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    • 专利摘要:
    Electron sensor for electron microscopy. The present invention is an electron sensor (1), and a system with a plurality of electron sensors (1) for electron microscopy performed by an electron microscope. More specifically, the electron microscope generates an electron beam (10) comprising at least one electron that impinges on a lateral reception surface (3) of said electron sensor (1) and this generates an electric charge of electron-hole pairs (eh) that are detected and/or measured by at least electrodes (6, 7) linked to an electrical circuitry unit (12) to form an image (11) with high dynamic range and measure the energy of the incident electrons in each pixel of the image. (Machine-translation by Google Translate, not legally binding)
    公开号:ES2653767A1
    申请号:ES201630925
    申请日:2016-07-07
    公开日:2018-02-08
    发明作者:Ricardo Carmona Galán；Lionel CERVERA GONTARD
    申请人:Consejo Superior de Investigaciones Cientificas CSIC；
    IPC主号:
    专利说明:

    ELECTRONIC SENSOR FOR ELECTRONIC MICROSCOPY
    OBJECT OF THE INVENTION
    The object of the present invention is an electron sensor for electron microscopy, and a system with a plurality of electron sensors for electron microscopy.
    Therefore, the present invention could be framed in the field of sensors for detecting electrons used in transmission electron microscopes (TEM), in scanning electron microscopes (SEM) or in scanning scanning microscopes (STEM). BACKGROUND OF THE INVENTION
    Currently, different applications in the field of electron microscopy detect and accumulate electrons to generate images, or energy spectra. These images, or spectra, are used in the study of materials in science and technology.
    Specifically, these applications are based on the irradiation of a sample, with electrons accelerated at energies between 2 keV and 400 keV. Although less frequent, there are also electronic TEM microscopes that operate with high-energy accelerated electrons up to 1.2 MeV.
    More specifically, in transmission electron microscopes (TEM), these accelerated electrons pass through the material that makes up a sample, and by means of magnetic lenses, two-dimensional enlarged images of the sample and diffraction patterns (two-dimensional images) are generated. On the other hand, in TEM applications of energy loss electron spectrometry (EELS or EFTEM in its acronyms in English) an energy filter made of electromagnetic lenses is used, with which an energy spectrum (monodimensional image) is obtained, or an image filtered in energy (two-dimensional image) with information on the chemical composition of the sample.


    In order to obtain the images, electronic microscopes comprise electron sensors that are manufactured with "pixelated" semiconductors. That is, semiconductors that, on the surface where photons, or electrons, impact, comprise a plurality of discrete electronic components. These discrete electronic components are organized as a single-dimensional, or two-dimensional, matrix to detect photons, or electrons, where each discrete electronic component is often referred to as "pixel." In this way, the "pixelated" semiconductors detect by each "pixel" the impact position of an electron, or a photon, in one, or two, spatial dimensions.
    Specifically, the "pixelated" electron sensors used in TEM are manufactured with CCD or CMOS technology. Particularly, the CCD sensors include in each “pixel” a sensor part in which the electrons and another part of electronic circuitry affect. Meanwhile, in CMOS sensors the electronics are distributed in each pixel, so that the electronics are irradiated by the electrons in the electron beam, making it susceptible to irradiation damage. In both cases, these technologies are sensitive to radiation damage due to the high energies of electrons used in electron microscopes.
    Another problem for these CMOS technologies, or CCD, is that electrons are absorbed in different directions including the depth and width of the electron sensor. In this way, the effective resolution of the electron sensor is limited, that is, it defines the proximity in which each “pixel” can be placed. This is because if two adjacent “pixels” are too close to each other, when an electron hits a “pixel” it also generates a signal that can be noticeable in the adjacent “pixels”. This effect is known as “charge sharing” or “cross-talk”. Thus, for these "pixels" to be sufficiently separated and a good spatial resolution can be obtained in electron microscopes, the electron sensor has to be very large.
    To avoid the first of these problems, that is, the one related to the sensitivity to damage due to irradiation, indirect CMOS or CCD sensors are usually used in TEM. In these sensors the electron does not directly affect the semiconductor but a scintillator that is optically coupled to the sensor, and that after the impact generates a cascade of photons, that is, these electrons are converted to photons. These low energy photons, within the visible spectrum, are the ones measured in the “pixelated” photon sensor. In return, this indirect detection of electrons converted into photons does not solve the problem of


    “Charge sharing” or “cross-talk” and degrades the operation of the sensor, affecting some of its technical characteristics such as quantum detection efficiency (DQE) and modulation transfer function (MTF). As a result, the quality of the images worsens, and it is necessary to increase the exposure time to form images with an adequate signal-to-noise ratio. This increased exposure time is counterproductive to examine many types of samples, such as biological samples, which are very susceptible to altering their atomic structure during the observation process in an TEM experiment.
    Recently, in order to avoid all these problems, CMOS sensors have been developed for direct use, that is, capable of measuring electrons without the need for photoconversion in transmission electron microscopes. These new CMOS sensors are based on a combination of known techniques such as: the use of submicron manufacturing technologies, “layout radhard” and backlighting to improve the resistance of the electronic circuitry part in the pixels to irradiation damage and to increase the fill factor or “fill factor”. As well as technologies of thinning of the substrate of the electron sensor to improve the spatial resolution of the sensor, by reducing the problem of “charge sharing”.
    The “Silicon-on-Insulator” technology is also used, which allows greater thinning of the substrate compared to conventional CMOS technology.
    In any of these cases, the process of thinning electron sensors is complex, and makes CMOS, or CCD, very fragile. This also reduces the manufacturing yield and makes the process more expensive. On the other hand, despite the "radhard layout", these CMOS sensors, or CCD, are still susceptible to radiation damage when high-energy electron beams are used, or with high current densities. Therefore, in their application in TEM they are usually accompanied by additional protection systems to control the irradiation dose.
    More specifically, when CMOS, or CCD, sensors are used to capture images of diffraction patterns, which are usually formed by discrete points distributed in the image with a high electron current density, these sensors are even more susceptible to being damaged. by irradiation.


    Other types of direct sensors are CMOS, or CCD, hybrids in which to avoid damage by irradiation with electrons, they use a “pixelated” sensor that is separated from the electronic circuitry by means of the “bump-bonding” technique. In this case, the “fill factor”, that is, the ratio between the area with “pixels” of the sensor and its total area, is 100%. In addition, electrons are completely absorbed in the electron sensor so that electronic circuitry is not damaged by irradiation. Despite this, this hybrid technology is not a conventional technology, the number of pixels is limited due to its own manufacturing technology, and additionally it presents “charge sharing” problems because the sensor cannot lose weight, which implies less spatial resolution
    Finally, electron sensors made with SSD (“silicon strip detectors”) technology have also been proposed, where the surface of the electron sensor perpendicular to the electron beam that impacts it contains a plurality of electrodes extended as parallel silicon bands and separated from each other forming one, or two layers. In this type of electron sensors, electrons can directly affect the sensor.
    In return, this type of SSD sensor reduces the “fill factor” of the electron sensor and its substrate has to be thinned below 50 μm to have a suitable spatial resolution for electron microscopes. In addition, they are not manufactured with conventional technology. All this entails an expensive, complex process that makes the sensor very delicate because it can be broken more easily by reducing the production yield.
    A final problem refers to the dynamic range of the “pixelated” electron sensors, that is to say the amplitude of the range of intensity values that can be measured in each “pixel”. In the sensors that receive the electrons directly an infinite dynamic range can be obtained, counting the number of electrons that impact on each “pixel” in a time interval. But this is not practical when the intensities in a “pixel” are very high since electronics are not able to process successive impacts with sufficient speed. In such situations, the detectors must be operated in integrative mode, that is, the sum of the load generated by a large number of impacts is measured in each pixel and not each individual impact. This value measured in integrator mode is an analog value that needs to be digitized, with a dynamic range that is determined by the number of bits of the analog-digital converter used. In today's “pixelated” detectors, each pixel has only one analog-to-digital converter with a typical dynamic range of 12 bits. This range is insufficient.


    in TEM when two-dimensional images of diffraction patterns are taken. As a result, in some pixels of the image the intensities go out of the dynamic range and their real value is not captured. DESCRIPTION OF THE INVENTION
    The present invention describes an electron sensor for electron microscopy performed by an electron microscope, wherein the electron sensor comprises a substrate, with an anterior plane and a posterior plane parallel to each other, which is intended to absorb at least one electron from a electron beam that passes through a sample and that is generated by the electron microscope, and this electron is capable of generating an electric charge of free electron-hole pairs (eh) in said substrate.
    More specifically, the electron sensor comprises:
    - a lateral receiving surface, located on one of the sides of the substrate to receive the electron beam perpendicularly,
    - a guard unit, with a lower plane and an upper plane, deposited in the previous plane parallel bordering at least the lateral reception surface crossed by the electron beam, to avoid leakage currents at the edge of the substrate,
    - a base unit, with a lower plane and an upper plane, deposited in the anterior plane following the guard unit, intended to measure the energy of electrons that impact on the lateral receiving surface,
    - an input unit, with a lower plane and an upper plane, deposited in the anterior plane between the lower plane of the guard unit and the upper plane of the base unit to detect the electron entry point of the electron beam ,
    - a contact unit, deposited on the backplane, and
    - an electronic circuitry unit, located next to the base unit and linked to at least the base unit, the contact unit and the input unit, which comprises an electric generator and electrical circuit.
    Wherein, said electric generator generates an electric polarization current, between the previous plane and the back plane, which draws the free electrons generated in the substrate towards the base unit and / or the input unit, and drags the free holes generated at


    substrate towards the contact unit; allowing electrons and holes to be captured by their respective units and conditioned and processing the free electrons by an electronic circuit included in said control unit to form a monodimensional or two-dimensional image with greater dynamic range and to measure the energy of the electrons that They form the image.
    More specifically, the input unit comprises a series of input electrodes, or "pixels", separated from each other, and the lower plane of the guard unit comprises at least one guard electrode with a plurality of grooves suitable to accommodate the plane top of the series of input electrodes without directly contacting these.
    More specifically, the base unit is intended to reduce cross-talk between adjacent input electrodes, as well as to measure the energy of electrons impacting the substrate.
    Additionally, the upper plane of the base unit comprises a base electrode with a plurality of grooves suitable to accommodate the lower plane of the series of input electrodes without directly contacting them.
    Preferably, the junction zone between the lower plane of the input unit and the upper plane of the base unit comprises an energy measurement unit to increase the accuracy of the measurement of the energy of the electrons that pass through the series of unit of entry.
    Said energy measurement unit comprises a series of energy measurement electrodes.
    Preferably, each energy measurement electrode comprises a superposition of measurement electrodes of substantially oval configuration.
    It should be noted that the input unit, the contact unit and the base unit are connected to an electronic circuitry unit by means of tracks deposited on the contact substrate with high electrical conductivity, for example aluminum, gold or polysilicon.
    Alternatively, the input unit, the contact unit, the energy measurement unit


    and the base unit is connected to an electronic circuitry unit by means of tracks deposited on the substrate of a contact with high electrical conductivity such as aluminum, gold or polysilicon.
    More specifically, the base electrode, each input electrode and each electrode of the superposition of electrodes of energy measurement are connected, by means of tracks deposited on the substrate of a contact with high electrical conductivity for example aluminum, gold or polysilicon.
    Said electronic circuitry unit is away from the base unit to avoid its exposure to the radiation of the electrons and to the secondary radiation generated in the substrate.
    Said electronic circuitry unit allows measuring the impact position and energy of electrons in at least two different ways.
    The circuitry unit can measure in position counting mode, where it counts how many electrons impact on each input electrode, in this way it can know in which part of the receiving side surface the electrons impact and the number of impacts. Additionally, the circuitry unit can measure in position integrator mode, where it adds up the total charge released by the electrons that impact on each input electrode for a certain time and knowing in which part of the lateral reception surface they have impacted. In both cases, the electrical charge generated in the sensor and which is not captured by the input electrode (electron impact point) is captured by the energy measuring electrodes and / or by the base electrode. In this way, the "crosstalk" between the neighboring input electrodes in the linear direction of the sensor is reduced.
    Additionally, the circuitry unit can measure in a counting and integrating mode, where it measures the number of electrons that impact on each input electrode knowing in which part of the lateral reception surface, while integrating, that is to say sum the total charge released by electrons that impact on each electrode of energy measurement for a certain time.
    Alternatively, the circuitry unit can measure in dual integrator mode, where it adds up the total charge released by the electrons that impact on each input electrode and on each


    electrode of energy measurement during a certain time and knowing in which part of the lateral surface of reception the impact takes place.
    Preferably, the electrodes of all the units of the back and front planes of the substrate are made of doping materials diffused in the substrate. More specifically, the diffusions of dopants type "p" or type "n" of the posterior and anterior faces of the substrate respectively and the doped of the substrate constitute an "array" of diodes with pn junctions.
    Thus, by means of said circuitry unit a polarization voltage is applied between the electrodes of the back and front faces of the substrate so that the "diodes" are polarized in reverse creating a depletion zone in the substrate.
    It should be noted that the proposed electron sensor is preferably a linear sensor, that is, it is formed by a single line, or electrode vector to measure a monodimensional or two-dimensional image, and allows the energy of the incident electrons in each pixel of the pixel to be measured. image.
    Preferably, this electron sensor can be manufactured with conventional lithographic techniques and electronic circuitry by means of CMOS microelectronic technology. More specifically, it can be manufactured using standard CMOS technology, so that while in one area of the substrate the electronic circuitry unit is manufactured, at the other end only the units comprising the different electrodes are manufactured.
    Additionally, this electron sensor allows its use as a direct "pixelated" detector of energy filters that are used in energy loss electron spectrometry applications (EELS or EFTEM in its acronyms in English). In the case of EELS the sensor measures the monodimensional energy spectrum dispersed by the energy filter. In the case of EFTEM the sensor is used to form two-dimensional images in a specific range of energy.
    Additionally, by arranging each pixel of the sensor of several electrodes at different depths (input electrode and energy measurement electrodes) to measure the charge generated by the impact of an electron, it is possible to measure the energy of the incident electron without


    need to use an energy filter.
    In this way, an electron sensor resistant to irradiation damage is obtained, which can directly measure the electrons that impact on it with a high spatial and energy resolution.
    Likewise, by having at each pixel not only one but several electrodes at different depths (input electrode and energy measurement electrodes), it is possible to measure the charge generated by the impact of electrons in a given time (integrator mode) using more than one electrode in each and thus obtain a greater dynamic range of the sensor compared to the existing pixelated detectors.
    Another advantage of this electron sensor is that it allows said two-dimensional images to be formed in a TEM microscope by scanning the electron beam by electromagnetic means and capturing the image line by line. This is a difference with respect to the sensor technologies used in imaging applications with optical photons, or X-rays, which are particles without electric charge and therefore are not likely to be scanned by sweeping the beam by electromagnetic means.
    Additionally, said electron sensor being formed by a single line of input electrodes, the problem of "charge sharing" is eliminated in the transverse direction of the sensor.
    On the other hand, because the side receiving surface does not contain electrodes, the “fill factor” of the electron sensor design proposed here is 100%. This allows the detection of electron impacts between two input electrodes using signal averaging techniques between adjacent input electrodes, known as subpixel techniques, and thereby increase the effective resolution of the sensor.
    As a summary, this electron sensor is easy to manufacture and allows the generation of monodimensional or two-dimensional images with greater dynamic range, as well as measuring the energy of the electron with electrodes at different depths of the substrate, without the electronics for controlling and processing the Sensor signals are exposed to irradiation of the electron beam.

    DESCRIPTION OF THE DRAWINGS
    To complement the description that is being made and in order to help a better understanding of the characteristics of the invention, according to a preferred example of practical implementation thereof, a set of drawings is attached as an integral part of said description. where, for illustrative and non-limiting purposes, the following has been represented:
    Figure 1.- Shows a perspective view of a preferred embodiment of the electron sensor.
    Figure 2.- Shows a schematic side view of the preferred embodiment of the electron sensor.
    Figure 3a.- Shows a schematic view in detail of the position of the electrodes.
    Figure 3b.- Shows a schematic view in detail of the position of the electrodes where an electron beam impacts on the lateral reception surface.
    Figure 4.- Shows a schematic view in detail of the electrode connections.
    Figure 5a.- Shows a schematic view of a first configuration of several electron sensors placed in parallel.
    Figure 5b.- Shows a schematic view of a second configuration of several electron sensors placed in parallel.
    Figure 5c.- Shows a schematic view of a third configuration of several electron sensors placed in parallel.
    Figure 5d.- Shows a schematic view of a fourth configuration of several electron sensors placed in parallel.


    electrons placed in parallel. PREFERRED EMBODIMENT OF THE INVENTION
    In a preferred embodiment of the invention, as shown in Figures 1 and 2, the electron sensor (1), for TEM electron microscopy, comprises a silicon substrate (2) that receives perpendicularly, via a receiving surface lateral (3), an electron beam (10) coming through a sample, not shown, to investigate. Wherein said electron beam (10) is produced by the TEM microscope, and comprises at least one electron with an electric charge and an energy. To form an image (11), the impact and / or energy position of a large number of electrons in the electron beam (10) is measured.
    The substrate (2) comprises a posterior plane (2p) and a anterior plane (2a) parallel to each other, and perpendicular to the lateral receiving surface (3). On said rear plane (2p) a contact unit is deposited, and on its previous plane (2a) they are deposited in order from least to greatest distance with the lateral reception surface (3): a guard unit, an input unit , an energy measurement unit, a base unit and an electronic circuitry unit (12).
    Preferably, the substrate (2) has a thickness between 300 and 600 μm, and is made of slightly doped silicon type P of resistivity between 2 and 10 kŸ.
    When this electron beam (10) hits the lateral receiving surface (3), the electrons in the electron beam (10) lose energy by generating a free charge of electron-hollow pairs (eh) in the substrate silicon (2). The generation of an electron-hollow pair in silicon requires 3.6 eV so that a single 100-keV electron that impacts on the lateral reception surface (3) generates approximately 27,777 e-h pairs.
    It should be ruled out that when the electron hits the lateral reception surface (3), it describes a random path and loses energy as it generates a free charge of e-h pairs. This electron is finally fully absorbed by the substrate (2) at a distance that can be hundreds of micrometers away from the lateral receiving surface.
    (3) that is the point of impact. Therefore, each electron that impacts ends up absorbed in


    Some point in an area usually called interaction volume. This interaction volume is usually in the shape of a pear, as shown schematically in Figure 2 and Figure 3b, and its size depends on the initial energy of the electron.
    More specifically, prior to impacting on the lateral reception surface (3) said electron beam (10) passes through a mask (9) opaque to the electrons, preferably made of platinum, with a groove that extends across the sensor width. electrons (1). More specifically, this groove has a width equal to the pitch between "pixels" of the input unit, and is preferably close to the lateral reception surface (3). In this way, the mask (9) defines the effective width of the "pixel" in the direction of the thickness of the substrate (2).
    Preferably, as shown in Figures 1, 2 and 3a, the contact unit comprising a contact electrode (4) substantially occupies the entire width of the backplane (2p) and has a maximum height of 400 μm. Said contact electrode (4) is a deposition of doped silicon type p + destined to capture the free holes generated in the substrate (2) by the impact of said electron of the electron beam (10) and which are dragged by an electric field of polarization towards the back plane (2p).
    Preferably, the guard unit comprises a guard electrode (5). The guard electrode (5) is deposited so that it extends across the width and length of the substrate (2), bordering the entire anterior plane (2a). Its geometry is substantially a set of strips in the form of four strips that form a frame, where the side closest to the lateral receiving surface (3) has a plurality of grooves. Said guard electrode (5) is a deposition of doped silicon type n with a height of 2 μm destined to capture the free electrons generated in the substrate (2) by the impact of said electron of the electron beam (10) and which are dragged by the electric polarization field towards the previous plane (2a).
    The input unit comprises a series of input electrodes (6) preferably of rectangular configuration and separated from each other, to capture the specific point of impact of the electrons of the electron beam (10) on the lateral reception surface (3). Said input electrodes (6) are depositions of doped silicon type n intended to capture the free electrons generated in the substrate (2) by the impact of said electron from the electron beam (10)


    and that are carried by the electric polarization field towards the previous plane (2a).
    Specifically, the input electrodes (6) have a substantially rectangular configuration with a height of 10 to 70 μm and a width of 4 to 20 μm. More specifically, its upper plane is housed in said plurality of slits of the guard electrode (5). Each of these input electrodes (6) are separated from the adjacent one by a distance between 10 to 50 μm. It should be noted that each slit of the guard electrode (5) has a height of at least 1 μm and a width of at least 6 μm, where said width is always at least 1 μm greater than the width of the input electrode (6) that hosts, so that they are never in direct contact, as can be seen in figure 3a.
    On the other hand, the number of input electrodes (6) determines the spatial resolution of the electron sensor (1). Thus, in this embodiment preferably, the number of input electrodes (6) or "pixels" is equal to 2048, the width of each input electrode (6) is 10 μm and the height is 50 μm, and The separation between each central vertical axis of each input electrode (6) is 25 μm. Therefore, the width of the electron sensor (1) is at least
    51,200 μm. It should be noted that these 2048 input electrodes (6) have not been fully represented in the figures to facilitate their understanding.
    Preferably, the lower plane of each of the input electrodes (6) is housed in a plurality of receptacles of the base unit. That is, the base unit comprises a base electrode (8) with said plurality of receptacles that partially cover each of the input electrodes (6).
    More specifically, this base electrode (8) extends over the entire width of the anterior plane (2a) and has a height between 100 and 400 μm. It should be noted that the size of these receptacles is variable, but preferably they have a substantially oval configuration with a height between 10 and 150 μm, and a width between 10 and 35 μm. Preferably, the base electrode (8) comprises a height of 200 μm, and each receptacle has a height 50 μm and a width of 20 μm. Said base electrode (8) is a deposition of doped silicon type n intended to capture the free electrons generated in the substrate (2) by the impact of said electron from the electron beam (10) and which are carried by the electric field of polarization towards the anterior plane (2a).


    It should be noted that for each input electrode (6) the guard electrode (5) has a groove, and the base electrode (8) has a receptacle.
    In this preferred embodiment, as shown in greater detail in Figure 3a, in the junction zone between each input electrode (6) and the base electrode (8), that is the area between the lower plane of the electrodes input (6) and the upper plane of the base electrode (8), the electron sensor (1) comprises the energy measurement unit. This unit of energy measurement in turn comprises an energy measurement electrode (7) for each input electrode (6). These energy measurement electrodes (7) increase the accuracy of the energy measurement of the electrons that pass through the series of input electrodes (6). Specifically, these energy measurement electrodes (7) are surrounded by the base electrode
    (8) and have a substantially oval shape with a height between 10 and 20 μm, and a width between 20 and 30 μm. Preferably, each energy measurement electrode
    (7)  It comprises a height of 20 μm and a width of 20 μm. Said energy measurement electrodes (7) are depositions of doped silicon type n intended to capture the free electrons generated in the substrate (2) by the impact of said electron from the electron beam (10) and which are carried by the electric field of polarization towards the anterior plane (2a). Thus, as shown in Figure 3b, the accuracy of the electron sensor is increased to measure the charge (and therefore the energy) generated in the substrate by the incident electrons (1).
    More specifically in Figure 3b, the probability that electrons in the electron beam (10) are absorbed at different depths in the substrate (2) is shown. Additionally, this figure 3b shows by which electrode or electrodes (6, 7, 8) the charge generated by the electron along its path through the substrate (2) will be detected. In this way, it can be verified how the electron sensor (1) detects with great precision where the electrons strike through the input electrode (6). Additionally, this electron sensor
    (one)  It allows measuring the electron energy of the electron beam (10) by detecting the free charge of e-h pairs generated at different depths, by means of electrodes (6, 8), (7, 8) or (6,7,8). These electrodes (6, 7, 8) detect the depth and lateral distribution at which the electrons are absorbed in the substrate (2), both the depth and the lateral distribution being proportional to the initial energy of the electrons.


    between 1 and 2 μm. More specifically, these separation zones are found in the following electrodes (5, 6, 7, 8):
    - between each slit of the guard electrode (5) and each input electrode (6),
    - between each guard electrode (5) and the base electrode (8),
    - between each input electrode (6) and each base electrode receptacle (8),
    - between each input electrode (6) and each energy measurement electrode (7),
    - between each energy measurement electrode (7) and each base electrode receptacle (8).
    Additionally, the base electrode (8), each input electrode (6) and each energy measurement electrode (7) are connected, by means of metal tracks (13, 13 ', 13' ') usually of aluminum deposited on the substrate (2), to an electronic circuitry unit
    (12) inserted in the anterior plane (2a) of the substrate (2) following the base electrode (8), as shown schematically in Figure 4. Additionally, contact electrode (4) is also connected to the electronic circuitry unit (12) by means of a metal track not shown.
    Said electronic circuitry unit (12) comprises an electric generator to generate a bias voltage between the electrodes (5, 6, 7, 8) of the anterior plane (2a) and the contact electrode (4) of the posterior plane (2p) . Specifically, the electrodes (5, 6, 7, 8) are at a negative polarization potential with respect to the contact electrode (4). In this way, the polarization voltage generates an electric field that serves to drag the holes or free electrons of the e-h pairs generated in the substrate (2) towards the back plane (2p) or towards the previous plane (2a).
    More specifically, the free electrons of the eh pairs generated by the impact of an electron are dragged towards the electrodes (5,6, 7, 8) of the anterior plane (2a) and the holes are dragged towards the single contact electrode (4 ) of the backplane (2p) of the electron sensor (1). This movement of charges induces an electric current in the electrodes (4, 5, 6, 7, 8) that through metal tracks (13, 13 ', 13 ") deposited on the substrate (2) is measured in the electronic circuitry unit (12).
    More specifically, the electronic circuitry unit (12) comprises at least one circuit


    electronic to condition and process the information captured by the electrodes (5, 6, 7, 8) by the impact of at least one electron from the electron beam (10) received on the lateral receiving surface (3).
    Preferably, several electron sensors (1) are placed in parallel with different configurations to obtain different advantages, as well as to generate two-dimensional images formed by successively adding monodimensional lines measured by each of the electron sensors (1).
    The first configuration of several electron sensors (1) in parallel, is shown in Figure 5a, where three electron sensors (1) are linked spaced apart. Each of these electron sensors (1) has electrode dimensions (4, 5, 6, 7, 8) optimized to detect a range of initial energies of electrons in the electron beam (10). In this case, preferably for TEM microscopes, each of the electron sensors (1) is configured to detect respectively the following energy ranges of the electrons: 60-120 keV, 120-200 keV and 200-300 kV. Thus, depending on the energy used in a specific application, the use of a single electron sensor (1) can be selected to form the image (11).
    The second configuration of several electron sensors (1) in parallel, is shown in Figure 5b, where two electron sensors (1) are positioned displaced from each other at a distance of half a pixel to double the spatial resolution. In this case both electron sensors (1) are used at the same time.
    The third configuration of several electron sensors (1) in parallel is shown in Figure 5c, where at least two electron sensors (1) are placed in parallel, although preferably three. In this way it is possible to acquire images at a higher speed, that is to say more frames per second, without reducing the exposure time using the "Time-Delay-Integration" technique that is applied with linear sensors in optical applications. This configuration is especially useful in applications that require the capture of series of two-dimensional images at high speed such as in dynamic applications with TEM microscopes (in-situ TEM).
    The fourth configuration of several electron sensors (1) in parallel, is shown in the


    Figure 5d, where at least two electron sensors (1) are placed in parallel and each of them comprises input electrodes (6) and / or energy measurement electrodes (7) with different sizes. This configuration allows to form the image (11) with different resolutions.
    The fifth configuration of several electron sensors (1) in parallel, is shown in Figure 5e, where a plurality of electron sensors (1) are connected to form a two-dimensional image (11) scanning the electron beam (10) successively in discrete steps and capturing with each electron sensor (1) a line of pixels in each position. That is, to form a two-dimensional image (11) of 2048 x 2048 pixels and if the electron sensor (1) comprises a line of 2048 input electrodes (6), 2048 lines would have to be measured in 2048 discrete positions. The process is more efficient, preferably placing 3 electron sensors (1) with a separation of 512 pixels. Thus, the electron beam (10) would be scanned an equivalent distance of 512 pixels instead of 2048 pixels, and the two-dimensional image (11) would be captured in a quarter of the time.
    It should be noted that the present electron sensor (1) is capable of measuring a single-dimensional or two-dimensional image.
    Preferably, to measure monodimensional images typically when used in combination with an energy filter, both the electron sensor (1) and the electron beam (10) projected from the electron microscope are kept in the same horizontal position.
    While at least four methods are used to measure two-dimensional images. In any of these methods, by means of the capture of multiple projection lines of the electron beam (10) with the electron sensor (1) the two-dimensional image (11) is formed.
    Preferably, in the first method, the electron sensor (1) is fixed at a position in the projection plane of the electron beam (10), and the representation projected by the TEM is scanned by means of electromagnetic systems (for example, projecting lens coils that are included in any TEM) that travels in a direction perpendicular to the linear direction of the sensor.


    Preferably, in the second method, the projection of the electron beam (10) is in a fixed position, and the electron sensor (1) is moved by mechanical means such as the use of an electric motor with a mechanical system that transforms the motor rotation in a linear displacement. The advantage of this method is that it is not necessary to control the
    5 electromagnetic systems of the TEM for scanning the beam.
    Preferably, in the third method, the projection of the electron beam (10) and the electron sensor (1) is in a fixed position, and the sample is moved by mechanical means such as the use of an electric motor with a system mechanical transformer
    10 the motor rotation in a linear displacement. The advantage of this method is that it is not necessary to control the electromagnetic systems of the TEM for scanning the beam or the sensor.
    Preferably, in the fourth method, when the sensor is used as a sensor in applications
    15 of EFTEM, the projection of the electron beam (10) filtered by an energy filter, the electron sensor (1) and the sample, are in a fixed position, and the electron beam filtered in energy is scanned in the perpendicular direction of the electron sensor (1) using the electromagnetic systems present in the energy filters that are commonly used in TEMs for spectrometry applications.
    In another preferred embodiment, not shown, the electron sensor (1) is also applicable to measure the energy of transmitted and secondary electrons in scanning mode scanning electron microscopes, called STEM and SEM, by scaling the sensor size. of electrons (1) and the number and geometry of the pixels or
    25 electrodes (4, 5, 6, 7 8), to adapt it to these applications and the particular energy ranges of the application.
    More specifically, in SEM and STEM applications the images the electron sensor
    (1) that we propose would be fixed in a microscope position since the images and 30 spectra in these applications are formed by sweeping a point-to-point beam.

    权利要求:
    Claims (19)
    [1]

    1.- Electron sensor (1) for electron microscopy performed by an electron microscope, where the electron sensor (1) comprises a substrate (2), with an anterior plane (2a) and a posterior plane (2p) parallel between yes, it is intended to absorb at least one electron from an electron beam (10) that passes through a sample and is generated by the electron microscope, and this electron is capable of generating an electric charge of electron-hollow pairs (eh) free on said substrate (2), characterized in that the sensor of electors (1) comprises:
    - a lateral receiving surface (3), located on one of the sides of the substrate (2) to receive perpendicularly the electron beam (10),
    - a guard unit, with a lower plane and an upper plane, deposited in the anterior plane (2a) bordering at least parallel the lateral reception surface (3) crossed by the electron beam (10), to avoid leakage currents in the edge of the substrate (2),
    - a base unit, with a lower plane and an upper plane, deposited in the previous plane (2a) following the guard unit, intended to measure the energy of electrons in the electron beam that impact on the lateral receiving surface (3),
    - an input unit, with a lower plane and an upper plane, deposited in the anterior plane (2a) between the lower plane of the guard unit and the upper plane of the base unit to detect the entry point of the electrons of the electron beam,
    - a contact unit, deposited on the backplane (2p), and
    - an electronic circuitry unit (12), located next to the base unit and linked to at least the base unit, the contact unit and the input unit, which comprises an electric generator and electric circuit,
    wherein said electric generator generates an electric polarization current, between the anterior plane (2a) and the posterior plane (2p), which draws the free electrons generated in the substrate (2) towards the base unit and / or the unit of entrance, and drag the free gaps towards the contact unit; allowing electrons and holes to be captured by their respective units and conditioned and processing free electrons by an electronic circuit comprised in said control unit to form a monodimensional or two-dimensional image (11) with greater dynamic range.

    [2]
    2. Electron sensor (1) according to claim 1, characterized in that the input unit comprises a series of input electrodes (6).
    [3]
    3. Electron sensor (1) according to claim 2, characterized in that the input electrodes (6) comprise a height between 10 and 70 μm, a width between 4 and 20 μm, and wherein said input electrodes (6 ) are separated from each other at a distance between their vertical axes between 10 and 50 μm.
    [4]
    4. Electron sensor (1) according to claim 3, characterized in that the input electrodes (6) comprise a height of 50 μm, a width of 10 μm, and are separated from each other at a distance between their vertical axes of 25 μm
    [5]
    5. Electron sensor (1) according to any one of claims 2 to 4, characterized in that the guard unit comprises at least one guard electrode (5) close to the lateral reception surface (3), in whose plane The lower part has a plurality of grooves to accommodate the upper plane of the input electrodes (6) without directly contacting.
    [6]
    6. Electron sensor (1) according to claim 5, characterized in that the guard electrode (5) is deposited as four strips that form a frame, two of them wide and two long of the substrate (2) in where the strip of the guard electrode (5) closest to the lateral receiving surface (3) has a plurality of grooves to accommodate the upper plane of the input electrodes (6) without directly contacting.
    [7]
    7. Electron sensor (1) according to any one of claims 5 to 6, characterized in that the guard electrode (5) comprises a height of 2 μm, and each slot has a height of at least 1 μm and a greater width at least 1 μm greater than the width of the input electrode (6).
    [8]
    8. Electron sensor (1) according to any one of claims 2 to 7, characterized in that the base unit comprises a base electrode (8) with a plurality of receptacles in its upper plane to accommodate the lower plane of those of input electrodes (6) without contacting directly.

    [9]
    9.- Electron sensor (1) according to claim 8, characterized in that the base electrode
    (8) It extends over the entire width of the substrate (2) and has a height between 100 and 400 μm.
    [10]
    10.- Electron sensor (1) according to claim 9, characterized in that the base electrode
    (8) It comprises a height of 200 μm.
    [11]
    11. Electron sensor (1) according to claim 8, characterized in that each base electrode receptacle (8) has a substantially oval configuration with a height between 10 and 150 μm, and a width between 10 and 35 μm.
    [12]
    12.- Electron sensor (1) according to claim 8, characterized in that each base electrode receptacle (8) comprises a height 50 μm and a width of 20 μm.
    [13]
    13. Electron sensor (1) according to any one of claims 8 to 12, characterized in that the junction zone between the lower plane of the input electrodes (6) and the upper plane of the base electrode (8) comprises a series of energy measurement electrodes (7) to measure the energy of the electrons that, upon impact on the lateral reception surface (3), pass through the input electrodes (6).
    [14]
    14.- Electron sensor (1) according to claim 13, characterized in that the energy measuring electrodes (7) have a substantially oval shape with a height between 10 and 20 μm, and a width between 20 and 30 μm.
    [15]
    15.- Electron sensor (1) according to claim 14, characterized in that the energy measuring electrodes (7) comprise a height of 20 μm and a width of 20 μm.
    [16]
    16. Electron sensor (1) according to claim 15, characterized in that each energy measurement electrode (7) comprises a superposition of measurement electrodes of substantially oval configuration.
    [17]
    17. Electron sensor (1) according to claim 1, characterized in that the contact unit comprises a contact electrode (4) that substantially occupies the entire width of the backplane (2p) and has a maximum height of 400 μm .

    [18]
    18. Electron sensor (1) according to claim 13, characterized in that the contact electrode (4), base electrode (8), each input electrode (6) and each energy measurement electrode (7) are connected, by means of metal tracks (13, 13 ', 13' ') deposited
    5 on the substrate (2), to the electronic circuitry unit (12) that is inserted in the anterior plane (2a) of the substrate (2) following the base electrode (8),
    [19]
    19.- Electron sensor (1) according to claim 16, characterized in that the contact electrode (4), the base electrode (8), each input electrode (6) and each electrode of the
    10 superposition of energy measurement electrodes are connected, by means of metal tracks (13, 13 ', 13' ') deposited on the substrate (2) to the electronic circuitry unit (12) that is inserted in the previous plane ( 2a) of the substrate (2) following the base electrode (8).
    20. System for electron microscopy performed by an electron microscope, characterized in that it comprises at least two electron sensors (1) according to any one of claims 1 to 17 placed in parallel to generate two-dimensional images formed by the successive addition of single-dimensional lines measured by each of the electron sensors (1).

     DRAWINGS 




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    同族专利:
    公开号 | 公开日
    US10811220B2|2020-10-20|
    EP3483916A1|2019-05-15|
    US20190393015A1|2019-12-26|
    EP3483916B1|2021-04-07|
    WO2018007669A1|2018-01-11|
    ES2653767B1|2019-03-28|
    EP3483916A4|2020-03-11|
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    US16/315,037| US10811220B2|2016-07-07|2017-07-06|Electron sensor for electron microscopy|
    PCT/ES2017/070489| WO2018007669A1|2016-07-07|2017-07-06|Electron sensor for electron microscopy|
    EP17823710.3A| EP3483916B1|2016-07-07|2017-07-06|Electron sensor for electron microscopy|
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