3D NAND Touchup Programming for Read Window Margin

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Solution Overview

Problem

The challenge in 3D NAND flash memory devices is the reduction in the gap width between threshold voltage distributions due to thermal noise, random telegraph signaling, and disturbances from adjacent cells, leading to susceptibility to charge loss and incorrect verification, which affects the read window budget and reliability.

Innovation Solution

A touchup programming process is implemented, where a selected portion of programmed cells undergo additional programming steps to increase the threshold voltage, particularly focusing on critical word lines prone to charge loss, and a staggered voltage reduction method is used to enhance electron evacuation during verification, ensuring a sufficient read window budget.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If memory cells are stacked vertically in multiple layers to increase density, then storage capacity is improved, but thermal noise and disturbances from adjacent cells increase, reducing the gap width between threshold voltage distributions

Engineering Contradiction:

Improvestorage capacityVSAvoidgap width between threshold voltage distributions

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent segments the programming process into multiple stages: initial programming to achieve target threshold voltages, followed by touchup programming specifically for critical word lines. This segmentation allows selective enhancement of vulnerable cells without re-programming the entire array, thereby maintaining the benefits of high-density stacking while mitigating thermal noise effects on critical cells.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies local quality by identifying and treating only critical word lines that are prone to charge loss through touchup programming. Instead of uniformly treating all cells, the system selectively applies additional programming pulses to specific word lines where the gap width is insufficient, thereby locally enhancing reliability without increasing overall power consumption or programming time for the entire array.

Inventive Principle:

Principle #3Local quality

2Reliability

If touchup programming is applied to critical word lines to increase threshold voltage and improve gap width, then reliability is improved, but additional programming time and power consumption are required

Engineering Contradiction:

Improvegap width between threshold voltage distributionsVSAvoidprogramming time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent implements partial action by applying touchup programming only to critical word lines that require additional margin, rather than re-programming the entire memory array. This selective approach achieves the necessary reliability improvement for vulnerable cells while minimizing the additional time required, as only a subset of word lines undergo the touchup process.

Inventive Principle:

Principle #16Partial or excessive action

3Reliability

If higher programming voltages are applied to increase threshold voltage for critical word lines, then the read window budget is improved, but disturbance to adjacent cells increases

Engineering Contradiction:

Improveread window budgetVSAvoiddisturbance to adjacent cells

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent applies local quality by selectively applying touchup programming voltages only to critical word lines that require enhanced margin. Non-critical word lines are left untouched, avoiding unnecessary disturbance to adjacent cells. This localized approach ensures that higher voltages are applied only where needed to improve the read window budget, minimizing collateral effects on neighboring cells.

Inventive Principle:

Principle #3Local quality

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 touchup programming process enhances the read window budget by improving the gap width between threshold voltage distributions, thereby increasing the reliability and accuracy of data storage in 3D NAND flash memory devices.

Implementation Method 1

a selected portion of programmed cells undergo additional programming steps to increase the threshold voltage

Methodology Applied

Scientific EffectThreshold voltage modulation:

Implementation Method 2

a staggered voltage reduction method is used to enhance electron evacuation during verification

Methodology Applied

Scientific EffectElectron evacuation:

Data Source

PatentUS12542187B2Apparatus and method to improve read window budget in a three dimensional NAND memory

Publication Date: 2026.02.03 INTEL NDTM US LLC

AI summary

The gap width in a threshold voltage (Vt) distribution for a 3D NAND Flash cell is improved by performing touchup program on a selected portion of the word lines in a block after all of the word lines in the block have been programmed.