JP2012101339A - Polishing pad - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a finishing polishing pad which causes few defects such as scratch and particle on the mirror surface to be polished in polishing and achieves the stable polishing characteristics providing small surface roughness of the mirror surface to be polished in the finishing polishing pad used for forming an excellent mirror surface on a silicon bare wafer, a glass, a compound semiconductor substrate and a hard disk substrate or the like.SOLUTION: The polishing pad has a polishing sheet (a) composed of three or more kinds of different layers and a cushion sheet b. The surface layer of the polishing sheet (a) is a porous polyurethane layer c mainly composed of polyurethane obtained by the wet-coagulation method, and any of other layers is a foamed plastic layer d having a compressive elastic modulus of 0.08-0.25 MPa. A plastic film (e) with a thickness of 10-45 μm is interposed between the porous polyurethane layer c of the surface layer and the foamed plastic layer d.

Description

  The present invention relates to a polishing pad suitable for finishing used for forming a good mirror surface in a silicon bare wafer, glass, a compound semiconductor substrate, a hard disk substrate and the like.

  Conventionally, a polishing sheet is made of a non-woven fabric or a woven fabric made of synthetic fibers and synthetic rubber, and a polyurethane-based solution is applied on the upper surface thereof. The polyurethane-based solution is coagulated by a wet coagulation method and has a continuous pore. A skin layer of a layer is formed, and the surface of the skin layer is ground and removed as necessary (hereinafter, the surface of which is ground may be expressed as suede). (See Patent Document 1).

  The polishing cloth comprising such a polishing sheet is already widely used from rough polishing for surface mirror polishing for electronic parts such as liquid crystal glass, glass disk, silicon wafer, compound semiconductor substrate and hard disk to polishing pad for finishing. Yes. However, in recent years, coupled with the development of measuring devices for mirror-polished surfaces, the quality required by users has increased, and there has been a demand for polishing pads that can perform mirror polishing with higher accuracy. A structured polishing cloth has been proposed (see Patent Document 2). However, with this technique, it has been difficult to reduce defects such as scratches and particles on the mirror-polished surface during polishing, and at the same time to reduce the surface roughness of the mirror-polished surface.

Japanese Patent Laid-Open No. 11-335979 JP-A-11-277408

  In view of the background of the above-described conventional technology, the object of the present invention is to polish a mirror surface during polishing in a polishing pad used to form a good mirror surface in a silicon bare wafer, glass, a compound semiconductor substrate, a hard disk substrate, and the like. It is an object of the present invention to provide a polishing pad suitable for finishing, which has few defects such as scratches and particles on the surface and can obtain stable polishing characteristics in which the surface roughness of the mirror surface is reduced.

  The present invention employs the following means in order to solve the above problems. That is, the polishing pad of the present invention is a polishing pad having a polishing sheet (a) and a cushion sheet (b) comprising three or more different layers, and the surface layer of the polishing sheet (a) is obtained by a wet coagulation method. A porous polyurethane layer (c) mainly composed of polyurethane, and any of the other layers is a foamed plastic layer (d) having a compression elastic modulus of 0.08 MP to 0.25 MPa, and the surface layer is porous A plastic film (e) having a thickness of 10 to 45 μm is interposed between the polyurethane layer (c) and the foamed plastic layer (d).

  According to the preferable aspect of the polishing pad of this invention, the average tensile elasticity modulus of the said plastic film (e) is 3.5-5.5 GPa.

  According to a preferred aspect of the polishing pad of the present invention, the cushion sheet (b) is made of foamed plastic, and the plastic sheet has a thickness of 100 to 300 μm between the polishing sheet (a) and the cushion sheet (b). (F) is interposed.

  According to a preferred embodiment of the polishing pad of the present invention, lattice grooves having a groove depth smaller than the thickness of the porous polyurethane layer (c) are formed in the surface porous polyurethane layer (c). It is.

  According to the present invention, in a polishing pad suitable for finishing used to form a good mirror surface in a silicon bare wafer, glass, a compound semiconductor substrate, a hard disk substrate, and the like, a scratch on the mirror-polished surface during polishing is obtained. -A polishing pad suitable for finishing, which has few defects such as particles and has a stable polishing characteristic in which the surface roughness of the mirror-polished surface is reduced, can be obtained.

FIG. 1 is a schematic cross-sectional view for illustrating the polishing pad obtained in Example 1 of the present invention.

  The polishing pad of the present invention is a polishing pad basically composed of a polishing sheet (a) and a cushion sheet (b) composed of three or more different layers. The surface layer of the polishing sheet (a) used in the present invention is a porous polyurethane layer (c) mainly composed of polyurethane obtained by a wet coagulation method, and any of the other layers is a foamed plastic layer (d). It is configured. A plastic sheet (e) is interposed between the porous polyurethane layer (c) and the foamed plastic layer (d).

  First, the porous polyurethane layer (c) of the surface layer constituting the polishing sheet (a) used in the present invention will be described.

  In the present invention, the above wet coagulation method means that the porous polyurethane layer is obtained by applying a polyurethane solution in which polyurethane is dissolved in an organic solvent to a sheet-like base material and then coagulating and regenerating the resin in an aqueous coagulation liquid. This is a method for producing (c).

  The porous polyurethane layer (c) in the present invention has a surface layer (skin layer) with a thickness of about several μm in which micropores accompanying the solidification regeneration of the polyurethane resin are densely formed, and the inside (surface layer) On the inner side, it has an inner layer in which a large number of coarse pores having a mean pore diameter of about 50 μm to 400 μm, which are larger than the fine pores of the skin layer, are formed. Since the micropores formed in the skin layer are dense, the surface of the skin layer has micro flatness. Using this micro flatness of the surface of the skin layer, finish polishing of a silicon bare wafer, glass, a compound semiconductor substrate, a hard disk substrate and the like, which are objects to be polished, is performed.

  The polyurethane used in the present invention is a polymer having a urethane bond or a urea bond polymerized from a prepolymer having a plurality of active hydrogens at a terminal and a compound having a plurality of isocyanate groups. Prepolymers having a plurality of active hydrogens at the terminals can be classified into polyester-based, polyether-based, polycarbonate-based, and polycaprolactan-based prepolymers according to the main chain skeleton.

  As the organic solvent used in the wet coagulation method, a solvent having polarity such as N, N-dimethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide, tetrahydrofuran, dioxane and N-methylpyrrolidone is used. As a solvent for dissolving the polyurethane, dimethylformamide (DMF) is particularly preferably used.

  Other resins such as polyvinyl chloride, polyester resin, polyethersulfone, and polysulfone can be appropriately blended with the polyurethane solution. In addition, an organic pigment typified by carbon, a surfactant that lowers the surface tension, a water repellent capable of imparting water repellency, and the like can be added to the polyurethane solution as necessary.

  Examples of the substrate used in the present invention include fibers such as cotton, rayon, polyamide, polyester, and polyacrylonitrile, or a woven or non-woven fabric made of a mixture thereof, or impregnated with a resin such as synthetic rubber or polyurethane. The obtained sheets or a polyester film etc. are mentioned.

  The uppermost surface layer can be obtained by peeling these substrates after coagulation regeneration of polyurethane.

  Examples of means for applying the polyurethane solution to the substrate include a roll coater, a knife coater, a knife over roll coater, and a die coater. After the polyurethane solution is applied, a coagulation bath that forms a porous layer uses a solvent that has an affinity for DMF but does not dissolve polyurethane. Generally, water or a mixed solution of water and DMF is used.

  The thickness of the porous polyurethane layer (c) in the present invention is preferably 300 μm to 1200 μm, more preferably 350 to 700 μm.

  Next, the foamed plastic layer (d) constituting the polishing sheet (a) used in the present invention will be described. In the present invention, it is important that the foamed plastic layer (d) other than the porous polyurethane layer (c) has a compression elastic modulus of 0.08 MPa to 0.25 MPa.

  The foamed plastic layer (d) used in the present invention is polyethylene, polypropylene, polyester, polyurethane, polyurea, polyamide, polyvinyl chloride, polyacetal, polycarbonate, polymethyl methacrylate, polytetrafluoroethylene, epoxy resin, ABS resin, AS It refers to foams such as resin, phenol resin, melamine resin, neoprene rubber, butadiene rubber, styrene butadiene rubber, ethylene propylene rubber, silicon rubber, and fluorine rubber.

  As a method for producing the foamed plastic layer (d), after adding a foaming agent to the resin, a dry foaming method in which foaming is performed by heating, or an additive that reacts with a functional group constituting the resin to generate gas is used. Examples include dry foaming methods that mix and foam, and are different from wet foaming methods such as the wet coagulation method of the upper layer, but in terms of uniform density distribution and easy control of the compression elastic modulus, A membrane method is preferably used. Among such resins, a resin mainly composed of polyurethane is preferably used in that the apparent density can be controlled relatively easily.

Compressive modulus in the present invention, compressed to the cross-sectional area of 1 cm ² indenter from 0 gf / cm ² using when pressurized to ^{50gf / cm 2, 16gf / cm} 2 and strain rate of 40 gf / cm ² (initial thickness This is a value calculated from (distortion amount). In the present invention, it is important that the compression elastic modulus of the foamed plastic sheet (d) is 0.08 MPa or more and 0.25 MPa or less, preferably 0.09 to 0.20 MPa, and more preferably 0.10. ~ 0.15 MPa.

  When the compression modulus is less than 0.08 MPa, the surface roughness of the mirror-polished surface is not reduced. Further, when the compression elastic modulus exceeds 0.25 MPa, defects such as scratches and particles increase.

  Here, the scratch refers to fine scratches generated on the wafer surface during polishing, and the particle refers to deposits such as pad scraps, wafer scraps and slurry scraps attached to the wafer surface during polishing. .

  In the present invention, the thickness of the foamed plastic layer (d) is preferably 150 μm to 550 μm, more preferably 200 μm to 450 μm. When the thickness is less than 150 μm, stable polishing characteristics may not be obtained, and when the thickness is greater than 550 μm, there is a concern that defects such as scratches and particles on the mirror surface are increased.

  The cushion layer (b) in the present invention is for absorbing fine unevenness of the polishing machine surface plate and leveling the polishing surface of the polishing pad, and includes polyethylene, polypropylene, polyester, polyurethane, polyurea, polyamide, Polyvinyl chloride, polyacetal, polycarbonate, polymethyl methacrylate, polytetrafluoroethylene, epoxy resin, ABS resin, AS resin, phenol resin, melamine resin, neoprene rubber, butadiene rubber, styrene butadiene rubber, ethylene propylene rubber, silicon rubber and fluorine Foams such as rubber, various woven fabrics, various non-woven fabrics, and the like are used. Among these, a foam is preferably used from the viewpoint of obtaining a more uniform thickness.

In the present invention, the apparent density of the cushion layer (b) is preferably 0.1 to 0.5 (g / cm ³ ), more preferably 0.2 to 0.4 (g / cm ³ ). is there. When the apparent density is less than 0.1 (g / cm ³ ), stable polishing characteristics may not be obtained. When the apparent density is greater than 0.5 (g / cm ³ ), the mirror-polished polishing surface There is a tendency for defects such as scratch particles to increase.

  In the present invention, the thickness of the cushion layer (b) is preferably 500 μm to 1300 μm, more preferably 600 μm to 1100 μm. When the thickness is less than 500 μm, stable polishing characteristics may not be obtained, and when the thickness is greater than 1300 μm, there is a concern that defects such as scratches and particles on the mirror-polished surface will increase.

  In the present invention, the plastic film (e) constituting the polishing sheet (a) is a film made of a polymer resin having a thickness of 10 to 45 μm. When the thickness exceeds 45 μm, defects such as scratches and particles increase. Further, when the thickness is smaller than 10 μm, the surface roughness of the mirror-polished surface is not reduced.

  Materials for forming the plastic film (e) used in the present invention include polyethylene, polypropylene, polyester, polyurethane, polyurea, polyamide, polyvinyl chloride, polyacetal, polycarbonate, polymethyl methacrylate, polytetrafluoroethylene, epoxy resin, and ABS resin. It is a film formed from AS resin, phenol resin, melamine resin, polyphenylene sulfide and the like. Among these, a polyester film is preferable, and polyethylene terephthalate is particularly preferably used.

  The plastic film (e) used in the present invention preferably has an average tensile modulus of 3.5 GPa or more and 5.5 GPa or less. The average tensile elastic modulus represents the average value of the tensile elastic modulus of MD (film forming direction) and TD (direction perpendicular to the film forming direction) because the polyethylene terephthalate film has anisotropy during film formation. When the average tensile elastic modulus is less than 3.5 GPa, the surface roughness of the mirror-polished surface tends to increase. Further, when the average tensile elastic modulus exceeds 5.5 GPa, defects such as scratches and particles tend to increase.

  In the present invention, the average tensile elastic modulus is obtained from an initial initial inclination by applying a tensile stress in a strip shape. An example of a measuring device is Tensilon Universal Tester RTF-1210 manufactured by Orientec. As measurement conditions, the test speed is 20 cm / min, the test piece shape is a dumbbell shape having a width of 10 mm and a sample length of 100 mm.

  The porous polyurethane layer (c) and the plastic film (e) used in the present invention are bonded together with an adhesive. Examples of adhesives include acrylic resin adhesives, α-olefin adhesives, urethane resin adhesives, and hot melt adhesives, but urethane resin adhesives and hot melt adhesives can be bonded in a short time. It is preferably used in terms of points. With respect to the urethane resin adhesive, a method in which an adhesive dissolved in various organic solvents is dry-coated with a laminator can be cited as a suitable example.

  “Hybon” (registered trademark) series manufactured by Hitachi Chemical Polymer Co., Ltd., “Takemelt” (registered trademark) MA series manufactured by Mitsui Takeda Chemical Co., Ltd., and “Aronmelt” manufactured by Toa Gosei Co., Ltd. (Registered trademark) R series, “Nittite” (registered trademark) ARX series of Nitta Gelatin Co., Ltd., and “Bond” (registered trademark) KUM series of Konishi Co., Ltd. may be mentioned.

  The thickness of the adhesive is preferably 30 to 150 μm, and more preferably 40 to 100 μm, from the viewpoint that the adhesive force can be maintained high.

  For joining the foamed plastic layer (d) and the plastic film (e) used in the present invention, there are a method of adhering with an adhesive and a method of thermally fusing the foamed plastic layer (d) to the plastic film (e). Can be mentioned. Adhesives include acrylic resin adhesives, α-olefin adhesives, urethane resin adhesives, and hot melt adhesives. Urethane resin adhesives and hot melt adhesives should be bonded in a short time. Can do.

  The plastic sheet (f) interposed between the polishing sheet (a) and the cushion sheet (b) used in the present invention is made of polyethylene, polypropylene, polyester, polyurethane, polyurea, polyamide, polyvinyl chloride, polyacetal, polycarbonate, poly It is a plastic sheet formed from methyl methacrylate, polytetrafluoroethylene, epoxy resin, ABS resin, AS resin, phenol resin, melamine resin, polyphenylene sulfide, and the like.

  The thickness of the plastic sheet (f) is preferably 100 μm to 300 μm, more preferably 150 μm to 250 μm. When the thickness is less than 100 μm, the edge sagging of the substrate to be polished may be increased, and when the thickness is more than 300 μm, defects such as scratch particles on the mirror-polished surface tend to increase.

  Examples of the procedure for laminating and forming the polishing pad of the present invention include a procedure of laminating each layer one by one. In addition, there is a procedure for wet coagulation of the surface layer directly to the second layer. In this case, the third layer and the subsequent layers may be laminated in order.

  As an example of a specific lamination procedure, first, the cushion sheet (b) is laminated on the plastic sheet (f), then the foamed plastic layer (d) is laminated on the opposite surface of the plastic sheet (f), and further the cushion sheet. Laminate a back tape on the opposite side of (b). A plastic film (e) is laminated on the opposite surface of the foamed plastic layer (d), and finally a porous polyurethane layer (c) is laminated on the opposite surface of the plastic film (e). It is preferable to use a urethane-based adhesive for laminating.

  The thickness of the polishing sheet of the present invention is preferably 500 μm to 1200 μm, more preferably 600 μm to 1100 μm.

  In order to obtain stable polishing characteristics, it is preferable that lattice grooves are formed on the upper surface of the upper porous polyurethane layer (c) on the polishing layer surface of the polishing pad of the present invention. Further, in order to obtain stable polishing characteristics, the groove width is 0.8 mm or more and 1.2 mm or less, the groove pitch is 7.5 mm or more and 15 mm or less, and the groove depth is greater than the thickness of the upper porous polyurethane layer. It is preferable to provide small square lattice grooves. If the groove depth is deeper than the thickness of the upper porous polyurethane layer, the slurry penetrates into the lower foamed plastic layer and the polishing characteristics become unstable, which is not preferable.

  The polishing pad of the present invention is suitably used for forming a good mirror polished surface on a silicon bare wafer, glass, compound semiconductor substrate, hard disk substrate and the like.

  Hereinafter, the details of the present invention will be described with reference to examples. However, the present invention is not construed as being limited by this embodiment. Polishing evaluation and each measurement were performed as follows.

[Polishing evaluation]
Using a polishing apparatus (model: SPP600) manufactured by Okamoto Machine Tool Manufacturing Co., Ltd., polishing evaluation was performed under the following conditions using a 6-inch silicon bare wafer after secondary polishing (using SUBA400 pad).
・ Platen rotation: 46rpm
・ Wafer head rotation: 49rpm
Head load: 100 g / cm ²
・ Slurry amount: 700 ml / min (slurry: colloidal silica slurry abrasive concentration 1%)
-Polishing time: 15 minutes.

(Measurement of compression modulus)
Measurement was performed under the following conditions using an automated compression tester (KESFB3-AUTO-A) manufactured by Kato Tech. This unit when pressurized from 0 gf / cm ² up to 50 gf / cm ^{2 using,} was calculated from the strain rate of 16gf / cm 2 (0.00157MPa) and 40gf ^/ cm 2 (0.00392MPa). (Average value of 5 measurements)
-Strain rate: (initial thickness-thickness at a predetermined pressure) / initial thickness-Compression modulus: (0.00392-0.00157) / (strain rate _{40 gf / cm2} -strain rate _{16 gf / cm2} )
[MPa]
Indenter area: 1.0 cm ²
Indenter speed: 0.02 mm / sec
Upper limit load: 50 gf / cm.

[Measurement of apparent density]
-It calculated from the thickness and weight of the sample punched out to 30 mm x 30 mm.

〔Surface roughness〕
Ra of the wafer surface after polishing was measured using a scanning white interferometer (NEW VIEW 6300) manufactured by ZYGO. (Average value of 5 measurements)
[Number of defects such as scratch particles]
The number of defects of 0.5 μm or more was measured using a product name “WM-3” manufactured by Topcon Corporation. (Average value of n = 2 measurement with 2 wafers)
[Average tensile elastic modulus]
Measurement was performed under the following conditions using a Tensilon universal testing machine RTM-100 manufactured by Orientec. (Average value of 5 measurements)
Test piece shape: Dumbbell shape with a width of 10 mm and a sample length of 100 mm Test speed: 20 cm / min.

      Next, the manufacturing method of each layer is illustrated.

[Method for producing porous polyurethane layer 1]
25 parts by mass of polyester MDI (diphenylmethane diisocyanate) polyurethane resin was dissolved in 100 parts by mass of N, N-dimethylformamide (DMF). Further, 2 parts by mass of carbon black and 2 parts by mass of a hydrophobic activator were added thereto to prepare a polyurethane solution.

  Next, the polyurethane solution is applied onto a polyester film substrate with a knife coater, immersed in a water bath to coagulate and regenerate the polyurethane, and after removing DMF in the polyurethane by washing with water, moisture is dried, and finally A coagulated and regenerated polyurethane sheet was prepared by peeling the polyester film substrate.

The microporous surface of the obtained coagulated and regenerated polyurethane sheet is buffed with # 200 sandpaper to adjust the opening diameter to a thickness of 400 μm, an apparent density of 0.25 g / cm ³ , and a compression recovery rate of 0.5. % Porous polyurethane 1 was obtained.

[Method for producing foamed plastic layer 1]
100 parts by weight of polyethylene glycol having a molecular weight of 2800, 5 parts by weight of 1,4-butanediol, 5 parts by weight of 4,4′-methylenebis (o-chloroaniline), 0.4 parts by weight of amine catalyst (DABCO) as a catalyst, A silicone foam stabilizer (KF6002; manufactured by Shin-Etsu Chemical Co., Ltd.) as a foaming agent, 3.0 parts by mass of water as a foaming agent, and 38 parts by mass of MDI as an isocyanate are mixed and stirred, and a release liner A polyether type soft polyurethane having a thickness of 300 μm, an apparent density of 0.49 g / cm ³ , a compression recovery rate of 55%, and a compression modulus of 0.11 MPa while being coated and foamed and heated for 20 minutes at a temperature of 100 ° C. A foamed plastic layer 1 was obtained.

[Method for producing foamed plastic layer 2]
100 parts by weight of polyethylene glycol having a molecular weight of 2800, 5 parts by weight of 1,4-butanediol, 5 parts by weight of 4,4′-methylenebis (o-chloroaniline), 0.4 parts by weight of amine catalyst (DABCO) as a catalyst, Silicone foam stabilizer (KF6002; manufactured by Shin-Etsu Chemical Co., Ltd.) as a foaming agent, 4.0 parts by mass of water as a foaming agent, and 38 parts by mass of MDI as an isocyanate are mixed and stirred, and release liner A polyether type soft polyurethane having a thickness of 800 μm, an apparent density of 0.20 g / cm ³ , a compression recovery rate of 55%, and a compression elastic modulus of 0.05 MPa while being coated and foamed for 20 minutes at a temperature of 100 ° C. A foamed plastic layer 2 was obtained.

[Method for producing foamed plastic layer 3]
80 parts by mass of polyethylene glycol having a molecular weight of 3200, 20 parts by mass of polypropylene glycol having a molecular weight of 2800, 6 parts by mass of 1,4-butanediol, 4 parts by mass of 4,4′-methylenebis (o-chloroaniline), an amine catalyst as a catalyst ( DABCO) 0.3 parts by mass, silicone foam stabilizer (KF6002; manufactured by Shin-Etsu Chemical Co., Ltd.) 3.5 parts by weight, water 0.3 parts by weight as a foaming agent, and 45 MDI as isocyanate. The parts were mixed and stirred, coated on a release liner and foamed, and heated for 20 minutes at a temperature of 100 ° C., thickness 300 μm, apparent density 0.51 g / cm ³ , compression recovery rate 35%, compression modulus 0 A 20 MPa polyether type soft polyurethane foamed plastic layer 3 was obtained.

[Method for producing foamed plastic layer 4]
100 parts by mass of polyethylene glycol having a molecular weight of 2500, 4 parts by mass of 1,4-butanediol, 7 parts by mass of 4,4'-methylenebis (o-chloroaniline), 0.4 parts by mass of amine catalyst (DABCO) as a catalyst, On a release liner, 3.0 parts by mass of a silicone foam stabilizer (KF6002; manufactured by Shin-Etsu Chemical Co., Ltd.) as a foaming agent, 0.2 parts by mass of water as a foaming agent, and 60 parts of MDI as an isocyanate are mixed and stirred. A polyether type soft polyurethane foam having a thickness of 300 μm, an apparent density of 0.53 g / cm ³ , a compression recovery rate of 75%, and a compression elastic modulus of 0.25 MPa. A plastic layer 4 was obtained.
[Method for producing foamed plastic layer 5]
100 parts by weight of polyethylene glycol having a molecular weight of 3500, 5 parts by weight of 1,4-butanediol, 0.25 parts by weight of amine catalyst (DABCO) as a catalyst, silicone foam stabilizer (KF6002; manufactured by Shin-Etsu Chemical Co., Ltd.) as a foam stabilizer ) 3.0 parts by weight, 0.3 parts by weight of water as a foaming agent, and 35 parts by weight of MDI as an isocyanate are mixed and stirred, coated on a release liner and foamed, at a temperature of 100 ° C. for 20 minutes. Heating was performed to obtain a polyether-type soft polyurethane foamed plastic layer 5 having a thickness of 300 μm, an apparent density of 0.33 g / cm ³ , a compression recovery rate of 45%, and a compression modulus of 0.13 MPa.

[Method for producing foamed plastic layer 6]
100 parts by mass of polyethylene glycol having a molecular weight of 2900, 3 parts by mass of 1,4-butanediol, 10 parts by mass of 4,4'-methylenebis (o-chloroaniline), 0.4 parts by mass of amine catalyst (DABCO) as a catalyst, A silicone foam stabilizer (KF6002; manufactured by Shin-Etsu Chemical Co., Ltd.) as a foaming agent, 3.0 parts by weight of water as a foaming agent, and 23 parts by weight of MDI as an isocyanate are mixed and stirred, and a release liner A polyether-type soft polyurethane having a thickness of 300 μm, an apparent density of 0.50 g / cm ³ , a compression recovery rate of 90%, and a compression modulus of 0.05 MPa while being coated and foamed for 20 minutes at a temperature of 100 ° C. A foamed plastic layer 6 was obtained.

[Method for producing foamed plastic layer 7]
100 parts by weight of polyethylene glycol having a molecular weight of 2800, 5 parts by weight of 1,4-butanediol, 25 parts by weight of 4,4'-methylenebis (o-chloroaniline), 0.4 parts by weight of amine catalyst (DABCO) as a catalyst, A silicone foam stabilizer (KF6002; manufactured by Shin-Etsu Chemical Co., Ltd.) as a foaming agent, 3.0 parts by weight of water as a foaming agent, and 45 parts by weight of MDI as an isocyanate are mixed and stirred, and a release liner A polyether type flexible polyurethane having a thickness of 300 μm, an apparent density of 0.34 g / cm ³ , a compression recovery rate of 55%, and a compression elastic modulus of 0.30 MPa while being coated and foamed for 20 minutes at a temperature of 100 ° C. A foamed plastic layer 7 was obtained.

[Method for producing foamed plastic layer 8]
100 parts by weight of polyethylene glycol having a molecular weight of 2800, 5 parts by weight of 1,4-butanediol, 5 parts by weight of 4,4′-methylenebis (o-chloroaniline), 0.4 parts by weight of amine catalyst (DABCO) as a catalyst, Silicone foam stabilizer (KF6002; manufactured by Shin-Etsu Chemical Co., Ltd.) as a foaming agent, 4.0 parts by mass of water as a foaming agent, and 38 parts by mass of MDI as an isocyanate are mixed and stirred, and release liner A polyether type soft polyurethane having a thickness of 300 μm, an apparent density of 0.20 g / cm ³ , a compression recovery rate of 55%, and a compression modulus of 0.08 MPa while being coated and foamed and heated for 20 minutes at a temperature of 100 ° C. A foamed plastic layer 2 was obtained.

[Example 1]
Adhering the foamed plastic layer 1 to a polyethylene terephthalate (PET) sheet having a thickness of 190 μm, and then attaching a PET film (thickness: 43 μm, average tensile elastic modulus: 3.5 GPa) to the opposite surface of the foamed plastics layer 1 It was. The porous polyurethane layer 1 was adhered to the front side of the PET film. Next, the foamed plastic layer 2 of the cushion sheet was bonded to the opposite surface of the PET sheet, and a back tape was attached to the opposite surface of the foamed plastic layer 2 to obtain a laminate. A urethane-based adhesive was used for bonding each layer.

  The obtained laminate was circled to a diameter of 610 mm to obtain a polishing pad. In FIG. 1, the schematic cross section of the laminated body (polishing pad) obtained in Example 1 is shown. In FIG. 1, the polishing pad is composed of a porous polyurethane layer (c), a plastic film (e) and a foamed plastic layer (d) in order from the top to form a polishing sheet (a). A cushion sheet (b) made of foamed plastic is laminated through a plastic sheet (f), and a back surface tape (g) is attached to the lower part thereof.

  Using the obtained polishing pad, a silicon wafer was polished with an Okamoto polishing machine, and the number of defects and the surface roughness were measured. As shown in Table 1, it was good.

[Example 2]
The polishing pad was used under the same conditions as in Example 1, except that the PET film of Example 1 was replaced with a film having a thickness of 12 μm and an average tensile modulus of 5.2 GPa, and the foamed plastic layer 2 was used instead of the foamed plastic layer 1. Produced. A silicon wafer was polished with an Okamoto polishing machine using the obtained polishing pad, and the number of defects and the surface roughness were measured. As shown in Table 1, it was good.

[Example 3]
A polishing pad was used under the same conditions as in Example 1 except that the PET film of Example 1 was replaced with one having a thickness of 38 μm and an average tensile elastic modulus of 4.5 GPa, and the foamed plastic layer 3 was used instead of the foamed plastic layer 1. Produced. A silicon wafer was polished with an Okamoto polishing machine using the obtained polishing pad, and the number of defects and the surface roughness were measured. As shown in Table 1, it was good.

[Example 4]
The same conditions as in Example 1 except that the PET film of Example 1 was made of polyphenylene sulfide, the thickness was 38 μm, and the average tensile modulus was 5.5 GPa, and the foamed plastic layer 4 was used instead of the foamed plastic layer 1. A polishing pad was manufactured. A silicon wafer was polished with an Okamoto polishing machine using the obtained polishing pad, and the number of defects and the surface roughness were measured. As shown in Table 1, it was good.

[Example 5]
The same conditions as in Example 1 except that the PET film of Example 1 was replaced with nylon 6 having a thickness of 45 μm and an average tensile elastic modulus of 3.8 GPa, and the foamed plastic layer 5 was used instead of the foamed plastic layer 1. A polishing pad was manufactured. A silicon wafer was polished with an Okamoto polishing machine using the obtained polishing pad, and the number of defects and the surface roughness were measured. As shown in Table 1, it was good.

[Example 6]
A polishing pad in which a lattice-like groove having a groove width of 1 mm, a groove pitch of 10 mm, and a groove depth of 0.35 mm was formed on the surface layer (porous polyurethane layer) of the same laminate as in Example 1 by using an NC router was polished. The number of defects and the surface roughness were measured. As shown in Table 1, it was good.

[Comparative Example 1]
A polishing pad was produced under the same conditions as in Example 1 except that the sticking of the PET film of Example 1 was omitted. A silicon wafer was polished with an Okamoto polishing machine using the obtained polishing pad, and the number of defects and the surface roughness were measured. As shown in Table 1, both the number of defects and the surface roughness were poor.

[Comparative Example 2]
A polishing pad was produced under the same conditions as in Example 1 except that the PET film of Example 1 was replaced with one having a thickness of 8 μm and an average tensile elastic modulus of 5.3 GPa. A silicon wafer was polished with an Okamoto polishing machine using the obtained polishing pad, and the number of defects and the surface roughness were measured. As shown in Table 1, both the number of defects and the surface roughness were poor.

[Comparative Example 3]
A polishing pad was produced under the same conditions as in Example 1 except that the PET film of Example 1 was replaced with a film having a thickness of 50 μm and an average tensile elastic modulus of 3.7 GPa. A silicon wafer was polished with an Okamoto polishing machine using the obtained polishing pad, and the number of defects and the surface roughness were measured. As shown in Table 1, the number of defects was poor.

[Example 7]
A polishing pad was produced under the same conditions as in Example 1 except that the PET film of Example 1 was replaced with one having a thickness of 38 μm and an average tensile elastic modulus of 3.3 GPa. A silicon wafer was polished with an Okamoto polishing machine using the obtained polishing pad, and the number of defects and the surface roughness were measured. As shown in Table 1, it was good.

[Example 8]
A polishing pad was produced under the same conditions as in Example 1 except that the PET film of Example 1 was replaced with a film having a thickness of 42 μm and an average tensile elastic modulus of 5.9 GPa. A silicon wafer was polished with an Okamoto polishing machine using the obtained polishing pad, and the number of defects and the surface roughness were measured. As shown in Table 1, it was good.

[Comparative Example 4]
A polishing pad was produced under the same conditions as in Example 3 except that the foamed plastic layer 3 in Example 3 was replaced with the foamed plastic layer 6. A silicon wafer was polished with an Okamoto polishing machine using the obtained polishing pad, and the number of defects and the surface roughness were measured. As shown in Table 1, the surface roughness was poor.

[Comparative Example 5]
A polishing pad was produced under the same conditions as in Example 3 except that the foamed plastic layer 3 in Example 3 was replaced with the foamed plastic layer 7. A silicon wafer was polished with an Okamoto polishing machine using the obtained polishing pad, and the number of defects and the surface roughness were measured. As shown in Table 1, the number of defects was poor.

[Example 9]
A polishing pad was produced under the same conditions as in Example 5 except that the 190 μm thick PET sheet of Example 5 was replaced with a 90 μm PET sheet. A silicon wafer was polished with an Okamoto polishing machine using the obtained polishing pad, and the number of defects and the surface roughness were measured. As shown in Table 1, it was good.

[Example 10]
A polishing pad was produced under the same conditions as in Example 5 except that the 190 μm thick PET sheet in Example 5 was replaced with a 320 μm PET sheet. A silicon wafer was polished with an Okamoto polishing machine using the obtained polishing pad, and the number of defects and the surface roughness were measured. As shown in Table 1, it was good.

[Example 11]
A polishing pad was prepared by forming a grid-like groove having a groove width of 1 mm, a groove pitch of 10 mm, and a groove depth of 0.45 mm on the surface layer (porous polyurethane layer) of the same laminate as in Example 1, and polishing was performed to determine the number of defects. And the surface roughness was measured. As shown in Table 1, it was good.

a. Polishing sheet b. Cushion sheet c. Porous polyurethane layer d. Foamed plastic layer e. Plastic film f. Plastic sheet g. Back tape

Claims (4)

  A polishing pad having a polishing sheet (a) comprising three or more different layers and a cushion sheet (b), wherein the surface layer of the polishing sheet (a) is a porous material mainly composed of polyurethane obtained by a wet coagulation method It is a polyurethane layer (c), and any of the other layers is a foamed plastic layer (d) having a compression modulus of 0.08 MPa or more and 0.25 MPa or less, and the porous polyurethane layer (c) of the surface layer and the above layer A polishing pad, wherein a plastic film (e) having a thickness of 10 to 45 μm is interposed between the foamed plastic layer (d).   The polishing pad according to claim 1, wherein the plastic film (e) has an average tensile elastic modulus of 3.5 to 5.5 GPa.   The cushion sheet (b) is made of foamed plastic, and a plastic sheet (f) having a thickness of 100 to 300 µm is interposed between the abrasive sheet (a) and the cushion sheet (b). Or 2 polishing pads.   The grid | lattice-like groove | channel whose groove depth is smaller than the thickness of the said porous polyurethane layer (c) is formed in the porous polyurethane layer (c) of a surface layer, The any one of Claims 1-3 characterized by the above-mentioned. Polishing pad.