Selective formation of a SnO₂ cap layer, its growth behavior, and oxidation resistance

In this paper, we propose a new method of cap-layer formation. The cap layer of SnO₂ is formed by the displacement plating of Sn, followed by the oxidation of the plated Sn. An excellent plating selectivity was found between Cu and SiO₂, but not with SiOCH. The SnO₂ layer of 90 nm thickness showed a good oxidation resistance of the underlying Cu after heat treatment at 480°C in air (P_O2 = 10⁵ Pa). In contrast, the SnO₂ layers of 6 and 9 nm thickness showed oxidation resistance at 400°C in Ar+10 ppm O₂ (P_O2 = 1 Pa), but not in Ar+1000 ppm O₂ (P_O2 = 100 Pa).