Wet Etching of Glass for MEMS Applications

The paper presents a review of the existing techniques of glass micromachining, explain the generation of the defects during wet etching process, proposed solution for the improving of wet etching techniques. Essential elements of glass wet etching process such as: influence of glass composition, etching rate, influence of the residual stress in the masking layer, characterization of the main masking materials, the quality of surface generated using wet etching process are analyzed. As a result of this analysis improved techniques for deep wet etching of glass are proposed. An 1 mm-thick Pyrex glass wafer was
etched through using a composite mask of amorphous silicon/silicon carbide/photoresist. From my knowledge this is the best result reported in the literature, in terms of deep etching of glass without defects generation. For achieving a smooth surface (for packaging applications) an optimal solution HF/HCl (10:1) was established for Pyrex and soda lime glasses. The paper presents also MEMS applications of the developed techniques.