Fluorine incorporation effects in Cl-2 plasma etching of silicon: Quadrupole mass spectrometer analysis

We investigated the etch characteristics of Si in Cl-2 plasmas with additio n of fluorine in an electron cyclotron resonance etching system. The additi on of fluorine-containing gas, SF6, increased the etch rate and selectivity , whereas anistropy was decreased. The ion-assisted etch mechanism was domi nant in a pure Cl-2-gas plasma, whereas chemical etching was dominant at th e ratio of 0.65 of Cl-2/total gas flow rate (Cl-2 + SF6). In the transition region, 0.65-0.9, the small addition of the fluorine-containing gas brough t about the generation of fluorine radicals, and this can chemically detach the chlorinated layer on feature sidewalls. Anistropy was abruptly reduced by this chemical etching. (C) 1999 The Electrochemical Society. S0013-4651 (99)04-034-3. All rights reserved.