Nanocrystalline Graphene Pellicle for EUV Lithography
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Solution Overview
Problem
Current pellicles for photomasks in lithography processes face challenges in maintaining high transmittance and durability, especially with short-wavelength light such as EUV, while also ensuring uniformity and resistance to contaminants.
Innovation Solution
A pellicle membrane made of nanocrystalline graphene with defects, including sp3 carbon, oxygen, nitrogen, and carbon vacancies, is used, with specific compositions and structures that enhance light transmittance, thermal conductivity, and mechanical strength, and optionally coated with protective layers for added durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional pellicle materials are used, then the photomask is protected from contaminants, but light transmittance decreases and durability against short-wavelength light is insufficient
Solution Approach 1:
The patent changes the material parameters by using nanocrystalline graphene with controlled defect densities (D/G ratio 0.5-2.0) and specific crystal grain sizes (1-100 nm), achieving both high EUV transmittance (90% or more) and durability. This resolves the contradiction by optimizing the structural parameters of graphene rather than using conventional materials.
Solution Approach 2:
The patent creates a composite structure by combining nanocrystalline graphene with specific defect configurations (sp3 carbon, oxygen, nitrogen, carbon vacancies) in controlled amounts. This composite approach at the nanoscale enables simultaneous achievement of high transmittance and durability against short-wavelength light.
2Illumination intensity
If the pellicle membrane is made thinner to increase transmittance, then light transmittance improves, but mechanical strength and uniformity decrease
Solution Approach 1:
The patent employs an ultra-thin nanocrystalline graphene film that maintains mechanical integrity through its unique nanocrystalline structure. The flexible yet strong graphene membrane achieves high transmittance while resisting mechanical failure, solving the contradiction between thinness and strength.
Solution Approach 2:
By controlling the crystal grain size (1-100 nm) and defect density (D/G ratio 0.5-2.0) parameters, the patent optimizes the mechanical properties of the thin graphene film, enabling it to maintain strength despite reduced thickness for high transmittance.
3Reliability
If the pellicle material is made more durable against EUV light, then resistance to short-wavelength light improves, but uniformity and surface quality may deteriorate
Solution Approach 1:
The patent achieves both durability and uniformity by precisely controlling the D/G ratio (0.5-2.0) and 2D/G ratio (0.05 or more) parameters of the nanocrystalline graphene. This parameter optimization ensures consistent defect distribution that provides EUV resistance while maintaining surface uniformity.
Solution Approach 2:
The nanocrystalline graphene structure with uniformly distributed defects and crystal grains creates a homogeneous material that provides consistent EUV resistance across the surface. The uniform nanoscale structure ensures both durability and manufacturing precision.
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 nanocrystalline graphene pellicle achieves high transmittance (up to 90% for EUV light), excellent thermal conductivity, and improved mechanical strength, ensuring uniformity and resistance to contaminants, thereby enhancing the precision and effectiveness of the lithography process.
Implementation Method 1
The pellicle has high transmittance with respect to light used in a lithography process... The pellicle membrane may have a transmittance of 80% or more with respect to extreme ultraviolet (EUV) light
Implementation Method 2
The pellicle has excellent characteristics in terms of uniformity, durability, stability, thermal conductivity, strength
Data Source
Figure 1~2
Figure 3A~3C
Figure 3D~3E
AI summary
A pellicle for a photomask, a reticle including the same, and an exposure apparatus for lithography are provided. The pellicle may include a pellicle membrane, and the pellicle membrane may include nanocrystalline graphene. The nanocrystalline graphene may have defects. The nanocrystalline graphene may include a plurality of nanoscale crystal grains, and the nanoscale crystal grains may include a two-dimensional (2D) carbon structure having an aromatic ring structure. The defects of the nanocrystalline graphene may include at least one of an sp3 carbon atom, an oxygen atom, a nitrogen atom, or a carbon vacancy.