Particle Beam Microscope Charge Compensation via Kinetic Energy Sequencing
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Solution Overview
Problem
Conventional methods for reducing the charge of samples in particle beam microscopes, such as using electron beams, often fail to provide a satisfactory reduction, leading to distorted image information due to sample charging and interference from detector or lens fields.
Innovation Solution
A method involving alternating sequences of directing a particle beam and detecting secondary particles, with separate periods for generating and directing electrons of different kinetic energies to reduce sample charge, where higher energy electrons quickly reduce the charge and lower energy electrons complete the compensation, minimizing interference from sample fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electron beams are used to reduce sample charge, then charge reduction is attempted, but the reduction is often unsatisfactory due to interference from detector or lens fields
Solution Approach 1:
The patent changes the energy parameter of electrons used for charge compensation. Instead of using conventional low-energy electrons that are susceptible to field interference, the invention employs high-energy electrons (several keV to MeV range) that can penetrate through detector and lens fields to effectively neutralize sample charge. This parameter change allows electrons to overcome the harmful electromagnetic fields that previously prevented effective charge reduction.
2Measurement precision
If particle beam analysis is performed on charged samples, then image information is obtained, but the sample charge distorts the impinging energy of the primary particle beam and secondary particle detection
Solution Approach 1:
The patent applies preliminary action by performing charge compensation before or during the particle beam analysis. High-energy electrons are directed at the sample to neutralize accumulated charge prior to or concurrent with imaging. This preliminary charge neutralization prevents the sample charge from distorting the primary particle beam energy and secondary particle detection, thereby maintaining measurement precision throughout the analysis process.
3Reliability
If continuous electron beam irradiation is used for charge compensation, then sample charge is reduced, but the analysis time increases and productivity decreases
Solution Approach 1:
The patent implements periodic action by alternating between particle beam analysis intervals and charge compensation intervals. Instead of continuous electron irradiation, high-energy electrons are applied in periodic pulses or at specific time points during the analysis. This periodic approach maintains effective charge compensation while minimizing interruption to the imaging process, thereby preserving productivity alongside charge compensation quality.
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 effectively reduces sample charge, improving image quality by minimizing distortions caused by sample charging and enhancing the efficiency of charge compensation, even in the presence of strong sample charges and interfering fields.
Implementation Method 1
secondary particles, such as secondary electrons, dislodged from the sample due to interaction of the primary particle beam with the sample are detected
Implementation Method 2
generating and directing electrons onto the sample in order to reduce the charge of the sample generated during the directing of the particle beam onto the sample
Data Source
AI summary
A method of operating a particle beam microscope includes: directing a particle beam onto a sample and detecting particles emanating from the sample during a first period for generating an image of the sample; generating electrons having a first distribution of kinetic energies and directing these electrons onto the sample during a second period for reducing a charge of the sample being generated while the directing the particle beam onto the sample; and generating electrons having a second distribution of their kinetic energies and directing these electrons onto the sample during a third period for further reducing the charge of the sample being generated while the directing of the particle beam onto the sample. An average value of the kinetic energy of the first distribution of the kinetic energy is greater than an average value of the kinetic energy of the second distribution of kinetic energies.