Laser beam application to thin film transistors

Laser crystallization and amorphization of silicon films are discussed. Poly-Si films with fine crystalline grains (< 100 nm) are formed by liquid/solid interface controlled growth with a velocity of 0.6 m/s by a XeCl excimer laser irradiation. Large grain growth of silicon films (> 1 mu m) is also discussed. An amorphous state is achieved via rapid solidification when silicon films are melted completely. Crystallization and amorphization are reversible. They are governed by the laser energy density. The application of the rapid laser heating method to fabrication of top-gate-type poly-Si and a-Si thin film transistors (TFTs) is discussed. TFTs with a high mobility, 620 cm(2)/Vs (poly-Si) and 2.6 cm(2)/Vs (a-Si) were achieved by a 270 degrees C fabrication process. Application of a laser-induced-forward transfer to TFT fabrication is proposed for a simple process with a low cost.