Interleaved Multi-Level Power Rails for Electromigration Mitigation
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Solution Overview
Problem
Modern integrated chips face electromigration issues due to increased current density in power rails, leading to premature failures and voltage drops, which limit the maximum current density requirement for mean time to failures (MTTF) and cause circuit timing and signal integrity problems.
Innovation Solution
An automatic place and route (APR) methodology is used to construct a local power network with multi-level local power rails, featuring interleaved segments of vertically adjacent metal wire layers, each segment being shorter than the characteristic Blech length to mitigate electromigration, thereby increasing the maximum current density (Jmax) for MTTF.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the length of metal wire segments in power rails is increased to reduce the number of segments, then the device complexity is reduced, but electromigration occurs leading to premature failures and voltage drops
Solution Approach 1:
The power rail is divided into multiple short metal wire segments, each shorter than the Blech length, arranged in an interleaved pattern across multiple layers. This segmentation prevents electromigration by ensuring no single segment exceeds the critical length threshold, while the interleaved arrangement minimizes the total number of segments needed.
Solution Approach 2:
The solution transitions from a single-layer power rail to a multi-layer interleaved structure. By distributing segments across multiple vertical layers and interleaving them, the design achieves both short segment lengths (for electromigration resistance) and reduced overall segment count (for lower complexity).
2Productivity
If the current density in power rails is increased to meet maximum current density requirements, then the productivity and performance are improved, but electromigration causes premature failures and voltage drops
Solution Approach 1:
By segmenting the power rail into short sections below the Blech length threshold, each segment can safely carry high current density without experiencing electromigration-induced failures. This enables the system to operate at higher current densities while maintaining reliability.
Solution Approach 2:
The invention changes the critical parameter of segment length to be below the Blech length threshold. This parameter change allows the system to support higher current densities without electromigration, as the short segment length fundamentally alters the electromigration dynamics.
3Area of moving object
If the wire dimensions are reduced to enable performance scaling, then the device density is improved, but electromigration becomes more prevalent causing failures
Solution Approach 1:
Segmenting the power rail into short sections below the Blech length threshold counteracts the increased electromigration risk associated with reduced wire dimensions. Each short segment maintains electromigration resistance even as overall wire size decreases, enabling continued scaling.
Solution Approach 2:
By changing the segment length parameter to be below the Blech length, the invention creates a scaling-friendly design where reduced wire dimensions do not lead to electromigration failures. The short segment length becomes a protective feature that enables aggressive scaling.
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 effectively alleviates electromigration within the power rails, allowing for increased current density without causing failures, thus enabling continued reduction in wire dimensions and performance scaling while maintaining circuit reliability.
Implementation Method 1
each interleaved metal wire layer segment has a length shorter than a predetermined characteristic length corresponding to a Blech length. By limiting the length of the interleaved metal wire layer segments, electromigration within the multi-level power rails is alleviated
Data Source
AI summary
The present disclosure relates to an electromigration tolerant power distribution network generated by an automatic place and route (APR) methodology. In some embodiments, an automatic place and route tool constructs a local power network having multi-level power rails. The multi-level power rails have interleaved segments of vertically adjacent metal layers, wherein each interleaved segment is shorter than a predetermined characteristic length corresponding to a Blech length. By limiting the length of the interleaved metallization segments, electromigration within the multi-level power rails is alleviated, allowing for the maximum current density requirement (Jmax) for mean time to failures (MTTF) to be increased.