Excimer laser crystallization of a-Si1-xGex thin films and its applications to the low-temperature poly-Si1-xGex TFTs

Abstract

In this study, excimer laser crystallization (ELC) of amorphous Si1-xGex (a-Si1-xGex) thin film has been demonstrated. A-Si1-xGex thin films with several Ge atomic concentrations were crystallized with different laser energy densities and laser shot numbers per unit area. According to the AES analysis results, the atomic concentration of Ge atom increased gradually toward the surface of the poly-Si1-xGex thin film after excimer laser irradiation. This would lead to the degraded electrical characteristics of the poly-Si1-xGex TFTs. Therefore, a novel Ge doping method has been proposed to fabricate high-performance poly-Si1-xGex TFTs. For small size TFTs, the hole mobility of the poly-Si1-xGex, TFTs was superior to that of poly-Si TFTs. The poly-Si0.91Ge0.09 TFT exhibited a high hole mobility of 112 cm(2)/V-s, while the hole mobility of the poly-Si counterpart was 73 cm(2)/V-s.