Method for modifying the dimensions of a body comprising silicon, in particular for watchmaking

Abstract

The invention relates to a method for modifying the dimensions of a body (1, 5), in particular for watchmaking, the method comprising a first step of forming the body (1, 5) from an initial material (2) comprising silicon, preferably in its entirety, the body (1, 5) comprising recesses (3, 6) extending from the surface towards the interior of the body (1, 5), characterised in that it comprises a second step of growing SiO2-type silicon oxide inside the recesses (3, 6), so as to fill the recesses and deform the body (1, 5) in order to modify the dimensions thereof.

Description

METHOD FOR MODIFYING THE DIMENSIONS OF A BODY CONTAINING SILICON, PARTICULARLY FOR WATCHMAKING Technical field of the invention

[0001] The present invention relates to the field of manufacturing components comprising silicon, particularly for watchmaking. Technological background

[0002] In certain technical fields, such as watchmaking, it is known to manufacture components including silicon, for example spiral springs or flexible guides.

[0003] To this end, these components are formed in silicon wafer-type wafers, using etching techniques such as laser etching, plasma etching, deep reactive ion etching (DRIE) or wet etching.

[0004] These manufacturing processes allow for the production of components with precise dimensions and physical characteristics. However, it may be necessary to modify the dimensions or geometry of a part of the component without affecting the rest of the component. These operations are particularly delicate when it is necessary to increase the dimensions of a component, for example by lengthening or bending it.

[0005] However, current processes do not allow for increasing the dimensions of silicon components after they have been manufactured. Summary of the invention

[0006] One aim of the present invention is to propose a method for modifying the dimensions of at least a part of a body comprising silicon, which makes it possible to meet the aforementioned needs.

[0007] To this end, the invention relates to a method for modifying the dimensions of a body, particularly for watchmaking, the component comprising at least one body, the method comprising a first step of forming the body in an initial material comprising silicon, preferably entirely, the body comprising recesses extending from the surface towards the interior of the body, comprises a second step of growing silicon oxide of the SiU2 type inside said recesses, so as to fill the recesses and deform the body in order to modify its dimensions.

[0008] The process is remarkable in that it includes a second stage of growth of silicon oxide of the SiU2 type inside said hollows, so as to fill the hollows and deform the body in order to modify its dimensions.

[0009] Thanks to the process, it is possible to modify the geometry of a body, especially after its manufacture, in particular by lengthening or bending it for example.

[0010] Indeed, not only does the growth of silicon oxide fill the voids, but it also transforms the silicon on which it grows. This silicon is transformed into silicon oxide, which has the characteristic of having a larger volume than silicon. Thus, the body deforms around the voids, increasing in volume.

[0011] In addition, such a process facilitates the design of certain components, especially when they are monolithic, and avoids having to assemble parts to form the component.

[0012] According to a particular embodiment of the invention, the silicon oxide growth step is produced by thermal oxidation, preferably carried out between 800 and 1200 °C under an oxidizing atmosphere using water vapor or dioxygen gas.

[0013] According to a particular embodiment of the invention, the recesses have trench shapes.

[0014] According to a particular embodiment of the invention, the recesses have a substantially constant width.

[0015] According to a particular embodiment of the invention, the recesses have a variable width depending on the depth of the trench.

[0016] According to a particular embodiment of the invention, the recesses are arranged on one side of the body, during the first step, to obtain a curved body after the second step.

[0017] According to a particular embodiment of the invention, in the first step, the hollows are hollowed out after the body has been formed, for example using a laser device.

[0018] According to a particular embodiment of the invention, during the first step, the recesses are hollowed out during the formation of the body.

[0019] According to a particular embodiment of the invention, the first step is carried out via a deep reactive ion etching process of the DRIE type.

[0020] According to a particular embodiment of the invention, the first step includes an oxidation-deoxidation process to enlarge the recesses. Brief description of the figures

[0021] Other features and advantages of the invention will become more apparent from the following description of a particular embodiment of the invention, given by way of simple illustrative and non-limiting example, and the accompanying figures, among which: Figures 1a) and 1b) are schematic representations showing a first type of component produced with the manufacturing process according to the invention, after the first step (Figure 1a) and after the second step (Figure 1b); and Figures 2a) and 2b) are schematic representations showing a second type of component produced with the manufacturing process according to the invention, after the first step (Figure 2a) and after the second step (Figure 2b). Detailed description of the invention

[0022] The invention relates to a method for modifying the dimensions of a body, particularly in watchmaking. The method comprises two main steps.

[0023] In a first formation stage, a body 1,5 is formed in an initial material 2 comprising silicon, preferably in its entirety.

[0024] The initial material can be single-crystal silicon regardless of its crystal orientation, doped single-crystal silicon regardless of its crystal orientation, amorphous silicon, porous silicon, polycrystalline silicon, silicon nitride, silicon carbide, quartz regardless of its crystal orientation.

[0025] Body 1, 5 is for example formed in a SOI wafer type wafer comprising a first layer of silicon.

[0026] First, a layer of silicon oxide is grown on the surface of the first silicon layer by exposing the wafer(s) to a High-temperature oxidizing atmosphere. The silicon oxide layer varies depending on the thickness of the silicon layer to be structured. It is typically between 1 and 4 µm.

[0027] Then, we will define, for example in a positive resin, the patterns that we wish to subsequently create in the silicon wafer using a mask.

[0028] This process includes the following operations: - the resin is deposited, for example on a rotating platform, in a very thin layer with a thickness between 1 and 2 µm; - once dried, this resin, with photolithographic properties, is exposed through a photolithographic mask (transparent plate covered with a layer of chrome, itself representing the desired patterns) using a light source; - In the specific case of a positive resin, the exposed areas of the resin are then removed using a solvent, revealing the first oxide layer. In this instance, the areas still covered with resin define the zones that are not to be etched in the subsequent deep reactive ion etching (DRE) operation of the silicon.

[0029] The exposed areas, or conversely, those covered with resin, are then exploited. A first etching process transfers the patterns defined in the resin during the previous stages into the previously raw silicon oxide. To ensure repeatability of the manufacturing process, the silicon oxide is then structured by a dry, directional plasma etching that replicates the quality of the resin's surface, which serves as a mask for this operation.

[0030] Once the silicon oxide is etched into the open areas of the resin, the silicon surface of the topmost layer is exposed and ready for DRIE etching. The resin can be retained or discarded depending on whether it is to be used as a mask during DRIE etching.

[0031] The exposed silicon, unprotected by the silicon oxide, is etched in a direction perpendicular to the wafer surface (Bosch® DRIE anisotropic etching). The patterns, formed first in the resin and then in the silicon oxide, are "projected" into the thickness of the layer.

[0032] The first silicon layer is then structured throughout its thickness by the defined patterns representing the body, which can be detached from the wafer.

[0033] This yields a body 1, which, for example, has a substantially parallelepiped shape. According to the process of the invention, the body 1, 5 comprises recesses 3, 6, which extend through the thickness of the body 1, 5 from the surface towards the interior of the body 1, 5.

[0034] In a first embodiment variant, the recesses 3, 6 are hollowed out during the formation of the body 1, 5, for example during the deep reactive ion etching process described previously.

[0035] Alternatively, the recesses 3, 6 are hollowed out after the formation of the body 1, 5, for example using a laser device or with the deep reactive ion etching process.

[0036] Optionally, the first step includes an oxidation-deoxidation process to precisely enlarge and dimension the 3, 6 recesses by removing some of the initial silicon material. The interior of the silicon 3, 6 recesses is oxidized to grow a SiU2 silicon oxide layer on the silicon.

[0037] Such a process can, for example, be achieved through thermal oxidation. Such thermal oxidation can, for example, be carried out Between 800 and 1200 °C under an oxidizing atmosphere using steam or oxygen gas, silicon oxide is formed in the cavities. This process exploits the fact that silicon oxide grows at a regular rate; the oxidation rate and resulting thickness are precisely controlled by those skilled in the art, ensuring the uniformity of the oxide layer.

[0038] Next, the silicon oxide layer formed in the recesses is removed. Since the silicon sublayer is oxidized, it is also removed. This removal is achieved by chemical etching. Such chemical etching can be carried out, for example, using a hydrofluoric acid vapor solution, which removes the silicon oxide.

[0039] Thus, the interior of recesses 3 and 6 is adjusted by carving into the silicon. Indeed, during the growth of silicon oxide on silicon, a silicon sublayer on which the silicon oxide grows is itself oxidized. In fact, the oxide diffuses into the silicon as it grows.

[0040] Thus, silicon oxide grows at the expense of the silicon on which it grows. In other words, not only does silicon oxide grow on silicon, but it also grows within silicon.

[0041] Preferably, recesses 3, 6 have a trench shape, preferably thin.

[0042] In a first variant of figures 1 a) and 1 b), the recesses 3 are substantially parallel, and are arranged on one side of the body 3 only to form a comb.

[0043] In a second variant of Figures 2a) and 2b), the recesses 6 are distributed uniformly throughout the body 5, notably in a zigzag pattern. This results in a body 5 in which the thickness of the initial material 2 is substantially the same throughout.

[0044] Preferably, the recesses 6 are arranged symmetrically with respect to a preferred axis A of elongation of the body. The recesses 6 are arranged to extend into the body perpendicularly to this preferred axis A.

[0045] Preferably, they are the same length, and / or have a constant spacing between them.

[0046] For example, recesses 3 and 6 have a width that is practically constant in depth.

[0047] Alternatively, the recesses 6 have a variable width depending on the depth of the trench, to achieve a gradual widening. Such variability helps to guide the deformation of the body.

[0048] According to the invention, the process includes a second step of growing silicon oxide 4 of the SiU2 type inside said recesses 3, 6, so as to fill the recesses and deform the body 1, 5 in order to modify its dimensions.

[0049] In this step, silicon oxide is grown inside the recesses 3 and 6 using the same oxidation process described previously. Preferably, the recesses 3 and 6 are completely filled with silicon oxide 4.

[0050] The mechanical properties of silicon oxide 4 cause a change in the dimensions of body 1, 5, because the growth of silicon oxide 4 deforms the initial material 2 due to oxygen diffusion within the silicon crystal lattice, which increases the material's volume. Furthermore, the hollows 3, 6 make body 1, 5 easily deformable.

[0051] In the case of body 1 in figures 1 a) and 1 b), the body becomes laterally curved after the second step, because the recesses 3 are arranged on the same side of body 1.

[0052] In the case of body 5 in figures 2a) and 2b), the latter is axially elongated after the second step, because the recesses 6 are arranged in body 5 in a homogeneous manner.

[0053] Thus, thanks to the invention, it is possible to modify the dimensions and / or geometry of bodies 1, 5.

[0054] To modulate the variation in the geometry of the body, we can vary the width and / or depth of the recesses 3, 6, as well as the number and position of the recesses arranged in the body 1, 5.

[0055] We can also modulate the amount of silicon oxide 4 arranged inside the recesses 3, 6 to increase its impact on the dimensions of the body 1, 5.

[0056] The second step may involve several phases of inserting silicon oxide 4 inside the recesses 6, to gradually adjust the deformation of the body 15. In particular, with recesses 6 having a progressive widening, this adjustment is even more precise.

[0057] Naturally, the invention is not limited to the embodiments described with reference to the figures, and variants could be envisaged without departing from the scope of the invention.

Claims

DEMANDS 1. A method for modifying the dimensions of a body (1, 5) for watchmaking, the method comprising a first step of forming the body (1, 5) in an initial material (2) comprising silicon, preferably entirely, the body (1, 5) having recesses (3, 6) extending from the surface towards the interior of the body (1, 5), characterized in that it comprises a second step of growing silicon oxide of the type SiO2 (4) inside said recesses (3, 6), so as to fill the recesses and deform the body (1, 5) in order to modify its dimensions, the recesses (3, 6) being arranged on one side of the body (1, 5) during the first step to obtain a curved body (1, 5) after the second step.

2. A process according to claim 1, characterized in that the silicon oxide growth step (4) is produced by thermal oxidation, preferably carried out between 800 and 1200 °C, using steam or dioxygen gas.

3. Method according to claim 1 or 2, characterized in that the recesses (3, 6) have trench shapes.

4. Method according to claim 3, characterized in that the recesses (3, 6) have a substantially constant width in depth.

5. Method according to claim 3, characterized in that the recesses (3, 6) have a variable width depending on the depth of the trench.

6. A method according to any one of the preceding claims, characterized in that, in the first step, the recesses (3, 6) are hollowed out after the formation of the body (1, 5), for example by means of a laser device.

7. A method according to any one of claims 1 to 5, characterized in that, during the first step, the recesses (3, 6) are hollowed out during the formation of the body (1, 5).

8. A method according to any one of the preceding claims, characterized in that the first step is carried out via a DRIE-type deep reactive ion etching process.

9. A method according to any one of the preceding claims, characterized in that the first step comprises an oxidation-deoxidation process to enlarge the recesses (3, 6).

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