Vacuum Holding Unit Flow Monitoring for Attraction Abnormalities
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Solution Overview
Problem
Existing holding devices struggle to accurately determine attraction abnormalities due to minute changes in surface state or foreign substances, leading to difficulties in maintaining precise holding of substrates and molds.
Innovation Solution
A holding device with a configuration that includes a holding unit, first and second pressure mechanisms, and a controller to measure flow rates between adjacent spaces, allowing for accurate detection of attraction abnormalities by monitoring pressure differentials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pressure sensor is used to monitor the pressure of the exhaust port to determine holding state, then the holding device can determine when the attracted object is held or released, but it becomes difficult to detect attraction abnormalities caused by minute foreign substances or surface state changes
Solution Approach 1:
The holding device is divided into multiple independent suction ports, each with its own flow rate measurement capability. This segmentation allows localized detection of attraction abnormalities in specific regions without affecting the overall holding determination, enabling precise detection of minute foreign substances or surface state changes at individual port locations.
Solution Approach 2:
A flow rate measurement unit is introduced as an intermediary between the pressure mechanism and the determination of attraction state. Instead of directly measuring pressure to detect abnormalities, the system measures the flow rate of gas through the suction port, which serves as an intermediate parameter that is more sensitive to minute changes in attraction caused by foreign substances or surface state changes.
2Device complexity
If the holding device uses a single pressure measurement point, then the device structure remains simple, but the ability to detect localized attraction abnormalities is insufficient
Solution Approach 1:
The single pressure measurement point is segmented into multiple flow rate measurement points, each corresponding to a specific suction port or region. This segmentation enables localized detection of attraction abnormalities while maintaining a relatively simple device structure by using the existing suction port infrastructure and adding only flow rate measurement capabilities at each segment.
Solution Approach 2:
The flow rate measurement unit serves multiple functions: it determines overall holding state, detects localized attraction abnormalities, and identifies the specific location of abnormalities. This multi-functionality allows the system to maintain simple structure while achieving high measurement precision across multiple detection objectives.
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
Enables high-accuracy detection of attraction abnormalities, preventing substrate or mold detachment and ensuring precise holding, thus maintaining device performance and preventing wear-related issues.
Implementation Method 1
a first pressure mechanism capable of depressurizing at least one first space among the plurality of spaces formed by the mold or the substrate and the holding unit
Implementation Method 2
a second pressure mechanism capable of setting at least one second space among the plurality of spaces to a pressure different from that of the first space
Data Source
AI summary
A holding device in a lithography apparatus for transferring a pattern formed on a mold to a substrate, for attracting/holding the mold or substrate by a reduced pressure, comprising: a holding unit holding the mold or substrate, having concave portions forming spaces together with the mold or substrate; a first pressure mechanism to depressurize at least one first space among the spaces formed by the mold or substrate and the holding unit; a second pressure mechanism setting at least one second space among the spaces to a pressure different from the first space; a controller controlling the first and second pressure mechanisms such that the first and second spaces are adjacent to each other; a measuring unit measuring a flow rate of at least the first or second pressure mechanisms; and a determining unit determining an abnormality related to attracting/holding of the mold or substrate based on the flow rate.