Shaped Ion Beam Alignment Using Reference Aperture Calibration
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Solution Overview
Problem
Existing focused ion beam systems face challenges in accurately aligning and optimizing shaped beams, particularly elliptical beams, which are difficult to calibrate due to complex beam profiles and unpredictable stigmator voltage and focus value settings, leading to poor beam quality and sample damage.
Innovation Solution
A method and system that optimizes shaped beams by determining a reference stigmator voltage through a reference beam-defining aperture and adjusting the focus value of an objective lens to align and focus a shaped working beam, using a unique combination of stigmator voltage and focus value to minimize beam dimensions and improve alignment accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a high beam current is used for quick material removal, then productivity increases, but manufacturing precision deteriorates due to beam unfocusing and sample damage
Solution Approach 1:
The patent segments the beam calibration process into two distinct phases: round beam calibration followed by shaped beam optimization. This segmentation allows the system to first establish a stable reference point with a round beam, then build upon that foundation to optimize shaped beams for high current operation, thereby maintaining precision at higher productivities
Solution Approach 2:
The patent performs preliminary calibration using a round beam aperture before optimizing the shaped beam parameters. This preliminary action establishes a known good reference state that the subsequent shaped beam optimization can build upon, ensuring that even at high currents, the beam maintains proper focus and alignment
2Manufacturing precision
If a low beam current is used for precise processing, then manufacturing precision improves, but productivity decreases due to longer processing time
Solution Approach 1:
The patent changes the operational parameters by introducing a two-stage calibration approach that enables shaped beams to operate at higher currents while maintaining precision. The key parameter change is the optimization of stigmator voltages and lens currents specifically for shaped beams, allowing them to achieve both high current and tight focusing simultaneously
3Device complexity
If traditional calibration methods are used for shaped beams, then device complexity remains simple, but measurement precision deteriorates due to unpredictable stigmator voltage and focus value settings
Solution Approach 1:
The patent implements a feedback mechanism where the system measures the actual beam characteristics after round beam calibration and uses this information to guide the shaped beam optimization. The iterative adjustment of stigmator voltages and focus values based on measured beam performance provides the feedback loop needed to achieve precise alignment without overly complicating the overall device
4Productivity
If shaped beam apertures are used to increase beam current, then productivity improves, but manufacturing precision deteriorates due to poor beam quality and alignment errors
Solution Approach 1:
The patent performs preliminary optimization of the shaped beam parameters including stigmator voltages and lens currents before actual milling operations. This preliminary action ensures that the shaped beam is properly aligned and focused, eliminating alignment errors and positioning inaccuracies that would otherwise occur when using shaped beam apertures for high current operation
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 method enhances beam alignment and focus optimization, enabling high-current, precise milling operations with reduced processing time and minimal sample damage, improving the efficiency and accuracy of charged particle beam systems.
Implementation Method 1
The lenses and other 'optical' elements (e.g., a stigmator) in the beam column may use electrostatic or magnetic fields to align the beam along the optical axis and focus the beam on the target plane.
Implementation Method 2
The lenses and other 'optical' elements (e.g., a stigmator) in the beam column may use electrostatic or magnetic fields to align the beam along the optical axis and focus the beam on the target plane.
Data Source
AI summary
A focused ion beam system includes an ion source, an aperture plate having a reference aperture and a shaped aperture, a stigmator, an objective lens, and a controller. The controller directs the ion source to emit ions to form an ion beam; determines, while the ion beam passes through the reference aperture to form a reference beam, a reference stigmator voltage to minimize a dimension of the reference beam; and determines, while the ion beam passes through the shaped aperture to form a shaped working beam and while operating the stigmator using the reference stigmator voltage, a focus value of the objective lens to optimize a size of the shaped working beam. A shape of the shaped working beam is different from a shape of the reference beam and has a first dimension corresponding to the dimension of the reference beam and a second dimension larger than the first dimension.