OPTICAL DIAGNOSTICS OF DC AND RF ARGON MAGNETRON DISCHARGES

The plasmas of d.c. and r.f. magnetron discharges have been analysed by emission spectroscopy for argon and metal atom radiative states and by optical absorption for the Ar(P-3(2), P-3(0)) metastable and Ar(P-3(1), P-1(1)) resonant atoms. In the 6-200 mTorr pressure range for W = 1-50 W in r.f, and I = 2-50 mA in d.c. the metastable and resonant atoms are three to five times more populous in r.f. than in d.c. The densities are saturated for I > 20 mA in d.c. and W > 5 W in r.f., reaching a maximum value n(Ar) (P-3(2)) approximate to 5 x 10(10) cm(-3). The emission line intensities I(lambda) vary as I(lambda) = W-beta in r.f., with beta approximate to 0.5 for neutral Ar lines and beta approximate to 1 for Ar ion and metal (Al, Mg, Mn) atom lines. In d.c. discharges I(lambda)) = I-beta with beta approximate to 2 for Ar ion and metal atom lines. These results suggest an electron density variation as n(c) proportional to W-0.5 in r.f. and an excitation mechanism proportional to n(c)(2) for Ar ions and metal atoms in both d.c. and r.f. discharges.