Sputtering Target und Verfahren zur Herstellung

[0001] The invention concerns a Sputtering target, at least which covers molybdenum (Mo) and a metal of the group 5 of the periodic system, whereby the middle content cm at group 5 metal 5 to 15 At% and the Mo-content amount to > 80 At%.

[0002] Sputtering, also cathodic sputtering mentioned, is a physical procedure, with which atoms are extracted from a Sputtering target by bombardment with ions high-energy and into the gaseous phase to change. Sputtering targets from Mo, which contain group of 5 metals, are well-known.

[0003] Thus the EP describes 0,285,130 A1 a Sputtering target from a mole craving, which contains 50 to 85 At% tantalum (Ta). The JP 2002 327264 A reveals a Sputtering target from a mole craving, which 2 to 50 At% niobium (Nb) and/or vanadium (V) contains, a relative density > 95%, a bending strength > 300 MPa and a grain size < 300 μm exhibits. The Sputtering target exhibits a diffusion phase and at least a pure phase or only a diffusion phase. The JP 2005 307226 A reveals a Sputtering target from a mole craving, which contains 0.1 to 50 At% of a transition metal. The Sputtering target exhibits a length > 1 m and a homogeneous density of > 98%. Alternatively the JP describes 2005 307226 A a Sputtering target, that over the entire length fluctuations of the composition of < 20% up.

[0004] Mo-Nb and Mo-Ta Sputtering target are used for example for the production of electrode layers for thin section transistors or of contact layers for Touch panels. The rising requirements in view to layer quality and - homogeneity and this in ever more largely becoming dimensions to become fair, is a goal of numerous development activities. Thus the JP describes 2008 280570 A a manufacture process for a Mo-Nb Sputtering target with a Nb-content from 0,5 to 50 At%, with which first a Mo-sintering is manufactured, which is broken again to powder. In such a way manufactured Mo-powder is submitted of a reducing treatment and mixed with Nb-powder. Subsequently, this mixture is consolidated by hot-isostatic pressing. With this process it is possible to reduce the oxygen content in the powder to obtain not however a further reduction of the oxygen content in the Sputtering target there hot-isostatic pressing in a closed container (can) taken place. Besides it is also not possible to distribute Nb in a homogeneity necessary for many applications in the Mo.

[0005] The JP 2005 290409 A again describes a Sputtering target from a mole craving, which contains 0.5 to 50 At% of a metal of the group of Ti, Zr, V, Nb and CR, whereby the oxygen contained in the target is arranged in the form of oxides in the boundary surface range Mo-rich phase/alloying element realm phase. The preferential manufacture method for it covers the steps mixing Mo-powder and powder of the alloying element, sinters, breaking the sintering to powder and consolidating in such a way produced powder by hot-isostatic pressing in the known condition. The oxides affect unfavorably the homogenization of the Sputtering target during hot-pressing, since the grain boundary diffusion speed is reduced. Besides the oxides affect unfavorably the sputtering behavior.

[0006] The JP 2013 83000 A describes the production of a Sputtering target from a mole craving, which contains 0.5 to 60 At% one or of several elements of the group of Ti, Nb and Ta, whereby Mo-powder with a hydride powder of the alloying element is mixed, this mixture with 300°C to 1.000qC is degassed and afterwards by hot-isostatic pressing consolidated. The hydride powder decomposes when degassing to the metallic powder, with further processing steps comes it however again to oxygen admission by adsorption at surfaces of the powder particles. This oxygen is not reduced when hot-isostatic pressing.

[0007] The descriptive Sputtering target does not fulfill the rising requirements in view to layer homogeneity, homogeneity of the sputtering behavior and avoidance of unwanted local melting on. Local one melting on are caused for example by Arc processes (local training of an arc).

[0008] With the descriptive manufacture technologies it is not possible to manufacture Sputtering target those the requirements described before fulfills from at least one of the following reasons:

[0009] a) of oxides obstruct the grain boundary diffusion;

[0010] b) an oxygen dismantling during the consolidation process is not possible;

[0011] c) the consolidation process does not lead to sufficient homogenization of the alloying elements;

[0012] d) Grenzflächenund grain boundary volume as well as defect density, which is jointly responsible for a sufficiently high rate of diffusion, are not sufficiently highly enough;

[0013] e) the consolidation process leads to an inadmissibly high Kornvergröberung;

[0014] f) the assigned powder leads to a coarse-grained Sputtering target.

[0015] It is ready task of the available invention a Sputtering target to place, which fulfills the requirements described before and/or which does not exhibit descriptive lack before. In particular it is ready task of the invention a Sputtering target to be placed, with that a very homogeneous layer, both in view to chemical composition, and layer thickness distribution be manufactured can and that to local melting on by Arc processes does not bend. Besides the Sputtering target is to exhibit an even sputtering behavior. By even sputtering behavior with the fact it is understood that the individual grains and/or the individual ranges of the Sputtering target with same speed can be cleared away, so that during the Sputtering process no relief structure within the range of the abgesputterten surface develops.

[0016] A further task of the available invention is the supply of a manufacture way, which permits in simple and process-constant way the manufacturing of a Sputtering to target, which exhibits the characteristics specified before.

[0017] The task is solved by the independent requirements. Special arrangement forms are descriptive in the Unteransprüchen.

[0018] The Sputtering target covers Mo and at least a metal of the group 5 of the periodic system. Group of 5 metals are Ta, Nb and V. the middle content cm at group 5 metal amounts to 5 to 15 At%, the Mo-content > 80 At%. The group the 5 metal is preferentially completely solved in the Mo, which affects an even sputtering behavior favorably. Under completely solved one understands with the fact that the content of group 5 metal, which elementarily (when Ta, Nb and/or V of grains) or as oxide is present, < 1 Vol,% amounts to. The Sputtering target exhibits a middle C/O (carbon/oxygen) relationship in (At%/At%) preferentially of > 1, > 1.2. For the determination of middle C/O of relationship Zentrumsund 3 edge samples are taken, analyzed from the Sputtering target 3 and computed the average value. Carbon is determined thereby by Verbrennungsanalyse (APPROX.), the oxygen by feed gas hot extraction (HE). In the following text is called the middle C/O relationship C/O relationship.

[0019] Group of 5 metals exercise in the solved condition a strongly mixed crystal-solidifying effect on Mo. With the Mischristallverfestigung accompanies a clear reduction of the ductility and the shaping ability. While two-phase (Mo-rich phase + group 5 metal rich phase) alloys can be processed in simpler and process-more constant way by shaping, since the group 5 metal exercises rich phase a duktilisierenden effect, this was not to date possible with very homogeneous mixed crystal alloys. By a C/an O relationship of > 1 is now ensured that the production can include a shaping step, while with a C/O relationship is not given with < 1 a process-safe manufacturing by shaping in sufficient measure. The reason for it lies probably in the fact justified that a C/an O relationship from > 1 to an increase of the grain boundary firmness leads, whereby Korngrenzenrisse can be avoided. How the shaping step positively affects the characteristics of the Sputtering target is described, in further consequence still in the detail. By a C/an O relationship in (At%/At%) from > 1 is now for the first time possible it to unite the positive effects of the alloy homogeneity and shaping texture in a product. Surprisingly a C/an O relationship of > 1 affects transformed Sputtering of target not only positively, but affected also in favorable way the sputtering behavior of only sintered or sintered and by hot-isostatic pressing consolidated Sputtering target. Hot-isostatic pressing effected thereby prefers without use of a can.

[0020] How a C/an O is process-constantly adjustable relationship of > 1 is described still exactly, in further consequence. The C/O relationship of > 1 makes the moreover one the attitude of a low oxygen content in the Sputtering for target possible. An oxygen content preferentially of < 0.04 At%, < 0.03 At%, in particular preferentially < 0.02 At% is realizable. Preferentially the Sputtering target is free from oxides. Unwanted Arc processes can be avoided thereby reliably. Freely about oxides it is to be understood in connection with this invention in such a way that during an investigation by means of scanning electron microscope with an enlargement of 1.000 x the number of detectable, oxidic particles is in a range from 0,01 mm2 < 1. Preferably the number of detectable, oxidic particles is < 1. in a range from 0,1 mm2.

[0021] The moreover one the Sputtering exhibits target prefers a shaping texture. A shaping texture develops like the name expresses with a shaping process. A shaping texture is lost to a Erholungsoder recrystallization annealing during a stored glow treatment, as for example. The Sputtering according to invention target can be present from there in a condition like-deformed, recovered, part-recrystallized or completely recrystallized. The shaping texture can be to due for example to a rolling, a Schmiedeoder extruding process. From the shaping process result grains, which are aligned to a large part with same or similar orientation to the surface of the Sputtering target. Thus the sputtering behavior becomes even, since the erosion rate depends on the orientation of the grains.

[0022] Favourably for an even sputtering erosion is also, if the shaping texture exhibits the following dominating orientations:

[0023] A. in shaping direction: 110

[0024] b. perpendicular to the shaping direction: at least an orientation of the group 100 and 111. [0025] During the shaping if the direction was changed, how this is possible with plattenförmigen geometry, the direction is to be understood as shaping direction, in which more strongly (with higher strain) was deformed. Under dominating orientation with highest intensity is understood. Typically the intensity is larger thereby than the 1,5-fache, prefers two-way of the underground intensity.

[0026] The shaping texture becomes by means of SEM (Scanning electron microscope/scanning electron microscope) and EBSD (Electron more backscatter diffraction/backscattering electron diffraction) determines. The sample is built in addition in an angle of 70°. The incident initiating electron jet is strewn inelastically at the atoms of the sample. If now some electrons meet in such a way on lattice surfaces that the Bragg condition is fulfilled, then it comes to constructional interference. This reinforcement happens now for all lattice surfaces in the crystal, so that the developing diffraction pattern (English: electron more backscatter pattern, also Kikuchi Pattern) all angle relations in the crystal and thus also the crystal symmetry contains. The measurement is accomplished thereby under the following conditions:

[0027] - accelerating voltage: 20 kV,

[0028] - screen 120 μm,

[0029] - work distance 22 mm

[0030] - high current mode - activated

[0031] - scanned surface: 1761 x 2643 μm2.

[0032] - index step size: 3 μm.

[0033] The preferential density of the Sputtering target, related to the theoretical density of the respective composition, amounts to > 88% in the only sintered condition, > 96% in the sintered and hot-isostatically consolidated condition and > 99.5%, preferentially > 99.9% in the transformed condition. Also the high density in connection with the low oxygen content ensures a Arc free sputtering.

[0034] Further it is favourable, if the d50 and the d90 value of the particle size distribution, transverse to the last shaping direction measured, which fulfills the following relationship: d90/d50 ≤ 5.

[0035] Preferentially d90/d50 is < 3, particularly preferential < 1,5.

[0036] For grain size regulation a transverse cross section is made and the grain boundaries by means of EBSD is made visible. The evaluation of the middle and maximum grain size takes place then via quantitative metallography. The evaluation takes place thereby including the ASTM E 2627-10. A grain boundary is defined in such a way with the fact that the orientation difference between two neighbouring grains is > 5°. The particle size distribution with d90 and d50 value is determined by means of quantitative Bildauswertung. It was shown that a close particle size distribution has a very positive influence on the homogeneity of the sputtering behavior. Contrary to other materials, more strongly off, than grains with a smaller grain diameter at Mo-group of 5 Sputtering targets of grains with a larger grain diameter sputter to metal. The cause for it is not clear yet, can be to due however to different defect density or also a Channelling effect (lattice steering/channeling effect - penetration of an ion due to linear ranges without lattice atoms). With the d90/d50 mentioned before relationship can do this unfavorable would unequal-measure sputtering behavior to be almost prevented.

[0037] The group the 5 metal is not only complete, but also in extraordinary way distributes evenly solved in Mo. The standard deviation σ the group 5 metal distribution measured by SEM/WDX fulfilled thereby prefers the relationship

σ < CMx 0.15, particularly prefers σ < CMx 0,1.

[0038] Since the sputtering rate depends on the respective alloying element content, a Sputtering target with a very homogeneous group 5 metal distribution exhibits an extremely even sputtering behavior in accordance with the invention. This even sputtering behavior causes on the one hand that the manufactured layers exhibit an extremely homogeneous thickness distribution, on the other hand that the Sputtering target exhibits still small Oberflächenrauigkeit/relief formation even after longer employment. This is again a condition for the fact that the sputtering behavior is even during a long period.

[0039] The moreover one is in preferential way the group 5 the metal Ta and/or Nb. Mo-Ta and Mo-Nb alloys exhibit particularly favorable Korrosionsund corroding behavior. The alloy exists in favourable way of Mo and 5 to 15 At% group 5 metal and typical impurities. By typical impurities one understands both impurities, which are to be usually already found in the raw materials or due to the manufacture process are.

[0040] In particularly favourable way a Sputtering target is in accordance with the invention as tubing target. It was shown that on the usual sputtering conditions for tubing targets of structure characteristics as for example oxides, homogeneity or the relationship of the middle to the maximum grain size a stronger influence to exercise, than this is with flat targets the case.

[0041] The Sputtering according to invention target can be manufactured in particularly simple and process-constant way, if the procedure covers the following steps:

[0042] - production of a powder substance comprehensively:

[0043] of ith > 80 At% Mo-powders;

[0044] iith powders at least a group 5 of metal, whereby the content of group amounts to 5 metal in the powder substance 5 to 15 At℅; and

[0045] iii. a C-source, whereby the C-quantity is so selected that in the powder substance the total content of C Σc in At℅ and the total content of O Σo in At℅ fulfill the following relationship: 0,2 < Σc/Σo ≤ 1,2; and

[0046] - consolidation of the powder substance.

[0047] By a Σc/a Σo relationship within the range of 0,2 to 1.2 is ensured that in the Sputtering target a C/an O relationship of > 1 can be stopped. The oxygen dismantling during further process steps effected prefers by reaction of the oxygen with carbon and hydrogen.

[0048] The total content Σo at oxygen in the powder substance covers thereby the oxygen content in the Mo-powder and the oxygen content in group 5 metal. The oxygen is present mainly in adsorbent form at the surface of the powder particles. With usual production and storage that is appropriate for oxygen content in the Mo-powder with a particle size after Fisher from 2 to 7 μm typically with 0,1 to 0.4 At℅. At group for 5 metals with a particle size of 4 to 20, measured after Fisher, μm that is appropriate for oxygen content typically with 0,3 to 3 At℅. The total content Σc at carbon covers the carbon content in the Mo-powder, the carbon content in group 5 the metal and the carbon content of the C-source. Source of carbon can be thereby for example soot, activated charcoal or graphitic powder. It can be however also a carbon-setting free connection, as for example Nb-carbide or Mo-carbide.

[0049] It is determined first with usual procedures Sauerstoffund carbon content of the assigned powders and determined then the necessary quantity of powders of the C-source. The powders are then mixed and consolidated by means of usual procedures. By consolidation procedures are understood, which lead to a compression. Preferred the consolidation takes place via cold-ISO-static pressing and sinters. By sinters procedures are understood with which the compression is to be attributed only to thermal effect and not to pressure (like this for example when hot-isostatic pressing the case is).

[0050] During a thermal treatment, preferentially during the sinter process, the carbon of source of carbon with the oxygen existing in the powder moves to C02 and to a smaller portion to CO. This conversion effected prefers at temperatures, where the sintering exhibits still open porosity. Compression processes, with which the material which can be consolidated is in a can, how this is for example when hot-isostatic pressing the case, is suitable less, in order to use the procedure according to invention favourably. If hot-isostatic pressing with can is accomplished, the inventive powder substance of a separate glowing/degassing treatment is to be submitted.

[0051] In preferential way the total carbon content Σc fulfills and the total oxygen contents Σo in the powder the following relationship:

≤ 1.1, particularly 0.6 < Σc/Σo prefers 0,4 < Σc/Σo ≤ 1 ■

[0052] Thus in particular a very high process security can be obtained.

[0053] The Pressvorgang takes place favourably with pressures from 100 to 500 MPa. The pressure does not amount to < 100 MPa can when sintering sufficient density be obtained. Pressures of > 500 MPa lead to the fact that during the sinter process, which are not removed from the reaction by carbon and oxygen developing connections sufficiently fast from the sintering, since the gas permeability is too low. Preferred the Sintertemperatur between 1.800 and 2.500qC amounts to. Temperatures under 1.800°C lead too much long sinter times and/or not sufficient density and homogeneity. Temperatures over 2.500 °C lead to grain growth, whereby the favourable homogeneity of the particle size distribution is affected unfavorably.

[0054] The favourable particle size of the Mo-powder amounts to 2 to 7 μm and those the group 5 of the metallic powder 4 to 20 μm. The particle size is determined thereby with the help of the Fisher method. The particle size the group 5 of the metal amounts to > 20 μm bends the alloy with employment of a pressure-free compression process strengthened to the formation of Kirkendall pores. The powder grain size the group 5 of the metal amounts to < 4 μm is that oxygen content (at the surface of the powder particles adsorbent oxygen) too high and the favourable, low oxygen values can only by expensive production steps, like special degassing steps, be reached.

[0055] If the particle size of the Mo-powder exceeds 7 μm, this leads to a decreased sinter activity. If the particle size is below 2 μm, the gas permeability is clearly worsened in the Grünling. Also the Grünling begins to already sinter at lower temperatures. Both effects lead to a worsened oxygen dismantling during the sinter process.

[0056] In preferential way the powder substance does not contain further alloying elements except Mo, group 5 metal and source of carbon. Impurities are present in an extent, as this is typical for these materials.

[0057] If further alloying elements are used, their total content may not exceed 15 At%. Thereby alloying elements which do not affect Sputterund corroding behavior unfavorably, work satisfactorily. As suitable alloy metals for example W and Ti are to be called.

[0058] Sintering is accomplished in favourable way in vacuum, an inert atmosphere and/or a reducing atmosphere. By inert atmosphere thereby a gaseous medium is to be understood, not with the alloy components reacts, as for example a noble gas. As reducing atmosphere in particular hydrogen is suitable. In favourable way the conversion is accomplished by C and O to C02 and/or CO in the vacuum or in an inert atmosphere, for example during the heating process. Thus the developing reaction products can be exhausted efficiently. Besides the education is avoided by hydrides of the group of 5 metals. The finished sinters effected then preferentially at least occasionally in a reducing atmosphere, prefers under hydrogen.

[0059] After the consolidation effected a shaping process prefers. Transforming can take place for example with flat targets via rollers, with tubing targets via extrusion or smithies. The preferential strain amounts to 45 to 90%. The strain is as follows defined thereby:

(Aa - outer ones)/Aa x 100 (in %)

Aa… cross-section area before shaping

Outer one… Cross-section area after shaping

[0060] With strains < 45% are affected unfavorably the density and uniformity of the sputtering behavior. Strains > 90% affect the production costs unfavorably. The transformation temperature amounts to preferentially at least occasional 900°C to 1.500qC. Under occasional with the fact it is understood that for example the first shaping steps are accomplished at this temperature. Afterwards the transformation temperature can amount to also under 900 `Q. The shaping can be accomplished thereby both in a step and in several steps.

[0061] If the Sputtering target is implemented as flat target, this is preferably soldered with a backing plate. Tubing targets can be connected with a supporting tube, be found preferably again by a soldering process, or as monolithic Sputtering target use. As soldering material prefers Indium or Indium realms an alloy used.

[0062] In the following the invention is exemplary explained on the basis of a manufacture example.

[0063] Figure 1 shows a SEM admission with WDX Scan of rolled Mo-10At℅ Nb.

[0064] In addition the following powders were used:

[0065] - Mo-powders with a Fisher particle size of 4,5 μm, an oxygen content of 0,24 At% and a carbon content of 0,03 At%

[0066] - Nb-powders with a Fisher particle size of 8 μm, an oxygen content of 1,26 At% and a carbon content of 0,46 At%

[0067] In order to obtain a Σc/a Σo value of 0,7 with a Mo-quantity required of 758 kg and a Nb-quantity required from 81,6 kg to, 0.336 kg of soot powder were blended with a Fisher grain size of 0,35 μm with the Mo and Nb powder in a mixer. Of this powder substance 4 plates were made by cold-ISO-static pressing with a pressing power by 180 MPa. The plates were sintered at a temperature of 2.150qC, whereby up to a temperature of 1,200°C the heating process took place by means of 3 hours in vacuum. Afterwards H2 was used as process gas. The sintered body exhibited a density of 8,9 g/cm3 (88.6% of the theoretical density), a C-content of 0,022 at% and a CO-content of 0,018 at%. C/O relationship amounted to 1,22.

[0068] The sintering was submitted of a SEM/a EDX investigation. Nb and Mo are completely into one another solved. No oxides could be detected.

[0069] Afterwards the sintering was rolled, whereby the transformation temperature amounted to 1450°C and the strain 78%. Out of the rolled plate a sample was taken and polished by means of usual metallographic procedures polished and. Assistance of SEM/EBSD the texture was determined by a longitudinal specimen.

[0070] In addition the following attitudes were used:

[0071] - accelerating voltage: 20 KV,

[0072] - work distance: 22 mm,

[0073] - high current mode activates,

[0074] - screen 120 μm

[0075] - scanned surface 1,761 x 2,643 μm2

[0076] - index step size 3 μm.

[0077] The evaluation of the inverse Polfigur resulted in the case of it in longitudinal direction (shaping direction) 110 as dominating texture with > 2 x underground. In normal direction (perpendicular to the shaping direction) both the 100 and the 111 orientation with > 2 x underground was measured.

[0078] Into a transverse cross section by means of EBSD the grain size was determined. As grain boundaries thereby all grain orientation differences between two neighbouring grains were defined of > 5°. The particle size distribution was determined assistance of quantitative image analysis. The d50 value within an evaluation range of 20.000 μm2 amounted to thereby 15 μm, the d90 value 35 μm. Dgo/d5o relationship amounted to 2,3. This measurement was determined in 10 further places in similar way and a middle d90/d5o relationship was determined. This amounted to 2,41. Also the rolled plate was examined by means of SEM/EDX and SEM/WDX for the homogeneity of the Nb-distribution. Figure 1 shows a WDXScan over a distance of 1 mm. Over this distance the standard deviation of the Nb-distribution of 1.02 At% amounted to measured.

[0079] The sputtering behavior of so manufactured Sputtering target became by sputtering attempts with acre (argon) - pressures within the range of 2,5 x 103 to 1 x 10 "² mbar and an output of 400 and/or 800 Watts determines. As substrate material Kalknatronglas was used. The Sputtering target let itself sputter without the occurrence of Arc processes. The specific electrical resistance of the solitary layers (Schichtdicke= 200 Nm) was low, as a function of the sputtering conditions at 13,7 to μΩcm. The layers exhibited compression stresses, within the range -1,400 bis-850 MPa.