Selective Cobalt-Copper Via Fill for High-Aspect-Ratio Interconnects

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Solution Overview

Problem

Existing technologies face challenges in efficiently filling high aspect ratio via structures in semiconductor devices, particularly in forming bit lines of three-dimensional memory devices like NAND strings, where conventional methods struggle to achieve complete filling and maintain structural integrity.

Innovation Solution

A method involving selective growth of a conductive via structure containing cobalt from the bottom of the via portion of the integrated line-and-via cavity, followed by forming a copper-based conductive line structure with copper content greater than 90%, ensuring complete filling and structural integrity of the via and line portions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If conventional filling methods are used for high aspect ratio via structures, then the process is simple, but complete filling and structural integrity cannot be achieved

Engineering Contradiction:

Improvevia filling completenessVSAvoidfill process complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The filling process is divided into two distinct stages: first forming a conductive via structure with cobalt and metal-semiconductor alloy in the via portion, then forming a separate copper-based conductive line structure in the line portion. This segmentation allows each material to be optimized for its specific function while achieving complete via filling.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The conductive via structure is formed first as a preliminary step before forming the copper-based conductive line structure. This preliminary action prepares the via cavity with appropriate materials and structures that enable subsequent complete filling and ensure structural integrity.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If selective metal deposition is used to form conductive structures, then material distribution is optimized, but process complexity increases

Engineering Contradiction:

Improveelectrical connectivityVSAvoiddeposition process complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

Different materials are selectively deposited in different locations: cobalt and metal-semiconductor alloy are deposited in the via portion to provide appropriate electrical and mechanical properties, while copper is deposited in the line portion for optimal conductivity. This local quality optimization ensures reliable electrical connectivity throughout the structure.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The conductive structure employs composite materials with copper-based conductive line structure containing greater than 90% copper and via structure containing cobalt and metal-semiconductor alloy. This composite approach leverages the advantages of each material - copper's high conductivity in lines and cobalt's properties in vias - to achieve superior overall reliability.

Inventive Principle:

Principle #40Composite materials

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

The method enables effective filling of high aspect ratio via structures, enhancing the performance and reliability of semiconductor devices by ensuring complete copper-based conductive lines, thereby improving the electrical connectivity and structural stability.

Implementation Method 1

selectively growing a conductive via structure containing cobalt from a bottom of the via portion of the integrated line-and-via cavity

Methodology Applied

Scientific EffectSelective metal deposition: Electrodeposition

Implementation Method 2

forming a copper-based conductive line structure that contains copper at an atomic percentage that is greater than 90% in the line portion of the integrated line-and-via cavity

Methodology Applied

Scientific EffectMetal deposition: Physical Vapour Deposition

Data Source

PatentUS12525487B2High aspect ratio via fill process employing selective metal deposition and structures formed by the same

Publication Date: 2026.01.13 SANDISK TECHNOLOGIES LLC

AI summary

A method of forming a semiconductor structure includes forming a semiconductor device over a substrate, forming a combination of a connection-level dielectric layer and a connection-level metal interconnect structure over the semiconductor device, where the connection-level metal interconnect structure is electrically connected to a node of the semiconductor device and is embedded in the connection-level dielectric layer, forming a line-and-via-level dielectric layer over the connection-level dielectric layer, forming an integrated line-and-via cavity through the line-and-via-level dielectric layer over the connection-level metal interconnect structure, selectively growing a conductive via structure containing cobalt from a bottom of the via portion of the integrated line-and-via cavity without completely filling a line portion of the integrated line-and-via cavity, and forming a copper-based conductive line structure that contains copper at an atomic percentage that is greater than 90% in the line portion of the integrated line-and-via cavity on the conductive via structure.