DE102004060670B4 - Method and arrangement for producing high-temperature-resistant scratch-resistant coatings with low surface roughness - Google Patents

Abstract

Method for producing dielectric high-temperature-resistant scratch-resistant layers with low surface roughness of metal oxide and / or metal nitride and / or metal carbide and / or metal oxonitride and / or metal carbonitride and / or metal oxocarbonitride by reactive magnetron sputtering, in which a stable operating point on a material-specific hysteresis curve of the transition region of the reactive sputtering process is regulated, characterized in that by means of the control (4, 5, 6) of the reactive gas flow (8) and by a power input (9) with a power density of more than 8 W per square centimeter target surface, the operating point of the reactive sputtering process in the immediate vicinity a material-specific threshold operating point is set, above which the deposited layers have absorbing properties, that is in a range from the threshold operating point to a point at which the deposited layers ei ne absorption in the infrared spectral range of 5%, and that the occurred in the deposited layers unwanted absorption from Ab subsequently by means of a heating by the coated substrates post-oxidation while preserving the mechanical and thermo-mechanical properties of the layers is removed again.

Description

The The invention relates to a method and a device for the production high temperature resistant Scratch protective layers with low surface roughness accordingly the features of the preamble of claim 1 and an arrangement for execution this method according to the features of the preamble of Claim 13.

High-temperature resistant scratch-resistant coatings are used, for example, as protective layers for glass-ceramic cooking surfaces. In particular, metal oxides are interesting, as they include, inter alia US 4,920,014 or WO 04/026786 A1 are known.

When cost-effective Deposition method, which allows thin layers over a large area reproducible to separate, the magnetron sputtering has become technically established. In this case, a low-temperature plasma in an inert gas, for. Argon, used to ablate a lying on the cathode target material and on an opposite substrate deposit. For the deposition of interconnect layers is reactive sputtering in which the sputtering gas is still a reactive gas (oxygen for oxides) is mixed. The type of reactive process control that u. a. through the Type and amount of reactive gas flow and the applied power density and so that the sputtering rate is determined, decide on the Properties of the deposited layer.

For use as protective layers for glass ceramic cooking surfaces in addition to the temperature resistance a low surface roughness in the With regard to low contamination and good cleaning behavior required. Furthermore should be the protective coatings for good heat transfer from the underlying heating element and a visually appealing Surface both be transparent in the visible and infrared spectral range.

The known methods for depositing scratch-resistant and at the same time high-temperature resistant layers are very expensive. In US 4,920,014 Moreover, it does not succeed in simultaneously achieving a smooth layer surface. In the WO 04/026786 A1 a layer system is described, which consists of columnar growing functional layers, between which thinner intermediate layers are incorporated for smoothing the growing columnar structure. Although these layers have satisfactory properties, however, their production is associated with a high process complexity and thus expensive.

Thiel et al., "Deposition and properties of yttriastabilized zirconia thin films using reactive direct current magnetron sputtering", J. Vac. Sci. Technol. A9 (6), 1991, 3054-3060, are yttrium - stabilized zirconia (YSZ) layers also having a columnar layer structure, as in the WO 04/026786 A1 , described for use in oxygen sensors and solid oxide fuel cells.

Aoki et al. "Preparation of in-plane textured Y ₂ O ₃ -doped ZrO ₂ thin film on polycrystalline metallic days by modified bias sputtering", J. Vac. Sci. Technol. A12 (2), 1994, 501-505 describes grain alignment in YSZ layers which serve as a substrate for superconducting thin films.

Of the The invention is therefore based on the object, an improved method and an apparatus for producing a high-temperature resistant scratch-resistant coating system with low surface roughness To show with which layers with the previously named properties easier and thus cheaper can be produced.

The solution This object is achieved by means of a method for production Dielectric high-temperature resistant scratch-resistant coatings with low surface roughness of metal oxide and / or metal nitride and / or metal carbide and / or Metal oxonitride and / or metal carbonitride and / or metal oxocarbonitride by reactive magnetron sputtering, where at a stable operating point on a material-specific hysteresis curve of the transition region the reactive sputtering process is regulated, the method characterized in that by means of the regulation of the reactive gas inflow and through a power input with a power density of more as 8 W per square centimeter of target area the working point of the reactive Sputtering process in the immediate vicinity of a material-specific Schwell operating point is placed, above which the deposited Have layers of absorbent properties, that is in one Range from immediately below the threshold operating point to to a point where the deposited layers have an absorption in the have infrared spectral range of 5%, and that in the Deposited layers occurred, undesirable in itself absorption then by means of a post-oxidation effected by heating the coated substrates while preserving the mechanical and thermomechanical properties the layers is removed again.

In a particularly advantageous embodiment of the method, the energy input can be increased by amplifying the ion current, by a dark field shield of Doppelmagnetrons or other conductive additional elements, the plasma region between the target and substrate surrounded, a positive bias is applied. This should be in the range of 30 to 200 volts, preferably in the range of 40 to 100 volts, and most preferably in the range of 50 volts to 100 volts.

to Achieving the desired Layer properties, it is procedurally also cheap, the Substrate during the deposition on an increased Substrate temperature of more than 150 ° C to heat.

In another cheap Embodiment of the method according to the invention can be a secondary in the process resulting stray steam with the help of extended to the substrate Apertures are cut off.

A particularly advantageous embodiment with regard to the process complexity is the deposition of the scratch-resistant layer in a thickness of at least 1500 nm in a single layer. As the layer material is in particular yttrium-stabilized zirconia, particularly preferably with a Y ₂ O ₃ content of about 7.8 Mol% suitable.

Alternatively, the scratch-resistant layer may be constructed by interposing dielectric sputtered interlayers as the alternating layer system, the thickness of the interlayers being about 2% of the thickness of the functional layers. The intermediate layers can be deposited from dielectric material such as SiO ₂ or Nb ₂ O ₅ .

Of the Sputtering process can be done in an inline facility with one or more runs of the substrate are carried out in the system.

The post-oxidation according to the invention the deposited layers may preferably be by means of a post-treatment at a temperature of about 400 ° C respectively.

The The object is further achieved by an arrangement for Production of dielectric high-temperature resistant scratch-resistant coatings with low surface roughness with Help of the above Method, wherein the arrangement is a magnetron sputter coating system with control devices for stable adjustment of operating points a reactive sputtering process in the transition mode, wherein the magnetron sputtering system means for generating a power density of more than 8 W per square centimeter of target area as well as facilities for Apply a positive bias to conductive elements that cover the plasma area surrounded between target and substrate. These conductive elements can In a particularly advantageous embodiment, the dark field shield the magnetron sputtering source.

According to one further advantageous embodiment can in the coating chamber the device according to the invention extended to the substrate Apertures to cut off a secondary build in the process Be provided with scattered steam.

With Help the above-specified system and the method according to the invention can be a dielectric layer system with high temperature resistance, Scratch resistance and surface smoothness Metal oxide and / or metal nitride and / or metal carbide and / or Metal oxonitride and / or metal carbonitride and / or metal oxocarbonitride be deposited by reactive magnetron sputtering, wherein the Layer system is characterized in that it after the deposition has an absorption in the infrared spectral range of up to 5% and this absorption by a thermal aftertreatment of the layer system is essentially eliminated, with the mechanical and thermomechanical Properties of the layer are preserved.

A particularly advantageous layer structure of a scratch-resistant layer with regard to the process outlay consists of a single layer in a thickness of at least 1500 nm, wherein as layer material in particular yttrium-stabilized zirconium oxide, particularly preferably with a Y ₂ O ₃ content of about 7.8 molar %, is suitable.

Alternatively, the layer system may be constructed as a alternating layer system in which dielectric sputtered intermediate layers are arranged between the scratch-resistant layers, wherein the thickness of the intermediate layers makes up about 2% of the thickness of the functional layers. The intermediate layers can be deposited from dielectric material such as SiO ₂ or Nb ₂ O ₅ .

Further Features and advantages of the invention are the following detailed Description based on an embodiment as well as the attached drawings. Showing:

1 qualitatively the relationship between the reactive gas inflow and various process parameters for a reactive magnetron sputtering process; and

2 a schematic diagram of an exemplary sputtering arrangement for carrying out the method according to the invention.

1 Illustrates in a graph the qualitative relationship between reactive gas inflow and voltage, intensity plasma and sputter rate, which correlates with the intensity of the plasma, for a reactive magnetron sputtering process. It can be seen that when the reactive gas flow is increased (oxygen in the case of oxide composite layers), the process tilts from the metallic mode (top left) to the reactive mode (bottom right). In the latter, the sputtering rate and hence the deposition rate is low, but the layers are stoichiometric. At an operating point in the metallic mode, strongly substoichiometric layers with a low reactive gas content result, which have a high absorption. The main challenge in reactive process management is to work stably in the intermediate transition region, which is not controllable by the reactive gas inlet alone. Stabilization of the reactive discharge is possible, for example with the aid of the ^® PEM Scheme (plasma emission monitor) of the applicant, still with reference to 2 will be explained in more detail. This allows the measurement of intensities targetmaterialspezifischer plasma emission lines and the resulting rapid control of the reactive gas flow (ie with a time constant well below 100 ms) a stable work in the so-called transition mode with operating points on the in 1 squares-marked material-specific hysteresis curve. This makes it possible to produce composite layers having a defined degree of reaction and thus defined properties.

What now the desired high-temperature resistant scratch protection layers smooth surface, so be for these excellent in connection with the application as protective coatings for glass ceramic cooking surfaces Transmission properties in the infrared spectral range with respect on a good heat transfer from the underlying heating element through the protective layer to cookware and a low or defined absorption in the visible spectral range in terms of visual appearance the surface required.

In order to obtain transparent layers, the working point of the reactive sputtering process would normally be placed in the lower part of the hysteresis curve, well below an operating point above which layers with absorbing properties emerge, ie in a region where there is a high degree of reactivity and almost ideally stoichiometric Layers are deposited. Surprisingly, it has now been found that dense-packed structures can be deposited via the detour of stoichiometric and thus to some extent absorbing layers in connection with a high power density (generator power per target area) and optionally a further increased energy input by applying a positive bias to the dark-field shield of the magnetron that no longer grow in columnar form, and that nevertheless a favorable layer morphology can be obtained, which is important for the desired layer properties. Thus, in the WO 04/026786 A1 required intermediate layers are omitted, making the deposition process considerably easier and thus cheaper. The occurring absorption in the layers can be eliminated by a subsequent heating process, in which it comes to a post-oxidation of the layers again.

The inventive method will now be explained in more detail with reference to an embodiment. High temperature resistant scratch protection layers of substantially yttrium-stabilized zirconium oxide were measured using an MF-double-magnetron sputtering process on CERAN ^® -Kochfeldern in an inline coating installation, such as is sold by the applicant, is deposited. Such equipment typically includes multiple vacuum chambers, including an in-feed chamber, pre-treatment chamber (s), coating chamber (s), optional aftertreatment chamber (s), and a discharge chamber through which the substrates are passed. 2 shows the schematic diagram of a planar double magnetron sputter assembly, as it may be included in one of the coating chambers of the inline system, together with the essential for the layer deposition control options.

For the deposition of oxide compound layers is in the coating space between the target lying on the cathode 2 and the substrate passing through the chamber 3 a plasma 10 generated. This argon is used as a sputtering gas and oxygen 8th embedded as a reactive gas. Accelerated in the electric field between the anode and cathode and by the magnetic field of the magnetron 1 Guided argon ions strike the target material 2 up and atomize this. The sputtered target particles react with the reactive gas and separate as a bonding layer on the substrate 3 from. A control loop ( 4 . 5 . 6 ,) uses in situ measurement 4 the intensity of spectral lines of the sputtered target material, with respect to a target value for the intensity 7 the feed 8th of the reactive gas to regulate oxygen as a function of the measured intensity signal ( 5 . 6 ). For the present embodiments, the ^PEM® 05 control loop to be used by the assignee of the present invention was used, which controls the number of impact ratios between the sputtered metal particles and the recessed reactive gas particles. At the desired operating point, this ratio is kept constant. This makes it possible to use almost every operating point in the transition region of the re stabilize active sputtering process. Alternatively, any other fast control system could be used which guarantees deposition at a stable, defined operating point of the reactive sputtering process.

In a first exemplary embodiment, yttrium-stabilized zirconium oxide having a Y ₂ O ₃ content of about 7.8 mol% of the (Y) Zr target with oxygen as the reactive gas was deposited in a layer thickness of about 2000 nm. The operating point of the reactive sputtering was placed with the aid of the ^® 05 PEM control in the upper transition region of the hysteresis curve of the material in which the layers begin to be absorbing. The deposition was carried out on preheated substrates with a substrate temperature of at least 150 ° C. Substrate preheating favors the formation of particularly strong (Y) ZrO _x phases, which otherwise would not form at room temperature. Oxygen-deficient (Y) ZrO _x layers with a transmission drop at λ = 900 nm of up to 5% were obtained. The initially occurring absorption could be eliminated by subsequent heating of the coated substrates to about 400 ° C and the post-oxidation of the layers thereby realized. At applied power densities ( 9 in 2 ) of more than 8 watts per square centimeter of target area, layers with a densely packed structure formed under these conditions and, in contrast to those of US Pat WO 04/026786 A1 known layers - just no longer columnar structure. As a result, the installation of intermediate layers for smoothing the otherwise columnar growing structures is unnecessary. By applying a positive bias ( 12 in 2 ) to the dark field shield 11 of the double magnetron, the roughness of the layers could be further reduced. This is due to an amplification of the ion current by deduction of electrons from the plasma and thus a further increase in the energy input. For this purpose, a voltage in the range of 30-200 V proved to be useful, best results were achieved at U> 50 volts. Alternatively, the positive bias could also be applied to other sheets in the area of the plasma between the target and the substrate.

In addition, proved it turns out to be cheap, while secondary to the process resulting stray steam with the help of extended to the substrate Cut off the panels.

In a second exemplary embodiment, a layer system of mutually approximately 150 nm thick functional layers of (Y) ZrO _x and approximately 3 nm thick intermediate layers of SiO _x in a total thickness of approximately 2000 nm was deposited under analogous process conditions.

The Layer deposition took place in an inline system in the multiple overflow mode (multiple pass mode) over a sputtering source or for the alternating layer system alternately over two different sputter sources.

at sufficiently many sputtering sources arranged one behind the other can the layer deposition also take place in a single pass. This process was used in the so-called sputter-up process, in which the substrate over the sputtering source is moved away, and in the so-called sputter-down method, in which the substrate is moved away under the sputtering source.

For the production of low defect density layers in the deposited layer the process also in a plant designed as a vertical plant, carried out become. It can be avoided that parasitic particles fall onto the substrate or the target. In such a facility the substrate is usually not exactly vertical, but in one Angle less than 10 ° to Vertical inclined.

The Method can also be performed using magnetron with rotating Target (so-called rotatable magnetron or C-Mag) are performed.

All Layers deposited according to the invention have a high scratch resistance and low roughness and hold the thermal and thermomechanical load when heated to 700 ° C and the subsequent fast cooling for at least 15 hours stood. Thus, the inventive method in context with the sputtering system according to the invention a possibility for easy and inexpensive Deposition of high temperature scratch resistant coatings with high surface smoothness.

1

magnetron

2

target

3

by running substratum

4

intensity measurement

5

PEM ^{® control}

6

control valve for reactive gas inlet

7

setpoint for intensity

8th

Reactive gas supply

9

generator power

10

plasma

11

Darkfield shield

12

preload for dark field screening

Claims (15)

Process for producing high dielectric temperature-resistant scratch-resistant layers with low surface roughness of metal oxide and / or metal nitride and / or metal carbide and / or metal oxonitride and / or metal carbonitride and / or metal oxocarbonitride by reactive magnetron sputtering, in which is regulated to a stable operating point on a material-specific hysteresis curve of the transition region of the reactive sputtering, characterized characterized in that by means of the scheme ( 4 . 5 . 6 ) of the reactive gas inflow ( 8th ) and by a service entry ( 9 ) with a power density of more than 8 W per square centimeter of target surface, the working point of the reactive sputtering process is placed in the immediate vicinity of a material-specific threshold operating point above which the deposited layers have absorbing properties, that is, in a range from the threshold operating point to one Point at which the deposited layers have an absorption in the infrared spectral range of 5%, and that the unwanted absorption occurred in the deposited layers is then removed again by means of a post-oxidation caused by heating of the coated substrates while preserving the mechanical and thermomechanical properties of the layers , A method according to claim 1, characterized in that the energy input by amplifying the ion current by applying a positive bias voltage ( 12 ) to a dark field shield ( 11 ) of the double magnetron or other conductive additional elements surrounding a plasma region between the target and the substrate. Method according to claim 2, characterized in that that the positive bias in the range of 30 to 200 volts, preferred 40 to 100 volts, and most preferably 50 volts to 100 volts. Method according to one of the preceding claims, characterized characterized in that the post-oxidation at a temperature of 400 ° C takes place. Method according to one of the preceding claims, characterized characterized in that a secondary in the process resulting stray steam with the help extended from to the substrate Apertures are cut off. Method according to one of the preceding claims, characterized characterized in that the substrate during the deposition on a Temperature of T> 150 ° C heated becomes. Method according to one of the preceding claims, characterized characterized in that the scratch-resistant layer is at a thickness of at least 1500 nm is deposited. Method according to one of the preceding claims, characterized in that the scratch-resistant layer is deposited as a layer of yttrium-stabilized zirconia with a Y ₂ O ₃ content of 7.8 mol%. Method according to one of the preceding claims, characterized characterized in that the scratch-resistant layer in a single layer is deposited. Method according to Claims 1 to 8, characterized that scratch-resistant layer by inserting dielectric sputtered Intermediate layers is constructed as a alternating layer system, wherein the Thickness of the intermediate layers 2% of the thickness of the functional layers accounts. A method according to claim 10, characterized in that as dielectric intermediate layers of SiO ₂ or Nb ₂ O _{5 are} deposited. Method according to one of the preceding claims, characterized characterized in that the sputtering process in an inline plant with one or more passes the plant is made. Arrangement for the production of dielectric high-temperature resistant scratch-resistant coatings with low surface roughness according to the claims 1 to 12, comprising a magnetron sputter coating machine with Control devices for stable adjustment of operating points a reactive sputtering process in the transition mode, characterized in that that the magnetron sputtering system means for generating a power density of more than 8 W per square centimeter of target area as well as facilities for Apply a positive bias to conductive elements that cover the plasma area surrounded between target and substrate. Arrangement according to claim 13, characterized the conductive elements surrounding the plasma region are the dark field shield the magnetron sputtering source. Arrangement according to claim 13 or 14, characterized that the coating chamber extended to the substrate towards aperture for cutting off a secondary generated in the process littering steam having.