Cobalt Interconnects Resolving Electromigration and Resistivity Trade-offs
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Solution Overview
Problem
Current metal interconnects, such as copper, are susceptible to electromigration, leading to void formation and failure, while tungsten interconnects offer resistance but have high electrical resistivity, degrading integrated circuit performance.
Innovation Solution
Cobalt interconnects with a cobalt seed layer and fill material are fabricated, eliminating the need for barrier layers and providing low resistance and high resistance to electromigration, thus enabling high-performance interconnect structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper interconnect structures are utilized, then electrical resistivity is low, but susceptibility to electromigration increases leading to void formation and failure
Solution Approach 1:
The patent changes the material parameter from copper to cobalt, fundamentally altering the electrical and mechanical properties of the interconnect. Cobalt provides higher resistance to electromigration while maintaining acceptable electrical conductivity, thus resolving the contradiction between low resistivity and electromigration resistance
Solution Approach 2:
The patent employs a composite structure consisting of a cobalt-based interconnect layer combined with a barrier layer (such as tungsten nitride or titanium nitride). This composite approach allows the cobalt to provide low resistivity while the barrier layer provides protection against electromigration and prevents void formation
2Reliability
If tungsten metallization is utilized, then resistance to electromigration is high, but electrical resistivity increases degrading circuit performance
Solution Approach 1:
The patent changes the material parameter from tungsten to cobalt, selecting a material with lower electrical resistivity while maintaining high resistance to electromigration. Cobalt's electrical resistivity is significantly lower than tungsten, thus reducing energy loss while preserving reliability
Solution Approach 2:
The patent applies different materials to different regions: cobalt is used for the interconnect lines where low resistivity is critical, while barrier layers are applied at interfaces and contact regions where protection against electromigration and diffusion is most needed. This localized material assignment optimizes both electrical performance and reliability
Data Source
AI summary
A metal interconnect comprising cobalt and method of forming a metal interconnect comprising cobalt are described. In an embodiment, a metal interconnect comprising cobalt includes a dielectric layer disposed on a substrate, an opening formed in the dielectric layer such that the substrate is exposed. The embodiment further includes a seed layer disposed over the substrate and a fill material comprising cobalt formed within the opening and on a surface of the seed layer.