Degradation mechanisms and improvement of thermal stability of CoSi2/polycrystalline Si layers

Abstract
Degradation mechanisms of CoSi2/polycrystalline Si (polycide) films have been investigated. CoSi2 was formed on various silicon substrates (stacked or one‐layer structures composed of polycrystalline Si 800–10 800 Å and amorphous Si 800–3000 Å). The thermal stability of these silicide films were examined using four‐point probe measurement. It was found that the microstructure of the underlying silicon substrate, rather than the grain size of the CoSi2 or the silicide/polycrystalline Si interface, has the greatest influence on the thermal stability of the polycide films. The CoSi2 formed on as‐deposited amorphous Si provides the maximum thermal stability. Those films are stable at 1000 °C up to 120 s, even for undoped polycide films.