Patent ID: 7757633

Claim:
A plasma processing apparatus comprising: a vacuum chamber; a wafer having a top surface, a diameter, and a circumferential edge; a wafer support within the vacuum chamber having: (a) a central wafer supporting member having a diameter that is substantially equal to the diameter of the wafer; and (b) a separate annular peripheral member surrounding the central wafer supporting surface and lying in a common plane with the central wafer supporting member, and wherein the annular peripheral member lies radially outward of the circumferential edge of the wafer; an RF generator coupled to the wafer support; and an annular permanent magnet assembly is located within the annular peripheral member of the wafer support, the annular permanent magnet assembly comprising: an outer annular magnet ring having a polar axis that is perpendicular to the central wafer supporting member of the wafer support; and an inner annular magnet ring having a polar axis that is perpendicular to the central wafer supporting member of the wafer support and the top surface of the wafer, wherein the polar axis of the inner annular magnet ring is opposite the polar axis of the outer annular magnet ring, wherein the inner and outer annular magnet rings are configured to form an annular magnetic tunnel above the annular peripheral member and surrounding the central wafer supporting member so as to trap plasma forming electrons in the annular magnetic tunnel and away from the top surface of the wafer and the central wafer supporting member such that a plasma formed in the annular magnetic tunnel diffuses inwardly from the annular magnetic tunnel and over the top surface of the wafer that is supported on the central wafer supporting member.