EUV Optical Element Laser Treatment for Reflectivity and Compaction Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for treating optical elements in the EUV wavelength range face challenges such as reflectivity suppression and compaction issues, particularly due to high intensity-related side effects and non-uniform illumination, which affect the reproducibility and accuracy of the process.
Innovation Solution
A method involving pulsed laser irradiation with pulse sequences, where pulses are separated by times of 100 ns or less, is used to modify optical elements, utilizing femtosecond laser pulses to control energy input and minimize unwanted structural displacements, allowing for deeper and more uniform treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If backside illumination is used to treat multilayer systems, then immunity to pattern load is improved, but high intensity-related side effects such as multilayer compaction and registration impact worsen
Solution Approach 1:
The patent applies periodic pulsed laser irradiation with specific pulse sequences (e.g., 100-1000 ps pulse duration, 10-100 kHz repetition rate) to treat the multilayer system. This periodic action allows controlled energy delivery that achieves the desired modification while limiting cumulative thermal effects that cause compaction, thereby resolving the contradiction between reliability and harmful effects
Solution Approach 2:
The patent dynamically adjusts laser parameters including pulse duration, repetition rate, and fluence based on the specific multilayer configuration and desired outcome. This dynamic control enables optimization of the treatment process to achieve immunity to pattern load while minimizing compaction effects through real-time parameter adaptation
2Productivity
If high intensity laser irradiation is used to modify optical elements, then treatment effectiveness is improved, but unwanted side effects such as multilayer compaction and registration impact worsen
Solution Approach 1:
The patent employs partial action by delivering laser energy in controlled pulse sequences rather than continuous high-intensity irradiation. This approach achieves sufficient treatment effectiveness through cumulative sub-threshold pulses while avoiding the excessive energy input that causes compaction and registration errors
Solution Approach 2:
The patent applies preliminary low-intensity pulses before higher intensity treatment to gradually prepare the multilayer system for modification. This staged approach allows the material to adapt progressively, achieving effective treatment while minimizing sudden thermal shocks that would cause compaction and registration issues
3Productivity
If conventional continuous laser irradiation is used, then treatment speed is improved, but non-uniform energy distribution and compaction effects worsen
Solution Approach 1:
The patent replaces continuous laser irradiation with periodic pulsed sequences, where the on/off cycling allows heat diffusion during pulse intervals. This prevents localized overheating and ensures uniform energy distribution across the treatment area while maintaining high productivity through rapid pulse repetition rates
Solution Approach 2:
The patent segments the continuous laser beam into discrete pulses with controlled duration and spacing. This segmentation distributes the total energy input over time, preventing concentrated thermal loading that causes compaction while maintaining treatment speed through high repetition rate pulse sequences
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 approach enhances reflectivity suppression and reduces compaction effects, improving critical dimension control and accuracy in optical element treatment, particularly for EUV lithography applications.
Implementation Method 1
the absorption of laser energy by free electrons occurs at a rate of υee ≈ 1014 s−1
Implementation Method 2
When processing an optical element using a laser to change the reflectivity in certain areas of the optical element, unwanted displacements of structures on the surface of the optical element may be generated, as the energy input into the energy input into the stack shifts it in the direction of the laser irradiation
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
A method for treating an optical element for the extreme ultraviolet (EUV) wavelength range, the method comprises providing a pulsed laser irradiation, wherein the pulsed laser irradiation comprises a plurality of pulse sequences, each pulse sequence comprising a plurality of pulses, wherein a first pulse and a second pulse of the plurality of pulses are separated by a time of 100 ns or less, and directing the laser irradiation onto the optical element for the EUV wavelength range.