Nonvolatile Memory Cell Current Comparison Feedback Control
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Solution Overview
Problem
Nonvolatile memory devices often exhibit non-uniform threshold voltages due to variations in fabrication process parameters, leading to potential malfunctions if deviations exceed allowable ranges.
Innovation Solution
A nonvolatile memory device with a memory cell and switching unit, where a cell transistor has a floating gate and a coupling capacitor, and a method involving a program voltage applied to the memory cell, with control based on the comparison of cell current with a reference current to achieve uniform threshold voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional programming methods are used without current comparison control, then programming speed is maintained, but threshold voltage uniformity deteriorates leading to device malfunctions
Solution Approach 1:
The patent implements feedback control by comparing the cell current with a reference current during programming and adjusting the program voltage accordingly. When the cell current exceeds the reference current, the program voltage is reduced to prevent threshold voltage deviation, ensuring uniform threshold voltages across all memory cells while maintaining programming functionality.
Solution Approach 2:
The patent replaces complex multi-stage programming mechanisms with a simplified current-comparison-based control system. Instead of using multiple programming stages with different voltages and timings, the invention uses real-time current monitoring and dynamic voltage adjustment, substituting mechanical/process complexity with electrical feedback control.
2Reliability
If program voltage is continuously applied to ensure thorough programming, then programming completeness is improved, but threshold voltage deviation increases due to process variations
Solution Approach 1:
The patent uses feedback control to monitor cell current during programming and dynamically adjust program voltage. When the cell current exceeds the reference current, indicating sufficient programming, the voltage is reduced to prevent over-programming and threshold voltage deviation, ensuring both programming completeness and uniformity.
Solution Approach 2:
The patent transforms the static programming approach into a dynamic process where program voltage is continuously adjusted based on real-time current comparison. This dynamic control allows the system to adapt to process variations and achieve uniform threshold voltages while ensuring thorough programming.
3Productivity
If higher program voltage is used to speed up programming, then programming speed is improved, but threshold voltage deviation increases beyond allowable ranges
Solution Approach 1:
The patent employs dynamic voltage adjustment based on real-time current comparison. The program voltage is initially set at a higher level for fast programming, then automatically reduced when the cell current exceeds the reference current, preventing threshold voltage deviation while maintaining high programming speed.
Solution Approach 2:
The patent implements feedback control where the cell current is continuously compared with the reference current during programming. This feedback mechanism allows the system to maintain high programming voltages for speed while automatically reducing voltage when sufficient programming is achieved, preventing threshold voltage uniformity degradation.
Data Source
AI summary
A nonvolatile memory device includes a memory cell, and a switching unit. The memory cell includes a cell transistor having a floating gate and a coupling capacitor connected to the floating gate. The switching unit is coupled between the coupling capacitor and a bias terminal, and switches on or off based on the comparison result between a cell current flowing through the memory cell with a reference current during a program operation for programming the memory cell.