A novel two-step laser crystallization technique for low-temperature poly-Si TFTs

We present investigations on a novel technique for preparing low-temperature poly-Si thin-film on glass substrates using two-step laser crystallization. In the first step, seeds are created by excimer laser induced crystallization of very thin (26 nm) amorphous silicon (a-Si) thin-films deposited by plasma enhanced chemical vapor deposition (PECVD). A second (a-Si) thin-film of 80-120 nm is used to obtain large crystalline grains grown around the seed crystallites during the second laser crystallization. Using this two-step crystallization (TSC) approach, we fabricated poly-Si thin-film transistors (TFTs) with electron mobility of 103 cm/sup 2//V/spl middot/s and ON/OFF current ratio of 10/sup 7/. They are two times and four times higher than those of the poly-Si TFTs fabricated in the same run using conventional single-step excimer laser crystallization.