(188e) Advancements In Materials and Processing for MEMS Packaging Applications

Low temperature, thermally decomposable sacrificial materials, such as polypropylene carbonates (PPC) have been investigated for a number of applications such as air clad transmission lines, MEMS packaging, and temporary adhesives. PPC provides benefits to these processes due to its easy spin coating, clean decomposition, and moderate temperature thermal decomposition. However the current sacrificial materials have processing limitations such as high solvent solubility, modest patterning capabilities, and high thermal reflow due to a low glass transition temperature. PPC has also been shown to be sensitive to processes such as sputtering, plasma etching, and laser ablation, resulting in the deformation of the film during processing. These problems limit its use into highly complex systems.

In this study, new processing and material advancements have been achieved for air-cavity packaging of MEMS devices. Improvements have been made to the process and overcoat materials for use with PPC. The use of epoxy-POSS as a high selectivity etching mask for PPC and overcoat has improved this process. The dry etching provides improved definability and clean decomposition of the material. The decomposition process and the overcoat material have been designed for clean removal of the material without damaging the cavity formed during the process. The cavity can then be metalized and tested for lead frame packaging. Additional investigations have investigated new polycarbonates for improved patterning, solvent resistance, chemical stability, thermal reflow, and decomposition properties. Improvements in these properties increase the quality and advantages of sacrificial polycarbonates for use in high energy systems and multistep processing.