Modulated Waveform Droplet Control for EUV Light Source
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Solution Overview
Problem
Current laser-produced plasma (LPP) EUV light sources face challenges in producing a stable stream of droplets with sufficient spacing to reduce the impact of plasma debris on subsequent droplets, leading to lower EUV output and increased source material consumption, due to limitations in droplet spacing caused by single frequency non-modulated disturbance waveforms.
Innovation Solution
A plasma generating system that uses a modulated disturbance waveform to produce droplets with varying initial velocities, allowing for droplet coalescence before reaching the irradiation region, thereby decreasing spacing between droplets and improving EUV output while reducing material consumption, utilizing electro-actuatable elements driven by waveforms such as square, rectangular, fast pulse, or sinc function waves to generate harmonics and achieve stable droplet formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If single frequency non-modulated disturbance waveforms are used to produce droplets, then droplet formation is simplified, but droplet spacing is insufficient leading to increased plasma debris impact and reduced EUV output
Solution Approach 1:
The patent applies dynamics by transitioning from a static single-frequency disturbance waveform to a dynamic modulated disturbance waveform. The modulation frequency is specifically chosen to control droplet spacing, causing droplets to coalesce before reaching the irradiation region. This dynamic adjustment of the disturbance waveform enables precise control over droplet spacing and timing, reducing plasma debris impact while maintaining high EUV output.
2Object-affected harmful factors
If droplet spacing is increased to reduce plasma debris impact, then harmful effects are reduced, but source material consumption increases and EUV output decreases
Solution Approach 1:
The patent employs periodic action through modulated disturbance waveforms with specific modulation frequencies. This periodic modulation creates a controlled pattern of droplet formation and coalescence, ensuring optimal spacing that reduces plasma debris impact without excessive material consumption. The periodic nature of the modulation allows for precise timing control of droplet arrival at the irradiation region.
3Manufacturing precision
If modulated disturbance waveforms are used to control droplet spacing, then droplet timing and position accuracy improve, but device complexity increases
Solution Approach 1:
The patent implements parameter changes by modulating the disturbance waveform frequency and amplitude. Specifically, the modulation frequency is selected to control droplet spacing and coalescence behavior. This parameter adjustment approach enables precise control over droplet timing and position without requiring fundamentally new device components, thereby managing complexity while achieving high precision.
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 modulated disturbance waveform system increases droplet spacing and stability, reducing the effect of plasma debris on subsequent droplets, enhancing EUV output and minimizing source material consumption, with improved timing and position accuracy of droplets at the irradiation site.
Implementation Method 1
a sub-system having an electro-actuatable element producing a disturbance in the fluid
Implementation Method 2
allowing for droplet coalescence before reaching the irradiation region, thereby decreasing spacing between droplets
Implementation Method 3
a laser producing a beam irradiating the droplets at an irradiation region, the plasma producing EUV radiation
Implementation Method 4
converting a material into a plasma state that has at least one element, e.g., xenon, lithium or tin, with one or more emission line in the EUV range
Data Source
Figure 1
Figure 2~2B
Figure 2C~2D
AI summary
A device is disclosed herein which may include a plasma generating system comprising a source of target material droplets and a laser producing a beam irradiating the droplets at an irradiation region, the plasma producing EUV radiation, wherein the droplet source comprises a fluid exiting an orifice and a sub-system producing a disturbance in the fluid which generates droplets having differing initial velocities causing the spacing between at least some adjacent droplets to decrease as the droplets travel to the irradiation region.