Memory Die Charge Loss Screening to Prevent False Retirement
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Solution Overview
Problem
Memory systems incorrectly retire memory dies due to transient charge loss issues during block family error avoidance scans, leading to undesirably high retirement rates and reduced performance.
Innovation Solution
Implement a method to identify and avoid sampling blocks associated with memory dies experiencing high charge loss rates by maintaining a counter for each die, classifying them as RDCL weak dies, and avoiding selection during subsequent block family error avoidance scans.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If block family error avoidance scans are performed to identify defective memory blocks, then memory reliability is improved, but memory die retirement rate increases due to transient charge loss false positives
Solution Approach 1:
The patent applies preliminary action by performing a charge loss assessment scan before the block family error avoidance scan to identify and exclude memory dies with transient charge loss issues. This preliminary classification prevents these dies from being incorrectly retired during subsequent scans, thereby maintaining productivity while preserving reliability improvements.
Solution Approach 2:
The patent introduces an intermediary mechanism - a charge loss weak die identifier and classifier that acts as a mediator between the block family error avoidance scan and the memory die retirement decision. This intermediary assesses charge loss characteristics and prevents false retirement by filtering out transient charge loss cases before they trigger retirement.
2Reliability
If memory dies with transient charge loss are retired to ensure data integrity, then data integrity is improved, but functional block availability decreases
Solution Approach 1:
The patent performs preliminary charge loss assessment to distinguish between transient and permanent charge loss issues before making retirement decisions. This preliminary action ensures that only memory dies with permanent defects are retired, maintaining data integrity while preserving functional blocks that have transient charge loss characteristics.
Solution Approach 2:
The patent implements feedback by using charge loss assessment results to inform and adjust the block family error avoidance scan process. The feedback mechanism allows the system to learn from charge loss patterns and adjust retirement decisions, ensuring that transient charge loss cases are not incorrectly retired while maintaining data integrity for permanent defects.
Data Source
AI summary
Methods, systems, and devices for charge loss weak die identification are described. The described techniques provide for a memory system to avoid sampling, during block family (BF) scans, blocks of memory cells associated with memory dies that are classified as read disturb charge loss (RDCL) weak dies. The memory system may identify a memory die as being an RDCL weak die based on a threshold quantity of blocks associated with the memory die experiencing relatively high charge loss. If the quantity satisfies a threshold value, the memory system may classify the memory die as an RDCL weak die and the memory system may refrain from selecting blocks from a BF that are associated with a memory die classified as an RDCL weak die.