High-performance low-temperature poly-Si TFTs for LCD

High-performance low-temperature poly-Si TFTs were developed by a 600°C process so that a glass substrate could be utilized. To achieve low threshold voltage (VTH) and high field effect mobility (µFE), effective hydrogenation using a thin poly-Si gate was employed. Furthermore, active layer poly-Si deposition conditions by LPCVD were optimized. Thinning the gate poly-Si was very effective in reducing VTHby hydrogenation. Crystallinity of poly-Si after therma annealing at 600°C depended closely on the poly-Si deposition temperature and was a maximum at 550-560°C. The developed TFTs, with poly-Si deposited at 550°C and a 1000 Å gate, had a VTHof 6.2 V and µFEof 37 cm²/V.s. These TFTs were successfully applied to LCDs with fully integrated drive circuits.