Tungsten Gapfill Stack With Plasma-Etched Nucleation Layer

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Solution Overview

Problem

As device geometries shrink, the formation of boron tungsten (BW) and tungsten silicide (WSi) nucleation layers leads to high resistance stacks, and tungsten physical vapor deposition (WPVD) overhangs limit gapfill performance in semiconductor manufacturing.

Innovation Solution

A method involving physical vapor deposition (PVD) of a first metal layer, followed by a nucleation presoak, plasma etching, and subsequent PVD of a second metal layer, with a plasma-etched nucleation layer to form a metal stack that reduces resistivity and overhang issues.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a nucleation layer comprising silicon or boron is deposited on PVD tungsten liners to promote bulk fill formation, then gapfill performance is improved, but resistivity increases due to boron tungsten and tungsten silicide formation

Engineering Contradiction:

Improvegapfill performanceVSAvoidresistivity

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The process segments the nucleation promotion function from the bulk fill deposition by using a separate nucleation presoak step followed by distinct PVD steps, allowing independent optimization of each function to reduce overall resistivity

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent changes the chemical composition parameters by eliminating boron and silicon from the nucleation layer, using a pure tungsten PVD process instead, thereby reducing resistivity while maintaining gapfill effectiveness through controlled deposition parameters

Inventive Principle:

Principle #35Parameter changes

2Ease of manufacture

If tungsten physical vapor deposition is used to fill gaps, then gapfill is achieved, but overhang formation limits performance

Engineering Contradiction:

Improvegapfill capabilityVSAvoidoverhang

Core Design Contradiction:

Ease of manufactureVSShape

Solution Approach 1:

The patent applies a preliminary nucleation presoak treatment before PVD tungsten deposition to prepare the surface and promote uniform nucleation, preventing overhang formation during subsequent bulk fill deposition

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent replaces the purely physical vapor deposition mechanism with a combined chemical-nuclear approach, using plasma-induced nucleation reactions followed by controlled PVD, substituting the mechanical deposition process with a chemically-assisted mechanism that prevents overhang

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 achieves a 25% reduction in resistivity and ensures gapfill without voids or seams, providing a low-resistance metal stack in semiconductor devices.

Implementation Method 1

depositing a first metal layer on a substrate surface by physical vapor deposition (PVD)

Methodology Applied

Scientific EffectPhysical vapor deposition: Physical Vapour Deposition

Implementation Method 2

exposing the nucleation layer to a plasma to etch the nucleation layer

Methodology Applied

Scientific EffectPlasma etching: Plasma

Data Source

PatentUS12473643B2Low resistivity gapfill for logic devices

Publication Date: 2025.11.18 APPLIED MATERIALS INC

AI summary

Embodiments of the disclosure relate to methods for metal gapfill of a logic device with lower resistivity. Specific embodiments provide integrated separate tungsten PVD processes with plasma-etch to solve the overhang issue caused by tungsten PVD and the high resistivity caused by nucleation.