JP7474087B2 - Holding pad, manufacturing method thereof, and manufacturing method of polished product - Google Patents

Description

The present invention relates to a holding pad, a manufacturing method thereof, and a manufacturing method for polished products.

Conventionally, polishing using polishing pads has been performed on materials such as semiconductor devices and electronic components, particularly materials that require good edge shapes, such as Si substrates (silicon wafers), GaAs (gallium arsenide) substrates, glass, and LCD (liquid crystal display) substrates. In such polishing, particularly in single-sided polishing, a holding pad may be used to hold the workpiece to be polished. Various holding pads have been proposed to improve the flatness, edge shape, and surface quality of the workpiece to be polished.

For example, Patent Document 1 discloses that a holding pad with high compression ratio is obtained using a polyurethane resin composition for a support pad, which is characterized by containing 3 to 50 wt % polyurethane resin, 40 to 90 wt % DMF solvent, and 0.1 to 5 wt % alkylbenzenesulfonic acid having 9 to 15 carbon atoms or its salt. Patent Document 1 describes that such a holding pad has long and large pores uniformly formed inside and has a low density, but also shows a high compression ratio and compression recovery rate, and therefore has excellent cushioning properties and adsorption power for the object to be polished.

Japanese Patent No. 5372090

However, after the inventors of the present invention conducted a detailed study of conventional holding pads, including the one described in Patent Document 1, they found that when a workpiece is held and polished using a conventional holding pad, problems arise with the shape of the end of the workpiece after polishing.

For example, when an object to be polished is held and polished using a holding pad with a high compression ratio as described in Patent Document 1, the object to be polished sinks excessively into the holding pad, resulting in a wavy or droopy edge of the object to be polished. Conversely, when an object to be polished is held and polished using a holding pad with a low compression ratio, localized stress is likely to be generated in the object to be polished during polishing, resulting in a wavy or droopy edge of the object to be polished. Therefore, there is a demand for a holding pad that can give the object to be polished a good edge shape regardless of the compression ratio.

The present invention was made in consideration of the above problems, and aims to provide a holding pad that can impart a good edge shape to the polished object after polishing, a manufacturing method thereof, and a manufacturing method of a polished product.

As a result of intensive research by the inventors to solve the above problems, they discovered that a holding pad that maintains a soft holding surface and has a certain range of wall thickness between bubbles near the surface can impart a good edge shape to the polished object after polishing, which led to the completion of the present invention.

That is, the present invention is as follows.
[1]
A holding pad including a resin sheet having a holding surface for holding an object to be polished,
The resin sheet has air bubbles therein,
A resin wall ratio _W50 at a depth of 50 μm from the holding surface is 20% or more and 40% or less,
The resin wall ratio W ₁₀₀ at a depth of 100 μm from the holding surface is 41% or more and 60% or less.
Holding pad.
[2]
The holding pad according to [1], wherein a reduction rate of the wall ratio _W50 to the wall ratio _W100 (( _{W100- W50} )/ _W100 x 100) is 30% or more and 60% or less.
[3]
The holding pad according to [1] or [2], wherein the 100% modulus at 23±2° C. of the resin constituting the resin sheet is 5 MPa or more and 20 MPa or less.
[4]
The holding pad according to any one of [1] to [3], further comprising an adhesive sheet on the opposite side of the resin sheet to the holding surface.
[5]
The holding pad according to [4], wherein the amount of compressive deformation of the laminate of the resin sheet and the adhesive sheet is 40 μm or more and 70 μm or less.
[6]
A step of applying a resin solution containing a resin dissolved in an organic solvent onto a film-forming substrate and coagulating the resin solution in a water-based coagulation liquid to obtain a resin sheet;
and stretching the obtained resin sheet.
A method for manufacturing a holding pad.
[7]
A holding step of holding an object to be polished on the holding pad according to any one of [1] to [5];
A polishing step of polishing the held object to be polished with a polishing pad.
Manufacturing method of polished products.

The present invention provides a holding pad that can impart a good edge shape to the polished object after polishing, a method for manufacturing the same, and a method for manufacturing a polished product.

4 is a schematic cross-sectional view of a resin sheet in the holding pad of the present embodiment. FIG. 1A to 1C are schematic diagrams illustrating a method for polishing an object to be polished using the holding pad of the present embodiment.

Below, an embodiment of the present invention (hereinafter referred to as "the present embodiment") will be described in detail with reference to the drawings as necessary, but the present invention is not limited to this, and various modifications are possible without departing from the gist of the invention. In the drawings, the same elements are given the same reference numerals, and duplicated explanations will be omitted. Furthermore, unless otherwise specified, the positional relationships such as up, down, left, and right will be based on the positional relationships shown in the drawings. Furthermore, the dimensional ratios of the drawings are not limited to those shown in the drawings.

[Retention pad]
The holding pad of this embodiment is a holding pad comprising a resin sheet having a holding surface for holding an object to be polished, the resin sheet having air bubbles therein, the resin wall ratio _W50 at a depth of 50 μm from the holding surface being 20% or more and 40% or less, and the resin wall ratio _W100 at a depth of 100 μm from the holding surface being 41% or more and 60% or less.

When an object to be polished is held by a holding pad such as the one described above and then polished, a good edge shape can be imparted to the object after polishing. The reasons for this are thought to be as follows. However, the reasons are not limited to those listed below.

When an object to be polished is held by a conventional holding pad with a high compression ratio and polished, the stress supporting the edge of the object to be polished is insufficient, and the edge of the object to be polished tends to sink excessively into the holding pad. As a result, the polishing rate of the center of the object to be polished increases, and the polishing surface of the object to be polished is prone to have a wavy or droopy shape. On the other hand, when an object to be polished is held by a conventional holding pad with a low compression ratio and polished, if localized polishing pressure is applied to the object to be polished, the polishing pressure cannot be distributed by stress. As a result, the polishing rate increases only for a portion of the object to be polished, and wavy or droopy shapes occur at the edge of the object to be polished.

In contrast, the holding pad of the present embodiment has the above-mentioned configuration, and therefore the stress supporting the end of the polished object can be sufficiently maintained while the polishing pressure can be stress-dispersed. As a result, the end shape of the polished object is improved. In particular, since the wall ratio _W50 of the resin at a depth of 50 μm from the holding surface is 20% or more and 40% or less, the holding surface is easily deformed, and the polishing pressure can be stress-dispersed. As a result, the end shape of the polished object is improved. In addition, since the wall ratio _W100 of the resin at a depth of 100 μm from the holding surface is 41% or more and 60% or less, the stress supporting the end of the polished object can be sufficiently maintained. As a result, the end shape of the polished object is improved.

Here, the "wall ratio W" is a value indicating the ratio of resin to bubbles, and is an index of the bubble structure. In this specification, the wall ratio W is defined as the ratio of resin in a cross section at a predetermined depth from the holding surface of the resin sheet, that is, it is defined by the following formula (1). The wall ratio W can be measured by the method described in the examples.
Wall ratio W (%) = 100 × {Ap / (Ap + Ab)} (1)
Ap: Area of the resin portion in a cross section of the resin sheet at a predetermined depth Ab: Area of the air bubble portion in a cross section of the resin sheet at a predetermined depth

Therefore, when the wall ratio at a given depth is close to 100%, it indicates that there is a large amount of resin at that depth, i.e., there are few air bubbles. Also, when the wall ratio is close to 0%, it indicates that there are many air bubbles. Therefore, in the holding pad of this embodiment, the proportion of air bubbles at a depth of 50 μm is greater than the proportion of air bubbles at a depth of 100 μm. As a result, as described above, the end shape of the resulting polished object is improved. Also, as described later, when the polished object is held by such a holding pad and polished, the flatness of the polished object tends to be further improved.

In this embodiment, "the flatness of the workpiece is improved" means that the polished surface of the workpiece is flatter overall. This can also be said to have good global flatness. Furthermore, "the edge shape is improved" means that the edge of the polished surface of the workpiece is flatter. This means, for example, that the sagging shape (also called "roll-off") and the jumping shape (also called "ski-jump shape") that occur on the outer periphery of the workpiece are suppressed.

[Resin sheet]
A schematic cross-sectional view of a resin sheet is shown in Fig. 1. As shown in Fig. 1, a resin sheet 1 of this embodiment has a holding surface 2 for holding an object to be polished, and has air bubbles 3 inside.

The holding surface of the resin sheet can be soaked in an appropriate amount of water and pressed against the object to be polished, thereby holding the object to be polished through the interaction between the holding surface and the surface of the object to be polished. The holding surface may be designed to be larger than the object to be polished so that it is easier to hold the object, or may be configured to hold multiple objects to be polished at the same time.

Furthermore, the structure of the resin sheet 1 in this embodiment is not particularly limited, but preferably has a film (skin layer) as the retaining surface 2, and vertically elongated air bubbles 3 in the thickness direction below the skin layer. The air bubbles 3 may also have a continuous air bubble structure that communicates with each other. Examples of vertically elongated air bubbles 3 include those having a shape in which the air bubble diameter gradually decreases toward the skin layer along the thickness direction of the resin sheet in this embodiment.

The shape of the bubbles inside the resin sheet is not particularly limited, but examples thereof include substantially spherical, cone-shaped, and spindle-shaped. In the case of cone-shaped and spindle-shaped, cone-shaped and spindle-shaped bubbles that are long in the thickness direction of the resin sheet are preferable. When the resin sheet contains bubbles having such a shape, the holding surface of the resin sheet is more likely to hold water, so that the holding pad tends to hold the polished object more reliably. In addition, when the resin sheet has cone-shaped or spindle-shaped bubbles that are long in the thickness direction of the resin sheet, it tends to be easy to form a resin sheet that satisfies the wall ratios W ₅₀ and W ₁₀₀ .

The wall ratio _W50 of the resin at a depth of 50 μm from the holding surface of the resin sheet is 20% or more and 40% or less, preferably 25% or more and 39% or less, more preferably 30% or more and 38% or less. When the wall ratio _W50 is in the above range, the holding surface is more easily deformed, and the polishing pressure can be more easily dispersed. As a result, the flatness of the obtained polished object is further improved, and the end shape is further improved. Furthermore, when the wall ratio _W50 is in the above range, the tracking ability of the holding pad to the polished object is further improved, so that the holding pad can more reliably adsorb the polished object in the thickness direction of the polished object.

The wall ratio _W100 of the resin at a depth of 100 μm from the holding surface of the resin sheet is 41% or more and 60% or less, preferably 45% or more and 58% or less, and more preferably 47% or more and 55% or less. By having the wall ratio _W100 in the above range, the stress supporting the end of the workpiece can be more sufficiently maintained.

The reduction rate of the wall ratio _W50 relative to the wall ratio _W100 (( _{W100- W50} )/ _W100 x 100) is preferably 30% or more and 60% or less, more preferably 31% or more and 50% or less, even more preferably 32% or more and 45% or less, and particularly preferably 32% or more and 40% or less. When the reduction rate (( _{W100- W50} )/ _W100 x 100) is within the above range, the balance of the ease of deformation of the holding surface, the ability of the holding pad to follow the workpiece to be polished, and the stress with which the holding pad supports the end of the workpiece to be polished is even better. As a result, the flatness of the resulting workpiece to be polished is further improved, and the end shape is further improved.

The wall ratio _W100 and the wall ratio _W50 are not particularly limited, but can be controlled, for example, by adjusting the content of the organic solvent in the resin solution, stretching the resin sheet, and adjusting the stretching ratio in the manufacturing method described later. The larger the content of the organic solvent in the resin solution, the larger the bubbles formed tend to be and the smaller the wall ratio tends to be, and the smaller the content of the organic solvent, the larger the wall ratio tends to be. In addition, by stretching the resin sheet, the wall ratio becomes smaller compared to the resin sheet before stretching, and the wall ratio can be adjusted by the stretching ratio.

From the viewpoint of more effectively and reliably achieving the effects of the present invention, the average thickness of the resin sheet is preferably 0.50 mm or more and 3.0 mm or less, more preferably 0.55 mm or more and 2.0 mm or less, and even more preferably 0.60 mm or more and 1.5 mm or less.

The amount of compressive deformation of the resin sheet is preferably 20 μm or more and 50 μm or less, more preferably 25 μm or more and 45 μm or less, and even more preferably 30 μm or more and 40 μm or less. When the amount of compressive deformation of the resin sheet is within the above range, the polished object can sink more appropriately into the holding pad, which tends to further improve the flatness of the polished object obtained and further improve the edge shape.

The amount of compressive deformation is a value calculated from the ratio of the thickness of the sample when pressed with a predetermined initial load to the thickness of the sample when pressed with a predetermined final load, and can be measured by the method described in the Examples in more detail. The amount of compressive deformation of the resin sheet can be controlled by appropriately adjusting the wall ratios _W50 and _W100 and the 100% modulus at 23±2°C of the resin constituting the resin sheet described later.

(resin)
The resin constituting the resin sheet is not particularly limited, but may be, for example, polyurethane resin, polysulfone resin, polyimide resin, or other resin used in the resin sheet portion of conventional polishing pads.From the viewpoint of more effectively and reliably achieving the effects of the present invention, polyurethane resin is preferred.The resin constituting the resin sheet may be used alone or in combination of two or more kinds.

The polyurethane resin is not particularly limited, but examples thereof include polyester-based polyurethane resin, polyether-based polyurethane resin, polyester-ether-based polyurethane resin, and polycarbonate-based polyurethane resin. One type of polyurethane resin may be used alone, or two or more types may be used in combination.

The resin sheet may contain other additives. There are no particular limitations on the other additives as long as they can be used in the resin sheet in the holding pad, but examples include pigments such as carbon black, film-forming stabilizers such as nonionic surfactants, and foam regulators such as anionic surfactants.

The 100% modulus at 23±2°C of the resin constituting the resin sheet is preferably 5.0 MPa or more and 20.0 MPa or less, more preferably 5.5 MPa or more and 10.0 MPa or less, and even more preferably 6.0 MPa or more and 8.0 MPa or less. By having the 100% modulus in the above range, the polished object can sink more appropriately into the holding pad, further improving the flatness of the polished object obtained and further improving the edge shape.

The "100% modulus" is the tensile force when a sheet made of the resin is stretched 100%, i.e., when it is stretched to twice its original length, divided by the initial cross-sectional area of the test piece. The 100% modulus of the resin at 23±2°C can be measured by the method described in the Examples.

[Adhesive sheet]
The holding pad of this embodiment may further include an adhesive sheet on the side opposite to the holding surface of the resin sheet, which allows the holding pad to be fixed to the polishing apparatus.

The adhesive contained in the adhesive sheet is not particularly limited, but examples include polyamide-based adhesives, polyester-based adhesives, ethylene-vinyl acetate-based adhesives, acrylic-based adhesives, olefin-based adhesives, epoxy-based adhesives, cyanoacrylate-based adhesives, polyurethane-based adhesives, and silicone-based adhesives.

The adhesive sheet is not particularly limited as long as it can bond the polishing device and the holding pad, but examples include a substrate in which the above-mentioned adhesive is applied to both sides. Examples of such substrates include, but are not particularly limited to, substrates made of aromatic ester resins and substrates made of PET resins.

The amount of compressive deformation of the laminate of the resin sheet and the adhesive sheet is preferably 40 μm or more and 70 μm or less, more preferably 50 μm or more and 68 μm or less, and even more preferably 55 μm or more and 65 μm or less. When the amount of compressive deformation of the laminate is within the above range, the polished object can sink more appropriately into the holding pad, which tends to further improve the flatness of the polished object obtained and further improve the end shape.

The method for manufacturing the holding pad of this embodiment is not particularly limited as long as it is a method capable of manufacturing a holding pad having the above-mentioned configuration, but for example, the method for manufacturing the holding pad described below can be suitably used.

[Method of manufacturing the holding pad]
The manufacturing method of the retaining pad of this embodiment includes a solidification process in which a resin solution containing a resin dissolved in an organic solvent is applied onto a film-forming substrate and the resin solution is solidified in a water-based coagulation liquid to obtain a resin sheet, and a stretching process in which the obtained resin sheet is stretched.

By having the above-mentioned solidification step and stretching step, it is possible to easily produce a resin sheet having a wall ratio _W50 of 20% or more and 40% or less and a wall ratio _W100 of 41% or more and 60% or less. Hereinafter, the resin sheet obtained by the solidification step is also called "resin sheet before stretching", and the resin sheet obtained by the stretching step is also called "resin sheet after stretching".

(Solidification process)
The solidification step is a step in which a resin solution containing a resin dissolved in an organic solvent is applied onto a film-forming substrate, and the resin solution is solidified in a water-based solidification liquid to obtain a resin sheet before stretching.

Generally, the wet film-forming method and the dry molding method (also called the molding method) are known as methods for forming a resin sheet, but the wet film-forming method is adopted 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 substrate, which is then immersed in a water-based coagulating liquid to coagulate and regenerate the resin into a sheet. The inside of the sheet obtained in this manner contains numerous bubbles that are generated as the resin coagulates and regenerates. This can then be washed and dried to obtain a long resin sheet. Each step of the wet film-forming method will be described in detail below.

Generally, the wet film forming method includes a preparation process, a coating process, and a solidification and regeneration process, and may also include a cleaning and drying process, and a grinding and removal process to flatten the surface of the resin sheet before stretching, if necessary.

In the preparation process, the resin is dissolved in an organic solvent that is capable of dissolving the resin and is miscible with water, and additives are added as necessary. The mixture is then mixed uniformly to prepare a resin solution. It is preferable to remove aggregates and the like from the resin solution by filtration, and then degas the solution under vacuum.

The resin may be any of the resins exemplified for the holding pad. The organic solvent is not particularly limited, but may be, for example, a polar solvent such as N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), tetrahydrofuran (THF), dimethylsulfoxide (DMSO), N-methylpyrrolidone (NMP), or methyl ethyl ketone (MEK). The above solvents are capable of dissolving polyurethane and are miscible with water.

In addition, the resin concentration in the resin solution is not limited, but can be, for example, 10% by mass or more and 50% by mass or less with respect to the entire resin solution. From the viewpoint of more easily making the wall ratio W ₅₀ of the resin sheet obtained by the manufacturing method of this embodiment 20% to 40% and more easily making the wall ratio W ₁₀₀ 41% to 60% or less, the resin concentration in the resin solution is preferably 15% by mass or more and 45% by mass or less with respect to the entire resin solution. From the same viewpoint, the resin concentration in the resin solution is more preferably 20% by mass or more and 40% by mass or less, and even more preferably 20% by mass or more and 35% by mass or less with respect to the entire resin solution. Note that the lower the resin concentration in the resin solution, the larger the bubbles formed and the smaller the wall ratio tends to be.

Additionally, additives such as foam regulators to control foaming, film-forming stabilizers to stabilize the solidification and regeneration of polyurethane, and carbon black to stabilize foam formation can be added to the resin solution.

The film-forming stabilizer is not particularly limited, but examples thereof include nonionic surfactants. Specific examples include compounds having an alkyl chain with 3 or more carbon atoms added, such as polyoxyethylene alkyl ether, polyoxypropylene alkyl ether, polyoxyethylene polyoxypropylene alkyl ether, perfluoroalkyl ethylene oxide adduct, glycerin fatty acid ester, and propylene glycol fatty acid ester.

The foaming regulator is not particularly limited, but examples thereof include anionic surfactants. Specific examples include sodium lauryl sulfate, carboxylates, sulfonates, sulfate ester salts, and phosphate ester salts.

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

Flexible films, nonwoven fabrics, woven fabrics, etc. can be used as the film-forming substrate. When using nonwoven fabric or woven fabric as the film-forming substrate, it is preferable to perform a pretreatment (sealing) by immersing the substrate in water or an aqueous organic solvent solution (such as a mixture of DMF and water) in order to prevent the polyurethane solution from penetrating into the film-forming substrate when the polyurethane solution is applied. When obtaining the film by peeling off the resin sheet from the film-forming substrate, it is more preferable to use a flexible film.

In the coagulation and regeneration process, the coating film obtained in the coating process (the film-forming substrate coated with the resin solution) is immersed in a water-based coagulation liquid (e.g., water or a solvent whose main component is water) that is a poor solvent for the resin, and the coating film of the resin solution is coagulated and regenerated into a sheet-like film with numerous bubbles inside.

In the aqueous coagulation liquid, a skin layer with a thickness of about several μm and micropores is generally formed on the surface of the applied resin solution, and then the organic solvent in the polyurethane solution is replaced with the coagulation liquid, causing the resin to coagulate and regenerate in a sheet on one side of the film-forming substrate. Typically, the organic solvent is removed from the resin solution and replaced with the coagulation liquid, forming a foam layer on the underside of the skin layer (the film-forming substrate side) with pores larger than the micropores formed in the skin layer and with roughly triangular cross-sections that are roughly evenly distributed in the thickness direction of the sheet, but the bubble structure is not limited to this.

In the washing and drying process, the resin sheet that has been solidified and regenerated in the solidification and regeneration process is peeled off from the film-forming substrate and washed in a washing liquid such as water to remove any organic solvent remaining in the resin. After washing, the resulting resin sheet is dried in a cylinder dryer or the like as necessary.

A cylinder dryer is a dryer equipped with a cylinder with an internal heat source, and the resin sheet is dried by passing it along the circumferential surface of the cylinder. After drying, the resin sheet is wound up into a roll.

(Stretching process)
The resin sheet before stretching wound up as described above is stretched at a predetermined stretch ratio by the stretching process. As a result, the resin sheet before stretching is stretched and the wall ratio changes. The stretch ratio of the resin sheet is 105% or more and 300% or less, more preferably 110% or more and 250% or less. Although it varies depending on the type of resin constituting the resin sheet, a stretch ratio of 105% or more tends to make the resin sheet after stretching have a predetermined wall ratio, and a stretch ratio of 300% or less tends to avoid breakage or excessive thinning of the resin sheet after stretching. Note that "stretch ratio is 105%" means that the resin sheet is stretched to a length 1.05 times the length of the resin sheet before stretching.

In the stretching process, the stretching mode is not particularly limited, but may be, for example, uniaxial stretching or biaxial stretching. From the viewpoint of more easily obtaining a resin sheet having a desired wall ratio, the stretching process is preferably uniaxial stretching. When uniaxial stretching is performed, the stretching direction is not particularly limited, and may be stretched in the vertical direction or the horizontal direction.

The manufacturing method of the holding pad of this embodiment may further include a grinding/removal process. The grinding/removal process refers to a process in which at least one of both sides of the resin sheet after stretching is ground and/or partially removed by buffing or slicing. The thickness of the resin sheet can be made uniform by buffing or slicing, and the surface of the resin sheet can be made flatter. As a result, the holding force for the polished object can be made more uniform, the flatness of the polished object can be further improved, and the end shape can be further improved. In addition, the wall ratio W ₁₀₀ and the wall ratio W ₅₀ can be appropriately controlled by appropriately adjusting the amount of buffing or slicing of the resin sheet surface after stretching.

The resin sheet in this embodiment can be manufactured from two types of thermoplastic polyurethanes with different 100% modulus by other methods, such as the supercritical gas foaming method disclosed in Japanese Patent No. 4624781, as well as the wet film formation method described above.

[Method of manufacturing polished products]
The manufacturing method of the polished product includes a holding step of holding the object to be polished on the holding pad, and a polishing step of polishing the held object to be polished using the polishing pad. Figure 2 shows a schematic cross-sectional view of the manufacturing method of the polished product. In Figure 2, first, the holding pad 10 is fixed on the holding platen 21 of the polishing machine to hold the object to be polished W. Next, while the object to be polished W is held on the holding surface of the holding pad 10, a polishing slurry 22 is supplied to the opposite surface (surface to be polished) of the object to be polished W, and the polishing pad 24 attached to the polishing platen 23 of the polishing device is pressed against the object to be polished W and rotated, thereby polishing the object to be polished W. Each step will be described below.

The holding step is not particularly limited as long as it is a step that can hold the object to be polished on the holding pad, but for example, a liquid, preferably an aqueous solution, is interposed between the holding surface of the holding pad and the object to be polished, and the object to be polished is held on the holding pad by the surface tension of the liquid. An example of such an aqueous solution is pure water. Alternatively, the holding step may hold the object to be polished on the holding pad by sucking the object to be polished through the holding pad.

The object to be polished is not particularly limited, but examples include materials such as semiconductor devices and electronic components, particularly materials that require a good edge shape, such as Si substrates (silicon wafers), GaAs (gallium arsenide) substrates, glass, and LCD (liquid crystal display) substrates.

The polishing process is a process in which the held object to be polished is polished using a polishing pad. As the polishing pad, various conventionally known polishing pads can be used. The polishing process may be a primary polishing (rough polishing), a secondary polishing (finish polishing), or a process that combines both of these polishing processes.

In the polishing process, the workpiece is pressed against the polishing pad by the holding platen while the holding platen and the polishing platen are rotated relative to each other, so that the processed surface of the workpiece is polished by the polishing pad. The holding platen and the polishing platen may rotate in the same direction at different rotational speeds, or in different directions.

In the polishing step, a polishing slurry may be used as an abrasive. Such a polishing slurry is not particularly limited, but may include, for example, a polishing slurry containing water, a chemical component such as an oxidizing agent represented by hydrogen peroxide, an additive, abrasive grains (abrasive particles; for example, SiC, _{SiO2 , Al2O3} , _CeO2 ), etc.

The present invention will be described in more detail below using examples and comparative examples, but the present invention is not limited to the following examples.
[Example 1]
A resin solution was obtained by mixing and stirring 100 parts by mass of a solution in which 30% polyester-based polyurethane resin having a 100% modulus of 9 MPa at 25°C was dissolved in dimethylformamide (DMF), 7.9 parts by mass of a 20% carbon black dispersion in DMF, 2.7 parts by mass of a film-forming stabilizer (nonionic surfactant), 1.2 parts by mass of a foaming adjuster (anionic surfactant), 8 parts by mass of water, and 55 parts by mass of DMF.

Next, a PET film was prepared as a film-forming substrate, and the above resin solution was applied to it using a knife coater to obtain a coating film.

The resulting coating film was then immersed together with the film-forming substrate in water, which was a coagulation liquid, to coagulate and regenerate the resin, yielding a resin sheet. The resin sheet was removed from the coagulation bath, and the film-forming substrate was peeled off from the resin sheet. The resin sheet was then immersed in a cleaning solution consisting of water to remove the solvent DMF. The resin sheet was then wound up while being dried.

The resulting resin sheet before stretching, with a thickness of 0.80 mm, was stretched laterally by 140%, and the surface of the stretched resin sheet was then buffed to obtain a resin sheet with a thickness of 0.64 mm.

A holding pad was obtained by attaching an adhesive sheet including a PET substrate with release paper to the side of the resin sheet obtained above that had not been buffed.

[Example 2]
A support pad was produced in the same manner as in Example 1, except that a polyester-based polyurethane resin having a 100% modulus of 6.3 MPa at 25° C. was used, and the obtained resin sheet before stretching was stretched 110% in the horizontal direction.

[Comparative Example 1]
A holding pad was produced in the same manner as in Example 1, except that the resin sheet obtained in the solidification step was not stretched.

[Comparative Example 2]
A supporting pad was produced in the same manner as in Example 1, except that the content of DMF 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 holding surface of the resin sheet (the surface opposite to the surface to which the adhesive sheet was attached) were obtained using a three-dimensional measurement X-ray CT device (TDM1000H-II (2K) manufactured by Yamato Scientific Co., Ltd.). Next, the area Ab occupied by the air bubble portion and the area Ap occupied by the resin portion were measured using image processing software (VG Studio MAX 3.0 manufactured by Volume Graphics Co., Ltd.) for the obtained tomographic images, and the wall ratio was calculated according to the above formula (1).

[Compressive deformation amount]
Using a Shopper-type thickness gauge (pressure surface: circular with a diameter of 1 cm), the amount of compressive deformation of the holding pad (a laminate of a resin sheet and an adhesive sheet) was measured in accordance with the Japanese Industrial Standards (JIS L 1021). Specifically, the thickness t0 was measured after applying pressure for 30 seconds under an initial load, and then the thickness t1 was measured after leaving it for 5 minutes under a final load. At this time, the initial load was 100 g/ ^cm2 , and the final load was 1120 g/ ^cm2 . The amount of compressive deformation was calculated using the following formula (2).
Compressive deformation amount (μm) = t0 - t1 (2)

[Polishing test]
The release paper was peeled off from the holding pads obtained in the Examples and Comparative Examples, and the holding pads after peeling were attached to the holding platen of a polishing machine with the adhesive sheet side. Then, a silicon wafer (diameter 12 inches × thickness 780 μm) as the object to be polished was polished under the polishing conditions shown below.
(Polishing conditions)
Polishing machine: Fujikoshi Corporation MCP-150X
Rotation speed: (platen) 40 rpm / (top ring) 41 rpm
Polishing pressure: 100g/ ^cm2
Oscillation: 20 mm
Polishing time: 20 minutes Polishing pad: Fujibo Ehime Co., Ltd. Suede pad #27
Abrasive: Fujimi Incorporated's GLANZOX 1306 (undiluted solution: water = 1:20)
Number of samples: 25 for each example

(End Shape)
The end shape of the polished object after the above polishing process was evaluated using an optical interference flatness measuring device (manufactured by KLA Tencor Corporation, product name "WaferSight"). More specifically, first, flatness measurement was performed on each silicon wafer after the above polishing test. From the obtained results, the maximum value (SFQRmax) of SFQR (site front least squares range) at the outer periphery of each silicon wafer was obtained. The SFQR at the outer periphery is a numerical value indicating the degree of sagging or flapping occurring at the end of the polished object. The SFQRmax obtained in the examples and comparative examples was standardized with the SFQRmax of Example 1 set to 100, and SFQRmax of 90 or less was rated as "A", SFQRmax of more than 90 and less than 100 was rated as "B", SFQRmax of more than 100 and less than 110 was rated as "C", and SFQRmax of 110 or more was rated as "D". The results are shown in Table 1.

The holding pad of the present invention is used to hold the workpiece when polishing materials such as semiconductor devices and electronic components, particularly materials that require good edge shapes, such as Si substrates (silicon wafers), GaAs (gallium arsenide) substrates, glass, and LCD (liquid crystal display) substrates, and has industrial applicability as a holding pad that is particularly suitable for use in polishing silicon wafers.

Claims (7)

A holding pad including a resin sheet having a holding surface for holding an object to be polished,
The resin sheet has air bubbles therein,
A resin wall ratio _W50 at a depth of 50 μm from the holding surface is 20% or more and 40% or less,
A resin wall ratio _W100 at a depth of 100 μm from the holding surface is 41% or more and 60% or less,
The resin constituting the resin sheet is a polyurethane resin .
Holding pad. 2. The holding pad according to claim 1, wherein a reduction rate of the wall ratio _W50 to the wall ratio _W100 (( _{W100- W50} )/ _W100 x 100) is 30% or more and 60% or less. The holding pad according to claim 1 or 2, wherein the 100% modulus at 23±2°C of the resin constituting the resin sheet is 5 MPa or more and 20 MPa or less. The holding pad according to any one of claims 1 to 3, further comprising an adhesive sheet on the side of the resin sheet opposite the holding surface. The holding pad according to claim 4, wherein the amount of compressive deformation of the laminate of the resin sheet and the adhesive sheet is 40 μm or more and 70 μm or less. A method for manufacturing a support pad according to any one of claims 1 to 5, comprising the steps of:
A step of applying a resin solution containing a polyurethane resin dissolved in an organic solvent onto a film-forming substrate and coagulating the resin solution in a water-based coagulation liquid to obtain a resin sheet;
and stretching the obtained resin sheet.
Production method. A holding step of holding an object to be polished on the holding pad according to any one of claims 1 to 5;
A polishing step of polishing the held object to be polished with a polishing pad.
Manufacturing method of polished products.