KR20190042597A - A sputtering target - Google Patents

Abstract

A sputtering target is known for producing a light absorbing layer comprising a target material containing an oxide phase and having a reduced oxygen content as compared to a stoichiometric composition. On the basis of such a sputtering target, in order to provide a sputtering target containing an electrically conductive phase and avoiding charge and particle formation, it is preferable that the target material contains a metal phase consisting of molybdenum (Mo-phase) , And the oxide phase contains zinc oxide (ZnO-phase) and a mixed oxide phase having the formula MNO _nx , where M represents zinc (Zn), which is a major component, and N represents niobium (Nb) And / or titanium (Ti), where x is greater than 0 and n indicates the number of oxygen atoms in the stoichiometric composition on the mixed oxide.

Description

A sputtering target

The present invention relates to a sputtering target for producing a light absorbing layer comprising a target material containing an oxide phase and having a reduced oxygen content as compared to a stoichiometric composition.

The light absorbing layer is used as a so-called " black matrix layer " for covering a conductor path of a liquid crystal display, for example, as a single layer or a layer system for absorbing heat in solar thermal applications.

Such a layer or layer system is fabricated by depositing successive layers, for example by cathode spraying (sputtering). In this case, a solid, that is, a compound or valence composed of a sputtering target is dissolved or converted into a gaseous phase by impact using energy-rich ions (typically rare gas ions). Atoms or molecules in the gaseous state are finally deposited on the substrate by condensation near the sputtering target to form a layer there.

In the case of a solar absorbing layer, the layer structure typically includes at least one cermet layer and a metal closure layer underlying it and used as an optional reflector. The conductive or metallic particles embedded in the cermet layer typically have a diameter of 5 to 30 nm.

The " cermet layer system " used in a liquid crystal display also often has an absorbing layer in which a region made of a metal is embedded in an oxide matrix.

To economically sputter a layer of high quality, "DC voltage sputtering" or "DC sputtering" (direct current sputtering) is provided. In this case, a DC voltage is applied between the anode and the anode (often the plant housing) connected as the cathode. A low pressure plasma is formed in the evacuated gas chamber by impact ionization of inert gas atoms and the positive charge component of the low pressure plasma is accelerated in a direction toward the target as a permanent particulate flow by the applied DC voltage, In this case, the fine particles are protruded out from the target, and the fine particles move again in the direction toward the substrate, where they are deposited as layers. DC sputtering requires an electrically conductive target material because otherwise the target will be charged due to the permanent flow of the electrically charged particulate, thereby compensating for the DC voltage field. This also applies to technically related MF-sputtering, in which two sputtering targets are alternately switched as cathodes and anodes in kHz-rhythms.

The final structuring of the layer is generally accomplished by a wet etch process or a dry etch process. However, the cermet layer system is difficult to etch because the oxide and buried metal particles require different etchants. Hence, a layer structure that exhibits high absorption and low reflectance in the visible spectral range, but which can be uniformly etched using a simple dilute acid without the formation of toxic substances and without particle residues, is desirable.

For this purpose, the patent literature provides a different approach. DE 10 2012 112 739 A1 and DE 10 2012 112 742 A1 propose cermet layers containing refractory metals and their oxides. DE 10 201 103 679 A1 describes a particularly preferred solution based on zinc oxide and niobium oxide with buried metal particles consisting of oxygen and molybdenum in sub stoichiometric amounts. In this case, the proportion of metallic molybdenum lies in the range of 25 to 50 wt.%, Which corresponds to a volume fraction of metallic Mo-phase generally less than 30%, depending on the density of the remaining layer constituents.

The distribution of the same type of oxides and metal particles in the target material, for example molybdenum, is proved to be difficult, especially when the particle sizes of the alloying elements are different. However, a uniform distribution is very important for a stable sputtering process, especially when the conductivity of individual phases or components is poor, such as in many oxides.

In addition, by the known solution approach, the desired electrical conductivity of the target material can not be reproducibly ensured. The reason for this is that sufficient electrical conductivity can mostly only be achieved through a continuous metal phase, such as a molybdenum phase. At least the required volume fraction of the conductivity is at least 30%, because otherwise the percolation network can not be formed. Such a minimum fraction applies to typical dimensions of the metal phase region or conductive particles; The smaller the dimension, the higher the minimum fraction.

One solution provides the use of electrical conductivity of the reduced oxide phase, as described in EP 0 852 266 A1. The sputtering target is made of a material containing a metal oxide having the formula MO _x wherein M is a metal selected from the group of Ti, Nb, Ta, Mo, W, Zr and Hf. For the target materials TiO ₂ and Nb ₂ O ₅ , the desired electrical conductivity is reached by reducing the oxygen content for the complete-stoichiometric oxide. X = 1.93 for TiO ₂ and 4.996 < x < 4.93 for Nb ₂ O ₅ , where x defines the degree of oxygen deficiency and the electrical conductivity . The target material may contain a complete-oxidizable additive of an oxide of Cr, Ce, Y, Si, Al and B. The result is a non-conductive phase in an electrically conductive matrix consisting of molybdenum and reduced Nb ₂ O ₅ or TiO ₂ . Thus, the target material is electrically conductive in the context of a percolation network.

WO 2016/026590 A1, in which a conventional sputtering target is known, comprises a target material containing tin, zinc, indium, or a mixture of these materials in the form of oxides or substoichiometric oxides and molybdenum, tungsten or an alloy of these materials &Lt; RTI ID = 0.0 &gt; a &lt; / RTI &gt; sputtering target. Complementary thereto, the target material may comprise a metal selected from the group consisting of niobium, hafnium, titanium, tantalum, vanadium, yttrium, zirconium, aluminum, and mixtures of these materials present as oxides or sub stoichiometric oxides .

However, it has been found that the simultaneous presence of electrically conductive and electrically insulating phases is not desirable for the sputtering process. The electrically insulating phase causes charged and uncontrolled discharges (also referred to in the literature as " arcing "). Arcing can cause staining through local melting, which negatively affects the properties of the deposited layer. Furthermore, arcing can cause local overheating of the sputtering target and associated local voltage spikes, which can lead to cracking and particle formation, and even destruction of the sputtering target.

Therefore, an object of the present invention is to provide a sputtering target containing an electrically conductive phase, which can be treated mechanically well, and avoids charge and particle formation.

This object is achieved by starting from a sputtering target of the type mentioned in the preamble, in which the target material comprises a molybdenum-containing metal phase ((Mo-phase)) and zinc oxide (ZnO- is solved by containing the mixed oxides having the MNO _nx, in this case M represents a zinc (Zn) main components, N denotes at least one of a secondary component, niobium (Nb) and / or titanium (Ti), the Where x is greater than 0 and n indicates the number of oxygen atoms in the stoichiometric composition on the mixed oxide.

The target material according to the present invention contains a metallic Mo-phase, a phase consisting of ZnO and a mixed oxide phase having a substoichiometric oxygen content. All of these phases exhibit unique electrical properties. The Mo-phase is metal-conductive, ZnO is a II-VI-semiconductor with a large band gap, and the mixed oxide phase is electrically conductive due to the oxygen deficiency point. The electrical conductivity on the mixed oxide depends on the degree of sub-stoichiometry of this phase, i. Near stoichiometry, the fact that the larger x is, the higher the electrical conductivity is. As the mixed oxide phase MNO _nx is oxidizing, the result is always less than 1 for x.

The mixed oxide phase is composed of one or more auxiliary components containing zinc, and niobium and / or titanium. The co-existence of the auxiliary component and the metallic Mo- phase combined with zinc tends to induce substoichiometry and has been found to cause sufficient electrical conductivity of the target material.

In addition, it has been found that molybdenum made of a metallic Mo-phase can diffuse into the phase of ZnO, resulting in an electrically excellent conductivity in the presence of ZnO-phase metallic molybdenum.

Therefore, the target material according to the present invention widely avoids the simultaneous presence of the electrically conductive phase and the electrically insulating phase. Thus, electrostatic charging of the electrical insulating phase during DC-sputtering or MC-sputtering is avoided, thereby avoiding uncontrolled discharging and local melting. This situation arises at low arcing rates when using the sputtering target according to the invention to create one layer, in a small number of molten smudges and in the possibility of low cracking.

With respect to the high electrical conductivity, the mixed oxide phase preferably consists of Zn ₃ Nb ₂ O _8-x and / or Zn ₂ TiO _4-x and / or ZnNb ₂ O _6-x .

The degree of reduction typically and preferably present on the mixed oxide is defined by the oxygen content of 80 to 95% of the maximum theoretically possible maximum oxygen content, but may be placed further below; Accordingly, in the empirical formula, x represents a value of 5 to 20% (based on the stoichiometric oxygen content).

In particularly preferred embodiments of the sputtering target such as to form a region of a size having a maximum area of 200 ㎛ ² is less than 300 ㎛ ² in the mixed oxide different cross-section, preferably in a desired manner in the target material.

The smaller the phase area, the less the risk of electrostatic charge. The mixed oxide phase generally results in sintering activity which is formed during the production of the target material, especially during compression at high temperatures, thereby positively affecting the compression of the target material. The smaller the particles of the starting material of the target production, the smaller the phase area can be reached. The short diffusion path contributes to faster and complete conversion to the desired mixed oxide phase and rapid compaction of the target material. At high temperatures and long periods of processing, undesirable coarsening of the phase region may occur.

Particularly in this regard, the ZnO-phase in the target material also preferably forms an image area of dimensions with a maximum area of less than 100 [mu] m &lt; ² &gt; The phase region of the ZnO-phase is particularly suitable when the ZnO-phase forms a maximum transverse dimension of less than 10 [mu] m, preferably less than 5 [mu] m.

The etch rate of the light absorbing layer is determined by the ratio of ZnO / Nb ₂ O ₅ or ZnO / TiO ₂ substantially as predetermined in the target material. Particularly in this regard, the volume fraction of ZnO-phase in the target material lies preferably in the range of 20 to 85%.

Molybdenum is present in the form of metal in the target material. For a thermodynamic reason, it can be assumed that a predetermined proportion is oxidized and exists, for example, as stoichiometric MoO _3-x . Regardless, the metallic Mo-phase is responsible for the absorption of the deposited layer as well as the degree of blackening in addition to the sub-stoichiometric oxide.

Particularly in this connection, it has been proved desirable to have a Mo-phase volume fraction within the range of 10 to 30% in the target material.

Furthermore, it has been found to be particularly advantageous if a volume fraction of more than 50% of the Mo- phase is embedded in the ZnO-phase.

The phase region of the metallic Mo surrounding the ZnO-phase has a positive influence on the structure of the target material due to the ductility of the metal and reduces the occurrence of mechanical stresses or cracks.

In particularly preferred embodiments of the sputtering target, the volume fraction of mixed oxide phase is at least 7%, preferably in the range of from 7 to 60%.

At a volume fraction of less than 7%, the electrical conductivity on the mixed oxide is created, and when the compression process is accelerated, the action of the mixed oxide phase is scarcely noticeable, making it difficult to manufacture a crack-free sputtering target without particle generation . If the volume fraction is greater than 60%, the above-described desirable effects of metallic Mo-phase and ZnO- are deemed less important.

In one preferred embodiment of the sputtering target, the volume fraction of the mixed oxide phase of Zn ₃ Nb ₂ O _{8 -x} in the target material lies in the range of 7 to 60%, where x> 0.6.

In another preferred embodiment of the sputtering target, the volume fraction of the mixed oxide phase of ZnNb ₂ O _6-x in the target material lies in the range of 0-10%, where x> 0.3.

In another preferred embodiment of the sputtering target, the volume fraction of the mixed oxide phase of Zn ₂ TiO _4-x in the target material lies in the range of 5 to 60%, in which case x> 0.2.

The mixed oxide phase of the sputtering target according to the present invention contains two or more components; This mixed oxide phase is at least binary. This, and in combination with the Mo-phase, ensures the desired electrical conductivity of the target material which leads to the desired effect described above in connection with less arcing and which leads to less particle formation of the target material and less cracking potential. The ratio of singlets does not show the same effect in some sub stoichiometries. Thus, the target material does not contain a singular phase having the formula NO _n in a preferred manner, where N is one of the auxiliary components niobium (Nb) and / or titanium (Ti) It is a number indicating the stoichiometric oxygen content of the individual phase. Or the target material contains the phases only in volume fractions of less than 10% each.

Particularly preferably, the target material contains a singular niobium oxide phase consisting of NbO ₂ or Nb ₂ O ₅ and a singular number of titanium oxide phases in the form of TiO ₂ or TiO in a total volume fraction of less than 10%.

If present, the dimension of the image area with a single image of the formula NO _n is preferably as small as possible, preferably said dimension represents a dimension in the cross-section having a maximum area of less than 100 μm ² .

Hence, in a particularly preferred embodiment, the sputtering target comprises 3 to 50 volume-% of a single oxide of 13 to 30 volume-% Mo, the formula being NO _n (in this case, N = niobium and / or titanium) And the remaining ZnO.

With respect to high electrical conductivity, it has proven useful when the Mo-phase is as finely distributed as possible in the target material and forms an image area with a maximum transverse dimension of less than 25 [mu] m.

In addition to the material composition, the grain size of the crystal structure has also been demonstrated as another critical factor in relation to the tendency to crack formation. The finer the structure, the smaller the grain size of the crystal structure. Therefore, in the case of the sputtering target according to the present invention, the target material preferably has a crystal structure having an average crystallite size of less than 200 nm.

The target material typically has a degree of reduction defined by a density of at least 95% of the theoretical density and an oxygen content of 30 to 70% of the theoretically maximum possible oxygen content. The target material has a homogeneous composition of the components forming the target material, in the sense that the composition of the five samples of 1 g each has a standard deviation of less than 5% of the respective materials. The degree of reduction is homogeneous in the sense that the degree of reduction of 5 samples of 1 g each has a standard deviation of reduction degree of less than 5%.

Definition and measurement method

Structure survey and area size

In order to investigate the microstructure, a piece of the sputtering target was embedded in an epoxy resin in a vacuum state, ground, and polished. The polished sections were processed in eight grinding steps (120, 320, 500, 800, 1200, 1500, 2400 and 4000) at 200 rpm on a Struers wet polishing machine Labo-Pol- (Diamond polishing paste Two-in-One) on a LaboPol-5 (at 250 rpm) until a fineness of 1 [mu] m was reached in one gloss process. Microscopic observation of the samples was performed on a scanning electron microscope Zeiss Ultra 55 and the composition was quantified using EDX Oxford Inka FET X3.

The area size of the image was determined by measuring the individual maximum horizontal length and vertical length in the REM. Area size was obtained by multiplying two maxima. The maximum value was determined from 40 individual areas.

Average particle size

The average particle size (M) was determined according to the following equation (DIN EN ISO 643).

M = (L ^* p) / (N ^* m) (1),

here L: Length of measuring line

p: the number of the measurement line

N: Number of cutting body

m: Scale

These values were determined at three different measurement points. An arithmetic mean is then formed from this.

Phase analysis and determination of percentage

The ground sample was inserted into the sample carrier while avoiding tissue formation using an agate mortar and measured in a transmission state using Stadi P, an X-ray-2-circular-powder diffraction system from Stoe & Cie. Linear Position Sensitive Detector (LPSD) with a range of 6.60 ° is used and is measured with a step width of 0.010 ° in the second-order measurement range (3,000 ° to 79,990 °). The measurement period is 240 seconds in the step of 0.55 (20 seconds / step), and the whole measurement lasts 6.47 hours. The work is done with Cu-K-a-1 radiation (= 1.54056 Angstroms). The generator used operates with a voltage of 40 kV and a current intensity of 30 mA. Adjustments and corrections of the diffractometer are made according to NIST-standard Si (640 d).

The X-ray diffraction diagram was evaluated using a quantitative phase analysis program: Rietveld SiroQuant, Version V4.0, whereby the relative fraction of the phase was determined from the linear intensity and the theoretical density And the volume was converted into a volume percentage.

Determination of crystallite size

The diffraction pattern obtained from the phase analysis was mathematically adjusted using the Stoe-program: Pattern-Fitting and the FWHM of the reflection (peak-half width) was determined. From the FWHM, the crystallite size was calculated using the Scherrer equation (Rietveld-method), and in relation to this, "Power diffraction, theory and practice" (R. Dinnebier and S. Billing, RSC Publishing, ed. Royal Soc. London 2008, ISBN 978-0-85404-231-9, in Chp. 13 (" Lattice defects and domain size effects ") p. The measurements obtained were calibrated against the device standard LaB6 NIST (660 b).

Density determination

Density was determined by buoyancy in water (according to the method of Archimedes). For this purpose, the sample was weighed using Mettler Toldedo's balance SB23001 DeltaRange. The weight of the sample in water was then determined. By measuring the wet sample freshly, the water absorbed by the sample was measured. To calculate the sample density, the density of water at 22.5 [deg.] C was assumed to be 0.99791 g / cm &lt; ^{3 &} gt ;. The density was calculated according to the following formula (weight expressed in g):

The Archimedes density and the index of 100% density represent the density of the body as a percentage.

anoxia

It is impossible to measure oxygen deficiency by oxidizing the material and then assigning a mass increase to the oxygen deficiency. The cause is the evaporation tendency of molybdenum as MoO _3, which distorts the mass balance.

Therefore, the oxygen deficiency was semi-quantitatively determined using EDX. In this case, the oxygen content was measured in Nb ₂ O ₅ samples at 10 points. As averages, at the theoretical values of 71.4 atomic-% O and 28.6 atomic-% Nb, 70.8 atoms-% +/- 1.1 were shown for oxygen and 29.2 atoms-% +/- 1.0 for niobium. Furthermore, the measurement accuracy of +/- 5% for the oxygen resulting from the device is relatively taken into account. Only if the theoretical oxygen fraction of the nominal phase composition is relatively less than 5%, ie if the oxygen is less than 67.83 atom%, the theoretical oxygen fraction of the nominal phase composition for Nb ₂ O ₅ is less than 5% Correspondingly, the phase was referred to as the oxygen deficiency. Correspondingly, the results are only considered within the yes-no category.

The present invention is described in more detail below with reference to patent drawings and one embodiment. in detail:
1 shows an electron microscope photograph of one end face of the target material in the first embodiment (Example 1)
Figure 2 shows an X-ray diffraction diagram of the target material of Figure 1,
3 shows an electron micrograph of one section of the target material in the second embodiment (Example 2)
Figure 4 shows an electron micrograph of a cross section of a third embodiment of the target material (Example 3)
Figure 5 shows an X-ray diffraction diagram of the target material of Figure 4,
Figure 6 shows an electron micrograph of a cross section in one embodiment of the target material according to Example 4,
Figure 7 shows an X-ray diffraction diagram of the target material of Figure 6,
Figure 8 shows an electron micrograph of a cross section in one embodiment (Example 5) of the target material, and
Figure 9 shows an X-ray diffraction diagram of the target material of Figure 8;

Example 1: 36 vol% Nb ₂ O ₅  And a sputtering target made of ZnO containing 18 vol% -molybdenum

ZnO, Nb ₂ O ₅ and molybdenum, each having a purity of 99.95%, were provided inside the mixing vessel in an amount corresponding to the nominal final composition. Like Nb ₂ O ₅ , ZnO was also a sub-micron powder, and molybdenum had a maximum particle size of less than 25 μm. A total of 210 g of powder batch was homogenized with 500 g of ZrO ₂ -mixed balls in a 1 hour milling and mixing process. The pulverized powder was passed through a sieve having a mesh width of 250 mu m to separate it from the grinding balls. 200 g of homogeneously blended and ground powder having the composition of Example 1 was inserted into an axial graphite-compression mold having an internal diameter of 75 mm and pre-compressed axially at 7 MPa at room temperature. The hot compression in the axial direction was carried out at a temperature of 1175 DEG C and in an inert atmosphere of 1000 mbar argon with a stamping pressure of 35 MPa.

The high temperature compacted disc has a weight of 198.9 g, which corresponds to an absolute density (relative density: greater than 99%) of 6.03 g / cm ³ and 99% or more of the initial weight.

Figure 1 shows one polished section of the sample in the REM. The phase assignment is made by balancing the X-ray diffraction and the EDX shown in Fig.

Figure 2 shows that the sintered sample shown in Example 1 is substantially composed of the three phases quantified in Table 2, namely Mo, ZnO and Nb ₂ Zn ₃ O ₈ . Phase are assigned in the scanning electron image: # A1 is Nb ₂ Zn ₃ O ₈ corresponds to, and # A2 corresponds to ZnO, the spherical fine particles of a white molybdenum.

The measurement result of the particle size of ZnO shows an average value of 1.3 탆, and none of the ZnO-phase regions is larger than 10 탆. The detectable coarse ZnO-region consists in part in a plurality of discrete phase regions. The maximum continuous area of the ZnO-phase region is less than 100 占 퐉 ² . It also contains a ZnO-region formed from a plurality of continuous ZnO-particles and agglomerated.

The binary oxide phase, Nb ₂ Zn ₃ O _8, has an average particle size of 4.5 μm, which in this case is also noticeably larger than the area of 200 μm ² , which is composed of continuous individual particles have.

The theoretical oxygen content of Nb ₂ Zn ₃ O ₈ , an oxide phase of 61.5 atomic%, was less than 5% at the measured 55.3 atomic%. Thus, this phase is depleted in oxygen by definition and thus has electrical conductivity.

Example 2: 28 parts by volume of Nb ₂ O ₅  And a sputtering target made of ZnO containing 16 vol-% molybdenum

The raw materials ZnO, Nb ₂ O ₅ and molybdenum were weighed according to Example 1. A total of 150 g of powder was placed in a micronization tool of Eirich for 30 minutes of concentration-mixing. The homogenized powder was inserted into a CIP mold made of silicon and compressed isotropically at 200 MPa. The relative density of the extrudate was 63%. The compressed extrudate was filled into graphite-coated steel cans and degassed at 400 ° C for 2 hours. The shaped body and the steel can were separated by a graphite layer and an Al ₂ O ₃ - separating layer approximately 1 cm thick. After the can was welded, it was pressurized at 150 MPa and 960 DEG C with high temperature isotropy. After separation from the mold, the resulting body has a density of 99% of the theoretical density.

Figure 3 shows one polished section of the sample in the REM. The phase assignment is made according to EDX as in Example 1. [ Images in the scanned electronic image can be assigned: # A1 corresponds to molybdenum, # A2 corresponds to Nb ₂ Zn ₃ O ₈ , and # A3 corresponds to ZnO.

The result of measuring the size of the ZnO-phase region shows an average value of 4.3 탆, but there is no larger than 10 탆 at all. Clearly there are successive larger ranges of up to 100 μm ² consisting of individual particulates. It is notable that the molybdenum particles are preferably embedded in the ZnO-phase region. The binary oxide phase, Nb ₂ Zn ₃ O ₈ , exhibits an average particle size of 4.2 μm, and here again the larger image area of up to 200 μm ² is apparently composed of individual particles, but only an apparently continuous area.

The theoretical oxygen value of the 61.5 atom-% phase was less than 5% by the measured 55.4 atom-%. Therefore, this phase is depleted in oxygen.

Example 3: 16 volume% TiO ₂  And a sputtering target made of ZnO containing 16 vol-% molybdenum

Unlike Example 1, the fraction of Nb ₂ O ₅ was replaced by TiO ₂ . Like TiO ₂ , ZnO was also a sub-micron powder and the molybdenum-raw material had a maximum particle size of less than 25 μm. The raw material having a purity of 99.95% was provided in the grinding vessel in an amount corresponding to the nominal final composition according to Example 1 and homogenized with 500 g of ZrO ₂ -grinding balls in a 1 hour milling and mixing process. The pulverized powder was passed through a sieve having a mesh width of 250 mu m to separate it from the grinding balls. 190.0 g of homogeneously blended and ground powder having the composition of Example 3 was inserted into an axial graphite-compression mold having an inner diameter of 75 mm and pre-compressed axially at 7 MPa at room temperature. The hot compression in the axial direction was carried out at a temperature of 1140 DEG C and in an inert atmosphere of 1000 mbar argon with a stamping pressure of 35 MPa. High temperature compacted discs have densities in excess of 99%.

Figure 4 shows one polished section of the sample in the REM. The allocation is made, and by reference to the analysis of Figure 5 in accordance with the EDX. In the scanned electronic image, the following images can be assigned: # A1 corresponds to molybdenum, # A2 corresponds to ZnO, and # A3 corresponds to Zn ₂ TiO ₄ .

The average size of the ZnO-phase region is 1.8 ㎛. In this case, the ZnO-region has a dendrite-like appearance and does not show a larger continuous surface, but it is made up of individual fine particles. The binary oxide phase, Zn ₂ TiO _4, has an average particle size of 2.2 μm. Again, you can see the continuous faces in the form of dendrites. As the ZnO phase and the Zn ₂ TiO ₄ phase are intimately engaged with each other, the resultant maximum size of the continuous mixed oxide phase does not exceed 100 μm ² .

The theoretical oxygen value of 57.1 atom-% Zn ₂ TiO ₄ - was less than about 15% as measured 48.7 atom-%. Thus, this phase is depleted in oxygen by definition.

Example 4 (comparative): 30 vol% Nb ₂ O ₅  And a sputtering target made of ZnO containing 13 vol-% molybdenum

A powder consisting of ZnO, Nb ₂ O ₅ and molybdenum, each having a purity of 99.95%, was provided inside the crushing vessel in an amount corresponding to a predetermined final composition. The raw materials used were molybdenum powders having sub-탆 particle size ZnO, partially reduced Nb ₂ O _4.8 having a particle size of less than 100 탆 larger than the starting powders of Examples 1 to 3 and a particle size of less than 25 탆 . The total batch of 190 g powder was homogenized with 500 g of ZrO ₂ -mixed balls in a 1 hour milling and mixing process. The pulverized powder was passed through a sieve having a mesh width of 250 mu m to separate it from the pulverized body. 180 g of homogeneously mixed and ground powder having the composition of Example 4 was inserted into an axial graphite-compression mold having an internal diameter of 75 mm and pre-compressed axially at 7 MPa at room temperature. The hot compression in the axial direction was carried out at a temperature of 1175 DEG C and in an inert atmosphere of 1000 mbar argon with a stamping pressure of 35 MPa.

The high temperature compacted disc has a weight of 178.4 g, which has an absolute density (relative density: greater than 99%) of 5.88 g / cm ³ and greater than 99% of the initial weight.

During the course of the scanning in the scanning electron microscope, the variously graded phase compositions were exhibited by the solid diffusion of the sub-micrometer-ZnO in the used sub stoichiometric NbO n -particles having a size of up to 100 μm (in this case n is a number representing the stoichiometric oxygen content of the individual phases). Very large diffusion seams are penetrated by cracks, that is, they are not desirable for mechanical stability and particle formation.

Figure 6 shows one polished section of the sample in REM. The phase assignments are made according to the EDX and the X-ray diffraction shown in Fig. 7, and the quantitative values are shown in Table 2.

An image may be assigned in the scanned electronic image. # A1 is 66.2 atom - corresponds to NbO ₂ containing oxygen in%. The area of the single phase NbO &lt;&quot;&gt; region is maintained at less than 500 mu m &lt; ^{2 &} gt ;. The Zn content increases through phase # A2 and # A3. In this case, # A2 corresponds to the top Zn ₃ Nb ₂ O ₈ and # A3 corresponds to the top ZnNb ₂ O ₆ phase. These phase zones also have an oxygen deficit of more than 5%, as in other examples. White spherical fine particles are molybdenum. As in other examples, ZnO (darker regions) and binary oxide phase Zn ₃ Nb ₂ O ₈ (brighter regions) can be found in the finely divided matrix. The results of measuring the particle size of ZnO in the above regions show an average value of 5.3 μm. What is also noticeable here is that molybdenum particles are preferably embedded in the ZnO matrix. Binary oxides merchant # A2 Zn ₃ Nb ₂ O _8, on average, represents the dimension of approximately 12 ㎛. Due to the relatively coarse Nb ₂ O ₅ particles used, considerably larger consecutive # A2-phase areas up to 10,000 μm ² appear. The coarse starting particles also cause incomplete conditions for conversion to the desired mixed oxide phase at a given treatment temperature and treatment period. Therefore, the fraction of the binary mixed oxide phase is relatively high (less than 7 vol%) and the fraction of NbO ₂ - phases in the singular is relatively high (greater than 5 vol%).

Of course, the longer treatment time and / or the higher treatment temperature will represent a higher degree of conversion to the binary mixed oxide, but are associated with the risk of overall coarsening of the structure.

Here, the crystallite size (Table 2) is also much larger to 260 nm than in Examples 1 to 3 according to the present invention of less than 200 nm.

Examples 5 to 8: Another sputtering target was prepared by the composition specified in Table 1, and raw ZnO, Nb ₂ O ₅ and molybdenum according to Example 1 were metered and mixed. Compression was likewise done in the same way as in Example 1, in which case a temperature of 1080 ° C was chosen for high temperature compression.

Figure 8 shows a REM-photograph of one polished section of a sample of Example 5 with a composition of 5 vol% -% ZnO and 16 vol% - molybdenum. The phase assignment is made by balancing the X-ray diffraction and the EDX shown in Fig.

Figure 9 shows that the sintered sample shown in Example 5 is substantially composed of the three phases quantified in Table 2, namely Mo, ZnO and Nb ₂ Zn ₃ O ₈ . Phase are assigned in the scanning electron image: # A2 corresponds to the Nb ₂ Zn ₃ O _8, and, # A3 corresponds to the ZnO, spherical fine particles as a white # A1 is molybdenum.

The hot compacted disc has a weight of 197.5 g, which corresponds to an absolute density (relative density: greater than 99%) of 6.3 g / cm ³ and greater than 98% of the initial weight. The result of the measurement of the particle size of ZnO shows an average value of 1.3 탆, and none of the ZnO-phase regions is larger than 30 탆. The detectable coarse ZnO-region consists in part in a plurality of discrete phase regions. Because Nb ₂ O ₅ is less mixed, there is a percolating ZnO- phase in this example, which is formed from adjacent, aligned, partially agglomerated ZnO-regions and associated ZnO-particles.

The binary oxide phase, Nb ₂ Zn ₃ O _8, has an average particle size of 4.1 μm, in which case the larger area area does not exceed 200 μm ² . The theoretical oxygen value of Nb ₂ Zn ₃ O _{8, which} is an oxide phase of 61.5 atomic%, was less than 5%, as measured by 58.1 atomic%. Thus, this phase is depleted in oxygen by definition and thus has electrical conductivity.

Table 1: Composition, up to 100 volume% - balance: ZnO

Table 2: Phase composition [volume-%]

In the table above, G means the total fraction of the ternary mixed oxide phase expressed in volume-%.

Example 4, has the higher the mixed oxide fraction, show a relatively coarse-phase region, the NO (more precisely is Nb ₂ O) containing the fraction of binary oxides of the type. The sputtering target showed a slight peeling and cracking phenomenon after machining, but could otherwise be continued.

The coatings were sputtered (500 V DC, at 1A, 500 W) on a low salt glass substrate with a sputtering target made to a size of 488 ^* 80 ^* 10 mm ^{3 in} the above examples and comparative examples. The layer thickness was 50 nm in each case. The arcing rates of the targets of Examples 1 to 3 were significantly lower than 1 x 10 ^-6 arcs / h. However, when the layer was deposited with the sputtering target 4, arcing was already observed increased by 50 x 10 ^-6 arcs / h. In the other sputtering target, no problem was observed in the mechanical treatment.

A summary comparison of the individual examples in Table 3 and their sputtering properties shows a stable sputtering behavior (expressed as a low arcing rate) and excellent mechanical machinability for the sputtering target according to the present invention.

Table 3: Properties of sputtering target

In the above table:

S is a qualitative value for the sputtering characteristics of the target, in particular the frequency of arcing during sputtering,

D _max means the maximum cross-sectional area of the mixed oxide phase in [탆 ² ]

M is a qualitative value for the machinability of the sputtering target, in particular a qualitative value of the post-machining exfoliation and cracking.

In this case, the symbol " ++ " of the qualitative evaluations described in rows " S " and " M " means very excellent, " + " means excellent, " 0 & "-" means bad, and "-" means very bad.

Claims (14)

A sputtering target for producing a light absorbing layer comprising a target material containing an oxide phase and having a reduced oxygen content as compared to a stoichiometric composition,
Wherein the target material contains a metal phase consisting of molybdenum (Mo-phase) and the oxide phase contains a mixed oxide phase with zinc oxide (ZnO-phase) and a formula MNO _nx , where M is zinc Wherein N represents at least one of niobium (Nb) and / or titanium (Ti) as auxiliary components, where x is greater than 0 and n is the number of oxygen atoms in the stoichiometric composition on the mixed oxide Wherein the sputtering target is a sputtering target. The sputtering target according to claim 1, wherein the mixed oxide phase comprises Zn ₃ Nb ₂ O _{8 -x} and / or Zn ₂ TiO _{4 -x} and / or ZnNb ₂ O _{6 -x} . According to claim 1 or 2, wherein less than 300 ㎛ ² in the mixed oxide different from the cross section in the target material, characterized in that for forming the dimension an area having a maximum area of 200 ㎛ ² the preferred exemplary method, a sputtering target. 4. The sputtering target according to any one of claims 1 to 3, wherein the ZnO-phase in the target material forms an image area of a dimension having a maximum area of less than 100 mu m &lt; ² &gt; 5. A sputtering target according to any one of claims 1 to 4, characterized in that the volume fraction of ZnO-phase in the target material lies in the range of 20 to 85%. 6. The sputtering target according to any one of claims 1 to 5, characterized in that the Mo-phase volume fraction in the target material lies in the range of 10 to 30%. 7. The sputtering target according to any one of claims 1 to 6, characterized in that the volume fraction of the mixed oxide phase is at least 7%, preferably in the range of 7 to 60%. 8. The method according to any one of claims 1 to 7, wherein the volume fraction of the mixed oxide phase composed of Zn ₃ Nb ₂ O _{8 -x} in the target material lies in the range of 7 to 60%, wherein x> 0.4 Wherein the sputtering target is a sputtering target. The method according to any one of claims 1 to 8 wherein the ZnNb volume fraction of mixed oxide consisting of ₂ O _6-x in the target material lies in the range of 0-10%, in this case, characterized in that x> 0.3 Sputtering target. The can according to any one of claims 1 to 9, wherein in the target material has a volume fraction of mixed oxide consisting of Zn ₂ TiO _4-x lie within the range of 5 to 60%, in this case x> characterized in that 0.2 Sputtering target. 11. The method according to any one of claims 1 to 10, wherein the target material is a single niobium oxide phase consisting of NbO ₂ or Nb ₂ O ₅ having the formula NO _n and a phase of the single phase of the TiO ₂ or TiO form in total 10 %, Wherein N represents at least one of niobium (Nb) and / or titanium (Ti) as auxiliary components. 12. The method according to claim 11, characterized in that the target material contains a number of niobium oxide phases consisting of NbO ₂ or Nb ₂ O ₅ and a number of titanium oxide phases in the form of TiO ₂ or TiO in a fraction of less than 10% Sputtering target. 13. The sputtering target according to any one of claims 1 to 12, wherein the MO-phase in the target material forms an image area having a maximum transverse dimension of less than 25 [mu] m. 14. The sputtering target according to any one of claims 1 to 13, characterized in that the target material has a crystal structure having an average crystallite size of less than 265 nm.

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