Nitrogen-Containing Noble Metal Cap for Interconnect Reliability
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Solution Overview
Problem
Semiconductor interconnect structures face issues with electromigration (EM) reliability, electrical shorts, and oxidation due to existing metal caps, particularly Co-containing and noble metal caps, which degrade performance and increase manufacturing costs.
Innovation Solution
A nitrogen-containing noble metal cap is self-aligned to the upper surface of a non-recessed conductive material within a low k dielectric material, preventing extension onto the dielectric surface and using a low-temperature chemical deposition process to form the cap, which acts as an effective oxygen diffusion barrier.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Co-containing alloy metal cap is selectively deposited atop the Cu conductor region, then electromigration resistance is enhanced, but metal cap extends onto the adjoining surface of the interconnect dielectric material causing electrical shorts
Solution Approach 1:
The patent applies local quality by creating a nitrogen-containing metal cap with non-uniform nitrogen distribution: a nitrogen-enriched region at the interface with the Cu conductor provides oxidation protection and EM resistance, while the nitrogen-poor upper region prevents extension onto the dielectric material. This spatial variation in nitrogen concentration resolves the contradiction between enhancing EM resistance and preventing electrical shorts.
Solution Approach 2:
The patent uses a composite metal cap structure consisting of a Cu conductor region topped with a nitrogen-containing metal cap layer. This composite structure combines the high conductivity of Cu with the oxidation resistance and EM protection of nitrogen-containing metal, while the controlled nitrogen distribution prevents harmful extension onto the dielectric.
2Reliability
If a noble metal cap is used, then oxidation of the conductive material is prevented, but the cap extends onto the dielectric surface causing electrical shorts
Solution Approach 1:
The nitrogen-containing metal cap exhibits local quality through its nitrogen concentration gradient: the nitrogen-enriched region at the Cu interface provides oxidation prevention, while the nitrogen-poor upper region maintains sharp boundaries that prevent extension onto the dielectric surface, thus resolving the contradiction between oxidation protection and short prevention.
3Object-generated harmful factors
If the conductive material is recessed below the dielectric surface, then a metal cap can be formed without extending onto the dielectric, but process cost increases
Solution Approach 1:
Instead of recessing the conductive material below the dielectric surface (the conventional approach), the patent inverts the approach by forming a nitrogen-containing metal cap on a non-recessed Cu conductor that is substantially coplanar with the dielectric surface. The nitrogen concentration gradient naturally confines the cap to the conductor region, eliminating the need for costly recess processes while preventing extension onto the dielectric.
4Reliability
If a metal cap is formed to enhance EM resistance, then electromigration reliability improves, but the structure complexity increases
Solution Approach 1:
The patent changes the chemical composition parameter of the metal cap by incorporating nitrogen into the metal cap layer. This parameter change (adding nitrogen) enhances EM resistance and oxidation protection without requiring complex multi-layer structures, as the nitrogen-containing metal forms a single-layer cap with beneficial properties.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances electromigration resistance, reduces electrical shorts, and prevents oxidation, improving the reliability and extendibility of semiconductor interconnects while maintaining low process costs.
Implementation Method 1
the nitrogen-containing noble metal cap... acts as an effective oxygen diffusion barrier
Implementation Method 2
using a low-temperature chemical deposition process to form the cap
Data Source
AI summary
An interconnect structure is provided that has enhanced electromigration reliability without degrading circuit short yield, and improved technology extendibility. The inventive interconnect structure includes a dielectric material having a dielectric constant of about 3.0 or less. The dielectric material has at least one conductive material embedded therein. A nitrogen-containing noble metal cap is located predominately (i.e., essentially) on an upper surface of the at least one conductive region. The nitrogen-containing noble metal cap does not extend onto an upper surface of the dielectric material. In some embodiments, the nitrogen-containing noble metal cap is self-aligned to the embedded conductive material, while in other embodiments some portion of the nitrogen-containing noble metal cap extends onto an upper surface of a diffusion barrier that separates the at least one conductive material from the dielectric material. A method of fabricating such an interconnect structure utilizing a low temperature (about 200° C. or less) chemical deposition process is also provided.