JP7323401B2 - Polishing pad, method for producing same, and method for producing abrasive product - Google Patents

Description

TECHNICAL FIELD The present invention relates to a polishing pad, a method for manufacturing the same, and a method for manufacturing a polished article.

2. Description of the Related Art Conventionally, an object to be polished such as a semiconductor wafer, glass, magnetic disk, or the like is polished using a polishing pad. Polishing is divided into primary polishing (rough polishing), which tends to emphasize polishing rate, and secondary polishing (final polishing), which tends to emphasize surface quality such as fewer scratches. can be classified.

From the viewpoint of improving surface quality, a polishing pad having a soft polishing layer is used in order to disperse local stress during polishing and reduce scratches. As such a soft abrasive layer, for example, a soft plastic sheet in which foams are formed by a wet film-forming method is known.

In general, soft plastic sheets are manufactured by coating a sheet-shaped substrate with a resin solution in which soft plastic is dissolved in a water-miscible organic solvent, and then solidifying and regenerating the resin in a water-based solidifying liquid (wet film formation). be done. Therefore, the soft plastic sheet (polishing layer 1) formed by wet film formation has a foamed structure 2 associated with the solidification and regeneration of the resin, and polishing can be performed while retaining the polishing liquid (see FIG. 1). ).

Such a soft plastic sheet normally has a cushion layer 4 on the side opposite to the polishing surface 3, but the soft plastic sheet (polishing layer 1) itself is flexible and easily deformable, and presses the object W to be polished. 1′ of the surface layer of the polishing layer 1, which is in contact with the peripheral portion of the object to be polished, is particularly stretched. The stress that the object receives from the stretched portion is higher than the stress that the object receives from the non-stretched portion. As a result, excessive stress F is applied to the peripheral portion W1 of the object W to be polished, roll-off W2 is likely to occur, and the flatness of the object W to be polished is reduced (see FIGS. 1 and 2). Note that the roll-off may also be referred to as edge sagging or edge sagging.

Patent Document 1 discloses a technique for adjusting the compressive deformation value of the pad to 70 to 100 based on the pad modulus value, with the aim of achieving both low surface roughness and good edge shape. , discloses polishing pads having essentially high pad modulus values and low compressive deformation values.

JP 2010-086597 A

However, if such a hard polishing pad is used, it is difficult to achieve a high-quality surface with few fine scratches, which is demanded these days.

The present invention has been made in view of the above problems, and provides a polishing pad that can suppress the occurrence of roll-off and scratches, a method for manufacturing the polishing pad, and a method for manufacturing a polished product using the polishing pad. intended to provide

The present inventors have made intensive studies to solve the above problems. As a result, while maintaining the polishing layer soft, the wall thickness between the bubbles in the vicinity of the surface layer of the polishing layer is kept within a certain range, thereby suppressing the stress received from the object to be polished and reducing roll-off during polishing. The inventors have found that the occurrence can be suppressed, and have completed the present invention.

That is, the present invention is as follows.
[1]
having a polishing layer with air bubbles inside,
The 100% modulus of the resin constituting the polishing layer at 23±2° C. is 5 to 20 MPa, and the wall ratio W ₁₀₀ of the resin at a depth of 100 μm from the polishing surface of the polishing layer is 20 to 40%.
polishing pad.
[2]
The reduction rate of the resin wall ratio W _{100 at a depth of 100 μm from the polished surface to the resin wall ratio W 50 at} a depth of 50 μm from the polished surface ((W _{50 -} W ₁₀₀ )/W ₅₀ ) is 30 to 60. %,
The polishing pad according to [1].
[3]
further comprising a cushion layer on the side opposite to the polishing surface of the polishing layer,
The polishing pad according to [1] or [2].
[4]
The amount of compressive deformation of the laminate of the abrasive layer and the cushion layer is 40 to 70 μm.
The polishing pad according to [3].
[5]
a step of applying a resin solution containing a resin dissolved in an organic solvent onto a film forming substrate and solidifying the resin solution in an aqueous coagulating liquid to obtain a resin sheet;
A step of stretching the obtained resin sheet,
A method for manufacturing a polishing pad.
[6]
A polishing step of polishing an object to be polished using the polishing pad according to any one of [1] to [4],
A method for producing an abrasive product.

According to the present invention, it is possible to provide a polishing pad that can suppress the occurrence of roll-off and scratches, a method for manufacturing the polishing pad, and a method for manufacturing a polished product using the polishing pad.

1 is a schematic view showing a polishing process using a conventional soft plastic sheet as a polishing layer; FIG. It is the schematic which shows the roll-off which arose in the edge part of to-be-polished material. It is a schematic diagram showing a polishing process using the polishing pad of the present embodiment.

Hereinafter, an embodiment of the present invention (hereinafter referred to as "this embodiment") will be described in detail, but the present invention is not limited to this, and various modifications are possible without departing from the gist thereof. is.

[Polishing pad]
The polishing pad of this embodiment has a polishing layer having air bubbles therein. The resin constituting the polishing layer has a 100% modulus of 5 to 20 MPa at 23±2° C., and a resin wall ratio W ₁₀₀ of 20 to 40% at a depth of 100 μm from the polishing surface of the polishing layer. .

As described above, conventional polishing pads using soft plastic are flexible and easily deformable, and are suitable for finishing polishing and the like. However, due to its flexibility, when the object to be polished is brought into pressure contact, an excessive stress is applied to the periphery of the object to be polished, which tends to cause roll-off.

One of the reasons why the stress applied to the object to be polished from the stretched portion is increased is thought to be that the foamed structure is crushed by the stretch and the flexibility of the stretched portion is reduced. On the other hand, the polishing pad 30 of this embodiment has a cell structure 32 that relieves the stress applied to the peripheral edge portion W1 of the object W to be polished when the object W to be polished is brought into pressure contact. More specifically, in order to ensure flexibility even when stretched and to reduce the stress that the object receives from the stretched portion, the relationship between the resin and the air bubbles at a predetermined depth from the polishing surface is set within a predetermined range. (see FIG. 3).

In addition to the above, the polishing pad 30 of the present embodiment may have a cushion layer 34 on the side of the polishing layer 31 opposite to the polishing surface 33 via an adhesive layer such as double-sided tape. Further, the polishing pad 30 of this embodiment may have an adhesive layer such as a double-sided tape for fixing the polishing pad to the polishing surface plate on the surface of the cushion layer 34 opposite to the polishing layer side. Each configuration will be described in detail below.

[Polishing layer]
The polishing layer has a polishing surface that comes into direct contact with the object to be polished when the object is polished with the polishing pad.

The 100% modulus of the resin constituting the polishing layer at 23±2° C. is 5 to 20 MPa, preferably 5 to 10 MPa, more preferably 6 to 9 MPa. When the 100% modulus is 5 MPa or more, the deformation of the polishing layer when the object to be polished is pressed against it is suppressed, and the roll-off is further suppressed. Moreover, since the 100% modulus is 20 MPa or less, the flexibility of the polishing layer is further improved, and the occurrence of scratches is further suppressed. Note that the 100% modulus is obtained when a non-foamed sheet (test piece) made of the same material as the layer to be measured is stretched 100% in an environment of room temperature 23 ± 2 ° C., that is, the original length of 2 It is the value obtained by dividing the tensile force when stretched twice by the initial cross-sectional area of the test piece.

In addition, as described above, the polishing layer of this embodiment has a cell structure that relieves the stress applied to the peripheral portion of the object to be polished. In this embodiment, as an index of such a cell structure, a wall ratio W ₁₀₀ indicating the ratio of resin and cells at a depth of 100 μm from the polishing surface of the polishing layer is used. The wall ratio W ₁₀₀ is 20-40%, preferably 22-37%, more preferably 25-35%. When the wall ratio W ₁₀₀ is 20% or more, the ratio of air bubbles becomes small, so that when the polishing layer is repeatedly pressurized, partial sinking occurs and it is difficult to return to the original state. Become. If settling occurs, the polishing rate may vary when the polishing pad is used repeatedly, but such variation can be suppressed by setting the wall ratio W ₁₀₀ to 20% or more. On the other hand, when the wall ratio W ₁₀₀ is 40% or less, the stress applied to the peripheral portion of the object to be polished can be suppressed to a lower level, and roll-off can be suppressed.

Furthermore, it is preferable that the wall ratio W decreases with increasing distance from the polishing surface, that is, the ratio of the cells to be occupied increases with increasing distance from the polishing surface. From this point of view, as an index of the cell structure, the reduction rate of the resin wall ratio W _{100 at a depth of 100 μm from the polished surface with respect to the resin wall ratio W 50 at} a depth of 50 μm from the polished surface ((W ₅₀ −W ₁₀₀ )/W ₅₀ ) can be used.

The reduction rate ((W ₅₀ −W ₁₀₀ )/W ₅₀ ) in this embodiment is preferably 30 to 60%, more preferably 33 to 57%, still more preferably 35 to 55%. The larger the reduction rate ((W ₅₀ - W ₁₀₀ )/W ₅₀ ), the more rapidly the ratio of bubbles occupied from the polished surface toward a depth of 100 μm, and the reduction rate ((W ₅₀ - W ₁₀₀ )/W ₅₀ ). As is larger, the proportion of air bubbles gradually increases from the polished surface to a depth of 100 μm. Therefore, when the reduction rate ((W ₅₀ −W ₁₀₀ )/W ₅₀ ) is 30% or more, the stress applied to the peripheral edge of the object to be polished tends to be more relaxed. Further, when the reduction rate ((W ₅₀ −W ₁₀₀ )/W ₅₀ ) is 60% or less, there is a tendency to suppress a decrease in the polishing rate due to an excessive increase in the flexibility of the polishing layer.

The wall ratios W ₁₀₀ and W ₅₀ can be determined by adjusting the amount of the organic solvent used in the resin solution, by stretching the resin sheet, or by adjusting the stretching ratio, in the manufacturing method described below. The larger the amount of organic solvent used in the resin solution, the larger the bubbles formed and the smaller the wall ratio, and the smaller the amount of organic solvent used, the larger the wall ratio. Further, by stretching the resin sheet, the wall ratio becomes smaller than that of the resin sheet before stretching, and the wall ratio can be adjusted by the stretching ratio. Also, the wall ratios W ₁₀₀ and W ₅₀ can be measured by the method described in Examples.

The three-dimensional shape of the bubbles in the polishing layer is not particularly limited, but examples thereof include substantially spherical, conical, and spindle shapes. In the case of a cone shape or a spindle shape, a cone shape elongated in the thickness direction of the polishing layer and a spindle shape are preferred. When the polishing layer contains air bubbles having such a shape, the polishing pad tends to easily retain slurry and easily accommodate polishing waste. In addition, when the polishing layer has conical or spindle-shaped cells that are long in the thickness direction of the polishing layer, it tends to be easier to form the polishing layer that satisfies the wall ratio W described above.

The resin constituting the polishing layer is not particularly limited, but examples thereof include polyurethane resin, polysulfone resin, polyimide resin, and other resins used for resin sheet portions of conventional polishing pads. Among these, polyurethane resins are preferred. By using such a resin, it tends to be possible to further suppress the occurrence of roll-off and scratches. In addition, there is a tendency to set the 100% modulus in the above range and to easily form a desired cell structure. One of the resins constituting the polishing layer may be used alone, or two or more of them may be used in combination.

Examples of polyurethane resins include, but are not limited to, polyester-based polyurethane resins, polyether-based polyurethane resins, polyester-ether-based polyurethane resins, and polycarbonate-based polyurethane resins. One type of polyurethane resin may be used alone, or two or more types may be used in combination.

The polishing layer may contain other additives. Other additives are not particularly limited as long as they can be used in the polishing layer of the polishing pad. Examples include pigments such as carbon black, film formation stabilizers such as nonionic surfactants, and anionic surfactants. and foam control agents such as

[Cushion layer]
The polishing pad of this embodiment may have a cushion layer on the surface of the polishing layer opposite to the surface for polishing the object to be polished (polishing surface). By providing the cushion layer, the influence of hardness and flatness of the surface plate tends to be more alleviated, and uneven contact between the workpiece and the polishing surface tends to be more prevented. As a result, it becomes possible to extend the service life of the polishing pad, and there is a tendency to more effectively prevent the occurrence of chipping such as chipping around the workpiece.

Materials for the cushion layer are not particularly limited, but examples thereof include resin-impregnated nonwoven fabric, synthetic rubber, polyethylene foam, and polyurethane foam. Among these, polyurethane foam is more preferable.

The thickness of the cushion layer is preferably 0.1-10 mm, more preferably 0.4-3 mm. When the thickness of the cushion layer is within the above range, the polishing pad tends to be less subject to mechanical restrictions when it is installed in a polishing machine, and the influence of the polishing surface plate can be sufficiently reduced.

In the polishing pad of this embodiment, it is preferable that the laminate of the polishing layer and the cushion layer has desired properties. From this point of view, the compression deformation amount of the laminate of the abrasive layer and the cushion layer is preferably 40 to 70 μm, more preferably 45 to 68 μm, and still more preferably 50 to 65 μm. When the amount of compression deformation is within the above range, roll-off and scratches tend to be more suppressed.

[Adhesive layer]
The polishing pad of this embodiment may have an adhesive layer between the polishing layer and the cushion layer or on the surface of the cushion layer opposite to the polishing layer. Here, the adhesive layer disposed between the abrasive layer and the cushion layer is for bonding the abrasive layer and the cushion layer, and the adhesive layer disposed on the side opposite to the abrasive layer side of the cushion layer is used for polishing. It is used to attach the polishing pad to the polishing surface plate of the machine.

The adhesive layer is not particularly limited, but examples thereof include double-sided tape and adhesives. In addition, in the case of double-sided tape, release paper may be attached to the adhesive surface.

[Method for producing polishing pad]
The method for producing a polishing pad of the present embodiment comprises the steps of: applying a resin solution containing a resin dissolved in an organic solvent onto a film-forming base material; and solidifying the resin solution in an aqueous solidifying liquid to obtain a resin sheet; and a step of stretching the obtained resin sheet.

A wet film forming method and a dry molding method (also referred to as a molding method) are generally known as methods for forming a resin sheet, but the wet film forming method is employed in this embodiment. In the wet film-forming method, a resin solution in which a resin is dissolved in a water-miscible organic solvent is continuously applied to a film-forming base material, and this is immersed in a water-based coagulating liquid to solidify and regenerate the resin into a sheet. Let The interior of the sheet thus obtained contains a large number of foams generated during the solidification and regeneration of the resin. A long resin sheet can be obtained by drying this after washing. Each step of the wet film forming method will be described in detail below.

In general, the wet film-forming process includes a preparation step, a coating step, a solidification regeneration step, and a washing and drying step. Furthermore, a grinding/removal process for flattening the surface of the sheet may be included as necessary.

In the preparation step, a resin solution is prepared by dissolving the resin in a water-miscible organic solvent capable of dissolving the resin, adding additives as desired, and mixing them uniformly. The resin solution is preferably defoamed under vacuum after removing aggregates and the like by filtration.

For example, water-miscible organic solvents capable of dissolving polyurethane include N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), tetrahydrofuran (THF), dimethylsulfoxide (DMSO), N-methyl Polar solvents such as pyrrolidone (NMP) and methyl ethyl ketone (MEK) are included.

Also, the resin concentration in the resin solution is not limited, but can be, for example, 10 to 50% by mass.

Further, the resin solution may be added with, for example, a foaming regulator for controlling foaming, a film formation stabilizer for stabilizing solidification and regeneration of polyurethane, and additives such as carbon black for stabilizing foam formation. can be done.

The film-forming stabilizer is not particularly limited, and examples thereof include nonionic surfactants. Specifically, for example, polyoxyethylene alkyl ethers, polyoxypropylene alkyl ethers, polyoxyethylene polyoxypropylene alkyl ethers, perfluoroalkylethylene oxide adducts, glycerin fatty acid esters, propylene glycol fatty acid esters with 3 carbon atoms such as Examples thereof include compounds to which the above alkyl chains are added.

Moreover, the foam control agent is not particularly limited, but an anionic surfactant can be used, for example. Specific examples include sodium lauryl sulfate, carboxylates, sulfonates, sulfate ester salts, and phosphate ester salts.

In the coating step, the resin solution prepared in the preparatory step is applied to a belt-shaped film-forming base material substantially uniformly at room temperature using a knife coater or the like to form a coating film. At this time, the coating thickness (coating amount) of the resin solution can be adjusted by adjusting the gap (clearance) between the knife coater and the film forming substrate.

A flexible film, a nonwoven fabric, a woven fabric, or the like can be used as the film-forming substrate. When a non-woven fabric or a woven fabric is used as the film-forming substrate, the substrate is pre-treated with water or an aqueous solution of an organic solvent (DMF and water) in order to prevent the polyurethane solution from penetrating into the film-forming substrate when the polyurethane solution is applied. It is preferable to perform a pretreatment (filling) by immersion in a mixed solution of (such as a mixture of).

In the coagulation regeneration step, the coating film (film-forming base material coated with the resin solution) obtained in the coating step is treated with a coagulation liquid that is a poor solvent for the resin (for example, water or a solvent containing water as the main component). to solidify and regenerate the coating film of the resin solution into a sheet having a large number of foams inside.

In the coagulating liquid, generally, a microporous skin layer having a thickness of about several μm is first formed on the surface of the applied resin solution. As it progresses, the resin solidifies and regenerates into a sheet on one side of the film-forming substrate. At this time, typically, the organic solvent is desolvated from the resin solution, and the organic solvent is replaced with the coagulating liquid, so that microscopic particles are formed on the skin layer below the skin layer (film formation substrate side). A foamed layer is formed in which foams having a pore diameter larger than that of the pores and having a substantially triangular cross-section with a roundness in the thickness direction of the sheet are dispersed substantially evenly, but the cell structure is not limited to this.

In the washing/drying step, the resin sheet coagulated and regenerated in the coagulation and regeneration step is separated from the film-forming substrate and washed in a washing liquid such as water to remove the organic solvent remaining in the resin. After washing, the obtained resin sheet is dried with a cylinder dryer or the like, if necessary.

A cylinder dryer is a dryer provided with a cylinder having a heat source inside, and the resin sheet is dried by passing along the peripheral surface of the cylinder. The resin sheet after drying is wound into a roll.

In order to obtain a polishing layer having a predetermined wall ratio in the vicinity of the surface layer, a method of adjusting the amount of organic solvent used in the resin solution, a method of stretching the resin sheet, a method of adjusting the amount of buffing on the surface of the resin sheet, a method of A method of adding a foaming aid to the solution and the like can be mentioned.

The resin sheet wound up as described above is stretched at a predetermined stretching ratio in a stretching step. Thereby, the resin sheet is stretched and the wall ratio is changed. The stretch ratio of the resin sheet is 105 to 300% (meaning 1.05 to 3 times the original length), more preferably 110 to 250%. Depending on the type of resin constituting the resin sheet, a stretch ratio of 105% or more makes it easier to form a polishing layer having a predetermined wall ratio, and a stretch ratio of 300% or less It tends to avoid breakage and excessive thinning of the resin sheet.

In the grinding/removal step, at least one of both surfaces of the sheet is ground and/or partially removed by buffing or slicing. The thickness of the sheet can be uniformed by buffing and slicing, and the surface of the sheet can be made flatter, so the pressing force on the object to be polished is made more uniform, and the flatness of the object to be polished is improved. can be made

The polishing layer in this embodiment is formed by not only the wet film forming method described above, but also by another method, for example, a supercritical gas foaming method as disclosed in Japanese Patent No. 4624781. It can also be made from thermoplastic polyurethane.

[Method for producing polished product]
The method for manufacturing a polished product according to this embodiment includes a polishing step of polishing an object to be polished using the polishing pad. The polishing step may be primary polishing (rough polishing), final polishing, or both.

First, a polishing pad is attached and fixed to a polishing surface plate of a polishing machine. Then, the object to be polished held on the holding surface plate arranged so as to face the polishing surface plate is pressed against the polishing surface of the polishing pad, and the polishing surface plate is supplied with slurry between the work and the polishing pad. And/or by relatively rotating the holding platen, the surface of the object to be polished is polished.

The slurry may contain strong oxidizers, solvents, and abrasive particles used in chemical mechanical polishing. Examples of the strong oxidizing agent include, but are not particularly limited to, potassium permanganate, sodium permanganate, and the like. Solvents include, for example, water and organic solvents. As the organic solvent, hydrocarbons are preferred, and hydrocarbons having a high boiling point are more preferred. Examples of hydrocarbons include, but are not particularly limited to, paraffinic hydrocarbons, olefinic hydrocarbons, aromatic hydrocarbons and alicyclic hydrocarbons. Hydrocarbons having a high boiling point include, for example, petroleum hydrocarbons having an initial boiling point of 220° C. or higher. A solvent is used individually by 1 type or in combination of 2 or more types.

The slurry may also contain other additives as needed. Examples of such additives include nonionic surfactants, anionic surfactants, carboxylic acid esters, carboxylic acid amides and carboxylic acids.

The object to be polished is not particularly limited, but examples include materials such as semiconductor devices and electronic components, particularly Si substrates (silicon wafers), SiC (silicon carbide) substrates, GaAs (gallium arsenide) substrates, glass, hard disks and LCDs. Thin substrates (objects to be polished) such as substrates for (liquid crystal displays) can be mentioned. Among these, the method for producing a polished object of the present embodiment is a method for producing difficult-to-process materials that are difficult to polish, such as materials that can be applied to power devices, LEDs, etc., such as sapphire, SiC, GaN, and diamond. It can be used preferably.

Hereinafter, the present invention will be described more specifically using examples and comparative examples. The present invention is by no means limited by the following examples.

(Example 1)
[Polishing layer preparation process]
100 parts by mass of a solution obtained by dissolving 30% of a polyester polyurethane resin having a 100% modulus of 9 MPa at 25°C in dimethylformamide (DMF), 7.9 parts by mass of carbon black, and a film-forming stabilizer (nonionic surfactant). 2.7 parts by mass, 1.2 parts by mass of a foam control agent (anionic surfactant), 8 parts by mass of water, and 55 parts by mass of DMF were added and mixed with stirring to obtain a resin solution.

Next, a PET film was prepared as a substrate for film formation, and the resin solution was applied thereon using a knife coater to obtain a coating film.

Next, the obtained coating film was immersed in water, which is a coagulating liquid, together with the film-forming base material, and the resin was coagulated and regenerated to obtain a resin sheet. After the resin sheet was taken out from the coagulating bath and the film-forming base material was peeled off from the resin sheet, the resin sheet was immersed in a washing liquid consisting of water to remove DMF as a solvent. After that, the resin sheet was wound while being dried.

The obtained resin sheet of 0.6 mm was stretched by 140% in the width direction, and the surface of the resin sheet was buffed to obtain a resin sheet with a thickness of 0.4 mm, which was used as a polishing layer.

[Cushion layer preparation process]
100 parts by mass of a solution of 30% polyester polyurethane resin with a 100% modulus of 24 MPa at 25°C dissolved in DMF, 5.4 parts by mass of carbon black, and 2.7 parts by mass of a film-forming stabilizer (nonionic surfactant) parts, 1.2 parts by mass of a foam control agent (anionic surfactant), 8 parts by mass of water, and 55 parts by mass of DMF for viscosity adjustment were added and mixed with stirring to obtain a resin solution.

Next, a PET film was prepared as a base material for film formation, and the resin solution was applied thereon using a knife coater to obtain a coating film.

Next, the obtained coating film was immersed in water, which is a coagulating liquid, together with the film-forming base material, and the resin was coagulated and regenerated to obtain a resin sheet. After the resin sheet was taken out from the coagulating bath and the film-forming base material was peeled off from the resin sheet, the resin sheet was immersed in a washing liquid consisting of water to remove DMF as a solvent. After that, the resin sheet was dried to form a cushion layer having a thickness of 0.4 mm.

[Polishing pad manufacturing process]
The cushion layer similarly obtained above was adhered to the side of the polishing layer obtained above that was not buffed using a polyurethane resin adhesive. Then, a double-faced tape made of a PET base material provided with release paper was adhered to the side of the cushion layer that was not adhered to the polishing layer, thereby forming a polishing pad.

(Example 2)
Everything was the same as in Example 1, except that a polyester polyurethane resin having a 100% modulus at 25°C of 6.3 MPa was used in the polishing layer preparation step, and the obtained resin sheet was stretched 110% in the width direction. A polishing pad was made with the recipe.

(Comparative example 1)
A polishing pad was produced with the same formulation as in Example 1, except that the obtained resin sheet was not stretched in the polishing layer producing step.

(Comparative example 2)
A polishing pad was produced with the same formulation as in Example 1, except that the amount of DMF added in the polishing layer production process was changed from 55 parts by mass to 30 parts by mass.

[Wall ratio]
Tomographic images at depths of 100 μm and 50 μm from the polished surface of the polishing layer were obtained using a three-dimensional measurement X-ray CT apparatus (TDM1000H-II (2K) manufactured by Yamato Scientific Co., Ltd.). Next, for the obtained tomographic image, image processing software (VG Studio MAX 3.0 manufactured by Volume Graphics) is used to calculate the area of the bubble portion and the resin portion, and the ratio of the resin portion area to the total area is defined as the wall ratio. calculated as

[Amount of compression deformation]
The amount of compression deformation of the polishing pad was measured in accordance with Japanese Industrial Standards (JIS L 1021) using a Shopper-type thickness gauge (pressure surface: circular with a diameter of 1 cm). Specifically, the thickness t0 was measured after pressing for 30 seconds under the initial load, and then the thickness t1 was measured after being left under the final load for 5 minutes. At this time, the initial load was 100 g/cm ² and the final load was 1120 g/cm ² . The compression deformation amount was calculated by the following formula (1).
Formula (1): Amount of compression deformation (mm) = t0-t1

[Polishing test]
The polishing pads obtained in Examples and Comparative Examples were attached to a polishing machine platen. Then, a silicon wafer (12 inches in diameter×780 μm in thickness) as an object to be polished was polished under the following polishing conditions.
(polishing conditions)
Rotation speed: (Surface plate) 40 rpm / (Top ring) 41 rpm
Polishing pressure: 100 g/cm ²
Oscillation: 20mm
Abrasive: GLANZOX 1306 manufactured by Fujimi Incorporated (undiluted solution: water = 1:20)

[Evaluation of roll-off]
SFQRmax (site front least squares range) of the peripheral portion of the silicon wafer after the polishing test was evaluated. SFQR is a numerical value that indicates the degree of wafer roll-off.

Regarding the results of Examples and Comparative Examples, ⊚ indicates an improvement of 10% or more from Example 1 based on the results of Example 1, and indicates an improvement of less than 10% from Example 1. ∘, Δ when less than 10% worse than in Example 1, and x when 10% or more worse than in Example 1.

[Presence or absence of scratches]
The surface of six objects to be polished after the polishing test was measured in a high-sensitivity measurement mode of a wafer surface inspection device (manufactured by KLA-Tencor, trade name "Surfscan SP1DLS"), and the presence or absence of scratches on the surface of the object to be polished. was counted and evaluated according to the following evaluation criteria.
(Evaluation criteria)
○: When there is no polished object with scratches ×: When there is one or more polished objects with scratches

The polishing pad of the present invention has industrial applicability as a polishing pad for polishing silicon wafers and the like.

Claims (3)

having a polishing layer with air bubbles inside,
100% modulus of the resin constituting the polishing layer at 23±2° C. is 5 to 20 MPa;
The resin wall ratio W ₁₀₀ at a depth of 100 μm from the polishing surface of the polishing layer is 20 to 40%,
further comprising a cushion layer on the side opposite to the polishing surface of the polishing layer;
The cushion layer has a thickness of 0.1 to 10 mm,
The reduction rate of the resin wall ratio W ₁₀₀ at a depth of 100 μm from the polished surface to the resin wall ratio W ₅₀ at a depth of 50 μm from the polished surface ((W _{50 -} W ₁₀₀ )/W ₅₀ ) is 30 to 60. % and
The amount of compressive deformation of the laminate of the abrasive layer and the cushion layer is 40 to 70 μm,
The abrasive layer and the cushion layer are made of a polyester-based polyurethane resin ,
polishing pad. A method for manufacturing the polishing pad according to claim 1,
a step of applying a resin solution containing a resin dissolved in an organic solvent onto a film-forming substrate, and solidifying the resin solution in an aqueous coagulating liquid to obtain a resin sheet;
and a step of stretching the obtained resin sheet,
A method for manufacturing a polishing pad. A polishing step of polishing an object to be polished using the polishing pad according to claim 1 ,
A method for producing an abrasive product.