Method and apparatus for controlling stress variation in a material layer formed via pulsed DC physical vapor deposition

An apparatus for controlling stress variation in a material layer formed via pulsed DC physical vapour deposition, the apparatus comprising:

• a chamber for housing a target from which the material layer is formed and a substrate upon which the material layer is formable, the chamber comprising an inlet for introducing a gas into the chamber;
• a platen disposed in the chamber, wherein the platen defines a recess at an outer surface of the platen that is exposed to the chamber;
• a plasma generating arrangement for generating a plasma within the chamber, wherein the plasma generating arrangement includes an anode ring disposed in the chamber;
• a DC power supply configured to apply pulsed DC power between the target and the anode ring;
• a voltage source for applying an RF bias voltage to the substrate that generates an electric field directed substantially perpendicular to the substrate;
• a first magnetic field generating arrangement configured to in use generate a first magnetic field proximate the target for localising the plasma adjacent the target;
• and
• a second magnetic field generating arrangement disposed in the recess of the platen extending in a direction substantially parallel with a plane of a flat surface of the substrate for generating in use a second magnetic field proximate the substrate that does not substantially interact with any other magnetic fields remote from the platen to steer gas ions from the plasma to selective regions upon the material layer formed on the substrate, wherein the second magnetic field generating arrangement comprises a plurality of magnets configured as an array, and wherein the plurality of magnets are disposed in elongate channels that extend across an upper surface of a cassette in a parallel configuration,
• wherein the gas ions steered by the second magnetic field are substantially unaffected by the first magnetic field, and wherein an ion density of the plasma where the electric field and the second magnetic field are perpendicularly oriented is increased compared to where the electric field and the second magnetic field are not perpendicularly oriented.