AT18482U1 - MoLa sputtering target - Google Patents

Abstract

The invention discloses a powder metallurgically produced sputtering target, wherein the sputtering target comprises 0.3 to 10 wt.% of an oxygen-containing lanthanum compound (La), the remainder molybdenum (Mo) and unavoidable impurities, characterized in that the sputtering target has a Mo phase and a La phase, wherein an average grain size of the Mo grains in the Mo phase is 1 to 200 μm and the sputtering target has an isotropic microstructure.

Description

Description

MOLA sputtering target

[0001] The present invention relates to a powder-metallurgically produced Mo (molybdenum) La (lanthanum) sputtering target (hereinafter referred to as MoLa), which comprises Mo and an oxygen-containing lanthanum compound, and to its use for the production of high-temperature stable thin films. The present invention further relates to a method for producing a MoLa sputtering target via a powder-metallurgical route.

[0002] Sputtering, also known as cathode sputtering, is a physical process in which atoms are released from a sputtering target by bombardment with high-energy ions and pass into the gas phase. In DC sputtering (direct current sputtering), a direct voltage of several hundred volts is applied between the target and a substrate to be coated in a vacuum chamber; it is therefore also called direct current sputtering. The target forms the negatively charged electrode and the substrate the positively charged electrode. Through impact ionization of the atoms of an inert gas (e.g. argon), a plasma forms in the gas space of the vacuum chamber. The plasma's components, negatively charged electrons and positively charged gas ions, such as Ar*, are accelerated towards the substrate or target by the applied direct voltage. A continuous current of positive ions and Ar atoms then strikes the target. Upon impact with the target, particles are ejected from the target by momentum transfer. These particles move away from the target toward the substrate, where they deposit as a thin layer (deposition). However, this process is only applicable to electrically conductive target materials.

[0003] Conductive layers with high temperature stability and improved properties in the high-temperature range have become important, for example, in the development of wireless SAW (Surface Acoustic Wave) temperature sensors. Although layers made of pure molybdenum exhibit high temperature stability, unlike metals with a low melting point, recrystallization occurs above a certain temperature (approximately 600°C) in the application, thus leading to a change in the layer.

[0004] It is known that oxide or carbide particles (as local barriers to diffusion and the movement of dislocations) can be used for dispersion strengthening in pure Mo materials, thereby improving the thermomechanical properties of such materials. When lanthanum oxide is used as a dispersoid, layers of molybdenum and lanthanum oxide are produced either by co-sputtering molybdenum targets and lanthanum oxide targets or by alternating (reactive) sputtering molybdenum targets and lanthanum targets. The disadvantage of co-sputtering is that lanthanum oxide targets degrade very quickly. The disadvantage of alternating sputtering molybdenum and lanthanum targets is that the lanthanum layer must subsequently be oxidized to a lanthanum oxide layer before the next molybdenum layer can be sputtered. However, if water, water vapor or humidity is still present in the sputtering chamber, the lanthanum oxide is immediately converted into lanthanum hydroxide.

[0005] Sputtering targets containing both molybdenum and lanthanum oxide are also known from the prior art.

[0006] Patent application CN114351095 A discloses a Mo alloy target comprising Mo and at least one of the dopants selected from Al2O3, ZrO2, and/or La2zO3. However, the exact proportion of these dopants is not disclosed. While the application states that the proportion of these elements is no more than 10%, it does not specify whether this is in terms of weight, volume, or mole percent.

Generally, a "small amount" is used. The dopants Al2O3s, ZrO2, and/or La2Os inhibit the growth of the Mo particles, allowing the production of a nanoscale powder. This allows the production of a nanocrystalline molybdenum alloy target with an ultrafine grain structure (grain size of < 300 nm). According to this patent,

According to the patent application, these nanocrystalline materials are superior to conventional (coarser-grained) materials in terms of surface properties. The examples in this patent application show the dopants Al2Os, ZrO2, or a combination of Al2Os and ZrO2. However, the production of such nanocrystalline powders is very complex, and the nanocrystalline powders are difficult to process due to their dust-like product form.

[0007] Patent application CN106591786 A describes a manufacturing process for a doped Mo target material containing 1 to 6 mass% lanthanum oxide based on the amount of molybdenum trioxide used. The application discloses a process in which twice as much molybdenum trioxide as molybdenum powder is used. If molybdenum trioxide is used, molybdenum dioxide subsequently forms, which must then be reduced to molybdenum in a further process step. Whether this reduction is completely successful is not further explained in the patent application (i.e., molybdenum trioxide or dioxide could still be present in the target). One step of this process discloses that lanthanum oxide is reduced to lanthanum powder (step 3). The total proportion of lanthanum oxide in the final target is therefore not disclosed. After sintering, the material is rolled so that the sputtering target has a deformed structure. In contrast, the sputtering target according to the invention has an isotropic (globulitic) microstructure.

[0008] Two disadvantages arise from the use of targets made of lanthanum oxide and molybdenum, which are not mentioned in the above-mentioned patent applications. First, DC sputtering is only applicable to electrically conductive target materials (the addition of La2Os reduces the conductivity of the target material), and second, lanthanum oxide reacts immediately with atmospheric humidity or water vapor to form lanthanum hydroxide. However, lanthanum hydroxide is undesirable as a (sputtering) end product because it impairs the uniform deposition behavior of lanthanum oxide and molybdenum and reduces the dispersoid effect.

[0009] The object of the present invention is to provide a MoLa sputtering target which has sufficient electrical conductivity and a high density, and which has a uniform or homogeneous distribution of a Mo phase and a La phase throughout the entire volume of the target. This enables uniform sputtering by removing both the Mo phase and the La phase from the sputtering target simultaneously in the same amount. Uniform sputtering or uniform sputtering behavior is understood to mean that the individual grains or individual regions of the sputtering target can be removed at the same rate, so that no relief structure is created in the region of the sputtered surface during the sputtering process.

In addition, the target according to the invention contains an extremely small amount of lanthanum hydroxide, which shows a different behavior during sputtering and thus prevents uniform sputtering.

[0010] In particular, it is an object of the invention to provide a sputtering target with which a very homogeneous layer can be produced, both in terms of chemical composition and in terms of layer thickness distribution.

[0011] A further object of the present invention is to provide a method that allows the production of a sputtering target having the aforementioned properties in a simple and process-constant manner.

[0012] The technical problem of the present invention is solved by the subject matter of claim 1 and the method in claim 11. Advantageous developments of the invention can be found in the dependent claims, which can be freely combined with one another.

[0013] According to the present invention, the powder metallurgically produced sputtering target comprises 0.3 to 10 wt.% of an oxygen-containing lanthanum compound (La), the remainder being molybdenum (Mo) and inevitable impurities, and is characterized in that the sputtering target has a Mo phase and a La phase, wherein an average grain size of the Mo grains in the Mo phase is 1 to 200 µm and the sputtering target has an isotropic microstructure.

[0014] The sputtering target preferably consists of 0.3 to 10 wt.% of an oxygen-containing lanthanum compound (La), the remainder molybdenum (Mo), and a maximum of 0.1 wt.% of unavoidable impurities. Oxygen is not considered unavoidable impurities because lanthanum is added in an oxygen-containing compound. The higher the amount of oxygen-containing La compound in the target, the higher the oxygen content in the target. The proportion of oxygen-containing lanthanum compound is preferably more than 0.7 to 10 wt.%, more preferably 0.8 to 10 wt.%. With this proportion of oxygen-containing lanthanum compound, the electrical conductivity of the sputtering target is sufficient for uniform sputtering in DC mode, and the proportion of undesirable lanthanum hydroxide formed is sufficiently low.

[0015] A powder-metallurgically produced sputtering target is understood to be a component whose production comprises the steps of pressing corresponding starting powder into a compact and sintering the compact. Furthermore, the production process may also include further steps, such as mixing and homogenizing (e.g., in a plowshare mixer) the powders to be pressed, etc. This results in a microstructure that is typical for this production process and is referred to as an isotropic microstructure. The isotropic microstructure is defined by the fact that the grains are uniformly (globulitic), i.e., there is no preferred direction in the grain structure of the sputtering target. This means that the mechanical and thermal properties of the material are identical in all directions. This differs from the prior art (see CN106591786), in which a preferred direction/forming structure of the grains is achieved via a rolling step.

[0016] For a sputtering target, a homogeneous distribution of the elements and a high density are crucial. The structure of a sputtering target differs significantly from the structure of other Mo-lanthanum oxide products (such as wires, sheets, or rods). In these products, the processing and addition of lanthanum oxide results in enlarged, elongated particles (i.e., a fibrous structure), which are crucial for properties such as creep resistance and higher recrystallization temperatures.

[0017] The advantage of the isotropic structure is a high uniformity of the properties after deposition of the material onto a substrate to be coated.

[0018] The microstructure of the sputtering target within the meaning of this invention is the microstructure which can be analyzed in a simple manner known to the person skilled in the art by means of a metallographic section and assessment under a light microscope or scanning electron microscope.

[0019] In the case of the sputtering target according to the invention, the microstructure has only one Mo phase and one La phase, which are homogeneously or evenly distributed throughout the entire volume of the sputtering target. It follows from the present application that, strictly speaking, the La phase should actually be referred to as the La2Os phase or the La2O3/La(OH)s phase. For simplification, however, it is referred to as a La phase. No mixed phases (containing both Mo and La) or intermetallic phases of Mo and La2Oz3 and/or La(OH)s occur. The Mo phase is the pure/elemental component Mo (i.e., Mo grains), as it is also used as the starting material. The La phase is either La2Os (as it is also used as the starting material) or a mixture of La2O3 and La(OH)s. Lanthanum oxide is extremely hygroscopic and can absorb water from the environment very easily and quickly. Lanthanum oxide reacts rapidly in humid air to form lanthanum hydroxide. In addition, other phases, such as pores, may be present in the target material. The presence of a pure Mo phase and a La phase in a sputtering target according to the invention can be easily confirmed or ruled out using X-ray diffraction (XRD) (taking into account the respective X-ray detection limit) with JCPDS cards.

[0020] The powder-metallurgically produced sputtering target exhibits a microstructure typical for powder-metallurgical production. This fine-grained microstructure enables uniform sputtering of the target. The average grain size of the Mo grains in the Mo phase

is between 1 and 200 μm, preferably between 1 and 50 μm, particularly preferably between 1 and 30 μm. These grain sizes lead to uniform sputtering behavior and thus to the deposition of very homogeneous layers with a uniform layer thickness. The average grain size of the Mo phase can be easily determined on a metallographic section using a line-intersection method, e.g., according to ASTM E112-12.

[0021] By adding 0.3 to 10 wt.% lanthanum oxide, the microstructure of the MoLa target is stabilized, so that the recrystallization behavior of the Mo-La target is changed compared to the base material molybdenum, specifically with regard to its thermomechanical behavior at extremely high temperatures. Although layers made of pure molybdenum exhibit high temperature stability, recrystallization processes and thus changes in the deposited layers can occur at high temperatures (e.g., more than 800°C) during application or during subsequent process steps. By adding lanthanum oxide, the targets exhibit a higher recrystallization temperature than pure molybdenum. This makes the targets according to the invention particularly suitable for high-temperature applications. If the amount of lanthanum oxide is below 0.3 wt.%, this effect cannot be detected. If the amount of lanthanum oxide exceeds 10 wt.%, the conductivity of the sputtering target decreases significantly, severely impairing sputtering in DC mode. A quantity of more than 0.7 to 10 wt.% is preferred.

[0022] The term "unavoidable impurities" refers to impurities that may be present in the target due to production, e.g., accompanying elements or gases that are found in the raw materials used or that enter the target through the tools or vessels used. A distinction can be made between metallic and non-metallic impurities. Non-metallic impurities can be gases such as C, N, H, S, etc. In the sputtering target according to the invention, the addition of La2Os3 (depending on the amount of La2Os used) results in a somewhat higher oxygen content, which can be up to 18,000 µg/g (18,000 ppm by weight), but is preferably below 10,000 µg/g, with a particularly preferred value of below 5,000 µg/g. For the other gases, the value is below 1,000 µg/g, preferably below 500 µg/g. Metallic impurities include Al, Cr, Cu, Fe, K, Mg, Ni, Si, V, Ti, W, Zr, etc. The proportion of such impurities is below 300 µg/g. In particular, the W content of the impurities is less than 160 ppm.

[0023] Suitable methods for chemical elemental analysis are known to depend on the chemical elements to be analyzed. For the chemical analysis of elements such as Al, Fe, Cu, etc., ICP-MS (inductively coupled plasma mass spectroscopy) or ICP-OES (inductively coupled plasma optical emission spectroscopy) was used. For the elements O or N, hot gas extraction analysis (see ASTM E1409-13) was applied. For the elements C (see ASTM E 1941-10) and S (see ASTM E 1019:2018), combustion analysis was used. The chemical analysis of the main components Mo and La2O3 in the sputtering target according to the invention was carried out using X-ray fluorescence analysis (XRF).

[0024] As already described above, the La phase can also comprise a mixture of lanthanum oxide and lanthanum hydroxide. However, the proportion of lanthanum hydroxide in the sputtering target should be kept as low as possible, since this proportion has a negative effect on the sputtering behavior, in particular the homogeneity of the deposition. It is therefore very important to prevent the formation of lanthanum hydroxide as much as possible and to keep the proportion of La(OH)s in the La phase as low as possible. The area fraction of lanthanum hydroxide (La(OH)3) in the La phase should be a maximum of 10%, measured against the cross-section of the target material. The proportion of La(OH)s can be between 0.1 and 10% area fraction. The area fraction of lanthanum hydroxide, measured against the cross-section of the target material, should particularly preferably be a maximum of 5%. The sputtering target according to the invention does not exhibit any intermetallic phases of La and Mo.

[0025] In a further embodiment, the La phase, measured at the cross section of the target material, has an area fraction of between 5 and 18%. The cross section of the

Material the proportion of the areas in relation to the Mo phase as well as in relation to the La phase.

[0026] According to a further development, the sputtering target according to the invention has a density of at least 95% of the theoretical density. A density of more than 97%, preferably more than 98% of the theoretical density, is particularly advantageous. The theoretical density is the maximum achievable density of the MoLa target, provided that no internal cavities and impurities (or intermetallic phases) form. The higher the density of the target, the more advantageous its properties. Targets with a low relative density have a relatively high proportion of pores, which can be a virtual leak and/or a source of impurities and particles during the sputtering process. Furthermore, low-density targets tend to absorb water or other impurities, which can lead to process parameters that are difficult to control. Furthermore, the removal rate of material that is only slightly densified during the sputtering process is lower than that of material with a higher relative density.

[0027] The theoretical density of composite materials can be calculated from the densities of the individual pure metals or compounds and their weight fractions. The density can be determined, for example, using the Archimedes method by determining the weight of the target in air and water (here, the sample can preferably be embedded in paraffin; see DIN EN ISO 2738:2000-02).

[0028] The installation of a sputtering target according to the invention in various coating systems and also for coating substrates with different geometries places different geometric demands on a sputtering target according to the invention. The target is preferably designed in the form of a planar sputtering target, for example, as a cuboid, disk, or plate. However, it can also be in the form of a tubular target.

[0029] Thin-film materials (typically less than 1000 nm thick) containing Mo-La2O3 systems exhibit superior ductility, toughness, and creep resistance at high temperatures. The sputtering target according to the invention is therefore preferably used for the deposition of metallic thin films, and particularly preferably for the deposition of high-temperature-resistant thin films, such as SAW temperature sensors, SAW sensor chips, and sensor antennas.

[0030] MoLa layers from the sputtering target according to the invention can also function as hydrogen barrier layer(s) (“hydrogen trap layer”), which is advantageous, for example, in hydrogen-sensitive oxide semiconductor layers.

[0031] The method according to the invention for producing the powder metallurgically produced MoLa sputtering target, which comprises 0.3 to 10 wt.% of an oxygen-containing lanthanum compound (La), the remainder molybdenum (Mo) and unavoidable impurities, is characterized by the following steps: mixing Mo powder and an oxygen-containing lanthanum compound in powder form to form a powder mixture; compacting the powder mixture by applying pressure, heat or pressure and heat to form a blank, wherein the sputtering target has a Mo phase and a La phase and wherein an average grain size of the Mo grains in the Mo phase is 1 to 200 µm and the sputtering target has an isotropic microstructure.

[0032] Before a powder mixture is produced, the oxygen-containing lanthanum compound is calcined, i.e., the compound is heated to such an intense level that it is completely dehydrated. Consequently, after this step, La2O3 powder is obtained. In a preferred embodiment, the lanthanum oxide powder is obtained by calcining lanthanum hydroxide. The lanthanum hydroxide is heated to a temperature of more than 1000°C. This dehydrates the powdered lanthanum hydroxide.

[0033] A powder mixture is then prepared by mixing 0.3 to 10 wt.% LazOs powder with Mo powder until a homogeneous distribution of the com-

components in the powder mixture is guaranteed.

[0034] The powder mixture thus produced is then compacted. Compaction within the scope of the process according to the invention is carried out by applying pressure, heat, or pressure and heat. This can be achieved through various process steps, for example, by pressing and sintering, cold isostatic pressing (CIP), hot isostatic pressing (HIP), hot pressing (HP), or spark plasma sintering (SPS), or a combination of these processes or other processes for compacting powder mixtures.

[0035] It has proven particularly advantageous that, in a process according to the invention for producing MoLa targets, the densification step is carried out by hot pressing, spark plasma sintering, or hot isostatic pressing. Temperatures of 1000°C to 1800°C are used. Preferably, the process is carried out at a pressure of 15 MPa or greater. If the densification step is carried out via HIP, pressures of up to 200 MPa can be used.

[0036] Sintering preferably takes place under vacuum, in an inert atmosphere, and/or in a reduced atmosphere. In this case, an inert atmosphere is understood to be a gaseous medium that does not react with the alloy components, e.g., a noble gas. A suitable reduced atmosphere is, in particular, hydrogen.

[0037] The method according to the invention makes it possible to produce a Mo-La sputtering target having an isotropic microstructure and in which the Mo phase and La phase are uniformly distributed. The average grain size of the Mo grains in the Mo phase is between 1 and 200 µm, and the sputtering target preferably has a density of at least 95% of the theoretical density.

[0038] Further advantages and benefits of the invention will become apparent from the following description of embodiments with reference to the accompanying figures.

[0039] Of the figures show

[0040] Fig. 1: Microstructure of a sputtering target according to the invention according to Example 1 in the scanning electron microscope (SEM) at a magnification of 200 times;

[0041] Fig. 2: Example 1: Distribution of the elements Mo and La by EDX (energy dispersive X-ray spectroscopy) mapping on the SEM at a magnification of 500 times;

[0042] Fig. 3: X-ray diffractogram of a sputtering target according to the invention according to Example 1; pure Mo and La2Os3 (cubic and hexagonal) detectable, no La(OH)s detectable;

[0043] Fig. 4: Example 2: Distribution of the elements Mo and La by EDX (energy dispersive X-ray spectroscopy) mapping on the SEM at a magnification of 500 times;

[0044] Fig. 5: X-ray diffractogram of a sputtering target according to the invention according to Example 2; pure Mo phase and La2O3 (cubic and hexagonal) detectable, no La(OH)3 detectable;

[0045] Fig. 6: Example 3: Distribution of the elements Mo and La by EDX (energy dispersive X-ray spectroscopy) mapping on the SEM at a magnification of 500 times;

[0046] Fig. 7: X-ray diffractogram of a sputtering target according to the invention according to Example 3; pure Mo phase, La2O3 (hexagonal) and La(OH)3s detectable;

MANUFACTURING EXAMPLES

EXAMPLE 1

[0047] In a first step, a lanthanum hydroxide is calcined, i.e., La(OH)3 is heated to over 1000°C for a sufficient time to obtain a La2O3 powder. This La2O3 powder has an average particle size of about 0.8 µm (D50 measurement according to Malvern).

Subsequently, the La:Os powder and a molybdenum powder with an average particle size of less than 20 µm (D90 measurement according to Malvern) are used as starting materials. Immediately after calcination, 98.6 wt.% molybdenum powder and 1.4 wt.% La2Os powder are placed in a closed container (no vacuum) and mixed in a shaker. The powder mixture is then poured into a container and sintered in an SPS (Spark Plasma Sintering) system at 1800°C at a pressure of approximately 15 MPa, thus producing a consolidated target.

[0048] Lanthanum oxide is extremely hygroscopic and can therefore quickly absorb moisture from the air, converting it back into lanthanum hydroxide. Therefore, the mixing step and the subsequent sintering should take place immediately after one another.

[0049] The disc-shaped, planar sputtering target thus produced has a relative density of 98.6%. The oxygen content is approximately 2000 μg/g, the μg/g, and the W content is approximately 160 μg/g. All other impurities are below 100 μg/g.

[0050] The target thus produced was used in a sputtering system and applied as a metallic thin film (approximately 100 nm) on thermally oxidized Si (SiOx). The sputtering target could be sputtered evenly, resulting in a thin film in which Mo and La2zO3 were homogeneously distributed. No La(OH)3s could be detected. The thin film exhibits higher temperature stability compared to a pure molybdenum coating.

[0051] Fig. 1 shows the isotropic structure of the sputtering target produced according to this example. The microstructure shows Mo grains (gray) and La2Os grains (dark gray). The black color indicates pores caused by the powder metallurgical production or artifacts that arose during the micrograph.

[0052] Figure 2 shows the distribution of Mo and La from Example 1 using energy-dispersive X-ray spectroscopy on a SEM section. Since the oxygen content is tightly bound to the La, the oxygen content cannot be shown separately in a black-and-white representation. La (and the oxide bound to it) are shown in dark. The Mo grains appear light gray. The uniform distribution of the La phase and the Mo phase is clearly visible.

[0053] Fig. 3 shows the X-ray diffraction pattern of this example, as well as its analysis by decomposition of the diffractogram. The samples were examined with a Bruker D8 Advance 9-0 diffractometer using Cu radiation (ΔKa1 = 0.15406 nm). The diffraction geometry is characterized by the following details:

- Primary optics: focusing polycapillary and UBC collimator (long version, width 1 mm), - Secondary optics: axial 2.5° Soller slit, Lynx Eye XET detector in 1D mode.

- Measurement mode: locked coupled, step size: 0.02°, time/step: 1 sec, sample rotation: 3 revolutions/min.

[0054] To clearly assign individual components to the peaks/phases, a search-match algorithm was used in the PDF (Powder Diffraction File)2 database (version 2020). PDF2 is a database for inorganic and organic diffraction data for phase identification and material characterization. The presence of the individual phases was confirmed by Rietveld refinement using the corresponding structural data (of Mo, La2Os (hexagonal (P321)), and La2Og3 (cubic (La-3)).

[0055] The dark grey curve shows 2Theta angles for pure molybdenum at 40.5°, 58° and 74°.

[0056] The dashed curve shows 2Theta angles for cubic lanthanum oxide at 27.4°, 31.9°, 45° and 54°.

[0057] The light grey curve shows 2Theta angles for hexagonal lanthanum oxide at 30°, 39.5°, 46°, 52° and 55.6°.

[0058] The points o correspond to the measured values (radiation intensities) in the diffraction

meters.

[0059] The curve Y calc (light grey) corresponds to all measured values (molybdenum, La2zOs (hexagonal) and La2zOs (cubic)) and shows the overall agreement.

[0060] The difference (Diff) (bottom line) shows hardly any deviations, so that the individual phases are well described.

[0061] From this figure it can be seen that the sputtering target consists of a pure Mo phase and a pure lanthanum oxide phase, with neither lanthanum hydroxide nor intermetallic phases having formed during production.

[0062] This target was deposited by sputtering on thermally oxidized Si with a layer thickness of approximately 100 nm. Compared to a pure Mo layer, the layer exhibits improved layer stability, thermal mechanical behavior, and creep behavior (especially at temperatures above 800°C).

EXAMPLE 2

[0063] The preparation is carried out as in Example 1, except that 97.2 wt.% of molybdenum powder with an average particle size of less than 20 µm (D90 measurement according to Malvern) and 2.1 wt.% of lanthanum oxide with an average particle size of about 0.8 µm (D50 measurement according to Malvern) are mixed in a mixer.

[0064] The mixed powder is then sintered at a pressure of approximately 15 MPa at 1800°C in a SPS (spark plasma sintering) system. The sputtering target then has a relative density of 98.9%. The oxygen content is approximately 3000 µg/g, and the W content is below 160 µg/g. All other impurities are below 100 µg/g. The planar circular target has a diameter of approximately 110 mm.

[0065] Fig. 4 shows the distribution of Mo and La using energy-dispersive X-ray spectroscopy (EDX) on a SEM section. Since the oxygen content is tightly bound to the La, it cannot be shown separately in a black-and-white representation. La (and the oxide bound to it) are shown in dark. The Mo grains appear light gray. The uniform distribution of the La phase and the Mo phase can be seen.

[0066] Fig. 5 shows the X-ray diffraction pattern of this example and its analysis. This was carried out analogously to Fig. 3 in Example 1.

[0067] The dark grey curve shows 2Theta angles for pure molybdenum at 40.5°, 58° and 74°.

[0068] The dashed curve shows 2Theta angles for cubic lanthanum oxide at 27.4°, 31.9°, 45° and 54°.

[0069] The light grey curve shows 2Theta angles for hexagonal lanthanum oxide at 30°, 39.5°, 46°, 52° and 55.6°.

[0070] The points o correspond to the measured values (radiation intensities) in the diffractometer.

[0071] The curve Y calc (light grey) corresponds to all measured values (molybdenum, La2Os (hexagonal) and La2Os (cubic)) and shows the overall agreement.

[0072] The difference (Diff) (bottom line) shows hardly any deviations, so that the individual phases are well described.

[0073] From this figure it can be seen that the sputtering target consists of a pure Mo phase and a pure lanthanum oxide phase, with neither lanthanum hydroxide nor intermetallic phases having formed during production.

[0074] This target was also deposited by sputtering on thermally oxidized Si with a layer thickness of approximately 100 nm. Compared to a pure Mo layer, the layer exhibits improved layer stability, thermomechanical behavior, and creep behavior.

(especially at temperatures above 800°C).

EXAMPLE 3

[0075] The preparation is carried out as in Example 1, except that 90 wt.% molybdenum powder with an average particle size of less than 20 µm (D90 measurement according to Malvern) and 10 wt.% lanthanum oxide with an average particle size of about 0.8 µm (D50 measurement according to Malvern) are mixed in a mixer.

[0076] The mixed powder is then sintered at a pressure of approximately 15 MPa at 1800°C in an SPS ("Spark Plasma Sintering") system. The sputtering target then has a relative density of 97.5%. The oxygen content is approximately 18,000 μg/g, and the W content is below 160 μg/g. All other impurities are below 100 μg/g.

[0077] Fig. 6 shows the distribution of Mo and La using energy-dispersive X-ray spectroscopy (EDX) on an SEM section. Since the oxygen or hydroxide content is closely bound to the La, it cannot be shown separately in a black-and-white representation. La (and the oxide bound to it) or lanthanum hydroxide are shown in dark. The Mo grains appear light gray. The uniform distribution of the La phase and the Mo phase can be seen.

[0078] Fig. 7 shows the X-ray diffraction pattern of this example and its analysis. This is carried out analogously to Fig. 3 in Example 1. Cubic lanthanum oxide is no longer detectable, but lanthanum hydroxide is.

[0079] The dark grey curve shows 2Theta angles for pure molybdenum at 40.5°, 58° and 74°.

[0080] The light grey curve shows 2Theta angles for hexagonal lanthanum oxide at 30°, 39.5°, 46°, 52° and 55.6°.

[0081] The dashed (light grey) curve shows no peaks for cubic lanthanum oxide.

[0082] The dark grey dashed curve shows 2Theta angles for lanthanum hydroxide at 27.5°; 28°; 31.8°; 39.6°; 42.5°; 47.3°; 48.9° and 50°.

[0083] The points ° correspond to the measured values (radiation intensities) in the diffractometer.

[0084] The curve Y calc (light grey) corresponds to all measured values (molybdenum, LazOs (hexagonal) and LazOHs) and shows the overall agreement.

[0085] The difference (Diff) (bottom line) shows hardly any deviations, so that the individual phases are well described.

[0086] From this figure it can be seen that the sputtering target also forms lanthanum hydroxide phases, whereby no intermetallic phases of Mo and La have formed.

[0087] Despite the large amount of lanthanum oxide, the sputtering target shows sufficient electrical conductivity so that it can be sputtered in DC mode.

[0088] This target was also deposited by sputtering on thermally oxidized Si with a layer thickness of approximately 100 nm. Compared to a pure Mo layer (despite the lanthanum hydroxide phases), the layer exhibits improved layer stability, thermomechanical behavior, and creep behavior (especially at temperatures above 800°C).

Claims (14)

Claims 1. A powder metallurgically produced sputtering target, wherein the sputtering target comprises 0.3 to 10 wt.% of an oxygen-containing lanthanum compound (La), the remainder molybdenum (Mo) and unavoidable impurities, characterized in that the sputtering target has a Mo phase and a La phase, wherein an average grain size of the Mo grains in the Mo phase is 1 to 200 µm and the sputtering target has an isotropic microstructure. 2. Sputtering target according to claim 1, characterized in that the La phase comprises lanthanum oxide (La2zOs) and lanthanum hydroxide (La(OH)s). 3. Sputtering target according to one of the preceding claims, characterized in that the La phase has an area fraction, measured on a cross-section of the target material, between 5 and 18%. 4. Sputtering target according to one of the preceding claims, characterized in that an area fraction of La(OH)s in the La phase, measured on a cross section of the target material, is not more than 10%. 5. Sputtering target according to one of the preceding claims, characterized in that the proportion of oxygen-containing lanthanum compound is > 0.7 wt.% to 10 wt.%. 6. Sputtering target according to one of the preceding claims, wherein the density of the sputtering target is at least 95% of the theoretical density. 7. Sputtering target according to one of the preceding claims, wherein the average grain size of the Mo grains in the Mo phase is between 1 and 50 µm. 8. Sputtering target according to one of the preceding claims, characterized in that it is a planar sputtering target. 9. Use of the sputtering target according to one of claims 1 to 8 for the deposition of metallic thin films. 10. Use of the sputtering target according to one of claims 1 to 8 for the deposition of high-temperature-resistant thin films. 11. A process for producing a sputtering target comprising 0.3 to 10 wt.% of an oxygen-containing lanthanum compound (La), the remainder molybdenum (Mo) and unavoidable impurities, by powder metallurgy, characterized in that it comprises at least the following steps: Mixing Mo powder and an oxygen-containing lanthanum compound in powder form to form a powder mixture; Compacting the powder mixture by applying pressure, heat or pressure and heat to a blank, characterized in that the sputtering target has a Mo phase and a La phase, wherein an average grain size of the Mo grains in the Mo phase is 1 to 200 µm and the sputtering target has an isotropic microstructure. 12. A method for producing a sputtering target according to claim 11, wherein the oxygen-containing lanthanum compound is obtained by calcination. 13. A method according to any one of the preceding claims 11 and 12, wherein the densification step is carried out by means of spark plasma sintering, hot pressing or hot isostatic pressing. 14. A method according to any one of the preceding claims 11 to 13, wherein the densifying step takes place at temperatures between 1000 to 1800°C. 4 sheets of drawings