Preparation and stability of low temperature cobalt and nickel silicides on thin polysilicon films

Silicides of cobalt and nickel are formed on thin (18–100 nm) polycrystalline silicon films by in situ vacuum annealing. The dependence of silicide sheet resistance on silicon film thickness and crystallinity, surface preparation, integrity of vacuum during metal deposition, and anneal temperature is shown. Cobalt and nickel silicides with sheet resistances as low as 30 and 20 Ω/□ were formed on 18-nm-thick polysilicon films. A surface preparation method to produce a passivated silicon surface compatible with large area glass substrates is demonstrated. The resistance of nickel and cobalt silicide to chemical reagents used in semiconductor processing is studied, as is the thermal stability of these films.