ARGON METASTABLES IN A HIGH-DENSITY PROCESSING PLASMA

Absolute densities of metastable argon atoms (Paschen 1 s(5), 1 s(3)) and the intermediate resonant state (1s(4)) were measured in a high de nsity plasma etching environment. Excited species densities were measu red ranging from 10(8) to 3x10(9) cm(-3), depending on the particular atomic state. A straightforward reaction rate formalism consisting of only two competing electron-atom collision rates accurately predicts s uch densities. Because of the low densities of these long-lived excite d state species, all excited argon species need to be considered only as energy loss channels in modeling high density (10(11)-10(12) cm(-3) ), low pressure (similar to 1 mTorr) plasma sources. Metastable produc tion rates were also used to identify energy transfer mechanisms under etching conditions of Cl-2/Ar mixtures and substrate biasing in the r eactor.