JP5324584B2 - Electron beam equipment - Google Patents

Description

  The present invention relates to an electron beam apparatus using an electron beam biprism.

  In the description of the present application, an electron biprism is used. An electron biprism is a device in an electron optical system that performs the same function as a Fresnel double prism in optics, and there are two types, an electric field type and a magnetic field type. Among these, the one that is widely used is an electric field type electron biprism having a shape as shown in FIG. That is, it is composed of a filament electrode 9 at the center and a parallel plate type ground electrode 99 held so as to sandwich the electrode. For example, when a positive voltage is applied to the central filament electrode 9, as shown in FIG. 1, the electron beams passing through the vicinity of the filament electrode are deflected in a direction facing each other by sensing the potential of the filament electrode (the electron beam). Orbit 27). A plane 25 is drawn perpendicularly to the electron trajectory 27 in FIG. 1. This is an equiphase surface when expressing an electron beam as a wave, and is generally a plane perpendicular to the electron orbit. Called the wavefront.

As the distance from the central filament electrode 9 increases, the potential acting on the electron beam decreases, but the spatial range in which it acts is long. As a result, the deflection angle of the electron beam does not depend on the incident position and the applied voltage to the central filament electrode 9 Is proportional to That is, when the deflection angle α is the deflection angle of the electron beam by the electron biprism, a simple relationship expressed by α = k * V _f is obtained using the voltage V _f applied to the central filament electrode 9 and the deflection coefficient k. . The fact that the deflection angle α of the electron beam does not depend on the incident position is an important feature for an electron optical device, and the plane wave is a plane wave and only the propagation direction is deflected and emitted from the electron biprism. This is called an electron biprism because it corresponds to the effect of a biprism in which two prisms are combined.

  A device that uses a potential to deflect an electron beam is called a field-type electron biprism, and a device that uses the Lorentz force between a magnetic field and an electron beam is called a magnetic-field electron biprism. In the present application, description will be made using an electric field type electron biprism.

  However, the present invention can be configured regardless of the electric field type or the magnetic field type as long as the electron beam biprism is an apparatus that can interfere with the electron beam, and is not limited to the electric field type biprism used in the description. In addition, in the present application, the term “electron biprism” means the entire electron biprism as an electron beam deflecting device including the central filament electrode 9, and is located at a precise position in the electron optical system. When referring to it, it is described as “central filament electrode of electron biprism” in principle.

  An electron biprism is an indispensable device for producing electron beam interference in an electron beam without a beam splitter like an optical half mirror. The reason for this lies in the function of separating the wavefront 25 of one electron beam into two waves and deflecting them in directions facing each other, as is apparent from FIG. As a result, the electron beam that has passed through the electron biprism and separated into two waves is superimposed on the downstream side of the electron biprism to generate interference fringes 8. Such electron optical systems are collectively referred to as an electron beam interference optical system (see Non-Patent Document 1).

<One-stage electron biprism interferometer>
The most common electron beam interferometer represented by electron beam holography has a single-stage electron beam biprism arranged between the objective lens 5 and the image plane 71 of the sample 3 as shown in FIG. 9 is an electron beam transmitted through the sample 3 by applying a positive voltage (object wave 21: hatched with an electron beam passing through the left side of the central filament electrode 9 in FIG. 2) and the side without the sample 3 The electron beam that has passed through (reference wave 23: an electron beam that passes through the right side of the central filament electrode 9 in FIG. 2) is superimposed to obtain an interference microscope image (31 and 8: an image in which interference fringes 8 are superimposed on the sample image 31). Have gained. There is a fixed relationship between the interference fringe interval s and the interference region width W at this time, and the interference fringe interval s _obj and the interference region width W _obj back-projected on the sample surface are expressed by the following equations.

S _obj = (1 / M _obj ) * (D * λ / 2 * α * (DL)) (1)

W _obj = (1 / M _obj ) * (2 * α * L- (D * d _f / (DL))) (2)

Here, α (rad) is the deflection angle of the electron beam by the electron biprism. Other characters mainly relate to distances between elements such as an object, a lens, and an image in the optical system and are shown in FIG. That is, D is the distance from the image plane 11 of the light source directly below the objective lens to the image plane 71 of the sample by the objective lens 5, and L is the distance from the central filament electrode 9 of the electron biprism to the image plane 71 of the sample. D _f is the diameter of the central filament electrode 9, M _obj is the magnification of the objective lens 5 M _obj = b / a (a is the distance between the sample 3 (object surface) and the objective lens 5, b is the objective lens 5 And the distance from the image plane 71 of the sample.

As can be seen from the equations (1) and (2), the interference fringe interval s _obj and the interference region width W _obj are both functions of the electron beam deflection angle α, and only the voltage V _f applied to the central filament electrode 9 is obtained. Thus, it is not possible to perform control independent of each other (see, for example, Non-Patent Document 1).

  Note that when charged particle beams such as electron beams pass through an electromagnetic lens, the charged particle beam has an azimuth rotation around the optical axis. In FIG. An equivalent surface including the optical axis 2 as an optical system is shown on the paper. Further, it is assumed that the central filament electrode 9 is arranged perpendicular to the paper surface, the cross section of the electrode is shown by a small circle, and the parallel plate type ground electrodes 99 on both sides of the central filament electrode 9 are omitted. Moreover, although the irradiation system 4 including the light source is drawn in a small square, this is applied to the sample 3 such as the electron gun 1, the acceleration tube 40 (see FIG. 4), the condenser lens system (41, 42) (see FIG. 4). This is the device part related to the irradiation of electron beams. The omission of the rotation of the azimuth angle and the omission of the display of the irradiation system and the like in the schematic diagram of the optical system are the same in the subsequent drawings.

<Two-stage electron biprism interferometer>
A multi-stage electron biprism interferometer has been developed to solve the disadvantage that the interference fringe spacing s and the interference area width W cannot be controlled independently of the one-stage electron biprism interferometer. FIG. 3 shows a two-stage electron biprism interference optical system having the simplest configuration of the multistage electron biprism interferometer.

  In this optical system, the first electron biprism 91 is disposed on the first image plane 71 of the sample 3 downstream of the objective lens 5, and the second electron biprism 95 is more electron beam than the first image plane 71. Between the image plane 12 of the light source imaged by the first imaging system lens 61 positioned downstream in the traveling direction of the first imaging system lens and the second image plane 72 of the sample downstream of the first imaging system lens. And in the shaded portion (represented by dark hatching in FIG. 3) of the central filament electrode 91 of the first electron biprism.

In FIG. 3, the central filament electrodes 91 and 95 are drawn so as to be arranged perpendicular to the paper surface, but this is arranged perpendicular to the same electro-optic plane including the optical axis described above. Means that The two parameters of the interference microscope image (32 and 8), the interference fringe interval s and the interference region width W are back-projected on the sample surface in the same manner as described above, and the interference fringe interval s _obj and the interference region width W _{obj are obtained.} Is expressed by the following formula.

S _obj = (1 / M _obj ) * (1 / M _I1 ) * (λ * D ₂ / (2 * ((b _s1 / a _s1 ) * D ₁ * α ₁ + (D ₂ -L ₂ ) * α ₂ ))) ... (3)

W _obj = (1 / M _obj ) * ((2 * L ₂ * α ₂ / M _I1 ) -d _f1 ) (4)

Here, α ₁ is the deflection angle of the electron beam by the first electron biprism 91, and α ₂ is the deflection angle by the second electron biprism 95. Here, λ is a wavelength. Characters in other formulas mainly relate to distances between elements such as objects, lenses, and images in the optical system and are shown in FIG.

That is, a _obj is the distance between the sample 3 (object surface) and the objective lens 5, b _obj is the distance between the objective lens 5 and the first image plane 71 of the sample, and a _I1 is the first image plane 71 (of the sample). (Object plane of the first imaging lens) and the first imaging lens 61, b _I1 is the distance between the first imaging lens 61 and the second image plane 72 of the sample, and a _s1 is the objective lens 5. The distance between the image plane 11 of the light source immediately below and the first imaging lens 61, b _s1 is the distance between the first imaging lens 61 and the image plane 12 of the light source immediately below the first imaging lens, and D ₁ is The distance from the image plane 11 of the light source immediately below the objective lens to the image plane 71 of the sample by the objective lens, D ₂ is the image plane of the sample by the first imaging lens from the image plane 12 of the light source immediately below the first imaging lens. 72 to a distance of, L ₂ is the distance der up to the second image plane 72 of the sample and the central filament electrode 95 of the second electron biprism (second image plane of the sample) . M _obj and M _I1 are magnifications of the imaging optical system M _obj = b _obj / a _obj and M _I1 = b _I1 / a _I1 (see FIG. 3), respectively, and d _f1 is the first electron beam bi-level. The diameter of the central filament electrode of the prism.

As can be seen from equations (3) and (4), the interference fringe spacing s _obj is expressed as a function of α ₁ and α ₂ , and the interference region width W _obj is expressed as a function of α ₂ and is completely independent. Not the order of operations to obtain the interference microscope image
(1) A voltage applied to the second electron biprism 95 is adjusted to be set to a predetermined interference area width W.
(2) The voltage applied to the first electron biprism 91 is adjusted to obtain a predetermined interference fringe interval s.
Thus, it can be controlled independently in effect. When the central filament electrode 95 of the second electron biprism is arranged on the image plane 12 of the light source by the first imaging lens in FIG. 3, that is, when the parameter D ₂ −L ₂ = 0, s _obj And W _obj can be controlled completely independently.

JP 2005-197165 A United States Patent # 7,102,145 by Domenicucci, et al. September 5, 2006 JP 2007-335083 A JP 2007-115409 A

A. Tonomura: Electron Holography, 2nd ed. (Springer, Heidelberg. Germany, 1999) Chapter 5. Ken Harada, Akira Tonomura, Yoshihiko Togawa, Tetsuya Akashi and Tsuyoshi Matsuda: Applied Physics Letters, Vol. 84, (2004) 3229. B. G. Frost, A. Thesen, D. C. Joy, Brendan Foran and Kanin Brand: J. Vac. Sci. Technol. B, Vol. 22, (2004) 427. Y.Y. Wang, M. Kawasaki, J. Bruley, M. Gribelyuk, A. Domeincucci and J. Gaudiello: Ultramicroscopy, Vol. 101, (2004) 63. Ken Harada, Tetsuya Akashi, Yoshihiko Togawa, Tsuyoshi Matsuda and Akira Tonomura: Journal of Electron Microscopy, Vol. 54, (2005) 19.

  In general, in an interference optical system, when trying to obtain an interference microscope image or an image containing sufficient information as a hologram, not only the magnification of the sample image but also the interval s (spatial resolution) of interference fringes superimposed on the sample. , Which is related to the phase resolution) and the interference region width W (a range which can be observed as an interference microscope image) are also important. In order to obtain an effective interference microscope image, it is not sufficient to use an optical system prepared in advance as an electron microscope. As apparent from FIGS. 2 and 3 and equations (1) to (4), the interference fringe spacing s and the interference region width W are the light source image (crossover) position immediately above the sample image, the position of the electron biprism, Since it is controlled by the deflection angle α of the electron beam by the electron biprism, in order to obtain an interference microscope image that matches the purpose, for example, a part of the electron lens other than the objective lens is subjected to weak excitation conditions (less energization amount) A method of constructing an optical system including a virtual image in a long focal length state (re-adjustment of the entire optical system of an electron microscope is necessary: see, for example, Non-Patent Document 3) A method of adjusting the relationship between the interference fringe spacing s and the interference area width W using an objective lens (having a long focal length) (needs replacement of the objective lens: see, for example, Non-Patent Document 3) or a specially prepared excitation Add a weak lens A method of using a pair with a lens (replacement of an objective lens and a control mechanism of an additional lens are required; for example, refer to Patent Document 2 and Non-Patent Document 4). Measures such as a method of moving in the axial direction (see Patent Document 3) are taken.

  However, the contrivance to the objective lens itself and the contrivance in operation are useful methods for realizing an image including a wide range of interference fringe spacing s and a wide range of interference region width W as an interference microscope. The construction of any interference optical system requires adjustment of each electron lens and deflection system, and the fact is that knowledge of the electron optical system and skill in handling are required.

  The object of the present invention is to input the parameters of the interference microscope image (for example, the interference fringe interval s and the interference area width W), and the optical system conditions of the electron microscope are set to an appropriate state as the interference optical system. The purpose is to provide what is built.

  The present invention is an electron beam apparatus having an objective lens, a biprism, and the like, wherein the electron beam apparatus forms a plurality of interference optical systems, and inputs the plurality of interference fringe intervals and interference area widths to thereby input the plurality of interference optical systems. The interference optical system is selected.

  In addition, when an appropriate optical system cannot be configured by inputting the interference fringe interval and the interference region width, the interference fringe interval and the interference region width can be input again.

  In addition, when there are a plurality of interference optical systems that can be selected, a selection means is provided that allows the user to select one of them.

  Further, the magnification is determined by an interference optical system selected from the plurality of interference optical systems.

  Further, the electron beam apparatus includes an objective lens, a biprism, and the like, wherein the electron beam apparatus constitutes a plurality of interference optical systems and can select whether or not the Fresnel fringes can be allowed.

  Further, when the Fresnel fringe is not allowed, a possible interference optical system is selected by inputting the interference region width.

  Further, when the Fresnel fringes are allowed, the plurality of interference optical systems are selected by inputting interference fringe intervals and interference area widths.

  In addition, when an appropriate optical system does not exist due to the input of the interference fringe interval and the interference region width, the interference fringe interval and the interference region width can be input again.

  In addition, when there are a plurality of the plurality of interference optical systems, a selection means is provided that allows the user to select one of them.

  Further, the magnification is determined by an interference optical system selected from the plurality of interference optical systems.

  In addition, when an appropriate optical system does not exist due to the input of the interference area width, the interference area width can be input again.

  In addition, when there are a plurality of the plurality of interference optical systems, a selection means is provided that allows the user to select one of them.

  Further, the magnification is determined by an interference optical system selected from the plurality of interference optical systems.

  In addition, an electron beam apparatus including at least an electron source, a lens, and a plurality of biprisms, the first lens on the downstream side of the electron source with respect to the traveling direction of the electron beam, and the downstream side of the first lens A first biprism, a first electron biprism interferometric optical system having a second biprism downstream of the first biprism, and the first lens downstream of the electron source, A second biprism having a first biprism downstream of the first lens, a second lens downstream of the first biprism, and a second biprism downstream of the second lens. The first electron biprism interference optical system and the second electron biprism interference optical system by inputting an interference fringe interval and an interference region width. It is possible to select

  An electron beam apparatus comprising at least an electron source, a lens, and a plurality of biprisms, wherein the first lens is on the downstream side of the electron source, and the first biprism is on the downstream side of the first lens. A first electron biprism interference optical system having a second biprism downstream of the first biprism, the first lens downstream of the electron source, and the first lens A second biprism having a first biprism downstream of the first biprism, a second lens downstream of the first biprism, and a second biprism downstream of the second lens. An interference optical system; a first biprism downstream of the electron source; a second lens downstream of the first biprism; and a second biprism downstream of the second lens. Third electron biprism interference light having a prism The first electron biprism interference optical system, the second electron biprism interference optical system, and the third electron by inputting an interference fringe interval and an interference region width. Any one of the line biprism interference optical systems can be selected.

  According to the present invention, the optical system condition of the electron microscope is set to an appropriate state as the interference optical system simply by inputting the parameters of the interference microscope image (for example, the interference fringe interval s and the interference region width W), and automatically Built.

  This allows the experimenter to obtain an appropriate interference microscope image simply by making final adjustments such as fine adjustment of the position of the electron biprism, fine adjustment of the deflection system, selection of the observation site in the sample and focusing. Can be obtained. It is possible to provide an electron beam apparatus capable of observing interference microscope images for a wide range of use to a wide range of technical level experimenters having various requirements.

It is a schematic diagram which shows the mode of interference of an electric field type | mold electron beam biprism and an electron beam. It is a schematic diagram which shows the optical system of a 1 step | paragraph electron beam biprism interferometer. It is a schematic diagram which shows the optical system of a two-stage electron beam biprism interferometer. It is a schematic diagram which outlines the whole electron beam apparatus of this application. It is a schematic diagram showing an optical system corresponding to high-magnification interference microscope image observation when a conventional two-stage electron biprism interferometer is incorporated in a general-purpose electron microscope. It is a schematic diagram which shows the optical system corresponding to interference microscope image observation of a medium magnification at the time of incorporating the conventional 2 step | paragraph electron biprism interferometer in a general purpose electron microscope. It is a schematic diagram showing an optical system corresponding to low-magnification interference microscope image observation when a conventional two-stage electron biprism interferometer is incorporated in a general-purpose electron microscope. It is a schematic diagram showing a general type two-stage electron biprism interference optical system constituting an enlarged imaging system. It is a schematic diagram showing a general two-stage electron biprism interference optical system constituting a virtual image magnification system. It is a schematic diagram showing a general-type two-stage electron biprism interference optical system constituting a reduction imaging system. It is a schematic diagram regarding Example 1 which shows the relationship between the magnification with respect to a sample, and an interference fringe space | interval. It is a schematic diagram regarding Example 1 which shows the relationship between the magnification with respect to a sample, and interference area width. FIG. 3 is a schematic diagram showing a system flow up to construction of an interference optical system with respect to Example 1. It is a schematic diagram regarding Example 2 which shows the relationship between the magnification with respect to a sample, and an interference fringe space | interval. It is a schematic diagram regarding Example 2 which shows the relationship between the magnification with respect to a sample, and interference area width. FIG. 10 is a schematic diagram showing a system flow up to construction of an interference optical system with respect to Example 2.

<Electron beam device>
FIG. 4 schematically shows the entire electron beam apparatus as a system relating to the present application. FIG. 4 is a schematic diagram assuming a case where a general-purpose transmission electron microscope is used for an interference microscope, but the present application is not limited to the form described in this schematic diagram.

  An electron gun 1 serving as an electron source is positioned at the most upstream portion in the direction in which the electron beam flows, and is converted into an electron flow at a predetermined speed (hereinafter referred to as an electron beam) by the accelerating tube 40. The sample 3 is irradiated with an electron beam through the condenser lenses 41 and 42). The electron beam transmitted through the sample 3 is imaged by the objective lens 5 on the downstream side of the sample 3 in the traveling direction of the electron beam. This imaging action is taken over by a plurality of imaging lens systems (61, 62, 63, 64) on the downstream side of the objective lens 5, and finally forms an image on the observation recording surface 89 of the electron beam apparatus. The image 8 is recorded on the image recording device 77 through a recording medium 79 such as an electron microscope film or a CCD camera. In the electron biprism, the first electron biprism 91 is located on the downstream side of the objective lens 5, and the second electron biprism 95 is located on the downstream side of the first imaging lens 61. Each element such as the voltage applied to each electron source 1 and the accelerating tube 40, the sample position and the inclination angle of the sample 3, the excitation state of the electron lens, the position of the electron biprism, and the application state of the potential are stored in the computer 51. It is controlled by a connected control system (19, 49, 48, 47, 39, 59, 97, 69, 96, 68, 67, 66). In an actual apparatus, there are a deflection system that changes the traveling direction of the electron beam, a diaphragm mechanism that restricts a region through which the electron beam passes, and the elements are also connected to the computer 51. It is controlled by the control system. However, since these devices are not directly related to the present application, they are omitted in this figure. As shown in this schematic diagram, the electro-optic element is assembled in the vacuum vessel 18 and continuously evacuated by a vacuum pump. The vacuum system is also omitted because it is not directly related to the present application.

<Basic configuration of interference optical system>
In this application, since it is assumed that it is applicable to the electron beam interferometer of a general-purpose electron microscope in addition to dealing with a wide range of interference microscope image observation conditions, an interference optical system using an electron biprism in two stages will be examined. . First, consider the case where the conventional two-stage electron biprism interferometer is extended to medium and low magnification image observation. Next, instead of allowing the generation of Fresnel fringes, the two-stage electron biprism interferometer Consider a system with a high degree of freedom in the optical system configuration.

<(1) Expansion of conventional two-stage electron biprism interferometer>
FIG. 5 shows the main optical system of the two-stage electron biprism interference system including the imaging lens system. The optical system of FIG. 5 is an optical system mainly used for high-resolution observation, which achieves a high magnification by using the entire imaging lens system under an enlarged imaging condition. The applicable magnification, interference area width, and interference fringe spacing must be determined for each specific electron beam apparatus. For example, an electron beam apparatus with an acceleration voltage of 300 kV can be used 200,000 times to 1.5 million times. Confirm that the degree is possible.

  FIG. 6 shows a conventional two-stage electron biprism interference optical system configured for intermediate magnification. Since the use condition of the objective lens 5 is automatically determined because the central filament electrode 91 of the first electron biprism needs to be disposed on the image plane 71 of the sample, the sample 3, the objective lens 5, and the first electron biprism 91 are also included. The configuration is the same as that of the optical system of FIG. By turning off the second lens 62 in the imaging lens system, the maximum reach magnification is reduced. As shown in FIG. 6, the second electron biprism 95 may be positioned upstream of the light source image 12 (crossover). In this case, the potential applied to the filament electrode 95 is positive or negative. Need to be reversed. It can handle magnifications of about 300,000 times or less.

  FIG. 7 shows a conventional two-stage electron biprism interference optical system configured for low magnification. The configuration of the sample, the objective lens 5 and the first electron biprism 91 is the same as that of the optical system in FIG. The first imaging lens 61 is turned off, and reduction projection is performed by the second imaging lens 62, thereby realizing imaging at a low magnification. It can handle magnifications of about 40,000 times or less.

  6 and 7, the magnification is adjusted by turning off one lens in the imaging lens system. In this case, since the degree of freedom of one lens is lost, the applicable range is small for the magnification, interference region width W, and interference fringe interval s that both optical systems can handle. If one stage of electron lens is added to the objective lens system as in the 1 MV holography electron microscope, the degree of freedom in the configuration of the interference optical system increases (see, for example, Patent Document 4 and Non-Patent Document 5).

<(2) General-type two-stage electron biprism interferometer (enlarged imaging system)>
FIG. 8 shows a two-stage electron biprism interference optical system mainly used for enlarged imaging. Both the first and second electron biprisms are inserted between the sample 3 and the image plane 71 of the sample. The filament electrode 95 of the second electron biprism only needs to be arranged in the shaded portion of the filament electrode 91 of the upper electron biprism, and does not limit the other positional relationship. . Although Fresnel fringes are superimposed on the interference microscope images (8 and 31), it is possible to obtain an interference microscope image having interference fringes with a necessary interval within a necessary interference region width.

The two parameters of the interference microscope image (8 and 31) with the configuration of FIG. 8, the interference fringe interval s and the interference region width W are back-projected onto the sample surface in the same manner as described above, and the interference fringe interval s _obj and the interference region width are W _obj is expressed by the following equation.

S _obj = (a _obj / b _obj ) * (D * λ / (2 * ((DL ₂ ) * α _2- (DL ₁ ) * α ₁ ))) (5)

W _obj = (a _obj / b _obj ) * (2 * L ₂ * α ₂ -2 * L ₁ * α _1- (D * d _f1 / (DL ₁ ))) (6)

Both equations (5) and (6) include the deflection angles α ₁ and α ₂ of the electron beam by both electron beam biprisms. That is, by combining the deflection angles α ₁ and α ₂ by the _two electron biprisms, the focal length of the electron lens or the like is not deflected at all (ie, without changing the magnification of the sample), and the interference fringe interval s _obj and It is possible to adjust the interference area width W _obj to a required value. This is, for example, a method (conditions) for securing the degree of freedom to the interference fringe interval s _obj and the interference region width W _obj with a combination of the weak excitation lens having a long focal length and the objective lens described in Non-Patent Document 4 described above. Each sample has a different magnification).

  To construct the optical system of FIG. 8 with a general-purpose electron microscope, the first imaging lens 61 (see 61 in FIG. 7) is turned off and the image plane 71 of the objective lens is placed downstream in the traveling direction of the electron beam. A simple method is to insert two electron biprisms between the objective lens 5 and the image plane 71 of the sample by the objective lens. However, it should be noted that when the first imaging lens 61 is turned off by one stage, the maximum magnification is about 300,000 times.

<(3) General-type two-stage electron biprism interferometer (virtual image magnification system)>
FIG. 9 shows a general two-stage electron biprism interference optical system that can be used in an interferometer with a medium magnification of about several tens of thousands to 100,000 times. Using an electron lens (objective lens 5) immediately below the sample 3 under weak excitation (long focal length) conditions, an enlarged virtual image 36 of the sample virtually existing above the sample is located downstream of the objective lens 5. This is an optical system that forms a reduced image with the first imaging lens 61. In this configuration, the objective lens 5 and the first imaging lens 61 are combined and used for imaging. Since the objective lens 5 performs virtual image enlargement and the first imaging lens 61 performs reduction imaging, An intermediate magnification can be ensured depending on the combination.

The two parameters of the interference microscope image (32 and 8), the interference fringe interval s and the interference region width W are back-projected on the sample surface in the same manner as described above, and the interference fringe interval s _obj and the interference region width are obtained. W _obj is expressed by a mathematical expression including the deflection angles α ₁ and α ₂ of both electron biprisms (omitted here).

<(4) General-type two-stage electron biprism interferometer (reduction imaging system)>
FIG. 10 shows an optical system that is effective when the interference region width W is large, mainly at a low magnification of several tens of thousands or less. Furthermore, since the distance between the sample 3 and the electron lens 61 immediately below the sample 3 can be increased, it is also a necessary optical system effective in preventing immersion of the magnetic field of the electron lens in the sample such as a magnetic material.

The two parameters of the interference microscope image (32 and 8), the interference fringe interval s and the interference region width W are back-projected on the sample surface in the same manner as described above, and the interference fringe interval s _obj and the interference region width are obtained. W _obj is expressed by a mathematical expression including the deflection angles α ₁ and α ₂ of both electron biprisms (omitted here).

In this application, regarding two or more interference optical systems for which these studies have been made, specific optical element conditions are stored, and the optical system is selected in accordance with parameters necessary for the experiment, such as the interference region width W _obj. Then, an operating condition of an optical element under the optical system is read, and if necessary, calculation is performed to set an appropriate condition, and a system for automatically constructing an interference optical system according to the setting is provided.

A system composed of two interference optical systems will be described. For example, for the two interference optical systems shown in FIGS. 8 and 9, the magnification M for the sample and the interference fringe spacing s _obj that can be realized at that time are shown in FIG. 11, and the magnification M and the interference area width W _obj for the sample are shown. Is shown in FIG. The plotted points in the frames in both figures show all the operating conditions (electron lens, deflection system, etc.) necessary to construct the optical system under the conditions where the interference optical system was actually constructed. The voltage applied to the biprism is known, and is stored in the storage device as a data file. In both FIG. 11 and FIG. 12, the area enclosed by the frame is an interference condition area that is determined to be achievable from the performance of the power source, and the specific operation condition is calculated from the plotted point condition (for example, linear). Interpolation or extrapolation). For areas outside the frame, such interference conditions (magnification, spacing between interference fringes and interference area width) cannot be constructed, or even if they can be constructed, fringes cannot be recorded as fringes from the resolution of the recording system (for example, 11 corresponds to a case where the interference fringes are finer than the pixel size of the CCD element in the lower left part of FIG.

  Such an electron beam apparatus is a system configured as shown in FIG. 4. Input processing, information storage / reading processing, arithmetic processing, setting processing, operation processing, and the like are performed by a computer, and instructions from the computer are made. Based on this, the control system unit controls each optical element.

  FIG. 13 is a chart showing the flow from the input of the interference optical system parameters by the system to the construction of the optical system. Each will be explained.

  (Step 1): The experimenter selects the interference optical system mode.

(Step 2): The system waits for input of parameter interference fringe interval s _obj and interference area width W _obj of the interference image.

(Step 3): The experimenter inputs the interference fringe interval s _obj and the interference region width W _obj to the input device.

  (Step 4): The storage device searches for a realizable interference optical system with reference to, for example, the data files obtained in FIGS.

  (Step 5): (1) When an appropriate optical system is found, the optical system to be constructed is displayed on the display device. (2) If an appropriate optical system cannot be found, this is displayed on the display device and the experimenter is instructed to re-enter the parameters. → Return to Step 3.

  (Step 6): (1) If one suitable optical system is found, that optical system is displayed on the display device. (2) If more than one suitable optical system is found, display that fact and instruct the experimenter to select. → The experimenter enters the selection.

  (Step 7): The magnification of the optical system to be constructed is determined (for example, a magnification with a good separation in the vicinity of the intermediate value in the range of magnifications that can be constructed may be used).

  (Step 8): (1) When there is stored data of the corresponding magnification, the storage device reads the stored data. (2) When there is no stored data of the corresponding magnification, the arithmetic unit creates operating condition data using neighboring data (for example, the energization amount to each system under the two operating conditions is calculated from that condition. Proportional distribution may be performed according to the amount of deviation).

  (Step 9): The operating conditions of each element for constructing the target optical system are set in the control system of the electron optical system.

  (Step 10): The control system is operated, and the optical system is constructed as an interference optical system that satisfies the set conditions.

  (Step 11): An electron biprism is inserted on the optical axis, and a voltage based on the condition set in the central filament electrode is applied to complete the automatic construction of the interference optical system. → The system returns to the parameter input waiting state. → The experimenter conducts an interference experiment.

  (Step 12): The experimenter ends the interference optical system mode.

  After step 11, the experimenter aligns the sample, finely adjusts the deflection system, finely adjusts the position of the electron biprism and the voltage applied to the central filament electrode, and observes the desired interference microscope. Record it if you do. The reason why the manual operation is left in the adjustment of the final board is to expand the possibility of dealing with various types of experiments and types of samples.

A substantially similar system can be constructed even in the case of three or more interference optical systems. First, for a plurality of interference optical systems, the magnification M for the sample and the interference fringe spacing s _obj that can be realized at that time are schematically shown in FIG. 14, and the relationship between the magnification M for the sample and the interference region width W _obj is schematically shown in FIG. Indicate. The area surrounded by the frame in both figures is the range of the observable interference image. As a result of examining all the interference optical systems described so far, the possibility of constructing a plurality of optical systems in most cases is depicted for one magnification. In particular, a region surrounded by a thick broken line in both figures is a range of an interference image that can be observed with a conventional two-stage electron biprism interference optical system. In view of the fact that Fresnel fringes are not superimposed on the interference image and the interference fringe spacing s _obj can be easily changed later, it is preferable to construct the optical system with priority on the conventional two-stage electron biprism interference optical system. It is judged. Therefore, when selecting an optical system, it is reasonable to first select a system that preferentially selects the conventional two-stage electron biprism interference optical system, but this is not a limitation.

  In both FIGS. 14 and 15, the area enclosed by a frame is an interference condition area determined to be achievable from the performance of the power source and the like, and the specific operation condition is calculated from the plotted point condition (for example, linear). Interpolation or extrapolation). The area outside the frame corresponds to the case where such interference conditions (magnification, interference fringe interval and interference area width) cannot be established, or even if the interference conditions can be established, fringes cannot be recorded as fringes from the resolution of the recording system. . These circumstances are the same as in the first embodiment.

  Further, such an electron beam apparatus has a configuration as shown in FIG. 4, and input processing, information storage / reading processing, arithmetic processing, setting processing, operation processing, and the like are performed by a computer. The control system unit controls each optical element based on the same as in the first embodiment.

  FIG. 16 is a chart showing the flow from the input of the interference optical system parameters to the construction of the optical system. Each will be explained. The step argument is a single digit number for the entire optical system, a teenage number for the conventional two-stage electron biprism interferometer, and the general two-stage electron biprism interferometer proposed in this application. Numbers in their twenties are attached to the related items.

  (Step 1): The experimenter selects the interference optical system mode.

  (Step 2): The experimenter inputs whether or not the Fresnel stripes are allowed. The system handles (1) a conventional two-stage biprism interferometer (eg, as described in FIGS. (2) When Fresnel stripes are possible, all stored optical systems (for example, described in FIGS. 5, 6, 7, 8, 9, and 10) are handled.

(Step 11): The system waits for input of the parameter interference area width W _obj of the interference image. / (Step 21): The system waits for input of parameter interference fringe interval s _obj and interference area width W _obj of the interference image.

(Step 12): The experimenter inputs the interference area width W _obj to the input device. / (Step 22): The experimenter inputs the interference fringe interval s _obj and the interference region width W _obj to the input device.

  (Step 13): The storage device searches the realizable interference optical system with reference to the data file. / (Step 23): The storage device searches the realizable interference optical system with reference to the data file.

  (Step 14): (1) When an appropriate optical system is found, the optical system to be constructed is displayed on the display device. (2) If an appropriate optical system is not found, display that effect on the display device and instruct the experimenter to (i) re-enter the parameters. → Return to Step 12. Or (ii) instructing a change to an optical system capable of fresnel fringes. → Go to step 21. / (Step 24): (1) When an appropriate optical system is found, the optical system to be constructed is displayed on the display device. (2) If an appropriate optical system cannot be found, this is displayed on the display device and the experimenter is instructed to re-enter the parameters. → Return to step 22.

(Step 15): (1) If one suitable optical system is found, that optical system is displayed on the display device. (2) If more than one suitable optical system is found, display that fact and instruct the experimenter to select. → The experimenter enters the selection. / (Step 25): (1) When one suitable optical system is found, the optical system is displayed on the display device. (2) If more than one suitable optical system is found, display that fact and instruct the experimenter to select. → The experimenter enters the selection.

  (Step 16): The magnification of the optical system to be constructed is determined (for example, a magnification with a good separation in the vicinity of the intermediate value in the range of magnifications that can be constructed may be set). / (Step 26): The magnification of the optical system to be constructed is determined (for example, a magnification with a good separation in the vicinity of an intermediate value in the range of magnifications that can be constructed may be used).

  (Step 17): (1) When there is stored data of the corresponding magnification, the storage device reads the stored data. (2) When there is no stored data of the corresponding magnification, the arithmetic unit creates operating condition data using neighboring data (for example, the energization amount to each system under the two operating conditions is calculated from that condition. Proportional distribution may be performed according to the amount of deviation). / (Step 27): (1) When there is stored data of the corresponding magnification, the storage device reads the stored data. (2) When there is no stored data of the corresponding magnification, the arithmetic unit creates operating condition data using neighboring data (for example, the energization amount to each system under the two operating conditions is calculated from that condition. Proportional distribution may be performed according to the amount of deviation).

  (Step 3): The operating conditions of each element for constructing the target optical system are set in the control system of the electron optical system.

  (Step 4): The control system is operated, and the optical system is constructed as an interference optical system that satisfies the set conditions.

  (Step 5): An electron biprism is inserted on the optical axis, and a voltage based on the conditions set in the central filament electrode is applied to complete the automatic construction of the interference optical system. → The system returns to the parameter input waiting state. → The experimenter conducts an interference experiment.

  (Step 6): The experimenter ends the interference optical system mode.

  After step 5, the experimenter aligns the sample, finely adjusts the deflection system, finely adjusts the position of the electron biprism and the voltage applied to the central filament electrode, and observes the desired interference microscope. Record it if you do. In order to expand the possibility of dealing with various types of experiments and types of samples, it is the same as in the first embodiment that the manual operation part is left in the adjustment of the final board.

  The present invention is applicable to an electron beam apparatus using an electron beam biprism.

  DESCRIPTION OF SYMBOLS 1 ... Electron source or electron gun, 2 ... Optical axis, 3 ... Sample, 4 ... Irradiation optical system, 5 ... Objective lens, 8 ... Interference fringe, 9 ... Electron beam biprism center filament electrode, 10 ... Electron by irradiation optical system Image of source (crossover), 11... Crossover image formed by objective lens, 12... Crossover image formed by first imaging lens, 13. Image of crossover imaged, 18 ... vacuum vessel, 19 ... electron source control unit, 21 ... object wave, 22 ... electron wavefront, 23 ... reference wave, 27 ... electron beam trajectory, 31 ... by objective lens An image of the imaged sample, 32... An image of the sample imaged by the first imaging lens, 36... A virtual image of the sample positioned above the objective lens, 39. ... First irradiation (capacitor Lens: 42... Second irradiation (condenser) lens 47. Second irradiation lens control unit 48. First irradiation lens control unit 49. Accelerator control unit 51. Control computer 52 ... control system computer monitor, 53 ... control system computer interface, 59 ... objective lens control unit, 61 ... first imaging lens, 62 ... second imaging lens, 63 ... third imaging lens, 64: Fourth imaging lens, 66: Fourth imaging lens control unit, 67: Third imaging lens control unit, 68: Second imaging lens control unit, 69: First Image forming lens control unit, 71... Sample image plane by objective lens, 72... Sample image plane by first image forming lens, 73... Sample image plane by second image forming lens, 74. Imaging 75, image plane of the sample by the fourth imaging lens, 76, monitor of the image observation / recording apparatus, 77 ... image recording apparatus, 78 ... control unit for the image observation / recording medium, 79 ... Image observation / recording medium, 89 ... observation / recording surface, 81s ... constructable interference condition (magnification and stripe spacing) area, 81W ... constructable interference condition (magnification and interference area width) area, 82s ... constructable Region of various interference conditions (magnification and fringe spacing), 82W... Region of constructable interference conditions (magnification and interference region width), 83s... Region of constructable interference conditions (magnification and fringe spacing), 83W. Interference condition (magnification and interference area width) area, 84 s ... constructable interference condition (magnification and stripe spacing) area, 84 W ... constructable interference condition (magnification and interference area width) area, 85 s ... constructable Area of interference conditions (magnification and stripe spacing) , 85W: Area of interference condition (magnification and interference area width) that can be constructed, 86s: Area of interference condition (magnification and stripe interval) that can be constructed, 86W: Area of interference condition (magnification and interference area width) that can be constructed 91, a central filament electrode of the first electron biprism, 95, a central filament electrode of the second electron biprism, 99, a parallel plate ground electrode.

Claims (13)

An electron beam apparatus having an objective lens and a plurality of biprisms,
The electron beam apparatus
A first lens on the downstream side of the electron source with respect to the traveling direction of the electron beam, a first biprism on the downstream side of the first lens, and a second biprism on the downstream side of the first biprism. A first electron biprism interference optical system comprising:
The first lens downstream of the electron source, the first biprism downstream of the first lens, the second lens downstream of the first biprism, and the second lens and a second electron biprism interference optical system having a second biprism configured downstream of,
By inputting an interference fringe interval and an interference area width, any one of the interference optical systems including the first electron biprism interference optical system and the second electron biprism interference optical system is selected ,
An electron beam apparatus characterized in that a magnification is determined by the selected interference optical system .   2. The electron according to claim 1, wherein when an appropriate optical system cannot be configured by inputting the interference fringe interval and the interference region width, the interference fringe interval and the interference region width can be input again. Wire device. According to claim 1, before the electron beam apparatus characterized in that a selection means for selecting either the user when hexene-option can interference optical system there are a plurality. 2. The electron beam apparatus according to claim 1, wherein it is possible to select whether or not the Fresnel fringes are acceptable. 5. The electron beam apparatus according to claim 4 , wherein when the Fresnel stripe is not allowed, an interference optical system is selected by inputting an interference region width. In claim 4, when the allowable said Fresnel fringes of the variable is the input of the interference fringe spacing and interference width, electron beam apparatus characterized by the selection. 7. The electron according to claim 6 , wherein when an appropriate optical system does not exist by inputting the interference fringe interval and the interference region width, the interference fringe interval and the interference region width can be input again. Wire device. 7. The electron beam apparatus according to claim 6 , further comprising selection means for allowing the user to select one of the plurality of selectable interference optical systems. In claim 6, an electron beam apparatus characterized by magnification is determined by the pre-hexene-option interference optical system. 6. The electron beam apparatus according to claim 5 , wherein when an appropriate optical system does not exist by inputting the interference area width, the interference area width can be input again. 6. The electron beam apparatus according to claim 5 , further comprising selection means for allowing a user to select one of the plurality of selectable interference optical systems. In claim 5, an electron beam apparatus characterized by magnification is determined by the pre-hexene-option interference optical system. The electron beam apparatus according to claim 1, further comprising:
A third biprism on the downstream side of the electron source; a second lens on the downstream side of the first biprism; and a second biprism on the downstream side of the second lens. And an electron biprism interference optical system of
By inputting an interference fringe interval and an interference area width, the first electron biprism interference optical system, the second electron biprism interference optical system, and the third electron biprism interference optical system are input. Any one of the interference optical systems including the above can be selected.

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