Read Disturb Charge Loss Scanning for High-Temperature Memory
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Solution Overview
Problem
Performing read operations at high temperatures in memory systems can cause read stress, leading to charge loss and voltage threshold shifts, which reduce the read window budget and result in errors during data retrieval.
Innovation Solution
Implementing a Read Disturb Charge Loss (RDCL) scan to identify errors due to voltage threshold shifts by scanning pages of word lines based on priority levels and operating parameters, and folding blocks with excessive errors to improve reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If read operations are performed at high temperatures, then data access speed is maintained, but charge loss and voltage threshold shifts occur reducing reliability
Solution Approach 1:
The system performs preliminary RDCL scans to detect charge loss and voltage threshold shifts before they cause data errors. By scanning at scheduled intervals and triggering when temperature thresholds are exceeded, the system identifies problematic blocks early and initiates data migration before reliability deteriorates, thus maintaining both speed and accuracy.
Solution Approach 2:
The system continuously monitors temperature and scan results as feedback signals. When temperature exceeds a threshold or error rates increase during scanning, the system adjusts its behavior by increasing scan frequency, migrating data from affected blocks, or modifying read operation parameters, thereby maintaining reliability without sacrificing access speed.
2Reliability
If RDCL scans are performed frequently to detect errors, then reliability is improved, but time consumption increases
Solution Approach 1:
Instead of continuous scanning, the system performs periodic RDCL scans at predetermined intervals and triggers scans only when temperature thresholds are exceeded or error rates indicate problems. This periodic approach with conditional triggers maintains reliable error detection while minimizing unnecessary scan time and computational resources.
Solution Approach 2:
The system applies partial scanning by focusing RDCL operations on specific blocks or pages identified as high-risk based on temperature distribution, error rates, or previous scan results, rather than scanning the entire memory array uniformly. This targeted partial action reduces total scan time while maintaining adequate reliability for the most critical data.
Data Source
AI summary
Methods, systems, and devices for read disturb charge loss handling are described. A memory system may be configured to perform a scan to identify errors from voltage threshold shift, due to performing read operations at high temperatures. The scan may be initiated based on detecting an operating temperature of the memory system and that a memory die of the memory system is unreliable. The memory system may determine a frequency for performing the scan, and perform the scan based on satisfying a threshold associated with the frequency. The scan may include scanning pages associated with word lines to determine whether a quantity of errors satisfies a threshold. After satisfying the threshold, the memory system may fold a block associated with the quantity of errors. In some examples, the pages scanned may be selected based on a priority level defined by a type of memory cells associated with the word lines.