Study of selective amorphous silicon etching to silicon nitride using a pin-to-plate dielectric barrier discharge in atmospheric pressure

Abstract

Remote-type atmospheric pressure plasmas were generated using a modified dielectric barrier discharge with the powered electrode consisting of multipins instead of a conventional blank planar plate. For the N2∕NF3 gas mixture, a high etch rate of a:Si close to 115nm∕s was obtained by adding 300SCCM (SCCM denotes cubic centimeter per minute at STP) of NF3 to N2 [50SLM (standard liters per minute)] at an ac rms voltage of 8.5kV (2.5kW, 30kHz). However, the selectivity of a:Si to Si3N4 was as low as 1.3. A selectivity of a:Si∕Si3N4>5.0 could be obtained while maintaining an etch rate of a:Si at 110nm∕s by adding 250SCCM CF4 to the N2 (50SLM)∕NF3 (300SCCM) mixture through the formation of a C–F polymer layer preferentially on the Si3N4 surface.