Aperture Axis Alignment in Charged Particle Beam Apparatus
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Solution Overview
Problem
Existing charged particle beam apparatuses face challenges in accurately and efficiently adjusting the center axis of the aperture to minimize off-axis aberration, particularly in high current regions and low acceleration voltage settings, leading to increased operational time and variability in adjustment accuracy among operators and apparatuses.
Innovation Solution
A charged particle beam apparatus equipped with a control system that forms and analyzes spot patterns on the sample surface to calculate and adjust the aperture axis position, using spot pattern forming, analyzing, and adjusting position determining means to automatically align the aperture axis with the object lens axis, thereby correcting off-axis aberration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If manual adjustment method is used to align aperture axis with object lens axis, then adjustment accuracy can be improved, but adjustment time and operational complexity increase significantly
Solution Approach 1:
The system uses the charged particle beam apparatus itself to perform the alignment by forming spot patterns on the sample, detecting their positions, and automatically calculating the required aperture adjustment, eliminating the need for external manual alignment tools and procedures
Solution Approach 2:
The system detects the actual positions of spot patterns formed on the sample, compares them with expected positions, and uses this feedback information to calculate and execute the precise aperture adjustment needed to align the aperture axis with the object lens axis
2Measurement precision
If manual adjustment method is used to align aperture axis, then alignment precision can be achieved, but variability among operators and apparatuses increases
Solution Approach 1:
The apparatus performs self-alignment by automatically forming spot patterns, detecting their positions, calculating the misalignment, and adjusting the aperture, eliminating operator-dependent manual procedures and ensuring consistent results across different operators and apparatuses
Solution Approach 2:
The manual mechanical adjustment process is replaced with an automated optical-detection-and-calculation system that uses spot pattern formation and position analysis to determine and execute the precise alignment adjustment
3Reliability
If conventional adjustment procedure is used, then off-axis aberration can be corrected, but the number of adjustment steps and device complexity increase
Solution Approach 1:
The alignment procedure is merged with the normal operation sequence by forming spot patterns on the sample during routine operations, allowing the alignment function to be integrated into the existing workflow without requiring separate adjustment procedures or additional hardware components
Solution Approach 2:
The spot pattern formation capability serves dual purposes: it is used for both normal sample analysis operations and for providing alignment reference marks, eliminating the need for separate alignment tools or procedures
Data Source
AI summary
A charged particle beam apparatus includes a charged particle source, an aperture, an object lens, an observing unit, an aperture driving portion, and a control portion. The control portion includes a spot pattern forming portion that forms a plurality of spot patterns on a surface of a sample by irradiating a charged particle beam, an analyzing portion that calculates a position of a spot center of the spot pattern and a geometrical center position of a halo, and an adjusting position determining portion that calculates an adjusting position based on a position of intersecting lines connecting the positions of the spot centers of the respective spot patterns and the center position of the halo. In this manner, the position of the aperture can be easily and accurately adjusted in a short period of time by moving the center axis of the aperture to the adjusting position.