CMP of PC, PMMA and SU-8 Polymers

Polymers such as PC (polycarbonate), PMMA (poly methyl methacryate) and SU-8 epoxy resin are replacing silicon as the major substrate in microfluidic system (or BioMEMS) fabrication. Chemical mechanical polishing (CMP) is an important technology for many advanced microelectromechanical system (MEMS) and micro-optoelectromechanical system applications. In this study, CMP of PC, PMMA and SU-8 polymers was investigated. Four types of slurry were tested for CMP of PC and PMMA. Experiments were then designed and performed to investigate effects of two key process parameters. The experimental results show that an increase in head load or table speed would cause an increase in material removal rates (MRRs). Within the chosen experimental parameter ranges, the variation of table speed introduced a more significant change in MRRs than that of head load. ANOVA was also carried out, and it was found that the interaction of head load and table speed had a significant (95% confidence) effect on surface finish of polished PMMA samples while table speed had a significant effect on surface finish of polished PC samples. CMP is also a process well suited for polishing high-aspect-ratio SU-8 structures. Polished PC, PMMA and SU-8 surfaces had nanometer-order surface roughness, acceptable to most MEMS applications.