Noble Metal Cap for Interconnect Electromigration and Short Prevention
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Solution Overview
Problem
Semiconductor interconnect structures face reliability issues due to electromigration (EM) failures, which cause voids in metal conductors and can lead to circuit failures, and existing metal caps can result in electrical shorts between adjacent interconnects.
Innovation Solution
A noble metal cap is directly applied to a conductive material embedded within a low dielectric constant dielectric material, with a chemical deposition process at 300°C or less, ensuring minimal extension onto the dielectric surface and no residues, thereby enhancing EM reliability and preventing shorts.
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 by greater than 100×, but electrical shorts between adjacent interconnects may arise due to metal cap extension onto the dielectric surface
Solution Approach 1:
A noble metal cap layer is introduced as an intermediary material between the Cu conductor and the dielectric material. This noble metal cap has superior selectivity for deposition on Cu surfaces compared to dielectric surfaces, acting as a mediator that achieves EM protection while preventing unwanted extension onto adjacent dielectric regions.
Solution Approach 2:
The invention changes the material parameter of the cap layer from Co-containing alloy to noble metal, which fundamentally alters the deposition behavior and surface selectivity. This parameter change enables precise control over where the cap material deposits, confining it to the Cu conductor region only.
2Reliability
If the metal cap is made to extend onto the dielectric surface to provide complete coverage, then EM protection is improved, but electrical shorts between adjacent interconnects occur
Solution Approach 1:
The noble metal cap exhibits local quality in its deposition behavior, selectively depositing only on Cu conductor surfaces while inherently avoiding dielectric surfaces. This local selectivity allows the cap to provide EM protection precisely where needed (on the conductor) without extending onto adjacent dielectric regions where it would cause shorts.
3Reliability
If conventional metal caps are used to protect against EM, then EM resistance is improved, but manufacturing precision is degraded due to metal residues on the dielectric surface
Solution Approach 1:
The noble metal cap material is designed to be inherently selective and self-limiting in its deposition, avoiding the need for complex removal processes. The material itself prevents residue formation on dielectric surfaces, eliminating the manufacturing precision issues associated with conventional caps that leave metal residues.
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
The solution significantly improves EM reliability and prevents electrical shorts, extending the lifespan of semiconductor interconnects while maintaining high signal transmission efficiency.
Implementation Method 1
a chemical deposition process at 300°C or less
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 noble metal cap is located directly on an upper surface of the at least one conductive region. The noble metal cap does not substantially extend onto an upper surface of the dielectric material that is adjacent to the at least one conductive region, and the noble cap material does not be deposited on the dielectric surface. A method fabricating such an interconnect structure utilizing a low temperature (about 300° C. or less) chemical deposition process is also provided.