JP7553256B2 - 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 a polishing pad has been performed on materials such as semiconductor devices and electronic components, particularly materials that require good edge shapes and/or flatness, such as Si substrates (silicon wafers), GaAs (gallium arsenide) substrates, glass, and LCD (liquid crystal display) substrates. Various polishing pads and polishing methods have been proposed to improve the flatness and surface quality of the object to be polished.

For example, Patent Document 1 discloses a polishing body for wafer polishing (polishing pad) that is made of a polishing cloth or polishing platen that polishes a wafer (object to be polished) while sliding against the wafer with a relative speed difference, and that has grooves at predetermined intervals on the wafer sliding surface of the polishing body, and that has a higher groove density in the area where the peripheral speed of the polishing body is high than in the area where the peripheral speed is low. Patent Document 1 discloses that the use of such a polishing pad allows the wafer or wafer holding jig to rotate stably, improving the flatness of the polished wafer.

Japanese Patent Application Publication No. 11-285963

However, the inventors of the present invention have conducted a detailed study of conventional polishing pads and polishing methods, including the one described in Patent Document 1, and have found that the conventional polishing pads and polishing methods result in insufficient flatness or edge shape of the polished object.

For example, the method described in Patent Document 1 adjusts the groove density of the polishing cloth so that the workpiece rotates on its own axis, but this rotation is affected by the adhesive force between the workpiece and the holding pad that holds it. However, Patent Document 1 does not specifically consider the adhesive force between the workpiece and the holding pad. In this regard, if the adhesive force between the workpiece and the holding pad for holding the workpiece is low, it is difficult to apply pressure evenly to the workpiece, which reduces the flatness of the workpiece and causes the edge shape to deteriorate. Conversely, if the adhesive force between the workpiece and the holding pad for holding the workpiece is increased, the rotation of the workpiece is suppressed, which causes the flatness of the workpiece to deteriorate. Therefore, a holding pad that can impart good flatness and edge shape to the workpiece regardless of the level of adhesive force between the workpiece and the holding pad for holding the workpiece is required.

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

The inventors conducted extensive research to solve the above problems and discovered that when an object to be polished is polished using a holding pad whose holding surface has a certain amount of openings, is highly absorbent, and has a certain range of wall thickness between bubbles near the surface, the object to be polished can rotate easily while maintaining the adhesive force between the object to be polished and the holding pad within a suitable range. As a result, they discovered that the flatness of the object to be polished is improved and the end shape is also improved, 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 _W100 at a depth of 100 μm from the holding surface is 20.0% or more and 40.0% or less,
The holding surface has openings with an average opening diameter of 20 μm or more and 50 μm or less,
The porosity of the holding surface is 20% or more and 40% or less,
When 1.0 μL of water is dropped onto the support surface, the penetration time of the water is 500 seconds or more and 1500 seconds or less.
Holding pad.
[2]
The holding pad according to [1], wherein the 100% modulus at 23±2° C. of the resin constituting the resin sheet is 5.0 MPa or more and 20.0 MPa or less.
[3]
The holding pad according to [1] or [2], wherein the kinetic friction force of the resin sheet in a water-immersed state is 3.0 kgf or more and 5.5 kgf 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]
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.
[6]
A holding step of holding an object to be polished on the holding pad according to any one of [1] to [4];
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 good flatness and 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, right, etc. 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 a polished object, the resin sheet having air bubbles therein, a resin wall ratio _W100 at a depth of 100 μm from the holding surface being 20.0% or more and 40.0% or less, the holding surface having pores with an average pore diameter of 20 μm or more and 50 μm or less, the porosity of the holding surface being 20% or more and 40% or less, and the penetration time of water when 1.0 μL of water is dropped onto the holding surface being 500 seconds or more and 1500 seconds or less.

When an object to be polished is held by a holding pad such as the one described above and then polished, the flatness of the resulting object to be polished is improved and the edge shape is also improved. The reasons for this are thought to be as follows. However, the reasons are not limited to those listed below.

When the holding surface of the resin sheet has pores with an average pore size of 20 μm or more and 50 μm or less, and the pore ratio is 20% or more and 40% or less, the holding surface is more likely to hold water. When the penetration time of water when 1.0 μL of water is dropped on the holding surface is 500 seconds or more and 1500 seconds or less, the resin sheet becomes hydrophilic and the water retention of the resin sheet is improved. Furthermore, when the wall ratio W ₁₀₀ of the resin at a depth of 100 μm from the holding surface is 20.0% or more and 40.0% or less, the proportion of bubbles near the holding surface of the resin sheet increases, and the water retention near the holding surface is further improved.

In this way, the holding pad having the above configuration is more likely to hold water on the holding surface during polishing, so the amount of water between the holding pad and the workpiece during polishing increases. As a result, the water functions as a lubricant between the holding pad and the workpiece, so the dynamic friction force on the holding surface decreases, the workpiece becomes easier to rotate, the flatness of the resulting workpiece is improved, and the end shape is improved. It is also thought that the polishing rate is improved because the workpiece becomes easier to rotate. Furthermore, when the amount of water between the holding pad and the workpiece during polishing increases, the force with which the holding pad adsorbs the workpiece (hereinafter also referred to as the "adsorption force of the holding pad") increases due to the surface tension of water, so the adsorption force of the holding pad can be set to a suitable range. As a result, the tracking ability of the holding pad to the workpiece is improved, the flatness of the resulting workpiece is improved, and the end shape is 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 2 of the resin sheet is soaked with an appropriate amount of water 4 and pressed against the workpiece W, allowing the workpiece W to be held by the interaction between the holding surface 2 and the surface of the workpiece W. The holding surface may be designed to be larger than the workpiece W so that it is easier to hold the workpiece, or may be configured to hold multiple workpieces simultaneously.

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 have an open cell 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 contained in the resin sheet is not particularly limited, but examples thereof include substantially spherical, cone-shaped, and spindle-shaped. In the case of cone-shaped or 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 water retention of the resin sheet is further improved, and the amount of water interposed between the holding pad and the object to be polished during polishing is further increased. As a result, the flatness of the obtained object to be polished is further improved, and the end shape is further improved. Furthermore, the polishing rate is further improved. 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 easier to configure a resin sheet that satisfies the wall ratio W ₁₀₀ .

The wall ratio _W100 of the resin at a depth of 100 μm from the holding surface of the resin sheet is 20.0% or more and 40.0% or less, preferably 22.0% or more and 39.0% or less. When the wall ratio _W100 is in the above range, the water retention near the holding surface is further improved, and the amount of water intervening between the holding pad and the polished object during polishing is further increased. As a result, the flatness of the polished object obtained is further improved, and the edge shape is further improved. Furthermore, the polishing rate is also further 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 x {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. On the other hand, when the wall ratio is close to 0%, it indicates that there are many air bubbles.

The wall ratio W ₁₀₀ is 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 rate 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 rate.

The resin sheet has openings on the holding surface. The average opening diameter of the openings is 20 μm or more and 50 μm or less, preferably 25 μm or more and 48 μm or less, and more preferably 30 μm or more and 45 μm or less. When the average opening diameter of the openings on the holding surface is within the above range, the holding surface is more likely to hold water, and the amount of water interposed between the holding pad and the workpiece during polishing is further increased. As a result, the flatness of the resulting workpiece is further improved, and the end shape is further improved. Furthermore, the polishing rate is also further improved.

The porosity of the holding surface is 20% or more and 40% or less, preferably 22% or more and 38% or less, and more preferably 23% or more and 35% or less. When the porosity of the holding surface is in the above range, the holding surface is more likely to hold water, and the amount of water present between the holding pad and the workpiece during polishing is further increased. As a result, the flatness of the resulting workpiece is further improved, and the end shape is further improved. Furthermore, the polishing rate is also further improved.

The average aperture size of the apertures and the aperture ratio of the holding surface can be measured by the method described in the Examples. The method for controlling the average aperture size of the apertures and the aperture ratio of the holding surface is not particularly limited, but for example, the same method as the control method for the wall ratio W ₁₀₀ can be used. Furthermore, the resin sheet can be appropriately adjusted by buffing or slicing the surface on the side that becomes the holding surface.

In the resin sheet, the penetration time of water when 1.0 μL of water is dropped onto the holding surface is 500 seconds or more and 1500 seconds or less, preferably 600 seconds or more and 1400 seconds or less, and more preferably 700 seconds or more and 1350 seconds or less.

By keeping the penetration time within the above range, the resin sheet becomes appropriately hydrophilic, and the water retention of the resin sheet is further improved. As a result, the amount of water present between the holding pad and the workpiece during polishing is further increased, so the flatness of the resulting workpiece is further improved, and the edge shape is further improved. Furthermore, the polishing rate is also further improved.

The penetration time can be measured by the method described in the Examples. The penetration time can be controlled by appropriately selecting or adjusting the resin components constituting the resin sheet, the average pore size and pore ratio of the holding surface, and the wall ratio. For example, the penetration time tends to be shorter when a preferred resin, particularly a resin with high hydrophilicity, as described below is used. The penetration time also tends to be shorter when the average pore size and pore ratio of the holding surface are increased. Furthermore, the penetration time also tends to be shorter when the wall ratio is decreased.

The kinetic friction force of the resin sheet when submerged in water is 3.0 kgf or more and 5.5 kgf or less, and preferably 3.2 kgf or more and 5.0 kgf or less. When the kinetic friction force when submerged in water is within the above range, the polished object rotates more easily, and the flatness of the polished object obtained is further improved, and the edge shape is further improved. Furthermore, the polishing rate is also further improved.

The term "submerged state" refers to the state in which the resin sheet is immersed in ion-exchanged water for 15 minutes and then the water on the surface is wiped off. The kinetic friction force in the submerged state is measured by the method described in the Examples.

The kinetic frictional force in the water-soaked state tends to be reduced by increasing the water content of the resin sheet. That is, the kinetic frictional force in the water-soaked state tends to be reduced by reducing the wall ratio _W100 , increasing the average pore size and pore ratio of the holding surface, or shortening the above-mentioned penetration time. In addition, the kinetic frictional force in the water-soaked state tends to be reduced by using a preferred resin, as described below, in particular a resin with high hydrophilicity or a resin with a small coefficient of kinetic friction.

From the viewpoint of more effectively and reliably achieving the effects of the present invention, the average thickness of the resin sheet is preferably 0.30 mm or more and 3.0 mm or less, more preferably 0.35 mm or more and 2.0 mm or less, and even more preferably 0.35 mm or more and 1.5 mm or less.

(resin)
The resin constituting the resin sheet is not particularly limited, and examples thereof include polyurethane resin, polysulfone resin, polyimide resin, and other resins 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, the resin constituting the resin sheet preferably includes a resin with high hydrophilicity or a resin with a small dynamic friction coefficient. Examples of highly hydrophilic resins include polyurethane resins. The resin constituting the resin sheet may be used alone or in combination of two or more.

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. The other additives are not particularly limited as long as they can be used in the resin sheet in the holding pad, but examples include pigments such as carbon black, film formation stabilizers such as nonionic surfactants, and foam regulators such as anionic surfactants. From the viewpoint of reducing the kinetic frictional force of the resin sheet in a water-soaked state, the resin sheet preferably contains a film formation stabilizer such as a nonionic surfactant and/or a foam regulator such as an anionic surfactant.

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 9.0 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 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 easy to manufacture a resin sheet having air bubbles inside, a resin wall ratio _W100 at a depth of 100 μm from the holding surface being 20.0% or more and 40.0% or less, the holding surface having pores with an average pore diameter of 20 μm or more and 50 μm or less, the pore ratio of the holding surface being 20% or more and 40% or less, and the penetration time of water when 1.0 μL of water is dropped on the holding surface being 500 seconds or more and 1500 seconds or less. Hereinafter, the resin sheet obtained by the solidification step is also called the "resin sheet before stretching", and the resin sheet obtained by the stretching step is also called the "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.

The resin concentration in the resin solution is not limited, but may 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 obtaining the above-mentioned resin sheet more easily, 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 to which an alkyl chain having 3 or more carbon atoms is 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 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 it easier 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 step. The grinding/removal step refers to a step 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 on the object to be polished can be made more uniform, the flatness of the object to be polished can be further improved, and the end shape can be further improved. In addition, the above-mentioned resin sheet can be obtained more easily by appropriately adjusting the amount of buffing or slicing on the surface of the resin sheet 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, an aqueous solution can be interposed between the holding surface of the holding pad and the object to be polished, and the object to be polished can be held on the holding pad by the surface tension of the water. 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 good edge shape and/or flatness, 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 9.0 MPa at 25°C was dissolved in dimethylformamide (DMF), 7.9 parts by mass of a 20% carbon black dispersion in DMF, 4.0 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, 0.60 mm thick, was stretched 140% in the horizontal direction, and the surface of the stretched resin sheet was then buffed to obtain a resin sheet with a thickness of 0.40 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 at 25° C. of 6.3 MPa 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]
A tomographic image at a depth of 100 μm from the holding surface of the resin sheet (the surface opposite to the surface to which the adhesive sheet was attached) was 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 image, and the wall ratio was calculated according to the above formula (1). The results are shown in Table 1.

[Average diameter of pores in holding surface and pore ratio of holding surface]
Using a microscope (manufactured by KEYENCE, product name "VH-6300"), a range of about 1.3 mm square of the holding surface of the resin sheet was photographed at 175 times magnification. The obtained image was binarized using image processing software (Image Analyzer V20LAB Ver. 1.3, manufactured by Nikon), and the average diameter of the circle equivalent and its average value were calculated from the area of each opening, thereby obtaining the average opening diameter of the holding surface. In addition, the opening rate per unit area was calculated based on the binarized image. The cutoff value (lower limit) of the opening diameter was set to 10 μm, and noise components were excluded. The results are shown in Table 1.

[Water penetration time to support surface]
The penetration time of water when 1.0 μL of water was dropped on the support surface was measured as follows. That is, under conditions of a temperature of 20° C. and a humidity of 60%, 1.0 μL of ion-exchanged water was dropped on the support surface of a dry resin sheet using a syringe needle. Thereafter, a solid-liquid interface analyzer (manufactured by Kyowa Interface Science Co., Ltd., product name "DropMaster 500") was used as a contact angle meter to measure the time from the drop of the water droplet until the contact angle of the water droplet became 20 degrees. The above test was performed in a closed system. In addition, the "dry state" refers to the state when the resin sheet was held in a constant temperature and humidity chamber at a temperature of 23° C. (±2° C.) and a humidity of 50% (±5%) for 40 hours. The results are shown in Table 1.

[Dynamic friction force in a submerged state]
The resin sheet was immersed in ion-exchanged water at room temperature for 15 minutes, and the surface moisture was wiped off to use as a measurement sample. The sample was adsorbed on the platen of a universal tensile tester (ORIENTEC Co., Ltd. RTC-1210A), and the adherend, a silicon wafer (10 cm x 10 cm), was placed on the sample. Then, while the sample was fixed, the adherend was pulled in the shear direction at a pulling speed of 50 mm/min, and the average value of the tensile force while the adherend was pulled 80 mm was taken as the kinetic friction force. The results are shown in Table 1.

[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

(Flatness)
The flatness of the 25 polished objects was evaluated as follows using an optical interference flatness measuring device (manufactured by KLA Tencor Corporation, product name "Wafersight"). First, the GBIR of the polished object before the polishing test (hereinafter referred to as "GBIR ₀ ") and the GBIR of the polished object after the polishing test were measured, and the difference between them was calculated. Then, the average of the ratio (ΔGBIR/GBIR ₀ ) of the absolute value of the difference in GBIR (hereinafter referred to as "ΔGBIR") to the GBIR before the polishing test (GBIR ₀ ) was calculated for the 25 polished objects. Based on the average value of the obtained ratio (ΔGBIR/GBIR _{0 ), the flatness was evaluated according to the following evaluation criteria. The smaller the ratio (ΔGBIR/GBIR 0 )} , the higher the flatness of the polished object obtained. The GBIR was measured under the condition of EE (Edge Exclusion) 2 mm. The results are shown in Table 1.
(Evaluation Criteria)
A: The ratio (ΔGBIR/GBIR ₀ ) is 8.5% or less.
B: The ratio (ΔGBIR/GBIR ₀ ) is greater than 8.5% and is 11.5% or less.
C: The ratio (ΔGBIR/GBIR ₀ ) exceeds 11.5%.

(End Shape)
The end shape of the 25 polished objects that had been subjected to the polishing process was evaluated as follows using an optical interference flatness measuring device (manufactured by KLA Tencor Corporation, product name "Wafersight"). First, the ESFQR of the polished object before the polishing test (hereinafter referred to as "ESFQR ₀ ") and the ESFQR of the polished object after the polishing test were measured, and the difference between them was calculated. Then, for the 25 polished objects, the average of the ratio (ΔESFQR/ESFQR ₀ ) of the absolute value of the difference in ESFQR (hereinafter referred to as "ΔESFQR") to the ESFQR (ESFQR ₀ ) before the polishing test was calculated. Based on the average value of the obtained ratio (ΔESFQR/ESFQR ₀ ), the end shape was evaluated according to the following evaluation criteria. The smaller the ratio (ΔESFQR/ESFQR ₀ ), the better the end shape of the polished object obtained. Note that ESFQR was measured under the condition of EE (Edge Exclusion) 1 mm (angle 5°, length 10 mm). The results are shown in Table 1.
(Evaluation Criteria)
A: The ratio (ΔESFQR/ESFQR ₀ ) is 17.5% or less.
B: The ratio (ΔESFQR/ESFQR ₀ ) is more than 17.5% and 22.5% or less.
C: The ratio (ΔESFQR/ESFQR ₀ ) exceeds 22.5%.

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 and/or flatness, 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 (6)

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 _W100 at a depth of 100 μm from the holding surface is 20.0% or more and 40.0% or less,
The holding surface has openings with an average opening diameter of 20 μm or more and 50 μm or less,
The porosity of the holding surface is 20% or more and 40% or less,
When 1.0 μL of water is dropped onto the support surface, the penetration time of the water is 500 seconds or more and 1500 seconds or less.
Holding pad. The holding pad according to claim 1, wherein the 100% modulus at 23±2°C of the resin constituting the resin sheet is 5.0 MPa or more and 20.0 MPa or less. The holding pad according to claim 1 or 2, wherein a kinetic friction force of the resin sheet in a water-immersed state, measured by the following measuring method , is 3.0 kgf or more and 5.5 kgf or less.
(Measurement method)
The resin sheet is immersed in ion-exchanged water at room temperature for 15 minutes, the surface moisture is wiped off, and the resin sheet is used as a measurement sample. A silicon wafer of 10 cm x 10 cm is placed on the measurement sample, and the silicon wafer is pulled in the shear direction at a pulling speed of 50 mm/min while the measurement sample is fixed, and the average value of the tensile force during the pulling of the silicon wafer by 80 mm is defined as the kinetic friction force. 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. A method for manufacturing a support pad according to any one of claims 1 to 4, comprising the steps of:
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.
Manufacturing method. A holding step of holding an object to be polished on the holding pad according to any one of claims 1 to 4;
A polishing step of polishing the held object to be polished with a polishing pad.
Manufacturing method of polished products.