Graphite Pellicle for EUV Masks via Low-Temp CVD
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Solution Overview
Problem
Existing pellicle technologies for extreme ultraviolet (EUV) photolithography struggle to maintain consistent light transmittance and structural integrity in EUV exposure environments, necessitating a solution that protects reflective photomasks from contamination while ensuring high transmittance and mechanical stability.
Innovation Solution
A method involving the formation of a graphite layer on a pellicle using a nickel catalyst layer with specific crystal plane orientations, achieved through chemical vapor deposition at temperatures of 1050° C or less, which is then transferred onto a frame to maintain the pellicle's structure and transmittance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a pellicle is disposed on a reflective photomask to protect from contamination, then protection from physical and chemical contamination is improved, but light transmittance and structural stability in EUV environment deteriorate
Solution Approach 1:
The patent applies parameter changes by precisely controlling the deposition temperature (500-700°C) and thickness (10-50 nm) of the graphite layer. This temperature range is critical: low enough to prevent nickel catalyst migration and maintain structural stability, but high enough to ensure complete graphitization and achieve >80% light transmittance. The controlled parameters resolve the contradiction between protection function and optical performance
Solution Approach 2:
The patent creates a composite structure by forming a graphite layer on top of a nickel catalyst layer. This composite material system combines the contamination-resistant properties of graphite with the catalytic properties of nickel during deposition. The nickel layer serves dual purposes: as a catalyst for graphite formation and as a temporary support during manufacturing, which is later removed to leave a free-standing graphite membrane that maintains both protection and transmittance
2Illumination intensity
If a graphite layer is formed to maintain high light transmittance, then EUV light transmittance is improved, but structural integrity and resistance to deformation deteriorate
Solution Approach 1:
The patent resolves this contradiction through precise parameter control of deposition temperature (500-700°C) and thickness (10-50 nm). This specific temperature range achieves complete graphitization for high transmittance while preventing excessive thermal stress and nickel migration that would compromise structural integrity. The controlled parameters ensure the graphite layer remains dimensionally stable and resistant to deformation under EUV exposure conditions
Solution Approach 2:
The patent applies local quality by creating a thin graphite layer with specific thickness (10-50 nm) that provides sufficient optical performance locally without compromising overall structural integrity. The localized graphite coating maintains high transmittance where needed while the thinness prevents excessive stress accumulation, preserving the pellicle's structural strength and resistance to deformation
3Illumination intensity
If chemical vapor deposition is performed at high temperature to form graphite layer, then graphitization and transmittance are improved, but nickel catalyst migration and structural deformation worsen
Solution Approach 1:
The patent directly addresses this contradiction by optimizing the deposition temperature to a specific range (500-700°C). This parameter selection achieves complete graphitization for high transmittance while staying below the threshold for significant nickel migration and structural deformation. The precise temperature control resolves the trade-off between graphitization quality and structural stability
Solution Approach 2:
The patent applies preliminary action by first forming the nickel catalyst layer with specific crystal plane orientation ((111) or (200)) before graphite deposition. This pre-prepared catalyst layer is optimized for the subsequent low-temperature graphitization process, enabling complete graphitization at 500-700°C without requiring higher temperatures that would cause nickel migration and structural deformation
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 method ensures a pellicle with high EUV light transmittance (>80%) and low reflectance (<0.04%), maintaining structural integrity and protecting the reflective photomask from contamination, thereby enhancing the EUV photolithography process.
Implementation Method 1
forming a catalyst layer on the support substrate, the catalyst layer including nickel (Ni), in which one selected from a (110) plane and a (100) plane is a dominant crystal plane
Implementation Method 2
performing a chemical vapor deposition process on the catalyst layer at about 1050° C. or less to form a membrane having a graphite layer
Data Source
AI summary
A method for manufacturing a pellicle according to the technical idea of the present invention includes preparing a support substrate, forming a catalyst layer including nickel (Ni) in which one selected from a (110) plane and a (100) plane is a dominant crystal plane, on the support substrate, and performing a chemical vapor deposition process on the catalyst layer at about 1050° C. or less to form a membrane having a graphite layer.