CN101558184A - Sputtering target and oxide semiconductor film - Google Patents

Abstract

The present invention provides a sputtering target containing oxides of indium , gallium (Ga) and zinc (Zn), wherein ZnGa is contained₂O₄The compound and InGaZnO₄The compounds shown.

Description

Sputtering target and oxide semiconductor film

technical field

The present invention relates to a sputtering target and an oxide semiconductor film.

Background technique

Oxide semiconductor films made of metal composite oxides have high mobility and visible light transmittance, and are currently used in switches for liquid crystal display devices, thin film electroluminescent display devices, electrophoretic display devices, and powder transfer display devices. Components, drive circuit components, etc.

Examples of the oxide semiconductor film formed of metal composite oxides include oxide semiconductor films formed of oxides of In, Ga, and Zn (IGZO). An oxide semiconductor film formed using an IGZO sputtering target has the advantage of having a higher degree of mobility than an amorphous silicon film, and is currently attracting attention (Patent Documents 1 to 10).

It is known that an IGZO sputtering target contains a compound represented by InGaO ₃ (ZnO) _m (m is an integer of 1 to 20) as a main component. However, when sputtering (for example, DC sputtering) using an IGZO sputtering target, there is a problem that abnormal growth of the compound represented by InGaO ₃ (ZnO) _m causes abnormal discharge, and defects occur in the obtained film.

In addition, the IGZO sputtering target is produced as follows: the raw material powder is mixed to prepare a mixture, the mixture is pre-fired, pulverized, granulated, and shaped to produce a shaped body, and then the shaped body is sintered and reduced. However, due to the number of processes Therefore, there are disadvantages in that the productivity of the sputtering target is lowered and the cost is increased.

Therefore, it is desirable to omit the above-mentioned steps, even if one is omitted, however, the steps have not been improved so far, and the conventional manufacturing steps are still followed.

In addition, the electrical conductivity of the obtained sputtering target was about 90 S/cm (volume specific resistance: 0.011 Ωcm), and the electrical resistance was high, so it was difficult to obtain a target material that would not be cracked during sputtering.

Patent Documents 11 to 15 describe InGaO ₃ (ZnO) ₂ , InGaO ₃ (ZnO) ₃ , InGaO ₃ (ZnO) ₄ , InGaO ₃ (ZnO) ₅ , and InGaO ₃ (ZnO) ₇ contained in IGZO sputtering targets. Compounds shown and methods for their manufacture.

However, in Patent Documents 11 to 15, compounds represented by ZnGa ₂ O ₄ and compounds represented by InGaZnO ₄ cannot be obtained. In addition, Patent Documents 11 to 15 only describe that the particle size of the raw material powder used is particularly preferably 10 μm or less. In addition, although it describes that it can be used for a semiconductor element, there is no description about a specific resistance value, and there is no description that it can be used for a sputtering target.

[Patent Document 1] Japanese Patent Laid-Open No. 8-295514

[Patent Document 2] Japanese Patent Laid-Open No. 8-330103

[Patent Document 3] Japanese Patent Laid-Open No. 2000-044236

[Patent Document 4] Japanese Patent Laid-Open No. 2006-165527

[Patent Document 5] Japanese Patent Laid-Open No. 2006-165528

[Patent Document 6] Japanese Patent Laid-Open No. 2006-165529

[Patent Document 7] Japanese Patent Laid-Open No. 2006-165530

[Patent Document 8] Japanese Patent Laid-Open No. 2006-165531

[Patent Document 9] Japanese Patent Laid-Open No. 2006-165532

[Patent Document 10] Japanese Patent Laid-Open No. 2006-173580

[Patent Document 11] Japanese Patent Laid-Open No. 63-239117

[Patent Document 12] Japanese Patent Laid-Open No. 63-210022

[Patent Document 13] Japanese Patent Laid-Open No. 63-210023

[Patent Document 14] Japanese Patent Laid-Open No. 63-210024

[Patent Document 15] Japanese Patent Laid-Open No. 63-265818

Contents of the invention

An object of the present invention is to provide a sputtering target capable of suppressing abnormal discharge when an oxide semiconductor film is formed by a sputtering method and capable of producing an oxide semiconductor having no abnormal film quality and excellent surface smoothness membrane.

In addition, it is also intended to provide a sputtering target that maintains the characteristics of an IGZO sputtering target, has low volume resistance, high density, has a uniform grain size and a finer structure, and has high bending strength.

Another object is to provide a sputtering target capable of suppressing occurrence of abnormal discharge even when an IGZO sputtering target is used for DC sputtering.

Another object is to provide a manufacturing method that can shorten the manufacturing process without impairing the characteristics as an IGZO sputtering target.

The present inventors have found that in an IGZO sputtering target containing oxides of indium (In), gallium (Ga), and zinc (Zn), a compound represented by ZnGa ₂ O ₄ can suppress InGaO ₃ (ZnO) _m (herein, m represents an integer from 2 to 20) can suppress abnormal growth of the compound represented by sputtering, and the compound represented by InGaZnO ₄ can suppress InGaO ₃ (ZnO) _m (herein, m represents 2 to 20 The abnormal growth of the compound represented by integer) can suppress the abnormal discharge in sputtering.

In addition, it has been found that the volume resistance of the sputtering target itself can be reduced and abnormal discharge can be suppressed by adding a metal element having a positive tetravalent or higher valence (the first invention).

In addition, it has been found that abnormal discharge during sputtering can be suppressed by adding a positive tetravalent metal element to an IGZO sputtering target mainly composed of InGaZnO ₄ (second invention).

In addition, it was found that in the production method of the IGZO sputtering target, indium oxide-gallium oxide-zinc oxide or raw material powders mainly composed of indium oxide-gallium oxide-zinc oxide were mixed and pulverized by a specific mixing and pulverizing method, and then the raw material mixed powder and pulverized powder were adjusted. The specific surface area or the median particle diameter can omit the calcining step and the reduction step (the third invention).

According to the present invention, the following sputtering targets can be provided.

[the first invention]

·The first way

1. A sputtering target, which is a sputtering target containing an oxide of indium (In), gallium (Ga) and zinc (Zn), wherein a compound represented by ZnGa ₂ O ₄ and a compound represented by InGaZnO ₄ are contained compound.

2. The sputtering target according to 1, wherein the atomic ratio represented by In/(In+Ga+Zn), the atomic ratio represented by Ga/(In+Ga+Zn), and the atomic ratio represented by Zn/(In+Ga The atomic ratio shown in +Zn) satisfies the following formula,

0.2＜In/(In+Ga+Zn)＜0.77

0.2＜Ga/(In+Ga+Zn)＜0.50

0.03＜Zn/(In+Ga+Zn)＜0.50

3. The sputtering target according to 1 or 2, wherein the atomic ratio represented by In/(In+Ga+Zn) and the atomic ratio represented by Ga/(In+Ga+Zn) satisfy the following formula,

In/(In+Ga+Zn)>Ga/(In+Ga+Zn).

4. The sputtering target according to any one of 1 to 3, which contains a metal element having a tetravalent or higher valency,

The content of the above-mentioned metal element having a valency of tetravalent or higher relative to all metal elements ([metal elements having a valence of tetravalent or higher/total metal elements: atomic ratio]) = 0.0001 to 0.2.

5. The sputtering target according to 4, wherein the metal element having a valence of tetravalent or higher is one or more elements selected from the group consisting of tin, zirconium, germanium, cerium, niobium, tantalum, molybdenum, and tungsten.

6. The sputtering target according to any one of 1 to 5, wherein the volume resistance is less than 5×10 ^-3 Ωcm.

7. An oxide semiconductor film obtained by sputtering the sputtering target according to any one of 1 to 6 to form a film.

[the first invention]

·Second way

1. A sputtering target, which is a sputtering target containing an oxide of indium (In), gallium (Ga) and zinc (Zn), wherein,

It contains a homogeneous structure compound represented by InGaO ₃ (ZnO) _m (m is an integer of 1 to 20) and a spinel structure compound represented by ZnGa ₂ O ₄ .

2. The sputtering target according to 1, which contains at least a homologous structure compound represented by InGaZnO ₄ .

3. The sputtering target according to 1 or 2, wherein the average particle diameter of the spinel structure compound represented by ZnGa ₂ O ₄ is 10 μm or less.

4. The sputtering target according to any one of 1 to 3, wherein the density of the sintered body is 6.0 g/cm ³ or more.

5. The sputtering target according to any one of 1 to 4, which has a surface roughness (Ra) of 2 μm or less and an average bending strength of 50 MPa or more.

6. The sputtering target according to any one of 1 to 5, wherein the contents of Fe, Al, Si, Ni, and Cu are each 10 ppm (weight) or less.

7. A method for manufacturing the sputtering target according to any one of 1 to 6, wherein the mixture is prepared by pulverizing indium oxide, gallium oxide and zinc oxide and mixing and granulating;

shaping the above mixture to prepare a shaped body;

The molded body is sintered at a temperature of not less than 1250°C and not more than 1450°C in an oxygen flow or in an oxygen pressurized state.

8. An oxide semiconductor film obtained by sputtering the sputtering target according to any one of 1 to 6 to form a film.

[the second invention]

1. A sputtering target comprising a compound represented by InGaZnO ₄ as a main component and containing a metal element having a positive tetravalent or higher valency.

2. The sputtering target according to 1, wherein the content of the metal element having a tetravalent or higher valence is 100 ppm to 10000 ppm with respect to all the metal elements in the sputtering target.

3. The sputtering target according to 1, wherein the content of the metal element having a valent tetravalent or higher is 200 ppm to 5000 ppm with respect to all the metal elements in the sputtering target.

4. The sputtering target according to 1, wherein the content of the metal element having a valent or higher tetravalent value is 500 ppm to 2000 ppm relative to all the metal elements in the sputtering target.

5. The sputtering target according to any one of 1 to 4, wherein the volume resistance is less than 1×10 ^-3 Ωcm.

6. The sputtering target according to any one of 1 to 5, wherein the above-mentioned metal element having a valency of tetravalent or higher is at least one selected from the group consisting of tin, zirconium, germanium, cerium, niobium, tantalum, molybdenum, and tungsten. element.

[the third invention]

1. A method for producing a sputtering target, comprising: mixing indium oxide powder with a specific surface area of 6 to 10 m ² /g, gallium oxide powder with a specific surface area of 5 to 10 m ² /g and a specific surface area of 2 to 4 m ² /g of zinc oxide powder and the mixed powder whose overall specific surface area is 5-8m ² /g is used as the raw material, and the above-mentioned raw materials are mixed and pulverized with a wet media agitation mill, so that the specific surface area is larger than the overall specific surface area of the mixed powder A step of adding 1.0 to 3.0 m ² /g; and a step of shaping the raw material after the above step and sintering it at 1250 to 1450°C in an oxygen atmosphere.

2. A method for producing a sputtering target, comprising: mixing indium oxide powder with a median particle size of 1 to 2 μm, gallium oxide powder with a median particle size of 1 to 2 μm, and a median particle size of 0.8 ~1.6μm zinc oxide powder and the mixed powder whose overall median particle size is 1.0~1.9μm is used as the raw material, and the above raw materials are mixed and pulverized with a wet media agitation mill, so that the median particle size of the raw material is 0.6~ a step of 1 μm; and a step of molding the raw material after the above step and sintering it at 1250-1450° C. in an oxygen atmosphere.

3. The method for producing a sputtering target according to 1 or 2, wherein the sintering is performed without pre-firing.

4. The method for producing a sputtering target according to any one of 1 to 3, wherein the density of the sintered body obtained through the sintering step is 6.0 g/cm ³ or more.

According to the present invention, it is possible to provide a sputtering target capable of suppressing abnormal discharge that occurs when an oxide semiconductor film is formed by a sputtering method, and capable of producing an oxide semiconductor having no abnormality in film quality and excellent surface smoothness membrane.

Description of drawings

[ Fig. 1 ] is an X-ray diagram of a target obtained in Example 1.

[ Fig. 2 ] is an X-ray diagram of a target obtained in Example 2.

[ Fig. 3 ] is an X-ray diagram of a target obtained in Example 3.

[ Fig. 4 ] is an X-ray diagram of a target produced in Comparative Example 1.

[ Fig. 5 ] is a graph showing the relationship between the addition amount of a metal element having a tetravalent or higher valency and the volume resistance of a sintered body.

[ Fig. 6 ] is an X-ray diffraction pattern of a target obtained by adding tin.

[ Fig. 7 ] is an X-ray diffraction pattern of a sintered body obtained in Example 8.

[ Fig. 8 ] is a graph showing the relationship between the amount of tin element added and the volume resistance value of the sintered body.

[ Fig. 9 ] is a graph showing the relationship between the addition amount of a metal element having a tetravalent or higher valency and the volume resistance of a sintered body.

Detailed ways

[the first invention]

·The first way

The sputtering target of the present invention (hereinafter, sometimes referred to as the target of the present invention) contains oxides of indium (In), gallium (Ga), and zinc (Zn), and contains compounds represented by ZnGa ₂ O ₄ and compounds represented by InGaZnO ₄ the indicated compounds.

In the sputtering target, by forming the compound represented by _ZnGa2O4 and the compound represented by _InGaZnO4 , the abnormal growth of the compound represented by _InGaO3 ( _ZnO ) _m (m is an integer of 2 to 20) can be suppressed, and the Suppresses abnormal discharge of the target during sputtering. In addition, since the crystal grain size can be reduced, oxygen deficiency can occur at the crystal interface, resulting in a decrease in volume resistance.

In addition, the sputtering target of the present invention contains a plurality of crystal systems such as compounds represented by InGaO ₃ (ZnO) _m (m is an integer of 2 to 20) and compounds represented by ZnGa ₂ O ₄ . Oxygen deficiency occurs due to the incoherence of the crystal, and carriers are generated in the target. The carriers lower the resistance of the target and suppress abnormal discharge during sputtering.

In the sputtering target of the present invention, the atomic ratio represented by In/(In+Ga+Zn), the atomic ratio represented by Ga/(In+Ga+Zn), and the atomic ratio represented by Zn/(In+Ga+Zn) The atomic ratio preferably satisfies the following formula:

0.2＜In/(In+Ga+Zn)＜0.77

0.2＜Ga/(In+Ga+Zn)＜0.50

0.03＜Zn/(In+Ga+Zn)＜0.50

In addition, the above-mentioned atomic ratio can be obtained by adjusting the mixing ratio of the indium compound, the gallium compound, and the zinc compound before sintering as described later.

When In/(In+Ga+Zn) is 0.77 or more, the conductivity of the formed oxide semiconductor film increases, and it may be difficult to use it as a semiconductor. On the other hand, when In/(In+Ga+Zn) is 0.2 or less, the carrier mobility of the formed oxide semiconductor film may decrease when it is used as a semiconductor.

When Ga/(In+Ga+Zn) is 0.5 or more, the carrier mobility of the formed oxide semiconductor film may decrease when used as a semiconductor. On the other hand, when Ga/(In+Ga+Zn) is 0.2 or less, the conductivity of the formed oxide semiconductor film may be high, and it may be difficult to use it as a semiconductor. In addition, due to external disturbances such as heating, semiconductor characteristics may change, or threshold voltage (Vth) may shift and increase.

When Zn/(In+Ga+Zn) is 0.03 or less, the oxide semiconductor film may be crystallized. On the other hand, when Zn/(In+Ga+Zn) is 0.5 or more, there may be a problem of stability of the oxide semiconductor film itself, and even a large Vth shift may occur.

In addition, the atomic ratio of each element in the above-mentioned target was obtained by measuring the amount of each element present by ICP (Inductively Coupled Plasma) measurement.

In the sputtering target of the present invention, the atomic ratio represented by In/(In+Ga+Zn) and the atomic ratio represented by Ga/(In+Ga+Zn) preferably satisfy the following formula.

In/(In+Ga+Zn)＞Ga/(In+Ga+Zn)

When a sputtering target satisfying this formula is formed to produce an oxide semiconductor film, the obtained oxide semiconductor film has high stability, can suppress Vth shift, and has excellent long-term stability.

The sputtering target of the present invention preferably contains a metal element with a valence of four or more, and the content of the metal element with a valence of four or more with respect to all the metal elements satisfies [metal elements with a valence of four or more/all metal elements: atomic ratio] = 0.0001 to 0.2 .

The sputtering target can reduce the volume resistance value of the target itself by containing a metal element with a positive tetravalent or higher value, and can suppress the occurrence of abnormal discharge during sputtering of the target.

When the content of the metal element having a tetravalent or higher valence ([metal elements having a tetravalent or higher valence/total metal elements: atomic ratio]) is less than 0.0001, the effect of lowering the volume resistance may be small. On the other hand, when the content of the metal element having a tetravalent or higher valence ([metal elements having a tetravalent or higher valence/total metal elements: atomic ratio) exceeds 0.2, there may be a problem with the stability of the oxide semiconductor film.

Preferable metal elements having a valence of tetravalent or higher include tin, zirconium, germanium, cerium, niobium, tantalum, molybdenum, and tungsten, more preferably tin, cerium, and zirconium.

To the raw material of the sputtering target of the present invention, the above-mentioned metal element having a positive tetravalent or higher valence can be added in the form of, for example, a metal oxide so that the content of the metal element falls within the above-mentioned range.

In addition, the sputtering target of the present invention may contain, for example, hafnium, rhenium, titanium, vanadium, etc., within the range that does not impair the effect of the present invention, in addition to the above-mentioned metal elements having a positive tetravalent or higher valence.

·Second way

The sputtering target of the present invention (hereinafter sometimes referred to as the target of the present invention) contains oxides of indium (In), gallium (Ga) and zinc (Zn), and contains InGaO ₃ (ZnO) _m (m is 1 to 20 Integers of the same family structure compounds represented by) and spinel structure compounds represented by ZnGa ₂ O ₄ .

Homologous structure compounds are compounds that have homogeneous phases.

The Homologous Series (Homologous Series: Homologous Series) refers to the Magneli (Magneli) phase shown by the composition formula of Ti _n O _2n-1 when n is a natural number, for example, and has a group of n in which n is continuously changed. compound group.

Specific examples of homologous structure compounds include In ₂ O ₃ ·(ZnO) _m (m is an integer of 2 to 20), InGaO ₃ (ZnO) _m (m is an integer of 2 to 20), and the like.

As disclosed in "Crystal Chemistry" (Kodansha, Nakahira Hikaru, 1973) etc., the spinel structure compound is generally called AB ₂ X ₄ type or A ₂ B X ₄ type as a spinel structure, and will have Compounds with this crystal structure are called spinel structure compounds.

Generally, in the spinel structure, anions (usually oxygen) form a cubic closest packing, and cations are present in a part of the tetrahedral interstitial and octahedral interstitial spaces.

In addition, substitution-type solid solutions in which atoms and ions in the crystal structure are partially substituted with other atoms, and intrusion-type solid solutions in which other atoms are added to positions between lattices are also included in the spinel structure compound.

The crystal state of the compound in the target can be judged by observing a sample taken out from the target (sintered body) by X-ray diffractometry.

The spinel structure compound which is _a structural component of the target material of this invention is a compound represented by _ZnGa2O4 . That is, X-ray diffraction shows a peak pattern of 38-1240 in the JCPDS (Joint Committee on Powder Diffraction Standards) database, or a similar (shifted) pattern.

By generating the compound represented by ZnGa ₂ O ₄ in the sputtering target, the abnormal growth of the compound represented by InGaO ₃ (ZnO) _m (m is an integer of 2 to 20) can be suppressed, and the target can be suppressed during sputtering. abnormal discharge. In addition, it is preferable that the abnormal growth of the compound represented by InGaO ₃ (ZnO) _m (m is an integer of 2 to 20) can be further suppressed by generating the compound represented by InGaZnO ₄ .

By suppressing the abnormal growth of the compound represented by InGaO ₃ (ZnO) _m (m is an integer of 2 to 20), the flexural strength of the target can be increased, and cracking of the target during sputtering can be suppressed.

The sputtering target of the present invention contains a plurality of crystal systems of homogeneous structure compounds represented by InGaO ₃ (ZnO) _m (m is an integer of 1 to 20) and spinel structure compounds represented by ZnGa ₂ O ₄ , so in Oxygen vacancies occur in these crystal grain boundaries due to crystal incoherence, and carriers are generated in the target. The carriers lower the resistance of the target and suppress abnormal discharge during sputtering.

In the target material of the present invention, the average particle size of the spinel structure compound represented by ZnGa ₂ O ₄ is preferably 10 μm or less, more preferably 5 μm or less.

By setting the average particle _size of the spinel structure compound represented by _ZnGa2O4 to 10 μm or less, the grain growth of the compound represented by _InGaO3 (ZnO) _m (m is an integer of 2 to 20) can be more reliably suppressed, Improve the bending strength of the target and suppress the cracking of the target during sputtering.

The average particle size of the above-mentioned spinel structure compound represented by ZnGa ₂ O ₄ can be evaluated, for example, by observing a secondary electron image of a scanning electron microscope (SEM).

The sputtering targets of the above-mentioned first and second embodiments preferably have a volume resistance of less than 5×10 ^-3 Ωcm, more preferably less than 2×10 ^-3 Ωcm. When the volume resistance is 5×10 ^-3 Ωcm or more, abnormal discharge may be induced during sputtering, or foreign matter (nodules) may be generated.

The volume resistance of the target material of the present invention can be measured by a four-probe method.

The sputtering target of the present invention preferably has a sintered body density of 6.0 g/cm ³ or more.

When the sintered body density of the target is 6.0 g/cm ³ or more, the bending strength of the target can be increased to suppress cracking of the target during sputtering. On the other hand, when the density of the sintered body of the target is less than 6.0 g/cm ³ , the surface of the target may be blackened or abnormal discharge may occur.

In order to obtain a sintered body having a high sintered body density, it is preferable to perform molding by cooling hydraulic pressure (CIP) or the like or sintering by hot hydrostatic pressure (HIP) or the like in the manufacturing method of the target material described later.

The target of the present invention preferably has a surface roughness (Ra) of 2 μm or less and an average flexural strength of 50 MPa or more, more preferably a surface roughness (Ra) of 0.5 μm or less and an average flexural strength of 55 MPa or more.

By setting the surface roughness (Ra) of the target to be 2 μm or less, the average bending strength of the target can be maintained at 50 MPa or more, and cracking of the target during sputtering can be suppressed.

In addition, the above-mentioned surface roughness (Ra) can be measured by the AFM method, and the average flexural strength can be measured according to JISR 1601.

In the target material of the present invention, the contents of Fe, Al, Si, Ni, and Cu are preferably 10 ppm (by weight) or less.

Fe, Al, Si, Ni, and Cu are impurities in the target of the present invention, and by making their respective contents 10 ppm (weight) or less, the threshold voltage of the oxide semiconductor film obtained by forming the target can be suppressed. changes, a stable working state can be obtained.

The content of the aforementioned impurity elements can be measured by inductively coupled plasma (ICP) emission analysis.

In addition, in addition to the oxides of indium (In), gallium (Ga), and zinc (Zn), the sputtering target of the present invention may also contain, for example, tetravalent metal elements within the range that does not impair the effects of the present invention. .

The oxide semiconductor film obtained by using the sputtering target of the present invention is amorphous and exhibits stable semiconductor characteristics without the effect of carrier generation (doping effect) even if it contains positive tetravalent metal elements.

·Manufacturing method of sputtering target

The sputtering targets of the above-mentioned first and second forms can be obtained, for example, by pulverizing indium oxide, gallium oxide and zinc oxide, mixing and granulating to prepare a mixture, and then shaping the mixture into a molded body. In an oxygen pressurized state, the molded body is heat-treated under the conditions of 250°C to less than 1450°C.

The raw materials of the sputtering target of the present invention are indium oxide, gallium oxide and zinc oxide, preferably indium oxide powder with a specific surface area of 6 to 10 m ² /g, gallium oxide powder with a specific surface area of 5 to 10 m ² /g and Zinc oxide powder with a specific surface area of 2 to 4 m ² /g, or indium oxide powder with a median particle size of 1 to 2 μm, gallium oxide powder with a median particle size of 1 to 2 μm, and a median particle size of 0.8 to 1.6 μm of zinc oxide powder.

In addition, the purity of each of the above raw materials is usually 2N (99% by mass) or higher, preferably 3N (99.9% by mass) or higher, more preferably 4N (99.99% by mass) or higher. If the purity is lower than 2N, impurities such as Fe, Al, Si, Ni, and Cu may be contained in a large amount. If these impurities are contained, the oxide semiconductor film produced by using the target may be unstable in operation.

For the fine pulverization of the above-mentioned raw materials, a common mixer pulverizer can be used, for example, a wet media agitation mill, a bead mill, or an ultrasonic device can be used to perform uniform mixing and pulverization.

The mixing ratio of each raw material is, for example, In:Ga:Zn=45:30:25 in weight ratio (In:Ga:Zn=1:1:1 in molar ratio), or In ₂ O ₃ :Ga ₂ O ₃ :ZnO=51:34:15 (In ₂ O ₃ :Ga ₂ O ₃ :ZnO=1:1:1 in molar ratio).

The mixing ratio of each raw material is the atomic ratio represented by In/(In+Ga+Zn), the atomic ratio represented by Ga/(In+Ga+Zn), and Zn/(In+ The atomic ratio represented by Ga+Zn) is mixed so that, for example, the following formula is satisfied.

0.2＜In/(In+Ga+Zn)＜0.77

0.2＜Ga/(In+Ga+Zn)＜0.50

0.03＜Zn/(In+Ga+Zn)＜0.50

The finely pulverized and mixed granulated raw materials can be prepared into a mixture, for example, in such a manner that the specific surface area of each raw material after mixed and granulated is increased by 1.0 to 2.5 m ² /g compared with the specific surface area of each raw material before mixed and granulated. , or the average median diameter of each raw material is 0.6 to 1.0 μm.

If the increase in the specific surface area of each raw material is less than 1.0 m ² /g, or the average median particle size of each raw material is less than 0.6 μm, there is a possibility that impurities from pulverizing machines, etc. may be mixed in during fine pulverization and mixing granulation. Increase.

In the above fine pulverization and mixing granulation, if the specific surface areas of indium oxide and gallium oxide before fine pulverization and mixing granulation are approximately equal, fine pulverization and mixing granulation can be performed more effectively, and the fine pulverization and mixing granulation before fine pulverization and mixing granulation The difference between the specific surface areas of indium oxide and gallium oxide is preferably 3 m ² /g or less. When the difference in specific surface area is out of the above range, fine pulverization and mixing granulation cannot be effectively performed, and gallium oxide particles may remain in the obtained sintered body.

In addition, if the median diameters of indium oxide and gallium oxide before fine pulverization and mixing granulation are approximately equal, fine pulverization and mixing granulation can be performed more effectively, and indium oxide and gallium oxide before fine pulverization and mixing granulation The difference in median particle size is preferably 1 μm or less. When the difference in median diameter is out of this range, gallium oxide particles may appear in the obtained sintered body.

The molding process for molding the above-mentioned mixture may, for example, be mold molding, casting molding, injection molding, etc., and in order to obtain a sintered body with a high density, it is preferably molded by CIP (cooling hydraulic pressure) or the like.

In addition, when performing molding treatment, molding aids such as polyvinyl alcohol, methylcellulose, polywax, and oleic acid can also be used.

The sintered body for sputtering targets of this invention can be manufactured by firing the molded body obtained by the said method.

The firing temperature is 1250°C to less than 1450°C, preferably 1300°C to less than 1450°C. In addition, the firing time is usually 2 to 100 hours, preferably 4 to 40 hours.

If the firing temperature is lower than 1250° C., the density of the fired body of the obtained sintered body may not increase. On the other hand, when the firing temperature is 1450° C. or higher, the composition of the sintered body may change due to zinc emission, and/or voids may appear in the target.

The above-mentioned firing is preferably performed in an oxygen flow or under oxygen pressure. By firing in an oxygen atmosphere, the emission of zinc can be suppressed, and a sintered body without voids can be produced. It was confirmed by X-ray diffraction that InGaZnO ₄ and ZnGa ₂ O ₄ were generated in this sintered body.

The sputtering target of the present invention can be produced by, for example, polishing the sintered body after firing to a desired surface roughness.

For example, the above-mentioned sintered body is ground with a flat grinding disc, so that the average surface roughness (Ra) reaches below 5 μm, preferably below 2 μm, and then the sputtering surface is subjected to mirror processing, so that the average surface roughness (Ra) can reach Below 1000 Angstroms.

The mirror finish (polishing) is not particularly limited, and known polishing techniques such as mechanical polishing, chemical polishing, and mechanochemical polishing (combination of mechanical polishing and chemical polishing) can be used. For example, after grinding with fixed abrasive polishing agent (POLISH liquid: water) at #2000 or above, or after grinding with free abrasive grinding tools (grinding material: SiC paste, etc.), then replace the grinding material with diamond paste. grind.

In the manufacturing method of the sputtering target of this invention, it is preferable to wash-process the obtained sputtering target.

As the washing treatment, for example, air jet, running water washing, etc. may be mentioned. For example, when performing cleaning treatment (removal of foreign substances) using an air jet, more effective removal can be achieved by suctioning air from the nozzle side with a dust collector.

It is preferable to perform ultrasonic cleaning or the like after the above-mentioned cleaning treatment such as air jet and running water cleaning. In this ultrasonic cleaning, it is effective to perform multiple oscillations at a frequency of 25 to 300 KHz. For example, between 25KHz and 300KHz, multiple vibrations of 12 kinds of frequencies every 25KHz may be used for ultrasonic cleaning.

By bonding the obtained sputtering target to a backing plate, it can be mounted on a sputtering apparatus and used.

The manufacturing method of the sputtering target of this invention does not require a pre-firing process at all, and can obtain the sintered body for sputtering targets of high density. In addition, a reduction step is not required at all, and a sintered body with low volume resistance can be obtained. Moreover, since the above-mentioned calcining step and reduction step can be omitted, the sputtering target of the present invention can be a highly productive sputtering target.

An oxide semiconductor film can be formed using the target of the present invention. As a film-forming method, RF magnetron sputtering method, DC magnetron sputtering method, electron beam vapor deposition method, ion plating method, etc. are mentioned, for example. Among them, the RF magnetron sputtering method is preferably used. When the volume resistance of the target exceeds 1Ωcm, if the RF magnetron sputtering method is used, no abnormal discharge will occur and a stable sputtering state can be maintained. In addition, when the volume resistance of the target material is 10 mΩcm or less, an industrially advantageous DC magnetron sputtering method can be employed.

In this way, a stable sputtering state can be maintained without abnormal discharge, and industrially continuous and stable film formation can be performed.

The oxide semiconductor film obtained by forming a film using the sputtering target of the present invention has the advantages of less occurrence of nodules and particles and film properties (no abnormality in film quality and excellent surface smoothness) due to the high density of the sputtering target. .

[the second invention]

The sputtering target of the present invention is an IGZO sputtering target mainly made of indium oxide, gallium oxide and zinc oxide, and is characterized in that it contains a compound represented by _InGaZnO4 as a main component and contains a metal element with a positive tetravalent or higher value. The IGZO sputtering target added with a metal element of positive tetravalent or higher can reduce the volume resistance value of the target itself, and can also suppress the occurrence of abnormal discharge during DC sputtering.

Moreover, in the manufacturing process of a target, the reduction process for reducing the volume resistance of a target can be omitted. Therefore, productivity improves and manufacturing cost can be reduced.

In addition, the compound (crystal) represented by InGaZnO ₄ as a main component means that no structure other than InGaZnO ₄ is confirmed in X-ray diffraction analysis, or even if it is confirmed, the intensity is lower than that of InGaZnO ₄ .

In the sputtering target of the present invention, it is preferable that the addition amount (weight) of the metal element having a tetravalent or higher valence is 100 ppm to 10000 ppm relative to all the metal elements in the target. If the amount added is less than 100 ppm, the effect of adding a metal element having a positive tetravalent or higher valence may be small. On the other hand, if it exceeds 10000 ppm, the stability of the oxide film may be problematic or the carrier mobility may be reduced. The addition amount of the metal element having a tetravalent or higher valency is preferably 200 ppm to 5000 ppm, more preferably 500 ppm to 2000 ppm.

In addition, in the sputtering target of the present invention, it is preferable that the volume resistance of the target material is less than 1×10 ⁻³ Ωcm. If the volume resistance is more than 1×10 ^-3 Ωcm, when DC sputtering is carried out continuously for a long time, the target will be broken due to the electric spark generated by abnormal discharge, or the particles ejected from the target will adhere to the component due to the electric spark. film substrate, resulting in a decrease in the performance of the resulting film as an oxide semiconductor film.

In addition, the volume resistance is a value measured by the four-probe method using a resistivity meter.

The sputtering target of the present invention can be produced, for example, by mixing powders of indium oxide, gallium oxide, zinc oxide, and a material containing a metal element having a tetravalent or higher valence, pulverizing and sintering the mixture.

As a material containing a metal element having a positive tetravalent or higher valence, for example, a single metal or an oxide can be used. In addition, as the metal element having a positive tetravalent or higher valency, one or more kinds may be suitably selected from tin, zirconium, germanium, cerium, niobium, tantalum, molybdenum, and tungsten.

The raw material powder preferably has a specific surface area of 8 to 10 m ² /g for indium oxide powder, 5 to 10 m ² /g for gallium oxide powder, and 2 to 4 m ² for zinc oxide powder. /g. In addition, it is preferable to set the median diameter of the indium oxide powder to 1 to 2 μm, the median diameter of the gallium oxide powder to 1 to 2 μm, and the median diameter of the zinc oxide powder to 0.8 to 1.6 μm.

In addition, it is preferable to use a powder in which the specific surface area of the indium oxide powder is substantially equal to the specific surface area of the gallium oxide powder. In this way, pulverization and mixing can be performed more efficiently. Specifically, the difference in specific surface area is preferably 3 m ² /g or less. If the difference in specific surface area is too large, pulverization and mixing may not be performed efficiently, and gallium oxide particles may remain in the sintered body.

In the raw material powder, the ratio of indium oxide powder, gallium oxide powder and zinc oxide powder (indium oxide powder: gallium oxide powder: zinc oxide powder) is roughly 45:30:25 by weight (molar ratio: In: Ga:Zn=1:1:1), approximately 51:34:15 (molar ratio In ₂ O ₃ :Ga ₂ O _{3 :} ZnO=1:1:1).

As mentioned above, the proportion of the material containing metal elements with a positive tetravalent or higher valence is preferably 100 ppm to 10000 ppm relative to all metal elements in the target, and is appropriately adjusted according to the usage amounts of indium oxide powder, gallium oxide powder, and zinc oxide powder.

In addition, as long as it is a mixed material containing indium oxide powder, gallium oxide powder, zinc oxide powder, and a metal element having a tetravalent or higher valence, other components that improve the characteristics of the sputtering target may be added.

The mixed powder is mixed and pulverized using, for example, a wet media agitation mill. At this time, it is preferable to pulverize to such an extent that the specific surface area after pulverization increases by 1.5 to 2.5 m ² /g compared with the specific surface area of the raw material mixed powder, or the average median particle size after pulverization becomes 0.6 to 2.5 m 2 /g. 1 μm degree. By using the raw material powder adjusted in this way, a high-density sintered body for an IGZO sputtering target can be produced without any need for a calcining step. In addition, a reduction step is not required.

In addition, if the specific surface area of the raw material mixed powder increases less than 1.0 m ² /g, or the average median particle size of the pulverized raw material mixed powder exceeds 1 μm, the sintered density may not be sufficiently increased. On the other hand, if the increase in the specific surface area of the raw material mixed powder exceeds 3.0 m ² /g or the average median particle size after pulverization is less than 0.6 μm, pollutants (impurities) from the pulverizer etc. Mixed amount) sometimes increases.

Here, the specific surface area of each powder is a value measured by the BET method. The median diameter of the particle size distribution of each powder is a value measured by a particle size distribution meter. These values can be adjusted by performing pulverization by a dry pulverization method, a wet pulverization method, or the like.

The raw material after the pulverization step is dried with a spray dryer or the like, and then molded. A known method can be used for molding, such as press molding and cold water pressure pressing.

Next, the obtained molded product is sintered to obtain a sintered body. The sintering is preferably sintering at 1500-1600°C for 2-20 hours. Thus, a sintered body for an IGZO sputtering target having a sintered body density of 6.0 g/cm ³ or more can be obtained. If the temperature is less than 1500°C, the density does not increase, and if it exceeds 1600°C, the composition of the sintered body changes due to zinc emission, or voids appear in the sintered body due to emission.

In addition, sintering may be performed in an oxygen atmosphere by passing oxygen, or may be performed under pressure. Emission of zinc can thereby be suppressed, and a sintered body without voids can be obtained.

The sintered body thus obtained has a high density of 6.0 g/cm ³ or more, and few nodules and particles appear during use, so that an oxide semiconductor film having excellent film characteristics can be produced.

The obtained sintered body was produced with InGaZnO ₄ as the main component. This can be confirmed by identification of the crystal structure by X-ray diffraction.

The obtained sintered body can be used as a sputtering target by subjecting it to the same polishing, cleaning, etc. as in the above-mentioned first invention.

An IGZO oxide semiconductor film mainly composed of oxides of In, Ga, and Zn can be formed on an object such as a substrate by sputtering using sputtering targets that have been bonded.

The oxide thin film obtained by the target material of the present invention is an amorphous film, and the added metal elements with a valence of more than four do not show a doping effect (the effect of carrier generation), so it becomes a very ideal one with reduced electron density. membrane. Thus, when used as an oxide semiconductor film, since the stability is high and Vth shift can be suppressed, it becomes a semiconductor film that also operates stably as a semiconductor.

[the third invention]

In the manufacturing method of the sputtering target of this invention, the mixed powder containing indium oxide powder, gallium oxide powder, and zinc oxide powder, or the powder containing indium oxide, gallium oxide, and zinc oxide as a main component is used as a raw material. Here, among the raw materials, it is one of the characteristics of the present invention to use a raw material having a specific surface area or a median diameter of a particle size distribution at a predetermined value.

In addition, it is characterized in that it includes: using a wet medium agitation mill to mix and pulverize the above-mentioned raw material powder, adjust the specific surface area or the median diameter of the particle size distribution, and shape the raw material after the pulverization process. The process of sintering at 1250-1450°C.

Hereinafter, the production method (1) of adjusting the specific surface area and the production method (2) of adjusting the median diameter of the particle size distribution will be described respectively.

(1) Manufacturing method for adjusting specific surface area of powder

In this method, a mixed powder containing each powder of the following (a) to (c) is used as a raw material powder.

(a) Specific surface area of indium oxide powder: 6-10m ² /g

(b) Specific surface area of gallium oxide powder: 5-10m ² /g

(c) Specific surface area of zinc oxide powder: 2-4m ² /g

Moreover, as mentioned later, you may add a 4th component other than (a)-(c) component. In this case, it is preferable that the total of the above three types accounts for 90% by weight or more of the whole raw material.

In addition, the specific surface area of the mixed powder as a raw material is adjusted to 5 to 8 m ² /g.

By setting the specific surface area of each oxide within the above range, the efficiency of mixing and pulverization can be improved.

Here, the specific surface area of each powder is a value measured by the BET method. In addition, the specific surface area can be adjusted by pulverizing the powder by a dry pulverization method, a wet pulverization method, or the like.

In the present invention, the specific surface areas of indium oxide and gallium oxide are preferably substantially equal. In this way, pulverization and mixing can be performed more efficiently. In addition, the difference in specific surface area between the raw material powders is preferably 3 m ² /g or less. If the difference in specific surface area is large, efficient pulverization and mixing may not be performed, and gallium oxide powder may remain in the sintered body.

The proportion of indium oxide and gallium oxide can be adjusted appropriately according to the application. In order to reduce the volume resistance of the target and obtain stable sputtering, the ratio (molar ratio) of indium oxide and gallium oxide is preferably the same, or mixed so that indium oxide is more than gallium oxide. When the molar ratio of gallium oxide is larger than that of indium oxide, excess gallium oxide crystal particles exist in the target, which may cause abnormal power generation.

The doping amount of zinc oxide is preferably equal to or less than the total amount of the compounding ratio (molar ratio) of indium oxide and gallium oxide.

Specifically, it is preferable that the indium oxide: gallium oxide: zinc oxide (weight ratio) is approximately 45:30:25 (In:Ga:Zn=1:1:1, molar ratio) or 50:35:15 (In ₂ O ₃ : Ga ₂ O ₃ : ZnO=1:1:1, molar ratio).

The above-mentioned raw material powder is mixed and pulverized by using a wet medium agitation mill, so that the specific surface area of the powder can be increased by 1.0-3.0 m ² /g compared with the specific surface area of the raw material mixed powder. By such an adjustment, a high-density sintered body for IGZO sputtering targets can be obtained without requiring a pre-firing step at all.

If the increase in the specific surface area after pulverization is less than 1.0 m ² /g, the density of the sintered body after the sintering process will not increase. On the other hand, if it exceeds 3.0 m ² /g, impurities from the pulverizer etc. The amount of mixing increased. The increase in specific surface area after pulverization is preferably 1.5 to 2.5 m ² /g.

In addition, the specific surface area of the raw material mixed powder before pulverization treatment means the specific surface area measured in the state which mixed each oxide powder.

As the wet medium agitation mill, commercially available devices such as bead mills, ball mills, roll mills, planetary mills, and jet mills can be used.

For example, when using a bead mill, the grinding media (beads) are preferably zirconia, alumina, titania, silicon nitride, stainless steel, mullite, glass beads, SiC, etc., and the particle size is preferably about 0.1 to 2 mm.

In the process of increasing the specific surface area of the powder by 1.0 to 3.0 m ² /g compared with the specific surface area of the raw material powder, it is only necessary to appropriately adjust the treatment time, the type of beads, the particle size, and the like. These conditions need to be adjusted according to the device used.

The raw material after the pulverization step described above is dried with a spray dryer or the like, and then molded. A known method can be used for molding, such as press molding and cold water pressure pressing.

Next, the obtained molded product is sintered to obtain a sintered body.

The sintering temperature is controlled to 1250-1450°C, preferably 1350-1450°C, and the sintering is carried out in an oxygen atmosphere by circulating oxygen or pressurizing oxygen. If it is less than 1250°C, the density of the sintered body cannot be increased, and if it exceeds 1450°C, zinc emission may occur, the composition of the sintered body may change, or voids may be generated in the sintered body due to emission. The sintering time is 2 to 72 hours, preferably 20 to 48 hours.

Sintering in an oxygen atmosphere can suppress the emission of zinc and obtain a sintered body without voids. In this way, the density of the sintered body can be made to be 6.0 g/cm ³ or more.

In addition, a sintered body having a volume resistance of less than 5 mΩcm can be obtained without a reduction step at all. When the volume resistance is 5 mΩcm or more, abnormal discharge may be induced during sputtering, or foreign matter (nodules) may be generated.

(2) Production method for adjusting the median particle size of powder

In this method, a mixed powder containing each powder of the following (a') to (c') is used as the raw material powder.

(a') The median diameter of the particle size distribution of indium oxide powder: 1-2 μm

(b') The median diameter of the particle size distribution of the gallium oxide powder: 1 to 2 μm

(c') The median diameter of the particle size distribution of the zinc oxide powder: 0.8 to 1.6 μm

Moreover, you may add a 4th component other than (a)-(c) component. In this case, it is preferable that the total of the above three types accounts for 90% by weight or more of the whole raw material.

In addition, the median diameter of the particle size distribution of the mixed powder as a raw material is adjusted to 1.0 to 1.9 μm.

By setting the specific surface area of each oxide within the above-mentioned range, the efficiency of mixing and pulverization is improved.

Here, the median diameter of the particle size distribution of each powder is a value measured using a particle size distribution meter. In addition, the median diameter can be adjusted by performing classification after applying dry pulverization or wet pulverization.

It is preferable to use powders in which the median diameters of indium oxide and gallium oxide are substantially equal. In this way, pulverization and mixing can be performed more efficiently. In addition, the difference in median diameter between the raw material powders is preferably 1 μm or less. If the difference in median diameter is too large, efficient pulverization and mixing may not be performed, and gallium oxide particles may remain in the sintered body.

The compounding ratio of indium oxide and gallium oxide and the pulverization process are the same as in the case of (1) above.

Through the pulverization step, the median diameter after pulverization is adjusted to 0.6 to 1 μm. In addition, the amount of change in the median diameter of the raw material before and after pulverization is preferably 0.1 μm or more. By using the raw material powder adjusted in this way, a high-density sintered compact for IGZO sputtering targets can be obtained without a calcining step at all. If the median particle size after pulverization exceeds 1 μm, the density of the sintered body will not increase. On the other hand, if it is less than 0.6 μm, the amount of impurities mixed from a pulverizer during pulverization increases.

In addition, the median diameter after pulverization means the median diameter of the whole mixed powder.

Molding and sintering of pulverized raw materials to produce a sintered body may be carried out in the same manner as in (1) above.

A sputtering target is formed by subjecting the sintered compact obtained in the above (1) or (2) to the same polishing, cleaning, etc. as in the above-mentioned first invention.

An oxide semiconductor film mainly composed of oxides of In, Ga, and Zn can be formed by sputtering using sputtering targets that have been bonded. The manufacturing method of the present invention can not only improve the productivity of the sputtering target, but also can increase the density of the obtained sputtering target to 6.0 g/cm ³ or more. Accordingly, it is possible to obtain an oxide semiconductor film with less occurrence of nodules and particles and excellent film properties. In addition, the upper limit of the density of the sputtering target is also affected by the composition, and is about 6.8 g/cm ³ .

In addition, in the present invention, in order to further reduce the volume resistance value of the sputtering target, for example, 200 to 5000 ppm (atomic ratio) of positive tetravalent metal elements may be contained in the sintered compact. Specifically, in addition to the aforementioned indium oxide, gallium oxide, and zinc oxide, SnO ₂ , ZrO ₂ , CeO ₂ , GeO ₂ , TiO ₂ , HfO ₂ , etc. may also be doped.

Thus, in the production method of the present invention, as long as indium oxide, gallium oxide, and zinc oxide are used as main components, other components that improve the characteristics of the sputtering target may be added to the raw material powder. For example, positive trivalent lanthanoids and the like can be added.

In addition, the obtained oxide semiconductor film is amorphous, and even if a positive tetravalent metal element is added, there is no effect of carrier generation (doping effect), and stable semiconductor characteristics are exhibited.

[Example]

The present invention is illustrated by comparing examples and comparative examples. In addition, the present embodiment shows only preferred examples, and the present invention is not limited to these examples. Therefore, the present invention includes modifications and other embodiments based on technical ideas.

[the first invention]

The measuring method of the characteristic of the sputtering target produced in the Example and the comparative example is shown below.

(1) Density

Calculated based on the weight and dimensions of the target cut to a certain size.

(2) Volume resistance of the target

Measurement was carried out by the four-probe method using a resistivity meter (manufactured by Mitsubishi Oil Chemicals, Loresta).

(3) Structure of the oxide present in the target

The structure of the oxide was identified by analyzing the pattern obtained by X-ray diffraction.

(4) The specific surface area of the raw material powder

Measured by BET method.

(5) Median particle size of raw material powder

Measured using a particle size distribution measuring device.

(6) Average bending strength

Obtained by three-point bending test.

(7) Weibull coefficient of sputtering target

The cumulative failure probability with respect to the bending strength was obtained by the median rank method, and the discrete Weibull coefficient (m value) indicating the failure probability was obtained based on the Weibull diagram of a single model. In addition, the Weibull coefficient is obtained by calculating the linear regression line to obtain the m value.

Example 1

Indium oxide powder with a specific surface area of 6 m ² /g and a purity of 99.99% was weighed in such a manner that the weight ratio was In ₂ O ₃ : Ga ₂ O ₃ : ZnO=45:30:25, the specific surface area was 6 m ² /g Ga gallium oxide powder with a purity of 99.99% and zinc oxide powder with a specific surface area of 3 m ² /g and a purity of 99.99% were mixed and pulverized using a wet media agitation mill. In addition, 1 mmφ zirconia beads were used for the media of the wet media agitation mill.

Then, after the specific surface area after mixing and pulverization of each raw material was increased by 2 m ² /g from the specific surface area before pulverization, it was dried with a spray dryer. The obtained mixed powder is filled into a mold and press-molded with a cold press to form a molded body.

The obtained molded body was sintered in an oxygen atmosphere at a high temperature of 1400° C. for 4 hours while circulating oxygen gas. In this manner, a sintered body for an IGZO sputtering target (sputtering target) having a sintered body density of 6.06 g/cm ³ was obtained without performing the calcining step. It was confirmed by X-ray diffraction that crystals of ZnGa ₂ O ₄ and InGaZnO ₄ existed in the sintered body. The X-ray diffraction pattern is shown in FIG. 1 .

In addition, the volume resistance of this sintered body was 4.2 mΩcm.

Impurities were measured for this sintered body by ICP analysis, and as a result, the contents of Fe, Al, Si, Ni, and Cu were all less than 10 ppm.

Example 2

_Indium oxide _powder with a median particle size of _1.5 μm, gallium oxide powder _with a median particle size of 2.0 μm, and medium Zinc oxide powder with a particle diameter of 1.0 μm was mixed and pulverized using a wet media agitation mill. In addition, 1 mmφ zirconia beads were used for the media of the wet media agitation mill.

After that, the average median diameter of each raw material after mixing and pulverization was 0.8 μm, and then dried with a spray dryer. The obtained mixed powder is filled into a mold and press-molded with a cold press to form a molded body.

The obtained molded body was sintered in an oxygen atmosphere at a high temperature of 1400° C. for 4 hours while circulating oxygen. In this way, a sintered body for an IGZO sputtering target with a sintered body density of 6.14 g/cm ³ was obtained without performing the calcining step. It was confirmed by X-ray diffraction that crystals of ZnGa ₂ O ₄ , InGaZnO ₄ , and In ₂ O ₃ (ZnO) ₄ were present in the sintered body. The X-ray diffraction pattern is shown in FIG. 2 .

In addition, the volume resistance of this sintered body was 3.8 mΩcm.

Example 3

Indium oxide powder with a median particle size of 1.5 μm and gallium oxide powder with a median particle size of 2.0 μm were weighed so that the weight ratio was approximately In ₂ O ₃ : Ga ₂ O ₃ : ZnO = 35:25:40 Zinc oxide powder with a median diameter of 1.0 μm was mixed and pulverized with a wet media agitation mill, and 1 mmφ zirconia beads were used as the medium of the wet media agitation mill.

After that, the average median diameter of each raw material after mixing and pulverization was 0.8 μm, and then dried with a spray dryer. The obtained mixed powder is filled into a mold and press-molded with a cold press to form a molded body.

The obtained molded body was sintered in an oxygen atmosphere at a high temperature of 1400° C. for 4 hours while circulating oxygen. In this way, a sintered body for an IGZO sputtering target with a sintered body density of 6.02 g/cm ³ was obtained without performing the calcining step. It was confirmed by X-ray diffraction that crystals of ZnGa ₂ O ₄ and InGaZnO ₄ existed in the sintered body. The X-ray diffraction pattern is shown in FIG. 3 .

In addition, the volume resistance of this sintered body was 4.9 mΩcm.

Comparative example 1

Indium oxide powder with a median particle size of 1.5 μm and gallium oxide powder with a median particle size of 2.0 μm were weighed so that the weight ratio was approximately In ₂ O ₃ : Ga ₂ O ₃ : ZnO = 34:46:20 and zinc oxide powder with a median diameter of 1.0 μm were mixed and pulverized using a wet media agitation mill. In addition, 1 mmφ zirconia beads were used for the media of the wet media agitation mill.

After that, the average median diameter of each raw material after mixing and pulverization was 0.8 μm, and then dried with a spray dryer. The obtained mixed powder is filled into a mold and press-molded with a cold press to form a molded body.

The obtained molded body was sintered at a temperature of 1200° C. for 4 hours in an oxygen atmosphere while circulating oxygen. In this way, a sintered body for an IGZO sputtering target with a sintered body density of 5.85 g/cm ³ was obtained without performing the calcining step. It was confirmed by X-ray diffraction that crystals of ZnGa ₂ O ₄ existed in the sintered body, but InGaO ₃ (ZnO) _m was not formed. The X-ray diffraction pattern is shown in FIG. 4 . The volume resistance of this sintered body was 450 mΩcm.

Example 4 and 5

Next, the IGZO sputtering target obtained in Example 1 was finely ground with a sintered body (Example 4: finely ground with a polishing agent, Example 5: flat ground in the longitudinal direction) to manufacture a sputtering target. Regarding the structure of the produced sputtering target, the secondary electron image of the scanning electron microscope (SEM) was observed, and the analysis of the target material surface was performed. As a result, the average particle diameters of the ZnGa ₂ O ₄ crystals in the targets of Example 4 and Example 5 were both 4.4 μm. In addition, as a result of measuring the surface roughness with a surface roughness meter, the surface roughness Ra of the target of Example 4 was 0.5 μm, and the surface roughness Ra of the target of Example 5 was 1.8 μm.

Comparative example 2

The sintered body for the IGZO sputtering target obtained in Comparative Example 1 was precisely ground (flat-ground in the longitudinal direction) to manufacture a sputtering target. The target surface was analyzed by observing the secondary electron image of the scanning electron microscope (SEM) with respect to the structure of the produced sputtering target. As a result, the average particle diameter of the ZnGa ₂ O ₄ crystals in the target was 14 μm. In addition, when the surface roughness of the target was measured with a surface roughness meter, the surface roughness Ra was 3.5 μm.

Next, the Weibull coefficient and the average bending strength were evaluated for the sputtering targets of Examples 4 and 5 and Comparative Example 2, respectively. The results are shown in Table 1.

【Table 1】

Grinding conditions Surface roughness Ra[μm] Weibull coefficient [-]   Average flexural strength [MPa] Example 4 polishing compound 0.5 10.4 58 Example 5 Grinding flat to the long side 1.8 10.2 54 Comparative example 2 Grinding flat to the long side 3.5 9.1 46

The larger the value of the Weibull coefficient, the smaller the dispersion in the maximum value of the non-destructive stress. From Table 1, it can be confirmed that the sputtering target of the present invention is a small and stable material.

In addition, the surface roughness after planar grinding generally corresponds to the crystal grain size. When the particle size is uneven, the larger the Ra is, the lower the flexural strength is.

From Table 1, it can be confirmed that the sputtering target of the present invention has a fine crystal grain size and a small surface roughness, and therefore has excellent quality.

Example 6

After the target material (4 inches φ, thickness 5mm) of Example 4 was lapped to the bottom plate, it was installed in a DC sputtering film forming device. In an Ar atmosphere of 0.3 Pa, continuous sputtering was performed at 100 W for 100 hours, and nodules appearing on the surface were measured. As a result, it was confirmed that granulomas did not occur on the surface.

Comparative example 3

The target material (4 inches φ, thickness 5 mm) of Comparative Example 2 was attached to the bottom plate, and then installed in a DC sputtering film formation device. In an Ar atmosphere of 0.3 Pa, continuous sputtering was performed at 100 W for 100 hours, and nodules appearing on the surface were measured. As a result, it was confirmed that granulomas appeared on approximately half of the surface of the target.

Example 7

In addition to adding tin oxide, zirconium oxide, germanium oxide, cerium oxide, niobium oxide, tantalum oxide, molybdenum oxide or tungsten oxide (metal element oxides more than positive tetravalent) to the starting material, the same operation as in Example 1, A sintered body was produced, and the volume resistance of the sintered body was measured. FIG. 5 shows the relationship between the amount of the metal element having a positive tetravalent or higher valency and the volume resistance of the sintered body. In addition, tin was used as a metal element having a positive tetravalent or higher valence, tin was added so that [tin element/all metal elements: atomic ratio]=0.001, and the X-ray diffraction pattern of the obtained sintered body for IGZO sputtering target is shown in FIG. 6 .

It can be seen from FIG. 5 that the volume resistance is reduced by adding a metal element with a positive tetravalent or higher value.

[the second invention]

Example 8

As raw material powders, indium oxide powder with a specific surface area of 6 m ² /g, gallium oxide powder with a specific surface area of 6 m ² /g and gallium oxide powder with a specific surface area of 3 m ² /g were weighed in a weight ratio of 45:30:25. In the zinc oxide powder, SnO ₂ , which is a positive tetravalent metal element, was weighed so that the content of Sn to all metal elements [Sn/(In+Ga+Zn+Sn):weight ratio] was 600 ppm.

The mixed powder of the raw materials is mixed and pulverized with a wet medium agitating mill. Zirconia beads of 1 mmφ were used in the medium. The specific surface area after pulverization was increased by 2 m ² /g from the specific surface area of the raw material mixed powder, and then dried with a spray dryer.

The pulverized mixed powder is filled into a mold and pressurized with a cold press. Sintering was carried out at 1550° C. for 8 hours in an oxygen atmosphere while circulating oxygen. In this manner, a sintered body for an IGZO sputtering target with a sintered body density of 6.12 g/cm ³ was obtained without performing the calcining step.

In addition, the density of the sintered body is calculated from the weight and external dimensions of the sintered body cut to a certain size.

The sintered body was analyzed by X-ray diffraction. Fig. 7 is an X-ray diffraction pattern of a sintered body. From this figure, it can be confirmed that InGaZnO ₄ crystals exist in the sintered body. In addition, since peaks of metal oxides other than InGaZnO ₄ were not observed, it was confirmed that a sintered body mainly composed of InGaZnO ₄ was obtained.

The volume resistance of the sintered body was measured by the four-probe method using a resistivity meter (manufactured by Mitsubishi Oil Chemicals, Loresta), and it was 0.95×10 ^-3 Ωcm.

Comparative example 4

A sintered body was obtained in the same manner as in Example 8, except that no metal oxide (tin oxide) containing a metal element having a positive tetravalent or higher valence was added.

As a result, the density of the sintered body was 5.98 g/cm ³ . In addition, from the analysis results based on X-ray diffraction, that is, crystals of InGaZnO ₄ are present, and peaks of metal oxides other than InGaZnO ₄ are not observed, it can be confirmed that a sintered body mainly composed of InGaZnO ₄ was obtained.

The volume resistance of this sintered body was 0.018 Ωcm.

FIG. 8 is a graph showing the relationship between the amount of tin element added and the volume resistance of the sintered body. The volume resistance of the sintered compacts prepared in the same manner as in Example 8 and Comparative Example 4 (the addition of tin element was 0 ppm), except that the addition of tin oxide powder was adjusted to 500ppm, 800ppm, and 1000ppm, is shown. As can be seen from FIG. 8 , the volume resistance of the sintered body can be reduced by adding the tin element which is a positive tetravalent metal element.

Examples 9-15

A sintered body was produced in the same manner as in Example 8, except that an oxide shown in Table 2 was used in a predetermined amount instead of tin oxide as the metal oxide containing a metal element having a tetravalent or higher valence. Table 2 shows the volume resistance value of the sintered body.

【Table 2】

Metal oxide Amount added (ppm by weight) Volume resistance (Ωcm) Example 9 Zirconia 1010 0.94×10 ^-3 Example 10 Germanium oxide 1020 0.89×10 ^-3 Example 11 Ceria 2000 0.92×10 ^-3 Example 12 niobium oxide 5000 0.95×10 ^-3 Example 13 Tantalum oxide 10000 0.96×10 ^-3 Example 14 Molybdenum oxide 1500 0.92×10 ^-3 Example 15 Tungsten Oxide 1020 0.91×10 ^-3

FIG. 9 is a graph showing the relationship between the amount of a metal element having a tetravalent or higher valence and the volume resistance of a sintered body for the results of Examples 9-15. It can be seen from FIG. 9 that the volume resistance of the sintered body can be reduced by adding a metal element having a positive tetravalent or higher value.

[the third invention]

Example 16

The following oxide powders were used and weighed as raw material mixed powders. In addition, the specific surface area was measured by the BET method.

(a) Indium oxide powder: 45% by weight, specific surface area 6m ² /g

(b) Gallium oxide powder: 30% by weight, specific surface area 6m ² /g

(c) Zinc oxide powder: 25% by weight, specific surface area 3m ² /g

The overall specific surface area of the mixed powder composed of (a) to (c) was 5.3 m ² /g.

The above mixed powders are mixed and pulverized using a wet medium agitation mill. Zirconia beads of 1 mmφ were used as pulverization media. In the pulverization process, while confirming the specific surface area of the mixed powder, the specific surface area was increased by 2 m ² /g from the specific surface area of the raw material mixed powder.

After pulverization, the mixed powder obtained by drying it with a spray dryer was filled into a mold (150mmφ20mm thick), and press-molded with a cold press.

After forming, the sintered body was produced in an oxygen atmosphere at 1400° C. for 40 hours while circulating oxygen.

The density of the obtained sintered body was calculated from the weight and external dimensions of the sintered body cut to a certain size, and it was 6.15 g/cm ³ . In this way, a sintered body for an IGZO sputtering target having a high density of the sintered body can be obtained without performing the calcining step.

In addition, as a result of analyzing the chart obtained by X-ray diffraction, it was confirmed that crystals of InGaZnO ₄ and Ga ₂ ZnO ₄ existed in the sintered body.

In addition, the volume resistance of the sintered body was measured by the four-probe method using a resistivity meter (manufactured by Mitsubishi Oil Chemical Co., Ltd., Loresta), and it was 4.2 mΩcm.

Example 17

The following oxide powders were used and weighed as raw material mixed powders. In addition, the median diameter was measured with a particle size distribution meter.

(a') Indium oxide powder: 50% by weight, median particle size 1.5 μm

(b') Gallium oxide powder: 35% by weight, median particle size 2.0 μm

(c') Zinc oxide powder: 15% by weight, median particle size 1.0 μm

The average median diameter of the mixed powder composed of (a') to (c') was 1.6 µm.

The above mixed powder was mixed and pulverized using a wet media agitation mill in the same manner as in Example 16. In the pulverization process, the median diameter of the mixed powder was confirmed to be 0.9 μm.

Thereafter, in the same manner as in Example 16, the mixed powder was molded to produce a sintered body and evaluated.

As a result, the density of the sintered body was 6.05 g/cm ³ , and a sintered body for an IGZO sputtering target with a high density of the sintered body could be obtained without performing a calcining step.

In addition, it was confirmed that crystals of InGaZnO ₄ and Ga ₂ ZnO ₄ existed in the sintered body.

In addition, the volume resistance of the sintered body was 3.8 mΩcm.

Comparative Example 5

The following oxide powders were used and weighed as raw material mixed powders.

(a) Indium oxide powder: 45% by weight, specific surface area 9m ² /g

(b) Gallium oxide powder: 30% by weight, specific surface area 4m ² /g

(c) Zinc oxide powder: 25% by weight, specific surface area 3m ² /g

The overall specific surface area of the mixed powder composed of (a) to (c) was 6 m ² /g.

The above-mentioned mixed powder was mixed and pulverized with a wet media agitation mill in the same manner as in Example 16. In the pulverization process, while confirming the specific surface area of the mixed powder, the specific surface area was increased by 1.4 m ² /g from the specific surface area of the raw material mixed powder.

Thereafter, except that the sintering condition was 1400° C. in the air for 40 hours, the mixed powder was molded in the same manner as in Example 16, and a sintered body was manufactured and evaluated.

As a result, the density of the sintered body was 5.76 g/cm ³ , and only a low-density sintered body was obtained.

In addition, since there was no reduction step, the volume resistance of the sintered body was 140 mΩcm.

In addition, crystals thought to be gallium oxide exist in the sintered body.

Comparative example 6

The following oxide powder was used and weighed as a mixed powder of raw materials.

(a') Indium oxide powder: 50% by weight, median particle size 2.5 μm

(b') Gallium oxide powder: 35% by weight, median diameter 2.5 μm

(c') Zinc oxide powder: 15% by weight, median particle size 2.0 μm

The average median diameter of the mixed powder composed of (a') to (c') was 2.4 µm.

The above mixed powder was mixed and pulverized using a wet media agitation mill in the same manner as in Example 16. In the pulverization process, the median diameter of the mixed powder was confirmed to be 2.1 μm.

Thereafter, except that the sintering condition was 1400° C. in the air for 40 hours, the mixed powder was molded in the same manner as in Example 16, and a sintered body was manufactured and evaluated.

As a result, the density of the sintered body was 5.85 g/cm ³ , and only a low-density sintered body was obtained.

In addition, since there was no reduction step, the volume resistance of the sintered body was 160 mΩcm.

In addition, crystals thought to be gallium oxide exist in the sintered body.

Comparative Example 7

In Comparative Example 5, a calcining step was implemented. Specifically, the mixed powder was calcined at 1200° C. for 10 hours in the same manner as in Comparative Example 5. The specific surface area of calcined powder is 2m ² /g.

The calcined powder was pulverized with a wet media agitation mill so that the specific surface area was increased by 2 m ² /g compared with the specific surface area of the calcined powder. Thereafter, drying and press molding were carried out in the same manner as in Example 16. Thereafter, it was sintered at 1450° C. for 4 hours in an oxygen atmosphere to manufacture a sintered body.

The density of this sintered body was 5.83 g/cm ³ . Although the density was improved compared with Comparative Example 5, it was inferior to the results of Examples 16 and 17 in which the calcining process was not performed. In addition, since the calcining process is included, the productivity of the sintered body is impaired.

This sintered body was subjected to a reduction treatment at 500° C. for 5 hours under a nitrogen flow. As a result, the volume resistance of the sintered body was 23 mΩcm.

Comparative Example 8

As in Comparative Example 6, the mixed powder was calcined at 1200° C. for 10 hours. The specific surface area of calcined powder is 2m ² /g.

The calcined powder was pulverized with a wet media agitation mill so that the specific surface area was increased by 2 m ² /g compared with the specific surface area of the calcined powder. Thereafter, drying and press molding were carried out in the same manner as in Example 16. Thereafter, sintering was carried out at 1450° C. for 40 hours in an oxygen atmosphere to manufacture a sintered body.

The density of this sintered body was 5.94 g/cm ³ . Although the density was improved compared with Comparative Example 6, it was inferior to the results of Examples 16 and 17 in which the calcining process was not performed. In addition, since the calcining step is included, the productivity of the sintered body is impaired.

The sintered body was subjected to a reduction treatment at 500° C. for 5 hours under a nitrogen gas flow. As a result, the volume resistance of the sintered body was 23 mΩcm.

Possibility of industrial use

The target of the present invention is suitable as a transparent target for various purposes such as obtaining a transparent conductive film for a liquid crystal display (LCD), a transparent conductive film for an electroluminescence (EL) display element, and a transparent conductive film for a solar cell by a sputtering method. Targets for conductive films and oxide semiconductor films. For example, electrodes for organic EL elements, transparent conductive films for transflective and semireflective LCDs, oxide semiconductor films for driving liquid crystals, and oxide semiconductor films for driving organic EL elements can be obtained. In addition, it is suitable as a raw material for oxide semiconductor films such as switching elements and driving circuit elements of liquid crystal display devices, thin film electroluminescent display devices, electrophoretic display devices, and powder transfer display devices.

Since the manufacturing method of the sputtering target of this invention does not require a calcining process and a reduction process, it is an excellent manufacturing method which can improve the productivity of a target.

Claims (23)

1. sputtering target,

It is the sputtering target that contains the oxide compound of indium (In), gallium (Ga) and zinc (Zn), wherein,

Contain ZnGa ₂O ₄Shown compound and InGaZnO ₄Shown compound.

2. sputtering target according to claim 1, wherein,

Contain InGaO ₃(ZnO) _mShown framework compound and ZnGa ₂O ₄Shown spinel structure compound, InGaO ₃(ZnO) _mIn, m is 1～20 integer.

3. sputtering target according to claim 1 and 2, wherein,

Atom shown in atomic ratio shown in the In/ (In+Ga+Zn), the Ga/ (In+Ga+Zn) the when atomic ratio shown in the Zn/ (In+Ga+Zn) satisfies following formula:

0.2＜In/(In+Ga+Zn)＜0.77

0.2＜Ga/(In+Ga+Zn)＜0.50

0.03＜Zn/(In+Ga+Zn)＜0.50。

4. according to each described sputtering target in the claim 1～3, wherein,

Atom shown in the In/ (In+Ga+Zn) the when atomic ratio shown in the Ga/ (In+Ga+Zn) satisfies following formula:

In/(In+Ga+Zn)＞Ga/(In+Ga+Zn)。

5. according to each described sputtering target in the claim 1～4, wherein,

Contain the above metallic element of positive tetravalence,

And with respect to whole metallic elements, the content of the metallic element that described positive tetravalence is above satisfies:

Metallic element/whole metallic elements that positive tetravalence is above: atomic ratio=0.0001～0.2.

6. sputtering target according to claim 5, wherein,

The above metallic element of described positive tetravalence is the element more than a kind that is selected from tin, zirconium, germanium, cerium, niobium, tantalum, molybdenum and the tungsten.

7. according to each described sputtering target in the claim 1～6, wherein,

The volume resistance of described sputtering target is less than 5 * 10 ^-3Ω cm.

8. sputtering target according to claim 2, wherein,

Described ZnGa ₂O ₄The median size of shown spinel structure compound is below the 10 μ m.

9. according to each described sputtering target in the claim 1～8, wherein,

The sintered density of described sputtering target is 6.0g/cm ³More than.

10. according to each described sputtering target in the claim 1～9,

The surfaceness of described sputtering target (Ra) is that the following and average bending strength of 2 μ m is more than the 50MPa.

11. according to each described sputtering target in the claim 1～10, wherein,

The content of Fe, Al, Si, Ni and Cu is respectively below the 10ppm (weight).

12. the manufacture method of each described sputtering target in the claim 1～11, wherein,

Indium sesquioxide, gallium oxide and zinc oxide are carried out the broken and mixing granulation of micro mist, the preparation mixture;

Described mixture is shaped, is made into body;

In Oxygen Flow or under the oxygen pressurized state, under more than 1250 ℃,, described molding is burnt till less than 1450 ℃ temperature.

13. an oxide semiconductor film,

It is by film forming being carried out in each described sputtering target sputter in the claim 1～12 and getting.

14. a sputtering target is characterized in that,

With InGaZnO ₄Shown compound is a main component, and contains the above metallic element of positive tetravalence.

15. sputtering target according to claim 14 is characterized in that,

With respect to the whole metallic elements in the sputtering target, the content of the metallic element that described positive tetravalence is above is 100ppm～10000ppm.

16. sputtering target according to claim 14 is characterized in that,

With respect to the whole metallic elements in the sputtering target, the content of the metallic element that described positive tetravalence is above is 200ppm～5000ppm.

17. sputtering target according to claim 14 is characterized in that,

With respect to the whole metallic elements in the sputtering target, the content of the metallic element that described positive tetravalence is above is 500ppm～2000ppm.

18. according to each described sputtering target in the claim 14～17, it is characterized in that,

The volume resistance of described sputtering target is less than 1 * 10 ^-3Ω cm.

19. according to each described sputtering target in the claim 14～18, it is characterized in that,

The element a kind or more of metallic element that described positive tetravalence is above for from the group that constitutes by tin, zirconium, germanium, cerium, niobium, tantalum, molybdenum and tungsten, selecting.

20. the manufacture method of a sputtering target, comprising:

With following mixed powder is raw material, with wet type medium stirring mill machine described raw material is mixed and pulverizes, and makes specific surface area increase by 1.0～3.0m than the specific surface area of mixed powder integral body ²It is 6～10m that the operation of/g, described mixed powder contain specific surface area ²The Indium sesquioxide powder of/g, specific surface area are 5～10m ²The gallium oxide powder of/g and specific surface area are 2～4m ²The specific surface area of the oxide powder and zinc of/g and powder integral body is 5～8m ²/ g; And

Raw material after the above-mentioned operation is shaped, and in oxygen atmosphere, carries out the agglomerating operation in 1250～1450 ℃.

21. the manufacture method of a sputtering target, comprising:

With following mixed powder is raw material, with wet type medium stirring mill machine described raw material is mixed pulverizing, the median particle diameter that makes raw material is the operation of 0.6～1 μ m, and the median particle diameter that described mixed powder contains size-grade distribution is that Indium sesquioxide powder, the median particle diameter of 1～2 μ m is that the gallium oxide powder of 1～2 μ m and oxide powder and zinc that median particle diameter is 0.8～1.6 μ m and the median particle diameter of powder integral body are 1.0～1.9 μ m; And

Raw material after the above-mentioned operation is shaped, and in oxygen atmosphere, carries out the agglomerating operation in 1250～1450 ℃.

22. according to the manufacture method of claim 20 or 21 described sputtering targets, wherein,

Do not carry out pre-burning and carry out described sintering.

23. according to the manufacture method of each described sputtering target in the claim 20～22, wherein,

Density by the described sintered compact that carries out the agglomerating operation and obtain is 6.0g/cm ³More than.

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