Characterization and control of defect states of polycrystalline silicon thin film transistor fabricated by laser crystallization

Abstract Improvement of characteristics of polycrystalline silicon thin film transistors (poly-Si TFTs) was achieved by defect reduction methods of oxygen plasma at 250 ° C and at 30 W and 1.25×106-Pa high-pressure H2O vapor heat treatments at 270 ° C . Numerical analysis of transfer characteristics revealed that the combination of oxygen plasma for 40 min with the high-pressure H2O vapor annealing for 3 h effectively reduced the densities of deep level states from 1.4×1018 (as crystallized) to 1.6×10 17 cm −3 and the densities of tail states from 9.2×1018 (as crystallized) to 2.7×10 18 cm −3 , respectively. The threshold voltage of transfer characteristics was reduced from 4.1 to 1.3 V through the defect reduction.