Metal Atomic Layer Etch Using Organic Ligands

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Solution Overview

Problem

Traditional metal atomic layer etching (ALE) processes are limited in speed, etch rate, surface adsorption coverage, selectivity, and the removal of certain metals due to the introduction of metal precursors, which can cause contamination and result in low volatility surface materials, leading to inefficient removal processes.

Innovation Solution

The implementation of an isotropic metal ALE system that uses organic vapors as ligands without metal precursors, performing atomistic adsorption and pulsed thermal annealing to form and remove metal complexes, allowing for efficient and selective etching of metals, metal oxides, and metal nitrides with improved etch rates and reduced thermal budget issues.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional metal ALE processes use metal precursors to modify metal oxide surfaces, then surface modification can be achieved, but the process speed is limited and contamination occurs

Engineering Contradiction:

Improvesurface modification qualityVSAvoidetch rate

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent removes metal precursors from the ALE process entirely, replacing them with organic ligands. This extraction of the problematic metal precursor component eliminates contamination while maintaining surface modification capability through alternative chemistry between organic ligands and metal surfaces.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent changes the chemical parameters of the surface modification step by substituting metal-based precursors with organic ligands. This parameter change enables faster reaction kinetics and higher etch rates while avoiding the contamination issues inherent in traditional metal precursor approaches.

Inventive Principle:

Principle #35Parameter changes

2Productivity

If plasma is used during ALE to remove modified surface layers, then removal efficiency is improved, but structural damage occurs to substrates including MRAM devices

Engineering Contradiction:

Improveremoval efficiencyVSAvoidstructural damage

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent substitutes the plasma-based removal mechanism with a thermal field-based mechanism. By using rapid thermal processing to desorb and remove metal complexes, the process avoids the ion bombardment and radical chemistry of plasma that cause structural damage, while still achieving efficient removal through thermally activated desorption.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Adaptability or versatility

If traditional metal ALE processes are used, then certain metal removal can be achieved, but the process is limited to specific metal types and lacks selectivity

Engineering Contradiction:

Improvemetal type compatibilityVSAvoidselectivity

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent creates a universal ALE process using organic ligands that can interact with multiple metal types through common coordination chemistry mechanisms. The organic ligand approach provides a multi-functional solution that works across different metal substrates (Cu, Al, Ti, Ta, W, etc.) while maintaining high selectivity through controlled ligand-surface interactions and thermal desorption parameters.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 etching processes that are up to 100 times faster than traditional methods, providing efficient surface modification and removal with high selectivity and depth control, capable of processing metals like tantalum, ruthenium, and titanium without thermal budget constraints.

Implementation Method 1

exposing the surface of the substrate to the at least one of the ligand or the organic species, where the at least one of the ligand or the organic species is void of a metal precursor and is selectively adsorbed to form a metal complex in the surface of the substrate

Methodology Applied

Scientific EffectAdsorption: Adsorption

Implementation Method 2

during the pulsed thermal annealing, pulsing the first heat source on and off multiple times to remove the metal complex from the substrate

Methodology Applied

Scientific EffectThermal annealing: Annealing

Data Source

PatentUS20220084838A1Metal atomic layer etch and deposition apparatuses and processes with metal-free ligands

Publication Date: 2022.03.17 LAM RES CORP

AI summary

An ALE system for performing a metal ALE process to etch a surface of a substrate includes a processing chamber, a substrate support, a heat source, a delivery system, and a controller. The substrate support is disposed in the processing chamber and supports the substrate. The delivery system supplies a ligand or organic species to the processing chamber. The controller controls the delivery system and the heat source to perform an isotropic metal ALE process that includes: during an iteration of the isotropic metal ALE process, performing atomistic adsorption and pulsed thermal annealing; during the atomistic adsorption, exposing the surface to the ligand or organic species, where the ligand or organic species is void of a metal precursor and is selectively adsorbed to form a metal complex in the surface; and during the pulsed thermal annealing, pulsing the heat source multiple times to remove the metal complex from the substrate.