Improved microcrystalline silicon TFTs

Electron field effect mobility of microcrystalline silicon TFTs, around 40 cm2/V s, is obtained thanks to an optimized process. This mobility is about 10 times the usual value of 1–2 cm2/V s. This jump is due to the present process where the undoped active layer and the doped layer are deposited in the same run, only by switching on the doping gas valve when the thickness of undoped μc-Si film is reached. The process allows to remove the interface between these two layers and to improve the crystalline fraction inside the doped μc-Si film.