Effect of multi-polar magnetic field on the properties of nanocrystalline silicon thin film deposited by internal-type inductively coupled plasma.

An internal linear-type inductively coupled plasma (ICP) source with multi-polar permanent magnets was used to deposit nanocrystalline silicon thin films on a large-area substrate (470 mm x 370 mm), and the effects of a magnetic field on the characteristics of the plasma and deposited film were investigated. By applying the magnetic field, it was possible to obtain a high-density plasma of 2.8 x 10(11) cm(-3) at 15 mTorr Ar and 4000 W of RF power, which is about 50% higher than was obtained for the source without the magnetic field. The application of the multi-polar magnet field to the ICP source during the deposition of silicon film using SiH4/H2 also increased the deposition rates of the silicon thin films and the ratio Halpha*/SiH*, which transformed the structure of the silicon films deposited on the glass substrates from amorphous to nanocrystalline. Furthermore, the use of the magnetic field increased crystalline volume fraction and dark conductivity while decreasing the absorption coefficient. The improved characteristics were related to the increase in the ionization rate and the dissociation rate of SiH4/H2, which confined the plasma to the chamber volume and avoided losses to the chamber wall. The decrease in the absorption coefficient of the nanocrystalline silicon film deposited with a higher H2 percentage and with the magnetic field present is also related to the increase in the crystallization volume fraction. At 70% H2 with the magnetic field present, the nanocrystalline silicon thin films had a high crystalline volume fraction (68%), a dark conductivity of 3.4E-7 omega(-1) cm(-1), a deposition rate of 10 angstroms/s, and grain sizes of approximately 15 nm.