JP2010082703A - Cushion sheet for polishing pad - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cushion sheet for a polishing pad capable of exhibiting a cushion property even at low load and maintaining the cushion property for a long period of time. <P>SOLUTION: The cushion sheet 3 is constituted by sticking two sheets of wet film-formed polyurethane sheets 3a, 3b through an adhesion layer 5 having elasticity in a laminated form. In the cushion sheet 3, a compression ratio is set to a range of 30-75%. In the cushion sheet 3, when operation for removing a pressure after the pressure is applied is repeated, a maintaining ratio of a compression modulus of elasticity after the operation is repeated at least 200 times relative to an initial compression modulus of elasticity becomes 70% or higher. The cushion sheet 3 constitutes the polishing pad 10 by sticking it onto a polishing sheet 2 having a polishing surface P. When the polishing pad 10 is used for polishing working, the cushion property of the cushion sheet 3 is exhibited. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a cushion sheet for imparting cushioning properties to a polishing pad, and more particularly, to a cushion sheet 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 brittle objects to be polished, it is desired that the flattening by the polishing process be made more accurate. 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 sheet and a cushion sheet are laminated is usually used as a polishing pad used in the above-described high-precision polishing process. By having such a structure of the polishing pad, the cushion sheet absorbs the entire waviness of the processed surface and applies a substantially uniform load (pressing force) to the processed surface. It becomes possible to flatten the unevenness. As a polishing pad provided with a polishing sheet and a cushion sheet, for example, a technique is disclosed in which the compression recovery rate of the cushion sheet 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. Also, in low-pressure polishing, the load during polishing is reduced, so the cushion sheet 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 regard, in the technique of Patent Document 1, the compression ratio of the cushion sheet is increased by performing unevenness processing by patterning on the surface of the cushion sheet on which the platen (the surface plate of the polishing machine) is bonded. However, since the bonding area between the platen bonding surface and the cushion sheet 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.

  An object of the present invention is to provide a cushion sheet for a polishing pad that exhibits cushioning properties even at low loads and can maintain the cushioning properties for a long period of time.

  In order to solve the above-described problems, the present invention provides a cushion sheet for imparting cushioning properties to a polishing pad, comprising at least two resin sheets having a foamed structure formed by wet film formation, and the at least two resin sheets. And the cushion sheet has a compression rate of 30% or more, and the compression and modulus of the compression modulus when the compression and decompression are repeated at least 200 times. The maintenance factor with respect to the compression elastic modulus before pressing is 70% or more.

  In the cushion sheet of the present invention, it is formed by laminating at least two wet-formed foamed resin sheets in a laminated form via an elastic adhesive layer, so that it has a compression rate of 30% or more, It can exhibit cushioning properties that are easily deformed even at low loads, and since it has a compression modulus maintenance rate of 70% or more, it can maintain cushioning properties even against repeated pressurization and depressurization. When used for a polishing pad, the polishing pressure applied to the object to be polished can be equalized, and the flatness of the object to be polished can be improved.

In this case, the thickness of the elastic adhesive layer may be adjusted to 0.5 mm or less. At this time, the elastic adhesive layer is preferably formed of a urethane resin. The thickness of the cushion sheet may be in the range of 1.0 mm to 3.5 mm. At this time, the compression elastic modulus before repeated pressurization and decompression of the cushion sheet can be 90% or more. At least two resin sheets may be initially made of the same quality and the same thickness. A hardness range of 10 to 40 degrees of the seat cushion, the bulk density can be in the range of ^{0.2g / cm 3 ~0.6g / cm 3} .

  According to the present invention, at least two wet-formed foam-structured resin sheets are laminated together via an elastic adhesive layer, and thus have a compression rate of 30% or more. It can easily be deformed even under load and can exhibit cushioning properties, and since it has a compression modulus maintenance rate of 70% or more, it can maintain cushioning properties even against repeated pressurization and decompression, When used for a polishing pad, it is possible to obtain an effect of equalizing the polishing pressure applied to the object to be polished and improving the flatness of the object to be polished.

  Hereinafter, an embodiment of a polishing pad provided with a cushion sheet to which the present invention is applied will be described with reference to the drawings.

(Polishing pad)
As shown in FIG. 1, the polishing pad 10 of this embodiment includes a polishing sheet 2 having a polishing surface P for polishing the surface of an object to be polished, and cushioning properties disposed on the surface side opposite to the polishing surface P. And a cushion sheet 3 for imparting. The polishing sheet 2 is formed into a wet film, and the cushion sheet 3 is formed by laminating polyurethane sheets 3a and 3b as two resin sheets formed into a wet film via an adhesive layer (elastic adhesive layer) 5 having elasticity. It is composed by pasting together.

  The polishing sheet 2 is formed into a sheet shape by wet film formation of a polyurethane resin, and is formed in a state in which the foam 4 is dispersed substantially uniformly inside. In the polishing sheet 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 in 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 cross-section rounded along the thickness direction of the polishing sheet 2 (vertical direction in FIG. 1), and the hole diameter on the polishing surface P side is smaller than that on the cushion sheet 3 side. Yes. 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 polishing sheet 2 is a continuous foam having a continuous foam structure in which the foam 4 and foam (not shown) communicate in a three-dimensional network.

  The polyurethane sheets 3a and 3b constituting the cushion sheet 3 are all formed into a sheet shape by wet-forming polyurethane resin. The polyurethane sheet 3a has a skin layer in which fine micropores (not shown) are formed on the polishing sheet 2 side, and foam 7 having a pore diameter larger than the micropores of the skin layer on the inner side (polyurethane sheet 3b side) from the skin layer. Are 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 sheet 3a, and the pore diameter on the polishing sheet 2 side is smaller than that on the polyurethane sheet 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 sheet 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 sheet 3b is produced in the same manner as the polyurethane sheet 3a. That is, the polyurethane sheet 3b is a continuous foam having a continuous foam structure in which the foam 7 is formed inside.

The cushion sheet 3 has a surface opposite to the skin layer of the polyurethane sheet 3 a bonded to a surface of the polyurethane sheet 3 b on the skin layer side through the adhesive layer 5. The adhesive layer 5 is made of an elastic resin. The adhesive layer 5 does not contain a substrate. For this reason, even if the polyurethane sheets 3 a and 3 b are bonded together via the adhesive layer 5, the compression rate and the compression elastic modulus of the cushion sheet 3 are not hindered. In the cushion sheet 3, the Shore A hardness, the compression rate, the compression elastic modulus, and the bulk density are set. For Shore A hardness, compression rate, compression modulus, and bulk density, select polyurethane resin and additives used for wet film formation of polyurethane sheets 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 sheet 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 bulk density of 0.2 to 0.6 g / cm. ³ is set in each range. The adhesive layer 5 is made of urethane resin in this example.

  In the polishing pad 10, the skin layer side surface of the polyurethane sheet 3 a and the surface opposite to the polishing surface P of the polishing sheet 2 are bonded together with an adhesive layer 6. In this example, the thickness ratio a / b of the thickness a of the polishing sheet 2 to the thickness b of the cushion sheet 3 is set in a range of 1/5 to 1/3. That is, the thickness b of the cushion sheet 3 is 3 to 5 times the thickness a of the polishing sheet 2. Further, the polishing sheet 2 and the polyurethane sheets 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 polishing sheet 2, since the skin layer is removed, the thickness is smaller than the initial film formation. In other words, the thickness a of the polishing sheet 2 is smaller than any of the polyurethane sheets 3a and 3b. In this example, the thickness of the polishing sheets 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 sheet 3 is in the range of 1.0 to 3.5 mm. 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. Furthermore, in this example, the polishing pad 10 has a hardness on the polishing surface P adjusted to a Shore A hardness of 10 to 40 degrees in a state where the polishing sheet 2 and the cushion sheet 3 are bonded together.

In the cushion sheet 3 in which the polyurethane sheets 3a and 3b are bonded together via the adhesive layer 5, when the operation of compressing by applying pressure (applying a load) and then removing (depressurizing) the pressure is repeated at least 200 times The retention rate of the compression modulus after repetition with respect to the original compression modulus is 70% or more. That is, the cushion sheet 3 initially has a compression elastic modulus of 90% or more, whereas the cushion sheet 3 has a compression elastic modulus of 63% or more even when the pressurization and depressurization are repeated at least 200 times. The cushion sheet 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. Moreover, the above-mentioned range is preferable as the bulk density, and when the bulk density is less than 0.2 g / cm ³ , foaming is crushed by repeated pressurization and depressurization, 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 the like, and the like.

  Further, 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 sheet 3 opposite to the polishing sheet 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 sheet 3 (the surface of the polyurethane sheet 3b opposite to the polyurethane sheet 3a) with an adhesive layer on one side of the substrate 8, and the other side (the side opposite to the cushion sheet 3). The adhesive layer 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 is manufactured by bonding the two polyurethane sheets 3a and 3b respectively produced by wet film formation to form the cushion sheet 3, and bonding the similarly produced polishing sheet 2 and cushion sheet 3 together. Is done. 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. The polishing sheet 2 and the polyurethane sheets 3a and 3b are produced through the steps. Hereinafter, preparation of the polishing sheet 2, formation of the cushion sheet 3, and bonding of the polishing sheet 2 and the cushion sheet 3 will be described in this order.

  In the preparation of the polishing sheet 2, in the preparation step, a polyurethane resin, N, N-dimethylformamide (hereinafter abbreviated as DMF), which is a water-miscible organic solvent capable of dissolving the polyurethane resin, and an additive are mixed to form a polyurethane. Dissolve the resin. 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. . That is, in the polyurethane resin solidified and regenerated into a sheet shape, a skin layer is formed on the upper part, and the size of the foam 4 is formed larger toward the lower side (see FIG. 1).

  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 polishing sheet 2 is wound up into a roll.

  Next, formation of the cushion sheet 3 will be described. The polyurethane sheets 3a and 3b are produced by wet film formation similar to the polishing sheet 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 the production of the polishing sheet 2.

  In the polyurethane sheets 3a and 3b, the polyurethane resin is coagulated and regenerated, whereby a skin layer is formed on each sheet. 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 cushion sheet 3 is formed on the surface of the polyurethane sheet 3a opposite to the skin layer by bonding the surface of the polyurethane sheet 3b on the skin layer side through an adhesive layer 5 having elasticity. That is, the polyurethane sheets 3a and 3b are bonded so that the vertical direction is the same. In this example, 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 is of the same quality as the polyurethane sheets 3a and 3b, it can obtain a strong adhesive force, has elasticity, and does not hinder the cushioning properties of the cushion sheet 3, so that the polyurethane sheets 3a and 3b It can be suitably used for bonding. As this polyurethane resin, the same polyurethane resin as the polyurethane sheets 3a and 3b is used. The amount of the polyurethane resin dissolved is only required to be able to join the polyurethane sheets 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 sheets 3a and 3b are brought into contact with each other through the bonding solution and heated while being pressurized. By evaporating DMF, the polyurethane sheets 3a and 3b are joined via the polyurethane resin. The adhesive layer 5 is not limited to a resin solution, but is made of an elastic resin and does not inhibit the cushioning property of the cushion sheet 3, for example, a pressure sensitive adhesive such as a urethane adhesive. Can be used. Moreover, in the adhesive tape etc. with which the adhesive agent was apply | coated to the base material, since the base material inhibits the cushioning property of the cushion sheet 3, it is not preferable.

  The polishing sheet 2 formed by wet film formation and the cushion sheet 3 formed by bonding the polyurethane sheets 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 sheet 3 a forming the cushion sheet 3 is bonded to the surface opposite to the polishing surface P of the polishing sheet 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 grinding | polishing sheet 2 of the cushion sheet 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 the present embodiment will be described focusing on the cushion sheet 3.

  Conventional polishing pads having a wet-formed polishing sheet include, for example, a polishing pad that does not have a cushion sheet, a polishing pad that has insufficient cushioning properties, and a polyurethane sheet that has been thickened by wet film formation. There is a polishing pad as a sheet. As a polishing pad which does not have a cushion sheet, the polishing pad which formed the polishing sheet by the wet coagulation method on the rigid base materials made from PET etc. can be mentioned, for example. Moreover, as a polishing pad with insufficient cushioning properties, a polishing pad in which a polishing sheet is formed by a wet coagulation method on a highly rigid cushion sheet 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. In addition, as the polishing sheet wears due to the polishing process, the compressibility of the polishing sheet disappears and the influence of the highly rigid base material and cushion sheet increases, so the rigidity of the polishing pad as a whole increases. The occurrence rate is increased, and the flatness of the object to be polished is lowered. Further, since the highly rigid base material or cushion sheet sinks into the portion where foaming of the polishing sheet 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 sheet 23 whose thickness is increased by wet film formation, coarse foam 27 is formed inside. Therefore, as shown in FIG. Such a pressure (external force) tends to cause distortion of the foam shape. For this reason, in the polishing pad using the cushion sheet 23 instead of the cushion sheet 3 described above, the degree of freedom of deformation (deformation amount) of the cushion sheet 23 is increased, and the polishing sheet 2 having the polishing surface P is effectively supported. Can not be. 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. This embodiment is a polishing pad provided with a cushion sheet that can solve these problems.

In the cushion sheet 3 of the present embodiment, the Shore A hardness is in the range of 10 to 40 degrees, the compression rate is in the range of 30 to 75%, the compression elastic modulus is 90% or more, and the bulk density is 0.2 to 0.6 g / cm. The physical property value of ³ is shown. Since the high compressibility and the high compressive elastic modulus are exhibited, the cushioning property of the cushion sheet 3 can be sufficiently exhibited even if the polishing pressure is reduced during the polishing process. Moreover, it has the characteristic that the maintenance factor of the compression elastic modulus becomes 70% or more when the operation of depressurization after pressurization is repeated at least 200 times. For this reason, even if pressurization and depressurization are repeated, the cushioning property of the cushion sheet 3 is maintained over a long period of time.

Here, the relationship between each physical property value of the cushion sheet 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. If the compression modulus after repeating pressurization and depressurization is less than 63%, it is weak against continuous pressurization, permanent deformation is likely to occur, and deterioration of the cushion sheet 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, when the bulk density is less than 0.2 g / cm ³ , the compression elastic modulus is lowered. On the other hand, when it exceeds 0.6 g / cm ³ , it becomes too hard and the cushioning property is insufficient. For this reason, the bulk density is preferably in the range of 0.2 to 0.6 g / cm ³ .

  Further, as shown in FIG. 2 (A), the cushion sheet 3 of the present embodiment is formed of polyurethane sheets 3a and 3b, and each of the polyurethane sheets 3a and 3b has a continuous foam structure in which foam 7 is formed therein. is doing. When the thickness of one polyurethane sheet is increased, the solidification regeneration at the time of wet film formation becomes insufficient. However, since the thickness of the cushion sheet 3 is increased by bonding the two polyurethane sheets 3a and 3b, the quality Can be stabilized, and variations between product lots can be reduced. Further, since it is not necessary to increase the thickness of each of the polyurethane sheets 3a and 3b, the time required for foam formation (coagulation regeneration) can be shortened, and productivity can be improved. Further, the cushion sheet 3 is deformed by the polishing pressure applied during the polishing process. However, as shown in FIG. 2B, the polishing pressure is dispersed in each layer of the polyurethane sheets 3a and 3b, so that the cushion sheet 3 is deformed as a whole. Can be kept small. Thereby, the elastic fatigue by compression and recovery | restoration of the polyurethane sheets 3a and 3b can be reduced, and the lifetime of the cushion sheet 3 can be improved.

  Furthermore, in the cushion sheet 3 of the present embodiment, the polyurethane sheets 3a and 3b are all adjusted to 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 sheet 3 is adjusted to a range of 1.0 to 3.5 mm. For this reason, in the polishing pad 10, the cushion sheet 3 can effectively exhibit cushioning properties, and can also cover the vibration caused by the driving of the polishing machine and the roughness of the surface of the surface plate on which the polishing pad is mounted. In consideration of effectively exhibiting the cushioning property of the cushion sheet 3, the thickness of the polyurethane sheets 3a and 3b is preferably in the range of 0.5 to 1.5 mm, and 0.7 to 1.5 mm. It is more preferable to set the range.

  Furthermore, in the cushion sheet 3 of this embodiment, the polyurethane sheets 3a and 3b are bonded together with an adhesive layer 5 of urethane resin having elasticity. Since the adhesive layer 5 does not have a base material or the like and has elasticity, it is possible to suppress a decrease in cushioning properties due to bonding, and elasticity due to compression / recovery of the polyurethane sheets 3a and 3b. Fatigue can be reduced. Therefore, the cushioning property described above can be exerted on the cushion sheet 3. Furthermore, the polyurethane sheet obtained by wet film formation usually has a thickness variation. However, since the cushion sheet 3 has the polyurethane sheets 3a and 3b bonded together, the thickness variation produced during the 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.

  Furthermore, in the polishing pad 10 of the present embodiment, the cushion sheet 3 exhibits cushioning properties as described above, and the cushioning properties are maintained over a long period of time. Therefore, the polishing surface P can follow the surface of the object to be polished in the low pressure polishing process for the object to be polished which is thinned or embrittled. 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. Moreover, in the polishing pad 10, the cushion sheet 3 exhibits cushioning properties, changes in physical properties over time due to polishing processing are suppressed, and the life can be improved.

  Further, the polishing pad 10 of the present embodiment has a polishing scrap that causes scratches because the hardness on the polishing surface P is 10 to 40 degrees Shore A hardness in a state where the polishing sheet 2 and the cushion sheet 3 are bonded together. Since foreign matters such as these are absorbed on the polishing surface P side, scratches can be suppressed. Furthermore, since the polishing sheet 2 has a continuous foaming structure by wet film formation, appropriate elasticity is imparted, and the polishing rate can be increased and the productivity can be improved.

  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, the cushion sheet 3 is formed of the polyurethane sheets 3a and 3b. However, 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. Further, in the present embodiment, an example is shown in which the same quality sheets formed by wet film formation are used for the polishing sheet 2 and the polyurethane sheets 3a and 3b, 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. Furthermore, it is also possible to use a plastic sheet formed by reaction curing instead of the wet-formed film 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 frame, to a slicing treatment or a surface grinding treatment. The obtained polyurethane sheet can be mentioned. In the case of such a polyurethane sheet, a (independent) foamed structure can be formed with water, spherical fine particles, or the like.

  Moreover, although the example which forms the cushion sheet 3 by the two polyurethane sheets 3a and 3b was shown in this embodiment, this invention is not limited to this. The cushion sheet 3 may be formed of three or more polyurethane sheets, for example, four sheets may be bonded together. Considering the bonding of a plurality of polyurethane sheets, it is preferable from the viewpoint of work efficiency to form with 2 to 4 polyurethane sheets. In particular, when the accuracy of the polishing machine, such as the flatness of the surface plate, is insufficient, the cushioning performance is effectively demonstrated by laminating 3-4 polyurethane sheets, so the polishing accuracy for the object to be polished Can be raised. On the other hand, when 5 or more polyurethane sheets are laminated or the thickness of the cushion sheet 3 exceeds 4 mm, the thickness is too large. The deviation (shear strain) between the bonding surface to the disk and the polishing 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 sheet 3 is 1.0 mm or less and five polyurethane sheets are laminated, the influence of the adhesive is greatly increased, the compressibility and flexibility are impaired, and the cushioning property is lowered. . Therefore, the thickness of the cushion sheet 3 is preferably in the range of 1.0 to 3.5 mm.

  Furthermore, in this embodiment, although the polyurethane sheet 3a, 3b which forms the cushion sheet 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 sheets 3a and 3b, or the skin layer of only one of the polyurethane sheets 3a and 3b may be removed. In the present embodiment, an example is shown in which the surface opposite to the skin layer of the polyurethane sheet 3a is bonded to the surface of the skin layer of the polyurethane sheet 3b, but the present invention is not limited to this. For example, the skin layer side surface of the polyurethane sheet 3a may be bonded to the skin layer side surface of the polyurethane sheet 3b, and the skin layer side surface of the polyurethane sheet 3a may be bonded to the surface of the polyurethane sheet 3b opposite to the skin layer. It may be pasted.

Furthermore, in this embodiment, the cushion sheet 3 has a Shore A hardness of 10 to 40 degrees, a compression rate of 30 to 75%, a compression modulus of 90% or more, and a bulk density of 0.2 to 0.6 g / cm. ^The example set to each of the range of ³ was shown. In consideration of improving the cushioning property of the cushion sheet 3 and supporting the polishing sheet 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 elastic modulus is 95. % Or more, and the bulk density is preferably set in the range of 0.2 to 0.3 g / cm ³ .

  Furthermore, in the present embodiment, an example is shown in which a double-sided tape is bonded to the surface of the cushion sheet 3 opposite to the polishing sheet 2 and the base material 8 of the double-sided tape also serves as the base material of the polishing pad 10. Is not limited to this. For example, by placing only the adhesive on the surface of the cushion sheet 3 opposite to the polishing sheet 2 without using the base material 8, it is possible to mount the polishing machine on 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 polishing sheet 2 and the cushion sheet 3 have flexibility, it has a base material to facilitate handling when the polishing pad 10 is transported or mounted on a surface plate. Is preferred.

  In the present embodiment, the example in which the thickness b of the cushion sheet 3 is adjusted to a range of 3 to 5 times the thickness a of the polishing sheet 2 is shown, but the present invention is not limited to this. Absent. When the thickness of the cushion sheet 3 becomes sufficiently larger than that of the polishing sheet 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. In addition, the cushioning property of the cushion sheet 3 is improved, so that the polishing load on the object to be polished can be easily controlled. Since the cushion sheet 3 shows compression / recovery even under a low load in the low-pressure polishing process, scratches can be suppressed. When the thickness b of the cushion sheet 3 is thinner than three times the thickness a of the polishing sheet 2, the thickness of the cushion sheet 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 sheet 3 is thicker than 5 times the thickness a of the polishing sheet 2, although the polishing stress is not concentrated, it is difficult to control the polishing pressure for effectively polishing the object to be polished, resulting in uneven polishing. It tends to occur. Therefore, it is preferable that the thickness b of the cushion sheet 3 is adjusted to a range of 3 to 5 times the thickness a of the polishing sheet 2.

  Hereinafter, the Example of the polishing pad 10 using the cushion sheet 3 manufactured according to this embodiment is demonstrated. A comparative polishing pad manufactured for comparison is also shown.

Example 1
In Example 1, a polyester MDI (diphenylmethane diisocyanate) polyurethane resin was used for producing the polyurethane sheets 3a and 3b forming the polishing sheet 2 and the cushion sheet 3, and a suede-like polyurethane sheet was produced by wet film formation. The cushion sheet 3 was prepared by cutting out the polishing sheet 2 and the polyurethane sheets 3a and 3b from the obtained polyurethane sheet and bonding the surface of the polyurethane sheet 3a opposite to the skin layer to the surface of the polyurethane sheet 3b on the skin layer side. In order to form the opening 9 on the polishing surface P, the polishing sheet 2 was removed by buffing so that the opening diameter of the opening 9 was about 50 μm. After the polishing sheet 2 and the cushion sheet 3 were bonded together, a double-sided tape having a base material 8 made of PET was bonded to the surface of the cushion sheet 3 opposite to the polishing sheet 2 to manufacture a polishing pad 10.

(Comparative Example 1)
In Comparative Example 1, a polishing pad was prepared in which one polyurethane sheet, which was wet-formed 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 sheet.

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

(Evaluation 1)
The thickness, bulk density, compression rate, compression elastic modulus, and hardness of each of the polishing pads and cushion sheets 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 bulk density, the weight of the sample cut into 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, bulk density, compression rate, compression modulus, and hardness. In addition, the physical property value in a polishing pad has shown the measured value from the upper surface of a polishing sheet or a cushion sheet to the release paper of a double-sided tape. The density in Table 1 indicates the bulk density.

As shown in Table 1, the cushion sheet of Comparative Example 2 in which the polyurethane sheets 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, in the cushion sheet 3 of Example 1 in which the polyurethane sheets 3a and 3b are bonded together with the adhesive layer 5 having no base material, the thickness is 2.17 mm, which is smaller than that of Comparative Example 2 due to the base material. It was. Moreover, since the cushion sheet of Comparative Example 2 has a base material, the hardness is higher and the compression ratio is lower than that of the cushion sheet 3 of Example 1. On the other hand, in the polishing pad of Comparative Example 1 having no cushion sheet, the hardness was 45.0 degrees, the density was 0.38 g / cm ³ , the compression rate was 38.6%, and the compression modulus was 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 sheet 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 of the polishing pad as a whole by using the cushion sheet 3 formed by bonding the polyurethane sheets 3a and 3b through the adhesive layer 5 having no base material. understood.

(Evaluation 2)
Moreover, the cushion sheet life of each example and comparative example was evaluated. Here, with respect to the measurement conditions of the compression elastic modulus in the evaluation 1 described above, the load is increased and the time is shortened to increase the load applied to the cushion sheet when the pressure-depressurization is repeated. The test was evaluated. That is, each cushion seat surface is compressed with a flat indenter having a diameter of 1 cm at a speed of 1 mm / min and a load of 500 gf / cm ² is compressed for 25 seconds, and then the load is removed and left for 25 seconds. The pressure 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 to the cushion sheets of Comparative Examples 1 and 2, the cushion sheet of Example 1 maintains a compressive 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 cushion sheet for a polishing pad that exhibits cushioning properties even at low loads and can maintain the cushioning properties for a long period of time, it contributes to the manufacture and sale of polishing pads, so that it can be used industrially. Have

It is sectional drawing which shows typically the polishing pad of embodiment provided with the cushion sheet to which this invention is applied. It is sectional drawing which shows typically the cushion sheet 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 sheet in which coarse foaming was formed, (A) is the state which has not applied the pressure before grinding | polishing process, (B) shows the state which deform | transformed with the pressure at the time of grinding | polishing process, respectively. 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 sheet of each Example and a comparative example.

Explanation of symbols

3 Cushion sheet 3a Polyurethane sheet (resin sheet)
3b Polyurethane sheet (resin sheet)
5 Adhesive layer (elastic adhesive layer)
10 Polishing pad

Claims (7)

  A cushion sheet for imparting cushioning properties to a polishing pad, comprising at least two wet-formed foamed resin sheets and an elastic adhesive layer for laminating the at least two resin sheets in a laminated form The cushion sheet has a compressibility of 30% or more, and a maintenance ratio of the compressive elastic modulus when the pressurization and depressurization are repeated at least 200 times to the compressive elastic modulus before the pressurization and depressurization is 70%. A cushion sheet characterized by the above.   The cushion sheet according to claim 1, wherein the elastic adhesive layer has a thickness adjusted to 0.5 mm or less.   The cushion sheet according to claim 2, wherein the elastic adhesive layer is formed of a urethane-based resin.   The cushion sheet according to claim 2, wherein the thickness is in a range of 1.0 mm to 3.5 mm.   The cushion sheet according to claim 4, wherein a compression elastic modulus before the pressurization and depressurization is 90% or more.   The cushion sheet according to claim 1, wherein the at least two resin sheets are initially made of the same quality and the same thickness. Cushion sheet according to claim 6 in which the range of the A hardness is 10 to 40 degrees, bulk density, characterized in that in the range of ^{0.2g / cm 3 ~0.6g / cm 3} .

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