Phenomenological model of reactive r.f.-magnetron sputtering of Si in Ar/O2 atmosphere for the prediction of SiOx thin film stoichiometry from process parameters

The process of reactive sputtering from a silicon target in an Ar/O2 gas mixture is investigated. An optical plasma regulating circuit using the intensity of the 251.9 nm Si I line as setpoint is employed to stabilize the sputtering process. A phenomenological model of the process is derived that, in contrast to previous models, allows to calculate the composition of the growing SiOx film exclusively from measurable process parameters and accounts for the non-uniform deposition at the substrate. Film compositions X predicted this way for different setpoints were verified by Rutherford back-scattering spectroscopy.
As an example, a SiO2/SiO1.5/SiO2 layer stack was prepared applying an appropriate setpoint sequence. During a subsequent high temperature anneal the stack transformes into an ultrathin layer of nanocrystalline silicon embedded in an oxide matrix, a structure that has high potential for applications in novel optoelectronic and non-volatile MOSFET memory devices (nanocrystal memories).