JP2006339573A - Polishing pad and polishing unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polishing pad which is used for forming a flat surface to glass, a semiconductor, a dielectric/metal composite, an integrated circuit, etc, capable of obtaining a stable polishing rate, and furthermore excellent in uniformity through its surface, and to provide a polishing unit. <P>SOLUTION: The polishing pad is composed of, at least, a polishing layer and a cushion layer. The polishing pad is characterized in that the cushion layer is formed of a foamless material, and the surface of the polishing layer has an arithmetic mean roughness Ra of 0.6 to 20.0 μm. The polishing unit is equipped with the polishing pad. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a polishing pad and a polishing apparatus used for forming a flat surface in a semiconductor, a dielectric / metal composite, an integrated circuit, and the like.

  As the density of semiconductor devices increases, the importance of multilayer wiring and the accompanying interlayer insulation film formation, electrode formation of plugs, damascene, and the like is increasing. Along with this, the importance of the planarization process of these interlayer insulation films and electrode metal films has increased, and as an efficient technique for this planarization process, a polishing technique called chemical mechanical polishing is known. Is popular.

  In general, a chemical mechanical polishing apparatus includes a polishing head that holds a semiconductor wafer that is an object to be processed, a polishing pad that performs polishing of the object to be processed, and a polishing surface plate that holds the polishing pad. Then, the polishing process of the semiconductor wafer uses a slurry made of an abrasive and a chemical solution to move the semiconductor wafer and the polishing pad relative to each other, thereby removing the protruding portion of the layer on the surface of the semiconductor wafer and smoothing the layer on the wafer surface. It is to make.

As a polishing pad used in such a polishing apparatus, a polishing pad made of a laminate of a foamed structure containing a microballoon (microcapsule) and a cushion layer made of foamed polyurethane has been introduced (see Patent Document 1). ). However, such a pad has a problem that a stable polishing rate cannot be obtained when a semiconductor wafer is continuously polished. This problem was particularly noticeable in polishing a large semiconductor wafer having a diameter of 300 mm. In order to solve this problem, a non-foamed cushion layer is proposed, but the adhesiveness between the polishing layer and the cushion layer is insufficient, and the polishing layer and the cushion layer peel off during continuous polishing, On the contrary, there was a problem that the polishing characteristics deteriorated.
Japanese National Patent Publication No. 11-512977

  In view of the background of such prior art, the present invention provides an adhesive strength between a cushion layer and a polishing layer in a polishing pad used to form a flat surface in glass, semiconductor, dielectric / metal composite, integrated circuit, and the like. In addition to obtaining a stable polishing rate by making the cushion layer and the polishing layer difficult to peel even during continuous polishing, and further providing a polishing pad and a polishing apparatus with excellent in-plane uniform characteristics. is there.

  In order to solve the above problems, the present invention employs the following means. That is, the polishing pad of the present invention is a polishing pad composed of at least a polishing layer and a cushion layer, the cushion layer is non-foamed, and the arithmetic average roughness Ra of the polishing layer side surface is 0.6 μm or more. It is characterized by being 20.0 μm or less. The polishing apparatus of the present invention is characterized by mounting such a polishing pad.

  According to the present invention, when a flat surface is formed on glass, a semiconductor, a dielectric / metal composite, an integrated circuit or the like, a stable polishing rate is achieved, and a polishing pad excellent in in-plane uniform characteristics and the same are used. A polishing apparatus can be provided.

  The polishing pad referred to in the present invention is composed of a polishing layer, a cushion layer, an adhesive member for bonding them, and a back surface tape for bonding the cushion layer and a surface plate of a polishing machine.

  The arithmetic average roughness Ra of the present invention refers to a value measured with an ultra-deep shape measuring microscope “VK-8500” manufactured by Keyence Corporation.

  The cushion layer of the present invention is non-foamed, and the arithmetic average roughness Ra of the polishing layer side surface is 0.6 μm or more and 20.0 μm or less, more preferably 1.5 μm or more and 10.0 μm or less. is there. When the arithmetic average roughness Ra is less than 0.6 μm, the contact area between the cushion layer and the pressure-sensitive adhesive member becomes small, and sufficient adhesive force cannot be obtained. As a result, stable polishing characteristics cannot be obtained. On the other hand, when the arithmetic average roughness Ra is larger than 20.0 μm, the cushion layer and the pressure-sensitive adhesive member are in a point contact state and the adhesive force is lowered, so that stable polishing characteristics cannot be obtained.

A means for obtaining a preferable arithmetic mean roughness Ra of the polishing layer side surface of the cushion layer is not particularly limited. For example, in the case of a thermosetting resin, a mold surface used for resin molding is formed with a desired roughness. A method of obtaining a sheet having a desired surface roughness by injecting the raw material into the mold and treating the substrate with a desired surface roughness. If it is a thermoplastic resin, a roller surface used at the time of molding is processed to a desired roughness to obtain a sheet having a desired surface roughness, and a separator having a desired surface roughness as a separator used at the time of molding. And a method of obtaining a sheet having a desired surface roughness by extruding a resin onto the separator. In addition, a method of grinding the sheet surface with a belt sander or sandblast can be selected as a means for obtaining a desired surface roughness.
The thickness of the cushion layer of the present invention refers to a value measured with a micrometer “PMU300-25DM” manufactured by Mitutoyo Corporation. The difference between the maximum value and the minimum value of the thickness of the cushion layer is preferably 200 μm or less, and more preferably 100 μm or less. When the difference between the maximum value and the minimum value of the thickness of the cushion layer is larger than 200 μm, the flatness of the polishing tends to deteriorate and a good polishing result tends not to be obtained.

  The cushion layer of the present invention preferably has a micro rubber A hardness of 60 or more and less than 95, more preferably 65 or more and 90 or less. When the micro rubber A hardness is less than 60, the polishing rate tends to be unstable. When the polishing rate is 95 or more, the in-plane uniformity tends to be extremely poor.

  The micro rubber A hardness of the polishing layer of the present invention refers to a value evaluated by a micro rubber hardness meter “MD-1” manufactured by Kobunshi Keiki Co., Ltd. The micro rubber A hardness tester “MD-1” is capable of measuring the hardness of thin and small objects that were difficult to measure with a conventional hardness tester, and is about 1 of the spring type rubber hardness tester (durometer) A type. Since it is designed and manufactured as a reduced model of / 5, a measurement value consistent with the hardness of the spring type hardness tester A type can be obtained. Since a normal polishing pad has a thickness of a polishing layer or a hard layer of less than 5 mm, it cannot be evaluated with a spring type rubber hardness tester type A. Therefore, evaluation is performed with the micro rubber “MD-1”.

  The cushion layer of the present invention includes natural rubber, acrylonitrile butadiene rubber, chloroprene rubber, ethylene propylene rubber, isobutylene isopropylene rubber, chlorosulfonated polyethylene rubber, styrene butadiene rubber, silicone rubber, polyurethane, and various elastomers based on these. However, it is not necessarily limited to these. Among these, polyurethane is preferable, and non-foamed polyurethane is more preferable. Any non-foamed polyurethane may be thermoplastic or thermosetting.

  The thickness of the cushion layer of the present invention is not particularly limited, but is preferably 0.5 mm or more and 3.5 mm or less, more preferably 0.8 mm or more and 2.5 mm or less. When the thickness is smaller than 0.5 mm, the polishing rate tends to be unstable. On the other hand, when the thickness is larger than 3.5 mm, the in-plane uniformity tends to be extremely poor.

  The polishing layer constituting the polishing pad is not particularly limited as long as it is a layer that can polish the substrate and retain the slurry and has a polishing function. For example, JP-A-8-500622 and WO00 / 12262, etc., a hard foam structure polishing layer having closed cells, a non-foam structure polishing layer provided with a fine slurry flow path on the surface described in JP-A-8-511210, A foamed structure polishing layer having continuous pores obtained by impregnating polyurethane into a nonwoven fabric can be used.

  The polishing layer of the polishing pad of the present invention is composed of a foam structure. Examples of the material forming the structure include 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, fluoro rubber, and these as main components Resin and the like. Even in such a resin, a material mainly composed of polyurethane is more preferable in that the closed cell diameter can be controlled relatively easily.

  The polyurethane in the present invention is a polymer synthesized based on polyisocyanate polyaddition reaction or polymerization reaction. The compound used as the symmetry of the polyisocyanate is an active hydrogen-containing compound, that is, a compound containing two or more polyhydroxy groups or amino groups. Examples of the polyisocyanate include tolylene diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate, but are not limited thereto. The polyhydroxy group-containing compound is typically a polyol, and examples thereof include polyether polyol, polytetramethylene ether glycol, epoxy resin-modified polyol, polyester polyol, acrylic polyol, polybutadiene polyol, and silicone polyol. The combination and optimum amount of polyisocyanate and polyol, catalyst, foaming agent, and foam stabilizer are preferably determined according to the hardness, the bubble diameter, and the expansion ratio.

  These polyurethanes preferably have closed cells because of the required polishing characteristics for the CMP polishing pad. As a method for forming closed cells in polyurethane, a chemical foaming method is generally used by blending various foaming agents into the resin at the time of polyurethane production. However, the resin is foamed by mechanical stirring and then cured. Can also be preferably used.

  The average cell diameter of such closed cells is preferably 20 μm or more and 150 μm or less because the flatness of local irregularities of the semiconductor substrate is good. The average cell diameter is more preferably 140 μm or less, and further preferably 130 μm or less. When the average bubble diameter is less than 20 μm, the slurry retainability deteriorates, which is not preferable. Moreover, when the average bubble diameter is larger than 150 μm, the flatness of local irregularities of the semiconductor substrate is deteriorated, which is not preferable. The average bubble diameter is a value measured by observing the cross section of the sample with a SEM at a magnification of 200, then measuring the bubble diameter of the recorded SEM photograph with an image processing apparatus, and taking the average value.

  Although the present invention is a pad containing a polymer polymerized from polyurethane and a vinyl compound and having closed cells, the polyurethane becomes brittle when the hardness is increased, and the toughness and hardness are increased only by the polymer from the vinyl compound. Although it can be increased, it has been difficult to obtain a uniform polishing pad having closed cells. By containing a polymer polymerized from polyurethane and a vinyl compound, it was possible to obtain a polishing pad containing closed cells and having high toughness and hardness.

  The vinyl compound in the present invention is not particularly limited, but a vinyl compound is preferable from the viewpoint of easy impregnation and polymerization in polyurethane. Specifically, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-butyl acrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, isodecyl methacrylate, n-lauryl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxy Propyl methacrylate, 2-hydroxybutyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, glycidyl methacrylate, ethylene glycol dimethacrylate, acrylic acid, methacrylic acid, fumaric acid, dimethyl fumarate, diethyl fumarate, dipropyl fumarate, maleic acid, Dimethyl maleate, diethyl maleate, dipropyl maleate, phenyl maleimide, B hexyl maleimide, isopropyl maleimide, acrylonitrile, acrylamide, vinyl chloride, vinylidene chloride, styrene, alpha-methyl styrene, divinylbenzene, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, and the like. These monomers can be used alone or in combination of two or more.

  Among the vinyl compounds described above, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, and isobutyl methacrylate are easy to form closed cells in polyurethane, have good monomer impregnation properties, and are easy to cure by polymerization. On the other hand, the foam structure containing a polymer polymerized from polymerized and cured polyurethane and a vinyl compound is preferable in that it has high hardness and good flattening characteristics.

  Polymerization initiators for these vinyl compounds include radical initiation of azobisisobutylnitrile, azobis (2,4-dimethylvaleronitrile), azobiscyclohexanecarbonitrile, benzoyl peroxide, lauroyl peroxide, isopropyl peroxydicarbonate, etc. Agents can be used. A redox polymerization initiator, for example, a combination of a peroxide and an amine can also be used. These polymerization initiators can be used not only alone but also by mixing two or more.

  As a method for impregnating a vinyl compound into polyurethane, a method in which polyurethane is immersed in a container containing a monomer and impregnated can be mentioned. In this case, it is also preferable to perform treatments such as heating, pressurization, decompression, stirring, shaking, and ultrasonic vibration for the purpose of increasing the impregnation rate.

  The amount of vinyl compound impregnated in polyurethane should be determined by the type of monomer and polyurethane used and the characteristics of the polishing pad to be produced. Is preferably 30% by weight or more and 90% by weight or less of the content ratio of the polymer obtained from the vinyl compound in the polymerized and cured foam structure. More preferably, it is 50 weight% or more and 90 weight% or less. When the content ratio of the polymer obtained from the vinyl compound is less than 30% by weight, the hardness of the polishing pad tends to be low, which is not preferable. Further, when the content ratio exceeds 90% by weight, the elasticity of the polishing layer tends to be impaired, which is not preferable. In addition, the polymer obtained from the vinyl compound in the polymerization-cured polyurethane and the polyurethane content can be measured by a pyrolysis gas chromatography / mass spectrometry method. As an apparatus that can be used in this method, a double shot pyrolyzer “PY-2010D” (manufactured by Frontier Laboratories) is used as a thermal decomposition apparatus, and “TRIO-1” (manufactured by VG) is used as a gas chromatograph / mass spectrometer. Can be mentioned.

  Various additives such as abrasives, antistatic agents, lubricants, stabilizers, and dyes may be added for the purpose of improving the characteristics of the manufactured polishing pad.

  The micro rubber A hardness of the polishing layer of the present invention refers to a value evaluated with a micro rubber hardness meter “MD-1” manufactured by Kobunshi Keiki Co., Ltd. The micro rubber A hardness tester “MD-1” is capable of measuring the hardness of thin and small objects that were difficult to measure with a conventional hardness tester, and is about 1 of the spring type rubber hardness tester (durometer) A type. Since it is designed and manufactured as a reduced model of / 5, a measurement value consistent with the hardness of the spring type hardness tester A type can be obtained. Since a normal polishing pad has a thickness of a polishing layer or a hard layer of less than 5 mm, it cannot be evaluated with a spring type rubber hardness tester type A. Therefore, evaluation is performed with the micro rubber “MD-1”.

  The polishing layer of the present invention needs to have a micro rubber A hardness of 80 or more, preferably 90 or more. When the micro rubber A hardness is less than 80, it is not preferable because the flatness of local irregularities of the semiconductor substrate tends to be poor.

  The density of the polishing layer of the present invention is a value measured using a Harvard pycnometer (JIS R-3503 standard) and water as a medium.

The polishing layer of the present invention preferably has a density in the range of 0.3 to 1.1 g / cm ³ . When the density is less than 0.3 g / cm ³ , the local flatness becomes poor and the global level difference becomes large. When the density exceeds 1.1 g / cm ³ , scratches are likely to occur. A more preferable density is 0.6 to 0.9 g / cm ³ , and a more preferable density is 0.65 to 0.85 g / cm ³ .

  The surface of the polishing layer of the polishing pad of the present invention is used in a shape that can be taken by a normal polishing pad, such as a grooving shape, a dimple shape, a spiral shape, or a concentric shape, in order to suppress the hydroplane phenomenon.

  In the polishing pad of the present invention, the surface of the polishing layer is usually dressed with a conditioner before or during polishing. As the dressing method, either batch dressing performed before polishing or in-situ dressing performed simultaneously with polishing can be performed.

  Next, the polishing apparatus of the present invention will be described.

  The polishing apparatus of the present invention includes at least means for supplying slurry between the polishing pad, the polishing pad, and the material to be polished as described above, and means for polishing by abutting and relatively moving the polishing pad and the substrate. It has. Means other than the polishing pad can be configured by combining conventionally known means. Using such an apparatus, with a slurry interposed between the polishing pad and the substrate, a load is applied between the polishing pad and the substrate, and the substrate and the polishing pad are moved relative to each other. The abrasive can be polished.

  Using the polishing pad of the present invention, the unevenness of the insulating film and the unevenness of the metal wiring on the semiconductor wafer are locally planarized using silica-based slurry, aluminum oxide-based slurry, cerium oxide-based slurry, etc. as the slurry. Can be reduced, global steps can be reduced, and dishing can be suppressed. As specific examples of the slurry, “CAB-O-SPERSE SC-1” for CMP, “CAB-O-SPERSE SC-112” for CMP, “SEMI-SPERSE AM100” for CMP, “SEMI-” for CMP manufactured by Cabot Corporation. SPERSE AM100C ”,“ SEMI-SPERSE 12 ”for CMP,“ SEMI-SPERSE 25 ”for CMP,“ SEMI-SPERSE W2000 ”for CMP,“ SEMI-SPERSE W-A400 ”for CMP, and the like. It is not limited to.

  The object of the polishing pad of the present invention is, for example, the surface of an insulating layer or metal wiring formed on a semiconductor wafer. As the insulating layer, an interlayer insulating film of metal wiring, a lower insulating film of metal wiring or element isolation The metal wiring is aluminum, tungsten, copper or the like, and there are structurally damascene, dual damascene, plug, and the like. When copper is used as the metal wiring, a barrier metal such as silicon nitride is also subject to polishing. As the insulating film, silicon oxide is mainly used at present, but a low dielectric constant insulating film is used due to the problem of delay time. With the polishing pad of the present invention, it is possible to satisfactorily measure the polishing state while polishing in a state where scratches are difficult to enter. In addition to semiconductor wafers, it can also be used for polishing magnetic heads, hard disks, sapphire, and the like.

The polishing pad of the present invention is suitably used for forming a flat surface on glass, semiconductors, dielectric / metal composites, integrated circuits 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. The measurement was performed as follows.

Micro rubber A hardness:
Measured with a micro rubber hardness meter “MD-1” manufactured by Kobunshi Keiki Co., Ltd. The configuration of the micro rubber hardness tester “MD-1” is as follows.
1.1 Sensor part (1) Load method: cantilever leaf spring (2) Spring load: 0 point / 2.24 gf. 100 points / 33.85 gf
(3) Spring load error: ± 0.32 gf
(4) Needle size: Diameter: 0.16 mm cylindrical shape. 0.5mm height
(5) Displacement detection method: Strain gauge type (6) Pressure leg size: Outer diameter 4mm Inner diameter 1.5mm
1.2 Sensor driving unit (1) Driving method: Vertical driving by a stepping motor. Descent speed control by air damper (2) Vertical movement stroke: 12mm
(3) Descent speed: 10-30mm / sec
(4) Height adjustment range: 0 to 67 mm (distance between sample table and sensor pressing surface)
1.3 Sample stage (1) Sample stage size: Diameter 80mm
(2) Fine movement mechanism: Fine movement by an XY table and a micrometer head. Stroke: 15mm for both X and Y axes
(3) Level adjuster: Level adjustment body legs and round level.
Arithmetic mean roughness Ra:
Measurement was performed with an ultra-deep shape measurement microscope “VK-8500” manufactured by Keyence Corporation, and analysis was performed with analysis software “VK-PC”. Measurement conditions and analysis conditions are as follows.
(1) Objective lens: 100 times (2) Measurement mode: Black and white super depth (3) Measurement pitch: 0.1 μm
(4) Gain: Auto (5) Offset: Auto (6) Shutter: Auto (7) Cutoff: 0.08mm
(8) Smoothing: Simple average ± 2
(9) Tilt correction: None Thickness:
A total of 16 points of 8 points 4 cm from the end and 8 points 25 cm from the end were measured with a micrometer “PMU300-25DM” manufactured by Mitutoyo Corporation, and the average value was obtained as the thickness. Further, the same measurement was performed, and the difference between the maximum value and the minimum value was obtained.

Example 1
30 parts by weight of polypropylene glycol, 40 parts by weight of diphenylmethane diisocyanate, 0.5 parts by weight of water, 0.3 parts by weight of triethylamine, 1.7 parts by weight of a silicone foam stabilizer and 0.09 parts by weight of tin octylate are mixed in a RIM molding machine. The foamed polyurethane sheet having a thickness of 2.3 mm (micro rubber A hardness: 37, density: 0.74 g / cm ³ , average cell diameter of closed cells: 37 μm).

  The foamed polyurethane sheet was immersed in methyl methacrylate to which 0.1 part by weight of azobisisobutylnitrile was added for 60 minutes. Next, 15 parts by weight of polyvinyl alcohol “CP” (degree of polymerization: about 500, manufactured by Nacalai Tesque), 35 parts by weight of ethyl alcohol (special grade reagent, manufactured by Katayama Chemical), water 50 The foamed polyurethane sheet surface layer was coated with polyvinyl alcohol by drying in a solution consisting of parts by weight and then drying.

  Next, the polyurethane foam sheet was sandwiched between two glass plates via a vinyl chloride gasket, and polymerized and cured by heating at 65 ° C. for 6 hours and at 120 ° C. for 3 hours. After releasing from between the glass plates and washing with water, vacuum drying was performed at 50 ° C. A polishing layer was prepared by slicing the hard foam sheet thus obtained to a thickness of 2.0 mm.

The methyl methacrylate content in the polishing layer was 66% by weight. The micro rubber A hardness of the polishing layer was 98, the density was 0.81 g / cm ³ , and the average cell diameter of closed cells was 50 μm.

Next, a commercially available thermosetting polyurethane rubber sheet having a thickness of 2 mm was prepared as a cushion layer, and the surface was ground with a belt sander to obtain a sheet having an arithmetic average roughness Ra of 5.3 μm on the polishing layer side surface (micro rubber A hardness: 89 degrees, thickness: 1.5 mm, difference between maximum value and minimum value of thickness: 60 μm).
The polishing layer and the cushion layer were bonded to each other with a double-sided adhesive tape “442JS” (manufactured by Sumitomo 3M), and a double-sided adhesive tape “442JS” (manufactured by Sumitomo 3M) was attached to the back surface. Next, the surface of the polishing layer was subjected to grid-like groove processing with a width of 2 mm, a depth of 0.9 mm, and a pitch width of 15 mm, and cut into a circular shape with a diameter of 508 mm to obtain a polishing pad. The polishing pad is attached to a polishing machine ("MIRRA" manufactured by Applied Materials), and 600 silicon wafers with 8-inch thermal oxide film are continuously polished using a slurry (Cabot, "SS-25" diluted 2 times). did.

  The average polishing rates of the 10th, 150th, 300th, 450th, and 600th sheets in order from the start of polishing are 2450 angstrom / min, 2450 angstrom / min, 2440 angstrom / min, 2430 angstrom / min. A stable polishing rate of 2440 angstroms / minute was obtained.

  In addition, good uniformity values of 10.1%, 9.8%, 10.5%, 10.1%, and 9.5% were obtained for each in-plane uniformity.

Example 2
A polishing layer similar to that of Example 2 was prepared as the polishing layer.
As a cushion layer, thermoplastic polyurethane was extruded to obtain a sheet having a thickness of 1.2 mm. (Micro rubber A hardness: 84, arithmetic average roughness Ra: 3.2 μm, difference between maximum and minimum thickness: 68 μm)
The polishing layer and the cushion layer were processed in the same manner as in Example 2 to produce a polishing pad.

  The prepared polishing pad is attached to a polishing machine (“MIRRA” manufactured by Applied Materials), and 600 pieces of silicon wafers with 8-inch thermal oxide film are continuously added using slurry (Cabot, “SS-25” 2-fold dilution). Polished.

  The average polishing rates of the 10th, 150th, 300th, 450th, and 600th sheets in order from the start of polishing are 2430 angstrom / min, 2480 angstrom / min, 2510 angstrom / min, 2530 angstrom / min. A stable polishing rate of 2520 angstroms / minute could be obtained.

  In addition, good uniformity values of 10.8%, 10.3%, 10.9%, 10.9%, and 10.7% were obtained for each in-plane uniformity.

Comparative Example 1
A commercially available microballoon-containing foamed polyurethane (density: 0.82 g / cm ³ , average cell diameter: 23 μm) was prepared as the polishing layer.

Next, a commercially available EPDM sheet (micro rubber A hardness: 70, arithmetic average roughness Ra of the polishing layer side surface: 0.4 μm, difference between the maximum value and the minimum value of thickness: 220 μm) was prepared as a cushion layer. .
The polishing layer and the cushion layer were processed in the same manner as in Example 1 to prepare a polishing pad.

  The prepared polishing pad is attached to a polishing machine (“MIRRA” manufactured by Applied Materials), and 600 pieces of silicon wafers with 8-inch thermal oxide film are continuously added using slurry (Cabot, “SS-25” 2-fold dilution). Polished.

  The average polishing rates of the 10th, 150th, 300th, 450th, and 600th sheets are 2230 angstrom / min, 2620 angstrom / min, 2130 angstrom / min, and 2040 angstrom / min in order from the start of polishing. The polishing rate was not stable at 1850 angstroms / minute. Also, the in-plane uniformity was not stable at 15.3%, 17.2%, 18.1%, 17.8%, and 18.5%, and good values were not obtained.

Comparative Example 2
A polishing layer similar to that of Example 2 was prepared as the polishing layer.

  A commercially available EPDM sheet having a thickness of 2 mm was prepared as a cushion layer, and the surface was ground with a belt sander to obtain a sheet having an arithmetic average roughness Ra of 22.4 μm on the polishing layer side surface (micro rubber A hardness: 70, thickness : 1.0 mm, the difference between the maximum value and the minimum value of the thickness: 115 μm). The polishing layer and the cushion layer were processed in the same manner as in Example 2 to produce a polishing pad.

  The prepared polishing pad is attached to a polishing machine (“MIRRA” manufactured by Applied Materials), and 600 pieces of silicon wafers with 8-inch thermal oxide film are continuously added using slurry (Cabot, “SS-25” 2-fold dilution). Polished.

  The average polishing rates of the 10th, 150th, 300th, 450th, and 600th sheets in order from the start of polishing are 2530 angstrom / min, 2610 angstrom / min, 1930 angstrom / min, 1910 angstrom / min The polishing rate was not stable at 2550 angstroms / minute.

Also, the in-plane uniformity of each was not stable at 17.3%, 20.8%, 18.1%, 17.8%, and 19.4%, and good values were not obtained.

Claims (8)

In a polishing pad composed of at least a polishing layer and a cushion layer, the cushion layer is non-foamed, and the arithmetic average roughness Ra of the polishing layer side surface is 0.6 μm or more and 20.0 μm or less. A characteristic polishing pad. The polishing pad according to claim 1, wherein the difference between the maximum value and the minimum value of the thickness of the cushion layer is 200 μm or less. The polishing pad according to claim 1, wherein the cushion layer is polyurethane. The polishing pad according to claim 1, wherein the polishing layer is a polyurethane-based foam. The polishing pad according to claim 4, wherein the polishing layer contains a polymer polymerized from a vinyl compound. The polishing pad according to claim 1, which is used for polishing a semiconductor substrate. The polishing pad according to any one of claims 1 to 6, a material to be polished, a slurry, a means for bringing the polishing pad and the substrate into contact with each other and moving relative to each other, and the polishing pad and the material to be polished A polishing apparatus comprising at least a means for supplying a slurry therebetween. A method for manufacturing a semiconductor device, comprising a process of polishing a surface of a semiconductor substrate using the polishing apparatus according to claim 7.