NAND Memory Read Scrub Using Neighbor-Page Reference Voltage
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Solution Overview
Problem
The charge stored in NAND-type memory cells changes over time and with repeated read operations and temperature variations, leading to increased read errors that exceed error correction capabilities, affecting data integrity and reliability.
Innovation Solution
A memory system and controller that perform a read scrub operation by obtaining and storing parameters for generating a target reference voltage based on a preset model, using a combination of parameters from a target physical page and its neighboring pages to improve read accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional read operations are performed without parameter adjustment, then operation speed is maintained, but read errors increase over time due to charge degradation
Solution Approach 1:
The patent pre-calculates and stores a retry table with optimized reference voltage parameters for different physical pages during manufacturing or initialization. This preliminary action allows the read scrub operation to directly query and apply pre-determined parameters without performing time-consuming real-time calculations, thus maintaining high read accuracy while minimizing operation time.
Solution Approach 2:
The patent dynamically adjusts the reference voltage parameters based on the specific physical page being read and its characteristics (such as charge retention properties). By making the read parameters adaptive rather than static, the system can quickly determine the optimal read voltage for each page, improving both reliability and efficiency of read scrub operations.
2Reliability
If a comprehensive retry table is built for all physical pages, then read error correction capability is improved, but memory controller resource consumption increases
Solution Approach 1:
Instead of maintaining complete and redundant retry tables for all physical pages, the patent uses a compact representation that stores essential parameter information in an optimized format. This copying approach allows the memory controller to generate the necessary retry information on-demand from a smaller set of stored parameters, reducing resource consumption while maintaining comprehensive error correction capability.
Solution Approach 2:
The patent extracts only the most critical parameters needed for read voltage adjustment and stores them in a condensed format. By taking out only the essential information from what would otherwise be a comprehensive retry table, the system reduces memory controller resource requirements while preserving the ability to correct read errors effectively.
3Reliability
If read scrub operations are performed frequently to maintain data integrity, then data reliability is improved, but system performance and productivity decrease
Solution Approach 1:
The patent performs preliminary setup of read parameters during initialization or manufacturing, creating a lookup structure that enables rapid parameter retrieval during read scrub operations. This preliminary action significantly reduces the time required for each read scrub operation, allowing frequent execution without substantial performance penalty.
Solution Approach 2:
The patent applies read parameter optimization selectively based on page characteristics and error patterns rather than uniformly to all pages. By focusing optimization efforts where most needed, the system maintains data integrity through effective read scrub operations while minimizing the overall impact on system performance and productivity.
Data Source
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AI summary
The examples of the present disclosure discloses a memory system and an operation method thereof, a memory controller and a storage medium, and the memory system comprises a memory device comprising a plurality of word lines, a plurality of storage units coupled to the same word line form at least one physical page; the memory controller is configured to: obtain a first parameter of a first physical page of the plurality of physical pages in a process of performing a read scrub operation, wherein the first parameter is a parameter in a preset model for generating a target reference voltage, and the target reference voltage is used as a read voltage of the physical page when the read operation is performed; the plurality of physical pages comprise a first physical page and a second physical page, the first physical page is a target physical page of the read scrub operation, and the second physical page is another physical page other than the first physical page; generate a first parameter of the second physical page according to the first parameter of the first physical page in combination with a location relationship of the second physical page and the first physical page; and store the first parameter of the first physical page and the first parameter of the second physical page.