KR20120073200A - Supporting pad - Google Patents

Abstract

The holding pad which can improve the flatness precision of a holding surface, and can improve the in-plane uniformity of a to-be-polished object. The holding pad 10 is provided with the urethane sheet 2. The urethane sheet 2 is formed by the wet coagulation method, and has the holding surface Sh for holding a to-be-polished object. The urethane sheet 2 has a skin layer 2a having a fine porous structure, and a plurality of foams 3 covering almost the entire thickness are formed inward from the skin layer 2a. In the urethane sheet 2, when it is set as thickness t, the bottom part of foam 3 is formed in the range from the back surface Sr to the inner side by thickness of 0.1t. In the lower layer portion Pr sandwiched between a cross section parallel to the back surface Sr on the inside by a thickness of 0.1t from the back surface Sr and a cross section parallel to the back surface Sr on the inside by a thickness of 0.4t, on the foam 3 Porosity is adjusted to a range of 75 to 95%. The amount of compressive strain in the lower layer portion Pr increases during polishing.

Description

Retention pad {SUPPORTING PAD}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a holding pad, and more particularly, to a holding pad provided with a resin sheet having a holding surface for forming a vertical foam by a wet coagulation method and for holding a polished object.

On the surface (processed surface) of various materials (abrasives), such as a semiconductor wafer WF, a glass substrate for a flat panel display (FPD), and a substrate for a hard disk, two surface plates are disposed to face each other in order to improve flatness. Polishing using a polishing machine is performed. Among these abrasives, for example, in the semiconductor WF, the abrasives supplied to the polishing process tend to increase in size in accordance with the miniaturization of portable devices to be used. In addition, in the glass substrate for FPD, in order to cope with the enlargement and thickness of FPD itself, there exists a tendency for the glass substrate which is a to-be-polished to enlarge and thin. There is an increasing demand for flatness even for such large and thinned abrasives.

When polishing the object to be polished, for example, one surface, a polishing pad is mounted on one surface plate of the polishing machine, and the polishing object is held on the other surface plate to face the polishing pad. At the time of grinding | polishing processing, the grinding | polishing slurry containing abrasive grains is supplied between a to-be-grinded object and a polishing pad, and a polishing pressure (pressing force) is applied to a to-be-grinded object. In order to prevent the to-be-damaged object from being damaged by contact with the surface plate, a holding pad is usually attached to the surface plate holding the object to be polished. That is, as the holding pad, the to-be-polished material can be temporarily held in the polishing process.

As the holding pad, a holding pad provided with a soft urethane film (resin sheet) having a foam structure formed by a wet coagulation method is used (see, for example, JP 2006-62059 A). In the urethane film formed by the wet coagulation method, since the surface (oil level) of the surface layer (skin layer) has smoothness, it is excellent in the retention of a to-be-polished object. Moreover, from the surface layer, the vertical foaming of the magnitude | size over almost the thickness is formed inside. Therefore, the cushioning property can be exhibited when compressed by the polishing pressure during polishing. If the cushioning property is too low, unevenness occurs in the stress applied to the polished object by the polishing pressure, so that stress is concentrated on the protrusions of the polished object recessed to the holding pad side, and the stress concentration portion is excessively polished to generate polishing unevenness. On the contrary, when cushioning property becomes high, it becomes difficult to produce a nonuniformity in the stress which a to-be-polished object carries, and the surface smoothness of a to-be-polished object improves, but recession may become large and the holding pad itself may be ground. Therefore, in the wet coagulation method, the size and formation state of foaming are adjusted by selection of resin and various additives.

However, in the urethane film obtained by the conventional wet coagulation method, since vertical foaming is formed, there exists a problem that density nonuniformity arises in the resin part between foaming part and foaming. Therefore, the amount of compressive deformation at the time of applying the polishing pressure at the time of polishing processing is different between the foamed forming portion and the resin portion, and it is sufficient to satisfy the high flatness requirement for the thinned and enlarged polished materials as described above. none. In other words, if there is a density nonuniformity in the holding pad, since the magnitude of the stress applied to the object to be polished is locally different, it is difficult to uniformly grind the processed surface over the entire area, thereby impairing the in-plane uniformity. If the nonuniformity of the amount of compression deformation can be reduced and the flatness accuracy of a holding surface can be improved, it becomes possible to satisfy the high in-plane uniformity requirement with respect to a to-be-grinded object.

This invention makes it a subject to provide the holding pad which can raise the flatness precision of a holding surface, and can improve the in-plane uniformity of a to-be-polished object in view of the said case.

MEANS TO SOLVE THE PROBLEM In order to solve the said subject, this invention is a holding pad provided with the resin sheet which has a holding | maintenance surface for holding | maintenance of a to-be-formed type | mold foaming by the wet coagulation | solidification method, and the said resin sheet is the back surface of the said holding surface. The bottom of the foam is formed in the range from to the inner side by 10% of the whole thickness, while the cross section parallel to the rear side and the inner side by 40% from the rear side by 10% of the entire thickness from the rear side. The porosity of the lower layer portion sandwiched between the cross sections parallel to the rear surface is 70% or more and 95% or less.

In the present invention, since the porosity of the lower layer portion by the predetermined thickness on the back side of the resin sheet holding surface is 70% or more and 95% or less, the cushioning force is ensured by the lower layer portion, so that the load applied to the polished object is dispersed and compressed by polishing. Since the burden on the to-be-polished material is reduced by changing the foam shape in the lower layer part, the in-plane uniformity of a to-be-polished object can be improved by raising the flatness precision of a holding surface.

In this case, the resin sheet is foamed in a cross section parallel to the holding surface in the lower layer, with the average diameter of the hole formed by foaming in the cross section parallel to the holding surface in the inner side by 10% of the entire thickness from the holding surface. When the maximum diameter of the hole formed by B is made into B, it is preferable that ratio B / A is the range of 20-50. In addition, the porosity of the upper layer portion sandwiched between the cross section parallel to the holding surface from the inside by 10% of the entire thickness from the holding surface of the resin sheet and the cross section parallel to the holding surface from the inside by 40% may be 35% or more and 55% or less. Can be. The porosity of the lower layer portion of the resin sheet is preferably 75% or more and 90% or less, and the porosity of the upper layer portion is preferably 40% or more and 50% or less. Moreover, in the lower layer part of a resin sheet, the maximum value of a ratio can be made into 80% or more and 95% or less in the cross section which the ratio of the total area of the hole formed by foaming per unit area among the cross sections parallel to a holding surface shows the maximum. You may form a resin sheet with a polyurethane resin. The polyurethane resin between foaming of a resin sheet may be formed in the fine porous shape. At this time, it is preferable to make 100% modulus of polyurethane resin smaller than 20 Mpa. Moreover, the adhesive material for attaching to a grinder may be apply | coated to the back side of a resin sheet. At this time, the support material for supporting a resin sheet can be further bonded between a resin sheet and an adhesive material.

According to the present invention, since the porosity of the lower layer portion by the predetermined thickness on the back side of the resin sheet holding surface is 70% or more and 95% or less, the cushioning property is further secured so that the load applied to the polished object is dispersed, which is accompanied by polishing. The pressure on the polished object is reduced by changing the foam shape at the lower layer when compressed, so that the effect of improving the flatness accuracy of the holding surface and improving the in-plane uniformity of the polished object can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing which shows typically the holding pad of embodiment to which this invention is applied.
FIG. 2: shows typically the formation state of foaming in the urethane sheet which comprises the holding pad of embodiment, (A) is sectional drawing of the thickness direction of a urethane sheet, (B) is B- of (A) It is explanatory drawing which shows typically the hole formed by foaming in B line cross section, (C) is explanatory drawing which shows typically the hole formed by foaming in C-C line cross section of (A).
3 is a cross-sectional view schematically showing a conventional holding pad.
FIG. 4: shows typically the formation state of foaming in the urethane sheet which comprises the conventional holding pad, (A) is sectional drawing of the thickness direction of a urethane sheet, (B) is B-B of (A) It is explanatory drawing which shows typically the hole formed by foaming in the cross section, and (C) is explanatory drawing which shows typically the hole formed by foaming in C-C line cross section of (A).
It is a graph which shows the opening ratio of the hole formed by foaming in the cross section for every thickness with respect to the thickness from the holding surface of the urethane sheet which comprises a holding pad.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of the holding pad which applied this invention with reference to drawings is demonstrated.

(Configuration)

As shown in FIG. 1, the holding pad 10 of this embodiment is equipped with the urethane sheet 2 as a resin sheet manufactured from the polyurethane resin. The urethane sheet 2 is formed by the wet coagulation method, and has the holding surface Sh for holding a to-be-polished object.

The urethane sheet 2 has the skin layer 2a in which dense fine pores were formed over the thickness of about several micrometers just under the holding surface Sh. That is, the skin layer 2a has a fine porous structure. In the inner side (inside) from the skin layer 2a of the urethane sheet 2, many foam 3 is formed in the state distributed substantially equally. The foam 3 has the size of almost the thickness of the urethane sheet 2, and is formed in the shape of a long, rounded cone in the thickness direction. Since the urethane sheet 2 has the skin layer 2a, the opening of the foam 3 is not formed in the holding surface Sh. Moreover, in the urethane sheet 2, the bottom part of the foam 3 is formed in the range from the back surface (hereinafter referred to as back surface Sr) of the holding surface Sh to 10% of the whole thickness. In the polyurethane resin between the foams 3, fine pores (not shown) smaller than the foams 3 are formed. In the urethane sheet 2, the fine pores of the skin layer 2a, the foam 3 and the fine pores communicate in a mesh shape, and have a continuous foam structure in which the foam is formed in a continuous foam shape.

In the urethane sheet 2, the lower layer portion Pr sandwiched between a cross section parallel to the back surface Sr from the back surface Sr by 10% of the entire thickness and a cross section parallel to the back surface Sr from the inside by 40%. The porosity of is adjusted to 70% or more and 95% or less. That is, when the thickness t of the urethane sheet 2 is set, in the lower layer portion Pr sandwiched between the inner end face by the thickness of 0.1t and the inner end face by the thickness of 0.4t from the back surface Sr, Porosity is in the range of 75 to 95%. On the other hand, from the holding surface Sh, the upper layer Ph interposed between the cross section parallel to the holding surface Sh from the inside by 10% of the entire thickness and the cross section parallel to the holding surface Sh from the inside by 40%. The porosity is adjusted to 35% or more and 55% or less. That is, in the upper layer Ph interposed between the inner end face by the thickness of 0.1t and the inner end face by the thickness of 0.4t from the holding surface Sh, the porosity by the foaming 3 is in the range of 35 to 55%. The porosity of such upper layer Ph and lower layer Pr can be adjusted by selecting the polyurethane resin to be used and setting conditions of a wet coagulation method (it will be explained in detail below).

Moreover, in the urethane sheet 2, let A be the average diameter of the hole formed by foaming 3 in the cross section parallel to the holding surface Sh from the inside by 10% of the whole thickness from the holding surface Sh, In the cross section parallel to the back surface Sr in the lower layer part Pr, the maximum aperture of the hole formed in the cross section in which the ratio of the total area of the hole formed by the foam 3 per unit area (hereinafter referred to as opening ratio) is the maximum value is shown. When B is used, the ratio B / A of the maximum aperture B to the average aperture A is adjusted in the range of 20 to 50. That is, the foam having a foam diameter of 20 to 50 times the size of the foam formed near the holding surface Sh is formed in the cross section in which the opening ratio at the lower layer portion Pr exhibits the maximum value. In addition, the maximum value of the aperture ratio is adjusted to 80% or more and 95% or less.

In this urethane sheet 2, compared with the hole formed in the cross section parallel to the holding surface Sh in the holding surface Sh, the hole formed in the cross section parallel to the back surface Sr in the vicinity of the back surface Sr is adjacent. Formed. As shown in Fig. 2A, the position in the vicinity of the holding surface (Sh) from the holding surface (Sh) by 10% of the thickness (t) of the urethane sheet (2), that is, by 0.1t (in position of the arrow B) The vicinity of the back surface Sr is set to a position (position of the arrow C) inward by 0.1t from the back surface Sr. In this case, as shown to FIG. 2B, in the B-B line cross section vicinity of holding surface Sh, the hole formed by foaming 3 is formed so that spaced apart from each other. On the other hand, as shown to FIG. 2C, the hole formed by foaming 3 adjoins in the C-C line cross section of back surface Sr vicinity.

Moreover, as for the holding pad 10, the double-sided tape 7 as an adhesive material for attaching the holding pad 10 to a grinder is bonded to the back surface Sr side of the urethane sheet 2. The double-sided tape 7 has a base material not shown, and pressure-sensitive adhesive layers (not shown) such as an acrylic pressure-sensitive adhesive are formed on both surfaces of the base material, respectively. As the base material, for example, a flexible film such as a film made of polyethylene terephthalate (hereinafter abbreviated as PET) is used. The double-sided tape 7 is bonded to the urethane sheet 2 in the pressure-sensitive adhesive layer on one side of the base material, and the pressure-sensitive adhesive layer on the other side (the side opposite to the urethane sheet 2) covers the surface with the release paper 8. . In addition, in this example, the base material of this double-sided tape 7 also serves as the support material for supporting the urethane sheet 2.

(Produce)

The holding pad 10 is manufactured by bonding the urethane sheet 2 and the double-sided tape 7 formed by the wet coagulation method. That is, the preparation process of preparing a polyurethane resin solution, the polyurethane resin solution is apply | coated to a film-forming base material, the coagulation | solidification regeneration process which solidifies a polyurethane resin solution and regenerates a polyurethane resin in a coagulation liquid, and wash | cleans a sheet-like polyurethane resin The holding pad 10 is manufactured through the washing and drying process of drying and the lamination process of bonding the obtained urethane sheet 2 and the double-sided tape 7 together. Hereinafter, it demonstrates in process order.

In the preparation step, the polyurethane resin is dissolved by mixing a polyurethane resin, a water miscible organic solvent which can dissolve the polyurethane resin, and an additive. Examples of the organic solvent include N, N-dimethylformamide (hereinafter abbreviated as DMF), N, N-dimethylacetamide (DMAc) and the like, but DMF is used in this example. The polyurethane resin can be selected from resins such as polyesters, polyethers, and polycarbonates. However, in order to form the above-mentioned foamed structure, a resin solution in which a polyurethane resin is dissolved at 20% by weight in DMF is used. About the resin, the resin of the range of 5-10 Pa.s of the viscosity measured at 25 degreeC using the Brookfield rotational viscometer is selected and used. Moreover, it is preferable that the polyurethane resin to be used has 100% modulus smaller than 20 Mpa. This polyurethane resin is melt | dissolved in DMF so that it may become the range of 10-30 weight%. Moreover, in order to control the size and quantity (number) of foam 3, pigments, such as carbon black, a hydrophilic additive which promotes foaming, a hydrophobic additive which stabilizes the regeneration of a polyurethane resin, etc. can be used. The obtained solution is defoamed under reduced pressure to obtain a polyurethane resin solution.

In the solidification regeneration step, the polyurethane resin solution obtained in the preparation step is uniformly applied in a sheet form to a strip-shaped film-forming base material by a coating apparatus such as a knife coater at room temperature. At this time, application | coating thickness (coating amount) of a polyurethane resin solution is adjusted by adjusting the clearance (clearance) of a knife coater etc. and a film-forming base material. As the film-forming substrate, a resin film, a fabric, a nonwoven fabric, or the like can be used, but in this example, a PET film is used.

The polyurethane resin solution applied to the film-forming substrate is continuously guided into a coagulation solution (aqueous coagulation solution) mainly containing water as a poor solvent with respect to the polyurethane resin. In order to adjust the regeneration rate of a polyurethane resin, you may add organic solvent, such as a polar solvent other than DMF and DMF, to a coagulation liquid, but water is used in this example. In the coagulation solution, a film is first formed at the interface between the polyurethane resin solution and the coagulation solution, and anhydrous fine pores constituting the skin layer 2a are formed in the polyurethane resin immediately below the film. Thereafter, the regeneration of the polyurethane resin having a continuous foam structure proceeds due to the cooperative phenomenon of diffusion of DMF into the coagulating solution of the polyurethane resin solution and intrusion of water into the polyurethane resin. At this time, since the PET film of the film forming base material does not penetrate water (coagulation liquid), the substitution of DMF and water occurs on the skin layer 2a side, and the film forming base material side is larger than the skin layer 2a side foam 4 Is formed.

Here, the foam formation accompanying the regeneration of the polyurethane resin will be described. In the polyurethane resin, since the cohesive force becomes large, regeneration is rapidly progressed in the polyurethane resin immediately under the coating to form the skin layer 2a. In this example, a polyurethane resin having a 100% modulus of less than 20 MPa is used. Moreover, the viscosity of a polyurethane resin solution shows the range of 5-10 Pa.s. That is, the polyurethane resin solution which melt | dissolved the low modulus polyurethane resin so that it may become low viscosity is used. Therefore, after the skin layer 2a is formed, the polyurethane resin in the polyurethane resin solution before solidification moves to the skin layer 2a side and aggregates. In connection with this, since the amount of polyurethane resin reduces on the film-forming base material side, the foaming 3 which enlarged compared with the skin layer 2a side is formed. In other words, as compared with the upper layer Ph, in the lower layer Pr, as the foam 3 enlarges, the porosity increases. In addition, skin layer 2a, foaming 3 and fine pores are formed by desolvation from the polyurethane resin solution of DMF, that is, DMF and water, and fine pores and foaming of skin layer 2a ( 3) and fine pores communicate in a mesh shape. In addition, since the polyurethane resin is regenerated on the film forming substrate, the opening of the foam 3 is not formed on the back surface Sr formed in contact with the surface of the film forming substrate.

In the washing and drying step, the polyurethane resin regenerated in the regeneration step is washed in a washing solution such as water to remove DMF remaining in the polyurethane resin and then dried. In drying of a polyurethane resin, in this example, the cylinder dryer provided with the cylinder which has a heat source inside is used. The polyurethane resin is dried by passing along the circumferential surface of the cylinder. The urethane sheet 2 obtained is wound in a roll form.

In the lamination process, the urethane sheet 2 and the double-sided tape 7 produced by the wet coagulation | solidification method are bonded together. At this time, the back surface Sr of the urethane sheet 2 and the double-sided tape 7 are bonded together. Then, after cutting into a desired shape and size, such as a circle or a square, the holding pad 10 is completed by inspection such as confirming that there is no adhesion of scratches, contamination, foreign matters, or the like.

(Action, etc.)

Next, operation | movement etc. of the holding pad 10 of this embodiment are demonstrated.

In order to demonstrate easily, the foam structure of the urethane sheet formed by the conventional wet coagulation method is demonstrated. In the conventional wet coagulation method, a polyurethane resin solution coated on a film formation substrate such as a PET film is solidified in a coagulation solution such as water. Therefore, as shown in FIG. 3, in the urethane sheet 12 which comprises the conventional holding pad 20, the thickness of the urethane sheet 12 is inward from the skin layer 12a formed initially at the time of wet solidification. Almost a whole number of foams 13 are formed. The foaming 13 has a diameter smaller on the holding surface Sh side than the back surface Sr side, and is formed in the vertical direction so as to follow the thickness direction.

Moreover, in the urethane sheet 12, the hole formed in the cross section parallel to the holding surface Sh in the vicinity of the holding surface Sh, and the hole formed in the cross section parallel to the back surface Sr in the vicinity of the back surface Sr are all spaced apart. It is formed to be. Since the diameter of the foam 13 is larger on the back surface Sr side than on the holding surface Sh side, the holding surface Sh side is larger as a spaced amount. That is, as shown in FIG. 4A, the inner surface (position of arrow B) and the rear surface Sr near the holding surface Sh by 10% of the thickness of the urethane sheet 12 from the holding surface Sh. It is set as the position (position of the arrow C) by 10% of the thickness of the urethane sheet 12 from (Sr). In this case, as shown to FIG. 4B, the hole formed by foaming 13 is formed in the B-B cross section vicinity of holding surface Sh so that spaced apart. As shown in FIG. 4C, it is also spaced apart from the hole formed by foaming 13 at the C-C cross section near the back surface Sr. Although the hole formed in the C-C line cross section is closer than the hole formed in the B-B line cross section, the hole formed in the cross section near the back surface Sr of the urethane sheet 2 which comprises the holding pad 10 mentioned above and They are formed spaced apart from each other (see FIG. 2C). In such a urethane sheet 12, considering the same area | region as the upper layer Ph and lower layer Pr in the urethane sheet 2 mentioned above, the porosity of an upper layer part is about 30 to 45%, and the porosity of a lower layer part is 70 It is about% or less.

In the conventional holding pad 20 using the urethane sheet 12, a density nonuniformity arises in the part in which the foam 13 was formed, and the resin part between the foam 13. Therefore, the amount of compressive deformation at the time of applying the polishing pressure at the time of polishing processing differs between the foaming forming portion and the resin portion, and it is difficult to satisfy the high flatness requirement for the polished object. That is, in the holding pad 20, since density nonuniformity arises and the magnitude | size of the stress applied to a to-be-polished object differs locally, it becomes difficult to uniformly grind the process surface of a to-be-polished object over the whole area | region. Therefore, in the holding pad 20, it cannot be said that it is enough to satisfy the high precision flatness calculated | required by the glass substrate for WF and FPD for semiconductors which tend to enlarge and thin.

On the other hand, in this embodiment, it is parallel with the back surface Sr from the back surface Sr of the urethane sheet 2 which comprises the holding pad 10 by 10% of the thickness t (by 0.1t). The porosity of the lower layer portion Pr sandwiched between the end face and the end face parallel to the back surface Sr by 40% (by 0.4t) is adjusted to 70% or more and 95% or less. Moreover, in the lower layer part Pr with respect to the average diameter A of the hole formed by foaming 3 in the cross section parallel to the holding surface Sh inwardly by 10% of the whole thickness from the holding surface Sh, The ratio B / A of the largest diameter B of the hole formed in the cross section which shows the maximum value among openings in the cross section parallel to the back surface Sr of is adjusted to the range of 20-50. In other words, the foam having a foam diameter of 20 to 50 times the average diameter of the foam formed near the holding surface Sh is formed in the cross section in which the opening ratio in the lower layer portion Pr exhibits the maximum value. Therefore, the lower layer portion Pr, which is flexible and has abundant foam 3, acts as an air cushion, so that the pressure (polishing pressure) applied to the polished object can be easily dispersed. In addition, when compressed along with polishing, the foam shape in the lower layer portion Pr is deformed in accordance with the pressure applied to the polished object, so that the burden (repulsive stress) on the polished object is reduced in accordance with the warpage and the undulation of the polished object. Since it can reduce, the flatness of a to-be-polished object can be improved highly. In consideration of securing the compressive deformation amount in the lower layer portion Pr, it is preferable to adjust the porosity of the lower layer portion Pr in the range of 75 to 90%.

Moreover, in this embodiment, the maximum value of the opening ratio which shows the ratio of the total area of the hole formed by foaming 3 per unit area among the cross sections parallel to the back surface Sr in lower layer part Pr is 80% or more and 95%. It is adjusted to the following. Therefore, the diameter of the foam 3 is enlarged in the lower layer part Pr, especially near the back surface Sr, and sufficient cushioning property can be ensured. Thereby, since the stress with respect to a to-be-polished object is equalized at the time of grinding | polishing processing, flatness improvement can be aimed at. Similarly to the porosity of the lower layer portion Pr, in consideration of securing the compression deformation amount, it is preferable to adjust the aperture ratio in the range of 82 to 90%.

In the present embodiment, from the holding surface Sh of the urethane sheet 2, the cross section parallel to the holding surface Sh from the inside by 10% (by 0.1t) of the thickness t and by 40% (0.4) The porosity of the upper layer Ph interposed between the end faces parallel to the holding surface Sh from the inner side by t) is adjusted to 35% or more and 55% or less. Therefore, since the partition of a polyurethane resin becomes thick and rigidity is ensured compared with lower layer part Pr, depression to the holding pad side of a to-be-polishing object can be suppressed at the time of grinding | polishing processing. If the holding pads have insufficient rigidity and the recessed object is large, the holding pad (urethane sheet) itself may be ground during polishing. On the other hand, since holding of the to-be-polished material is suppressed in the holding pad 10, grinding | polishing process can be continued without grinding the urethane sheet 2. If the porosity of the upper layer Ph is less than 35%, the stiffness is increased but the hardness is increased, so that it is difficult to improve the flatness. In consideration of securing rigidity from the viewpoint of improving the flatness, it is preferable to adjust the porosity of the upper layer portion Ph in the range of 40 to 50%.

Furthermore, in this embodiment, since the urethane sheet 2 has the above-mentioned foamed structure, the rigidity necessary for suppressing the depression of the to-be-polished material is ensured at the upper layer Ph, and the stress to the to-be-polished object is lowered at the lower layer Pr. Since the cushion property required for equalization of the sheet is secured, the one urethane sheet 2 can make both the rigidity and the cushion property compatible. Although it is also possible to join and comprise the resin sheet which has rigidity, and the resin sheet which has cushion characteristics, in this case, two resin sheets may peel at the time of grinding | polishing processing. Therefore, in the holding pad 10, the urethane sheet 2 has rigidity and cushioning property, and the flatness of a to-be-polished object can be aimed at.

In addition, in this embodiment, although the holding pad 10 provided with the urethane sheet 2 made of polyurethane resin was illustrated, this invention is not limited to this. Instead of the polyurethane resin, for example, a resin such as polyethylene may be used, and there is no particular limitation as long as it is a resin capable of forming the above-described foamed structure by a wet coagulation method.

Moreover, in this embodiment, although the holding pad 10 which comprised the urethane sheet 2 and the double-sided tape 7 which has a base material was bonded together was illustrated, this invention is not limited to this. As the holding pad, the urethane sheet 2 and the pressure-sensitive adhesive for mounting on the polishing machine may be provided. For example, instead of the double-sided tape 7, only the various pressure-sensitive adhesives are used on the back surface of the urethane sheet 2 ( Sr)) may be applied. In addition, in this embodiment, although the base material of the double-sided tape 7 showed the example which serves as the support material of the holding pad 10, this invention is not limited to this, The urethane sheet 2 and the double-sided tape 7 are shown. You may make it join another support material. There is no restriction | limiting in particular as such a support material, Film, such as PET, Nonwoven fabric, etc. are mentioned.

Moreover, in this embodiment, although not specifically mentioned, when the thickness nonuniformity of the urethane sheet 2 formed by the wet coagulation | solidification method became large, the back surface Sr side was made so that the holding surface Sh and the back surface Sr might become parallel. It is preferable to make it smooth by methods, such as a buff and a slice. In this way, the flatness of the holding surface Sh can be further improved.

Example

Next, the Example of the holding pad 10 manufactured by this embodiment is demonstrated. Moreover, the comparative example manufactured for comparison is also demonstrated together.

(Example 1)

In Example 1, 100% resin modulus was used to prepare the urethane sheet 2, and 10 MPa of polyester MDI (diphenyl methane diisocyanate) polyurethane resin was dissolved in DMF at a ratio of 18% by weight. 1 weight% of a hydrophilic additive with respect to a polyurethane resin, and 5 weight% of carbon black with respect to a polyurethane resin were added, and the polyurethane resin solution which has a viscosity of 3.3 Pa * s was prepared with the B type rotational viscometer. When applying the polyurethane resin solution, the clearance of the coating device was set to 0.7 mm. After apply | coating a polyurethane resin solution to the film-forming base material of PET film, it immersed in water (coagulation liquid) of temperature 25 degreeC, and the polyurethane resin was fully regenerated. After washing and drying, the back surface (Sr) side of the obtained urethane sheet 2 was buffed, the double-sided tape 7 was bonded to the buff surface, and the holding pad 10 was produced.

(Example 2)

In Example 2, the same polyurethane resin as in Example 1 was dissolved in DMF in a proportion of 20% by weight, and then 1% by weight of hydrophilic additive based on the polyurethane resin, and 5% by weight of carbon black based on the polyurethane resin. Was added and the polyurethane resin solution which has a viscosity of 5.3 Pa * s was prepared with the B-type rotational viscometer. The clearance of the coating device was set to 1.0 mm, the polyurethane resin solution was applied to the film-forming substrate, and then immersed in water at a temperature of 10 ° C. to completely regenerate the polyurethane resin. After washing and drying, the back surface (Sr) side of the obtained urethane sheet 2 was buffed, the double-sided tape 7 was bonded to the buff surface, and the holding pad 10 was produced.

(Example 3)

In Example 3, the same polyurethane resin as in Example 1 was dissolved in DMF in a proportion of 21% by weight, then 3% by weight of hydrophilic additive based on the polyurethane resin, and 5% by weight of carbon black based on the polyurethane resin Was added and the polyurethane resin solution which has a viscosity of 8.2 Pa.s was prepared with the B-type rotational viscometer. The clearance of the coating device was set to 1.0 mm, the polyurethane resin solution was applied to the film-forming substrate, and then immersed in water at a temperature of 10 ° C. to completely regenerate the polyurethane resin. After washing and drying, the back surface (Sr) side of the obtained urethane sheet 2 was buffed, the double-sided tape 7 was bonded to the buff surface, and the holding pad 10 was produced.

(Example 4)

In Example 4, the same polyurethane resin as in Example 1 was dissolved in DMF in a proportion of 21% by weight, and then 5% by weight of hydrophilic additive based on the polyurethane resin, and 5% by weight of carbon black based on the polyurethane resin. Was added and the polyurethane resin solution which has a viscosity of 7.9 Pa * s was prepared with the B-type rotational viscometer. The clearance of the coating device was set to 1.0 mm, the polyurethane resin solution was applied to the film-forming substrate, and then immersed in water at a temperature of 25 ° C. to completely regenerate the polyurethane resin. After washing and drying, the back surface (Sr) side of the obtained urethane sheet 2 was buffed, the double-sided tape 7 was bonded to the buff surface, and the holding pad 10 was produced.

(Example 5)

In Example 5, the same polyurethane resin as in Example 1 was dissolved in DMF at a ratio of 21.5% by weight, then 1% by weight of hydrophilic additive based on the polyurethane resin, and 5% by weight of carbon black based on the polyurethane resin. Was added and the polyurethane resin solution which has a viscosity of 9.5 Pa * s was prepared with the B-type rotational viscometer. The clearance of the coating device was set to 1.2 mm, the polyurethane resin solution was applied to the film-forming substrate, and then immersed in water having a temperature of 10 ° C. to completely regenerate the polyurethane resin. After washing and drying, the back surface (Sr) side of the obtained urethane sheet 2 was buffed, the double-sided tape 7 was bonded to the buff surface, and the holding pad 10 was produced.

(Comparative Example 1)

In Comparative Example 1, the same polyurethane resin as in Example 1 was dissolved in DMF at a ratio of 21% by weight, and then 1% by weight of hydrophilic additive based on the polyurethane resin, and 5% by weight of carbon black based on the polyurethane resin. Was added and the polyurethane resin solution which has a viscosity of 8.2 Pa.s was prepared with the B-type rotational viscometer. The clearance of the coating device was set to 0.7 mm, the polyurethane resin solution was applied to the film-forming substrate, and then immersed in water at a temperature of 25 ° C. to completely regenerate the polyurethane resin. After washing and drying, the back surface (Sr) side of the obtained urethane sheet 12 was buffed, the double-sided tape 7 was bonded to the buff surface, and the holding pad 20 was produced. That is, the holding pad 20 of the comparative example 1 is a conventional holding pad (refer FIG. 3).

(Rating 1)

About the urethane sheet of each obtained Example and a comparative example, the foam diameter ratio (Max / Min) which shows the ratio of the porosity of the upper layer part (Ph) and the lower layer part (Pr), the maximum value of an opening ratio, and the maximum foam diameter with respect to a minimum foam diameter was measured. . The porosity was measured as follows. That is, the cross section was scanned using the three-dimensional measurement X-ray CT apparatus (manufactured by Yamato Scientific, TDM1000-IS / SP), and a continuous tomographic image of 10 µm interval was obtained from the holding surface Sh. Each obtained tomographic image was image-processed by SEM image analysis software "Scandium" (made by Olympus Soft-Imaging Solutions), and each had an image with a tint. For each of the shaded images, the portion having a higher density was set as an opening so that the density range (threshold value) was coincident with the image, and integrated as the opening, whereby the ratio of the total opening area occupied per observation area was determined as the opening ratio. Subsequently, the sum of the aperture ratios obtained from the tomographic images in the regions of the upper layer Ph and the lower layer Pr was respectively obtained, and the percentage divided by the sum of the observation areas of the upper layer Ph and the lower layer Pr was defined as the porosity. As a simple method, such a porosity can be calculated by buffing or slicing from the surface of the urethane sheet by a predetermined thickness, and the porosity can be obtained by observing the grinding surface by SEM or microscope. The maximum value of the aperture ratio was calculated from the aperture ratio determined by the measurement of the porosity. Foam diameter ratio was calculated | required as follows. That is, the average opening diameter of the opening formed in the range of 3.3 mm2 in the cross section parallel to the holding surface Sh from the holding surface Sh to the inside of 10% of the entire thickness is calculated by using "Scandium" to minimize the opening. It was made into the foam diameter. Maximum opening diameter formed by using "Scandium" in the range of 3.3 mm <2> in the cross section which shows the maximum value of an opening ratio in the area | region of lower layer part Pr, and which does not contact the boundary of an observation area, using "Scandium" The ratio of the maximum foam diameter to the minimum foam diameter was obtained as the foam diameter ratio, since the minimum foam diameter and the maximum foam diameter correspond to the above-described average aperture A and maximum aperture B, respectively. The cost represents the ratio B / A described above, and the measurement results of the porosity, the maximum value of the opening ratio, and the foam diameter ratio are shown in Table 1 below.

As shown in Table 1, in the urethane sheet of the comparative example 1, the porosity of the upper layer part Ph was 41.4%, and the porosity of the lower layer part Pr was 68.6%. As is apparent from Fig. 5, the larger the thickness from the surface, that is, the closer to the back surface Sr, the larger the opening ratio, but the opening ratio is about 75% at maximum. On the other hand, in each urethane sheet 2 of Examples 1-5, the porosity of the upper layer Ph was 38.3%-50.2%, and the porosity of the lower layer Pr was 77.2-88.3%. Moreover, in the urethane sheet 2 of Example 1, as shown in FIG. 5, the opening ratio exceeding 80% continuously is shown in the cross section over thickness of 100 micrometers or more in the thickness area of lower layer part Pr. As a result, in the urethane sheet 2 of each example, it was found that the porosity of the upper layer Ph was about the same as that of Comparative Example 1, but the porosity of the lower layer Pr was large. In addition, from the measurement result of foam diameter ratio, in the comparative example 1, the largest foam diameter in lower layer part Pr was 18.7 times with respect to the average aperture diameter near the holding surface Sh, In each Example, it is 34.0-38.2 times. It became clear that size was shown

(Evaluation 2)

Using the holding pad of each Example and a comparative example, the glass substrate (470 mm x 370 mm x 0.7 mm) for liquid crystal displays is grind | polished on the following polishing conditions, and Japanese Industrial Standards (JIS B 0601: '82) Flatness (a) was calculated | required from the filter center undulation by the method according to). In the measurement of flatness (a), it measured on the following measurement conditions using the surface roughness shape measuring instrument (Tokyo Precision Co., Ltd. product, SURFCOM480A). From the measurement curve obtained due to the irregularities of the substrate surface, the width W between the convex portions (mountains) and the convex portions adjacent to each other, and the height S of the convex portions and the concave portions (bones) are calculated. , And the distribution chart which made width W the horizontal axis and height S the vertical axis was created. From the distribution chart, the approximate straight line of linear equation S = aW was calculated | required and the inclination a was made into the final flatness a after grinding | polishing process. As the flatness increases, the width W increases and the height S decreases, so that the smaller the inclination a, the better the flatness. The measurement result of flatness (a) was shown in Table 1 together.

(Polishing condition)

Grinding machine used: Oscar polishing machine (SP-Palm, SP-1200)

Polishing Speed (Rotation Speed): 61rpm

Working pressure ： 76gf / cm ²

Slurry: Cerium Slurry

Polishing time: 30min

(Filter center relief measurement conditions)

Evaluation length: 90mm

Measurement speed: 3.0mm / s

Cut-off value: 0.8-8.0mm

Filter type: 2RC

Measurement range: ± 40.0μm

Tilt correction: Spline

As shown in Table 1, in the grinding | polishing process using the holding pad 20 of the comparative example 1, the flatness (a) of the glass substrate after processing showed 0.0007. On the other hand, in the grinding | polishing process using each holding pad 10 of Examples 1-5, the flatness a showed 0.0003-0.0005, and all showed the outstanding result compared with the comparative example 1. Therefore, the urethane sheet (3) formed by the wet coagulation | solidification method is formed in the range whose porosity in the upper layer Ph is 35-55%, and in the range which the porosity in the lower layer Pr is 70-95% ( By using the holding pad 10 provided with 2), it became clear that the flatness accuracy of the holding surface Sh and the in-plane uniformity of the to-be-polished object can be improved.

Industrial availability

Since this invention provides the holding pad which can raise the flatness precision of a holding surface, and can improve the in-plane uniformity of a to-be-polished object, since it contributes to manufacture and sale of a holding pad, it has industrial applicability.

Claims (10)

 In a holding pad having a resin sheet having vertical holding foam formed by a wet coagulation method and having a holding surface for holding a to-be-polished object, the resin sheet is extended from the rear surface of the holding surface to the inner side by 10% of the entire thickness. The bottom part of the foam is formed in the range of, while the porosity of the lower layer portion sandwiched between the end face parallel to the back face from the back side by 10% and the end face parallel to the back face by 40% from the inside The holding pad, which is 70% or more and 95% or less. The method of claim 1,
The said resin sheet has the average diameter of the hole formed by the said foaming in the cross section parallel to the said holding surface inside by 10% of the said whole thickness from the said holding surface as A, and is a cross section parallel to the said holding surface in the said lower layer part. A holding pad, wherein the ratio B / A is in the range of 20 to 50 when the maximum aperture of the hole formed by the foaming is set to B. The method of claim 2,
The resin sheet has a porosity of 35% or more and 55% or less between a cross section parallel to the holding surface at an inner side by 10% of the entire thickness from the holding surface and a cross section parallel to the holding surface at an inner side by 40%. A holding pad, characterized in that. The method of claim 3, wherein
The said resin sheet has the porosity of 75% or more and 90% or less of said lower layer part, and the retention pad of 40% or more and 50% or less of said upper layer part. The method of claim 2,
In the lower layer part of the said resin sheet, the holding pad of Claim 1 which is 80%-95% of the maximum of the said ratio in the cross section in which the ratio of the total area of the hole formed by the said foaming per unit area among the cross sections parallel to the said holding surface shows the maximum. The method of claim 3, wherein
The said resin sheet is formed with the polyurethane resin, The holding pad characterized by the above-mentioned. The method according to claim 6,
The said resin sheet is a holding pad characterized by the polyurethane resin between the said foams being formed in fine pore shape. The method of claim 7, wherein
The polyurethane resin has a holding pad, characterized in that 100% modulus is less than 20MPa. The method of claim 1,
And a pressure-sensitive adhesive material for mounting to a polishing machine on the rear side of the resin sheet. The method of claim 9,
A holding pad for bonding the resin sheet to the resin sheet and the pressure-sensitive adhesive is further bonded.

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