Wafer Edge Detection Using Retroreflective Reference Surface
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Solution Overview
Problem
Conventional semiconductor wafer inspection methods are insufficient and complicated for accurately detecting the edge and notch of wafers, leading to challenges in positioning and mapping defects within the wafer's coordinate system.
Innovation Solution
A detection system utilizing a camera with a retroreflecting surface portion carrying a multitude of retroreflectors, positioned at a distance from the camera, allows for precise detection of the wafer's edge and notch by analyzing the angular intensity distribution of reflected light, enabling accurate positioning and defect mapping within the wafer's coordinate system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional tools and methods are used for wafer edge and notch detection, then the inspection process can be performed, but the detection accuracy is insufficient and the process becomes complicated
Solution Approach 1:
A retroreflecting surface is introduced as an intermediary element positioned between the camera and the wafer. This retroreflecting surface serves as a mediator that provides stable reference points for coordinate system determination, eliminating the need for complex conventional edge and notch detection tools while improving measurement precision.
2Measurement precision
If conventional reflection surfaces are used behind the object, then the setup is simpler, but the edge and outline detection accuracy is lower
Solution Approach 1:
The optical properties of the reflection surface are changed by using retroreflectors instead of conventional Lambertian surfaces. This parameter change in the reflection characteristics enables high-accuracy edge and outline detection by providing stable, direction-independent reference signals that significantly improve 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
The system achieves high accuracy in determining the position and orientation of semiconductor wafers, allowing for precise defect detection and comparison across multiple wafers, enhancing the efficiency of semiconductor wafer inspection processes.
Implementation Method 1
at least one surface portion carrying a multitude of retroreflectors, wherein the surface portion is disposed farther away from the camera such that the object overlaps, when seen from the camera, with the surface portion carrying the multitude of retroreflectors
Data Source
AI summary
A wafer inspection system comprises a camera having a field of view, an object mount configured to position at least a portion of surface 5 of an object 3 at an object plane 15 relative to the camera and within the field of view of the camera and at least one surface portion 41 carrying a multitude of retroreflectors 95 disposed at a greater Δd distance from the camera than the object plane and within the field of view of the camera.