Inspection System for Semiconductor Wafer Edge Defect Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing inspection systems for flat semiconductor objects, such as wafers and solar cells, face challenges in detecting defects on chamfers or slanted edges, particularly the leading and trailing edges, due to limited depth of field and uneven illumination, leading to inaccurate detection and increased complexity in the inspection process.
Innovation Solution
The solution involves using a line scan camera with a tilted observation angle and a 3D camera or Time-of-Flight camera to identify and isolate only the sharp pixels within the depth of field, combining images to create a clear representation of the edges, and employing a mirror arrangement to image both leading and trailing edges without rotating the wafer, ensuring consistent detection sensitivity across all edges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the wafer is rotated to inspect all four edges, then complete edge inspection is achieved, but the inspection process becomes more complex and time-consuming
Solution Approach 1:
The patent uses a tilted observation angle (e.g., 45 degrees) to inspect wafer edges without rotation. By changing the observation dimension from perpendicular to tilted, the imaging system captures edge information including chamfers in a single pass, eliminating the need for rotational movement while maintaining inspection completeness
Solution Approach 2:
Instead of rotating the wafer to achieve complete edge inspection, the patent inverts the approach by tilting the observation angle of the imaging system. This allows the same inspection goal to be achieved by modifying the observer's perspective rather than the object's orientation
2Measurement precision
If the observation angle is increased to capture more edge information, then detection sensitivity improves, but the depth of field decreases leading to blurred images
Solution Approach 1:
The patent optimizes the observation angle parameter (e.g., 45 degrees) to achieve an optimal balance between capturing sufficient edge information and maintaining adequate depth of field. This parameter adjustment allows the imaging system to capture both edge defects and chamfer geometry with acceptable sharpness without requiring extreme angles
3Productivity
If the wafer is transported at high speed for high throughput, then productivity increases, but the exposure time decreases reducing detection sensitivity
Solution Approach 1:
The patent implements continuous transport of the wafer through the inspection system at constant high speed, with the imaging system continuously capturing edge information. The tilted observation angle ensures that edge defects are captured during the brief exposure period, maintaining both high throughput and adequate detection sensitivity without requiring speed reduction
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 method allows for reliable and sensitive detection of defects on chamfers and slanted edges without rotating the wafer, improving accuracy and reducing operational complexity, while maintaining high throughput and cost-effectiveness.
Implementation Method 1
The optical axis of each line scan camera is positioned perpendicular to one of the two wafer surfaces... Two line scan illuminators are mounted with an angle of 45° to the wafer surface
Implementation Method 2
employing a mirror arrangement to image both leading and trailing edges without rotating the wafer, ensuring consistent detection sensitivity across all edges
Data Source
Figure 1~1a
Figure 2~3(c)
Figure 4(a)~5
AI summary
The invention relates to an inspection method for inspecting flat semiconductor objects (1), such as wafer, solar cells or intermediate stages thereof, in respect of defects (20a, 20b), particularly defects on chamfers or slanted edges, said inspection method comprising the steps of: - transporting flat object (1) along a transport path (17) in a longitudinal transport direction (T), the transport movement defining a leading edge (4) and a trailing edge (5) of flat object (1), - taking sequentially a plurality of images of flat object (1), particularly of a leading portion and/or a trailing portion of flat object (1), during the movement of flat object (1) along the transport path (17) with at least one imaging system (8, 9), preferably a camera, - selecting from the plurality of images the image data, which were taken from object points of the flat object (1) within the depth of field of the imaging system (8, 9), - recognizing defects (20a, 20b) of flat object (1) essentially by means of the selected image data. The invention also relates to an inspection system for inspecting flat semiconductor objects.