Flexible substrate comprising a support layer, an adhesive layer and a magnetic layer

Abstract

Flexible substrate comprising a support layer, an adhesive layer and a magnetic layer The present description relates to a flexible substrate (100) comprising at least one support layer (102), an adhesive layer (104), and a magnetic layer (106) disposed between the support layer (102) and the adhesive layer (104) or such that the support layer (102) is disposed between the magnetic layer (106) and the adhesive layer (104), and comprising a first main adhesive face (107) formed by the adhesive layer (104). Figure for abstract: Figure 1

Description

Title of the invention: Flexible substrate comprising a support layer, an adhesive layer and a magnetic layer Technical field

[0001] The present description relates to a flexible substrate comprising, in the form of a stack, a support layer, an adhesive layer and a magnetic layer. Such a flexible substrate is for example suitable for carrying out a transfer of a functional layer from a first substrate to a second substrate, for example for transferring this functional layer from an initial substrate from which the functional layer is produced, to a final destination substrate. Prior art

[0002] A "functional layer" means a single layer or a stack of several layers. More particularly, the functional layer may have a characteristic allowing the operation of at least one active component (for example a laser, a diode, a transducer, an actuator or actuator, a memory cell, a battery, etc.) or passive component (for example an electrical capacitor, an optical waveguide, a lens, etc.). This characteristic may be linked to the composition and / or the structural organization of the functional layer from which emerge remarkable properties which may be mechanical, thermal, electrical, dielectric, piezoelectric, magnetic, optical, etc., and which are the basis of the operation of the component.

[0003] There are many situations where it is necessary to carry out the transfer of a functional layer from an initial substrate to a final destination substrate.

[0004] For example, the preparation of the functional layer may require particular processing conditions (for example in terms of temperature, pressure, chemistry, etc.) and / or particular substrates on which the composition and / or structural organization of the functional layer can be achieved. Thus, the optimal initial substrate used for the preparation of the functional layer may differ from the final substrate on which the functional layer is integrated. For example, it is possible that the final substrate does not support the preparation conditions of the functional layer, or the final substrate may comprise other components and / or elements that do not support these preparation conditions, or the final substrate may not allow the preparation of the functional layer.It is also possible that the initial substrate is not suitable for the use of the functional layer once the product is finalized, for example because it is too fragile, too thick, not flexible enough, etc.

[0005] According to another example, it may be necessary to transfer the functional layer from the initial substrate used for its preparation to the final substrate when a step of treating the face of the functional layer located against the initial substrate must be implemented.

[0006] By way of example, the functional layer may correspond to a layer of material comprising, for example, at least one of the following semiconductor materials: silicon, silicon carbide, germanium, III-V compound such as AsGa, InP or GaN, II-IV compound such as CdTe or ZnO. It may also correspond to a layer of material comprising, for example, at least one piezoelectric material such as LiNbO3, LiTaO3, PZT or PMN-PT. It may also correspond to a layer of magnetic material or functional oxide such as ZrO2, YSZ, yttrium-stabilized ZrO2, SrTiO3 or GaO2.

[0007] The material of the functional layer may be monocrystalline. It is also possible for the material of the functional layer to be polycrystalline, for example when the production conditions are optimized to obtain, for example, a particular density and size of crystalline grains and / or a preferential crystalline orientation.

[0008] According to another example, the functional layer may comprise at least one junction and include, for example, a doping variation of the pn type or of the npn or pnp type, or correspond to a power diode or a solar cell. The functional layer may correspond to an optical stack that can be used to produce a laser, for example of the VCSEL type, or a light-emitting diode (including a junction and a multiple quantum well structure). The functional layer may also be used to produce an actuator and / or a piezoelectric sensor comprising a metal / piezoelectric material stack, or even a solid-state battery. According to another example, the functional layer may comprise electronic components produced by monolithic 3D integration.

[0009] Such a transfer may be achieved by implementing a prior transfer of the functional layer from the initial substrate to a rigid temporary, or sacrificial, substrate. For example, such a transfer may involve the creation of a fracture, or embrittlement, interface in the initial substrate, under the functional layer, then the implementation of direct bonding of the functional layer against the temporary substrate, then a separation of the functional layer from the initial substrate at the fracture interface. The functional layer is then transferred to the final substrate using the temporary substrate as a mechanical handle. The temporary substrate is then destroyed to release the functional layer.

[0010] The transfer method described above can be applied to carry out, for example, a full-plate transfer of the functional layer onto the final substrate. It is also possible for this method to be implemented to carry out a collective transfer of several elements or portions of material, for example in chip format, and together forming a functional layer.

[0011] A disadvantage of the above transfer method is its high cost due to the destruction of the temporary substrate at the end of the method. Furthermore, no temporary substrate is suitable for carrying out a transfer of a functional layer onto a curved, or more generally non-planar, substrate.

[0012] Document US 2021 / 0260859 A1 describes another transfer method. Again, this method is not suitable for carrying out a transfer of a functional layer onto a curved or non-planar substrate.

[0013] Document US 6,100,166 A1 describes a method for transferring a functional layer using a flexible substrate to separate the functional layer from the initial substrate. The flexible substrate used is however not suitable for carrying out manipulation of the structure obtained, nor for further processing or transfer of the functional layer. Summary of the invention

[0014] There is a need to provide a flexible substrate which does not have at least some of the drawbacks set out above.

[0015] One embodiment overcomes all or part of the drawbacks of the known solutions and proposes a flexible substrate comprising at least one support layer, an adhesive layer, and a magnetic layer arranged between the support layer and the adhesive layer or such that the support layer is arranged between the magnetic layer and the adhesive layer, and comprising a first main adhesive face formed by the adhesive layer.

[0016] According to a particular embodiment, the flexible substrate comprises a thickness of between 10 μm and 800 μm.

[0017] According to a particular embodiment, the support layer comprises a polymer and / or a metallic material.

[0018] According to a particular embodiment, a material of the adhesive layer comprises adhesive properties that can be modified by implementing a step of treating the adhesive layer.

[0019] According to a particular embodiment, the adhesive layer comprises a material whose adhesive properties are reduced when this material is subjected to UV treatment, or a material whose adhesive properties are reduced when this material is subjected to heat treatment.

[0020] According to a particular embodiment, the material of the adhesive layer comprises photodegradable nitrogen-based compounds, or acrylic.

[0021] According to a particular embodiment, the magnetic layer corresponds to a ferromagnetic and / or diamagnetic and / or paramagnetic layer.

[0022] According to a particular embodiment, the flexible substrate comprises dimensions adapted to the implementation of a method for transferring a functional layer from a first substrate to a second substrate.

[0023] There is also provided a method of transferring a functional layer from a first substrate to a second substrate, comprising at least the steps of:

[0024] - securing a first adhesive face of a flexible substrate according to a method of particular embodiment of the functional layer arranged on the first substrate;

[0025] - separation of the functional layer and the first substrate, forming an assembly comprising the functional layer secured to the flexible substrate;

[0026] - arrangement of the assembly against at least one magnetic element and such that the assembly is held against the magnetic element by magnetic forces of attraction exerted between the magnetic element and the magnetic layer of the flexible substrate;

[0027] - transfer of the functional layer onto the second substrate, including a separation of the functional layer and the flexible substrate.

[0028] According to a particular embodiment, the magnetic element comprises a first roller of a roll-to-roll transfer equipment and against which the support layer of the flexible substrate is arranged, and the separation of the functional layer and the flexible substrate is implemented by rotating the first roller and a second roller of the transfer equipment in opposite directions and such that the functional layer adheres against the second roller during its passage between the first and second rollers.

[0029] According to a particular embodiment, the magnetic element forms a flat support against which the support layer of the flexible substrate is arranged.

[0030] According to a particular embodiment, the transfer method further comprises, between the steps of arranging the assembly against the magnetic element and of separating the functional layer and the flexible substrate, at least one step of treating the functional layer.

[0031] According to a particular embodiment, the magnetic element comprises a mask arranged against the functional layer.

[0032] According to a particular embodiment, the transfer method further comprises, before the first adhesive face of the flexible substrate is secured to the functional layer, the creation of a weakening region between the layer functional layer and the first substrate, and the separation of the functional layer and the first substrate is carried out at the weakening region.

[0033] According to a particular embodiment, the transfer method further comprises, during the method, the implementation of at least one step of treatment of the adhesive layer, modifying the adhesive properties of the adhesive layer. Brief description of the drawings

[0034] These characteristics and advantages, as well as others, will be explained in detail in the following description of particular embodiments given without limitation in relation to the attached figures among which:

[0035] [Fig.l] represents an example of a flexible substrate according to a particular embodiment;

[0036] [Fig.2], [Fig.3], [Fig.4] and [Fig.5], represent steps of a method of transferring a functional layer using a flexible substrate according to a particular embodiment;

[0037] [Fig.6] and [Fig.7] each represent a step in a method of transferring a functional layer according to embodiment variants. Description of the embodiments

[0038] The same elements have been designated by the same references in the different figures. In particular, the structural and / or functional elements common to the different embodiments may have the same references and may have identical structural, dimensional and material properties.

[0039] For the sake of clarity, only the steps and elements useful for understanding the described embodiments have been shown and are detailed.

[0040] 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 connected by means of one or more other elements.

[0041] In the following description, when reference is made to absolute position qualifiers, such as the terms "front", "back", "top", "bottom", "left", "right", etc., or relative position qualifiers, such as the terms "above", "below", "upper", "lower", "on", "under", etc., or to orientation qualifiers, such as the terms "horizontal", "vertical", etc., reference is made, unless otherwise specified, to the orientation of the figures corresponding to a normal position of use.

[0042] In the figures, in order to facilitate their reading, the different elements and the different layers are not represented on the same scale relative to each other.

[0043] Unless otherwise specified, the expressions "about", "approximately", "substantially", and "of the order of" mean to within 10%, preferably to within 5%.

[0044] Each layer of material may correspond to a single layer of material or a stack of several stacked layers.

[0045] An exemplary embodiment of a flexible substrate 100, or flexible substrate, is described below in connection with [Fig.l].

[0046] The flexible substrate 100 comprises a support layer 102, an adhesive layer 104 and a magnetic layer 106 arranged one above the other to form a stack of layers. The magnetic layer 106 is arranged between the support layer 102 and the adhesive layer 104, or such that the support layer 102 is arranged between the magnetic layer 106 and the adhesive layer 104.

[0047] According to an exemplary embodiment, the support layer 102 has for example a thickness equal to 90 μm, the adhesive layer 104 has for example a thickness equal to 10 μm and the magnetic layer 106 has for example a thickness equal to 5 μm or 10 μm. Alternatively, the thicknesses of the layers of the flexible substrate 100 may be different from these examples. Generally, the thickness of the flexible substrate 100 may be between 10 μm and 800 μm.

[0048] According to an exemplary embodiment, the support layer 102 comprises a polymer, for example PET (polyethylene terephthalate), PE (polyethylene), PP (polypropylene), PVC (polyvinyl chloride), PO (polyolefin), etc., and / or comprises a metallic material.

[0049] According to an exemplary embodiment, a material of the adhesive layer 104 may comprise adhesive properties that can be modified by implementing a step of treating the adhesive layer 104. This modification of the adhesive properties of the adhesive layer 104 may correspond to a reduction, or even a suppression, of these adhesive properties, for example to facilitate the detachment of the adhesive layer 104 during the use of the flexible substrate 100. For example, such a modification of the adhesive properties of a material of the adhesive layer 104 may be carried out by implementing an exposure of this material to a certain temperature and / or to radiation at a certain wavelength.

[0050] Alternatively, this modification of the adhesive properties of the adhesive layer 104 may correspond to an increase in the adhesive properties of the treated layer, to strengthen the adhesive strength of the adhesive layer 104 when using the flexible substrate 100.

[0051] In a particular configuration, the adhesive layer 104 may comprise a material whose adhesive properties are reduced when this material is subjected to UV treatment, comprising for example photodegradable nitrogen-based compounds (whose adhesive properties become very weak after exposure to UV radiation). In another particular configuration, the adhesive layer 104 may comprise a material whose adhesive properties are reduced when this material is subjected to a heat treatment, for example acrylic (whose adhesive properties become very weak after exposure to a certain temperature, for example greater than approximately 190°C for acrylic based on methacrylate monomers).

[0052] For example, the adhesive properties of the adhesive layer 104 may be such that their adhesive strength is between 0.01 N / cm and 15 N / cm. The adhesive strength of the adhesive layer 104 may be measured in accordance with the measurement method known as “Peel Adhesion”, or peel adhesion, as described in the ASTM D3330 or AFERA ​​4001 standard.

[0053] In the example of [Fig.l], the flexible substrate 100 comprises a first face 107 formed by one of the main faces of the adhesive layer 104, and a second face 109 formed by one of the main faces of the support layer 102. In the example described, unlike the second face 109, the first face 107 of the flexible substrate 100 has adhesive properties making it possible to stick this first face 107 of the flexible substrate 100 against an element to which the flexible substrate 100 is intended to be secured.

[0054] The magnetic layer 106 corresponds to a layer of at least one material having magnetic properties. This magnetic layer 106 may correspond to a ferromagnetic layer and may comprise, for example, iron, nickel or cobalt. It is also possible for the magnetic layer 130 to correspond to a diamagnetic layer comprising, for example, carbon, copper or silver. It is also possible for the magnetic layer 130 to correspond to a paramagnetic layer comprising, for example, tungsten, aluminium or lithium. It is also possible for the magnetic layer 130 to comprise several magnetic materials, combining or not these different magnetic properties. The magnetic layer 106 may be produced by implementing a deposition on the support layer 102, for example by evaporation, PECVD deposition (plasma-enhanced chemical vapour deposition), electrochemical deposition, etc.

[0055] In addition to the above characteristics relating to the adhesive properties of the adhesive layer 104, the layers 102 to 106 of the flexible substrate 100 are such that the substrate 100 is flexible, or supple. Considering the flexural rigidity of the STF 100, this can be defined by the equation:

[0056] d = 12(U2)

[0057] with D the flexural rigidity of STF 100, in GPa.pm3;

[0058] E the Young's modulus of STF 100, in GPa;

[0059] h the thickness of the STF 100, in pm;

[0060] v the Poisson's ratio of the STF 100.

[0061] The flexural rigidity D of the STF 100 can be between 1 GPa.pm3 and 107 GPa.pm3.

[0062] An example of a method for transferring a functional layer 110 using the flexible substrate 100 is described below in connection with Figures 2 to 5. In the described method, the flexible substrate 100 serves as a temporary substrate with which the functional layer 110 is transferred from a first substrate 112 to a second substrate 122.

[0063] In the example of [Fig. 2], the flexible substrate 100 is secured, at its first face 107, to the functional layer 110. In the embodiment described, before implementing this securing, a weakening region 114 is formed between the functional layer 110 and the first substrate 112. Different techniques can be implemented to produce the weakening region 114, the choice of the technique used being a function in particular of the material(s) of the functional layer 110 and of the first substrate 112. According to a first example, the weakening region 114 can be formed by carrying out an ion implantation in the first substrate 112, followed by an annealing resulting in the formation of bubbles allowing the subsequent separation of the functional layer 110 from the first substrate 112.According to a second example, the weakening region 114 may be formed by porosification in the first substrate 112, the subsequent separation of the functional layer 110 from the first substrate 112 being able to be carried out by etching. According to a third example, the weakening region 114 may be formed by laser lift-off. Other techniques may be implemented to form the weakening region 114.

[0064] Alternatively, it is possible that the weakening region 114 is replaced by an interface of low adhesion force as described for example in document FR3082997A1.

[0065] According to an exemplary embodiment, the functional layer 110 may correspond to a thin upper part of the first substrate 112. In this case, it is the production of the weakening region 114 which may define the functional layer 110 whose material (or at least one of the materials) corresponds to that of the first substrate 112. For example, the first substrate 112 may correspond to a substrate of piezoelectric material and the functional layer 110 may correspond to a thin upper part from the first substrate 112. According to another exemplary embodiment, the functional layer 110 may correspond to a layer of material produced by epitaxy on the first substrate 112. More generally, the material of the layer functional 110 may correspond to a monocrystalline material which cannot be obtained directly, without transfer, on the final substrate.

[0066] The thickness of the functional layer 110 may be less than 20 μm, or even less than or equal to 1 μm. Furthermore, the thickness of the functional layer 110 may depend on its nature, i.e. whether it corresponds to a single layer of materials or to a stack of several layers of materials, and / or whether it comprises electrical and / or electronic elements and / or components.

[0067] The technique(s) implemented to secure the flexible substrate 100 to the functional layer 110 may depend in particular on the materials of the flexible substrate 100 and of the functional layer 110. In the exemplary embodiment described here, the flexible substrate 100 is applied for example by lamination onto the functional layer 110. Other techniques may be implemented to achieve this securing. The securing between the flexible substrate 100 and the functional layer 110 is ensured by the adhesive properties of the adhesive layer 104, at the first face 107 of the flexible substrate 100.

[0068] In the exemplary embodiment described, as shown in [Fig. 3], a separation of the functional layer 110 and the first substrate 112 is then carried out. During this separation, the adhesion forces between the different layers of the flexible substrate 100 and between the adhesive layer 104 and the functional layer 110 are greater than an adhesion force between the functional layer 110 and the first substrate 112. According to an exemplary embodiment, this separation may correspond to a tearing carried out by securing a rigid peripheral element (not visible in the figures) to the flexible substrate 100 and using this element as a mechanical handle. Other separation methods are possible, whether mechanical, thermal, by lift-off, etc.

[0069] In the embodiment example described, as shown in [Fig. 4], the assembly comprising the functional layer 110 secured to the flexible substrate 100 is arranged against at least one magnetic element corresponding, in this example, to a first roller 116 of a roll-to-roll transfer equipment. This assembly is here arranged such that the second face 109 of the flexible substrate 100 is arranged against the first roller 116.

[0070] The adhesion between the first roller 116 and the assembly comprising the flexible substrate 100 and the functional layer 110, and therefore the holding of this assembly against the first roller 116, is obtained thanks to the magnetic forces of attraction exerted between the first roller 116 and the magnetic layer 106. These magnetic forces of attraction between the first roller 116 and the magnetic layer 106 exist because the first roller 116 comprises at least one magnetic material or at least one magnetic element. For example, the first roller 116 may comprise at least one of the materials previously mentioned for the magnetic layer 106.

[0071] As shown in [Fig. 5], the functional layer 110 is transferred onto a second roller 118 of the transfer equipment. In the described embodiment, the two rollers 116, 118 rotate in opposite directions and are arranged at a distance from each other such that when the assembly comprising the flexible substrate 110 and the functional layer 110 is between the two rollers 116, 118, the flexible substrate 100 is arranged against the first roller 116 and the functional layer 110 is arranged against the second roller 118.Furthermore, in this example, the second roll 118 has adhesive properties such that, after the assembly comprising the flexible substrate 100 and the functional layer 110 has passed between the rolls 116, 118, the functional layer 110 detaches from the adhesive layer 104 and remains attached to the second roll 118 thanks to the adhesive force between the functional layer 110 and the second roll 118 which is greater than the adhesive force between the adhesive layer 104 and the functional layer 110 during this separation. After this passage of the assembly comprising the flexible substrate 100 and the functional layer 110 between the two rolls 116, 118, the flexible substrate 100 remains attached to the first roll 116 thanks to the magnetic attraction forces applied between the first roll 116 and the magnetic layer 106.

[0072] When passing between the rollers 116, 118, so that the flexible substrate 100 remains secured to the first roller 116 and the functional layer 110 remains secured to the second roller 118, the adhesive force between the functional layer 110 and the second roller 118 is greater than the adhesive force between the functional layer 110 and the adhesive layer 104. To facilitate the detachment of the functional layer 110 from the adhesive layer 104, if the material of the adhesive layer 104 has adhesive properties that can be modified by a treatment of the adhesive layer 104, this treatment can be implemented when the flexible substrate 100 and the functional layer 110 pass between the rollers 116, 118. In [Fig. 5], this treatment, corresponding for example to exposure to UV radiation or to a heat treatment, is symbolized by arrows designated by reference 120.For example, when the material of the adhesive layer 104 comprises acrylic, this treatment may correspond to a heat treatment, for example carried out at a temperature of at least 190°C.

[0073] A final step of depositing the functional layer 110 against the second substrate 122 can then be implemented, by placing the second substrate 122 close to the second roller 118 and such that the rotation of the second roller 118 causes the functional layer 110 to be deposited against the second substrate 122. When the functional layer 110 passes between the roller 118 and the second substrate 122, in order that the functional layer 110 detaches from the second roller 118 and is deposited on the second substrate 122, the adhesion force between the functional layer 110 and the second substrate 122 is greater than the adhesion force between the functional layer 110 and the second roller 118.

[0074] Throughout the method described above, the flexible substrate 100 is used as a transport element of the functional layer 110 from the first substrate 112 to the second substrate 122.

[0075] In the example of [Fig. 5], the second substrate 122 corresponds to a rigid substrate on which an adhesive layer, comprising for example a silicone gel, is arranged to ensure the joining between the functional layer 110 and the second substrate 122. As a variant, it is possible for the second substrate 122 to correspond to a PCB, or to a flexible substrate for example similar or different from the support layer 102. Furthermore, although this is not the case in the example shown in [Fig. 5], the second substrate 122 may comprise a curved surface on which the functional layer 110 can be transferred.

[0076] Alternatively, the functional layer 110 may be secured to the second substrate 122 by an adhesive layer comprising a solder paste or an electrically conductive film (deposited anisotropically or isotropically) making it possible to recover electrical contact with the portion(s) of the functional layer 110. If it is not necessary to recover electrical contact with the portion(s) of the functional layer 110, this adhesive layer may comprise, for example, an epoxy or acrylic resin.

[0077] As a variant of the transfer method described above, other techniques may be implemented to separate the functional layer 110 from the flexible substrate 100. Equipment other than the roll-to-roll transfer equipment described above may be used. For example, the separation between the functional layer 110 and the flexible substrate 100 may correspond to a peeling carried out by applying a mechanical force pulling on the flexible substrate 100 and opposing the force holding the functional layer 110.

[0078] In the example transfer method described above, a treatment step is implemented to reduce the adhesive force of the adhesive layer 104 during the separation between the functional layer 110 and the flexible substrate 100. As an alternative or in combination with this step of reducing the adhesive force of the adhesive layer 104, it is possible to implement, during the transfer method, one or more treatment steps of the adhesive layer 104 reinforcing its adhesive force. For example, before the separation between the piezoelectric layer 110 and the first substrate 112, it is possible to implement a treatment step increasing the adhesive force of the adhesive layer 104. For example, a such a step of strengthening the adhesive strength of an adhesive layer may correspond to crosslinking by UV treatment in the case of an adhesive layer comprising an acrylic glue, or temperature curing in the case of an adhesive layer comprising an epoxy glue.

[0079] Furthermore, during the various steps of the method, the cohesive force of the functional layer 110 and the cohesive force of the various layers of the flexible substrate 100 between them are greater than the adhesion force between the adhesive layer 104 and the functional layer 110.

[0080] As a variant of the example of the transfer method described above, it is possible to implement, for example before the securing of the flexible substrate 100 to the functional layer 110 and / or between the separation of the functional layer 110 and the first substrate 112 and the securing of the functional layer 110 to the second substrate 122, one or more steps of treatment of the functional layer 110. Such treatment steps correspond for example to steps of cleaning, etching (for example by laser, plasma, etc.), deposition, activation, etc. Such treatment steps can be implemented for one and / or the other of the faces of the functional layer 110 given that each of the faces of the functional layer 110 is accessible during the transfer method thanks to the use of the flexible substrate 100.

[0081] According to another variant of the method described above, it is conceivable to have, in addition to the magnetic layer 106, at least one other magnetic layer interposed between the functional layer 110 and the flexible substrate 100. Such a configuration can make it possible to increase the overall magnetic attraction force compared to the magnetic attraction forces obtained with the magnetic layer 106 alone, or else make it possible to combine different magnetic properties of two distinct magnetic layers. It is also possible to have several distinct magnetic layers present in the flexible substrate 100.

[0082] The presence of the magnetic layer 106 in the flexible substrate 100 makes it possible to improve the handling and processing of the assembly comprising the flexible substrate 100 and the functional layer 110 during the various steps of the method. Thus, in the method example described above, the presence of the magnetic layer 106 in the flexible substrate 100 makes it possible to ensure the adhesion of the assembly formed by the flexible substrate 100 and the functional layer 110 against the first roller 116.

[0083] The presence of the magnetic layer 106 can also make it possible to ensure the flatness of the assembly comprising the flexible substrate 100 and the functional layer 110 during the process, for example by using a magnetic flat tool to which this assembly is held thanks to the presence of the magnetic layer 106. [Fig. 6] represents such a configuration in which, after the separation of the functional layer 110 from the first substrate 112 as previously described in connection with [Fig. 3], the assembly is arranged on a support 124 having magnetic properties allowing the assembly to be held and pressed against the support 124 thanks to the magnetic forces of attraction between the magnetic layer 106 and the support 124. In this configuration, the functional layer 110 may undergo one or more treatments, for example polishing or deposition of at least one material on the functional layer 110. After this or these treatments, the assembly comprising the flexible substrate 100 and the functional layer 110 may be separated from the support 124, then the functional layer 110 may be separated from the flexible substrate 100, for example by implementing the steps previously described in connection with FIGS. 4 and 5.Alternatively, the functional layer 110 may be separated from the flexible substrate 100 while holding the flexible substrate 100 against the support 124.

[0084] The presence of the magnetic layer 106 can also make it possible to plate, thanks to the magnetic forces generated by this layer 106, other objects to this assembly, for example for the implementation of certain treatment steps of the functional layer 110. [Fig. 7] represents such a configuration in which, after the separation of the functional layer 110 and the first substrate 112 as previously described in connection with [Fig. 3], the assembly comprising the flexible substrate 100 and the functional layer 110 is arranged on a support 126, which may or may not have magnetic properties. A mask 128 having magnetic properties is arranged against the functional layer 110 and held against it thanks to the magnetic forces of attraction exerted between the mask 128 and the magnetic layer 106. The functional layer 110 can be subjected to one or more surface deposits or treatments through this mask 128.After this or these treatments or deposits, the mask 128 can be removed and the assembly comprising the flexible substrate 100 and the functional layer 110 can be separated from the support 126. The functional layer 110 can then be separated from the flexible substrate 100, for example by implementing the steps previously described in connection with FIGS. 4 and 5. Alternatively, it is possible to remove the mask 128 after having separated the support 126 and the assembly comprising the flexible substrate 100 and the functional layer 110.

[0085] In all the exemplary embodiments, the first substrate 112 and / or the second substrate 122 may correspond to cylindrical wafers such as those used in the field of microelectronics.

[0086] In all the exemplary embodiments, before the flexible substrate 100 is used, it is possible for its first face 107 to be protected by a removable protective layer, not shown in the figures. This removable protective layer may serve to preserve the adhesive properties of the first face 107. This removable protective layer is in this case removed before using the flexible substrate 100.

[0087] Thus, in an exemplary embodiment of this transfer method, from an initial substrate, a functional layer 110 can be detached by being fixed to the flexible substrate 100 having a structure allowing a posteriori transfer to the second substrate 122.

[0088] For all the embodiments described, the flexible substrate 100 can allow:

[0089] - a control of the flatness of the assembly comprising the flexible substrate 100 and the functional layer 110 during the different stages of the transfer process;

[0090] - protection of the functional layer 110;

[0091] - easier handling of the functional layer 110;

[0092] - access to the two main faces of the functional layer 110 during the transfer process;

[0093] - a transfer onto a final flat or curved substrate thanks to the flexible nature of the substrate 100.

[0094] Various embodiments and variations have been described. Those skilled in the art will understand that certain features of these various embodiments and variations could be combined, and other variations will occur to those skilled in the art.

[0095] Finally, the practical implementation of the embodiments and variants described is within the reach of those skilled in the art from the functional indications given above.

Claims

Claims

1. A flexible substrate (100) comprising at least a support layer (102), an adhesive layer (104), and a magnetic layer (106) disposed between the support layer (102) and the adhesive layer (104) or such that the support layer (102) is disposed between the magnetic layer (106) and the adhesive layer (104), and comprising a first main adhesive face (107) formed by the adhesive layer (104).

2. The flexible substrate (100) of claim 1, comprising a total thickness of the flexible substrate (100) of between 10 pm and 800 pm.

3. Flexible substrate (100) according to one of the preceding claims, wherein the support layer (102) comprises a polymer and / or a metallic material.

4. Flexible substrate (100) according to one of the preceding claims, wherein a material of the adhesive layer (104) has adhesive properties that can be modified by carrying out a step of treating the adhesive layer (104).

5. The flexible substrate (100) of claim 4, wherein the adhesive layer (104) comprises a material whose adhesive properties are reduced when that material is subjected to UV treatment, or a material whose adhesive properties are reduced when that material is subjected to heat treatment.

6. The flexible substrate (100) of claim 5, wherein the material of the adhesive layer (104) comprises photodegradable nitrogen-based compounds, or acrylic.

7. Flexible substrate (100) according to one of the preceding claims, wherein the magnetic layer (106) corresponds to a ferromagnetic and / or diamagnetic and / or paramagnetic layer.

8. Method for transferring a functional layer (110), from a first substrate (112) onto a second substrate (122), comprising at least the steps of: - securing a first adhesive face (107) of a flexible substrate (100) according to one of the preceding claims to the functional layer (110) arranged on the first substrate (112); - separation of the functional layer (110) and the first substrate (112), forming an assembly comprising the functional layer (110) secured to the flexible substrate (100); - arrangement of the assembly against at least one magnetic element (116, 124, 128) and such that the assembly is held against the magnetic element (116, 124, 128) by magnetic attraction forces exerted between the magnetic element (116, 124, 128) and the magnetic layer (106) of the flexible substrate (100); - transfer of the functional layer (110) onto the second substrate (122), including a separation of the functional layer (110) and the flexible substrate (100).

9. The transfer method according to claim 8, wherein the magnetic element comprises a first roller (116) of a roll-to-roll transfer equipment and against which the support layer (102) of the flexible substrate (100) is arranged, and wherein the separation of the functional layer (110) and the flexible substrate (100) is implemented by rotating the first roller (116) and a second roller (118) of the transfer equipment in opposite directions and such that the functional layer (110) adheres against the second roller (118) when it passes between the first and second rollers (116, 118).

10. A transfer method according to claim 8, wherein the magnetic element (124) forms a planar support against which the support layer (102) of the flexible substrate (100) is disposed.

11. Transfer method according to one of claims 8 to 10, further comprising, between the steps of arranging the assembly against the magnetic element (116, 124, 128) and of separating the functional layer (110) and the flexible substrate (100), at least one step of treating the functional layer (110).

12. A transfer method according to claim 8, wherein the magnetic element comprises a mask (128) disposed against the functional layer (110).

13. Transfer method according to one of claims 8 to 12, further comprising, before the securing of the first adhesive face (107) of the flexible substrate (100) to the functional layer (110), a production of a weakening region (114) between the

14. functional layer (110) and the first substrate (112), and wherein the separation of the functional layer (110) and the first substrate (112) is carried out at the weakening region (114). Transfer method according to one of claims 8 to 13, further comprising, during the method, the implementation of at least one step of treatment of the adhesive layer (104), modifying the adhesive properties of the adhesive layer (104).

Images