Cryo-CMOS Floating-Gate Compensation for Threshold Voltage Spread
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Solution Overview
Problem
Cryogenic cooling of CMOS devices leads to increased threshold voltage variance and scattering, limiting power savings due to the need for larger supply voltages and inconsistent transistor switching, which conventional methods fail to address effectively.
Innovation Solution
Implementing a system with floating gates and control logic to actively compensate for threshold voltage offsets by injecting or removing charge, narrowing the distribution of threshold voltages through Fowler-Nordheim tunneling and Hot Carrier Injection processes, allowing for reduced supply voltage and dynamic power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If cryogenic cooling is applied to CMOS devices, then power consumption is reduced, but threshold voltage variance increases
Solution Approach 1:
The patent changes the physical state parameters by operating devices at cryogenic temperatures (e.g., 4K) while simultaneously adjusting threshold voltage compensation parameters. The system measures and compensates threshold voltage offsets by applying programming voltages to floating gates, effectively changing the electrical parameters to maintain device performance despite temperature-induced variance.
Solution Approach 2:
The patent implements a feedback mechanism where the system measures the actual threshold voltage of each device at cryogenic temperature and compares it against a target value. Based on this comparison, the control logic dynamically adjusts the floating gate charge to compensate for deviations, creating a closed-loop system that continuously maintains optimal threshold voltage despite temperature effects.
2Reliability
If supply voltage is increased to compensate for threshold voltage variance, then device switching reliability is improved, but power consumption increases
Solution Approach 1:
The patent applies preliminary action by pre-compensating threshold voltage offsets before normal operation. During an initialization phase, the system measures each device's threshold voltage and programs the floating gate to establish the correct threshold voltage before the device begins switching operations, ensuring reliable operation at lower supply voltages.
Solution Approach 2:
The patent introduces dynamics by making the threshold voltage adjustable and adaptive rather than fixed. The control logic dynamically modifies the floating gate charge based on measured threshold voltage offsets, allowing the system to adapt to temperature changes and device variations, thereby maintaining reliability without requiring excessive supply voltage margins.
3Manufacturing precision
If threshold voltage offset compensation is implemented, then device consistency is improved, but system complexity increases
Solution Approach 1:
The patent applies self-service by enabling each device to self-compensate for its own threshold voltage offset. The control logic measures the threshold voltage of each individual device and programs its floating gate independently, allowing devices to self-adjust without requiring manual calibration or complex external intervention, thereby improving consistency while limiting complexity growth.
Solution Approach 2:
The patent segments the compensation process into independent per-device operations. Each device's threshold voltage is measured and compensated separately through its own floating gate, allowing the system to handle device consistency issues in a modular fashion. This segmentation prevents the need for complex system-wide compensation mechanisms.
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 system achieves reduced power consumption by stabilizing threshold voltages, enabling lower supply voltages and quadratic power savings, suitable for cryogenic environments and quantum computing applications.
Implementation Method 1
narrowing the distribution of threshold voltages through Fowler-Nordheim tunneling and Hot Carrier Injection processes
Implementation Method 2
narrowing the distribution of threshold voltages through Fowler-Nordheim tunneling and Hot Carrier Injection processes
Data Source
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AI summary
Systems and methods related to low power cryo-CMOS circuits with non-volatile threshold voltage offset compensation are provided. A system (700) includes a plurality of devices (760) configured to operate in a cryogenic environment (<300 K), where a first distribution of a threshold voltage associated with the plurality of devices (760) has a first value indicative of a measure of spread of the threshold voltage. The system (700) further includes control logic (712, 714), coupled to each of the plurality of devices (760), configured to modify (714out) a threshold voltage associated with each of the plurality of devices (760) such that the first distribution is changed to a second distribution having a second value of the measure of spread of the threshold voltage representing a lower variation among threshold voltages of the plurality of devices.