Method for manufacturing a timepiece component

Abstract

The present invention relates to a method for manufacturing at least one watch component (1), in which a substrate (100) comprising a useful silicon layer (10) is provided, and cavities are etched into this useful layer (10) from a first side (101) of the substrate (100) in at least two distinct areas (A, B). The etching is a deep reactive etching performed simultaneously on the different areas (A, B), with a different nominal cavity width in each area. The etching is stopped after a chosen time t such that at least one area, referred to as the primary area (A), is etched to the full thickness (e) of said useful layer (10), while at least one other area, referred to as the secondary area (B), is etched to an intermediate thickness (e') strictly less than the full thickness (e) of the useful layer (10).

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] Certain applications in the field of watchmaking require the use of complex components. A complex component may, for example, include one or more blind cavities, intended to lighten its structure and / or reduce its inertia and / or create mechanical functions.

[0003] Also, in recent years, silicon has started to be used for the manufacture of watch components.

[0004] Techniques have therefore also been developed to enable the manufacture of complex silicon components.

[0005] Multilevel components are a type of complex silicon component. For example, a manufacturing process for multilevel watch components is described in the applicant's patent application EP 4 283 408. According to this process, a monolithic silicon wafer is etched on one side, then the etched side is coated with an etching stop layer, and finally, the wafer is etched on its other side, at least locally down to the stop layer.

[0006] But this process remains relatively complex. Summary of the invention

[0007] 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.

[0008] To this end, the invention relates to a method for manufacturing at least one watch component, comprising 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) cavities are etched in said useful layer, from the first side of the substrate, on at least two distinct areas, the etching being a deep reactive ion etching carried out simultaneously on said at least two areas, with a different nominal cavity width on each area, and said etching is stopped after a time t chosen such that at the end of this time t at least one area called the main area is etched over the total thickness of said useful layer while at least one other area called the secondary area is etched over an intermediate thickness strictly less than the total thickness of the useful layer.

[0009] Steps a) and d) are typically carried out in this order, with possible interposition of other complementary steps.

[0010] 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.

[0011] 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, dials, spirals or even elements with flexible blade(s).

[0012] 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.

[0013] The process according to the invention allows the manufacture of a watch component with at least two levels, in other words, a component delimited transversely by an upper face, a lower face, and at least one intermediate surface between said upper and lower faces. At each secondary zone, the component has a thickness equal to the difference between the total thickness of the usable layer and the intermediate thickness etched on said zone.

[0014] A component obtained by the process according to the invention is, for example, provided with one or more blind cavities of any shape. The bottom surface of such a cavity is an intermediate surface as defined above.

[0015] The process according to the invention makes it possible to form different levels of the component, or at least parts of these different levels, during the same step d) of etching.

[0016] Step d) can form all or part of the watch component. In other words, at the end of step d), the component(s) may be fully formed, with its at least two levels, or the process may include additional steps before or after step d), intended to complete the formation of the component.

[0017] In step d), the usable layer can be etched to form the component directly with its target final dimensions. Alternatively, the usable layer can be etched to form the component with dimensions larger than these target final dimensions. This alternative is particularly advantageous when at least one oxidation-deoxidation sequence of the component or the substrate carrying said component is planned after etching.

[0018] The etching technique used in step d) is a deep reactive ion etching, also known as DRIE (Deep Reactive Ion Etching). It has been observed that with this method, the etch width also impacts the etch speed. In other words, the wider the etched area, the faster the etch will progress. The process exploits this phenomenon to control the etch advance in distinct areas of the substrate and thus manage the etched thicknesses to form the multi-layered component.

[0019] Throughout this application, the nominal width of an area, sub-area, or cavity means its smallest dimension measured in a plane orthogonal to the transverse direction corresponding to the direction of the engraving and, in that plane, generally in a direction orthogonal to the direction of extension of the cavity, in the case of an elongated area. It is typically a diameter in the case of a circular area or the band width when the cavity has a band shape.

[0020] The engraving in step d) is preferably a continuous step, in the sense that it is carried out in one go, without resuming.

[0021] The duration t of step d) can either be defined in advance, in particular by calculation or empirically, or during the engraving, by continuous monitoring of the progress of the engraving and stopping when the desired result is obtained.

[0022] The primary and secondary zones are areas of the useful layer to be released over at least part of the thickness of said layer.

[0023] A main zone can delimit at least a first level of the watch component.

[0024] A secondary zone can define at least a second level of the watch component. It can typically define a blind cavity of a component.

[0025] The component can also have more than two levels. For this, the nominal widths of the cavities etched on different secondary areas can be adapted appropriately so that in step d) at least two secondary areas are etched on different intermediate thicknesses.

[0026] As an example, at least one principal area can define an outer edge of the watch component. For instance, a principal area can form a continuous groove defining a closed contour. In this case, and if this area defines an outer edge of the component, the component has a finite contour. In other words, in a direction orthogonal to the transverse direction, each watch component is externally bounded by a lateral face forming a continuous, closed contour. In another case, a principal area can correspond to the outer edge of the component except for an unetched portion called a lug, which connects the part to the rest of the working layer. This case corresponds to the situation where it is desirable to release a wafer carrying the watch components rather than individual components.Note that it is also possible to make the said attachment with a lower height than the thickness of the useful layer by providing a secondary area inducing a partial engraving at the desired location for this attachment.

[0027] According to one example, at least one main area can also define a through cavity of the component.

[0028] The primary and secondary zones may be disjoint or at least one primary zone and one secondary zone may be contiguous.

[0029] The dimensions of the secondary zone(s) are not limited. In particular, a secondary zone can be large enough to form a functional part of the component on its own. For example, the depth of cavities etched on a secondary zone can be at least 50 microns.

[0030] As an alternative or complement, a plurality of adjacent secondary zones of very small dimensions can be incorporated to create a textured surface on one face of the component. In this case, the depth of the cavities etched in step d) can, for example, be between 5 and 10 microns.

[0031] Depending on the specific arrangement, a primary and / or secondary zone may be circular or square. It may also be a band of substantially constant width, meaning a width varying by a maximum of 10%, preferably a maximum of 5%, along its entire length. Such a band may have any suitable contour but is typically straight or curved. For example, it may be in the form of a ring or loop with a circular or toothed profile. All the aforementioned shapes are considered in a plane orthogonal to the transverse direction corresponding to the engraving direction.

[0032] A primary and / or secondary zone can also have a completely random shape.

[0033] According to a particular embodiment of the invention, in step d), at least one primary or secondary area can be engraved over only a portion of its extent so as to retain at least one residual protrusion on said area, and the process can then include an additional step e) in which said residual protrusion is removed. This two-step process makes it possible to control the engraving depth even on areas that do not have a constant width. The engraved cavities then have a constant nominal width and are therefore engraved to the same depth. The residual protrusions are removed in a second step to completely free the area.

[0034] In this application, a sub-area shall be defined as a portion of an area to be freed that is etched during step (d) of etching and whose extent is strictly smaller than the entire area. The etched cavity on this sub-area shall be referred to as a temporary cavity. The residual portion of this area shall be referred to as a residual protrusion.

[0035] For example, one can engrave at least one temporary cavity forming a regular or irregular pattern and / or a network, for example a spiral or a grid, and delimiting the residual protrusion(s).

[0036] To ensure a regular edge, one can also engrave at least one temporary peripheral cavity, one edge of which forms a continuous contour closed on itself, externally delimiting the area.

[0037] Step e) of removing protrusions may include at least thermal oxidation and deoxidation of the substrate.

[0038] According to one example, the process may include, prior to step e), a step e0) of determining the thickness of silicon to be removed during the oxidation of step e) as a function of the width of the protrusions.

[0039] As an alternative or in addition, at step d), at least one primary or secondary area can be etched across its entire extent. In this case, the etching cavity extends over the entire area to be cleared.

[0040] According to one example, the substrate in step a) can be a bulk substrate, in the form of a single monolithic silicon layer (useful layer).

[0041] 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-Insulator (SOI) substrate, has the advantage that the etch 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. Furthermore, the use of an SOI substrate with an integrated arrest layer, reinforced by its stiffening layer, allows for good etch quality. 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 a stop layer, can notably be made of silicon dioxide.

[0042] The substrate, whether solid or SOI type, is a generally thin and flat element, having two main sides opposed to each other in a transverse direction corresponding to the direction of its thickness and the direction in which it is engraved during the process.

[0043] As an example, the process includes, prior to step d), a step c) in which a mask is prepared on the first side of the substrate for etching each primary and secondary area. This mask is generally made with a photosensitive resin using a photolithography process.

[0044] According to one example, the process further includes, prior to step d), and where appropriate prior to step c), a step b) in which an oxide layer is formed on at least the first side of the substrate. The substrate is, for example, thermally oxidized.

[0045] According to one example, step c) includes the following substeps, generally in this order: The first side of the substrate, possibly previously coated with oxide, is covered with a layer of photosensitive resin. By photolithography, at least one opening corresponding to at least one main zone and at least one opening corresponding to at least one secondary zone are formed in said resin layer. Optionally, the oxide layer resulting from step b) is etched through said openings, and the useful layer is etched through said openings.

[0046] According to one example, the duration of the engraving in step d) is adjusted according to the desired intermediate thickness.

[0047] The process may further include, after step d), a step f) of releasing at least one fabricated component. For this purpose, in the case of a SOI substrate, the intermediate layer of the substrate is removed at least opposite the component, for example by vapor-phase etching, in particular by hydrofluoric acid vapor etching. In the case of a bulk substrate, a stop layer of etching produced prior to step d) on the second side of the substrate is removed, at least opposite the component. This step f) results in releasing either an individual component when it has been etched without a support, or a wafer bearing the component when it has been etched with a support.

[0048] In the case where the areas have been etched over only part of their extent during step d), and if the process further includes a step e) of removing residual protrusions resulting from step d), then step f) can either be an additional step carried out after step e), or constitute the deoxidation substep of step e).

[0049] At the end of step d), and where applicable step e) and / or f), a step g) can still be carried out at least once, comprising oxidation and deoxidation of the component.

[0050] And the process may further include, at the end of step d), and where appropriate step e) and / or f) and / or g), a final oxidation step h) of the component.

[0051] When it is a wafer that has been released in step f), the process may further include a final step i) of detaching the components of said wafer. Brief description of the drawings

[0052] The features and advantages of the present invention will become apparent in more detail in the following description, with an illustrative and non-limiting example given by reference to the accompanying drawings where: THE Figures 1A to 1G illustrate different stages of the process according to one implementation method of the invention, the figure 2 is a top view along direction D of the figure 1D , there figure 3 illustrates an example of a part obtained using the process according to the invention, the Figures 4 and 5 illustrate a second method of implementing the invention, where the figure 4 illustrates the usable layer of a substrate after step d) of etching, showing temporary etching cavities and residual protrusions on two secondary areas, and the figure 5 illustrates the two secondary zones after the removal of residual protrusions, the figure 6illustrates a possible distribution of temporary cavities and residual protrusions for the formation of a component comprising a randomly shaped opening. Detailed description

[0053] The process according to the invention allows in particular the manufacture of a component or a plurality of components in silicon at at least two levels in a silicon layer called herein the useful layer.

[0054] THE figures 1G And 3 illustrate as an example a two-level component 1 that can be manufactured using this process.

[0055] Component 1 is delimited, in a transverse direction Z', by a parallel upper face 2 and lower face 3, separated by a distance e corresponding to the total thickness of component 1. The component has an external edge 4, here with a circular cross-section of diameter d1, and a blind cavity 5, here also with a circular cross-section but of diameter d2, opening onto the upper face 2 and delimited by an edge 6 (internal edge of the component) and a bottom 7. The cavity 5 being blind, its depth e' is less than the total thickness e.

[0056] A first level I of component 1 is delimited between the lower face 3 of component 1 and a plane P parallel to this lower face 3 and including the bottom 7 of the blind cavity 5.

[0057] A second level II is delimited between this same plane P and the upper face 2 of component 1.

[0058] THE Figures 1A to 1Gillustrate one method of implementing the process according to the invention, for manufacturing a component 1 as illustrated in the figure 3 and described above. The figure 2 is a top view along direction D of the figure 1D .

[0059] 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.

[0060] In step a) of the process illustrated on the Figure 1A , we provide a substrate 100 comprising a useful layer 10 of silicon.

[0061] The substrate 100 is generally thin and flat, and extends, 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.

[0062] In the illustrated example, substrate 100 is a SOI (Silicon On Insulator) substrate which, in addition to the 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 an SOI substrate 100 is advantageous for several reasons: the etching stop layer is integrated into the substrate, thus eliminating the need for an additional step of preparing a dedicated stop layer. Furthermore, the stiffening layer prevents substrate deformation that could adversely affect the shape and strength of the formed watch components.

[0063] 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.

[0064] The thickness e1 of the useful layer 10 of the substrate 100 determines the total thickness e of component 1 (in particular, e can be equal to e1 in the absence of thermal oxidation operations as described below). The thickness e1 can, for example, be between 50 and 500 µm.

[0065] The stiffening layer 20 is generally thicker than the useful layer.

[0066] 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).

[0067] In step b) illustrated on the figure 1BAn oxide layer 40 is formed at least on the first side 101 of the substrate 100, for example by thermal oxidation, generally in a furnace heated to a temperature typically around 1000°C. The thickness of the oxide layer 40 formed around the substrate is typically between 0.5 and 4 microns. Note that thermal oxidation slightly reduces the silicon thickness of the useful layer 10, as silicon dioxide is formed at the expense of silicon (the thickness of the useful layer decreases from e1 to e, as can be seen in the Figures 1A and 1B ).

[0068] In step c) illustrated on the figure 1C , we then prepare on the first side 101 of the substrate 100 an etching mask 50 for the etching of a main area A, part of whose contour corresponds to the outer edge 4 of the component 1, and of a secondary area B, whose contour corresponds to the inner edge 6 of the component 1.

[0069] As illustrated in particular on the figure 2which shows the substrate with its etching mask 50 in top view, the main area A forms a continuous band defining a closed contour. The component 1 delimited externally by this area A therefore has a finite contour.

[0070] Alternatively, the main zone A could also have a discontinuity. In this case, component 1 would remain connected to the rest of the useful layer by a bond formed at this discontinuity.

[0071] The etching mask 50 is made by covering the first side of the substrate with a layer of photosensitive resin 52. Then by photolithography using a photomask M (generally made of quartz), openings 54 delimiting the main areas A and secondary areas B are formed in this layer of resin 52.

[0072] In the presence of an oxide layer 40 formed during a prior step b), this layer 40 is also etched through the resin mask 50 ( figure 1D ).

[0073] The 54 openings, delimiting zones A and B already described previously, are more clearly visible on the figure 2 .

[0074] Step d) of etching is then carried out through the openings of the etching mask 50 and – where applicable – the oxide layer 40 from step b). This step is visible on the Figures 1E and 1F .

[0075] The etching is a deep reactive ion etching (also called DRIE for Deep Reactive Ion Etching).

[0076] The main area A and secondary area B are engraved simultaneously, over their entire extent, for a given period of time t.

[0077] The duration t of the deep reactive ion etching operation is such that at the end of the etching, the useful layer 10 is etched over its entire thickness e at the main zone A so as to form a cavity CA, and is etched over an intermediate thickness e' less than the total thickness e of the layer 10 at the secondary zone B, so as to form a cavity CB which will correspond to the blind cavity 5. The intermediate thickness e' therefore corresponds to the desired depth for this blind cavity 5.

[0078] The width l2 of cavity 5, in other words its diameter d2, as well as its depth, are parameters of the component determined during its design. The etching time will therefore depend on the width l2=d2 and the depth e'.

[0079] The duration t is either determined in advance, notably by calculation or empirically, or during the engraving, by continuous monitoring of the progress and stopping when the desired result is obtained.

[0080] Conversely, the width l1 of the main zone was chosen based on the width l2 of the cavity 5 and the desired depth e', so that, in the time t required to etch the cavity 5 to an intermediate thickness e', the main zone A is etched to the entire thickness e of the useful layer 10. The main zone A here has an annular or substantially annular shape whose inner contour externally delimits the component 1. The width l1 of the main zone A therefore has no impact on the final shape of the component 1.

[0081] In a step c') not shown, the photosensitive resin 52 used for the etching mask 50 is removed from the first side 101 of the substrate, for example by multidirectional ion bombardment with oxygen plasma or chemically.

[0082] Then in a step f), the substrate 100 is deoxidized, typically with acid (usually hydrofluoric acid) in the vapor phase, so as to remove the intermediate layer 30 at least opposite the watch components and, in the example, also the oxide layer 40 from step b).

[0083] In the illustrated case of etched components 1 without attachment, deoxidation leads to the release of individual components ( figure 1G ).

[0084] In the case of components 1 etched with attachment, deoxidation would result in the release of a wafer, comprising all or part of the useful layer 10 of the substrate 100 and carrying the components 1.

[0085] The process may still include at least one additional sequence g) of thermal oxidation followed by deoxidation of the wafer or of the component(s) 1.

[0086] The process may further include, at the end of step f), and where applicable step g), a final oxidation step h of the component(s) 1 (where applicable on their wafer).

[0087] And finally, in the case of a wafer, the process may include a step i) in which the components 1 are detached from their wafer.

[0088] THE Figures 4 and 5 illustrate another embodiment of the invention, allowing the engraving depth to be adjusted as needed, independently of the width of each zone B1, B2 to be freed (each of which can be either a primary or secondary zone).

[0089] Here, each zone B1, B2 is not engraved over its entire extent, as in the implementation method of figures 1 to 3but on a sub-zone respectively S1, S2 which only covers part of its extent. An etching cavity called a temporary cavity C1, C2 is made on each sub-zone S1, S2 by DRIE type etching, retaining several residual protrusions R1, R2 on the rest of the zone. In a subsequent step e) of the process, these residual protrusions are removed to completely free each zone B1, B2 (to the depth etched during step d) of etching).

[0090] On the figure 5 Two zones, B1 and B2, were thus represented, to be etched into a useful layer 10 of a substrate 100, which could be of the same type as that described previously. The first zone, B1, is narrower than the second, B2, but must be etched to a greater depth e1' than the etching depth e2' of zone B2. Such a result cannot be obtained with an implementation method as described previously in connection with the figures 1 to 3 .

[0091] Each zone to be freed B1, B2 is therefore subdivided into one or more sub-zones to be engraved S1, S2 and one or more unengraved sub-zones T1, T2.

[0092] The nominal widths L1 and L2 of the sub-areas S1 and S2 to be engraved are selected for each zone B1 and B2, based on the desired final engraving depths in both zones. Specifically, the nominal width L1 of the sub-area S1 to be engraved in zone B1 (which must have a greater depth) is greater than that L2 in zone B2. Therefore, the nominal engraving width in a given zone is independent of the total width of that zone.

[0093] The width of the residual sub-zones T1 and T2 may differ across the different zones. However, for reasons that will be detailed later, it is advantageous for these residual sub-zones T1 and T2 to be of the same shape and dimensions (orthogonally to the transverse direction) across all zones. They may, in particular, have a square cross-section as in the illustrated example, or a round, rectangular, or any other suitable shape.

[0094] Each sub-zone to be engraved, S1 and S2, forms, in this example, a regular, grid-like pattern. This example is not exhaustive, however, and each zone could include several separate sub-zones. Furthermore, the sub-zones, whether separate or not, could form an irregular pattern or a regular pattern of a different shape, for example, a spiral.

[0095] During the etching step (step d), the sub-zones to be etched S1, S2 are etched by DRIE etching, so as to form so-called temporary cavities C1, C2 with dimensions corresponding to the said sub-zones S1, S2.

[0096] The unengraved areas T1, T2, delimited by these temporary cavities C1, C2, form the residual projections R1, R2 typically taking the form of ribs or spikes.

[0097] There figure 4 illustrates the useful layer 10 at the end of step d) of etching, showing the temporary etching cavities C1, C2 and the residual protrusions R1, R2.

[0098] The process then includes an additional step e) aimed at eliminating these residual protrusions.

[0099] This step e) typically includes at least one thermal oxidation of substrate 100, carried out in a thermal oxidation furnace, and a deoxidation of substrate 100.

[0100] As is well known, the thermal oxidation of silicon leads to the formation of silicon dioxide at the expense of silicon. The silicon front retreats to create a new interface with the silicon dioxide. During deoxidation, the interface between the silicon and the silicon dioxide then becomes the new outer surface of the component.

[0101] Thus, by adjusting the thickness of silicon to be removed during oxidation so that it corresponds at least to the minimum half-width of the protrusions R1, R2, it is possible to eliminate these by oxidation.

[0102] Silicon shrinkage during oxidation is advantageously taken into account upstream of etching (d), to define the etching depth and the dimensions of the etched component. In particular, it can be advantageous, during step (d), to form the component with dimensions larger than the final target dimensions for said component (in width and / or in the thickness direction).

[0103] Note that the deoxidation of step e) can allow the release from the substrate of a wafer carrying the components or individual components, depending on whether these have been etched or not with a fastener.

[0104] There figure 6 illustrates a possible distribution of temporary cavities C and residual protrusions R for the formation of a randomly shaped cavity in a component.

[0105] As in the previous example, one or more temporary cavities C of nominal width L are engraved, delimiting residual projections R of identical dimensions, here in the form of pillars with a square section.

[0106] To ensure a regular internal edge for the component cavity, it is advantageous, during step d), to etch a temporary peripheral cavity CP whose edge forms a continuous contour closed on itself, externally delimiting the area to be freed.

[0107] The removal of residual protrusions R is carried out using the same method as described previously in connection with the Figures 4 and 5 .

Claims

1. A method for manufacturing at least one watch component (1), comprising the steps: a) providing a substrate (100) 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) etching cavities (CA, CB, C1, C2, C, CP) in said useful layer (10), from the first side (101) of the substrate (100), on at least two distinct areas (A, B, B1, B2), the etching being a deep reactive etching carried out simultaneously on said at least two areas (A, B, B1, B2), with a different nominal width (l1, l2, L1, L2, L) of the cavities on each area,and we stop said engraving after a chosen time t such that at the end of this time t at least one area called the main zone (A) is engraved over the total thickness (e) of said useful layer (10) while at least another area called the secondary zone (B) is engraved over an intermediate thickness (e') strictly less than the total thickness (e) of the useful layer (10).

2. Method according to claim 1, wherein at least one principal area (A) delimits an outer edge (4) of the component (1).

3. Method according to claim 1 or 2, wherein at least one principal area (A) delimits a through hole of the component (1).

4. Method according to any one of claims 1 to 3, wherein at least one secondary zone (B) delimits a blind cavity of the component (1).

5. A method according to any one of claims 1 to 4, wherein in step d), at least one primary or secondary area (A, B, B1, B2) is engraved over only part of its extent so as to retain on said area at least one residual protrusion (R, R1, R2), and the method comprises an additional step e) in which said residual protrusion (R, R1, R2) is eliminated.

6. A process according to claim 5, wherein step e) comprises thermal oxidation and deoxidation of the substrate (100).

7. Method according to claim 6, comprising, prior to step e), a step e0) of determining the thickness of silicon to be removed during the oxidation of step e) as a function of the width of the residual protrusions (R, R1, R2).

8. A method according to any one of claims 5 to 7, wherein in step d), at least one provisional cavity (C1, C2, C) is engraved forming a regular or irregular pattern and / or a grid, for example a spiral or a grid, and delimiting the residual protrusion(s).

9. A method according to any one of claims 5 to 8, wherein in step d), at least one peripheral temporary cavity (CP) is engraved, one edge of which forms a continuous contour closed on itself externally delimiting the zone.

10. A method according to any one of claims 1 to 9, wherein in step d), at least one primary or secondary area (A, B) is engraved over its entire extent.

11. A method according to any one of claims 1 to 10, wherein one or each primary (A) or secondary (B) zone has a circular or square shape or a band shape of substantially constant width.

12. A method according to any one of claims 1 to 11, wherein the duration t is adjusted according to the desired intermediate thickness(es) (e', e1', e2').

13. A method according to any one of claims 1 to 12, wherein the duration t is determined before step d), in particular by calculation or empirically.

14. A method according to any one of claims 1 to 13, further comprising, prior to step d), a step c) in which a mask (50) is prepared for the engraving of each primary (A) and secondary (B) area.

15. A method according to any one of claims 1 to 14, wherein the substrate of step a) comprises said useful layer (10), an intermediate layer (30) of oxide and a stiffening layer (20) superimposed in the transverse direction (Z), between the first (101) and the second side (102) of the substrate (100).

16. Method according to claim 15, further comprising, after step d), a step f) in which the intermediate layer (30) of the substrate (100) is removed at least with respect to said watch component (1).

17. A method according to any one of claims 1 to 16, wherein in step d), the useful layer for forming the component is etched with dimensions greater than the final target dimensions for said component.

18. A method according to any one of claims 1 to 17, wherein the depth of the cavities etched on a secondary area is at least equal to 50 microns.

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