JP2010120803A - Multiple oxide sintered compact - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multiple oxide sintered compact which can control the generation of an abnormal discharge phenomenon during sputtering and suppress reduction in the yield caused by particles. <P>SOLUTION: The multiple oxide sintered compact comprises zinc, and an element(s) A which can take a positive trivalent or more valence whose ion radius when six-coordination is assumed in oxygen ions is 0.7 to 1.1 Å and an element(s) M different from the element(s) A which can take a positive trivalent or more valence whose ion radius when 4-coordination is assumed in oxygen ions is 0.5 to 0.7 Å by at least one or more kinds, respectively, and in which diffraction peaks detected within the range of 2θ=30 to 40° in an X-ray diffraction pattern (XRD) with Cu as a beam source are composed only of the (100) face, (002) face and (101) face belonging to a hexagonal wurtzite type structure. Thus, the generation of an abnormal discharge phenomenon can be suppressed, and reduction in the yield caused by particles can be suppressed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a composite oxide sintered body mainly composed of zinc oxide and a sputtering target composed of the composite oxide sintered body.

  An indium oxide film containing tin as a dopant is called an ITO (Indium Tin Oxide) film, and is widely used as a transparent conductive film because a low-resistance film can be easily obtained. However, In, which is the main raw material of the ITO film, is a rare metal and expensive, so there is a limit to reducing the cost when this film is used.

  Therefore, development of materials for transparent conductive films in place of ITO has been actively promoted, and zinc oxide films containing Group III elements of the periodic table mainly composed of zinc oxide are inexpensive and chemically It is attracting attention because it is stable and has excellent transparency and conductivity.

  As a method for forming such a transparent conductive film, a sputtering method using a sputtering target is often employed because it can form a film with a uniform thickness over a large area. However, this sputtering method has problems such as a decrease in operating rate of the sputtering apparatus and a decrease in product yield due to the influence of generated particles due to an abnormal discharge phenomenon during sputtering.

  As a means for suppressing an abnormal discharge phenomenon that occurs during sputtering, for example, use of a high-density target has been proposed (see, for example, Patent Document 1). In addition, it has been proposed to use a target having a high density of the target and an aluminum component aggregation diameter caused by aluminum oxide added as an oxide of a group III element in the periodic table of 5 μm or less at maximum ( For example, see Patent Document 2).

  However, only by increasing the density of the target and controlling the agglomerated diameter of the second component derived from the additive element in the target, the occurrence of abnormal discharge during sputtering cannot be completely avoided. Therefore, there is a problem that the yield decreases due to the particles to be generated, and therefore the productivity is unavoidable, and further suppression of the abnormal discharge phenomenon is demanded.

JP-A-2-14959 JP-A-7-258836

  The subject of this invention is providing the complex oxide sintered compact which can control generation | occurrence | production of the abnormal discharge phenomenon during sputtering and can suppress the yield fall by a particle.

  In order to solve the above problems, the present inventors have conducted extensive studies on a composite oxide sintered body in which elements having a specific ionic radius and having a positive trivalent or higher valence can be combined at a specific atomic ratio. The present invention has been completed.

  Aspects of the present invention are as follows.

  (1) Zinc, element A capable of taking a valence of positive trivalent or higher with an ionic radius of 0.7 to 1.1Å when assuming 6-coordination with oxygen ions, and assuming 4-coordination with oxygen ions Of an X-ray diffraction pattern (XRD) containing at least one element M different from the element A and having Cu as a radiation source, which can have a positive trivalent or higher valence having an ion radius of 0.5 to 0.7% The diffraction peak detected in the range of 2Θ = 30 to 40 ° is composed of only the (100) plane, (002) plane, and (101) plane belonging to the hexagonal wurtzite structure. Composite oxide sintered body.

  (2) The composite oxide sintered body according to (1), wherein the element A includes at least one element selected from the group of In, Ti, Zr, and Sn.

  (3) The composite oxide sintered body according to (1) or (2), wherein the element M contains at least one element selected from the group consisting of Al, Ga, and Nb.

  (4) The composite oxide sintered body according to any one of (1) to (3), wherein a relative density of the sintered body is 95% or more.

  (5) A powder of a zinc compound and a compound powder of an element A and an element M having a primary particle size smaller than the primary particle size of the powder is expressed by A / (A + M) as each atomic ratio of zinc, element A, and element M. A step of mixing raw material powder so that the atomic ratio (A + M) / (Zn + A + M) is 0.001 to 0.17, and a step of forming the mixed powder to form a molded body, The composite oxide sintered body according to any one of (1) to (4), including a step of firing the molded body within a range of 1000 to 1600 ° C. to produce a sintered body. Production method.

  (6) A composite oxide sputtering target comprising the composite oxide sintered body according to any one of (1) to (4).

  (7) A transparent conductive film formed by using the composite oxide sputtering target according to (6).

  Hereinafter, the present invention will be described in detail.

  The composite oxide sintered body of the present invention is an element A having an ionic radius of 0.7 to 1.1 Å when zinc and hexagonal coordination are assumed among elements capable of taking a valence of positive trivalent or higher. Including at least one element M having an ionic radius of 0.5 to 0.7% when assuming four-coordination to oxygen ions among elements capable of taking at least one kind of valence of positive trivalent or more. It is characterized by being.

  In addition, CR (crystal radius) which is a reported value of “RD Shannon, Acta Crystallogr. A32, 751-767 (1976)” is used as the ionic radius in the present invention. According to this report, there is no element having the same ionic radius in the oxygen tetracoordinate and the oxygen hexacoordinate with the same element.

  The element A is preferably selected from the group of In (0.94 Å), Ti (0.75 Å), Zr (0.86 Å), Sn (0.83 Å), and more preferably In. By selecting these elements as the element A, it is possible to further reduce abnormal discharge during sputtering.

  The element M is preferably selected from the group consisting of Al (0.53Å), Ga (0.61Å), and Nb (0.62Å), and more preferably Al. By selecting these elements as the element M, it is possible to further reduce abnormal discharge during sputtering.

  The atomic ratio A / (A + M) between the element A and the element M is 0.4 or more, and preferably 0.45 or more. The atomic ratio (A + M) / (Zn + A + M) is 0.001 or more and 0.17 or less, and preferably 0.05 or more and 0.15 or less. When sputtering is performed within this range, abnormal discharge during sputtering can be further reduced.

  In general, in a zinc oxide-based sputtering target in which zinc oxide contains an additive element such as a group III element of the periodic table, a hexagonal structure mainly composed of zinc oxide in which the additive element is partly dissolved. The microstructure is composed of a second phase having a spinel structure which is a reaction product of a parent phase, an additive element and zinc oxide.

  However, when a composite oxide sintered body in which each atomic ratio of zinc, element A, and element M is within the above-mentioned range is analyzed by X-ray analysis, XRD using Cu as a radiation source is within a range of 2Θ = 30-40 °. The detected diffraction peak is composed of only the (100) plane, (002) plane, and (101) plane that belong to the hexagonal wurtzite structure substantially containing zinc oxide. It was found that the second phase having a spinel structure, which is a reaction product of zinc oxide and high electrical resistance, disappeared in an X-ray manner.

Therefore, “consisting only of the (100) plane, (002) plane, (101) plane attributed to the hexagonal wurtzite structure” in the present invention is attributed to the spinel structure of the second phase. The integrated intensity I _{(311) of the (311} ) plane X-ray diffraction peak and the integrated intensity I _{(101) of the} (101) plane X-ray diffraction peak attributed to the hexagonal wurtzite structure The value of I ₍₃₁₁₎ / (I ₍₁₀₁₎ + I ₍₃₁₁₎ ) is 2.5% or less, preferably 0%.

In addition, when a phase other than the spinel structure is formed as the second phase, the X-ray diffraction peak attributed to the integrated intensity of the X-ray diffraction peak attributed to the phase and the hexagonal wurtzite structure is also observed. The relationship with the integrated intensity I ₍₁₀₁₎ of the peak is the same as described above.

  This is because, when the element A and the element M are present in the composite oxide sintered body in the above-described composition, the element A and the element M are respectively 4-coordinated or 6-coordinated to oxygen in zinc oxide, and oxidized. This is probably because it does not react with zinc and does not generate a second phase such as a spinel structure.

  The relative density of the composite oxide sintered body of the present invention is preferably 95% or more, and more preferably 97% or more. If it deviates from this range, abnormal discharge during sputtering increases remarkably, and a problem of breakage in machining or the like occurs in order to adjust the shape.

The relative density is expressed as a relative value with respect to the theoretical density Y (g / cm ³ ) obtained by arithmetically calculating the sintered density X (g / cm ³ ) measured by the Archimedes method in accordance with JIS-R1634-1998. ).

Relative density (%) = (X / Y) × 100 (1)
Here, the arithmetic theoretical density Y is obtained by determining the volume ratio from the specific gravity and the composition weight ratio when zinc, element A, and element M are converted into oxides, and the specific gravity of the oxide of zinc, element A, and element M is the volume. Calculated by ratio distribution.

  The average particle size of the composite oxide sintered body of the present invention is preferably 20 μm or less. This is because if the average particle diameter exceeds 20 μm, a problem of breakage in machining or the like may occur in order to adjust the shape.

  In addition, the measuring method of the particle size in the composite oxide in the present invention is as follows.

  After cutting the composite oxide sintered body of the present invention into an appropriate size, the observation surface is polished, and then chemical etching is performed with a dilute acetic acid solution to clarify the grain boundaries. This sample is image-processed using a scanning electron microscope (SEM), and an observation photograph of the polished surface of the sintered body is subjected to image processing, 500 to 1000 major axes are obtained, and the average is obtained as the average grain size.

  Next, a method for producing the composite oxide sintered body of the present invention will be described.

  In the method for producing a composite oxide sintered body of the present invention, (1) a zinc compound powder, an element A compound powder having a primary particle size smaller than the primary particle size of the powder, and an element M compound powder are predetermined. (2) a step of forming the mixed powder to produce a molded body, and (3) firing the molded body within a range of 1000 to 1600 ° C. And a step of producing a sintered body.

  Hereinafter, the manufacturing method of the composite oxide sintered body of the present invention will be described for each step.

(1) Raw material mixing step The raw material powder is not particularly limited, and for example, metal salt powder, chloride, nitrate, carbonate and the like can be used. . Since the finer the powder particle size is, the finer the powder is, the better the sinterability is. Therefore, usually, a powder having a primary particle diameter of 10 μm or less is preferably used, and a powder of 1 μm or less is particularly preferably used.

  Furthermore, the compound powder of the element A and the element M needs to use a compound powder having a primary particle size smaller than the primary particle size of the zinc compound powder. This is because if the primary particle size of the zinc compound powder is smaller or the same, the homogeneity of the mixed state is poor.

  The mixing of each of these powders is not particularly limited, but dry, wet media agitation type mills or medialess container rotary mixing, mechanical agitation types using balls and beads such as zirconia, alumina, nylon resin, etc. Examples of the mixing method include mixing. Specific examples include a ball mill, a bead mill, an attritor, a vibration mill, a planetary mill, a jet mill, a V-type mixer, a paddle mixer, and a twin-shaft planetary agitation mixer.

  Further, although pulverization is performed simultaneously with mixing of the powder, the finer the particle size of the powder after pulverization, the better. At this time, when a wet ball mill, bead mill, attritor, vibration mill, planetary mill, jet mill, or the like is used, the pulverized slurry needs to be dried. This drying method is not particularly limited, and examples thereof include filtration drying, fluidized bed drying, and spray drying.

  Moreover, when mixing powders other than oxide powder, it is preferable to calcine at 500-1000 degreeC after mixing, and to grind | pulverize, when the particle size of calcined powder becomes large.

  The purity of each raw material powder is usually 99% or higher, preferably 99.9% or higher, more preferably 99.99% or higher. This is because if the purity is low, the impurity material may affect the transparent conductive film formed by the sputtering target using the composite oxide sintered body of the present invention.

  The composition of these raw materials is such that the atomic ratio A / (A + M) of the elements A and M is 0.4 or more, and the atomic ratio (A + M) / (Zn + A + M) of each element is 0.001 to 0.17. It is necessary to mix the raw materials to become.

(2) Molding process It is important to select a molding method that can form a mixed powder of metal oxide (or a calcined mixed powder if calcined) into a desired shape, and is particularly limited. Is not to be done. Examples thereof include a press molding method, a casting molding method, and an injection molding method.

  The molding pressure is not particularly limited as long as it is a molded body that does not generate cracks and can be handled, but it is preferable to increase the molding density as much as possible. Therefore, it is also possible to use a method such as cold isostatic pressing (CIP) molding.

  In the molding treatment, molding aids such as polyvinyl alcohol, acrylic polymer, methyl cellulose, waxes, oleic acid and the like may be used.

(3) Firing step Next, the obtained molded body is fired at 1000 to 1600 ° C. Although the microstructure of the composite oxide sintered body can be obtained by this firing temperature range, the volatilization disappearance peculiar to the zinc oxide-based composite oxide is suppressed, and the sintering density can be relatively increased, so that the sintering density is relatively high. Is more preferable.

  According to the present invention, by controlling the microstructure of the composite oxide sintered body as described above, for example, even if a high sintered density such as a relative density of 99% or more cannot always be obtained, abnormal discharge during sputtering is performed. The phenomenon can be remarkably suppressed. However, if the sintered density is too low, damage or the like may occur during handling or sputtering. Therefore, a relative density of 95% or more is generally preferable, and a range of 97% or more is particularly preferable.

  The firing time is not particularly limited, but usually 1 to 48 hours is usually used, and 3 to 24 hours is particularly preferable. This is to ensure the homogeneity in the composite oxide sintered body of the present invention, and it is possible to ensure the homogeneity even if it is maintained for a longer time than 24 hours, but the influence on the productivity is considered. Then 24 hours or less is sufficient.

  The rate of temperature increase is not particularly limited, but is more preferably 50 ° C./h or less in the temperature range of 800 ° C. or higher. This is because the composite oxide sintered body of the present invention is substantially constituted only by particles having a hexagonal wurtzite structure mainly containing zinc oxide.

  Although the firing atmosphere is not particularly limited, for example, the atmosphere, oxygen, inert gas atmosphere, and the like are appropriately selected, but an atmosphere having a lower oxygen concentration than the atmosphere is more preferable.

  This makes it easier to introduce oxygen defects into the composite oxide sintered body of the present invention, and therefore, the resistivity of the composite oxide sintered body decreases and the cause of abnormal discharge can be further reduced. This is because it becomes possible. Moreover, the pressure at the time of baking is not specifically limited, In addition to a normal pressure, baking in a pressurization and pressure reduction state is also possible. Moreover, a hot isostatic pressure (HIP) method, hot press sintering, etc. are also possible.

  According to the present invention, zinc and element A capable of taking a valence of positive trivalent or higher with an ion radius of 0.7 to 1.1 と き when assuming 6-coordination to oxygen ions, 4-coordination to oxygen ions. The composite oxide sintered body of the present invention, which contains at least one element M different from the element A that can have a positive trivalent or higher valence having an ionic radius of 0.5 to 0.7%, is spinel. The second phase with a high electrical resistance having a mold structure disappears, and there is little variation in the electrical resistance of the sintered body, and it is possible to obtain a complex oxide sintered body that hardly causes abnormal discharge during sputtering.

  The present invention will be specifically described by the following examples, but the present invention is not limited thereto.

(Examples 1-12 and Comparative Examples 1-4)
Zinc oxide powder having a purity of 99.8% and an average particle size of 0.6 μm (primary particle size), and an element A and an element having a purity of 99.99% and an average particle size of 0.1 to 0.3 μm (primary particle size) M oxide powder was mixed and granulated by a wet ball mill so as to have the composition shown in Table 1, and CIP-molded at 3.0 ton / cm ² .

(Baking conditions)
・ Sintering temperature: 1400 ° C
・ Temperature increase rate: 50 ° C / h
・ Cooling rate: 100 ° C / h
-Holding time: 5 hours-Sintering atmosphere: Nitrogen atmosphere After processing the obtained composite oxide sintered body, it is mirror-polished, and the polished surface is XRD, SEM, electron beam microanalyzer (EPMA), scanning probe Analysis was performed with a microscope (SPM), and the crystal phase and particle size were analyzed. The results of XRD analysis are shown in Table 1, classified into hexagonal wurtzite phase, spinel phase and other phases.

Furthermore, the obtained sintered body was processed into a 4 inch φ size as a target, and sputtering evaluation was performed.
(Measurement conditions for X-ray diffraction test)
-X-ray source: CuKα
・ Power: 40kV, 30mA
・ Scanning speed: 1 ° / min (sputtering film formation conditions)
-Equipment: DC magnetron sputtering equipment-Magnetic field strength: 1000 Gauss (directly above the target, horizontal component)
-Substrate temperature: 200 ° C
・ Achieved vacuum: 5 × 10 ⁻⁵ Pa
・ Sputtering gas: Ar
・ Sputtering gas pressure: 0.5 Pa
・ DC power: 300W
Sputtering time: 30 hours Discharge characteristics were evaluated by performing sputtering for 30 hours and evaluating the number of abnormal discharges per unit time as less than 0.5 times / hour as “◯”, and 0.5-10 times / hour as “ [Delta] "More than 10 times / hour was designated as" x ". The results are shown in Table 1.

以上のように、実施例と比較例を比較することにより、酸化亜鉛と、特定のイオン半径を有する正三価以上の価数を取り得る元素を特定の原子比で組み合わせることにより、異常放電を著しく抑制することが可能であることがわかる。

As described above, by comparing the example and the comparative example, by combining zinc oxide and an element having a specific ionic radius and having a positive trivalent or higher valence at a specific atomic ratio, abnormal discharge is significantly reduced. It can be seen that it can be suppressed.

A comparison of the X-ray diffraction peaks of Example 1 and Comparative Example 1 is shown.

Claims (7)

Zinc, an element A that can take a valence of positive trivalent or higher with an ionic radius of 0.7 to 1.1Å when assuming 6-coordination for oxygen ions, and an ionic radius when assuming 4-coordination for oxygen ions Is an X-ray diffraction pattern (XRD) of 2Θ = 30 containing at least one element M different from the element A and having Cu as a radiation source. A complex oxide characterized in that a diffraction peak detected within a range of ˜40 ° is composed only of (100) plane, (002) plane, and (101) plane belonging to a hexagonal wurtzite structure Sintered body. 2. The composite oxide sintered body according to claim 1, wherein the element A includes at least one element selected from the group of In, Ti, Zr, and Sn. The complex oxide sintered body according to claim 1 or 2, wherein the element M contains at least one element selected from the group consisting of Al, Ga, and Nb. The composite oxide sintered body according to claim 1, wherein a relative density of the sintered body is 95% or more. A zinc compound powder and a compound powder of an element A and an element M having a primary particle size smaller than the primary particle size of the powder, and each atomic ratio of zinc, element A, and element M, A / (A + M) is 0 4 or more, and the step of mixing the raw material powder so that the atomic ratio (A + M) / (Zn + A + M) is 0.001 to 0.17, the step of forming the mixed powder to produce a molded body, The method for producing a composite oxide sintered body according to any one of claims 1 to 4, further comprising a step of firing the molded body within a range of 1000 to 1600 ° C to produce a sintered body. A complex oxide sputtering target comprising the complex oxide sintered body according to claim 1. A transparent conductive film formed using the complex oxide sputtering target according to claim 6.

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