Charged Particle Beam Axial Calibration for Optical Axis Alignment
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Solution Overview
Problem
Existing charged particle beam systems suffer from deviations of the beam centroid from the optical axis, leading to increased spherical aberrations and reduced resolution due to imperfect alignment of electrostatic or magnetostatic elements, which affects beam spot size and delivery accuracy.
Innovation Solution
A method involving capturing under-focused and over-focused images of a calibration target to determine an offset vector, adjusting the charge distribution of alignment electrodes to align the beam centroid with the optical axis, and iteratively refining this alignment to minimize deviations using computer vision analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If electrostatic or magnetostatic elements are used to deflect and focus the beam, then beam shaping and positioning capability is improved, but alignment deviations occur causing beam centroid to deviate from optical axis
Solution Approach 1:
The system captures under-focused and over-focused images of a calibration target, determines an offset vector between the images, and uses this feedback to iteratively adjust the charge distribution of alignment electrodes. This closed-loop feedback mechanism continuously corrects beam alignment deviations, resolving the contradiction between beam shaping capability and alignment precision.
Solution Approach 2:
The invention dynamically changes the charge distribution parameter of the alignment electrodes based on the measured offset vector. By adjusting the electrical charge parameters in response to measured alignment deviations, the system maintains precise beam alignment despite the presence of deflectors and focusing lenses, thus resolving the contradiction between adaptability and manufacturing precision.
2Manufacturing precision
If alignment electrodes are adjusted to correct beam offset, then beam alignment accuracy is improved, but additional calibration steps and time are required
Solution Approach 1:
The system performs a preliminary calibration by capturing under-focused and over-focused images to determine the offset vector before final alignment adjustments. This preliminary action allows the system to pre-calculate the necessary charge distribution adjustments, making the actual alignment process more efficient and reducing overall calibration time while maintaining high accuracy.
Solution Approach 2:
The calibration system is self-adjusting through automated image capture, offset vector determination, and charge distribution adjustment. The system performs its own calibration without requiring external intervention, which streamlines the process and reduces the time penalty associated with manual alignment procedures, thus resolving the contradiction between alignment accuracy and calibration time.
3Manufacturing precision
If iterative adjustment of charge distribution is performed, then beam alignment is minimized from optical axis, but processing time increases
Solution Approach 1:
The system performs iterative adjustments of charge distribution, applying partial corrections in successive steps rather than attempting a single perfect adjustment. This approach allows the beam alignment to converge to the optical axis through multiple smaller adjustments, achieving high precision while managing the time cost through efficient iteration rather than exhaustive searching, thus resolving the contradiction between alignment minimization and processing throughput.
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 reduces or minimizes beam deviations from the optical axis, thereby reducing spherical aberrations and improving beam resolution and accuracy in charged particle beam tools.
Implementation Method 1
one or more electrostatic or magnetostatic deflectors, as well as one or more focusing lenses that aim the beam at the targeted area
Implementation Method 2
one or more electrostatic or magnetostatic deflectors, as well as one or more focusing lenses that aim the beam at the targeted area
Implementation Method 3
a detector is used to measure electrons scattered from the target (backscattered electrons), and/or emitted from the target (secondary electrons), into the active area of the detector
Data Source
AI summary
In described examples, a method of operating a charged particle beam tool including a charged particle beam column configured to generate a charged particle beam includes capturing an under-focused image of a calibration target using the beam and capturing an over-focused image of the target using the beam. After determining an offset vector between the under-focused and over-focused images, if a magnitude of the offset vector is greater than a threshold, a charge distribution of the alignment electrodes is adjusted so that the charged particle beam has an adjusted alignment. The adjustment is made in response to the offset vector, to reduce a disalignment of the beam from an optical axis of the column. The method is then repeated using the adjusted alignment. If the magnitude of the offset vector is less than the threshold, the substrate is processed using the adjusted alignment.