Ion Beam Current Calculation Without Ionization Disturbance
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Solution Overview
Problem
Conventional sample preparation apparatuses face issues with measuring ion beam current at a location different from the sample position, leading to inaccurate milling and disturbance of the ionization state due to secondary electrons generated by the current detection plate.
Innovation Solution
The apparatus computes ion beam current values by measuring the electrical current flowing into the extraction electrode, using a relationship between argon gas flow rate and ion beam current, allowing for accurate ion beam current calculation without inserting the current detection plate into the ion beam path, thus maintaining the ionization state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a current detection plate is inserted into the ion beam path to measure ion beam current, then the ion beam current can be measured, but the ionization state within the ion source is disturbed due to secondary electron generation
Solution Approach 1:
The invention extracts the measurement function from the ion beam path by using the current detection plate to measure extraction current at the extraction electrode location rather than inserting it into the ion beam path. This separates the measurement activity from the ionization process, eliminating secondary electron generation while maintaining measurement capability
Solution Approach 2:
The invention uses extraction current as an intermediary parameter to indirectly determine ion beam current. By measuring the extraction current at the extraction electrode and using the pre-established relationship between extraction current and ion beam current, the system obtains ion beam current information without direct measurement that would disturb the ionization state
2Object-affected harmful factors
If the current detection plate is positioned at a location different from the sample position, then the ionization state is maintained, but the measured current does not accurately reflect the actual ion beam current at the sample
Solution Approach 1:
The invention establishes a feedback mechanism where the measured extraction current is used to calculate the actual ion beam current at the sample position through a pre-determined relationship. This allows the system to obtain accurate ion beam current information at the sample location while maintaining the ionization state by measuring at the extraction electrode
Solution Approach 2:
The invention performs preliminary calibration to establish the relationship between extraction current and ion beam current before actual measurement. This pre-established relationship enables accurate determination of ion beam current at the sample position from extraction current measurements taken at the extraction electrode
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 method enables precise monitoring and optimization of ion beam current during sample milling, preventing disturbance of the ionization state and providing real-time feedback for adjusting the argon gas flow rate, ensuring accurate sample preparation.
Implementation Method 1
A Penning-type ion source is incorporated in each such apparatus
Implementation Method 2
An ion optical system 1 having a cross section polisher (CP) ion source mounted therein is shown in FIG. 2
Implementation Method 3
an annular extraction electrode (ground electrode) 14. The cathodes 12 and 13 are opposite to each other
Implementation Method 4
the ion beam is caused to directly impact on a metallic current detection plate 31, and the resulting electrical current through the current detection plate 31 is measured
Implementation Method 5
secondary electrons are generated on the irradiated surface of the current detection plate 31 inserted between the ion source 10 and the sample 3 by irradiating the current detection plate 31 with an ion beam
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
Computation of ion beam current values without disturbing the state of ionization of an ion source. One embodiment of the present invention has: a high-voltage circuit (20) for applying a voltage between an anode (11) and at least one cathode (12, 13) of an ion source (10) based on a voltage condition and supplying its output current to the anode (11); a gas flow rate adjusting mechanism (82) for adjusting the flow rate of a gas (Ar) being an ion source material for generating ions and to be admitted into the ion source (10); a memory (73) in which there is stored information representing a relationship between the flow rate of the gas and the value of an extraction current flowing through an extraction electrode (14); and an arithmetic processor (72A) for finding the extraction current corresponding to the flow rate of the gas based on the information stored in the memory (73) and subtracting the value of the extraction current from the value of the output current supplied to the anode (11) by the high-voltage circuit (20) to compute the electrical current value of the ion beam.