Focused Ion Beam Alignment Using Secondary Electron Feedback
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Solution Overview
Problem
In focused ion beam (FIB) systems, the position of the ion beam during sample milling differs from the position during sample observation, leading to a deviation in the field of view that requires manual adjustment by the operator.
Innovation Solution
A FIB system with a controller that automatically corrects the deviation of the ion beam's field of view by varying the strength of the objective lens, measuring secondary electron signal intensity, adjusting the focus, and acquiring a secondary electron image to determine the position of the ion beam trace, allowing for precise correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If manual adjustment of field of view deviation is performed, then the position difference between milling and observation can be corrected, but operational efficiency decreases and time is lost
Solution Approach 1:
The system performs preliminary action by automatically measuring the position deviation between milling beam and observation beam using a secondary electron detector, and pre-calculating the correction amount. This preliminary measurement and calculation eliminate the need for time-consuming manual adjustments during actual operation, as the correction is ready in advance.
Solution Approach 2:
The system implements self-service by automatically detecting the field of view deviation using secondary electrons generated during ion beam irradiation, and autonomously calculating and applying the correction without operator intervention. The system serves itself by using its own secondary electron detector to measure and correct the positioning error.
2Productivity
If automatic correction is implemented, then operational efficiency improves, but device complexity increases
Solution Approach 1:
The system uses feedback by continuously monitoring the position of the ion beam during both milling and observation modes using the secondary electron detector. The detected position information is fed back to the control system, which automatically calculates the deviation and adjusts the beam position to maintain alignment, creating a closed-loop control system that improves efficiency without requiring complex external intervention.
Solution Approach 2:
The system achieves multi-functionality by using the secondary electron detector for dual purposes: both for detecting secondary electrons during normal operation and for measuring the position deviation of the ion beam. This universal use of existing components avoids adding separate complex measurement devices, thereby improving productivity while limiting the increase in device complexity.
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 system enables automatic correction of the ion beam's field of view deviation, improving operational efficiency and reducing the need for manual adjustments, thereby enhancing the accuracy and reliability of FIB system operations.
Implementation Method 1
a lens system which includes an objective lens having a strength and which is operative to focus the ion beam as the focused ion beam onto the sample
Implementation Method 2
measuring the intensity of signal arising from secondary electrons during the variation of the strength of the objective lens
Data Source
AI summary
An FIB system includes an ion source for producing the ion beam, a lens system which includes an objective lens and which is operative to focus the ion beam onto a sample such that secondary electrons are produced from the sample, a detector for detecting the secondary electrons, and a controller for controlling the lens system. The controller operates i) to provide control so that a focus of the ion beam is varied by directing the ion beam onto the sample, ii) to measure a signal intensity from the secondary electrons produced from the sample during the variation of the strength of the objective lens, iii) to adjust the focus of the ion beam, iv) to acquire a secondary electron image containing an image of a trace of a spot, and v) to correct the deviation of the field of view of the ion beam.