Dual Beam System Ion Path Correction Immersion Lens
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Solution Overview
Problem
Dual beam systems with scanning electron microscopes (SEM) and focused ion beam (FIB) columns face challenges in operating the ion beam column when the SEM is in immersion mode due to magnetic field deflections, which limit simultaneous operation and result in lower resolution and increased processing time.
Innovation Solution
A deflection correction system using electrostatic deflectors to compensate for the magnetic field of the immersion lens, allowing simultaneous high-resolution SEM and FIB operation by deflecting the ion beam to its original path, both within and outside the ion column, using shielding and mid-column deflectors to minimize aberration and maintain resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the SEM operates in immersion mode with a significant magnetic field extending to the sample, then the SEM resolution is improved to ultrahigh resolution, but the ion beam is deflected from its intended path by the Lorentz force
Solution Approach 1:
An electrostatic deflector is introduced as an intermediary device between the ion source and the sample. This deflector applies an electrostatic force to counteract the magnetic deflection caused by the immersion lens, serving as a mediator that allows both the strong magnetic field (for SEM resolution) and accurate ion beam delivery to coexist
Solution Approach 2:
The system dynamically adjusts the electrostatic deflector parameters (voltage, field strength) to compensate for the magnetic field effects. By changing the electrostatic field parameters in response to the magnetic field conditions, the system maintains ion beam accuracy while preserving the immersion mode magnetic field for high-resolution SEM imaging
2Manufacturing precision
If the SEM magnetic lens is turned off when using the ion beam, then the ion beam deflection is eliminated, but the system requires significant time to reach thermal equilibrium and become stable
Solution Approach 1:
The electrostatic deflector is configured and calibrated in advance to compensate for magnetic field effects. This preliminary setup allows the system to maintain the immersion lens on continuously without requiring repeated thermal stabilization cycles, as the deflector is pre-configured to handle the magnetic deflection
Solution Approach 2:
The immersion lens remains continuously energized during both SEM and FIB operations, maintaining thermal equilibrium. The electrostatic deflector provides continuous compensation for magnetic deflection, eliminating the need to turn the lens on and off and thereby maintaining continuous useful action without thermal stabilization delays
3Measurement precision
If the immersion lens produces a significant magnetic field extending to the sample, then the SEM resolution is improved, but the magnetic field deflects the ion beam by hundreds of microns
Solution Approach 1:
The electrostatic deflector generates an electrostatic force that acts as a counterweight to the magnetic Lorentz force. By applying an equal and opposite electrostatic deflection, the system cancels out the magnetic deflection of the ion beam, allowing the strong magnetic field to remain active for high-resolution SEM imaging
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
Enables simultaneous or interlaced operation of FIB and ultra-high resolution SEM with millisecond switching times, maintaining high resolution and reducing processing time by compensating for magnetic field deflections without significant degradation of FIB performance.
Implementation Method 1
A deflection correction system using electrostatic deflectors to compensate for the magnetic field of the immersion lens
Implementation Method 2
the lens 300 produces a significant magnetic field 302, e.g., greater than about 0.025 Tesla, extending to the sample 306
Implementation Method 3
the magnetic field produced by the electron lens deflects the ion beam from its intended path due to the Lorentz force on the ions
Data Source
Figure 1~3
Figure 4
Figure 5~6
AI summary
A dual beam system (500) provides for operation of a focused ion beam column (530) in the presence of a magnetic field from an ultra-high resolution electron lens (510), in particular an immersion lens. The ion beam is deflected by deflectors (536,538A,538B) to compensate for the presence of the magnetic field.