Fabrication of SOI MEMS inertial sensors with dry releasing process

In this paper, a dry releasing process for making high aspect ratio SOI MEMS devices is presented. The proposed process can not only avoid the stiction effects which will cause the device failure, but also partially suppress the footing effect during the deep reactive ion etching (DRIE) of the de vice structures. The basic idea is to use the pre-defined releasing hole to completely remove the buried oxide underneath the device just before the final structure etching, therefore avoid the wet process during the structure release. The on-chip testing structures for etching end point of DRIE are also designed to precisely monitor the etching results. A capacitive accelerometer was fabricated and tested using the proposed process. The preliminary results imply the dry releasing process can effectively avoid the stiction problem.