Optimization of Protective Layer Process for Micro-bridge Structure based MEMS/Sensors Application

In this work, erosion problem was found in MEMS micro-bridge structure based sensor product during dry releasing process. Failure analysis was implemented to found the root cause. It was found that there was a void formed on the electrode layer pattern edge, and the protective layer here was much thinner than other location which introduced a weak point during releasing process. And the sensing material below was damaged by releasing gas at this weak point which causing the erosion problem. Process model was proposed for the weak point formation, and electrode layer etching process and protective layer deposition process were optimized to avoid the erosion problem. After process optimization, better step coverage performance was obtained with no void formation, and erosion problem was well solved.