FIG. 1 shows a layout of a target holding apparatus in accordance with a first embodiment.
FIG. 2
a shows a section through the target holding apparatus in accordance with FIG. 1.
FIG. 2
b shows a T-nut with a groove into which a contact lamella is pushed, wherein the upper illustration is a sectional side view taken along the lines as indicated by arrows X in the lower illustration.
FIG. 3 shows a layout of a target holding apparatus in accordance with a second embodiment.
FIG. 4 shows a section through a target holding apparatus in accordance with FIG. 3.
FIG. 5 shows a layout of a target holding apparatus in accordance with a third embodiment.
FIG. 6 shows a section through the target holding apparatus in accordance with FIG. 5.
FIG. 7 shows a layout of a target holding apparatus in accordance with a fourth embodiment.
FIG. 8 shows a section through the target holding apparatus in accordance with FIG. 7.
FIG. 1 shows the arrangement of a target segment 9 which is secured in the coating source to a target holder 1. Each target segment 9 is screwed to the cooling body outer wall 2 by means of a T-nut 8. The T-nut includes a cylinder 22 and an appended part 23, which has a T-shaped cross-section. The cylinder 22 is received by a bore in the cooling body 13. The T-shaped appended part 23 projects beyond the surface of the inner side of the cooling body 21. A contact lamella 10 of low-alloyed copper or nickel, in particular of CuBe, CuCoBe or NiBe is attached to the T-nut and/or a galvanic coating is applied. At least one target segment 9 is plugged onto the T-nut 8, with the T-nut and the target segment having an intermediate space in which the contact lamella 10 is arranged. In FIG. 1 the target segment 9 is plugged onto the T-shaped appended part 23. A groove 24 is provided in the target segment, which is broadened to the shape of a T, which is designed to match the shape of the appended part 23. The T-shaped appended part 23, which engages into an associated groove 24 of the target segment 9, can serve to receive at least one target segment 9. A possible variant is illustrated in FIG. 1 in which a T-shaped appended part 23 serves to receive a plurality of target segments 9. A target is pushed into its position on the T-shaped appended part 23 in the same way as the target segments already plugged into place, with the number of the target segments per T-nut being dependent on the width of the segment, which in turn is in direct relation to the size of the source. The target segments are all plugged onto the T-nuts and/or associated contact lamellae and/or associated galvanic coatings. Each of the target segments 9 is received in a counter-shape corresponding to the shape of the appended part 23, with a groove in the form of a T being shown in FIG. 1. However, other form-locked connections can be used, by means of which the T-nuts and/or the contact lamellae can be embraced, at least in part. In particular a dovetail groove can be provided in the target segment 9. A contact lamella 10 is arranged in the groove of the target segment 9. The contact lamellae and/or the galvanic coatings conduct the heat from the target segment in the direction of the cooling system as a result of their good heat conducting characteristics. For the improvement of the heat transfer from the target segment 9 to the contact lamellae 10, a galvanic coating can also be provided on the contact lamellae. The galvanic coating is in particular located on the surface of the contact lamellae 10 facing the target segment or segments 9 when the contact lamellae are held in the T-nut. When the contact lamella is received in the target segment 8 the galvanic coating is on the side of the contact lamella facing the T-nut. The atoms and/or ions of an inert gas impact on the target segment 9 in operation, in other words during the coating process. They knock atoms out of the target segment material. By means of the impacts of the ions striking on the target segment material thermal energy is carried into the target segment 9, which is carried off to the cooling body 13 via the contact lamellae 10, the T-nut 8 and also the attachment screw 7.
In FIG. 2a the target holder 1 from FIG. 1 is illustrated in section. In FIG. 2a the attachment screw 7 is only illustrated in the upper part of the drawing, in the lower part the attachment screw 7 is left out, in order to increase clarity. The lowest shown attachment screw in FIG. 2a shows a simplified variant, when a positioning of the T-nut in the cooling body is not necessary due to the cylinder 22 of the T-nut 8 projecting into the interior of the cooling body 13. This variant can be used when the target only consists of a small number of a target segments or when the position of the target segment is already determined by adjoining target segments. Adjoining target segments can touch each other when the temperature load is too low to cause a noticeable thermal expansion or when the target segments are composed of a coating material or of a combination of coating materials, the thermal expansion of which is negligible, i.e. less than 0.5 mm, in particular less than 0.1 mm, preferably less than 0.05 mm. In the variant shown right at the bottom in FIG. 2a it is furthermore shown that the target segment has a recess 32 in the groove 24 in order to receive a contact lamella 10.
The size of a target segment can be adjusted in such a way that at the desired power input the target segment has such small length, breadth and also depth dimensions that the maximum possible heat input via the target segment surface, which is exposed to the flow of gas, remains limited. The securing apparatus is dimensioned in such a way that all the heat can be led away via the T-nut 8 or the forked plug device 12 and/or via the attachment screw 7 with the associated contact lamella 3, so that the cooling capacity of the cooling system designed as the cooling body 13 becomes the limiting factor for the heat transfer.
Through each of the illustrated contact lamellae 10 not only is an improvement of the thermal transfer achieved by the enlargement of the thermal transfer surface but also a compensation of the thermal stresses of the temperature loaded target segment. The contact lamella 10 acts as a spring mechanism the function of which consists of resiliently taking up the thermal expansion effects of the coating material, by means of which the gap spacings known from the prior art and other solutions, which include dowel pins, are no longer needed. The use of the contact lamellae 10 also has the advantage that the connection to the heat dissipation through the cooling body 13 and the connection to the power transmission take place in a uniform manner for the duration of the entire coating process. It can be guaranteed by means of the contact lamellae that the power transmission and also the heat dissipation can take place in a largely constant manner time-wise by thermal conduction, whereby a sputtering process is made possible which takes place under consistent conditions for both power transmission and heat dissipation. A flexible foil can be used as a contact lamella.
A contact lamella which can be routinely obtained can also be used to advantage, as is illustrated in FIG. 2b. The contact lamella 10 is pushed into a groove 33 of the T-nut 8 and can be received in this groove under prestress and/or can be secured against axial displacement via a locking element. To increase the pre-stress, a contact lamella can include first regions 35 which are supported in the installed state on the surface of the T-nut spanned by the contact lamella and also second regions 36 which maintain a contact with the target segment in the installed state. Moreover the heat dissipation takes place by means of thermal conduction from the target segment to the T-nut via the second regions 36 and/or via the first regions 35 and also via the rib 37 received in the groove. The heat conduction via the contact lamella and the T-nut takes place so fast that the amount of heat to be led away is limited by the cooling capacity of the cooling body. Thus, through the use of the contact lamella not only does a uniform contact for the input of the electrical current into the target segment result but also an improved heat transfer. Since the contact lamella acts as a spring mechanism, any desired pre-stress can be set depending on the design of the contact lamella. On the one hand, the possibility exists of varying the wall thickness of the contact lamellae, on the other hand, the proportion of the first and second regions (35, 36) can be varied in order to achieve an exactly defined and reproducible pre-stress. The contact lamella is then preferably deformed in the elastic region so that it can be used for repeated assembly and dismantling cycles.
In the interior of the part of the T-nut 8 formed in particular as a cylinder 22 there is located an internal thread 25, as is illustrated in FIG. 2a. The external thread of the attachment screw engages into the internal thread 25. The attachment screw consists in particular of copper or low alloy copper, such as CuBe, CuCoBe, CuTeP. The two securing solutions illustrated in the lowest part of FIG. 2 show the installation of a sleeve 6 as a modification of the upper part. This sleeve 6 is additionally used for the removal of the thermal energy to the cooling body and is also termed a screw-in lamella or screw-in lamella sleeve in specialist literature. The chief function of the sleeve 6 is to improve the thermal and electrical contact between the attachment screw 7 and the cooling body 13. The sleeve 6 is screwed into the cooling body 13 or plugged onto it so that a good heat transfer is guaranteed by the connection, which is designed in particular as a screw connection or as a press fit.
For the further illustration of the connection of the target segment 9 to the cooling body reference is again made to FIG. 2a. The connection of the target segment 9 to the cooling body 13 and to the power contact, which is not illustrated, is effected here through the contact lamellae between the target segment 9 and the surface on the target segment side of the appended part 23, through the rear side target segment surface of the target segment 9 to the T-nut 8, via the T-nut and the internal thread 25 of the cylinder 22 of the T-nut to a contact lamella 3 arranged in the internal thread 25 and also from it into the attachment screw 7 and also from the attachment screw 7 directly to the cooling body or alternatively to this via the sleeve 6 to the cooling body 13. The contact lamella 3 is either part of the attachment screw 7 as illustrated in the upper part of FIG. 2a, or is part of the cylinder 22 of the T-nut 8, as is illustrated in the lower part of FIG. 2a. The sleeve 6 is illustrated in FIG. 2a with direct contact to the coolant, which flows through the cooling passages 17. The insulation of the coating source against discharges to the outer sides takes place by means of an isolating zone 16. The isolating zone 16 is located at the outer wall 15, which also contains recesses for the screw heads 4 of the attachment screws 7.
In a further embodiment in accordance with FIG. 3 and FIG. 4 the connection of the target segment 9 to the cooling body 13 and to the power contact, which is not illustrated, is effected by means of a connector 26. The connector 26 contains an internal thread 28 at its surface on the cooling body side, which serves to receive an attachment screw 7, which is made the same as the attachment screw from the embodiment in accordance with FIG. 1 or FIG. 2a. The connector 26 includes a contact lamella 27 and/or a galvanic coating at its surface at the cooling body side for increasing the current and/or heat transfer. In this arrangement the contact lamella 27 does not need to be restricted to the internal thread 27, but is able to encompass the entire contact surface. The advantage is that heat can be transferred directly from the connector 26 to the inside of the cooling body 21. The coolant passages 17, which are illustrated in FIG. 3 as a non-visible element, are located in the illustrated variant in the direct vicinity of the surface of the connector 26 on the cooling body side and its contact lamella 27 and/or its galvanic coating. The contact lamellae 11 are provided in a slit-like recess 29 between the target segment 9 and the surface of the connector 26 at the target segment side. The recess 29 serves to receive a rib 14 of the target segment 9, which is intended for engagement into the slit-like recess 29.
In accordance with an alternative embodiment which is likewise illustrated in FIG. 3, a connector 26 extends over the whole length of the cooling body. In this case it is possible that the connector 26 is secured to the cooling body by means of a plurality of attachment screws 7. A material with comparable thermal expansion coefficients should fundamentally be selected for the connector 27 and the cooling body. Essentially the same demands are made on the material in the case of the cooling body and also in the case of the connector, namely good thermal conductivity and also good electrical conductivity. Copper or copper alloys have proved to be particularly suitable for this purpose. Through the use of materials with the same or similar coefficients of thermal expansion, the connector and the cooling body will expand by the same amount, so that impermissible stresses can not result, either in the attachment screw 7 or in the connector 26. A plurality of target segments (9′, 9″, 9′″ . . . ) can then be received in one connector 26.
In accordance with a further embodiment which is not shown in FIG. 3, the connector 26 could also be designed to be integral with the cooling body. The slit-like recesses 29 would then extend over the whole inner side 21 of the cooling body. In this connection crossed, channel like structures can also be used, so that target segments 9 can be attached to crossing points. Accordingly ribs which cross would also be possible instead of a simple rib 14 which would have the advantage that on the assembly of the target segment 9 its position is also fixed.
As in the first embodiment the thermal transfer also takes place between the target segment 9 and the target segment side surface of the slit-like recess 29 via the rib 14 of the target segment, through the connector 26 via the internal thread 28 and a contact lamella 3 optionally arranged in the interior thread 28 into the attachment screw 7 and also from the attachment screw 7 directly to the cooling body or, alternatively to this, via the sleeve 6 to the cooling body 13. The contact lamella 3 is either part of the attachment screw 7, as is illustrated in the upper part of FIG. 4, or however of the internal thread 28 of the connector 26, as is illustrated in the lower part of FIG. 4. The sleeve 6 is illustrated in FIG. 4 not in direct contact to the coolant which flows through the coolant channels 17. Contact lamellae 11 can be arranged within the slot-like recesses 29 so that an improvement of the current transfer and of the heat transfer and a compensation for length changes, which occur through heating up of the target, can be achieved as in the embodiments described with respect to FIG. 1 or FIG. 2.
The variant of the installation of the sleeve 6 illustrated in FIG. 4 can also be applied to the embodiment according to FIG. 2. The sleeve 6 is screwed into the cooling body or pressed into it. For this purpose receiving means 20 are provided in the cooling body, which are bores for the attachment screw 7 and/or the sleeve 6. As an alternative the sleeve can also have a fixed connection to the attachment screw 7, i.e. a screw connection or comparable shape matched or form locked connection or a pressed connection. A forked plug device 12 can also be received in the slit-like recess 29, as will be described in the following embodiments in accordance with FIG. 5 to FIG. 8. The forked plug device 12 includes in particular a slit-like recess which contains contact lamellae at its inside.
In a further embodiment in accordance with FIG. 5 the target holder 1 is simultaneously formed as a cooling system. The target holder 1 includes the cooling body 13 in which grooves 30 are located, into each of which at least one forked plug device 12 can be received. The cooling body 13 comprises a material of good thermal and electrical conductivity, such as in particular copper or low alloy copper. The forked plug device 12 is provided with contact lamellae 11, which likewise consist of material with good thermal and electrical conductivity, in particular low alloy copper. The contact lamellae 11 can be galvanically coated for the reduction of the contact resistance. A contact resistance of this kind is always present between the surfaces bordering on one another of two directly adjacent bodies lying next to one another in areal contact, particularly if these are bodies made of different materials, as are the target segment and the target holder in this case. A reduced thermal transfer takes place at a boundary surface of this kind due to the surface roughness and the distances to the oppositely disposed surface caused by this, which can be improved by the galvanic coating i.e. by the filling up of this surface roughness. The T-nuts and the attachment screws are left out in the present embodiment as is shown in FIG. 6. The rib 14 of the target segment 9 does not extend across the whole height of the target segment in FIG. 5 or FIG. 6. It is possible to provide further connecting means in the intermediate spaces, which are not shown in detail. Thus conical sliders, eccentric shafts, locking devices by means of plug contacts, tension springs or pneumatically operating plates can be used in order to guarantee a good retention of the target segment 9 in the forked plug device 12. Alternatively the possibility also exists of providing one of the aforementioned connecting means or a combination of the same instead of the forked plug device 12, so that the target segment is attached in the cooling body 13 itself.
A section through the arrangement of two adjoining target segments (9, 9′) is shown in FIG. 6. Each target segment includes a rib 14, which is received by a forked plug device 12, with contact lamellae 11 being provided at the side walls of and/or in the base region of the forked plug device. A part of the only schematically illustrated contact lamellae 11 is visible because the rib 14 has a smaller longitudinal dimension than the groove 30 in which the forked plug device 12 is fitted. To improve the thermal transfer the rib 14 can also extend over the largest part of the longitudinal dimension of the groove. The rib 14 should be able to expand unimpeded in the longitudinal direction, so that the introduction of thermal stresses into the target segment is avoided.
A further embodiment is not illustrated in which a series of grooves lying above one another or a row of grooves lying next to each other is combined to a single channel in which a succession of forked plug devices 12 is located. By means of spring elements the manner of operation of which corresponds to the contact lamella, forked plug devices of this kind can be received in the groove 30 without danger of being lost and also thermal expansions are compensated via the spring tension.
In accordance with a further embodiment in accordance with FIG. 7 and FIG. 8 the target segments can be plugged directly to the cooling body 13. In certain materials this necessity arises for reasons of difficulty of processing them mechanically or chemically by means of a material removing process. Pressed powder or sintered powder are to be named as an example, which were pressed into the shape of a cuboid target segment and for which subsequent alterations in shape are hardly possible. Additionally the processing costs can be reduced by the design of the plug connection, and the material costs can be reduced and the installation can be simplified. The connection of the target segments to the cooling body and the power connection takes place directly via the machined ribs 14 by means of the forked plug devices 12. The attachment of the forked plug devices 12 to the cooling body takes place, in contrast to the previous embodiment, not by plugging into grooves of the cooling body but by means of a bonded connection, such as for example an adhesive connection. Contact lamellae 11, so-called forked plug lamellae are inserted into the forked plug devices 12. It is also possible, as an alternative, to either braze or screw the forked plug devices onto the cooling body or to machine them out of the cooling body by means of a chip-forming machining process such as milling.
The target segments are plugged and fixed directly into these forked plug devices. The target segments are machined using suitable machining methods (according to material: e.g. EDM, milling) in such a way that their rib fits precisely and with firm contact into the forked plug device 12 of the cooling body 13. Milling or EDM (electrical discharge machining) are used in particular as machining methods. Electrical discharge machining is a high precision machining process, by means of which material is cut or drilled. A machining of even extremely hard, tough or brittle material types is made possible by means of electro-physical vaporisation by the application of an electrical potential to an electrode.
The best coating results can be achieved with the following dimensions for the target in which the width of the target amounts to 10 to 1000 mm, in particular 25 to 500 mm, preferably 80 to 140 mm.
The width of the target segment lies preferably in the range of 0.05 to 10 mm, in particular in a range of 0.05 to 50 mm, particularly preferably in a range of 0.05 to 30 mm.
Optimum coating results can be achieved at a distance of the component to be coating from the target of 10 to 1000 mm, in particular of 20 to 500 mm, preferably of 20 to 150 mm.
In accordance with any one of the previous embodiments the target segments 9 can be plugged into the target holding apparatus 1 and can be removed again in this manner. Individual target segments can thus also be replaced in all versions completely independently of the other target segments. A large effective thermal transfer surface arises by means of the areal contact from the target segments to the forked plug devices, so that the target holder apparatus is directly connected to the cooling system.
The heat arising in the target segment can then be led away simply, so that a high cooling rate can be achieved.
Very soft materials come into consideration as material for the target segments, in particular pure aluminium or magnesium. For these materials the poor ability to solder them has been a limiting factor up to now for the increase of the power input for the acceleration of the coating method. Through the coupling in of higher currents the duration of the application of a layer can be shortened by an increased sputtering rate in particular for the application in an HS-PVD method.
The universal nature of the use of target segments in combination with one of the above described coating apparatuses is shown by the fact that very hard or brittle materials such as McrAlY can be energised with at least the same power input as ductile coating materials.
A target which includes a plurality of target segments is used in a method for the coating of a component. For this method a sputtering source is required which includes the target and also a gas for the transport of sputtered coating material to the component and the method includes the steps of: contact of the gas with the target surface, releasing of particles out of the target surface, transport of the released particles with the flow of gas, coating of the component with particles from the flow of gas with the flow of gas proportionally releasing the particles of the component to be coated from each target segment. The particles include charged particles such as in particular ions and/or neutral particles, such as atoms in particular. For the carrying out of the sputtering method the sputtering source including a target which contains the previously described target segments, impact producing means, in other words gas atoms and/or ions and also moving means, in particular a moved gas flux are needed. The impact producing means contact the target in order to release particles from the surface of the target by means of their impulse-like impact on the target surface using the impact energy of the incident impact producing means. A moving means serves for the transport of the sputtered particles from the sputtering source to a component to be coated.
In particular, in accordance with the previously described method, particles are released from the target segments by the stream of gas in such a way that the proportion of the different coating materials or coating material combinations on the component corresponds to the proportion of the target segments with corresponding layer materials or layer material combinations on the target, so that the component is proportionally coated with a first coating material or a first coating layer material combination of a first target segment and with a second coating material or a second coating material combination of a second target segment.
In accordance with an advantageous embodiment the proportion of the different coating materials or layer material combinations sputtered by the flow of gas is altered by a gas distribution unit movable relative to the target. The proportional releasing of coating material from each target segment is based on the following relationship which has been established experimentally in the composition of the layers when varying the proportion of coating materials which are different from one another and which could, moreover, be proved mathematically. The association between the arrangement of the target segments of different layer materials and the layer composition achievable on the coated component results from a statistical analysis which takes into account that particles sputtered from a target are deposited onto a target segment again which is located at a short distance from the component to be coated, after they have travelled a certain distance, until the end of the target at the component side has been reached and the particles are deposited onto the surface of the component to be coated.
At a certain power input the mean path travelled by a particle located at a certain point, i.e. on a first target segment with the pre-determined composition, from its sputtering to its renewed deposition at another place of the first target segment or on a second target segment which is arranged between the first target segment and the component to be coated is known. From the whole distance to be travelled by the particle from the target segment to the component to be coated and from the duration of a single sputtering and deposition sequence the duration up to the deposition of each particle can be calculated with the assumption of the constant speed of flow of gas.
This means that a particle originally located on a target segment which is lying further away from the component to be coated, requires a longer period of time to be deposited on the component than a particle which is arranged at a smaller distance from the component to be coated. Thus per unit of time more particles of the composition are deposited on the component to be coated which are arranged on target segments which are closer to the component to be coated, because they have fewer sputtering and deposition sequences to run through. Through the arrangement of target segments with particles of certain composition at defined points of the target, the composition of the coating on the component can be adjusted exactly by exploiting the knowledge of this fact.
In the last paragraph a particle should include a charged particle, in other words an ion or a neutral particle, in particular an atom and/or a molecule formed from a plurality of the afore-named groups or of a particle of crystalline or amorphous structure.
The use of target segments results in the possibility of arranging different materials on one target and, on taking the sputtering and deposition sequences into account, of predicting in which amount and at which speed each of the materials are deposited on the component.
After the conclusion of each coating process a component of a different coating composition can be produced by means of the alteration of the position of the target segments, so that individual coating solutions can be realised by means of the use of target segments.
Alternatively to, or in combination with the previous solutions it is possible to vary the speed and/or the amount of gas. A variably positionable gas distributor can be provided in particular. Depending on its position the gas distributor covers all the target segments or only some of them, depending on its position, so that the point in time at which different regions of the target are sputtered can be freely set. A variation of this kind can be used in particular for the manufacture of multiple layered coatings. Moreover, very thin layers can be produced since the position of the gas distributor can be altered as fast as desired. By means of a variable gas distributor and/or the arrangement of target segments for the setting of a certain layer composition monomolecular or monoatomic layers can be produced. Layers of this kind have a layer thickness in the nano range and are suitable for the manufacture of a layer transfer from metallic to ceramic layers to which end TGO layers (thermally grown oxides) are used today with a layer thickness of a few micrometres.
REFERENCE NUMERAL LIST
1. Target holder
2. Cooling body external wall
3. Contact lamella
4. Screw head of the securing screw
5. Plate spring
6. Sleeve
7. Securing screw
8. T-nut
9. Target segment
10. Contact lamella for the T-nut
11. Contact lamella for the target segment
12. Forked plug device
13. Cooling body
14. Rib
15. External wall
16. Screening apparatus
17. Coolant passage
18. Inlet coolant
19. Outlet coolant
20. Receiving means
21. Inner side of the cooling body
22. Cylinder of the T-nut
23. Appended part
24. Groove in the target segment
25. Internal thread T-nut
26. Connector
27. Contact lamella
28. Internal thread connector
29. Slot-like recess
30. Groove
31. Rounded surface
32. Recess
33. Groove in the T-nut
34. Locking element
35. First region of the contact lamella
36. Second region of the contact lamella
37. Rib
Patent Application
20070251814
