Polishing pad

Abstract

This suppresses the waviness that occurs along the boundary of the airbag on the holding platen. [Solution] The present invention relates to a polishing pad 1 comprising a polishing layer 11 on which a polishing surface 11a for polishing the object to be polished 3 is formed, and a base layer 12 provided on the side of the polishing layer 11 opposite to the polishing surface 11a. Multiple radial grooves 15 are formed radially on at least one of the following surfaces: the adhesive surface 12a on the base layer 12 side facing the polishing layer 11, the adhesive surface 11b on the polishing layer 11 side facing the base layer 12, or the holding surface 12b on the polishing platen side facing the base layer 12. The ends of the radial grooves 15 on the central side of the base layer 12 or the polishing layer 11 are separated from each other to form a flat portion 16a (16b, 16c) in the central part of the base layer 12 or the polishing layer 11.

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.

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 table of a polishing apparatus and used, and the object to be polished is held on a holding table (Patent Document 1). In the above polishing apparatus, while pressing the object to be polished against the polishing pad, the holding table and the polishing table 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. 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 table, 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 table on the object to be polished is adjusted to improve the flatness of the object to be polished.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, if concentric airbags are provided on the above-mentioned holding platen, the pressing force at the boundary between adjacent airbags becomes low, and the repulsive force from the polishing pad concentrates at this boundary, which may cause it to bulge towards the workpiece. As a result, the bulging portion of the polishing pad could cause the workpiece to be polished excessively, creating concentric, wavy irregularities along the boundary of the airbag. The inventor decided to refer to this type of polishing defect originating from the airbag of the holding platen as "Wavy." 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]

[0005] In other words, the polishing pad according to claim 1 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, The present invention is characterized in that a plurality of radial grooves are formed radially on at least one of the following surfaces: the adhesive surface on the polishing layer side of the base layer, the holding surface on the polishing platen side of the base layer, or the adhesive surface on the base layer side of the polishing layer, and the ends of the radial grooves on the central side of the base layer or the polishing layer are separated from each other to form a flat portion in the central part of the base layer or the polishing layer. [Effects of the Invention]

[0006] According to the above invention, by providing the radial grooves on at least one surface among the adhesive surface of the base layer, the holding surface of the base layer, or the adhesive surface of the polishing layer, when the polishing pad is pressed against the workpiece to be polished, the radial grooves distribute the stress on the polishing pad, preventing the rebound force from the polishing pad from concentrating at the boundary position of the airbag of the holding platen. This makes it possible to suppress the occurrence of wavy. [Brief explanation of the drawing]

[0007] [Figure 1] Diagram of the polishing device [Figure 2] Cross-sectional view of polishing device and polishing pad [Figure 3] Plan view of the base material layer of the polishing pad [Figure 4] Plan view of the base material layer of the polishing pad according to the second embodiment. [Figure 5] Cross-sectional view of a polishing pad according to the third embodiment. [Figure 6] Figure showing experimental results regarding the amount of wavy [Figure 7] This figure shows experimental results regarding the surface condition of the workpiece. [Figure 8] Cross-sectional view of a polishing pad according to the fourth embodiment. [Modes for carrying out the invention]

[0008] The following describes the illustrated embodiment. Figure 1 shows a polishing apparatus 2 equipped with a polishing pad 1 according to the present invention, which is used to polish an object to be polished 3 such as a semiconductor substrate. The polishing apparatus 2 described above comprises a polishing platen 4 located below to support the polishing pad 1, a holding platen 5 located above to support the object to be polished 3, and a slurry supply means 6 for supplying the slurry S. The polishing pad 1 and the workpiece 3 described above are both roughly disc-shaped, with the polishing pad 1 having a larger diameter than the workpiece 3. The polishing pad 1 is held on the upper surface of the polishing platen 4 by double-sided tape or the like, and the workpiece 3 is held on the lower surface of the holding platen 5 via an airbag A, which will be described later. The rotation center of the holding platen 5 is positioned offset from the rotation center of the polishing platen 4. When the polishing platen 4 and the holding platen 5 are rotated by a driving means (not shown), the polishing pad 1 and the workpiece 3 slide against each other while rotating relative to each other. The slurry supply means 6 supplies a slurry S, in which abrasive particles are mixed in a required liquid, to the polishing surface of the polishing pad 1. This allows the slurry S to penetrate between the polishing surface and the workpiece 3, thereby performing so-called chemical mechanical polishing (CMP).

[0009] Figure 2 shows a cross-sectional view of the polishing apparatus 2 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 comprises a disc-shaped top ring 5a that rotates by the above-mentioned driving means, concentric first to sixth airbags A1 to A6 provided on the lower surface of the top ring 5a, and a retainer ring 7 provided so as to surround the first to sixth airbags A1 to A6. The rotation center of the holding platen 5 is set to the center of the first to sixth airbags A1 to A6, and each airbag A has a roughly rectangular cross-section, with a flat lower surface that is processed to allow it to adhere closely to and hold the surface of the workpiece 3 to be polished. Furthermore, each of the first to sixth airbags A1 to A6 can apply a different pressure to the workpiece 3, and the pressure applied by the first to sixth airbags A1 to A6 can be adjusted according to the workpiece 3 being polished and various polishing conditions. Furthermore, since such a holding plate 5 is known from the above-mentioned Patent Document 1, no further detailed explanation will be provided.

[0010] The retainer ring 7 is provided so as to protrude below the lower surfaces of the first to sixth airbags A1 to A6, and when the workpiece 3 is held by the airbag A during polishing, the workpiece 3 is housed inside the retainer ring 7. As described above, when the polishing platen 4 and the holding platen 5 are rotated, the workpiece 3 moves in a trajectory that rotates on its own axis while revolving around the center of the polishing pad 1, as shown in Figure 3, and a ring-shaped range of movement M is formed on the polishing pad 1 by the workpiece 3 and the retainer ring 7. The movement range M of the workpiece 3 and the retainer ring 7 does not protrude beyond the outer peripheral edge of the polishing pad 1, and a portion that does not contact the workpiece 3 and the retainer ring 7 is formed in the central portion of the polishing pad 1.

[0011] The polishing pad 1 includes a polishing layer 11 having a polishing surface 11a that contacts the workpiece 3, a base material layer 12 provided on a surface opposite to the polishing surface 11a of the polishing layer 11, and an adhesive layer 13 that adheres the polishing layer 11 and the base material layer 12. Although not particularly limited, a polyurethane sheet can be used for the polishing layer 11. As such a polyurethane sheet, an isocyanate-terminated prepolymer (hereinafter sometimes simply referred to as a prepolymer), a curing agent, and a hollow body are mixed to form a polyurethane resin molded body, and the polyurethane resin molded body is sliced to form a foamed polyurethane sheet in which innumerable voids are formed inside. Here, the polyurethane sheet refers to a polyurethane-based resin including polyurethane and polyurethane-polyurea. The polyurethane sheet used for the polishing layer 11 can be set to have a thickness of 0.5 to 2 mm, a Shore D hardness of 20.0 to 70.0, preferably 35.0 to 65.0,and a density of 0.60 to 1.10 g / cm 3 respectively. By setting the Shore D hardness of the polishing layer 11 within the above range, the generation of scratches can be suppressed. Although not particularly limited, a urethane sponge can be used for the base material layer 12, and a commercially available polyurethane sponge can be used as such a urethane sponge. Note that a polyurethane sheet similar to the polishing layer 11 may be used as the base material layer 12. The urethane sponge used for the base material layer 12 can be set to have a thickness of 0.5 to 2 mm, a Shore A hardness of 20.0 to 75.0, preferably 45.0 to 65.0,and a density of 0.20 to 0.70 g / cm 3 respectively. The above-mentioned adhesive layer 13 is formed by applying a pressure-sensitive adhesive such as an acrylic adhesive 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 and used from known double-sided tapes in the technical field.

[0012] A plurality of concentric circular grooves 14 are formed on the polishing surface 11a of the above-mentioned polishing layer 11. Such circular grooves formed on the polishing surface 11a are conventionally known and have the effect of improving the polishing performance by holding the slurry inside when polishing the workpiece 3. The center of the circular groove 14 on the polishing surface 11a may be set at the center of the polishing pad 1 or may be set at a distance from the center of the polishing pad 1. There is no limitation on the pitch and cross-sectional shape of adjacent circular grooves 14, but here the cross-section of each groove is substantially rectangular. In addition to the above-mentioned circular grooves 14, radial grooves formed radially from the center of the polishing pad 1 or grid grooves formed in a grid pattern may be provided. These grooves have the effect of discharging polishing debris generated during polishing, together with the slurry, to the outside of the polishing pad 1.

[0013] Figure 3 shows a plan view of the above-mentioned base material layer 12. A plurality of radial grooves 15 are provided on the adhesive surface 12a on the side of the polishing layer 11 in the base material layer 12, which are formed radially in the radial direction from the center of the base material layer 12. There is no limitation on the cross-sectional shape of the radial grooves 15, but here the cross-section of each groove is substantially rectangular. In the radial grooves 15 of this embodiment, the ends on the center side of the base material layer 12 are separated from each other, and a flat portion 16a is formed in the central portion of the base material layer 12. The flat portion 16a is provided inside the movement range M of the above-mentioned workpiece 3 and the retainer ring 7. The movement range M in this embodiment is a region in the range of 7% to 98% with respect to the radius from the center of the polishing pad 1, and the range of the region varies depending on the polishing apparatus 2 used. Furthermore, the radial grooves 15 are formed in the radial direction, and when each radial groove 15 is extended toward the center of the base layer 12, they intersect at the center of the base layer 12.

[0014] On the other hand, the radial grooves 15 are formed such that the outer peripheral end of the base layer 12 does not reach the outer peripheral edge of the base layer 12, and are provided outside the range of movement M of the workpiece 3 and retainer ring 7 that move relative to the polishing pad 1. By not extending the outer peripheral edge of the base layer 12 to the outer edge of the base layer 12 in the radial groove 15, holes formed by the radial groove 15 are prevented from being formed on the side surface of the polishing pad 1 after the polishing layer 11 and the base layer 12 are bonded together by the adhesive layer 13. This prevents the slurry S that flows down the side of the polishing pad 1 from entering between the base layer 12 and the adhesive layer 13 via the radial grooves 15 when polishing the workpiece 3 with the polishing pad 1, thereby preventing the base layer 12 and the adhesive layer 13 from separating during polishing. On the other hand, by extending the outer peripheral end of the base material layer 12 in the radial groove 15 to the outside of the movement range M of the workpiece 3, the stress when the workpiece 3 is pressed against the polishing pad 1 is distributed, and wavy can be reduced. In this embodiment, eight radial grooves 15 are formed, and the angle between adjacent radial grooves 15 is set to 45°. When adjacent radial grooves 15 are spaced apart in this way, it is desirable to form the ends of the radial grooves 15 on the central side of the base layer 12 to the inside of the movement range M. This distributes the stress when the workpiece 3 is pressed against the polishing pad 1, and reduces wavy. The number of radial grooves 15, the width of the radial grooves 15, and the position of the central end of each radial groove 15 in the base layer 12 can be set in various ways depending on the hardness of the polishing layer 11 and the base layer 12, and the pressure applied to the workpiece 3 to be polished. The groove depth of the radial grooves 15 is not particularly limited, but is preferably 20% or more of the thickness of the base layer 12, more preferably 30% or more, and even more preferably 50% or more. When the groove depth of the radial grooves 15 is 20% 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. Furthermore, it is also possible to slightly incline the radial grooves 15 with respect to the radial direction.

[0015] Figure 4 shows a plan view of the base material layer 12 of the polishing pad 1 according to the second embodiment, in which the angle between adjacent radial grooves 15 is set smaller compared to the embodiment in Figure 3. In this embodiment, the angle between the radial grooves 15 is set to 22.5°, and accordingly, long radial grooves 15a and short radial grooves 15b are provided alternately. Similar to the embodiment in Figure 3, the long radial groove 15a is formed so that the central end of the base layer 12 extends inside the movement range M, while the central end of the short radial groove 15b of the base layer 12 remains inside the movement range M. This configuration prevents the radial grooves 15 from coming into excessive proximity near the flat portion 16a of the base layer 12, thereby preventing the central part of the polishing pad 1 from being excessively deformed by the workpiece 3, and reducing wavyness. In contrast, if the central ends of all radial grooves 15 in the base layer 12 are set to the same position, the radial grooves 15 will come into close proximity near the flat portion 16a of the base layer 12, which may cause the polishing pad 1 to deform excessively and potentially result in wavy surface. Furthermore, the angle between the radial grooves 15a and 15b, and the position of the central end of each radial groove 15 in the base layer 12, can be set in various ways depending on the hardness of the polishing layer 11 and the base layer 12, and the pressure applied to the workpiece 3 to be polished.

[0016] By using the polishing pad 1 having the above configuration, the waviness generated when polishing the workpiece 3 can be reduced. To consider the principle of wave generation, when polishing the workpiece 3 with the polishing device 2, the workpiece 3 is pressed against the polishing pad 1, and while the workpiece 3 is revolving around the polishing pad 1, it is also rotated on its own axis. At that time, concentric airbags A provided on the holding platen 5 apply different radial pressures to the workpiece 3. When a workpiece 3 is pressed with a holding platen 5 equipped with multiple airbags A in this manner, at the boundary between adjacent airbags A, the pressure from each airbag A is not transmitted to the workpiece 3, resulting in a lower pressing force at that boundary compared to other parts. As a result, when the polishing pad 1 is pressed by the object to be polished 3, the repulsive force from the polishing pad 1 concentrates at the part corresponding to the boundary of the airbag A, and that part may bulge. As a result, the bulging portion of the polishing pad 1 causes the portion of the workpiece 3 corresponding to the boundary of airbag A to be excessively polished, and it is thought that wavy patterns consisting of concentric ridges and depressions formed along the boundary of airbag A are generated. In other words, the polishing pad of the present invention is suitable for polishing devices equipped with a holding platen in which a plurality of concentrically arranged airbags can each press the workpiece to be polished with the required pressure.

[0017] In this embodiment, the polishing pad 1 is provided with radial grooves 15 on the adhesive surface 12a of the base layer 12, and a flat portion 16a is formed in the central part of the base layer 12, thereby dispersing the repulsive force when the object to be polished 3 is pressed against the polishing pad 1. As a result, the repulsive force from the polishing pad 1 will no longer be concentrated at the boundary of airbag A, and the wavy effect caused by the concentrically arranged airbag A will be prevented.

[0018] Figure 5 shows a cross-sectional view of the polishing pad 1 according to the third embodiment, and compared to the first and second embodiments described above, radial grooves 15 are provided on the adhesive surface 11b on the base material layer 12 side of the polishing layer 11. The shape and arrangement of the radial grooves 15 can be the same as those of the polishing pad 1 according to the first and second embodiments, that is, the ends of the polishing layer 11 on the central side of the radial grooves 15 are separated from each other so that a flat portion 16b is formed in the central part of the polishing layer 11, and the ends of the polishing layer 11 on the outer side of the radial grooves 15 are formed so that they do not reach the outer edge of the polishing layer 11. This configuration prevents the radial grooves 15 from coming into excessive proximity near the flat portion 16b of the polishing layer 11, thereby preventing the central part of the polishing pad 1 from being excessively deformed by the workpiece 3, and reducing wavyness. Here, the lower limit of the groove depth of the radial grooves 15 is preferably 15% or more, or 20% or more, of the thickness of the polishing layer 11, and the upper limit is preferably 40% or less, or 35% or less. When the groove depth of the radial grooves 15 is within the above numerical range, the stress when the workpiece 3 is pressed against the polishing pad 1 is more easily distributed, and wavy is more easily reduced. Furthermore, the groove depth of the radial groove 15 can be appropriately set according to the thickness of the polishing layer 11 and the groove depth of the circular groove 14, since the circular groove 14 and the radial groove 15 are formed on the polishing surface 11a and the adhesive surface 11b, respectively. Preferably, the central end of the polishing layer 11 in the radial groove 15 is located at a distance of 5% or more, 10% or more, or 13% or more of the radius from the center of the polishing layer 11, and preferably the outer peripheral end of the polishing layer 11 in the radial groove 15 is located at a distance of 99% or less, 95% or less, or 93% or less of the radius from the center of the polishing layer 11. When each end of the radial groove 15 is within the above numerical range, the stress when the workpiece 3 is pressed against the polishing pad 1 is more easily distributed, and wavy is more easily reduced.

[0019] The following describes how to manufacture the polishing pad 1 comprising the polishing layer 11 and the base layer 12 described above. The polyurethane sheet constituting the polishing layer 11 is manufactured by a prepolymer method, in which a polyurethane composition is obtained by curing a polyurethane composition obtained by adding and mixing a curing agent (chain extender) such as diamines or diols, a foaming agent, a catalyst, etc., using an isocyanate-terminated prepolymer, which is a reaction intermediate between a polyol component and an isocyanate component. The above-mentioned prepolymerization method includes, but is not limited to, a preparation step of preparing a urethane bond-containing isocyanate compound as an isocyanate-terminated prepolymer, a curing agent, and a hollow body; a mixing step of mixing at least the urethane bond-containing isocyanate compound and the curing agent to obtain a mixed liquid for molding a molded article; and a molded article molding step of molding a polyurethane polyurea resin molded article from the mixed liquid for molding a molded article. One method for manufacturing the urethane sponge constituting the base layer 12 is to heat a composition containing a resin prepolymer, a curing agent, and a foaming agent, thereby curing the composition while causing it to foam. The prepolymer and curing agent used in manufacturing the sponge can be those exemplified in the method for manufacturing the abrasive layer. The disc-shaped polishing pad 1 according to this embodiment is obtained by performing a polishing layer forming step of slicing a polyurethane polyurea resin molded body obtained by such a prepolymer method to a predetermined thickness to obtain a polishing layer 11, a base layer forming step of slicing a urethane sponge to a predetermined thickness to obtain a base layer 12, a groove forming step of forming the above-mentioned circular groove and radial groove in the polishing layer 11 and base layer 12, and a cutting step of bonding the polishing layer 11 and base layer 12 and then cutting them into a circular shape.

[0020] In the above preparation step for manufacturing the polishing layer 11, at least a urethane bond-containing isocyanate compound, a curing agent, and a hollow body are used as raw materials for the polyurethane resin molded article. Furthermore, a polyol compound may be used together with the above components, and other components may be used in combination as long as they do not impair the effects of the present invention. The urethane bond-containing isocyanate compound prepared in this preparation step is a compound obtained by reacting the following polyisocyanate compound and polyol compound under commonly used conditions, and contains a urethane bond and an isocyanate group within its molecule. Furthermore, other components may be included in the urethane bond-containing isocyanate compound, as long as they do not impair the effects of the present invention. The urethane bond-containing isocyanate compound may be a commercially available one, or one synthesized by reacting a polyisocyanate compound with a polyol compound. There are no particular restrictions on the above reaction, and the addition polymerization reaction can be carried out using known methods and conditions in the production of polyurethane resins. For example, it can be manufactured by adding a polyisocyanate compound heated to 50°C to a polyol compound heated to 40°C while stirring under a nitrogen atmosphere, raising the temperature to 80°C after 30 minutes, and then reacting at 80°C for another 60 minutes.

[0021] First, the term "polyisocyanate compound" refers to a compound having two or more isocyanate groups in its molecule. Furthermore, there are no particular limitations on what constitutes a polyisocyanate compound, as long as it has two or more isocyanate groups in its molecule. For example, diisocyanate compounds having two isocyanate groups in the molecule include m-phenylenediisocyanate, p-phenylenediisocyanate, 2,6-tolylenediisocyanate (2,6-TDI), 2,4-tolylenediisocyanate (2,4-TDI), naphthalene-1,4-diisocyanate, diphenylmethane-4,4'-diisocyanate (MDI), 4,4'-methylene-bis(cyclohexyl isocyanate) (hydrogenated MDI), 3,3'-dimethoxy-4,4'-biphenyldiisocyanate, and 3,3'-dimeth Examples include diphenylmethane-4,4'-diisocyanate, xylylene-1,4-diisocyanate, 4,4'-diphenylpropane diisocyanate, trimethylene diisocyanate, hexamethylene diisocyanate, propylene-1,2-diisocyanate, butylene-1,2-diisocyanate, cyclohexylene-1,2-diisocyanate, cyclohexylene-1,4-diisocyanate, p-phenylene diisothiocyanate, xylylene-1,4-diisothiocyanate, and ethyridine diisothiocyanate. Furthermore, diisocyanate compounds are preferred as polyisocyanate compounds, with 2,4-TDI, 2,6-TDI, MDI, and hydrogenated MDI being more preferred, and particularly preferred to contain 2,4-TDI and / or 2,6-TDI. These polyisocyanate compounds may be used individually or in combination of multiple polyisocyanate compounds.

[0022] Next, the term "polyol compound" refers to a compound having two or more alcoholic hydroxyl groups (OH) within its molecule. Polyol compounds used in the synthesis of the above-mentioned urethane bond-containing isocyanate compounds include diol compounds such as ethylene glycol, diethylene glycol (DEG), and butylene glycol, triol compounds, etc.; polyether polyol compounds such as poly(oxytetramethylene) glycol (or polytetramethylene ether glycol) (PTMG), polyethylene glycol (PEG), and polypropylene glycol (PPG); polyester polyol compounds such as reaction products of ethylene glycol and adipic acid or reaction products of butylene glycol and adipic acid; polycarbonate polyol compounds, polycaprolactone polyol compounds, etc., and combinations thereof. In addition, trifunctional propylene glycol to which ethylene oxide has been added can also be used. Among these, combinations of polyester polyols such as PTMG and DEG, PPG and DEG, or a reaction product of butylene glycol and adipic acid with DEG are preferred. The above polyol compounds may be used individually or in combination of multiple polyol compounds.

[0023] Here, the NCO equivalent of the isocyanate-terminated prepolymer, which indicates the molecular weight of PP (isocyanate-terminated prepolymer) per NCO group, is preferably 200 to 800, more preferably 300 to 700, and even more preferably 400 to 600. Specifically, the NCO equivalent of the above isocyanate-terminated prepolymer can be determined as follows. The NCO equivalent of an isocyanate-terminated prepolymer = (parts by mass of polyisocyanate compound + parts by mass of polyol compound) / [(number of functional groups per molecule of polyisocyanate compound × parts by mass of polyisocyanate compound / molecular weight of polyisocyanate compound) - (number of functional groups per molecule of polyol compound × parts by mass of polyol compound / molecular weight of polyol compound)]

[0024] As the curing agent (also called a chain extender), for example, polyamine compounds and / or polyol compounds can be used. Polyamine compounds refer to compounds that have two or more amino groups in their molecule, and aliphatic and aromatic polyamine compounds, especially diamine compounds, can be used. Examples include ethylenediamine, propylenediamine, hexamethylenediamine, isophoronediamine, dicyclohexylmethane-4,4'-diamine, 3,3'-dichloro-4,4'-diaminodiphenylmethane (methylenebis-o-chloroaniline) (hereinafter abbreviated as MOCA), and polyamine compounds having a similar structure to MOCA. Furthermore, the polyamine compound may have a hydroxyl group, and examples of such amine compounds include 2-hydroxyethylethylenediamine, 2-hydroxyethylpropylenediamine, di-2-hydroxyethylethylenediamine, di-2-hydroxyethylpropylenediamine, 2-hydroxypropylethylenediamine, and di-2-hydroxypropylethylenediamine. As for the polyamine compound, diamine compounds are preferred, with MOCA, diaminodiphenylmethane, and diaminodiphenylsulfone being more preferred, and MOCA being particularly preferred. Polyamine compounds may be used individually or in combination of multiple polyamine compounds. It is preferable to degas the polyamine compounds under reduced pressure while heated as necessary, in order to facilitate mixing with other components and / or to improve the uniformity of bubble diameter in subsequent molded product formation processes. For degassing under reduced pressure, any known method used in polyurethane production can be employed; for example, degassing can be performed using a vacuum pump at a vacuum level of 0.1 MPa or less. When a solid compound is used as a curing agent (chain extender), it can be melted by heating while being degassed under reduced pressure.

[0025] Furthermore, any polyol compound, such as diol compounds or triol compounds, can be used as a curing agent without any particular restrictions. It may also be the same as or different from the polyol compound used to form the isocyanate-terminated prepolymer. Specific examples include low molecular weight diols such as ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, pentanediol, 3-methyl-1,5-pentanediol, and 1,6-hexanediol, as well as high molecular weight polyol compounds such as poly(oxytetramethylene) glycol, polyethylene glycol, and polypropylene glycol. The above polyol compounds may be used individually or in combination of multiple polyol compounds.

[0026] Here, the components are mixed so that the R value, which is the equivalent ratio of the active hydrogen groups (amino groups and hydroxyl groups) present in the curing agent to the isocyanate groups present at the ends of the urethane bond-containing isocyanate compound, is 0.60 to 1.40. The R value is preferably 0.65 to 1.30, and more preferably 0.70 to 1.20.

[0027] The term "hollow body" as used above refers to a microsphere containing voids. Microspheres include spherical, elliptical, and nearly spherical shapes. Examples of hollow bodies include unexpanded, heat-expandable microspheres consisting of an outer shell (polymer shell) made of thermoplastic resin and low-boiling point hydrocarbons enclosed within the outer shell, as well as unexpanded, heat-expandable microspheres that have been heated and expanded. As the polymer shell, thermoplastic resins such as acrylonitrile-vinylidene chloride copolymer, acrylonitrile-methyl methacrylate copolymer, and vinyl chloride-ethylene copolymer can be used, as disclosed in Japanese Patent Publication No. 57-137323, etc. Similarly, as the low-boiling point hydrocarbon encapsulated in the polymer shell, for example, isobutane, pentane, isopentane, petroleum ether, etc. can be used.

[0028] Next, the mixing process will be described. In this mixing process, the urethane bond-containing isocyanate compound, curing agent, and hollow body prepared in the preparation process described above are supplied into a mixer and stirred and mixed. The mixing process is carried out under conditions where the mixture is heated to a temperature that ensures the fluidity of each component. There are no particular restrictions on the mixing order, but it is preferable to prepare a mixture of a urethane bond-containing isocyanate compound and a hollow body, and a mixture of a curing agent and other components as needed, and then supply both mixtures into a mixer and mix and stir them. In this way, a mixture for molding a molded body is prepared.

[0029] Next, in the molding process, the mixed liquid for molding the molded body prepared in the mixing process is poured into a mold at 50 to 130°C and cured to form a polyurethane resin molded body. At this time, the mixture hardens as the isocyanate-terminated prepolymer and the curing agent react to form a polyurethane resin.

[0030] The sponge used in the above-mentioned base layer 12 may be manufactured by known methods or may be obtained commercially. Polyurethane foam manufactured by Inoac Corporation, polyurethane foam manufactured by Sekisui Chemical Co., Ltd., or polyurethane foam manufactured by NHK Spring Co., Ltd. may be used.

[0031] Next, in the polishing layer formation step, the obtained polyurethane resin molded body is sliced ​​into a sheet of the required thickness to obtain the polishing layer 11. Similarly, in the base layer formation process, the obtained urethane sponge is sliced ​​into a sheet of the required thickness to obtain the base layer 12. The polishing layer 11 and base layer 12 obtained in this way are rectangular sheets. In the groove forming step, circular grooves 14 are formed on the surface of the sheet-like polishing layer 11 corresponding to the polishing surface, and radial grooves 15 are formed on at least one surface among the adhesive surface of the base layer 12, the holding surface of the base layer 12, or the surface corresponding to the adhesive surface of the polishing layer 11. Next, the polishing layer 11 with the circular groove 14 and the base material layer 12 are bonded together using double-sided tape or the like that which constitutes the adhesive layer 13. Subsequently, in the cutting process described above, a disc-shaped polishing pad 1 is obtained by cutting the bonded polishing layer 11 and the base material layer 12 into a circular shape.

[0032] Figures 6 and 7 show the experimental results for the polishing pad 1 (example) according to the third embodiment described above and the polishing pad 1 (comparative example) as a comparison. Figure 6 shows the amount of wavy in the response area of ​​each airbag, and Figure 7 is a graph showing the surface state of the workpiece 3 polished using the polishing pad 1.

[0033] Examples The polishing pad 1 in the example had a diameter of 740 mm. The polishing layer 11 used a polyurethane sheet with a density of 0.88 g / cm³, a D hardness of 44.0, and a thickness of 1.6 mm. The base layer 12 used a urethane sponge with a thickness of 1.0 mm and a Shore A hardness of 71. The adhesive layer used double-sided tape with a PET core material that was 0.05 mm thick. Furthermore, the storage modulus (at 40°C) of the abrasive layer 11 was 98.2 MPa, while the storage modulus (at 40°C) of the base layer 12 was 7.2 MPa. As a result, the ratio of the storage modulus of the abrasive layer 11 to that of the base layer 12 was 13.6. Of the circular grooves 14 formed on the polishing surface 11a of the polishing layer 11, the innermost circular groove 14 was positioned at a radius of 11 mm from the center of the polishing pad 1, and grooves with a pitch of 1.7 mm, a width of 0.4 mm, and a depth of 0.8 mm were provided outside of it. At this time, the radius of the outermost circular groove 14 was 358.4 mm. Furthermore, the radial grooves 15 formed on the adhesive surface 11b of the polishing layer 11 were set to have 32 grooves (groove angle pitch of 11.25°), a groove width of 1.5 mm, and a groove depth of 0.5 mm. The central end of each radial groove 15 of the polishing layer 11 was located 55 mm from the center of the polishing layer 11, which was at 15% of the radius of the polishing layer 11. The outer circumferential end of each radial groove 15 of the polishing layer 11 was located 335 mm from the center of the polishing layer 11, which was at 91% of the radius of the polishing layer 11.

[0034] Comparative Example 1 For the comparative example, the polishing pad 1 used in the above example had the same hardness and other properties as the polishing pad 1 of the example, and also used the same adhesive layer. In the comparative example, circular grooves 14 were formed on the polished surface 11a of the polished layer 11 in the same arrangement as in Example 1, while radial grooves 15 were not formed on the adhesive surface 11b.

[0035] Next, the polished layers 11 of the above examples and comparative examples were obtained as follows. A first isocyanate-terminated urethane prepolymer with an NCO equivalent of 560 is prepared by reacting 2,4-tolylene diisocyanate (TDI), polypropylene glycol (PPG) with a number average molecular weight of 1000, and diethylene glycol (DEG). A second isocyanate-terminated urethane prepolymer with an NCO equivalent of 600 is prepared by reacting 2,4-tolylene diisocyanate (TDI), a polyester polyol with a number average molecular weight of 2000 obtained by reacting adipic acid and 1,4-butanediol, and diethylene glycol (DEG). Next, the first and second isocyanate-terminated urethane prepolymers prepared are mixed in a weight ratio of 50:50 to prepare a mixed isocyanate-terminated urethane prepolymer with an NCO equivalent of 580. Furthermore, 3.5 parts of unexpanded microspheres with an average particle size of 8.5 μm, in which the outer shell consists of an acrylonitrile-vinylidene chloride copolymer and isobutane gas is contained within the shell, were added and mixed to 100 parts of the prepared mixed isocyanate-terminated urethane prepolymer to obtain a urethane prepolymer mixture. The obtained urethane prepolymer mixture was placed in the first liquid tank and kept warm at 80°C. Separately from the first liquid tank, 20.9 parts of 3,3'-dichloro-4,4'-diaminodiphenylmethane (methylenebis-o-chloroaniline) (MOCA) was placed in the second liquid tank as a curing agent, heated and melted at 120°C, and mixed to obtain a curing agent molten solution. Next, the liquids from the first and second liquid tanks were injected through the respective inlets of a mixer equipped with two inlets, and the mixture was stirred and mixed to obtain a mixed solution. At this time, the mixing ratio was adjusted so that the R value, which represents the equivalent ratio of amino groups and hydroxyl groups present in the curing agent to the isocyanate groups present at the ends of the urethane prepolymer, was 0.90. The resulting mixture was poured into a mold preheated to 80°C and allowed to undergo primary curing at 80°C for 30 minutes. The formed block-shaped molded material was removed from the mold and subjected to secondary curing in an oven at 120°C for 4 hours to obtain a polyurethane resin molded body. After the obtained polyurethane resin molded body was allowed to cool to 25°C, it was heated again in an oven at 120°C for 5 hours, and then sliced ​​to a thickness of 1.6 mm to obtain a polished layer 11.

[0036] On the other hand, the base layer 12 in the above examples and comparative examples was obtained by purchasing polyurethane foam from Sekisui Chemical Co., Ltd. and buffing it to a thickness of 1.0 mm.

[0037] The density (g / cm3) of the polished layer 11 in the above examples and comparative examples was measured in accordance with the Japanese Industrial Standard (JIS-K-6505). Furthermore, the Shore D hardness of the abrasive layer 11, which is made of polyurethane sheet, was measured using a D-type hardness tester in accordance with the Japanese Industrial Standard (JIS-K-6253). Here, the measurement sample was obtained by stacking multiple abrasive layers 11 as needed, so that the total thickness was at least 4.5 mm. On the other hand, the Shore A hardness of the base material layer 12, which is made of urethane sponge, was measured using a Type A hardness tester in accordance with the Japanese Industrial Standard (JIS-K-7311). Here, the measurement sample was obtained by stacking multiple base material layers 12 as needed, so that the total thickness was at least 4.5 mm. (Dynamic viscoelasticity test) Dynamic viscoelasticity tests were performed on the polishing layer 11 and the base layer 12 based on the following measurement conditions. Dry polishing layer 11 and base layer 12, which had been kept for 40 hours in a constant temperature and humidity chamber at a temperature of 23°C (±2°C) and relative humidity of 50% (±5%), were used as samples. Measurements were taken in a normal atmospheric environment (dry state), with the polishing layer measured in tensile mode and the base layer in compression mode. (Measurement conditions: polishing layer) Measuring device: RSA-G2 (TA Instruments Co., Ltd.) Sample size (polished layer): 5cm (length) x 0.5cm (width) x 0.16cm (thickness) Test length: 1cm Test mode: Tensile mode Frequency: 10 rad / s (1.6 Hz) Measurement temperature: 20~100℃ Heating rate: 5°C / min Distortion range: 0.10% Initial load: 148g Measurement interval: 2 points / ℃ (Measurement conditions: base material layer) Measuring device: RSA-G2 (TA Instruments Co., Ltd.) Frequency: 1Hz Sample size (substrate layer): 1cm (length) x 1cm (width) x 0.1cm (thickness) Test mode: Compression Measurement temperature: 20~100℃ Heating rate: 3°C / min Distortion range: 0.10% Initial load: 100g

[0038] The polishing pads 1 of the above examples and comparative examples obtained in this manner were subjected to polishing on a Cu film substrate under the following polishing conditions. When the predetermined polishing was completed, the polished surface of the workpiece 3 was measured, and it was determined from the experimental results shown in Figures 6 and 7 whether or not wavy material had formed on the polished surface of the workpiece 3.

[0039] (polishing conditions) Polishing machine: F-REX300X (manufactured by Ebara Corporation) Disk: 34J (manufactured by KINIK) Rotation speed: (Holding plate) 90 rpm, (Grinding plate) 81 rpm Polishing pressure: 2.7 psi Abrasive temperature: 20℃ Abrasive discharge rate: 350 ml / min Abrasive: CSL-9044C (Use a mixture of CSL-9044C concentrate and pure water in a weight ratio of 1:9) (Manufactured by Fujifilm Planar Solutions Co., Ltd.) Workpiece to be polished 3 (metal film): Cu film substrate (disc shape with a diameter of 300 mm) Polishing time: 60 seconds Pad Break: 20N 60 minutes Conditioning: In-situ, 20N Here, the workpiece 3 to be polished is held so that its center coincides with the holding platen 5 that constitutes the polishing machine, and the rotation center of the holding platen 5 is set to a position 125 mm away from the rotation center of the polishing platen 4. The holding platen 5 of the polishing machine described above is equipped with airbags A1 to A6, which are positioned radially outward in the following ranges: A1: 0-20mm, A2: 20-50mm, A3: 50-75mm, A4: 75-100mm, A5: 100-120mm, and A6: 120-130mm. A retainer ring 7 is provided on the outer circumference of airbag A6.

[0040] Figure 6 shows the measurement results for the amount of wavy in the response area of ​​each airbag. The horizontal axis represents the pressure response areas of the first to sixth airbags A1 to A6, corresponding to Figure 2, and the vertical axis represents the amount of wavy in each pressure response area. The horizontal pressure response area refers to the range over which the pressure applied to the workpiece 3 by each airbag A1 to A6 of the holding platen 5 is transmitted. Here, the ranges are as follows, moving radially outward from the center of the workpiece 3: Airbag A1: 0-30mm, A2: 15-65mm, A3: 45-87mm, A4: 70-112mm, A5: 95-130mm, A6: 115-140mm. Here, the reason why the pressure response areas of each airbag A1 to A6 overlap is that each airbag A1 to A6 exerts a certain degree of stress on the workpiece 3. The wavy amount on the vertical axis represents the difference between the maximum and minimum polishing rates, calculated within the range of the airbag's response area. The experimental results show that when using polishing pad 1 of the example, the amount of wavy in each response area is reduced compared to when using the polishing pad of the comparative example.

[0041] Figure 7 is a graph showing the surface condition of the workpiece 3. The horizontal axis represents the distance from the center of the workpiece 3 towards the radial outer edge, and the vertical axis represents the polishing rate at the position corresponding to the distance from the center of the workpiece 3. In other words, the vertical axis represents the surface condition of the workpiece. For convenience, the comparative example and the example are shown side by side to facilitate comparison of the surface conditions of the workpieces. Here, the boundary positions of airbags A1 to A6 on the holding platen 5 correspond to positions of 20 mm, 50 mm, 75 mm, 100 mm, 120 mm, and 130 mm, respectively, relative to the center of the workpiece 3. The experimental results showed that when using polishing pad 1 of the example, the difference in polishing rate between the boundary positions of each airbag A and the intermediate portions between each boundary position was smaller compared to when using polishing pad 1 of the comparative example, confirming that wavy caused by the airbag boundaries was reduced.

[0042] Figure 8 shows a cross-sectional view of the polishing pad 1 according to the fourth embodiment, and compared to the first to third embodiments described above, radial grooves 15 are provided on the holding surface 12b on the polishing platen 4 side of the base layer 12. The shape and arrangement of the radial grooves 15 can be the same as those of the polishing pad 1 according to the first to third embodiments, that is, the ends of the radial grooves 15 on the central side of the base material layer 12 are separated from each other so that a flat portion 16c is formed in the central part of the base material layer 12, and the ends of the radial grooves 15 on the outer side of the base material layer 12 are formed so that they do not reach the outer edge of the base material layer 12. This configuration prevents the radial grooves 15 from coming into excessive proximity near the flat portion 16c of the base layer 12, thereby preventing the central part of the polishing pad 1 from being excessively deformed by the workpiece 3, and reducing wavyness.

[0043] Furthermore, even if the polishing device 2 has a configuration in which a pressure adjustment means composed of multiple pressing means arranged concentrically is provided instead of the airbag A of the holding platen 5, wavy may occur at the boundary between each pressing means. Therefore, by using the polishing pad 1 according to the present invention, it is possible to suppress the occurrence of such wavy. Furthermore, in the polishing pad 1 of each of the above embodiments, it is also possible to fill the radial grooves 15 with the required resin, rubber, or other material. As the resin, UV-curable resin, urethane resin, silicone resin, acrylic resin, etc. can be used, and as the rubber, natural rubber, nitrile rubber, polyurethane rubber, etc. can be used. The above materials may be used individually or in combination of multiple materials. By filling the radial grooves 15 with resin or rubber in this way, the repulsive force when the object to be polished 3 is pressed against the polishing pad 1 can be made different between the portion where the base material layer 12 and the polishing layer 11 are formed and the portion where the resin or rubber-filled radial grooves 15 are formed, and the same effect as the polishing pad 1 of each of the above embodiments can be expected. [Explanation of Symbols]

[0044] 1. Polishing pad 2. Polishing device 3 Object to be polished 4 Polishing surface plate 5. Holding platen 11. Polishing layer 12 Base layer 14 Circular groove 15. Radial groove 15a. Long radial groove 15b Short radial grooves 16a Flat area on the adhesive surface of the substrate layer 16b Flat portion on the bonding surface of the polished layer 16c Flat portion on the holding surface of the substrate layer M Movement range

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, A polishing pad characterized in that a plurality of radial grooves are formed radially on at least one of the following surfaces: the adhesive surface on the polishing layer side of the base layer, the adhesive surface on the base layer side of the polishing layer, or the holding surface on the polishing platen side of the base layer, and the ends of the radial grooves on the central side of the base layer or the polishing layer are separated from each other to form a flat portion in the central part of the base layer or the polishing layer.

2. The polishing pad according to claim 1, characterized in that the outer peripheral end of the radial groove does not reach the outer peripheral of the base material layer or the polishing layer.

Images