Across Substrate Lateral Dimensional Repeatability Using a Highly-Anisotropic Deep Etch Process on Fused Silica Material Layers

This letter reports the research performed on the measurement of the repeatability of the resultant lateral dimensions across fused silica substrates that were etched using an inductively-coupled plasma reactive-ion etch process. We have developed and previously reported a highly-anisotropic plasma etch process with the demonstrated etch depths of over 100 microns deep into fused silica substrates and aspect ratios greater than 10 to 1. The across substrate repeatability of the lateral dimensions of the etched features is an extremely important parameter for any plasma etch process. The measured etched feature lateral dimensional repeatability for an average etch depth of 100 microns was found to be approximately 2.41% across each wafer over a total of 120 measurements taken. The capability to etch highly-anisotropic deep features with repeatable dimensional control into fused silica has important implications for a number of important MEMS applications.