NUMERICAL-SIMULATION OF A SINGLE-WAFER ISOTHERMAL PLASMA-ETCHING REACTOR

A two-dimensional finite element simulation of gas flow and reactive species distribution in a parallel-plate single-wafer isothermal reactor was conducted. The oxygen plasma etching of polymer under high pressure (~1 torr), high frequency (13.56 MHz) conditions was chosen as a model system for analysis with emphasis on chemical etching. Etching rate and uniformity were examined as a function of reactor geometry and operating conditions. A maximum in etching rate with flow rate was observed, and this maximum shifted to higher flow rates as the power increased. The pressure dependence of the etching rate was complex, but in general a broad maximum in etching rate with pressure existed, which shifted to higher pressures as the flow rate increased. Etching rate increased but etching uniformity degraded as the wafer reactivity increased. A shower radius at least equal to the wafer radius, and a plasma radius slightly greater than the wafer radius were found to give the best etching rate and uniformity results under the conditions examined. Two novel reactor designs were also studied, namely, a reactor with a graded gas velocity at the shower, and a pulsed-plasma reactor. When compared to the conventional reactor, the new designs can yield improved uniformity and etching rate (the etching rate of the pulsed-plasma reactor was prorated by the duty cycle). © 1990, The Electrochemical Society, Inc. All rights reserved.