Wafer Edge Detection via Collimated Light Imaging
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for detecting the conditions of semiconductor wafers in a cassette, such as shade scanning and image-based brightness profile analysis, are either time-consuming, susceptible to local disturbances, or unreliable due to reflectance issues with coated wafers, and require multiple sensors for accurate detection.
Innovation Solution
A substrate detection apparatus using a surface light source with a point light source, collimating reflector, and retroreflector, which forms a passing light image of wafer edges, allowing for accurate detection of wafer presence, orientation, and projection without mechanical scanning, utilizing a single camera for reliable and efficient image processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a transmission light switch is used for mechanical scanning of wafer edges, then detection reliability is improved, but detection time increases and device complexity increases
Solution Approach 1:
The patent replaces the mechanical scanning system with a light source and camera system. Instead of mechanically moving a transmission light switch across wafer edges, the invention uses optical fields (light) to illuminate wafers and a camera to capture images, thereby eliminating mechanical movement while maintaining detection capability and improving speed.
Solution Approach 2:
The patent creates an optical copy (image) of the wafer edges by capturing reflected light with a camera. This optical copying process replaces the need for direct mechanical contact and scanning, allowing parallel detection of multiple wafers simultaneously, thus reducing detection time while maintaining reliability.
2Reliability
If a transmission light switch is used for mechanical scanning, then detection reliability is improved, but device complexity increases due to additional sensors
Solution Approach 1:
The patent makes the light source serve multiple functions: it illuminates the wafers for imaging and also provides the light that reflects off wafer edges for detection. This single light source replaces the need for separate transmission light switches and other dedicated sensors, reducing device complexity while maintaining detection reliability through the camera-based imaging system.
3Productivity
If image processing based on brightness profile lines is used, then detection speed is improved, but measurement precision deteriorates due to susceptibility to local disturbance
Solution Approach 1:
The patent segments the wafer edge detection into multiple brightness profile lines that are extracted from different regions of the wafer edge in the captured image. By analyzing multiple segmented profile lines rather than relying on a single line, the system maintains high detection speed while improving measurement precision through redundancy and reduced susceptibility to local disturbances.
4Productivity
If brightness profile line analysis is used for detecting wafer conditions, then detection speed is improved, but reliability deteriorates when wafers are coated with coating agents
Solution Approach 1:
The patent detects wafer conditions by analyzing brightness variations and patterns in the captured images rather than relying on specific reflectance characteristics. This approach allows the system to detect wafer presence, orientation, and coating status through image processing of brightness distribution, maintaining reliability even when coating agents alter the reflectance properties of coated wafers.
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 solution provides rapid, reliable, and accurate detection of wafer conditions, including presence, orientation, and projection, with reduced susceptibility to reflectance issues and mechanical scanning time, enabling improved throughput and system compactness.
Implementation Method 1
a collimating reflector, which reflects and collimates light from the point light source
Implementation Method 2
a retroreflector, which reflects light, having been reflected and collimated by the collimating reflector, toward the collimating reflector
Data Source
Figure 1A~1B
Figure 2
Figure 3~4
AI summary
The substrate detection apparatus includes: a collimating reflector located on one side of substrates; an illumination unit configured to radiate light in a planar state toward the collimating reflector such that edge portions of the substrates are located in an optical path of the light; an image acquiring unit configured to acquire a passing light image including the edge portions formed on the collimating reflector with the light radiated in the planar state from the illumination unit; and an image processing unit configured to process the passing light image obtained by the image acquiring unit, thereby detecting the conditions of the substrates.