EUV Radiation Source Fuel Trajectory and Debris Management
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Solution Overview
Problem
Current EUV radiation sources for lithographic apparatuses face challenges such as debris contamination, inaccurate targeting of fuel droplets, and significant pulse-to-pulse variations in output power, which affect the generation of sufficient intensity and spectral purity of EUV radiation.
Innovation Solution
A radiation source design featuring a fuel dispenser emitting fuel along a trajectory parallel to the first radiation beam, with a beam guiding system directing the radiation to a focal point to excite the fuel into a plasma, and a collector to collect and direct the emitted radiation, while incorporating a debris trap and gas flow management to minimize contamination and improve targeting accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a laser-produced plasma source is used to generate EUV radiation, then sufficient intensity and spectral purity can be achieved, but large amounts of debris are generated which contaminate the source module and migrate into other parts of the lithographic apparatus
Solution Approach 1:
The source module is divided into separate functional zones: a fuel delivery system, a plasma generation chamber, a debris collection trap, and a radiation collection system. The debris trap is positioned to intercept and collect debris before it can migrate into the lithographic apparatus, while the fuel droplets are delivered along a trajectory that passes through the focal point without being contaminated by debris
Solution Approach 2:
The harmful debris is extracted and removed from the system by introducing a gas flow that directs debris into a dedicated debris trap. The gas flow creates a separate pathway for debris removal that does not interfere with the EUV radiation collection or the fuel delivery, effectively isolating the contamination problem from the rest of the system
2Power
If fuel droplets are targeted with laser pulses, then EUV radiation can be generated, but there are significant pulse-to-pulse variations in source position and output power
Solution Approach 1:
The fuel droplets are pre-formed and delivered along a controlled trajectory before laser irradiation. The dispenser system ensures that droplets are released at precise intervals and positions, establishing a predictable starting point for each laser pulse. This preliminary positioning control reduces variations in plasma formation location and improves output consistency
Solution Approach 2:
The system incorporates monitoring of droplet delivery timing and position, allowing for real-time adjustment of the dispenser operation. By tracking the actual position and timing of each droplet, the system can compensate for variations and maintain consistent plasma generation conditions across pulses
3Productivity
If the fuel trajectory intersects with the collected radiation path, then efficient radiation collection is possible, but debris generated from fuel excitation contaminates the collection system
Solution Approach 1:
The system uses asymmetric positioning where the fuel trajectory and the radiation collection path are separated in space. The fuel is delivered along a trajectory that does not intersect with the path of collected EUV radiation, while the debris trap is positioned to intercept debris without blocking the radiation collection. This asymmetric arrangement allows both functions to operate simultaneously without interference or contamination
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 design enhances the accuracy of fuel targeting, reduces debris contamination, and increases the power of the EUV radiation output, leading to improved throughput and efficiency in lithographic apparatuses.
Implementation Method 1
fuel at the focal point is excited into a plasma that emits second radiation
Implementation Method 2
a collector arranged to collect the second radiation and direct it in a second beam to a second focal point
Data Source
AI summary
A radiation source, e.g. for EUV for use in a lithographic apparatus, generates radiation by illuminating droplets of fuel with first radiation to form a plasma and collects second radiation omitted by the plasma using a collector (CO). The collector has an aperture and the fuel passes along a vertical trajectory through that aperture before being irradiated by the first radiation. In an embodiment the first radiation is directed along a beam, the final part of which is coincident with the final part of the trajectory of the fuel droplets. In an embodiment a gas flow is arranged coincident with the fuel trajectory and/or the beam of first radiation.