HIGH-PERFORMANCE POLY-SI TFTS FABRICATED USING PULSED-LASER ANNEALING AND REMOTE PLASMA CVD WITH LOW-TEMPERATURE PROCESSING

Key technologies for fabricating polycrystalline silicon thin film transistors (poly-Si TFTs) at a low temperature are discussed. Hydrogenated amorphous silicon films were crystallized by irradiation of a 30 ns-pulsed XeCl excimer laser. Crystalline grains were smaller than 100 nm. The density of localized trap states in poly-Si films was reduced to 4 x 10(16) cm(-3) by plasma hydrogenation only for 30 seconds. Remote plasma chemical vapor deposition (CVD) using mesh electrodes realized a good interface of SiO2/Si with the interface trap density of 2.0 x 10(10) cm(-2) eV(-1) at 270 degrees C. Poly-Si TFTs were fabricated at 270 degrees C using laser crystallization, plasma hydrogenation and remote plasma CVD. The carrier mobility was 640 cm(2)/Vs for n-channel TFTs and 400 cm(2)/Vs for p-channel TFTs. The threshold voltage was 0.8 V for n-channel TFTs and -1.5 V for p-channel TFTs. The leakage current of n-channel poly-Si TFTs was reduced from 2 x 10(-10) A/mu m to 3 x 10(-13) A/mu m at the gate voltage of -5 V using an offset gate electrode with an offset length of 1 mu m.