Carbon-Based EUV Pellicle With Low Aqueous Outgassing
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Solution Overview
Problem
The deterioration of pellicle films due to oxidation under extreme ultra violet (EUV) light exposure environments is exacerbated by the generation of hydrogen radicals, hydrogen ions, and hydroxy radicals, which is not a significant concern under deep ultra violet (DUV) conditions, particularly affecting carbon-based pellicle films.
Innovation Solution
A pellicle comprising a carbon-based film with a carbon content rate of 40 mass % or more, a support frame, and an adhesive layer with controlled aqueous outgas, totaling 5.0×10−4 Pa·L/sec or less, to suppress film deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a carbon-based pellicle film is used in EUV light exposure, then the pellicle can maintain structural integrity and thermal stability, but the pellicle is highly susceptible to oxidation and deterioration due to generation of hydrogen radicals, hydrogen ions, and hydroxy radicals
Solution Approach 1:
The patent applies inert atmosphere principle by creating a vacuum environment (1×10−3 Pa or less) inside the pellicle to exclude oxygen and other reactive gases that would cause oxidation. This vacuum environment acts as an inert atmosphere that protects the carbon-based pellicle film from oxidation while allowing EUV light exposure to proceed effectively
Solution Approach 2:
The patent uses an adhesive layer as an intermediary substance between the pellicle film and the support frame. This adhesive layer serves as a barrier that prevents direct contact between the pellicle film and potentially harmful substances, while also providing necessary mechanical attachment and structural support
2Strength
If the adhesive layer has high moisture content, then the adhesive provides strong bonding, but the adhesive generates excessive aqueous outgas that deteriorates the pellicle film under EUV exposure
Solution Approach 1:
The patent applies parameter changes by precisely controlling the moisture content parameter of the adhesive layer to be 2.00 mass % or less. This parameter control reduces the amount of aqueous outgas generated during EUV exposure while maintaining sufficient bonding strength, thereby protecting the pellicle film from oxidation deterioration
Solution Approach 2:
The patent applies local quality by limiting the adhesive layer to specific locations only where mechanical attachment is needed (between pellicle film and support frame), rather than covering the entire pellicle surface. This localized application minimizes the total amount of adhesive and consequently the total aqueous outgas while maintaining necessary bonding strength
3Productivity
If the pellicle is exposed to EUV light, then the exposure process can be performed, but the pellicle experiences repeated heating and cooling cycles that accelerate oxidation and deterioration
Solution Approach 1:
The vacuum environment created inside the pellicle serves as an inert atmosphere that prevents oxygen from reaching the carbon-based pellicle film during thermal cycles. This protects the pellicle from oxidation that would otherwise be accelerated by the repeated heating and cooling during EUV exposure
Solution Approach 2:
The patent extracts oxygen and other reactive gases from the environment inside the pellicle by creating a vacuum (1×10−3 Pa or less). This removal of harmful gases eliminates the oxidizing agents that would otherwise accelerate deterioration during thermal cycles, while allowing the pellicle to maintain structural integrity during EUV exposure
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 effectively reduces the generation of radicals and maintains film integrity by controlling outgas emissions, thereby preventing oxidation and ensuring reliable EUV lithography performance.
Implementation Method 1
hydrogen gas present in an exposure atmosphere absorbs EUV light to be ionized, and hydrogen radicals, hydrogen ions, hydrogen plasma, and the like are generated
Implementation Method 2
residual moisture or the like present in the exposure atmosphere absorbs EUV light to generate hydroxy radicals, oxygen radicals, and the like
Implementation Method 3
the total amount of aqueous outgas of 5.0×10−4 Pa·L/sec or less in an atmosphere of 23° C. and 1×10−3 Pa or less
Data Source
AI summary
A pellicle including: a pellicle film including a carbon-based film having a carbon content rate of 40 mass % or more; a support frame that supports the pellicle film; and an adhesive layer containing an adhesive, the pellicle having the total amount of aqueous outgas of 5.0×10−4 Pa·L/sec or less in an atmosphere of 23° C. and 1×10−3 Pa or less.