Effects of O2 gas flow ratio and flow rate on the formation of RuO2 thin films by reactive sputtering

RuO2 thin films were grown by sputtering a Ru target in Ar and O-2 mixed gas, and the effects of O-2 gas flow ratio and flow rate on the formation of RuO2 films were studied. Based on changes in the deposition rate and plasma emission spectra observed when the O-2 Row ratio was varied, the formation process of RuO2 films is categorized into two classes: (1) oxidation of Ru atoms at the substrate surface (metallic target mode) in a lower O-2 Row ratio region and (2) sputtering of the oxidized target (oxide target mode) in a higher O-2 flow ratio region. In addition, the supplied O-2 flow rate, rather than the O-2 flow ratio, is found to be the dominant factor in the formation of RuO2 thin films. At an O-2; gas supply at which twice as many oxygen molecules as sputtered Ru atoms are introduced into the sputtering chamber, RuO2 thin films begin to be deposited in the metal target mode. (C) 2000 American Vacuum Society. [S0734-211X(00)03503-4].