Holding Device Load Detection via Pressure Segmentation
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Solution Overview
Problem
Existing transport devices for substrates in lithographic apparatuses face issues with accurate load presence detection due to substrate shape irregularities, such as concavity, convexity, warpage, and holes, which can lead to erroneous detection and inadequate adsorption pressure changes.
Innovation Solution
A transport device with a holding device that includes a base with an intake hole and an exhaust flow path, a movable support member that contacts the substrate, and a pressure determination unit to assess adsorption pressure changes, ensuring accurate load presence detection regardless of substrate shape through frictional holding rather than vacuum adsorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If vacuum adsorption is used to hold the substrate, then the substrate can be secured during transport, but load presence detection becomes inaccurate when the substrate has shape irregularities such as holes, concavities, or warpage
Solution Approach 1:
The holding surface is divided into multiple independent adsorption holes instead of using a single large adsorption area. This segmentation allows the system to detect load presence through pressure changes in individual holes, making detection more reliable even when the substrate has irregularities in certain areas.
Solution Approach 2:
The adsorption holes serve dual functions: they enable vacuum adsorption to hold the substrate during transport, and they simultaneously provide pressure change detection for load presence detection. This multi-functionality eliminates the need for separate detection mechanisms and ensures both functions work reliably together.
2Force
If an adsorption hole is provided in the holding portion for vacuum adsorption, then the substrate can be held securely, but the adsorption pressure force change becomes insufficient when the substrate has holes or concavities
Solution Approach 1:
Multiple adsorption holes are distributed across the holding surface, allowing the system to accumulate pressure force changes from multiple contact points. This segmentation ensures that even if some holes have reduced contact due to substrate irregularities, the overall pressure force change remains sufficient for reliable detection.
Solution Approach 2:
The exhaust flow path acts as an intermediary that transmits pressure changes from the adsorption holes to the pressure sensor. By monitoring the pressure in this intermediate flow path, the system can accurately detect load presence even when direct contact between the substrate and holding surface is imperfect.
3Measurement precision
If a pressure sensor is added to detect adsorption pressure changes for load presence detection, then detection accuracy improves, but device complexity and cost increase
Solution Approach 1:
The exhaust unit and exhaust flow path, which are already necessary for vacuum adsorption, are utilized dual-purpose for both substrate holding and load presence detection. This eliminates the need for additional dedicated detection components, maintaining device simplicity while achieving accurate detection.
Solution Approach 2:
The system uses its own exhaust flow path and pressure characteristics to perform self-diagnosis of load presence. The pressure sensor monitors the natural pressure changes in the exhaust flow path that occur during normal operation, allowing the system to detect substrate loading without requiring external or additional complex detection mechanisms.
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 enables reliable load presence detection without being affected by substrate shape irregularities, improving detection accuracy and preventing substrate movement or drop during transport, while being cost-effective and compact compared to using optical or contact sensors.
Implementation Method 1
determine whether the moving member holds the substrate on the basis of changes in pressure of the exhaust flow path exhausted by an exhaust unit
Implementation Method 2
a moving member which is movable in a gravity direction by coming into contact with the substrate
Data Source
AI summary
A holding device for holding a substrate includes a base including an intake hole and an exhaust flow path communicating with the intake hole, a moving member which is movable in a gravity direction by coming into contact with a substrate, and a determination unit configured to determine whether a moving member holds a substrate on the basis of changes in pressure of the exhaust flow path exhausted by an exhaust unit.