Ultra high aspect-ratio and thick deep silicon etching (UDRIE)

Abstract

We report an advanced deep-reactive-ion-etching (DRIE) process developed specifically for etching ultra-deep structures in thick (>500μm) silicon wafers with high aspect-ratio and straight sidewalls across a wide range of feature sizes and patterns. This is achieved by ramping critical process parameters throughout the etching duration. 600-800μm deep trenches with widths as small as 20-40μm are etched in 1mm-thick silicon wafer, and are expected to be etched through a 1mm wafer with thicker and/or higher selectivity masking materials. We have produced holes >500μm deep with hole diameters as small as 25μm, and potentially with 10-15μm diameter holes. This ultra-deep silicon etching process will benefit both IC integration and emerging MEMS applications at micrometer and millimeter scale that demand high-resolution deep DRIE.