Optical Dust Metrology Near Gas Discharge Chamber Elements
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Solution Overview
Problem
Existing gas discharge light sources, such as excimer lasers, face contamination issues from dust particles that can damage optical elements, leading to reduced performance and shortened lifetime, despite the use of dust particle trap systems.
Innovation Solution
A metrology apparatus is employed to detect and estimate properties of dust particles near optical elements in the gas discharge chamber using a probe apparatus, detection apparatus, and processing apparatus, allowing for real-time monitoring without disrupting the light source operation, and enabling adjustments to the dust particle trap system based on the detected data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dust particle trap systems are used in gas discharge light sources, then optical elements are protected from contamination, but the system complexity increases and operational disruptions occur during maintenance
Solution Approach 1:
The metrology apparatus performs preliminary detection of dust particles before they can contaminate optical elements. By continuously monitoring the gas discharge chamber environment and identifying particles in advance, the system enables proactive intervention (such as adjusting trap system operation or alerting operators) before contamination occurs, thereby protecting optical elements without requiring complex real-time mechanical barriers or frequent shutdowns for inspection
Solution Approach 2:
The invention replaces mechanical inspection methods (which would require physical access, disassembly, or shutdown of the gas discharge chamber) with optical detection methods. The metrology apparatus uses light scattering, absorption, or other optical phenomena to detect dust particles remotely through the chamber window, substituting mechanical maintenance routines with non-intrusive optical monitoring that maintains system continuity and reduces operational disruptions
2Reliability
If real-time monitoring of dust particles is implemented, then optical element contamination is prevented, but the measurement and detection difficulty increases
Solution Approach 1:
The metrology apparatus introduces an intermediary detection system that operates through the existing chamber window rather than requiring direct access to the gas discharge environment. The optical detection path uses the window as a mediator to observe particles in the chamber, avoiding the need to penetrate the high-pressure gas environment or interrupt the discharge process. This intermediary approach simplifies the detection task by leveraging existing optical access points and avoiding direct interaction with challenging measurement conditions
Solution Approach 2:
The metrology apparatus creates an optical copy or representation of the particle distribution in the gas discharge chamber by detecting light interactions (scattering, absorption) as particles pass through the probe beam. Rather than directly manipulating or physically contacting the particles, the system measures their optical signatures, creating a detectable signal that replicates particle presence, position, and characteristics without requiring direct particle manipulation or complex in-situ sensors
3Productivity
If the gas discharge chamber operates continuously, then productivity is maintained, but dust particles accumulate and threaten optical elements
Solution Approach 1:
The metrology apparatus implements continuous feedback monitoring of dust particle levels in the gas discharge chamber. By constantly measuring particle concentration and distribution, the system provides real-time information about accumulation trends, enabling dynamic adjustment of trap system operation, gas flow rates, or operational parameters to maintain particle levels below contamination thresholds while sustaining continuous production
Solution Approach 2:
The system performs preliminary detection and warning when particle accumulation reaches critical levels, allowing operators to intervene (activate enhanced trapping, adjust parameters, or schedule maintenance) before actual contamination of optical elements occurs. This proactive approach enables continuous operation by predicting and preventing contamination events rather than reacting to them after damage occurs
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 metrology apparatus effectively tracks and detects dust particles, preventing contamination of optical elements, thereby extending the lifetime of the gas discharge chamber and maintaining light source performance by enabling proactive adjustments.
Implementation Method 1
The detection apparatus can be configured to capture light produced from the interaction between the light sheet and the one or more particles
Implementation Method 2
The detection apparatus can be configured to capture light from the light sheet that is scattered or reflected from the one or more particles
Implementation Method 3
an excimer laser uses a combination of one or more noble gases, which can include argon, krypton, or xenon, and a reactive gas, which can include fluorine or chlorine. The excimer laser can create an excimer, a pseudo-molecule, under appropriate conditions of electrical simulation (energy supplied) and high pressure
Implementation Method 4
The excimer in an energized state gives rise to amplified light in the ultraviolet range
Data Source
AI summary
A metrology apparatus includes: a probe apparatus configured to produce a probe in a vicinity of an optical element that is in fluid communication with a gain medium of a gas discharge chamber and is exposed to one or more dust particles; a detection apparatus configured to detect an interaction between the probe and one or more dust particles, and to produce an output signal based on the detected interaction; and a processing apparatus configured to receive the output signal and to estimate a property of the one or more dust particles.