EUV Optical Element Cleaning via Ionized Purge Gas
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Solution Overview
Problem
Extreme ultraviolet (EUV) optical systems face contamination issues due to unavoidable contaminants in the vacuum environment, leading to carbon and oxide growth on optical surfaces, which reduces reflectivity and degrades the optics over time.
Innovation Solution
The system employs electrical biasing of optical elements and the use of ionizable gases, such as hydrogen, to attract and react with contaminants, generating cleaning agents like atomic hydrogen and methane, which are then removed via vacuum pumps, and incorporates a homogenizer tunnel with ionizing mechanisms to enhance cleaning efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If EUV optics operate in a vacuum environment, then system reliability is improved, but contaminants still accumulate on optical surfaces causing reflectivity degradation
Solution Approach 1:
The patent converts the harmful EUV radiation that causes contamination into a useful cleaning tool by using it to ionize gas molecules, creating reactive ions that automatically clean the optical surfaces. The same radiation that creates the problem is harnessed to solve it through in-situ cleaning.
Solution Approach 2:
The system performs self-cleaning by using the EUV radiation present in the system to generate cleaning agents (reactive ions) that automatically remove contaminants from optical surfaces without external intervention, maintaining continuous operation without manual cleaning stops.
2Object-affected harmful factors
If gas is introduced for cleaning, then contaminant removal is improved, but system complexity increases
Solution Approach 1:
The patent introduces a gas medium as an intermediary that, when ionized by EUV radiation, creates reactive species that mediate the cleaning process between the EUV radiation and the contaminant layers on optical surfaces.
Solution Approach 2:
The system changes the physical state of the introduced gas from neutral to ionized/excited state through EUV radiation, transforming it into reactive cleaning agents that can chemically interact with and remove contaminants from optical surfaces.
3Productivity
If continuous operation is maintained, then productivity is improved, but optical degradation accelerates
Solution Approach 1:
The patent implements continuous cleaning action during EUV operation by maintaining a gas atmosphere that is continuously ionized by the EUV radiation, creating a persistent cleaning environment that operates without interruption throughout the system's operational life.
Solution Approach 2:
The system performs preliminary cleaning by continuously removing contaminants before they can significantly degrade optical performance, preventing the accumulation that would otherwise require system shutdowns for maintenance.
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 method effectively recovers lost reflectivity by removing carbon and oxide growth, maintaining the integrity of EUV optics and extending the system's operational lifespan by continuously cleaning the optical surfaces.
Implementation Method 1
the light emitted by the illumination source is capable of ionizing a purge gas contained within the vacuum chamber
Implementation Method 2
a voltage between about -100 Volts and -10,000 Volts is applied to the EUV optic to attract ions generated by ionization of the purge gas
Implementation Method 3
The vacuum chamber is equipped with a vacuum pump configured to remove molecules of the purge gas from the vacuum chamber
Data Source
Figure 1A
Figure 1B~1C
Figure 1D~1E
AI summary
A system for cleaning or suppressing contamination or oxidation in a EUV optical setting includes an illumination source, a detector, a first set of optical elements to direct light from the illumination source to a specimen and a second set of optical elements to receive illumination from the specimen and direct the illumination to the detector. The system also includes one or more vacuum chambers for containing the first and second set of optical elements and containing a selected purge gas ionizable by the light emitted by the illumination source. The first or second set of optical elements includes an electrically biased optical element having at least one electrically biased surface. The electrically biased optical element has a bias configuration suitable to attract one or more ionic species of the selected purge gas to the electrically biased surface in order to clean contaminants from the electrically biased surface.