NAND Flash Memory Redundant Data Storage for Defect Tolerance
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Solution Overview
Problem
Three-dimensional NAND flash memory systems face reliability issues due to opening defects in memory holes, which can lead to incorrect data reading and writing, especially during power-on operations, as these defects can cause cell currents to be misinterpreted, affecting the accuracy of data storage and retrieval.
Innovation Solution
The system implements a redundancy mechanism by storing ROM fuse information in multiple pages or blocks, allowing correct data reading even if an opening defect occurs in one string unit, and executes multiple sense and strobe operations to reduce current consumption and enhance reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If data is stored in a single page in three-dimensional NAND flash memory, then storage capacity is maximized, but reliability deteriorates due to opening defects in memory holes causing incorrect data reading
Solution Approach 1:
The patent stores identical data in multiple different pages within the same block. When reading, the system reads from multiple pages and uses majority voting to determine the correct data value. This copying approach resolves the contradiction by improving reliability through redundancy while maintaining the same physical storage capacity, as the redundant copies are created within the existing memory structure rather than requiring additional hardware components.
Solution Approach 2:
The patent proactively stores redundant copies of data before any defects occur, preparing compensation measures in advance. During normal operation, the system maintains multiple valid copies of critical data in different pages. When an opening defect is detected in a memory hole, the system can immediately retrieve the correct data from the redundant copies without data loss. This beforehand cushioning resolves the contradiction by establishing reliability safeguards prior to defect occurrence, avoiding the need for complex real-time error correction mechanisms.
2Reliability
If multiple sense and strobe operations are executed to read data from multiple pages, then reliability is improved through error detection and correction, but current consumption increases
Solution Approach 1:
The patent executes sense and strobe operations on multiple pages, but not all pages need to be fully processed. The system performs partial reading operations where it senses data from multiple pages and applies strobe signals selectively based on preliminary detection results. This partial action approach resolves the contradiction by obtaining sufficient redundancy information to ensure reliability without exhaustively processing every possible page, thereby reducing overall current consumption compared to complete multi-page verification.
Solution Approach 2:
The patent implements periodic sense and strobe operations rather than continuous operation. The system performs sensing in periodic cycles, where each cycle reads from multiple pages and determines whether correction is needed. The strobe operations are applied periodically to refresh and verify data integrity at intervals rather than continuously. This periodic action resolves the contradiction by maintaining reliability through regular verification while allowing the system to enter lower-power states between operations, significantly reducing average current consumption.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach improves the operational reliability of NAND flash memory by ensuring accurate data reading and writing, even in the presence of defects, and reduces current consumption during power-on operations by strategically managing bit line currents.
Implementation Method 1
a memory cell array that is capable of storing data in a nonvolatile manner
Implementation Method 2
executes a reading operation on the plurality of pages that store the data redundantly to read the data
Data Source
AI summary
A semiconductor memory device includes a memory cell array that is capable of storing data in a nonvolatile manner, and a control section that controls data access to the memory cell array. The memory cell array stores the same data redundantly in a plurality of pages. The control section executes a reading operation on the plurality of pages that store the same data redundantly to read the data. The data that is stored redundantly may be management data or user data.