Wafer Mark Detection Using Wavelength Filtering and Aperture Stops
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Solution Overview
Problem
Existing exposure methods for manufacturing devices, such as semiconductor and liquid crystal display devices, face challenges in accurately detecting back surface marks on wafers due to defocused infrared light from front surface marks, leading to degraded detection precision of back surface marks.
Innovation Solution
A measuring and exposure method that uses a detection system with a wavelength filter and aperture stop to selectively use visible light for detecting front surface marks and infrared light for back surface marks, preventing noise from front surface marks and allowing high-precision detection of back surface marks by keeping them out of the same field of view.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If infrared light is used to detect back surface marks, then the detection of back marks is enabled, but the front surface marks generate diffracted or scattered light that degrades the contrast of the back surface mark image
Solution Approach 1:
The detection process is segmented into two separate operations: first detecting the front surface mark, then detecting the back surface mark. During back mark detection, the optical system is configured to exclude the front mark from the field of view, thereby preventing the generation of harmful diffracted or scattered light while maintaining infrared light transmission for back mark detection.
2Manufacturing precision
If both front surface mark and back surface mark are detected simultaneously, then overlay inspection can be performed, but the front surface mark interferes with the detection precision of the back surface mark
Solution Approach 1:
The detection system performs periodic sequential detection: first detecting the front surface mark, then detecting the back surface mark in succession. This periodic action allows both marks to be detected for overlay inspection while preventing interference by ensuring that when the back mark is detected, the front mark is excluded from the field of view.
3Adaptability or versatility
If the field of view includes both front surface mark and back surface mark, then both marks can be detected, but the contrast of the back surface mark image is degraded
Solution Approach 1:
The field of view is configured with local quality control: when detecting the back surface mark, the optical system is adjusted so that only the back mark is within the field of view while the front mark is excluded. This localized field configuration maintains high contrast for back mark detection while still enabling versatile detection of both surfaces through sequential operation.
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-precision detection of back surface marks by avoiding interference from front surface marks, improving overlay inspection precision and reducing measurement errors, thus enhancing the accuracy of wafer alignment and exposure processes.
Implementation Method 1
a wavelength filter and aperture stop to selectively use visible light for detecting front surface marks and infrared light for back surface marks
Implementation Method 2
a wavelength filter and aperture stop to selectively use visible light for detecting front surface marks and infrared light for back surface marks, preventing noise from front surface marks
Implementation Method 3
detecting the back marks on the wafer with infrared light
Implementation Method 4
When the light is focused on the back surface mark, the front surface mark becomes defocused
Implementation Method 5
the front surface mark is also irradiated with the infrared light and diffracted light or scattered light of the infrared light from the front surface mark is generated
Implementation Method 6
diffracted light or scattered light of the infrared light from the front surface mark is generated
Implementation Method 7
the front surface mark becomes defocused so that the diffracted light or the scattered light of the infrared light from the front surface mark is incident on the photoelectric conversion element that detects the infrared light and degrades a contrast of an image of the back surface mark
Data Source
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AI summary
A method for measuring a relative position of a first mark and a second mark by using a detection optical system that irradiates a mark formed on the substrate to detect an image of the mark, includes performing a first processing to detect an image of the first mark by using the detection optical system to irradiate the first mark from the first surface side, performing a second processing to detect an image of the second mark by using the detection optical system to irradiate the second mark from the first surface side with light having a wavelength passing through the substrate in a state where the first mark is out of the field of view of the detection optical system, and calculating a relative position of the first mark and the second mark.