Defect Reduction in Polycrystalline Silicon Thin Films by Heat Treatment with High-Pressure H2O Vapor

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We investigated defect reduction in laser crystallized polycrystalline silicon (poly-Si) films by heat treatment with $1.3\times 10^{6}$ Pa H2O vapor. The H2O vapor heat treatment at 260 °C for 6 h reduced the spin density in laser crystallized poly-Si films from $2.0\times 10^{18}$ (initial) to $6.5\times 10^{16}$ cm-3. The activation energy of the reaction for defect reduction was 0.26 eV. Photoconductivity under 532 nm light illumination at 100 mW/cm2 was increased from $2.7\times 10^{-6}$ (initial) to $3.3\times 10^{-5}$ S/cm by heat treatment for 1 h. The oxygen concentration in the silicon films was increased by $1.1\times 10^{19}$ cm-3 by heat treatment, although the hydrogen concentration was decreased by $1.4\times 10^{20}$ cm-3. This suggests that oxygen atoms have an important role in defect state reduction in polycrystalline silicon films.
2007-03-30