Dynamic 1-Tier Scanning for Representative 3D NAND Verification

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Solution Overview

Problem

The existing 1-tier scan method for 3D NAND flash memory is ineffective when the selected tier is not representative of the overall cell population, leading to under/over programming due to variations in cell programming speeds, resulting in data errors.

Innovation Solution

A dynamic 1-tier scan method that involves multiple program loops, where each loop counts memory cells from different sub-groups within the word line, adjusting programming pulses based on the verification status of these sub-groups until the numeric threshold is met across all sub-groups.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If a 1-tier scan method is used to reduce verification time, then productivity is improved, but measurement precision deteriorates because the selected tier may not be representative of the overall cell population

Engineering Contradiction:

Improveverification timeVSAvoidverification accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The patent implements a dynamic 1-tier scan method that adaptively selects which tier to scan based on real-time programming status. Instead of statically selecting a fixed tier, the system dynamically determines the most representative tier for verification, allowing the verification target to change adaptively throughout the programming process. This resolves the contradiction by making the verification system both fast (1-tier) and accurate (representative sampling).

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the parameter of tier selection from a fixed value to a dynamically determined value based on programming progress. By monitoring programming status and adjusting which tier is selected for verification, the system maintains measurement precision while preserving the speed benefits of 1-tier scanning.

Inventive Principle:

Principle #35Parameter changes

2Ease of operation

If programming pulses are applied uniformly to all cells, then ease of operation is improved, but manufacturing precision deteriorates due to variations in cell programming speeds

Engineering Contradiction:

Improveprogramming operation simplicityVSAvoidprogramming accuracy

Core Design Contradiction:

Ease of operationVSManufacturing precision

Solution Approach 1:

The patent applies local quality by differentiating the programming process for different tiers based on their specific characteristics. Instead of treating all cells uniformly, the system identifies tiers with varying programming speeds and applies appropriate verification thresholds and pulse adjustments to each tier, ensuring accurate programming for fast and slow cells alike while maintaining operational simplicity.

Inventive Principle:

Principle #3Local quality

3Reliability

If multiple program loops are executed to ensure all cells reach verify level, then reliability is improved, but loss of time increases

Engineering Contradiction:

Improveprogramming reliabilityVSAvoidprogramming time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent reduces unnecessary program loops by dynamically determining when verification can be performed. Instead of executing a fixed number of loops for all cells, the system adapts the verification process to actual programming progress, performing verification only when representative tiers have reached appropriate states. This eliminates redundant loops while maintaining reliability.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent uses partial verification action by scanning only one representative tier at a time rather than all tiers. This partial scanning approach reduces the total verification time and number of required program loops while still ensuring reliable programming through strategic selection of representative samples.

Inventive Principle:

Principle #16Partial or excessive action

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 ensures accurate verification by accounting for variations in cell programming speeds, reducing the likelihood of under/over programming and improving programming efficiency.

Implementation Method 1

The programming circuit applying one or more programming pulses to the word line... the programming circuit increases a voltage of the programming pulses

Methodology Applied

Scientific EffectThreshold voltage change:

Implementation Method 2

the determination/counting circuit counting a number of first memory cells that have achieved a verify level... determining, based on the number of the first memory cells that have achieved the verify level

Methodology Applied

Scientific EffectThreshold voltage detection:

Data Source

PatentUS12380954B2Dynamic 1-tier scan for high performance 3D NAND

Publication Date: 2025.08.05 SANDISK TECHNOLOGIES LLC

AI summary

A method and system for executing a dynamic 1-tier scan on a memory array are provided. The memory array includes a plurality of memory cells organized into a plurality of sub-groups. The dynamic 1-tier scan includes executing an program loop in which cells of a first sub-group are counted to determine whether a numeric threshold is met, and, if the numeric threshold is met with respect to the first sub group, at least one additional program loop is executed in which cells of a second sub-group are counted to determine whether the numeric threshold is met with respect to the second sub-group.