Graphite Thin Film Pellicle for EUV Transmittance
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Solution Overview
Problem
Conventional pellicles face challenges in achieving both high and uniform extreme ultraviolet (EUV) transmittance.
Innovation Solution
A pellicle comprising a graphite thin film with a film thickness of 5 nm to 30 nm, a specific intensity ratio of D-band to G-band in Raman spectra, and controlled surface roughness, which enables high EUV transmittance and uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional pellicle material is used, then the pellicle can be manufactured, but it cannot achieve both high EUV transmittance and uniformity in EUV transmittance
Solution Approach 1:
The patent applies parameter changes by precisely controlling the film thickness (5-30 nm), surface roughness (Sa: 0.1-500 nm), and crystalline structure (Raman spectrum I(D)/I(G) ratio: 0-0.5) of the graphite thin film to achieve both high EUV transmittance and uniformity. By optimizing these physical and structural parameters, the pellicle achieves 80% or more EUV transmittance with low standard deviation, resolving the contradiction between transmittance and uniformity.
Solution Approach 2:
The patent uses composite material structure by combining graphite thin film with pellicle frame, creating a composite pellicle system. The graphite thin film serves as the functional layer providing EUV transmittance, while the pellicle frame provides structural support. This composite approach enables simultaneous achievement of high transmittance and uniformity by leveraging the properties of each material component.
2Reliability
If the film thickness is reduced to increase EUV transmittance, then transmittance improves, but film strength deteriorates
Solution Approach 1:
The patent resolves the contradiction between transmittance and strength by optimizing the film thickness parameter to a specific range (5-30 nm). This thinness provides sufficient EUV transmittance (80% or more) while maintaining adequate film strength. Additionally, controlling the surface roughness (Sa: 0.1-500 nm) and crystalline structure (Raman spectrum I(D)/I(G) ratio: 0-0.5) further enhances both transmittance and mechanical properties, allowing the film to be thin yet strong.
3Ease of manufacture
If the surface roughness is increased, then manufacturing is easier, but EUV transmittance uniformity deteriorates
Solution Approach 1:
The patent resolves this contradiction by controlling the surface roughness parameter within a specific range (Sa: 0.1-500 nm). This controlled roughness level is achievable through conventional manufacturing processes while still providing sufficient EUV transmittance uniformity. The patent demonstrates that moderate surface roughness does not significantly impact transmittance uniformity, making the pellicle easier to manufacture without sacrificing performance.
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 pellicle achieves excellent EUV transmittance of 80% or more and uniformity in EUV transmittance with a low standard deviation, while maintaining sufficient film strength and thermal conductivity.
Implementation Method 1
a graphite thin film having a film thickness of 5 nm to 30 nm, a ratio (I (D)/I (G)) of a D-band intensity (I (D)) to a G-band intensity (I (G)) in a Raman spectrum of 0 or more and 0.5 or less
Implementation Method 2
maintaining sufficient film strength and thermal conductivity
Data Source
Figure 1~2
AI summary
Conventional pellicles have had a problem in achieving both a high extreme ultraviolet (EUV) transmittance and a uniformity in EUV transmittance. The present invention provides a pellicle achieving both a high EUV transmittance and a uniformity in EUV transmittance by using a graphite thin film having a film thickness of 5 nm or more and 30 nm or less and a surface roughness (Sa) of 0.1 nm or more and 500 nm or less.