Backside Support Pillars for 3D Memory Stack Stability

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Solution Overview

Problem

Current three-dimensional memory devices face challenges in achieving high density and efficient integration of support pillar structures within their architecture, which affects the overall performance and reliability of the memory stack structures.

Innovation Solution

The proposed solution involves forming alternating stacks of insulating and conductive layers over a substrate, with strategically placed backside trenches and support pillar structures that extend through multiple tiers, allowing for vertical semiconductor channels and memory films to be integrated efficiently, and replacing sacrificial material layers with conductive layers to create a robust memory device architecture.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If support pillar structures are integrated into three-dimensional memory devices, then structural stability and reliability are improved, but device complexity and manufacturing difficulty increase

Engineering Contradiction:

Improvestructural stabilityVSAvoidarchitecture complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The support pillar structures are nested within the alternating stacks of insulating and conductive layers, with pillars extending through multiple tiers of the memory device. This nesting approach provides structural stability while integrating the support function within the existing memory architecture rather than adding separate external support structures.

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

The support pillar structures are segmented into multiple discrete pillars distributed throughout the alternating stacks, rather than using a single continuous support structure. This segmentation allows the support function to be distributed across multiple locations, improving overall structural stability while maintaining manufacturability through standardized fabrication processes.

Inventive Principle:

Principle #1Segmentation

2Reliability

If auxiliary support pillar structures are added to enhance structural integrity, then reliability is improved, but manufacturing process complexity increases

Engineering Contradiction:

Improvestructural integrityVSAvoidfabrication complexity

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The auxiliary support pillar structures are formed during the preliminary stages of manufacturing, concurrent with the formation of the alternating stacks and memory openings. By establishing the support pillars early in the fabrication sequence, the structural integrity is ensured from the outset without requiring additional later processing steps.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The auxiliary support pillar structures serve multiple functions: providing structural integrity during subsequent processing steps, serving as alignment references for memory opening formation, and potentially functioning as electrical contacts or interconnect elements. This multi-functionality reduces the need for separate dedicated support structures.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Quantity of substance

If multiple tiers of alternating stacks are integrated, then memory density is improved, but structural stability and manufacturing precision requirements increase

Engineering Contradiction:

Improvememory densityVSAvoidalignment precision

Core Design Contradiction:

Quantity of substanceVSManufacturing precision

Solution Approach 1:

The alternating stacks are formed with uniform layer thicknesses and consistent material compositions across multiple tiers, creating equipotential conditions for subsequent processing. This uniformity ensures that etching, deposition, and other fabrication steps proceed evenly across all tiers, maintaining alignment precision while achieving high memory density.

Inventive Principle:

Principle #12Equipotentiality

Solution Approach 2:

The auxiliary support pillar structures serve as intermediary reference elements between the multiple tiers of alternating stacks. These pillars provide physical and visual references that guide alignment during memory opening formation and subsequent processing steps, enabling precise multi-tier integration without requiring excessive manufacturing precision.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS11637119B2Three-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 row of backside support pillar structures is formed through a first-tier alternating stack of first-tier insulating layers and first-tier sacrificial material layers. At least one upper-tier alternating stack can be formed, and memory stack structures can be formed through the alternating stacks. A backside trench can be formed through the alternating stacks selective to the row of backside support pillar structures. The sacrificial material layers are replaced with electrically conductive layers, and the backside trench can be filled with a backside trench fill structure, which includes the row of backside support pillar structures. The row of backside support pillar structures reduces or prevents tilting or collapse of the alternating stacks during replacement of the sacrificial material layers with the electrically conductive layers.