Methods and apparatus for post treating an oxide layer on a semiconductor substrate are disclosed. In one or more embodiments, the oxide layer is formed by thermal oxidation or plasma oxidation and treated with a plasma comprising helium. The helium-containing plasma may also include hydrogen, neon, argon and combinations thereof. In one or more embodiments, a SiO2 oxide layer is formed on a silicon substrate and treated with a plasma to improve the interface between the silicon substrate and the SiO2 oxide layer.