JPH03176953A - Laser excitation form high current density type electron beam generator - Google Patents

Abstract

PURPOSE: To generate an electron beam having high electric current density by covering a front face of a transparent substrate with a semitransparent film, and exaporating a photoelectron emitting material on it. CONSTITUTION: A light beam emitted from a laser 10 is controlled on its beam intensity by a modulator 11, and is deflected, and is introduced by an optical vertical train 12, and a focus is adjusted on a photoelectron emitting cathode 16 through lens 15. The cathode has a photoelectron emitting surface formed of, for example, Cs3 Sb to emit an electron when irradiated with a laser beam. A transparent substrate 40 to pass the light is arranged in the cathode 16, and a metallic coating layer 42 is deposited on one surface of the substrate 40 except for a central area 44. Next, a translucent conductive layer 46 is deposited on the layer 42 and the area 44, and lastely, a layer 48 of a photoelectron emitting material is generated in the area 44. By this constitution, a strong laser beam can be applied from a back face of the substrate 40, and high density photoelectron gas can be generated in the forward direction of the substrate 40.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Applications] The present invention has the ability to emit a high current density electron beam in response to irradiation with a laser beam of appropriate wavelength and energy, and is particularly applicable to electron beam semiconductor lithography. The present invention relates to an electron beam generator for photoelectron emission suitable as an electron source for.

BACKGROUND OF THE INVENTION As the number of devices placed on a semiconductor chip increases, lithographic apparatuses with high resolution must be developed to produce more devices on the chip.

However, optical lithography equipment operating at visible wavelengths has a resolution limit of fl, 25 microns. Electron beams have been proposed and used successfully to reduce feature sizes below this limit. Due to the short de Broglie wavelength of high-energy electrons, such devices can have submicron resolution.

Since modern phosphorography equipment has to achieve high resolution as well as high speed writing (high throughput), their electron energy beams must also have high brightness, which means that the electron beam has a high current density. This corresponds to the case where it is requested. This property is particularly important in the application of the so-called direct writing method, in which a highly complex pattern is exposed directly onto the semiconductor chip, and the electron beam is deflected and modulated at high speed. This direct writing method is in contrast to traditional projection lithography techniques, which use mask elements to define the entire pattern for simultaneous exposure of all features onto the chip.

Bright electron sources used in lithography are known.

For example, tungsten and LaBe hot cathodes, barium impregnated cathodes, and heated W10/Zr type field emitters have been used. Such field emitters reach a nominal brightness of 5 x 10'A/cm2/sr (Ampere/square centimeter/steradian).

[Problems to be Solved by the Invention] However, each of these electron sources has undesirable properties. Tungsten filaments have a high evaporation rate at operating temperatures. La5s is easily contaminated by environmental impurities, has difficulty maintaining stable bonds at operating temperatures, and forms undesirable current density lobes. Impregnated cathodes tend to evaporate at operating temperatures and are more easily rendered unusable. Additionally, heated cathode support devices are subject to thermal strain at elevated temperatures. Such distortions tend to cause compositional changes in the electron beam. Finally, field emitters can also be easily damaged, causing spot migration or flickering.
Unpredictable reprocessing is often necessary and, if heated, beam errors can be introduced as well due to geometric distortions induced by the hot support equipment. Hot cathode emitters are limited by a finite heating time, which precludes rapid density modulation of the electron source. In lithographic apparatus with hot cathodes, beam modulation on the target surface is performed electrostatically, requiring further complexity of the blanking electrodes located inside the lithographic column.

Cold cathode emitters are known as environmentally stable photoemissive cathodes such as cesium iodide and palladium. These photoelectron emitting cathodes operate in low vacuum conditions in the range of 0-4 to 1O-5) and are irradiated with ultraviolet light to provide electrons to the lithography column; It is limited to use in projection lithography because of its low energy consumption (approximately 10-50 A/cm2/sr).

Another criterion for high-resolution lithography is that the electron source has the ability to emit an electron beam that is uniform, monochromatic in nature, and has a small energy range. Monochromatic electron energy is necessary for high-resolution imaging because a narrowly divergent electron beam can be focused to form a spot of minimum size.

A first object of the present invention is to provide an electron beam generator for generating a high current density electron beam from a photoelectronic radiation source operating at low temperatures.

A second object of the present invention is that the generated electron beam is virtually monochromatic (single energy) and that the electron beam can be focused on the smallest dimensions, allowing for high resolution imaging. The object of the present invention is to provide a method for manufacturing a unique electron source.

A third object of the invention is to provide a photoemissive cathode with a spectral response compatible with existing optically monochromatic visible continuous wave (CW) lasers.

A fourth object of the invention is to provide a photoemissive surface that is easy to form and reproduce.

A fifth object of the present invention is to provide an apparatus suitable as an electron source for lithography, forming an electron beam whose intensity can be modulated by modulating a laser beam for activation, thereby allowing electron beam return. The purpose is to provide line cancellation and reduce proximity effects.

A sixth object of the invention is to provide an electron source whose emitted beam is spatially uniform and can be shaped by shaping the irradiated light beam.

[Means for Solving the Problems] A laser-excited high current density electron beam generator of the present invention comprises: a continuous wave laser; and a modulator for changing the intensity or deflecting the optical output beam of the laser. and gallium phosphide, gallium arsenide, composed of cesium antimonide or sodium potassium antimonide, or coated with cesium or cesium and oxygen, positioned to be irradiated by the output beam of the laser. , gallium arsenide phosphide, or other materials of Groups TI and V of the periodic table, which act to emit electrons when irradiated by the laser. a photoemission cathode including a translucent film that can be placed between the laser and the cathode, the film emitting electrons to form an electron image determined by a laser light pattern; an optical column of light for producing a pattern of laser light with the output beam of the laser on the back side of the photoemission cathode, the photoemission cathode further being optically transparent to the laser light; a substrate having a back surface facing the output beam side of the laser light and a front surface facing away from the output beam side of the laser light; and an optically translucent substrate coated on the front surface of the substrate. a conductive film, and a translucent film of the photoelectron emitting material is coated on the conductive film.

The device according to the invention includes a photoemission cathode operable to emit a high current density electron beam upon irradiation with a suitable laser energy, and a photoemission cathode, and
and an electron beam generator suitable for a semiconductor lithography apparatus. In addition to the photoemission cathode, the electron beam generator includes a continuous wave laser and a modulator for deflecting the laser output beam or varying its intensity;
an optical column of light (consisting of an array of electron lenses, etc., through which the electron beam passes in sequence A column of optical elements through which light rays pass sequentially is called an optical column of light or an optical train of light. In one embodiment of the present invention, a photoelectron emitting cathode for generating an electron beam in response to laser light irradiation is provided with a substrate that is optically transparent at the laser excitation wavelength and a conductive substrate that is optically translucent. A film deposited on a conductive film and a translucent film deposited on a conductive film.
A photoelectron emitting film capable of emitting photoelectrons is included. The photoemission cathode operates in a high vacuum environment and is oriented to emit electrons from the photocathode in response to back illumination with laser light. Although back-illuminated cathodes are preferred for applications such as lithography, front-illuminated cathodes formed by depositing a photoemissive film onto an opaque, electrically conductive optoelectronic substrate may also be used.

According to one embodiment of the invention, the laser is 4545-514
It is an argon ion continuous wave laser that can operate at a wavelength between . Suitable substrates for photoemission cathodes are quartz, glass, or sapphire. Translucent conductive films are formed by depositing a film of conductive material, such as chromium, onto a substrate. As an example, the photoemission film is cesium antimonide (Cs3Sb) formed by sequentially depositing antimony and cesium. Other suitable photoemissive surface films for the cathode can be formed from cesium potassium antimonide (Na2KSb), or a single crystal compound of gallium, phosphorus, and arsenic with cesium or cesium and oxygen.

[Example] Next, one example of the present invention will be described in detail with reference to the drawings.

FIG. 1 schematically shows an electron beam phosphorography apparatus employing a photoemission electron source capable of back illumination and laser excitation according to the present invention. This device has 45
4.5.457.9.465.8.472.7476,
5488.0496.5.50+, 7.514.5n
includes a laser 10 in the form of an argon ion laser operable to generate a coherent beam of light at any of m wavelengths. The strongest wavelength is 48
8.Onm and 514.5nm. Suitable lasers are available from Control Laser Company (Contr) in Aurant, Florida.
olLaser Corporation of 0r
550, available from Lando, Florida)
series of argon ion lasers.

Beam modulator 11 is placed in the optical cavity of laser 10 or at another location near the laser. The modulator 11 is an optical, electro-optical or acousto-optic device suitable for controlling or deflecting the beam intensity.

The light beam being emitted by the laser 10 is guided by a light optical column i2 comprising a plate 13 with an aperture 14 of a specified geometry, for example square. The lens 15 focuses the laser beam as an image of the aperture 14 onto a photoelectron emitting cathode 16'', which will be described in detail later. The photoemission cathode 16 and the electro-optical part for processing the electrons emitted by the cathode 16 are housed inside a vacuum chamber, which is schematically illustrated by the dashed enclosure. A high vacuum is maintained within the vacuum chamber 18 at a pressure of less than 10 -9 Torr.

Opposite the photoemission cathode 16 from the laser 10 is an anode 20 that operates to accelerate the electrons emitted from the cathode 16. Furthermore, a negative voltage was applied to Uninel (W
An electrode (not shown) is placed between the photoemission cathode 16 and the anode 20. From the anode 20, the electron beam then passes through various known electro-optic sections that shape and position the electron beam so that it is directed toward a target 21. After being accelerated by the anode 20, the electron beam passes through an electron lens 22, an electrostatic beam shaping deflector 26, and a beam shaping aperture 28. Beam shaping deflector 26 operates to change the position of the electron image of the photoelectron emitting electron source above beam forming aperture 28 to form an electron beam with variable shape and variable dimensions. The beam then passes through a reduction lens 29 and, as a result, through a beam-limiting aperture 30. The final projection lens 32 is equipped with a dynamic focusing coil 34 for focusing the beam on the target 21, and a dynamic astigmatism corrector 36 for correcting astigmatism on the beam. , and a deflection yoke 38 for scanning the beam on the target 21.

The photoelectron emitting cathode 16 is instantaneously irradiated by the laser Ic).
responds, so the electron beam intensity is modulated by modulating the laser beam intensity. Modulation of this light beam is facilitated by placing a beam modulator outside the high vacuum chamber 18. In prior art phosphorographic electron beam devices, beam modulation is performed by special blanking electrodes, which must be placed between the electron source and the target in a vacuum vessel. In the lithographic apparatus according to the invention, the manufacture and operation of the lithographic column is facilitated by substituting similar functional elements placed outside the vacuum vessel instead of any elements placed inside the vacuum vessel. The general feature is that everything can be simplified.

As explained in more detail below, photoemissive cathode 16 includes a photoemissive surface formed of, for example, cesium antimonide, Cs3Sb, which emits electrons when irradiated with argon ion laser light. FIG. 2 is a graph of the spectral response (electron current in mA per irradiation radiation IW) of various photoemissive materials as a function of irradiation wavelength. 488. At the strongest argon ion laser irradiation wavelengths of Onm and 514.5 nm, cesium antimonide has a quantum efficiency of 6% or more and is the highest sensitivity.

The combination of intense monochromatic radiation from the argon ion laser and good matching of the argon ion laser wavelength to the spectral response of cesium antimonide results in high current density radiation from this photocathode. habo52
(Other lasers operating at wavelengths below lnm would also be suitable for this application.

Other suitable photoemissive surfaces of the cathode 16 include sodium potassium antimonide (NaJ
There is Sb). Although this surface is more difficult to fabricate than Cs3Sb due to the need for a well-defined sodium to potassium ratio, this cathode is more stable because it does not require the highly volatile cesium. . NaJS
The fabrication embodiment of b is virtually similar to that described below for Cs+Sb, and the spectral responses of these two surfaces are similar, as shown in FIG. Consequently, NaJSb is also sensitive to argon ion laser radiation.

Other suitable photoemission surfaces are single crystals composed of elements from groups I and V of the periodic table, such as gallium, phosphorus, and cesium, or arsenic coated with cesium and oxygen. It can be formed by

Such a surface has a negative electron affinity, effectively increasing the electron escape depths. This property allows electrons to be emitted with a particularly low energy spread. Gallium phosphide (GaP) or gallium arsenide phosphide (Ga (AsxP + -j)) is the easiest to incorporate into photoelectron emitting surfaces for use in lithographic applications; Only cesium is needed instead of (cesium and oxygen) to convert

In one method of manufacturing these surfaces, GaP
A transparent layer of is first grown on an optically transparent substrate, and a photoemissive surface is co-grown on this layer. The electron emission can then be excited using an argon ion laser or a suitable semiconductor injection laser. The argon ion laser emits energy at a radiation wavelength near the optimum quantum efficiency for the photoelectron emitting surfaces of gallium phosphide and gallium arsenide phosphide,
This maximizes electron emission. Although injection lasers emit energy at much lower power levels, they are made to operate near the long wavelength values of these photoemissive materials, thereby minimizing the spread of the emitted electron energy. There is. The superior properties of cathodes with photoemissive surfaces composed of compounds of elements of groups III and V are offset by the increased difficulty of manufacturing such surfaces as used in transmission mode. become.

The back-illuminated photoelectron emitting cathode of the present invention and a preferred method of manufacturing the cathode will be described with reference to FIGS. 3 and 4. Referring first to FIG. 3, photoemissive cathode 16 includes a transparent, light-transmissive substrate 40, which is preferably quartz or sapphire, but may also be glass. As explained more fully with reference to FIG. 4, a thick metal coating H42 is deposited on one side of the substrate 40. Suitable materials include, for example, chromium, tungsten, and aluminium. As can be seen in FIGS. 3 and 4, the layer 42 is structured so that it does not extend into the central region 44;
The structure is formed by masking the central region 44 during the deposition of the structure. Next, a thin translucent conductive layer 46 of, for example, chromium is deposited over the metal coating 42 and the central region 44. (This semi-transparent conductive layer may not be necessary for cathodes using gallium phosphide or gallium arsenide phosphide as the photoemissive surface.) Finally, a layer 48 of photoemissive material such as cesium antimonide. is generated inside the central region 44.

Next, manufacturing of the cathode 16 will be explained with reference to FIG. First, a suitable transparent substrate 40 such as crystal, sapphire, or glass is selected. A coating of, e.g., chromium, is applied in vacuum onto selected surfaces of the substrate 40 of sufficient thickness to contact the external leait wires and to form a low resistance conductive path to the central region 44. . This coating can be done by evaporating chromium from resistance heated nichrome wire 52. masks the central region 44 of yO 102 mm2 or more to prevent a thick layer of chromium from being deposited on the central region 44. Thereafter, the mask is removed and a thin translucent conductive film 46 of chrome is deposited in vacuum over the selected side of the substrate, including the previously masked central region 44. The chromium can be supplied from a nichrome wire 52 and resistive heating is performed to deposit the chromium onto the substrate 40. Nichrome wire 52 is heated until a conductive translucent chrome layer 46 is deposited in central region 44 . The appropriate thickness for this thin translucent chrome layer is 1100 mm.
Å or less, and such a semi-transparent chromium layer 46 reduces the transmission of visible light passing through the central region 44 to about 40-50% of the visible light passing through the transparent substrate 40. A thin translucent chrome layer 46 acts as an electrical path between the thick annular metal coating 42 and the central region 44. Next, a bead of antimony 54 is fused onto the nichrome support wire 56.
Resistance heating is performed in a vacuum to deposit a thin layer of antimony onto the portion of the translucent chromium layer 46 that is within the central region 44 . Translucent chrome layer 4 outside the central region 44
The deposition of antimony on portion 6 does not affect the photoemission behavior of the device.

The thickness of the antimony film should be such that the visible light transmission across the central region 44 is reduced to about 30-40% of the visible light transmission through the transparent substrate 40. The substrate 40, which is provided with a chromium and antimony coating and placed in vacuum, is then placed in a high vacuum chamber pumped to a pressure below 2X10-9 Torr, which includes a ring tube containing a photoemissive cathode 16. This will be the relevant part of the Rafi column. Next, the substrate 40 inside the high vacuum chamber 50 is heated to flOO° C. by a nichrome heater wire 58 wrapped around the substrate 40. A cesium source channel 60 containing a mixture of cesium chromide and a reducing agent, such as silicon, is placed in the vacuum chamber 50 therewith. Channel 60 is resistively heated by electrical connection wire 62 to deposit pure cesium onto the heated antimony film in central region 44 . Deposition of cesium on the antimony or chromium layer outside the central region 44 does not affect the photoemissive behavior of the system in which this cathode is used. In this way, a thin layer of cesium antimonide or a photoemissive material [48
is generated in the central region 44. During the cesium deposition process, the photoemission cathode 16 is illuminated, for example by an argon ion laser, and the photocurrent is measured by collecting the emitted electrons using a nichrome wire 52. When the photocurrent reaches its maximum value, the current passing through the wire 62 and the nichrome heater wire 58 for heating the substrate
Current flow through is stopped to prevent further cesium from being deposited in region 44. If the photocurrent decreases during the cooling period of the substrate, additional cesium is deposited onto the cold substrate 44. If the central area 44
If the photocurrent does not return to its maximum value with additional cesium deposited on the substrate, more antimony is deposited on the substrate, followed by additional cesium, until the maximum value is reached again. let

Degradation of the Cs+Sb cathode occurs both with and without photoemission from the cathode surface due to loss of cesium or contamination of antimony by impurities. Such deterioration may occur in the central region 4, as detailed above.
It can be recovered by additionally depositing antimony and cesium onto 4.

During operation of this photoemission cathode, a laser beam from a laser, such as an argon ion laser, is emitted onto a transparent substrate 40.
The electrons pass through the cesium antimonide layer 48 and the semi-transparent chromium layer 46, and are transmitted to the cesium antimonide layer 48, causing electrons to be emitted from the cesium antimonide. The electron beam emitted from the photoemission cathode 16 has a high current density in the range of 1-100 mA/cm2. At the plane of the target, the beam current density will be several hundred amperes per cm. Values in this range 7 are suitable for direct-write phosphorography equipment, in which the electron beam is controlled to produce complex patterns on the semiconductor chip.

Such electron beams can also be used in different applications other than lithography, such as in the production of masks for projection phosphorography, or in electron beam microscopy.

In the present invention, the photoemission cathode 16 is
If back-illuminated through a semi-transparent chromium layer with ~60% optical loss, it has a quantum efficiency of more than 3% and additional cesium or By vapor deposition with antimony, it can be easily regenerated in its used state. The photoemission cathode 16 is capable of generating currents with high current densities in the range of 1 to 100 mA/cm 2 and can provide current densities of several hundred amperes per cm 2 at the target 21 . Furthermore, the energy spread of electrons is low, in the range of (2 to 3)/10ev or less. This small spread of energy is a direct result of the fact that the radiated electron loses most of its initial energy during its transition from the confined state of the valence band to the vacuum level, becoming lower in energy. It won't happen. The maximum intensity of the emitted electron energy depends on the difference between the photon energy of the laser and the threshold energy of the electron emission, which are determined by the transition of the electrons between the top of the valence band of the photoemissive material and its vacuum level. 514.5 nm (2,43 eV) argon ion laser light and 2. ○eV Cs3Sb
For the photoelectron emission threshold of , the maximum radiant energy of electrons is 0.43 eV, which therefore gives the maximum energy spread of electrons. The nominal energy spread is based on the half-width of the distribution curve plotting the number of emitted electrons versus energy, and is effectively lower than this width.

In the present invention, since the cathode operates at low temperatures, such as room temperature, support problems as in the case of hot cathodes do not arise. Furthermore, since electrons are generated instantaneously in response to laser light irradiation, no preheating time is required. Modulation of the electron beam can be easily achieved by modulating the laser beam outside the vacuum chamber 18. Furthermore, beam formation into a complex shape, that is, pattern formation, can be performed using a laser 1 placed outside the vacuum vessel 18.
This is easily accomplished by an aperture in the optical column between 0 and the photoemissive cathode 16, or by a mask.

It should be understood that modifications and improvements to the photoemissive cathode in combination with the modulated laser light source disclosed in this invention will be apparent to those skilled in the art. All such modifications and variations are intended to be included within the scope of the appended claims.

[Effect of the invention] As explained above, the present invention has the following effects.

1. In the photoelectron emitting cathode of the present invention, at least a portion of the front surface of a transparent substrate is covered with a semi-transparent film, and a photoelectron emitting material is deposited thereon, so that a strong laser beam can be irradiated from the back side of the substrate. It is possible to generate a high-density photoelectron gas in the front direction of the substrate. Since a metal coating is applied to a portion of the front surface of the substrate other than at least a portion of the substrate, this portion can be used as an electrode to generate a photocurrent with a high current density. Since the semi-transparent film is electrically conductive, the film is spatially negative to the photoelectron gas.
Provides various electric fields. As a result, a spatially uniform electron beam with high current density can be obtained.

2. By selecting a laser beam with a wavelength that approximately corresponds to the energy difference between the upper end of the valence band of the photoelectron emitting material and the vacuum level, an electron beam with a narrow energy width can be obtained. Therefore, in combination with the above-mentioned spatial characteristics of the electron beam, the present invention allows for high resolution imaging.

3. Laser light does not pass through the metal coating, so even if a photoelectron emitting material is deposited on this part, it does not participate in the generation of an electron beam. Therefore, the present invention provides a photoelectron emitting cathode whose photoelectron emitting surface can be easily formed and reproduced.

4. As mentioned above, the photoelectron emitting cathode manufactured by the method of the present invention generates a spatially-shaped electron beam, so the laser beam can be shaped by passing through an aperture of a desired shape. The electron beam can be shaped or modulated by the method, thereby providing an electron beam suitable for beam lithography according to the invention.

[Brief explanation of drawings]

FIG. 1 is a diagram schematically showing the basic parts of an electron beam phosphorography apparatus employing a photoelectron emission cathode according to the present invention;
FIG. 2 is a graph of the spectral response of various photoemissive materials as a function of irradiation wavelength; FIG. 3 is a cross-sectional view of a back-illuminated photoemission cathode prepared by the method of the present invention; FIG. 3 is an explanatory diagram of a preferred method of manufacturing the cathode shown in the figure. 6... Photoelectron emission cathode, O... Substrate, 2... Metal coating, 4... Central region, 6... Transparent conductive film (semitransparent chromium layer) 8... Photoelectron emission material Layer, O...high vacuum chamber, 2...nichrome wire, 4...beat, 6...support wire, 8...nichrome heater wire, O...channel, 2...electrical connection wire.

Claims (11)

[Claims] (1) a continuous wave laser; a modulator for varying the intensity or deflecting the optical output beam of the laser; and a modulator positioned to be irradiated by the output beam of the laser; Gallium phosphide, gallium arsenide, gallium arsenide phosphide, or other groups III and V of the periodic table composed of cesium or sodium/potassium antimonide or coated with cesium or cesium and oxygen a photoelectron-emitting cathode comprising a photoelectron-emitting material composed of a substance formed of an element, and including a translucent film capable of emitting electrons when irradiated with the laser; The laser beam pattern is placed between the cathode and the laser beam pattern on the back side of the photoemission cathode such that the translucent film emits electrons for forming an electron image determined by the laser beam pattern. an optical column of light operative to produce an output beam of light, the photoemission cathode further being optically transparent to the laser light and having a back surface facing the output beam side of the laser light. , a substrate having a front surface facing away from the output beam side of the laser light, and an optically translucent conductive film coated on the front surface of the substrate, wherein the semitransparent film of the photoelectron emissive material is A laser-excited high current density electron beam generator coated on the conductive film. (2) a continuous wave laser; a modulator for varying the intensity of or deflecting the optical output beam of the laser; and a modulator positioned to be irradiated by the output beam of the laser; Gallium phosphide, gallium arsenide, gallium arsenide phosphide, or other elements of Periodic Table I composed of cesium or sodium/potassium antimonide or coated with cesium or cesium and oxygen
A photoemissive cathode comprising a photoemissive material composed of a material formed of elements of groups II and V, and comprising a translucent film capable of emitting electrons when irradiated by said laser. and the laser is placed between the laser and the cathode on the back side of the photoemission cathode such that the translucent film emits electrons for forming an electron image determined by the laser light pattern. an optical column of light for producing a pattern of light in the output beam of the laser, the photoemission cathode further being optically transparent to the laser light, the back surface being in the output beam of the laser light; facing the side,
a substrate with a front surface facing away from the output beam side of the laser light; and a metal coating covering the entire front surface of the substrate except for the part of the front surface that is to be irradiated by the laser. . A laser-stimulated high current density electron beam generator, wherein the translucent film of photoemissive material covers at least the portion of the front surface of the substrate to be irradiated by the laser. (3) The electron beam generator according to claim 1 or 2, wherein the modulator is an acousto-optic device. (4) An electron beam generator according to claim 1 or 2, wherein the modulator is an electro-optical device. (5) a substrate that is optically transparent to laser light; an optically translucent conductive film that coats the substrate; The conductive film is made of cesium oxide or sodium/potassium antimonide, or is made of gallium, phosphorus, arsenic, or other elements of group III and group V of the periodic table coated with cesium or cesium and oxygen, and is formed on the conductive film. An electron source for producing an intense electron beam which is virtually monochromatic and capable of being modulated and shaped upon irradiation with said laser light, comprising a semi-transparent film of photoemissive material coated thereon. (6) a substrate that is optically transparent to laser light; and a metal coating that covers the entire surface of the selected surface of the substrate, except for the portion that is to be irradiated by the laser. , positioned to be irradiated by the output beam of said laser light, and made of cesium antimonide or sodium potassium antimonide, or coated with cesium, or cesium and oxygen, gallium phosphide, gallium arsenide, phosphide; Gallium arsenide or other periodic table I
a translucent film of a photoemissive material comprising a Group II and Group V element and coated on at least a portion of the selected side of the substrate to be irradiated by the laser; An electron source for producing an intense electron beam that is virtually monochromatic and can be modulated and shaped during irradiation. (7) The electron source according to claim 5 or 6, wherein the substrate is made of a material selected from the group consisting of quartz and sapphire. (8) The electron source according to claim 5, wherein the semitransparent conductive film is made of chromium. (9) the photoemission cathode further includes a thick metal coating applied to the front surface of the substrate prior to coating with the film, the thick metal coating being applied to the front surface of the substrate except for the portion irradiated by the laser; The electron beam generator according to claim 1, wherein the entire surface of the electron beam generator is coated. (10) The photoelectron emissive substance comprises at least two of the elements.
coat the compound formed by the two on an optically transparent substrate, then irradiate the substrate with a laser and measure the photocurrent generated by the electrons emitted by the laser irradiation. 3. An electron beam generator as claimed in claim 1 or 2, formed by evaporating cesium or cesium and oxygen onto the coated compound until the maximum value is reached. (11) The electron emitting cathode according to claim 1 or 2, wherein the photoelectron emitting cathode is regenerated in situ by depositing cesium or cesium and oxygen on the photoelectron emitting material. beam generator.