Surface morphology and recrystallization behavior of amorphous Si after ArF laser irradiation

Abstract

193nm-ArF excimer laser irradiation of amorphous silicon (a-Si) thin film has great potential on the production of poly-crystalline silicon (poly-Si) thin film transistor liquid crystal displays (TFT-LCDs). The main reason for applying poly-Si thin films instead of a-Si thin films on fabricating high performance electronics devices is due to its higher electron mobility, which is strongly influenced by the film's surface morphology, grain size, microstructure and defect density. The specimens used in this study have a 100 nm-thick a-Si thin films deposited on glass substrate by plasma enhanced chemical vapor deposition (PECVD) technique. The effects of annealing parameters, such as shot number, repetition rate and the fluence, on the surface morphology and recrystallization behaviour of a-Si thin films were investigated. The results showed that the threshold fluence of partial melting of a-Si thin films at 1Hz and single shot was around 150 mJ/cm². Further increasing the fluence and shot numbers leads to the formation of microvoids trapped inside poly-Si film due to the evolution of hydrogen gas during the laser annealing process. The surface morphology formed during the recrystallization of amorphous Si thin films is found depending upon the laser fluence and shot numbers. The super-lateral grown (SLG) poly-Si grain can be obtained at the fluence around 190 mJ/cm².