3D NAND Flash Memory Programming Disturb Mitigation
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Solution Overview
Problem
In 3D NAND flash memory devices, programming disturb occurs due to residual electrons trapped in dummy memory cells at the junction of stacked decks, affecting the programming of adjacent memory cells, as the bit line pre-charge becomes ineffective and threshold voltage shifts, leading to channel potential reduction.
Innovation Solution
Applying a negative pre-pulse signal to dummy word lines during the pre-charge period to repel electrons and enhance channel potential, thereby reducing programming disturb by using a control method that includes a bit line pre-pulse, selected and unselected word line signals, and a negative pre-pulse signal applied to dummy word lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bit line pre-charge is applied to dummy memory cells during programming, then initial state is maintained, but threshold voltage becomes low and residual electrons are trapped causing programming disturb
Solution Approach 1:
A negative pre-pulse signal is applied to the dummy memory cells before the actual programming operation to create a potential barrier that prevents residual electrons from being trapped. This preliminary counter-action occurs during the pre-charge period and establishes conditions that oppose the harmful electron trapping effect that would otherwise occur during subsequent programming operations.
Solution Approach 2:
The voltage parameter of the dummy word line is dynamically changed by applying a negative pre-pulse signal during the pre-charge period. This parameter change transforms the dummy memory cell threshold voltage to a higher state, preventing the low threshold voltage condition that causes residual electron trapping and programming disturb.
2Stability of the object's composition
If dummy memory cells are arranged in initial state, then threshold voltage shift is avoided, but channel boost potential is reduced affecting adjacent memory cell programming
Solution Approach 1:
The voltage parameter of dummy memory cells is dynamically adjusted by applying a negative pre-pulse signal during the pre-charge period. This creates a temporary parameter change that maintains threshold voltage stability while simultaneously providing the necessary channel boost potential for adjacent memory cell programming through the stacked deck structure.
Solution Approach 2:
The negative pre-pulse signal is applied in advance during the pre-charge period to prepare the dummy memory cells for the upcoming programming operation. This preliminary action establishes the appropriate electrical conditions that enable both threshold voltage stability and sufficient channel boost potential for reliable programming of adjacent memory cells.
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
The negative pre-pulse signal effectively reduces charge trap effects and increases channel potential, minimizing programming disturb and improving data storage reliability in 3D NAND flash memory devices.
Implementation Method 1
Applying a negative pre-pulse signal to dummy word lines during the pre-charge period to repel electrons and enhance channel potential
Data Source
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AI summary
A non-volatile memory device is disclosed. The non-volatile memory device includes a memory array, a plurality of word lines, a plurality of dummy word lines, a first control circuit and a second control circuit. The plurality of word lines are connected to a plurality of top memory cells and bottom memory cells of a memory string of the memory array. The plurality of dummy word lines are connected to a plurality of dummy memory cells connected between the plurality of top memory cells and bottom memory cells. The first control circuit is configured to apply a bit line pre-pulse signal to the bit line during a pre-charge period. The second control circuit is configured to apply a selected word line signal to a selected word line, apply an unselected word line signal to unselected word lines and apply a negative pre-pulse signal to the plurality of dummy word lines.