Laser-to-Droplet Alignment via Stereoscopic Optical Sensing
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Solution Overview
Problem
Current lithographic apparatuses face challenges in accurately aligning laser beams with droplets in extreme ultraviolet (EUV) light sources, leading to thermal drifts and costly service actions due to direct interaction with high-power lasers, resulting in inefficient EUV source performance and production interruptions.
Innovation Solution
A system utilizing two optical sensing devices, including a photoreceiver and an imaging device, configured to generate sensing data at different rates for model-based estimation of laser-to-droplet alignment, providing stereoscopic vision and eliminating direct contact with high-power lasers, thus preventing thermal transients and simplifying repair processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If direct interaction with high-power lasers is used for alignment, then alignment precision is improved, but thermal drift and service actions increase
Solution Approach 1:
The patent introduces optical sensing devices as intermediaries between the laser beam and droplet. These devices detect alignment without direct interaction with the high-power laser, preventing thermal drift while maintaining measurement precision. The sensing devices convert optical information into electrical signals for processing, serving as a buffer that eliminates harmful thermal effects.
Solution Approach 2:
The patent replaces direct mechanical/optical interaction with high-power lasers with an optical sensing and model-based estimation system. Instead of using the laser itself for alignment detection, the system uses separate sensing devices to monitor alignment and computational models to determine precise positioning, substituting physical interaction with informational processing.
2Power
If high-power lasers are used for EUV generation, then EUV output is improved, but thermal transients and maintenance costs increase
Solution Approach 1:
The optical sensing devices serve as intermediaries that monitor the laser-droplet interaction without being damaged by the high-power laser. This allows continuous operation of the high-power laser system while enabling preventive maintenance through accurate alignment monitoring, reducing unexpected failures and maintenance complexity.
Solution Approach 2:
The system implements feedback through optical sensing devices that continuously monitor alignment parameters. This feedback enables real-time adjustments and predictive maintenance, allowing the high-power laser system to operate at full capacity while preventing thermal drift-related failures that would increase maintenance complexity.
3Measurement precision
If single optical sensing device is used, then device complexity is reduced, but measurement accuracy and stereoscopic vision are lost
Solution Approach 1:
The patent merges data from multiple optical sensing devices with different viewing angles to create a comprehensive alignment measurement. By combining the sensing data and applying stereoscopic vision algorithms, the system achieves three-dimensional alignment information that is more accurate than any single device could provide alone.
Solution Approach 2:
The system transitions from two-dimensional measurements by single sensors to three-dimensional stereoscopic vision by using multiple sensing devices at different angles. This dimensional enhancement provides complete spatial alignment information, enabling precise determination of laser beam and droplet positions in three-dimensional space.
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 solution achieves precise and stable EUV light source alignment with reduced thermal drifts, enhancing productivity and reducing maintenance costs by providing absolute and accurate laser-to-droplet measurements without thermal issues, leading to improved EUV source performance and increased productivity.
Implementation Method 1
a photoreceiver (e.g., a quadrant-cell photoreceiver (quad-cell)) configured to generate first sensing data at a first rate
Implementation Method 2
an imaging device (e.g., a photodetector, photodiode, camera, or other suitable device) configured to generate second sensing data at a second rate
Implementation Method 3
converting a material that has an element, for example, xenon (Xe), lithium (Li), or tin (Sn), with an emission line in the EUV range to a plasma state. For example, in one such method called laser produced plasma (LPP), the plasma can be produced by irradiating a target material
Implementation Method 4
Extreme ultraviolet (EUV) radiation, for example, electromagnetic radiation having wavelengths of around 50 nanometers (nm) or less
Data Source
AI summary
Systems, apparatuses, and methods are provided for steering aligning a laser beam and a fuel target. An example method can include generating, at a first rate, first sensing data indicative of a first overlap between a fuel target and a laser beam. The example method can further include generating, at a second rate, second sensing data indicative of a second overlap between the fuel target and the laser beam. The method can further include generating, at a third rate, and based on the first sensing data and the second sensing data, a steering control signal configured to steer the laser beam or the fuel target. In some aspects, the second rate can be different from the first rate, and the third rate can be about equal to the first rate. In other aspects, the first rate and the second rate can be about equal to the third rate.