Relinking Scheme in Sub-Block Mode for Flash Storage
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Solution Overview
Problem
Flash storage devices face reduced die yield and memory capacity due to bad blocks, as existing technologies are limited in relinking operable sub-blocks across planes to form new metablocks, leading to potential read-only mode and capacity loss.
Innovation Solution
The controller links sub-blocks with different sub-block addresses across multiple planes to form metablocks, enabling the formation of new metablocks even when some sub-blocks are identified as bad, and issues separate program commands for each word line in the sub-blocks to maintain data integrity and capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the controller links sub-blocks with the same sub-block address across planes to form metablocks, then the programming operation is simplified, but the adaptability to handle bad blocks is reduced
Solution Approach 1:
The patent implements a dynamic metablock formation mechanism that adapts to the presence of bad blocks. The controller can form metablocks with sub-blocks having different sub-block addresses when bad blocks are detected, transitioning from a static same-address requirement to a flexible different-address approach. This dynamic adaptation allows the system to maintain programming efficiency while handling bad blocks effectively.
2Device complexity
If the controller restricts metablock formation to sub-blocks with the same sub-block address, then the programming complexity is reduced, but the memory capacity utilization is worsened due to lost metablocks
Solution Approach 1:
The patent changes the addressing parameter requirement for metablock formation. Instead of requiring identical sub-block addresses, the system allows different sub-block addresses when bad blocks are present. This parameter change enables the controller to form valid metablocks that would otherwise be lost, thereby increasing memory capacity utilization without significantly increasing programming complexity.
3Reliability
If bad blocks are identified and removed from usable memory, then the reliability of individual blocks is improved, but the overall memory capacity is reduced
Solution Approach 1:
The patent implements a recovery mechanism for metablocks that would otherwise be lost due to bad blocks. By allowing metablock formation with sub-blocks having different sub-block addresses, the system recovers capacity that would be discarded when bad blocks are removed. This enables the system to maintain high reliability by removing bad blocks while simultaneously preserving memory capacity through alternative metablock configurations.
Data Source
AI summary
Aspects of a storage device including a memory and a controller are provided which allow sub-blocks with different sub-block addresses to be linked across multiple planes to form metablocks. The memory includes multiple blocks in different planes, where each of the blocks includes multiple sub-blocks. The controller links a first sub-block in a first plane and a second sub-block in a second plane with different sub-block addresses to form the metablock. After forming the metablock, the controller programs different word lines in the first and second sub-blocks when writing data to the metablock. Thus, the controller may write data to linked or relinked metablocks with different sub-block addresses, thereby improving die yield and memory capacity of the storage device.