Immersion Lithography Bubble Reduction via Gap Covering
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Solution Overview
Problem
Bubbles in the immersion liquid of lithographic apparatuses can negatively impact the quality of the patterned image projected onto substrates due to trapped gas, rough surfaces, temperature changes, and chemical reactions, leading to unpredictable effects and reduced image quality.
Innovation Solution
The lithographic projection apparatus minimizes bubble formation by reducing gaps between objects and the support table, using a cover plate to cover gaps, and employing a slanted surface for self-centering, along with a segmented or elastic cover plate to adaptively cover and minimize gaps, and a membrane to bridge gaps, thereby reducing the area where bubbles can form.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the substrate is immersed in a liquid bath for immersion lithography, then the effective NA is increased and depth of focus is increased, but turbulence in the liquid and bubble formation occur leading to unpredictable effects and reduced image quality
Solution Approach 1:
The patent extracts and removes bubbles from the liquid path by implementing a gas outlet that allows bubbles to escape before reaching the projection system. This directly addresses the bubble formation problem while maintaining the benefits of immersion lithography.
Solution Approach 2:
The patent introduces a gas outlet as an intermediary mechanism between the liquid supply and the projection system. This intermediary component provides a controlled path for gas to escape, preventing bubbles from interfering with the projection beam while maintaining liquid immersion.
2Manufacturing precision
If a liquid supply system is implemented with inlets and outlets, then localized liquid coverage is achieved, but gas bubbles can still be trapped in the liquid flow path
Solution Approach 1:
The gas outlet acts as an intermediary element in the liquid flow path, providing a dedicated escape route for bubbles before they can reach the projection system. This mediator component allows continuous liquid supply while preventing harmful bubble accumulation.
Solution Approach 2:
The system extracts bubbles from the liquid flow by providing a gas outlet that actively removes gas bubbles before they can contaminate the projection path, thereby maintaining image quality while preserving localized liquid coverage.
3Ease of manufacture
If gaps are present between objects and the support table, then ease of assembly is improved, but bubble formation is increased
Solution Approach 1:
The patent employs a flexible membrane that can be stretched to cover gaps between objects and the support table. This thin film provides a seal that prevents bubble formation while maintaining the ease of assembly by not requiring precise gap elimination.
Solution Approach 2:
The patent changes the physical state or configuration of the gap-filling element by using a flexible membrane that can be stretched or deformed to conform to the gap geometry, thereby sealing gaps without requiring precise manufacturing tolerances.
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 approach effectively reduces bubble formation in the immersion liquid, enhancing the quality of the projected image by minimizing gas traps and maintaining a stable liquid interface, thus improving the precision and reliability of the lithographic process.
Implementation Method 1
immerse 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
Implementation Method 2
a membrane to bridge gaps
Data Source
AI summary
In an immersion lithographic apparatus, bubble formation in immersion liquid is reduced or prevented by reducing a gap size or area on a substrate table and/or covering the gap.