Sub-block Granularity Defect Management for NAND Flash Memory
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Solution Overview
Problem
Conventional NAND memory technologies treat entire erase blocks as defective upon sub-block erase failure, leading to unnecessary memory capacity wastage and high redundancy overhead due to large erase block sizes.
Innovation Solution
Implementing a method to track and manage sub-block erase failures independently, allowing for the identification and exclusion of only defective sub-blocks while permitting the use of remaining sub-blocks, thereby optimizing user-exposed memory capacity and reducing redundancy overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If entire erase blocks are treated as defective upon sub-block erase failure, then reliability is ensured, but user-exposable memory capacity is wasted unnecessarily
Solution Approach 1:
The patent divides the erase block into smaller sub-blocks and tracks failure status at the sub-block level rather than treating the entire block as defective. This segmentation allows the system to isolate failures to specific sub-blocks while keeping other sub-blocks functional, thereby maintaining user-exposable memory capacity while ensuring reliability through targeted defect management.
2Reliability
If entire erase blocks are treated as defective upon sub-block erase failure, then reliability is ensured, but redundancy overhead becomes unnecessarily high
Solution Approach 1:
By segmenting the block into sub-blocks and tracking failures at this finer granularity, the system can apply redundancy only where needed. Instead of allocating redundancy for the entire block, the system can manage redundancy at the sub-block level, reducing overall redundancy overhead while maintaining reliability through targeted protection mechanisms.
3Quantity of substance
If sub-block erase failures are tracked and managed independently, then user-exposable memory capacity is optimized, but device complexity increases
Solution Approach 1:
The patent implements segmentation at the sub-block level to enable independent tracking and management of erase failures. This allows the system to optimize user-exposable memory capacity by excluding only defective sub-blocks rather than entire blocks. The increased device complexity is managed through structured failure tracking mechanisms that operate at the sub-block granularity, enabling precise defect management.
Data Source
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AI summary
Systems, apparatuses and methods may provide for initiating an erase of a block of non-volatile memory in response to an erase command, wherein the block includes a plurality of sub-blocks. Additionally, a failure of the erase with respect to a first subset of the plurality of sub-blocks may be tracked on an individual sub-block basis, wherein the erase is successful with respect to a second subset of the plurality of sub-blocks. In one example, use of the second subset of the plurality of sub-blocks is permitted, whereas use of the first subset of the plurality of sub-blocks is prevented.