Polishing pad, polishing apparatus, method for producing polishing pad and method for producing polished object

Abstract

A polishing pad that may obtain high polishing rate and high processing quality. A polishing pad having a resin including a void. A surface layer forming a surface to be a polishing surface of the polishing pad comprises a first resin. A region of the polishing pad comprises a second resin. When a value of a circle-equivalent diameter of the void in the polishing surface is defined as a void diameter of a front surface, and a value of a circle-equivalent diameter of the void in a surface opposite to the polishing surface is defined as a void diameter of a back surface, a difference between the void diameter of the front surface and the void diameter of the back surface is within 15%.

Description

BACKGROUNDTechnical Field

[0001] The present technique relates to a polishing pad for finishing the surface of an object to be polished flat, a polishing apparatus, a method for producing the polishing pad and a method for producing a polished object.Description of the Related Art

[0002] Conventionally, in optical materials such as optical lenses and reflecting mirrors as well as materials such as substrates for hard discs, silicon wafers, and glass substrates for liquid crystal displays (polished objects), highly accurate flatness has been required and, therefore they have been submitted to polish processing using a polishing pad. In such a polish processing, the polishing pad is stuck to a base, and the processing is performed by supplying a polishing liquid including a polishing particle between an object to be polished and the polishing pad, while allowing the object to be polished and the polishing pad to be in contact with each other and to relatively move.

[0003] As the polishing pad, a pad having various properties that hardness and Young's modulus in the thickness direction are various is widely used, which is because high processing quality may be obtained by providing a hard layer having moderate stiffness in the polishing surface in order to improve the flatness, and providing a soft layer having an elasticity sufficient to follow warpage of a wafer in a layer under the hard layer.

[0004] For example, in Japanese Patent Application Laid-Open No. 2003-220550, a void diameter of a surface layer including a polishing surface is set small to increase an apparent hardness, thereby forming a layer. The void diameter of a layer under the hard layer is set large to reduce the apparent hardness, thereby forming a soft layer. In this manner, high processing quality is achieved.SUMMARY

[0005] The present disclosure is a polishing pad comprising a resin having a void, wherein the resin includes a first resin and a second resin, a hardness of the first resin being higher than a hardness of the second resin, wherein a surface layer forming a polishing surface of the polishing pad comprises the first resin, wherein a region of the polishing pad comprises the second resin, and wherein, when a value of a circle-equivalent diameter of the void in the polishing surface is defined as a void diameter of a front surface, and a value of a circle-equivalent diameter of the void in a surface of the polishing pad opposite to the polishing surface is defined as a void diameter of a back surface, a difference between the void diameter of the front surface and the void diameter of the back surface is within 15%.

[0006] In addition, the present disclosure is a polishing apparatus including: the polishing pad; a fixing part for fixing the polishing pad; and a holding part for holding an object to be polished.

[0007] In addition, the present disclosure is a method for producing a polishing pad, the method including: preparing a resin including a void; and subjecting a surface layer including one surface of the resin to curing treatment to provide a cured resin layer having a higher hardness than a hardness of an other region of the resin, wherein, when a circle-equivalent diameter of the void in the cured surface is defined as a void diameter of a front surface, and a circle-equivalent diameter of the void in a surface opposite to the cured surface is defined as a void diameter of a back surface, a difference between the void diameter of the front surface and the void diameter of the back surface is within 15%.

[0008] In addition, the present disclosure is a method for producing a polished object including polishing an object to be polished with the polishing pad.

[0009] Further features of the present disclosure will become apparent from the following description of exemplary embodiments with reference to the attached drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0010] FIG. 1 is a schematic view of the polishing apparatus of the present disclosure.

[0011] FIG. 2A is a schematic perspective view of the polishing pad of the present disclosure.

[0012] FIG. 2B is a sectional view along the A-A straight line of FIG. 2A.DESCRIPTION OF THE EMBODIMENTS

[0013] Example embodiments of the present disclosure will now be described in detail in accordance with the accompanying drawings.

[0014] Using a conventional polishing pad in which the void diameter of the surface layer is set small to form a hard layer causes a problem that polishing rate decreases. The void (e.g., air bubble) is formed by a spherical recess in the polishing pad, and the void holds the polishing slurry and supplies polishing slurry to the surface being processed. Reducing the void in size decreases the holding performance of the slurry to deteriorate the property of supplying the slurry to the surface being processed, thereby decreasing the polishing rate. Accordingly, an aspect of the present disclosure is to provide a polishing pad that may achieve high polishing rate and high processing quality.First Embodiment

[0015] The first embodiment is about a polishing pad.

[0016] The polishing pad of the present disclosure is a polishing pad having a resin including a void, wherein a surface layer including a surface to be a polishing surface of the resin is a first resin having a higher hardness than a hardness of an other region of the resin, and wherein, when a value of a circle-equivalent diameter of the void in the polishing surface is defined as a void diameter of a front surface, and a value of a circle-equivalent diameter of the void in a surface opposite to the polishing surface is defined as a void diameter of a back surface, a difference between the void diameter of the front surface and the void diameter of the back surface is within 15%.

[0017] The embodiment will hereinafter be described.[Polishing Apparatus]

[0018] The polishing apparatus of the present disclosure includes a polishing pad of the present disclosure, a fixing part for fixing the polishing pad, and a holding part for holding an object to be polished. FIG. 1 is a schematic view of the polishing apparatus of the present disclosure. A polishing apparatus 1 is a wet polish-processing apparatus that has a polishing pad 10, a base 5 for fixing and holding the polishing pad 10 (a fixing part for fixing the polishing pad), a supply part 2 for supplying a polishing slurry S including water, a chemical liquid, and etc. to a polishing surface of the polishing pad 10, and a carrier holding base 4 (a holding part for holding an object to be polished).

[0019] In FIG. 1, the carrier holding base 4 (a holding part for holding an object to be polished) applies a pressure to a work 3, which is an object to be processed, from above to hold the work 3 so that the work 3 is in contact with the polishing surface of the polishing pad 10, and the polish processing of the work 3 is performed in this configuration.

[0020] Examples of the work 3 (an object to be polished) include: semiconductor substrates; optical materials such as optical lenses and reflecting mirrors; substrates for hard discs; silicon wafers; and glass substrates for liquid crystal displays. Herein, a work 3 that has been subjected to polish processing is defined as an object.[Polishing Pad]

[0021] The polishing pad of the present disclosure is a polishing pad having a resin including a void. FIGS. 2A and 2B are each a schematic view of the polishing pad of the present disclosure. FIG. 2A is a perspective view, and FIG. 2B is an A-A sectional view when the polishing pad is cut from a z-axis direction passing along an A-A straight line of FIG. 2A.

[0022] In FIGS. 2A and 2B, a surface horizontal to a polishing surface 6S is defined as an xy plane, and an axis perpendicular to the xy plane is defined as the z axis. The A-A straight line illustrated with a dashed line in FIG. 2A is parallel to the x axis, and orthogonal to a y axis.

[0023] The polishing pad 10 has, from the polishing surface 6S, in a minus z direction, a surface layer 6 and an underlayer 7 laid side by side. The surface layer 6 has a polishing surface 6S. The polishing surface 6S is a portion of the polishing pad 10 to be in touch with the work 3.

[0024] The surface layer 6 and the underlayer 7 each have a void 11. The void 11 has a function of holding the slurry S and supplying the slurry to the polishing surface 6S. In the present disclosure, the polishing surface 6S of the polishing pad is referred to as a front surface, and a surface opposite to the polishing surface 6S is referred to as a back surface.

[0025] In the polishing pad of the present disclosure, when a value of a circle-equivalent diameter of the void in the polishing surface 6S is defined as a void diameter of a front surface, and a value of a circle-equivalent diameter of the void in a surface opposite to the polishing surface 6S is defined as a void diameter of a back surface, a difference between the void diameter of the front surface and the void diameter of the back surface is within 15%. The difference between the void diameter of the front surface and the void diameter of the back surface is preferably 5% or more and 13% or less, and more preferably 5.1% or more and 12.8% or less.

[0026] Here, the difference between the void diameter of the front surface and the void diameter of the back surface refers to a value obtained by dividing an absolute value of the difference between the void diameter of the front surface and the void diameter of the back surface by the void diameter of the back surface. The circle-equivalent diameter is specifically a diameter of a circle having the same region as the projected region of the void. In this manner, the polishing pad of the present disclosure may achieve high polishing rate.

[0027] In the polishing pad of the present disclosure, when a proportion of a region of the void in the polishing surface based on a region of the polishing surface is defined as a void area proportion of the front surface, and a proportion of a region of the void in the surface opposite to the polishing surface based on a region of the surface opposite to the polishing surface is defined as the void area proportion of the back surface, a difference between the void area proportion of the front surface and the void area proportion of the back surface is preferably within 10% (−10% or more and +10% or less). In this manner, the polishing pad of the present disclosure may achieve a higher polishing rate.

[0028] For the same reason, in the polishing pad of the present disclosure, the average void diameter of the front surface is preferably 100 μm or more and 500 μm or less, and more preferably 150 μm or more and 300 μm or less. The void area proportion of the front surface is not particularly limited, but is, for example, in the range of 40% or more and 80% or less. In order to obtain a higher polishing rate, the difference between an average void density of the front surface and an average void density of the back surface is preferably within ±10%.

[0029] In the polishing pad of the present disclosure, the surface layer 6 including a surface to be a polishing surface of the resin is a first resin 8 having a higher hardness than a hardness of the other region of the resin (second resin 9). The surface layer 6 has the first resin 8, and the underlayer 7 has the second resin 9. The first resin 8 is integrally formed with the second resin 9 to be a resin formed product, and a same raw material is used for each of the first resin 8 and the second resin 9. The first resin 8 has been imparted with a higher hardness than the hardness of the second resin 9 by further promoting crosslinking after the first resin 8 is integrally formed with the second resin 9. The crosslinking method will be described later.

[0030] In order to achieve both flatness of the surface of the work and followability to warpage of the work, the polishing pad of the present disclosure has the hardness of the first resin 8 preferably 1.2 times or more the hardness of the other region (second resin 9), and more preferably twice or more and 10 times or less the hardness of the other region (second resin 9).

[0031] For the same reason, the polishing pad of the present disclosure has the hardness of the first resin 8 preferably 20 MPa or more and 100 MPa or less, more preferably 25 MPa or more and 60 MPa or less, and further preferably 26 MPa or more and 58 MPa or less. The hardness refers to a nano-indenter hardness which will be described later.

[0032] Similarly, in order to ensure followability to a warpage of the work, thickness of the first resin (the thickness of the surface layer 6 in the minus z direction) is preferably 0.1 μm or more and 100 μm or less, and more preferably 5 μm or more and 50 μm or less.

[0033] The polishing pad 10 is a resin formed product. That is, the polishing surface 6S, the surface layer 6 and the underlayer 7 are integrally formed together without interposing an adhesive agent. The raw material of the resin material (a resin including a void), which is a cured product included in the resin formed product, is not particularly limited, but examples of the raw material to be used include: polyurethane, polyethylene, polypropylene, polystyrene, polyester, nylon, polyvinyl chloride, polyvinylidene chloride, polybutene, polyacetal, polyphenylene oxide, polyvinyl alcohol, polymethyl methacrylate, polysulfone, polyethersulfone, polyetherketone, polyether ether ketone, polyamideimide, polycarbonate, polyarylate, Liquid crystal polymers, aromatic polysulfone resins, biodegradable polyester resins, polyamide resins, polyimide resins, fluororesins, ethylene-propylene resins, ethylene-ethyl acrylate resins, epoxy resins, acrylic resins, norbornene resins, styrene copolymers (for example, vinyl polyisoprene-styrene copolymers, butadiene-styrene copolymers, acrylonitrile-styrene copolymers and acrylonitrile-butadiene-styrene copolymers), natural rubbers, synthetic rubbers and thermoplastic elastomers.

[0034] These examples of the resin material may be used alone, or the materials may be mixed or copolymerized. From a viewpoint of excellent abrasion resistance and easier production process, in the polishing pad of the present disclosure, the resin having the void preferably includes polyurethane as a main component, and the first resin preferably includes a polyurethane having an allophanate bond.

[0035] In the present disclosure, a main component of the resin formed product refers to, when a resin formed product includes a plurality of resin materials, a resin material (component) that is heaviest in mass of all the resin materials included in the resin formed product. The proportion of polyurethane in the resin formed product is 50 mass % or more, and preferably 70 mass % or more. The proportion is more preferably 90 mass % or more.

[0036] As described above, the polishing pad 10 of the present disclosure may achieve both an ability of improving the flatness of the polished work (a polished object) and a followability to warpage by using the polishing pad 10 if the hardness of the resin region of the surface layer 6 is higher than the hardness of the resin region of the underlayer 7, whereby high processing quality may be obtained.

[0037] When a value of a circle-equivalent diameter of the void in the polishing surface is defined as a void diameter of a front surface, and a value of a circle-equivalent diameter of the void in a surface opposite to the polishing surface is defined as a void diameter of a back surface, the polishing pad of the present disclosure may achieve high polishing rate if a difference between the void diameter of the front surface and the void diameter of the back surface is within 15%. Therefore, the polishing pad of the present disclosure may achieve a higher polishing rate while obtaining high processing quality than conventional polishing pads.Second Embodiment

[0038] The second embodiment is about a method for producing a polishing pad.

[0039] The method for producing a polishing pad of the present disclosure is a method including: preparing a resin including a void; and subjecting a surface layer including one surface of the resin to curing treatment to provide a cured resin having a higher hardness than a hardness of an other region of the resin, wherein, when a circle-equivalent diameter of the void in the cured surface is defined as a void diameter of a front surface, and a circle-equivalent diameter of the void in a surface opposite to the cured surface is defined as a void diameter of a back surface, a difference between the void diameter of the front surface and the void diameter of the back surface is within 15%.

[0040] Next, the method for producing a first resin 8 of a surface layer 6 of a polishing pad 10 will be described. The method for producing the polishing pad 10 of the present disclosure is not particularly limited, but a preferred aspect will be described. In the production method of the present disclosure, the first resin 8 is produced by irradiating a resin including a void with, for example, ionizing radiation to promote crosslinking of the resin of the surface layer of the polishing pad.

[0041] In the polyurethane resin that forms a resin including a void, an uncrosslinked urethane bond having a linear main chain is present. In the curing, for example, irradiation of ionizing radiation cut the molecular chain of the uncrosslinked urethane resin to form an allophanate bond having a branch structure when re-crosslinking occurs. The allophanate bond enables formation of a first resin.

[0042] Each process will hereinafter be described in detail. Each item described in the First Embodiment will be omitted.(Preparing)

[0043] The method for producing the polishing pad of the present disclosure includes preparing a resin including a void. First, a resin including a void is prepared. The resin including a void is, for example, polyurethane as described above. A ready-made resin including a void may be procured from outside, or the resin may be produced by chemical synthesis. Then, the resin including a void is cut into a desired shape, and then adhered to a base for holding.

[0044] The hardness of the resin including a void used here is preferably 10 MPa or more and 40 MPa or less, and the void area proportion is preferably 40% or more and 80% or less. The method for adhering the resin including a void to the base is not particularly limited, but the adhesion may be performed by, for example, using a double-sided tape (manufactured by Nitto Denko Corporation: No5000NS).(Heating)

[0045] The method for producing the polishing pad of the present disclosure preferably further includes heating the resin before the curing, and the resin is preferably heated at 100° C. or more and 180° C. or less for 1 hour or more in the heating. The heating method is, for example, heating with an oven, but the method is not limited to the heating with an oven as long as the heating may be performed.

[0046] The moisture content in the resin including a void is reduced by the heating. The reason is that a large moisture content may inhibit cutting of the molecular chain of urethane and re-crosslinking reaction during irradiation of ionizing radiation in the curing. After the heating, it is preferred that the resin is taken out of the oven and then cooled to room temperature. The cooling is preferably performed in a desiccator in which humidity is controlled.(Curing)

[0047] The method for producing the polishing pad of the present disclosure includes subjecting a surface layer including one surface of the resin to curing treatment to provide a cured resin having a higher hardness than a hardness of the other region of the resin. The curing method in the curing is preferably a method by irradiation of ionizing radiation, but the method may be, for example, a method by treatment with a chemical agent. The method is not limited to these methods, as long as the curing may be performed. In the present disclosure, a method by irradiation of ionizing radiation will be described.

[0048] Where the resin including a void is irradiated with ionizing radiation, examples of the ionizing radiation include y ray, electron beam, X ray, neutron beam and high-energy ion. Of these, from a viewpoint of versatility of the apparatus, electron beam is preferred. Irradiation of electron beam is performed in the present Examples.

[0049] Here, depth of the first resin layer to be formed may be controlled by changing a dose and an irradiation time. In the method for producing the polishing pad of the present disclosure, it is preferred that an allophanate bond is formed in the one surface of the resin in the curing.

[0050] The typical dose of the ionizing radiation for the curing is in the range of 1 to 1000 kGy, and in particular in the range of 50 to 200 kGy, and the dose needed to allow the uncrosslinked urethane resin to form an allophanate bond may be appropriately selected. The irradiation time is preferably 10 minutes or more and, similarly, the time needed to allow the uncrosslinked urethane resin to form an allophanate bond may be appropriately selected.

[0051] The resin including a void may be heated in the irradiation of ionizing radiation. The irradiation of the ionizing radiation is preferably performed under an atmosphere of low oxygen, in particular, under an atmosphere substantially free from oxygen. As a specific atmosphere, an atmosphere of an oxygen concentration of 1000 ppm or less is preferred.

[0052] As long as the oxygen concentration is 1000 ppm or less, the irradiation may be performed in vacuum or under an atmosphere of an inert gas such as nitrogen and argon. From the viewpoint of the cost, a nitrogen atmosphere is preferred. Thus, the polishing pad produced by the method for producing the polishing pad of the present disclosure may obtain high processing quality by providing a first resin.

[0053] In the method for producing the polishing pad of the present disclosure, when a circle-equivalent diameter of the void in the cured surface is defined as a void diameter of a front surface, and a circle-equivalent diameter of the void in a surface opposite to the cured surface is defined as a void diameter of a back surface, a difference between the void diameter of the front surface and the void diameter of the back surface is within 15%. The difference between the void diameter of the front surface and the void diameter of the back surface is preferably 5% or more and 13% or less, and more preferably 5.1% or more and 12.8% or less.

[0054] Here, the difference between the void diameter of the front surface and the void diameter of the back surface refers to a value obtained by dividing the absolute value of the difference between the void diameter of the front surface and the void diameter of the back surface by the void diameter of the back surface. The circle-equivalent diameter is specifically a diameter of a circle having the same region as the projected region of the void.

[0055] In this manner, the polishing pad produced by the method for producing the polishing pad of the present disclosure may achieve high polishing rate. Therefore, the polishing pad produced by the method for producing the polishing pad of the present disclosure may achieve a higher polishing rate while obtaining high processing quality than conventional polishing pads.Third Embodiment

[0056] The third embodiment is about a method for producing a polished object.

[0057] The method for producing a polished aspect of the present disclosure includes polishing an object to be polished with the polishing pad.

[0058] The description on polishing of an object to be polished with a polishing pad is as described above (for example, the description in the [Polishing Apparatus]), and polishing methods using a polishing apparatus are known techniques and, accordingly, description on the detail of the methods will be omitted.EXAMPLES

[0059] The present disclosure will hereinafter be described with reference to Examples in more detail, but the present disclosure is not limited thereby.

[0060] Before description on examples of production, a method for evaluating Examples and Comparative Examples will be described.<Hardness of Resin>

[0061] The hardness of the first resin and the hardness of the resin of the underlayer were measured in the following manner. A nano indenter (manufactured by Agilent Technologies Japan, Ltd.: G-200) was used as a measurement apparatus. The polishing pad was cut into a piece of around 3 cm square and set on the measurement base. The resin region of the polishing pad was selected as a measurement range, and the measurement was performed and the average value of the values measured at 10 places was defined as the hardness.

[0062] The hardness of the underlayer of the polishing pad was measured by a method in which the pad is cut in the thickness direction and the cross-section is measured, or a method in which the pad is cut in a direction parallel to the thickness direction and the parallel section is measured. For the hardness of the first resin, the pad was cut in the thickness direction, and the hardness of the cross-section was measured at a plurality of places in the thickness direction to determine the hardness from the variation in the measured values.<Void Area Proportion>

[0063] The void area proportion was evaluated in the following manner. By using a color 3D laser microscope (manufactured by KEYENCE CORPORATION: VK-9700) as a measurement apparatus, the surface of the polishing pad (front surface) was measured at 10 places with a 10× objective lens. The measured image was binarized by using an image-processing software (manufactured by National Institutes of Health: ImageJ) to separate the resin region from the void region of the polishing pad.

[0064] In order to remove noise, a void having a region of 200 μm2 or more was determined as a void. The void area proportion was calculated by totaling the region of the void region and then dividing the total by the region of the whole image. The void area proportion of the surface opposite to the surface of the polishing pad (back surface) was calculated in the same manner.<Average Void Diameter>

[0065] The average void diameter was evaluated in the following manner. By using a color 3D laser microscope (manufactured by KEYENCE CORPORATION: VK-9700) as a measurement apparatus, the surface of the polishing pad (front surface) was measured at 10 places with a 10× objective lens. The measured image was binarized by using an image-processing software (manufactured by National Institutes of Health: ImageJ) to separate the resin region from the void region of the polishing pad.

[0066] In order to remove noise, a void having a region of 200 μm2 or more was determined as a void. Voids were each shaped to a shape close to a circle, and the void diameter of each of the void was calculated from the region of the void. The average value of the void diameters was defined as an average void diameter. The average void diameter of the surface opposite to the surface of the polishing pad (back surface) was determined in the same manner. The difference in the average void diameter described in Table 1 refers to a difference between the average void diameter of the front surface and the average void diameter of the back surface, and the difference is a value obtained by dividing the absolute value of the difference between the average void diameter of the front surface and the average void diameter of the back surface by the average void diameter of the back surface.<Polishing Rate>

[0067] The polishing rate was evaluated in the following manner. S-FSL5 (manufactured by OHARA INC.) (Φ: 50; thickness: 10 mm) was used as a glass material of the glass substrate to be polished. To prepare the slurry used for the polishing, cerium oxide (manufactured by MITSUI MINING & SMELTING CO., LTD.: HL40) and water were mixed together and then the content of cerium oxide was adjusted to 1 wt %.

[0068] The polishing pad was fixed on the base plate with a double-sided tape, and polishing was performed while supplying the slurry at a rotation speed of the base plate of 500 rpm for 30 minutes. The masses of the glass substrate before and after the polishing were measured, and the polishing rate was calculated from the mass difference.

[0069] The value of the polishing rate was evaluated based on the following criteria, and where the polishing rate was evaluated as A or B, the polishing pad was determined to have a sufficient polishing ability and therefore have high polishing rate.

[0070] A: polishing rate of 1.3 μm / min or more

[0071] B: polishing rate of 0.5 μm / min or more and less than 1.3 μm / min

[0072] C: polishing rate of less than 0.5 μm / min<Processing Quality>

[0073] The processing quality was evaluated in the following manner. The lens polished by using the following polishing pad was evaluated for the flatness of the surface of the lens with an interferometer (manufactured by ZYGO: Verifire). The flatness was evaluated from the numerical value of the flatness based on the following criteria, and where the flatness was evaluated as A or B, it was determined that a sufficient processing quality might be ensured.

[0074] A: flatness of less than 10 nm

[0075] B: flatness of 10 nm or more and less than 30 nm

[0076] C: flatness of 30 nm or moreExample 1

[0077] A urethane pad including cerium oxide (manufactured by KOKONOE ELECTRIC Co., Ltd.: KSP66A, thickness: 0.5 mm) was used as a resin including a void. The resin including a void was fixed on the base plate with a double-sided tape, and then was heated in an oven at 100° C. for 1 hour. Thereafter, the resin including a void was taken out of the oven and allowed to stand to be cooled to room temperature.

[0078] Next, the resin including a void was irradiated with electron beam in order to promote crosslinking in the front surface of the resin. The resin including a void was irradiated with electron beam at a dose of 100 kGy for 20 minutes to obtain a polishing pad 1 having a first resin in the surface layer.Example 2

[0079] A urethane pad including cerium oxide (manufactured by KOKONOE ELECTRIC Co., Ltd.: KSP66A, thickness: 0.5 mm) was used as a resin including a void. The resin including a void was fixed on the base plate with a double-sided tape, and then was heated in an oven at 100° C. for 1 hour. Thereafter, the resin including a void was taken out of the oven and allowed to stand to be cooled to room temperature.

[0080] Next, the resin including a void was irradiated with electron beam in order to promote crosslinking in the front surface of the resin. The resin including a void was irradiated with electron beam at a dose of 100 kGy for 10 minutes to obtain a polishing pad 2 having a first resin in the surface layer.Example 3

[0081] A filler-free urethane pad (manufactured by KOKONOE ELECTRIC Co., Ltd.: KSP90, thickness: 0.5 mm) was used as a resin including a void. The resin including a void was fixed on the base plate with a double-sided tape, and then was heated in an oven at 100° C. for 1 hour. Thereafter, the resin including a void was taken out of the oven and allowed to stand to be cooled to room temperature.

[0082] Next, the resin including a void was irradiated with electron beam in order to promote crosslinking in the front surface of the resin. The resin including a void was irradiated with electron beam at a dose of 150 kGy for 10 minutes to obtain a polishing pad 3 having a first resin in the surface layer.Example 4

[0083] A filler-free urethane pad (manufactured by Fujibo Ehime Co., Ltd.: FXA9H, thickness: 0.8 mm) was used as a resin including a void. The resin including a void was fixed on the base plate with a double-sided tape, and then was heated in an oven at 100° C. for 1 hour. Thereafter, the resin including a void was taken out of the oven and allowed to stand to be cooled to room temperature.

[0084] Next, the resin including a void was irradiated with electron beam in order to promote crosslinking in the front surface of the resin. The resin including a void was irradiated with electron beam at a dose of 150 kGy for 10 minutes to obtain a polishing pad 4 having a first resin in the surface layer.Example 5

[0085] A urethane pad including cerium oxide (manufactured by KOKONOE ELECTRIC Co., Ltd.: KSP66A, thickness: 0.5 mm) was used as a resin including a void. The resin including a void was fixed on the base plate with a double-sided tape, and then was heated in an oven at 100° C. for 1 hour. Thereafter, the resin including a void was taken out of the oven and allowed to stand to be cooled to room temperature.

[0086] Next, the resin including a void was irradiated with electron beam in order to promote crosslinking in the front surface of the resin. The resin including a void was irradiated with electron beam at a dose of 50 kGy for 3 minutes to obtain a polishing pad 5 having a first resin in the surface layer.Comparative Example 1

[0087] A urethane pad including cerium oxide (manufactured by KOKONOE ELECTRIC Co., Ltd.: KSP66A, thickness: 0.5 mm) was used as a resin including a void. The resin including a void was fixed on the base plate with a double-sided tape, and then was heated in an oven at 100° C. for 1 hour. Thereafter, the resin including a void was taken out of the oven and allowed to stand to be cooled to room temperature to obtain a polishing pad 6. In Comparative Example 1, the resin was not irradiated with electron beam.Comparative Example 2

[0088] A urethane pad including cerium oxide (manufactured by KOKONOE ELECTRIC Co., Ltd.: KSP66A, thickness: 0.5 mm) was used as a resin including a void. The resin including a void was irradiated with a laser to form a void having a diameter of approximately 450 μm in the surface layer. The resin including a void was fixed on the base plate with a double-sided tape, and then was heated in an oven at 100° C. for 1 hour. Thereafter, the resin including a void was taken out of the oven and allowed to stand to be cooled to room temperature.

[0089] Next, the resin including a void was irradiated with electron beam in order to promote crosslinking in the front surface of the resin. The resin including a void was irradiated with electron beam at a dose of 50 kGy for 3 minutes to obtain a polishing pad 7 having a first resin in the surface layer.

[0090] The evaluation results of the polishing pads of Examples 1 to 5 and Comparative Examples 1 and 2 are shown in Table 1. The polishing pads of Comparative Examples resulted in failure in achieving both high processing quality and high polishing rate. On the other hand, the polishing pad of each Example was found that both high processing quality and high polishing rate might be achieved because the polishing pad had a first resin in the surface layer and had a small difference in the average void diameter.TABLE 1Void areaHardnessHardnessThicknessAverage void diameterproportionof firstof resin ofof firstFrontBackFrontBackresinunderlayerresinsurfacesurfaceDifferencesurfacesurfacePolishingProcessing(MPa)(MPa)(μm)(μm)(μm)(%)(%)(%)ratequalityExample 15816502502624.670.275.6AAExample 24318352362505.669.571.6AAExample 336154210211712.863.562.6ABExample 431143861577.030.933.5BAExample 5261252422555.176.873.6ABComparative—1402572483.673.272.2ACExample 1Comparative2115545026669.279.875.4BCExample 2

[0091] As described above, according to the polishing pad of the present disclosure, high flatness of the processed surface of the polished object may be obtained because the polishing pad has a hard surface layer, and the followability to a shape of the work is high because the underlayer of the polishing pad may have flexibility. Also, according to the polishing pad of the present disclosure, high polishing rate may be achieved because the polishing pad has an appropriate void diameter.

[0092] While the present disclosure has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

[0093] This application claims the benefit of Japanese Patent Application No. 2024-069291, filed Apr. 22, 2024, which is hereby incorporated by reference herein in its entirety.

Examples

first embodiment

[0015]The first embodiment is about a polishing pad.

[0016]The polishing pad of the present disclosure is a polishing pad having a resin including a void, wherein a surface layer including a surface to be a polishing surface of the resin is a first resin having a higher hardness than a hardness of an other region of the resin, and wherein, when a value of a circle-equivalent diameter of the void in the polishing surface is defined as a void diameter of a front surface, and a value of a circle-equivalent diameter of the void in a surface opposite to the polishing surface is defined as a void diameter of a back surface, a difference between the void diameter of the front surface and the void diameter of the back surface is within 15%.

[0017]The embodiment will hereinafter be described.

[Polishing Apparatus]

[0018]The polishing apparatus of the present disclosure includes a polishing pad of the present disclosure, a fixing part for fixing the polishing pad, and a holding part for holding a...

second embodiment

[0038]The second embodiment is about a method for producing a polishing pad.

[0039]The method for producing a polishing pad of the present disclosure is a method including: preparing a resin including a void; and subjecting a surface layer including one surface of the resin to curing treatment to provide a cured resin having a higher hardness than a hardness of an other region of the resin, wherein, when a circle-equivalent diameter of the void in the cured surface is defined as a void diameter of a front surface, and a circle-equivalent diameter of the void in a surface opposite to the cured surface is defined as a void diameter of a back surface, a difference between the void diameter of the front surface and the void diameter of the back surface is within 15%.

[0040]Next, the method for producing a first resin 8 of a surface layer 6 of a polishing pad 10 will be described. The method for producing the polishing pad 10 of the present disclosure is not particularly limited, but a pre...

third embodiment

[0056]The third embodiment is about a method for producing a polished object.

[0057]The method for producing a polished aspect of the present disclosure includes polishing an object to be polished with the polishing pad.

[0058]The description on polishing of an object to be polished with a polishing pad is as described above (for example, the description in the [Polishing Apparatus]), and polishing methods using a polishing apparatus are known techniques and, accordingly, description on the detail of the methods will be omitted.

BACKGROUNDTechnical Field

[0001] The present technique relates to a polishing pad for finishing the surface of an object to be polished flat, a polishing apparatus, a method for producing the polishing pad and a method for producing a polished object.Description of the Related Art

[0002] Conventionally, in optical materials such as optical lenses and reflecting mirrors as well as materials such as substrates for hard discs, silicon wafers, and glass substrates for liquid crystal displays (polished objects), highly accurate flatness has been required and, therefore they have been submitted to polish processing using a polishing pad. In such a polish processing, the polishing pad is stuck to a base, and the processing is performed by supplying a polishing liquid including a polishing particle between an object to be polished and the polishing pad, while allowing the object to be polished and the polishing pad to be in contact with each other and to relatively move.

[0003] As the polishing pad, a pad having various properties that hardness and Young's modulus in the thickness direction are various is widely used, which is because high processing quality may be obtained by providing a hard layer having moderate stiffness in the polishing surface in order to improve the flatness, and providing a soft layer having an elasticity sufficient to follow warpage of a wafer in a layer under the hard layer.

[0004] For example, in Japanese Patent Application Laid-Open No. 2003-220550, a void diameter of a surface layer including a polishing surface is set small to increase an apparent hardness, thereby forming a layer. The void diameter of a layer under the hard layer is set large to reduce the apparent hardness, thereby forming a soft layer. In this manner, high processing quality is achieved.SUMMARY

[0005] The present disclosure is a polishing pad comprising a resin having a void, wherein the resin includes a first resin and a second resin, a hardness of the first resin being higher than a hardness of the second resin, wherein a surface layer forming a polishing surface of the polishing pad comprises the first resin, wherein a region of the polishing pad comprises the second resin, and wherein, when a value of a circle-equivalent diameter of the void in the polishing surface is defined as a void diameter of a front surface, and a value of a circle-equivalent diameter of the void in a surface of the polishing pad opposite to the polishing surface is defined as a void diameter of a back surface, a difference between the void diameter of the front surface and the void diameter of the back surface is within 15%.

[0006] In addition, the present disclosure is a polishing apparatus including: the polishing pad; a fixing part for fixing the polishing pad; and a holding part for holding an object to be polished.

[0007] In addition, the present disclosure is a method for producing a polishing pad, the method including: preparing a resin including a void; and subjecting a surface layer including one surface of the resin to curing treatment to provide a cured resin layer having a higher hardness than a hardness of an other region of the resin, wherein, when a circle-equivalent diameter of the void in the cured surface is defined as a void diameter of a front surface, and a circle-equivalent diameter of the void in a surface opposite to the cured surface is defined as a void diameter of a back surface, a difference between the void diameter of the front surface and the void diameter of the back surface is within 15%.

[0008] In addition, the present disclosure is a method for producing a polished object including polishing an object to be polished with the polishing pad.

[0009] Further features of the present disclosure will become apparent from the following description of exemplary embodiments with reference to the attached drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0010] FIG. 1 is a schematic view of the polishing apparatus of the present disclosure.

[0011] FIG. 2A is a schematic perspective view of the polishing pad of the present disclosure.

[0012] FIG. 2B is a sectional view along the A-A straight line of FIG. 2A.DESCRIPTION OF THE EMBODIMENTS

[0013] Example embodiments of the present disclosure will now be described in detail in accordance with the accompanying drawings.

[0014] Using a conventional polishing pad in which the void diameter of the surface layer is set small to form a hard layer causes a problem that polishing rate decreases. The void (e.g., air bubble) is formed by a spherical recess in the polishing pad, and the void holds the polishing slurry and supplies polishing slurry to the surface being processed. Reducing the void in size decreases the holding performance of the slurry to deteriorate the property of supplying the slurry to the surface being processed, thereby decreasing the polishing rate. Accordingly, an aspect of the present disclosure is to provide a polishing pad that may achieve high polishing rate and high processing quality.First Embodiment

[0015] The first embodiment is about a polishing pad.

[0016] The polishing pad of the present disclosure is a polishing pad having a resin including a void, wherein a surface layer including a surface to be a polishing surface of the resin is a first resin having a higher hardness than a hardness of an other region of the resin, and wherein, when a value of a circle-equivalent diameter of the void in the polishing surface is defined as a void diameter of a front surface, and a value of a circle-equivalent diameter of the void in a surface opposite to the polishing surface is defined as a void diameter of a back surface, a difference between the void diameter of the front surface and the void diameter of the back surface is within 15%.

[0017] The embodiment will hereinafter be described.[Polishing Apparatus]

[0018] The polishing apparatus of the present disclosure includes a polishing pad of the present disclosure, a fixing part for fixing the polishing pad, and a holding part for holding an object to be polished. FIG. 1 is a schematic view of the polishing apparatus of the present disclosure. A polishing apparatus 1 is a wet polish-processing apparatus that has a polishing pad 10, a base 5 for fixing and holding the polishing pad 10 (a fixing part for fixing the polishing pad), a supply part 2 for supplying a polishing slurry S including water, a chemical liquid, and etc. to a polishing surface of the polishing pad 10, and a carrier holding base 4 (a holding part for holding an object to be polished).

[0019] In FIG. 1, the carrier holding base 4 (a holding part for holding an object to be polished) applies a pressure to a work 3, which is an object to be processed, from above to hold the work 3 so that the work 3 is in contact with the polishing surface of the polishing pad 10, and the polish processing of the work 3 is performed in this configuration.

[0020] Examples of the work 3 (an object to be polished) include: semiconductor substrates; optical materials such as optical lenses and reflecting mirrors; substrates for hard discs; silicon wafers; and glass substrates for liquid crystal displays. Herein, a work 3 that has been subjected to polish processing is defined as an object.[Polishing Pad]

[0021] The polishing pad of the present disclosure is a polishing pad having a resin including a void. FIGS. 2A and 2B are each a schematic view of the polishing pad of the present disclosure. FIG. 2A is a perspective view, and FIG. 2B is an A-A sectional view when the polishing pad is cut from a z-axis direction passing along an A-A straight line of FIG. 2A.

[0022] In FIGS. 2A and 2B, a surface horizontal to a polishing surface 6S is defined as an xy plane, and an axis perpendicular to the xy plane is defined as the z axis. The A-A straight line illustrated with a dashed line in FIG. 2A is parallel to the x axis, and orthogonal to a y axis.

[0023] The polishing pad 10 has, from the polishing surface 6S, in a minus z direction, a surface layer 6 and an underlayer 7 laid side by side. The surface layer 6 has a polishing surface 6S. The polishing surface 6S is a portion of the polishing pad 10 to be in touch with the work 3.

[0024] The surface layer 6 and the underlayer 7 each have a void 11. The void 11 has a function of holding the slurry S and supplying the slurry to the polishing surface 6S. In the present disclosure, the polishing surface 6S of the polishing pad is referred to as a front surface, and a surface opposite to the polishing surface 6S is referred to as a back surface.

[0025] In the polishing pad of the present disclosure, when a value of a circle-equivalent diameter of the void in the polishing surface 6S is defined as a void diameter of a front surface, and a value of a circle-equivalent diameter of the void in a surface opposite to the polishing surface 6S is defined as a void diameter of a back surface, a difference between the void diameter of the front surface and the void diameter of the back surface is within 15%. The difference between the void diameter of the front surface and the void diameter of the back surface is preferably 5% or more and 13% or less, and more preferably 5.1% or more and 12.8% or less.

[0026] Here, the difference between the void diameter of the front surface and the void diameter of the back surface refers to a value obtained by dividing an absolute value of the difference between the void diameter of the front surface and the void diameter of the back surface by the void diameter of the back surface. The circle-equivalent diameter is specifically a diameter of a circle having the same region as the projected region of the void. In this manner, the polishing pad of the present disclosure may achieve high polishing rate.

[0027] In the polishing pad of the present disclosure, when a proportion of a region of the void in the polishing surface based on a region of the polishing surface is defined as a void area proportion of the front surface, and a proportion of a region of the void in the surface opposite to the polishing surface based on a region of the surface opposite to the polishing surface is defined as the void area proportion of the back surface, a difference between the void area proportion of the front surface and the void area proportion of the back surface is preferably within 10% (−10% or more and +10% or less). In this manner, the polishing pad of the present disclosure may achieve a higher polishing rate.

[0028] For the same reason, in the polishing pad of the present disclosure, the average void diameter of the front surface is preferably 100 μm or more and 500 μm or less, and more preferably 150 μm or more and 300 μm or less. The void area proportion of the front surface is not particularly limited, but is, for example, in the range of 40% or more and 80% or less. In order to obtain a higher polishing rate, the difference between an average void density of the front surface and an average void density of the back surface is preferably within ±10%.

[0029] In the polishing pad of the present disclosure, the surface layer 6 including a surface to be a polishing surface of the resin is a first resin 8 having a higher hardness than a hardness of the other region of the resin (second resin 9). The surface layer 6 has the first resin 8, and the underlayer 7 has the second resin 9. The first resin 8 is integrally formed with the second resin 9 to be a resin formed product, and a same raw material is used for each of the first resin 8 and the second resin 9. The first resin 8 has been imparted with a higher hardness than the hardness of the second resin 9 by further promoting crosslinking after the first resin 8 is integrally formed with the second resin 9. The crosslinking method will be described later.

[0030] In order to achieve both flatness of the surface of the work and followability to warpage of the work, the polishing pad of the present disclosure has the hardness of the first resin 8 preferably 1.2 times or more the hardness of the other region (second resin 9), and more preferably twice or more and 10 times or less the hardness of the other region (second resin 9).

[0031] For the same reason, the polishing pad of the present disclosure has the hardness of the first resin 8 preferably 20 MPa or more and 100 MPa or less, more preferably 25 MPa or more and 60 MPa or less, and further preferably 26 MPa or more and 58 MPa or less. The hardness refers to a nano-indenter hardness which will be described later.

[0032] Similarly, in order to ensure followability to a warpage of the work, thickness of the first resin (the thickness of the surface layer 6 in the minus z direction) is preferably 0.1 μm or more and 100 μm or less, and more preferably 5 μm or more and 50 μm or less.

[0033] The polishing pad 10 is a resin formed product. That is, the polishing surface 6S, the surface layer 6 and the underlayer 7 are integrally formed together without interposing an adhesive agent. The raw material of the resin material (a resin including a void), which is a cured product included in the resin formed product, is not particularly limited, but examples of the raw material to be used include: polyurethane, polyethylene, polypropylene, polystyrene, polyester, nylon, polyvinyl chloride, polyvinylidene chloride, polybutene, polyacetal, polyphenylene oxide, polyvinyl alcohol, polymethyl methacrylate, polysulfone, polyethersulfone, polyetherketone, polyether ether ketone, polyamideimide, polycarbonate, polyarylate, Liquid crystal polymers, aromatic polysulfone resins, biodegradable polyester resins, polyamide resins, polyimide resins, fluororesins, ethylene-propylene resins, ethylene-ethyl acrylate resins, epoxy resins, acrylic resins, norbornene resins, styrene copolymers (for example, vinyl polyisoprene-styrene copolymers, butadiene-styrene copolymers, acrylonitrile-styrene copolymers and acrylonitrile-butadiene-styrene copolymers), natural rubbers, synthetic rubbers and thermoplastic elastomers.

[0034] These examples of the resin material may be used alone, or the materials may be mixed or copolymerized. From a viewpoint of excellent abrasion resistance and easier production process, in the polishing pad of the present disclosure, the resin having the void preferably includes polyurethane as a main component, and the first resin preferably includes a polyurethane having an allophanate bond.

[0035] In the present disclosure, a main component of the resin formed product refers to, when a resin formed product includes a plurality of resin materials, a resin material (component) that is heaviest in mass of all the resin materials included in the resin formed product. The proportion of polyurethane in the resin formed product is 50 mass % or more, and preferably 70 mass % or more. The proportion is more preferably 90 mass % or more.

[0036] As described above, the polishing pad 10 of the present disclosure may achieve both an ability of improving the flatness of the polished work (a polished object) and a followability to warpage by using the polishing pad 10 if the hardness of the resin region of the surface layer 6 is higher than the hardness of the resin region of the underlayer 7, whereby high processing quality may be obtained.

[0037] When a value of a circle-equivalent diameter of the void in the polishing surface is defined as a void diameter of a front surface, and a value of a circle-equivalent diameter of the void in a surface opposite to the polishing surface is defined as a void diameter of a back surface, the polishing pad of the present disclosure may achieve high polishing rate if a difference between the void diameter of the front surface and the void diameter of the back surface is within 15%. Therefore, the polishing pad of the present disclosure may achieve a higher polishing rate while obtaining high processing quality than conventional polishing pads.Second Embodiment

[0038] The second embodiment is about a method for producing a polishing pad.

[0039] The method for producing a polishing pad of the present disclosure is a method including: preparing a resin including a void; and subjecting a surface layer including one surface of the resin to curing treatment to provide a cured resin having a higher hardness than a hardness of an other region of the resin, wherein, when a circle-equivalent diameter of the void in the cured surface is defined as a void diameter of a front surface, and a circle-equivalent diameter of the void in a surface opposite to the cured surface is defined as a void diameter of a back surface, a difference between the void diameter of the front surface and the void diameter of the back surface is within 15%.

[0040] Next, the method for producing a first resin 8 of a surface layer 6 of a polishing pad 10 will be described. The method for producing the polishing pad 10 of the present disclosure is not particularly limited, but a preferred aspect will be described. In the production method of the present disclosure, the first resin 8 is produced by irradiating a resin including a void with, for example, ionizing radiation to promote crosslinking of the resin of the surface layer of the polishing pad.

[0041] In the polyurethane resin that forms a resin including a void, an uncrosslinked urethane bond having a linear main chain is present. In the curing, for example, irradiation of ionizing radiation cut the molecular chain of the uncrosslinked urethane resin to form an allophanate bond having a branch structure when re-crosslinking occurs. The allophanate bond enables formation of a first resin.

[0042] Each process will hereinafter be described in detail. Each item described in the First Embodiment will be omitted.(Preparing)

[0043] The method for producing the polishing pad of the present disclosure includes preparing a resin including a void. First, a resin including a void is prepared. The resin including a void is, for example, polyurethane as described above. A ready-made resin including a void may be procured from outside, or the resin may be produced by chemical synthesis. Then, the resin including a void is cut into a desired shape, and then adhered to a base for holding.

[0044] The hardness of the resin including a void used here is preferably 10 MPa or more and 40 MPa or less, and the void area proportion is preferably 40% or more and 80% or less. The method for adhering the resin including a void to the base is not particularly limited, but the adhesion may be performed by, for example, using a double-sided tape (manufactured by Nitto Denko Corporation: No5000NS).(Heating)

[0045] The method for producing the polishing pad of the present disclosure preferably further includes heating the resin before the curing, and the resin is preferably heated at 100° C. or more and 180° C. or less for 1 hour or more in the heating. The heating method is, for example, heating with an oven, but the method is not limited to the heating with an oven as long as the heating may be performed.

[0046] The moisture content in the resin including a void is reduced by the heating. The reason is that a large moisture content may inhibit cutting of the molecular chain of urethane and re-crosslinking reaction during irradiation of ionizing radiation in the curing. After the heating, it is preferred that the resin is taken out of the oven and then cooled to room temperature. The cooling is preferably performed in a desiccator in which humidity is controlled.(Curing)

[0047] The method for producing the polishing pad of the present disclosure includes subjecting a surface layer including one surface of the resin to curing treatment to provide a cured resin having a higher hardness than a hardness of the other region of the resin. The curing method in the curing is preferably a method by irradiation of ionizing radiation, but the method may be, for example, a method by treatment with a chemical agent. The method is not limited to these methods, as long as the curing may be performed. In the present disclosure, a method by irradiation of ionizing radiation will be described.

[0048] Where the resin including a void is irradiated with ionizing radiation, examples of the ionizing radiation include y ray, electron beam, X ray, neutron beam and high-energy ion. Of these, from a viewpoint of versatility of the apparatus, electron beam is preferred. Irradiation of electron beam is performed in the present Examples.

[0049] Here, depth of the first resin layer to be formed may be controlled by changing a dose and an irradiation time. In the method for producing the polishing pad of the present disclosure, it is preferred that an allophanate bond is formed in the one surface of the resin in the curing.

[0050] The typical dose of the ionizing radiation for the curing is in the range of 1 to 1000 kGy, and in particular in the range of 50 to 200 kGy, and the dose needed to allow the uncrosslinked urethane resin to form an allophanate bond may be appropriately selected. The irradiation time is preferably 10 minutes or more and, similarly, the time needed to allow the uncrosslinked urethane resin to form an allophanate bond may be appropriately selected.

[0051] The resin including a void may be heated in the irradiation of ionizing radiation. The irradiation of the ionizing radiation is preferably performed under an atmosphere of low oxygen, in particular, under an atmosphere substantially free from oxygen. As a specific atmosphere, an atmosphere of an oxygen concentration of 1000 ppm or less is preferred.

[0052] As long as the oxygen concentration is 1000 ppm or less, the irradiation may be performed in vacuum or under an atmosphere of an inert gas such as nitrogen and argon. From the viewpoint of the cost, a nitrogen atmosphere is preferred. Thus, the polishing pad produced by the method for producing the polishing pad of the present disclosure may obtain high processing quality by providing a first resin.

[0053] In the method for producing the polishing pad of the present disclosure, when a circle-equivalent diameter of the void in the cured surface is defined as a void diameter of a front surface, and a circle-equivalent diameter of the void in a surface opposite to the cured surface is defined as a void diameter of a back surface, a difference between the void diameter of the front surface and the void diameter of the back surface is within 15%. The difference between the void diameter of the front surface and the void diameter of the back surface is preferably 5% or more and 13% or less, and more preferably 5.1% or more and 12.8% or less.

[0054] Here, the difference between the void diameter of the front surface and the void diameter of the back surface refers to a value obtained by dividing the absolute value of the difference between the void diameter of the front surface and the void diameter of the back surface by the void diameter of the back surface. The circle-equivalent diameter is specifically a diameter of a circle having the same region as the projected region of the void.

[0055] In this manner, the polishing pad produced by the method for producing the polishing pad of the present disclosure may achieve high polishing rate. Therefore, the polishing pad produced by the method for producing the polishing pad of the present disclosure may achieve a higher polishing rate while obtaining high processing quality than conventional polishing pads.Third Embodiment

[0056] The third embodiment is about a method for producing a polished object.

[0057] The method for producing a polished aspect of the present disclosure includes polishing an object to be polished with the polishing pad.

[0058] The description on polishing of an object to be polished with a polishing pad is as described above (for example, the description in the [Polishing Apparatus]), and polishing methods using a polishing apparatus are known techniques and, accordingly, description on the detail of the methods will be omitted.EXAMPLES

[0059] The present disclosure will hereinafter be described with reference to Examples in more detail, but the present disclosure is not limited thereby.

[0060] Before description on examples of production, a method for evaluating Examples and Comparative Examples will be described.<Hardness of Resin>

[0061] The hardness of the first resin and the hardness of the resin of the underlayer were measured in the following manner. A nano indenter (manufactured by Agilent Technologies Japan, Ltd.: G-200) was used as a measurement apparatus. The polishing pad was cut into a piece of around 3 cm square and set on the measurement base. The resin region of the polishing pad was selected as a measurement range, and the measurement was performed and the average value of the values measured at 10 places was defined as the hardness.

[0062] The hardness of the underlayer of the polishing pad was measured by a method in which the pad is cut in the thickness direction and the cross-section is measured, or a method in which the pad is cut in a direction parallel to the thickness direction and the parallel section is measured. For the hardness of the first resin, the pad was cut in the thickness direction, and the hardness of the cross-section was measured at a plurality of places in the thickness direction to determine the hardness from the variation in the measured values.<Void Area Proportion>

[0063] The void area proportion was evaluated in the following manner. By using a color 3D laser microscope (manufactured by KEYENCE CORPORATION: VK-9700) as a measurement apparatus, the surface of the polishing pad (front surface) was measured at 10 places with a 10× objective lens. The measured image was binarized by using an image-processing software (manufactured by National Institutes of Health: ImageJ) to separate the resin region from the void region of the polishing pad.

[0064] In order to remove noise, a void having a region of 200 μm2 or more was determined as a void. The void area proportion was calculated by totaling the region of the void region and then dividing the total by the region of the whole image. The void area proportion of the surface opposite to the surface of the polishing pad (back surface) was calculated in the same manner.<Average Void Diameter>

[0065] The average void diameter was evaluated in the following manner. By using a color 3D laser microscope (manufactured by KEYENCE CORPORATION: VK-9700) as a measurement apparatus, the surface of the polishing pad (front surface) was measured at 10 places with a 10× objective lens. The measured image was binarized by using an image-processing software (manufactured by National Institutes of Health: ImageJ) to separate the resin region from the void region of the polishing pad.

[0066] In order to remove noise, a void having a region of 200 μm2 or more was determined as a void. Voids were each shaped to a shape close to a circle, and the void diameter of each of the void was calculated from the region of the void. The average value of the void diameters was defined as an average void diameter. The average void diameter of the surface opposite to the surface of the polishing pad (back surface) was determined in the same manner. The difference in the average void diameter described in Table 1 refers to a difference between the average void diameter of the front surface and the average void diameter of the back surface, and the difference is a value obtained by dividing the absolute value of the difference between the average void diameter of the front surface and the average void diameter of the back surface by the average void diameter of the back surface.<Polishing Rate>

[0067] The polishing rate was evaluated in the following manner. S-FSL5 (manufactured by OHARA INC.) (Φ: 50; thickness: 10 mm) was used as a glass material of the glass substrate to be polished. To prepare the slurry used for the polishing, cerium oxide (manufactured by MITSUI MINING & SMELTING CO., LTD.: HL40) and water were mixed together and then the content of cerium oxide was adjusted to 1 wt %.

[0068] The polishing pad was fixed on the base plate with a double-sided tape, and polishing was performed while supplying the slurry at a rotation speed of the base plate of 500 rpm for 30 minutes. The masses of the glass substrate before and after the polishing were measured, and the polishing rate was calculated from the mass difference.

[0069] The value of the polishing rate was evaluated based on the following criteria, and where the polishing rate was evaluated as A or B, the polishing pad was determined to have a sufficient polishing ability and therefore have high polishing rate.

[0070] A: polishing rate of 1.3 μm / min or more

[0071] B: polishing rate of 0.5 μm / min or more and less than 1.3 μm / min

[0072] C: polishing rate of less than 0.5 μm / min<Processing Quality>

[0073] The processing quality was evaluated in the following manner. The lens polished by using the following polishing pad was evaluated for the flatness of the surface of the lens with an interferometer (manufactured by ZYGO: Verifire). The flatness was evaluated from the numerical value of the flatness based on the following criteria, and where the flatness was evaluated as A or B, it was determined that a sufficient processing quality might be ensured.

[0074] A: flatness of less than 10 nm

[0075] B: flatness of 10 nm or more and less than 30 nm

[0076] C: flatness of 30 nm or moreExample 1

[0077] A urethane pad including cerium oxide (manufactured by KOKONOE ELECTRIC Co., Ltd.: KSP66A, thickness: 0.5 mm) was used as a resin including a void. The resin including a void was fixed on the base plate with a double-sided tape, and then was heated in an oven at 100° C. for 1 hour. Thereafter, the resin including a void was taken out of the oven and allowed to stand to be cooled to room temperature.

[0078] Next, the resin including a void was irradiated with electron beam in order to promote crosslinking in the front surface of the resin. The resin including a void was irradiated with electron beam at a dose of 100 kGy for 20 minutes to obtain a polishing pad 1 having a first resin in the surface layer.Example 2

[0079] A urethane pad including cerium oxide (manufactured by KOKONOE ELECTRIC Co., Ltd.: KSP66A, thickness: 0.5 mm) was used as a resin including a void. The resin including a void was fixed on the base plate with a double-sided tape, and then was heated in an oven at 100° C. for 1 hour. Thereafter, the resin including a void was taken out of the oven and allowed to stand to be cooled to room temperature.

[0080] Next, the resin including a void was irradiated with electron beam in order to promote crosslinking in the front surface of the resin. The resin including a void was irradiated with electron beam at a dose of 100 kGy for 10 minutes to obtain a polishing pad 2 having a first resin in the surface layer.Example 3

[0081] A filler-free urethane pad (manufactured by KOKONOE ELECTRIC Co., Ltd.: KSP90, thickness: 0.5 mm) was used as a resin including a void. The resin including a void was fixed on the base plate with a double-sided tape, and then was heated in an oven at 100° C. for 1 hour. Thereafter, the resin including a void was taken out of the oven and allowed to stand to be cooled to room temperature.

[0082] Next, the resin including a void was irradiated with electron beam in order to promote crosslinking in the front surface of the resin. The resin including a void was irradiated with electron beam at a dose of 150 kGy for 10 minutes to obtain a polishing pad 3 having a first resin in the surface layer.Example 4

[0083] A filler-free urethane pad (manufactured by Fujibo Ehime Co., Ltd.: FXA9H, thickness: 0.8 mm) was used as a resin including a void. The resin including a void was fixed on the base plate with a double-sided tape, and then was heated in an oven at 100° C. for 1 hour. Thereafter, the resin including a void was taken out of the oven and allowed to stand to be cooled to room temperature.

[0084] Next, the resin including a void was irradiated with electron beam in order to promote crosslinking in the front surface of the resin. The resin including a void was irradiated with electron beam at a dose of 150 kGy for 10 minutes to obtain a polishing pad 4 having a first resin in the surface layer.Example 5

[0085] A urethane pad including cerium oxide (manufactured by KOKONOE ELECTRIC Co., Ltd.: KSP66A, thickness: 0.5 mm) was used as a resin including a void. The resin including a void was fixed on the base plate with a double-sided tape, and then was heated in an oven at 100° C. for 1 hour. Thereafter, the resin including a void was taken out of the oven and allowed to stand to be cooled to room temperature.

[0086] Next, the resin including a void was irradiated with electron beam in order to promote crosslinking in the front surface of the resin. The resin including a void was irradiated with electron beam at a dose of 50 kGy for 3 minutes to obtain a polishing pad 5 having a first resin in the surface layer.Comparative Example 1

[0087] A urethane pad including cerium oxide (manufactured by KOKONOE ELECTRIC Co., Ltd.: KSP66A, thickness: 0.5 mm) was used as a resin including a void. The resin including a void was fixed on the base plate with a double-sided tape, and then was heated in an oven at 100° C. for 1 hour. Thereafter, the resin including a void was taken out of the oven and allowed to stand to be cooled to room temperature to obtain a polishing pad 6. In Comparative Example 1, the resin was not irradiated with electron beam.Comparative Example 2

[0088] A urethane pad including cerium oxide (manufactured by KOKONOE ELECTRIC Co., Ltd.: KSP66A, thickness: 0.5 mm) was used as a resin including a void. The resin including a void was irradiated with a laser to form a void having a diameter of approximately 450 μm in the surface layer. The resin including a void was fixed on the base plate with a double-sided tape, and then was heated in an oven at 100° C. for 1 hour. Thereafter, the resin including a void was taken out of the oven and allowed to stand to be cooled to room temperature.

[0089] Next, the resin including a void was irradiated with electron beam in order to promote crosslinking in the front surface of the resin. The resin including a void was irradiated with electron beam at a dose of 50 kGy for 3 minutes to obtain a polishing pad 7 having a first resin in the surface layer.

[0090] The evaluation results of the polishing pads of Examples 1 to 5 and Comparative Examples 1 and 2 are shown in Table 1. The polishing pads of Comparative Examples resulted in failure in achieving both high processing quality and high polishing rate. On the other hand, the polishing pad of each Example was found that both high processing quality and high polishing rate might be achieved because the polishing pad had a first resin in the surface layer and had a small difference in the average void diameter.TABLE 1Void areaHardnessHardnessThicknessAverage void diameterproportionof firstof resin ofof firstFrontBackFrontBackresinunderlayerresinsurfacesurfaceDifferencesurfacesurfacePolishingProcessing(MPa)(MPa)(μm)(μm)(μm)(%)(%)(%)ratequalityExample 15816502502624.670.275.6AAExample 24318352362505.669.571.6AAExample 336154210211712.863.562.6ABExample 431143861577.030.933.5BAExample 5261252422555.176.873.6ABComparative—1402572483.673.272.2ACExample 1Comparative2115545026669.279.875.4BCExample 2

[0091] As described above, according to the polishing pad of the present disclosure, high flatness of the processed surface of the polished object may be obtained because the polishing pad has a hard surface layer, and the followability to a shape of the work is high because the underlayer of the polishing pad may have flexibility. Also, according to the polishing pad of the present disclosure, high polishing rate may be achieved because the polishing pad has an appropriate void diameter.

[0092] While the present disclosure has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

[0093] This application claims the benefit of Japanese Patent Application No. 2024-069291, filed Apr. 22, 2024, which is hereby incorporated by reference herein in its entirety.

Examples

first embodiment

[0015]The first embodiment is about a polishing pad.

[0016]The polishing pad of the present disclosure is a polishing pad having a resin including a void, wherein a surface layer including a surface to be a polishing surface of the resin is a first resin having a higher hardness than a hardness of an other region of the resin, and wherein, when a value of a circle-equivalent diameter of the void in the polishing surface is defined as a void diameter of a front surface, and a value of a circle-equivalent diameter of the void in a surface opposite to the polishing surface is defined as a void diameter of a back surface, a difference between the void diameter of the front surface and the void diameter of the back surface is within 15%.

[0017]The embodiment will hereinafter be described.

[Polishing Apparatus]

[0018]The polishing apparatus of the present disclosure includes a polishing pad of the present disclosure, a fixing part for fixing the polishing pad, and a holding part for holding a...

second embodiment

[0038]The second embodiment is about a method for producing a polishing pad.

[0039]The method for producing a polishing pad of the present disclosure is a method including: preparing a resin including a void; and subjecting a surface layer including one surface of the resin to curing treatment to provide a cured resin having a higher hardness than a hardness of an other region of the resin, wherein, when a circle-equivalent diameter of the void in the cured surface is defined as a void diameter of a front surface, and a circle-equivalent diameter of the void in a surface opposite to the cured surface is defined as a void diameter of a back surface, a difference between the void diameter of the front surface and the void diameter of the back surface is within 15%.

[0040]Next, the method for producing a first resin 8 of a surface layer 6 of a polishing pad 10 will be described. The method for producing the polishing pad 10 of the present disclosure is not particularly limited, but a pre...

third embodiment

[0056]The third embodiment is about a method for producing a polished object.

[0057]The method for producing a polished aspect of the present disclosure includes polishing an object to be polished with the polishing pad.

[0058]The description on polishing of an object to be polished with a polishing pad is as described above (for example, the description in the [Polishing Apparatus]), and polishing methods using a polishing apparatus are known techniques and, accordingly, description on the detail of the methods will be omitted.

Claims

1. A polishing pad comprising:a resin having a void,wherein the resin includes a first resin and a second resin, a hardness of the first resin being higher than a hardness of the second resin,wherein a surface layer forming a polishing surface of the polishing pad comprises the first resin,wherein a region of the polishing pad comprises the second resin, andwherein, when a value of a circle-equivalent diameter of the void in the polishing surface is defined as a void diameter of a front surface, and a value of a circle-equivalent diameter of the void in a surface of the polishing pad opposite to the polishing surface is defined as a void diameter of a back surface, a difference between the void diameter of the front surface and the void diameter of the back surface is within 15%.

2. The polishing pad according to claim 1, wherein the difference between the void diameter of the front surface and the void diameter of the back surface is 5% or more and 13% or less.

3. The polishing pad according to claim 1, wherein the hardness of the first resin is 1.2 times or more the hardness of the second resin.

4. The polishing pad according to claim 1, wherein the hardness of the first resin is twice or more and 10 times or less the hardness of the second resin.

5. The polishing pad according to claim 1, wherein a thickness of the first resin is 0.1 μm or more and 100 μm or less.

6. The polishing pad according to claim 1, wherein an average void diameter of the front surface is 100 μm or more and 500 μm or less.

7. The polishing pad according to claim 1, wherein, when a proportion of a region of the void in the polishing surface based on a region of the polishing surface is defined as a void area proportion of the front surface, and a proportion of a region of the void in the surface opposite to the polishing surface based on a region of the surface opposite to the polishing surface is defined as a void area proportion of the back surface, a difference between the void area proportion of the front surface and the void area proportion of the back surface is 10% or less.

8. The polishing pad according to claim 1, wherein the hardness of the first resin is 25 MPa or more and 60 MPa or less.

9. The polishing pad according to claim 1,wherein the resin comprising the void comprises polyurethane, andwherein the second resin comprises the polyurethane comprising an allophanate bond.

10. A polishing apparatus comprising:a polishing pad comprising a resin comprising a void,wherein the resin includes a first resin and a second resin, a hardness of the first resin being higher than a hardness of the second resin,wherein a surface layer comprising a polishing surface of the polishing pad comprises the first resin,wherein a region of the polishing pad comprises the second resin, andwherein, when a value of a circle-equivalent diameter of the void in the polishing surface is defined as a void diameter of a front surface, and a value of a circle-equivalent diameter of the void in a surface of the polishing pad opposite to the polishing surface is defined as a void diameter of a back surface, a difference between the void diameter of the front surface and the void diameter of the back surface is within 15%;a fixing part for fixing the polishing pad; anda holding part for holding an object.

11. A method for producing a polishing pad, the method comprising:preparing a resin having a void; andsubjecting a surface layer forming one surface of the resin to curing treatment to provide the resin with a first resin and a second resin, a hardness of the first resin being higher than a hardness of the second resin,wherein, when a circle-equivalent diameter of the void in the cured surface is defined as a void diameter of a front surface, and a circle-equivalent diameter of the void in a surface of the resin opposite to the cured surface is defined as a void diameter of a back surface, a difference between the void diameter of the front surface and the void diameter of the back surface is within 15%.

12. The method for producing the polishing pad according to claim 11, the method further comprising heating the resin before the curing,wherein the resin is heated at 100° C. or more and 180° C. or less for 1 hour or more in the heating.

13. The method for producing the polishing pad according to claim 11, wherein an allophanate bond is formed in the one surface of the resin in the curing.

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