JP2006015421A - Polishing pad and polishing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polishing pad capable of preventing the occurrence of scratches on the surface of a substrate, and also, capable of optically excellently measuring a polishing state during polishing in the polishing pad used for forming a flat face to glass, a semiconductor, a dielectric-substance/metal composite substance, and an integrated circuit or the like, and also, to provide a polishing device. <P>SOLUTION: The polishing pad is composed of at least a polishing layer 1 and a cushion layer 5. The polishing layer comprises a transparent foamed structure. An opening part 7 is not provided to the polishing layer but provided to an adhesive layer and layers below the cushion layer. <P>COPYRIGHT: (C)2006,JPO&NCIPI

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 associated interlayer insulation film formation, electrode formation of plugs, damascenes, and the like is increasing. Along with this, the importance of the flattening process of these interlayer insulating films and electrode metal films has increased, and a polishing technique called CMP (Chemical Mechanical Polishing) has become widespread as an efficient technique for this flattening process. is doing. In this polishing system using CMP technology, the polishing surface is measured by irradiating the surface to be polished of the substrate with laser light or visible light from the back side (the surface plate side) of the polishing pad while polishing a substrate such as a wafer. The apparatus which attracts attention attracts attention as an important technique (refer patent document 1). As a polishing pad used in such a polishing apparatus, a pad useful for polishing an integrated circuit mounted wafer, at least a part of which is made of a hard uniform resin sheet having no essential ability to absorb and transport slurry particles. As the resin sheet, a polishing pad through which light passes through a wavelength in the range of 190 to 3500 nanometers has been introduced (see Patent Document 2). This polishing pad is represented by Rodel IC-1000, and the light transmission rate of the polishing layer itself comprising a microballoon (microcapsule) -containing foam structure is insufficient. A cushion layer laminated with a double-sided adhesive tape or the like on the layer, and an opening that penetrates all of the polishing layer, the double-sided adhesive tape and the cushion layer is formed at a predetermined position of the polishing pad. A window member made of a solid, transparent, thermosetting, hard, uniform resin is fitted on the polished surface side of the portion. However, in such a polishing pad using a transparent hard uniform resin as a window member, the window member comes into contact with the surface of the substrate, which is the surface to be polished. There was a problem of slur leaking. In addition, there is a problem that the manufacturing process becomes complicated because openings having different shapes are formed in the polishing layer and the cushion layer. Further, there is a process problem that the molding cycle time becomes long in the production of a thermosetting hard uniform resin.
Japanese Patent Laid-Open No. 9-7985 Japanese National Patent Publication No. 11-512977

  In view of the background of such prior art, the present invention provides a polishing pad used for forming a flat surface in glass, semiconductors, dielectric / metal composites, integrated circuits and the like. It is an object of the present invention to provide a polishing pad and a polishing apparatus capable of optically measuring the polishing state.

  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 comprising at least a polishing layer and a cushion layer, the polishing layer is made of a transparent foam structure, and is not provided on the polishing layer, The layer is provided with an opening. 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 a glass, a semiconductor, a dielectric / metal composite, an integrated circuit, etc., there is little generation of scratches on the substrate surface, and the polishing state can be measured optically well during polishing. In addition, a semiconductor device can be provided in a simplified manner.

  The present invention, the above-mentioned problem, that is, a scratch on the substrate surface is less likely to occur, a polishing pad capable of optically measuring the polishing state during polishing, earnestly examined, using a transparent foam structure as the polishing layer, When this transparent polishing layer is not provided with an opening, and the following is provided, that is, the opening for observation of the polishing state is provided below the adhesive layer and the cushion layer, this problem can be solved at once. Has been investigated.

  That is, the point of the present invention is that a transparent foam structure is used as it is as a polishing layer intact, and an opening for observing the polishing state is provided in a layer below the polishing layer.

  As the polishing pad in the present invention, a structure having a polishing layer and an adhesive member, a laminate structure having an abrasive layer, a cushion layer, an adhesive member, and an adhesive tape can be used.

  The polishing layer constituting the polishing pad is not particularly limited as long as it is transparent and can polish the substrate, and holds the slurry and has a polishing function. A hard foamed structure polishing layer having closed cells as described in Japanese Patent No. 500622 and WO00 / 12262, and a fine slurry flow path provided on the surface described in Japanese Patent Publication No. 8-511210. A foam structure polishing layer or a foam structure polishing layer having continuous pores obtained by impregnating a nonwoven fabric with polyurethane can be used.

  The term “transparent” as used in the present invention means that the transmittance of light having a wavelength of 500 to 850 nm with respect to the thickness per 1 mm of the polishing layer is preferably 25% or more, more preferably 30% or more. Particularly preferably, it is 35% or more from the viewpoint of the observation performance of the polished state of the material to be polished from the opening.

The transmittance of the present invention refers to the Lambert-Beer type t ₁ = t ^{(−1 /} − from the transmittance value of the sample obtained using a U-3410 spectroscopic hardness meter manufactured by Hitachi, Ltd. ^L) is converted into a value per 1 mm thickness. Here, t ₁ is the transmittance per ₁ mm thickness, t is the transmittance of the sample obtained from the spectrophotometer, and L is the thickness (mm) of the sample.

  The polishing layer of the polishing pad of the present invention is composed of a transparent foam structure. Examples of the material forming the structure include polyethylene, polypropylene, polyester, polyurethane, polyurea, polyamide, polyvinyl chloride, polyacetal, and 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 the 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 from the standpoint of required polishing characteristics for CMP polishing pads and light transmittance. 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 30 μm or more and 150 μm or less from the standpoint that both good light transmittance and good flatness of local irregularities of the semiconductor substrate can be achieved. The average cell diameter is more preferably 140 μm or less, and further preferably 130 μm or less. An average bubble diameter of less than 30 μm is not preferable because the light transmittance decreases. Moreover, when the average bubble diameter is 150 μm or more, 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-hydroxypropyl 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, maleic Dimethyl acid, diethyl maleate, dipropyl maleate, phenylmaleimide, 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. A foamed structure containing a polymer polymerized from polymerized and cured polyurethane and a vinyl compound is preferable in that it has a high hardness and good flattening characteristics.

  Examples of polymerization initiators for these vinyl compounds include azobisisobutyronitrile, azobis (2,4-dimethylvaleronitrile), azobiscyclohexanecarbonitrile, benzoyl peroxide, lauroyl peroxide, isopropyl peroxydicarbonate, and the like. A radical initiator 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. The content ratio of the polymer obtained from the vinyl compound in the polymerized and cured foam structure and polyurethane is preferably 30/70 to 90/10 by weight. When the content ratio of the polymer obtained from the vinyl compound is less than 30, the hardness of the polishing pad is lowered, which is not preferable. On the other hand, if the content ratio exceeds 90, the elasticity of the polishing layer is 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 meter MD-1 is capable of measuring the hardness of thin and small items that were difficult to measure with a conventional hardness meter, and is about 1/5 of a spring type rubber hardness meter (durometer) A type. Since it is designed and manufactured as a reduced model, a measured value that matches 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 A type.

  The polishing layer of the present invention requires a micro rubber A hardness of 80 degrees or more, preferably 90 degrees or more. When the micro rubber A hardness is less than 80 degrees, the flatness of the local unevenness of the semiconductor substrate becomes poor, which is not preferable.

  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. When the density is less than 0.3, the local flatness becomes poor and the global level difference becomes large. When the density exceeds 1.1, scratches are likely to occur. A more preferable density is in the range of 0.6 to 0.9, and a more preferable density is in the range of 0.65 to 0.85.

  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, dressing is usually performed on the polishing layer surface with a conditioner to which diamond abrasive grains are attached by electrodeposition 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.

  The cushion layer of the present invention is required to have a bulk modulus of 40 MPa or more and a tensile modulus of 1 MPa to 20 MPa. The volume modulus is a volume change measured by applying an isotropic applied pressure to an object whose volume has been measured in advance. Volume modulus = applied pressure / (volume change / original volume).

  The volume modulus of elasticity of the present invention was measured as follows. Place a sample piece and water at 23 ° C into a stainless steel measuring cell with an internal volume of about 40 mL, and install a 0.5 mL borosilicate glass pipette (minimum scale 0.005 mL) as shown in Fig. 5. did. Separately, a tube made of polyvinyl chloride resin (inner diameter 90 mmφ × 2000 mm, wall thickness 5 mm) is used as a pressure vessel, and the measurement cell in which the above sample piece is placed is placed therein. V1 was measured. Subsequently, the sample was not put in the measurement cell, and nitrogen was pressurized at the pressure P shown in Table 1, and the volume change V0 was measured. A value obtained by dividing the pressure P by ΔV / Vi = (V1−V0) / Vi was calculated as the volume modulus of the sample.

  The bulk modulus of the present invention is the bulk modulus when a pressure of 0.04 to 0.14 MPa is applied to the sample at 23 ° C.

  The volume elastic modulus of the cushion layer of the present invention is preferably 40 MPa or more. If it is less than 40 MPa, the uniformity of the flatness (uniformity) of the entire surface of the semiconductor substrate is impaired. A more preferable range of the bulk modulus is 200 MPa or more.

  The tensile modulus of the present invention is determined by applying a tensile stress to a dumbbell shape and measuring the tensile stress in a range of tensile strain (= change in tensile length / original length) from 0.01 to 0.03. Elastic modulus = ((tensile stress when tensile strain is 0.03) − (tensile stress when tensile strain is 0.01)) / 0.02. An example of a measuring device is Tensilon Universal Testing Machine RTM-100 manufactured by Orientec. As measurement conditions, the test speed is 5 cm / min, the test piece shape is a dumbbell shape having a width of 5 mm and a sample length of 50 mm.

  The tensile elastic modulus of the cushion layer of the present invention is preferably 1 MPa or more and 20 MPa or less. If the tensile elastic modulus is less than 1 MPa, the uniformity of the flatness (uniformity) of the entire surface of the semiconductor substrate is impaired, which is not preferable. A tensile modulus exceeding 20 MPa is also not preferable because the flatness uniformity (uniformity) of the entire surface of the semiconductor substrate is impaired. A more preferable tensile elastic modulus range is 1.2 MPa or more and 10 MPa or less.

  As such a cushion layer, non-foamed elastomers such as natural rubber, nitrile rubber, neoprene rubber, polybutadiene rubber, polyurethane rubber, and silicone rubber can be raised, but are not particularly limited thereto. The preferred thickness of the cushion layer is in the range of 0.1 to 100 mm. If it is less than 0.1 mm, the uniformity of the flatness (uniformity) of the entire surface of the semiconductor substrate is impaired, which is not preferable. If it exceeds 100 mm, the local flatness is impaired, which is not preferable. A more preferable thickness range is 0.2 mm or more and 5 mm or less. A more preferable range is 0.5 mm or more and 2 mm or less.

  By providing a light scattering layer or an antireflection layer on the back surface of the polishing layer, which is the same position as the opening of the cushion layer of the present invention, so that measurement light from the back surface of the surface plate is not directly reflected, good measurement can be performed. Therefore, it is preferable. As a method for forming the light scattering layer, a method for roughening the back surface of the light transmissive material by sandblasting or chemical etching, or a method for forming a light scattering layer by coating a solution containing silica sol having a particle size of about 1 to 30 μm. Etc. As a method for forming the antireflection layer, for example, a film having a refractive index lower than that of an elastomer is formed by wet coating or vacuum deposition dry coating so that the optical film thickness is 1/4 or an odd multiple of the light wavelength. By doing so, there is a method of providing a minimum reflectance, that is, a maximum transmittance. Here, the optical film thickness is given by the product of the refractive index of the film and the film thickness of the film. The antireflection film may be a single layer or a multilayer, and an optimum combination is determined in consideration of the refractive index of the elastomer, the antireflection property and the adhesiveness.

  The polishing pad of the present invention is characterized in that the polishing state can be confirmed without providing an opening in the polishing layer.

  As an example of a cushion layer of a polishing pad having an opening formed in a part of the present invention, there is a structure as shown in FIG.

  As shown in FIG. 2, the polishing pad of the present invention has a polishing layer, a cushion layer, and a polishing state observation opening formed in a part of the cushion layer.

  The shape of the opening of the polishing pad is preferably an oval, a circle, or a rectangle, but more preferably a circle from the viewpoint of simplicity of the bonding process. Further, the size of the opening of the polishing pad of the present invention may be larger than the size capable of optically measuring the polishing state during polishing.

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

  The polishing apparatus of the present invention comprises a polishing pad as described above, a means for supplying slurry between the polishing pad and the material to be polished, a means for performing polishing by contacting and relatively moving the polishing pad and the substrate, and the above-mentioned It comprises at least means for optically measuring the polishing state through a translucent material provided on the polishing pad. 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 polishing material can be polished, and the polishing state of the polishing material can be optically determined by irradiating the polishing material with light.

  Specifically, for example, an apparatus configured as shown in FIG. A hole 11 is formed in the surface plate 17 and the opening of the cushion layer of the polishing pad is placed on the hole 11. While the platen 17 is rotating, the position of the hole 11 is determined so that it can be seen from the material 9 to be polished held by the polishing head 10. When the light source 13 is under the surface plate 17 and the hole 11 is close to the workpiece 9, the incident light 15 emitted from the light source 13 passes through the hole 11 of the surface plate 17, the polishing layer 1, and above it. It fixes to the position which hits the surface of the material 9 to be polished. The reflected light 16 on the surface of the material 9 to be polished is guided to the light detection unit 14 by the beam splitter 12, and the waveform of the intensity of light detected by the light detection unit 14 is analyzed to polish the surface of the material to be polished. The state can be measured.

  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. Specific examples of the slurry include CAB-O-SPERSE SC-1 for CMP, CAB-O-SPERSE SC-112 for CMP, SEMI-SPERSE AM100 for CMP, SEMI-SPERSE AM100C for CMP, and SEMI- for CMP. Examples include, but are not limited to, SPERSE 12, SEMI-SPERSE 25 for CMP, SEMI-SPERSE W2000 for CMP, SEMI-SPERSE W-A400 for CMP, and the like.

  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:
It is 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.

Bubble diameter measurement:
Using a SEM2400 scanning electron microscope manufactured by Hitachi, Ltd., and analyzing the photograph observed at 200 times magnification with an image analyzer, all the bubble diameters present in the photograph are measured, and the average value is averaged. The bubble diameter was used.

Transmittance measurement:
Using a U-3410 spectral hardness meter manufactured by Hitachi, Ltd., the transmittance (%) of the sample with respect to light having a wavelength of 500 to 850 nm was measured.

A value per 1 mm thickness was calculated from the obtained value using the Lambert-Beer formula t ₁ = t ^{(−1 / L)} . Here, t ₁ is the transmittance per ₁ mm thickness, t is the transmittance of the sample, and L is the thickness (mm) of the sample.

Measurement of bulk modulus:
Into a stainless steel measuring cell with an internal volume of about 40 mL, 27 g of NBR rubber sheet (specific gravity 1.29, initial volume 21 ml) and 23 ° C. water are placed, and 0.5 mL of borosilicate glass is added to this as shown in FIG. A female pipette (minimum scale 0.005 mL) was attached. Separately, a tube made of polyvinyl chloride resin (inner diameter 90 mmφ × 2000 mm, wall thickness 5 mm) was used as a pressure vessel, and the measurement cell containing the above sample piece was put therein, and nitrogen was applied at the pressure P shown in Table 1. The volume was changed and the volume change V1 was measured. Subsequently, without putting the sample into the measurement cell, nitrogen was pressurized at the pressure P shown in Table 1, and the volume change V0 of only water was measured. A value obtained by dividing the pressure P by ΔV / Vi = (V1−V0) / Vi was calculated as the volume modulus of the sample.

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 azobisisobutyronitrile was added for 60 minutes. Next, the foamed polyurethane sheet was prepared by adding 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 Co., Ltd.), 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 1.25 mm.

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

  The polishing layer was cut into a circle having a diameter of 508 mm, and a lattice-shaped groove with a width of 2 mm, a depth of 0.5 mm, and a pitch width of 15 mm was formed on the surface.

  Next, a 1 mm thick NBR rubber sheet (tensile modulus is 1.3 MPa, volume modulus is listed in Table 1) and double-sided adhesive tape are laminated, and a cushion layer having an opening as shown in FIG. 1 is created by punching. did.

  Finally, the cushion layer and the polishing layer were bonded to form a two-layer polishing pad.

  The prepared polishing pad is attached to a polishing machine (Applied Materials "MIRRA") having an end point detection function as shown in FIG. 3, and slurry (Cabot, W2000) is used to make an 8-inch wafer with a tungsten pattern. When polishing was performed, the end point could be detected.

  When scratches of 0.5 μm or more were measured on the polished wafer using a product name “WM-3” manufactured by Topcon Corporation, the number of scratches was as good as 4.

  When the transmittance of the polishing layer was measured and calculated, it was about 39% as shown in FIG.

  Further, the polishing was continued for 9 hours, but the end point could be detected.

  When the polishing pad was peeled off from the surface plate, there was no leakage of slurry.

Example 2
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 with a RIM molding machine. Then, the foamed polyurethane sheet (micro rubber A hardness = 25 degrees, density: 0.47 g / cm ³ , average closed cell diameter: 72 μm) having a thickness of 2.2 mm was prepared by discharging into a mold and performing pressure molding. .

  The foamed polyurethane sheet was immersed in methyl methacrylate to which 0.1 part by weight of azobisisobutylnitrile was added for 10 minutes. The polyurethane foam in which methyl methacrylate was swollen was sandwiched between glass plates and heated at 65 ° C. for 6 hours, and then heated at 100 ° C. for 3 hours. After heating, it was removed from the glass plate and vacuum dried at 50 ° C.

The obtained hard foam sheet was ground on both sides to prepare a polishing layer having a thickness of 1.25 mm. The polymethyl methacrylate content of the polishing layer was 65% by weight. The micro rubber A hardness of the polishing layer was 87 degrees, the density was 0.50 g / cm ³ , and the average closed cell diameter was 109 μm.

  Subsequent processing was performed in the same manner as in Example 1 to prepare a polishing pad.

  The prepared polishing pad is attached to a polishing machine (Applied Materials "MIRRA") having an end point detection function as shown in FIG. 3, and slurry (Cabot, W2000) is used to make an 8-inch wafer with a tungsten pattern. When polishing was performed, the end point could be detected.

  When the transmittance of the polishing layer was measured and calculated, it was about 45%.

Example 3
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 with a RIM molding machine. Then, the foamed polyurethane sheet (micro rubber A hardness = 37 degrees, density: 0.70 g / cm ³ , average closed cell diameter: 37 μm) having a thickness of 2.2 mm was produced by discharging into a mold and performing pressure molding. .

  The foamed polyurethane sheet was immersed in methyl methacrylate to which 0.1 part by weight of azobisisobutylnitrile was added for 28 minutes. The polyurethane foam in which methyl methacrylate was swollen was sandwiched between glass plates and heated at 65 ° C. for 6 hours, and then heated at 100 ° C. for 3 hours. After heating, it was removed from the glass plate and vacuum dried at 50 ° C.

The obtained hard foam sheet was ground on both sides to prepare a polishing layer having a thickness of 1.25 mm. The polymethyl methacrylate content in the polishing layer was 63% by weight. The micro rubber A hardness of the polishing layer was 94 degrees, the density was 0.76 g / cm ³ , and the average closed cell diameter was 45 μm.

  Subsequent processing was performed in the same manner as in Example 1 to prepare a polishing pad.

  The prepared polishing pad is attached to a polishing machine (Applied Materials "MIRRA") having an end point detection function as shown in FIG. 3, and slurry (Cabot, W2000) is used to make an 8-inch wafer with a tungsten pattern. When polishing was performed, the end point could be detected.

  When the transmittance of the polishing layer was measured and calculated, it was about 42%.

Example 4
30 parts by weight of polypropylene glycol, 40 parts by weight of diphenylmethane diisocyanate, 0.8 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 with a RIM molding machine. The foamed polyurethane sheet (micro rubber A hardness = 39 degrees, density: 0.72 g / cm ³ , average closed cell diameter: 37 μm) having a thickness of 2.2 mm was prepared by discharging into a mold and performing pressure molding. .

  The foamed polyurethane sheet was immersed in methyl methacrylate to which 0.1 part by weight of azobisisobutylnitrile was added for 28 minutes. The polyurethane foam sheet swelled with methyl methacrylate was sandwiched between glass plates and heated at 65 ° C. for 24 hours, and then heated at 100 ° C. for 3 hours. After heating, it was removed from the glass plate and vacuum dried at 50 ° C.

The obtained hard foam sheet was ground on both sides to prepare a polishing layer having a thickness of 1.2 mm. The polymethyl methacrylate content in the polishing layer was 60% by weight. The micro rubber A hardness of the polishing layer was 93 degrees, the density was 0.75 g / cm ³ , and the average closed cell diameter was 44 μm.

  Subsequent processing was performed in the same manner as in Example 1 to prepare a polishing pad.

  The prepared polishing pad is attached to a polishing machine (Applied Materials "MIRRA") having an end point detection function as shown in FIG. 3, and slurry (Cabot, W2000) is used to make an 8-inch wafer with a tungsten pattern. When polishing was performed, the end point could be detected.

  When the transmittance of the polishing layer was measured and calculated, it was about 42%.

Example 5
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 with a RIM molding machine. The foamed polyurethane sheet having a thickness of 2.2 mm (micro rubber A hardness = 25 degrees, density: 0.60 g / cm ³ , average closed cell diameter: 54 μm) was produced by discharging into a mold and performing pressure molding. .

The foamed polyurethane sheet was immersed in methyl methacrylate to which 0.1 part by weight of azobisisobutylnitrile was added for 7 minutes. The polyurethane foam sheet swelled with methyl methacrylate was sandwiched between glass plates and heated at 65 ° C. for 24 hours, and then heated at 100 ° C. for 3 hours. After heating, it was removed from the glass plate and vacuum dried at 50 ° C.

The obtained hard foam sheet was ground on both sides to prepare a polishing layer having a thickness of 1.25 mm. The polymethyl methacrylate content in the obtained polishing layer was 57% by weight. The micro rubber A hardness of the polishing layer was 91 degrees, the density was 0.69 g / cm ³ , and the average closed cell diameter was 65 μm.

  Subsequent processing was performed in the same manner as in Example 1 to prepare a polishing pad.

  The prepared polishing pad is attached to a polishing machine (Applied Materials "MIRRA") having an end point detection function as shown in FIG. 3, and slurry (Cabot, W2000) is used to make an 8-inch wafer with a tungsten pattern. When polishing was performed, the end point could be detected.

  When the transmittance of the polishing layer was measured and calculated, it was about 39%.

Example 6
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 with a RIM molding machine. The foamed polyurethane sheet (micro rubber A hardness = 30 degrees, density: 0.53 g / cm ³ , average closed cell diameter: 57 μm) having a thickness of 2.2 mm was prepared by discharging into a mold and performing pressure molding. .

  The foamed polyurethane sheet was immersed in methyl methacrylate to which 0.1 part by weight of azobisisobutylnitrile was added for 6 minutes. The polyurethane foam sheet swelled with methyl methacrylate was sandwiched between glass plates and heated at 65 ° C. for 24 hours, and then heated at 100 ° C. for 3 hours. After heating, it was removed from the glass plate and vacuum dried at 50 ° C.

The obtained hard foam sheet was ground on both sides to prepare a polishing layer having a thickness of 1.2 mm. The polymethyl methacrylate content in the obtained polishing layer was 55% by weight. The micro rubber A hardness of the polishing layer was 83 degrees, the density was 0.59 g / cm ³ , and the average diameter of closed cells was 79 μm.

  Subsequent processing was performed in the same manner as in Example 1 to prepare a polishing pad.

  The prepared polishing pad is attached to a polishing machine (Applied Materials "MIRRA") having an end point detection function as shown in FIG. 3, and slurry (Cabot, W2000) is used to make an 8-inch wafer with a tungsten pattern. When polishing was performed, the end point could be detected.

  When the transmittance of the polishing layer was measured and calculated, it was about 36%.

Comparative Example 1
Example 1 except that a commercially available microballoon-containing foamed polyurethane IC-1000 (Rodel, Inc.) (density: 0.82 g / cm ³ , average cell diameter: 23 μm) was used instead of the polishing layer of Example 1. As well as. Polishing was performed with the obtained pad, but the end point could not be detected.

  When the transmittance of the polishing layer was measured and calculated, the maximum was 23% as shown in FIG.

  When IC-1000 was analyzed by IR (manufactured by NICOLET, AVATAR 360FT-IR), it was found that polyvinylidene chloride forming a microballoon was contained in addition to polyurethane.

Comparative Example 2
Instead of the polishing layer of Example 1, an opening of 57 mm × 19 mm was punched into IC-1000 (Rodel), which is a commercially available foamed polyurethane containing microballoons, and used as a polishing layer.

  “Suba400” provided with a 50 mm × 13 mm punch opening was used as a cushion layer, and was bonded using an adhesive sheet so that the center of the polishing layer and the opening overlapped.

  300 g of a polyether urethane polymer uni-royal adiprene (R) L-325 containing a reactive isocyanate group in a liquid state and 76 g of 4,4′-methylene-bis 2-chloroaniline as a cross-linking agent were mixed, It was cast into a mold having a thickness of 1.25 mm and heat-treated with a dryer for 17 hours to cure the resin, thereby producing a solid plate of rigid polyurethane. A window member of 57 mm × 19 mm was produced by punching, and was fixed to the opening of the polishing pad with an adhesive sheet to produce a polishing pad with a window member.

  When polishing was performed with the prepared polishing pad, end point detection was possible.

  When scratches of 0.5 μm or more were measured on the polished wafer with a product name “WM-3” manufactured by Topcon Corporation, the number of scratches was 56.

  Further, when polishing was continued for 9 hours, the central part of the window member on the polishing surface side was dented, and the end point could not be detected due to the presence of slurry.

  When the polishing pad was peeled off from the surface plate, the slurry leaked near the opening of the cushion layer.

This figure is a plan view showing an example of a cushion layer having an opening of the present invention. This figure shows an example of a cross-sectional structure of a polishing pad having an opening of the present invention. This figure is a schematic diagram illustrating the principle of optically measuring the polishing state using an example of the polishing apparatus of the present invention. This figure is a graph of the transmittance with respect to the wavelength of Example 1 and Comparative Example 1 of the present invention. This figure is a schematic side view illustrating a measurement cell including a volume change detection unit used in the present invention. This figure is a schematic side view for illustrating the bulk modulus measurement apparatus of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Polishing layer 4 Adhesive layer 5 Cushion layer 7 Opening part 8 Adhesive layer 9 Material to be polished 10 Polishing head 11 Opening part (hole)
12 Beam splitter 13 Light source 14 Photodetector 15 Incident light 16 Reflected light 17 Surface plate 21 Measuring cell 22 Mespipet 23 Container 24 Rubber stopper 25 Sample chamber 26 Lid 27 Lid 28 Mating part 29 Mating part 30 Pressure vessel 31 Pressure gauge 32 Addition Pressure valve 33 Pressure release valve

Claims (12)

In a polishing pad comprising at least a polishing layer and a cushion layer, the polishing layer is formed of a transparent foam structure, and is not provided in the polishing layer, but an opening is provided in a layer below the cushion layer. A polishing pad characterized by that. 2. The polishing pad according to claim 1, wherein the polishing layer has transparency in which the transmittance of light having a wavelength of 500 to 850 nm with respect to the thickness per 1 mm is 25% or more. The polishing pad according to claim 1 or 2, wherein the polishing layer is a foam structure having a micro rubber A hardness of 80 or more and containing a polymer polymerized from polyurethane and a vinyl compound. The polishing pad according to claim 3, wherein the polymer polymerized from the polyurethane and the vinyl compound is integrated. 5. The polishing pad according to claim 4, wherein the content ratio of the polymer polymerized from the vinyl compound is 50% by weight or more and 90% by weight or less. The polishing pad according to claim 5, wherein the vinyl compound is CH ₂ = CR1COOR2 (R1: methyl group, ethyl group, R2: methyl group, ethyl group, propyl group, butyl group). The polishing pad according to claim 1, wherein the density of the polishing layer is in the range of 0.3 to 1.1. The polishing pad according to any one of claims 1 to 7, wherein the polishing layer is a closed-cell transparent foam structure and has an average cell diameter of 30 µm to 150 µm. An opening is formed in the adhesive layer for bonding the polishing layer and the cushion layer, and the back tape of the cushion layer, and the position of the opening of the adhesive layer and the position of the opening of the back tape are the openings of the cushion layer. The polishing pad according to claim 1, wherein the polishing pad is set to overlap with the polishing pad. The polishing pad according to claim 9, wherein the cushion layer has a tensile elastic modulus of 1 to 20 MPa and a bulk elastic modulus of 40 MPa or more. The polishing pad according to any one of claims 1 to 10, means for bringing the polishing pad and the substrate into contact with each other and relatively moving them, and supplying slurry between the polishing pad and the material to be polished A polishing apparatus comprising at least a means and a means for optically measuring a polishing state through a polishing layer of the polishing pad. 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 11.

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