Zone-Based Program Speed Adjustment for Non-Volatile Memory
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Solution Overview
Problem
Non-volatile memory systems face challenges in reducing the width of threshold voltage distributions to minimize errors during data storage and retrieval without significantly increasing programming time.
Innovation Solution
Implementing a zone-based program speed adjustment method, where non-volatile memory cells are categorized into zones based on their threshold voltages, allowing for differential programming speed adjustments to narrow the threshold voltage distributions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If uniform programming speed is applied to all memory cells, then programming process is simple, but threshold voltage distribution width increases causing more errors
Solution Approach 1:
The patent applies different programming speeds to different zones of memory cells based on their threshold voltage characteristics. Fast programming speed is applied to memory cells in the first threshold voltage distribution (erased state), while slow programming speed is applied to memory cells in the second threshold voltage distribution (programmed state). This local differentiation narrows the overall threshold voltage distribution width, reducing read errors and improving data storage reliability without requiring complete redesign of the programming system.
2Productivity
If programming speed is increased to improve productivity, then programming time decreases, but threshold voltage distribution width increases causing more errors
Solution Approach 1:
The patent dynamically adjusts the programming speed based on the current state of memory cells. The system monitors threshold voltage distributions and automatically switches between fast programming mode (for erased cells) and slow programming mode (for cells approaching target threshold). This dynamic adaptation allows the system to maintain high overall programming productivity while ensuring that individual memory cells are programmed at the appropriate speed to minimize threshold voltage distribution width and prevent read errors.
3Reliability
If slow programming speed is used to narrow threshold voltage distribution, then data storage reliability improves, but programming time increases significantly
Solution Approach 1:
The patent segments the memory cell population into two distinct groups based on their threshold voltage distributions: erased memory cells and programmed memory cells. Each segment is programmed at an optimized speed - erased cells use fast programming speed since they start from a uniform low threshold state, while programmed cells use slow programming speed to precisely control the threshold voltage and narrow the distribution width. This segmentation strategy achieves high data storage reliability without the penalty of uniformly slow programming across all cells, thereby reducing total programming time.
Data Source
AI summary
In order to decrease the width of threshold voltage distributions of programmed memory cells without unreasonably increasing the time needed to complete programming, a non-volatile memory uses a zone based program speed adjustment. The non-volatile memory starts programming a first set of the non-volatile memory cells until a minimum number of memory cells of the first set of non-volatile memory cells reach a first threshold voltage. In response to the minimum number of memory cells reaching the first threshold voltage, the first set of non-volatile memory cells are categorized into zones/groups based on threshold voltage. The speed of programming is then adjusted differently for each zone/group and programming is completed for the first set of non-volatile memory cells.