Immersion Lithography Edge Gas Buffer Seal
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Solution Overview
Problem
In lithographic apparatuses, immersion liquids can penetrate too far under the substrate, causing localized cooling, temperature fluctuations, and potential contamination, due to two-phase flows which are difficult to control effectively.
Innovation Solution
A system is implemented with a gas inlet near the substrate edge to create a gas buffer, preventing liquid from penetrating into the low-pressure area beneath the substrate, and using a single-phase flow to reduce energy gradients and prevent liquid from reaching the substrate's bottom surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If liquid is supplied to fill the space between the projection system and substrate, then imaging precision is improved, but liquid penetrates under the substrate causing temperature fluctuations and contamination
Solution Approach 1:
The space between the projection system and substrate is divided into two distinct regions: a first region filled with liquid for imaging, and a second region beneath the substrate maintained at low pressure to prevent liquid penetration. This segmentation allows each region to serve its specific function independently, resolving the contradiction between achieving imaging precision and preventing temperature fluctuations.
Solution Approach 2:
A gas seal is introduced as an intermediary barrier between the liquid-filled first region and the low-pressure second region. The gas seal prevents liquid from penetrating under the substrate while allowing the imaging benefits of liquid immersion to be achieved, thus eliminating temperature fluctuations and contamination without sacrificing imaging precision.
2Manufacturing precision
If liquid is supplied to fill the space between the projection system and substrate, then imaging precision is improved, but liquid reaches the substrate bottom surface causing curling
Solution Approach 1:
The space is segmented into a first region for liquid filling and a second region beneath the substrate maintained at low pressure. This segmentation ensures that liquid remains in the first region for imaging purposes while preventing it from reaching the substrate bottom surface, thereby maintaining substrate stability and preventing curling.
Solution Approach 2:
The gas seal acts as an intermediary that blocks liquid penetration into the second region. By maintaining a pressure barrier at the interface between regions, the gas seal protects the substrate from liquid contact, preventing curling while preserving the imaging precision benefits of liquid immersion.
3Manufacturing precision
If liquid is supplied to fill the space between the projection system and substrate, then imaging precision is improved, but two-phase flows cause uncontrollable liquid penetration
Solution Approach 1:
The space is divided into a first region filled with liquid and a second region beneath the substrate maintained at low pressure. This segmentation eliminates the interface where two-phase flows occur, preventing uncontrollable liquid penetration while maintaining imaging precision in the first region.
Solution Approach 2:
The gas seal serves as an intermediary barrier that prevents two-phase flows from causing liquid penetration into the second region. By maintaining a stable pressure boundary, the gas seal ensures reliable flow control while allowing the liquid-filled first region to provide improved imaging precision.
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 keeps the substrate's bottom surface dry, minimizing curling and temperature fluctuations, and preventing contamination by ensuring the liquid does not penetrate, thus maintaining substrate integrity and pattern accuracy.
Implementation Method 1
a gas inlet located near a bottom edge of the substrate when held by the substrate holder, the gas inlet configured to supply gas to a space between the substrate and the substrate holder so as to create a gas buffer at the bottom edge of the substrate through which the liquid may not substantially penetrate
Implementation Method 2
an outlet configured to provide a low pressure between the substrate and the substrate holder
Implementation Method 3
using a single-phase flow to reduce energy gradients and prevent liquid from reaching the substrate's bottom surface
Data Source
AI summary
A method of helping to prevent liquid reaching under a substrate is disclosed that includes introducing a gas at a bottom edge of the substrate so that a buffer is created at the edge of the substrate, helping to keep immersion liquid that is present at the top and edge of the substrate away from the bottom surface of the substrate.