Self-terminating electrochemical etching of stainless steel for the fabrication of micro-mirrors

A novel, self-terminating electrochemical etch process is proposed for the fabrication of scanning steel micro-mirrors. The process uses single mask photolithography, and the etching step is terminated automatically, which at the same time enables the depth profile shaping of the fabricated structure. The proposed process is characterized and then used to fabricate two versions of one-dimensional (1D) steel micro-scanners: one with selective thinning of the predefined parts and one without thinning. The fabricated devices are characterized and compared with respect to their resonance frequencies and mechanical quality factors. The thickness of the starting substrate is selectively thinned down by approximately 150 mu m in order to decrease the mass of the mirror and eventually to increase the resonance frequency of the fundamental mode. The resonance frequency of the structure is increased from 4210 Hz to 6060 Hz resulting in a normalized frequency shift of 15%.