Deep trench etching of single crystal silicon

Claim 1

A process for high speed, anisotropically, reactive ion mode plasma etching of single crystal silicon through an apertured mask to produce a deep trench with essentially vertical sidewalls comprising the steps of: (a) providing a single crystal silicon substrate with an apertured mask selected from the group consisting of silicon dioxide and silicon nitride; (b) exposing said substrate to an atmosphere of nitrogen trifluoride (NF 3 ) and a halofluorocarbon (HFC) compound containing only one carbon atom in a ratio of 1 to 2 NF 3 :1 to 3 HFC in an etching zone; and (c) generating a plasma with the atmosphere and anisotropically reactive ion etching said substrate by directing ions from said plasma through the apertures of said mask into the single crystal silicon substrate, wherein the etching is performed at a high speed in the range of at least 0.1 micron per minute using a power of 500-2000 watts and a frequency of 1-50 MHz to produce a deep trench in said substrate having a vertical depth in the range of 3-15 microns and essentially vertical sidewalls, essentially no undercutting of said mask and essentially no bowing in the trench.