The present invention is directed on a tool with a tool body and a wear resistant layer system, wherein the layer system comprises at least one layer of MeX, wherein - Me comprises titanium and aluminum, - X is at least one of nitrogen and of carbon.

Definition: The term Q1 is defined as the ratio of the diffraction inten- sities I(200) to I(111), assigned respectively to the (200) and (111) plains in the X ray diffraction of a material using the 0-20 method. Thus, there is valid1 = I(200)/I(lll). The intensity values were measured with the following equipment and with the following settings: Siemens Diffractometer D500 Power: Operating voltage: 30 kV Operating current: 25 mA Aperture Diaphragms: Diaphragm position I: 10 Diaphragm position II: 0.10 Detector Diaphragm: Soller slit Time constant: 4 s 29 angular speed: 0.0S0/min Radiation: Cu-Ka(0.15406 nm) When we refer to "measured according to MS" we refer to this equipment and to these settings. Thereby, all quantitative re-

sults for Q1 and I throughout this application have been meas- ured by MS.

We understand by "tool body" the uncoated tool.

We understand under "hard material" a material with which tools which are mechanically and thermally highly loaded in operation are coated for wear resistance. Preferred examples of such materials are referred to below as MeX materials.

It is well-known in the tool-protecting art to provide wear re- sistant layer systems which comprise at least one layer of a hard material, as defined by MeX.

The present invention has the object of significantly improving the lifetime of such tools. This is resolved by selecting for said at least one layer a Q1 value, for which there is valid Q1 2 1 and wherein the tool body is made of high speed steel (HSS) or of cemented carbide, whereby said tool is not a solid carbide end mill or a solid carbide ball nose mill. Further, the value of I(200) is higher by a factor of at least 20 than the inten- sity noise average level as measured according to MS.

According to the present invention it has been recognised that the Q1 values as specified lead to an astonishingly high im- provement of wear resistance, and thus of lifetime of a tool, if such a tool is of the kind as specified.

Up to now, application of a wear resistant layer systems of MeX hard material was done irrespective of interaction between tool body material and the mechanical and thermal load the tool is

subjected to in operation. The present invention thus resides on the fact that it has been recognised that an astonishing im- provement of wear resistance is realised when selectively com- bining the specified Q; value with the specified kind of tools, thereby realising a value of I(200) higher by a factor of at least 20 than the average noise intensity level, both measured with MS.

With respect to inventively coating cemented carbide tool bod- ies, it has further been recognised that a significant improve- ment in lifetime is reached if such cemented carbide tools are inserts, drills or gear cutting tools, as e.g. hobs or shaper cutters, whereby the improvement is especially pronounced for such inserts or drills.

The inventively reached improvement is even increased if QT is selected to be at least 2, and an even further improvement is realised by selecting QT to be at least 5. The largest improve- ments are reached if Q1 is at least 10. It must be stated that Q1 may increase towards infinite, if the layer material is re- alised with a unique crystal orientation according to a dif- fraction intensity I(200) at a vanishing diffraction intensity I(111). Therefore, there is not set any upper limit for Q1 which is only set by practicability.

As is known to the skilled artisan, there exists a correlation between hardness of a layer and stress therein. The higher the stress, the higher the hardness.

Nevertheless, with rising stress, the adhesion to the tool body tends to diminish. For the tool according to the present inven- tion, a high adhesion is rather more important than the highest possible hardness. Therefore, the stress in the MeX layer is

advantageously selected rather at the lower end of the stress range given below.

These considerations limit in practice the Q, value exploit- able.

In a preferred embodiment of the inventive tool, the MeX mate- rial of the tool is titanium aluminum nitride, titanium alumi- num carbonitride or titanium aluminum boron nitride, whereby the two materials first mentioned are today preferred over ti- tanium aluminum boron nitride.

In a further form of realisation of the inventive tool, Me of the layer material MeX may additionally comprise at least one of the elements boron, zirconium, hafnium, yttrium, silicon, tungsten, chromium, whereby, out of this group, it is preferred to use yttrium and/or silicon and/or boron. Such additional element to titanium and aluminum is introduced in the layer ma- terial, preferably with a content i, for which there is valid 0.05 at.t < i < 60 at.t, taken Me as 100 at.

A still further improvement in all different embodiments of the at least one MeX layer is reached by introducing an additional layer of titanium nitride between the MeX layer and the tool body with a thickness d, for which there is valid 0.05 µm # d # 5 µm.

In view of the general object of the present invention, which is to propose the inventive tool to be manufacturable at lowest possible costs and thus most economically, there is further

proposed that the tool has only one MeX material layer and the additional layer which is deposited between the MeX layer and the tool body.

Further, the stress 6 in the MeX is preferably selected to be 1 GPa < 6 < 4 GPa, thereby most preferably within the range 1.5 GPa < a < 2.5 GPa The content x of titanium in the Me component of the MeX layer is preferably selected to be 70 at W 2 x > 40 at , thereby in a further preferred embodiment within the range 65 at W > x > 55 at W.

On the other hand, the content y of aluminum in the Me compo- nent of the MeX material is preferably selected to be 30 at W < y < 60 at , in a further preferred embodiment even to be 35 at % < y < 45 at W.

In a still further preferred embodiment, both these ranges, i.e. with respect to titanium and with respect to aluminum are fulfilled.

The deposition, especially of the MeX layer, may be done by any known vacuum deposition technique, especially by a reactive PVD coating technique, as e.g. reactive cathodic arc evaporation or

reactive sputtering. By appropriately controlling the process parameters, which influence the growth of the coating, the in- ventively exploited Q1 range is realised.

To achieve excellent and reproducible adhesion of the layers to the tool body a plasma etching technology was used, as a pre- paratory step, based on an Argon plasma as described in Appen- dix A, which document is integrated to this description by ref- erence, with respect to such etching and subsequent coating.

This document accords with the US application No. 08/710 095 of the same inventor (two inventors!) and applicant as the present application.

Examples 1 An arc ion plating apparatus using magnetically controlled arc sources as described in Appendix A was used operated as shown in table 1 to deposit the MeX layer as also stated in table 1 on cemented carbide inserts. The thickness of the MeX layer de- posited was always 5 ptm. Thereby, in the samples Nr. 1 to 7, the inventively stated Q: values where realised, whereas, for comparison, in the samples number 8 to 12 this condition was not fulfilled. The I(200) value was always significantly larger than 20 times the noise average value, measured according to MS. The coated inserts were used for milling under the follow- ing conditions to find the milling distance attainable up to delamination. The resulting milling distance according to the lifetime of such tools is also shown in table 1.

Test cutting conditions: - Material being cut: SKD 61 (HRC45)

- Cutting speed: 100 m/min - Feed speed: 0.1 m/edge - Depth of cut: 2 mm The shape of the inserts coated and tested was in accordance with SEE 42 TN (G9).

It is clearly recognisable from table 1 that the inserts, coated according to the present invention, are significantly more protected against delamination than the inserts coated ac- cording to the comparison conditions.

Further, the result of sample 7 clearly shows that here the stress and thus hardness of the layer was reduced, leading to lower cutting distance than would be expected for a high Q1 of 22.5, still fulfilling the stress-requirements as defined above.

(Table 1) Coating Conditions Qt = Residual Attainable Sample No. Layer I(200)/ Stress GPa Cutting Dis- x y I [111] tance (m) Remarks (distance Bias Arc till delami- Voltage N2 pressure Current nation) (-V) (mbar) (A) 1 60 2.0 x 10-2 150 (TixAlY)N 0.5 0.5 1.5 5.2 2.2m (2.1m) 2 60 8.0 x 10-2 150 (TixAlY)N 0.5 0.5 6.7 4.8 2.8m (2.5m) Present 3 40 2.0 x 102 150 (TixAlY)N 0.5 0.5 8.1 4.2 8.8m (8.5m) face lapping Invention 4 40 3.0 x 10-2 150 (TixAlY)N 0.4 0.6 10.2 3.9 3.9m (3.5m) 5 40 0.5 x 10-2 150 (TixAlY)N 0.5 0.5 6.0 5.8 2.0m (1.7m) 6 30 2.0 x 10-2 150 (TixAlY)N 0.5 0.5 15.4 2.5 4.2m (4.0m) 7 20 2.0 x 10-2 150 (TixAlY)N 0.5 0.5 22.5 1.2 3.3m (3.3m) 8 60 0.5 x 10-2 150 (TixAlY)N 0.5 0.5 0.8 6.1 1.0m (0.8m) 9 100 2.0 x 10-2 150 (TixAlY)N 0.5 0.5 0.7 5.5 0.9m (0.9m) Comparison 10 100 3.0 x 10-2 150 (TixAlY)N 0.5 0.5 0.9 4.8 0.8m (0.7m) 11 150 2.0 x 10-2 150 (TixAlY)N 0.5 0.5 0.2 7.2 0.1m (0.1m) 12 100 0.5 x 102 150 (TixAlY)N 0.4 0.6 0.1 6.8 0.2m (0.1m)

Examples 2: The apparatus as used for coating according to Example 1 was also used for coating the samples Nr. 13 to 22 of table 2. The thickness of the overall coating was again 5 Hm. It may be seen that in addition to the coating according to Example 1 there was applied an interlayer of titanium nitride between the MeX layer and the tool body and an outermost layer of the respec- tive material as stated in table 2. The condition with respect to I(200) and average noise level, measured according to MS was largely fulfilled.

It may be noted that provision of the interlayer between the MeX layer and the tool body already resulted in a further im- provement. An additional improvement was realised by providing an outermost layer of one of the materials titanium carboni- tride, titanium aluminum oxinitride and especially with an out- ermost layer of aluminum oxide. Again, it may be seen that by realising the inventively stated Q1 values with respect to the comparison samples number 19 to 22, a significant improvement is realised.

The outermost layer of aluminum oxide of 0.5 Hm thickness, was formed by plasma CVD.

The coated inserts of cemented carbide were tested under the same cutting conditions as those of Example 1, Q1 was measured according to MS.

(Table 2) Sampole No. Inter- TiAl Layer x y Outermost Qr = Attainable Cutting I (200)/ layer Layer Distance (m) (distance I (111) (µm) till delamination) 13 TiN (TixAlY)N 0.5 0.5 - 1.5 4.5m (4.2) (0.4 µm) (4.6 µm) Present 14 TiN (TixAlY)N 0.5 0.5 TiCN 7.2 7.8 (7.6m) (0.4 µm) (4.1 µm) (0.5 µm) Invention 15 TiN (TixAlY)N 0.5 0.5 TiCN 6.8 6.0m (5.5m) (0.4 µm) (4.4 µm) (0.5 µm) 16 TiCN (TixAlY)N 0.5 0.5 (TiAl)NO 5.2 6.2m (6.0m) (0.4 µm) (4.1 µm) (0.5 µm) 17 TiN (TixAlY)N 0.5 0.5 Al2O3 12.5 10.1m (9.8m) (0.4 µm) (4.1 µm) (0.5 µm) 18 TiN (TixAlY)N 0.5 0.5 Al2O3 7.0 9.8m (9.5m) (0.4 µm) (4.1 µm) (0.5 µm) 19 TiN (TixAlY)N 0.5 0.5 - 0.8 1.5m (1.2m) Comparison 20 TiN (TixAlY)N 0.5 0.5 TiCN 0.8 1.9m (1.5m) 21 TiN (TixAlY)N 0.5 0.5 TiCN 0.7 1.8m (1.5m) 22 TiN (TixAlY)N 0.5 0.5 (TiAl)NO 0.1 0.6m (0.4m)

Example 3: Again, cemented carbide inserts were coated with the apparatus of Example 1 with the MeX layer as stated in table 3, still fulfilling the Q1 conditions as inventively stated and, by far, the condition of I(200) with respect to average noise level, measured according to MS. Thereby, there was introduced one of zirconium, hafnium, yttrium, silicon and chromium, with the amount as stated above, into Me.

The coated inserts were kept in an air oven at 7500C for 30 min. for oxidation. Thereafter, the resulting thickness of the oxide layer was measured. These results are also shown in table 3. For comparison, inserts coated inventively with different Me compounds of the MeX material were equally tested. It becomes evident that by adding any of the elements according to samples 23 to 32 to Me, the thickness of the resulting oxide film is significantly reduced. With respect to oxidation the best re- sults were realised by adding silicon or yttrium.

It must be pointed out, that it is known to the skilled arti- san, that for the MeX material wear resistant layers there is valid: The better the oxidation resistance and thus the thinner the resulting oxide film, the better the cutting performance.

(Table 3) Sample No. Layer Composition w x y z Thickness of Oxide Film (µm) 23 (TiXAlYYZ)N 0.48 0.5 0.02 0.7 24 (TiXAlYCrZ)N 0.48 0.5 0.02 0.9 25 (TiXAlYZrZ)N 0.48 0.5 0.02 0.7 Present 26 (TiXAlYZ)N 0.25 0.5 0.25 0.1 Invention 27 (TiXAlYZr)N 0.25 0.5 0.25 0.5 28 (TiXAlYWZ)N 0.4 0.5 0.1 0.8 29 (TiXAlYSiZ)N 0.4 0.5 0.1 0.1 30 (TiXAlYSiZ)N 0.48 0.5 0.02 0.2 31 (TiXAlYHfW)N 0.4 0.5 0.1 0.9 32 (TiXAlYZSiW)N 0.1 0.3 0.5 0.1 0.05 33 (TiXAlY)N 0.4 0.6 1.8 Comparison 34 (TiXAlYNbZ)N 0.4 0.5 0.1 2.5 35 (TiXAlYTaZ)N 0.4 0.5 0.1 3.3

Example 4: An apparatus and a coating method as used for the samples of Example 1 was again used.

HSS drills with a diameter of 6 mm were coated with a 4.5 m MeX and a TiN interlayer was provided between the MeX layer and the tool body, with a thickness of 0.1 ptm. The test condition were: Tool: HSS twist drill, dia. 6 mm Material: DIN 1.2080 (AISI D3) Cutting parameters: Vc = 35 m/min f = 0.12 mm/rev.

15 mm deep blind holes with coolant.

(Table 4) Bias N2- Arc inter- layer x y z Q1 Residual Number of Voltage Pressur current layer Stress (GPa) drilled (-V) (mbar) (A) holes 36 40 3.0 x 10-2 200 TiN (TixAly)N 0.6 0.4 5.4 2.1 210 Present 0.1 µm Invention 37 40 3.0 x 102 200 TiN (TiXAlyBx)N 0.58 0.4 0.02 3.8 2.3 190 38 150 1.0 x 102 200 TiN (TixAly)N 0.6 0.4 0.03 4.5 30 0.1 µm Comparison 39 150 1.0 x 102 200 TiN (TixAlyBz)N 0.58 0.4 0.02 0.1 4.8 38 0.1 µm

The lifetime of the tool was determined by the number of holes which could be drilled before failure of the drill.

The results of the inventively coated drills are shown as sam- ples No. 36 and 37 in Table 4, the samples No. 38 and 39 again show comparison samples. Again, I(200) exceeded 20 times inten- sity average noise level by far, for samples 36, 37, as meas- ured by MS.

Example 5: Again, the apparatus and method as mentioned for Example 1 was used for coating HSS roughing mills with a diameter of 12 mm with a 4.5 Stm MeX layer. There was provided a titanium nitride interlayer with a thickness of 0.1 µm between the MeX layer and the tool body. The test conditions were: Tool: HSS roughing mill, dia. 12 mm z = 4 Material: AISI H13 (DIN 1.2344) 640 N/mm2 Cutting parameters: vc = 47.8 m/min = = 0.07 mm ap = 18 mm a e = 6 mm climb milling, dry.

The HSS roughing mill was used until an average width of flank wear of 0.2 mm was obtained.

Sample No. 40 in Table No. 5 shows the results of the inven- tively coated tool, sample 41 is again for comparison. Again, I(200) of sample Nr. 40 fulfilled the condition with respect to noise, as measured by MS.

(Table 5) Bias N2- Arc inter- layer x y Q1 Residual Cutting Voltage Pressure current layer Stress (GPa) distance (-V) (mbar) (A) (m) 40 40 3.0 x 10-2 200 TiN (TixAly)N 0.6 0.4 5.4 2.1 35m Present 0.1 µm Invention 41 150 1.0 x 10-2 200 TiN (TixAly)N 0.6 0.4 0.03 4.5 11m Comparison 0.1 µm (chipping and pee- ling off)

Example 6: Again, the apparatus and coating method according to Example 1 was used. Solid carbide end mills with a diameter of 10 mm with 6 teeth were coated with a 3.0 Hm MeX layer. There was provided a titanium nitride interlayer with a thickness of 0.08 Hm be- tween the MeX and the tool body. Test conditions for the end mills were: Tool: Solid carbide end mill, dia. 10 mm z = 6 Material: AISI D2 (DIN 1.2379) 60 HRC Cutting parameters: v, = 20 m/min <BR> <BR> <BR> <BR> <BR> <BR> = = 0.031 mm<BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> = = 15 mm a e = 1 mm Climb milling, dry The solid carbide end mills were used until an average width of flank wear of 0.20 mm was obtained. It is to be noted that solid carbide end mills do not belong to that group of tool which is inventively coated with a hard material layer having Q1 > 1. From the result in Table 6 it may clearly be seen that for this kind of tools Q1 > 1 does not lead to an improvement.

Again, the I(200) to noise condition, measured with MS, was fulfilled for sample No. 42, for sample No. 43 the I(111) to noise condition was fulfilled.

(Table 6) Bias N2 Arc inter- layer x y Q1 Residual Cutting Voltage Pressure current layer Stress (GPa) distance (-V) (mbar) (A) (m) 42 40 3.0 x 10-2 200 TiN (TixAly)N 0.6 0.4 5.0 2.2 17m Present 0.08 µm Invention 43 150 1.0 x 10-2 200 TiN (TixAly)N 0.6 0.4 0.05 4.7 32m Comparison 0.08 µm

Example 7: Again, an apparatus and method as used for the samples of Exam- ple 1 were used.

Solid carbide drills with a diameter of 11.8 mm were coated with a 4.5 llm MeX layer. There was provided a TiN interlayer between the MeX layer and the tool body.

Test conditions: Tool: Solid carbide drill, diam. 11.8 mm Workpiece: Cast iron GG25 Machining conditions: vc = 110 m/min f = 0.4 mm/rev.

Blind hole 3 x diam.

No coolant The solid carbide drills were used until a maximum width of flank wear of 0.8 mm was obtained. The I(200) to noise condi- tion was again fulfilled, measured with MS.

(Table 7) Bias N2- Arc inter- layer x y Q1 Residual Drilling Voltage Pressure current layer Stress (GPa) distance (-V) (mbar) (A) (m) 44 40 3.0 x 10-2 200 TiN (TixAly)N 0.6 0.4 5.4 2.1 95m present 0.1 µm Invention 45 150 1.0 x 10-2 200 TiN (TixAly)N 0.6 0.4 0.03 4.5 48.5m Comparison 0.1 µm

Example 8: Again, the apparatus and method as stated in Example 1 were used.

Cemented carbide inserts for turning with a shape in accordance with CNGP432 were coated with a 4.8 Hm MeX layer. There was provided a TiN interlayer with a thickness of 0.12 pm between the MeX layer and the tool body. The test conditions were: Tool: Carbide insert (CNGP432) Material: DIN 1.4306(X2CrNi 1911) Cutting parameters: v, = 244 m/min f = 0.22 mm/rev.

= = 1.5 mm with emulsion The tool life was evaluated in minutes. The indicated value is an average of three measurements. Again, I(200)/noise condi- tion, measured with MS, was fulfilled.

(Table 8) Bias N2- Arc inter- layer x y Q1 Residual Tool life Voltage Pressure current layer Stress (GPa) (min) (-V) (mbar) (A) 46 40 3.0 x 10-2 200 TiN (TixAlv)N 0.6 0.4 5.8 1.9 18.1 min Present 0.12 µm Invention 47 150 1.0 x 10-2 200 Tin (TixAly)N 0.6 0.4 0.04 4.9 5.5 min Comparison 0.12 µm

In Fig. 1 there is shown, with linear scaling a diagram of ni- trogen partial pressure versus bias voltage of the tool body as applied for reactive cathodic arc evaporation as the reactive PVD deposition method used to realise the Examples which were discussed above.

All the process parameters of the cathodic arc evaporation process, namely - arc current; - process temperature; - deposition rate; - evaporated material; - strength and configuration of magnetic field adjacent the arc source; - geometry and dimensions of the process chamber and of the workpiece tool to be treated were kept constant. The remaining process parameters, namely partial pressure of the reactive gas - or total pressure - and bias voltage of the tool body to be coated as a workpiece and with respect to a predetermined electrical reference potential, as to the ground potential of the chamber wall, were varied.

Thereby, titanium aluminum nitride was deposited. With respect to reactive gas partial pressure and bias voltage of the tool body, different working points were established and the result-

ing QI values at the deposited hard material layers were meas- ured according to MS.

It turned out that there exists in the diagram according to fig. 1 an area P, which extends in a first approximation line- arly from at least adjacent the origin of the diagram co- ordinates, wherein the resulting layer leads to very low XRD intensity values of I(200) and I(111). It is clear that for ex- actly determining the limits of P, a high number of measure- ments will have to be done. Therein, none of the I(200) and I(111) intensity values is as large as 20 times the average noise level, measured according to MS.

On one side of this area P and as shown in fig. 1 Q1 is larger than 1, in the other area with- respect to P, Q1 is lower than 1. In both these areas at least one of the values I(200), I(111) is larger than 20 times the average noise level, meas- ured according to MS.

As shown with the arrows in fig. 1, diminishing of the partial pressure of the reactive gas - or of the total pressure if it is practically equal to the said partial pressure - and/or in- creasing of the bias voltage of the tool body being coated, leads to reduction of QI. Thus, the inventive method for pro- ducing a tool which comprises a tool body and a wear resistant layer system, which latter comprises at least one hard material layer, comprises the steps of reactive PVD depositing the at least one hard material layer in a vacuum chamber, thereby pre- selecting process parameter values for the PVD deposition proc- ess step beside of either or both of the two process parame- ters, namely of partial pressure of the reactive gas and of bias voltage of the tool body. It is one of these two parame-

ters or both which are then adjusted for realising the desired QI values, thus, and according to the present invention, bias voltage is reduced and/or partial reactive gas pressure is in- creased to get Q1 values, which are, as explained above, at least larger than 1, preferably at least larger than 2 or even 5 and even better of 10. Beside the inventively exploited QI value, in this "left hand" area, with respect to P, I(200) is larger, mostly much larger than 20 times the average noise level of intensity, measured according to MS.

In fig. 2 a typical intensity versus angle 20 diagram is shown for the titanium aluminum nitride hard material layer deposited in the Q1 2 1 region according to the present invention of fig.

1, resulting in a Q1 value of 5.4. The average noise level N* is much less than I(200)/20. Measurement is done according to MS.

In Fig. 3 a diagram in analogy of that in fig. 2 is shown, but the titanium aluminum nitride deposition being controlled by bias voltage and nitrogen partial pressure to result in a QT < 1. The resulting Q1 value is 0.03. Here the I(111) value is larger than the average noise level of intensity, measured ac- cording to MS.

Please note that in fig. 1 the respective QI values in the re- spective regions are noted at each working point measured (according to MS).

In fig. 4 a diagram in analogy to that of the figs. 2 and 3 is shown for working point P1 of fig. 1. It may be seen that the intensities I(200) and I(111) are significantly reduced com- pared with those in the area outside P. None of the values

I(200) and I(111) reaches the value of 20 times the noise aver- age level N*.

Thus, by simply adjusting at least one of the two Q1- controlling reactive PVD process parameters, namely of reactive gas partial pressure and of workpiece bias voltage, the inven- tively exploited Q, value is controlled.

In fig. 1 there is generically shown with #QI < 0 the adjusting direction for lowering Qr, and it is obvious that in opposite direction of adjusting the two controlling process parameters, and increase of Q1 is reached.

"Appendix A" process and apparatus for workpiece coating The present invention relates to a coating arrangement ac- cording to the generic specification of claim 1 as well as a process for coating workpieces according to the generic specification of claim 14.

In many known vacuum treatment processes, cleaning of the workpiece surface is performed prior to vacuum coating. In addition, the workpieces may be heated to the desired tem- perature before or after the cleaning step. Such steps are principally needed to ensure adequate bonding strength of the coating to be deposited. This is especially important in applications where workpieces, and tools in particular, are to be coated with a wear protection coating. On tools such as drills, milling cutters, broaches and shaping dies such coatings are subjected to very high mechanical and abrasive stress. An extremely good bond with the substrate is, there- fore, essential for useful and economical use. A proven method for pre-treating such tools is heating with electron bombardment, and etching by means of ion etching1 for exam- ple, sputter etching. Heating by means of electron bombard- ment from a plasma discharge is known, for example1 from DE 33 30 144.

A plasma discharge path can also be used for creating heavy noble gas ions, for example, argon ions, which are acceler- ated from this plasma toward the workpiece or the substrate on which they cause sputter etching as described in DE 28 23 876.

In addition to sputter etching another known technique is to operate plasma discharges with additional reactive gases and to etch the workpieces chemically, however, also process techniques combining reactive etching and sputter etching are feasible. The objective of all these pre-treatment proc- eases is to prepare the workpiece surface in such a way that the subsequently deposited coating adheres well to the sub- strate.

Appendix A" For plasma generation the aforementioned arrangements use a low-voltage arc discharge that is arranged in the central axis of the apparatus whereas the workpieces are arranged at a certain distance around this arc along a cylindrical sur- face. The coating is subsequently deposited by means of thermal evaporation or sputtering. Depending on the process management, an additional ion bombardment is generated dur- ing the coating through a corresponding substrate bias, a technique which is known as ion plating. The advantage of this arrangement is that large ion currents with small par- ticle energy can be drawn from the low-voltage arc which affords gentle treatment of the workpiece. The disadvantage ie, however, that the workpieces must be arranged in a zone defined radially to the discharge and that as a rule they must be rotated round the central axis as well as their own axis in order to achieve uniform and reproducible results.

Another disadvantage is that due to the relatively narrow admissible cylindrical processing band width either the processable workpiece size is limited or the batch size is limited for a large number of small workpieces which se- verely limits the cost-effectiveness of the known arrange- ments. This limitation is due to the fact that the low-volt- age arc discharge which centrally penetrates the process chamber requires a certain dimension for itself. In order to produce good and reproducible results, the workpieces must have a suitable distance from the discharge which means that a large portion of the central process chamber space cannot be utilized.

Also known are sputtering arrangements with so-called diode discharges. Such diode discharges are operated with high voltages of up to 1000 Volt and even higher. Diode etching devices have proven to be unsuited to applications with demanding requirements. On the one hand the achievable etch- ing rates and consequently the efficiency is low, and on the other hand these high voltages can produce defects on sensi- tive substrates. In particular workpieces that require three-dimensional processing such as tools cannot be readily processed by such an arrangement. Tools, for example, are Appendix A" designed with a number of fine cutting edges on which such discharges tend to concentrate, with the result that uncon- trolled effects such as overheating and even destruction of the functional edge can occur on such fine edges and points.

In the patent application DE 41 25 365 an approach for solv- ing the aforementioned problem is described. It assumes that the coating is deposited by means of a so-called arc evapo- ration process. In order to produce well-bonding coatings with such evaporators, the arc of the evaporator itself was used prior to the actual coating in such a way that the ions produced in the arc, particularly the metal ions, are accel- erated out of the evaporation target toward the workpieces by means of a negative acceleration voltage of typically > 500 Volt, but often also in the range of 800 to 1000 volt so that more material is sputtered off the workpiece than de- posited. After this etching process the evaporator is oper- ated as a coating source. The description mentions that in the usual processes based on the arc coating technology such high voltages are essential for producing well-adhering coatings through the arc evaporation process.

To prevent the problem of overheating or etching on uneven mass distribution or on fine workpiece geometries, the de- scription proposes to operate, in addition to the arc plasma, an auxiliary discharge path with high voltage that causes supplementary ionization which is coupled to the evaporation arc. An additional DC source causes ions to be extracted from the plasma and accelerated to the workpiece and thereby produce the desired etching effect. An addi- tional anode with another discharge path operated from a separate power supply is envisioned for increasing the ef- fect. During the etching process the arc evaporator is oper- ated with a closed shutter so that the substrate is shielded from the direct effect of the evaporator, thereby preventing so-called droplets on the substrate.

The disadvantage of the above arrangement is that it also requires a high voltage, that only limited processing homo- "Appendix A" geneities are achievable, and that through the coupling of the different plasma paths also the adjustment capabilities in the operating environments are limited. In addition this arrangement is very complicated and consequently costly to build and operate which seriously impairs the economy of a production system. The utilization of voltages in excess of 1000 Volt requires additional safety precautions.

Systems that are based on the current technology are not well suited to high throughputs if also high processing quality is required. Systems that accommodate coating widths of up to 1000 mm and more can be built only with great dif- ficulty, if at all.

The purpose of the present invention is to eliminate the aforementioned disadvantages of the current technology, in particular by creating a coating arrangement and by propos- ing a process that is suitable for depositing well-adhering coatings on a large number of workpieces, or on individual large workpieces with uneven mass distribution, without damaging the fine structures but with the desired homogene- ity and the required highly economical processing rate.

This is achieved by designing the process arrangement men- tioned at the beginning in accordance with the characteriz- ing portion of claim 1, and by the coating process designed according to the characterizing portion of claim 14.

Accordingly the workpiece surface to be coated is exposed to a plasma source designed as a hot cathode low-voltage arc discharge arrangement by transporting it transversely to the linear extent of the latter's discharge path. The workpiece is connected to a negative voltage so that ions are ex- tracted from the arc discharge and accelerated to the work- piece, causing the latter to be sputter etched. Subsequently the workpiece is coated from the same side from which the low-voltage arc discharge was effective.

Appendix A" The preferred design variants of the coating arrangement conforming to the invention are described in the subsidiary claims 2 to 13, and the preferred design variants of the process in claims 14 to 17.

Etching with a hot cathode low-voltage arc discharge ar- rangement as the ion source is particularly advantageous because such arc discharges can be operated with discharge voltages of < 200 volt which means that this process is not afflicted by the disadvantages of high-voltage etching.

Etching with low-voltage arc discharges is also particularly harmless to the workpiece, that is, the fine structures on larger workpieces such as cutting edges are adversely af- fected neither by thermal overload nor edge rounding caused by high-energy ion bombardment.

Despite the relatively low discharge voltage in the working range of 30 to 200 Volt DC, but preferably within the range of 30 to 120 Volt, a very high discharge current of a few 10 to a few 100 ampere, preferably from 100 to 300 ampere, is feasible. This means that this type of discharge is able to produce a very high ion current at low energy. Due to the high ion current available, a high etching rate can be achieved on the substrate at a relatively low acceleration voltage, and as has been mentioned before, with gentle treatment of the workpiece. The extraction voltage or the acceleration voltage on the substrate is within the range of -50 Volt to -300 Volt, preferably within the range of -100 Volt to -200 Volt. The ion current drawn to the workpieces achieves values of 5 to 20 ampere, with a preferred working range from 8 to 16 ampere. The processing width for the workpiece or workpieces can be up to 1000 mm. With a some- what more elaborate equipment design also larger processing widths are feasible. The achievable values depend not only on the operating values for the arc discharge but also on their geometric arrangement relative to the workpiece, as well as on the selected working pressure. Typical working pressures are of the order of 10-3 mbar. For operating the "Appendix A" arc discharge a noble gas is used as the working gas, pref- erably a heavy noble gas such as argon.

In the past, low-voltage arc discharge arrangements were rotation symmetrical which means that the arc discharge was arranged in the center and the workpieces were rotated around this arc discharge located in the central axis. The assumption was that the rotation symmetrical arrangement with the centrally arranged arc discharge would offer the best possible result with respect to uniformity and speed of the etching operation. Surprisingly it has been shown, how- ever, that the asymmetrical arrangement proposed by the invention is overall much more advantageous than the afore- mentioned rotation symmetrical arrangement. With a rotation symmetrical arrangement with the arc discharge in the cen- tral axis the placement of large volume workpieces is re- stricted toward the center by the arc discharge itself. In addition such workpieces have to be rotated not only around the central axis but also around their own axis so that after the etching process the etched workpiece surfaces can be coated immediately with the coating sources arranged on the chamber wall. Only in this way is adequate distribution of the etching process and the coating thickness ensured.

It has also been shown that the distance of the workpiece from the arc discharge is more critical in a rotation sym- metrical arrangement than in an asymmetrical arrangement in which the workpiece is exposed only from one side toward the arc discharge.

In the apparatus according to the invention it is possible to pass large-volume workpieces in front of the arc dis- charge without additional rotation, with the result that the size of the process chamber can be kept within reasonable limits and the handling of heavy workpieces is greatly sim- plified. This has a significant influence on the economy of production systems. The arrangement according to the inven- tion is advantageous not only for large-volume workpieces but it is also possible to accommodate and simultaneously "Appendix A" process a correspondingly large number of smaller work- pieces.

Another advantage of the arrangement according to the inven- tion is that the etching apparatus no longer has to be con- structed as an integral part of the process chamber because it needs to be arranged only in the area of the process chamber wall which means that it can be arranged as an elon- gated, smaller discharge chamber on the latter's outer wall so that far greater freedom is achieved in the design of the process chamber. It has even been found that this arrange- ment is far less critical with respect to the distance be- tween the arc discharge and the workpiece surface, which means that higher reproducibility of the results is achieved with larger spacing variations that typically occur with larger workpieces. The total ion current that can be ex- tracted from the arc discharge still reaches advantageously high values and can be concentrated fully on the workpieces, thereby producing the desired high etching rates. The actual separation of the low-voltage arc discharge or the plasma source from the process chamber or from the treatment zone also affords a higher degree of freedom in the design of this source and consequently a much more flexible adaptation of the source design to the process requirements than is the case with the integral rotation-symmetrical arrangement with discharge in the central axis of the equipment.

For depositing a well-bonding coating after the etching process, one or more additional evaporation sources acting from the same side are arranged on the process chamber wall.

Particularly suited are sources that can be arranged in such a way that, like the elongated low-voltage discharge, they coat the workpieces transported in front of them across a correspondingly elongated area. Suited are sources such as sputtering sources or arc evaporation sources. Practice has shown that so-called cathodic spark evaporators or arc evaporators are particularly suited because well-bonding coatings can be economically produced by these and the pre- ceding etching process. Test tools processed through this "Appendix A" arrangement achieved a useful life that was significantly and reproducibly longer than achieved by known arc evapo- rated coatings with preceding high-voltage etching. For example, the useful life of cutting tools such as milling cutters was improved by a factor of at least 1.5; in par- ticularly favorable cases even by a multiple over conven- tional techniques. In addition a very homogenous etch dis- tribution was achieved which is far less dependent on the workpiece geometry and also allows mixing of different sub- strates in a batch.

With the proposed arrangement it is also easily possible to implement processes not only with noble gases but also with chemically active gases because the low-voltage arc dis- charge activates gases such as N2, H2 very well. Unwanted parasitic discharges produced by insulating surfaces can be easily controlled with the low-voltage discharge. The low- voltage arc discharge is preferably operated with a separate cathode chamber or ionization chamber that accommodates a hot cathode and communicates with the discharge chamber or the process chamber only through a small opening. The gases are preferably admitted via this cathode chamber. This re- sults in a certain gas separation between the process cham- ber and the coating sources which reduces or eliminates the problem of target contamination. With this arrangement it is also possible to perform activation on the workpiece with different process gases during the actual coating phase. The desired working conditions can be established by choosing a corresponding negative or even positive voltage on the work- piece.

As the workpieces generally have to be passed in front of the sources several times during a process step in order to achieve the necessary etching depth or coating thickness as well as uniform and reproducible treatment, it is advanta- geous to design the apparatus in such a way that the work- pieces can be rotated around a central axis and to arrange the sources on the chamber wall in such a way that they all work from the outside toward the inside. In this case a very "Appendix A" large workpiece can be arranged for processing in such a way that it rotates on its central axis. In the same space, however, also a large number of small workpieces, even of different size, can be arranged on a holder and passed across the sources while rotating around this central axis in order to achieve homogenous results. Such an arrangement is particularly compact and easy to build which is essential for an economical process.

The plasma source or the low-voltage arc discharge is pref- erably arranged on the process chamber wall, transversely to the transport direction. The low-voltage arc discharge de- vice can, for example, and preferably be arranged in a box- like attachment, here in the form of a discharge chamber, which is connected to the process chamber by a long narrow opening in such a way that the low-voltage arc is arranged directly opposite the workpiece(s) or the zone to be proc- essed. The low-voltage arc discharge is generated by an electrically heated or thermionic emission cathode and an anode arranged at a certain distance. A corresponding dis- charge voltage is applied to this anode, causing an arc current to be drawn. This discharge features a gas inlet port through which the arc discharge is supplied with the working gas. This arrangement is preferably operated with a noble gas such as argon, but as has been mentioned above, also reactive gases can be added. The size of the discharge path should be at least 80% of the treatment zone width and be positioned relative to the treatment zone in such a way that the desired treatment distribution or homogeneity can be attained. To achieve the corresponding sputter etching on the workpiece, the latter or the workpiece holder is oper- ated with a negative voltage relative to the arc discharge arrangement. Depending on the process, such as in reactive processes during the coating, the arrangement can also be operated without such a voltage or even with a positive voltage, that is, with electron bombardment. Aside from a DC voltage also a medium or high-frequency AC voltage can be used, and also superposition of DC on AC is feasible. The DC voltage can also be pulsating, and it is possible to super- "Appendix A" pose only part thereof on the AC supply. With such a supply it is possible to control certain reactive processes. It also can in particular avoid or prevent parasitic arcs if dielectric zones exist or are formed on the equipment and the workpiece surfaces.

The desired distribution with respect to the processing zone can be set via the length of the discharge and its location.

Another parameter for controlling the distribution is the plasma density distribution along the arc discharge. This distribution can e.g. be influenced with the aid of addi- tional magnetic fields which are arranged in the area of the discharge chamber. For the setting and correction of the process parameters, permanent magnets are positioned along the discharge chamber. Better results are achieved, however, if the discharge path is operated with additional, sepa- rately powered anodes which are arranged along the discharge path in accordance with the distribution requirements. With such an arrangement even the distribution curve can be in- fluenced to a certain degree. Preferred is, therefore, the arrangement without correction magnets and with more than one anode along the discharge path. However, it is also possible to combine this preferred arrangement with addi- tional correction magnets. Additional anodes can be readily operated in combination with a single cathode. It is advan- tageous, however, to have an emission cathode opposite each anode in order to achieve optimum decoupling of these cir- cuits which in turn improves the controllability.

The thermionic emission cathode is preferably arranged in a separate, small cathode chamber which communicates with the discharge chamber through a small opening. This cathode chamber is preferably equipped with an inlet port for noble gas. If desired also reactive gases can be admitted via this gas inlet. Preferably, reactive gases are not admitted into the cathode chamber but, for example, into the discharge chamber. Through the opening in the cathode chamber the electrons are drawn to the anode or anodes so that the gas which is a least partially ionized also emerges from this "Appendix A" opening. The process chamber is preferably designed in such a way that the central axis around which the workpieces are rotating, is arranged vertically. The cathode or the cathode chamber is preferably arranged above the anode. In the cath- ode chamber the exit opening is preferably arranged down- ward. These arrangements simplify the entire handling of the system and help to avoid problems that can be caused by particle formation.

In addition to the low-voltage arc discharge arrangement the process chamber is equipped with at least one additional source, preferably in the form of an arc evaporator. These sources act radially in the same direction from the outside toward the central axis or the processing zone. It is sdvan- tageous if the low-voltage arc discharge is arranged before the coating source with respect to the transport direction.

An arc evaporator, like the arc discharge arrangement, usu- ally has a linear extent that is transverse to the transport direction so that the entire processing zone can be coated with the desired homogeneity. In the proposed coating ar- rangement several round arc evaporators are preferably used which are distributed along the chamber wall in such a way that the desired homogeneity is achieved. The advantage is that the high power consumption of the evaporator can be split up and that coating thickness distribution can be better controlled or to a certain degree be even adjusted by means of the power supply. In this way exceptionally high coating rates can be achieved which results in high economy.

For example, a process for tools, particularly shaping dies, would be configured as follows: Process example The system configuration corresponds to illustrations 2 and 3. The tools are not rotated around their own axis but only passed in front of the sources by rotating the workpiece holder around its central axis. A coating zone with a width b of 1000 mm and a diameter d of 700 mm is formed, within which the workpieces are arranged. The process chamber has a diameter of 1200 mm and a height of 1300 mm.

"Appendix A" Etching parameters: Low-voltage arc current ILVA - 200 A Arc discharge voltage ULVA = 50 V Argon pressure PAr = 2.0 x 10-3 mbar Etching current Isub = 12A Etching time t = 30 min Etching depth 200 nm Coating: Current for each arc evaporator 1ARC = 200 A (8 evaporators with 150 mm diam. titanium targets) Arc discharge voltage UARC = 20 V Nitrogen pressure PN2 = 1.0 x 10 mbar Bias pressure UBias = -100 V Coating time t = 45 min Coating thickness TiN 6 m The process cycle time for one batch, including heating and cooling, is 150 min.

The voltage generation equipment for the negative accelera- tion voltage on the workpiece is usually operated with volt- ages of up to 300 Volt DC, but to protect the workpieces the voltage is preferably kept within the range of 100 to 220 Volt at which good etching rates are still feasible without defects. The low-voltage arc arrangement must be operated at least 10 cm away from the workpiece, but the distance should preferably be > 15 cm, or preferably within the range of 15 to 25 cm at which high rates with a good distribution are achieved.

The coating system according to this invention is particu- larly suitable for processing tools such as drills, milling cutters and shaping dies. The holders and the transport device are designed specifically for this type of tools. The present coating arrangement is generally able to achieve good results even if the workpieces to be coated are rotated only around the central axis of the equipment. In particu- "Appendix A" larly critical cases or if a very large number of small parts are to be loaded into the system, the rotation around the central axis can easily be supplemented in this design concept by adding additional rotating axes which in turn rotate around the central axis.

The invention is subsequently exemplified and schematically explained by means of the following illustrations: Fig. l A coating arrangement with low-voltage discharge according to the conventional technology. (State of the art).

Fig. 2 Cross-section of a typical coating system accord- ing to the invention, with peripheral discharge chamber for low-voltage discharge Fig. 3 Horizontal section of the system illustrated in Fig. 2.

Fig. 4a Cross-section of a part of the arrangement with discharge chamber for low-voltage arc discharge and multiple anodes arranged inside the chamber.

Fig. 4b Same as Fig. 4a but illustrated with separate cathode-anode discharge paths with the cathodes arranged in separate cathode chambers.

Fig. 4c Same as Figs. 4a and 4b, also with separate cath- ode-anode discharge paths, but with the cathodes arranged in a common cathode chamber.

Fig. 5 Service life comparison curves for tools coated with the conventional technology and the technol- ogy according to the present invention.

Fig. 1 illustrates a known workpiece coating arrangement. A vacuum chamber serves as process chamber 1 for accommodating a low-voltage arc discharge 18 which runs in the center of "Appendix A" vacuum chamber 1 along the latter's central axis 16 and to which magnetron sputtering sources 14 are flanged at the periphery from the outside to the chamber wall of process chamber 1. On the top of process chamber 1 there is a cath- ode chamber 2 that holds a thermionic hot cathode 3 which can be supplied via gas inlet 5 with the working gas, typi- cally a noble gas like argon. For reactive processes also active gases can be added. Cathode chamber 2 communicates with process chamber 1 via a small hole in shutter 4. The cathode chamber is usually insulated from processing chamber by means of insulators 6. Shutter 4 is additionally insu- lated from the cathode chamber via insulator 6 so that shut- ter 4 can be operated on floating potential or auxiliary potential, as required. Anode 7 is arranged in the direction of the central axis 16 on the opposite side of cathode cham- ber 2. Anode 7 can have the form of a crucible and holds the material to be evaporated by the low-voltage arc discharge.

During the etching process this evaporation option is not used; only ions are extracted from the low-voltage arc discharge and accelerated toward the workpieces in such a way that that the latter are sputter etched. For operating the low-voltage arc discharge 18 cathode 3 is heated with a heater supply unit so that cathode 3 emits electrons. Be- tween cathode 3 and anode 7 there is an additional power supply 8 for operating the arc discharge. It usually pro- duces a positive DC voltage on anode 7 in order to sustain the low-voltage arc 18. Between arc discharge 18 and the chamber wall of processing chamber 1, workpiece holders are arranged that hold the workpieces 11 which can be rotated around their vertical central axis 17 in order to achieve adequate process uniformity. The workpiece holders 10 are supported on an additional workpiece holder arrangement 12 which is equipped with a rotary drive by which these work- piece holders 10 are rotated around the central axis 16. In this type of equipment it is additionally necessary to focus the low-voltage arc discharge 18 via additional coils 13, for example in the form of Helmholz coils. It is evident that the workpieces 11 can be processed with the low-voltage arc discharge 18, that ion bombardment occurs when a nega- "Appendix A" tive voltage is applied to the substrate, and that electron bombardment is possible by applying a positive substrate voltage. In this way the workpieces can be pre-treated with the aid of a low-voltage arc discharge either by means of electron bombardment induced by heating, or through ion bombardment with sputter etching. Subsequently the workpiece 11 can be coated, either through evaporation of material from crucible 7 by means of the low-voltage arc, or through sputtering with magnetron sputter source 14 which is sup- plied by the power supply 15.

It is readily apparent that the mechanical assembly for substrate movement and the arrangement of the low-voltage arc discharge are rather complex in this layout. On the other hand the degree of freedom is severely restricted because the workpieces can only be arranged between the low- voltage arc discharge located in the center and the outer chamber wall. A system of this type is uneconomical to oper- ate for large workpieces or large batch quantities.

An example of a preferred coating arrangement according to the invention is illustrated as a cross-section in Fig. 2.

Process chamber 1 contains a workpiece holder 11 which is arranged in such a way that the workpieces can be rotated around the central axis 16 of the process chamber. The cham- ber is usually pumped down by the vacuum pumps 19 that main- tain the working pressures required for the process steps.

In the proposed arrangement a large workpiece 11 which ex- tends beyond the central axis 16 can, for example, be ar- ranged in process chamber 1 in such a way that this large workpiece 11 can be processed by the sources arranged on the process chamber wall. The zone available for loading the workpieces essentially fills process chamber 1 completely.

In such an arrangement it is possible to position either a single large workpiece 11 or a large number of smaller work- pieces which essentially fill the chamber volume.

The workpiece holder that rotates the workpieces 11 around the central axis 16, spans coating width b transversely to 'Appendix A" the rotation direction. In the system according to the in- vention it is particularly advantageous that uniform and reproducible coating results can be achieved either across large coating widths b or across a large depth range that extends from the central axis 16 to the periphery of the coating width, that is, within the entire diameter D. Based on the known concentric arrangement according to the conven- tional technology in which these conditions were critical, it was not to be expected that an eccentric arrangement according to the present invention would produce better results. A large variety of workpiece geometries with fine edges and cutting edges can be handled in this large area without problems related to thermal stress or unwanted oc- currence of arcs.

On the outer wall of the process chamber the etching and coating sources are positioned in such a way that they all act from the outside toward the workpieces. For the impor- tant preparatory sputter etching process the chamber wall features a slot shaped opening, the length of which corre- sponds at least to processing width b. Behind his opening 26 there is a box shaped discharge chamber 21 in which the low- voltage arc discharge 18 is generated. This low-voltage arc discharge 18 runs essentially parallel to processing width b and has an effective length which shall be at least 80% of processing width b. Preferably the discharge length should be equal to the processing width b or extend even beyond it.

The axis of arc discharge 18 has a distance d from the near- est processing zone, that is, the next workpiece section.

This distance d shall be at least 10 cm, preferably 15 to 25 cm. This results in good process uniformity and a high sput- tering rate can be maintained. In the lower part of dis- charge chamber 21, cathode chamber 2 is flanged on which communicates with discharge chamber 21 via orifice 4. Cath- ode chamber 2 contains a hot cathode 3 which is supplied via the heating power supply unit 9. This supply can be operated with AC or DC. Cathode chamber 2 features a gas inlet port 5 for supplying the working gas, normally a noble gas like "Appendix A" argon, or a noble gas - active gas mixture for certain reac- tive processes. It is also possible to admit working gases via process chamber 1 by means of auxiliary gas inlet 22.

Active gases are preferably admitted directly into process chamber 1 via gas inlet 22.

In the upper part of discharge chamber 21 there is an elec- trode 7 which is designed as a anode. DC supply 8 is con- nected between cathode 3 and anode 7 in such a way that the positive pole is on anode 7 and a low-voltage arc discharge can be drawn. By applying a negative voltage to the work- piece holder or to the workpieces 11 with the aid of voltage generator 20 between the low-voltage arc discharge arrange- ment and the workpiece 11, argon ions are accelerated toward the workpieces so that the surface is sputter etched. This can be achieved with acceleration voltages of up to 300 Volt DC, but preferably with a voltage in the range of 100 Volt to 200 Volt to ensure gentle processing of the workpieces 11. The process uniformity can be set through appropriate positioning of cathode chamber 2, and by arranging anode 7 relative to processing width b of the workpieces to be proc- essed in accordance with the process specifications. Another factor is the shape of anode 7. The latter can, for example, have either a flat, dished, or rectangular shape, or be designed as a tubular, cooled anode.

Fig. 3 shows a horizontal cross-section of the system based on Fig. 2. Shown is again the box-like discharge chamber 21 on the outer wall of process chamber 1 which communicates with the treatment zone through slot opening 26. Of course, several such discharge chambers can be arranged on a system as required, for example to further boost the processing effect. Also illustrated are the evaporation sources 23 which are flanged to the chamber wall. For example, magne- tron sputter sources can be used as evaporation sources 23 but for achieving high processing speeds at low costs, so- called arc evaporation sources are preferably used. The advantage of this arrangement is that the arc evaporation sources 23 can be freely arranged from the outside in such a "Appendix A" way that through the distributed arrangement of multiple sources the desired coating homogeneity can be set and a high coating rate can be maintained. It has been shown that it is more advantageous not to use single, rectangular evaporation sources but several smaller, round sources that are arranged on the periphery of the system in accordance with the process requirements.

Fig. 4a illustrates another advantageous variant of the arrangement according to the invention in which cathode chamber 2 fs located on the top of discharge chamber 21. The advantage is that the operating of the discharge path is least disturbed by particles which always occur in such a coating system. Also shown is a the possibility of subdivid- ing the discharge path by using several anode-cathode cir- cuits and making the intensity along discharge 1 adjustable.

The main discharge is generated with power supply 8 between main anode 7 and cathode chamber 2. Additional ancillary discharges can be generated with auxiliary anodes 24 and auxiliary power supplies 25. In this way it is possible to adjust the power density of the discharge along the entire discharge path between anode 7 and cathode 2 locally and with respect to the intensity to the homogeneity require- ments of the workpiece.

Fig. 4b shows an alternative arrangement. The anode-cathode paths can be kept completely apart, or even decoupled by using separate anodes 7, 24, separate cathodes 3, 3', and separate cathode chambers 2, 2'. Another version is illus- trated in Fig. 4c in which two separates anodes 7, 24 are used, but a common cathode chamber 2 with two hot cathodes 3 and 3'.

Fig. 5 illustrates the test results of HSS finish milling cutters that were processed according to the invention (curve b) and the conventional technology (curve a). In both cases the milling cutters were given a 3.5 mm TiN coating.

For the milling cutter according to the conventional tech- nology (curve a) high-voltage etching was first performed in "Appendix A" the conventional manner whereas for the milling cutter rep- resented by curve b the process according to the invention was used. The test conditions were as follows HSS finish milling cutter: Diam. 16 mm Number of teeth: 4 Test material: 42 CrMo4 (DIN 1.7225) Hardness: HRC 38.5 Infeed: 15 mm x 2.5 mm Cutting speed 40 m/min Feed per tooth 0.088 mm Feed 280 mm/min End of life: Spindle torque 80 (arbitrary unit) The result shows clear improvements in the life of the tool treated according to the invention. An improvement by a factor of 1.5 or more is easily reached. Important is not only the extension of the tool life but also the flatter progressing of the torque curve which is indicative of the deterioration in tool quality toward the end of the tool life. In the example according to Fig. 5 this is clearly recognizable at a total milling depth of 15 m. Curve a which represents the conventional technology shows a sharp degra- dation in tool quality at a total milling depth of 15 m.

This shows that the cutting quality achievable with the conventional technology has a greater variance across the entire tool life which means that it is not very consistent.

Systems built in accordance with the invention as illus- trated in Figures 2 to 4 achieve far greater throughputs with the aforementioned high quality than system 1 which conforms to the conventional technology. Throughputs can easily be doubled or even increased by a factor of 3 to 5 which dramatically increases the economy.

"Appendix A" Summary For depositing hard coatings on high-performance tools that must be sputter etched before Coating, the invention pro- poses to sputter etch the tools with a low-voltage arc dis- charge and to subsequently coat them from the direction they have been etched.

Patent claims 1. Coating arrangement for treating workpieces (11) with a vacuum process chamber (1) and a plasma source (18) ar- ranged on the chamber, and with a coating source (23) arranged inside said chamber, and said chamber being equipped with a holding and/or transport device which defines a treatment zone (b) for positioning or passing the workpieces (11) in front of the sources, with said sources being arranged at a certain distance to the workpiece and acting from the same direction, character- ized by a plasma source (18) designed as a hot cathode low-voltage discharge arrangement, the linear extent (1) of which in a direction transverse to the workpiece transport direction essentially corresponds to width (b) of the processing zone, and containing a device for gen- erating an electrical field (20) between the arc dis- charge (18) and the workpiece (11).

2. Arrangement according to claim 1 in which the holding and transporting device for the workpieces (11) is ar- ranged rotatable around central axis (16) of process chamber (1) and with sources (18, 23) arranged on the chamber wall in such a way that they all act radially from the outside in the direction of the central axis (16).

3. Arrangement according to claim 1 or 2 in which the plasma source of a discharge chamber (21) is arranged on the outer wall of chamber (1) where inside or on dis- charge chamber (21) a thermionic emission cathode (3), and at least 80% of the processing zone width away and along processing zone width (b), an anode (7) for gener- "Appendix A" ating a low-voltage arc discharge (18) is positioned and in which arrangement a noble gas port (5) in discharge chamber 21 with a voltage generator (20) is arranged be- tween the anode-cathode circuit and workpiece (11) in such a way that the negative pole is on workpiece (11) so that the plasma source arrangement (2, 7, 18, 21) functions as a sputter etching device.

4. Arrangement according to one of the preceding claims in which at least one additional anode (24) extending along the plasma path at a certain distance from said plasma path is arranged between emission cathode (3) and anode (7) for adjusting the plasma density distribution along arc discharge (18).

5. Arrangement according to one of the preceding claims in which anode (7) and the additional anode (24) are con- nected to separate, adjustable power supplies (25), and featuring an opposite cathode (3) preferably for each anode (7, 25) which together with the corresponding an- ode (7,25) and the separate power supply (8, 25) forms it's own adjustable power circuit.

6. Arrangement according to one of the preceding claims in which the emission cathode (3) is arranged in a cathode chamber (2) separate from discharge chamber (21) and with said cathode chamber (2) communicating with the discharge chamber (21) via opening (4) through which the electrons can emerge, with the noble gas inlet port (5) preferably arranged on this cathode chamber (2).

7. Arrangement according to one of the preceding claims 2 to 6 in which process chamber (1) with its central axis (16) is arranged vertically, and cathode (3) or cathode chamber (2) is arranged above the anode (7, 24), and the opening (4) of cathode chamber (2) is preferably point- ing downward.

8. Arrangement according to one of the preceding claims in which at least one coating source (23) which preferably consists of at least one arc evaporator (23) is arranged "Appendix A" on the process chamber wall next to the plasma source (18) which is located further ahead in the transport di- rection.

9. Arrangement according to one of the preceding claims in which the voltage generator (20) is designed for volt- ages of up to 300 V DC, preferably for 100 V to 200 V.

10. Arrangement according to one of the preceding claims in which the low-voltage arc discharge arrangement (18) is located at least 10 cm but preferably 15 to 25 cm away from workpiece (11).

11. Arrangement according to one of the preceding claims in which the holding and transport device is designed as a tool holder, particularly for drills, milling cutters and shaping dies.

12. Arrangement according to one of the preceding claims in which at least one magnetic field generator is arranged in or on discharge chamber (21) for adjusting the plasma density distribution.

13. Arrangement according to one of the preceding claims in which discharge chamber (21) has an opening along the full width (b) of the processing zone and with the open- ing facing the latter so that the processing zone is ex- posed to the arc discharge.

14. Process for at least partially coating workpieces (11) in a vacuum process chamber (1) with a plasma source (18) arranged on the process chamber and a coating source (23) and with a holding and/or transport device arranged in chamber (1) with said device determining a treatment zone (b) for positioning or passing the work- pieces (11) in front of the sources (18, 23), where the sources act from the same side and are arranged at a certain distance from workpiece (11), and in which proc- ess the plasma source (18) generates a hot cathode low- voltage arc (18) in a direction transverse to the work- piece transport direction essentially at least across Appendix A" 80% of width (b) of the treatment zone and in which process a voltage is applied between the arc discharge and the workpiece for extracting charge carriers from the plasma so that they can be accelerated toward the substrate.

15. Process according to claim 14 in which the workpieces rotate preferably continuously around central axis (16) of a processing chamber and pass in front of the sources (18, 23), and in which process the plasma treatment oc- curs through charge carrier bombardment in a first step and the coating of workpiece (11) in a second step.

16. Process according to claim 14 or 15 in which the charge carriers consist of ions that are extracted from the arc discharge (18) directly with the aid of a negative work- piece voltage in such a way that they sputter etch the workpiece (11).

17. Process according to one of the claims 14 to 16 in which the homogeneity of the etch distribution across coating zone (b) can be set to predetermined values by selecting arc length, the distance (d) between the arc and the workpiece, the position of the arc relative to the work- piece, as well as by adjusting the plasma density dis- tribution along the arc.

"Appendix A" Fig. 5 Spindle torque [a.u] End of tool life High-voltage etching + 3.5 µm TiN (arc coating) Low-voltage arc coating + 3.5 µm TiN (arc coating), (Invention) Total milling depth [m]