JP6357291B2 - Polishing pad - Google Patents

Description

  The present invention relates to a polishing pad, and more particularly to a polishing pad having a polyurethane foam sheet formed by wet film formation as a polishing layer.

  Integrated circuits patterned on semiconductor wafers are being miniaturized and densified, and insulating materials with lower dielectric constants (low-k and ultra-low-k insulators) to realize their wiring structure ) And copper wiring are being used. In such semiconductor devices, low-k and ultra-low-k insulators have lower mechanical strength and weaker adhesion than conventional insulators during polishing for surface planarization. There is a problem that defects (polishing scratches such as scratches) are likely to occur. In addition, a higher level of topography (planarization characteristics such as dishing erosion) is required due to the higher density of the wiring structure.

  On the other hand, in polishing processing of such a semiconductor device or the like, a polishing pad having a polyurethane foam sheet formed by a dry molding method or a wet film forming method as a polishing layer is used.

  As a polishing pad by a dry molding method, for example, as described in Patent Document 1, a resin solution obtained by adding hollow fine particles to a resin solution is disclosed.

  As a polishing pad by a wet film forming method or the like, for example, as disclosed in Patent Document 2, a suede type soft plastic foam having a foam structure is bonded to a high hardness film or the like.

Japanese Patent No. 3013105 Japanese Patent No. 4555559

  However, although a hard polishing pad according to the conventional dry molding method is excellent in topography, the amount of scratches becomes an unacceptable level, and the defect suppression performance (defect rate reduction performance) is sacrificed.

  Further, a soft polishing pad formed by a conventional wet film formation method can exhibit a high level of defect suppression performance, but is inferior to topography.

  An object of the present invention is to improve both defect suppression performance and topography in a polishing pad.

  The invention according to claim 1 is a polishing pad having a polyurethane foam sheet formed by wet film formation as a polishing layer, wherein the sheet is made of a polyurethane resin to which hollow microspheres made of a shell having high solvent resistance are added. It is formed as a main component, and the 100% resin modulus of the polyurethane resin is in the range of 5 to 25 MPa, and a large number of polyurethane foams and a large number of hollow microspheres are uniformly dispersed in the polyurethane resin. Polyurethane foam communicates with each other in a network through communication holes, and each hollow microsphere exists with closed cells, and a polyurethane foam opening and a hollow microsphere bubble opening are formed on the surface of the polishing layer. ing.

  The invention according to claim 2 is the invention according to claim 1, wherein the outer shell having high solvent resistance is a thermosetting resin.

The invention according to claim 3, further in the invention according to claim 1 or 2, the specific gravity of the hollow microspheres consisting of high the solvent resistance outer shell is 0.8g / cm ³ ~1.1g / cm ³ .

  The invention according to a fourth aspect is the invention according to any one of the first to third aspects, wherein the addition amount of the hollow microsphere made of the outer shell having a high solvent resistance is 1% by mass to 50% by mass.

  The invention according to claim 5 is the invention according to any one of claims 1 to 4, wherein, in the cross section of the sheet, an average void diameter due to foaming of polyurethane and bubbles of hollow microspheres is 10 μm to 30 μm.

The invention according to claim 6 is the invention according to any one of claims 1 to 5, wherein the sheet has a Shore A hardness of 35 degrees to 70 degrees and a density of 0.30 g / cm ^{3 to} 0.70 g / cm. ^Three .

  The invention according to claim 7 is the invention according to any one of claims 1 to 6, wherein the sheet has a tear strength of 0.50 N / mm to 1.60 N / mm.

  According to the present invention, both the defect suppression performance and the topography in the polishing pad can be improved.

1 is a cross-sectional view (SEM 1000 times) of a polyurethane foam sheet of Example 1. FIG.

1. Configuration of Polishing Pad The polishing pad of the present invention has a polyurethane foam sheet formed by wet film formation as a polishing layer.

  The polyurethane foam sheet is formed mainly of a polyurethane resin to which hollow microspheres made of an outer shell having high solvent resistance are added, and the 100% resin modulus of the polyurethane resin is in the range of 5 to 25 MPa. .

  The resin modulus is an index representing the hardness of the resin, and is a value obtained by dividing the load applied when the non-foamed resin sheet is stretched 100% (up to twice the original length) by the unit area ( Hereinafter, it may be referred to as 100% resin modulus). If the 100% resin modulus of the polyurethane resin is less than 5 MPa, the polishing surface of the polishing pad (the polishing layer (skin layer) in which fine micropores are formed during wet film formation is removed by grinding or dressing) The surface) of the surface of the object to be polished follows too much, and the topography of the object to be polished required by the polishing process deteriorates, and the flattening characteristics required for the object to be polished cannot be obtained. When the 100% resin modulus of the polyurethane resin exceeds 25 MPa, the topography is improved, but the dressing property of the polishing surface of the polishing pad is deteriorated and the polishing rate (polishing amount per unit time) is lowered and the defect is increased. To do. The resin modulus of the product of the present invention was measured by dissolving a polyurethane foam sheet with N, N-dimethylformamide (DMF) to obtain a low-concentration polyurethane resin DMF solution, and filtering the hollow microspheres with a filter. It can be measured by vaporizing DMF by a method to form a non-foamed resin sheet.

  By using a wet-formed polishing pad, a good low defect rate (defect suppression performance) can be achieved. In addition, polar solvents (eg, DMF, DMAc, THF, DMSO, NMP, acetone, etc.) widely used in the art as good solvents for polyurethane resins used as the main component of the polishing pad have an outer shell made of acrylonitrile-vinylidene chloride. Hollow microspheres made of a thermoplastic resin such as a polymer, acrylonitrile-methyl methacrylate copolymer, and urethane resin are easily dissolved, and the formation of voids by the hollow microspheres is hindered. On the other hand, when hollow microspheres made of an outer shell having high solvent resistance are used, the hollow microspheres can be uniformly dispersed in the polishing layer without losing voids. The index of high solvent resistance can be determined by whether or not it dissolves in DMF. When it is insoluble in DMF, hollow fine particles having high solvent resistance are obtained. As a specific determination method, for example, a urethane sheet is placed in 100 parts by weight of DMF and allowed to stand at room temperature overnight and then stirred for 30 minutes. it can.

By setting the specific gravity of the hollow microspheres made of the outer shell having high solvent resistance to 0.8 to 1.1 g / cm ³ , it is possible to approach the specific gravity of the polyurethane resin solution, and the hollow microspheres are placed in the polyurethane resin solution. It is possible to uniformly disperse, and as a result, hollow microspheres can be distributed substantially uniformly from the sheet surface of the polishing pad to the sheet thickness direction and to the polishing surface direction. The specific gravity of the hollow microsphere is such that the shell thickness of the hollow microsphere is 10 to 70% of the diameter of the hollow microsphere to increase the thickness of the shell, or a high-density resin is used as the resin material of the hollow microsphere shell. It can be adjusted by using it.

  The addition amount of the hollow microspheres composed of the outer shell having high solvent resistance is 1 to 50% by mass with respect to the total mass of the polyurethane resin. If the amount of hollow microspheres added is less than 1% by mass, the dressing property of the polishing surface of the polishing pad is deteriorated and the polishing rate is lowered. If the amount of hollow microspheres exceeds 50% by mass, the wet film-forming property of the sheet deteriorates, and a polyurethane foam sheet cannot be produced.

  In the cross section of the polyurethane foam sheet, when the average void diameter of the polyurethane foam and the hollow microsphere bubbles is in the range of 10 to 30 μm, the polishing slurry can be well retained and the polishing rate can be improved.

When the Shore A hardness of the polyurethane foam sheet is 35 to 70 degrees and the density is in the range of 0.30 to 0.70 g / cm ³ , the rigidity of the polishing pad can be maintained and the wear resistance of the polishing pad is improved. be able to.

When the Shore A hardness of the polyurethane foam sheet is 35 to 70 degrees, the density is 0.30 to 0.70 g / cm ³ , and the average void diameter of the polyurethane foam and the hollow microsphere is 10 to 30 μm. The rigidity of the pad can be maintained, and the wear resistance of the polishing pad can be improved.

  When the tear strength of the polyurethane foam sheet is in the range of 0.50 to 1.60 N / mm, the abrasion resistance of the polishing pad is excellent, and the product life can be extended.

  The polishing pad has a polyurethane foam sheet as a soft plastic foam sheet formed of a polyurethane resin. In the polishing pad, the dense skin layer (skin layer) formed at the beginning of the wet film formation is removed. In the polyurethane foam sheet, a large number of hollow microsphere cells dispersed in a polyurethane resin and a large number of polyurethane foams are arranged as voids capable of holding the slurry. Each polyurethane foam has an average diameter (void diameter) equal to or less than that of the hollow microsphere, and communicates in a three-dimensional network with communication holes having a diameter smaller than the average diameter of the foam. Each hollow microsphere is a hollow microsphere having a bubble diameter (void diameter) of 10 to 80 μm, and is communicated with foaming and communication holes in a three-dimensional network polyurethane resin surrounding the hollow microsphere. It exists with closed cells without. Accordingly, the polyurethane foam sheet has polyurethane foam and hollow microsphere bubbles formed substantially uniformly (equally) in the sheet thickness direction and in the polishing surface direction. The polyurethane foam and the hollow microsphere bubbles located in the vicinity of the polishing surface of the polishing pad form an opening that opens on the polishing surface. In the present specification, the bubble is a space surrounded by the outer shell of the hollow microsphere, and is entirely surrounded by the wall (not connected to other bubbles or bubbles), and thus exists as an independent bubble. .

  The polishing pad is selected from a flexible film such as a film made of polyethylene terephthalate (hereinafter abbreviated as PET), a nonwoven fabric, and a woven fabric on the opposite side (lower surface side) to the polishing surface of the polyurethane foam sheet. It has a seed support member. On the lower surface side of the support member, a double-sided tape for attaching a polishing pad to a polishing surface plate having a release paper on the other surface side (lowermost surface side) is bonded.

2. Manufacturing method of polishing pad The polishing pad of the present invention comprises a wet film forming method, for example, a step of preparing a polyurethane resin solution in which a polyurethane resin, DMF, a foaming modifier, and hollow microspheres are mixed and dispersed, and a polyurethane resin solution. It can be produced by a method comprising a step of applying to a substrate and a step of coagulating and regenerating the polyurethane resin by immersing the substrate coated with the polyurethane resin solution in a coagulating liquid.

(1) Step of preparing a polyurethane resin solution
i. The foam regulator used in the preparation process of the urethane resin solution can be uniformly mixed or dispersed in the polyurethane resin solution and has a water solubility lower than DMF or a urethane resin solubility lower than DMF. (A solvent having a polarity smaller than that of DMF).

  Solvents whose solubility in water is lower than DMF or whose urethane resin is lower than DMF are specifically ester solvents such as methyl acetate, ethyl acetate, isopropyl acetate, isobutyl acetate, methyl formate, ethyl formate and propyl formate. And ketone solvents such as methyl ethyl ketone, methyl-n-propyl ketone, acetone and methyl isobutyl ketone, alcohols such as isopropyl alcohol, and aromatic solvents such as toluene.

  These solvents have a slow replacement rate with the coagulating liquid (water), and the polyurethane resin coagulates in almost the entire region from the upper layer (surface layer side) to the lower layer (base material side) in the polyurethane resin solution (the solvent is the coagulating liquid). As a result of the (substitution of water) and solidifying) progresses slowly and uniformly, a large number of voids are foamed uniformly in the polyurethane resin, and a large number of polyurethane foams are formed from the surface of the polishing pad. It can be distributed almost uniformly in the thickness direction. Foaming of each polyurethane forms a substantially spherical foam having an average diameter equal to or smaller than the bubbles of the hollow microsphere without forming a vertically long foam in the sheet thickness direction. Foaming of each polyurethane is communicated with each other through a three-dimensional network-like communicating hole comprising a solvent and water substitution path.

  The density | concentration of the urethane resin in a polyurethane resin solution is 10-50 mass%, for example, Preferably it is 20-40 mass%. Within this concentration range, the sheet density is adjusted to an appropriate range, and a desired foam structure can be formed.

  ii. DMF, which is a good solvent for polyurethane resin, can be mixed at an arbitrary ratio with respect to water, so the replacement speed with the coagulation liquid (water) is fast, and the lower layer (base material side) of the polyurethane resin solution The DMF on the side moves quickly to the upper layer (surface layer) side, and relatively large foaming (foaming longitudinally in the sheet thickness direction) tends to be formed on the lower layer side. Therefore, in the present invention, the foam regulator is mixed so that the vertical foam is not formed and the average diameter does not exceed 30 μm (smaller than the hollow microsphere). The mixing ratio of the foaming modifier used in the preparation process with respect to DMF in the polyurethane resin solution is 0 to 67% by mass.

  iii. Thermosetting hollow microspheres to be mixed and dispersed in a polyurethane resin are microspheres having hollow portions (bubbles) inside and are made of an outer shell having high solvent resistance. The outer shell having high solvent resistance may be insoluble in DMF, but is preferably made of a thermosetting resin outer shell that is not softened or deformed by polishing heat. As the outer shell of the thermosetting resin, a cross-linked polymethyl methacrylate or phenol resin is used.

By setting the specific gravity of the hollow microspheres to 0.8 to 1.1 g / cm ^{3 as} described above, it is possible to approach the specific gravity of the polyurethane resin solution, and the hollow microspheres are uniformly dispersed in the polyurethane resin solution. be able to.

  iv. The polyurethane resin solution may further contain an additive as necessary. The additive is not particularly limited, but in the process of solidifying and regenerating the polyurethane resin, the solidification rate of the polyurethane resin is adjusted to form a desired foamed shape, so that a pigment such as carbon black, a hydrophobic active agent, a hydrophilic property An activator is preferred. These additives can be used alone or in combination of two or more. The compounding quantity of an additive is not restrict | limited in particular, For example, it is 30 mass parts or less with respect to 100 mass parts of urethane resin containing solutions, Preferably it is 20 mass parts or less (for example, 1-15 mass parts). However, it is preferable not to use additives such as carbon black that can cause defects.

(2) Polyurethane resin solution coating process The base material used in the polyurethane resin solution coating process may be a flexible material, such as a plastic film (eg, a polyester film, a polyolefin film), a non-woven fabric, or the like. Can be mentioned. The method of applying the polyurethane resin-containing solution to the substrate is not particularly limited, and examples thereof include a method of applying using a conventional coater (knife coater, reverse coater, roll coater, etc.). The coating thickness is, for example, 0.5 to 2.5 mm, preferably 1.0 to 2.0 mm, and more preferably 1.2 to 1.8 mm from the viewpoint of forming a predetermined foam structure.

(3) Polyurethane resin coagulation regeneration step In the polyurethane resin coagulation regeneration step, the coagulation liquid for immersing the base material coated with the polyurethane resin solution contains a poor solvent (such as water) for the polyurethane resin as a main component. Examples of the coagulating liquid include water, a mixed solution of water and a polar solvent (for example, DMF, DMAc, THF, DMSO, NMP, acetone, and the like). The concentration of the polar solvent in the mixed solution is preferably 0.5 to 30% by mass.

  A polyurethane foam sheet solidified on the substrate can be obtained by the solidification regeneration process of the polyurethane resin. The manufacturing method of the polishing pad of the present invention may further include a step of washing and drying the polyurethane foam sheet obtained by coagulation on the substrate, if necessary, after peeling from the substrate.

(4) Washing and drying process of polyurethane resin By washing and drying, DMF, foaming modifier and coagulating liquid (water) remaining in the polyurethane resin are removed. Water is usually used as the cleaning liquid used for cleaning. The drying is usually performed at 80 to 150 ° C. for about 5 to 60 minutes.

  In the method for producing a polishing pad of the present invention, the front surface or the front surface and the back surface may be further subjected to a grinding treatment, or if necessary, a surface treatment such as grooving or embossing by cutting may be performed.

  The method for grinding (buffing) is not particularly limited, and examples thereof include a sandpaper method. The surface to be ground (buffed) may be either the former of the polished surface (surface layer side surface) and the non-polished surface (surface plate attachment side surface) or both. The grinding processing amount (buff processing amount) is, for example, 0.05 to 0.3 mm, preferably 0.1 to 0.2 mm, depending on the desired surface shape. Thus, polyurethane foam openings and hollow microsphere bubble openings are formed in the surface layer of the polishing pad, and the thickness of the sheet is made uniform.

  In grooving and embossing, the processing temperature and processing pressure are not particularly limited, but the processing temperature is, for example, 100 to 200 ° C., preferably 120 to 180 ° C., and the processing pressure is, for example, 3 to 6 MPa, preferably 4 to 5 MPa. The processing time is not particularly limited, but is, for example, 30 to 300 seconds, preferably 60 to 180 seconds.

  The concave portions formed by grooving or embossing may be formed randomly, but may be formed regularly (for example, in a lattice shape, a concentric circle shape, a radial shape, or a honeycomb shape). The width of the recess is, for example, 0.3 to 3.0 mm, preferably 0.5 to 1.5 mm, and more preferably 0.8 to 1.2 mm. The average center-to-center distance between adjacent concave portions is, for example, 1 to 100 mm, preferably 2 to 20 mm. Thereby, supply and discharge of the slurry to the surface layer side of the polishing pad can be promoted.

3. Action of polishing pad, etc.
(1) A large number of polyurethane foams and a large number of hollow microsphere bubbles are dispersed almost uniformly in the polyurethane resin as voids for holding the polishing pad slurry. Each foam communicates with each other through a communication hole, and each bubble exists as a closed cell.

  The foaming of the polyurethane and the bubbles of the hollow microspheres are opened on the polishing surface of the polishing pad by dressing. The slurry supplied at the time of the polishing process is uniformly distributed in the polishing surface while being held in these openings, and acts on the surface of the object to be polished to contribute to the polishing process. Further, the slurry held at the opening of the polyurethane foam penetrates the foam in the polyurethane resin through the communication hole. Therefore, the start-up time of polishing can be shortened faster than when the familiarity of the slurry does not have a communication hole at the start of polishing.

  (2) In the above (1), when the abrasive grains in the slurry held in the openings of the polyurethane foam and the hollow microsphere bubbles in the surface layer of the polishing pad are pressed against the object to be polished on the polishing surface, Backed up by hollow microspheres inside the polishing pad, the pressing force is increased, and the polishing rate is increased.

  At this time, foaming of a large number of polyurethanes around the hollow microspheres becomes a cushion for the hollow microspheres, and the excessive pressing force exerted on the abrasive grains by the hollow microspheres is absorbed, and the scratches that the abrasive grains give to the object to be polished And the flatness of the surface of the object to be polished can be improved.

  (3) In the above (1) and (2), a large number of polyurethane foams and a large number of hollow microsphere bubbles are uniformly dispersed in the polishing layer of the polishing pad, from the polishing surface to the sheet thickness direction, and Distributed almost uniformly in the direction of the polished surface. As a result, the above-mentioned (1) foaming of the polyurethane and the creation of each opening by dressing the bubbles of the hollow microspheres, and the backup effect on the abrasive particles of the foaming of the hollow microspheres and polyurethane of the above (2) are polished by polishing. Even if the wear of the pad progresses, it is exerted continuously. Accordingly, it is possible to suppress changes with time in the polishing rate, the amount of generated scratches, and the flatness.

  (4) By setting the 100% resin modulus of the polyurethane resin forming the polishing pad in the range of 5 to 25 MPa, the flatness of the surface of the object to be polished is improved, the deterioration of the dressing property of the polishing surface is suppressed, and the polishing rate is also increased. It can be improved.

  (5) By using a thermosetting resin as the outer shell of the hollow microsphere, even if the polyurethane resin is softened by the polishing heat and the polyurethane foam opening on the polishing surface is blocked, the thermosetting hollow microsphere Since the opening of the bubbles is secured without being softened, the slurry is stably held and can be supplied to the polishing surface, the polishing rate can be maintained.

(6) The polishing pad has a Shore A hardness of 35 to 70 degrees, a density of 0.30 to 0.70 g / cm ³ , and an average pore diameter of polyurethane foam and hollow microsphere bubbles of 10 to 30 μm. Thus, it is possible to maintain the rigidity of the polishing pad while maintaining the rigidity of the polishing pad, and to improve the abrasion resistance of the polishing surface.

  (7) When the polishing pad has a tear strength in the range of 0.50 to 1.60 N / mm, the abrasion resistance of the polished surface can be improved and the product life can be improved.

4). Specific implementation results
4-1. The polishing pads of Examples and Comparative Examples shown in Table 1 were produced.
[Example 1]
100% resin modulus 24 polyester polyurethane resin having a concentration of 30% DMF solution (100 parts), a solution containing ethyl acetate (30 parts), isopropyl alcohol (5 parts), and the outer shell is crosslinked polymethacrylic acid 10 parts of hollow microspheres (average particle diameter 20 μm, shell thickness 5 μm), which is a methyl resin, were added (33% with respect to the total mass of the polyurethane resin) and mixed to obtain a resin-containing solution.

  The obtained resin-containing solution was cast on a polyester film (thickness: 250 μm). Thereafter, the polyester film cast with the resin-containing solution was immersed in a coagulation bath (coagulation liquid was water) to coagulate the resin-containing solution, and then washed and dried to obtain a polyurethane foam sheet. 1 is a cross-sectional view (SEM 1000 times) of a polyurethane foam sheet of Example 1. FIG.

  The skin layer side formed on the surface of the obtained polyurethane foam sheet was ground (grinding amount: 150 μm). Thereafter, a part of the sheet was embossed with a lattice mold, and a double-sided adhesive tape was bonded to the back surface of the sheet to obtain a polishing pad. Unless otherwise specified, “part” means part by mass.

[Example 2]
Example 1 except that a solution containing 100% resin modulus 6 polyester polyurethane resin with a concentration of 30% DMF solution (100 parts), ethyl acetate (30 parts) and isopropyl alcohol (5 parts) is used. Thus, a polishing pad was obtained.

[Examples 3-5 and Comparative Examples 1-3, 6]
A polishing pad was produced in the same manner as in Example 2 except that the 100% resin modulus of the polyurethane resin was as shown in Table 1, and the material and amount of the hollow microspheres were as shown in Table 1.

  In Example 3, 6% 100% resin modulus of polyurethane resin and 3% by mass of hollow microspheres whose outer shell is made of cross-linked polymethyl methacrylate resin are added to the total mass of the polyurethane resin.

  In Example 4, 6% 100% resin modulus of polyurethane resin and 33% by mass of hollow microspheres whose outer shell is made of phenol resin are added to the total mass of polyurethane resin.

  In Example 5, 6% 100% resin modulus of polyurethane resin and 1% by mass of hollow microspheres whose outer shell is made of cross-linked polymethyl methacrylate resin are added to the total mass of the polyurethane resin.

  In Comparative Example 1, 45% by mass of 100% resin modulus of polyurethane resin and 45% by mass of hollow microspheres whose outer shell is made of cross-linked polymethyl methacrylate resin with respect to the total mass of the polyurethane resin.

  Comparative Example 2 is obtained by adding 100% resin modulus of polyurethane resin to 3.5 and 33% by mass of hollow microspheres whose outer shell is made of cross-linked polymethyl methacrylate resin based on the total mass of the polyurethane resin.

  In Comparative Example 3, 47% 100% resin modulus of polyurethane resin and 33% by mass of hollow microspheres whose outer shells are made of cross-linked polymethyl methacrylate resin are added to the total mass of the polyurethane resin.

  Comparative Example 6 is obtained by adding 6% 100% resin modulus of polyurethane resin and 33% by mass of crosslinked polymethyl methacrylate resin microspheres (spherical particles) having no hollow portion based on the total mass of the polyurethane resin.

[Comparative Example 4]
In Comparative Example 4, a polishing pad was produced in the same manner as in Example 2 except that the hollow microspheres were not used.

[Comparative Example 5]
In Comparative Example 5, IC1000 (trade name, manufactured by Nitta Haas), which is a dry-molded commercially available polishing pad containing hollow fine particles, was used.

4-2. The physical properties of the polishing pads of Examples and Comparative Examples were evaluated, and the results shown in Table 1 were obtained.
About the polyurethane foam sheet which comprises the polishing pad of each Example and a comparative example, the Shore A hardness, the polishing layer density, the polyurethane foaming, the average void diameter of the bubble of a hollow microsphere, and tear strength were measured.

(Shore A hardness)
Shore A hardness is obtained by cutting out a polyurethane foam sheet sample piece (10 cm × 10 cm) from a polishing pad, and stacking a plurality of the sample pieces to a thickness of 4.5 mm or more. Measured according to JIS K7311).

(Polishing layer density)
The polishing layer density was determined by cutting a polyurethane foam sheet sample piece (10 cm × 10 cm) from the polishing pad, measuring the mass of the sample piece with an automatic balance,
Density (g / cm ³ ) = Mass (g) / (10 (cm) × 10 (cm) × Sample piece thickness (cm))
It calculated and calculated | required by.

(Polyurethane foam and average void diameter of hollow microspheres)
The average void diameter of polyurethane foam and hollow microspheres was expanded by 50 times in the range of about 5 mm square by scanning electron microscope (JSM-5000LV, cross section of polyurethane foam sheet sample piece). 9 points were observed. This image is binarized by image processing software (Image Analyzer V20LAB Ver.1.3, manufactured by Nikon) to check the total number of voids (polyurethane foam and hollow microsphere bubbles) present in the sheet. From the void area, the equivalent circle diameter and the average value were calculated as the average void diameter. In the measurement of the void diameter, the cut-off value (lower limit) of the void diameter was 11 μm, and noise components were excluded. In addition, void-like voids that occurred accidentally during film formation were also excluded from the measurement target. In addition, the space | gap shown here refers to both the foaming of a polyurethane, and the bubble of a hollow microsphere.

(Tear strength)
A 70 mm cut is made from the end of the polyurethane foam sheet sample piece (100 mm × 25 mm) in the longitudinal direction, and two places at 25 mm along the cut from the end of the cut in the sample piece are clamped and fixed. The two specimens are pulled with the universal material testing machine Tensilon (A & D Tensilon type universal testing machine RTC-1210 Co., Ltd.) in the opposite direction along the notch (direction in which one of the two places is rotated 180 degrees with respect to the other). The measurement was performed until it broke, and the strength (maximum load) N at which the measured value reached its peak was determined. The tear strength was determined from tear strength (N / mm) = strong (maximum load) N / thickness (mm).

  4-3. The polishing pads of each Example and Comparative Example were polished under the following polishing conditions, and the polishing rate, polishing uniformity, and presence / absence of defects were measured, and the results shown in Table 2 were obtained. When the polishing pad is used, the polishing pad is attached to the polishing surface plate of the polishing machine so that the polishing surface of the polishing layer faces the object to be polished. Then, while supplying the slurry to the polishing surface of the polishing pad, the polishing surface plate is rotated to polish the processed surface of the object to be polished.

As an object to be polished, a substrate (uniformity (CV%) of 13%) in which tetraethoxysilane was formed on a 12-inch silicon wafer by CVD so that the insulating film had a thickness of 1 μm was used. The 25 substrates were polished according to the polishing rate and the stability of the rate was evaluated from the polishing rate and the polishing uniformity of the 1st, 10th and 25th substrates.
Polishing machine: EBARA F-REX300
Polishing head: GII
Slurry: Planar Slurry (colloidal silica, pH: 9.7)
Workpiece: 300mmφSIO2 (TEOS)
Pad diameter: 740mmφ
Pad break: 9 N x 30 minutes, diamond dresser 54 rpm, surface plate rotation speed 80 rpm,
Polishing pressure: 175 hPa
Ultrapure water: 200ml / min
Polishing: surface plate rotation speed 70rpm, head rotation speed 71rpm, slurry flow rate 200ml / min, polishing time 60 seconds

(Polishing rate)
The polishing rate is the amount of polishing per minute expressed in thickness (Å). The average value was determined from the thickness measurement results at 17 locations for the insulating films of the substrate before and after polishing. The thickness was measured in the DBS mode of an optical film thickness measuring device (ASET-F5x, manufactured by KLA Tencor).

(Existence of defects)
In the defect evaluation, 25 substrates were repeatedly and sequentially polished three times, and the high sensitivity of the pattern-less wafer surface inspection system (Surfscan SP2 manufactured by KLA Tencor) was applied to the 21st to 25th substrates after polishing. Measurement was performed in measurement mode to evaluate the presence or absence of defects on the substrate surface.

(Topography evaluation)
The level difference between the metal wiring and the oxide film wiring was evaluated using a level difference, surface roughness, and fine shape measuring device (P-16 +, manufactured by KLA Tencor).

(Abrasion evaluation)
The X-axis straight line and the Y-axis straight line are set with the center of the polishing pad as the zero point, and within the range of ± 150 mm to ± 230 mm from the pad center, the thickness of the polishing pad before polishing and the polishing pad after polishing 600 wafers The thickness was measured at 10 mm intervals. The thickness difference before and after polishing at each point was determined from the wear amount of the polishing pad after polishing 600 sheets at each point, and the average value of the thickness difference at all measurement points was defined as the average wear amount.

The average wear amount of the polishing pads of Examples and Comparative Examples was evaluated according to the following criteria.
◎… Average wear amount is 0.4mm or less ○… Average wear amount is more than 0.4mm to 0.6mm or less △… Average wear amount is more than 0.6mm to 0.7mm or less ×… Average wear amount is more than 0.7mm

  The polishing pads of Examples 1 to 4 were found to have a high polishing rate, good defect suppression performance, excellent topography, and excellent wear resistance.

  In the polishing pad of Example 5, as compared with Examples 1 to 4, the amount of hollow microspheres added was as low as 1% by mass. As a result, the slurry retention and dressing properties deteriorated and the polishing rate decreased.

  In the polishing pad of Comparative Example 1, the amount of hollow microspheres added was an excessive amount of 45% by mass. As a result, the film formability deteriorated and a polyurethane foam sheet could not be produced.

  The polishing pad of Comparative Example 2 had an excessively low 100% polyurethane resin modulus of 3.5 MPa, resulting in poor wear resistance and poor topography.

  The polishing pad of Comparative Example 3 had an excessive polyurethane resin 100% modulus of 47 MPa. As a result, the dressability deteriorated and the defect suppression performance also deteriorated.

  As a result of the hollow microspheres not being added to the polishing pad of Comparative Example 4, the dressability deteriorated and the polishing rate also decreased.

  As a result of the dry molding, the defect suppression performance of the polishing pad of Comparative Example 5 was extremely deteriorated.

  In the polishing pad of Comparative Example 6, the hollow microspheres were not added, and the non-hollow microspheres were added. As a result, the polishing rate was lowered.

However, according to Examples 1 to 5 and Comparative Examples 1 to 6, the preferred value of the polyurethane resin 100% modulus is 5 to 25 MPa, the addition amount of the hollow microspheres is 1 to 50% by mass, and the Shore A hardness of the polyurethane foam sheet The preferred value of 35 to 70 degrees, the preferred value of the density of the polyurethane foam sheet is 0.30 to 0.70 g / cm ³ , the preferred value of the average void diameter of the polyurethane foam sheet is 10 to 30 μm, and the tear strength of the polyurethane foam sheet The preferred value of is 0.50 to 1.60.

According to Examples 1 to 4 in which the polishing rate, the defect suppression performance, the topography, and the wear resistance were all uniformly good, the more preferable value of the polyurethane resin 100% resin modulus is 6 to 24 MPa, A more preferable value of the added amount of the hollow microspheres is 3 to 35% by mass, a more preferable value of the density of the polyurethane foam sheet is 0.35 to 0.60 g / cm ³ , and a more preferable value of the tear strength of the polyurethane foam sheet is 0. .55 to 1.50 N / mm.

  According to the present invention, both the defect suppression performance and the topography in the polishing pad can be improved.

Claims (7)

In a polishing pad having a polyurethane foam sheet formed by wet film formation as a polishing layer,
The sheet is formed mainly of a polyurethane resin to which hollow microspheres made of a shell having high solvent resistance are added, and the 100% resin modulus of the polyurethane resin is in the range of 5 MPa to 25 MPa,
In the polyurethane resin, a large number of polyurethane foams and a large number of hollow microspheres are evenly dispersed, and each polyurethane foam communicates with each other in a mesh shape through communication holes, and each hollow microsphere has closed cells. A polishing pad comprising: a polyurethane foam opening and a hollow microsphere bubble opening formed on a surface of the polishing layer.   The polishing pad according to claim 1, wherein the outer shell having high solvent resistance is a thermosetting resin. The polishing pad according to claim 1 or 2 specific gravity of the hollow microspheres consisting of high the solvent resistance shell is ^{0.8g / cm 3 ~1.1g / cm 3} .   The polishing pad according to any one of claims 1 to 3, wherein the amount of hollow microspheres comprising the outer shell having high solvent resistance is 1% by mass to 50% by mass.   The polishing pad according to any one of claims 1 to 4, wherein, in a cross section of the sheet, an average void diameter due to foaming of polyurethane and bubbles of hollow microspheres is 10 µm to 30 µm. The sheet, the polishing pad according to any one of claims 1 to 5 35 to 70 degrees Shore A hardness, the density 0.30g / cm ³ ~0.70g / cm ³ to.   The polishing pad according to claim 1, wherein the sheet has a tear strength of 0.50 N / mm to 1.60 N / mm.