EP1702345A2

EP1702345A2 - Divergence-controlled hybrid multiple electron beam -emitting device

Info

Publication number: EP1702345A2
Application number: EP04816492A
Authority: EP
Inventors: Yohan Desieres; Pierre Nicolas; Charlotte Gillot; Serge Gidon; Jean-Luc Martin
Original assignee: Commissariat a lEnergie Atomique CEA
Current assignee: Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Priority date: 2003-12-30
Filing date: 2004-12-29
Publication date: 2006-09-20
Also published as: WO2005074001A3; WO2005074001A2; US20070080647A1; JP2007518223A; US7838839B2

Abstract

The invention concerns an electron-emitting device (50) with multiple electron beams (59) comprising a first structure (6) including a plurality of sources (61) of electron beams (69), hybridized with a second structure (7) comprising a plurality of lens apertures 8).

Description

HYBRID MULTI-BEAM ELECTRONIC TRANSMISSION DEVICE WITH CONTROLLED DIVERGENCE

DESCRIPTION OF THE FIELD AND STATE OF THE ART

The present invention relates to electronic emission devices emitting electron beams, and more particularly to an ultibeam emission device comprising several sources of electron emission capable of emitting several electron beams in parallel, with a system to focus these electron beams. In the industrial sector, electronic emission devices are used as means of observation and microscopic analysis, better known under the name of scanning electron microscopy (SEM), as means of exposure and engraving (lithography) , especially in the lithography of integrated circuits, or as test and measurement means, or as writing or storage means. In industrial applications, single-source electronic emission devices are also used, emitting a single electron beam. Industrial applications are considerably limited by the use of single-source devices which offer only a small accessible field surface and a low speed for writing / writing integrated circuits. inherent in the slow scanning of the electron beam. To break free from these constraints, development is moving towards a “parallelization” of several sources, each sweeping a smaller area. In the field of multi-beam electronic emission devices, two types of distinct structures are known, the assembled structure and the monolithic structure. The document entitled "Arrayed miniature electron beam columns for high throughput sub-100 nm lithography" written by THPChang and DPKern, published in "Journal of Vacuum Science Technology (American Vacuum Society)", volume B10 (6), pages 2743 to 2748, published in November / December 1992, describes a multi-beam electronic emission device 1 composed of individual miniature columns 10 with a matrix-assembled structure, as illustrated in FIG. 1A. As detailed in FIG. 1B, each column 10 consists of an electron field emission tip 12, associated with an extraction grid 13, a diaphragm 14 and a series of Einzel microlenses 15, 16, 17 to focus the electron beam, and to a group of several lateral deflectors 18 for deflecting the beam so as to obtain an electron focal point which scans a small surface on a patch of substrate 1000 corresponding to the integrated circuit chip 100 to be etched . Each column comprises an assembly of electrostatic silicon microlenses, produced independently by MEMS technology (ElectroMechanical Microsystem, in English "Micro Electro Mechanical System"). Each column also has a double feedback system, on the one hand between the field emission tip 12 and the scanning tunneling microscope 11, and on the other hand between the sample 1000 and the STM microscope for checking and rectify the position of the emitting tip 12 and the focusing of the beam. A certain number of these independent columns 10 are grouped together and assembled in a checkerboard or mosaic 1 fashion to engrave in parallel a series of integrated circuit chips. The disadvantage of such a structure is that no element is integrated, neither axially within a column 10, nor at a transverse level between the neighboring columns l. The density of emitters therefore remains low and the time d consistent writing. The monolithic matrix structures make it possible to integrate a greater number of sources of emission of electron beams in a single device of given size and therefore to envisage writing speeds that are much higher. Typically steps of a few tens of microns can be obtained. The document WO 89/11157 describes a multi-beam electronic transmission device with a matrix structure integrated on a substrate. As illustrated in FIG. 2, each emitting source 21 of an electron beam 29 comprises only an electron-emitting tip 22 (cathode) and an annular grid 23 for extracting the electrons, the sources 21 being associated with a primitive focusing system formed by a metal plate 24 at the rear of the resistive substrate 20 which generates field lines 25,25 'projecting at the front of the substrate, except in front of the sources themselves. This primary focusing system has the disadvantage of being placed close to and especially in the posterior position relative to the sources of emission of the electron beam. It does not actually have an adequate focusing optic arranged in the path of the beam (neither electrode, nor focusing lens). It therefore does not allow resolutions below 50 nm to be reached. Document US Pat. No. 5,430,347 describes a device for the individual emission of an electron beam intended for the display of images and produced by depositing layers and depositing metallization on a substrate illustrated in FIG. 3. The source comprises a emitting tip, an annular grid and one or two focusing grids, a luminescent cathode screen being placed opposite, in front of the source. Document US Pat. No. 5,430,347 announces a resolution of an image point in the focal plane with a diameter of ten micrometers at a distance of one millimeter of focus (spot from 10 μ to 1 mm). Such a resolution is entirely insufficient for applications such as electron microscopy or the production of integrated circuits, an area in which it is sought to obtain a resolution much less than a micrometer, the order of a few tens of nanometers, which is the order of magnitude of the patterns to be produced. The document entitled "Digital Electrostatic Electron-Bea Array Lithography" by LR Baylor & al. published in the “Journal of Vacuum Science Technology”, volume B20 (6), published in November / December 2002, describes a matrix structure of multibeam electron emission integrated on a silicon substrate and illustrated in FIGS. 3A and 3B. Each beam emission site 31 of the matrix 30 comprises a point source 32 formed by a nanometric carbon emitting tip, in the axis of which is superimposed a series of annular electrodes 33,34,35,36. The first electrode 33 is an extraction grid whose function is to extract the electrons from the emitting tip 32 which forms the cathode. The following successive electrodes 34, 35, 36, subjected to potentials VE, VC, VA, have the function of focusing the beam 39 of electrons emitted on an anode 38 facing the device. The resolution announced for this device is 50 nm in diameter at a focusing distance W of only 100 μm. The disadvantage of all these monolithic structures is that they require extremely advanced alignment control in etching the layers. In particular, the different successive metallization levels of electrodes 33,34,35,36 must be engraved with very precise openings and alignment, one above the other, and this to a depth of 4 μm, which is particularly delicate in self-aligned microelectronic technology. Another problem, the deposition of each emitter 32 at the bottom of the cavity 31 'formed by the stacking of the annular electrodes can only be obtained by deposition after the complete completion of the cavity. The transmitter must be precisely aligned and oriented along the axis of the electrode openings and also limited in height. In addition, this deposition must be controlled in a homogeneous manner for all of the emitters of the matrix in order to obtain homogeneous optical behaviors during the focusing of each source, which generates significant constraints on the deposition. In addition, field effect transmitters inherently have emission homogeneities between transmitters (the divergence of the beams varies from one source to another). Likewise, the emission of each field effect source has instabilities over time, which are generally impossible to predict and control. These inhomogeneities and its instabilities will result, in the case of the device presented by Baylor, by a variation of the resolution of a transmitter over time, as well as by an inhomogeneity of resolution between the different transmitters, which is incompatible with high resolution applications. Indeed, for this type of application, it is necessary to have a spot size stable over time and homogeneous between each source. The object of the invention is therefore to provide a programmable, compact multibeam electronic transmission device without the aforementioned drawbacks and with an optical resolution which is stable over time and uniform between the transmitters. In particular, an objective of the invention is to provide a set of sources of electron beams whose divergence is small and stable over time. Another objective of the invention is to be able to use this device to form a set of electronic spots of nanometric dimension.

STATEMENT OF THE INVENTION

To solve these problems, the invention provides for hybridizing a diaphragm structure, or diaphragm means, a structure comprising a plurality of sources of emission of electron beams or means forming source of electron emission. This brings on the one hand an improvement to the problem of the resolution limitation linked to the excessive divergence of each emitting source, and, on the other hand, a solution to the problems of instability and inhomogeneity of the emitting sources or of the angular openings over time and from one source to another. The hybridization device aligns and separates, at a given distance, the diaphragm structure relative to the structure of electron emission sources. On the other hand, the invention provides that the diaphragm structure acts simultaneously as an electrostatic focusing system. That is, each diaphragm opening is polarized and formed to form an electrostatic lens. In addition, the invention provides for using this hybridized emission source in a magnetic focusing system called here magnetic or electrostatic or electromagnetic projection optics. The invention thus provides for hybridizing a diaphragm electrode structured on a matrix base structure of transmitters implanted in a substrate. The structured electrode plays in particular the role of diaphragm for each electron beam emitted by each source with corresponding field effect. According to one embodiment, the emitter matrix structure can be a simple basic structure, itself not comprising a focusing system, that is to say without an integrated level of focusing in the substrate. The invention applies in particular to matrix structures of transmitters in which the emission sources are arranged according to a network with micrometric steps, that is to say with a spacing between sources of the order of one micrometer to one millimeter. Advantageously according to the invention, the production of the matrix structure of the transmitter is greatly simplified. The invention is carried out with an electronic transmission device with several beams of electrons comprising a first structure, or first means, comprising a plurality of sources of emission of electron beams hybrid with a second structure, or second means, comprising a plurality of diaphragm apertures. According to the invention the second structure is formed by an electrode or a membrane, metallic or conductive. According to the invention, the hybridization between the first structure of emission of electron beams and the second structure of diaphragm electrode is carried out by means of metallic balls in particular of balls composed of alloy of fusible metals or beads composed of gold. Alternatively, the hybridization between the first and the second structure can be carried out by means of one or more films with anisotropic conduction. Preferably, the first structure comprises a periodic arrangement of the electron emission sources, the first structure having for example a matrix arrangement or a multi-linear arrangement or a linear arrangement; the arrangement can be periodic and regular or irregular. Likewise, the second structure preferably has a periodic arrangement of the diaphragm openings, the second structure having for example a matrix arrangement or a multi-linear arrangement or a linear, periodic and regular or irregular arrangement. This arrangement can be similar to that of the first structure or different depending on the application. It is expected that at least one side of the diaphragm electrode structure is immersed in an electric field of electron acceleration. The device according to the invention may also include an electrostatic and / or magnetic focusing system disposed beyond the second structure, that is to say after the hybridization interval between the first beam emission structure of electrons and the second diaphragm opening structure. Advantageously, the device can be bathed in a uniform magnetic field resulting from a magnetic projection device. The first emission source structure may also itself include a system of electrostatic collimation electrodes participating in the focusing and arranged above each emission source implanted on the substrate. According to the invention, it is provided that the second diaphragm electrode structure is subjected to a bias potential and thus itself contributes to the focusing process of the beams. According to an improved embodiment, the second diaphragm electrode structure has asymmetrical diaphragm openings on one side relative to the other side of the wall formed by the diaphragm. According to one embodiment, each diaphragm opening has edges of openings cut in a bevel, for example in a flat bevel, or edges of openings of concave shape or even edges of openings of convex shape. It is intended, in particular, that each opening or at least one diaphragm opening has an upper opening surface on one side of the diaphragm relative to the opposite opening surface on the other side of the diaphragm. Advantageously in this case, provision is made for the diaphragm openings to be oriented so that the opening with a larger surface faces an electric field of greater value than the opening with a smaller surface. According to another embodiment, the second structure comprises two levels of electrodes or two levels of metallic or conductive membranes, distinct, separated by an insulating material or dielectric layers, so as to independently control the electric field at the input and the diaphragm outlet. According to another embodiment, it is provided that each opening of the structured electrode is subjected to a different electrical polarization from the other openings, the openings being arranged in portions of conductive or metallic membrane, separated from each other by parts insulating. According to another embodiment, the first structure comprises a substrate, a cathode, electron emitting means, a grid extraction, and in which the second structure forms current collection means, isolated from the extraction grid and arranged so as to collect part of the current emitted by the emitting means, means for measuring the collected current, and means for controlling, as a function of a measurement of the collected current, the current emitted by the electron emitting means. Advantageously, the electron emitting means comprise at least one microtip or one nanotube. According to one embodiment, the means for controlling the current emitted by the electron emitting means comprise means for polarization in pulses of the extraction grid. According to another embodiment, the means for controlling the current emitted by the electron emitting means comprise means for pulse polarization of the cathode. Advantageously, the substrate is a CMOS substrate. According to a particular embodiment, electrical bushings making it possible to connect the collection means and the extraction grid to the CMOS substrate. According to another particular form, the collection means are connected by electrical and mechanical interconnection means formed by the balls or a pillar to a conductive area. Advantageously, the current measurement means are located in the substrate. It can also be provided that the current measurement means are produced on a substrate on which the collection means are located. Advantageously, the current measurement means comprise an amplifier on which a capacitor or a resistor is mounted in feedback. And in particular, the current measurement means comprise a measurement assembly by current mirror. Preferably, the openings are circular or comprising circular sectors.

BRIEF EXHIBITION OF DRAWINGS

Other characteristics, objectives and advantages of the invention will appear on reading the following description of embodiments of the invention, given by way of nonlimiting example, with reference to the appended drawings, in which: FIGS. 1A and 1B represent a multi-beam electronic transmission device with a matrix structure, composed of several individual miniature columns assembled one next to the other, according to the state of the art; FIG. 2 represents a multi-beam electronic emission device with a matrix structure integrated on a substrate, with a primary focusing system at the rear of the substrate, according to the state of the art; FIGS. 3A and 3B represent a multi-beam electronic emission device with an integrated structure on a substrate comprising several levels of focusing electrodes above each source, according to the state of the art; FIG. 4 represents a block diagram of the structure of a programmable hybrid multibeam electronic transmission device, according to the invention; FIG. 5 represents an overall view of a programmable hybrid multibeam electronic emission device, coupled with an electromagnetic focusing system and an electrostatic acceleration anode, according to the invention; FIG. 6 represents in detail, an embodiment of the structure of emission of electron beams of the device, according to the invention; FIGS. 7A and 7B show details of two embodiments of the electrode structure comprising diaphragm openings of the device, according to the invention; - Figures 8A, 8B and 8C show details of embodiments of the diaphragm openings of the device, according to the invention; FIG. 9 shows details of an embodiment of a hybridization system between the diaphragm structure and the structure of emission of electron beams of the device, according to the invention; FIG. 9 'represents another embodiment of the hybridization system of the device, according to the invention, the views 9' A, 9'B and 9'C showing alternative embodiments of the system hybridization as a function of the structure of the emission matrix; FIGS. 10, 11 and 12 show views of assemblies of devices comprising an emission source structure hybridized with a diaphragm opening structure, according to the invention, arranged in a two-dimensional matrix arrangement, a linear arrangement and a multi-linear arrangement; - Figures 13a to 16B illustrate an embodiment of the device.

DETAILED PRESENTATION OF EMBODIMENTS OF THE INVENTION

Figures 4 and 5 show the general architecture of the electronic transmission device implemented by the invention. According to the overall embodiment of a complete device illustrated in FIG. 5, the electronic transmission device according to the invention can in particular be implemented within a global high resolution multibeam electronic transmission system 5 which comprises an anode 40 and a focusing system 4 called here "focusing optics". The focusing optic 4 is intended to focus each electron beam 59 emitted by a point source with field effect, in the form of an electronic spot, that is to say a point image concentrated in the plane focal, materialized here by the anode 40, which can also be a screen or even a sample, whether it is a microscopic sample to be observed or a substrate i- conductor ("wafer") covered with a resin to be exposed. The anode 40 is used to accelerate the electron beams. The focusing optics 4 can be a magnetic projection system, or a system combining electrostatic and / or magnetic lenses. In the case of a magnetic projection, the focusing optic 4 is distributed over the entire device. FIG. 4 represents the architecture of the electronic transmission device 50 itself, according to the invention. The device according to the invention comprises a first structure 6 formed for example of a semiconductor substrate wafer 60, for example made of silicon, on which is located an addressing circuit, in CMOS technology for example, and comprising a plurality of sources 61 of emission of electron beams, arranged in matrix form or at least according to a regular periodic arrangement, or irregular. The device 50 according to the invention, on the other hand, comprises a second structure 7 formed by a structured electrode 70 comprising a plurality of diaphragm openings 8 also arranged in a matrix arrangement or at least in a regular, irregular or irregular periodic arrangement , and which advantageously corresponds to the arrangement of the emission sources of the first structure 6. According to the invention, the substrate wafer

60 comprising the plurality of effect emission sources field 61 forming the basic structure 6, is hybridized with the structured electrode 70 comprising the plurality of diaphragm openings 8 and forming the second structure 7, by means of a hybridization system 9-9 '. The second structure 7 comprising diaphragm openings 8, is preferably made in a metal electrode or in a conductive membrane 70. In general, part or all of the second structure 7 is conductive in order to be able to evacuate the electronic charges transferred by the electrons whose propagation is interrupted by the diaphragm 70. According to the embodiment illustrated in FIG. 4, the hybridization system 9 consists of hybridization balls 90 advantageously composed of metal or of fusible metal alloy and of shape spherical or oblong, in the form of a tampon or mushroom for example. The hybridization system 9, 9 ′ advantageously makes it possible to position the structure 7 horizontally and vertically on the structure 6. The spacing distance X between these two structures is defined by the size of the hybridization balls 90. It can be chosen over a very wide range of value going from the order of the micrometer to the order of the millimeter. As shown diagrammatically in FIG. 4, the advantage of the invention is that each opening 8 transmits only an emerging electron beam 59 of reduced divergence, compared to the divergence initial of the electron beam 69 from the emitting source 61. This divergence becomes in particular independent of the instabilities of the sources and the emission inhomogeneities of the sources. According to the diagram of FIG. 4, the device according to the invention comprises three distinct structures: the emission matrix structure 60 which comprises a plurality of source of emission of electron beams 61, an electrode structure 7 comprising a plurality of structured diaphragm openings, and a 9-9 'hybridization system interposed between the emission matrix structure 6 and the structured electrode 7. The invention makes it possible to control, on the one hand, the dimensions of the openings 8, and, on the other hand, the spacing of the second diaphragm structure 7 relative to the first electron emission structure 6, which makes it possible to control the divergence of each electron beam emerging from a diaphragm opening and get the desired divergence. With a reasonable magnetic projection optics (corresponding to a uniform magnetic field of 0.3 teslas), a divergence of a few degrees makes it possible to envisage focusing the beams in the form of spot spots with a nanometric resolution. The electrode 70 pierced with diaphragm openings 8, which forms the second structure 7, a, when it is placed in a non-zero anode field, itself a lens effect. This effect must be controlled because it can, depending on the case, interfere or participate in focusing. It is in fact provided, for most applications, that the complete device 5 is immersed in an electric acceleration field, such a uniform electric field E being able to be generated by the polarization of the emitter matrix 60, of the electrode hybridized 70 and an anode 40 which faces the electron emission device 50. Each opening 8 arranged in the hybridized electrode 70 then has a focusing lens effect. According to an advantageous embodiment, the apertures of the diaphragm 8 can have a bevelled profile, which makes it possible to limit the aberrations of the electron beam near the edge of the apertures and to increase the resolution accessible with this device. This is why the electronic emission device 50 according to the invention advantageously integrates as an emission source in a high resolution multibeam electronic system 5, such as that illustrated in FIG. 5 which includes a focusing system 4 and an anode 40 for accelerating electron beams 59/49. The invention makes it possible to obtain a series of parallel electron beams 59 at the output of the electronic emission device 50, each beam having only an angle of divergence of the order of a fraction of a degree to a few degrees. By implementing a focusing system 4 (for example a magnetic projection system generating a magnetic field B of the order of a few hundredths of Tesla to several tenths of Tesla), the invention makes it possible to obtain nanometric resolutions. The invention thus advantageously allows: the separate production of a first structure 6 comprising a one or two-dimensional matrix of sources of emission of electron beams, and of a second structure 7 comprising a matrix of diaphragm openings ; the transfer of the second structure 7 to the first structure 6; controlling the spacing X between the second structure 7 and the first structure 6; - Alignment control between the openings 8 of the second structure 7 and the emission sources 61 of the first structure 6; and, the placing in electrical contact between certain conductive parts 60 of the first structure 6 and certain conductive parts 70 of the second structure 7. Now, exemplary embodiments of the first electron emission structure, of the electrode diaphragm forming the second structure, diaphragm openings as well as the hybridization system will be detailed below. FIG. 6 represents an exemplary embodiment of the structure for emitting electron beams implemented according to the invention. As shown in Figure 6, the electron emission source structure is integrated on a support 60 of semiconductor substrate, for example silicon, on which is installed an integrated circuit such as a matrix addressing circuit for writing and programming the electron beams, which may include logic gates or memories, realized in CMOS technology (technology of implantation of component on Complementary Metal Oxide Semiconductor). The electron emitting sources 62 are located on the surface of the substrate 60 which is connected to ground. The emitters 62 may consist of metallic tips or semiconductor tips, nanometric tubes made of carbon fibers (in English "carbon nanofibers"), or even thin films of carbon or porous silicon for example. Several transmitting points 62 may possibly be grouped together to constitute a single source 61 of electronic emission. The emitting sources 62 can be implemented in a one-dimensional or two-dimensional matrix network: x dimensions, in particular according to a regular periodic arrangement in two dimensions, or a linear arrangement with regular pitch in one dimension, or a multilinear arrangement on several axes parallel to one dimension, or in an irregular pitch arrangement. The emitting sources 62 are deposited in openings arranged in a dielectric layer 63 of insulating material, for example an oxide layer. The thickness of the oxide layer 63 is of the order of a few tens to a few thousand nanometers. A level of metallization 64 is deposited on the surface of the insulating layer 63 to form a extraction electrode polarized at a positive voltage Vg. Apertures, typically circular, are arranged in the axis of the emitting sources 62 so as to form an annular grid around each emitting tip 62 which constitutes a cathode. The opening of the annular grid can reach a dimension of the order of a few tenths of a micrometer to a few micrometers, depending on the type of emitting source used. According to the alternative embodiment illustrated in FIG. 6, the extraction electrode 64 is surmounted by another dielectric layer 65 and by another level of metallization 66 forming a second electrode electrically isolated from the extraction electrode 64. This second electrode 66 is pierced with openings, typically circular, of dimensions generally greater than the extraction grid openings of the first electrode 64. The second electrode 64 is polarized at a voltage Ve, so as to form a first level of lenses of focus. The typical thickness of the conductive electrodes is of the order of a few hundred nanometers. According to the invention, the diaphragm electrode 70 which constitutes the second structure 7 is transferred by hybridization 9 to the first emission structure 6 formed by the base substrate wafer 60, on which the matrix arrangement of the sources is located. field effect transmitters 61. Hybridization consists in transferring and assembling the second structure 70 onto the first structure 60 by placing, in an intermediate manner, hybridization means 9 and 9 '. According to the embodiment described above (Figure 4), the hybridization means 9 are formed by metal balls 90. In a first embodiment, the hybridization balls are composed of fusible metal alloys. The balls can be circular, oblong or any other shape, for example mushroom-shaped in particular. The height X of the hybridization balls 90 makes it possible to control the spacing between the diaphragm electrode 70 which forms the second structure 7 and the emission substrate 60 which forms the first basic structure 6. The hybridization balls 90 preferably have micrometric dimensions, these microbeads preferably having a size of between one micrometer and several hundred micrometers. Such hybridization means make it possible to maintain a spacing distance X between the second structure 7 and the first structure 6 comprised between a fraction of a micrometer and a millimeter, depending on the hybridization means used. Hybridization techniques using a fusible alloy ball also make it possible to achieve automatic and controlled alignment (to the nearest micrometer) of the diaphragm openings 8 of the second structure 7 with respect to the emitting sources 61 of the first structure 6. This is the melting of the balls which allows (via surface tension forces) to achieve this self-alignment between the structures 6 and 7. This technique therefore allows in particular a self-alignment between the means for emitting electron beams and the means for reducing the divergence according to the invention. In the case of hybridization with gold beads, the assembly is carried out not by melting the beads but by thermocompression. The assembly precision is then given by the precision of the machines for aligning the structures to be assembled. These different hybridization techniques are for example described in the article: "Electronic production and test - Advanced Packaging", p. 32 - 34, April 1999. Figures 9 to 9'C illustrate several hybridization configurations at the interface between the second diaphragm electrode structure 70 and the first basic electronic emission structure 60. Figure 9 shows a first embodiment in which the hybridization balls 90 are inserted in the peripheral zones of the device between the edges of the second structure 7 and the edges of the first structure 6. Thus, according to this embodiment, the balls 90 hybridization are arranged outside the propagation areas of the electron beams and where the diaphragm electrode 70 which forms the second structure 7 can be considerably thickened to strengthen its mechanical strength. FIG. 9 'represents another embodiment in which several hybridization microbeads 90 are arranged, not only in the peripheral zones between the edge of the electrode of diaphragm 7 and the edge of the substrate plate 60 forming the second electronic emission structure 6, but also in the central zone corresponding to the active part of the substrate 60 comprising the electron emission sources 61 and the central zone of the diaphragm electrode 70 which has the diaphragm openings 8. The hybridization microbeads 90 are then placed around each field effect emission cell, and stand up like columns in the intervals separating the propagation spaces from the parallel electron beams. The hybridization microbeads arranged in the central zone or active part of the device have the function, alternately or cumulatively, of reinforcing the strength of the mechanical assembly between the thin diaphragm electrode 70 (second structure) and the substrate wafer 60 ( first structure), and / or putting the conductive parts of the diaphragm electrode 70 into electrical contact with certain conductive parts of the substrate wafer 60. Such an arrangement applies particularly to the production of a device according to the invention comprising a diaphragm electrode 7 with a crosslinked or cellular structure and comprising insulating partitions separating conductive boxes in which the diaphragm openings 8 are arranged. FIG. 9 'A illustrates a first embodiment in which the microbeads of hybridization 91 arranged in the central zone bring parts of the substrate 60 into direct contact with the conductive zones 70 surrounding the openings 80. FIG. 9'B illustrates an alternative embodiment in which the hybridization microbeads 92 of the central zone are supported on the electrode 64 of the electron extraction grid deposited on a dielectric layer which separates it and isolates it from the substrate 60, in which the electron emitting sources 61 are arranged or implanted. Here, the balls of hybridization 92 electrically connect the zones of the diaphragm electrode 70 extending around the openings 80 with the electronic extraction electrode 64 which is subjected to a potential or an extraction grid voltage Vg. FIG. 9'C illustrates another alternative embodiment in which hybridization microbeads 93 are supported on the focusing electrode 66 which is provided in certain embodiments of the first structure 6, for example that of FIG. 6, and which surmounts the electronic extraction grid electrode 64 deposited above the semiconductor substrate 60 in which the electron emitting sources 61 are implanted. In this embodiment, the hybridization microbeads arranged in the central part allow the areas of the diaphragm electrode 70 surrounding the openings 80 to be electrically connected with the focusing electrode 66 which is subjected to a potential or a bias voltage Ve. FIGS. 7A and 7B represent two embodiments of the second structure and show the general appearance of the hybrid electrode 70. The beveled profiles of the diaphragm openings, detailed later, are not shown in FIGS. 7A and 7B. FIG. 7A represents a first embodiment in which the second structure is composed of a conductive membrane 70 surmounted by an extra thickness 72 of the conductive material or the thickness 72 of depositing a layer of another material which can be either conductive, semiconductor or dielectric. The thickness of the diaphragm conductive membrane 70 which intercepts the electron beams around the diaphragm openings 8 is of the order of a fraction of micrometers (for example 0.1 μm) to several hundred micrometers (for 500 μm). Outside the areas surrounding the diaphragm openings 8, the thickness of the second structure can reach much greater values, for example cumulative thicknesses of up to around one millimeter, in particular at the edges, at the periphery of the second. structure in order to improve the mechanical strength or the resistance to deformations of thermal origin of the whole of the second structure 7A. The conductive part 70 of the hybridized electrode 7A is subjected to a bias potential

Vd to control the electric field of acceleration electrons between the emission device and the anode and / or obtain an electrostatic focusing effect, as detailed below. FIG. 7B represents another more complex embodiment of the second structure 7B which here comprises two successive electrodes 70 and 75, in order to increase the polarization strategies of the structure 7B. In the embodiment of FIG. 7B, as in the example of FIG. 7A, the second structure 7B comprises a first conductive or semi-conductive membrane 70 forming a first electrode pierced with diaphragm openings 8. The membrane is surmounted by a layer of dielectric material 71, of average thickness of the order of a micrometer, pierced with embrasures 73 at the locations corresponding to the right of the diaphragm openings 8, the embrasures 73 preferably being of dimensions greater than the dimension of the diaphragm openings themselves. The thickness of the conductive part 70 can be reduced to a thickness of the order of a few tenths of a micrometer. The dielectric layer is surmounted by a uniform conductive membrane 75 which forms a second electrode. The thickness of the dielectric layer 71 electrically insulating the electrodes 70 and 75 between them, can range from one micron to ten microns. The thickness of the conductive membrane 70 in the areas which intercept the electron beams, around the diaphragm openings 8, can range from around a tenth of a micrometer to several hundred micrometers (for example 500 μm). However, the second electrode 75 can be thickened or surmounted by a layer 76-77 of another conductive, semiconductor or dielectric material, the thickness of which can reach up to about one millimeter. These extra thicknesses, whether they are arranged in the same body of the material of the second electrode 75, or in a different material, conductive or insulating 77, are arranged outside the areas of diaphragm openings 8, in particular on the peripheral edges of the electrode to improve the mechanical or thermal behavior of the second structure 7B. Embrasures 78 are then arranged in line with the diaphragm openings 8. According to the example in FIG. 7B, the embrasures 78 arranged in the extra thicknesses of the second electrode have dimensions greater than the dimensions of the diaphragm openings 8 arranged in the second electrode. 75 itself. The diameter of the smallest diaphragm openings 8 arranged in the electrodes can reach a tenth of a micrometer to several tens of micrometers (for example 50 μm), the upper dimension of the largest diaphragm openings being not limited. Each electrode 70.75 formed by a conductive membrane is subjected to a respective polarization potential to form a field of electrostatic acceleration of the electrons on each side of the second structure and between the two electrodes 70, 75. In the exemplary embodiments of FIG. 7A and 7B, each electrode 70 or 75 is subjected to a potential Vd, Vdl or Vd2 uniform over the entire surface of each electrode 70 or 75. All the diaphragm openings 8 of each electrode 70 or 75 are therefore subject to the same electrical potentials. Alternatively, according to another embodiment not illustrated, it is provided that the openings can be subjected respectively to separate individual potentials. The second structure can thus be implanted in a substrate or a material with a cellular or cross-linked structure, comprising silicon boxes separated by strips of insulators, in particular by using bricks according to the technology known under the name SIBOX. In this type of technological material, each semiconductor well is electrically isolated from the other neighboring semiconductor wells. The second structure 7 is implanted in this substrate or this technological material, each individual isolated box then being pierced with one or more diaphragm openings 8. The opening or the group of diaphragm openings belonging to a box can then be individually subjected to a respective potential, so as to focus, individually or in groups, each electron beam which crosses these diaphragm openings. An advantage of this embodiment is that it makes it possible to control the divergence and the optical quality of the transmitted beams. FIG. 8C is a diagram showing the shape of the trajectories of the electrons coming from a point emission source through a diaphragm opening 70 with beveled profile. As seen in the lower corner of Figure 8C, the first effect of the diaphragm opening is to limit the angular opening of the electron beam transmitted through the second diaphragm structure 70. For example, with a diaphragm opening of 5 micrometers in size, placed at a distance of 20 micrometers from the point emitting source, the narrowest part of the diaphragm opening 84 limits the angular opening of the beam to +/- 4 degrees of angle . In the example of FIG. 8C, the electric field is zero (E1 = 0) between the emitting source situated at the origin and the first side 85 of the diaphragm structure 70. On the other side of the second structure 70 , a uniform electric field of the order of 1 volt / micrometer (E2 = 10 ⁶ V / m) is imposed by an anode (not shown) which faces the electrode 70 formed by the second structure. All of the electron trajectories are subjected to a uniform magnetic field of the order of a few tenths of Tesla (for example 0.3 T). It is then observed that the trajectories of the electrons 86, 87, 88, 89 are curved and fall back towards the axis of propagation 89 under the effect of electrostatic acceleration and magnetic focusing. The beveled opening profile 80 makes it possible to limit the aberrations of the electron beam when crossing the diaphragm 70, along of the opening edge 83. The diaphragm effect is produced in the part of the second diaphragm structure 70 where the opening is the smallest 84. Such an arrangement makes it possible to obtain excellent quality of the electron beam. The beveling of the upper part 83 of the diaphragm makes it possible to achieve a resolution of less than 10 nm and thus to divide by five the dimensions of the spot (focal point) obtained with the device according to the invention, relative to diaphragm openings without beveling, which is the consequence of the reduction in aberrations when crossing the diaphragm 70. Thus advantageously the beveling of the diaphragm openings of the device according to the invention, makes it possible to quintuple the resolution of the focal point of a beam electronic. In addition, the invention provides that the electric field E is not uniform when passing through the diaphragm, each side of the diaphragm electrode being exposed to electric fields E1, E2 of different values. According to the invention, the orientation of the opening of the bevel 83 preferably depends on the orientation of the electric field gradient at the crossing of the diaphragm 70. It is expected that the narrowest part 81 or 84 of the opening 80 diaphragm faces a smaller electric field than the widest part 82 or 83 of the diaphragm opening 80. The orientation of the bevel 83 of the opening 80 therefore depends on the polarization of the electrode 70 with respect to the emission device electronic 60 and vis-à-vis the accelerating or focusing anode 40, for example. FIG. 8A represents a first embodiment in which the apertures 80 of diaphragm 70 form bevels 83 opening out in the direction of propagation of the electron beams and are subjected to a gradient of electric field E1 / E2 increasing in the direction of propagation of the electrons . The bevel 83 of the opening 80 is oriented so that the first side of the diaphragm 70 having the narrowest opening 81, or having the lower opening section 81, is exposed to an electric field El having a first lower value at a second electric field value E2 which bathes the other side 82 of the diaphragm 70. The second side of the opening 80 which has a through opening width 82 greater than the first opening 81, or at least a section of opening of area 82 greater than the opening area 81 of the first side, is exposed to a second value of electric field E2 greater than the first value of electric field El which faces the first side 81 of the diaphragm 70. In particular , the electric field may be absent, that is to say of substantially zero value (El≤O) between the diaphragm and the emission device. This particular case corresponds to the case where the electrode of the diaphragm structure 70 is polarized at the same electrical potential as the emission device 50 (Vd = Vg or Vd = Ve or Vdl = Vg or Vdl≈Ve). In the case of FIG. 8A, after having been diaphragms at the place where the diaphragm opening 80 is the narrowest 81, the electron beams are secondly focused or accelerated by the strong electric field E2 at the where the opening 80 is the widest 82. Strong electrostatic effects occur in this area, but since the paths of the electron beams transmitted at this level then pass further from the edges of the opening ends, the paths experience fewer aberrations. The device according to the invention comprises means for applying bias potentials or electrical voltages to each of the above-mentioned electrodes. FIG. 8B shows another embodiment in which, this time, the electron beams are exposed to a gradient of electric field decreasing in their direction of propagation, during the crossing of the apertures 80 'of diaphragm 70. In this case , as illustrated in the embodiment of FIG. 8B according to the invention, the beveled profile openings are preferably oriented so that each diaphragm opening 80 'narrows in the direction of propagation of the electron beams . In this case, the bevel-cut apertures 80 ′ are oriented so that the opening of greater width 81 ′ is arranged on the first side facing the electron-emitting sources, and are exposed to a electric field of value E1 'greater than the electric field value E2' which bathes the second side of the diaphragm 70. The second side of the diaphragm has openings 82 'having a narrower width or an opening section 82' of lower area, these narrow openings 82 'facing the accelerating or focusing anode 40. In the case of FIG. 8B, the electron beams: are exposed to a decreasing electric field gradient El '/ E2' in their direction of propagation and are first of all, focused or accelerated by the strong electric field El 'at where the opening 80 'is widest 81', before being diaphragms at. the place where the aperture 80 'of the diaphragm is the narrowest 82', which happens to be the place where the value of electric field E2 'is the lowest, see zero. Optionally, the electric field may indeed be absent on the second side of the diaphragm 70, which. corresponds for example to a case where the anode is polarized at the same potential as the diaphragm 70. Advantageously according to the invention, the diaphragm effect is produced on the side of the diaphragm where the electric field E2 is the weakest which corresponds alongside narrower 82 'openings. The trajectories of the electron beams which pass very close to the edge of the opening then undergo little. aberrations. It can be seen that, thanks to the invention, the larger the bevel angle of the openings, the more marked the previous effects and the less aberrations occur when crossing the diaphragm. The value of the angle of the bevel of the openings is only limited by the density of the emitter on the surface of the device. FIG. 8C thus shows a diaphragm aperture profile cut at a bevel with a large angle θ of inclination of approximately 15 ° relative to the axis of propagation of the electrons. In other embodiments, not illustrated, the diaphragm openings can be bevelled with a non-linear profile, that is to say that the bevel is not strictly flat but can be convex or concave for example . Such aperture profiles are also favorable for the reduction of aberrations when the electron beam passes through the diaphragm. The production of an electronic transmission device according to the invention can be the subject of several embodiments and variants of the basic architecture, in particular of a two-dimensional matrix arrangement, of a linear arrangement with a dimension or a multi-linear arrangement with two dimensions, with regular steps or with irregular steps. FIG. 10 illustrates an overall view of an embodiment of a two-dimensional matrix architecture with regular steps, comprising a network of emitting sources 6 and apertures 8 of diaphragm 7 arranged in a regular grid. FIG. 11 illustrates an overall view of an embodiment of an electronic transmission device according to the invention, comprising a transmission structure 6 comprising a single row of sources and a diaphragm structure 7 comprising a row of corresponding openings 8 arranged in linear bars in a periodic arrangement with a dimension with regular steps. Alternatively, the emitting sources and the diaphragm openings 8 may be arranged at irregular intervals. FIG. 12 illustrates an overall view of another embodiment of electronic transmission device according to the invention, in which the first structure 6 and the second structure 7 comprise several parallel rows relatively spaced from emitting sources and openings 8 diaphragm arranged in two dimensions with regular periodic steps. Alternatively, the emitting sources and the diaphragm openings 8 may be arranged at irregular intervals. The spacing of the emitting sources and the corresponding apertures 8 can vary on the order of one micrometer to one hundred micrometers, the matrix pitch typically being a few micrometers or a few tens of micrometers, for example about fifty micrometers. Such a structure is particularly advantageously integrated in a high resolution multibeam electronic transmission system, according to the diagram in FIG. 5B which further comprises a focusing optic 57 and an electrostatic acceleration anode. At the exit of the diaphragm openings of the emission device 50, the angular opening of the beams is reduced to a few degrees, or even below the degree thanks to the invention. The focusing lens 57 is preferably a magnetic projection optics generating a magnetic field of the order of a few hundredths of Tesla to a few Tesla, typically a few tenths of Tesla. Advantageously, such a device according to the invention makes it possible to obtain electron spots having a nanometric resolution. In FIGS. 13A to 16B, we can see another embodiment in which the diaphragm also forms means for collecting part of the current emitted by the emitting means so as to collect part of the emitted current, and is connected to means for measuring this part of the current emitted, said means for measuring being in turn connected to means for polarizing the means emitting electrons. According to the embodiment shown in FIGS. 13A and 13B, the electron emitting means comprise a cathode 120, micro-emitters of electrons 124 (tip or nanotube) and a first extraction grid 126, the grid distance from extraction-cathode being regulated by the thickness of a dielectric 128, which is for example of the order of a micrometer. Polarization means 134 make it possible to polarize the extraction grid and the cathode respectively and thus to control the current emitted by the micro-emitters. The device of the invention also comprises collection means 140, for example comprising an electrode or a collection grid, can be positioned above the emission site. They are connected to means 142 for measuring the current. These collection means are therefore placed on the path of the emitted electrons in order to take a part of them and to allow the remainder of the emitted electrons to pass to the anode. For this, orifices (or openings) are provided at these collection means. These orifices can be circular, oval or rectangular, they can also have other advantageous geometries. As illustrated in FIGS. 15A and 15B, they can also have the form of circular sectors 100, 102, 104 or even the form illustrated in FIG. 15C (indented circle). One can, according to the chosen geometry and the applied polarization, determine, according to the classical laws of optics and electromagnetics, the share of the electrons collected and that of the electrons actually transmitted towards the anode. Thus, the measurement of the collected current will give a precise indication of the electrons arriving on the anode (and therefore of the emitted dose). Compared to a circular orifice, these orifices cut out in FIGS. 15A - 15C allow the collection of electrons with several levels of electron beam and not only at the edges of the beam, thus making it possible to be less sensitive to the inhomogeneities which can appear on edges. These orifices typically have, depending on the application envisaged, diameters of the order of a few microns to a few tenths of a micron. The current collection means 140 are positioned in the emission axis, the distance relative to the first extraction grid 126 being adjusted by hybridization means 90, for example a micro-ball 90 or any other means interconnection (pillar, ...). In fact, the grid or the collection means are connected by the means 90 to a conductive zone 171, located in the conventional emission device at the level of the extraction grid but isolated in this extraction grid by the insulating zone. 127 (for example Si02). The hybridization means 90 make it possible to maintain a gap between these elements which, combined with the insulating zone 127, ensures the insulation effect between them. The height of these hybridization balls 90 makes it possible to control the spacing between the electrode 140 and the substrate which contains the emission means 124. Such hybridization means make it possible to maintain a fairly precise distance of spacing between the means 140 and the emission grid 126, typically of the order of a few hundred microns and this, with an accuracy of the order of a fraction of microns. By placing the current measurement means 142 (ammeter) in the supply circuit of the collection means, it is possible to measure the electron beam, or a quantity proportional to the anode current, and to interact on the current of the micro-emitter, either via the control of the extraction grid 126 and / or via the control of the cathode 120. An adjustment can be made using feedback means. These means of feedback may for example be composed of a current-voltage converter associated with an amplification module and, if necessary, an inverter. They thus make it possible, from the current collected at the collection grid, to establish the voltage to be applied at the cathode and / or the extraction grid. The invention therefore makes it possible to use means for controlling and regulating anode current separate from the extraction grid. The grids 126 are of metallic type.

More generally they are conductive (for example in Polycrystalline Silicon). The emitting tips 124 are conductive, for example made of silicon or molybdenum. The extraction grid 126 has for example a thickness of a few hundred nm to a few micrometers. The thickness of the dielectric 128 is typically a few hundred nm (for example between 0.4 and 0.7 μm). The distance between the substrate 120 and the anode 136 is approximately 1 mm for the application envisaged. It can vary from 10 μm to 10 mm depending on the application. A first voltage generator 134 establishes for example a positive ddp between the first extraction grid 126 and the cathode 120 to allow the electrons to escape from the point in vacuum. The electron beam is directed towards the anode 136 with a certain angular opening. To collect the electrons, the anode 136 is for example brought to a few hundred volts positively. The means 140 collect electrons, which the means 142 convert into a current measurement, information that the feedback means can use to regulate the extraction of the electrons as a function, for example, of a set value of the current emitted. The operating frequencies of the source are preferably in the high frequency range, beyond 1 MHz. The physical production of known micro-sources according to the prior art requires non-ideal structures. Parasitic capacitances between the tip 124 and the grid 140 induce, in particular, large displacement currents, at the time of the switching operations. In the embodiment shown in FIGS. 13A and 13B, it is possible to connect the extraction grids 126 and the collection grids 140 to current control and grid control blocks located in the CMOS substrate, by electrical bushings. . These processing blocks use a mixed LV / HV (low voltage / high voltage) technology, the control and command being done in LVCMOS and the control of the emission in HVCMOS. A collective manufacturing process makes it possible to align the collection grid 140 with the emissive tip 124. As illustrated in FIG. 13A, a silicon wafer can be used as a substrate for producing the collection grid. This substrate could then also be used to produce, at the same level as the collection grid, the means of current measurement and associated processing. We could thus speak of an “active” collection grid. An advantage of this variant is to increase the surface available for producing the electronic processing blocks and above all to differentiate the low voltage analog part at the level of the silicon substrate of the collection grid 140, and the analog part 134 of high voltage switching at level of the base silicon substrate 160, thus limiting, inter alia, the problems of interference between these two parts and also allowing the use of two substrates of completely different technologies. In the device illustrated in FIG. 13B, it is a “passive” collection grid, where the means 142 for measuring current and processing the collected current are located in the CMOS substrate 160. In one embodiment, the control is carried out by the extraction grid, the cathode potential is maintained at a constant voltage, the potential of the extraction grid is drawn between a high level and a low level (see the voltage Vg on the timing diagram in Figure 16A). The high level corresponds to a period during which the micro-transmitter transmits, the low level corresponds to a period during which the micro-transmitter does not transmit (see the anode current in FIG. 16A). According to the invention it is possible, from the current Ig collected at the level of the collection grid (proportional to the anode current in its central part), to act on the potential of the extraction grid to modulate the emission of the micro-transmitter. One can for that, either modulate the high level of the voltage Vg, or modify the duration of emission by playing on the duration of this high level. It can be seen, in FIG. 16A, that at the time of switching of the potential of the extraction grid, large current peaks, transiently at the level of the current of the collection grid. It may therefore be advantageous to defer the measurement of the collection current so as to avoid the disturbances linked to these commutations. In another embodiment, the control of the micro-transmitter is governed by the cathode. The potential of the extraction grid is therefore constant while the cathode potential is drawn between a high level and a low level, the latter level corresponding to the emission period of the microemitter. According to the invention, it is possible, from the collected current Ig, to act on the potential of the cathode (Vcathode) to modulate the emission of the microemitter. For this, the low level of the cathode voltage can be modulated in amplitude or in duration. It can be seen, FIG. 16B, that the current collected in the case where the control of the microemitter is governed by the cathode, is less sensitive to the switching of the cathode voltage than in the previous case. The example in FIG. 14A illustrates the means for measuring the current of a measurement signal is amplified by an amplifier 180 on which a capacitor 182 is mounted in feedback. It is then possible to convert the measured current into voltage, a quantity that can be more easily used with a limited number of components (CTIA). The variation of the output voltage is then expressed by:

-Igate * T

where T represents the integration time of the current, or the analysis time. This structure is relatively insensitive to rapid variations in current. The value of the capacitor 182 is for example of the order of 10FF, which leads to sensitivities of the order of 20 μV / electron. The structure illustrated in FIG. 14B, with a feedback resistance 184, makes it possible to represent instantaneous variations in output voltage on instantaneous variations in the input current. The output voltage variation is expressed in this case: Δ vs = - R. Igate

Finally, FIG. 14C illustrates an assembly with measurement by current mirror: an image of the collection grid current Ig can be used to generate a difference current Iref-Ig, which can be exploited. A device according to the invention, whatever the embodiment envisaged, makes it possible to compensate for technological spatial non-uniformities or the non-uniformities of known electron sources. Other forms of arrangement, variants and embodiments may be implemented by those skilled in the art, without departing from the scope of the present invention.

Claims

CLAIMS 1. Electronic emission device (50) with several electron beams (59) comprising a first structure (6) comprising a plurality of sources (61) of electron beam emission (69), hybridized (9 ) with a second structure (7) comprising a plurality of diaphragm openings (8).

2. Device according to the preceding claim, wherein the second structure (7) is formed by an electrode or a membrane (70), metallic or conductive or semi-conductive.

3. Device according to claim 1 or 2, wherein the hybridization (9-9 ') between the first and the second structure (6-7) is carried out by means of metal balls (90), in particular of compound balls alloy of fusible metals and / or balls composed of gold.

4. Device according to claim 1 or 2, wherein the hybridization (9-9 ') between the first and the second structure (6-7) is carried out by means of one or more films with anisotropic conduction.

5. Device according to one of claims 1 to 4, wherein at least one diaphragm opening (80) has two surfaces of opposite openings (81/82) different, the opening surface (81) on one side diaphragm (70) having a area greater than the area of the other opening surface (82) on the other side of the diaphragm (70).

6. Device according to one of claims 1 to 5, wherein each diaphragm opening (80) (70) has an opening edge profile (83) bevel, flat, concave or convex.

7. Device according to one of claims 1 to 6, wherein each structure

(6,7) includes a periodic arrangement of the sources

(61,62) electron emission or diaphragm openings (8,80), the structures (6,7) having in particular a matrix arrangement or a multi-linear arrangement or a linear arrangement, regular or irregular.

8. Device according to one of claims 1 to 7, wherein the sources (61,62) of electron beam emission (69) and the apertures (8,80) of diaphragm (70) are arranged with a spacing of the order of a few microns to a millimeter.

9. Device according to one of claims 1 to 8, further comprising means or a system (4) for electrostatic or magnetic or electromagnetic focusing of the electron beams.

10. Device according to one of claims 1 to 9, further comprising means or a magnetic projection focusing system (40).

11. Device according to one of claims 1 to 10, further comprising third means, or a third structure (40), of anode or polarized electrode disposed beyond the second structure (7) of openings diaphragm (70).

12. Device according to one of claims 1 to 11, wherein the second structure (7) comprises at least one conductive part (70,75) and at least one dielectric part (71,72,76,77).

13. Device according to one of claims 1 to 12, wherein the second structure (7) comprises two levels (70,75) of electrodes or membranes, metallic, conductive, attached to at least one dielectric layer ((71 , 72).

14. Device according to one of claims 1 to 13, wherein the second structure (7) has, around the zones (73,78) of apertures (8) of diaphragm (70), a thickness of the order of '' a fraction of a micrometer to a few hundred micrometers.

15. Device according to one of claims 1 to 14, wherein the second structure (7) has, outside the zones (73,78) of apertures (8) of diaphragm, a thickness (71,72,76,77) of the order of a micrometer to about one millimeter.

16. Device according to one of claims 1 to 15, wherein the second structure (7) has a honeycomb structure isolating each opening (8) or several groups of openings between them, so that each opening or each group of openings is subject to a respective bias potential.

17. Device according to one of claims l to 16, wherein at least one side (82, 82 ', 83) of the diaphragm (70) of the second structure is immersed in an electric field (E2) of acceleration or focusing of electrons.

18. Device according to one of claims 1 to 17, wherein the second diaphragm opening structure (7) (70) has two opposite sides (81/82), one side (81) facing an electric field (El), the other side (82) facing another electric field (E2).

19. Device according to claim 5 or

6 taken in combination with claim 17 or 18, wherein the diaphragm openings (80,80 ') (70) are oriented so that the upper area opening surface (82,81') faces the field electric of higher value (E2, E1 '), the opening area of lower area (81,82') facing the electric field of lower value (E1, E2 ') or the absence of electric field.

20. Device according to one of claims 1 to 19, in which the second structure (70) is subjected to at least one bias potential (Vd, Vdl, VD2).

21. Device according to one of the preceding claims, in which the first structure comprises a substrate (160), a cathode (120), electron-emitting means (124), an extraction grid (126), and in which the second structure forms means (140) for collecting current, isolated from the extraction grid and arranged so as to collect part of the current emitted by the emitting means, means (142) for measuring the collected current, and means for controlling, as a function of a measurement of the collected current, the current emitted by the electron emitting means.

22. Device according to claim 21, the means (124) emitting electrons comprising at least one micro-tip or a nanotube.

23. Device according to claim 21 or 22, in which the means for controlling the current emitted by the electron emitting means comprise means (134) for pulse polarization of the extraction grid (126).

24. Device according to claim 21 or 22, in which the means for controlling the current emitted by the electron-emitting means comprise means (134) for pulse polarization of the cathode.

25. Device according to one of claims 21 to 24, in which the substrate is a CMOS substrate (160).

26. Device according to claim 25, electrical bushings making it possible to connect the collection means (140) and the extraction grid (126) to the CMOS substrate (160).

27. Device according to one of claims 21 to 25 in combination with claim 3, wherein the collection means (140) being connected by electrical and mechanical interconnection means formed by the balls or a pillar to a conductive area (171).

28 Device according to claim 27, the current measuring means (142) being located in the substrate.

29. Device according to one of claims 21 to 27, the means (142) for measuring current being produced on a substrate on which the collection means are located.

30. Device according to one of claims 21 to 29, the current measurement means (142) comprising an amplifier (180) on which a capacitor (182) or a resistor (184) is mounted in feedback.

31. Device according to the preceding claim, the means (142) for current measurement comprising a measurement assembly by current mirror.

32. Device according to claim 31, the openings being circular or comprising circular sectors (100, 102, 104).