Wet Atomic Layer Etching of Noble Metals via Segmented Passivation
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Solution Overview
Problem
Existing etch processes for noble metals like ruthenium, gold, platinum, and iridium are inefficient, using aggressive chemicals that lead to surface roughness, metal contamination, and environmental concerns.
Innovation Solution
A wet atomic layer etching (ALE) process using a first etch solution with a persulfate salt and a chloride ion source to form a noble metal salt passivation layer, which is then selectively dissolved in a second etch solution, allowing for precise and controlled etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional aggressive etchants are used to etch noble metals, then etching speed is improved, but surface roughness increases and metal contamination occurs
Solution Approach 1:
The etching process is divided into two separate sequential steps: (1) surface modification step where the noble metal surface is treated with a first etchant to create a modified surface layer, and (2) removal step where a second etchant selectively removes the modified layer. This segmentation allows each step to be optimized independently - the first step creates the necessary chemical modification for etching, while the second step removes only the modified material with controlled morphology, preventing the surface roughness and contamination issues that occur when using aggressive single-step etchants
Solution Approach 2:
The surface modification step creates an intermediate modified surface layer that serves as a mediator between the noble metal substrate and the removal etchant. This intermediate layer has different chemical properties than the original noble metal surface, making it selectively removable by the second etchant. This intermediary approach enables precise control over etching speed and surface quality, as the removal process acts on the modified layer rather than directly on the bulk noble metal, thereby preventing uncontrolled roughness and contamination
2Productivity
If conventional aggressive etchants are used to etch noble metals, then etching capability is improved, but metal contamination and environmental harm increase
Solution Approach 1:
The invention converts the typical harmful byproducts of aggressive etching into beneficial outcomes. Instead of using strong acids that generate toxic waste and metal contamination, the two-step process uses milder etchants where the first step creates a controlled modified surface layer and the second step selectively removes it. This approach maintains effective etching capability while eliminating the harmful contamination and environmental damage associated with conventional aggressive etchants, effectively turning the etching process from a harmful operation into a clean, controlled process
3Device complexity
If single-step etching is used for noble metals, then process simplicity is maintained, but etching uniformity and precision deteriorate
Solution Approach 1:
The etching process is divided into two separate sequential steps: (1) surface modification step where the noble metal surface is treated with a first etchant to create a modified surface layer, and (2) removal step where a second etchant selectively removes the modified layer. This segmentation allows each step to be optimized independently - the first step creates the necessary chemical modification for etching, while the second step removes only the modified material with controlled morphology, preventing the surface roughness and contamination issues that occur when using aggressive single-step etchants
Solution Approach 2:
The surface modification step creates an intermediate modified surface layer that serves as a mediator between the noble metal substrate and the removal etchant. This intermediate layer has different chemical properties than the original noble metal surface, making it selectively removable by the second etchant. This intermediary approach enables precise control over etching speed and surface quality, as the removal process acts on the modified layer rather than directly on the bulk noble metal, thereby preventing uncontrolled roughness and contamination
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 process achieves uniform and precise etching of noble metals, reducing surface roughness and metal contamination, while being cost-effective and environmentally friendly.
Implementation Method 1
exposing the surface of the substrate to a surface modification solution to chemically modify the noble metal surface and form a modified surface layer
Implementation Method 2
exposing the surface of the substrate to a dissolution solution to remove the modified surface layer from the substrate
Data Source
AI summary
The present disclosure provides improved wet etch processes and methods for etching noble metals. More specifically, the present disclosure provides various embodiments of wet etch processes and methods that utilize new etch chemistries for etching noble metals, such as ruthenium (Ru), gold (Au), platinum (Pt) and iridium (Ir), in a wet etch process. In general, the disclosed embodiments expose a noble metal surface to a first etch solution to chemically modify the noble metal surface and form a noble metal salt passivation layer, which can then be selectively dissolved in a second etch solution to etch the noble metal surface.