Low-Temperature Crystallization of Amorphous Si Films by Metal Adsorption and Diffusion

We developed a new process for low-temperature crystallization of amorphous Si films, by adsorbing metal ions on the films. Amorphous Si films were deposited by low-pressure chemical vapor deposition, spin-coated by metal solutions and subsequently annealed in Ar atmosphere. The amorphous Si films coated with Cu and Au from 1000 ppm solutions almost completely crystallized at 530°C after 20 h. The fractal size of the Cu-adsorbed Si films was 30–50 µm at 530°C within 10 h. The application of Ag, Zn, Fe, Cr and Al solutions did not enhance crystallization of amorphous Si films. The enhancement of low-temperature crystallization by Cu and Au adsorption was deduced from the electronegativity, eutectic temperature and diffusion length. Secondary ion mass spectroscopy analysis indicated that the adsorbed Cu induced crystallization of amorphous Si films. The field-effect mobility of polycrystalline silicon thin-film transistors fabricated using the annealed Si films with Cu adsorption was 6–10 cm2/V·s before hydrogen passivation.