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

Improvement of characteristics of polycrystalline silicon thin film transistors (poly-Si TFTs) was achieved by defect reduction methods of oxygen plasma at 250 degreesC and at 30 W and 1.25 x 10(6)-Pa high-pressure H2O vapor heat treatments at 270 degreesC. 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 x 10(18) (as crystallized) to 1.6 x 10(17) cm(-3) and the densities of tail states from 9.2 x 10(18) (as crystallized) to 2.7 x 10(18) cm(-3). respectively. The threshold voltage of transfer characteristics was reduced from 4.1 to 1.3 V through the defect reduction. (C) 2002 Published by Elsevier Science B.V.