HIGH-PERFORMANCE BOTTOM GATE TFTS BY EXCIMER-LASER CRYSTALLIZATION AND POST HYDROGENATION

Small grain poly-Si has defects of the order of 10(18) to 10(19) spins /cm(3). Hydrogen is generally used to terminate these defects, which i s introduced from a hydrogen plasma. Damage caused by UV emitted from the plasma glow discharge was identified as one of the causes limiting the quality of the bottom gate thin him transistor (TFT) devices. The effect of UV on the TFT transfer characteristics was studied. ESR was used to measure the change in the poly-Si dangling bond density as a result of UV irradiation. It was confirmed that plasma UV creates dama ge in the poly-Si. A combination of plasma hydrogenation and SiNx:H pa ssivation and thermal annealing was found to be particularly effective in reducing the defect density by reconstruction of dangling bonds an d redistribution of hydrogen without hydrogen loss. The excellent char acteristics obtained using this hydrogenation method are presented.