Wafer Stocker Shutter System for Clean Atmosphere Control
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Solution Overview
Problem
In semiconductor manufacturing, wafer stockers face challenges in preventing external atmosphere infiltration, maintaining a clean environment, and minimizing gas consumption during wafer storage and conveyance, which can lead to dust contamination and incomplete processing due to natural oxide film formation.
Innovation Solution
A storage container design with a shutter system that maintains a higher internal pressure than the external environment, using a nozzle to supply inert gas and prevent dust infiltration, and allows for vertical motion of shield plates to minimize contact and gas leakage, enabling efficient wafer conveyance and storage while maintaining a clean atmosphere.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If storage rings are lifted by the opening means to enable wafer conveyance, then wafer access is enabled, but dust is generated from collision between storage rings which contaminates wafers
Solution Approach 1:
A shutter is introduced as an intermediary component between the storage rings and the external environment. The shutter opens to enable gripper access to storage rings during wafer conveyance, and closes to prevent dust generated from storage ring movement from contaminating the wafers. This mediator allows selective access while maintaining protection.
Solution Approach 2:
The storage container maintains an inert gas atmosphere (nitrogen or other inert gas) at a pressure higher than the external environment. This positive pressure inert atmosphere prevents external dust from entering and also suppresses the dispersion of dust generated during storage ring operations, keeping the internal environment clean for wafer storage.
2Ease of operation
If a large opening area is provided for wafer conveyance, then wafer access is improved, but external atmosphere including dust is sucked into the storage space
Solution Approach 1:
Instead of creating a negative pressure environment that would suck external atmosphere in, the invention inverts the approach by maintaining positive pressure inside the storage container. The internal inert gas pressure is higher than external atmospheric pressure, so when the shutter is open, gas flows outward rather than allowing external atmosphere to infiltrate inward.
Solution Approach 2:
The shutter acts as a controllable intermediary that separates the internal clean environment from the external environment. It allows selective opening for gripper access while maintaining the pressure differential that prevents external atmosphere infiltration during the brief periods when access is required.
3Object-affected harmful factors
If inert gas is supplied to maintain internal atmosphere, then dust infiltration is prevented, but gas consumption increases
Solution Approach 1:
The shutter operates periodically - remaining closed most of the time to maintain the inert gas atmosphere with minimal consumption, and opening only briefly when wafer conveyance is required. This periodic operation reduces the total amount of inert gas needed to maintain the internal atmosphere compared to continuous operation.
Solution Approach 2:
The system monitors the internal pressure and oxygen concentration, adjusting the inert gas supply rate accordingly. When the shutter is closed and the environment is stable, gas supply is minimized. When the shutter opens or oxygen concentration increases, gas supply is increased to restore the proper atmosphere, optimizing gas consumption based on actual conditions.
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 prevents external atmosphere infiltration, reduces dust contamination, and minimizes gas consumption, ensuring a clean environment for wafer storage and processing, thereby enhancing processing yield and efficiency.
Implementation Method 1
a body opening portion through which a wafer is conveyed; a shutter that opens and closes the body opening portion; a nozzle that supplies clean gas into the internal space
Implementation Method 2
a shutter opening/closing unit that opens and closes the shutter; a lift drive portion that moves the shutter in the vertical direction
Implementation Method 3
multiple shelf plates that are layered and fixed at regular intervals through spacers so as to be parallel to each other in the vertical direction
Data Source
Figure 1
Figure 2
Figure 3(a)~3(c)
AI summary
Provided is a wafer stocker that can prevent the inflow of an external atmosphere, maintain a wafer storage space at a desired atmosphere with a relatively small amount of gas, and prevent dust from being attached to a wafer surface. A shutter portion, including multiple shield plates having the same height as an interval between shelf plates disposed in a storage container, is disposed with a slight space from a body portion, and by supplying clean gas into the storage container, a clean atmosphere of a higher pressure than an external environment is maintained, and a shutter portion is opened and closed by moving up and down the shield plate independently from the shelf plate that supports a wafer.