Unstable Erased Memory Cell Detection in Nonvolatile Memory
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Solution Overview
Problem
Existing semiconductor memory systems face issues with write operation failures and data reliability due to unstable erased memory cells, which affect the utilization efficiency of memory regions.
Innovation Solution
A method and system that determine unstable erased memory cells based on read and write data, comparing threshold voltages and data patterns, and prohibit their use when they exceed a threshold number to prevent write operation failures, ensuring data reliability and efficient memory utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If erased memory cells are used for write operations, then memory utilization efficiency is improved, but write operation failures increase due to unstable memory cells
Solution Approach 1:
The patent applies preliminary action by performing a read operation on erased memory cells before write operations to identify unstable cells. The controller reads data from erased memory cells, determines if they are unstable based on threshold voltage comparisons, and prohibits writing to these cells in advance, preventing write failures before they occur.
Solution Approach 2:
The patent implements feedback by using read data from erased memory cells to determine their stability status. The controller reads data from memory cells, compares threshold voltages, and uses this feedback information to decide whether to allow or prohibit subsequent write operations to specific cells, dynamically adjusting write permissions based on cell stability.
2Reliability
If unstable erased memory cells are identified and managed, then data reliability is improved, but device complexity increases due to additional determination steps
Solution Approach 1:
The patent applies parameter changes by monitoring threshold voltage parameters of erased memory cells to determine their stability. The controller reads threshold voltage values from memory cells and compares them against reference values, using these parameter changes to identify unstable cells and prevent write operations to them, ensuring data reliability through parameter-based detection.
Data Source
AI summary
A method for operating a memory system includes determining at least one erased memory cell among a plurality of erased memory cells as an unstable memory cell based on read data read from the at least one erased memory cell; determining the unstable memory cell as an unwritable memory cell based on write data to be written in the unstable memory cell; and prohibiting the plurality of erased memory cells from being used, depending on the number of erased memory cells as the unwritable memory cell among the plurality of erased memory cells.