JP2006278069A - Wien filter type energy analyzer and discharge electron microscope - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a Wien filter type energy analyzer capable of suppressing deterioration of sensitivity by fully making the best use of its aberration correcting characteristics to reduce electrons lost in the analyzer. <P>SOLUTION: This Wien filter type energy analyzer 11 has 12 magnetic poles formed by electrodes 13 and yokeless coils 14. Therefore, this Wien filter type energy analyzer can generate an electric field E and a magnetic field B capable of erasing aberration from secondary aberration up to tertiary aperture aberration. The yokeless coil 14 is formed by replacing the magnetic pole only with a coil, and is disposed on a coil receiving stand 15. Since the magnetic pole is replaced with the coil, the inner diameter of the Wien filter type energy analyzer 11 can be enlarged and its sensitivity can be enhanced. In addition, since a magnetic body is not used, it is not required to take into consideration of hysteresis of the magnetic body, and a magnetic field having good reproducibility can be obtained. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention is classified in the field of beam optics, and in particular, a Wien filter type energy analyzer that selects only an electron beam having a specific energy using a Wien filter and an energy selection type in which the Wien filter type energy analyzer is provided in an electron lens system. The present invention relates to an electron microscope apparatus. This energy selective electron microscope apparatus is a combination of a photoelectron spectrometer and an electron microscope, and is widely applied to surface analysis.

  In addition to being used in devices such as Auger electron spectroscopy and photoelectron spectroscopy, energy analyzers are used for energy-filtering microscopy in which only electron beams with specific energy are selected and imaged in an electron microscope. Also used for. In such an apparatus, one of the main factors that determine the performance as an electron spectroscopy system, that is, the energy resolution and sensitivity, is the aberration of the analyzer. This determines the upper limit of the electron beam opening angle allowed at the analyzer entrance. The smaller this aberration is, the wider the angle at which electrons can be taken in, and the sensitivity under a certain energy resolution can be improved. It is the same, but the energy resolution under a certain sensitivity can be improved. On the contrary, if this aberration is large, the beam is blurred at the outlet of the analyzer, that is, the energy selection surface, and the energy resolution and sensitivity are impaired. Therefore, the problem of reducing the aberration of the analyzer is an important issue for improving the performance of the electron spectrometer.

  Conventionally, as described in Patent Document 1 below, a Wien filter is used as an energy analyzer. A Wien filter consists of an electric field and a magnetic field that are orthogonal to each other. In the Wien filter, for electrons having a specific energy, forces from the electric field and the magnetic field cancel each other, and the electrons can pass through the filter, but electrons that are not so deflected cannot pass.

  The Wien filter has the following characteristics compared to other types of energy analyzers. First, the optical axis is a curved line without exception, whereas only the Wien filter has a straight optical axis. This is consistent with the fact that other optical elements of the electron spectroscopy system are mostly composed of axisymmetric lenses, facilitating axial alignment and optical adjustment. This is a very important advantage, especially in energy selective microscopes where the adjustment is delicate.

In addition, aberration coefficients of other energy analyzers are determined depending on the type. For example, in the electrostatic hemisphere energy analyzer (HSA) most frequently used in electron spectrometers, assuming that the radius of the optical axis is r0, the aberration Δx of the beam in the energy dispersion direction at the exit at the incident angle α0 is , it is given by Δx = 2r0α0 ^2. This 2r0 is called a secondary aperture aberration coefficient. What determines the performance of the energy analyzer is an aberration proportional to the nth power of the incident angle in the energy dispersion direction, which is called an nth-order aperture aberration. The smaller n, the greater the influence of aberration, and the second order is the lowest order. The degree of performance of the energy analyzer can be understood from what order the aperture aberration starts. In HSA, there is no method for effectively correcting this aberration, and the degree of aberration falls into a large class.

  On the other hand, in the Wien filter, aberrations can be corrected by adjusting the shape of the electrodes and magnetic poles that generate an electric field and a magnetic field, or the voltage and excitation applied to them.

  FIG. 17 is a cross-sectional view of a Wien filter analyzer currently used in an energy selective X-ray photoelectron emission microscope. This Wien filter analyzer comprises four electrodes 1, 2, 3 and 4 and two magnetic poles 5 and 6. In FIG. 17, the electrode 1 and the magnetic pole 5 are electromagnetic poles that serve as both the electrode and the magnetic pole. The electrode 3 and the magnetic pole 6 are also electromagnetic poles that serve as both the electrode and the magnetic pole. The principle of this Wien filter type analyzer uses an electric field E and a magnetic field B which are orthogonal to each other, and selects electrons having a specific kinetic energy from the balance of electrostatic force and Lorentz force acting on the electrons.

  FIG. 18 is a diagram showing the electron selection principle of the Wien filter type energy analyzer. Electrons travel in an electric field E formed by the four electrodes 1, 2, 3 and 4 and a magnetic field B formed by the two magnetic poles 5 and 6. Electrons other than the specific kinetic energy are blocked from traveling using the slit 7.

The primary orbital equations of electrons in the Wien filter are expressed by the following equations (1) and (2).

However, in the equations (1) and (2), x and y are orthogonal to the optical axis z, and the x direction is the energy dispersion direction. Further, v is the velocity of electrons in the Wien filter, and has a relationship of ½ mv ² = eφ0.

As a condition for selecting electrons having a specific kinetic energy, a straight traveling condition in which the right side of the expression (1) is 0 is given by the expression (3).

Since this requires the dipole component of the electric lift E and the magnetic field B, it requires at least two electrodes and magnetic poles. Further, as a condition for making the lens action in the x direction and the y direction the same, a condition for the second item of the expressions (1) and (2) to be the same is given by the expression (4).

  This requires at least the electric field E or the quadrupole component of the magnetic field B. For this reason, in the apparatus mentioned here, four electrodes 1, 2, 3, and 4 are used.

  FIG. 19 is a diagram comparing electron trajectories when a quadrupole component is used (upper diagram) and when a dipole component is used (lower diagram). The horizontal axis is the distance on the optical axis z. The position where the image plane is formed on the z-axis is assumed to be 0, and the distance between the front and back is indicated by ±. The vertical axis indicates the distance on the x-axis and y-axis perpendicular to the optical axis z. The position of the optical axis z is set to 0, and the vertical distance is indicated by ±. From this figure, it is clear that when the quadrupole component is used (upper), the angle of incident electrons can be increased and the trajectory of electrons can be narrowed at the exit.

The above is the principle of energy dispersion of the device mentioned here, but the operation including the lens conditions is as follows. First, the kinetic energy of electrons is lowered by a certain amount using a deceleration lens. Then, the diffraction surface 8 shown in FIG. 20, that is, the focal point is brought to the entrance of the analyzer shown in FIG. Then, the image plane 9 is brought to the center of the analyzer, and the diffraction plane 10 conjugate with the entrance is brought to the outlet of the analyzer. That is, as shown in FIG. 20, the analyzer lens action is used for the beam at the analyzer entrance to bring the focus to the exit. Electrons other than specific kinetic energy are dispersed while passing through the analyzer, and electrons having a desired kinetic energy are taken out using the slits 7 installed at the outlet. Further, the electrons passing through the slit 7 are accelerated to the original kinetic energy by the acceleration lens.
Japanese Patent Laid-Open No. 11-233062

  By the way, in the conventional Wien filter type analyzer, since the yoke used for the magnetic pole occupies most of the core device, the inner diameter through which the electrons pass cannot be increased. Therefore, the Wien filter performance is sufficiently exhibited for the following reasons. I couldn't.

One is that the aberration correction characteristics of the Wien filter cannot be fully utilized. If the aberration correction of the analyzer is performed by making full use of the aberration correction characteristics of the Wien filter, even if electrons that are incident at a large angle are taken in, the aberration given by the analyzer output will be reduced, leading to a decrease in energy resolution. There is no. However, in reality, electrons entering at a large angle have a large radial direction of the orbit. When the optical axis direction is z and the analyzer input z = z0, initial conditions of x (z0) = 0, x ′ (z0) = tan α0 are given, and the radius of the orbit is obtained by solving the above equations (1) and (2). The direction component r is given as equation (5).

However, α0 and L correspond to the incident angle and the length of the analyzer, respectively. From equation (5), it can be seen that the component r in the radial direction of the orbit increases as the incident angle increases. Therefore, in order to correct aberration without causing a decrease in sensitivity due to electrons lost in the analyzer, it is necessary to increase the inner diameter of the analyzer in order to reduce electrons lost in the analyzer.

Another is that the energy resolution cannot be increased. The energy resolution ΔE of the Wien filter is expressed by equation (6).

Here, d and φ0 are the slit width and the kinetic energy of the electrons with respect to the analyzer output, respectively. (6) It turns out that energy resolution improves, so that L is enlarged. That is, the Wien filter that is longer in the direction of the optical axis z has a better performance. However, as can be seen from equation (5), when L is increased, the radial component r (z) of the orbit also increases, so that it is necessary to increase the inner diameter of the analyzer in order to improve energy resolution.

  When the yoke and the core are used for the magnetic pole in this way, it is limited to the component r in the radial direction of the track, and it is difficult to increase the size of the analyzer, and the performance of the analyzer cannot be fully exhibited.

  On the other hand, a magnetic field and an electric field cannot be generated from the same position by simply changing the magnetic pole to a coil. In particular, the dipole component is a field that imparts deflection to electrons, and if the potential distribution on the optical axis of the magnetic field and the electric field are greatly different, aberration is increased in the analyzer.

  The present invention has been made in view of the above circumstances, and is a Wien filter type analyzer that can fully utilize the aberration correction characteristics of a Wien filter and reduce the loss of electrons in the analyzer to suppress the decrease in sensitivity. For the purpose of provision. It is another object of the present invention to provide a Wien filter type analyzer capable of improving the energy resolution and sufficiently exhibiting the performance of the analyzer.

  Another object of the present invention is to provide an energy-selective electron microscope that can reduce the loss of electrons by an analyzer and suppress a decrease in sensitivity and can perform surface analysis of a material with high accuracy.

  In order to solve the above problems, a Wien filter type energy analyzer according to the present invention is a Wien filter type energy analyzer that selects an electron having a specific energy using a Wien filter. A plurality of n (n is a natural number) electrodes disposed in the vacuum portion to form a plurality of n yokeless coils disposed in the atmosphere outside the vacuum portion to form a magnetic field in the vacuum portion; And the electric field and the dipole component of each potential of the magnetic field are made to coincide with each other.

  This Wienfill type energy analyzer is a Wien filter type energy analyzer comprising an electrode in a vacuum and a yokeless coil that is installed in the atmosphere by replacing the magnetic pole with only a coil, and has an electric field potential and a magnetic field potential. The dipole component is matched. In order to match the electric field potential and the dipole component of the magnetic field potential, there is a means to taper the electrode so that the intensity of the dipole component of the electric field potential at the analyzer entrance and exit is reduced to match the magnetic pole potential. is there. There is also a means for increasing the intensity of the dipole component of the magnetic field potential at the analyzer entrance and exit so that the length in the optical axis direction of the coil is longer than that of the electrode so as to match the potential of the electric field.

  In order to solve the above problems, an energy selective electron microscope according to the present invention is a sample stage on which a quantum beam source generating a quantum beam and a sample irradiated with the quantum beam generated from the quantum beam source are placed. A Wien filter type energy analyzer that selects only electrons having a specific energy that are emitted from the sample placed on the sample stage, and the electrons selected by the Wien filter type energy analyzer. A screen on which the image of the image is formed, a photographing unit for photographing the image on the screen, and a display unit for displaying the image photographed by the photographing unit, wherein the Wien filter type energy analyzer passes electrons A plurality of n (n is a natural number) electrodes arranged in the vacuum part to form an electric field in the vacuum part, and a magnetic field is formed in the vacuum part And a yoke-less coil of the plurality n arranged in the atmosphere of the vacuum outer in order to match the dipole component of each potential of the electric field and the magnetic field.

The Wien filter type energy analyzer according to the present invention can make full use of the aberration correction characteristics of the Wien filter, reduce electrons lost in the analyzer, and suppress a decrease in sensitivity. In addition, the energy-resolving electron microscope according to the present invention, which can improve the energy resolution and sufficiently exhibit the performance of the analyzer, can reduce the loss of electrons by the analyzer and suppress the decrease in sensitivity. It can be performed with high accuracy.

  Hereinafter, the best mode for carrying out the present invention will be described. This embodiment is a Wien filter type energy analyzer constituting an electron lens system used in an energy selection electron microscope or an emission electron microscope. The Wien filter type energy analyzer selects only electrons with a specific energy from the electrons emitted from the electron beam irradiated from the electron beam source of the energy selective electron microscope and forms an image on the fluorescent screen. .

  FIG. 1 is a cross-sectional view of the Wien filter type energy analyzer 11 as viewed from the side, and shows a longitudinal section with the inlet 11-IN on the left and the outlet 11-OUT on the right. 2, 3, and 4 are cross-sectional views of the vicinity of the inlet 11 -IN, the center 11 -CEN, and the vicinity of the outlet 11 -OUT shown in FIG. 1, showing a cross section in a direction perpendicular to the longitudinal direction. ing.

  The Wien filter type energy analyzer 11 includes twelve electrodes 13 provided in the vacuum in the chamber 12 and twelve yokeless coils 14 provided in the atmosphere outside the chamber 12. That is, the Wien filter type energy analyzer 11 has 12 magnetic poles by the electrode 13 and the yokeless coil 14. For this reason, the Wien filter type energy analyzer 11 can generate an electric field E and a magnetic field B that can eliminate the secondary aberration and the tertiary aperture aberration.

  The yokeless coil 14 has a magnetic pole replaced with only a coil, and is disposed on a coil cradle 15. By replacing the magnetic pole with a yokeless coil, the Wien filter type energy analyzer 11 can increase the inner diameter of the analyzer and improve the sensitivity. Further, since no magnetic material is used, it is not necessary to consider the hysteresis of the magnetic material, and a magnetic field with good reproducibility can be obtained.

  In the Wien filter type energy analyzer 11, the length of the analyzer in the optical axis direction is longer than that of the conventional analyzer. For this reason, the resolution of energy was able to be improved.

  The shunt 17 has a rectangular cross section at each of the analyzer inlet 11-IN and outlet 11-OUT. Further, the shunt 17 is disposed in a vacuum inside the chamber 12 and is designed to be magnetically closed with a magnetic shielding shield 19 disposed on the atmosphere side outside the chamber 12. For this reason, the fringes of the dipole components of the electric field E and the magnetic field B can be matched. The shunt 17 is equal to the potential of the deceleration electrode of the deceleration lens.

  In addition, the Wien filter type energy analyzer 11 connects each electrode 13 to the inlet 11 so as to reduce the intensity of the dipole component of the electric field E potential at the analyzer inlet 11-IN and outlet 11-OUT to match the potential of the magnetic pole 14. The electrode 13 is tapered toward the IN and the outlet 11-OUT so that the thickness of the electrode 13 is smoothly reduced. In other words, the thickness of the cross section is parallel to the periphery of the center 11-CEN, but the thickness of the electrode 13 is gradually reduced by tapering toward the inlet 11-IN and the outlet 11-OUT.

  Further, the length M of the yokeless coil 14 in the optical axis z direction is set to the length of the electrode so that the intensity of the dipole component of the potential of the magnetic field B at the analyzer inlet 11-IN and outlet 11-OUT is increased to match the potential of the electric field. Longer than N (M> N).

  The gaps between the twelve electrodes 13 and the gaps between the electrodes 13 and the casing of the chamber 12 are insulated by insulators 16.

  In the sectional view of the inlet 11-IN shown in FIG. 2, the electrode 13 is indicated by a broken line. In the vicinity of the inlet IN, the electrode 13 is hidden by the rectangular shunt 17, but the electrode 13 is positioned on the extension of the shunt 17, so that the configuration of the electrode 13 near the inlet is described. That is, the yokeless coil 14 whose length in the optical axis z direction is M so as to increase the intensity of the dipole component of the potential of the magnetic field B at the analyzer inlet 11-IN and match the electric field potential, and a length shorter than M. The electrode 13 having a length N is arranged so as to be slightly concentric from the inlet 11-IN so as to sandwich the casing of the chamber 12 on the same core toward the opening 18 described later. However, as described above, the twelve electrodes 13 are located in the vacuum because they are inside the chamber 12, but the twelve yokeless coils 14 are located outside the chamber 12, so they are placed in the atmosphere. Yes. Electrons emitted from the sample enter the analyzer 11 through the opening 18 at the inlet IN.

  According to the cross-sectional view near the central portion 11-CEN shown in FIG. 3, it can be seen that each electrode 13 is thicker than each electrode 13 near the inlet 11-IN and near the outlet 11-OUT. That is, each electrode 13 is thinner in the vicinity of the inlet 11-IN and the outlet 11-OUT than the central portion 11-CEN. Thereby, as described above, the Wien filter type energy analyzer 11 can reduce the intensity of the dipole component of the potential of the electric field E at the analyzer inlet 11-IN and the outlet 11-OUT to match the potential of the magnetic pole 14. . The Wien filter type energy analyzer 11 is covered with a magnetic shield 19 equal to the GND potential. The magnetic shield 19 is disposed on the atmosphere side outside the chamber 12, but is designed to be magnetically closed from the shunt 17 disposed in the vacuum inside the chamber 12.

  Also in the cross-sectional view near the outlet OUT shown in FIG. Even in the vicinity of the outlet OUT, the electrode 13 is hidden by the shunt 17, but the electrode 13 is positioned on the extension of the shunt 17. That is, the yokeless coil 14 whose length in the optical axis L direction is M so as to increase the intensity of the dipole component of the potential of the magnetic field B at the analyzer outlet 11-OUT and match the electric field potential, and a length shorter than M. The electrode 13 having a length N is arranged so as to be concentrically with respect to the optical axis x so as to sandwich the housing of the chamber 12 at a position slightly toward the center from the outlet 11-OUT. The electrons emitted from the sample are sorted out by the slit 56 having a passage portion substantially equal to the diameter of the opening 21 of the outlet OUT and go out of the analyzer 11. The slit 56 is equal to the potential of the deceleration electrode. The electrons that are selected by the slit 56 and emitted from the analyzer 11 travel in the electric field formed by the electric field forming electrode 20. The electric field forming electrode 20 is equal to the potential of the deceleration electrode.

  Hereinafter, the reason why the shape of the Wien filter type energy analyzer 11 is shown in FIGS. 1 to 4 will be described according to the preconditions and the characteristic requirements.

First, the prerequisites for matching the electric field potential 28 and the magnetic field potential 29 will be described. The electromagnetic field in the Wien filter type analyzer is expressed by equations (7) and (8) by multiplying the electric and magnetic field potentials Φ (x, y) and Ψ (x, y).

Here, each term represents the potential of the multipole component.

  In order to correct aberrations, it is necessary to formulate the aberrations of the Wien filter analyzer. The aberration coefficients are the coefficients of the multipole component potentials E1, B1, E2, B2, E3, B3, E4, B4 It is represented by The aberration correction described here is to eliminate the aberration by setting the aberration coefficient to zero. Note that the second-order aberration and the third-order aperture aberration are corrected here. In order to provide a potential coefficient such that the aberration coefficient becomes zero electrically and magnetically, electrodes and magnetic poles must be arranged in multiple poles. In order to obtain the necessary potential distribution, it is necessary to establish a calculation method for the required voltage value and current value. Moreover, it is necessary to arrange | position an electrode and a magnetic pole accurately. With respect to the former, it is necessary to be able to calculate the voltage and current values by using the potential coefficient that makes the aberration coefficient zero and the equations (7) and (8). It is also applicable to a multipole Wien filter type analyzer with four magnetic poles and two magnetic poles. On the other hand, the arrangement for obtaining the accuracy of the multipole electrode and the magnetic pole can be sufficiently achieved by using a technique for manufacturing a deflector.

  In order to increase the energy dispersion length of the analyzer, it is desirable that the kinetic energy of electrons passing through the analyzer is low. Therefore, a deceleration lens is inserted just before the analyzer entrance. This method is already adopted in many energy analyzers, and the technical aspect is well established.

  Next, the requirements that characterize the present invention, which is a main part of the reason why the Wien filter type analyzer 11 has the shape shown in FIG. 1, will be described. FIG. 5 is a diagram showing that the spot size at the exit can be reduced even if electrons incident at a large angle are taken in by performing aberration correction. FIG. 5A is given as a comparative example, and shows a spot shape at the analyzer outlet when aberration correction is not performed. Aberrations occur in both the x-axis and y-axis directions. FIG. 5B shows a spot shape at the analyzer outlet when aberration correction is performed. Slightly remaining aberration can be removed by a subsequent slit.

  Further, FIG. 6 is a diagram showing from numerical calculation that the number of electrodes and magnetic poles necessary for reducing aberrations is 12 poles from the viewpoint of potential multipole component control. FIG. 6A shows the characteristics of aberration correction performed with eight electrodes and magnetic poles. In the aberration correction in the case of octupole, it can be seen that considerable aberrations remain on the x-axis and y-axis. FIG. 6B shows the characteristics of aberration correction performed with 10 electrodes and magnetic poles. It can be seen that aberrations still remain on the x-axis and the y-axis. FIG. 6C shows the characteristics of aberration correction performed with 12 electrodes and magnetic poles. It can be seen that the aberrations were corrected more than the octupole and 10-pole aberrations shown in FIGS. 6 (a) and 6 (b). Further, FIG. 6D shows the aberration correction characteristics when the number of electrodes and magnetic poles is 18 poles, but the correction situation is almost the same as the case of 12 poles shown in FIG. Considering this aspect, it can be determined that 12 poles are suitable.

  FIG. 7 is a view showing a 12-pole Wien filter using 12 electrodes and 12 magnetic poles. FIG. 7A is a cross-sectional view seen from the side along the longitudinal direction, and FIG. 7B is a cross-sectional view perpendicular to the longitudinal direction. The twelve electrodes and the magnetic pole 25 are formed with a uniform thickness in the axis z direction parallel to the optical axis L.

  Thus, the Wien filter type energy analyzer needs to perform aberration correction, and further needs to control the multipole component of the potential in order to efficiently perform aberration correction. It becomes a multipole type, for example, a 12-pole, with many magnetic poles attached. With this multipole type, even if electrons that are incident at a large angle are captured by performing aberration correction, the spot size at the exit is small and high energy resolution can be realized.

  By the way, when energy selection is performed on electrons incident on the analyzer at a large angle, it is necessary to increase the inner diameter through which the electrons pass in order to transport the electrons to the analyzer outlet with a small loss. In order to increase the diameter, there is a method of replacing the magnetic pole with only the coil by removing the yoke and core constituting the magnetic pole.

  FIG. 8B is a diagram showing the configuration of a Wien filter in which the magnetic pole is a coil 26. Inside the twelve coils 26 arranged on the concentric circles, twelve electrodes 27 are arranged on the concentric circles as well. The inner diameter of the analyzer is db. For comparison, FIG. 8A shows the configuration of a Wien filter using 12 electromagnetic poles 28. The inner diameter of the analyzer is da. As shown in FIG. 8B, it can be seen that the Wien filter having the magnetic pole as the coil 26 can enlarge the inner diameter db of the analyzer (db> da).

  However, since it is difficult to arrange the coil 26 in a vacuum from the viewpoint of the cooling method, it is difficult to arrange the electrode 27 and the coil 26 at the same position, and the electrode 27 and the coil having the same length in the optical axis x direction. By simply arranging 26, the dipole components of the electric field E and magnetic field B potential contributing to electron deflection could not be matched.

  Therefore, the Wien filter type energy analyzer 11 according to the present embodiment uses the following (I), (II), (III), (IV) for the electrode shape, the coil, and the shunt to match the dipole components of the potentials of the two. The structure shown in FIGS. 1, 2, 3 and 4 is provided.

  (I) The electrode was tapered to reduce the intensity of the dipole component of the electric field potential at the analyzer entrance. (II) The length of the coil in the optical axis direction was made longer than that of the electrode in order to increase the strength of the dipole component of the potential of the magnetic field at the analyzer entrance. (III) The shunt shape was characterized in order to match the fringes of the dipole components of both potentials. (IV) The magnetic shielding shield arranged on the atmosphere side and the shunt arranged on the vacuum side were magnetically closed.

  In accordance with the characteristics mentioned above, the Wien filter type analyzer 11 realizes multipolarization, coiling of magnetic poles, and optimization of electrodes and magnetic pole shapes. For this reason, the Wien filter type analyzer 11 was able to realize an analyzer with high transmittance.

  FIG. 9 is a diagram for comparing potential distributions in the optical axis direction before and after aberration correction using the Wien filter type analyzer 11. FIG. 9A shows the potential distribution before correction, and FIG. 9B shows the potential distribution after correction. In the potential in the optical axis direction before aberration correction (FIG. 9A), the electric field potential 28 and the magnetic field potential 29 are inconsistent, but in the potential in the optical axis direction after correction (FIG. 9B), the electric field potential 28 and The magnetic field potential 29 coincided.

  As described above, the Wien filter type analyzer 11 of the present embodiment has twelve electrodes 13 in the vacuum in the chamber and twelve yokeless coils 14 in the atmosphere outside the chamber, and The electrode 13 is tapered so that the dipole component of the potential of the electric field E at the analyzer entrance / exit is lowered to match the potential of the magnetic pole, and the dipole component of the potential of the magnetic field B at the analyzer entrance / exit is increased. The length of the coil in the optical axis direction is longer than the length of the electrode in the optical axis direction so that it matches the potential of the electrode, so that the characteristics of aberration correction of the Wien filter are fully utilized to reduce the electrons lost in the analyzer. A decrease in sensitivity can be suppressed. Further, the energy resolution can be improved and the performance of the analyzer can be sufficiently exhibited.

  Next, an energy selection type electron microscope in which the Wien filter type energy analyzer 11 is built in an electron lens system will be described.

  Although this method can use a quantum beam (electron beam, photon, charged particle, etc.) as a radiation source, the case of using a photon as an example of a quantum beam will be described below.

  FIG. 10 is a front view of the energy selective electron microscope, and FIG. 11 is a side view. The energy selective electron microscope 30 includes an X-ray source 31 that is a light source that generates characteristic X-rays, a stage 32 on which a sample irradiated with the characteristic X-rays generated from the X-ray source 31 is placed, and a driving mechanism thereof. A sample stage drive mechanism 33, an analysis chamber 34 for analyzing the sample, a sample preparation chamber 35 for preparing the sample, a manipulator 36 for moving the sample from the sample preparation chamber 35 to the analysis chamber 34, and analysis An exhaust system 37 that evacuates the chamber 34 and the sample preparation chamber 35 and an exhaust system controller 38 that controls the exhaust system of the exhaust system 37 are provided. The energy selecting electron microscope 30 controls the generation of X-rays by the electron lens system 39 incorporating the Wien filter type energy analyzer 11, the electron lens system controller 40 for controlling the electron lens system 39, and the X-ray source 31. And an X-ray generation controller 41. The energy selecting electron microscope 30 includes a system control personal computer 42 in which software for controlling the electronic lens system 39 is installed, a CCD camera 43 that acquires an image via the electronic lens system 39, a CCD And a CRT 44 that captures an image obtained from the camera 43.

The X-ray source 31 is a light source for exciting core electrons and secondary electrons on the sample surface. The more intense the light source is used, the more photoelectrons are obtained. Here, using the characteristic X-ray, the spectral crystal part (about 10 ⁻⁶ Pa) is monochromatized and condensed, and the sample surface is irradiated with light. The X-ray light source 31 emits characteristic X-rays from the front side of the drawing in the front view of FIG. 10 and obliquely downward as seen from the side view of FIG. The X-ray source 31 is electrically connected to the X-ray generation controller 41. The X-ray generation controller 41 stores a power source and a controller for generating and controlling X-rays in the X-ray source 31. The characteristic X-rays emitted from the X-ray light source 31 are guided to the sample on the stage 32 of the sample stage drive mechanism 33 by bending the optical path by an optical path bending unit (not shown). That is, the X-ray light source 31 and the sample stage drive mechanism 33 are mechanically connected.

  The sample stage drive mechanism 33 can move the stage 32 on which the sample is placed in directions such as x, y, and z, and can be inclined at angles such as θ and φ. The sample stage drive mechanism 33 adjusts the position of the sample. The sample stage drive mechanism 33 is mechanically connected to an analysis chamber 34 described later.

The analysis chamber 34 is an ultrahigh vacuum chamber for analyzing a sample using an electron lens system using inner-shell electrons. The degree of vacuum is about 10 ⁻⁸ Pa. The sample preparation chamber 35 is an ultra high vacuum chamber of about 10 ⁻⁶ Pa for sample insertion and surface cleaning. The sample preparation chamber 35 is mechanically connected to the manipulator 36. Further, the analysis chamber 34 and the sample preparation chamber 35 are mechanically connected, and the sample inserted by the sample preparation chamber 35 and the surface of which has been cleaned is moved to the analysis chamber by the manipulator 36.

  The exhaust system 37 stores a system for exhausting the analysis chamber 34 and the sample preparation chamber 35 to an ultrahigh vacuum. The exhaust system 37 is electrically connected to an exhaust system controller 38, and the exhaust system controller 38 incorporates a system for controlling the exhaust system 37.

  The electron lens system 39 is mechanically connected to the analysis chamber 34. When electrons emitted from the sample are incident, the electron lens system 39 collects the electrons, decelerates after limiting the angle and the field of view, and the Wien filter type. Pass through the analyzer 11. As described above, the Wien filter type analyzer 11 selects only electrons having a specific kinetic energy and forms an image on a fluorescent screen.

  The electronic lens system controller 40 is electrically connected to the electronic lens system 39, and stores a controller for controlling the voltage and current of the electronic lens system 39, and a power source. The electronic lens system controller 40 is also electrically and mechanically connected to a system control personal computer 42. The system control personal computer 42 is installed with software for applying an appropriate voltage and current to the electronic lens system 39.

  The system control personal computer 42 is also electrically connected to the CCD camera 43 and the CRT 44. The CCD camera 43 is used for acquiring and storing an image imaged on the fluorescent screen of the electronic lens system 39. The CRT 44 is a display unit for projecting an image obtained from the CCD camera 43. The system control personal computer 42 is also electrically connected to the sample stage drive mechanism 33. The system control personal computer 42 captures and stores an image signal obtained from the CCD camera 43.

  Next, the operation of the energy selective electron microscope 30 shown in FIG. 10 will be described.

  First, the exhaust system 37 exhausts the sample preparation chamber 35, the analysis chamber 34, and the electron lens system 39 under the control of the exhaust system controller 38. The sample that has been inserted by the sample preparation chamber 35 and whose surface has been cleaned is moved by the manipulator 36 to the sample stage 32 without the analysis chamber 34. The sample stage 32 on which the sample is placed is moved to an appropriate position by driving the sample stage drive mechanism 33.

  The X-ray generation controller 41 supplies appropriate tube voltage and tube current to the X-ray source (X-ray generator) 31. The X-ray source 31 generates characteristic X-rays, and the characteristic X-rays are applied to the sample on the sample stage 32 in the analysis chamber 34. The system control personal computer 42 transmits a signal indicating appropriate voltage value and current value to the electronic lens system controller 40. The electronic lens system controller 40 supplies an appropriate voltage and current value to the electronic lens system 39 based on the control of the system control personal computer 42.

  Then, the electrons radiated from the sample by the irradiation of the characteristic X-rays enter the electron lens system 39, are condensed, decelerated after being subjected to angle restriction and field restriction, and passed through the Wien filter type analyzer 11. The Wien filter type analyzer 11 selects only electrons having a specific kinetic energy and forms an image on a fluorescent screen by the above-described operation.

  The image formed on the fluorescent screen is photographed by the CCD camera 43 and imaged on the CRT 44. An image signal photographed by the CCD camera 43 is taken into the system control personal computer 42 and stored in a storage medium such as a built-in HDD or RAM.

  First, FIG. 12 is a diagram showing a detailed configuration of an electron lens system 39-1 which is a first specific example of the electron lens system 39. As shown in FIG. This block diagram also shows the electron trajectory and potential distribution. The same applies to the following specific examples.

  The electron lens system 39-1 includes an objective lens 51, an input lens 52, an angle limiting diaphragm 53 in the input lens 52, a field limiting diaphragm 54 in the input lens 52, and a deceleration lens 55. The electron lens system 39-1 includes a Wien filter type energy analyzer 11, an exit slit 56, a projection lens 57, an MCP 58 which is an electron multiplication mechanism, and a fluorescent screen 59. Further, a deflector (not shown) for correcting the optical axis of the electron lens system is provided between the lenses. The electrodes of the electron lens system 39-1 are insulated by insulators.

  The objective lens 51 is a lens used to collect electrons using a magnetic field type objective lens. The input lens 52 is a lens used for image enlargement and image formation. The angle limiting diaphragm 53 is an opening for limiting the electrons that are emitted from the sample and enter the large angle with respect to the optical axis of the electron lens. By using this, the spherical aberration of the electron lens can be reduced. it can. The field limiting diaphragm 54 is used to limit the field of view observed with a microscope.

  The decelerating lens 55 is a lens that decelerates the speed of electrons incident on the analyzer. The slower the electrons passing through the analyzer 11, the longer the dispersion effect can be received and the higher the energy resolution. For this reason, electrons are decelerated by the deceleration lens 55.

  As described with reference to FIGS. 1 to 4, the Wien filter type energy analyzer 11 has twelve electrodes 13 in the vacuum in the chamber and twelve yokeless coils 14 in the atmosphere outside the chamber. In addition, the electrode 13 is tapered so that the intensity of the dipole component of the electric field E potential at the analyzer entrance / exit is lowered to match the potential of the magnetic pole, and the intensity of the dipole component of the magnetic field B potential at the analyzer entrance / exit is increased. The length of the coil in the optical axis direction is made longer than the length of the electrode in the optical axis direction so that it matches the potential of the electric field E. Therefore, taking advantage of the aberration correction characteristics of the Wien filter, It is possible to select electrons having specific kinetic energy while reducing the decrease in sensitivity. In addition, the energy resolution can be improved and the performance of the analyzer can be fully exerted to select electrons having a specific kinetic energy.

  The exit slit 56 is a partition for passing only electrons near the specific kinetic energy. The projection lens 57 is a lens for enlarging an image. The MCP 58 is an electron multiplication mechanism for increasing the sensitivity by multiplying the transported electrons. The fluorescent screen 59 is a mechanism for converting electrons into actual light.

  Therefore, when the energy selection type electron microscope 30 including the electron lens system 39-1 is the first example, the energy selection type electron microscope 30-1 of the first example is configured to store electrons lost in the analyzer 11. Since the reduction in sensitivity can be suppressed by the reduction, surface analysis of the material can be performed with high accuracy.

  This is because the Wien filter type energy analyzer 11 provided in the electron lens system 39-1 has the following effects. That is, the Wien filter type energy analyzer 11 used in the electron lens system 39-1 of the energy selective electron microscope 30-1 has 12 poles of electrodes and yokeless coils. An electric field E and a magnetic field B that can eliminate the aperture aberration can be generated. Further, by replacing the magnetic pole with a yokeless coil, the inner diameter of the analyzer can be increased, and the sensitivity can be improved. Further, since no magnetic material is used, it is not necessary to consider the hysteresis of the magnetic material, and a magnetic field with good reproducibility can be obtained.

  Moreover, since the Wien filter type energy analyzer 11 has a longer analyzer length in the optical axis direction, the energy resolution can be improved.

  In addition, by tapering the electrodes, the strength of the dipole component of the electric field potential at the entrance and exit of the analyzer can be lowered to match the dipole component of the electrostatic potential and the scalar potential of the magnetic field. In addition, the length of the coil in the direction of the optical axis can be made longer than the electrode to increase the strength of the dipole component of the magnetic field potential at the analyzer entrance and exit, so that the dipole component of the electrostatic potential and the scalar potential of the magnetic field can be matched. It was.

  Moreover, since the shunt shape is rectangular, the fringes of the dipole components of both potentials can be matched.

  In addition, since the magnetic shielding shield arranged on the atmosphere side and the shunt arranged on the vacuum side are designed to be magnetically closed, the fringes of the dipole components of the potentials of both can be matched.

  FIG. 13 is a diagram showing a detailed configuration of the electron lens system 39-2. This electron lens system 39-2 also includes the Wien filter type analyzer 11, and has a configuration in which the speed of electrons incident on the analyzer is reduced by the decelerating lens 55. The difference is that a sting meter 60 is used after the slit 56. The sting meter is disposed at the tip of the projection lens 57 and is a lens for correcting astigmatism of electrons emitted from the analyzer 11. Other configurations are the same as those of the electron lens system 39-1, and thus the description thereof is omitted.

  Therefore, the energy selection type electron microscope 30-2 of the second embodiment provided with this electron lens system 39-2 can reduce the loss of electrons by the analyzer and suppress the decrease in sensitivity. Since the aberration can be corrected, the surface analysis of the material can be performed with high accuracy.

  FIG. 14 is a diagram showing a detailed configuration of the electron lens system 39-3. The electron lens system 39-3 also includes the Wien filter type analyzer 11, and has a configuration in which the speed of electrons incident on the analyzer is reduced by the deceleration lens 55. The electron lens system according to the first embodiment is used. It differs from 39-1 in having a cathode objective lens 61 after the objective lens 51. The cathode objective lens 61 is used by applying a voltage to the sample holder. Other configurations are the same as those of the electron lens system 39-1, and thus the description thereof is omitted.

  Therefore, the energy selective electron microscope 30-3 according to the third embodiment including the electron lens system 39-3 can also reduce the loss of electrons in the analyzer and suppress the decrease in sensitivity. Surface analysis can be performed with high accuracy.

  FIG. 15 is a diagram showing a detailed configuration of the electron lens system 39-4. The electron lens system 39-4 also includes the Wien filter type analyzer 11 and has a configuration in which the speed of electrons incident on the analyzer is reduced by the deceleration lens 55. The electron lens system according to the first embodiment is used. It differs from 39-1 in having a beam separator 62 after the objective lens 51.

  Unlike the energy-selective electron microscope 30-1 of the first embodiment, the energy-selective electron microscope 30-4 of the fourth embodiment having this electron lens system 39-4 is not an X-ray source but an electron. A gun is used. For this reason, in the configuration diagrams shown in FIGS. 10 and 11, the electron gun 71 irradiates the sample on the sample stage 32 with an electron beam. For this reason, an electron gun controller 72 is provided in place of the X-ray generation controller 41. The electron gun controller 72 is electrically connected to the electron gun 71, and stores a power source and a controller for generating and controlling an electron beam from the electron gun 71.

  Therefore, as described above, the electron lens system 39-4 shown in FIG. 15 includes the beam separator 62 after the objective lens 51, and irradiates the electron beam emitted from the electron gun 71 perpendicularly to the sample surface. The reflected electrons on the sample surface are used to guide the input lens 52.

  Therefore, the energy selective electron microscope 30-4 of the fourth embodiment irradiates the sample with the electron beam emitted from the electron gun 71, and the electron emitted from the sample is not sensitive to the analyzer without being lost. The surface analysis of the material can be performed with high accuracy while suppressing the decrease.

  FIG. 16 is a diagram showing a detailed configuration of the electron lens system 39-5. This electron lens system 39-5 has a cathode objective lens 61 after the objective lens 51, unlike the electron lens system 39-1 of the first embodiment. Another difference is that an acceleration lens 63 is provided in front of the exit slit 56 of the Wien filter type analyzer 11.

  The acceleration lens 63 is a lens for returning electrons sent to the projection lens 57 in the subsequent stage to a speed before being decelerated by the deceleration lens 55.

  Therefore, the energy selective electron microscope 30-5 of the fifth embodiment can reduce the loss of electrons by the analyzer and suppress the decrease in sensitivity, so that the surface analysis of the material can be performed with high accuracy.

  Further, in the energy selecting electron microscope 30-6 of the sixth embodiment, an ultraviolet light source 81 is used instead of the X-ray source 31 of the first embodiment, and an ultraviolet light generation controller 82 is used instead of the X-ray generation controller 41. An apparatus having a configuration using the above may be used. The ultraviolet light source 81 is supplied with appropriate tube voltage and tube current from the ultraviolet light generation controller 82, generates ultraviolet light, and irradiates the sample on the sample stage 32. Other configurations and operations are omitted.

  Further, in the energy selection type electron microscope 30-7 of the seventh embodiment, a radiation source 91 is used instead of the X-ray source 31 of the first embodiment, and a radiation generation controller 92 is used instead of the X-ray generation controller 41. An apparatus having a configuration using the above may be used. The radiation source 91 is supplied with appropriate tube voltage and tube current from the radiation generation controller 92, generates radiation, and irradiates the sample on the sample stage 32. Other configurations and operations are omitted.

  Note that the Wien filter type energy analyzer 11 shown in FIGS. 1 to 4 has a taper on the electrode 13 so that the electrostatic potential and the scalar potential dipole component of the magnetic field coincide with each other. Although the intensity of the dipole component is reduced and the length of the coil in the optical axis direction is made longer than the length of the electrode in the optical axis direction, the intensity of the dipole component of the potential of the magnetic field B at the analyzer entrance / exit is increased. There is no need to use both means together. Any one of the means can be used as long as the dipole component of the electrostatic potential and the scalar potential of the magnetic field can be matched. Of course, it is necessary to increase the inner diameter of the analyzer by replacing the magnetic pole with a yokeless coil and use any means.

It is sectional drawing seen from the side surface side of a Wien filter type energy analyzer. It is sectional drawing of the entrance vicinity of a Wien filter type | mold energy analyzer. It is sectional drawing of center vicinity of a Wien filter type | mold energy analyzer. It is sectional drawing of exit vicinity of a Wien filter type | mold energy analyzer. It is a figure which shows the spot shape at the analyzer exit when not performing aberration correction and when correcting aberration. FIG. 6 is a characteristic diagram of aberration correction performed with the number of electrodes and magnetic poles being 8, 10, 12, and 18 poles. It is a figure which shows the Wien filter type | mold energy analyzer of 12 poles using 12 electrodes and 12 magnetic poles. It is sectional drawing of the Wien filter of 12 poles using the Wien filter using 12 electromagnetic poles, 12 electrodes, and 12 coils. It is a figure which shows distribution of the potential before correction | amendment, and distribution of the potential after correction | amendment. It is a front view of an energy selection type electron microscope. It is a side view of an energy selection type electron microscope. It is a figure which shows the detailed structure of the 1st specific example of an electron lens system. It is a figure which shows the detailed structure of the 2nd specific example of an electron lens system. It is a figure which shows the detailed structure of the 3rd specific example of an electron lens system. It is a figure which shows the detailed structure of the 4th specific example of an electron lens system. It is a figure which shows the detailed structure of the 5th example of an electron lens system. It is sectional drawing of the conventional Wien filter type | mold analyzer. It is a figure which shows the electronic selection principle of a Wien filter type | mold analyzer. It is a comparison figure of the orbit of an electron when a quadrupole is used and a dipole is used. It is a figure which shows the position of the diffraction surface and image plane in a Wien filter type | mold energy analyzer.

Explanation of symbols

  11 Wien filter type energy analyzer, 12 chamber, 13 electrodes, 14 yokeless coil, 15 yoke holder, 16 insulator, 17 shunt, 19 magnetic shield, 20 electric field forming electrode, 30 energy selective electron microscope, 31 X-ray source , 32 Sample stage, 33 Sample stage drive mechanism, 34 Analysis chamber, 35 Sample preparation chamber, 36 Manipulator, 37 Exhaust system, 38 Exhaust system controller, 39 Electronic lens system, 40 Electronic lens system controller, 41 X-ray generation controller , 42 System control personal computer, 43 CCD camera, 44 CRT, 51 Objective lens, 52 Input lens, 53 Angle limit stop, 54 Field limit stop, 55 Deceleration lens, 56 Exit slit

Claims (6)

In the Wien filter type energy analyzer that uses the Wien filter to select electrons with a specific energy,
A plurality of n (n is a natural number) electrodes disposed in the vacuum part to form an electric field on the electron beam path;
A plurality of n yokeless coils disposed in the atmosphere outside the vacuum unit to form a magnetic field in the vacuum unit;
Furthermore, the Wien filter type energy analyzer characterized by matching the dipole components of the potentials of the electric field and the magnetic field.   Each of the plurality of n electrodes is tapered so that the thickness is smoothly reduced toward the inlet and outlet so that the dipole component of the electric field potential at the inlet and outlet of the analyzer is lowered to match the magnetic pole potential. The Wien filter type energy analyzer according to claim 1, wherein   The length of each of the plurality of n yokeless coils in the optical axis direction is longer than the length of the electrode so that the dipole component of the potential of the magnetic field at the inlet and outlet of the analyzer is increased to match the potential of the electric field. The Wien filter type energy analyzer according to claim 1.   2. The Wien filter type energy analyzer according to claim 1, wherein the shunt at the entrance / exit of the energy analyzer is also disposed in the vacuum part and is magnetically closed with a magnetic shielding shield disposed on the atmosphere side.   The Wien filter type energy analyzer according to claim 1, wherein a 12-pole Wien filter using 12 electrodes and 12 yokeless coils is used. A quantum source that generates quantum rays; and
A sample stage on which a sample irradiated with quantum beams generated from the quantum beam source is placed;
A Wien filter type energy analyzer for selecting an electron beam having a specific energy by being incident with electrons emitted from a sample placed on the sample stage;
A screen on which an image of electrons selected by the Wien filter type energy analyzer is formed;
A photographing unit for photographing an image on the screen;
A display unit for displaying an image photographed by the photographing unit;
The Wien filter type energy analyzer includes a plurality of n (n is a natural number) electrodes arranged in a vacuum part for forming an electric field in a vacuum part through which electrons pass, and the vacuum for forming a magnetic field in the vacuum part. An energy-selective electron microscope comprising: a plurality of n yokeless coils arranged in an outside atmosphere; and the electric field and the dipole component of each potential of the magnetic field are made to coincide with each other.

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