Foreign Substance Detection Device Using Laser Light Flattening
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Solution Overview
Problem
Current foreign substance detection methods in semiconductor manufacturing struggle to accurately detect microscopic particles and abnormal polymers in chemical liquids due to decreased signal-to-noise ratios, making it difficult to achieve high accuracy in detecting small particles and distinguishing them from normal polymer noise.
Innovation Solution
A foreign substance detection device and method that uses a laser light irradiation unit with an optical system to flatten and lengthen laser light intersecting with the fluid flow path, combined with multiple light receiving elements arranged along the optical path, allowing for comparison of signal levels to detect foreign substances based on interference patterns generated by the substances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a laser light is used to detect foreign substances in chemical liquid, then the detection capability is improved, but the signal-to-noise ratio decreases when detecting microscopic particles
Solution Approach 1:
The patent transforms the detection approach from measuring scattered light intensity directly to analyzing the temporal waveform characteristics of the signal. By examining the rise time, fall time, and integrated area of the waveform generated when particles pass through the laser beam, the system can distinguish between actual particles and noise based on their temporal signal profiles rather than just intensity thresholds.
Solution Approach 2:
The patent changes the detection parameter from static light intensity measurement to dynamic waveform analysis. By monitoring temporal parameters such as signal rise time, fall time, and integrated area of the waveform, the system can differentiate between microscopic particles and noise signals, effectively improving the signal-to-noise ratio while maintaining detection capability.
2Measurement precision
If the detection sensitivity is increased to detect smaller particles, then the measurement precision is improved, but the noise from normal polymers increases
Solution Approach 1:
The patent segments the detection process into multiple temporal phases: signal rise time, peak holding time, and fall time. By analyzing each phase separately and comparing the integrated area of the waveform to predetermined thresholds, the system can identify actual particles while filtering out noise from normal polymers, thus maintaining high detection sensitivity without being overwhelmed by polymer noise.
Solution Approach 2:
The system uses feedback mechanisms by comparing the measured waveform characteristics (integrated area, rise time, fall time) against predetermined threshold values. This feedback loop enables real-time discrimination between genuine particles and noise signals, allowing the system to maintain high detection sensitivity while automatically filtering out polymer-induced noise.
3Loss of information
If a particle counter is used to monitor foreign substances, then the monitoring capability is improved, but it becomes difficult to distinguish microscopic particles from noise
Solution Approach 1:
The patent introduces dynamic temporal analysis to the monitoring process. Instead of relying on static intensity thresholds, the system captures the time-varying waveform characteristics as particles pass through the laser beam. By analyzing the dynamic evolution of the signal (rise time, fall time, waveform shape), the system can distinguish microscopic particles from noise with high accuracy while maintaining comprehensive monitoring capability.
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 enables high-accuracy detection of small foreign substances by improving the signal-to-noise ratio and reducing noise interference from normal polymers, enhancing the detection accuracy of particles and abnormal polymers in chemical liquids.
Implementation Method 1
measure the amount of the foreign substances by receiving scattered light from the foreign substances
Implementation Method 2
compare a signal level according to a signal level of an electric signal corresponding to intensity of light received by each of the multiple light receiving elements with a threshold value corresponding to a signal level of an electric signal obtained when an interference pattern is generated by the foreign substance in the fluid
Data Source
AI summary
A foreign substance detection device includes a flow path unit through which a fluid is flown; an optical system configured to flatten a laser light from a laser source to be lengthened in a direction intersecting with a flow direction of the fluid; a laser light irradiation unit provided such that an optical path intersects with the flow direction and configured to irradiate the laser light into the flow path unit; a light detection unit which is provided on the optical path having passed through the flow path unit and includes light receiving elements arranged in a lengthwise direction of a transversal cross section of the optical path; a foreign substance detection unit configured to compare a signal level corresponding to intensity of light received by each light receiving element with a threshold value and configured to detect the foreign substances based on a comparison result.