3D Memory Channel Structure With Enlarged Joint CD

Solution Overview

Problem

The existing 3D memory devices face challenges with cost, reliability, and performance due to the shrinking cell size, which results in a narrow joint critical dimension (CD) that hinders the entry of chemicals into the lower channel holes during fabrication.

Innovation Solution

The method involves etching and oxidizing silicon nitride layers abutting the sidewall of channel holes to form native oxide layers, thereby enlarging the joint CD and allowing easier access for chemicals during subsequent processes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If cell size is shrunk to increase memory density, then memory density is improved, but joint critical dimension becomes narrow hindering chemical access

Engineering Contradiction:

Improvememory densityVSAvoidchemical access to lower channel holes

Core Design Contradiction:

Quantity of substanceVSEase of operation

Solution Approach 1:

The method performs preliminary etching and oxidation of silicon nitride layers before forming the complete memory structure. By etching the silicon nitride layers abutting the sidewall of channel holes and oxidizing them to form native oxide layers, the joint critical dimension is enlarged in advance, ensuring chemical access is not hindered in subsequent fabrication steps.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The invention changes the physical and chemical parameters of the silicon nitride layers by etching them and then oxidizing them to form native oxide layers. This parameter change (from silicon nitride to native oxide) results in an enlarged joint critical dimension, transforming the narrow opening into a sufficiently large aperture for chemical access while maintaining the shrunk cell size for high memory density.

Inventive Principle:

Principle #35Parameter changes

2Quantity of substance

If cell size is shrunk to increase memory density, then memory density is improved, but manufacturing precision becomes challenging

Engineering Contradiction:

Improvememory densityVSAvoidfabrication control

Core Design Contradiction:

Quantity of substanceVSManufacturing precision

Solution Approach 1:

The method performs preliminary etching and oxidation of silicon nitride layers before forming the complete memory structure. By etching the silicon nitride layers abutting the sidewall of channel holes and oxidizing them to form native oxide layers, the joint critical dimension is enlarged in advance, ensuring chemical access is not hindered in subsequent fabrication steps.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The invention changes the physical and chemical parameters of the silicon nitride layers by etching them and then oxidizing them to form native oxide layers. This parameter change (from silicon nitride to native oxide) results in an enlarged joint critical dimension, transforming the narrow opening into a sufficiently large aperture for chemical access while maintaining the shrunk cell size for high memory density.

Inventive Principle:

Principle #35Parameter changes

3Device complexity

If conventional fabrication process is used, then process simplicity is maintained, but under-etching and over-etching issues occur

Engineering Contradiction:

Improvefabrication processVSAvoidetching uniformity

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The method performs preliminary etching and oxidation of silicon nitride layers before forming the complete memory structure. By etching the silicon nitride layers abutting the sidewall of channel holes and oxidizing them to form native oxide layers, the joint critical dimension is enlarged in advance, ensuring chemical access is not hindered in subsequent fabrication steps.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The native oxide layer formed by oxidizing the etched silicon nitride layers acts as an intermediary structure. This intermediary layer provides a controlled interface that prevents both under-etching and over-etching issues by ensuring proper chemical access and reaction control during subsequent fabrication steps, thereby improving etching uniformity and reliability.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 enlarges the joint CD, preventing issues like under-etching and over-etching, and enhances the reliability and performance of 3D memory devices by ensuring proper chemical access and uniformity in the channel structure.

Implementation Method 1

etching and oxidizing silicon nitride layers abutting the sidewall of channel holes

Methodology Applied

Scientific EffectEtching:

Implementation Method 2

etching and oxidizing silicon nitride layers abutting the sidewall of channel holes to form native oxide layers

Methodology Applied

Scientific EffectOxidation: Oxidation

Data Source

PatentEP3963629B1Three-dimensional memory devices with enlarged joint critical dimension and methods for forming the same

Publication Date: 2025.03.05 YANGTZE MEMORY TECH CO LTD

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Figure 2A
Figure 2B

AI summary

A 3D memory device (200, 300) and a method for forming the device are provided. The 3D memory device (200, 300) with an enlarged joint critical dimension includes a substrate (202, 302), a memory stack (207, 307) having a plurality of interleaved conductor layers (209, 309) and dielectric layers (206, 306) on the substrate (202, 302), and a memory string extending vertically through the first memory stack and having a memory film (210, 310) along a sidewall of the memory string. The memory film (210, 310) includes a discontinuous blocking layer (212, 312) interposed by the dielectric layers (206, 306).