Ring Oscillator Leakage Sensor for IC Degradation Prediction
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Solution Overview
Problem
Integrated circuits (ICs) face challenges in accurately measuring and tracking leakage current and other operational characteristics, such as temperature, due to limitations in existing chip thermal sensors, which are not sensitive enough and can be affected by process technology variations, leading to inaccurate leakage power determination and inadequate prediction of IC degradation and failure.
Innovation Solution
A semiconductor IC design incorporating a ring oscillator (ROSC) circuit proximate to a functional transistor, with a processor that determines operating conditions based on ROSC oscillation frequency, enabling leakage and temperature detection, and predicting workload and stress levels, thereby facilitating more accurate degradation estimation and time-of-failure prediction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If chip thermal sensors are used to measure temperature and leakage current, then temperature monitoring is enabled, but measurement precision is insufficient due to process technology variations and lack of sensitivity
Solution Approach 1:
The patent divides the IC into multiple test structures distributed across different locations on the chip. Each test structure includes ring oscillators and transistors configured to measure local leakage current and temperature independently. This segmentation allows precise measurement of specific regions without being affected by process variations across the entire chip, thereby improving measurement precision and reliability.
Solution Approach 2:
The patent utilizes the temperature-dependent frequency characteristics of ring oscillators and the voltage-dependent leakage current characteristics of transistors as measurement parameters. By monitoring frequency shifts in ring oscillators and current variations in transistor test structures, the system converts physical parameters (temperature, leakage current) into electrical signals that can be precisely measured and correlated to environmental conditions.
2Measurement precision
If existing thermal sensors are used, then temperature monitoring is provided, but the sensors are not sensitive enough to detect changes in leakage current and temperature accurately
Solution Approach 1:
The patent introduces ring oscillators as intermediary elements that convert temperature changes into frequency variations. These ring oscillators serve as sensitive indicators that amplify temperature effects, making them easier to detect and measure. The oscillation frequency changes provide a magnified signal that enhances detection sensitivity for temperature and leakage current variations.
Solution Approach 2:
The patent replaces traditional thermal sensors with electronic test structures that use transistor leakage current and ring oscillator frequency characteristics as sensing mechanisms. This substitution of mechanical/thermal sensing with electronic sensing enables higher sensitivity and precision in measuring temperature and leakage current at the circuit level.
3Productivity
If process technology variations are present in IC manufacturing, then IC production is enabled, but sensor accuracy is degraded due to variations in transistor characteristics
Solution Approach 1:
The patent creates local test structures with controlled transistor dimensions and configurations at specific locations on the chip. These local structures are designed to be representative of the production process variations while providing consistent measurement reference points. By focusing on local characteristics rather than global averages, the system maintains measurement precision despite process variations across the entire wafer.
Solution Approach 2:
The patent incorporates multiple copies of identical test structures (ring oscillators and transistor configurations) at different locations on the chip. These copies serve as parallel measurement references that can be used to characterize process variations and calibrate measurements. The replicated structures allow statistical analysis of variations and provide robust measurement data that compensates for manufacturing tolerances.
4Reliability
If leakage current is not accurately measured, then power consumption cannot be determined, but accurate degradation prediction requires precise leakage current data
Solution Approach 1:
The patent implements a feedback mechanism where the measured leakage current and temperature data from test structures are fed back to a processor that continuously monitors IC degradation. The system uses this feedback information to update degradation models and predict future failure conditions. This closed-loop approach ensures that accurate real-time measurements drive continuous improvement in prediction accuracy.
Solution Approach 2:
The patent performs preliminary measurements of leakage current and temperature using dedicated test structures during IC operation. These preliminary data are collected and analyzed to establish baseline degradation rates and identify trends before actual failure occurs. By conducting measurements in advance and monitoring changes over time, the system enables predictive maintenance and extends device reliability.
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 provides precise measurement of leakage current and temperature, enabling effective workload and stress analysis, leading to improved IC degradation estimation and predictive maintenance, thereby extending IC lifespan and preventing failures.
Implementation Method 1
the temperature sensitivity may be a consequence of the process technology of the inverters used in the ring oscillator
Implementation Method 2
sub-threshold leakage may be considered a parasitic leakage in a state that would ideally have no current
Data Source
AI summary
An integrated circuit (IC) comprising: a margin measurement circuit configured to monitor multiple data paths of the IC and to output, at different times, different ranges of remaining margins of the multiple data paths; a workload sensor configured to output a value representing aggregate operational stress experienced by the IC over a period of time ending at each of the different times; and a processor configured to: (i) compute, based on the value output by said workload sensor, an upper bound and a lower bound of change of the remaining margin of the IC, and (ii) compute upper and lower bounds of a current remaining margin of the IC, based on (a) the upper and lower bounds of change, and (b) a remaining margin indicated by a border between two adjacent ranges outputted by the margin measurement circuit.