Reactive ion etching of glass for biochip applications: Composition effects and surface damages

Abstract

Due to its insulating properties, transparency, and well known surface chemistry, glass represents an interesting alternative to silicon or polymers for biochip processing. However, high aspect-ratio posts for DNA electrophoresis have only been reported in expensive quartz substrates. Therefore, we investigate here metal mask transfer by fluorocarbon plasma etching in nine silica or glasses of different grades. With increasing amounts of non-SiO 2/non-B 2O 3 oxides in the material, the etch rate decreases and, in some cases, strong surface roughening appears. Furthermore, even for fused silica, surface damages such as cone-like defects were observed. Consequently, soda-lime slides coated with silica by plasma enhanced chemical vapor deposition (PECVD) were used as a good compromise between etching quality and cost. Electrophoresis chips with features down to 100 nm and aspect-ratio up to 10 could then be fabricated.