Charged Particle Beam Device Dual Detector Segmentation
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Solution Overview
Problem
State-of-the-art charged particle beam devices face challenges in secondary electron detection efficiency due to the acceleration of secondary charged particles to high energies by immersion lenses, making it difficult to detect these particles effectively, especially in low voltage microscopy applications where sensitive specimens require precise imaging and minimal damage.
Innovation Solution
A charged particle beam device with a detection module that decelerates primary charged particles between a first unit and a center unit, and accelerates them between the center unit and a second unit, minimizing the low kinetic energy region and optimizing secondary electron detection efficiency by using a potential configuration that allows for efficient detection of secondary and backscattered electrons.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an immersion lens is used to accelerate primary charged particles to high energy, then the beam energy on impingement on the specimen can be reduced (lowering damage to sensitive specimens), but the secondary charged particles are also accelerated to high energies making them difficult to detect
Solution Approach 1:
The detection system is segmented into multiple detectors positioned at different locations: an in-lens detector within the objective lens for detecting secondary electrons, and an upper detector above the objective lens for detecting backscattered electrons. This segmentation allows each detector to be optimized for its specific detection task, overcoming the limitation of single-detector systems where secondary particles are accelerated to high energies.
Solution Approach 2:
The objective lens acts as an intermediary element that serves dual functions: it focuses the primary beam onto the specimen while also serving as a collection system for secondary electrons through the in-lens detector. This intermediary structure enables the detection of secondary electrons before they are fully accelerated, resolving the detection difficulty caused by high energy acceleration.
2Measurement precision
If the detector is positioned within the objective lens (in-lens detector), then the working distance is shortened improving resolution, but the secondary charged particles are accelerated to high energies reducing detection efficiency
Solution Approach 1:
The detection system is divided into two separate detection paths: the in-lens detector positioned within the objective lens for secondary electron detection, and the upper detector positioned above the objective lens for backscattered electron detection. This segmentation allows the in-lens detector to maintain short working distance for high resolution while the upper detector handles the detection of higher energy backscattered electrons.
Solution Approach 2:
Different detection regions are assigned different detection capabilities: the in-lens detector is optimized for detecting low-energy secondary electrons with high spatial resolution, while the upper detector is optimized for detecting high-energy backscattered electrons. This local optimization of detection quality resolves the contradiction between resolution and detection efficiency.
3Difficulty of detecting and measuring
If the detector is positioned above the objective lens, then secondary charged particles can be detected, but the working distance increases reducing imaging properties and resolution
Solution Approach 1:
The detection system is segmented into an in-lens detector for secondary electron detection (maintaining short working distance) and an upper detector for backscattered electron detection (positioned above the lens). This segmentation allows each detector type to be optimally positioned for its specific function, with the in-lens detector preserving high resolution imaging properties.
Solution Approach 2:
The dual-detector configuration creates a universal detection system that can detect both secondary electrons (via in-lens detector) and backscattered electrons (via upper detector) simultaneously. This multi-functional detection system resolves the position contradiction by enabling both close-proximity detection for resolution and elevated detection for particle access.
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 enhances the resolution and detection efficiency of secondary electrons, particularly useful for imaging sensitive specimens, by reducing electron-electron interactions and allowing for high back-scattered and secondary electron detection, especially from the bottom of holes in semiconductor technology, thereby improving imaging properties and signal capturing.
Implementation Method 1
a center unit positioned between the first unit and the second unit, being capable of providing a third potential different from the potentials of the first and the second unit for decelerating the primary charged particles to a first low energy
Implementation Method 2
a center unit positioned between the first unit and the second unit, being capable of providing a third potential different from the potentials of the first and the second unit for accelerating the primary charged particles to a second high energy
Implementation Method 3
the first unit and/or the second unit is a detector for detecting charged particles released at a specimen
Data Source
AI summary
The present invention relates to a charged particle device with improved detection scheme. The device has a charged particle source providing a beam of primary charged particles; a first unit for providing a potential; a second unit for providing a potential; and a center unit positioned between the first unit and the second unit. The center unit is capable of providing a potential different from the potential of the first and the second unit for decelerating the primary charged particles to a first low energy and for accelerating the primary charged particles to a second high energy. Therein, the first unit and/or the second unit is a detector for detecting secondary electrons released at a specimen.