Charged Particle Beam Scan Correction for Deflection Linearity
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Solution Overview
Problem
The imaging of samples with charged particle beams in scanning particle microscopes is hindered by image errors due to unsatisfactory linearity of deflection systems, leading to distortions and artefacts in overlaid images.
Innovation Solution
A method and device that correct image errors by dividing the scanned region into partial regions, determining correction values for each region based on target positions, and adjusting the beam deflection using these values to linearize the beam deflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple scanning procedures are overlaid to reduce scan artefacts, then image quality improves, but image errors such as distortions and ghost images occur due to non-linear deflection
Solution Approach 1:
The scanned region is divided into multiple partial regions, with at least one calibration structure located in each partial region. This segmentation allows for region-specific correction values to be determined and applied, addressing local deflection non-linearities in different areas of the scanned region independently.
Solution Approach 2:
Correction values are determined for each partial region based on the positions of calibration structures, and these parameter changes are applied to the deflection signals to linearize the beam deflection. The correction values modify the deflection parameters to compensate for non-linearities in each specific region.
2Manufacturing precision
If correction values are determined for each partial region, then image errors are reduced, but device complexity increases
Solution Approach 1:
The calibration structures are integrated directly into the sample, allowing the sample itself to serve as the calibration reference. This self-service approach eliminates the need for separate calibration artifacts or complex external calibration systems, reducing device complexity while maintaining correction accuracy.
Solution Approach 2:
Correction values are determined in advance for each partial region based on calibration structure positions, and these correction values are stored for subsequent application. This preliminary calculation approach simplifies the actual scanning process, as the correction data is prepared beforehand rather than computed in real-time during scanning.
3Measurement precision
If the scanned region is divided into multiple partial regions, then correction accuracy improves, but processing time increases
Solution Approach 1:
While the scanned region is divided into multiple partial regions for improved correction accuracy, the patent applies correction values selectively to only those partial regions where calibration structures are present. This partial action approach maintains high correction accuracy in critical regions while avoiding unnecessary processing overhead in regions that do not require correction.
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 method effectively reduces image errors such as distortions and artefacts, allowing for accurate overlay of images from different scanning directions without the need for computationally intensive postprocessing.
Implementation Method 1
Microscopes that use particles with mass, for example electrons, to scan a sample have a high diffraction-limited resolution when imaging a nanostructure by way of scanning the particle beam over the sample, on account of the short de Broglie wavelength of the particles in the particle beam thereof
Implementation Method 2
In the case of electrically nonconductive samples or samples with poor electrical conductivity, which typically comprise a quartz substrate, for instance a photolithographic mask, the surface of the sample may become electrically charged when images are recorded using a charged particle beam
Implementation Method 3
Electrostatic deflection systems for scanning a sample 110 by scanning 120, 220, 230 a charged particle beam usually have the demanded linearity on account of their high bandwidth
Implementation Method 4
Magnetic deflection systems can be used as an alternative to electrostatic deflection systems for the purpose of scanning 120, 220, 230 a charged particle beam over a sample 110
Data Source
AI summary
The present application relates to a method and a device for correcting at least one image error when scanning a charged particle beam of a scanning particle microscope over a sample, the method comprising the steps of: (a) dividing a scanned region of the charged particle beam into at least two partial regions, with each of the at least two partial regions containing at least one structure element; (b) determining a correction value for the at least one structure element with regards to a target position of the at least one structure element for each of the at least two partial regions; and (c) correcting a beam deflection of the charged particle beam for at least one of the at least two partial regions using the determined correction value.