Electron Beam Scanning With RF Deflection for Low-Dose Inspection
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Solution Overview
Problem
Conventional scanning electron microscopes face challenges in increasing scan rates due to the use of electric or magnetic deflectors, which are limited by finite capacitance or inductance, leading to inefficiencies and sample damage from high electron doses.
Innovation Solution
The use of microwave or RF wave supporting structures to create oscillating electromagnetic fields for deflecting electron beams, enabling scan rates exceeding 1 GHz, and synchronized deflection patterns for efficient electron distribution and reduced sample charging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional electric or magnetic deflectors are used to scan the electron beam, then the scanning system can operate at lower frequencies, but the scan rate is limited to the MHz range due to finite capacitance or inductance
Solution Approach 1:
The patent replaces conventional electric or magnetic deflectors (which rely on finite capacitance or inductance) with a microwave cavity that generates oscillating electromagnetic fields. This substitution enables scan rates exceeding 1 GHz by eliminating the electrical limitations of traditional deflector designs, while maintaining a relatively simple cavity structure.
2Productivity
If the scan rate is increased to improve throughput, then productivity increases, but sample damage from high electron doses worsens
Solution Approach 1:
The patent employs periodic oscillating electromagnetic fields from the microwave cavity to deflect the electron beam in a scanning pattern. This periodic action at frequencies exceeding 1 GHz enables rapid scanning that reduces the dwell time and electron dose per pixel, thereby improving throughput while minimizing sample damage and charging artifacts.
3Ease of manufacture
If conventional deflectors are used, then the system structure is simpler to implement, but the electron dose per pixel increases causing sample charging artifacts
Solution Approach 1:
The patent changes the operating frequency parameter from the MHz range (conventional deflectors) to frequencies exceeding 1 GHz (microwave cavity). This parameter change reduces the electron dose per pixel by increasing the scan rate, thereby minimizing charging artifacts while the microwave cavity provides a practical implementation path.
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 approach allows for faster scanning with reduced electron dose per pixel, minimizing sample damage and charging artifacts while maintaining image quality, thereby enhancing throughput.
Implementation Method 1
a microwave or RF (radio Frequency) wave supporting structure, like a cavity or a stripline, to provide a first oscillating electromagnetic field to periodically deflect the charged particle beam
Implementation Method 2
to provide a first oscillating electromagnetic field to periodically deflect the charged particle beam in order to scan the charged particle beam over the area of the sample
Data Source
AI summary
The present disclosure relates to an inspection tool having a charged particle source to provide a charged particle beam, a sample holder to hold a sample, and a scanning system configured to scan the charged particle beam over an area of the sample in a scanning pattern. The scanning system may comprise a microwave or RF wave supporting structure to provide a first oscillating electromagnetic field to periodically deflect the charged particle beam in order to scan the charged particle beam over the area of the sample. The charged particle beam may be an electron beam, so that the inspection tool may be a scanning electron microscope. The scanning system may be configured to continuously scan the charged particle beam over the area of the sample.