Memory Cell Corrective Reads for Data Retention Recovery
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Solution Overview
Problem
Memory devices experience RWB degradation due to cell-to-cell interference and intrinsic charge loss, leading to increased bit errors and error rates, which are exacerbated by corrective read operations that require a large number of reads, impacting performance and reliability.
Innovation Solution
Implement corrective reads with improved recovery by assigning target cells to bins using a pre-defined operation on the cell state information of adjacent cells, such as a linear combination of their threshold voltages, reducing the number of reads needed and minimizing read disturb effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If corrective read operations are performed to recover from data retention loss, then reliability is improved, but productivity deteriorates due to the large number of reads required
Solution Approach 1:
The patent segments the corrective read process by dividing target cells into different bins based on the states of their adjacent cells. This segmentation allows the system to apply different read strategies to different groups of cells, reducing the overall number of reads needed while maintaining reliability.
Solution Approach 2:
The patent applies partial action by performing reads only on necessary target cells based on adjacent cell states. Instead of reading all target cells uniformly, the system selectively reads only those cells that require correction, reducing the total number of reads while maintaining reliability.
2Reliability
If corrective read operations are performed to improve recovery from data retention loss, then reliability is improved, but loss of time increases due to the large number of reads
Solution Approach 1:
The patent performs preliminary action by determining the states of adjacent cells before performing corrective reads on target cells. This preliminary assessment allows the system to identify which target cells actually need correction, avoiding unnecessary reads and reducing time loss.
Solution Approach 2:
The system performs only the necessary reads based on adjacent cell states, avoiding excessive reads on cells that don't require correction. This partial action approach reduces the total time required for corrective read operations.
3Reliability
If a large number of reads are performed during corrective read operations, then reliability is improved through better recovery, but read disturb effects increase impacting performance
Solution Approach 1:
The patent applies partial action by performing reads only on target cells that actually need correction based on adjacent cell states. This reduces the total number of reads and consequently minimizes read disturb effects on other cells while maintaining reliability.
Solution Approach 2:
The patent converts the potential harm of read disturb effects into a benefit by using adjacent cell states to identify and correct only the necessary target cells. This selective approach ensures that read operations are performed only where needed, transforming what could be harmful excessive reads into beneficial targeted corrections.
Data Source
AI summary
A memory device can include a memory array and control logic, operatively coupled with the memory array, to perform operations including identifying a first base state information bin associated with a first index value and a second base state information bin associated with a second index value, determining a third index value based on the first index value and the second index value, assigning a target cell of the memory array to a target cell state information bin associated with the third index value, and causing the target cell, assigned to the target cell state information bin, to be read.