Boron Nitride Nanotube Pellicles for EUV Plasma Resistance
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Solution Overview
Problem
Current pellicle materials, including carbon nanotube (CNT) based ones, have limited lifetimes due to reactions with gases and plasmas in lithographic processes, and there is a need for materials with superior mechanical, temperature, and chemical stability to withstand these conditions without deteriorating or reacting with free radicals.
Innovation Solution
Boron nitride nanotube (BNNT) based pellicles are developed, which have high thermal stability and chemical resistance to lithographic process gases and plasmas, allowing for heat treatment to remove contaminants, and are fabricated with aligned BNNTs to form self-supporting films with high transparency and controlled porosity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current pellicle materials (CNT-based) are used, then they can be fabricated and provide basic filtration function, but they have limited lifetimes due to reactions with gases and plasmas in lithographic processes
Solution Approach 1:
The patent changes the material composition parameter from carbon-based (CNT) to boron nitride-based nanotubes, which fundamentally alters the chemical stability parameter. BNNTs have higher thermal and chemical stability thresholds that exceed the reaction temperatures and chemical environments of lithographic processes, thereby eliminating the harmful reactions that limit CNT pellicle lifetimes.
Solution Approach 2:
The patent employs boron nitride nanotubes as a composite material structure that combines the mechanical strength of nanotubes with the chemical stability of boron nitride. This composite structure provides both the filtration function and the resistance to chemical degradation, resolving the contradiction between providing basic filtration and resisting chemical reactions.
2Reliability
If pellicle materials are made more stable to withstand lithographic processes, then chemical resistance improves, but mechanical properties and fabricability may be compromised
Solution Approach 1:
The patent changes the material parameters to boron nitride nanotubes which inherently possess high mechanical strength and thermal stability. The material parameters (thermal stability threshold, chemical reaction threshold) are changed to values exceeding lithographic process conditions, allowing the material to be fabricated and used without sacrificing mechanical properties for chemical resistance.
3Illumination intensity
If pellicles are made thinner to improve light transmission, then transparency increases, but mechanical strength and structural integrity decrease
Solution Approach 1:
The patent uses boron nitride nanotube thin films that maintain structural integrity at reduced thicknesses. The nanotube structure provides inherent mechanical strength even in thin configurations, allowing the pellicle to be made thinner for improved light transmission while maintaining the necessary mechanical strength and structural integrity.
Solution Approach 2:
The patent employs boron nitride nanotubes as a composite material that provides both optical transparency and mechanical strength in thin film configurations. The unique structure of BNNTs allows for thin-film formation that maintains both light transmission capability and structural integrity, resolving the contradiction between thickness reduction for transparency and maintenance of mechanical strength.
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
BNNT pellicles maintain shape and transparency, effectively preventing particulate entry while allowing gas exchange, with improved mechanical, temperature, and chemical stability, reducing adverse reactions and extending lifespan.
Implementation Method 1
BNNTs also provide excellent thermal conductivity, which may be advantageous for reducing undesirable temperature increases during processing
Implementation Method 2
the BNNT pellicles can be heat treated to temperatures that will outgas or otherwise remove contaminants that may collect on the pellicles from gases and plasmas utilized in the lithographic processes
Data Source
AI summary
Described herein are thin-film BNNT materials, and methods for making the same. Such materials are especially useful for forming BNNT-based pellicles used in, e.g., Extreme Ultraviolet (EUV) lithographic processes. BNNTs have thresholds for thermal stability and chemical reactions that are above the reaction temperatures associated with EUV lithography and the gases and plasmas formed therein, and in addition, the BNNT-based pellicles can be heat treated to temperatures that will outgas or otherwise remove contaminants that may collect on the pellicles from gases and plasmas utilized in the lithographic processes. BNNTs are have favorable transmissivity and also provide excellent thermal conductivity, which may be advantageous for reducing undesirable temperature increases during processing. Thin-film BNNT materials described herein have the mechanical and tensile strengths to self-support, and withstand lithography processes without mechanical failure.