Development of Orderly Micro Asperity on Polishing Pad Surface for Chemical Mechanical Polishing (CMP) Process using Anisotropic Etching

Abstract

CMP is one of the most essential processes in ULSI manufacture. However, the polishing characteristics during CMP remain unidentified because pad surface roughness such as asperity or texture is complicated and random. Thus, this study specifies the orderly micro asperity arrayed on surface of a polishing pad instead of complicated random asperity on conventional pad, in order to discuss and to improve the polishing performance. Particularly, design of surface geometry on polishing pad is proposed and then its orderly micro patterned pad has been firstly developed by applying lithographic technology, which is commonly used in MEMS manufacturing process. The orderly micro pyramidal asperity’s design has 12 μm pitch with base width of 7 x 7 μm 2 and 4.95 μm height. Next our developed pad surface was 3D-microscopically observed. The dimension errors of the micro pyramid were less than 0.5 μm. Furthermore, the duplicating process of the micro patterned pad also has been developed for mass production trial. Finally, the developed pads were employed in CMP experiments in order to compare the material removal characteristic of the micro pyramidal asperity pad with a conventional pad. As the experimental results, the MRR (material removal rate) of the developed pad trended similar to that of a conventional pad, and the unobservable MRR of non-asperity pad, implying efficiency of the orderly asperity