Effects of processing conditions on the characteristics of platinum silicide Schottky barrier diodes

Abstract

A study has been carried out to determine the effects of various processing conditions on the formation of PtSi schottky barrier diodes. Various surface preparation techniques were experimented. Comparisons were made between oxide etching by wet etch (BHF) and reactive ion etching (RIE) predeposition cleaning by wet etch or in situ Ar sputter cleaning, and the use of different thicknesses of Pt. The interaction between PtSi and the contact metallurgy during subsequent annealing was also examined. The study shows that each component has a distinct effect on the quality of the PtSi film. The results indicate that oxide etching by wet etch is probably incomplete, leaving residues or suboxides on the surface of Si substrates which interfere with subsequent PtSi formation. Though RIE seems more effective in removing the oxide, data support the view that a damaged layer of Si is formed, which should be consumed by the PtSi formation for optimum electrical characteristics. Finally, even if the formation of the PtSi is ideal, interaction between the PtSi and a commonly used Ti/Al-Cu/Si contact metallurgy at elevated temperatures could degrade the PtSi film qualities if a suitable diffusion barrier is not used. © 1988.