Exemplary semiconductor processing chambers may include showerhead. The chambers may include a pedestal configured to support a semiconductor substrate, where the showerhead and pedestal at least partially define a processing region within the semiconductor chamber. The chamber may include a spacer characterized by a first surface in contact with the showerhead and a second surface opposite the first surface. The chamber may include a pumping liner characterized by a first surface in contact with the spacer and a second surface opposite the first surface. The pumping liner may define a plurality of apertures within the first surface of the pumping liner.