Robust Co alloy design for Co interconnects using a self-forming barrier layer.

Area of Science:

• Materials Science
• Semiconductor Device Physics
• Nanotechnology

Background:

• Rising copper (Cu) resistivity necessitates advanced interconnect materials like cobalt (Co).
• Cobalt interconnects show promise for reduced resistivity but suffer from extrinsic time-dependent dielectric breakdown.
• Existing diffusion barriers like Ta/TaN are effective but add area, increasing RC delay.

Purpose of the Study:

• To design a thermodynamically stable, self-forming diffusion barrier for cobalt interconnects.
• To enhance the reliability and lifetime of cobalt interconnects.
• To develop an ultrathin barrier minimizing area occupation and RC delay.

Main Methods:

• Thermodynamic modeling for alloy design, focusing on dopants like Cr, Mn, Sn, and Zn.
• Investigating dopant diffusion behavior and interfacial phase formation.
• Fabrication and testing of Co-Cr alloys and their self-forming barriers.

Main Results:

• Cr dopants in Co alloys facilitate diffusion to the dielectric interface.
• A self-forming diffusion barrier of chromium oxide (Cr2O3) was successfully created.
• The Cr2O3 barrier demonstrated a breakdown voltage over 200% higher than pure Co interconnects.
• An ultrathin 1.2 nm Cr2O3 barrier was achieved.

Conclusions:

• The self-forming Cr2O3 barrier effectively enhances the reliability of Co interconnects.
• This ultrathin barrier offers a superior alternative to current bilayer systems, reducing RC delay.
• The findings pave the way for high-performance, reliable cobalt interconnects in future electronic devices.