A method of making a polyurethane polishing pad by a solventless doctor blade coating process

Abstract

The application discloses a kind of polyurethane polishing pad prepared by solventless blade coating method, comprising the following steps: step one, slurry preparation: with mass fraction, polyurethane prepolymer 100 parts, stannous octoate 0.3-1 parts, silicone foam stabilizer 0.3-1 parts, water 0.09-0.94 parts, microsphere foaming agent 0.3-2.5 parts, 3.21-4.64 parts of trimethylolpropane, 1,4-butanediol 6.42-9.27 parts are loaded into reaction kettle, and stirred uniformly;Step two, using dry production line, slurry is cast on polyester film, and blade coating is formed into film, then it is cured at 70-160 DEG C temperature for 20-60 min, after cooling, it is coiled, and polyurethane / polyester film composite material is obtained;Step three, polyurethane / polyester film composite material is skinned;Step four, after cutting, runner engraving, polishing pad is obtained;Process is simple, cost is low, can adjust the cell rate, cell size, crosslinking degree, coating thickness, hardness of polishing pad according to demand, and the performance of polishing pad is improved, and solventless process is used, and environment-friendly and pollution-free.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of semiconductor processing equipment, and relates to a polishing pad for semiconductor processing, in particular to a method for preparing a polyurethane polishing pad by means of a solvent-free doctor blade coating method. BACKGROUND

[0002] Semiconductor material is the basis of modern integrated circuit industry and the material carrier for integrated circuit manufacturing, and has important strategic significance for today's society. At present, chemical mechanical polishing (CMP) technology is adopted for chip polishing. In a fixed polishing machine, a polishing liquid is applied to a polishing pad, the polishing pad is in contact with the surface of a wafer, a chemical reaction occurs, and the polishing pad and the wafer perform a rotating motion on the machine to produce a shearing mechanical action. The chemical action and the mechanical action together polish the wafer. In the CMP polishing process, the service life of the polishing pad is very short, generally 45-75 hours, and the polishing pad is a consumable.

[0003] Different wafers have different process flows and polishing requirements. Currently, there are generally three methods for manufacturing polishing pads, namely, a wet solidification forming process, a reaction forming process and a thermoplastic forming process.

[0004] The wet solidification forming process originates from the polyurethane synthetic leather process, and the product is called polishing leather. A slurry of polyurethane, dimethylformamide (DMF) and fillers is applied to a substrate by means of doctor blade coating, and then enters a solidification bath composed of DMF and water. Since DMF is infinitely miscible with water, water displaces DMF, so that the polyurethane is solidified into a film with a microporous structure, and finally a microporous polyurethane film and the substrate form a composite material. Then, the substrate is cut into a sheet with a desired shape, and a lathe or cutting machine is used to cut the surface of the polishing pad to form the required groove pattern to obtain the polishing pad. In general, the substrate is a fiber sheet or a polyester (PET) film. This process is suitable for the production of soft polishing pads, and the biggest problem is the pollution of DMF. Since DMF is used as a solvent in the production process, it will cause environmental pollution. Moreover, there will be residual DMF solvent in the product, which will affect the safety of the product.

[0005] The production of reaction forming type polishing pads adopts a casting reaction forming process. The process is to mix polyurethane prepolymer and chain extender, pour them into a mold, and form a polymer by reaction. In order to form specific cells in the formed body, various foaming aids need to be added. The formed body is cut into sheets with various thicknesses and shapes according to needs, and then the substrate is attached, and a lathe or cutting machine is used to cut the surface to perform runner engraving, so as to form the required groove pattern to obtain the polishing pad. This process is more suitable for the production of hard polishing pads, and there is no pollution in the production process.

[0006] The polymer material needs to be injected into the mold for molding, and the reaction molding is taken out from the mold, the surface layer is removed, the cutting is performed according to the required thickness, the runner is engraved, and the base material is bonded. The process is very complicated, time-consuming, and the thickness is not easy to control when the surface layer is removed and cut according to the required thickness, which will affect the stability of the polishing pad during use.

[0007] The preparation process of the thermoplastic polyurethane polishing pad is similar to the calendering process of the thermoplastic polyurethane synthetic leather. The thermoplastic polyurethane particles and additives are prepared according to the formula, mixed, plasticized by closed mixing and fine plasticizing, extruded by a screw extruder, then fed into a calendering machine, and calendered into a film according to the required thickness of the polishing pad. Then, the film is bonded with the base material, cut into the required shape of the sheet, and the surface of the polishing pad is cut by a lathe or cutting machine to form the required groove pattern to obtain the polishing pad.

[0008] Although the thermoplastic polyurethane polishing pad can be arranged and combined in various types according to the formula and performance, it is still very difficult to develop high-end polyurethane polishing pads according to the mutual restrictions of raw materials during formula design and industrial production. The processing and molding properties of the thermoplastic polyurethane polishing pad production process are poor, and the cost is high. SUMMARY

[0009] In view of the deficiencies of the prior art, the purpose of the present application is to provide a method for preparing a polyurethane polishing pad by a solvent-free blade coating method, which is simple, low in cost, and can adjust the cell rate, cell size, crosslinking degree, coating thickness and hardness of the polishing pad according to the requirements to improve the performance of the polishing pad, and uses a solvent-free process, which is environmentally friendly and pollution-free.

[0010] In order to achieve the above-mentioned purpose, the following technical solutions are adopted:

[0011] A method for preparing a polyurethane polishing pad by a solvent-free blade coating method, comprising the following steps:

[0012] Step one, slurry preparation: 100 parts of NCO-terminated polyurethane prepolymer, 0.3-1 parts of stannous octoate, 0.3-1 parts of silicone foam stabilizer, 0.09-0.94 parts of water, 0.3-2.5 parts of microspheres foaming agent, 3.21-4.64 parts of trimethylolpropane, and 6.42-9.27 parts of 1, 4-butanediol are loaded into a reaction kettle and stirred uniformly;

[0013] Step two, using a dry production line, the prepared slurry is cast on a polyester film, and then blade coating is performed to form a film, and then the film is placed in an oven for curing at a temperature of 70-160℃ for 20-60min, and then wound after cooling to obtain a polyurethane / polyester film composite material;

[0014] Step three, the polyurethane / polyester film composite prepared in step two is sanded;

[0015] Step four, cutting according to the size required by the customer, and flow channel engraving, to obtain the polishing pad.

[0016] The present application also has the following technical features:

[0017] Preferably, the NCO-terminated polyurethane prepolymer in step one is synthesized from isophorone diisocyanate and polytetrahydrofuran diol, with a molecular weight of 2000-10000 and an NCO mass fraction of 8-15%.

[0018] Preferably, the stirring in step one is performed using a magnetic stirrer for 20-30 min.

[0019] Preferably, the film in step two is applied with a thickness of 0.5-2 mm.

[0020] Preferably, the sanding in step three is performed using a through-feed leather sander, with 100-200 mesh sand belt for the first time, and 400-600 mesh sand belt for the second time.

[0021] Compared with the prior art, the present application has the following technical effects:

[0022] The present application uses a dry production line and direct coating technology, combining wet coagulation process and reaction molding process, and applying on the substrate according to the required number of filaments, which eliminates the processes of injection molding, cutting according to a certain thickness and bonding the substrate, simplifies the process, and easily controls the thickness, thereby improving the stability of the polishing pad during use.

[0023] The process can produce soft polishing pads, and can also produce hard polishing pads, and the softness and hardness can be realized by adjusting the content of raw materials in the slurry formula.

[0024] In the production process, no solvent is used, no solvent pollution is generated, and the process is environmentally friendly. The product has no solvent residue and is a green product. The solvent-free system does not have any pollution, and the solvent-free polyurethane can meet various safety and environmental protection indicators. The process does not emit solvent vapor, water vapor, or even little heat, and truly achieves zero emission.

[0025] Compared with the wet coagulation process, the present application achieves the same foaming effect, has fewer wet processes, workshops and equipment than ordinary wet processes, and has stable process and competitive cost. The dry resin price obtained by dividing the unit price by the solid content is significantly lower than that of other processes, and is suitable for large-scale production.

[0026] The present application can adjust the cell ratio, cell size, crosslinking degree, coating thickness, etc. by the formula to improve the performance of the polishing pad. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 Process flow chart for the preparation method of the present application;

[0028] Figure 2 SEM image of the polyurethane polishing pad prepared in Example 1 of the present application. DETAILED DESCRIPTION

[0029] The specific content of the present application is further explained in detail in combination with the following examples.

[0030] In the following examples, the NCO-terminated polyurethane prepolymer is synthesized from isophorone diisocyanate and polytetrahydrofuran diol, with a molecular weight of 2000-10000 and a mass fraction of NCO of 8-15%;

[0031] Stannous octoate is of analytical purity;

[0032] The silicone cell uniformizing agent is SiCare-2003;

[0033] The microsphere foaming agent is UNICELL-PG30.

[0034] Example 1:

[0035] Step one, slurry preparation: 100 parts of NCO-terminated polyurethane prepolymer (mass fraction of NCO is 8%), 0.5 parts of stannous octoate, 0.5 parts of silicone cell uniformizing agent, 0.09 parts of water, 0.3 parts of microsphere foaming agent, 4.64 parts of trimethylolpropane, and 9.27 parts of 1,4-butanediol are loaded into a reaction kettle in mass fraction, and stirred uniformly for 25 min using a magnetic stirrer;

[0036] Step two, using a dry production line, the prepared slurry is cast on a polyester film, and a film is scraped and coated, with the scraping and coating thickness of the film controlled at 1.5 mm, and then enters an oven for curing at a temperature of 120℃ for 40 min, and after cooling, is wound up to obtain a polyurethane / polyester film composite material;

[0037] Step three, the polyurethane / polyester film composite material prepared in step two is buffed: a through-type buffing machine is used to buff the first time with a 150-mesh sand belt, and then buff the second time with a 500-mesh sand belt;

[0038] Step four, according to the size required by the customer, the polishing pad is obtained after cutting and flow channel engraving.

[0039] The polyurethane abrasive pad obtained in Example 1 has a thickness of 1.96 mm, a Shore hardness of 92D, a mass loss rate of 0.22% after 2500 abrasions, and a mass loss rate of 0.41% after 5000 abrasions.

[0040] After the polyurethane abrasive pad is soaked in a NaOH solution with a pH of 10 for 24 hours, the water absorption rate is 3.86%, the surface has no obvious change, the mass loss rate is 0.59%, and the mass loss rate after 2500 abrasions is 0.27%.

[0041] Example 2:

[0042] Step 1, slurry preparation: 100 parts of NCO-terminated polyurethane prepolymer (mass fraction of NCO is 12%), 0.3 parts of stannous octoate, 0.3 parts of silicone foam stabilizer, 0.51 parts of water, 1 part of microsphere foaming agent, 3.92 parts of trimethylolpropane, and 7.85 parts of 1,4-butanediol are weighed and loaded into a reaction kettle, and the mixture is stirred uniformly for 20 min using a magnetic stirrer;

[0043] Step 2, using a dry production line, the prepared slurry is cast on a polyester film, and a film is formed by scraping, with the scraping thickness of the film being controlled at 0.5 mm, and then the film is subjected to curing in an oven at a temperature of 70°C for 60 min, and after cooling, the film is wound up to obtain a polyurethane / polyester film composite material;

[0044] Step 3, the polyurethane / polyester film composite material prepared in Step 2 is ground: a through-type leather grinding machine is used to grind the film for the first time using a 100-mesh sand belt, and then for the second time using a 400-mesh sand belt;

[0045] Step 4, the abrasive pad is obtained by cutting according to the required size and engraving the flow channel.

[0046] The polyurethane abrasive pad obtained in Example 2 has a thickness of 1.21 mm, a Shore hardness of 82D, a mass loss rate of 0.35% after 2500 abrasions, and a mass loss rate of 0.70% after 5000 abrasions.

[0047] After the polyurethane abrasive pad is soaked in a NaOH solution with a pH of 10 for 24 hours, the water absorption rate is 3.66%, the surface has no obvious change, the mass loss rate is 0.63%, and the mass loss rate after 2500 abrasions is 0.28%.

[0048] Example 3:

[0049] Step one, slurry preparation: in mass fraction, NCO terminated polyurethane prepolymer (mass fraction of NCO is 10%) 100 parts, stannous octoate 1 part, silicone foam stabilizer 1 part, water 0.94 part, microsphere foaming agent 2.5 parts, trimethylolpropane 3.21 parts, 1,4-butanediol 6.42 parts are loaded into the reaction kettle, and the magnetic stirrer is used for stirring for 30 min until uniform;

[0050] Step two, using dry production line, the prepared slurry is cast on the polyester film, and the film is scraped to form a film, and the scraping thickness of the film is controlled to be 2 mm, then enters the oven, and is cured at a temperature of 160℃ for 20 min, and after cooling, is wound to obtain a polyurethane / polyester film composite material;

[0051] Step three, the polyurethane / polyester film composite material prepared in step two is sanded: a through-type leather grinding machine is used, and 200 mesh sand belt is used for the first time, and then 600 mesh sand belt is used for the second time;

[0052] Step four, according to the size required by the customer, the flow channel is engraved to obtain the grinding pad.

[0053] The thickness of the polyurethane grinding pad obtained in example 3 is 2.65 mm; the shore hardness is 78D; the mass loss rate after grinding 2500 times is 0.26%; the mass loss rate after grinding 5000 times is 0.53%.

[0054] After the polyurethane grinding pad is soaked in NaOH solution with pH of 10 for 24 hours, the water absorption rate is 4.41%, the surface has no obvious change, the mass loss rate is 0.71%, and the mass loss rate after grinding 2500 times is 0.31%.

[0055] Example 4:

[0056] Step one, slurry preparation: in mass fraction, NCO terminated polyurethane prepolymer (mass fraction of NCO is 15%) 100 parts, stannous octoate 0.8 parts, silicone foam stabilizer 0.6 parts, water 0.3 parts, microsphere foaming agent 1.5 parts, trimethylolpropane 4.28 parts, 1,4-butanediol 8.56 parts are loaded into the reaction kettle, and the magnetic stirrer is used for stirring for 30 min until uniform;

[0057] Step two, using dry production line, the prepared slurry is cast on the polyester film, and the film is scraped to form a film, and the scraping thickness of the film is controlled to be 1.42 mm, then enters the oven, and is cured at a temperature of 100℃ for 50 min, and after cooling, is wound to obtain a polyurethane / polyester film composite material;

[0058] Step three, the polyurethane / polyester film composite material prepared in step two is sanded: a through-type leather grinding machine is used, and 100 mesh sand belt is used for the first time, and then 600 mesh sand belt is used for the second time;

[0059] Step four, cutting according to the size required by the customer, after the flow channel is engraved, the polishing pad is obtained.

[0060] The polyurethane polishing pad obtained in Example 4 has a thickness of 2.00 mm, a Shore hardness of 86D, a mass loss rate of 0.25% after 2500 polishing, and a mass loss rate of 0.60% after 5000 polishing.

[0061] After the polyurethane polishing pad is soaked in a NaOH solution with a pH of 10 for 24 hours, the water absorption rate is 4.21%, the surface has no obvious change, the mass loss rate is 0.66%, and the mass loss rate after 2500 polishing is 0.29%.

[0062] The above examples are only used to illustrate the technical solutions of the present application, but not to limit it; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions recorded in the foregoing examples can still be modified, or some or all of the technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the present application.

Claims

1. A method of making a polyurethane polishing pad by a solventless blade coating process, characterized by, It comprises the following steps: Step one, slurry preparation: in mass fraction, 100 parts of NCO terminated polyurethane prepolymer, 0.3-1 parts of stannous octoate, 0.3-1 parts of silicone foam stabilizer, 0.09-0.94 parts of water, 0.3-2.5 parts of microsphere foaming agent, 3.21-4.64 parts of trimethylolpropane, 6.42-9.27 parts of 1, 4-butanediol are loaded into a reaction kettle and stirred uniformly; The NCO terminated polyurethane prepolymer is synthesized from isophorone diisocyanate and polytetrahydrofuran diol, has a molecular weight of 2000-10000 and an NCO mass fraction of 8-15%; Step two, the prepared slurry is cast on a polyester film using a dry production line, scraped to form a film, then enters an oven, cured at a temperature of 70-160℃ for 20-60 min, cooled and wound up to obtain a polyurethane / polyester film composite material; Step three, the polyurethane / polyester film composite material prepared in step two is sanded; Step four, cutting according to the size required by the customer, flow channel engraving to obtain a polishing pad.

2. The method of making a polyurethane abrasive pad by solventless doctor blading of claim 1, wherein, The stirring in step one is stirring for 20-30 min using a magnetic stirrer.

3. The method of making a polyurethane abrasive pad by solventless doctor blading of claim 1, wherein, The film scraping thickness in step two is controlled at 0.5-2 mm.

4. The method of making a polyurethane abrasive pad by solventless doctor blading of claim 1, wherein, The sanding in step three is first sanding with 100-200 mesh sand belt using a through-type leather sanding machine, then second sanding with 400-600 mesh sand belt.

Images