Partial Superblock Memory Management for NAND Flash
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Solution Overview
Problem
Traditional superblock formation in NAND memory devices is hindered by bad blocks, leading to reduced performance and increased costs due to the need for redundant blocks and smaller die sizes, while partial superblocks attempt to mitigate this by reallocating good blocks, but often result in noticeable performance decreases.
Innovation Solution
Implementing partial superblock memory management by reallocating good blocks to replace bad blocks within the same plane, forming partial superblocks with a quantity of bad blocks that satisfies a threshold, thereby increasing the number of usable partial superblocks while limiting performance degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional superblock formation is used, then reliability is improved by avoiding bad blocks, but productivity deteriorates due to reduced usable memory capacity and increased manufacturing costs
Solution Approach 1:
The patent segments the superblock into multiple planes, allowing individual planes to be evaluated and managed separately. This enables the system to identify and exclude only the specific bad blocks within affected planes while maintaining functionality of good blocks in the same superblock structure, thereby improving memory utilization without compromising reliability.
Solution Approach 2:
The patent applies local quality by treating each plane within a superblock differently based on its actual condition. Instead of discarding entire superblocks due to isolated bad blocks, the system selectively manages bad blocks at the plane level, preserving usable capacity while maintaining reliability through targeted exclusion of defective areas.
2Productivity
If partial superblocks are used to increase usable capacity, then productivity is improved, but reliability deteriorates due to performance degradation from bad blocks
Solution Approach 1:
The patent implements partial action by allowing partial superblocks to be formed and used when they meet minimum performance thresholds. Instead of requiring complete superblocks for all operations, the system selectively activates partial superblocks with sufficient good blocks, thereby increasing usable capacity while maintaining acceptable performance through threshold-based validation.
Solution Approach 2:
The patent changes the parameter thresholds for superblock acceptance, allowing superblocks with a certain percentage of bad blocks (e.g., up to 25%) to be used if they still contain sufficient good blocks. This parameter adjustment enables the system to utilize previously discarded partial superblocks, improving productivity while maintaining reliability through controlled tolerance levels.
3Productivity
If bad blocks are concentrated in fewer superblocks, then productivity is improved by maximizing usable capacity, but reliability deteriorates due to noticeable performance decreases in those superblocks
Solution Approach 1:
The patent extracts and isolates bad blocks into specific planes within superblocks, separating them from good blocks. This extraction allows the system to clearly identify and manage defective areas while preserving the functionality of good blocks, enabling better distribution of bad blocks across multiple superblocks to maintain performance consistency.
Solution Approach 2:
The patent implements dynamic management of bad blocks by continuously monitoring and redistributing them across superblocks based on current performance thresholds and capacity needs. This dynamic approach allows the system to adaptively balance between maximizing usable capacity and maintaining performance consistency, preventing concentration of bad blocks in any single superblock.
Data Source
AI summary
An apparatus can include a partial superblock memory management component. The partial superblock memory management component can identify bad blocks in respective planes of a block of non-volatile memory cells. The partial superblock memory management component can determine that a plane of the respective planes includes at least good block in at least one different block of non-volatile memory cells. The partial superblock memory management component can perform an operation to reallocate the at least one good block in the plane to the at least one bad block in the plane to form blocks of non-volatile memory cells having a quantity of bad blocks that satisfies a bad block threshold.