Four-Terminal Polycrystalline-Silicon Thin-Film Transistors with High-k HfO2 Dielectric on Glass Substrate

In this study, four-terminal polycrystalline-silicon thin-film transistors (4T poly-Si TFTs) with high-k HfO2 gate dielectric were fabricated on glass substrate and tested. Double layer top gate dielectric was made of SiO2 and HfO2, which led to a capacitance equivalent thickness of 30 nm. Furthermore, the bottom gate was made of SiO2 gate dielectric with a thickness of 150 nm. Continuous-wave laser lateral crystallization was used to form poly-Si film. We achieved a high field-effect mobility of260 cm
²
/Vs and subthreshold swing of 0.19 V/dec for TG drive. In addition, γ-value, defined by γ=|ΔVth/VBG| was found to be approximately equal to the theoretically predicted value.