Patent ID: 8101510

Claim:
A plasma processing apparatus comprising: a process chamber; a platen positioned in the process chamber for supporting a workpiece; a source configured to generate a plasma in said process chamber having a plasma sheath adjacent to a front surface of the workpiece; an insulating modifier, having a gap therein, wherein a gap plane is defined by portions of said insulating modifier closest to said sheath and proximate said gap, and a gap angle is an angle between said gap plane and a workpiece plane defined by the front surface of the workpiece facing the plasma, and wherein said gap angle is non-zero; and a bias source configured to bias said workpiece to attract ions from the plasma across the plasma sheath towards the workpiece for treating the workpiece, wherein a range of incident angles of the ions relative to the workpiece plane is dependent on a shape of a boundary between the plasma and the plasma sheath, and wherein said range of incident angles comprises a center angle and an angular distribution about said center angle, and said center angle is not perpendicular to said workpiece plane.