NAND Flash Channel Voltage Uniformity via Position-Dependent Precharge
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In NAND flash memory devices, the channel boosting method for program-inhibited cells leads to varying channel voltages based on the position of word lines, resulting in increased error bits due to inconsistent channel conditions during programming operations.
Innovation Solution
The method involves precharging the channel region of program-inhibited cells to specific levels based on their position relative to word line groups between the drain and source select lines, using different select voltages to maintain uniform channel boosting across all cells, thereby ensuring consistent programming operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If channel boosting is performed with fixed conditions for all word lines, then the programming operation can be simplified, but the channel voltage becomes non-uniform across different word line positions leading to increased error bits
Solution Approach 1:
The patent applies local quality by differentiating the precharge voltage levels based on the position of word lines within the memory array. Word lines closer to the source select line receive different precharge voltages compared to those closer to the drain select line, ensuring uniform channel voltage conditions across all memory cells regardless of their spatial location. This position-dependent approach resolves the contradiction by maintaining simplified operation while improving reliability through localized optimization.
Solution Approach 2:
The patent implements parameter changes by dynamically adjusting the precharge voltage level according to the word line position. The control circuit modifies the precharge voltage parameter based on the detected position of the current word line, transforming the fixed parameter approach into a variable one that compensates for position-induced voltage variations. This enables uniform channel boosting across all word lines while maintaining operational simplicity.
2Reliability
If uniform channel boosting is achieved through position-dependent precharge, then error bits are suppressed, but the control mechanism becomes more complex
Solution Approach 1:
The patent employs feedback by implementing a control circuit that detects the position of the current word line and uses this information to determine the appropriate precharge voltage level. The control circuit receives feedback about the word line position and automatically adjusts the precharge voltage accordingly, creating a closed-loop system that ensures uniform channel conditions. This feedback mechanism achieves high reliability while managing complexity through automated position-aware control.
Solution Approach 2:
The patent applies segmentation by dividing the word lines into different groups based on their position relative to the source and drain select lines. The control mechanism segments the word lines into multiple categories (e.g., first word line group closer to source, second word line group closer to drain) and applies different precharge voltage levels to each segment. This segmentation strategy achieves uniform channel boosting while managing control complexity through systematic categorization.
3Manufacturing precision
If different precharge levels are applied to different word line groups, then channel voltage uniformity is improved, but the programming operation time increases
Solution Approach 1:
The patent implements preliminary action by performing position detection and precharge voltage selection before the actual programming operation begins. The control circuit determines the word line position and applies the appropriate precharge voltage in advance, ensuring that the channel is properly prepared for programming. This preliminary positioning and preparation action achieves uniform channel voltage conditions while minimizing the overall programming time by avoiding delays during the actual programming process.
Data Source
AI summary
An operating method of a semiconductor memory device includes precharging a channel region of a program-inhibited cell of first memory cells coupled to a first word line, selected from a first one of word line groups between a drain select line and a source select line, to a first level based on first data; performing a first program operation for storing the first data in the first memory cells; precharging the channel region of a program-inhibited cell of second memory cells coupled to a second word line, selected from a second one of the word line groups, to a second level based on second data to be stored in the second memory cells; and performing a second program operation for storing the second data in the second memory cells.