JP2001143648A - Photoexcited electron beam source and apparatus for applying electron beam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high performance electron beam by placing objective lens in vacuum for photoexcited electron beam for reducing the size of light focused as well as preventing vibration. SOLUTION: An objective lens is arranged close to a photo cathode in vacuum to sufficiently narrow the light focused to the photo cathode, and to achieve an electron beam source of high performance not drifted by vibration.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoexcitation electron beam source, and more particularly to a high-brightness electron beam source suitable for an electron microscope.

[0002]

2. Description of the Related Art An example in which a conventional photocathode is applied to an SEM electron gun is disclosed in C.I. A. Sanford, Journal of Vacuum Science and Techn
ology) B, 1988, Vol. 6, 2005, page 20
There is one described on page 08.

FIG. 2 shows a schematic diagram of this. In the figure, 2
Is an electron extraction electrode, 3 is an electron beam, 4 is convergent light, 7 is a window, 10 is a vacuum vessel, 21 is a fixed photocathode, 22 is a light source device, and 23 is an atmospheric objective lens.

In this case, the photocathode 21 in a vacuum is
It is formed of a transparent substrate and a photocathode film mainly composed of GaAs adhered to the surface thereof. The so-called transmission type photocathode emits light from the transparent substrate side and emits electrons from the photocathode film side into a vacuum. I have. The condenser lens 23 is in the atmosphere, and irradiates the condensed light 4 to the photocathode 31 through the window 7 attached to the vacuum vessel 10.

Japanese Patent Application Laid-Open No. 11-509 discloses an example in which the transmission type photocathode 21 is used as an electron gun for an electron beam apparatus.
There is an electron source described in JP-A-360. In this case, a thin film of a photocathode is formed on a glass substrate, a window is provided in a vacuum chamber on the back surface of the glass substrate, a condenser lens is provided outside the window, and light is converged to about 1 μm on the photocathode,
A method of extracting electrons generated from the opposite side is employed.

[0006]

By the way, in the SEM using the photocathode as shown in FIG. 2, even if the focus of light is formed on the photocathode film 21 by the ordinary condensing lens 23, the light converges on the optical path of the convergent light. Because of the presence of the window 7, there is a problem that the interference and the shift of the optical wavefront are caused by this and the focus is blurred. Therefore, the region where electrons are generated is widened, and the electron lens cannot be used to stop down to a small focal point. As a result, there is a problem that the resolution of the SEM image is low.

On the other hand, in Japanese Patent Application Laid-Open No. 11-509360, a lens having a configuration similar to that shown in FIG. 2 and having a spherical aberration corrected for the converging lens 23 is used, and the light reaches the diffraction limit after passing through the glass window 7 and the transparent substrate of the photocathode 21. It is shown that focusing can be performed.

[0008] The limit in focusing light is determined by diffraction according to wavelength, and is determined by a factor of λ / NA. This λ
Is the wavelength of light and NA is the numerical aperture (Neumerical Apertu
re), which is determined by NA = sin θ. θ is the opening angle of the light, tan θ = r / f, r is the radius of the light beam, and f is the focal length of the lens. When the wavelength is constant, the minimum radius of the convergent light decreases as the NA increases. The maximum value of NA is 1, which is a condition of a focal length f = 0 or a lens diameter = infinity. Under practical use conditions such as an optical microscope, NA = 0.4 to 0.9. It is about.

However, as apparent from FIG. 2,
A window for introducing light into the vacuum chamber needs to have a certain thickness to withstand the atmospheric pressure, and the thickness is required as the diameter of the window increases. Therefore, in order to obtain a large NA value in order to obtain a small convergent light,
There is a problem that a large lens and a complicated optical system are required.

[0010] This causes not only problems such as an increase in manufacturing cost and an increase in the size of the device, but also problems such as an increase in vibration and positional fluctuation (drift) of the light source position. This is a factor that becomes the biggest problem when the above-mentioned electron source is used in an electron beam application device such as an electron microscope and an electron beam exposure device. When narrowing an electron beam to a fine point or expanding the electron beam from the fine point, it is necessary that the source of the electron beam, that is, the focal position of the convergent light in this case does not fluctuate. However, there is a problem that the vibration is easy due to the size and weight. In addition, there has been a problem that positional fluctuation due to thermal expansion is large.

Therefore, in the case of the conventional electron source, even if the electron source is applied to a high-resolution electron microscope, the electron beam is narrowed to a small point due to problems such as vibration of the source of the electron beam and increased convergent light. The resolution is limited due to the difficulty of the resolution. Other electron beam application devices have the same problem, and sufficient performance cannot be obtained.

A first object of the present invention is to propose a high-performance electron source which converges convergent light to a photocathode sufficiently small and has no problem of vibration or drift. A second object of the present invention is to propose a high-performance electron beam application device using a photocathode.

[0013]

According to the present invention, in order to achieve the above object, a photocathode which is a means for emitting electrons by light incidence in a vacuum, a light source device for incident excitation light, and a photocathode. In a photo-excited electron beam source comprising an extraction electrode for extracting generated electrons, between the light source and the photocathode, there is at least one optical lens or a mirror for converging the excitation light or an image forming means. At least one of the constituent lenses or mirrors is in the same vacuum layer as the photocathode.

The photocathode preferably utilizes negative electron affinity, and is made of a p-type semiconductor such as GaAs,
III such as AlAs, InP, InAs, GaP, GaN
-Group V or group IV of Si, C, Ge or the like, or a mixture thereof. The surface adsorption layer is composed of an alkali metal such as Cs or Na, or an alkali metal such as Cs or Na and oxygen, or an alkaline earth such as Ba and oxygen, or a mixture thereof.

The excitation light source device may be constituted by optical components including a semiconductor laser and a collimator lens, or
The apparatus may include a laser light source, an optical fiber, and an optical coupling device for both, and the means for converging the excitation light may include at least one lens or mirror.

The means for converging the excitation light includes a reflecting mirror on the electron emission surface side of the photocathode.
Excitation light that is incident from the lateral direction with a degree of inclination is reflected in the photocathode direction, has a focal point of the excitation light near the photocathode surface by the light condensing means, and the reflecting mirror and the light condensing means have an electron beam passing therethrough. A structure having a passage may be used.

Further, there may be a light condensing means on the back side of the photocathode as viewed from the electron emission surface, and the photocathode may have a structure comprising a thin film or a thin film supported on a transparent substrate.

Further, an electron beam application apparatus using at least one of an electron lens, a vacuum pump, an electron detector, an electron beam deflector and the like using the photoexcited electron beam source according to the present invention is constructed.

[0019]

(Embodiment 1) FIG. 1 is a schematic view of an electron source according to the present invention. The light source device 8 is mounted on the vacuum vessel 10 via a light source mounting base 13. Mounting base 13
May have a fine movement adjustment mechanism (not shown here) if necessary. Parallel light 6 generated from the light source device 8
Passes through the window 7 and the objective lens 5 to become convergent light 4, and focuses on the photocathode film 12. The photocathode 1 is formed by attaching a GaAs / AlGaAs photocathode film 12 on a transparent substrate 11 such as glass. The GaAs layer has a thickness of 1 μm or less and contains Zn as an impurity in an amount of 5 × 10 ³ per cm ^{3.
About 18} doped p-type semiconductors, C
s and oxygen are adsorbed, and the work function of the surface is 1.4 eV or less.

When the convergent light 4 is incident on the photocathode film 12, a negative electron affinity (NEA) is obtained.
Due to the affinity effect, electrons are emitted into the vacuum.
The incident light has bandgap energy (1.
Energy greater than 4 eV) is required. In this case, the condition is a wavelength of 880 nm or less. More practically, a laser diode and a lens group of 600 to 780 nm
Is optimal.

Further, electron emission can be obtained even when the surface adsorption layer of Cs and oxygen is smaller and the work function is 1.4 eV or more. In this case, an electron beam with good monochromaticity can be obtained. In such a case, when the work function (φb) of the electron emission surface becomes larger than the band gap energy (Eg) of the p-type semiconductor by 1 eV or more, the amount of emitted electrons decreases sharply. Sufficient amounts are required so as not to exceed.

The photocathode film 12 is in electrical contact with the metal cathode holder 9 and is supplied with a cathode voltage Vc of -3 kV. The opposing extraction electrode 2 is at 0 V, and the emitted electrons are accelerated by the electric field generated by the two, and an electron beam 3 is obtained. This electron beam has an energy width of 0.3 to
It is a single color of 0.08 eV. Further, since the wide-angle of the electron beam is narrow and 1 mrad or less, the brightness is high.

In this embodiment, the objective lens 5 is provided with the transparent substrate 1
1 (1.2 mm), spherical aberration corrected, NA =
0.45 to 0.55 is used. Therefore, the focus of the excitation light is on the order of 1 μm, and the current is 1 μA.
In this case, the luminance is extremely high, about 10 ⁸ A / sr / cm ^2, and a value equivalent to that of a field emission electron source can be obtained. The thickness of the transparent substrate 11 can be adjusted from 1 mm to 1.5 mm without significant deterioration by adjusting the lens position.

FIG. 3A shows an example of the configuration of the light source device section 8. The light source includes a laser diode 30, a collimator lens 31, and an anamorphic prism pair 33, and the light output is controlled by an electronic circuit (not shown). In this embodiment, since the optical system can be configured to be extremely compact and lightweight, there is an advantage that disturbance due to vibration and drift is small. This is because the objective lens in vacuum has a weight of less than 0.2 g and is lightweight and compact.

Here, since the light from the laser diode has an aspect ratio, the light 34 after passing through the collimator lens 31 is a parallel light, but has an elliptical cross section. In this state, the focal diameter at the time of convergence is different in the vertical and horizontal directions.

By adjusting not only this method but also the aspect ratio of the beam, for example, one beam shaping prism 36 may be used as shown in FIG. 3B, or a collimating prism 36 as shown in FIG. Before turning the light into light, a cylindrical lens 37 may be inserted to make the ratio of the opening angles the same.

If a strict circular cross section is not required due to the use of the electron beam, the beam shaping prism may be omitted. In this case, the structure can be simplified. Further, even if a beam shaping prism is not used, as shown in FIG. 5, the distribution characteristics can be made extremely uniform by passing through a single mode optical fiber 51 by several cm or more. This is adhered to a fiber holder 52, attached to a light source tube 54 via a fine adjustment screw 53, and a circular parallel light 35 is obtained through the collimator lens 31.

The circular parallel light 35 obtained by this method is a Gaussian beam having a very uniform distribution.
The focus obtained by the objective lens is also a very accurate circle. In this case, the light source portions of the laser diode 30 and the fiber couple lens 50 are separated by an optical fiber 51. For this reason, there is an advantage that a portion requiring measures against vibration and drift is more compact and more stable.

When this optical fiber is used, the degree of freedom of the light source is increased. For example, unique characteristics other than a semiconductor laser such as a gas laser or a YAG laser, such as short wavelength light, ultraviolet light, high output light, and pulse light There is a feature that a light source such as circularly polarized light can be used. In the case of short wavelength light, further miniaturization of the focus can be expected. In the case of circularly polarized light, a spin-polarized electron beam is obtained. In the case of pulsed light, a pulsed electron beam is obtained. If light is introduced into a vacuum using an optical fiber, the window 7 can be omitted. In this case, there is an advantage that only one condenser lens is required instead of the collimator lens and the objective lens.

FIG. 4 shows an example of a mechanism for finely adjusting the focal position of light for higher performance. Objective lens 5 is holder 13
Is suspended from the vacuum flange 44, and the vacuum flange 44 is connected to the vacuum vessel 10 via the bellows 41 with a degree of freedom in position. The position of the flange 44 is adjusted by the position fine adjustment mechanism 45.

The position fine adjustment mechanism 45 is most simply constituted by a pair of cylindrical male and female screws, and rotates one of the screws.
By fixing the other end to the flange 44, the height can be adjusted. The movable width in the height direction may be about ± 0.1 mm, and the accuracy is about 10 to 3 μm. It is most desirable to determine the optimum position by measuring the electron beam 3. However, if it is difficult depending on the applied device, a beam splitter 46 is inserted in the optical path of the parallel light 6 as shown in FIG.
What is necessary is just to look at the reflected light 43 from 2.

The reflected light 43 is a parallel light having the same shape as the incident light 6 only when the position of incidence on the photocathode film 12 is completely at the minimum radius of the convergent light 4. If this is confirmed using the CCD camera 42 or the like, the optimum position can be adjusted. Instead of using a CCD camera, more simply, a photodetector or the like may be used to take the maximum value of the reflected light power. Further, if the position fine adjustment mechanism 45 is provided with an angle fine adjustment mechanism using a fine adjustment screw or the like, the positioning can be performed with higher accuracy.

If the position fine adjustment mechanism 45 is provided with a fine movement mechanism in a direction perpendicular to the optical axis, it can be used for adjusting the axis of the electron beam. When the accuracy at the time of assembling is high, the reflected light intensity returning to the laser light source may be checked without using a beam splitter. This may be done by looking at the response when the return light enters the semiconductor laser, or by looking at the signal of a photodetector located on the side opposite to the laser emission surface.

In this embodiment, the energy of the electron beam is 3
Although the voltage is set to kV, this voltage gives a desired energy of the electron beam, and may be any value as long as the withstand voltage of the electric wirings permits.

In this embodiment, G is used as the photocathode film.
Although aAs was used, other materials such as GaAs, AlAs, InP, InAs, GaP, and G may be used if they are p-type semiconductors.
III-V group such as aN or a mixture thereof, Si,
The same effect can be obtained by using a group IV group such as C and Ge or a mixture thereof.

Although Cs and oxygen are used as the surface adsorption layer, any material may be used as long as the work function is reduced to about the band gap energy of the p-type semiconductor, and only an alkali metal such as Cs and Na, or Alkali metals such as Na and oxygen, or alkaline earths such as Ba and oxygen, or a mixture thereof have the same effect. Note that when diamond, which is a single crystal of carbon, is used, it can be used without a surface adsorption layer. In this case, ultraviolet light is required as excitation light. The transparent substrate 11 is not always necessary for a high strength film such as Si.

In this embodiment, N is used as the photocathode.
Although an EA photocathode was used, other photoelectric films, for example,
A metal plate or film of gold, Ta, etc., a film of chalcogen or the like, or a film having a work function reduced by providing a surface adsorption layer thereon,
When irradiated with light having an energy higher than the work function, electrons are emitted. Therefore, the present invention is useful as a fine electron source.

Further, in this embodiment, a transmission type photocathode in which the light incident direction and the electron emission direction coincide with each other is used.
When the optical system as shown in FIG. 6 is used, the photocathode does not need to be a thin film, and there is an advantage that a reflective photocathode can be used.

In FIG. 6A, parallel light is incident through the window 7 from the direction perpendicular to the electron emission axis, passes through the perforated 45-degree mirror 62, the perforated objective lens 60, the perforated transparent extraction electrode 61, and passes through the photocathode 1 Is focused on the electron emission surface of the substrate. This photocathode 1 has p-GaAs / Ga on the surface of a GaAs substrate.
It has an AlAs structure, and has the advantage of being easier to manufacture and lower in cost than the transmission type photocathode of FIG. As the cathode material, other materials such as Si mentioned in the above examples can be used without thinning.

Further, in this structure, since a space above the photocathode 1 is opened, a heater 64 can be provided to clean the surface of the cathode. In the case of the electron source shown in FIG. 1, the processing of cleaning the surface and forming the surface adsorption layer is performed in a place different from the electron gun. However, in the present structure, all of the processing can be performed in the electron gun chamber. There is an advantage that it can be used after processing. In this case, a transparent conductive film such as an ITO or Nesa film is required on the cathode side of the transparent extraction electrode.

In addition to this, as shown in FIG. 6B, a metal extraction electrode 2 having a hole expanded in a portion through which convergent light passes.
May be.

As an optical system, a reflecting mirror may be used as shown in FIG. In this case, there is an advantage that adjustment is not required because there is no chromatic aberration due to wavelength. In addition, since all the optical systems can be made of metal, there is no need to worry about charge-up. FIG. 7A shows a case where an off-axis parabolic mirror 70 is used. The focus of the paraboloid is on the cathode 1. FIG. 7B shows a case where a reflection objective is used. One of the two focal points F1 and F2 of the spheroidal concave mirror 72 is at the surface of the photocathode 1 and the other is at the focal point of the parabolic convex mirror 71. The light reflected by the parabolic convex mirror 71 is focused on the cathode 1 by the spheroidal concave mirror 72. In this case, it is characterized in that the value of NA can be increased to 0.5 to 0.9. Further, since there is no chromatic aberration or absorption, even a short wavelength light such as ultraviolet light can be focused, so that a sub-μm light spot can be formed. There is an advantage.

In this embodiment, the photocathode and the focusing lens and mirror are separated from each other. However, the same effect can be obtained by integrally manufacturing the photocathode if the above-mentioned required conditions are satisfied. .

(Embodiment 2) FIG. 8 shows an example in which the electron source according to the present invention is applied to a scanning electron microscope. 77 is a deflector, 7
Reference numeral 8 denotes a sample moving table, 79 denotes an observation sample, 80 denotes an electron gun according to the present invention, 81 denotes a photocathode processing chamber, 82 denotes a vacuum pump, 83 denotes a first aperture, 84 denotes a first electron lens, 85 denotes a partition, and 86 denotes a partition. Reference numeral 87 denotes a second electron lens, 88 denotes an electron detector, and 89 denotes a third electron lens.

The photocathode (not shown) activated in the photocathode processing chamber 81 is put into the electron source 80 having the configuration described in the first embodiment, and the electron beam 3 is generated by photoexcitation (not shown). The electron beam 3 has a small opening angle but a large electron source size of about 1 μm to 3 μm.
Fourth, the second electron lens 87, the third electron lens 89 and the three-stage lens are used to reduce the size from 1/700 to 1/2000 and irradiate the sample 79 with the electron beam. At 88, secondary electrons and reflected electrons from the sample 79 are detected, and an SEM image is obtained.

Since the electron source 80 requires an ultra-high vacuum, it has a dedicated vacuum pump 82, and performs two-stage differential evacuation by means of a first throttle 83 and a partition 85. Further, in the present electron gun, the generation of the electron beam is stopped by cutting off the excitation light except when necessary for the measurement, so that a blanking plate or the like is not required.

Since the electron beam according to the present invention has a narrow energy width as described above, the energy of the electron beam is several k to 1 kV.
Since the chromatic aberration can be suppressed to a small value at a low level, the resolution is high. This feature is suitable for observing samples with defects due to electrons and charge-up problems.
For example, it is suitable for inspection during a manufacturing process of an integrated circuit board.

At the same accelerating voltage as that of the conventional electron microscope, the aberration becomes smaller, so that a higher resolution can be achieved.

In this embodiment, a scanning electron microscope is taken as an example. However, since the present invention is used for a transmission electron microscope or an electron beam exposure apparatus, the same advantage can be obtained because the above-mentioned advantages can be obtained.

[0050]

As has been described with reference to the embodiments, by using the present invention, it is possible to obtain a high-performance electron source which converges convergent light to the photocathode sufficiently small and has no problem of vibration and drift. Can be Further, by using the present invention, a high-performance electron beam application device can be obtained.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an electron source according to an embodiment of the present invention.

FIG. 2 is a longitudinal sectional view of a conventional electron source.

FIG. 3 is a longitudinal sectional view showing a configuration example of a light source device section according to one embodiment of the present invention.

FIG. 4 is a longitudinal sectional view showing a configuration example of a focus position fine adjustment mechanism of excitation light in one embodiment of the present invention.

FIG. 5 is a cross-sectional view illustrating a configuration example of a light source unit according to an embodiment of the present invention.

FIG. 6 is a longitudinal sectional view showing a configuration example of a light source unit according to one embodiment of the present invention.

FIG. 7 is a longitudinal sectional view showing a configuration example of a light source device unit according to one embodiment of the present invention.

FIG. 8 is a schematic longitudinal sectional view of an electric microscope according to one embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Photo cathode, 11 ... Transparent substrate, 12 ... Photo cathode film, 2 ... Electron extraction electrode, 3 ... Electron beam, 4 ... Convergent light, 5 ... Objective lens, 6 ... Parallel light, 7 ... Window, 8 ... Light source device, 9 ... Cathode holder, 10 ... Vacuum container, 13 ... Light source mount, 21 ... Fixed photocathode, 22 ... Light source device, 2
3 ... atmosphere objective lens, 30 ... laser diode, 31
... a collimator lens, 32 ... a lens holder, 33 ... an anamorphic prism pair, 34 ... an elliptical parallel beam, 3
5: circular parallel beam, 36: beam shaping prism, 37
... Cylindrical lens, 38 ... Light source chassis, 41 ... Bellows,
42: CCD camera, 43: reflected light, 44: vacuum flange, 45: position fine adjustment mechanism, 46: beam splitter, 5
0: fiber couple lens, 51: single mode optical fiber, 52: fiber holder, 53: fine adjustment screw,
54: Light source cylinder, 60: Perforated objective lens, 61: Perforated transparent extraction electrode, 62: Perforated 45 degree mirror, 63: Anode electrode, 64: Heater, 70: Off-axis parabolic mirror,
71: rotating parabolic convex mirror, 72: spheroidal concave mirror, 77 ...
Deflector, 78: Sample moving table, 79: Observed sample, 80: Electron gun according to the present invention, 81: Photocathode processing chamber, 82:
Vacuum pump, 83 first diaphragm, 84 first electron lens,
85 ... partition wall, 86 ... second aperture, 87 ... second electron lens,
88: Electronic detector, 89: Third electronic lens.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Hiroyuki Shinada 1-280, Higashi Koigakubo, Kokubunji-shi, Tokyo Inside the Central Research Laboratory, Hitachi, Ltd. Within the measuring instruments group (72) Hideo Todokoro 882, Ma, Hitachinaka-shi, Ibaraki F-term within the measuring instruments group, Hitachi, Ltd. BA09

Claims (22)

[Claims] 1. A photo-excited electron beam source comprising a photocathode, which is a means for emitting electrons by light incidence in a vacuum, a light source device for incident excitation light, and an extraction electrode for extracting generated electrons, wherein a light source and a photocathode are provided. There is converging means or image forming means for the excitation light comprising at least one optical lens or mirror, and at least one of the lenses or mirrors constituting the means has the same vacuum as the photocathode. A photoexcited electron beam source characterized by being in a layer. 2. The electron beam source according to claim 1, wherein the electron emission surface of the photocathode has a p-type semiconductor or a surface adsorption layer of one molecular layer or less on the surface of the p-type semiconductor, and the energy of the excitation light is the p-type semiconductor. The band-gap energy (Eg) of the p-type semiconductor or more, and the surface adsorption layer is selected under the condition that the work function (φb) of the electron emission surface does not exceed the bandgap energy (Eg) of the p-type semiconductor by 1 eV or more. Characterized photoexcited electron beam source. 3. The electron beam source according to claim 2, wherein said p-type semiconductor is GaAs, AlAs, InP, InAs,
A photoexcited electron beam source comprising a group III-V material such as GaP or GaN, or a mixture thereof. 4. The electron beam source according to claim 2, wherein said p-type semiconductor is made of a group IV material such as Si, C, Ge, or a mixture thereof. 5. The electron beam source according to claim 2, wherein said surface adsorption layer is made of an alkali metal such as Cs, Na or the like.
A photoexcited electron beam source comprising an alkali metal such as s and Na and oxygen, or an alkaline earth such as Ba and oxygen, or a mixture thereof. 6. The electron beam source according to claim 1, further comprising a photocathode surface activation processing means comprising a photocathode surface cleaning means using a heater or the like and a surface adsorption layer forming means. Photoexcited electron beam source. 7. An electron beam source according to claim 1, wherein said excitation light source device is constituted by an optical component including a semiconductor laser and a collimator lens. 8. An electron beam source according to claim 7, wherein said light source device is fixed to a window of a vacuum chamber via a table or a table having a position adjusting mechanism. . 9. The photoexcited electron beam source according to claim 7, wherein said light source device has a beam shaping means for making an elliptical beam from the semiconductor laser closer to a circle. 10. An electron beam source according to claim 9, wherein said beam shaping means comprises one or two prisms. 11. The electron beam source according to claim 1, wherein the light source device includes a laser light source, an optical fiber, and an optical coupling device for both, and the means for converging the excitation light includes at least one lens or mirror. A photoexcited electron beam source, comprising: 12. A photo-excited electron beam source according to claim 1, further comprising means for supplying Cs to an electron emission surface. 13. An electron beam source according to claim 1, further comprising a reflecting mirror and a condensing means on the electron emission surface side of said photocathode, wherein said reflecting mirror has a tilt of 45 ° ± 5 °. Exciting light incident from the lateral direction is reflected in the photocathode direction, the light condensing means has a focal point of the excitation light near the photocathode surface, and the reflecting mirror and the light condensing means have a passage for electron beam passage. A photoexcitation electron beam source characterized by the above-mentioned. 14. The electron beam source according to claim 13, wherein
A light-excited electron beam source, wherein the condensing means is a convex lens having a spherical aberration corrected, and a hole having a circular cross section is provided at the center of the convex lens. 15. The electron beam source according to claim 13, wherein
A photo-excited electron beam source, wherein a transparent or opaque extraction electrode is provided between the condensing means and the photocathode. 16. The electron beam source according to claim 13, wherein
A light-excited electron beam source, wherein the focusing means is an off-axis parabolic mirror or a concave mirror approximating a rotating paraboloid. 17. The electron beam source according to claim 13, wherein
The light-excited electron beam source is characterized in that the condensing means is a reflection objective comprising two kinds of mirrors: a paraboloid of revolution or a paraboloid of convex approximation thereof and a spheroid or concave spheroid of approximation thereof. . 18. An electron beam source according to claim 1, further comprising a condensing means on a back surface side of the photocathode as viewed from an electron emission surface, wherein the photocathode is supported on a thin film or a transparent substrate. A photoexcited electron beam source comprising a thin film. 19. The electron beam source according to claim 18, wherein
A photo-excited electron beam source, characterized in that the condensing means is a convex lens whose spherical aberration has been corrected so as to focus on the back surface of the photocathode thin film or on the back surface of the photocathode thin film via a transparent substrate. 20. The electron beam source according to claim 19,
The thickness of the transparent substrate of the photocathode is from 1.0 mm to 1.
A photoexcited electron beam source having a length of 5 mm, more preferably 1.0 mm to 1.2 mm. 21. An electron lens, a vacuum pump, an electron detector, and an electron beam source according to any one of claims 1 to 20.
An electron beam application device using a combination of at least one of an electron beam deflector and the like. 22. The electron beam application apparatus according to claim 21, wherein the energy of the electron beam at the time of irradiating the sample is 1 kV or less.