Advanced long throw PVD for contact to silicon and via applications

Abstract

In W-plug processing, Ti contact and TiN barrier layers are essential prerequisites for successful device manufacture. Physically collimated or long throw PVD techniques are commonly used to deposit these layers. In this work, a new long throw sputtering technology was evaluated in a high volume DRAM production environment. The new module uses an extended distance of 430 mm between source and substrate to increase the proportion of near-normal metal flux arriving at the substrate. In this way, the base coverage of Ti in deep contact holes and vias can be significantly improved. The 430 mm process was compared to the earlier long throw generation using 245 mm source-to-substrate distance in both contact and via structures. Electrical results are given showing that using the 430 mm process, Ti thickness can be reduced without compromising device characteristics. The paper looks at the benefits of such an approach. New data are presented to show that base coverage can be further increased by working at pressures low enough to approach a zero gas scatter state, potentially extending the technique to ≤0.18 μm.