On-Chip EM Sensors for Real-Time Reliability Monitoring
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Solution Overview
Problem
Conventional electro-migration (EM) reliability tests for integrated circuits are limited by high temperatures, costly and time-consuming module-level testing, difficulty in modeling chip-level EM, poor confidence bounds due to limited sample sizes, and the challenge of real-time monitoring during actual chip operation.
Innovation Solution
Incorporating on-chip sensors powered with stress and nominal currents, along with control switches to measure resistance changes and analyze delta values, allowing for real-time EM performance evaluation during chip operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional EM reliability tests are performed at extremely high temperatures to accelerate failure times, then failure detection speed is improved, but competing degradation effects such as stress migration and low-k film material degradation occur
Solution Approach 1:
The patent changes the test parameters from extreme high temperatures to moderate temperatures combined with elevated current densities. This allows EM degradation to be accelerated through current stress rather than thermal stress, avoiding the harmful side effects of high temperature while still achieving accelerated failure detection
Solution Approach 2:
The patent incorporates on-chip EM sensors and measurement circuits during the manufacturing process, allowing EM degradation to be monitored continuously from early stages. This preliminary monitoring capability enables detection of EM effects before they lead to catastrophic failures, without requiring extreme test conditions
2Measurement precision
If module level testing is performed to assess EM reliability, then comprehensive EM performance evaluation is achieved, but testing cost and time consumption increase significantly
Solution Approach 1:
The patent implements self-service by integrating EM measurement circuits and sensors directly on the chip during manufacturing. The chip performs its own EM monitoring continuously during operation without requiring external module-level testing equipment or processes, eliminating the time and cost overhead of separate reliability tests
Solution Approach 2:
The patent merges the EM measurement function with the operational circuitry by using the same interconnect structures for both signal transmission and EM sensing. The on-chip sensors are integrated into the existing chip architecture, combining production and reliability assessment into a single process
3Ease of manufacture
If limited sample sizes are used in EM reliability tests, then testing cost is reduced, but confidence bounds of projection become poor and multi-modal sub-group distributions cannot be separated
Solution Approach 1:
The patent implements continuous monitoring of EM degradation through on-chip sensors that operate throughout the chip's operational lifetime. This continuous data collection from numerous chips in the field provides large statistical samples over time, enabling accurate confidence bounds and distribution analysis without requiring large initial test sample sizes
Solution Approach 2:
The patent establishes feedback loops where EM sensor measurements from operating chips are continuously collected and analyzed. This feedback mechanism enables ongoing statistical analysis and projection refinement as more data accumulates, improving measurement precision progressively while maintaining cost-effectiveness
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
Enables accurate, cost-effective, and real-time monitoring of EM performance, reducing the risk of electrical failures and improving chip reliability by continuously assessing EM degradation.
Implementation Method 1
Electro-migration (EM) refers to mass transport due to the momentum exchange between conducting electrons and diffusing metal atoms in metallic interconnects
Implementation Method 2
obtaining a first resistance measurement from the first on-chip sensor and a second resistance measurement from the second on-chip sensor
Data Source
AI summary
An integrated circuit, testing structure, and method for monitoring electro-migration (EM) performance. A method is described that includes method for measuring on-chip electro-migration (EM) performance, including: providing a first on-chip sensor continuously powered with a stress current; providing a second on-chip sensor that is powered only during measurement cycles with a nominal current; obtaining a first resistance measurement from the first on-chip sensor and a second resistance measurement from the second on-chip sensor during each of a series of measurement cycles; and processing the first and second resistance measurements.