Deep etched and released microstructures in Zerodur in a fluorine-based plasma

Abstract

In this paper, we demonstrate the dry-etch release of free-standing mechanical elements with a high aspect ratio from a Zerodur wafer. Our previous research was focussed on deep plasma etching of Zerodur and the determination of characteristic process parameters such as selectivity, sidewall angle and etch rate. Nevertheless, the releasing of structures is more challenging. The achievable sidewall angle in fluorine-based plasma of 71°, and a low selectivity limits the etch depth. Here, we show a double-sided process, which allows a high aspect ratio and structure heights of 150 μm and above. We implement a process that allows a damage-free finishing of the micromechanical elements. The chemical sidewall composition of the released structures was carefully investigated. A strong build up of non-volatile products at specified positions of the structures results from the two-directional process and the structure geometry. This is discussed in the article and can be applied to other glasses and glass ceramics with complex composition, too.