JP7540931B2 - Polishing pad and method for producing the same - Google Patents

Description

The present invention relates to a polishing pad and a manufacturing method thereof, and in particular to a polishing pad for chemical mechanical polishing (CMP) having a light-transmitting region and a manufacturing method thereof. More specifically, the present invention relates to a polishing pad having an end point detection window that allows the end point of polishing to be optically detected.

Chemical mechanical polishing (hereinafter referred to as "CMP") is used in semiconductor manufacturing processes (particularly, planarization of interlayer insulating films in a multilayer wiring formation process, metal plug formation, or embedded wiring formation). CMP is a technique for polishing a wafer by using a slurry in which abrasive grains are dispersed while the surface to be polished is pressed against the polishing surface of a polishing pad. Polishing pads used in CMP are broadly classified into hard polishing pads and soft polishing pads. Hard polishing pads are mainly used in a dry molding method in which a curable composition containing a urethane prepolymer is poured into a mold and cured, while soft polishing pads are mainly used in a wet film formation method in which a urethane resin solution is formed into a film in a coagulation bath and dried. In recent years, low defectivity and step elimination of the polished object have been highly required, and the number of cases in which soft polishing pads are used in the finish polishing process and the like has increased.
In recent years, semiconductor elements have been rapidly multi-layered and highly fine, and further improvement in the yield and throughput of semiconductor elements is required, and polishing pads are required to be defect-free and have high planarization without dishing. In order to meet these requirements and perform high-precision CMP, it is necessary to determine the polishing end point, and it is necessary to detect the time when the desired surface characteristics and flatness are reached, and therefore the end point has been detected by optical measurement.

Optical measurement is a method of observing the surface of a wafer through a measurement window provided in a polishing pad. When providing a measurement window in a polishing pad for optical measurement, a transparent material of a different material from the polishing pad must be placed in the window, since polishing pads are generally not transparent. The light transmittance of this transparent material decreases due to various factors, such as scratches on the surface during polishing, or condensation on the back side of the transparent material due to slurry leaking from the gap between the polishing area and the transparent material. This makes it difficult to maintain high accuracy in determining the polishing end point from the beginning to the end of polishing. In addition, when a soft polishing pad is used in the finish polishing process, the window protrudes onto the polishing surface when the polishing pad is pressed against the wafer, and this protruding window, which does not have the polishing ability, may hit the wafer and cause polishing scratches. In addition, polishing products (polishing debris that is an aggregate of pad pieces, polishing objects, polishing slurry, etc. generated after polishing) are generated during polishing, and these gradually adhere and adhere to the surface of the window member on the polishing side, making stable optical measurement difficult.

As a pad with a window for detecting the end point, Patent Document 1 proposes a polishing pad in which the window member is recessed below the polishing surface to prevent polishing scratches caused by the window member coming into contact with the workpiece.

Patent Document 2 also proposes a polishing pad that prevents the moisture from the slurry from condensing on the back surface of the window member, even if the slurry leaks from the joint between the polishing area and the window member onto the back surface of the window member, by subjecting the back surface of the window member to a hydrophilic treatment, thereby preventing a decrease in light transmittance.

JP 2014-104521 A JP 2008-221367 A

However, the polishing pad of Patent Document 1 has a problem in that the polishing debris contained in the slurry sinks into the recessed window area and adheres to the window surface, resulting in a decrease in light transmittance over time. The polishing pad of Patent Document 2 focuses on solving the problem of condensation that occurs when condensation leaks onto the side or back surface of the window member, but does not improve the problem of polishing debris adhering to and adhering to the polishing surface of the window member.

The present invention has been made in consideration of the above, and aims to provide a polishing pad that can reduce adhesion and fixation of polishing debris to the polishing surface side of a translucent resin member (window member).

The inventors discovered that by graft polymerizing a hydrophilic monomer onto the surface of the polishing side of a translucent resin member, it is possible to reduce adhesion and fixation of polishing debris to the surface of the polishing side of a translucent resin member (window member), and thus completed the present invention.
That is, the present invention provides the following.

[1] A polishing pad having a light-transmitting resin member and a polishing layer,
the polishing layer has a polishing surface for polishing an object to be polished, and the polishing pad has a through hole extending from the polishing surface to an opposite surface thereof;
the light-transmitting resin member is arranged such that, when viewed in the thickness direction of the polishing pad from the polishing surface side of the polishing pad, the light-transmitting resin member is present in the through hole, and a hydrophilic monomer is graft-polymerized on the surface of the light-transmitting resin member facing the polishing surface.
[2] The polishing pad according to [1], wherein the water contact angle of the polishing surface of the translucent resin member is 80 degrees or less.
[3] The polishing pad according to [1] or [2], wherein the hydrophilic monomer is an acrylic monomer.
[4] The polishing pad according to [3], wherein the grafted surface resin is an ion complex formed with a complex-forming polymer selected from polyethylene glycol, polyvinylpyrrolidone, polyxylyl viologen, polyethyleneimine and polyvinylpyridinium chloride.
[5] The polishing pad according to any one of [1] to [4], wherein when the polishing surface is the upper surface and the opposite surface is the lower surface, the surface to which the translucent resin member is grafted is lower than the polishing surface.
[6] The polishing pad according to any one of [1] to [5], wherein the polishing surface has grooves.
[7] The polishing pad according to [6], wherein the grooves are embossed grooves.
[8] The polishing pad according to [6] or [7], wherein, when the polishing surface is the upper surface and the opposite surface is the lower surface, the grafted surface of the translucent resin member is at the same position as or lower than the lowest part of the groove.
[9] The polishing pad according to any one of [1] to [8], wherein the through holes have a circular shape when viewed in the thickness direction of the polishing pad from the polishing surface side of the polishing pad.
[10] When the through hole of the polishing layer is a first through hole, the polishing pad further includes another layer having a second through hole having a smaller circle equivalent diameter than the first through hole,
The other layer is located on the opposite side to the polishing surface of the polishing layer,
When the polishing pad is viewed in a thickness direction from a polishing surface side, the first through hole and the second through hole at least partially overlap each other,
The polishing pad according to any one of claims 1 to 9, wherein the translucent resin member is arranged so that the translucent resin member is present within the first through hole when viewed in the thickness direction of the polishing pad from the polishing surface side of the polishing pad.
[11] A step of preparing a polishing layer and a light-transmitting resin member having at least one surface on which a hydrophilic monomer is graft-polymerized;
providing a through hole in the polishing layer; and disposing the light-transmitting resin member so that the light-transmitting resin member is present in the through hole when viewed in the thickness direction of the polishing pad from the polishing surface side of the polishing pad, wherein the light-transmitting resin member is disposed so that the grafted surface of the light-transmitting resin member faces the polishing surface.
The method for producing a polishing pad according to any one of [1] to [10], comprising:
[12] The manufacturing method according to [11], further comprising a step of subjecting the at least one surface of the light-transmitting resin member to a plasma graft treatment.

The present invention provides a polishing pad that can reduce adhesion and adhesion of polishing debris to the polishing surface of a translucent resin member (window member). This enables stable light detection.

FIG. 1 is a perspective view of a polishing pad according to one embodiment of the present invention, as viewed in the thickness direction from the polishing surface. FIG. 2 is a schematic cross-sectional view (cut end surface) in the thickness direction of a polishing pad according to one embodiment of the present invention. FIG. 3 is a schematic cross-sectional view (cut end surface) in the thickness direction of a polishing pad according to one embodiment of the present invention. FIG. 4 is a schematic cross-sectional view (cut end surface) in the thickness direction of a polishing pad according to one embodiment of the present invention. FIG. 5 is a schematic cross-sectional view (cut end surface) in the thickness direction of a polishing pad according to one embodiment of the present invention. FIG. 6 is a schematic cross-sectional view (cut end surface) in the thickness direction of a polishing pad according to one embodiment of the present invention.

The following describes how to implement the present invention.

<<Polishing pad>>
The polishing pad of the present invention is a polishing pad having a translucent resin member and a polishing layer, wherein the polishing layer has a polishing surface for polishing an object to be polished, the polishing pad has a through hole extending from the polishing surface to the opposite surface, the translucent resin member is arranged such that, when viewed from the polishing surface side of the polishing pad in the thickness direction of the polishing pad, the translucent resin member is present in the through hole, and a hydrophilic monomer is graft polymerized on the surface of the polishing surface side of the translucent resin member.
The polishing pad of the present invention may also be referred to as a polishing pad having a translucent resin member and a polishing layer, the polishing layer having a polishing surface for polishing an object to be polished, the polishing pad having a through hole penetrating from the polishing surface to the opposite surface, the translucent resin member being arranged such that, when viewed from the polishing surface side of the polishing pad in the thickness direction of the polishing pad, the translucent resin member is present within the through hole, and the resin on the surface of the polishing surface side of the translucent resin member has a polymer containing a hydrophilic monomer as a constituent unit in its side chain.

In this specification and claims, a polishing layer is a layer having a surface (polishing surface) that comes into contact with an object to be polished, such as a semiconductor device, to perform polishing. There are no particular limitations on the object to be polished, and examples include product substrates containing multiple memory or processor dies, test substrates, bare substrates, and gate substrates. The substrate can be at various stages of integrated circuit manufacturing, for example, the substrate can be a bare wafer or can be one or more deposition and/or patterned layers.

<Light-transmitting resin member>
The polishing pad of the present invention has a light-transmitting resin member, i.e., a window member. By irradiating the workpiece with light through the light-transmitting resin member, it is possible to detect the time when the workpiece reaches the desired surface characteristics and flatness. For optical end point detection, a visible light (white light) laser, lamp, etc. is used.
The light-transmitting resin member is disposed so that the light-transmitting resin member exists within the through hole when viewed in the thickness direction of the polishing pad from the polishing surface side of the polishing pad. Here, "arranged so that a translucent resin member is present in the through hole when viewed in the thickness direction of the polishing pad from the polishing surface side of the polishing pad" intends that the translucent resin member is arranged so that it can be confirmed when the inside of the through hole is viewed in the thickness direction from the polishing surface of the polishing pad, and includes the concept of (1) the case where the translucent resin member is arranged so as to contact (or adhere) to the side surface (side wall) of the through hole provided in the polishing layer as shown in Figures 2 to 3, (2) the case where another layer having a through hole with a circle equivalent diameter smaller than the circle equivalent diameter of the through hole of the polishing layer is provided under the polishing layer as shown in Figure 4, and the translucent resin member is arranged on the exposed portion 7 resulting from the difference in size between the through hole of the polishing layer and the through hole of the other layer, (3) the case where the translucent resin member is sandwiched between the polishing layer and the other layer as shown in Figure 5, and is arranged so that a part of the translucent resin member is exposed in the through hole, and (4) the case where a through hole is provided in both the polishing layer and the other layer as shown in Figure 6, and the translucent resin member is arranged so as to contact (or adhere) to the side surface of either or both of the through holes. Among these, (1), (2) or (4) is preferable, (1) or (2) is more preferable, and (2) is even more preferable.

The translucent resin member is not particularly limited as long as it is a resin that has a transparency sufficient to transmit light. For example, thermosetting resins such as polyurethane resin, polyester resin, phenol resin, urea resin, melamine resin, epoxy resin, and acrylic resin, thermoplastic resins such as polyurethane resin, polyester resin, polyamide resin, cellulose-based resin, acrylic resin, polycarbonate resin, halogen-based resin (polyvinyl chloride, polytetrafluoroethylene, polyvinylidene fluoride, etc.), polystyrene resin, and olefin-based resin (polyethylene, polypropylene, etc.), rubbers such as butadiene rubber and isoprene rubber, photocurable resins that are cured by light such as ultraviolet light or electron beams, and photosensitive resins can be used. Among these, acrylic resin, polyurethane resin, polyester resin, and polystyrene resin are preferred, and acrylic resin is more preferred.

The translucent resin member preferably has a visible light transmittance (sometimes simply referred to as light transmittance in this specification) of 60% or more when irradiated with light having a wavelength of 380 nm to 780 nm, more preferably has a visible light transmittance of 65% or more, even more preferably has a visible light transmittance of 70% or more, even more preferably has a visible light transmittance of 75% or more, and even more preferably has a visible light transmittance of 80% or more. Visible light transmittance can be measured by measuring the transmission spectrum of wavelengths of 300 to 1000 nm with a spectrophotometer and calculating the visible light transmittance (%) according to the Japanese Industrial Standards (JIS A5759:2008).

(Grafting)
In the polishing pad of the present invention, a hydrophilic monomer is graft-polymerized onto the polishing surface side of the light-transmitting resin member.
In this specification and claims, "a hydrophilic monomer is graft-polymerized onto the polishing surface of the light-transmitting resin member" means that a hydrophilic monomer is bonded to the light-transmitting resin on the polishing surface by graft polymerization. Therefore, the resin present on the polishing surface of the light-transmitting resin member has a polymer containing a hydrophilic monomer as a constituent unit in its side chain.

The polishing pad of the present invention can reduce adhesion and fixation of polishing debris to the surface of the translucent resin member by graft polymerization of a hydrophilic monomer (hereinafter, sometimes referred to as grafting). The reason why grafting can reduce adhesion and fixation of polishing debris to the surface of the translucent resin member is not clear, but it is presumed as follows. That is, in the polishing pad of the present invention, the resin on the surface of the translucent resin member on the polishing side has long side chains due to grafting. These long side chains adsorb water molecules to form a water film, making it difficult for polishing debris that has flowed onto the surface of the translucent resin member to adhere and fix to the surface of the translucent resin member, and it is presumed that the adhesion and fixation of polishing debris to the surface of the translucent resin member can be prevented by causing the polishing debris to flow out from the surface of the translucent resin member due to the centrifugal force during polishing.

The grafting is preferably carried out by plasma graft polymerization, which is a method for forming a graft polymerized surface by reacting a monomer such as acrylic acid with radicals formed by plasma surface treatment as the initiation point (Sen-i-gakkaishi Journal, Vol. 41, No. 10, pp. 388-393, 1985).
The plasma treatment refers to a treatment in which a solid surface is irradiated with plasma generated by ionization of an inert gas by discharging the inert gas in an inert gas atmosphere.
Examples of the inert gas in the plasma treatment include nitrogen gas, argon gas, oxygen gas, helium gas, neon gas, and xenon gas.
The plasma can be generated by any of the known methods for generating plasma, for example, by placing the monomer under vacuum between parallel plate electrodes connected to a radio frequency generator, the plasma can be generated using parallel plates either external or internal to the vacuum chamber, an electric field can be created by an external induction coil to generate a plasma of an ionized gas, or the plasma can be generated by placing spaced oppositely charged electrodes directly into the vacuum chamber.

Grafting with a hydrophilic monomer is preferably performed, for example, by subjecting the polished surface of the translucent resin member to plasma treatment, removing the translucent resin member from the plasma treatment device, and immersing it in an aqueous solution containing the hydrophilic monomer, thereby graft polymerizing the hydrophilic unsaturated monomer onto the translucent resin member.

In this specification and claims, a hydrophilic monomer refers to a monomer having a functional group capable of adsorbing water molecules around it.
As the hydrophilic monomer, a hydrophilic monomer having an unsaturated double bond is preferable, and a hydrophilic monomer having a vinyl group or an allyl group is more preferable.
The hydrophilic monomer used for grafting is not particularly limited as long as it is a hydrophilic monomer, and conventionally known monomers can be used. Examples of the hydrophilic monomer include acrylamide, methacrylamide, N-vinylpyrrolidone, acrylic acid, methacrylic acid, p-styrenesulfonic acid, vinylsulfonic acid, 2-methacryloyloxyethylsulfonic acid, 3-methacryloyloxy-2-hydroxypropylsulfonic acid, allylsulfonic acid, methacrylic acid, and ammonium salts and alkali metal salts of these acids, dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, diethylaminoethyl acrylate, diethylaminoethyl methacrylate, 2-vinylpyridine and 4-vinylpyridine hydrochloride, nitric acid, dimethyl sulfate, diethyl sulfate, or ethyl chloride quaternized products. Among these, acrylic monomers are preferred, with acrylic acid, methacrylic acid, 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, acrylamide, methacrylamide, 2-acrylamido-2-methylpropanesulfonic acid, N,N-dimethylaminoethyl methacrylate and N,N-dimethylaminoethyl acrylate being more preferred, with acrylic acid and methacrylic acid being even more preferred, and acrylic acid being even more preferred.
The hydrophilic monomer may be used alone or in combination of two or more kinds.

The light-transmitting resin member may be formed into a complex by reacting a graft polymer formed by grafting the polishing surface with a further polymer. When the graft polymer is a polymer (anionic polymer) containing or made of a monomer having a carboxylic acid group such as an acrylic monomer (e.g., acrylic acid, methacrylic acid) or maleic anhydride, the complex-forming polymer may be a cationic polymer such as polyethylene glycol, polyvinylpyrrolidone, polyxylyl viologen, polyethyleneimine, polyvinylpyridinium chloride, or polyvinylbenzyl trimethylammonium chloride. When the graft polymer is a polymer (cationic polymer) containing or made of a basic monomer such as acrylamide, methacrylamide, vinylpyridine, N,N-dimethylaminoethyl methacrylate, or N,N-dimethylaminoethyl acrylate, the complex-forming polymer may be an anionic polymer such as polyacrylic acid, polymethacrylic acid, poly2-acrylamido-2-methylpropanesulfonic acid, polystyrenesulfonic acid, or polyvinylsulfonic acid.
Among these, the resin on the surface grafted with an acrylic monomer is preferably bound by intermolecular interactions with a complex-forming polymer selected from polyethylene glycol, polyvinylpyrrolidone, polyxylyl viologen, polyethyleneimine, polyvinylpyridinium chloride, and polyvinylbenzyltrimethylammonium chloride, and more preferably bound by intermolecular interactions with polyvinylbenzyltrimethylammonium chloride. A complex consisting of an ion complex is formed by intermolecular interactions, such as hydrogen bonds and ionic bonds, between the polymer chains formed by graft polymerization and the complex-forming polymer.
By forming a complex with the complex-forming polymer, the ions present in the graft group and the counter ions of the complex-forming polymer increase the number of adsorption points for water molecules, further decreasing the contact angle and further increasing the hydrophilicity of the surface of the light-transmitting resin member. In addition, a water film is easily formed on the surface, making it difficult for dirt such as polishing dust to adhere and stick to the surface.
The complex formed by the complex-forming polymer can be formed, for example, by immersing a light-transmitting resin member to which a hydrophilic monomer has been graft-polymerized in an aqueous solution of the complex-forming polymer for a predetermined period of time.

The translucent resin member may be grafted with resin not only on the surface facing the polishing surface, but also on the surface (back surface) and side surfaces opposite the polishing surface, but grafting the back surface and side surfaces also leads to increased costs, while grafting the back surface and side surfaces is unrelated to the effects of the present invention. In addition, if resin is grafted on the side surfaces and back surface of the translucent resin member, the surface in contact with the polishing layer becomes hydrophilic, and the translucent resin member may swell and deform due to the slurry, peeling off from the polishing area, or causing slurry leakage. For the above reasons, it is preferable that only the resin on the surface facing the polishing surface is grafted.

(Water Contact Angle)
In the polishing pad of the present invention, the water contact angle of the surface of the polishing surface side of the light-transmitting resin member is 80 degrees or less. The water contact angle is preferably 60 degrees or less, more preferably 50 degrees or less, even more preferably 30 degrees or less, even more preferably 20 degrees or less, even more preferably 1 to 20 degrees, even more preferably 2 to 15 degrees, and even more preferably 3 to 10 degrees. When the water contact angle is within the above range, it is easy to prevent adhesion and fixation of polishing debris to the surface of the polishing surface side of the light-transmitting resin member (window member).
The reason why the adhesion and fixation of polishing debris to the polished surface side of the light-transmitting resin member (window member) can be easily prevented by having the water contact angle within the above range is presumed to be as follows.
As described above, in the polishing pad of the present invention, due to grafting, the resin on the surface of the polishing surface of the translucent resin member has long side chains, and while water molecules are adsorbed to the side chains, adjacent side chains are repelled because they have the same charge, so that a large number of water molecules are adsorbed and wettability is improved. At this time, since the surface of the polishing surface of the translucent resin member is hydrophilic, with a water contact angle of 80 degrees or less, the water molecules attached to the side chains tend to form a water film, and polishing debris can be easily discharged from the translucent resin member together with the slurry. As a result, it is believed that adhesion and adhesion of polishing debris can be suppressed.

In the polishing pad of the present invention, there is no particular restriction on the water contact angle of the back surface or side surface of the light-transmitting resin member. Therefore, the water contact angle of the back surface or side surface may be more than 80 degrees. In other words, the back surface or side surface of the light-transmitting resin member does not need to be grafted.
The window member used in the conventional polishing pad generally has a water contact angle of more than 80 degrees. If a window having a water contact angle of 80 degrees or less is used over the entire surface of the window member, the window may swell and deform due to the slurry, and may peel off from the polishing area or cause slurry leakage. Therefore, the window member material is preferably a hydrophobic window member having a water contact angle of more than 80 degrees, and it is preferable that only the surface on the polishing surface side has a water contact angle of 80 degrees or less. In the present invention, it is preferable to use a translucent resin member in which only the resin on the surface on the polishing surface side is grafted, and thus the water contact angle of the surface on the polishing surface side is 80 degrees or less (the water contact angle of the side surface and back surface is more than 80 degrees).

In the polishing pad of the present invention, when the polishing surface is the upper surface and the opposite surface is the lower surface, the grafted surface 9 of the translucent resin member (upper surface of the translucent resin member) may be the same as the polishing surface or lower than the polishing surface, but is preferably lower than the polishing surface (Figure 2). By making the grafted surface 9 of the translucent resin member lower than the polishing surface, it is possible to prevent the occurrence of polishing scratches caused by the translucent resin member, which is harder than the polishing layer. In addition, when the upper surface of the translucent resin member is lower than the polishing surface, polishing debris generally enters the recess surrounded by the translucent resin member and the side of the through hole, and tends to adhere and stick to the surface of the translucent resin member, so that the light transmittance decreases over time. However, in the polishing pad of the present invention, since the resin present on the surface of the translucent resin member is grafted with a hydrophilic monomer, even if polishing debris enters the recess, the entered polishing debris can be flushed out to the side surface of the recess or the groove together with the slurry, making it easier to prevent the polishing debris from adhering and sticking to the surface of the translucent resin member.

(Through hole)
The through holes are holes that penetrate from the polishing surface to the opposite surface when viewed in the thickness direction of the polishing pad from the polishing surface side of the polishing pad. The through holes preferably penetrate the polishing layer parallel to the thickness direction or perpendicular to the polishing surface.
The polishing layer may have one through-hole, or two or more through-holes that are spaced apart and independent from each other.
The shape of the through hole when viewed from the polishing surface side of the polishing pad in the thickness direction of the polishing pad or the shape of the through hole on the polishing surface may be a circle, an ellipse, a triangle, a rectangle, a hexagon, an octagon, etc. Alternatively, the shape may be a shape in which the same or different multiple shapes partially overlap each other. Among these, a circle is particularly preferred because it does not form corners where polishing debris is likely to accumulate.

(Circle equivalent diameter)
In this specification and the claims, the term "circle equivalent diameter" refers to the diameter of a perfect circle that corresponds to the area of the figure to be measured.
The circular equivalent diameter of the through hole is the circular equivalent diameter of the through hole when viewed in the thickness direction of the polishing pad from the polishing surface side of the polishing pad, and corresponds to the diameter when the shape of the through hole when viewed in the thickness direction of the polishing pad from the polishing surface side of the polishing pad is circular.
The equivalent circle diameter of the through hole is not particularly limited, but is preferably 5 to 40 mm, more preferably 5 to 30 mm, and even more preferably 10 to 28 mm.
The area of the through holes in the polished surface is preferably 0.003 to 0.5% of the total area of the polished surface, more preferably 0.004 to 0.4%, and even more preferably 0.05 to 0.3%.

(Configuration of the polishing layer)
Resins constituting the polishing layer include polyurethane-based resins such as polyurethane and polyurethane polyurea, acrylic resins such as polyacrylate and polyacrylonitrile, vinyl resins such as polyvinyl chloride, polyvinyl acetate and polyvinylidene fluoride, polysulfone-based resins such as polysulfone and polyethersulfone, acylated cellulose-based resins such as acetylated cellulose and butyrylated cellulose, polyamide-based resins, and polystyrene-based resins. Among these, polyurethane resins are more preferable in terms of compression characteristics and flexibility.
The abrasive layer may be made of one type of resin, or may be made of two or more types of resins.
The polishing layer preferably has open cells. The open cells referred to here refer to foams in which adjacent cells are connected to each other by communicating holes. Specifically, the foam may be made of resin by a wet film-forming method, or by dry molding or injection molding. The wet film-forming method is preferable, as it is expected to provide good bending and stretching movements.
In this specification, the resin by the wet film-forming method means a resin (preferably a polyurethane resin) formed by the wet film-forming method. The wet film-forming method is a method in which the resin to be formed into a film is dissolved in an organic solvent, the resin solution is applied to a sheet-shaped substrate, and then the resin is solidified by passing it through a coagulating liquid. The resin formed by the wet film-forming method generally has a plurality of teardrop-shaped bubbles (anisotropic, with a structure in which the diameter increases from the polishing surface of the polishing pad to the bottom). Therefore, the resin formed by the wet film-forming method can also be referred to as a resin having a plurality of teardrop-shaped bubbles. The plurality of teardrop-shaped bubbles are preferably in the form of continuous bubbles.

(groove)
The polishing pad of the present invention preferably has grooves formed on the polishing surface of the polishing layer. The grooves do not penetrate the polishing layer and can be distinguished from through-holes.
Examples of the groove include an embossed groove obtained by embossing the polishing surface, and a cut groove obtained by cutting with a cutting tool. Among these, an embossed groove is preferred. By providing a groove such as an embossed groove, it is possible to obtain a polishing pad that is less likely to produce burrs on the polishing surface and is suitable for finish polishing.
The depth of the groove is not particularly limited as long as it is smaller than the thickness of the polishing layer, but it is preferably 50-90% of the thickness of the polishing layer, and more preferably 60-80%. If the groove disappears due to polishing of the object to be polished, the flow and discharge of the polishing slurry is lost, the polishing performance is reduced, and the polishing pad reaches the end of its life, so the groove depth is preferably deep. On the other hand, in order to increase the groove depth of the embossed groove, it is necessary to increase the processing pressure or the processing temperature, which may cause the substrate (PET) on the back surface of the polishing layer to deform or the surface of the polishing layer to deteriorate. If the depth of the groove is within the above range, these problems are unlikely to occur.
The cross-sectional shape of the groove is not particularly limited, and may be an arc shape, a U-shape, a V-shape, a rectangle, a trapezoid, or other polygonal shape, or a combination of two or more of these shapes. The number and shape of the grooves are also not particularly limited, and may be adjusted appropriately according to the purpose of use of the polishing pad. Examples of shapes include a lattice shape, a radial shape, a concentric circle shape, a honeycomb shape, and the like, and these may be combined.
In the polishing pad of the present invention, the surface of the polishing layer may be opened by grinding (buffing) or may be sliced.

In the polishing pad of the present invention, when the polishing surface is the upper surface and the opposite surface is the lower surface, the grafted surface 9 of the light-transmitting resin member (i.e., the upper surface 4' of the light-transmitting resin member) may be located higher than the lowest portion 8' of the groove, at the same position as the lowest portion 8', or lower than the lowest portion 8', but it is preferably located at the same position as the lowest portion 8' of the groove or lower, and it is more preferable that the grafted surface 9 of the light-transmitting resin member is located lower than the lowest portion 8' of the groove. Generally, the life of a polishing pad ends when polishing is performed until the grooves provided on the polishing surface disappear, but if the top of the light-transmitting resin member is located at the same position as the lowest portion of the groove or lower, the polishing pad can be used until the grooves disappear.
In addition, in conventional polishing pads, if the upper surface 4' of the light-transmitting resin member is generally at the same position as or lower than the bottom 8' of the groove, the slurry and polishing debris are difficult to discharge from the groove, which can cause a problem of a decrease in light transmittance over time. In contrast, in the polishing pad of the present invention, the polishing debris is difficult to adhere to or stick to the surface of the light-transmitting resin member, so that the decrease in the light attenuation rate can be suppressed. In addition, particularly in the polishing pad of one embodiment of the present invention (the polishing pad of FIG. 4), even if the polishing debris that has entered the recess in the first through hole moves to the side of the first through hole due to the centrifugal force during polishing and a part of it remains without being discharged from the groove, it becomes difficult to see from the second through hole having a smaller circle equivalent diameter, so that the decrease in light transmittance can be further prevented. This enables stable light detection.

(Shore A hardness)
In this specification, the Shore A hardness refers to a value measured in accordance with Japanese Industrial Standards (JIS K7311).
In the polishing pad of the present invention, the Shore A hardness of the polishing layer is preferably 5 to 70 degrees (°), more preferably 8 to 65 degrees. When the Shore A hardness of the polishing layer is within the above range, excessive contact of polishing debris with the workpiece is suppressed, making it difficult for scratches to occur.
In the polishing pad of the present invention, the polishing layer is preferably softer than the light-transmitting resin member, and more preferably has a lower Shore A hardness than the light-transmitting resin member.

(Compressibility and Compressive Elasticity)
In this specification, the compressibility is an index of softness, and the compressive elastic modulus is an index of the ease of return to normal after compressive deformation.
The compressibility and compressive elasticity can be determined using a Chopper-type thickness gauge (pressure surface: circular with a diameter of 1 cm) in accordance with the Japanese Industrial Standards (JIS L1021). Specifically, the method is as follows.
The thickness _t0 is measured after the initial load is applied for 30 seconds from the no-load state, and then the thickness _t1 is measured after the final load is applied for 5 minutes from the thickness _t0 state. Next, all loads are removed from the thickness _t1 state, and the sample is left for 5 minutes (to be in a no-load state), after which the initial load is again applied for 30 seconds and the thickness _t0 ' is measured.
The compression ratio can be calculated by the formula: compression ratio (%)=100×(t ₀ −t ₁ )/t ₀ (initial load is 100 g/cm ² , final load is 1120 g/cm ² ).
The compressive elastic modulus can be calculated by the formula: compressive elastic modulus (%)=100×(t ₀ '-t ₁ )/(t ₀ -t ₁ ) (initial load is 100 g/cm ² , final load is 1120 g/cm ² ).
The compressibility of the polishing layer is preferably 1 to 60%, more preferably 3 to 50%. The compressive elastic modulus of the polishing layer is preferably 50 to 100%, more preferably 60 to 98%. When the compressibility and compressive elastic modulus are within the above ranges, the polishing layer is compressed when the workpiece passes over the through-hole, and has excellent recovery after being pressed by the workpiece, so that the bending and stretching movement of the polishing layer creates a flow of slurry inside the through-hole, the slurry circulates without remaining in the through-hole, and the polishing waste that enters the through-hole together with the slurry is easily discharged outside the through-hole by the compression and recovery action. This makes it easier to prevent the polishing waste from accumulating in the through-hole.

(Thickness)
The thickness can be measured using a Chopper-type thickness measuring instrument (pressure surface: circular with a diameter of 1 cm) in accordance with the Japanese Industrial Standards (JIS K6505). Specifically, the thickness is measured as follows.
Prepare a sample that is 10 cm square by 10 cm long. Place the sample on the measuring device with the surface facing up. Place a pressure surface with a load of 100 g/ ^cm2 on the sample and measure the thickness after 5 seconds. Measure 5 points on each sheet and take the average thickness. If a 10 cm square sample cannot be obtained, use the average of the 5 points.
There is no particular limitation on the thickness of the polishing layer, but it is preferably 0.5 to 2 mm, and more preferably 0.75 to 1.55 mm.

(Layers other than the polishing layer)
The polishing pad of the present invention may have a layer (another layer) other than the polishing layer. The other layer may be present in one or more layers on the surface opposite to the polishing surface of the polishing layer. The other layer has through holes like the polishing layer.
In addition, the shapes of the through holes in the polishing layer and the other layers may be the same or different, but it is preferable that the through holes in the polishing layer and the other layers at least partially overlap when the polishing pad is viewed in the thickness direction from the polishing surface side, so that when light is irradiated onto the light-transmitting resin member, the light passes through the light-transmitting resin member.

In one embodiment of the present invention, when the polishing pad has another layer, the polishing pad may have another layer having a through hole (second through hole) having a smaller circle equivalent diameter than the through hole (first through hole) present in the polishing layer ( FIG. 4 ). The other layer is a layer located on the opposite side of the polishing surface of the polishing layer.
In the polishing pad of this aspect, it is preferable that the first through hole and the second through hole at least partially overlap when viewed in the thickness direction from the polishing surface side of the polishing pad, and the light-transmitting resin member is preferably disposed so that the light-transmitting resin member is present in the first through hole when viewed in the thickness direction of the polishing pad from the polishing surface side of the polishing pad.

In this embodiment of the polishing pad, when viewed in the thickness direction from the polishing surface side of the polishing pad, it is preferable that the outer periphery of the first through hole 5 is arranged to cover part or all of the outer periphery of the second through hole 6, and it is more preferable that the outer periphery of the first through hole 5 is arranged to cover the entire outer periphery of the second through hole 6, and it is even more preferable that both the first through hole 5 and the second through hole 6 are cylindrical, and that the cylindrical central axis of the first through hole 5 and the cylindrical central axis of the second through hole 6 coincide (see FIG. 4).

Here, when viewed in the thickness direction from the polishing surface side, the first through hole and the second through hole at least partially overlap means that when viewed in the thickness direction from the polishing surface side, the opening position of the first through hole and the opening position of the second through hole at least partially coincide. In this embodiment of the polishing pad, when viewed in the thickness direction, the opening position of the first through hole and the opening position of the second through hole at least partially coincide, so that the first through hole and the second through hole are connected in the thickness direction of the polishing pad. Since the positions of the first through hole and the second through hole at least partially overlap when viewed in the thickness direction from the polishing surface side, light can be transmitted from the second through hole side to the first through hole side through the translucent resin member provided in the first through hole, and the surface condition of the polished object during polishing can be optically detected.

In the polishing pad of this embodiment, when viewed in the thickness direction of the polishing pad from the polishing surface side of the polishing pad, the light-transmitting resin member 4 is preferably disposed so that the light-transmitting resin member 4 is present in the first through hole 5. In addition, the light-transmitting resin member 4 is preferably provided in the first through hole 5.
Here, when the light-transmitting resin member is arranged so that it is present within the first through hole when viewed in the thickness direction of the polishing pad from the polishing surface side of the polishing pad, this means that the light-transmitting resin member can be confirmed when viewing inside the first through hole in the thickness direction of the polishing pad from the polishing surface side of the polishing pad.
In addition, the first through hole 5 is preferably arranged so that a part of the other layer 3 (hereinafter, referred to as the exposed portion 7 of the other layer) and at least a part of the second through hole 6 are exposed when the polishing pad 1 is viewed in the thickness direction from the polishing surface side. This allows the translucent resin member 4 to be disposed in the first through hole 5 and on the second through hole 6 and the exposed portion 7 of the other layer 3. Preferably, the first through hole 5 is arranged so that a part of the other layer 3 and all of the second through hole 6 are exposed when the first through hole 5 is viewed from the polishing surface side. In addition, the translucent resin member 4 is preferably provided in the first through hole 5 and bonded to the exposed portion 7 of the other layer 3.
4, in the thickness direction cross section of the polishing pad 1 of the present invention, the first through hole 5 is provided in the polishing layer 2 on the second through hole 6 and the exposed portion 7. An additional layer may be provided between the polishing layer 2 and the other layer 3 having the exposed portion 7. In this case, it is preferable that the through hole in the additional layer has the same cross-sectional shape (cross-sectional shape in a horizontal direction to the polishing surface) as the through hole (first through hole) of the polishing layer 2, and completely overlaps with the first through hole 5 when viewed in the thickness direction from the polishing surface. It is preferable that the translucent resin member 4 is disposed on the second through hole 6 and the exposed portion 7, and inside the first through hole 5 of the polishing layer 2 and the through hole of the additional layer.

The second through hole may be provided in one other layer, or two or more through holes that are spaced apart and independent from each other may be provided. It is preferable that the number of first through holes is equal to the number of second through holes. When a plurality of first through holes and a plurality of second through holes are provided, it is preferable that each first through hole is provided on each second through hole provided in the other layer and its exposed portion.

The second through holes preferably penetrate the other layer parallel to the thickness direction or perpendicular to the polishing surface.
In the polishing pad of the present invention, the cross-sectional shape of the first through hole and the cross-sectional shape of the second through hole when cut perpendicular to the thickness direction may be the same or different, but it is preferable that they have the same shape.
The shape of the second through hole when viewed in the thickness direction of the polishing pad from the polishing surface side of the polishing pad, the cross-sectional shape of the second through hole when cut perpendicularly to the thickness direction of the polishing pad, and/or the shape of the second through hole on the surface of the other layer may be a circle, an ellipse, a triangle, a rectangle, a hexagon, an octagon, or a combination of these shapes. Alternatively, the shape may be a shape in which a plurality of the same or different shapes partially overlap each other. Among these, a circle is particularly preferred.

(Circle equivalent diameter)
In this specification and claims, the circle equivalent diameter of the second through hole is the circle equivalent diameter of the second through hole when viewed in the thickness direction of the polishing pad from the polishing surface side of the polishing pad, and corresponds to the diameter when the shape of the second through hole when viewed in the thickness direction of the polishing pad from the polishing surface side of the polishing pad is circular.
The circle-equivalent diameter of the first through hole is preferably larger than the circle-equivalent diameter of the second through hole. As long as the circle-equivalent diameter of the first through hole is larger than the circle-equivalent diameter of the second through hole, there is no particular restriction on the circle-equivalent diameter of the second through hole, but the circle-equivalent diameter of the second through hole is preferably 1 to 20 mm, more preferably 2 to 18 mm, and even more preferably 5 to 15 mm. In addition, there is no particular restriction on the difference between the circle-equivalent diameter of the first through hole and the circle-equivalent diameter of the second through hole, but the circle-equivalent diameter of the first through hole is preferably 5 to 30 mm larger than the circle-equivalent diameter of the second through hole, more preferably 6 to 25 mm larger, and even more preferably 7 to 20 mm larger.
Furthermore, when viewed in the thickness direction from the polishing surface side of the polishing pad, the outer periphery of the first through hole is arranged to cover the entire outer periphery of the second through hole, and the circular equivalent diameter of the first through hole is preferably 5 to 30 mm larger than the circular equivalent diameter of the second through hole, more preferably 6 to 25 mm larger, even more preferably 7 to 20 mm larger, even more preferably 8 to 20 mm larger, even more preferably 9 to 20 mm larger, and even more preferably 10 to 20 mm larger.
Furthermore, when viewed in the thickness direction from the polishing surface side of the polishing pad, the outer periphery of the first through hole is arranged to cover the entire outer periphery of the second through hole, and the circular equivalent diameter of the first through hole is preferably 1.5 to 4 times the circular equivalent diameter of the second through hole, more preferably 2 to 4 times, and even more preferably 2.5 to 3 times.

Furthermore, when viewed from the polishing surface side of the polishing pad in the thickness direction of the polishing pad, it is preferable that the shortest distance between the outer periphery of the second through hole and the outer periphery of the first through hole (i.e., the shortest distance between any point on the outer periphery of the second through hole and any point on the outer periphery of the first through hole) is greater than 0, it is more preferable that the shortest distance is 2 to 15 mm, it is even more preferable that the shortest distance is 3 to 12 mm, and it is even more preferable that the shortest distance is 4 to 10 mm.
When the difference in size between the first through hole and the second through hole is within the above range, the slurry and polishing debris that have entered the recess in the first through hole are moved to the outer periphery of the first through hole by the centrifugal force during polishing and are difficult to see from the second through hole with a smaller circle equivalent diameter, so that it is possible to prevent the polishing debris from blocking the light path when light is irradiated onto the translucent resin member. Therefore, it is possible to maintain excellent light transmittance and obtain a stable signal strength for end point detection during polishing. In addition, since the area of the exposed portion is sufficiently large, it is possible to maintain the adhesive strength between the translucent resin member and other layers and prevent the translucent resin member from peeling off.
Furthermore, even if most of the slurry migrates to the side of the recess and only a small amount of slurry remains on the surface of the translucent resin member, the polishing pad of the present invention is less likely to experience variations in light transmittance due to the presence or absence of slurry, making stable light detection possible.

In another embodiment, when the polishing pad of the present invention includes another layer, a sheet-like light-transmitting resin member may be sandwiched between the polishing layer and the other layer, and a part of the light-transmitting resin member may be exposed in the through-hole (FIG. 5). In this case, when viewed in the thickness direction from the polishing surface side, it is preferable that the through-hole (second through-hole) in the other layer and the through-hole (first through-hole) in the polishing layer at least partially overlap, and more preferably completely overlap. In this case, it is preferable that the polishing layer has continuous cells with communicating holes.
When the polishing layer has open cells with communicating holes, the open cells also open on the side of the first through holes provided in the polishing layer, and some of them communicate with the polishing surface or the groove region. As a result, the slurry and polishing debris that enter the first through holes during polishing are moved to the side of the first through holes by the centrifugal force generated during polishing and are discharged to the polishing surface or the groove region through the open cells with communicating holes, which prevents a decrease in light transmittance over time due to the polishing debris accumulating in the first through holes, leading to a longer life for the polishing pad.

In another embodiment, when the polishing pad of the present invention includes another layer, a through hole may be provided in both the polishing layer and the other layer provided below it, and a translucent resin member may be arranged so as to contact (or adhere) to the side of either or both of the through holes (preferably the side of the other layer) (FIG. 6). At this time, when viewed in the thickness direction from the polishing surface side, it is preferable that the through hole (second through hole) present in the other layer and the through hole (first through hole) present in the polishing layer at least partially overlap, and more preferably completely overlap. It is preferable that the translucent resin member is adhered to the side of the second through hole. It is also preferable that the translucent resin member does not exist in the first through hole.
By bonding the light-transmitting resin member to the side of the second through hole of the other layer, the thickness of the polishing layer available for polishing is maximized, and even if the polishing surface is scraped by wear during dressing or polishing, the light-transmitting resin member does not protrude on the polishing surface, and the occurrence of scratches can be reduced. In general, the softer the polishing layer of the polishing pad, the more likely it is that the polishing pad will sink when pressed against the wafer, causing the light-transmitting resin member to protrude, and the polishing pad with the protrusion cannot be used for polishing the object to be polished. This type of polishing pad can prevent the light-transmitting resin member from protruding, so that the life of the polishing pad can be extended. In addition, if the light-transmitting resin member is not bonded to the polishing layer but is bonded to the side of the second through hole, even if the polishing layer has an expansion and contraction mechanism so that the polishing chips that have entered the first through hole are easily discharged to the groove or polishing surface, distortion is unlikely to occur at the adhesive portion of the light-transmitting resin member, and this can suppress peeling of the light-transmitting resin member.

(Configuration of other layers)
Examples of materials constituting the other layer include polyolefin-based sheets such as polyethylene (PE), polypropylene (PP), and ethylene-propylene copolymers, polyester-based sheets such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN), vinyl chloride-based sheets, vinyl acetate-based sheets, polyimide-based sheets, polyamide-based sheets, fluororesin-based sheets, resin-impregnated nonwoven fabrics, nonwoven fabrics, and woven fabrics. The other layer is preferably a non-porous sheet into which the slurry does not penetrate. Among these, the other layer is more preferably a polyester-based sheet, which is a non-porous sheet into which the slurry does not penetrate, from the viewpoint of physical properties (e.g., dimensional stability, thickness accuracy, processability, tensile strength), and economic efficiency, and among these, a sheet made of polyethylene terephthalate (hereinafter abbreviated as PET) is particularly preferred.
As a method for bonding the other layer to the polishing layer or the other layer to another other layer, for example, a sheet such as a PET sheet coated with an adhesive on one or both sides can be used as the other layer, and the other layer can be bonded to the polishing layer or the other other layer via the adhesive. It is also possible to prepare a sheet such as a PET sheet not coated with an adhesive as the other layer, and separately prepare the polishing layer or the other other layer and an adhesive, and bond the other layer to the polishing layer or the other other layer via the adhesive.
The polishing pad of the present invention can be produced, for example, by the following method.

<<Method of manufacturing polishing pad>>
The manufacturing method of the present invention includes the steps of preparing a polishing layer and a light-transmitting resin member having at least one surface on which a hydrophilic monomer has been graft-polymerized, providing a through hole in the polishing layer, and arranging the light-transmitting resin member so that it is present within the through hole when viewed in the thickness direction of the polishing pad from the polishing surface side of the polishing pad (wherein the light-transmitting resin member is arranged so that the grafted surface of the light-transmitting resin member faces the polishing surface). The method of manufacturing a polishing pad according to any one of claims 1 to 10.
It is.
Each step will be described.

<1. Step of preparing a polishing layer and a light-transmitting resin member having at least one surface thereof graft-polymerized with a hydrophilic monomer>
In this step, a polishing layer and a light-transmitting resin member having at least one surface on which a hydrophilic monomer is graft-polymerized are prepared.
In this specification and claims, the phrase "a hydrophilic monomer is graft-polymerized onto at least one surface" means that a hydrophilic monomer is bonded to a light-transmitting resin on at least one surface by graft polymerization.
It is preferable that only one surface of the light-transmitting resin member is graft-polymerized with a hydrophilic monomer.
The above-mentioned materials can be used as the polishing layer and the light-transmitting resin member. The polishing layer and the light-transmitting resin member may be commercially available or manufactured. Commercially available light-transmitting resin members include "Diafoil T910E" and "Diafoil T600E" made of polyester resin by Mitsubishi Chemical Corporation, "Cosmoshine A4300", "Cosmoshine A2330", "Cosmoshine TA017", "Cosmoshine TA015", "Cosmoshine TA042", "Cosmoshine TA044", "Cosmoshine TA048", and "Soft Shine TA009" made by Toyobo Co., Ltd., "Acryplene HBXN47" and "Acryplene HBS010" made of polymethyl methacrylate resin by Mitsubishi Chemical Corporation, and "Panlite Film PC-2151" made by Teijin Chemical Co., Ltd. , "Sunduren SD009" and "Sunduren SD010" manufactured by Kaneka Corporation, "C000" manufactured by Sumitomo Chemical Co., Ltd. made of polycarbonate resin, "Iupilon H-3000" manufactured by Teijin Chemical Co., Ltd., "C001" manufactured by Sumitomo Chemical Co., Ltd. made of acrylic resin/polycarbonate resin, "S000", "S001G", and "S014G" manufactured by Sumitomo Chemical Co., Ltd. made of acrylic resin, "ACRYPLEN HBS006" manufactured by Mitsubishi Chemical Corporation, "ZEONOR ZF14" and "ZEONOR ZF16" manufactured by Zeon Corporation made of alicyclic polyolefin resin, "ARTON FILM" manufactured by JSR Corporation, and the like can be obtained as commercially available products. When manufacturing the polishing layer, for example, it can be manufactured by wet-forming a polyurethane resin with reference to Patent No. 5421635 and Patent No. 5844189, and laminating it with a flexible sheet made of PET resin.

The manufacturing method of the present invention may further include a step of subjecting at least one surface of the translucent resin member to plasma grafting. Examples of the method of plasma grafting include those described above. By subjecting at least one surface of the translucent resin member to plasma grafting, it is possible to obtain a translucent resin member having at least one surface graft-polymerized with a hydrophilic monomer.

<2. Step of Providing Through Holes in the Polishing Layer>
In this step, a through hole is provided in the polishing layer. The through hole is a hole that penetrates from the polishing surface of the polishing layer to the opposite surface. For example, the method of providing a through hole in the polishing layer can be provided by using a die (preferably a circular die) of a circular, elliptical, polygonal, etc. to open a hole in the thickness direction of the polishing layer. By using a die, the circle equivalent diameter of the through hole in any polishing layer cross section obtained by cutting the polishing layer of the polishing pad perpendicularly to the thickness direction can be made the same as the circle equivalent diameter of the through hole in any other polishing layer cross section.

<3. Step of arranging the light-transmitting resin member so that the light-transmitting resin member is present in the through-hole when viewed in the thickness direction of the polishing pad from the polishing surface side of the polishing pad>
In this step, the light-transmitting resin member is disposed so that it is present in the through-hole when viewed in the thickness direction of the polishing pad from the polishing surface side of the polishing pad, with the grafted surface of the light-transmitting resin member facing the polishing surface.
Examples of methods for arranging the light-transmitting resin member so that it is present in the through-hole include (1) a method in which the light-transmitting resin member is arranged so as to be in contact with (or adhered to) the side surface of the through-hole provided in the polishing layer as shown in FIGS. 2 and 3; (2) a method in which another layer having a through-hole with a smaller circle equivalent diameter is provided under the polishing layer as shown in FIG. 4, and the light-transmitting resin member is arranged on the exposed portion resulting from the difference in size between the through-hole in the polishing layer and the through-hole in the other layer, thereby arranging the light-transmitting resin member so that the light-transmitting resin member is visible in the through-hole; (3) a method in which the light-transmitting resin member is sandwiched between the polishing layer and the other layer as shown in FIG. 5, and a part of the light-transmitting resin member is exposed in the through-hole; and (4) a method in which the same shaped through-hole is provided in both the polishing layer and the other layer provided under it as shown in FIG. 6, and the light-transmitting resin member is arranged so as to be in contact with (or adhered to) the side surface of either or both of the through-holes. Among these, (1), (2) or (4) is preferable, (1) or (2) is more preferable, and (2) is even more preferable.

The manufacturing method of the present invention may have a step of preparing a layer other than the polishing layer, or may have a step of bonding a layer other than the polishing layer (another layer) and the polishing layer. The other layer has a through hole that is the same as or different from the through hole of the polishing layer. The through hole in the other layer may be provided before bonding the other layer to the polishing layer, or may be provided after bonding the other layer to the polishing layer. The other layer and the through hole may be the same as those described above.
The manufacturing method of the present invention may also include a step of providing second through holes in another layer, the second through holes having a smaller circle equivalent diameter than the through holes (first through holes) in the polishing layer.

When the polishing pad of the present invention is used, the polishing pad is attached to the polishing platen of a polishing machine so that the polishing surface of the polishing layer faces the workpiece, and the polishing platen is rotated while supplying the slurry to polish the processed surface of the workpiece.
Examples of objects to be polished with the polishing pad of the present invention include bare silicon and semiconductor devices. Among these, the polishing pad of the present invention is suitable for polishing semiconductor devices, particularly finish polishing, and is therefore preferred.
The slurry may be any slurry containing water (aqueous slurry) without any particular limitation, and examples thereof include colloidal silica slurry and cerium oxide slurry.

By using the polishing pad of the present invention, for example, during the CMP polishing process, a light beam is irradiated onto the wafer through the polishing pad via the translucent resin member in the through hole, and the interference signal generated by the reflection is monitored, so that while polishing the workpiece, the surface characteristics of the workpiece, such as a semiconductor wafer, and the point at which the workpiece reaches a flat state can be optically detected.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

Example 1
An acrylic resin sheet (Mitsubishi Chemical Corporation, Acryplene HBS006) measuring 20 mm in length, 20 mm in width, and 0.15 mm in thickness was subjected to a plasma treatment with argon gas at a flow rate of 10 sccs, a reaction time of 2 minutes, and a pressure of 50 Pa. The sheet was then immersed in an aqueous solution of 40 mol % acrylic acid and subjected to a graft polymerization reaction at 80° C. for 1 hour while bubbling nitrogen gas, followed by ultrasonic cleaning in distilled water for 2 hours and vacuum drying at 80° C. for 6 hours. The obtained light-transmitting resin member was used as the light-transmitting resin member of Example 1.

Example 2
An acrylic resin sheet (Mitsubishi Chemical Corporation, Acryplene HBS006) with a length of 20 mm, width of 20 mm, and thickness of 0.15 mm was subjected to plasma polymerization with argon gas at a flow rate of 10 sccs, a reaction time of 2 minutes, and a pressure of 50 Pa. The sheet was then immersed in an aqueous solution of 40 mol% acrylic acid, and graft polymerization reaction was carried out at 80°C for 1 hour while bubbling nitrogen gas, followed by ultrasonic cleaning in distilled water for 2 hours and vacuum drying at 80°C for 6 hours. The acrylic resin sheet after graft polymerization was stirred for 30 minutes in 25 ml of an aqueous solution of 5% by weight of polyvinylbenzyltrimethylammonium chloride (molecular weight 43000) to carry out a polymer complex formation reaction. The film was then washed with water and dried to form a polymer composite. The obtained light-transmitting resin member was used as the light-transmitting resin member of Example 2.

<Comparative Example 1>
An acrylic resin sheet (manufactured by Mitsubishi Chemical Corporation, ACRYPLEN HBA001P ACRYPLEN HBS006) having a length of 20 mm, a width of 20 mm and a thickness of 0.15 mm was used as the light-transmitting resin member of Comparative Example 1.

<Comparative Example 2>
An acrylic resin sheet (ACRYPLEN HBA001P ACRYPLEN HBS007, manufactured by Mitsubishi Chemical Corporation) having a length of 20 mm, a width of 20 mm and a thickness of 0.15 mm was subjected to plasma treatment with argon gas at a flow rate of 10 sccs, a reaction time of 2 minutes and a pressure of 50 Pa. The obtained light-transmitting resin member was used as the light-transmitting resin member of Comparative Example 2.

<Contact angle maintenance evaluation>
In order to evaluate the change in hydrophilicity over time, the water contact angle was measured two days and two weeks after the production of the light-transmitting resin members of Examples 1 and 2 and Comparative Examples 1 and 2. The water contact angle was measured by the following method using an automatic contact angle meter DropMaster DM500 (manufactured by Kyowa Interface Science Co., Ltd.).
(1) Fill the syringe with distilled water, attach the dispenser, and set it in the DM500.
(2) Cut the measurement sample to a size of 5 mm x 50 mm and attach it to the stage.
(3) Start the analysis software, select Contact Angle Measurement [Seasleet Method], and set each parameter.
Waiting time until measurement: 1000 ms
Measurement time interval: 1000ms
Number of continuous measurements: 180 times (4) Set the droplet volume to be measured and the injection needle position on the image monitor, and optimize the focus value of the image monitor.
(5) A droplet is placed on the sample and measurement is started, and the water contact angle is read 10 seconds after the start of measurement.
The results of the water contact angle measurement test are shown in Table 1.
As a result of the measurement, if the contact angle after 2 days and after 2 weeks was 80 degrees (°) or less, it was evaluated as ◯, and if not, it was evaluated as ×.

<Window Residue Evaluation>
Using the light-transmitting resin members of Examples 1 and 2 and Comparative Examples 1 and 2, polishing pads were manufactured as follows.
A resin-containing solution was obtained by adding 60 parts by mass of DMF and 5 parts by mass of water to 100 parts by mass of a solution containing 30 parts by mass of a polyester polyurethane resin with a 100% modulus of 7.8 MPa and 70 parts by mass of DMF. The obtained resin-containing solution was filtered to remove insoluble components. The solution was cast onto a polyester sheet using a knife coater so that the coating thickness was 0.8 mm. Thereafter, the polyester sheet onto which the resin-containing solution was cast was immersed in a coagulation bath (coagulation liquid was water) to coagulate the resin-containing solution, and then the polyester sheet was peeled off, washed and dried to obtain a polyurethane resin sheet. The surface of the obtained polyurethane resin sheet was buffed to a thickness of 0.73 mm, and then a PET resin substrate with a thickness of 0.188 mm was bonded to the side opposite to the buffed surface with an adhesive, and the polyurethane resin sheet was embossed from the surface side, and a groove with a rectangular cross section and a lattice pattern with a groove width of 1 mm, a groove interval of 4 mm, and a groove depth of 0.45 mm was provided on the surface. The grooved polyurethane resin sheet was punched out into a circle with a diameter of 740 mm using a die, and three holes were made at equal intervals and independently of each other on a concentric circle at a position that is 1/2 the radius from the center of the circular polyurethane resin sheet on the grooved surface side using a circular die with a diameter of 18 mm to provide a first through hole. A circular double-sided tape with a thickness of about 0.1 mm and a diameter of 790 mm (PET substrate thickness 0.023 mm, adhesive component thickness on the front and back sides of the PET substrate both 0.004 mm) having a release paper on one side as a second layer was adhered to the surface side of the resin substrate where the polyurethane resin sheet was not attached, and the excess double-sided tape was cut off to have the same diameter as the polyurethane resin sheet. Next, a circular die with a diameter of 9 mm was fitted into the first through hole with a diameter of 18 mm, and a second through hole was opened so as to penetrate the double-sided tape and the release paper. At this time, the hole was drilled so that the center of the first through hole and the center of the second through hole were approximately the same. The transparent resin members produced in Example 1, Example 2, Comparative Example 1, and Comparative Example 2 were each cut into three pieces with a diameter of 17 mm, and the double-sided tape exposed in a ring shape in the first through hole was adhered to the transparent resin member to produce a polishing pad.
Next, as the object to be polished, a pattern substrate with lines made of tungsten (W) and spaces made of TEOS (silicon oxide film) was prepared, and 500 substrates were polished using each polishing pad under the conditions described below. After that, the cross section of the translucent resin member was observed with an energy dispersive X-ray spectrometer (EDS) to evaluate whether any residue was attached to the surface of the polished side of the translucent resin member.
Polishing machine used: EBARA F-REX300
Polishing pressure: 2.5 psi
Polishing pad: H600 manufactured by Fujibo Ehime Co., Ltd.
Abrasive: Planar, model number "BSL8176C"
Dresser: 3M diamond dresser, model number "A188"
Pad break 30N x 30 min, diamond dresser 54 rpm, platen rotation speed 80 rpm, ultrapure water 200 mL/min
Conditioning: Ex-situ, 30N, 4 scans, 16 seconds Polishing: Platen rotation speed 70 rpm, head rotation speed 71 rpm, slurry flow rate 200 mL/min
Polishing time: about 60 seconds. The results are shown in Table 1.

As a result of the above test, in Comparative Example 1, which was not surface-treated, the water contact angle after 2 days and 2 weeks was high at about 87 degrees, and wettability was poor. As a result of window residue evaluation performed using EDS, a large amount of Si element was found on the surface of the light-transmitting resin member when polishing was performed using the polishing pad having the light-transmitting resin member of Comparative Example 1. It is believed that Si remained on the highly hydrophobic window surface and progressed in adhesion.
In Comparative Example 2, where only plasma treatment was performed, the contact angle after two days was smaller than that of the untreated product, but after two weeks it returned to the same contact angle as the untreated product, and the surface modification effect of the plasma treatment was lost. Furthermore, EDS measurement confirmed the presence of Si element on the surface of the light-transmitting resin member, which is considered to be due to the accumulation of Si on the window surface, which is not sufficiently hydrophilic.
On the other hand, Example 1, which was subjected to graft polymerization treatment, maintained a low contact angle even after two weeks, and Example 2, in which a graft polymer was composited, had an even lower contact angle than Example 1 and was able to maintain that contact angle even after two weeks. Furthermore, in both Examples 1 and 2, the Si element was not confirmed by EDS measurement.
As a result of the above, it was found that the polishing pad containing the light-transmitting resin member of Examples 1 and 2 can reduce the adhesion and adhesion of polishing debris to the surface of the polishing side of the light-transmitting resin member (window member), enabling stable light detection.

According to the present invention, it is possible to provide a polishing pad that can reduce adhesion and adhesion of polishing debris to the polishing surface side of a translucent resin member (window member). Therefore, the polishing pad of the present invention is extremely useful industrially.

1... polishing pad 2... polishing layer 3... other layer 4... light-transmitting resin member 4'... uppermost part of light-transmitting resin member 5... through hole (first through hole)
6: second through hole 7: exposed portion 8: groove 8': lowest portion of groove 9: grafted surface portion

Claims (10)

A polishing pad having a light-transmitting resin member and a polishing layer,
the polishing layer has a polishing surface for polishing an object to be polished, and the polishing pad has a through hole extending from the polishing surface to an opposite surface thereof;
the light-transmitting resin member is disposed so as to be present within the through hole when viewed in a thickness direction of the polishing pad from the polishing surface side of the polishing pad ,
the light-transmitting resin member has a hydrophilic monomer graft-polymerized on its polishing surface side;
The hydrophilic monomer is an acrylic monomer, and
the grafted resin on the surface is a complex-forming polymer selected from polyethylene glycol, polyvinylpyrrolidone, polyxylyl viologen, polyethyleneimine, polyvinylpyridinium chloride, and polyvinylbenzyltrimethylammonium chloride, forming an ion complex;
The polishing pad. The polishing pad according to claim 1, wherein the water contact angle of the polishing surface of the translucent resin member is 80 degrees or less. 3. The polishing pad according to claim 1, wherein when the polishing surface is taken as an upper surface and the opposite surface is taken as a lower surface, the surface to which the light-transmitting resin member is grafted is lower than the polishing surface. The polishing pad of any one of claims 1 to 3 , wherein the polishing surface has grooves. The polishing pad of claim 4 , wherein the grooves are embossed grooves. 6. The polishing pad according to claim 4, wherein when the polishing surface is the upper surface and the opposite surface is the lower surface, the grafted surface of the translucent resin member is at the same position as or lower than the lowest part of the groove. 7. The polishing pad according to claim 1 , wherein the through holes have a circular shape when viewed in the thickness direction of the polishing pad from the polishing surface side of the polishing pad. When the through hole of the polishing layer is defined as a first through hole, the polishing pad further includes another layer having a second through hole having a smaller circle equivalent diameter than the first through hole,
The other layer is located on the opposite side to the polishing surface of the polishing layer,
When the polishing pad is viewed in a thickness direction from a polishing surface side, the first through hole and the second through hole at least partially overlap each other,
The polishing pad according to any one of claims 1 to 7, wherein the light-transmitting resin member is arranged so that the light-transmitting resin member is present within the first through hole when viewed in the thickness direction of the polishing pad from the polishing surface side of the polishing pad. A step of preparing a polishing layer and a light-transmitting resin member having a hydrophilic monomer graft-polymerized on at least one surface thereof;
providing a through hole in the polishing layer; and disposing the light-transmitting resin member so that the light-transmitting resin member is present in the through hole when viewed in the thickness direction of the polishing pad from the polishing surface side of the polishing pad, wherein the light-transmitting resin member is disposed so that the grafted surface of the light-transmitting resin member faces the polishing surface.
The method for producing the polishing pad according to any one of claims 1 to 8 , comprising: The manufacturing method according to claim 9 , further comprising a step of subjecting the at least one surface of the light-transmitting resin member to a plasma graft treatment.

Images