Charged Particle Beam Inspection Stabilizing Sample Potential
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Solution Overview
Problem
Charged particle beam inspection apparatuses face challenges in stabilizing the potential on non-conductive or electrically floating sample surfaces, leading to unstable measurements due to charging phenomena, which affects measurement accuracy and throughput.
Innovation Solution
A charged particle beam inspection apparatus with an electron gun, condenser lenses, and a control unit that regulates the excitation currents to increase the electron beam current for a predetermined time to stabilize the sample surface potential quickly, using a beam control panel to focus the electron beam and adjust focal distances of condenser lenses for optimal current distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the electron beam current is increased to stabilize the sample surface potential quickly, then the stabilization speed is improved, but the measurement precision deteriorates due to excessive beam current affecting measurement accuracy
Solution Approach 1:
The patent applies preliminary action by performing stabilization irradiation before the actual measurement. The control unit irradiates the electron beam onto the sample at a first position (different from measurement position) to stabilize the surface potential in advance, then performs measurement at a second position. This separates the stabilization function from the measurement function, allowing rapid stabilization without compromising measurement precision.
Solution Approach 2:
The patent segments the sample surface into different functional zones: a first position for stabilization irradiation and a second position for measurement. By spatially separating these functions, the system can apply high beam current for stabilization at the first position while maintaining appropriate beam current for precise measurement at the second position, thus resolving the contradiction between stabilization speed and measurement precision.
2Stability of the object's composition
If the electron beam is emitted continuously to maintain stable measurement, then the measurement stability is improved, but the charging phenomenon worsens causing potential drift
Solution Approach 1:
The patent implements periodic action by alternating between stabilization irradiation mode and measurement mode. The control unit periodically performs stabilization irradiation at the first position to prevent charging accumulation, then switches to measurement at the second position. This periodic switching maintains measurement stability while preventing harmful charging effects that would occur with continuous beam emission.
Solution Approach 2:
The patent uses the first position as an intermediary zone between the electron beam source and the measurement position. By directing the electron beam to the first position for stabilization purposes before measuring at the second position, the system creates a mediator region that absorbs the charging effect, protecting the measurement area from severe charging while maintaining overall measurement stability.
3Ease of operation
If the acceleration voltage is changed to control secondary electron yield, then the charging control is improved, but the measurement accuracy deteriorates due to potential changes affecting beam conditions
Solution Approach 1:
The patent segments the operational modes into distinct acceleration voltages: a first acceleration voltage for stabilization irradiation that generates appropriate secondary electron yield for charging control, and a second acceleration voltage for measurement that maintains stable beam conditions. The control unit switches between these segmented modes, allowing effective charging control during stabilization while preserving measurement accuracy during the measurement phase.
Solution Approach 2:
The patent applies preliminary action by performing charging control operations at the first acceleration voltage before switching to the second acceleration voltage for measurement. This preliminary charging control establishes a stable surface potential state, which then allows accurate measurements to be performed without the interference of charging effects, thus resolving the contradiction between ease of charging control and beam condition stability.
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 rapid stabilization of the sample surface potential, ensuring accurate and stable measurements by increasing the electron beam current through the beam control panel, thereby reducing measurement time and labor.
Implementation Method 1
an electron gun (1) which emits an electron beam (9)
Implementation Method 2
a first condenser lens (2a) and a second condenser lens (2b) which focus the electron beam (9)
Implementation Method 3
in accordance with the charge potential on the surface of the sample, the emitted secondary electrons may be accelerated or drawn onto the sample
Data Source
AI summary
A charged particle beam inspection apparatus includes: an electron gun emitting an electron beam; first and second condenser lenses used to focus the electron beam; a beam control panel disposed between the first and second condenser lenses; and a control unit performing stabilizing processing in which excitation currents respectively supplied to the first condenser lens and the second condenser lens are set to have predetermined values, thereby the current amount of the electron beam passing through an opening of the beam control panel is regulated so that the electron beam to be emitted onto the sample has a larger current amount than that at a measurement, and then the electron beam is emitted onto the sample for a predetermined time period. After the stabilizing processing, the control unit sets the values of the excitation currents back to values for the measurement in order to measure dimensions of the sample, the excitation currents respectively supplied to the first and second condenser lenses.