Niobium Etching Prevention Film for EUV Reflective Mask
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Solution Overview
Problem
The existing reflective mask blanks face challenges in protecting the multilayer reflection film during the manufacturing process, particularly due to damage from etching gases and cleaning liquids, which leads to a reduction in reflectance and film thickness.
Innovation Solution
Incorporating an etching prevention film made of niobium (Nb) between the protection film and the absorption film in the reflective mask blank, which is free of ruthenium (Ru), helps to prevent damage from dry etching gases containing chlorine and oxygen, and from sulfuric acid-hydrogen peroxide cleaning mixtures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protection film is formed on the multilayer reflection film to protect it during manufacturing, then the multilayer reflection film is protected from direct exposure to etching gas and cleaning liquids, but the protection film itself is damaged by dry etching using chlorine-containing gases and sulfuric acid-hydrogen peroxide mixtures, leading to reduced film thickness and reflectance
Solution Approach 1:
An etching prevention film containing niobium (Nb) is introduced as an intermediary layer between the protection film and the absorption film. This intermediary layer specifically resists damage from dry etching gases containing chlorine and oxygen, as well as sulfuric acid-hydrogen peroxide cleaning mixtures, thereby protecting the protection film from deterioration while allowing the multilayer reflection film to be protected throughout the manufacturing process
Solution Approach 2:
The reflective mask blank employs a composite structure with multiple functional layers: a multilayer reflection film (Mo/Si alternating layers), a protection film (ruthenium-based), and an etching prevention film (niobium-containing). This composite material structure combines the high reflectance of the Mo/Si multilayer with the protection capabilities of the ruthenium-based film and the etching resistance of the niobium-containing film, achieving both protection and durability
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 use of a niobium-based etching prevention film effectively prevents damage to the protection film, maintaining its thickness and reflectance, thereby enhancing the durability and performance of the reflective mask blank during the EUV lithography process.
Implementation Method 1
a multilayer reflection film that is formed on one main surface of the substrate, and reflects the exposure light
Implementation Method 2
an absorption film that is formed on the protection film, and absorbs the exposure light
Data Source
AI summary
As a reflective mask blank that includes a protection film containing ruthenium (Ru), a reflective mask blank in which the protection film is hard to be damaged and can be suppressed decrease of the thickness is provided by a reflective mask blank including a substrate, a multilayer reflection film, a protection film, an absorption film, and an etching prevention film that contains niobium (Nb) and is free of ruthenium (Ru) between the protection film and the absorption film.