A method disclosed herein includes forming a polishing pad configured for a chemical-mechanical polishing (CMP) process and polishing a workpiece using the polishing pad and a CMP slurry. Forming the polishing pad includes forming an interpenetrating polymer network having a first phase and a second phase embedded in the first phase, removing the second phase from the interpenetrating polymer network, thereby forming a porous top pad that includes a network of pores embedded in the first phase, and adhering the porous top pad to a sub pad, thereby forming the polishing pad. The second phase is different from the first phase in composition, and the interpenetrating polymer network has a substantially periodic pattern. Surface roughness of the porous top pad is consistent during the polishing of the workpiece.