Scanning Electron Microscope 3D Imaging Aperture Angle
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Solution Overview
Problem
Commonly available scanning electron microscopes face challenges in reliably determining the exact three-dimensional shape of an object surface without varying the tilt angle of the electron beam, leading to ambiguous interpretations of the three-dimensional topology due to signal height dependence on tilt angle and atomic number contrast.
Innovation Solution
A method and apparatus for a scanning particle beam microscope that operates in both high-resolution and 3D modes, with a particle beam aperture angle in the 3D mode being at least 2 times greater than in the high-resolution mode, allowing for accurate three-dimensional representation by maintaining equal beam energy and focus distance across both modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a small aperture angle is used for the particle beam, then high lateral resolution is achieved, but the depth of focus is large making three-dimensional representation difficult
Solution Approach 1:
The patent divides the imaging process into two distinct modes: a high-resolution mode with a first aperture angle for obtaining detailed two-dimensional images, and a 3D mode with a second aperture angle (at least 2 times greater) for acquiring three-dimensional information. This segmentation allows each mode to be optimized for its specific purpose without compromise
Solution Approach 2:
The patent transitions from two-dimensional imaging (high-resolution mode) to three-dimensional representation (3D mode) by changing the aperture angle. The 3D mode uses a significantly larger aperture angle to reduce depth of focus and enable accurate three-dimensional surface topography acquisition through focus variation
2Loss of information
If the aperture angle is increased for three-dimensional imaging, then depth of focus is reduced improving 3D representation, but lateral resolution deteriorates
Solution Approach 1:
The patent employs dynamic adjustment of the aperture angle based on the imaging mode. The aperture angle is changed from a first value (for high-resolution 2D imaging) to a second value at least 2 times greater (for 3D imaging). This dynamic adaptation allows the system to optimize performance for the current operational requirement
Solution Approach 2:
The patent changes the aperture angle parameter between two distinct modes. In the high-resolution mode, a smaller aperture angle provides large depth of focus and high lateral resolution. In the 3D mode, the aperture angle is increased to at least 2 times the first value, reducing depth of focus and enabling accurate three-dimensional surface reconstruction
3Reliability
If beam energy or focus distance are changed between modes, then optimization for specific mode is achieved, but alignment and comparison between modes becomes difficult
Solution Approach 1:
The patent maintains equal beam energy and focus distance between the high-resolution mode and the 3D mode. This equipotential approach ensures that the particle beam conditions are consistent across both modes, facilitating direct comparison and correlation of images acquired in different modes without requiring complex recalibration
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 efficient and accurate inspection of object surfaces by combining high lateral resolution images with high-resolution three-dimensional data, allowing for precise visualization of surface topography and compositional contrast.
Implementation Method 1
the signal height of a secondary electron detector depends on a tilt angle of the surface portion, which is irradiated with the primary electron beam
Data Source
AI summary
A method of inspecting an object using a scanning particle beam microscope, the method comprising: operating the microscope in a high-resolution mode by laterally scanning a particle beam of the high-resolution mode; operating the microscope in a 3D-mode for acquiring a three-dimensional representation of the object by laterally scanning a particle beam of the 3D-mode; wherein the particle beam of the high-resolution mode and the particle beam of the 3D-mode have a same beam energy and a same focus distance; and wherein an aperture angle of the particle beam of the 3D-mode is at least 2 times greater, or at least 5 times greater, or at least 10 times greater, or at least 100 times greater than an aperture angle of the particle beam of the high-resolution mode.