Static and Radio-Frequency Characteristics of Green-Nanoseconds Laser-Crystallized Poly-Si Thin-Film Transistors

In this study, we investigate the static and radio-frequency characteristics of poly-Si thin-film transistors (TFTs) with the channels treated by using either green-nanoseconds laser crystallization (GLC) or solid phase crystallization (SPC) processes. The influences of the crystallization schemes on the granular structures of the resulted poly-Si as well as the device characteristics were studied and compared. Scanning Electron Microscope observations indicate that mean grain size of the 50 nm-thick poly-Si films is approximate 70 nm following the SPC process, whereas GLC process enlarges the mean grain size to 0.5 μm. As a consequence, GLC poly-Si TFTs exhibit greatly improved electron mobility and transconductance as compared to the SPC ones. Moreover, superior high-frequency characteristics with cut-off frequency (fT) and maximum oscillation frequency (fmax) of 21.1 GHz and 24.1 GHz, respectively, are recorded in GLC devices with channel length of 0.26 μm.