Top-grate microcrystalline silicon TFTs processed at low temperature (<200 °C)

N-type as well P-type top-gate microcrystalline silicon thin film transistors (TFTs) are fabricated on glass substrates at a maximum temperature of 200 degrees C. The active layer is an undoped mu c-Si film, 200 mn thick, deposited by Hot-Wire Chemical Vapor. The drain and source regions are highly phosphorus (N-type TFTs) or boron (P-type TFTs)-doped mu c-films deposited by HW-CVD. The gate insulator is a silicon dioxide film deposited by RF sputtering. Al-SiO2-N type c-Si structures using this insulator present low flat-band voltage,-0.2 V, and low density of states at the interface D-it=6.4 X 10(10) eV(-1) cm(-2). High field effect mobility, 25 cm(2)/V s for electrons and 1.1 cm(2)/V s for holes, is obtained. These values are very high, particularly the hole mobility that was never reached previously. (C) 2005 Published by Elsevier B.V.