Debris-Receiving Surface Temperature Control for EUV Lithography
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Solution Overview
Problem
Lithographic radiation sources using liquid fuels face contamination issues due to 'spitting' phenomena, where gas bubbles nucleate and eject fuel particles, contaminating optically-active surfaces, which is not effectively mitigated by existing methods.
Innovation Solution
Maintaining the debris-receiving surfaces at a temperature significantly higher than the melting point of the fuel, typically above 300°C, to reduce the formation of gas bubbles and prevent spitting, while ensuring the surfaces are not excessively heated to avoid vapor pressure issues and corrosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If debris-receiving surfaces are maintained at a temperature significantly higher than the melting point of the fuel (above 300°C), then the formation of gas bubbles is reduced and spitting is prevented, but excessive heating may cause vapor pressure issues and corrosion
Solution Approach 1:
The patent applies parameter changes by precisely controlling the temperature of debris-receiving surfaces to a specific range (above the melting point but below excessive temperatures). This temperature parameter optimization reduces gas bubble formation and prevents spitting while avoiding vapor pressure issues and corrosion that would occur at excessively high temperatures.
Solution Approach 2:
The patent implements beforehand cushioning by maintaining debris-receiving surfaces at elevated temperatures before fuel debris can accumulate and cause contamination. This preventive heating approach reduces gas bubble nucleation and prevents spitting events before they can occur, rather than attempting to address contamination after it happens.
2Stability of the object's composition
If debris-receiving surfaces are maintained at a moderate temperature (20°C above melting point), then the fuel remains liquid and some spitting is prevented, but gas bubbles still form and eject fuel particles contaminating optically-active surfaces
Solution Approach 1:
The patent applies parameter changes by increasing the temperature of debris-receiving surfaces from moderate levels (20°C above melting point) to significantly higher levels (above 300°C). This temperature parameter change substantially reduces gas bubble formation rates and prevents spitting, while maintaining the fuel in a liquid state through controlled heating.
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
Substantially reduces the contamination of optically-active surfaces by fuel debris, with a marked decrease in secondary debris particles, effectively preventing spitting and maintaining the fuel in a liquid state to prevent contamination, thus improving the longevity and performance of radiation sources.
Implementation Method 1
gas bubbles nucleate and eject fuel particles
Implementation Method 2
Maintaining the debris-receiving surfaces at a temperature significantly higher than the melting point of the fuel, typically above 300°C
Implementation Method 3
A radiation system for producing EUV radiation may include an excitation beam such as a laser (for instance and infra-red laser) for exciting a fuel to provide the plasma
Implementation Method 4
The plasma may be created, for example, by directing a laser beam (i.e., initiating radiation) at a fuel
Implementation Method 5
The resulting plasma emits output radiation, e.g., EUV radiation, which is collected using a radiation collector. The radiation collector may be a mirrored normal incidence radiation collector (sometimes referred to as a near normal incidence radiation collector), which receives the radiation and focuses the radiation into a beam
Data Source
AI summary
A radiation source suitable for providing radiation to a lithographic apparatus generates radiation from a plasma (12) generated from a fuel (31) within an enclosure comprising a gas. The plasma generates primary fuel debris collected as a fuel layer on a debris-receiving surface ((33a), (33b)). The debris-receiving surface is heated to a temperature to maintain the fuel layer as a liquid, and to provide a reduced or zero rate of formation gas bubbles within the liquid fuel layer in order to reduce contamination of optical surfaces (14) by secondary debris arising from gas bubble eruption from the liquid fuel layer. Additionally or alternatively, the radiation source may have a debris receiving surface positioned and/or oriented such that substantially all lines normal to the debris receiving surface do not intersect an optically active surface of the radiation source.