ETCH RATE AND PLASMA-DENSITY RADIAL UNIFORMITY MEASUREMENTS IN A CUSPED FIELD HELICON PLASMA ETCHER

Experiments on the University of Wisconsin helicon etcher were conduct ed to study the effects on uniformity of applying a cusped magnetic fi eld to the etching chamber. Also a comparison was made between long an d short antenna/substrate separation distances. The plasma radial dens ity uniformities, measured using a Langmuir probe over the inner 10 cm diameter of the chamber, gave maximum density variations of +/- 22% w ith the cusp off and +/- 1.28% at the zero field region of the cusp. T he maximum SiO2 etch rate in CF4/Ar plasmas occurred at 50% Ar concent ration in the long source configuration. Etch rate uniformity of SiO2 etching in a CF4/Ar/O-2 plasma improved from +/- 8.1% to +/- 2.6% for a 82.5 mm wafer by shortening the antenna-substrate separation distanc e from 108 to 47 cm. Azimuthal asymmetry of the plasma produced from t he Nagoya type III antenna was observed in the shea source configurati on in which the SiO2 etch rate uniformity varied from +/- 1.5% across the vertical axis of a 150-mm-diam wafer to +/- 12% across the horizon tal axis of the wafer. (C) 1996 American Vacuum Society.