Non-Volatile Memory Read Voltage Adjustment for Coupling Error Reduction
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Solution Overview
Problem
Non-volatile multi-level memory devices face read errors due to coupling effects between adjacent memory cells, particularly affecting erased cells, which are more susceptible to word-line coupling, leading to increased error probabilities during data retrieval.
Innovation Solution
A method is introduced where read voltages are dynamically adjusted based on the state of adjacent memory cells to distinguish between different programmed states, using a greater number of read voltages to differentiate between erased and first programmed states and fewer to differentiate between second and third programmed states, thereby reducing read errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the number of bits stored in a memory cell is increased to improve data storage density, then storage capacity per unit area is improved, but coupling effects between adjacent cells increase causing read errors
Solution Approach 1:
The patent applies local quality by differentiating read operations based on the specific state of adjacent memory cells. When an erased cell is detected in an adjacent cell, a first read voltage is applied; when programmed cells are detected, a second read voltage is applied. This localized adaptation of read parameters to specific cell states reduces coupling-induced read errors while maintaining high storage density
Solution Approach 2:
The patent changes the read voltage parameter dynamically based on the operational context. The system switches between different read voltages (first read voltage for erased cell detection, second read voltage for programmed cell detection) to optimize the distinction between states and minimize coupling effects, thereby improving reliability without sacrificing storage capacity
2Ease of operation
If a single read voltage is used to distinguish between all memory cell states, then the read operation is simple, but read errors increase due to coupling effects between adjacent cells
Solution Approach 1:
The patent introduces dynamics into the read operation by making the read voltage selectable based on the detected state of adjacent cells. The system transitions from a static single-voltage approach to a dynamic multi-voltage approach, choosing between first and second read voltages depending on whether erased or programmed cells are detected in adjacent positions, thereby improving read accuracy without significantly complicating the operation
3Reliability
If multiple read voltages are used to distinguish between different memory cell states, then read accuracy is improved, but the complexity of the read operation increases
Solution Approach 1:
The patent applies preliminary action by first detecting the state of adjacent memory cells before performing the read operation on the target cell. This preliminary detection of adjacent cell states enables the system to pre-determine which read voltage should be used, thereby improving read accuracy through appropriate voltage selection without requiring complex real-time adjustments during the read operation itself
Data Source
AI summary
A non-volatile memory device, a data read method thereof and a recording medium are provided. The method includes receiving a data read command for a first word line in a memory cell array, reading data from a second word line adjacent to the first word line, and reading data from the first word line using a different voltage according to a state of the data read from the second word line. The number of read voltages used to distinguish an erased state and a first programmed state is greater than the number of read voltages used to distinguish a second programmed state and a third programmed state.