Integration of PECVD Tungsten Nitride as a Barrier Layer for Copper Metallization

Abstract

AbstractAmorphous tungsten nitride (WNx) is a promising diffusion barrier for extending Cu metallization beyond 0.18 μm. This study evaluates the barrier performance, adhesion, and step coverage of PECVD WN 0.5 integrated with a CVD Cu seed layer. The WN0.5 films exhibit amorphous structure with 33% bottom and side-wall step coverage in 0.14 μm wide structures with 9:1 aspect ratio. The potential of 50 Å WN0.5 as an effective Cu barrier is shown by the absence of Secco etch-pits in the Si substrate after a 30 min anneal at 500°C. When deposited on PECVD WN0.5 the CVD Cu films exhibit uniform nucleation, and as deposited resistivity of 2.5 μΩ-cm. Step coverage of the CVD Cu is better than 95% in 0.14 μm structures. Adhesion exceeding epoxy strength of the CVD Cu seed layer even to air-exposed WN0.5 is demonstrated using stud-pull adhesion tests.