JP2010069551A - Polishing pad - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polishing pad allowing the improvement in the flatness of a polishing object thinned and embrittled for a long period. <P>SOLUTION: This polishing pad 10 includes a polyurethane foam 2 having a polishing surface P for polishing the surface of the polishing object and a cushion layer 3 arranged on a surface side opposite to the polishing surface P. The polyurethane foam 2 is made by wet film forming. The cushion layer 3 is composed by adhering two sheets of polyurethane foams 3a and 3b made by wet film forming. In the cushion layer 3, a compression rate is set in the range of 30 to 75%, and has 3 to 5 times as thick as the polyurethane foam 2. When an operation for eliminating pressure is repeated after pressure is applied in the cushion layer 3, the maintenance ratio of a compressive elastic modulus after repeating the operation at least two hundred times in relation to the first compressive elastic modulus becomes 70% or more. In even low pressure polishing, the polishing surface P follows the surface of the polishing object. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a polishing pad, and more particularly to a polishing pad including a polishing layer having a foam structure having a polishing surface for polishing an object to be polished, and a cushion layer having a foam structure formed by wet film formation.

  Optical materials, silicon wafers, hard disk substrates, semiconductor substrates, and the like are required to have higher precision and higher density, so that an object to be polished is becoming thinner or brittle. In these thinned or embrittled workpieces, it is desired to further improve the leveling by polishing. For this reason, it is necessary to improve cushioning properties as a polishing pad used for polishing.

  Typical examples of the optical material include two glass substrates called a color filter substrate of a liquid crystal display and a thin film transistor substrate. In recent years, in order to improve the response speed during moving image reproduction, the distance (cell gap) between the color filter substrate and the thin film transistor substrate tends to be narrowed from about 10 μm to 5 μm or less. If the surface of the glass substrate has undulations or irregularities, it may cause a display failure of the liquid crystal display. In addition, since the thickness of the oxide film (insulating film) disposed on the gate electrode is small in the thin film transistor, if there are fine irregularities on the surface of the glass substrate on which the thin film transistor is formed, a short circuit occurs in the thin film transistor portion. Leads to display failure. Therefore, high precision flatness is required for these glass substrates.

  In addition, the color filter substrate has a non-uniform film thickness when forming a color material film composed of minute resin films containing three primary color pigments of red (R), green (G), and blue (B). Color unevenness as a main cause is likely to occur, and since the color filter substrate itself is a thin film having a thickness of 1 to 2 μm, surface irregularities and foreign matter adhesion greatly affect the image quality of the liquid crystal display. For this reason, the color filter substrate is required to have a high degree of surface accuracy (flatness) and is subjected to a polishing process in order to make the film thickness of the color material film uniform. However, since the glass substrate tends to be thinned or brittle, a polishing process with a low load (low pressure) that reduces the polishing load on the color filter substrate is desired.

  Another typical example of a thinned or embrittled thin film is a semiconductor substrate. The semiconductor substrate is formed by laminating an interlayer insulating film and metal wiring whose surface (processed surface) is polished with high precision on a silicon wafer. In recent years, introduction of a specific dielectric constant film and Cu wiring has been promoted in order to obtain a higher capacity device. Since the mechanical strength and the interfacial adhesion strength are lowered in the specific dielectric constant film, a low-damage polishing process is required. As a low-damage polishing means, low-pressure polishing that is conventionally performed at 4 psi (27580 Pa) with a load during polishing of 2 psi (13790 Pa) or less is considered effective.

  A polishing pad in which a polishing layer and a cushion layer are laminated is usually used as the polishing pad used for the above-described high-precision polishing. By having such a structure of the polishing pad, the entire waviness of the processed surface is absorbed by the cushion layer, and a substantially uniform load (pressing force) is applied to the processed surface. It becomes possible to flatten the unevenness. As a polishing pad including a polishing layer and a cushion layer, for example, a technique is disclosed in which the compression recovery rate of the cushion layer is limited to improve the compression characteristics (see Patent Document 1).

Japanese Patent No. 3460712

  However, with a conventional polishing pad, when polishing a thinned or embrittled workpiece, a substantially uniform load cannot be applied to the entire processing surface due to insufficient compression characteristics, and high surface accuracy is achieved. Difficult to get. Further, in low-pressure polishing, the load during polishing is reduced, so that the cushion layer is difficult to deform, the waviness of the processed surface cannot be absorbed, and it is difficult to flatten the entire processed surface substantially uniformly. . In this respect, in the technique of Patent Document 1, the compression rate of the cushion layer is increased by performing unevenness processing by patterning on the surface of the cushion layer on the side of the platen (the surface plate of the polishing machine). However, since the bonding area between the platen bonding surface and the cushion layer is insufficient, there is a drawback that peeling at the bonding interface is likely to occur. Furthermore, although it aims at reducing the residual distortion and the change of compression characteristics with respect to a repeated load, it cannot be said to be sufficient to reduce the change of the compression characteristics with time during polishing. For this reason, when a drop in elasticity (sagging) is caused with respect to a repeated load, a substantially uniform load cannot be applied to the entire processed surface, and damage or breakage of the object to be polished is caused. Furthermore, when the rigidity of the polishing layer is increased, the cushion layer is not deformed by low-pressure polishing, and the waviness of the processed surface cannot be absorbed.

  An object of the present invention is to provide a polishing pad capable of improving the flatness of an object that has been thinned or embrittled over a long period of time.

  In order to solve the above-mentioned problems, the present invention is bonded to a polishing layer having a foam structure having a polishing surface for polishing an object to be polished, and a surface opposite to the polishing surface of the polishing layer, and at least 2 A sheet of wet-formed foam-structured resin sheet is laminated to form a laminate, and a cushion layer having a thickness 3 to 5 times that of the polishing layer, and the cushion layer, The compression rate is 30% or more, and the retention rate of the compression modulus when the pressurization and depressurization are repeated at least 200 times with respect to the compression modulus before the pressurization and depressurization is 70% or more. It is a polishing pad to be used.

  In the present invention, the cushion layer formed by laminating at least two wet-formed foamed resin sheets in a laminated form has a compression rate of 30% or more and is 3 to 5 times as thick as the polishing layer. Therefore, the cushion layer is easily deformed even under a low load, and exhibits cushioning properties. Accordingly, the pressing force against the thinned or embrittled workpiece is equalized, and the compressive elastic modulus retention rate is 70% or more. Thus, the cushioning property is maintained against repeated pressurization and depressurization, so that the flatness of the object to be polished can be improved over a long period of time.

In this case, the cushion layer may have a thickness in the range of 1.0 mm to 3.5 mm, in which at least two resin sheets are bonded together via an adhesive layer. At this time, the compression elastic modulus before repeated pressurization and decompression of the cushion layer can be 90% or more. The thickness of the adhesive layer may be adjusted to 0.5 mm or less. The polishing layer may be made of a wet-formed resin. Moreover, the polishing layer may be bonded to the cushion layer with an adhesive, and the thickness of the adhesive may be adjusted to 0.5 mm or less. The polishing layer and at least two resin sheets may be initially made of the same quality and the same thickness, and the polishing layer may have a hole formed in the polishing surface by buffing or slicing. At this time, the polishing layer can have the same thickness as each of the at least two resin sheets or a smaller thickness. The polishing layer and cushioning layer bonded, A hardness can range from 10 to 40 degrees, bulk density in the range of ^{0.2g / cm 3 ~0.6g / cm 3} . A base material may be further bonded to the surface of the cushion layer opposite to the polishing layer.

  According to the present invention, the cushion layer formed by laminating at least two wet-formed foamed resin sheets in a laminated form has a compression rate of 30% or more, which is 3 to 5 times that of the polishing layer. Since it has a thickness, the cushion layer easily deforms even under a low load, and exhibits cushioning properties. Accordingly, the pressing force against the thinned or embrittled workpiece is equalized, and the compressive elastic modulus retention rate is 70. Since the cushioning property is maintained against repeated pressurization and depressurization, the flatness of the object to be polished can be improved over a long period of time.

  Hereinafter, embodiments of a polishing pad to which the present invention is applied will be described with reference to the drawings.

(Polishing pad)
As shown in FIG. 1, a polishing pad 10 of this embodiment includes a polyurethane foam 2 as a polishing layer having a polishing surface P for polishing a surface of an object to be polished, and a surface opposite to the polishing surface P. And a cushion layer 3 disposed. The polyurethane foam 2 is formed into a wet film, and the cushion layer 3 is formed by laminating two polyurethane foams 3a and 3b formed into a wet film.

  The polyurethane foam 2 is formed into a sheet shape by wet film formation of a polyurethane resin, and the foam 4 is formed in a state in which the foam 4 is dispersed substantially uniformly. In the polyurethane foam 2, the skin layer formed during the wet film formation is removed by buffing or slicing, and an opening 9 in which the foam 4 is opened is formed on the polishing surface P. The opening 9 has an opening diameter adjusted to a range of 20 to 100 μm. The foam 4 is formed in a triangular shape with a rounded cross section along the thickness direction (vertical direction in FIG. 1) of the polyurethane foam 2, and the pore diameter on the polishing surface P side is smaller than that on the cushion layer 3 side. ing. That is, the diameter of the foam 4 is reduced on the polishing surface P side. In the polyurethane resin between the foams 4, foam having a pore diameter smaller than that of the foam 4 is not shown. The polyurethane foam 2 is a continuous foam having a continuous foam structure in which the foam 4 and the foam (not shown) are connected in a three-dimensional network.

  The polyurethane foams 3a and 3b constituting the cushion layer 3 are each formed into a sheet shape by wet-forming polyurethane resin. The polyurethane foam 3a has a skin layer in which dense micropores (not shown) are formed on the polyurethane foam 2 side, and the pore diameter is larger than the micropores of the skin layer on the inner side (polyurethane foam 3b side) than the skin layer. The foam 7 is formed in a substantially uniformly dispersed state. The foam 7 is formed in a triangular cross-section rounded along the thickness direction of the polyurethane foam 3a, and the pore diameter on the polyurethane foam 2 side is smaller than that on the polyurethane foam 3b side. In the polyurethane resin between the foams 7, foam (not shown) having a pore size larger than the micropore formed in the skin layer and smaller than the foam 7 is formed. The polyurethane foam 3a is a continuous foam having a continuous foam structure in which the skin layer micropores, foam 7 and foam (not shown) communicate in a three-dimensional network. On the other hand, the polyurethane foam 3b is produced in the same manner as the polyurethane foam 3a. That is, the polyurethane foam 3b is a continuous foam having a continuous foam structure in which the foam 7 is formed inside.

The cushion layer 3 has a surface opposite to the skin layer of the polyurethane foam 3 a bonded to the surface of the polyurethane foam 3 b on the skin layer side through the adhesive layer 5. In the cushion layer 3, the Shore A hardness, the compression rate, the compression elastic modulus, and the density are set. For Shore A hardness, compression rate, compression modulus and density, select polyurethane resin and additives used for wet film formation of polyurethane foams 3a and 3b, adjust the continuous foam structure, and select components of adhesive layer 5 By doing so, the desired range can be set. In this example, the cushion layer 3 has a Shore A hardness in the range of 10 to 40 degrees, a compression rate in the range of 30 to 75%, a compression modulus of 90% or more, and a density of 0.2 to 0.6 g / cm ^3. Each of these ranges is set.

  In the polishing pad 10, the surface of the polyurethane foam 3 a on the skin layer side and the surface opposite to the polishing surface P of the polyurethane foam 2 are bonded together with an adhesive layer 6. The thickness ratio a / b of the thickness a of the polyurethane foam 2 to the thickness b of the cushion layer 3 is set in a range of 1/5 to 1/3. That is, the thickness b of the cushion layer 3 is 3 to 5 times the thickness a of the polyurethane foam 2. The polyurethane foam 2 and the polyurethane foams 3a and 3b are all of the same quality formed by wet film formation, and are all formed to the same thickness at the beginning of film formation. In the polyurethane foam 2, since the skin layer is removed, the thickness is smaller than the initial film formation. In other words, the thickness a of the polyurethane foam 2 is smaller than any thickness of the polyurethane foams 3a and 3b. In this example, the thickness of the polyurethane foams 2, 3a, 3b is formed in the range of 0.2 to 1.5 mm at the beginning of film formation, and the thickness of the cushion layer 3 is 1.0 to 3.5 mm. The range has been adjusted. Further, the thicknesses of the adhesive layer 5 and the adhesive layer 6 are both adjusted to 0.5 mm or less.

In the cushion layer 3 in which the polyurethane foams 3a and 3b are bonded together via the adhesive layer 5, the pressure is applied (added load) and compressed, and then the operation of removing (removing) the pressure is repeated at least 200. The retention rate of the compressive modulus after repeated repetitions with respect to the initial compressive modulus is 70% or more. That is, the cushion layer 3 initially has a compression elastic modulus of 90% or more, but has a compression elastic modulus of 63% or more even when the pressurization and depressurization are repeated at least 200 times. The cushion layer 3 having such characteristics can be obtained, for example, by selecting a polyurethane resin during wet film formation and adjusting the foam structure and density. As the foam structure, it is preferable that the ratio of communicating the foams 7 adjacent to each other is small, and the foams 7 are separated from each other by a polyurethane resin. Further, the density is preferably in the above-mentioned range. When the density is less than 0.2 g / cm ³ , the foaming is crushed by repeated pressurization and slow pressure, so that cushioning properties cannot be obtained. As a method for obtaining a suitable foamed structure, for example, a method using a polyurethane resin having a number average molecular weight of 10,000 or more, and a high-polymerization degree polyurethane resin having a number average molecular weight of 50,000 or more as an additive is in the range of 0 to 20% by weight. And a method of using a urethane-based adhesive having elasticity as a component of the adhesive layer 5.

  The polishing pad 10 has a double-sided tape for attaching the polishing pad 10 to a polishing machine attached to the surface of the cushion layer 3 opposite to the polyurethane foam 2. The double-sided tape has, for example, a flexible film substrate 8 such as a film made of polyethylene terephthalate (hereinafter abbreviated as PET), and pressure sensitive adhesive such as an acrylic adhesive on both surfaces of the substrate 8. Each agent layer (not shown) is formed. The double-sided tape is bonded to the cushion layer 3 (surface opposite to the polyurethane foam 3a of the polyurethane foam 3b) with an adhesive layer on one side of the substrate 8, and the other surface (opposite to the cushion layer 3). ) Is covered with release paper (not shown). The base material 8 of this double-sided tape also serves as the base material of the polishing pad 10.

(Manufacture of polishing pad)
The polishing pad 10 forms a cushion layer 3 by bonding two polyurethane foams 3a and 3b respectively produced by wet film formation, and bonds the polyurethane foam 2 and the cushion layer 3 produced in the same manner. Manufactured by. In wet film formation, a preparation process for preparing a polyurethane resin solution, a coagulation regeneration process in which the polyurethane resin solution is applied to a film formation substrate and the polyurethane resin is coagulated and regenerated into a sheet, and cleaning and drying in which the sheet polyurethane resin is washed and dried Each polyurethane foam is produced through a process. Hereinafter, the production of the polyurethane foam 2, the formation of the cushion layer 3, and the bonding of the polyurethane foam 2 and the cushion layer 3 will be described in this order.

  In the preparation of the polyurethane foam 2, a polyurethane resin, a water-miscible organic solvent N, N-dimethylformamide (hereinafter abbreviated as DMF), and an additive are mixed in a preparation step. The polyurethane resin is dissolved. The polyurethane resin is selected from polyester, polyether, polycarbonate, and the like and used, for example, dissolved in DMF so that the polyurethane resin becomes 30%. As the additive, a pigment such as carbon black, a hydrophilic activator that promotes foaming, a hydrophobic activator that stabilizes the coagulation regeneration of the polyurethane resin, and the like are used to control the size and amount (number) of foam 4. be able to. The obtained solution is filtered to remove aggregates and the like, and then defoamed under vacuum to obtain a polyurethane resin solution.

  In the coagulation regeneration process, the polyurethane resin solution obtained in the preparation process is applied substantially uniformly to the belt-shaped film forming substrate by a knife coater or the like at room temperature. At this time, the application thickness (application amount) of the polyurethane resin solution is adjusted by adjusting the gap (clearance) between the knife coater and the film forming substrate. A flexible film, a nonwoven fabric, a woven fabric, etc. can be used for the film-forming substrate. Hereinafter, in this example, the film forming substrate is described as a PET film.

  The film-forming substrate on which the polyurethane resin solution is applied is immersed in a coagulating liquid whose main component is water, which is a poor solvent for the polyurethane resin. In the coagulation liquid, first, micropores are formed on the surface side of the applied polyurethane resin solution, and a skin layer having a thickness of about several μm is formed. Thereafter, the polyurethane resin coagulates and regenerates in the form of a sheet on the film-forming substrate as the substitution of the DMF in the polyurethane resin solution and the coagulating liquid proceeds. When DMF is removed from the polyurethane resin solution and DMF and the coagulating liquid are replaced, foam 4 and foam not shown are formed in the polyurethane resin inside the skin layer, and foam 4 and foam are omitted. Communicates in a three-dimensional network. At this time, since the PET film of the film forming substrate does not penetrate water, desolvation occurs on the surface side (skin layer side) of the polyurethane resin solution, and foam 4 is formed on the film forming substrate side larger than the surface side. .

  In the washing and drying process, the polyurethane resin solidified and regenerated in the coagulation regeneration process (hereinafter referred to as film forming resin) is peeled off from the film forming substrate, washed in a cleaning liquid such as water, and DMF remaining in the film forming resin is removed. Removed. After cleaning, the film forming resin is dried with a cylinder dryer. The cylinder dryer includes a cylinder having a heat source therein. The film-forming resin is dried by passing along the peripheral surface of the cylinder. The dried film-forming resin is subjected to buffing or slicing on the skin layer side to remove the skin layer and form an opening 9. At this time, the amount removed by buffing or slicing is adjusted so that the opening diameter of the opening 9 is in the range of 20 to 100 μm. The obtained polyurethane foam 2 is wound up into a roll.

  Next, formation of the cushion layer 3 will be described. The polyurethane foams 3a and 3b are produced by wet film formation similar to the polyurethane foam 2 described above. In this example, the polyurethane resin to be used, the composition of the polyurethane resin solution, the conditions at the time of coagulation regeneration, and the like were set to be the same as those for the production of the polyurethane foam 2.

  In the polyurethane foams 3a and 3b, the skin layer is formed by solidifying and regenerating the polyurethane resin. Inside the skin layer, the foam 7 having a pore size larger than the fine pore of the skin layer and the foam (not shown) are formed substantially evenly, and the fine pore, the foam 7 and the foam (not shown) of the skin layer are communicated in a three-dimensional network. The surface on the skin layer side of the polyurethane foam 3b is bonded to the surface of the polyurethane foam 3a opposite to the skin layer via the adhesive layer 5 to form the cushion layer 3. As a component of the adhesive layer 5, a resin solution in which a small amount of polyurethane resin is dissolved in DMF is used. Since this resin solution has the same quality as the polyurethane foams 3a and 3b, a strong adhesive force can be obtained and the cushioning property of the cushion layer 3 is not hindered. Therefore, this resin solution is suitable for bonding the polyurethane foams 3a and 3b. Can be used. The same polyurethane resin as the polyurethane foams 3a and 3b is used for this polyurethane resin. The amount of the polyurethane resin dissolved is only required to be able to join the polyurethane foams 3a and 3b, and may be, for example, about 1 to 5%. Further, the coating amount of the resin solution is adjusted so that the thickness of the adhesive layer 5 formed after volatilization of the solvent DMF is 0.5 mm or less. The polyurethane foams 3a and 3b are brought into contact with each other through the bonding solution and heated while being pressurized. By evaporating DMF, the polyurethane foams 3a and 3b are joined via the polyurethane resin. The adhesive layer 5 is not limited to the resin solution, and an adhesive that does not inhibit the cushioning property of the cushion layer 3, for example, a pressure-sensitive adhesive such as an acrylic adhesive can be used. Moreover, when the adhesive tape etc. with which the adhesive agent was apply | coated to the base material are used, since the base material inhibits the cushioning property of the cushion layer 3, it is not preferable.

  The polyurethane foam 2 formed by wet film formation and the cushion layer 3 formed by bonding the polyurethane foams 3 a and 3 b formed by wet film formation are bonded together via an adhesive layer 6. As the adhesive of the adhesive layer 6, a pressure sensitive adhesive such as an acrylic adhesive is used. At this time, the surface on the skin layer side of the polyurethane foam 3 a forming the cushion layer 3 is bonded to the surface opposite to the polishing surface P of the polyurethane foam 2. Moreover, the application amount of the adhesive is adjusted so that the thickness of the adhesive layer 6 is 0.5 mm or less. Then, the double-sided tape which has the base material 8 on the surface on the opposite side to the polyurethane foam 2 of the cushion layer 3 is bonded together. Then, after cutting into a desired shape such as a circle or a square, an inspection such as confirming that there is no adhesion of dirt or foreign matter is performed to complete the polishing pad 10.

(Action etc.)
Next, the operation and the like of the polishing pad 10 of this embodiment will be described.

  Conventional polishing pads having a wet-formed polishing layer include, for example, polishing pads that do not have a cushion layer, polishing pads that have insufficient cushioning properties, and polyurethane foam that has been thickened by wet film formation. There is a polishing pad as a cushion layer. As a polishing pad which does not have a cushion layer, the polishing pad which formed the polishing layer on the rigid base material made from PET etc. by the wet coagulation method can be mentioned, for example. Moreover, as a polishing pad with insufficient cushioning properties, a polishing pad in which a polishing layer is formed by a wet coagulation method on a highly rigid cushion layer obtained by impregnating a polyester-based nonwoven fabric with a polyurethane resin can be used.

  When a polishing pad that does not have cushioning properties or has insufficient cushioning properties is used for polishing, waviness of the workpiece (one of the measurement items for evaluating the flatness of the workpiece) And measured with an optical non-contact surface roughness meter.) And the polishing pad cannot be deformed so as to sink in the object to be polished. It is difficult to flatten the entire processed surface of an object substantially uniformly. Also, as the polishing layer wears due to the polishing process, the compressibility of the polishing layer disappears, and the influence of the highly rigid base material and cushion layer increases. The occurrence rate is increased, and the flatness of the object to be polished is lowered. Further, since a highly rigid base material or cushion layer sinks into the portion where foaming of the polishing layer is crushed by the polishing process, the polishing pad surface (polishing surface) and eventually the polishing head (fixed by the polishing machine) The polishing pressure received from the disk) is not applied substantially evenly, resulting in uneven polishing.

  Further, as shown in FIG. 3 (A), in the cushion layer 23 whose thickness is increased by wet film formation, coarse foam 27 is formed inside, and therefore, during polishing as shown in FIG. 3 (B). Such a pressure (external force) tends to cause distortion of the foam shape. For this reason, in the polishing pad using the cushion layer 23 instead of the cushion layer 3 described above, the degree of freedom of deformation (deformation amount) of the cushion layer 23 is increased, and the polyurethane foam 2 having the polishing surface P is effectively supported. I can't do that. Moreover, there is a possibility that coagulation regeneration is insufficient during wet film formation by increasing the thickness. For this reason, the quality stability of a polishing pad cannot be ensured, and the variation between product lots will become large. In order to solve this, it is necessary to lengthen the foam formation time (coagulation regeneration time) or increase the number of manufacturing steps, thereby reducing productivity. Furthermore, in these conventional polishing pads, the compression elastic modulus decreases when pressurization and depressurization are repeated, that is, sag occurs, so that the pressing force against the object to be polished is equalized as the polishing process is repeated. Therefore, the flatness of the object to be polished is impaired. Therefore, it becomes difficult to obtain a sufficient polishing performance in a polishing process under a low load with a thinned or embrittled workpiece. The present embodiment is a polishing pad that can solve these problems.

  The polishing pad 10 of this embodiment has a cushion layer 3 formed by bonding two polyurethane foams 3a and 3b. The cushion layer 3 has a characteristic that the retention rate of the compressive elastic modulus becomes 70% or more when the operation of depressurization after pressurization is repeated at least 200 times. For this reason, the cushioning property of the cushion layer 3 is maintained even after repeated pressurization and depressurization. Therefore, the polishing surface P follows the surface of the object to be polished in the low-pressure polishing process for the object to be thinned or embrittled. be able to. As a result, the pressing force on the object to be polished is equalized, so that the flatness of the object to be polished can be improved over a long period even in low-pressure polishing.

  In the polishing pad 10 of the present embodiment, the cushion layer 3 bonded to the polyurethane foam 2 is formed of two polyurethane foams 3a and 3b, and the thickness b of the cushion layer 3 is the thickness of the polyurethane foam 2. It is adjusted to a range of 3 to 5 times a. Since the cushion layer 3 is sufficiently thicker than the polyurethane foam 2, the polishing pad 10 can easily follow the object to be polished, and the swell can be improved. Furthermore, since the pressure applied to the object to be polished is equalized (excessive load is reduced), overpolishing can be suppressed. Further, the cushioning property of the cushion layer 3 improves, so that it is easy to control the polishing load on the object to be polished. Since the cushion layer 3 shows compression / recovery even under a low load in low-pressure polishing, scratching can be suppressed. When the thickness b of the cushion layer 3 is less than three times the thickness a of the polyurethane foam 2, the thickness of the cushion layer 3 is insufficient, so that the pressure applied to the object to be polished is not equalized. For this reason, overpolishing occurs, and the flatness of the object to be polished is impaired. When the thickness b of the cushion layer 3 is thicker than 5 times the thickness a of the polyurethane foam 2, the polishing stress is not concentrated, but it is difficult to control the polishing pressure for effectively polishing the object to be polished, resulting in uneven polishing. Is likely to occur.

  Furthermore, in the polishing pad 10 of this embodiment, the polyurethane foams 3a and 3b constituting the cushion layer 3 each have a thickness of 0.2 to 1.5 mm, and the adhesive layer 5 has a thickness of 0.5 mm or less. The thickness of the entire cushion layer 3 is adjusted to a range of 1.0 to 3.5 mm. For this reason, cushioning properties can be exhibited effectively, and vibration caused by driving of the polishing machine and roughness of the surface of the surface plate on which the polishing pad is mounted can be covered. In consideration of effectively exhibiting cushioning properties, the thickness of each of the polyurethane foams 3a and 3b is preferably in the range of 0.5 to 1.5 mm, and more preferably in the range of 0.7 to 1.5 mm. It is more preferable.

Furthermore, the polishing pad 10 of this embodiment has a cushion layer 3 formed by laminating two polyurethane foams 2. The cushion layer 3 has a Shore A hardness in the range of 10 to 40 degrees, and a compression rate. Is in the range of 30 to 75%, the compression elastic modulus is 90% or more, and the density is 0.2 to 0.6 g / cm ³ . Since the high compressibility and the high compressive elastic modulus are exhibited, the cushioning property of the cushion layer 3 can be sufficiently exhibited even when the polishing pressure is reduced during the polishing process, and the flatness of the object to be polished can be improved. Furthermore, since the compression elastic modulus of the cushion layer 3 is maintained at 70% or more even after repeated pressure and pressure release, the change in physical properties over time due to the polishing process is suppressed, and the life of the cushion layer 3 and thus the polishing pad 10 is improved. Can be made. In addition, the polyurethane foam usually obtained by wet film formation varies in thickness. However, since the polyurethane foams 3a and 3b are bonded together in the cushion layer 3, the thickness variation generated during wet film formation is buffered. For this reason, the flatness of the polishing pad 10 itself can be improved, and the flatness of the object to be polished can be improved.

Here, the relationship between each physical property value of the cushion layer 3 and the polishing performance will be described. When the Shore A hardness is less than 10 degrees, or when the compression ratio exceeds 75%, the sinking of the polishing pad 10 becomes excessively large during polishing, and it becomes difficult to obtain flatness of the object to be polished. In addition, when the Shore A hardness exceeds 40 degrees, when the compression elastic modulus is less than 90%, or when the compression rate is less than 30%, the cushioning property is insufficient. It can happen. In particular, if the compression rate is less than 30%, it will not be deformed when the polishing pressure is reduced, and a uniform load cannot be applied to the entire object to be polished. The flattening accuracy of the polished article cannot be obtained. For this reason, it is preferable to make a compression rate into the range of 30 to 75%. Further, when the compressive elastic modulus is less than 90%, the flattening accuracy of the object to be polished required due to the decrease in elasticity (sagging) cannot be obtained. When the compression elastic modulus after repeating the pressurization and depressurization is less than 63%, it is weak against continuous pressurization, permanent deformation is likely to occur, and deterioration of the cushion layer is accelerated. For this reason, it is preferable to make the maintenance factor of the compression elastic modulus 70% or more when pressurization and depressurization are repeated. On the other hand, if the density is less than 0.2 g / cm ³ , the compression elastic modulus is lowered. Conversely, if the density exceeds 0.6 g / cm ³ , it becomes too hard and the cushioning property is insufficient. For this reason, it is preferable to make a density into the range of 0.2-0.6 g / cm < ³ >.

  Further, in the polishing pad 10 of the present embodiment, as shown in FIG. 2A, the cushion layer 3 is formed of polyurethane foams 3a and 3b, and the polyurethane foams 3a and 3b are respectively formed with foam 7 inside. It has a continuous foam structure. If the thickness of one polyurethane foam is increased, solidification regeneration at the time of wet film formation becomes insufficient, but the thickness of the cushion layer 3 is increased by bonding the two polyurethane foams 3a and 3b together. The quality can be stabilized, and the variation between product lots as the polishing pad 10 can be reduced. Further, since it is not necessary to increase the thickness of each of the polyurethane foams 3a and 3b, the time required for foam formation (coagulation regeneration) can be shortened, and productivity can be improved.

  Further, the cushion layer 3 is deformed by the polishing pressure applied during the polishing process, but as shown in FIG. 2B, the polishing pressure is dispersed in each of the polyurethane foams 3a and 3b, and the cushion layer 3 is deformed as a whole. The amount can be kept small. Thereby, the elastic fatigue by compression and recovery of the polyurethane foams 3a and 3b can be reduced, and the life of the cushion layer 3 can be improved.

  Furthermore, the polishing pad 10 of the present embodiment causes a scratch because the hardness on the polishing surface P is 10 to 40 degrees on the polishing surface P when the polyurethane foam 2 and the cushion layer 3 are bonded together. Since foreign matters such as polishing debris are absorbed on the polishing surface P side, scratches can be suppressed. Furthermore, since the polyurethane foam 2 has a continuous foam structure by wet film formation, it can be provided with an appropriate elasticity, and can increase the polishing rate and improve the productivity.

  Furthermore, in the polishing pad 10 of the present embodiment, the opening 9 having an opening diameter in the range of 20 to 100 μm is formed on the polishing surface P. If the opening diameter is less than 20 μm, the slurry holding ability is insufficient and the polishing performance is lowered, and if the opening diameter exceeds 100 μm, the unevenness of the polishing surface P becomes large and the object to be polished cannot be highly planarized. . By setting the aperture diameter in the range of 20 to 100 μm, the slurry holding performance and the flatness of the polishing surface P are ensured, so that the polishing performance can be improved and the flatness of the object to be polished can be improved.

  In the present embodiment, an example in which the polyurethane foam 2 formed by wet film formation is used as the polishing layer is shown, but the present invention is not limited to this. For example, polyethylene or polyester may be used instead of polyurethane, and the continuous foam structure may be formed by wet film formation. It is also possible to use a plastic sheet formed by reactive curing instead of the wet-formed polyurethane foam 2. As such a plastic sheet, for example, by subjecting a polyurethane molded product obtained by reaction hardening of an isocyanate group-containing compound and a chain extender such as a polyamine compound or a polyol compound in a mold, to a slicing treatment or a surface grinding treatment. Mention may be made of the obtained polyurethane foam. In the case of such a polyurethane foam, an (independent) foam structure can be formed by water, spherical fine particles, or the like. Further, in the present embodiment, an example is shown in which a homogeneous sheet formed by wet film formation on each of the polyurethane foams 2, 3a, and 3b is used, but the present invention is not limited to this. For example, the composition of the polyurethane resin and the sizes of the foams 4 and 7 may be different.

  In the present embodiment, the cushion layer 3 is formed of two polyurethane foams 3a and 3b. However, the present invention is not limited to this. The cushion layer 3 may be formed of three or more polyurethane foams, for example, four may be bonded together. Considering the bonding of a plurality of polyurethane foams, it is preferable from the viewpoint of work efficiency to form 2 to 4 polyurethane foams. In particular, when the accuracy of the polishing machine such as the flatness of the surface plate is insufficient, the cushioning property is effectively exhibited by laminating 3 to 4 polyurethane foams. The accuracy can be increased. On the other hand, when five or more polyurethane foams are laminated or the thickness of the cushion layer 3 exceeds 4 mm, the thickness is too large. The deviation (shear strain) between the surface to be bonded to the surface plate and the polished surface P becomes large. Since it takes time to recover the deformation (displacement), it becomes impossible to apply a substantially uniform polishing pressure to the object to be polished consistently, resulting in uneven polishing. When the thickness of the cushion layer 3 is 1.0 mm or less and five polyurethane foams are laminated, the influence of the adhesive is greatly increased, the compressibility and flexibility are impaired, and the cushioning property is reduced. Become. Accordingly, the thickness of the cushion layer 3 is preferably in the range of 1.0 to 3.5 mm.

  Furthermore, in this embodiment, although the polyurethane foam 3a, 3b which forms the cushion layer 3 showed the example which has a skin layer, this invention is not limited to this. For example, the skin layer may be removed from both the polyurethane foams 3a and 3b, or the skin layer of only one of the polyurethane foams 3a and 3b may be removed. Furthermore, in this embodiment, although the surface on the opposite side to the skin layer of the polyurethane foam 3a showed the example bonded together with the surface of the skin layer of the polyurethane foam 3b, this invention is not limited to this. . For example, the skin layer side surface of the polyurethane foam 3a may be bonded to the skin layer side surface of the polyurethane foam 3b, and the skin layer side surface of the polyurethane foam 3a is opposite to the skin layer of the polyurethane foam 3b. It may be bonded to the side surface.

In the present embodiment, the cushion layer 3 has a Shore A hardness of 10 to 40 degrees, a compression rate of 30 to 75%, a compression elastic modulus of 90% or more, and a density of 0.2 to 0.6 g / cm ^3. An example of setting each in the range is shown. In consideration of improving the cushioning property of the cushion layer 3 and supporting the polyurethane foam 2 reliably, the Shore A hardness is in the range of 15 to 30 degrees, the compression rate is in the range of 30 to 60%, and the compression modulus is It is preferable to set the density to 95% or more and the range of 0.2 to 0.3 g / cm ³ , respectively.

  Furthermore, in the present embodiment, an example is shown in which a double-sided tape is bonded to the surface of the cushion layer 3 opposite to the polyurethane foam 2 and the base material 8 of the double-sided tape also serves as the base material of the polishing pad 10. The invention is not limited to this. For example, by placing only the adhesive on the surface of the cushion layer 3 opposite to the polyurethane foam 2 without using the base material 8, it is possible to attach the polishing machine to the surface plate. Further, another base material may be bonded together instead of the base material 8 of the double-sided tape. Considering that the polyurethane foam 2 and the cushion layer 3 have flexibility, a base material is provided to facilitate handling when the polishing pad 10 is transported or mounted on a surface plate. It is preferable.

  Hereinafter, examples of the polishing pad 10 manufactured according to the present embodiment will be described. A comparative polishing pad manufactured for comparison is also shown.

Example 1
In Example 1, polyester MDI (diphenylmethane diisocyanate) polyurethane resin was used for the production of polyurethane foams 3a and 3b forming the polyurethane foam 2 and cushion layer 3 serving as a polishing layer, and a suede-like polyurethane foam was formed by wet film formation. Was made. Cut out polyurethane foams 2, 3a, 3b from the obtained polyurethane foam and prepare cushion layer 3 by bonding the surface of polyurethane foam 3a opposite to the skin layer to the skin layer side of polyurethane foam 3b. did. In order to form the opening 9 on the polishing surface P, the polyurethane foam 2 was removed by buffing the skin layer side so that the opening diameter of the opening 9 was about 50 μm. After the polyurethane foam 2 and the cushion layer 3 were bonded together, a double-sided tape having a PET substrate 8 was bonded to the surface of the cushion layer 3 opposite to the polyurethane foam 2 to produce a polishing pad 10.

(Comparative Example 1)
In Comparative Example 1, a polishing pad was prepared in which a single polyurethane foam formed by wet deposition as in Example 1 was bonded to a PET substrate. That is, the polishing pad of Comparative Example 1 is a conventional wet-formed polishing pad that does not have a cushion layer.

(Comparative Example 2)
In Comparative Example 2, a polishing pad was produced in the same manner as in Example 1 except that the polyurethane foams 3a and 3b forming the cushion layer 3 were bonded with a double-sided tape having a PET substrate.

(Evaluation 1)
The thickness, density, compression rate, compression elastic modulus, and hardness of each of the polishing pads and the cushion layer of each example and comparative example were measured. The thickness was measured using a dial gauge (minimum scale 0.01 mm) and applying a load of 100 g / cm ² . In the measurement of hardness, the Shore A hardness was determined from the indentation depth of the push needle pressed against the surface of the test piece via a spring in accordance with Japanese Industrial Standard (JIS K 6253). In the measurement of the density, the weight of the sample cut out to a predetermined size was measured, and calculated from the volume obtained from the size and the measured weight. The compressibility and the compressive elastic modulus were determined using a shopper type thickness measuring instrument (pressure surface: circular shape with a diameter of 1 cm) in accordance with Japanese Industrial Standard (JIS L 1021). Specifically, the thickness t ₀ after over 30 seconds initial load from a no-load state is measured, then the thickness t ₁ after applying a final pressure 30 seconds from the state of the thickness t ₀ It was measured. Except for all loads from the thickness t ₁ state, after allowed to stand for 5 minutes (to the no-load state), the thickness was measured t _{0 'after} over 30 seconds initial load again. The compression rate is calculated by the equation of compression rate (%) = 100 × (t ₀ −t ₁ ) / t ₀ , and the compression modulus is calculated by compressive modulus (%) = 100 × (t ₀ ′ −t ₁ ). / (T ₀ −t ₁ ) At this time, the initial load was 100 g / cm ² and the final pressure was 1120 g / cm ² . Table 1 shows the measurement results of thickness, density, compression rate, compression modulus, and hardness. In addition, the physical property value in the polishing pad indicates a measured value from the upper surface of the polishing layer or the cushion layer to the release paper of the double-sided tape.

As shown in Table 1, the cushion layer of Comparative Example 2 in which the polyurethane foams 3a and 3b were bonded with a double-sided tape having a base material had a thickness of 2.36 mm. On the other hand, the cushion layer 3 of Example 1 in which the polyurethane foams 3a and 3b are bonded together with the adhesive layer 5 having no base material has a thickness of 2.17 mm, which is smaller than that of Comparative Example 2 in terms of the base material. became. Moreover, since the cushion layer of the comparative example 2 has a base material, compared with the cushion layer 3 of Example 1, hardness became high and the compression rate became small. On the other hand, the polishing pad of Comparative Example 1 having no cushion layer has a hardness of 45.0 degrees, a density of 0.38 g / cm ³ , a compression rate of 38.6%, and a compression modulus of 87.4%. Shown respectively. In Comparative Example 2, the hardness of the polishing pad was 39.5 degrees, the density was 0.34 g / cm ³ , the compression rate was 29.5%, and the compression modulus was 91.3%. Was 43.5 degrees, the density was 0.39 g / cm ³ , the compression rate was 24.3%, and the compression modulus was 93.8%. On the other hand, in Example 1, the hardness of the polishing pad 10 is 15.5 degrees, the density is 0.25 g / cm ³ , the compression rate is 46.3%, and the compression elastic modulus is 96.5%, The cushion layer 3 had a hardness of 19.0 degrees, a density of 0.30 g / cm ³ , a compression rate of 40.7%, and a compression modulus of 97.6%. From these results, it is possible to improve the cushioning property as a whole polishing pad by using the cushion layer 3 formed by bonding the polyurethane foams 3a and 3b through the adhesive layer 5 having no base material. I understood.

(Evaluation 2)
Moreover, the cushion layer of each Example and the comparative example was used, and the lifetime of the cushion layer was evaluated. Here, the acceleration test in which the load applied to the cushion layer is increased by repeating the pressurization and release by increasing the load and shortening the time with respect to the measurement condition of the compression elastic modulus in the evaluation 1 described above. It was evaluated with. That is, each cushion layer surface is compressed by applying a load of 500 gf / cm ² at a speed of 1 mm / min with a flat indenter having a diameter of 1 cm for 25 seconds, and then removing the load and letting it stand for 25 seconds. The cycle test was repeated 350 times, and the compression modulus was measured. The load used in this cycle test is larger than the conventional polishing pressure (about 100 g / cm ² ), and harsh conditions are adopted to compare the durability.

  As shown in FIG. 4, compared with the cushion layers of Comparative Examples 1 and 2, the cushion layer of Example 1 maintains a compression modulus of 70% or more even after 350 cycle tests (which satisfy at least 200 times). It was found that the extension of the product life was obvious.

  Since the present invention provides a polishing pad that can improve the flatness of an object that has been thinned or embrittled over a long period of time, it contributes to the manufacture and sale of the polishing pad, and thus has industrial applicability.

It is sectional drawing which shows typically the polishing pad of embodiment to which this invention is applied. It is sectional drawing which shows typically the cushion layer which comprises the polishing pad of embodiment, (A) is the state which has not applied the pressure before grinding | polishing process, (B) is the state which deform | transformed with the pressure at the time of grinding | polishing process, respectively. Show. It is sectional drawing which shows typically the cushion layer which comprised the polishing pad of the comparative example 1, and the coarse foam was formed, (A) is the state which has not applied the pressure before grinding | polishing processing, (B) is at the time of grinding | polishing processing Each of the states deformed by pressure is shown. It is a graph which shows the change of the compression elastic modulus with respect to the frequency | count of a cycle when a pressure-decompression cycle test is implemented about the cushion layer of each Example and a comparative example.

Explanation of symbols

P Polished surface 2 Polyurethane foam (polishing layer)
3 Cushion layer 3a Polyurethane foam (resin sheet)
3b Polyurethane foam (resin sheet)
5 Adhesive layer 6 Adhesive layer 10 Polishing pad

Claims (10)

A foamed polishing layer having a polishing surface for polishing an object to be polished;
The polishing layer is bonded to the surface opposite to the polishing surface, and is formed by laminating at least two wet-formed foamed resin sheets in a laminated form, and is 3 to 5 times the polishing layer. A cushion layer having a double thickness;
With
The cushion layer has a compression rate of 30% or more, and a retention rate of the compression elastic modulus when the pressurization and depressurization are repeated at least 200 times with respect to the compression elastic modulus before the pressurization and depressurization is 70% or more. A polishing pad characterized by being.   2. The polishing pad according to claim 1, wherein the cushion layer has the at least two resin sheets bonded together through an adhesive layer, and has a thickness in a range of 1.0 mm to 3.5 mm. .   The polishing pad according to claim 2, wherein the cushion layer has a compressive elastic modulus of 90% or more before the pressurization and decompression.   The polishing pad according to claim 3, wherein the adhesive layer has a thickness adjusted to 0.5 mm or less.   The polishing pad according to claim 1, wherein the polishing layer is made of a resin formed by a wet film formation.   The polishing pad according to claim 5, wherein the polishing layer is bonded to the cushion layer with an adhesive, and the thickness of the adhesive is adjusted to 0.5 mm or less.   The polishing layer and the at least two resin sheets are initially made of the same quality and the same thickness, and the polishing layer has an opening formed in the polishing surface by buffing or slicing. The polishing pad according to claim 1.   The polishing pad according to claim 7, wherein the polishing layer has a thickness that is the same as or smaller than a thickness of each of the at least two resin sheets. Wherein the bonded abrasive layer and the cushion layer, claim, wherein the range A hardness of 10 to 40 degrees, bulk density is in the range of ^{0.2g / cm 3 ~0.6g / cm 3} 8 The polishing pad described in 1.   The polishing pad according to claim 1, wherein a base material is further bonded to a surface of the cushion layer opposite to the polishing layer.

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