Dual Objective Lens Ion Beam Column for Chromatic Aberration Control
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Solution Overview
Problem
Conventional focused ion beam apparatuses face challenges in achieving a small beam diameter with reduced acceleration voltage due to complex apparatus configurations and asymmetric electric fields, leading to chromatic aberration and damaged layers during sample processing.
Innovation Solution
A charged particle beam apparatus with an ion beam column featuring a first and second objective lens electrode, where the second lens is positioned closer to the sample, forming an Einzel lens configuration to minimize chromatic aberration and aberration correction using deflection and scanning electrodes, allowing for precise focusing and small beam diameter even at lower acceleration voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the focused ion beam is accelerated with a low acceleration voltage, then the thickness of the damaged layer formed in the sample lamella can be made smaller, but chromatic aberration of the ion beam optical system becomes larger
Solution Approach 1:
The ion beam column is divided into two separate objective lens systems: a first objective lens for high acceleration voltage operation and a second objective lens for low acceleration voltage operation. This segmentation allows each lens to be optimized for its specific voltage range, enabling small beam diameter and reduced chromatic aberration even at low acceleration voltages while minimizing damaged layer thickness
2Measurement precision
If the beam diameter of the focused ion beam is made small, then high-resolution imaging is achieved, but the apparatus configuration becomes complex
Solution Approach 1:
The ion beam column is designed with dual objective lens capability, where the same ion beam column structure can operate with either the first objective lens or the second objective lens depending on the acceleration voltage requirements. This multi-functionality allows small beam diameter to be achieved without requiring entirely separate apparatus configurations for different operating conditions
3Measurement precision
If the retarding method is used to reduce ion beam energy, then aberration can be made smaller, but the electric field becomes asymmetric when an electron beam column is provided
Solution Approach 1:
Instead of using a retarding field that would create asymmetric electric fields, the invention segments the focusing function into two separate objective lenses. The second objective lens is specifically designed for low acceleration voltage operation and provides symmetric focusing without requiring asymmetric retarding fields, thus maintaining electric field symmetry even when an electron beam column is present
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 precise sample processing with a thin damaged layer and reduced aberration, maintaining high-resolution imaging and efficient beam alignment without complex apparatus configurations, while preventing external electric field interference.
Implementation Method 1
an ion source housed on a proximal side of the ion beam column, for generating the ion beam
Implementation Method 2
a first objective lens electrode for focusing the ion beam on the sample; and a second objective lens electrode for focusing an ion beam accelerated with a second acceleration voltage
Implementation Method 3
an ion beam column for accelerating an ion beam with an acceleration voltage
Data Source
AI summary
A charged particle beam apparatus includes an ion beam column having an ion source for generating an ion beam, a first objective lens electrode which forms a first objective lens for focusing the ion beam on a sample, and a second objective lens electrode which is disposed at a position closer to the sample than the first objective lens electrode and forms a second objective lens for focusing an ion beam accelerated with a lower acceleration voltage on the sample.