NAND Flash Memory Inter-Cell Interference Control
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Solution Overview
Problem
NAND flash memory devices face significant inter-cell interference effects, particularly in multi-level storage methods with narrow threshold distributions, which affect data storage capacity and reliability.
Innovation Solution
A control circuit is used to apply a writing voltage to adjacent word lines before programming a memory cell, thereby setting the threshold voltage distribution of adjacent cells to reduce inter-cell interference and enhance data storage reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If multi-level storage method is used to increase data storage capacity, then data storage capacity is improved, but inter-cell interference effect becomes more serious
Solution Approach 1:
The patent applies preliminary action by writing data to the n-th word line before writing data to the (n-1)-th word line. This sequential approach ensures that adjacent memory cells have stable threshold voltage distributions before charge injection occurs, thereby reducing inter-cell interference effects while maintaining multi-level storage capacity.
2Reliability
If charge is injected into charge storage layer to store data, then data storage function is achieved, but threshold value of adjacent memory cell shifts
Solution Approach 1:
The patent implements preliminary action by pre-writing data to adjacent word lines before the actual charge injection process. This ensures that the threshold voltage distribution of adjacent memory cells is stabilized beforehand, preventing threshold value shifts during the charge injection process and maintaining manufacturing precision.
Solution Approach 2:
The patent applies preliminary anti-action by establishing stable threshold voltage distributions in adjacent memory cells before charge injection. This preemptive stabilization counteracts the potential harmful effects of inter-cell interference during the writing process, thereby protecting against threshold value shifts.
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
This approach effectively reduces inter-cell interference, improves data storage capacity, and enhances the reliability of NAND flash memory devices by stabilizing the threshold voltage distribution, even in multi-level storage methods.
Implementation Method 1
When charge is injected into a charge storage layer of a memory cell in a NAND flash memory, the potential of a charge storage layer of an adjacent memory cell that was written before this memory cell may be changed (inter-cell interference effect)
Data Source
AI summary
According to one embodiment, a nonvolatile semiconductor memory device includes memory cells storing data in a nonvolatile manner, word lines connected to the memory cells and including a first word line and a second word line which is n-th (n is an integer of 1 or more) from the first word line, and a control circuit configured to control a voltage of a word line to write data to a memory cell so that data are written in order from the first word line to the second word line. In a write sequence of the first word line, the control circuit applies a writing voltage to the second word line before writing a memory cell connected to the first word line.