Single-Crystal Silicon Pellicle for High-EUV Transmittance
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Solution Overview
Problem
Current pellicle films for extreme ultraviolet (EUV) lithography face challenges in achieving high transmittance and chemical stability, with existing materials like silicon resulting in high absorption coefficients and optical degradation due to stress, especially when used in amorphous or polycrystalline forms.
Innovation Solution
A pellicle film made from a single-crystal silicon film with an absorption coefficient of 0.005/nm or lower at 13.5 nm wavelength, preferably oriented on a (100) plane, combined with a protective film of materials like SiC, SiO2, or metal films, using a gas cluster ion beam deposition method to ensure low absorption and chemical stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If silicon film is deposited by sputtering or CVD to form pellicle film, then the pellicle film can be manufactured, but the absorption coefficient in EUV region becomes high and transmissivity becomes low
Solution Approach 1:
The invention changes the crystal structure parameter of silicon from amorphous or polycrystalline to single-crystal form. This parameter change dramatically reduces the absorption coefficient in the EUV region from high levels to 0.005/nm or lower, thereby achieving high transmissivity of 50% or more while maintaining manufacturability through specialized growth techniques
Solution Approach 2:
The invention creates a composite structure by combining single-crystal silicon film with specific crystal plane orientation ((100), (110), or (111)) and controlled thickness (1-100 nm) with the pellicle substrate. This composite approach optimizes both the mechanical properties for manufacturability and the optical properties for high EUV transmissivity
2Ease of manufacture
If silicon crystal film is formed using sputtering or CVD method, then the pellicle film can be manufactured, but strong stress is introduced and optical characteristics degrade or become nonuniform
Solution Approach 1:
The invention changes the deposition method parameter from conventional sputtering or CVD to a method that produces single-crystal structure with specific orientation. This parameter change eliminates the strong stress inherent in amorphous or polycrystalline films deposited by sputtering or CVD, resulting in uniform optical characteristics across the pellicle film while maintaining manufacturability
Solution Approach 2:
The invention applies local quality control by specifying particular crystal plane orientations ((100), (110), or (111)) for the single-crystal silicon film. This local crystalline structure optimization ensures uniform stress distribution and consistent optical properties across the entire pellicle film area, preventing degradation and nonuniformity
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 provides a pellicle film with 50% or higher transmittance for EUV light and improved chemical stability, preventing optical degradation and foreign matter adhesion, thus enhancing the practicality of EUV lithography.
Implementation Method 1
coating with a protective film like SiC, SiO2, or metal films using gas cluster ion beam deposition
Data Source
AI summary
A pellicle of the present invention is provided with a silicon crystal film, the absorption coefficient of which is 0.005/nm or lower with respect to light having a wavelength of 13.5 nm, as a pellicle film. The silicon crystal film is an indirect transition type semiconductor film and, therefore, the optical absorption coefficient thereof is relatively low. In particular, a single-crystal silicon film has a lower absorption coefficient than an amorphous silicon film and a polysilicon film. Thus, it is easy to obtain desired transmissivity required of a pellicle film for EUV from the single-crystal silicon film. Such a pellicle film as described above can be fabricated from an SOI film obtained by thin-filming an SOI substrate (including an SOQ substrate and an SOG substrate).