TOP-GATE MICRO-CRYSTALLINE 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°C. The active layer is an undoped μc-Si film, 200 nm thick, deposited by Hot-Wire Chemical Vapor. The drain and source regions are highly phosphorus (N-type TFTs) or boron (P-type TFTs) doped μc-films deposited by HW-CVD. The gate insulator is a silicon dioxide film deposited by RF sputtering. Al-SiO2N type c-Si structures using this insulator present low flat-band voltage, -0.2V, and low density of states at the interface Dit=6,4 x 10 eVcm. High field effect mobility, 25 cm/V.s for electrons and 1.1 cm/V.s for holes, is obtained. These values are very high particularly the hole mobility that it was never reached previously. .