Multi-Beam Charged-Particle Optics for Low-Dispersion Imaging
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Solution Overview
Problem
In electron microscopy for inspecting integrated circuits, beam dispersion introduced by optical components like beam separators compromises imaging resolution, particularly as feature sizes shrink, making it difficult to accurately detect defects in sub-100 nanometer IC components.
Innovation Solution
A charged particle optical system is designed with a deflector to form a virtual image of the charged particle source and a transfer lens to form a real image on an image plane near the beam separator, reducing dispersion influence and improving imaging resolution by adjusting the magnification and beam focus.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple charged-particle beams are used to increase inspection throughput, then productivity is improved, but imaging resolution deteriorates due to beam dispersion from optical components
Solution Approach 1:
A beam separator is introduced as an intermediary component between the multiple charged-particle beams and the detector. This beam separator uses magnetic fields to separate primary beams from secondary electrons, enabling multiple beams to be used simultaneously while maintaining the ability to detect secondary electrons for imaging, thus resolving the contradiction between using multiple beams for productivity and maintaining imaging resolution
Solution Approach 2:
The beam path is segmented into separate channels using the beam separator, allowing primary charged-particle beams to be directed toward the sample for high-speed inspection while secondary electrons are separated into a different path toward the detector, enabling simultaneous high-throughput inspection and high-resolution imaging
2Ease of operation
If a beam separator is used to separate primary beams from secondary electrons, then ease of operation is improved, but imaging resolution deteriorates due to beam dispersion
Solution Approach 1:
The beam separator uses adjustable magnetic field parameters to control the separation of beams. By optimizing the magnetic field strength and configuration, the system achieves effective beam separation while minimizing dispersion effects on the secondary electron paths, thus maintaining imaging resolution while providing ease of operation
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 enhances imaging resolution by minimizing beam dispersion, allowing for smaller probe spots and improved defect detection in nanometer-scale IC components, thereby increasing inspection accuracy and yield.
Implementation Method 1
a deflector configured to form a virtual image of a charged particle source
Implementation Method 2
a transfer lens configured to form a real image of the charged particle source on an image plane
Implementation Method 3
a beam separator configured to separate primary charged particles generated by the charged particle source and secondary charged particles generated by interaction of the primary charged particles with a sample
Data Source
AI summary
Systems and methods for observing a sample in a multi-beam apparatus are disclosed. A charged particle optical system may include a deflector configured to form a virtual image of a charged particle source and a transfer lens configured to form a real image of the charged particle source on an image plane. The image plane may be formed at least near a beam separator that is configured to separate primary charged particles generated by the source and secondary charged particles generated by interaction of the primary charged particles with a sample. The image plane may be formed at a deflection plane of the beam separator. The multi-beam apparatus may include a charged-particle dispersion compensator to compensate dispersion of the beam separator. The image plane may be formed closer to the transfer lens than the beam separator, between the transfer lens and the charged-particle dispersion compensator.