Embodiments described herein are directed to an apparatus for generating a precursor for a semiconductor processing system. In one embodiment, an apparatus for generating a precursor gas during a vapor deposition process is described. The apparatus includes a canister containing an interior volume between a lid and a bottom, a gaseous inlet and a gaseous outlet disposed on the lid, a plurality of silos coupled to the bottom and extending from a lower region to an upper region of the interior volume, and a tantalum precursor having a chlorine concentration of about 5 ppm or less contained within the lower region of the canister.