Effects of hydrogen on poly- and nano-crystallization of a-Si:H prepared by RF magnetron sputtering

Effects of hydrogen species on the formation of polycrystalline silicon (poly-Si) deposited by RF magnetron sputtering were studied. In order to control the amount of Si–H bonds which affected crystallinity of Si films, inductive coupled plasma (ICP) was used with hydrogen during Si film deposition. Poly-Si films were fabricated by supplying hydrogen without generating ICP, while nanocrystalline Si was formed in amorphous Si films deposited with hydrogen and ICP. Si–H bonds formed during sputtering with hydrogen led the crystallization of Si films, but a large amount of Si–H bonds produced by ICP reduced the crystallization of Si. It is believed that Si–H bonds enhance the crystallization of the Si films since they increase the diffusion length of Si on the substrate surface by occupying the Si dangling bonds. However, excessive amount of Si–H bonds degraded the crystallinity of the Si films by interrupting the formation of Si–Si bonds.