Mirror Electron Contrast Optimization in Charged Particle Beam Devices
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Solution Overview
Problem
Existing methods for adjusting the reflection surface in mirror electron microscopes require human input and are not capable of automatically optimizing the contrast of defects, leading to variations in image quality and inefficiencies in defect detection.
Innovation Solution
A charged particle beam device that includes a charged particle source, power sources for the source and sample, and an imaging system that detects mirror electrons while excluding secondary electrons, allowing for automatic adjustment of the reflection surface based on acquired signals to optimize defect contrast.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a method using secondary electrons and mirror electrons is used to control the reflection surface, then the contrast of charged sample images is improved, but the method cannot actively optimize the contrast of images formed using only mirror electrons and requires manual adjustment
Solution Approach 1:
The patent extracts only the mirror electron signal from the mixed signal of secondary electrons and mirror electrons by using an energy filter. This allows the imaging optical system to form images using exclusively mirror electrons, enabling automatic optimization of defect contrast without manual intervention while maintaining high contrast performance
Solution Approach 2:
The patent implements an automatic adjustment mechanism where the control unit acquires images at different potential differences between the charged particle source and sample, evaluates the contrast of defects in these images, and automatically determines the optimal potential difference setting. This feedback loop eliminates the need for manual adjustment and consistently achieves optimal defect contrast
2Measurement precision
If manual adjustment of the reflection surface is performed to optimize defect contrast, then image quality is improved, but variations occur among operators and the process is time-consuming
Solution Approach 1:
The patent enables the system to automatically perform the adjustment task that previously required human operators. The control unit autonomously acquires images at multiple potential differences, evaluates defect contrast, and determines the optimal setting without human intervention. This self-service capability eliminates operator variations and significantly reduces the time required for reflection surface optimization
Solution Approach 2:
The patent replaces the manual mechanical adjustment process with an automated electronic control system. Instead of operators manually adjusting potentials, the control unit electronically controls the potential difference between the charged particle source and sample, automatically optimizing the reflection surface based on image evaluation algorithms
3Measurement precision
If an energy filter is used to control energy distribution of electron beam, then contrast of defect is improved, but the device complexity increases
Solution Approach 1:
The patent integrates the energy filter into the existing imaging optical system, allowing it to perform multiple functions: filtering electrons by energy to separate mirror electrons from secondary electrons, and working in conjunction with the potential difference control to optimize defect contrast. This multi-functionality approach improves contrast without proportionally increasing device complexity
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 high-accuracy, automated control of the reflection surface, improving defect detection accuracy and throughput by optimizing the contrast of defects within a wide field of view.
Implementation Method 1
a first power source that applies a first voltage to the charged particle source, a second power source that applies a second voltage to a sample
Implementation Method 2
the imaging optical system forms an image of mirror electrons returned by an electric field generated at the sample due to a potential difference between the first and second voltages
Data Source
AI summary
In order to optimize defect contrast in a charged particle beam device that inverts charged particles directly above a sample and observes the electrons, this charged particle beam device is provided with a charged particle source, an electron gun control device which applies a first voltage to the charged particle source, a substrate voltage control device which applies a second voltage to a sample, an image forming optical system which includes an imaging lens for imaging charged particles incident from the direction of the sample, a detector which includes a camera for detecting the charged particles, and an image processing device which processes the detected signal, wherein the imaging optical system is configured so as not to image secondary electrons emitted from the sample, but forms an image with mirror electrons bounced back by the electric field formed on the sample by means of the potential difference between the first and the second voltages. The image processing device generates a control signal for controlling the potential difference on the basis of the acquired signal, and optimizes defect contrast by controlling the reflection surface of the mirror electrons.