Heat Pipe Substrate Holder for Uniform Lithography Temperature
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Solution Overview
Problem
The presence of liquid and/or gas flows in lithographic apparatuses can lead to non-uniform cooling of substrates, causing temperature inconsistencies and resulting in undesirable defects such as overlay errors during the imaging process.
Innovation Solution
A heat pipe system is integrated into the lithographic apparatus, comprising a chamber with a liquid reservoir and a vapor space, along with a heating element and a liquid transporter, to maintain a substrate at a substantially uniform temperature. The heat pipe utilizes condensation and evaporation processes to regulate temperature, ensuring thermal equilibrium across the substrate surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If liquid is used for immersion lithography to increase numerical aperture and reduce wavelength, then imaging precision is improved, but non-uniform cooling and temperature variations occur on the substrate
Solution Approach 1:
The substrate table is divided into multiple independent heating zones, each capable of independent temperature control. This segmentation allows localized temperature compensation across different regions of the substrate, counteracting the non-uniform cooling effects caused by liquid immersion and enabling uniform temperature distribution while maintaining high imaging precision
Solution Approach 2:
Different regions of the substrate table are provided with different heating characteristics and control parameters tailored to local thermal conditions. Areas experiencing greater cooling are provided with higher heating power, while areas with less cooling receive proportionally less heating, achieving uniform temperature distribution across the entire substrate surface
2Temperature
If liquid flows are used for cooling and temperature control, then temperature regulation is improved, but non-uniform cooling and thermal variations occur
Solution Approach 1:
Temperature sensors are distributed across the substrate table to provide real-time feedback on local temperature conditions. The control system continuously monitors these temperature readings and dynamically adjusts the heating power in each zone to compensate for variations in cooling effects, maintaining uniform temperature distribution despite the presence of liquid flows
Solution Approach 2:
The heating parameters (power, duration, distribution) are dynamically changed based on real-time temperature measurements and predicted thermal conditions. The system adjusts heating intensity and timing to counteract the varying cooling effects of liquid flows across different substrate regions, achieving uniform temperature control
3Temperature
If a heat pipe system with liquid reservoir and vapor space is used, then temperature uniformity is improved, but device complexity increases
Solution Approach 1:
The heat pipe system utilizes the natural phase change cycle of the working liquid (evaporation at heated regions, condensation at cooler regions, and gravitational or capillary return to the reservoir) to automatically redistribute heat across the substrate table. This self-regulating mechanism eliminates the need for external pumps, valves, or complex control systems, achieving temperature uniformity while minimizing device complexity
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 heat pipe effectively mitigates temperature variations, maintaining a uniform substrate temperature and reducing the risk of defects by efficiently distributing heat and maintaining thermal stability during the imaging process.
Implementation Method 1
a heating element configured to heat liquid in the reservoir and positioned partly in the reservoir and partly in the vapor space
Implementation Method 2
a heat pipe configured to maintain the substrate holder at a substantially uniform temperature
Implementation Method 3
a chamber containing a liquid reservoir and a vapor space
Data Source
AI summary
A lithographic apparatus is provided that includes a substrate holder configured to hold a substrate, and a heat pipe to maintain the substrate holder at a substantially uniform temperature. The heat pipe has a chamber containing a liquid reservoir and a vapor space, and a heating element at least partly in contact with liquid in the chamber.