Characterization of BCl3/N-2 plasmas

Abstract

Optical emission spectroscopy, quadrupole mass spectrometry, and electron density measurements were used to study the effect of the percentage of N-2 on the characteristics of BCl3/N-2 plasmas and their resulting etch processes. The etch rate of GaAs increased from 80 Angstrom/min in pure BCl3 to over 1000 Angstrom/min in a 40:60 BCl3:N-2 mixture (15 mTorr, 50 W, 20 sccm). The optical emission intensities of both molecular and atomic chlorine exhibited maxima near 30% N-2, and an argon actinometer indicated a large increase in argon emission as a function of the increase in N-2 percentage. Microwave measurements indicated that the average electron density increased only slightly with an increase in nitrogen percentage up to 60% N-2. Mass spectrometric analysis of the plasmas showed that both the dissociation of BCl3 and the production of molecular chlorine were significantly enhanced by the addition of N-2. These results suggest that an increase in the electron temperature as a result of electron attachment heating (and possibly energy transfer from N-2 metastables) is responsible for the increased dissociation and enhanced production of etch species. (C) 2003 American Institute of Physics.