DE19740610C2 - Silicon carbide coating on a substrate and method for producing a silicon carbide coating on a substrate and use of the silicon carbide coating - Google Patents

Description

The present invention relates to a silicon carbide coating on a substrate and a Process for producing a silicon carbide coating and the use of the Silicon carbide coating on a substrate.

Single layers of silicon carbide on substrates, for example metallic or glass-like Substrates are widely used for surface treatment. silicon carbide Hard material layers on such substrates provide protection against corrosive or corrosive substances and also offer a due to their scratch resistance mechanical protection. There are particularly suitable ones for such applications Layer thicknesses of the silicon carbide layers in orders of magnitude of greater than 300 nm.

A problem with such silicon carbide layers, however, is that protective layers with a Thickness that meets sufficient mechanical requirements due to the difference in thermal expansion coefficient between silicon carbide and substrate to cracking and flaking tend. Therefore, layers that serve as anti-corrosion layers can no longer perform their protective function.

To overcome this problem, DE 44 29 825 C1 proposes one out Silicon carbide and at least one other, a lower hardness and a smaller one Modulus of elasticity as a component comprising silicon carbide, composite layer Apply quartz glass. This layer should be constructed as a gradient layer, i. H. the Concentration of the other component increases over the layer thickness from the inside to the outside from. A silicon-containing substance is to be used as a further component, the contains in particular silicon, silicon nitride and / or silicon oxide.

The abstract of Japanese patent JP 60-052 577 A describes a heat-resistant coating presented. This coating consists of a layer sequence that alternates Has silicon carbide layers and silicon dioxide layers. The silicon carbide layers ensure heat resistance, while the thinner silicon dioxide layers for Ensure firmness.  

In the specialist book by Rother / Vetter "Plasma coating processes and hard material layers" Dt. Verlag für Grundstoffindustrie, Leipzig 1992 on pages 202-204 the Importance of multilayered layers based on monophase, multiphase or multi-component individual layers explained. After that, often between the substrates and the functional layers, intermediate layers as adhesion promoters and Diffusion protection layers applied. It also mentions that layers that are extremely thin individual layers are built up, have a very high crack resistance. to Overcoming the above-mentioned problems with different thermal There are no indications of expansion coefficients.

EP 0 328 571 describes a magnetron sputtering system and an associated method described. It is stated that selected in the magnetron sputtering system Atomizing devices or ion beam sources can be operated around selected To be able to deposit material. When flowing onto the substrate to be coated with a Gas, in which the atomized materials are located, the material to be applied on deposited on the substrate. Layer systems can thus be applied to a substrate become. It is mentioned that carbon-containing mixtures and oxides are applied can.

The present invention is therefore based on the object of a silicon carbide coating to create, which has a thickness that meets the mechanical requirements in sufficient measure is sufficient, but which does not tend to cracking or flaking and on adheres well to the substrates. In addition, the present invention has the object to provide a method for producing such a silicon carbide coating. According to the present invention, the object is achieved by the silicon carbide coating Claim 1 and solved by the method according to claim 6.  

The preferred embodiments are the subject of the dependent claims.

The silicon carbide coating according to the invention is also advantageous as Corrosion protection coating can be used.

In particular, a method for Manufacture of a silicon carbide coating provided by that too Protective layers of sufficient thickness without cracks and well adhering to substrates can be separated.

The present invention is essentially based on the finding that the Thin film properties of the coating material silicon carbide significantly distinguish the volume properties of this material. Therefore, by Application of a layer stack of thin silicon carbide layers and Substrate material layers are caused that the thermal Coefficient of expansion of silicon carbide matches that of the substrate. Thereby can the problem underlying the invention with respect to the difference of thermal expansion coefficient between layer and substrate solved become.

Sufficiently thin layers show even with large differences in the Expansion coefficient good adhesion to various substrate materials and stand due to their small thickness under a reduced external mechanical Tension. By applying layer sequences, for example from a Silicon carbide layer and the substrate material can be high Total layer thicknesses are applied, which otherwise with the same layer thickness would flake off or tear.

The layer thickness of the silicon carbide layers can be within the layer sequence and / or the substrate material layers vary. For example, the Layer thickness of the individual silicon carbide layers from the substrate to the surface  increase and / or the layer thickness of the individual layers of substrate material can decrease from the substrate to the surface.

The minimum layer thickness of the thin silicon carbide layers is 2 nm, and the maximum layer thickness of the thin silicon carbide layers is 200 nm. It is within these limits to achieve optimal mechanical properties the deposited silicon carbide coating advantageous, as many thin as possible Deposit silicon carbide layers. So it is preferred, for example one Silicon carbide layer thickness of 300 nm rather through 10 thin silicon carbide layers with 30 nm than with 6 thin silicon carbide layers with 50 nm.

The silicon carbide / substrate layer stack to be produced in each case has a Total thickness from several hundred nm down to the µm range. The total thickness is set depending on the type of application.

The silicon carbide layers and the are preferably deposited CVD substrate material layers, for example, in only one reactor. This means, by switching back and forth between different raw material gases a desired sequence of layers can be easily realized, so that many very thin layers are to be applied economically. The silicon carbide layers can but also used by sputtering or others in solid state technology Deposition processes are applied.

As an example, a method will now be described in which quartz glass is used for raising the corrosion resistance in hydrofluoric acid is coated with silicon carbide.

On an optically smooth surface (i.e. the surface roughness is less than 40 nm) of a quartz glass substrate are replaced by a thermally activated chemical Gas phase process (CVD) at a temperature of 600 to 1000 ° C and one Pressure of 26.6 Pa (200 mTorr) alternating 20 nm thick silicon carbide layers and 20 nm thick silicon dioxide layers applied until a total layer thickness of 520 nm is reached. As raw material gases for the silicon carbide layers  can be silane and acetylene or hexamethylene disilazane (HMDS) be used. This stacked layer structure makes it possible to adapt the Silicon carbide structure forced onto the silicon dioxide structure. The lesser Layer thickness of the individual silicon carbide layers leads to a reduction in external mechanical stresses that no longer flake off the layer allow.

The quartz substrate with the resulting silicon carbide coating thus points a significantly better corrosion resistance to hydrofluoric acid due to the stacked layer structure no cracking and no flaking of the coating is caused.

Claims (15)

1. silicon carbide coating on a metallic or glass-like substrate, in particular a quartz substrate, characterized in that the silicon carbide coating is constructed from a layer sequence of individual silicon carbide layers and layers of substrate material, each of which is thin compared to the total thickness of the silicon carbide coating. 2. silicon carbide coating according to claim 1, wherein the layer thickness of the individual silicon carbide layers increases from the substrate to the surface. 3. silicon carbide coating according to claim 1 or 2, wherein the layer thickness of the individual layers of substrate material decreases from the substrate to the surface. 4. Silicon carbide coating according to one of claims 1 to 3, wherein the The minimum layer thickness of the individual silicon carbide layers is 2 nm. 5. silicon carbide coating according to one of claims 1 to 4, wherein the The maximum layer thickness of the individual silicon carbide layers is 200 nm.   6. Process for producing a silicon carbide coating on a metallic or glassy substrate, in particular a quartz substrate, characterized in that a layer sequence of individual silicon carbide layers and layers on the substrate is applied from substrate material, the individual layers each thin in Are compared to the total thickness of the silicon carbide coating.   7. The method according to claim 6, characterized in that for the production of Layer sequence in the region of the layer sequence facing the substrate Silicon carbide layer of a selected thickness is applied, in the direction of the Region of the layer sequence facing away from the substrate with silicon carbide layers increasing thickness can be applied. 8. The method according to claim 6 or 7, characterized in that for the production of Layer sequence in the region of the layer sequence facing the substrate Substrate layer of a selected thickness is applied, in the direction of the Region of the layer sequence facing away from the substrate Thickness can be applied. 9. The method according to any one of claims 6 to 8, characterized in that for Production of the layer sequence of silicon carbide layers with a thickness of at least 2 nm be applied. 10. The method according to any one of claims 6 to 9, characterized in that for Production of the layer sequence of silicon carbide layers with a thickness of at most 200 nm are applied.   11. The method according to any one of claims 6 to 10, characterized in that the deposition of the silicon carbide layers and the layers of substrate material done by a CVD process. 12. The method according to any one of claims 6 to 10, characterized in that the deposition of the silicon carbide layers and the layers of substrate material done by sputtering. 13. The method according to claim 11, characterized in that the deposition the silicon carbide layers and the layers of substrate material by an LPCVD Procedure is carried out. 14. The method according to any one of claims 6 to 13, characterized in that the deposition of the silicon carbide layers and the layers of substrate material takes place in a reactor. 15. Use of the silicon carbide coating according to one of claims 1 to 5 as a corrosion protection coating.