GB2154249A

GB2154249A - Cathode sputtering

Info

Publication number: GB2154249A
Application number: GB08502734A
Authority: GB
Inventors: Klaus Goerke; Dr Erich Hodes; Michael Steeg
Original assignee: GLYCO METALL WERKE
Current assignee: GLYCO METALL WERKE
Priority date: 1984-02-11
Filing date: 1985-02-04
Publication date: 1985-09-04
Also published as: IT8519200A0; AT383145B; GB2154249B; ES540255A0; CH663220A5; ES8605589A1; IT1184136B; BR8500587A; DE3404880A1; ATA6285A; FR2559507A1; GB8502734D0; JPS60184676A

Abstract

The bond strength and bond reliability between the cleaned and roughened surface of the carrier layer and the layer sputtered onto it as well as the bond strength and bond reliability also between layers sputtered onto one another in succession are considerably improved by the targets used for sputtering-on the layers being cleaned, i.e., free-sputtered by cathode sputtering against a shield over the surface to be eroded, and by a reverse sputtering from the surface to be coated prior to sputtering-on of the surface layer or layers. The reverse sputtering from the surface to be coated is to be carried out not only as far as cleaning but as far as perceptible roughening of the surface to be coated on the carrier layer, that is, after the style of an etching. The time between the conclusion of this etching and the start of the sputtering-on of the desired surface layer is to be kept so short that no surface contamination occurs. in like manner successive sputterings-on of further layers are to follow at such short intervals that no surface contamination can arise.

Description

SPECIFICATION Method of production of laminar material or laminar workpieces The invention relates to a method of production of laminar material or laminar workpieces by the application of at least one layer having a substantially metallic matrix on to the previously cleaned and roughened surface of a carrier workpiece by the cathode sputtering method whilst utilizing at least one cathode-sputtering target which contains the substances corresponding to the desired composition of the layer which is to be created.

In the case of the laminar materials known from the West German Patents Nos. 2853724 and 2914 618, having a sliding or friction coating applied by the cathode sputtering method, and in the case of the methods known from them for the production of such laminar materials, considerable difficulties have resulted as regards the achievement of high adhesive strength and bond strength between the surface of the carrier layer and the applied sliding or friction coating.

It is therefore the aim of the invention to solve the problem of how to essentially improve the methods known from the West German Patents Nos. 28 53 724 and 29 14618.7-14 in such a way that high bond strength between the surface of the carrier layer and a surface layer applied by cathode sputtering is reproducibly achieved. In addition at least just as high bond strength is to be reproducibly achieved between layers applied one after another by cathode sputtering.Underlying the solution of this problem is the knowledge gained by experiments, that irregularities in the bond strength between the surface of the carrier layer and the surface layer applied through cathode sputtering are to be attributed on the one hand to the state of the surface of the carrier layer existing at the start of coating by cathode sputtering and on the other hand to the prevailing state of the surfaces of the target or targets utilized for the cathode sputtering at the start of the cathode sputtering.

For the solution of the problem as posed it is therefore in accordance with the invention proposed that: - after generation of the vacuum provided for in cathode sputtering, in the container enclosing the target or targets and the carrier material which is to be coated or respectively the carrier workpieces which are to be coated, a free-sputtering of the target or targets is first of all performed against the surfaces which are to be eroded, the surfaces to be coated on the carrier material or respectively on the carrierworkpieces being protected against the application of target material;; - after the free-sputtering of the surfaces of the target or targets, which are to be eroded, an etching of the surfaces which are to be coated on the carrier material or respectively on the carrier workpieces in an electrical corona discharge after the style of a cathode sputtering is performed, in which the surfaces of the target or targets are protected against the application of workpiece material; and -subsequent to the etching the coating of the surfaces of the carrier material or respectively of the carrier workpieces is performed by the cathod sputtering method from the free-sputtered target surfaces.

In the method in accordance with the invention both the cleaning of the surfaces of the target or targets respectively which are to be eroded, and also the etching, i.e., the cleaning and roughening of the surfaces of the carrier material or respectively of the ca r, ier workpieces which are to be coated, are performed directly before the coating, that is, with the vacuum generated in the container. While doing so the surfaces which are to be subjected to the actual coating by the cathode sputtering method, are protected during the prior treatment of the other respective surfaces against the application of foreign material.One might to begin to assume that it is adequate on the whole only to clean by freesputtering the surfaces of the target or targets which are to be eroded and by reversed free sputtering the surface of the material or respectively the workpieces which is to be coated, especially since the ASLETRANSACTIONS 12,36-43(1969), in particular page 38, the practice is known of cleaning by reversed sputtering the surface of a carrier layer which is to be coated by means of cathode sputtering with a MoS2 layer. But on the other hand in accordance with the invention, after the freesputtering of the surface of the target or targets, which is to be eroded, an etching of the surfaces which are to be coated is to be performed in an electrical corona discharge, whereby not only is cleaning of these surfaces effected but also an intensive roughening.After this etching, i.e., cleaning and roughening of the surfaces which are to be coated there is next, i.e., without significant delay, to be performed the coating of the surfaces of the carrier material or respectively of the carrier workpieces by the cathod sputtering method from the free-sputtered target surfaces. Even if all of these procedures are effected in vacuo, i.e. in a gaseous ambient kept under a reduced pressure suitable for the maintenance of the electrical discharge causing the cathode sputtering, it has been found within the scope of the invention that it is of considerable importance that coating of the surfaces of the carrier material or respectively of the carrier workpieces is made to start practically directly subsequently to the etching.Between the free sputtering of the surfaces of the target or targets, which are to be eroded, and the start of the actual cathode sputtering for the coating of the surfaces of the carrier material or respectively of the carrier workpieces there may in accordance with the invention be left an interval of time so long as the vacuum in the container is not broken or essentially impaired.

If two or more layers are to be applied one after another to the laminar material or respectively to the laminar workpieces by the cathode sputtering method, it is in accordance with the invention proposed that the targets necessary for the creation of the various layers are all inserted together in the same container and before the etching of the surfaces to be coated on the carrier material or respectively the carrier workpieces, are all freesputtered together, and that the layers to be applied on top of one another are created by cathode sputterings from different targets, succeeding one another directly in time, i.e. without intermediate free sputtering and intermediate etching. Hence the application of the further layers is effected upon the fresh surface of the layer applied previously in each case.Hence there is achieved also between layers applied one after another an optimum surface bond.

During the free sputtering, that is, before the etching of the surfaces which are to be coated, this prior treatment is in accordance with the invention to be performed on the whole of the targets which are to be utilized, so that no intermediate free sputtering is necessary. In further development of the invention it is therefore proposed that in the case of utilization of a number of targets, in particular of targets of different compositions, the free-sputtering of the individual targets is performed one after another in time and at least the already free-sputtered targets are during the free sputtering of other targets, protected against the application of foreign material.

For the achievement of a suitable protection against the application of foreign material to the target surfaces and to the surfaces which are to be coated, it is recommended within the scope of the invention that for the free-sputtering a shield is placed opposite the target and the free-sputtering is performed essentially against this shield. In a corresponding manner, during etching a shield may be placed opposite the carrier material or respectively the carrierworkpieces and the etching be performed as a cathode sputtering from the surfaces to be coated on the carrier material or carrier workpieces essentially against this shield.

For the continuous production of laminar material or respectively laminarworkpieces it is in further development of the invention recommended that the carrier material or respectively the carrier workpieces are within the container which is kept under vacuum, led through two or more stations in which the etching and coating are performed continuously, the free sputtering of the target or targets being performed only once after closing of the container and generation of the vacuum, whilst if necessary the carrier material or respectively the carrier workpieces may be introduced through an airlock into the container and the laminar material or respectively the laminarworkpieces removed from the container through an airlock.

An embodiment of the invention is explained in greater detail below with reference to the accompanying diagrammatic drawings, in which: Figure lisa plan for the production of laminar workpieceswith dual coating; Figure 2 is a diagram for the free sputtering of two different targets; and Figure 3 is a diagram for the etching of the surface oftheworkpiecewhich is to be coated.

The invention is described below with the aid of the production of laminar workpieces having a carrier layer, a thin barrier and bonding layer of NiSn20 and sliding layer of Al Sn20.

In a container 10 three stations are provided for the treatment of the workpieces 11 which are to be coated, namely, one station A for the etching of the surfaces of the workpieces which are to be coated, one station B for the application of the first layer to the etched surface of the workpiece and one station C for the application of the second layer over the first layer of the workpiece.

The device reproduced diagrammatically in Figure 1 provides for a rotary table arrangement 12 inside the container 10 and, to correspond with the three stations A, B and C, this rotary table arrangement has three supports 13 for workpieces, which are moved according to the arrows 14 in steps through the three stations A, B and C. To these workpiece supports 13 are to be applied electrical voltages corresponding with the steps of the treatment which are to be performed, where known circuitry and known electrical components are to be employed which for the sake of clarity are not shown. Similarly the devices provided for the evacuation of the container 10 and for the drive of the rotary table arrangement 12 are for the sake of clarity not shown.

In the container 10 an etching shield 15 is mounted pivotally in order to be swung over the workpiece supportwhich has been moved into the station A at the time. In this swung-in position the etching shield 15 is connected, or may be connected, to a positive electrical potential. But the etching shield 15 may also be firmly fixed in the station A and be connectable at will to positive electrical potential. The wo;kpiece support 13 is connected in the station Ato negative electrical potential.Further, there are provided inside the container two target shields 16 and 18, which may be moved according to the arrows 17 and 19 into the region of the stations B and C, that is, in front of the target 20 which is to be inserted in the station B in a position opposite the workpiece support 13 when it has been moved there, and the target 21 which is to be inserted in the station C in a corresponding manner. Mechanisms provided for the movement and adjustment of the shields 15, 16 and 18 are for the sake of clarity not shown.

The method according to the invention is carried out by the device described above as follows: First of all the workpieces 11 which are to be coated are placed on the workpiece support 13 of the rotary table arrangement 12. In the station B is inserted a target 20 of the material provided for the barrier and bonding layer, for example, NiSn20 or an appropriate non-ferromagnetic chromium-nickel alloy. In the station C a target is inserted, corresponding with the desired composition of the sliding layer, for example ofAlSn20. The container 10 is closed and evacuated. While doing so, a flushing may be performed with gas or a mixture of gases required for the cathode sputtering method. During this evacuation the pressure is set and maintained inside the container 10, which is necessary for the ignition and maintenance of the electrical gas discharge which brings about the cathode sputtering.

As soon as this setting of the pressure is reached, the shields 16 and 18 are brought in front of the targets 20 and 21, if this has not already been done previously. Positive potential is then applied to the target shield 16 and negative potential to the target 20, the electrical valtage prevailing between the two parts being set in such a way that an electrical discharge is ignited and maintained. A cathode sputtering process is then effected, in which the shield 16 acts as anode, in the event that no other anode is provided. In any case the material eroded from the surface of the target 20 during this cathode sputtering process gets caught by the target shield 16.Through this first cathode sputtering the surface of the target 20 which is to be eroded gets freesputtered so that upon further ignition of an electrical gas discharge a highly effective sputtering with the desired material composition leaves the target 20.

After the target 20 has been free-sputtered at its surface which is to be eroded, there is effected in a corresponding way the free sputtering of the surface of the target 21 which is to be eroded, with the aid of the target shield 18. Figure 2 shows the stage in which the free sputtering of the surface of the target 21 which is to be eroded is performed, whilst the free sputtering of the target 20 at the surface which is to be eroded has already been effected.

After the free sputtering of the two targets 20 and 21 at their surfaces which are to be eroded, the etching process is started in the station A; in the event that the etching shield 15 has not already been swung previously into the station A or is not in any case fixed in station A, this swinging-in is now performed with the etching shield 15 which thereupon arrives over the workpiece support 13 and the workpiece 11 laid on it. Positive electrical potential is then applied to the etching shield 15 and negative electrical potential to the workpiece support 13 and thereby to the workpiece 11. The electrical voltage prevailing between the workpiece 11 and the etching shield 15 is so set that an electrical corona discharge is ignited and maintained.In this electrical corona discharge the surface material of the workpiece 11 is eroded as a kind of target through cathode sputtering and caught by the etching shield 15. This reversed cathode sputtering is performed until the surfaces of the workpiece 11 which are to be coated, have not only been cleaned but also noticeably roughened. Figure 3 shows the workpiece 11 lying in the station A on the workpiece support 13 in position opposite the etching shield 15 during the reversed cathode sputtering. As soon as the workpiece has been adequately roughened at the surfaces of it which are to be coated, the reversed cathode sputtering is interrupted and by turning the rotary table arrangement 12 the workpiece 11 is brought directly from the station A into the station B.The time of transition between station A and station B is to be so short that no significant contamination of the freshly etched surface of the workpiece 11 can occur. As soon as the workpiece 11 provided with the freshly etched surface has arrived in the station B, the target 20 is energized at negative electrical potential and the workpiece support 13 carrying the workpiece 11 at positive electrical potential and the target shield 16 is removed (in the event that this has not been done previously). An effective cathode sputtering immediately starts from the target 20 onto the freshly etched surface of the workpiece 11.

This cathode sputtering is pursued until the barrier and bonding layer of NiSn20 or a chromium nickel alloy formed on the freshly etched workpiece surface has reached the desired thickness. After the formation of the barrier and bonding layer the workpiece 11 through further turning of the rotary table arrangement 12 is brought from the station B directly into the station C. There the application of the sliding layer is effected through cathode sputtering, by the target 21 being energized at negative electrical potential and the workpiece support 13 and thereby the workpiece 11 at positive electrical potential or connected to earth. The target shield 18 is taken away, if this has not already been done. The cathode sputtering is continued in the station C until the sliding layer has reached the desired thickness.

If during the preparation of the working sequence the whole of the workpiece support 13 of the rotary table arrangement 12 has been loaded with workpieces, procedure may be such that one and the same workpiece support 13 with the workpieces 11 mounted on it, is always subjected one after another to all three working steps. When the workpieces 11 mounted on this one workpiece support 13 have been treated, another workpiece support 13 with the workpieces loaded on it may be subjected to the three working steps following one another directly.

This may be continued until all of the workpieces have been treated.

But if the durations of treatment in the three stations A, B and C match or largely match, it may also be provided that three workpiece supports 13 with workpieces 11 placed on them get taken into treatment simultaneously, that is, one in station A, one in station B and one in station C. But in that case it must be ensured that the transfer of the workpieces from the one step of the treatment to the next step of the treatment is effected within the shortest possible time.

Naturally other embodiments of installations for treatment and for the performance of the method may also be used. For example, it may be provided that the three stations A, B and C are arranged one behind the other, where the workpieces or a strip of material are introduced inside the container via an airlock, carried through the treatment stations and the laminar workpieces or respectively the strip of laminar material after the treatment is led out of the container through an airlock.

Instead of the three treatment stations A, B and C explained in the above example, still more treatment stations may be provided in the event that more than two layers are to be applied to the carrier material or respectively the carrier workpieces. On the other hand it is also possible to provide only two treatment stations if only one layer is to be applied. But in any case it has to be ensured that after the generation of the vacuum after the closing of the contained or after regeneration of the vacuum after a possible interme dilate considerable rise in pressure, the free sputtering of the targets or target is performed before the etching of th surfaces which are to be coated is effected. Furthermore, it has in any case to be ensured that between the etching and the first coating or respectively between successive coatings the shortest possible intervals of time are maintained in order that no significant contamination occurs of the freshly etched or freshly generated surfaces of the coatings.

Claims

1. A method of production of laminar material or laminar workpieces by the application of at least one layr having an essentially metallic matrix on to the previously cleaned and roughened surface of a carrier workpiece by the cathode sputtering method whilst using at least one cathode-sputtering target which contains the substances corresponding to the desired composition of the layer which is to be created, the method comprising the following steps:: after generation of the vacuum provided for in cathode sputtering, in the container enclosing the target or targets and the carrier material which is to be coated or the carrier workpieces which are to be coated, a free sputtering of the target or targets is first of all performed at the surfaces which are to be eroded, while the surfaces to be coated on the carrier material or on the carrierworkpieces being protected against the application of target material; after the free sputtering of the surfaces of the target or targets, which are to be eroded, an etching of the surfaces which are to be coated on the carrier material or on the carrier workpieces in an electrical corona discharge after the style of a cathode sputtering is performed, in which the surfaces of the target ortargets are protected against the application of workpiece material; and subsequent to the etching the coating of the surfaces of the carrier material or respectively of the carrier workpieces is performed by the cathode sputtering method from the free-sputtered target surfaces.

2. A method according to claim 1, wherein for the production of laminar material orlaminarwork- pieces having two or more layers applied on top of one another by the cathode sputtering method, the targets necessary for the creation of the various layers are all inserted together in the same container and before the etching of the surfces to be coated on the carrier material or the carrier workpieces, are all free-sputtered together, and the layers to be applied on top of one another are created by cathode sputterings from different targets, succeeding one another directly in time, i.e. without intermediate free sputtering and intermediate etching.

3. A method according to claim 1 or 2, wherein if several targets are used, in particular targets of different compositions, the free sputtering of the individual targets is performed one after another in time and at least the already free-sputtered targets are during the free sputtering of other targets, protected against the application of foreign material.

4. A method according to any one of claims 1 to 3, wherein for the free sputtering a shield is placed opposite the target and the free sputtering is effected essentially against this shield.

5. A method according to any one of claims 1 to 4, wherein during etching a shield is placed opposite the carrier material or the carrier workpieces and the etching is effected as a cathode sputtering from the surfaces to be coated on the carrier material or carrier workpieces essentially against this shield.

6. A method according to any of claims 1 to 5, wherein for the continuous production of laminar material or laminar workpieces the carrier material or the carrier workpieces are within the container which is kept under vacuum, led through two or more stations in which the etching and coating are performed continuously, the free sputtering of the target or targets being performed only once after closing of the container and generation of the vacuum, whilst if necessary the carrier material is, or the carrier workpieces are, introduced through an airlock into the container and the laminar material is, or the laminarworkpieces are, removed from the container through an airlock.

7. A method according to claim 1 substantially as herein described.

8. A product made by, or with the use of, a method according to any one of claims 1 to 7.