Comparative Study of Various Release Methods for Gold Surface Micromachining

A. Sharma, M. Kaur, P. Jhanwar, D. Bansal. P. Kumar, D. Kumar, S. Singh, K.J. Rangra
Central Electronics Engineering Research Institute (CEERI- CSIR), IN

Keywords: surface micromachining, plasma ashing, critical point drying (CPD), MEMS test structures

Summary:

This paper presents a comparison of dry and wet release methods for surface micromachining of metallic structures used as RF MEMS Switches, test structures, bridges and cantilevers.The dry release process is optimized by varying the concentration of O2 and CF4 plasma and RF power. Wet release process using CPD is investigated for reduced residual stress. The plasma ashing of photoresist as sacrificial layer typically results in damage to metallic structures or stress related deformation due to rise in temperature (>800C). CPD being a low temperature (~300C) process is more suitable for compliant structures without any deformation.