FD-SOI Well Bias Feedback for TID and Aging Compensation
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Solution Overview
Problem
Fully-Depleted Silicon-On-Insulator (FD-SOI) semiconductors experience parametric shifts due to Total Ionizing Dose (TID), temperature, and aging, leading to performance degradation and errors in critical applications like satellites and guided vehicles, where existing biasing techniques are sub-optimal and static.
Innovation Solution
A self-optimizing circuit with an analog feedback loop dynamically adjusts the well bias beneath the BOX layer to counteract parametric shifts, using a TID dosimeter and reference circuit to regulate well potentials, eliminating the need for digital circuits and incorporating a charge pump to maintain optimal performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fixed design biasing is used for wells in FD-SOI semiconductors, then device threshold voltages are stabilized, but compensation against TID, aging, and temperature effects is sub-optimized
Solution Approach 1:
The patent implements dynamic biasing of the wells by continuously adjusting the well voltage based on feedback from a dosimeter that measures threshold voltage shifts. This dynamic adjustment allows the system to adapt to changing environmental conditions (TID, temperature, aging) rather than relying on fixed design biasing, thereby improving compensation effectiveness while maintaining adaptability.
Solution Approach 2:
The patent employs a feedback mechanism where a dosimeter monitors the threshold voltage of FD-SOI devices and feeds this information back to a control circuit that adjusts the well bias accordingly. This closed-loop feedback system enables real-time compensation for parametric shifts caused by TID, aging, and temperature variations, resolving the contradiction between reliable compensation and adaptability to environmental changes.
2Reliability
If analog feedback loop is used to dynamically adjust well bias, then parametric shifts are mitigated, but circuit complexity increases
Solution Approach 1:
The patent implements a self-service mechanism where the system uses a portion of itself (the dosimeter) to monitor its own state (threshold voltage shifts) and automatically adjusts its own biasing without external intervention. This self-regulating approach mitigates parametric shifts while avoiding the need for complex external control systems, thereby improving circuit accuracy without excessive complexity increase.
Solution Approach 2:
The patent merges the dosimeter function with the bias control function into an integrated system where the same circuit elements serve multiple purposes. The dosimeter that measures threshold voltage shifts is directly coupled to the bias adjustment mechanism, creating a unified system that mitigates parametric shifts without requiring separate complex control circuits, thus balancing reliability improvement with acceptable complexity.
Data Source
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AI summary
A self-optimizing circuit for a FD-SOI device includes a static biasing circuit, a dosimeter, a reference circuit, an amplifier, a voltage source, and a feedback circuit. The static biasing circuit supplies a first bias. The dosimeter includes a dosimeter FD-SOI device and generates a dosimeter voltage sensitive to parametric shifts in the primary FD-SOI device. The reference circuit supplies a reference voltage. The amplifier is coupled to the dosimeter and the reference circuit, and supplies a second bias at an output of the static biasing circuit, the second bias proportional to a difference between the dosimeter voltage and the reference voltage. The voltage source generates a drive voltage to which the first bias and the second bias are referenced. The feedback circuit regulates supply of the drive voltage to a well of the dosimeter FD-SOI device according to the first bias and the second bias.