We claim the ornamental design for a plasma reactor showerhead face plate having concentric ridge pattern, as shown and described.
FIG. 1 is a lower front perspective view of a plasma reactor showerhead face plate having concentric ridge pattern showing our new design, wherein dashed lines represent holes and are unclaimed as part of this invention;
FIG. 2 is a top plan view thereof;
FIG. 3 is a bottom plan view thereof;
FIG. 4 is a side elevational view thereof, all sides being identical thereto; and,
FIG. 5 is a cross-sectional view thereof, taken generally along line 5—5 in FIG. 3, showing succinctly the surface contours seen in FIGS. 1 and 3.