High-Voltage Switch Feedback to Relieve Fowler-Nordheim Gate Stress
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Solution Overview
Problem
High-voltage switch circuits in memory devices, particularly in NAND flash memory, face significant stress due to Fowler-Nordheim tunneling, leading to threshold voltage shifts and limited lifetime, which affects the reliability and longevity of these components.
Innovation Solution
Incorporating a high-voltage diode structure that couples the output node of the high-voltage switch to the gate of the high-voltage p-type field effect transistor, providing feedback to relieve stress and prevent the dielectric from entering the Fowler-Nordheim regime, thereby ensuring infinite lifetime relative to FN stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a high voltage switch is used to shift voltage to memory cells for program and erase operations, then the memory device can perform high voltage operations, but the components experience large stress that limits their lifetime
Solution Approach 1:
The patent implements a feedback mechanism where the output voltage of the high voltage switch is fed back to the gate of the p-type high voltage transistor through a diode structure. This feedback prevents the voltage across the dielectric from entering the Fowler-Nordheim regime by dynamically adjusting the gate voltage based on the output voltage, thereby relieving stress on the dielectric and extending component lifetime while maintaining high voltage operation capability
2Ease of operation
If high voltage is applied to the gate of the p-type high voltage transistor, then the switch can be turned on, but the dielectric enters the Fowler-Nordheim regime causing threshold voltage shifts
Solution Approach 1:
The feedback connection through the diode structure continuously monitors the output voltage and adjusts the gate voltage accordingly. When the output voltage reaches levels that would cause Fowler-Nordheim tunneling, the feedback mechanism reduces the voltage across the dielectric by adjusting the gate voltage, preventing threshold voltage shifts while maintaining the ability to turn on the switch when needed
3Power
If the dielectric voltage enters the Fowler-Nordheim regime, then high voltage switching occurs, but stress relief is needed to ensure infinite lifetime
Solution Approach 1:
The diode structure provides a feedback path that automatically adjusts the gate voltage to prevent the dielectric voltage from entering the Fowler-Nordheim regime. This feedback mechanism relieves harmful stress on the dielectric during high voltage switching operations, ensuring infinite lifetime relative to FN stress while maintaining high voltage switching functionality
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
This solution effectively prevents voltage across the dielectric from entering the Fowler-Nordheim regime, maintaining the high-voltage switch's functionality and extending its lifespan, reducing engineering resources needed for stress mitigation.
Implementation Method 1
High-voltage switch circuits in memory devices, particularly in NAND flash memory, face significant stress due to Fowler-Nordheim tunneling, leading to threshold voltage shifts and limited lifetime
Data Source
AI summary
A variety of applications can include a high voltage switch configured to translate supply voltages or other voltages to specific magnitudes in memory devices, with the high voltage switch designed to provide enhanced lifetime of components of the high voltage switch. A high voltage switch can include a high voltage diode coupled to an output node and to a gate of a high voltage transistor coupled to the output node. The high voltage diode can provide feedback of an output voltage to the gate of the high voltage transistor to relieve Fowler-Nordheim stress on the dielectric coupled to the gate in the transistor, where large shifts in threshold voltage of the transistor could otherwise result from the Fowler-Nordheim stress. The high voltage diode can be structured using a high voltage field effect transistor. Additional devices, systems, and methods are discussed.