TWI490085B - Keep the pad - Google Patents

Description

Hold pad

The present invention relates to a holding mat, and more particularly to a holding mat having a resin sheet for holding a holding surface for an object to be polished. This resin sheet is formed into a vertical foam by a wet coagulation method.

At present, the surface (processed surface) of various materials (the object to be polished) such as a semiconductor wafer for wafer (WF), a glass plate for parallel plane (FPD), or a substrate for a hard disk is used to improve the flatness. The grinding machine for the two platforms arranged is ground. In the above-mentioned object to be polished, a semiconductor wafer (WF) is required to be manufactured with a small size of a portable device or the like, and the substrate is efficiently produced. There is a tendency to increase in size. In addition, in the glass substrate for FPD, the glass substrate of the object to be polished tends to be large and thin, in order to increase the size of the FPD itself. In the case of such a large-sized, thin-plated object to be polished, the requirement for flatness is also increasing.

For example, when the object to be polished is subjected to single-side grinding, a polishing pad is mounted on one of the platforms of the grinding machine, and on the other platform, the object to be polished is kept opposite to the polishing pad. At the time of the polishing process, a polishing slurry containing abrasive particles (abrasive grains) is supplied between the workpiece and the polishing pad, and a polishing pressure (pressing force) is applied to the workpiece. In order to avoid damage due to contact between the object to be polished and the platform, a holding mat is usually mounted on the platform for holding the object to be polished. That is, by keeping the mat in progress During the grinding process, the object to be polished is temporarily held.

A conventionally disclosed technique is a holding pad using a soft urethane sheet (resin sheet) having a foaming structure formed by a wet coagulation method as disclosed in Japanese Laid-Open Patent Publication No. 2006-62059. The above polishing treatment is used as a holding mat. In the urethane sheet formed by the wet coagulation method, since the surface (holding surface) of the surface layer (surface layer) has smoothness, the retained property of the object to be polished is excellent. Further, a vertical foam having a size spanning substantially the entire thickness is formed on the inner side of the surface layer. Therefore, when it is compressed by the polishing pressure at the time of grinding processing, the longitudinal foaming can be used as a cushioning property. When the cushioning property is too low, the stress applied to the object to be polished is uneven due to the polishing pressure, and the stress is concentrated on the convex portion of the object to be stuck which is caught toward the holding pad side, and the stress concentration portion is excessively ground. And the problem of uneven grinding. On the other hand, when the cushioning property of the vertical foaming is increased, the stress applied to the object to be polished is less likely to cause unevenness, and although the surface smoothness of the object to be polished can be improved, the degree of sinking is also increased. As a result, the holding mat itself has the possibility of being ground. Therefore, in the wet coagulation method, the size of the foaming, the state of formation, and the like are usually adjusted by the selection of the resin and various additives.

However, in the urethane sheet obtained by the wet coagulation method, since the longitudinal foaming is formed, density unevenness occurs in the portion where the foamed portion and the foamed resin are formed. The problem arises. Therefore, in the foam forming portion and the resin portion, the amount of compressive deformation when the polishing pressure is applied during the polishing process is different, and the height of the object to be polished which is thinned and enlarged as described above cannot be sufficiently satisfied. Sexual requirements. That is, while the density unevenness is present on the holding mat, the magnitude of the stress applied to the object to be polished is locally different, so that it becomes difficult to uniformly grind the entire area of the processed surface, and there is In-plane uniformity . If the unevenness of the amount of compression deformation can be reduced, and the flatness accuracy of the holding surface can be improved, the requirement for the in-plane uniformity of the height of the object to be polished can be satisfied.

In view of the above-mentioned conventional problems, it is an object of the present invention to provide a retaining mat, in particular, a retaining mat which can improve the flatness accuracy of the retaining surface and improve the in-plane uniformity of the workpiece.

In order to solve the above problems, the holding mat of the present invention comprises a resin sheet having a vertical foam formed by a wet coagulation method and a holding surface for holding the object to be polished. In the above-described resin sheet, the foamed bottom portion is formed within a range from the back surface of the holding surface to the inner thickness of 10% by weight. And a total of 10% of the thickness from the back surface to the inner side, a cross section parallel to the back surface, and a total thickness of 40% from the back surface to the inner side, and a cross section parallel to the back surface, the two sections are covered. The porosity of the lower layer portion is 70% or more and 95% or less.

In the present invention, since the porosity of the lower layer portion having a certain thickness portion of the resin sheet on the back surface side of the holding surface is 70% or more and 95% or less, the lower layer portion can be used to secure the cushioning property. Since the load on the object to be polished can be dispersed, the foaming shape change in the lower layer portion when compressed by the polishing process can be reduced, and the load on the object to be polished can be increased, and the flatness accuracy of the holding surface can be improved. The in-plane uniformity of the abrasive increases.

In this case, the resin sheet has a thickness of 10% of the entire thickness from the self-supporting surface, and the average pore diameter of the pores formed by foaming is set to A in the cross section parallel to the holding surface, and is in the lower layer portion. , on the section parallel to the holding surface, by the foaming station When the maximum aperture of the formed hole is set to B, the ratio B/A is preferably in the range of 20 to 50. In addition, the total thickness of the inner surface is 10% by weight, the cross section parallel to the holding surface, and the thickness of the inner side from the holding surface are 40%, and the cross section parallel to the holding surface is included in the two sections. The void ratio of the upper portion of the crucible may be between 35% and 55%. The porosity of the lower portion of the resin sheet is preferably from 75% to 90%, and the void ratio in the upper portion is preferably from 40% to 50%. In the lower layer portion of the resin sheet, the cross-sectional area in which the ratio of the total area of the pores formed by the foaming is maximum is shown per unit area in the cross section parallel to the holding surface, and the maximum value of the ratio may be 80%. Above 95%. The resin sheet can also be formed of a polyurethane resin. The polyurethane resin in the respective foams of the resin sheet may also be formed in a microporous shape. At this time, it is preferred to set the 100% modulus value of the polyurethane resin to less than 20 MPa. It is also possible to apply an adhesive material for mounting on a grinder on the back side of the resin sheet. At this time, a support material for supporting the resin sheet may be bonded between the resin sheet and the adhesive.

According to the present invention, since the porosity of the lower layer portion having a certain thickness portion of the resin sheet on the back surface side of the holding surface is 70% or more and 95% or less, the cushioning property can be ensured by the lower layer portion, so that it is applied to the Since the load on the polishing material can be dispersed, the foaming shape change in the lower layer portion when compressed by the polishing process can be reduced, and the load on the object to be polished can be increased, and the flatness accuracy of the holding surface can be improved. The effect of the in-plane uniformity of the abrasive.

2, 12.‧ ‧ urethane sheets

2a, 12a‧‧‧ surface layer

3, 13‧‧‧ foaming

7‧‧‧Double-sided tape

8‧‧‧ peeling paper

10, 20‧‧‧ Keep pad

Sh‧‧‧ Keep face

Sr‧‧‧Back

Ph‧‧‧Upper Department

Pr‧‧‧ Lower Department

Fig. 1 is a schematic cross-sectional view showing a holding mat suitable for use in an embodiment of the present invention; and Fig. 2 is a view showing the hair in a urethane sheet constituting the holding mat of the embodiment. A schematic view of the state of formation of the bubble, wherein the second (A) diagram is a cross-sectional view in the thickness direction of the urethane sheet, and the second (B) diagram is shown in the BB section in the second (A) diagram, respectively. FIG. 2(C) is a schematic explanatory view showing a hole formed by foaming on the CC section in FIG. 2(A), and FIG. 3 is a schematic view showing a hole formed by foaming on the CC section; BRIEF DESCRIPTION OF THE DRAWINGS FIG. 4 is a schematic view showing a state of formation of foam in a urethane sheet constituting a conventional holding mat, wherein the fourth (A) diagram is an aminocarboxylic acid. A cross-sectional view of the thickness direction of the ester sheet, and a fourth (B) diagram showing a schematic view of the pores formed by foaming on the BB section in the fourth (A) diagram, respectively, and the fourth (C) diagram is respectively A schematic view showing pores formed by foaming on the CC cross section in the fourth (A) diagram; and Fig. 5 is a graph showing thickness with respect to the holding surface of the urethane sheet constituting the holding mat, A graph comparing the aperture ratios of the holes formed by the foaming in each of the thickness ranges.

Hereinafter, an embodiment in which the holding mat of the present invention is applied will be described with reference to the drawings.

In the present embodiment, the holding mat 10 is provided with a urethane sheet 2 as a resin sheet made of a polyurethane resin. The polyurethane sheet 2 is formed by a wet coagulation method and has a holding surface Sh for holding the object to be polished.

The urethane sheet 2 has a surface layer 2a in which a dense microporous layer is formed in a thickness range of approximately several μm across the holding surface Sh. That is, the surface layer 2a has a microporous structure. A plurality of foams 3 in a slightly uniform dispersion state are formed on the inner side (inside) of the surface layer 2a of the urethane sheet 2 . The size of foam 3 is about straddle The urethane sheet 2 has a thickness of approximately the entire thickness of the urethane sheet 2, and is formed in a longitudinal shape in a thickness direction and has a circular conical shape. Since the urethane sheet 2 has the surface layer 2a, the opening of the foam 3 is not formed on the holding surface Sh. In the urethane sheet 2, the bottom portion of the foam 3 is formed in a range from the back surface of the holding surface Sh (hereinafter referred to as the back surface Sr) to the entire thickness of the inner surface by 10%. In the polyurethane resin foamed between the three, a microporous (not shown) smaller than the foaming 3 is formed. In the urethane sheet 2, the microporous, foamed 3, and microporous of the surface layer 2a communicate with each other in a mesh shape, and foaming is a continuous foaming structure in which a continuous foaming state is formed.

In the urethane sheet 2, a cross section parallel to the back surface Sr is 10% of the total thickness from the back surface Sr, and a 40% portion of the entire thickness is parallel to the back surface Sr. In the cross section, the porosity of the lower portion Pr surrounded by the two sections is adjusted to be 70% or more and 95% or less. That is, when the thickness of the urethane sheet 2 is set to t, a cross section of a thickness portion of 0.1 t from the back surface Sr toward the inner side, and a thickness portion of a thickness of 0.4 t toward the inner side, the two sections are covered. In the lower layer portion Pr, the void ratio based on the foaming 3 is in the range of 75 to 95%. In contrast, the self-retaining surface Sh is a cross section parallel to the holding surface Sh of 10% of the entire thickness of the holding surface Sh, and a cross section parallel to the holding surface Sh of 40% of the total thickness in the inner side. The porosity of the upper portion Ph of the package is adjusted to be between 35% and 55%. That is, a cross section of a thickness portion which is 0.1 t inward from the holding surface Sh, and a cross section which is 0.4 t in thickness toward the inner side, and the void ratio of the foaming 3 in the upper portion Ph of the two cross sections It is in the range of 35 to 55%. The void ratio of the upper layer portion Pb or the lower layer portion Pr can be adjusted by the selection of the polyurethane resin to be used and the condition setting of the wet solidification method (for example, Later).

Further, in the urethane sheet 2, a section formed by the foaming 3 is formed on the cross section which is parallel to the holding surface Sh by 10% of the total thickness from the holding surface Sh, and the hole is formed by the foaming 3 When the average pore diameter is set to A, the ratio of the total area of the pores formed by the foaming 3 (hereinafter referred to as the aperture ratio) per unit area in the cross section in which the lower layer portion Pr is parallel to the back surface Sr is the maximum value. In the cross section, a hole is formed in the cross section, and when the maximum aperture of the hole is set to B, the ratio B/A of the maximum aperture B to the average aperture A is adjusted to be in the range of 20 to 50. That is, the foaming aperture is a foam having a size of 20 to 50 times that of the foamed average pore diameter adjacent to the holding surface Sh, and the foaming is a section in which the opening ratio formed in the lower layer portion Pr is the maximum value. on. Further, the maximum value of the aperture ratio can be adjusted to be 80% or more and 95% or less.

In the urethane sheet 2, the pores formed in the cross section parallel to the back surface Sr and the back surface Sr are formed in comparison with the pores formed in the cross section parallel to the holding surface Sh and the holding surface Sh. Close state. As shown in Fig. 2(A), the position adjacent to the holding surface Sh from the holding surface Sh is 10% of the thickness t of the urethane sheet 2, that is, the position toward the inner side at the amount of 0.1 t parts (arrow) The position of B is adjacent to the back surface Sr from the back surface Sr from the position of 0.1 t parts toward the inner side (the position of the arrow C). In this case, as shown in Fig. 2(B), in the cross section of the line B-B adjacent to the holding surface Sh, the holes formed by the foaming 3 are alienated from each other. On the other hand, as shown in Fig. 2(C), the holes formed by the foaming 3 in the C-C line cross section adjacent to the back surface Sr are close to each other.

Further, in the holding mat 10, a double-sided tape 7 as an adhesive material is bonded to the back surface Sr side of the urethane sheet 2 to mount the holding mat 10 to the grinder. The double-sided tape 7 has a substrate (not shown), and a pressure-sensitive adhesive layer (not shown) such as an acrylic adhesive is formed on both surfaces of the substrate. The substrate is used, for example, polyparaphenylene A flexible film such as a film made of ethylene glycol diester (hereinafter abbreviated as PET). The double-sided tape 7 is an adhesive layer which is bonded to the urethane sheet 2 by the adhesive layer on one side of the substrate, and the adhesive layer of the other side (the opposite side of the urethane sheet 2) The surface is covered by a release paper 8. Further, in the present embodiment, the base material of the double-sided tape 7 may also serve as a support for supporting the urethane sheet 2.

Hereinafter, the manufacturing method of the holding mat will be described. The holding mat 10 is produced by bonding the urethane sheet 2 formed by the wet coagulation method and the double-sided tape 7 to each other. That is, the preparation step of preparing the polyurethane resin solution, coating the polyurethane resin solution on the film-forming substrate, and solidifying the polyurethane resin solution in the coagulating liquid to form a polyurethane resin reconstitution step, and flaking the polyurethane The holding mat 10 is prepared by washing the resin, drying and drying the drying/drying step, and laminating the obtained urethane sheet 2 and the double-sided tape 7. Hereinafter, the description will be made in accordance with the order of each step.

The preparation step is to dissolve the polyurethane resin by mixing a polyurethane resin, a water-miscible organic solvent capable of dissolving the polyurethane resin, and an additive. N,N-dimethylformamide (hereinafter abbreviated as DMF) or N,N-dimethylacetamide (DMAc) may be mentioned as an organic solvent. In the present embodiment, DMF is used as an organic solvent. The polyurethane resin can be used by selecting one of a resin such as a polyester type, a polyether type, or a polycarbonate type. When it is considered that the foaming structure described above is to be formed, the viscosity of the resin solution which is soluble in 20% by weight of the polyurethane resin in the DMF is preferably selected at 25 ° C using a B-type rotational viscometer. 5~10Pa. Resin between the range of s is used. Further, the polyurethane resin to be used preferably has a 100% modulus value of less than 20 MPa, and the polyurethane resin can be dissolved in DMF to be in the range of 10 to 30% by weight. Further, as an additive, since the size or the number (number) of the foam 3 is to be controlled, A pigment such as carbon black, a hydrophilic additive that promotes foaming, a hydrophobic additive that stabilizes regeneration of the polyurethane resin, and the like can be used. The obtained solution was defoamed under reduced pressure to obtain a polyurethane resin solution.

In the coagulation and regeneration step, the polyurethane resin solution obtained in the preparation step is applied to the strip-shaped film-forming substrate in a sheet form at a normal temperature by a coating device such as a knife coater. At this time, the coating thickness (coating amount) of the resin solution can be adjusted by adjusting the clearance between the knife coater and the like and the film formation substrate. A film made of a resin, a cloth, a non-woven fabric or the like can be used as the film-forming substrate, and in the present embodiment, a film made of PET is used.

The polyurethane resin solution applied to the film-forming substrate is continuously guided to a coagulating liquid (aqueous coagulating liquid) containing water as a main component of the polyurethane resin. In order to adjust the regeneration rate of the polyurethane resin, an organic solvent such as a polar solvent other than DMF or DMF may be added to the coagulation liquid. However, in the present embodiment, water is used. In the coagulating liquid, first, a film is formed at the interface between the polyurethane resin solution and the coagulating liquid, and microporous which can constitute the surface layer 2a is formed in the polyurethane resin close to the film. Next, the polyurethane resin having a continuous foaming structure is regenerated by the diffusion of DMF in the polyurethane resin solution into the coagulating liquid and the incorporation of water into the polyurethane resin. At this time, since the water (coagulating liquid) of the film-forming substrate is not allowed to permeate, the DMF and the water are replaced on the surface layer 2a side, and the film-forming substrate side is formed to have a larger surface than the surface layer 2a side. Bubble 3.

Here, the foam formation accompanying the regeneration of the polyurethane resin will be described. In the polyurethane resin, since the cohesive force is increased, the polyurethane layer resin close to the film is rapidly regenerated to form the surface layer 2a. In the present embodiment, a polyurethane resin having a 100% modulus value of less than 20 MPa is used. And show this polyurethane tree The viscosity of the lipid solution is between 5 and 10 Pa. The scope of s. That is, a low-viscosity polyurethane resin solution is dissolved using a low-modulus polyurethane resin. Therefore, after the formation of the surface layer 2a, the polyurethane resin in the polyurethane resin solution before solidification moves to the side of the surface layer 2a and aggregates, and the amount of the polyurethane resin decreases with the surface of the film-forming substrate side, and thus the surface layer 2a Compared to the side, foaming 3 is formed. In other words, in the lower layer portion Pr compared to the upper layer portion Ph, the void ratio is increased due to the enlargement of the foaming 3 . Further, the desolvent from the DMF urethane resin solution, that is, the surface layer 2a, the foam 3 and the microporous are formed by DMF and water replacement, and the surface layer 2a is microporous and foamed. And the microporous system is connected to each other in a mesh shape. Further, since the polyurethane resin is recyclable on the film-forming substrate, the opening of the foam 3 is not formed in the back surface Sr formed in contact with the surface of the film-forming substrate.

In the washing/drying step, the polyurethane resin to be regenerated in the regeneration step is washed with a washing liquid such as water to remove DMF remaining in the polyurethane resin, and then dried. In the drying of the polyurethane resin, in the present embodiment, a cylinder dryer having a heat source containing cylinder is used. It is dried by passing the polyurethane resin along the circumferential surface of the cylinder. The obtained urethane sheet 2 was taken up in a roll shape.

In the laminating step, the urethane sheet 2 and the double-sided tape 7 which are formed by the wet coagulation method are attached. At this time, the back surface Sr of the urethane sheet 2 is bonded to the double-sided tape 7. Next, after cutting into a desired shape and size such as a circle or a polygon, it is checked whether there is damage or adhesion of dirt or foreign matter, that is, the holding pad 10 is completed.

Next, the effect and the like achieved by the holding mat 10 of the present embodiment will be described.

In order to facilitate the understanding of the description, the foaming structure of the urethane sheet formed by the conventional wet coagulation method will be described. In the conventional wet coagulation method, the polyurethane resin solution applied to a film-forming substrate such as a PET film is solidified in a coagulating liquid such as water. Therefore, as shown in Fig. 3, in the urethane sheet 12 constituting the conventional holding mat 20, the surface layer 12a formed at the initial stage during wet solidification is also on the inner side, and is formed across The urethane sheet 12 has a large amount of foam 13 in its entirety. The diameter of the foam 13 on the holding surface Sh side is smaller than the diameter of the back surface Sr side, and is formed in the vertical direction along the thickness direction.

Further, in the urethane sheet 12, a hole formed in a cross section parallel to the holding surface Sh adjacent to the holding surface Sh, and a hole formed in a cross section parallel to the back surface Sr and the back surface Sr, Any one of the holes is alienated from each other. Since the diameter of the foam 13 on the side of the back surface Sr is larger than the diameter of the hole on the side of the holding surface Sh, the degree of the detachment becomes larger on the side of the holding surface Sh. That is, as shown in Fig. 4(A), adjacent to the holding surface Sh, the holding surface Sh is directed toward the inner side by a distance of 10% of the thickness of the urethane sheet 12 (the position of the arrow B), and adjacent to the back surface. Sr is a position (the position of the arrow C) on the inner side of the back surface Sr from the inner side of the thickness of the urethane sheet 12 by 10%. In this case, as shown in Fig. 4(B), the hole formed in accordance with the foam 13 is formed in the cross section of the line B-B adjacent to the holding surface Sh. As shown in Fig. 4(C), the hole formed in accordance with the foam 13 is also formed in the C-C line cross section adjacent to the back surface Sr. In the CC line section, the hole formed is closer to the hole formed in the BB line section, but is formed on the cross section adjacent to the back surface Sr of the urethane sheet 2 constituting the above-mentioned holding pad 10. The pores are formed in an alienated manner (see Fig. 2(C)). In the urethane sheet 12, the same ratio as the upper layer portion Ph and the lower layer portion Pr in the urethane sheet 2 described above is considered, and the porosity of the upper layer portion is about 30 to 45%, and the lower layer portion is used. Null The gap ratio is about 70% or less.

In the conventional holding mat 20 using the urethane sheet 12, density unevenness occurs between the portion where the foam 13 is formed and the resin portion between the foams 13. Therefore, the foam forming portion and the resin portion are different in the amount of compressive deformation when subjected to the polishing pressure during the polishing process, and thus it becomes difficult to satisfy the height flatness required for the object to be polished. That is, in the holding mat 20, the density unevenness occurs, and the magnitude of the stress applied to the object to be polished is locally different, so that it becomes difficult to spread over the entire area of the processed surface of the object to be polished. The ground is uniformly ground. Therefore, the high-precision flatness required for the glass substrate for WF and FPD for semiconductors for the purpose of thinning and increasing the size of the above-mentioned tends is not sufficiently satisfied.

In the case of the holding mat 20 which is conventionally used for the urethane sheet 12, when the polishing process is performed, when the polishing pressure is applied, the object to be polished is caught on the side of the holding mat 20 due to the buffering amine group. The formate flakes 12 are compressed to stress the abrasive. In the case where the density of the holding mat 20 is uneven, that is, in the case where the foaming 13 is unevenly formed, the stress applied to the object to be polished is different in each density uneven portion. . Therefore, the pressing force applied to the object to be polished is changed in a regional manner, so that it is difficult to uniformly polish the processed surface of the object to be polished across the entire region. As a result, in the object to be polished after the polishing process, for example, the polishing margin between the outer edge portion and the center portion is different, and a phenomenon of so-called outer edge depression occurs. In other words, the polishing pad is held by the holding mat 20, and the polishing process is performed to impair the flatness of the machined surface. As is apparent from the above, the conventional holding mat 20 cannot sufficiently satisfy the high-precision flatness required for the glass substrate for WF or FPD for semiconductors, which is required for high-integration, defect-free base wiring or display of high-quality images. .

In contrast, in the present embodiment, the urethane sheet constituting the holding mat 10 is formed. The back surface Sr of 2 has a thickness of 10% by weight (0.1 t part) toward the inner side, a cross section parallel to the back surface Sr, and a cross section which is 40% by weight (0.4 t portion) in the direction of the inner side, and is parallel to the back surface Sr. The porosity of the lower portion Pr surrounded by the two sections can be adjusted to be 70% or more and 95% or less. Further, the distance from the holding surface Sh toward the inner side is 10% of the total thickness, and in the cross section parallel to the holding surface Sh, there is a hole formed by the foaming 3, and the average pore diameter of the hole can be set to A, and In the lower layer portion Pr, in the cross section parallel to the back surface Sr, a hole having a maximum aperture ratio is formed, and a hole is also formed. The maximum aperture of the hole can be set to B, and the ratio B/A can be adjusted to be 20 Range of ~50. That is, the foaming aperture is a foam having a size of 20 to 50 times that of the foamed average pore diameter adjacent to the holding surface Sh, and the foaming is a section in which the opening ratio formed in the lower layer portion Pr is the maximum value. on. Therefore, the lower portion Pr which can be formed in a large amount by the soft foam 3 can play the role of air cushioning, and the pressure (grinding pressure) applied to the workpiece can be easily dispersed. Further, when compressed by the polishing process, the foamed shape of the lower layer portion Pr is compressed and deformed in accordance with the pressure applied to the object to be polished, thereby coping with the warpage and undulation of the object to be polished, thereby reducing the object to be polished. The burden (reverse stress) can greatly improve the flatness of the object to be polished. When it is considered that the amount of compressive deformation of the lower layer portion Pr is to be secured, the void ratio of the lower layer portion Pr is preferably adjusted to be in the range of 75 to 90%.

Further, in the present embodiment, the ratio of the total area of the holes formed by the foaming 3, that is, the maximum value of the aperture ratio, can be adjusted per unit area in the cross section parallel to the back surface Sr in the lower layer portion Pr. It is between 80% and 95%. Therefore, in the lower layer portion Pr, particularly adjacent to the back surface Sr, the pore diameter of the foaming 3 is enlarged, and sufficient cushioning property can be ensured. Thereby, since the stress on the object to be polished can be equalized during the polishing process, the flatness can be improved. And the void ratio of the lower layer Pr For example, when considering the amount of compression deformation, it is preferable to adjust the aperture ratio to be in the range of 82 to 90%.

In the present embodiment, the distance from the holding surface Sh of the urethane sheet 2 to the inner side is 10% by weight (0.1 t part) of the thickness t, and the cross section parallel to the holding surface Sh is spaced apart from the inner side. It is a cross section parallel to the holding surface Sh of 40% by weight (0.4 t part), and the void ratio of the upper layer Ph surrounded by the two cross sections can be adjusted to be 35% or more and 55% or less. Therefore, since the partition wall of the polyurethane resin is thicker than the lower layer portion Pr, the rigidity can be ensured, so that the object to be polished can be prevented from sinking toward the holding mat side during the polishing process. When the rigidity of the holding mat is insufficient to cause the object to be polished to become large, the holding mat (urethane sheet) itself may be ground during the polishing process. In contrast, since the holding mat 10 can suppress the sinking of the object to be polished, the polishing process can be continued without the urethane sheet 2 being ground. When the porosity of the upper layer portion Ph is less than 35%, the rigidity is increased to increase the rigidity, but it is difficult to improve the flatness. When it is considered to ensure rigidity by the concept of improving flatness, it is preferable to adjust the void ratio of the upper layer portion Ph to be in the range of 40 to 50%.

Further, in the present embodiment, since the urethane sheet 2 has the above-described foaming structure, it is ensured that the upper layer portion Ph can have rigidity required to suppress the sinking of the object to be polished, and the lower layer portion Pr can be secured. Since the cushioning property required for equalizing the stress of the workpiece is obtained, the rigidity and cushioning properties can be achieved by the single urethane sheet 2 alone. Although a rigid resin sheet and a cushioning resin sheet may be bonded together, in this case, the two resin sheets may be peeled off from each other during the polishing process. Therefore, in the holding mat 10, the urethane sheet 2 has both rigidity and cushioning properties, and the flatness of the object to be polished can be improved.

Further, in the present embodiment, an amine group made of a polyurethane resin is exemplified. The pad 10 of the acid ester sheet 2 is held, but the invention is not limited thereto. A resin such as polyethylene may be used instead of the polyurethane resin, and any resin which can form the above-described foaming structure by a wet coagulation method can be used.

Further, in the present embodiment, the holding mat 10 in which the urethane sheet 2 and the double-sided tape 7 having the substrate are bonded is exemplified, but the present invention is not limited thereto. As long as the urethane sheet 2 and the holding mat for the adhesive for the grinder are provided, it can be used as a holding mat, for example, instead of the double-sided tape 7, and only various adhesives can be applied to the amine base. Acid sheet 2 (back side Sr). Further, in the present embodiment, the base material of the double-sided tape 7 can be exemplified as the support material of the holding mat 10, but the present invention is not limited thereto. It is also possible to form a support material between the urethane sheet 2 and the double-sided tape 7. A film made of PET or the like, a nonwoven fabric or the like can be exemplified as such a support material, and there is no particular limitation.

Further, in the present embodiment, although the thickness unevenness of the urethane sheet 2 formed by the wet coagulation method is increased, the holding surface Sh and the back surface Sr may be parallel. It is preferable to smooth the back Sr side by polishing or cutting in advance. In this way, the flatness of the holding surface Sh can be further improved.

Next, an embodiment in which the holding mat 10 is produced according to the present embodiment will be described. Also, it is described as a comparative example produced for comparison.

Example 1

In Example 1, in the preparation of the urethane sheet 2, the 100% modulus of the resin used was a polyester MDI (methylene diphenyl diisocyanate, diphenylmethane diisocyanate) having a modulus of less than 10 MPa. Resin, after dissolving in a ratio of 18% by weight in DMF, adding 1% by weight of hydrophilicity to the polyurethane resin Additives, and add 5% by weight of carbon black to the polyurethane resin to prepare a 3.3-fold measured by a B-type rotational viscometer. s viscosity of the polyurethane resin solution. When the polyurethane resin solution was applied, the gap of the coating device was set to 0.7 mm. The polyurethane resin solution was applied onto a film-forming substrate of a PET film, and then immersed in water (coagulating liquid) at a temperature of 25 ° C to completely regenerate the polyurethane resin. After washing/drying, the back surface Sr side of the obtained urethane sheet 2 is polished, and the double-sided tape 7 is bonded to the polishing surface to complete the production of the holding mat 10.

Example 2

In Example 2, the same polyurethane resin as in Example 1 was used, and after dissolving in a ratio of 20% by weight in DMF, 1% by weight of a hydrophilic additive was added to the polyurethane resin, and 5% by weight of carbon was added to the polyurethane resin. Black and modulated to have a B-type rotational viscometer with 5.3 Pa. s viscosity of the polyurethane resin solution. The gap of the coating device was set to 1.0 mm. After coating the polyurethane resin solution on the film-forming substrate, it was immersed in water at a temperature of 10 ° C to completely regenerate the polyurethane resin. After washing/drying, the back surface Sr side of the obtained urethane sheet 2 is polished, and the double-sided tape 7 is bonded to the polishing surface to complete the production of the holding mat 10.

Example 3

In Example 3, the same polyurethane resin as in Example 1 was used, and after dissolving in a ratio of 21% by weight in DMF, 3% by weight of a hydrophilic additive was added to the polyurethane resin, and 5% by weight of carbon was added to the polyurethane resin. Black and modulated to have a B-type rotational viscometer with 8.2Pa. s viscosity of the polyurethane resin solution. The gap of the coating device was set to 1.0 mm. After coating the polyurethane resin solution on the film-forming substrate, it was immersed in water at a temperature of 10 ° C to completely regenerate the polyurethane resin. After washing/drying, the surface of the obtained urethane sheet 2 is polished to the side of the Sr side to make a polished surface. The manufacture of the holding mat 10 is completed by attaching the double-sided tape 7 thereto.

Example 4

In Example 4, the same polyurethane resin as in Example 1 was used, and after dissolving in a ratio of 21% by weight in DMF, 5% by weight of a hydrophilic additive was added to the polyurethane resin, and 5% by weight of carbon was added to the polyurethane resin. Black and prepared with a B-type rotational viscometer measured with 7.9Pa. s viscosity of the polyurethane resin solution. The gap of the coating device was set to 1.0 mm. After coating the polyurethane resin solution on the film-forming substrate, it was immersed in water at a temperature of 25 ° C to completely regenerate the polyurethane resin. After washing/drying, the back surface Sr side of the obtained urethane sheet 2 is polished, and the double-sided tape 7 is bonded to the polishing surface to complete the production of the holding mat 10.

Example 5

In Example 5, the same polyurethane resin as in Example 1 was used, and after dissolving in a ratio of 21.5 wt% in DMF, 1% by weight of a hydrophilic additive was added to the polyurethane resin, and 5% by weight of carbon was added to the polyurethane resin. Black and prepared to have a B-type rotational viscometer with 9.5Pa. s viscosity of the polyurethane resin solution. The gap of the coating device was set to 1.2 mm. After coating the polyurethane resin solution on the film-forming substrate, it was immersed in water at a temperature of 10 ° C to completely regenerate the polyurethane resin. After washing/drying, the back surface Sr side of the obtained urethane sheet 2 is polished, and the double-sided tape 7 is bonded to the polishing surface to complete the production of the holding mat 10.

Comparative example 1

In Comparative Example 1, the same polyurethane ester resin as in Example 1 was used, and after dissolving in a ratio of 21% by weight in DMF, 1% by weight of a hydrophilic additive was added to the polyurethane resin, and 5% by weight of carbon was added to the polyurethane resin. Black and modulated to have a B-type rotational viscometer with 8.2Pa. s viscosity of the polyurethane resin solution. Intercoating device The gap is set to 0.7 mm. After coating the polyurethane resin solution on the film-forming substrate, it was immersed in water at a temperature of 25 ° C to completely regenerate the polyurethane resin. After washing/drying, the back surface Sr side of the obtained urethane sheet 12 is polished, and the double-sided tape 7 is bonded to the polishing surface to complete the production of the holding mat 20. That is, the holding mat 20 of Comparative Example 1 is a conventional holding mat (see also FIG. 3).

With respect to the obtained urethane sheets of the respective Examples and Comparative Example 1, the void ratio of the upper layer portion Ph and the lower layer portion Pr, the maximum value of the aperture ratio, and the ratio of the maximum foaming pore diameter to the minimum foaming pore diameter were The foaming pore ratio (Max/Min) or the like was measured. The measurement of the void ratio was carried out in the following manner. In other words, a scanning profile was performed using a three-dimensional side X-ray computed tomography apparatus (YAMATO SCIENTIFIC, TDM1000-IS/SP), and a continuous tomographic image with a distance of 10 μm from the holding surface Sh was obtained. The obtained tomographic image was read by the SEM image analysis software "Scandium" (manufactured by Olympus Soft-Imaging Solutions Co., Ltd.), and image processing was performed to obtain images of different shades. For each of the images of different shades, the rich portion is used as an opening, and the concentration range (threshold value) can be visually set so as to match the image, and the concentrated portion is accumulated as an opening portion to obtain an average observed area. The ratio of the total open area is taken as the aperture ratio. Then, the sum of the aperture ratios obtained from the tomographic images in the region of the upper layer portion Ph and the lower layer portion Pr is obtained, and the percentage after the sum of the observed areas of the upper layer portion Ph and the lower layer portion Pr is determined as Void rate. In order to obtain the void ratio, for example, it is possible to grind the thickness of the urethane sheet by polishing or cutting, and to observe the surface of the urethane by a SEM or a microscope to obtain a void ratio. The method is used as an easy method. The maximum value of the aperture ratio is obtained from the aperture ratio obtained by measuring the porosity. The foaming aperture ratio was determined as follows. that is By using "Scandium", the average opening diameter of the opening in the range of 3.3 mm 2 in the cross section parallel to the holding surface Sh is 10% of the total thickness from the holding surface Sh, and the minimum opening diameter is calculated. Aperture. Using Scandium, the range of 3.3 mm 2 in the cross section showing the maximum value of the aperture ratio in the region of the lower layer portion Pr, and the maximum opening diameter among the openings not in contact with the boundary of the observation region are calculated as the maximum foaming. Aperture. The ratio of the maximum foaming pore diameter to the minimum foaming pore diameter was determined as the foaming pore diameter ratio. Since the minimum foaming pore diameter and the maximum foaming pore diameter correspond to the above-described average pore diameter A and maximum pore diameter B, respectively, the foaming pore diameter ratio can be used to express the above ratio B/A. Table 1 below shows the measurement results of the void ratio, the maximum aperture ratio, and the foaming pore ratio of each of Examples and Comparative Example 1.

As shown in Table 1, in the urethane sheet of Comparative Example 1, the void ratio of the upper layer portion Ph was 41.4%, and the void ratio of the lower layer portion Pr was 68.6%. Further, as is clear from Fig. 5, the larger the thickness from the surface, that is, the closer the opening Sr is, the larger the aperture ratio is, but the aperture ratio is at most about 75%. On the other hand, in each of the urethane sheets 2 of the first to fifth embodiments, the void ratio of the upper layer portion Ph is in the range of 38.3% to 50.2%, and the void ratio of the lower layer portion Pr is between 77.2 and 88.3. The range of %. Further, in the urethane sheet 2 of Example 1, it can be clearly confirmed from Fig. 5. It is understood that the cross section having a thickness of 100 μm or more across the thickness region of the lower layer portion Pr continuously exceeds an aperture ratio of 80%. As a result, in the urethane sheet 2 of each of the examples, the void ratio of the upper layer portion Ph was the same as that of the comparative example 1, and the void ratio of the lower layer portion Pr was large. Further, from the measurement results of the foaming aperture ratio, it can be understood that in Comparative Example 1, the maximum opening diameter of the lower foaming portion Pr in the lower layer portion Pr is 18.7 times with respect to the adjacent opening surface Sh, which is relatively the same in each of the examples. It is displayed as a size of 34.0~38.2 times.

For the evaluation of the polishing performance, the glass substrate for liquid crystal display (470 mm × 370 mm × 0.7 mm) was polished under the following polishing conditions using the holding mats of the respective Examples and Comparative Examples, and the Japanese Industrial Standard (JIS) was used. B 0601: '82) is a reference method in which the flatness a is obtained from the fluctuation of the corrugated center. In the measurement of the flatness a, the measurement was carried out according to the following measurement conditions using a surface roughness measuring machine (manufactured by Tokyo Seimi Co., Ltd., surfcom 480A). The width W between the adjacent convex portion (mountain portion) and the convex portion and the height S between the convex portion and the concave portion (valley portion) are calculated from the measurement curve obtained by the unevenness on the surface of the substrate, and the width W is calculated. On the horizontal axis, the height S is a scatter diagram of the vertical axis. The approximate straight line of the equation S=aW is obtained from the scattergram, and the slope a is set to the final flatness a after the grinding process. The higher the flatness, the larger the width W and the smaller the height S. Therefore, the flatness is more excellent when the slope a is smaller.

Grinding condition

Grinding machine: OSCAR grinding machine (SP-DFAM, SP-1200)

Grinding speed (number of revolutions): 61 rpm

Processing pressure: 76gf/cm ²

Grinding slurry: mash

Grinding time: 30min

Corrugated center undulation measurement conditions

Evaluation length: 90mm

Measuring speed: 3.0mm/s

Interrupt value: 0.8~8.0mm

Film species category: 2RC

Measuring range: ±40.0μm

Tilt compensation: smooth curve

As shown in Table 1, in the polishing process using the holding mat 20 of Comparative Example 1, the flatness a of the glass substrate after the processing was shown to be 0.0007. On the other hand, in the polishing process using each of the holding mats 10 of the first to fifth embodiments, the flatness a was displayed to be 0.0003 to 0.0005, which was superior to the comparative example 1 . Therefore, it is clear that the foaming ratio formed by the wet solidification method is such that the void ratio in the upper layer Ph is in the range of 35 to 55%, and the void ratio in the lower layer Pr is formed in the range. 70~95% range. By using the holding mat 10 having the urethane sheet 2 having the foaming 3, the flatness accuracy of the holding surface Sh can be improved, and the in-plane uniformity of the object to be polished can be improved.

The present invention provides a holding mat which can improve the flatness accuracy of the holding surface and improve the in-plane uniformity of the object to be polished, and thus contributes to the manufacture and sale of the holding mat, and is an industrially useful invention. .

The above is intended to be illustrative only and not limiting. Any equivalent modifications or alterations to the spirit and scope of the invention are intended to be included in the scope of the appended claims.

2‧‧‧Carbamate flakes

2a‧‧‧Surface

3‧‧‧Foaming

7‧‧‧Double-sided tape

8‧‧‧ peeling paper

10, 20‧‧‧ Keep pad

Sh‧‧‧ Keep face

Sr‧‧‧Back

Ph‧‧‧Upper Department

Pr‧‧‧ Lower Department

Claims (8)

A holding mat comprising: a resin sheet having a longitudinal shape foam formed by a wet coagulation method and having a holding surface for holding the object to be polished, wherein the resin sheet is from the resin sheet The bottom surface of the holding surface is formed in a range from 10% by weight of the entire thickness to the inner side, and the resin sheet is formed to have a distance of 10% of the entire thickness from the back surface toward the inner side. a portion, a cross section parallel to the back surface, and a distance from the inside to the inside is 40% of the entire thickness, a lower layer portion covered by another cross section parallel to the back surface; and 10 from the holding surface toward the inside from the entire thickness % by weight, a cross section parallel to the holding surface, and a 40% by weight of the inner side, a single piece of the upper layer portion covered by another cross section parallel to the holding surface, wherein the lower layer portion has a void ratio The content is 70% or more and 95% or less, and the porosity of the upper layer portion is 35% or more and 55% or less. In the resin sheet, the resin between the foams forms a microporous shape, and the foaming and micro-foaming Porous system Shape with each other. The holding mat according to the first aspect of the invention, wherein the resin sheet has a distance of 10% of the entire thickness of the holding surface, and a cross section parallel to the holding surface, the foaming a hole formed having an average pore size of A, and on another cross section of the lower layer portion parallel to the holding surface, another hole is formed by the foaming, and the maximum pore diameter of the other hole When the system is B, the ratio B/A system is in the range of 20 to 50. The holding mat according to claim 2, wherein in the resin sheet, The porosity of the lower layer portion is 75% or more and 90% or less, and the porosity of the upper layer portion is 40% or more and 50% or less. The holding mat according to the second aspect of the invention, wherein the lower layer portion of the resin sheet has a total area of the hole formed by the foaming per unit area in a cross section parallel to the holding surface The profile is one of the largest profiles, and the maximum of the ratio of the profile is between 80% and 95%. The holding mat of claim 2, wherein the resin sheet is formed of a polyurethane resin. The holding mat of claim 5, wherein the polyurethane resin has a 100% modulus value of less than 20 MPa. The holding mat according to claim 1, wherein an adhesive material is further coated on the back side of the resin sheet to mount the resin sheet in a grinder. The holding mat of claim 7, further comprising a support material attached between the resin sheet and the adhesive material to support the resin sheet.