Embodiments of collimators for use in substrate processing chambers are provided herein. In some embodiments, a collimator includes: a body having a central region, a peripheral region, and a transitional region disposed between the central and peripheral regions; a first plurality of apertures in the central region having a first aspect ratio; a second plurality of apertures in the peripheral region having a second aspect ratio less than the first aspect ratio; and a third plurality of apertures in the transitional region, wherein the third plurality of apertures are cut so the transitional region forms a conical shape surrounding the central region.