CH700139B1 - Micro-mechanical part in monocrystalline silicon carbide. - Google Patents

Abstract

The present invention relates to a micromechanical component made of monocrystalline silicon carbide. It also relates to a method for producing such a part, comprising the following steps: – be equipped with a monocrystalline silicon carbide plate, – transfer the image of the part to be made to the aid of a mask on the silicon carbide plate, – engrave by dry etching under controlled atmosphere, the plate provided with the mask, – remove the mask to get the silicon carbide piece.

Description

Technical area

The present invention relates to the field of micromechanics and relates, more particularly, a micromechanical component.

State of the art

[0002] Silicon carbide is known for its hardness properties and its friction behavior. This material has been used for micromechanical parts mainly as part coating, the core of which is made of another material. For example, US Pat. No. 4,495,254 teaches the use of a protective layer, in particular of silicon carbide, deposited on a metal part.

[0003] Document FR 2 322 113 also discloses the possibility of making polycrystalline silicon carbide parts. However, polycrystalline silicon carbide is restrictive to implement and does not allow to make complex parts of very small size accurately. Document US 2002/0 114 225 also gives examples of parts made of polycrystalline silicon carbide.

The present invention aims to retain the advantages of silicon carbide, by applying them to complex parts, with great precision.

Disclosure of the invention

More specifically, the invention relates to a micromechanical component made of monocrystalline silicon carbide. In other words, at least the core of the part is made of silicon carbide.

Advantageously, the part comprises at least two parallel faces and is obtained by dry etching from a plate (wafer).

The piece advantageously takes the form of a watch component, such as a wheel, in particular exhaust, or an anchor.

The invention also relates to a production method for producing a micromechanical component made of monocrystalline silicon carbide, comprising at least two parallel faces. This process comprises the following steps: - obtain a monocrystalline silicon carbide plate, Transfer the image of the part to be produced using a mask on the silicon carbide plate, - engrave by dry etching in a controlled atmosphere, the plate provided with the mask, Remove the mask to obtain the silicon carbide piece.

[0009] Several masking and etching steps can be performed to obtain a part having different levels of etching.

One can also mask and etch both sides of the monocrystalline silicon carbide plate are masked and etched.

Brief description of the drawings

Other features of the present invention will appear more clearly on reading the description which follows, with reference to FIG. 1Annexé representing a part according to the invention.

Mode (s) of realization of the invention

The monocrystalline silicon carbide has a low density, a very good mechanical strength, a high hardness, a high modulus of elasticity, a very good thermal and chemical stability, and interesting tribological characteristics. In a natural way, the monocrystalline silicon carbide is transparent yellow in color. Despite its remarkable properties, monocrystalline silicon carbide has not been used to produce massive micromechanical parts.

For their manufacture, the monocrystalline silicon carbide parts are made from thin plates or wafers of various sizes, by dry etching in a controlled atmosphere, which allows for a large number of parts in a batch. It will be noted that, depending on the intended applications, it is possible to start from plates with parallel faces or from a substrate having, beforehand, one or more concave or convex faces.

To do this, we just transfer the image of the part or parts to be made using an etching mask on a silicon carbide plate. This mask can be produced by means of a photosensitive layer, transferred by photolithographic process or by physical etching. It is also possible to use different layers as an etching mask in which the images of the parts to be produced are transferred by chemical, physical or lift-off etching. These masking layers can be of different types, metallic, organic, various oxide, various nitride, ceramic ...

The silicon carbide is then etched by dry etching process under controlled atmosphere. One or more points of connection can be maintained between the part and the plate, so as to facilitate the subsequent processing, the part not being detached from the plate at the very end of operation. The masking layer is then removed to obtain the silicon carbide pieces. The etching may comprise several levels of etching and this, on both sides of the silicon carbide wafers.

[0016] Reference can be made to EP 0 732 635 for a description of the possible steps for carrying out masking and for a dry etching process.

Typically, it is possible to achieve pieces of different types and size that fit on a monocrystalline silicon carbide substrate, with a precision of the order of a micrometer. By way of illustration, it is shown in FIG. 1 a watch exhaust wheel made of monocrystalline silicon carbide, according to the invention.

An additional advantage offered by silicon carbide is to allow many possibilities in terms of coating. Thus, the solid piece of silicon carbide obtained above and having, in particular, qualities of interest in terms of weight, elasticity and thermal stability, can be covered with different layers of various properties depending on the chosen applications. These additional layers can improve the mechanical strength, the behavior in terms of friction or lubrication, or allow to decorate the room. It may also be noted that subsequent surface treatments may make it possible to modify the aesthetic appearance of a solid piece of silicon carbide.

The benefits arising from the use of monocrystalline silicon carbide for micromechanical parts are numerous, particularly for horological or medical applications, particularly with reference to monocrystalline silicon, which is nowadays widely used to produce complicated parts. Its total chemical inertness and thermal stability make it easier to use than monocrystalline silicon. After shaping, its tribological properties and in terms of wear, are much higher than those of silicon. It can thus be used without additional coating of oxide or diamond. Its intrinsic hardness combined with its elasticity and its resistance to fracture make it possible to envisage the manufacture of new parts of unconventional shape.

In addition, silicon carbide having a higher molecular mass than monocrystalline silicon, but being less dense than metals, many applications can be envisaged in the medical field, for micro- and nanostructures, especially under difficult conditions. Its excellent thermal conductivity combined with its resistance to thermal shock, make it possible to achieve new types of welding and bonding, especially with ceramics, which was not possible with single crystal silicon.

Claims (6)

1. Micromechanical part made of monocrystalline silicon carbide. 2. Part according to claim 1, characterized in that it comprises at least two parallel faces. 3. Part according to claim 2, characterized in that it is a watch component. 4. A method of producing a part according to one of claims 2 and 3, characterized in that it comprises the following steps: - obtain a monocrystalline silicon carbide plate, Transfer the image of the part to be produced using a mask on the silicon carbide plate, - engrave by dry etching in a controlled atmosphere, the plate provided with the mask, Remove the mask to obtain the silicon carbide piece. 5. Method according to claim 4, characterized in that it comprises several steps of masking and etching, to obtain the piece having different levels of etching. 6. Method according to claim 5, characterized in that the two faces of the monocrystalline silicon carbide plate are masked and etched.