Non-Volatile Memory Soft Program Voltage Control
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Solution Overview
Problem
The program operation in non-volatile memory devices is inefficient due to the widening distribution of threshold voltages in memory cells after an erase operation, leading to increased time and voltage requirements for raising threshold voltages during the soft program method.
Innovation Solution
The method involves erasing a memory cell block and performing a soft program operation by supplying a first drain turn-on voltage higher than the target level to the drain select line and a soft program voltage to the word lines, which helps in reducing the potential difference between word lines and efficiently raising the threshold voltages of memory cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a program voltage is supplied to all of the word lines coupled to the erased memory cell block, then the threshold voltages of memory cells are raised, but the distribution of threshold voltages becomes widened due to capacitive coupling between adjacent word lines
Solution Approach 1:
The patent applies different voltages to different word lines based on their position. Word lines adjacent to select lines receive a first program voltage, while other word lines receive a second program voltage. This local differentiation compensates for the capacitive coupling effect that causes threshold voltage distribution widening, thereby improving manufacturing precision without excessive time penalty.
Solution Approach 2:
The patent changes the voltage parameter supplied to word lines based on their position relative to select lines. By adjusting the program voltage levels differently for adjacent versus non-adjacent word lines, the method optimizes the threshold voltage distribution while managing the program operation time.
2Quantity of substance
If the threshold voltages of erased memory cells are lowered, then more memory cells can be erased, but the time required for program operation increases and program voltage level rises
Solution Approach 1:
The patent differentiates the program voltage applied to word lines based on their position. Word lines adjacent to select lines receive a higher first program voltage, while other word lines receive a lower second program voltage. This local quality approach ensures that all memory cells are effectively programmed without requiring uniformly high voltages across all word lines, thereby reducing overall program operation time while maintaining the ability to erase large numbers of memory cells.
3Stability of the object's composition
If a program voltage is supplied to all word lines, then threshold voltages are raised uniformly, but the potential difference between word lines increases due to capacitive coupling
Solution Approach 1:
The patent implements local quality by supplying different program voltages to different groups of word lines. Word lines adjacent to select lines receive a first program voltage, while other word lines receive a second program voltage. This approach maintains threshold voltage uniformity across memory cells while managing the complexity of voltage control through a systematic differentiation strategy.
Solution Approach 2:
The patent segments the word lines into different groups based on their proximity to select lines. This segmentation allows for differentiated voltage control, where adjacent word lines receive one voltage level and non-adjacent word lines receive another, thereby managing potential differences while maintaining overall threshold voltage uniformity.
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 approach reduces the time required for the program operation and narrows the distribution of threshold voltages, enhancing the efficiency of the soft program method in non-volatile memory devices.
Implementation Method 1
capacitive coupling between adjacent word lines
Data Source
AI summary
A method of operating a non-volatile memory device includes erasing a memory cell block, supplying a first drain turn-on voltage higher than a target level to the drain select line of the memory cell block, and performing a soft program operation by supplying a soft program voltage to the word lines of the memory cell block.