Non-Volatile Memory Page Counters for Program Disturb Refresh
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Solution Overview
Problem
Existing techniques for managing program disturb in non-volatile memory are inefficient, leading to excessive refresh operations and premature determinations of page unusability, which reduces the efficiency and adaptability of non-volatile memory systems.
Innovation Solution
Implementing tracking bits for each page to store freshness and endurance counters, allowing accurate determination of when to refresh pages and prevent future operations based on program disturb and endurance thresholds, with the use of scratch pages for reliable refreshes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing techniques are used to manage program disturb, then the memory system operates with simple structure, but refresh operations become excessive and pages are determined unusable prematurely
Solution Approach 1:
The memory system is segmented into multiple independent tracking structures: a sector-level freshness counter and page-level endurance counters. This segmentation allows granular tracking of program operations at different hierarchical levels, enabling precise determination of when pages need refreshing or should be marked unusable, thereby improving reliability without causing excessive refresh operations.
Solution Approach 2:
The patent implements feedback mechanisms through tracking bits that continuously monitor program operation counts. The freshness counter in the sector provides feedback on overall sector usage, while endurance counters in each page provide feedback on individual page wear. This feedback enables the system to make informed decisions about page usability and refresh timing, preventing premature determination of unusability while maintaining high efficiency.
2Measurement precision
If tracking bits are implemented for each page to store freshness and endurance counters, then accurate tracking of page refresh needs is achieved, but device complexity increases
Solution Approach 1:
Tracking functionality is segmented into two distinct components: a sector-level freshness counter that tracks overall sector program operations, and page-level endurance counters that track individual page wear. This segmentation distributes the tracking complexity across multiple small structures rather than requiring a single complex system, achieving precise measurement while managing device complexity through modular organization.
Solution Approach 2:
The patent adds a temporal dimension to tracking by implementing counters that accumulate program operation counts over time. The freshness counter provides sector-level temporal tracking, while endurance counters provide page-level temporal tracking. This dimensional approach enables accurate measurement of program operation history without requiring complex real-time monitoring circuitry, as the counters passively accumulate data during normal operations.
3Reliability
If sector-level freshness counter and page-level endurance counters are used, then page usability is accurately determined, but more memory resources are consumed for tracking
Solution Approach 1:
Tracking resources are segmented into two hierarchical levels: a single freshness counter per sector that uses minimal space to track overall sector usage, and compact endurance counters per page that track individual page wear. This segmentation optimizes memory resource usage by using coarse-grained tracking at the sector level and fine-grained tracking only where necessary at the page level, achieving reliable program disturb management without excessive resource consumption.
Solution Approach 2:
The patent applies different tracking qualities to different memory locations based on their specific needs. The sector-level freshness counter provides uniform tracking across the entire sector, while page-level endurance counters provide localized tracking only for pages that require individual monitoring. This local quality approach ensures reliable program disturb management by concentrating tracking resources where they are most needed while minimizing overall resource consumption.
Data Source
AI summary
A program operation targeted to a first page in a sector of non-volatile memory is identified. The sector includes an array of memory cells comprising a set of pages including the first page, and each page in the set of pages includes a set of tracking bits reserved for storing values of a freshness counter. A processing device determines a second page in the set of pages has been exposed to a maximum number of program operations in the set of pages based on a value of the freshness counter stored in the set of tracking bits of the second page. The maximum number of program operations is determined to exceed a program disturb threshold for the sector. The second page in the sector of non-volatile memory is refreshed in response to determining that the maximum number of program operations exceeds the program disturb threshold for the sector.