NAND Memory Page Migration for Read Reclaim Delay Reduction
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Solution Overview
Problem
As the number of read operations in memory devices increases or time elapses, data stored in NAND memory can degrade, leading to delayed operations due to read reclaim operations.
Innovation Solution
A memory system that performs a data migration operation on specific pages based on the degradation type of threshold voltage distributions, using a memory controller to determine target pages for migration based on the operating state and degradation type of memory blocks, and includes an error correction circuit to manage threshold voltage degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a read reclaim operation is performed to prevent data degradation, then data reliability is improved, but operation delay increases
Solution Approach 1:
The patent segments the read memory block into multiple pages and selectively migrates only the target pages that require data migration, rather than migrating all pages. This segmentation approach reduces the overall migration time and minimizes operation delay while still addressing the degradation issues in specific pages.
Solution Approach 2:
The patent applies local quality by determining the degradation type of each page and selectively migrating only the pages that have threshold voltage distribution degradation. This allows the system to focus migration resources on affected areas rather than uniformly processing the entire block, thereby reducing overall operation time.
2Reliability
If data migration operation is performed on all pages in a read memory block, then data reliability is improved, but migration cost and time increase
Solution Approach 1:
The patent applies partial action by migrating only the necessary target pages that have degradation issues rather than migrating all pages in the read memory block. This partial migration approach maintains data reliability for affected pages while significantly reducing the overall migration cost and time.
Solution Approach 2:
The patent changes the parameter of migration scope from all pages to selected pages based on degradation type. By determining the degradation type (read disturb type or retention type) and selecting pages accordingly, the system optimizes the migration process to achieve reliability improvement with minimal time cost.
Data Source
AI summary
Provided herein may be a memory system, a memory controller, and a method of operating the memory system. The memory system may include a memory device including a plurality of blocks, and a memory controller configured to determine a page type in which a data migration operation is to be performed based on an operating state of the memory device and a degradation type of a first block that is read among the plurality of blocks, and control the memory device to perform the data migration operation of migrating data of target pages to pages in a second block, the target pages determined based on the page type among multiple pages included in the first block.