E. Kusano et A. Kinbara, Time-dependent O-2 mass balance change and target surface oxidation duringmode transition in Ti-O-2 reactive sputtering, J APPL PHYS, 87(4), 2000, pp. 2015-2019
Time-dependent O-2 mass balance change among the amounts injected into the
chamber, pumped out from the chamber, gettered by sputtered Ti metal, resid
ing in the chamber, and consumed to oxidize the target surface has been inv
estigated as a function of time elapsed after the discharge ignition in Ti-
O-2 reactive sputtering. From the mass balance results obtained, target sur
face coverage has been estimated. In the period of up to 10 s after dischar
ge ignition, the gettering of O-2 by sputtered Ti dominated the process cha
nge. In this period, the target surface oxidation rate was low. In the peri
od of 20-50 s, the amount of O-2 consumed to target surface oxidation surpa
ssed the amount of O-2 gettered by deposited Ti, resulting in a drastic inc
rease in the target coverage. After the target surface oxidation was comple
ted, the process became stable. In this period, the amount of O-2 pumped ou
t without causing any process changes increased and a very small amount of
O-2 was consumed to oxidize the target surface. The equilibrium in the bala
nce between the formation and sputter etching of the oxide layer on the tar
get surface resulted in the stable condition. Calculated target coverage ac
hieved more than 250 monolayers at 600 s after the glow discharge ignition.
This value equated with the oxide thickness of about 100 nm. It is conclud
ed that the nonlinear target surface oxidation process causes a nonlinear p
rocess change occurring during the mode transition. (C) 2000 American Insti
tute of Physics. [S0021-8979(00)05904-1].