U-Shaped Semiconductor Layer Void Management in 3D NAND

Solution Overview

Problem

Voids formed in the columnar semiconductor layer of 3-dimensional semiconductor storage devices can disrupt the functionality of memory transistors by contacting the gate insulating film, reducing carrier mobility and affecting the performance of memory strings.

Innovation Solution

A nonvolatile semiconductor storage device design that incorporates a U-shaped semiconductor layer with a first semiconductor layer and a second semiconductor layer, where the second layer is doped with carbon, oxygen, or nitrogen to fill voids and maintain carrier mobility while restraining void movement, ensuring the desired characteristics of memory transistors are maintained.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the columnar semiconductor layer is formed to increase carrier mobility, then the memory transistor functions improve, but voids are formed inside the layer which can move and contact the gate insulating film, reducing reliability

Engineering Contradiction:

Improvememory transistor functionalityVSAvoidvoid movement contacting gate insulating film

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent converts the harmful effect of voids into a beneficial structure by intentionally forming a hollow columnar semiconductor layer with controlled voids. The key insight is that while voids naturally form during fabrication, instead of trying to eliminate them completely, the invention embraces their presence and designs the structure to accommodate them. The hollow columnar layer with voids is deliberately created, and the structure is engineered so that these voids do not compromise device functionality, thus converting a manufacturing defect into an acceptable design feature.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent applies local quality by creating different structural characteristics in different regions of the columnar semiconductor layer. The outer region maintains sufficient semiconductor material to ensure carrier mobility and transistor functionality, while the inner region allows for void formation. This spatial differentiation of structural properties enables the layer to simultaneously achieve good electrical characteristics and accommodate voids without compromising overall device reliability.

Inventive Principle:

Principle #3Local quality

2Object-affected harmful factors

If the columnar semiconductor layer is made denser to prevent void formation, then reliability improves, but carrier mobility decreases, affecting memory transistor performance

Engineering Contradiction:

Improvevoid formationVSAvoidcarrier mobility

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The patent applies local quality by creating different structural characteristics in different regions of the columnar semiconductor layer. The outer region maintains sufficient semiconductor material to ensure carrier mobility and transistor functionality, while the inner region allows for void formation. This spatial differentiation of structural properties enables the layer to simultaneously achieve good electrical characteristics and accommodate voids without compromising overall device reliability.

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 solution effectively increases carrier mobility and minimizes void movement, allowing the device to operate as a NAND-type flash memory despite the presence of voids, ensuring reliable data storage and retrieval.

Implementation Method 1

a second semiconductor layer surrounding a hollow columnar portion via the memory gate insulating film 34. The second semiconductor layer is doped with carbon, oxygen, or nitrogen

Methodology Applied

Scientific EffectDoping: Dopants

Data Source

PatentUS9171948B2Nonvolatile semiconductor storage device and fabrication method thereof

Publication Date: 2015.10.27 KIOXIA CORP

AI summary

A nonvolatile semiconductor storage device has a plurality of memory strings in which electrically rewritable memory cells are connected in series. The memory strings have word-line electroconductive layers laminated at a prescribed interval to sandwich an interlayer insulating film onto a semiconductor substrate and through holes that penetrate through the word-line electroconductive layers and the interlayer insulating films. The gate insulating film is formed along an inner wall of the through holes and includes a charge-accumulating film. The columnar semiconductor layer is formed inside the through holes to sandwich the gate insulating film along with the word-line electroconductive layer. The columnar semiconductor layer contains carbon, oxygen, or nitrogen.