Shallow magnetic fields for generating circulating electrons to enhance plasma processing

摘要

The present invention is embodied in a plasma reactor for processing a workpiece such as a semiconductor wafer having an axis of symmetry, the reactor including a reactor chamber with a ceiling, a pedestal for supporting the workpiece within the chamber under the ceiling, a processing gas supply inlet into the chamber, an RF plasma power source coupled to the pedestal, and a magnetic field source near the ceiling providing a radially symmetrical magnetic field relative to the axis of symmetry within a portion of the chamber near the ceiling. The magnetic field source can include an electromagnet or plural magnets disposed over the ceiling in a radially symmetrical fashion with respect to the axis of symmetry. The plural magnets may be permanent magnets or electromagnets. The radially symmetrical magnetic field penetrates from the ceiling into the chamber to a shallow depth, and the height of the ceiling above the workpiece exceeds the depth.