A single mask dry releasing process for making high aspect ratio soimemsdevices

A novel single mask dry releasing process for making high aspect ratio SOI MEMS devices is presented. The proposed process takes advantage of lag effect in DRIE. The basic idea is that the buried oxide layer is completely removed using the wide trench and releasing holes defined in the first DRIE, then the second DRIE is carried out to released the narrow trenches. Not only stiction problem is avoided, but also the footing effect can be partially suppressed during the DRIE. The on-chip testing structures for etching end point of DRIE are also designed to precisely monitor the etching results. A capacitive accelerometer is fabricated successfully to demonstrate the process feasibility.