Comparison of F2-based gases for high-rate dry etching of Si

Four different F-2-based gases (SF6, NF3, PF5, and BF3) were examined for high rate inductively coupled plasma (ICP) etching of Si. Etch rates up to similar 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 feedstock gases under the same plasma conditions showed the Si etch rate to increase 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 efficiently dissociated NF3, but the etched Si surface morphologies were significantly worse with this gas than with the other three gases. (C) 1999 The Electrochemical Society. S0013-4651(99)03-045-1. All rights reserved.