Single-Crystal Silicon Pellicle Structure for EUV Transmission
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Solution Overview
Problem
Current pellicles for extreme ultra violet (EUV) lithography face challenges in achieving high transmission, chemical stability, and fabrication yield, with silicon films exhibiting high absorption coefficients and optical property deterioration due to stress and defects during processing.
Innovation Solution
A pellicle comprising a silicon single crystal film with a crystal plane inclined 3 to 5° from {100} or {111} planes, integrated with a base substrate and a reinforcing frame, providing a high open area ratio and a protection film with low absorption coefficients, enhancing mechanical and chemical stability and reducing warpage and distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a silicon film is deposited by sputtering or CVD method, then the pellicle film can be formed, but the absorption coefficient in the EUV region becomes high and transmittance becomes low
Solution Approach 1:
The patent changes the crystallographic orientation parameter of the silicon film from conventional orientations to specifically (100) or (110) planes, which fundamentally alters the optical properties by reducing the absorption coefficient for EUV light while maintaining the effectiveness of conventional deposition processes
Solution Approach 2:
The patent creates a composite structure combining silicon film with specific crystal orientation and controlled thickness (10-100 nm) with the substrate, achieving optimal balance between mechanical support and EUV light transmission by leveraging the unique properties of oriented single crystal silicon
2Length of moving object
If a silicon crystal is made into a thin film in pellicle production process, then the pellicle can be formed, but cracks or defects occur during stripping, etching, and handling
Solution Approach 1:
The patent optimizes the thickness parameter to 10-100 nm and specifies crystal orientations of (100) or (110) planes, which provide optimal mechanical strength and flexibility balance, preventing cracks during handling while maintaining thin film characteristics for high light transmission
Solution Approach 2:
The patent applies different crystal orientations to different regions or layers of the pellicle structure, using (100) or (110) oriented silicon films specifically in regions subject to mechanical stress during fabrication and handling, thereby locally enhancing reliability without compromising overall performance
3Ease of manufacture
If a strong stress is introduced into a silicon crystal by sputtering or CVD methods, then the film can be formed, but optical film properties deteriorate and become uneven
Solution Approach 1:
The patent specifies precise crystal orientation parameters ((100) or (110) planes) and controlled thickness ranges (10-100 nm) that inherently reduce stress accumulation during deposition, maintaining uniform optical properties across the film while preserving the benefits of conventional deposition methods
Solution Approach 2:
The patent uses a thin film thickness (10-100 nm) that is sufficient to provide the required mechanical support and optical function but thin enough to minimize stress accumulation and deformation, achieving optimal performance without excessive material deposition
4Illumination intensity
If the open area ratio of the base substrate is increased, then the EUV light transmittance is improved, but the mechanical strength and stability are reduced
Solution Approach 1:
The patent optimizes the open area ratio parameter to 50-90%, achieving optimal balance between light transmission and mechanical strength, while the thin silicon film thickness (10-100 nm) provides sufficient structural integrity even with high open area ratios
Solution Approach 2:
The patent uses a thin silicon film (10-100 nm) as a flexible yet strong membrane that can span large open areas without requiring excessive support structure, enabling high open area ratios (50-90%) while maintaining mechanical stability through the inherent strength and flexibility of the oriented silicon film
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 achieves high transmission, excellent mechanical and chemical stability, and increased fabrication yield while minimizing defects and warpage, ensuring practicality and cost-effectiveness for EUV pellicles.
Implementation Method 1
silicon has relative high transmittance for the light having such a wavelength... high transmission for EUV light
Data Source
AI summary
A pellicle film of a silicon single crystal film and a base substrate supporting the pellicle film are formed of a single substrate using an SOI substrate. The base substrate is provided with an opening whose ratio in area to an exposure region when a pellicle is used on a photomask (an open area ratio) is 60% or more, and provided with a reinforcing frame in a non-exposure region of the base substrate. Since the pellicle film and the base substrate supporting the pellicle film are formed of the single substrate (an integrated structure), and the base substrate is provided with the reinforcing frame, the effect of increased strength is obtained. Moreover, a principal plane of a silicon single crystal film is a crystal plane inclined at 3 to 5° from any lattice plane belonging to {100} planes or {111} planes.