Memory Scan Fragmentation for Weak Wordline Degradation Control
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Solution Overview
Problem
Existing memory sub-systems face challenges in balancing scan frequency to mitigate memory degradation while maintaining performance, as increasing scan frequency degrades system performance and reducing frequency leads to unacceptable memory degradation.
Innovation Solution
Implementing a scan fragmentation method that identifies 'weak' wordlines susceptible to degradation, scanning these more frequently and ensuring all blocks are scanned within system time constraints by alternating between mandatory and scheduled wordlines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If scan frequency is increased to control memory degradation, then memory degradation control is improved, but system performance deteriorates
Solution Approach 1:
The scan operation is segmented into multiple scan fragments, each targeting specific wordlines. Instead of scanning all wordlines uniformly, the system divides the scan into smaller units that can be selectively executed based on degradation susceptibility, thereby reducing overall scan overhead while maintaining degradation control.
Solution Approach 2:
The patent applies different scan frequencies to different wordlines based on their individual degradation characteristics. Wordlines identified as 'weak' or more susceptible to degradation are scanned more frequently, while other wordlines are scanned less frequently. This localized approach optimizes the balance between degradation control and performance.
2Productivity
If scan frequency is decreased to maintain performance, then system performance is improved, but memory degradation control worsens
Solution Approach 1:
The scan frequency is made dynamic rather than static. The system adaptively adjusts scan frequencies based on real-time or historical degradation data, allowing performance optimization while ensuring degradation control through increased scanning of vulnerable wordlines when needed.
Solution Approach 2:
The system uses feedback from degradation monitoring to adjust scan operations. By tracking which wordlines exhibit degradation patterns, the system can intensify scanning of those specific wordlines while reducing scanning of stable wordlines, thus maintaining overall degradation control with reduced performance impact.
3Ease of manufacture
If uniform scan frequency is applied to all wordlines, then implementation simplicity is maintained, but degradation control effectiveness deteriorates due to varying susceptibility
Solution Approach 1:
The uniform scan approach is segmented into targeted scan fragments. Each fragment focuses on specific wordlines with similar degradation characteristics, making the complex differentiated scanning manageable through modular organization while improving effectiveness.
Solution Approach 2:
Instead of uniform treatment, each wordline receives customized scan attention based on its degradation susceptibility. This local quality approach ensures that resources are allocated efficiently to where they are most needed, improving degradation control effectiveness.
4Loss of time
If full scan is completed within predetermined time, then system requirements are met, but performance degradation occurs due to frequent scanning
Solution Approach 1:
The full scan is divided into multiple scan fragments that can be executed in parallel or interleaved with data operations. This segmentation allows the system to meet scan completion requirements while minimizing performance impact by distributing scan operations throughout available time windows.
Solution Approach 2:
Scan operations are performed periodically rather than continuously, with scan fragments interspersed between data operations. This periodic approach ensures scan completion within predetermined time while maintaining system performance by avoiding continuous scanning overhead.
Data Source
AI summary
A memory system includes a memory device and a processing device, operatively coupled to the memory device. The processing device performs operations comprising: identifying one or more mandatory scan wordlines of the memory device and one or more remaining wordlines of the memory device; performing a plurality of scan iterations with respect to a plurality of pages of the memory device, such that performing each scan iteration comprises: identifying, among the remaining wordlines, one or more scheduled scan wordlines of the memory device, scanning a subset of pages of the memory device that are addressable by the mandatory scan wordlines and the scheduled scan wordlines; wherein a combination of a first plurality of pages addressable by the scheduled scan wordlines selected by the plurality of scan iterations and a second plurality of pages addressable by the mandatory wordlines comprises the plurality of pages of the memory device.