JPH1027571A - Spectroscopic device having toroidal spectroscope - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To increase the solid angle taken in and improve the resolution. A toroidal spectrometer rotationally symmetric with respect to a rotation center axis, and a conical lens system provided at a stage preceding the toroidal type spectrometer through an annular entrance slit and rotationally symmetric with respect to the rotation center axis. From a charged particle generation source for generating charged particles taken into the conical lens system, an annular exit slit provided on the exit side of the toroidal spectrometer, and a detector for detecting charged particles exiting from the annular exit slit. It is characterized by becoming. In addition, the traveling direction of electrons at the exit of the toroidal spectrometer is set to be perpendicular to or close to the rotation center axis, and a transaxial lens is provided between the exit of the toroidal spectrometer and the electron detector. Install and perform multiplex detection.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spectroscopic device using a toroidal spectroscope, which has a large solid angle and variable resolution.

[0002]

2. Description of the Related Art Conventionally, many types of spectroscopes for analyzing the kinetic energy of electrons have been considered.
At present, two types of concentric spherical spectrometers and cylindrical mirror type electrostatic spectrometers are frequently used, and the two are most frequently used because of their excellent This is because it has features.

The concentric sphere type electrostatic spectrometer is designed to fly charged particles through an electric field formed between concentric spherical electrodes and perform energy analysis. The resolution can be changed by installing a deceleration lens in a preceding stage. If the degree of deceleration is increased, higher-resolution energy analysis can be performed. In addition, there is a characteristic that the focus positions of electrons having different energies are shifted in the energy dispersion direction (radial direction between the concentric spherical electrodes) by an amount proportional to the energy difference (this is referred to as “having energy dispersibility”). Multiple detection is possible by arranging a detector at this position.

The cylindrical mirror type electrostatic spectroscope is designed to fly charged particles through an electric field formed between cylindrical electrodes and perform energy analysis. The charged solid particles have a large solid angle and high sensitivity can be obtained.

[0005]

However, both have drawbacks, and this is one of the factors that limit the performance of current electron spectrometers such as Auger electron spectrometers and photoelectron spectrometers such as spatial resolution and detection limit concentration. Has become.

In the concentric spherical electrostatic spectrometer, the solid angle at which charged particles to be analyzed can be taken between the concentric spherical electrodes can be set to 0.1 to 0.1 through a well-designed front lens.
Although it can take up to about 0.2str (steradian), it is considerably smaller than a cylindrical mirror type electrostatic spectrometer. Although this disadvantage can be compensated to some extent by the multiple detection method, the sensitivity improvement is only several times.

[0007] The cylindrical mirror type electrostatic spectroscope has a relatively large solid angle of about 0.5 to 0.7 str, but it is difficult to place a lens in the front stage, so that the solid angle is further improved. It is impossible to change the resolution. In addition, multiple detection is difficult because of insufficient energy dispersibility. As described above, at present, there is no spectroscope that has a large capturing solid angle and variable resolution at the same time.

It is an object of the present invention to provide an electron spectrometer capable of increasing the solid angle of capture and changing the resolution to achieve higher resolution.

[0009]

According to a first aspect of the present invention, there is provided a spectroscopic device having a toroidal type spectroscope, which comprises a toroidal type spectrometer which is rotationally symmetric with respect to a center axis of rotation, and which has a conical lens system disposed in front thereof. The charged particles are focused and made incident on a spectroscope, and the charged particles subjected to energy analysis are focused again near the exit slit, and the charged particles passing through the exit slit are detected by a detector. At this time, the solid angle captured by the toroidal spectrometer can be much larger than that of the concentric spherical spectrometer, and the energy resolution can be improved by changing the speed of charged particles incident on the spectrometer with the conical lens system. It is possible to make it variable and to increase the resolution.

A spectrometer having a toroidal spectrometer according to a second aspect of the present invention is provided in front of the toroidal spectrometer via an annular entrance slit and a toroidal spectrometer which is rotationally symmetric with respect to a rotation center axis. A conical lens system that is rotationally symmetric with respect to the rotation center axis, a charged particle generation source that generates charged particles captured by the conical lens system, and a transaxial lens provided at an outlet of the toroidal spectroscope, And a plurality of detectors for detecting charged particles focused by the transaxial lens. According to this, multiplex detection can be performed.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION

[First Embodiment] Hereinafter, a first embodiment of the electron spectroscopy apparatus of the present invention will be described.
An embodiment will be described. The present invention intends to increase the solid angle taken in by using a toroidal spectrometer, and at the same time, to make the resolution variable so as to increase the resolution. First, this toroidal spectrometer will be described.

In general, an electrostatic spectrometer applies different potentials to two electrodes, forms an electric field between the electrodes, and has a specific energy when a charged particle, for example, an electron passes through the electric field. Only those that pass through a specific orbit and those with other energies use the phenomenon of traveling out of that orbit. The shape of the two electrodes forming the electric field is spherical in the case of a concentric spherical electrostatic spectrometer, and cylindrical in the case of a cylindrical mirror electrostatic spectrometer.

The spectroscope according to the present invention utilizes a surface formed when a circle having a radius r is rotated about a straight line having a distance R from the center of the circle as a center axis. A spectroscope utilizing this surface is called a “toroidal spectroscope”.

As shown in FIG. 1, when a concentric circle having a radius r ₁ and a radius r ₂ is rotated about a straight line separated from the center O of the circle by a distance R as a center axis (rotation center axis), the circle is surrounded by two toroidal surfaces. A space is created. However, when a part of the circle enters the opposite side of the rotation center axis, there is no part of the arc.

Now, in FIG. 1, the radius r (r ₁ <r <r
₂ ) Consider the circle. If this circle is also centered on point O, a toroidal surface due to this circle will be formed between the other two toroidal surfaces. As shown in the figure, an angle ω, an x-axis (circular direction), a y-axis (radial direction), and a z-axis (a direction perpendicular to the paper surface) are defined. In addition, a toroidal surface formed by a circle having a radius r is simply referred to as an “r toroidal surface” below.

The radius of curvature of the toroidal surface of r in the x-axis direction is r, and the radius of curvature R 'in the z-direction perpendicular thereto is given by the following equation. R ′ = r + R · cosecω (1) Let these ratios be c. That is, c = r / R ′ = r / (r + R · cosecω) (2) Here, c may be called an electric field coefficient of a toroidal electric field.

A spherical or cylindrical surface corresponds to this special case, where c = 1 (R = 0) for a spherical surface and c = 0 (R = ∞) for a cylindrical surface. As is well known, an electric field in a space between two different potential spherical surfaces or cylindrical surfaces is uniquely determined when the respective potentials are determined. E (r) = k (r / r 0) -n ... (3) However, the _{r 0 = (r 1 + r} 2) / 2. N = 2 for a spherical surface and n = 1 for a cylindrical surface. k is a constant determined by r ₁ , r ₂ and the potential of the surface, and is different between a spherical surface and a cylindrical surface.

When an electric field is applied in this manner, the radius r
_The following equation is known as a solution of the paraxial orbit equation of an electron starting on the circumference of ₀ . (R / r ₀ ) −1 = (1 / (3-n) ^1/2 ) · sin {(3-n) ^1/2 · ω｝ · α (4) where α is the radius r ₀ This is the angle between the tangent to the circumference of the circle and the direction of the initial velocity of the electrons.

The condition for the electron starting at a certain angle α from the x axis at the starting point to reach the x axis again, that is, the condition for converging the orbit (r = r ₀ ) is as follows. sin ｛(3-n) ^1/2 · ω｝ = 0 (5) Therefore, if the deflection angle ω at the point of focusing is φ,
Φ = π for a spherical surface, φ = π / 2 ^1/2円 筒 for a cylindrical surface
127.28 °. Note that a spectroscope using a deflection angle of 127.28 ° is called a cylindrical spectroscope and may be used for a special purpose such as a scattering experiment. Cylindrical mirror spectrometers
It is the same in that it uses the space created between two concentric cylindrical surfaces, but it does not use the focusing characteristics of Eq. (5).

For a toroidal surface, c is a function of ω, where 0 <c (ω) <1. Thus, the electric field can be written as

[0021]

(Equation 1)

Where 1 <n (c (ω)) <2 and c
N (c) → 1 when → 0, and n (c) → 2 when c → 1.

As described above, the electric field generated by the toroidal surface has an intermediate property between a spherical surface and a cylindrical surface. Although the trajectory of the electrons as they move in this electric field cannot be analyzed analytically, they can be expected to have the same focusing action as in the case of concentric sphere type or cylindrical type spectrometers.

According to the result of the numerical calculation simulation, as shown in FIGS. 2A and 2B, in the electric field formed by the two toroidal surfaces, the point Q (the circle of the circle having the radius r ₀ ) An electron starting at a specific energy within an angle of ± α with respect to the x-axis from one point on the circumference) converges to almost one point at point F if α is relatively small, about 5 degrees. However, the convergence angle φ slightly changes depending on the position of Q.

Further, this result indicates that both points Q and F are located at one of the central axes in the figure, that is, either above or below, that is, the trajectory of the electron moves between points Q and F. As long as it does not cross the center axis of rotation when passing, and both points Q and F are located not so close to the center axis of rotation, this is always true independent of the position of point Q. Point Q
Alternatively, if the point F is close to the rotation center axis, the electric field in the vicinity of the point F is disturbed from the original shape formed by the toroidal surface, so that the above-described focusing characteristics cannot be established.

For convenience in the following description, a ratio ν of R to r ₀ is introduced as a parameter indicating the geometrical characteristics of the toroidal surface. That is, ν = R / r ₀ (7) An angle φ at which electrons are deflected from point Q to point F with respect to ν
Is as shown in FIG. 3 according to the result of the simulation. In FIG. 3, the left end side is a spherical type, and the right end side is a case close to a cylindrical type. In the present invention, φ is an intermediate value between the spherical type and the cylindrical type, that is, an intermediate value between π and π / ^21/2 . Take the value. Here, the potential difference between the two electrodes is selected to be an appropriate value proportional to the electron energy. Note that the curve shown in FIG. 3 is for the case where the point Q is placed as shown on the left side of FIG. 2, and the shape of the curve changes as shown on the right side of FIG. Where 180 ° when ν = 0 and 127.3 when ν = ∞
° is the same.

[Example of Configuration of Electron Spectrometer Using Toroidal Spectroscope] FIG. 4 shows an example in which a toroidal spectrometer having the above-mentioned characteristics is used. In FIG. 4A,
The toroidal spectrometer includes an outer electrode 2 and an inner electrode 3 that are rotationally symmetric with respect to the rotation center axis 1, and a conical electrostatic lens 6 (a rotation center axis 1 (Rotationally symmetrical with respect to the axis), and electrons incident through the entrance slit 4 exit from the exit slit 5 near the rotation center axis 1, are deflected by the deflectors 10 and 11, and detected by the electron detector 12. It has become.

The electron source 9 converts the sample 8 into an electron gun, X
The excitation is performed by a primary excitation source 7 including a radiation source, an ultraviolet irradiation device, and the like. As shown in a detailed view of FIG. The emitted electrons are focused by the conical electrostatic lens 6 near the entrance slit 4 of the toroidal spectroscope. Details of the vicinity of the entrance slit of the toroidal spectroscope are as shown in FIG. The electrons are transferred to the outer electrode 2 of the toroidal spectrometer.
Energy analysis is performed by the electric field formed between the inner electrode 3 and the inner electrode 3, and the light is focused again near the exit slit 5. Only electrons that have passed through the slit 5 are detected by the electron detector 12, and only electrons within a specific energy range among electrons starting from the electron source 9 are selected. In addition, since it is a rotationally symmetric system, both the entrance slit 4 and the exit slit 5 are annular.

The electrons exiting the exit slit 5 are shown in FIG.
As shown in the detailed view of FIG. 1, the electron detector is deflected by a deflection electric field created between a deflector 11 to which a positive potential is applied from the exit slit and a deflector 10 to which a negative potential is applied than the exit slit. Reach the 12th entrance. A hole is formed in the deflector 11 so that electrons can pass therethrough. Further, a potential difference of about 100 V is provided between the exit slit 5 and the foremost portion of the electron detector 12, and low-energy electrons are accelerated here and enter the electron detector 12.

Although not shown, in order to prevent a magnetic field from being present on the electron orbit, a magnetic shield plate covering the entire lens and spectroscope, a power supply and a controller for applying a voltage to each system are provided. In addition, an ion etching apparatus for cleaning the sample surface, a sample stage, a vacuum pump, a sample exchange apparatus, and the like are provided.

The potential applied to each part is such that when the energy of the electrons to be split is E _k = eΦ (eV),
The case of the configuration example of FIG. 4 is as follows. Conical electrostatic lens first electrode 0 (ground potential) Second electrode a ₁ Φ + b ₁ Third electrode a ₂ Φ + b ₂ Fourth electrode k _R Φ Toroidal spectrometer outer electrode k _O Φ Toroidal spectrometer inner electrode k _I Φ Inlet and outgoing slit Same as the fourth electrode of the electrostatic lens Deflector 10 (1 + δ) k _R Φ Deflector 11 (1−δ) k _R Φ Electron detector tip k _R Φ + (about 100 V) a, b, k, δ And other parameters are adjusted according to the energy of the electrons to be dispersed, so that the electron intensity E _k
A graph showing the dependence, that is, an electronic spectrum is obtained.

If an appropriate number of electrodes and a conical lens system having an appropriate shape are selected, the angle γ can be increased, so that electrons can be collected from a wide range. Also,
It becomes possible to focus electrons near the entrance slit while decelerating the electrons by the lens system, so that the resolution of energy analysis can be improved.

Further, this toroidal spectrometer has energy dispersibility as shown in FIG. That is, in this toroidal spectrometer, as shown in FIG. 5, the convergence positions of the electrons having different energies are shifted in the direction of the energy dispersion by an amount proportional to the difference in the energy. "). Therefore, this spectrometer enables multiple detection. That is, it is possible to simultaneously detect electrons having different energies. The example of FIG. 5 shows the inner electrode (potential) of a toroidal spectrometer.
0) radius r ₁ = 35 mm, radius r _{2 of} the outer electrode (potential −100 V) r ₂ = 60 mm, and ν = 0.8. As shown in the drawing, focusing is performed with an energy difference of 5 eV from 90 eV to 110 eV. Thus, multiple detection is possible by arranging a detector at each focusing point.

[Determination of Specific Dimension of Electron Spectrometer] Next, a method of determining a specific dimension of the toroidal spectrometer of the present invention will be described below. First, each dimension of the spectrometer is defined as shown in FIG. L
Is the distance from the electron source Q to the entrance of the toroidal spectrometer, and is the sum of the length of the conical lens and the distance from the lens tip to the electron source. Point F is the focal point of the toroidal spectrometer.

It is assumed that the distance of the point F from the rotation center axis is d, and this is determined by the ratio to the aforementioned r ₀ . d = ur ₀ (8) Here, u is determined in consideration of various conditions when installing the detector. For example, in order to perform multiple detection, u needs to be relatively large because a sufficient space is required for installing a deflector and an electron detector. As in the example shown in FIG. 4, when only a single detector is installed, a very large space is not required, so that u may be a small value.

[0036] θ and u will be determined first and other parameters will be determined accordingly. The specific method may be as follows. The equations derived from FIG. 6 are the following two. _ro · cos (π−φ + θ) = R−d (9) L · tan θ = r ₀ + R / cos θ (10) The expression indicating the deflection angle of the toroidal spectrometer (the expression representing the curve in FIG. 3) is given by Do as follows. φ = f (ν) (11) From equations (7), (8) and (9), φ = cos ⁻¹ (u−ν) + θ (12) If θ and u are determined to be appropriate values, Ν and φ are obtained from the intersection of the graphs of equations (11) and (12). FIGS. 7 and 8 show examples of these graphs.

FIG. 7 shows that u is set to 0.2 and θ is changed from 0 ° to 90 °.
FIG. 7 is a graph showing the value of φ given by equation (12) when the angle is changed in increments of 5 ° up to °, and the curve of FIG. 3 (curve represented by equation (11)).

As described in the explanation of FIG. 3, the shape of the curve represented by the equation (11) changes strictly depending on θ. Only things are shown. FIG. 8 is a graph showing the value of φ given by equation (12) when θ is set to 35 ° and u is changed from 0.0 to 1.0 in steps of 0.1, and the curve of FIG. ) Are shown at the same time.

In FIGS. 7 and 8, ν and φ are obtained from the intersection of both curves. From equation (10), r ₀ = L sin θ / (ν + cos θ) (13) Therefore, if L is determined to be an appropriate value, r ₀ and R are obtained from equations (13) and (7), All dimensions will be determined.

[Comparison of Captured Solid Angle] The capture solid angle of the spectroscopic device of the present invention configured as described above can be obtained by a simple calculation. The results obtained are shown in Table 1 in comparison with the concentric hemispherical electrostatic spectrometer and the cylindrical mirror type electrostatic spectrometer. In the case of the spectroscopic device according to the present invention, nine values of θ are selected.

Table 1 [Capturing solid angle] (unit is str) γ Spectroscopic device according to the present invention Hemisphere Cylindrical (θ = 60,55,50,45,40,35,30,25,20 degrees) mirror type θ = 60 55 50 45 40 35 30 25 20 3 O.57 0.54 O.50 0.47 0.42 0.38 0.33 0.28 0.22 0.01 0.35 4 0.76 0.72 0.67 0.62 0.56 0.50 0.44 0.37 0.30 0.02 0.47 5 0.95 0.90 0.84 0.77 0.70 0.63 0.55 0.46 0.37 0.02 0.59 6 1.14 1.08 1.01 0.93 0.84 0.75 0.66 0.56 0.45 0.03 0.71 7 1.33 1.25 1.17 1.08 0.98 0.88 0.77 0.65 0.52 0.05 − 8 1.51 1.43 1.34 1.24 1.12 1.00 0.87 0.74 0.60 0.06 − 9 1.70 1.61 1.51 1.39 1.26 1.13 0.98 0.83 0.67 0.08 − 10 1.89 1.79 1.67 1.54 1.40 1.25 1.09 0.92 0.75 0.10 −12 2.26 2.14 2.00 1.85 1.68 1.50 1.31 1.10 0.89 0.14 −15 2.82 2.66 2.49 2.30 2.09 1.87 1.63 1.38 1.11 0.21 −18 3.36 3.18 2.97 2.75 2.50 2.23 1.94 1.64 1.33 0.31 − Hemispherical In most cases, the practical range is 0.10
It is about 0.21. In the case of a cylindrical mirror type, γ (= α)
If is larger than 6 degrees, the convergence becomes poor, and practical resolution cannot be obtained. In the case of cylindrical mirror type,
A mesh for electric field correction must be provided at the entrance and exit of the inner cylinder. Since the transmittance of the mesh is at most about 90%, the total transmittance is about 80% because there are two meshes. This effect is also included in the numerical values in Table 1. In contrast, as can be seen from Table 1, the spectroscopic device according to the present invention has a large solid angle of capture. Further, if the aberration of the conical lens at the front stage is reduced as much as possible, γ can be increased to about 18 degrees, so that higher sensitivity than any other type of spectroscopic device can be realized. Further, the resolution can be changed.

FIG. 9 is a view showing another example of the toroidal spectrometer of the present invention, in which an electron beam irradiation apparatus and a spectrometer are coaxially arranged. In FIG. 9, an electron beam irradiation device 20 includes an electron gun as a primary excitation source, a lens, an axis adjusting device, and the like. An electron optical system 21 disposed in the spectrometer along the rotation center axis of the spectrometer is an electron lens. , Diaphragm, electron current measuring device, etc. These electron beam irradiation devices 2
0. If the size of the electron optical system 21 can be made sufficiently small, everything from the electron gun to the lens system can be put in the entire spectroscopic device. In this device, the sample can be irradiated with an electron beam flying along the rotation center axis perpendicularly to the sample, so that no shadow is produced even when the sample surface has irregularities. Not only the electron beam irradiator but also an X-ray irradiator can be coaxially arranged.

The present invention is not limited to the spectrometer shown in FIGS. 4 and 9, and various modifications are possible. For example, while the conical electrostatic lens system has three gaps, the number of electrodes can be increased or reduced to form the required optical system. Further, it is also possible to insert a mesh or the like in the middle, correct the electric field to a convenient shape, and achieve further optimization.

Further, in the examples shown in FIGS. 4 and 9, all of 360 ° with respect to the rotation center axis are used, but only a part thereof (for example, 180 °, 90 °, etc.) is cut out. Shapes can also be used. This is particularly effective when the space around the sample is limited.

Further, in an empty space near the center of the conical electrostatic lens, means for detecting other signals, such as a secondary electron detector and a backscattered electron detector, can be provided. . Further, another slit for preventing scattering can be arranged in the vicinity of the entrance slit or the exit slit as needed.

In the example described above, the electron orbit has only one focal point in the toroidal spectrometer, but it is also possible to focus two or more times. In that case, if the focal point of the front lens is brought before the entrance of the toroidal spectroscope and the energy dispersion plane at the final focusing point is adjusted to be almost perpendicular to the rotation center axis of the spectroscope, a commercially available multi-lens can be used. Channel plate is now available,
Realization becomes extremely easy. Further, even if the focal point of the front-stage lens is brought near the entrance of the toroidal spectroscope, a focusing point can be generated at a position distant from the exit of the toroidal spectroscope. Furthermore, one of the deflectors 10 and 11 can be set to the same potential as the exit slit, and the exit slit and the entrance slit are not set to the same potential as the fourth electrode of the conical electrostatic lens. Can be modified for the purpose of correction.

[Second Embodiment] As described with reference to FIG. 5, the above-mentioned toroidal spectrometer has a characteristic that the energy dispersion is linear, so that multiple detection is possible. In the configuration shown in FIG. 4, the exit slit 5 is disposed at the exit of the toroidal spectroscope, so that the electron detector 12 detects only electrons within a certain energy width that can pass through the exit slit 5. It can be said that the characteristic that the energy dispersion is linear is not fully utilized.

Therefore, in the following, as a second embodiment, a spectrometer having a toroidal spectrometer capable of multiplex detection using a commercially available electron detector such as a channeltron or a multichannel plate is described. The device will be described.

In the case of performing multiple detection, a toroidal spectrometer rotated 360 ° with respect to the rotation center axis as shown in FIGS. 4 and 9 cannot be used. As shown in FIG. 10, the spectroscope uses a part, for example, a part used for 90 degrees, as shown in FIG. That is, FIG.
In (b), only the portion indicated by the solid line is used. FIG. 10B is a diagram of FIG. 10A viewed from above. The dimensions defined in the above item [Determining Specific Dimensions of Electron Spectroscopy Apparatus] are also satisfied in this embodiment.

In this toroidal spectrometer, the traveling direction of the electrons at the exit of the toroidal spectrometer is set so as to be perpendicular or nearly perpendicular to the center axis of rotation. That is, the dimension is set so that φ−θ = π / 2 (14) or φ−θ ≒ π / 2 (15).

In this toroidal spectrometer, a transaxial lens is arranged between the exit of the toroidal spectrometer and the electron detector.

Hereinafter, these two elements will be specifically described. To satisfy the above equation (14) or (15),
First, the angle θ is determined. This may be determined as appropriate based on a primary excitation source including an electron gun, an X-ray source, an ultraviolet irradiation device, an irradiation system including a lens and an axis adjusting device, a moving range of a sample, and the like. Thus, φ is determined from Expression (14) or Expression (15). Next, from the graph shown in FIG. 3 showing the relationship between ν and the deflection angle φ, the ratio ν corresponding to the determined φ
Ask for.

Next, the distance L from the electron source Q to the entrance of the toroidal spectrometer and the radius r ₀ of the central orbit of the toroidal spectrometer in the direction along the electron orbit satisfy the equation (13). To decide. L is a parameter that determines the blur of the image at the focal point of the conical lens and the opening angle when the light enters the toroidal spectroscope. The larger the value, the smaller the opening angle, which is desirable. Further, r ₀ is a parameter related to the energy resolution of the toroidal spectroscope, and the larger the value, the higher the resolution of the spectroscope. As described above, since the performance increases as both L and r ₀ increase, it is sufficient to appropriately determine both of them so that they do not become too large.

When r ₀ is determined in this manner, R is determined by equation (7) using the value of ν obtained earlier.
Now, for example, when θ = 45 °, φ satisfying the expression (14) is obtained, φ = 135 °. At this time, ν = 1.75 from FIG.
Becomes If L = 400 mm and r ₀ = 115 mm, R = 201 mm from equation (7). As described above, it is possible to determine a parameter that satisfies the expression (14) or (15).

Next, the arrangement of the transaxial lens will be described. The transaxial lens has a configuration in which an electrostatic lens in which two plate electrodes are arranged to face each other is arranged in a plurality of stages in the traveling direction of the charged particle beam, and the two plate electrodes face each other. With respect to the direction, it is known to have a lens action on electrons similar to that of a normal cylindrical electrostatic lens or the like (in this regard, for example, PWHawk
es, E.Kasper; Principles of Electron Optics Vol.1 A
cademic Press 1989).

FIG. 11 shows a configuration example of a transaxial lens. FIG. 11A is a plan view, and FIG.
3A shows a cross section taken along line AA. The transaxial lens shown in FIG. 11 includes three stages of electrostatic lenses G1, G2, and G3. As can be seen from FIG. 11A, the electrodes of each stage of the electrostatic lens are formed in a sector shape. The electrodes of the G1 and G3 lenses are set to the ground potential, and the electrodes of the G2 lens are set to a predetermined potential. With this configuration, as shown in FIG. 11B, the electron beam incident on the transaxial lens from below is focused by the lens function of the transaxial lens. However, there is no focusing action in the ω direction of FIG.

Such a transaxial lens is arranged on the exit side of the toroidal spectroscope. FIG. 12 shows an example of the configuration. In FIG. 12, an exit slit 30 having a plurality of openings is provided at the exit of the toroidal spectroscope.
Are arranged, and a transaxial lens 31 composed of three stages of electrostatic lenses G1, G2, and G3 is arranged for each opening of the exit slit 30. FIG.
In the configuration shown in (1), since the transaxial lens corresponding to the opening adjacent to the exit slit 30 shares an electrode, if the number of openings of the exit slit 30 is n,
There are a total of 3 (n + 1) fan-shaped plate-like electrodes required to form a transaxial lens.

The G of the transaxial lens 31
A voltage is applied to both the electrodes of the electrostatic lenses 1 and G3 so as to have the same potential as the potential of the central orbit of the toroidal spectrometer, and a different voltage is applied to the electrodes of the electrostatic lens of G2. You. In this case, since this lens system performs the same lens operation as that of a normal cylindrical electrostatic lens such as an Einzel lens, the electron beam converged near the exit slit 30 as shown in FIG. Focusing is performed again near the exit of the transaxial lens 31.
In FIG. 13, 1 indicates the distance between the exit slit 30 and the focusing position near the exit of the transaxial lens 31. The transaxial lens 31
The purpose of providing is to prevent the electrons emitted from the respective openings of the emission slit 30 from diverging and to prevent their orbits from overlapping with each other, so that a perfect image cannot be obtained due to aberration, Blurred images are not very problematic.

As shown in FIG. 14, an electron detector 32, for example, a channeltron, is disposed at the exit side of each transaction lens 31. FIG.
14A is a plan view, and FIG. 14B is a cross-sectional view. Originally, the electron detector may be directly disposed on the exit side of the toroidal spectrometer, but the size of the electron detector itself becomes extremely large. In fact, in the case of the dimensions described above, an electron detector having a radius of about 200 mm is required. It is for this reason that the transaxial lens 31 is disposed on the exit side of the toroidal spectrometer, and this makes it possible to use an electron detector of a size generally available on the market and to reduce the cost. It can be configured as follows.

The distance l between the exit slit 30 and the focal position of the transaxial lens 31 can be adjusted within a certain range by controlling the voltage applied to the electrode of the G2 electrostatic lens. The size may be determined from the viewpoint of the size of the electronic device 32 and how much space is left behind the electron detector 32.

FIG. 14 shows the case where l = R. In this case, if the aberration of the transaxial lens 31 and the toroidal spectroscope is neglected, each aperture of the exit slit 30 when l = R is obtained. Since the electron beam emitted from the unit is focused on one point on the rotation center axis, an extremely small electron detector can be installed.

Although the second embodiment has been described above, the present invention is not limited to the above-described embodiment, and various modifications are possible.

For example, an electron irradiation system or the like occupies the vicinity of the rotation center axis of the toroidal spectrometer, and the space on the back side of the electron detector may be limited. In this case, a microchannel is used as the electron detector. Plates can be used. FIG. 15 shows a configuration example in that case,
A plurality of microchannel plates 33 are arranged on the exit side of the transaxial lens 31. In this case, as is apparent from FIG. 15, the electron detection surface of the microchannel plate 33 and the transaxial lens 3
When the potential of the intermediate electrode (electrode of the electrostatic lens of G2) of the transaxial lens 31 is adjusted so that the distance from the exit 1 is not constant and focuses on a certain location of the microchannel plate 33, Although the focus slightly shifts, as described above, the purpose of the transaxial lens 31 is to prevent the electrons emitted from the emission slit 30 from diverging, and to prevent the orbits from overlapping each other. It does not mean that less imaging is required. Therefore, even if the focus is slightly shifted, it does not become an obstacle. In this case, the multi-channel plate 3
Since the gap between the three cannot be completely eliminated, a loss of sensitivity is inevitably caused.

Although FIG. 14 shows an example where l = R, a case where l> R can be considered. In this case as well, FIG.
As shown in (1), electrons can be detected using a microchannel plate. However, in this case, the arrangement of the microchannel plates is such that the side of the electron incident surface is concave.

Further, when the traveling direction of electrons and the center axis of rotation are not strictly perpendicular to each other at the exit of the toroidal spectroscope, that is, when the above equation (15) is used, FIG.
As shown in FIG. 6A or FIG. 16B, the transaxial lens 31 may be inclined. In this case, when a multi-channel plate is used as the electron detector, the plate shape of the multi-channel plate may be a trapezoid instead of a rectangle.

In the above description, electrons have been described as an example. However, it goes without saying that the present invention can be used for general spectroscopy of charged particles such as ions.

[0067]

As is apparent from the above description, according to the present invention, charged particles emitted from a charged particle generation source are efficiently collected at a large solid angle in an annular shape by a conical lens system at the preceding stage. In addition, if the electrons are decelerated by the conical lens system and then incident on the toroidal spectrometer, energy analysis with higher resolution can be realized.

The direction of the electrons at the exit of the toroidal spectrometer is set to be perpendicular to or close to the center axis of rotation, and the translator is disposed between the exit of the toroidal spectrometer and the electron detector. By installing a xial lens, multiplex detection can be performed using a commercially available electron detector such as a channeltron or a microchannel plate, and the characteristic that the energy dispersion of a toroidal spectrometer is "linear". Can be fully exhibited.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a toroidal surface.

FIG. 2 is a diagram illustrating a focusing action of electrons in an electric field generated on a toroidal surface.

FIG. 3 is a diagram illustrating a relationship between ν indicating a geometric shape of a toroidal surface and a deflection angle φ.

FIG. 4 is a diagram showing an example of an electron spectrometer of the present invention using a toroidal spectroscope.

FIG. 5 is a diagram for explaining energy dispersion characteristics of a toroidal spectrometer.

FIG. 6 is a diagram illustrating a method for determining various dimensions of the spectroscopic device.

FIG. 7 shows ν and φ when θ is changed in 5 ° steps.
FIG.

FIG. 8 shows ν and φ when u is changed in 0.1 steps.
FIG.

FIG. 9 is a diagram showing an example in which an electron beam irradiation device and an electron spectroscopy device are coaxially arranged.

FIG. 10 is a diagram for describing a toroidal spectrometer used in the second embodiment.

FIG. 11 is a diagram showing an example of a transaxial lens.

FIG. 12 is a diagram illustrating an example of an arrangement of a transaxial lens in a second embodiment.

FIG. 13 is a diagram for explaining electron trajectories in a transaxial lens.

FIG. 14 is a diagram illustrating an example of an arrangement in a case where a channeltron is used as an electron detector in the second embodiment.

FIG. 15 is a diagram illustrating an example of an arrangement in a case where a microchannel plate is used as an electron detector in the second embodiment.

FIG. 16 shows that in the second embodiment, the transaxial lens 31 may be tilted when the traveling direction of electrons and the rotation center axis are not exactly perpendicular to each other at the exit of the toroidal spectroscope. FIG.

[Explanation of symbols]

Reference numeral 1 denotes a center axis of rotation; 2 denotes an outer electrode of a toroidal spectroscope; 3
... inner electrode of toroidal spectrometer, 4 ... entrance slit, 5
... Emission slit, 6 ... Conical electrostatic lens, 7 ... Primary excitation source, 8 ... Sample, 9 ... Electron generation source, 10, 11 ... Deflector, 12 ... Electron detector, 20 ... Electron beam irradiation device, 2
DESCRIPTION OF SYMBOLS 1 ... Electronic optical system, 30 ... Emission slit, 31 ... Transaxial lens, 32 ... Electron detector (channeltron), 33 ... Electron detector (micro channel plate).

Claims (2)

[Claims] 1. A toroidal spectroscope which is rotationally symmetric with respect to a rotation center axis, and a conical lens system which is provided in front of the toroidal spectrometer via an annular entrance slit and is rotationally symmetric with respect to the rotation center axis. And a charged particle generation source that generates charged particles captured by the conical lens system, an annular exit slit provided on the exit side of the toroidal spectrometer, and a detector that detects charged particles exiting from the annular exit slit. A spectrometer having a toroidal spectrometer comprising: 2. A toroidal spectroscope rotationally symmetric with respect to a rotation center axis, and a conical lens system provided in front of the toroidal spectrometer via an annular entrance slit and rotationally symmetric with respect to the rotation center axis. And a charged particle source for generating charged particles taken into the conical lens system, a transaxial lens provided at the exit of the toroidal spectrometer, and a plurality of detections for detecting the charged particles focused by the transaxial lens A spectroscopic device having a toroidal spectrometer comprising a spectroscope.