Polishing pad, method of producing the same, and cushion layer for polishing pad
The polishing pad of this invention is a polishing pad effecting stable planarizing processing, at high polishing rate, materials requiring surface flatness at high level, such as a silicon wafer for semiconductor devices, a magnetic disk, an optical lens etc. This invention provides a polishing pad which can be subjected to surface processing to form a sheet or grooves, is excellent in thickness accuracy, attains a high polishing rate, achieves a uniform polishing rate, and also provides a polishing pad which is free of quality variations resulting from an individual variation, easily enables a change the surface patterns, enables fine surface pattern, is compatible with various materials to be polished, is free of burrs upon forming the pattern. This invention provides a polishing pad which can have abrasive grains mixed at very high density without using slurry, and generates few scratches by preventing aggregation of abrasive grains dispersed therein. The polishing pad of this invention has a polishing layer formed from a curing composition to be cured with energy rays, the polishing layer being formed surface pattern thereon by photolithography. The polishing pad of this invention comprises a polishing layer resin having abrasive grains dispersed therein, the resin containing ionic groups in the range of 20 to 1500 eq/ton.
1. A polishing pad having a polishing layer, wherein the polishing layer comprises:
a polishing surface layer having a concave-convex surface; and
a backside layer having a patterned surface, said backside layer having cushion property,
wherein the polishing surface layer and the backside layer are constituted by a common composition as a single piece.
2. The polishing pad according to claim 1 , wherein the polishing layer has a static friction coefficient of 1.49 or less and a dynamic friction coefficient of 1.27 or less with a glass under a loading of 4400 gf.
3. The polishing pad according to claim 1 , wherein the curing composition comprises a solid polymer compound.
4. The polishing pad according to claim 1 , wherein the backside of the polishing layer is provided with a cushion layer.
5. The polishing pad according to claim 4 , characterized in that the polishing layer is free of pores and has a storage elastic modulus of 200 MPa or more, and the storage elastic modulus of the cushion layer is lower than that of the polishing layer.
6. The polishing pad according to claim 1 , wherein the polishing layer comprises a polishing surface layer and a backside layer, and the hardness of the polishing surface layer is higher than the hardness of the backside layer, and the difference in hardness in Shore D hardness is 3 or more.
7. The polishing pad according to claim 1 , wherein the polishing surface layer and the backside layer have difference degrees of curing and different hardness.
8. The polishing pad according to claim 1 , characterized in that the surface of the polishing layer has concave and convex to form grooves through which slurry used in polishing flows.
9. The polishing pad according to claim 1 , characterized in that the surface of the polishing layer has concave and convex to form grooves in which slurry used in polishing is stored.
10. The polishing pad according to claim 1 , characterized in that the material to be polished therewith is a semiconductor wafer or a glass substrate for precision instruments.