In-Lens Deflector Reduces Coma Aberration in Charged Particle Beam
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Solution Overview
Problem
Conventional charged particle beam apparatuses face challenges in scanning wide visual fields without degrading the resolution of the electron beam, due to significant deflection coma aberration and turbulence in the electrostatic lens field caused by overlapping magnetic fields.
Innovation Solution
Incorporating an in-lens deflector with a toroidal coil positioned closer to the objective lens coil than the aperture, surrounded by upper and lower magnetic paths, to reduce deflection coma aberration and maintain on-axis resolution, while coordinating multiple deflectors to minimize adverse effects on lens performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If an electromagnetic deflector is used to scan a wide visual field, then the inspection area is enlarged, but deflection coma aberration increases and resolution degrades
Solution Approach 1:
The in-lens deflector is nested within the objective lens structure, specifically positioned inside the magnetic path of the electromagnetic lens. This nested configuration allows the deflector to operate within the lens field without occupying external space, enabling wide visual field scanning while maintaining compact structure and reducing deflection coma aberration through optimized field overlap
Solution Approach 2:
The patent combines the deflection function and lens function into a single integrated structure. The in-lens deflector merges with the electromagnetic lens by positioning the deflector coil within the lens magnetic path, allowing both deflection and focusing functions to work cooperatively, thereby reducing deflection coma aberration while maintaining resolution
2Manufacturing precision
If the electromagnetic deflector is positioned to overlap with the electromagnetic lens field, then deflection coma aberration is reduced, but the lens field becomes turbulent and lens performance degrades
Solution Approach 1:
The patent applies local quality by creating distinct functional zones within the objective lens structure. The in-lens deflector is positioned at a specific location within the magnetic path (closer to the lens coil than the aperture) where it generates a localized deflection field that overlaps with the lens field only in the necessary region, minimizing turbulence while maintaining aberration correction
Solution Approach 2:
The patent employs dynamic field coordination between the in-lens deflector and the electromagnetic lens. By independently controlling the current in the deflector coil and the lens coil, the system dynamically adjusts the overlap between deflection field and lens field, optimizing the balance between aberration reduction and lens performance under different operating conditions
3Manufacturing precision
If a larger electrostatic lens field is used to improve on-axis resolution, then resolution is enhanced, but the complexity of the lens system increases
Solution Approach 1:
The patent combines multiple functions into the electromagnetic lens system. The in-lens deflector integrated within the electromagnetic lens performs both deflection and contributes to focusing, eliminating the need for separate deflection systems and reducing overall system complexity while maintaining or improving resolution
Solution Approach 2:
The electromagnetic lens system is designed with multi-functionality. The in-lens deflector serves dual purposes: it provides beam deflection for wide visual field scanning and simultaneously contributes to beam focusing and aberration correction, reducing the need for additional dedicated components
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 effectively reduces deflection coma aberration and maintains high on-axis resolution when scanning wide visual fields, allowing for precise observations and accurate inspections with minimal resolution degradation.
Implementation Method 1
an electromagnetic objective lens irradiating the charged particle beam deflected by the upper stage deflector onto a sample
Implementation Method 2
an in-lens deflector including a toroidal coil and arranged closer to the objective lens coil than an end of the aperture
Data Source
AI summary
In order to provide a charged particle beam apparatus enabling reduction of deflecting coma aberration in cases such as where wide field-of-view scanning is carried out, a charged particle beam apparatus is provided with an electromagnetic objective lens and a stage on which a sample is placed, wherein the electromagnetic objective lens is provided with the following: a plurality of magnetic paths; an objective lens coil; an opening disposed so as to face the sample; an inner lens deflector disposed more on the objective lens coil side than the end of the opening.