Single Mask Selective Release Process for Complex SOI MEMS Device

We present a single mask selective release process for complex SOT MEMS device. Comparing to the one-step dry release process, there are two improvements, the first one is to ensure that the bottom of the suspension beams will not be notching, and have sufficient strength and rigidity, the second one is to ensure that the released structures will not be damaged during wafer dicing. According to the proposed design rules, in the dry release step, most of the device area is released, except the boundaries of the proof mass and the suspension beams. Then, in the wet release step, all the structures will be released, and also increased the gap below the structure. So the suspension beams is protect enabled that the device has sufficient rigidity and not easy to break. To verify this method, a micromachined gyroscope is fabricated and test.