DOES HIGH-DENSITY LOW-PRESSURE ETCHING DEPEND ON THE TYPE OF PLASMA SOURCE

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.