Wafer Container Ballast System for Stability
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Solution Overview
Problem
Front opening wafer containers, especially those for 300 mm and 450 mm diameter wafers, face stability and seating issues due to their design, which causes the center of gravity to shift forward, leading to potential contamination and instability during handling and purging processes.
Innovation Solution
A low-profile ballast system is introduced that can be retrofitted to existing wafer containers, adjusting the center of gravity by adding weight to the kinematic coupling plate without modifying the container's shell, thereby enhancing stability and preventing 'lift off' during purging operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a door and frame are added to the front of the wafer container for sealing and access, then the container can be opened and closed robotically, but the center of gravity shifts forward causing instability and pitching during handling
Solution Approach 1:
A ballast weight is added to the rear of the wafer container to counterbalance the forward shift in center of gravity caused by the door and frame assembly. The ballast creates a counteracting moment that stabilizes the container during robotic handling, preventing excessive pitching while maintaining the ability to open and close the door robotically.
2Productivity
If the container size is increased to accommodate larger 450 mm wafers, then more wafers can be processed, but the container becomes less stable and harder to seat precisely on machine interfaces
Solution Approach 1:
The ballast weight compensates for the increased moment of inertia and reduced stability of larger 450 mm wafer containers, enabling precise seating on kinematic coupling interfaces despite the increased size and weight of the container.
3Device complexity
If the center of gravity is positioned forward to accommodate the door assembly, then the container structure is simplified, but the container experiences lift-off during purging operations
Solution Approach 1:
The rear-mounted ballast weight prevents lift-off of the container during nitrogen purging operations by providing a downward moment that counteracts the upward force generated by purge gas flow under the container, ensuring reliable retention on the machine interface.
4Stability of the object's composition
If a traditional ballast system is used to correct center of gravity, then stability is improved, but the container requires modifications to the shell which increases complexity
Solution Approach 1:
The ballast system is designed as a separate, modular component that attaches to the rear of the container without requiring modifications to the container shell. This segmentation allows the ballast to be installed independently, preserving the original container design while achieving the desired center of gravity adjustment.
Solution Approach 2:
A mounting bracket or adapter serves as an intermediary component between the ballast weight and the container, allowing the ballast to be attached to the rear flange or bottom surface without drilling or modifying the container shell, thus maintaining structural integrity while achieving stability.
Data Source
AI summary
Apparatuses and methods providing a ballast system for adjusting the center of gravity of a standardized front opening wafer container. Various embodiments of the disclosure present ballast systems that are low profile, do not require modifications to the shell of the wafer container, and can be retrofit to existing wafer carriers. In some embodiments, these capabilities are accomplished by a ballast that mounts to a kinematic coupling plate of the wafer container. In one embodiment, the ballasting can also provide sufficient counter force to the lifting forces associated with purging of the wafer container, thereby preventing “lift off” of the wafer container during purging operations. The ballasts can be removed for shipping of the wafer container, thereby decreasing shipping costs.