Defect Inspection Apparatus Using Matrix Illumination and Signal Addition
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Solution Overview
Problem
Existing defect inspection technologies face challenges in accurately detecting micro defects on semiconductor substrates due to weak scattering light signals, which are often buried in noise, and struggle to balance sensitivity with thermal damage prevention, leading to inefficient inspection times and costly lens production.
Innovation Solution
A defect inspection method that illuminates a specimen surface with controlled light distribution, separates scattering light into orthogonal directions, performs addition processing on light from the same area, and computes defect presence and size using polarization control and optical elements like diffractive optical elements and spatial light modulators to enhance detection accuracy and speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If illumination power per unit area is increased to improve detection sensitivity, then defect detection accuracy is improved, but thermal damage on the specimen surface occurs
Solution Approach 1:
The illumination is divided into multiple discrete spots rather than using a single large beam. This segmentation allows the total illumination power to be distributed across multiple locations, reducing the power density at each individual spot and thereby minimizing thermal damage while maintaining sufficient total light for defect detection
Solution Approach 2:
The patent transitions from one-dimensional linear scanning to two-dimensional matrix scanning of illumination spots. By arranging multiple illumination spots in a matrix pattern and scanning across both dimensions, the system can cover the entire specimen surface more efficiently, reducing the time each spot is illuminated and thus reducing thermal accumulation while improving overall detection coverage
2Measurement precision
If inspection time per unit area is increased to improve detection accuracy, then defect detection precision is improved, but the time needed to inspect the entire specimen surface increases
Solution Approach 1:
The inspection process is segmented into multiple parallel illumination spots arranged in a matrix. Instead of sequentially scanning the entire surface at one location, multiple spots illuminate different regions simultaneously, allowing parallel processing of multiple areas and thus reducing total inspection time while maintaining detection precision through repeated measurements at each spot
Solution Approach 2:
The system maintains continuous illumination and detection across multiple spots without interruption. By keeping the illumination source active across the entire matrix of spots simultaneously rather than sequentially, the system achieves continuous useful action across the whole specimen surface, improving throughput while maintaining measurement quality
3Measurement precision
If scattering light detection sensitivity is increased to detect micro defects, then defect detection capability is improved, but the weak scattering light signal becomes buried in noise
Solution Approach 1:
The patent combines the signals from multiple illumination spots and multiple detection angles into a unified detection process. By merging the scattering light signals from all spots and angular components through coordinated scanning and signal processing, the system accumulates sufficient signal strength to overcome noise while maintaining the ability to resolve individual micro defects
Solution Approach 2:
The system uses periodic scanning of the illumination spots across the specimen surface in a matrix pattern. This periodic action allows the same region to be illuminated and detected multiple times from different positions and angles, enabling signal accumulation and averaging that improves the signal-to-noise ratio while maintaining defect detection capability
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
Enables fast and accurate detection of micro defects across an entire specimen surface in a short time, reducing thermal damage and improving defect size measurement precision while minimizing lens production complexities.
Implementation Method 1
uses an aspherical lens and a diffractive optical element to shape the illuminating light so as to position multiple illuminating spots on a test surface
Implementation Method 2
detect scattering light from a defect and inspect an area ranging from several tens of nanometers to several micrometers for defects
Data Source
AI summary
A defect inspection method includes: illuminating an area on surface of a specimen as a test object under a specified illumination condition; scanning a specimen to translate and rotate the specimen; detecting scattering lights to separate each of scattering lights scattered in different directions from the illuminated area on the specimen into pixels to be detected according to a scan direction at the scanning a specimen and a direction approximately orthogonal to the scan direction; and processing to perform an addition process on each of scattering lights that are detected at the step and scatter approximately in the same direction from approximately the same area of the specimen, determine presence or absence of a defect based on scattering light treated by the addition process, and compute a size of the determined defect using at least one of the scattering lights corresponding to the determined defect.