Nonvolatile Memory Programming via Cell Group Segmentation
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Solution Overview
Problem
Newer flash memory devices face reduced sensing margins due to widening threshold voltage distributions caused by electrical coupling and program disturb effects, impacting the reliability of multi-level cell storage.
Innovation Solution
A method of programming nonvolatile memory devices by loading multi-bit data into page buffers, verifying and programming multi-level cells to intermediate states, and generating cell group information based on program loops and threshold voltage changes to apply distinct voltages for fast and slow cell groups, ensuring accurate storage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If multi-level cells are programmed using conventional methods, then integration density increases, but threshold voltage distributions widen due to electrical coupling and program disturb effects, reducing sensing margins and device reliability
Solution Approach 1:
The patent segments the memory cells into fast cell group and slow cell group based on their programming characteristics. By dividing the cell population and applying different program voltages to each group, the method prevents threshold voltage distribution widening while maintaining high integration density, thus resolving the contradiction between density and reliability.
Solution Approach 2:
The patent applies different program voltages (first program voltage for fast cells, second program voltage for slow cells) to different cell groups based on their local characteristics. This localized approach ensures each group receives optimal programming conditions, preventing threshold voltage spread and maintaining sensing margins while achieving high integration density.
2Device complexity
If uniform program voltage is applied to all multi-level cells, then programming process is simple, but program time increases due to varying cell characteristics
Solution Approach 1:
The patent dynamically adjusts the program voltage based on cell characteristics by classifying cells into fast and slow groups. This dynamic approach allows the system to adapt programming parameters to individual cell needs, reducing overall program time while adding manageable complexity through automated classification and differential voltage application.
3Productivity
If higher program voltage is applied to reduce program time, then programming speed increases, but threshold voltage distributions widen, reducing sensing margins
Solution Approach 1:
The patent applies different program voltages to different cell groups: fast cells receive lower program voltage while slow cells receive higher program voltage. This localized voltage application maintains narrow threshold voltage distributions (preserving sensing margins) while achieving fast programming speeds by optimizing voltage for each cell group's characteristics.
Data Source
AI summary
In method of programming a nonvolatile memory device, multi-bit data are loaded into a plurality of page buffers. Multi-level cells included in a multi-level cell block are programmed to a plurality of intermediate program states including a first intermediate program state and a second intermediate program state which is higher than the first intermediate program state based on the multi-bit data. Whether the multi-level cells are programmed to the plurality of intermediate program states is verified. Cell group information for the first intermediate program state is generated by checking whether a result of the verification for the second intermediate program state satisfies a predetermined criterion. The multi-level cells are programmed to a plurality of target program states corresponding to the multi-bit data based on the cell group information.