Integration of chemical vapor deposition titanium nitride for 0.25 μm contacts and vias

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Abstract
A chemical vapor deposition (CVD) TiN liner process was developed and integrated into 0.25 μm contact and via process modules as an adhesion layer and barrier for tungsten plug deposition. The previous physical vapor deposition (PVD) TiN process used for 0.35 μm contacts and vias was found to be inadequate for the next generation 0.25 μm technology due to poor conformality. Three major advantages were achieved for CVD over the previous PVD technology: (1) the CVD TiN liner is able to fill higher aspect ratio contacts resulting in high yield and low contact resistance, (2) the CVD TiN liner produces a conformal adhesion layer that was found to prevent against WF6 attack of underlying silicide for unlanded contacts, and (3) via electromigration resistance was greatly improved through the elimination of early fails. The final process incorporates deposition of a collimated PVD Ti/TiN underlayer which was found to improve contact resistance. Details of the process and supporting electrical and reliability results are presented.

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