Micro-machined transparent components are of interest for optical MEMS and miniaturized biological systems. The glass ceramic GC6 developed by Corning is optically transparent, has a softening point in excess of 900°C, and a thermal expansion coefficient matched to silicon. These properties make it useful for the construction of devices that combine thin film silicon electronics with MEMS systems.
Both the ceramic precursor (green glass) and the glass ceramic etch at a similar rate, about 1/3 to 1/4 of that of SiO2 etched under the same conditions, indicating that chemistry rather than microstructure control the etch rate. The cleaning steps used to clean the glass precursor profoundly influence the degree of surface roughness that develops during subsequent plasma etching. In glass ceramics, the morphology of plasma etched surface is always very smooth and independent of the cleaning steps used. Assuming that the removal of spinel crystals is the rate limiting step in plasma etching glass ceramics can explain this observation.