Flash Memory Read Adjustment via Adjacent Cell Feedback
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Solution Overview
Problem
Flash memory devices experience reduced reliability in read operations due to floating gate to floating gate (FG-FG) interference, which causes shifts in threshold voltage values, affecting the accuracy of information retrieval.
Innovation Solution
The solution involves reading adjacent cells to obtain feedback information on shift threshold voltage values, which are then used to adjust the read operation of target cells, thereby reducing the impact of FG-FG interference and improving data reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If read operation is performed on target cell, then data retrieval is enabled, but threshold voltage shifts due to FG-FG interference reduce reliability
Solution Approach 1:
The patent implements a feedback mechanism where the read operation on the target cell is adjusted based on the threshold voltage value obtained from the adjacent cell. The controller reads the adjacent cell first, obtains its threshold voltage value, and uses this information to determine the appropriate read voltage for the target cell. This feedback loop compensates for FG-FG interference effects, thereby maintaining measurement precision while enabling reliable data retrieval.
Solution Approach 2:
The patent performs a preliminary read operation on the adjacent cell before reading the target cell. By obtaining the threshold voltage value of the adjacent cell in advance, the system can pre-calculate the appropriate read voltage for the target cell, accounting for potential FG-FG interference. This preliminary action enables the system to compensate for interference effects before the actual target cell read operation occurs.
2Reliability
If adjacent cells are read to obtain feedback information, then reliability of target cell read is improved, but operation time increases
Solution Approach 1:
The patent applies partial action by reading only the necessary adjacent cells (typically one or two neighboring cells) rather than all cells in the memory array. This selective approach provides sufficient feedback information to compensate for FG-FG interference on the target cell while minimizing the additional time required. The system performs exactly the minimum necessary read operations on adjacent cells to achieve reliable target cell read.
3Quantity of substance
If FG-FG interference is present, then cell density can be increased, but threshold voltage shifts reduce information accuracy
Solution Approach 1:
The feedback mechanism reads adjacent cells to determine their threshold voltage values, which indicate the presence and magnitude of FG-FG interference. This information is used to adjust the read voltage for the target cell, compensating for interference effects and maintaining measurement precision even in high-density configurations where FG-FG interference is more pronounced.
Data Source
AI summary
Various embodiments include methods, apparatus, and systems for reading an adjacent cell of a memory array in an electronic device to determine a threshold voltage value of the adjacent cell, the adjacent cell being adjacent a target cell, and reading the target cell of the memory array using a wordline voltage value based on the threshold voltage value of the adjacent cell. Additional apparatus, systems, and methods are described.