Polishing pad with improved crosslinking density and process for preparing the same
The present invention provides a polishing pad whose crosslinking density is adjusted to enhance the performance of the CMP process such as polishing rate and cut pad rate. In addition, in the process for preparing a polishing pad according to the embodiment, it is possible to implement such a crosslinking density by a simple method of controlling the preheating temperature of the mold for curing. Thus, the polishing pad may be applied to a process of preparing a semiconductor device, which comprises a CMP process, to provide a semiconductor device such as a wafer of excellent quality.
1. A polishing pad, which comprises a polishing layer comprising a porous polyurethane-based resin, wherein the polishing layer has a swelling ratio of 100% to 350% in dimethylformamide (DMF) based on the volume or weight of the polishing layer, and
the polishing layer has a swelling ratio of 150% to 450% in N-methyl-2-pyrrolidone (NMP) based on the volume or weight of the polishing layer, when the polishing layer is stored in each of DMF and NMP at room temperature for 24 hours.
2. The polishing pad of claim 1 , wherein the polishing layer has a swelling ratio of 150% to 300% in DMF based on the volume of the polishing layer and a swelling ratio of 200% to 350% in DMF based on the weight of the polishing layer.
3. The polishing pad of claim 1 , wherein the polishing layer has a swelling ratio of 200% to 350% in NMP based on the volume of the polishing layer and a swelling ratio of 300% to 450% in NMP based on the weight of the polishing layer.
4. The polishing pad of claim 1 , wherein the porous polyurethane-based resin comprises a first crosslinking unit in which two urethane groups are crosslinked by a diisocyanate.
5. The polishing pad of claim 4 , wherein the first crosslinking unit comprises a structure of Formula 1:
6. The polishing pad of claim 1 , wherein the porous polyurethane-based resin comprises a second crosslinking unit in which two urea groups are crosslinked by a diisocyanate.
7. The polishing pad of claim 6 , wherein the second crosslinking unit comprises a structure of Formula 2:
8. The polishing pad of claim 1 , wherein the polishing layer has an elongation of 100% to 120% and a modulus of 30 kgf/cm 2 to 100 kgf/cm 2 .
9. The polishing pad of claim 1 , wherein the polishing layer has a polishing rate (or removal rate) of 3,000 Å/min to 4,000 Å/min against a silicon oxide layer.
10. A process for preparing a semiconductor device, which comprises polishing the surface of a semiconductor substrate using a polishing pad, wherein the polishing pad comprises a polishing layer comprising a porous polyurethane-based resin, and the polishing layer has a swelling ratio of 100% to 350% in dimethylformamide (DMF) based on the volume or weight of the polishing layer, and wherein the polishing layer has a swelling ratio of 150% to 450% in N-methyl-2-pyrrolidone (NMP) based on the volume or weight of the polishing layer, when the polishing layer is stored in each of DMF and NMP at room temperature for 24 hours.