Defect Reduction in Polycrystalline Silicon Thin Films by Heat Treatment with High-Pressure H_2O Vapor

摘要

We investigated defect reduction in laser crystallized polycrystalline silicon (poly-Si) films by heat treatment with 1.3 x 10~6 Pa H_2O vapor. The H_2O vapor heat treatment at 260℃ for 6 h reduced the spin density in laser crystallized poly-Si films from 2.0 x 10~(18) (initial) to 6.5 x 10~(16)cm~(-3). The activation energy of the reaction for defect reduction was 0.26 eV. Photoconductivity under 532nm light illumination at 100mW/cm~2 was increased from 2.7 x 10~(-6) (initial) to 3.3 x 10~(-5) S/ cm by heat treatment for 1 h. The oxygen concentration in the silicon films was increased by 1.1 x 10~(19)cm~(-3) by heat treatment, although the hydrogen concentration was decreased by 1.4 x 10~(20)cm~(-3). This suggests that oxygen atoms have an important role in defect state reduction in polycrystalline silicon films.