Deep Wet and Dry Etching of Pyrex Glass: a Review

This paper is a review of wet and dry etching of one of the most common types of glass: Pyrex. The paper analyzes the methods for increasing the glass etch rate in HF solutions, namely, annealing, concentration, ultrasonic agitation and temperature. The limitations of the wet etching of glass are also presented. Mashing layers commonly used for deep wet etching of glass are analyzed, in terms of the process time required until the defects are generated in the masking layer. The improvement of the surface roughness for deep wet etching of Pyrex glass is another subject that will be explored. The highest etch depth – 500 μm – of annealed Pyrex glass is achieved by wet etching in highly concentrated HF solution, using Cr/Au with the assistance of photoresist as a masking layer. The paper also reports a new technique of dry etching of Pyrex glass in C4F8 using bulk silicon mask.