Lithographic Substrate Table Segmented Heaters
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Solution Overview
Problem
In lithographic apparatuses, local heat load variations due to liquid immersion systems can cause thermal expansion and contraction issues, leading to overlay errors and inefficient temperature control, especially when using localized liquid supply systems.
Innovation Solution
A substrate table with a plurality of independently controllable heaters positioned non-parallel to each other along different segments of the edge, surrounding the substrate supporting area, to compensate for local heat loads and maintain a consistent temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a localized liquid supply system is used to immerse the substrate area, then imaging resolution is improved due to shorter wavelength in liquid, but local heat load variations occur causing thermal expansion and contraction issues
Solution Approach 1:
The substrate table is divided into multiple zones with independently controllable heating elements positioned at different locations (edge, corner, center). Each zone can be heated independently to compensate for local heat load variations caused by the localized liquid supply, ensuring uniform temperature distribution across the substrate area while maintaining high imaging resolution.
2Productivity
If immersion liquid is supplied to localized area only, then productivity is improved by reducing liquid volume, but thermal expansion and contraction effects are not compensated leading to overlay errors
Solution Approach 1:
Temperature sensors are positioned at multiple locations on the substrate table to monitor local temperature variations in real-time. The control system uses this feedback information to adjust the heating elements dynamically, compensating for thermal expansion and contraction effects that would otherwise cause overlay errors, thereby maintaining manufacturing precision while using localized liquid supply for improved productivity.
3Temperature
If multiple heating zones are implemented, then temperature control uniformity is improved, but device complexity increases
Solution Approach 1:
The heating system is segmented into multiple independent heating zones with individual control, allowing precise temperature management in different areas of the substrate table. This segmentation enables targeted compensation for local heat loads without requiring a completely complex system redesign, as each zone can be controlled independently based on local temperature sensor feedback.
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 effectively reduces thermal expansion and contraction effects, ensuring more uniform temperature control and minimizing overlay errors by precisely managing heat distribution around the substrate table.
Implementation Method 1
a plurality of heaters, at least two of the plurality of heaters being positioned in a non-parallel way adjacent different portions of an edge of the substrate supporting area
Implementation Method 2
local heat load variations due to liquid immersion systems can cause thermal expansion and contraction issues
Implementation Method 3
local heat load variations due to liquid immersion systems can cause thermal expansion and contraction issues
Data Source
AI summary
A substrate table is disclosed in which heaters are provided to account for a heat load which may be applied to the substrate. The heaters are grouped in segments to improve control. A temperature sensor per segment may be provided. The temperature sensor may be embedded in the substrate table.