Wafer Thickness Detection Using String Bearing and Optical Interference
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Solution Overview
Problem
Existing methods for detecting the thickness and bow of large-sized wafers are inaccurate due to the influence of gravity, which causes deformation and bending, especially in unsupported areas, leading to unreliable measurements despite the use of multi-point or vertical support systems.
Innovation Solution
A system comprising a transportation mechanism, a handling mechanism with vacuum suction cups, and a detection mechanism using a bearing structure of parallel strings and an optical detection structure with a rotating camera and LCD panel to project a grating, capturing interference fringe images and calculating thickness and bow based on pixel coordinates and pre-calibrated parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multi-point or vertical support systems are used, then the wafer can be supported during detection, but gravity influence on unsupported areas still causes inaccurate thickness and bow detection
Solution Approach 1:
The support structure is segmented into multiple discrete support points (at least three, preferably four or more) distributed across the wafer surface. This segmentation allows each support point to independently counteract gravity's influence, providing comprehensive support coverage that eliminates detection inaccuracies caused by gravitational deformation in unsupported areas.
Solution Approach 2:
The support system provides localized support at specific points across the wafer surface rather than uniform support. By positioning support points strategically (including edges and center), the system addresses local gravitational effects in different regions of the wafer, ensuring accurate thickness and bow detection across the entire wafer surface.
2Ease of operation
If the wafer is placed on a carrier for detection, then the wafer can be positioned for measurement, but the wafer's weak rigidity causes deformation under its own gravity
Solution Approach 1:
The support points function as counterweight elements that oppose the gravitational force acting on the wafer. By distributing multiple support points across the wafer surface, the system creates counterbalancing forces that prevent gravitational deformation, maintaining the wafer's natural shape during detection while keeping the positioning process simple and operational.
3Measurement precision
If reference wafer inversion, sample wafer inversion, and theoretical modeling are used to eliminate gravity influence, then detection accuracy can be improved, but the detection process becomes more complex
Solution Approach 1:
The system performs preliminary support establishment by positioning multiple support points on the wafer before the detection process begins. This preliminary action of providing comprehensive gravitational counterbalance eliminates the need for subsequent complex correction procedures such as wafer inversion or theoretical modeling, thereby maintaining high measurement precision while simplifying the overall detection process.
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 provides uniform support to minimize distortion and deformation, improving detection accuracy and efficiency while simplifying the optical detection structure compared to traditional methods.
Implementation Method 1
The handling mechanism includes a mechanical arm, an end of the mechanical arm is provided with multiple vacuum suction cups
Implementation Method 2
the LCD panel is configured to project a grating onto the wafer to be detected
Implementation Method 3
the camera is configured to rotate 900 successively to take four interference fringe images of the wafer to be detected
Data Source
AI summary
A system for detecting a thickness and a bow of a large-sized wafer and a method for detecting a thickness and a bow of a large-sized wafer are provided and relate to wafer detection, the system includes a transportation mechanism, a handling mechanism and a detection mechanism. The transportation mechanism includes a transportation belt and is configured to transport the wafer. The handling mechanism includes a mechanical arm, an end of the mechanical arm is provided with multiple vacuum suction cups, and the handling mechanism is configured to transport the wafer from the handling mechanism to the detection mechanism. The detection mechanism includes a bearing structure and an optical detection structure, and is configured to detect the thickness and the bow of the wafer. The bearing structure includes multiple strings configured to bear the wafer. The optical detection structure includes a camera and a liquid crystal display (LCD) panel.