Nonvolatile Memory Flag Cell MSB Detection Reliability
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Solution Overview
Problem
Nonvolatile memory devices face reliability issues due to defective or erroneous flag cells, which can lead to read errors and impair the detection of whether memory cells have been programmed with Most Significant Bit (MSB) data, affecting the overall reliability of the device.
Innovation Solution
A nonvolatile memory device with a memory cell array and flag cells arranged in rows and columns, including a page buffer to read flag data and a judgment unit that judges MSB programming based on flag data, and optionally using redundant cell regions to replace abnormal flag cell strings, ensuring accurate MSB detection and improving reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If flag cells are used to store MSB program state, then MSB programming detection capability is improved, but device reliability deteriorates due to defective or erroneous flag cells
Solution Approach 1:
The patent applies local quality by differentiating between normal flag cells and defective flag cells through separate read paths. The judgment unit analyzes flag data to identify defective cells and excludes them from the final MSB state determination, allowing the system to maintain high detection accuracy while compensating for local defects in individual flag cells.
Solution Approach 2:
The patent implements feedback through the judgment unit that continuously monitors flag cell data and dynamically adjusts the MSB programming detection process. When defective flag cells are detected, the system feeds back this information to modify the read operation, selecting only reliable flag data for final determination, thus maintaining reliability despite the presence of defective cells.
2Reliability
If multiple flag cells are used to store flag data, then reliability can be improved through redundancy, but device complexity increases
Solution Approach 1:
The patent segments the flag cell array into multiple independently addressable flag cells organized in rows and columns. This segmentation allows the judgment unit to selectively read from specific flag cells based on their reliability, enabling redundancy without requiring a completely restructured system architecture.
Solution Approach 2:
The patent changes the operational parameters by implementing dynamic selection of flag cells based on their detected quality. The judgment unit modifies which flag cells are read and how their data is weighted, allowing the system to adapt to varying conditions and maintain reliability without fixed complex redundancy structures.
3Quantity of substance
If flag cells are arranged in a dense array, then storage capacity is improved, but difficulty of detecting and measuring defective cells increases
Solution Approach 1:
The patent applies preliminary action by performing a preliminary read operation to assess the quality of flag cells before using them for definitive MSB programming detection. This preliminary assessment allows the judgment unit to identify defective cells in advance, making the subsequent detection process more efficient despite the dense array configuration.
Solution Approach 2:
The patent implements partial action by reading only the necessary subset of flag cells required for reliable MSB detection rather than reading all flag cells in the dense array. The judgment unit determines the minimum set of reliable flag cells needed, reducing the measurement burden while maintaining detection accuracy in the dense configuration.
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
The solution enhances the reliability of flag data storage by disregarding or replacing defective flag cell data, allowing for accurate MSB programming detection and improving the overall reading performance of the memory device.
Implementation Method 1
a page buffer configured to read one or more flag data bits from one or more flag cells in a selected row among the rows via the one or more second columns
Implementation Method 2
a judgment unit configured to judge whether memory cells in the selected row are programmed with MSB data based on the one or more flag data bits read by the page buffer
Data Source
AI summary
A nonvolatile memory device comprises a memory cell array comprising memory cells arranged in rows and first columns and flag cells arranged in the rows and second columns. The device further comprises a page buffer configured to read flag data bits from flag cells in a selected row via the second columns, and a judgment unit configured to judge whether memory cells in the selected row are programmed with MSB data based on the flag data bits read by the page buffer.