Polishing pad

Abstract

To provide a polishing pad which can suppress time required for dressing from lengthening and suppress a polishing rate from dropping.SOLUTION: A polishing pad 1 is a polishing pad having a polyurethane resin foam. The polishing pad has a polishing surface 1a and the polishing surface is composed of a surface of the polyurethane resin foam. The polyurethane resin foam has a Young's modulus of 600 MPa or more and 900 MPa or less, a void ratio which exceeds 0% and has 10% or less, and tanδ of 0.2 or more and 0.6 or less at 80°C.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a polishing pad. More specifically, the present invention relates to a lapping polishing pad used for lapping a workpiece to be polished.

Background Art

[0002] Conventionally, in order to roughly smooth the surface of a workpiece to be polished such as a semiconductor wafer, it is known to polish the polished surface of the workpiece to be polished using a lapping polishing machine, that is, to lap the polished surface of the workpiece to be polished. The polishing of the polished surface of the workpiece to be polished using the lapping polishing machine is carried out using a single-sided polishing machine equipped with a head and a surface plate or a double-sided polishing machine equipped with a pair of surface plates arranged opposite to each other. For example, in the single-sided polishing machine, the polishing of the polished surface of the workpiece to be polished is carried out as follows. (1) In a lapping polishing machine having a head above and a surface plate below, a workpiece to be polished (such as a semiconductor wafer) cut out in a disk shape is attached to a holding member provided on the bed, and a disk-shaped polishing pad is attached to the upper surface of the surface plate. (2) The head is moved closer to the surface plate so that the exposed surface (polished surface) of the workpiece to be polished and the exposed surface (polishing surface) of the polishing pad are brought into contact with each other. (3) While supplying a polishing slurry to the contact portion in a state where the polished surface and the polishing surface are in contact with each other, the head and the surface plate are rotated, so that the polished surface of the workpiece to be polished is polished by the polishing surface of the polishing pad. In the polishing using a lapping polishing machine as described above, usually, a mixture of abrasive grains and a lubricant is used as the polishing slurry.

[0003] As described above, in the polishing using a lapping polishing machine, it is known to use a polishing pad made of a polyurethane resin foam (for example, Patent Documents 1 and 2 below). Patent Document 1 below describes how to suppress the foaming of the polyurethane resin foam to make the polyurethane resin foam high density and hardness (high hardness), and Patent Document 2 below describes how to promote the foaming of the polyurethane resin foam to make the polyurethane resin foam low density and hardness (low hardness). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2014-117794 [Patent Document 2] Japanese Patent Publication No. 2015-134402 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] Before lapping with an abrasive pad, a process called dressing is performed, in which the abrasive surface of the abrasive pad is ground down to ensure good contact with the workpiece. If the polishing surface is constructed from a high-density, high-hardness resin foam, as described in Patent Document 1 above, a lot of time will be required for dressing. On the other hand, when polishing an object, it is advantageous for the abrasive grains to come into contact with the object if there are fewer voids in the polishing surface and the polishing surface is mostly composed of resin, resulting in a higher polishing rate for the object. Therefore, while constructing the polishing surface with a low-density, low-hardness resin foam, as described in Patent Document 2 above, may suppress the lengthening of the grinding time during dressing, there is a risk that the polishing rate will decrease.

[0006] Therefore, in view of the above circumstances, the object of the present invention is to provide a polishing pad that can suppress the time required for dressing and also suppress the decrease in polishing rate. [Means for solving the problem]

[0007] The polishing pad according to the present invention is A polishing pad containing polyurethane resin foam, Having a polished surface, The polished surface is composed of the surface of the polyurethane resin foam, The polyurethane resin foam has a Young's modulus of 600 MPa or more and 900 MPa or less, a porosity greater than 0% and 10% or less, and a tanδ of 0.2 or more and 0.6 or less at 80°C.

[0008] With this configuration, it is possible to suppress the time required for dressing and also to suppress the decrease in the polishing rate.

[0009] In the aforementioned polishing pad, The polyurethane resin for forming the polyurethane resin foam comprises constituent units derived from a plurality of urethane prepolymers, including a first urethane prepolymer and a second urethane prepolymer. The first urethane prepolymer has polytetramethylene ether glycol (PTMG) as the polyol, The second urethane prepolymer preferably has polypropylene glycol (PPG) as the polyol.

[0010] With this configuration, the time required for dressing can be further suppressed, and the decrease in the polishing rate can be further suppressed.

[0011] In the aforementioned polishing pad, In the constituent unit derived from the urethane prepolymer, Preferably, the mass ratio of the first urethane prepolymer is 30% by mass or more and 90% by mass or less, and the mass ratio of the second urethane prepolymer is 10% by mass or more and 70% by mass or less.

[0012] According to such a configuration, it is possible to further suppress an increase in the time required for dressing, and moreover, it is possible to further suppress a decrease in the polishing rate.

Effect of the Invention

[0013] According to the present invention, it is possible to provide a polishing pad that can suppress an increase in the time required for dressing and moreover, can suppress a decrease in the polishing rate.

Brief Description of the Drawings

[0014] [Figure 1] Schematic cross-sectional view showing the usage state of the polishing pad according to the present embodiment. [Figure 2] Schematic plan view of the test piece used for measuring the cut rate and the polishing rate. [Figure 3] Schematic plan view of the dresser used for measuring the cut rate and the polishing rate.

Mode for Carrying Out the Invention

[0015] Hereinafter, an embodiment of the present invention will be described. In the following, an embodiment of the present invention may be simply referred to as the present embodiment.

[0016] As shown in FIG. 1, the polishing pad 1 according to the present embodiment is used for polishing the workpiece 2 in a polishing machine 100 including a surface plate 10 and a head 20. In the present embodiment, the polishing machine 100 includes a slurry supply unit 30 for supplying polishing slurry in addition to the surface plate 10 and the head 20. Further, in the present embodiment, the head 20 of the polishing machine 100 includes a holding member 20a for holding the workpiece 2. As shown in FIG. 1, the polishing pad 1 according to the present embodiment is used for polishing the polished surface 2a of the workpiece 2 attached to the holding member 20a of the head 20 by the polishing surface 1a of the polishing pad 1 after being attached to the surface plate 10. Although Figure 1 illustrates an example in which the polishing pad 1 according to this embodiment is attached to a single-sided polishing machine for polishing one side of a workpiece 2, the polishing pad 1 according to this embodiment may also be used attached to a double-sided polishing machine. More specifically, the polishing pad 1 according to this embodiment may be used in a double-sided polishing machine equipped with a pair of facing surface plates, attached to each of the pair of surface plates.

[0017] The polishing pad 1 according to this embodiment comprises a polyurethane resin foam containing polyurethane resin. As described above, the polishing pad 1 according to this embodiment has a polishing surface 1a for polishing the surface 2a of the object to be polished 2, and the polishing surface 1a is made of the surface of a polyurethane resin foam. In this embodiment, the polishing pad 1 polishes the surface to be polished 2a by interposing a polishing slurry containing abrasive grains between the polishing surface 1a and the exposed surface of the object to be polished (the surface to be polished 2a), thereby causing the polishing surface 1a and the surface to be polished 2a to slide against each other. Examples of materials to be polished (2) include Si wafers and SiC wafers. Furthermore, when lapping a workpiece 2 using the polishing pad 1 according to this embodiment, a mixture of abrasive grains and a lubricant is typically used as the polishing slurry.

[0018] The surface of the polyurethane resin foam is provided with an open region where voids are open and a resin region made of polyurethane resin. In the polishing surface 1a of the polishing pad 1 of this embodiment, the resin region is provided as a single continuous region, and the open region is provided as a plurality of scattered regions. The polishing of the surface to be polished is greatly influenced by the abrasive grains present between the resin region and the surface to be polished. If the proportion of resin is small, the amount of abrasive grains that can come into contact with the surface being polished will also decrease. If the resin region deforms excessively in the direction away from the surface to be polished when it comes into contact with the surface to be polished, the polishing effect of the abrasive grains will also decrease. In the polishing pad 1 of this embodiment, the polishing surface 1a is made of a polyurethane resin foam that has a small porosity and a good Young's modulus, and exhibits an appropriate tanδ when the temperature rises due to frictional heat during polishing of the workpiece. Therefore, the polishing pad 1 of this embodiment is also excellent in that it does not require a long time for grinding with dressing and can polish the workpiece at a high polishing rate.

[0019] The aforementioned polyurethane resin foam has a Young's modulus of 600 MPa or more and 900 MPa or less. The Young's modulus is preferably 620 MPa or higher, and more preferably 640 MPa or higher. The Young's modulus is preferably 880 MPa or less, and more preferably 860 MPa or less. The Young's modulus can be determined by following the procedure below. (1) In accordance with JIS K 6251, a dumbbell-shaped test specimen (dumbbell-shaped test specimen No. 1) is prepared using the polyurethane resin foam. (2) Using a tensile testing machine, the dumbbell-shaped test piece is pulled in the length direction at a tensile speed of 100 mm / min to obtain multiple test force values ​​and strain values ​​corresponding to each test force. Then, using these values, a graph is created with the test force on the X axis and the strain on the Y axis. (3) In the range of the test force from 0.5 N to 15 N shown in the graph, an approximate straight line is found by the least squares method, and the slope of the approximate straight line is determined as Young's modulus (in MPa).

[0020] The Young's modulus of the polyurethane resin foam can be adjusted by adjusting the composition of the polyurethane resin or by adjusting the porosity of the polyurethane resin foam. First, in adjusting the composition, for example, the Young's modulus of the polyurethane resin foam can be adjusted by adjusting the ratio of soft segment content to hard segment content in the polyurethane resin. More specifically, the Young's modulus of the polyurethane resin foam can be increased by reducing the molecular weight of the soft polyol and relatively increasing the proportion of isocyanate groups. Furthermore, the Young's modulus of the polyurethane resin foam can also be increased by lowering the equivalent ratio (NCO / OH equivalent ratio) of the urethane prepolymer and increasing the equivalent ratio (amine equivalent ratio) of the rigid amine curing agent. Next, the porosity can be adjusted by adjusting the amount of foaming agent. More specifically, the Young's modulus of the polyurethane resin foam can be increased by reducing the amount of foaming agent and thereby decreasing the porosity.

[0021] The polyurethane resin foam has a porosity greater than 0% and less than or equal to 10%. The porosity is preferably 1% or more, more preferably 3% or more, and even more preferably 5% or more. The porosity is preferably 9% or less, more preferably 8% or less, and even more preferably 7% or less. The aforementioned porosity can be determined using an X-ray CT scanner (for example, a TDM1000H-I manufactured by Yamato Scientific Co., Ltd.) as follows. (1) After measuring the volume of each bubble within the measurement area of ​​the polyurethane foam (for example, two sections of 0.7 mm × 1.6 mm × 1.6 mm), the volumes of each bubble are added together to determine the total volume of the bubbles. (2) Calculate the ratio (percentage) of the total volume of bubbles obtained in (1) above to the volume of the polyurethane foam to be measured.

[0022] The polyurethane resin foam is obtained by foaming the polyurethane resin, as will be described later. Furthermore, in the polishing pad according to this embodiment, the polyurethane resin foam has a small void ratio of 10% or less, as described above. In order to obtain the polyurethane resin foam having such a small porosity, it is preferable to foam the polyurethane resin without using a foaming agent.

[0023] The polyurethane resin foam has a tanδ of 0.2 or more and 0.6 or less at 80°C. The tanδ at 80°C is preferably 0.22 or higher, more preferably 0.25 or higher, and even more preferably 0.28 or higher. The tanδ at 80°C is preferably 0.58 or less, more preferably 0.55 or less, and even more preferably 0.52 or less. The tanδ at 80°C refers to the ratio (E'' / E') of the loss modulus E'' at 80°C to the storage modulus E' at 80°C. The storage modulus E' and loss modulus E'' at 80°C can be measured under the following conditions in accordance with JIS K7244-4:1999 "Plastics - Test methods for dynamic mechanical properties - Part 4: Tensile vibration - Non-resonant method". • Measurement temperature range: 0℃ to 100℃ • Heating rate: 5°C / min • Frequency: 1Hz • Strain: 0.5%

[0024] The tanδ of the polyurethane resin foam can be adjusted by various methods. For example, in the polyurethane resin foam, the value of tanδ can be reduced by increasing the number of crosslinking points, and the value of tanδ can be increased by reducing the number of crosslinking points. More specifically, by reacting excess NCO groups with the hydroxyl and amine groups of the curing agent to form allophanate and biuret bonds, which serve as crosslinking sites, the number of crosslinking sites in the polyurethane resin foam can be increased, thereby lowering the value of tanδ. In contrast, by increasing the molecular weight of the polyol in the urethane prepolymer, the value of tanδ can be increased in the polyurethane resin foam by reducing the number of crosslinking points and decreasing the crosslinking density.

[0025] In the polishing pad according to this embodiment, it is important that the polyurethane resin foam has a Young's modulus of 600 MPa or more and 900 MPa or less, a porosity greater than 0% and 10% or less, and a tanδ of 0.2 or more and 0.6 or less at 80°C, as described above.

[0026] By having a Young's modulus of 600 MPa or more and 900 MPa or less, the polishing pad can be made to have an appropriate hardness. In other words, the abrasive particles (free abrasive particles) contained in the polishing slurry can be embedded in the polishing pad while being appropriately protruding from the polishing surface of the polishing pad. If the polyurethane resin foam is too soft and the free abrasive particles are excessively embedded in the polishing pad, or if the polyurethane resin foam is too hard and the free abrasive particles cannot be sufficiently embedded in the polishing pad, in either case the polishing rate decreases when the polishing surface of the workpiece is polished with the polishing surface of the polishing pad. However, as described above, by embedding the free abrasive particles in the polishing pad in a state where they protrude appropriately from the polishing surface of the polishing pad, it is possible to suppress the decrease in the polishing rate when the polishing surface of the workpiece is polished with the polishing surface of the polishing pad. Furthermore, having a Young's modulus of 600 MPa or higher allows for relatively small deformation of the polishing pad in the thickness direction when polishing the surface of the workpiece with the polishing surface of the polishing pad. This makes it possible to suppress edge roll-off (edge ​​rounding) at the edges of the workpiece after polishing the surface of the workpiece. Since the void ratio is greater than 0% and less than or equal to 10%, the free abrasive grains can be embedded in the polishing pad so that they protrude appropriately from the polishing surface of the polishing pad. When the porosity of the polyurethane resin foam exceeds a high value of 10%, the free abrasive particles become too embedded in the polishing pad, reducing the frequency of contact between the free abrasive particles and the polishing surface of the workpiece. This reduces the polishing speed (rate) when polishing the polishing surface of the workpiece with the polishing pad. However, by embedding the free abrasive particles in the polishing pad so that they protrude appropriately from the polishing surface of the polishing pad, the decrease in the frequency of contact between the free abrasive particles and the polishing surface of the workpiece can be suppressed, thus preventing a decrease in the polishing speed (rate) when polishing the polishing surface of the workpiece with the polishing pad. Thus, by having a Young's modulus of 600 MPa or more and 900 MPa or less, and a porosity of more than 0% and less than or equal to 10%, it is possible to suppress a decrease in polishing speed (rate) when polishing the surface of the workpiece with the polishing surface of the polishing pad.

[0027] As explained earlier, after the polishing pad 1 is attached to the surface plate 10, the outer surface (polishing surface 1a) of the polishing pad 1 is usually ground to a sufficiently flat surface using a dresser or the like. Furthermore, when grinding the polishing surface 1a of the polishing pad 1 using a dresser or the like, the temperature of the polishing surface 1a while being ground with the dresser or the like reaches a high temperature (for example, 80°C). In this case, it is considered that a sufficient crystalline structure is formed in the polyurethane resin foam by the polyurethane resin contained in the polyurethane resin foam. Therefore, if the value of tanδ at 80°C is too low, the crystalline structure of the polyurethane resin foam will not easily collapse, and consequently, there is a concern that the polishing surface 1a of the polishing pad 1 will not be easily worn down. On the other hand, if the value of tanδ at 80°C is too high, the elastic modulus of the polyurethane resin foam becomes too low, resulting in the polyurethane resin foam being too soft. Thus, if the polyurethane resin foam is too soft, the polishing speed (rate) tends to decrease when the polishing surface 1a of the polishing pad 1 polishes the polishing surface 2a of the workpiece 2, and edge roll-off (sagging of the edge portion) is more likely to occur. However, in the polishing pad according to this embodiment, the polyurethane resin foam has a moderate tanδ of 0.2 to 0.6 at 80°C, that is, it has moderate hardness, so it is possible to suppress the length of grinding time required to flatten the polishing surface 1a of the polishing pad 1 by polishing it with a dresser or the like. Furthermore, in the polishing pad according to this embodiment, even if the proportion of the resin region of the polyurethane resin foam is large, it is possible to suppress the fact that the polishing surface 1a is less likely to wear down. In addition, it is possible to suppress the fact that the polishing speed (rate) tends to decrease and edge roll-off (sagging of the edge portion) tends to occur due to the polyurethane resin foam being too soft.

[0028] The polyurethane resin foam has an apparent density of 1.00 g / cm³. 3 Preferably, it is 1.05 g / cm³ or more. 3 It is more preferable that the above conditions are met. The polyurethane resin foam has an apparent density of 1.20 g / cm³. 3 Preferably, it is 1.10 g / cm³. 3 The following is more preferable: The apparent density of the polyurethane resin foam can be measured in accordance with JIS K 7222:2005.

[0029] The polyurethane resin contained in the polyurethane resin foam according to this embodiment can be the same type as that used in general polishing pads. The polyurethane resin comprises a polyisocyanate compound (for example, a prepolymer having isocyanate groups at both ends of the molecular chain) and a curing agent. In other words, the polyurethane resin foam according to this embodiment can be obtained by preparing a liquid mixture containing the polyisocyanate compound and the curing agent, and then curing the mixture.

[0030] Examples of polyisocyanate compounds according to this embodiment include urethane prepolymers that comprise one or more polyols and one or more polyisocyanates as constituent units, and have isocyanate groups at their terminal ends. The polyisocyanate compound according to this embodiment may be a mixture of multiple urethane prepolymers, or it may be one or more polyisocyanates as shown later. The polyisocyanate compound according to this embodiment may be a mixture of one or more urethane prepolymers and one or more polyisocyanates.

[0031] The polyurethane resin according to this embodiment preferably comprises constituent units derived from a plurality of urethane prepolymers, including a first urethane prepolymer and a second urethane prepolymer, wherein the first urethane prepolymer has polytetramethylene ether glycol (PTMG), described later, as the polyol, and the second urethane prepolymer has polypropylene glycol (PPG), described later, as the polyol. Since the first urethane prepolymer has PTMG without side chains as a polyol, curing such a first urethane prepolymer results in the formation of a relatively dense crystalline structure. Polyurethane foams with such a relatively dense crystalline structure tend to become too hard. Here, since PPG has methyl groups in its side chains, by including a second urethane prepolymer having PPG as a polyol in addition to the first urethane prepolymer in the polyurethane resin, the formation of a crystalline structure can be mitigated when cured. Therefore, polyurethane foams in which the formation of the crystalline structure is relaxed in this way have a moderate hardness. In other words, polishing pads made of such polyurethane resin foam can suppress the time required for dressing and also suppress the decrease in polishing rate.

[0032] In the constituent units derived from the urethane prepolymer, it is preferable that the mass ratio of the first urethane prepolymer is 30% by mass or more and 90% by mass or less, and the mass ratio of the second urethane prepolymer is 10% by mass or more and 70% by mass or less. Furthermore, in the constituent units derived from the urethane prepolymer, it is more preferable that the mass ratio of the first urethane prepolymer is 35% by mass or more and 85% by mass or less, and the mass ratio of the second urethane prepolymer is 15% by mass or more and 65% by mass or less, and it is even more preferable that the mass ratio of the first urethane prepolymer is 40% by mass or more and 80% by mass or less, and the mass ratio of the second urethane prepolymer is 20% by mass or more and 60% by mass or less.

[0033] The first urethane prepolymer and the second urethane prepolymer may have isocyanate groups at their terminal ends.

[0034] Examples of the aforementioned polyols include aromatic polyols such as 1,4-benzenedimethanol and 1,4-bis(2-hydroxyethoxy)benzene; aliphatic polyols such as ethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 1,9-nonanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 2-methyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, and 2-methyl-1,8-octanediol; alicyclic polyols such as 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, and hydrous bisphenol A; and polyfunctional polyols such as glycerin, trimethylolpropane, tributylolpropane, pentaerythritol, and sorbitol.

[0035] The polyol may be, for example, a polyol polymer such as polyester polyol, polyester polycarbonate polyol, polyether polyol, or polycarbonate polyol. The polyol polymer may be a polyfunctional polyol polymer having three or more hydroxyl groups in its molecule.

[0036] Examples of the polyester polyol include polyethylene adipate glycol, polybutylene adipate glycol, polycaprolactone polyol, and polyhexamethylene adipate glycol.

[0037] Examples of the polyester polycarbonate polyol include reaction products of polyester glycols such as polycaprolactone polyol and alkylene carbonates, and reaction products obtained by reacting ethylene carbonate with a polyhydric alcohol and further reacting the resulting product with an organic dicarboxylic acid.

[0038] Examples of the aforementioned polyether polyols include polytetramethylene ether glycol (PTMG), polypropylene glycol (PPG), polyethylene glycol (PEG), and ethylene oxide-added polypropylene polyol.

[0039] Examples of the polycarbonate polyol include reaction products of diols such as 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, polyethylene glycol, polypropylene glycol, or polytetramethylene ether glycol with phosgene, diallyl carbonate (e.g., diphenyl carbonate), or cyclic carbonate (e.g., propylene carbonate).

[0040] Examples of the aforementioned polyisocyanates include aromatic diisocyanates, aliphatic isocyanates, and alicyclic isocyanates.

[0041] Examples of the aromatic isocyanates include tolylene diisocyanate (TDI), 1,5-naphthalene diisocyanate, xylylene diisocyanate, 1,3-phenylene diisocyanate, and 1,4-phenylene diisocyanate. Furthermore, examples of the aromatic isocyanates include diphenylmethane diisocyanate (MDI) and modified diphenylmethane diisocyanate (MDI).

[0042] Modified products of diphenylmethane diisocyanate (MDI) include, for example, carbodiimide-modified products, urethane-modified products, allophanate-modified products, urea-modified products, biuret-modified products, isocyanurate-modified products, and oxazolidone-modified products. Specifically, an example of such a modified product is carbodiimide-modified diphenylmethane diisocyanate (carbodiimide-modified MDI).

[0043] Examples of the aliphatic diisocyanates include ethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, and hexamethylene diisocyanate (HDI).

[0044] Examples of the aforementioned alicyclic diisocyanates include 1,4-cyclohexane diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, isophorone diisocyanate, norbornane diisocyanate, and methylenebis(4,1-cyclohexylene) diisocyanate.

[0045] In this embodiment, the curing agent may be, for example, a polyamine.

[0046] Examples of the aforementioned polyamines include 4,4'-methylenebis(2-chloroaniline) (MOCA), 4,4'-methylenedianiline, trimethylenebis(4-aminobenzoate), 2-methyl4,6-bis(methylthio)benzene-1,3-diamine, 2-methyl4,6-bis(methylthio)-1,5-benzenediamine, 2,6-dichloro-p-phenylenediamine, 4,4'-methylenebis(2,3-dichloroaniline), Examples include 3,5-bis(methylthio)-2,4-toluenediamine, 3,5-bis(methylthio)-2,6-toluenediamine, 3,5-diethyltoluene-2,4-diamine, 3,5-diethyltoluene-2,6-diamine, trimethylene glycol-di-p-aminobenzoate, 1,2-bis(2-aminophenylthio)ethane, and 4,4'-diamino-3,3'-diethyl-5,5'-dimethyldiphenylmethane.

[0047] The curing agent may be the polyol. The curing agent may be a mixture of the polyol and the polyamine.

[0048] Here, the polyurethane resin foam according to this embodiment is obtained by foaming the polyurethane resin as described above. Furthermore, the polyurethane resin foam according to this embodiment has a void ratio greater than 0% and less than or equal to 10%. From the viewpoint of achieving a porosity within the range described above, it is preferable that the polyurethane resin foam according to this embodiment is obtained by foaming polyurethane resin without using a foaming agent. Examples of foaming agents include water.

[0049] The polishing pad of this embodiment can achieve a desired surface roughness by subjecting the surface of the polyurethane resin foam, which is manufactured as described above, to the following treatment. The integral value (Rvi) is set to the desired value (2.00 mm) 2 Examples of surface treatment methods for achieving the above include slicing, surface buffing, laser processing, and blasting. Among these methods, slicing is preferred.

[0050] Examples of objects to be polished with the polishing pad according to this embodiment include Si wafers and SiC wafers, as described earlier. Furthermore, the polishing pad according to this embodiment is suitably used for lapping to roughly smooth the surface of an object to be polished.

[0051] Furthermore, the polishing pad according to the present invention is not limited to the embodiments described above. Also, the polishing pad according to the present invention is not limited by the effects described above. Moreover, the polishing pad according to the present invention can be modified in various ways without departing from the spirit of the invention. [Examples]

[0052] Next, the present invention will be described in more detail with reference to examples and comparative examples. The following examples are provided to further illustrate the present invention and do not limit its scope.

[0053] (Example 1) A dispersion was obtained by mixing a PTMG-containing prepolymer and a PPG-containing prepolymer in the proportions shown in Table 1 below, and then mixing them at 70°C, thereby obtaining a dispersion in which air was dispersed as bubbles. Next, after adding a curing agent to the dispersion, the dispersion containing the curing agent was mixed to polymerize the PTMG-containing prepolymer and the PPG-containing prepolymer with the curing agent, thereby obtaining the polyurethane resin foam according to Example 1, i.e., the polishing pad according to Example 1. The curing agent was added in an amount of 24.2 parts by mass per 100 parts by mass of the total of the PTMG-containing prepolymer and the PPG-containing prepolymer.

[0054] The PTMG-containing prepolymer, the PPG-containing prepolymer, and the curing agent are as follows: • PTMG-containing prepolymer A PTMG-containing prepolymer (a prepolymer containing an isocyanate group (NCO group) as a terminal group) obtained by reacting polytetramethylene ether glycol (PTMG) with tolylene diisocyanate (TDI). • PPG-containing prepolymer A PPG-containing prepolymer (a prepolymer containing isocyanate groups (NCO groups) as terminal groups) obtained by reacting polypropylene glycol (PPG) with tolylene diisocyanate (TDI). • Hardener: MOCA (4,4'-methylenebis(2-chloroaniline)) The polyurethane resin foam according to Example 1 contained isocyanate groups (NCO groups) as terminal groups, and the NCO group content was 7.99% by mass.

[0055] (Example 2) The polyurethane resin foam according to Example 2, i.e., the polishing pad according to Example 2, was obtained in the same manner as in Example 1, except that the blending ratio of the PTMG-containing prepolymer and the PPG-containing prepolymer was as shown in Table 1 below, and 23.4 parts by mass of the curing agent was added to a total amount of 100 parts by mass of the PTMG-containing prepolymer and the PPG-containing prepolymer. Furthermore, the polyurethane resin foam according to Example 2 also contained isocyanate groups (NCO groups) as terminal groups, and the NCO group content was 7.74% by mass.

[0056] (Example 3) Except for the mixing ratio of the PTMG-containing prepolymer and the PPG-containing prepolymer being as shown in Table 1 below, and adding 23.4 parts by mass of the curing agent to a total amount of 100 parts by mass of the PTMG-containing prepolymer and the PPG-containing prepolymer, a polyurethane resin foam according to Example 3, i.e., a polishing pad according to Example 3, was obtained in the same manner as in Example 1. Furthermore, the polyurethane resin foam according to Example 3 also contained isocyanate groups (NCO groups) as terminal groups, and the NCO group content was 7.74% by mass. In Example 3, the polyurethane resin foam had the same blending ratio of the PTMG-containing prepolymer to the PPG-containing prepolymer as in Example 2, but the obtained physical properties (apparent density, Young's modulus, tanδ at 80°C, and porosity; see Table 1) were different from those of the polyurethane resin foam in Example 2.

[0057] (Comparative Example 1) A polyurethane resin foam according to Comparative Example 1, i.e., a polishing pad according to Comparative Example 1, was obtained in the same manner as in Example 1, except that only a PTMG-containing prepolymer was used instead of a PPG-containing prepolymer, 23.9 parts by mass of the curing agent was added to 100 parts by mass of the PTMG-containing prepolymer, and water was used as a foaming agent. Furthermore, the polyurethane resin foam in Comparative Example 1 also contained isocyanate groups (NCO groups) as terminal groups, and the NCO group content was 8.38% by mass. Furthermore, water was added as a foaming agent at a ratio of 0.11 parts by mass per 100 parts by mass of the PTMG-containing prepolymer.

[0058] (Comparative Example 2) A polyurethane resin foam, i.e., a polishing pad according to Comparative Example 2, was obtained in the same manner as in Example 1, except that only a PTMG-containing prepolymer was used instead of a PPG-containing prepolymer, 26.3 parts by mass of the curing agent was added to 100 parts by mass of the PTMG-containing prepolymer, and water was used as a foaming agent. Furthermore, the polyurethane resin foam in Comparative Example 2 also contained isocyanate groups (NCO groups) as terminal groups, and the NCO group content was 9.49% by mass. Furthermore, water was added as a foaming agent at a rate of 0.075 parts by mass per 100 parts by mass of the PTMG-containing prepolymer. The polyurethane resin foam in Comparative Example 2 also used a PTMG-containing prepolymer and water as a blowing agent, similar to Comparative Example 1. However, the obtained physical properties (apparent density, Young's modulus, tanδ at 80°C, and porosity; see Table 1) differed from those of the polyurethane resin foam in Comparative Example 1.

[0059] (Comparative Example 3) A polyurethane resin foam, i.e., a polishing pad according to Comparative Example 3, was obtained in the same manner as in Example 1, except that only a PTMG-containing prepolymer was used instead of a PPG-containing prepolymer, and 27.7 parts by mass of the curing agent was added to 100 parts by mass of the PTMG-containing prepolymer. Furthermore, the polyurethane resin foam in Comparative Example 3 also contained isocyanate groups (NCO groups) as terminal groups, and the NCO group content was 9.15% by mass.

[0060] (Comparative Example 4) A polyurethane resin foam, i.e., a polishing pad according to Comparative Example 4, was obtained in the same manner as in Example 1, except that only a PTMG-containing prepolymer was used instead of a PPG-containing prepolymer, 24.0 parts by mass of the curing agent was added to 100 parts by mass of the PTMG-containing prepolymer, and water was used as a foaming agent. Furthermore, the polyurethane resin foam in Comparative Example 4 also contained isocyanate groups (NCO groups) as terminal groups, and the NCO group content was 8.40% by mass. Furthermore, water was added as a foaming agent at a ratio of 0.22 parts by mass per 100 parts by mass of the PTMG-containing prepolymer. The polyurethane resin foam in Comparative Example 4 also used a PTMG-containing prepolymer and water as a blowing agent, similar to Comparative Example 1. However, the obtained physical properties (apparent density, Young's modulus, tanδ at 80°C, and porosity; see Table 1) differed from those of the polyurethane resin foam in Comparative Example 1.

[0061] [Table 1]

[0062] (Apparent density) The apparent density of the polyurethane resin foam in each example was measured. The apparent density was measured according to the method described earlier. The results are shown in Table 1 above.

[0063] (Young's modulus) The Young's modulus was measured for the polyurethane resin foam in each example. Young's modulus was measured according to the method described earlier. The results are shown in Table 1 above.

[0064] (tanδ at 80°C) For each example, the tanδ was measured at 80°C for the polyurethane resin foam. The tanδ at 80°C was measured according to the method described earlier. The results are shown in Table 1 above.

[0065] (porosity) The porosity was measured for the polyurethane resin foam in each example. The porosity was measured according to the method described earlier. The results are shown in Table 1 above.

[0066] (Cut rate) The cut rate (in μm / min) was measured using the polyurethane resin foam for each example as an abrasive pad. The cut rate refers to the grinding speed when grinding (dressing) the abrasive surface of an abrasive pad using a dresser or similar tool. A higher cut rate means a faster grinding speed (dressing speed). As test specimens for measuring the cut rate, polishing pads for each example were processed into a donut shape (outer diameter: 500 mm, inner diameter: 90 mm, thickness: approximately 1.0 mm), as shown in Figure 2. Furthermore, as shown in Figure 2, the test specimen had six 5 mm through holes drilled at equal intervals from the inner diameter to the outer diameter. The device used was the LP-18 (manufactured by High Technos Co., Ltd.). Furthermore, the pad grooves were machined to have a width of 2.5 mm and a pitch of 7.5 mm. Furthermore, the temperature of the surface plate chiller was set to 25°C.

[0067] The cut rate was measured according to the following procedure. (1) Attach one side of the test specimen to the surface plate of the apparatus and measure the depth of each hole (6 holes) (initial depth D1 to D6). (2) While applying water to the other side (exposed side) of the test specimen, the head equipped with a surface plate and dresser is rotated to grind the test specimen from the other side, and then the depth of each hole (6 holes) (depth after grinding D'1 to D'6) is measured. (3) For each hole, the value obtained by subtracting the depth after grinding from the initial depth is calculated (D1-D'1 to D6-D'6), and the cut rate is determined by taking the arithmetic mean of these six calculated values. In measuring the cut rate, the grinding time was adjusted according to the grinding speed, and in all cases, the test specimens were ground to a thickness of 30 μm or more. The results of measuring the cut rate for each polishing pad in each example are shown in Table 1 above. The cut rate was measured under the conditions shown in Table 2 below. Additionally, 24 cylindrical dressers were prepared. Then, 24 cylindrical dressers D were arranged at equal intervals on one end edge of the cylindrical head H (see Figure 3). Specifically, 24 cylindrical dressers D were arranged on one side of the cylindrical head H at equal intervals along the outer circumference. The distance between the center of head H and the center of dresser D was 106 mm.

[0068] [Table 2]

[0069] (Polishing speed (rate)) The polishing speed (rate) when polishing a SiC wafer using the polishing pads associated with each example after measuring the cut rate was measured. The polishing rate was measured under the conditions shown in Table 3 below. The polishing rate was measured according to the following procedure. (1) After measuring the initial mass W0 of the SiC wafer, the SiC wafer is mounted on a head equipped with a template. (2) Polishing (lapping) is performed for 2 minutes on the surface of the SiC wafer to be polished, using the load, platen rotation speed, and head rotation speed shown in Table 3 below, while applying the polishing slurry (6g abrasive grains / 1L lubricant) prepared as shown in Table 3 below. (3) Remove the polished SiC wafer from the head and measure the post-polishing mass W1. (4) Calculate the value obtained by subtracting the polished mass W1 from the initial mass W0 (W0-W1). (5) The calculated mass change obtained in (4) above is used with the specific gravity of SiC (3.22 g / cm³). 3 The change in SiC wafer thickness per unit time is calculated by dividing the polishing surface area by the polishing time. The calculated change in SiC wafer thickness per unit time is then defined as the polishing speed. The above measurements were performed on three SiC wafers. Then, the arithmetic mean of the SiC wafer polishing rates (i.e., the change in SiC wafer thickness per unit time) obtained for the three SiC wafers was taken as the representative polishing rate (RR) for each polishing pad. Furthermore, the above measurements were performed on both the Si side and the C side of the SiC wafer. Table 1 above shows the results of measuring the polishing speed on the Si surface (Si surface-RR) and the polishing speed on the C surface (C surface-RR) for each example of the polishing pad.

[0070] [Table 3]

[0071] Table 1 shows that the polishing pads in each embodiment exhibit a sufficiently high cut rate. From this, it can be seen that the polishing pads in each embodiment can suppress the increase in the time required for dressing. In contrast, the polishing pads in Comparative Examples 1-3 show lower cut rates, suggesting that the dressing time will be longer. Furthermore, it can be seen that the polishing pads in each embodiment show relatively high values ​​for Si-face-RR and C-face-RR. From this, it can be seen that the polishing pads according to each embodiment can suppress the decrease in polishing rate. In contrast, the polishing pad relating to Comparative Example 4 shows extremely low values ​​for Si-surface-RR and C-surface-RR, suggesting that it is not possible to suppress the decrease in polishing rate. [Explanation of symbols]

[0072] 1 polishing pad, 2 workpiece, 10 surface plate, 20 head, 30 slurry supply unit, 100 polishing machine, 1a polished surface, 2a polished surface, 20a holding material.

Claims

1. A polishing pad containing polyurethane resin foam, Having a polished surface, The polished surface is composed of the surface of the polyurethane resin foam, The polyurethane resin foam has a Young's modulus of 600 MPa or more and 900 MPa or less, a porosity greater than 0% and 10% or less, and a tanδ of 0.2 or more and 0.6 or less at 80°C. Polishing pad.

2. The polyurethane resin for forming the polyurethane resin foam comprises constituent units derived from a plurality of urethane prepolymers, including a first urethane prepolymer and a second urethane prepolymer. The first urethane prepolymer has polytetramethylene ether glycol (PTMG) as the polyol, The second urethane prepolymer has polypropylene glycol (PPG) as the polyol. The polishing pad according to claim 1.

3. In the constituent unit derived from the urethane prepolymer, The mass ratio of the first urethane prepolymer is 30% by mass or more and 90% by mass or less, and the mass ratio of the second urethane prepolymer is 10% by mass or more and 70% by mass or less. The polishing pad according to claim 2.

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