Volume/surface effects on electron energy and dissociation reactions in large-volume plasma reactors

The effect of changing the gap width on the bulk plasmas was examined by th e simple model calculation and by the diagnostics for ultrahigh frequency ( UHF) (nonmagnetized) nd UHF electron cyclotron resonance (ECR) (magnetized) plasma. Higher volume/surface ratio (wider gap width at constant chamber d iameter) brought higher electron density and lower electron temperature in the bulk plasma. The uniform discharge model explained the effects of the g ap width change on these basic plasma parameters by the particle and energy balance. The latest spectroscopic and spectrometric measurements were appl ied to Ar/c-C4F8-based oxide etching plasma, and monitored the change of th e electron impact reaction rate coefficients ([sigma upsilon]) for argon em ission, c-C4F8 dissociation, and fluorine radical generation. The results q uantitatively showed that the wider gap width (lower electron temperature) suppressed these electron impact reactions, In addition, UHF and UHF-ECR sh owed different gap width dependency in these [sigma upsilon]'s by the effec t of magnetic confinement for the UHF-ECR plasma. Higher N-e condition was achieved at the wider gap width without changing the fluorine density. As a result, higher etching rate of the thermal oxide was achieved in the wider gap width. (C) 1999 American Vacuum Society.. [S0734-2101(99)19304-7].