Oxide sputtering target, method for manufacturing same, and oxide powder

Abstract

The present disclosure addresses the problem of providing: an oxide sputtering target containing strontium (Sr), metal element M (M is at least one of Nb, Mo, W, or Ta), and oxygen (O), and having a low volume resistivity; and a method for manufacturing same. An oxide sputtering target containing strontium (Sr), metal element M (M is at least one of Nb, Mo, W, or Ta), and oxygen (O), and having a volume resistivity of 100Ω∙cm or less. An oxide powder having a crystalline phase represented by SrxMO3 (0.5≤x≤1.2, and M is at least one of Nb, Mo, W, or Ta).

Description

Oxide sputtering target, its manufacturing method, and oxide powder

[0001] The present disclosure relates to an oxide sputtering target and a method for producing the same, and an oxide powder.

[0002] Strontium (Sr) and niobium (Nb) composite oxides are ２ Nb ２ O ７ Crystalline phase and SrNbO ３ They form a crystalline phase and are used for dielectric films, conductive films, etc. For example, in Patent Document 1, Sr ２ Nb ２ O ７ The sintered ceramic target was sputtered to obtain Sr ２ Nb ２ O ７ In addition, Non-Patent Document 1 describes that an amorphous film of Sr is deposited and then heat-treated to form a crystalline phase. ２ Nb ２ O ７ The sputtering target was RF sputtered to obtain Sr ｘ NbO ３ It is described that a thin film is formed.

[0003] Regarding composite oxides of strontium (Sr) and molybdenum (Mo), Patent Document 2 states that Sr １－ｘ Ba ｘ MoO ３ A method for producing a thin film of a conductive oxide where x=0 to 1 is disclosed. Specifically, SrCO ３ and MoO ３ was reacted at 800°C to obtain SrMoO ４ is then reduced with hydrogen to give SrMoO ３ It is described that a sintered target is produced, and that thin film deposition is carried out using a planar type rf magnetron sputtering device.

[0004] JP 2002-270828 A JP 60-91504 A

[0005] Joseph Roth et al. “Sputtered SrxNbO3as a UV-Transparent Conducting Film” ACS Applied Materials & Interfaces 2020, 12, 30520-30529

[0006] As mentioned above, Sr ２ Nb ２ O ７ SrO and Nb ２ O ５ By using a sputtering target made of a composite oxide of Sr ２ Nb ２ O ７ film and SrNbO ３ However, the Sr ２ Nb ２ O ７ Since the sputtering target is an insulator, DC sputtering is not possible, resulting in poor productivity and unstable discharge. ３ Regarding SrMoO ３ By using the synthetic powder of SrMoO ３ Although there is a report of a sputtering target containing the above (Patent Document 2), the manufacturing method has not been optimized, and no target capable of stable sputtering has yet been reported.

[0007] In view of the above-mentioned problems, an object of the present disclosure is to provide an oxide sputtering target containing strontium (Sr) and a metal element M (M is one or more of Nb, Mo, W, and Ta), which has a low volume resistivity and is capable of DC sputtering, a method for producing the same, and oxide powder.

[0008] In order to solve the above problems, the present inventors have conducted extensive research and have found that an oxide sputtering target having a low volume resistivity can be obtained by devising a manufacturing method and conditions.

[0009] The present disclosure provides an oxide sputtering target containing strontium (Sr), a metal element M (M is at least one of Nb, Mo, W, and Ta), and oxygen (O), and having a volume resistivity of 100 Ω cm or less. ｘ MO ３ (0.5≦x≦1.2, M is one or more of Nb, Mo, W, and Ta).

[0010] According to the present disclosure, it is possible to provide an oxide sputtering target containing strontium (Sr), a metal element M (M is one or more of Nb, Mo, W, and Ta), and oxygen (O), which has a low volume resistivity and is capable of DC sputtering, and a method for manufacturing the same.

[0011] Below, the present disclosure will be described with reference to specific embodiments, but each configuration and combination thereof in each embodiment is merely an example, and addition, omission, substitution, and other modifications of configurations are possible as appropriate within the scope that does not deviate from the gist of the present disclosure.

[0012] (Oxide sputtering target) The oxide sputtering target according to an embodiment of the present disclosure contains strontium (Sr), a metal element M (M is one or more of Nb, Mo, W, and Ta), and oxygen (O), and has a volume resistivity of 100 Ω cm or less. Because the oxide sputtering target according to this embodiment has a low volume resistivity, it is expected that DC sputtering, which enables high-speed film formation, can be stably performed.

[0013] This embodiment is an oxide sputtering target containing strontium (Sr) and a metal element M (M is one or more of Nb, Mo, W, and Ta). Impurities such as carbon may be mixed in during the process of producing the sputtering target (raw materials, mixing, sintering, etc.). However, the sputtering target may contain impurities within a range that does not significantly affect its properties, and the total impurity content is preferably 1.0 mass% or less.

[0014] The oxide sputtering target according to this embodiment has a volume resistivity of 100 Ω·cm or less. A lower volume resistivity has the advantage that DC (direct current) sputtering, which allows high-speed film formation, can be stably performed. Preferably, the volume resistivity is 10 Ω·cm or less, more preferably 500 mΩ·cm or less. Particularly preferably, the volume resistivity is 50 mΩ·cm or less.

[0015] The oxide sputtering target according to this embodiment contains Sr ｘ MO ３ (0.5≦x≦1.2, M is one or more of Nb, Mo, W, and Ta). For example, when the metal element M is niobium (Nb), Sr ｘ NbO ３ (0.5≦x≦1.2), and in the case of molybdenum (Mo), Sr ｘ MoO ３ (0.5≦x≦1.2), and in the case of tungsten (W), Sr ｘ WO ３ (0.5≦x≦1.2), and in the case of tantalum (Ta), Sr ｘ TaO ３ (0.5≦x≦1.2). ｘ Mo ｙ Nb １－ｙ O ３ For example, (0.5≦x≦1.2, 0<y<1), M may be a crystalline phase consisting of two or more elements. If these crystalline phases are contained, the volume resistivity of the sputtering target decreases. However, it is sufficient that these crystalline phases are contained, and other crystalline phases may also be contained. Furthermore, the resistance may be reduced by containing Nb, Mo, or the like as a metal in the sputtering target.

[0016] The oxide sputtering target according to this embodiment preferably has a relative density of 75% or more. The higher the relative density, the more likely it is that particles will be reduced during sputtering. The relative density is preferably 80% or more, more preferably 90% or more, and particularly preferably 95% or more. As mentioned above, when sintering is performed by hot pressing, the volume resistivity can be reduced, but it can be difficult to obtain a high-density sintered body. However, according to the present disclosure, by appropriately controlling the sintering conditions, an oxide sputtering target having a low volume resistivity and a high relative density can be obtained.

[0017] In the oxide sputtering target according to this embodiment, it is preferable that the metal element M (M is one or more of Nb, Mo, W, and Ta) is contained in an atomic ratio of M / (M+Sr) of 0.4 or more and 0.6 or less. By setting the atomic ratio of M / (M+Sr) to 0.4 or more and 0.6 or less, high conductivity and high transmittance in the ultraviolet region can be achieved when a thin film is formed. Preferably, the atomic ratio of M / (M+Sr) is 0.45 or more, and preferably the atomic ratio of M / (M+Sr) is 0.55 or less.

[0018] The oxide sputtering target according to this embodiment contains Sr ｘ MO ３ The maximum XRD peak intensity in the range of 44°≦2θ≦47°, which is attributed to the crystalline phase of (0.5≦x≦1.2, M is one or more of Nb, Mo, W, and Ta), is defined as I. ＴＧ The average value of the XRD intensity in the range of 42.5°≦2θ≦43.5° is taken as the background I ＢＧ When I ＴＧ / I ＢＧ It is preferable that the ratio is ≧3. More preferably, I ＴＧ / I ＢＧ ≧10, and particularly preferably I ＴＧ / I ＢＧ ≧50. ｘ MO ３ The higher the proportion of the crystalline phase, the lower the resistance of the sputtering target can be expected.

[0019] A method for manufacturing an oxide sputtering target according to an embodiment of the present disclosure will be described. However, the manufacturing conditions and the like below are not limited to the disclosed range, and it is clear that some omissions and modifications may be made. Note that detailed descriptions of well-known manufacturing steps and processing operations will be omitted to avoid unnecessarily obscuring the disclosed manufacturing method.

[0020] (Raw material powder) Strontium carbonate (SrCO ３ ) and molybdenum oxide (MoO ３ ), niobium oxide (Nb ２ O ５ ), tantalum oxide (Ta ２ O ５ ), tungsten oxide (WO ３ These raw material powders are weighed out to obtain a desired composition ratio, and then mixed to obtain a mixed powder.

[0021] (Primary Firing Step) Next, the mixed powder is sintered in air at 700°C or higher and 1200°C or lower to form SrCO ３ When the metal element M is molybdenum (Mo), a composite oxide is prepared. ３ and MoO ３ and SrMoO ４ When the metal element M is niobium (Nb), a composite oxide such as SrCO ３ and Nb ２ O ５ and Sr ２ Nb ２ O ７ Alternatively, a composite oxide such as SrCO can be prepared. ３ and Nb ２ O ５ and SrNbO were synthesized in a 1:1 ratio. ６ Alternatively, a composite oxide such as SrCO can be prepared. ３ and Nb ２ O ５ and Sr ５ Nb ４ O １５When the metal element M is tantalum (Ta), a composite oxide can be produced. ３ and Ta ２ O ５ and Sr ２ Ta ２ O ７ Alternatively, a composite oxide such as SrCO can be prepared. ３ and Ta ２ O ５ and SrTa were synthesized in a 1:1 ratio. ２ O ６ Alternatively, a composite oxide such as SrCO can be prepared. ３ and Ta ２ O ５ and Sr ５ Ta ４ O １５ When the metal element M is tungsten (W), a composite oxide can be produced. ３ and W.O. ４ and SrWO ４ A composite oxide can be produced.

[0022] (Primary pulverization step: optional) After the primary firing, the composite oxide is pulverized (for convenience, this is referred to as primary pulverization). The primary pulverization is an optional step. There are various pulverization methods depending on the desired particle size and the material to be pulverized, and wet or dry ball mills, vibration mills, bead mills, etc. can be used. The average particle diameter (median diameter: D ５０ ) is preferably adjusted to be 0.1 μm or more and 5.0 μm or less.

[0023] (Secondary Firing Step) The powder of the crushed or uncrushed composite oxide is heated in a vacuum or inert gas atmosphere (Ar, N ２ The mixture is baked at 800°C or higher and 1600°C or lower under a high temperature. At this time, a reducing agent is mixed in. Carbon (graphite) can be used as the reducing agent, but other reducing agents (e.g., H ２ , Nb, Mo, etc.) may be used. ３ , SrNbO ３ , SrWO ３ , SrTaO ３ , SrMoｙ Nb １－ｙ O ３ It is possible to obtain oxide powders of a crystalline phase represented by (0<y<1) and the like.

[0024] (Secondary pulverization step: optional) After the secondary firing, the oxide powder is pulverized (for convenience, this is referred to as secondary pulverization). Secondary pulverization is an optional step. There are various pulverization methods depending on the desired particle size and the material to be pulverized, and wet or dry ball mills, vibration mills, bead mills, etc. can be used. The average particle diameter (median diameter: D ５０ It is preferable to adjust the particle size so that the particle size is 20 μm or less, preferably 10 μm or less. In the case of wet grinding, if pure water is used, there is a risk of oxidation during drying, so wet grinding using an organic solvent or dry grinding is more preferable.

[0025] (Hot press sintering process) The obtained oxide powder (SrMoO ３ , SrNbO ３ , SrWO ３ , SrTaO ３ ) in a vacuum or inert gas atmosphere (Ar, N ２ The hot press sintering is carried out under the conditions of (a) a sintering holding temperature of 800°C or more and 1600°C or less. The pressing pressure during hot press sintering can be adjusted as appropriate, but is, for example, 200 to 500 kgf / cm. ２ The sintering holding time is preferably 1 to 20 hours or more. If the holding temperature is too low, the relative density of the sintered body will not increase sufficiently, and if the holding temperature is too high, the relative density will decrease due to evaporation of oxides.

[0026] (Finishing Process) The sintered body obtained through the above sintering process is processed into a desired shape using a processing machine such as a surface grinder, a cylindrical grinder, or a machining device. There are no particular restrictions on the shape of the sputtering target, and it can be a flat disk, a rectangle, a cylinder, or the like. In addition, the sputtering target can be used by bonding it to a backing plate.

[0027] The following description will be given based on examples and comparative examples. Note that these examples are merely examples and are not intended to limit the scope of the present invention. That is, the present invention is limited only by the scope of the claims and includes various modifications other than the examples included in this disclosure. Note that, since sputtering targets are produced by machining a sintered body, the physical properties of the sputtering target are, in principle, equivalent to those of the sintered body.

[0028] The evaluation methods used in the examples and comparative examples are as follows: (Composition analysis) The composition of the sintered body was analyzed using the following apparatus: Apparatus: SPS3500DD manufactured by SII Corporation Method: ICP-OES (inductively coupled plasma optical emission spectroscopy)

[0029] (Volume Resistivity) The volume resistivity of the sintered body was measured using the following device: Device: Resistivity measuring device Σ-5+ manufactured by NPS System: Constant current application method Method: DC four-probe method Measurement temperature: Room temperature (20 to 25°C)

[0030] (Relative Density) The relative density was calculated using the following formula: Relative density (%) = Archimedes density / true density × 100 Archimedes density: A measurement sample was prepared by grinding the top and bottom surfaces of the sintered body to a thickness of 1 mm and grinding the outer peripheral surface to a thickness of 5 mm, and the Archimedes density was calculated using the Archimedes method. True density: The sintered body was subjected to a component analysis, and the true density was calculated using the oxide mass ratio (mass%) calculated by converting the atomic ratio (at%) of each of Sr and M (at least one of Nb, Mo, W, and Ta) to the total of 100 at% of the constituent elements, and the theoretical density of the oxide shown below. True density (g / cm ３ ) = (W1 + W2) / (W1 / D1 + W2 / D2) × 100 W1: mass ratio of SrO (mass%) W2: MoO ２ , NbO ２ , TaO ２ , W.O. ２ Mass ratio (mass%) of either Theoretical density: D1: 4.70 g / cm ３ (SrO) D2: 6.44g / cm ３ (MoO ２ ), 5.90g / cm３ (NbO ２ ), 10.2g / cm ３ (TaO ２ ), 10.8g / cm ３ (W.O. ２ )

[0031] (Analysis of Crystalline Phase) Analysis of the crystalline phase was performed using the following equipment. Principle: X-ray diffraction method Equipment: Smart Lab manufactured by Rigaku Corporation Tube: Cu-Kα ray tube Voltage: 40 kV Current: 30 mA Measurement method: 2θ-θ reflection method Scan speed: 20° / min Sampling interval: 0.02° Measurement range (2θ): 10° to 60° Divergence slit: 1° Divergence vertical limiting slit: 10 mm Scattering slit: 8 mm Receiving slit: Open state Goniometer: Sample horizontal type Sample measurement location: Sputtered surface side Sr ｘ MO ３ (0.5≦x≦1.2, M is one or more of Nb, Mo, W, and Ta) in the range of 44°≦2θ≦47° is defined as I ＴＧ The average value of the XRD intensity in the range of 42.5°≦2θ≦43.5° is defined as the background I ＢＧ Define it as: I ＴＧ / I ＢＧ If ≧3, Sr ｘ MO ３ (0.5≦x≦1.2, M is one or more of Nb, Mo, W, and Ta) crystal phase.

[0032] Example 1 SrCO ３ Powder, MoO ３ Powders were prepared, weighed and mixed to obtain a desired ratio, and the resulting mixed powder was first fired at 780°C in air to obtain SrMoO ４ The composite oxide was then synthesized. ４ The composite oxide is wet-pulverized to obtain a median diameter D ５０ After adjusting the thickness to 1.3 μm, carbon (graphite) was mixed and secondary sintering was performed at 1300° C. in an argon atmosphere to form SrMoO ３ The oxide powder was prepared. ５０The thickness of this SrMoO ３ Sintering of oxide powder: Holding temperature: 1250°C, Surface pressure: 250 kgf / cm ２ The oxide sintered body having an outer diameter of 213 mm was produced by hot press sintering with a sintering holding time of 4 hours. The relative density and volume resistivity of the obtained sintered body were determined. The results are shown in Table 1. As shown in Table 1, in Example 1, a sintered body having good properties was obtained.

[0033]

[0034] Example 2 SrCO ３ powder, Nb ２ O ５ The powders were prepared, weighed and mixed to obtain the desired ratio, and the resulting mixed powder was first fired at 1100°C in air to obtain Sr ２ Nb ２ O ７ Next, we synthesized composite oxides such as Sr ２ Nb ２ O ７ After wet-pulverizing the composite oxide, carbon (graphite) was mixed and the mixture was subjected to secondary firing at 1500°C in an argon atmosphere to obtain SrNbO ３ The oxide powder was then prepared. ３ The oxide powder is dry-milled to obtain a median diameter D ５０ The thickness of this SrNbO ３ Sintering of oxide powder: Holding temperature: 1400°C, Surface pressure: 300 kgf / cm ２ The oxide sintered body having an outer diameter of 210 mm was produced by hot press sintering with a sintering holding time of 5 hours. The relative density and volume resistivity of the obtained sintered body were determined. The results are shown in Table 1. As shown in Table 1, in Example 2, a sintered body with good properties was obtained.

[0035] (Comparative Example 1) SrCO ３ powder, Nb ２ O ５ The powders were prepared, weighed and mixed to obtain the desired ratio, and the resulting mixed powder was first fired at 1100°C in air to obtain Sr ２ Nb ２ O ７ The composite oxide was then synthesized. ２ Nb２ O ７ The oxide powder was pulverized in a wet bead mill to obtain a median diameter D ５０ The thickness of this Sr ２ Nb ２ O ７ Sintering of oxide powder: Holding temperature: 1150°C, Surface pressure: 100 kgf / cm ２ The oxide sintered body having an outer diameter of 213 mm was produced by hot press sintering with a sintering holding time of 4 hours. The relative density and volume resistivity of the obtained sintered body were determined. The results are shown in Table 1. As shown in Table 1, in Comparative Example 1, the volume resistivity was 1 MΩ cm or more.

[0036] According to the present disclosure, the low volume resistivity allows stable film formation using DC sputtering, which enables high-speed film formation. Shortening lead times and stable film formation in the film formation process lead to a stable supply of products and reduced loss of metal raw materials, which are limited resources. Therefore, one embodiment of the present invention may contribute to the achievement of Goal 9 of the United Nations-led Sustainable Development Goals (SDGs), "Build resilient infrastructure, promote inclusive and sustainable industrialization and foster technological innovation," and Goal 12, "Ensure sustainable consumption and production patterns."

[0037] The oxide sputtering target of the present disclosure is useful for forming transparent conductive films for displays, touch panels, solar cells, etc., or thin films for electronic devices such as LSIs.

Claims

1. An oxide sputtering target containing strontium (Sr), a metal element M (M is one or more of Nb, Mo, W, and Ta), and oxygen (O), and having a volume resistivity of 100 Ω·cm or less.

2. Sr ｘ MO ３ 2. The oxide sputtering target according to claim 1, having a crystalline phase represented by the formula (x) where x is a number in the range of 0.5 to 1.2, and M is at least one of Nb, Mo, W, and Ta.

3. The oxide sputtering target according to claim 1 or 2, which has a relative density of 75% or more.

4. The oxide sputtering target according to claim 1 or 2, containing the metal element M in an atomic ratio of M / (M+Sr) of 0.4 or more and 0.6 or less.

5. Sr ｘ MO ３ (0.5≦x≦1.2, M is one or more of Nb, Mo, W, and Ta) in the range of 44°≦2θ≦47° is defined as I ＴＧ The average value of the XRD intensity in the range of 42.5°≦2θ≦43.5° is taken as the background I ＢＧ When I ＴＧ / I ＢＧ 3. The oxide sputtering target according to claim 1, wherein the Mn content is ≥ 3.

6. Sr ｘ MO ３ (0.5≦x≦1.2, M is one or more of Nb, Mo, W, and Ta).

7. Sr ｘ MO ３ (0.5≦x≦1.2, M is one or more of Nb, Mo, W, and Ta) in the range of 44°≦2θ≦47° is defined as I ＴＧ The average value of the XRD intensity in the range of 42.5°≦2θ≦43.5° is taken as the background I ＢＧ When I ＴＧ / I ＢＧ 7. The oxide powder according to claim 6, wherein the saturation coefficient is ≥ 3.

8. Average particle diameter D ５０ 8. The oxide powder according to claim 6, wherein the particle size is 20 μm or less.

9. The raw material powder is fired at 700°C to 1200°C to prepare a composite oxide, and the composite oxide is fired together with a reducing agent at 800°C to 1600°C in a vacuum or in an inert gas atmosphere to obtain Sr ｘ MO ３ (0.5≦x≦1.2, M is one or more of Nb, Mo, W, and Ta), and hot-press sintering the oxide powder at 800°C or higher and 1600°C or lower in an inert gas atmosphere.

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