Argon metastables in a high density processing plasma

Abstract

Absolute densities of metastable argon atoms (Paschen 1s5, 1s3) and the intermediate resonant state (1s4) were measured in a high density plasma etching environment. Excited species densities were measured ranging from 108 to 3×109 cm−3, depending on the particular atomic state. A straightforward reaction rate formalism consisting of only two competing electron-atom collision rates accurately predicts such densities. Because of the low densities of these long-lived excited state species, all excited argon species need to be considered only as energy loss channels in modeling high density (1011–1012 cm−3), low pressure (∼1 mTorr) plasma sources. Metastable production rates were also used to identify energy transfer mechanisms under etching conditions of Cl2/Ar mixtures and substrate biasing in the reactor.