Reduction of plasma-induced damage by electron beam excited plasma CVD

Abstract The electron beam excited plasma (EBEP-) CVD has succeeded in making nano-crystaline films. On the other hand, the existence of the plasma-induced damage by EBEP-CVD has been confirmed using the hydrogen plasma by measuring the photoluminescence (PL). After plasma exposure, broad band peak appears in the region of 1.0–0.78 eV (1.2–1.6 μm), and intensity of bound exciton peak with energy of 1.093 eV, which is measured and the non-irradiated silicon has been decreased. The same experiment was also performed with RF plasma and the peak appeared not only for EBEP but also for conventional RF plasma. The damage peak tends to disappear over 420°C of the substrate temperature. The damage recovery analysis has been done in relation to the annealing temperature of the substrate after the plasma exposure. Exciton peak has been increased by increasing the temperature especially at 350°C. Furthermore, plasma-induced peak intensity has been decreased at temperature higher than 500°C. Similar peak has been observed in the samples irradiated with high-energy protons. Therefore, positive ions in the plasma are thought to be the source of the damage of the silicon. The origin of the plasma-induced defect in Si is also considered. According to these results, the electric potential of substrate was controlled in order to avoid collision with positive ions in the plasma. When it was set to zero, plasma-induced peaks did not appear.