Compositional analysis of SiOxNy : H films by heavy-ion ERDA: the problem of radiation damage

Abstract

Films of SiOxNy:H were deposited at room temperature on Si substrates by the electron cyclotron resonance (ECR) plasma method. By varying the flow rates of the precursor gases SiH4, O-2. and N-2, the whole composition range between pure silicon oxide and nitride could be covered. Heavy-ion elastic recoil detection analysis (HI-ERDA) with a 150 MeV Kr-86 ion beam and time-of-flight (ToF) mass separation was applied to determine the absolute atomic concentrations of all film components, including hydrogen. Additionally, the bonding configuration of the films was studied by infrared (IR) spectroscopy. Extended ion beam exposure was found to decrease the intensity of the N-H phonon band as well as the nitrogen and hydrogen concentrations. By storing the ion scattering data event by event and by recalculating a zero-dose composition, this effect was taken into account. The corrected Hl-ERDA results revealed clear relations to the deposition parameters (e.g. the O-2/SiH4 flow ratio). The hydrogen incorporated in the films turned out to be bonded predominantly to nitrogen. The damage effects were strongest in the medium composition range. They were found to scale with the relative concentration of SiO2N2-type basic tetrahedrons, suggesting that this bonding configuration is most sensitive against irradiation during the HI-ERDA measurement. Copyright (C) 2002 John Wiley Sons, Ltd.