Extreme Contact Scaling with Advanced Metallization of Cobalt

Extending tungsten contact for the most advanced nodes (≤ 7 nm) is challenging due to the growing impact of contact resistance on the overall resistance of a device and to the increasing difficulty of gapfill in features with <; 20 nm critical dimensions. The paper presents a gapfill material using metalorganic chemical vapor deposition (MO-CVD) cobalt for contact plug. Highlights of new gapfill material include proven seamless, voidless gapfill and contact resistance reduction. CVD Cobalt anneal parameters are discussed that can be optimized in combination with the deposition process to achieve desired gapfill. A proprietary electron-beam imaging technology was used to qualify the cobalt fill for void-free performance. Various process flows are discussed that lead to the best-known fill and resistance reduction values.