Immersion Lithography Barrier and Liquid Jet Confinement
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Solution Overview
Problem
Immersion lithography faces challenges such as thermal contraction due to evaporation of residual liquid, overlay errors, and bubble formation in the immersion liquid, particularly with water, which affects the precision and reliability of the process.
Innovation Solution
A lithographic apparatus with a barrier member surrounding the space between the projection system and the substrate, utilizing an inwardly-directed liquid jet to confine and manage the immersion liquid, reducing escape and evaporation, and enhancing liquid flow to prevent bubble formation and temperature deviations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a large body of liquid is used for immersion lithography, then imaging precision is improved due to shorter wavelength in liquid, but turbulence and unpredictable effects occur during scanning exposure
Solution Approach 1:
The patent divides the immersion liquid into two distinct regions: a stationary bulk liquid region that provides the refractive index benefit for high-resolution imaging, and a localized liquid layer in the exposure field that remains stable during scanning. This segmentation prevents turbulence while maintaining the optical advantages of immersion lithography.
Solution Approach 2:
The patent applies different liquid conditions to different spatial zones: the bulk liquid reservoir provides high refractive index for wavelength reduction, while the exposure field region maintains a controlled, stable liquid layer with minimal movement. This local differentiation resolves the contradiction between needing liquid for precision and avoiding turbulence for reliability.
2Reliability
If immersion liquid is supplied to localized area only, then turbulence is reduced, but liquid supply system complexity increases
Solution Approach 1:
The barrier member is designed to be movable rather than fixed, allowing it to dynamically adjust its position to maintain an optimal gap with the substrate during scanning. This dynamic adjustment simplifies the liquid supply system by eliminating the need for complex pumping and flow control mechanisms, while still achieving stable localized liquid confinement.
Solution Approach 2:
The stationary bulk liquid automatically supplies the localized exposure field region through capillary action and pressure equilibrium, eliminating the need for active pumping systems. The system self-regulates liquid distribution, reducing complexity while maintaining process stability.
3Productivity
If substrate is scanned at high speed, then productivity is improved, but liquid turbulence and overlay errors increase
Solution Approach 1:
By separating the liquid into a stationary bulk region and a stable localized exposure layer, the patent enables high-speed scanning without turbulence. The stationary bulk does not move with the substrate, while the exposure field liquid remains stable, allowing fast scanning speeds to be achieved without compromising overlay precision.
4Reliability
If liquid flow is increased to prevent bubble formation, then reliability is improved, but liquid escape and evaporation increase
Solution Approach 1:
The patent applies high liquid flow only in the localized exposure field region where bubble formation is critical, while the bulk liquid remains stationary with minimal flow. This localized flow approach prevents bubbles in the exposure area without causing widespread evaporation, resolving the contradiction between reliability and substance loss.
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 confines the immersion liquid, reducing thermal contraction, overlay errors, and bubble issues, while improving liquid flow and contaminant removal, thereby enhancing the precision and reliability of the lithography process.
Implementation Method 1
a nozzle for connection to a source of liquid, the nozzle shaped and oriented to direct a jet of liquid into the gap and substantially towards the center of the image field
Implementation Method 2
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.
Implementation Method 3
a barrier member configured to surround a space between the projection system and the substrate, the barrier member configured to at least partly confine liquid to the space
Data Source
AI summary
An immersion lithographic apparatus has a barrier member surrounding a space between the projection system and the substrate so as to at least partly confine liquid in the space. A jet of liquid is directed radially inwardly in a gap between the barrier member and the substrate and/or between the barrier member and the projection system, to help prevent escape of liquid.