Electromigration Resistant Semiconductor Device With Segmented Voltage Rails
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Solution Overview
Problem
Semiconductor devices are susceptible to electromigration, which can lead to open circuits due to void formation and short circuits due to ion/atom accumulation, posing challenges in maintaining the reliability of integrated circuits like ASICs.
Innovation Solution
Incorporating a header with a pair of virtual source reference rails and a footer with a pair of virtual reference voltage rails, connected by a cell circuit, which disperses current and reduces current density, thereby mitigating electromigration through the use of transistor units and via units to manage voltage rails effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional standard cell layouts are used, then device complexity is reduced and manufacturing is easier, but electromigration resistance deteriorates leading to circuit failures
Solution Approach 1:
The voltage rail is segmented into multiple parallel rails (first voltage rail, second voltage rail, third voltage rail) instead of using a single rail. This segmentation distributes the current across multiple paths, reducing current density in each individual rail and thereby improving electromigration resistance while maintaining a structured and manageable cell design
Solution Approach 2:
A fourth voltage rail is introduced as an intermediary element coupled to the first, second, and third voltage rails. This intermediate rail helps balance voltages across the segmented structure and provides additional current distribution paths, further enhancing electromigration resistance without significantly increasing overall device complexity
2Reliability
If current is concentrated in single voltage rails, then device structure is simpler, but current density increases causing electromigration and void formation
Solution Approach 1:
The voltage distribution network is divided into multiple parallel voltage rails (first, second, and third voltage rails) that carry current simultaneously. This segmentation reduces the current burden on each individual rail, lowering current density and preventing electromigration-related failures such as void formation and ion accumulation
Solution Approach 2:
Multiple voltage rails are combined in parallel to form a unified voltage distribution system. The fourth voltage rail acts as a common intermediary that connects and balances the other three rails, creating a merged structure that distributes current more evenly and improves overall electromigration resistance
Data Source
AI summary
A semiconductor device includes first and second transistors, a pair of first source/drain regions, a pair of second source/drain regions, and a cell. Each of the first source/drain regions corresponds to a first source/drain terminal of a respective one of the first and second transistors. Each of the second source/drain regions corresponds to a second source/drain terminal of a respective one of the first and second transistors. The cell includes a first voltage rail, a pair of second voltage rails, and a cell circuit. The first voltage rail is coupled to the first source/drain regions. Each of the second voltage rails is coupled to a respective one of the second source/drain regions and is configured to be coupled to the first voltage rail. The cell circuit is coupled to one of the second voltage rails.