Recently, a new inline tool for high rate deposition of silicon nitride for (multi) crystalline silicon solar cells, the "DEPx", was introduced. This tool uses the so called expanding thermal plasma (ETP) technique operated on an Ar-NH3 gas mixture to dissociate SiH4. We will discuss some of the important properties of this remote and high density plasma in terms of ion densities, radical densities (N, NH, NH2) and the NH3 consumption degree