Surface Position Sensing Using Multi-Wavelength Reflectance Compensation
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Solution Overview
Problem
Existing surface position detection devices face challenges in accurately aligning the surface of a photosensitive substrate with the image surface of a projection optical system due to the shallow depth of focus and non-flat exposed surfaces, particularly in exposure apparatuses where reflectance variations affect detection accuracy.
Innovation Solution
A surface position detection device that uses a configuration of detection light division and polarization separation to form sinusoidal light distributions on the substrate surface, allowing for precise detection of surface position changes by calculating the Z position based on photoelectric conversion signals from multiple wavelength components, thereby minimizing the impact of reflectance variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional surface position detection methods are used, then the device complexity is low, but the measurement precision deteriorates due to reflectance variations affecting detection accuracy
Solution Approach 1:
The detection light is divided into multiple wavelength components (first detection light and second detection light with different wavelengths) that are radiated onto the detected surface at different positions. By segmenting the light into multiple wavelengths and detecting their respective reflections, the system can calculate surface position while compensating for reflectance variations, thereby improving measurement precision without excessive complexity increase
Solution Approach 2:
The invention changes the wavelength parameter of the detection light to improve measurement accuracy. By using detection lights of different wavelengths and analyzing the photoelectric conversion signals from these multiple wavelength components, the system can determine surface position that is not susceptible to reflectance changes, resolving the contradiction between measurement precision and device complexity
2Manufacturing precision
If the photosensitive substrate surface is non-flat, then the depth of focus is exceeded, but the manufacturing precision deteriorates due to inaccurate position alignment
Solution Approach 1:
The invention measures surface position in the Z-direction (optical axis direction) by detecting the reflection characteristics of multiple wavelength components. By adding this depth dimension measurement capability, the system can accurately determine the position of non-flat substrate surfaces along the optical axis, enabling precise position alignment even when the substrate surface is not flat, thus improving manufacturing precision without requiring perfect surface flatness
3Measurement precision
If reflectance variations are present on the substrate surface, then the detection signal varies, but the measurement precision deteriorates due to inaccurate surface position detection
Solution Approach 1:
The system uses photoelectric conversion elements to detect the reflection characteristics of multiple wavelength components and feeds back this information to calculate the surface position. By continuously monitoring the photoelectric conversion signals from different wavelengths and using this feedback to determine position, the system can compensate for reflectance variations and maintain high measurement precision
Solution Approach 2:
By changing the wavelength parameter and using multiple wavelength components for detection, the invention makes the surface position measurement independent of reflectance variations. The calculation unit analyzes the combined information from multiple wavelengths to determine position, effectively eliminating the harmful effect of reflectance changes on measurement precision
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 highly accurate surface position detection that is not susceptible to reflectance changes, improving the alignment of substrate surfaces with projection optical systems and reducing measurement errors in exposure processes.
Implementation Method 1
a light reception unit that has light detection portions arranged at an optically conjugated position with respect to the detected surface, receives reflected detection lights, and outputs photoelectric conversion signals
Implementation Method 2
A surface position detection device uses a configuration of detection light division and polarization separation to form sinusoidal light distributions on the substrate surface
Data Source
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AI summary
A surface position detection device that obtains position information of a detected surface along an axis that intersects the detected surface includes: a light transmission unit by which 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 from a direction having a direction component in the first direction and which forms an irradiation region on the detected surface; a light reception unit that has a light detection portion having a light reception surface arranged at an optically conjugated position 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 each photoelectric conversion signal of the plurality of detection lights; and a calculation unit that calculates position information of the detected surface based on the photoelectric conversion signal of the plurality of detection lights output from the light reception unit.