Introducing porous silicon as a getter using the self aligned maskless process to enhance the quality factor of packaged MEMS resonators

Vacuum encapsulated MEMS resonators are used in frequency references and gyroscopes. We present the use of porous silicon as a getter material for MEMS devices. Two types of devices were fabricated using the electrochemical etching and compared for quality factor. One type was with a cavity in the substrate of an SOI die, which helps in reducing the parasitic capacitance and the air damping. The other was with cavity and porous silicon (getter) in the substrate. The measured resonant profiles show that the device with the getter material has 2× higher quality factor than the one without the getter.