Wafer Cassette Stocker Drying Chamber for Haze Prevention
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Solution Overview
Problem
Wafer cassettes, particularly those made of polycarbonate, suffer from time-dependent haze (TDH) due to residual moisture, leading to contamination of silicon wafers stored in them.
Innovation Solution
A wafer cassette stocker equipped with chambers and a humidity controller that supplies compressed dry air to remove moisture, using a system of supply and discharge lines, heaters, and panels with varying hole sizes to control humidity and temperature, ensuring effective drying.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wafer cassettes are cleaned and stored in a stocker, then the cassettes are ready for use, but residual moisture causes time-dependent haze (TDH) on the wafers
Solution Approach 1:
The patent applies preliminary action by implementing a drying process before storing the cleaned wafer cassettes in the stocker. The drying chamber removes residual moisture from the cassettes using heated air circulation and heating elements, ensuring that cassettes are completely dry before being transferred to storage chambers. This preliminary drying action prevents TDH from occurring during subsequent storage.
Solution Approach 2:
The patent applies parameter changes by controlling temperature and humidity parameters in the drying chamber. The heating elements increase the temperature to evaporate moisture, while the air circulation system controls humidity levels. By adjusting these parameters, the system effectively removes residual moisture from the cassettes, preventing TDH formation during storage.
2Reliability
If compressed dry air is supplied to remove moisture from cassettes, then TDH is prevented, but the system complexity increases
Solution Approach 1:
The patent applies universality by designing the stocker system to perform multiple functions within a single integrated structure. The stocker includes both drying chambers with heating and air circulation capabilities, and storage chambers, all within one system. The compressed air supply system serves both drying purposes and potential cleaning functions, reducing the need for separate dedicated systems.
Solution Approach 2:
The patent applies self-service by implementing air circulation systems within the chambers that automatically distribute compressed dry air throughout the storage and drying spaces. The system uses internal fans and ducts to ensure uniform moisture removal without requiring external manual intervention, simplifying operation while maintaining effective humidity control.
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 the occurrence of time-dependent haze by removing moisture from wafer cassettes, maintaining a suitable environment and preventing haze formation on the wafers.
Implementation Method 1
a heater installed between the supply lines
Implementation Method 2
supplying compressed dry air (CDA) to interiors of the chambers, thereby controlling humidity of the cassettes
Data Source
AI summary
An embodiment provides a wafer cassette stoker comprising: a cassette on which a plurality of wafers are loaded; a plurality of chambers disposed in one line while forming at least one layer, wherein the cassette after being cleaned is inserted in each of the chambers and a humidity control unit for supplying a compressed dry air (CDA) into the insides of the chambers so as to control humidity of the cassette.