DEGRADATION MECHANISMS AND IMPROVEMENT OF THERMAL-STABILITY OF COSI2/POLYCRYSTALLINE SI LAYERS

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 angstrom and amorphous Si 800-3000 angstrom). 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-degrees-C up to 120 s, even for undoped polycide films.