EP2646596A1

EP2646596A1 - Method for producing a carbon-containing layer system and apparatus for implementing the method

Info

Publication number: EP2646596A1
Application number: EP11788773.7A
Authority: EP
Inventors: Sven Meier
Original assignee: Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Current assignee: Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Priority date: 2010-11-29
Filing date: 2011-11-24
Publication date: 2013-10-09
Also published as: DE102011009347B4; WO2012072215A1; DE102011009347A1

Abstract

The invention relates to a method for producing a carbon-containing layer system, in particular to increase the wear resistance of components, and to an apparatus for implementing the method. In the method, by means of plasma deposition, first a diamond layer (20) is deposited and then an amorphous carbon-containing layer (21) is deposited, forming a transition layer (22). The layers are deposited one after the other without the vacuum or the continuous or pulsed plasma required for the layer deposition being interrupted between the depositions of the layers. The combination of the two layers in conjunction with the deposition technique used permits the production of layer systems which lead to a high wear resistance of the components.

Description

Process for the preparation of a carbon-containing layer system and apparatus for carrying out the process

Technical application

The present invention relates to a method for producing a carbon-containing layer system, in particular for increasing the wear resistance of tools or components, in which a diamond layer by means of plasma deposition on the

Tool or component is deposited. The invention also relates to a device for carrying out the method.

During cold and hot forming as well as during cutting and cutting of sheet metal components and milling of composite materials, the tools are subject to strong forces

Wear, which leads to low tool life and poor component quality. The wear is due to the high local mechanical stresses, mainly due to shear stresses and the sliding paths at the edges of the tools. Under sheet metal components are in this context

Components from all industrially used metals and metallic alloys to understand, which are usually cold or hot-formed, separated or cut. Even when working on non-metallic components such problems

occur. Examples of the components mentioned are aluminum sheets, stainless steel sheets, copper sheets, zinc sheets, carbon fiber reinforced plastics (CFRP), glass fiber reinforced plastics (GRP), etc. This is of course not an exhaustive list. Another technical field in which components are exposed to high local mechanical stresses is the use of highly resilient mechanical seals (liquid and gas seals).

State of the art

To increase the strength or wear resistance of such components, it is customary to apply a carbon-containing layer with a high hardness to the components. For example, diamond-coated ceramics (polycrystalline diamond in layer form) represent a significant advance in innovative mechanical seals, which are used in the fields of energy, chemical, pharmaceutical and pharmaceutical industry

Food technology are of great importance as they transition to permanently touching

Can allow mechanical seals.

Numerous experiments have shown that the

Shear forces leading to the high wear on the

Components or tools can be significantly reduced by amorphous or semi-crystalline hydrocarbon layers (DLC), since they have comparatively low coefficients of friction of typically 0.1. However, for the purposes described above, these layers are not tough enough to permanently improve tool life and durability

To ensure operational behavior. For this purpose, the layers produced are not only too thin, but wise also not the appropriate ratio of hardness to

Elasticity module (modulus of elasticity) on.

The previously available carbonaceous

Layers can therefore not ensure sufficiently high wear resistance of the tools or components in many applications.

EP 1 272 683 B1 discloses a method for producing a DLC layer system in which, after the deposition of a DLC layer on a suitable adhesion and transition layer, an amorphous carbon-containing layer is applied as a sliding layer which has a different chemical composition than the DLC layer. Layer has. The layers are applied by means of plasma deposition in the middle frequency range. This allows the deposition of DLC layers but not of

Diamond layers.

The object of the present invention is to provide a method for producing a carbon-containing layer system and an apparatus for carrying out the method, with which a layer system can be produced, which significantly increases the wear resistance of components

allows. The components here are to be understood as meaning the components mentioned above, it being understood that the layers produced by the method can also be applied to other components which are subject to mechanical wear. Presentation of the invention

The task is with the method, the

Layer system and the device according to the

Claims 1 and 8 solved. advantageous

Embodiments of the method and the device are the subject of the dependent claims or can be found in the following description and the embodiment. In the proposed method is a

Diamond layer, preferably with a hardness> 6000 HV (Vickers hardness) and an E modulus> 800 GPa, deposited by means of plasma deposition. Subsequently, a transition layer and an amorphous carbonaceous layer are deposited on this first layer by means of plasma deposition. The deposition of the layers is carried out successively under vacuum conditions, without the vacuum and the continuous or pulsed plasma required for the layer deposition between the

Separation of the individual layers to interrupt. An interruption here means a period during which, due to the missing

Plasmas no more layer growth takes place. In this way, a layer system of two carbon-containing layers with an intermediate transfer or transition layer is obtained, which comprises the

Requirements to increase the wear resistance of the component on which the layer system was deposited, much better than previously meet

used layers.

It was recognized that an ideal layer system for the mentioned in the introduction Applications is a multi-layer system with completely different layer properties, which can not be met by a single layer alone. Above the interface to the component or

Tool as hard as possible (Vickers hardness preferably> 6000 HV) and preferably thick layer (layer thickness> 10 μπι) with very high E- odul (preferably> 800 GPa) are applied, which of a layer with a lower modulus, preferably <250 GPa, is covered. This second layer in the sense of a functional layer should ideally have a material opposite the material to be formed or separated

the lowest possible coefficient of friction of ^ 0,1

exhibit. Irrespective of the ratio of the edge radius of the tool to the layer thickness, this layer system has improved insert properties, in particular high wear resistance and high forming quality. This could be done on the basis of simulation data

be determined.

In a particularly advantageous embodiment, a combination of a polycrystalline

Diamond layer, preferably with an E-modulus of about 900 GPa, and a DLC-like layer (diamond-like amorphous carbon) with an E-modulus <200 GPa, preferably about 120 GPa produced. This layer system fulfills the requirements for increasing the

Wear resistance required properties

especially good.

An essential feature of the proposed

Method is that the two layers with the intervening transition or transfer Layer under vacuum by means of plasma deposition

be deposited without intermittently interrupting the vacuum or the continuous or pulsed plasma. Only in this way is it possible to achieve a connection between the diamond layer and amorphous carbon-containing layer that is sufficiently strong for the applications mentioned. Overcoating a diamond layer with a DLC layer after transfer from the diamond coating facility to the DLC coating facility will disrupt the vacuum and plasma conditions through which the compound will be subjected

is completely insufficient between the two layers without the necessary transition or transfer layers. Diamond layers and DLC layers, however, hitherto required different coating systems, so that a specially designed apparatus for plasma deposition was developed for implementing the proposed method. The device essentially comprises an inert gas chamber and a separate reactive gas chamber, which are connected to one another via an electron gate. In the reactive gas chamber, a slide is arranged, which is designed as an electrode for the generation of a high-frequency plasmas. The counter electrode is arranged in the inert gas chamber. In the proposed

Device, the reactive gas chamber is designed as a microwave ring resonator.

The diamond layer is deposited here with a microwave plasma, while the amorphous carbonaceous layer is deposited with a capacitively coupled high-frequency plasma. For the transition from the diamond layer to the amorphous carbonaceous layer is the Microwave power is reduced continuously or stepwise while increasing the high frequency power continuously or stepwise. The diamond layer deposited with the microwave plasma may have any thickness and shape of the crystals. This diamond layer is then overcoated with the amorphous carbonaceous layer without process interruption. During the transition from the crystalline diamond to the amorphous carbonaceous layer, preferably DLC layer, the capacitive high-frequency plasma source, which during the diamond deposition becomes only a passive high-temperature capable

Slide is, put into operation. Due to the gradual reduction of the microwave power and the associated temperature reduction (from about 800 ° C to 900 ° C to about 100 ° C) while increasing the capacitive coupled via the now active slide high frequency power are the

Deposition conditions switched from diamond growth to DLC growth. This creates an ideal thermodynamic transfer layer between the diamond and the DLC. This between the diamond layer and the DLC (a-C: H)

lying transfer layer (nanocrystalline diamond and ta-C: H) determines the properties, but especially the inner cohesion of the multi-phase layer, i. of the present layer system, decisively with. The DLC layer is to realize a particularly high wear resistance preferably with a

Layer thickness> 50 μπι deposited.

The layer system produced by the method thus consists of at least two carbon-based Layers that are connected by a transition layer. The lower layer is a diamond layer, which preferably has a high hardness> 6000 HV and an E-modulus of preferably> 800 GPa. The upper layer is an amorphous carbonaceous

Layer with a smaller modulus of elasticity of preferably <250 GPa. This layer system combines the positive properties of crystalline and amorphous carbon-based layers. The lower layer, ie the crystalline diamond layer, is preferably deposited on the substrate via a suitable adhesive layer, which is adapted to the type of substrate and can correspond to the prior art. In a particularly advantageous embodiment, a layer of carbon nanotubes is deposited as an adhesive layer. This layer considerably increases the adhesion of the layer system to the component, especially in the case of hard metal components, and can advantageously be deposited with the microwave plasma of the microwave ring resonator. Also in this case, therefore, all layers including the adhesive layer are deposited on the device without interrupting the vacuum as well as the continuous or pulsed plasma. The proposed device, which is suitable for carrying out the method, has a plasma chamber in which at least one electrode is arranged as a slide and at least one wall region and / or at least one arranged in the plasma chamber component forms a counter electrode, and one connected to the electrode High-frequency unit with which a plasma is generated in the plasma by applying a high-frequency alternating voltage between the electrode and the counter electrode. chamber is generated. The plasma chamber of the pre ^¬ chosen device is divided by a separator into at least two partial volumes of which contain a first partial volume for a reactive gas, the electrode and a second partial volume for an inert gas an active at the plasma generating region of the counter electrode. The separating device is suitable for enabling a plasma exchange of electrons in the plasma between the partial volumes required for the generation of the plasma and for providing a diffusion barrier for the plasma

To form reactive gas. The separating device is also referred to in the present patent application as an electron gate. The partial volume for the reactive gas

(Reactive gas chamber) is in this device as

Microwave ring resonator designed to be a

To generate microwave lasma.

With this device, the deposition of the layer system proposed here is made possible. The device allows multi-phase carbon based

Layer systems in a process, ie without interrupting vacuum and plasma, to deposit. The device corresponds to a combination of a known from DE 10 2005 049 266 A device for the deposition of DLC coatings with a device for deposition of diamond layers, as is known for example under the name Cyrannus ^®. The known apparatus for depositing DLC layers enables the process-technical separation of plasma density and ion energy. Only with this device and the associated

Coating method, it is possible, particularly thick DLC layers (typically> 50 μπι) and selectively microstructured or ultra-smooth surfaces to produce almost all metal, ceramic and plastic substrates. Due to the design, the two-chamber configuration present in this device enables the integration of a further microwave-based deposition technology for the production of crystalline diamond layers, which is known as a single process from the prior art. In the

Combination of the known plasma device for

Deposition of DLC layers with a microwave ring resonator for the production of diamond layers, it is only necessary to carry out the existing capacitive source in the interior of the now acting as a reactive gas boiler microwave ring resonator high temperature.

The electron gate of the proposed device is preferably also used as a plasma source,

in particular as a downstream plasma source. This may be, for example, an inductively coupled high-frequency plasma source or a

Act microwave plasma source. In this way, the function of the electron gate is realized very advantageously and at the same time the undesired diffusion of reactive neutral particles between the two

Chambers effectively suppressed.

Brief description of the drawings.

The proposed method and the associated device are described below with reference to a

Embodiment in conjunction with the drawings briefly explained again. Hereby show: Fig. 1 shows an example of a device

Deposition of DLC layers;

Fig. 2 is a schematic representation

Example of the proposed

Contraption; and

Fig. 3 is a schematic representation of

Deposition of a layer system.

Ways to carry out the invention

Fig. 1 shows schematically an example of a device for plasma separation (PECVD technology), which can be configured according to the present patent application. The plasma chamber 1 is divided into two and is supplied with process gases by two separate gas systems. The division into an inert gas region or an inert gas chamber 2 and a reactive gas region or a reactive gas chamber 3 via a partition wall 4 with an electron gate 5. The structural design of the plasma chamber 1 and the supply and pumping system for the gases is designed so that the in Reactive gas (eg CH ₄ ) which has flowed into the reactive gas chamber 3 can not enter the inert gas chamber 2 or only to a small extent. For this purpose, the reactive gas chamber 3 has a feed 6 for reactive gases and an outlet 7 for a pump. The inert gas chamber 2 accordingly has a feed 8 for inert gases (eg argon). The non-RF-acted parts of the reactive gas chamber 3 are electrically isolated. Alternatively, they can be removed or removed from the RF ground an electrical insulator, for example made of glass or ceramic, be made. For the latter two options must be an RF technical

suitable and shielded ground line from the Inertgas kanuner 2 to the inside of the figure not

shown matching network (matchbox) can be realized. In the present example, the walls of the reactive gas chamber 3 are covered with electrical insulation 9, so that the active region of the counterelectrode, which is formed by the metallic walls of the inert gas chamber 2, lies only in the inert gas region. Now, when a plasma is ignited by applying a high-frequency voltage to the electrode, which is formed by the slide 10 for the samples to be coated 24, the neutral plasma column burns in the upper and lower combustion chamber in the form of a dumbbell. For the operation of such a device, reference is made to DE 10 2005 049 266 AI. In order to also be able to produce diamond in this system technology, the active biasable electrode is made high-temperature capable, in particular of high-temperature-resistant metals and alloys, e.g. made of molybdenum. The executed in Fig. 1 as an insulator

Reactive gas chamber is replaced by a microwave ring resonator. Of course, this must not be connected to the RF ground of the capacitive plasma source. If the passage between the two combustion chambers or chambers designed so that a

unhindered exchange between the two parts of the neutral plasma column is possible, so is in the

Reactive gas chamber (lower combustion chamber) only the slide active (passive chamber areas are either isolated for RF currents from the plasma or removed from the RF ground) and in the inert gas (upper combustion chamber) only the electrically conductive

Counter electrode. In the reactive gas range, the coating-effective ions fly only on the active

Slides and in the inert gas only noble gas ions on the conductive executed chamber walls. The additionally generated in front of the active surfaces plasma densities do not lead in the region of the counter electrode

Deposits, which avoid charging effects. Only the reactive gas plasma limiting

floating surfaces are occupied by ions delivered by the ambipolar diffusion. However, a thin electrically insulating patina on a passive and electrically insulating chamber wall does not affect the discharge sustainably.

In order to realize constant plasma densities independently of the substrate surface, the counter electrode and the volume of the recipient are made flexible. For this purpose, an intermediate ring principle

proposed. The lower isolated area of the plant can be adapted to the different size of possible components. The upper area, which is responsible for creating the necessary DC bias, is designed to preserve the area ratios of possible previous processes.

Thus, there is some level of scalability, since, in a first approximation, only the power corresponding to the increased / decreased glimmed area and the gas flow must be changed for constant plasma residence times of the species involved. The bias voltage necessary for the process is thus independent of the plasma necessary for the process ^¬ residence time of reactive species adjustable.

The junction between the two

Combustion chambers are designed in such a way that neither charged nor neutral portions of the reactive gas can reach the inert gas range. This is achieved by the electronic gate 5 present between the two areas. The task of the electron gate is to connect the two plasma columns and to allow unimpeded electron exchange without any back diffusion of neutral and charged reactive gases into the inert gas region. The processes responsible for this are the ambipolar diffusion, through which the largely stationary ions reach the respective other combustion chamber without such an electron gate, as well as diffusion and diffusion

Flow processes between the chambers, through which neutral parts of the gas can be exchanged.

The permanent supply of an inert gas flow in the inert gas region (upper combustion chamber) without its own pump opening acts as a barrier gas flow in the passage region and, if suitably executed, reduces the entry of neutral reactive gases into the inert gas region

(upper combustion chamber). In the simplest case, the electron gate may be a simple hole in the partition wall of the two combustion chambers. This has the dark space distance as the theoretically smallest diameter. To avoid the gas exchange or the back diffusion of reactive gas into the inert gas, however, the hole would have to be made very small and elongated or the inert gas stream would have to be very big. However, both do not meet the requirements of a real PECVD litigation.

In this case, the electrical resistance in the passage region should be as small as possible so that the capacitive coupling over the reactor walls in the reactive gas region is suppressed as much as possible. However, this requires the largest possible opening between the separated

Areas, typically about 5 cm in diameter. Furthermore, the inert gas content of the process gases is seldom more than 50% and therefore can not be arbitrarily increased.

In order to prevent the back diffusion of neutral particles from the reactive gas region into the inert gas region, the electron gate is therefore used as the downstream

Plasma source carried out, which is mounted or disposed above the opening in the partition wall and a

maintains inductive or microwave coupled plasma.

Since ambipolar diffusion is a physical condition of any plasma, any surface confining the plasma is also bombarded with ions outside the active surfaces. The only way to prevent this is to use the

Movement of all the plasma leaving

Carriers (positive and negative) by a

To manipulate the magnetic field so that it can not reach the floating surface. All inactive

Areas of the reactive gas area are therefore in the

present example with the homogeneous magnetic field of a Helmholtz coil 11 (see Fig. 1) or with a system of Helmholtz coils coated. The coils must be arranged so that the resulting magnetic field lines between electrode and electron gate parallel to the floating chamber wall of the reactive gas region or the active walls of the ring resonator.

Fig. 2 shows again an example of the structure of the proposed device in a schematic representation. Reactive gas chamber 3 and inert gas chamber 2 are connected to each other via the electron gate 5. The electron gate 5 itself is an inductive plasma source or microwave downstream plasma source

executed and with an RF generator / Matchbox for the inductive plasma source or a magnetron of the

A microwave downstream plasma source connected (reference 12). The reactive gas chamber 3 is designed as a microwave ring resonator 13, which is connected via an E / H tuner 14 and a circulator 15 with a magnetron 16. The reactive gas chamber 3 is further surrounded by Helmholtz coils 11. The generation of the capacitively coupled RF plasma for the production of DLC layers takes place via the coupling of RF power via the electrode (slide 10), which is connected via a match box 17 to an RF generator 18.

In principle, this device can also be used exclusively polycrystalline

Diamond layers or only DLC layers produce. For the production of single polycrystalline diamond layers, it is sufficient to have only the ring resonator 13 in operation. Optionally, however, the plasma source between the chamber regions (in the region of the electron gate 5) and the active object carrier 10 as a capacitive RF plasma source together or alone supportive to influence the layer growth. For the production of DLC layers, the sole operation of the capacitive RF plasma source is sufficient. Supportive operation of all other plasma sources is optional.

For the production of the here proposed

SchichtSystems is on the component 19 first using the microwave ring resonator 13 a

Diamond layer 20 deposited. Here can also support the two other plasma sources

(Downstream plasma source at the electron gate and capacitively coupled high-frequency plasma) are switched supportive. After deposition of this layer, the microwave power is reduced while increasing the power of the capacitive high-frequency plasma. This results in a transfer layer 22, which finally passes into a DLC layer (a-C: H) 21 after setting the appropriate plasma parameters.

This DLC layer 21 is preferably deposited on the diamond layer 20 with a thickness of> 50 μm. This is shown very schematically in FIG. The following table shows an example of parameters and process times for depositing the layers.

Process diamond layer Transfera-C: H

parameter layer

Pressure 70 hPa -> 1 Pa

Gas 1 - »50 sccm Argon

Gas 2 400 sccm H2 - »20 sccm TMS

Gas 3 20 sccm CH4 - 50 sccm C2H2

RF power 0 - »150 W M power 2, 5 kW - 0 kW

Bias voltage 0 V - 450 V.

Time 180 min 5 min 60 min

Temperature 900 ° C - 120 ° C

In addition, an intermediate layer 23 of carbon nanotubes, which lies between the component 19 and the diamond layer 20, is additionally indicated in FIG. This intermediate layer is deposited with the microwave plasma of the microwave ring resonator 13 directly on the component 19 and increases the adhesion of the diamond layer 20 on the component 19, in particular in the case of components made of hard metal.

LIST OF REFERENCE NUMBERS

I plasma chamber

2 inert gas chamber / inert gas area

3 Reactive gas chamber / reactive gas area

4 partition

5 electron gates

6 Reactive gas supply

7 Reactive gas discharge

8 inert gas feed

9 isolation

10 slides (electrode)

II Helmholtz coils

12 High frequency generator / Matchbox for the inductive plasma source or magnetron of the microwave downstream source

13 microwave ring resonator

14 E / H tuners

15 circulator

16 magnetrons

17 matchbox

18 high-frequency generator of the capacitive

plasma source

19 component

20 diamond layer

21 DLC layer

22 transfer layer

23 layer of carbon nanotubes

24 samples

Claims

claims

Process for producing a carbon-containing layer system, in particular for increasing the

Wear resistance of components, with the following steps:

Depositing a diamond layer (20) by means of plasma deposition,

Depositing a transition layer (22) and an amorphous carbon-containing layer (21) on the diamond layer (20) by means of plasma deposition,

- The layers (20, 21, 22) are deposited successively under a vacuum, without the vacuum and for the layer deposition

required continuous or pulsed plasma between the deposition of the layers (20, 21, 22) to interrupt.

Method according to claim 1,

characterized,

in that an a-C: H layer is deposited as the amorphous carbonaceous layer (21).

Method according to claim 1 or 2,

characterized,

in that the diamond layer (20) is deposited with a microwave plasma and the amorphous carbon-containing layer (21) with a capacitively coupled radio-frequency plasma. Method according to claim 3,

characterized,

that for the transition from the diamond layer (20) to the amorphous carbon layer (21), the microwave power continuously or step-wise ^¬ reduced and the high-frequency power can be increased at the same time continuously or stepwise.

Method according to one of claims 1 to 4,

characterized,

that the amorphous carbonaceous layer (21) is deposited with a layer thickness> 50 μτα.

Method according to one of claims 1 to 5,

characterized,

in that before deposition of the diamond layer (20) a layer (23) of carbon nanotubes is deposited, to which subsequently the

Diamond layer (20) is deposited directly or via another transition layer.

Method according to one of claims 1 to 6,

characterized,

in that the plasma deposition of the layers (20-23) takes place with a plasma system which has a

Inert gas chamber (2) and one separate

Reactive gas chamber (3) having a

Electronic gate (5) are interconnected, wherein in the reactive gas chamber (3) a slide (10) is arranged, which is designed as an electrode for the generation of a high frequency plasma, in the inert gas chamber (2) a counter electrode ange- is arranged and the reactive gas chamber (3) is designed as a microwave ring resonator (13).

Device suitable for carrying out the method according to one of Claims 1 to 7, having a plasma chamber (1) in which at least one

Electrode is arranged as a slide (10) and at least one wall portion of the plasma chamber (1) and / or at least one arranged in the plasma chamber (1) component forms a counter electrode, and a connected to the electrode radio frequency unit (18) with which by applying a high-frequency alternating voltage between electrode and counter electrode a high-frequency plasma in the plasma chamber (1) can be generated,

wherein the plasma chamber (1) by a separating device (4, 5) is divided into at least two sub-volumes, of which a first partial volume (3) for a reactive gas, the electrode and a second partial volume (2) for an inert gas in the high-frequency plasma generation Include active region of the counter electrode, wherein the first sub-volume (3) as a microwave ring resonator (13) and connected to generate a microwave plasma with a magnetron (16), and wherein the separating device (4, 5) is suitable, a for the generation of high-frequency plasma required electron exchange in the high-frequency plasma between the sub-volumes (2, 3)

allow and a diffusion barrier for the

To form reactive gas.

9. Apparatus according to claim 8, wherein the the

Separating device has an electron gate (5), which is designed as a plasma source.