JP5522929B2 - Polishing pad and polishing method - Google Patents

Description

  The present invention provides a metal film deposited on a wafer surface by supplying an electrolyte and applying a voltage between the wafer and the polishing pad in order to planarize the surface of the wafer using the polishing pad. The present invention relates to a method for polishing a wafer while being electrolyzed (electrolytic CMP method) and a polishing pad used therefor.

  In recent years, with high integration of integrated circuits and multilayer wiring, semiconductor wafers on which integrated circuits are formed are required to have high precision flatness.

  As a polishing method for polishing a semiconductor wafer, a chemical mechanical polishing method (CMP) in which a polishing pad is pressed against the wafer while supplying a slurry containing abrasive grains and a chemical solution to chemically and mechanically planarize the surface of the wafer. )It has been known.

  In CMP, a polishing pad made of polyurethane having a closed cell structure is widely used. When polishing a wafer having a copper film (Cu film) formed thereon using such a polyurethane polishing pad, there is a problem that surface defects such as scratches are likely to occur due to the low hardness of the copper film. It was. In order to reduce the occurrence of such surface defects, it is conceivable to reduce the pressing force during polishing or reduce the amount of slurry used during polishing. However, these methods have a problem that the polishing rate is lowered.

  As a method for solving such a problem, in Patent Documents 1 to 4 below, a voltage is applied between a wafer with a conductive film and a surface plate to electrolyze the conductive film formed on the wafer surface. An electrolytic CMP method for removal is described. Such an electrolytic CMP method will be specifically described below.

By applying a voltage between the conductive film formed on the wafer surface and the polishing pad, a potential difference is generated between the conductive film and the polishing pad. Then, due to this potential difference, electrons are transferred between the conductive film and the electrolytic solution, and the conductive film formed on the wafer surface, for example, the Cu film, becomes Cu → Cu ²⁺ + 2e ⁻ as an anode, and is ionized. Elutes into the electrolyte. In this way, the conductive film formed on the wafer surface is easily decomposed and removed.

  The inter-electrode gap for applying a voltage between the wafer and the polishing pad is formed by applying a negative potential to the surface plate and a positive potential to the wafer. In this case, since the polishing pad used in the electrolytic CMP method is usually formed of an insulating material, an insulating portion corresponding to the thickness of the polishing pad, for example, a thickness of 1 to 3 mm exists between the electrodes. Become. This insulating portion hinders sufficient energization.

  In contrast to such a polishing pad made of an insulating material, Patent Document 5 below discloses a polishing pad containing conductive fibers in order to impart conductivity. However, when a large amount of conductive material is added to provide the necessary conductivity, there are problems that the life of the polishing pad is shortened or the fibers are broken and the wafer is easily damaged. .

Further, among the polishing pads, fiber type polishing pads composed only of fibers are also known, but these have a low bending elastic modulus and a low polishing rate.
JP 2003-197585 A JP 2004-134734 A JP-A-2005-139480 JP 2008-62324 A JP 2004-111940 A

  An object of this invention is to provide the electrolytic CMP method excellent in the polishing rate, and the polishing pad used therefor.

  The polishing pad of the present invention is configured such that the polishing pad is pressed against a wafer having a metal film deposited on the surface thereof while supplying an electrolytic solution, and a voltage is applied between the wafer and the polishing pad. A polishing pad used in an electrolytic chemical mechanical polishing method for polishing a wafer while electrolyzing a film, and an ultrafine fiber entangled body and polymer containing ultrafine fibers having an average fineness of 0.01 to 0.8 dtex The elastic body is integrated, the bending elastic modulus is in the range of 150 to 650 MPa, the porosity is in the range of 25 to 65% by volume, and has communication holes. According to such a polishing pad, since the electrolytic solution can be retained in the communication hole, the front surface and the back surface of the polishing pad can be sufficiently conducted by the electrolytic solution. An appropriate potential difference can be ensured between the two. As a result, electrolytic CMP that provides an excellent polishing rate can be realized.

  It is preferable that the ultrafine fibers exist as a bundle of fibers bundled in a range of 5 to 70, and the bundle of fibers is bundled by the polymer elastic body. In such a case, since the fiber density can be further increased, the bending strength can be sufficiently improved, and the liquid retention rate of the electrolytic solution can be improved.

  The polymer elastic body is preferably a non-porous polyurethane resin from the viewpoint of sufficient bending strength and high binding property to ultrafine fibers.

  The method of electrochemical chemical mechanical polishing of a wafer according to the present invention includes pressing the polishing pad against a wafer having a metal film deposited on the surface while supplying an electrolytic solution, and between the wafer and the polishing pad. The wafer is polished while electrolyzing the metal film by applying a voltage to the substrate. According to such a method, it is possible to realize electrolytic CMP that provides an excellent polishing rate.

  According to the polishing pad of the present invention, an electrolytic CMP method that provides an excellent polishing rate can be realized.

  First, the polishing pad of this embodiment will be described with reference to FIG.

  FIG. 1 is a schematic cross-sectional view of a polishing pad 10 of the present embodiment. In FIG. 1, 1 is an ultrafine fiber entangled body containing ultrafine fibers having an average fineness of 0.01 to 0.8 dtex, and 2 is a high The molecular elastic body 3 is a communication hole. The polymer elastic body 2 is impregnated and integrated with the ultrafine fiber entangled body 1 to constitute a polishing pad 10.

  The ultrafine fiber entangled body 1 contains ultrafine fibers having an average fineness of 0.01 to 0.8 dtex, preferably 0.05 to 0.5 dtex, and particularly preferably 0.07 to 0.1 dtex. When the average fineness of the ultrafine fibers is less than 0.01 dtex, it becomes difficult to sufficiently separate the ultrafine fibers, so that the holding power of the electrolytic solution due to the capillary phenomenon is reduced, and the polishing uniformity and polishing efficiency are reduced. To do. On the other hand, when the average fineness of the ultrafine fibers exceeds 0.8 dtex, the stress is excessively applied during polishing, and scratches are likely to occur.

  In addition, it is preferable that an ultrafine fiber exists in a polishing pad as a fiber bundle formed by focusing about 5 to 70, and further about 10 to 50 ultrafine fibers. When the polishing pad of this embodiment contains ultrafine fibers in the form of a fiber bundle, the bundle of fiber bundles expresses the characteristics of a single fiber, resulting in high strength and flexural modulus. On the other hand, since the substantial fineness is low, it is difficult to generate scratches because it is easily separated by stress. Furthermore, according to the fiber bundle, since the fiber density per unit volume of the polishing pad can be increased, the electrolytic solution can be sufficiently retained by the capillary phenomenon due to the gap formed by the fiber bundle. If the number of ultrafine fibers per bundle is too high, the fiber density tends to be too high and the electrolyte holding power tends to decrease. Further, when the number of ultrafine fibers per bundle is too small, there is a tendency that sufficient bending elastic modulus cannot be obtained.

  Specific examples of fibers forming ultrafine fibers include, for example, aromatic polyester fibers formed from polyethylene terephthalate (PET), isophthalic acid modified polyethylene terephthalate, sulfoisophthalic acid modified polyethylene terephthalate, polybutylene terephthalate, polyhexamethylene terephthalate, and the like. An aliphatic polyester fiber formed from polylactic acid, polyethylene succinate, polybutylene succinate, polybutylene succinate adipate, polyhydroxybutyrate-polyhydroxyvalerate copolymer, etc .; polyamide 6, polyamide 66, polyamide 10, Polyamide fibers formed from polyamide 11, polyamide 12, polyamide 6-12, etc .; polypropylene, polyethylene, polybutene, polymethylpentene, A polyolefin fiber such as a base polyolefin; a modified polyvinyl alcohol fiber formed from a modified polyvinyl alcohol containing 25 to 70 mol% of an ethylene unit; and an elastomer such as a polyurethane elastomer, a polyamide elastomer, and a polyester elastomer. And elastomer fibers. These may be used alone or in combination of two or more.

  The average length of the fiber bundle is not particularly limited, but 100 mm or more, further 200 mm or more can sufficiently increase the fiber density of the ultrafine fibers, and can sufficiently increase the rigidity of the polishing pad. It is preferable from the point which can be performed, and the point which can suppress omission of a fiber. When the length of the fiber bundle is too short, it is difficult to increase the density of the ultrafine fibers, sufficient rigidity is not obtained, and the ultrafine fibers tend to come off easily during polishing. An upper limit is not specifically limited, For example, when it contains the fiber entanglement body derived from the nonwoven fabric manufactured by the spunbond method mentioned later, unless it cut | disconnects physically, several m, several hundred m, several km Alternatively, longer fiber lengths may be included.

  Next, the polymer elastic body 2 impregnated and integrated with the ultrafine fiber entangled body 1 will be described in detail.

  Specific examples of the polymer elastic body used in the polishing pad of the present embodiment include, for example, a polyurethane resin, a polyamide resin, a (meth) acrylate ester resin, a (meth) acrylate ester-styrene resin, ( (Meth) acrylic acid ester-acrylonitrile resin, (meth) acrylic acid ester-olefin resin, (meth) acrylic acid ester- (hydrogenated) isoprene resin, (meth) acrylic acid ester-butadiene resin, styrene- Butadiene resin, styrene-hydrogenated isoprene resin, acrylonitrile-butadiene resin, acrylonitrile-butadiene-styrene resin, vinyl acetate resin, (meth) acrylate ester-vinyl acetate resin, ethylene-vinyl acetate resin, Ethylene-olefin resin, silicone Resin, fluorine-based resins, and include an elastic body made of a polyester resin. These may be used alone or in combination of two or more. Among these, polymer elastic bodies (hydrogen-bonding polymer elastic bodies) that crystallize or aggregate by hydrogen bonding, such as polyurethane resins, polyamide resins, and polyvinyl alcohol resins, bind to ultrafine fibers. Since the wearing property is high, it is preferable from the viewpoint of improving the shape retention of the fiber entangled body and suppressing the fiber from coming off. In particular, the polyurethane resin has excellent adhesive properties for focusing ultrafine fibers, constraining fiber bundles, and binding fiber bundles. It is preferable from the viewpoint of excellent stability over time. Furthermore, the polyurethane-based resin having at least one hydrophilic group selected from the group consisting of a carboxyl group, a sulfonic acid group, and a polyalkylene glycol group having 3 or less carbon atoms is used for the rigidity, wettability, and polishing of the polishing pad. This is preferable because the stability over time is high. Such a hydrophilic group can be introduced into the polymer elastic body by copolymerizing a monomer component having a hydrophilic group as a monomer component for producing the polymer elastic body. The copolymerization ratio of the monomer component having such a hydrophilic group is 0.1 to 10% by mass, and further 0.5 to 5% by mass while minimizing swelling and softening due to water absorption. From the point that water absorption and wettability can be increased moderately.

  The polymer elastic body is particularly preferably a polymer elastic body having a water absorption of 0.2 to 5% by mass, more preferably 0.5 to 3% by mass when saturated water absorption is performed at 50 ° C. When the water absorption rate of the polymer elastic body is within such a range, the liquid retainability of the electrolytic solution is improved, and thereby, a high polishing rate, polishing uniformity, and polishing stability can be maintained.

  The polymer elastic body having such a water absorption rate can be obtained by adjusting the composition of the polymer constituting the polymer elastic body, adjusting the crosslinking density, selecting the hydrophilic functional group amount, and the like.

  The polymer elastic body has a storage elastic modulus at 23 ° C. and 50 ° C. of 90 to 900 MPa, more preferably 200 to 800 MPa, and it is easy to adjust the bending elastic modulus of the polishing pad within the range of the present invention. Is preferable. By setting the storage elastic modulus of the polymer elastic body in the range of 23 ° C. and 50 ° C. to 90 MPa or more, the rigidity during polishing becomes sufficient, and the planarization performance tends to be improved. In addition, the polymer elastic body is less likely to swell by the electrolytic solution during polishing, and the stability over time tends to be improved. By setting the storage elastic modulus at 23 ° C. and 50 ° C. to 900 MPa or less, the polymer elastic body is less likely to fall off during polishing, and scratches tend not to occur. In addition, the convergence force of the ultrafine fibers is increased, and the stability over time during polishing is improved.

  As shown in the schematic cross-sectional view of FIG. 1, the polishing pad of this embodiment has a structure in which a polymer elastic body is impregnated and integrated into an ultrafine fiber entangled body and combined.

  The ultrafine fibers constituting the ultrafine fiber entangled body exist in the form of a fiber bundle, the polymer elastic body exists inside the fiber bundle, and a part or most of the ultrafine fibers constituting the fiber bundle are polymer elastic. It is preferable that it is restrained by the binding force of the body from the viewpoint that the bending elastic modulus of the polishing pad can be easily adjusted. A polishing pad having a high flexural modulus can be obtained by constraining the fiber bundle with the polymer elastic body to impart rigidity to the fiber bundle. Further, by preventing the fibers from coming off, it is possible to prevent the abrasive grains from aggregating on the removed fibers. Thereby, generation | occurrence | production of a scratch can be suppressed. Here, the ultrafine fibers are restrained by the polymer elastic body means a state in which most of the ultrafine fibers existing inside the fiber bundle are bonded and bound by the polymer elastic body existing inside the fiber bundle. means.

  In addition, a plurality of fiber bundles are bound together by a polymer elastic body existing outside the fiber bundle, and it is easy to obtain a polishing pad having a high bending elastic modulus when present in a lump (bulk) shape. To preferred. By binding the fiber bundles in this way, the form stability of the polishing pad is improved and the polishing stability is improved.

  The converging / restraining state of the ultrafine fibers and the binding state of the fiber bundles can be easily confirmed by an electron micrograph of the cross section of the polishing pad.

  The polymer elastic body is preferably non-porous. The non-porous state is a state substantially free of voids (closed cells) as possessed by a porous or sponge-like (hereinafter also simply referred to as porous) polymer elastic body. Means. Specifically, it means that it is not a polymer elastic body having a large number of fine bubbles, for example, obtained by coagulating solvent-based polyurethane. By using a non-porous polymer elastic body, the binding force of the ultrafine fibers is increased, and a polishing pad having a high flexural modulus is easily obtained. Furthermore, since the adhesive strength with respect to the ultrafine fibers is increased, it is possible to suppress the occurrence of scratches due to the fiber coming off. Furthermore, since higher rigidity is obtained, a polishing pad having excellent planarization performance can be obtained. Note that when a polymer elastic body having a large number of bubbles is used, the polishing stability becomes low, and metal polishing debris and pad debris easily accumulate in the bubbles during polishing, and the polishing pad wears out. This tends to make it difficult to maintain a high polishing rate for a long time.

  The polishing pad of this embodiment has a flexural modulus in the range of 150 to 650 MPa, a porosity in the range of 25 to 65% by volume, and has communication holes.

  The flexural modulus of the polishing pad is in the range of 150 to 650 MPa, preferably in the range of 250 to 600. When the flexural modulus is less than 150 MPa, the rigidity of the polishing pad is significantly reduced as the polishing progresses. As a result, the polishing rate and planarization performance are reduced. In addition, when the flexural modulus exceeds 650 MPa, the rigidity is too high, the surface to be polished is likely to be scratched, the followability to the object to be polished is deteriorated, and polishing spots are easily generated. Since the porosity is inevitably low, it is impossible to secure a sufficient communication hole as an energization path, thereby reducing the polishing rate.

  Moreover, the porosity of the polishing pad of this embodiment is 25-65 volume%, Preferably it is 40-60 volume%. When the porosity of the polishing pad is less than 25% by volume, the electrolytic solution is not sufficiently retained, and the polishing efficiency and the polishing uniformity are lowered. Further, when the porosity of the polishing pad exceeds 65% by volume, the planarization performance is lowered and the polishing efficiency is lowered.

  The polishing pad used in this embodiment has a communication hole. The communication hole acts to sufficiently hold the electrolytic solution. When the communication hole is not provided, the electrolytic solution cannot be sufficiently retained, and therefore, polishing uniformity and polishing efficiency are lowered. Here, the communication hole means a hole communicating from the front surface to the back surface of the polishing pad. Presence of such a communication hole can be confirmed by the water dripped on the surface of the polishing pad appearing on the back surface of the polishing pad through the communication hole of the polishing pad. In the case of a polishing pad having only a closed cell structure, the electrolyte solution is held only by the closed cells present on the surface, so that the amount of the electrolyte solution retained is reduced.

  In addition, the polishing pad of this embodiment has a porosity in the range of 25 to 65% by volume, and exhibits excellent water absorption by having communication holes. As the water absorption rate, for example, in the birec method water absorption height test in accordance with JIS L1907-1994, the water absorption height after 60 minutes (hereinafter also simply referred to as the water absorption height) is 10 mm or more, and further 20 mm or more. Preferably there is. According to the polishing pad having high water absorption, the electrolytic solution can be sufficiently retained. In addition, the electrolytic solution can be uniformly held over the entire polishing surface of the polishing pad. As a result, a high polishing rate and excellent polishing uniformity and polishing stability can be obtained. Also, the break-in polishing can be shortened. The upper limit is not particularly limited, but is preferably 500 mm or less from the viewpoint of reducing waste of the amount of electrolyte used. However, this is not the case if weirs are provided on the edges of the pads attached to the surface plate.

  The water absorption height is also affected by the fiber density of the ultrafine fibers in the polishing pad and the type of the polymer elastic body. In order to further increase the water absorption height, at least one selected from the group consisting of ultrafine fibers at a high density and a polymer elastic body comprising a carboxyl group, a sulfonic acid group and a polyalkylene glycol group having 3 or less carbon atoms. More preferably, it contains a seed hydrophilic group.

The apparent density of the polishing pad of the present embodiment is in the range of 0.4 to 0.9 g / cm ³ , and more preferably in the range of 0.5 to 0.8 g / cm ^3. From the point which is excellent in it. If the apparent density is too high, the water absorption tends not to be sufficiently high.

  The content ratio of the ultrafine fiber entangled body to the total amount of the ultrafine fiber entangled body and the polymer elastic body in the polishing pad is 55 to 95% by mass, more preferably 60 to 90% by mass, and 150 to 800 MPa. This is preferable from the viewpoint of easily obtaining a polishing pad having a flexural modulus in the range and a porosity in the range of 20 to 65 volume%. When the content ratio of the ultrafine fiber entangled body is too low, the temporal stability during polishing tends to decrease or the polishing efficiency tends to decrease. Further, when the content ratio of the ultrafine fiber entangled body is too high, the binding force of the polymer elastic body inside the fiber bundle is reduced, and the flattening performance and the wear resistance of the polishing pad are deteriorated over time. There is a tendency that the mechanical stability tends to decrease.

  In addition, the polishing pad of this embodiment preferably has a water absorption rate of 20 to 100% by mass, more preferably 30 to 80% by mass when saturated and swollen with hot water at 50 ° C. When the water absorption rate is too low, it is difficult to hold the electrolytic solution, and the planarization performance tends to be lowered.

The polishing pad according to the present embodiment separates the fiber bundle existing near the surface by performing a pad flattening process by buffing or the like, a conditioning process before polishing using a pad dressing such as diamond, or a conditioning process during polishing. Fine fibers can be formed on the surface of the polishing pad by forming fibers or fibrils. The fiber density of the ultrafine fibers on the surface of the polishing pad is preferably 600 fibers / mm ² or more, more preferably 1000 fibers / mm ² or more, and particularly preferably 2000 fibers / mm ² or more. When the fiber density is too low, the retention of the electrolytic solution tends to be insufficient. The upper limit of the fiber density is not particularly limited, but is about 1,000,000 pieces / mm ² from the viewpoint of productivity. Further, the ultrafine fibers on the surface of the polishing pad may be raised or not raised. When the ultrafine fibers are raised, the surface of the polishing pad becomes softer and the effect of reducing scratches becomes higher. On the other hand, when the degree of napping of the ultrafine fibers is low, it is advantageous for applications in which microflatness is important. Thus, it is preferable to appropriately select the surface state according to the application.

  Next, an example of the manufacturing method of the polishing pad of this embodiment will be described in detail.

  The polishing pad of the present embodiment includes, for example, a web manufacturing process for manufacturing a long fiber web made of sea-island type composite fibers obtained by melt spinning a water-soluble thermoplastic resin and a water-insoluble thermoplastic resin, and a long fiber web. A web entanglement step for forming a web entanglement sheet by entanglement with a plurality of sheets, a wet heat shrinkage treatment step for wet heat shrinkage of the web entanglement sheet, and heat the water-soluble thermoplastic resin in the web entanglement sheet A fiber entanglement forming step for forming a fiber entangled body made of ultrafine fibers by dissolving in water, and a polymer elastic body filling step for impregnating the fiber entangled body with an aqueous liquid of a polymer elastic body and drying and solidifying the fiber entangled body. It can obtain by the manufacturing method of a polishing pad provided with these.

  In the above manufacturing method, the web entangled sheet containing the long fibers is subjected to the heat and heat shrinkage process, so that the web entangled sheet is largely contracted as compared with the case where the web entangled sheet containing the short fibers is subjected to the heat and heat shrinkage. For this reason, the fiber density of the ultrafine fibers becomes dense. And the fiber entanglement body which consists of a fiber bundle is formed by melt-extracting the water-soluble thermoplastic resin of a web entanglement sheet. At this time, voids are formed in the portion where the water-soluble thermoplastic resin is dissolved and extracted. Then, by impregnating and drying and solidifying an aqueous solution of a polymer elastic body in the void, the ultrafine fibers constituting the fiber bundle are focused and the fiber bundles are also focused. In this way, a highly rigid polishing pad with high fiber density and converged ultrafine fibers can be obtained.

  Each step will be described in detail below.

(1) Web manufacturing process In this process, first, a long fiber web made of sea-island composite fibers obtained by melt spinning a water-soluble thermoplastic resin and a water-insoluble thermoplastic resin is manufactured.

  The sea-island type composite fiber is obtained by melt-spinning a water-soluble thermoplastic resin and a water-insoluble thermoplastic resin having low compatibility with the water-soluble thermoplastic resin and then combining them. Then, the ultrafine fiber is formed by dissolving or removing the water-soluble thermoplastic resin from the sea-island type composite fiber. The thickness of the sea-island type composite fiber is preferably 0.5 to 3 dtex from the viewpoint of industrial properties.

  In this embodiment, the sea-island type composite fiber will be described in detail as the composite fiber for forming the ultra-fine fiber, but a known ultra-fine fiber generating type fiber such as a multilayer laminated cross-section fiber is used instead of the sea-island type fiber. May be.

  As the water-soluble thermoplastic resin, a resin that can be dissolved or removed by water, an alkaline aqueous solution, an acidic aqueous solution, or the like and that can be melt-spun is preferably used. Specific examples of such a water-soluble thermoplastic resin include, for example, polyvinyl alcohol resins (PVA resins) such as polyvinyl alcohol and polyvinyl alcohol copolymers; copolymers of polyethylene glycol and / or alkali metal sulfonates. Modified polyesters contained as components; polyethylene oxide and the like. Among these, PVA-based resins are particularly preferably used for the following reasons.

  When a sea-island type composite fiber having a PVA-based resin as a water-soluble thermoplastic resin component is used, the ultrafine fibers formed by dissolving the PVA-based resin are greatly crimped. As a result, a fiber entangled body having a high fiber density can be obtained. In addition, when a sea-island type composite fiber containing a PVA resin as a water-soluble thermoplastic resin component is used, when the PVA resin is dissolved, the formed ultrafine fibers and polymer elastic body are not substantially decomposed or dissolved. Therefore, the physical properties of the ultrafine fiber and the polymer elastic body are hardly lowered. Furthermore, the environmental load is small. Even if a small amount remains, the adverse effect on the polishing performance is small, and conversely, the wettability of the polishing pad tends to be increased. Therefore, the amount of PVA-based resin remaining on the polishing pad is relative to the total amount of the polishing pad It is about 0.01-0.2 mass%, Preferably, it is about 0.02-0.1 mass%.

  The PVA-based resin can be obtained by saponifying a copolymer mainly composed of vinyl ester units. Specific examples of vinyl monomers for forming the vinyl ester unit include, for example, vinyl acetate, vinyl formate, vinyl propionate, vinyl valelate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, Examples include vinyl pivalate and vinyl versatate. These may be used alone or in combination of two or more. Among these, vinyl acetate is preferable from the viewpoint of industrial properties.

  The PVA-based resin may be a homo PVA composed only of vinyl ester units or a modified PVA containing a comonomer unit other than the vinyl ester unit as a constituent unit. Modified PVA is more preferable from the viewpoint of controlling melt spinnability, water solubility, and fiber properties. Specific examples of the comonomer unit other than the vinyl ester unit include, for example, α-olefins having 4 or less carbon atoms such as ethylene, propylene, 1-butene and isobutene; methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether. And vinyl ethers such as isopropyl vinyl ether and n-butyl vinyl ether. The content ratio of the comonomer units other than the vinyl ester unit is preferably 1 to 20 mol%, more preferably 4 to 15 mol%, and particularly preferably 6 to 13 mol%. Among these, ethylene-modified PVA containing 4 to 15 mol%, more preferably 6 to 13 mol% of ethylene units is preferable from the viewpoint of improving the physical properties of the sea-island composite fibers.

  The viscosity average degree of polymerization of the PVA-based resin is 200 to 500, more preferably 230 to 470, and particularly 250 to 450, so that a stable sea-island structure is formed and the melt spinnability is excellent. It is preferable from the point of showing melt viscosity and the high dissolution rate at the time of dissolution. The degree of polymerization is measured according to JIS-K6726. That is, after re-saponifying and purifying the PVA resin, it is obtained from the intrinsic viscosity [η] measured in water at 30 ° C. by the following equation.

Viscosity average degree of polymerization P = ([η] × 103 / 8.29) (1 / 0.62)
The saponification degree of the PVA-based resin is 90 to 99.99 mol%, more preferably 93 to 99.98 mol%, particularly 94 to 99.97 mol%, particularly 96 to 99.96 mol%. It is preferable that it is the range of these. When the saponification degree is in such a range, a PVA resin having excellent water solubility, excellent thermal stability, excellent melt spinnability, and excellent biodegradability can be obtained.

  The melting point of the PVA-based resin is 160 to 250 ° C., more preferably 170 to 227 ° C., particularly 175 to 224 ° C., particularly 180 to 220 ° C., in view of mechanical properties and thermal stability. It is preferable from the viewpoint of excellent point and melt spinnability. When the melting point of the PVA-based resin is too high, the melting point and the decomposition temperature are close to each other, so that the melt spinnability tends to be reduced by causing decomposition during melt spinning.

  Moreover, when the melting point of the PVA-based resin is too low as compared with the melting point of the water-insoluble thermoplastic resin, it is not preferable because the melt spinnability is lowered. From this point of view, it is preferable that the melting point of the PVA-based resin is not lower than 60 ° C. or even 30 ° C. or higher compared to the melting point of the water-insoluble thermoplastic resin.

  As the water-insoluble thermoplastic resin, a resin that can be melt-spun and is a thermoplastic resin that is not dissolved or removed by water, an alkaline aqueous solution, an acidic aqueous solution, or the like.

  As a specific example of the water-insoluble thermoplastic resin, various thermoplastic resins used to form the ultrafine fibers constituting the polishing pad described above can be used.

  The water-insoluble thermoplastic resin may contain various additives. Specific examples of additives include, for example, catalysts, anti-coloring agents, heat-resistant agents, flame retardants, lubricants, antifouling agents, fluorescent whitening agents, matting agents, coloring agents, gloss improvers, antistatic agents, and fragrances. , Deodorants, antibacterial agents, acaricides, inorganic fine particles, conductive agents and the like.

  Next, a method for forming a sea-island type composite fiber by melt spinning a water-soluble thermoplastic resin and a water-insoluble thermoplastic resin and forming a long fiber web from the obtained sea-island type composite fiber will be described in detail.

  The long fiber web is obtained, for example, by compounding by melt spinning a water-soluble thermoplastic resin and a water-insoluble thermoplastic resin, and then stretching and depositing by a spunbond method. In this way, by forming the web by the spunbond method, a long fiber web made of sea-island type composite fibers with less fiber loss, high fiber density, and good shape stability can be obtained. In addition, a long fiber is a fiber manufactured without passing through a cutting process like manufacturing a short fiber.

  In the production of a sea-island type composite fiber, a water-soluble thermoplastic resin and a water-insoluble thermoplastic resin are melt-spun and combined. The mass ratio of the water-soluble thermoplastic resin to the water-insoluble thermoplastic resin is preferably in the range of 5/95 to 50/50, more preferably 10/90 to 40/60. When the mass ratio of the water-soluble thermoplastic resin to the water-insoluble thermoplastic resin is within such a range, a high-density fiber entangled body can be obtained, and the formability of ultrafine fibers is excellent.

  A method for forming a long fiber web by a spunbond method after combining a water-soluble thermoplastic resin and a water-insoluble thermoplastic resin by melt spinning will be described in detail below.

  First, a water-soluble thermoplastic resin and a water-insoluble thermoplastic resin are melt-kneaded by separate extruders, and molten resin strands are discharged simultaneously from different spinnerets. Then, after the discharged strands are combined with the composite nozzle, the sea-island type composite fibers are formed by discharging from the nozzle holes of the spinning head. In melt composite spinning, the number of islands in a sea-island type composite fiber is 4 to 4000 islands / fiber, more preferably 10 to 1000 islands / fiber, so that a fiber bundle having a small single fiber fineness and a high fiber density can be obtained. To preferred.

After the sea-island type composite fiber is cooled by a cooling device, it is drawn by a high-speed air flow at a speed corresponding to a take-up speed of 1000 to 6000 m / min so as to obtain a desired fineness using a suction device such as an air jet nozzle. . Thereafter, the stretched composite fibers are deposited on a movable collection surface to form a long fiber web. At this time, the long fiber web deposited may be partially crimped as necessary. The basis weight of the fiber web is preferably in the range of ^{20 to} 500 g / m ² , so that a uniform fiber entangled body can be obtained, and it is preferable from the viewpoint of industrial properties.

(2) Web entanglement process Next, the web entanglement process which forms a web entanglement sheet | seat by accumulating and intertwining a plurality of obtained long fiber webs is demonstrated.

  The web entangled sheet is formed by performing an entanglement treatment on the long fiber web using a known nonwoven fabric manufacturing method such as needle punching or high-pressure water flow treatment. Below, the entanglement process by a needle punch is demonstrated in detail as a typical example.

  First, a silicone oil agent or a mineral oil agent such as a needle breakage prevention oil agent, an antistatic oil agent, and an entanglement improving oil agent is applied to the long fiber web. In order to reduce unevenness in weight per unit area, two or more fiber webs may be overlapped with a cross wrapper and an oil agent may be applied.

Thereafter, for example, an entanglement process is performed in which the fibers are entangled three-dimensionally by a needle punch. By performing the needle punching process, a web entangled sheet having a high fiber density and hardly causing the fiber to come off can be obtained. The basis weight of the web-entangled sheet is appropriately selected according to the thickness of the target polishing pad, and specifically, for example, the handling property is in the range of 100 to 1500 g / m ² . From the point which is excellent in it.

The conditions for increasing the delamination force of the web entangled sheet are appropriately selected as the needle conditions such as the type and amount of the oil agent, the needle shape in the needle punch, the needle depth, and the number of punches. The number of barbs is preferably as large as possible without causing needle breakage. Specifically, for example, the number of barbs is selected from 1 to 9 barbs. The needle depth is preferably set so that the barb penetrates to the overlapped web surface, and in a range where the pattern after needle punching does not appear strongly on the web surface. The number of needle punches is adjusted depending on the shape of the needle, the type and amount of oil used, and specifically, 500 to 5000 punches / cm ² is preferable. In addition, the fiber density can be obtained by performing the entanglement process so that the basis weight after the entanglement process is 1.2 times or more by mass ratio of the basis weight before the entanglement process, and further 1.5 times or more A high fiber entangled body can be obtained, and it is preferable from the viewpoint that the loss of fibers can be reduced. The upper limit is not particularly limited, but is preferably 4 times or less from the viewpoint of avoiding an increase in manufacturing cost due to a decrease in processing speed.

  The delamination force of the web entangled sheet is 2 kg / 2.5 cm or more, more preferably 4 kg / 2.5 cm or more, the shape retention is good, the fibers are not easily pulled out, and the fiber density is high. This is preferable from the viewpoint of obtaining a fiber entangled body. Note that the delamination force is a measure of the degree of three-dimensional entanglement. When the delamination force is too small, the fiber density of the fiber entangled body is not sufficiently high. Moreover, although the upper limit of the delamination force of an entangled nonwoven fabric is not specifically limited, It is preferable that it is 30 kg / 2.5 cm or less from the point of an entanglement process efficiency.

  In addition, for the purpose of adjusting the hardness of the polishing pad, the web entangled sheet, which is a nonwoven fabric obtained as described above, is further made of ultrafine fibers, as long as the effects of the present invention are not impaired. A knitted fabric or a woven fabric (knitted fabric) is entangled by needle punching and / or high-pressure water flow treatment, and the knitted fabric is entangled and integrated, for example, a knitted fabric / entangled nonwoven fabric. A laminated structure such as entangled nonwoven fabric / knitted fabric / entangled nonwoven fabric may be used as the web entangled sheet.

  The ultrafine fibers constituting the knitted fabric are not particularly limited. Specifically, for example, polyester fiber formed from polyethylene terephthalate (PET), polytrimethylene terephthalate, polybutylene terephthalate (PBT), polyester elastomer, etc .; from polyamide 6, polyamide 66, aromatic polyamide, polyamide elastomer, etc. Polyamide fibers to be formed; fibers made of urethane polymers, olefin polymers, acrylonitrile polymers and the like are preferably used. In these, the fiber formed from PET, PBT, polyamide 6, polyamide 66 etc. is preferable from an industrial point.

  Specific examples of the removal component of the sea-island composite fiber for forming the knitted fabric include polystyrene and its copolymer, polyethylene, PVA resin, copolymer polyester, copolymer polyamide, and the like. Among these, PVA-based resins are preferably used because they cause large shrinkage when dissolved and removed.

(3) Wet heat shrinkage treatment step Next, a wet heat shrinkage treatment step for increasing the fiber density and the degree of entanglement of the web entangled sheet by shrinking the web entangled sheet with heat and moisture will be described. In this step, the web-entangled sheet containing long fibers is contracted by wet heat, so that the web-entangled sheet is contracted greatly compared to the case where the web-entangled sheet containing short fibers is contracted by wet heat. As a result, the fiber density of the ultrafine fibers is particularly high.

  The wet heat shrinkage treatment is preferably performed by steam heating. As the steam heating condition, it is preferable to perform heat treatment for 60 to 600 seconds at an atmospheric temperature in the range of 60 to 130 ° C. and a relative humidity of 40% or more, and further a relative humidity of 50% or more. Such heating conditions are preferable because the web-entangled sheet can be shrunk at a high shrinkage rate. In addition, when relative humidity is too low, there exists a tendency for shrinkage | contraction to become inadequate because the water | moisture content which contacted the fiber dries rapidly.

  In the wet heat shrinkage treatment, the web entangled sheet is preferably shrunk so that the area shrinkage rate is 35% or more, and further 40% or more. By contracting at such a high contraction rate, a high fiber density can be obtained, and the flexural modulus and porosity can be easily set within a desired range. The upper limit of the area shrinkage rate is not particularly limited, but is preferably about 80% or less from the viewpoint of shrinkage limit and processing efficiency.

The area shrinkage rate (%) is expressed by the following formula (1):
(Area of sheet surface before shrinking process−Area of sheet surface after shrinking process) / Area of sheet surface before shrinking process × 100 (1) The area means an average area of the surface area and the back surface area of the sheet.

  The web entangled sheet thus subjected to the wet heat shrinkage treatment may be further increased in fiber density by heating roll or hot pressing at a temperature equal to or higher than the heat deformation temperature of the sea-island type composite fiber.

  In addition, as a change in the basis weight of the web-entangled sheet before and after the wet heat shrinkage treatment, the basis weight after the shrinkage treatment is 1.2 times (mass ratio) or more compared to the basis weight before the shrinkage treatment, It is preferably 1.5 times or more, 4 times or less, and more preferably 3 times or less.

(4) Fiber bundle binding step Before the ultra-fine fiberization treatment of the web entangled sheet, for the purpose of increasing the form stability of the web entangled sheet and reducing the porosity of the resulting polishing pad, If necessary, a fiber bundle may be bound in advance by impregnating the web-entangled sheet subjected to the shrink treatment with an aqueous liquid of a polymer elastic body and drying and solidifying it.

  In this step, the web entangled sheet is filled with the polymer elastic body by impregnating the contracted web entangled sheet with the aqueous liquid of the polymer elastic body and drying and solidifying it. The polymer elastic body can be formed by impregnating the polymer elastic body in the state of an aqueous liquid and drying and coagulating it. Since the aqueous liquid of the polymer elastic body has a high concentration and a low viscosity and is excellent in impregnation permeability, it is easy to be filled with a high amount. Moreover, the adhesiveness with respect to a fiber is also excellent. Therefore, the polymer elastic body filled in this step firmly binds the long-sea sea-island composite fiber. The aqueous solution of the polymer elastic body is an aqueous solution in which the component forming the polymer elastic body is dissolved in the aqueous medium, or the aqueous dispersion liquid in which the component forming the polymer elastic body is dispersed in the aqueous medium. is there. The aqueous dispersion includes a suspension dispersion and an emulsion dispersion. In particular, it is more preferable to use an aqueous dispersion from the viewpoint of excellent water resistance.

  As the aqueous liquid of the polymer elastic body, an aqueous polyurethane resin is preferable from the viewpoint of excellent wettability of the electrolytic solution or the electrolytic solution containing abrasive grains.

  The method for making the polyurethane resin into an aqueous solution or an aqueous dispersion is not particularly limited, and a known method can be used. Specifically, for example, by adding a monomer unit having a hydrophilic group such as a carboxyl group, a sulfonic acid group, or a hydroxyl group, a method of imparting dispersibility to an aqueous medium to a polyurethane resin, or a surface activity of the polyurethane resin. The method of emulsifying or suspending by adding an agent is mentioned. Further, such an aqueous polymer elastic body has excellent wettability with respect to water, and thus has an excellent property of holding a large amount of electrolyte solution.

  Examples of the polyurethane resin include various polyurethane resins obtained by reacting a polymer polyol having an average molecular weight of 200 to 6000, an organic polyisocyanate, and a chain extender in a predetermined molar ratio.

  Specific examples of the polymer polyol include, for example, polyether polyols such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, poly (methyltetramethylene glycol) and copolymers thereof; polybutylene adipate diol, polybutylene sebacate Diol, polyhexamethylene adipate diol, poly (3-methyl-1,5-pentylene adipate) diol, poly (3-methyl-1,5-pentylene sebacate) diol, isophthalic acid copolymer polyol, terephthalic acid co Polyester polyols such as polymerized polyol, cyclohexanol copolymer polyol, polycaprolactone diol, and copolymers thereof; polyhexamethylene carbonate diol, poly (3-methyl-1,5- Polycarbonate-type polyols such as butylene carbonate) diol, polypentamethylene carbonate diol, polytetramethylene carbonate diol, poly (methyl-1.8-octamethylene carbonate) diol, polynonamethylene carbonate diol, polycyclohexane carbonate, and their co-polymers Polyester carbonate polyol etc. are mentioned. If necessary, a trifunctional alcohol such as trimethylolpropane or a polyfunctional alcohol such as tetrafunctional alcohol such as pentaerythritol, or ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol. A short chain alcohol such as These may be used alone or in combination of two or more.

  Specific examples of the organic polyisocyanate include, for example, non-yellowing diisocyanates such as aliphatic or alicyclic diisocyanates such as hexamethylene diisocyanate, isophorone diisocyanate, norbornene diisocyanate, and 4,4′-dicyclohexylmethane diisocyanate; 2,4-tri Examples thereof include aromatic diisocyanates such as range isocyanate, 2,6-tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate, and xylylene diisocyanate polyurethane. Moreover, you may use together polyfunctional isocyanates, such as trifunctional isocyanate and tetrafunctional isocyanate, as needed. These may be used alone or in combination of two or more. Among these, 4,4′-dicyclohexylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate, and xylylene diisocyanate have high adhesion to fibers, Moreover, it is preferable from the point by which a polishing pad with high hardness is obtained.

  Specific examples of the chain extender include, for example, diamines such as hydrazine, ethylenediamine, propylenediamine, hexamethylenediamine, nonamethylenediamine, xylylenediamine, isophoronediamine, piperazine and derivatives thereof, adipic acid dihydrazide, and isophthalic acid dihydrazide. Triamines such as diethylenetriamine; tetramines such as triethylenetetramine; ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,4-bis (β-hydroxyethoxy) benzene, 1, Diols such as 4-cyclohexanediol; Triols such as trimethylolpropane; Pentaols such as pentaerythritol; Aminoethyl alcohol, Aminopropyl alcohol Amino alcohols such as such as Le and the like. These may be used alone or in combination of two or more. Among these, hydrazine, piperazine, hexamethylenediamine, isophoronediamine and derivatives thereof, and triamines such as ethylenetriamine are used in combination of two or more to provide high adhesion to fibers and high hardness polishing. This is preferable because a pad can be obtained. In addition, during the chain extension reaction, together with the chain extender, monoamines such as ethylamine, propylamine, and butylamine; carboxyl group-containing monoamine compounds such as 4-aminobutanoic acid and 6-aminohexanoic acid; methanol, ethanol, propanol, butanol, etc. Monools may be used in combination.

  In addition, a polyurethane containing a carboxyl group-containing diol such as 2,2-bis (hydroxymethyl) propionic acid, 2,2-bis (hydroxymethyl) butanoic acid, 2,2-bis (hydroxymethyl) valeric acid, etc. By introducing an ionic group such as a carboxyl group into the skeleton of the elastic body, the wettability to water can be further improved.

  Moreover, in order to control the water absorption rate and storage elastic modulus of the polyurethane-based elastic body, a cross-linking agent containing two or more functional groups capable of reacting with the functional group of the monomer unit forming the polyurethane in the molecule, polyisocyanate It is preferable to form a crosslinked structure by adding a self-crosslinking compound such as a compound based on polyfunctional block isocyanates.

  As a combination of the functional group of the monomer unit and the functional group of the crosslinking agent, carboxyl group and oxazoline group, carboxyl group and carbodiimide group, carboxyl group and epoxy group, carboxyl group and cyclocarbonate group, carboxyl group and aziridine group, Examples thereof include a carbonyl group and a hydrazine derivative or a hydrazide derivative. Among these, a combination of a monomer unit having a carboxyl group and a crosslinking agent having an oxazoline group, a carbodiimide group or an epoxy group, a combination of a monomer unit having a hydroxyl group or an amino group and a crosslinking agent having a blocked isocyanate group, and carbonyl A combination of a monomer unit having a group and a hydrazine derivative or a hydrazide derivative is particularly preferred because crosslinking is easy and the resulting polishing pad has excellent rigidity and wear resistance. The crosslinked structure is preferably formed in the heat treatment step after applying the polyurethane resin to the fiber entangled body from the viewpoint of maintaining the stability of the aqueous liquid of the polymer elastic body. Among these, a carbodiimide group and / or an oxazoline group are particularly preferable because they are excellent in crosslinking performance and pot life of an aqueous liquid and have no problem in safety. Examples of the crosslinking agent having a carbodiimide group include water-dispersed carbodiimide compounds such as “Carbodilite E-01”, “Carbodilite E-02”, and “Carbodilite V-02” manufactured by Nisshinbo Industries, Ltd. Examples of the crosslinking agent having an oxazoline group include water-dispersed oxazoline compounds such as “Epocross K-2010E”, “Epocross K-2020E”, and “Epocross WS-500” manufactured by Nippon Shokubai Co., Ltd. As a compounding quantity of a crosslinking agent, it is preferable that the active ingredient of a crosslinking agent is 1-20 mass% with respect to a polyurethane resin, It is more preferable that it is 1.5-1 mass%, 2-10 mass% More preferably.

  The content of the polymer polyol component in the polyurethane-based resin is 65% by mass or less, further 60% by mass or less, 40% by mass or more, and further 45% by mass or more. It is preferable from the point that generation | occurrence | production of a scratch can be suppressed by providing.

  Polyurethane resins are penetrants, antifoaming agents, lubricants, water repellents, oil repellents, thickeners, extenders, curing accelerators, antioxidants, UV absorbers, antifungal agents, foaming agents, polyvinyl You may further contain water-soluble high molecular compounds, such as alcohol and carboxymethylcellulose, dye, a pigment, an inorganic fine particle, a electrically conductive agent.

  Examples of the method of impregnating the web entangled sheet with the aqueous polymer elastic liquid include a method using a knife coater, a bar coater, or a roll coater, or a dipping method.

  The polymer elastic body can be solidified by drying the web entangled sheet impregnated with the aqueous liquid of the polymer elastic body. As a drying method, the method of heat-processing in a 50-200 degreeC drying apparatus, the method of heat-processing in a dryer after infrared heating, etc. are mentioned.

  In addition, when the web entangled sheet is impregnated with the aqueous liquid of the polymer elastic body and then dried, the aqueous liquid migrates to the surface layer of the web entangled sheet, so that a uniform filling state cannot be obtained. Sometimes. In such a case, the particle size of the polymer elastic body of the aqueous liquid is adjusted; the kind and amount of ionic groups of the polymer elastic body are adjusted, or the stability is adjusted by pH or the like. Monovalent or divalent alkali metal salts or alkaline earth metal salts, nonionic emulsifiers, associative water-soluble thickeners, associative thermosensitive gelling agents such as water-soluble silicone compounds, water-soluble polyurethane compounds, Alternatively, migration can be suppressed by, for example, reducing the water dispersion stability at about 40 to 100 ° C. by using, for example, an organic substance or an inorganic substance whose pH is changed by heat. In addition, you may make it migrate so that a polymeric elastic body may be unevenly distributed on the surface as needed.

(5) Ultrafine fiber formation process Next, the ultrafine fiber formation process, which is a process of forming ultrafine fibers by dissolving a water-soluble thermoplastic resin in hot water, will be described.

  This step is a step of forming ultrafine fibers by removing the water-soluble thermoplastic resin. At this time, voids are formed in the portion of the web entangled sheet where the water-soluble thermoplastic resin is dissolved and extracted. Then, in this later step of filling the voids with the polymer elastic body, the ultrafine fibers are restrained by filling the polymer elastic body.

  The ultrafine fiber treatment is performed by hydrothermally treating a web entangled sheet or a composite of a web entangled sheet and a polymer elastic body with water, an aqueous alkaline solution, an acidic aqueous solution, etc. It is a process of dissolving and removing or decomposing and removing.

  As a specific example of the hot water heat treatment conditions, for example, as a first stage, after being immersed in hot water at 65 to 90 ° C. for 5 to 300 seconds, further as a second stage, hot water at 85 to 100 ° C. It is preferable to perform the treatment for 100 to 600 seconds. Moreover, in order to improve dissolution efficiency, you may perform the nip process by a roll, a high pressure water flow process, an ultrasonic process, a shower process, a stirring process, a stagnation process, etc. as needed.

  In this step, the ultrafine fiber is greatly crimped when the ultrafine fiber is formed by dissolving the water-soluble thermoplastic resin from the sea-island type composite fiber. Since the fiber density becomes dense due to this crimp, it is easy to obtain a high-density fiber entangled body, and the bending elastic modulus is easily set in the range of 150 to 650 MPa.

(6) Polymer elastic body filling step Next, the polymer elastic body is filled into the fiber bundle formed from the ultrafine fibers, thereby restraining the ultrafine fibers and restraining the fiber bundles, and between the fiber bundles. The process of binding the will be described.

  In the ultrafine fiber forming step (5), the sea-island type composite fiber is subjected to ultrafine fiber treatment, whereby the water-soluble thermoplastic resin is removed and voids are formed inside the fiber bundle. In this step, by filling a polymer elastic body into such voids, the fine fibers are focused, the fiber bundles are constrained, and the fiber bundles are bound together, thereby reducing the porosity of the polishing pad. It is easy to decrease and to obtain a desired flexural modulus. When the ultrafine fibers form a fiber bundle, the ultrafine fibers are more easily focused and constrained because the aqueous polymer liquid is easily impregnated by capillary action.

  The aqueous polymer liquid used in this step may be the same as the aqueous polymer elastic liquid described in the fiber bundle binding step (4).

  A method similar to the method used in the fiber bundle binding step (4) can be applied to the method of filling the polymer elastic body into the fiber bundle formed from the ultrafine fibers in this step. In this way, a polishing pad is formed.

(7) Post-processing of the polishing pad The obtained polishing pad may be subjected to post-processing such as molding, flattening, raising, laminating, surface treatment, and washing as necessary.

  The molding process and the flattening process are processes in which the obtained polishing pad is hot press molded to a predetermined thickness by grinding or cut into a predetermined outer shape. The polishing pad is preferably ground to a thickness of about 0.5 to 3 mm.

  The raising process is a process for separating the focused ultrafine fibers by applying mechanical frictional force or polishing force to the surface of the polishing pad with sandpaper, needle cloth, diamond or the like. By such raising treatment, the fiber bundle existing in the surface portion of the polishing pad is fibrillated, and a large number of ultrafine fibers are formed on the surface.

  The laminating process is a process of adjusting rigidity by laminating the obtained polishing pad on a base material. For example, by laminating the polishing pad with an elastic sheet having low hardness, the global flatness of the surface to be polished (flatness of the entire non-polishing substrate) can be further improved. The adhesion at the time of lamination may be fusion adhesion or adhesion via an adhesive or a pressure-sensitive adhesive. Specific examples of the substrate include, for example, an elastic sponge body made of polyurethane or the like; a nonwoven fabric impregnated with polyurethane (for example, trade name Suba400 manufactured by Nita Haas Co.); natural rubber, nitrile rubber, polybutadiene rubber, silicone Examples thereof include elastic resin films composed of rubbers such as rubber, thermoplastic elastomers such as polyester-based thermoplastic elastomers, polyamide-based thermoplastic elastomers, and fluorine-based thermoplastic elastomers; foamed plastics; sheet-like substrates such as knitted fabrics and woven fabrics.

  Further, the surface treatment is a treatment for forming grooves, holes such as lattices, concentric circles, spirals, etc. on the surface of the polishing pad in order to adjust the retention and discharge of the electrolytic solution or electrolytic solution containing abrasive grains. It is.

  In the cleaning treatment, impurities such as particles and metal ions adhering to the obtained polishing pad are washed with cold water or warm water, or an aqueous solution containing an additive having a cleaning action such as a surfactant or the like. This is a process of washing with a solvent.

  Next, an embodiment of the electrolytic CMP method according to the present invention will be described with reference to the drawings.

  FIG. 2 is a schematic diagram for explaining an example of the polishing apparatus 100 used in the present embodiment. In FIG. 2, 10 is a polishing pad, 12 is a surface plate, 13 is a polishing head, 14 is a voltage applying means, and 15 is an electrolyte supply pipe. The surface plate 12 rotates by the driving means M1. The polishing pad 10 is attached to the upper surface of the surface plate 12 with a conductive double-sided tape 16. The polishing head 13 holds the wafer W to be polished, and presses the surface of the wafer W against the polishing pad 10 while being rotated by the driving unit M2. A metal wiring film L is formed on the surface of the wafer W. The metal wiring film L extends to the side surface of the wafer W and is electrically connected to the conductive double-sided tape 17 on the side surface.

  Then, a positive potential is applied to the metal wiring film L of the wafer W via the double-sided tape 17 by the voltage applying unit 14, and a negative potential is applied to the polishing pad 10 from the surface plate 12 via the double-sided tape 16. The

  The electrolytic solution supply pipe 15 supplies the electrolytic solution 18 to the upper surface of the polishing pad 10. In addition, abrasive grains may be dispersed in the electrolytic solution 18 as necessary.

  Specific examples of the electrolyte include, for example, sulfuric acid, hydrochloric acid, phosphoric acid, perhydrogen acid, formic acid, acetic acid, lactic acid, citric acid, succinic acid, malic acid, aspartic acid, sulfonic acid, sulfamic acid, or an electrolyte thereof. Examples include salts. These may be used alone or in combination of two or more. The concentration of the electrolyte is not particularly limited, but is preferably 0.1 N or more, more preferably 1 N or more from the viewpoint of excellent electrolytic polishing efficiency, and preferably 10 N or less from the viewpoint of the stability of the electrolytic solution over time.

  As the abrasive grains, an abrasive such as silica, aluminum oxide, cerium oxide, zirconium oxide, silicon carbide, diamond, etc. is used and dispersed in a dispersion medium containing an electrolytic solution.

  In addition, you may further mix | blend components, such as a base, an acid, and surfactant, with electrolyte solution as needed. Furthermore, for the purpose of suppressing dishing, it is preferable to add an additive such as benzotriazole capable of forming a complex with a metal. Moreover, when performing CMP, you may supply lubricating oil, a coolant, etc. with electrolyte solution as needed.

  Next, the operation of the polishing apparatus 100 configured as described above will be described. First, the wafer W is held on the polishing head 13 via the conductive double-sided tape 17. At this time, the wafer W is bonded to the opposite surface of the metal wiring film L to be polished by the double-sided tape 17. Then, a positive potential is applied to the metal wiring film L of the wafer W via the double-sided tape 17 by the voltage applying unit 14, and a negative potential is applied to the polishing pad 10 from the surface plate 12 via the double-sided tape 16. The

  In this state, the surface plate 12 is rotated and the electrolytic solution 18 is supplied from the electrolytic solution supply pipe 15 to the upper surface of the polishing pad 10. The polishing pad 10 holds the electrolytic solution 18 in the gap. The electrolytic solution held in this way makes the front surface and the back surface of the polishing pad 10 conductive.

  On the other hand, the wafer W held by the polishing head 13 is pressed against the polishing pad 10 while being rotated. The metal wiring film L formed on the surface of the pressed wafer W and the upper surface of the polishing pad 10 have an extremely narrow space where only the electrolytic solution 18 is interposed. Electrolysis acts in the narrow gap between the electrodes, and the metal wiring film is electrolytically eluted.

  It is also preferable to condition the surface of the polishing pad with diamond or a brush before or during polishing. The number of conditioning treatment is preferably # 50 to # 1000, more preferably in the range of # 100 to # 1000, and the range of # 150 to # 1000 reduces the wear loss in the thickness direction of the polishing pad surface during conditioning. On the other hand, it is preferable because the fibers on the surface can be separated to keep the electrolyte solution uniformly. Conditioning may be performed before polishing the wafer W or during polishing. Further, the polishing of the wafer W and the conditioning of the polishing pad may be performed alternately.

  When the polishing pad of this embodiment is used for polishing a semiconductor wafer, the surface of the polishing pad is gently conditioned so that the wear loss in the thickness direction is 0.3 μm / min or less, thereby polishing the polishing pad. This is preferable because the performance can be maintained in a stable state for a long time. In order to make the wear loss within the above range, in addition to adjusting the count of the abrasive grains, it is possible to employ conditioning using a water flow. As a conditioning method using water flow, for example, high pressure water cleaning such as high pressure jet water cleaning, high pressure micro jet water cleaning, high pressure bubble jet water cleaning, and water spray cleaning, ultrasonic water cleaning, nylon brush, etc. were used. Brush cleaning or the like can be employed. In addition, a method that uses a blocky type diamond dresser, a method that uses a low conditioning pressure, a method that shortens the conditioning time, high-pressure jet cleaning, which is generally a gentle conditioning process compared to diamond dressing, and a high-pressure micro High pressure water cleaning such as jet cleaning and high pressure bubble jet cleaning, spray cleaning, ultrasonic cleaning, brush cleaning and the like can also be employed. Among these, high-pressure water cleaning is preferable from the viewpoint of cleaning efficiency. The wear loss in the thickness direction of the polishing pad surface was measured from the average of 10 cross-sectional photographs obtained by enlarging the difference in pad thickness before and after conditioning 200 times and divided by unit time (minutes). Ask.

  Hereinafter, the present invention will be specifically described by way of examples. In addition, this invention is not limited at all by the Example.

First, a method for evaluating the characteristics of the polishing pad will be described together below.
[Evaluation method]
(Confirmation of average fiber diameter of ultrafine fibers and converging state of ultrafine fibers)
A cutting surface in the thickness direction was formed by cutting the polishing pad in the thickness direction with a cutter blade. The obtained cut surface was stained with osmium oxide. Then, the stained cut surface was observed with a scanning electron microscope (SEM) at 500 to 1000 times, and an image thereof was taken. And the average cross-sectional area of the ultrafine fiber which exists in a cut surface was calculated | required from the obtained image. The average cross-sectional area was a value obtained by averaging 100 cross-sectional areas randomly selected from the image. And the fineness was computed from the obtained average cross-sectional area and the density of resin which forms a fiber. In addition, by observing the obtained image, not only the ultrafine fibers constituting the outer periphery of the fiber bundle, but also the case where the internal ultrafine fibers are bonded and integrated by the polymer elastic body is “focused”, The state where the polymer elastic body was not present inside the fiber bundle or only a few were present and the ultrafine fibers were hardly bonded and integrated was judged as “no focusing”.

(Flexural modulus)
Using a universal testing machine (AG-5000B, manufactured by Shimadzu Corporation), the flexural modulus of the polishing pad was measured 5 times, and the average value was taken as the flexural modulus. In addition, each measured value used the average value when each grind | polishing longitudinal direction and a horizontal direction are measured. In addition, the sample to measure was measured about the polishing pad precursor before a groove process, when grooving the surface. Measurement conditions are as follows. (Test mode: single, test type: 3-point bending, control: stroke, head speed: 0.6 mm / min, load cell: 500 kg, between chucks: 2.2 cm, number of tests: 5)

(Apparent density of polishing pad and porosity of polishing pad)
The apparent density of the obtained polishing pad was measured according to JIS K7112. Further, the theoretical density of the composite of the fiber entangled body and the polymer elastic body in the absence of voids was calculated from the constituent ratio of each constituent constituting the polishing pad and the density of each constituent. Then, the ratio of the apparent density to the theoretical density was defined as a polishing pad filling rate (volume ratio of a portion excluding voids of the polishing pad). Then, the “porosity of polishing pad (%)” was determined from the formula “porosity of polishing pad (%) = 100% −polishing pad filling rate (%)”. The density of each component is, for example, modified PET (1.38 g / cm ³ ), polyurethane elastic body (varies depending on the composition, but approximately 1.03 to 1.15 g / cm ³ ), PVA resin (1.25 g / cm ² ). cm ³ ) was used.

(Confirm communication holes)
Observe both sides of the polishing pad with an optical microscope (200x) to confirm the presence of pores, color the surface of the polishing pad with holes confirmed with a dye, and if necessary add water drops with a surfactant. It was confirmed that it dropped and reached the back surface.

(Water absorption height)
In the birec method water absorption height test based on JIS L1907-1994, the water absorption height after 60 minutes was measured. The measurement sample was measured four times, and the average value was taken as the water absorption height.

(Glass transition temperature of polymer elastic body, storage elastic modulus at 23 ° C and 50 ° C)
A film sample having a length of 4 cm, a width of 0.5 cm, and a thickness of 400 μm ± 100 μm was prepared using a polymer elastic body constituting the polishing pad. Then, using a dynamic viscoelasticity measuring device (DVE Rheospectr, manufactured by Rheology Co., Ltd.), the dynamic viscoelastic modulus at 23 ° C. and 50 ° C. under conditions of a frequency of 11 Hz and a temperature rising rate of 3 ° C./min. The storage modulus was measured and calculated. The main dispersion peak temperature of the loss elastic modulus at 23 ° C. was defined as the glass transition temperature. In addition, when using 2 types of polymer elastic bodies, the sample was created and measured separately, respectively, and the sum of the value which multiplied each measured value by the mass ratio was calculated | required.

(Water absorption rate of polyurethane elastic body)
A film having a thickness of 200 μm obtained by drying a polyurethane elastic body at 50 ° C. was heat-treated at 130 ° C. for 30 minutes, and then allowed to stand at 20 ° C. and 65% RH for 3 days. The dried sample was immersed in water at 0 ° C. for 2 days. Then, the water-swollen sample was obtained after wiping off excess water droplets and the like on the outermost surface of the film immediately after being taken out of water at 50 ° C. with JK Wiper 150-S (manufactured by Crecia Corporation). The masses of the dried sample and the water-swelled sample were measured, and the water absorption rate was determined according to the following formula. In addition, when using 2 types of polyurethane elastic bodies, a sample was created and measured separately, respectively, and the sum which multiplied the mass ratio was made into the value of the water absorption rate of a polyurethane elastic body.
Water absorption (%) = [(mass of water swelled sample−mass of dried sample) / mass of dried sample] × 100

(Average particle diameter of aqueous polyurethane)
Measured by dynamic light scattering method using “ELS-800” manufactured by Otsuka Chemical Co., Ltd. and analyzed by cumulant method (described in “Colloid Chemistry Vol. IV Colloid Chemistry Experimental Method” published by Tokyo Chemical Doujinsha) The average particle size of the aqueous dispersion of molecular elastic material was measured.

[Example 1]
Water-soluble thermoplastic polyvinyl alcohol resin (hereinafter referred to as PVA resin) and isophthalic acid-modified polyethylene terephthalate having a degree of modification of 6 mol% (water absorption 1% by mass when saturated with water at 50 ° C., glass transition) (Temperature 77 ° C.) (hereinafter referred to as modified PET) was discharged from the melt composite spinning die at a ratio of 20:80 (mass ratio) to form a sea-island composite fiber. The base for melt composite spinning had 36 islands / fiber and the base temperature was 260 ° C. Then, by adjusting the ejector pressure to a spinning speed of 3700 m / min and collecting long fibers having an average fineness of 2.4 dtex on the net, a spunbond sheet (long fiber web) having a basis weight of 40 g / m ² is collected. )was gotten.

The resulting spunbonded sheets stacked 12 sheets by cross lapping, the total basis weight was produced overlay web 480 g / m ^2. And the needle | hook breaking prevention oil agent was sprayed on the obtained web. Next, using the needle needle of No. 42 with 1 barb and the needle needle of No. 42 with 6 barbs, the overlap web is entangled by needle punching at 2000 punch / cm ^2. It was. At this time, the basis weight of the sheet was 770 g / m ² .

Next, the obtained sheet was steam-treated for 90 seconds at 110 ° C. and 50% RH. And after drying in 120 degreeC oven, the web entanglement sheet | seat of the fabric weight 1300g / m < ² >, apparent density 0.56g / cm < ³ >, and thickness 2.3mm was obtained by heat-pressing at 120 degreeC. .

Next, the hot-pressed web entangled sheet was impregnated with an aqueous dispersion of polyurethane elastic body A (solid content concentration 12 mass%) as the first polyurethane elastic body. The polyurethane elastic body A contains an amorphous polycarbonate polyol and a polyalkylene glycol having 2 to 3 carbon atoms in a ratio of 99.7: 0.3 (molar ratio), and further contains a carboxyl group-containing monomer. Is an amorphous polycarbonate non-yellowing polyurethane resin containing 1.5 wt% by weight. The polyurethane elastic body A has a water absorption rate of 3% by mass, a storage elastic modulus at 23 ° C. of 300 MPa, a storage elastic modulus at 50 ° C. of 150 MPa, a glass transition temperature of −20 ° C., and the average particle size of the aqueous dispersion is 0.03 μm. is there. The web-entangled sheet impregnated with the aqueous dispersion is dried and solidified in an atmosphere of 90 ° C. and 50% RH, and further dried at 160 ° C. to obtain a basis weight of 1400 g / m ² and an apparent density of 0.1. A sheet having a thickness of 80 g / cm ³ and a thickness of 1.8 mm was obtained.

Next, the PVA resin is dissolved and removed by continuously performing a nip treatment for 10 minutes while immersing the web entangled sheet filled with the polyurethane elastic body A in 95 ° C. hot water, and further drying. As a result, a composite of polyurethane elastic body A and fiber entangled body having an average fineness of ultrafine fibers of 0.08 dtex, a basis weight of 1000 g / m ² , an apparent density of 0.54 g / cm ³ , and a thickness of 1.89 mm was obtained. .

Then, the composite was further impregnated with an aqueous dispersion of polyurethane elastic body B (solid content concentration: 15% by mass) as the second polyurethane elastic body. The polyurethane elastic body B was obtained by adding 100 parts by mass of a non-yellowing polyurethane resin obtained from a composition containing an amorphous polycarbonate polyol as a polyol component and 1.7% by mass of a carboxyl group-containing monomer. It is a polyurethane resin having a crosslinked structure formed by adding a mass part and heat-treating it. The polyurethane elastic body B has a water absorption rate of 2% by mass, a storage elastic modulus at 23 ° C. of 450 MPa, a storage elastic modulus at 50 ° C. of 250 MPa, a glass transition temperature of −25 ° C., and the average particle size of the aqueous dispersion is 0.04 μm. there were. Next, the web entangled sheet impregnated with the aqueous dispersion was coagulated at 90 ° C. in an atmosphere of 50% RH, and further dried at 150 ° C. And the polishing pad precursor was obtained by hot-pressing it at 160 degreeC. The obtained polishing pad precursor had a basis weight of 1000 g / m ² , an apparent density of 0.55 g / cm ³ , a thickness of 1.8 mm, a porosity of 58%, a flexural modulus of 420 MPa, and a water absorption height of 200 mm. It was also confirmed that the fiber bundles were bundled and communication holes existed.

The obtained polishing pad precursor was ground for surface flattening to have a basis weight of 750 g / m ² , an apparent density of 0.55 g / cm ³ , and a thickness of 1.4 mm. Further, a circular polishing pad was obtained by cutting into a circular shape with a diameter of 40 cm and forming grooves with a width of 2.0 mm and a depth of 1.0 mm on the surface in a lattice shape at intervals of 15.0 mm. The mass ratio of the fiber entangled body and the polyurethane elastic body in the polishing pad was 84/16, and the ratio of the polyurethane elastic body A to the polyurethane elastic body B was 50:50. Then, the polishing performance of the polishing pad was evaluated by the following method.

(Polishing pad polishing performance evaluation method)
The polishing performance of the polishing pad was evaluated as follows using the polishing apparatus 100 as shown in FIG. A conductive adhesive tape 16 was attached to the back surface of the circular polishing pad 10 and then mounted on the surface plate 12. Then, using a # 200 (blocky type) diamond dresser, conditioning was performed by grinding the surface of the polishing pad 10 for 18 minutes while flowing distilled water at a rate of 50 mL / min.

Next, on the surface of the polishing pad 10 under the conditions of the rotation speed of the platen 12 (platen rotation speed) of 90 rpm or 60 rpm and a polishing pressure of 45 g / cm ³ (0.6 psi), 5% by mass of citric acid, benzotriazole 0 A 3 mass% aqueous solution was supplied at a rate of 30 ml / min, and four 15 mm × 15 mm Cu plates were polished for 10 minutes while a voltage of 10 V was applied between the polishing head 13 and the surface plate 12. At this time, the polishing head 13 included in the polishing apparatus 100 was rotated according to the number of rotations of the surface plate 12. The polishing rate [μm / min] was determined by measuring the weight difference between the Cu plates before and after polishing, converting the polished thickness from the weight difference, and dividing the polished thickness by the polishing time. The determination of the polishing rate is ○ when the polishing rate when 5 V is applied is 30 (nm / min.) Or more and the polishing rate when 10 V is applied exceeds 60 [nm / min]. X. The results are shown in Table 1.

[Example 2]
The same process as in Example 1 was performed until the web entangled sheet was produced.

Next, without impregnating the hot-pressed web-entangled sheet with the aqueous dispersion of polyurethane elastic body A, the PVA-based resin is dissolved and removed by immersing in hot water at 95 ° C. for 10 minutes. A fiber entangled body consisting of a fiber bundle was obtained. Then, the obtained fiber entangled body was impregnated with an aqueous dispersion of polyurethane elastic body B (solid content concentration 30% by mass). Next, the fiber entangled body impregnated with the aqueous dispersion was dried at 150 ° C., and further hot pressed at 160 ° C. to obtain a polishing pad precursor. Then, the obtained polishing pad precursor was post-processed in the same manner as in Example 1, with a basis weight of 1170 g / m ² , an apparent density of 0.72 g / cm ³ , a thickness of 1.68 mm, a porosity of 45%, a bending A polishing pad having an elastic modulus of 550 MPa and a water absorption height of 140 mm was obtained. It was also confirmed that the fiber bundles were bundled and communication holes existed. Furthermore, it was cut into a circular shape having a diameter of 40 cm, and grooves having a width of 2.0 mm and a depth of 1.0 mm were formed on the surface in a lattice shape at intervals of 15.0 mm, thereby obtaining a circular polishing pad. Then, the polishing performance of the polishing pad was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[Comparative Example 1]
The same process as in Example 1 was performed until the web entangled sheet was created.

Next, the hot-pressed web entangled sheet was impregnated with an aqueous dispersion of polyurethane elastic body A (solid content concentration 40% by mass). The web entangled sheet impregnated with the aqueous dispersion is dried and coagulated in an atmosphere of 90 ° C. and 50% RH, and further dried at 160 ° C. to obtain a basis weight of 1690 g / m ² and an apparent density of 0.1. A sheet having a thickness of 94 g / cm ³ and a thickness of 1.8 mm was obtained.

Next, the PVA resin is dissolved and removed by continuously performing a nip treatment for 10 minutes while immersing the web entangled sheet filled with the polyurethane elastic body A in 95 ° C. hot water, and further drying. Thus, a composite of the polyurethane elastic body A and the fiber entangled body having an average fineness of ultrafine fibers of 0.08 dtex, a basis weight of 1300 g / m ² , an apparent density of 0.75 g / cm ³ , and a thickness of 1.8 mm was obtained. .

Then, the composite was impregnated with an aqueous dispersion of polyurethane elastic body B (solid content concentration: 15% by mass). Next, the web entangled sheet impregnated with the aqueous dispersion was coagulated at 90 ° C. in an atmosphere of 50% RH, and further dried at 150 ° C. And the polishing pad precursor was obtained by hot-pressing it at 160 degreeC. The obtained polishing pad precursor had a basis weight of 1500 g / m ² , an apparent density of 0.88 g / cm ³ , a thickness of 1.7 mm, a porosity of 33%, a flexural modulus of 700 MPa, and a water absorption height of 18 mm. In addition, the presence of communication holes was confirmed.

  The obtained polishing pad precursor is ground for surface flattening, and grooves having a width of 2.0 mm and a depth of 1.0 mm are formed on the surface in a lattice shape at intervals of 15.0 mm. A shaped polishing pad was obtained. The mass ratio of the fiber entangled body and the polyurethane elastic body in the polishing pad was 74/26, and the ratio of the polyurethane elastic body A to the polyurethane elastic body B was 55:45. Then, the polishing performance of the polishing pad was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[Comparative Example 2]
The polishing performance of the polishing pad was evaluated in the same manner as in Example 1 using a non-woven polishing pad (SUBA400 manufactured by R & H) manufactured by impregnating polyethylene terephthalate fiber having a fineness of 2 dtex with a solvent-based polyurethane resin. The apparent density of the nonwoven fabric polishing pad was 0.3 g / cm ³ , the water absorption height was 2 mm, and the flexural modulus was 50 MPa. Moreover, the presence of the communication hole was confirmed. The results are shown in Table 1. As shown in Table 1, the polishing rate under a low voltage was remarkably low.

[Comparative Example 3]
The polishing performance of the polishing pad was evaluated in the same manner as in Example 1 except that a polyurethane polishing pad having independent holes (IC-1000 manufactured by R & H) was used as the polishing pad. The polyurethane polishing pad does not have communication holes, has a basis weight of 960 g / m ² , an apparent density of 0.77 g / cm ³ , a thickness of 1.25 mm, a porosity of 33%, a flexural modulus of 430 MPa, and a high water absorption. It was 0 mm. The results are shown in Table 1. As shown in Table 1, no polishing was possible.

[Comparative Example 4]
The same operation as in Example 1 was performed except that polishing was performed without applying a voltage. The results are shown in Table 1.

[Comparative Example 5]
The same procedure as in Example 2 was performed except that polishing was performed without applying a voltage. The results are shown in Table 1.

  The polishing pad of the present invention is preferably used as a polishing pad for a conductive material film such as Cu that is polished using an electrolyte solution. Also, by dispersing abrasive grains in the electrolyte, silicon wafers, compound semiconductor wafers, semiconductor wafers, semiconductor devices, liquid crystal members, optical elements, crystals, optical substrates, electronic circuit substrates, electronic circuit mask substrates, multilayer wiring substrates, It is also used for polishing hard disks, MEMS (micro-electro-mechanical systems) substrates and the like. Specific examples of semiconductor wafers and semiconductor devices include, for example, insulating films such as silicon, silicon oxide, silicon oxyfluoride, and organic polymers; wiring material metal films such as copper, aluminum, and tungsten; tantalum, titanium, tantalum nitride, and nitride Examples thereof include a base material having a barrier metal film such as titanium on the surface.

  In the polishing, it is used for any polishing such as primary polishing, secondary polishing (adjustment polishing), finish polishing, mirror polishing and the like. Moreover, as a grinding | polishing part, any of the surface of a base material, a back surface, and an end surface may be sufficient.

FIG. 1 is a schematic cross-sectional view of a polishing pad 10 according to an embodiment. FIG. 2 is a schematic explanatory view of the polishing apparatus 100 used in the embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Superfine fiber entanglement body 2 Polymer elastic body 3 Communication hole 10 Polishing pad 12 Surface plate 13 Polishing head 14 Voltage application means 15 Electrolyte supply pipe 16, 17 Conductive double-sided tape 18 Electrolyte solution 100 Polishing apparatus W Wafer L Metal wiring M1, M2 drive means

Claims (6)

A wafer having a metal film deposited on the surface is pressed against the polishing pad while supplying an electrolytic solution, and a voltage is applied between the wafer and the polishing pad to electrolyze the metal film and the wafer. A polishing pad used in an electrochemical chemical mechanical polishing method,
An ultrafine fiber entangled body containing ultrafine fibers having an average fineness of 0.01 to 0.8 dtex is integrated with a polymer elastic body,
A polishing pad having a bending elastic modulus in a range of 150 to 650 MPa, a porosity in a range of 40 to 60 % by volume, and a communication hole.   The polishing pad according to claim 1, wherein the ultrafine fibers are present as a bundle of fibers bundled in a range of 5 to 70, and the bundle of fibers is bundled by the polymer elastic body.   The polishing pad according to claim 1, wherein the polymer elastic body is a non-porous polyurethane resin.   The polishing pad according to claim 1, wherein the polymer elastic body has a water absorption rate of 0.2 to 5 mass% when saturated water absorption is performed at 50 ° C. 5.   The polishing pad according to any one of claims 1 to 4, wherein the polymer elastic body has a storage elastic modulus of 90 to 900 MPa at 23 ° C and 50 ° C.   The polishing pad according to any one of claims 1 to 5 is pressed against the wafer having a metal film deposited on the surface while supplying an electrolytic solution, and a voltage is applied between the wafer and the polishing pad. A method for electrolytically polishing a wafer by polishing the wafer while electrolyzing the metal film by applying

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