Abstract
A target includes a target plate and a stabilizing layer which is joined to the rear side of the target plate. The stabilizing layer was produced by high-kinetic-energy spraying of stabilizing material onto the target plate. A process for producing a target is also provided.
Claims
1-8. (canceled)
9. A target, comprising: a target plate having a rear side; and a stabilizing layer joined to said rear side of said target plate, said stabilizing layer having characteristics of having been applied to said target plate by high-kinetic-energy spraying of stabilizing material.
10. The target according to claim 9, wherein said target plate is made of a material selected from the group consisting of aluminum-based materials, chromium-based materials, titanium-based materials and ceramics.
11. The target according to claim 9, wherein said stabilizing layer is made of one or more materials selected from the group consisting of copper, copper alloys including brass and bronzes, aluminum, aluminum alloys, titanium, titanium alloys and steel.
12. The target according to claim 9, wherein said stabilizing layer has a composition with a gradient.
13. The target according to claim 9, wherein a ratio of a thickness of said stabilizing layer to a thickness of said target plate is in a range of from 1/1 to 1/5.
14. The target according to claim 9, wherein a ratio of a thickness of said stabilizing layer to a thickness of said target plate is in a range of from 1/2 to 1/4.
15. The target according to claim 9, wherein said rear side of said target plate has at least one depression formed therein.
16. A process for producing a target, the process comprising the following steps: providing a target plate having a rear side; and spraying stabilizing material onto the target plate by using a high-kinetic-energy spraying process producing a stabilizing layer on the rear side of the target plate.
17. The process according to claim 16, which further comprises applying a diffusion-promoting layer to aid bonding.
Description
[0060] Embodiments of the invention will be illustrated with the aid of the figures. The figures show:
[0061] FIG. 1 a schematic depiction of part of a spraying apparatus for a high-kinetic-energy spraying process,
[0062] FIG. 2a-b two sectional schematic side views of two embodiments of a target,
[0063] FIG. 3 an etched polished cross section of a copper bulk material,
[0064] FIG. 4 an etched polished cross section of a copper layer which has been applied by means of a high-kinetic-energy spraying process (cold gas spraying),
[0065] FIG. 5 an etched polished cross section of the boundary region between a target plate composed of AlCr 70/30 at % and a sprayed stabilizing layer composed of Cu, and
[0066] FIG. 6 an etched polished cross section of the boundary region between a target plate composed of Cr and a sprayed stabilizing layer composed of steel.
[0067] FIG. 1 shows a schematic depiction of part of a spraying apparatus 1 for a high-kinetic-energy spraying process to illustrate the principle. A spray gun housing 4 has a convergent/divergent nozzle 10 in order to accelerate process gas T supplied through a process gas line 8 to supersonic velocity. A spray material S, i.e. a plurality of particles, is introduced into the accelerated process gas stream T via a spray material line 6 and this is accelerated by the process gas stream T in the direction of the rear side 20 of the target plate 14. There, the spray material impinges and remains adhering to the rear side of the target plate 14. The front side 18 of the target plate 14 corresponds to the side facing a substrate to be coated in a PVD process.
[0068] As a result of the spraying, a layer of the spraying material S is built up on the rear side 20 of the target plate 14. As shown in FIG. 2a-b, the spraying operation is carried out until a stabilizing layer 16a-b has been formed. The spraying material S adheres extremely strongly to the target plate 14a-b or to the target material as a result of the spraying. This is particularly advantageous when the target plate used is difficult to join to the material used for the stabilizing layer because of the technologically determined production route or the technological boundary conditions.
[0069] In one embodiment, the composition of the stabilizing material is changed during spraying, so that a gradient is obtained in the stabilizing layer 16a-b. Here, the composition is changed in such a way that the strength and stiffness of the stabilizing layer 16a-b produced is increased. For example, pure copper is used at the beginning of spraying and one or more elements are gradually added to the copper so that a stabilizing layer having increased strength and stiffness is obtained. As an alternative, the entire stabilizing layer can be made homogeneously of one copper alloy or one copper composite.
[0070] As can be seen in FIG. 2a, the stabilizing layer 16a projects at the side beyond the target plate 14a and forms a (continuous or interrupted) flange by means of which the target 2a can be fastened in a PVD apparatus.
[0071] As can be seen in FIG. 2b, the target plate 14b and the stabilizing layer 16b can, as an alternative, be flush at the side, depending on the type of fastening device present in the PVD apparatus.
[0072] FIG. 2b shows a further embodiment of a target 2b in which the rear side of a target plate 14b has a plurality of depressions or raised regions into which the stabilizing material is sprayed during production by means of a high-kinetic-energy spraying process, i.e. the surface area of the target plate 14b is increased by the profiling, as a result of which the stability of the bond between target plate 14b and stabilizing layer 16b is increased and, in addition, the stiffness of the target 2b is increased by the geometric profiling. The heat removal is also improved by the increased surface area.
[0073] FIG. 3 shows an etched polished cross section of a copper bulk material. For comparison, FIG. 4 shows an etched polished cross section of a copper layer which has been applied by means of cold gas spraying, with the particle boundaries having been etched in order to make the microstructure more clearly visible. The copper powder used has an average particle size of less than 45 m, but it is also possible to use copper powders having other particle sizes, for example particle sizes in the 100 m range (from a few tens of m to about 150 m particle size). Specifically, a powder having an average particle size of 31.0 m, a D10 of 11.2 m, a D50 of 28.9 m and a D90 of 53.8 m was used for the copper layer depicted in FIG. 4.
[0074] Comparing FIG. 3 and FIG. 4, it can clearly be seen that a deformed microstructure is formed by the spray operation. In this example, there is therefore an elongation of the Cu particles with an average aspect ratio of greater than 2.
Example 1
[0075] FIG. 5 shows an etched polished cross section of the boundary region between a target plate and a cold-gas-sprayed stabilizing layer composed of pure copper. The microstructure of the target plate composed of AlCr 70/30 at % consists of a densified mixture of aluminum particles with embedded chromium particles, i.e. an aluminum-chromium composite. A stabilizing layer of copper was applied thereto by means of cold gas spraying. The cold gas spraying produces an extremely strong bond between the two materials copper and the aluminum-chromium composite. In particular, the copper is shot into the target plate by the high acceleration in cold gas spraying, so that the two materials are intermeshed in the boundary region. The achieved relative density of the cold-gas-sprayed copper as stabilizing material is in the case depicted 99.3%; no additional gas uptake into the layer caused by the spraying operation could be observed. The average particle size of the stabilizing layer composed of copper is, in this example, <45 m in the direction of the thickness of the target. The stabilizing layer was sprayed in lines at a pressure of 32 bar and a temperature of 500 C. using nitrogen, the spray angle was 90 and the distance from the target plate was 30 mm.
Example 2
[0076] FIG. 6 shows an etched polished cross section of the boundary region between a target plate composed of chromium and a stabilizing layer composed of steel produced by means of a steam application process. A layer of steel can be used both as single stabilizing layer and additionally as a supplement to a layer composed of a copper alloy or copper, particularly when a rear plate having a further increased yield point or stiffness is to be produced. The two materials (copper and steel) have two different functions in this case: copper ensures that the heat is efficiently conducted away from the target plate and the target material is therefore not thermally overloaded, while steel ensures, by means of the higher yield point and higher stiffness, that the target material withstands the pressures determined by the apparatus and thus protects the material against deformation or fracture.
[0077] The stabilizing layer composed of steel depicted in FIG. 6 was applied directly to a target plate composed of chromium. A 1.4404 steel powder having an average powder particle size of <63 m was employed here. Specifically, a powder having an average particle size of 55.9 m, a D10 of 26.9 m, a D50 of 53.8 m and a D90 of 88.1 m was used for the steel layer depicted in FIG. 6. The achieved relative density of the steam-applied steel as stabilizing material is in the case depicted 98%; no additional gas uptake in the layer caused by the spraying operation could be found. The stabilizing layer composed of steel was sprayed in a plurality of lines and a plurality of successive layers onto the substrate at a temperature of 400 C. using steam, the spraying angle was 90 and the distance from the target plate was 65 mm.
LIST OF REFERENCE SYMBOLS
[0078] 1 Spraying apparatus for a high-kinetic-energy spraying process [0079] 2a-b Target [0080] 4 Spray gun housing [0081] 6 Spray material line [0082] 8 Process gas line [0083] 10 Convergent/divergent nozzle [0084] 12 Spray material supply+carrier gas supply [0085] 14, 14a-b Target plate [0086] 16a-b Rear plate/stabilizing layer [0087] 18 Target plate front side [0088] 20 Target plate rear side [0089] S Spray material stream+carrier gas stream [0090] T Process gas stream
