Patent ID: 8470127

Claim:
A showerhead electrode adapted for use in a showerhead electrode assembly in a capacitively coupled plasma processing chamber wherein the showerhead electrode assembly comprises a backing plate having gas injection holes extending between upper and lower faces thereof, an alignment ring, a plurality of cam locks comprising studs and rotatable cam shafts which attach the showerhead electrode to the backing plate, and a plurality of alignment pins; the showerhead electrode comprising: a plasma exposed surface on a lower face thereof; a mounting surface on an upper face thereof; a plurality of gas injection holes extending between the plasma exposed surface and the mounting surface thereof and arranged in a pattern matching the gas injection holes in the backing plate; a plurality of unthreaded blind holes in the mounting surface configured to receive the alignment pins; an annular groove concentric with a center of the mounting surface and configured to receive the alignment ring; and concentric rows of threaded blind holes in the mounting surface configured to receive studs which attach the showerhead electrode to the backing plate, the concentric rows including an inner row comprising 8 threaded blind holes located on a radius ⅛ to ½ a total distance from a center to an outer edge of the showerhead electrode, a middle row comprising 8 threaded blind holes located on a radius ½ to ¾ the total distance from the center to the outer edge of the showerhead electrode, and an outer row comprising 8 threaded blind holes located on a radius ¾ to ⅞ the total distance from the center to the outer edge of the showerhead electrode, wherein a line passing through the center of the showerhead electrode passes through two of the threaded blind holes of the inner row and two of the threaded blind holes of the middle row to allow the camshaft to simultaneously engage and actuate inner and middle rows of the cam locks on the showerhead electrode.