Crystallization of poly-silicon film by different annealing techniques

Abstract

Poly-Silicon is widely used in semiconductor devices especially in TFTs technology. Performance of silicon thin film depends on the degree of crystallization. Enhancing the crystalline is the ultimate goal in this annealing process. The best annealing process will be identified. Initially Al doped Si film was prepared via PVD technique. Three different annealing processes were investigated. The first two techniques dealing with a single step annealing process, that were conventional heat treatment CHT and an excimer laser annealing ELA. The third technique, involved two-step annealing processes which combination from two techniques. The structural surface of the annealed poly-silicon thin film was characterized via AFM. The crystallization was measured based on the grain size. The result showed that the crystallization was extremely small with single step annealing process. In contrast, two step annealing process induced fine nanostructure and maximum crystallization. The optimum grain size was obtained as 129 nm at super lateral growth energy of 356 mJcm-2.