Correlation between gas phase composition of rf plasma of argon diluted tetraethylgermanium and chemical structure of therewith deposited Ge/C films

Quadrupole mass spectrometry (QMS) and optical emission spectroscopy (OES) have been applied to the characterization of rf plasma of tetraethylgermanium-argon mixture. QMS analysis shows that under low power input conditions, when organogermanium plasma polymer films are deposited, the gas phase consists primarily of monomer molecules and their largest fragments. In contrast, at high power input, under conditions of hydrogenated germanium/carbon alloy film formation, tetraethylgermanium undergoes nearly complete fragmentation forming atomic germanium, atomic and molecular hydrogen, and a number of hydrocarbon species. A dramatic increase of molecular hydrogen concentration with the increasing rf power is confirmed by OES actinometric measurements. Strong dependence of atomic hydrogen concentration in the gas phase on rf power supports the concept of the formation of Ge-H bonding in the films via saturation of germanium dangling bond with hydrogen and, therefore, provides an argument to the hypothesis of a competition between Ge-H and Ge-O bond formation. (C) 1996 American Vacuum Society.