Method for manufacturing clock components

Abstract

Method for manufacturing watch components (100), comprising the steps of: (a) taking a wafer (10) comprising a support layer (20), a working layer (30) and a buried layer (40) formed of graphene and separating the working layer (30) from the support layer (20), (b) etching at least a part of the watch components into the working layer (30), (c) separating the working layer (30) from the support layer (20) and / or the buried layer (40) formed of graphene.

Description

Technical field of the invention

[0001] The present invention relates generally to the manufacture of watch components, and in particular, the invention relates to the manufacture of watch components from a base substrate comprising at least one support layer and a working layer supported by the support layer, in which the watch components are etched. Such a manufacturing process generally includes microfabrication steps including lithography and etching of a wafer comprising a silicon layer to form the patterns of the watch components, as well as post-etching manufacturing steps such as component release and surface finishing. State of the art

[0002] The fabrication of silicon watch components, such as balance springs, cams, springs, pawls, wheels, and pallet forks, using microfabrication processes is well established. Advantageously, several hundred watch components can be manufactured on a single wafer using these technologies. For example, it is known to produce a multitude of silicon resonators with very high precision using photolithography and etching processes on a silicon wafer. The processes for manufacturing these watch components generally use monocrystalline silicon wafers, but polycrystalline or amorphous silicon wafers are also suitable.

[0003] Silicon is a diamagnetic material, and its use in the manufacture of watch components, particularly for the regulating organ components of a mechanical watch movement, is advantageous because no remanent effect is observed after exposing this material to magnetic fields. Furthermore, variations in the Young's modulus of a silicon watch component with temperature can be compensated for by adding an oxide layer to the component. When watch components are made from a single-crystal silicon wafer, any one of the three crystal orientations <100> , <110> or <111> can be used.

[0004] Silicon wafers can be supplied as a single layer without a support layer, for example, single-sided polished (SSP) or dual-sided polished (DSP) wafers. Document EP3495894 describes a process for manufacturing silicon watch components using such a wafer comprising a single silicon layer without a support layer. According to this document, the single wafer has a thickness approximately equal to the maximum thickness of the watch components to be manufactured, and to form the watch components, an etching step is performed through the entire thickness of the wafer, thus using all the component material present in the wafer to form the watch components, without any support function within the wafer.After their formation, the watch components are structurally supported only by thin bonding bridges that hold them attached to the remaining portions of the single silicon layer, and subsequent manufacturing steps can be performed on almost the entire external surface of the components without the need for a prior component release step. However, in the manufacturing process described in document EP3495894, the etching step is delicate because it takes place on a relatively thin, and therefore fragile, wafer without any support.

[0005] According to other approaches, and particularly to overcome the aforementioned problem of insufficient support for single-layer wafers, SOI (silicon-on-insulator) wafers are also frequently used for manufacturing watch components. An SOI wafer comprises a silicon working layer (the "device" layer) in which the watch components are manufactured, a typically silicon support layer that serves as a substrate or support during component manufacturing (the "handle" layer), and a buried silicon oxide layer located between the two silicon layers (the "buried oxide layer" or BOX layer). The surface of the working layer and possibly the surface of the support layer can also be polished to facilitate lithography steps on these layers.

[0006] After the lithography and etching steps initially form the watch components in the working layer of a SOI wafer, these components are typically released from the support layer and the buried oxide layer of the SOI wafer using microfabrication techniques to facilitate subsequent manufacturing steps. In this way, after release, the watch components are structurally supported only by thin bonding bridges that hold them attached to the remaining portions of the working layer. This allows subsequent manufacturing steps to be performed across the entire external surface of the wafer components. These subsequent steps may include oxidation and deoxidation to smooth the component surfaces.Subsequent steps may also include oxidation and deoxidation steps to adjust the dimensions of the components (e.g., to correct stiffness when the components are spirals or resonators) and / or oxidation steps to form an outer layer of silicon oxide on the components for thermal compensation and / or mechanical strengthening.

[0007] The release of watch components on a silicon dioxide (SOI) wafer can be achieved using various methods. According to an approach described in patent WO2019180596, after component formation, the working layer (or a portion of this layer containing the components) is separated from the support layer. This separation can be facilitated by etching a groove around the components as well as openings in the working layer. Subsequently, the buried oxide layer is etched with hydrofluoric acid (HF) vapor passing through the openings in the working layer, and the portion of the working layer defined by the groove is separated from the support layer of the SOI wafer. Another release approach is described in patent documents JP2017219520 and WO2019180177. According to this approach, after component formation by etching, a silicon dioxide layer is grown on the silicon surface.This oxide layer protects the formed components. Subsequently, photolithography and etching are performed to expose the silicon in the support layer. The support layer is then etched from the side opposite the components, removing the support layer beneath them. To complete the liberation process using this method, the buried layer of the SOI wafer beneath the components, as well as the protective layer on the components themselves, is removed.

[0008] These approaches to releasing watch components into a silicon-on-insulated (SOI) wafer involve additional microfabrication steps in a cleanroom and are therefore relatively lengthy, complex, and expensive. A simpler, faster, and less costly manufacturing process for silicon watch components would thus be desirable. Description of the invention

[0009] One object of the present invention is to address the disadvantages of the prior art mentioned above and in particular, first of all, to propose a method for manufacturing a plurality of watch components on a wafer comprising a silicon working layer, a support layer and a buried layer arranged between the working layer and the support layer, the manufacturing method making it possible to avoid or overcome the disadvantages above, or at least to offer a better compromise between these disadvantages.

[0010] To this end, a first aspect of the invention relates to a method for manufacturing watch components, comprising the steps of: (a) to have a plate comprising a support layer, a working layer and an underground layer formed of graphene and separating the working layer from the support layer, (b) to etch at least part of the watch components into the working layer, (c) to separate the working layer from the support layer and / or the underground layer formed of graphene.

[0011] According to the above implementation, the manufacturing process is carried out on a wafer comprising a buried layer. In particular, the buried layer is made of graphene. Once the working layer is etched, it is released from the graphene buried layer, notably without etching the support layer, and / or without performing additional etching dedicated to release the working layer, and / or without etching the buried layer with hydrofluoric acid (since there is no need to remove the buried layer, which is typically made of silicon oxide in the prior art. However, it is not excluded that a silicon oxide layer may be present, particularly between the graphene layer and the support layer).

[0012] The manufacturing process may include the following features, taken individually or in combination.

[0013] In one embodiment, step (c) includes a mechanical separation step to separate the working layer from the support layer and / or the buried layer. Such a mechanical separation step, particularly one free from the use of solvents or chemical etching or etching agents, is rapid and / or requires minimal equipment. The working layer can be mechanically separated from the support layer by cleaving the buried graphene layer, i.e., by propagating a crack between sp2 layers of graphene through judicious mechanical force. The process may include, in step (c) or a subsequent step of step (c), a step of burning the carbon constituting the graphene to clean the surface of the working layer and / or the support layer to complete the fabrication, or any other cleaning process (plasma or liquid cleaning, for example).

[0014] In one embodiment, step (c) includes applying a stress applicator or a tensile interface, such as an adhesive strip, to at least a portion of the working layer. Such a stress applicator distributes a tensile or pull-out stress across the working layer to enable mechanical separation without locally exceeding the elastic limit or the breaking limit of the working layer. In one embodiment, this may be a direct application of an adhesive, for example, a reversible adhesive such as a UV-sensitive adhesive. The delamination force can be directly applied to separate the edges with an adhesive.

[0015] In one embodiment, adhesives can also be applied only to non-functional areas of the working layer (i.e., outside the watch components). In another embodiment, a support plate can be used to bond these non-functional areas via the adhesive points before applying a peel force to the support plate to separate the working layer from the backing layer and / or the buried layer.

[0016] According to one embodiment, reversible or solvent-soluble glue can also be used.

[0017] According to one embodiment, a porous surface or membrane can also be used, a vacuum or suction applied, to separate the working layer from the support layer and / or the buried layer by pulling on this porous surface or membrane.

[0018] In one embodiment, step (c) includes a step of applying a pull-out force to the stress applicator to separate the working layer from the support layer and / or the buried layer. The stress applicator serves as a docking, tension, or pull-out interface to separate the working layer from the support layer and / or the buried layer.

[0019] In one embodiment, step (c) includes a step of applying a tensile force application interface to at least a portion of the stress applicator, such as, for example, a step of applying adhesive tape to the stress applicator. In another embodiment, step (c) includes a step of applying a tensile force application interface to at least a portion of the working layer, such as, for example, a step of applying adhesive tape to at least a portion of the working layer.

[0020] According to one embodiment, step (c) includes a step of inserting a wedge, such as a blade, between the working layer and the buried layer. Such a blade may have a thickness of less than 0.2 mm, less than 0.1 mm, or less than 0.05 mm.

[0021] In one embodiment, step (c) is followed by a step involving the reuse of the support layer, and optionally the buried layer, to support a new working layer for manufacturing other watch components. Such reuse of the support layer (and optionally the buried layer) provides significant resource savings and substantially reduces the impact on raw material requirements.

[0022] According to one embodiment, the new working layer is formed directly on the preserved buried layer, preferably the new working layer is formed by epitaxial growth from the preserved buried layer.

[0023] According to one embodiment, the reuse of the support layer includes: Optionally, the removal of the buried layer, the formation of a new buried layer of graphene, the formation of the new working layer on the new buried layer.

[0024] According to one embodiment, step (a) or reuse includes a step of forming the buried layer on the support layer.

[0025] According to one embodiment, step (a) or reuse includes a step of directly forming the buried layer on the support layer, for example by epitaxial growth. For example, chemical vapor deposition can be used to create the graphene buried layer.

[0026] According to one embodiment, step (a) or reuse includes the steps of: deposit graphene under vacuum on one of the support layer and the new working layer, or on both, then vacuum-bond the support layer and the new working layer, so as to achieve a bond or assembly between the support layer and the new working layer.

[0027] According to one embodiment, step (a) or reuse includes the steps of: The buried layer is formed on a donor substrate, and the buried layer is transferred from the donor substrate to the support layer. In this embodiment, the graphene buried layer is first formed on another substrate (the donor substrate) and then transferred to the support layer. For example, chemical vapor deposition (CVD) can be performed on the donor substrate. The donor substrate may consist of nickel or copper. Alternatively, the donor substrate may consist of at least one of SiO₂, HfO₂, Al₂O₃, Si₃N₄, or another planar material that is compatible with the high temperatures required by chemical vapor deposition. The graphene layer may be coated with a polymer (e.g., PMMA deposited on a spin-coating), or the donor substrate may be dissolved (e.g., in FeCl₃ in the case of a copper donor substrate).One can plan to deposit the graphene layer (along with the PMMA layer) onto the support layer and then remove the PMMA layer (with a solvent such as acetone, and / or by annealing, for example, at 350°C). Alternatively, one can plan to redeposit the graphene layer (along with the PMMA layer) onto a second donor substrate, remove the PMMA layer (with a solvent such as acetone, and / or by annealing, for example, at 350°C), and deposit a new graphene layer before transferring it to the support layer (via the application of a PMMA layer, dissolution of the second support substrate, transfer to the support layer, and removal of the PMMA layer).

[0028] According to one embodiment, the step of transferring the buried layer from the donor substrate to the support layer comprises the steps of: attach to the buried layer still placed on the donor substrate a support film comprising, for example, a thick film of poly(methyl methacrylate), preferably dissolve the donor substrate in acid if it is metallic (for example, dissolve a copper donor substrate in iron(III) chloride - FeCl3), transfer the buried layer from the donor substrate to the support layer, and dissolve the support film once the buried layer is placed on the support layer, or attach to the buried layer still placed on the donor substrate a buffer layer comprising an elastomeric material such as polydimethylsiloxane, strip the donor substrate, transfer the buried layer to the support layer, and detach, for example, mechanically, the buffer layer from the buried layer placed on the support layer.or attach a self-adhesive layer, for example polystyrene, poly(isobutylene), or Teflon, to the buried layer still placed on the donor substrate; place a pad in contact with the self-adhesive layer; etch the donor substrate to leave the pad-self-adhesive layer-buried layer assembly free; transfer the buried layer from the donor substrate to the support layer; and once the buried layer is in place on the support layer, detach, for example mechanically, the pad and dissolve the self-adhesive layer, for example with acetone.

[0029] According to one embodiment, once the buried layer has been formed on the support layer, step (a) or reuse includes the formation of the working layer on the buried layer, for example by epitaxial growth.

[0030] In one embodiment, the buried layer comprises a single graphene monolayer or a plurality of graphene monolayers. With a single graphene monolayer, epitaxial growth can be predicted to produce the working layer, with a lattice match to the support layer. With a plurality of graphene layers, the use of graphene as a seed for producing the working layer is possible notwithstanding the existence of a partial lattice mismatch between the silicon of the working layer and the graphene, because the graphene facilitates Van der Waals epitaxy of the working layer. It is also possible for both the support layer and the graphene layer to serve as seeds for the growth of the working layer.

[0031] According to one embodiment, the manufacturing process includes a step of: (d) performing at least one manufacturing operation on the watch components of the separated working layer, by manipulating the working layer alone or coupled to a support plate and / or by performing an operation or treatment on at least one face of the watch components freed from the buried layer and preferably on one upper and one lower face of the watch components. During this manufacturing step on the watch components of the separated working layer, the watch components are still bridged or attached to the working layer. Typically, at least one of the following operations may be provided: oxidation of the silicon watch components, deoxidation of the watch components, application of thermal compensation, detachment of the watch components... Description of the figures

[0032] Other features and advantages of the present invention will become more apparent upon reading the following detailed description of embodiment(s) of the invention given by way of non-limiting example(s) and illustrated by the accompanying drawings, in which: [ fig. 1a-1h ] schematically represent a series of manufacturing steps for a watch component in a SOI wafer according to an embodiment; [ fig. 2a-2b ] schematically represent a first implementation of mechanical separation of a working layer of the SOI wafer worked at figures 1a-1h ; fig. 2c ] schematically represents an alternative to the first implementation of mechanical separation of figures 2a et 2b of a working layer of the SOI plate worked at figures 1a-1h ; fig. 3a-3b ] schematically represent a second implementation of mechanical separation of a working layer of the SOI wafer worked at figures 1a-1h ; fig. 4a-4c ] schematically represent a first implementation of reusing a support layer of the SOI wafer processed at figures 1a-1h ; fig. 5a-5b ] schematically represent a second implementation of reusing a support layer of the SOI wafer worked at figures 1a-1h . Detailed description of implementation method(s)

[0033] In all that follows, orientations are the orientations of the figures. In particular, terms like "upper", "lower", "left", "right", "above", "below", "forward" and "backward" are generally understood in relation to the direction in which the figures are represented.

[0034] THE figures 1a-1h illustrate a series of schematic manufacturing steps for a watch component in a composite wafer 10, similar to a conventional SOI wafer, but comprising an embedded graphene layer, according to an embodiment of the invention. Of course, several watch components can be manufactured in the wafer 10 simultaneously, but the views of the figure 1a-1h are focused on a single component for greater simplicity. The process begins with an SOI 10 wafer illustrated in the figure 1a , this wafer comprising a silicon support layer 20, a silicon working layer 30, and a buried layer 40 made of graphene separating the two silicon layers 20, 30.

[0035] As an alternative, the support layer 20 can be made of another material and can include at least one of SiO2, SiC, HfO2, Al2O3, Si3N4.

[0036] Graphene is a two-dimensional carbon nanomaterial composed of carbon atoms in a hexagonal honeycomb lattice with sp2 hybrid orbitals. Graphene can be one of the thinnest artificially produced materials, with a thickness of only one carbon atom, or about 0.335 nm. Graphene is an allotropic form of carbon, the stacking of which technically constitutes graphite. However, several monolayers of graphene are also often referred to as graphene assemblies (and the term is also used in this way in the present description).

[0037] The drawing is not to scale, but as an example, the support layer 20 can be 500 µm thick, the working layer 30 can be roughly the same thickness as the components to be formed, for example, 120 µm thick, and the buried layer 40 can be very thin, especially if a single graphene monolayer is planned. Of course, multiple graphene layers are possible. The support and working layers can be of the same type of silicon or different types—for example, monocrystalline silicon with any crystal orientation, polycrystalline silicon, or amorphous silicon. The silicon layers 20, 30, and especially the working layer 30, can be N-type or P-type doped.For example, the use of heavily doped silicon can be advantageous for the manufacture of resonators because, for example, less deformation of the doped material is observed during thermal oxidation under certain conditions.

[0038] In the figure 1b A lithography step begins with the formation of a silicon oxide layer 50 on the upper surface of the work layer 30. "Lithography" refers to all the operations involved in transferring an image or pattern onto or above the wafer 10. The oxide layer 50 can, for example, have a thickness of between 0.4 and 6 µm, and it can be formed by thermal oxidation or alternatively by PVD, CVD, or ALD deposition. If the oxide layer 50 is formed by a directional deposition process such as CVD or PVD, the oxide forms only on the upper surface of the support layer, as illustrated in Figure 10. figure 1b Alternatively, if the oxide layer 50 is formed by thermal oxidation, it is generally observed that the oxide 50 forms simultaneously on the surface of the support layer 20 (if the latter is not covered by a masking device), or a second directional deposition of the CVD or PVD type can be carried out on the surface of the support layer 20. Generally, the formation of the oxide layer 50 occurs before the deposition of a resin layer (see the figure 1c ) allows a relatively thin layer of resin to be deposited, which can therefore be quite uniform with good surface homogeneity and thus optimize the subsequent engraving of fine and deep patterns in the working layer 30. However, in other embodiments, it is also possible to carry out a lithography step without the oxide layer, in particular by using a thicker photosensitive resin which may be less uniform.

[0039] To the figure 1c The oxide layer 50 is covered with a resin layer 60, which is typically a positive or negative type photosensitive resin. This resin layer can have a thickness of between 0.5 and 12 µm, purely for illustrative purposes. Subsequently, in the figure 1d The resin layer 60 is preferably structured using a photolithography step with an ultraviolet light source 80 and, for example, an exposure mask 70 such as a photomask. A stepper and reticle system can also be used for the photolithography step, or alternatively, a direct writing system (i.e., without a photomask) such as a laser or electron beam lithography system (e-beam lithography). In the illustrated example, the layer 60 comprises a negative-type photosensitive resin (e.g., SU-8) in which the parts of the resin exposed to light become insoluble in a developer, while the unexposed parts remain soluble. Alternatively, a positive-type photosensitive resin can be used in which the parts of the resin exposed to light become soluble in a developer, while the unexposed parts remain insoluble.

[0040] In the figure 1e The resin layer 60 is opened after being developed with a developer, specifically a solvent that chemically removes the unexposed parts of the resin (in the case of a positive-type photosensitive resin, the solvent chemically removes the exposed parts of the resin). Then, at the figure 1f The portions of the oxide layer 50 that were located beneath the unexposed areas of the resin are also removed from the surface of the working layer 30, for example, by using directional selective plasma etching with one or more fluorinated gases (such as CHF3, C4F8, and / or SF6) in combination with at least one of the gases He and / or H2, depending on the desired selectivities and etching speeds. The use of a directional etching technique is generally preferred at this stage because it is more precise, but alternatively, hydrofluoric acid (HF) vapor etching can also be used.

[0041] At the stage illustrated in the figure 1g , the remaining part of the 60 resin layer is removed and then, in the next step figure 1h Patterns are engraved into the working layer 30 through the structured layer 50 to form the watch component 100. Generally, the engraved patterns extend across the entire thickness of the working layer 30, as illustrated, and the buried layer 40 can act as a stop during the engraving process. In this way, the thickness of the watch component 100 corresponds to the thickness of the working layer 30.

[0042] The engraving at the stage of figure 1h This can be achieved, in particular, using a deep reactive ion etching technique (also known as DRIE). DRIE etching can be performed in pulses and allows for the creation of deep holes and trenches in the 30th layer with a high width-to-height ratio, making it well-suited for micromechanical components such as watch components. The etching can be either RIE or DRIE, using SF6 as the etching agent. DRIE etching is highly selective and terminates completely on the graphene, even with a single graphene monolayer, allowing for atomically precise control of etch depths.

[0043] It is also possible for the remaining portion of the resin layer 60 to still be present during the etching step (DRIE or other) of the working layer 30. This remaining portion of the resin layer can be removed after etching, and in this case, the working layer 30 is etched through both structured layers 50 and 60 (or only through the structured layer 60 if an oxide layer 50 is not present). As an example, a positive resin can be removed with solvents such as acetone or dimethyl sulfoxide (DMSO) or with an O2 plasma either before or after the etching step. For a negative resin such as SU-8, a CF4 / O2 plasma can be used for its removal.

[0044] After the etching of the working layer to form the watch components, it is known that the surfaces of the flanks of the structured patterns of these components possess a relatively high roughness. In DRIE etching, this roughness manifests as a surface with undulations, often called "scallops," with peaks. In fact, DRIE etching alternates between a silicon etching phase and a passivation phase, resulting in the undulating surface. After DRIE etching, or any other type of etching, the surface roughness can be reduced by a smoothing step, which mechanically strengthens these surfaces by limiting the initiation of fractures. This smoothing can be achieved, in particular, by a thermal oxidation step followed by a deoxidation step, such as wet etching or vapor etching with hydrofluoric acid (HF).As is known, during thermal oxidation, silicon at the surface is consumed, and this consumption is generally faster towards the peaks, resulting in a smoother silicon surface after deoxidation. Preferably, such smoothing can occur after the release of the step. figure 1h described below, but smoothing of the flank surfaces can also take place before this step.

[0045] At the stage of the figure 1h The watch components 100 are formed in the working layer 30 and are still attached to the wafer 10. Instead of chemically releasing them, as with a buried silicon oxide layer, the present invention proposes to take advantage of the weak adhesion of the buried graphene layer 40 to mechanically separate the working layer 30. Indeed, the low van der Waals force of graphene does not allow for strong bonding with adjacent materials. This enables relatively easy mechanical separation at the interface between the working layer 30 and the buried graphene layer 40 to achieve the release.In particular, if the buried graphene layer 40 was formed by PVD deposition on a silicon dioxide layer initially present on the support layer 20, and / or if the working layer 30 was applied by pressure to the buried graphene layer 40, then the buried graphene layer 40 will preferentially remain on the support layer 20: delamination will be preferential on the side of the working layer 30.

[0046] After the separation of the working layer 30, the watch components 100 are released and are structurally supported within the working layer only by connecting bridges (not shown). This allows subsequent manufacturing steps to be carried out on almost the entire external surface of the watch components. Such subsequent manufacturing steps may include a first (or other) thermal oxidation step followed by a deoxidation step, and may be performed to smooth the surfaces of the components.

[0047] Operations to remove carbon atoms from the buried graphene layer 40 that remain attached to the working layer 30 (or the support layer 20, if applicable) can be planned (immediately after separation of the working layer 30 or subsequently). These operations may include a baking, annealing, combustion, plasma cleaning, or liquid cleaning step.

[0048] In addition, another oxidation step can be carried out followed by deoxidation to adjust the dimensions of the components, or a permanent silicon oxide (SiO2) layer can be formed on at least part of the entire external surface of the watch components 100. In the context of a balance spring or other type of watch resonator, such a permanent oxide layer can compensate for the variations in the Young's modulus of the silicon core of the watch component as a function of temperature.

[0049] Furthermore, the formation of such an outer layer of silicon oxide on watch components of any type can also serve to mechanically strengthen these components. Other types of materials can also be formed on watch components, for example, by an ALD-type coating. It is also possible to perform a pre-assembly or machining step on watch components while they are still attached to the released working layer, such as for assembling the component to a shaft, stud, pin, or ferrule.

[0050] THE figures 2a, 2b schematically represent a first implementation of mechanical separation of the working layer 30 from the wafer 10. According to this first embodiment, the working layer 30 can be separated using a stress applicator 91 attached to the working layer 30. For example, a high-strength film, such as a nickel film deposited by chemical vapor deposition at 1 x 10⁻⁵ Torr, can be used. An adhesive strip 92 can then be applied to the stress applicator 91 to exert a tensile or peeling force on the working layer 30, separating it from the embedded graphene layer 40 and the support layer 20, as shown in the figure. figure 2b .

[0051] According to an alternative represented figure 2c It is possible to apply adhesive strip 92 directly to the working layer 10. It is possible to cover part of the watch components (as shown in the figure 2c ), but it is possible to plan for coating all the watch components. One could use an adhesive strip that deteriorates under UV light, allowing the working layer to be peeled off, and then expose it to UV light to weaken the adhesive strip's bonding forces. Alternatively, one could use an adhesive strip that dissolves after peeling off the working layer 10, by applying a solvent.

[0052] THE figures 3a And 3b schematically represent a second implementation of mechanical separation of the working layer 30 from the insert 10. According to this second embodiment, a blade 93 can be used which is inserted ( figure 3a ) between the working layer 30 and the support layer 20, to separate them from each other ( figure 3b ).

[0053] It can be noted that the mechanical separation of the working layer 30 is rapid and does not require the use of chemical etching agent as for a buried silicon oxide layer.

[0054] Advantageously, after the release of the working layer 30, the support layer 20 and the buried graphene layer 40 can be reused for a new manufacturing cycle with another working layer 30' that can be formed on these layers. Alternatively, the buried graphene layer 40 can also be mechanically released or separated from the support layer 20, or the buried graphene layer 40 can be removed by chemical etching (e.g., O₂- or O₂ / Ar-based plasma etching). In this case, a new buried graphene layer 40 can be formed on the support layer 20, and another working layer 30 can be formed on this buried graphene layer 40 before starting the next manufacturing cycle with a new fabrication wafer 10.In all these cases, the buried graphene layer 40 protects the support layer 20 from damage, allowing for its repeated use and reducing manufacturing costs. The use of the buried graphene layer 40 promotes reuse because it creates an atomically smooth release surface. Both the buried graphene layer 40 and the support layer 20 can then be reused for multiple manufacturing cycles of watch components without requiring a polishing step for the support layer 20 and without damaging the buried graphene layer 40, due to its mechanical robustness.

[0055] THE figure 4a-4c schematically represent a first implementation of reusing the support layer 20 of the SOI 10 plate processed at figures 1a-1h .

[0056] Firstly, the buried graphene layer 40 can be formed directly on the support layer 20 as shown in the figure 4a The buried graphene layer 40 may comprise epitaxial graphene with a single-crystal orientation growing on a suitable crystalline substrate that promotes this growth. For example, if the support layer is not silicon, the graphene layer may be formed on the silicon face of a hexagonal silicon carbide (0001) 4H-SiC crystalline substrate. In this case, the fabrication of the buried graphene layer 40 may involve several annealing steps. A first annealing step may be carried out in H₂ gas to perform surface etching, and a second annealing step may be carried out in Ar for high-temperature graphitization (e.g., above 1575 °C).

[0057] In another example, the buried graphene layer 40 can be developed on a substrate formed by the support layer 20 by chemical vapor deposition (CVD). The substrate can include nickel or copper. Alternatively, the substrate can include at least one of SiO₂, HfO₂, Al₂O₃, Si₃N₄, or another planar material that is compatible with the high temperatures required by CVD deposition.

[0058] Once the buried graphene layer 40 has formed, or if the buried graphene layer 40 has remained on the support layer 20, a new working layer 30' can be applied directly onto the buried graphene layer 40 by pressure. Pressure and temperature are parameters to be controlled during this pressing.

[0059] Alternatively, a new working layer 30' can be formed directly on the buried graphene layer 40. As an example, epitaxial growth can be expected during chemical vapor deposition ( figure 4b ) at temperatures between 1000°C and 1200°C with source gases such as dichlorosilane or trichlorosilane to obtain a 30' working layer ( figure 4c ) and a plate of 10 ready to follow a new manufacturing cycle of watch components, illustrated in the figure 1a .

[0060] In detail and according to a first approach, where the buried layer 40 in graphene is sufficiently thin (for example it consists of a single monolayer of graphene) the working layer 30 in silicon is in crystalline lattice agreement with the support layer 20 and the latter serves as a seed for the growth of the working layer 30. Here, the working layer 30 and the support layer 20 can in particular be of the same type (or even of the same orientation) of monocrystalline silicon.

[0061] According to another approach, where the buried graphene layer 40 is sufficiently thick and includes several graphene monolayers, the buried graphene layer 40 can serve as a seed for the working layer 30. In general, the use of graphene as a seed for the fabrication of the working layer 30 is possible notwithstanding the existence of a partial lattice mismatch between the silicon of the working layer 30 and the graphene, because the graphene facilitates Van der Waals epitaxy of the working layer 30. It is also possible for the support layer 20 and the buried graphene layer 40 to serve as seeds for the growth of the working layer 30.

[0062] THE figures 5a-5b schematically represent a second implementation of reusing the support layer 20 of the SOI 10 plate worked at figures 1a-1h .

[0063] In this second implementation, the buried graphene layer 40 can be developed on a donor substrate 21 by chemical vapor deposition (CVD) as shown in the figure 5a The donor substrate 21 may comprise nickel or copper. Alternatively, the donor substrate 21 may comprise at least one of SiO2, HfO2, Al2O3, Si3N4, or another planar material that is compatible with the high temperatures required by CVD deposition.

[0064] Various methods can be used to transfer the buried graphene layer 40 from the first donor substrate 21 to the support layer 20. In one example, a support film can be attached to the buried graphene layer 40. The support film can be a thick poly(methyl methacrylate) (PMMA) film or a heat-sealable tape, and the attachment can be achieved by a spin-coating process. Once the combination of the support film and the buried graphene layer 40 is deposited on the support layer 20, the support film can be dissolved (e.g., in acetone). The resulting support layer 20 and buried graphene layer 40 are shown in the figure. figure 5b .

[0065] In another example, a buffer layer comprising an elastomeric material such as polydimethylsiloxane (PDMS) can be attached to the buried graphene layer 40, and the donor substrate 21 can be stripped away, leaving the combination of the buffer layer and the buried graphene layer 40. Once the buffer layer and the buried graphene layer 40 are placed on the support layer 20, the buffer layer can be removed by mechanical detachment, producing the buried graphene layer 40 for the next step.

[0066] In yet another example, a self-adhesive transfer method (including, for example, polystyrene, poly(isobutylene), or Teflon) can be used to transfer the graphene-buried layer 40 onto the support layer 20. In this method, a self-adhesive layer is first spun onto the graphene-buried layer 40 on the donor substrate 21. An elastomeric pad is then placed in contact with the self-adhesive layer. The donor substrate can be etched to leave the combination of the pad layer, the self-adhesive layer, and the graphene layer. Once this combination is placed on the support layer 20, the stamping layer can be mechanically removed, and the self-adhesive layer can be dissolved (for example, with acetone) under mild conditions in a suitable solvent.

[0067] After transfer from the donor substrate 21, the buried graphene layer 40 tends to adhere to the support layer 20. The main factors affecting graphene adhesion are (i) tuning the intrinsic interaction with the substrate, i.e., ensuring that the target substrate provides a stronger interaction than the donor substrate or a temporary polymer support used for the transfer; (ii) tuning the intrinsic interaction with the graphene; and (iii) manipulating the distance between the graphene and the substrate, where close conformal contact between the graphene and the target substrate will tend to mitigate potential problems arising during re-bonding, such as wrinkles.

[0068] Once the buried graphene layer 40 is in place, the working layer 30 can be applied or deposited, as explained above in relation to the figure 4c . Industrial application

[0069] A manufacturing process according to the present invention is capable of industrial application.

[0070] It will be understood that various modifications and / or improvements obvious to a person skilled in the art can be made to the different embodiments of the invention described in this description without departing from the scope of the invention.

Claims

1. Method for manufacturing watch components (100), comprising the steps of: (a) taking a wafer (10) comprising a support layer (20), a working layer (30) and an underground layer (40) formed of graphene and separating the working layer (30) from the support layer (20), (b) etching at least a part of the watch components into the working layer (30), (c) separating the working layer (30) from the support layer (20) and / or the underground layer (40) formed of graphene.

2. Manufacturing method according to claim 1, wherein step (c) includes a mechanical separation step to separate the working layer (30) from the support layer (20) and / or the buried layer (40).

3. Manufacturing method according to claim 2, wherein step (c) includes a step of applying a stress applicator (91) or a tensile interface such as an adhesive strip (92) to at least a portion of the working layer (30).

4. Manufacturing method according to claim 3, wherein step (c) includes a step of applying a pull-out force on the stress applicator (91) to separate the working layer (30) from the support layer (20) and / or the buried layer (40).

5. A manufacturing method according to any one of claims 3 or 4, wherein step (c) includes a step of applying a tensile interface to at least a part of the stress applicator (91), such as, for example, a step of applying an adhesive strip (92) to the stress applicator (91).

6. A manufacturing method according to any one of claims 2 to 5, wherein step (c) includes a step of inserting a wedge, such as a blade (93), between the working layer (30) and the buried layer (40).

7. A manufacturing method according to any one of claims 1 to 6, wherein step (c) is followed by a step of reusing the support layer (20), and optionally the buried layer (40), to support a new working layer (30') in order to manufacture other watch components (100).

8. Manufacturing method according to claim 7, wherein the new working layer (30') is directly formed on the retained buried layer (40), preferably wherein the new working layer (30') is formed by epitaxial growth from the retained buried layer (40), or wherein the new working layer (30') is brought onto the retained buried layer (40), for example with application of controlled pressure.

9. Manufacturing method according to claim 7, wherein the reuse of the support layer (20) comprises: - optionally, the removal of the buried layer (40), - the formation of a new buried layer (40) in graphene, - the formation of the new working layer (30') on the new buried layer (40).

10. Manufacturing method according to any one of claims 1 to 9, wherein step (a), or reuse of claim 7, includes a step of forming the buried layer (40) on the support layer (20).

11. Manufacturing method according to claim 10, wherein step (a), or reuse of claim 7, includes a step of directly forming the buried layer (40) on the support layer (20), for example by epitaxial growth.

12. Manufacturing method according to claim 10, wherein step (a), or reuse of claim 7, comprises the steps of: - forming the buried layer (40) on a donor substrate (21), - transferring the buried layer (40) from the donor substrate (21) to the support layer (20).

13. A manufacturing method according to claim 12, wherein the step of transferring the buried layer (40) from the donor substrate (21) to the support layer (20) comprises the steps of: - attaching to the buried layer (40) still disposed on the donor substrate (21) a support film comprising, for example, a thick film of poly(methyl methacrylate), preferably dissolving the donor substrate, if metallic, in acid, transferring the buried layer (40) from the donor substrate (21) to the support layer (20), and dissolving the support film once the buried layer (40) is disposed on the support layer (20), or - attaching to the buried layer (40) still disposed on the donor substrate (21) a buffer layer comprising an elastomeric material such as polydimethylsiloxane, stripping the donor substrate (21), transferring the buried layer (40) to the support layer (20), and detach,for example, mechanically remove the buffer layer of the buried layer (40) placed on the support layer (20), or - attach to the buried layer (40) still placed on the donor substrate (21) a self-adhesive layer comprising for example polystyrene or poly(isobutylene) or Teflon, place a buffer in contact with the self-adhesive layer, etch the donor substrate (21) to leave the buffer-self-adhesive layer-buried layer (40) assembly free, transfer the buried layer (40) from the donor substrate (21) to the support layer (20), and once the buried layer (40) is placed on the support layer (20), detach, for example mechanically, the buffer and dissolve the self-adhesive layer, for example with acetone.

14. A manufacturing method according to any one of claims 10 to 13, wherein, once the buried layer (40) has been formed on the support layer (20), step (a), or reuse of claim 7, comprises the formation of the working layer (30) on the buried layer (40), for example by epitaxial growth.

15. A manufacturing method according to any one of claims 1 to 14, wherein the buried layer (40) comprises a single graphene monolayer, or a plurality of graphene monolayers.

16. A manufacturing method according to any one of claims 1 to 15, comprising a step of: (d) performing at least one manufacturing operation on the watch components (100) of the separated working layer (30), by manipulating the working layer (30) alone or coupled to a support plate and / or by performing an operation or treatment on at least one face of the watch components (100) freed from the buried layer and preferably on an upper and a lower face of the watch components (100).

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