The formation of multi-axis micromechanical gyroscopes and accelerometers using surface micromachining

The process flow of unified integral multi-axis micromechanical gyroscopes and accelerometers fabrication by surface micromachining was developed. The process flow for typical n-type silicon wafer Si (100) contains over 20 primary operations, including 5 lithography steps using 5 masks with minimum features size of 1 jam. Special operations were discussed. Experimental results of sacrificial SiO2 etching for poly-Si-on-SiO2 structures using buffered solution of hydrofluoric acid and ammonium fluoride (1:4) were obtained. The undercut etching rate was approximately of about 20 nm/sec and the minimum time required for sacrificial SiO2 removing under beams of 0.5-2.5 width was in in the range of 11 to 62.5 seconds. Finally two and three-axis micromechanical gyroscopes and accelerometers were fabricated.