Auxiliary Support Pillars for 3D Memory Backside Trenches

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Solution Overview

Problem

Current three-dimensional memory devices face challenges in efficiently forming support pillar structures that effectively contact backside trench fill structures, leading to issues with electrode filling and electrical connectivity due to silica precipitates and pattern collapse in the contact region.

Innovation Solution

The formation of alternating stacks of insulating and sacrificial material layers, followed by an anisotropic etch process to create memory openings and support pillar structures, with auxiliary support pillars extending through the first alternating stack to reduce sacrificial material volume and mitigate precipitate formation, allowing for complete electrode filling and improved structural integrity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional support pillar structures are formed in contact regions, then structural support is provided, but silica precipitates and pattern collapse occur leading to poor electrode filling and electrical connectivity

Engineering Contradiction:

Improveelectrical connectivityVSAvoidsilica precipitates and pattern collapse

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The support pillar structure is segmented into two distinct types: first support pillars extending through the entire alternating stack, and second support pillars extending only through the first alternating stack. This segmentation allows different regions of the contact region to be supported differently, preventing pattern collapse while enabling complete electrode filling without silica precipitates

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different support pillar configurations are applied to different locations within the contact region. The first support pillars provide full-height support in regions requiring maximum structural stability, while the second support pillars provide localized support sufficient for electrode filling. This local differentiation resolves the contradiction between needing structural support and avoiding harmful precipitates and collapse

Inventive Principle:

Principle #3Local quality

2Object-generated harmful factors

If sacrificial material volume is reduced, then precipitate formation is mitigated, but structural support during fabrication may be compromised

Engineering Contradiction:

Improveprecipitate formationVSAvoidstructural support

Core Design Contradiction:

Object-generated harmful factorsVSStrength

Solution Approach 1:

The sacrificial material removal is segmented into two stages corresponding to the two support pillar types. First support pillars retain sufficient sacrificial material for structural support, while second support pillars have reduced sacrificial material volume to minimize precipitate formation. This segmented approach simultaneously achieves both goals of reducing precipitates and maintaining structural support

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The volume of sacrificial material is changed differently for different support pillars. Second support pillars have their sacrificial material volume reduced to mitigate precipitate formation, while first support pillars maintain adequate sacrificial material for structural support during fabrication. This parameter differentiation resolves the contradiction between reducing precipitates and maintaining strength

Inventive Principle:

Principle #35Parameter changes

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 enhances the filling of backside recesses with conductive layers, reduces electrode open circuits and short circuits, and prevents pattern collapse, resulting in improved electrical connectivity and device reliability.

Implementation Method 1

forming backside trenches through the alternating stack by performing an anisotropic etch process, wherein the anisotropic etch process etches peripheral portions of a first subset of the array of support pillar structures

Methodology Applied

Scientific EffectAnisotropic etching:

Data Source

PatentUS11637118B2Three-dimensional memory device containing auxiliary support pillar structures and method of making the same

Publication Date: 2023.04.25 SANDISK TECHNOLOGIES LLC

AI summary

A alternating stack of insulating layers and sacrificial material layers is formed over a substrate. An array of memory opening fill structures and an array of support pillar structures are formed through the alternating stack. Backside trenches are formed through the alternating stack by performing an anisotropic etch process. The anisotropic etch process etches peripheral portions of a subset of the array of support pillar structures. The sacrificial material layers are replaced with electrically conductive layer by forming backside recesses while the support pillar structures provide mechanical support to the insulating layers.