Appeal No. 95-2728
Application 07/735,668
wherein the high acceleration voltage is selected to
remove a residue from etched portions of the sample, the
residue occurring as a result of the sample being cooled to a
temperature not higher than OEC while being etched, the high
acceleration voltage being generated for a time sufficient to
remove the residue from the etched portions of the sample, and
wherein the low acceleration voltage is selected to etch the
sample with a high selectivity ratio.
48. A plasma etching method for etching a sample with a
gas plasma comprising the steps of:
generating a first acceleration voltage for accelerating
ions in the gas plasma toward the sample with a first ion
energy corresponding to the first acceleration voltage to etch
the sample such that a residue is produced; and
generating a second acceleration voltage higher than the
first acceleration voltage for accelerating ions in the gas
plasma toward the sample with a second ion energy
corresponding to the second acceleration voltage to eliminate
the residue;
wherein the step of generating a first acceleration
voltage and the step of generating a second acceleration
voltage are alternately repeated.
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