Charged Particle Beam Contrast via Angular Discrimination
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Solution Overview
Problem
Current charged particle beam devices face challenges in achieving sufficient topographic contrast, especially in scanning beam instruments, due to weak topographic features and background noise, which hinders effective inspection and imaging at the micrometer and nanometer scale.
Innovation Solution
The implementation of a charged particle beam device with a combined magnetic and electrostatic objective lens and a detector system that focuses secondary electrons by their starting angles, using apertures to block unwanted high-energy electrons and enhance the detection of low-angle secondary electrons, thereby improving contrast and reducing noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a broad range of starting angles is used for collecting secondary electrons, then the signal intensity is improved, but the topographic contrast deteriorates
Solution Approach 1:
The detector is divided into multiple segments or zones, each detecting secondary electrons from specific angular ranges. This segmentation allows the system to collect signals from multiple angle ranges simultaneously while maintaining the ability to distinguish topographic features through angular discrimination, thus resolving the contradiction between signal intensity and topographic contrast.
Solution Approach 2:
The invention introduces angular discrimination as an additional dimension for signal collection. Instead of simply collecting all secondary electrons regardless of angle, the system categorizes them by their emission angles, adding an angular dimension to the detection process. This enables simultaneous achievement of high signal intensity (through comprehensive angular coverage) and high topographic contrast (through angularly-resolved detection).
2Quantity of substance
If high-energy electrons are detected along with secondary electrons, then the signal intensity is improved, but the background noise increases
Solution Approach 1:
The detector is designed with different detection zones that have specialized characteristics for detecting specific electron types. Certain zones are optimized for low-energy secondary electrons while others detect higher-energy electrons at different angles. This local quality differentiation allows the system to selectively detect secondary electrons while minimizing background noise from high-energy electrons through angular and energy-selective detection geometries.
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 allows for distinct topographic contrast and improved imaging signals by discriminating secondary electrons based on their angles of incidence, effectively reducing background noise and enhancing the resolution of defects and features at the specimen surface.
Implementation Method 1
a magnetic focusing lens 13 and an electrostatic focusing lens 14 to focus the primary electron beam 7 onto a specimen 3
Implementation Method 2
The electrostatic focusing lens 14 of Fig. 1 is comprised of the lower-end elements 9a of the high voltage beam tube 9, the cone-like shaped elements 26a, i.e. conical cap, of yoke 26
Implementation Method 3
If the electric field between the conical cap 26a and specimen 3 is adjusted in such a way that it decelerates the primary electron beam 7, i.e. if a retarding electrical field is employed, the spatial resolution of the probing primary electron beam can be increased
Implementation Method 4
focusing the secondary charged particle beam, such that particles from the first group and from the second group exhibit crossovers in substantially the same distance from the specimen
Implementation Method 5
The electrostatic focusing lens 14 of Fig. 1 is comprised of the lower-end elements 9a of the high voltage beam tube 9
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A charged particle beam device for inspecting a specimen comprises a charged particle beam source (5) adapted to generate a primary charged particle beam (7); an objective lens device (40, 45) adapted to direct the primary charged particle beam onto the specimen (3); a retarding field device adapted to accelerate secondary charged particles starting from the specimen, a first detector device (15, 150) having a central opening, comprising at least two azimuthal detector segments for detecting secondary particles, wherein the objective lens device is adapted such that particles with different starting angles from the specimen exhibit crossovers at substantially the same distance from the specimen between the objective lens and the detector device, and an aperture (100) located between the objective lens and the crossovers (90), having an opening which is equal to or smaller than the central opening (16) in the detector device (15).