Wafer stocker
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Solution Overview
Problem
In semiconductor device manufacturing, existing wafer stockers face challenges in maintaining a clean atmosphere around wafers due to dust and moisture from FOUPs, which are difficult to control when the entire FOUP is stored, leading to contamination and reduced cleanliness.
Innovation Solution
A wafer stocker design that stores wafers in multiple stages within smaller wafer cassettes, using a loading device, wafer transfer robot, wafer cassette delivery device, and fan filter unit to generate a laminar flow, reducing dust scattering and improving transfer efficiency while minimizing gas usage and running costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the entire FOUP is stored in the stocker, then the storage capacity is increased, but the atmosphere around wafers deteriorates due to dust and moisture from the FOUP
Solution Approach 1:
The patent divides the storage system into two separate components: the FOUP (front-opening unified pod) for bulk storage and the wafer cassette for individual wafer handling. The FOUP stores multiple wafers in a sealed environment, while the wafer cassette holds a limited number of wafers (typically 25) and is the only component that enters the cleanroom stocker. This segmentation allows the stocker to maintain a clean atmosphere by excluding the larger FOUP containers, thus resolving the contradiction between storage capacity and atmospheric purity.
Solution Approach 2:
The wafer cassette acts as an intermediary between the FOUP and the cleanroom stocker environment. Wafers are transferred from the FOUP to the cassette in a controlled manner, and the cassette serves as the interface that interacts with the stocker's clean atmosphere. This intermediary approach allows the system to maintain high storage capacity through FOUPs while preserving the clean atmosphere in the stocker through the use of smaller cassettes.
2Object-affected harmful factors
If smaller wafer cassettes are used instead of entire FOUPs, then the atmosphere cleanliness is improved, but the device complexity increases due to additional transfer mechanisms
Solution Approach 1:
The system employs automated transfer mechanisms that operate autonomously without requiring manual intervention. The FOUP loader automatically loads FOUPs into the stocker, the wafer transfer robot autonomously transfers wafers between FOUP and cassette, and the cassette delivery device self-manages cassette positioning. This automation reduces operational complexity despite the multi-component system, as the devices serve themselves through programmed sequences.
Solution Approach 2:
The patent replaces manual mechanical operations with automated robotic systems. Instead of manually transferring wafers from FOUP to cassette, a wafer transfer robot with automated grippers and positioning systems performs the task. The FOUP loader and cassette delivery device similarly replace manual loading and positioning operations. This substitution reduces operational complexity by eliminating human intervention while maintaining precise control over the transfer processes.
3Quantity of substance
If multiple wafer cassettes are stored in the stocker, then the number of stored wafers is increased, but the footprint of the stocker increases
Solution Approach 1:
The patent utilizes vertical space by arranging wafer cassettes in multiple stages or levels within the stocker. Instead of placing cassettes only in a single horizontal plane, the system stacks them vertically across multiple floors or tiers. This three-dimensional arrangement allows the stocker to accommodate a large number of cassettes (and thus wafers) while maintaining a compact horizontal footprint, effectively resolving the contradiction between storage quantity and device area.
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 maintains a clean atmosphere around wafers, reduces contamination, allows for a more compact and efficient storage system, and decreases the footprint of the stocker while increasing the number of stored wafers, thereby enhancing the overall cleanliness and operational efficiency.
Implementation Method 1
a fan filter unit configured to generate a laminar flow in a wafer transfer space of the housing in which the wafer transfer robot is arranged and in a wafer cassette transfer space of the housing in which the wafer cassette delivery device is arranged
Data Source
AI summary
A wafer stocker is capable of further improving an environment around wafers. The wafer stocker includes a housing, a loading device provided on a front surface of the housing, a wafer cassette shelf arranged in the housing, a wafer transfer robot configured to move the wafers from a transfer container mounted on the loading device to a wafer cassette in the wafer cassette shelf, a wafer cassette delivery device configured to move the wafer cassette in the wafer cassette shelf to a stage having a different height, and a fan filter unit configured to generate a laminar flow in a wafer transfer space and in a wafer cassette transfer space.