Methods and apparatus for processing substrates are disclosed herein. The process chamber includes a chamber body, a substrate support pedestal, a pump port and a gas injection funnel. The chamber body has an inner volume and the substrate support pedestal is disposed in the inner volume of the chamber body. The pump port is coupled to the inner volume and is disposed off-center from a central axis of the substrate support pedestal. The pump port provides azimuthally non-uniform pumping proximate to a surface of the substrate support pedestal and creates localized regions of high pressure and low pressure within the inner volume during use. The gas injection funnel is disposed in a ceiling of the chamber body and opposite the substrate support pedestal. The gas injection funnel is offset from the central axis of the substrate support pedestal and is disposed in a region of low pressure.