Maskless etching of silicon using patterned microdischarges

Abstract

Microdischarges in flexible copper-polyimide structures with hole diameters of 200 μm have been used as stencil masks to pattern bare silicon in ${\mathrm{CF}}_4/\mathrm{Ar\hspace{0.5em}chemistry}.$ The discharges were operated at 20 Torr using the substrate as the cathode, achieving etch rates greater than 7 μm/min. Optical emission spectroscopy provides evidence of excited fluorine atoms. The etch profiles show a peculiar shape attributed to plasma expansion into the etched void. Forming discharges in multiple hole and line shapes permits direct pattern transfer in silicon and could be an alternative to ultrasonic milling and laser drilling.