High electron mobility polycrystalline silicon thin-film transistors on steel foil substrates

Thin-film transistors have been fabricated in polycrystalline silicon films on steel foil. The polycrystalline silicon films were formed by the crystallization of hydrogenated amorphous silicon, which had been deposited on 200-μm-thick foils of stainless steel coated with ∼0.5-μm-thick layers of SiO₂. We employed crystallization temperatures (and duration) of 600°C (6 h), 650°C (1 h), and 700°C (10 min). Top-gate transistors made from films crystallized at 650°C have an average electron field-effect mobility of 64 cm²/V s, with equal values in the linear and saturated regimes. Thus steel substrates permit a substantial reduction in crystallization time over glass substrates, and afford polysilicon with high electron mobility.