Laser Beam Metrology System for EUV Lithography
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Solution Overview
Problem
Existing laser beam metrology systems for EUV radiation sources face measurement errors due to complex routing of laser beam signals, which affects the accurate alignment of laser beam pulses to targets, such as tin droplets, in EUV lithographic apparatuses.
Innovation Solution
A laser beam metrology system that directs a first laser beam pulse and a second laser beam pulse along two independent optical paths, utilizing a beam steering device and detection system to determine the relative orientation between the pulses, ensuring accurate alignment by receiving and analyzing reflections of both pulses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a complex routing of laser beam signals is used to determine alignment, then the alignment measurement can be performed, but measurement errors are introduced
Solution Approach 1:
The patent extracts the alignment measurement function from the complex signal routing system and implements it through a simplified direct detection method. By using a beam steering device to redirect the laser beam along a fixed optical path to a detector, the system eliminates the need for complex signal routing while maintaining measurement capability, thereby reducing measurement errors.
Solution Approach 2:
The patent introduces a beam steering device as an intermediary component that simplifies the optical path. This device redirects the laser beam along a predetermined path to the detector, acting as a mediator between the laser source and detection system. This intermediary approach reduces the complexity of signal routing while ensuring accurate alignment measurement.
2Productivity
If accurate alignment between laser beam pulses and target is ensured, then efficient conversion of laser pulse energy to EUV radiation is achieved, but the system complexity increases
Solution Approach 1:
The patent implements a self-aligning mechanism where the beam steering device automatically directs the laser beam along the correct optical path without requiring complex external alignment procedures. The system uses the reflected light from the target to feedback-align the beam path, enabling the system to self-correct and maintain accurate alignment, thereby ensuring efficient energy conversion while avoiding increased system complexity.
Solution Approach 2:
The patent employs a feedback mechanism where the detector receives light reflected from the target and uses this information to adjust the beam steering device. This feedback loop ensures continuous accurate alignment between the laser beam and target, maximizing energy conversion efficiency. The feedback approach maintains alignment accuracy without requiring overly complex alignment systems.
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 configuration enhances the accuracy of laser beam alignment, leading to more efficient conversion of laser pulse energy to EUV radiation, thereby improving the generation of EUV radiation in EUV lithographic apparatuses.
Implementation Method 1
a beam steering device configured to: redirect a portion of a reflection of the first laser beam pulse along a first direction, the reflection being reflected off of the target; reflect a portion of the second laser beam pulse along a first direction
Implementation Method 2
a detection system configured to: receive the reflected portion of the second laser beam; receive the redirected portion of the first laser beam, and determine a relative orientation between the reflection of the first laser beam pulse and the second laser beam pulse
Implementation Method 3
a retro-reflector configured to: receive the portion of the reflection of the first laser beam pulse, and retro-reflect the portion of the reflection of the first laser beam pulse substantially along the first direction
Data Source
AI summary
A laser beam metrology system (500) configured to co-operate with a laser beam system that is configured to sequentially direct a first laser beam pulse and a second laser beam pulse (430) to a target along two independent optical paths, the laser beam metrology system comprising a beam steering device (470) and a detection system (510). A laser beam system comprising the laser beam metrology system and a EUV source is also described.