Magnetically enhanced plasma chamber with non-uniform magnetic field

摘要

A plasma chamber having a magnet which produces a magnetic field such that, within a region parallel to and adjacent to the workpiece, the direction of the magnetic field is approximately the vector cross product of (1) the gradient of the magnitude of the magnetic field, and (2) a vector extending perpendicularly from the workpiece surface toward the plasma. Alternatively, the plasma chamber includes a north magnetic pole and a south magnetic pole located at distinct azimuths around the periphery of the workpiece. The azimuth of the south magnetic pole relative to the north magnetic pole is clockwise around the central axis, and each magnetic pole faces a direction which is more toward than away from a central axis of the workpiece area. An additional aspect of the invention is a plasma chamber having a rotating magnetic field produced by electromagnets spaced around the periphery of the workpiece which receive successive fixed amounts of electrical current during successive time intervals. During each transition between the time intervals, the current supplied to each electromagnet is changed relatively slowly or relatively quickly according to whether the current change includes a change in polarity.