Charged Particle Beam Autofocus for Faster Wide-Area Imaging
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Solution Overview
Problem
Existing charged particle beam devices, such as scanning electron microscopes, face challenges in efficiently photographing wide areas due to the need for frequent autofocus adjustments, which increases photographing time and can result in inaccurate images due to scan marks or beam damage.
Innovation Solution
A charged particle beam device equipped with an electron gun, objective lens, sample stage, detector, and control unit that includes an image processing control circuit. This device enables automatic continuous photographing of multiple fields with an autofocus function that calculates focus values for each field, using adjacent focus value calculation visual fields to optimize focusing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If autofocus is performed every time photographing is executed in wide area photographing, then focusing accuracy is improved, but photographing time increases significantly
Solution Approach 1:
The patent performs autofocus in advance in a first visual field before photographing the second visual field. By calculating the focus value in the first visual field beforehand, the system prepares the optimal focus position in advance, eliminating the need to perform autofocus again when photographing the second visual field, thus reducing total photographing time while maintaining focusing accuracy
Solution Approach 2:
The patent implements autofocus periodically rather than continuously - specifically performing autofocus in the first visual field before photographing, and then using the calculated focus value for subsequent photographing operations. This periodic approach reduces the frequency of autofocus operations while still achieving adequate focusing accuracy
2Measurement precision
If autofocus is performed frequently, then focusing accuracy is maintained, but scan marks and beam damage appear in the photographed images
Solution Approach 1:
The patent performs autofocus in advance in the first visual field before photographing the second visual field. By calculating the focus value beforehand and using it for subsequent photographing, the system reduces the frequency of autofocus operations during actual photographing, thereby minimizing scan marks and beam damage while still achieving adequate focusing accuracy
Solution Approach 2:
The patent uses the focus value calculated in the first visual field as a reference for photographing the second visual field. By copying and reusing the focus information from the first visual field, the system avoids performing autofocus again, thereby reducing beam exposure and minimizing harmful effects like scan marks and beam damage
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 solution significantly reduces photographing time while ensuring high accuracy of the images obtained, as it allows for efficient autofocus adjustments and minimizes the impact of scan marks or beam damage.
Implementation Method 1
an electron gun capable of emitting an electron beam
Implementation Method 2
an objective lens for focusing the electron beam
Implementation Method 3
a detector capable of detecting secondary electrons or reflection electrons emitted from the sample as a signal when the sample is installed on the stage and the sample is irradiated with the electron beam
Implementation Method 4
a detector capable of detecting secondary electrons or reflection electrons emitted from the sample
Data Source
AI summary
There is provided a technique capable of shortening a photographing time and obtaining a more accurate photographed image when photographing a sample SAM using a charged particle beam device 1. The charged particle beam device 1 includes an electron gun 3, an objective lens 6, a stage 8, detectors 10 and 11, an integrated control unit C0, a photographing function, and an autofocus function. Each of a plurality of photographing visual fields is focused in a focus value calculation visual field 64 adjacent to a designated visual field 61 designated as a photographing target among the plurality of photographing visual fields, and a focus value calculated in the focus value calculation visual field 64 is used for calculating focus values of each of the plurality of photographing visual fields.