EUV Lithography Optical Element Hydrogen Diffusion Barrier
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
EUV lithography optical elements face reflectivity and lifetime reduction due to contamination from reactive hydrogen, which can cause layer detachment and blistering, especially in the presence of high hydrogen fluence.
Innovation Solution
A protective layer system with a first layer having low hydrogen solubility and a second layer with high hydrogen solubility is applied, where the second layer absorbs hydrogen and acts as a diffusion barrier, and a third layer with high recombination rate for hydrogen is used to prevent hydrogen penetration and blistering, ensuring long-term stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protective layer system is applied to prevent contamination, then the lifetime and reflectivity are improved, but the device complexity increases due to multiple layers
Solution Approach 1:
The protective layer system is segmented into multiple functional layers: a first protective layer directly on the multilayer system, a second protective layer with different material properties, and optionally a third protective layer. Each layer serves specific functions such as preventing oxidation, reducing carbon contamination, and minimizing stress, thereby achieving comprehensive protection through divided functional zones rather than a single complex layer
Solution Approach 2:
The protective layer system employs composite materials with different chemical and physical properties arranged in specific sequences. For example, combining materials with low stress properties adjacent to the multilayer system and materials with high erosion resistance on the outer surface creates a composite structure that simultaneously achieves multiple protection functions while managing mechanical stress
2Stability of the object's composition
If a protective layer system with multiple layers is applied to prevent hydrogen penetration, then the stability is improved, but the manufacturing complexity increases
Solution Approach 1:
The protective layer system is applied in advance during the manufacturing process to prevent hydrogen penetration and contamination before the optical element is put into operation. This preliminary protection avoids the need for complex post-manufacturing treatments and ensures stability from the outset
Solution Approach 2:
Different regions of the protective layer system have different material properties tailored to local requirements: the layer adjacent to the multilayer system uses materials with low stress properties to prevent delamination, while outer layers use materials with high erosion resistance and hydrogen barrier properties, creating local quality variations that address specific functional needs
3Reliability
If the protective layer system uses materials with high erosion resistance, then the lifetime is improved, but the stress on the multilayer system increases causing delamination
Solution Approach 1:
The protective layer system is divided into functional zones with different material properties: an inner layer adjacent to the multilayer system uses materials with low stress properties to prevent delamination, while outer layers use materials with high erosion resistance. This segmentation allows each layer to optimize for its specific function without compromising the other
Solution Approach 2:
The protective layer system exhibits local quality variations where materials with low stress properties are strategically placed adjacent to the multilayer system to minimize stress and prevent delamination, while materials with high erosion resistance are positioned on the outer surface to withstand environmental degradation, achieving both low stress and high erosion resistance through spatial differentiation
4Reliability
If reactive hydrogen is used to clean carbon contaminations, then the reflectivity is improved, but hydrogen penetration causes blistering and layer detachment
Solution Approach 1:
The protective layer system converts the potentially harmful effect of hydrogen penetration into a beneficial outcome by using materials that absorb and neutralize hydrogen atoms. The protective layers act as hydrogen traps, preventing hydrogen from reaching the multilayer system and causing blistering, while still allowing the cleaning process to proceed
Solution Approach 2:
The protective layer system serves as an intermediary barrier between the reactive hydrogen used for cleaning and the multilayer system. This intermediate layer allows the hydrogen to pass through or be neutralized without causing damage to the underlying optical coatings, enabling the cleaning process to proceed safely
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 solution effectively prevents hydrogen diffusion into the multilayer system, reducing blistering and layer detachment, allowing for stable operation of EUV lithography optical elements even after numerous gigapulses, with minimal impact on reflectivity.
Implementation Method 1
a second layer which is arranged further away from the multilayer system than the first layer and has a higher solubility for hydrogen than the first layer
Implementation Method 2
the second layer absorbs hydrogen and acts as a diffusion barrier
Implementation Method 3
a third layer with high recombination rate for hydrogen is used to prevent hydrogen penetration and blistering
Data Source
AI summary
An optical element (50), comprising: a substrate (52), an EUV radiation reflecting multilayer system (51) applied to the substrate, and a protective layer system (60) applied to the multilayer system and having at least a first and a second layer (57, 58). The first layer (57) is arranged closer to the multilayer system (51) than is the second layer (58) and serves as a diffusion barrier for hydrogen. This first layer (57) has a lower solubility for hydrogen than does the second layer (58), which serves for absorbing hydrogen. Also disclosed are an optical system for EUV lithography with at least one such optical element, and a method for treating an optical element in order to remove hydrogen incorporated in at least one layer (57, 58, 59) of the protective layer system and/or in at least one layer (53, 54) of the multilayer system (51).