Protection device for an electronic component, and associated protection system and electronic circuit

Abstract

One aspect of the invention relates to a protection device (3) for an electronic component, comprising two doped semiconductor layers (4, 6) separated by an insulating layer (8), wherein an opening (9) is formed in the insulating layer (8) in order to align the first and second electrodes (4, 6), and wherein a distance (h46) separating the two semiconductor layers (4, 6) is less than 5 µm.

Description

DESCRIPTION TITLE: PROTECTION DEVICE FOR ELECTRONIC COMPONENTS, PROTECTION SYSTEM AND ASSOCIATED ELECTRONIC CIRCUIT TECHNICAL FIELD OF THE INVENTION

[0001] The technical field of the invention is that of the protection of electronic components against overvoltages and / or overcurrents typical of a lightning strike. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0002] An electronic component can be subjected to a current or voltage overload, known respectively as "overcurrent" and "overvoltage." These overcurrents or overvoltages generally have a very short rise time, on the order of a few microseconds, and high amplitudes. They can occur following a lightning strike, the operation of a switch, an electrostatic discharge, or an electromagnetic pulse (for example, of nuclear origin).

[0003] One way to protect a component from overvoltage or overcurrent is to clip the overvoltage or limit the overcurrent. One method of doing this is to short-circuit all or part of the overvoltage and introduce a high impedance in series with the component to be protected.

[0004] There are several technologies for creating a short circuit, with different response times and discharge power.

[0005] A Zener diode can be used, for example. A Zener diode can be made by joining two semiconductor materials with different doping levels or conductivities. When the voltage across the Zener diode exceeds its threshold voltage, the diode conducts and forms a short circuit. As soon as the voltage decreases, the diode returns to a blocked state.

[0006] A variable resistor, which is highly nonlinear, can also be used. Nonlinearity can be an intrinsic property of certain materials such as ZnO or SiC. Above a certain voltage threshold, the impedance of the variable resistor drops to short-circuit the overvoltage. As the voltage decreases, the impedance of the variable resistor increases.

[0007] A gas discharge tube can also be used. A gas discharge tube consists, for example, of two nozzles placed a short distance apart. A voltage surge causes a breakdown between the nozzles and the formation of an electric arc. This arc then short-circuits the voltage surge. As soon as the voltage across the nozzles falls below the arc voltage, the short circuit breaks.

[0008] It is also known to create a short circuit by implementing electrostatic discharges, called "ESD" for "electro-static discharges" in English.

[0009] For example, US patent 2012 / 0236450 A1 discloses an ESD protection device. The device comprises two conductive electrodes separated by an air gap. The breakdown voltage of the devices allows them to short-circuit an overvoltage.

[0010] Documents KR100781487 B1 and US 2014 / 0240878 A1 also disclose ESD protection devices. Unlike the aforementioned device, the breakdown voltage of these devices is controlled by the presence of conductive and / or semiconducting protrusions or particles dispersed between the two electrodes.

[0011] These devices, however, do not limit the current when they are conducting. The component is therefore not completely protected. An additional device is necessary to limit the current. Furthermore, they can also be quite bulky due to their significant thickness (the thickness being measured parallel to the current flow in the air gap). This thickness is generally greater than 5 mm.

[0012] Climate change is a major concern for many legislative and regulatory bodies worldwide. Indeed, various restrictions on carbon emissions have been, are being, or will be adopted by various states. In particular, an ambitious standard applies to both new types aircraft, as well as those currently in operation, require the implementation of technological solutions to bring them into compliance with current regulations. Civil aviation has been actively contributing to the fight against climate change for several years now.

[0013] Technological research efforts have already led to very significant improvements in the environmental performance of aircraft. The Applicant takes into account the factors impacting all phases of design and development in order to obtain less energy-intensive and more environmentally friendly aeronautical components and products whose integration and use in civil aviation have moderate environmental impacts, with the aim of improving the energy efficiency of aircraft.

[0014] Consequently, the Applicant is constantly working to reduce its climate impact by using methods and operating virtuous development and manufacturing processes that minimize greenhouse gas emissions to the minimum possible in order to reduce the environmental footprint of its activity.

[0015] This sustained research and development work focuses on new generations of aircraft engines, the weight reduction of aircraft, particularly through the materials used and lighter on-board equipment, the development of the use of electrical technologies to provide propulsion, and, as essential complements to technological progress, aviation biofuels.

[0016] To this end, there is a need to provide a protection device that can clip overvoltages while limiting the current flowing when it is conducting and has a small footprint. SUMMARY OF THE INVENTION

[0017] The invention offers a solution to the problems mentioned above by providing a protection device that exploits the tunnel effect and / or the field effect, thereby clipping overvoltages while limiting the current flowing when conductive. Furthermore, this device has the advantage of being less bulky than devices according to the prior art.

[0018] The invention relates primarily to a protection device for an electronic component remarkable in that it comprises: a first doped semiconductor layer, called the "first electrode", extending parallel to a plane; a second doped semiconductor layer, called the "second electrode", also extending parallel to the plane; an insulating layer separating the first electrode from the second electrode, an opening being provided in the insulating layer to bring the first and second electrodes into contact, a distance separating the first electrode from the second electrode, measured perpendicular to the plane, being less than 5 pm.

[0019] By "insulating layer", we mean an electrically insulating layer.

[0020] Opening the electrically insulating layer (also called the "insulating layer") creates an air gap between the two electrodes. This air gap forms a potential barrier between them. The small distance between the two electrodes allows for a thin air gap. This makes it possible to exploit the flow of electrons through the air gap by tunneling or by field effect.

[0021] The term "tunneling effect" refers to a quantum effect in which an electron has a non-zero probability of crossing a potential barrier formed by the air gap, even if its energy does not exceed the potential of the barrier.

[0022] The term "field effect" refers to an effect whereby an electric field modulates the height of the potential barrier formed by the air gap, thus allowing an electron to cross this barrier.

[0023] Doping the semiconductor layers that form the electrodes allows them to conduct an electric current at lower electrical potential values ​​than those required for an intrinsic semiconductor. Thus, applying a voltage between the electrodes, when it exceeds a threshold voltage, allows the flow of electrons, either by tunneling or by field effect through the air gap. The threshold voltage therefore determines the voltage at which an overvoltage is clipped. Furthermore, the modulation of the Doping in the electrodes also allows modulation of the threshold voltage and therefore the clipping voltage of the device. The threshold voltage of the device also depends on the distance separating the electrodes (in other words, the thickness of the air gap).

[0024] The thinner the air gap, the lower the threshold voltage.

[0025] Figure 1 shows several current-voltage characteristics (referred to as "I-V characteristics") obtained on the same device. Current flow is zero as long as the applied voltage between the first and second electrodes of the device remains below a threshold voltage, called "Vthreshold". Once this voltage exceeds + / - Vthreshold, current flow begins. Specifically, the current is established by tunneling. In this example, the electrodes are made from doped silicon. An example of an I-V characteristic is shown in Figure 1. The plateaus observed on the characteristics for + / - 0.02 A correspond to a current limit of the measurement system, independent of the device being characterized.

[0026] Unlike a prior art device, the amplitude of the current flowing in the device according to the invention is limited. Triggering the current flow at a threshold value allows the protection device to clip overvoltages while limiting the current. This current limitation is achieved through the non-linear current-voltage behavior of the device. As the voltage across the device increases, the current flowing through the device increases less rapidly than in an ohmic conductor. This limitation depends on two factors: the average speed of electrons crossing the air gap; and the electron density crossing this air gap.

[0027] The electron density is limited by the electron emission mechanism, which, whether tunneling or field-effect, depends on the work function of the negatively polarized electrode. Semiconductor electrodes exhibit high work functions, thus limiting the emitted electron density. Furthermore, the work functions of semiconductor materials vary little with doping. It is therefore possible to fabricate a device with a predefined current limit, using a threshold voltage modulated by the electrode doping.

[0028] The speed of electrons passing through the air gap depends on the electric field within the air gap. This field depends, in particular (at constant potential), on the materials and geometry of the electrodes, the distance separating the electrodes, and the permittivity within the air gap. Modifying these parameters therefore allows for adjusting the current limit through the device.

[0029] For purely metallic electrodes, the electric field is established between the external surfaces of the metal electrodes. The electric field resulting from a potential applied to the metallic electrodes is therefore concentrated between these external surfaces. Conversely, for semiconductor electrodes, such as those implemented in the invention, the electric field is established partly within the volume of the electrodes. The apparent distance over which the electric field is established is therefore greater than for metallic electrodes. Consequently, the velocity of electrons in the air gap is reduced.

[0030] The distance between the electrodes, in other words the thickness of the air gap, allows the electric field seen by the electrons to be adjusted and therefore the current limitation in the device to be modulated.

[0031] Modulating the area of ​​the facing surfaces (for example by changing the size of the opening in the insulating layer) can also allow the current limitation to be adjusted without changing the threshold voltage.

[0032] The height of the device is limited by the distance between the two electrodes and the thickness of the semiconductor electrodes themselves. The electric field between the electrodes is established at least partially within the volume of the electrodes. However, it remains localized in the immediate vicinity of the facing surfaces, and particularly within the first few hundred micrometers from these surfaces. An electrode thickness of a few hundred micrometers, for example, between 200 µm and 800 µm, is therefore sufficient to benefit from the effects related to the penetration of the electric field into the electrodes while still providing thin electrodes. Thus, a fully functional device according to the invention can have a height of 2 mm or less, which is significantly less than the height of prior art devices, which generally exceed 5 mm.

[0033] Advantageously, the opening of the insulating layer has a width and / or length between 10 pm and 2000 pm, measured parallel to the plane.

[0034] Advantageously, the protection device further includes a first cavity made in the first electrode and communicating with the opening.

[0035] Advantageously, the first cavity opens partially onto the electrically insulating layer.

[0036] Advantageously, the opening in the insulating layer is laterally delimited by an edge; the first electrode bearing on the electrically insulating layer at a distance from the edge of the opening so that the electrically insulating layer forms a lip extending between the first cavity and the second electrode.

[0037] Advantageously, the first electrode includes a first protrusion extending into the first cavity towards the second electrode; the first protrusion being distant from the second electrode by a distance, measured perpendicular to the plane, of less than 5 pm.

[0038] Advantageously, the first protrusion has a free end facing the second electrode; the protection device includes an additional insulating layer extending against the free end of the first protrusion, masking at least a part of the free end of said at least a first protrusion.

[0039] Advantageously, a peripheral trench extending perpendicularly to the plane is made in the first electrode, the peripheral trench comprising a bottom having a width, measured parallel to the plane, said bottom being distant from the second electrode by a height, measured perpendicular to the plane, of between two times and ten times the width of the peripheral trench.

[0040] Advantageously, the protective device further comprises a second cavity formed in the second electrode and communicating with the opening; the second electrode comprising a second protrusion extending in the second cavity perpendicularly to the plane, in the direction of the first electrode; the second protuberance being at a distance from the first electrode, measured perpendicular to the plane, of less than 5 pm.

[0041] Advantageously, the first doped semiconductor layer has a concentration of doping impurities between 1 and 10 17 at / cm 3 and 1 -10 22 at / cm 3 ; the second doped semiconductor layer has a concentration of doping impurities between 1 and 10 17 at / cm 3 and 1 ■ 10 22 at / cm 3 .

[0042] Advantageously, the first electrode and the second electrode are made from the same doped material.

[0043] Advantageously, the facing surfaces are coated with a native oxide. The presence of an oxide on the electrode surfaces provides a way to control threshold voltages. Furthermore, heat transfer by radiation between the two electrodes can be improved. For example, the emissivity of silicon is around 0.2, while the emissivity of silicon dioxide (SiO2) is around 0.8.

[0044] Advantageously, the first electrode and the second electrode are doped with the same type.

[0045] Advantageously, the first electrode and / or the second electrode includes within it a thin insulating layer extending parallel to the plane and having a thickness, measured perpendicular to the plane, of between 1 nm and 10 nm.

[0046] The invention further relates to a method for manufacturing a protection device for an electronic component, comprising: the provision of a first doped semiconductor layer, referred to as the "first electrode"; the provision of a second doped semiconductor layer, referred to as the "second electrode"; the formation of at least one insulating layer in contact with the first electrode; the provision of an opening in said at least one insulating layer to expose the first electrode; the welding or bonding of the second electrode to said at least one insulating layer such that the first and second electrodes are facing each other through the opening of said at least one insulating layer and that a distance separating the first electrode from the second electrode after the bonding step is less than 5 pm.

[0047] The invention also relates to a protection system for an electronic component comprising a plurality of conductive layers and a plurality of protection devices, the protection devices being distributed so as to form a plurality of distinct protection chains, for each protection chain the protection devices of said protection chain are electrically connected in series, the conductive layers being connected two by two by one of the protection chains, each protection device comprising: a first doped semiconductor layer, called the "first electrode", extending parallel to a plane; a second doped semiconductor layer, called the "second electrode", also extending parallel to the plane;an insulating layer separating the first electrode from the second electrode and extending into contact with the first electrode and into contact with the second electrode, an opening being provided in the insulating layer to bring the first and second semiconductor layers into contact, a distance separating the first electrode from the second electrode, measured perpendicular to the plane, being less than 5 pm.;

[0048] Implementing protection devices within each protection chain allows the threshold voltages of the series-connected devices to be summed. The current limitation in the chain is imposed by the device exhibiting the highest current limiting at a given voltage. In other words, for a first voltage, the first device in the chain can limit the current flowing through the chain, while for a second voltage, a second device in the chain can limit the current flowing through the chain. The current limitation is maximal regardless of the voltage applied across the chain.

[0049] The protection system offers a particular advantage in that it forms a predefined assembly of protection devices. In other words, it forms a generic protection system that allows for the selection of different clipping voltages and current limits. The selection of different pairs of conductive layers, or the connection of these pairs of conductive layers together, allows a user to select different assemblies of protection devices, for example, chains of devices of different lengths and / or a series assembly of chains (to form a long equivalent chain) and / or a parallel assembly of chains (to reduce the clipping voltage and / or lessen the effect of the current limit).

[0050] Furthermore, the implementation of protection devices according to the invention makes it possible to offer a protection system that is easily integrated with a semiconductor-based electronic circuit.

[0051] Advantageously, when a first protective chain from the plurality of protective chains and a second protective chain from the plurality of protective chains connect the same conductive layer, said first and second protective chains are arranged side by side. Preferably, all protective chains are arranged side by side, two by two.

[0052] Advantageously: the insulating layer of a first protective device belonging to the first chain of protection; and the insulating layer of a second protective device belonging to the second chain of protection, are common and formed by the same layer.

[0053] Advantageously: one of the electrodes of a first protection device belonging to the first protection chain; and one of the electrodes of a second protection device belonging to the second protection chain, are common and formed by the same layer.

[0054] Advantageously, in the same protection chain, said protection chain includes a third protection device and a fourth protection device connected in series with the third protection device: one of the electrodes of the third protection device; and one of the electrodes of the fourth protection device, are common and formed by the same layer.

[0055] Advantageously, each protection device is bidirectional. In other words, the first and second electrodes are made from the same doped semiconductor material. Thus, the system is also bidirectional.

[0056] Advantageously, the chains of devices are electrically connected in series with each other.

[0057] The invention also relates to an electronic circuit comprising: a first electronic component to be protected, including a first terminal; and a protection system according to the invention, the first terminal of the first electronic component being connected to a first conductive layer of the plurality of conductive layers of the protection system.

[0058] Advantageously, the electronic circuit includes an additional protection system according to the invention, the first terminal of the first electronic component being connected to one of the conductive layers of the additional protection system.

[0059] Advantageously, the first electronic component to be protected further includes a second terminal, the protection system being connected between the first and second terminals of the first electronic component such that: the first terminal of the first electronic component is connected to the first conductive layer of the protection system; the second terminal of the first electronic component is connected to a second conductive layer of the plurality of conductive layers of the protection system.

[0060] Advantageously, the electronic circuit includes a second electronic component to be protected, comprising a third terminal and a fourth terminal, the protection system also being connected between the third and fourth terminals of the second electronic component such that: the third terminal is connected to a third conductive layer of the plurality of conductive layers of the protection system;and the fourth terminal is connected to the second conductive layer of the protection system or connected to a fourth conductive layer of the plurality of conductive layers of the protection system, the first and second conductive layers being connected to each other by at least one first protection chain of the plurality of protection chains of the protection system, the third conductive layer being connected to the second conductive layer or to the fourth conductive layer by at least one second protection chain of the plurality of protection chains of the protection system.;

[0061] The invention also relates to aircraft protection equipment comprising a protection system for an electronic component according to the invention or an electronic circuit according to the invention. BRIEF DESCRIPTION OF THE FIGURES

[0062] The invention and its various applications will be better understood upon reading the following description and examining the accompanying figures. The figures are provided for illustrative purposes only and are not intended to limit the scope of the invention.

[0063] Figure 1 shows several examples of characteristics that can be obtained by a protection device according to one embodiment of the invention.

[0064] Figures [Fig. 2] and [Fig. 3] show a perspective and a cross-section of an embodiment of the protection device according to the invention.

[0065] Figures [Fig. 4], [Fig. 5], [Fig. 6], [Fig. 7], [Fig. 8], [Fig. 9], [Fig. 10], [Fig. 11] and [Fig. 12] show nine embodiments of the protection device according to the invention.

[0066] Figures [Fig. 13] and [Fig. 14] show cross-sections of an embodiment of the protection device according to the invention.

[0067] Figures [Fig. 15] and [Fig. 16] show cross-sections of an embodiment of the protection device according to the invention.

[0068] Figure 17 shows a cross-section of a first embodiment of a protection system according to the invention.

[0069] Figure 18 shows examples of characteristics that can be obtained by the protection system according to one embodiment of the invention.

[0070] Figures 19, 20, 21 and 22 show three cross-sections of three embodiments of an electronic circuit according to the invention, including in particular a protection system according to one embodiment of the invention. DETAILED DESCRIPTION

[0071] The invention aims to provide protection for an electronic component against overvoltages, for example due to lightning.

[0072] Figure 1 has already been described previously.

[0073] The invention relates initially to a protection device 3 for an electronic component. Different embodiments of said protection device 3 are illustrated in Figures 2 to 16.

[0074] An orthonormal coordinate system {X; Y; Z} is shown in Figures 2, 3, 14 and 16. The coordinate system used for Figures 4 to 13 and 15 (but not shown in these figures) is that of Figure 3 (i.e. the sections follow the same plane).

[0075] Common to the embodiments shown in Figures 2 to 16, the protection device 3 comprises a first semiconductor layer 4 extending parallel to a plane called the "layer plane" (parallel to the {X; Y} plane in the figures). The first semiconductor layer 4 is doped so as to be conductive under the influence of an electric field. It is called the "first electrode".

[0076] The protection device 3 further comprises a second semiconductor layer 6 extending parallel to the same plane {X; Y} as the first electrode 4. The second semiconductor layer 6 is also doped, so that it becomes conductive under the effect of an electric field. It is called the "second electrode".

[0077] The first and second electrodes 4, 6 are superimposed on each other. The two electrodes 4, 6 form the terminals of the protection device 3. An electrical voltage or overvoltage can be clipped when applied between these two electrodes 4, 6.

[0078] The protective device 3 includes an electrically insulating layer 8 (simply called the "insulating layer") extending between the first and second electrodes 4, 6. It isolates the two electrodes 4, 6 from direct electrical contact between them. For example, the insulating layer 8 can be made from: SiO2, SiN, or Al2O3. It can also be made from SixOyNz.

[0079] The first electrode 4 can extend against the insulating layer 8, with which it can be in contact (i.e., in direct contact). The insulating layer 8 can in turn extend against the second electrode 6, with which it can also be in contact. In this way, the two electrodes are separated from each other only by the insulating layer 8.

[0080] The two electrodes 4 and 6 are separated from each other by a minimum distance h46. This distance h46 is measured perpendicular to the {X; Y} plane. It is measured between the two closest portions of electrodes 4 and 6. In Figure 3, electrodes 4 and 6 are planar. This minimum distance h46 is simply measured perpendicular to the {X; Y} plane (and in this case, equal to the thickness h8 of the insulating layer 8). In Figures 11 to 16, electrodes 4 and 6 have semiconductor protrusions 17. These protrusions 17 form projections of semiconductor material extending towards the second electrode (6). The distance h46 to be considered in these cases is then measured between the closest semiconductor portions. In the case of figures 11 to 16, the distance h46 is measured at the level of the semiconductor protuberances 17.In the case of Figure 15, the semiconductor protrusions 17 are in contact with insulating layers 28 and the second electrode 6 also has protrusions 25. The distance h46 is then measured between the semiconductor protrusions 17, 25 of the two layers, independently of the insulating layers 28.

[0081] To achieve current flow via tunneling between the two electrodes 4 and 6, the minimum distance h46 separating them is less than 5 pm. It is understood that this distance h46 is not zero (i.e., the electrodes are never in contact). This distance allows current flow between the two electrodes 4 and 6 by tunneling and / or by field effect.

[0082] The insulating layer 8 may include several insulating sub-layers. The sub-layers may be made of different insulating materials.

[0083] An opening 9 is formed in the insulating layer 8 so as to allow passage through the insulating layer 8 completely. The opening 9 is delimited by an inner edge 15 of the insulating layer 8. It allows the first electrode 4 to be brought into contact with the second electrode 6. The absence of conductive material between the two electrodes 4 and 6 forms a potential barrier through which electrons can tunnel. The absence of insulating material in the opening 9, however, allows the potential barrier to be formed with a limited height. Thus, a tunneling current (also called a tunnel current) is preferentially established through the opening 9 rather than through the material of the insulating layer 8. The localization of the tunneling current allows for improved control of the tunneling current, in particular the threshold voltage for initiating its flow, as well as the reproducibility of the initiation.

[0084] The opening 9 in the insulating layer can have a width, measured parallel to the {X; Y} plane, of between 10 pm and 2000 pm. The opening 9 can also have a length, measured parallel to the {X; Y} plane and perpendicular to its width, of between 10 pm and 2000 pm. These dimensions of the opening 9 allow the tunneling current to be localized to a small portion of electrodes 4, 6, so that the conditions for the establishment of the tunneling current change very little. In other words, these dimensions allow for the maintenance of reproducible tunneling current initiation conditions.

[0085] The opening 9 is advantageously sealed. This sealing is achieved, for example, by sealing the electrodes 4, 6 to the insulating layer 8. This ensures that no species that could influence the establishment of the tunneling current enters the opening 9.

[0086] Opening 9 can be empty, that is, containing a gas at a partial pressure less than 50 10' 1 mbar (where 1 mbar is equal to 100 Pa). The protective device 3 may include a neutral gas in the aperture 9, such as nitrogen, argon, neon, xenon, or a mixture of these gases. An empty aperture 9 or one containing a neutral gas prevents the contents of the aperture 9 from changing, so that the potential barrier formed by the aperture remains constant over time.

[0087] The invention also relates to the manufacture of a protective device 3 as illustrated by figures 2 to 16.

[0088] In one embodiment, the fabrication of a device 3 initially involves supplying two doped semiconductor layers intended to form the first and second electrodes 4, 6. The two layers are, for example, made from two different semiconductor substrates, preferably doped. These layers can be machined separately to form cavities or protrusions as described below. The semiconductor substrates are, for example, doped silicon. The doping in the areas intended to be in contact can be reinforced before the layers (which will form the electrodes) are brought into contact. This reinforcement can be achieved by implantation.

[0089] The fabrication of the device also includes the formation or deposition of the insulating layer 8 on one or even both of the aforementioned semiconductor layers. The insulating layer 8 (or the insulating sublayers formed on each semiconductor layer) is produced, for example, by the growth of a thermal oxide (e.g., thermal SiU2) or by chemical (CVD) or physical (PECVD) deposition of an oxide such as SiU2. The formation of the insulating layer 8 is carried out so that the inter-electrode distance is less than 5 pm. The thickness of the insulating layer 8 can therefore be limited to 5 pm.

[0090] The fabrication of device 3 also includes creating the opening 9 in the insulating layer 8 (or in each insulating sublayer) to expose the semiconductor layer on which it rests. Creating the opening 9 can be done by lithography and dry etching or wet etching.

[0091] The fabrication of device 3 finally includes soldering or bonding the remaining semiconductor layer to the insulating layer 8 to form the stack defining device 3. Soldering is, for example, performed using a method known as "silicon fused bonding." Bonding can be achieved using Van der Waals forces between the layers. To prepare for soldering or bonding, the surface of the semiconductor layer to be bonded can be prepared by plasma or chemical solutions to make its surface hydrophilic. The semiconductor layer is then brought into contact with the insulating layer 8 under vacuum or in a neutral gas atmosphere. It is preferable that the bonding or soldering of the insulating layer 8 to the semiconductor layer be carried out in such a way as to ensure the airtightness of the opening 9.When the insulating layer 8 is created by growing or depositing an insulating sublayer on each of the semiconductor layers, the two insulating sublayers can be brought into contact with each other under vacuum or in a neutral gas atmosphere. It is also preferable that the bonding or welding of the two insulating sublayers be carried out in such a way as to ensure the airtightness of the opening 9. The bonding or welding is preferably carried out in such a way as to guarantee airtightness over time, for example, for 20 years. This ensures good performance for the device.

[0092] The fabrication of device 3 can be completed with an initialization step to ensure its full functionality. Previous fabrication steps, such as deposition or etching, can deposit material on the surfaces facing electrodes 4 and 6. The initialization step cleans these surfaces and establishes a tunneling current between electrodes 4 and 6, reproducibly when a voltage higher than the threshold voltage is applied.

[0093] To achieve this, the initialization step involves applying an initial voltage to electrodes 4 and 6 so that device 3 transitions from the blocked state to the conducting state. The voltage between electrodes 4 and 6 is, for example, gradually increased until device 3 transitions from the blocked state to the conducting state. The initial voltage is reached when device 3 transitions to the conducting state. The conducting state can be characterized by a minimum current. Applying the initial voltage between the electrodes applies an electric field to the Species that can influence the establishment of the tunneling current. The passage of a current will clean, for example thermally, physically, or even chemically, the surfaces in contact with it. This initialization is preferably performed at least once. It can be performed several times to properly remove the troublesome species. However, a single initialization is generally sufficient to obtain a stable threshold voltage that no longer changes over time. Initialization is not necessarily achieved by the gradual application of a voltage until device 3 becomes conducting. The initialization voltage can have a predefined amplitude such that device 3 transitions directly to the conducting state. Initialization is thus faster. The predefined voltage can be determined from previously initialized devices.

[0094] Figure 1 shows an example of initialization. A first voltage ramp is performed, with the voltage applied between electrodes 4 and 6 of a device. When the device becomes conducting, the initialization voltage is reached. Figure 1 shows several voltage ramps performed on the same device. After initialization (for an initialization voltage close to 100 V), the device transitions from the blocked state to the conducting state for voltages centered on an average value corresponding to the threshold voltage (approximately 32 V).

[0095] The first electrode 4 preferably has a thickness h4, measured perpendicular to the {X; Y} plane, of less than 1 mm. For example, it is between 200 pm and 800 pm. Similarly, the second electrode 6 preferably has a thickness h6 of less than 1 mm, for example, between 200 pm and 800 pm. Thus, the stack formed by the two electrodes 4 and 6 and the insulating layer 8 has a maximum height of 2005 pm, that is, a maximum height approximately equal to 2 mm. The protective device 3 therefore has a reduced vertical footprint. Preferably, the maximum height of the stack formed by the three elements can be approximately between 400 pm and 1600 pm, thus having an even smaller footprint.

[0096] The first electrode 4 is made from a doped semiconductor material. It is preferably made from doped silicon. It could also be made from another doped semiconductor material such as a so-called "III-V" doped alloy, comprising two materials belonging to the columns Elements III and V of the periodic table. Examples include GaAs or InP. The second electrode, 6, is made from a second doped semiconductor material. Like the first electrode, 4, it is preferably made from doped silicon. However, it could be made from another doped semiconductor material such as an III-V alloy. It is also possible for the first and second electrodes, 4 and 6, to be made from different semiconductor materials. Using the same doped semiconductor material for both electrodes, 4 and 6, simplifies manufacturing since it eliminates the need for different fabrication technologies. Furthermore, using the same doped semiconductor material for both electrodes, 4 and 6, results in the same threshold voltage regardless of the circuit's polarity. Thus, the resulting device ensures bidirectional operation.In other words, no matter which way device 3 is connected, it will function the same way, with the electrodes acting as either cathode or anode.

[0097] By "same doped material" we mean that the electrodes are made from the same element or the same alloy of elements (for example in Si or InP) and doped in the same way (for example both of type N or type P and with the same level of concentration).

[0098] The first electrode 4 can be doped with a first type, for example type N or type P. The second electrode 6 can be doped with a second type, for example type N or type P. Preferably, both electrodes 4, 6 are doped with the same type, for example type N or type P, in order to ensure bidirectional operation of the device.

[0099] In an alternative embodiment, the doping of the first and second electrodes 4, 6 are of different types. For example, the first electrode is N-doped and the second electrode is P-doped, or vice versa. The difference in doping between the two electrodes 4, 6 results in a different threshold voltage depending on the polarity of the voltage applied between the first and second electrodes 4, 6. The device 3 therefore has a preferred polarization direction, for example, the polarization direction in which the threshold voltage is lowest. The device is said to be "unidirectional".

[0100] The current limitation can depend on the doping applied to electrodes 4 and 6. If electrodes 4 and 6 are made from the same doped material (specifically, having the same concentration of doping impurities and the same type of doping), then the expected current limitation is bidirectional. That is to say, it is identical regardless of the direction of the voltage across device 3. In other words, the connection direction of the device has no impact on the current limitation.

[0101] If electrodes 4 and 6 are doped differently (different doping types and / or concentrations), the expected current limitation may vary depending on which electrode is involved in the emission mechanism. This is because doping affects the density and / or mobility of charge carriers in the electrodes. Therefore, electron emission from an electrode can vary significantly depending on whether it is heavily or lightly doped. Different doping levels for electrodes 4 and 6 allow the current limitation to be adjusted according to the direction of current flow.

[0102] The first electrode 4 can be doped with doping impurities such as boron or gallium (for example, to obtain a P-type silicon electrode) or phosphorus, antimony, or arsenic (for example, to obtain an N-type silicon electrode). The doping impurities of the first electrode are advantageously present at a concentration between 1 and 10 17 at / cm 3 and 1 ■ 10 22 at / cm 3 This concentration of impurities makes the first electrode 4 conductive to highly conductive.

[0103] The second electrode 6 can also be doped with doping impurities such as boron, gallium, phosphorus, antimony, or arsenic. The doping impurities can be present at concentrations ranging from 1 to 10 17 at / cm 3 and 1 ■ 10 22 at / cm 3. In the same way as the first electrode 6, this concentration of impurity makes the second electrode 6 conductive to highly conductive.

[0104] Doping electrodes 4 and 6 allows for efficient conduction of electric current. Electrodes 4 and 6 made of doped semiconductor material, even at high concentrations or even in degenerate forms, offer advantages over metal electrodes. Metal electrodes do not allow for control The tunneling current is efficient even at very short inter-electrode distances. Field lines emitted by a metal electrode originate solely from its surface. The tunneling current tends to thermally assist the reorganization of the metal electrode surface, potentially even vaporizing the electrode itself, thus significantly reducing the inter-electrode distance and the reproducibility of threshold voltages. These vaporizations and reorganizations can also lead to direct contact between the electrodes, rendering the device inoperable. Field lines emitted by a doped semiconductor electrode originate from a volume near the electrode surface. This emission of field lines reduces the risk of reorganization or vaporization of the semiconductor electrode, thus preserving its integrity.Thus, the initiation and maintenance of the tunnel current is facilitated, and the reproduction of the tunnel effect is possible. Therefore, the device according to the invention has the advantage of being reusable. Protection devices according to the prior art may be single-use and require replacement after each surge suppression.

[0105] Furthermore, in a metal, electric field lines are organized at the external surfaces of the metal, without penetrating it (unlike in a semiconductor, as discussed previously). Consequently, it remains difficult to obtain the electric fields required to induce field emission or tunneling, as submicron distances must be maintained. While achieving such precision is achievable in the microelectronics industry, it is more difficult to obtain without the use of specialized, high-precision methods specific to that industry.

[0106] The first and second electrodes 4, 6 can be doped with the same type of doping impurity with equal concentrations. Alternatively, they can be doped with the same type of doping impurity with different concentrations.

[0107] In the embodiments shown in Figures 9 to 16, a first cavity 14 is formed in the first electrode 4. This cavity is a recessed area of ​​the surface, intended to provide lift. As such, the first cavity 14 can also be called a "recess." In other words, the first cavity 14 is a free volume formed within the first electrode 4 and does not opening onto only one of the faces of said first electrode 4. In other words, the first cavity 14 does not pass completely through the first electrode 4.

[0108] The first cavity 14 communicates with the opening 9. In other words, the first cavity 14 is brought into contact with the second electrode 6 through the opening 9.

[0109] The first cavity 14 in the first electrode 4 sets back the surface of the first electrode 4 (which can be called the "bottom" of the cavity) in relation to the second electrode 6.

[0110] Figure 9 shows, for example, that the distance h46 separating the two electrodes 4, 6, at the opening 9 can be greater than the thickness h8 of the insulating layer 8. It is thus possible to use a very thin insulating layer 8 while still being able to adjust the distance h46 between the electrodes 4, 6.

[0111] In the embodiment of figures 10, 15 and 16, a second cavity 29 (or recess) is provided in the second electrode 6. In the same way as the first cavity 14, the second cavity 29 communicates with the opening 9.

[0112] The cavities 14, 29 can be made during the manufacture of the device 3. They are made for example before bonding or soldering the semiconductor layers onto the insulating layer 8. They can be made in each semiconductor layer by wet etching such as KOH or dry etching, for example by SFe plasma, through an etching mask.

[0113] Tunneling current tends to establish itself where the electric field lines are most concentrated. The edge effects observed near the edge of the opening 9 tend to concentrate the field lines at the edge of the opening 9. Thus, without special precautions, tunneling current can establish itself near the insulating layer. However, this layer can be damaged by the high intensity of the current flowing through it. Therefore, it is advisable to keep the tunneling current away from the insulating layer 8 and, preferably, to locate it at the center of the opening 9.

[0114] In the embodiments of Figures 9 and 10, the insulating layer 8 is laterally delimited by an inner edge 15. The first electrode 4 preferentially bears against the insulating layer 8 at a distance from the inner edge 15, set back from the inner edge 15 of the insulating layer. Thus, the first cavity 14 opens partly onto the electrically insulating layer 8 and partly into the opening 9. In other words, the insulating layer 8 forms a narrowing in relation to the first cavity 14. This narrowing takes the form of a lip 16 advancing into the free space formed by the first cavity 14 and the opening 9. The lip 16 is all the more evident in figure 10 where it protrudes into the volume formed by the first and second cavities 14, 29 and the opening 9.

[0115] The electric field lines at the edge of the first cavity 14 are therefore forced to lengthen to bypass the insulating lip 16 and reach the second electrode 6. This lengthening of the field lines reduces the probability that a tunneling current will be established at the edge of the air gap where it may be more difficult to control or where it could induce damage to the insulating layer 8.

[0116] The insulating lip 16 can extend laterally relative to the first cavity 14 over a distance of 1 pm.

[0117] In the embodiments shown in Figures 11 to 16, the first electrode 4 incorporates a structure. This structure is designed to improve the localization of the tunnel current at the center of the aperture 9, where it will be least affected. The structure of the first electrode 4 takes particular advantage of the concentration of electric field lines by the point effect.

[0118] In Figures 11 to 16, the first cavity 14 includes at least one first protrusion 17 extending perpendicularly to the plane {X; Y] and in the direction of the second electrode 6. In other words, it is a portion of the first electrode 4 projecting outwards towards the second electrode 6. It serves to exacerbate the electric field between the tip formed by the first protrusion 17 and the second electrode 6. That is to say, each first protrusion 17 traverses all or part of the first cavity 14 as it extends towards the second electrode 6. In order to ensure the establishment of a tunneling current, each first protrusion 17 is then formed so that it has a distance h46 (discussed previously) with the second electrode 6, which is advantageously less than 5 pm.

[0119] Each first protrusion 17 is distant from the second electrode 4 and preferably at least 0.2 pm.

[0120] The first electrode 4 may comprise a single first protrusion 17 or a plurality of first protrusions 17 (as illustrated by Figures 11 to 16).

[0121] Figures 13 and 14 show the same embodiment in a first section, referred to as the "side view" (Figure 13), and a second section, referred to as the "top view" (Figure 14). Similarly, Figures 15 and 16 show another embodiment in the same way, in a side view (Figure 15) and a top view (Figure 16).

[0122] In the embodiments of figures 11 to 16, each first protrusion 17 is distant from the insulating layer 8 and in particular from the inner edge 15 of the insulating layer 8. It has for example a distance d178 with the inner edge 15 greater than 5 pm (the distance d178 is illustrated in figure 14).

[0123] It is advantageous for the prominences not to be too narrow, as otherwise the field concentration at their apex can induce the emission of very strong currents that can damage the prominences. Therefore, each first prominence 17 can have a width d17, measured parallel to the plane {X; Y], preferably greater than 5 pm.

[0124] In the embodiments of Figures 13 to 16, the first electrode 4 comprises a plurality of first protrusions 17 arranged in a square lattice. In order to minimize interference between the current emissions at the protrusions 17, the first protrusions 17 are advantageously spaced from each other by a distance d1717 preferably strictly greater than 5 pm.

[0125] In the embodiment of Figures 15 and 16, the second electrode 6 also includes a structure designed to promote the localization of the tunnel current at the center of the opening 9. The structure of the second electrode 6 can be complementary to the structure of the first electrode 4 or replace it entirely.

[0126] The structuring of the second electrode 6 includes at least one second protrusion 25 extending perpendicularly to the plane {X; Y] and in the direction of the first electrode 4. Each second protrusion 25 is advantageously located less than 5 pm from the first electrode 4.

[0127] The formation of the first and / or second protrusions 17, 25 can be achieved by etching the electrode(s), for example, using a plasma, through an etching mask. Adjusting the etching speed and the aspect ratio of the etching mask (known as the "ARDE" technique for "Aspect Ratio Dependent Etching") allows the formation of protrusions of varying heights by dry etching. The protrusions 17, 25 can also be formed by wet etching. For example, repeating successive wet etches with different masks allows the electrodes to be etched while retaining the protrusions.

[0128] In the embodiments of Figures 12, 15 and 16, the protection device includes at least one additional insulating layer 28 disposed on one end of a first protrusion 17 or disposed on one end of a second protrusion 25. Each protrusion has two ends: a first end, called the "foot" or "base", in contact with the first electrode 4; and a second end, opposite the base and called the "head" or "distal" end.

[0129] In particular, each additional insulating layer 28 extends against the head of a first or second protrusion 17, 25. It then covers at least part of the head of a protrusion 17, 25. This covering forms a masking of the head of a protrusion which forces the electric field lines to bypass the additional layer 28. This bypassing, more or less pronounced depending on whether the additional layer 28 masks a large part of the head of the protrusion, makes it possible to exacerbate the concentration of the electric field lines more or less strongly and thus adjust the conditions for the establishment of a tunneling current.

[0130] In the embodiments of Figures 15 and 16, each additional insulating layer 28 extends from a protrusion to the second electrode 6. It may extend to a protrusion of the second electrode 6 if necessary. The additional insulating layers 28 may be wider than the protrusions 17 so as to completely mask the free end of the protrusions 17. The additional layers may, for example, have a width d28 strictly greater than the width d17 of the protrusions 17. Their width d28 is, for example, in the range of d17 + 1 pm to d17 + 2 pm.

[0131] The additional insulating layers 28 in Figure 16 are arranged in a square lattice. For example, they are spaced apart by a distance d2828 that can be greater than or equal to 5 pm. However, if the additional layers are closer together, they can contribute to concentrating the electric field lines. It is nevertheless necessary that a space between the additional layers 28 allow the electrodes to be aligned.

[0132] The additional layers 28 are preferentially kept away from the insulating layer 8, for example by a distance d288 greater than or equal to 5 pm.

[0133] Each additional insulating layer 28 can be obtained by depositing SiO2 or SiN and partially etching this layer.

[0134] In the embodiments of Figures 13 and 14, the structure of the first electrode 4 includes a peripheral trench 23 designed to reduce the establishment of a tunneling current near the insulating layer without resorting to an insulating lip 16 (although the use of an insulating lip 16 is compatible). The peripheral trench 23 increases the volume of the first cavity 14, near the insulating layer 8. The first cavity 14 is, for example, delimited by an inner edge 22 which can be aligned with the inner edge 15 delimiting the opening 9. The peripheral trench 23 then forms a trench cut into the first electrode 4 and running along the inner edge 22 of the first cavity 14. The peripheral trench 23 thus increases the distance between the two electrodes 4, 6, near the insulating layer 8, so as to reduce the risk of a tunneling current establishing itself at this point.

[0135] The peripheral trench 23 may have a bottom with a width d23. This width is, for example, measured from the inner edge 22 of the first cavity (or from the inner edge 15 of the insulating layer 8). The bottom of the peripheral trench 23, preferably located at a distance h23 from the second electrode 6, measured perpendicular to the plane ({X; Y}), is between twice the width d23 of the peripheral trench 23 and from two to ten times the width d23 of the peripheral trench 23.

[0136] In the embodiment of Figure 15, a peripheral trench 23 is also made in the second electrode 6. Tl

[0137] In the embodiments shown in Figures 2 to 16, the protection device 3 comprises a first conductive layer 12 and a second conductive layer 13. The first conductive layer 12 is electrically connected to the first electrode 4. Similarly, the second conductive layer 13 is electrically connected to the second electrode 6. These conductive layers 12 and 13 form the terminals of the protection device 3, across which the electrical voltage to be clipped is applied. In other words, they are the electrical contacts of the device 3.

[0138] Conductive layers can be made of silver, gold, aluminum, nickel, platinum, palladium, tungsten, or an alloy of these materials. Advantageously, they have a thickness of less than 30 µm. They can be formed, for example, by evaporation, sputtering, or electrolytic growth.

[0139] The first conductive layer 12 extends advantageously against the first electrode 4, in electrical contact with it. The first electrode, for example, has a first part 10, called the "upper part," and a second part 5, called the "lower part," opposite, with respect to the plane {X; Y], its upper part 10. The terms "upper" and "lower" are used with reference to the figures. The orientation of the first electrode 4 is such that the insulating layer 8 is in contact with the lower part 5 of the first electrode 4. A portion of the lower part 5 of the first electrode 4 is therefore opposite the second electrode 6 through the opening 9 in the insulating layer 8.

[0140] In the embodiments of figures 2 to 16, the first conductive layer 12 extends into contact with the upper part 10 of the first electrode 4. Thus, the first electrode 4 is sandwiched between the insulating layer 8 and the first conductive layer 12.

[0141] The second conductive layer 13 advantageously extends against the second electrode 6 and is in electrical contact with it. The second electrode may have, similarly to the first electrode 4, a first part 7, called the "upper part", and a second part 11, called the "lower part", opposite, with respect to the plane {X; Y], to its upper part 7. The orientation of the second electrode 6 is such that the insulating layer 8 is in contact with the upper part 7 of the second electrode 6.

[0142] In the embodiments of figures 2, 3 and 6 to 16, the second conductive layer 13 extends into contact with the lower part 11 of the second electrode 6. Thus, the second electrode 6 is sandwiched between the insulating layer 8 and the second conductive layer 13. More particularly, in these figures it is the entire stack of layers 4, 6, 8 that is sandwiched between the first and second conductive layers 12, 13.

[0143] This mode of connection with the conductive layers 12, 13 does not constrain the extent of the electrodes 4, 6 or of the insulating layer parallel to the plane {X ; Y}.

[0144] Figure 4 shows an alternative embodiment in which the second conductive layer 13 extends into contact with the upper part 7 of the second electrode 6. The second electrode 6 is not sandwiched. Instead, the insulating layer 8 and the second conductive layer 13 both extend over the second electrode 6. However, in this embodiment, it is advantageous for the second conductive layer 13 not to be placed too close to the opening 9. It is preferably placed at a distance from the opening 9 greater than 200 pm, for example between 200 pm and 1000 pm, and preferably between 200 pm and 800 pm (equivalent to the thickness range of the second electrode 6).

[0145] Figure 5 presents a variant of the embodiment shown in Figure 4. In this embodiment, a shoulder 20 is formed in the second electrode 6, extending from the upper part 7 of the second layer 6. By "shoulder," we mean a recess made on one edge of the second electrode 6, extending from the upper part 7 of the electrode 6, leaving a free surface that extends parallel to the {X; Y} plane. The shoulder 20 can also be called a "base." Figure 5 shows a second electrode 6 delimited laterally, for which the shoulder follows the edge of the second electrode 6, encircling the insulating layer 8. The second electrode 6 could, however, extend continuously in the {X; Y} plane. In this case, the shoulder 20 would result from a a flat-bottomed trench made in the second electrode 6 and surrounding, for example, at least partly the insulating layer 8.

[0146] In the embodiment of Figure 5, the second conductive layer 13 extends to the contact of the shoulder 20 (or to the contact of the bottom of the flat-bottomed trench as discussed above).

[0147] The shoulder 20 allows the second conductive layer 13 to be brought laterally closer to the insulating layer 8. This configuration thus reduces the lateral bulk of the device 3. It also reduces the concentration of electric field lines in the vicinity of the insulating layer 8. Indeed, a strong electric field applied through a portion of the insulating layer 8 could induce breakdown through said insulating layer 8, which could damage the latter.

[0148] The depth h20 of shoulder 20, measured perpendicular to the plane {X ; Y] is preferably greater than 50 pm.

[0149] The embodiments in Figures 4 and 5 show that the protection device 3 can include two second conductive layers 13 extending on either side of the insulating layer 8 and in particular of the opening 9 of the latter.

[0150] In a variant of the embodiments shown in Figures 4 and 5, the first and second electrodes 12, 13 can be interchanged. The first conductive layer 12 can, for example, extend against the lower part 5 of the first electrode 4. The first conductive layer 12 can also extend against a shoulder formed in the first electrode 4, from the lower part 5 of said first electrode 4.

[0151] Common to the embodiments shown in Figures 2 to 16, the first electrode 4 and the insulating layer 8 are delimited by an outer flank 19, common to both elements. This outer flank 19 is obtained, for example, by dry etching using a plasma or by wet etching, depending on the materials to be etched.

[0152] In the embodiments of figures 4 and 5, this side 19 allows the second conductive layers 13 to be placed in the vicinity of the insulating layer 8.

[0153] In the embodiments of figures 2 to 3 and 6 to 16, the second electrode 6 is also delimited by the outer flank 19, common with the first electrode 4 and the insulating layer 8. This outer flank 19, over the entire height of the device 3, is obtained for example by sawing with a grinding wheel, by laser cutting or by anisotropic engraving with a plasma.

[0154] In these embodiments, the boundary of device 3 is shaped so that it has a parallelepiped form. This boundary could be shaped so that device 3 has a different form, such as a circular one.

[0155] The insulating layer 8 is delimited such that a distance d8 between the outer edge 19 and the opening 9 is greater than 5 pm and preferably greater than or equal to 50 pm. This distance d8 is measured parallel to the {X; Y} plane. A sufficient distance d8 ensures adequate sealing of the opening 9. Thus, the probability of external species entering and contaminating the space between electrodes 4 and 6 is minimized. The reproducibility of the tunneling current is thereby improved.

[0156] The device 3 may have an external width (measuring the lateral extent of the outer flank 19) of between 1 mm and 10 mm. The device 3 may have an external length of between 1 mm and 10 mm. The external width and length of the device are preferably chosen according to the width and length of the opening 9, so that the distance d8 separating the outer flank 19 is always sufficiently far from the opening 9 to ensure the latter remains watertight.

[0157] In the embodiments of Figures 7 and 8, the device 3 includes an additional insulating layer 27, extending between the two electrodes 4, 6 and at least partially surrounding the insulating layer 8. The additional insulating layer 27 extends, for example, against the lower part 5 of the first electrode 4 and against the upper part 7 of the second electrode 6. The additional insulating layer 27 provides support for the first and second electrodes 4, 6, which can thus extend beyond the insulating layer 8. The outer edges of the electrodes 4, 6 (i.e., the edges located at the outer flank 19) are therefore kept away from the insulating layer 8. A breakdown between the electrodes 4, 6 occurs at the level The edges of electrodes 4 and 6 are therefore distant from the insulating layer 8. The integrity of the insulating layer 8 is thus preserved. The additional insulating layer 27 is preferentially used when the device 3 is laterally delimited by an outer edge 19.

[0158] The additional insulating layer 27 is formed from an insulating material with a low dielectric constant (called a "low-k" material). This is, for example, parylene.

[0159] In the embodiment of Figure 8, the device 3 includes an insulating coating 18 extending at least against the outer flank 19 of the first electrode 4 and the second electrode 6. The insulating coating 18 reduces the risk of a short circuit occurring between the two electrodes 4 and 6 outside the opening 9. Preferably, the insulating coating 18 extends continuously between the outer flank 19 of the first electrode 4 and the outer flank 19 of the second electrode 6. Even more preferably, and as illustrated in Figure 8, the insulating coating 18 also covers an edge of the first conductive layer 12 and an edge of the second conductive layer 13. However, a portion of the first and second conductive layers 12 and 13 should preferably be left free so as to allow contact with these layers 12 and 13.

[0160] The insulating coating 18 is also formed from an insulating material with a low dielectric constant such as parylene.

[0161] Layers or coatings made of materials with low dielectric constant are, for example, formed by chemical deposition.

[0162] In the embodiment of Figure 6, the protection device 3 comprises at least one first insulating thin layer 21. This first insulating thin layer 21 is inserted into the first electrode 4. It extends, for example, parallel to the plane {X; Y}. It may be inserted between two portions of the first electrode 4. The first insulating thin layer 21 may have a thickness, measured perpendicular to the plane {X; Y}, of between 1 nm and 10 nm. Its role is to improve the electrical insulation capacity of the device 3 when it is subjected to direct currents or low-frequency currents or voltages. In this way, it blocks direct currents or low-frequency leakage currents that may originate from the component to be protected. According to one variation, the first insulating layer The additional layer 21 extends against the first electrode 4, making electrical contact with it. The first conductive layer 12 can then extend into contact with the first additional insulating layer 21.

[0163] The device 3 may include a second thin insulating layer 21 extending within the second electrode 6 or in contact with it.

[0164] The insulating thin films 21 can be formed at the same time as the electrodes 4, 6, for example by using a semiconductor-on-insulator (SOI) substrate during the fabrication of the device 3. Alternatively, these thin films 21 can be formed by implantation or diffusion.

[0165] The invention also relates to a protection system 30 for an electronic component. Various embodiments of said system 30 are illustrated in Figures 17, 19 to 22. Figure 17 shows a simplified system 30. Figures 19 to 22 show a system 30 comprising more elements and connected within an electronic circuit.

[0166] Common to the embodiments of Figures 17 and 19 to 21, the protection system 30 comprises at least two conductive layers 12, 13, for example at least a first conductive layer 12 and at least a second conductive layer 13. The conductive layers 12, 13 form the contact areas of the system 30. In other words, the first and second conductive layers 12, 13 form the anodes and cathodes of the system 30. The conductive layers 12, 13 are, for example, metallic layers in ohmic contact with the silicon electrodes.

[0167] The conductive layers 12, 13 use the same naming convention as the conductive layers described with reference to devices 3 in figures 2 to 16.

[0168] The system 30 also includes a plurality of protective devices 3 such as those described previously. In the embodiments shown in Figures 17 and 19 to 21, the protective devices 3 differ from the previously presented embodiments in that the openings 9 in the insulating layers are not completely closed. Indeed, the embodiments in Figures 2 to 16 show devices 3 in which the atmosphere in the opening 9 (which may be a vacuum or an inert gas) is maintained by means of an airtight seal. Electrodes 4 and 6 are placed against the insulating layer. In the embodiments shown in Figures 17 and 19 to 21, the vacuum or neutral gas atmosphere is maintained by encapsulating the system, a feature not shown in the figures. Therefore, the openings 9 do not need to be closed.

[0169] The devices 3 in Figures 17 and 19 to 22 correspond, for example, to the devices 3 in Figures 2 to 16 sectioned along a plane perpendicular to the plane of the layers. Each device 3 in Figures 17 and 19 to 22 then corresponds to half of a device 3 in Figures 2 to 16.

[0170] The protective devices 3 are arranged to form a plurality of chains 31 of devices, referred to as "protection chains." Each protection chain 31 may comprise a single device 3 or a plurality of devices 3. Within each chain 31, the devices 3 are electrically connected in series. Electrically connected in series means a connection between a second electrode 6 of a first device 3 and a first electrode 4 of a second device 3. Thus, a first electrode 4 of a first extremal device 3 forms one end of the chain 31, and a second electrode 6 of a second extremal device of the chain 31 forms the other end of the chain 31. In the case where a chain comprises only one device 3, the first and second electrodes 4, 6 of said device 3 form the ends of the chain 31.

[0171] The conductive layers 12, 13 are connected in pairs to one of the chains 31 of devices. The conductive layers 12, 13 and the protective chains 31 thus form a garland of conductive layers 12, 13 joined by protective chains 31.

[0172] The system 30 thus forms an assembly of devices 3. Depending on the pairs of conductive layers connected, it is possible to connect one or more chains in series and / or in parallel (a parallel connection can be obtained by short-circuiting the chains, for example, by connecting them so that the ends of the two chains 31 are connected in pairs). A series connection adds the threshold voltages of the devices 3 forming the chains 31. A parallel connection adds the limiting currents of the devices 3 forming the chains 31. The threshold voltage and / or the limiting current can thus be adapted to the intended use. The configuration of these parallel or series associations of the chains can be done via an external encapsulation box of the structure 30.

[0173] Figure 18 shows examples of the lV characteristics that can be obtained using the same protection system 30. These characteristics are obtained by connecting different conductive layers 12, 13. They allow, for example, the connection of one chain 31, two chains 31 in series, and three chains 31 in series. The total threshold voltage thus increases with each addition of a chain 31 in series.

[0174] To form a chain 31, whose devices 3 are connected in series, the devices 3 of the same chain 31 can be arranged one on top of the other, forming a stack of devices. In the embodiments shown in Figures 17 and 19 to 22, the devices 3 are bidirectional. That is to say, the threshold voltage of each device does not depend on the direction of the voltage applied to its electrodes 4, 6. The electrodes 4, 6 of the interconnected devices, for example, have the same type of doping. The electrodes 4, 6 between two devices are therefore shared. Two electrodes 4, 6 of two devices 3 connected in series, for example, form a single layer. The chains 31 of devices can thus have a reduced footprint.

[0175] The devices 3 of each chain 31 can be stacked one on top of the other to form chains oriented perpendicular to the plane of the layers. This arrangement allows the chains 31 to be placed side by side. For example, they are arranged side by side in pairs. They can also be arranged in a square or rectangular grid by being placed next to each other.

[0176] The chains 31 of devices are preferably connected in series with each other. The conductive layers 12, 13 can serve as electrical connections between the chains 31.

[0177] Two devices 3 belonging to different but adjacent chains 31 may share common layers. For example, they may share the same layer to form an electrode. This may be the same first electrode 4 (for example, as illustrated in the embodiments of Figures 18 to 20) or the same second electrode 6. The layers may be common are preferentially the layers in contact with one of the conductive layers 12, 13.

[0178] The use of a common layer between two chains 31 makes it possible to further reduce the bulk of the system 30. Indeed, it is not necessary to use an additional means of connection to make the electrical connection of the chains together.

[0179] Two devices 3 belonging to different but adjacent chains can also share the same insulating layer. This insulating layer separates the electrodes 4, 6 of a first device 3 and extends to a second device 3 to separate its electrodes 4, 6. Thus, two openings 9 can be made in the same insulating layer 8.

[0180] The invention further relates to an electronic circuit comprising a protection system 30 and an electronic component C1 to be protected. Various embodiments of said circuit are illustrated in Figures 19 to 22.

[0181] Common to the embodiments of Figures 19 to 21, the first electronic component C1 comprises a first terminal 32 and a second terminal 33. The protection system 30 comprises twelve devices 3 distributed among six protection chains 31. The protection system 30 also comprises seven conductive layers 12, 13 connected by means of the six chains 31.

[0182] In these embodiments, the protection system 30 is connected in parallel between the first and second terminals 32, 33 of component C1. A first conductive layer 12 is connected to the first terminal 32 and a second conductive layer 13 is connected to the second terminal 32.

[0183] In Figure 19, the first and second terminals 32, 33 of component C1 are connected in parallel with a single protection chain 31. In Figure 20, the first and second terminals 32, 33 of component C1 are connected in parallel with six protection chains 31, said chains 31 being connected in series. Finally, in Figure 21, the first and second terminals 32, 33 of component C1 are connected in parallel with three protection chains 31, connected in series. For each of Figures 19 to 21, an example of the path taken by an electric current when the devices 3 are conducting is shown in dashed lines.

[0184] In the embodiment of Figure 21, the electronic circuit further includes a second electronic component C2 to be protected. This second component C2 includes a third terminal 34 and a fourth terminal 35. In the embodiments of Figures 19 and 21, the protection system 30 is also connected in parallel between the third and fourth terminals 34, 35 of the second component C2. In the embodiment of Figure 19, the second component C2 is connected in parallel with a single protection chain 31, while in the embodiment of Figure 21, the second component C2 is connected in parallel with three protection chains 31, said chains 31 being connected in series.

[0185] Figure 22 shows another embodiment of the electronic circuit. Unlike the circuits in Figures 19 to 21, this circuit includes an additional protection system 30'. In this embodiment, the two protection systems 30, 30' are similar to system 30 in Figure 17 in that they each comprise two protection chains 31, each comprising two devices 3.

[0186] In Figure 22, the two protection systems 30 and 30' are connected in series between a potential VIN and ground. The additional protection system 30' is connected so that its two protection chains 31 are in series between the potential VIN and ground. The protection system 30 is connected so that its two protection chains 31 are connected in parallel. In particular, its first two conductive layers 12 are connected to each other.

[0187] The electronic component C1 is connected in parallel with the protection system 30. The first and second terminals 32, 33 of component C1 are respectively connected to the first conductive layers 12 and the second conductive layer 13 of the protection system 30. Thus, component C1 is connected in parallel with the two protection chains 31 of the protection system 30.

[0188] The additional protection system 30' thus limits the current flowing between the VIN potential and ground. It therefore limits the current flowing through component C1. The protection system 30' also limits the voltage across terminals 32 and 33 of component C1.

Claims

DEMANDS

1. A protection device (3) for an electronic component characterized in that it comprises: a first doped semiconductor layer (4), referred to as the "first electrode", extending parallel to a plane ({X ; Y}); a second doped semiconductor layer (6), referred to as the "second electrode", also extending parallel to the plane ({X ; Y}); an insulating layer (8) separating the first electrode (4) from the second electrode (6), an opening (9) being provided in the insulating layer (8) to bring the first and second electrodes (4, 6) into contact, a distance (h46) separating the first electrode from the second electrode, measured perpendicular to the plane ({X ; Y}), being less than 5 pm, the opening of the insulating layer (8) having a width and / or a length between 10 pm and 2000 pm, measured parallel to the plane ({X ; Y}).

2. Protective device (3) according to claim 1, further comprising a first cavity (14) arranged in the first electrode (4) and communicating with the opening (9).

3. Protective device (3) according to claim 2, wherein the opening (9) in the insulating layer (8) is laterally delimited by an edge (15); and wherein the first electrode (4) bears against the electrically insulating layer (8) at a distance from the edge (15) of the opening (9) so that the electrically insulating layer (8) forms a lip (16) extending between the first cavity (14) and the second electrode (6).

4. Protective device (3) according to any one of claims 2 or 3, wherein the first electrode (4) comprises a first protrusion (17) extending into the first cavity (14) in the direction of the second electrode (6); and wherein the first protrusion (17) is distant from the second electrode (6) by a distance, measured perpendicular to the plane ({X; Y}), of less than 5 pm.

5. A protective device (3) according to claim 4, wherein the first protrusion (17) has a free end facing the second electrode (6); and wherein the protective device (3) comprises an additional insulating layer (28) extending against the free end of the first protuberance (17), masking at least a part of the free end of said at least a first protuberance (17).

6. A protective device (3) according to any one of claims 2 to 5, further comprising a second cavity (29) arranged in the second electrode (6) and communicating with the opening (9); and in which the second electrode (6) comprises a second protrusion (25) extending in the second cavity (29) perpendicularly to the plane ({X; Y}), in the direction of the first electrode (4); and in which the second protrusion is distant from the first electrode (4) by a distance, measured perpendicular to the plane ({X; Y}), of less than 5 pm.

7. Protective device (3) according to any one of claims 1 to 6, wherein a peripheral trench (23) extending perpendicularly to the plane ({X; Y}) is made in the first electrode (4), the peripheral trench (23) comprising a bottom having a width (d23), measured parallel to the plane ({X; Y}), said bottom being distant from the second electrode by a height (h23), measured perpendicular to the plane ({X; Y}), of between two times and ten times the width (d23) of the peripheral trench (23).

8. A protection device (3) according to any one of claims 1 to 7, wherein the first doped semiconductor layer (4) has a concentration of doping impurities between 1 and 10 17 at / cm 3 and 1 ■ 10 22 at / cm 3 ; and in which the second doped semiconductor layer (6) has a concentration of doping impurities between 1 and 10 17 at / cm3 and 1 ■ 10 22 at / cm 3 .

9. Protective device (3) according to any one of claims 1 to 8, wherein the first electrode (4) and / or the second electrode (6) comprises, within it, a thin insulating layer (21) extending parallel to the plane ({X; Y}) and having a thickness, measured perpendicular to the plane ({X; Y}), of between 1 nm and 10 nm.

10. A method for manufacturing a protective device (3) for an electronic component, comprising: providing a first doped semiconductor layer (4), referred to as the "first electrode"; providing a second doped semiconductor layer (6), referred to as the "second electrode"; forming at least one insulating layer (8) in contact with the first electrode (4); and providing an opening (9) in said at least one insulating layer (8) for exposing the first electrode (4), welding or gluing the second electrode (6) on said at least one insulating layer (8) so that the first and second electrodes (4, 6) are facing each other through the opening (9) of said at least one insulating layer (8) and that a distance separating the first electrode from the second electrode after the welding or gluing step is less than 5 pm, the opening of the insulating layer (8) having a width and / or a length between 10 pm and 2000 pm, measured parallel to the plane ({X ; Y}).

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