Crystallization of double-layered silicon thin films by solid green laser annealing

A new laser annealing crystallization method for enhancing the crystallinity of polycrystalline Si (poly-Si) is demonstrated. This method utilizes double-layered amorphous Si films and the high penetration property of the green laser in poly-Si films. The simultaneous crystallization of the upper and lower a-Si layers of the double-layered substrate is achieved, with the upper a-Si layer becoming poly-Si with very large crystal grains. Furthermore, the crystallization laser energy of this double-layered substrate is reduced by approximately 30% compared with that of a conventional single-layer a-Si substrate, suggesting a thermal reserving role of the lower a-Si layer when it crystallizes upon the irradiation of green laser light.