Electrostatic Substrate Holder for Immersion Lithography
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Solution Overview
Problem
In high-throughput lithographic apparatuses, substrates experience high accelerations, requiring secure clamping to prevent distortion, especially in immersion systems where temperature control is critical due to liquid evaporation effects, and existing clamping methods like vacuum clamping are ineffective in low-pressure environments.
Innovation Solution
A substrate holder with a conductive layer integral to its main body and burls, allowing for electrostatic clamping and integrated temperature control through heaters and sensors, ensuring precise temperature management and secure substrate positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If vacuum clamping is used to secure the substrate, then the substrate can be held firmly during high acceleration, but it becomes ineffective in low-pressure environments
Solution Approach 1:
The patent replaces the vacuum-based mechanical clamping system with an electrostatic clamping system. The electrostatic clamp uses electrical fields to generate holding forces on the substrate, eliminating dependence on pressure differentials. This allows the substrate to be securely held in both atmospheric and low-pressure environments, resolving the contradiction between clamping effectiveness and environmental adaptability.
2Manufacturing precision
If the substrate is clamped securely to prevent distortion during high acceleration, then positioning accuracy is maintained, but thermal stress and overlay errors occur due to temperature variations in immersion systems
Solution Approach 1:
The patent incorporates temperature sensors that continuously monitor the substrate temperature and provide feedback to the control system. Based on this feedback, the system adjusts heating elements to maintain optimal temperature, compensating for thermal variations caused by immersion liquid evaporation. This feedback mechanism prevents thermal stress and overlay errors while maintaining secure substrate clamping during high acceleration.
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 substrate holder effectively clamps the substrate with electrostatic force and maintains accurate temperature control, reducing thermal stress and overlay errors in immersion lithography systems.
Implementation Method 1
A substrate holder with a conductive layer integral to its main body and burls, allowing for electrostatic clamping
Implementation Method 2
integrated temperature control through heaters and sensors, ensuring precise temperature management
Implementation Method 3
the substrate in the lithographic projection apparatus in a liquid having a relatively high refractive index, e.g. water, so as to fill a space between the final element of the projection system and the substrate
Data Source
AI summary
A method of manufacturing a substrate holder for use in a lithographic apparatus, the method including providing a main body having a surface and a plurality of burls projecting from the surface and having end surfaces to support a substrate, providing a carrier surface adjacent the main body surface, and forming a conductive layer on at least part of the main body surface and an integral part on at least part of the carrier surface.