Reticle Pod Window Assembly for Sealed Alignment Verification
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Solution Overview
Problem
EUV lithography reticles are sensitive to contamination and misalignment during transportation and processing, leading to defective patterns on semiconductor wafers due to the lack of transparent materials for EUV radiation and relative movement between the reticle and container.
Innovation Solution
A pod for transporting reticles with a window assembly that includes a transparent plate and a seal, retained by a flange and retainer, allowing for alignment verification and minimizing contamination by eliminating the need for threaded fasteners, which reduces particle generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a sealed container is used to prevent contamination, then contamination protection is improved, but alignment verification becomes difficult
Solution Approach 1:
The container is segmented into a sealed interior space and an exterior environment, with a transparent window creating a controlled boundary that allows optical detection without compromising the sealed environment. This segmentation enables simultaneous contamination protection and alignment verification.
Solution Approach 2:
A transparent window assembly acts as an intermediary element between the sealed container interior and the external sensing equipment. It transmits EUV radiation and allows alignment verification while maintaining the seal integrity, serving as a mediator that reconciles the conflicting requirements.
2Strength
If threaded fasteners are used to secure the window assembly, then retention strength is improved, but particle generation increases
Solution Approach 1:
The patent replaces the traditional threaded mechanical fastening system with a friction-based retention system using a retainer and flange structure. This substitution eliminates threads that could generate particles, while maintaining adequate retention strength through distributed contact forces.
Solution Approach 2:
A flexible seal element (O-ring) is used in conjunction with the retainer to create a compliant sealing system that accommodates minor misalignments and maintains the seal without requiring rigid threaded fasteners. The flexible seal provides retention while minimizing particle generation risks.
3Object-affected harmful factors
If the container is completely sealed, then contamination protection is improved, but alignment sensing becomes impossible
Solution Approach 1:
The container wall is segmented to include a transparent window portion that allows EUV radiation transmission and alignment sensing, while the rest of the container remains fully sealed. This segmentation enables simultaneous contamination protection and precise alignment sensing.
Solution Approach 2:
The transparent window material is selected to have specific optical transmission properties that allow EUV radiation to pass through for alignment verification. The material's optical characteristics enable precise alignment sensing while maintaining the sealed environment for contamination protection.
Data Source
AI summary
A pod for transporting reticles includes an inner cover and an inner base plate. The inner base plate cooperates with the cover to establish a space for mounting a reticle. The inner base plate includes a hole having a perimeter and first and second flanges extending inward from the perimeter. A window assembly is mounted in the hole. The window assembly includes a transparent plate, a seal and a retainer. The seal contacts the outer or side planar surface of the transparent plate and the perimeter of the hole to seal an interface between the window assembly and the hole. The retainer contacts the second flange to retain the seal and transparent plate within the hole.