Ultrahigh-Performance Polycrystalline Silicon Thin-Film Transistors on Excimer-Laser-Processed Pseudo-Single-Crystal Films

Thin-film transistors (TFTs) were fabricated on polycrystalline silicon (poly-Si) films formed by position-controlled large-grain growth technology using an excimer laser. The field-effect mobility, on-off transition slope, and threshold voltage were 914 cm2 V-1 s-1, 93 mV/decade, and 0.58 V for the n-channel device, and 254 cm2 V-1 s-1, 122 mV/decade, and -0.43 V for the p-channel device, respectively. These values indicate that TFTs had an ultrahigh performance comparable to that of {100}-oriented crystal-silicon metal–oxide–semiconductor (MOS) transistors. Furthermore, their effective mobilities had the same effective field and temperature dependences as those of MOS transistors, indicating that electrons and holes were predominantly scattered not by random grain boundaries or defects in the Si film, but by phonons at the SiO2–Si interface, similarly to those of crystal-silicon MOS transistors. These attractive results were obtained as a result of the fact that the TFT channel region was made up of nearly {100}-oriented single grains.