Nanotube Pellicle Membrane for EUV Lithography
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Solution Overview
Problem
Current EUV lithography pellicles lack chemical durability and stability against hydrogen radicals, limiting their use in high-intensity EUV environments, and existing materials with high EUV transmittance are difficult to commercialize due to crystallization, thickness uniformity, and defect control challenges.
Innovation Solution
A nanotube-based pellicle membrane with a reticular structure, incorporating uncoated and coated nanotubes coated with metals or metal compounds like Mo, Si, Zr, Nb, Ru, Y, La, or Ce, and their alloys, which are chemically vapor deposited or physically vapor deposited, and heat-treated for enhanced stability and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional pellicle materials are used for EUV lithography, then EUV transmittance can be maintained, but chemical durability and stability against hydrogen radicals are insufficient
Solution Approach 1:
The patent employs composite materials by combining nanotubes (carbon nanotubes, boron nitride nanotubes, silicon carbide nanotubes, or boron carbon nitride nanotubes) with metal or metal compound coatings (such as Mo, Si, Zr, Nb, Ru, Y, La, Ce, or their alloys). This composite structure provides both the mechanical stability and EUV transmittance of nanotubes and the chemical durability of metal coatings, resolving the contradiction between reliability and ease of manufacture.
Solution Approach 2:
The patent changes the physical and chemical parameters of the pellicle membrane by controlling the thickness of the nanotube network (0.6 to 200 nm) and the coating layer, and by selecting specific metal compounds (nitride, oxide, carbide, boride, silicide, phosphide, or sulfide). These parameter optimizations enable the membrane to withstand hydrogen radicals while maintaining EUV transmittance and manufacturability.
2Illumination intensity
If existing materials with high EUV transmittance are used, then optical properties are improved, but crystallization, thickness uniformity, and defect control become difficult
Solution Approach 1:
The patent uses a flexible nanotube-based thin film structure with thickness of 0.6 to 200 nm that can be deposited as a uniform network. The nanotube network forms a reticular structure that inherently provides thickness uniformity while maintaining high EUV transmittance, avoiding the crystallization and defect issues associated with conventional thin film materials.
Solution Approach 2:
The nanotube-based membrane forms a porous reticular structure that allows precise control of thickness and uniformity. The interconnected nanotube network provides both high EUV transmittance through the porous structure and manufacturing precision through controlled deposition processes, eliminating the trade-off between optical properties and thickness uniformity.
3Illumination intensity
If the pellicle membrane is made thinner to improve EUV transmittance, then optical properties are enhanced, but mechanical stability and resistance to mechanical stress decrease
Solution Approach 1:
The patent applies local quality by creating a non-uniform nanotube distribution where the edge portion has a higher density of nanotubes than the central portion. The edge portion, which requires higher mechanical stability to support the membrane structure, has increased nanotube density, while the central portion maintains lower density for optimal EUV transmittance. This resolves the contradiction between thickness/transmittance and mechanical stability.
Solution Approach 2:
The composite structure of nanotubes provides exceptional mechanical strength-to-thickness ratio. The nanotube network maintains mechanical stability even at thicknesses of 0.6 to 200 nm, enabling high EUV transmittance while resisting mechanical stress through the inherent strength of the nanotube composite material.
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 membrane improves chemical durability while maintaining optical, thermal, and mechanical stability, effectively withstanding mechanical stress and hydrogen radicals, and supports higher EUV output intensities.
Implementation Method 1
The coating layer is formed by coating at least part of the nanotubes with a metal or metal compound through chemical vapor deposition (CVD)
Implementation Method 2
The coating layer is formed by coating at least part of the nanotubes with a metal or metal compound through physical vapor deposition (PVD)
Implementation Method 3
The capping layer may be formed by coating the metal or the metal compound on the core layer and then performing heat treatment at a temperature of 200 to 1500° C.
Data Source
AI summary
Proposed is a pellicle for extreme ultraviolet (EUV) lithography based on a nanotube and having good optical properties, thermal stability, mechanical stability and chemical durability. The pellicle may include a frame having an opening formed in a central portion, and a pellicle membrane supported by the frame and covering the opening. The pellicle membrane may be formed in a reticular structure based on nanotubes, and include a coating layer formed by coating at least part of the nanotubes with a metal or metal compound. The metal or metal compound may be based on at least one of Mo, Si, Zr, Nb, Ru, Y, La, or Ce, or any alloy thereof.