Does high density endash low pressure etching depend on the type of plasma source?

Etching of SiO2 with CF4 in three types of high density endash low pressure (5x1011 cm-3, 1 endash 10 mTorr) etch tools: electron cyclotron resonance (ECR), inductively coupled (ICP), and helicon (HRF) is described. Although 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 depends only on the ion energy flux to the wafer, rather than on the details of the chemical species. Etch rate control depends only on the wafer bias power. Experimental results are device independent so the etch rate in high density endash low pressure plasma sources does not depend on the plasma source power. Major differences in tool etch rate characteristics are more likely determined by tool wall material (and wall chemistry) and tool geometry rather than the physical process that is used to produce the plasma. copyright 1996 American Institute of Physics