Wafer Edge Defect Detection via X-ray Diffraction
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Solution Overview
Problem
Existing methods for detecting defects at the edge of silicon wafers, such as cracks and delamination, are not sufficiently sensitive or efficient, leading to potential catastrophic failures in processing stages like rapid thermal annealing.
Innovation Solution
An X-ray diffraction imaging system that uses a rotating disk and dual X-ray source/detector pairs to generate composite images in a polar coordinate system, enhancing sensitivity and throughput by detecting defects through Bragg reflections and processing images from both sides of the wafer edge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If ultrasonic or laser detection units are used to detect wafer edge defects, then detection capability is provided, but sensitivity and throughput are insufficient
Solution Approach 1:
The patent replaces conventional mechanical inspection systems (ultrasonic detection units, laser detection units) with an X-ray diffraction imaging system. This substitution enables simultaneous achievement of high sensitivity through Bragg reflection detection and high throughput through rapid image acquisition and processing, resolving the contradiction between measurement precision and productivity
Solution Approach 2:
The patent changes the detection parameter from mechanical/optical surface inspection to X-ray diffraction imaging with Bragg reflections. By adjusting X-ray energy levels and detection angles, the system achieves enhanced sensitivity for detecting subsurface defects while maintaining high inspection throughput through efficient image processing
2Measurement precision
If light diffusers and imaging systems are used for wafer edge inspection, then surface defects can be detected, but sensitivity for cracks and delamination is insufficient
Solution Approach 1:
The patent replaces complex optical imaging systems with X-ray diffraction imaging. This substitution provides superior sensitivity for detecting cracks and delamination through Bragg reflections while simplifying the overall system architecture by eliminating the need for light diffusers, multiple optics, and complex illumination systems
3Reliability
If conventional inspection methods are used, then inspection can be performed, but catastrophic failures occur due to undetected defects
Solution Approach 1:
The patent replaces conventional inspection methods with X-ray diffraction imaging that detects defects through Bragg reflections. This provides the measurement precision needed to detect subsurface cracks and delamination that conventional methods miss, thereby improving wafer processing reliability and preventing catastrophic failures
Solution Approach 2:
The patent performs inspection before critical processing stages such as rapid thermal annealing. By detecting defects early through high-sensitivity X-ray diffraction imaging, the system enables preliminary action to remove or flag defective wafers before they undergo processing that would cause catastrophic failure
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 effectively detects cracks and other defects with high sensitivity and throughput, reducing the risk of wafer breakage and improving overlay alignment in advanced lithography processes.
Implementation Method 1
An X-ray detector is positioned to receive and form input images of the X-rays that are diffracted from the area of the first side of the disk in a reflective mode
Data Source
AI summary
Apparatus for inspection of a disk, which includes a crystalline material and has first and second sides. The apparatus includes an X-ray source, which is configured to direct a beam of X-rays to impinge on an area of the first side of the disk. An X-ray detector is positioned to receive and form input images of the X-rays that are diffracted from the area of the first side of the disk in a reflective mode. A motion assembly is configured to rotate the disk relative to the X-ray source and detector so that the area scans over a circumferential path in proximity to an edge of the disk. A processor is configured to process the input images formed by the X-ray detector along the circumferential path so as to generate a composite output image indicative of defects along the edge of the disk.