Reticle SMIF Pod Layered Filter and Purge System
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Solution Overview
Problem
Current reticle/mask carriers in semiconductor manufacturing face challenges in controlling particulate and gas-phase contaminants, leading to contamination and degradation of the reticle surface during storage, transport, and processing, especially in extreme ultraviolet (EUV) photolithography, where existing solutions fail to maintain a clean environment effectively.
Innovation Solution
A reticle/mask carrier equipped with a layered filter system that selectively captures contaminants and can be regenerated by pressurized gas flow, combined with a large filter surface area to prevent particulate settlement on the reticle and a purging system using extremely clean dry air to control moisture levels and flush out contaminants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a hermetically sealed carrier is used to protect the reticle, then protection from external contaminants is improved, but pressure changes and turbulence inside the sealed environment cause particulate migration and contamination
Solution Approach 1:
The patent extracts the breathing apparatus and filtration system from the hermetically sealed carrier to address internal particulate migration. A filter is integrated into the carrier door that allows controlled air exchange while filtering out particulates, thereby maintaining the benefits of hermetic sealing while eliminating the harmful internal contamination effects.
Solution Approach 2:
The patent introduces a filter as an intermediary component between the internal sealed environment and the external atmosphere. This filter mediates the air exchange process, allowing pressure equalization and temperature regulation while blocking particulate contaminants, thus resolving the contradiction between maintaining hermetic seal and preventing internal contamination.
2Ease of operation
If the carrier door is opened for reticle access, then ease of operation is improved, but particulate incursion into the controlled environment increases
Solution Approach 1:
The patent implements preliminary action by equipping the carrier door with a filter before the door is opened. This pre-installed filter is ready to immediately filter air as the door opens, preventing particulate incursion during the critical transition period when the sealed environment is compromised, thus allowing easy reticle access while maintaining contamination protection.
Solution Approach 2:
The patent uses a filter integrated into the carrier door structure that acts as a flexible barrier. This filter allows the door to open for reticle access while maintaining the protective function, enabling operational ease without sacrificing contamination protection through the use of a thin film or filter material that can accommodate door movement.
3Ease of manufacture
If thin-walled SMIF pods are used for transport, then ease of manufacture and weight are improved, but wall movement due to pressure changes compromises sealing and allows particulate entry
Solution Approach 1:
The patent applies local quality by placing a filter specifically at the carrier door location where sealing is most vulnerable to pressure changes. This localized solution addresses the sealing integrity issue without requiring the entire pod structure to be thick-walled, thus maintaining ease of manufacture while improving reliability at the critical sealing point.
Solution Approach 2:
The patent effectively uses a composite structure combining the thin-walled pod material with a filter material at the door. This composite approach allows the pod to maintain its lightweight, easy-to-manufacture thin walls while the added filter component provides the necessary sealing and filtration function to maintain reliability under pressure changes.
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 solution effectively reduces the accumulation of contaminants within the carrier, extending the useful life of the reticle by maintaining a clean environment and preventing crystalline salt formation, thereby ensuring higher quality and longer functionality of the photomask.
Implementation Method 1
a first physisorptive filter element configured to specifically remove acids, organic and inorganic condensable contaminants
Implementation Method 2
a second filter element configured to specifically capture ammonia and moisture
Implementation Method 3
The filter media is selected to weakly bind to the contaminants so that the contaminants could be expelled from the filter by subjecting the filter to a flow of pressurized gas thereby regenerating the filter.
Implementation Method 4
a purging system using extremely clean dry air to control moisture levels and flush out contaminants
Data Source
AI summary
The present invention provides a standardized mechanical interface (SMIF) reticle pod that is configured to provide a controlled environment for supporting a reticle wherein the controlled environment is maintained substantially free of crystal growth causing contaminants. Accordingly, there is provided a layered filter with filter elements capable of filtering particulates and adsorbing gaseous contaminants. The filter has an inwardly facing face generally planar shaped with a surface area that is substantially half or more of the area of the reticle face. The inwardly facing face is placed in close proximity to the reticle patterned surface and has an area that is a significant fraction of the reticle patterned surface area. The SMIF pod is also provided with a purge system configured to inject a very dry gas within the controlled environment to flush the controlled environment of contaminants as well as to regenerate the filter.