Fabrication of amorphous silicon nitride thin films by radio-frequency sputtering assisted by an inductively coupled plasma

We have investigated the preparation of amorphous silicon nitride (a-Si1-xNx:H) thin films by reactive RF sputtering assisted by inductively coupled plasma (ICP) with argon (Ar), hydrogen (H2) and nitrogen (N2). The ICP assist system gives the high density ICP mode plasma near the substrate with relatively low plasma potential and electron temperature by applying > 50 W to the ICP antenna coil. The E04 band gap is successfully controlled from 2.2 eV to 3.3 eV by changing the RF power to the antenna coil. The ICP mode plasma significantly enhances the formation of Si-N bonds in a-Si1-xNx:H films, due to the effective generation of N radicals near the substrate. The ICP mode plasma also gives the high deposition rate for wide band gap a-Si1-xNx:H films. A small N2 gas ratio (< 1%) is enough to produce wide band gap a-Si1-xNx:H films, therefore, a sufficient Ar gas ratio can be maintained for the Si sputtering. This method gives a simple and effective process to produce wide band gap a-Si1-xNx:H films with a relatively high deposition rate.