Polishing pad

Abstract

The present invention provides a polishing pad that can suppress polishing defects (wavy) that occur at the boundary of the airbag on the holding platen without significantly altering the polishing characteristics by modifying the material of the polishing layer. [Solution] A polishing pad comprising a polishing layer 11 on which a polishing surface for polishing the workpiece 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 a polishing device, The surface on the front side and / or the back side of the base material layer are processed to be a surface 14 with a flat-concave or curved shape that changes in height.

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 the polishing platen of a polishing apparatus and used, while 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] The polishing amount of the object to be polished in CMP is affected by various polishing conditions. As a general tendency, the relationship between the polishing amount and the polishing conditions is expressed by Preston's equation shown in the following (Equation 1). Preston Equation: RR = k·P·v (Equation 1) Here, RR represents the polishing rate, P represents the pressure (polishing pressure) for pressing the object to be polished against the polishing pad, v represents the relative speed between the object to be polished and the polishing pad, and k represents an empirical parameter depending on the type and temperature of the slurry, etc. As can be seen from the above (Equation 1), the polishing amount and the polishing pressure are in a proportional relationship. Therefore, in semiconductor device manufacturing, in order to improve the production throughput, a method of increasing the polishing pressure is often used. Thus, 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 described in Patent Document 1, multiple airbags are provided concentrically on the holding platen, and the pressure is adjusted for each of the multiple regions divided radially in the workpiece, thereby adjusting the pressure that the polishing platen acts on the workpiece and improving the flatness of the workpiece.

[0005] 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.

[0006] 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."

[0007] Furthermore, Patent Document 2 discloses a polishing pad in which the edge shape is improved by reducing the amount of compressive deformation of the base layer. Changing the constituent materials of the polishing pad in this way results in a significant change in the polishing characteristics of the polishing pad, which necessitates a separate search for optimal polishing conditions and carries the risk of reducing the throughput of semiconductor manufacturing. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Special Publication No. 2008-528300 [Patent Document 2] Japanese Patent Publication No. 2024-39241 [Overview of the project] [Problems that the invention aims to solve]

[0009] In view of these circumstances, the present invention provides a polishing pad that can suppress polishing defects (wavy) that occur at the boundary portion of the airbag in the holding platen without significantly changing the polishing characteristics by modifying the material of the polishing layer. [Means for solving the problem]

[0010] A polishing pad according to an embodiment of the invention 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, The surface on the front side and / or the back side of the base material layer are characterized by being processed to have a flat-concave or curved shape with varying heights. [Effects of the Invention]

[0011] The polishing pad according to an embodiment of the present invention comprises a polishing layer having a polishing surface 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 on the polishing platen of a polishing device. The surface on the front side and / or the back side of the base layer are processed to have a flat-concave or curved shape with varying heights. As a result, the base layer having these varying heights deforms flexibly in response to a load, making it less likely for pressure to concentrate in a specific area, and it is expected that the rebound of the polishing layer that occurs at the boundary of the airbag will be reduced in the base layer.

[0012] This makes it possible to suppress the occurrence of Wavy without significantly altering the polishing properties due to material modification of the polishing layer. [Brief explanation of the drawing]

[0013] [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]Perspective view of the height change surface when viewed from the front side (or back side) of the base material layer according to the first embodiment. [Figure 5] Explanatory drawing of the profiling used in the embodiment of the present invention. [Figure 6] Explanatory drawing of the result of profiling used in the embodiment of the present invention. [Figure 7] Schematic view of the mountain part M having a ridge line with a changing height and the valley part V having an inclined surface with a changing height on the height change surface according to the embodiment of the present invention, viewed from the side, and a schematic view of the mountain part M having a ridge line with a changing height and the valley part V having an inclined surface with a changing height, viewed from the plan. [Figure 8] Partial perspective view when viewed from the front side (or back side) of the base material layer according to the second embodiment. [Figure 9] Partial perspective view when viewed from the front side (or back side) of the base material layer according to the second embodiment.

MODE FOR CARRYING OUT THE INVENTION

[0014] Hereinafter, a 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 assigned to the same components, and redundant 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.

[0015] 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 polishing in contact with the workpiece 3 is formed on the upper surface of the polishing pad 1. This polishing surface has a configuration in which slurry is supplied 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.

[0016] 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 bag A.

[0017] 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 sections provided concentrically on the lower surface of the top ring 5a, and an annular retainer ring 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 ring 5b.

[0018] The polishing platen 4 and the holding platen 5 are each rotated by driving means (not shown), 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.

[0019] The slurry supply means 6 supplies a slurry in which abrasive grains are mixed in a required liquid to the polishing surface of the polishing pad 1. As a result, the slurry enters between the polishing surface and the workpiece 3, and so-called chemical mechanical polishing (CMP) is performed.

[0020] 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 explanation. The holding platen 5 includes first to sixth air bags A1 to A6 provided concentrically on the lower surface of the top ring 5a. The cross-section of each air bag A has a substantially rectangular shape, and the lower surface formed flat is processed so as to be able to hold the surface of the workpiece 3 in close contact.

[0021] As shown in Figure 3, the first to sixth airbags A1 to A6 are arranged concentrically, consisting of a circular first airbag A1 located in the center and ring-shaped second to sixth airbags A2 to A6 surrounding the first airbag A1. Each airbag A (A1 to A6) is capable of applying different pressures (P1 to P6) to the workpiece 3.

[0022] Furthermore, the pressure applied to the first to sixth airbags A1 to A6 can be adjusted according to the workpiece 3 to be polished and various polishing conditions, and since such a holding plate 5 is known from the above-mentioned Patent Document 1, etc., further detailed explanation will be omitted.

[0023] As shown in Figure 2, the polishing pad 1 comprises a polishing layer 11 having a polishing surface that contacts the object to be polished 3, 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 adheres the polishing layer 11 and the base layer 12. The adhesive layer 13 can be made of a core material made of polyethylene terephthalate (PET) with a pressure-sensitive adhesive such as an acrylic adhesive formed on the front and back surfaces, respectively. There are no particular restrictions on the adhesive layer 13, and it can be arbitrarily selected from various double-sided tapes.

[0024] 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, and which has countless voids formed inside. Here, a polyurethane sheet refers to a polyurethane-based resin containing polyurethane and polyurethane polyurea.

[0025] A urethane sponge can be used for the base layer 12, and commercially available polyurethane sponges can be used as such. Alternatively, the same polyurethane sheet as the polishing layer 11 may be used as the base layer 12.

[0026] 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, and a density of 0.60 to 1.10 g / cm³. 3 Each of these can be set accordingly. By setting the Shore D hardness of the polishing layer 11 within the above range, the occurrence of scratches can be suppressed.

[0027] The urethane sponge used in the base layer 12 has a thickness of 0.5 to 2 mm, a Shore A hardness of 20.0 to 75.0, and a density of 0.20 to 0.70 g / cm³. 3 Each of these can be set accordingly. By setting the Shore A hardness of the base layer 12 within the above range, the cushioning of the polishing pad 1 is improved, and the polishing rate can be increased.

[0028] 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.

[0029] 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.

[0030] As described above, when using a holding platen 5 equipped with multiple airbags A, at the boundary 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 location becomes lower than at other locations.

[0031] 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 between the airbags A and the other airbag A. This causes the portion to be excessively polished, resulting in the formation of concentric irregularities along the boundary, which is thought to cause the wavy appearance.

[0032] In this embodiment, the base material layer 12 in the polishing pad 1 has the following configuration. That is, the surface and / or back surface of the base material layer 12 in this embodiment are processed to be a surface 14 with a flat-concave or curved shape that changes in height.

[0033] As shown in Figure 4, the polishing pad 1 of the first embodiment has its surface and / or the height-changing surface 14 on the back side of the base material layer 12 processed into a curved shape by profile processing, where the surface on the front side and / or the height-changing surface 14 on the back side consists of a series of peaks M having height-changing ridges and valleys V having height-changing inclined surfaces.

[0034] Here, profiling is known as the following processing method. As shown in Figure 5, for example, pressure P is applied to the required part of a rectangular elastic body, indicated by the dashed line, using a roller to compress it and create a recessed portion in the plane in the M and X directions. In this state, it is sliced ​​by a horizontal plane H, the roller is removed, and the pressure is released.

[0035] As shown in Figure 6, the material is then divided into two pieces, with the portion that was under pressure returning to its original shape to form a peak M, and the portion that was not under pressure forming a valley V. In practice, this involves applying pressure using a roller with precisely sized grooves to create peaks M and valleys V of the desired size.

[0036] In the embodiment shown in Figure 4, the dimension L (Figure 7) connecting the vertex of the peak M and the bottom point of the valley V, along a straight line when the peak M and valley V are viewed from above, is processed to be continuous with the same dimension.

[0037] In the embodiment shown in Figure 4, the dimension L (Figure 6) connecting the vertex of the peak M and the bottom point of the valley V with a straight line when the peak M and valley V are viewed from above is shown to be the same. However, this dimension L may be of multiple types and manufactured accordingly.

[0038] A height-changing surface 14, which is a curved surface formed by profile processing, consisting of a peak M having a height-changing ridge and a valley V having a height-changing sloping surface, can also be defined by the area of ​​the valley when the peak and valley are viewed from above. Figure 7 shows a schematic diagram of the peak M having a height-changing ridge and the valley V having a height-changing sloping surface in a side view in Figure 7(a). Figure 7(b) shows a schematic diagram of the peak M having a height-changing ridge and the valley V having a height-changing sloping surface in a plan view. In Figure 7(b), the area of ​​the peak M when viewed from above is shown by S1, and the area of ​​the valley V is shown by S2. Furthermore, the height dimension (d in Figure 6) between the vertex of the peak M and the base of the valley V may be processed in multiple types.

[0039] The height dimension d between the peak of the peak M and the bottom of the valley V is not particularly limited, but is preferably 20% to 80% of the thickness of the base layer 12, more preferably 25% to 75%, and even more preferably 30% to 70%. When the height dimension d between the peak of the peak M and the bottom of the valley V is 20% to 80% of the thickness of the base layer 12, the stress when the workpiece 3 is pressed against the polishing pad 1 is more easily distributed, and wavy is more easily reduced.

[0040] The distance between the vertex of one peak M and the adjacent vertex of another peak M is not particularly limited, but is preferably 2 mm or more and 10 mm or less. By having a distance of 2 mm or more and 10 mm or less between the vertex of one peak M and the adjacent vertex of another peak M, the adhesion between the polishing layer 11 and the base material layer 12 is ensured, and the stress when the workpiece 3 is pressed against the polishing pad 1 is more easily distributed, making it easier to reduce wavy.

[0041] In this embodiment, when the peak M and the valley V are viewed from above, the area S1 of the peak M may be the same or different. Of course, when the peak M and the valley V are viewed from above, the area S1 of the peak M and the area S2 of the valley V may be different, the same, or even set to any desired area. Furthermore, the height dimension between the vertex of the peak M and the base of the valley V may be processed to be of multiple types or a single type.

[0042] In any case, polishing is performed with the area above the polishing layer 12 supported near the peak of the peak M on the height-changing surface 14, allowing for flexible movement in response to the load and dispersing the repulsive force on the workpiece 3. Therefore, it can be inferred that the irregularities generated at the boundary of the airbag A on the workpiece 3 will be smaller compared to conventional polishing pads, leading to a reduction in wavy.

[0043] Figures 8 and 9 are perspective views of a portion of the base material layer 12 as seen from the front (or back) side according to the second embodiment. In this second embodiment, the surface on the front side and / or the height-changing surface 14 on the back side of the base material layer 12 is processed to have a bottomed porous structure. In this embodiment, the height-changing surface 14 is processed so that each hole in the bottomed porous structure is continuous. Here, continuous means that the holes are close together and have a width or diameter equal to or the same as the width or diameter of the holes. Therefore, although the space between a hole and an adjacent hole on the height-changing surface 14 is flat, it has a function equivalent to the peak M in the first embodiment.

[0044] In this embodiment, the opening shape of the holes in the bottomed porous structure can be of several different types. In Figures 8 and 9, the opening shapes are shown as circular and elliptical, but they may also be oval, polygonal, or irregular in shape. Furthermore, the depth of the holes may also be of multiple types.

[0045] The depth of the holes is not particularly limited, but is preferably 20% to 80% of the thickness of the base layer 12, more preferably 25% to 75%, and even more preferably 30% to 70%. When the depth of the holes is 20% to 80% of the thickness of the base layer 12, the stress when the workpiece 3 is pressed against the polishing pad 1 is more easily distributed, making it easier to reduce wavy.

[0046] In this embodiment, since each hole is continuous and the space between adjacent holes functions as a ridge M, polishing is performed with the upper part of the polishing layer supported by the space between adjacent holes, and it is expected that the pad will move flexibly in response to the load, thereby dispersing the repulsive force on the workpiece 3. For this reason, it is presumed that even at the position corresponding to the boundary of the airbag A on the workpiece 3, the irregularities that occur at the boundary of the airbag A will be smaller than those of conventional polishing pads, and it is expected that this will lead to a reduction in wavy.

[0047] The distance between the ridge M formed between one hole and an adjacent hole and the adjacent ridge M is not particularly limited, but is preferably 2 mm to 10 mm. By having the distance between the ridge M and the adjacent ridge M be 2 mm to 10 mm, the adhesion between the polishing layer 11 and the base material layer 12 is ensured, while the stress when the workpiece 3 is pressed against the polishing pad 1 is more easily distributed, making it easier to reduce wavy. [Explanation of Symbols]

[0048] 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 14. Height change surface

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, A polishing pad characterized in that the surface on the front side and / or the back side of the base material layer are processed to have a flat-concave or curved shape with varying heights.

2. The polishing pad according to claim 1, characterized in that the surface on the front side and / or the height-changing surface on the back side of the base material layer are processed to have a bottomed porosity.

3. The polishing pad according to claim 2, characterized in that the height-changing surface processed to form a bottomed porous surface is processed so that each hole in the bottomed porous surface is continuous.

4. The polishing pad according to claim 3, characterized in that the opening shape of the holes in the bottomed porous structure is of several different types.

5. The polishing pad according to claim 2, characterized in that the area shape of the opening of the holes in the bottomed porous structure is of several different types.

6. The polishing pad according to claim 2, characterized in that the depth of the holes in the bottomed porous area is of multiple types.

7. The polishing pad according to claim 6, characterized in that the surface and / or back surface of the base material layer are divided into a plurality of areas, and the depth of the holes in the bottomed pores is different.

8. The polishing pad according to claim 1, characterized in that the surface on the front side and / or the height-changing surface on the back side of the base material layer is shaped by profile processing as a curved surface having a series of peaks with height-changing ridges and valleys with height-changing inclined surfaces.

9. The polishing pad according to claim 8, characterized in that the apex of the peak and the bottom of the valley are processed so that the distance connecting them by a straight line when the peak and valley are viewed from above is the same and continuous.

10. The polishing pad according to claim 8, characterized in that the dimensions of the line connecting the peak of the peak and the bottom of the valley, when viewed from above, are of multiple types.

11. The polishing pad according to claim 8, characterized in that when the peak portion and the valley portion are viewed from above, the area of ​​the peak portion is the same or different.

12. The polishing pad according to claim 8, characterized in that when the peak portion and the valley portion are viewed from above, the area of ​​the valley portion is the same or different.

13. The polishing pad according to claim 8, characterized in that the height dimension between the peak of the peak and the bottom of the valley is of multiple types and is processed accordingly.

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