CVD/PVD Cu seed layer for sub 0.10μm interconnects

摘要

In order to improve current generation Cu interconnects yields and reliability, and to extend the electrochemical deposition (ECD) technology to the sub 0.10μm interconnects, the current technology Cu seed layer must overcome significant shortcomings. In general, PVD Cu seed layer does not provide adequate step coverage of very narrow openings (trenches or vias). As a result, the Cu seed layer is often discontinuous on the sidewalls, leading to voids of the plated copper inside features of high aspect ratio. Such voids result in low yields and poor reliability. On the other hand, CVD Cu seed layer, while conformal and providing good step coverage, has poor adhesion to the refractory metal barrier and is often too thin on the field (for adequate surface conduction) and/or too thick on the sidewalls. This paper reports the use of a combined CVD/PVD Cu seed layer. It provides good adhesion to the barrier, minimal thickness inside the features with excellent continuous bottom and sidewall coverage, and sufficient thickness on the field (to ensure adequate surface conduction).