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 and / or back surface of the base material layer 12 are provided with notches 14 in an auxetic pattern.

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 formed with a polishing surface for polishing an object to be polished, 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 formed with a polishing surface 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, 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 further, 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.

[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 represented by Preston's equation shown in the following (Equation 1). Preston's 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 manufacturing 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] In other words, 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 by the polishing platen of a polishing device, The substrate layer is characterized by having notches formed by an auxetic pattern on its surface and / or back surface. [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. Since the surface and / or back side of the base layer are provided with notches in an auxetic pattern, the base layer deforms flexibly in response to load due to the movement of these notches, so that pressure is less likely 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.

[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] A plan view of the substrate layer according to the first embodiment, as seen from the front (or back) side. [Figure 5] Plan view of the main part in a state where a stress is applied to the base material layer in the first embodiment and the cut portion has spread. [Figure 6] Plan view when viewed from the front side (or back side) of the base material layer according to the second embodiment. [Figure 7] Plan view of the main part in a state where a stress is applied to the base material layer in the second embodiment and the cut portion has spread. [Figure 8] Plan view of the main part when viewed from the front side (or back side) of the base material layer 12 according to the third embodiment. [Figure 9] Plan view of the main part in a state where a stress is applied to the base material layer in the third embodiment and the cut portion has spread. [Figure 10] Plan view of the main part when viewed from the front side (or back side) of the base material layer 12 according to the fourth embodiment. [Figure 11] Plan view of the main part when viewed from the front side (or back side) of the base material layer 12 according to the fifth embodiment.

Mode for Carrying Out the Invention

[0014] The polishing pad according to the embodiment of the present invention will be described below with reference to the accompanying drawings. In each figure, the same reference numerals are given 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 the embodiment of the present invention, and is configured to polish a workpiece 3 such as a semiconductor substrate. The polishing apparatus 2 includes a polishing platen base plate 4 provided below to support the polishing pad 1, and a holding platen base plate 5 provided above to hold the workpiece 3.

[0015] The polishing pad 1 and the workpiece 3 are both roughly disc-shaped, with the polishing pad 1 having a larger diameter than the workpiece 3. The upper surface of the polishing pad 1 has a polishing surface that contacts the workpiece 3 to perform polishing. Slurry is supplied to this polishing surface from the slurry supply means 6. The lower surface of the polishing pad 1 is fixed to the polishing platen 4 by double-sided tape or the like.

[0016] As shown in Figures 2 and 3, the holding platen 5 comprises a disc-shaped top ring 5a and a plurality of airbags A arranged concentrically on the lower surface of the top ring 5a, so that the disc-shaped workpiece 3 is held in close contact with the lower surface of the airbags A.

[0017] 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 ring 5b that holds the outer periphery of the airbag A and the workpiece 3. The disc-shaped workpiece 3 is held in close contact with the lower surface of the airbag A inside the retainer ring 5b.

[0018] 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 3 held by the holding platen 5 slides radially along the polishing surface of the rotating polishing pad 1 while rotating.

[0019] The slurry supply means 6 supplies a slurry, in which abrasive particles are mixed in a required liquid, to the polishing surface of the polishing pad 1. This allows the slurry to penetrate between the polishing surface and the workpiece 3, thereby performing so-called chemical mechanical polishing (CMP).

[0020] Figure 2 shows a cross-sectional view of the polishing apparatus 2 and polishing pad 1 according to this embodiment. Note that the dimensions of each part in each figure are exaggerated for illustrative purposes. The above-mentioned holding platen 5 is equipped with first to sixth airbags A1 to A6 concentrically on the lower surface of the top ring 5a, and each airbag A has a substantially rectangular cross-section, and its flat lower surface is processed to allow it to adhere closely to and hold the surface of the workpiece 3 to be polished.

[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. 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.

[0031] In this embodiment, the polishing pad 1 employs the following configuration for the polishing layer 11. Specifically, the surface and / or back surface of the base material layer 12 according to this embodiment are provided with notches 14 in an auxetic pattern.

[0032] Here, an auxetic structure is characterized by the fact that when stress is applied to stretch or compress it, it expands or contracts in a direction perpendicular to the stress, and unlike ordinary materials and structures, it has the characteristic of having a negative Poisson's ratio. Furthermore, auxetics are said to be geometric patterns with numerous periodically placed incisions on a plane, and they have the characteristic of expanding vertically when stretched horizontally.

[0033] The above Poisson's ratio is ν x =-ε x / ε z ,ν y =-ε y / ε z It is represented as follows.

[0034] In other words, when a uniaxial stress (a stress acting in only one direction) is applied to an object in the z-axis direction, the object's dimensions in the z-axis direction elongate due to its elasticity, generating a longitudinal strain εx. Incidentally, transverse strains εx and ε also occur in the x and y axes perpendicular to the z-axis. This phenomenon is called the Poisson effect. The Poisson ratio is obtained by dividing this transverse strain by the longitudinal strain and multiplying by -1.

[0035] Figure 4 is a plan view of the base material layer 12 as seen from the front (or back) side according to the first embodiment. In this embodiment, as shown in Figure 4(b), three cuts 14 along the line segments extending from each vertex of an equilateral triangle to the centroid of the triangle are considered as one unit. A linear cut section C is formed by arranging a large number of triangles with their vertices facing upwards in the figure. In this way, the cuts 14 are provided along discontinuous cut line segments.

[0036] Figure 5 is a plan view of the first embodiment in which stress is applied to the base layer 12 and the notch C is expanded. In this way, during polishing, the notch C is expected to move to exhibit a closed state and an expanded state, thereby dispersing the repulsive force on the workpiece 3. For this reason, it can be inferred that even at the position corresponding to the boundary position of the airbag A on the workpiece 3, the irregularities generated at the boundary position of the airbag A will be smaller compared to conventional polishing pads, and this is expected to lead to a reduction in wavy.

[0037] The depth of the notch 14 in the base layer 12 is not particularly limited, but is preferably 70% or more of the thickness of the base layer 12, more preferably 80% or more, and even more preferably 90% or more. When the depth of the notch 14 is 70% or more 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.

[0038] Figure 6 is a plan view of the base material layer 12 as seen from the front (or back) side according to the second embodiment. As shown in Figure 6(b), this second embodiment has a shape in which a dashed line H extending in the vertical direction and a dashed line L extending in the horizontal direction are perpendicular to each other at the break point S of each dashed line. The portion of the line segments of dashed line H and dashed line L is a cut line. In this way, the cut 14 is provided along the discontinuous cut line segment.

[0039] Figure 7 is a plan view of the second embodiment in which stress is applied to the base layer 12 and the notch C is expanded. In this way, during polishing, the notch is expected to move between a closed state and an expanded state, thereby dispersing the repulsive force on the workpiece 3.

[0040] Figure 8 is a plan view of the base material layer 12 as seen from the front (or back) side according to the third embodiment. This third embodiment has a shape in which two trapezoids without a top base are joined at the top base side, and the resulting sake bottle shape is continuous both vertically and horizontally. Cut lines are formed on the sides of the trapezoids without a top base, excluding the vertices. That is, the cuts are made along discontinuous cut line segments. The shape in which two trapezoids without a top base are joined at the top base side, and the resulting sake bottle shape is continuous both vertically and horizontally, can be called a cell region, and a pattern is formed on the front and / or back side of the base material layer 12 in which a large number of cell regions surrounded by the discontinuous cut line segments are arranged.

[0041] Figure 9 is a plan view showing the state in which stress is applied and the notch expands in the base layer 12 in the third embodiment. In this way, during polishing, it is expected that the notch will move to exhibit a closed state and an expanded state, thereby dispersing the repulsive force on the workpiece 3.

[0042] Figure 10 is a plan view of the notch 14 as seen from the surface (or back) side of the base layer 12 according to the fourth embodiment. In this fourth embodiment, horizontal dashed lines, in which line segments of a predetermined length are arranged horizontally at predetermined intervals, are arranged vertically at predetermined intervals. Multiple first diagonal dashed lines are arranged diagonally by arranging line segments of a predetermined length at predetermined intervals so as to connect the gaps where the line segments in each horizontal dashed line are interrupted. Multiple second diagonal dashed lines are arranged diagonally by arranging line segments of a predetermined length at predetermined intervals so as to connect the gaps where the line segments in the first diagonal dashed lines are interrupted. The positions of these line segments are designated as the notch 14. In this embodiment as well, it is expected that the notch will move to exhibit a closed state or an open state, thereby dispersing the repulsive force on the workpiece 3.

[0043] Figure 11 is a plan view of the notch 14 as seen from the surface (or back) side of the base layer 12 according to the fifth embodiment. This notch 14 is formed by joining a first V-shaped line, which is formed by joining two line segments from the left and right at a first angle, and a second V-shaped line, which is formed by joining two line segments from the left and right at a second angle, to create a V-shape. A shape is created by arranging these V-shapes horizontally, and multiple rows of these horizontally arranged V-shapes are provided vertically. The notch 14 is provided along this V-shape. This notch 14 forms a notch with an auxetic pattern. The V-shaped portion described above can be called a cell region. In the base layer 12 of this fifth embodiment, it is expected that during polishing the notch portion will move to exhibit a closed state or an open state, thereby dispersing the repulsive force on the workpiece 3.

[0044] In each of the above embodiments, the cell regions on the front or back surface of the base layer 12 can be the same or different in size (area). That is, cell regions of the same size may be continuous, or cell regions of different sizes (areas) may be continuous. Furthermore, the numerous cell regions may be the same or different in shape. Therefore, the shape of the notches 14 provided in the cell regions may be the same or different for each cell region.

[0045] Furthermore, the surface and / or back surface of the base material layer 12 may be divided into multiple areas, and the depth of the cuts may be different or the same. The depth of the cuts is preferably 70% or more of the thickness of the base material layer 12, more preferably 80% or more, and even more preferably 90% or more. When the depth of the cuts is 70% or more of the thickness of the base material 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. [Explanation of Symbols]

[0046] 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 cuts

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 and / or back surface of the base material layer are provided with notches in an auxetic pattern.

2. The polishing pad according to claim 1, characterized in that the aforementioned cuts are provided along discontinuous cut segments.

3. The polishing pad according to claim 2, characterized in that a pattern is formed on the surface and / or back side of the base material layer, in which a number of cell regions surrounded by the discontinuous cut segments are arranged.

4. The polishing pad according to claim 3, characterized in that the numerous cell regions are the same or different in size (area).

5. The polishing pad according to claim 3, characterized in that the numerous cell regions are the same or different in shape.

6. The polishing pad according to claim 1, characterized in that the surface and / or back surface of the base material layer are divided into multiple areas, and the depth of the cuts differs for each area.

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