Abstract: Gas injector with a vacuum channel having an inlet opening in the front face and an outlet opening in the back face of the injector are described. The vacuum channel comprises a first leg extending a first length from the inlet opening in the front face at a first angle relative to the front face and a second leg extending a second length from the first leg to the outlet opening in the back face at a second angle relative to the front face. Processing chambers and methods of use comprising a plurality of processing regions bounded around an outer peripheral edge by one or more vacuum channel. A first processing region has a first vacuum channel with a first outer diameter and a second processing region has a second vacuum channel with a second outer diameter, the first outer diameter being less than the second outer diameter.