Positional relationships are established in a process chamber. An upper electrode is configured with a first surface to support a wafer, and an electrode has a second surface. A linear drive is mounted on the base and a linkage connected between the drive and the upper electrode. Linkage adjustment defines a desired orientation between the surfaces. The linear drive and linkage maintain the desired orientation while the assembly moves the upper electrode with the surfaces moving relative to each other. An annular etching region defined between the electrodes enables etching of a wafer edge exclusion region extending along a top and bottom of the wafer. Removable etch defining rings are configured to define unique lengths along each of the top and bottom of the wafer to be etched. Positional relationships of the surfaces enable limiting the etching to those unique lengths of the exclusion region.