JP5145683B2 - Polishing method, polishing pad, and manufacturing method of polishing pad - Google Patents

Description

  The present invention relates to a polishing method, a polishing pad, and a method for manufacturing a polishing pad. Furthermore, the surface of an insulating layer formed on a semiconductor substrate such as silicon or the surface of a wiring made of a metal and / or a metal compound is mechanically applied. The present invention relates to a polishing method, a polishing pad, and a method for manufacturing a polishing pad that can be used in a step of flattening.

  Large scale integrated circuits (LSIs) typified by semiconductor memories have been integrated year by year, and accordingly, the manufacturing technology of large scale integrated circuits has also been increased in density. Furthermore, with this increase in density, the number of stacked semiconductor device manufacturing locations has also increased. Due to the increase in the number of stacked layers, unevenness of the main surface of the semiconductor substrate caused by stacking, which has not been a problem in the past, has become a problem. For this reason, chemical mechanical polishing (CMP) technology is used to compensate for insufficient depth of focus at the time of exposure due to unevenness caused by lamination or to improve wiring density by flattening the through-hole portion. Planarization of the used semiconductor substrate has been studied (for example, Non-Patent Document 1).

  In general, a CMP apparatus includes a polishing head that holds a semiconductor substrate that is an object to be polished, a polishing pad that performs polishing of the object to be polished, and a polishing surface plate that holds the polishing pad. Then, the polishing process of the semiconductor substrate is performed by using a polishing slurry composed of an abrasive (abrasive grains) and a chemical solution to move the semiconductor substrate and the polishing pad relative to each other, thereby removing the protruding portion of the semiconductor substrate surface layer. The layer on the substrate surface is smoothed.

  As a typical polishing pad currently used in CMP, a polyurethane-impregnated nonwoven fabric, a soft foamed polyurethane, etc., which is a cushion layer, are bonded to a hard polyurethane having a fine foam structure (bubble diameter: about 30-50 μm), which is a polishing layer. A combined two-layer polishing pad can be mentioned (for example, Patent Document 1, Non-Patent Document 2).

  In addition, as an object to be polished provided on a semiconductor substrate of an object to be polished, an interlayer insulating film typified by silicon dioxide has heretofore been mostly, but in recent years a metal typified by aluminum, tungsten, or copper is used. The scope of wiring is also expanding. In polishing metal wiring, the metal that is the object to be polished is soft, so defects such as polishing scratches and dishing and erosion that cause the wiring to be cut into a concave shape are likely to occur. Since the insulating film (Low-k film) is fragile, there are various problems such that film peeling is likely to occur. At present, these defects are reduced by reducing the polishing pressure, that is, low-pressure polishing. On the other hand, however, the low-pressure polishing has a problem that the polishing rate is lowered and the in-plane uniformity (uniformity) is deteriorated due to variations in the polishing rate in the semiconductor substrate surface.

That is, particularly in the polishing of metal wiring, the conventional polishing method is insufficient to achieve both reduction of defects and maintenance of polishing characteristics.
Nikkei Microdevices July 1994, pages 50-57 JP 2006-128563 A CMP Technology Group, Global Net Co., Ltd. (2006), pp. 478-481

  Accordingly, the present inventors have conducted extensive studies on the overall CMP process, such as the polishing pad material, structure, polishing slurry composition, supply amount, polishing pressure, rotation speed, and other polishing conditions in order to solve these problems. By using a polishing pad having a polishing layer having a specific bubble size range, specifically a larger bubble size range than conventional polishing layers, and polishing at low pressure, polishing characteristics such as polishing rate and in-plane uniformity It has been found that defects such as scratches, dishing, and erosion and film peeling can be suppressed without lowering the thickness, that is, it is possible to both reduce defects and maintain polishing characteristics.

  Although it is not clear why it is possible to achieve both reduction of defects and maintenance of polishing characteristics by using a polishing pad having a polishing layer having a larger bubble diameter range than the conventional polishing layer and polishing at low pressure, Estimated as follows. First, regarding the reduction of defects, it is considered that the damage to the object to be polished should be reduced. On the other hand, it is considered that a difference occurs in the polishing characteristics depending on the bubble diameter of the polishing layer. That is, when polishing is performed at a low pressure using a conventional polishing layer, the level difference (roughness) between the surface of the polishing layer (contact surface with the object to be polished) and the bottom of the bubbles exposed on the surface of the polishing layer is small. Since the polishing slurry retention in the inside is small, it is easy to form a thick slurry layer between the object to be polished and the polishing layer, and the object to be polished is lifted, so the polishing rate is lowered and the in-plane uniformity is On the other hand, when polishing is performed at a low pressure using a polishing layer having a larger bubble diameter range than the conventional polishing layer, the level difference (roughness) between the polishing layer surface and the bottom of the bubbles exposed on the polishing layer surface Because of the large retention of abrasive slurry in the bubbles, the slurry layer between the object to be polished and the polishing layer does not become thick, and lifting of the object to be polished can be suppressed, so the polishing rate does not decrease and the surface is uniform. It is considered that the sex does not deteriorate.

  An object of the present invention is to provide a polishing method for polishing a surface of an insulating layer or metal wiring formed on a semiconductor substrate, a polishing pad, and a polishing pad manufacturing method. An object of the present invention is to provide a polishing method, a polishing pad, and a manufacturing method of the polishing pad that can be both maintained, and can exert a remarkable effect particularly in polishing metal wiring.

In order to solve the above problems, the present invention has the following configuration.
“(1) A polishing pad in which the polishing layer has closed cells, the average bubble diameter is 100 to 300 μm, and the ratio of bubbles having a bubble diameter of 50 μm or less in all the bubbles in the polishing layer is 10% or less. Polishing is performed by rotating the polishing head and / or the polishing surface plate in a state where the object to be polished fixed to the polishing surface plate is in contact with the polishing pad at a polishing pressure of 0.1 to 5 psi. A polishing method characterized by the above.
(2) The polishing layer has closed cells, the average bubble diameter is 100 to 300 μm, the ratio of bubbles having a bubble diameter of 50 μm or less in the total bubbles of the polishing layer is 10% or less, and per 1 mm A polishing pad characterized by having a light transmittance of a wavelength of 500 to 850 nm with respect to the thickness of 60% or more.
(3) A first raw material composition in which a gas is mixed or dissolved in a proportion of 5 to 50% by volume with respect to a raw material composition containing polyol as a main component, and a second raw material composition containing isocyanate as a main component. A method for producing a polishing pad using a polyurethane foam obtained by mixing a mixing head, pouring into a molding die at a speed of 600 g / s or more and curing , as a polishing layer, and the polishing layer has closed cells. And the average bubble diameter is 100-300 micrometers, and the ratio of the bubble whose diameter is 50 micrometers or less in all the bubbles is 10% or less, The manufacturing method of the polishing pad characterized by the above-mentioned. "

  According to the present invention, it is possible to provide a polishing method, a polishing pad, and a method for manufacturing a polishing pad that can achieve both reduction of defects and maintenance of polishing characteristics. In particular, a remarkable effect can be exhibited in a polishing method for mechanically flattening the surface of a metal wiring formed on a semiconductor substrate, a polishing pad, and a manufacturing method of the polishing pad.

The polishing method of the present invention, in order to achieve both the maintenance of reduced and the polishing characteristics of the defect, the polishing layer has closed cells, the average cell diameter is 100 to 300 [mu] m, bubbles in the total bubble abrasive layer In a state where the ratio of bubbles having a diameter of 50 μm or less is 10% or less, the polishing pad is fixed to the polishing platen, and the workpiece fixed to the polishing head is brought into contact with the polishing pad at a polishing pressure of 0.1 to 5 psi. It is essential to perform polishing by rotating the polishing head and / or the polishing platen.

  The polishing layer used in the polishing method of the present invention must have closed cells. In the case of open cells, the abrasive penetrates into the polishing layer during polishing, and the polishing properties may deteriorate due to changes in the properties of the polishing layer such as hardness and elastic modulus over time.

  The average cell diameter of the polishing layer used in the polishing method of the present invention is essential to be 100 to 300 μm. When the average bubble diameter is less than 100 μm, a thick slurry layer is easily formed between the object to be polished and the polishing layer when polished at a low pressure, and the polishing rate tends to decrease and the in-plane uniformity tends to deteriorate. It is not preferable. In addition, when the average bubble diameter exceeds 300 μm, the polishing layer such as the flattening characteristic deteriorates due to the decrease in the rigidity of the polishing layer, or the life of the polishing pad using the polishing layer tends to be shortened. It is not preferable. The average cell diameter is more preferably 100 to 250 μm. The average bubble diameter refers to a value measured by observing a cross section of the polishing layer with a magnification of 200 times, measuring the bubble diameter of the next recorded SEM photograph with an image processing apparatus, and taking the average value.

  Even if the polishing pad used in the polishing method of the present invention is a single layer using only the above-mentioned polishing layer, it is a multi-layered one in which another layer such as a cushion layer is laminated on the polishing layer. Or either. The method of laminating other layers such as a cushion layer on the polishing layer is not particularly limited. Specific examples include a double-sided tape, a method of bonding with an adhesive, and a method of heat-sealing.

  The method for fixing the polishing pad to the polishing surface plate in the polishing method of the present invention is not particularly limited. Specific examples include a double-sided tape, a method of bonding with an adhesive, and a method of vacuum adsorption.

  In the polishing method of the present invention, the method for fixing the object to be polished to the polishing head is not particularly limited. Specific examples include a method of bonding with a double-sided tape, an adhesive, wax or the like, a method of vacuum adsorption, a method of water adsorption, and the like. Among these, the method of vacuum adsorbing and the method of water adsorbing are preferable in that the object to be polished can be fixed without inclination and the removal of the object to be polished after polishing is simple.

  The polishing pressure in the polishing method of the present invention must be in the range of 0.1 to 5 psi. If the polishing pressure is less than 0.1 psi, the object to be polished may be detached from the polishing head during polishing, or precise control of the polishing pressure is difficult, and polishing characteristics tend to become unstable. . In addition, when the polishing pressure exceeds 5 psi, scratches are easily generated on the object to be polished, and particularly when the object to be polished is a metal and / or metal compound provided on a semiconductor substrate, defects such as scratches, dishing, and erosion are caused. And film peeling tends to occur frequently. The polishing pressure is preferably 0.3-4 psi, and more preferably 0.5-3 psi.

  In the polishing method of the present invention, it is essential to perform polishing by rotating the polishing head and / or the polishing platen while the object to be polished is in contact with the polishing pad. The rotation direction of the polishing head and the polishing surface plate is not particularly limited. Further, when both the polishing head and the polishing surface plate are rotated, the respective rotation directions may be the same direction or the opposite directions. The rotational speed of the polishing head and polishing platen is not particularly limited. Further, when both the polishing head and the polishing surface plate are rotated, the rotational speeds of the polishing head and the polishing surface plate may be the same or different. Among these, it is preferable to rotate both the polishing head and the polishing surface plate in the same direction at the same rotation speed because the speed is constant on the entire surface of the object to be polished and uniform polishing can be performed. In addition, the polishing surface plate in the present invention is not only one that rotates about a general axis (rotary type), but one that eccentric shaft moves in a small circle (orbital type), belt type (linear type) The rotation mechanism is not particularly limited, and includes all members for fixing the polishing pad.

  In recent polishing, for the purpose of detecting the polishing end point, it is possible to measure the polishing state by irradiating the polishing surface of the object to be polished with laser light or visible light from the back side (the surface plate side) of the polishing pad during polishing. It is being actively conducted. As the polishing pad used here, since the light transmittance of the polishing layer itself is insufficient, a laminated pad having a polishing layer and a cushion layer laminated on the polishing layer with a double-sided adhesive tape or the like is used. An opening that penetrates all of the polishing layer, the double-sided adhesive tape, and the cushion layer is formed at a predetermined position, and a window member made of a transparent thermosetting hard uniform resin having no bubbles on the polishing surface side of the opening is provided. The ones that are embedded are typical. However, on the other hand, in a polishing pad using such a transparent hard uniform resin as a window member, the window member is in contact with the substrate surface, which is the surface to be polished, so that scratches are likely to occur on the substrate surface. There is a problem that the manufacturing process becomes complicated because the slurry leaks and the openings having different shapes are formed in the polishing layer and the cushion layer.

In view of such a problem, as the polishing pad of the present invention, the polishing layer has closed cells, the average bubble diameter is 100 to 300 μm, and the ratio of bubbles having a bubble diameter of 50 μm or less in all the bubbles in the polishing layer Is 10% or less, and the optical transmittance through the polishing layer is not provided even if a window member is not provided by using a polishing pad having a light transmittance of a wavelength of 500 to 850 nm with respect to the thickness per 1 mm of 60% or more. It is possible to accurately measure the polishing state and detect the polishing end point. In addition, in that case, when it is set as the adhesive tape located in the lower layer of a grinding | polishing layer and a cushion layer, the cushion layer and adhesive tape which are further located in the lower layer have the light transmittance of the wavelength of 500-850 nm. It is preferable to use the highest possible one for improving the end point detection accuracy, and when the adhesive tape is located under the polishing layer, and when it is a laminated pad with the cushion layer, the cushion layer and the adhesive located under that layer are further used. It is more preferable to cut out a portion located in the optical end point detection mechanism of the tape polishing apparatus. It is possible to solve all the above-mentioned problems by not providing the window member. The higher the light transmittance at a wavelength of 500 to 850 nm with respect to the thickness per 1 mm of the polishing layer, the higher the accuracy of detection of the polishing end point, but there is no particular upper limit, but it is 65% or more, and more preferably 70% or more. It is more preferable. The transmittance of the present invention refers to the Lambert-Beer type t ₁ = t ^{(1 / (1} ) from the transmittance value of the sample obtained by measurement using a U-3410 spectrophotometer 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.

In the polishing pad of the present invention, it is essential that the ratio of bubbles having a bubble diameter of 50 μm or less in all bubbles in the polishing layer is 10% or less . It can increase the light transmittance of the wavelength of 500~850nm for thickness per 1mm of the polishing layer, because the accuracy of the polishing end point detection can be increased. The ratio of bubbles having a bubble diameter of 50 μm or less in all the bubbles in the polishing layer is preferably as low as possible, but there is no particular lower limit, but it is more preferably 5% or less.

  Further, in the polishing method of the present invention, the polishing pad described above, that is, the polishing layer has closed cells, the average cell diameter is 100 to 300 μm, and 500 to 500 mm relative to the thickness per 1 mm. In a state where a polishing pad having a light transmittance of 850 nm wavelength is 60% or more is fixed to a polishing platen, and an object fixed to the polishing head is in contact with the polishing pad at a polishing pressure of 0.1 to 5 psi, While optically measuring the polishing state of the object to be polished through the polishing layer, the polishing is performed by rotating the polishing head and / or the polishing platen, while reducing both defects and maintaining the polishing characteristics, and the window member. It is preferable that the optical polishing state can be measured and the polishing end point can be detected through the polishing layer without further providing, and further, the bubble diameter is 50 μm or less in all the bubbles of the polishing layer. It is preferable to use a polishing pad having a bubble ratio of 10% or less because the light transmittance at a wavelength of 500 to 850 nm with respect to the thickness per mm of the polishing layer can be increased and the accuracy of detection of the polishing end point can be increased.

  The material of the polishing layer in the polishing method and polishing pad of the present invention is not particularly limited. Specifically, polyethylene, polypropylene, polyester, polyurethane, polyurea, polystyrene, polyvinyl chloride, polyvinylidene fluoride, polymethyl methacrylate, polycarbonate, polyamide, polyacetal, polyimide, epoxy resin, unsaturated polyester resin, melamine resin, phenol resin, Various laminates such as ABS resin, bakelite, epoxy resin / paper, epoxy resin / fiber, FRP, natural rubber, neoprene rubber, chloroprene rubber, butadiene rubber, styrene butadiene rubber, acrylonitrile butadiene rubber, ethylene propylene rubber, silicone rubber, fluorine Various rubbers such as rubber can be used.

  A known method can be used as a method for forming the foam structure on the polishing layer. For example, various foaming agents are blended in the monomer or polymer, followed by foaming by heating or the like, hollow microbeads are dispersed and cured in the monomer or polymer, and the microbead portion is closed cell A method in which a molten polymer is mechanically stirred and foamed, and then cooled and cured, and a solution in which the polymer is dissolved in a solvent is formed into a sheet, and then in a poor solvent for the polymer. Examples include a method of immersing and extracting only a solvent, a method of impregnating a monomer into a sheet-like polymer having a foamed structure, and then curing by polymerization. Among these, the formation of the foam structure of the polishing layer and the control of the bubble diameter are relatively simple, and the monomer is impregnated into the sheet-like polymer having the foam structure in that the preparation of the polishing layer is also simple. Thereafter, a polymerization and curing method is preferred.

  The material of the sheet-like polymer having a foam structure is not particularly limited as long as it can be impregnated with a monomer. Specifically, polyurethane, polyurea, soft vinyl chloride, natural rubber, neoprene rubber, chloroprene rubber, butadiene rubber, styrene butadiene rubber, acrylonitrile butadiene rubber, ethylene propylene rubber, silicone rubber, fluoro rubber, etc. Resin sheet, cloth, nonwoven fabric, paper and the like. In addition, these sheet-like polymers may contain various additives such as abrasives, lubricants, antistatic agents, antioxidants, stabilizers and the like for the purpose of improving the characteristics of the polishing pads to be produced. good. Among these, a material mainly composed of polyurethane is preferable in that the bubble diameter can be controlled relatively easily.

  Polyurethane 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.

  The average cell diameter of the sheet-like polymer having a foam structure is not particularly limited as long as the average cell diameter of the produced polishing layer is in the range of 100 to 300 μm.

The density of the sheet-like polymer having a foamed structure should be determined by the type of monomer and sheet-like polymer to be used and the characteristics of the polishing layer to be produced. Is preferably 0.5 to 1.0 g / cm ³ . If it is lower than 0.5 g / cm ^{3, the} flattening characteristics tend to deteriorate due to a decrease in the rigidity of the produced polishing layer. If it is higher than 1.0 g / cm ³ , the uniformity of the produced polishing layer tends to increase. This is not so preferable because it tends to deteriorate and scratches and dust tend to be generated on the polished semiconductor substrate surface. More preferably, it is 0.6 to 0.9 g / cm ³ . The density means a value measured by the method described in Japanese Industrial Standard (JIS) K7222.

When the sheet-like polymer used in the present invention is a polyurethane foam, in the method for producing a polishing pad of the present invention, the molding method is a ratio of 5 to 50% by volume with respect to the raw material composition mainly composed of polyol. After mixing the first raw material composition in which the gas is mixed or dissolved in step 2 and the second raw material composition mainly composed of isocyanate with a mixing head, the mixture is injected into the mold at a rate of 600 g / s or more. The use of the polyurethane foam obtained by curing has an average cell diameter of 100 to 300 μm, and a light transmittance of a wavelength of 500 to 850 nm with respect to the thickness per 1 mm is 60% or more, In addition, it is essential because a polishing layer in which the proportion of bubbles having a bubble diameter of 50 μm or less in all the bubbles in the polishing layer can be produced is 10% or less. The gas mixed or dissolved in the raw material composition containing the polyol as a main component acts to control the bubble diameter and improve the fluidity when injecting the raw material. When the amount of gas to be mixed or dissolved is less than 5% by volume, the effect of improving the fluidity at the time of pouring the raw material and injecting the raw material is reduced. When the volume exceeds 50% by volume, mixing or dissolution tends to be difficult due to the characteristics of the raw materials and the performance of the apparatus. It is more preferable that 7 to 40% by volume of gas is mixed or dissolved in the raw material composition containing the polyol as a main component in order to stably obtain the effect of controlling the bubble diameter and improving the fluidity when injecting the raw material. The method for mixing or dissolving the gas is not particularly limited. A method in which the back pressure of the raw material tank containing the raw material composition is pressurized with a gas that dissolves the raw material composition, and the raw material composition is stirred with a mixer is simple and preferable. Moreover, if a commercially available apparatus (for example, an air loading unit “TA-200A-12” manufactured by Polymer Engineering Co., Ltd.) capable of automatically controlling the mixing or dissolution amount of the gas and the stirring speed of the raw material is used, the mixing of the gas is performed. Alternatively, it is preferable because the amount of dissolution can be easily adjusted. The type of gas is not particularly limited. Specific examples include air, nitrogen, argon, helium, carbon dioxide and the like. Among these, it is preferable to use at least one gas selected from air, nitrogen, and argon from the viewpoint of easy control of gas mixing or dissolution. After mixing the raw material composition based on polyol and the raw material composition based on isocyanate in separate raw material tanks, mixing or dissolving the gas and adjusting the temperature, supply a predetermined amount to the mixing head by a metering pump, Simultaneously with mixing, the desired polyurethane foam can be obtained by pouring into a mold and curing at a rate of 600 g / s or more. It is essential that the injection rate is 600 g / s or more. When it is 600 g / s or less, the cell diameter of the obtained polyurethane foam tends to be small. Although there is no upper limit in particular, it is preferable that it is 1500 g / s or less from the discharge amount of a general shaping | molding apparatus. The injection rate is more preferably in the range of 700 g / s to 1200 g / s.

  The monomer is not particularly limited as long as it undergoes a polymerization reaction such as addition polymerization, polycondensation, polyaddition, addition condensation, and ring-opening polymerization. Specific examples include vinyl compounds, epoxy compounds, isocyanate compounds, dicarboxylic acids and the like. Among these, a vinyl compound is preferable because it is easy to impregnate and polymerize a sheet-like polymer. Specifically, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, n-butyl acrylate, n-butyl methacrylate, isobutyl acrylate, isobutyl methacrylate, methyl (α-ethyl) acrylate, ethyl (α- Ethyl) acrylate, propyl (α-ethyl) acrylate, butyl (α-ethyl) acrylate, 2-ethylhexyl methacrylate, isodecyl methacrylate, n-lauryl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl Methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, glycidyl methacrylate , Isobornyl methacrylate, acrylic acid, methacrylic acid, fumaric acid, dimethyl fumarate, diethyl fumarate, dipropyl fumarate, maleic acid, dimethyl maleate, diethyl maleate, dipropyl maleate, N-isopropylmaleimide, N- Cyclohexylmaleimide, N-phenylmaleimide, N, N ′-(4,4′-diphenylmethane) bismaleimide, bis (3-ethyl-5-methyl-4-maleimidophenyl) methane, acrylonitrile, acrylamide, vinyl chloride, vinylidene chloride , Styrene, α-methylstyrene, divinylbenzene, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, Methacrylate, and the like. Among these, acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, n-butyl acrylate, n-butyl methacrylate, isobutyl acrylate, isobutyl methacrylate, methyl (α-ethyl) Acrylate, ethyl (α-ethyl) acrylate, propyl (α-ethyl) acrylate, and butyl (α-ethyl) acrylate are preferable in terms of easy impregnation and polymerization of the sheet-like polymer. In addition, these monomers may be 1 type or may mix 2 or more types. In addition, various additives such as abrasives, lubricants, antistatic agents, antioxidants, stabilizers, chain transfer agents, and polymerization inhibitors are added to these monomers for the purpose of improving the properties of the produced polishing layer. An agent may be added.

  In the polishing pad of the present invention, the polishing layer is made of polyurethane and a vinyl compound because the structure of the polishing layer, such as the bubble diameter, and the physical properties such as hardness and rigidity are relatively easy to control and the polishing layer is easy to produce. It is preferable to contain a polymer to be polymerized.

  The monomer polymerization initiator and curing agent used in the polishing layer of the polishing pad of the present invention are not particularly limited, and can be appropriately used depending on the type of monomer. For example, when a vinyl compound is used as the monomer, azobisisobutyronitrile, azobis (2,4-dimethylvaleronitrile), azobiscyclohexanecarbonitrile, benzoyl peroxide, lauroyl peroxide, isopropyl peroxydicarbonate Can be used. In addition, a redox polymerization initiator, for example, a combination of peroxide and amine can also be used. These polymerization initiators and curing agents can be used singly or in combination of two or more.

  Further, as a method for producing a polishing layer in the polishing pad of the present invention, a monomer is brought into contact with a sheet-like polymer having a foam structure in a container containing the monomer, and the monomer is contained inside. The method of polymerization and curing can be employed. 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 monomer impregnated into the sheet-like polymer having a foam structure should be determined by the type of monomer and sheet-like polymer used and the characteristics of the polishing layer to be produced. However, for example, when methyl methacrylate is used as the monomer and polyurethane is used as the sheet-like polymer, the content ratio of the polymer polymerized from the monomer in the polymerized cured product to the polyurethane is 30 by weight. / 70 to 70/30 is preferable. When the content ratio of the polymer obtained from the monomer mixture is less than 30, it is not preferable because the flattening characteristics tend to be poor due to the decrease in hardness and rigidity. On the other hand, when the content ratio exceeds 70, the uniformity and hardness are increased, and dust and scratches tend to increase. More preferably, the content ratio of the polymer polymerized from the monomer to the polyurethane is 35/65 to 65/35 by weight. In addition, the polymer and polyurethane content obtained from the monomer in the polymerized cured product can be measured by a pyrolysis gas chromatography / mass spectrometry technique. 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.

  Examples of the polymerization curing method include a method in which a sheet-like polymer having a foam structure impregnated with a monomer is sealed in a gas barrier material and heated, but is not limited to this method. Examples of gas barrier materials include inorganic glass, metals such as aluminum, copper, iron, and SUS, polyvinyl alcohol (PVA), ethylene-vinyl alcohol copolymer (EVAL), polyamide-based resins, films, and multilayers. Laminated resin, film, aluminum of resin having gas barrier properties such as polyvinyl alcohol (PVA), ethylene-vinyl alcohol copolymer (EVAL), polyamide, etc., produced by methods such as extrusion molding, laminating, coating, etc. And polyolefin resins and films deposited with aluminum oxide (alumina) and silicon dioxide (silica), and laminated resins and films of these and polyolefin resins. The method for sealing the sheet-like polymer having a foam structure impregnated with the monomer in the gas barrier material is not particularly limited. Specifically, a gasket made of an elastic material having gas barrier properties such as soft vinyl chloride, neoprene rubber, butadiene rubber, styrene butadiene rubber, and ethylene propylene rubber is disposed around the sheet-like polymer, and 2 is interposed through the gasket. A method of sandwiching a sheet-like polymer between two sheets of a gas barrier material, a method of inserting and sealing a sheet-like polymer in a casing made of a gas barrier material, and a sheet polymer in a bag made of a gas barrier film The method of inserting and sealing is mentioned. Moreover, when there is a possibility of tearing during polymerization and curing like a bag, it is also preferable to put it in a casing having gas barrier properties. In addition, when polymerized and cured without sealing in the gas barrier material, the monomer is volatilized from the sheet-like polymer, and thus the quality reproducibility of the produced polishing layer tends to be insufficient, As a result, the polishing characteristics tend to become unstable, which is not preferable. The gas barrier material here refers to a material in which the monomer does not volatilize outside when a sheet-like polymer having a foam structure impregnated with the monomer is inserted and sealed.

  Moreover, the order of the step of impregnating the monomer into the sheet-like polymer having a foam structure and the step of inserting the sheet-like polymer having the foam structure impregnated with the monomer into the gas barrier material is particularly limited. It is not a thing. Specifically, (1) A method in which a sheet-like polymer is immersed in a tank containing a monomer so that the monomer is impregnated, and then taken out from the tank, inserted into a gas barrier material, and sealed. (2) A method in which after the sheet-like polymer is inserted into the gas barrier material, the monomer is injected and sealed in the mold and impregnated with the monomer. Can be mentioned. Among these, (2) is preferable in that the monomer odor is not scattered and the working environment is good.

  The heating method for polymerization and curing is not particularly limited. Specifically, heating in an air bath such as a hot air oven, heating in a water bath or oil bath, heating by a jacket or hot press, and the like can be given. Of these, heating in a water bath, an oil bath, or a jacket is preferable because the heat capacity of the heat medium is large and the heat generated during polymerization can be quickly dissipated. The heating temperature and time should be determined by the monomer, the type and amount of the polymerization initiator, the thickness of the resin plate, etc. For example, methyl methacrylate as the monomer and azobisisobutyronitrile as the polymerization initiator In the case where polyurethane is used for the sheet-like polymer, it can be polymerized and cured by heating at 70 ° C. for about 10 hours and then at 120 ° C. for about 3 hours.

  Examples of polymerization and curing methods other than heating include polymerization and curing by irradiation with light, electron beam, and radiation. In addition, it is preferable to mix | blend a polymerization initiator, a sensitizer, etc. in a monomer as needed in that case.

  For example, when a vinyl compound is used as a monomer and polyurethane is used as a sheet-like polymer, the polymerized cured product contains a polymer obtained from the vinyl compound and polyurethane in an integrated manner. Is preferable because the polishing characteristics are stable. Here, the inclusion of the polymer obtained from the vinyl compound and the polyurethane in an integrated manner means that the polymer phase obtained from the vinyl compound and the polyurethane phase are not separated, but quantitatively expressed. Then, the infrared spectrum obtained by observing various portions of the polishing layer essentially having a polishing function with a micro-infrared spectrometer having a spot size of 50 μm shows the infrared spectrum of the polymer obtained from the vinyl compound. It has an absorption peak and an infrared absorption peak of polyurethane, and the infrared spectra at various points are almost the same. Examples of the microinfrared spectroscopic device used here include “IR μs” (manufactured by SPECTRA-TECH).

  The polishing layer can be completed by grinding the front and back surfaces of the polymerized cured product to the required thickness or by slicing to the required thickness. The grinding process is not particularly limited, and devices such as NC routers, diamond disks, belt sanders, etc., and the slicing process is not particularly limited, such as a band knife, a cutting board, or the like, and known devices can be used.

  The thickness of the polishing layer in the polishing method and polishing pad of the present invention is preferably 0.1 to 10 mm. When the thickness is less than 0.1 mm, the mechanical characteristics of the cushion layer preferably used as the base of the polishing pad or the polishing surface plate located under the cushion layer are more significantly reflected in the polishing characteristics than the mechanical characteristics of the polishing layer itself. On the other hand, if it is thicker than 10 mm, the mechanical properties of the cushion layer are not reflected, the followability to the undulation of the semiconductor substrate is lowered, and the uniformity tends to deteriorate. In addition, when optical end point detection is performed, there is a problem that end point detection accuracy is lowered due to a decrease in light transmittance. More preferably, it is 0.2-5 mm, and more preferably 0.5-3 mm.

The density of the polishing layer in the polishing method and polishing pad of the present invention is preferably 0.5 to 1.0 g / cm ³ . If it is lower than 0.5 g / cm ^{3, the} flattening characteristics tend to deteriorate due to a decrease in the rigidity of the produced polishing layer. If it is higher than 1.0 g / cm ³ , the uniformity of the produced polishing layer tends to increase. This is not so preferable because it tends to deteriorate and scratches and dust tend to be generated on the polished semiconductor substrate surface. More preferably, it is 0.6 to 0.9 g / cm ³ .

  In the polishing method of the present invention, the surface of the polishing layer in the polishing pad is processed with grooves, holes, etc. for the purpose of improving the retention and fluidity of the polishing slurry and improving the removal efficiency of polishing debris from the polishing layer surface. It is preferable to apply. The method for forming grooves and holes on the surface of the polishing layer is not particularly limited. Specifically, the method of forming grooves by cutting the surface of the polishing layer using a device such as a router, the heated layer surface is contacted with a heated mold, heat rays, etc., and the contact portion is dissolved. The method of forming a groove | channel by the method, The method of forming the grinding | polishing layer which formed the groove | channel from the beginning using the metal mold | die etc. in which the groove | channel was formed, the method of forming a hole with a drill, a Thomson blade, etc. are mentioned. Further, the shape and diameter of the groove and hole are not particularly limited. Specific examples include a grid shape, a dimple shape, a spiral shape, and a concentric shape.

  The polishing pad of the polishing method and polishing pad of the present invention can be preferably used even if it is composed of a single layer or a plurality of layers. However, when the polishing pad according to the present invention is used for planarization of a semiconductor substrate by CMP, the polishing pad is composed of at least two layers having different hardness from the viewpoint of excellent followability to the waviness of the semiconductor substrate. Is preferred. Further, the hardness of the layer constituting the polishing pad is preferably such that the hardness of the outermost surface is higher than the hardness of the adjacent layer. In this case, the layer having the highest hardness on the outermost surface functions as a polishing layer, and the layer having a lower hardness adjacent thereto functions as a cushion layer. That is, in the case of a single layer, a polishing layer, a double-sided adhesive tape or an adhesive are bonded together in this order. In the case of two layers, an abrasive layer, a double-sided adhesive tape or an adhesive, a cushion layer, a double-sided adhesive tape or an adhesive are added. It becomes what was pasted together.

  The hardness of the outermost layer, that is, the polishing layer, is preferably 80 degrees or more in micro rubber A hardness. When the micro rubber A hardness is less than 80 degrees, the planarization characteristic tends to deteriorate, which is not preferable. More preferably, it is 90 degrees or more. The hardness of the layer adjacent to the outermost layer, that is, the cushion layer, is preferably lower than the hardness of the polishing layer, and more preferably 10 degrees or more in order to obtain good cushioning properties. In addition, the micro rubber A hardness in the present invention refers to a value measured with a micro rubber hardness meter MD-1 manufactured by Kobunshi Keiki Co., Ltd. The micro rubber hardness tester MD-1 is capable of measuring the hardness of thin and small samples, which are difficult to measure with a conventional hardness tester, and is approximately 1 / of the spring type rubber hardness tester (durometer) A type. Since it is designed and manufactured as a reduced model of 5, the measured value can be considered to be the same as the measured value in the spring type rubber hardness tester A type. In addition, since the thickness of a normal polishing pad or a hard layer is too thin at 5 mm or less, a spring type rubber hardness meter cannot be evaluated, but it can be evaluated with the micro rubber hardness meter MD-1.

  The material of the cushion layer is not particularly limited. Specifically, polyurethane-impregnated nonwoven fabric, polyethylene, polypropylene, polyester, polyurethane, polyurea, polystyrene, polyvinyl chloride, and other plastic foams that are currently commonly used, neoprene rubber, butadiene rubber, styrene butadiene rubber, acrylonitrile Various rubbers such as butadiene rubber, ethylene propylene rubber, silicone rubber, urethane rubber, and fluorine rubber, and foams thereof can be used. When the cushion layer is a foam, the bubbles may be either open cells or closed cells. The method for forming bubbles is not particularly limited. Specifically, a foaming agent is mixed in the cushion layer material and then heated and foamed, a thermal expandable microparticle is mixed in the cushion layer material and then heated to foam the microparticles, and a hollow microparticle in the cushion layer material A method of curing after mixing, a method of mechanically mixing bubbles in the cushion layer material, a method of curing, a method of immersing a solution in which the cushion layer material is dissolved in a good solvent, and then wet coagulating, etc. Can be mentioned.

  The preferable thickness of the cushion layer is 0.1 to 10 mm. If it is smaller than 0.1 mm, the uniformity tends to deteriorate. Moreover, when larger than 10 mm, there exists a tendency for global flatness and local flatness to be impaired. It is preferably 0.2 to 5 mm, more preferably 0.5 to 3 mm.

  In the polishing method of the present invention, it is preferable to roughen the surface of the polishing pad using a dresser before polishing the semiconductor substrate in order to obtain good polishing characteristics. A dresser is a wheel in which diamond abrasive grains are electrodeposited and fixed. The grain size of the diamond abrasive grains can be selected in the range of 10 μm to 300 μm. The pressing pressure of the dresser is not particularly limited. In addition, in order to stabilize the polishing rate for both batch dressing in which a polishing pad is conditioned using a dresser after the completion of one or more polishings, and in-situ dressing in which dressing is performed simultaneously with polishing. It can be preferably implemented.

  The object to be polished in the polishing method and polishing pad of the present invention is not particularly limited. Specific examples include semiconductor substrates, optical glass, optical lenses, magnetic heads, hard disks, color filters for liquid crystal displays, optical members such as a back plate for plasma displays, ceramics, sapphire, and the like. Among these, application to a semiconductor substrate is particularly preferable. More specifically, the surface of the wiring made of an insulating layer, metal and / or metal compound provided on the semiconductor substrate is preferable as the object to be polished. Specifically, the insulating layer includes an interlayer insulating film or lower insulating film of metal wiring, shallow trench isolation (STI) used for element isolation, and the metal wiring includes aluminum, tungsten, copper, and the like. Structurally, there are damascene, dual damascene, plug, etc. Currently, silicon dioxide is mainly used as the insulating film. However, the use of a low dielectric constant insulating film is being studied due to the problem of delay time, and any of them can be polished in the present invention. In addition, when copper is used for the metal wiring, a barrier metal such as silicon nitride is also subject to polishing. Among these, an object to be polished is provided on a semiconductor substrate because of the characteristics of the present invention that defects such as scratches, dishing, and erosion and film peeling can be suppressed without reducing polishing characteristics such as polishing rate and in-plane uniformity. The present invention can be preferably applied to a wiring made of a metal and / or a metal compound.

  According to the present invention, it is possible to provide a polishing method, a polishing pad, and a method for manufacturing a polishing pad that can achieve both reduction of defects and maintenance of polishing characteristics.

  Hereinafter, the details of the present invention will be described with reference to examples. Various evaluations of the polishing pad were performed as follows.

  The micro rubber A hardness of the polishing layer and the cushion layer was measured with a micro rubber A hardness meter “MD-1” (manufactured by Kobunshi Keiki Co., Ltd.).

  The density of the polishing layer was measured by the method described in JIS K7222.

  The average bubble size and bubble size distribution of the polishing layer were determined by analyzing a photograph of the pad cross section observed at 200 times magnification using a scanning electron microscope “SEM2400” (manufactured by Hitachi, Ltd.) with an image processing apparatus. All the bubble diameters present in the photograph were measured, and the average value was taken as the average bubble diameter. In addition, the bubble size distribution was calculated from all the bubble size measurements.

Light transmittance of the polishing layer, after measuring the light transmittance at a wavelength of 500~850nm using Hitachi Ltd. U-3410 spectrophotometer, and the average value was calculated, Lambert-Beer equation t ₁ = T ^{(1 / L)} was used to convert to 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.

  Polishing evaluation was performed as follows.

1. Polishing Rate, Uniformity, Scratch (1) Test Wafer As a semiconductor substrate, an 8 inch silicon wafer having a thickness of 2 μm formed by plating was used.
(2) Evaluation method A polishing pad was affixed on a surface plate of a polishing machine “MIRRA (registered trademark)” (Applied Materials Co., Ltd.), and the thickness of the Cu film on the surface was measured in advance by a metal film thickness meter “VR-120S” (Hitachi). A test wafer measured using Kokusai Denki Co., Ltd. was attached to a polishing head, and 150 ml of polishing slurry “iCue5003” (manufactured by Cabot Microelectronics Japan Co., Ltd.) having the composition used in the instruction manual was attached. Rotating in the same direction as the polishing platen at a predetermined polishing pressure, a polishing platen rotation speed of 45 rpm, and a polishing head rotation number of 45 rpm while being supplied onto the polishing pad at / min. The thickness of the Cu film was measured using a metal film thickness meter “VR-120S” (manufactured by Hitachi Kokusai Electric Co., Ltd.), and the polishing rate at each point according to the following formula (1) The uniformity was calculated by the following equation (2).

  Polishing rate = (thickness of oxide film before polishing−thickness of oxide film after polishing) / polishing time (1).

  Uniformity (%) = (maximum polishing rate−minimum polishing rate) / (maximum polishing rate + minimum polishing rate) × 100 (2).

  Next, scratches of 0.2 μm or more were counted with a dust inspection device “WM-3” (manufactured by Topcon Corporation).

2. Dishing (1) Test wafer As a semiconductor substrate, an 8 inch silicon wafer with grooves of 100 μm width and 0.7 μm depth formed at intervals of 100 μm, and copper is formed on this by plating with a thickness of 2 μm is used. did.
(2) Evaluation method A polishing pad is affixed on a surface plate of a polishing machine “MIRRA (registered trademark)” (Applied Materials Co., Ltd.), a test wafer is attached to a polishing head, and polishing of the composition used is described in the instruction manual While supplying slurry “iCue5003” (manufactured by Cabot Microelectronics Japan Co., Ltd.) onto the polishing pad at 150 ml / min, the polishing platen at a predetermined polishing pressure, polishing platen rotation speed of 45 rpm, and polishing head rotation number of 45 rpm After rotating for 150 seconds and polishing for 150 seconds, the thickness of the copper wiring center and the copper wiring edge of the test wafer was measured using the step measurement device “P-15” (manufactured by KLA Tencor). The difference was taken as the dishing amount.

3. Polishing end point detection A polishing machine “MIRRA (registered trademark)” (manufactured by Applied Materials) with an end point detection function was used to perform the above polishing using the end point detection function to determine whether end point detection was possible.

Example 1
Polyether polyol maintained at a liquid temperature of 40 ° C .: “Sanix (registered trademark) FA-909” (manufactured by Sanyo Chemical Industries, Ltd.) 100 parts by weight, chain extender: 8 parts by weight of ethylene glycol, amine catalyst: 1 part by weight of “Dabco (registered trademark) 33LV” (produced by Air Products Japan), amine catalyst: 0.1 part by weight of “Toyocat (registered trademark) ET” (produced by Tosoh Corporation), silicone foam stabilizer: "TEGOSTAB (registered trademark) B8462" (manufactured by Th. Goldschmidt AG) 0.5 part by weight, foaming agent: A liquid obtained by mixing 0.2 part by weight of water, and isocyanate maintaining the liquid temperature at 40 ° C: "Sunform (registered trademark) NC-703" 95 parts by weight of B liquid was collided with a RIM molding machine at a discharge pressure of 15 MPa, and then kept at 60 ° C. Discharging a discharge rate 800 g / sec within, by standing for 10 minutes, size 700 × 700 mm, foamed polyurethane block thickness 10 mm (micro rubber A hardness: 47 degrees, a density: 0.77 g / cm ^3, average cell (Diameter: 95 μm). Thereafter, the foamed polyurethane block was sliced with a slicer to a thickness of 3 mm.

Next, the foamed polyurethane sheet was immersed in methyl methacrylate to which 0.1 part by weight of azobisisobutyronitrile was added for 45 minutes. Next, the foamed polyurethane sheet impregnated with methyl methacrylate was sandwiched between two glass plates via a vinyl chloride gasket, and polymerized and cured by heating at 70 ° C. for 10 hours and at 120 ° C. for 3 hours. After releasing from between the glass plates, vacuum drying was performed at 50 ° C. A polishing layer was prepared by grinding both surfaces of the hard foam sheet thus obtained to a thickness of 2 mm. The obtained polishing layer had a micro rubber A hardness of 92 degrees, a density of 0.77 g / cm ³ , an average cell diameter of 124 μm, and a polymethyl methacrylate content of 55 wt% in the polishing layer. The polishing layer was cut into a circle having a diameter of 508 mm, and a lattice-shaped groove with a width of 1 mm, a depth of 0.8 mm, and a pitch width of 25 mm was formed on the surface. Next, a double-sided pressure-sensitive adhesive tape “442JS” (manufactured by Sumitomo 3M Co., Ltd.) is attached to the polishing layer, and this is attached to a nonwoven fabric wet polyurethane (thickness 1 mm, micro rubber A hardness 53 degrees) as a cushion layer, Further, a double-sided adhesive tape “442JS” (manufactured by Sumitomo 3M Limited) was attached under the cushion layer to prepare a two-layer polishing pad, and polishing evaluation was performed at a polishing pressure of 2 psi. The polishing rate was 7200 angstroms / minute. The uniformity was 4%. There were 29 scratches. The dishing was 90 angstroms. Further, no film peeling was observed on the surface of the test wafer after polishing.

Example 2
Polyether polyol maintained at a liquid temperature of 25 ° C .: “Sanix (registered trademark) FA-909” (manufactured by Sanyo Chemical Industries, Ltd.) 100 parts by weight, chain extender: 8 parts by weight of ethylene glycol, amine catalyst: 1 part by weight of “Dabco (registered trademark) 33LV” (produced by Air Products Japan), amine catalyst: 0.1 part by weight of “Toyocat (registered trademark) ET” (produced by Tosoh Corporation), silicone foam stabilizer: "TEGOSTAB (registered trademark) B8462" (manufactured by Th. Goldschmidt AG) 0.5 part by weight, foaming agent: A liquid obtained by mixing 0.2 part by weight of water, and isocyanate maintaining the liquid temperature at 25 ° C: "Sunform (registered trademark) NC-703" 95 parts by weight of B liquid was collided with a RIM molding machine at a discharge pressure of 15 MPa, and then kept at 60 ° C. Discharged at a discharge amount 1000 g / sec within, by standing for 10 minutes, size 700 × 700 mm, foamed polyurethane block thickness 10 mm (micro rubber A hardness: 48 degrees, a density: 0.77 g / cm ^3, average cell (Diameter: 152 μm). Thereafter, the foamed polyurethane block was sliced with a slicer to a thickness of 3 mm. A polishing layer was prepared in the same manner as in Example 1 except that the polyurethane foam sheet was used. The obtained polishing layer had a micro rubber A hardness of 92 degrees, a density of 0.79 g / cm ³ , an average cell diameter of 192 μm, and a polymethyl methacrylate content of 55 wt% in the polishing layer. Next, a two-layer polishing pad was prepared in the same manner as in Example 1 except that the polishing layer was used, and polishing evaluation was performed at a polishing pressure of 2 psi. The polishing rate was 7400 angstroms / minute. The uniformity was 4%. There were 31 scratches. The dishing was 80 angstroms. Further, no film peeling was observed on the surface of the test wafer after polishing.

Comparative Example 1
A two-layer polishing pad was prepared in the same manner as in Example 1, and polishing evaluation was performed at a polishing pressure of 5.5 psi. The polishing rate was 13100 angstroms / minute. Uniformity was 23%. There were 340 scratches. The dishing was 820 angstroms. Moreover, film peeling was observed on the test wafer surface after polishing.

Comparative Example 2
Polyether polyol maintained at a liquid temperature of 40 ° C .: “Sanix (registered trademark) FA-909” (manufactured by Sanyo Chemical Industries, Ltd.) 100 parts by weight, chain extender: 8 parts by weight of ethylene glycol, amine catalyst: "Dabco (registered trademark) 33LV" (produced by Air Products Japan) 1.5 parts by weight, amine catalyst: "Toyocat (registered trademark) ET" (produced by Tosoh Corp.) 0.15 parts by weight, silicone foam stabilizer Agent: “TEGOSTAB (registered trademark) B8462” (manufactured by Th. Goldschmidt AG) 1.5 parts by weight, foaming agent: liquid A prepared by mixing 0.2 parts by weight of water, and the liquid temperature was kept at 40 ° C. Isocyanate: “Sunfoam (registered trademark) NC-703” 95 parts by weight of B liquid was impact-mixed with a RIM molding machine at a discharge pressure of 15 MPa, and then maintained at 60 ° C. Was in the mold is ejected by the discharge rate 500 g / sec, by standing for 10 minutes, size 700 × 700 mm, thickness 10mm foamed polyurethane block (micro rubber A hardness: 48 degrees, a density: 0.77 g / cm ³ , Average bubble diameter: 38 μm). Thereafter, the foamed polyurethane block was sliced with a slicer to a thickness of 3 mm. A polishing layer was prepared in the same manner as in Example 1 except that the polyurethane foam sheet was used. The obtained polishing layer had a micro rubber A hardness of 92 degrees, a density of 0.78 g / cm ³ , an average cell diameter of 44 μm, and a polymethyl methacrylate content of 55 wt% in the polishing layer. Next, a two-layer polishing pad was prepared in the same manner as in Example 1 except that the polishing layer was used, and polishing evaluation was performed at a polishing pressure of 2 psi. The polishing rate was 5600 Å / min. The uniformity was 10%. There were 23 scratches. The dishing was 80 angstroms. Further, no film peeling was observed on the surface of the test wafer after polishing.

Comparative Example 3
A two-layer polishing pad was prepared in the same manner as in Comparative Example 2, and polishing evaluation was performed at a polishing pressure of 5.5 psi. The polishing rate was 11400 angstroms / minute. Uniformity was 26%. There were 350 scratches. The dishing was 650 angstroms. Moreover, film peeling was observed on the test wafer surface after polishing.

Comparative Example 4
Polyether urethane polymer “Adiprene (registered trademark)” L-325 (manufactured by Uniroyal) 78 parts by weight, 4,4′-methylene-bis (2-chloroaniline) 20 parts by weight, hollow polymer microspheres 1.8 parts by weight of “Expancel (registered trademark)” 551DE (manufactured by Kemanobel) was mixed with a RIM molding machine and discharged into a mold to prepare a polymer molded body. This polymer molded body was sliced with a slicer to a thickness of 1.25 mm to produce a rigid foamed polyurethane sheet, which was used as a polishing layer. The obtained polishing layer had a micro rubber A hardness of 98 degrees, a density of 0.81, and an average cell diameter of 33 μm. Next, a two-layer polishing pad was prepared in the same manner as in Example 1 except that the polishing layer was used, and polishing evaluation was performed at a polishing pressure of 2 psi. The polishing rate was 5010 Å / min. The uniformity was 11%. There were 103 scratches. The dishing was 260 angstroms. Further, no film peeling was observed on the surface of the test wafer after polishing.

Example 3
Polyether polyol maintained at a liquid temperature of 40 ° C .: “Sanix (registered trademark) FA-909” (manufactured by Sanyo Chemical Industries, Ltd.) 100 parts by weight, chain extender: 8 parts by weight of ethylene glycol, amine catalyst: 1 part by weight of “Dabco (registered trademark) 33LV” (produced by Air Products Japan), amine catalyst: 0.1 part by weight of “Toyocat (registered trademark) ET” (produced by Tosoh Corporation), silicone foam stabilizer: "TEGOSTAB (registered trademark) B8462" (manufactured by Th. Goldschmidt AG) 0.5 parts by weight, foaming agent: 12 parts of nitrogen was dissolved in liquid A by mixing 0.2 parts by weight of water, and then liquid A And isocyanate having a liquid temperature of 40 ° C .: “Sunfoam (registered trademark) NC-703” 95 parts by weight of B liquid was impregnated with a RIM molding machine at a discharge pressure of 15 MPa. After mixing, the foamed polyurethane block having a size of 700 × 700 mm and a thickness of 10 mm (micro rubber A hardness: 47 °, Density: 0.77 g / cm ³ , average bubble diameter: 98 μm). Thereafter, the foamed polyurethane block was sliced with a slicer to a thickness of 3 mm.

Next, the foamed polyurethane sheet was immersed in methyl methacrylate to which 0.1 part by weight of azobisisobutyronitrile was added for 45 minutes. Next, the foamed polyurethane sheet impregnated with methyl methacrylate was sandwiched between two glass plates via a vinyl chloride gasket, and polymerized and cured by heating at 70 ° C. for 10 hours and at 120 ° C. for 3 hours. After releasing from between the glass plates, vacuum drying was performed at 50 ° C. A polishing layer was prepared by grinding both surfaces of the hard foam sheet thus obtained to a thickness of 2 mm. The obtained polishing layer has a micro rubber A hardness of 92 degrees, a density of 0.77 g / cm ³ , an average bubble diameter of 124 μm, a ratio of bubbles of 50 μm or less is 8%, and a thickness of 500 to 850 nm with respect to the thickness per 1 mm of the polishing layer. The light transmittance at a wavelength of 67% was 67%, and the content of polymethyl methacrylate in the polishing layer was 55% by weight. The polishing layer was cut into a circle having a diameter of 508 mm, and a lattice-shaped groove with a width of 1 mm, a depth of 0.8 mm, and a pitch width of 25 mm was formed on the surface. Next, a double-sided pressure-sensitive adhesive tape “442JS” (manufactured by Sumitomo 3M Co., Ltd.) is attached to the polishing layer, and this is attached to a nonwoven fabric wet polyurethane (thickness 1 mm, micro rubber A hardness 53 degrees) as a cushion layer, Further, a double-sided adhesive tape “442JS” (manufactured by Sumitomo 3M Limited) was attached under the cushion layer to prepare a two-layer polishing pad, and polishing evaluation was performed at a polishing pressure of 2 psi. End point detection was possible with high accuracy in polishing evaluation. The polishing rate was 7200 angstroms / minute. Uniformity was 5%. There were 26 scratches. The dishing was 90 angstroms. Further, no film peeling was observed on the surface of the test wafer after polishing.

Example 4
Polyether polyol maintained at a liquid temperature of 25 ° C .: “Sanix (registered trademark) FA-909” (manufactured by Sanyo Chemical Industries, Ltd.) 100 parts by weight, chain extender: 8 parts by weight of ethylene glycol, amine catalyst: 1 part by weight of “Dabco (registered trademark) 33LV” (produced by Air Products Japan), amine catalyst: 0.1 part by weight of “Toyocat (registered trademark) ET” (produced by Tosoh Corporation), silicone foam stabilizer: "TEGOSTAB (registered trademark) B8462" (manufactured by Th. Goldschmidt AG) 0.5 parts by weight, foaming agent: 15 parts of nitrogen was dissolved in liquid A by mixing 0.2 parts by weight of water, and then liquid A And isocyanate whose liquid temperature was kept at 25 ° C .: “Sunfoam (registered trademark) NC-703” B liquid consisting of 95 parts by weight was discharged with a RIM molding machine at a discharge pressure of 15 MPa. After mixing, the foamed polyurethane block having a size of 700 × 700 mm and a thickness of 10 mm (micro rubber A hardness: 48 degrees, by discharging at a discharge rate of 1000 g / sec into a mold kept at 60 ° C. and leaving for 10 minutes. Density: 0.77 g / cm ³ , average bubble diameter: 148 μm). Thereafter, the foamed polyurethane block was sliced with a slicer to a thickness of 3 mm. A polishing layer was prepared in the same manner as in Example 1 except that the polyurethane foam sheet was used. The obtained polishing layer has a micro rubber A hardness of 92 degrees, a density of 0.79 g / cm ³ , an average bubble diameter of 192 μm, a ratio of bubbles of 50 μm or less of 4%, and a thickness of 500 to 850 nm with respect to the thickness per 1 mm of the polishing layer. The light transmittance at a wavelength of 71% was 71%, and the content of polymethyl methacrylate in the polishing layer was 55% by weight. Next, a two-layer polishing pad was prepared in the same manner as in Example 1 except that the polishing layer was used, and polishing evaluation was performed at a polishing pressure of 2 psi. End point detection was possible with high accuracy in polishing evaluation. The polishing rate was 7300 Å / min. The uniformity was 4%. There were 23 scratches. The dishing was 80 angstroms. Further, no film peeling was observed on the surface of the test wafer after polishing.

Comparative Example 5
Polyether polyol maintained at a liquid temperature of 40 ° C .: “Sanix (registered trademark) FA-909” (manufactured by Sanyo Chemical Industries, Ltd.) 100 parts by weight, chain extender: 8 parts by weight of ethylene glycol, amine catalyst: "Dabco (registered trademark) 33LV" (produced by Air Products Japan) 1.5 parts by weight, amine catalyst: "Toyocat (registered trademark) ET" (produced by Tosoh Corp.) 0.15 parts by weight, silicone foam stabilizer Agent: “TEGOSTAB (registered trademark) B8462” (manufactured by Th. Goldschmidt AG) 1.5 parts by weight, foaming agent: After dissolving 10% of nitrogen in liquid A mixed with 0.2 part by weight of water, Liquid A and isocyanate maintained at 40 ° C .: “Sunfoam (registered trademark) NC-703” 95 parts by weight of liquid B was discharged by a RIM molding machine at a discharge pressure of 15 MP. After the impact mixing in the mold, it was discharged at a discharge rate of 500 g / sec into a mold maintained at 60 ° C. and left for 10 minutes, thereby allowing a foamed polyurethane block having a size of 700 × 700 mm and a thickness of 10 mm (micro rubber A hardness: 48 Degree, density: 0.77 g / cm ³ , average bubble diameter: 38 μm). Thereafter, the foamed polyurethane block was sliced with a slicer to a thickness of 3 mm. A polishing layer was prepared in the same manner as in Example 1 except that the polyurethane foam sheet was used. The obtained polishing layer has a micro rubber A hardness of 92 degrees, a density of 0.78 g / cm ³ , an average bubble diameter of 44 μm, a ratio of bubbles of 50 μm or less of 64%, and a thickness of 500 to 850 nm with respect to the thickness per 1 mm of the polishing layer. The light transmittance at a wavelength of 49% was 49%, and the content of polymethyl methacrylate in the polishing layer was 55% by weight. Next, a two-layer polishing pad was prepared in the same manner as in Example 1 except that the polishing layer was used, and polishing evaluation was performed at a polishing pressure of 2 psi. In polishing evaluation, the accuracy of end point detection was poor and unstable. The polishing rate was 5700 angstroms / minute. The uniformity was 10%. There were 25 scratches. The dishing was 80 angstroms. Further, no film peeling was observed on the surface of the test wafer after polishing.

Claims (6)

The polishing layer has closed cells, the average bubble diameter is 100 to 300 μm, the ratio of the bubbles having a bubble diameter of 50 μm or less in the total bubbles of the polishing layer is 10% or less, and the polishing pad is used as a polishing platen The polishing is carried out by rotating the polishing head and / or the polishing platen in a state where the object to be polished fixed to the polishing head is in contact with the polishing pad at a polishing pressure of 0.1 to 5 psi. Polishing method. The light transmittance at a wavelength of 500 to 850 nm with respect to the thickness per mm of the polishing layer of the polishing pad is 60% or more, and polishing is performed while optically measuring the polishing state of the object to be polished through the polishing layer. The polishing method described. The polishing method according to claim 1, wherein the object to be polished is a semiconductor substrate. The polishing method according to claim 1, wherein the object to be polished is an insulating layer provided on a semiconductor substrate and a wiring made of a metal and / or a metal compound. The polishing layer has closed cells, the average bubble diameter is 100 to 300 μm, the ratio of the bubbles having a bubble diameter of 50 μm or less in the total bubbles of the polishing layer is 10% or less, and the thickness per 1 mm A polishing pad, wherein the light transmittance at a wavelength of 500 to 850 nm is 60% or more. A mixing head comprising a first raw material composition in which a gas is mixed or dissolved in a proportion of 5 to 50% by volume with respect to a raw material composition containing a polyol as a main component and a second raw material composition containing an isocyanate as a main component. After mixing, it is a method for producing a polishing pad using a polyurethane foam obtained by pouring into a mold at a rate of 600 g / s or more and curing , and the polishing layer has closed cells, A method for producing a polishing pad, wherein an average bubble diameter is 100 to 300 μm, and a ratio of bubbles having a bubble diameter of 50 μm or less in all bubbles is 10% or less .