Method for manufacturing a timepiece component

Abstract

The present invention relates to a method for manufacturing at least one watch component, in which, on a first side of a monolithic silicon wafer (100), a first primary etching mask (200) is made and then the wafer (100) is etched through the first mask (200) to form the edges of a first level of the component; at least one stop layer (400) is made on the first etched side (101) of the wafer (100); On the second side of the wafer (102) opposite to the first side (101), a second secondary etching mask (300) is made and then the wafer (100) is etched through this second mask (300) to form the edges of a second level of the component, the secondary etching reaching at least locally the stop layer.

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, certain applications require the use of complex components necessitating the assembly of several separately manufactured elements. This is the case, for example, with anchors, in which the tang is assembled onto and surmounts the fork designed to cooperate with a regulating organ of a watch mechanism.

[0003] 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.

[0004] A few years ago, new materials, including silicon, began to be used for the manufacture of watch components.

[0005] A majority of watch components produced today are made from a SOI type substrate comprising a first silicon-based layer in which the components must be formed, a second layer called "support" also silicon-based and used to stiffen the substrate and, between these two layers, an intermediate layer also called "stop layer", made of silicon oxide.

[0006] The components are etched from the first layer by deep ion reactive etching (DRIE) through a photosensitive resin mask formed by photolithography on said first layer. Since the stop layer behind the first layer is less sensitive to etching, it is not etched, or only very slightly, during DRIE etching. The substrate and stop layer are then locally removed, or completely removed, by chemical etching, thus releasing a wafer from the first layer of the substrate bearing the components or component parts.

[0007] Silicon is a brittle material, making it difficult to use the previously mentioned press-fit assembly method. This method is particularly unsuitable for the industrial production of silicon components, as the proportion of components broken during assembly and subsequently discarded remains too high.

[0008] Therefore, there is still a need to improve the manufacturing process for complex silicon components. Summary of the invention

[0009] One aim of the present invention is to propose a method for manufacturing a silicon watch component, which makes it possible to overcome the disadvantages of the aforementioned prior art and which can in particular be implemented on an industrial scale.

[0010] According to a first aspect, the invention relates to a method for manufacturing at least one watch component, said method comprising at least the following steps: Provide a monolithic silicon wafer. On one side of the wafer, create a first primary etch mask with at least one opening. Etch the wafer through said at least one opening of the first primary etch mask to form the edges of a first level of the component, the target depth of primary etch being such that said primary etch does not pass through the wafer. Create at least one stop layer on the first etched side of the wafer. On the second side of the wafer opposite the first side, create a second secondary etch mask with at least one opening. Etch the wafer through said at least one opening of the second mask to form the edges of a second level of the component, the target depth of secondary etch being such that at least locally said secondary etch reaches said at least one stop layer.

[0011] The process according to the invention makes it possible to produce one or more multilevel components in a simple way, by eliminating the prior art assembly step which, on the one hand, is laborious when it comes to manufacturing large series of components, and on the other hand, can prove complex due to the fragile nature of silicon.

[0012] The process allows for the rapid manufacture of a large number of components: Although the process aims to manufacture at least one component, in practice a plurality of components (identical or different) will generally be formed simultaneously in the same silicon wafer.

[0013] Since the resulting component is also monolithic, the problems of possible separation of the different levels are eliminated.

[0014] The process according to the invention can in particular, but not exclusively, be implemented for the manufacture of anchors or wheels or plates or needles or spirals or an element with flexible blade(s).

[0015] In this application, a complex or multilevel component is defined as a component on which it is possible to identify at least two parts superimposed in a so-called transverse direction (corresponding to the direction of the engraving which made it possible to form said component or to the direction of the thickness of the wafer in which the component is formed).

[0016] In a multi-level component according to the invention, the superimposed parts are layers or levels of a monolithic block. The boundaries between levels are therefore not physically marked, but these levels are defined as follows: Each level is defined between two boundary planes orthogonal to the transverse direction, each level has a constant thickness (within an engraving depth tolerance) in the transverse direction.

[0017] The resulting components can have only two levels. As a variant, they can also have an intermediate level between the first and second levels: in this case, the intermediate level has a common boundary plane with each of the other two levels.

[0018] In this application, the first and second sides of the plate are opposite each other in the transverse direction. The engraving on the first side of the plate is designated as the primary engraving, and that on the second side as the secondary engraving. More generally, the adjectives primary and secondary are used with reference to the first and second sides of the plate, respectively. Thus, a primary surface is oriented towards the first side of the plate, and a secondary surface is oriented towards its second side.

[0019] In this application, a primary or secondary surface of a component level extends in a plane orthogonal to the transverse direction. An edge is globally orthogonal to these primary and / or secondary surfaces (taking into account the inclination of the flanks resulting from the etching process).

[0020] Furthermore, the edges of the first and second levels refer to the edges of said levels, excluding any attachment zone retained to maintain a bond between the component and the rest of the wafer during manufacturing and which can be broken at the end of the process to release the component. This zone may be located on the first level, on the second level, or may extend across the entire thickness of the component and therefore across both levels, as long as it ultimately allows the component to be detached (for this, it should normally be on the outermost contour of the component).

[0021] In this application, monolithic means an element (in particular a wafer or component) made of a single material. In other words, a monolithic silicon wafer is a wafer made of a single material, namely silicon. Such a wafer is therefore a solid block, forming in particular a single layer of silicon.

[0022] To ensure good surface quality on both sides of the component, the wafer is preferably polished on both sides.

[0023] The monolithic silicon wafer is etched through the openings of a first primary etching mask on the first side and a second secondary etching mask on the second side of the wafer.

[0024] The primary and / or secondary etching is typically a deep reactive ion etching (DRIE).

[0025] The primary etching performed through at least one opening of the first mask is intended to form at least some edges, preferably all the edges, of the first level of the component(s). In some cases, it may also form some edges of an intermediate level, and / or a primary surface of the second level facing the first side of the wafer.

[0026] In other words, the cavity or cavities resulting from this primary engraving are at least partially delimited by what must be the edges of the first level and possibly some edges of an intermediate level and / or a primary surface of the second level.

[0027] In a specific example, the primary surface of the second level of the component, formed by primary etching, is, at least in a boundary area, delimited by an edge of the second level. The opening of the first mask covers this enlarged primary surface, at the boundary area, by a safety distance greater than 10 microns, preferably between 10 and 100 microns. Enlarging the opening of the first mask prevents the edge of the secondary etch—forming the edge of the second level—from coinciding with the edge of the primary etch. This safety distance ensures that the edge of the secondary etch, forming the edge of the second level, intersects the stop layer at the desired depth and prevents the formation of an undesirable material residue at this edge.

[0028] The secondary etching performed through at least one opening in the second mask is intended to form at least some edges, preferably the edges, of the second level of the component (or components). In some cases, it may also form some edges of an intermediate level, and / or a secondary surface of the first level facing the second side of the wafer.

[0029] In other words, the cavity or cavities resulting from this secondary engraving are at least partially delimited by what must be the edges of the second level and possibly some edges of an intermediate level and / or a secondary surface of the first level.

[0030] In a specific example, the secondary surface of the first level of the component, formed by secondary etching, is, at least in a boundary area, delimited by an edge of the first level. The opening of the second mask covers this enlarged secondary surface, at the boundary area, by a safety distance greater than 10 microns, preferably between 10 and 100 microns. Again, enlarging the opening to a safety distance prevents material residue from remaining at the edge of the secondary surface of the first level, thus preventing the component from detaching later and / or the secondary etching from damaging the first level of the component.

[0031] As an example, at least a portion of an opening in the first mask, or the second mask respectively, defining a contour of the first level, or the second level respectively, has a width between 20 and 200 microns, preferably constant. Since the inclination of the etching flanks depends on the width of the etched surface, it is preferable, to ensure that the inclination (relative to the transverse direction) of the edges or as many edges as possible of the component is constant, for the width of an etching border around a level of said component to be constant wherever possible.

[0032] Each mask can be made of a single layer or several layers of different materials. If a mask is made from or comprises several layers, these layers are not necessarily produced or deposited at the same stage of the process.

[0033] Furthermore, the secondary engraving mask can be created, in whole or in part, before or after the primary engraving.

[0034] The secondary etching mask can also be created either before or after the primary etching mask.

[0035] Furthermore, the secondary etching mask can be made before or after the deposition / creation of at least one stop layer, or be made in conjunction with such a stop layer.

[0036] To ensure alignment of the first and second levels, the first and second masks are referenced to each other. More specifically, the process may include, during the creation of one of the first and second masks, identifying the position of an existing etch on the opposite side and indexing the mask to be created to that position. For example, alignment marks are made on one side of the wafer and aligned with marks on a photolithography mask used for etching on the other side, possibly using a camera-based referencing system.

[0037] According to one example, the creation of the primary etching mask and / or the creation of the secondary etching mask includes the structuring by photolithography of a layer of resin deposited on the first side, respectively the second side, of the wafer, to form openings defining the edges of the first level, respectively the second level, of the component.

[0038] According to a first example of implementation, the resin layer can be deposited directly onto the silicon wafer (i.e. on the primary surface, respectively the secondary surface of the wafer).

[0039] As an alternative, it may be advantageous to first deposit a layer of silicon oxide on the first side, or the second side of the wafer, and then deposit the resin layer on top of this silicon oxide layer. In this case, the creation of the primary etching mask and / or the creation of the secondary etching mask may include: the deposition of a resin layer onto a previously prepared oxide layer on the first side, or the second side, of the wafer; the structuring of said resin layer by photolithography to form openings defining at least the edges of the first level of the component, or at least the second level; the opening of the oxide layer at said openings. and possibly the removal of the resin layer.

[0040] A layer of silicon oxide can be deposited onto the silicon wafer (notably by Physical Vapor Deposition) or obtained by silicon oxide growth (in other words, by thermal oxidation of the wafer). In the second case (silicon oxide growth), the oxidation, carried out in a thermal oxidation furnace, occurs equally over the entire wafer and, consequently, simultaneously on the first and second sides of the wafer.

[0041] In some embodiments, the process includes, after etching the wafer through the primary etching mask, oxidizing the wafer so that the oxide layer resulting from this oxidation forms a stop layer on the first etched side of the wafer, and then forming the secondary etching mask from said oxide layer on the second side of the wafer.

[0042] In this case, the process may specifically include, in this order: the creation of the first primary etching mask, possibly including the prior creation of an oxide layer on at least the first side of the wafer, advantageously by thermal oxidation of the wafer, the primary etching, where applicable, the removal of the silicon oxide as well as any resin resulting from the first mask creation step; the creation of the second secondary etching mask, including a prior oxidation of the wafer, and the creation of the secondary etching (the oxide layer serving as a stop layer for said secondary etching).

[0043] According to an advantageous arrangement, at least one additional stop layer can be made on the first etched side of the wafer, after the oxidation of the wafer: in this case, there are finally two stop layers on the first side at the time of secondary etching: an oxide layer and the additional stop layer.

[0044] At least one stop layer deposited or formed on the first side of the wafer conforms to the surfaces and parts of the component defined during the primary etching.

[0045] A stop layer is made of a material less sensitive to etching, especially DRIE etching, so that it is suitable for stopping secondary etching (while being itself little or not at all damaged) if it comes into contact with it.

[0046] The arrest layer prevents process gases from passing between the two sides of the wafer, which would lead to degradation of the etching.

[0047] According to one example, at least one arrest layer may include a silicon oxide layer and / or an aluminum layer and / or a parylene layer.

[0048] For example, it may include a layer of parylene with a thickness of between 1 and 5 microns and / or a layer of silicon oxide with a thickness of between 0.5 and 5 microns, and / or a layer of aluminum with a thickness of between 0.1 and 5 microns.

[0049] A single arrest layer can be used. Alternatively, several arrest layers can be deposited and / or formed so that they are superimposed on the first side of the wafer.

[0050] The target engraving depths on the first and second sides are the theoretically desired depths for the engraving. A skilled professional can determine, for example through calculation or empirically, the engraving time or number of engraving cycles (DRIE engraving being performed in successive stages / layers) to achieve these depths.

[0051] The effective etching depth at a given point may differ from the target depth when, during the etching time or the aforementioned sequence of etching cycles, the cavity or part of the etching cavity encounters the stop layer. Preferably, in cases where etching stops at the stop layer, a target depth greater than the effective depth should be chosen to avoid rounded etching edges.

[0052] According to the invention, the target depth of secondary etching is such that, at least locally, the secondary etching reaches the stop layer. The sum of the target depths of primary and secondary etching is at least equal to the wafer thickness (measured in the transverse direction).

[0053] According to one example, the sum of the target depths of primary and secondary etching is strictly greater than a thickness of the wafer (measured in the transverse direction), so as to guarantee the crossing of the primary and secondary etches.

[0054] The sum of the target depths of primary and secondary engraving is understood here as the sum of said depths in absolute value, without taking into account the direction of engraving.

[0055] According to one example, the sum of the first and second target etching depths is such that the component formed at the end of the secondary etching has, between the first and second level, an intermediate level some of whose edges are in continuation of edges of the first level and other edges are in continuation of edges of the second level.

[0056] According to one example, the process also includes, after secondary etching, the removal of the stop layer(s).

[0057] According to one example, the process further includes, after secondary etching and possibly the removal of the stop layer(s), at least one oxidation and deoxidation sequence of the wafer bearing at least one component, in order to smooth the surfaces of the component(s) and / or modify their dimensions.

[0058] According to one example, the process further includes, after secondary etching and possibly the removal of the stop layer and / or said at least one oxidation-deoxidation sequence, at least one oxidation (called final) of the wafer bearing the at least one component, in order to improve its mechanical characteristics.

[0059] According to one example, the process further comprises, after secondary etching and optionally removal of the stop layer and / or of said at least one oxidation-deoxidation sequence and / or of said final oxidation of the wafer, a step in which said at least one component is detached from the wafer.

[0060] According to a second aspect, the invention relates to a watch component, in particular obtained by implementing the process as defined above, in particular an anchor or a wheel or a plate or a hand or a spiral or an element with flexible blade(s), said component comprising at least a first level and a second level at least partially superimposed in a transverse direction of said component, and said component being a monolithic component. Brief description of the drawings

[0061] 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 which represent: There figure 1 is an overview of a watch component manufactured according to the invention, The figure 2 is a cross-sectional view along the component's symmetry plane P1, The figures 3a to 3jshow sectional views along P1 illustrating corresponding steps a to j of the process according to a particular implementation example, The figure 4 is a sectional view according to plane P2 illustrated on the figure 1 , following the engraving operations of the process, The figure 5 illustrates the first resin mask used for engraving the first side of the plaque, The figure 6 illustrates the second resin mask used for engraving the second side of the plaque.

[0062] There figure 1 represents a multilevel anchor 10 that can be manufactured by implementing the process according to the invention.

[0063] Such an anchor 10 is intended to equip an escapement of a clock movement (not shown). The illustrated anchor 10 includes a fixing part 30, pierced with a hole 37 intended to receive a pivot pin for the anchor (not shown).

[0064] In the example, the fixing part 30 has an overall T-shape with a central rod 30a and, at one end of said rod 30a, a head 30b extending substantially orthogonally to the rod 30a. The hole 37 is located here at the junction between the rod 30a and the head 30b.

[0065] The anchor 10 also includes two pallets 31, 32, connected to the mounting part 30, and designed to cooperate with an escape wheel (not shown). As illustrated, each pallet 31, 32 is respectively fixed to one end of the head 30b.

[0066] The anchor 10 further includes a fork 33 intended to cooperate with a regulating organ (not shown) of the movement, for example a balance wheel and hairspring. The base 33a of the fork 33 is connected to the fixing part 30, here at the end of the rod 30a opposite the head 30b.

[0067] The fork 33 comprises two horns 34, 35 delimiting between them a housing 36. The housing 36 is surmounted by a dart 20 integral with a dart support 21 surmounting the base 33a of the fork 33.

[0068] The aforementioned elements form a three-level assembly 11, 13, 12 superimposed in that order along a transverse direction Z, as illustrated on the figure 2 , which is a cross-sectional view according to plane P1.

[0069] For the remainder of this description, a first side 10a of the anchor 10 is defined as the side on which the dart 20 is located, in the transverse direction Z. The second side 10b is defined as the side opposite this first side.

[0070] Furthermore, in the following, a boundary plane, a surface or a primary part of an element or a level is located towards the first side of the anchor, in the transverse direction Z. A boundary plane, a surface or a secondary part of an element or a level is located towards the second side of the anchor, in the transverse direction Z.

[0071] Finally, a thickness or depth will be measured along the transverse direction Z, while a width will be measured in a plane orthogonal to said transverse direction Z.

[0072] A first level 11 of the anchor is delimited by the primary boundary planes PL1 and secondary boundary planes PL2 of the dart 20. The thickness of this first level 11 is the thickness of the dart 20, that is to say z1.

[0073] A second level 12 of the anchor is delimited by the primary boundary planes PL3 and secondary boundary planes PL4 of the fixing part 30, the pallets 31, 32 and the fork 33. The thickness of this second level 12 is z2.

[0074] In the example, the thickness z3 of the dart support 21 is greater than the thickness z1 of the dart 20. Furthermore, the primary surfaces of the dart 20 and the dart support 21 are defined in the same boundary plane PL1, while the secondary surfaces of the dart 20 and the dart support 21 are located in the plane PL2 and the plane PL3, respectively. The dart 20 is thus offset by a distance z4 equal to z3 - z1 from the fork 33, in the transverse direction Z of the anchor.

[0075] An intermediate level 13 of the anchor is thus delimited by the planes PL2 and PL3 and formed by the part 23 of the dart support 21, hereafter called secondary part of the dart support, of thickness z4.

[0076] The manufacturing steps of such an anchor 10, according to an example of implementation of the process according to the invention, will now be described with reference to figures 3a to 3j In practice, however, a plurality of 10 identical anchors and / or other components will generally be manufactured simultaneously (in the same wafer).

[0077] In step a) of the process, a monolithic silicon wafer 100 is supplied.

[0078] The wafer is advantageously made of monocrystalline silicon and doped, in particular phosphorus-doped. Advantageously, the silicon is doped to have a resistivity less than or equal to 0.1 Ω·cm⁻¹, for example, a resistivity of 0.05 Ω·cm⁻¹. Doped silicon, being electrically conductive, is more dimensionally stable and has better mechanical strength. Preferably, the silicon used has a {1,1,1} orientation. As an alternative, however, any suitable silicon may be used, in particular polycrystalline and / or undoped and / or with an orientation other than {1,1,1}.

[0079] The plate 100 has a primary surface 100a, which is flat, on a first side 101 and a secondary surface 100b, which is flat and parallel to the primary surface 100a, on its second side 102.

[0080] For the remainder, we define a transverse direction Z of the plate, orthogonal to the primary surface 100a and secondary surface 100b.

[0081] The primary and secondary surfaces 100a, 100b are preferably polished.

[0082] In a step b) of the process, on the first side 101 of the plate 100, a first primary engraving mask 200 is made, for each anchor to be manufactured, having at least one opening 210 such that a primary engraving made through this opening 210 forms the edges of the first level 11 of the anchor 10, part of the edges of the intermediate level 13, as well as the primary surface 12a of the second level 12.

[0083] In the example, the first engraving mask 200 has, for each anchor 10 to be manufactured, an opening 210. The figure 5 illustrates a portion of the first mask 200 including such an opening 210.

[0084] The primary engraving is intended to form the edges of the dart 20 and the dart support 21 which form the first level 11.

[0085] The mask 200 is therefore open to a first zone 211 having a border, here internal 2111, delimiting the contour of the first level 11. A width L1 of this first zone 211 is advantageously between 20 and 200 microns and preferably constant, to guarantee an adequate inclination of the etching flanks.

[0086] In the particular example considered, the primary engraving is also intended to form the primary surface 12a of the second level 12. For this purpose, the mask 200 is also open onto a second area 212 covering this planned primary surface of the second level 12 (delimited by dotted lines on the figure 5). For reasons which will be explained later, and as illustrated, the second zone 212 is advantageously wider than the said forecast surface, where the latter is delimited by an edge of the second level 12. The widening of the opening, or safety distance S, is constant or not and preferably greater than 10 microns, more preferably between 10 and 100 microns (measured orthogonally to the contour of the forecast primary surface).

[0087] In this case, the first and second zones 211, 212 partially overlap, together they form the opening 210 of the first mask 200.

[0088] The first engraving mask 200, equipped with its opening 210 for each anchor 10, is, for example, made in the manner described below. Although, for the sake of simplicity, the description and drawings refer to a single anchor 10, each step is in practice carried out simultaneously for each anchor or component manufactured in the same wafer.

[0089] In a first substep b1), a layer of silicon oxide 230 is grown over the entire surface of the wafer 100.

[0090] Then a layer of photosensitive resin 240 is deposited on this layer of silicon oxide 230, on the first side 101 of the wafer (substep b2).

[0091] In substep b3), the resin layer 240 is exposed to light radiation R from a light source (not shown), through a photolithographic mask 250 equipped with a window 251 corresponding to the desired primary etching contours. The radiation R may, in particular, be radiation including UV, i.e., ultraviolet radiation, or even consist of UV radiation.

[0092] Then, in the case of a positive resin as shown, the irradiated photosensitive resin is locally removed by solubilizing it in an appropriate chemical bath, to form an opening 241 corresponding to the desired primary etching contours.

[0093] In a substep b4), the silicon oxide layer 230 is then etched under the opening 241 of the resin, in particular by plasma etching, forming a corresponding opening 231.

[0094] Then, in step b5), the resin layer 240 is removed, notably by plasma etching. The mask 200 is then formed only by the silicon oxide layer 230, whose opening 231 forms the opening 210 of the mask.

[0095] Alternatively, the resin layer 240 can be retained for primary etching. In this case, the etching mask 200 is formed from the resin layer 240 and the silicon oxide layer 230, whose openings 231 and 241 respectively coincide to form the opening 210 of the mask 200.

[0096] As an alternative, the silicon oxide layer could also be omitted. In this case, the mask 200 is formed solely by the resin layer 240, whose opening 241 forms the opening of the mask 200.

[0097] Once the first mask 200 is in place, and in a new step c) of the process, the plate 100 is engraved through the opening 210 of the mask 200 to form the first level 11 of the anchor 10, the primary surface 12a of the second level 12, and the edges of the intermediate level 13.

[0098] The etching is a deep reaction ion etching, also called DRIE etching (acronym for "deep reaction ion etching", which is the English designation for deep reaction ion etching) or etching according to the Bosch process.

[0099] The target depth d1 of the primary etching is less than a wafer thickness d corresponding to the silicon thickness between surfaces 100a and 100b, in a Z direction transverse to said faces, at the time of etching. Thus, the primary etching does not penetrate the wafer 100.

[0100] The target depth d1 here corresponds to the sum z3 of the thicknesses z1 and z4 respectively of the first level 11 and the intermediate level 13.

[0101] We determine beforehand, by calculation or empirically, an engraving time or a number of engraving cycles to obtain the depth d1.

[0102] In a subsequent step d) of the process, the first side 101 of the wafer 100, thus engraved, is covered with at least one stop layer 400.

[0103] By 400 stop layer, we mean a layer made of a material that is not very sensitive to etching, especially DRIE etching, so that it is suitable for stopping such etching (with little or no deterioration) if it comes into contact with it.

[0104] If a layer of photosensitive resin 240 has been retained to form the first etching mask 200, this layer is previously removed, notably by plasma, before the arrest layer is made.

[0105] If a layer of silicon 230 oxide has been formed as described previously, it can also be removed at this stage, or it can be retained, as in the illustrated example.

[0106] The 400 stop layer conforms to the surfaces and parts of the component defined during the primary etching of step c).

[0107] A single 400 layer can be created, as shown in the figure 3d , or we can successively create several layers one on top of the other.

[0108] A 400 arrest layer can be, for example, a silicon oxide layer, in particular with a thickness between 0.5 and 5 microns, or an aluminum layer, in particular with a thickness between 0.1 and 5 microns, or a parylene layer, in particular with a thickness between 1 and 5 microns.

[0109] The arrestor layer 400 can be deposited, for example by vacuum deposition, especially if it is made of parylene or aluminum, as in the illustrated example. When depositing such an arrestor layer, the opposite side can be masked beforehand.

[0110] According to an alternative embodiment (not shown), the arrest layer can also be obtained by growth, particularly in the case of a silicon oxide layer. For example, the silicon oxide 230 layer can be removed, and the wafer oxidized again. A new silicon oxide layer is then formed over the entire wafer, and in particular on its first side, forming the arrest layer. This silicon oxide layer can then be used to create the secondary etching mask, in a manner similar to that described below.

[0111] In a step e) of the process, a second engraving mask 300 is made on the second side 102 of the plate 100, having at least one opening 310, 320 such that a secondary engraving made through this opening forms the edges of the second level 12 of the anchor 10 as well as the secondary surface 11b of the first level 11.

[0112] For practical reasons, the plate is usually returned between steps d) and e).

[0113] In the example considered, and as illustrated on the figure 6 , the second engraving mask 300 has, for each anchor 10 to be manufactured, two openings 310, 320, defined as follows.

[0114] The secondary engraving is intended to form the edges of the second level 12. In the illustrated example, these edges include the edges of the hole 37, as well as the (external) edges of the pallets 31, 32, the fork 33 and the fastening part 30, except for one area – referenced as 324 in the example of the figure 6 - forming an attachment intended to maintain a link between the component and the rest of the wafer.

[0115] The mask must therefore at least be open on areas bordering said edges, with a width of said areas advantageously between 20 and 200 microns and preferably constant, to guarantee an adequate inclination of the engraving sides.

[0116] For this purpose, the mask 300 is opened on a first area 311, delimiting the hole 37. In this case, the area forms a first circular opening 310 of the mask, the diameter of the hole 37 being too small for the realization of an engraving border of constant width.

[0117] The mask 300 is also open to a second zone 321 whose border, here internal 3211, delimits the contour of the fixing part 30, the pallets 31, 32 and the fork 30 of the anchor 10 and of constant width L2, between 20 and 200 microns.

[0118] Since the secondary etching is also intended to form a secondary surface 11b of the first level 11, the second mask 200 is also open to a third zone 322 covering this secondary surface 11b. As illustrated, the third zone 322 is advantageously widened by a safety distance S, preferably greater than 10 microns, and even more preferably between 10 and 100 microns.

[0119] In this case, the second and third zones 321, 322 partially overlap, together they form a second opening 320 of the mask 300.

[0120] The production of the second etching mask 300, equipped with its openings 310, 320, includes for example sub-steps e1 to e4, similar respectively to the steps b2 to b5 described previously and detailed below: At this stage of the process, in the illustrated example, a layer of silicon oxide 230 is already present on the second side 102 of the wafer 100, as a result of the step b1 carried out previously.

[0121] (In the alternative embodiment mentioned above, a silicon oxide layer resulting from the reoxidation of the wafer after primary etching and forming a stop layer on the first side 101 would replace this layer 230 on the second side 102. The rest of the process would remain similar.)

[0122] In a substep e1), a layer of photosensitive resin 340 is deposited on said layer of silicon oxide 230.

[0123] In a substep e2), the resin layer 340 is exposed to the light radiation R from a light source (not shown), through a photolithographic mask 350 equipped with windows 351, 352 corresponding to the desired secondary etching contours.

[0124] To ensure the correct relative positioning of the different levels of anchor 10, an additional referencing step (not shown) can be performed at this stage. This step involves indexing the position of the photolithographic mask 350 to alignment marks engraved during the primary etching process. For example, these alignment marks can be aligned with marks on the photolithographic mask 350, possibly using a camera-based referencing system.

[0125] Once the photolithography operation is completed, the irradiated photosensitive resin is locally removed by dissolving it in an appropriate chemical bath, to form openings 341, 342 corresponding to the desired secondary etching contours.

[0126] In a substep e3), the silicon oxide layer 230 is etched under the openings 341, 342 of the resin 340, in particular by plasma etching, to form corresponding openings 232, 233.

[0127] Then, in step e4, the resin layer 340 is removed, notably by plasma etching. In this case, the mask 300 is formed only by the silicon oxide layer 230, whose openings 232, 233 form the openings 310, 320 of the second mask 300.

[0128] As explained previously, the 340 resin layer could be retained for etching. And the 230 silicon oxide layer could also be omitted.

[0129] Once the second mask 300 is in place, and in a new step f) of the process, the plate 100 is engraved through the openings 310, 320 of the mask 300 to form the second level 12 of the anchor 10, the secondary surface 11b of the first level 11, and the edges of the intermediate level 13.

[0130] The etching is once again typically a deep reactive ionic etching.

[0131] According to the invention, the target depth d2 of this secondary etching is such that the secondary etching reaches at least locally the arrest layer 400. The depth d2 is here equal to the sum of the thicknesses z2 and z4 of the second level 12 and the intermediate level 13, respectively. In practice, the sum of the first and second target depths d1, d2 is at least equal to the thickness d of the wafer. In the particular example of the anchor 10 of the figure 1 , this sum exceeds the thickness d by a value z4. In other words: the secondary etching extends beyond the primary etching background surfaces, by a depth z4, in areas where the etching is not prematurely stopped by the 400 stop layer, and the secondary etching stops at a depth d2' equal to d-d1 at the primary etching background surfaces.

[0132] At the right of the first level 11, the secondary engraving is only stopped at the target depth d2. The bottom surface of the engraving forms, in this case, the secondary surface 11b of the first level 11.

[0133] Thanks to the safety distance S maintained during the primary etching, the secondary etching edges forming the edges of the second level 12 intersect the stop layer 400 cleanly at the depth d2', thus avoiding the formation of excess material.

[0134] There figure 4This illustrates the secondary etching edges delimiting the lugs 34 and 35 of the fork 33. Due to the safety distance S established during primary etching, these edges clearly intersect the stop layer 400. In the example shown, the safety distance S is equal to the width L2 of a secondary etching border. This example is not exhaustive, however, and the safety distance S could be smaller while still remaining non-zero.

[0135] Similarly, thanks to the safety distance S maintained during secondary engraving, excess material is avoided at the edge of the first level.

[0136] In a subsequent step g) of the process, the stop layer(s) 400 are removed.

[0137] If the arrest layer 400 is a silicon oxide layer, the wafer 100 is immersed in a suitable chemical bath, typically a hydrofluoric acid bath. If it is an aluminum layer, the wafer 100 is also immersed in a suitable liquid to dissolve the aluminum. Finally, an oxygen plasma can be used to remove a parylene layer.

[0138] Optionally, in a step h), one or more oxidation and deoxidation sequences of the plate 100 can then be carried out, in order to smooth the surfaces of the anchors 10 and / or modify their dimensions.

[0139] We can finally proceed to step i) of oxidation of the plate in order to improve the mechanical characteristics of the anchors 10.

[0140] Then we detach the anchors 10 from the plate (step j), by breaking the fasteners 324 holding them to the rest of the plate.

[0141] In the process described above, the steps can follow each other in the order a, b, c, d, e, f and, where applicable, g and / or h and / or i and / or j, described previously. Some steps can, however, be reversed or omitted. Thus, for example, step e) can be carried out before step d) and even possibly before step c) or before step b).

[0142] In general, the process is not limited to a particular sequence of steps, and can be carried out according to any suitable sequence of steps allowing primary etching and then secondary etching to be performed, using, to stop at least locally the secondary etching, at least one stop layer made beforehand on the first side of the wafer once etched.

Claims

1. A method for manufacturing at least one watch component (10), said method comprising at least the following steps: - Providing a monolithic silicon wafer (100), - On a first side of the wafer (101), creating a first primary etching mask (200) having at least one opening (210), - Etching the wafer (100) through said at least one opening (210) of the first primary etching mask (200) to form the edges of a first level (11) of the component, the target depth (d1) of the primary etching (101) being such that said primary etching does not penetrate the wafer, - Creating at least one stop layer (400) on the first etched side (101) of the wafer (100), - On the second side of the wafer (102) opposite the first side (101), creating a second secondary etching mask (300) having at least one opening (310, 320), - Engrave the plate (100) through said at least one opening (310,320) of the second mask (300) to form edges of a second level (12) of the component, the target depth of secondary etching being such that at least locally said secondary etching reaches said at least one stop layer.

2. Method according to claim 1, wherein the sum of the primary and secondary target etching depths (d1, d2) is strictly greater than a thickness (d) of the wafer.

3. Method according to claim 1 or 2, wherein the sum of the target depths of primary and secondary etching (d1, d2) is such that the component formed at the end of the secondary etching comprises, between the first and second level (11, 12), an intermediate level (13) of which some edges are in continuation of edges of the first level and other edges are in continuation of edges of the second level.

4. A method according to any one of claims 1 to 3, wherein at least one arrest layer (400) comprises a silicon oxide layer and / or an aluminum layer and / or a parylene layer.

5. Method according to any one of claims 1 to 4, wherein the primary etching of the wafer (100) through said at least one opening (210) of the first mask (200) further forms a primary surface (12a) of the second level (12) oriented towards the first side (101) and optionally at least an edge portion of an intermediate level of the component.

6. Method according to claim 5, wherein said primary surface of the second level (12) of the component (10) is, at least on a boundary part, delimited by an edge of the second level, and the opening of the first mask (200) covers said primary surface enlarged, at the right of said boundary part, by a safety distance (S) greater than 10 microns, preferably between 10 and 100 microns.

7. Method according to any one of claims 1 to 6, wherein the secondary etching of the wafer (100) through said at least one opening (310, 320) of the second mask (300) further forms a secondary surface (11b) of the first level (11) oriented towards the second side (102) and optionally at least an edge portion of an intermediate level of said component.

8. Method according to claim 7, wherein said secondary surface of the first level (11) of the component (10) is, at least on a boundary part, delimited by an edge of the first level, and the opening of the second mask (200) covers said secondary surface enlarged, at the right of said boundary part, by a safety distance (S) greater than 10 microns, preferably between 10 and 100 microns.

9. A method according to any one of claims 1 to 8, wherein at least a portion of an opening of the first mask (200), respectively of the second mask (300), defining a contour of the first level, respectively of the second level, has a width between 20 and 200 microns.

10. Method according to any one of claims 1 to 9, wherein the production of the primary etching mask and / or the production of the secondary etching mask comprises the photolithographic structuring of a resin layer deposited on the first side (101), respectively the second side (102), of the wafer (100), to form openings defining the edges of the first level (11), respectively the second level, of the component.

11. A method according to claim 10, wherein the fabrication of the primary etching mask and / or the fabrication of the secondary etching mask comprises: - the deposition of a resin layer onto an oxide layer previously prepared on the first side, respectively the second side of the wafer, - the structuring by photolithography of said resin layer to form openings defining at least the edges of the first level (11), respectively the second level, of the component, - the opening of the oxide layer at said openings, and optionally the removal of the resin layer.

12. A method according to any one of claims 1 to 11, wherein the method comprises, after etching the wafer through the primary etching mask, an oxidation of the wafer such that the oxide layer resulting from this oxidation forms a stop layer on the first etched side of the wafer, and then the formation of the secondary etching mask from said oxide layer on the second side of the wafer.

13. Method according to any one of claims 1 to 12, wherein at least one watch component (10) is an anchor or a wheel or a plate or a hand or a spiral or a flexible blade element(s).

14. Method according to any one of claims 1 to 13, wherein the plate (100) is polished on both sides (101, 102).

15. A method according to any one of claims 1 to 14, further comprising the removal of at least one stop layer (400).

16. A method according to any one of claims 1 to 15, further comprising, after secondary etching, oxidation of the wafer bearing at least one component (100).

17. Silicon watch component, in particular obtained by implementing the process according to any one of claims 1 to 16, said component comprising at least a first level and a second level at least partially superimposed in a transverse direction of said component, and said component being a monolithic component.

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