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

Abstract

RuO 2 thin films were grown by sputtering a Ru target in Ar and O2 mixed gas, and the effects of O2 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 O2 flow 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 O2 flow ratio region and (2) sputtering of the oxidized target (oxide target mode) in a higher O2 flow ratio region. In addition, the supplied O2 flow rate, rather than the O2 flow ratio, is found to be the dominant factor in the formation of RuO2 thin films. At an O2 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.