A new plasma source for next generation MEMS deep Si etching: Minimal tilt, improved profile uniformity and higher etch rates

The demand for evermore sensitive MEMS sensor devices, such as gyroscopes, has driven the need for the manufacturing processes to deliver smaller tolerances. This is especially evident when considering the DRIE process used to fabricate the intricate sensor features on the silicon wafer. Aspect ratios have become higher with CDs reducing and etch depths increasing. But of particular significance when referring to MEMS gyroscopes is profile tilt. Device design and signal processing can no longer compensate for innate tilt, and so the manufacturing methods have to improve to deliver the levels of tilt necessary for the next generation of devices at a cost effective throughput. This paper will describe data from a new plasma source design, the Pegasus Rapier, employed to improve the tilt performance of the Bosch DRIE process [1] for the productionisation of next generation MEMS gyroscopes. This data will show <±0.15° profile tilt capability on 200mm wafers at rates of 7µm/min for a 20:1 aspect ratio trench.