanol or di - n - butylamine.

3. The preparation method of the polishing pad substrate according to claim 1, wherein: The inorganic fillers include one or more combinations of carbon black, silica, calcium carbonate, cerium oxide, and iron oxide, and the particle size range is 30 - 100 nm. The surfactants include one or more combinations of non - ionic surfactants and anionic surfactants.

4. The preparation method of the polishing pad substrate according to claim 1, characterized in that: The curing liquid is an aqueous solution of N,N - dimethylformamide, and the concentration is 5% - 15%.

5. A polishing pad substrate, characterized in that, The polishing pad substrate is prepared by the method described in any one of claims 1 - 4.

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