Method and apparatus for fabrication of a DLC layer system

The present invention relates to a method according to claim 1. Preferred embodiments of the invention are disclosed in the dependent claims 2 to 17. Despite the outstanding properties of diamond-like carbon layers (DLC layers), such as high hardness and excellent sliding properties, and a long-term worldwide research activity, it has not been possible to produce pure DLC layers, which are still suitable for larger layer thicknesses (> 1 μm) show sufficient adhesion to the industrial use in typical wear protection applications and have sufficient conductivity, in order to be able to dispense with the high-frequency (HF) process with many production-related disadvantages.

As typical wear protection applications here on the one hand applications in the engineering sector, such as protection against sliding wear, pitting, cold welding, etc., especially on components with mutually moving surfaces, such as gears, pump and bucket tappets, piston rings, injector needles, complete bearing sets or their individual components, etc. On the other hand, applications in the field of material processing to protect the tools used for machining or forming machining and injection molds.

In addition to the versatile application possibilities in the wear protection area, the corrosion protection is expressly mentioned here as another promising field of application of such DLC layers.

Due to the high residual stresses and the associated problematic adhesion, especially in highly stressed surfaces, pure DLC coatings can now be deposited in wear protection only with low layer thicknesses which are inadequate for many applications or have to be prepared by additional incorporation of foreign atoms, such as silicon, various metals and the like Fluorine can be changed in their properties. However, the resulting reduction in the layer's residual stresses and the improvement in adhesion were always associated with a significant loss of hardness, which can often have a negative effect on the life of the coated article, especially in the area of ​​wear protection.

An additional application of inlet layers containing, for example, graphitic carbon and / or a mixture of metal or metal carbide and carbon, could therefore not be taken into account because on the one hand by the necessary to achieve the Einlaufeffekts minimum layer thickness further harmful layer stresses were built and on the other hand Adhesion to pure carbon layers was problematic. Only such layers can but by the combination of the very hard carbon layer, or diamond layer with the deposited sliding or inlet layer meet the increasing requirements for components, as required for example for individual components in modern engine.

In today's conventional plasma-assisted processes for the production of DLC layers are due to the high electrical resistance of hard DLC layers often to avoid disturbing charges during coating, processes with an RF bias or plasma (as HF = high frequency are hereinafter all frequencies> 10 MHz understood), in particular with the industrial frequency 13.56 MHz applied. The known disadvantages of this technique are difficult to control disturbances of electronically sensitive process control units (RF feedback, transmitter effect,...) An increased effort to avoid RF-beating, antenna effect of the substrates to be coated and a relatively large minimum distance between the coating material, which prevents optimal space and land use in the coating chamber. For example, it must be ensured with HF procedures that there is no overlap of dark rooms due to excessive loading density, incorrect substrate / support distances, etc., which causes harmful secondary plasmas. On the one hand, such secondary plasmas form energy sinks and thus additionally burden the plasma generators; on the other hand, such local plasma concentrations frequently result in thermal overheating of the substrates and undesired graphitization of the layer.

Due to the exponential dependency of the substrate voltage on the substrate surface, which is calculated in HF processes <maths id="math0001"><math display="block"><mrow><mi>US</mi><mo>/</mo><mi>UE</mi></mrow><mo>=</mo><mrow><mi>CE</mi><mo>/</mo><mi>CS</mi></mrow><mo>=</mo><mfenced><mrow><mi>AE</mi><mo>/</mo><mi>AS</mi></mrow><mi mathvariant="normal"> </mi></mfenced><mn>4</mn></math><img file="EP1362931B2_D0001.tif" /></maths> where U stands for the voltage, C for the capacitance, A for the surface and the indices S for substrate and E for the counter electrode, it comes with increasing substrate surface AS to a large drop in the substrate voltage US accompanied by a sharp increase in power loss. Therefore, depending on the performance of the generators used, only a certain maximum area can be coated. Otherwise, either insufficient power can be introduced into the system or the potential difference (substrate voltage) can not be set high enough to achieve the ion-plating effect necessary for well-adhering dense layers.

Furthermore, on the plant side in HF processes usually additional expenditure on equipment is necessary to dynamically adapt generator and plasma impedances by electrical networks, such as a so-called matchbox, during the process. In the following, various methods or layer systems known from the prior art are briefly cited.

The <patcit id="pcit0001" dnum="EP87836A"><text>EP 87 836</text></patcit> discloses a DLC layer system with a 0.1-49.1% level of metallic components deposited by, for example, cathodic sputtering.

The <patcit id="pcit0002" dnum="DE4343354A1"><text>DE 43 43 354 A1</text></patcit> describes a method for producing a multilayer Ti-containing layer system with a hard material layer of titanium nitrides, titanium carbides and titanium borides, and a friction-reducing C-containing surface layer, wherein the Ti and N content in the direction of the surface is progressively reduced.

A pulsed plasma jet uses that in the <patcit id="pcit0003" dnum="US5078848A"><text>US 5 078 848</text></patcit> described method for the preparation of DLC layers. Due to the directed particle radiation from a source with a small outlet cross-section, however, such processes are only of limited suitability for the uniform coating of larger areas.

Various CVD processes or SiDLC / DLC mixed layers produced by such processes are described in the following documents: The <patcit id="pcit0004" dnum="EP651069A"><text>EP-A-651,069</text></patcit> describes a friction reducing wear protection system of 2-5000 alternating DLC ​​and SiDLC layers. A process for depositing a-DLC layers with a Si interlayer and adjoining a-SiC: H transition zone to improve adhesion is disclosed in US Pat<patcit id="pcit0005" dnum="EP600533A"><text>EP-A-600 533</text></patcit> described. Also in the<patcit id="pcit0006" dnum="EP885983A"><text>EP-A-885 983</text></patcit> and the <patcit id="pcit0007" dnum="EP856592A"><text>EP-A-856 592</text></patcit> Various methods for producing such layers are described. In the<patcit id="pcit0008" dnum="EP885983A"><text>EP-A-885 983</text></patcit> For example, the plasma is generated by a DC-heated filament and the substrates with negative DC voltage or MF between 20 - 10,000 kHz applied (as MF = center frequency is understood in the following the frequency range between 1 and 10,000 kHz).

The <patcit id="pcit0009" dnum="US4728529A"><text>US 4,728,529</text></patcit> describes a method for the deposition of DLC using an HF plasma, in which the layer formation takes place in a pressure range between 103 and 1 mbar from an oxygen-free hydrocarbon plasma, to which noble gas or hydrogen is added as needed.

The Indian <patcit id="pcit0010" dnum="DE19513614C"><text>DE-C-195 13 614</text></patcit> described process uses a bipolar substrate voltage with a shorter positive pulse duration in a pressure range between 50-1000 Pa. This layer is deposited in the range of 10 nm to 10 microns and a hardness between 15 - 40 GPa.

A CVD process with substrate voltage generated independently of the coating plasma is described in US Pat <patcit id="pcit0011" dnum="DE19826259A"><text>DE-A-198 26 259</text></patcit> described, wherein preferably bipolar, but also other periodic changes in substrate voltages are applied. However, this requires a relatively complex, as to be provided in duplicate, electrical supply unit for performing the method.

Furthermore, processes from a combination of traditional hard material layers with a carbon-rich cover layer with favorable sliding properties have been known for some time. For example disclosed <patcit id="pcit0012" dnum="US5707748A"><text>US 5,707,748</text></patcit> a layer combination of metal-containing hard coatings (TiN, TiAIVN, WC) and a less hard metal carbide layer with increasing content of graphitic, ie in sp² Hybridization, bound carbon. Due to the good sliding properties of metal / - or metal carbide / carbon layers (MeC / C), these are preferably used in tribosystems, where in addition to the protection of the coated part, a reduction of the frictional forces and / or protection of the counter body to be effected. In this regard, MeC / C layers with a high C content have proven to be particularly effective, in which the soft cover layer on the one hand achieves an enema effect, and on the other hand, by transferring C particles, a lubricating effect for the entire tribosystem. Similar layer combinations with a adhesion enhancing metallic intermediate layer between the hard material layer and the graphitic carbon-containing metal or MeC layer are disclosed in US Pat<patcit id="pcit0013" dnum="WO9955929A"><text>WO 99-55929</text></patcit> described.

The item "<nplcit id="ncit0001" npl-type="b"><text>DLC multilayer coatings for wear protection "by Deng J. et al., Diamond and Related Materials, Elsevier Science Publishers, Amsterdam, NL, Vol. 4, No. 7, May 15, 1995, pp. 936-943</text></nplcit> discloses a DLC multilayer coating for wear protection. The DLC layer is deposited on a Ti adhesive layer and a multilayer transition layer of a sequence of TiN, TiCN and TiC. The transition layer is a multi-layered gradient layer in which the nitrogen content decreases and the carbon content increases toward the DLC layer.

The publication <patcit id="pcit0014" dnum="FR2596775"><text>FR 2 596 775</text></patcit> shows a process for the production of a layer system and the layer system itself. The special plant geometry aims at the highest possible ionization of the process gas or the metal vapor. A third electrode is provided to prevent drift of electrons against the walls. An electron gun is located in the lower part of the housing.

The <patcit id="pcit0015" dnum="US5709784A"><text>US 5,709,784</text></patcit> relates to a device for coating by means of a low-voltage arc discharge. The device comprises, in addition to the usual components, in particular also means for applying a Substratbiasspannung to the substrate, and Helmholtz coils for generating a magnetic field. By means of this system, a low-voltage arc process can be performed. In addition to a cathode and an anode, an additional voltage source for generating a positive DC voltage at the anode is provided.

Accordingly, it is the object of the present invention to provide a method for producing relatively thick DLC layer systems with high hardness and excellent adhesion, which in addition still have a sufficiently high conductivity to be able to be deposited without HF bias, the method and the device used for this do not require much effort and have high efficiency for industrial use.

This object is achieved by the method according to feature set 1. Advantageous embodiments are the subject of the sub-feature sets.

It is therefore an object of the present invention, in particular, to provide a process for producing a DLC or a diamond layer having excellent adhesive strength and high wear resistance, which has improved sliding properties and, if desired, running-in properties compared to conventional DLC or diamond coatings. Such a DLC overlay system may be advantageous for wear protection, corrosion protection, and slip resistance, especially when properties which are difficult to realize in a sheeting system are desired at the same time.

This is solved according to the independent claim.

LAYER SYSTEM

A DLC layer system produced by the method according to the invention is achieved by producing a layer with the following layer structure.

Directly on the substrate is an adhesive layer with at least one element from the group of elements of the IV, V and VI subgroup and Si. Preferably, an adhesive layer of the elements Cr or Ti is used, which have been found to be particularly suitable for this purpose.

This is followed by a transition layer which is preferably in the form of a gradient layer, in the course of which, perpendicular to the substrate surface, the metal content decreases and the C content increases.

The transition layer essentially comprises carbon and at least one element from the group of elements which form the adhesion layer. Additionally, in a preferred embodiment, hydrogen may be included. In addition, both the transition layer and the adhesive layer include unavoidable impurities, such as those caused by atoms incorporated into the layer from the surrounding atmosphere, such as the noble gases used in the preparation, such as argon or xenon.

In the formation of the transition layer in the form of a gradient layer, the increase of the carbon in the direction of the cover layer can be carried out by increasing possibly different carbide phases, by increasing the free carbon, or by a mixture of such phases with the metallic phase of the transition layer. As is known to the person skilled in the art, the thickness of the gradient or transition layer can be adjusted by setting suitable process ramps. The increase in the C content or decrease in the metallic phase can be carried out continuously or stepwise, and also a sequence of metal-rich and C-rich individual layers can be provided for further degradation of layer stresses at least in one part of the transition layer. As a result of the mentioned embodiments of the gradient layer, the material properties (for example modulus of elasticity, structure, etc.) of the adhesion and the final DLC layer are substantially continuously adapted to one another and thus the risk of crack formation along an otherwise occurring metal or Si / DLC layer. Counteracted interface.

The conclusion of the layer package forms a layer consisting essentially exclusively of carbon and preferably hydrogen, with a greater layer thickness compared to the adhesion and transition layer. In addition to carbon and hydrogen, noble gases such as argon or xenon can also occur here. It is essential here, however, that is completely dispensed with additional metallic elements or silicon.

The hardness of the entire DLC layer system is set to a value greater than 15 GPa, preferably greater than or equal to 20 GPa and an adhesive strength better than or equal to HF 3, preferably better or equal to HF 2, in particular equal to HF 1 according to VDI 3824 sheet 4 is achieved. The hardness will be determined by the Knoop hardness measurement with o, 1 N load, ie HK0,1. The surface resistance of the DLC layer is between δ = 10-6Ω and δ = 5MΩ, preferably between 1Ω and 500 kΩ, with an electrode spacing of 20 mm. At the same time, the present DLC layer is characterized by the low coefficient of friction typical for DLC, preferably μ ≦ 0.3 in the pin / Scheib test.

The layer thicknesses are in total&gt; 1 .mu.m, preferably&gt; 2 .mu.m, wherein the adhesive layer and the transition layer preferably have layer thicknesses of 0.05 .mu.m to 1.5 .mu.m, in particular from 0.1 .mu.m to 0.8 .mu.m, while the cover layer preferably has a thickness of 0.5 μm to 20 μm, in particular 1 μm to 10 μm.

The H content in the cover layer is preferably 5 to 30 atom%, especially 10 to 20 atom%.

In SEM images, such deposited DLC layer systems show fracture surface, which, in contrast to conventional DLC layers, have no glassigamorphic but a fine-grained structure, the particle size preferably being ≦ 300 nm, in particular ≦ 100 nm.

In tribological tests under high stress, the coating shows a multiple lifetime compared to other DLC layers, such as metal carbon, especially WC / C layers. Thus, on a DLC-coated injector for internal combustion engines in the test after 1000h only a slight wear was found, whereas in the same test a WC / C coated nozzle already after 10h due to a high surface wear to the base material precipitated.

The layer roughness of the corresponding DLC ​​layer preferably has a value of Ra = 0.01-0.04; where Rz measured to DIN &lt;0.8, preferably &lt;0.5.

The advantages of a corresponding DLC ​​layer system with the above properties lie in the first successful combination of large layer thicknesses with excellent adhesion, which still have sufficient conductivity to allow a relatively simple process control in industrial production.

Despite the high hardness of&gt; 15 GPa, preferably ≥ 20 GPa, the layer shows a significantly improved adhesion due to its structure and the inventive process steps. Conventional layer systems require doping in the functional layer (DLC) in order to reduce the layer stress, but this also reduces the hardness.

Also REM fractions of the corresponding layer show, in contrast to previously known DLC layers, which have the typical fracture shape of an amorphous brittle layer with partly mussel outbreaks, a fine-grained straight fracture surface. Layers with the property profile described above are particularly suitable for applications in mechanical engineering, such as for coating highly loaded pump or bucket tappets and valve trains, cams or Camshafts as used for automotive internal combustion engines and transmissions, but also for the protection of highly loaded gears, plungers, pump spindles and other components where a particularly hard and smooth surface with good sliding properties is needed.

Due to their high hardness and very smooth surface, these coatings can be used for cutting tools (presses, stamping, deep drawing, ...) and injection molding tools, but also, with certain limitations in the processing of ferrous materials, for cutting tools , Especially when a low coefficient of friction coupled with a high hardness is necessary for the application.

The growth rate of the DLC layer is about 1-3 μm / h, the layer stress for the whole system at 1-4 GPa and thus in the usual range of hard DLC layers. Due to the above explanations, the conductivity becomes approximately between δ = 10^-6Ω and δ = 5 MΩ, preferably between δ = 10^-3 Ω and δ = 500 kΩ (measured here was the surface resistance at a distance of the measuring electrodes of 20 mm). Although the sliding properties achieved with such deposited DLC layer systems are more favorable than those of other, for example, nitridic and / or carbide hard coatings, they neither achieve the extremely small coefficients of friction which can be realized with metal / carbon layers, nor are they suitable as running-in layers. If the sliding or running-in properties of the DLC layer or of the DLC layer system are to be further improved, it is still advisable to apply a final, softer, relatively large proportion of graphitic carbon-containing sliding layer. The latter can also be advantageously applied to other DLC layers and layer systems as well as to diamond layers, in particular to nanocrystalline diamond layers.

The following is the structure of a <b>DLC-slipping layer system</b> described, which advantageously, but by no means limiting, consists of a DLC layer system as described above with a sliding layer deposited thereon. Surprisingly, it has been found that it is possible with very different sliding layers built in addition to the improvement of sliding and possibly run-in properties, despite the increased layer thickness to obtain the excellent adhesion of the DLC layer system for the DLC sliding layer system. A particularly advantageous embodiment of the friction-reducing layer which is particularly suitable for application to the above-described inventive DLC layer system is a DLC structure, without a metallic additional element, but with an increasing proportion of sp²-Bindungen, preferably applied in graphitic layer structure, whereby the hardness of the outer layer is reduced, and the sliding and optionally enema properties are improved.

Another advantageous embodiment of the sliding layer can take place by forming a second, inverse gradient layer, in which the metal content to the surface increases, but the C content decreases. The metal content is increased until the friction coefficient reaches a desired low value. Preference is given to one or more metals from the IV, V, VI subgroup, and Si used. Particularly preferably Cr, W, Ta, Nb and / or Si. The metal content of the layers should be between 0.1 and 50 atom%, preferably between 1 and 20 atom%. A further preferred embodiment of the Reibmindernden layer can be achieved by applying a metallic or carbide, in particular a Cr or WC intermediate layer, on which substantially exclusively of carbon and hydrogen existing layer, are prepared, followed in turn followed by a similarly formed the first gradient gradient cover with decreasing metal and increasing C content. Advantageously, but not necessarily, the same or the same metallic elements as in the first gradient layer are used in order to minimize the complexity of the coating apparatus. Again, the metal content of the layers should be between 0.1 and 50 atom%, preferably between 1 and 20 atom%. Surprisingly, it has been shown that even metal-containing overlays can also bring about a marked improvement in the performance on conventionally deposited DLC layers. One reason for the resulting low impact on the overall adhesion of such systems could be due to the easily adjustable, low additionally introduced layer stresses. For all three possibilities, it has proved to be advantageous to provide a final region with unchanged ie constant layer composition in order to maintain the properties of the layer optimized for the respective application (eg coefficient of friction, surface tension and wettability,...) Even over a certain layer wear receive and allow a shrinkage of the layer. The coefficient of friction can be adjusted between μ = 0.01 and μ = 0.2, depending on the metal used and the excess excess of chapitic carbon (refers to the pin / shake test under normal atmosphere with approx. 50% air humidity).

The hardness of the DLC layer is preferably set to a value greater than 15 GPa, preferably greater than or equal to 20 GPa, the hardness of the overlying softer sliding layer is adjusted as required. The integral hydrogen content of the corresponding layer system is preferably set to a content of between 5 and 30 atom%, in particular between 10 and 20 atom%. The layer roughness can have a Ra value of less than 0.04, preferably less than 0.01, or a RzDIN value of less than 0.8, preferably less than 0.5 can be set. The advantages of such a DLC sliding layer system lie in the combination of the high hardness of the DLC layer, coupled with an improved sliding properties compared to the already good running behavior of the DLC layer by up to an order of magnitude. For example, the coefficient of friction can thus be reduced below μ = 0.1. Furthermore, for the first time, it is also possible for DLC layers to impart run-in behavior through initial layer removal and graphitic counter-body lubrication, as a result of which the wear of an uncoated counter body can be significantly reduced.

Furthermore, by using a pure DLC layer described above, a lower Rz or Ra number, ie a lower roughness of the coated surfaces, than with conventionally used hard coatings, in particular applied by the Arc method, can be set. In such known hard / overlay combinations can be disturbed by particularly hard roughness peaks often the running of the tribosystem, if not prevented and become, which can lead to the partial or total destruction of the surface of a counter body, especially if it is not itself protected by a hard layer. This is particularly important in tribosystems with high sliding share, such as tilt and slide lever on bucket tappets, different gears, etc. important. The superiority of DLC overlay systems has been demonstrated in various applications both over known hard / overlay combinations and over pure DLC layer systems.

Due to their high hardness and very smooth surface, these coatings can also be used to advantage in the tool area, especially for forming (pressing, stamping, deep drawing, ...) and injection molding machines, but also with certain limitations when machining iron materials for cutting tools. in particular if a particularly low coefficient of friction, possibly paired with a defined inlet effect, is desired for the application. For example, with such coated drills after a single use (a hole) a polishing effect on the Spanablauffläche was observed, which is for example for deep hole drilling advantage. Thus, in such coated tools so expensive renumbering the chip flow surfaces can be dispensed with. Corresponding DLC ​​sliding layer systems can be deposited more smoothly than conventional hard-material / lubricant layer combinations (eg TiA1N / / WC / C) deposited with arc evaporators and can be integrated more easily in a continuous process than, for example, likewise known Ti-DLC // MoSx layer combinations.

METHOD

The inventive method for producing the DLC layer system is characterized by the features of claim 1.

The parts to be coated are cleaned in a manner known for PVD methods and mounted on a fixture. In contrast to HF methods, holding devices can advantageously be used, which are adapted to the geometry of the particles, 1, 2, or even 3 essentially parallel axes of rotation, as a result of which a greater loading density can be achieved. The holding device with the parts to be coated is brought into the process chamber of a coating system and after pumping to a starting pressure of less than 10-4 mbar, preferably 10-5 mbar, the process sequence is started.

The first part of the process, the cleaning of the substrate surfaces, is performed, for example, as a heating process to remove the still adhering to the surface of the parts of volatile substances. For this purpose, a noble gas plasma is preferably ignited by means of a high-current / low-voltage discharge between one or more filaments arranged on a negative potential in a ionization chamber adjacent to the process chamber and the holding devices with the parts placed at positive potential. This causes an intense electron bombardment and thus a heating of the parts. In this case, the use of an Ar / H 2 mixture has proved to be particularly favorable since the reducing effect of the hydrogen simultaneously achieves a cleaning effect of the parts surfaces. The high current / low voltage arc discharge can be performed with a static or advantageously substantially locally variably moving magnetic field. Instead of the ionization chamber described above, a hollow cathode or other known ion or Be used electron source.

Alternatively, of course, other heating methods such as radiant heating or inductive heating can be used.

After reaching a Termperaturniveaus to be determined depending on the base material of the parts, additionally or alternatively, an etching process can be started as a cleaning process, for example by a low-voltage arc is ignited between the ionization chamber and an auxiliary anode, and the ions by means of a negative bias voltage of 50-300 V on the parts to be pulled. The ions bombard the surface and remove any remaining impurities. Thus, a clean surface is achieved. The process atmosphere can contain not only noble gases, such as argon, but also hydrogen.

The etching process is carried out by applying a pulsed substrate bias voltage without or with the assistance of a low-voltage arc as just described, using a middle-frequency bias in the range of 1 to 10,000 kHz, in particular between 20 and 250 kHz.

In order to ensure the adhesion of the DLC layer system on the substrate, a preferably metallic, in particular consisting of Cr or Ti adhesive layer with a known PVD or plasma CVD method, such as by Arcverdampfen, various ion plating method, but preferably by cathodic sputtering at least of a target evaporated. To support the vapor deposition, a negative substrate bias voltage is applied to the substrate. The ion bombardment and the resulting layer compaction during the sputtering process may additionally be effected by a parallel-operated low-voltage arc and / or a magnetic field applied for stabilizing or intensifying the plasma, and / or by applying a DC bias voltage to the substrate or by applying a medium-frequency bias Substrate and process chamber in the range of 1 to 10,000, in particular between 20 to 250 kHz are supported.

The thickness of the adhesive layer is adjusted in a known manner by a choice of the sputtering or vapor deposition time and power corresponding to the respective plant geometry.

For example, given present system geometry Cr, for a period of 6 minutes, two advantageously opposing targets at a pressure between 10-4 to 10-3 mbar, a substrate bias of Ubias = -75 V and a power of about 8 kW sputtered in an Ar atmosphere.

After application of the adhesive layer according to the invention by applying a transition layer as smooth as possible transition between the adhesive layer and DLC layer is ensured.

The application of the transition layer takes place in such a way that, in addition to the plasma-assisted vapor deposition of the adhesive layer components, carbon is deposited at the same time from the gas phase. This is preferably done by a plasma CVD method, in which a carbon-containing gas, preferably a hydrocarbon gas, in particular acetylene is used as the reaction gas.

During the application of the transition layer, a "pulsed", medium-frequency substrate bias voltage is applied to the substrate and a magnetic field is superimposed.

For the preferred formation of a gradient layer, during the application of the transition layer, the proportion of carbon deposition is increased stepwise or continuously with increasing thickness of the transition layer, until in the end substantially only a carbon deposition takes place.

In this process stage, the diamond-like carbon layer is then produced as a cover layer by plasma CVD deposition of carbon from the gas phase, wherein a carbon-containing gas, preferably a carbon dioxide gas, in particular acetylene, is used as the reaction gas. At the same time, a substrate bias voltage is maintained at the substrate and the superimposed magnetic field is maintained.

In a preferred embodiment, the reaction gas for depositing carbon to form the transition layer and the diamond-like carbon overcoat may further include hydrogen and rare gas, preferably argon or xenon, in addition to the carbon-containing gas. The set pressure in the process chamber is between 10-4 to 10-2 mbar.

During the deposition of the cover layer of diamond-like carbon, it is preferable to increase the proportion of the carbon-containing gas and to reduce the proportion of noble gas, in particular argon.

The substrate bias voltage applied to the substrate at least during the process steps for vapor deposition of the adhesion layer, application of the transition layer and deposition of the cover layer is a unipolar (negative) or bipolar substrate bias voltage pulsed in a medium frequency range of 1 to 10000 kHz, preferably 20 to 250 kHz. The pulse shape may be symmetrical, for example, sinusoidal, sawtooth, or rectangular, or asymmetric, so that long negative and short positive pulse times or large negative and small positive amplitudes are applied.

Moreover, during the deposition of the overcoat layer and the deposition of the overcoat layer, preferably throughout the deposition process, the plasma is stabilized by a magnetic field, while superimposing the transition layer and the diamond-like cladding layer over the substrate, a longitudinal magnetic field with uniform field line progression is applied to the substrate, wherein the magnetic field is spatially continuously or stepwise changeable.

Preferably, when applying the transition layer, first a medium-frequency generator is connected to the holder device, which emits its sapping pulses (regulation via control of the introduced power is also possible, but not preferred) in the form of a sinusoidal signal, or another bi- or also unipolar signal waveform , The frequency range used here is between 1 and 10,000 kHz, preferably between 20 and 250 kHz, the amplitude voltage between 100 and 3,000 V, preferably between 500 and 2,500 V. In another advantageous embodiment, a medium-frequency voltage is also applied to the substrates for carrying out the etching process created. When using a bipolar substrate voltage, it has been found to be particularly advantageous to apply asymmetric pulse shapes, for example, the positive pulse may be applied either shorter or at a lower voltage than the negative pulse, since the electrons follow the field more rapidly and due to their low mass upon impact especially lead to additional heating of the parts, which can lead to damage due to overheating, especially with temperature-sensitive base materials. This danger can be counteracted in other signal curves by providing a so-called "OFF-time", in which a zero signal is applied between the application of single or multiple signal periods with power component (= "ON-time").

At the same time or with a time delay after application of the medium frequency signal, when using a DC bias for applying the adhesive layer, or after vapor deposition of the desired layer for the adhesive layer using a Mittelfrequenzbias, is a hydrocarbon gas, preferably acetylene with a gradual or preferably continuously increasing Gas flow embedded in the recipient. Likewise, at the same time or with an optionally different time delay, the power of the at least one metallic or Si target is preferably shut down stepwise or continuously. In this case, the target is preferably shut down to a minimum power which can easily be determined by a person skilled in the art, depending on the hydrocarbon flow achieved, in which stable operation without poisoning phenomena by the reactive gas is still possible. Subsequently, the at least one target is preferably shielded with one or more movably arranged diaphragms against the process chamber, and switched off. This measure largely prevents a coverage of the target with a DLC layer, which can be dispensed with an otherwise necessary free sputtering between individual DLC coating batches. At the next batch to be carried out, it suffices to provide a start-up of the at least one target with the shutters closed, in order to again achieve a completely blank target surface suitable for the application of the adhesive layer.

An essential contribution to the stabilization of the DLC coating process according to the invention is achieved by the formation of a longitudinal magnetic field. The magnetic field is formed so that a uniform field line course is given in the process chamber. For this purpose, preferably by two substantially the process chamber on opposite sides bounding electromagnetic coils current is introduced so that a co-directional, mutually reinforcing magnetic field is formed on both coils. With smaller chamber dimensions, a sufficient effect may also be achieved with only one coil. This achieves an approximately uniform distribution of the medium-frequency plasma over larger chamber volumes. Nevertheless, due to different geometries of the parts to be coated or of the holding devices, sporadic formation of secondary plasmas may still occasionally occur if certain geometric and electromagnetic boundary conditions are fulfilled. This can be counteracted by a temporally and spatially variable magnetic field by the coil currents are shifted with each other or preferably against each other. For example, the first coil is first flowed through for 120 seconds by a stronger current I than the second coil. During the following 90 seconds, the current is inverse, ie the second magnetic field is stronger than the first magnetic field. These magnetic field settings can be made periodically, as described, stepwise or continuously and thus avoid the formation of stable Nebenplasmen by a suitable choice of the corresponding coil currents. Only by using the magnetic field and the significant increase in the plasma intensity achieved as a result is it possible, in contrast to the prior art, even in low pressure ranges of, for example, 10^-3 until 10^-2 mbar to achieve a stable CVD process for the deposition of pure DLC layers with high deposition rates in the range of 0.5 to 5, preferably between 1 - 4 microns / h. In addition to the substrate current, the plasma intensity is directly proportional to the activation of the magnetic field. In addition, both parameters depend on the size of the surfaces provided with a bias. By applying lower process pressures, smoother layers can be deposited, with fewer growth defects and less contamination from interfering foreign elements.

The growth rate depends not only on the process parameters but also on the load and the mounting. In particular, this affects whether the parts to be coated 1-, 2- or 3-turn, on magnetic brackets, or clamped or plugged attached. The total mass and Plasmendurchgängikeit the brackets is important, so for example, with lightly built brackets, eg achieved by using storage plates, instead of plates made of solid material, higher growth rates and an overall better layer quality.

To further increase the plasma-amplifying magnetic field, additional local magnetic fields-so-called near fields-can be provided in addition to the longitudinal magnetic field (far field) penetrating the entire process chamber. Particularly advantageous is an arrangement in which in addition to at least one magnetron magnet system of the at least one target more preferably permanent magnet systems are attached to the walls bounding the plasma chamber, which have a similar or the same magnetic effect as the at least one magnetron magnet system. In this case, either in all magnetron and other magnetic systems, the same structure or preferably a reversal of the polarity can be made. This makes it possible to form the individual near fields of the magnetic or magnetron magnet systems, as it were, as a magnetic confinement surrounding the process chamber in order to prevent absorption of the free electrons on the walls of the process chamber.

Only by combining the essential features of the inventive process is it possible to produce a layer as described above. Only the use of stabilized by magnetic fields plasmas and the coordinated use of Substratbiasspannung allows the use of optimized for conventional PVD processes mounts with high packing density and process reliability. The procedure shows how the sequence or the combination of DC and medium frequency plasmas can be used optimally for the deposition of a DLC layer.

Various methods are used to construct the different sliding layers. To separate one <b>graphitized DLC layer</b> After applying the pure DLC layer, with otherwise substantially the same or similar process parameters set, the bias voltage either gradually or continuously to a value above 2000 V, preferably set between 2000 and 2500 volts. As the voltage increases, the proportion of graphitic sp²Bond growing C atoms. In this way, in a particularly simple manner, the previously deposited pure DLC layer can be given improved sliding properties. To apply a <b>inverse gradient layer</b> There are different possibilities. In the simplest case, while retaining the same parameters as in the preceding DLC ​​layer, the process can be carried out with the addition of one or more metallic or metal carbide components. However, it has proven to be advantageous either to first lower the hydrocarbon fraction in the gas flow, to increase the noble gas fraction, or to carry out both measures together in order to avoid poisoning of the targets and thus unstable process conditions. Furthermore, it may be advantageous to approach the targets behind initially closed diaphragms in order to avoid possible dropsplets on the substrates. Subsequently, the power of the at least one target is increased stepwise or preferably continuously up to a value at which the layer has certain desired layer properties (coefficient of friction,...). The remaining parameters are preferably left unchanged, but an additional adjustment is possible at any time if desired. Subsequently, the process is preferably continued while keeping the setting constant until a desired layer thickness of the inverse gradient layer is reached. A further advantageous possibility for forming an inverse gradient layer results if, in addition to or instead of the mentioned hydrocarbon gas, silicon-containing or silicon and oxygen or Nitrogen-containing gases, such as mono- and disilanes, siloxanes, hexamethyldisiloxane, hexamethyldisilazane, dimethyldiethoxysilane, tetramethysilane, etc. are admitted to influence the properties of the layer, in particular their hardness and friction coefficients. Thus, it is also possible without additional switching on one or more sputtering targets to produce a gradient layer with, for example, to the surface increasing silicon, oxygen and / or nitrogen content. The application of a sliding layer as a gradient cover layer can be carried out either directly on a DLC layer or after application of a metallic or carbide intermediate layer. For example, for the generation of the friction-reducing cover layer, the at least one source used for this purpose is, as described above, but turned on more strongly to 0% lowering of the carbon content of the process gas. Carbide or metallic targets can be used to produce the friction-reducing cover layer, with the carbide targets offering the advantage of an overall higher C content, with very high load-bearing capacity of the layers. The content of graphitic carbon is in turn adjusted by introducing a C-containing reactive gas, advantageously increasing the gas flow from switching on the targets used to produce the MeC / C layer, or with a time delay, by means of a ramp function and at the end of the coating for a certain time is kept constant. A particularly advantageous embodiment of the layer results when first a thin (0.01-0.9 μm) carbidic, such as WC layer, is deposited on the DLC layer. Surprisingly, it has been shown that especially carbide layers are particularly suitable as adhesion promoters on a DLC layer already deposited. To the outside, the layer structure of a WC / C layer with an increasing C content and a thickness of about 0.1-5 microns is completed. Advantageously, the layer thickness of the MeC / C layer is chosen to be smaller than that of the pure DLC layer.

A further preferred embodiment of a DLC sliding layer system results when the final sliding layer is applied to a diamond layer which has been deposited, for example, by means of a high current low voltage arc discharge or the hot filament technique.

INVESTMENT

An apparatus for carrying out the coating method comprises a vacuum chamber with a pumping system for generating a vacuum in the vacuum chamber, substrate holders for receiving the substrates to be coated, at least one gas supply unit for metering process gas, at least one Verdamper device for providing coating material for vapor deposition, an arc generating device for igniting a DC low voltage arc, a device for generating a Substratbiasspannun and at least one or more magnetic field generating means for forming a magnetic far field.

Preferably, the magnetic field generating means are formed by at least one Helmholtz coil, preferably a pair of Helmholtz coils.

When Helmholtz coils are used, the producible magnetic field or the magnetic flux density can be controlled both locally and temporally by the current intensity in the coils.

Another possibility for generating a longitudinal magnetic field results when two magnetrons are arranged on opposite sides of the recipient, and these are additionally associated with at least one respective electromagnetic coil. The respective associated coil is advantageously mounted so as to limit substantially the entire lateral extent of the magnetron assembly. The polarities of the opposite magnetron magnet systems are aligned in the same direction, ie the north pole of the one system is opposite a south pole of the other system and vice versa. At the same time, the respective associated coils are connected to a power source such that the fields of the magnetic coils complement each other according to a Helmholtz arrangement to form a closed magnetic field and the polarity of the outer poles of the magnetron magnet systems and of the magnet coils is in the same direction. Such devices can be used advantageously both to amplify the magnetron plasma and to increase the ionization during the plasma CVD process.

Furthermore, the device comprises a device for generating a Substratbiasspannung, which can continuously or stepwise change the applied Substratbiasspannun and is also bipolar or unipolar operable accordingly. The device is suitable for generating a substrate bias voltage pulsed in the middle frequency range.

The evaporators used in the apparatus include sputtering targets, particularly magnetron sputtering targets, arc sources, thermal vaporizers, and the like. It is advantageous that the evaporator device can be separated from the rest of the process chamber, for example, by pivotable diaphragms.

The device advantageously has a substrate heating in the form of an inductive heating, radiant heating or the like in order to clean the substrates in a heating step before the coating can. Preferably, however, the ignition of a plasma is used.

Among other things, a low-voltage arc generating device is provided in the device, which comprises an ion source with a filament, preferably a refractory filament, in particular tungsten, tantalum or the like in an ionization chamber and an anode and a DC voltage supply. The ion source is in this case connected to the negative pole of the DC voltage supply. The positive pole of the DC supply is connected to the anode, so that a low-voltage arc between the ion source and the anode can be ignited. Like the evaporator device, the ion source can also be separated from the actual process chamber, for example by a pinhole, for example made of tungsten, tantalum or a similar refractory metal.

In order to enable a uniform coating process for all sides of the substrates, it is further provided that the substrate holders are movable and can preferably rotate about at least one or more axes.

The advantageous combination of the medium-frequency substrate voltage supply and a Helmholtz coil arrangement, which can be realized by laterally mounted, two opposing targets comprehensive coils, it is now possible for the first time on an industrial scale, even at low pressures to use a stable medium-frequency plasma for performing a DLC process , The layers made therewith have greatly improved properties, unlike DLC layers made with other systems.

With the present coating system and the method described above can be prepared for the first time thick pure DLC layers with excellent adhesion. In addition, when changing the process parameters and a large part of the previously known plasma process for the production of metal carbon or mixed layers with other elements such as Silicon or F and for the production of multilayer films or of simple, known, deposited by PVD and / or CVD coating systems are performed.

Furthermore, DLC sliding layer systems with adjustable sliding and running behavior can be deposited.

Further advantages, characteristics and features of the invention will become apparent from the following detailed description of preferred embodiments with reference to the accompanying drawings. The figures show all in a purely schematic manner in<dl id="dl0001" compact="compact"><dt>FIG. 1</dt><dd>a device in cross section</dd><dt>FIG. 2</dt><dd>the device of <figref idref="f0001">FIG. 1</figref> in plan view</dd><dt>FIG. 3</dt><dd>Influence of the coil current on the substrate current</dd><dt>FIG. 4</dt><dd>Process parameter gradient layer</dd><dt>FIG. 5</dt><dd>Process parameters DLC layer</dd><dt>FIG. 6</dt><dd>SEM fracture image of a DLC layer</dd><dt>FIG. 7</dt><dd>Process parameters overall course</dd><dt>FIG. 8</dt><dd>Process parameter graphitized DLC layer</dd><dt>FIG. 9</dt><dd>Process parameters inverse gradient layer</dd><dt>FIG. 10</dt><dd>Process parameter gradient layer</dd><dt>FIG. 11</dt><dd>Process parameters H₂-rich layer</dd></dl>

<figref idref="f0001">FIG. 1</figref> shows a schematic cross section through the process chamber 1 of a coating system. The parts to be coated 2 are mounted on one or more support devices 3, which comprises means for generating an at least simple 4, if necessary, two times 5 rotation of the parts. In a particularly advantageous embodiment, the support devices 3 are positioned on a carousel 7 which is additionally rotatable about the installation axis 6.

Via gas inlets 8, the different process gases, in particular Ar and acetylene, can be supplied into the process chamber by means of suitable control devices, not shown here.

A high vacuum suitable pumping station 9 is flanged to the chamber.

An ion source 10 is preferably arranged in the region of the system axis, which is connected to the negative output of a DC voltage supply 11. Depending on the process step, the positive pole of the DC voltage supply 11 can be connected via a switch 12 to the carousel 7 or to the holding device 3 and the parts 2 (heating process) or to the auxiliary anode 13 (etching process or, if necessary, also during the coating processes) ).

At least one evaporator source 14, preferably a magnetron or an arc evaporator for applying the adhesive and gradient layer, is provided on the walls of the process chamber 1. In another embodiment, not shown here, of the evaporator source 14, this can be mounted as an anodically connected crucible centrally in the bottom of the process chamber 1. In this case, the vaporization material for producing the transition or gradient layer is converted by heating through the low-voltage arc 15 in the gas phase.

Furthermore, an additional electrical power supply 16 is provided, with the aid of which a periodically variable middle frequency voltage in the range between 1-10,000, preferably between 20 and 250 kHz, can be applied to the substrates.

The electromagnetic coils 17 for generating a longitudinal, the plasma chamber penetrating magnetic field are arranged on opposite boundary walls of the process chamber 1 and are fed by at least one, preferably two separate, not shown here DC voltage sources in the same direction.

All coating experiments were similar on one <figref idref="f0001">FIG. 1</figref> executed process chamber of the following dimensions: Chamber height 920 mm, diameter 846 mm, volume 560 1.

As additional measures for amplifying or more uniform shaping of the magnetic field and thus of the MF plasma 18, magnetic systems 20 for forming a plurality of magnetic near fields 21 can be attached to the side walls 19 of the plasma chamber 1. In this case, if appropriate, including the at least one magnetron magnet system 22, such as, for example, in US Pat<figref idref="f0002">FIG. 2</figref> alternately arranged magnet systems with NSN or SNS polarity and thus causes a magnetic tunnel-shaped, loop-shaped enclosure of the plasma in the process chamber.

Preferably, the magnetic systems 20 are formed for near field generation as magnetron magnet systems. The individual systems of the coating system are advantageously set in relation to each other by a process control. This makes it possible, in addition to the basic functions of a Vakummbeschichtungsanlage (pumping station control, safety control loops, etc.), the various plasma-generating systems such as magnetrons with the magnetron supply, ionization chamber 1 and auxiliary anode 13 and not described in detail here Carousel 7 and DC power supply 11, and carousel 7 and center frequency generator 16, and the corresponding adjustment of the gas flows, as well as the control of possibly different coil currents in a flexible manner to adapt to each other and to optimize for different processes.

<figref idref="f0003">FIG. 3</figref> shows the relationship between substrate current and coil current when using Helmholtz coils to build a magnetic field. It turns out that the substrate current, and thus the plasma intensity, are directly proportional to the coil current and thus to the magnetic field structure. This clearly shows the positive effect of a superimposed magnetic field.

In <figref idref="f0004">FIG. 4</figref> For example, the course of individual parameters during the application of a gradient layer is shown: With parameters that are otherwise constant with respect to the adhesion layer, the substrate bias is switched from direct current to medium frequency with a preferred amplitude voltage between 500 and 2500 V and a frequency between 20 and 250 kHz. After about 2 minutes, an acetylene ramp is started at 50 sccm and driven for about 30 minutes to 350 sccm. Approximately 5 Minutes after switching on the medium-frequency generator, the power of the Cr targets used is reduced to 7 kW, after another 10 minutes to 5 kW, and held there for another 2 minutes constant. Subsequently, diaphragms are moved in front of the targets and these are switched off, whereby the deposition of the "pure" DLC layer essentially composed of carbon, in small amounts of hydrogen and even smaller amounts of argon atoms begins.

For this purpose, in the simplest case, the process with turned off evaporation sources, but otherwise the same parameters as in the previous gradient layer to be completed. However, it has proved to be advantageous in the course of the deposition of the pure DLC layer to either increase the content of hydrocarbons in the gas flow, to lower the proportion of noble gas or, more preferably, to carry out both measures together. Again, again, as described above, a longitudinal magnetic field of particular importance for the maintenance of a stable plasma.

In the <figref idref="f0004">FIGS. 4</figref> and <figref idref="f0005">5</figref> the course of individual parameters during the application of the pure DLC layer is shown as an example: After switching off the Cr targets used, while the medium frequency supply and the argon flow remain constant, the acetylene ramp started during the gradient layer becomes uniform for about 10 minutes until the flow is between about 200 - Increased 400 sccm. Subsequently, the flow of argon over a period of 5 minutes is continuously reduced to a flow between about 0 - 100 sccm. The next 55 minutes, the process is completed at the same settings completed.

<figref idref="f0006">FIG. 6</figref> shows a scanning electron micrograph of a fracture surface of a thus prepared DLC layer system. It can be clearly seen that a fine-grained structure is present in the region of the cover layer of diamond-like carbon, so that the DLC layer has a polycrystalline character.

<figref idref="f0007">FIG. 7</figref> shows by way of example the overall course of individual process parameters during the application of a DLC layer system produced in this way.

<figref idref="f0008">FIG. 8</figref> shows by way of example the overall course of individual process parameters during the application of a thus produced DLC sliding layer system with graphitized sliding layer. For this purpose, after applying the DLC layer, depending on the desired layer thickness, for example, after 33 to 60 minutes coating time, with otherwise constant process parameters, the pulsed Substratbias set by means of a voltage ramp to a value between 1500 and 2500 V and then deposited an inlet layer under constant conditions.<figref idref="f0009">FIG. 9</figref> shows by way of example the overall course of individual process parameters during the application of a thus produced DLC sliding layer system with an inverse gradient layer. For this purpose, after applying the DLC layer, depending on the desired layer thickness, for example, after 33 to 60 minutes coating time, the performance of the at least one target behind closed aperture 10 minutes, with 5 kW, freedputtert behind the panels, then opened the panels and within approx 20 minutes to 7 kW. At the same time, the acetylene ramp is started, for example, at 350 sccm and driven for about 30 minutes to 50 sccm. Subsequently, the process is preferably continued while maintaining the settings until a desired layer thickness of the inlet layer is reached.<figref idref="f0010">FIG. 10</figref> shows by way of example the course of individual process parameters during the application of a gradient layer as a sliding layer. This can be similar to the transition layer, but also without a metallic adhesive layer, executed. Advantageously, an enema layer with constant parameters is also provided here as a layer closure.<figref idref="f0011">FIG. 11</figref> shows by way of example the overall course of individual process parameters during the application of a DLC sliding layer system produced in this way with an H₂-rich overlay. For this purpose, after applying the DLC layer, a methane ramp is started and, for example, driven from 0 to 100 sccm over about 30 minutes. At the same time, for example, an acetylene ramp is started at 350 sccm and shut down to 120 sccm for about 30 minutes. The run-in layer is run as a layer finish with constant parameters.

Examples (not according to the invention)

Process examples 1

heating process

The process chamber is pumped down to a pressure of about 10-5 mbar and the process sequence is started. As a first part of the process, a heating process is carried out to bring the substrates to be coated to a higher temperature and to remove volatile substances from the surface. In this process, an Ar-hydrogen plasma is ignited by means of the low-voltage arc between the ionization chamber and an auxiliary anode. The following table 1 shows the process parameters of the heating process:<tables id="tabl0001" num="0001"><table frame="all"><tgroup cols="2"><colspec colnum="1" colname="col1" colwidth="77mm" /><colspec colnum="2" colname="col2" colwidth="71mm" /><tbody><row><entry>Ar flow</entry><entry>75 sccm</entry></row><row><entry>Substrate Bias Voltage [V]</entry><entry>0</entry></row><row><entry>Electricity of low voltage arc</entry><entry>100 A</entry></row><row><entry>Hydrogen flow</entry><entry>170 sccm</entry></row><row><entry>Current upper coil</entry><entry>Threshold between 20 and 10 A</entry></row><row><entry>Current lower coil</entry><entry>At the same threshold between 20 and 5 A</entry></row><row><entry>Period between max. and min. coil current</entry><entry>1.5 min</entry></row><row><entry>heating</entry><entry>20 min</entry></row></tbody></tgroup></table></tables>

The Helmholtz coils are used to activate the plasma and are cyclically controlled. The current of the upper coil is thereby varied with a period of 1.5 min between 20 and 10 A, the current of the lower coil alternates in the same cycle equal to between 5 and 20 A.

The substrates heat up and the interfering volatile substances adhering to the surfaces are driven into the gas atmosphere, where they are sucked off by the vacuum pumps.

etching process

When a uniform temperature is reached, an etching process is started by drawing the ions from the low-voltage arc onto the substrates by means of a negative bias voltage of 150V. The alignment of the low-voltage arc and the intensity of the plasma are supported by the pair of Helmholtz coils mounted in a horizontal orientation. The following table shows the parameters of the etching process.<tables id="tabl0002" num="0002"><table frame="all"><tgroup cols="2"><colspec colnum="1" colname="col1" colwidth="39mm" /><colspec colnum="2" colname="col2" colwidth="17mm" /><tbody><row><entry>Ar flow</entry><entry>75 sccm</entry></row><row><entry>substrate voltage</entry><entry>-150 V</entry></row><row><entry>Low-voltage arc current</entry><entry>150 A</entry></row></tbody></tgroup></table></tables>

Cr adhesion layer

The application of the Cr adhesion layer is begun by activating the Cr magnetron sputtering targets. The Ar gas flow is set at 115 sccm. The Cr sputter targets are driven at a power of 8 kW and the substrates are now rotated past the targets for a period of 6 minutes. The resulting pressure range is then between 10-3 mbar and 10-4 mbar. The sputtering process is assisted by the application of the low-voltage arc and the application of a negative DC bias voltage of 75 V to the substrate.

After half the Cr sputtering time, the low voltage arc is turned off and deposition is made for the remainder of the Cr sputtering time only with the aid of the plasma active in front of the Cr target.

gradient

After this time, a plasma is ignited by switching on a sine wave generator. Acetylene gas is introduced at an initial pressure of 50 sccm and the flow is increased by 10 sccm every minute.

The sine plasma generator is set at a frequency of 40 kHz to an amplitude voltage of 2400 V. The generator ignites a plasma discharge between the substrate holders and the housing wall. The Helmholtz coils attached to the recipient are both activated with a constant current flow of 3 A in the lower coil and 10 A in the upper coil. At an acetylene flow of 230 sccm, the Cr targets are deactivated.

DLC coating

When the flow of acetylene reaches the value of 350 sccm, the Ar flow is reduced to a value of 50 sccm.

The table shows the parameters of the example at a glance:<tables id="tabl0003" num="0003"><table frame="all"><tgroup cols="2"><colspec colnum="1" colname="col1" colwidth="46mm" /><colspec colnum="2" colname="col2" colwidth="18mm" /><tbody><row><entry>River Argon</entry><entry>50 sccm</entry></row><row><entry>Flow acetylene</entry><entry>350 sccm</entry></row><row><entry>Excitation current upper coil</entry><entry>10 A</entry></row><row><entry>Excitation current lower coil</entry><entry>3 A</entry></row><row><entry>voltage amplitude</entry><entry>2400 V</entry></row><row><entry>Excitation frequency f</entry><entry>40 kHz</entry></row></tbody></tgroup></table></tables>

In these conditions, a high deposition rate is ensured and the ionization of the plasma is maintained by means of the Ar gas. The deposition rate, which now sets in the coating process, will be in the range between 0.5 and 4 μm / h, which also depends on the area to be coated in the process chamber.

After the coating time, the sine generator and the gas flow is turned off, and removed the substrates of the process chamber.

The properties of the resulting layer are shown in the following table<tables id="tabl0004" num="0004"><table frame="all"><tgroup cols="2"><colspec colnum="1" colname="col1" colwidth="31mm" /><colspec colnum="2" colname="col2" colwidth="21mm" /><thead><row><entry namest="col1" nameend="col2" align="left" valign="top">Properties Example 1</entry></row></thead><tbody><row><entry>microhardness</entry><entry>about 2200 HK</entry></row><row><entry>deposition rate</entry><entry>1-2μm / h</entry></row><row><entry>liability</entry><entry>HF1</entry></row><row><entry>resistance</entry><entry>&lt;10 kΩ</entry></row><row><entry>Hydrogen content</entry><entry>12%</entry></row><row><entry>Coefficient of friction</entry><entry>0.2</entry></row><row><entry>Internal tension</entry><entry>about 2 GPa</entry></row><row><entry>fracture behavior</entry><entry>Not glassy</entry></row></tbody></tgroup></table></tables>

Process Example 2

Process Example 2 provides a procedure similar to Example 1. In contrast to Example 1, the plasma is generated by a pulse generator. The excitation frequency is 50 kHz with an amplitude voltage of 700V.

The table shows the parameters of the second example.<tables id="tabl0005" num="0005"><table frame="all"><tgroup cols="2"><colspec colnum="1" colname="col1" colwidth="46mm" /><colspec colnum="2" colname="col2" colwidth="18mm" /><tbody><row><entry>River Argon</entry><entry>50 sccm</entry></row><row><entry>Flow acetylene</entry><entry>350 sccm</entry></row><row><entry>Excitation current upper coil</entry><entry>10 A</entry></row><row><entry>Excitation current lower coil</entry><entry>3 A</entry></row><row><entry>voltage amplitude</entry><entry>700 V</entry></row><row><entry>Excitation frequency f</entry><entry>40 kHz</entry></row></tbody></tgroup></table></tables>

The coating produced has a hardness of 25 GPa, an adhesive strength of HF1 and gives a coefficient of friction of 0.2.<tables id="tabl0006" num="0006"><table frame="all"><tgroup cols="2"><colspec colnum="1" colname="col1" colwidth="31mm" /><colspec colnum="2" colname="col2" colwidth="22mm" /><thead><row><entry namest="col1" nameend="col2" align="left" valign="top">Properties Example 2</entry></row></thead><tbody><row><entry>HK</entry><entry>about 2400</entry></row><row><entry>deposition rate</entry><entry>about 1.5 μm / h</entry></row><row><entry>liability</entry><entry>HF1</entry></row><row><entry>resistance</entry><entry>&gt; 500k</entry></row><row><entry>Hydrogen content</entry><entry>13%</entry></row><row><entry>Coefficient of friction</entry><entry>0.2</entry></row><row><entry>Internal tension</entry><entry>Approximately 3 GPa</entry></row></tbody></tgroup></table></tables>

Process Example 3

Process Example 3 provides a procedure similar to Example 1. In contrast to Example 1, the plasma is excited by a unipolar pulse voltage, the parameters of the experiment are shown in the following table.<tables id="tabl0007" num="0007"><table frame="all"><tgroup cols="2"><colspec colnum="1" colname="col1" colwidth="46mm" /><colspec colnum="2" colname="col2" colwidth="18mm" /><tbody><row><entry>River Argon</entry><entry>50 sccm</entry></row><row><entry>Flow acetylene</entry><entry>350 sccm</entry></row><row><entry>Excitation current upper coil</entry><entry>10 A</entry></row><row><entry>Excitation current lower coil</entry><entry>3 A</entry></row><row><entry>voltage amplitude</entry><entry>1150 V</entry></row><row><entry>Excitation frequency f</entry><entry>30 kHz</entry></row></tbody></tgroup></table></tables>

The coating produced has the properties described in the following table.<tables id="tabl0008" num="0008"><table frame="all"><tgroup cols="2"><colspec colnum="1" colname="col1" colwidth="31mm" /><colspec colnum="2" colname="col2" colwidth="22mm" /><thead><row><entry namest="col1" nameend="col2" align="left" valign="top">Properties Example 3</entry></row></thead><tbody><row><entry>microhardness</entry><entry>&gt; 2500 HK</entry></row><row><entry>deposition rate</entry><entry>approx. 1.8 μm / h</entry></row><row><entry>liability</entry><entry>HF1</entry></row><row><entry>resistance</entry><entry>&gt; 1 kΩ</entry></row><row><entry>Hydrogen content</entry><entry>12-16%</entry></row><row><entry>Coefficient of friction</entry><entry>0.2</entry></row><row><entry>Internal tension</entry><entry>about 2 GPa</entry></row></tbody></tgroup></table></tables>

Process Example 4

In comparison with Process Example 1, in Example 4, a process without assistance of a longitudinal magnetic field was performed. The current flowing through the two coils was reduced to a value of 0 A. The table shows the process parameters.<tables id="tabl0009" num="0009"><table frame="all"><tgroup cols="2"><colspec colnum="1" colname="col1" colwidth="46mm" /><colspec colnum="2" colname="col2" colwidth="18mm" /><tbody><row><entry>River Argon</entry><entry>50 sccm</entry></row><row><entry>Flow acetylene</entry><entry>350 sccm</entry></row><row><entry>Excitation current upper coil</entry><entry>0 A</entry></row><row><entry>Excitation current lower coil</entry><entry>0 A</entry></row><row><entry>voltage amplitude</entry><entry>2400 V</entry></row><row><entry>Excitation frequency f</entry><entry>40 kHz</entry></row></tbody></tgroup></table></tables>

It turns a plasma, which is stable compared to Example 1 only at higher pressures than in Example 1, is distributed inhomogeneously over the process chamber and is very much influenced by geometric effects. Therefore, there is an inhomogeneous in the process chamber and because of the set process pressure compared to Example 1 lower deposition rate. At the desired process pressures was a plasma formation without the use of a second plasma source such as a target or the connection of the filament not possible. Only by using the Helmholtz coils it was possible to stabilize the plasma in the process chamber and to achieve homogeneous deposition across the height of the process chamber. Without the use of the coils, a plasma ignited in the region of the ionization chamber, where locally high temperatures are generated and destruction must be feared.<tables id="tabl0010" num="0010"><table frame="all"><tgroup cols="2"><colspec colnum="1" colname="col1" colwidth="26mm" /><colspec colnum="2" colname="col2" colwidth="29mm" /><thead><row><entry namest="col1" nameend="col2" align="left" valign="top">Properties Example 4</entry></row></thead><tbody><row rowsep="0"><entry>HK</entry><entry>inhomogeneous</entry></row><row><entry /><entry>1200 - 2500</entry></row><row><entry>deposition rate</entry><entry>inhomogeneous</entry></row><row><entry>liability</entry><entry>Not definable</entry></row><row><entry>resistance</entry><entry>inhomogeneous</entry></row></tbody></tgroup></table></tables>

Overlay systems

In the following, different sliding layers were applied to the DLC layers as described above to prepare a layer system. Care must be taken that the process containing all plasma pretreatments and coating steps is continuously run without interruption of the vacuum in order to achieve optimum layer adhesion.<tables id="tabl0011" num="0011"><table frame="all"><title>Table 5</title><tgroup cols="4"><colspec colnum="1" colname="col1" colwidth="49mm" /><colspec colnum="2" colname="col2" colwidth="53mm" /><colspec colnum="3" colname="col3" colwidth="24mm" /><colspec colnum="4" colname="col4" colwidth="25mm" /><thead><row><entry namest="col1" nameend="col4" align="left" valign="top">shows different process examples with a graphitized overlay:</entry></row><row><entry valign="top"><b>process example</b></entry><entry valign="top"><b>5</b></entry><entry valign="top"><b>6</b></entry><entry valign="top"><b>7</b></entry></row></thead><tbody><row><entry>DLC coating system example</entry><entry>like 1 but voltage sample. 1000V</entry><entry>2</entry><entry>3</entry></row><row><entry>River Argon</entry><entry>50 sccm</entry><entry>50 sccm</entry><entry>50 sccm</entry></row><row><entry>Flow acetylene</entry><entry>350 sccm</entry><entry>350 sccm</entry><entry>350 sccm</entry></row><row><entry>Excitation current upper coil</entry><entry>10 A</entry><entry>10 A</entry><entry>10 A</entry></row><row><entry>Excitation current lower coil</entry><entry>3 A</entry><entry>3 A</entry><entry>3 A</entry></row><row><entry>Substrate voltage amplitude</entry><entry>2400 V</entry><entry>2400 V</entry><entry>2400 V</entry></row><row><entry>Ramp voltage</entry><entry>15 min</entry><entry>25 min</entry><entry>15 min</entry></row><row><entry>Excitation frequency f</entry><entry>40 kHz</entry><entry>40 kHz</entry><entry>30 kHz</entry></row><row><entry>excitation type</entry><entry>AC sine</entry><entry>bipolar pulse</entry><entry>unipolar pulse</entry></row></tbody></tgroup></table></tables><tables id="tabl0012" num="0012"><table frame="all"><title>Table 6</title><tgroup cols="4"><colspec colnum="1" colname="col1" colwidth="55mm" /><colspec colnum="2" colname="col2" colwidth="34mm" /><colspec colnum="3" colname="col3" colwidth="38mm" /><colspec colnum="4" colname="col4" colwidth="40mm" /><thead><row><entry namest="col1" nameend="col4" align="left" valign="top">shows various possibilities for forming a sliding layer such as a final gradient layer (No. 8), an inverse gradient layer (No. 9), or a hydrogen-rich C layer (No. 10):</entry></row><row><entry valign="top">process example</entry><entry valign="top">8th*</entry><entry valign="top">9</entry><entry valign="top">10</entry></row></thead><tbody><row><entry>DLC layer no.</entry><entry>3</entry><entry>2</entry><entry>2</entry></row><row><entry>River Argon 1</entry><entry>30 sccm</entry><entry>50 sccm</entry><entry>50 sccm</entry></row><row><entry>River Argon 2</entry><entry>30 (100) sccm</entry><entry>-</entry><entry>-</entry></row><row><entry>Ramp argon</entry><entry>0 (10 min)</entry><entry>-</entry><entry>-</entry></row><row><entry>Flow of acetylene 1</entry><entry>0 sccm</entry><entry>350 sccm</entry><entry>350 sccm</entry></row><row><entry>Flow acetylene 2</entry><entry>250 sccm</entry><entry>180 sccm</entry><entry>150 sccm</entry></row><row><entry>Ramp acetylene</entry><entry>15 min</entry><entry>20 min</entry><entry>20 min</entry></row><row><entry>River methane 1</entry><entry>-</entry><entry>-</entry><entry>0 sccm</entry></row><row><entry>River methane 2</entry><entry>-</entry><entry>-</entry><entry>150 sccm</entry></row><row><entry>Ramp methane</entry><entry>-</entry><entry>-</entry><entry>20 min</entry></row><row><entry>Power Cr-Target 1</entry><entry>8th kW</entry><entry>7 kW</entry><entry>-</entry></row><row><entry>Power Cr-Target 2</entry><entry>7 kW</entry><entry>-</entry><entry>-</entry></row><row><entry>Ramp Cr-Target</entry><entry>20 min</entry><entry>30 min</entry><entry>-</entry></row><row><entry>Excitation current upper coil</entry><entry>10 A</entry><entry>10 A</entry><entry>10 A</entry></row><row><entry>Excitation current lower coil</entry><entry>3 A</entry><entry>3 A</entry><entry>3 A</entry></row><row><entry>Substrate voltage amplitude</entry><entry>2400 V</entry><entry>700 V</entry><entry>1150 V</entry></row><row><entry>Excitation frequency f</entry><entry>40 kHz</entry><entry>40 kHz</entry><entry>30 kHz</entry></row><row><entry>excitation type</entry><entry>AC sine</entry><entry>bipolar pulse</entry><entry>unipolar pulse</entry></row></tbody></tgroup></table></tables>

The acetylene ramp can also be started with a delay of 5-10 minutes after switching on the Cr targets. Such a procedure is particularly advantageous when DLC and sliding layer are applied in different process chambers or coating equipment. In this case, a DC voltage source for applying the Suabstratbias can be used instead of the sine wave generator.

Furthermore, the graphite content can be increased by simultaneous or delayed co-sputtering of carbide, for example, WC and / or graphite targets. If one wants to use the particularly favorable sliding properties of W or Ta or Nb / C layers, it is advantageous to switch off the Cr targets after the formation of an adhesion or gradient layer, or to control them down and to process them only with the corresponding metal and / or To finish metal carbide targets.

The properties of the corresponding DLC ​​layers are <b>Table 8</b> and<tables id="tabl0013" num="0013"><table frame="all"><tgroup cols="4"><colspec colnum="1" colname="col1" colwidth="27mm" /><colspec colnum="2" colname="col2" colwidth="17mm" /><colspec colnum="3" colname="col3" colwidth="17mm" /><colspec colnum="4" colname="col4" colwidth="17mm" /><thead><row><entry valign="top">VersuchNr.</entry><entry valign="top"><b>5</b></entry><entry valign="top"><b>6</b></entry><entry valign="top"><b>7</b></entry></row></thead><tbody><row><entry>liability</entry><entry>HF 1</entry><entry>HF 1</entry><entry>HF 1</entry></row><row><entry>resistance</entry><entry>&lt;100 kΩ</entry><entry>&lt;100 kΩ</entry><entry>&lt;100 kΩ</entry></row><row><entry>Coefficient of friction</entry><entry>about 0.10</entry><entry>approx. 0.15</entry><entry>approx. 0.12</entry></row></tbody></tgroup></table></tables><tables id="tabl0014" num="0014"><table frame="all"><title><b>Table 9</b> refer to:</title><tgroup cols="4"><colspec colnum="1" colname="col1" colwidth="31mm" /><colspec colnum="2" colname="col2" colwidth="17mm" /><colspec colnum="3" colname="col3" colwidth="17mm" /><colspec colnum="4" colname="col4" colwidth="21mm" /><thead><row><entry valign="top">VersuchNr.</entry><entry valign="top"><b>8th</b></entry><entry valign="top"><b>9</b></entry><entry valign="top"><b>10</b></entry></row></thead><tbody><row><entry>liability</entry><entry>HF 1</entry><entry>HF 1</entry><entry>HF 1</entry></row><row><entry>resistance</entry><entry>&lt;1 kΩ</entry><entry>&lt;1 kΩ</entry><entry>&lt;100 kΩ</entry></row><row><entry>Hydrogen content</entry><entry>ng</entry><entry>ng</entry><entry>&gt; 30 atom%</entry></row><row><entry>Coefficient of friction</entry><entry>about 0.08</entry><entry>about 0.07</entry><entry>approx. 0.13</entry></row></tbody></tgroup></table></tables>

<u>LIST OF REFERENCE NUMBERS</u>

<dl id="dl0002" compact="compact"><dt>1.</dt><dd>process chamber</dd><dt>Second</dt><dd>parts to be coated</dd><dt>Third</dt><dd>mounting device</dd><dt>4th</dt><dd>simple rotation</dd><dt>5th</dt><dd>double rotation</dd><dt>6th</dt><dd>line of sliding</dd><dt>7th</dt><dd>carousel</dd><dt>8th.</dt><dd>gas inlet</dd><dt>9th</dt><dd>pumping</dd><dt>10th</dt><dd>ion source</dd><dt>11th</dt><dd>DC power supply</dd><dt>12th</dt><dd>counter</dd><dt>13th</dt><dd>auxiliary anode</dd><dt>14th</dt><dd>evaporation source</dd><dt>15th</dt><dd>Low-voltage arc</dd><dt>16th</dt><dd>power supply</dd><dt>17th</dt><dd>electromagnetic coil</dd><dt>18th</dt><dd>MF Plasma</dd><dt>19th</dt><dd>Side wall</dd><dt>20th</dt><dd>magnet systems</dd><dt>21st</dt><dd>near fields</dd><dt>22nd</dt><dd>Magnetronmagnetsysteme</dd></dl>