Lithographic Apparatus Protrusion for Liquid Meniscus Control
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Solution Overview
Problem
Existing lithographic apparatuses face challenges in controlling the level of immersion liquid between the projection system and the substrate, leading to issues such as overflow and bubble inclusion, which affect imaging quality.
Innovation Solution
A lithographic apparatus with a barrier member and a protrusion that creates a reservoir for the liquid, where the surface of the protrusion is closer to the projection system than the barrier member, increasing resistance against the liquid meniscus and preventing overflow, and a liquid supply system that directs liquid flow downwards and radially inwardly from above the projection system's bottom surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a barrier member is used to contain liquid in a reservoir, then liquid containment is improved, but liquid level control becomes difficult leading to overflow or bubble inclusion
Solution Approach 1:
The barrier member incorporates a protrusion that creates a localized region with different geometric properties. This protrusion defines a specific area within the reservoir where liquid level is naturally controlled by the protrusion's height, creating local quality variation that prevents overflow and bubble inclusion while maintaining overall containment.
Solution Approach 2:
The protrusion extends into the reservoir volume from the barrier member surface, adding a dimensional feature that creates a stepped geometry. This dimensional change establishes a maximum liquid level reference plane, allowing the liquid to be contained effectively while providing a natural level control mechanism without complex active control systems.
2Manufacturing precision
If liquid is supplied in a localized area between the projection system and substrate, then imaging quality is improved, but liquid flow control becomes complex
Solution Approach 1:
The liquid supply system targets a localized region defined by the protrusion's position within the reservoir. Liquid is supplied specifically to the area where the protrusion creates a controlled meniscus, ensuring that only the necessary localized region receives liquid for optimal imaging while simplifying the overall flow control by concentrating supply to a defined zone.
Solution Approach 2:
The protrusion acts as an intermediary structure between the liquid supply system and the imaging zone. It mediates the liquid flow by creating a controlled meniscus and defining the liquid-air interface, thereby simplifying the liquid supply mechanism while maintaining precise liquid positioning for high-quality imaging.
3Productivity
If the substrate is scanned during exposure, then productivity is improved, but liquid turbulence increases causing unpredictable effects
Solution Approach 1:
The liquid reservoir is effectively segmented by the protrusion into distinct zones: a contained liquid region and an air region. This segmentation allows the liquid to remain stable in its confined portion while the substrate scans through the exposure field, reducing turbulence and unpredictable effects during dynamic operation.
Solution Approach 2:
The liquid forms a controlled thin film or meniscus around the protrusion, creating a flexible liquid interface that can accommodate substrate movement during scanning. This thin film configuration reduces liquid volume and minimizes turbulence while maintaining stable liquid properties for consistent imaging during high-speed substrate traversal.
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 configuration reduces the likelihood of overflow and bubble inclusion, maintaining a stable liquid meniscus and enhancing imaging quality by controlling the liquid flow effectively.
Implementation Method 1
It has been proposed to 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. The point of this is to enable imaging of smaller features since the exposure radiation will have a shorter wavelength in the liquid. (The effect of the liquid may also be regarded as increasing the effective NA of the system and also increasing the depth of focus.)
Implementation Method 2
a protrusion which surrounds the projection system and is on the barrier member such that a surface of the protrusion is closer to the projection system than a part of the barrier member on a radially outward side of the protrusion
Data Source
AI summary
A protrusion is provided on a barrier member which at least partly confines a liquid between a projection system and a substrate. The protrusion is closer to the projection system than other parts of the barrier member to promote a meniscus of liquid to adhere between the protrusion and the projection system.