Plasma Photon Source UV Filtering for Ozone Control
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Solution Overview
Problem
Current plasma-based photon sources for lithographic metrology face challenges in achieving high brightness while managing ozone generation and chemical contamination associated with ultraviolet radiation, leading to increased costs and reduced lamp lifetime.
Innovation Solution
A radiation-produced plasma-based photon source apparatus with a hermetically sealed second container that filters out ultraviolet components from the output radiation, reducing ozone generation and extending lamp lifetime by encapsulating ozone within the container.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a plasma-based photon source emits ultraviolet radiation to achieve high brightness, then the brightness and spectral bandwidth are improved, but ozone generation and chemical contamination occur leading to reduced lamp lifetime and increased operational costs
Solution Approach 1:
The harmful ultraviolet component is extracted and removed from the radiation spectrum by placing an absorbing filter in the optical path. The filter selectively absorbs UV radiation while allowing visible and near-infrared wavelengths to pass through, thereby eliminating ozone generation while preserving the useful brightness and spectral bandwidth for lithographic metrology applications
Solution Approach 2:
The ultraviolet radiation that causes harmful ozone generation is converted into a beneficial filtering mechanism. By introducing an absorbing filter that selectively blocks UV wavelengths, the harmful effect is transformed into a controlled spectral selection process, allowing the system to maintain high brightness in the useful wavelength ranges while eliminating the harmful UV component
2Object-generated harmful factors
If purging systems are implemented to remove ozone, then ozone generation is controlled, but the device complexity and operational costs increase
Solution Approach 1:
The harmful ultraviolet component is extracted and removed from the radiation spectrum by placing an absorbing filter in the optical path. The filter selectively absorbs UV radiation while allowing visible and near-infrared wavelengths to pass through, thereby eliminating ozone generation while preserving the useful brightness and spectral bandwidth for lithographic metrology applications
Solution Approach 2:
An absorbing filter is introduced as an intermediary element between the plasma source and the environment. This filter acts as a mediator that selectively interacts with ultraviolet radiation, absorbing it before it can generate ozone, while remaining transparent to the useful wavelength ranges. This simple intermediary component replaces complex purging systems
3Illumination intensity
If the plasma source operates continuously to maintain high brightness, then the illumination intensity is improved, but the lamp lifetime is reduced due to solarization effects
Solution Approach 1:
The harmful ultraviolet component is extracted and removed from the radiation spectrum by placing an absorbing filter in the optical path. The filter selectively absorbs UV radiation while allowing visible and near-infrared wavelengths to pass through, thereby eliminating ozone generation while preserving the useful brightness and spectral bandwidth for lithographic metrology applications
Solution Approach 2:
The spectral parameters of the radiation are changed by selectively filtering out ultraviolet wavelengths. This parameter change in the radiation spectrum prevents solarization effects that would otherwise occur in the glass envelope, thereby extending lamp lifetime while maintaining high brightness in the useful wavelength ranges
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 solution enhances the brightness of the photon source while eliminating the need for costly ozone removal systems and extending the lifespan of the light source, thereby reducing operational costs and improving efficiency.
Implementation Method 1
a first container for containing a gaseous medium in which a plasma is generated following excitation by a driving radiation
Implementation Method 2
the radiation produced plasma-based photon source apparatus is operable to emit output radiation comprising a plurality of component wavelengths
Implementation Method 3
the second container is hermetically sealed and operable to substantially remove the ultraviolet component from the output radiation
Data Source
AI summary
A radiation driven light source comprises laser and focusing optics. These produce a beam of radiation focused on a plasma forming zone within a first container containing a gas (e.g. Xe). Collection optics collects photons emitted by a plasma maintained by the laser radiation to form a beam of output radiation. First container is enclosed within a hermetically sealed second container. Any ozone generated within the second container as a result of ultraviolet components of the output radiation is completely contained within the second container. Second container further filters out the ultraviolet components. Microwave radiation may be used instead of laser radiation to form the plasma.