Comparison of F-2-based gases for high-rate dry etching of Si

Four different F-2-based gases (SF6, NF3, PF5, and BF3) were examined for h igh rate inductively coupled plasma (ICP) etching of Si. Etch rates up to s imilar to 8 mu m/min were achieved with pure SF6 discharges at high source power (1500 W) and pressure (35 mTorr). A direct comparison of the four fee dstock gases under the same plasma conditions showed the Si etch rate to in crease in the order BF3 < NF3 < PF5 < SF6. This is in good correlation with the average bond energies of the gases, except for NF3, which is the least strongly bound. Optical emission spectroscopy showed that the ICP source e fficiently dissociated NF3, but the etched Si surface morphologies were sig nificantly worse with this gas than with the other three gases. (C) 1999 Th e Electrochemical Society. S0013-4651(99)03-045-1. All rights reserved.