Integrated Optical Element for Lithographic Level Sensor
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Solution Overview
Problem
Conventional level sensors in lithographic apparatuses have complex structures that result in significant light loss and low signal-to-noise ratios, requiring high-powered radiation sources which can lead to pre-exposure of substrates and light contamination.
Innovation Solution
Integration of detection gratings and optical elements into a single compact optical element, reducing the optical path length and minimizing light loss, while using a collimator lens and reflective surfaces to focus beams onto detectors, thereby improving signal quality without increasing radiation power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional level sensors use separate detection gratings and optical elements, then the optical path is longer and light loss is significant, but integrating them into a single element reduces optical path length and minimizes light loss
Solution Approach 1:
The patent integrates the detection grating and optical elements into a single integrated optical element, merging previously separate components. This integration reduces the optical path length and minimizes light loss while maintaining the necessary detection functionality, directly resolving the contradiction between energy loss and device complexity.
2Illumination intensity
If high-powered radiation sources are used to compensate for light loss, then the signal strength is sufficient, but pre-exposure of substrates and light contamination occur
Solution Approach 1:
The patent converts the previously harmful effect of light loss into a benefit by integrating the optical elements. Instead of using high-powered radiation sources that cause pre-exposure and contamination, the integration efficiently utilizes the available light, maintaining signal strength while eliminating the harmful effects of excessive radiation power.
3Adaptability or versatility
If multiple separate optical elements are used in the detection unit, then the design is more flexible, but the volume required for the level sensor increases
Solution Approach 1:
The patent combines multiple optical elements into a single integrated optical element, reducing the overall volume required for the level sensor. The integration maintains the functional versatility of the separate elements while compacting them into a smaller footprint, resolving the contradiction between design flexibility and sensor volume.
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 signal-to-noise ratio and reduces the volume required for the level sensor, allowing accurate substrate position measurement without the drawbacks of high-powered radiation sources, such as pre-exposure and contamination.
Implementation Method 1
a collimator lens and reflective surfaces to focus beams onto detectors
Implementation Method 2
focus beams onto detectors
Data Source
AI summary
The invention provides a level sensor to measure a position of a surface of a substrate, comprising a projection unit arranged to direct a beam of radiation to the surface of the substrate and a detection unit. The detection unit comprises a detection grating arranged to receive the beam of radiation reflected on the surface of the substrate, one or more detectors, one or more optical elements to direct the beam of radiation from the detection grating to the one or more detectors, and a processing unit to determine the position of the surface of the substrate on the basis of the beam of radiation received by the one or more detectors. The detection grating and the one or more optical elements are integrated in a single integrated optical element.