Patent ID: 8002946

Claim:
A plasma reactor for processing a rectangular-shaped workpiece, comprising: a vacuum chamber having a ceiling and a cylindrical sidewall; a workpiece support pedestal within said chamber including a cathode having a rectangular-shaped surface for supporting the rectangular-shaped workpiece, wherein said cathode comprises: an inner disk-shaped member of a first electrical characteristic, an intermediate annular member of a second electrical characteristic different from said first electrical characteristic, and having a circular inner boundary conforming with said inner disk-shaped member and a rectangular outer boundary congruent with a boundary of said rectangular support surface; an outer annular member having a rectangular inner boundary conforming with said rectangular outer boundary of said intermediate annular member, and comprising two layers of respective third and fourth electrical characteristics surrounding said intermediate annular member; wherein said first electrical characteristic corresponds to that of a metallic material, said second electrical characteristic corresponds to that of an insulator material, and said third and fourth electrical characteristics corresponds to those of different dielectric materials.