KR102740804B1 - Optimization method using pre-lens retarding field energy analyzer for measuring energy distribution - Google Patents

Abstract

The present invention relates to a method for optimizing a lens-type delay potential energy analyzer for measuring energy distribution. The purpose of the present invention is to provide a method for optimizing the energy distribution of a charged particle beam by controlling the position between a beam generation source and an analyzer and the lens voltage applied to an electrostatic lens so that energy distribution measurement can be performed correctly and accurately by using a delay potential energy analyzer including an electrostatic lens, a delay electrode, and a collector.

Description

{Optimization method using pre-lens retarding field energy analyzer for measuring energy distribution}

The present invention relates to a method for measuring the energy distribution of a charged particle beam created by an electron source, an electron gun, an ion source, an ion gun, etc., and more specifically, to a method for optimizing a lens-type delay potential energy analyzer for measuring energy distribution.

Electron microscopes, transmission electron microscopes, X-ray generators, etc. that use electron beams and ion beams (hereinafter referred to as “beams”) are equipped with electron sources, electron guns, ion sources, ion guns, etc. to generate such charged particle beams. It is necessary to accurately measure the energy distribution of such beam generators in order to analyze the characteristics of beam-based devices, improve their performance, etc. To explain in more detail, accurately measuring the energy width of the generated charged particle beam is essential for utilizing the charged particle beam, and the design of equipment that applies it can be accurately done only when the characteristics of the energy spread are understood. The greater the spread of the beam’s energy distribution, the greater the chromatic aberration that occurs, and by accurately measuring the energy distribution, the chromatic aberration of the electron gun can be calculated. In other words, accurate measurement of the energy distribution is very important for improving the performance of the electron microscope.

In the past, various devices have been researched, developed, and used to measure energy distribution. Representative examples include the hemispherical energy analyzer and the grid-type retarding field energy analyzer.

A hemispherical energy analyzer measures the energy distribution by separating a beam by energy by deflecting the beam by applying voltage or magnetic field to a hemispherical electrode. The resolution (ΔE/E ₀ < 10 ^-6 ) is determined by the size of the hemispherical electrode, and generally a fairly complex optical system is required before the beam is incident on the hemispherical electrode. The size of the hemispherical electrode including this is configured to be approximately 700 mm, but it may be larger in the future when designed considering performance. As such, hemispherical energy analyzers have the great advantage of high resolution and are widely used in various analysis equipment, but their size (~700 mm) is so large that they are mostly used solely for analysis by specialized research facilities.

The grid-type delay potential energy analyzer analyzes energy distribution by delaying a beam using grid mesh electrodes. More specifically, it measures energy distribution by separating the beam by energy in such a way that beams with energy higher than the voltage applied to the grid mesh are transmitted and beams with lower energy are delayed. Although it is relatively smaller than the hemispherical analyzer, it has limitations in the accuracy and precision of the measurement results due to its low resolution (ΔE/E ₀ < 10 ^-3 ). The reason why the resolution of the grid-type delay potential energy analyzer is relatively low is because the potential formed on the grid mesh electrodes is formed unevenly, which causes a potential sag problem that the beam receives. In addition, there is a problem that the grid mesh electrodes are easily contaminated by the beam. In addition, the measurement electron beam is absorbed by the grid mesh, which reduces the measurement accuracy. In other words, the grid-type delay potential energy analyzer is smaller than the hemispherical energy analyzer, so it has greater freedom of use, but has limitations in resolution.

In order to solve this problem, a lens-type delay potential energy analyzer device is disclosed in Korean Patent Registration No. 2231035 ("Delay Energy Analyzer", March 17, 2021, hereinafter referred to as "prior patent"). The delay potential energy analyzer of the prior patent basically includes an electrostatic lens, a delay electrode, and a collector. The electrostatic lens refracts an incident charged particle beam, and includes a lens electrode to which a voltage is applied for this purpose. The delay electrode is formed so that a focus of the charged particle beam refracted by the electrostatic lens is created inside it, but only passes through the charged particle beam having energy greater than the potential generated inside it. The collector measures the energy distribution of the charged particle beam that arrives at the charged particle passing through the delay electrode. In addition, a grounded blocking electrode may be placed between the electrostatic lens and the delay electrode.

The lens-type delay potential energy analyzer by the prior art patent of this configuration has a great advantage in that it can be formed into a very small size (~860 mm) and thus can be easily applied to various devices. In addition, by using a cylindrical electrode instead of a grid, the collision between the beam and the electrode is minimized, thereby improving durability and measurement reliability. In addition, by using an electrostatic lens, the measurement error due to potential unevenness inside the delay electrode is reduced, thereby improving the analysis performance. In addition, if the above-mentioned blocking electrode is additionally provided, the measurement reliability can be further improved by reducing the interference of the potential.

However, in the lens-type delay potential energy analyzer according to the prior patent, the focus position of the electron beam may vary depending on the voltage applied to the electrostatic lens. Accordingly, if the focus is not formed within the delay electrode, the beam does not pass through the device and is emitted outside the analyzer, which prevents proper measurement. In addition, since the number of electrons collected by the collector varies depending on the focus position of the electron beam, there is a concern that the consistency of the measurement results may decrease. In order to resolve this problem, it is necessary to introduce a systematic optimization method to ensure that normal measurements are performed smoothly in the lens-type delay potential energy analyzer.

Korean Patent Registration No. 2231035 (“Delay Energy Analyzer”, 2021.03.17.)

Accordingly, the present invention has been made to solve the problems of the prior art as described above, and an object of the present invention is to provide a method for optimizing a lens-type delay potential energy analyzer for energy distribution measurement. More specifically, in measuring the energy distribution of a charged particle beam with a delay potential energy analyzer including an electrostatic lens, a delay electrode, and a collector, the present invention provides a method for optimizing the position between a beam generation source and an analyzer and the lens voltage applied to the electrostatic lens so that the energy distribution measurement can be performed correctly and accurately.

In order to achieve the above-described purpose, the present invention provides a method for optimizing a lens-type delay potential energy analyzer for energy distribution measurement, which comprises a lens-type delay potential energy analyzer including an electrostatic lens (100) equipped with a lens electrode (110), a delay electrode (200), and a collector (300), for measuring the energy distribution of a charged particle beam irradiated from a beam generator, the method including: a position optimization step in which alignment between the beam generator and the analyzer is optimized; and a voltage optimization step in which a lens voltage applied to the lens electrode (110) within the analyzer is optimized.

At this time, the position optimization step is performed by changing the position of the analyzer based on the beam generator while the lens voltage is fixed to a preset reserve lens voltage, and obtaining a collector current-delay voltage graph for each position. In the collector current-delay voltage graph for each position, a position where the current measured from the collector (300) rapidly decreases in a region where the beam energy and the delay voltage applied to the delay electrode (200) are at equal levels can be determined as the optimized position.

In addition, the above-described position optimization step may be configured to first find a preliminary optimization position where the current rapidly decreases while moving the analyzer in a horizontal direction, and then find an optimal position where the current rapidly decreases while moving the analyzer in a vertical direction from the preliminary optimization position.

In addition, the voltage optimization step obtains a current-delay voltage graph for each of the delay electrode (200) and the collector (300) by changing the lens voltage while the position of the analyzer is fixed to the optimal position, and the lens voltage at which the current flowing through the delay electrode (200) converges to 0 on the current-delay voltage graph for each voltage can be determined as the optimal voltage.

In addition, in the above-described method for optimizing the lens-type delay potential energy analyzer, the delay voltage interval for obtaining a position-specific collector current-delay voltage graph during the position optimization step can be formed to be larger than the delay voltage interval for obtaining a voltage-specific collector current-delay voltage graph during the voltage optimization step.

In addition, the method for optimizing the lens-type delay potential energy analyzer may further include an energy distribution measurement step in which the energy distribution of a charged particle beam irradiated from the beam generator by the analyzer is measured while the analyzer is set to the optimized position obtained in the position optimization step and the optimized voltage obtained in the voltage optimization step.

At this time, the energy distribution measurement step can calculate the energy distribution by differentiating the collector current-delay voltage graph obtained by measuring the current measured by the collector (300) while changing the delay voltage applied to the delay electrode (200).

In addition, the analyzer may include the electrostatic lens (100) that refracts a charged particle beam irradiated from the beam generator using an electric potential applied through the lens electrode (110), the delay electrode (200) that creates a focus of the charged particle beam refracted by the electrostatic lens (100) inside, generates an electric potential inside to reduce the energy of the incident charged particle beam, and allows only charged particles having energy greater than the electric potential generated inside to pass through, and the collector (300) that measures the energy distribution of the charged particle beam when the charged particles passing through the delay electrode (200) arrive.

In addition, the analyzer may further include a blocking electrode (400) arranged between the electrostatic lens (100) and the delay electrode (200) to block interference of potential occurring between the electrostatic lens (100) and the delay electrode (200).

In addition, the analyzer may further include an aperture (600) that adjusts the size of the charged particle beam incident on the electrostatic lens (100).

According to the present invention, when measuring the energy distribution of a charged particle beam using a lens-type delay potential energy analyzer, the reliability of the measurement result is greatly improved by enabling the measurement to be performed in an optimized state. In addition, when the measurement is performed in an optimized state prior to measurement based on the methodology suggested by the present invention, even an unskilled user with a low level of theoretical understanding of the device can obtain accurate measurement results, thereby improving user convenience and measurement consistency.

In addition, according to the present invention, as described above, the measurement reliability, user convenience, and measurement consistency of the lens-type delay potential energy analyzer are improved, thereby expanding the usability of the lens-type delay potential energy analyzer. At this time, it is known that the lens-type delay potential energy analyzer has a high degree of freedom of use because it can be easily installed in various devices for measurement because the resolution is appropriately high and the size is small. Therefore, according to the present invention, by ultimately increasing the usability of the lens-type delay potential energy analyzer, there is an effect of improving the user convenience and the reliability of the measurement results in the measurement of the energy distribution of a charged particle beam in general fields.

Figure 1 is a schematic diagram of a lens-type delay potential energy analyzer.
Figure 2 shows the results of an EOD simulation of electron beam trajectories according to lens voltage inside a lens-type delay potential energy analyzer.
Figure 3 shows the results of EOD simulation of electron beam trajectories according to delay voltage under optimal lens voltage conditions (-300 V).
Figure 4 shows the change in the number of electrons reaching the collector as the delay voltage increases.
Figure 5 shows the results of EOD simulation of electron beam trajectories according to lens voltage in the delay unit (blocking electrode + delay electrode + collector).
Figure 6 is a graph of the collector current-delay voltage according to horizontal alignment to obtain the optimal distance condition between the electron gun and the analyzer (the horizontal position of the analyzer changes at 1 mm intervals).
Figure 7 is a graph of the collector current-delay voltage according to vertical alignment to obtain the optimal distance condition between the electron gun and the analyzer (the vertical position of the analyzer changes at 1 mm intervals).
Figure 8 shows the current change of each electrode at a lens voltage of -310 V.
Figure 9 shows the current change of each electrode at a lens voltage of -314 V (optimization conditions).
Figure 10 shows the collector current-delay voltage graph and energy distribution under optimal conditions.

Hereinafter, a method for optimizing a lens-type delay potential energy analyzer for energy distribution measurement according to the present invention having the configuration described above will be described in detail with reference to the attached drawings.

FIG. 1 is a block diagram of a lens-type delay potential energy analyzer. Referring to FIG. 1, the block diagram of the lens-type delay potential energy analyzer will first be briefly described. The lens-type delay potential energy analyzer used in the present invention basically includes an electrostatic lens (100) provided with a lens electrode (110), a delay electrode (200), and a collector (300). The electrostatic lens (100) refracts a charged particle beam irradiated from the beam generator using a potential applied through the lens electrode (110). The delay electrode (200) creates a focus inside the charged particle beam refracted by the electrostatic lens (100), generates a potential inside to reduce the energy of the incident charged particle beam, and allows only charged particles having greater energy than the potential generated inside to pass therethrough. The above collector (300) measures the energy distribution of the charged particle beam upon which the charged particles passing through the delay electrode (200) arrive.

In addition, the lens-type delay potential energy analyzer may further include a blocking electrode (400) and an aperture (600). The blocking electrode (400) is arranged between the electrostatic lens (100) and the delay electrode (200) to block interference of potentials occurring between the electrostatic lens (100) and the delay electrode (200). The aperture (600) serves to adjust the size of a charged particle beam incident on the electrostatic lens (100).

Additionally, a spacer (140) may be provided between the electrodes to stably maintain an appropriate spacing between the electrodes, and an optical system frame (500) may be provided to stably fix the optical system itself composed of the electrodes and the spacer (140). In addition, a housing (700) including a housing body (710), a front housing cover (720), and a rear housing cover (730) may be provided to stably fix and protect the arrangement positions of each component, and an aperture cover (800) for stably fixing the aperture (600) may be provided by being coupled to the front housing cover (720).

The detailed structure and operating principle of the above-described lens-type delay potential energy analyzer are described in detail in Korean Patent Registration No. 2231035 (“Delay Energy Analyzer”, March 17, 2021), which is a prior art of the present invention, and therefore, further description is omitted herein. In addition, for the sake of brevity, it is hereby notified in advance that “lens-type delay potential energy analyzer” will be abbreviated to “analyzer” when necessary.

Fig. 2 illustrates the results of an electron beam trajectory EOD simulation according to lens voltage inside a lens-type delay potential energy analyzer. As clearly shown in the three upper, middle, and lower drawings of Fig. 2, it can be confirmed that the focal position of the electron beam changes as the lens voltage applied to the electrostatic lens (100) (more specifically, the lens electrode (110) that applies voltage to the electrostatic lens (100)) changes to -250 V, -300 V, and -350 V. More specifically, the simulation of Fig. 2 was performed under the conditions of an electron beam energy of 500 eV, a distance of 60 mm between an electron gun (i.e., beam generator) and the analyzer, and the upper drawing of Fig. 2 shows a case where the lens voltage is -250 V, at which time the focus of the electron beam is formed on the surface of the collector (300), the middle drawing of Fig. 2 shows a case where the lens voltage is -300 V, at which time the focus of the electron beam is formed in front of the delay electrode (200), and the lower drawing of Fig. 2 shows a case where the lens voltage is -350 V, at which time the focus of the electron beam is formed immediately after the electrostatic lens (100).

As briefly explained above, charged particles having energy lower than the potential generated by the delay voltage applied to the delay electrode (200) cannot pass through the delay electrode (200), and only charged particles having greater energy can pass through the delay electrode (200) and reach the collector (300). That is, by changing the delay voltage and measuring the amount of charged particles (which is expressed as a current value) passing through the delay electrode (200), the energy distribution of the corresponding charged particle beam can be measured.

Considering this principle, it can be inferred that the condition in which the focus of the electron beam is formed in front of the delay electrode (200), as shown in the middle drawing of Fig. 2, is the condition for measuring the energy distribution with optimal high resolution.

Fig. 3 illustrates the results of an EOD simulation of an electron beam trajectory according to a delay voltage under the optimal lens voltage condition (-300 V). As described with reference to Fig. 2, the electron beam focus is formed in front of the delay electrode (200), and the delay voltage applied to the delay electrode (200) is changed to -490 V, -499.9 V, and -500.5 V. The results are illustrated in the three upper, middle, and lower drawings of Fig. 3, respectively. Comparing the three upper, middle, and lower drawings of Fig. 3, it can be confirmed that as the delay voltage is greater than the energy of the initially incident electron beam, the number of charged particles that are delayed, fail to penetrate, and are emitted outside the analyzer increases.

FIG. 4 is a graph illustrating a change in the number of electrons reaching a collector according to an increase in delay voltage, and is a graph that can be obtained during the process of performing the same experiment as FIG. 3. In FIG. 4, the horizontal axis represents the delay voltage (“Retarding voltage”) applied to the delay electrode (200), and the vertical axis represents the number of electrons (“Collecting count”) collected and measured by the collector (300). By differentiating this electron count-delay voltage graph, the energy distribution of the corresponding charged particle beam can be obtained. Referring to the graph of the optimal lens voltage of -300 V (green inverted triangle) in FIG. 2, the collection rate of electrons reaches almost 100% up to a delay voltage of -499 V, and the collection rate is maintained at 90% or higher up to -499.9 V, but it can be confirmed that it rapidly decreases in the delay voltage range of -500 to -500.3 V, and the collection rate reaches 0% at -500.5 V or higher.

At this time, as shown in Fig. 4, the shape of the electron count-delay voltage graph changes depending on the lens voltage change. First, the graphs measured while changing the lens voltage at 10 V intervals near the optimal lens voltage of -300 V show a similar pattern to the optimal lens voltage of -300 V (green inverted triangle) graph to some extent, but the -310 V (purple diamond) graph shows a considerably unstable pattern near the inflection point, and the -290 V (blue triangle) graph shows a pattern that changes more slowly than when it is optimal near the inflection point, which are elements that are unsuitable for analysis. That is, it can be confirmed that the optimal resolution is shown when the electron beam energy is 500 eV, the distance between the electron gun (i.e. beam generator) and the analyzer is 60 mm, and the lens voltage is -300 V.

Meanwhile, when the lens voltage is -250 V or -350 V, the shape of the electron count-delay voltage graph changes greatly. Fig. 5 illustrates the results of an EOD simulation of an electron beam trajectory according to the lens voltage in a delay unit (blocking electrode + delay electrode + collector), and is a diagram to explain why the results differ so greatly when the lens voltage is optimized and when it is not. The middle diagram of Fig. 5 is an electron beam trajectory when the lens voltage is optimal, that is, -300 V, and as illustrated, all electrons naturally pass through the passage between the electrodes. However, if the lens voltage is too high or low (i.e., not the optimal voltage) such as -250 V/-350 V as shown in the upper/lower drawings of Fig. 5, the incident electrons may collide with the delay electrode (200) and cause loss, or the beam focus may be formed again due to the lens effect of the delay unit (blocking electrode (400) + delay electrode (200) + collector (300)), so that proper collection may not occur.

If the energy distribution is measured in a condition that is not set to a good measurement condition, such as when the lens voltage is set to -250 V, it is obvious that the results are not reliable. However, if the user is an inexperienced user who does not have a high level of theoretical understanding of the device, it is difficult to know what the optimal conditions are, and even if the user knows the theoretical optimal conditions, it may be difficult to easily figure out how to apply them in what order to find the optimal conditions.

As explained above in Fig. 2, the theoretical optimal condition may be [that the focus of the charged particle beam is formed in front of the delay electrode]. However, the focal point of the charged particle beam cannot be adjusted by visually observing it, and the test device itself is quite expensive and requires a lot of operating costs such as electricity. Therefore, finding the actual optimal condition by trial and error with only the theoretical optimal condition described above may cause significant losses in terms of time and economy.

The present invention is intended to solve precisely this problem, and to provide an optimization method for a lens-type delay potential energy analyzer that allows anyone to easily set conditions optimized for measuring energy distribution by applying a systematic and intuitive methodology. Accordingly, even inexperienced users as described above can obtain accurate measurement results smoothly by applying the methodology of the present invention, thereby improving user convenience and measurement consistency.

At this time, the factors directly related to the [focus position of the charged particle beam] can be, firstly, the position of the analyzer with respect to the beam generator (an electron gun in the case of an electron beam, an ion gun in the case of an ion beam, etc.), and secondly, the lens voltage. Therefore, in the present invention, when measuring the energy distribution of a charged particle beam irradiated from a beam generator using a lens-type delay potential energy analyzer, a methodology is proposed to easily set the optimization conditions of the lens-type delay potential energy analyzer by sequentially optimizing the two factors described above, that is, the analyzer position (with respect to the beam generator) and the lens voltage.

That is, the optimization method of the lens-type delay potential energy analyzer of the present invention includes, very briefly, a position optimization step in which the alignment between the beam generator and the analyzer is optimized, and a voltage optimization step in which the lens voltage applied to the lens electrode (110) within the analyzer is optimized. Additionally, an energy distribution measurement step may be further included in which the energy distribution is measured in such an optimized state to confirm whether the optimization has been properly performed. Each step will be described in more detail below.

In the above position optimization step, the alignment between the beam generator and the analyzer is optimized as described above. More specifically, while the lens voltage is fixed to a preset reserve lens voltage, the position of the analyzer is changed with respect to the beam generator, a collector current-delay voltage graph is obtained for each position, and the optimized position is found based on the change pattern of the graph. At this time, since the voltage optimization step will be performed later anyway, the reserve lens voltage here may be determined to a degree that appropriately satisfies the above-described theoretical optimization condition, that is, the condition that [the focus of the charged particle beam is formed in front of the delay electrode].

FIG. 6 illustrates a collector current-delayed voltage graph (the horizontal position of the analyzer changes at 1 mm intervals) according to horizontal alignment to obtain the optimal condition for the distance between the electron gun and the analyzer, and FIG. 7 illustrates a collector current-delayed voltage graph (the vertical position of the analyzer changes at 1 mm intervals) according to vertical alignment to obtain the optimal condition for the distance between the electron gun and the analyzer. To be specific, the beam generator used in the experiment to obtain the results of FIGS. 6 and 7 is a Schottky electron gun, and therefore, in this case, the charged particle beam is an electron beam. Of course, this is only one example, and the beam generator can be various devices such as an electron source, an electron gun, an ion source, or an ion gun, and the charged particle beam can be an electron beam, an ion beam, etc.

If the alignment of the beam generator and the analyzer is not performed properly, as shown in FIGS. 6 and 7, as the retarding voltage increases, the current reaching the collector (300) (“collecting current”) does not maintain more than 90% but gradually decreases. Or, even if the collector current decreases rapidly, it may decrease in a region much lower than the beam energy.

If the beam generator and the analyzer are properly aligned, the current measured at the collector (300) will show a rapid decrease in a region where the beam energy and the delay voltage applied to the delay electrode (200) are at equal levels. At this time, the beam energy is a value already known from the specification of the beam generator, and the delay voltage is also a value that the user determines and applies to the analyzer, and is a value already known. Therefore, it is easy to determine where the beam energy and the delay voltage are similar while changing the delay voltage. For example, by setting the delay voltage as [a region where it is 0.9 to 1.1 times the beam energy] as the 'judgment region' and checking whether the current measured at the collector (300) shows a rapid decrease within the judgment region, it is possible to determine whether the alignment is achieved. In other words, you can obtain multiple collector current-delay voltage graphs by location, and then find a graph among the graphs that shows a sharp decrease in current within the judgment region, and decide the location where that graph was obtained as the optimal location.

In summary, in the above position optimization step, while the lens voltage is fixed to a preset reserve lens voltage, the position of the analyzer is changed based on the beam generator, and a collector current-delay voltage graph is obtained for each position. In the collector current-delay voltage graph for each position, a position where the current measured from the collector (300) rapidly decreases in a region where the beam energy and the delay voltage applied to the delay electrode (200) are at equal levels is determined as the optimized position.

At this time, if the experiment is conducted while changing the position of the analyzer in both the horizontal and vertical directions, there is a risk of missing the optimal position. Therefore, in order to do it more systematically, it is preferable to perform the alignment by first aligning in the horizontal direction and then performing the vertical alignment. In other words, this is a method of sequentially performing the experiments of FIGS. 6 and 7. To explain more clearly, it is preferable that the position optimization step is performed in the following order: first, finding a preliminary optimization position where the current rapidly decreases while moving the analyzer in the horizontal direction, and then finding an optimal position where the current rapidly decreases while moving the analyzer in the vertical direction from the preliminary optimization position.

In the voltage optimization step, as described above, the lens voltage applied to the lens electrode (110) within the analyzer is optimized. More specifically, while the position of the analyzer is fixed to the optimized position, the lens voltage is changed, and a current-delay voltage graph is obtained for each of the delay electrode (200) and the collector (300) for each voltage, and the optimized voltage is found based on the change pattern of this graph.

Fig. 8 illustrates the current change of each electrode at a lens voltage of -310 V, and Fig. 9 illustrates the current change (optimization condition) of each electrode at a lens voltage of -314 V. Fig. 8 shows a state in which the lens voltage is not optimized, and Fig. 9 shows a state in which the lens voltage is optimized. As examined above in Fig. 4, when the lens voltage is optimized, in a region where the beam energy and the delay voltage are at equal levels, that is, centered on the judgment region, in a region where the delay voltage is lower than the judgment region, the current measured by the collector (300) is maintained at approximately 90% or more, and in a region where the delay voltage is higher than the judgment region, the current measured by the collector (300) is maintained at approximately 0%.

In the graph of Fig. 9, that is, the graph when the lens voltage is -314 V, the current measured at the collector (300) shows the same aspect as described above, that is, it can be seen that the lens voltage is optimized. In this state, the current flowing in the delay electrode (200) converges to almost 0 in the entire region. On the other hand, in the graph of Fig. 8, that is, the graph when the lens voltage is -310 V, the current measured at the collector (300) shows an aspect of decreasing at the delay voltage of -492 V and then increasing again at -495 V, and in this region, the current flowing in the delay electrode (200) shows an aspect of increasing and then decreasing. Considering these various matters, it can be seen that when the lens voltage is optimized, the current flowing in the delay electrode (200) is always formed close to 0, and conversely, if the current flowing in the delay electrode (200) shows an aspect of converging to 0, it can be seen that the lens voltage at this time is the optimized voltage.

In summary, in the voltage optimization step, while the position of the analyzer is fixed to the optimal position, the lens voltage is changed, and a current-delay voltage graph is obtained for each of the delay electrode (200) and the collector (300) for each voltage. In the current-delay voltage graph for each voltage, the lens voltage at which the current flowing through the delay electrode (200) converges to 0 is determined as the optimal voltage.

In this way, the optimization method of the present invention first optimizes the position and then optimizes the lens voltage. At this time, several current-delay voltage graphs must be obtained at each step, which actually takes a considerable amount of time. However, since the voltage optimization step is performed after the position optimization step, it is not necessary to obtain a very precise current-delay voltage graph in the position optimization step. In other words, in the position optimization step, the graph can be obtained by changing the delay voltage only to the extent that a certain tendency can be seen. In fact, in FIGS. 6 and 7 corresponding to the position optimization step, the experiment was performed with the delay voltage interval set to a fairly large value of 1 V, whereas in FIGS. 8 and 9 corresponding to the voltage optimization step, the experiment was performed with the delay voltage interval set to a very small value of 0.05 V. That is, in order to save time for the overall optimization process, it is preferable that the delay voltage interval for obtaining a collector current-delayed voltage graph for each position during the position optimization step be formed to be larger than the delay voltage interval for obtaining a collector current-delayed voltage graph for each voltage during the voltage optimization step.

In the energy distribution measurement step, the energy distribution of the charged particle beam irradiated from the beam generator is measured by the analyzer while the analyzer is set to the optimized position obtained in the position optimization step and the optimized voltage obtained in the voltage optimization step. Strictly speaking, the energy distribution measurement step does not need to be included in the optimization method. However, it may be necessary to confirm whether the optimization has been properly performed by measuring the energy distribution in the optimized state through the position optimization step and the voltage optimization step, and in this case, broadly speaking, the energy distribution measurement step may be included in the optimization method.

Fig. 10 illustrates a collector current-delayed voltage graph and energy distribution under optimal conditions. As illustrated, the current reaching the collector (300) changes in the range of a delay voltage of -495 V to -499 V, but the current measured at the collector (300) changes rapidly in the range where the beam energy and the delay voltage are at equal levels, and the collection rate converges to 100% in the range where the delay voltage is smaller than this range, and the collection rate converges to 0% in the range where the delay voltage is larger than this range. By measuring the current measured at the collector (300) while changing the delay voltage applied to the delay electrode (200) in this way, the energy distribution can be calculated by differentiating the collector current-delayed voltage graph, which is the graph indicated as "dI/dV" in Fig. 10. The half-width calculated based on this graph is the energy width (ΔE).

The present invention is not limited to the above-described embodiments, and the scope of application is diverse. Anyone with ordinary skill in the art can make various modifications without departing from the gist of the present invention as claimed in the claims.

100: electrostatic lens 110: lens electrode
200 : Delay electrode 300 : Collector
400 : Blocking electrode 500 : Optical frame
600 : Aperture 700 : Housing
800 : Aperture cover

Claims (10)

In a method for optimizing a lens-type delay potential energy analyzer for measuring the energy distribution of a charged particle beam irradiated from a beam generator by using a lens-type delay potential energy analyzer including an electrostatic lens (100) equipped with a lens electrode (110), a delay electrode (200), and a collector (300),
A position optimization step in which alignment between the beam generator and the analyzer is optimized;
A voltage optimization step in which the lens voltage applied to the lens electrode (110) within the above analyzer is optimized;
Including,
The above location optimization step is,
While the lens voltage is fixed to a preset reserve lens voltage, the position of the analyzer is changed based on the beam generator, and a collector current-delay voltage graph is obtained for each position.
A method for optimizing a lens-type delay potential energy analyzer, characterized in that a position in a collector current-delay voltage graph by position is determined as an optimal position at which a collector current measured from the collector (300) rapidly decreases in a region where beam energy and the delay voltage applied to the delay electrode (200) are at equal levels.
delete In the first paragraph, the position optimization step,
First, move the analyzer horizontally to find the preliminary optimization position where the current decreases rapidly.
A method for optimizing a lens-type delay potential energy analyzer, characterized in that the method comprises finding an optimal position at which the collector current rapidly decreases while moving the analyzer in the vertical direction from the above-mentioned preliminary optimization position.
In the first paragraph, the voltage optimization step,
With the position of the analyzer fixed to the optimal position, the lens voltage is changed, and a current-delay voltage graph is obtained for each of the delay electrode (200) and the collector (300) for each voltage.
A method for optimizing a lens-type delay potential energy analyzer, characterized in that the lens voltage at which the current flowing through the delay electrode (200) converges to 0 on a voltage-dependent current-delay voltage graph is determined as the optimal voltage.
In the fourth paragraph, the method for optimizing the lens-type delay potential energy analyzer is as follows:
During the above location optimization step, the delay voltage interval for obtaining the collector current-delay voltage graph for each location is
A method for optimizing a lens-type delay potential energy analyzer, characterized in that the delay voltage interval is formed to be larger than that for obtaining a voltage-specific collector current-delay voltage graph during the above voltage optimization step.
In the first paragraph, the method for optimizing the lens-type delay potential energy analyzer is as follows:
An energy distribution measurement step in which the energy distribution of a charged particle beam irradiated from the beam generator is measured by the analyzer while the analyzer is set to the optimized position obtained in the position optimization step and the optimized voltage obtained in the voltage optimization step;
A method for optimizing a lens-type delay potential energy analyzer, characterized in that it further includes a.
In the 6th paragraph, the energy distribution measurement step,
A method for optimizing a lens-type delay potential energy analyzer, characterized in that the energy distribution is calculated by differentiating a collector current-delay voltage graph obtained by measuring the current measured at the collector (300) while changing the delay voltage applied to the delay electrode (200).
In the first paragraph, the analyzer,
The electrostatic lens (100) that refracts the charged particle beam irradiated from the beam generator using the potential applied through the lens electrode (110),
The delay electrode (200) in which the charged particle beam refracted by the electrostatic lens (100) is focused inside, generates an electric potential inside to reduce the energy of the incident charged particle beam, and allows only charged particles with energy greater than the electric potential generated inside to pass through.
The collector (300) that measures the energy distribution of the charged particle beam when the charged particle passes through the delay electrode (200)
A method for optimizing a lens-type delay potential energy analyzer, characterized by including a .
In the 8th paragraph, the analyzer,
A blocking electrode (400) is arranged between the electrostatic lens (100) and the delay electrode (200) and is provided to block interference of potential occurring between the electrostatic lens (100) and the delay electrode (200).
A method for optimizing a lens-type delay potential energy analyzer, characterized in that it further includes a.
In the 8th paragraph, the analyzer,
An aperture (600) that controls the size of the charged particle beam incident on the above-mentioned electrostatic lens (100).
A method for optimizing a lens-type delay potential energy analyzer, characterized in that it further includes a.

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