JP2021146461A - Holding pad, method for manufacturing the same, and method for manufacturing polished product - Google Patents

Abstract

To provide a holding pad which can impart good flatness and end shape to a polished product after polishing.SOLUTION: A holding pad has a resin sheet having a holding surface for holding a polished object, in which the resin sheet has air bubbles therein, a wall ratio W100 of the resin at a depth of 100 μm from the holding surface is 20.0% or more and 40.0% or less, the holding surface has an aperture having an average opening diameter of 20 μm or more and 50 μm or less, an aperture rate of the holding surface is 20% or more and 40% or less, and water penetration time when water of 1.0 μL is dropped onto the holding surface is 500 seconds or longer and 1,500 seconds or shorter.SELECTED DRAWING: Figure 1

Description

The present invention relates to a holding pad, a method for manufacturing the same, and a method for manufacturing a polished product.

Conventionally, good edge shape and / or flatness of materials such as semiconductor devices and electronic components, particularly Si substrates (silicon wafers), GaAs (gallium arsenide) substrates, glass, and LCD (liquid crystal display) substrates, etc. Polishing processing using a polishing pad is performed on the required material. Various polishing pads and polishing methods have been proposed in order to improve the flatness and surface quality of the object to be polished.

For example, in Patent Document 1, in a polishing body made of a polishing cloth or a polishing platen that polishes the wafer while sliding with a wafer (object to be polished) with a relative speed difference, the wafer of the polishing body. A polishing body for wafer polishing, which is characterized in that grooves are provided on the sliding surface at predetermined intervals and the groove density of a portion of the polishing body having a high peripheral speed is increased with respect to the groove density of a portion having a low peripheral speed. (Abrasive pad) is disclosed. According to Patent Document 1, it is disclosed that by using such a polishing pad, the wafer or the wafer holding jig rotates stably, so that the flatness of the polishing wafer is improved.

Japanese Unexamined Patent Publication No. 11-285963

However, when the present inventors have examined in detail conventional polishing pads and polishing methods such as those described in Patent Document 1, the flatness of the object to be polished obtained by the conventional polishing pads and polishing methods It was found that at least one of the sex and the end shape was inadequate.

For example, the method described in Patent Document 1 adjusts the object to be polished so as to rotate according to the groove density of the polishing cloth. Such rotation adjusts the adsorption force between the object to be polished and the holding pad that holds the object to be polished. Affected by. However, Patent Document 1 does not specifically study the suction force between the object to be polished and the holding pad. In this regard, when the suction force between the object to be polished and the holding pad for holding the object to be polished is low, it is difficult to apply pressure evenly to the object to be polished, the flatness of the object to be polished is lowered, and the edge It causes deterioration of the part shape. On the contrary, when the suction force between the object to be polished and the holding pad for holding the object to be polished is increased, the rotation of the object to be polished is suppressed, which causes the flatness of the object to be polished to be lowered. Therefore, there is a need for a holding pad that can impart good flatness and end shape to the object to be polished regardless of the level of adsorption force between the object to be polished and the holding pad for holding the object to be polished.

The present invention has been made in view of the above problems, and is a holding pad capable of imparting good flatness and end shape to an object to be polished after polishing, a method for manufacturing the same, and manufacturing of a polished product. The purpose is to provide a method.

As a result of diligent research to solve the above problems, the present inventors have a holding surface having a predetermined opening, high water absorption, and a constant wall thickness between bubbles near the surface layer. It has been found that when the object to be polished is polished using the holding pad in the range, the object to be polished tends to rotate while maintaining the adsorption force between the object to be polished and the holding pad in a suitable range. Further, as a result, it has been found that the flatness of the obtained object to be polished is improved and the shape of the end portion is improved, and the present invention has been completed.

That is, the present invention is as follows.
[1]
A holding pad provided with a resin sheet having a holding surface for holding an object to be polished.
The resin sheet has air bubbles inside and
_{The resin wall ratio W 100 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 having an average opening diameter of 20 μm or more and 50 μm or less.
The opening rate of the holding surface is 20% or more and 40% or less.
The permeation time of the water when 1.0 μL of water is dropped on the holding surface is 500 seconds or more and 1500 seconds or less.
Holding pad.
[2]
The holding pad according to [1], wherein the 100% modulus of the resin constituting the resin sheet at 23 ± 2 ° C. is 5.0 MPa or more and 20.0 MPa or less.
[3]
The holding pad according to [1] or [2], wherein the dynamic frictional 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 side of the resin sheet opposite 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 an aqueous coagulation liquid to obtain a resin sheet.
It has a step of stretching the obtained resin sheet.
Manufacturing method of holding pad.
[6]
A holding step of holding the object to be polished on the holding pad according to any one of [1] to [4], and
It has a polishing step of polishing the held object to be polished using a polishing pad.
Manufacturing method of polished products.

According to the present invention, it is possible to provide a holding pad capable of imparting good flatness and end shape to an object to be polished after polishing, a method for producing the same, and a method for producing a polished product.

It is the schematic sectional drawing of the resin sheet in the holding pad of this embodiment. It is a schematic diagram which illustrates the method of polishing the object to be polished using the holding pad of this embodiment.

Hereinafter, embodiments 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 thereto, and a gist thereof. Various deformations are possible within the range that does not deviate from. In the drawings, the same elements are designated by the same reference numerals, and duplicate description will be omitted. In addition, the positional relationship such as up, down, left, and right shall be based on the positional relationship shown in the drawings unless otherwise specified. Furthermore, the dimensional ratios in the drawings are not limited to the ratios shown.

[Holding pad]
The holding pad of the present embodiment is a holding pad including a resin sheet having a holding surface for holding an object to be polished, and the resin sheet has air bubbles inside and is made of resin at a depth of 100 μm from the holding surface. The wall ratio W ₁₀₀ is 20.0% or more and 40.0% or less, the holding surface has holes having an average hole diameter of 20 μm or more and 50 μm or less, and the holding surface has a hole opening rate of 20% or more. It is 40% or less, and the permeation 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.

When the object to be polished is held by the holding pad as described above and the object to be polished is polished, the flatness of the obtained object to be polished is further improved and the shape of the end portion is improved. It can be thought of as. However, the factors are not limited to the following.

When the holding surface of the resin sheet has holes having an average opening diameter of 20 μm or more and 50 μm or less and the opening rate is 20% or more and 40% or less, the holding surface easily holds water. Further, when the permeation 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 capacity of the resin sheet is improved. _{Further, when the resin wall ratio W 100 at} a depth of 100 μm from the holding surface is 20.0% or more and 40.0% or less, the proportion of air bubbles near the holding surface of the resin sheet increases, so that the holding near the holding surface is maintained. Hydropower is improved.

As described above, since the holding pad having the above structure easily holds water on the holding surface during polishing, the amount of water intervening between the holding pad and the object to be polished during polishing increases. As a result, since water functions as a lubricant between the holding pad and the object to be polished, the dynamic friction force on the holding surface is reduced, the object to be polished is easily rotated, and the flatness of the obtained object to be polished is obtained. Is further improved, and the shape of the end is improved. In addition, it is considered that the polishing rate is improved by making it easier for the object to be polished to rotate. Further, when the amount of water intervening between the holding pad and the object to be polished during polishing increases, the force of the holding pad to adsorb the object to be polished due to the surface tension of the water (hereinafter, "retaining pad of the holding pad"). Since the suction force (also referred to as “adsorption force”) is improved, the suction force of the holding pad can be set in a suitable range. As a result, the followability of the holding pad to the object to be polished is further improved, the flatness of the obtained object to be polished is further improved, and the shape of the end portion is improved.

In the present embodiment, "the flatness of the object to be polished is further improved" means that the polished surface of the object to be polished is flatter as a whole. It can also be said that the global flatness is good. Further, "improving the shape of the end portion" means that the end portion of the surface of the polished surface of the object to be polished is flatter. This means that, for example, the sagging shape (also referred to as “roll-off”) and the splash shape (also referred to as “ski jumping shape”) that occur on the outer periphery of the object to be polished are suppressed.

[Resin sheet]
FIG. 1 shows a schematic cross-sectional view of the resin sheet. As shown in FIG. 1, the resin sheet 1 of the present embodiment has a holding surface 2 for holding an object to be polished, and has bubbles 3 inside.

By impregnating the holding surface 2 of the resin sheet with an appropriate amount of water 4 and pressing the object to be polished W, the object to be polished can be held by the interaction between the holding surface 2 and the surface of the object W to be polished. .. Further, the holding surface may be designed to be larger than the object to be polished so as to easily hold the object to be polished, or may be configured to be able to hold a plurality of objects to be polished at the same time.

Further, the structure of the resin sheet 1 in the present embodiment is not particularly limited, but it is preferable that the holding surface 2 is provided with a film (skin layer), and the lower portion of the skin layer is provided with vertically elongated bubbles 3 in the thickness direction. Further, the bubbles 3 may have an open cell structure in which they communicate with each other. Examples of the vertically long bubbles 3 include those having a shape in which the bubble diameter gradually decreases toward the skin layer along the thickness direction of the resin sheet in the present embodiment.

The shape of the bubbles contained in the resin sheet is not particularly limited, and examples thereof include a substantially spherical shape, a conical shape, and a spindle shape. In the case of a cone shape or a spindle shape, a cone shape or a spindle shape that is long in the thickness direction of the resin sheet is preferable. Since the resin sheet contains air bubbles having such a shape, the water retention capacity of the resin sheet is further improved, so that the amount of water intervening 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 shape of the end portion is further improved. Furthermore, the polishing rate is further improved. Further, since the resin sheet has cone-shaped or spindle-shaped bubbles long in the thickness direction of the resin sheet, it tends to be easy to form a resin sheet satisfying the _{wall ratio W 100.}

_{The resin wall ratio W 100 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 W ₁₀₀ is in the above range, the water retention capacity in the vicinity of the holding surface is further improved, so that the amount of water intervening 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 shape of the end portion is further improved. Furthermore, the polishing rate is further improved.

Here, the "wall ratio W" is a value indicating the ratio of the resin and the bubbles, and is an index of the bubble structure. In the present specification, the wall ratio W is defined as the ratio of the resin in the cross section at a predetermined depth from the holding surface of the resin sheet, that is, 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 occupied by the resin portion in the cross section of the resin sheet at a predetermined depth Ab: Area occupied by the bubble portion in the cross section of the resin sheet at a predetermined depth

Therefore, when the wall ratio at a predetermined depth is close to 100%, it indicates that there are many resin components at that depth, that is, there are few bubbles. Further, when the wall ratio is close to 0%, it indicates that there are many bubbles.

The wall ratio W ₁₀₀ is not particularly limited, but for example, in the production method described later, a method of adjusting the content of the organic solvent in the resin solution, a method of stretching the resin sheet, and a method of adjusting the stretching ratio thereof. It can be controlled by such as. The larger the content of the organic solvent in the resin solution, the larger the bubbles formed and the smaller the wall ratio, and the smaller the content of the organic solvent, the larger the wall ratio tends to be. 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.

The resin sheet has holes on the holding surface. The average opening diameter of the holes 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 holes on the holding surface is within the above range, the holding surface can more easily hold water, so that the amount of water intervening between the holding pad and the object to be polished during polishing is further increased. To increase. As a result, the flatness of the obtained object to be polished is further improved, and the shape of the end portion is further improved. Furthermore, the polishing rate is further improved.

The opening rate 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 opening ratio of the holding surface is in the above range, the holding surface can more easily hold water, so that the amount of water intervening 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 shape of the end portion is further improved. Furthermore, the polishing rate is further improved.

The average opening diameter of the holes and the opening rate of the holding surface can be measured by the method described in the examples. The method for controlling the average opening diameter of the holes and the opening rate 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.} Further, it can be appropriately adjusted by applying a buff or a slice to the surface on the side serving as the holding surface of the resin sheet.

In the resin sheet, the permeation 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, preferably 600 seconds or more and 1400 seconds or less, and more preferably 700 seconds or more and 1350 seconds. It is as follows.

When the permeation time is within the above range, the resin sheet becomes appropriately hydrophilic, and the water retention capacity of the resin sheet is further improved. As a result, the amount of water intervening between the holding pad and the object to be polished during polishing is further increased, so that the flatness of the obtained object to be polished is further improved and the shape of the end portion is further improved. Furthermore, the polishing rate is further improved.

The permeation time can be measured by the method described in Examples. Further, the permeation time can be controlled by appropriately selecting or adjusting the resin component constituting the resin sheet, the average opening diameter of the holding surface, the opening rate of the holding surface, and the wall ratio. For example, when a preferable resin as described later, particularly a highly hydrophilic resin, is used, the permeation time tends to be short. Further, when the average opening diameter of the holding surface and the opening rate of the holding surface are increased, the permeation time tends to be shortened. Further, the smaller the wall ratio, the shorter the permeation time tends to be.

The dynamic frictional force of the resin sheet in a flooded state is 3.0 kgf or more and 5.5 kgf or less, preferably 3.2 kgf or more and 5.0 kgf or less. When the dynamic friction force in the flooded state is in the above range, the object to be polished is more easily rotated, so that the flatness of the obtained object to be polished is further improved and the shape of the end portion is further improved. Furthermore, the polishing rate is further improved.

The "immersed state" refers to a 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. Further, the dynamic friction force in the flooded state is measured by the method described in the examples.

The dynamic friction force in the flooded state tends to be reduced by increasing the water content of the resin sheet. That is, when the wall ratio W ₁₀₀ is reduced, the average opening diameter of the holding surface and the opening rate of the holding surface are increased, or the permeation time is shortened, the dynamic friction force in the flooded state tends to decrease. Further, when a preferable resin as described later, particularly a resin having high hydrophilicity or a resin having a small dynamic friction coefficient is used, the dynamic friction force in a flooded state tends to be small.

From the viewpoint of more effectively and surely exerting the effect 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 further. It is 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 for the resin sheet portion of the conventional polishing pad. From the viewpoint of more effectively and surely exerting the effects of the present invention, the resin constituting the resin sheet preferably contains a resin having high hydrophilicity or a resin having a small dynamic friction coefficient. Examples of the highly hydrophilic resin include polyurethane resin. As the resin constituting the resin sheet, one type may be used alone, or two or more types may be used in combination.

The polyurethane resin is not particularly limited, and examples thereof include 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 resin sheet may contain other additives. The other additives are not particularly limited as long as they can be used for the resin sheet in the holding pad, and are, for example, pigments such as carbon black, film forming stabilizers such as nonionic surfactants, and anionic surfactants. Foaming modifiers such as. From the viewpoint of reducing the dynamic frictional force of the resin sheet in a water-immersed state, the resin sheet preferably contains a film-forming stabilizer such as a nonionic surfactant and / or a foaming conditioner such as an anionic surfactant.

The 100% modulus of the resin constituting the resin sheet at 23 ± 2 ° C. 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 further preferably 6.0 MPa or less. It is 9.0 MPa or less. When the 100% modulus is in the above range, the object to be polished can be more appropriately subducted into the holding pad, the flatness of the obtained object to be polished is further improved, and the shape of the end portion is further improved.

The "100% modulus" is a value obtained by dividing the tensile force of the resin sheet when it is stretched 100%, that is, when it is stretched to twice the original length, by the initial cross-sectional area of the test piece. Is. Further, the 100% modulus of the resin at 23 ± 2 ° C. can be measured by the method described in Examples.

[Adhesive sheet]
The holding pad of the present embodiment may further have an adhesive sheet on the side opposite to the holding surface of the resin sheet. With such an adhesive sheet, the holding pad can be fixed to the polishing device.

The adhesive contained in the adhesive sheet is not particularly limited, and for example, a polyamide adhesive, a polyester adhesive, an ethylene-vinyl acetate adhesive, an acrylic adhesive, an olefin adhesive, an epoxy adhesive, etc. Examples thereof include 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, and examples thereof include those in which the above-mentioned adhesive is applied to both sides of the base material. Such a base material is not particularly limited, and examples thereof include a base material made of an aromatic ester resin and a base material made of a PET resin.

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

[Manufacturing method of holding pad]
The method for manufacturing the holding pad of the present embodiment includes a coagulation 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 an aqueous coagulation liquid to obtain a resin sheet. It has a stretching step of stretching the obtained resin sheet.

By having the solidification step and the stretching step as described above, air bubbles are easily formed inside, and the resin wall ratio W _{100 at} a depth of 100 μm from the holding surface is 20.0% or more and 40.0% or less. Yes, the holding surface has openings with an average opening diameter of 20 μm or more and 50 μm or less, the opening rate of the holding surface is 20% or more and 40% or less, and when 1.0 μL of water is dropped on the holding surface. It is possible to produce a resin sheet having a water permeation time of 500 seconds or more and 1500 seconds or less. Hereinafter, the resin sheet obtained by the solidification step is also referred to as "resin sheet before stretching", and the resin sheet obtained by the stretching step is also referred to as "resin sheet after stretching".

(Coagulation process)
The coagulation step is 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 an aqueous coagulation liquid to obtain a resin sheet before stretching.

Generally, as a method for forming a resin sheet, a wet film forming method and a dry molding method (also referred to as a molding method) are known, but in the present embodiment, the wet film forming method is adopted. In the wet film formation method, a resin solution in which a resin is dissolved in a water-miscible organic solvent is continuously applied to a film-forming substrate, and the resin is coagulated and regenerated into a sheet by immersing it in an aqueous coagulation liquid. .. The inside of the sheet thus obtained contains a large number of foams generated by solidification and regeneration of the resin. Then, this can be washed and then dried to obtain a long resin sheet. Hereinafter, each step of the wet film forming method will be described in detail.

In general, the wet film forming method includes a preparation step, a coating step, and a solidification / regeneration step, and if necessary, includes a cleaning / drying step and a grinding / removing step for flattening the surface of the resin sheet before stretching. It may be.

In the preparatory step, the resin is dissolved in an organic solvent that is soluble and miscible in the resin, and if necessary, additives are added, and then they are mixed so as to be uniform. , Prepare a resin solution. The resin solution is preferably defoamed under vacuum after removing agglomerates and the like by filtration.

As the resin, the resin exemplified by the holding pad can be used. The organic solvent is not particularly limited, but for example, N, N-dimethylformamide (DMF), N, N-dimethylacetamide (DMAc), tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), N-methylpyrrolidone (N-methylpyrrolidone). Polar solvents such as NMP) and methyl ethyl ketone (MEK) can be used. The above solvent is soluble in polyurethane and miscible with water.

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 obtaining the above resin sheet, 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 further preferably 20% by mass or more and 35% by mass or less with respect to the entire resin solution. The lower the resin concentration in the resin solution, the larger the bubbles formed and the smaller the wall ratio tends to be.

Further, for example, an foaming regulator for controlling foaming, a film forming stabilizer for stabilizing the solidification and regeneration of polyurethane, and an additive such as carbon black for stabilizing foaming are added to the resin solution. Can be done.

The film-forming stabilizer is not particularly limited, and examples thereof include nonionic surfactants. Specifically, for example, the number of carbon atoms such as polyoxyethylene alkyl ether, polyoxypropylene alkyl ether, polyoxyethylene polyoxypropylene alkyl ether, perfluoroalkylethylene oxide adduct, glycerin fatty acid ester, and propylene glycol fatty acid ester. Examples thereof include compounds to which 3 or more alkyl chains are added.

The foaming modifier is not particularly limited, and examples thereof include an anionic surfactant. Specific examples thereof include sodium lauryl sulfate, carboxylic acid salt, sulfonate, sulfate ester salt, and phosphate ester salt.

In the coating step, the resin solution prepared in the preparatory step is applied substantially uniformly to the strip-shaped film-forming substrate using a knife coater or the like at room temperature 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.

As the film-forming base material, a flexible film, a non-woven fabric, a woven fabric, or the like can be used. When a non-woven fabric or woven fabric is used as the film-forming base material, the base material is previously prepared with water or an aqueous organic solvent solution (DMF and water) in order to prevent the polyurethane solution from penetrating into the film-forming base material when the polyurethane solution is applied. It is preferable to perform pretreatment (sealing) by immersing in a mixed solution of When the resin sheet is peeled off from the film-forming substrate, it is more preferable to use a flexible film.

In the solidification / regeneration step, the coating film (the film-forming base material coated with the resin solution) obtained in the coating step is subjected to an aqueous coagulation liquid (for example, water or a solvent containing water as a main component) which is a poor solvent for the resin. ), The coating film of the resin solution is solidified and regenerated into a sheet having a large number of foams inside.

In the aqueous coagulation liquid, generally, first, a skin layer having a thickness of about several μm in which microporous formation is formed is formed on the surface of the applied resin solution, and then the organic solvent in the polyurethane solution is replaced with the coagulation liquid. As the process progresses, the resin solidifies and regenerates in the form of a sheet on one side of the film-forming base material. At this time, typically, the organic solvent is desolved from the resin solution, and the organic solvent and the coagulating liquid are replaced, so that the fine particles formed in the skin layer on the lower side (deposition base material side) of the skin layer are typically formed. A foam layer having a larger pore diameter than the porous surface and having a rounded shape in the thickness direction of the sheet and having a substantially triangular cross section is formed in a state of being substantially evenly dispersed, but the bubble structure is not limited to this.

In the washing / drying step, the resin sheet solidified and regenerated in the solidification / regeneration step is peeled off from the film-forming substrate, washed in a cleaning liquid such as water, and the organic solvent remaining in the resin is removed. After cleaning, 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 dried resin sheet is wound into a roll.

(Stretching process)
The unstretched resin sheet wound as described above is stretched at a predetermined stretching ratio by a stretching step. 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 depends on the type of resin constituting the resin sheet, when the draw ratio is 105% or more, the stretched resin sheet tends to have a predetermined wall ratio, and the draw ratio is 300% or less. As a result, it tends to be possible to avoid breakage of the resin sheet after stretching and excessive thinning. In addition, "the stretching ratio is 105%" means that the resin sheet is stretched to a length 1.05 times the length before stretching.

In the stretching step, the stretching mode is not particularly limited, but may be uniaxial stretching or biaxial stretching, for example. The stretching step is preferably uniaxial stretching from the viewpoint that a resin sheet having a desired wall ratio can be obtained more easily. In the case of uniaxial stretching, the stretching direction is not particularly limited, and it may be stretched in the vertical direction or in the horizontal direction.

The method for manufacturing the holding pad of the present embodiment may further include a grinding / removing step. The grinding / removing step is a step of grinding and / or partially removing at least one of both sides of the stretched resin sheet 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 object to be polished can be further equalized, the flatness of the object to be polished can be further improved, and the shape of the end portion can be further improved. Further, the above resin sheet can be obtained more easily by appropriately adjusting the amount of buffing or slicing of the surface of the resin sheet after stretching.

The resin sheet in the present embodiment is not limited to the above-mentioned wet film forming method, but two types having different 100% modulus by other methods, for example, a supercritical gas foaming method as disclosed in Japanese Patent No. 4624781. It can also be manufactured from thermoplastic polyurethane.

[Manufacturing method of polished products]
The method for producing a 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. FIG. 2 shows a schematic cross-sectional view of a method for manufacturing a polished product. In FIG. 2, first, the holding pad 10 is fixed on the holding surface plate 21 of the polishing machine to hold the object W to be polished. Next, while the object W to be polished is held on the holding surface of the holding pad 10, the polishing slurry 22 is supplied to the surface opposite to the object W to be polished (the surface to be polished), and the polishing platen 23 of the polishing apparatus The object W to be polished can be polished by pressing the polishing pad 24 mounted on the object W against the object W to be polished and rotating it. Hereinafter, each step will be described.

The holding step is not particularly limited as long as it can hold the object to be polished on the holding pad, but for example, water can be provided by interposing an aqueous solution between the holding surface of the holding pad and the object to be polished. The surface tension may be used to hold the object to be polished on the holding pad. Examples of such an aqueous solution include pure water and the like. Alternatively, in the holding step, the object to be polished may be held 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 for example, materials such as semiconductor devices and electronic parts, particularly Si substrate (silicon wafer), GaAs (gallium arsenide) substrate, glass, LCD (liquid crystal display) substrate and the like. Examples thereof include materials that require good end shape and / or flatness.

The polishing step is a step of polishing the held object to be polished using a polishing pad. As the polishing pad, various conventionally known polishing pads can be used. The polishing step may be primary polishing (coarse polishing), secondary polishing (finish polishing), or both of them.

In the polishing process, the machined surface of the object to be polished is polished by the polishing pad by relatively rotating the holding surface plate and the polishing surface plate while pressing the object to be polished toward the polishing pad side with the holding surface plate. It will be processed. The holding surface plate and the polishing surface plate may rotate in the same direction at different rotation speeds, or may rotate in different directions.

In the polishing step, a polishing slurry may be used as the polishing agent. Such a polishing slurry is not particularly limited, but is, for example, chemical components such as water and an oxidizing agent typified by hydrogen peroxide, additives, and abrasive grains (abrasive particles; for example, SiC, SiO ₂ , Al ₂ O). ₃ , CeO ₂ ), etc. are included.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. The present invention is not limited to the following examples.
[Example 1]
100 parts by mass of a solution of 30% polyester polyurethane resin having a 100% modulus of 9.0 MPa at 25 ° C. in dimethylformamide (DMF), 7.9 parts by mass of a 20% carbon black DMF dispersion, stable film formation A resin solution is obtained by mixing and stirring 4.0 parts by mass of an agent (nonionic surfactant), 1.2 parts by mass of a foaming conditioner (anionic surfactant), 8 parts by mass of water, and 55 parts by mass of DMF. rice field.

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

Next, the obtained coating film was immersed in water as a coagulating liquid together with the film-forming substrate, and the resin was coagulated and regenerated to obtain a resin sheet. The resin sheet was taken out from the coagulation bath, the film-forming base material was peeled off from the resin sheet, and then the resin sheet was immersed in a cleaning liquid consisting of water to remove DMF as a solvent. Then, the resin sheet was wound while being dried.

The obtained resin sheet having a thickness of 0.60 mm before stretching is stretched 140% in the lateral direction, and then the surface of the stretched resin sheet is buffed to obtain a resin sheet having a thickness of 0.40 mm. Obtained.

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

[Example 2]
A holding pad was provided in the same manner as in Example 1 except that a polyester 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 lateral direction. Made.

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

[Comparative Example 2]
A holding pad was produced in the same manner as in Example 1 except that the DMF content was changed from 55 parts by mass to 30 parts by mass.

[Wall ratio]
A three-dimensional measurement X-ray CT device (TDM1000H-II (2K) manufactured by Yamato Scientific Co., Ltd.) captures a tomographic image at a depth of 100 μm from the holding surface of the resin sheet (the surface opposite to the surface on which the adhesive sheet is attached). Was obtained using. Next, the area Ab occupied by the bubble portion and the area Ap occupied by the resin portion were measured with respect to the obtained tomographic image using image processing software (VG Studio MAX 3.0 manufactured by Volume Graphics), and the above formula (1). ), The wall ratio was calculated. The results are shown in Table 1.

[Average opening diameter of holes on the holding surface and opening rate of the holding surface]
Using a microscope (manufactured by KEYENCE, trade name "VH-6300"), a range of about 1.3 mm square on the holding surface of the resin sheet was magnified 175 times and photographed. The obtained image is binarized by image processing software (Image Analyzer V20LAB Ver. 1.3, manufactured by Nikon), and the equivalent circle diameter and its average value are calculated from the area of each hole to hold the holding surface. The average opening diameter of was calculated. 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 the noise component was excluded. The results are shown in Table 1.

[Water permeation time on the holding surface]
The permeation time of water when 1.0 μL of water was dropped on the holding surface was measured as follows. That is, under the conditions of a temperature of 20 ° C. and a humidity of 60%, 1.0 μL of ion-exchanged water was dropped onto the holding surface of the dry resin sheet using an injection needle. Then, using a solid-liquid interface analyzer (manufactured by Kyowa Interface Science Co., Ltd., trade name "DropMaster500") as a contact angle meter, the time from the dropping of the water droplet to the contact angle of the water droplet reaching 20 degrees was measured. The above test was performed in a closed system. The "dry state" represents a state when the resin sheet is held in a constant temperature and humidity chamber having 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 flooded state]
After immersing in ion-exchanged water at room temperature for 15 minutes, a resin sheet whose surface was wiped off was used as a measurement sample. A sample was adsorbed on a surface plate of a universal tensile tester (RTC-1210A manufactured by Orientec Co., Ltd.), and a silicon wafer (10 cm × 10 cm) as an adherend was placed on the sample. Then, while the sample was fixed, the adherend was pulled in the shearing direction at a tensile speed of 50 mm / min, and the average value of the tensile forces while pulling the adherend by 80 mm was taken as the dynamic friction force. The results are shown in Table 1.

[Polishing test]
The release paper was peeled off from the holding pads obtained in Examples and Comparative Examples, and the peeled holding pad was attached to the holding surface plate of the polishing machine on the adhesive sheet side. Then, the silicon wafer (diameter 12 inches × thickness 780 μm) to be polished was polished under the polishing conditions shown below.
(Polishing conditions)
Polishing machine: MCP-150X manufactured by Nachi-Fujikoshi Co., Ltd.
Rotation speed: (Surface plate) 40 rpm / (Top ring) 41 rpm
Polishing pressure: 100 g / cm ²
Swing: 20 mm
Polishing time: 20 minutes Polishing pad: Suede pad # 27 manufactured by Fujibo Ehime Co., Ltd.
Abrasive: GLANZOX 1306 manufactured by Fujimi Incorporated (stock solution: water = 1:20)
Number of samples: 25 for each example

(Flatness)
The flatness of a total of 25 objects to be polished, which had been subjected to the above polishing process, was evaluated as follows using a light interference type flatness measuring device (manufactured by KLA Corporation, trade name "Wafersight"). First, the GBIR of the object to be polished before the polishing test (hereinafter referred to as "GBIR ₀ ") and the GBIR of the object to be polished after the polishing test were measured, and the difference between them was determined. 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 (GBIR ₀ ) before the polishing test was calculated for 25 objects to be polished. The flatness was evaluated according to the following evaluation criteria based on the average value of the obtained ratios (ΔGBIR / GBIR _0). The smaller the ratio (ΔGBIR / GBIR ₀ ), the higher the flatness of the obtained object to be polished. GBIR was measured under the condition of EE (Edge Expression) 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 more than 8.5% and 11.5% or less.
C: The ratio (ΔGBIR / GBIR ₀ ) exceeds 11.5%.

(End shape)
A total of 25 objects to be polished were subjected to the above polishing process, and the end shapes were evaluated as follows using a light interference type flatness measuring device (manufactured by KLA Tencor Co., Ltd., trade name "Wafersight"). First, the ESFQR of the object to be polished before the polishing test (hereinafter referred to as "ESFQR ₀ ") and the ESFQR of the object to be polished after the polishing test were measured, and the difference between them was determined. Then, 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 for the 25 objects to be polished. Based on the average value of the obtained ratios (ΔESFQR / ESFQR ₀ ), the end shape was evaluated according to the following evaluation criteria. The smaller the ratio (ΔESFQR / ESFQR ₀ ), the better the shape of the end portion of the obtained object to be polished. The ESFQR was measured under the condition of EE (Edge Expression) 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 has good edge shapes such as materials for semiconductor devices and electronic components, particularly Si substrates (silicon wafers), GaAs (gallium arsenide) substrates, glass, and LCD (liquid crystal display) substrates. / Or is used to hold an object to be polished when polishing a material for which flatness is required, and has industrial utility as a holding pad particularly preferably used for polishing a silicon wafer.

Claims (6)

A holding pad provided with a resin sheet having a holding surface for holding an object to be polished.
The resin sheet has air bubbles inside and
_{The resin wall ratio W 100 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 having an average opening diameter of 20 μm or more and 50 μm or less.
The opening rate of the holding surface is 20% or more and 40% or less.
The permeation time of the water when 1.0 μL of water is dropped on the holding surface is 500 seconds or more and 1500 seconds or less.
Holding pad. The holding pad according to claim 1, wherein the 100% modulus of the resin constituting the resin sheet at 23 ± 2 ° C. is 5.0 MPa or more and 20.0 MPa or less. The holding pad according to claim 1 or 2, wherein the dynamic frictional force of the resin sheet in a water-immersed state is 3.0 kgf or more and 5.5 kgf 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 to the holding surface. 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 an aqueous coagulation liquid to obtain a resin sheet.
It has a step of stretching the obtained resin sheet.
Manufacturing method of holding pad. A holding step of holding an object to be polished on the holding pad according to any one of claims 1 to 4,
It has a polishing step of polishing the held object to be polished using a polishing pad.
Manufacturing method of polished products.

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