Methods and apparatus for processing a substrate

1. A method for processing a substrate comprising:

applying a DC target voltage to a target disposed within a processing volume of a plasma processing chamber;

rotating a magnet disposed above the target at a default speed to direct sputter material from the target toward a substrate support disposed within the processing volume;

controlling an in-situ DC voltage in the processing volume via controlling rotating of the magnet;

measuring the in-situ DC voltage in the processing volume, the in-situ DC voltage measured between the target and the substrate support and is different from the DC target voltage;

determining if a measured in-situ DC voltage is greater than a preset value;

if the measured in-situ DC voltage is less than or equal to the preset value, maintaining the magnet at the default speed; and

if the measured in-situ DC voltage is greater than the preset value, rotating the magnet at a speed less than the default speed to decrease the in-situ DC voltage.

2. The method of claim 1 , wherein the default speed is based on a radius of the substrate to be plasma processed.

3. The method of claim 1 , wherein rotating the magnet at the speed less than the default speed is based on a dwell time for a radius of the substrate to be plasma processed, and wherein the dwell time is a duration spent per inch along a pathway of the magnet.

4. The method of claim 1 , wherein maintaining the magnet at the default speed and rotating the magnet at the speed less than the default speed is performed while maintaining the DC target voltage to the target.

5. The method of claim 1 , wherein a magnet radius of rotation is about 6 inches to about 7 inches.

6. The method of claim 1 , wherein the preset value is 1000V.

7. The method of claim 1 , wherein the in-situ DC voltage is about 870V to about 1000V.

8. The method of claim 1 , wherein rotating the magnet comprises rotating the magnet at about 0.5 rps to about 1.2 rps.