3D Memory Through-Stack Contact Via with Bulged Layer Contact

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Solution Overview

Problem

Existing three-dimensional memory devices face challenges in efficiently forming through-stack contact via structures, which are crucial for enhancing memory performance and integration, due to complex manufacturing processes and material compatibility issues.

Innovation Solution

The formation of a device structure involving alternating stacks of insulating and conductive layers with stepped surfaces, retro-stepped dielectric material portions, and contact via structures with bulging and offset portions, along with methods that include patterning, etching, and replacing sacrificial materials to create efficient contact via structures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If conventional through-stack contact via structures are formed in three-dimensional memory devices, then memory device integration is improved, but manufacturing process complexity increases

Engineering Contradiction:

Improvememory device integrationVSAvoidmanufacturing process complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The contact via structure is segmented into distinct functional portions: a laterally bulging portion for lateral contact with conductive layers, an upper vertical portion for upward extension through dielectric material, and a lower vertical portion for downward extension through conductive layers. This segmentation allows each portion to be optimized for its specific function while simplifying the overall manufacturing process

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The laterally bulging portion is formed in advance to establish lateral contact with the first electrically conductive layer before the upper and lower vertical portions are completed. This preliminary action ensures proper alignment and contact establishment, reducing subsequent manufacturing complexity

Inventive Principle:

Principle #10Preliminary action

2Reliability

If contact via structures with lateral bulging portions are formed to contact conductive layers, then electrical conductivity is improved, but structural complexity increases

Engineering Contradiction:

Improveelectrical conductivityVSAvoidstructural complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The contact via structure exhibits local quality variation: the laterally bulging portion provides enhanced lateral contact area with the first electrically conductive layer for optimal electrical conductivity, while the upper and lower vertical portions maintain simpler geometries for structural efficiency. Each portion's geometry is locally optimized for its specific functional requirement

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The contact via structure transitions from a simple vertical via to a three-dimensional structure with lateral extension. The laterally bulging portion extends in the lateral dimension to contact the first electrically conductive layer, while the upper and lower portions extend in the vertical dimension, creating a multi-dimensional contact architecture that improves electrical connectivity

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Manufacturing precision

If retro-stepped dielectric material portions are formed over stepped surfaces, then alignment precision is improved, but manufacturing steps increase

Engineering Contradiction:

Improvealignment precisionVSAvoidmanufacturing steps

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The retro-stepped dielectric material portion is formed in advance over the stepped surfaces of the alternating stack. This preliminary formation establishes precise alignment references and contact surfaces for subsequent contact via structure fabrication, ensuring accurate positioning while consolidating multiple alignment functions into a single preparatory step

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS20250386499A1Three-dimensional memory device with through-stack contact via structures and methods for forming the same

Publication Date: 2025.12.18 SANDISK TECHNOLOGIES LLC

AI summary

A device structure includes at least one alternating stack of respective insulating layers and respective electrically conductive layers, at least one retro-stepped dielectric material portion overlying portions of the at least one alternating stack, a memory stack structure vertically extending through each layer within the at least one alternating stack, and a contact via structure including a laterally bulging portion in contact with a first electrically conductive layer of the electrically conductive layers within the at least one alternating stack, an upper portion that vertically extends upward from the laterally bulging portion and through the at least one retro-stepped dielectric material portion, and a lower portion that vertically extends through second electrically conductive layers of the electrically conductive layers that underlie the first electrically conductive layer.