Reactive Ion Etching of Silicon Oxides with Ammonia and Trifluoromethane. The Role of Nitrogen in the Discharge

A 4% , RIE discharge accurately reproduced micron‐sized features in or P‐glass/Si substrates which had been patterned with either photoresist or x‐ray trilevel resist. Etch rates of up to 600 and 1200 A/min were obtained with and P‐glass, respectively; etch rate ratios for and P‐glass/Si were approximately 15 and 30, respectively. Erosion of the resist was slow enough that it did not interfere with pattern transfer. In addition, no undercutting occurred and sidewalls in etched features were nearly vertical. Ammonia inhibited fluorocarbon polymer deposition by reaction with any deposit formed to make volatile cyanogen derivatives. Moreover, moderated deterioration of the resist by the plasma.