Patent ID: 7552736

Claim:
A process for removing polymer from a backside of a workpiece, comprising: supporting said workpiece on the backside in a vacuum chamber while leaving at least a peripheral annular portion of the backside exposed; confining gas flow at the edge of said workpiece within a gap at the edge of said workpiece on the order of about 1% of the diameter of the chamber, said gap defining a boundary between an upper process zone containing said wafer front side and a lower process zone containing said wafer backside; providing a polymer etch precursor gas underneath the backside edge of the workpiece and applying RF power to a region underlying the backside edge of the workpiece to generate a first plasma of polymer etch species concentrated in an annular ring concentric with and underneath the backside edge of the workpiece; removing polymer etch species from said upper process zone, wherein removing polymer etch species from said upper process zone comprises generating a second plasma from a precursor gas of a scavenger of the polymer etch species, and introducing scavenger by-products from said second plasma into said upper process zone.