Energy-Discrimination Detection Device for LVSEM
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Solution Overview
Problem
Existing energy filters in low-voltage scanning electron microscopes (LVSEM) face challenges in achieving fine energy-discrimination power and high uniformity of energy-discrimination powers over a large field of view due to their energy-angle-depending and position-depending filtering, which limits image contrast and throughput.
Innovation Solution
An energy filter of reflection type is designed with a beam-adjusting lens to make the charged particle beam incident onto a potential barrier as a substantially parallel beam, allowing for fine energy-discrimination power at the center and high uniformity over the entire field of view, and separate detectors are used to detect secondary electrons and backscattered electrons within different energy ranges for enhanced image contrast.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an energy filter is used to achieve energy-discrimination detection, then image contrast is improved, but energy-angle-depending and position-depending filtering reduces uniformity of energy-discrimination power over large field of view
Solution Approach 1:
A beam-adjusting lens is introduced as an intermediary component between the charged particle beam source and the potential barrier. This lens acts as a mediator that transforms the divergent beam into a substantially parallel beam before it reaches the energy filter, thereby eliminating the position-dependent variations in incident angles and achieving uniform energy-discrimination power across the entire field of view.
Solution Approach 2:
The patent changes the beam parameter (incident angle distribution) by using a beam-adjusting lens to transform the beam from a divergent state to a parallel state. This parameter change ensures that charged particles from different positions in the field of view all incident onto the potential barrier at the same angle, achieving uniform energy filtering across the large field of view.
2Device complexity
If conventional electron detectors are used, then detection is simple, but sensitivity to electron energies is low resulting in poor image contrast
Solution Approach 1:
An energy filter is introduced as an intermediary device between the charged particle beam and the detector. This filter acts as a mediator that performs energy discrimination on the charged particles before they reach the detector, enabling the detector to receive only particles within a specific energy range and thereby achieving high energy sensitivity without compromising detection simplicity.
3Measurement precision
If secondary electrons are detected for topography contrast, then surface features are visible, but charging effects on specimen surface deteriorate image quality
Solution Approach 1:
The patent changes the detection parameter from secondary electrons to backscattered electrons with specific energy ranges. By detecting backscattered electrons instead of secondary electrons, the system maintains topography detection capability while avoiding the charging effects that occur when secondary electrons are collected, thus eliminating the harmful charging effects on the specimen surface.
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 improves image contrast and resolution by providing fine energy-discrimination power and high uniformity over a large field of view, enabling the simultaneous detection of topography, material, and voltage contrasts, thus enhancing the defect inspection and yield management in semiconductor manufacturing.
Implementation Method 1
a beam-adjusting lens below the grid electrode and being excited to make the charged particle beam become a substantially parallel beam to be incident onto the potential barrier
Implementation Method 2
a grid electrode being set at a first potential to form a potential barrier, while a first plurality of particles of the charged particle beam, which has initial kinetic energies higher than a specific value and thus is able to cross the potential barrier, passes through the grid electrode
Data Source
AI summary
This invention provides a method for improving performance of a reflective type energy filter for a charged particle beam, which employs a beam-adjusting lens on an entrance side of a potential barrier of the energy filter to make the charged particle beam become a substantially parallel beam to be incident onto the potential barrier. The method makes the energy filter have both a fine energy-discrimination power over a large emission angle spread and a high uniformity of energy-discrimination powers over a large FOV. A LVSEM using this method in the energy filter can obviously improve image contrast. The invention also provides multiple energy-discrimination detection devices formed by using the advantages of the method.