Oblique Surface Position Sensing for Reflectance-Stable Exposure Alignment
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Solution Overview
Problem
Existing exposure apparatuses face challenges in accurately aligning the surface of photosensitive substrates with the image surface of the projection optical system due to the shallow depth of focus and non-flat exposed surfaces.
Innovation Solution
A surface position detection device that radiates detection lights with smoothly modulated intensity onto the substrate surface obliquely, forming an irradiation region, and uses a light reception unit with optically conjugated light detection portions to calculate the surface position based on photoelectric conversion signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If oblique-incidence detection method is used, then surface position detection is enabled, but detection accuracy is affected by reflectance variations
Solution Approach 1:
The detection surface is divided into multiple detection regions, each illuminated by separate detection light beams. By segmenting the measurement into multiple independent regions and combining their signals, the system achieves more reliable surface position detection that is less sensitive to local reflectance variations.
Solution Approach 2:
Different detection regions are illuminated with detection lights having different intensity distributions. The light intensity in each region is optimized locally to account for variations in surface reflectance, ensuring consistent detection accuracy across the entire measurement surface despite local reflectance differences.
2Reliability
If multiple detection lights are used to improve measurement coverage, then detection reliability improves, but device complexity increases
Solution Approach 1:
The detection optical system is designed to perform multiple functions: it illuminates multiple detection regions simultaneously, collects reflected light from each region, and processes the combined signals to determine surface position. This multi-functional design achieves reliable multi-point detection without requiring separate optical systems for each function.
Solution Approach 2:
Multiple detection light beams and their corresponding reflected light paths are merged into a unified detection process. The optical system combines the signals from multiple detection regions through a single light reception unit, reducing overall system complexity while maintaining the benefits of multi-point measurement.
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 solution enables highly accurate detection of surface positions, unaffected by variations in reflectance, thereby improving the precision of position alignment between the substrate surface and the projection optical system.
Implementation Method 1
a plurality of detection lights having a smoothly modulated intensity in the detected surface in a first direction within the detected surface are radiated and superimposed onto the detected surface obliquely
Implementation Method 2
receives at a different position of each light reception surface, the plurality of detection lights reflected by a detection region and outputs each photoelectric conversion signal of the plurality of detection lights
Data Source
AI summary
A surface position detection device that information of a detected surface along an axis that intersects the detected surface includes: a light transmission unit having a modulated intensity in the detected surface in a first direction within the detected surface are radiated and superimposed onto the detected surface obliquely from a direction having a direction component in the first direction and forms an irradiation region on the detected surface; a light reception unit arranged with respect to the detected surface, receives at a different position of each light reception surface, the plurality of detection lights reflected by a detection region of which a width in the first direction is a predetermined value in the irradiation region, and outputs photoelectric conversion signal of the plurality of detection lights; and calculates the detected surface based on the photoelectric conversion signal of the plurality of detection lights output from the light reception unit.