Absolute densities of long lived species in an ionized physical vapor deposition copper-argon plasma

Optical absorption spectroscopy has been used to measure absolute, average gas phase densities of neutral copper, ground and metastable states, and ne utral argon, metastable and resonance states, in an ionized physical vapor deposition plasma. Spectroscopic measurements were carried with a xenon arc lamp as a high intensity, continuum light source, and an optical multichan nel detector. Copper radiative transitions in the wavelength range of 324.8 -510.6 nm and argon radiative transitions in the 706.7-811.5 nm range were employed. The curve of growth method has been used to calculate the absolut e line average densities from fractional absorption data. For a copper-argo n plasma of neutral pressure 30 and 10 mTorr copper metastable state densit ies were found to lie in the range of 10(10)-10(12) cm(-3). Comparison of t hese densities with neutral copper densities derived from independent measu rements of neutral copper flux at the substrate indicate gas phase temperat ures greater than 1500 K under certain experimental conditions. These value s of inferred temperatures indicate the copper metastable state density to be significant in comparison with neutral copper ground state densities at 10 and 30 mTorr with radio frequency heating power of 1 kW. The concentrati ons of argon 4s sublevels of the first excited state were found to be in th e range of 4.5x10(8)-1.5x10(11) cm(-3) for the experimental conditions stud ied. The ordering of the relative densities of the argon 4s sublevels and t he variation of the lumped first excited state with experimental parameters are discussed. (C) 2000 American Institute of Physics. [S0021-8979(00)0281 9-X].