Focused Ion Beam Energy Filtering for Low-Spread High-Current Beams
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Solution Overview
Problem
Existing focused ion beam (FIB) devices face challenges in producing charged-particle beams (CPBs) with variable beam currents and energy spreads, which are essential for various semiconductor, material science, and life science applications.
Innovation Solution
The system employs an extractor aperture plate to create both axial and off-axis CPBs, with the off-axis beam being chromatically dispersed and filtered to select specific energy spreads. A beam steering deflector directs the selected CPB portion to a workpiece, allowing for the delivery of CPBs with tailored currents and energy spreads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If beam current is limited to suppress Coulomb interactions, then spot size is improved, but beam current is reduced which is not practical for many FIB applications
Solution Approach 1:
The beam is segmented into multiple components with different energies using chromatic dispersion. A filter aperture selects specific energy portions, creating a filtered beam that maintains current while reducing Coulomb interactions through energy distribution control.
Solution Approach 2:
The system changes the energy parameter of the beam by using chromatic aberration to disperse the beam into different energy components. A filter aperture then selects specific energy ranges, allowing control over both beam current and energy spread to optimize spot size without excessive current limitation.
2Quantity of substance
If a beam-limiting diaphragm is used with energy dispersion to produce central and eccentric beams, then current distribution is improved, but device complexity increases
Solution Approach 1:
The filter aperture serves multiple functions: it limits beam current, controls energy spread, and shapes the beam profile. This multi-functionality reduces the need for separate components, thereby managing device complexity while achieving improved current distribution.
3Productivity
If beam current is increased for substantial current applications, then productivity is improved, but Coulomb interactions increase which limits spot size
Solution Approach 1:
The system utilizes chromatic dispersion to create energy-separated beam components. By filtering specific energy portions, the system maintains high beam current for productivity while the energy spread control reduces Coulomb interactions, enabling both high current and acceptable spot size.
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 enables the selective delivery of CPBs with varying currents and energy spreads, improving the versatility and precision of FIB applications by reducing sputtering or damage to the workpiece.
Implementation Method 1
The off-axis CPB is chromatically dispersed and a filter aperture is used to select a portion of the chromatically dispersed, off-axis CPB
Implementation Method 2
A beam steering deflector is situated optically downstream of the filter aperture and is operable to direct the spectrally selected, off-axis CPB portion to a workpiece along an axis
Implementation Method 3
A filtering deflector is operable to select which portion of the chromatically spread, off-axis is transmitted by a filter aperture
Data Source
Figure 1A
Figure 1B
Figure 1C~1E
AI summary
Charged-particle beam (CPB) optical systems can include a beam acceptance aperture plate defining a first acceptance aperture and at least one second acceptance aperture, situated with respect to a CPB source so that a first CPB is transmitted by the first acceptance aperture and a second CPB is transmitted by a second acceptance aperture. A CPB lens is situated to receive the first and second CPBs from the beam acceptance aperture plate and direct the first and second CPBs towards a filter aperture plate to transmit selected spectral portion of the second CPB. The selected spectral component of the first CPB can be selectively directed to a workpiece by a beam steering deflector along the same axis. In some examples, the first and second CPBs have different beam currents and only one is directed to a workpiece.