WO2014073210A1

WO2014073210A1 - Sputtering target, oxide semiconductor thin film, and methods for producing these products

Info

Publication number: WO2014073210A1
Application number: PCT/JP2013/006573
Authority: WO
Inventors: 望但馬; 一晃江端; 麻美西村; 美佐砂川; 将之糸瀬
Original assignee: 出光興産株式会社
Priority date: 2012-11-09
Filing date: 2013-11-07
Publication date: 2014-05-15
Also published as: TW201434788A; JP2014111818A

Abstract

A sputtering target which comprises an oxide containing an indium element (In), a tin element (Sn), a zinc element (Zn) and at least one element (X) selected from the group (X) mentioned below, and contains a bixbyite structure compound represented by In₂O₃ and a spinel structure compound. Group (X): Mg, Al, Ga, Si, Sc, Ti, Y, Zr, Hf, Ta, La, Nd and Sm.

Description

Sputtering target, oxide semiconductor thin film, and manufacturing method thereof

The present invention relates to a sputtering target for producing an oxide thin film such as an oxide semiconductor or a transparent conductive film, a thin film produced using the target, a thin film transistor including the thin film, and a method for producing them.

Field effect transistors such as thin film transistors (TFTs) are widely used as unit electronic elements, high frequency signal amplifying elements, liquid crystal driving elements, etc. for semiconductor memory integrated circuits, and are currently the most widely used electronic devices. . In particular, with the remarkable development of display devices in recent years, in various display devices such as liquid crystal display devices (LCD), electroluminescence display devices (EL), and field emission displays (FED), a driving voltage is applied to the display elements. TFTs are often used as switching elements for driving display devices.

As a material for a semiconductor layer (channel layer) which is a main member of a field effect transistor, a silicon semiconductor compound is most widely used. In general, a silicon single crystal is used for a high-frequency amplifying element or an integrated circuit element that requires high-speed operation. On the other hand, an amorphous silicon semiconductor (amorphous silicon) is used for a liquid crystal driving element or the like because of a demand for a large area.

Although an amorphous silicon thin film can be formed at a relatively low temperature, its switching speed is slower than that of a crystalline thin film, so when used as a switching element for driving a display device, it may not be able to follow the display of high-speed movies. is there. Specifically, in a liquid crystal television with a resolution of VGA, amorphous silicon having a mobility of 0.5 to 1 cm ² / Vs could be used, but when the resolution is SXGA, UXGA, QXGA or higher, 2 cm ² / Mobility greater than Vs is required. Further, when the driving frequency is increased in order to improve the image quality, higher mobility is required.

On the other hand, although the crystalline silicon-based thin film has a high mobility, there are problems such as requiring a large amount of energy and the number of processes for manufacturing, and a problem that it is difficult to increase the area. For example, when annealing a silicon-based thin film, laser annealing using a high temperature of 800 ° C. or higher and expensive equipment is necessary. In addition, a crystalline silicon-based thin film is difficult to reduce costs such as a reduction in the number of masks because the element configuration of a TFT is usually limited to a top gate configuration.

In order to solve such a problem, a thin film transistor using an oxide semiconductor thin film containing indium oxide, tin oxide, and zinc oxide has been studied (for example, Patent Documents 1 to 3). It has been reported that this thin film has selective etching properties (for example, Patent Document 1). By using this thin film for the active layer, the electrode can be patterned by wet etching (back channel etching) without stacking an etching stopper on the oxide semiconductor thin film, thereby reducing the mask process when manufacturing the thin film transistor. In addition, the cost can be reduced and the productivity can be improved.

However, the oxide semiconductor thin film containing indium oxide, tin oxide, and zinc oxide of the prior art is likely to be crystallized when the amount of indium is increased, and the etching rate with the oxalic acid-based etching solution is slow, and the residue is likely to remain. For this reason, it was necessary to limit the amount of In to a limited range. For this reason, it was difficult to improve mobility.

International Publication No. 2008/117810 International Publication No. 2009/147969 JP 2008-66276 A

An object of the present invention is to provide a sputtering target that contains indium oxide, tin oxide, and zinc oxide and realizes good TFT characteristics in a wide range of In amount. Furthermore, it aims at providing the sputtering target which can manufacture TFT which has a favorable characteristic by a back channel etching method.

According to the present invention, the following sputtering target and the like are provided.
1. A bixbite structure composed of an oxide containing at least one element X selected from indium element (In), tin element (Sn), zinc element (Zn), and the following group X, and represented by In ₂ O ₃ A sputtering target comprising a compound and a spinel structure compound.
X group: Mg, Al, Ga, Si, Sc, Ti, Y, Zr, Hf, Ta, La, Nd, Sm
2. 2. The sputtering target according to 1, wherein an atomic ratio of the indium element, tin element, zinc element and element X satisfies the following formulas (1) to (4).
0.20 ≦ In / (In + Sn + Zn + X) ≦ 0.85 (1)
0.01 ≦ Sn / (In + Sn + Zn + X) ≦ 0.35 (2)
0.01 ≦ Zn / (In + Sn + Zn + X) ≦ 0.70 (3)
0.01 ≦ X / (In + Sn + Zn + X) ≦ 0.30 (4)
(In the formula, In, Sn, Zn, and X each represent an atomic ratio of each element in the sputtering target.)
3. The sputtering target according to 1 or 2, wherein the spinel structure compound contains any one of XIn ₂ O ₄ , ZnX ₂ O ₄ , and Zn ₂ XO ₄ .
4). 4. The sputtering target according to any one of 1 to 3, wherein the element X is Mg, Al, Ti, Si, or Ga.
5. The sputtering target according to any one of 1 to 3, wherein the element X is Al, and the spinel structure compound contains ZnAl ₂ O ₄ .
6). The sputtering target according to any one of 1 to 5, wherein the spinel structure compound contains Zn ₂ SnO ₄ .
7). 7. The sputtering target according to any one of 1 to 6, having a relative density of 98% or more and a bulk specific resistance of 10 mΩcm or less.
8. An oxide semiconductor thin film formed by sputtering using the sputtering target according to any one of 1 to 7.
9. 9. The oxide semiconductor thin film according to 8, which is insoluble in a phosphoric acid etching solution and is soluble in an oxalic acid etching solution.
10. 10. The oxide semiconductor thin film according to 9, wherein an etching rate at 35 ° C. with the phosphoric acid-based etching solution is 10 nm / min or less and an etching rate at 35 ° C. with the oxalic acid etching solution is 20 nm / min or more.
11. Oxidation formed by sputtering using a sputtering target according to any one of 1 to 7 in an atmosphere of a mixed gas containing one or more selected from water vapor, oxygen gas and nitrous oxide gas and a rare gas Method for manufacturing a semiconductor thin film.
12 12. The method for producing an oxide semiconductor thin film according to 11, wherein the oxide semiconductor thin film is formed in an atmosphere of a mixed gas containing at least water vapor and a rare gas.
13. 13. The method for producing an oxide semiconductor thin film according to 11 or 12, wherein a ratio of water vapor contained in the mixed gas is 0.1% to 25% in terms of partial pressure ratio.
14 14. The method for producing an oxide semiconductor thin film according to any one of 11 to 13, wherein a ratio of oxygen gas contained in the mixed gas is 0.1% to 30% in terms of partial pressure ratio.
15. The oxide semiconductor thin film is formed by sequentially transporting the substrate to a position facing three or more targets arranged in parallel in the vacuum chamber at a predetermined interval, and from each AC power source to each target. In the case of alternately applying a negative potential and a positive potential, at least one of the outputs from the AC power supply is switched between two or more targets that are branched and connected while switching the target to which the potential is applied. 15. The method for producing an oxide semiconductor thin film according to any one of 11 to 14, which is performed by a sputtering method in which plasma is generated on a target to form a film on a substrate surface.
16. 16. The method for producing an oxide semiconductor thin film according to 15, wherein the AC power density of the AC power source is 3 W / cm ² or more and 20 W / cm ² or less.
17. 17. The method for producing an oxide semiconductor thin film according to 15 or 16, wherein the frequency of the AC power source is 10 kHz to 1 MHz.
A thin film transistor having the oxide semiconductor thin film according to any one of 18.8 to 10 as a channel layer.
19. 19. The thin film transistor according to 18, wherein the field effect mobility is 10 cm ² / Vs or more.
A thin film transistor having a protective film containing at least SiNx (x is an arbitrary number) on the oxide semiconductor thin film according to any one of 20.8 to 10.
21. A method of manufacturing a thin film transistor using the oxide semiconductor thin film according to any one of 8 to 10 as a semiconductor active layer, wherein the semiconductor thin film and the electrode are different from each other without stacking an etching stopper on the semiconductor thin film. A method of manufacturing a thin film transistor, comprising a step of patterning using an etching solution, and the step of contacting the semiconductor thin film directly with the etching solution when patterning an electrode.
22. A display device comprising the thin film transistor according to any one of 18.18 to 20.

According to the present invention, it is possible to provide a sputtering target that includes indium oxide, tin oxide, and zinc oxide and realizes good TFT characteristics in a wide range of In amount.
In addition, it is possible to provide a sputtering target capable of manufacturing a TFT having favorable characteristics by a back channel etching method.

2 is an X-ray chart of a sintered body obtained in Example 1. 3 is an X-ray chart of a sintered body obtained in Example 2. 4 is an X-ray chart of a sintered body obtained in Example 3. 6 is an X-ray chart of a sintered body obtained in Example 4. 6 is an X-ray chart of a sintered body obtained in Example 5. 6 is an X-ray chart of a sintered body obtained in Example 6. 6 is an X-ray chart of a sintered body obtained in Example 7. 6 is an X-ray chart of a sintered body obtained in Example 8. 10 is an X-ray chart of a sintered body obtained in Example 9. It is a figure which shows the sputtering device used for one Embodiment of this invention.

Hereinafter, the sputtering target, the oxide semiconductor thin film, the thin film transistor, the display device, and the manufacturing method thereof according to the present invention will be described in detail, but the present invention is not limited to the following embodiments and examples.

The sputtering target of the present invention is composed of an oxide containing indium element (In), tin element, (Sn), zinc element (Zn), and one or more elements X selected from the following group X, and includes In ₂ O _3. The bixbite structure compound represented by these and a spinel structure compound are included.
X group: Mg, Al, Ga, Si, Sc, Ti, Y, Zr, Hf, Ta, La, Nd, Sm

The presence or absence of the bixbite structure compound and the spinel structure compound can be confirmed by X-ray diffraction.

In the sputtering target of the present invention, the atomic ratio of indium element, tin element, zinc element and element X preferably satisfies the following formulas (1) to (4).
0.20 ≦ In / (In + Sn + Zn + X) ≦ 0.85 (1)
0.01 ≦ Sn / (In + Sn + Zn + X) ≦ 0.35 (2)
0.01 ≦ Zn / (In + Sn + Zn + X) ≦ 0.70 (3)
0.01 ≦ X / (In + Sn + Zn + X) ≦ 0.30 (4)
(In the formula, In, Sn, Zn, and X each represent an atomic ratio of each element in the sputtering target.)

In the above formula (1), if the amount of In element is 0.20 or more, the bulk resistance value of the sputtering target is hardly increased, and DC sputtering is possible.
On the other hand, if the amount of In element is 0.85 or less, it is difficult to form a conductor due to an increase in carrier concentration of a thin film produced using the target, and it can be used as a semiconductor thin film.

From the above, the In concentration is preferably 0.20 ≦ In / (In + Sn + Zn + X) ≦ 0.85. The amount of In element [In / (In + Sn + Zn + X)] is preferably 0.20 to 0.75, and more preferably 0.25 to 0.60.

In the above formula (2), when the amount of Sn element is 0.01 or more, the selectivity of the resulting thin film to the etching solution can be secured, and back channel etching can be performed.
On the other hand, if the amount of Sn element is 0.35 or less, the etching property with respect to the oxalic acid-based etching solution is not lost, and the in-plane is easily made uniform.
Accordingly, the Sn concentration is preferably 0.01 ≦ Sn / (In + Sn + Zn + X) ≦ 0.35.
The amount of Sn element [Sn / (In + Sn + Zn + X)] is preferably 0.03 to 0.30, and more preferably 0.05 to 0.25.

In the above formula (3), if the amount of Zn element is 0.01 or more, the target density is improved and the target resistance is easily lowered, so that DC sputtering can be performed.
On the other hand, if the amount of Zn element is 0.70 or less, the dissolution rate of the obtained thin film in the etching solution is too fast, and wet etching is not difficult.

From the above, the Zn concentration is preferably 0.01 ≦ Zn / (In + Sn + Zn + X) ≦ 0.70.
The amount of Zn element [Zn / (In + Sn + Zn + X)] is preferably 0.03 to 0.60, and more preferably 0.05 to 0.60.

In the above formula (4), when the amount of the element X is 0.01 or more, it becomes easy to suppress the carrier concentration of a thin film manufactured using the target, and it can be used as a thin film for a semiconductor.
On the other hand, if the amount of the element X is 0.30 or less, the oxide of the element X is difficult to appear alone, and the target resistance can be prevented from increasing.
From the above, the concentration of X is preferably 0.01 ≦ X / (In + Sn + Zn + X) ≦ 0.30.
The amount of the element X [X / (In + Sn + Zn + X)] is preferably 0.02 to 0.27, and more preferably 0.02 to 0.25.

The bixbite structure means that the X-ray diffraction pattern of the sintered body matches the crystal structure of the bixbital diffraction pattern obtained from JCPDS (Joint Committee of Powder Diffraction Standards) card or The Inorganic Crystal Structure Database (ICSD). Can be confirmed. Examples of the compound having a bixbite structure include In ₂ O ₃ .

Bixbyte is also referred to as rare earth oxide C-type or Mn ₂ O ₃ (I) -type oxide. As disclosed in “Technology of Transparent Conductive Films” (Ohm Publishing Co., Ltd., Japan Society for the Promotion of Science, Transparent Oxide / Optoelectronic Materials 166th Committee, 1999), the stoichiometric ratio is M ₂ X ₃ (M is a cation, X is an anion, usually an oxygen ion), and one unit cell is composed of 16 molecules of M ₂ X ₃ , a total of 80 atoms (M is 32, X is 48) Yes.

The bixbite structure is X-ray diffraction, and is No. of JCPDS database. A peak pattern of 06-0416 or a similar (shifted) pattern is shown.
The bixbite structure compound also includes a substitutional solid solution in which atoms and ions in the crystal structure are partially substituted with other atoms, and an interstitial solid solution in which other atoms are added to interstitial positions.

The spinel structure can be confirmed by observing the peak of the spinel structure compound as a result of X-ray diffraction measurement of the sintered body.
The spinel structure is described in detail in “Introduction to West Solid Chemistry” (Kodansha Scientific). According to this, the spinel structure is as follows.

Spinel has a composition formula of AB ₂ O ₄ and is classified into a normal spinel structure, a reverse spinel structure, and an intermediate structure between the two when classified according to the coordination state of A ions and B ions.
The regular spinel has a structure in which A is filled in one-eighth of the tetrahedral gap of the solid face-centered lattice formed by O ²⁻ and B is filled in one-half of the octahedral gap. The reverse spinel structure has a structure in which one-eighth of the tetrahedral gap is filled with B and half of the octahedral gap is filled with A and B. Generally, it is a cubic crystal, but some of the cubic crystals are distorted.

Also included in the spinel structure compound are substituted solid solutions in which atoms and ions in the crystal structure are partially substituted with other atoms, and interstitial solid solutions in which other atoms are added to interstitial positions.
Examples of the spinel structure compound include ZnAl ₂ O ₄ , Zn ₂ SnO ₄ , MgIn ₂ O ₄ , Zn ₂ TiO ₄ , ZnGa ₂ O ₄ , Zn ₂ SiO _{4 and the} like.

For example, the spinel structure of ZnAl ₂ O ₄ is X-ray diffraction, and the JCPDS database No. It shows a peak pattern of 05-0669 or a similar (shifted) pattern. Similarly, other spinel structures show an X-ray pattern obtained from JCPDS or ICSD by X-ray diffraction or a similar (shifted) pattern.

Since the sputtering target of the present invention contains a bixbite structure compound represented by In ₂ O ₃ , the element X can easily form a bixbite structure and a substitutional solid solution or an interstitial solid solution, thereby increasing the resistance of the target. It is possible to prevent the oxide of the element X from appearing alone.

In addition, the inclusion of the spinel structure compound makes it easier for the element X to form a spinel structure and a substitutional solid solution or an interstitial solid solution, and the oxide of the element X that may increase the resistance of the target appears alone. Can be prevented.

In a preferred embodiment of the present invention, by containing Zn ₂ SnO ₄ as the spinel structure compound, the element X hardly forms a crystal structure with In, Sn, Zn, and even if the oxide of the element X tends to appear alone, _{When the} element X is dissolved in ₂ SnO ₄ , the resistance of the target can be lowered. As a result, the amount of element X added can be increased, and an excellent semiconductor thin film can be produced without increasing the oxygen partial pressure during film formation.

In another preferred embodiment of the present invention, the element X further constitutes a spinel structure such as XIn ₂ O ₄ , ZnX ₂ O ₄ , Zn ₂ XO ₄ , that is, the spinel structure compound is XIn ₂ O. ₄ , ZnX ₂ O ₄ , or Zn ₂ XO ₄ , which makes it difficult for an oxide of element X to appear alone, and makes a high-density, low-resistance target even if the amount of element X is large. Can do.

The element X is preferably Mg, Al, Ti, Si, or Ga. Thereby, it can be set as a high-density and low-resistance target. This is presumably because the element X is likely to form a bixbite or spinel structure compound and a substitutional solid solution or an interstitial solid solution, or the element X is likely to form a spinel structure.

In particular, it is preferable that the element X is Al and the spinel structure compound is ZnAl ₂ O ₄ . Thereby, it can be set as a target with higher density and lower resistance. This is because Al is an element that becomes a positive trivalent ion, so that it can be easily replaced with In in the bixbyite structure compound represented by In ₂ O ₃ , and moreover, In, Sn, Zn and a stable crystalline phase It is thought that this is easy to form.
Incidentally, the target of the present invention may also include a well if it contains bixbyite structure compound and spinel structural compound represented by an In ₂ O _3, other crystalline phases.

The atomic ratio of each element contained in the sputtering target can be determined by quantitative analysis of the contained elements using an inductively coupled plasma emission spectrometer (ICP-AES).
Specifically, when a solution sample is atomized with a nebulizer and introduced into an argon plasma (about 6000 to 8000 ° C.), the elements in the sample are excited by absorbing thermal energy, and orbital electrons have a high energy from the ground state. Move to the level orbit. These orbital electrons move to a lower energy level orbit in about 10 ⁻⁷ to 10 ⁻⁸ seconds. At this time, the energy difference is emitted as light to emit light. Since this light shows a wavelength (spectral line) unique to the element, the presence of the element can be confirmed by the presence or absence of the spectral line (qualitative analysis).

In addition, since the magnitude (luminescence intensity) of each spectral line is proportional to the number of elements in the sample, the sample concentration can be obtained by comparing with a standard solution having a known concentration (quantitative analysis).
After identifying the elements contained in the qualitative analysis, the content is obtained by quantitative analysis, and the atomic ratio of each element is obtained from the result.

As described above, the metal element contained in the sputtering target is substantially composed of In, Sn, Zn, and metal X, and may contain other inevitable impurities as long as the effects of the present invention are not impaired. .
In the present invention, “substantially” means that the effect as a sputtering target is caused by the above In, Sn, Zn and element X, or 95% by weight to 100% by weight (preferably 98% by weight) of the metal element of the sputtering target. % Or more and 100% by weight or less) means In, Sn, Zn, and element X.

The sputtering target used in the present invention preferably has a relative density of 98% or more. In the case where an oxide semiconductor film is formed by increasing the sputtering output on a large substrate (1G size or more), the relative density is preferably 98% or more. The relative density is a density calculated relative to the theoretical density calculated from the weighted average. The density calculated from the weighted average of the density of each raw material is the theoretical density, which is defined as 100%.

If the relative density is 98% or more, a stable sputtering state is maintained. When film formation is performed with a large substrate at an increased sputtering output, the target surface may be blackened or abnormal discharge may occur if the relative density is less than 98%. The relative density is preferably 98.5% or more, more preferably 99% or more.

The relative density can be measured by Archimedes method. The relative density is preferably 100% or less. If it is 100% or less, metal particles are less likely to be generated in the sintered body and lower oxides are less likely to be produced, and it is not necessary to strictly adjust the oxygen supply amount during film formation.

Further, after sintering, the density can be adjusted by performing a post-treatment step such as a heat treatment operation under a reducing atmosphere. As the reducing atmosphere, an atmosphere of argon, nitrogen, hydrogen, or a mixed gas atmosphere thereof is used.

More preferably, the sputtering target of the present invention has a relative density of 98% or more and a bulk specific resistance of 10 mΩcm or less. Thereby, when sputtering a target, generation | occurrence | production of abnormal discharge can be suppressed. The sputtering target of the present invention can form a high-quality oxide semiconductor thin film efficiently, inexpensively and with energy saving.
A bulk specific resistance can be measured by the method as described in an Example, for example. The bulk specific resistance is preferably 5 mΩcm or less.

It is desirable that the maximum crystal grain size in the sputtering target of the present invention is 8 μm or less. Generation of nodules can be prevented if the crystal has a particle size of 8 μm or less.

When the target surface is cut by sputtering, the cutting speed varies depending on the direction of the crystal plane, and irregularities are generated on the target surface. The size of the unevenness depends on the crystal grain size present in the sputtering target. In the target having a large crystal grain size, the unevenness is increased, and it is considered that nodules are generated from the convex portion.

When the shape of the sputtering target is circular, the maximum grain size of these sputtering target crystals is the center point (one place) of the circle and the center point and the peripheral part on two center lines orthogonal to the center point. At a total of five intermediate points (four locations), and when the sputtering target has a quadrangular shape, the central point (one location) and the intermediate point (4) between the central point and the corner on the diagonal of the quadrangle. The maximum diameter of the maximum particles observed in a 100 μm square frame at a total of five locations is measured, and is expressed as an average value of the particle sizes of the maximum particles present in each of these five locations. The particle size is measured for the major axis of the crystal grains. The crystal grains can be observed with a scanning electron microscope (SEM).

The manufacturing method of the sputtering target of the present invention includes the following two steps.
(1) Step of mixing raw material compounds and molding to form a molded body (2) Step of sintering the molded body

Hereinafter, each step will be described.
(1) Process of mixing raw material compounds and molding to form a molded body The raw material compound is not particularly limited, and is a compound containing In, Sn, Zn and element X, and the sintered body has the following atomic ratio. A compound that can be used may be used.

0.20 ≦ In / (In + Sn + Zn + X) ≦ 0.85 (1)
0.01 ≦ Sn / (In + Sn + Zn + X) ≦ 0.35 (2)
0.01 ≦ Zn / (In + Sn + Zn + X) ≦ 0.70 (3)
0.01 ≦ X / (In + Sn + Zn + X) ≦ 0.30 (4)
(In the formula, In, Sn, Zn, and X each represent an atomic ratio of each element in the sputtering target.)

For example, a combination of indium oxide, tin oxide, zinc oxide and a single element X, a combination of indium oxide, tin oxide, zinc oxide and an oxide of element X, or the like can be given.
The raw material is preferably a powder, and more preferably a mixed powder of indium oxide, tin oxide, zinc oxide and an oxide of element X.
When a single metal is used as a raw material, for example, when a combination of indium oxide, tin oxide, zinc oxide and a single element X is used as a raw material powder, grains of the single element X exist in the obtained sintered body, During the film formation, the metal particles on the target surface may melt and not be released from the target, and the composition of the resulting film and the composition of the sintered body may differ greatly.

The average particle diameter of the raw material powder is preferably 0.1 μm to 1.2 μm, more preferably 0.1 μm to 1.0 μm or less. The average particle diameter of the raw material powder can be measured with a laser diffraction type particle size distribution apparatus or the like.

For example, In ₂ O ₃ powder with an average particle size of 0.1 μm to 1.2 μm, SnO ₂ powder with an average particle size of 0.1 μm to 1.2 μm, ZnO powder with an average particle size of 0.1 μm to 1.2 μm In addition, an oxide containing an element X oxide powder having an average particle diameter of 0.1 μm to 1.2 μm is used as a raw material powder, and these are prepared at a ratio satisfying the above formulas (1) to (4).

The mixing and forming method in step (1) is not particularly limited, and can be performed using a known method. For example, an aqueous solvent is blended into a raw material powder containing a mixed powder of oxide containing indium oxide powder, tin oxide, zinc oxide and oxide powder of element X, and the resulting slurry is mixed for 12 hours or more. Solid-liquid separation, drying, and granulation are performed, and then this granulated product is put into a mold and molded.

For mixing, a wet or dry ball mill, vibration mill, bead mill, or the like can be used. In order to obtain uniform and fine crystal grains and vacancies, a bead mill mixing method is most preferable because the crushing efficiency of the agglomerates is high in a short time and the additive is well dispersed.

The mixing time by the ball mill is preferably 15 hours or more, more preferably 19 hours or more. This is because if the mixing time is insufficient, a high resistance compound such as an oxide of metal X may be formed in the finally obtained sintered body.
The pulverization and mixing time by the bead mill varies depending on the size of the apparatus and the amount of slurry to be processed, but is appropriately adjusted so that the particle size distribution in the slurry is all uniform at 1 μm or less.

Also, when mixing, it is preferable to add an arbitrary amount of a binder and mix them at the same time. As the binder, polyvinyl alcohol, vinyl acetate, or the like can be used.

Next, granulated powder is obtained from the raw material powder slurry. In granulation, it is preferable to perform rapid drying granulation. As an apparatus for rapid drying granulation, a spray dryer is widely used. Since specific drying conditions are determined by various conditions such as the slurry concentration of the slurry to be dried, the temperature of hot air used for drying, and the amount of air, it is necessary to obtain optimum conditions in advance.

When natural drying is performed, the sedimentation speed varies depending on the specific gravity difference of the raw material powder, so that separation of In ₂ O ₃ powder, Sn ₂ O ₂ powder, ZnO powder and metal X oxide powder occurs, and uniform granulated powder is formed. There is a risk that it will not be obtained. When a sintered body is produced using this non-uniform granulated powder, an oxide of element X or the like is present inside the sintered body, which may cause abnormal discharge in sputtering.
The granulated powder is usually molded by a die press or cold isostatic press (CIP) at a pressure of, for example, 1.2 ton / cm ² or more to obtain a molded body. The pressure may be greater than this value.

(2) Step of Sintering Molded Body The obtained molded product can be sintered at a sintering temperature of 1200 to 1650 ° C. for 10 to 50 hours to obtain a sintered body.
The sintering temperature is preferably 1300 to 1600 ° C, more preferably 1350 to 1550 ° C, and still more preferably 1400 to 1500 ° C. The sintering time is preferably 12 to 40 hours, more preferably 13 to 30 hours.

When the sintering temperature is 1200 ° C. or more and the sintering time is 10 hours or more, the oxide of the element X or the like is hardly formed inside the target, and an abnormal discharge hardly occurs. On the other hand, if the firing temperature is 1650 ° C. or less and the firing time is 50 hours or less, the increase in the average crystal grain size due to remarkable crystal grain growth, the generation of coarse pores, etc. can be suppressed, and the strength of the sintered body is reduced or abnormal. Discharge can be made difficult to occur.

As a sintering method used in the present invention, a pressure sintering method such as hot press, oxygen pressurization, hot isostatic pressurization and the like can be employed in addition to the atmospheric pressure sintering method. However, it is preferable to employ a normal pressure sintering method from the viewpoints of reducing manufacturing costs, possibility of mass production, and easy production of large sintered bodies.

In the normal pressure sintering method, the compact is sintered in an air atmosphere or an oxidizing gas atmosphere, preferably an oxidizing gas atmosphere. The oxidizing gas atmosphere is preferably an oxygen gas atmosphere. The oxygen gas atmosphere is preferably an atmosphere having an oxygen concentration of, for example, 10 to 100% by volume. In the method for producing a sintered body, the density of the sintered body can be further increased by introducing an oxygen gas atmosphere in the temperature raising process.

Further, it is preferable that the heating rate during sintering is from 800 ° C. to a sintering temperature (1200 to 1650 ° C.) of 0.1 to 2 ° C./min.
In the sputtering target of oxide containing indium element (In), tin oxide (Sn), zinc element (Zn) and element X, the temperature range above 800 ° C. is the range where the sintering proceeds most. When the rate of temperature rise in this temperature range is faster than 0.1 ° C./min, it becomes easy to prevent significant crystal grain growth and to increase the density. On the other hand, by making the temperature increase rate slower than 2 ° C./min, it becomes easy to prevent the oxide of element X and the like from being precipitated inside the target, and the target resistance is likely to be lowered.

The heating rate from 800 ° C. to the sintering temperature is preferably 0.1 to 1.3 ° C./min, more preferably 0.1 to 1.1 ° C./min.
Furthermore, it is preferable to add a calcining step of maintaining the temperature in the temperature range of 700 to 900 ° C. for 1 to 5 hours before raising the temperature to the sintering temperature (1200 to 1650 ° C.). Since heat shrinkage proceeds rapidly from around 800 ° C., maintaining the temperature in the temperature range of 700 to 900 ° C. for 1 to 5 hours can suppress the generation of pores, and the target resistance tends to decrease.

In order to make the bulk resistance of the sintered body obtained in the firing step uniform over the entire target, a reduction step may be provided as necessary.
Examples of the reduction method include a method using a reducing gas, vacuum firing, or reduction using an inert gas.
In the case of reduction treatment with a reducing gas, hydrogen, methane, carbon monoxide, a mixed gas of these gases and oxygen, or the like can be used.

In the case of reduction treatment by firing in an inert gas, nitrogen, argon, a mixed gas of these gases and oxygen, or the like can be used.
The temperature during the reduction treatment is usually 100 to 800 ° C, preferably 200 to 800 ° C. The reduction treatment time is usually 0.01 to 10 hours, preferably 0.05 to 5 hours.

To summarize the above, for example, an aqueous solvent is blended with a raw material powder containing a mixed powder of indium oxide powder, tin oxide powder, zinc oxide powder and oxide of element X, and the resulting slurry is mixed for 12 hours or more. Thereafter, solid-liquid separation, drying, and granulation are performed, and then this granulated product is put into a mold and molded. Thereafter, the obtained molded product is heated in an oxygen atmosphere from 800 ° C. to a sintering temperature. The sintered body used in the present invention can be obtained by firing at 1200 to 1650 ° C. for 10 to 50 hours at 0.1 to 2 ° C./min. Further, it is preferable to add a calcining step for maintaining the temperature in the temperature range of 700 to 900 ° C. for 1 to 5 hours.

The sputtering target of the present invention can be obtained by processing the sintered body obtained above. Specifically, a sputtering target material can be obtained by cutting the sintered body into a shape suitable for mounting on a sputtering apparatus, and a sputtering target can be obtained by bonding the target material to a backing plate.

In order to use the sintered body as a target material, the sintered body is ground with, for example, a surface grinder to obtain a material having a surface roughness Ra of 0.5 μm or less. Here, the sputter surface of the target material may be further mirror-finished so that the average surface roughness Ra may be 1000 angstroms or less.

Mirror surface processing (polishing) can be performed using a known polishing technique such as mechanical polishing, chemical polishing, mechanochemical polishing (a combination of mechanical polishing and chemical polishing). For example, polishing to # 2000 or more with a fixed abrasive polisher (polishing liquid: water), or lapping with loose abrasive lapping (abrasive: SiC paste, etc.), and then lapping by changing the abrasive to diamond paste Can be obtained. Such a polishing method is not particularly limited.

The surface of the target material is preferably finished with a diamond grindstone of No. 200 to 10,000, and particularly preferably finished with a diamond grindstone of No. 400 to 5,000. If a diamond grindstone smaller than 200 or larger than 10,000 is used, the target material may be easily broken.

It is preferable that the target material has a surface roughness Ra of 0.5 μm or less and has a non-directional ground surface. If Ra is 0.5 μm or less and a non-directional polished surface is provided, there is little risk of abnormal discharge or generation of particles.
Next, the obtained target material is cleaned. Air blow or running water washing can be used for the cleaning treatment. When removing foreign matter by air blow, it is possible to remove the foreign matter more effectively by suctioning with a dust collector from the opposite side of the nozzle.

In addition, since there is a limit in the above air blow and running water cleaning, ultrasonic cleaning and the like can also be performed. This ultrasonic cleaning is effective by performing multiple oscillations at a frequency of 25 to 300 KHz. For example, it is preferable to perform ultrasonic cleaning by oscillating 12 types of frequencies in 25 kHz increments between frequencies of 25 to 300 KHz.

The thickness of the target material is usually 2 to 20 mm, preferably 3 to 12 mm, particularly preferably 4 to 6 mm.
A sputtering target can be obtained by bonding the target material obtained as described above to a backing plate. Further, a plurality of target materials may be attached to one backing plate to substantially serve as one target.

The oxide semiconductor thin film of the present invention is formed by a sputtering method using the above-described sputtering target of the present invention.
The oxide semiconductor thin film of the present invention contains indium, tin, zinc, element X, and oxygen, and usually has an atomic ratio of (1) to (4).

In the above formula (1), if the amount of In element is 0.20 or more, the mobility can be increased when the formed film is applied to the channel layer of the TFT.
On the other hand, when the amount of In element is 0.85 or less, when the formed film is applied to the channel layer of the TFT, it becomes difficult to conduct and the TFT can be operated.

In the above formula (2), if the amount of Sn element is 0.01 or more, the selectivity of the resulting thin film to the etching solution can be ensured.
On the other hand, if the amount of Sn element is 0.35 or less, the etching property with respect to the oxalic acid-based etching solution can be secured and the in-plane uniformity is hardly lost.

In the above formula (3), if the amount of Zn element is 0.01 or more, the obtained film is easily stabilized as an amorphous film. On the other hand, if the amount of Zn element is 0.70 or less, the dissolution rate of the resulting thin film in the etching solution is too high, and wet etching does not become difficult.

In the above formula (4), when the amount of the element X is 0.01 or more, the carrier concentration in the film can be suppressed and the TFT can be easily operated. On the other hand, when the amount of the element X is 0.30 or less, the mobility is not lowered and good TFT characteristics can be obtained.
Since the sputtering target of the present invention has high conductivity, a DC sputtering method having a high deposition rate can be applied.

The sputtering target of the present invention can be applied to an RF sputtering method, an AC sputtering method, and a pulsed DC sputtering method in addition to the DC sputtering method, and enables sputtering without abnormal discharge.
The oxide semiconductor thin film can also be manufactured by a vapor deposition method, an ion plating method, a pulse laser vapor deposition method, or the like using the above sputtering target.

As the sputtering gas (atmosphere), a mixed gas of a rare gas such as argon and an oxidizing gas can be used. Examples of the oxidizing gas include O ₂ , CO ₂ , O ₃ , water vapor (H ₂ O), and N ₂ O. The sputtering gas is preferably a mixed gas containing a rare gas and one or more selected from water vapor, oxygen gas and nitrous oxide gas, and more preferably a mixed gas containing at least a rare gas and water vapor.
The carrier concentration of the oxide semiconductor thin film is usually 10 ¹⁹ cm ⁻³ or less, preferably 10 ¹³ to 10 ¹⁸ cm ⁻³ , more preferably 10 ¹⁴ to 10 ¹⁸ cm ⁻³ , and particularly preferably 10 ¹³ cm ^−3. ¹⁵ to 10 ¹⁸ cm ⁻³ .

When the carrier concentration of the oxide layer is 10 ¹⁹ cm ⁻³ or less, generation of leakage current can be suppressed when an element such as a thin film transistor is formed. Further, it is possible to prevent the normally-on state and the on-off ratio from becoming small. Further, when the carrier concentration is 10 ¹³ cm ⁻³ or more, the number of carriers is sufficient and the TFT can be driven.
The carrier concentration of the oxide semiconductor thin film can be measured by a Hall effect measurement method.

The oxygen partial pressure ratio during sputtering film formation is preferably 0% or more and 30% or less. A thin film manufactured under a condition where the oxygen partial pressure ratio exceeds 30% may significantly reduce the carrier concentration and the carrier concentration may be less than 10 ¹³ cm ⁻³ .
The oxygen partial pressure ratio is preferably 0% to 30%, particularly preferably 0% to 20%.

The partial pressure ratio of water molecules contained in the sputtering gas (atmosphere) during oxide thin film deposition in the present invention, that is, [water vapor (H ₂ O)] / ([water vapor (H ₂ O)] + [rare gas] + [ The other gas molecules]) are preferably 0.1 to 25%.
Also, if the water partial pressure ratio is 25% or less, the film density can be prevented from decreasing, and the overlap of the 5s orbitals of In will not be reduced, so that the mobility is unlikely to decrease. The partial pressure ratio of water in the atmosphere during sputtering is more preferably 0.7 to 13%, particularly preferably 1 to 6%.

The substrate temperature when forming a film by sputtering is preferably 25 to 120 ° C., more preferably 25 to 100 ° C., and particularly preferably 25 to 90 ° C. If the substrate temperature at the time of film formation is 120 ° C. or lower, it is possible to prevent the intake of oxygen or the like introduced at the time of film formation from being reduced, and the carrier concentration of the thin film after heating is easily reduced to 10 ¹⁹ cm ⁻³ or lower. Further, if the substrate temperature during film formation is 25 ° C. or higher, the film density of the thin film does not decrease, and the mobility of the TFT is difficult to decrease.

The oxide thin film obtained by sputtering is preferably further annealed by holding at 150 to 500 ° C. for 15 minutes to 5 hours. The annealing temperature after film formation is more preferably 200 ° C. or higher and 450 ° C. or lower, and further preferably 250 ° C. or higher and 350 ° C. or lower. By performing the annealing, semiconductor characteristics can be obtained.

The atmosphere during heating is not particularly limited, but from the viewpoint of carrier controllability, an air atmosphere or an oxygen circulation atmosphere is preferable.
In the post-treatment annealing step of the oxide thin film, a lamp annealing device, a laser annealing device, a thermal plasma device, a hot air heating device, a contact heating device, or the like can be used in the presence or absence of oxygen.

The distance between the target and the substrate at the time of sputtering is preferably 1 to 15 cm, more preferably 2 to 8 cm in the direction perpendicular to the film formation surface of the substrate. If this distance is 1 cm or more, the kinetic energy of the target constituent element particles reaching the substrate does not become too large, and good film characteristics can be obtained, and the in-plane distribution of film thickness and electrical characteristics can be made uniform easily. Become. On the other hand, when the distance between the target and the substrate is 15 cm or less, the kinetic energy of the target constituent particles reaching the substrate is not too small, and a dense film can be obtained and good semiconductor characteristics can be obtained. .

The oxide thin film is preferably formed by sputtering in an atmosphere having a magnetic field strength of 300 to 1500 gauss. When the magnetic field strength is 300 gauss or more, the plasma density can be increased, so that even a high resistance sputtering target can be sputtered without problems. On the other hand, when it is 1500 gauss or less, the film thickness and the electrical characteristics in the film can be easily controlled.

The pressure in the gas atmosphere (sputtering pressure) is not particularly limited as long as the plasma can be stably discharged, but is preferably 0.1 to 3.0 Pa, more preferably 0.1 to 1.5 Pa. Particularly preferred is 0.1 to 1.0 Pa. If the sputtering pressure is 3.0 Pa or less, the mean free path of sputtered particles can be lengthened and the density of the thin film can be easily improved. Moreover, when the sputtering pressure is 0.1 Pa or more, it becomes easy to prevent the formation of microcrystals in the film during film formation. The sputtering pressure refers to the total pressure in the system at the start of sputtering after introducing a rare gas atom such as argon, water vapor, oxygen gas or the like.

Alternatively, the oxide semiconductor thin film may be formed by AC sputtering as described below.
The substrate is sequentially transported to a position facing three or more targets arranged in parallel at a predetermined interval in the vacuum chamber, and negative and positive potentials are alternately applied to each target from an AC power source. Then, plasma is generated on the target to form a film on the substrate surface.

At this time, at least one of the outputs from the AC power supply is performed while switching the target to which the potential is applied between two or more targets that are branched and connected. That is, at least one of the outputs from the AC power supply is branched and connected to two or more targets, and film formation is performed while applying different potentials to adjacent targets.

Note that when an oxide semiconductor thin film is formed by AC sputtering, for example, sputtering is performed in an atmosphere of a mixed gas containing a rare gas atom and one or more selected from water vapor, oxygen gas, and nitrous oxide gas. It is preferable to perform sputtering in a mixed gas atmosphere containing at least a rare gas and water vapor.

When the film is formed by AC sputtering, an oxide layer having industrially excellent large area uniformity can be obtained, and improvement in the utilization efficiency of the target can be expected.
Further, when sputtering film formation is performed on a large-area substrate having a side exceeding 1 m, it is preferable to use an AC sputtering apparatus for large-area production as described in, for example, Japanese Patent Application Laid-Open No. 2005-290550.

Specifically, the AC sputtering apparatus described in Japanese Patent Laid-Open No. 2005-290550 includes a vacuum chamber, a substrate holder disposed inside the vacuum chamber, and a sputtering source disposed at a position facing the substrate holder. . FIG. 10 shows a main part of the sputtering source of the AC sputtering apparatus. The sputter source has a plurality of sputter units, each of which has plate-like targets 31a to 31f, and the surfaces to be sputtered of the targets 31a to 31f are sputter surfaces. It arrange | positions so that it may be located in. Each target 31a to 31f is formed in an elongated shape having a longitudinal direction, each target has the same shape, and edge portions (side surfaces) in the longitudinal direction of the sputtering surface are arranged in parallel with a predetermined interval therebetween. Therefore, the side surfaces of the adjacent targets 31a to 31f are parallel.

AC power supplies 17a to 17c are arranged outside the vacuum chamber, and one of the two terminals of each AC power supply 17a to 17c is connected to one of the two adjacent electrodes. The other terminal is connected to the other electrode. Two terminals of each of the AC power supplies 17a to 17c output voltages of positive and negative different polarities, and the targets 31a to 31f are attached in close contact with the electrodes, so that the two adjacent targets 31a to 31f are adjacent to each other. AC voltages having different polarities are applied from the AC power sources 17a to 17c. Therefore, when one of the targets 31a to 31f adjacent to each other is placed at a positive potential, the other is placed at a negative potential.

Magnetic field forming means 40a to 40f are disposed on the surface of the electrode opposite to the targets 31a to 31f. Each of the magnetic field forming means 40a to 40f has an elongated ring-shaped magnet whose outer periphery is substantially equal to the outer periphery of the targets 31a to 31f, and a bar-shaped magnet shorter than the length of the ring-shaped magnet.

Each ring-shaped magnet is arranged in parallel with the longitudinal direction of the targets 31a to 31f at the position directly behind the corresponding one of the targets 31a to 31f. As described above, since the targets 31a to 31f are arranged in parallel at a predetermined interval, the ring magnets are also arranged at the same interval as the targets 31a to 31f.

The AC power density when an oxide target is used in AC sputtering is preferably 3 W / cm ² or more and 20 W / cm ² or less. When the power density is 3 W / cm ² or more, the deposition rate can be increased, which is economical in production. It can prevent that a target breaks that it is 20 W / cm < ² > or less. A more preferable power density is 3 W / cm ² to 15 W / cm ² .

The frequency of AC sputtering is preferably in the range of 10 kHz to 1 MHz. When the frequency is 10 kHz or more, the problem of noise hardly occurs. If it does not exceed 1 MHz, it is possible to prevent the plasma from spreading too much, and it is possible to prevent the sputtering from being performed at a position other than the desired target position and the uniformity to be lost. A more preferable frequency of AC sputtering is 20 kHz to 500 kHz.
What is necessary is just to select suitably the conditions at the time of sputtering other than the above from what was mentioned above.

The oxide semiconductor thin film of the present invention is preferably insoluble in a phosphoric acid etching solution and soluble in an oxalic acid etching solution. As described above, the oxide thin film is etched by oxalic acid-based etching because it has selectivity with respect to the etching liquid, and the electrode formed in this oxide thin film shape is further used with a phosphoric acid-based etching liquid. Patterning becomes possible.

“Insoluble in the etching solution” means that the etching rate at 35 ° C. is 10 nm / min or less, and “soluble in the etching solution” means that the etching rate at 35 ° C. is larger than 10 nm / min.

Preferably, the etching rate at 35 ° C. with a phosphoric acid etching solution is less than 10 nm / min, more preferably 5 nm / min or less, and further preferably 1 nm / min or less, and 35 with the oxalic acid etching solution. The etching solution at 20 ° C. is 20 nm / min or more, preferably 30 nm / min or more. When the etching rate is in the above range, the selectivity of the etching solution can be exhibited, and a TFT can be manufactured by back channel etching.

Examples of the oxalic acid-based etching solution include ITO-06N (manufactured by Kanto Chemical Co., Inc.). Preferably, it contains 0.5 to 10 wt% oxalic acid. However, in addition to oxalic acid, carboxylic acid such as malonic acid, succinic acid, and acetic acid and other acids may be included, and oxalic acid is not necessarily included.

Examples of the phosphoric acid-based etching solution include PAN-based etching solutions containing phosphoric acid, acetic acid, and nitric acid. The PAN-based etching solution is preferably in the range of 45 to 95 wt% phosphoric acid, 3 to 50 wt% acetic acid, and 0.5 to 5 wt% nitric acid.

The oxide semiconductor thin film of the present invention can be used for a thin film transistor, and can be particularly suitably used as a channel layer.
The element structure of the thin film transistor of the present invention is not particularly limited as long as it includes the above-described oxide semiconductor thin film of the present invention as a channel layer, and various known element structures can be employed.

The thickness of the channel layer in the thin film transistor of the present invention is usually 10 to 300 nm, preferably 20 to 250 nm, more preferably 30 to 200 nm, still more preferably 35 to 120 nm, and particularly preferably 40 to 80 nm. When the thickness of the channel layer is 10 nm or more, the non-uniformity of the film thickness when the film is formed in a large area can be reduced, and the characteristics of the manufactured TFT can be prevented from becoming non-uniform in the plane. On the other hand, if the film thickness is 300 nm or less, the film formation time does not become too long, which is industrially advantageous.

The channel layer in the thin film transistor of the present invention is usually used in an N-type region, but a PN junction transistor or the like in combination with various P-type semiconductors such as a P-type Si-based semiconductor, a P-type oxide semiconductor, and a P-type organic semiconductor. It can be used for various semiconductor devices.

The channel layer of the thin film transistor of the present invention may have any crystal composition. That is, it may be amorphous or crystalline. Further, at least part of the region overlapping with the gate electrode may be crystallized after the annealing treatment. Here, crystallization means that crystal nuclei are generated from an amorphous state or crystal grains are grown from a state where crystal nuclei are generated. In particular, when a part of the back channel side is crystallized, reduction resistance is improved with respect to a plasma process (CVD process or the like), and the reliability of the TFT is improved.
The crystallized region can be confirmed from, for example, an electron beam diffraction image of a transmission electron microscope (TEM).

The thin film transistor of the present invention preferably includes a protective film on the channel layer. The protective film in the thin film transistor of the present invention preferably contains at least SiN _x . Since SiN _x can form a dense film as compared with SiO ₂ , it has an advantage of a high TFT deterioration suppressing effect.
Note that x is an arbitrary number, and the stoichiometric ratio of SiN _x may not be constant.

In addition to SiN _x , the protective film may be, for example, SiO ₂ , Al ₂ O ₃ , Ta ₂ O ₅ , TiO ₂ , MgO, ZrO ₂ , CeO ₂ , K ₂ O, Li ₂ O, Na ₂ O, Rb ₂ O, Sc ₂ O ₃ , Y ₂ O ₃ , HfO ₂ , CaHfO ₃ , PbTiO ₃ , BaTa ₂ O ₆ , Sm ₂ O ₃ , SrTiO _3, or an oxide such as AlN can be included.

The oxide semiconductor thin film containing indium element (In) tin element (Sn), zinc element (Zn), and element X of the present invention contains element X, so that the reduction resistance by the CVD process is improved, and protection is achieved. The back channel side is not easily reduced by the process of forming the film, and SiN _x can be used as the protective film.

Before forming the protective film, the channel layer is preferably subjected to ozone treatment, oxygen plasma treatment, nitrogen dioxide plasma treatment or nitrous oxide plasma treatment. Such treatment may be performed at any timing after the channel layer is formed and before the protective film is formed, but is preferably performed immediately before the protective film is formed. By performing such pretreatment, generation of oxygen defects in the channel layer can be suppressed.

In addition, if hydrogen in the oxide semiconductor film diffuses during driving of the TFT, the threshold voltage may shift and the reliability of the TFT may be reduced. By performing ozone treatment, oxygen plasma treatment or nitrous oxide plasma treatment on the channel layer, the In—OH bond is stabilized in the thin film structure, and diffusion of hydrogen in the oxide semiconductor film can be suppressed. .

A thin film transistor usually includes a substrate, a gate electrode, a gate insulating layer, an organic semiconductor layer (channel layer), a source electrode, and a drain electrode. The channel layer is as described above, and a known material can be used for the substrate.

The material for forming the gate insulating film in the thin film transistor of the present invention is not particularly limited, and a commonly used material can be arbitrarily selected. Specifically, for _{_{_{_{example, SiO 2, SiN x, Al}}}} 2 O 3, Ta 2 O 5, TiO 2, MgO, ZrO 2, CeO 2, K 2 O, Li 2 O, Na 2 O, Rb 2 O, Compounds such as Sc ₂ O ₃ , Y ₂ O ₃ , HfO ₂ , CaHfO ₃ , PbTiO ₃ , BaTa ₂ O ₆ , SrTiO ₃ , Sm ₂ O ₃ , and AlN can be used. Among these, SiO ₂ , SiN _x , Al ₂ O ₃ , Y ₂ O ₃ , HfO ₂ and CaHfO ₃ are preferable, and SiO ₂ , SiN _x , HfO ₂ and Al ₂ O ₃ are more preferable.

The gate insulating film can be formed by, for example, a plasma CVD (Chemical Vapor Deposition) method.
When a gate insulating film is formed by plasma CVD and a channel layer is formed on the gate insulating film, hydrogen in the gate insulating film may diffuse into the channel layer, leading to deterioration in channel layer quality and TFT reliability. is there. In order to prevent deterioration in channel layer quality and TFT reliability, the gate insulating film may be subjected to ozone treatment, oxygen plasma treatment, nitrogen dioxide plasma treatment or nitrous oxide plasma treatment before forming the channel layer. preferable. By performing such pretreatment, it is possible to prevent deterioration of the channel layer film quality and TFT reliability.

Note that the number of oxygen in the oxide does not necessarily match the stoichiometric ratio, and may be, for example, SiO ₂ or SiO _x .
The gate insulating film may have a structure in which two or more insulating films made of different materials are stacked. The gate insulating film may be crystalline, polycrystalline, or amorphous, but is preferably polycrystalline or amorphous that can be easily manufactured industrially.

There are no particular limitations on the material for forming each of the drain electrode, the source electrode, and the gate electrode in the thin film transistor of the present invention, and a commonly used material can be arbitrarily selected. For example, a transparent electrode such as ITO, IZO, ZnO, or SnO ₂ , a metal electrode such as Al, Ag, Cu, Cr, Ni, Mo, Au, Ti, or Ta, or a metal electrode made of an alloy including these electrodes may be used. it can.

The thin film transistor of the present invention can be manufactured by back channel etching without forming an etching stopper on the oxide thin film which is an active layer by utilizing the etching solution selectivity of the oxide thin film.

Thin-film transistors using an active layer of a normal oxide semiconductor thin film such as an IGZO system prevent etching on the oxide semiconductor thin film because the oxide semiconductor thin film is also etched against the etchant used to etch the electrodes. For this purpose, it is necessary to form an etching stopper such as SiOx. Productivity has been reduced by including a step of forming an etching stopper.

However, the oxide semiconductor thin film of the present invention has a high productivity because it is not necessary to form an etching stopper by appropriately selecting an etching solution for patterning the semiconductor thin film and the electrode when a thin film transistor is manufactured. improves.

That is, in the thin film transistor using the oxide semiconductor thin film of the present invention as the semiconductor active layer, the semiconductor thin film and the electrode are patterned using different etching solutions without stacking the etching stopper on the semiconductor thin film, and the electrode is patterned. In this case, it can be manufactured by a manufacturing method including a step in which the etching solution directly contacts the semiconductor thin film.

Specifically, a solution capable of etching such as an oxalic acid-based etching solution is used for patterning the oxide thin film, while a transparent conductive material such as IZO, ZnO, SnO ₂ is used for patterning the electrode. Etching is possible for electrode materials such as oxides, metals such as Al, Ag, Cu, Cr, Ni, Mo, Ti, Ta, or alloys containing them, and etching is performed for the oxide thin films. For example, by using phosphoric acid etching, it is not necessary to form an etching stopper because the semiconductor thin film is not etched even when the electrode etchant directly contacts the semiconductor thin film.

The drain electrode, the source electrode, and the gate electrode may have a multilayer structure in which two or more different conductive layers are stacked. In particular, since the source / drain electrodes have a strong demand for low-resistance wiring, a good conductor such as Al or Cu may be sandwiched with a metal having excellent adhesion such as Ti or Mo.

The thin film transistor of the present invention preferably has an S value of 0.8 V / dec or less, more preferably 0.5 V / dec or less, further preferably 0.3 V / dec or less, and particularly preferably 0.2 V / dec or less. If it is 0.8 V / dec or less, the drive voltage becomes small and there is a possibility that power consumption can be reduced. In particular, when used in an organic EL display, it is preferable to set the S value to 0.3 V / dec or less because of direct current drive because power consumption can be greatly reduced.

The S value (Swing Factor) is a value indicating the steepness of the drain current that rises sharply from the off state to the on state when the gate voltage is increased from the off state. As defined by the following equation, an increment of the gate voltage when the drain current increases by one digit (10 times) is defined as an S value.
S value = dVg / dlog (Ids)
The smaller the S value, the sharper the rise ("All about Thin Film Transistor Technology", Ikuhiro Ukai, 2007, Industrial Research Committee). When the S value is large, it is necessary to apply a high gate voltage when switching from on to off, and power consumption may increase.

The S value can be derived from the reciprocal of this slope by creating a Log (Id) -Vg graph from the result of the transfer characteristics. The unit of the S value is V / decade and is preferably a small value.

The thin film transistor of the present invention preferably has a field effect mobility of 10 cm ² / Vs or more, more preferably 15 cm ² / Vs or more. The field effect mobility can be measured by the method described in the examples.

The thin film transistor of the present invention can be applied to various integrated circuits such as a field effect transistor, a logic circuit, a memory circuit, and a differential amplifier circuit. Further, in addition to the field effect transistor, it can be applied to an electrostatic induction transistor, a Schottky barrier transistor, a Schottky diode, and a resistance element.

As the structure of the thin film transistor of the present invention, known structures such as a bottom gate, a bottom contact, and a top contact can be adopted without limitation.
In particular, the bottom gate structure is advantageous because high performance can be obtained as compared with thin film transistors of amorphous silicon or ZnO. The bottom gate configuration is preferable because it is easy to reduce the number of masks at the time of manufacturing, and it is easy to reduce the manufacturing cost for uses such as a large display.

The thin film transistor of the present invention can be suitably used for a display device. For large-area displays, a channel-etched bottom-gate thin film transistor is particularly preferable. A channel-etched bottom-gate thin film transistor has a small number of photomasks in the photolithography process, and can be manufactured at a low cost. Among these, channel-etched bottom gate and top contact thin film transistors are particularly preferable because they have favorable characteristics such as mobility and are easily industrialized.

Examples 1 to 39
[Production of sintered body]
The following powder was used as a raw material powder. The average particle size of each powder was measured with a laser diffraction particle size distribution analyzer SALD-300V (manufactured by Shimadzu Corporation), and the median particle size was a median diameter D50.

Indium oxide powder: average particle size 0.98 μm
Tin oxide powder: Average particle size 0.96μm
Zinc oxide powder: Average particle size 0.98μm
Element X oxide powder: average particle size 0.90 to 1.00 μm

Each of the above powders was weighed so as to have the atomic ratio (percentage) shown in Table 1, and was uniformly pulverized and mixed, and then granulated by adding a molding binder. Next, the raw material grains were uniformly filled in a mold and subjected to pressure molding with a cold press machine at a press pressure of 140 MPa.
The obtained molded body was sintered as follows. First, the compact was placed in a sintering furnace, and oxygen was introduced at a rate of 5 liters / minute per volume of 0.1 m ³ in the sintering furnace. The molded body was sintered at 1400 ° C. for 24 hours in this atmosphere.

At this time, the temperature in the sintering furnace was increased to 1 ° C./min up to 800 ° C., held at 800 ° C. for 3 hours, and then increased from 800 ° C. to 1400 ° C. at 1 ° C./min. Thereafter, after sintering at 1400 ° C. for 24 hours, the temperature lowering rate was 5 ° C./min. An oxygen atmosphere was used during the temperature rise and the sintering temperature maintenance, and the atmosphere (atmosphere) was used during the temperature fall.

The relative density of the obtained sintered body was measured by the Archimedes method. It was confirmed that the sintered bodies of Examples 1 to 39 had a relative density of 98% or more.
Further, the bulk specific resistance (conductivity) of the obtained sintered body was measured based on the four-probe method (JIS R 1637) using a resistivity meter (Made by Mitsubishi Chemical Corporation, Loresta). The results are shown in Table 1. As shown in Table 1, the bulk specific resistance of the sintered bodies of Examples 1 to 39 was 10 mΩcm or less.

[Analysis of sintered body]
The obtained sintered body was subjected to ICP-AES analysis, and the atomic ratios shown in Table 1 were confirmed.
In addition, the crystal structure of the obtained sintered body was examined using an X-ray diffraction measurement apparatus (XRD). The measurement conditions of XRD are as follows.
・ Equipment: Ultimate-III manufactured by Rigaku Corporation
-X-ray: Cu-Kα ray (wavelength 1.5406mm, monochromatized with graphite monochromator)
・ 2θ-θ reflection method, continuous scan (1.0 ° / min)
・ Sampling interval: 0.02 °
・ Slit DS, SS: 2/3 °, RS: 0.6 mm

The X-ray diffraction charts of the sintered bodies obtained in Examples 1 to 9 are shown in FIGS. As a result of analyzing the chart, a bixbite structure of In ₂ O ₃ and a spinel structure of ZnAl ₂ O ₄ and a homologous structure of InAlZn ₂ O ₅ and InAlZnO ₄ were observed in the sintered body of Example 1.
The crystal structure can be confirmed with a JCPDS (Joint Committee of Powder Diffraction Standards) card.

In ₂ O ₃ has a big byte structure of JCPDS card no. The spinel structure of ZnAl ₂ O ₄ is JCPDS card no. 05-0669, and the homologous structure of InAlZn ₂ O ₅ is JCPDS card no. 40-0259, the homologous structure of InAlZnO ₄ is JCPDS card no. 40-0258.
Also in Examples 2 to 39, as shown in Table 1, a bixbite structure and a spinel structure of In ₂ O ₃ were observed.

In Examples 2 to 39, the bibyte structure of In ₂ O ₃ is JCPDS card no. For the spinel structure, ZnAl ₂ O ₄ is JCPDS card no. 05-0669, Zn ₂ SnO ₄ is JCPDS card no. 24-1470, ZnGa ₂ O ₄ is JCPDS card no. No. 38-1240 and MgIn ₂ O ₄ is JCPDS card No. 40-1402, Zn ₂ SiO ₄ is ICSD # 161024, and Zn ₂ TiO ₄ is ICSD # 80849.

For the homologous structure, InAlZnO ₄ is JCPDS card no. 40-0258, InAlZn ₂ O ₅ is JCPDS card no. 40-0259, and In ₂ Zn ₂ O ₅ is JCPDS card no. 20-1442, and In ₂ Zn ₃ O ₆ is JCPDS card no. 00-1140 or ICSD # 162450, In ₂ Zn ₄ O ₇ is ICSD # 162451, InGaZnO ₄ is ICSD # 9003, InGaZn ₂ O ₅ is ICSD # 380305, Y ₂ Sn ₂ O ₇ The pyrochlore structure of JCPDS card no. 20-1418, and the ZnSnO ₃ ilmenite structure is JCPDS card no. 00-1197, and In ₂ TiO ₄ is JCPDS card no. 30-0640.

For the oxide of element X, SnO ₂ is JCPDS card no. 00-1024, Al ₂ O ₃ is ICSD # 9770, and MgO is JCPDS card no. Is 45-0946, _Ga 2 _{O 3} is ICSD # 603563, TiO ₂ is ICSD # 603563, SiO ₂ is JCPDS card No. Is 33-1161, ZnO is ICSD # 57156, _Sc 2 _{O 3} is ICSD # 24200, HfO ₂ is ICSD # 27313, ZrO ₂ is an ICSD # 66781.

Regarding the sintered bodies of Examples 1 to 39, when the dispersion of the element X in the obtained sintered body was examined by electron beam microanalyzer (EPMA) measurement, an aggregate of more than 25 μm containing the element X was not observed. It was. The sintered body of the present invention is extremely excellent in dispersibility and uniformity. The measurement conditions of EPMA are as follows.

Device name: JEOL Ltd. JXA-8200
・ Measurement conditions Acceleration voltage: 15 kV
Irradiation current: 50 nA
Irradiation time (per point): 50 ms

[Manufacture of sputtering target]
The surfaces of the sintered bodies obtained in Examples 1 to 39 were ground with a surface grinder, the sides were cut with a diamond cutter, and bonded to a backing plate to produce sputtering targets each having a diameter of 4 inches.
In Examples 1 to 11, 14, 22, 24, and 25, six targets each having a width of 200 mm, a length of 1700 mm, and a thickness of 10 mm were prepared for AC sputtering film formation.

[Check for abnormal discharge]
The obtained sputtering target having a diameter of 4 inches was mounted on a DC sputtering apparatus, a mixed gas in which water vapor was added to argon gas at a partial pressure ratio of 2% as an atmosphere, a sputtering pressure of 0.4 Pa, a substrate temperature of room temperature, DC 10 kWh continuous sputtering was performed at an output of 400 W. Voltage fluctuations during sputtering were accumulated in a data logger, and the presence or absence of abnormal discharge was confirmed. The results are shown in Table 1.

Note that the presence or absence of the abnormal discharge was performed by monitoring the voltage fluctuation and detecting the abnormal discharge. Specifically, the abnormal discharge was determined when the voltage fluctuation generated during the measurement time of 5 minutes was 10% or more of the steady voltage during the sputtering operation. In particular, when the steady-state voltage during sputtering operation varies by ± 10% in 0.1 second, a micro arc, which is an abnormal discharge of the sputter discharge, has occurred, and the device yield may decrease, making it unsuitable for mass production. is there.

[Check for nodule occurrence]
In addition, using the obtained sputtering target having a diameter of 4 inches, using a mixed gas obtained by adding 3% of hydrogen gas to argon gas at a partial pressure ratio, sputtering was performed continuously for 40 hours, and no nodules were generated. It was confirmed.

As a result, no nodules were observed on the surfaces of the sputtering targets of Examples 1 to 39.
The sputtering conditions were a sputtering pressure of 0.4 Pa, a DC output of 100 W, and a substrate temperature of room temperature. Hydrogen gas was added to the atmospheric gas to promote the generation of nodules.

For the nodules, a change in the target surface after sputtering was observed by magnifying it 50 times with a stereomicroscope, and a method of measuring the number average of nodules having a size of 20 μm or more generated in a visual field of 9 mm ² was adopted. Table 1 shows the number of nodules generated.

Comparative Examples 1-11
Raw material powders were mixed at an atomic ratio (percentage) shown in Table 1, and a sintered body and a sputtering target were produced and evaluated in the same manner as in Example 1. The results are shown in Table 1.
In the target of Comparative Example 1, a homologous structure of InAlZnO ₄ , a corundum structure of Al ₂ O ₃ , and a rutile structure of SnO ₂ were observed. The comparative examples 2 to 11 are also as shown in Table 1.

In the sputtering targets of Comparative Examples 1 to 6, abnormal discharge occurred during sputtering, and nodules were observed on the target surface. Comparative Examples 7 to 11 had high resistance and could not be discharged.

Examples 40-80
[Preparation of oxide semiconductor thin film]
A 4-inch target having the composition shown in Table 2 prepared in Examples 1 to 39 was mounted on a magnetron sputtering apparatus, and a slide glass (# 1737 manufactured by Corning) was mounted as a substrate. An amorphous film having a thickness of 50 nm was formed on the slide glass by a DC magnetron sputtering method. As an atmosphere during film formation, a mixed gas in which O ₂ gas and / or water vapor was introduced into Ar gas at a partial pressure ratio (%) shown in Table 2 was used.

The sputtering conditions are as follows.
-Substrate temperature: 25 ° C
-Ultimate pressure: 8.5 × 10 ⁻⁵ Pa
Atmosphere gas: Ar gas, O ₂ gas, water vapor mixed gas (see Table 2 for partial pressure ratio of O ₂ gas and water vapor, Ar gas partial pressure ratio is the remainder)
・ Sputtering pressure (total pressure): 0.4 Pa
-Input power: DC100W
・ S (substrate) -T (target) distance: 70 mm

The crystal structure of the thin film formed on the glass substrate was examined by an X-ray diffraction measurement (XRD) apparatus (Rigaku Ultimate-III). In Examples 40 to 80, a diffraction peak was not observed immediately after deposition of the thin film, and it was confirmed that the film was amorphous.
The measurement conditions of XRD are as follows.
・ Equipment: Ultimate-III manufactured by Rigaku Corporation
-X-ray: Cu-Kα ray (wavelength 1.5406mm, monochromatized with graphite monochromator)
・ 2θ-θ reflection method, continuous scan (1.0 ° / min)
・ Sampling interval: 0.02 °
・ Slit DS, SS: 2/3 °, RS: 0.6 mm

Next, the substrate over which the amorphous film was formed was heated in the atmosphere at 300 ° C. for 60 minutes to form an oxide semiconductor film. The substrate formed on this glass substrate was used as a Hall effect measurement element and set in ResiTest 8300 type (manufactured by Toyo Technica Co., Ltd.), and the Hall effect (Hall mobility) was evaluated at room temperature.
ICP-AES analysis confirmed that the atomic ratio of each element contained in the oxide semiconductor thin film was the same as that of the sputtering target.

[Manufacture of thin film transistors]
As the substrate, a conductive silicon substrate with a thermal oxide film having a thickness of 100 nm was used. The thermal oxide film functions as a gate insulating film, and the conductive silicon portion functions as a gate electrode.
A 50 nm-thick amorphous thin film was formed by sputtering on the gate insulating film. OFPR # 800 (manufactured by Tokyo Ohka Kogyo Co., Ltd.) was used as a resist, and coating, pre-baking (80 ° C., 5 minutes), and exposure were performed. After development, it was post-baked (120 ° C., 5 minutes), etched with oxalic acid, and patterned into a desired shape. Thereafter, heat treatment (annealing treatment) was performed at 300 ° C. for 60 minutes in a hot air heating furnace.

Thereafter, Mo (100 nm) was formed by sputtering film formation by the lift-off method, and the source / drain electrodes were patterned into a desired shape. Further, a nitrous oxide plasma treatment was performed on the oxide semiconductor film as a treatment before the formation of the protective film. Then, SiOx was formed into a protective film by plasma CVD method (PECVD). A contact hole was opened using hydrofluoric acid to produce a thin film transistor.

[Evaluation of etching rate]
The etching rate was evaluated using the oxide semiconductor thin films of Examples 40 to 80 formed under the same conditions except that the thickness of the amorphous film was 100 nm.
An oxide semiconductor thin film was immersed in ITO-06N (Kanto Chemical Co., Ltd.), which is an oxalic acid-based etching solution, at 35 ° C., and the etching rate was calculated from the immersion time and the film thickness before and after the immersion.
Further, a PAN etching solution (phosphoric acid 91.4 wt%, nitric acid 3.3 wt%, acetic acid 5.3 wt%) is set to 35 ° C., and the oxide semiconductor thin film is immersed, and the immersion time is as follows: The etching rate was calculated from the film thickness before and after the immersion.

[Evaluation of Thin Film Transistor]
The thin film transistors manufactured in Examples 40 to 80 were evaluated for field effect mobility (μ) and threshold voltage (Vth). These characteristic values were measured using a semiconductor parameter analyzer (4200SCS manufactured by Keithley Instruments Co., Ltd.) at room temperature in a light-shielding environment (in a shield box). Vth is the gate voltage (Vg) when the drain current (Id) is 1 nA.

The transfer characteristics of the mounted transistors were evaluated with a drain voltage (Vd) of 5 V and a gate voltage (Vg) of −15 to 25 V. The results are shown in Table 2. The field effect mobility (μ) was calculated from the linear mobility and defined as the maximum value of Vg−μ.

Next, a DC bias stress test was performed on the TFTs of Examples 40 to 80. Table 2 shows the amount of change ΔVth in Vth before and after the application of DC stress (stress temperature of 80 ° C.) of Vg = 15 V and Vd = 15 V for 10,000 seconds. It can be seen that the threshold voltage variation of the TFT of the present invention is very small and is hardly affected by DC stress.

In addition, in Examples 40 to 50, the crystallinity of the channel layer of the thin film transistor was evaluated by an electron beam diffraction pattern using a cross-sectional TEM (Transmission Electron Microscope). As the apparatus, Hitachi field emission type transmission electron microscope HF-2100 was used.
As a result of cross-sectional TEM analysis of the channel layers of the elements of Examples 41 and 43, the front channel side was amorphous from the observed diffraction pattern, but the diffraction pattern was partially observed on the back channel side, It was found to have a crystallized region. On the other hand, in the elements of Examples 40, 42 and 44 to 50, no diffraction pattern was observed on the front channel side and the back channel side, and it was confirmed that the elements were amorphous.

Comparative Examples 12-14
Each of the 4-inch targets prepared in Comparative Examples 1, 3, and 5 was used, except that the atmosphere during sputtering film formation was changed to a mixed gas of Ar gas and a gas having a partial pressure ratio shown in Table 2. Example 40 Similarly, an oxide semiconductor thin film and a thin film transistor were manufactured and evaluated. The results are shown in Table 2.

As shown in Table 2, it can be seen that Comparative Examples 12 to 14 have a field effect mobility of less than 10 cm ² / Vs, which is significantly lower than Examples 40 to 80.

Examples 81-95
A thin film transistor was manufactured by performing AC sputtering using the film forming apparatus disclosed in Japanese Patent Laid-Open No. 2005-290550. The atmosphere during AC sputtering is a mixed gas of Ar gas and a gas having a partial pressure ratio shown in Table 3, and the obtained amorphous film is subjected to heat treatment (annealing treatment) under the conditions shown in Table 3. A thin film transistor was fabricated and evaluated in the same manner as in Examples 40-80 except that the drain patterning was performed by dry etching. The results are shown in Table 3.
ICP-AES analysis confirmed that the atomic ratio of each element contained in the oxide thin film was the same as that of the sputtering target.

Specifically, AC sputtering was performed using the apparatus shown in FIG.
The six targets 31a to 31f having a width of 200 mm, a length of 1700 mm, and a thickness of 10 mm produced in Examples 1 to 11, 14, 22, 24, and 25 are parallel to each other as shown in FIG. They were arranged at intervals of 2 mm. The width of the magnetic field forming means 40a to 40f was 200 mm, which is the same as that of the targets 31a to 31f. Ar, water vapor and / or O ₂ as sputtering gases were introduced into the system from the gas supply system.

For example, in Example 81, the film forming atmosphere was 0.5 Pa, the power of the AC power source was 3 W / cm ² (= 10.2 kW / 3400 cm ² ), and the frequency was 10 kHz.
Under the above conditions, the film formation rate was as high as 66 nm / min, which was suitable for mass production.

Comparative Examples 15-17
Using the six targets having a width of 200 mm, a length of 1700 mm, and a thickness of 10 mm prepared for Comparative Examples 1, 3, and 5, the sputtering conditions were changed to those shown in Table 3 and the same as in Example 81. An oxide semiconductor thin film and a thin film transistor were fabricated and evaluated. The results are shown in Table 3.
As shown in Table 3, it can be seen that Comparative Examples 15 to 17 have a field effect mobility of less than 10 cm ² / Vs, which is significantly lower than that of Examples 81 to 95.

Examples 96-105
Back channel using a PAN (phosphoric acid 91.4 wt%, nitric acid 3.3 wt%, acetic acid 5.3 wt%) etching solution using the sputtering target having the composition shown in Table 4 prepared in Examples 1 to 39 and Mo patterning Table 4 shows the results of TFT characteristics produced under the same conditions as in Examples 40 to 80 except that the etching was performed.
It can be seen that good TFT characteristics can also be obtained by back channel etching.

The sputtering target of the present invention can be used for production of oxide thin films such as oxide semiconductors and transparent conductive films. The oxide thin film of the present invention can be used for a transparent electrode, a semiconductor layer of a thin film transistor, an oxide thin film layer, and the like.

Although several embodiments and / or examples of the present invention have been described in detail above, those skilled in the art will appreciate that these exemplary embodiments and / or embodiments are substantially without departing from the novel teachings and advantages of the present invention. It is easy to make many changes to the embodiment. Accordingly, many of these modifications are within the scope of the present invention.
All the contents of the Japanese application specification that is the basis of the priority of Paris in this application are incorporated herein.

Claims

A bixbite structure composed of an oxide containing at least one element X selected from indium element (In), tin element (Sn), zinc element (Zn), and the following group X, and represented by In 2 O 3 A sputtering target comprising a compound and a spinel structure compound.
X group: Mg, Al, Ga, Si, Sc, Ti, Y, Zr, Hf, Ta, La, Nd, Sm
The sputtering target according to claim 1, wherein an atomic ratio of the indium element, tin element, zinc element and element X satisfies the following formulas (1) to (4).
0.20 ≦ In / (In + Sn + Zn + X) ≦ 0.85 (1)
0.01 ≦ Sn / (In + Sn + Zn + X) ≦ 0.35 (2)
0.01 ≦ Zn / (In + Sn + Zn + X) ≦ 0.70 (3)
0.01 ≦ X / (In + Sn + Zn + X) ≦ 0.30 (4)
(In the formula, In, Sn, Zn, and X each represent an atomic ratio of each element in the sputtering target.)
The spinel structure compound, XIn 2 O 4, ZnX 2 O 4, Zn 2 of XO 4 containing either sputtering target according to claim 1 or 2.
The sputtering target according to any one of claims 1 to 3, wherein the element X is Mg, Al, Ti, Si, or Ga.
The sputtering target according to any one of claims 1 to 3, wherein the element X is Al and the spinel structure compound contains ZnAl 2 O 4 .
The sputtering target according to any one of claims 1 to 5, wherein the spinel structure compound contains Zn 2 SnO 4 .
The sputtering target according to claim 1, wherein the relative density is 98% or more and the bulk specific resistance is 10 mΩcm or less.
An oxide semiconductor thin film formed by sputtering using the sputtering target according to any one of claims 1 to 7.
The oxide semiconductor thin film according to claim 8, wherein the oxide semiconductor thin film is insoluble in a phosphoric acid etching solution and soluble in an oxalic acid etching solution.
10. The oxide semiconductor according to claim 9, wherein an etching rate at 35 ° C. with the phosphoric acid-based etching solution is 10 nm / min or less, and an etching rate at 35 ° C. with the oxalic acid etching solution is 20 nm / min or more. Thin film.
A film is formed by a sputtering method using the sputtering target according to any one of claims 1 to 7 in an atmosphere of a mixed gas containing one or more selected from water vapor, oxygen gas, and nitrous oxide gas and a rare gas. A method for manufacturing an oxide semiconductor thin film.
The method for producing an oxide semiconductor thin film according to claim 11, wherein the oxide semiconductor thin film is formed in an atmosphere of a mixed gas containing at least water vapor and a rare gas.
The method for producing an oxide semiconductor thin film according to claim 11 or 12, wherein a ratio of water vapor contained in the mixed gas is 0.1% to 25% in terms of partial pressure ratio.
14. The method for producing an oxide semiconductor thin film according to claim 11, wherein a ratio of oxygen gas contained in the mixed gas is 0.1% to 30% in terms of partial pressure ratio.
The oxide semiconductor thin film is formed by sequentially transporting the substrate to a position facing three or more targets arranged in parallel in the vacuum chamber at a predetermined interval, and from each AC power source to each target. In the case of alternately applying a negative potential and a positive potential, at least one of the outputs from the AC power supply is switched between two or more targets that are branched and connected while switching the target to which the potential is applied. The method for producing an oxide semiconductor thin film according to any one of claims 11 to 14, wherein the method is performed by a sputtering method in which plasma is generated on a target to form a film on a substrate surface.
The method for manufacturing an oxide semiconductor thin film according to claim 15, wherein the AC power density of the AC power source is 3 W / cm 2 or more and 20 W / cm 2 or less.
The method for producing an oxide semiconductor thin film according to claim 15 or 16, wherein the frequency of the AC power source is 10 kHz to 1 MHz.
A thin film transistor comprising the oxide semiconductor thin film according to any one of claims 8 to 10 as a channel layer.
The thin film transistor according to claim 18, wherein the field effect mobility is 10 cm 2 / Vs or more.
A thin film transistor having a protective film containing at least SiNx (x is an arbitrary number) on the oxide semiconductor thin film according to any one of claims 8 to 10.
A method of manufacturing a thin film transistor using the oxide semiconductor thin film according to any one of claims 8 to 10 as a semiconductor active layer, wherein the semiconductor thin film and the electrode are formed without stacking an etching stopper on the semiconductor thin film. A method of manufacturing a thin film transistor, comprising: a step of patterning with a different etching solution, and the step of contacting the semiconductor thin film directly with the etching solution when patterning the electrode.
A display device comprising the thin film transistor according to any one of claims 18 to 20.