High performance LTPS thin-film transistors using low cost polycrystalline silicon by blue laser annealing

Crystallization of amorjyhous silicon (a-Si) to polycrystalline silicon (p-Si) by a continuous-wave blue laser diode of wavelength 445 nm is investigated for high throughput thin-film transistor applications (TFT). As the laser scan speed is changed at constant laser power, laser scanned p-Si films show three kinds of grain shape that can be distinguished according to grain growth mechanism: (1) solid phase crystallization (SPC), (2) partial melting growth (PMG), and (3) full melting growth (FMG). These three growth mechanisms are as a result of different laser irradiation time to a-Si and relative absorbed laser energy difference, therefore, they achieve different grain size and crystaUinity. By using this blue laser annealing (BLA) system, we can obtain the high performance and low cost low temperature polycrystalline silicon (L TPS) TFTs with large grain size.