Embedded BTI Characterization for MOSFET Aging Monitoring
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Solution Overview
Problem
Existing methods for characterizing Bias Temperature Instability (BTI) effects in MOSFET transistors require external equipment or disrupt the normal operation of the host product, making them inefficient and impractical for real-time monitoring.
Innovation Solution
An embedded system with self-testing capabilities uses local power supply generation and standard cell-based Ring Oscillators to characterize BTI degradation rates without affecting the host functionality, allowing concurrent operation and accurate measurement of P-type and N-type MOSFET transistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If standalone test structures with external equipment are used for BTI characterization, then measurement capability is achieved, but device complexity and operational disruption increase
Solution Approach 1:
The patent merges the BTI characterization functionality directly into the host product chip by integrating ring oscillator circuits and measurement logic within the same device. This eliminates the need for separate standalone test structures and external testing equipment, thereby reducing device complexity while maintaining measurement capability.
Solution Approach 2:
The embedded system enables the host product to perform self-testing for BTI degradation characterization. The ring oscillators and measurement circuits are integrated within the product itself, allowing it to autonomously monitor its own transistor degradation without requiring external test equipment or specialized testing infrastructure.
2Measurement precision
If the host product changes or stops operations during stress and measurement, then accurate BTI characterization is achieved, but productivity and operational continuity deteriorate
Solution Approach 1:
The patent segments the chip functionality into distinct regions: dedicated ring oscillator circuits for BTI measurement and the main host product operational circuits. This segmentation allows the measurement subsystem to operate independently and concurrently with the host product, enabling accurate BTI characterization without disrupting normal product operations.
Solution Approach 2:
The embedded ring oscillator circuits continue to oscillate and provide measurement data throughout the entire operational lifetime of the host product. The system enables continuous monitoring of transistor degradation while the host product maintains its normal functionality, ensuring both measurement accuracy and operational continuity simultaneously.
3Ease of manufacture
If conventional embedded structures are used, then integration is achieved, but operational disruption during testing occurs
Solution Approach 1:
The patent implements dynamic control of the ring oscillator circuits through programmable power supply voltage adjustment. The oscillators can be dynamically enabled or disabled based on testing requirements, allowing the system to adapt between measurement modes and normal operation modes without physical reconfiguration or product shutdown.
Solution Approach 2:
The system utilizes parameter changes in the power supply voltage to control the ring oscillator operation during testing. By adjusting the voltage supplied to the oscillators independently from the host product, the system can initiate and terminate measurement cycles dynamically without affecting the operational parameters or functionality of the main product circuits.
Data Source
AI summary
A novel system for in-product Bias Temperature Instability (BTI) characterization that allows for characterization of transistor degradation rates is disclosed; it is self-testing and can be embedded in real products without impacting the host functionality. The test data collected during product chip testing (at Electrical Wafer Sort) can be used for identification of abnormal material and for material disposition, or to predict the chip aging rate and premature failure risk due to BTI degradation. The system can also collect the data from the real time device aging in the field, during the host chip operational lifetime. The system is equipped with local programmable power supply generation and self-test capabilities to allow concurrent operations with the host application. The Devices Under Test (DUTs) consist of standard cell-based Ring Oscillators (ROs) which have the unique capability of decoupling the BTI effects on N-type and P-type MOSFET transistors. New switching circuitry is implemented that provides for minimal delay between the stress and measurement phases, thus giving the system the capability of fully characterizing the BTI relaxation dynamic.