Non-volatile Memory Read Voltage Grouping
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Solution Overview
Problem
Non-volatile memory devices face challenges in maintaining reliable read performance due to changes in threshold voltage distributions over time, leading to read errors and reduced data retention, especially as memory cells age and are affected by factors like leakage and read disturb effects.
Innovation Solution
The implementation of an operating method for non-volatile memory devices that classifies target memory cells into groups based on adjacent data read from adjacent memory cells, sets a read voltage level for each group, and performs read operations using the optimized voltage level to improve read accuracy and reduce errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed read voltage level is used for all memory cells, then the device complexity is reduced and operation is simplified, but read performance deteriorates due to threshold voltage distribution changes over time
Solution Approach 1:
The patent segments the memory cells into multiple groups based on their threshold voltage characteristics and adjacent data patterns. Each group is assigned a specific read voltage level, allowing differentiated voltage control that adapts to varying threshold voltage distributions without requiring complete redesign of the voltage control system.
Solution Approach 2:
The patent implements dynamic read voltage adjustment by determining read voltage levels based on adjacent data read from neighboring memory cells. This dynamic approach allows the read voltage to adapt to changing threshold voltage distributions over time and across different memory cell groups, improving read reliability without requiring static pre-calculation of all voltage levels.
2Measurement precision
If read voltage levels are adjusted for each memory cell individually, then read accuracy is improved, but the device complexity and operation difficulty increase significantly
Solution Approach 1:
The patent applies local quality by assigning different read voltage levels to different groups of memory cells based on their specific threshold voltage characteristics and adjacent data patterns. This localized voltage adjustment improves read accuracy for each group without requiring individual voltage control for every single memory cell, thus balancing precision with manageable complexity.
Solution Approach 2:
The patent uses adjacent data from neighboring memory cells as an intermediary to determine the appropriate read voltage level for target memory cells. This intermediary approach allows the system to infer threshold voltage characteristics without directly measuring each cell's threshold voltage, simplifying the voltage control mechanism while maintaining high read accuracy.
3Reliability
If adjacent data is read and used for classification, then read performance is improved through better voltage level selection, but additional read operations increase time consumption
Solution Approach 1:
The patent performs preliminary reading of adjacent data before determining the read voltage level for target memory cells. By obtaining adjacent data in advance and using it to classify and voltage-calibrate the target cells, the system prepares optimal read conditions beforehand, improving subsequent read performance without requiring repeated voltage adjustments during the actual read operation.
Solution Approach 2:
The patent merges the adjacent data read operation with the voltage level determination process. By combining these operations into a unified workflow where adjacent data serves dual purposes (both as information to be retrieved and as calibration reference for voltage selection), the system reduces overall time consumption compared to performing separate read and voltage-adjustment operations.
Data Source
AI summary
An operating method for a non-volatile memory device includes; performing a read operation on adjacent memory cells connected to an adjacent word line proximate to a target word line to determine adjacent data, classifying target memory cells connected to the target word line into groups according to the adjacent data, setting a read voltage level for each of the groups by searching for a read voltage level for target memory cells in at least one of the groups, and performing a read operation on target memory cells using the read voltage level set for each of the groups.