EUV Photomask Unit Pellicle Frame Positioning
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Solution Overview
Problem
The challenge in forming microscopic patterns of 32 nm or smaller on a photoresist film using EUV exposure techniques is exacerbated by the difficulty in preventing outgassing from organic materials in conventional pellicle frames, which can degrade the flatness of the photomask and reduce yield ratios in semiconductor and liquid crystal display panel manufacturing.
Innovation Solution
A photomask unit is designed with a pellicle frame fixed onto a stage outside the photomask's attachment area, using electrostatic chucks or mechanical means to prevent outgassing, ensuring the pellicle frame does not directly attach to the photomask, thus maintaining photomask flatness and preventing exposure interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pellicle frame is attached to the photomask using organic adhesive materials, then the pellicle can be securely mounted to protect against dust particles, but outgassing from the organic materials degrades the photomask flatness and reduces manufacturing yield
Solution Approach 1:
The patent removes the pellicle frame from the photomask surface entirely, extracting the source of outgassing. Instead of attaching the frame to the photomask, it is positioned separately, eliminating the harmful interaction while preserving the protective function through alternative means.
Solution Approach 2:
The patent introduces a barrier layer as an intermediary between the pellicle frame and the photomask. This barrier prevents direct contact and eliminates the outgassing pathway from organic adhesives while still allowing the pellicle to perform its dust protection function.
2Strength
If organic adhesive materials are used to mount the pellicle frame, then secure attachment is achieved, but outgassing occurs that interferes with EUV exposure and reduces yield ratios
Solution Approach 1:
The patent extracts the pellicle frame from direct contact with the photomask, removing the source of outgassing. The frame is repositioned separately, eliminating the harmful effect while the attachment function is maintained through alternative positioning strategies.
Solution Approach 2:
The patent creates an inert environment by positioning the pellicle frame outside the vacuum exposure chamber or using non-outgassing materials, thereby eliminating the harmful outgassing effect that would otherwise occur with organic adhesives in the EUV exposure environment.
3Reliability
If the pellicle frame is positioned to cover the entire photomask area, then complete dust protection is achieved, but the complexity of the structure increases and manufacturing becomes more difficult
Solution Approach 1:
The patent divides the protective function into segments: the pellicle membrane provides the primary dust barrier, while the frame serves as a structural support positioned separately. This segmentation reduces overall structural complexity while maintaining protective coverage.
Solution Approach 2:
The patent makes the pellicle membrane itself multi-functional by designing it to provide both the dust barrier function and the structural support that was previously required from the frame, thereby eliminating the need for a separate complex frame structure.
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
This configuration allows for reliable formation of microscopic patterns of 32 nm or smaller on photoresist films using EUV exposure while maintaining the photomask's flatness and preventing adverse effects from outgassing, thereby improving yield ratios in semiconductor and liquid crystal display panel production.
Implementation Method 1
a pellicle membrane (6) made of a material having a high transmittance with respect to an exposure light
Implementation Method 2
fixing the pellicle frame (7) onto the stage (3) at a region outside of a region of the stage (3) onto which the photomask (2) is fixed
Data Source
Figure 1
Figure 2
Figure 3
AI summary
It is an object of the present invention to provide a photomask unit suitable for forming a microscopic pattern of 32 nm or smaller on a photoresist film using the EUV exposure technique and being able to reliably prevent the flatness of a photomask from being lowered. The photomask unit 1 according to the present invention includes a pellicle membrane 6, a pellicle frame 7 onto one surface of which a region of the pellicle membrane 6 in the vicinity of side portions of the pellicle membrane 6 is fixed, a photomask 2 and a stage 3 onto one surface of which the photomask 2 and the pellicle frame 7 are fixed, and the pellicle frame 7 is fixed onto the stage 3 at a region outside of a region of the stage 3 onto which the photomask 2 is fixed.