JP7728210B2 - Polishing body, polishing machine, and wafer polishing method - Google Patents

Description

The present invention relates to a polishing body , a polishing machine, and a method for polishing a wafer .

A polishing machine equipped with a platen and a carrier is known. The platen has a fixed surface extending in a direction perpendicular to the axis and is rotated around the axis. The carrier holds a flat workpiece to be polished so that it can rotate relative to the platen.

When using this polishing machine to polish wafers made of silicon carbide (SiC), gallium nitride (GaN), or other materials, the polishing body is fixed to the fixed surface of the platen, and the wafer is held in a carrier so that it can rotate relative to the platen. 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 platen. If the polishing liquid contains chemical components such as acid or alkali, the wafer surface is polished using CMP (Chemical Mechanical Polishing).

Abrasive bodies used in CMP polishing are desirably made of materials with excellent chemical resistance. Patent Document 1 discloses an abrasive 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 approximately 4.5 to 5.5 is used as the polishing liquid during CMP polishing. This abrasive body uses a silicone-based adhesive as the adhesive for the double-sided adhesive sheet that is adhered to the polishing pad.

The polishing body disclosed in Patent Document 1 also has a cushion layer made of polyurethane foam between the polishing pad and the platen, and the flexible cushion layer aims 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.

Japanese Patent Application Laid-Open No. 2019-145689

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 such cases, the polishing body disclosed in Patent Document 1 above has the risk of its components, such as the polishing pad and cushion layer, deteriorating and shortening its lifespan.

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. This makes it difficult to reuse polishing bodies that have been detached from the surface plate, and there are many cases where expensive polishing bodies are discarded after a short period of time. In actual polishing processes at processing sites, while the number of polishing machines is limited, the polishing body to be used must be selected for each material of the workpiece, and the polishing body must be replaced frequently. If expensive polishing bodies that need to be replaced frequently could not be reused, the cost of polishing wafers would skyrocket.

The present invention has been made in consideration of the above-mentioned conventional situation, and aims to provide a polishing body , a polishing machine, and a wafer polishing method that can suppress deterioration even when polishing using a strongly acidic polishing liquid, and that allows the polishing body to be repeatedly attached and detached to the surface plate, thereby contributing to a reduction in the polishing cost of the object to be polished.

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,
The polishing 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 to find that the warpage is 30 mm or less .

According to tests conducted by the inventors, because 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, because the cushion layer is silicone-based, the cushion layer is resistant to deterioration, even when polishing with a strongly acidic polishing liquid. Furthermore, because 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.

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 polishing 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 to find that the warpage of the polishing body is 30 mm or less .
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 polishing 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 to find that the warpage of the polishing body is 30 mm or less .

Therefore, the polishing body , polishing machine, and wafer polishing method of the present invention can suppress deterioration even when polishing using a strongly acidic polishing liquid, and can allow the polishing body to be repeatedly attached and detached to the surface plate, which can ultimately contribute to reducing the polishing costs of the object being polished.

The polishing body , polishing machine, and wafer polishing method of the present invention can suppress deterioration even when polishing using a strongly acidic polishing liquid, and can allow the polishing body to be repeatedly attached and detached to the surface plate, which can ultimately contribute to reducing the polishing costs of the object being polished.

FIG. 1 is a schematic cross-sectional view showing an enlarged portion of the polishing body of Example 1. FIG. 2 is a schematic cross-sectional view showing an enlarged portion of the polishing pad constituting the polishing body of Example 1. FIG. 3 is a schematic cross-sectional view showing an enlarged portion of the polishing body of Example 1 fixed to a platen. FIG. 4 is a schematic cross-sectional view of a wafer polishing machine.

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 the 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.

The polishing body of the present invention is fixed to the fixed surface of a surface plate and polishes the workpiece in the presence of a polishing liquid under a specified surface pressure. The polishing liquid may be pure water, oil-based, or may contain an acidic or alkaline chemical. The polishing body of the present invention can suppress deterioration even when using a strongly acidic polishing liquid such as one with a pH of 3 or less or a pH of 1 or less.

The workpiece to be polished using the polishing body of the present invention can be a semiconductor wafer. The polishing body of the present invention is particularly suitable for polishing difficult-to-process materials such as silicon carbide (SiC), gallium nitride (GaN), and aluminum nitride (AlN).

A polishing machine to which the polishing body of the present invention can be attached can be suitably used in the lapping process, which involves rough processing of semiconductor wafers and then finishing them. The lapping process can be either a single-sided lapping process, in which only one side of the semiconductor wafer being polished is lapped, or a double-sided lapping process, in which both sides of the semiconductor wafer are simultaneously lapped using a pair of polishing bodies.

The polishing body of the present invention comprises a polishing pad, an adhesive layer, and a cushion layer. The layers are stacked in the following order: cushion layer, adhesive layer, polishing pad. In other words, the adhesive layer is interposed between the polishing pad and the cushion layer, adhering them to each other.

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 used with a strongly acidic polishing solution with a pH of 1 or less. The base material also has multiple pores formed in it. The abrasive particles are held within the base material or the pores.

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 an interconnected pore structure, and particularly preferably has an interconnected pore structure in the region of the polishing pad that includes the interface with the adhesive layer. In other words, it is preferable that interconnected pores are open at the interface with the adhesive layer of the polishing pad. If interconnected pores are open at the interface with the adhesive layer of the polishing pad, the adhesive component can easily penetrate through the openings. Therefore, a pad-side impregnated layer is easily formed at the interface with the adhesive layer of the polishing pad.

Abrasive particle materials that can be used include silica, ceria, alumina, zirconia, titania, diamond, manganese oxide, barium carbonate, chromium oxide, and iron oxide. These may be used alone or in combination of two or more.

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

The cushion layer, which is made of a porous material, adheres to the fixed surface of the surface plate in a manner that allows it to be repeatedly attached and detached. The pores in the cushion layer may include closed pores, but from the perspective of improving the cushion layer's adhesive properties, it is preferable that the cushion layer have a continuous porosity of approximately 90% or more.

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 the region of the cushion layer that includes the interface with the adhesive layer. In other words, it is preferable that interconnected pores are open at the interface of the cushion layer with the adhesive layer. If interconnected pores are open at the interface of the cushion layer with the adhesive layer, the adhesive component can easily penetrate through the openings. Therefore, a cushion-side impregnated layer is easily formed at the interface of the cushion layer with the adhesive layer.

It is preferable that the polishing pad have a pad-side impregnated layer and the cushion layer have a cushion-side impregnated layer. In this case, the pad-side impregnated layer improves the bond between the polishing pad and the adhesive layer, and the cushion-side impregnated layer improves the bond between the cushion layer and the adhesive layer. Therefore, even when polishing using a strongly acidic polishing liquid, the bond integrity between the polishing pad, adhesive layer, and cushion layer is less likely to deteriorate.

The thickness of the cushion layer is preferably between 100 μm and 500 μm. In this case, good adhesion to the fixed surface of the surface plate can be ensured. Furthermore, the flexible cushion layer's elastic deformation allows the cushion layer to more effectively perform its functions, improving the processing flatness of the polished surface and suppressing the occurrence of micro-scratches on the polished surface.

The flexibility of the cushion layer and its adhesion to the surface plate can be adjusted by appropriately setting the foaming ratio, open porosity, hardness, etc.

The adhesive layer contains a silicone-based adhesive component. Silicone-based adhesives containing silicone-based adhesive components are resistant to deterioration even when using a strongly acidic polishing solution with a pH of 1 or less.

During the manufacturing process, the abrasive body may warp due to differences in the amount of expansion and contraction between the layers. 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 the surface plate. The warpage of the abrasive body can be determined by placing the abrasive body with the concave side facing up on a flat measuring table and measuring the height of the most warped edge from the measuring table.

The components of the polishing body of the present invention are resistant to deterioration even when using a strongly acidic polishing solution with a pH of 1 or less. Furthermore, the adsorption properties of the cushion layer allow for repeated attachment and detachment to the platen. Therefore, the polishing body of the present invention can contribute to reducing the cost of polishing objects.

(Example)
Examples embodying the present invention will be described below, 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 of a second adhesive layer and its type, and the amount of warping of the polishing body are shown in Table 1.

As shown in Figure 1, the polishing body 1 of the embodiment has a polishing pad 3, an adhesive layer 5, a cushion layer 7, and a release paper 9. As shown in Figure 3, the release paper 9 is peeled off from this polishing body 1, and the polishing body 1 is attached to the fixing surface 13a of the surface plate 13.

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.

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. More specifically, numerous interconnected pores 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.

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

The polishing pad 3 is disc-shaped with a diameter of 300 mm and a thickness of 1.5 mm.

The cushion layer 7 is made of silicone rubber foam. The cushion layer 7 is in the shape of a disk with a diameter of 300 mm and a thickness of 300 μm.

The cushion layer 7 has an adsorption surface 7a and an adherend surface 7b facing away from the adsorption surface 7a and spaced apart in the thickness direction from the adsorption surface 7a. The 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.

The cushion layer 7 has a continuous porosity of approximately 90% or more and has a continuous pore structure in the region including the interface with the adhesive layer 5. In other words, continuous pores open at the interface between the cushion layer 7 and the adhesive layer 5. The adhesive component penetrates through these openings, forming a cushion-side impregnated layer 71 at the interface between the cushion layer 7 and the adhesive layer 5.

The adhesive that makes up adhesive layer 5 is a commercially available silicone adhesive.

The release paper 9 is made of PET film. The release paper 9 is peeled off from the suction surface 7a of the cushion layer 7 when the abrasive body 1 is attached to the surface plate 13. By keeping the release paper 9 attached to the suction surface 7a until just before attachment, the suction surface 7a is protected and the suction surface 7a is prevented from adhering to other components, improving the ease of handling of the abrasive body 1.

The polishing pad 3 in this polishing body 1 was manufactured as follows.

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

<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.

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

<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.

<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.

<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 and 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.

The warpage of the resulting abrasive body 1 was 20 mm.

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

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

The abrasive body of Comparative Example 1 had too much warping and could not be attached to the fixing surface 13a of the surface plate 13.

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

Other configurations are the same as in Example 1.

(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. In other words, the polishing body of Comparative Example 3 does not have a cushion layer 7.

(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 attached to the fixing surface 13a of the surface plate 13 with a second contact layer made of an acrylic adhesive.

Other configurations are the same as in the example.

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

Other configurations are the same as in the example.

(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.

Other configurations are the same as in the example.

(Evaluation of the life of the polishing body)
The abrasive body 1 of the example and the abrasive bodies of the comparative examples 1 to 6 were evaluated for their lifespan.

Each polishing body was cut into a 20 mm × 20 mm square to prepare a test specimen, which was then immersed in an aqueous potassium permanganate (KMnO ₄ ) 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.

The lifespan was evaluated as follows: complete deterioration was marked x, partial deterioration was marked △, and no deterioration was marked 〇. The results are shown in Table 2.

In the example polishing body, which used polyvinylidene fluoride as the resin for the base material 33, a silicone 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.

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

The cushioning layers of Comparative Examples 4 and 6, which used foamed polyurethane, were partially deteriorated after 50 hours and completely deteriorated after 100 hours.

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

The adhesive layer 5 of Comparative Examples 5 and 6, which used an acrylic adhesive, was partially deteriorated after 50 hours and was completely deteriorated after 100 hours.

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

This evaluation was performed by peeling the abrasive body 1 of the example and each of the abrasive 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 lift of the abrasive body (poor attachment), a rating of "Good" was given, and if there was lift of the abrasive body, a rating of "Poor" was given. The results are shown in Table 2.

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

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 via the adhesive layer 5, had poor adhesion.

The abrasive 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 adhesion.

(Processing test)
A wafer polishing machine (Engis EJW-380) shown in FIG. 4 was prepared, and a lapping test was conducted to polish a wafer 20 using a fixed abrasive grindstone 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.

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 Figure 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 into 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.

The surface plate 13 is a horizontal, circular plate that contains all of the carriers 22. A surface plate rotation shaft 30 protrudes vertically from the underside of the surface plate 13. The upper surface of the surface plate 13 serves as the fixed surface 13a. The polishing body 1 of Example 1 or the polishing bodies of Comparative Examples 2 to 6 are attached to the fixed surface 13a so as to face each wafer 20.

The drive unit 24 comprises a main drive unit 24a, a secondary drive unit 24b, and a pressure unit 24c. The main drive unit 24a drives the surface plate rotation shaft 30 to rotate at a predetermined speed around the first axis O1. The secondary drive unit 24b drives each carrier rotation shaft 28 to rotate at a predetermined speed around the second axis O2. The pressure unit 24c applies a predetermined load to each carrier rotation shaft 28 and the secondary drive unit 24b toward the surface plate 13.

The polishing liquid supply device 26 is installed above the surface plate 13. The polishing liquid supply device 26 interposes a polishing liquid 26a between each wafer 20 and the polishing body 1. The polishing liquid 26a consists of an aqueous potassium permanganate solution adjusted to pH 1 and does not contain abrasive particles.

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

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

In this evaluation, the amount of processing was measured at five points on the polished surface 20a after the processing test: the center point on the wafer surface 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), ΔR > 3 μm, it was marked as ×, and if ΔR ≦ 3 μm, it was marked as ◯. The results are shown in Table 2.

The polishing bodies 1 and other examples, which have a cushion layer 7 made of silicone rubber foam, all had ΔR values of 3 μm or less, demonstrating good processing flatness.

The polishing body of Comparative Example 3, which does not have a cushion layer, exhibited reduced processing flatness.

The present invention has been described above with reference to examples, but it goes without saying that the present invention is not limited to the above examples and can be modified and applied as appropriate without departing from the spirit of the invention.

The present invention can be used in semiconductor device manufacturing equipment.

REFERENCE SIGNS LIST 1 abrasive body 3 abrasive pad 5 adhesive layer 7 cushion layer 31 pad-side impregnated layer 33 base material 35 abrasive particles 37 pores 71 cushion-side impregnated layer

Claims (5)

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 . 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 . 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 . The wafer polishing method according to claim 3, wherein the wafer is a SiC wafer. 5. The wafer polishing method according to claim 4, wherein the polishing liquid is a strongly acidic polishing liquid having a pH of 1 or less .