[en] An analysis is given of the net mass flux from target to film during steady-state substrate biased rf sputtering. Expressions are derived for film composition and growth rate in terms of relative sputtering rates of atomic species in the surface region of the target and film, and the geometrical transfer efficiencies between target and film. Calculations have been carried out of predicted film composition as a function of substrate bias voltage for several cases, and a comparison is made with experimental data