Immersion Lithography Fluid Handling Structure Bubble Control
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Solution Overview
Problem
In lithographic apparatuses, the immersion liquid can include bubbles due to meniscus collisions with droplets, leading to imaging errors by interfering with the projection beam during substrate imaging.
Innovation Solution
A fluid handling structure with a meniscus pinning feature and a gas knife or gas supply openings in a linear array surrounding the meniscus pinning feature to prevent the passage of immersion fluid outward and recover liquid, reducing bubble inclusion by maintaining a stable liquid film and controlling gas flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the substrate is submersed in a large body of liquid for immersion lithography, then the refractive index is increased to enable imaging of smaller features, but turbulence in the liquid may lead to undesirable and unpredictable effects
Solution Approach 1:
The patent divides the immersion liquid into two distinct regions: a large stationary reservoir that provides the desired refractive index, and a small localized exposure region where imaging occurs. This segmentation is achieved through a substrate table with a through-opening and a liquid confinement structure that limits liquid movement to the exposure area, preventing turbulence while maintaining high refractive index benefits.
Solution Approach 2:
The patent extracts the imaging function from the bulk liquid environment by creating a confined exposure region. The liquid confinement structure removes the problematic turbulent portion of the liquid from the imaging path, allowing only a controlled, stationary layer of immersion liquid to participate in the exposure process while the bulk liquid remains stationary in the reservoir.
2Reliability
If the immersion liquid is confined to a localized area, then turbulence is reduced, but a meniscus forms at the boundary which may collide with droplets and include bubbles in the liquid
Solution Approach 1:
The patent introduces a gas seal as an intermediary between the confined liquid region and the external environment. This gas seal prevents direct contact between the meniscus and droplets that might cause bubble inclusion, while still allowing the liquid confinement structure to maintain its localized configuration. The gas seal acts as a protective barrier that eliminates the harmful interaction without compromising liquid stability.
3Object-affected harmful factors
If gas flow is increased to control the meniscus and prevent droplet collision, then bubble inclusion is reduced, but gas consumption increases
Solution Approach 1:
The patent applies gas flow control locally at the critical meniscus boundary rather than throughout the entire liquid volume. The gas seal is positioned specifically where meniscus-droplet interaction occurs, providing targeted protection against bubble inclusion. This localized approach minimizes gas consumption by concentrating the gas flow only where it is needed to prevent harmful effects, rather than using excessive gas flow throughout the system.
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 solution effectively reduces the likelihood of bubble inclusion in the immersion liquid, enhancing imaging accuracy by stabilizing the liquid film and improving gas flow efficiency, thereby minimizing imaging errors.
Implementation Method 1
providing gas through a plurality of gas supply openings in a linear array to a position adjacent a meniscus of the immersion liquid
Implementation Method 2
a meniscus pinning feature to resist passage of immersion fluid in a radially outward direction from the space
Implementation Method 3
recovering liquid which passes through adjacent gas supply openings of the plurality of gas supply openings in a linear array through a gas recovery opening
Data Source
AI summary
A fluid handling structure for a lithographic apparatus, the fluid handling structure having, at a boundary from a space configured to contain immersion fluid to a region external to the fluid handling structure: a meniscus pinning feature to resist passage of immersion fluid in a radially outward direction from the space; a plurality of gas supply openings in a linear array at least partly surrounding and radially outward of the meniscus pinning feature; and a gas recovery opening radially outward of the plurality of gas supply openings in a linear array.