Porous polyurethane polishing pad and preparation method thereof
Embodiments relate to a porous polyurethane polishing pad for use in a chemical mechanical planarization (CMP) process of semiconductors and a process for producing the same. In the porous polyurethane polishing pad, it is possible to control the size and distribution of pores, whereby the polishing performance (i.e., polishing rate) of the polishing pad can be adjusted, by way of employing thermally expanded microcapsules as a solid phase foaming agent and an inert gas as a gas phase foaming agent.
1. A porous polyurethane polishing pad, which comprises a polyurethane resin and pores distributed in the polyurethane resin,
wherein in the pore size distribution of the pores based on the cross-sectional area of the polishing pad, the pore size at the maximum peak is smaller than the average pore size,
the pore size at the maximum peak is 18 to 28 μm,
the average pore size is 24 to 36 μm, and
the sum of the cross-sectional areas of the pores having a pore size larger than the pore size at the maximum peak by 15 μm or more is larger than the sum of the cross-sectional areas of the pores having a pore size larger than the pore size at the maximum peak by 10 μm to less than 15 μm,
wherein the porous polyurethane polishing pad contains the pores in an amount of 30 to 70% by volume based on the total volume of the polishing pad, and
wherein the porous polyurethane polishing pad has a tensile strength of 10 to 100 kgf/cm 2 and an elongation of 30% to 300%.
2. The porous polyurethane polishing pad of claim 1 , wherein the difference between the sum of the cross-sectional areas of the pores having a pore size larger than the pore size at the maximum peak by 15 μm or more and the sum of the cross-sectional areas of the pores having a pore size larger than the pore size at the maximum peak by 10 μm to less than 15 μm, based on 100% of the sum of the cross-sectional areas of the pores, is 1 to 10%.
3. The porous polyurethane polishing pad of claim 1 , wherein the difference between the sum of the cross-sectional areas of the pores having a pore size larger than the pore size at the maximum peak by 15 μm or more and the sum of the cross-sectional areas of the pores having a pore size larger than the pore size at the maximum peak by 10 μm to less than 15 μm, based on 100% of the sum of the cross-sectional areas of the pores, is 5 to 9%.
4. The porous polyurethane polishing pad of claim 1 , wherein the pores comprise first pores formed by a solid phase foaming agent and second pores formed by a gas phase foaming agent.
5. The porous polyurethane polishing pad of claim 4 , wherein the second pores comprise pores having a pore size larger than the pore size at the maximum peak by 15 μm or more and pores having a pore size smaller than the pore size at the maximum peak.
6. The porous polyurethane polishing pad of claim 1 , which further comprises a silicone-based surfactant; and at least one reaction rate controlling agent including at least one of a tertiary amine-based compound and an organometallic compound.
7. The porous polyurethane polishing pad of claim 1 , further comprising a reaction rate controlling agent, and wherein the reaction rate controlling agent comprises at least one selected from the group consisting of triethylene diamine, dimethyl ethanol amine, tetramethyl butane diamine, 2-methyl-triethylene diamine, dimethyl cyclohexyl amine, triethyl amine, triisopropanol amine, 1,4-diazabicyclo(2,2,2)octane, bis(2-methylaminoethyl) ether, trimethylaminoethylethanol amine, N,N,N,N,N″-pentamethyldiethylene triamine, dimethylaminoethyl amine, dimethylaminopropyl amine, benzyldimethyl amine, N-ethylmorpholine, N,N-dimethylaminoethylmorpholine, N,N-dimethylcyclohexyl amine, 2-methyl-2-azanorbornane, dibutyltin dilaurate, stannous octoate, dibutyltin diacetate, dioctyltin diacetate, dibutyltin maleate, dibutyltin di-2-ethylhexanoate, and dibutyltin dimercaptide.
8. The porous polyurethane polishing pad of claim 1 , the pore size at the maximum peak is smaller than the average pore size by 1 to 10 μm.
9. The porous polyurethane polishing pad of claim 1 , which has a polishing rate of silicon oxide (SiO x ) of 0.8 to 0.99 when the polishing rate of tungsten is 1.