Tunable unit cell array for reconfigurable antenna and method of making the same

Abstract

The invention relates to a reconfigurable phased array antenna, intended to operate in sub-terahertz frequency bands, and more particularly to an array of tunable unit cells for a reconfigurable antenna and its manufacturing method. The array of radiating elements excited by signals with controllable phase shift (in a set of discrete values) 1 comprises: • a first substrate 11 based on fused silica or quartz, • at least one tile 12 resulting from a cut in a second substrate 21 based on fused silica or quartz, each tile being fixed to the first substrate to form a tunable unit cell 10 of the array, each cell comprising at least one phase change material switch 101. The invention finds application in medical and industrial control imaging, Earth and deep space observation, and for radars and broadband telecommunications systems.

Description

TECHNICAL FIELD

[0001] The present invention relates to an antenna array intended to operate in sub-terahertz frequency bands, for example of the order of one or several hundred gigahertz. The present invention relates more particularly to a reconfigurable antenna array and its manufacturing method. The invention finds application, for example, in medical and industrial control imaging, Earth and deep space observation, as well as for radars and broadband telecommunications systems. STATE OF THE ART

[0002] A reconfigurable antenna is an antenna capable of dynamically changing its frequency and radiation properties in a controlled and reversible manner. To provide a dynamic response, reconfigurable antennas may incorporate actuators (such as phase-change material-based radio frequency (RF) switches, varactors, mechanical actuators, or tunable materials) that allow the intentional redistribution of RF currents across the antenna surface and produce reversible changes in its properties; these are sometimes referred to as phased array antennas. The reconfigurability of reconfigurable antennas, including antenna arrays, is used to maximize antenna performance in a changing scenario or to meet changing operating requirements.

[0003] A reconfigurable antenna array is made up of a set of reconfigurable unit radiating elements that correspond to an array of tunable unit cells arranged according to a particular geometry, in the same frequency band in order to produce a reconfigurable radiation pattern. A unit cell can be made up of a low RF loss substrate. A metal ground plane is deposited on one side of this substrate and a patch or radiating metal element is deposited on the other side. A second substrate can be assembled on the radiating metal element in order to improve its performance. A third metal layer can also be deposited on this second substrate in order to further improve the performance of the radiating element.This metallic layer may itself comprise one or more secondary radiating elements excited by coupling by the first radiating element and behaves like a structure with superimposed patch antennas and makes it possible to improve the frequency band and the scanning range of the beam radiated by the network.

[0004] Most reconfigurable antennas are obtained today by implementing manufacturing processes that consist of transferring a first wafer comprising actuators onto at least a second wafer comprising cells based on a low RF loss material. This type of reconfigurable antenna is obtained today by implementing manufacturing processes that consist of manufacturing unitary tunable radiating elements with RF switches on a first wafer and transferring a second entire substrate with elements allowing the improvement of the overall performance of the antenna. The unitary tunable element is thus made up of the stack of 2 substrates made of low RF loss material with three metallization levels (one on each side of the stack and one between the two substrates).

[0005] For example, the scientific paper by P. Pahlavan et al., titled "Metamaterial Based Compact Patch Antenna Array for Antenna-in-Package Solutions in Frequency Handover Applications," and published in 2023 IEEE 73rd Electronic Components and Technology Conference (ECTC), Orlando, FL, USA, 2023, pp. 475-480 (doi: 10.1109 / ECTC51909.2023.00085) discloses an antenna cell array of dimensions 2×2: a. manufactured from: i. a first wafer based on fused silica, having a thickness of 330 microns and ii. a second wafer based on fused silica, having a thickness of 180 microns assembled to the first wafer, and b. further comprising three levels of metallization, one to constitute a power supply line, one to constitute a connection plug, or patch, per cell and one to constitute a ground plane, the latter serving as an interface between the two wafers.

[0006] The antenna proposed in this scientific document has the following advantages: a. to avoid problems linked to different thermal expansion coefficients between the wafers to be assembled, due to the fact that they have the same basic composition, namely fused silica, b. to avoid having to form interconnection vias through the fused silica of each of the two wafers, which again could have posed manufacturing problems, particularly in terms of thermal balance.

[0007] On the other hand, the solution proposed in this scientific document presents, like many other manufacturing methods, the disadvantage of involving the handling of two relatively thin slices, for slice diameters of 100 mm, from which arise assembly difficulties and risks of damaging at least one of the two slices.

[0008] It is further known, from patent documents US 2017 / 0033462 A1 and US 11,757,203 B2, a transmission unit cell for a reconfigurable antenna and an antenna array, respectively.

[0009] An objective of the present invention is to overcome at least one of the drawbacks of the prior art, preferably while retaining the advantages it presents. SUMMARY

[0010] To achieve this objective, according to a first aspect of the invention, a tunable unit cell array for a reconfigurable antenna is provided, comprising: a. a first substrate based on one of fused silica, quartz and a glass having a loss tangent of less than 0.005 at frequencies above 100 GHz, b. at least two tiles cut from at least one second substrate based on one of fused silica, quartz and a glass having a loss tangent of less than 0.005 at frequencies above 100 GHz, said at least two tiles being attached to the first substrate to form at least two unit cells of the tunable unit cell array, each tunable unit cell comprising at least one phase change material switch comprised by, formed in, or located in the first substrate and each tile may have a different thickness.

[0011] According to a second aspect of the invention, a method of manufacturing a tunable unit cell array for a reconfigurable antenna is provided, comprising: a. providing a first substrate based on one of fused silica, quartz and a glass having a loss tangent of less than 0.005 at frequencies above 100 GHz, and comprising an array of phase change material switches, b. providing a second substrate based on one of fused silica, quartz and a glass having a loss tangent of less than 0.005 at frequencies above 100 GHz, c. cutting at least two first tiles from one of the first substrate and the second substrate, d. transferring said at least two first tiles onto the other of the first substrate and the second substrate, such that each first tile forms with the part of the substrate on which it is transferred at least one tunable unit cell of the network of tunable unit cells.

[0012] The invention according to each of its different aspects can thus consist of a first substrate on which is fixed in pieces, or equivalently in blocks, a second substrate from which the pieces or blocks have been cut. This advantageously avoids having to transfer a large substrate (larger than 50 mm) onto another substrate of equivalent dimensions, thus relaxing the constraints of flatness of the assembly surfaces and / or reducing the risk of breakage of the substrates during their handling and / or their manufacture when they are subjected to thermomechanical constraints. And it is advantageous to have blocks of different thicknesses making it possible to adjust or fix the focusing of the antenna. BRIEF DESCRIPTION OF THE FIGURES

[0013] The aims, objects, as well as the characteristics and advantages of the invention will emerge more clearly from the detailed description of an embodiment thereof which is illustrated by the following accompanying drawings in which: There Figure 1 schematically represents a partial sectional view of an array of tunable unit cells according to a first embodiment of the first aspect of the invention. The Figure 2 schematically represents a perspective view of an array of tunable unit cells according to the first aspect of the invention. The figures 3 to 10 schematically represent partial sectional views illustrating a first embodiment of the second aspect of the invention. The figures 11, 12 And 13 , 14 And 15schematically represent partial sectional views illustrating, respectively, three variants of embodiments of the first aspect of the invention and of implementation of the second aspect of the invention relative to those illustrated on the Figure 10 . THE figures 16 to 19 schematically represent partial sectional views illustrating a second mode of implementation of the second aspect of the invention.

[0014] 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 to the scale of practical applications. In particular, the relative thicknesses of different layers illustrated are not necessarily representative of reality. DETAILED DESCRIPTION

[0015] 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:

[0016] According to an example of the first aspect of the invention, the first substrate has a characteristic transverse dimension greater than or equal to 100 mm, or even greater than or equal to 200 mm, and / or said at least two blocks cut from the second substrate each have a characteristic transverse dimension greater than or equal to 200 µm and strictly less than 50 mm, preferably less than 5 mm.

[0017] According to an example of the first aspect of the invention, the cutting of said at least two first blocks comprises a cutting, for example by laser or by saw, in the thickness of the substrate concerned.

[0018] According to an example of the first aspect of the invention, the phase change material switch is at least partially encapsulated in silicon oxide.

[0019] According to an example of the first aspect of the invention, at least four, preferably at least sixteen, tiles are attached to the first substrate so as to give the array of tunable unit cells the shape of a two-dimensional matrix of tunable unit cells.

[0020] According to an example of the first aspect of the invention, at least one pad comprises a primary layer based on one or other of fused silica, quartz and a glass having a loss tangent of less than 0.005 at frequencies above 100 GHz, and a pattern or structuring of a metallic layer and / or a radiating element (for example a patch antenna) on the face of the primary layer which is opposite that by which said primary layer is fixed to the first substrate.

[0021] According to an example of the first aspect of the invention, at least one tile is attached to the first substrate via a layer of glue.

[0022] According to an example of the first aspect of the invention, at least one pad is attached to the first substrate by thermocompression of a metal layer deposited on said at least one pad with metal layer deposited on the first substrate.

[0023] According to an example of the first aspect of the invention, at least one pad is fixed to the first substrate by reflowing metal balls, for example gold-based, previously deposited on at least one of a metal layer deposited on said at least one pad and a metal layer deposited on the first substrate.

[0024] According to any one of the three preceding examples of the first aspect of the invention, the phase change material switch is comprised by, or formed in, or located in, the first substrate.

[0025] According to an example of the first aspect of the invention, at least one block is fixed to the first substrate by hybrid bonding, said at least one block and the first substrate having, at the level of the fixing of said at least one block on the first substrate, surface structures substantially overlapping each other.

[0026] According to an alternative example to the previous one, at least one block is fixed to the first substrate by reflowing metal balls, for example gold-based, deposited beforehand on at least one of a metallization layer deposited on said at least one block and a metallization layer deposited on the first substrate, said at least one block and the first substrate having, at the level of the fixing of said at least one block on the first substrate, surface structures substantially overlapping each other.

[0027] According to the six examples above, the network of tunable unit cells according to the first aspect of the invention can advantageously take as many configurations as there are ways of fixing each tile to the first substrate. These ways being at least four in number, these are four fixing configurations, and therefore four embodiments of each tunable unit cell, which are conceivable for each of the tiles fixed to the first substrate. This makes it possible to choose the fixing configuration most compatible with the thermal budget that the tiles and the first substrate can support.

[0028] According to an example of the first aspect of the invention, the tunable unit cell array comprises tiles of different thicknesses. It is thus possible to advantageously modulate the focusing of the beam transmitted or reflected by the tunable unit cell array to a greater extent.

[0029] According to an example of the first aspect of the invention, the tunable unit cell array further comprises, connected to each phase change material switch, a thermal actuation guide, for example of an optical or electrical nature. According to an example, the fabrication of the thermal actuation guide may be carried out during the fabrication of the first substrate comprising the phase change material switch.

[0030] According to an example of the first aspect of the invention, the thermal actuation guide, like the phase change material switch, is at least partially encapsulated in silicon oxide.

[0031] According to an example of the first aspect of the invention, the tunable unit cell array further comprises, for each phase change material switch, a metallization level forming an interconnection RF line and / or a radiating element (eg a patch antenna), of the phase change material switch. According to this example, the tunable unit cell array does not require an additional level of interconnections, which makes it possible to save at least one metal level.

[0032] According to an example of the first aspect of the invention, the metallization level, like the phase change material switch, is at least partly encapsulated in silicon oxide.

[0033] According to an example of the first aspect of the invention, the tunable unit cell array is silicon-free. This limits radiofrequency radiation losses.

[0034] According to another example of the first aspect of the invention, the tunable unit cell array may comprise at least one level of metal interconnections between said at least two tiles and the first substrate, which is accessible without etching the material constituting said at least two tiles and / or the first substrate to ensure an electrical connection between said at least two tiles and the first substrate at their attachment interface. In other words, the tunable unit cell array is advantageously free of vias through the material from which said at least two tiles and / or the first substrate are made. This avoids difficulties in respecting the thermal budget during manufacturing, low-temperature processes being less good, and / or this avoids bonding with metal continuity on several levels which requires additional steps and increases the cost, while increasing the risk of breakage.

[0035] According to another example of the first aspect of the invention, said at least two blocks and the first substrate are made from the same material chosen from fused silica, quartz and a glass having a loss tangent of less than 0.005 at frequencies above 100 GHz. According to this example, the thermal expansion coefficients of said at least one block and the first substrate are of the same value, which advantageously limits the thermomechanical constraints during the manufacture of the tunable unit cell array.

[0036] According to an example of the second aspect of the invention, the cutting of said at least two first blocks comprises a cutting, for example by laser or by saw, in the thickness of the substrate concerned.

[0037] According to an example of the second aspect of the invention, each first tile forms with the part of the substrate on which it is transferred a single tunable unit cell of the network of tunable unit cells.

[0038] According to an example of the second aspect of the invention, each of the first substrate and the second substrate has a characteristic transverse dimension greater than or equal to 100 mm, or even greater than or equal to 200 mm, and / or said at least two blocks each have a characteristic transverse dimension greater than or equal to 200 µm and strictly less than 50 mm, preferably less than 5 mm.

[0039] According to an example of the second aspect of the invention, each phase change material switch is intended to form in part a tunable unit cell.

[0040] According to an example of the second aspect of the invention, the first substrate and the second substrate are based on the same material.

[0041] According to an example of the second aspect of the invention, at least four, preferably at least sixteen, tiles are cut and then transferred, so that the tiles form, with the parts of the substrate on which they are transferred, an array of tunable unit cells taking the form of a matrix of tunable unit cells.

[0042] According to an example of the second aspect of the invention, the method comprises providing at least one third substrate, cutting at least one third tile from the third substrate and transferring said at least one third tile onto the substrate onto which said at least two first tiles have been transferred, the third substrate preferably having a thickness different from the substrate from which said at least two first tiles have been cut. Thus, the tiles may come from different substrates, and the latter may for example have different thicknesses from each other, so that the tiles cut therefrom may be transferred onto the same substrate to form tunable unit cells of different thicknesses in the same network of tunable unit cells.

[0043] According to an example of the second aspect of the invention, providing the first substrate comprises: a. providing a silicon-based growth substrate, b. forming the phase change material switches on the growth substrate, c. forming thermal actuation guides for the phase change material switches, d. forming a metallization level for forming interconnection lines and / or radiating elements (e.g., patch antennas) of each phase change material switch, and e. transferring a first layer based on one of fused silica, quartz, and a glass having a loss tangent of less than 0.005 at frequencies above 100 GHz, f. optionally forming a ground plane on said layer based on one of fused silica, quartz, and a glass having a loss tangent of less than 0.005 at frequencies above 100 GHz, then, g.the removal by grinding of the growth substrate, each phase change material switch, each thermal actuation guide and each interconnection line or radiating element being at least partly encapsulated in silicon oxide. It is thus possible to provide the first substrate using conventional manufacturing processes in microelectronics, and in particular in CMOS (Complementary Metal Oxide Semiconductor) foundries.

[0044] According to an example of the second aspect of the invention, the transfer of said first layer is carried out by means of a layer of silicon oxide.

[0045] According to an example of the second aspect of the invention, the method further comprises, after grinding the growth substrate, at least one step of opening, for example by etching, a layer of silicon oxide at the level of an interconnection line of the radiating metal element.

[0046] According to an example of the second aspect of the invention, providing the second substrate comprises: a. providing a support substrate based on any of fused silica, quartz and a glass having a loss tangent of less than 0.005 at frequencies above 100 GHz, and b. forming, on the support substrate, a metal layer, and c. etching the metal layer to form patterns or structurings for each tunable unit cell to be formed, and wherein the cutting step relates to the second substrate and comprises cutting tiles in the second substrate by rotating around each pattern or structuring.

[0047] According to an example of the second aspect of the invention, the transfer of at least one first block is carried out by means of a layer of glue.

[0048] According to an example of the second aspect of the invention, the transfer of at least one first block is carried out by thermocompression of a metallic layer of said at least one block with a metallic layer of the first substrate.

[0049] According to an example of the second aspect of the invention, the transfer of at least one first block is carried out by remelting metal balls, for example gold-based, deposited beforehand on at least one of a metal layer of said at least one block and a metal layer of the first substrate.

[0050] According to any one of the three preceding examples, the cutting of said at least two first blocks is carried out in the second substrate.

[0051] According to an example of the second aspect of the invention, the transfer of at least one first block is carried out by hybrid bonding, said at least one block and the first substrate having, at the level of the fixing of said at least one first block on the first substrate, surface structures substantially overlapping each other.

[0052] According to an example of the second aspect of the invention, the transfer of at least one first block is carried out by remelting metal balls, for example gold-based, deposited beforehand on at least one of a metal layer of said at least one block and a metal layer of the first substrate, said at least one block and the first substrate having, at the level of the fixing of said at least one block on the first substrate, surface structures substantially overlapping each other.

[0053] According to any one of the two preceding examples, the cutting of said at least two first blocks is carried out in the first substrate.

[0054] A film or layer based on a material A means a film or layer comprising this material A and possibly other materials.

[0055] A parameter that is "substantially equal to / greater than / less than" a given value means that this parameter is equal to / greater than / less than the given value, within plus or minus 20% or even 10% of this value. A parameter that is "substantially between" two given values means that this parameter is at least equal to the smallest given value, within plus or minus 20% or even 10% of this value, and at most equal to the largest given value, within plus or minus 20% or even 10% of this value.

[0056] It is specified that, in the context of the present invention, the terms "on", "surmounts", "overhangs", "covers", "underlies" and their equivalents do not necessarily mean "in contact with". Thus, for example, the transfer, application or deposition of a first layer on a second layer does not necessarily mean that the two layers are directly in contact with each other, but means that the first layer at least partially covers the second layer by being either directly in contact with it, or by being separated from it by at least one other layer or at least one other element.

[0057] Unless otherwise specified, when referring to two elements connected to each other, this means directly connected without intermediate elements other than conductors, and when referring to two elements connected (in English "coupled") to each other, this means that these two elements can be connected or be linked by means of one or more other elements or by electromagnetic coupling without being directly connected.

[0058] Generally speaking, phase change materials are materials capable of alternating, under the effect of a variation in temperature, between a crystalline phase and an amorphous phase, the amorphous phase having a higher electrical resistance than the crystalline phase.

[0059] In the following description, substrate, film or layer thicknesses are generally measured in directions perpendicular to the main plane of extension of the substrate, film or layer.

[0060] A first embodiment of the tunable unit cell array 1 according to the first aspect of the invention is described below with reference to the Figure 1 .

[0061] The tunable unit cell array 1 for reconfigurable antenna, as illustrated in the Figure 1 , understand : a. a first substrate 11 based on one or other of fused silica, quartz and a glass having a loss tangent of less than 0.005 at frequencies above 100 GHz, and b. at least one block 12 resulting from a cut in a second substrate 20 based on one or other of fused silica, quartz and a glass having a loss tangent of less than 0.005 at frequencies above 100 GHz.

[0062] Each pad 12 is attached to the first substrate 11, here via a layer of glue 13, to form a tunable unit cell 10 of the tunable unit cell array 1. Each tunable unit cell 10 comprises at least one phase change material switch 101 comprised by, or formed in, or located in, the first substrate 11.

[0063] The schematic representation offered by the Figure 1 is only partial. The entire tunable unit cell network 1 is illustrated on the Figure 2 which shows a matrix organization of 4×4 tunable unit cells 10. The square nature of the two-dimensional matrix, as well as the number of tunable unit cells 10 it can comprise, are however not limited to the example illustrated in the Figure 2. Also, there could be multiple phase change material switches 101 and / or multiple radiating elements in the same tunable unit cell, unlike the representation provided by Figure 2 .

[0064] The embodiment illustrated by the Figure 1 and relatively equivalent to that illustrated by the Figure 10 . THE figures 3 to 9 thus illustrate both a mode of implementation of the manufacturing process of the embodiment of the network which is illustrated on the Figure 1 , that a mode of implementing the manufacturing method of the embodiment which is illustrated in the Figure 10 . This mode of implementation illustrated on the figures 3 to 9 is described below with reference to said figures.

[0065] As illustrated on the Figure 3, the mode of implementation of the manufacturing method according to the second aspect of the invention firstly comprises the provision of a silicon-based growth substrate 30 on which phase change material switches 101 are formed, thermal actuation guides 102 of said switches, as well as a metallization level 103 intended to form an interconnection line and / or a radiating element 1031 per cell 10, as it appears on the Figure 6 .

[0066] The implementation steps described above are the first steps of a whole which makes it possible to obtain the supply of the first substrate 11 mentioned above. Said supply continues with the following steps.

[0067] A first layer 31 based on one or other of fused silica, quartz and a glass having a loss tangent of less than 0.005 at frequencies above 100 GHz is transferred onto a silicon oxide layer 104 encapsulating, above the growth substrate 30, the phase change material switches 101, the thermal actuation guides 102 and the metallization level 103. This transfer can be carried out by means of a silicon oxide layer 33 deposited on the face of the first layer 31 by which the transfer is intended to be carried out. The transfer is therefore carried out between two silicon oxide layers 33 and 104. This results in a stack as illustrated in the figures 4 And 5 .

[0068] Where appropriate, the provision of the first substrate 11 may comprise the formation of a ground plane 32 on the face of the layer 31 which is opposite that by which the transfer is intended to be carried out.

[0069] Once the transfer is carried out, the provision of the first substrate 11 comprises the grinding of the growth substrate 30, until reaching the silicon oxide encapsulating the phase change material switches 101, the thermal actuation guides 102 and the metallization level 103.

[0070] Once the growth substrate 30 has been ground, an opening step 105 is provided, for example by etching, of the silicon oxide layer 104 at the level of a part of the metallization level 103 to form the interconnection line and / or the radiating metallic element 1031, and thus arrive at a first substrate 11 as illustrated in the Figure 6 .

[0071] The presently detailed implementation method then comprises, with reference to the Figure 7 , providing a second substrate 20 based on one or other of fused silica, quartz and a glass having a loss tangent of less than 0.005 at frequencies above 100 GHz. More particularly, the second substrate 20 comprises a layer 201 based on one or other of fused silica, quartz and a glass having a loss tangent of less than 0.005 at frequencies above 100 GHz, on which a metallization level 202 can be deposited, which, as illustrated in the figure 8 , can be etched to form a plurality of connecting plugs 122.

[0072] In reference to the Figure 9 , the second substrate 20 is then cut into blocks 12. Preferably, each block 12 can be topped with at least one structuring in the aforementioned metal layer 122. If the Figure 9illustrates a cutting of the second substrate 20 into two blocks 12, it is understood that the cutting of the second substrate 20 can lead to the manufacture of a plurality of at least four blocks 12, preferably at least sixteen blocks 12, or even more.

[0073] Let us note here that the first and second substrates 11 and 12 preferably have a characteristic transverse dimension greater than or equal to 100 mm, while each block 12 may have a characteristic transverse dimension greater than or equal to 200 µm, but strictly less than 50 mm and preferably less than or equal to 35 mm. There is therefore sufficient space on the first substrate 11 to transfer there a plurality of blocks 12 going beyond four, or even beyond sixteen. This will be even more verified when the characteristic transverse dimension of the first substrate 11 is substantially equal to 200 mm, or even 300 mm, as is the case for most existing first substrates 11. However, each tunable unit cell is intended to comprise at least one phase change material switch 101, accompanied by its thermal actuation guide 102.

[0074] Preferably, the first substrate 11 and the second substrate 12 are made from the same material. Thus, the thermal expansion coefficients of said at least one block 12 and of the first substrate 11 are of the same value, which advantageously limits the thermomechanical constraints during the manufacture of the network of tunable unit cells 1.

[0075] It is possible to consider that the cutting of the blocks 12, for example using a laser, is carried out around each pattern or structuring of the metal layer 122 in the thickness of the second substrate 20, and that each pattern or structuring of the metal layer 122 is intended to form in part a tunable unit cell 10. It is furthermore possible to consider that the cutting of the blocks 12 is carried out so that the pattern or structuring of the metal layer 122 gives rise to a block 12 and that the patterns or structurings of the metal layer 122 etched in the metallization level 202 are distributed over the entire surface of the second substrate 20.Therefore, the cutting in the second substrate 20 of the plurality of blocks 12 which is defined there by the patterns or structures of the metal layer and the transfer of the blocks 12 thus obtained onto the first substrate 11 amounts, in a way, to recreating by blocks the second substrate 20 on the first substrate 11, a distance, at least equal to the width of the material of the second substrate destroyed during its cutting into blocks 12, being provided between the first blocks 12 neighboring each other which have been transferred.

[0076] The transfer of each tile 12 is carried out so that each tile 12 forms, with the part of the first substrate 11 on which it is transferred, a tunable unit cell 10 of the network of tunable unit cells 1. It should be noted that the transfer of each tile 12 could lead to the production of a plurality of tunable unit cells 10, for example because the cutting of the second substrate 20 into tiles 12 would be done so as to obtain, on each tile 12, a matrix of 2×2, or even 4×4, or even more, patterns or structures of the metal layer 122.

[0077] As already mentioned above, said transfer can be achieved by means of a simple layer of glue 13, to achieve a network of tunable unit cells 1 as partially illustrated in the Figure 10 (or equivalently on the Figure 1 ) is as represented in its entirety on the Figure 2 .

[0078] The embodiment of the tunable unit cell array 1 according to the first aspect of the invention which is illustrated in the Figure 11 is a variation of the one illustrated on the Figure 10 ; it shows that the metallic pattern (or structuring) 122 which runs over or overhangs each block 12 is optional.

[0079] In a manner not illustrated in the figures, the person skilled in the art will understand that it is possible that certain tiles 12 to be transferred onto the first substrate 11 do not come from the second substrate 20, but from a third substrate having for example a thickness different from that of the second substrate 20, and more particularly a layer based on one of fused silica, quartz and a glass having a loss tangent of less than 0.005 at frequencies above 100 GHz having a thickness different from that of the layer 201 of the second substrate 20. Thus, the tiles 12 may come from different substrates, and the latter may for example have different thicknesses from each other, so that the tiles 12 which are cut therein may be transferred onto the same first substrate 11 for an array of tunable unit cells 1 whose tunable unit cells 10 have different thicknesses from each other.

[0080] The embodiment illustrated on the Figure 12 can be considered as a variant of the embodiment illustrated in the Figure 10 . To obtain the embodiment of the tunable unit cell array 1 which is illustrated in the Figure 12 , a second opening step 105, for example by etching, of the silicon oxide layer 104 may be provided in line with a part of the metal layer 1031 on the other side of the phase change material switch 101 relative to the first opening 105 mentioned above, and each pad 12 may comprise a metal layer 123 by which it is intended to be transferred, on the first substrate 11, in line with the second opening 105, for example by thermocompression between the connection plug 123 and the part of the metal layer 1031 which is exposed via the second opening 105. Note that here again, the connection plug 122 illustrated on the Figure 12is optional. Once the report is made a network of tunable unit cells 1 as partially illustrated on the Figure 13 is obtained.

[0081] According to a variant of the embodiment illustrated in the Figure 12 , this variant being illustrated on the figures 14 And 15 , the transfer of each block 12 may further involve the fusion of metal balls 124, for example gold-based, deposited, before the transfer, on the connection plug 123 or in the second opening 105. According to this variant, the embodiments of the network of tunable unit cells 1 which is illustrated in the Figure 15 .

[0082] Another embodiment of the first aspect of the invention and of implementing the second aspect of the invention is illustrated in the figures 16 to 19 .

[0083] According to this other mode of implementation, and with reference to the figure 16, the provision of the first substrate 11 comprises: a. providing a silicon-based growth substrate 30, b. forming the phase change material switches 101 on the growth substrate 30, c. forming the thermal actuation guides 102 of the phase change material switches 101, and d. forming a metallization level 103 flush in places to form at least one metal layer 1031 of each phase change material switch 101, then e.the transfer of a substrate comprising a first layer 31 based on one or other of fused silica, quartz and a glass having a loss tangent of less than 0.005 at frequencies above 100 GHz, where appropriate a ground plane 32 on said layer 31 extending on the face of this layer which is opposite the growth substrate 30, and a surface structuring on the face of the layer 31 which is intended to be connected to said at least one metal layer 1031 of each phase change material switch 101.

[0084] There figure 16 clearly shows that the two assembled elements have surface structures on their assembly face that correspond to each other.

[0085] Once the assembly is completed, as illustrated in the Figure 17 , the silicon can be ground, to achieve a first substrate 11 as illustrated in the figure 18 , silicon-free.

[0086] Starting from the substrate illustrated on the figure 18 , it is possible to report there, as illustrated on the figure 19 , a block 12 as described above, and, in the example illustrated, by a layer of glue 13. The other transfer methods described above obviously remain portable to the embodiment described with reference to the figure 19 .

[0087] The embodiments previously described have as a common factor that the substrate cut is not the one comprising the active elements of the tunable unit cells 10, namely the phase change material switches 101 and their thermal actuation guide 102. On the contrary, in the embodiments of the invention which are illustrated in FIGS. 20 to 25, it is the substrate in which the active elements of the tunable unit cells 10 are located which is cut.

[0088] The various embodiments of the tunable unit cell array 1 described above advantageously make it possible to avoid having to transfer an entire large substrate (>50 mm transverse dimension) onto another entire substrate, thus relaxing the flatness constraints of the assembly surfaces and / or reducing the risk of breakage of the substrates during their handling and / or their manufacture when they are subjected to thermomechanical constraints. Another advantage consists in the fact that it is therefore possible to fix to the first substrate 11 blocks 12 of different thicknesses.

[0089] Let us recall here that the present invention relates to a reconfigurable phase-shifted array antenna, intended to operate in millimeter and sub-terahertz frequency bands, for example between 100 GHz and 500 GHz.

[0090] The invention is not limited to the embodiments previously described and extends to all embodiments covered by the invention.

Claims

1. Tunable unit cell array (1) for reconfigurable antenna, comprising: • a first substrate (11) based on one or other of fused silica, quartz and a glass having a loss tangent of less than 0.005 at frequencies above 100 GHz, • at least two tiles (12) resulting from a cut in at least one second substrate (20) based on one or other of fused silica, quartz and a glass having a loss tangent of less than 0.005 at frequencies above 100 GHz, said at least two tiles (12) being fixed to the first substrate (11) to form at least two tunable unit cells (10) of the tunable unit cell array (1), each tunable unit cell (10) comprising at least one phase change material switch (101) included in the first substrate (11) and each tile being able to have a different thickness.

2. Tunable unit cell array (1) according to the preceding claim, wherein at least four, preferably at least sixteen, tiles are fixed to the first substrate (11) so as to give the tunable unit cell array (1) the shape of a two-dimensional matrix of tunable unit cells (10).

3. A tunable unit cell array (1) according to any preceding claim, wherein at least one tile (12) comprises a primary layer (121) based on one or other of fused silica, quartz and glass having a loss tangent of less than 0.005 at frequencies above 100 GHz, and a pattern or structuring of a metal layer and / or a radiation element (122) on the face of the primary layer (121) which is opposite that by which said primary layer (121) is fixed to the first substrate (11).

4. Tunable unit cell array (1) according to any one of the preceding claims, wherein at least 2 tiles (12) are attached to the first substrate (11) by thermocompression of a metal layer (123) deposited on said at least one tile (12) with a metal layer (111) deposited on the first substrate (11).

5. Tunable unit cell array (1) according to any one of the preceding claims, comprising tiles (12) of different thicknesses.

6. Tunable unit cell array (1) according to any one of the preceding claims, further comprising, connected, or even connected, to each phase change material switch (101), a thermal actuation guide (102), for example of an optical or electrical nature.

7. A tunable unit cell array (1) according to any preceding claim, further comprising, for each phase change material switch (101), a metallization level (103) forming an interconnecting RF line (1031) and / or a radiating metallic element of the phase change material switch (101).

8. A method of manufacturing a tunable unit cell array (1) for a reconfigurable antenna, comprising: • providing a first substrate (11) based on one or other of fused silica, quartz and a glass having a loss tangent of less than 0.005 at frequencies above 100 GHz, and comprising a matrix of phase change material switches (101), • providing a second substrate (20) based on one or other of fused silica, quartz and a glass having a loss tangent of less than 0.005 at frequencies above 100 GHz, • cutting at least two first tiles (12) from one of the first substrate (11) and the second substrate (20), • transferring said at least two first tiles (12) onto the other of the first substrate (11) and the second substrate (20),so that each first tile (12) forms with the part of the substrate (11 or 20) on which it is transferred at least one tunable unit cell (10) of the network of tunable unit cells (1)., 9. Manufacturing method according to the preceding claim, in which at least four, preferably at least sixteen, blocks (12) are cut out and then transferred, so that the blocks (12) form, with the parts of the substrate (11 or 20) on which they are transferred, a network of tunable unit cells (1) taking the form of a matrix of tunable unit cells (10).

10. Manufacturing method according to any one of the two preceding claims, comprising providing at least one third substrate, cutting at least one third block in the third substrate and transferring said at least one third block onto the substrate (11 or 20) onto which said at least two first blocks (12) have been transferred, the third substrate preferably having a thickness different from the substrate from which said at least two first blocks (12) have been cut.

11. Manufacturing method according to any one of the three preceding claims, wherein the provision of the first substrate (11) comprises: • providing a silicon-based growth substrate (30), • forming the phase change material switches (101) on the growth substrate (30), • forming thermal actuation guides (102) of the phase change material switches (101), • forming a metallization level (103) intended to form interconnection lines (1031) and / or radiating metallic elements of each phase change material switch (101), and • transferring a first layer (31) based on one or other of fused silica, quartz and a glass having a loss tangent of less than 0.005 at frequencies above 100 GHz, • where appropriate, forming a ground plane (32) on said layer (31) based on either fused silica,quartz and a glass having a loss tangent of less than 0.005 at frequencies above 100 GHz, then, • removing by grinding the growth substrate (30), each phase change material switch (101), each thermal actuation guide (102) and each interconnection line or radiating metallic element (1031) being at least partly encapsulated in silicon oxide (104)., 12. A method according to any one of the four preceding claims, wherein providing the second substrate (20) comprises: • providing a support substrate (201) based on one of fused silica, quartz and a glass having a loss tangent of less than 0.005 at frequencies above 100 GHz, and • forming, on the support substrate (201), a metal layer (202), and • etching the metal layer (202) to form patterns or structurings (122) for each tunable unit cell (10) to be formed, and wherein the cutting step relates to the second substrate (20) and consists of cutting tiles (12) in the second substrate (20) by rotating around each pattern or structuring (122).

13. Method according to any one of claims 8 to 12, in which the transfer of at least one first block (12) is carried out by hybrid bonding, said at least one first block (12) and the first substrate (11) having, at the level of the fixing of said at least one first block (12) on the first substrate (11), surface structures substantially overlapping each other.

14. Method according to any one of claims 8 to 12, in which the transfer of at least one first block (12) is carried out by remelting metal balls (125), for example based on gold, deposited beforehand on at least one of a metal layer (126) of said at least one first block (12) and a metal layer (111) of the first substrate (11), said at least one first block (12) and the first substrate (11) having, at the level of the fixing of said at least one first block (12) on the first substrate (11), surface structures substantially overlapping each other.

15. Method according to any one of the two preceding claims, in which the cutting of said at least two first blocks (12) is carried out in the first substrate (11).

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