Hybrid Metallization Interconnects for Electromigration Resistance
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Solution Overview
Problem
Integrated circuits face electromigration failures due to high operating temperatures, particularly in multi-finger applications and devices with high current densities, where existing interconnect structures lack sufficient resistance to current limiting mechanisms.
Innovation Solution
A hybridized metallization structure is introduced, featuring two different metals within a single metallization level, with one metal chosen for low resistivity and good electromigration reliability at elevated temperatures and the other for normal operating temperatures, strategically positioned based on temperature zones within the IC.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single metal material is used in the interconnect structure, then the manufacturing process is simple, but the resistance to electromigration at high temperatures is insufficient
Solution Approach 1:
The patent applies local quality by using different metal materials in different regions of the interconnect structure. Specifically, copper is used in high-temperature zones where electromigration resistance is critical, while aluminum is used in normal temperature zones. This regional differentiation optimizes electromigration resistance without unnecessarily complicating the entire metallization structure.
Solution Approach 2:
The patent employs composite materials by combining copper and aluminum in a single metallization level. The interconnect structure consists of multiple segments with different metal compositions, creating a hybrid metallization system that leverages the superior electromigration resistance of copper in critical areas while maintaining the benefits of aluminum in other areas.
2Reliability
If different metals are used in high and normal temperature zones, then electromigration resistance is improved, but the manufacturing process complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the interconnect structure into distinct high-temperature and normal-temperature zones, each filled with appropriate metal materials. The fabrication process separates the formation of copper and aluminum regions into distinct fabrication stages, allowing each metal to be deposited and patterned independently, which simplifies the overall manufacturing complexity.
Solution Approach 2:
The patent resolves manufacturing complexity by transitioning to a planar, single-level metallization structure. Instead of using multiple stacked metallization layers with complex via connections, the invention places different metals side-by-side in the same metallization level, eliminating the need for complex vertical interconnections and simplifying the fabrication process.
3Reliability
If copper and aluminum are used in the same metallization level, then electromigration reliability is enhanced, but the top surfaces become non-co-planar
Solution Approach 1:
The patent applies local quality by allowing different surface heights in different regions of the interconnect structure. The copper and aluminum segments have different top surfaces that are non-co-planar, but this local variation is acceptable because each region is optimized for its specific function. The non-co-planar surfaces do not interfere with device operation since the interconnects are embedded in dielectric material that accommodates the height differences.
Data Source
AI summary
An electronic interconnect structure having a hybridized metal structure near regions of high operating temperature on an integrated circuit, and methods of making the same. The hybridized metal structure features at least two different metals in a single metallization level. The first metal is in a region of high operating temperature and the second region is in a region of normal operating temperatures. In a preferred embodiment the first metal includes aluminum and is in a first level metallization over an active area of the device while the second metal includes copper. In some embodiments, the first and second metals are not in direct physical contact. In other embodiments the first and second metals physically contact each other. In a preferred embodiment, a top surface of the first metal is not co-planar with a top surface of the second metal, despite being in the same metallization level.