Multi-Deck Read Level Management for 3D NAND Charge Imbalance
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Solution Overview
Problem
Memory devices experience performance degradation over time due to changes in threshold or processing voltage levels, leading to errors and imbalances in stored charge levels across different groupings of memory cells, particularly in 3D NAND architectures.
Innovation Solution
Implementing a read level management mechanism that dynamically adjusts read levels based on real-time conditions, using a combination of default, dynamic, and tuning voltages to account for charge imbalances across different decks in memory cells, thereby maintaining data integrity and reducing error rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single read level is used for all decks, then device complexity is reduced, but data integrity deteriorates due to charge imbalances between decks programmed at different times
Solution Approach 1:
The memory device divides the memory array into multiple decks (first deck and second deck) that are programmed at different times. Each deck is assigned a separate read level (first read level and second read level) to account for charge imbalances. This segmentation allows independent optimization of read levels for each deck, improving data integrity while managing complexity through structured organization.
Solution Approach 2:
Different read levels are applied to different decks based on their specific programming characteristics. The first deck programmed at a first time receives a first read level, while the second deck programmed at a second time receives a second read level. This local quality approach ensures that each deck's read operations are optimized for its specific charge state, improving overall data integrity.
2Reliability
If read levels are dynamically adjusted for each deck, then data integrity is improved, but device complexity increases
Solution Approach 1:
The system performs preliminary determination of read levels for each deck based on their programming times. The controller pre-establishes first and second read levels for the first and second decks respectively, before actual read operations occur. This preliminary action allows the system to proactively compensate for charge imbalances without adding complex real-time adjustment mechanisms during read operations.
Solution Approach 2:
The memory device automatically manages different read levels for different decks without requiring external intervention. The controller inherently tracks which deck is being accessed and applies the appropriate read level based on the deck's programming history. This self-service mechanism improves data integrity while keeping the control logic relatively simple and integrated into the existing memory control architecture.
Data Source
AI summary
Methods, apparatuses and systems related to managing read levels across multiple groupings or decks are described. The apparatus may include a read level management mechanism configured to controls or dynamically adjusts the read levels for the different groupings according to a real-time condition/measure associated with the programming delays.