SG193877A1

SG193877A1 - Hard material layer

Info

Publication number: SG193877A1
Application number: SG2013068739A
Authority: SG
Inventors: Juergen Ramm; Beno Widrig; Wolfgang Kalss
Original assignee: Oerlikon Trading Ag
Priority date: 2005-03-24
Filing date: 2006-01-19
Publication date: 2013-10-30
Also published as: KR101361240B1; SG160397A1; CA2601729C; JP5877147B2; WO2006099760A3; EP1863947A1; JP2013079452A; EP2355126A3; CA2601729A1; ATE527392T1; PL1864314T3; BRPI0609466A2; EP1864314A2; WO2006099760A2; PT1863947E; KR101235393B1; EP1864314B1; PT1864314E; PL1863947T3; CA2601722C

Abstract

The invention relates to a hard material layer, deposited on a workpiece (30) as a functional layer (32) by means of an arc-PVD method. Said layer is essentially embodied by an electrically insulating oxide of at least one of the metals (Me) of the transition metals of the sub-groups IV, V, VI of the periodic table and Al, Si, Fe, Co, Ni, Co, or Y and the functional layer (32) contains no noble gas or haiogen.Fig. 4

Description

Hard Material Layer

The invention relates to a hard material layer deposited as oxidic arc PVD functional fayer (32) on a workpiece (30) according to the preamble of claim 1 as well as to a method for coating a workpiece with a hard material layer according to the preamble of claim 21.

The operation of arc evaporator sources, also known as spark cathodes, by feeding with electrical pulses has been known in prior art for a relatively long time. With arc evaporator sources high evaporation rates, and therewith high deposition rates, can be achieved economically in coating. in addition, the structure of such a source can technically be realized relatively simply. These sources operate at currents typically in the range of approximately 100 A and more and at voltages of a few volts to a few tens of volts, which can be realized with relatively cost-effective DC power supplies. A significant disadvantage with these sources comprises that in the proximity of the cathode spot very rapidly proceeding melting occurs on the target surface, whereby drops are formed, so-called droplets, which are huried away as splatters and subsequently condense on the workpiece and consequently have an undesirable effect on the layer properties. For example, thereby the layer structure becomes inhomogeneous and the surface roughness becomes inferior. With nigh requirements made of the layer quality, layers generated thusly, can often not be commercially applied. Attempts have therefore already been made to reduce these problems by cperating the arc evaporator source in pure puise operation of the power supply.

However, until now only marginal improvements in the spiatier formation couid be achieved therewith.

The use of reactive gases for the deposition of compounds from a metallic target in a reactive plasma was until now limited to the production only of eiectrically conductive layers. In the production of electrically nonconducting. thus dielectric lavers, such as for example of oxides using oxygen as the reactive gas, the problem of splatter formation is intensified. The re-coating of the target surfaces of the arc evaporator and of the counterelectrodes, such as the anodes and also other parts of the vacuum process installation, with a non-conducting layer leads to entirely unstable conditions and even to the quenching of the arc. In this case the latter would have to be repeatedly newly ignited or it would thereby become entirely impossible to conduct the process.

EP 0 666 335 B1 proposes for the deposition of purely metallic materials with an arc evaporator to superimpose onto the DC current a pulsing current in order to be able to lower hereby the DC base current for the reduction of the splatter formation. Pulse currents up to 5000 A are herein necessary, which are to be generated with capacitor discharges at relatively low pulse frequencies in the range of 100 Hz to 50 kHz. This approach is proposed to prevent the droplet formation in the non-reactive evaporation of purely metallic targets with an arc evaporator source. A solution for the depesition of non-conducting dielectric layers is not stated in this document. in the reactive coating by means of arc evaporator saurce there is a lack of reactivity and process stability, especially in the production of insulating iayers. In contrast to other PVD processes (for example sputtering}, insulating layers can currently only be produced by means of arc evaporation with electrically conducting targets. Working with high frequency, such as is the case during sputtering, has so far failed due to the lacking technique of being able to operate high-power supplies with high frequencies.

Working with puised power supplies appears to be an option. However, in this case the spark, as stated, must be ignited repeatedly or the pulse frequency must be selected so large that the spark is not extinguished. This appears to function to some degree in applications for special materials, such as graphite, as described in DE 3901401. i should, however, be noted that graphite is not an insulator, but rather is electrically conductive, even if it is a poorer conductor than normal metals.

In oxidized target surfaces a renewed igniting with mechanical contact and by means of

DC supplies is not possible. The actual problem in reactive arc evaporation are the coatings with insulating layers on the target and the anode, or on the coating chamber connected as the anode. In the course of their formation, these insulating coatings increase the burn voltage of the spark discharge, lead to increased splatters and sparkovers, an unstable process, which ends in an interruption of the spark discharge.

Entailed therein is a coating of the target with isiand growth, which decreases the conducting surface. A highly diluted reactive gas (for exampie argon/oxygen mixture) can delay the accretion on the target, however it cannot solve the fundamental probiem of process instability. While the proposal according to US 5,103,766 of alternately operating the cathode and the anode with renewed ignition each time results in process stability, it does however lead to increased splatters.

The resolution via a puised power supply as is possible for exampie in reactive sputtering, cannot be applied in classic spark evaporation. The reason lies therein that a glow discharge has a “ionger life” than a spark when the power supply is interrupted. in order to circumvent the problem of the coating of the target with an insulating taver. in reactive processes for the production of insulating layers either the reactive gas inlet is locally separated from the target (in that case the reactivity of the process is only ensured if the temperature on the substrate also permits an oxidation reaction) or a separation between splatters and ionized fraction is carried out (so-called filtered arc) and after the filtering the reactive gas is added to the ionized vapor.

There is further the wish for additional reduction or scaling capability of the thermal ioading of the substrates and the ability to conduct low-temperature processes in cathodic spark coating.

In WO 03018862 the pulse operation of plasma sources is described as a feasible path for reducing the thermat ioading on the substrate, Howsver, the reasons offered there apply to the field of sputier processes. No reference is established to spark evaporation. in the application field of hard material coatings there has in parficular been for a long time the need to be abie to produce oxidic hard materials with appropriate hardness, adhesive strength and under control according to the desired tribological properties.

Herein aluminum oxides, in particular aluminum chromoxides, could play an important role. Prior art in the field of PVD (Physical Vapor Deposition) deals herein most often only with the production of gamma and aipha aluminum oxide. The method most frequently mentioned is duat magnetron sputtering, which in this application entails great disadvantages with respect to process reliability and costs. Japanese patents concentrate more on layer systems in connection with the tools and cite, for example, the arc ion plating process as the production method. There is the general wish to be able to deposit alpha aluminum oxide. However, in current PVD methods, substrate temperatures of approximately 700EC or more are required in order to obtain this structure. Some users elegantly attempt to avoid these high temperatures through nucleation layers (oxidation of TIAIN, Al-Cr-O system). However, this does not necessarily make the process less expensive and faster. Until now it also did not appear possible 10 be able to produce satisfactorily alpha aluminum oxide layers by means of arc evaporation.

With respect to prior art the following disadvantages are summarized, in particular regarding the production of oxidic layers with reactive process: 1. Stable conduction of the process is not possible for the deposition of insulating layers, if there is no spatial separation between arc evaporator cathode or anode of the arc discharge and the substrate region with reactive gas inlet. 2. There 1s no fundamental solution of the problematic of droplets: conglomerates {droplets splatters) are not fully through-reacted, wherein metallic components occur in the layer, increased roughness of the layer surface is generated and the constancy of the layer composition and the sioichiometry is disturbed.

3. insufficient possibilities for realizing low-temperature processes, since insufficiently the thermal loading of the substrate is too high for the production of oxides with high-temperature phases. 4, The production of flat graduated intermediate layers for insulating layers has so far not been possibie by means of arc evaporation. in contrast to sputtering, coating by means of cathodic spark is substantially a evaporation process. tis supposed that in the transition between hot cathode spot and its margin parts are entrained which are not of atomic size. These conglomerates impinge as such onto the substrate and result in rough layers, and it has not been possible fully to react-through the splatters. Avoidance or fragmentation of these splatters was so far not successful, especially not for reactive coating processes. In these, on the cathode of the arc evaporator source, for example in oxygen atmosphere, additionally a thin oxide iaver forms, which tends {0 increased splatter formation.

The present invention addresses the problem of eliminating the listed disadvantages of prior art. The problem addressed is in particular to deposit economically layers with better properties with at least one arc evaporator source, such that the reactivity in the process is increased through better ionization of the vaporized material, and of the reactive gas involved in the process is increased. in this reactive process the size and frequency of the splatiers is to be significantly reduced, in particular in reactive processes for the production of insulating layers. Further, better process control is fo be made possible, such as the control of the evaporation rates, increase of the layer quality, settability of the {ayer properties, improvement of homogeneity of the reaction, as well as the reduction of surface roughness of the deposited layer. These improvements are in particuiar also of importance in the production of graduated layers and/or alioys. The process stability in reactive processes for the production of insulating layers is to be generally increased.

In particular, an arc evaporation process is to be made possible which permits the economic deposition of oxidic hard material layers, aluminum oxide and/or aluminum chromoxide layers which preferably have substantially alpha and/or gamma structure.

Moreover, a low-temperature process should be realized, preferably below 700RC, also at high economy of process. Furthermore the expenditure for the device and in particular for the power supply for pulsed operation should be kept low. Said tasks may occur singly as well as aiso combined with one another, depending on the particular required application area.

The problem is solved according to the invention through a hard material layer applied with an arc evaporation PVD method according fo claim 1 and by proceeding according to a method as claimed in claim 21 for the production of such a layer on a workpiece.

The dependent claims define further advantageous embodiments,

The problem is solved according to the invention thereby that a hard material layer is deposited as arc PVD functional layer onto a workpiece, this layer substantially being formed as an electrically insulating oxide, comprised of at ieast one of the metals (Me)

Af, Cr, Fe, Ni, Co, Zr. Mo, Y and the functional layer comprises a content of inert gases and/or halogens of less than 2%. The content of inert gases is preferably less than 0.1%, in particular less than 0.05% or even better is zero and/or the content of halogens is less than 0.5%. in particular less than 0.1%, or even better is zero. These gases should be incorporated into the layer to as small an extent as possible and the arc evaporation process should thereiore exclusively {ake place with pure reactive gas or a pure reactive gas mixiure without inert gas component, such as He, Ne, Ar, or halogen gases, such as F;, Ci, Bry, Jz, or halogen-containing compounds such as CF: or the ike.

The known CVD processes use halogen with which at undesirably high temperatures of approximately 1100EC a layer is depositad. Even under reactive process conditions, &

the known sputter processes are operated with a high proportion of inert gas, such as with argon. The content of such gases in the layer should be below said values or preferably be zero. The pulse arc evaporation process according to the invention also permits sufficing without such process gases.

The preceding patent application with the application number CH00518/05 shows essentially already an approach to a solution. A first solution is specified which is especially well suited for completely reacted target surfaces and has a marked reduction of splatter formation compared ic DC-operated arc evaporator targets. This application proposes superimposing a high-current pulse onto the DC feed of an arc evaporator source with a pulsed power supply, as is shown schematically in Figure 2.

A further reduction of the splatters and their size at higher economy is attained through the approach according to the succeeding patent application CH 01289/05 which claims priority of CH 00518/05 and represents a further development. in this application a vacuum process installation for the surface working of workpieces with at least one arc evaporator source is provided comprising a first electrode connected to a DC power supply, a second electrode disposed separated from the arc evaporator source basing provided and that the two electrodes are connected to a single pulsed power supply.

Between the two electrodes, consequently an additional discharge gap is operated with only a single pulsed power supply which makes possible an especially high ionization of the invoived materials at very good controliability of the process.

The second electrode can herein be a further arc evaporator source, a workpiece holder or the workpiece itself, whereby in this case the second electrode can also be implemented as an evaporation crucible forming the anode of a low-voltage arc evaporator.

An especially preferred embodiment comprises that both elecirodes are the cathodes of one arc evaporator source gach and that each of these arc evaporator sources by itself is connected directly to a DC power suppty for the purpose of maintaining a holding current and wherein the two cathodes are connected to a single puised power supply such that the arcs, or the arc discharges, of the two sources are not extinguished in operation. In this configuration, consequently, only one pulsed power supply is required since this supply is interconnected directly between the two cathodes of the arc evaporators. Apart from the high degree of ionization and the good controliability of the process, high efficiency of the configuration alse results. Between these two electrodes and the puise discharge gap additionally generated thereby, compared io this discharge gap, a bipolar puise forms electrically from negative and positive components, whereby the entire period duration of this fed AC voltage can be utilized for the process. in fact. no unused pulse pauses are generated and the negative as well as also the positive pulses without interruption contribute overall to the process. The deposition rate can thereby be additionally increased without having to employ additional expensive pulsed power supplies. This configuration with two arc evaporator sources is especially suited for the deposition of layers from a metallic target utifizing reactive gas. With this configuration it becomes even possibie to omit entirely supporting inert gases, such as argon, and it is possible to work with pure reactive gas, even unexpectedly with pure oxygen. Through the high degree of ionization attainable therewith of the vaporized material as well as also of the reactive gas, such as for exampie oxygen, nonconducting tayers with high quality are generated which nearly reach the quality of the bulk material. The process runs very stably and herein the splatter formation is, unexpectediy, also reduced or entirely avoided. However, said advantages can aiso be attained by using other sources as the secend electrode, such as, for example, a bias eiectrode or a low-voltage arc evaporator crucible, although said advantageous effects are not atfained to the same degree as in the implementation of the configuration with two arc evaporators,

The present application claims priority of the two cited preceding applications CH 00518/05 and 01289/05 which substantially disclose a first approach to a solution for the present problem formation of the deposition of electrically nonconducting oxidic layers. The invention introduced in the present patent application represents a further development regarding the conduction of the process and the application. These two applications are consequently an integrating component of the present application. in the foliowing the invention will be described in further detail by example and schematically with Figures. Therein depict:

Fig. 1 schematically an illustration of an arc evaporator coating installation, such as corresponds to prior art,

Fig. 2 a first configuration according to the invention with a DC-fed arc evaporator source in operation with superimposed high-current pulse,

Fig. 3 a second configuration with two DC-fed arc evaporator sources and high-power pulsed supply connected between them according to the invention. a dual pulse arc evaporator configuration,

Fig. 4 a cross section through a deposited layer as a multilayer according to the invention,

Fig. 5 an enlarged cross section of the layer according to Figure 4.

Figure 1 shows a vacuum process installation which depicts a configuration known from prior art for operating an arc evaporator source § with a DC power supply 13. The instaliation 1 is equipped with a pump system 2 for setting up the required vacuum in the chamber of the vacuum process instaliation 1. The pump system 2 permits the operation of the coating installation at pressures < 107 mbar and also ensures the operation with the typical reactive gases, such as O,, No. SiH, hydrocarbons, etc. The reactive gases are introduced via a gas inlet 11 into the chamber 1 and here distributed accordingly. It is additionally possible to introduce additional reactive gases through further gas iniets or also inert gases, such as argon, as is necessary, for example, for etching processes or for the deposition of nonreactive layers in order to use the gases singly and/or in mixtures. The workpiece holder 3 located in the installation serves for receiving and for electrical contacting of the workpiece, not shown here, which are conventionally fabricated of metallic materials, and for the deposition of hard material layers using such processes. A bias power supply 4 is electrically connected with the workpiece holder 3 for applying a substrate voltage or a bias voltage to the workpieces.

The bias power supply 4 can be a DC, an AC or a bipolar or a unipolar pulse substrate power supply. Via a process gas inlet {11) an inert or a reactive gas can be introduced in order to set and to control process pressure and gas composition in the treatment chamber.

Component parts of the arc evaporator source 5 are a target 5" with cooling plate placed behind it, and an ignition finger 7, which is disposed in the peripheral region of the target surface, as well as an anode encompassing the target. A switch 14 permits setecting between a floating operation of the anode 6 of the positive pole of the power supply 13 and operation with defined zero or ground potential, When igniting the arc of the arc evaporator source 5 a brief contact is established of the ignition finger 7 with the cathode and the former is subsequently withdrawn whereby a spark is ignited. The ignition finger 7 Is for this purpose connected via a current iimiter resistor to anode potential.

The vacuum process instaliation 1 can additionally optionally. should the conduction of the process require such, be equipped with an additional plasma source 9. in this case the plasma source 9 is implemented as a source for generating a low-voltage arc with a hot cathode. The hot cathode is, for example. formed as a filament disposed in a small ionization chamber, in which with a gas iniet 8 a working gas, such as for example argon, is introduced for the generation of a low-voltage arc discharge which extends into the main chamber of the vacuum process installation 1. An anode 15 for developing the low-voltage arc discharge is located at an appropriate position in the chamber of the vacuum process instaftation 1 and is operated, in known manner, with a DC power supply between cathode and plasma source 9 and anode 15. if required. additional ceils 10, 10" can be provided, such as for example Helmholtz-like configurations which are placed about the vacuum process installation 1 for the magnetic focusing or guiding of the low-voltage arc plasma.

Proceeding according to the invention, as depicted in Figure 2. the arc evaporator source 9 is operated being fed additionally with a pulsed high-power supply 16". This pulsed power supply 16' is advantageously directly superimposed onto the DC power supply. [tis understood that for their protection the two supplies must be operated electrically decoupled with respect to each other. This can be carried out in conventional manner with filters, such as with inductors, such as is familiar to a person of skill in the art. With this configuration it is already possible according fo the invention to deposit layers exclusively with pure reactive gas or reactive gas mixtures, such as oxides, nitrides, efc.. without undesirable support gas components, such as for example argon in PVD sputter processes or halogens of the precursors in CVD processes. iis, in particular, possible 0 generate therewith the pure, electrically nonconducting oxides, which are very difficult to obtain economically, in the desired crystaliine form and to deposit them as layers. This reactive pulsed arc evaporation method is herewith denoted as RPAE method. :

In a further improved and preferred embodiment of a vacuum process configuration, apart from a first arc evaporator source 5, a second arc evaporator source 20 is provided with the second target electrode 20’, as is shown in Figure 3. Both arc evaporator sources 8, 20 are operated with one DC power supply 13 and 13' each, such that the DC power supplies ensure with a base current the maintenance of the arc discharge. The DC power supplies 13, 13’ correspond to prior art and can be realized cost-effectively, The two electrodes 5°, 20", which form the cathode of the two arc evaporator sources 5, 20, are connected according to the present invention to a single pulsed power supply 16, which is capable of outputting to the two electrodes 5', 20" high pulse currents with defined form and edge slope of the pulses. in the depicted configuration according to Figure 3 the anodes 6 of the two arc evaporator sources 5,

are referred to the electrical potential of the ground of the process instaliation 1. This is herewith also denoted as Dual Pulsed Arc Evaporation (DPAE). lt is possible to operate the spark discharges with reference to ground or also floatingty. in the preferred case of floating operation, the first DC power supply 13 is connected with its negative pole to the cathode §' of the first arc evaporator source 5 and its positive pole with the opposing anode of the second arc evaporator source 20. The second arc evaporator source 20 is operated analogously and the second power supply 13" is connected to the positive pole of the anode of the first arc evaporator source 5.

This opposing operation of the anodes of the arc evaporator sources leads to better ionization of the materials in the process. However, the ground-free operation, or the floating operation, of the arc evaporator source 5, 20 can also take place without using the opposing anode feed. In addition, it is possibile to provide a switch 14, as shown in

Figure 1, in order fo be able to change over optionally between floating and ground-fied operation,

The supply for this “Dual Pulsed Mode" must be abie to cover different impedance ranges and yet not be “hard” in the voltage. This means that the supply must supply high current, yet, in spite of it, be largely operabie voltage-stably. An application of an example of such a supply was filed under the No. CH 518/05 paraliel with the same date as said patent application No. CH 1289/05.

The first and preferred application field of this invention is that of cathodic spark evaporation with two pulsed arc evaporator sources {5, 20) as is depicted in Figure 3. ror these applications the impedances are at intervals of approximately 0.01 to 15. it should be noted here that usually the impedances of the sources, between which “dual pulsing” is carried out are different. The reason may be that these are comprised of different materials or alloys, that the magnetic field of the sources is different or that the material erosion of the sources is at a different state. The “Dual Puised Mode” now permits a balance via the setting of the puise width such that both sources draw the same current. This leads consequently fo different voltages at the sources. The supply can, of course, also be loaded asymmetrically with respect to the current if such appears desirable for the process conduction, which is the case, for exampie, for graduated layers of different materials. The voltage stability of a supply is increasingly more dificult to realize the lower the impedance of the particular plasma. The capability of change-over switching ar the controlied active tracking of a supply to different output impedances is of therefore of special advantage if the full range of its power is to be utilized, thus for example in the range of 500 V/100 A to 50 V/1000 A or as it is realized in the paraliel application No. CH 518/05.

The advantages of such dual pulsed cathode configuration and in particuiar one comprised of two arc evaporator sources are summarized as foliows: 1. increased electron emission at steep puises resulls in higher current {also substrate current) and increased ionization of the vaporized material and of the reactive gas.

Z The increased slectron density contributes also to a fast discharge of the substrate surface in the production of insulating layers, je. relatively short charge- reversal times on the substrate {or also only puise pauses of the bias voltage) are sufficient in order to discharge the insulating layer which is forming. 3. The bipolar operation between the two cathodic arc evaporator sources permits a guasi-100% pulse pause ratio {duty cycle), while the puising of a source atong always necessarily requires a pause and therefore the efficiency is not so high. 4, The dual pulsed operation of two cathode spark sources, which are opposite to one another, immerses the substrate region into a dense plasma and increases the reactivity in this region even of the reactive gas. This is also reflected in the increase of {he substrate current. 5. in reactive processes under oxygen atmosphere in pulsed operation still higher electron emission values can be attained, and it appears that a melting of the spark region, as is the case in classic evaporation of metallic targets; can be largely avoided.

Working in purely oxidic reactive mode without further foreign or support gases is now readily possible.

To be able io attain said advantageous process properties in said different possible embodiments of the invention, the pulsed power supply 16, 168’ must satisfy different conditions. in bipolar pulse presentation it should be possible to carry out the process at a frequency which is in the range of 10 Hz {0 500 kHz. Due to the ionization conditions, herein the maintainable edge slopes of the pulses is important. The magnitudes of the leading edges U2/(12 - t1), U1/(t6 - £5), as well as also of the trailing edges U2/(t4 - 13) and U1/{i8 - 17) should have a siope in the range of 0.02 Vins to 2

Vins and this at least in open-circuit operation, thus without load, however preferably also under load. ii is understood that the edge slope has an effect in operation, depending on the corresponding magnitude of the oad or the connected impedance of the corresponding settings. The nuise widths in bipolar presentation for t4 to t1 and t8 to t5 are advantageously 31 :s, the pauses tb to t4 and 18 to t8 can advantageously be essentially ¢, however, under certain conditions, they can also be 30 :s. if the pulse : pauses are > Q, this operation is referred {oc as time-gapped and through, for example, variabie time shift of the puise gap widths the specific and purposeful introduction of energy into a plasma and its stabilization can be set. tis especially advantageous if the pulsed power supply is laid out such that a pulse option up to 500 A at 1000 V voltage is possible, wherein herein the pulse/pause ratio (duty cycle) must be appropriately taken into consideration or must be adapied for the laid out possible power of the supply.

Apart from the edge siope of the pulse voltage it is necessary to observe that the pulsed power supply (18) is capable of handling a current rise to 200 A in at least 1 :=.

With the operation intreduced here of arc evaporator sources with DC feed and superimposed high-current pulsed feed (RPAE, DPAE} it is possible to deposit with high quality starting from one or several metal {argets with reactive gas atmosphere corresponding metal compounds onto a workpiece 30. This is in particular suited for the generation of purely oxidic layers, since the method does not require additional support gases, such as inert gases, customarily argon. The plasma discharge of the arc evaporator 5, 20 can thus, for example and preferably, take place in pure oxygen atmosphere at desired working pressure without the discharge being unstable, is prevenied or yields unusable resulis, as foo high a splatter formation or poor {ayer properties. I is also not necessary to use, as is the case in CVD methods, halogen compounds. This permits, firs, to produce economically wear-resistant oxidic hard material layers of high quality at low process temperatures, preferably below 500EC, which, as a result, are nevertheless high temperature-rasistant, preferably > 800EC and which are chemically highly stable, such as, for exampie, have high resistance to oxidation. Furthermore, to attain a stabie layer system the diffusion of oxygen with the oxidation entalied therein in the deeper layer system and/or on the workpiece should as much as possible be avoided. if is now readily possible 10 produce oxidic layers in pure oxygen as reactive gas from the transition metals of the subgroups IV, V, Vi of the periodic system of elements and

Al, Si Fe, Co, Ni, Y, with Al, Cr, Mo, Zr as well as Fe, Co, Ni, Y being preferred. The functional layer 32 is to contain as the oxide one or several of these metals, no inert gas and/or halogen, such as Cl, however at least less than 0.1% or better less than 0.05% inert gas and less than 0.5% or betier less than 0.1% halogen in order fo attain the desired layer quality.

Such functional layers 32 or multiple layer system 33 (multilayer) should, in particular, as hard material layer have a thickness in the range of 0.5 to 12 :m, preferably from 1.0 tc 5.0 :m. The functional aver can be deposited directly onto the workpiece 30 which is a tool, a machine part, preferably a cutting tool, such as an indexable insert. Between this layer and the workpiece 30 at least one further layer or a layer system can aiso be deposiied, in particular for the formation of an intermediate layer 31, which forms in particular an adhesion layer and comprises preferably one of the metals of the subgroups Va, Va and Via of the periodic system of elements and/or Al or Sior a mixture of these. Good adhesive properties are achieved with compounds of these metals with N, C, O, B or mixtures thereof, the compound comprising N being preferred.

The layer thickness of the intermediate layer 31 should be in the range of 0.05 to 5 1m, preferably 0.1 to 0.5 :m. Atleast one of the functional layers 32 and/or of the intermediate layer 31 can advantageously be implemented as a progression layer 34, whereby a better transition of the properties of the particular layers is brought about.

The progression can be from metallic over nitridic to nitrooxidic and up to the pure oxide. Thus a progression region 34 is formed where the materials of the abutting fayers, or, if no intermediate layer is present, the workpiece material, are mixed into one another.

On the functional layer 32 a further layer or a layer system 35 can be deposited as cover layer, should this be required. A cover layer 35 can be daposited as additional friction-reducing layer for further improvement of the tribological behavior of the coated workpiece 30.

Depending on the requirements, one or more layers of said layers or layer systems can be developed as progression layers 34 in the region where they border on one another or within individual layers concentration gradients of any type can be generated. in the present invention this is simply possibile through the conirolled introduction of the reactive gases info the vacuum process installation 1 for setting the particular types of gas necessary for this purpose and of the gas quantities for the reactive arc plasma process.

As functional layer 32 with the desired hard material properties, now aluminum oxide layers (Al,Os), layers can now readily be produced which even have substantially stoichiometric composition. Especially advantageous hard material layers as functional layer 32 are substantially comprised of an (Al,Me.,),O;, where Me is preferably one of the metals Cr, Fe, Ni, Co, Zr, Mo, Y singly or also in mixtures, settable depending on the desired proportions x, y and z of the involved substances. Further is especially preferred chromium as the metal Me in the metal mixed oxide of the (Al,Me..,),0. which consequently forms (Al,Cri},O ; or (AICr),0,. Herein the proportion 1-x of the metal chromium in the layer should be & to 80 atom %, preferably 10 to 60 atom %.

Well suited as hard material functional layer 32 is also a metal nitride, in particuiar the aluminum chromium nitride (AICriN ; or at most also (AITi)N,.

Through the intentional capability of process conduction it is now also possible in the case of aluminum and aluminum chromoxides to be able fo attain the especially desired alpha and/or gamma structure.

Due to said simple settability of the layer conditions with their composition via the controt of the supply of the reactive gases and due to the stabie process condition, itis for the first time possible to produce multilayer systems (muliiiayer) 33 with any number of layers and any composition and even with progressions. Several layers can herein be generated of different materials or, and this appears often to be of advantage, with the aliernating identical materials as a type of sandwich. For functional hard material layers 32, a layer system with repeated layer sequence pairs 33, in which the material composition changes periodically, is advantageous. tspecially a structure from Me. to an Me; -oxide and/or from an Me, -nitride to an Me. -oxide and/or from an Me, -nitride io an Me. -oxide yields excellent results with respect to endurance and less fissuring of the functional layer or of this layer system. An exampie of a functional layer 32 as a multilayer 33 is shown in Figure 4 and in enlarged cross section in Figure 5. Shown is a preferred material pairing of alternating aluminum chromium nitride (AICT),N, with aluminum chromoxide (AIC), 0, produced with the method according to the invention, preferably in stoichiometric material composition. The laver packet in this example comprises 42 layer pairs with aliernating materials. as stated above. The entire layer thickness of this funcional layer 32 as multilayer system 33 is approximately 4.1 :m, the thickness of a layer pair, thus two deposits, being 98 nm. Further preferred material pairings are alternating aluminum zirconium nitride (AlZr)N , with aluminum zirconium oxide {AiZr),O , produced with the method according to the invention, preferably in stoichiometric material composition. For hard material layers as functional layer 32 itis of advantage if the multilayer system 33 includes at least 20 deposits, preferably up to 500 deposits. The thickness per deposit should be in the range from 0.01 to 0.5 1m, preferably in the range from 0.2 to 0.1 :m. In the region of the individual bordering deposits of the layers progressions 34 are alse evident, which ensure for good behavior of the transitions. in the example according {o Figure 4 as an example a cover taver 35 is also deposit as a friction-reducing layer over the functional layer 32, 33. The cover iaver is comprised of titanium nitride and is approximately 0.83 :m thick.

Under the functional layer as an example additionally an intermediate layer 31 is disposed as adhesion layer which is approximatety 1.37 :m thick and has been deposited as an AI-Cr-N intermediate layer with RPAE onto the workpiece 30.

The coatings introduced here, whether single laver or multilayer system should preferably have an R; vaiue of not iess than 2 :m andior an KR, value of not iess than 0.2 :m. These valuss are in each instance measured directly on the surface before a potential after-treatment of the surface, such as brushing, blasting, polishing, efc. Thus, the values represent a purely process-gependent surface roughness. By R, value is understood the mean rough value according {o DIN 4768. This is the arithmetic mean of ali deviations of the roughness profile R from the center iine within the total measuring path [. By R; is understood the mean roughness depth according to DIN 4768. This is the mean value of the individual roughness depths of five successive individual measuring paths |; in the roughness profile. R, depends only on the distance of the highest peaks to the deepest valisys. By forming the mean value the effect of an individual peak (valley) is reduced and the mean width of the band. in which the R profile is inciuded, is calculated.

The introduced coating according io the invention is especially suited for workpieces such as cutting, forming, injection molding or punching and stamping tools, however, very specifically for indexable inserts. in the following a typical sequence of a substrate treatment in a reactive pulse arc evaporation coating process is described using the present invention. Apart from the coating process proper, in which the invention is realized, the other process sieps will also be described, which involve the pretreatment and postireatiment of the workpieces.

All of these steps allow wide variations, some can also be omitted under certain conditions, shortened or extended or be combined differently. in a first step the workpieces are customarily subjected to wei-chemical cleaning, which, depending on the material and prior history, is carried out in different manner. txample 1;

Description of a typical process sequence for the production of an AI-Cr-O ayer 32 (as well as of an Al-Cr-N/AI-Cr-O multilayer 33) and A-Cr-N intermediate layer 31 by means of RPAE (reactive pulse arc evaporation) for coaiing workpieces 30, such as cutting tools, preferably indexabie inserts. 1. Pretreatment (cleaning. etc.) of the workpieces (30) (substrates) as known to the person of skill in {he art. 2. Placing the substrates into the holders intended for this purpose and transfer into the coating system. 3. Pumping the coating chamber 1 to a pressure of approximately 10” mbar by means of a pump system as known to the person of skill in the art (forepumps/difiusion pump, forepumps/iurbomaoliecular pump, final pressure approximately 10° mbar attainable). 4. Starting the substrate pretreatment in vacuo with a heating step in an argon- hydrogen plasma or ancther known plasma treatment. Without restrictions, this pretreatment can be carried out with the following parameters:

Plasma of a low-voltage arc discharge with approximately 100 A discharge current, up to 200 A, to 400 A, the substrates are preferably connected as anode for this low- voltage arc discharge:

Argon flow 50 scom

Hydrogen fiow 300 sccm

Substrate temperature 500EC (partially through plasma heating, partially through radiative heating)

Process time 45 min

It is preferred that during this step a supply is connected between substrate 30 and ground of another reference potential, which can act on the substrates with DC (preferably positive) or DC pulsed (unipolar, bipotar) or as iF (intermediate frequency) or

RF (high frequency). 5. As the next process step etching is started. For this purpose the low-voltage arc is operated between the filament and the auxiliary anode. A DC, pulsed DC, IF or RF supply is connected between substrates and ground and the substrates are preferably acted upon with negative voltage. in the pulsed and iF, RF supplies positive voltage is also impressed on the substrates. The supplies 4 can be operated unipolarly or bipoiarly. The typical, however not exclusive, process parameters during this step are:

Argon fiow 60 sccm

Discharge current low-voltage arc 150 A

Substrate temperature 500 EC (partially through plasma heating, partially through radiative heating)

Process time 30 min

To ensure the stability of the low-voltage arc discharge during the production of insulating layers, the work is either carried out with a hot, conductive auxiliary anode 15, or a pulsed high-power supply is connected between auxiliary anode and ground. 6. Start of coating with the intermediate layer 31 (approximately 15 min)

CrN intermediate layer 300 nm by means of spark evaporation {source current 140 A,

Ar 80 scem, N2 1200 scem, with bias of -80 V or of -100 V down to - 60 V or 40 V, respectively.

The coating can take place with and without low-voltage arc. 7. Transition to the functional iayer 32 (approximately 5 min)

In the transition to the functional layer proper, onic the spark sources are additionally superposed unipolar DC pulses of a second power supply connected in parallel, which can be operated with 50 kHz (Fig. 2). An Al targst is additionally operated in the same manner in order to produce AICr as a layer. In the example work took place with 10 's pulse/1G :s pause and in the pulsed currents up to 150 A generated. Oxygen at 200 scem was subsequently let in. 8. Driving back of the AICTN coating

After the oxygen gas flow has been stabilized, the AICIN coating is brought down. For this purpose the N2 gas flow is reduced. This ramp takes place over approximately 10 min. The Ar flow is subsequently reduced to zero {uniess work is carried cut with low- voltage arc). 8. Coating with functional layer 32

The coating of the substrates with the functional layer proper takes place in pure reactive gas {in this case oxygen). The most important process parameters are:

Oxygen fiow 400 sccm

Substrate temperature 500EC

DC source current 60 A

Onto the DC source current a pulsed DC current (unipolar) of 150 A is superimposed with a pulse frequency of 50 kHz and a pulse characteristic of 10 :s pulse/10 :s pause.

Process pressure in the coating chamber 9x10° mbar. The bias at the substrates is reduced to -40 V. Since aluminum oxide layers are insulating layers, a bias supply is utilized, which is operated either DC pulsed or as IF {50 kHz - 350 kHz).

The coating can also be carried out simultaneously with the low-voltage arc. in this case a higher reactivity is attained. The simultaneous use of the low-voltage arc during the coating has furthermore the advantage that the DC component in the sources can be reduced. At higher arc current, it can be further reduced.

The coating process conducted in this way is stable even over several hours. The target 5, 5's covered with a thin smooth oxide layer. However, no insulating islands are formed, although the target surface changes through the oxygen, which is also reflected in the increase of the burn voltage. The target surface remains significantly smoother. The spark runs quieter and divides into several smaller sparks. The number of splatiers is significantly reduced.

The described process is a fundamental preferred version since it keeps the requirements made of the pulsed power supply low. The DC supply supplies the minimum or holding current for the spark and the pulsed high-power supply 16, 16° serves for avoiding the splatters and ensures the process.

One feasibility of generating multitayer systems 33, thus multiple layers 33, for the above layer example comprises that the oxygen flow during the layer deposition is decreased or even switched off entirely, while the nitrogen flow is added. This can take piace periodically as well as aperiodically, with layers of exclusive or mixed oxygen- nitrogen conceniration. in this way multilayers 33 are produced such as are shown in

Figure 4, and enlarged in Figure 5, by example in cross section. In many cases this functional layer 32 forms the termination of the coating to the outside, without a further layer following thereon.

Depending on the application and requirement, wear properties can be “topped” with one or several cover layers 35. The example of the AICrN/AICFO multilayer already described above with a TiN top layer is also shown in Figure 4. The at least one cover layer 35 can in this case be, for example, a friction-reducing layer, wherein in this case the hard material layer 32, or the functional ayer or the multiple layer serves as support layer for the friction-reducing layer 35. if there is the wish fo produce multitayer functional layers 33 or multilayer intermediate layers with especially thin oxide-containing layer thickness, in a preferred process variant this can also take place thereby that the operation of the oxide-forming target under oxygen flow takes place just until the target exhibits first poisoning signs (voltage rise, most often after a few minutes) and then switching again to. for exampie, nitrogen flow. The process variant is especially simpie and can be reaiized with the existing prior art (Fig. 1) thus without target pulse operation. However, this does not permit a free adaptation of the layer thickness to the particular requirements.

The implementation of said example in duat pulsed operation with two or more arc evaporator sources yields, in addition, advantages with respect fo the conduction of the process and economy.

Example 2:

Coating of workpieces 30, such as cutting tools, preferably indexable inserts, with an Al-

Cr-O hard material layer system 32 and Cr-N intermediate ayer 31 by means of DPAE {Dual Pulsed Arc Evaporator)

Steps 1 to and including 5 analogous to Example 1. 6. Starting the coating with the intermediate layer (approximately 15 min}

AICrN intermediate ayer 300 nm by means of spark evaporation (target material AlCr

(50%, 50%), source current 180 A, N2 800 sccm, with bipolar bias of -180 V (36 :s negative, 4 :s positive).

The coating can take place with and without low-voltage arc.

Up to this point the method follows prior art such as is shown for example in Fig. 1. 7. Transition to functional layer 32 (approximately 5 min) in the transition to the functional layer 32 proper, the nitrogen is ramped down from 800 sccm to approximately 800 scom and subsequently an oxygen flow of 400 scem is switched on. The nitrogen flow is now switched off. 8. Coating with the functional iayer 32

The bipolar pulsed high-power supply 16, as shown in Fig. 3, between both arc evaporator cathodes 5, 20 is now taken into operation. In the described process work took place with a pesitive or negative time mean value of the current of approximately oC A. The pulse durations were each 10 :s for the positive as well as negative voltage range with 10 :s pauses each in between at a voltage of 160 V. The peak value of the current through the bipolar pulsed power supply 16 depends on the particular pulse form. The difference of DC current through the particular arc evaporator cathode 5, 20 and peak vaiue of the bipolarty puised current must not fall below the so-called holding current of the arc evaporator cathode 5, 20, since otherwise the arc (spark) is extinguished.

During the first 10 minutes of the coating the bias is ramped from -180 V to -60 V. The typical coating rates for double rotating workpieces 30 are between 3 :m/hr and 6 :m/hr.

The coating of the workpieces 30 with the functional layer 32 proper thus takes piace in pure reactive gas (in this example oxygen). The most important process parameters are once again summarized:

Oxygen flow 400 sccm

Workpiece temperature 500EC

DC source current 180 A, for the Al as well as also for the Cr source.

The bipolarly pulsed DC current between the two cathodes has a frequency of 25 kHz.

Process pressure approximately 9x10° mbar.

As already stated, the coating can also take place simultaneously with the operation of the low-voltage arc. In this case a further increase of the reactivity especially in the proximity of the workpiece is attained. in addition, the simultaneous utilization of the low-voltage arc during the coating has also the advantage that the DC component at the sources can be reduced. With higher arc current, this can be further reduced.

The coating process conducted in this way is stable even over several hours. Targets 5", 20" of the arc evaporators 5, 20 are covered with thin, smooth oxide layer. This is desirable and is also the precondition for a largely splatter-free and stable process. The covering is manifested in an increase of the voltage at the target.

Workpieces were coated with different coatings and under the same conditions subjected io a practical comparison test.

Test conditions for the rotation tests: :

As the measure for these tests known TiAIN layers and known alpha aluminum oxide layers deposited by means of CVD are used. in all test layers a layer thickness of 4 :m was tested. As est material were used stainless steel (1.1192). As rotation cycies were selected 1, 2 and 4 min each. The cutting rate was 350 m/min, advance 0.3 mmirev. Engagement depth 2 mm. The conditions were selected such that short test times are atiainable at high temperatures on the cutiing sedge of the workpiece.

The wear on the end flank and the chipping edge as well as the surface roughness of the worked steel were tested, and the length of time was determined before a certain increased roughness occurred. As the quantitative measure for wear, this service time was determined,

Resuits:

a) CVD {ayer alpha aluminum oxide (prior art} layer thickness d = 4 :m

The tool survived the 4-minute test. However, after the test in the SEM there was no ionger any layer material on the chipping edge. bj TIAIN layer (prior art), d = 4 1m

This layer showed already after less than 2 min initial signs of destructions and supplied a rough surface on the workpiece. invention: c} AICrN intermediate layer, d = 0.4 :m

AICHIN/AICTO multilayer, d = 3.6 1m

TiN top layer, d = 0.8 :m

Endurance 4 min d) AICN intermediate layer, d = 0.4 :m

AICHN/AICEO multilayer, d = 3.6 :m 3mind4ls e) AICIN intermediate layer, d = 0.3 :m

AICrO single layer, d = 2.9m

TiN top layer, d = 0.9 :m 4 min f) AICrN intermediate javer, d = 0.35 :m

AlICrO single layer, d = 3.5 :m 3min20s g) ZrN intermediate layer, d = 0.3 1m

ZrN/AICrG multilayer, d = 3.8 1m

ZrN top layer, d = 0.5m 3min 10s n) ZN intermediate layer, d = 0.2 :m

ZrQ/AICHO multitayer, d = 6.4 :m

ZrN top layer, ¢ = 0.8 1m 4 min i) AICIN intermediate layer, d = 0.5 1m

AICrO/alpha alumina multilayer, d = 8.2 :m 4 min k) (Ti, AICIN) intermediate layer, d = 0.4 :m

AICrO/MIAICHN multilayer, d = 4.5 1m 3minbd0s

Layers of or multitayers comprising oxidic layers of the stated materials show markedly less wear at high cutting rates. Conducting layers (TIAIN) according fo prior art at high cutting rates are markedly inferior to the oxide systems according to the invention.

Systems according to the present invention of (AICr},0, and {AlZr),O. show similarly low wear as known CVD layers of v-aluminum oxide, however without its disadvantage of high temperature loading or ioading through aggressive chemicals of the workpiece during the coating process. The conduction of the process, furthermore, can be carried out substantially simpier, for example through changing-over of gases or controlled change of the gas components {for example O- to Nz) and/or changing-over from one target, or changing of the components of the target feed under control, to the othar, while in CVD processes intermediate flushing as well as adaptation of the temperature level for individual layers of a multilayer layer system are necessary.

Claims

CLAIMS: 1) Hard material layers deposited on a workpiece (30) as Arc - PVD functional layer (32) wherein this layer is formed substantially as an electrically insulating oxide of at least one of the metals (Me) from the transition metals of subgroups IV, V, VI of the periodic system of elements and Al, Si, Fe, Ca, Ni, Y, characterized in that the functional layer (32) has a content of inert gas and/or of a halogen of less than 2%. 2) Hard material layer as claimed in claim 1, characterized in that the content of inert gas in the functional layer (32) is maximally 0.1%, preferably maximally 0.05%. and/or that of halogen maximally 0.5%, preferably maximally

0.1%, preferably comprises substantially no inert gas and/or halogen. 3) Hard material layer as claimed in one of the preceding claims, characterized in that the functional layer (32) has a thickness in the range from

0.5:m to 12 :m, preferably 1.010 5m. 4} Hard material layer as claimed in one of the preceding claims, characterized in that the functional layer (32) is substantially an aluminum metal mixed oxide of the form (Al,M+.},O; wherein Me is preferably one of the metals Al, Cr, Mo, Zr, Fe, Co, Ni, Y, singly or also in mixtures thereof. 5) Hard material layer as claimed in claim 4, characterized in that Me is the meatal chromium and forms the form (Al Cri yO, 6) Hard material layer as claimed in claim 5, characterized in that the fraction of the metal chromium in the layer is § io 80 atom%, preferably 10 to 60 atom%.

7) Hard material layer as claimed in one of claims 1 to 3, characterized in that the functional layer (32) is substantially a stoichiometric aluminum oxide layer of the form AlLO,. 8) Hard material layer as claimed in one of the preceding claims, characterized in that the functional layer (32) forms the cutermaost layer or an additional support layer, with at least one superjacent cover layer (35), such as in particular a friction-reducing layer {35}. 9} Hard material layer as claimed in one of the preceding claims, characterized in that the functional layer (32) has a temperature resistance of greater than 800EC and that it is chemically stable. 10} Workpiece with a hard material layer as claimed in one of claims 1 {0 9, characterized in that the workpiece (30) is a tool, a machine part, preferably an indexable insert. 11) Workpiece as claimed in ciaim 10, characterized in that between the functional iayer (32) and the workpiece (30) a further layer forming an intermediate layer (31) is disposed, and this layer forms in particular an adhesion layer (31) and such adhesion layer preferably comprises ong of the metals of the subgroups IV, V and V1 of the periodic system of elements and/or Al, 3i, Fe, Co, Ni, Y or a mixture thereof. 12) Waorkpiece as claimed in claim 11, characterized in that the metals of the intermediate layer (31) are compounds with N, C, O, B or mixtures thereof, the compound with N being preferred.

13) Workpiece as claimed in one of claims 11 to 12, characterized in that the {ayer thickness of the intermediate layer (31) is 0.05 {0 5 :m, preferably is in the range of 0.1 fo 0.5 :m.

14) Workpiece as claimed in one of claims 10 to 13, characterized in that at least one of the layers, in particular the functional layer (32) and or the intermediate layer {31) is implemented as a progression layer (34), such as from metallic over nitridic and/or from nitridic to nitrooxidic and up to the oxide.

15) Workpiece as claimed in one of claims 10 to 14, characterized in that at ieast one of the layers, in particular the functional layer (32), is implemented as a multilayer system (33) with different material composition, in which preferably several deposits (33) alternately repeat with respect io their essential composition and that the mullilayer system {33) preferably comprises at least 3 deposits.

16} Workpiece as claimed in claim 15, characterized in that the repeating layer sequence pairs of the layer system aliernately change the material composition, such as preferably from an Me4 to an Me; -oxide and/or from an Mey -nitride to an Mey -oxide andfor from an May -nitride fo an Me, -oxide.

17) Workpiece as claimed in one of claims 15 or 16. characterized in that the repeating layer sequence pair of the layer system alternately comprises the material composition of (AlkCri.x} yN; and {AlxCrix}y OC; and these preferably in stoichiometric composition such as (ALCr .,ON and (Al Cri): Cs.

18) Workpiece as claimed in one of claims 15 or 16, characterized in that the repeating layer sequence pairs of the layer system comprise alternately the material composition (AlZr)xNy and (AiZr), Oy and these preferabiy in stoichiometric composition such as (Al, Zr.

JN and (Al, Zr. )205. 19} Workpiece as claimed in one of claims 15 to 18, characterized in that the multilayer system (33) comprises at least 20 deposits, preferably up to 500 deposits. 20) Workpiece as claimed in one of claims 15 to 19, characterized in that the layer thickness of ons deposit of the multilayer system (33) is in the range of 0.01 to 0.5 :m, preferably in the range of 0.02 to 0.1 1m. 21) Method for coating a workpiece (3) in a vacuum process installation (1) with a hard material layer (32) deposited as functional fayer, which is implemented as an electrically insulating oxide of at least one of the metals (Me) of the transition metals of the subgroups IV, V, Vi of the periodic system of elements and Al, 8i, Fe, Co, Ni, Co, Y, and that the layer is deposited with an arc evaporator source (5) operated with a DC power supply (13), characterized in that a pulsed power supply (16, 16") is superimposed, wherein the target (5', 20) cf the arc evaporator source (5, 20) comprises one of the metals and the metal vapor-depesited in this way is reacted to the oxide in an oxygen-coniaining reactive gas aimosphere. 22) Method as claimed in claim 21, characterized in that in the reactive gas atmosphere of the process chamber of the vacuum installation (1) so small a quantity of inert gas and/or halogen gas is supplied that in the deposited layer maximally 0.8% of such gases, preferably substantially none of these gases, are incorporated. 23) Method as claimed in one of claims 21 to 22, characterized in that two DC-fed arc evaporator sources (5, 20) ars operated, wherein additionally a single pulsed power supply (16) is connected to the two sources (5, 20) and in this manner forms a dual pulse arc evaporator configuration (5, 20). 24) Method as claimed in one of claims 21 to 23, characterized in that the warkpiece is substantially comprised of steel, an iron-, chromium-, cobalt- or nickel-containing alloy of one or several metals, a hard metal, a ceramic, a cermet, or cubic boron mononitride, wherein at least one further layer is deposited by means of a PVD method and one of the layers is an adhesion layer {31} which borders directly on the workpiece (30), wherein the or at least one of the following layers, the functional layer (32), is substantially comprised of Al,O; or (AlMe),O3, wherein Me comprises at least one transition metal of the group IV, V or VI of the pericdic system of elements or silicon and at least the aluminum or aluminum metal oxide layer is deposited with an arc evaporator (5, 20}, in which from at ieast one target {5', 20"), poisoned on the surface, aluminum oxide, metal oxide or aluminum metal oxide is vaporized in an oxygen-containng atmosphere. 25) Method as claimed in one of claims 21 to 24, characterized in that the coating attains a roughness value RK, of not less than 0.2 :m. 26) Method as claimed in one of claims 21 (oc 25, characterized in that at least one further layer is deposited which comprises substantially an aluminum- free one or several metal oxides comprising oxide layer, wherein the metal oxide comprises at least one transition metal of group IV, V or Vi of the periodic system of elements or silicon, howaver preferably chromium or zirconium. 27) Method as claimed in one of claims 24 to 26, characterized in that the adhesion layer {31) comprises at least one of the transition metals of group IV, V or VI of the periodic system of elements and/or aluminum or silicon.

28) Method as claimed in one of claims 24 10 27, characterized in that the adhesion layer {31) comprises a hard layer which comprises a nitride, carbide or boride, at least one of the transition metals of group IV, V or Vi of the periodic system of elements and/or aluminum or silicon or a mixture of these compounds. 29) Method as claimed in one of claims 21 to 28, characterized in that the functional layer {32) is deposited as hard material laver system which comprises several deposits (33) of a nitride, carbide, boride or oxide of af least one of the transition metals of group IV, V or VI of the periodic system of elements and/or aluminum or silicon or a mixture of these compounds, wherein at least directly succeeding deposits differ by the stoichiometry of their metal or nonmetal content. 303 Method as claimed in claim 29, characterized in that the deposition of the hard material layer system (32) takes place with one or several deposits (33) of aluminum chromoxide-containing layers. 31) Method as claimed in one of claims 29 to 30, characterized in that transitions between the individual deposits {33) of the hard material layer system (32) with respect to the stoichiometry of their metal or nonmetal content are increased or decreased smoothly and continuously or stepwise. 32) method as claimed in one of claims 29 to 31, characterized in that the layer of the individual deposits of the hard material layer system (32) is deposited with a thickness between 0.01 and 0.5 :m, preferably betwen 0.02 and G.1 :m. 33) Method as claimed in one of claims 30 to 32, characterized in that nitride-, carbide- or boride-containing avers are deposited alternately with aluminum chromoxide-containing layers.

34) Method as claimed in one of claims 24 to 33, characterized in that at least one transition from the adhesion layer (31) to the aluminum oxide- containing layer or to the hard material layer system (32) or from the hard material layer system (32) or the aluminum oxide-containing layer tc the cover layer (35) with respect {o the stoichiometry of their metal or nonmetal content are increased or decreased smoothly and continuously or stepwise, 35) Method as claimed in one of claims 21 to 34, characterized in that the aluminum oxide-containing layer is substantially deposited as (Al 1.x Cry 320s, wherein 0.05 < x < 0.80, however preferably 0.01 <x < (0.60. 36) Method as claimed in one of claims 21 to 35, characterized in that as workpiece {30} a tool, in particular a cutling, forming or injection molding tool is coated. 377 Method as claimed in one of claims 21 to 36, characterized in that as workpisce (30) a part, in particular a part for an internal combustion engine or a turbine, is coated.