Inspection Device Using Divided Aperture Lens for High-Sensitivity Defect Detection
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Solution Overview
Problem
Existing defect inspection techniques for semiconductor substrates face challenges in detecting minute defects with high precision, consistency, and speed, often requiring increased illumination energy which can damage samples, and struggle to capture scattered light effectively across various angles.
Innovation Solution
The inspection device employs a thin-line illuminated area with a converging optical system using a lens group with divided apertures and a parallel photon counting sensor with a matrix of partitions, allowing for high-sensitivity detection of minute defects by forming multiple images and reducing background noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the wavelength of illumination light is shortened or laser output is increased to increase the defect detection signal, then the sensitivity for detecting minute defects is improved, but the risk of damaging the sample increases
Solution Approach 1:
The detector is divided into multiple detector elements arranged in a two-dimensional array, allowing the system to detect scattered light from defects with high sensitivity without concentrating excessive energy on a single point, thereby reducing sample damage risk while maintaining detection precision
Solution Approach 2:
The patent transitions from single-point detection to two-dimensional array detection, capturing scattered light from multiple spatial positions simultaneously. This dimensional expansion allows comprehensive defect detection across the illuminated area without requiring increased laser power per unit area
2Device complexity
If a single detector element is used for photon counting, then the device complexity is reduced, but the capability to detect multiple photons incident within a short time is lost
Solution Approach 1:
The detector is segmented into multiple independent detector elements that can simultaneously count photons from different spatial positions. This segmentation enables the system to handle multiple photons incident within short time intervals by distributing the detection load across multiple elements
Solution Approach 2:
Multiple detector elements are combined into a two-dimensional array that functions as an integrated detection system. The individual detection capabilities of each element are merged to achieve comprehensive photon counting across the entire illuminated area, maintaining high detection throughput
3Measurement precision
If the optical detection aperture is enlarged to capture all scattered light from defects, then the measurement precision is improved, but the device complexity and alignment difficulty increase
Solution Approach 1:
The optical detection system uses multiple detector elements arranged in a two-dimensional array, each capturing scattered light from specific angular ranges. This segmentation of the detection aperture allows comprehensive light collection without requiring a single complex large-aperture optical system
Solution Approach 2:
The two-dimensional detector array serves multiple functions simultaneously: it detects scattered light from defects, determines defect positions, and measures defect sizes. This multi-functionality reduces the need for separate optical systems for each measurement task, simplifying the overall optical configuration
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 configuration enables fast and sensitive detection of minute defects with high precision, ensuring consistent results and minimizing sample damage, while effectively capturing scattered light across various angles, thus improving inspection throughput and accuracy.
Implementation Method 1
a focused laser beam is applied onto the sample surface while weak light scattered from the defect is converged and detected
Implementation Method 2
a converging optical system for converging light from the sample
Implementation Method 3
In a detector including a plurality of APD (Avalanche Photo Diode) elements arranged in a two-dimensional array, the sum of pulse currents generated upon incidence of photon on the individual elements is calculated
Data Source
AI summary
An inspection device has an illuminating optical system for forming an illuminated area on a sample, a converging optical system for converging the light from the sample, and a detector for detecting the light converged by the converging optical system. The converging optical system includes an image forming element that includes a lens group that has divided apertures and is configured so as to form a plurality of images. The detector detects a signal for the images formed by the image forming element. The detector has a plurality of partitions disposed in a matrix, the partitions include first and second pixels, and the images are projected onto the partitions.