Etching of SiO2 with CF4 in three types of high density-low pressure (
5X10(11) cm(-3), 1-10 mTorr) etch tools: electron cyclotron resonance
(ECR), inductively coupled (ICP), and helicon (HRF) is described. Alth
ough the physical processes that produce the plasma in the three types
of sources are quite different, the etch rate processes are identical
when viewed from the wafer sheath boundary. Measurements demonstrate
that if sufficient fluorine is present, the etch rate limiting step de
pends only on the ion energy flux to the wafer, rather than on the det
ails of the chemical species. Etch rate control depends only on the wa
fer bias power. Experimental results are device independent so the etc
h rate in high density-low pressure plasma sources does not depend on
the plasma source power. Major differences in tool etch rate character
istics are more likely determined by tool wall material (and wall chem
istry) and tool geometry rather than the physical process that is used
to produce the plasma. (C) 1996 American Institute of Physics.