Defect Reduction in Polycrystalline Silicon Thin Films at 150 °C

Abstract

We report defect reduction in 50-nm-thick laser-crystallized polycrystalline silicon (poly-Si) films by a combination of hydrogen plasma at 100 W for 5 s at room temperature with 4.7×105 Pa H2O vapor heat treatment at 150 °C for 6 h. The present treatment increased the photoconductivity to 1×10-3 S/cm for undoped poly-Si films under the illumination of 532 nm light at 100 mW/cm2. It also increased the electrical conductivity to 30 S/cm for 2×1019 cm-3 phosphorus-doped poly-Si films. Those values were comparable to those for samples treated with 1.3×106 Pa H2O vapor heat treatment for 3 h at 260 °C. Hydrogen concentration increased from 1.6 to 5.4 at. % as hydrogen plasma duration increased from 5 to 120 s. It was decreased by subsequent H2O vapor heat treatment at 150 °C, and ultimately ranged from 1.1 to 4.5 at. %. Hydrogen atoms play a catalytic role in the dissociation of H2O molecules at 150 °C.