Comparative study on crystallinity of laser-annealed polysilicon thin films for various laser sources

Abstract

In this study, we compared the crystallinities of polycrystalline silicon thin films annealed using green laser annealing (GLA) with a 532-nm pulsed laser, near-ultraviolet laser annealing (NULA) with a 355-nm pulsed laser, and blue laser diode annealing (BLDA) with 450-nm continuous-wave (CW) lasers. Three-dimensional heat transfer simulations were performed to obtain the temperature distributions in a 100 nm-thick amorphous silicon layer, and optimum laser conditions were determined for each laser annealing. GLA, NULA, and BLDA experiments were conducted based on the thermal simulation results, and the crystallinity of the annealed samples was quantitatively analyzed via spectroscopic ellipsometry. The analysis results indicated that GLA and BLDA resulted in good crystallinity that was comparable to the result of furnace annealing, whereas NULA resulted in a relatively poor crystal quality. The difference in the crystallinities produced by the annealing lasers could be explained using the thermal simulation results. This study provides an insight into the optimum laser annealing conditions for realizing high-quality poly-silicon thin films.