Heat Treatment of Amorphous and Polycrystalline Silicon Thin Films with H2O Vapor

Changes in electrical and optical properties induced by heat treatment with H2O vapor at 350 °C are reported for laser-induced amorphous silicon, low pressure chemical vapor amorphous silicon (LPCVD a-Si) and laser crystallized polycrystalline silicon films. The dark conductivity was reduced and the photoconductivity was increased by the heat treatment for these films. The optical absorption in the photon energy range lower than 1.5 eV was reduced for the a-Si films. The optical band gap was slightly increased from 1.48 eV to 1.51 eV for the LPCVD a-Si. The increase in hydrogen concentration was less than 2×1020 cm-3 after the treatment. These results show that the heat treatment with H2O vapor reduces the defect density in the silicon films with a small amount of hydrogen incorporation.