Low temperature polycrystalline silicon (LTPS) thin film transistors are necessary for creating high performance liquid crystal displays and organic light emitting diode displays. Excimer lasers have been used as the laser source for this process. However, this method presents two problems: 1) daily maintenance, which includes exchanging the laser gas and cleaning the laser windows, and 2) the limited process window of the optimum laser energy density for obtaining maximum mobility. To overcome these problems, we applied a green laser (second harmonics of a Q-switched Nd: YAG laser) instead of an excimer laser. This paper describes the high power green laser for LTPS, the annealing optical system for green lasers, and the poly-Si crystallization by a green laser.
