A method and apparatus are for controlling stress variation in a material layer formed via pulsed DC physical vapour deposition. The method includes the steps of providing a chamber having a target from which the material layer is formed and a substrate upon which the material layer is formable, and subsequently introducing a gas within the chamber. The method further includes generating a plasma within the chamber and applying a first magnetic field proximate the target to substantially localise the plasma adjacent the target. An RF bias is applied to the substrate to attract gas ions from the plasma toward the substrate and a second magnetic field is applied proximate the substrate to steer gas ions from the plasma to selective regions upon the material layer formed on the substrate.