3D Memory Backside Trench Bridges to Prevent Stack Collapse

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Solution Overview

Problem

Three-dimensional memory devices face challenges in maintaining structural integrity during replacement processes, leading to potential stack collapse.

Innovation Solution

Incorporation of bridge structures spanning backside trenches between layer stacks, formed by alternating insulating and sacrificial material layers, which are later replaced with conductive layers to provide structural support.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If bridge structures are incorporated to provide structural support, then stack collapse is prevented and structural stability is enhanced, but device complexity increases

Engineering Contradiction:

Improvestructural stabilityVSAvoiddevice complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The backside trench is divided into multiple segments by introducing bridge structures at different lateral positions. These bridge structures segment the trench into multiple regions, providing distributed structural support throughout the trench rather than relying on a single continuous support structure. This segmentation approach enhances stability while allowing each bridge to be independently formed and optimized.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Bridge structures are introduced spanning across the backside trench in the lateral direction, creating a three-dimensional support network. The bridges extend from one side of the trench to the other, forming arch-like structures that provide mechanical support in the vertical dimension while being formed through lateral processing steps. This dimensional approach allows structural support without requiring additional vertical height.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Ease of manufacture

If alternating insulating and sacrificial material layers are formed, then bridge structures can be created, but manufacturing process complexity increases

Engineering Contradiction:

Improveease of forming bridge structuresVSAvoidmanufacturing process complexity

Core Design Contradiction:

Ease of manufactureVSDevice complexity

Solution Approach 1:

Alternating insulating and sacrificial material layers are formed in advance before the bridge structures are finalized. The sacrificial material layers are deposited and patterned beforehand, creating a template that guides subsequent bridge formation. This preliminary action allows the bridges to be formed using standard deposition and etching processes without requiring complex in-situ structural formation.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

Sacrificial material layers serve as intermediary structures during bridge formation. These temporary layers are deposited between the insulating layers and are later removed to create the final bridge structures. The sacrificial materials act as mediators that enable bridge formation through simple removal processes rather than requiring complex direct deposition of bridge structures.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Ease of operation

If sacrificial trench fill structures are removed, then bridge structures are exposed, but structural support is temporarily reduced

Engineering Contradiction:

Improveease of bridge structure exposureVSAvoidstructural support during replacement

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The bridge structures are formed to span across the backside trench and provide structural support before the sacrificial trench fill structures are removed. The bridges act as pre-installed support elements that maintain trench integrity during the subsequent removal process. This beforehand cushioning ensures that structural support is not compromised when the sacrificial materials are taken away.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

Bridge structures are introduced to counteract the potential structural collapse that would occur when sacrificial trench fill structures are removed. The bridges provide preliminary anti-action by creating an opposing support force that prevents the trench walls from collapsing inward during the sacrificial material removal process.

Inventive Principle:

Principle #9Preliminary anti-action

Data Source

PatentUS12457742B2Three-dimensional memory device including trench bridges and methods of forming the same

Publication Date: 2025.10.28 SANDISK TECHNOLOGIES LLC

AI summary

A three-dimensional memory device includes layer stacks each of which includes a first-tier alternating stack of first insulating layers and first electrically conductive layers and a second-tier alternating stack of second insulating layers and second electrically conductive layers separated by a backside trench. Memory opening fill structures vertically extend through a respective layer stack, and includes a respective vertical stack of memory elements and a respective vertical semiconductor channel. In one embodiment, a bridge structure spans an entire width of the backside trench such that a top surface of the bridge structure is located below a top surface of the second-tier alternating stack, and a bottom surface of the bridge structure is located above a bottom surface of the first-tier alternating stack. In another embodiment, a perforated bridge structure includes a plurality of vertically-extending openings.