Nanocrystalline silicon films deposited with a modulated hydrogen dilution ratio by catalytic CVD at 200 °C

Nanocrystalline silicon (nc-Si) thin films that are deposited at low-temperatures (<200 °C) often contain an incubation layer as thick as 10 nm. This incubation layer deteriorates performance of electronic devices, such as bottom-gate thin-film transistors, fabricated from the nc-Si film. We found that the crystallinity of the nc-Si films could be improved by adding a large quantity of hydrogen to the source gas. However, the hydrogen dilution degraded the deposition rate. We attempted a modulation of the hydrogen dilution ratio in a catalytic chemical vapor deposition (Cat-CVD) system to achieve both a minimal incubation layer and high throughput. We obtained an incubation-layer thickness of 3 nm and were able to grow a 200-nm-thick film in 18 min.