Wafer Bevel Defect Detection With Adaptive Imaging Schemes
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Solution Overview
Problem
Existing defect observation technologies struggle to accurately detect defects on the outer circumferential or bevel portions of semiconductor wafers due to variations in coordinate systems between inspection and observation apparatuses, leading to missed detections and reduced accuracy.
Innovation Solution
A defect observation method using a computer system with a processor and memory that captures bevel images and employs a determination step to identify wafer edges, notches, and orientation flats, followed by a scheme switching step to apply the most appropriate defect detection scheme based on imaging position, magnification, and visual field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single defect detection scheme is used for all bevel images, then the device complexity is reduced, but the measurement precision deteriorates due to variations in imaging positions and features
Solution Approach 1:
The patent implements a dynamic defect detection scheme that automatically adapts to different imaging conditions. The system determines the appropriate detection scheme based on imaging position, magnification, and visual field characteristics, allowing the detection method to change dynamically rather than using a fixed single scheme throughout.
Solution Approach 2:
The patent changes detection parameters based on imaging conditions. By analyzing imaging position, magnification level, and visual field content, the system selects different detection schemes optimized for specific parameter ranges, thereby improving measurement precision across varying conditions without requiring a completely complex system redesign.
2Reliability
If wide visual field imaging is performed to compensate for coordinate deviations, then the reliability of defect detection is improved, but the measurement precision of defect positions deteriorates
Solution Approach 1:
The patent segments the imaging process into two distinct stages: a wide visual field imaging stage to locate defect candidates reliably, and a high-magnification imaging stage to precisely measure defect positions. This segmentation allows each stage to optimize for its specific purpose without compromising the other.
Solution Approach 2:
The patent performs preliminary wide visual field imaging to identify and locate defect candidates before conducting high-magnification imaging for precise measurement. This preliminary action ensures that defects are reliably detected first, then precisely measured in a subsequent step, resolving the contradiction between reliability and precision.
3Productivity
If automatic defect classification is implemented to improve productivity, then the loss of time is reduced, but the measurement precision of defect characteristics may deteriorate due to automation errors
Solution Approach 1:
The patent implements feedback mechanisms in the automatic defect classification system. By analyzing classification results and comparing them against known defect patterns and imaging conditions, the system can adjust and improve its classification accuracy over time, maintaining high productivity while minimizing automation errors through continuous refinement.
Data Source
AI summary
A defect observation method includes, as steps executed by a computer system, a first step of acquiring, as a bevel image, an image captured using defect candidate coordinates in a bevel portion as an imaging position by using a microscope or an imaging apparatus; and a second step of detecting a defect in the bevel image. The second step includes a step of determining whether there is at least one portion among a wafer edge, a wafer notch, and an orientation flat in the bevel image, a step of switching and selectively applying a defect detection scheme of detecting the defect from the bevel image from a plurality of schemes which are candidates based on a determination result, and a step of executing a process of detecting the defect from the bevel image in conformity with the switched scheme.