Ruthenium Capping Layer Oxidation Prevention in EUV Mask Cleaning
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Solution Overview
Problem
The degradation of optical characteristics in reflective masks used in EUV lithography due to the oxidation of ruthenium-containing capping layers during cleaning processes, which reduces reflectance and affects the mask's performance.
Innovation Solution
A cleaning apparatus and method that utilize a combination of a first solution containing an organic solvent or surfactant and a second solution, which can be a reducing solution or oxygen-free solution, to prevent oxidation of the ruthenium-containing capping layer, thereby maintaining the optical integrity of the mask.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If cleaning with ozone water or mixed solution of sulfuric acid and hydrogen peroxide water is used to remove organic matter from the reflective mask, then the organic matter is effectively removed, but the ruthenium in the capping layer is oxidized into ruthenium oxide, decreasing the reflectance and degrading optical characteristics
Solution Approach 1:
The patent introduces a reducing atmosphere environment (using ammonia water or reducing gas) during the cleaning process to prevent oxidation of the ruthenium-containing capping layer. This inert/reducing environment counteracts the oxidizing conditions that would otherwise form ruthenium oxide and degrade optical properties, allowing effective removal of organic matter while preserving the reflective mask's optical characteristics.
Solution Approach 2:
The patent changes the chemical parameters of the cleaning environment by introducing ammonia water (basic solution) or reducing gas to alter the oxidation-reduction potential. This parameter change transforms the cleaning chemistry from an oxidizing environment that damages ruthenium to a reducing environment that protects it, enabling simultaneous organic matter removal and optical property preservation.
2Ease of operation
If the reflective mask is exposed to oxygen-containing atmosphere during processing and transport, then the mask can be handled and processed, but ruthenium oxide forms in the exposed portions, decreasing reflectance and degrading optical characteristics
Solution Approach 1:
The patent employs a reducing atmosphere (ammonia water or reducing gas) that creates a protective environment during handling and processing. This inert/reducing atmosphere prevents oxygen from contacting and oxidizing the ruthenium-containing capping layer, allowing the mask to be handled and processed without forming ruthenium oxide that would degrade optical properties.
3Ease of manufacture
If conventional cleaning methods are used to remove resist mask, then the resist mask is effectively removed, but the cleaning process oxidizes the ruthenium-containing capping layer, causing reflectance decrease
Solution Approach 1:
The patent replaces conventional oxidizing cleaning methods with a reducing atmosphere cleaning process using ammonia water or reducing gas. This inert/reducing environment enables effective resist mask removal while preventing oxidation of the ruthenium-containing capping layer, thereby maintaining reflectance and optical properties.
Solution Approach 2:
The patent fundamentally changes the chemical parameters of the cleaning process by using ammonia water (basic solution) or reducing gas instead of oxidizing cleaners. This parameter change alters the chemical environment from oxidizing to reducing, enabling effective resist removal without compromising the ruthenium capping layer's reflectance.
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 proposed solution effectively suppresses the degradation of the ruthenium-containing capping layer, ensuring the reflective mask's optical characteristics are preserved, enhancing its performance and longevity.
Implementation Method 1
a first supply section configured to supply a first solution containing at least one of an organic solvent and a surfactant to a ruthenium-containing capping layer
Implementation Method 2
a first supply section configured to supply a first solution containing at least one of an organic solvent and a surfactant to a ruthenium-containing capping layer
Implementation Method 3
a second supply section configured to supply at least one of a reducing solution and an oxygen-free solution to the capping layer
Implementation Method 4
supply at least one of a reducing solution and an oxygen-free solution to the capping layer
Implementation Method 5
a third supply section configured to supply a plasma product produced from a reducing gas to a ruthenium-containing capping layer
Implementation Method 6
supply a plasma product produced from a reducing gas to a ruthenium-containing capping layer
Data Source
AI summary
A reflective mask cleaning apparatus according to an embodiment comprises a first supply section configured to supply a first solution containing at least one of an organic solvent and a surfactant to a ruthenium-containing capping layer provided in a reflective mask; and a second supply section configured to supply at least one of a reducing solution and an oxygen-free solution to the capping layer.A reflective mask cleaning apparatus according to an alternative embodiment comprises a third supply section configured to supply a plasma product produced from a reducing gas to a ruthenium-containing capping layer provided in a reflective mask; and a second supply section configured to supply at least one of a reducing solution and an oxygen-free solution to the capping layer.