A DRIE CMOS-MEMS gyroscope

The gyroscope reported in this paper is a lateral-axis angular rate sensor with in-plane vibration and out-of-plane Coriolis acceleration sensing. The sensor plus on-chip CMOS circuitry is about 1 mm by 1 mm in size and is fabricated by a post-CMOS micromachining process that uses interconnect metal layers as etching mask(s) and a single-crystal silicon layer as the structural material. The resultant device incorporates both 1.8 μm-thick thin-film structures and 60 μm-thick bulk Si structures to simultaneously achieve spring beams with either in-plane or out-of-plane compliance. The microstructure is flat and avoids the curling problem existing in thin-film CMOS gyroscopes. A unique silicon electrical isolation technique is used to obtain individually controllable comb fingers. The noise floor of the gyroscope is 0.02°/s/Hz¹2/ at 5 Hz.