Coherence Adjuster Waveguide for Fast, Accurate Optical Metrology
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Solution Overview
Problem
Existing metrology systems in lithographic processes face challenges in achieving fast and accurate measurements of parameters such as critical dimensions and overlay error, with a need for improved illumination systems to enhance measurement speed and accuracy.
Innovation Solution
A metrology system comprising a radiation source, coherence adjuster, detector, and processor, utilizing a waveguide device and actuator to adjust the coherence of radiation beams for precise target measurement, with features like multimode waveguides and diffusers to optimize impingement characteristics and interference patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If spatially coherent radiation is used for metrology measurements, then measurement speed and brightness can be increased, but speckle patterns appear causing measurement errors
Solution Approach 1:
The patent employs a dynamic coherence adjustment mechanism that modulates the coherence of radiation in real-time. By dynamically varying the coherence state of the radiation beam, the system captures multiple measurements with different interference patterns and averages them, thereby eliminating speckle-related errors while preserving the high brightness and speed advantages of coherent radiation sources.
2Loss of time
If the amount of radiation detected is increased to shorten measurement time, then measurement speed improves, but coherence-related errors increase
Solution Approach 1:
The system implements periodic modulation of the radiation coherence through a coherence adjuster that cyclically varies the coherence state. This periodic action allows the system to rapidly acquire multiple measurements with different interference characteristics, enabling time-averaging that reduces coherence errors while maintaining short overall measurement times suitable for high-throughput metrology applications.
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
Enhances measurement accuracy and speed by adjusting coherence and impingement characteristics of radiation beams, allowing for faster and more precise determination of target parameters.
Implementation Method 1
An interference pattern of the coherence adjusted beam is adjusted based on the change of the impingement characteristic
Implementation Method 2
converting spatially coherent radiation into a coherence-adjusted beam that reduces speckle patterns and enhances measurement accuracy and speed by averaging out the interference pattern over time
Data Source
AI summary
A metrology system (400) includes a multi-source radiation system. The multi-source radiation system includes a waveguide device (502) and the multi-source radiation system is configured to generate one or more beams of radiation. The metrology system (400) further includes a coherence adjuster (500) including a multimode waveguide device (504). The multimode waveguide device (504) includes an input configured to receive the one or more beams of radiation from the multi-source radiation system (514) and an output (518) configured to output a coherence adjusted beam of radiation for irradiating a target (418). The metrology system (400) further includes an actuator (506) coupled to the waveguide device (502) and configured to actuate the waveguide device (502) so as to change an impingement characteristic of the one or more beams of radiation at the input of the multimode waveguide device (504).