Copper Layer Capping Method and Copper Interconnect Manufacturing Method Using the Same

Selective Copper Interconnect Capping via Cobalt Chemical Vapor Deposition and Ammonia Plasma

This technology is a copper layer capping method that involves heating a substrate with a copper layer, performing chemical vapor deposition of cobalt exclusively onto the copper using a cobalt cyclopentadienyl dicarbonyl precursor and hydrogen gas, followed by post-treatment with ammonia plasma. It also includes a copper interconnect manufacturing method that applies this capping process after insulating layer patterning and copper filling.

As semiconductor integration increases and copper interconnect line widths shrink, electromigration (EM) has become a significant issue, shortening interconnect lifespan. To prevent this, capping technology that heat-treats copper-manganese alloy interconnects to precipitate manganese on the surface has been commercialized, but it has the limitation of increased interconnect resistance due to the use of alloys.

This technology combines a 25-minute deposition at 30 mTorr chamber pressure with 400 sccm of hydrogen, followed by a 2-minute plasma treatment at 300 W RF power and 200 sccm of ammonia, enhancing EM resistance while maintaining the low resistance of pure copper. Since cobalt is formed selectively only on the copper surface, it prevents short circuits between interconnects caused by residual metal on the insulating film. It can be applied to back-end-of-line (BEOL) interconnect formation for fine-pitch logic and memory semiconductors, securing both interconnect lifespan and yield without resistance loss.

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Key Features:

• Heating the substrate with the formed copper layer to 180–250°C, preferably 200°C, to prepare for deposition
• Forming a cobalt layer via chemical vapor deposition in a 30 mTorr chamber for 25 minutes using cobalt cyclopentadienyl dicarbonyl as a precursor and hydrogen as a reaction gas
• Supplying 30 sccm of inert gas to a precursor canister maintained at 0°C and 400 sccm of hydrogen to the chamber
• Maintaining the substrate temperature at 180–250°C and performing a 2-minute treatment by generating plasma with 200 sccm of ammonia and 300 W of RF power

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This invention was developed with support from the Ministry of Science, ICT and Future Planning for ultra-fine, high-reliability interconnect technology.

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