Electron and negative ion density have been measured in a modified Applied
Materials decoupled plasma source commercial metal etch chamber using gas m
ixtures of BCl3, Cl-2 and Ar. Measurements were performed for four differen
t substrate types to examine the influence of surface material on the bulk
plasma properties: aluminum, alumina, photoresist, and 50% patterned alumin
um/photoresist. Electron densities in the Cl-2/BCl3 mixtures varied from 0.
25 to 4 X 10(11) cm(-3). Photodetachment measurements of the negative ion d
ensity indicate that the negative ion density was smaller than the electron
density and that the electron to negative ion density ratio varied between
1 and 6. The presence of photoresist had a dominant influence on the elect
ron and negative ion density compared to alumina and aluminum surfaces. In
most cases, the electron density above wafers covered with photoresist was
a factor of 2 lower, while the negative ion density was a factor of 2 highe
r than the aluminum or alumina surfaces. (C) 1999 American Vacuum Society.
[S0734-2101(99)01006-4].