High-Voltage Switch Gate Feedback to Mitigate Fowler-Nordheim 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 efficiency of memory operations.
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 voltage across the dielectric from entering the Fowler-Nordheim regime, thereby ensuring infinite lifetime and maintaining the transistor in a turned-on state.
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 maintains the gate voltage at a level that prevents the transistor from turning off, thereby relieving stress on the transistor and extending its operational lifetime while maintaining high-voltage switching capability
Solution Approach 2:
The patent introduces a diode structure as an intermediary element between the output node and the gate of the p-type high-voltage transistor. This diode acts as a voltage reference that mediates the feedback process, ensuring the gate voltage remains appropriate to keep the transistor in a turned-on state and prevent Fowler-Nordheim tunneling stress
2Productivity
If the high-voltage switch operates with large voltage shifts, then program and erase operations can be performed, but Fowler-Nordheim tunneling causes threshold voltage shifts and stress on components
Solution Approach 1:
The patent applies preliminary anti-action by preemptively establishing a feedback mechanism that counteracts the harmful effects of Fowler-Nordheim tunneling before they can cause significant damage. The feedback continuously adjusts the gate voltage to prevent the transistor from experiencing extreme stress conditions, thereby protecting against threshold voltage shifts and component degradation during program and erase operations
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, ensuring the high-voltage switch circuit operates indefinitely and maintains the transistor in a stable, turned-on state, enhancing the reliability and longevity of memory device operations.
Implementation Method 1
stress on one or more of these components from operation by the HV switch can be quite large to a point at which the stress can limit the lifetime of these components... Fowler-Nordheim tunneling, leading to threshold voltage shifts
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.