Characteristics of thin-film transistors fabricated on nucleation-controlled poly-si films by surface steps

Polycrystalline Si films were prepared on SiO₂/Si substrates by solid-phase crystallization of vacuum-evaporated amorphous Si with a nucleation-controlled process by steps formed at the substrate surface. Crystallinity of the Si films and characteristics of n- and p-channel thin-film transistors fabricated on the Si films have been investigated. The Si films were found to be composed of stripe-shaped grains elongated in the direction perpendicular to the step. The vast majority of the grains had the 〈111〉 axis in the direction perpendicular to the substrate surface. Concerning the in-plane crystal orientation, a tendency for the 〈211〉 axis to align in the direction perpendicular to the step was found. Both n- and p-channel transistors fabricated on the Si films showed improved channel carrier mobility compared to those fabricated on Si films prepared by solid-phase crystallization without nucleation control. The improvement was more pronounced in n-channel transistors, which suggested that p- channel transistor performances were less sensitive to grain boundaries.