Polishing pad

Abstract

This polishing pad includes a base material and a polishing layer layered on the base material. The polishing layer has a polishing surface on which a plurality of grooves are formed by embossing. The base material has a first surface on which the polishing layer is layered and a second surface opposite from the first surface. The second surface is an attachment surface to which double-sided tape for fixing the polishing pad to a surface plate of a polishing device is attached. A first thermal deformation amount in a first direction of the base material measured by thermomechanical analysis is greater than a second thermal deformation amount in a second direction intersecting the first direction.

Description

Polishing pad Cross-reference to Related Applications

[0001] The present application claims priority from Japanese Patent Application No. 2025-052159, which is incorporated herein by reference.

[0002] The present invention relates to a polishing pad.

[0003] Conventionally, polishing pads have been used for chemical mechanical polishing (CMP) in the manufacture of semiconductor devices. For example, in the planarization process of wafers, while both the disk-shaped wafer fixed to a rotating head and the disk-shaped polishing pad fixed to a surface plate are rotated, a polishing slurry containing abrasive grains is supplied between the wafer and the polishing pad to polish the wafer.

[0004] As a polishing pad for such applications, one comprising a base material such as a PET film and a polishing layer laminated on a first surface of the base material is known. Further, a plurality of grooves opened on the polishing surface are formed in the polishing layer. The plurality of grooves can function as flow paths for the polishing slurry and discharge paths for polishing debris.

[0005] In order to facilitate fixing to a surface plate on the user side, the polishing pad may be provided as a polishing pad with double-sided tape, in which a double-sided tape is bonded to the second surface of the base material (the surface opposite to the first surface in the thickness direction). The double-sided tape includes adhesive layers laminated on both sides of a support film, and one adhesive layer is bonded to the second surface of the base material. The other adhesive layer is to be bonded to the surface plate of a polishing apparatus.

[0006] Incidentally, in order to obtain stable polishing performance, it is important to suppress peeling of the polishing pad from the surface plate. However, due to the influence of embossing for forming a plurality of grooves in the polishing layer, irregularities can also be formed on the second surface of the base material. Such irregularities may also appear on the adhesive surface of the double-sided tape with the surface plate, which may reduce the adhesiveness of the polishing pad to the surface plate.

[0007] To address this problem, Patent Document 1 proposes using a substrate with thickness to increase the thermal resistance of the substrate, thereby suppressing the conduction of heat during embossing to the second surface of the substrate, and reducing the surface roughness of the second surface of the substrate to which the double-sided tape is attached.

[0008] Japanese Patent Application Publication No. 2010-234458

[0009] Incidentally, in CMP, the temperature of the polishing surface is an important factor in polishing performance, so the temperature of the polishing pad is controlled. However, in CMP using the polishing pad described in Patent Document 1, the thickness of the substrate can hinder the heat conduction necessary for temperature control, potentially reducing polishing performance.

[0010] In view of the above circumstances, the object of the present invention is to provide a polishing pad that can easily form an adhesive surface having excellent adhesion to a polishing device without using a thick base material.

[0011] A polishing pad comprising a base material and a polishing layer laminated on the base material, wherein the polishing layer has a polishing surface in which a plurality of grooves are formed by embossing, the base material has a first surface on which the polishing layer is laminated and a second surface opposite to the first surface in the thickness direction, the second surface is an adhesion surface to which double-sided tape for fixing the polishing pad to the base plate of a polishing device is attached, and the amount of first thermal deformation of the base material in a first direction, as measured by thermomechanical analysis, is greater than the amount of second thermal deformation in a second direction intersecting the first direction.

[0012] According to the present invention, it is possible to provide a polishing pad that can easily form an adhesive surface having excellent adhesion to a polishing device without using a thick substrate.

[0013] This is a schematic diagram of a polishing apparatus according to one embodiment. This is a schematic cross-sectional view of a polishing pad as one embodiment. This is a schematic cross-sectional view of a polishing pad with double-sided tape as one embodiment. This is a schematic cross-sectional view illustrating the shape of the base material of the polishing pad in Figure 2. This is a graph comparing the height frequency distribution of the second surface of the base materials of Example 1 and Comparative Example 1.

[0014] The following describes an embodiment of the polishing pad according to the present invention, with reference to the drawings.

[0015] As shown in Figure 1, the polishing pad 1 according to this embodiment is incorporated into a polishing apparatus 100 and used for chemical mechanical polishing (CMP). The polishing apparatus 100 comprises a disc-shaped polishing pad 1, a base plate 2 having a surface 21 for fixing the polishing pad 1, a rotating head 3 equipped with a holding material 31 for fixing a disc-shaped workpiece W, and a slurry supply device 4 for supplying polishing slurry containing abrasive grains to the polishing pad 1. The base plate 2 is configured to rotate the polishing pad 1 circumferentially in a horizontal plane. The rotating head 3 is configured to rotate the workpiece W circumferentially in a horizontal plane. The polishing apparatus 100 is configured to polish the workpiece W and the polishing pad 1 by supplying polishing slurry between the workpiece W's polishing surface w1 and the polishing pad 1 while rotating the workpiece W and polishing pad 1 respectively using the base plate 2 and the rotating head 3, thereby polishing the workpiece w1. The base plate 2 is also configured to control the temperature of its surface 21 so that the polishing pad 1 can be cooled or heated.

[0016] As shown in Figure 2, the polishing pad 1 of this embodiment comprises a base material 11 made of a resin film and a polishing layer 12 laminated on the base material 11. The base material 11 has a first surface 111 on which the polishing layer 12 is laminated, and a second surface 112 on the opposite side of the first surface 111 in the thickness direction. The polishing layer 12 has a polishing surface 121 that comes into contact with the object to be polished in CMP. Examples of the object to be polished include a wafer as a substrate and a semiconductor device manufactured using the wafer. Examples of the substrate include a Si wafer, a SiC wafer, a GaN wafer, a sapphire wafer, and a substrate for LCDs.

[0017] As shown in Figure 3, the polishing pad 1 of this embodiment is fixed to the surface plate of the polishing device via double-sided tape T. The double-sided tape T according to this embodiment comprises a first adhesive layer t1 that is bonded to the polishing pad 1 and a second adhesive layer t2 that is bonded to the surface of the surface plate. The double-sided tape T also comprises a resin support film t3, the first adhesive layer t1 being laminated on a first support surface of the support film t3, and the second adhesive layer t2 being laminated on a second support surface opposite to the first support surface in the thickness direction. The bonding surface of the first adhesive layer t1 is the contact surface with the second surface of the base material 11 of the polishing pad 1. The bonding surface of the second adhesive layer t2 is the contact surface with the surface of the surface plate of the polishing device. Hereinafter, the polishing pad 1 before the double-sided tape T is bonded will be referred to as polishing pad 1x, and the polishing pad 1 after the double-sided tape T is bonded will be referred to as polishing pad 1y.

[0018] The adhesive layer of the double-sided tape according to this embodiment is composed of a pressure-sensitive adhesive. Examples of the pressure-sensitive adhesive include a (meth)acrylate (co)polymer; synthetic rubber such as polyisoprene rubber, polybutadiene rubber, or chloroprene rubber, or natural rubber, used as a base polymer, and obtained by blending a crosslinking agent, a tackifier, etc., with the base polymer. Examples of the support film include a resin film such as a PET film.

[0019] One method for bonding double-sided tape is to first bond double-sided tape to a rectangular polishing pad 1x having an area large enough to cut off at least one polishing pad 1y, thereby creating a laminate, and then cut off one or more polishing pads 1y of a predetermined shape (e.g., disc-shaped) from the laminate. In creating the laminate, it is generally considered that the polishing pad 1x and the double-sided tape are laminated sequentially from the leading edge in one direction (e.g., the length direction) to suppress the inclusion of air between the polishing pad 1x and the double-sided tape. In other words, when bonding the polishing pad 1x and the double-sided tape, it is common to laminate the polishing pad 1x and the double-sided tape sequentially from the leading edge in one direction (e.g., the length direction) to suppress the inclusion of air between two points that come into contact simultaneously in one direction (e.g., the length direction).

[0020] The polishing layer in this embodiment is made of polyurethane resin foam. The polishing layer in this embodiment is formed by forming a porous layer on the substrate using a wet solidification method using polyurethane, and then buffing the surface of the porous layer. In other words, the polishing pad in this embodiment is a so-called soft type polishing pad.

[0021] The polishing layer has a plurality of grooves that open on the polishing surface. The plurality of grooves have a patterned shape. For example, the plurality of grooves may be in a grid pattern. More specifically, when the polishing pad is viewed from the polishing surface side (i.e., in a plan view), the plurality of grooves have a plurality of longitudinal grooves formed parallel to each other and a plurality of transverse grooves formed parallel to each other while intersecting the plurality of longitudinal grooves. The intersection angles of the longitudinal grooves and the transverse grooves are, for example, 45° to 90°, 60° to 90°, 75° to 90°, or 80° to 90°.

[0022] The aforementioned multiple grooves are formed by embossing the polishing layer after buffing. This results in a polishing pad 1x. Embossing is performed, for example, by pressing a mold having multiple protrusions corresponding to the grooves to be formed onto the surface of the polishing layer. At this time, the surface of the mold is usually heated to a temperature at which the polyurethane resin foam can soften (for example, 150°C to 200°C). Due to the pressure of the mold during such embossing, multiple protrusions may be formed on the second surface of the base material of the polishing pad 1x on the opposite side of where the multiple grooves are formed. How to cancel (level out) these protrusions and flatten the adhesive surface of the double-sided tape (the surface that adheres to the surface plate) is important for improving the adhesion of the polishing pad 1y to the surface plate. Furthermore, it is efficient if these protrusions can be canceled out when bonding the double-sided tape to the polishing pad 1x (the second surface of the base material).

[0023] Therefore, the polishing pad of this embodiment uses a substrate that exhibits anisotropic thermal deformation. Specifically, when the thermal deformation of the substrate is measured by thermomechanical analysis (TMA), the substrate is configured such that the first thermal deformation in the first direction in the planar direction is greater than the second thermal deformation in the second direction intersecting the first direction in the planar direction. Note that the measurement target here is limited to substrates before any thermal history is applied, such as by embossing. (Measurement conditions for thermomechanical analysis) Apparatus: Hitachi High-Tech Corporation, TMA7100 Temperature program: 30℃ to 170℃ Heating rate: 5℃ / min Load: 100mN Sample width: 5mm Measurement sample length: 20mm

[0024] The estimated mechanism by which adhesion is obtained with the above-described substrate will be explained with reference to Figure 4. First, because the amount of first thermal deformation of the substrate 11 in the first direction D1 is greater than the amount of second thermal deformation in the second direction, during embossing, the substrate 11 stretches significantly in the first direction D1 at the position corresponding to the ridge of the mold, and the degree of stretching is suppressed in the second direction compared to the first direction D1. As a result, the substrate 11 forms undulations with repeating bumps and dips along the first direction D1. On the other hand, the formation of such undulations is suppressed in the second direction. Furthermore, in the method for manufacturing the laminate described above, by correlating the first direction D1 of the substrate 11 in the polishing pad 1x with the pulling direction of the double-sided tape, and sequentially laminating the polishing pad 1x and the double-sided tape from the leading edge side of the substrate 11 in the first direction D1 (the length direction of the double-sided tape), it is thought that the repeated bumps along the first direction D1 (the length direction of the double-sided tape) of the substrate 11 are sequentially pressed down by the double-sided tape and canceled out (smoothed out). Furthermore, since the protrusions are sequentially canceled out from the leading edge side in the first direction D1 (the length direction of the double-sided tape) of the base material 11, it is considered that it is possible to suppress the simultaneous contact of adjacent protrusions with the double-sided tape in the first direction D1 and the inclusion of air between them. Thus, with the polishing pad 1x of this embodiment, the uneven shape of the base material caused by embossing can be easily canceled out by a general method for manufacturing laminates.

[0025] The abrasive layer preferably has a plurality of grooves that intersect the first direction of the substrate and are parallel to each other. The intersection angle between the plurality of grooves and the first direction of the substrate is preferably 45° to 90°, more preferably 60° to 90°, even more preferably 75° to 90°, and even more preferably 80° to 90°. More specifically, if the plurality of grooves are in a grid shape, it is preferable that the substrate is arranged such that the first direction of the substrate is aligned with one of the longitudinal grooves and the transverse grooves. This makes it easier to form undulations that repeat in the first direction. The shape of the plurality of grooves is not limited to a grid shape; for example, even if the plurality of grooves are concentric circles, each groove partially intersects the first direction of the substrate, so it is presumed that the above-described undulation-based mechanism will be achieved.

[0026] The intersection angle of the first direction and the second direction of the substrate is, for example, 45° to 90°, 60° to 90°, 75° to 90°, or 80° to 90°.

[0027] At any of the temperatures of the thermomechanical analysis, the ratio (A2:A1) of the first thermal deformation amount (A1) to the second thermal deformation amount (A2) is preferably 1:2 or greater, more preferably 1:3 or greater, and even more preferably 1:4 or greater. The ratio (A2:A1) is preferably 1:3 or greater at 80°C, and preferably 1:4 or greater at 165°C. The ratio at 165°C may be, for example, 1:10 or less, and may also be 1:8 or less.

[0028] The first thermal deformation amount is, for example, 100 μm or more at 80°C. The first thermal deformation amount may be, for example, 250 μm or more, 280 μm or more, or 300 μm or more at 165°C. The first thermal deformation amount is, for example, 200 μm or less, or 150 μm or less at 80°C. The first thermal deformation amount is, for example, 500 μm or less, or 400 μm or less at 165°C.

[0029] On the other hand, the second amount of thermal deformation is, for example, 50 μm or less at 80°C. The second amount of thermal deformation is, for example, 150 μm or less, or 100 μm or less, at 165°C. The second amount of thermal deformation is, for example, 20 μm or more at 80°C. The second amount of thermal deformation is, for example, 50 μm or more at 165°C.

[0030] The amount of thermal deformation of the substrate can be adjusted by the stretching ratio of the resin film constituting the substrate. For example, in the manufacture of a resin film, by making the orientation in the mid-to-mid direction greater than that in the t-direction direction (TD), the amount of thermal deformation in the TD direction can be made greater than that in the MD direction. Furthermore, the difference in thermal deformation based on orientation can be increased by including fillers in the substrate. Specifically, in the manufacture of a stretched resin film, since the filler, which has a lower coefficient of thermal expansion than the resin, also orients in the MD direction, the amount of thermal deformation is suppressed in the MD direction and increased in the TD direction. To further increase the difference in orientation in each direction, it is conceivable to use fibrous fillers that are easily oriented.

[0031] When the surface properties of the adhesive surface (adhesion surface to the surface of the polishing plate) of the double-sided tape of the polishing pad 1y according to this embodiment are measured under the following measurement conditions, the arithmetic mean height Sa in the surface direction of the adhesive surface may be 1.5 μm or less, 1.0 μm or less, or 0.9 μm or less. Here, the arithmetic mean height Sa is, for example, 0.5 μm or more, or 1 μm or more. The adhesive surface of the double-sided tape with reduced roughness in this way can increase the contact surface with the surface of the polishing plate of the polishing device, and therefore has excellent adhesion. (Measurement conditions for arithmetic mean height Sa) Equipment: Keyence Corporation, VK-X1050 Illumination: Coaxial incident light 100 Lens magnification: ×10 Scan range: 13500 μm × 11000 μm (Analysis conditions) Tilt correction is performed as pretreatment, and the field of view is 12000 μm × 10000 μm, with no filter.

[0032] A thermoplastic resin is preferred as the resin constituting the base material. Examples of thermoplastic resins include polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate, and polyethylene naphthalate; polyolefins such as polyethylene and polypropylene; ethylene-vinyl acetate copolymers; acrylonitrile butadiene styrene copolymers; polyacetal; polyvinyl chloride; polyvinylidene chloride; polycarbonate; polystyrene; polymethyl methacrylate; polymethylpentene; polysulfone; polyetheretherketone; polyethersulfone; polyamide; and polyimide. The resin constituting the base material is preferably a polyester such as polyethylene terephthalate (PET).

[0033] The substrate is preferably made of a single layer of PET film. The thickness of the substrate is, for example, 20 μm to 400 μm. The thickness of the substrate is preferably 20 μm to 250 μm.

[0034] The polyurethane resin constituting the abrasive layer can be obtained, for example, by reacting a diisocyanate, a polyol, and a chain extender. The polyurethane resin is one or more selected from the group consisting of polyester-based polyurethane resins, polyether-based polyurethane resins, and polycarbonate-based polyurethane resins.

[0035] Examples of the diisocyanates include diphenylmethane-4,4'-diisocyanate, trilene-2,4-diisocyanate, xylylene diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, and hexamethylene diisocyanate.

[0036] Examples of the aforementioned polyols include polyester polyols such as polyethylene adipate glycol, polypropylene adipate glycol, polyethylene propylene adipate glycol, polybutylene adipate glycol, polyethylene butylene adipate glycol, and polypentamethylene adipate glycol; polyether polyols such as polyethylene ether glycol, polypropylene ether glycol, polytetramethylene ether glycol, and polyhexamethylene ether glycol; and polycarbonate polyols such as polytetramethylene carbonate, polypentamethylene carbonate, and polyhexamethylene carbonate.

[0037] Examples of the chain extenders include glycols such as ethylene glycol, propylene glycol, butylene glycol, and diethylene glycol; diamines such as ethylenediamine, trimethylenediamine, propylenediamine, and butylenediamine; and amino alcohols.

[0038] As described above, while embodiments have been presented as examples, the polishing pad according to the present invention is not limited to the configuration of the above embodiments. Furthermore, the polishing pad according to the present invention is not limited by the effects and advantages described above. The polishing pad according to the present invention can be modified in various ways without departing from the spirit of the present invention.

[0039] This disclosure includes the following: (1) a polishing pad comprising a base material and a polishing layer laminated on the base material, wherein the polishing layer has a polishing surface on which a plurality of grooves are formed by embossing, the base material has a first surface on which the polishing layer is laminated and a second surface opposite to the first surface in the thickness direction, the second surface is an adhesion surface to which double-sided tape for fixing the polishing pad to a base plate of a polishing device is attached, and the amount of first thermal deformation of the base material in a first direction, as measured by thermomechanical analysis, is greater than the amount of second thermal deformation in a second direction intersecting the first direction.

[0040] (2) The polishing pad according to (1) above, wherein the ratio (A2:A1) of the first thermal deformation amount (A1) to the second thermal deformation amount (A2) is 1:2 or more.

[0041] (3) The polishing pad according to (1) or (2) above, wherein a ratio of the first thermal deformation amount (A1) to the second thermal deformation amount (A2), (A2:A1), is 1:4 or more at 165°C.

[0042] (4) The polishing pad according to any one of (1) to (3) above, wherein the double-sided adhesive tape is bonded to the second surface.

[0043] Hereinafter, the present invention will be further described with reference to examples, but the present invention is not limited thereto.

[0044] As shown in Table 1, in Example 1, a PET film having different thermal deformation amounts in a first direction (TD) and a second direction (MD) orthogonal to the first direction (TD) (the thermal deformation amount in the first direction is larger) was used. On the other hand, in Comparative Example 1, a PET film having equivalent thermal deformation amounts in the first direction (TD) and the second direction (MD) orthogonal to the first direction (TD) was used. The method for measuring the thermal deformation amount is as described above.

[0045]

[0046] [Production of Example 1] (Preparation of polishing pad 1x) A polyurethane resin and a surfactant were dissolved in DMF to prepare a resin solution. A coating layer was formed on the first surface of the substrate using the resin solution. The substrate having the coating layer formed thereon was immersed in a DMF-containing coagulation liquid to coagulate the polyurethane resin in the coating layer, thereby forming a porous layer. Subsequently, buffing was performed on the surface of the porous layer. Subsequently, a plurality of grooves were formed in the porous layer by embossing (mold temperature: 165°C) to obtain a polishing layer. The obtained polishing pad 1x had large waviness caused by repeated irregularities along the first direction of the base material. (Preparation of polishing pad 1y) While drawing out the double-sided adhesive tape in the longitudinal direction, the polishing pad 1x and the double-sided adhesive tape were sequentially laminated from the distal end side in the longitudinal direction such that the first direction of the base material of the polishing pad 1x was aligned with the drawing direction of the double-sided adhesive tape, to obtain a laminated body. During bonding, the polishing pad 1x was heated to about 40°C.

[0047] [Evaluation Method 1: Arithmetic mean height Sa of the second surface of the base material of polishing pad 1y] By the measurement method described above, the arithmetic mean height (Sa1) on the second surface of the base material of the polishing pad 1x after embossing, and the arithmetic mean height (Sa2) on the second surface of the base material of the polishing pad 1y after lamination with the double-sided tape were measured. Furthermore, to evaluate the extent to which waviness has been canceled, Sa2 / Sa1 was calculated. The results are shown in Table 2.

[0048]

[0049] [Evaluation Method 2: Height frequency distribution of the second surface of the base material of polishing pad 1y] Under the following measurement conditions, the height frequency distribution on the second surface of the base material of the polishing pad 1y was measured. The results are shown in Figure 5. (Measurement conditions) Apparatus: VK-X1050, manufactured by Keyence Corporation; Illumination: coaxial epi-illumination 100; Lens magnification: ×10; Scanning range: 13500 μm × 11000 μm (Analysis conditions) As pretreatment, tilt correction was performed, and a histogram was obtained from the stitched image using analysis software.

[0050] As shown in Table 2, it was confirmed that the arithmetic mean height Sa of the second surface of the base material of the polishing pad 1y according to Example 1 is extremely small compared with that of Comparative Example 1. Therefore, it is considered that the adhesive surface of the double-sided tape bonded to the second surface also has excellent flatness and can exhibit excellent adhesiveness to the surface of the surface plate. Furthermore, as shown in Figure 5, it was confirmed that the second surface of the base material of Example 1 has a uniform concavo-convex shape compared with that of Comparative Example 1. Therefore, it is considered that the adhesive surface of the double-sided tape bonded to the second surface also has a uniform concavo-convex shape, and variation in adhesive force on the surface of the surface plate can be suppressed.

[0051] 100: Polishing apparatus, 1: Polishing pad, 2: Surface plate, 3: Rotating head, 31: Holding member, 4: Slurry supply apparatus, W: Object to be polished, w1: Surface to be polished, 1x, 1y: Polishing pad, 11: Base material, 111: First surface, 112: Second surface, 12: Polishing layer, 121: Polishing surface, T: Double-sided tape, t1: First adhesive layer, t2: Second adhesive layer, t3: Support film, D1: First direction

Claims

1. A polishing pad comprising a base material and a polishing layer laminated on the base material, wherein the polishing layer has a polishing surface in which a plurality of grooves are formed by embossing, the base material has a first surface on which the polishing layer is laminated and a second surface opposite to the first surface in the thickness direction, the second surface is an adhesion surface to which double-sided tape for fixing the polishing pad to a base plate of a polishing device is attached, and the amount of first thermal deformation of the base material in a first direction, as measured by thermomechanical analysis, is greater than the amount of second thermal deformation in a second direction intersecting the first direction.

2. The polishing pad according to claim 1, wherein the ratio (A2:A1) of the first thermal deformation amount (A1) to the second thermal deformation amount (A2) is 1:2 or greater.

3. The polishing pad according to claim 1, wherein the ratio (A2:A1) of the first thermal deformation amount (A1) to the second thermal deformation amount (A2) is 1:4 or more at 165°C.

4. The polishing pad according to any one of claims 1 to 3, wherein the double-sided tape is attached to the second surface.

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