Polishing pad

Abstract

This suppresses the waviness that occurs at the boundary of the airbag in the holding platen. [Solution] The polishing pad 3 comprises a polishing layer 11 on which a polishing surface for polishing the workpiece 2 is formed, and a base layer 12 provided on the side of the polishing layer 11 opposite to the polishing surface. The polishing surface of the polishing layer 11 has at least one surface structure selected from the group consisting of grid grooves, radial grooves, spiral grooves, concentric grooves, and through holes, and the adhesive surface of the base layer 12 on the polishing layer side has at least one surface structure selected from the group consisting of grid grooves, radial grooves, spiral grooves, concentric grooves, and through holes.

Description

Technical Field

[0001] The present invention relates to a polishing pad, and more particularly to a polishing pad having 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.

Background Art

[0002] 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 on a holding platen (Patent Document 1). 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 supplied between the object to be polished and the polishing pad, so-called chemical mechanical polishing (Chemical Mechanical Polishing, CMP) is performed.

[0003] 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 of a plurality of regions divided in the radial direction of the object to be polished, so that the pressure exerted by the polishing platen on the object to be polished is adjusted to improve the flatness of the object to be polished.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, when concentric airbags are provided on the holding platen, the pressing force on the workpiece is reduced at the boundary between adjacent airbags, and the repulsive force from the polishing pad pressed by the workpiece is concentrated at this boundary. As a result, the portion of the workpiece corresponding to the boundary is over-polished, and concentric, wavy irregularities are formed in the radial direction of the workpiece. The inventors have decided to refer to these irregularities originating from the boundaries of the airbags on the holding platen as "wavy."

[0006] In view of these problems, the present invention provides a polishing pad that can suppress polishing defects (wavy) that occur at the boundary portion of the airbag in a holding platen. [Means for solving the problem]

[0007] The polishing pad of the invention comprises a polishing layer having a polishing surface for polishing an object to be polished, and a base layer provided on the side opposite to the polishing surface of the polishing layer, wherein the polishing surface of the polishing layer has at least one surface structure selected from the group consisting of grid grooves, radial grooves, spiral grooves, concentric grooves, and through holes, and the adhesive surface of the base layer on the polishing layer side has at least one surface structure selected from the group consisting of grid grooves, radial grooves, spiral grooves, concentric grooves, and through holes. [Effects of the Invention]

[0008] According to the invention, it is possible to provide a polishing pad that can suppress polishing defects (wavy) that occur at the boundary portion of the airbag in the holding platen. [Brief explanation of the drawing]

[0009] [Figure 1] This is a perspective view of the polishing apparatus. [Figure 2] This is a cross-sectional view of a polishing device and a polishing pad. [Figure 3] This is a bottom view of the airbag. [Figure 4]This figure illustrates combinations of surface structure patterns used on the polishing surface of the polishing pad and the adhesive surface on the polishing layer side of the substrate layer. [Modes for carrying out the invention]

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Figure 1 is a perspective view of a polishing apparatus 1 equipped with a polishing pad 3 used for polishing a workpiece 2 such as a semiconductor substrate, which is one embodiment of the present invention, and Figure 2 is a cross-sectional view of the polishing apparatus 1 and the polishing pad 3. Note that the dimensions of each part in the following figures are exaggerated for illustrative purposes.

[0011] The polishing apparatus 1 comprises a polishing platen 4 located below to support the polishing pad 3, a holding platen 5 located above to support the workpiece 2, and a slurry supply means 6 for supplying slurry S. The polishing pad 3 and the workpiece 2 are each substantially disc-shaped, with the polishing pad 3 having a larger diameter than the workpiece 2. The upper surface of the polishing pad 3 has a polishing surface that contacts the workpiece 2 to perform polishing, and the lower surface of the polishing pad 3 is fixed to the polishing platen 4 by double-sided tape or the like.

[0012] As shown in Figure 2, the holding platen 5 comprises a disc-shaped top ring 5a, an airbag A consisting of multiple concentrically arranged compartments on the lower surface of the top ring 5a, and an annular retainer 5b that holds the airbag A and the outer periphery of the workpiece 2. The disc-shaped workpiece 2 is held in close contact with the lower surface of the airbag A inside the retainer 5b.

[0013] The polishing platen 4 and the holding platen 5 are each rotated by a driving means (not shown), and the holding platen 5 is further reciprocated radially from the center position of the polishing platen 4. As a result, the workpiece 2 held by the holding platen 5 slides radially along the polishing surface of the rotating polishing pad 3 while rotating.

[0014] The slurry supply means 6 supplies a slurry, in which abrasive particles are mixed in the required liquid, to the polishing surface of the polishing pad 3. This allows the slurry to penetrate between the polishing surface and the workpiece 2, thereby performing so-called chemical mechanical polishing (CMP).

[0015] Next, referring to Figure 3, which is a bottom view of airbag A, the configuration of airbag A provided on the holding platen 5 will be described. As shown in Figure 3, the holding platen 5 is equipped with first to sixth airbags A1 to A6 arranged concentrically on the lower surface of the top ring 5a, and consists of a cylindrical first airbag A1 located in the center and ring-shaped second to sixth airbags A2 to A6 surrounding the first airbag A1. Each of the first to sixth airbags A1 to A6 has a roughly rectangular cross-section, and the flat lower surface is processed to allow it to adhere closely to and hold the surface of the workpiece 2 to be polished. Different pressures (P1 to P6) can be applied to the workpiece 2 to each of the first to sixth airbags A1 to A6.

[0016] The pressure applied to the first to sixth airbags A1 to A6 can be adjusted according to the workpiece 2 to be polished and various polishing conditions. Since such a holding plate 5 is known from the above-mentioned Patent Document 1, further detailed explanation will be omitted.

[0017] As shown in Figure 2, the polishing pad 3 comprises a polishing layer 11 having a polishing surface that contacts the object to be polished 2, a base layer 12 provided on the side of the polishing layer 11 opposite to the polishing surface and held by the polishing platen 4, and an adhesive layer 13 that bonds the polishing layer 11 and the base layer 12.

[0018] The polishing layer 11 can use a polyurethane sheet. As such a polyurethane sheet, an isocyanate-terminated prepolymer (hereinafter sometimes simply referred to as a prepolymer), a curing agent, and hollow bodies are mixed to form a polyurethane resin molded body, and the polyurethane resin molded body is sliced to form a foamed polyurethane sheet having innumerable voids inside, which can be used. Here, the polyurethane sheet refers to a polyurethane-based resin including polyurethane and polyurethane-polyurea.

[0019] For the base material layer 12, a urethane sponge can be used. As such a urethane sponge, a commercially available urethane sponge or the like can be used. Note that the same polyurethane sheet as the polishing layer 11 may be used as the base material layer 12.

[0020] The adhesive layer 13 is formed by applying pressure-sensitive adhesives such as acrylic adhesives to the front and back surfaces of a core material made of polyethylene terephthalate (PET). There is no particular limitation on the adhesive layer 13, and it can be arbitrarily selected from known double-sided tapes in the technical field.

[0021] As the polyurethane sheet used for the polishing layer 11, the thickness can be set to 0.5 to 2 mm, the Shore D hardness can be set to 20.0 to 70.0, preferably 35.0 to 65.0, and the density can be set to 0.60 to 1.10 g / cm 3 respectively. By setting the D hardness of the polishing layer 11 within the above range, the generation of scratches can be suppressed.

[0022] As the urethane sponge used for the base material layer 12, the thickness can be set to 0.5 to 2 mm, the Shore A hardness can be set to 20.0 to 75.0, preferably 45.0 to 65.0, and the density can be set to 0.20 to 0.70 g / cm 3 respectively.

[0023] Furthermore, the storage modulus (at 40°C) of the polishing 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 polishing 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 edge shape of the workpiece.

[0024] The polishing surface of the polishing pad 3 and the adhesive surface of the base layer 12 on the polishing layer side each have a surface structure having recesses including grooves and holes of a specific pattern. In this embodiment, the polishing surface of the polishing pad 3 is provided with at least one surface structure selected from the group consisting of, for example, grid grooves, radial grooves, spiral grooves, concentric grooves, and through holes, and the adhesive surface of the base layer 12 on the polishing layer side is provided with at least one surface structure selected from the group consisting of, for example, grid grooves, radial grooves, spiral grooves, concentric grooves, and through holes. The selection of the surface structures on the polishing surface of the polishing pad 3 and the adhesive surface of the base layer 12 on the polishing layer side is arbitrary, and various combinations can be adopted. The surface structure of the adhesive surface of the base layer 12 on the polishing layer side is provided in a range that does not reach the outer circumference of the base layer 12 so that slurry does not penetrate into the adhesive layer 13 through the recesses.

[0025] In this embodiment, the surface structure provided on the base layer 12 is described as being provided on the adhesive surface on the polishing layer side. However, a similar surface structure may also be provided on the adhesive surface of the base layer 12 on the polishing platen side, or on the back surface of the polishing layer 11 (the adhesive surface on the base layer side). In these cases as well, it is possible to suppress polishing defects (wavy) that occur at the boundary of the airbag in the holding platen, just as when the surface structure is provided on the adhesive surface of the base layer 12 on the polishing layer side.

[0026] Figure 4 shows an example of a combination of multiple surface structure patterns used on the polishing surface of the polishing pad 3 and the adhesive surface on the polishing layer side of the base layer 12. The first row of Figure 4 schematically shows an example of the five types of surface structure patterns (from left to right: grid groove, radial groove, spiral groove, concentric groove, and through hole) applied to the adhesive surface on the polishing layer side of the base layer 12. On the other hand, the first column on the left of Figure 4 schematically shows an example of four of the five types of surface structure patterns (from top to bottom: grid groove, radial groove, spiral groove, and concentric groove) applied to the polishing surface of the polishing pad 3. In other words, Figure 4 illustrates 20 different patterns, which are combinations of the five types of surface structure patterns of the base layer 12 and the four types of surface structure patterns of the polishing pad 3. In each combination, the polishing pad is shown as viewed from above, with solid lines representing the surface structure of the polishing surface of the polishing layer 11 and dotted lines representing the surface structure of the base layer 12.

[0027] As shown in Figure 4, the surface structure patterns used in the polishing pad 3 and the base layer 12 may be the same or different, but it is preferable that the grooves, holes, and other recesses in both are offset from each other (for example, that the grooves intersect as much as possible, or that the grooves (holes) are offset from each other). Therefore, when the same type and size of surface structure pattern is used in the polishing pad 3 and the base layer 12, the arrangement of the recesses in both surface structure patterns is offset by shifting the center position and orientation (rotation angle) of the two surface structure patterns.

[0028] For example, when a grid groove is applied to the polishing layer 11 and a grid groove or radial groove is applied to the base layer 12, or vice versa, the grid lines and radial lines are made so as not to overlap, and the grid points and the centers of the radial lines are shifted vertically and horizontally so as not to overlap. Also, when radial grooves or helical grooves are applied to both the polishing layer 11 and the base layer 12, the center positions of each surface structure pattern are shifted, and the phases of the radial grooves or helical grooves in both surface structure patterns are shifted by relatively rotating both surface structure patterns. Furthermore, when helical grooves or concentric grooves are applied to both the polishing layer 11 and the base layer 12, the center positions of each surface structure pattern are shifted, for example, horizontally. On the other hand, in combinations of different surface structure patterns other than those described above, such as those shown in Figure 4, if the recesses are offset (intersect) from each other even when simply overlapped, it is not necessary to shift the surface structures of the polishing layer 11 and the base layer 12.

[0029] Figure 2 shows a cross-sectional view along the grid groove 12a passing through the center of the polishing pad 3 when, among the combinations of the above surface structure patterns, concentric grooves 11a are used on the polishing surface of the polishing pad 3 and grid grooves 12a are used on the adhesive surface on the polishing layer side of the base layer 12. That is, in Figure 2, the center of the concentric groove 11a on the polishing surface is set to the center of the polishing pad 3, and one of the grid grooves 12a on the adhesive surface on the polishing layer side of the base layer 12 is arranged along the diameter of the polishing pad 3. The pitch between the concentric grooves 11a and the pitch between the grid grooves 12a, and the cross-sectional shape of the grooves 11a and 12a are arbitrary, but they may be rectangular as shown in Figure 2.

[0030] When the polishing pad is viewed from a plan view, the grooves (recesses) formed in the polishing layer 11 and the grooves (recesses) formed in the base layer 12 intersect at multiple points. Therefore, the repulsive force from the polishing pad is dispersed when the workpiece is pressed against the polishing pad. As a result, the repulsive force from the polishing pad does not concentrate at the points corresponding to the boundaries of the first to sixth airbags A1 to A6 of the holding platen on the workpiece, and the occurrence of the above-mentioned wavy is suppressed. [Explanation of Symbols]

[0031] 1 Polishing equipment 2 Object to be polished 3. Polishing pads 4. Polishing surface plate 5. Holding plate 11 Polishing layer 11a Grooves (recesses) in the surface structure of the polished surface of the polished layer 12 Base material layer 12a Grooves (recesses) on the adhesive surface of the substrate layer on the polished layer side

Claims

1. A polishing pad comprising a polishing layer having a polishing surface for polishing an object to be polished, and a base layer provided on the side opposite to the polishing surface of the polishing layer, The polished surface of the polished layer comprises at least one surface structure selected from the group consisting of grid grooves, radial grooves, spiral grooves, concentric grooves, and through holes. The adhesive surface of the base layer on the polishing layer side comprises at least one surface structure selected from the group consisting of grid grooves, radial grooves, spiral grooves, concentric grooves, and through holes. A polishing pad characterized by the following features.

2. The polishing pad according to claim 1, characterized in that the surface structure of the adhesive surface of the base material layer on the polishing layer side does not reach the outer circumference of the base material layer.

3. The polishing pad according to claim 1, characterized in that the surface structure of the adhesive surface of the base material layer on the polishing layer side and the surface structure of the polishing surface of the polishing layer have the same surface pattern.

4. The polishing pad according to claim 3, characterized in that the arrangement of recesses in the surface structure of the polishing surface of the polishing layer is misaligned with the arrangement of recesses in the surface structure of the adhesive surface of the base layer on the polishing layer side.

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