Control of the initial stage of nanocrystallite silicon growth monitored by in-situ spectroscopic ellipsometry

The early stage of nanocrystallite silicon (nc-Si:H) growth from plasma-enhanced chemical vapor deposition (PECVD) was investigated through in-situ monitoring by UV-visible spectroscopic ellipsometry. The film structure was an amorphous up to about 500 Angstrom thickness on SiO2 substrate, which was very sensitive to the selection of the substrate including its surface roughness. Especially, the thickness of the transition layer from amorphous to nc-Si phase is thicker on SiO2 substrate than that on Cr or c-Si with native oxide one under an identical plasma condition. The SiH4 gas heating technique has been proposed to enhance the crystallinity at the early stage of growth on SiO2.