Charged Particle Beam Objective Lens Segmentation
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Solution Overview
Problem
Conventional charged particle beam apparatuses face challenges in achieving high-resolution and high-contrast imaging due to limitations in magnetic flux distribution and aberrations, particularly when observing microscopic defects in semiconductor devices, leading to insufficient contrast and resolution in SEM images.
Innovation Solution
A charged particle beam apparatus with a retarding method and a magnetic field type objective lens, where the lower magnetic pole member is divided into upper and lower stages, allowing for controlled magnetic flux distribution and potential adjustment to concentrate magnetic flux on the sample, thereby enhancing lens action and reducing aberrations, and preventing electric discharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the energy of a primary charged particle beam is reduced to lower the landing energy, then the probe diameter increases due to aberrations and observational resolution is degraded, but high-resolution observation is required
Solution Approach 1:
The objective lens is divided into a first objective lens and a second objective lens with different focal lengths. The first objective lens focuses the charged particle beam at a first position, while the second objective lens focuses it at a second position. This segmentation allows selective use of lenses based on required resolution and landing energy conditions, resolving the contradiction between maintaining resolution and controlling landing energy.
2Illumination intensity
If the beam current value is increased to improve image contrast, then the probe diameter expands due to the Coulomb's law and resolution is degraded, but high-contrast imaging is required
Solution Approach 1:
The system dynamically switches between different objective lenses based on operational requirements. When high contrast is needed, the system can select the lens configuration that allows higher beam current without excessive probe expansion. This dynamic adaptation resolves the contradiction between achieving high contrast and maintaining resolution.
3Force
If a magnetic field type objective lens is used to focus the beam, then lens action can be intensified by increasing excitation magnitude, but magnetic saturation restricts the magnetic flux and lens action cannot be sufficiently intensified
Solution Approach 1:
The magnetic lens system is segmented into multiple objective lenses with different magnetic circuit configurations. The first objective lens has a magnetic circuit optimized for one range of excitation, while the second objective lens has a different magnetic circuit optimized for another range. This segmentation allows the system to operate in different magnetic flux regimes without encountering saturation limitations, intensifying lens action as needed.
4Manufacturing precision
If the working distance of the objective lens is decreased to reduce aberrations, then high-resolution observation is improved, but electric discharge may occur between the lens and sample
Solution Approach 1:
The system uses two different objective lenses with different working distances. The first objective lens operates at a first working distance suitable for high-resolution observation, while the second objective lens operates at a second working distance that reduces electric discharge risk. The system selectively switches between lenses based on whether resolution or discharge prevention is the priority, resolving the contradiction between these two requirements.
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 configuration enables the production of a charged particle beam apparatus that achieves high contrast and resolution, allowing for effective observation, measurement, and assessment of microscopic defects, particularly in semiconductor devices, by concentrating magnetic flux and alleviating aberrations and electric discharge risks.
Implementation Method 1
the lower magnetic pole member is divided into upper and lower stages, allowing for controlled magnetic flux distribution and potential adjustment to concentrate magnetic flux on the sample, thereby enhancing lens action and reducing aberrations
Implementation Method 2
If the amount of beam current increases, a probe diameter expands due to the Coulomb's law
Data Source
AI summary
A lower pole piece of an electromagnetic superposition type objective lens is divided into an upper magnetic path and a lower magnetic path. A voltage nearly equal to a retarding voltage is applied to the lower magnetic path. An objective lens capable of acquiring an image with a higher resolution and a higher contrast than a conventional image is provided. An electromagnetic superposition type objective lens includes a magnetic path that encloses a coil, a cylindrical or conical booster magnetic path that surrounds an electron beam, a control magnetic path that is interposed between the coil and sample, an accelerating electric field control unit that accelerates the electron beam using a booster power supply, a decelerating electric field control unit that decelerates the electron beam using a stage power supply, and a suppression unit that suppresses electric discharge of the sample using a control magnetic path power supply.