TWI532864B - Conductive oxide and its manufacturing method and oxide semiconductor film - Google Patents

Description

Conductive oxide, method of manufacturing the same, and oxide semiconductor film

The present invention relates to a conductive oxide, a method for producing the same, and an oxide semiconductor film, and more particularly to a conductive oxide for forming a target when an oxide semiconductor film is formed by a sputtering method, and a method for producing the same.

In a liquid crystal display device, a thin film EL (Electro-luminescence) display device, an organic EL display device, or the like, an amorphous germanium film is mainly used as a channel layer of a TFT (Thin Film Transistor). In recent years, an oxide semiconductor film containing In-Ga-Zn composite oxide (IGZO) as a main component has been attracting attention as a semiconductor film instead of an amorphous germanium film.

For example, in JP-A-2008-199005 (Patent Document 1), it is disclosed that an amorphous oxide semiconductor is formed by a sputtering method using a target including a sintered body of an oxide powder exhibiting conductivity. Membrane technology. The oxide semiconductor film formed in this manner has an advantage that the mobility of the carrier is larger than that of the amorphous germanium film.

In the sputtering method disclosed in Japanese Laid-Open Patent Publication No. 2008-199005 (Patent Document 1), first, the target and the substrate are opposed to each other in the sputtering apparatus. Then, a voltage is applied to the target to sputter rare gas ions on the surface of the target to cause the constituent atoms of the target to fly out. An IGZO (In-Ga-Zn-O composite oxide) film is formed by depositing constituent atoms of the target on a substrate.

As used above preferably by sputtering a target made of the IGZO film, Japanese Patent Laid-Open Publication No. 2008-214697 (Patent Document 2) discloses the compound ₄ represented by InGaZnO will have it as a main component and containing tetravalent positive The sputtering target of the metal element.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2008-199005

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2008-214697

However, the IGZO sputtering target disclosed in Japanese Patent Laid-Open Publication No. 2008-199005 (Patent Document 1) and Japanese Patent Laid-Open Publication No. 2008-214697 (Patent Document 2) has a high price because of the expensive Ga. . Therefore, it has been demanded to develop a conductive oxide which is inexpensive compared with IGZO and which can be preferably used for sputtering a target to obtain an oxide semiconductor film having high physical properties.

An object of the present invention is to provide a conductive oxide which is inexpensive and which can be preferably used for a target of sputtering to obtain a high-performance oxide semiconductor film, a method for producing the same, and an oxide semiconductor film.

According to a certain aspect of the present invention, the present invention is a conductive oxide containing In, Al, at least one element selected from the group consisting of Zn and Mg, M, and O, and containing crystalline Al ₂ MO ₄ .

In the conductive oxide of the present invention, crystalline Al ₂ ZnO ₄ may be contained as the crystalline Al ₂ MO ₄ . Here, the ratio of the crystalline Al ₂ ZnO ₄ to the cross-sectional area of the conductive oxide can be set to 10% or more and 60% or less. Here, it may further comprise a crystal selected from the group consisting of crystalline In ₂ Al _2(1-m) Zn _1-q O _7-p (0≦m<1, 0≦q<1, 0≦p≦3m+q) and crystal At least one crystal of the group consisting of In ₂ O ₃ .

The conductive oxide of the present invention may contain crystalline Al ₂ MgO ₄ as crystalline Al ₂ MO ₄ . Here, the ratio of the crystalline Al ₂ MgO ₄ to the cross-sectional area of the conductive oxide can be 2% or more and 60% or less. Here, it may further comprise a crystal selected from the group consisting of crystalline In ₂ Al _2(1-n) Mg _1-t O _7-s (0≦n<1, 0≦t<1, 0≦s≦3n+t) and crystal At least one crystal of the group consisting of In ₂ O ₃ .

In the conductive oxide of the present invention, when the atomic ratio of the total of In, Al, and M is 100 atom%, 10 to 50 atom% of In, 10 to 50 atom% of Al, and 15 to 40 may be contained. M of atomic %. Further, it may further contain at least one additive element selected from the group consisting of N, Al, Si, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, W, Sn, and Bi.

The conductive oxide of the present invention can be used as a target for sputtering.

According to another aspect of the present invention, the present invention provides an oxide semiconductor film formed by using the conductive oxide described above.

Further, according to still another aspect of the present invention, the present invention provides a method for producing a conductive oxide, comprising the steps of: when at least one element selected from the group consisting of Zn and Mg is M; comprising a first step of preparing a mixture of powder and powder MO of Al ₂ O _3; calcining the mixture by the first to prepare crystalline Al ₂ MO ₄ powder of step; preparing a crystalline Al ₂ MO ₄ In ₂ O ₃ powder a step of forming a second mixture of the powder; a step of obtaining a shaped body by molding the second mixture; and a step of sintering the formed body.

In the method for producing a conductive oxide of the present invention, the MO powder may be a ZnO powder, and the crystalline Al ₂ MO ₄ powder may be a crystalline Al ₂ ZnO ₄ powder to prepare a crystalline Al ₂ ZnO ₄ powder. In the step, the calcination temperature of the first mixture is 800 ° C or more and less than 1200 ° C, and the sintering temperature of the molded body in the step of sintering the formed body is set to 1280 ° C or more and less than 1500 ° C.

In the method for producing a conductive oxide of the present invention, the MO powder may be MgO powder, and the crystalline Al ₂ MO ₄ powder may be a crystalline Al ₂ MgO ₄ powder to prepare a crystalline Al ₂ MgO ₄ powder. In the step, the calcination temperature of the first mixture is 800 ° C or more and less than 1200 ° C, and the sintering temperature of the molded body in the step of sintering the formed body is 1300 ° C or more and 1500 ° C or less.

According to the present invention, it is possible to provide a conductive oxide which is inexpensive and which can be preferably used for a target of sputtering to obtain a high-performance oxide semiconductor film, a method for producing the same, and an oxide semiconductor film.

[conductive oxide]

The conductive oxide according to an embodiment of the present invention contains In, Al, at least one element M selected from the group consisting of Zn and Mg, and O, and contains crystalline Al ₂ MO ₄ . Since the conductive oxide of the present embodiment contains at least one element M and O selected from the group consisting of Zn and Mg, the conductive oxide does not contain the expensive Ga contained in IGZO, and thus IGZO is cheaper than the one. Further, since the conductive oxide of the present embodiment contains the crystalline Al ₂ MO ₄ , the characteristics of the oxide semiconductor film obtained by sputtering using the conductive oxide as a target are stabilized. In crystalline Al ₂ MO ₄ , since the valence of Zn and Mg corresponding to M is +2 and the ionic radius is very similar, both crystalline Al ₂ ZnO ₄ and crystalline Al ₂ MgO ₄ have a spinel type. Crystal structure.

In the conductive oxide of the present embodiment, it is preferred to contain crystalline Al ₂ ZnO ₄ as crystalline Al ₂ MO ₄ . By containing the crystalline Al ₂ ZnO ₄ , the characteristics of the oxide semiconductor film obtained by sputtering with a conductive oxide as a target can be stabilized, and the etching rate can be improved. Therefore, the conductive oxide containing the crystalline Al ₂ ZnO ₄ can be preferably used as a target for forming an oxide semiconductor film by a sputtering method.

Here, crystalline Al ₂ ZnO ₄ containing crystalline Al sectional area of the conductive oxide _{4 2} ZnO (cross-sectional area when the cutting means in any of a surface of a conductive oxide, the same applies hereinafter) as The proportion is preferably from 10% to 60%, more preferably from 14% to 50%. If the ratio of the crystalline Al ₂ ZnO ₄ to the cross-sectional area of the conductive oxide is less than 10%, the characteristics of the oxide semiconductor film obtained by sputtering using the conductive oxide as a target may become It is unstable and the etching rate is lowered. If the proportion of the crystalline Al ₂ ZnO ₄ in the cross-sectional area of the conductive oxide is more than 60%, the surface roughness of the oxide semiconductor film obtained by sputtering using the conductive oxide as a target Ra becomes rough.

Crystalline Al ₂ ZnO ₄ to the cross sectional area containing crystalline Al ₂ ZnO ₄ of the conductive oxide proportion may be determined by the EDX (energy dispersive X-ray analysis) method. More specifically, electrons (reflected electron images) reflected from the cross section of the incident electron beam of the sample of the conductive oxide are observed. Then, the contrast of regions except for the X-ray fluorescence analysis to determine the crystalline regions Al ₂ ZnO _4, the ratio can be measured whereby the area of the region of crystalline Al ₂ ZnO ₄ in the cross-sectional area of the occupied. Further, the surface roughness Ra is an arithmetic mean roughness Ra defined in JIS B0601:2001, and can be measured by AFM (Atomic Force Microscope) or the like.

Further, the conductive oxide containing the crystalline Al ₂ ZnO ₄ preferably further contains a crystal selected from the group consisting of crystalline In ₂ Al _2(1-m) Zn _1-q O _7-p (0≦m<1, 0≦q) At least one of the group consisting of <1, 0≦p≦3m+q) and crystalline In ₂ O ₃ . By containing the crystalline In ₂ Al _2(1-m) Zn _1-q O _7-p , the surface roughness Ra of the oxide semiconductor film obtained by sputtering with a conductive oxide as a target can be changed. Be subtle. Since the thermal conductivity of the conductive oxide is increased by containing the crystalline In ₂ O ₃ , the discharge is stabilized when DC sputtering is performed using the conductive oxide as a target. Further, the field-effect mobility of the oxide semiconductor film obtained by sputtering with a conductive oxide as a target can be improved.

In the conductive oxide containing crystalline Al ₂ ZnO _{4 ,} the presence of crystalline Al ₂ ZnO ₄ , crystalline In ₂ Al _2(1-m) Zn _1-q O _7-p and crystalline In ₂ O ₃ It can be confirmed based on the chemical composition determined by ICP (inductively coupled plasma) spectroscopic analysis and the crystal phase identified by X-ray diffraction. For example, the X-ray diffraction peak of the crystalline In ₂ Al _2(1-m) Zn _1-q O _{7-p can} be compared with the X-ray diffraction peak of the crystalline In ₂ Al ₂ Zn ₁ O ₇ The high-angle side shifts, and the presence of crystalline In ₂ Al _2(1-m) Zn _1-q O _7-p is confirmed. Furthermore, the crystalline Al ₂ ZnO ₄ has a spinel-type crystal structure, and the crystalline In ₂ Al _2(1-m) Zn _1-q O _7-p has a hexagonal crystal structure, crystalline In ₂ O ₃ has a cubic crystal structure.

Further, in the conductive oxide of the present embodiment, it is preferable to contain crystalline Al ₂ MgO ₄ as crystalline Al ₂ MO ₄ . By containing the crystalline Al ₂ MgO ₄ , the characteristics of the oxide semiconductor film obtained by sputtering with a conductive oxide as a target can be stabilized, and the field-effect mobility of the oxide semiconductor film can be improved. Therefore, the conductive oxide containing the crystalline Al ₂ MgO ₄ can be preferably used as a target for forming an oxide semiconductor film by a sputtering method.

Here, crystalline Al ₂ MgO ₄ to the cross sectional area containing crystalline Al ₂ MgO ₄ of the conductive oxide in the proportion of 2% or more preferably 60% or less, more preferably 5% or more to 20% or less. An oxide semiconductor film having a high field effect mobility can be produced by using a conductive oxide containing crystalline MgAl ₂ O ₄ in the above-mentioned area ratio as a target of sputtering. Further, when the conductive oxide containing the crystalline Al ₂ MgO ₄ further contains the crystalline In ₂ O ₃ , the ratio of the crystalline In ₂ O ₃ to the cross-sectional area of the conductive oxide is preferably 40. More than 98% of the above, more preferably 40% or more and 60% or less. By using the above-described area ratio containing crystalline conductive oxide In ₂ O ₃ as the sputter targets fabricated of an oxide semiconductor film can be made of a high field effect mobility of the oxide semiconductor film.

Here, the ratio of the crystalline Al ₂ MgO ₄ and the crystalline In ₂ O ₃ to the cross-sectional area of the conductive oxide is calculated as follows. First, the peaks of the crystalline Al ₂ MgO ₄ and the crystalline In ₂ O _{3 were} confirmed by X-ray diffraction. Then, the conductive oxide is cut at an arbitrary surface. The incident surface of the conductive oxide was irradiated with an incident electron beam, and an electron (reflected electron image) reflected from the cross section was observed using an analytical scanning electron microscope. Fluorescence X-ray analysis was performed on the regions of contrast in the reflected electron image, whereby the regions where Al and Mg were mainly observed were determined to be crystalline Al ₂ MgO ₄ , and the region where only the peak of In was observed was determined to be crystalline. In ₂ O ₃ . Thus, the ratio of the area of the crystalline MgAl ₂ O ₄ and the crystalline In ₂ O ₃ to the cross section was calculated.

Further, the conductive oxide containing the crystalline Al ₂ MgO ₄ preferably further contains a crystal selected from the group consisting of crystalline In ₂ Al _2(1-n) Mg _1-t O _7-s (0≦n<1, 0≦t) At least one of the group consisting of <1, 0≦s≦3n+t) and crystalline In ₂ O ₃ .

By containing crystalline In ₂ Al _2(1-n) Mg _1-t O _7-s , the field-effect mobility of the oxide semiconductor film obtained by sputtering with a conductive oxide as a target can be improved. Such a crystalline In ₂ Al _2(1-n) Mg _1-t O _7-s is modified by mixing crystalline In ₂ Al ₂ MgO ₇ with crystalline Al ₂ MgO ₄ crystal powder under specific conditions. The quality is formed by depleting Al and Mg in the crystalline In ₂ Al ₂ MgO ₇ . If Al and Mg are deficient (that is, if both n and t are n>0, t>0), the atomic ratio of oxygen is less than the value of "7" corresponding to the stoichiometric ratio of the defect (ie, The case of s>0). By using an oxide oxide containing such a crystalline In ₂ Al _2(1-n) Mg _1-t O _7-s conductive oxide as a sputtering target, an oxide semiconductor film can be produced, and a field-effect mobility can be made high. An oxide semiconductor film.

Although it is difficult to directly calculate the values of n and t in the above crystalline In ₂ Al _2(1-n) Mg _1-t O _7-s , it is confirmed whether or not the crystalline In ₂ Al _2(1-n) Mg _{1- t} O _{7-s is} present. Confirm whether crystalline _{In 2 Al 2 (1-n} ) Mg 1-t O 7-s exists based composition obtained by ICP emission spectrometry of a conductive oxide, and identified by X-ray diffraction crystalline phase is carried out. For example, when the atomic concentration ratio of In:Al:Mg in the conductive oxide is determined to be 2:2:1 by ICP spectral analysis, it is confirmed by X-ray diffraction that In ₂ Al ₂ MgO is present in the conductive oxide. _{At 7} o'clock, it was judged that in the conductive oxide, crystal In ₂ Al _2(1-n) Mg _1-t O _7-s was present together with the crystalline Al ₂ MgO ₄ (0<n<1, 0<t <1, 0≦s≦3n+t). Further, when it is confirmed by X-ray diffraction that crystalline In ₂ O ₃ , In ₂ Al ₂ MgO ₇ and Al ₂ MgO ₄ are present, the composition obtained by ICP spectral analysis is analyzed and analyzed. The composition ratio of In ₂ O ₃ , In ₂ Al ₂ MgO ₇ , and Al ₂ MgO ₄ determined by an electron microscope is compared and the composition is understood. If AlMg is insufficient, it is considered that In ₂ Al _2(1-n) Mg is present. _1-t O _7-s .

Since the thermal conductivity of the conductive oxide is increased by containing the crystalline In ₂ O ₃ , the discharge is stabilized when DC sputtering is performed using the conductive oxide as a target. Further, the field-effect mobility of the oxide semiconductor film obtained by sputtering with a conductive oxide as a target can be improved.

In the conductive oxide containing crystalline Al ₂ MgO _{4 ,} the presence of crystalline Al ₂ MgO ₄ , crystalline In ₂ Al _2(1-n) Mg _1-t O _7-s and crystalline In ₂ O ₃ It can be confirmed based on the chemical composition determined by ICP spectral analysis and the crystal phase identified by X-ray diffraction. For example, the X-ray diffraction peak of the crystalline In ₂ Al _2(1-n) Mg _1-t O _{7-s can} be compared with the X-ray diffraction peak of the crystalline In ₂ Al ₂ Mg ₁ O ₇ The high-angle side shifts, and the presence of crystalline In ₂ Al _2(1-n) Mg _1-t O _7-s is confirmed. Furthermore, the crystalline Al ₂ MgO ₄ has a spinel-type crystal structure, and the crystalline In ₂ Al _2(1-n) Mg _1-t O _7-s has a hexagonal crystal structure, crystalline In ₂ O ₃ has a cubic crystal structure.

In the conductive oxide of the present embodiment, when the atomic ratio of the total of In, Al, and M is 100 atom%, it is preferable to contain 10 to 50 atom% of In, 10 to 50 atom% of Al, and 15 to 15%. 40 atomic % of M. Such an atomic ratio conductive oxide is inexpensive and can be preferably used for a sputtering target to obtain an oxide semiconductor film having high physical properties (for example, a large etching rate, a high field effect mobility, etc.).

The conductive oxide of the present embodiment preferably further contains at least one selected from the group consisting of N, Al, Si, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, W, Sn, and Bi. The additive element is more preferably contained in an amount of 0.1 × 10 ²² atm / cc or more and 5.0 × 10 ²² atm / cc or less. In other words, the concentration of the entire additive element contained in the conductive oxide of the present embodiment is preferably 0.1 × 10 ²² atm / cc or more and 5.0 × 10 ²² atm / cc or less. Here, the additive element and the atomic concentration contained in the conductive oxide can be measured by SIMS (Secondary Ion Mass Spectrometry).

The conductive oxide of this embodiment can be preferably used for a target of a sputtering method. Here, the "target of the sputtering method" is a method of processing a material for forming a film by a sputtering method into a plate shape, or attaching the plate-shaped material to a backing plate (for attaching a target material) The backing plate can be made of raw materials such as oxygen-free copper, steel, stainless steel, aluminum, aluminum alloy, molybdenum, titanium, and the like. The shape of the target is not particularly limited, and may be a circular shape or a square shape. Further, the size of the target may be a disk shape having a diameter of 1 cm (a flat plate shape), or may be a square (plate rectangle) having a diameter of more than 2 m like a sputtering target for a large LCD (Liquid Crystal Display Device).

[Oxide semiconductor film]

In the oxide semiconductor film according to another embodiment of the present invention, the conductive oxide of the above-described embodiment is used, and it is preferable that the conductive oxide of the above embodiment is used for a target and formed by a sputtering method. . Since the oxide semiconductor film of the present embodiment is formed using the conductive oxide of the above embodiment, its characteristics are stabilized, the etching rate thereof is improved, and/or its field-effect mobility is increased. In addition, the sputtering method refers to a method in which a target is placed opposite to a substrate in a sputtering apparatus, a voltage is applied to the target, and rare gas ions are sputtered on the surface of the target to fly the constituent atoms of the target, and the target is made. The constituent atoms are deposited on the substrate, thereby forming an oxide semiconductor film.

[Method of Manufacturing Conductive Oxide]

Referring to Fig. 1, a method for producing a conductive oxide according to still another embodiment of the present invention includes the following steps: when at least one element selected from the group consisting of Zn and Mg is M, step-containing Al ₂ O ₃ powder and the mixture of the first powder of MO (SlO); by calcining the first mixture to prepare crystalline Al ₂ MO ₄ powder of step (S20); preparing a crystalline powder of Al ₂ MO ₄ a step (S30) of forming a second mixture with the In ₂ O ₃ powder; a step of obtaining a molded body by molding the second mixture (S40); and a step of sintering the formed body (S50).

According to the method for producing a conductive oxide of the present embodiment, by including the above steps, it is possible to efficiently produce a conductive oxide which is preferably used for forming a semiconductor oxide film and which is inexpensive, and more specifically, A conductive oxide which is preferably used for forming a target of an oxide semiconductor film by a sputtering method and which is inexpensive in cost can be produced with high efficiency.

(Preparation step of the first mixture)

When at least one element selected from the group consisting of Zn and Mg is M, the step (S10) of preparing the first mixture containing the Al ₂ O ₃ powder and the MO powder is by mixing Al as a raw material powder. _{The 2} O ₃ powder is carried out with MO powder (i.e., ZnO powder and/or MgO powder). Here, the purity of the Al ₂ O ₃ powder and the MO powder is not particularly limited, and from the viewpoint of improving the quality of the conductive oxide to be produced, it is preferably 99.9% by mass or more, and more preferably 99.99% by mass or more. Further, the mixing ratio of the Al ₂ O ₃ powder and the MO powder is not particularly limited, and from the viewpoint of improving the yield of the crystalline Al ₂ MO ₄ powder, Al ₂ O ₃ : MO = is preferably used in terms of molar ratio. 1:0.95~1.05.

Further, the method of mixing the Al ₂ O ₃ powder and the MO powder is not particularly limited, and may be a dry mixing method or a wet mixing method. As such a mixing method, a method of mixing by a ball mill, mixing by a planetary ball mill, mixing by a bead mill, stirring by ultrasonic waves, or the like can be preferably used. The drying method in the case of using a wet mixing method may be natural drying or forced drying using a spray dryer or the like.

(Step of producing crystalline Al ₂ MO ₄ powder)

The step (S20) of producing the crystalline Al ₂ MO ₄ powder is carried out by calcining the above first mixture. The calcination temperature of the first mixture is preferably 800 ° C or more and less than 1200 ° C. When the calcination temperature is less than 800 ° C, unreacted raw material powder remains, and it is difficult to produce crystalline Al ₂ MO ₄ powder having sufficient crystallinity. When the calcination temperature is 1200 ° C or higher, the grain size of the crystalline Al ₂ MO ₄ powder obtained by calcination becomes large, and if it is used as it is, it is difficult to obtain a dense sintered body in the subsequent sintering step, so it takes time before the sintering step Al ₂ MO ₄ crystalline powder was pulverized. The calcining environment is not particularly limited, and from the viewpoint of suppressing the detachment of oxygen from the powder and being simple, it is preferably an atmospheric environment.

The crystal Al ₂ MO ₄ powder can be confirmed by calcination based on the chemical composition determined by ICP spectral analysis and the crystal phase identified by X-ray diffraction.

The crystalline Al ₂ MO ₄ powder obtained in this manner preferably has an average particle diameter of 0.1 μm or more and 1.5 μm or less. Here, the average particle diameter of the powder is a value calculated by a light scattering method.

(Preparation step of the second mixture)

And preparing a crystalline Al ₂ O ₃ powder In Step ₂ MO ₄ of the second powder mixtures (S30) based crystalline by mixing powder of Al ₂ MO ₄ and In ₂ O ₃ powder is carried out. Here, the purity of the In ₂ O ₃ powder is not particularly limited, and from the viewpoint of improving the quality of the conductive oxide to be produced, it is preferably 99.9% by mass or more, and more preferably 99.99% by mass or more. Further, the mixing ratio of the crystalline Al ₂ MO ₄ powder and the In ₂ O ₃ powder is not particularly limited, and from the viewpoint of improving the conductivity of the conductive oxide, it is preferable to use a molar ratio of crystal Al ₂ MO. ₄ : In ₂ O ₃ =1: 0.95~1.

Further, the method of mixing the crystalline Al ₂ MO ₄ powder and the In ₂ O ₃ powder is not particularly limited, and may be a dry mixing method or a wet mixing method. As such a mixing method, a method of mixing by a ball mill, mixing by a planetary ball mill, mixing by a bead mill, stirring by ultrasonic waves, or the like can be preferably used. The drying method in the case of using a wet mixing method may be natural drying or forced drying using a spray dryer or the like.

Further, in the case of producing a conductive oxide containing an additive element, the mixed content of the crystalline Al ₂ MO ₄ powder and the In ₂ O ₃ powder is selected from the group consisting of N, Al, Si, Ti, V, Cr, and Zr. A raw material powder of at least one of the additive elements of the group consisting of Nb, Mo, Hf, Ta, W, Sn, and Bi. The additive element raw material powder is not particularly limited, and from the viewpoint of suppressing the separation of the impurity element other than the constituent element and the additive element from oxygen, AlN powder, Al ₂ O ₃ powder, SiO ₂ powder, TiO ₂ can be preferably used. Powder, V ₂ O ₅ powder, Cr ₂ O ₃ powder, ZrO ₂ powder, Nb ₂ O ₃ powder, MoO ₂ powder, HfO ₂ powder, Ta ₂ O ₃ powder, WO ₃ powder, SnO ₂ powder and Bi ₂ O ₃ powder. By adding the above-mentioned additive element raw material powder, the conductive oxide is contained in a group selected from the group consisting of N, Al, Si, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, W, Sn, and Bi. At least one type of additive element can produce a conductive oxide capable of producing an oxide semiconductor film having a high field effect mobility.

(forming step)

In the step (S40) of obtaining a molded body by molding the second mixture, the method of molding the second mixture is not particularly limited, and from the viewpoint of high productivity, press forming, CIP can be preferably used. (cold isostatic pressing) forming, casting, and the like. Moreover, from the viewpoint of high-efficiency molding in stages, it is preferred to perform CIP molding after press molding.

(sintering step)

A conductive oxide is obtained by a step (S50) of sintering the formed body. The sintering temperature of the molded body differs depending on the type of the crystalline Al ₂ MO ₄ powder (here, M is at least one element selected from the group consisting of Zn and Mg) contained in the molded body.

When the molded body contains crystalline Al ₂ ZnO ₄ powder as the crystalline Al ₂ MO ₄ powder, the sintering temperature of the formed body is preferably 1280 ° C or more and less than 1500 ° C. When the sintering temperature is less than 1280 ° C, the sintering of the crystalline Al ₂ ZnO ₄ powder and the In ₂ O ₃ powder is insufficient, and it is difficult to produce a dense sintered body which is necessary as a target of sputtering. When the sintering temperature is 1500 ° C or higher, crystal Al ₂ ZnO ₄ cannot be formed and only crystalline In ₂ Al _{2 (1-m)} Zn _1-q O _{7-p is formed} , so that a conductive oxide is used as a target. The oxide semiconductor film obtained by the sputtering becomes unstable in characteristics, the surface roughness Ra thereof becomes large, and the etching rate thereof is lowered. Here, when the sintering temperature of the molded body is 1280 ° C or more and less than 1300 ° C, the crystal phase forms crystalline Al ₂ ZnO ₄ and crystalline In ₂ O ₃ . When the sintering temperature of the formed body is 1300 ° C or more and less than 1500 ° C, the crystal phase forms crystalline Al ₂ ZnO ₄ and crystalline In ₂ Al _{2 (1-m)} Zn _1-q O _7-p .

When the molded body contains crystalline Al ₂ MgO ₄ powder as the crystalline Al ₂ MO ₄ powder, the sintering temperature of the formed body is preferably 1300 ° C or more and 1500 ° C or less. When the sintering temperature is less than 1300 ° C, the sintering of the crystalline Al ₂ MgO ₄ powder and the In ₂ O ₃ powder is insufficient, and it is difficult to produce a dense sintered body which is necessary as a target of sputtering. When the sintering temperature is higher than 1500 ° C, Mg is detached, and the composition of the sintered body is uneven and becomes heterogeneous. Here, when the sintering temperature of the molded body is 1300 ° C or higher and less than 1390 ° C, the crystal phase forms crystalline Al ₂ MgO ₄ and crystalline In ₂ O ₃ . When the sintering temperature of the formed body is 1390 ° C or more and less than 1500 ° C, the crystal phase forms crystalline Al ₂ ZnO ₄ and crystalline In ₂ Al _{2 (1-n)} Zn _1-t O _7-s .

[Examples] [Example A]

1. Preparation of the first mixture

Al ₂ O ₃ powder (purity: 99.99% by mass, BET (Brunauer-Emmett-Teller) specific surface area: 10 m ² /g) and ZnO powder (purity: 99.99% by mass, BET ratio) using a ball mill Surface area: 4 m ² /g) The mixture was pulverized and mixed at a molar mixing ratio of Al ₂ O ₃ :ZnO=1:1 for 3 hours, whereby an Al ₂ O ₃ -ZnO mixture was prepared as the first mixture. As the dispersion medium at the time of pulverization and mixing, water is used. The mixture was dried using a spray dryer, thereby obtaining a first mixture.

2. Production of crystalline Al ₂ ZnO ₄ powder

The obtained first mixture was placed in a crucible made of alumina and calcined at 900 ° C for 5 hours in an atmospheric environment. Thus, a crystallized Al ₂ ZnO ₄ powder which is a calcined powder formed of crystalline Al ₂ ZnO _{4 was obtained} . The presence of crystalline Al ₂ ZnO ₄ was confirmed based on the chemical composition determined by ICP spectral analysis and the crystal phase identified by X-ray diffraction.

3. Preparation of the second mixture

The obtained crystalline Al ₂ ZnO ₄ powder (calcined powder) and In ₂ O ₃ powder (purity: 99.99% by mass, BET specific surface area: 5 m ² /g) were crystallized as Al ₂ ZnO ₄ using a ball mill apparatus. The molar mixing ratio of In ₂ O ₃ = 0.95 was pulverized and mixed for 6 hours, thereby preparing a mixture of In ₂ O ₃ -crystalline Al ₂ ZnO ₄ as the second mixture. As the dispersion medium at the time of pulverization and mixing, water is used. The mixture was dried using a spray dryer, thereby obtaining a second mixture.

4. Forming

The obtained second mixture was press-formed under the conditions of a surface pressure of 1.0 tf/cm ² , and CIP molding was carried out under the conditions of a surface pressure of 2.0 tf/cm ² , thereby obtaining eight diameters of 100 mm and thickness. A disk-shaped formed body of about 9 mm.

5. Sintering

The obtained eight molded bodies were at 1,250 ° C (Example A1), 1280 ° C (Example A2), 1300 ° C (Example A3), 1350 ° C (Example A4), 1375 ° C (Example A5), and 1400 ° C (Example A6). The temperatures of 1450 ° C (Example A7) and 1500 ° C (Example AR1) were respectively sintered for 5 hours, thereby obtaining eight sintered bodies (Examples A1 to A7 and AR1) having different crystal composition ratios as conductive oxidation. Things.

The relative density of the obtained sintered body (conductive oxide) was calculated by the following method. First, the bulk density of the obtained sintered body was measured by the Archimedes method. Then, the sintered body was pulverized, and the true density of the powder was measured by a pycnometer method. Then, the relative density of the sintered body was calculated by dividing the bulk density by the true density.

Further, the main surface of the conductive oxide is polished, and EDX (energy dispersive X-ray analysis) is performed on the main surface after polishing to calculate crystalline Al ₂ ZnO ₄ and crystalline In ₂ Al _{2 (1-m). The ratio of} Zn _1-q O _7-p and crystalline In ₂ O ₃ to the cross-sectional area of the conductive oxides. The results are summarized in Table 1.

6. Fabrication and evaluation of an oxide semiconductor film obtained by sputtering

Eight oxide semiconductor films were produced by DC (direct current) magnetron sputtering using the obtained eight conductive oxides as targets. Specifically, a 25 mm × 25 mm × 0.6 mm thick synthetic quartz glass substrate was placed as a film formation substrate on the water-cooled substrate holder in the deposition chamber of the sputtering apparatus. The conductive oxide is disposed at a distance of 40 mm so that the main surface thereof faces the main surface of the synthetic quartz glass substrate. Here, a part of the main surface of the synthetic quartz glass substrate is covered by a metal mask.

Then, the pressure in the film forming chamber was reduced to 1 × 10 ^-4 Pa. Then, in a state where a shutter is placed between the synthetic quartz glass substrate and the conductive oxide (target), Ar gas is introduced into the deposition chamber until a pressure of 1 Pa is reached, and a DC of 30 W is applied. The electricity causes a sputter discharge, whereby the conductive oxide (target) surface is cleaned (presputtered) for 10 minutes. Then, Ar gas was introduced into the deposition chamber until the pressure of 20 Pa was reached, and 50 W of DC power was applied to cause sputtering discharge, and the baffle was removed, and film formation was performed for 1 hour to form an oxide semiconductor film. Furthermore, the substrate holder is not particularly biased and is only water cooled. After the oxide semiconductor film is formed, the synthetic quartz glass substrate is taken out from the film forming chamber, and it is seen that the oxidation of the In-Al-Zn composite oxide (IAZO) is formed only in the region of the synthetic quartz glass substrate that is not covered by the metal mask. Semiconductor film. The obtained semiconductor film was evaluated for crystallinity by X-ray diffraction (SmartLab manufactured by Rigaku Co., Ltd.), and as a result, it was amorphous (amorphous).

(1) Evaluation of surface roughness Ra

The surface roughness Ra of the obtained oxide semiconductor film was measured by AFM (atomic force microscope) in the range of 10 μm × 10 μm square. The results are summarized in Table 1.

(2) Evaluation of etching rate

On the synthetic quartz glass substrate, the step difference between the region where the oxide semiconductor film was formed and the region where the oxide semiconductor film was not formed was measured by a stylus type surface roughness meter, thereby obtaining a The thickness of the oxide semiconductor film formed.

Thereafter, an etching aqueous solution of phosphoric acid: acetic acid: water = 4:1:100 was prepared in a molar ratio, and a synthetic quartz glass substrate on which an oxide semiconductor film was formed was immersed in the etching liquid. At this time, the etching liquid was heated to 50 ° C in a heat bath. The immersion time was set to 2 minutes, and the thickness of the oxide semiconductor film remaining without being etched therebetween was measured by a stylus type surface roughness meter. The etching rate was calculated by dividing the thickness difference of the oxide semiconductor film before and after the etching by the etching time. The results are summarized in Table 1.

As is clear from Table 1, as shown in Examples A1 to A7, a conductive oxide containing In, Al, Zn, O and containing crystalline Al ₂ ZnO ₄ can be produced by sputtering as a target. An oxide semiconductor film having characteristics and a high etching rate. Further, as shown in Examples A3 to A7, the conductive oxide having a ratio of the crystalline Al ₂ ZnO ₄ in the cross-sectional area of 10% or more and 60% or less can be formed by sputtering the target as a target. A fine oxide semiconductor film having a roughness Ra.

[Example B] (Examples B1~B6)

In Examples B1 to B6 of Example B, conductive oxidation containing crystalline Al ₂ MgO ₄ and crystalline In ₂ Al _2(1-n) Mg _1-n O _7-4n (0≦n<1) was prepared. Things.

1. Preparation of the first mixture

Al ₂ O ₃ powder (purity: 99.99% by mass, BET specific surface area: 5 m ² /g) and MgO powder (purity: 99.99% by mass, BET specific surface area: 6 m ² /g) were mixed at a molar mixing ratio The Al ₂ O ₃ :MgO=1:1 was placed in the ball mill apparatus. The powders were pulverized and mixed using water as a dispersion solvent for 30 minutes. Thereafter, water was volatilized by a spray dryer, whereby a first mixture containing a mixture of Al ₂ O ₃ -MgO was obtained.

2. Production of crystalline Al ₂ MgO ₄ powder

Then, the first mixture described above was placed in a crucible made of alumina, and calcined in an atmosphere of 900 ° C for 5 hours to obtain a crystalline Al ₂ MgO ₄ powder. The presence of crystalline Al ₂ MgO ₄ was confirmed by the chemical composition determined by ICP spectral analysis and the crystal phase identified by X-ray diffraction.

3. Preparation of the second mixture

The above crystalline Al ₂ MgO ₄ powder and In ₂ O ₃ powder (purity: 99.99% by mass, BET specific surface area: 8 m ² /g) were Al ₂ MgO ₄ :In ₂ O ₃ =1 at a molar mixing ratio. The method of 1: is loaded into the ball milling device. Then, the particles were pulverized and mixed for 6 hours using water as a dispersion solvent. Thereafter, water was volatilized by a spray dryer, whereby a second mixture, that is, an In ₂ O ₃ -crystalline Al ₂ MgO ₄ mixture was obtained.

4. Forming

The second mixture obtained above was press-formed under the conditions of a surface pressure of 1.0 tf/cm ² , and CIP molding was carried out at a surface pressure of 2.0 tf/cm ² to thereby produce a diameter of 100 mm and a thickness of about 9 mm. A disk-shaped formed body.

5. Sintering

The molded body obtained in this manner was calcined in an atmosphere at a temperature shown in the column of "sintering temperature" in Table 2 below for 5 hours to prepare a conductive oxide. Further, by setting the sintering temperature to 1390 ° C or more and 1500 ° C or less, conductive oxidation containing crystalline Al ₂ MgO ₄ and crystalline In ₂ Al _{2 (1-n)} Mg _1-n O _{7-4n is obtained} . Things.

(Example B7)

The conductive oxide of Example B7 was produced in the same manner as in Example B1 except that the preparation method of the second mixture was different from the sintering temperature of the molded body with respect to Example B1. That is, in the step B7, in the step of preparing the second mixture, in addition to the crystalline Al ₂ MgO ₄ powder and the In ₂ O ₃ powder, AlN powder was also added (purity: 99.99% by mass, BET specific surface area: 5 m ^{2 )} /g), whereby a second mixture comprising a mixed powder of In ₂ O ₃ -AlN-crystalline Al ₂ MgO ₄ is obtained. Using this second mixture, it was sintered at a sintering temperature of 1390 ° C for 5 hours under atmospheric pressure and a nitrogen atmosphere to prepare a disk-shaped molded body having a diameter of 100 mm and a thickness of about 9 mm.

(Examples B8~B20)

In Examples B8 to B20, the conductive oxides of Examples B8 to B20 were produced in the same manner as in Example B7 except that the preparation method of the second mixture was different from the sintering temperature and the sintering environment of the molded article with respect to Example B7. . That is, in Examples B8 to B20, the AlN powder of Example B7 was replaced with an oxide powder containing an additive element (Al ₂ O ₃ powder, SiO ₂ powder, TiO ₂ powder, V ₂ O ₅ powder, Cr ₂ O ₃ powder). , ZrO ₂ powder, Nb ₂ O ₃ powder, MoO ₂ powder, HfO ₂ powder, Ta ₂ O ₃ powder, WO ₃ powder, SnO ₂ powder, Bi ₂ O ₃ powder), at the sintering temperature shown in Table 2 in the atmosphere Sintering was carried out to prepare conductive oxides of Examples B8 to B20.

(example BR1)

In Example BR1, a conductive oxide was produced by a procedure different from the method for producing a conductive oxide of Examples B1 to B20. That is, in the method for producing a conductive oxide of the example BR1, first, Al ₂ O ₃ powder (purity: 99.99% by mass, BET specific surface area: 11 m ² /g), and MgO powder (purity: 99.99% by mass, BET specific surface area: 4 m ² /g) and In ₂ O ₃ powder (purity: 99.99% by mass, BET specific surface area: 5 m ² /g) in a molar mixing ratio of In ₂ O ₃ :Al ₂ O ₃ :MgO 1:1: 1:1 was loaded into the bead mill. Then, the mixed powders were pulverized and mixed using water as a dispersion solvent for 30 minutes. Thereafter, water was volatilized by a spray dryer, whereby an In ₂ O ₃ -Al ₂ O ₃ -MgO mixture was obtained.

Then, the obtained mixture was placed in a crucible made of alumina, and calcined in an atmosphere of 1200 ° C for 5 hours, thereby obtaining a crystalline In ₂ Al ₂ MgO ₇ powder.

The above-formed crystalline In ₂ Al ₂ MgO ₇ powder was molded by uniaxial press molding to prepare a disk-shaped molded body having a diameter of 100 mm and a thickness of 9 mm. This molded body was fired at 1500 ° C for 5 hours in an atmosphere to prepare a conductive oxide of the example BR1. Since the mixing method of the powder and the sintering temperature are 1500 ° C or more, only the crystalline In ₂ Al ₂ MgO ₇ is formed, and the crystalline MgAl ₂ O ₄ and the crystalline In ₂ Al _2(1-n) Mg _1-n O are not formed. _7-4n .

(example BR2)

In Example BR2, a conductive oxide was produced by a procedure different from the method for producing a conductive oxide of Examples B1 to B20. That is, first, In ₂ O ₃ powder (purity: 99.99% by mass, BET specific surface area: 5 m ² /g) was placed in a bead mill. Then, the In ₂ O ₃ powder was pulverized and mixed using water as a dispersion solvent for 30 minutes. Thereafter, water was volatilized by a spray dryer, whereby a granulated powder composed only of In ₂ O ₃ was obtained.

Then, the granulated powder obtained above was molded by uniaxial press molding to prepare a disk-shaped molded body having a diameter of 100 mm and a thickness of 9 mm. The molded body produced in this manner was sintered at 1,500 ° C for 5 hours in an atmosphere to prepare a conductive oxide of the example BR2.

(Examples B21~B26)

The conductive oxides of Examples B21 to B26 were produced in the same manner as in Example B1 except that the mixing ratio of the raw material powders in the first mixture and the second mixture was different from that in Example B1, and the sintering temperature was not at 1390 °C. In the examples B21 to B26, the mixing ratio of the Al ₂ O ₃ powder, the MgO powder, and the In ₂ O ₃ particles was adjusted so as to be an atomic ratio shown in the column of "atomic concentration ratio" in Table 3. Further, by setting the sintering temperature to less than 1390 ° C, the conductive oxide does not contain crystalline In ₂ Al _{2 (1-n)} Mg _1-n O _7-4n .

(Example B27)

The conductive oxide of Example B27 was produced in the same manner as in Example B7 except that the sintering temperature was different from that in Example B7. Further, by setting the sintering temperature to less than 1390 ° C, the conductive oxide does not contain crystalline In ₂ Al _{2 (1-n} )Mg _1-n O _7-4n .

(Example B28~B40)

The conductive oxides of each of Examples B28 to B40 were produced in the same manner as in each of Examples B8 to B20 except that the sintering temperatures were different for each of Examples B8 to B20. Further, by setting the sintering temperature to less than 1390 ° C, the conductive oxide does not contain crystalline In ₂ Al _{2 (1-n)} Mg _1-n O _7-4n .

The atomic ratio (unit: atomic %) of In, Al, and Mg was measured by ICP spectrometry for the conductive oxides of B1 to B40 and BR1 to BR2. The results are shown in the columns of "atomic concentration ratio" in Tables 2 and 3. Further, the conductive oxides produced in the examples B1 to B40 and the examples BR1 to BR2 were cut at one side, and the cut surface was subjected to fluorescent X-ray analysis using an analytical scanning electron microscope to calculate the crystal quality. The ratio of Al ₂ MgO ₄ in the cross-sectional area of the conductive oxide and the ratio of the crystalline In ₂ O ₃ to the cross-sectional area of the conductive oxide. The results are shown in the columns of "Al ₂ MgO ₄ ratio in the cross-sectional area" and "In ₂ O ₃ ratio in the cross-sectional area" in Tables 2 and 3. Further, in the cross sections of the conductive oxides of Examples B1 to B20 and the evaluation by X-ray diffraction, the region of the crystalline In ₂ O _{3 was} not confirmed.

The conductive oxides prepared in Examples B1 to B40 were subjected to crystallization analysis by a powder X-ray diffraction method. Specifically, the Kα ray of Cu was irradiated as X-rays, and the diffraction angle 2θ was measured. From the diffraction peaks, it was confirmed that both In ₂ O ₃ and Al ₂ MgO ₄ were crystalline. On the other hand, regarding the conductive oxide produced in the example BR1, the presence of Al ₂ MgO _{4 was} not confirmed even by the evaluation using an analytical scanning electron microscope and X-ray diffraction, and X-ray diffraction was performed. The diffraction peak of In ₂ Al ₂ MgO _{7 was} confirmed.

Further, the composition of the additive element in the conductive oxide produced in the examples B1 to B40 and the examples BR1 to BR2 and the atomic number (atom/cm ³ ) per 1 cm ³ of the additive element were calculated by SIMS. The results are shown in the columns of "Additional Elements" and "Concentrations" in Tables 2 and 3.

(Evaluation: field effect mobility)

The conductive oxide obtained in Examples B1 to B40 and Examples BR1 to BR2 was used as a target, and an oxide semiconductor film was formed by DC (Direct Current) magnetron sputtering. The TFT including the oxide semiconductor film as a channel layer was prepared, and the field-effect mobility of each TFT was calculated to evaluate the performance of the conductive oxides of Examples B1 to B40 and Examples BR1 to BR2.

The field effect mobility described above is specifically calculated as follows. First, the conductive oxides obtained in Examples B1 to B40 and BR1 to BR2 were processed into targets having a diameter of 3 inches (76.2 mm) and a thickness of 5.0 mm. Then, the target was placed in the sputtering apparatus so that the surface having a diameter of 3 inches became the sputtering surface. On the other hand, a film-forming substrate containing a conductive Si wafer (<0.02 Ωcm) of 25 mm × 25 mm × 0.5 mm was placed on the water-cooled substrate holder of the sputtering apparatus, and a film was formed using a metal mask. Partially covered with one of the surfaces of the substrate. At this time, the distance between the target and the substrate for film formation was 40 mm.

Then, the inside of the sputtering apparatus is evacuated until it reaches about 1×10 ⁻⁴ Pa, and Ar gas is introduced into the film forming chamber in a state where a baffle is placed between the substrate and the target to form a film forming chamber. The pressure was 1 Pa, and a 120 W DC power was applied to the target to perform a sputtering discharge, thereby cleaning the target surface (pre-sputtering) for 10 minutes.

Thereafter, Ar gas containing 15% by volume of oxygen in a flow ratio ratio was introduced into the film forming chamber to have a pressure of 0.8 Pa in the film forming chamber, and 120 W of sputtering DC power was applied to the target, thereby being applied to the glass substrate. An oxide semiconductor film having a thickness of 70 nm was formed. Furthermore, the substrate holder is only water cooled and no bias voltage is applied.

In order to process the oxide semiconductor film thus produced into a specific channel width and channel length, a resist of a specific shape is applied onto the oxide semiconductor film, and exposure and development are performed. Then, the glass substrate with the oxide semiconductor film is immersed in an etching aqueous solution adjusted to a molar ratio of phosphoric acid:acetic acid:water=4:1:100, thereby etching the oxide semiconductor film to a specific channel width. And channel length.

Then, a resist is applied onto the oxide semiconductor film so that the portion where only the source electrode and the drain electrode are formed on the oxide semiconductor film is exposed, and exposure and development are performed. In the portion (electrode forming portion) where the resist is not formed, a metal layer containing Ti, a metal layer containing Al, and a metal layer containing Mo are sequentially formed by sputtering, whereby Ti/Al/Mo is used. The layer structure forms a source electrode and a drain electrode having a film thickness of 100 nm. Thereafter, the resist on the oxide semiconductor film is peeled off, whereby a TFT including an oxide semiconductor film containing In-Al-Mg-O as a channel layer is produced.

The field effect mobility (μ _fe ) was calculated for the TFT fabricated in the above manner as follows. First, a voltage of 5 V is applied between the source electrode and the drain electrode of the TFT, so that the voltage (V _gs ) applied between the source electrode and the gate electrode including the Si wafer is changed from -10 V to 20 V, by substituting the current drain current (I _ds ) into the equation (1), thereby calculating the g _m value at V _gs = 10 V. Then, the field-effect mobility (μ _fe ) was calculated by substituting the above calculated g _m value into the formula (2) and substituting W=20 μm and L=15 μm. The results are shown in the columns of "Field Effect Mobility" in Tables 2 and 3. Furthermore, the higher the value of the field effect mobility, the better the characteristics of the TFT.

g _m =dI _ds /dV _gs .........(1)

μ _fe =g _m . L/(W.C _i .V _ds ).........(2)

(evaluation results and inspection)

According to the results shown in Tables 2 and 3, the oxide semiconductor film produced using the conductive oxides of Examples B1 to B40 and the oxide semiconductor film produced by using the conductive oxides of Examples BR1 to BR2 were used. The field effect mobility shows a higher value. It is considered that the conductive oxides of Examples B1 to B40 contain In, Al, Mg, and O, and crystal Al ₂ MgO _{4 is} contained as crystal.

The embodiments and examples disclosed herein are to be considered as illustrative and not restrictive. The scope of the present invention is defined by the scope of the claims, and is intended to be

[Industrial availability]

The conductive oxide of the present invention can be preferably used as a target for sputtering film formation.

S10‧‧‧Steps for preparing the first mixture

S20‧‧‧Steps for making crystalline Al ₂ MO ₄ powder

S30‧‧‧Steps for preparing the second mixture

S40‧‧‧Steps for obtaining shaped bodies

S50‧‧‧Steps for sintering the shaped body

Fig. 1 is a flow chart showing a method of producing a conductive oxide.

S10‧‧‧Steps for preparing the first mixture

S20‧‧‧Steps for making crystalline Al ₂ MO ₄ powder

S30‧‧‧Steps for preparing the second mixture

S40‧‧‧Steps for obtaining shaped bodies

S50‧‧‧Steps for sintering the shaped body

Claims (8)

A conductive oxide containing In, Al, at least one element selected from the group consisting of Zn and Mg, M, and O, and containing crystalline Al ₂ ZnO ₄ or crystalline Al ₂ MgO ₄ as crystal Al ₂ MO ₄ ; which contains the above crystalline Al ₂ ZnO ₄ , further contains a crystal selected from the group consisting of crystalline In ₂ Al _2(1-m) Zn _1-q O _7-p (0≦m<1, 0≦q< At least one crystal of the group consisting of: 0≦p≦3m+q) and crystalline In ₂ O ₃ ; and containing the crystalline Al ₂ MgO ₄ , further containing a crystal selected from In ₂ Al _{2 ( 1-n)} Mg _1-t O _7-s (0≦n<1, 0≦t<1, 0≦s≦3n+t) and at least one crystal of the group consisting of crystalline In ₂ O ₃ quality. When the conductive oxide of claim 1 contains the crystalline Al ₂ ZnO ₄ , the ratio of the crystalline Al ₂ ZnO ₄ to the cross-sectional area of the conductive oxide is 10% or more and 60% or less. When the conductive oxide of claim 1 contains the crystalline Al ₂ MgO ₄ , the ratio of the crystalline Al ₂ MgO ₄ to the cross-sectional area of the conductive oxide is 2% or more and 60% or less. The conductive oxide according to any one of claims 1 to 3, wherein the atomic ratio of the total of In, Al, and M is 100 atom%, and 10 to 50 atom% of In, 10 to 50 atom% is contained. Al, 15 to 40 atom% of M. The conductive oxide according to any one of claims 1 to 3, which further comprises a component selected from the group consisting of N, Al, Si, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, W, Sn and Bi. At least one of the added elements in the group. The conductive oxide according to any one of claims 1 to 3, which is used for a target of a sputtering method. An oxide semiconductor film formed by using the conductive oxide according to any one of claims 1 to 6. A method for producing a conductive oxide, comprising the steps of preparing a first powder containing Al ₂ O ₃ powder and MO powder when at least one element selected from the group consisting of Zn and Mg is M a step of the mixture (S10); a step of preparing a crystalline Al ₂ MO ₄ powder by calcination of the first mixture (S20); preparing a powder containing the above crystalline Al ₂ MO ₄ powder and In ₂ O ₃ powder a step of the second mixture (S30); a step of obtaining a shaped body by molding the second mixture (S40); and a step of sintering the formed body (S50); the MO powder is ZnO powder or MgO powder; When the MO powder is ZnO powder, the crystalline Al ₂ MO ₄ powder is a crystalline Al ₂ ZnO ₄ powder, and the calcination temperature of the first mixture in the step (S20) of preparing the crystalline Al ₂ ZnO ₄ powder is 800° C. or more and less than 1200° C., in the step (S50) of sintering the formed body, the sintering temperature of the formed body is 1280° C. or more and less than 1500° C.; when the MO powder is MgO powder, the crystalline Al _{2 is used.} MO ₄ powder is a crystalline powder of Al ₂ MgO _4, prepared above crystalline powder of Al ₂ MgO ₄ Temperature calcination step (S20), mixtures of the above-described first above 800 ℃ and less than 1200 ℃, the above-described step of sintering the formed body (S50) sintering the shaped body in the temperature is less than 1300 ℃ 1500 ℃.