Visible Light Substrate Center Finder for Transparent Wafers
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Solution Overview
Problem
Existing substrate positioning systems for semiconductor manufacturing, particularly with optically transparent substrates, face reliability issues due to lack of contrast in transmissive and reflective detection methods, leading to inaccurate center finding and alignment challenges.
Innovation Solution
A substrate positioning system utilizing an array of visible light sources and an image sensor array to illuminate and detect the edges of substrates, determining the center based on edge point coordinates, and adjusting algorithms for different substrate types and processing stages, with the system controller controlling light source positions and data analysis for precise alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If transmissive detection methods using collimated laser light sources are used, then center finding capability is provided, but reliability deteriorates with optically transparent substrates due to lack of contrast
Solution Approach 1:
The patent changes the wavelength range from infrared laser to visible light spectrum (380-740 nm), exploiting the visual contrast that transparent substrates provide in the visible range. This allows the substrate to appear as a visible object with defined edges rather than being invisible to the detection system.
Solution Approach 2:
The system changes the illumination parameters by using visible light wavelengths instead of infrared, and employs multiple light sources at different positions and angles to create varied illumination patterns that enhance edge detection contrast for transparent substrates.
2Measurement precision
If reflective detection methods are used, then center finding capability is provided, but reliability deteriorates with optically transparent substrates due to lack of contrast
Solution Approach 1:
The system transitions from using laser light (typically infrared or single wavelength) to visible light spectrum, where transparent substrates exhibit sufficient reflectivity and edge contrast. The visible light range (380-740 nm) provides natural contrast at substrate edges that enables reliable detection.
Solution Approach 2:
The illumination system is divided into multiple independent light sources positioned at different locations and angles around the substrate. This segmentation allows selective illumination from optimal angles to maximize edge contrast and enables the system to adapt to different substrate types and orientations.
3Measurement precision
If multiple light source positions and multiple scans are used, then measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The detection system is segmented into multiple light sources and sensor positions, with each combination providing independent measurement data. This segmentation enables comprehensive edge mapping through multiple scans while allowing the system to process and integrate data from various angles to achieve high measurement accuracy.
Solution Approach 2:
The array of visible light sources and image sensor array are designed to perform multiple functions: illumination from different angles, edge detection, and center calculation. The system can adapt the same hardware configuration to detect different substrate types (transparent, opaque, semi-transparent) without requiring specialized components for each case.
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
The system provides accurate and reliable center finding for various substrate types, including transparent ones, enhancing alignment precision and adaptability, while being safe, easy to maintain, and compatible with existing systems.
Implementation Method 1
an image sensor array including a plurality of pixels operable to receive visible light and secondary emissions from the substrate
Data Source
AI summary
A method and apparatus for locating the center of a substrate are provided. The substrate-positioning system uses an array of visible light sources to illuminate the substrate and its edges. The light sources are non-laser in nature and typically emit in the visible spectrum. The light sources are typically LEDs so that the individual elements may be switched-on or switched-off extremely rapidly, which allows for multiple images to be taken using different light sources at any given substrate rotation position. The substrate-positioning system further includes an image sensor array with the ability to process data rapidly, which allows for the digitization (quantization) of each pixel being viewed. Algorithms analyze the values for patterns and determine the true edge position at each rotational angle of the substrate. The systems and methods described herein are able to locate the center of various types of substrates composed of different materials and/or edge types.