Electrically conductive element

Abstract

Title: Electrically Conductive Element The invention relates to a microelectronic device comprising a support (1) and an electrically conductive element comprising, stacked successively above a first face of the support (1), a first layer based on a metal and a second layer, in contact with the first layer, based on a material selected from MoSix and WSiy. Figure for the abstract: Fig. 2A

Description

Title of the invention: Electrically conductive element Technical field

[0001] The present invention relates to the field of electrically conductive elements for microelectronic devices. By microelectronic device is meant any type of device produced using microelectronic means. These devices include, in particular, in addition to devices for purely electronic purposes, micromechanical or electromechanical devices (MEMS, NEMS, etc.) as well as optical or optoelectronic devices (MOEMS, etc.).

[0002] In particular, the aim is to target microelectronic devices having electrodes, in the field of electrochemical energy storage, in particular in the form of a micro-battery (thus producing an electrochemical microstorage component). The invention finds application in the manufacture of microelectronic devices offering such storage. This includes in particular devices of the battery, accumulator or capacitor type using an electrolyte, preferably solid.

[0003] Also covered are microelectronic devices having electrodes in stacks with an electroactive layer such as piezoelectric layers, in particular for the production of sensors or actuators; these may be devices using materials of the PZT ceramic type (PbZrTiO3).

[0004] Furthermore, still non-limitingly, the invention is also of interest for the production of microelectronic devices comprising microelectronic circuits, in particular for portions of radiofrequency transmitter and / or receiver circuits, for example to form capacitance or induction parts, or electrical contact parts for such circuits; these may be filter parts for mobile telephony, for example using materials having high coupling coefficients such as LiNbO3 or LiTaO3. STATE OF THE ART

[0005] To take the case of electrochemical energy storage, current systems are, in general, produced by successive depositions on a substrate of a first current collector, a first electrode, an electrolyte or ionic conductor, a second electrode, and a second current collector. Encapsulation, by means of deposition of an additional layer, or by applying a cover, is often necessary to protect the system from chemical reactivity with oxygen and water vapor.

[0006] The current collectors, each connected to one of the different electrodes, are accessible from the outside of the stack of the electrochemical storage device, for reconnection. The first electrode (or positive electrode used in a conventional lithium or sodium battery) can potentially be used in a microbattery, and the most common is LiCoO2.

[0007] This type of component has the disadvantage of having at least one step with a high thermal budget during its technological process. In particular, in the case of LiCoO2 mentioned above for the formation of the first electrode, thermal oxidation is generally carried out in air or in dioxygen, the purpose of which is to crystallize the material of the first electrode; frequently, the temperatures of this heat treatment are between 500 and 700°C.

[0008] This particularity conditions restrictive specifications on the first current collector. Indeed, the current collector must retain its electrical conduction properties after treatment at high temperature under an oxidizing atmosphere. Conventionally, the material used is platinum, an expensive material but capable of retaining its electrical conduction properties after heat treatment due to its almost zero oxidizability. When other materials are used, the degradation of the efficiency of the microelectronic device is significant because of the oxidation of the conductive parts induced by the heat treatment.

[0009] Generally speaking, forming parts of microelectronic devices with good electrical conduction properties is always difficult, because quality electrical conductors that resist oxidation are few and expensive.

[0010] An object of the present invention is therefore to propose an alternative to the electrical conductors currently used.

[0011] SUMMARY

[0012] To achieve this objective, according to one embodiment, a microelectronic device is provided, comprising a support and an electrically conductive element comprising, in a stack and successively above a first face of the support, a first layer based on a metal and a second layer, in contact with the first layer, based on a material chosen from MoSix and WSiy.

[0013] This combination of layers of selected materials ensures a very satisfactory level of electrical conductivity, since it is easy to achieve less than 3 ohms of electrical resistance. At the same time, the MoSi or WSi-based layer effectively protects the underlying layer, in particular against oxidation.

[0014] A preferred, but not limiting, application concerns devices involving heat treatments in the presence of dioxygen. It is not excluded that a thin layer of oxide forms on the surface of the second layer in such contexts, but its thickness is so small, due to the materials selected, that this does not impact not in practice the conductivity of the whole.

[0015] Potential uses of the electrically conductive element are the formation of all or part of an electrode of an electro-active layer system, of a current collector, of part of circuits, in particular of a radiofrequency transmitter / receiver.

[0016] Preferably, but optionally, the MoSix chosen is such that x = 1, i.e. it is MoSi. While this material turns out to be more crystalline than other solutions, such as MoSi2, which is almost amorphous, the applicant has obtained surprising, more favorable results with MoSi.

[0017] Another aspect relates to a method for manufacturing a microelectronic device comprising an electrically conductive element, the method comprising providing a support and, above a first face of the support, forming a stack successively comprising forming a first layer based on a metal, and, in contact with the first layer, forming a second layer based on a material chosen from MoSix and WSiy. BRIEF DESCRIPTION OF THE FIGURES

[0018] The aims, objects, as well as the features and advantages will become more apparent from the detailed description of one embodiment which is illustrated by the following accompanying drawings in which:

[0019] [fig. 1] [fig.l] represents an example of an application context of the invention.

[0020] [fig.2A] [fig.2A] represents a possible stacking.

[0021] [fig.2B] [fig.2B] shows a variation of [fig.2A] with a surface layer.

[0022] [fig.2C] [fig.2C] shows a diagram of a circuit of the conductive element.

[0023] [fig.3] [fig.3] is a graph of the evolution of the electrical resistivity of the conductive element according to the parameter x.

[0024] [fig.4] [fig.4] is a graph of the evolution of the total electrical resistance of the conductive element depending on the thickness of the second layer.

[0025] [fig.5] [fig.5] is a graph of the evolution of the total electrical resistance of the conductive element as a function of the thickness of the first layer, in Mo.

[0026] [fig.6] [fig.6] is a graph of the evolution of the total electrical resistance of the conductive element as a function of the thickness of the first layer, in Cu.

[0027] [fig.7] [fig.7] is a graph of the evolution of the electrical resistance of a layer oxide of the conductive element in different heat treatment situations under oxygen.

[0028] The drawings are given as examples and are not limiting of the invention. They constitute schematic representations of principle intended to facilitate the understanding of the invention and are not necessarily on the scale of the applications practices. DETAILED DESCRIPTION

[0029] Before beginning a detailed review of embodiments of the invention, optional features which may possibly be used in combination or alternatively are set out below: • the material chosen is MoSix, with X = 1; • the material chosen is WSiy, preferably WSi2 or W3Si5; • the thickness of the second layer 22 is less than or equal to 100 nm; • the metal is chosen from: Cu, Mo, W, Al, Cr, Ni; • the electrically conductive element comprises, above and in contact with at least a portion of the second layer 22, an oxide layer 23 of the material of the second layer 22; • the electrically conductive element is a battery collector. • the device comprises a first current collector 2 formed at least in part by the electrically conductive element, a first electrode 3, a solid active layer 4, a second electrode 6 and a second current collector 5; • the electrically conductive element forms at least in part an electrode electrically connected to an electro-active member; • the electrical component forms at least in part a portion of an electrical circuit, preferably a portion of an antenna, a portion of an inductive element, a portion of a capacitive element.

[0030] The invention also relates to a method for manufacturing a microelectronic device comprising an electrically conductive element, the method comprising providing a support 1 and, above a first face of the support 1, forming a stack successively comprising forming a first layer 21 based on a metal, and, in contact with the first layer, forming a second layer 22 based on a material chosen from MoSix and WSiy in which: • the formation of the second layer 22 comprises a deposition by co-sputtering or sputtering of a mixture, respectively, of Mo and Si or of W and Si, on one face of the first layer 21; • the formation of the second layer 22 comprises an alternating deposition, on one face of the first layer 21, of at least one sub-layer, respectively, of Mo or W, and of at least one sub-layer of Si; • the formation of the second layer 22 comprises, after deposition, a heat treatment configured to form MoSix molecules or, res respectively, of WSiy; • the heat treatment is carried out in the presence of oxygen; • the method is configured to manufacture a microelectronic device for storing electrochemical energy, comprising a step of forming an electrode, the heat treatment being configured to produce a crystallization annealing of the electrode; • the electrode is based on LiCo, the heat treatment being configured to produce a crystallization annealing of the electrode so as to form LiCoO2 • the method is configured so that the electrical resistance of the electrically conductive element is less than or equal to 3 ohms.

[0031] It is specified that, in the context of the present invention, the term "on" or "above" does not necessarily mean "in contact with". Thus, for example, the deposition of a layer on another layer or on a support does not necessarily mean that these two parts are directly in contact with each other but it does mean that one at least partially covers the other by being either directly in contact with it or by being separated from it by a film, or another layer or another element. A layer may also be composed of several sub-layers of the same material or of different materials.

[0032] It is specified that in the context of the present invention, the thickness of a layer or of the support is measured in a direction perpendicular to the surface along which this layer or this support has its maximum extension.

[0033] Certain parts of the device of the invention may have an electrical function. Some are used for electrical conduction properties and by electrode, collector or equivalent, elements formed from at least one material having sufficient electrical conductivity, in the application, to perform the desired function. Conversely, by electrical insulator or dielectric, we mean a material which, in the application, provides an electrical insulation function.

[0034] A layer or equivalent “based” on a material M is understood to mean a substrate, a layer, a device comprising this material M only or this material M and possibly other materials, for example alloying elements, impurities or doping elements.

[0035] An element or part of a device is said to be electroactive when it is configured to convert a force and / or a deformation into an electrical signal, and vice versa. These conversions can be achieved through physical phenomena such as expansion, electrostriction, the piezoelectric effect, the change of state or phase, the thermoelectric effect, the pyroelectric effect, etc.

[0036] A non-limiting example of the invention applies to a microelectronic device comprising at least, on a substrate, a first current collector and a first electrode. For the purposes of the present application, the term "collector" means a part of the device having the function of connecting an electrode to an element external to the device, i.e. located outside the stack of layers of the device, generally encapsulated. The term "electrode" means a part of the device in electrical continuity with an active layer (in particular an electrolyte, preferably solid, for the case of electrochemical storage or even a piezoelectric layer for example). The current collector is connected to its electrode so as to establish electrical continuity between these two parts.

[0037] Generally speaking, a storage system of the invention, an example of which is visible in [fig.l], may comprise a stack of layers on a support 1; it may be an inorganic material, such as glass or silicon, preferably covered with a layer of dielectric silicon dioxide.

[0038] This stack makes it possible to produce the various components of an electrochemical storage device, comprising a stack itself comprising: • a first collector 2, • a first electrode 3 (generally the cathode, for example made of LiCoO2 or another material requiring heat treatment, in particular for its crystallization); it may have a layer thickness in particular between 3 pm and 20 pm; • an electrolyte 4; this is preferably LiPON. Solid electrolyte or glass-based superionic materials are among the best candidates for inorganic solid electrolytes applicable to any all-solid-state battery. A wide range of sulfide and glassy oxysulfide electrolyte systems has been developed, as well as a series of superionic sulfide glass-ceramics Li2S-P2S5, whose Li+ ion conductivity is comparable to that of liquid electrolytes. As for the electrolyte for sodium batteries, there is the same glass family, e.g. Na3PS4; • a second electrode 6; • and a second collector 5.

[0039] Overall, the sequence of these layer fabrications can be carried out with traditional microelectronics technologies. In particular, all of the above layers can be deposited by the technology known by the acronym PVD (physical vapor deposition). This can be full-plate deposition and each part can be shaped by conventional photolithography and etching steps. A heat treatment of the first electrode 3 can comprise annealing in an oxidizing atmosphere at a temperature greater than or equal to 300°C, possibly greater than or equal to 500°C, or even greater than or equal to 700°C; this treatment is advantageously configured to crystallize it.

[0040] The electrolyte 4 is a portion interposed between the two separate conductive portions and consisting respectively of the first collector 2 and the first electrode 3, and of the second electrode 6 and the second collector 5.

[0041] Ionic exchanges between these two conductive portions take place through the electrolyte 4, advantageously solid, according to the principle of electrochemical energy storage. Protection against external aggression, in particular against oxidation, is possible by means of an encapsulation element, as represented by the layer 7 in [fig.l]; for information purposes, this may be silicon nitride. The latter advantageously covers the entire device, except for the collector portions which must remain accessible from the outside for reestablishing contact. Optionally, additional protection, for example based on metal, may then be deposited.

[0042] The example given with reference to [fig.l] falls within the field of electrochemical energy storage, using an electrolyte advantageously in the form of a solid ionic conductor. Nevertheless, other microelectronic devices are concerned by the present invention, by implementing equivalent steps for the manufacture of the first collector and the first electrode, the following steps being able to vary according to the application. For example, the invention can be applied to active layers of an electro-active nature, in particular piezoelectric in sensors or in actuators in particular. The electrolyte is therefore then replaced by a piezoelectric layer then covered with the second electrode and the second collector.

[0043] As indicated previously, the production of an electrically conductive element as is the case of the first collector 2 faces significant constraints, in terms of the required level of electrical conductivity and resistance to oxidation, in the environment of use of the device and / or in the environment of its manufacture, in particular when heat treatment phases comprising the oxygen species are involved.

[0044] An electrically conductive element is proposed here comprising a plurality of layers and in particular a two-layer system, an example of which is visible on the upper face of the support 1 in [fig.2A]. The first layer 21 is based on at least one metal. Thanks to the second layer described later in detail, the choice of material for the first layer 21 can be quite broad; it can be a layer based on or consisting of: copper, molybdenum, tungsten, aluminum, chromium, nickel. Advantageously, the thickness of this layer is greater than or equal to 15 nm and / or less than or equal to 200 nm. Advantageously, to promote electrical conductivity, a thickness of layer 21 greater than or equal to 100 nm can be chosen, and preferably greater than or equal to 150 nm; this makes it possible to use a layer 22 of a thickness sufficiently high so as not to make manufacturing difficult, thickness for example greater than 50 nm, and preferably greater than or equal to 100 nm. Such a thickness of metal layer also makes it possible, in the hypothesis of a MoSi layer of 100 nm, to use all common metals with satisfactory electrical conductivity.

[0045] The second layer 22 is based on, or consists of, MoSix or WSiy.

[0046] According to one possibility, layers 21 and 22 are deposited by PVD, which can be do in the same equipment for these two layers. These two layers are formed on the upper surface of the substrate. A support is understood to mean an element which allows the stack to be received. Intermediate layers may be present between the upper face of the substrate and the stack of layers 21, 22. Furthermore, the device may comprise several substrates or supports and the electrically conductive element may be carried by one of them only.

[0047] The layers 21, 22 follow one another immediately so that the upper face of the layer 21 is in contact with the lower face of the layer 22.

[0048] It is understood that the second layer 22 is derived from the Mo and Si species. The present invention proposes advantageous conditions for producing this layer. According to a first possibility, the Si and Mo species are co-sputtered onto the substrate with the desired molar distribution; for example, in the case of traditional cathode sputtering, it is sufficient to adjust the sputtering rates of the two components. According to another possibility, a mixture of Mo and Si is produced upstream with the desired distribution and this mixture is itself sputtered onto the substrate.

[0049] Another possibility is to carry out successive deposits of elementary layers of Mo and Si, in an alternating manner. At least one layer of Mo and at least one layer of Si are thus deposited. Their thickness can be between 1 nm and 10 nm; for example, elementary layers with a thickness of 2 nm for the Mo and 5 nm for the Si can be retained. Advantageously, it is arranged so that the resulting thickness of the layer 22 is 200 nm.

[0050] In both cases above (mixture spraying / co-spraying and laminated elementary layers), this deposit is subjected to a heat treatment, for example a heat treatment in the form of rapid thermal annealing, at a temperature less than or equal to 600°C. These preparation methods limit the thermal budget necessary for the manufacture of layer 22.

[0051] Furthermore, co-spraying or spraying a mixture may be preferred. Indeed, it has been found that this manufacturing method makes it possible to limit the electrical resistivity of the layer 23 potentially formed with an oxidizing heat treatment. At the same time, all of the deposition arrangements indicated above are satisfactory from the point of view of surface tensions, so as to obtain sufficient adhesion relative to the underlying layer.

[0052] The table below gives an example of an advantageous thickness for a layer 21 formed of a metal, depending on the metal of which it is made, for a first case of a second layer of MoSi 100 nm thick, and a second case of a second layer of MoSi 200 nanometers thick, all to obtain a level of electrical resistivity sufficiently low to serve as a first collector in the example given in [fig.l].

[0053] [Tableauxl] Mêlais Thickness for Wü nm-KWt nm)® Thickness ■ Min for -2œnm■ MsSHnm)® Cua 21a 15a Mon 93^ 80® W» 90» 80» Ai® 26e 23» cm 130® 112® Ni» 70« 60®

[0054] [Fig. 2B] shows that the conductive element may comprise an additional layer 23 resulting from oxidation, in particular when this element is subjected to external oxidizing conditions during the manufacture of the rest of the device. This will typically be an oxide layer of the material of the second layer 22. In practice, it has been found that the thickness of the layer 23, under the heat treatment conditions necessary for the crystallization of the first electrode (conditions of strong oxidation by rapid thermal annealing at 600°C for 30 minutes, under a flow of dioxygen), remains very low, which makes it possible not to make this step too unfavorable to the final electrical conductivity of the first collector. If the oxidation were too significant, the electrical resistance would increase rapidly. It will be noted that the limited oxidation behavior of the MoSi silicide alloy (in particular when x=1) is remarkable.

[0055] To verify the electrical properties of the conductive element thus formed, tests were carried out on the basis of a simple electrical assembly corresponding to the illustration in [fig.2C]: a pad 24 was placed on the surface of the conductive element and access to the first layer 21 was opened. In this way, a measurement of electrical conductivity through the element, from the layer 21 to the pad 24, could be carried out under different conditions.

[0056] [Fig.3] presents a graph comparing the evolution of the electrical resistivity, as a function of the parameter X of MoSix, of an element according to [Fig.2C] obtained by co-sputtering (with annealing at 600°C in an oxidizing atmosphere (for 30 minutes for the curve A, and without annealing for curve B), with a resulting thickness of layer 22 of 100 nm. To isolate the electrical resistivity parameters of layer 22, in the context of [fig.3], layer 22 was directly formed on the substrate, so as to measure conditions specific to this layer, in the absence of layer 21.

[0057] Both curves are monotonous and show an increase in resistivity with increasing X. Consequently, it appears that the best molar distribution in terms of electrical conductivity corresponds to X = 1. This result is surprising insofar as, under these conditions, the material appears well crystallized while it becomes significantly more amorphous subsequently, and in particular in the case where X = 2 for which the applicant found that it was almost amorphous.

[0058] It should be noted that X is not necessarily a natural integer. In particular, it can take decimal values ​​such as those between 1 and 2 in [fig.3]. The same is true for the parameter Y of WSiy. Furthermore, X-ray diffractometry studies can be used to determine the amorphous or crystallized character of the MoSix material (which can include MoSi2 and Mo5Si3 phases upon observation) and of the WSiy material (in particular WSi2 and W3Si5). The behavior is similar for WSiy relative to MoSix, and in particular WSi2 and W3Si5. Indeed, these two materials show very good resistance against degradation at temperature under an oxidizing atmosphere (for example air). WSi2 remains amorphous over a wide temperature range, then passes into the crystalline phase above 580°C. As for W3Si5, it is amorphous up to 529°C and crystalline beyond.In particular, they can be used with deposited thicknesses equivalent to those given in the MoSix example.

[0059] Still to characterize the layer 22 alone, the curve of [fig.4] shows the evolution of the resistance of the layer 22 as a function of its thickness, under the conditions of preparation of the layer 22 indicated for [fig.3], retaining only the embodiment in which X = 1 (MoSi). The electrical resistance decreases very quickly. By fixing a suitable total resistance value at 3Q, indicated by the letter M in the figure, it is noted that a very significant thickness of the layer 22 alone would be required to achieve a satisfactory level of conductivity.

[0060] The first layer 21 provides a solution to this difficulty thanks to the invention. The curves of figures 5 to 6 show in fact changes in total resistance, that is to say of the complete electrically conductive element comprising the layer 21, the layer 22 and the oxide layer 23, under the conditions of [fig.2C].

[0061] In the case of [fig.5], the first layer is made of molybdenum, with several thicknesses tested. The second layer 22 is made of MoSi with a thickness of 100 nm. A rapid drop in the total electrical resistance is immediately noted, the indicative target M is reached from a thickness of 90 nm, which is very reasonable.

[0062] In the case of [fig.6], the first layer is made of copper, with several thicknesses tested. The second layer 22 is identical to that used for the case of [fig.5]. As in this case, a rapid drop in the total electrical resistance is noted. In particular, the indicative target M is reached from a thickness of 16 nm of copper.

[0063] The above results show that the combination of the first layer and the second layer of the invention ensures electrical resistance levels that can easily be adapted to the intended application. In particular, for the production of electrochemical storage device collectors, the target M indicated on the curves is largely satisfactory and practical production is easy. For example, if a 200 nm copper layer 21 and a 200 nm MoSi layer 22 are used, the overall resistance obtained is 0.55Ω, which leaves a large margin compared to the acceptable resistance levels in the field.

[0064] [Fig. 7] seeks to examine the influence of an oxidizing heat treatment on the electrical results of the stack (corresponding to the pair of layers 22 and 23) of materials proposed in the invention. In the previous cases, the measurements had been made with a heat treatment condition under dioxygen at 600°C for 30 minutes. For the case of [Fig. 7], several temperature levels are tested, with increasing oxidation times (corresponding to the heat treatment time). Curve 01 corresponds to a treatment temperature of 550°C; curve 02 corresponds to 600°C; curve 03 corresponds to 650°C; curve 04 corresponds to 700°C. The indicative resistance target M is identical to the previous case, at 3Q. The resistance provided is that of the oxide layer formed during the treatment. A measurement of the current and voltage makes it easy to determine this resistance.

[0065] It is noted that all the results are satisfactory, in the sense that the electrical resistance experiences a significant inflection with the increase in the oxidation time. Thus, the increase in this resistance is measured. This is all the more true for cases 01, 02 and 03 for which the indicative target M is not reached, despite oxidation times of up to two hours. Even for case 04, corresponding to a temperature of 700°C, the measured increase in resistance remains well below the indicative target M until more than one hour of treatment.

[0066] Generally speaking, it is confirmed that the total electrical resistance remains quite suitable, at least up to an oxidation time of less than or equal to one hour. Thereafter, the total electrical resistance increases more significantly. It will be noted that up to 20 minutes or even 40 minutes, the duration of the heat treatment has little or no influence on the resistance.

[0067] In practice, a heat treatment lasting less than or equal to 60 minutes guarantees sufficiently low electrical resistance conditions to comply with the indicative target M, regardless of the temperature conditions, even high (700°C). For temperatures lower than or equal to 650°C, the heat treatment time has little influence on the result, which leaves a great freedom of choice of treatment parameters for devices in manufacture.

[0068] The invention is not limited to the embodiments previously described and extends to all the embodiments covered by the claims.

Claims

Claims

1. Microelectronic device comprising a support (1) and an electrically conductive element comprising, in a stack and successively above a first face of the support (1), a first layer (21) based on a metal and a second layer (22), in contact with the first layer (21), based on a material chosen from MoSi and WSiy.

2. Device according to the preceding claim, in which the material chosen is MoSi.

3. Device according to any one of the preceding claims, wherein the thickness of the second layer (22) is less than or equal to 100 nm.

4. Device according to any one of the preceding claims, in which the metal is chosen from: Cu, Mo, W, Al, Cr, Ni.

5. A device according to any preceding claim, wherein the electrically conductive element comprises, above and in contact with at least a portion of the second layer (22), an oxide layer (23) of the material of the second layer (22).

6. A device according to any preceding claim, wherein the electrically conductive element is a battery collector.

7. Device according to the preceding claim, comprising a first current collector (2) formed at least in part by the electrically conductive element, a first electrode (3), a solid active layer (4), a second electrode (6) and a second current collector (5).

8. Device according to any one of claims 1 to 5, in which the electrically conductive element forms at least in part an electrode electrically connected to an electro-active member, configured to convert a force and / or a deformation into an electrical signal, and vice versa.

9. Device according to any one of claims 1 to 5, in which the electrical component forms at least in part a portion of an electrical circuit, preferably a portion of an antenna, a portion of an inductive element, a portion of a capacitive element.

10. A method of manufacturing a microelectronic device comprising an electrically conductive element, the method comprising providing a support (1) and, above a first face of the support (1), a formation of a stack successively comprising a formation of a first layer (21) based on a metal, and, in contact with the first layer, a formation of a second layer (22) based on a material chosen from MoSi and WSiy.

11. A method according to the preceding claim, wherein the formation of the second layer (22) comprises deposition by co-sputtering or sputtering of a mixture, respectively, of Mo and Si or of W and Si, on one face of the first layer (21).

12. A method according to claim 10, wherein the formation of the second layer (22) comprises an alternating deposition, on one face of the first layer (21), of at least one sub-layer, respectively, of Mo or W, and of at least one sub-layer of Si.

13. A method according to any one of claims 11 or 12, wherein the formation of the second layer (22) comprises, after deposition, a thermal treatment configured to form molecules of MoSi or, respectively, of WSiy.

14. Method according to the preceding claim, in which the heat treatment is carried out in the presence of dioxygen.

15. Method according to any one of the two preceding claims, configured to manufacture a microelectronic device for storing electrochemical energy, comprising a step of forming an electrode, the heat treatment being configured to produce a crystallization annealing of the electrode.

16. Method according to the preceding claim, in which the electrode is based on LiCo, the heat treatment being configured to produce a crystallization annealing of the electrode so as to form LiCoO2.

17. A method according to any one of claims 10 to 16, configured so that the electrical resistance of the electrically conductive element is less than or equal to 3 ohms.

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