Sub-block Manager for Uncorrectable Error Reclaim in Flash Memory
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Solution Overview
Problem
Integrated circuit memory devices face performance degradation due to uncorrectable errors (UECC) caused by threshold voltage changes in flash memory cells, leading to read failures and data loss, as existing technologies lack effective methods to manage and recover from such errors.
Innovation Solution
A storage device with a memory controller and sub-block manager that determines whether a sub-block is a reclaim sub-block when an uncorrectable error occurs, and reclaims the affected sub-blocks to healthy sub-blocks in the same or another memory block, thereby reducing performance degradation and maintaining data integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If threshold voltage changes occur in flash memory cells due to coupling noise, pass voltage disturbance, program voltage disturbance, or read pass voltage disturbance, then data retention is affected and read failures occur, but the memory device cannot effectively recover from these errors
Solution Approach 1:
The system performs preliminary actions by monitoring threshold voltage changes and proactively identifying sub-blocks at risk of uncorrectable errors before they occur. The memory device predicts potential failures and takes preventive measures to migrate data or perform reclaim operations, thereby avoiding read failures and maintaining data retention reliability.
Solution Approach 2:
The system introduces an intermediary mechanism through the sub-block manager and reclaim operations. When threshold voltage changes cause errors, the system uses reclaim operations as an intermediary process to transfer data from affected sub-blocks to healthy sub-blocks, thereby recovering from uncorrectable errors and maintaining data integrity.
2Reliability
If a reclaim operation is performed to recover from uncorrectable errors, then data integrity is maintained, but memory block performance degrades due to additional operations required
Solution Approach 1:
The system segments the memory block into multiple sub-blocks, allowing selective reclaim operations on only the affected sub-blocks rather than the entire block. This segmentation enables targeted recovery operations that maintain data integrity in specific areas while minimizing the performance impact on the overall memory block by avoiding unnecessary operations on healthy sub-blocks.
Solution Approach 2:
The system applies local quality by performing reclaim operations only on sub-blocks that require recovery, rather than uniformly treating the entire memory block. The sub-block manager identifies and treats only the affected local areas, maintaining data integrity where needed while preserving performance in unaffected regions.
3Reliability
If the memory device continuously monitors and manages threshold voltage changes, then uncorrectable errors are detected early, but device complexity increases due to additional monitoring and management mechanisms
Solution Approach 1:
The system implements self-service by enabling the memory device to autonomously monitor threshold voltage changes and manage reclaim operations without external intervention. The sub-block manager automatically detects errors, identifies affected sub-blocks, and executes recovery operations, thereby providing reliable error detection while minimizing the added complexity through automated self-managed processes.
Data Source
AI summary
A non-volatile integrated circuit memory device includes a first memory block having first and second memory sub-blocks therein, and a second memory block having third and fourth memory sub-blocks therein. A sub-block manager is also provided, which is configured to: (i) determine whether the second memory sub-block is a reclaim sub-block when the first memory sub-block has an uncorrectable error (UECC) therein, and (ii) reclaim the first and second memory sub-blocks to the third and fourth memory sub-blocks, respectively, in response to determining that the second memory sub-block is a reclaim sub-block.