Reclaim Program Mode for Flash Memory Data Retention
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Solution Overview
Problem
Flash memory systems face reliability issues due to data degradation over time and read disturbances, leading to increased error bits that exceed correction limits, necessitating frequent read reclaim operations which impact performance and latency.
Innovation Solution
A memory system with a nonvolatile memory device that employs a reclaim program mode, where data is programmed with a larger read margin than normal program modes, allowing the memory controller to detect error bits and reprogram data into a new block, reducing the width of threshold voltage distribution and improving data retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If normal program mode is used to program data in flash memory, then programming speed is maintained, but data reliability degrades over time due to larger threshold voltage distribution width
Solution Approach 1:
The patent applies local quality by implementing different programming modes (normal program mode and read reclaim program mode) with distinct threshold voltage distribution characteristics in different operational contexts. The read reclaim program mode creates a narrower threshold voltage distribution specifically for data that requires enhanced reliability, while normal program mode maintains broader distribution for standard operations.
Solution Approach 2:
The patent changes the programming parameters by adjusting the threshold voltage distribution width through different programming algorithms and voltage pulse sequences. The read reclaim program mode uses modified programming parameters that result in a narrower threshold voltage distribution, thereby improving data retention characteristics compared to the normal program mode.
2Reliability
If read reclaim operations are performed frequently to maintain data reliability, then data retention is improved, but system performance and latency increase
Solution Approach 1:
The patent applies preliminary action by proactively programming data with enhanced reliability characteristics (narrower threshold voltage distribution) during the read reclaim program mode before errors occur. This preventive approach reduces the frequency of subsequent read reclaim operations needed to maintain data integrity, thereby improving overall system performance.
Solution Approach 2:
The patent effectively creates a more durable data storage state that lasts longer without requiring frequent reprogramming. By investing in a more robust programming mode initially, the system reduces the need for repeated read reclaim operations, lowering the overall operational burden.
3Measurement precision
If narrow threshold voltage distribution is achieved through read reclaim program mode, then read margin increases and data reliability improves, but programming complexity increases
Solution Approach 1:
The patent segments the programming function into distinct modes: normal program mode for standard operations and read reclaim program mode for enhanced reliability operations. This segmentation allows the system to use the simpler normal mode by default while reserving the more complex read reclaim mode for specific scenarios where improved read margin is critical.
Data Source
AI summary
A memory system includes a nonvolatile memory device and a memory controller. The nonvolatile memory device has a first program mode and a second program mode. The second program mode programs data to have a larger read margin than the first program mode. The memory controller controls the nonvolatile memory device to program the data according to the second program mode for a read reclaim operation.