Hollow Pellicle Frame Design for PID Suppression
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Solution Overview
Problem
Conventional pellicle frames cause Pellicle Induced Distortion (PID) in photomasks due to stress and deformation, which affects the positional accuracy of patterns in semiconductor manufacturing, and existing solutions either increase the surface area for particle inspection or provide limited PID suppression.
Innovation Solution
A pellicle frame with a polygonal shape and hollow portions inside the corner and straight sections, where the hollow portion in the corner has a larger cross-sectional area than in the straight section, reducing the sectional secondary moment of inertia and stress, thereby effectively suppressing PID.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the pellicle frame is made with conventional solid structure, then the frame maintains structural integrity, but the frame causes Pellicle Induced Distortion (PID) and stress when attached to the photomask
Solution Approach 1:
The pellicle frame incorporates hollow portions (void spaces) within its structure, creating a porous-like configuration that reduces the frame's rigidity and stress generation. The hollow portions are positioned strategically inside the frame body without compromising the overall structural integrity, thereby reducing PID while maintaining reliability.
Solution Approach 2:
The pellicle frame uses a composite structure combining solid frame material with hollow portions, creating a lightweight yet strong configuration. This composite approach allows the frame to maintain sufficient structural integrity while reducing the secondary moment of inertia and minimizing stress-induced distortion on the photomask.
2Manufacturing precision
If the pellicle frame cross-sectional area is reduced to suppress PID, then the distortion is reduced, but the frame strength and rigidity are compromised
Solution Approach 1:
The pellicle frame is segmented into multiple regions including hollow portions and solid portions. This segmentation allows different parts of the frame to have different functional characteristics - the hollow portions reduce the secondary moment of inertia for PID suppression, while the solid portions maintain necessary strength and rigidity.
Solution Approach 2:
The frame structure exhibits local quality variations with hollow portions positioned at specific locations to reduce stress concentration and secondary moment of inertia where it most affects PID. The solid portions are positioned where structural strength is critical, creating a non-uniform distribution of material properties that optimizes both PID suppression and frame strength.
3Manufacturing precision
If hollow portions are added to the pellicle frame to reduce PID, then the sectional secondary moment of inertia is reduced, but the manufacturing complexity increases
Solution Approach 1:
The frame manufacturing process is segmented into distinct steps: forming the hollow portions first, then forming the solid portions. This segmentation simplifies the overall manufacturing complexity by breaking down the complex hollow structure into manageable sequential operations rather than attempting to create the entire complex structure in one step.
Data Source
AI summary
There is provided a pellicle frame and a pellicle using the frame, which has a hollow space inside a corner portion of the frame and optionally one or more hollow spaces in a straight portion (bar) of the frame, and also a hollow space in a corner portion of the frame may communicate with a neighboring hollow space in a straight portion of the frame.