The effect of sub micron device via density on via fills was studied. A two-step cold/hot aluminum sputtering process was used to evaluate the effect of via density and ratio of deposition times on via fills. As via density increases, via fill becomes more challenging with a two-step cold/hot aluminum sputtering process. The via fill percentage was increased by changing the ratio of cold/hot deposition times. Results show that denser via structures require extended cold deposition times to compensate for higher via density. For a successful via fill, a conformal nucleation layer of aluminum must be formed with cold deposition, which acts as a seed and wetting layer to promote aluminum reflow into vias during subsequent hot deposition. It was found that by changing the ratio of cold/hot deposition times from 60:40 to 79:21 on dense via structure, the via fill was improved by 30%. (C) 2003 Elsevier B.V.. All rights reserved.