Charged Particle Beam Apparatus for Height-Difference Dimension Measurement
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Solution Overview
Problem
Charged particle beam apparatuses, such as scanning electron microscopes, face challenges in achieving high-reliability dimension measurements when height differences exist within the field-of-view due to shallow focal depth and focusing accuracy issues, leading to decreased measurement accuracy and potential beam damage to sensitive materials.
Innovation Solution
Acquiring multiple SEM images with varying focus within the focal depth range of the electron-optics system, evaluating image sharpness degrees to select the optimal image for measurement, and using a minimum beam irradiation amount to minimize focusing errors and beam damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high-resolution implementation is pursued in electron beam apparatus, then resolution is improved, but focal depth decreases
Solution Approach 1:
The field-of-view is divided into multiple measurement domains, each with its own optimal focus position. Instead of attempting to focus the entire field uniformly, the system segments the measurement task into domain-specific focus adjustments, allowing high resolution in each local region despite shallow overall focal depth.
Solution Approach 2:
The focus position is made dynamic and adjustable for each measurement domain. The system automatically determines and adjusts the optimal focus position for each domain based on height information, rather than using a fixed focus setting for the entire field-of-view. This dynamic adaptation enables high-resolution measurements across regions with varying heights.
2Extent of automation
If automatic focus adjustment is performed across entire field-of-view, then focusing is automated, but measurement accuracy decreases due to height differences
Solution Approach 1:
Instead of applying a uniform focus setting across the entire field-of-view, the system applies locally optimized focus positions to different measurement domains. Each domain receives a focus setting tailored to its specific height characteristics, improving measurement accuracy while maintaining automation through computer-controlled adjustment.
Solution Approach 2:
The system uses height information from the sample surface as feedback to automatically determine the optimal focus position for each measurement domain. This feedback mechanism enables the automatic focus adjustment to adapt to local height variations, preventing the loss of measurement accuracy that would occur with a single global focus setting.
3Reliability
If multiple SEM images with different focuses are acquired, then measurement reliability can be improved, but beam irradiation amount increases causing beam damage
Solution Approach 1:
The system performs preliminary acquisition of height information about the sample surface before conducting dimension measurements. This preliminary action allows the optimal focus position for each measurement domain to be determined in advance, enabling direct measurement at the correct focus without requiring multiple trial images and reducing beam irradiation.
Solution Approach 2:
The system changes the focus parameter dynamically for each measurement domain based on height information, rather than acquiring multiple images at fixed focus positions. This parameter adaptation allows the measurement to be performed at the optimal focus for each domain with minimal beam irradiation, improving reliability without increasing 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
Enables high-reliability dimension measurements with improved accuracy and reduced beam damage by optimizing focusing conditions and minimizing beam exposure, even in scenarios with significant height differences within the field-of-view.
Implementation Method 1
In the charged particle beam apparatuses like this, in electron beam apparatuses in particular, diffraction phenomenon of the electrons is conspicuous and dominant.
Implementation Method 2
a narrowly converged charged particle beam is scanned on a sample
Data Source
AI summary
There is provided a charged particle beam apparatus which allows implementation of a high-reliability and high-accuracy dimension measurement even if height differences exist on the surface of a sample. The charged particle beam apparatus includes the following configuration components: An acquisition unit for acquiring a plurality of SEM images whose focus widths are varied in correspondence with the focal depths, a determination unit for determining, from the plurality of SEM images acquired, a SEM image for which the image sharpness degree of the partial domain including a dimension-measuring domain becomes the maximum value, and a measurement unit for measuring the dimension of the predetermined domain from the SEM image whose image sharpness degree is the maximum value.