Self-Aligned Contact Via Structures in 3D Memory

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Solution Overview

Problem

Current three-dimensional memory devices face challenges in efficiently forming self-aligned contact via structures with vertically-extending concave sidewalls, which are crucial for enhancing memory density and performance.

Innovation Solution

A method involving the formation of an alternating stack of insulating and sacrificial material layers over a substrate, followed by the creation of stepped surfaces, retro-stepped dielectric material, and isotropic etching to form concave dielectric pillar structures, which are then replaced with conductive material to create contact via structures with vertically-extending concave sidewalls.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If conventional contact via formation methods are used, then manufacturing simplicity is maintained, but manufacturing precision of self-aligned contact via structures with vertically-extending concave sidewalls deteriorates

Engineering Contradiction:

Improveprecision of contact via structuresVSAvoidcomplexity of formation process

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

Dielectric pillar structures are formed preliminarily with concave sidewalls before the actual contact via formation. These pre-formed pillars serve as self-aligned templates that define the precise location and shape of the contact vias, eliminating the need for separate alignment steps and achieving high manufacturing precision without proportionally increasing process complexity

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

Dielectric pillar structures act as intermediary elements between the alternating stack and the final contact via structures. These pillars with concave sidewalls serve as temporary mediators that guide the etching process and ensure precise self-alignment, and are later replaced with conductive material to form the actual contact vias

Inventive Principle:

Principle #24Intermediary (Mediator)

2Quantity of substance

If memory density is enhanced through self-aligned contact via structures, then memory performance improves, but device complexity increases

Engineering Contradiction:

Improvememory densityVSAvoidstructural complexity

Core Design Contradiction:

Quantity of substanceVSDevice complexity

Solution Approach 1:

The dielectric pillar structures are self-aligned to the alternating stack, meaning they automatically position themselves correctly without requiring complex external alignment mechanisms. This self-service capability allows for enhanced memory density through precise structure placement while avoiding the need for complex alignment equipment and processes that would otherwise increase device complexity

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The contact via structures are formed by replacing the dielectric pillar structures within the alternating stack, creating a nested configuration where the final conductive structures are embedded within the pre-formed dielectric framework. This nesting approach allows for high memory density by efficiently utilizing the three-dimensional space while maintaining a relatively simple overall device architecture

Inventive Principle:

Principle #7Nested doll (Nesting)

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 enables the fabrication of three-dimensional memory devices with improved memory stack structures and contact via configurations, enhancing memory density and performance by ensuring precise alignment and conductivity.

Implementation Method 1

forming a continuous cavity by isotropically etching the insulating layers and the retro-stepped dielectric material portion selective to the sacrificial material layers

Methodology Applied

Scientific EffectIsotropic etching:

Implementation Method 2

replacing the sacrificial material layers and the dielectric pillar structures with conductive material portions, wherein the conductive material portions comprise combinations of an electrically conductive layer that replaces a respective sacrificial material layer and a contact via structure that replaces a respective dielectric pillar structure

Methodology Applied

Scientific EffectMaterial replacement:

Data Source

PatentUS10192784B1Three-dimensional memory device containing self-aligned contact via structures and methods of manufacturing the same

Publication Date: 2019.01.29 SANDISK TECHNOLOGIES LLC

AI summary

An alternating stack of insulating layers and sacrificial material layers including stepped surfaces is formed over a substrate. After formation of a retro-stepped dielectric material portion over the stepped surfaces, an array of cylindrical openings is formed through the retro-stepped dielectric material portion and the alternating stack. A continuous cavity is formed by isotropically etching the insulating layers and the retro-stepped dielectric material portion selective to the sacrificial material layers. Remaining portions of the retro-stepped dielectric material portion include dielectric pillar structures. A continuous fill material portion is formed in the continuous cavity. Memory stack structures are formed through the alternating stack. The sacrificial material layers and the dielectric pillar structures are replaced with combinations of an electrically conductive layer and a contact via structure. The contact via structures are self-aligned to the electrically conductive layers.