Polysilicon Etching in SF 6 RF Discharges: Characteristics and Diagnostic Measurements

Abstract

The response of polysilicon etching characteristics and various diagnostic measurements to pressure, power, and flow rate in discharges is reported and discussed. The etching rate increases with increasing power, decreasing pressure, and increasing flow. As a function of discharge pressure, the etching rate is not proportional to the bulk fluorine concentration as measured by optical emission using Ar actinometry. However, the etching rate is related to the bulk fluorine concentration with a model that includes diffusion of fluorine from the bulk plasma to the wafer surface and the subsequent reaction of the fluorine with the silicon. The electric field to pressure ratios of 95–200 V/cm‐torr across the bulk of the plasma were measured and are consistent with previous measurements of electric field to pressure ratios at which the rates for electron attachment and ionization are equal.