阅读说明：本技术 电子射线应用装置及电子射线应用装置的电子束的射出方法 (Electron beam application device and method for emitting electron beam of electron beam application device ) 是由 西谷智博 于 2020-10-13 设计创作，主要内容包括：本发明提供一种适用于包括光电阴极的电子枪的电子射线应用装置以及该电子射线应用装置的电子束的射出方法。本发明包括电子枪部分、本体部分以及控制部的电子射线应用装置。所述电子枪部分包括光源、通过接收自光源所照射的激发光而射出电子束的光电阴极、以及阳极。所述本体部分包括用以将自所述电子枪部分照射的电子束进行聚焦的物镜。所述控制部至少用以根据自所述光电阴极射出的电子束的尺寸而控制所述物镜的聚焦强度。(The invention provides an electron beam application device suitable for an electron gun including a photocathode and an electron beam emission method of the electron beam application device. The invention relates to an electron beam application device including an electron gun part, a body part and a control part. The electron gun section includes a light source, a photocathode that emits an electron beam by receiving excitation light irradiated from the light source, and an anode. The body portion includes an objective lens to focus an electron beam irradiated from the electron gun portion. The control unit is configured to control the focus intensity of the objective lens at least in accordance with a size of the electron beam emitted from the photocathode.)

1. An electron beam applying apparatus comprising:

an electron gun portion;

a body portion; and

a control unit;

the electron gun portion includes:

a light source;

a photocathode that emits an electron beam by receiving excitation light irradiated from the light source; and

an anode;

the body portion includes:

an objective lens for focusing the electron beam irradiated from the electron gun part;

the control unit is configured to control the focus intensity of the objective lens at least in accordance with a size of the electron beam emitted from the photocathode.

2. The electron beam applying apparatus according to claim 1, wherein the control section is configured to control an intensity of the excitation light irradiated from the light source.

3. The electron beam applying apparatus according to claim 1 or 2, further comprising:

an excitation light size control section for controlling the size of excitation light irradiated from the light source to the photocathode;

the exciting light size control part is arranged between the light source and the photoelectric cathode.

4. The electron beam applying apparatus according to any one of claims 1 to 3, wherein:

the objective lens electrostatic lens;

the control part is used for controlling the voltage value flowing into the electrostatic lens.

5. The electron beam applying apparatus according to any one of claims 1 to 4, wherein:

an intermediate electrode is disposed between the photocathode and the anode;

the intermediate electrode has:

an electron beam passage hole for passing an electron beam emitted from the photocathode;

a drift space is formed in the electron beam passage hole, and the influence of an electric field can be ignored when the electric field is formed between the photocathode and the anode by applying a voltage.

6. The electron beam applying apparatus according to any one of claims 1 to 5, wherein the electron beam emitted from the photocathode does not hold a focal point between the photocathode and the objective lens.

7. The electron beam applying apparatus according to claim 5, wherein the electron beam emitted from the photocathode has a focal point between the photocathode and the objective lens.

8. The electron beam application device according to any one of claims 1 to 7, wherein the electron beam application device is selected from the group consisting of:

a free electron laser accelerator;

an electron microscope;

an electron beam holography apparatus;

an electron beam patterning device;

an electron beam diffraction device;

an electron beam inspection device;

an electron beam metal lamination molding device;

an electron beam lithography apparatus;

an electron beam machining device;

an electron beam hardening device;

an electron beam sterilization device;

an electron beam sterilization device;

a plasma generating device;

an atomic element generating device;

a rotating polarized electron beam generating device;

a cathode light emitting device; or

An inverse photon emission spectroscopy apparatus.

9. A method of emitting an electron beam of an electron beam application apparatus, wherein:

the electron ray application device comprises an electron gun part, a body part and a control part;

the electron gun portion includes:

a light source;

a photocathode that emits the electron beam by receiving excitation light irradiated from the light source; and

an anode;

the body portion includes:

an objective lens for focusing the electron beam irradiated from the electron gun part;

the injection method comprises the following steps:

an electron beam emitting step of emitting the electron beam from the photocathode by receiving the excitation light irradiated from the light source;

an electron beam advancing step of advancing the electron beam emitted in the electron beam emitting step toward the objective lens disposed in the main body portion; and

a step of focusing the electron beam reaching the body portion by the electron beam proceeding step with the objective lens;

in the electron beam advancing step, the electron beam emitted from the photocathode is advanced in a state of not being focused before reaching the objective lens.

10. The ejection method of claim 9, wherein:

in the electron beam focusing step, the control section controls a focusing intensity of the objective lens in order to control a degree of focusing of the electron beam.

11. The ejection method according to claim 9 or 10, wherein:

the electron beam emitting step includes an excitation light intensity control step of controlling the intensity of the excitation light irradiated from the light source by the control unit.

12. The ejection method according to any one of claims 9 to 11, wherein:

an excitation light size control unit configured between the light source and the photocathode, the excitation light size control unit being configured to control a size of excitation light irradiated from the light source to the photocathode;

before the electron beam emitting step, the control section performs an electron beam size control step of controlling a size of the electron beam irradiated from the photocathode by the excitation light size control means.

13. The ejection method according to any one of claims 9 to 12, wherein:

an intermediate electrode is disposed between the photocathode and the anode;

in the electron beam advancing step, the control section controls the intermediate electrode in such a manner that the electron beam emitted from the photocathode:

traveling between the photocathode and the objective lens without holding a focal point; or

The lens is moved between the photocathode and the objective lens with a focal point.

Technical Field

The present invention relates to an electron beam application device and an electron beam emission method for the electron beam application device.

Background

An electron microscope including an electron gun and the like are known. As the type of the electron gun, a thermionic emission (thermionic emission) type, a Field Emission (FE) type, a Schottky (Schottky) type, and the like are known. However, the electron beam emitted from the electron gun has energy that is diffused. Since the electron microscope must obtain a bright image and high resolution, various measures are taken before the electron beam emitted from the electron gun is irradiated to the sample. Fig. 1 is a schematic view of an electron microscope equipped with a thermionic emission type electron gun. In the example shown in fig. 1, (1) the focusing of the electron beam irradiated from the electron gun by the condenser lens (condenser lens) is repeated, and the peripheral portion of the electron beam which becomes a cause of aberration (aberration) is removed by the aperture (aperture), and the like; (2) finally, the electron beam with improved mass is irradiated to the sample by using an objective lens to perform detection (see non-patent document 1).

In contrast, an electron gun including a photocathode (photocathode) of a different kind from the above-described one, and an electron beam application apparatus including the electron gun are known (see patent document 1). The electron gun having the photocathode mounted thereon described in patent document 1 is developed to include the photocathode by irradiating the photocathode with excitation light to emit a bright and clear electron beam.

Prior art documents

Patent document

Patent document 1: japanese patent No. 5808021.

Non-patent document

Non-patent document 1: Man-Jin Park1 et al, "Design and failure of scanning electron using a fine electron analysis for electron optical system", Journal of Mechanical Science and Technology,22(2008), p 1734-1746

Disclosure of Invention

Problems to be solved by the invention

Among the types of electron guns, the thermal electron emission type is excellent in terms of probe (probe) current amount, current stability, price, and the like, and is widely used in general-purpose SEM (scanning electron microscope), EPMA (electron probe micro analyzer), and Auger (Auger) analysis devices. Therefore, as described in non-patent document 1, the control of the electron beam in the electron beam application device equipped with the electron gun is often an example of the control in the case of using a thermionic emission type electron gun.

As described above, since an electron gun having a photocathode mounted thereon can emit a bright and clear electron beam, development has been underway in recent years. However, an electron gun having a photocathode mounted thereon is still under development, and at present, an electron gun including a photocathode is still replacing an electron gun portion of an electron beam application device. Therefore, the control of the electron beam of the electron ray application apparatus including the electron gun having the photocathode has hardly been studied at present.

After the present inventors have made extensive studies, they have newly developed:

(1) the electron beam emitted from the photocathode can obtain a more parallel electron beam than the electron beam emitted from an electron gun of a thermionic emission type or the like;

(2) the size of the electron beam emitted from the photocathode (the diameter of the electron beam) is determined according to the size of the excitation light to be irradiated;

(3) therefore, the electron beam can be focused by controlling the focusing intensity of the objective lens (objective lens) according to the size of the electron beam emitted from the photocathode; and

(4) as a result, the control of the electron beam is simplified.

The present invention relates to an electron beam application device suitable for an electron gun including a photocathode and a method of emitting an electron beam from the electron beam application device.

Means for solving the problems

The present invention relates to an electron beam application device and an electron beam emission method for the electron beam application device, which are described below.

(1) The electron beam application apparatus of the present invention includes:

an electron gun portion;

a body portion; and

a control unit;

the electron gun portion includes:

a light source;

a photocathode that emits an electron beam by receiving excitation light irradiated from a light source; and

an anode;

the body portion includes:

an objective lens for focusing the electron beam irradiated from the electron gun part;

the control unit is configured to control the focus intensity of the objective lens at least in accordance with a size of the electron beam emitted from the photocathode.

(2) The electron beam application apparatus according to the above (1), wherein the control unit controls an intensity of the excitation light irradiated from the light source.

(3) The electron beam application apparatus according to the above (1) or (2), further comprising:

an excitation light size control section for controlling the size of excitation light irradiated from the light source to the photocathode;

the exciting light size control part is arranged between the light source and the photoelectric cathode.

(4) The electron beam application apparatus according to any one of the above (1) to (3), wherein:

the objective lens electrostatic lens;

the control part is used for controlling the voltage value flowing into the electrostatic lens.

(5) The electron beam application apparatus according to any one of the above (1) to (4), wherein:

an intermediate electrode is disposed between the photocathode and the anode;

the intermediate electrode has:

an electron beam passage hole through which an electron beam emitted from the photocathode passes;

a drift space is formed in the electron beam passage hole, and the influence of an electric field can be ignored when the electric field is formed between the photocathode and the anode by applying a voltage.

(6) The electron beam application apparatus according to any one of the above (1) to (5), wherein the electron beam emitted from the photocathode does not have a focal point between the photocathode and the objective lens.

(7) The electron beam application apparatus according to (5) above, wherein the electron beam emitted from the photocathode has a focal point between the photocathode and the objective lens.

(8) The electron beam application device according to any one of the above (1) to (7), wherein the electron beam application device is selected from the group consisting of:

a free electron laser accelerator;

an electron microscope;

an electron beam holography apparatus;

an electron beam patterning device;

an electron beam diffraction device;

an electron beam inspection device;

an electron beam metal lamination molding device;

an electron beam lithography apparatus;

an electron beam machining device;

an electron beam hardening device;

an electron beam sterilization device;

an electron beam sterilization device;

a plasma generating device;

an atomic element generating device;

a rotating polarized electron beam generating device;

a cathode light emitting device; or

An inverse photon emission spectroscopy apparatus.

(9) The present invention provides an electron beam irradiation method for an electron beam application apparatus, comprising:

the electron ray application device comprises an electron gun part, a body part and a control part;

the electron gun portion includes:

a light source;

a photocathode that emits an electron beam by receiving excitation light irradiated from a light source; and

an anode;

the body portion includes:

an objective lens for focusing the electron beam irradiated from the electron gun part;

the injection method comprises the following steps:

an electron beam emitting step of emitting an electron beam from the photocathode by receiving excitation light irradiated from the light source;

an electron beam advancing step of advancing the electron beam emitted in the electron beam emitting step toward an objective lens disposed in the body portion; and

a step of focusing the electron beam reaching the body portion by the electron beam proceeding step by using the objective lens;

in the electron beam advancing step, the electron beam emitted from the photocathode is advanced in a state of not being focused before reaching the objective lens.

(10) The emission method according to the above (9), wherein in the electron beam focusing step, the control unit controls a focusing intensity of the objective lens in order to control a degree of focusing of the electron beam.

(11) The emission method according to (9) or (10) above, wherein, prior to the electron beam emission step, an excitation light intensity control step is provided in which the control unit controls an intensity of the excitation light emitted from the light source.

(12) The injection method according to any one of the above (9) to (11), wherein:

an excitation light size control unit configured between the light source and the photocathode, the excitation light size control unit being configured to control a size of excitation light irradiated from the light source to the photocathode;

before the electron beam emitting step, the control section performs an electron beam size control step of controlling a size of the electron beam irradiated from the photocathode by the excitation light size control means.

(13) The injection method according to any one of the above (9) to (12), wherein:

an intermediate electrode is disposed between the photocathode and the anode;

in the electron beam advancing step, the control section controls the intermediate electrode in such a manner that the electron beam emitted from the photocathode:

traveling between the photocathode and the objective lens without holding a focal point; or

The lens is moved between the photocathode and the objective lens with a focal point.

Effects of the invention

By the present disclosure, control of an electron beam in an electron ray application apparatus including an electron gun having a photocathode can be simplified.

Drawings

Fig. 1 is a schematic view of an electron microscope equipped with a thermionic emission type electron gun.

FIG. 2 is a schematic cross-sectional view of a Scanning Electron Microscope (SEM) device used as the electron beam application device 1A of the first embodiment.

Fig. 3 is a flowchart of a first embodiment of an injection method.

Fig. 4 is a schematic cross-sectional view of an electron beam application device 1B according to a second embodiment.

Fig. 5 is a schematic cross-sectional view of an electron beam application device 1C according to a third embodiment.

Fig. 6 is a schematic cross-sectional view of an electron beam application device 1D according to a fourth embodiment.

FIG. 7 is a schematic cross-sectional view of the cathode 3, intermediate electrode 8, anode 4 of FIG. 7A; FIG. 7B is a cross-sectional view X-X' of FIG. 7A; FIG. 7C is a cross-sectional view Y-Y' of FIG. 7A.

Fig. 8 is a schematic diagram illustrating the movement of electrons under the influence of an electric field generated between the cathode 3, the intermediate electrode 8, and the anode 4.

Fig. 9 is a schematic diagram for explaining the technical significance of the intermediate electrode 8 of the electron beam application device 1D according to the fourth embodiment.

Fig. 10 is a photograph showing the substitution of the drawing, and the left side of the broken line is a picture of the sample taken in comparative example 1, and the right side is a picture of the sample taken in example 1.

Detailed Description

Hereinafter, an electron beam application device and a method of emitting an electron beam from the electron beam application device will be described in detail with reference to the drawings. In this specification, the same or similar reference numerals are given to components having the same functions. Note that, in some cases, the same or similar reference numerals denote the same or similar components, and the redundant description thereof may be omitted.

In addition, the position, size, range, and the like of each structure shown in the drawings are not shown in practice in some cases for easy understanding. Accordingly, the disclosure in this document is not necessarily limited to the positions, sizes, ranges, etc. of the disclosure in the drawings.

(definition of orientation)

In this specification, a direction in which an electron beam emitted from a photocathode travels is defined as a Z direction. The Z direction is, for example, a vertically downward direction, but the Z direction is not limited to the vertically downward direction.

(first embodiment of the Electron Beam application apparatus 1A)

An electron beam application device 1A according to a first embodiment is described with reference to fig. 2. FIG. 2 is a schematic cross-sectional view of a case where a Scanning Electron Microscope (SEM) is used as the electron beam application device 1A of the first embodiment.

The electron beam application device 1A of the first embodiment includes an electron gun section 1A, a main body section 1b, and a control section 1 c.

The electron gun section 1a includes at least a light source 2, a photocathode 3, and an anode 4. A photocathode container 5 for containing the photocathode 3 may be optionally additionally included. And optionally additionally a first power supply 6a to generate an electric field between the photocathode 3 and the anode 4.

The body portion 1b includes at least an objective lens (objective lens) 7. Further, although fig. 2 illustrates the Scanning Coil (SC), the sample (sample) S and the detector (detector) D as an example of the electron beam application apparatus 1A, the SEM is not an essential structure but an optional additional structure essential to the SEM. When the electron beam application device 1A is used as a device other than the SEM, the structure necessary for the device may be added to the structure of the electron beam application device 1A disclosed in the present specification. Further, in the example of the SEM shown in fig. 2, the scanning coil SC is used to scan the electron beam B emitted from the photocathode 3 over the sample S. Although the drawings are omitted, the scanning coil SC is controlled by the control unit 1 c.

The light source 2 is not particularly limited as long as it can emit the electron beam B by irradiating the photocathode 3 with the excitation light L. Examples of the light source 2 include a high-output (watt level), a high-frequency (several hundred MHz), an ultra-short pulse laser (pulse laser) light source, a relatively inexpensive laser diode (laser diode), and a light-emitting diode (LED). The excitation light L to be irradiated may be either pulsed light or continuous light, and may be appropriately adjusted according to the purpose. In the example shown in fig. 2, the light source 2 is disposed outside the vacuum chamber (vacuum chamber) CB and the pumping light L is irradiated from the first surface (surface on the anode 4 side) of the photocathode 3. It can also be alternatively set as: when the photocathode substrate described later is formed of a transparent material, the light source 2 is disposed above the vacuum chamber CB, and the pumping light L is irradiated from the back surface (the surface opposite to the first surface) of the photocathode 3. The light source 2 may be disposed in the vacuum chamber CB.

The photocathode 3 emits an electron beam B upon receiving the excitation light L emitted from the light source 2. More specifically, electrons in the photocathode 3 are excited by the excitation light L, and the excited electrons are emitted from the photocathode 3. The emitted electrons form an electron beam B by an electric field formed by the anode 4 and the cathode 3. In the present specification, the description of "photocathode" and "cathode" refers to "photocathode" in the sense of emitting an electron beam and "cathode" in the sense of the opposite pole of "anode", but 3 is used for the reference symbol regardless of the "photocathode" or "cathode".

The photocathode 3 is formed of a substrate such as quartz glass or sapphire (sapphire) glass, and a photocathode film (not shown) bonded to a first surface (surface on the anode 4 side) of the substrate. The photocathode material for forming the photocathode film is not particularly limited as long as it can emit an electron beam by irradiation with excitation light, and examples thereof include materials requiring EA surface treatment (treatment for lowering electron affinity), materials not requiring EA surface treatment, and the like. Examples of the material to be surface-treated with EA include group III-V semiconductor materials and group II-VI semiconductor materials. Specifically, AlN, Ce2Te, GaN, a compound of one or more alkali metals and Sb, AlAs, GaP, GaAs, GaSb, InAs, and the like, and mixed crystals thereof are exemplified. Other examples include metals, specifically, Mg, Cu, Nb, LaB6, SeB6, Ag, and the like. The photocathode 3 can be produced by subjecting the photocathode material to EA surface treatment, and the photocathode 3 can select excitation light in a near ultraviolet-infrared light wavelength region corresponding to the gap energy (gap energy) of a semiconductor, and can also enable electron beam source performance (quantum yield), durability, monochromaticity, time reactivity, and spin polarization (spin polarization) according to the use of an electron beam by selecting the material or structure of the semiconductor.

Further, as the material not requiring EA surface treatment, for example, a metal simple substance such as Cu, Mg, Sm, Tb, and Y, an alloy, a metal compound, diamond, WBaO, Cs2Te, or the like can be given. A photocathode that does not require EA surface treatment may be produced by a known method (for example, see japanese patent No. 3537779). The entire contents of japanese patent No. 3537779 are incorporated herein by reference. As described above, the photocathode 3 is formed by bonding a photocathode film to the first surface of the substrate. Therefore, the photocathode 3 does not include a rounded tip portion like the photocathode. That is, the photocathode 3 is rejected to have a rounded leading end portion for releasing electrons.

The anode 4 is not particularly limited as long as it can form an electric field with the cathode 3, and an anode commonly used in the field of electron guns can be used.

The photocathode container 5 includes an electron beam passage hole 5h through which the electron beam B emitted from the photocathode 3 passes. Further, a surface treatment material 5m for subjecting the photocathode 3 to EA surface treatment (in other words, electron affinity reduction treatment) may be disposed in the photocathode accommodating container 5 as necessary. The surface treatment material 5m is not particularly limited as long as it can be surface-treated with EA. Examples of the surface treatment material 5m include Li, Na, K, Rb, Cs, Te, Sb, Cs2CrO4, Rb2CrO4, Na2CrO4, and K2CrO 4.

The first power supply 6a is not particularly limited in arrangement of power supplies as long as it can form an electric field between the cathode 3 and the anode 4 and emit the electron beam B emitted from the photocathode 3 toward the anode 4 by irradiation with the excitation light L. In the example shown in fig. 1, an electric field can be formed by arranging the first power source 6a so as to generate a potential difference between the cathode 3 and the anode 4.

The objective lens 7 is for focusing the electron beam B emitted from the photocathode 3. The focusing intensity of the electron beam B generated by the objective lens 7 is controlled by a control unit 1c described later. Therefore, the electron beam application apparatus 1A according to the first embodiment can control the resolution (resolution) or contrast (contrast) by the control unit 1 c. The objective lens 7 is not particularly limited as long as it can control the focusing intensity of the electron beam B. Examples thereof include electrostatic lenses (static lenses), magnetic field lenses (electromagnetic lenses), and combinations thereof. In the case of an electrostatic lens, the focusing intensity of the electron beam B can be controlled by controlling the applied voltage. In the case of a magnetic field lens, the focusing intensity of the electron beam B can be controlled by controlling the current. In this case, the convergence position of the electron beam B can be controlled by controlling the acceleration voltage of the electron beam and the physical distance from the anode 4.

In order to focus the electron beam B to a predetermined size, it is necessary to control the focusing intensity of the objective lens 7 according to the size of the electron beam B when reaching the objective lens 7. The size of the electron beam B emitted from the photocathode 3 is determined according to the size of the excitation light L irradiated to the photocathode 3. Then, the divergence of the electron beam B emitted from the photocathode 3 is very small compared to the electron beam B emitted from the electron gun of the related art. In other words, the electron beam B, which is not easily diverged and has directivity, is emitted.

Therefore, if the resolution and the contrast of the following items are measured under various changes and the same conditions are used, the reproducibility is high.

(1) Initial emission (emittance) of the electron beam at the cathode 3;

(2) the size of the excitation light L;

(3) voltage, distance and electric field distribution between the cathode 3 and the anode 4;

(4) the distance of the anode 4 from the objective lens 7;

(5) the focusing intensity of the objective lens 7.

The control unit 1c has a memory (memory), and stores the actual measurement data (data) in the memory, thereby calculating the focusing intensity of the objective lens 7 necessary for the focused electron beam B to have a predetermined size based on information such as the initial emission of the electron beam at the cathode 3, the size of the excitation light L, the voltage, distance, and electric field distribution between the cathode 3 and the anode 4, and the distance between the anode 4 and the objective lens 7, and controlling the objective lens 7.

The above example illustrates an example of the control unit 1c, and the control unit 1c may control the objective lens 7 by another method as long as the electron beam B can be focused so as to have a predetermined size. For example, if at least one of the above (1) to (4) is a fixed value, the data relating to the fixed value may not be included in the memory. Although the above example illustrates the example of referring to the actual measurement data, a correlation equation (correlation equation) may be created from the actual measurement data, and the focus intensity of the objective lens 7 may be calculated from the correlation equation.

Alternatively, the movement of electrons can be simulated (simulation) using the conditions (1) to (4). Therefore, the focusing intensity of the objective lens 7 can also be calculated by simulation instead of the actual measurement value.

Next, the control unit 1c controls the drive source 71 based on the calculated focus intensity, and controls the current value, the voltage value, and the like applied to the objective lens 7, thereby controlling the focus intensity of the objective lens 7. As the drive source 71, a general dc stabilization power source may be used. In the case of using a permanent magnet as the objective lens 7, the control unit 1c may control the acceleration voltage of the electron beam B or the distance between the sample S and the objective lens 7. More specifically, in the example shown in fig. 2, the electric field intensity between the cathode 3 and the anode 4 may be controlled by controlling the voltage value applied to the cathode 3 from the first power supply 6 a. When the distance between the sample S and the objective lens 7 is controlled, a stage (not shown) capable of moving the sample S and/or the objective lens 7 in the Z-axis direction may be provided, and the stage may be controlled by the controller 1 c. The control of the table may be performed by, for example, controlling the drive source 71 to control the current flowing to the motor included in the table.

(first embodiment of the method for emitting an electron beam from an electron beam application apparatus)

A first embodiment of an electron beam emission method (hereinafter, simply referred to as "emission method") of an electron beam application apparatus will be described with reference to fig. 2 and 3. Fig. 3 is a flowchart of a first embodiment of an injection method.

In the first step (ST1), an electron beam emitting step is performed. In the electron beam emission step (ST1), as shown in fig. 2, excitation light L is irradiated from the light source 2 toward the photocathode 3, and an electron beam B is emitted from the photocathode 3.

In the second step (ST2), an electron beam advancing step is performed. In the electron beam advancing step (ST2), the electron beam B emitted from the photocathode 3 advances toward the objective lens 7 disposed in the body portion by an electric field formed between the cathode 3 and the anode 4. In the emission method of the first embodiment, in the electron beam advancing step (ST2), in other words, the electron beam B emitted from the photocathode 3 advances without being focused before reaching the objective lens 7. In the present specification, the term "focal point" means a point at which the beam diameter of the electron beam B is widened again after the beam diameter of the electron beam B is squeezed.

In the electron beam application apparatus of the prior art, the electron beam B emitted from the electron gun is designed on the premise of easy divergence. More specifically, the body portion of the electron beam application apparatus must repeatedly squeeze the arriving electron beam, which is easily diverged, with the condenser lens, remove poor quality electrons and the like at the peripheral portion of the electron beam, and finally use the objective lens to control the resolution or contrast. In contrast, in the first embodiment, a member for cutting out (cut) a condenser lens or a diaphragm around the electron beam is not required. Therefore, the electron beam B emitted from the photocathode 3 does not have a focal point while traveling between the photocathode 3 and the objective lens 7. The electron beam application device 1A of the first embodiment, in other words, the electron beam application device including no member for focusing an electron beam other than the objective lens in the body portion 1b can be said.

In the third step (ST3), an electron beam focusing step is performed. In the electron beam focusing step (ST3), the electron beam B reaching the body portion 1B by the electron beam advancing step (ST2) is focused by the objective lens 7. To what extent the electron beam B is focused, the focusing intensity of the objective lens 7 may be controlled.

The related art electron beam applying apparatus performs control of the electron beam for resolution or contrast control using the electron beam after reaching the body portion due to the following factors.

(1) The electron beam emitted from the electron gun is designed on the premise of divergence;

(2) therefore, in order to improve resolution or contrast, the electron beam with poor quality at the peripheral portion of the electron beam is cut off, and only the electron beam with good quality at the central portion is focused for use;

(3) to what extent the electron beam is focused by the condenser lens, to what extent the electron beam is cut by the aperture, to what extent the electron beam is focused by the objective lens, not individual control of the respective components but control of the whole by making the mutual components related is essential;

(4) if the control described in (3) includes control such as the size or intensity of the electron beam, the control parameters described in (3) must be recalculated in accordance with the conditions of the electron beam, which results in excessively complicated control.

In contrast, the electron beam application device 1A and the method of emitting an electron beam using the electron beam application device 1A according to the first embodiment do not require a condenser lens and an additional aperture. Therefore, the following effects can be achieved at the same time.

(a) The body portion of the electron beam application apparatus 1A can be miniaturized.

(b) Since the electron beam B emitted from the photocathode 3 is a beam of a quality better than that of the prior art, it is not necessary to cut the electron beam at the peripheral portion. Thus, since the electron beam emitted from the photocathode 3 can be used as it is, a large current with small energy dispersion can be used. Therefore, in the electron beam application apparatus 1A of the first embodiment, imaging can be obtained with high resolution, high scanning speed, and the like.

(c) Since the electron beam B emitted from the photocathode 3 is a beam of a quality better than that of the prior art, it is not necessary to cut the electron beam at the peripheral portion. Thus, since the electron beam emitted from the photocathode 3 can be used as it is, power saving can be achieved.

(d) Since the control target of the main body portion 1b controlled by the control section 1c is only the focus intensity of the objective lens 7, the control mechanism is simple. Therefore, even when the size of the excitation light L is controlled manually or the like, for example, the focus intensity of the objective lens 7 can be easily controlled by inputting (inputting) the information to the control unit 1 c.

(e) The intensity (amount of electrons) of the electron beam B emitted from the photocathode 3 depends on the intensity of the (dependent on) excitation light L, and the size (diameter) of the electron beam B depends on the size (diameter) of the excitation light L. Next, even if the intensity of the electron beam B is changed as long as the size of the electron beam B is the same, the focus intensity of the electron beam B is not changed as long as the focus intensity of the objective lens 7 is the same. Therefore, when it is determined that the electron beam application device 1A according to the first embodiment needs to control the resolution, brightness, or the like by a monitor (monitor) or the like, for example, the degree of focusing of the electron beam B is not changed even if the intensity of the light source 2 is manually controlled. Thus, in the operation (operation) of the electron beam application device 1A, the controllability of the resolution and the brightness can be improved without changing the degree of focusing (focal size) of the electron beam B.

(second embodiment of the Electron Beam application apparatus 1 and second embodiment of the emission method)

A second embodiment of the electron beam application apparatus 1 and the emission method will be described with reference to fig. 4. Fig. 4 is a schematic cross-sectional view of an electron beam application device 1B according to a second embodiment. The electron beam application device 1B is the same as the electron beam application device 1A of the first embodiment except that the control unit 1c controls the focal intensity of the objective lens 7 and also controls the light source 2. Therefore, although the second embodiment is described mainly with respect to the control of the control unit 1c, the description overlapping with the description of the first embodiment will be omitted.

In the electron beam application apparatus 1A of the first embodiment, the control of the intensity of the light source 2 is manually performed. In contrast, in the second embodiment, the control section 1c controls the intensity of the excitation light L by controlling the light source 2 in addition to the focused intensity of the objective lens 7. In the case of using the electron beam application device 1B of the second embodiment, an effect can be obtained such that the intensity control of the excitation light L can be automated, for example.

When the intensity of the electron beam B needs to be changed in the emission method using the electron beam application apparatus 1B of the second embodiment, an excitation light intensity control step of controlling the intensity of the excitation light L emitted from the light source 2 by the control unit 1c may be executed before the electron beam emission step (ST 1).

(third embodiment of the Electron Beam application apparatus 1 and third embodiment of the emission method)

A third embodiment of the electron beam application device 1 and the emission method will be described with reference to fig. 5. Fig. 5 is a schematic cross-sectional view of an electron beam application device 1C according to a third embodiment. The electron beam application device 1C is the same as the electron beam application device 1A of the first embodiment except that it further includes an excitation light size control member 21 disposed between the light source 2 and the photocathode 3 and configured to control the size of the excitation light L irradiated from the light source 2 to the photocathode 3, and the control section 1C controls the focusing intensity of the objective lens 7 and also controls the excitation light size control member 21. Therefore, although the third embodiment is mainly described with respect to the control of the excitation-light size control member 21 and the control unit 1c, descriptions overlapping with those already described in the first embodiment will be omitted.

The excitation-light size control means 21 is not particularly limited as long as the size of the excitation light L irradiated from the light source 2 and irradiated to the photocathode 3 can be changed. Examples thereof include optical lenses (optical lenses) and iris diaphragms (iris diaphragms).

As the electron beam application apparatus 1C, for example, when adjusting the size of the electron beam (probe size) on the surface of the sample S, the focal intensity of the objective lens 7 may be fixed to control the diameter of the electron beam B. In adjusting the size of the electron beam (probe size) on the surface of the sample S, when the adjustment is performed beyond the adjustment range based on the diameter of the electron beam B, it is sometimes the case that both the focusing intensity of the objective lens 7 and the diameter of the electron beam B are to be controlled. In the electron beam application device 1C according to the third embodiment, in addition to the effects achieved by the electron beam application device 1A according to the first embodiment, an effect is achieved that the focusing intensity of the objective lens 7 and the diameter of the electron beam B emitted from the photocathode 3 can be controlled in a correlated manner.

When the emission method using the electron beam application apparatus 1C of the third embodiment requires the size of the electron beam B to be changed, an electron beam size control step of controlling the size of the electron beam B emitted from the photocathode 3 by the excitation light size control unit 21 by the control unit 1C may be executed before the electron beam emission step (ST 1).

(fourth embodiment of the Electron Beam application apparatus 1 and fourth embodiment of the emission method)

A fourth embodiment of the electron beam application device 1 and the emission method will be described with reference to fig. 6 to 9. Fig. 6 is a schematic cross-sectional view of an electron beam application device 1D according to a fourth embodiment. The electron beam application device 1D is the same as the electron beam application device 1A of the first embodiment except that the intermediate electrode 8 is disposed between the photocathode 3 and the anode 4, and the second power source 6b is optionally additionally disposed. Therefore, although the fourth embodiment is described mainly with respect to the control of the intermediate electrode 8 and the control unit 1c, descriptions overlapping with those already described in the first embodiment will be omitted.

The intermediate electrode 8 is used to adjust the beam diameter of the electron beam B emitted from the photocathode 3 when the electron beam B reaches the objective lens 7.

(outline of intermediate electrode 8)

First, an outline of the intermediate electrode 8 will be described with reference to fig. 7. FIG. 7A is a schematic cross-sectional view of the cathode 3, the intermediate electrode 8, and the anode 4; FIG. 7B is a cross-sectional view X-X' of FIG. 7A; FIG. 7C is a cross-sectional view Y-Y' of FIG. 7A. In the example shown in fig. 7, the intermediate electrode 8 is formed as a hollow cylinder. The intermediate electrode 8 has an electron beam passage hole 81 formed therein through which the electron beam emitted from the photocathode 3 passes, an electron beam entrance 82 formed on the photocathode 3 side of the electron beam passage hole 81, and an electron beam exit 83 formed on the anode 4 side of the electron beam passage hole 81. By applying a voltage using the first power source 6a and the second power source 6b so as to generate a potential difference between the cathode 3 and the anode 4 and also applying a voltage to the intermediate electrode 8, as shown in fig. 7A, an electric field EF is generated between the cathode 3 and the intermediate electrode 8 and between the intermediate electrode 8 and the anode 4.

However, the range in which the generated electric field EF strongly influences the movement of the electron beam in the gap is within a sphere having a maximum cross section when the opening of the gap is circular. In other words, when the diameter of the electron beam entrance 82 shown in fig. 7B is defined as "a", the electric field EF generated is strongly influenced within a sphere having a radius of "a/2" with the center of the electron beam entrance 82 of the electron beam passage hole 81 as the center of the sphere. Similarly, when the diameter of the electron beam exit 83 shown in fig. 7C is defined as b, the electric field EF generated in a sphere having a radius b/2 of the center of the sphere, which is the center of the electron beam exit 83 of the electron beam passage hole 81, is influenced. Therefore, when the length of the electron beam passage hole 81 in the central axis direction is defined as D, in a situation where D/(a/2+ b/2) is larger than 1, a drift space 84 which is not affected by the electric field EF is formed in the electron beam passage hole 81.

As described above, when D/(a/2+ b/2) is larger than 1, the drift space 84 is formed. Although there is no particular limitation as long as D/(a/2+ b/2) is larger than 1, the drift space 84 preferably has a certain length, and may be appropriately set to, for example, 1.5 or more, 2 or more, 3 or more, 4 or more, 5 or more, or the like. In contrast, the electron beam emitted from the photocathode 3 has no particular upper limit on D/(a/2+ b/2) as long as it is within a range that allows the electron beam to pass through the electron beam passing hole 81. However, when D/(a/2+ b/2) becomes large, in other words, when the length D of the electron beam passage hole 81 is excessively long, there is a problem that the size of the electron gun section 1b becomes large. Therefore, from the viewpoint of device design, D/(a/2+ b/2) is preferably set to 1000 or less, and may be appropriately set to 500 or less, 100 or less, 50 or less, and the like as needed.

Further, in the example shown in fig. 7, although the intermediate electrode 8 has a hollow cylindrical shape and the electron beam passage hole 81 has a conical shape, the shape is not particularly limited as long as the intermediate electrode 8 has the electron beam passage hole 81 and the drift space 84 is formed. For example, the cross section of the electron beam passage hole 81 may be polygonal, and in this case, "a" and "b" may be set to the diameter of the circumscribed circle of the polygon. In this case, a line connecting the centers of the circumscribed circles may be set to be in the "central axis direction". In the case where the cross section of the electron beam passage hole 81 is an ellipse, the "a" and "b" may be set as the major axes of the ellipse. In this case, a line connecting intermediate points of the major axis may be set to be in the "central axis direction". In the example shown in fig. 7, although the electron beam entrance 82 is smaller than the electron beam exit 83, in other words, a < b is satisfied, a and b may be a ═ b or a > b. Further, in the example shown in fig. 7A, although the line segment linking the electron beam inlet 82 and the electron beam outlet 83 is a straight line in the cross-sectional view, it may be made non-straight in the cross-sectional view. For example, the electron beam passage hole 81 may be formed in a substantially barrel shape by making the length of the cross section of the center portion of the electron beam passage hole 81 (the cross section of the portion where the drift space is formed) longer than a and b. Further, although the beam diameter of the electron beam is widened in the drift space 84, it is preferable that the electron beam whose beam diameter is widened does not impinge on the wall surface of the electron beam passage hole. Therefore, the size of the cross section of the electron beam passage hole 81 may be calculated based on the adjustment range of the focal point, and the degree to which the beam diameter of the electron beam is to be widened may be determined as appropriate.

Although the intermediate electrode 8 may be disposed between the cathode 3 and the anode 4, when the position of the intermediate electrode 8 is too close to the cathode 3 or the anode 4, in other words, exceeds the discharge limit, the electron beam does not fly. Therefore, the intermediate electrode 8 may be disposed so that the distance between the cathode 3 and the anode 4 does not exceed the discharge limit.

In the example shown in fig. 7, the intermediate electrode 8 is formed as a single member, but may be a divided structure in which a plurality of members are combined as long as the electric field EF formed between the cathode 3 and the anode 4 does not enter the electron beam passage hole 81 from a portion other than the electron beam entrance 82 and the electron beam exit 83.

Next, the movement of electrons (electron beams) in the case where the intermediate electrode 8 having the drift space 84 is provided between the cathode 3 and the anode 4 will be described with reference to fig. 8 and 9. Fig. 8 is a schematic diagram illustrating the movement of electrons under the influence of an electric field generated between the cathode 3, the intermediate electrode 8, and the anode 4. Fig. 9A is a schematic cross-sectional view showing a behavior when the first electron beam B1 travels toward the objective lens 7 when the electron beam is emitted under the first condition, and fig. 9B is a schematic cross-sectional view showing a behavior when the second electron beam B2 travels toward the objective lens 7 when the electron beam is emitted under the second condition.

It is known that when an electron beam (electron) passes through an Electric Field (EF), the force is applied from the electric field based on the following principle.

Principle 1: the more outward the electron beam is from the center axis, the stronger the force applied to the electron beam.

Principle 2: the more equipotential lines the electron beam crosses per unit length, the stronger the force it is subjected to.

Principle 3: when an electron beam crosses an equipotential line, the larger the energy in the traveling direction of the electron beam, the smaller the force applied in the vertical direction (with respect to the traveling direction).

More specifically, as shown in fig. 8, an electric field EF is generated between the cathode 3 and the intermediate electrode 8, and between the intermediate electrode 8 and the anode 4 due to a potential difference. At this time, an equipotential line EL is formed in the electric field EF, and a force ELV in the normal direction is generated with respect to the equipotential line EL. That is, the electron beam (electron) is affected by the force ELV in the normal direction. Therefore, as shown in fig. 8, electrons (arrow Bc in the figure) at the center of the electron beam B receive only the force in the straight direction, but electrons (not shown) at the peripheral portion of the electron beam B receive the force spreading to the outside.

Next, the technical significance of the intermediate electrode 8 of the electron beam application device 1D according to the fourth embodiment will be described with reference to fig. 9A to 9C. Fig. 9A to 9C show the electron beam B in a state where the objective lens 7 is not caused to function. The voltage values shown in fig. 9A to 9C are examples for easy understanding, and actually differ from the voltage value applied to the intermediate electrode 8.

First, in the example shown in fig. 9A and 9B, the voltage applied to the intermediate electrode 8 is changed as a method of changing the electric field between the cathode 3 and the intermediate electrode 8 and between the intermediate electrode 8 and the anode 4 from the first condition to the second condition. In the example shown in fig. 9A and 9B, the voltage (-50kV) applied to the cathode 3 and the voltage difference applied to the anode 4(0kV) are fixed, and the voltage value applied to the intermediate electrode 8 is changed to the first condition (fig. 9A, -20kV) and the second condition (fig. 9B, -30 kV). The voltage difference between the cathode 3 and the intermediate electrode 8 becomes 30kV in FIG. 9A and 20kV in FIG. 9B. That is, the potential difference between the cathode 3 and the intermediate electrode 8 is smaller as the voltage applied to the intermediate electrode 8 is closer to the value of the voltage of the cathode 3. Next, since the density of equipotential lines between the cathode 3 and the intermediate electrode 8 decreases as the potential difference decreases, the second electron beam B2 shown in fig. 9B is more easily expanded than the first electron beam B1 shown in fig. 9A with respect to the electron beam emitted from the photocathode 3. Further, since the drift space is formed in the intermediate electrode 8, the first electron beam B1 and the second electron beam B2, which are easily expanded, are further expanded in the drift space.

In contrast, since the potential difference between the cathode 3 and the anode 4 is constant, the potential difference between the intermediate electrode 8 and the anode 4 becomes opposite to the potential difference between the cathode 3 and the intermediate electrode 8. That is, since the potential difference between the intermediate electrode 8 and the anode 4 becomes larger in fig. 9B compared to fig. 9A, the density of equipotential lines between the intermediate electrode 8 and the anode 4 also becomes larger. Further, since fig. 9B becomes larger than fig. 9A due to the beam diameter of the electron beam after leaving the drift space, the electron beam leaving the intermediate electrode 8 is easier to focus on the second electron beam B2 shown in fig. 9B than the first electron beam B1 shown in fig. 9A. That is, the larger the potential difference between the intermediate electrode 8 and the anode 4 is, the more the focal point F can be moved to the short focal point side. Therefore, the beam diameter of the electron beam B when the electron beam B reaches the objective lens 7 can be adjusted by adjusting the position of the focal point F of the electron beam B by the intermediate electrode 8. In the example shown in fig. 9A and 9B, even when the intermediate electrode 8 is used, the electron beam B does not have a focal point between the photocathode 3 and the objective lens 7, as in the first embodiment.

In contrast, fig. 9C shows an example in which by making the value of the negative voltage applied to the intermediate electrode 8 larger (-40kV) than the example shown in fig. 9B, the electron beam B3 holds the focal point F between the photocathode 3 and the objective lens 7. In the example shown in fig. 9C, the beam diameter at which the electron beam B3 widened from the focal point F reaches the objective lens 7 is controlled by controlling the position of the focal point F between the photocathode 3 and the objective lens 7. As shown in fig. 9C, in the case where the electron beam application device 1D includes the intermediate electrode 8, the focal point F may be positioned between the photocathode 3 and the objective lens 7 using the function of the intermediate electrode 8 in addition to the examples shown in fig. 9A and 9B. Further, by including the intermediate electrode 8, the number of focal points between the photocathode 3 and the objective lens 7 is 1.

The control unit 1c of the electron beam application device 1D according to the fourth embodiment controls the voltage value applied from the second power supply 6b to the intermediate electrode 8 in addition to the control of the focusing intensity of the objective lens 7, thereby controlling the position of the focal point F.

When the beam diameter of the electron beam B reaching the objective lens 7 needs to be changed, the emission method using the electron beam application device 1D according to the fourth embodiment may execute an electron beam focal point position control step of controlling the position of the focal point F of the electron beam B by controlling the voltage value applied to the intermediate electrode 8, prior to the electron beam emission step (ST 1).

The electron beam application device 1D of the fourth embodiment has the following effects by including the intermediate electrode 8 in addition to the effects achieved by the electron beam application device 1A of the first embodiment.

(1) The electron beam B emitted from the photocathode 3 travels relatively straight, but has some scalability. However, by controlling the position of the focal point using the intermediate electrode 8, the size of the electron beam B when incident on the objective lens 7 can be controlled.

(2) In order to increase the parallelism of the electron beam B emitted from the photocathode 3, it is considered that the electric field is enhanced by shortening the distance between the photocathode 3 and the anode 4. However, if the distance between the photocathode 3 and the anode 4 is shortened to increase the electric field, the electric field strength between the components inside the electron gun becomes strong, which causes a problem that the discharge becomes easy. In contrast, when the intermediate electrode 8 is used, since the size of the electron beam reaching the objective lens 7 can be controlled, the electron beam having a desired size can reach the objective lens 7 while maintaining the electric field strength in a range in which no discharge is generated.

The first to fourth embodiments described above show an example of the electron beam application device 1 and the method of emitting the electron beam of the electron beam application device disclosed in the present application, and various design changes may be made. For example, any of the embodiments selected from the first to fourth embodiments may be combined.

The electron beam application device includes a known device equipped with an electron gun. Examples of the electron beam irradiation apparatus include a free electron laser (free electron laser) accelerator, an electron microscope, an electron beam holography apparatus, an electron beam patterning apparatus, an electron beam diffraction (electron diffraction) apparatus, an electron beam inspection apparatus, an electron beam metal layer deposition modeling apparatus, an electron beam lithography apparatus, an electron beam processing apparatus, an electron beam hardening apparatus, an electron beam sterilization apparatus, a plasma generation apparatus, an atomic element generation apparatus, a spin polarization electron beam generation apparatus, a cathode luminescence (cathode luminescence; CL) apparatus, and an Inverse Photon Emission Spectroscopy (IPES) apparatus.

The embodiments disclosed in the present application will be specifically described below by way of examples, but these examples are only illustrative of the embodiments. And are not meant to limit or restrict the scope of the invention disclosed herein.

(examples)

< example 1>

[ production of Electron gun portion ]

A laser light source (iBeamSmart, manufactured by Toptica) is used as the light source 2. Photocathode 3 an InGaN (indium gallium nitride) photocathode was manufactured by a known method described in Daiki SATO et al.2016 jpn.j.appl.phys.5505fh05. NEA treatment of the photocathode surface is performed by known methods.

[ production of Electron Beam application apparatus (SEM) ]

The electron gun portion of the commercially available SEM was replaced with the fabricated electron gun portion. Further, the specification of commercially available SEM uses a cold field emission electron source (CFE) on an electron gun, and the acceleration voltage of the electron beam can be 30kV at the maximum and can be observed at 80 ten thousand times at the maximum. Further, it is designed to make the electron beam incident to the objective lens with a predetermined size by controlling the electron beam reaching the body portion by using a plurality of condensing lenses or the like. In example 1, the objective lens was modified so that the commercially available SEM condenser lens did not function, that is, the objective lens was modified to focus the electron beam incident on the body portion.

< comparative example 1>

Only the electron gun portion of the commercially available SEM was replaced with the electron gun portion that was completed, and the SEM of comparative example 1 was set in a state in which the condenser lens functioned.

Next, using the SEM prepared in example 1 and comparative example 1, the sample was photographed under the same conditions. The left side of the dotted line in fig. 10 is a picture of the sample photographed in comparative example 1, and the right side is a picture of the sample photographed in example 1. As clearly shown in fig. 10, the SEM manufactured in example 1 has more excellent resolution than comparative example 1. The SEM of the prior art carries an electron gun that emits an electron beam that diverges. Therefore, in order to obtain a good quality electron beam, it is considered that a combination of a condenser lens and an aperture is necessary. However, it has been confirmed that in the case of using an electron gun including a photocathode as an electron beam source of an electron beam application device, a combination of a condenser lens and an aperture becomes an obstacle factor in obtaining a high resolution.

Industrial applicability

When the electron beam application device and the method for emitting an electron beam of the electron beam application device disclosed in the present application are used, the control is simple, the size can be reduced, and the control of the light source can be further performed. Therefore, it is advantageous for manufacturers of electron beam application apparatuses.

(symbol description)

1,1A to 1E, an electron beam application device, 1A an electron gun portion, 1B a body portion, 1c a control portion, 2 a light source, 21 an excitation light size control means, 3 photocathode/cathode, 4 an anode, 5 a photocathode storage container, 5h an electron beam passage hole, 5m a surface treatment material, 6a first power source, 6B a second power source, 7 an objective lens, 71A drive source, 8 an intermediate electrode, 81 an electron beam passage hole, 82 an electron beam inlet, 83 an electron beam outlet, 84 a drift space, B an electron beam, D a detector, CB, EF an electric field, EL equipotential line, ELV a force in a normal direction to EL, F focus, L excitation light, S a sample, and SC a scanning coil.