Tungsten-Doped Indium Oxide Thin Film as an Effective High-Temperature Copper Diffusion Barrier

The barrier property of reactive plasma deposited tungsten-doped indium oxide (IWO) thin film was investigated for copper diffusion at high temperature. The Cu 100 nm/IWO 80 nm/Si stacks were annealed between 500°C and 850°C. X-ray diffraction, scanning electron microscopy and current-voltage measurements reveal that the polycrystalline IWO film exhibits high thermal stability and effectively prevents copper diffusion up to 800°C. At 850°C, Cu 3 Si phase was formed due to the inter-diffusion of Si and Cu through the IWO barrier. The results show that IWO is the excellent high-temperature barrier material for copper-based photovoltaics.