Embodiments of the invention contemplate the formation of a high efficiency solar cell using a novel plasma oxidation process to form a passivation film stack on a surface of a solar cell substrate. In one embodiment, the methods include providing a substrate having a first type of doping atom on a back surface of the substrate and a second type of doping atom on a front surface of the substrate, plasma oxidizing the back surface of the substrate to form an oxidation layer thereon, and forming a silicon nitride layer on the oxidation layer.