Nonvolatile Memory Bad Block Management Reliability
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Solution Overview
Problem
Nonvolatile semiconductor memory devices face reliability issues due to defects in control information, particularly in three-dimensionally stacked memory cells, which can lead to decreased reliability of flash memory devices and increased defect rates, affecting the yield and accuracy of data storage.
Innovation Solution
A nonvolatile memory device with a memory cell array divided into areas for memory management information and user data, utilizing a decoder, page buffer, and control logic to iteratively program and manage memory management information across different column locations, and employing a majority decision algorithm to recover and rearrange data, ensuring high reliability and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If memory management information is stored in a specific area of three-dimensionally stacked memory cells, then storage density is improved, but reliability deteriorates due to column direction defects
Solution Approach 1:
The memory cell array is divided into multiple areas (first area for memory management information, second area for user data) with different storage patterns. The first area stores management information iteratively at different column locations across multiple pages, while the second area uses conventional storage. This segmentation allows the management information to be distributed across multiple physical locations, so that defects in one column direction do not compromise the entire management information.
Solution Approach 2:
The patent transitions from conventional single-location storage to multi-dimensional storage by iterating the writing of memory management information across different pages and column locations. This creates a distributed storage pattern where the same management information is stored at multiple positions in the memory array, effectively adding a dimensional aspect to the storage structure to compensate for column direction defects.
2Speed
If memory management information is stored at fixed column locations, then access speed is improved, but reliability deteriorates due to column direction defects
Solution Approach 1:
The system performs preliminary actions by iteratively writing memory management information at different column locations before actual read operations. This pre-distribution of information across multiple locations ensures that when defects occur in column direction, the information has already been replicated elsewhere, enabling reliable recovery without requiring complex real-time correction.
Solution Approach 2:
The patent implements copying by repeatedly storing the same memory management information at different column locations across multiple pages. Instead of storing information once at a fixed location, the system creates multiple copies at distributed locations, so that if one copy is corrupted by column direction defects, other copies remain intact and can be used for recovery.
3Device complexity
If conventional storage method is used for memory management information, then device complexity is reduced, but defect rate increases
Solution Approach 1:
The memory cell array is segmented into multiple areas with different storage strategies. The first area uses iterative storage at different column locations for management information, while the second area uses conventional fixed-location storage for user data. This segmentation allows the system to apply enhanced reliability techniques only where needed (for management information) while maintaining simplicity for user data storage.
Solution Approach 2:
The patent applies local quality by implementing different storage patterns in different areas of the memory array. The first area (for management information) uses distributed iterative storage to achieve high reliability, while the second area (for user data) uses conventional storage for simplicity. This localized differentiation ensures that enhanced reliability features are applied only where defects would have the most critical impact.
Data Source
AI summary
A nonvolatile memory device is provided. The nonvolatile memory device includes a memory cell array comprising a first area that stores memory management information and a second area that stores user data, a decoder configured to select at least one of rows of the first area or the second area based on an address, a page buffer configured to store data in memory cells connected to the selected at least one row or to detect data stored in the memory cells, and control logic configured to control the decoder and the page buffer in response to a specific command, to access the first area. The memory management information is iteratively programmed by a specific memory unit and is written at different columns of specific memory units.