Nanotube-Coated EUV Pellicle for High Transmittance and Strength
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Solution Overview
Problem
In extreme ultraviolet (EUV) lithography, existing pellicles face challenges with high EUV light source power decay due to environmental adsorption, requiring high transparency and low reflectivity, along with mechanical strength and heat dissipation to prevent damage from EUV radiation and hydrogen radicals.
Innovation Solution
A pellicle for EUV photo masks is developed using a network membrane composed of nanotubes, such as single wall or multiwall carbon nanotubes, coated with silicide or silicide-nitride layers to enhance mechanical and chemical strength, and further coated with additional layers like AlN or TiN for improved EUV transmittance and protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a conventional pellicle is used, then mechanical strength is provided, but EUV transmittance is reduced due to environmental adsorption
Solution Approach 1:
The pellicle uses a composite structure combining nanotube membrane with multiple coating layers (silicide, AlN, TiN). The nanotube membrane provides mechanical strength while the thin coating layers enhance chemical stability and maintain high EUV transmittance, resolving the contradiction between strength and light transmission.
Solution Approach 2:
The pellicle employs an ultrathin nanotube membrane structure that provides mechanical support with minimal material thickness. This thin film approach ensures high EUV transmittance while maintaining necessary mechanical strength through the nanotube network architecture.
2Illumination intensity
If the pellicle is made thinner to improve EUV transmittance, then transparency increases, but mechanical strength and protection capability decrease
Solution Approach 1:
The combination of nanotube membrane with multiple thin coating layers creates a composite structure where each component contributes specific properties. The nanotubes provide structural integrity while the coating layers add chemical stability, achieving both high transmittance and adequate strength in a thin configuration.
Solution Approach 2:
Different regions of the pellicle structure have specialized functions: the nanotube membrane provides mechanical support, while specific coating layers (silicide, AlN, TiN) are applied in thin configurations to provide localized chemical stability and surface protection without compromising overall transmittance.
3Reliability
If coating layers are added to enhance chemical stability, then protection from hydrogen radicals improves, but EUV transmittance may be reduced
Solution Approach 1:
Multiple thin coating layers (silicide, AlN, TiN) are applied in sequence, each providing specific chemical stability properties. The cumulative thickness is controlled to remain thin, ensuring that chemical protection is enhanced while EUV transmittance is maintained through optimized layer thickness and material selection.
Solution Approach 2:
The thickness and composition of each coating layer are precisely controlled as parameters. By adjusting these parameters, the pellicle achieves optimal balance between chemical stability (protection from hydrogen radicals) and EUV transmittance, with each layer contributing to protection while minimizing light loss.
4Ease of manufacture
If the pellicle structure is simplified, then manufacturing is easier, but protection capability against EUV radiation and hydrogen radicals is reduced
Solution Approach 1:
The multi-layer composite structure (nanotube membrane + silicide coating + AlN coating + TiN coating) provides comprehensive protection against EUV radiation and hydrogen radicals. Each layer is applied using standard thin-film deposition techniques, making the manufacturing process manageable despite the multiple layers.
Solution Approach 2:
The protection function is segmented into multiple specialized layers: nanotube membrane for structural support, silicide layer for chemical stability, AlN layer for additional protection, and TiN layer for surface properties. This segmentation allows each layer to be optimized for its specific function while using established manufacturing techniques.
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 nanotube-based pellicle achieves high EUV transmittance and mechanical strength, effectively preventing damage from EUV radiation and hydrogen radicals, ensuring prolonged operation and maintaining high transparency.
Implementation Method 1
a first coating layer made of silicide or a silicide-nitride is formed over each of the plurality of nanotubes
Implementation Method 2
The nanotube-based pellicle achieves high EUV transmittance and mechanical strength
Implementation Method 3
protect the photo mask from damage, dust and/or moisture
Data Source
AI summary
A pellicle for an extreme ultraviolet (EUV) photomask includes a pellicle frame and a main membrane attached to the pellicle frame. The main membrane includes a plurality of nanotubes, and each of the plurality of nanotubes is covered by a coating layer containing Si and one or more metal elements.