Via-Node Electromigration Rule-Check Methodology
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Solution Overview
Problem
Existing methods for assessing electromigration reliability in integrated circuits are inadequate as they solely consider the magnitude of current density in individual leads, failing to account for the specific layout of leads on via nodes and the direction of electron flow, which affects interconnect reliability.
Innovation Solution
A method that calculates the net effective current density at via nodes by considering the effective current densities of individual leads, taking into account the direction of electron flow and applying factors such as branch interaction, width, and length effects to accurately assess electromigration reliability, and adjusts the design layout to ensure compliance with target current densities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing methods solely consider the magnitude of current density in individual leads, then the assessment process is simple, but the electromigration reliability assessment is inaccurate
Solution Approach 1:
The patent segments the current density assessment into multiple components: individual lead current densities are calculated separately, then combined at via nodes with consideration of electron flow direction. This segmentation allows for more accurate local assessment at critical via nodes while maintaining a systematic overall evaluation process.
Solution Approach 2:
The patent adds a new dimension to the assessment by considering the direction of electron flow (towards or away from via nodes) in addition to the magnitude of current density. This transforms the assessment from a scalar evaluation to a vector-based evaluation, capturing the bidirectional nature of electromigration effects at via nodes.
2Productivity
If the minimum feature size of interconnect structures is scaled down, then the integration density increases, but the electromigration-induced failure risk increases
Solution Approach 1:
The patent performs preliminary electromigration reliability assessment during the design layout phase, before manufacturing. By calculating net effective current densities and comparing them against target values, potential reliability issues are identified and corrected in the design stage, preventing failures before they occur in the scaled-down interconnect structures.
Solution Approach 2:
The patent implements a feedback mechanism where the calculated net effective current density is continuously compared against target effective current density values. If the calculated value exceeds the target, the design layout is modified to reduce the current density, creating a closed-loop process that ensures reliability compliance even as feature sizes are scaled down.
3Reliability
If the net effective current density is not controlled within target values, then the design layout flexibility is maintained, but the interconnect failure risk increases
Solution Approach 1:
The electromigration reliability rule-check is performed during the design layout phase, identifying via nodes with excessive net effective current density before manufacturing. This preliminary detection allows designers to modify layouts proactively, avoiding costly post-manufacturing failures and reducing the need for design iterations after fabrication.
Data Source
AI summary
A method of method of manufacturing an integrated circuit. The method comprises performing an electromigration reliability rule-check for at least one of via node of an integrated circuit, including: calculating a net effective current density of the via node. Calculating the net effective current density including determining a sum of effective current densities for individual leads that are coupled to the via node. Leads configured to transfer electrons away from said via node are assigned a positive polarity of the effective current density. Leads configured to transfer electrons towards the via node are assigned a negative polarity of the effective current density.