Three step deep reactive ion etch for high density trench etching

摘要

A three step Deep Reactive Ion Etch (DRIE) process is developed to etch trenchesof 10 μm wide to a depth of 130 μm into silicon with an etch rate of 2.5 μm min−1 . The aim ofthis process is to obtain sidewalls with an angle close to 90°. The process allows the etching ofmultiple trenches with high aspect ratios that are closely placed together. A three step approachis used as opposed to the more conventional two step approach in an attempt to improve theetching selectivity with respect to the masking material. By doing so, a simple AZ6632 positivephotoresist could be used instead of the more commonly used metal masks which are harderto remove afterwards. In order to develop this process, four parameters, which are the biaspower, processing pressure, step times and number of cycles, are evaluated an optimized on aPlasmaPro 300 Cobra DRIE tool from Oxford Plasma Technology.