The Roles of Ions and Neutral Active Species in Microwave Plasma Etching

The roles of ions and neutral active species in microwave plasma etching are investigated. Silicon wafers are etched in a (CF4 ~- O2) mixture dis-charge. The results of three different experiments agree and are suggestive of the following: Si wafers can be etched only when ions impinge on the wafer surface at pressures lower than 0.13 Pa (1 • 10- ~ Torr), Si wafers are etched by neutral active species at pressures higher than 1.3 Pa (1 • 10-2 Torr), and both by ions and neutral active species at pressures between 0.13 Pa (I • I0-8 Torr) and 1.3 Pa (I X 10-2 Torr). Recently, plasma-etching techniques involving chem-ical reactions were studied for fine-pattern etching of high density electronic ircuits (1, 2). Such etching techniques are classified by the discharge methods used, these being radio frequency (rf) glow discharge and microwave discharge