METALLIZATION FOR A THIN-FILM COMPONENT, PROCESS FOR THE PRODUCTION THEREOF AND SPUTTERING TARGET

Abstract

A metallization for a thin-film component includes at least one layer composed of an Mo-based alloy containing Al and Ti and usual impurities. A process for producing a metallization includes providing at least one sputtering target, depositing at least one layer of an Mo-based alloy containing Al and Ti and usual impurities, and structuring the metallization by using at least one photolithographic process and at least one subsequent etching step. A sputtering target is composed of an Mo-based alloy containing Al and Ti and usual impurities. A process for producing a sputtering target composed of an Mo-based alloy includes providing a powder mixture containing Mo and also Al and Ti and cold gas spraying (CGS) of the powder mixture onto a suitable support material.

Claims

1-16. (canceled)

17. A metallization for a thin-film component, the metallization comprising: at least one layer composed of an Mo-based alloy containing Al and Ti and usual impurities.

18. The metallization according to claim 17, wherein the metallization is oxidation-resistant up to 350° C.

19. The metallization according to claim 17, wherein the metallization is oxidation-resistant up to 400° C.

20. The metallization according to claim 17, wherein said at least one layer composed of an Mo-based alloy contains from 10 to 40 at % of Al and from >0 to 15 at % of Ti, with a sum of contents of Al and Ti not exceeding 50 at %.

21. The metallization according to claim 17, wherein said at least one layer composed of an Mo-based alloy contains from 15 to 30 at % of Al.

22. The metallization according to claim 17, wherein said at least one layer composed of an Mo-based alloy contains from 5 to 10 at % of Ti.

23. The metallization according to claim 17, which further comprises at least one metallic layer composed of Al, Cu, Ag or Au or an alloy based on one of Al, Cu, Ag or Au.

24. The metallization according to claim 23, wherein said at least one layer composed of an Mo-based alloy is applied to a side of said at least one metallic layer composed of Al, Cu, Ag or Au or an alloy of Al, Cu, Ag or Au facing away from a substrate.

25. A conductor track or electrode, comprising: a metallization according to claim 17.

26. A process for producing a metallization for a thin-film component, the process comprising the following steps: providing at least one sputtering target; depositing at least one layer of an Mo-based alloy containing Al and Ti and usual impurities; and structuring the metallization by using at least one photolithographic process and at least one subsequent etching step.

27. A sputtering target, comprising: an Mo-based alloy; Al; Ti; and usual impurities.

28. The sputtering target according to claim 27, wherein: a content of said Al is from 10 to 40 at %; a content of said Ti is from >0 to 15 at %; and a sum of said contents of Al and Ti does not exceed 50 at %.

29. The sputtering target according to claim 27, wherein the sputtering target does not contain any proportions of intermetallic phases being detectable by X-ray diffraction (XRD).

30. The sputtering target according to claim 27, wherein a content of said Al is from 15 to 30 at %.

31. The sputtering target according to claim 27, wherein a content of said Ti is from 5 to 10 at %.

32. The sputtering target according to claim 27, wherein the sputtering target has a hardness below 400 HV10.

33. A process for producing a sputtering target composed of an Mo-based alloy, the process comprising the following steps: providing a powder mixture containing Mo, Al and Ti; and cold gas spraying (CGS) the powder mixture onto a suitable support material.

Description

EXAMPLES

Example 1

[0104] In the present example, a thin-film component as shown in FIG. 2a was constructed.

[0105] In the series of experiments, various metallizations each containing a layer of an Mo-based alloy having a different chemical composition were produced. The layers were deposited from sputtering targets composed of pure molybdenum, pure aluminium, pure titanium and Mo-based alloys containing 10 at % of Ti and 20 at % of Ti. The layers composed of Mo-based alloys containing Al and Ti were produced by cosputtering of 2 or 3 different sputtering targets. Here, the chemical composition of the layer was varied via the combination of different sputtering targets and the sputtering power applied to the sputtering targets. The chemical composition of the layers produced is shown in Table 1.

[0106] To determine the suitability of the layers composed of Mo-based alloys as covering layer, glass substrates (Corning Eagle XG®, 50×50×0.7 mm.sup.3) were coated with the layers composed of Mo-based alloys and their corrosion resistance and oxidation resistance were subsequently tested. In the test for oxidation resistance, the layers were heated at 330° C. in air for 1 hour. To test the corrosion resistance, the specimens were stored in a temperature- and humidity-controlled chamber at 85° C. and 85% relative atmospheric humidity for 250 hours and 500 hours. Pure Mo, MoTi10 and MoTi20 served as reference materials.

[0107] FIG. 3 shows the various layers after the test for oxidation resistance. The reference materials and the layer composed of the Mo-based alloy containing 8 at % of Al and 8 at % of Ti display a highly discoloured surface and thus low oxidation resistance.

[0108] FIG. 4 shows the various layers after the test for corrosion resistance. After 250 hours in the temperature- and humidity-controlled chamber, both the reference materials and the layer composed of the Mo-based alloy containing 8 at % of Al and 8 at % of Ti and also the layer composed of the Mo-based alloy containing 9 at % of Al and 16 at % of Ti display corrosion damage. The result of the 500 hour temperature- and humidity-controlled chamber test (see FIG. 5) is comparable to the result of the 250 hour test.

[0109] The reflectivity of all layers was measured directly on the surface of the layers using a Perkin Elmer Lambda 950 photospectrometer using the W geometry (VW measurement attachment) at wavelengths from 250 to 850 nm. The results are likewise summarized in Table 1. The greater the difference between the measured value and the starting state (“as coated”), the greater is the damage to the surface. Even a difference of more than 3% can be perceived by the human eye. As limit for possible use, a reduction in the reflectivity relative to the starting state of 5% was set down in this experiment.

TABLE-US-00001 TABLE 1 Reflectivity at 550 nm (%) 250 h, 500 h, Composition of As 330° C., 85° C., 85% 85° C., 85% the layer (at. %) coated 1 h, air relative hum. relative hum. Mo 59.6 41.8 34.1 5.5 MoTi 10 57.4 28.3 14.0 16.4 MoTi 20 56.6 38.3 40.2 29.7 MoAlTi 8-8 57.1 36.4 27.9 12.9 MoAlTi 16-8* 56.4 53.1 57.2 55.5 MoAlTi 24-6* 55.8 53.8 56.5 55.9 MoAlTi 9-16 56.7 51.4 54.1 51.0 MoAlTi 16-15* 56.2 52.9 56.9 56.0 MoAlTi 24-14* 55.3 53.3 56.3 55.2 *indicates particularly advantageous embodiments according to the invention

[0110] The specific electrical resistance of the layers and of the reference materials was measured in the starting state, after the test for oxidation resistance and after the test for corrosion resistance. The structure as shown in FIG. 2a was selected in order to be able to ensure a very precise measurement of the specific electrical resistance. The deposited layer thickness was in each case 300 nm. The measurement was carried out using the 4 point method using a commercially available 4 point measuring head from Jandel and a Keithley SourceMeter. Here, a constant current of 10 mA was applied and the decrease in voltage was measured. The specific electrical resistance over the layer thickness was calculated therefrom. 6 measurement points per specimen were averaged. The results are summarized in Table 2. The test for oxidation resistance did not significantly influence the conductivity (the specific electrical resistance) of the layers examined. The highly corroded specimens (test for corrosion resistance), however, had inhomogeneous measurement values through to insulating places on the surface (no measurement possible). The specimens having the high contents of Al and Ti display a corrosion resistance and oxidation resistance which is significantly improved compared to the reference materials.

TABLE-US-00002 TABLE 2 Specific electrical resistance [μ Ohm cm] 250 h, 500 h, Composition of As 330° C., 85° C., 85% 85° C., 85% the layer (at. %) coated 1 h, air relative hum. relative hum. Mo 12 13 inhomogeneous inhomogeneous MoTi 10 28 28 inhomogeneous inhomogeneous MoTi 20 36 41 inhomogeneous inhomogeneous MoAlTi 8-8 100 103 109 inhomogeneous MoAlTi 16-8* 121 122 145 147 MoAlTi 24-6* 149 152 152 148 MoAlTi 9-16 93 96 85 85 MoAlTi 16-15* 124 126 113 111 MoAlTi 24-14* 152 155 148 148 *indicates particularly advantageous embodiments according to the invention

[0111] To examine the etching behaviour, the layers having a thickness of in each case 300 nm were etched in a stirred PAN solution containing 66% by weight of phosphoric acid, 10% by weight of acetic acid, 5% by weight of nitric acid and water (balance) at 40° C. The phosphoric acid used consists of an 85% strength aqueous solution, the nitric acid of a 65% strength aqueous solution and the acetic acid is pure (100%). To determine the etching rate, the specimens were each dipped for 5 seconds into the etching solution and subsequently rinsed with deionized water and dried. The dry specimens were subsequently weighed on a precision balance. The steps were repeated until the entire layer had been dissolved. The etching rate (wet etching rate) was calculated from the decrease in mass over the etching time. The results are summarized in Table 3. All layers examined can be etched in PAN solution, with the etching rate decreasing greatly with increasing Ti content.

TABLE-US-00003 TABLE 3 Composition of Wet etching the layer (at. %) rate (nm/min) Mo 1550 MoTi 10 1443 MoTi 20 208 MoAlTi 8-8 1154 MoAlTi 16-8* 842 MoAlTi 24-6* 611 MoAlTi 9-16 180 MoAlTi 16-15* 165 MoAlTi 24-14* 140 *indicates particularly advantageous embodiments according to the invention

Example 2

[0112] In the series of experiments, metallizations containing layers composed of Mo-based alloys containing 20 at % of Al and 5 at % of Ti (MoAlTi 20-5), 25 at % of Al and 5 at % of Ti (MoAlTi 25-5) and 25 at % of Al and 10 at % of Ti (MoAlTi 25-10) were produced. The layers were deposited from sputtering targets having the corresponding chemical compositions. To determine the suitability of the layers composed of the Mo-based alloys as diffusion barrier against Si, Si wafers (diameter 3 inches, thickness 380 μm) were coated with the corresponding layers composed of the Mo-based alloys (layer 3, see FIG. 2c) and in each case Cu layers (metallic layer 4, see FIG. 2c). The structure as shown in FIG. 2c was selected since additional layers can block the view onto the Cu layers. The layer thickness was 50 nm for the layers composed of the Mo-based alloys and 200 nm for the Cu layers.

[0113] To test the suitability of the layers composed of the Mo-based alloys as diffusion barrier, the metallizations were heat treated at various temperatures under reduced pressure (10.sup.−5 mbar) for 30 minutes. Pure Mo and an Mo alloy containing 50 at % of Al served as reference materials.

[0114] The suitability of the layer as diffusion barrier is no longer ensured when the surface of the Cu layer displays silvery discoloration and the electrical surface resistance increases significantly. This is an indication that intermetallic phases composed of Cu and Si have been formed. The electrical surface resistance was calculated/measured after coating (starting state) and after the heat treatments. The measurement was carried out using the 4 point method (commercially available 4 point measuring head). The results are summarized in FIG. 6.

[0115] The layer composed of the Mo-based alloy containing 20 at % of Al and 5 at % of Ti loses its suitability as diffusion barrier against silicon at about 650° C. This is an only insignificantly lower temperature than in the case of the reference specimen with Mo layer (700° C.). At a higher Al content in the layer, for example in the case of the Mo alloy containing 50 at % of Al, the suitability as diffusion barrier is lost at as low as 300° C. (FIG. 6). Increasing the Ti content in the layers composed of Mo-based alloys enables the suitability as diffusion barrier to be improved further at relatively high Al contents in the alloy (comparison of MoAlTi 25-5 and MoAlTi 25-10 in FIG. 6). These layers thus satisfy the suitability as diffusion barrier required for use together with the above-described advantages of an increased corrosion resistance and oxidation resistance in an optimal manner (see Example 1).

Example 3

[0116] Commercial Mo, Al and Ti powders suitable for cold gas spraying were sprayed by means of cold gas spraying onto an Al tube as support material. The powders were conveyed from separate containers. The chemical composition was set via the transport rates of the individual powders. The microstructure of the resulting sputtering target containing 20 at % of Al and 5 at % of Ti is shown in cross section (scanning electron micrograph) in FIG. 7. The microstructure is typical of a material produced by cold gas spraying, having longitudinal grains whose longer axis is arranged parallel to the surface of the support material. As a result of the cold gas spraying, no intermetallic phases are formed in the production of the sputtering target, as the X-ray diffraction pattern in FIG. 8 shows. This was recorded by means of a D4 Endeavor diffractometer from Bruker using CuKα radiation in the Bragg-Brentano geometry.

Example 4

[0117] A thin-film component as shown in FIG. 2a was constructed in this example.

[0118] In the series of experiments, various metallizations each containing a layer composed of an Mo-based alloy having a different chemical composition were produced. The layers composed of Mo-based alloys containing Al and Ti were deposited from sputtering targets having the corresponding chemical compositions. Layers composed of Mo-based alloys containing 20 at % of Al and 5 at % of Ti (MoAlTi 20-5), 20 at % of Al and 10 at % of Ti (MoAlTi 20-10), 25 at % of Al and 5 at % of Ti (MoAlTi 25-5) and 25 at % of Al and 10 at % of Ti (MoAlTi 25-10) were deposited.

[0119] To determine the suitability of the layers composed of Mo-based alloys as covering layer, glass substrates (Corning Eagle XG®, 50×50×0.7 mm.sup.3) were coated with the layers composed of Mo-based alloys and the oxidation resistance thereof was subsequently tested. For the test for oxidation resistance, the layers were heated at 400° C. in air for 1 hour.

[0120] FIG. 9 shows the various layers after the test. The layers composed of Mo-based alloys having a total proportion of Al and Ti of greater than or equal to 30 at % display no discoloration of the surface and are thus oxidation-resistant up to 400° C.

[0121] The figures show:

[0122] FIG. 1: phase diagram of the system Al—Mo (source: ASM International's Binary Alloy Phase Diagrams, Second Edition).

[0123] FIG. 2: possible structure of thin-film components comprising at least one metallization according to the invention in cross section. [0124] 1: substrate; 2: metallization; 3: layer of an Mo-based alloy; 4: layer of Al, Cu, Ag or Au or an alloy based on these metals; 5: other intermediate layer/diffusion barrier; 6: other covering layer.

[0125] FIG. 3: surface photograph of the layers examined after the test for oxidation resistance (heating at 330° C. in air for 1 hour). * indicates particularly advantageous embodiments according to the invention.

[0126] FIG. 4: surface photographs of the layers examined after the test for corrosion resistance (250 hours in the temperature- and humidity-controlled chamber at 85° C. and 85% relative atmospheric humidity). * indicates particularly advantageous embodiments according to the invention.

[0127] FIG. 5: surface photographs of the layers examined after the test for corrosion resistance (500 hours in the temperature- and humidity-controlled chamber at 85° C. and 85% relative atmospheric humidity). * indicates particularly advantageous embodiments according to the invention.

[0128] FIG. 6: surface resistance of the heat-treated specimens (50 nm layer of Mo or Mo-based alloy and 200 nm Cu layer on silicon substrate) vs. heat treatment temperature.

[0129] FIG. 7: scanning electron micrograph of a sputtering target containing 20 at % of Al and 5 at % of Ti. Dark regions at lower margin of the image: support material composed of Al. Dark regions in the microstructure: Al and Ti. Light-coloured regions: Mo.

[0130] FIG. 8: X-ray diffraction pattern of a sputtering target containing 20 at % of Al and 5 at % of Ti. No intermetallic phases can be detected.

[0131] FIG. 9: surface photographs of the layers examined after the test for oxidation resistance (heating at 400° C. in air for 1 hour).