Method for manufacturing a timepiece component

Abstract

The present invention relates to a method for manufacturing a watch component in a substrate (100) comprising a useful layer (10) of silicon. By a first side (101) of the substrate (100), a so-called primary etching is made of at least one primary zone (A) of said useful layer (10), so as to form at least one edge of a first level (I) of the component (1), and by the same first side (101), a so-called secondary etching is made of at least one secondary zone (B) of the useful layer (10), so as to form at least one edge of a second level (II) of the component (1).

Description

Technical field of the invention

[0001] The present invention relates to the field of watchmaking. More specifically, it concerns a method for manufacturing a watch component, in particular a silicon watch component. State of the art

[0002] In the field of watchmaking, some applications require the use of complex or multi-level components.

[0003] These components are typically obtained by assembling several separately manufactured elements. This is the case, for example, with anchors, in which the tang is assembled onto the fork intended to cooperate with a regulating organ of a watch mechanism.

[0004] In the past, this assembly was carried out using a technique called "driving," which consists of forcing an axle of one element to be assembled into a hole in the other element.

[0005] A few years ago, we also started using new materials for the manufacture of watch components, including silicon.

[0006] Silicon is a brittle material, making it difficult to use the previously mentioned press-fit assembly method, or at the very least, poorly suited to industrial production due to the high losses associated with breakage. Therefore, researchers sought new techniques for manufacturing complex silicon components.

[0007] A method for manufacturing multilevel watch components by etching in a monolithic silicon wafer has, for example, been described in patent application EP 4 283 408. According to this method, the wafer is etched on one of its sides, then the etched side is covered with an etching stop layer, and finally the wafer is etched on its second side, at least locally down to said stop layer.

[0008] But this process remains relatively complex. Summary of the invention

[0009] The present invention proposes a new process for the manufacture of multilevel silicon components, which is an alternative to the known process of the prior art and which is in particular simpler to implement.

[0010] To this end, the invention relates to a method for manufacturing at least one watch component, comprising at least the following steps: a) a substrate is provided having a first side and a second side opposite in a transverse direction, said substrate comprising a useful silicon layer, d) through the first side of the substrate, a so-called primary etch is made of at least one primary area of ​​said useful layer, so as to form at least one edge of a first level of the component, and i) through the first side of the substrate, a so-called secondary etch is made of at least one secondary area of ​​the useful layer, so as to form at least one edge of a second level of the component.

[0011] Steps a), d) and i) are typically carried out in this order, with possible interposition of other complementary steps.

[0012] The process according to the invention allows the manufacture of a watch component with at least two levels, in other words a component comprising an upper face, a lower face and at least one intermediate surface between said upper and lower faces, the upper face, the lower face and the intermediate surface being orthogonal or substantially orthogonal to a transverse direction corresponding to the transverse direction of the substrate from which the component is derived and therefore to the direction of the engraving which made it possible to obtain it.

[0013] To form these two levels, the remaining thickness of silicon after etching is different in the primary zone and in the secondary zone.

[0014] Typically, in one of the primary and secondary etching processes, the useful layer is etched to its full thickness (i.e., the remaining silicon thickness is zero), and in the other of the primary and secondary etching processes, the useful layer is etched to an intermediate thickness strictly less than its total thickness.

[0015] Etching on an intermediate thickness of the useful layer leaves, on this area, a thickness of silicon forming at least one level of the component.

[0016] The components obtained using the process according to the invention are monolithic silicon components. A monolithic component is understood here to be a solid block made of a single material.

[0017] The process according to the invention can in particular, but not limited to, be implemented for the manufacture of anchors, wheels, balance wheels, plates, hands, spirals or even elements with flexible blade(s).

[0018] It can also be used for the simultaneous manufacture, on the same substrate, of a plurality of watch components of the same type or of different types, and of the same shape or of different shapes.

[0019] The primary and secondary etchings are advantageously deep reactive ion etchings (also called DRIE etchings).

[0020] The primary and secondary zones may be separate, or at least one primary zone and one secondary zone may be contiguous. For example, at least one primary or secondary zone, etched across the entire thickness of the usable layer, defines an outer edge of the watch component.

[0021] Such an area can form a continuous groove defining a closed contour. In this case, the component has a finite contour; in other words, in a direction orthogonal to the transverse direction, each watch component is externally delimited by a lateral face forming a continuous and closed contour.

[0022] In another case, this area may correspond to the outer edge of the component, except for an unetched portion called a junction, which connects the component to the rest of the active layer. This case corresponds to the situation where a single wafer is desired, carrying the watch component(s) rather than one or more individual components.

[0023] According to one example, at least one primary or secondary zone can also delimit a through hole in the component.

[0024] The substrate in step a) can be a bulk substrate, in the form of a single monolithic silicon layer (useful layer).

[0025] As an advantageous alternative, the substrate in step a) can comprise the silicon work layer, an intermediate oxide layer, and a stiffening layer, superimposed in that order between the first and second sides. This type of substrate, known as a Silicon-on-Insulation (SOI) substrate, has the advantage that the etching arrest layer is directly integrated into it. This eliminates the need for the step of creating such an arrest layer, which is present in the earlier process described in EP 4 283 408. In an SOI substrate, the work layer is also called the "device" layer. Its thickness is, for example, between 50 microns and 500 microns. The stiffening layer is also called the "handle" layer and can, for example, be made of silicon. The intermediate layer, which forms the arrest layer, can, in particular, be made of silicon dioxide.

[0026] The substrate, whether solid or of the SOI type, is generally a thin and flat element, its transverse direction being orthogonal to its first and second sides, that is to say corresponding to the direction of its thickness and to the direction in which it is engraved during the process.

[0027] For example, in a step (b) prior to step (d), an oxide layer is formed on at least the first side of the substrate, for example by thermal oxidation of the substrate. The thickness of the oxide layer thus formed is typically between 0.5 and 4 microns. In the remainder of this application, this oxide deposited at the very beginning of the process will be referred to as the "initial" oxide layer.

[0028] The initial oxide can notably be used to create a sub-mask for etching (secondary). In this case, the process includes a step c1) in which the oxide layer previously formed on the first side of the substrate is etched to form at least one opening covering and / or delimiting the secondary area.

[0029] Step c1) may include the following sub-steps: c1.1) the oxide layer is covered with a layer of photosensitive resin, c1.2) by photolithography, at least one opening is formed in said resin layer covering and / or delimiting the secondary zone, c1.3) the oxide layer is etched through said opening, c1.4) optionally, the resin layer is removed.

[0030] At least one opening in step c1 can cover both the primary and secondary zones. It can also partially delimit the primary and / or secondary zones.

[0031] According to one example, the process includes, prior to step d), a step c2) of creating a primary etching mask having at least one opening of which at least one edge delimits the primary area.

[0032] The creation of this primary engraving mask may, for example, include the following steps, carried out in this order: c2.1) the first side of the substrate is covered with a layer of photosensitive resin, c2.2) by photolithography, at least one opening is formed in said resin layer, at least one edge of which delimits the primary zone, c2.3) optionally, the underlying oxide layer is etched through said opening (in the case where a step b) and / or c1) has taken place previously).

[0033] Depending on whether a step b) and / or c1) has been carried out previously or not, the resin layer of step c2.1) can be deposited directly on the useful layer or on the initial oxide layer formed during this step b).

[0034] If a step c1) was performed before c2) (in other words, if a secondary etching sub-mask is present), it is possible, to facilitate alignment, to create one or more openings in the resin at step c2.2), with at least one edge slightly offset outwards from the edge of the underlying oxide opening. This ensures that the entire oxide opening is free for the etching step.

[0035] According to an advantageous aspect of the present invention, the edges resulting from the primary etching are protected during the secondary etching step (i). For this purpose, and as will be described later, the process may include active or passive treatment of these edges. Active treatment is typically treatment of the primary etching edge(s) (that is, the edges of the useful layer extending transversely or substantially in that direction and formed during the primary etching), and is carried out between the primary and secondary etching stages. In the case of passive treatment, the protection may be inherent in the primary etching stage, and the process may include preserving this protection after the primary etching, in particular by a suitable selection of the intermediate steps between the primary and secondary etching stages.

[0036] According to one example, the process includes, after step d) of primary etching and before step i) of secondary etching, in particular after step d) and before a possible step f) of protecting the edges of primary etching, a step e) of removing resin (in particular resin from step c2) and used for primary etching) on ​​the first side of the substrate.

[0037] According to one example, and in particular in the case of passive treatment of the primary etching edges as mentioned previously, step i) of etching can be carried out by keeping as protection of at least one edge of the first level the passivation layer of the edges of the etching of step d) (with the passivation layer resulting from the primary etching previously carried out by DRIE).

[0038] In this case, to preserve the passivation edges, step e) of removing the resin used for the primary etching can be carried out by directional plasma, i.e., by directional ion bombardment, here in the transverse direction of the substrate. To preserve the oxide and silicon, a directional oxygen plasma is advantageously used.

[0039] According to another example, and in particular in the case of an active treatment as mentioned above, the process may also include, between steps d) and i), at least one step f) in which at least one edge of the first level etched in step d) is treated for its protection against etching in step i).

[0040] In this case, the resin layer from step c2.1) may or may not be removed before step f) of treatment.

[0041] According to one example, step f) may include covering at least one edge of the first level with a protective layer.

[0042] Depending on the material used, the protective layer can be applied by spray coating, printing, pattern transfer, PVD (vapor deposition), or any other suitable technique.

[0043] For example, the protective layer could be a polymer layer, such as parylene, or a resin. The resin could be a photosensitive resin, such as Su-8.

[0044] As an example, the protective layer can be an oxide layer, in particular silicon oxide.

[0045] According to yet another example, the protective layer can also be a nitride layer.

[0046] In the case of a protective layer in oxide or nitride, it can for example have a thickness of less than 300 nm, preferably less than 200 nm, and even more preferably less than 150 nm.

[0047] According to an example, in step f), the etching cavities from step d) are completely filled with the protective layer.

[0048] According to an example, in step f) the first side of the substrate is also covered with the protective layer and then in step g) a secondary etching mask is prepared, for the etching of step i), in said protective layer.

[0049] For example, step g) may include the following substeps: g1) At least one opening is formed in the protective layer, at least one edge of which delimits the secondary zone; g2) Optionally, the underlying oxide is etched through said opening. This case is particularly suitable when the protective layer is a resin layer, and especially a photosensitive resin layer.

[0050] According to a second example, in a case where the process includes a step c1) of creating a submask within an initial oxide layer, and if the protective layer is also an oxide protective layer, then the oxide submask can be recovered by removing the portion of the protective layer located on the first side of the substrate (i.e., extending orthogonally to the transverse direction) while retaining it at the primary etching edges. To allow the removal of the protective layer while preserving the submask, however, the thickness of the protective layer must be significantly less than that of the submask. For this purpose, the oxide protective layer advantageously has a thickness of less than 300 nm, preferably less than 200 nm, and even more preferably less than 150 nm.

[0051] As an alternative, particularly in the absence of a sub-mask and in cases where the protective layer does not cover the entire first side of the substrate, and in particular only covers at least one edge of the first level etched in step d), the process may include, instead of step g), a step h) for creating a mask for the etching in step i) in addition to the protective layer deposited on at least one edge of the first level. In this case, step h) may include the following sub-steps, in this order: h1) a layer of photosensitive resin is deposited on the first side of the substrate, h2) by photolithography, at least one opening is formed in said resin layer, at least one edge of which delimits the secondary zone, h3) optionally, the underlying oxide is etched through said opening.

[0052] According to one example, the process further includes, after step i), a step j) of removing the protective layer and / or a layer of resin on the first side of the substrate.

[0053] Regardless of the substrate type, the process may include, after steps a), d), and i), and where applicable after step j), a step I) for releasing the manufactured component. In the case of a SOI substrate, the intermediate layer of the substrate is removed at least opposite the component. The release step is carried out, for example, by vapor-phase etching, in particular by hydrofluoric acid vapor etching. In the case of a bulk substrate, the stop layer used for etching the component is removed at least opposite the component. Step I) results in releasing either an individual component when it has been etched without a tab, or a wafer comprising at least a portion of the usable layer bearing the watch component when it has been etched with a tab.

[0054] According to an example, at the end of step I), a step m) is carried out at least once, comprising oxidation and deoxidation of the component.

[0055] We can also perform several iterations of step m)

[0056] According to one example, the process further includes, at the end of step l), and where applicable step m), a final oxidation step n) of the component.

[0057] When it is a wafer that has been released in step I), the process may further include at the end of step I) or where appropriate step m) or n), a step o) consisting of detaching at least one watch component from the wafer. Brief description of the drawings

[0058] The features and advantages of the present invention will become apparent in more detail in the following description, with several illustrative and non-limiting examples of embodiments given by reference to the accompanying drawings, which represent: THE Figures 1A And 1B illustrate the different stages of a first example of implementing the process according to the invention, The figure 2 illustrates a variant of the process of Figures 1A And 1B , There figure 3 illustrates the different stages of a second example of implementing the process according to the invention, The figure 4 illustrates the different stages of a third example of implementing the process according to the invention, The figure 5 illustrates a two-level anchor that can be manufactured using the process according to the invention. Detailed description

[0059] The method according to the invention, described later in connection with the figures 1 to 5 , allows the manufacture of a component or a plurality of components 1 in silicon at least two levels in a substrate 100 comprising a useful layer 10 of silicon.

[0060] For the sake of brevity and clarity, this description will focus on the fabrication of a single component. However, even though it is theoretically possible to manufacture only one component at a time, it is generally desirable to simultaneously manufacture multiple watch components on the same substrate. These components may be of the same type or different types, the same shape or different shapes.

[0061] There figure 5 This represents, as an example, a two-level anchor 1 that can be manufactured using this process. This example is not limiting, however, and the process can be applied in an equivalent or similar manner to any other type of watch component, for example wheels, balance wheels, plates, hands, balance springs, or elements with flexible blade(s).

[0062] An anchor 1 as illustrated on the figure 5is intended to equip an escapement of a watch movement (not shown). The anchor 1 is a monolithic silicon element. It has a parallel upper face 1a and lower face 1b, with the distance between these two faces corresponding to the total thickness e of the anchor, measured in a transverse direction Z'. This total thickness e corresponds to the thickness of the useful layer 10 from which the anchor 1 is formed.

[0063] The anchor 1 here has an overall T-shape with a central stem 2 and, at one end of this stem 2, a head 3 with a through hole 4 for receiving a pivot pin (not shown). The anchor 1 also includes two pallets 5a, 5b formed respectively at one end of the head 3 and, at the end of the stem 2 opposite the head 3, a fork 6 for cooperating with a regulating organ (not shown) of the movement, for example, a balance wheel and hairspring. The fork 6 has two horns 7a, 7b dividing between them a thin dart 8, itself delimited in the transverse direction by an intermediate surface 9 located between the two main faces 1a, 1b.

[0064] The intermediate surface 9 of the dart forms a junction surface between two levels I, II of the anchor, superimposed along the transverse direction Z'.

[0065] The first level I has a height H1. The second level II has a height H2.

[0066] The substrate 100 in which the component is formed is generally thin and flat, and delimited, in the direction of its thickness or transverse direction Z, between a first side 101 and a second side 102. As will be shown from later, the transverse direction Z' of the components 1 which will be formed there will be parallel to this transverse direction Z.

[0067] The substrate 100 is typically a Silicon On Insulation (SOI) substrate, which, in addition to its active layer 10, comprises a second layer or stiffening layer 20 and an intermediate oxide layer 30 interposed between the active layer 10 and the stiffening layer 20 in the transverse Z direction. The use of such a substrate 100, known as a Silicon On Insulation (SOI) substrate, is advantageous for several reasons: the etching stop layer 30 is integrated into the substrate, thus eliminating the need for an additional step of preparing a dedicated stop layer. Furthermore, the stiffening layer 20 prevents deformations of the substrate 100 that could adversely affect the shape and strength of the formed watch components 1.

[0068] The use of an SOI substrate is not limiting, however, and the substrate could also be a bulk substrate in the form of a monolithic silicon wafer.

[0069] The method according to the invention comprises at least one primary etching and one secondary etching of the useful layer 10 of the substrate 100, carried out one after the other, from the first side 101 of the substrate, on areas respectively primary and secondary, and on different thicknesses of said layer.

[0070] Typically, one of these engravings is made over the entire thickness of layer 10, in other words up to the intermediate layer 30, the other is made over an intermediate thickness less than the total thickness of the useful layer 10, so as to stop at a distance from the intermediate layer 30.

[0071] In the implementation examples described below, more specifically, the first etching – called primary etching – is that which extends over the entire thickness of the useful layer 10, while the secondary etching extends only over an intermediate thickness. This is not, however, a limiting factor.

[0072] As an illustration, we will subsequently consider the section plane V of the figure 5 To form this part of the anchor 1, a secondary zone B, intended to form the dart 8, will be engraved on an intermediate thickness corresponding to the height H2 of the second level II. A first primary zone A1 intended to form the through hole 4 and a second primary zone A2, adjoining the secondary zone B and intended to form the external contour of the dart 8, will be engraved over the entire thickness of the useful layer 10.

[0073] THE Figures 1A And 1Bschematically illustrate, in relation to this section plane V, different stages of the process according to a first method of implementing the invention.

[0074] In step a) of the process, a substrate of type SOI (for the English "Silicon On Insulation"), of the type already defined previously, is provided.

[0075] The initial thickness e1 of the active layer 10 of the substrate 100 determines the total thickness e of the final component 1. The thickness e1 is, for example, between 50 and 500 µm. However, e1 is not necessarily equal to e. If, for example, the substrate undergoes a thermal oxidation process, silicon dioxide is formed on its surface at the expense of the silicon, causing the silicon interface to recede and thus reducing the thickness of the active layer 10. Therefore, the total thickness e of the layer at the time of primary etching may differ from its initial thickness e1.

[0076] The stiffening layer 20 is generally (but not necessarily) thicker than the useful layer 10.

[0077] The intermediate layer 30 forms a bonding layer between the active layer 10 and the stiffening layer 20, and also serves as a stop layer during deep reactive ion etching (DRIE) operations, which will be described in more detail later. It is typically made of silicon dioxide (SiO2, also commonly called silicon oxide).

[0078] In step b), an oxide layer 40 is formed on the substrate, typically by thermal oxidation, usually in a thermal oxidation furnace heated to approximately 1000°C. The thickness of the oxide layer 40 formed around the substrate is typically between 0.5 and 4 microns. Simultaneously, and as explained previously, the silicon thickness of the useful layer is reduced to a value e less than e1. Hereafter, the oxide formed in this preliminary step is referred to as the initial oxide.

[0079] In the particular example considered, and although it remains optional, the initial oxide is used for the preparation, on the first side 101 of the substrate 100, of an oxide sub-mask 44 intended later for the etching of the primary and secondary areas.

[0080] According to an example, in a step c1.1), the oxide layer 40 is covered with a layer of photosensitive resin 50. In a step c1.2), an opening 52 is formed in the resin layer 50 by photolithography using a mask M1, which delimits or covers the secondary area B. In a step c1.3) the oxide layer 40 is etched through said opening 52, to form a corresponding opening 42. Then the resin layer is removed (c1.4).

[0081] An opening 42 of the submask 44 can also, in addition, cover or partially delimit a primary area (A2, in the example).

[0082] In a step c2), an etching mask 64 is then prepared for the primary etching. For this, in a step c2.1) the first side 101 of the substrate 100 is covered with a layer of photosensitive resin 60. Then by photolithography using a mask M2, openings 62 are formed in this layer of resin 60 delimiting the primary areas A1, A2 (c2.2).

[0083] The underlying oxide layer 40 is then engraved through the openings 62 (c2.3), except at the location of any openings 42 of the sub-mask 44.

[0084] When a sub-mask 44 is present, it can sometimes be difficult to align the openings 42 of the sub-mask 44 with those 62 of the resin 60. Therefore, it can be advantageous to create, in step c2.2), one or more openings 62 with at least one edge slightly offset outwards from the edge of the underlying oxide opening 42, as illustrated in the variant of the figure 2 .

[0085] The primary etching step (d) can finally be carried out through the openings 62 of the primary etching mask 64 thus formed in the resin 60, so as to form at least the edges of the first level I of component 1 and possibly some edges of the second level II, when these are aligned with the edges of the first level. The usable layer 10 of the substrate 100 is etched over its entire thickness e.

[0086] The primary etching is performed by deep reactive ion etching (also called DRIE for Deep Reactive Ion Etching).

[0087] In a step e) following the etching, the photosensitive resin used for the primary etching mask is removed from the first side 101 of the substrate 100, for example by multidirectional ion bombardment with oxygen plasma or by chemical means, typically by spraying or in a bath.

[0088] In a step f), the edges 12 engraved during step d) are advantageously treated to protect them against the second engraving step (secondary engraving) to come.

[0089] In the illustrated embodiment, this treatment consists of depositing or creating an oxide layer 70 on the first side 101 of the substrate 100, preferably by thermally oxidizing the substrate. During oxidation, the entire surface of the substrate is covered with oxide, including the primary etching edges 12 and the first side 101 of the substrate 100. The protective oxide layer 70 is a thin layer, preferably less than 300 nm thick, even more preferably less than 200 nm, and even more preferably less than 150 nm.

[0090] In step g), the entire first side 101 of the substrate 100 is etched by DRIE or RIE etching. Since the etching is unidirectional, it does not attack the oxide layer protecting the primary etch edges but only the layer extending orthogonally to the ion path. On the first side 101 of the substrate 100, an oxide thickness at least equal to the thickness of the protective layer 70 but strictly less than the sum of the thickness of the initial oxide 40 and the protective layer 70 is removed, preserving on this first side 101 a mask 44 for secondary etching.

[0091] In a new step i), the useful layer 10 is then etched over an intermediate thickness e', strictly less than the total thickness of the useful layer 10, to form the edge or edges of the second level II of component 1. The etching is always of the DRIE type.

[0092] In practice, either the progress of the etching is controlled in real time and the etching is stopped as soon as the secondary area is etched to the predetermined intermediate thickness e' (corresponding to the preservation of a desired underlying silicon thickness - here H1), or a duration t is determined beforehand - empirically or by calculation - for which the intermediate thickness must be etched, and the etching is stopped after this duration t. These two control methods can also be combined.

[0093] A wall of silicon and oxide 72 may eventually persist at the junction between the primary A2 and secondary B zones, as illustrated in figure 1 Bi).

[0094] In a new step I) the substrate 100 is deoxidized with acid, in particular with hydrofluoric acid, in vapor phase, so as to eliminate the intermediate layer 30 at least opposite the watch component 1.

[0095] In the case of etched components with attachment, deoxidation can lead to the release of a wafer 200, comprising all or part of the useful layer 10 and carrying the components 1.

[0096] In the case of components 1 etched without attachment, deoxidation leads to the release of individual components.

[0097] The process can then include at least one sequence m) of thermal oxidation followed by deoxidation of the wafer 200 or of the individual component(s) 1. This optional sequence allows in particular the removal of any silicon and oxide walls 72 remaining on the components 1.

[0098] The process may optionally include, after step l), and where appropriate step m), a final oxidation step n) of the component(s) 1 (where appropriate on their wafer 200).

[0099] And finally, the process may include a step o) in which the components 1 are detached from their wafer 200, if applicable.

[0100] There figure 3 illustrates different stages of the process according to a second implementation method.

[0101] Certain steps, particularly steps a ( figure 3a ), b ( figure 3b ), c2.1-c2.2-c2.3 ( figure 3c ), d ( figure 3d ), e ( figure 3e ), i ( figure 3i ) and following, are identical or similar to those already described previously and will not be detailed again.

[0102] Note that in this example the oxide layer 40 from step b) is not pre-etched in order to create an etching sub-mask 44, as described previously in connection with steps c1.1), c1.2), c1.3), c1.4. This nevertheless constitutes a possible variant.

[0103] As in the first implementation method described with reference to the figure 1, the edges 12 of the primary engraving are protected during the secondary engraving.

[0104] There is no protective oxide layer here, as in the first mode, but an 80 polymer protective layer, in particular parylene or a resin such as photosensitive resin, for example Su-8.

[0105] The application of the protective layer 80 can be done, depending on the material used, by spraying, printing, pattern transfer, vapor deposition (PVD), or any other suitable technique.

[0106] In the illustrated example, the protective layer 80 is a photosensitive resin, which completely fills the primary etching cavities 11 and also covers the entire first side 101 of the substrate 100. Therefore, by choosing a photosensitive resin as the protective material from the outset, and by coating the first side 101 with this resin, the secondary etching mask can be directly created in this resin 80: using photolithography with a mask M3, at least one opening 82 is formed in the protective layer 80, at least one edge of which delimits the secondary area (step g1). Then, if, as in the illustrated example, no sub-mask has been previously prepared, the underlying oxide is etched through this opening (step g2).

[0107] As an alternative, particularly in a case where the protective layer 80 does not cover the first side 101 of the substrate 100, the process could include, instead of step g), a step h) for creating a mask for the etching in step i) in addition to the protective layer 80 deposited on at least one edge 12 of the primary etch. In this case, step h) may include the following substeps, in this order: h1) a layer of photosensitive resin is deposited on the first side of the substrate, h2) by photolithography, at least one opening is formed in said resin layer, at least one edge of which delimits the secondary zone, h3) optionally, the underlying oxide is etched through said opening.

[0108] During the secondary etching step i), the useful layer 10 is etched onto the intermediate thickness e' while the primary etching edges 12 remain protected by the protective layer 80.

[0109] The protective layer 80 can be removed in a subsequent step j).

[0110] There figure 4 schematically illustrates a third method of implementing the invention.

[0111] Here again, certain steps, in particular steps a, b, c1, c2, d, e and i and following, are identical or similar to those already described previously in connection with the first mode and will not be detailed again.

[0112] It should be noted, however, that in this example the oxide layer 40 from step b) is pre-etched so as to form an etching sub-mask 44, as described previously in connection with steps c1.1) to c1.4) of the first implementation method.

[0113] This third implementation differs from the previous two in that no protective layer is actively formed on the edges of the primary etch 12 after this first etching step. The protection of the etch edges 12 is inherent to the primary etch, which is a deep reactive ion etch (DRIE).

[0114] As is well known, the DRIE etching process alternates between phases of silicon etching using a fluorinated gas (SF6) and phases of passivation of the etched edges using a fluorocarbon-based gas (C4F8, C2F6, CF4, or CHF3-Ar). During each passivation step, a thin fluorine-type layer, called the passivation layer, 90, is deposited on the edges 12 and the bottom 13 of the etching cavity 11. During the next etching operation, the passivation layer 90 present on the bottom 13 of the etching cavity 11 is destroyed by ion bombardment, but it is preserved on the edges 12. By repeating etching and passivation cycles, a deep etch with vertical edges is eventually achieved, with the edges 12 protected by the accumulation of successive passivation layers formed during the cycles.

[0115] In this third implementation, the passivation layer 90 formed on the edges 12 of the primary etch is preserved, remaining in place during the secondary etch. This preservation requires specific measures, particularly during the removal of the primary etch mask 64 (step e). Indeed, a photosensitive resin of the type conventionally used for the primary etch mask 64 is generally removed either chemically, notably with a liquid spray, or by multidirectional plasma. These methods simultaneously remove the passivation layer. To preserve the passivation layer 90, the photosensitive resin layer 60 forming the primary etch mask 64 is removed here by directional plasma, in other words, by ion bombardment 92 directed towards the first side 101 of the substrate 100 and in the transverse direction Z of said substrate.To preserve the oxide and silicon, a directional oxygen plasma will be advantageously used.

[0116] This removal step can be done in the DRIE etcher used for primary and secondary etching, since this type of machine allows ionic orientation, unlike conventional plasma machines in which the bombardment is intentionally in all directions to attack all faces of the treated substrate.

[0117] Once the primary etching mask 64 has been eliminated, the secondary etching of step i) is carried out through the sub-etching mask 44, the edges 12 of the primary etching being protected by the passivation layer 90.

[0118] The rest of the process can then be continued in a similar manner to the two embodiments described above.

Claims

1. Method for manufacturing at least one watch component (1), comprising at least the following steps: a) a substrate (100) is provided having a first side (101) and a second side (102) opposite in a transverse direction (Z), said substrate comprising a useful layer (10) of silicon, d) through the first side (101) of the substrate (100), a so-called primary etching is made of at least one primary zone (A) of said useful layer (10), so as to form at least one edge of a first level (I) of the component (1), and i) through the first side (101) of the substrate (100), a so-called secondary etching is made of at least one secondary zone (B) of the useful layer (10), so as to form at least one edge of a second level (II) of the component (1).

2. A method according to claim 1, wherein the remaining thickness of silicon after etching is different on the primary zone and on the secondary zone.

3. Method according to claim 1 or 2, wherein in one of the primary and secondary etching the useful layer is etched over its entire thickness and in the other of the primary and secondary etching the useful layer is etched over an intermediate thickness strictly less than its total thickness.

4. A method according to any one of claims 1 to 3, wherein the primary etching and / or secondary etching is a deep reactive ion etching.

5. A method according to any one of claims 1 to 4, wherein the substrate (100) of step a) comprises the useful silicon layer (10), an intermediate oxide layer (30) and a stiffening layer (20) superimposed in that order between the first side (101) and the second side (102).

6. Method according to claim 5, further comprising, after steps a), d) and i), a step I) in which the intermediate layer (30) of the substrate (100) is removed at least with respect to said watch component (1).

7. A method according to any one of claims 1 to 6, wherein, in a step b) prior to step d), an oxide layer (40) is formed on the first side (101) of the substrate (100).

8. Method according to any one of claims 1 to 7, comprising, prior to step d), a step c2) of producing a primary etching mask having at least one opening (62) delimiting the primary area (A).

9. Method according to claim 8, further comprising, prior to step c2), a step c1) in which the oxide layer (40) previously formed on the first side (101) of the substrate (100) is etched to form at least one opening (42) covering and / or delimiting the secondary zone (B).

10. Method according to claim 8 or 9, further comprising, after step d) and before step i), in particular after step d) and before any possible step f), a step e) of resin removal on the first side (101) of the substrate (100).

11. A method according to any one of claims 1 to 10, wherein the secondary etching step i) is carried out while retaining as protection of at least one edge of the first level (I) the passivation layer of the edges of the primary etching of step d).

12. Method according to claims 10 and 11, wherein step e) of resin removal is carried out by directional plasma.

13. A method according to any one of claims 1 to 10, comprising, between steps d) and i), at least one step f) in which at least one edge of the first level etched in step d) is treated for its protection against secondary etching in step i).

14. Method according to claim 13, wherein, in step f), at least one edge of the first level is covered with a protective layer (70, 80).

15. Method according to claim 14, wherein the protective layer (80) is a polymer layer.

16. Method according to claim 14, wherein the protective layer (70) is an oxide layer, in particular silicon oxide.

17. Method according to claim 16, wherein the protective layer (70, 80) has a thickness of less than 300 nm, preferably less than 200 nm, more preferably less than 150 nm.

18. A method according to any one of claims 14 to 17, wherein, in step f), the etching cavities (11) from step d) are completely filled with the protective layer (80).

19. A method according to any one of claims 14 to 18, wherein in step f) the first side (101) of the substrate (100) is also covered with the protective layer (70, 80), and then, in a step g), a mask for the etching of step i) is made in said protective layer (80).

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