Polishing pad

Abstract

This invention provides a polishing pad capable of suppressing polishing defects (wavy) that occur at the boundary of the airbag in a holding platen. [Solution] The polishing pad 1 comprises a polishing layer 11 on which a polishing surface for polishing the object to be polished 3 is formed, and a base layer 12 provided on the opposite side of the polishing surface of the polishing layer 11 and held on the polishing platen of the polishing device 2, Between the base layer 12 and the polishing layer 11, a first group of grooves 32 excavated from the base layer 12 towards the polishing layer 11 and / or a second group of grooves 31 excavated from the polishing layer 11 towards the base layer 12 are formed, and an adhesive layer is provided to bond the base layer 12 and the polishing layer 11. The first groove group 32 and the second groove group 31 have wall portions at the position where they reach the periphery of the adhesive layer.

Description

Technical Field

[0001] The present invention relates to a polishing pad used for polishing an object to be polished.

Background Art

[0002] The polishing pad has a polishing layer on which a polishing surface for polishing an object to be polished is formed, and a base material layer provided on the side opposite to the polishing surface of the polishing layer and held by a polishing platen. Conventionally, when polishing an object to be polished such as a semiconductor substrate, a disk-shaped polishing pad having a polishing layer on which a polishing surface is formed and a base material layer provided on the side opposite to the polishing surface of the polishing layer is used. The polishing pad is mounted on a polishing platen of a polishing apparatus and used, and the object to be polished is held by a holding platen (Patent Document 1).

[0003] In the above polishing apparatus, while pressing the object to be polished against the polishing pad, the holding platen and the polishing platen are relatively rotated, and a slurry containing a chemical component is further supplied between the object to be polished and the polishing pad, so-called chemical mechanical polishing (Chemical Mechanical Polishing, CMP) is performed.

[0004] Here, it is known that the polishing amount of the object to be polished in CMP can be increased by increasing the polishing pressure. In the polishing apparatus of Patent Document 1, a plurality of air bags are provided concentrically on the holding platen, and the pressure is adjusted for each region divided into a plurality in the radial direction of the object to be polished, so as to adjust the pressure exerted by the polishing platen on the object to be polished and improve the flatness of the object to be polished.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, if concentric airbags are provided on the above-mentioned holding platen, the pressing force on the workpiece becomes lower at the boundary between adjacent airbags, and the rebound force from the polishing pad pressed by the workpiece concentrates at this boundary.

[0007] As a result, the portion of the workpiece corresponding to the aforementioned boundary was excessively polished, sometimes creating concentric, wavy irregularities in the radial direction of the workpiece. The inventors of this application have decided to refer to such irregularities originating from the boundary portion of the airbag of the holding platen as "wavy."

[0008] In view of these problems, the present invention provides a polishing pad capable of suppressing polishing defects (wavy) that occur at the boundary portion of the airbag in a holding platen. [Means for solving the problem]

[0009] In other words, the polishing pad according to claim 1 comprises a polishing layer having a polishing surface formed thereon for polishing an object to be polished, and a base layer provided on the opposite side of the polishing surface of the polishing layer and held by a polishing platen of a polishing device, Between the base layer and the polishing layer, a first group of grooves excavated from the base layer side toward the polishing layer and / or a second group of grooves excavated from the polishing layer side toward the base layer are formed, and an adhesive layer is provided to bond the base layer and the polishing layer, characterized in that the first group of grooves and the second group of grooves have a wall portion at the position where they reach the periphery of the adhesive layer. [Effects of the Invention]

[0010] According to the polishing pad according to an embodiment of the present invention, an adhesive layer is provided between the base layer and the polishing layer to bond the base layer and the polishing layer. A first group of grooves is excavated from the base layer side toward the polishing layer and / or a second group of grooves is excavated from the polishing layer side toward the base layer. As a result, the gaps formed between the base layer and the adhesive layer and / or between the polishing layer and the adhesive layer by these grooves can disperse the repulsive force from the polishing pad when the object to be polished is pressed against the polishing pad.

[0011] As a result, the rebound force from the polishing pad does not concentrate at the portion of the workpiece that corresponds to the boundary of the airbag on the holding platen, thereby suppressing the occurrence of wavy. [Brief explanation of the drawing]

[0012] [Figure 1] A perspective view showing a polishing device. [Figure 2] Cross-sectional view of the polishing device and polishing pad. [Figure 3] Bottom view of the support plate. [Figure 4] A plan view of the passage area E through which the object to be polished passes in the adhesive layer during polishing. [Figure 5] A plan view showing a group of grooves, which are radial grooves, formed in the adhesive layer. [Figure 6] A plan view showing a group of concentric grooves formed in the adhesive layer. [Figure 7] A plan view showing a group of grooves formed in the adhesive layer, combining grid grooves and spiral grooves. [Figure 8] A plan view showing a group of grooves formed in the adhesive layer, consisting of radial grooves and through holes. [Modes for carrying out the invention]

[0013] The polishing pad according to an embodiment of the present invention will be described with reference to the accompanying drawings. In each figure, the same reference numerals are given to the same components, and overlapping descriptions are omitted. Also, the dimensions of each part in each figure are exaggerated for the purpose of explanation, and the ratios thereof are also different from the actual ones. FIG. 1 shows a perspective view of a polishing apparatus 2 provided with a polishing pad 1 according to an embodiment of the present invention, which is configured to polish a workpiece 3 such as a semiconductor substrate. The polishing apparatus 2 includes a polishing platen 4 provided below to support the polishing pad 1 and a holding platen 5 provided above to hold the workpiece 3.

[0014] The polishing pad 1 and the workpiece 3 each have a substantially disk shape, and the polishing pad 1 is formed to have a larger diameter than the workpiece 3. A polishing surface for performing polishing in contact with the workpiece 3 is formed on the upper surface of the polishing pad 1. The polishing surface is configured to receive slurry S from a slurry supply means 6. The lower surface of the polishing pad 1 is fixed to the polishing platen 4 by a double-sided tape or the like.

[0015] As shown in FIGS. 2 and 3, the holding platen 5 includes a disk-shaped top ring 5a and a plurality of air bags A provided concentrically on the lower surface of the top ring 5a. The disk-shaped workpiece 3 is held in close contact with the lower surface of the air bags A.

[0016] As shown in FIG. 2, the holding platen 5 includes a disk-shaped top ring 5a, an air bag A composed of a plurality of concentrically provided sections on the lower surface of the top ring 5a, and an annular retainer 5b that holds the outer peripheral portions of the air bag A and the workpiece 3. The disk-shaped workpiece 3 is held in close contact with the lower surface of the air bag A inside the retainer 5b.

[0017] The polishing platen 4 and the holding platen 5 are rotated by driving means (not shown), respectively, and the holding platen 5 is further reciprocated in the radial direction from the center position of the polishing platen 4. As a result, the workpiece 3 held by the holding platen 5 slides along the radial direction while rotating on the polishing surface of the rotating polishing pad 1.

[0018] The slurry supply means 6 supplies a slurry in which abrasive grains are mixed into the polishing surface of the polishing pad 1, whereby the slurry enters between the polishing surface and the workpiece 3 to be polished, and so-called chemical mechanical polishing (CMP) is performed.

[0019] FIG. 2 shows a cross-sectional view of the polishing apparatus 2 and the polishing pad 1 according to the present embodiment. Note that the dimensions of each part in each figure are exaggerated for the purpose of explanation. The holding platen 5 is provided with first to sixth air bags A1 to A6 concentrically on the lower surface of the top ring 5a. Each air bag A has a substantially rectangular cross-section, and the lower surface formed flat is processed so as to be able to adhere to and hold the surface of the workpiece 3 to be polished.

[0020] As shown in FIG. 3, the first to sixth air bags A1 to A6 are arranged concentrically, and are composed of a circular first air bag A1 located at the center and ring-shaped second to sixth air bags A2 to A6 surrounding the first air bag A1. Each air bag A (A1 to A6) can apply different pressures (P1 to P6) to the workpiece 3 to be polished. Note that the pressures applied to the first to sixth air bags A1 to A6 can be adjusted according to the workpiece 3 to be polished and various polishing conditions. Since such a holding platen 5 is known in Patent Document 1 and the like, further detailed description thereof will be omitted.

[0021] As shown in FIG. 2, the polishing pad 1 includes a polishing layer 11 on which a polishing surface that contacts the workpiece 3 to be polished is formed, a base material layer 12 provided on the surface opposite to the polishing surface of the polishing layer 11 and held by the polishing platen 4, and an adhesive layer 13 that adheres the polishing layer 11 and the base material layer 12.

[0022] A polyurethane sheet can be used for the polishing layer 11. As such a polyurethane sheet, a foamed polyurethane sheet can be used, which is formed by mixing an isocyanate-terminated prepolymer (hereinafter sometimes simply referred to as prepolymer), a curing agent, and a hollow body to form a polyurethane resin molded body, and then slicing the polyurethane resin molded body, thereby creating countless voids inside. Here, a polyurethane sheet refers to a polyurethane-based resin containing polyurethane and polyurethane polyurea.

[0023] A urethane sponge can be used for the base layer 12, and commercially available urethane sponges can be used as such. Alternatively, the same polyurethane sheet as the polishing layer 11 may be used as the base layer 12.

[0024] The polyurethane sheet used for the polishing layer 11 has a thickness of 0.5 to 2 mm, a Shore D hardness of 20.0 to 70.0, preferably 35.0 to 65.0, and a density of 0.60 to 1.10 g / cm³. 3 Each of these can be set accordingly. By setting the D hardness of the polishing layer 11 within the above range, the occurrence of scratches can be suppressed.

[0025] The urethane sponge used for the base layer 12 has a thickness of 0.5 to 2 mm, a Shore A hardness of 20.0 to 75.0, preferably 45.0 to 65.0, and a density of 0.20 to 0.70 g / cm³. 3 Each can be set accordingly.

[0026] Furthermore, the storage modulus (at 40°C) of the abrasive layer 11 is 55 to 400 MPa, preferably 70 to 130 MPa, and the storage modulus (at 40°C) of the base layer 12 is 1 to 10 MPa, preferably 2 to 8 MPa. It is desirable that the ratio of the storage modulus of the abrasive layer 11 to the storage modulus of the base layer 12 be in the range of 2 to 60, preferably 5 to 50. By setting it in this way, it becomes possible to polish the workpiece without damaging the shape of its edges.

[0027] Surface structures such as grooves and through holes can be arbitrarily formed on the polishing surface of the polishing layer 11. These surface structures allow the slurry to be retained on the polishing surface when polishing the workpiece 3, or allow the slurry on the polishing surface to be discharged to the outside. Conventional known shapes can be used as surface structures, such as grid grooves, radial grooves, concentric grooves, and through holes.

[0028] In the polishing pad 1 described above, in order to uniformly polish the workpiece 3 while pressing it with a large pressing force, concentric airbags A are provided on the holding platen 5 to apply different radial pressures to the workpiece 3.

[0029] As described above, when using a holding platen 5 equipped with multiple airbags A, at the boundary position B between adjacent airbags A, the pressure from each airbag A is not transmitted to the workpiece 3 to be polished, and the pressing force at that position becomes lower than at other parts. As a result, the rebound force from the polishing pad 1 due to compression is concentrated in the portion of the workpiece 3 corresponding to the boundary position B between the airbags A and the other airbags A. This causes the portion to be excessively polished, resulting in the formation of concentric irregularities along the boundary position B, which is thought to cause the wavy appearance.

[0030] In this embodiment, the adhesive layer 13 in the polishing pad has the following configuration: The adhesive layer 13 adheres the base layer 12 and the polishing layer 11. The adhesive layer 13 may consist of a core material made of polyethylene terephthalate (PET) with adhesive formed on both the front and back surfaces. The adhesive can be rubber-based, acrylic-based, silicone-based, or urethane-based, and can be pressure-sensitive or hot-melt. When the adhesive layer is provided with grooves (described later), a pressure-sensitive acrylic type is preferably used. Furthermore, the polyethylene terephthalate (PET) core material is not required. There are no particular restrictions on the adhesive layer 13; it can be arbitrarily selected from various types of double-sided tapes.

[0031] The adhesive layer 13 interposed between the base layer 12 and the polishing layer 11 has a first group of grooves 32 excavated from the base layer 12 towards the polishing layer 11 and / or a second group of grooves 31 excavated from the polishing layer 11 towards the base layer 12 (Figure 2). Here, a group of grooves obviously refers to multiple continuous grooves. In addition, even a single continuous groove in a spiral shape can be referred to as a group of grooves if multiple adjacent recesses (grooves) are formed in a plane.

[0032] The first groove group 32 and the second groove group 31 have walls at the point where they reach the periphery of the adhesive layer 13, so that there are no groove groups at the periphery of the adhesive layer 13. In this way, when there are no groove groups at the periphery of the adhesive layer 13, adhesion between the base layer 12 and the polishing layer 11 can be accurately achieved at the periphery, and peeling can be prevented. The first groove group 32 and the second groove group 31 described above have shapes selected from the group consisting of, for example, grid grooves, radial grooves, spiral grooves, concentric grooves, and holes.

[0033] When polishing is performed using the polishing pad 1 according to this embodiment, the passage area E through which the workpiece 3 passes on the polishing pad 1 is shown in Figure 4. It is preferable to provide the first groove group 32 and the second groove group 31 at positions on the surface of the adhesive layer 13 corresponding to the passage area E. Figure 5 shows the case of radial grooves. The center of the passage area E is a non-passage area through which the workpiece 3 does not pass. The center positions of the first groove group 32 and the second groove group 31 may coincide with the center of the passage area E, or they may be offset (mismatched) as shown in Figure 6. The groove group shown in Figure 6 represents concentric grooves. The groove group may also be a combination of two or more patterns. Figure 7 shows a combination (overlap) of grid grooves and spiral grooves, and Figure 8 shows a combination of radial grooves and holes. Of course, it is also possible to combine (overlap) two patterns selected from the group consisting of grid grooves, radial grooves, spiral grooves, concentric grooves, and holes.

[0034] Even with the polishing pad 1 according to the above embodiment, the adhesive layer 13, which has a first group of grooves 32 excavated from the base layer 12 toward the polishing layer 11 and / or a second group of grooves 31 excavated from the polishing layer 11 toward the base layer 12, is expected to have a reduced repulsive force on the workpiece 3 due to the gaps formed between the base layer 12 and the adhesive layer 13 and / or between the polishing layer 11 and the adhesive layer 13 by the presence of the grooves, thereby dispersing the repulsive force on the workpiece 3. For this reason, it is inferred that even at the position corresponding to the boundary position B of the airbag A on the workpiece 3, the irregularities that occur at the boundary position of the airbag A will be smaller than with conventional polishing pads, and this is expected to lead to a reduction in wavy. [Explanation of symbols]

[0035] 1. Polishing pad 2. Polishing device 3 Object to be polished 4 Polishing surface plate 5. Holding plate 5a. Top ring 6. Slurry supply means 11. Polishing layer 12 Base material layer 13 Adhesive layer 31 Second groove group 32 First groove group

Claims

1. A polishing pad comprising a polishing layer having a polishing surface formed thereon for polishing an object to be polished, and a base layer provided on the opposite side of the polishing surface of the polishing layer and held by the polishing platen of a polishing device, Between the base layer and the polishing layer, a first group of grooves excavated from the base layer side toward the polishing layer and / or a second group of grooves excavated from the polishing layer side toward the base layer are formed, and an adhesive layer is provided to bond the base layer and the polishing layer. The polishing pad is characterized in that the first groove group and the second groove group have a wall portion at the position where they reach the periphery of the adhesive layer.

2. The polishing pad according to claim 1, characterized in that the first group of grooves and / or the second group of grooves are formed in the polishing surface in a range corresponding to the area in which the object to be polished moves.

3. The polishing pad according to claim 1 or 2, characterized in that the grooves of the first groove group and the grooves of the second groove group are formed around predetermined positions in areas corresponding to the surface region of the base material layer and the surface region of the polishing layer, respectively, and the centers of the first groove group and the centers of the second groove group are not coincident.

4. The polishing pad according to claim 1 or 2, characterized in that the grooves of the first groove group and the grooves of the second groove group are concentric, radial, grid-like, spiral, or perforated.

5. The polishing pad according to claim 1, characterized in that the adhesive layer has an adhesive layer on the polishing layer side and an adhesive layer on the substrate layer side, separated by a PET layer.

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