Plasma reactor having a variable coupling of low frequency rf power to an annular electrode

Abstract

A plasma reactor having tunable low frequency RF power coupling to annular electrode. The reaction chamber has electrically conductive base connected to a low frequency RF source via RF match. An electrostatic chuck is attached to the electrically conductive base. An outer sidewall of the electrically conductive base is coated with plasma corrosion-resistance dielectric layer. A coupling ring is made of a dielectric material and surrounds an outer perimeter of the base. A focus ring is disposed above the coupling ring, the focus ring being arranged to surround the electrostatic chuck and be exposed to the plasma. The plasma reactor further comprises an annular electrode that is disposed above the coupling ring but below the focus ring, a wire having a first end electrically connected to the base, and a second end connected to the annular electrode. A variable capacitance is serially connected to the wire.