Droplet Timing Sensor EUV Light Source Control
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Solution Overview
Problem
Existing droplet timing sensors in extreme ultraviolet light generating apparatuses face challenges in accurately detecting droplet passage timing due to variations in light income caused by contaminations and disturbances, leading to inconsistent EUV light generation and semiconductor microfabrication issues.
Innovation Solution
A droplet timing sensor system comprising a light source unit, a light receiving unit, and a light source controller that irradiates and detects illumination light changes, extracts frequency-distributed light incomes, and controls the light source output based on maximum frequency or target value differences to accurately determine droplet passage timing, thereby stabilizing EUV light generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional droplet timing sensor is used to detect droplet passage timing, then the detection can be performed, but the accuracy is degraded due to variations in light income caused by contaminations and disturbances
Solution Approach 1:
The patent applies partial action by selectively using only the mode signal (most frequent light income value) from multiple measurements to control the light source output. By ignoring outlier measurements caused by contaminations or disturbances and focusing only on the predominant mode value, the system achieves reliable droplet passage timing detection despite environmental variations.
Solution Approach 2:
The patent implements feedback control by continuously monitoring light income variations, determining the mode signal from multiple measurements, and adjusting the light source output accordingly. This closed-loop feedback mechanism ensures that the illumination remains stable and compensates for variations caused by contaminations or disturbances on optical components.
2Reliability
If multiple light income measurements are taken to improve detection accuracy, then the reliability improves, but the processing complexity increases
Solution Approach 1:
The patent changes the control parameter from direct light income values to the mode signal (most frequent value) derived from multiple measurements. This parameter transformation simplifies the control logic by converting complex multi-dimensional measurement data into a single representative value that captures the essential illumination condition, making the controller more manageable despite multiple measurements.
Solution Approach 2:
The patent creates a simplified representation (mode signal) that copies the essential characteristic of multiple light income measurements. Instead of processing all raw measurement data, the system creates a condensed mode value that represents the typical illumination condition, reducing processing complexity while maintaining reliability.
Data Source
AI summary
A droplet timing sensor that detects droplet passage timing by receiving a light from a light source unit with which a droplet is irradiated in an extreme ultraviolet light generating apparatus eliminates an influence of droplet passage on light source control for obtaining a constant light income. The droplet timing sensor includes: a light source unit configured to irradiate a droplet with an illumination light at a predetermined position; a light receiving unit (70) configured to receive the illumination light having passed through the predetermined position and detect a change in a light income; and a light source controller (301) configured to obtain a frequency distribution of light incomes measured multiple times with time using a statistical processing unit (76), and control an output of the light source unit based on a light income at maximum frequency.