Polishing body, polishing machine, and wafer polishing method

Abstract

To provide a polishing body which can suppress deterioration even if it polishes using a strongly acidic polishing liquid, can be repeatedly detached from / attached to a surface plate, and can contribute to reduction of polishing cost of a polished object.SOLUTION: A polishing machine includes a surface plate 13 rotating around a shaft center O1, and a carrier 22 for holding a wafer 20 as a polished object so as to be relatively rotatable with respect to the surface plate 13. A polishing body 1 is fixed to a fixed surface 13a of the surface plate 13. The polishing body 1 has a polishing pad 3, an adhesive layer 5, and a cushion layer 7. The polishing pad 3 has a base material 33 having a plurality of pores 37, and polishing particles 35 held in the base material 33 or the pores 37. The base material 33 is made of polyvinylidene fluoride. The cushion layer 7 is composed of an elastically deformable silicone-based porous body, and is adsorbed to the fixed surface 13a in a detachable / attachable manner. The adhesive layer 5 contains a silicone-based adhesive component.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an abrasive body , polishing machine and wafer polishing method Regarding. [Background technology]

[0002] A polishing machine is known that includes a platen and a carrier. The platen has a fixed surface extending in a direction perpendicular to its axis and is rotated about the axis. The carrier holds a flat workpiece to be polished so that it can rotate relative to the platen.

[0003] When using this polishing machine to polish wafers made of silicon carbide (SiC), gallium nitride (GaN), or the like, a polishing body is fixed to the fixed surface of a surface plate, and the wafer is held in a carrier so that it can rotate relative to the surface plate. The polishing pad of the polishing body is then brought into contact with the wafer at a predetermined surface pressure in the presence of a polishing liquid, while the wafer is rotated relative to the surface plate. If the polishing liquid contains chemical components such as acid or alkali, the wafer surface is polished by CMP (Chemical Mechanical Polishing).

[0004] A polishing body used in CMP polishing is desirably made of a material with excellent chemical resistance. Patent Document 1 discloses a polishing body in which the polishing pad is difficult to peel off from the double-sided adhesive sheet even when an oxidizing aqueous solution with a pH of about 4.5 to 5.5 is used as the polishing liquid in CMP polishing. In this polishing body, a silicone-based adhesive is used as the adhesive for the double-sided adhesive sheet that is adhered to the polishing pad.

[0005] The polishing body disclosed in Patent Document 1 has a cushion layer made of polyurethane foam between the polishing pad and the platen, and the flexible cushion layer is intended to improve the processing flatness of the polished surface of the wafer. This cushion layer is adhered to the polishing pad with the above-mentioned silicone-based adhesive and to the platen with an acrylic-based adhesive. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2019-145689 Summary of the Invention [Problem to be solved by the invention]

[0007] However, in polishing processes where the workpiece is a difficult-to-process material such as SiC or GaN, a strongly acidic polishing solution with a pH of 3 or less is often used. In this case, the polishing body disclosed in Patent Document 1 may have components such as a polishing pad and a cushion layer deteriorated, resulting in a shortened lifespan.

[0008] Furthermore, the polishing body disclosed in Patent Document 1 is fixed to the surface plate with an adhesive. In this case, if the polishing body is detached from the surface plate when replacing the polishing body, the adhesive strength of the adhesive inevitably decreases. For this reason, it is difficult to reuse the polishing body detached from the surface plate, and there are many cases where expensive polishing bodies are discarded within a short period of time. In actual polishing processes such as those at manufacturing sites, the number of polishing machines is limited, and the polishing body to be used must be selected for each material of the workpiece, so the polishing body is replaced frequently. If expensive polishing bodies that need to be replaced frequently could not be reused, the cost of wafer polishing would skyrocket.

[0009] The present invention has been made in view of the above-mentioned conventional circumstances, and is capable of suppressing deterioration even when polishing using a strongly acidic polishing solution, and is also capable of preventing deterioration of a surface plate. Polishing body A polishing body that can be repeatedly attached and detached, thereby contributing to reducing the cost of polishing an object to be polished , polishing machine and wafer polishing method The problem to be solved is to provide the following. [Means for solving the problem]

[0010] The polishing body of the present invention is used in a polishing machine including a platen having a fixing surface extending in a direction perpendicular to an axis and rotated around the axis, and a carrier that holds a flat plate-shaped object to be polished so that the object can rotate relatively to the platen, a polishing body that is fixed to the fixing surface and polishes the object to be polished under a predetermined surface pressure in the presence of a polishing liquid, a polishing pad comprising a base material made of polyvinylidene fluoride and having a plurality of pores formed therein, and abrasive particles held within the base material or the pores; a cushion layer made of an elastically deformable silicone porous body and removably attached to the fixing surface without using an adhesive; an adhesive layer containing a silicone adhesive component and interposed between the polishing pad and the cushion layer to bond the polishing pad and the cushion layer; 、 the polishing pad has a pad-side impregnated layer impregnated with the adhesive component at the interface with the adhesive layer, the cushion layer has a cushion-side impregnated layer impregnated with the adhesive component at the interface with the adhesive layer, The thickness of the cushion layer is 100 μm to 500 μm, Place the polishing body on a flat measuring table with the concave surface facing up, measure the height of the most warped edge from the measuring table, and determine that the warpage is 30 mm or less. It is characterized by the following.

[0011] According to the inventors' tests, since the base material of the polishing pad is made of polyvinylidene fluoride, the polishing pad is resistant to deterioration, even when polishing with a strongly acidic polishing liquid. Furthermore, since the cushion layer is silicone-based, the cushion layer is resistant to deterioration, even when polishing with a strongly acidic polishing liquid. Furthermore, since the adhesive component of the adhesive layer is silicone-based, the adhesive layer is resistant to deterioration, even when polishing with a strongly acidic polishing liquid.

[0012] Furthermore, the polishing body of the present invention can be repeatedly attached to and detached from the platen due to the adsorption action of the cushion layer, which is resistant to deterioration even when polishing using a strongly acidic polishing solution. The polishing machine of the present invention is a polishing machine comprising: a platen having a fixing surface extending in a direction perpendicular to an axis and rotated around the axis; a carrier that holds a flat workpiece to be polished so that the workpiece can rotate relatively to the platen; and a polishing body that is fixed to the fixing surface and polishes the workpiece in the presence of a polishing liquid under a predetermined surface pressure, The polishing body is a polishing pad made of polyvinylidene fluoride, the polishing pad having a base material having a plurality of pores formed therein and abrasive particles held within the base material or the pores; a cushion layer made of an elastically deformable silicone porous body and removably attached to the fixing surface without using an adhesive; an adhesive layer containing a silicone adhesive component and interposed between the polishing pad and the cushion layer to bond the polishing pad and the cushion layer; 、 the polishing pad has a pad-side impregnated layer impregnated with the adhesive component at the interface with the adhesive layer, the cushion layer has a cushion-side impregnated layer impregnated with the adhesive component at the interface with the adhesive layer, The thickness of the cushion layer is 100 μm to 500 μm, The abrasive body is placed on a flat measuring table with the concave surface facing up, and the height of the most curved edge of the abrasive body measured from the measuring table is found to be 30 mm or less. It is characterized by the following. The wafer polishing method of the present invention is a wafer polishing method for polishing a wafer as an object to be polished using a polishing machine including a platen having a fixing surface extending in a direction perpendicular to an axis and rotated about the axis, a carrier for holding a flat object to be polished so as to be rotatable relative to the platen, and a polishing body fixed to the fixing surface and for polishing the object to be polished under a predetermined surface pressure in the presence of a polishing liquid, The polishing body is a polishing pad made of polyvinylidene fluoride, the polishing pad having a base material having a plurality of pores formed therein and abrasive particles held within the base material or the pores; a cushion layer made of an elastically deformable silicone porous body and removably attached to the fixing surface without using an adhesive; an adhesive layer containing a silicone adhesive component and interposed between the polishing pad and the cushion layer to bond the polishing pad and the cushion layer; 、 the polishing pad has a pad-side impregnated layer impregnated with the adhesive component at the interface with the adhesive layer, the cushion layer has a cushion-side impregnated layer impregnated with the adhesive component at the interface with the adhesive layer, The thickness of the cushion layer is 100 μm to 500 μm, The abrasive body is placed on a flat measuring table with the concave surface facing up, and the height of the most curved edge of the abrasive body measured from the measuring table is found to be 30 mm or less. It is characterized by the following.

[0013] Therefore, the abrasive body of the present invention According to the polishing machine and wafer polishing method Even when polishing with a strong acid polishing solution, deterioration can be suppressed and the surface plate Polishing body It can be repeatedly attached and detached, which can contribute to reducing the cost of polishing the object to be polished. [Effects of the Invention]

[0014] The abrasive body of the present invention According to the polishing machine and wafer polishing method Even when polishing with a strong acid polishing solution, deterioration can be suppressed and the surface plate can be Polishing body This can be detached, which can contribute to reducing the cost of polishing the object to be polished. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a schematic cross-sectional view showing an enlarged portion of the polishing body of Example 1. [Figure 2] FIG. 2 is a schematic cross-sectional view showing an enlarged portion of the polishing pad constituting the polishing body of Example 1. As shown in FIG. [Figure 3] FIG. 3 is a schematic cross-sectional view showing an enlarged portion of the polishing body of Example 1 fixed to a platen. [Figure 4] FIG. 4 is a schematic cross-sectional view of a wafer polishing machine. DETAILED DESCRIPTION OF THE INVENTION

[0016] The polishing body of the present invention is used in a polishing machine equipped with a platen and a carrier. The platen has a fixing surface extending in a direction perpendicular to its axis and is rotated about its axis. The carrier holds a flat workpiece to be polished so that it can rotate relative to the platen.

[0017] The polishing body of the present invention is fixed to the fixing surface of a surface plate and polishes an object to be polished under a predetermined surface pressure in the presence of a polishing liquid. The polishing liquid may be pure water, an oil-based liquid, or a liquid containing an acidic or alkaline chemical. The polishing body of the present invention can suppress deterioration even when a strongly acidic polishing liquid having a pH of 3 or less or a pH of 1 or less is used.

[0018] The polishing body of the present invention can be used to polish semiconductor wafers, and is particularly suitable for polishing difficult-to-process materials such as silicon carbide (SiC), gallium nitride (GaN), and aluminum nitride (AlN).

[0019] The polishing machine to which the polishing body of the present invention is attached can be suitably used in a lapping process for rough processing of semiconductor wafers or for subsequent finishing processing. The lapping process may be either a single-sided lapping process in which only one side of the semiconductor wafer as the workpiece is lapped, or a double-sided lapping process in which both sides of the semiconductor wafer are simultaneously lapped by a pair of polishing bodies.

[0020] The polishing body of the present invention comprises a polishing pad, an adhesive layer, and a cushion layer. The cushion layer, adhesive layer, and polishing pad are laminated in this order. That is, the adhesive layer is interposed between the polishing pad and the cushion layer and adheres them to each other.

[0021] The polishing pad has a base material and abrasive particles. The base material is made of polyvinylidene fluoride (PVDF). The base material made of polyvinylidene fluoride is resistant to deterioration even when a strongly acidic polishing solution with a pH of 1 or less is used. In addition, multiple pores are formed in the base material. The abrasive particles are held within the base material or the pores.

[0022] The polishing pad preferably has a pad-side impregnated layer impregnated with an adhesive component at the interface with the adhesive layer of the polishing pad. The pad-side impregnated layer can improve the bonding between the polishing pad and the adhesive layer. The polishing pad preferably has a continuous pore structure, and particularly preferably has a continuous pore structure in the region of the polishing pad including the interface with the adhesive layer. That is, it is preferable that continuous pores are open at the interface with the adhesive layer of the polishing pad. If continuous pores are open at the interface with the adhesive layer of the polishing pad, the adhesive component can easily be impregnated through the openings. Therefore, a pad-side impregnated layer is easily formed at the interface with the adhesive layer of the polishing pad.

[0023] The abrasive particles may be made of silica, ceria, alumina, zirconia, titania, diamond, manganese oxide, barium carbonate, chromium oxide, iron oxide, etc. These may be used alone or in combination of two or more.

[0024] The cushion layer is made of an elastically deformable silicone-based porous material. The silicone-based cushion layer is resistant to deterioration even when a strongly acidic polishing solution with a pH of 1 or less is used. The cushion layer is preferably made of a silicone rubber foam.

[0025] The cushion layer is made of a porous material and has an adhesive action that allows the cushion layer to be repeatedly attached and detached to the fixing surface of the surface plate. The pores in the cushion layer may include closed pores, but from the viewpoint of improving the adhesive action of the cushion layer, it is preferable that the continuous porosity of the cushion layer is about 90% or more.

[0026] The cushion layer preferably has a cushion-side impregnated layer impregnated with an adhesive component at the interface with the adhesive layer. The cushion-side impregnated layer can improve the bonding between the cushion layer and the adhesive layer. The cushion layer preferably has an interconnected pore structure in a region of the cushion layer including the interface with the adhesive layer. That is, it is preferable that interconnected pores are open at the interface with the adhesive layer in the cushion layer. If interconnected pores are open at the interface with the adhesive layer in the cushion layer, the adhesive component can easily be impregnated through the openings. Therefore, a cushion-side impregnated layer is easily formed at the interface with the adhesive layer in the cushion layer.

[0027] It is preferable that the polishing pad has a pad-side impregnated layer and the cushion layer has a cushion-side impregnated layer. In this case, the pad-side impregnated layer improves the bonding strength between the polishing pad and the adhesive layer, and the cushion-side impregnated layer improves the bonding strength between the cushion layer and the adhesive layer. Therefore, even when polishing using a strongly acidic polishing liquid, the bonding integrity of the polishing pad, adhesive layer, and cushion layer is less likely to deteriorate.

[0028] The thickness of the cushion layer is preferably 100 μm to 500 μm. In this case, good adhesion to the fixed surface of the surface plate can be ensured. Furthermore, the flexible cushion layer can be elastically deformed, which allows the cushion layer to more effectively perform its function of improving the processing flatness of the polished surface and suppressing the occurrence of micro-scratches on the polished surface.

[0029] The flexibility of the cushion layer and its adhesiveness to the surface plate can be adjusted by appropriately setting the expansion ratio, open porosity, hardness, etc.

[0030] The adhesive layer contains a silicone adhesive component. A silicone adhesive containing a silicone adhesive component is resistant to deterioration even when a strongly acidic polishing liquid with a pH of 1 or less is used.

[0031] During the manufacturing process, the abrasive body may warp due to the difference in the amount of expansion and contraction between each layer. The warpage of the abrasive body of the present invention is preferably 30 mm or less. Abrasive bodies with a warpage exceeding 30 mm may not be able to be attached to the fixed surface of a surface plate. The warpage of the abrasive body can be determined by placing the abrasive body with the concave surface facing up on a flat measuring table and measuring the height of the most warped edge from the measuring table.

[0032] The components of the polishing body of the present invention are resistant to deterioration even when a strongly acidic polishing solution with a pH of 1 or less is used. Furthermore, the cushion layer's adsorption properties allow the polishing body to be repeatedly attached to and detached from the platen. Therefore, the polishing body of the present invention can contribute to reducing the cost of polishing the object to be polished.

[0033] (Example) Below, examples embodying the present invention will be described, along with comparative examples 1 to 6. In the examples and comparative examples 1 to 6, the type of resin used in the base material of the polishing pad, the type of adhesive used in the adhesive layer, the type of material used in the cushion layer, the presence or absence and type of a second adhesive layer, and the amount of warping of the polishing body are shown in Table 1.

[0034] [Table 1]

[0035] 1, the polishing body 1 of the embodiment includes a polishing pad 3, an adhesive layer 5, a cushion layer 7, and a release paper 9. The release paper 9 is peeled off from the polishing body 1, and the polishing body 1 is attached to the fixing surface 13a of the surface plate 13, as shown in FIG.

[0036] The polishing pad 3 has a polishing surface 3a and an adherend surface 3b facing away from the polishing surface 3a and spaced apart in the thickness direction from the polishing surface 3a. An adhesive layer 5 is adhered to the adherend surface 3b of the polishing pad 3. The polishing pad 3 has a pad-side impregnated layer 31 at the interface with the adhesive layer 5, which is impregnated with the adhesive component of the adhesive layer 5.

[0037] As shown in FIG. 2, the polishing pad 3 has a base material 33 and abrasive particles 35. The base material 33 is made of polyvinylidene fluoride (PVDF). A plurality of pores 37 are formed in the base material 33. The polishing pad 3 has an interconnected pore structure. Specifically, a large number of interconnected pores are open at the interface between the polishing pad 3 and the adhesive layer 5. The adhesive component penetrates through these openings, forming a pad-side impregnated layer 31 at the interface between the polishing pad 3 and the adhesive layer 5.

[0038] The abrasive particles 35 are made of silica particles with an average particle size of 0.3 μm.

[0039] The polishing pad 3 is in the shape of a disk with a diameter of 300 mm and a thickness of 1.5 mm.

[0040] The cushion layer 7 is made of a silicone rubber foam and has a disk shape with a diameter of 300 mm and a thickness of 300 μm.

[0041] The cushion layer 7 has an adsorbing surface 7a and an adherend surface 7b facing away from the adsorbing surface 7a and spaced apart from the adsorbing surface 7a in the thickness direction. An adhesive layer 5 is adhered to the adherend surface 7b of the cushion layer 7. The cushion layer 7 has a cushion-side impregnated layer 71 at the interface with the adhesive layer 5, which is impregnated with the adhesive component of the adhesive layer 5.

[0042] The cushion layer 7 has an interconnected porosity of about 90% or more, and has an interconnected pore structure in a region including the interface with the adhesive layer 5. That is, interconnected pores are open at the interface of the cushion layer 7 with the adhesive layer 5. The adhesive component penetrates through these openings, forming a cushion-side impregnated layer 71 at the interface of the cushion layer 7 with the adhesive layer 5.

[0043] The adhesive constituting the adhesive layer 5 is made of a commercially available silicone adhesive.

[0044] The release paper 9 is made of a PET film. The release paper 9 is peeled off from the adhesive surface 7a of the cushion layer 7 when the polishing body 1 is attached to the surface plate 13. Since the release paper 9 remains attached to the adhesive surface 7a until just before attachment, the adhesive surface 7a can be protected and the adhesive surface 7a can be prevented from being attached to other members, thereby improving the ease of handling of the polishing body 1.

[0045] The polishing pad 3 in this polishing body 1 was produced as follows.

[0046] <Preparation process> A binder resin of PVDF, abrasive particles of silica particles, and a solvent of N-methyl-2-pyrrolidone were prepared.

[0047] <Mixing process> A paste was obtained by mixing 15 parts by mass of binder resin, 15 parts by mass of abrasive particles, and 70 parts by mass of solvent in a compounding ratio.

[0048] <Forming process> The obtained paste was used to obtain a sheet-like molded body using a T-die.

[0049] <Pore formation process, drying process> The obtained molded body was immersed in water to replace the solvent in the molded body with water, thereby forming numerous interconnected pores. After a predetermined time, the molded body was taken out of the water and dried to obtain an intermediate body.

[0050] <Grinding process> The surface of the obtained intermediate was ground to a predetermined thickness, to obtain a polishing pad 3 having a polishing surface 3a.

[0051] <Adhesion process> A silicone adhesive was applied to the adherend surface 3b of the obtained polishing pad 3, and the same silicone adhesive was also applied to the adherend surface 7b of the cushion layer 7 cut to a predetermined shape, and the adherend surfaces 3b, 7b were pressed together. This resulted in the polishing pad 3 and cushion layer 7 being bonded together by the adhesive layer 5. Finally, a release paper 9 was attached to the adsorption surface 7a of the cushion layer 7 to complete the polishing body 1.

[0052] The resulting abrasive body 1 had a warpage of 20 mm.

[0053] The polishing body 1 thus obtained is used as a fixed abrasive grinding tool by attaching the adsorption surface 7a of the cushion layer 7, from which the release paper 9 has been peeled off, to the fixing surface 13a of the surface plate 13 by adsorption.

[0054] (Comparative Example 1) The structure is the same as that of the example except that the warp is 40 mm.

[0055] The abrasive body of Comparative Example 1 could not be attached to the fixing surface 13a of the surface plate 13 because the warpage was too large.

[0056] (Comparative Example 2) The resin of the base material 33 in the polishing pad 3 was polyethersulfone (PES).

[0057] The other configurations are the same as those in the first embodiment.

[0058] (Comparative Example 3) A silicone adhesive was applied to the adherend surface 3b of the polishing pad 3 obtained in the same manner as in the Examples, and the pad was then attached directly to the fixing surface 13a of the platen 13. That is, the polishing body of Comparative Example 3 does not have a cushion layer 7.

[0059] Comparative Example 4 A polyurethane foam having an open pore structure was used as the cushion layer 7. The cushion layer 7 made of this polyurethane foam was then attached to the fixing surface 13a of the surface plate 13 with a second contact layer made of an acrylic adhesive.

[0060] The other configurations are the same as those of the embodiment.

[0061] (Comparative Example 5) An acrylic adhesive was used as the adhesive for the adhesive layer 5 .

[0062] The other configurations are the same as those of the embodiment.

[0063] (Comparative Example 6) An acrylic adhesive was used as the adhesive for adhesive layer 5. A polyurethane foam having an open pore structure was used for cushion layer 7. Cushion layer 7 made of polyurethane foam was then attached to fixing surface 13a of base plate 13 with a second contact layer made of an acrylic adhesive.

[0064] The other configurations are the same as those of the embodiment.

[0065] (Evaluation of the life of the polishing body) The polishing body 1 of the example and the polishing bodies of Comparative Examples 1 to 6 were evaluated for their life span.

[0066] Each polished body was cut into a 20 mm x 20 mm square to form a test specimen, which was then immersed in an aqueous potassium permanganate (KMnO4) solution adjusted to a pH of 1. The degree of deterioration of each component was then visually observed 50 hours after the start of immersion and 100 hours after the start of immersion.

[0067] The lifespan was evaluated as follows: complete deterioration was marked x, partial deterioration was marked △, and no deterioration was marked ◯. The results are shown in Table 2.

[0068] In the polishing body of the example, which used polyvinylidene fluoride as the resin for the base material 33, a silicone-based adhesive for the adhesive layer 5, and silicone rubber for the cushion layer 7, none of the components had deteriorated even 100 hours after the start of immersion.

[0069] The polishing pad of Comparative Example 2, which used polyethersulfone as the resin for the base material 33, was completely deteriorated after 50 hours.

[0070] The cushion layers of Comparative Examples 4 and 6, which used foamed polyurethane, were partially deteriorated after 50 hours had passed, and were completely deteriorated after 100 hours had passed.

[0071] Furthermore, the second contact layer made of the acrylic adhesive in the abrasive bodies of Comparative Examples 4 and 6 was completely deteriorated after 50 hours.

[0072] The adhesive layers 5 of Comparative Examples 5 and 6, which used an acrylic adhesive, were partially deteriorated after 50 hours had passed, and were completely deteriorated after 100 hours had passed.

[0073] (Evaluation of repeated attachment / detachment to the surface plate) The abrasive body 1 of the example and the abrasive bodies of Comparative Examples 2 to 6 were evaluated for their repetitive attachment and detachment to and from the platen 13.

[0074] This evaluation was carried out by peeling each of the polishing bodies 1 of the example and the polishing bodies 2 to 6 from the fixing surface 13a of the surface plate 13 and then reattaching them to the fixing surface 13a. If there was no lifting of the polishing body (poor attachment), it was evaluated as ◯, and if there was lifting of the polishing body, it was evaluated as ×. The results are shown in Table 2.

[0075] The polishing body 1 of the example, which is attached to the surface plate 13 by the adhesiveness of the cushion layer 7 made of silicone rubber foam, had no adhesion defects and could be repeatedly attached and detached to the surface plate.

[0076] The polishing body of Comparative Example 3, which did not have a cushion layer and in which the polishing pad 3 was adhered to the platen 13 by the adhesive layer 5, had poor adhesion.

[0077] The polishing bodies of Comparative Examples 4 and 6, in which a cushion layer made of foamed polyurethane was attached to the platen 13 with an acrylic adhesive, had poor attachment.

[0078] (Processing test) A wafer polishing machine (Engis EJW-380) shown in Figure 4 was prepared, and a lapping test was conducted to polish a wafer 20 using a fixed abrasive grinding tool in which the polishing body 1 of the example and the polishing bodies of Comparative Examples 2 to 6 were attached to a surface plate 13.

[0079] This wafer polishing machine is equipped with multiple carriers 22, a surface plate 13, a drive unit 24, and a polishing liquid supply unit 26. Although only a single carrier 22 is shown in FIG. 4, the wafer polishing machine actually has multiple carriers 22. Each carrier 22 is shaped like a horizontal disk. A wafer fixing surface 22a is recessed in the underside of each carrier 22, and a wafer 20 is fixed to the wafer fixing surface 22a. A carrier rotation shaft 28 protrudes vertically from the upper surface of each carrier 22. The polished surface 20a, which is the Si surface of each wafer 20, faces downward.

[0080] The surface plate 13 is a horizontal disk-like plate that contains all of the carriers 22. A surface plate rotation shaft 30 protrudes vertically from the lower surface of the surface plate 13. The upper surface of the surface plate 13 is a fixing surface 13a. The polishing body 1 of Example 1 or the polishing bodies of Comparative Examples 2 to 6 are attached to the fixing surface 13a so as to face each wafer 20.

[0081] The drive device 24 has a main drive device 24a, an auxiliary drive device 24b, and a pressure device 24c. The main drive device 24a drives the surface plate rotation shaft 30 to rotate at a predetermined speed around the first axis O1. The auxiliary drive device 24b drives each carrier rotation shaft 28 to rotate at a predetermined speed around the second axis O2. The pressure device 24c applies pressure to each carrier rotation shaft 28 and the auxiliary drive device 24b toward the surface plate 13 with a predetermined load.

[0082] The polishing liquid supply device 26 is provided above the surface plate 13. The polishing liquid supply device 26 provides a polishing liquid 26a between each wafer 20 and the polishing body 1. The polishing liquid 26a is an aqueous potassium permanganate solution adjusted to pH 1 and does not contain abrasive particles.

[0083] Using this wafer polishing machine, a processing test was carried out to polish the wafer 20 under the following conditions. Wafer 20 as the workpiece: 4-inch diameter 4H-SiC single crystal Flow rate of polishing liquid 26a: 10 mL / min Load: 30kPa Rotation speed of surface plate 13: 60 rpm Carrier 22 rotation speed: 60 rpm Processing time: 60 minutes

[0084] (Evaluation of the flatness of the polished surface) After the above processing test, the processed flatness of the polished surface 20a of the wafer 20 was evaluated.

[0085] In this evaluation, the amount of processing was measured at five points on the polished surface 20a after the processing test, including the center point within the wafer and four points on the wafer's periphery. The maximum processing amount was defined as Rmax, and the minimum processing amount was defined as Rmin. If the difference ΔR between the maximum and minimum processing amounts (ΔR = Rmax - Rmin) was ΔR > 3 μm, it was evaluated as ×, and if ΔR ≦ 3 μm, it was evaluated as ◯. The results are shown in Table 2.

[0086] The polishing members 1 and the like of the examples having the cushion layer 7 made of a silicone rubber foam all had ΔR values ​​of 3 μm or less, and had good processing flatness.

[0087] The polishing body of Comparative Example 3, which did not have a cushion layer, exhibited reduced processing flatness.

[0088] [Table 2]

[0089] Although the present invention has been described above with reference to the examples, it goes without saying that the present invention is not limited to the above examples and can be modified and applied as appropriate within the scope of the invention. [Industrial Applicability]

[0090] The present invention can be used in semiconductor device manufacturing equipment. [Explanation of symbols]

[0091] 1...Abrasive body 3...Polishing pad 5...adhesive layer 7...Cushion layer 31...Pad side impregnation layer 33...Base material 35...Abrasive particles 37... Stoma 71...Cushion side impregnated layer

Claims

1. The present invention is used in a polishing machine including a surface plate having a fixing surface extending in a direction perpendicular to an axis and rotated around the axis, and a carrier that holds a flat workpiece to be polished so that the workpiece can rotate relatively to the surface plate, a polishing body that is fixed to the fixing surface and polishes the object to be polished under a predetermined surface pressure in the presence of a polishing liquid, a polishing pad comprising a base material made of polyvinylidene fluoride and having a plurality of pores formed therein, and abrasive particles held within the base material or the pores; a cushion layer made of an elastically deformable silicone porous body and removably attached to the fixing surface without using an adhesive; an adhesive layer containing a silicone adhesive component and interposed between the polishing pad and the cushion layer to bond the polishing pad and the cushion layer; the polishing pad has a pad-side impregnated layer impregnated with the adhesive component at the interface with the adhesive layer, the cushion layer has a cushion-side impregnated layer impregnated with the adhesive component at the interface with the adhesive layer, The thickness of the cushion layer is 100 μm to 500 μm, The abrasive body is placed on a flat measuring table with the concave surface facing up, and the height of the most warped edge portion from the measuring table is measured, and the warpage is found to be 30 mm or less.

2. A polishing machine comprising: a surface plate having a fixing surface extending in a direction perpendicular to an axis and rotated around the axis; a carrier for holding a flat workpiece to be polished so that the workpiece can rotate relatively to the surface plate; and a polishing body fixed to the fixing surface for polishing the workpiece in the presence of a polishing liquid under a predetermined surface pressure, The polishing body is a polishing pad made of polyvinylidene fluoride, the polishing pad having a base material having a plurality of pores formed therein and abrasive particles held within the base material or the pores; a cushion layer made of an elastically deformable silicone porous body and removably attached to the fixing surface without using an adhesive; an adhesive layer containing a silicone adhesive component and interposed between the polishing pad and the cushion layer to bond the polishing pad and the cushion layer; the polishing pad has a pad-side impregnated layer impregnated with the adhesive component at the interface with the adhesive layer, the cushion layer has a cushion-side impregnated layer impregnated with the adhesive component at the interface with the adhesive layer, The thickness of the cushion layer is 100 μm to 500 μm, A polishing machine characterized in that the polishing body is placed on a flat measuring table with the concave surface facing up, and the height of the most warped edge of the polishing body from the measuring table is measured to find that the warpage of the polishing body is 30 mm or less.

3. A wafer polishing method for polishing a wafer as an object to be polished using a polishing machine including a platen having a fixing surface extending in a direction perpendicular to an axis and rotated about the axis, a carrier for holding a flat object to be polished so as to be rotatable relative to the platen, and a polishing body fixed to the fixing surface and for polishing the object to be polished under a predetermined surface pressure in the presence of a polishing liquid, comprising: The polishing body is a polishing pad made of polyvinylidene fluoride, the polishing pad having a base material having a plurality of pores formed therein and abrasive particles held within the base material or the pores; a cushion layer made of an elastically deformable silicone porous body and removably attached to the fixing surface without using an adhesive; an adhesive layer containing a silicone adhesive component and interposed between the polishing pad and the cushion layer to bond the polishing pad and the cushion layer; the polishing pad has a pad-side impregnated layer impregnated with the adhesive component at the interface with the adhesive layer, the cushion layer has a cushion-side impregnated layer impregnated with the adhesive component at the interface with the adhesive layer, The thickness of the cushion layer is 100 μm to 500 μm, A wafer polishing method characterized in that the polishing body is placed on a flat measuring table with the concave surface facing up, and the height of the most warped edge of the polishing body from the measuring table is measured to determine that the warpage of the polishing body is 30 mm or less.

4. 4. The wafer polishing method according to claim 3, wherein the wafer is a SiC wafer.

5. A wafer polishing method as described in claim 4, wherein the polishing liquid is a strongly acidic polishing liquid having a pH of 1 or less.

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