JP2000123716A - Micro electron source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To offer a constitution of a micro electron source using a laser emitting element capable of integration equal to that of a NEA(negative electron affinity) photo-cathode and capable of obtaining electron beams having high- brightness and a low energy dispersion characteristic, and to provide an electron beam device capable of downsizing device constitution and improving the throughput. SOLUTION: This micro electron source comprises a laser emitting element 10 constructed on a semiconductor substrate, and an electron emitting element 20 constructed on the semiconductor substrate, as a basic structure. The laser emitting element 10, as for example a planer emitting laser, etc., has a characteristic emitting a laser A from one side of the semiconductor substrate in the direction perpendicular to the principal plane of the substrate. Also, the electron emitting element 20, as for example a photo-cathode, etc., has a characteristic exciting electrons in the semiconductor substrate by excited light irradiated on one (rear) side of the substrate, and emitting the electrons (electron beam) B from the other (front) side in the perpendicular direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a micro electron source, and more particularly to a micro electron source most suitable for use in a micro electron beam apparatus.

[0002]

2. Description of the Related Art Conventionally, as an electron source applied to an electron beam apparatus, a hot cathode electron gun using a tungsten filament, lanthanum hexaboride LaB ₆ or the like, and electrons are extracted from inside a metal by applying a strong electric field. Field emission electron guns and the like are known. A hot cathode electron gun energizes a filament (such as tungsten or LaB ₆ ) and heats it to a high temperature to make it easier to emit electrons, thereby extracting electrons. A field emission electron gun uses, for example, the tip of a tungsten wire having a diameter of 0.1 mm. Since the electrode was sharpened to about 0.1 μm and a voltage of several kV or more was applied between the electrode and the counter electrode to extract electrons from the tip of the tungsten electrode, the size of the electron gun itself was several cm, and there is a problem that, when attempting to multiplex electron beams from the viewpoint of improving the throughput (production efficiency), the device configuration becomes large and the integration is difficult.

On the other hand, among field emission types, silicon field emission electron guns can be manufactured by using a semiconductor process technology, so that miniaturization is easy and two-dimensional integration with high density is possible. Application to a display or the like, and application to an electron gun such as an electron beam (EB) lithography or a scanning electron microscope (SEM) are also being studied.

In general, an electron gun applied to an electron beam apparatus is required to have characteristics of high brightness and low energy dispersion, but the above-mentioned field emission electron gun (the latter).
Since they have higher brightness and lower energy dispersion characteristics than hot cathode electron guns (the former), they have recently been used as electron sources for electron beam devices.

As an electron source applied to the above-described field emission electron gun, a negative electron affinity (NE) is used.
A: A photocathode utilizing a negative electron affinity (hereinafter referred to as a NEA photocathode) has attracted attention. As is well known, a photocathode is formed by forming a thin-film crystal on a semiconductor substrate using an epitaxial technique or the like, and emits photoelectrons by irradiating the thin-film surface with excitation light (photoelectric effect). However, it has a characteristic that the energy distribution is relatively small (the distribution range is narrow) as compared with other electron sources.

In particular, by irradiating the surface of the semiconductor thin film of the photocathode with the excitation light (laser light) in the NEA state, it is possible to extract an electron beam having high brightness and a sufficiently small energy distribution. The application to the beam device has an advantage that the irradiation spot diameter can be minimized. An electron beam apparatus employing a NEA photocathode as an electron source will be described with reference to FIG.

As shown in FIG. 10, the conventional electron beam apparatus is roughly divided into a laser beam generator 100 and an electron beam generator 200. The laser light generator 100 includes:
YAG laser 1 oscillating laser light of wavelength 10.6 μm
01, a dye (dye) laser 1 excited by a YAG laser beam and capable of continuously changing the oscillation frequency
02, a beam splitter 103 that divides the oscillated laser light into two directions, that is, an electron beam generating unit 200 and a photodiode 106, which will be described later, and a light that transmits the laser light from a laser light source to the electron beam generating unit 200. It has a fiber 104 and a focusing lens 105 for focusing beam light for irradiating the electron beam generator 200.

The electron beam generating section 200 includes a photocathode 201 for emitting an electron beam by irradiating a laser beam guided from the laser light generating section 100, a plurality of stages of electromagnetic lenses, an electromagnetic deflection coil, and the like. The electron optical system 202 and the sample 110 to be irradiated with the electron beam
Is mounted on the sample table 203. Note that a part of the laser light split by the beam splitter 103 enters the photodiode 106 and
The oscillation frequency of the laser light output from 2 is detected, and a pulse voltage having a predetermined frequency is applied to the sample 110 on the sample stage 203 by the pulse oscillator 107.

[0009]

In the above-described electron beam apparatus, the photocathode portion for emitting the electron beam and the electron optical system can be made sufficiently small and integrated, but FIG. As shown, the configuration of the laser light generating device is large, and even if a relatively small device configuration such as a semiconductor laser is used, integration is attempted to an extent corresponding to the degree of integration of the photocathode portion, and There is a problem that it is difficult to form an array.

Therefore, a multi-electron gun source using the NEA photocathode has not been sufficiently studied. An object of the present invention is to solve such a problem and to obtain an electron beam having high brightness and low energy dispersion characteristics by using a laser light emitting element which can be integrated as well as a NEA photocathode. An object of the present invention is to provide a configuration of a micro electron source capable of providing an electron beam device capable of reducing the size of the device configuration and improving the throughput.

[0011]

In order to achieve the above object, a micro electron source according to claim 1 is formed on a first semiconductor substrate, and a laser is provided in a direction perpendicular to the first semiconductor substrate. A laser light-emitting element that emits light, and an electron-emitting element that is formed on a second semiconductor substrate and emits an electron beam from the other surface by irradiating the laser light emitted from the laser light-emitting element to one surface. And the following.

According to a second aspect of the present invention, in the micro electron source according to the first aspect, the laser light emitted from the laser light emitting element is focused between the laser light emitting element and the electron emitting element. Further, an optical element for irradiation is arranged on one surface side of the electron-emitting device. According to a third aspect of the present invention, in the microelectron source according to the first or second aspect, the laser light emitting element and the electron emitting element, or the laser light emitting element and the optical element and the electron emitting element are transparent. It is characterized in that it is laminated via a substrate having optical properties.

[0013] The invention described in claim 4 is based on claim 1,
4. The microelectron source according to item 2 or 3, wherein the plurality of laser light emitting devices are two-dimensionally arranged on the first semiconductor substrate, and the two-dimensional laser beams emitted from the plurality of laser light emitting devices are emitted by the electron emission device. By irradiating one surface of the element, a two-dimensional electron beam is emitted from the other surface.

According to a fifth aspect of the present invention, in the micro electron source according to the fourth aspect, a plurality of the optical elements are two-dimensionally arranged corresponding to a two-dimensional laser beam emitted from the laser light emitting element. Then, each of the two-dimensional laser beams emitted from the plurality of laser light emitting elements is focused and irradiated on one surface side of the electron emitting element.

[0015] The invention according to claim 6 is based on claim 1,
6. The microelectron source according to 2, 3, 4 or 5, wherein the laser light emitting element is formed by laminating a laser resonator oscillating in a direction perpendicular to the first semiconductor substrate on the first semiconductor substrate. It is a surface emitting laser configured by: Further, according to a seventh aspect of the present invention, in the micro electron source according to the first, second, third, fourth or fifth aspect, the electron-emitting device is irrespective of an irradiation position of the laser beam irradiated on the one surface side. A photocathode from which a predetermined electron beam is emitted from the other surface side.

According to an eighth aspect of the present invention, in the micro electron source according to the first, second, third, fourth, or fifth aspect, the optical element is provided with an optional refraction inside a transparent substrate having a flat plate shape. A microlens is provided, which is provided with a region having a refractive index, and refracts the laser beam to irradiate the electron-emitting device with a desired focused state. In other words, the microelectron source of the present invention uses a surface emitting laser as a laser emitting device, in particular, among semiconductor laser devices that have attracted attention in recent years, stacks this surface emitting laser with a photocathode, and uses a two-dimensional surface emitting laser. The configuration is such that the electron source is miniaturized and integrated to enable emission of an electron beam having high luminance and low energy dispersion characteristics by being arranged in an array arranged in a uniform manner.

Therefore, according to the micro electron source of the present invention, the laser light emitting element and the electron emitting element are respectively formed on the semiconductor substrate, and the electron beam is emitted from the electron emitting element by the laser light emitted from the laser light emitting element. Accordingly, the configuration of each element can be easily miniaturized and integrated using a semiconductor process technology, and an electron source having high brightness and low energy dispersion characteristics can be realized, and an electron beam with improved throughput The device can be realized.

Further, by arranging an optical element between the laser light emitting element and the electron emitting element, the spot diameter of the laser beam irradiated on the electron emitting element can be narrowed, so that the laser light is emitted from the electron emitting element. The electron beam diameter can be reduced to emit an electron beam with high brightness and excellent low energy dispersion characteristics. Further, by interposing a glassy base material between the laser light emitting element and the electron emitting element, or between the laser light emitting element and the optical element, or between the optical element and the electron emitting element, each element can be accurately and easily formed. Since the layers can be stacked at a desired distance, an electron beam having excellent characteristics can be emitted.

Further, by arranging the laser light emitting elements in an array having a two-dimensional arrangement, it is possible to irradiate a plurality of laser beams to the electron emitting element, so that a plurality of electron beams can be emitted two-dimensionally. A multi-electron beam that can be realized can be realized. In addition, by arranging optical elements two-dimensionally corresponding to each of the laser light emitting elements arranged in an array, each laser beam can be narrowed to a desired spot diameter. A multi-electron beam that can be emitted two-dimensionally can be realized.

Further, by adopting a surface emitting laser, for which a manufacturing method using a semiconductor process technology is established, as a laser light emitting element, it is possible to greatly reduce the size of the device and achieve high brightness and low energy dispersion characteristics. An electron source that emits a better electron beam can be realized. Further, as the electron-emitting device, by adopting a photocathode that can emit a predetermined electron beam regardless of the irradiation position of the laser light that is the excitation light, a manufacturing method based on semiconductor process technology is established,
Since the stacked structure of the elements can be easily formed, an electron source capable of emitting a multi-electron beam having high luminance and excellent low energy dispersion characteristics can be realized.

By adopting a microlens having a flat plate shape as the optical element, a laminated structure of the elements can be easily formed, so that a multi-electron having more excellent high luminance and low energy dispersion characteristics can be obtained. A beam can be emitted. (Basic Concept) The basic concept of the microelectron source according to the present invention will be described with reference to FIG.

As shown in FIG. 1, a micro-electron source according to the present invention comprises a laser light emitting device 10 formed on a semiconductor substrate.
And an electron-emitting device 20 formed on a semiconductor substrate and emitting electrons by irradiation with excitation light. The laser light emitting device 10 applied to the present invention has a characteristic of emitting laser light A from one surface side of a semiconductor substrate in a direction perpendicular to the main surface of the substrate, such as a surface emitting laser. .

On the other hand, the electron-emitting device 2 applied to the present invention
Numeral 0 indicates that electrons in the semiconductor substrate are excited by the excitation light applied to one surface (back surface) of the substrate, such as a photocathode, and electrons (electron beams) are emitted vertically from the other surface (front surface). It has the property of releasing B. By arranging such a laser light emitting element 10 and an electron emitting element 20 in parallel at a predetermined distance as shown in FIG. 1, the laser light A emitted from the laser light emitting element 10 becomes
The electron B emitted to the back surface of the electron-emitting device 20 and excited from the surface of the electron-emitting device 20 by the irradiation of the laser beam A
Is released into a vacuum.

Here, since a manufacturing method for manufacturing the laser light emitting element 10 and the electron emitting element 20 on a semiconductor substrate by using a semiconductor process technology has been established, as described later, each element has a high In addition to being able to be integrated with high accuracy and high density, it is possible to easily stack the layers in an arbitrary arrangement. Next, a laser light emitting device and an electron emitting device applied to the present invention will be described in detail with reference to the drawings.

First, a surface emitting laser applied as a laser light emitting element will be described with reference to FIGS. FIG. 2A is a diagram showing a schematic configuration of a vertical cavity type which is a typical example of a surface emitting laser. As shown in FIG. 2A, a vertical cavity surface emitting laser 10a includes an active layer 12 which becomes a resonator in a vertical direction on one surface side (lower side in the drawing) of a semiconductor substrate 11 such as a gallium arsenide substrate GaAs. A reflection electrode 13 is formed on the semiconductor substrate 11 by lamination, and a groove 14 is formed from the other surface side (upper side of the drawing) of the semiconductor substrate 11 by chemical etching or the like. , Which are taken out in a direction perpendicular to the main surface of the semiconductor substrate 11.

Since such a surface emitting laser 10a is manufactured by using a semiconductor process technology, a plurality of laser elements (surface emitting lasers 10a) are formed on the same substrate 11 as shown in FIG. Thus, the two-dimensional laser array 10b that emits the two-dimensional laser light A 'can be easily formed. FIG. 3 shows a specific structure example of a two-dimensional laser array. FIG. 3 is a diagram of a main part of the 5 × 5 GaAlAs / GaAs laser array viewed from one surface side.

As shown in FIG. 3, the two-dimensional laser array has an n-GaAs substrate 11a on one side of an n-GaAlA substrate.
s layer 11b, p-GaAs active layer 12a, p-GaAl
As layer 11c, n-GaAs layer 11d and p-GaAs
A layered body in which a layer 11e is sequentially stacked, and a ring electrode 13a having a diameter of 10 μm is formed on the p-GaAs layer 11e in a matrix having a pitch of 20 μm, for example.
The bottom surface of a groove formed from the other surface side of the -GaAs substrate 11a, reflector 15a made of Au / Si ₃ N _4, but also,
On the other surface side of the substrate 11a, a thin film electrode 13b of Au / Ge is formed.

The surface emitting laser applied to the present invention is not limited to the one having the above-described vertical resonator structure. For example, as shown in FIGS. 4A to 4C, a so-called horizontal cavity surface emitting laser in which a laser cavity 12 is formed in a direction horizontal to the main surface of the substrate 11 can be used. . FIG. 4A is a so-called external 45-degree reflecting mirror type in which a reflecting mirror 15b is formed at an angle of approximately 45 ° with respect to the main surface of the substrate 11 so as to face the end surface of the laser resonator 12. b) forms a groove 14 at 45 ° with respect to the main surface of the substrate 11 by anisotropic etching such as RIE (reactive ion etching), and inserts the end face of the laser resonator 12 formed obliquely into an internal reflecting mirror. In FIG. 4C, a grating (diffraction grating) 1 is arranged near a part of the laser resonator 12.
This is a so-called diffraction grating type surface emitting laser in which 5d is formed and outgoing light is extracted in a direction orthogonal to the main surface of the substrate 11.

In short, the laser device applied to the laser light emitting device of the present invention may be any device that can emit laser light in a direction perpendicular to the main surface of the substrate. Next, a photocathode applied as an electron-emitting device will be described with reference to FIG. Here, a description will be given of a NEA photocathode capable of emitting an electron beam excellent in high luminance and low energy dispersion characteristics, which is optimally used for an electron beam apparatus.

FIG. 5A shows the energy band at the NEA photocathode. The energy band level of the GaAs semiconductor is obtained by forming a thin layer by adsorbing cesium oxide CsO on the GaAs semiconductor surface. Is reduced at the interface BL with the adsorbed CsO layer, and the electrons excited by the irradiation of the laser beam easily cross the potential barrier, so that the electrons easily jump into the vacuum. Here, L _V is a vacuum level, and NEA is a negative electron affinity.

FIG. 5B shows the NEA photocathode 20.
1 schematically shows the configuration of a, a semiconductor substrate 21 made of GaAs, an active layer 22 having CsO adsorbed on the upper surface of the substrate 21, and an A layer formed on the lower surface of the substrate 21.
a buffer layer 23 made of lGaAs;
It consists of an antireflection coating layer 24 on the lower surface. N
The EA photocathode 20a is a semiconductor substrate (particularly GaAs).
Since the compound surface (compound semiconductor such as s) 21 serves as a cathode surface, a predetermined electron beam is emitted even if any part of the substrate is irradiated with excitation light (laser light). Hereinafter, unless otherwise specified, the NEA photocathode
Simply referred to as a photocathode.

As described above, according to the microelectron source of the present invention, by employing the surface emitting laser and the photocathode for which the manufacturing method by the semiconductor process technology has been established, it is possible to greatly reduce the size and integration. In addition, it is possible to emit an electron beam having high brightness and excellent low-energy dispersion characteristics. Therefore, by combining the micro electron source of the present invention with the micro optical element, a high-performance micro lens barrel can be manufactured, so that it can be favorably applied to various electron beam devices.

[0033]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to embodiments. Embodiment 1 A first embodiment of a micro electron source according to the present invention will be described with reference to FIG. As shown in FIG. 6, the microelectron source of this embodiment is the above-described surface emitting laser 10.
A flat microlens 30 constituting an optical element is interposed between the photocathode a and the photocathode 20a.

The flat plate microlens 30 is formed by changing the refractive index of a partial region 32 of a flat light-transmitting substrate 31 such as plastic or glass so that the transmitted light is refracted in the direction of higher refractive index. This achieves a lens function of focusing and focusing. With such a configuration, the laser light A emitted from the surface emitting laser 10a can be converged by the flat microlens 30 and irradiated as the condensed light C having a narrowed spot diameter to the photocathode 20a. The electron beam B emitted from 20a can be made high brightness and fine.

Further, by using such a flat optical element, unlike the conventional configuration employing a spherical lens, the surface is flat, so that it has good matching with the surface emitting laser 10a and the photocathode 20a. The electron sources can be stacked, and a high-quality electron source can be provided. next,
FIG. 7 shows a second embodiment of the microelectron source according to the present invention.
This will be described with reference to FIG. Here, the same components as those in the above-described embodiment are denoted by the same reference numerals, and description thereof will be omitted.

As shown in FIG. 7, the microelectron source of this embodiment is a flat microlens array 30a in which a plurality of flat macrolens lens regions 32a are formed corresponding to the laser emitting portion of the surface emitting laser 10a. Is a surface emitting laser 1
0a and the photocathode 20a, and are stacked. That is, as shown in FIG. 8, the flat microlens array 30a is formed on the transparent substrate 31 in a matrix at a predetermined pitch.
A plurality of lenses 2a are formed, and the lens regions are formed at positions where the grooves 14a of the surface emitting laser 10a and the optical axis center coincide. In addition, between the surface emitting laser 10a and the flat microlens array 30a, and between the flat microlens array 30a and the photocathode 20a,
Light-transmitting substrates 41 and 42 such as glass are interposed,
It is laminated.

Therefore, each of the two-dimensional laser light (beam) A two-dimensionally emitted from the surface emitting laser 10a is applied to each lens area 3 of the flat microlens array 30a.
2a, the light is refracted and focused so as to become a focused light C having a predetermined spot diameter, and is irradiated on the photocathode 20a. Therefore, a fine electron beam B corresponding to the spot diameter of the laser light emitted from the photocathode 20a is formed. Released.

With such a configuration, the lens array can be flattened and laminated with the surface-emitting laser 10a and the photocathode 20a with the light-transmitting substrates 41 and 42 with good consistency. Small and integrated
A micro-electron source array having high brightness and low energy dispersion characteristics can be easily manufactured. Next, regarding an application example of the above-mentioned micro electron source array to an electron beam device,
This will be described with reference to FIG.

FIG. 9 shows an example in which the micro electron source of the present invention is applied to an SEM. In FIG. 9, reference numeral 1 denotes a microelectron source array which is mounted on the XY table 2 and adjusts the electron beam axis to a desired optical axis. Reference numeral 3 denotes an aligner for axial alignment, 4 denotes a deflector for operating an electron beam, 5 denotes an objective lens for focusing the electron beam, and 6 denotes a sample to be observed.

As described above, by employing the micro electron source of the present invention as a lens barrel, the SE of the conventional configuration shown in FIG.
Compared with M, the device scale can be reduced to several tenths or less, and excellent high luminance and low energy dispersion characteristics can be realized, so that extremely high resolution can be realized.

[0041]

As described above, according to the present invention,
By stacking a surface emitting laser and a photocathode, and forming an array of surface emitting lasers in a two-dimensional array, the electron source can be compactly integrated to produce an electron beam with high brightness and low energy dispersion characteristics. Can be released.

Therefore, it is possible to emit an electron beam having high brightness and low energy dispersion characteristics,
In addition, since it is possible to realize a micro electron source that can be miniaturized and integrated by arraying devices, it is necessary to manufacture a high-performance micro lens barrel by combining with micro optical elements such as micro lenses and micro detectors And SE
Good application to electron beam devices such as M, length measuring SEM, lithography, etc.

[Brief description of the drawings]

FIG. 1 is a basic conceptual diagram of a micro electron source according to the present invention.

FIG. 2 is a conceptual diagram of a surface emitting laser applied to a laser light emitting device according to the present invention.

FIG. 3 is a diagram showing a structural example of a two-dimensional laser array.

FIG. 4 is a conceptual diagram showing various structural examples of a surface emitting laser.

FIG. 5 is an NEA applied to the electron-emitting device according to the present invention.
It is a conceptual diagram of a photocathode.

FIG. 6 is a configuration diagram of a micro electron source according to the first embodiment of the present invention.

FIG. 7 is a configuration diagram of a microelectron source according to a second embodiment of the present invention.

FIG. 8 is a diagram showing a structural example of a flat microlens array applied to the optical element according to the present invention.

FIG. 9 is a diagram showing an application example of the micro electron source according to the present invention.

FIG. 10 is a diagram showing a schematic configuration of a conventional electron beam device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Laser light emitting element 10 10a Surface emitting laser 11 Semiconductor substrate 12 Active layer 13 Reflection electrode 14 Groove 20 Electron emission element 20a Photocathode 30 Optical element 30a Flat plate microlens array 31 Translucent substrate 32a Lens area

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5C030 CC02 CC10 5C035 CC07 CC10 5F073 AB05 AB16 AB25 AB27 BA09

Claims (8)

[Claims] A first semiconductor substrate configured to emit a laser beam in a direction perpendicular to the first semiconductor substrate; and a second semiconductor substrate configured to emit a laser beam. By irradiating the emitted laser light on one side,
An electron-emitting device that emits an electron beam from the other surface side. 2. An optical element which focuses laser light emitted from the laser light emitting element and irradiates the laser light onto one surface of the electron emitting element between the laser light emitting element and the electron emitting element. The micro electron source according to claim 1, wherein: 3. The laser light emitting device and the electron emitting device, or the laser light emitting device, the optical device, and the electron emitting device are laminated via a base material having a light transmitting property. The micro electron source according to claim 1 or 2, wherein: 4. A plurality of laser light emitting devices are two-dimensionally arranged on the first semiconductor substrate, and a two-dimensional laser beam emitted from the plurality of laser light emitting devices is directed to one surface side of the electron emitting device. By irradiating, 2
4. The micro electron source according to claim 1, wherein the micro electron source emits a two-dimensional electron beam. 5. The two-dimensional laser light emitted from the plurality of laser light-emitting elements, wherein the plurality of optical elements are two-dimensionally arranged corresponding to the two-dimensional laser beam emitted from the laser light-emitting element. 5. The microelectron source according to claim 4, wherein the electron beam is focused and irradiated on one surface side of the electron-emitting device. 6. The surface emitting laser according to claim 6, wherein the laser light emitting element is formed by laminating a laser resonator oscillating in a direction perpendicular to the first semiconductor substrate on the first semiconductor substrate. The micro electron source according to claim 1, 2, 3, 4, or 5, wherein 7. The device according to claim 1, wherein the electron-emitting device is a photocathode that emits a predetermined electron beam from the other surface regardless of the irradiation position of the laser light irradiated to the one surface. The microelectron source according to claim 1, 2, 3, 4, or 5. 8. An optical element, wherein a region having an arbitrary refractive index is provided inside a light-transmitting substrate having a flat plate shape, and the laser beam is refracted to irradiate the electron-emitting device in a desired focused state. The micro electron source according to claim 1, 2, 3, 4, or 5, which is a micro lens.