JP2002131249A - Field radiation type low-energy electron diffraction equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact and highly safe field radiation type low-energy electron diffraction equipment, which can irradiate electron beams to a minimum local region of a sample surface and can highly accurately detect atomic sequence information of several atomic layers of the region. SOLUTION: The field radiation type low-energy electron diffraction equipment has a sharpened probe for radiating field radiation electrons, a power source part for impressing to the prove, a voltage for field radiation to the sample, a probe controller for controlling the distance between the probe and the sample to flow a prescribed field radiation current, a retracting electrode for retracting scattering electrons generated from the sample, when the field radiation electrons enter, an inelastic scattering electron-removing part, where a prescribed stop potential for stopping inelastic scattering electrons passing the retracting electrode to pass is impressed, and a diffraction pattern-detecting part for generating a diffraction pattern due to elastic scattering electrons passing the inelastic scattering electron-removing part. By impressing the voltage between the probe and the sample, an electron beam irradiation area at the sample surface by the field radiation electrons is reduced, and at the same time, scattering electrons are scattered from the inside several atomic layers of the sample surface and are moreover emitted, to throw off an electric field formed between the probe and the sample.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention obtains atomic arrangement and structural information of a local surface area by irradiating a local area on a sample surface with an electron beam and detecting a diffraction pattern of the area by elastic scattered electrons. The present invention relates to a field emission type low-energy electron diffractometer capable of performing the following.

[0002]

2. Description of the Related Art A conventional low-speed electron diffractometer utilizes thermoelectrons. FIG. 6 is a conceptual diagram of a conventional low-speed electron diffraction apparatus. 50 is a filament, 51 is a sample, 52 is an acceleration electrode, 53 is a lens electrode, and 54 is a screen.
As shown in FIG. 6, the thermoelectrons emitted from the filament 50 are accelerated by an electric field formed by the accelerating electrode 57, converged by the lens electrode 53, and radiated to the surface of the sample 51. Among them, the inelastic scattered electrons are removed using a grid, and the elastic scattered electrons are removed from the screen 5.
4 had been detected. However, the energy of this electron beam is 500 eV or less, and it is difficult to converge such a low-speed electron beam finely by the lens electrode 53.
The limit of the electron beam irradiation area on the surface was about 1 μm ² . For this reason, it was not possible to examine the surface structure formed only in a narrow region of 1 μm ² or less.

On the other hand, a method for irradiating a narrow area of a sample with field-emitted electrons from a sharpened probe to examine the surface morphology includes (a) low-speed electron holography (Ph.
ysical Review Letters, Vol. 65, p. 1204) and (b) Scanning secondary electron detection method (English magazine, PhysicaScripta, vol. 38, p. 260). FIG. 7 is a conceptual diagram of a conventional low-speed electron holography method, and FIG. 8 is a conceptual diagram of a conventional scanning secondary electron detection method.

In FIG. 7, 55 is a probe, 56 is a sample,
57 is a sample supporting electrode, and 58 is a screen. In FIG. 8, 59 is a probe control mechanism, 60 is a probe, 61 is a sample, and 62 is a secondary electron detector such as a channeltron.

First, in (a) low-speed electron holography, as shown in FIG. 7, electrons are emitted from a probe 55 to a thin film sample 56 supported by a sample support electrode 57 by electric field emission, and the electrons transmitted through the thin film. Is projected on the screen 58. Therefore, this low-speed electron holography method cannot be applied unless the sample 56 is a thin film. Further, it is difficult to obtain a diffraction pattern because the intensity of transmitted electrons is high. For this reason, it is still impossible to investigate the surface structure with atomic precision.

In the (b) scanning secondary electron detection method, as shown in FIG. 8, electrons are emitted from a probe 60 controlled by a probe control mechanism 59 to a sample 61 by electric field emission, and the total amount of scattered electrons is reduced. It is measured by the secondary electron detector 62. Surface morphological information is obtained by synchronizing and imaging the scanning of the probe 60 and the secondary electron detection. However, since the total amount of secondary electrons is detected, it is not possible to obtain information on the atomic arrangement in the electron beam irradiation region. The disclosure of a scanning microscope based on this detection method is disclosed in
No. 295696.

Japanese Unexamined Patent Publication No. 9-89815 discloses a reflection high-speed electron diffraction method (RHEED) for obtaining a reflection high-speed electron diffraction pattern, not by electric field emission by a probe. FIG. 9 is a conceptual diagram of a conventional reflection high-speed electron diffraction method. In FIG. 9, 63 is an electron gun, 64 is a sample, and 65 is a screen. This reflection high-energy electron diffraction is suitable for in-situ observation during the growth of a thin film because a space is formed on the crystal surface, and is generally used as a monitor for the growth of the thin film. In the reflection high-energy electron diffraction method, a high-speed electron beam (acceleration voltage of about 10 kV or more) is irradiated on the surface of the sample 64 by the electron gun 63 at a glancing angle (approximately 0 ° to 6 °), and then reflected and diffracted. The electron beam group is projected on the fluorescent screen 65, and the geometrical pattern and intensity of the reflected high-speed electron diffraction pattern are analyzed to obtain knowledge on the surface atomic structure.

[0008]

As described above,
Conventional low-energy electron diffractometers have an electron beam energy of 50
It was 0 eV or less, and it was difficult to converge finely by the lens electrode 53 if the filament 50 was used, and the electron beam irradiation area on the surface could converge only to about 1 μm ² . In this case, the arrangement information of several atomic layers in the local region of the sample surface could not be measured at all.

In addition, the low-speed electron holography method (a) of detecting the surface structure using the probe 55 has an essential weakness that it cannot be measured unless the sample 56 is a thin film. In addition, it was difficult to obtain a diffraction pattern due to the high intensity of transmitted electrons. Further, in the (b) scanning secondary electron detection method, since only the total amount of scattered electrons is detected by the secondary electron detector 62 and the average value of the scattering power at various points in the scanning is measured, several atoms in the local region are measured. No layer structure information is available. As described above, the conventional method of detecting the surface structure of the sample by electric field emission by the probe succeeded in narrowing the irradiation area of the electron beam and improved the resolution, but it was not possible to obtain a diffraction pattern, It was of a structure that basically could not be obtained, such as obtaining structural information of several atomic layers on the surface.

Next, the reflection high-energy electron diffraction (RHEED) disclosed in Japanese Patent Application Laid-Open No. 9-89815 can obtain information on the crystal structure, and inelastic scattering, which is a weak point of the reflection high-speed electron diffraction, is known. Although the background was removed by electrons, very high-speed electrons (10
(KeV or more), there is a problem that the sensitivity to the surface of the sample 64 is low and the possibility of breaking the surface of the sample 64 is high. In addition, since the incident light is incident at a slight angle on the surface of the sample 64, the electron beam irradiation area on the surface of the sample spreads ten times or more in the incident direction, and it is impossible to achieve high spatial resolution.
Furthermore, a high accelerating voltage is required to obtain high-speed electrons, and the entire electron diffraction apparatus is expensive and bulky.

Therefore, in order to obtain accurate arrangement information of several atomic layers in a local region on the sample surface, a low-speed electron diffractometer is basically provided, and a low-speed electron beam irradiation area is narrowed as much as possible to increase the resolution. Innovative approaches are the most influential. And, since the low-speed electron diffraction device is a low-speed electron beam (about 500 eV or less), even if a grid is used to block inelastic scattered electrons, it can function satisfactorily at a low voltage and discharge between the grids and the grid with respect to energy resolution. The mesh width does not matter. For this reason, if the electron beam is narrowed down, the structural information of the surface atoms in the local region can be obtained from the diffraction pattern, and the possibility of noise entering the process of generating the diffraction pattern is extremely low.
It should be possible to obtain a detection device that has a low acceleration voltage, a low voltage, and high safety.

In order to solve the above-mentioned problems, the present invention can irradiate an electron beam to a very small local region of a sample surface, and detect the atomic arrangement information of several atomic layers in that region with high accuracy. It is an object of the present invention to provide a small, highly safe field emission type low-energy electron diffraction apparatus.

[0013]

In order to solve the above-mentioned problems, a field emission type slow electron diffractometer of the present invention comprises a sharpened tip for emitting field emission electrons, and an electric field applied to the sample relative to the tip. A power supply unit for applying a voltage for emission, a probe control device for controlling a distance between the probe and the sample so that a predetermined field emission current flows, and scattering generated from the sample when field emission electrons are incident. A drawing electrode for drawing electrons;
An inelastic scattered electron removing section to which a predetermined blocking potential for preventing the inelastic scattered electrons from passing through the pull-in electrode is applied; and a diffraction in which a diffraction pattern is generated by the elastic scattered electrons passing through the inelastic scattered electron removing section. A pattern detection unit is provided, and by applying the voltage between the probe and the sample, the electron beam irradiation area on the sample surface of the field emission electrons is reduced, and scattered electrons are scattered from within several atomic layers on the sample surface, In addition, the electric field generated between the probe and the sample is shaken off and emitted.

This makes it possible to irradiate an electron beam to a very small local region of the sample surface, to detect the atomic arrangement information of several atomic layers in that region with high accuracy, and to obtain a small, highly safe field emission type low-speed device. It can be an electron diffraction device.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 is characterized in that a probe which is sharpened and emits field emission electrons, a sample holder provided opposite to the probe and on which a sample is placed, and a probe are provided. A power supply unit for applying a voltage for field emission to the sample and a probe are attached, and the probe is mounted so that a predetermined field emission current flows.
A probe control device for controlling the distance between samples, a drawing electrode for taking in scattered electrons generated from the sample when field emission electrons are incident, and an inelastic scattered electron provided adjacent to the drawing electrode and passing through the drawing electrode An inelastic scattered electron removing unit to which a predetermined blocking potential capable of blocking the passage of
A diffraction pattern detection unit that generates a diffraction pattern by elastic scattered electrons that have passed through the inelastic scattered electron removal unit,
By applying the voltage between the probe and the sample, the electron beam irradiation area on the sample surface of the field emission electrons is reduced, scattered electrons are scattered from within several atomic layers on the sample surface, and the space between the probe and the sample is reduced. Since the field emission type slow electron diffraction device is characterized by being emitted after shaking off the electric field formed in the region, the electron beam irradiation area is minimized due to the slow electric field irradiation using a sharpened probe. nm level), and the field emission electrons can be reduced to several atomic layers (9-1 to 1 nm).
Scattering is possible without penetrating more than the depth of 0 atomic layer or less, and the elastic scattered electrons scattered at this time can have arrangement and structural information of several atomic layers (10 atomic layers or less). In addition, even a low-speed electron can be shaken out of the electric field formed at this time without collision between the probe and the sample, and can be detected by the diffraction pattern detection unit. The elastic scattered electrons themselves are also slow, and the slower inelastic scattered electrons that become the background are removed by the inelastic scattered electron removal unit, so noise may enter the inelastic scattered electron removal unit and the diffraction pattern detection unit. Is very low, the acceleration voltage is low and the safety is high.

According to a second aspect of the present invention, the tip of the probe is
2. The field emission type low-energy electron diffraction apparatus according to claim 1, wherein the diameter of the electron beam irradiation area on the sample surface of the field emission electrons is several angstrom to less than 0 °. It can be set to several hundred nm (nm level), and the electron beam irradiation area can be reliably narrowed to a minimum region.

According to a third aspect of the present invention, the pull-in electrode is a cylindrical electrode that can include a region on one side of the sample and the probe, and an area surrounded by the extended surface of the sample and the minimum scattering angle orbit. The field emission type slow electron diffractometer according to claim 1 or 2, wherein the pull-in electrode effectively takes in the scattered electrons without collision, and a clear diffraction pattern of the slow electrons can be obtained. .

According to a fourth aspect of the present invention, the scattering angle of the minimum scattering angle orbit is 20 °.
In the field emission type slow electron diffractometer according to any one of the above, the electron orbit of 20 ° is calculated as the scattering angle at the scattering position, and the pull-in electrode is included so as to include the area surrounded by the extended surface of the sample. With this arrangement, the lead-in electrode can be easily arranged at the optimum position.

The invention according to claim 5 is characterized in that the drawing electrode has a central axis coincident with the trajectory of the average scattering angle of scattered electrons generated from the sample. Since the field emission type low-speed electron diffractometer of (1), the center axis of the attracting electrode coincides with the trajectory of the average scattering angle of the scattered electrons, the attracting electrode can effectively attract the scattered electrons.

According to a fifth aspect of the present invention, there is provided the field emission type slow electron diffraction apparatus according to any one of the first to fifth aspects, wherein a potential of 0 V to +3 kV is applied to the pull-in electrode. Therefore, by adjusting, it is possible to draw in the scattered electrons without leaking. (Embodiment) Hereinafter, a field emission type slow electron diffraction apparatus according to an embodiment of the present invention will be described. FIG. 1 is a structural view of a field emission type slow electron diffraction apparatus according to an embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes a probe which is sharpened and emits field emission electrons by a tunnel effect. 2 is provided with a probe 1 at the tip of a piezo element which expands and contracts by a control current,
This is a probe control device for controlling the distance between the probe and the sample so that a predetermined field emission current selected from the range of 1 pA to 10 nA flows. 3 is a sample to be measured for detecting the atomic structure of the surface, 4 is a sample holder on which the sample 3 can be exchangeably mounted, 5 is an inchworm which supports the sample holder 4 and can fine-tune the plane position, 6 is a sample holder Reference numeral 4 denotes a support table for supporting the probe control device 2, and reference numeral 7 denotes an anti-vibration spring for holding the support table 6 and preventing noise due to vibration. In the present embodiment, the probe control device 2, the sample 3, the sample holder 4, and the inch worm 5 provided on the support base 6 constitute an electron emitting portion for obtaining scattered electrons. Spring 7
Absorbs the vibration of the electron emitting portion. Numeral 8 applies a predetermined voltage described later between the probe 1 and the sample 3 (however, in this embodiment, the probe 1 is set to a ground potential), and further applies the voltage to the probe controller 2 and the inchworm 5 and the like. A power supply unit 9 for applying a predetermined potential, a control unit 9 including a computer or the like for controlling the probe control device 2 and the inchworm 5 and the like by controlling the power supply unit 8 to convert it to a predetermined potential and apply the same. It is.

The probe 1 is a small conical needle formed at the tip of the needle body, and is formed by electrolytic polishing. In the case of low speed and low potential as in this embodiment, when the opening angle of the tip of the probe 1 exceeds 10 °, the potential for attracting scattered electrons to the sample side protrudes greatly, and the scattered electrons collide with the sample side. Therefore, it is desirable to take a value smaller than 10 ° as much as possible. At this time, together with applying a predetermined voltage between the probe 1 and the sample 3, the diameter of the electron beam irradiation region on the surface of the sample 3 is several angstrom to several hundred nm.
(Nm level), and the electron beam irradiation area can be reliably reduced to a minimum area smaller than 1 μm ² .
When a high voltage is applied, a large angle can be selected as a general tendency. However, since the diameter of the electron beam irradiation area is increased and the resolution is reduced, the angle is preferably as small as 10 °.
It is desirable to take a smaller value. Moreover, at this time, the smaller the radius of curvature of the tip of the probe 1, the smaller the irradiation area.

The control unit 9 controls the power supply unit 8 so that practically 0 V to 150 V, at least 10 V to 1 V, is applied between the probe 1 and the sample 3.
A voltage of 00 V is applied, and at this time, the probe control device 2 is controlled so that the electric field emission current flowing between the probe 1 and the sample 3 becomes a predetermined value within 1 pA to 10 nA. The control unit 9 and the probe control device 2 control the voltage and the electric field emission current to be within predetermined ranges within this range, so that the distance between the probe and the sample is controlled to a suitable position for narrowing the electron beam irradiation area. Is done.

Next, 10 is a drawing electrode for drawing scattered electrons generated from the sample 3 and forming a beam, and 11 is provided behind the drawing electrode 10 to disperse the electron beam of scattered electrons e to an appropriate size. The electron lens 12 is applied with a blocking potential of 0 V to +100 V to the probe 1 in order to prevent low-speed inelastic scattered electrons from passing through the scattered electrons e dispersed by the electron lens 11. Three or four grid electrodes, 13 is a multi-channel plate for amplifying elastic scattered electrons passing through the grid electrode 12, 14 is a fluorescent screen for generating a diffraction pattern of the elastic scattered electrons amplified by the multi-channel plate 13, Reference numeral 15 includes a pull-in electrode 10, an electron lens 11, a grid electrode 12, a multi-channel plate 13, and a fluorescent screen 14. A moving mechanism that can move as a whole child detector.

In the present embodiment, the lead-in electrode 10 is
It is a cylindrical electrode having a conical cylindrical portion having an opening with a diameter of 6 mm formed on the entrance side.
9 applies a potential of 0 V to +3 kV. This opening includes a region surrounded by a minimum scattering angle trajectory of scattered electrons described later and an extended surface of the sample 3 so that almost all scattered electrons e can be taken in.

The electron lens 11 has a voltage of 0 V to +3 kV.
Is applied, the beam diameter of the electron beam of the scattered electrons e is adjusted, dispersed to obtain a diffraction pattern of an appropriate size, and the orbital direction is adjusted. The grid electrode 12 is 100
A # 0 (+100 mesh per inch) mesh is applied, and a potential of 0 V to +100 V is applied to the probe 1 from the power supply unit 19 for the electron detection unit. Inelastic scattered electrons below this potential are blocked. The grid electrode 12 is the inelastic scattered electron removing unit in the present invention. The multi-channel plate 13 on which the electron beam emitted from the grid electrode 12 is incident is an aggregate of a large number of channels, and a secondary electron emission surface is formed around each channel. The light is amplified while repeatedly colliding with the secondary electron emission surface, and is emitted to the fluorescent screen 14. The multi-channel plate 13 and the fluorescent screen 14 constitute a diffraction pattern detector of the present invention. Multi-channel plate 1
3, +100 V to +200 V is applied to the grid electrode 12 side, and +1 kV to +2 k to the fluorescent screen 14 side.
V is applied. Also, the fluorescent screen 14 has + 3k
V to +7 kV is applied.

Reference numeral 16 denotes a vacuum chamber having a degree of vacuum of 10 ⁻⁶ Torr or less for accommodating the above-described field emission section and electron detection section, and 1.
Reference numeral 7 denotes a viewing window through which the fluorescent screen 14 can be observed from the atmosphere side, and reference numeral 18 denotes a camera (including a video camera) for observing a diffraction pattern from the viewing window 17. The diffraction pattern generated on the fluorescent screen 14 can be observed with the naked eye in addition to being measured by the camera 18. 19 is
Attraction electrode 10, electron lens 11, grid electrode 1
2, multi-channel plate 13, fluorescent screen 1
4 is a power supply unit for an electron detection unit for applying a predetermined potential to each of them. In the present embodiment, the power supply unit 19 for the electron detection unit is provided separately from the power supply unit 8, but the power supply unit 8 may have its function.

Next, the operation and operation of the field emission type low-speed electron diffraction apparatus of the present embodiment will be described. FIG. 2 is a diagram showing the relationship between the depth (atomic layer) into which field emission electrons enter and the electron energy. FIG. 3 is a diagram showing the electric field between the probe and the sample and the field emission of the field emission type slow electron diffraction apparatus according to one embodiment of the present invention. FIG. 4 is a conceptual diagram showing the trajectory of electrons, FIG. 4 is a conceptual diagram showing the trajectory of scattered electrons exiting from between the probe and the sample of the field emission type slow electron diffractometer according to one embodiment of the present invention, and FIG. FIG. 2 is a conceptual diagram showing an energy diagram between a probe and a sample of the field emission type slow electron diffraction apparatus according to one embodiment.

When a voltage E of (work function of sample + 10 V) or more is applied to the sample 3 to the probe 1 and the distance S between the probe and the sample shown in FIG. Electrons are emitted by field emission. As shown in FIG. 5, if there is no energy exceeding the work function, no electric field is radiated from the probe 1 into the vacuum, so that the voltage must be at least higher than the work function. Most sample 3 has a work function of 3V to 6
V. And even if the electric field is emitted,
In order for scattered electrons to emerge from a region of 10 atomic layers or less on the surface of the sample, it must be equal to or more than (work function of sample + 10 V). As shown in FIG. 2, the electron energy is 10 V
In the following, the field emission electrons jump into a depth of 10 atomic layers or more, and the sensitivity to the surface decreases. On the other hand, at around 10 V, the depth jumps only to 8 to 9 atomic layers, at around 50 V, the depth becomes about 3 atomic layers, and at 85 V, it jumps again to 3 to 4 atomic layers. Therefore, several atomic layers on the surface of sample 3 (9 to 10 atomic layers or less)
It can be seen that in order to obtain the atomic arrangement and structural information of, it must be equal to or more than (work function of sample + 10 V). Therefore, in the present invention, a voltage E of (work function of sample + 10 V) or more is applied to the sample 3 to the probe 1, and electrons are emitted by field emission.

The field-emitted electrons are applied to a region having a diameter d, which is separated from the probe-sample distance S, as shown in FIG.
The probe-sample distance S increases with the applied voltage E in order to maintain the field emission current at a predetermined value when the applied voltage E is increased. Accordingly, the diameter d of the electron beam irradiation area on the surface of the sample 3 also increases. In addition to the applied voltage E, the field-emission current and the shape (for example, radius of curvature) of the probe 1 are considered to affect the probe-sample distance S and the diameter d.
Etc. However, the diameter d and the probe-sample distance S increase exponentially with the increase in the voltage E, and depend most on the voltage E. The size of E is important. Hereinafter, Table 1 shows data obtained by actually measuring the effect of the voltage E on the diameter d. The electric field emission current is 0.5 nA.

[0031]

[Table 1] Table 1 shows that when the applied voltage E exceeds about 85 V, the electron beam irradiation area becomes 1 μm ² or more.
Since the influence of the tip shape of the probe 1 and the like can be effectively used as described above, at least 85
If it is less than V, the electron beam irradiation area can be almost certainly reduced to 1 μm ² or less. Conversely, if the applied voltage E is higher than 85 V, the electron beam irradiation area becomes 1 μm ² or more, and high spatial resolution cannot be expected.

As described above, the voltage E applied between the probe and the sample is not less than (work function of sample + 10 V) and
It is appropriate to set the voltage to 85 V or less. An applied voltage E is applied within this range, and the electric field emission current detected at this time is 1 p.
The probe control unit 2 and the inchworm 5 control the probe-sample distance S by the control unit 9 so that the probe-sample distance S becomes an appropriate value within the range of A to 10 nA, so that the electron beam irradiation area is 1 μm ^2.
A field emission type low-energy electron diffraction apparatus capable of obtaining the following atomic arrangement and structural information of the minimum local region can be realized.

Next, a specific mode implemented by the field emission type low-energy electron diffraction apparatus of the present embodiment will be described below. First, when the voltage applied between the probe 1 and the sample 3 was set to 30 V, the probe-sample distance S required to obtain a field emission current of 0.5 nA was 100 nm. The state of the electric field between the probe 1 and the sample 3 at this time is as shown in FIG. As can be seen from the equipotential surface of FIG. 3, the electrons emitted from the probe 1 fly to the sample 3 as shown by the arrow, and the diameter d of the irradiation area on the surface of the sample 3 is 10 n.
m. Considering the shape of the tip of the probe 1 as described above, the irradiation area can be narrowed as the radius of curvature of the tip of the probe 1 is small. Therefore, the radius of curvature may be reduced to increase the resolution.

According to the energy diagram of the present embodiment shown in FIG. 5, the voltage applied between the probe 1 and the sample 3 is 30 V, and if the work function of the sample 3 is 5 V, the voltage applied to the surface of the sample 3 The kinetic energy of the incident electron beam is 25
eV. The number of electrons elastically scattered backward on the surface of sample 3 is 2
It has a kinetic energy of 5 eV. As described above, if there is no kinetic energy of about 10 eV in addition to the work function, it is extremely difficult for emitted electrons to jump into several atomic layers and jump out of the electric field, but if the kinetic energy is 25 eV, this can be sufficiently achieved. The calculated trajectory of the scattered electrons at this time is the trajectory of the scattered electrons in FIG. FIG. 4 shows that the scattered electrons are pulled back toward the sample 3 by the electric field between the probe and the sample. Although it depends on the shape of the probe 1 and the position of the lead-in electrode 10, if the opening angle of the probe 1 is within 10 ° and the voltage between the probe and the sample is in the range of (work function of sample + 10V) to 85V, The scattered electrons can fly out without substantially colliding with the probe 1 or the sample 3, and the trajectory of the trajectory is approximately in the range of 20 ° to 80 ° when the scattering angle at the scattering position is θ. Here, as shown in FIG. 4, the scattering angle θ is an intersection angle from the direction perpendicular to the surface of the sample to the scattering direction with 0 °.
The trajectory that protrudes from the tip 1 side in a collisionless state is the minimum scattering angle trajectory. If the scattering angle is set to 20 °, the minimum scattering angle trajectory can be easily approximated.

Next, a specific mode of the electron detection unit according to this embodiment will be described. The position of the lead-in electrode 10 is adjusted by the moving mechanism 15 so as to have a predetermined distance beside the position of the probe 1 and the sample 3. This distance is determined by the minimum scattering angle trajectory and the area surrounded by the extension of the surface of the sample 3 and the opening of the lead-in electrode 10 (6 in the present embodiment).
When the central axis of the opening is close to the trajectory of the average scattering angle of the scattered electrons generated from the axial sample (scattering angle at the center position, scattering angle around 40 °),
In addition, it is a distance that can completely include this area, and is usually 5 m
m to 10 mm. Thus, when the central axis of the aperture coincides with the trajectory of the average scattering angle, the optimal pull-in electrode 1
A position of 0 can be realized.

When the distance from the probe 1 to the pull-in electrode 10 is set to 5 mm and a potential of +500 V or more is applied to the pull-in electrode 10, drawing of the scattered electrons into the electron detecting portion is promoted, which is more reliable. The scattered electrons e introduced into the electron detector are dispersed by the electron lens 11 so that a diffraction pattern of an appropriate size is obtained. Further, a blocking potential is applied to the grid electrode 12 for removing inelastic scattered electrons so that inelastic scattered electrons cannot pass through.
The passed elastic scattered electrons are transmitted to the multi-channel plate 13.
And a diffraction pattern is generated by the fluorescent screen 14. What is necessary is just to observe this diffraction pattern through the viewing window 17. Camera 1 for recording diffraction patterns
8 (including a video camera).

Since the obtained diffraction pattern has structural information of a few atomic layers on the surface of a very small local region having a diameter of about 10 nm, the atomic arrangement of the local region can be determined by analyzing the information. Further, since the diffraction pattern indicates the periodicity of the surface of the sample 3, the scanning electron microscope image reflecting the surface periodic structure can be obtained by scanning the probe 1 in the surface parallel direction while measuring the diffraction pattern. it can.

As described above, when a voltage of (work function of sample + 10 V) to 85 V is applied as in this embodiment, emitted electrons can penetrate to a depth of several atomic layers, and at this time, the electron beam irradiation area is smaller than 1 μm ^2. It is possible to narrow down to a minimum area. Furthermore, at the same time, it is possible to give a kinetic energy sufficient to shake off the electric field by taking a trajectory in which the scattered electrons do not collide with the probe 1 or the sample 3, thereby observing a diffraction pattern having structural information of several atomic layers. become,
It is possible to realize a high-resolution field emission type low-energy electron diffraction apparatus which has been considered impossible in the past.

[0039]

As described above, according to the present invention,
By irradiating field emission electrons to a minimal local region of the sample surface, it becomes possible to detect a diffraction pattern due to back elastic scattered electrons having atomic arrangement information of several atomic layers in the region. As a result, it is possible to obtain information on the atomic arrangement in the local region of the surface, which was impossible with the conventional low-energy electron diffraction method. In addition to using slow electrons, the possibility of introducing noise is very low because the inelastic scattered electrons, which are the background, are eliminated.The diffraction pattern is clear, the acceleration voltage is low and the safety is high. .

The present invention relates to an ultra-high integration LSI.
It can be used for all technologies dealing with nanometer-sized structures, such as field-emission type, and can be used instead of current electron microscopes and scanning microscopes, or complementary to them, to obtain structural information on these surfaces A low-speed electron diffraction device can be realized.

[Brief description of the drawings]

FIG. 1 is a structural view of a field emission type slow electron diffraction apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a relationship between a depth (atomic layer) into which field emission electrons enter and electron energy.

FIG. 3 is a conceptual diagram showing an electric field between a probe and a sample and a trajectory of field emission electrons in the field emission type slow electron diffraction apparatus according to one embodiment of the present invention.

FIG. 4 is a conceptual diagram showing the trajectory of scattered electrons exiting from between the probe and the sample of the field emission type slow electron diffraction apparatus according to one embodiment of the present invention.

FIG. 5 is a conceptual diagram showing an energy diagram between a probe and a sample of the field emission type slow electron diffraction apparatus according to one embodiment of the present invention.

FIG. 6 is a conceptual diagram of a conventional low-speed electron diffraction apparatus.

FIG. 7 is a conceptual diagram of a conventional low-speed electron holography method.

FIG. 8 is a conceptual diagram of a conventional scanning secondary electron detection method.

FIG. 9 is a conceptual diagram of a conventional reflection high-energy electron diffraction method.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 probe 2 probe control device 3 sample 4 sample holder 5 inch worm 6 support base 7 anti-vibration spring 8 power supply unit 9 control unit 10 lead-in electrode 11 electron lens 12 grid electrode 13 multi-channel plate 14 fluorescent screen 15 moving mechanism 16 vacuum Vessel 17 Viewing window 18 Camera 19 Power supply for electronic detector

Claims (6)

[Claims] A sharpened probe for emitting field emission electrons; a sample holder provided opposite to the probe for mounting a sample; and a probe for field emission of the sample with respect to the probe. A power supply unit for applying a voltage, a probe control device that is mounted with the probe, and controls a distance between the probe and the sample so that a predetermined field emission current flows, and from the sample when the field emission electrons are incident. A pull-in electrode for capturing generated scattered electrons, and an inelastic scattered electron removing unit provided adjacent to the pull-in electrode, to which a predetermined blocking potential capable of blocking the passage of the inelastic scattered electrons passing through the pull-in electrode is applied. A diffraction pattern detection unit that generates a diffraction pattern by elastic scattered electrons that have passed through the inelastic scattered electron removal unit, and the electric field is applied by applying the voltage between the probe and the sample. The electron beam irradiation area on the sample surface of the emitted electrons is narrowed, and the scattered electrons are scattered from within a few atomic layers on the sample surface, and are emitted while shaking off the electric field formed between the probe and the sample. A field emission type slow electron diffraction apparatus characterized by the following. 2. The field emission type slow electron diffraction apparatus according to claim 1, wherein the tip of said probe is sharpened at an opening angle of 10 ° or less. 3. The method according to claim 1, wherein the pull-in electrode is a cylindrical electrode that can enclose a region surrounded by an extended surface of the sample and a minimum scattering angle trajectory on one side of the sample and the probe. The field emission type slow electron diffraction device according to claim 1. 4. The field emission type slow electron diffraction apparatus according to claim 1, wherein a scattering angle of the minimum scattering angle orbit is 20 °. 5. A field emission type low-speed device according to claim 1, wherein said pull-in electrode has a central axis coincident with a trajectory of an average scattering angle of scattered electrons generated from said sample. Electron diffraction device. 6. The field emission type slow electron diffraction apparatus according to claim 1, wherein a potential of 0 V to +3 kV is applied to said pull-in electrode.