Complementary Ring Oscillator Stress Sensor for IC Monitoring
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Solution Overview
Problem
Integrated circuits face mechanical stresses due to property mismatches between materials in their packages, which can vary with aging and temperature, impacting reliability and potentially leading to catastrophic failures.
Innovation Solution
A stress sensor system using complementary ring oscillators formed on the integrated circuit, with one oscillator's frequency dependent on NMOS devices and the other on PMOS devices, allows for in-situ stress monitoring in different directions, compensated by a temperature sensor to decouple temperature effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the die size of integrated circuits is increased to improve chipset performance, then the performance increases, but the mechanical stress on the die increases due to property mismatches between different materials in the package
Solution Approach 1:
The patent applies preliminary action by implementing stress sensors and monitoring circuits before catastrophic failure occurs. The system proactively measures stress levels using ring oscillators and piezoresistive elements, enabling early detection and prevention of stress-related failures before they compromise the integrated circuit.
Solution Approach 2:
The patent replaces direct mechanical stress measurement with an electrical measurement system. Ring oscillators and piezoresistive elements convert mechanical stress into electrical signals (frequency changes, resistance changes) that can be measured and processed electronically, enabling non-intrusive stress monitoring.
2Temperature
If the package lid is removed to reduce thermal resistance, then heat dissipation improves, but the mechanical stress on the integrated circuit increases due to direct attachment of heat spreader
Solution Approach 1:
The patent replaces mechanical stress measurement with electrical measurement using ring oscillators and piezoresistive elements. These components convert mechanical stress from heat spreader attachment into electrical signals, enabling monitoring of stress without interfering with the thermal management structure.
Solution Approach 2:
The patent introduces stress sensors as intermediary elements between the heat spreader and the integrated circuit. These sensors (ring oscillators, piezoresistive elements) act as mediators that measure stress caused by heat spreader attachment without preventing the thermal contact, thus maintaining both thermal performance and stress monitoring capability.
3Reliability
If stress monitoring is implemented to prevent catastrophic failure, then reliability improves, but device complexity increases due to additional sensors and circuits
Solution Approach 1:
The patent applies universality by designing stress sensors that can monitor multiple stress components (sigma_x, sigma_y, tau_xy) using a unified measurement approach. The ring oscillator and piezoresistive element configurations enable multi-axis stress monitoring through a single integrated sensor structure, reducing overall system complexity while maintaining comprehensive monitoring capability.
Solution Approach 2:
The patent uses ring oscillators that replicate standard digital circuit elements, allowing stress sensing functionality to be integrated using familiar CMOS circuit designs. This copying of standard cell structures into sensor applications simplifies manufacturing and integration while maintaining reliability benefits.
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
Effectively determines stress levels along multiple directions on integrated circuits, preventing system failures by enabling real-time monitoring and compensation for temperature variations.
Implementation Method 1
A first ring oscillator circuit is formed on an integrated circuit... The stress determination circuit is configured to receive a first frequency signal generated by the first ring oscillator circuit... and to determine from the first frequency signal and a second frequency signal generated by a second ring oscillator circuit stress values
Implementation Method 2
each having a first P-channel metal-oxide-semiconductor field-effect transistor (PMOS) device and a first N-channel metal-oxide-semiconductor field-effect transistor (NMOS) device connected in series... such that the first NMOS device limits current flowing through the inverter stage relative to the first PMOS device
Data Source
AI summary
The disclosure relates to technology for determining stress on integrated circuits. These include using ring oscillators formed on the integrated circuit, where one ring oscillator has its frequency dependent on the current flowing through its stages being limited by its NMOS devices and another ring oscillator has its frequency dependent on the current flowing through its stages being limited by its PMOS devices. This allows the stress on the integrated circuit to be determined in different directions along the integrated circuit. A temperature sensor can be used to compensate for temperature dependence on the frequencies of the ring oscillators.