Abstract

Optoelectronic technology often asks for conductive materials transparent to optical radiation. Transparent contacts can sensibly improve efficiency and integration of optoelectronic devices, opening the possibility for new concept designs. Realization of transparent electrodes has always been a challenging task, dense of difficulties. The commonly adopted solution is to use doped large band gap semiconductors, like transparent conducting oxides (TCOs) [1], However, in many cases of advanced technology, use of TCOs may present problems in terms of process reproducibility, material compatibility, reliability and costs. We have investigated the feasibility to realize uniform transparent electrodes by sputtering deposition of ultra-thin metal films. Such a solution has been always limited in the past by the minimum thickness one can reach before the film becomes discontinuous. In order to have an optical transmittance >60% and low resistance, metal films should be continuous with a thickness below 100Å. Such films could not be obtained till the advent of the most recent UHV deposition systems. We have studied thin film properties of a selection of metals (nickel, aluminum, titanium, chromium) deposited with a batch sputtering system customized for process manufacturing. The final goal is to define an industrial technology for the realization of transparent metal electrodes.

© 2007 IEEE