Pellicle Frame Para-xylylene Polymer Coating Haze Reduction
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Solution Overview
Problem
The increasing energy of shorter wavelength exposure light in photolithography processes leads to the occurrence of haze on photomask substrates due to the release of acidic components from anodized coatings on pellicle frames, which reduces semiconductor production yield, and existing countermeasures either compromise visibility during extraneous-material inspection or do not completely prevent haze.
Innovation Solution
A pellicle frame coated with a transparent layer of para-xylylene-based polymer, particularly poly-chloro-para-xylylene, is used to inhibit the release of sulfate and ammonium ions, reducing haze occurrence while maintaining visibility for inspection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If anodized coating is applied to the pellicle frame, then the exposure light reflection is prevented and inspection visibility is improved, but acidic components are released under exposure environment causing haze occurrence
Solution Approach 1:
The coating is divided into two functional layers: an anodized coating layer for light absorption and inspection visibility, and a para-xylylene-based polymer coating layer to prevent ion release and haze formation. This segmentation allows each layer to perform its specific function without interfering with the other.
Solution Approach 2:
The para-xylylene-based polymer coating acts as an intermediary layer between the anodized coating and the exposure environment. It prevents the release of sulfate and ammonium ions from the anodized coating while allowing the anodized coating to maintain its light-absorbing function for inspection visibility.
2Productivity
If shorter wavelength exposure light is used, then the resolution and productivity are improved, but the energy increases causing more haze occurrence due to ion release
Solution Approach 1:
The para-xylylene-based polymer coating is applied in advance to the anodized pellicle frame to create a protective barrier that prevents the release of sulfate and ammonium ions before exposure to high-energy shorter wavelength light occurs. This preliminary protective action eliminates the harmful effect of ion release while allowing the benefits of high-productivity shorter wavelength 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 use of a para-xylylene-based polymer coating on the pellicle frame effectively reduces the release of ions causing haze, thereby inhibiting its occurrence under exposure environments and ensuring clear inspection without compromising visibility.
Implementation Method 1
a pellicle frame of a pellicle, coated with a layer containing a para-xylylene-based polymer... effectively reduces the release of ions causing haze
Implementation Method 2
The reason why the aluminum alloy used for the pellicle frame is subjected to the black alumite process is to prevent the exposure light from being reflected by the pellicle frame
Data Source
AI summary
The present invention is directed to a pellicle frame of a pellicle for use in photolithography, comprising: a coating of a layer containing a para-xylylene-based polymer. The invention can inhibit release of sulfate ions, ammonium ions and so on from the pellicle frame and thereby reduce the occurrence of haze under exposure environment.