The embodiments described herein generally relate to a substrate support assembly for use in a plasma processing chamber to provide non-uniform gas flow flowing between the substrate support assembly and sidewalls of the plasma processing chamber. In one embodiment, a substrate support assembly includes a substrate support assembly including a substrate support body defining at least a first side of the substrate support body, and a corner region and a center region formed in the first side of the substrate support body, wherein the corner region has a corner width that is smaller than a center width of the center region, the widths defined between a center axis and the first side of the substrate support body.