Lithographic Apparatus Gas Flow Cooling for Overlay Accuracy
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Solution Overview
Problem
In lithographic apparatuses, the patterning device absorbs radiation, leading to thermal expansion and resulting in spatially non-uniform temperature distribution, which causes overlay errors during the imaging of substrates.
Innovation Solution
A support structure with outlet and inlet openings is used to direct and recycle a gas flow over the patterning device, enhancing heat transfer through turbulent gas flow to maintain a consistent temperature and reduce thermal expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the patterning device is used to pattern the radiation beam, then the desired pattern is transferred onto the substrate, but the patterning device absorbs radiation and heats up causing thermal expansion and overlay errors
Solution Approach 1:
A gas flow system is introduced to cool the patterning device. Gas is supplied through outlets positioned near the patterning device and extracted through inlets, creating a controlled gas flow that removes heat from the patterning device surface, thereby reducing thermal expansion and maintaining overlay accuracy during lithographic exposure.
Solution Approach 2:
A gas medium is used as an intermediary between the radiation source and the patterning device environment. The gas flow acts as a heat transfer medium that carries away thermal energy from the patterning device without interfering with the radiation patterning process, thus maintaining temperature control while preserving patterning functionality.
2Temperature
If a gas flow is introduced to cool the patterning device, then thermal expansion is reduced, but the gas flow may interfere with the radiation beam and measurement systems
Solution Approach 1:
The gas flow outlets and inlets are positioned at specific locations around the patterning device, creating localized gas flow zones that target the heating areas without obstructing the radiation beam path. The gas flow is confined to regions where it is most effective for cooling while minimizing interference with optical and measurement systems.
Solution Approach 2:
The gas flow system is divided into multiple outlets and inlets distributed around the patterning device. This segmentation allows the gas flow to be directed at specific heated regions while leaving other areas clear for radiation beam passage and measurement system operation, thus achieving selective cooling without compromising overall system functionality.
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
This solution significantly reduces overlay errors by decreasing the patterning device's heating by a factor of five, achieving a heat transfer coefficient of 100 W/m2K and minimizing thermal-induced deformation.
Implementation Method 1
enhancing heat transfer through turbulent gas flow to maintain a consistent temperature and reduce thermal expansion
Implementation Method 2
A support structure with outlet and inlet openings is used to direct and recycle a gas flow over the patterning device, enhancing heat transfer
Data Source
AI summary
A lithographic apparatus has a support structure configured to support a patterning device, the patterning device serving to pattern a radiation beam according to a desired pattern and having a planar main surface through which the radiation beam passes; an outlet opening configured to direct a flow of a gas onto the patterning device; and an inlet opening configured to extract the gas which has exited the outlet opening, wherein the outlet opening and inlet opening are in a facing surface facing the planar main surface of the patterning device.