Substrate comprising vias and associated manufacturing processes

Abstract

Substrate comprising vias and associated manufacturing methods The invention relates to a substrate comprising a first layer (30) based on a semiconductor material, and a second layer (31) overlying the first layer. The substrate (3) comprises a plurality of buried hollow vias (32) extending from the second layer (31) over a portion of the first layer (30). The invention further relates to the method of manufacturing the substrate and the method of manufacturing a microelectronic device using the substrate. The substrate comprising hollow vias for subsequent use, the manufacturing of the vias is facilitated. Figure for abstract: Fig.2A

Description

Title of the invention: Substrate comprising vias and associated manufacturing methods Technical field

[0001] The present invention relates to the field of substrates intended for manufacturing electronic devices and more particularly microelectronic devices, these substrates ultimately allowing an electrical and mechanical connection of electrical elements of components. The invention finds advantageous, but not limiting, application in the manufacture of microelectronic devices, and for example microelectronic devices for computing applications. STATE OF THE ART

[0002] There is an interest in manufacturing, as for example illustrated by [Fig.l], assemblies of components 4' on substrates 3 comprising vias 32 to form through contacts in order to be able to interconnect these components on the front face 3a and on the rear face 3b of the substrate 3, to obtain a microelectronic device 4. The components 4' can thus be connected to a printed circuit for example by means of a package 5. These substrates 3 can in particular be semiconductor substrates, for example of the semiconductor-on-insulator type, and in particular silicon-on-insulator SOI (abbreviated from the English Silicon-On-Insulator).

[0003] The etching and metallization of these vias 32 (commonly referred to as TSV, abbreviated from the English Through-Silicon-Via for silicon-based substrates) are fairly specific process steps and are often carried out by assemblers (commonly referred to as OSAT, from the English Outsourced Semi-conductor Assembly and Test) and not by foundries.

[0004] There are two types of vias depending on their manufacturing time in the manufacturing chain of a microelectronic device. So-called "TSV-middle" vias are generally manufactured in the middle of the process, after the manufacturing of the patterns of a component during the Front-end-of-line (abbreviated FEOL, which can be translated as start of manufacturing line) but before the deposition of the metal layers of the Back-end-of-line (abbreviated BEOL, which can be translated as end of manufacturing line). This generally requires a transfer of the substrate and components from the foundry to the assembler for the manufacturing of the vias, then a return to the foundry for the BEOL steps, and finally another transfer to the assembler to finalize the process. These manufacturing steps are very constrained in terms of flatness and contamination, which is not very compatible with these back-and-forths between the foundry and the assembler.

[0005] The “TSV-last” vias can be manufactured at the end of the process, after the steps of FEOL and BEOL. This generally requires a single transfer from the foundry to the assembler, after the BEOL steps. However, the via geometries that can be achieved are limited. In particular, the via density that can be achieved is limited. This is particularly limiting for certain applications such as computing.

[0006] There is therefore a need to obtain these structures without depending on other manufacturing steps in the chain.

[0007] An object of the present invention is therefore to facilitate the fabrication of vias in a microelectronic device.

[0008] Other objects, features and advantages of the present invention will become apparent from a consideration of the following description and accompanying drawings. It is understood that other advantages may be incorporated. SUMMARY

[0009] To achieve this objective, according to one embodiment, a substrate is provided comprising: - a first layer based, preferably made, on a semiconductor material, - a second layer over the first layer.

[0010] Advantageously, the substrate comprises a plurality of buried hollow vias extending from the second layer over a portion of the first layer, each via being delimited by a side wall, a bottom wall, and an upper wall opposite the bottom wall.

[0011] Thus, the substrate comprises non-opening hollow vias for subsequent filling with an electrically conductive or semiconductive member. This makes it possible to provide the hollow vias independently of the other steps of producing a microelectronic device. The substrate comprising the buried hollow vias can be used to carry out the deposition of layers, for example FEOL and BEOL, then the hollow vias can be opened to produce the desired electrically conductive or semiconductive member, for example electrical interconnections. In addition, since the vias are manufactured beforehand, the geometries of the vias are not limited.

[0012] This has several advantages. These hollow vias are compatible with FEOL steps taking place at high temperature, unlike existing solutions using metallized vias, for example in copper or tungsten.

[0013] It is therefore understood that the manufacture of the vias is facilitated, in particular with regard to the other stages of manufacture of a microelectronic device. The manufacture of the vias filled by the electrically conductive or semi-conductive member is more particularly facilitated.

[0014] According to one example, at least the bottom wall and the side wall are made of dielectric material. The walls made of dielectric materials being formed beforehand, they allow good insulation of the vias once filled with the conductive or semiconducting material, while being compatible with the FEOL or temporary mounting steps of a support. This is particularly advantageous when the form factor of the vias is greater than or equal to 10, for which it is simpler to produce these walls prior to the manufacture of a microelectronic device.

[0015] A second aspect relates to a method of manufacturing the substrate according to the first aspect, comprising: - a provision of a support sub-substrate comprising at least a first layer based on, preferably made of, a semiconductor material, the support sub-substrate having an exposed surface, - etching a plurality of vias such that the vias extend from the exposed surface over a portion of the first layer, each via being delimited by a side wall and a bottom wall, - a supply of a donor sub-substrate comprising a surface layer having an exposed surface, - an assembly of the support sub-substrate and the donor sub-substrate by their exposed surfaces, so as to cover the vias, each via then being delimited by the side wall, the bottom wall, and an upper wall opposite the bottom wall.

[0016] This method thus allows the manufacture of hollow vias buried on the substrate. This method has the effects and advantages described in relation to the first aspect.

[0017] A third aspect relates to a method of manufacturing a microelectronic device comprising: - a provision of a substrate according to the first aspect or a substrate manufactured by the method according to the second aspect, having a front exposed surface and a rear exposed surface, - a formation of at least one portion of the device layer by a deposition, on the front exposed surface of the substrate, of said portion, and / or an etching of the front exposed surface of the substrate, configured so as to form said portion, - at the level of at least one via, an etching by the rear exposed surface of the substrate, in which one wall among the upper wall and the bottom wall of the at least one via is etched so as to open into the via, then continuing the etching to reach the at least one portion of layer of the device, to form a cavity, - the deposition of an electrically conductive or semi-conductive organ so as to fill the cavity.

[0018] Thus, the substrate provided allows the formation of a microelectronic device, then the opening of buried hollow vias to create the desired electrically conductive or semiconducting component. This can be achieved more easily than existing solutions. BRIEF DESCRIPTION OF THE FIGURES

[0019] The aims, objects, as well as the characteristics and advantages of the invention will emerge more clearly from the detailed description of embodiments thereof, illustrated by the following accompanying drawings.

[0020] [Fig.l] [Fig.l] represents a cross-sectional view of a microelectronic device comprising a substrate comprising vias, according to a general example of the state of the art.

[0021] [Fig.2A][Fig.2B][Fig.2C] Figures 2A to 2C represent cross-sectional and top views of the substrate according to two exemplary embodiments.

[0022] [Fig.3A][Fig.3B] Figures 3A and 3B each represent a cross-sectional view of the substrate according to two other exemplary embodiments, in which the substrate comprises grooves surrounding the vias.

[0023] [Fig.3C] [Fig.3C] represents a top view of the substrate illustrated according to any one of Figures 3A and 3B.

[0024] [Fig.4A][Fig.4B][Fig.5] Figures 4A to 9C represent sectional views cross-section of the steps of the substrate manufacturing process according to exemplary embodiments, including: - [Fig.6A][Fig.6B] Figures 6A and 6B represent cross-sectional views of the etching and the formation of the walls in dielectric material, according to an exemplary embodiment, - [Fig.ôC] [Fig.ôC] represents a cross-sectional view of the etching of the vias, according to another exemplary embodiment, - [Fig.7A][Fig.7B][Fig.7C] Figures 7A to 7C represent cross-sectional views of the etching and the formation of the walls in dielectric material, according to two other exemplary embodiments in which the substrate comprises grooves surrounding the vias. - [Fig.8A][Fig.8B] Figures 8A and 8B represent cross-sectional views of the assembly of the support sub-substrate and the donor sub-substrate according to an exemplary embodiment, - [Fig.9A][Fig.9B] Figures 9A and 9B represent cross-sectional views of the assembly of the support sub-substrate and the donor sub-substrate according to another exemplary embodiment, - [Fig.9C] [Fig.9C] represents a cross-sectional view of the assembly of the support sub-substrate and the donor sub-substrate according to another example of realization.

[0025] Figures 10 to 17 represent cross-sectional views of the steps of the method of manufacturing the microelectronic device according to exemplary embodiments, among which: - [Fig. 10] [Fig. 11] Figures 10 and 11 represent cross-sectional views of the deposition of a portion of the device layer and the mounting of a support, according to an exemplary embodiment, - [Fig.l2A][Fig.l2B][Fig.l2C][Fig.l2D] Figures 12A to 12D represent cross-sectional views of an example of selection of the vias to be etched, - [Fig.l2E][Fig.l2F][Fig.l2G][Fig.l2H] Figures 12E to 12H represent cross-sectional views of a second example of selection of the vias to be etched, - [Fig.l3A][Fig.l3B][Fig.l3C] Figures 13A to 13C represent cross-sectional views of a third example of selection of the vias to be etched, [Fig.l4A][Fig.l4B][Fig.l4C][Fig.l4D][Fig.l4E][Fig.l4F] Figures 14A to 14F represent cross-sectional views of an example of the method in which the substrate comprises grooves surrounding the vias, - [Fig.l5][Fig.l6][Fig.l7] Figures 15 to 17 represent cross-sectional views of the steps following the deposition of the conductive or semi-conductive member, according to an exemplary embodiment.

[0026] 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 practical applications. In particular the relative dimensions of the sub-substrates and substrate, the layers, the vias and the walls are not representative of reality. DETAILED DESCRIPTION

[0027] Before commencing a detailed review of embodiments of the invention, optional features which may optionally be used in combination or alternatively are set out below.

[0028] According to one example, the second layer is a layer based on, and preferably made of, a material chosen from a dielectric material, for example an oxide, a semiconductor material or a piezoelectric material.

[0029] According to one example, the second layer is a layer of dielectric material, for example an oxide, buried and topped by a third layer based on a material chosen from a semiconductor material or a piezoelectric material. The substrate may be of the “Semiconductor-on-Insulator” type, and for example of the “Silicon-on-Insulator” type.

[0030] According to one example, each via has at least one transverse dimension, for example a diameter, substantially between 1 μm and 30 μm.

[0031] According to one example, at least a portion of the vias has a form factor greater than or equal to 10, with the longest dimensions oriented along a thickness dimension of the first and second layers. This form factor is particularly suitable for obtaining a high density of vias on the substrate, and in particular in synergy with the ranges of pitch values stated above.

[0032] According to one example, the plurality of vias forms a periodic matrix. Thus, the substrate comprises a matrix of hollow vias that can be selected in order to produce the desired interconnections. The generic substrate comprising these vias therefore makes it possible to facilitate the manufacture of the vias and the conductive or semi-conductive member, in particular by being able to adapt to different microelectronic devices.

[0033] According to one example, the vias are separated two by two by a constant pitch following at least one direction of the main extension plane of the first and second layers.

[0034] According to one example, the pitch is substantially between 50 pm and 300 pm, preferably between 100 pm and 200 pm. This pitch allows for a better density of the hollow vias in the substrate. Thus, a greater interconnection density is possible. In addition, the adaptability of the substrate to different microelectronic devices is improved.

[0035] According to one example, the vias are parallel to each other.

[0036] According to one example, the vias have a longitudinal dimension oriented along a thickness dimension of the first and second layers.

[0037] According to one example, the vias extend in a direction parallel to the normal to the main extension plane of the first and second layers.

[0038] According to one example, the vias are cylindrical. Thus, the bottom wall of the vias is more homogeneous than for non-cylindrical shapes, for example a square shape for which the corners will be less deep than the center, following the etching of the vias. A cylindrical shape minimizes this effect. In addition, the mechanical stresses are lower for cylindrical vias which do not have the singularities of the corners. This is advantageous for heat treatments during the fabrication of the circuits.

[0039] According to example, at least one via, and preferably each via, over at least a portion of a longitudinal dimension of said via, is completely surrounded by a groove extending from the second layer over a portion of the first layer. The groove makes it possible to improve the electrical insulation between the vias. The groove is thus manufactured beforehand and independently of the other manufacturing steps of the microelectronic device. The groove is thus compatible with the FEOL steps taking place at high temperature. In addition, since the groove is manufactured beforehand, its geometry is not limited by the other manufacturing steps of the microelectronic device.

[0040] According to one example, each groove is not filled with a solid material. Each groove is preferably filled with an electrically insulating gaseous atmosphere, for example air, nitrogen or argon, optionally at a pressure less than or equal to ambient pressure.

[0041] According to one example, each groove is delimited by a bottom wall, a side wall and a top wall opposite the bottom wall. For at least one groove, and preferably for each groove, at least a portion of the side wall and the bottom wall may be made of the same material as that of the first layer. The insulation of the vias is in fact sufficient thanks to the insulating atmosphere contained in the groove. Alternatively, for at least one groove, and preferably for each groove, at least a portion of the side wall and the bottom wall may be made of a dielectric material, for example the same dielectric material as the walls of the via. Thus, the electrical insulation of the via is further improved.

[0042] According to one example, the groove is concentric with said via. This makes it possible in particular to reduce the parasitic capacitance between the via and the substrate and to increase the breakdown voltage.

[0043] According to one example, the groove extends from the second layer into the first layer over a longitudinal dimension less than or equal to the longitudinal dimension of the via, preferably plus or minus 5 μm. Thus, the groove surrounds the via over at least a portion and preferably substantially the entire longitudinal dimension.

[0044] According to one example, the substrate further comprises a marker configured to allow the alignment of the substrate. This makes it possible to further facilitate the manufacturing of the microelectronic device, by facilitating the alignment of the substrate, and in particular for carrying out the photolithography steps necessary for the construction of the FEOL and the BEOL, and therefore the opening of the vias.

[0045] According to one example, the semiconductor material is chosen from the group consisting of silicon Si, germanium Ge, SiGe, a III-V material (for example GaN, InN, InGaAs, GaP, InP, InAs, AsGa...), a II-VI material, materials with a wide band gap, for example greater than 3 eV.

[0046] According to one example, the semiconductor material comprises, and preferably is, silicon.

[0047] According to one example, the piezoelectric material is selected from lithium tantalate (LiTaO3), lithium niobate (LiNbO3), potassium sodium niobate (KxNabx NbO3 or KNN), barium titanate (BaTiO3), quartz, lead zirconate titanate (PZT), a compound of lead magnesium niobate and lead titanate (PMN-PT), zinc oxide (ZnO), aluminum nitride (AIN) or aluminum scandium nitride (AIScN).

[0048] According to one example, the dielectric material is a semiconductor oxide, and preference for silica with the chemical formula SiO2.

[0049] According to one example, following the etching of the plurality of vias and preferably before the assembly of the support sub-substrate and the donor sub-substrate, the method comprises, for each via, a formation of a dielectric material at least on the bottom wall and the side wall. Thus, the hollow vias formed in the substrate have a dielectric layer at least on their bottom wall and side wall, prior to the use of the substrate in a method for manufacturing a microelectronic device.

[0050] According to one example, forming a dielectric material at least at the bottom wall and the side wall of the plurality of vias comprises - thermal oxidation so as to oxidize the semiconductor material of the first layer at least at the bottom wall and the side wall, and / or - a deposit of the dielectric material at least at the level of the bottom wall and the side wall.

[0051] These techniques, and particularly thermal oxidation, make it possible to obtain good conformity of the walls made of dielectric material. Since thermal oxidation is conformal, it makes it possible to obtain an oxide that is both dense and of uniform thickness on the bottom and side walls. Thermal oxidation is therefore particularly advantageous in synergy with high form factors of the vias. Compared to a deposit, thermal oxidation also allows smoothing of the etched wall of the vias and limits the presence of defects between the semiconductor material of the first layer and the dielectric.

[0052] According to one example, when at least the bottom wall and the side wall are made of dielectric material, the bottom wall of the plurality of vias has a longitudinal dimension substantially between 50 nm and 600 nm, preferably substantially equal to 400 nm.

[0053] According to one example, when at least the bottom wall and the side wall are made of dielectric material, the side wall of the plurality of vias has a transverse dimension substantially between 50 nm and 600 nm, preferably substantially equal to 400 nm.

[0054] According to one example, the surface layer of the donor sub-substrate is a layer based on, and preferably made of, a material chosen from a dielectric material, for example an oxide, a semiconductor material or a piezoelectric material.

[0055] According to one example, - the support sub-substrate further comprises a surface layer based on, and preferably made of, a dielectric material, for example an oxide, overlying the first layer (10), the surface layer having the exposed surface, and / or - the surface layer of the donor sub-substrate is a layer based on, and preferably made of, a dielectric material, for example an oxide, overlying a layer based on a material chosen from a semiconductor material or a piezoelectric material.

[0056] It is therefore understood that the buried oxide layer of the substrate can come from the donor sub-substrate and / or the support sub-substrate.

[0057] According to one example, the surface layer of the donor substrate is based on, preferably made of, one of a semiconductor material or a dielectric material. Depending on whether the surface layer is based on a semiconductor material or a dielectric material, it is understood that the upper wall of the vias, and where appropriate of the grooves, is based on or made of a semiconductor material or a dielectric material.

[0058] According to one example, the etching of the plurality of vias is configured to form a periodic array. The effects and advantages described in relation to the array of vias are thus obtained.

[0059] According to one example, the method for manufacturing the substrate further comprises, prior to the assembly of the support sub-substrate and the donor sub-substrate, an etching of a groove completely surrounding at least one via over at least a portion of a longitudinal dimension of said via, the groove extending from the surface layer into the first layer. The effects and advantages described in relation to the groove are therefore obtained.

[0060] According to one example, the method comprises forming a weakening zone at a depth of the surface of the surface layer of the donor substrate, and then separating the donor substrate at the weakening zone.

[0061] According to one example, the method for manufacturing the microelectronic device comprises, prior to etching by the rear exposed surface of the substrate, a selection of at least one via to be etched from among the plurality of vias comprising: - the application, on the rear exposed surface of the substrate, of a mask comprising openings located directly above the at least one via to be etched, and - an etching of the first layer so as to reach said wall of the at least one via to be etched. Thus, it is possible to select the vias to be etched from among the existing vias. The process is thus adaptable according to the desired microelectronic device configuration. This selection is particularly advantageous in synergy with the characteristic whereby the vias form a matrix of vias.

[0062] According to one example, selecting the at least one via to be etched comprises applying the mask and then etching the first layer through the openings in the mask. This avoids any potential weakening of the wall of the vias to be etched. This etching thus etches the first layer at the right of the at least one via to be etched until it opens into the at least one via to be etched.

[0063] According to one example, the selection of the at least one via to be etched comprises etching the first layer so as to reach said wall of the at least one via to be etched, then applying the mask. Thus, the side wall made of dielectric material may be present along the entire longitudinal dimension of the cavity that will be formed. It is not necessary to isolate the portion of the cavity to complete the wall made of dielectric material of the via. The first layer is more particularly etched over its entire main extension plane.

[0064] According to one example, the deposition of the electrically conductive or semiconductive member is configured so as to further cover with an electrically conductive or semiconductive layer at least a portion of the rear exposed surface of the substrate.

[0065] According to one example, the method comprises patterning the back electrically conductive or semiconductive layer.

[0066] According to one example, the method comprises passivating the rear exposed surface of the substrate.

[0067] According to one example, the method of manufacturing a microelectronic device comprises: - between the formation of the at least one layer portion of the device, and the etching by the rear exposed surface of the substrate, the mounting of a support on the front exposed surface of the substrate, and - after depositing the electrically conductive or semi-conductive organ so as to fill the electrical cavity, dismantling the support. The support thus makes it easier to handle the substrate.

[0068] 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, as well as optical or optoelectronic devices. It may be a device intended to provide an electronic, optical, mechanical, etc. function. It may also be an intermediate product intended solely for the production of another microelectronic device. It may also be a structure of passive electrical interconnections.

[0069] 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 does not necessarily mean that the two layers are directly in contact with each other but it does mean that one of the layers at least partially cover the other by being either directly in contact with it or by being separated from it by a film, yet another layer or another element.

[0070] A layer may also be composed of several sub-layers of the same material or of different materials.

[0071] An element “based on” a material A is understood to mean an element comprising this material A only or this material A and possibly other materials.

[0072] In the detailed description which follows, terms such as "longitudinal", "transverse" may be used. These terms must be interpreted relative to the substrate or the thickness dimension of the devices. Thus, a longitudinal dimension, a height, a depth or a thickness of an element or a layer means a dimension according to the thickness of the substrate which carries or contains it. A width, or even a section or a transverse dimension means a dimension perpendicular to the thickness of the substrate.

[0073] Certain parts of the substrate or device of the invention may have an electrical function. Some are used for electrical conduction properties and electrically conductive or equivalent means elements formed from at least one material having sufficient conductivity, in the application, to achieve the desired function. Other parts, on the contrary, are used for electrical insulation properties and all materials having sufficient resistivity to achieve this insulation are concerned and are in particular called dielectric or electrically insulating.

[0074] The word "dielectric" more particularly qualifies a material whose electrical conductivity is sufficiently low in the given application to serve as an insulator. In the present invention, a dielectric material preferably has a dielectric constant of less than 4.

[0075] The term "direct bonding" means bonding without the addition of adhesive material (in particular of the glue or polymer type) which consists of bringing relatively smooth surfaces into contact (with a root mean square roughness RMS, typically less than 5 Å, 10 10 m), for example carried out at room temperature and in an ambient atmosphere, in order to create adhesion between them.

[0076] According to one embodiment, the direct bonding of two substrates means that the bonding is obtained by the chemical bonds which are established between the two surfaces brought into contact. These chemical bonds may be, for example, Van der Waals bonds and / or strong, covalent chemical bonds, in particular when the bonding is assisted by plasma activation or followed by a strengthening heat treatment (typically 200 to 1200°C for 1 h).

[0077] Direct bonding can be achieved without requiring the application of pressure im bearing on the structure to be assembled. Light pressure can simply be applied to initiate bonding. Thermal annealing can also be carried out to strengthen the bond.

[0078] A parameter “substantially equal / greater / less than” a given value means that this parameter is equal / greater / less than the given value, to within plus or minus 10%, or even plus or minus 5%, of this value.

[0079] The substrate 3 is now described according to several exemplary embodiments with reference to FIGS. 2A to 3C.

[0080] As for example illustrated by [Fig.2A], the substrate 3 comprises a first layer 30, based on or made of a semiconductor material. According to one example, the semiconductor material comprises, and preferably is, silicon. The first layer 30 has a thickness L30, for example substantially between 100 pm and 800 pm.

[0081] The substrate 3 further comprises a second layer 31. As illustrated by [Fig.2A], the second layer 31 may be based on or made of a dielectric material. According to one example, the semiconductor material comprises, and preferably is, a semiconductor oxide, for example silica of formula SiO2. The second layer 31 surmounts the first layer 30, preferably by being in direct contact with it. As illustrated by [Fig.2C], the second layer 31 may be based on or made of a semiconductor material or a piezoelectric material. The second layer 31 may have a thickness L3b, for example greater than or equal to 10 nm, preferably 100 nm. The thickness L3i may be less than or equal to 1000 nm.

[0082] According to one example, for example illustrated by [Fig.2A] the second layer 31 is surmounted by a third layer 33 based on or made of a semiconductor material or a piezoelectric material. According to one example the semiconductor material comprises, and preferably is, silicon. The third layer 33 has a thickness L33, for example substantially between 10 nm and 1000 nm. The substrate 3 thus comprises a structure of the semiconductor-on-insulator type, and in particular of the silicon-on-insulator (SOI) type. Note that it can be provided that the second layer 31 is not surmounted by a third semiconductor layer.

[0083] In the following, unless explicitly stated otherwise, it is considered, without limitation, that the substrate 3 is an SOI substrate, the first layer 30 being made of monocrystalline silicon, the second layer of SiO2 and the third layer of monocrystalline silicon.

[0084] The substrate 3 comprises hollow vias 32 extending from the second layer 31 into the first layer 30. The vias 32 may be parallel to each other. The vias 32 preferably extend over a longitudinal dimension L32 oriented in the direction of the thickness of the first 30 and second 31 layers. The vias 32 are buried in the substrate 3, i.e. they do not open onto either of the surfaces. exposed 3a, 3b of the substrate 3. The vias 32 therefore define a closed volume. The vias 32 being hollow, they are not filled with a solid material. They are preferably filled with a gaseous atmosphere such as air, nitrogen and / or argon, possibly at a pressure less than or equal to ambient pressure.

[0085] Thus, the substrate 3 comprises hollow vias 32 for subsequent filling. This makes it possible to provide the hollow vias independently of the other steps of producing a microelectronic device 4, as described later with reference to the method of manufacturing a microelectronic device.

[0086] The longitudinal dimension L32 may be chosen so as to extend over at least a portion of the thickness L3i of the second layer, and only a portion of the thickness L30 of the first layer 30, as for example illustrated in [Fig.2A]. Alternatively, the vias 32 may be flush with the surface of the first layer 30, as for example illustrated in [Fig.2C].

[0087] The vias 32 are delimited by a side wall 320, a bottom wall 321 and an upper wall 322 opposite the bottom wall 321. The bottom wall 321 is arranged towards the rear surface 3b of the substrate 3 and the upper wall 322 is arranged towards the front surface 3a of the substrate 3.

[0088] Among these walls, at least the bottom wall 321 and the side wall 320 may be made of dielectric material, for example SiO2. Thus, the via 32 once filled with an electrically conductive or semiconductive material will be electrically insulated from the first layer 30 and the other vias 32. As illustrated in [Fig.2A], all the walls of the vias 32 may be made of dielectric material. According to a variant, the upper wall 322 may be made of the same material as the third layer 33, as for example illustrated in [Fig.9A] described in more detail later with reference to the method of manufacturing the substrate 3.

[0089] Alternatively, as for example illustrated by [Fig.2C], the walls of the vias 32 may be made of semiconductor material, and more particularly of the same material as that of the first layer 30. The electrical insulation of the vias 32 may be done subsequently during the manufacturing process of the microelectronic device from the substrate 3, described later.

[0090] The vias may have a transverse dimension D32, for example a diameter, substantially less than or equal to 30 pm, preferably substantially between 1 pm and 30 pm, preferably substantially between 5 pm and 15 pm, and even more preferably between 8 and 12 pm. Thus, the lateral dimension D32 is smaller than the typical dimensions of TSV-last, which makes it possible to have a greater number of vias 32 for the same surface area of the substrate 3 in the main extension plane of the first 30 and second 31 layers, i.e. a greater density of vias 32. The longitudinal dimension of the vias L32 may be of the order of the thickness L30 of the layer 30, the vias 32 being non-emerging. L32 may be substantially less than or equal to 200 pm, preferably substantially between 50 and 150 pm, for example substantially equal to 100 pm. These length ranges make it possible to facilitate the formation of an electrically conductive or semiconducting through-member, for example a through-interconnection by the via 32, of the substrate 3 during the manufacture of the microelectronic device 4.

[0091] The vias 32 may have a form factor substantially greater than or equal to 5, and preferably greater than or equal to 10. By form factor is meant the ratio between the longest dimension and the shortest dimension. Here the form factor F is such that F = L32 / D32. This form factor makes it possible to facilitate the formation of an electrically conductive or semiconducting through member, for example a through interconnection by the via 32, during the manufacture of the device, and to increase the density of the vias 32 on the substrate, in synergy with the pitch separating them.

[0092] According to an example that can be illustrated by [Fig.2B], the vias 32 form a periodic matrix, that is to say that the vias 32 are arranged at regular intervals in the main extension plane of the first 30 and second 31 layers. Thus, the substrate 3 can be a generic substrate comprising a matrix of vias, in which vias to be etched and filled 32' will be chosen according to the electrically conductive or semiconductive member to be formed, as described in more detail later.

[0093] For this, the vias 32 may be separated two by two by a first pitch A along a first direction contained in the main extension plane of the first 30 and second 31 layers. The vias 32 may be separated two by two by a second pitch B along a second direction contained in the main extension plane of the first 30 and second 31 layers, distinct from the first. Preferably, these first and second directions are perpendicular. One and / or the other of these pitches A and B may be substantially between 50 pm and 300 pm, preferably between 100 pm and 200 pm. These pitches may be different from each other or equal to each other, depending on the desired matrix geometry. This pitch is measured center to center between two vias 32 directly following each other.

[0094] According to an example that can be illustrated by Figures 3A and 3B, the substrate 3 can comprise at least one and preferably several groove(s) 35 configured to improve the electrical insulation of the vias 32. The substrate 32 is thus particularly suitable for high frequency applications and / or as a replacement for a high resistivity substrate for applications requiring it. For this, at least one via 32, and preferably each via 32, has a cross-section completely surrounded by the groove 35, taken in the main extension plane of the first 30 and second 31 layers. The groove 35 can surround the via 32 over at least a portion of its longitudinal dimension L32. The grooves 35 are preferably arranged so as to isolate the vias 32 from each other, a groove 35 preferably surrounding a single via 32. The grooves 35 preferably do not touch each other. The groove 35 may more particularly extend from the second layer 31 over a portion of the first layer 30.

[0095] Each groove 35 is preferably buried, that is to say that it does not open onto one or the other of the exposed surfaces 3a, 3b of the substrate 3. Each groove 35 therefore defines a closed volume. Each groove 35 is preferably hollow, it is not filled with a solid material. Each groove 35 is preferably filled with a gaseous atmosphere such as air, nitrogen or argon, possibly at a pressure less than or equal to ambient pressure.

[0096] Each groove 35 is delimited by a side wall 350, a bottom wall 351 and an upper wall 352 opposite the bottom wall 351. The bottom wall 351 is arranged towards the rear surface 3b of the substrate and the upper wall 352 is arranged towards the front surface 3a of the substrate 3. Among these walls, at least the bottom wall 351 and the side wall 350 may be made of dielectric material, for example SiO2. As illustrated in [Fig. 3A], all the walls may be made of dielectric material. According to a variant not shown in the drawings, the upper wall 352 may be made of the same material as the second layer 31. It is also possible to provide for the groove 35 to be flush with the surface of the first layer 30, like the vias 32 illustrated in [Fig. 2C]. According to another variant which may for example be illustrated by [Fig.3B], all the walls may be of the same material as the layer in which or against which they extend, of dielectric or semiconducting material depending on the layer considered.

[0097] As illustrated for example by [Fig.3A], each groove 35 may have a longitudinal dimension, or equivalently a depth, L35 substantially equal to or less than that of the via L32, according to one example equal to plus or minus 5 μm.

[0098] As illustrated for example by Figures 3A and 3B, each groove 35 may have a transverse dimension D35 taken on either side of the via 32, for example a diameter, substantially less than or equal to 50 pm, preferably substantially between 20 pm and 30 pm. Each groove 35 may have a width substantially less than or equal to 5 pm, for example substantially between 2 and 4 pm. Thus, similarly to the dimensions of the vias 32, an improvement in the electrical insulation can be obtained while making it possible to obtain a high density of vias 32. Synergistically, it is particularly advantageous to use these grooves 35 when the vias 32 are close to each other, as is the case for a high density of vias 32 on the substrate 3, in order to improve their electrical insulation. By high density, for example the pitches A and / or B are less than or equal to 100 pm. may provide that the grooves 35 have equal or distinct dimensions between the different grooves 35.

[0099] Depending on the dimensions of the grooves 35 in the main extension plane of the first 30 and second 31 layers, the pitch can be adapted so that the grooves 35 are distinct from each other. Each groove 35 can be cylindrical, and preferably concentric with the via 32 which it surrounds.

[0100] As illustrated for example in FIGS. 2A to 3C, the substrate 3 may comprise at least one mark or equivalently a reference mark 34 allowing the alignment of the substrate 3 with other elements. Thus, the placement of the vias 32 during the manufacturing process of the microelectronic device is made more reliable. This reference mark 34 may be formed by one or more portion(s) of layer of dielectric material at the level of the first layer 30 and / or second layer 31. Note that the person skilled in the art may well envisage other variants of reference mark, such as for example a marking arranged on the front surface 3a of the substrate 3.

[0101] The method of manufacturing the substrate 3 is now described with reference to FIGS. 4A to 9B.

[0102] The method comprises providing a sub-substrate 1. The sub-substrate 1 comprises at least a first layer 10, intended to form the first layer 30 of the substrate 3 which will be obtained, as illustrated in FIGS. 4A and 4B. The sub-substrate 1 may further comprise, as for example illustrated by [Fig.4A], a surface layer 11 intended to form at least in part the second layer 31 of the substrate 3. The surface layer 11 is preferably based on or made of a dielectric material. The sub-substrate 1 further has an exposed surface 1a, at the level of the first layer 10 or the surface layer 11.

[0103] As for example illustrated by Figures 5 and 6A, 6C, the vias 32 can be formed by etching, and preferably by deep reactive ion etching (commonly abbreviated DRIE, from the English “Deep Reactive Ion Etching”). To form the vias 32, the etching step can comprise the application of a mask 12 comprising openings 120 from which the vias 32 will be etched, as illustrated for example in [Fig.5]. The mask 12 is preferably a resin mask. It is possible to provide for the mask to be hard, for example with the application of a resin mask 12 then the etching of the surface layer 11, removing this mask and etching the first layer 10 using the so-called “hard” oxide mask thus formed. Note that the surface layer 11 can be removed after etching the vias 32, and the vias 32 electrically isolated by depositing a dielectric layer thereafter.

[0104] The etching is preferably configured to obtain the characteristics of the vias 32 described previously, and in particular their dimensions and the pitches separating them. For example, the dimensions of the mask 12 and / or the etching time and speed are adjusted for this.

[0105] To form the vias 32, the method may then comprise forming a dielectric material at least at the bottom wall 321 and the side wall 320, as illustrated for example in [Fig.6B].

[0106] This formation can be done by thermal oxidation, for example at a temperature of substantially 1050°C in an atmosphere comprising oxygen.

[0107] Alternatively or additionally, the dielectric material, for example silica SiO2, may be deposited at least at the walls 320, 321 of the vias 32. This deposition may be a chemical vapor deposition (commonly abbreviated CVD) from gaseous precursors comprising oxygen and silicon, for example tetraethyl orthosilicate (commonly abbreviated TEOS) or silane of chemical formula SiH4, optionally combined with dioxygen. The deposition is for example a subatmospheric pressure CVD (commonly abbreviated SACVD), or a plasma-enhanced chemical phase deposition (commonly abbreviated PECVD).

[0108] Preferably, the mask 12 is removed prior to the formation of these walls made of dielectric material. In the case where the layer 11 serves as a hard mask, it is preferable to remove it as well.

[0109] Preferably, the formation of the walls 320, 321 is configured so that the walls 320, 321 of dielectric material have a dimension substantially between 50 nm and 600 nm, and preferably substantially equal to 400 nm. For the side wall 320, this dimension is the transverse dimension. For the bottom wall 321, this dimension is the longitudinal dimension. For example, the thermal oxidation time or the deposition time and / or the deposition rate can be adjusted for this.

[0110] The method may comprise, simultaneously or concomitantly with the etching of the vias 32 and where appropriate with the formation of the walls in dielectric material, a step of forming the mark 34. For this, the mask may further comprise openings, not shown here, for etching for example openings 34' in the second layer 31 up to in the first layer 30, illustrated for example in [Fig.6A]. The openings 34' may be filled with the dielectric material during the formation of the walls. The formation of the mark 34 may be distinct from these steps, for example by the application of a mask specific to this mark 34, etching and filling of the openings 34'. If the formation of the mark 34 is distinct from these steps, it would advantageously be carried out before, to serve as a mark for the positioning of the vias 32.

[0111] Figures 7A to 7C illustrate examples in which grooves 35 are formed around the vias 32. Only one groove is shown to simplify the figures. The formation of the grooves 35 may comprise the same steps as for the etching of the vias 32 and, where appropriate, for the formation of the walls made of dielectric material. The grooves 35 may be formed simultaneously with the vias 32, the mask 12 then comprising openings corresponding to the grooves 35 to be etched. The grooves 35 may alternatively be etched before or after the etching of the vias 32, for example by applying a mask and etching specific to the grooves 35. According to one example, once the grooves 35 and vias 32 have been etched, a dielectric material may be formed at the walls 350, 351, 320, 321 as previously described. Alternatively, the grooves 35 can be formed after the formation of the dielectric material at the walls 320 and 321. It can be provided that a new formation of dielectric material is made at the walls 350, 351, according to the methods previously described.The etching of the grooves 35 may otherwise not be followed by a formation of dielectric material at the walls 350 and 351, as illustrated for example in [Fig.7C]. The grooves 35 and the vias 32 may not have a wall made of dielectric material, according to a variant not illustrated.

[0112] Following the formation of the vias 32 and, where appropriate, the grooves 35, these structures can be covered to be buried during the assembly of the sub-substrate 1 with a donor sub-substrate 2. The method can therefore comprise the provision of a donor sub-substrate 2 having an exposed surface 2a.

[0113] As illustrated by Figures 8A to 9C, the support 1 and donor 2 sub-substrates can be assembled by bringing their respective surfaces 1a, 2a into contact by direct bonding. The donor substrate 2 can then be thinned, for example by cleavage using the process known as Smart-Cut®.

[0114] The assembly may for this purpose comprise, before bringing the surfaces 1a, 2a into contact, the formation of a weakening zone 22 at a non-zero depth of the surface 2a of the donor sub-substrate 2. This weakening zone 22 is for example formed by implantation of ions, such as hydrogen and / or helium ions. Note that any other technique for forming a weakening zone, and in particular any other technique used in the methods for producing SOI-type stacks, may be envisaged.

[0115] Following the assembly of the support sub-substrate 1 and the donor sub-substrate 2, the method may comprise the separation of a surface layer of the donor sub-substrate 2, at the level of the weakening zone 22, as in the examples illustrated in FIGS. 8B and 9B. This separation may be done thermally or mechanically, according to steps known to those skilled in the art.

[0116] Following separation, the surface 3a obtained may be irregular and damaged. Polishing, chemical smoothing, chemical and / or mechanical and / or thermal and / or ion beam healing based on atom clusters or based on monomers of the surface 3a can be achieved, so that the surface 3a has a crystalline quality and a roughness suitable for other subsequent processes. Any chemical-mechanical polishing (CMP) or thermal polishing method intended to smooth a surface based on semiconductors, particularly silicon, can be considered.

[0117] According to one example, the donor sub-substrate 2 comprises a layer 20 based on or made of a semiconductor material, for example silicon and more particularly monocrystalline silicon. The donor sub-substrate 2 may further comprise a layer 21 based on or made of a dielectric material, for example silica SiO2.

[0118] According to an example that can be illustrated by Figures 8A and 8B, the layer 21 can form the surface layer of the donor sub-substrate 2. In particular, it is possible to carry out direct bonding of semiconductor oxide, for example silicon oxide, against semiconductor oxide, for example silicon oxide. Following their assembly, the layer 21 and the layer 11 will form the second layer 31 of the substrate 3. Their respective thicknesses can therefore be chosen to obtain the desired thickness L31. According to this example, it is understood that the upper wall 322 of the vias 32 and, where appropriate, the upper wall 352 of the grooves 35 can be formed from a dielectric material. The upper wall 322 of the vias 32 and, where appropriate, the upper wall 352 of the grooves 35 can, for example, have a thickness substantially between 1 nm and 600 nm.

[0119] According to an example that can be illustrated by Figures 9A and 9B, the layer 20 can form the surface layer of the donor sub-substrate 2. Direct bonding of semiconductor oxide, for example silicon oxide, against semiconductor, and in particular silicon, can be carried out. Following their assembly, the layer 11 alone will form the second layer 31 of the substrate 3. Its thickness can therefore be chosen to obtain the desired thickness L3i. According to this example, it is understood that the upper wall 322 of the vias 32 and, where appropriate, the upper wall 352 of the grooves 35 can be formed from a semiconductor material.

[0120] According to an example that can be illustrated by [Fig.9C], the layer 20 can form the surface layer of the donor sub-substrate 2. It is possible to carry out a direct bonding of semiconductor or piezoelectric against semiconductor, and in particular silicon, when the layer 20 is based on a semiconductor or piezoelectric material. It is possible to carry out a direct bonding of semiconductor oxide against semiconductor, and in particular silicon, when the layer 20 is based on a dielectric material, and in particular an oxide. Following their assembly, the layer 20 will form the second layer 31 of the substrate 3. Its thickness can therefore be chosen to obtain the desired thickness L3i.

[0121] Note that it is preferable to have a material thickness of di for the assembly electrical, and in particular oxide, of at least 10 nm at the bonding interface to avoid the appearance of defects.

[0122] The method of manufacturing a microelectronic device 4 is now described with reference to FIGS. 10 to 17.

[0123] In this method, the vias 32 may be used to establish interconnections. The vias 32 may alternatively or additionally be used to form portions of a microelectronic device without necessarily being metallic interconnections, for example in a MEMS device. The vias may be intended to be filled with a semiconductor material, Poly-Si for example.

[0124] The method may comprise a provision of the substrate 3. The method may comprise the deposition of component layers 4' (illustrated in [Fig.l]), for example transistor, diode, memory point. This deposition may for example comprise the FEOL steps.

[0125] As for example illustrated in [Fig.10], the method may comprise the deposition of at least one portion of layer 40, also called device portion 40, on the front surface 3a of the substrate 3. In the following, it is considered, without limitation, that several portions 40 are deposited. Alternatively or in addition, the device portion(s) may be etched in the front exposed surface 3a of the substrate 3.

[0126] These portions 40 may be metallic and may in particular form metallic interconnection lines. Typically, these metallic portions 40 may be used to redistribute electrical signals. These metallic portions may also be designated metallization levels. There may be several metallic portions 40 with interconnections between these portions. This deposition may, for example, comprise the BEOL steps.

[0127] In the following, it is considered, without limitation, that these portions 40 are metallic and that the etched via 32 is used to establish an interconnection. The following steps apply entirely to the case where non-metallic portions 40 of device 4 are deposited and / or etched, and / or where a semiconductor member 45 is produced in the via 32.

[0128] In order to facilitate the handling of the substrate 3, the method may then comprise the mounting of a support 41 on the side of the exposed front surface 3a of the substrate 3, for example by means of a bonding 410 made on the previous deposits, as illustrated by [Fig. 11] for example. This also makes it possible to protect the deposits made on the front surface 3a of the substrate 3.

[0129] After the deposition of the metal portions 40, if necessary after the mounting of the support 41, the method comprises the etching of at least one via 32 in order to produce at least one interconnection with one of the metal portions 40. For this, several Examples are possible and are now described. In the following, we consider, without limitation, that we etch and fill several vias 32.

[0130] According to a first example, as illustrated by [Fig.l2A], 12E and 12F, from the rear surface 3b of the substrate 3, the first layer 30 can be etched until it is flush with, or exceeds, the bottom wall 321 of the vias 32. The bottom wall 321 of the vias 32 is thus exposed. For this, the first layer 30 can be thinned and etched by selective etching of the material of the first layer 30 relative to the dielectric material of the walls 320, 321. According to the example illustrated in [Fig.l2A], the etching can for example be a selective etching of the silicon relative to the silica SiO2 in reactive ion etching using a precursor such as SF6. By “selective etching of a material A with respect to a material B” is meant that the etching speed of material A is 10 and preferably 100 times higher than that of material B. It is also possible to envisage carrying out a partial mechanical thinning of the substrate 3 completed by selective plasma or chemical etching.

[0131] The wall of dielectric material can then be selectively etched relative to the material of the first layer 30, to open into the via 32.

[0132] If it is desired to etch and then fill only a portion of the vias 32, in particular when the substrate 3 is a generic substrate comprising a matrix of vias 32, the method may comprise a selection of vias to be etched 32'. As for example illustrated by FIGS. 12B and 12G, a mask 42 may be deposited on the rear surface 3b of the substrate 3. This mask 42 may comprise openings 420 located directly above the vias to be etched 32'. The walls 321 may then be etched through the opening, to open into the vias 32.

[0133] Whether all or part of the vias 32 are etched, the etching can be continued to form at least one cavity 43, for example an electrical connection cavity 43 extending from the via 32 to the portion 40 located below the via 32, as for example illustrated in FIGS. 12C and 12G. In the following, it is considered, without limitation, that several cavities 43 are formed. For example, the etching of the dielectric material at the wall 321 can be a reactive ion etching. The etching of the semiconductor material at the wall 321 can be similar to that done to etch the layer 30.

[0134] When the walls of the vias 32' to be etched are not made of dielectric material, the method may comprise the formation of a dielectric layer at least at the level of the side wall 320, according to the methods previously described with reference to the method of manufacturing the substrate 3. This example may be illustrated by [Fig.12H].

[0135] Once the cavities 43 have been formed, the method may comprise an electrically conductive or semi-conductive member 45. This member 45 may be based on or made of a metallic material 45, for example electrolytic copper or tungsten. CVD. Alternatively, this member 5 may be based on or made of a semiconductor material, for example poly-Si. The deposition may be configured so as to fill these cavities 43 with the metallic material to form an electrical interconnection or a portion of device 4, as for example illustrated by [Fig.l2D]. The deposition may further be configured so as to further cover with a metallic or semiconductor layer 46 at least a portion of the rear exposed surface 3b of the substrate 3.

[0136] Between the formation of the cavities 43 and the deposition of the member 45, the method may comprise at least one of: - the removal of the mask 42, - a passivation of the exposed rear surface 3b of the substrate 3, for example by forming a layer of dielectric material 44, also called passivation layer 44. This formation can be done by depositing a dielectric material, for example as described previously, - etching of the cavities 43 so as to remove any possible oxide layer which may have formed at the bottom of the cavity, in particular during the formation of the passivation layer 44. This possible oxide layer may in fact limit the resumption of electrical contact on the portion 40.

[0137] According to a second example illustrated by figures 13A to 13C, the mask 42 can first be deposited on the rear surface 3b of the substrate 3. This mask 42 can comprise openings 420 located directly above the vias 32. If it is desired to etch and then metallize only a portion of the vias 32, in particular when the substrate 3 is a generic substrate comprising a matrix of vias 32, the selection of vias to be etched 32' can be made by arranging the openings 420 above the vias to be etched 32'.

[0138] The first layer 30 can be etched through the openings 420 until it is flush with, or even exceeds, the bottom wall 321 of the vias. The etching can be continued to form at least one cavity 43 extending from the via 32 to the metal portion 40 located below the via 32, as for example illustrated in [Fig. 13B]. Here too, it is considered, without limitation, that several cavities 43 are formed. This etching step can be a reactive ion etching.

[0139] The subsequent steps can then be carried out as previously described, as illustrated by way of example in [Fig. 13C]. The layer 44 then also passivates the top of the cavities 43, in continuity with the side wall 320.

[0140] This exemplary embodiment is also applicable when the vias 32' do not have a wall made of dielectric material. As previously described, the method may comprise the formation of a dielectric layer at least at the level of the side wall 320 after the opening of the vias to be etched 32'.

[0141] When the substrate 3 comprises grooves 35, the two examples previously described may apply. Figures 14A to 14F illustrate the first example previously described. According to one or other of these examples, in order not to fill the grooves of the conductive or semi-conductive member, the openings 420 of the mask 42 may be arranged so as not to allow the etching of the grooves 35. More particularly, the mask may cover the rear surface 3b of the substrate directly above the grooves 35, as illustrated for example in [Fig. 14D]. During the steps subsequent to the formation of the cavities 43, the grooves 35 preferably remain closed and are therefore not filled by the member 45.

[0142] Following the deposition of a metal layer 46 on the rear surface 3b of the substrate, regardless of the embodiment example previously described, the method may comprise the production of patterns 46' in this metal layer 46, for example to delimit different interconnections. This may be illustrated by way of example by [Fig. 15]. This pattern production may be done by masking, followed for example by ion etching or by ion beam etching or by wet etching.

[0143] The method may comprise, as an alternative or in addition to this production of patterns 46', a passivation 47 of the rear surface 3b of the substrate, as illustrated by way of example in [Fig. 16]. This passivation may be carried out by depositing an organic compound such as a construction photosensitive resin, for example of the polyimide or benzocyclobutene polymer type.

[0144] As illustrated for example in [Fig.16], the method can further comprise a metallization 48 called UBM (from the English Under Bump Metallization, which can be translated as under bump metallization) so as to connect the electrical interconnections obtained and the housing 5 illustrated in [Fig.l].

[0145] Once the manufacturing steps taking place on the rear surface 3b of the substrate 3 have been completed, the support 41 can be dismantled as illustrated by the passage from [Fig. 16] to [Fig. 17],

[0146] In view of the foregoing description, it is clear that the invention provides a substrate, its manufacturing method and a method of manufacturing a microelectronic device making it possible to facilitate the manufacturing of vias in a microelectronic device.

[0147] The invention is not limited to the embodiments previously described and extends to all embodiments covered by the invention. The present invention is not limited to the examples previously described. Many other variant embodiments are possible, for example by combining previously described characteristics, without departing from the scope of the invention. In addition, the characteristics described in relation to one aspect of the invention may be combined with another aspect of the invention. In particular, the substrate may have any characteristic resulting from its manufacturing process and conversely, this process may comprise any step configured to obtain a characteristic of the substrate. The method of manufacturing a microelectronic device can implement any characteristic of the substrate.

[0148] In the examples described, the semiconductor material is silicon. Note that the invention can be applied to other mono- or poly-crystalline semiconductors, possibly doped, and in particular to Si, Ge, SiGe, SiC, III-V material (for example AIN, GaN, InN, InGaAs, GaP, InP, InAs, AsGa, etc.) and II-VI material. The dielectric material can be a semiconductor oxide or nitride, for example SiO2, SiN, Al2O3. The piezoelectric material may, for example, be lithium tantalate (LiTaO3), lithium niobate (LiNbO3), potassium sodium niobate (KxNabxNbO3 or KNN), barium titanate (BaTiO3), quartz, lead zirconate titanate (PZT), a compound of lead magnesium niobate and lead titanate (PMN-PT), zinc oxide (ZnO), aluminum nitride (AIN) or aluminum scandium nitride (AIScN), other materials may naturally be considered.

Claims

Claims

1. Substrate (3) comprising: • a first layer (30) based on a semiconductor material, • a second layer (31) surmounting the first layer, characterized in that the substrate (3) comprises a plurality of buried hollow vias (32) extending from the second layer (31) over a portion of the first layer (30), each via (32) being delimited by a side wall (320), a bottom wall (321), and an upper wall (322) opposite the bottom wall (321), each via (32) having a transverse dimension less than or equal to 30 μm.

2. Substrate according to the preceding claim, in which at least the bottom wall (321) and the side wall (320) are made of dielectric material.

3. Substrate according to any one of the preceding claims, wherein the second layer (31) is a layer based on, and preferably made of, a material chosen from a dielectric material, for example an oxide, a semiconductor material or a piezoelectric material.

4. Substrate according to any one of the preceding claims, in which the second layer (31) is a layer of dielectric material, for example an oxide, buried and surmounted by a third layer (33) based on a material chosen from a semiconductor material or a piezoelectric material.

5. Substrate according to any one of the preceding claims, in which each via (32) has at least one transverse dimension between 1 pm and 30 pm.

6. Substrate according to any one of the preceding claims, in which at least a portion of the vias (32), and preferably each via (32), has an aspect ratio greater than or equal to 10, with the longest dimensions oriented along a thickness dimension of the first (30) and second (31) layers.

7. Substrate (3) according to any one of the preceding claims, wherein the plurality of vias (32) forms a periodic array.

8. Substrate (3) according to the preceding claim, in which the vias (32) are separated two by two by a constant pitch along at least one direction of the main extension plane of the first and second layers, the pitch is between 50 pm and 300 pm, preferably between 100 pm and 200 pm.

9. Substrate (3) according to any one of the preceding claims, wherein at least one via (32) on at least a portion of a longitudinal dimension of said via (32), is integrally surrounded by a groove (35) extending from the second layer (31) over a portion of the first layer (30).

10. Substrate (3) according to the preceding claim, in which the groove (35) extends from the second layer (31) into the first layer (30) over a longitudinal dimension less than or equal to the longitudinal dimension of the via (32).

11. Substrate (3) according to any one of the preceding claims, wherein the substrate (3) further comprises a mark (34) configured to allow alignment of the substrate (3).

12. A method of manufacturing the substrate (3) according to any one of the preceding claims, comprising: • providing a support sub-substrate (1) comprising at least a first layer (10) based on a semiconductor material, the support sub-substrate (1) having an exposed surface (la), • etching a plurality of vias (32) such that the vias (32) extend from the exposed surface (la) over a portion of the first layer (10), each via being delimited by a side wall (320) and a bottom wall (321), each via (32) having a transverse dimension less than or equal to 30 μm, • providing a donor sub-substrate (2) comprising a surface layer (20, 21) having an exposed surface (2a), • assembling the support sub-substrate (1) and the donor sub-substrate (2) by their exposed surfaces (la, 2a), so as to cover the vias (32),each via then being delimited by the side wall (320), the bottom wall (321), and an upper wall (322) opposite the bottom wall (321).,

13. Method according to the preceding claim, in which following the etching of the plurality of vias (32) and preferably before the assembly of the sub- support substrate (1) and the donor sub-substrate (2), the method comprises, for each via (32), a formation of a dielectric material at least at the bottom wall (321) and the side wall (320).

14. Method according to the preceding claim, in which the formation of a dielectric material at least at the bottom wall (321) and the side wall (320) of the plurality of vias (32) comprises: • thermal oxidation so as to oxidize the semiconductor material of the first layer (10) at least at the bottom wall (321) and the side wall (320), and / or • deposition of the dielectric material at least at the bottom wall (321) and the side wall (320).

15. A method according to any one of the three preceding claims, wherein the surface layer (20, 21) of the donor sub-substrate is a layer based on, and preferably made of, a material chosen from a dielectric material, for example an oxide, a semiconductor material or a piezoelectric material.

16. Method according to any one of the four preceding claims, in which: • the support sub-substrate (1) further comprises a surface layer (11) based on, and preferably made of, a dielectric material, for example an oxide, overlying the first layer (10), the surface layer having the exposed surface (la), and / or • the surface layer (21) of the donor sub-substrate is a layer based on, and preferably made of, a dielectric material, for example an oxide, overlying a layer (20) based on a material chosen from a semiconductor material or a piezoelectric material.

17. A method according to any one of the five preceding claims, wherein the etching of the plurality of vias (32) is configured to form a periodic array.

18. A method according to any one of the six preceding claims, wherein the method further comprises, prior to assembly of the support sub-substrate (1) and of the donor sub-substrate (2), an etching of a groove (35) completely surrounding at least one via (32) over at least a portion of a longitudinal dimension of said via (32), the groove (35) extending from the surface layer (11) into the first layer (10).

19. A method of manufacturing a microelectronic device (4) comprising: • providing a substrate (3) according to any one of claims 1 to 11 or a substrate (3) manufactured by the method according to any one of claims 12 to 18, having a front exposed surface (3a) and a rear exposed surface (3b), • forming at least one layer portion (40) of the device (4) by depositing, on the front exposed surface (3a) of the substrate (3), said portion, and / or etching the front exposed surface (3a) of the substrate (3), configured so as to form said portion, • at at least one via, etching by the rear exposed surface (3b) of the substrate (3), in which one wall among the top wall (322) and the bottom wall (321) of the at least one via is etched so as to open into the via (32), then continuing the etching to reach the at least one layer portion (40) of the device (4),to form a cavity (43), • the deposition of an electrically conductive or semi-conductive member (45) so as to fill the cavity (43).,

20. Method according to the preceding claim, comprising, prior to etching by the rear exposed surface (3b) of the substrate (3), a selection of at least one via to be etched (32') from among the plurality of vias (32) comprising: • the application, on the rear exposed surface (3b) of the substrate (3), of a mask (42) comprising openings (420) located directly above the at least one via to be etched (32'), and • an etching of the first layer (30) so as to reach said wall of the at least one via to be etched (32').

21. Method according to the preceding claim, in which the selection of the at least one via to be etched (32') comprises the application of the mask (42) then the etching of the first layer (30) through the openings (420) of the mask (42).

22. The method of claim 20, wherein selecting the at least one via to be etched (32') comprises etching the first layer (30) so as to reach said wall of the at least one via to be etched (32'), then applying the mask (42).

23. A method according to any one of the four preceding claims, wherein the deposition of the electrically conductive or semiconductive member (45) is configured to further cover with an electrically conductive or semiconductive layer (46) at least a portion of the rear exposed surface (3b) of the substrate (3),

24. Method according to any one of the five preceding claims, in which the method comprises: • between the formation of the at least one layer portion (40) of the device (4), and the etching by the rear exposed surface (3b) of the substrate (3), the mounting of a support (41) on the front exposed surface (3a) of the substrate (3), and • after the deposition of the electrically conductive or semi-conductive member (45) so as to fill the cavity (43), the dismantling of the support (41).

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