Surface passivation of silicon with the Plasmodul®

Gas mixtures of silane (SiH4) and ammonia (NH3) are used for plasma enhanced chemical vapour deposition (PECVD) of silicon nitride films (SiN). These films were deposited in a plasma reactor, called Plasmodul®. The plasma is excited by 2.45 GHz microwaves in the pressure range of 5–20 000 Pa. The silicon nitride films were deposited on silicon wafers, aluminium foils and molybdenum mirrors on a heatable substrate holder. The silicon wafers were used for electron lifetime determination. Aluminium foils and molybdenum mirrors were used for Fourier transform infrared (FTIR) spectroscopy and refractive index measurements. The plasma was characterised by measurements of the electron density distribution using Langmuir probes. The chemical composition of the films was investigated by FTIR spectroscopy and X-ray photoelectron spectroscopy (XPS) in dependence of the SiH4:NH3 monomer mixture ratio. The optical properties were determined by refractive index measurements. To investigate the passivation effect on silicon, the electron lifetime was measured by microwave detected photo conductance decay (MWPCD).