EFFECTS OF DEGREE OF DISSOCIATION ON ALUMINUM ETCHING IN HIGH-DENSITYCL-2 PLASMAS

At the same input power (1000 W), inductive coupled plasma (ICP) and u ltrahigh frequency (UHF) plasma sources produced electron densities of 1 x 10(11) cm(-3) at 3.5 mTorr, yet the UHF plasma was much less diss ociated (30%) than the ICP plasma (70%). This can be attributed to dif ferences in the electron energy distribution functions in the UHF and ICP plasmas, especially at low pressure. Under these conditions, Al et ching profiles were investigated to understand the influences of thr d egree of dissociation on the etching reactions. UHF plasmas could comp letely accomplish anisotropic etching with just Cl-2 as the feed gas, whereas the ICP produced isotropic etching profiles under the same con ditions. This implies that the degree of dissociation strongly influen ces etching of the Al sidewall, as well as the anisotropic etching rat e in a high density Cl-2 plasma.