Co contamination of Si: Plating & aging.

Area of Science:

• Materials Science
• Semiconductor Physics
• Nanotechnology

Background:

• Cobalt is a promising material for 10 nm interconnects, offering an alternative to copper.
• Understanding cobalt diffusion in silicon is critical for its application in semiconductor devices.

Purpose of the Study:

• To investigate cobalt atom contamination in silicon.
• To determine the diffusion barrier properties of cobalt silicide layers.

Main Methods:

• Transmission electron microscopy (TEM) for interface analysis.
• First-principles calculations to model atomic interactions and diffusion.

Main Results:

• A dense, few-nanometer cobalt silicide (CoSi) layer forms at the cobalt/silicon interface.
• The CoSi layer acts as an effective diffusion barrier for cobalt atoms.
• Cobalt diffusion into silicon is hindered by the semiconducting nature of the CoSi layer and interface effects.

Conclusions:

• The formation of a CoSi layer prevents cobalt diffusion into silicon.
• No additional barrier layer is required when depositing cobalt metal on silicon chips.
• Cobalt is a viable material for localized interconnect layers in advanced semiconductor technology.