TWI755648B - Sintered oxide body, sputtering target and method for producing oxide thin film - Google Patents

Abstract

A sintered oxide body according to an embodiment of the embodiment of the present invention is an oxide sintered body containing indium, gallium, and zinc at a ratio satisfying the following formulas (1) to (3), the oxide sintered body is composed of a single phase crystal phase, and the average particle diameter of the crystal phase is 15.0 μm or less.

0.01≦In/(In+Ga+Zn)<0.20 .. (1)

0.10≦Ga/(In+Ga+Zn)≦0.49 .. (2)

0.50≦Zn/(In+Ga+Zn)≦0.89 .. (3)

Description

Oxide sintered body, sputtering target, and method for producing oxide thin film

Embodiments of the present invention relate to an oxide sintered body, a sputtering target, and a method for producing an oxide thin film.

The sputtering method, which is a thin film formation method using a sputtering target, is extremely effective as a method of forming a thin film with a large area and high precision, and the sputtering method is widely used in display devices such as liquid crystal display devices. In recent years, in the technical field of semiconductor layers such as thin film transistors (hereinafter also referred to as "TFT"), oxides represented by In-Ga-Zn composite oxide (hereinafter also referred to as "IGZO") have replaced amorphous silicon. Material semiconductors are attracting attention, and sputtering is also used in the formation of IGZO thin films (for example, see Patent Document 1).

In the above-described sputtering method, there are cases in which problems such as abnormality in the quality of the formed thin film or cracking of the sputtering target occur during sputtering due to occurrence of abnormal discharge or the like. As one of the methods to avoid these problems, there is a method of increasing the density of the sputtering target.

Furthermore, high-density targets may also generate abnormal discharges. For example, when the crystal phase constituting the target is a composite phase, and there is a difference in resistance between different crystal phases, there is a risk of abnormal discharge.

When an IGZO thin film is used in the semiconductor layer of a TFT, its semiconductor properties are greatly changed by the ratio of In, Ga, and Zn, and various ratios are being examined. For example, Patent Document 2 examines that the ratio of each metal element is the ratio of In<Ga<Zn. The ratio of In, Ga, and Zn of the IGZO sputtering target can be appropriately adjusted to obtain specific semiconductor properties. For example, with regard to IGZO sputtering targets, targets showing homologous crystal structures represented by InGaZnO ₄ or In ₂ Ga ₂ ZnO ₇ are under review.

On the other hand, with regard to the IGZO sputtering target containing a large amount of Zn, a target composed of a composite phase of a homologous crystal structure and a spinel structure of Ga ₂ ZnO ₄ has also been examined (for example, refer to Patent Document 3).

However, Ga ₂ ZnO ₄ has a higher risk of abnormal discharge due to its higher resistance compared with the case of homologous crystal structure. Therefore, the sputtering target is preferably a single phase with a homologous crystal structure.

On the other hand, a high-density sputtering target composed of a single phase tends to have a larger grain size than a sputtering target composed of a composite phase. Furthermore, when the crystal grain size is enlarged, the mechanical strength of the sputtering target is lowered, and cracks may occur during sputtering.

Furthermore, it is also important that the distribution of the above-mentioned characteristics of the sputtering target in the sputtering surface is uniform. If the distribution of density, etc. in the plane is not uniform, abnormal discharge or cracking during sputtering may occur. In the case of IGZO sputtering target, the unevenness of the characteristic distribution of the sputtering surface may appear in the form of chromatic aberration.

[Prior Art Literature] [Patent Literature]

Patent Document 1: Japanese Patent Laid-Open No. 2007-73312

Patent Document 2: Japanese Patent Laid-Open No. 2017-145510

Patent Document 3: Japanese Patent Laid-Open No. 2008-163441

One aspect of the embodiment of the present invention is made in view of the above-mentioned circumstances, and aims to provide a sputtering target capable of stably sputtering, and an oxide sintered body for producing the sputtering target.

One aspect of the embodiment of the present invention is an oxide sintered body, which contains indium, gallium and zinc in ratios satisfying the following formulae (1) to (3), the oxide sintered system is composed of a single-phase crystal phase, and The average particle diameter of the crystal phase is 15.0 μm or less.

0.01≦In/(In+Ga+Zn)<0.20‧‧(1)

0.10≦Ga/(In+Ga+Zn)≦0.49‧‧(2)

0.50≦Zn/(In+Ga+Zn)≦0.89‧‧(3)

According to one aspect of the embodiment of the present invention, sputtering can be performed stably.

Figure 1 is an SEM image (50x) of the oxide sintered body in Example 1.

FIG. 2 is an SEM image (500 times) of the oxide sintered body in Example 1. FIG.

Fig. 3 is an SEM image (500 times) of the oxide sintered body in Comparative Example 2.

FIG. 4 is an X-ray diffraction diagram of the oxide sintered body in Example 1. FIG.

Fig. 5 compares the X-ray diffraction pattern of the oxide sintered body in Example 1 and the peak positions in the X-ray diffraction patterns of InGaZnO ₄ , In ₂ Ga ₂ ZnO ₇ and Ga ₂ ZnO ₄ picture.

Hereinafter, embodiments of the oxide sintered body, the sputtering target, and the method for producing the oxide thin film disclosed in the present invention will be described with reference to the accompanying drawings. In addition, the present invention is not limited to the embodiments shown below.

The oxide sintering system of the embodiment contains an oxide sintered body of indium (In), gallium (Ga), and zinc (Zn), which can be used as a sputtering target.

The oxide sintering system of the embodiment is composed of a single-phase crystal phase, and the average particle size of the crystal phase is 15.0 μm or less. Thereby, the flexural strength of the oxide sintered body can be improved. Furthermore, when the above-mentioned oxide sintered body is subjected to polishing processing, the surface roughening can be suppressed by peeling off the enlarged particles on the surface, so that a smooth surface can be easily obtained.

Further, the oxide sintered body of the embodiment preferably has an average particle size of 10.0 μm or less, more preferably 8.0 μm or less, still more preferably 6.0 μm or less, and still more preferably 5.0 μm or less. In addition, the lower limit value of the average particle diameter is not particularly limited, but is usually 1.0 μm or more.

Furthermore, the oxide sintering system is composed of a single-phase crystal phase, so that the elements in the oxide sintered body can be uniformly distributed. Therefore, according to the embodiment, each element in the oxide semiconductor thin film formed by sputtering can be uniformly distributed.

Furthermore, in the oxide sintered body of the embodiment, the atomic ratio of each element satisfies the following formulae (1) to (3).

0.01≦In/(In+Ga+Zn)<0.20‧‧(1)

0.10≦Ga/(In+Ga+Zn)≦0.49‧‧(2)

0.50≦Zn/(In+Ga+Zn)≦0.89‧‧(3)

Thereby, a semiconductor layer suitable for use in a TFT can be obtained.

In addition, the atomic ratio of each element of the oxide sintering system of the embodiment preferably satisfies the following formulae (4) to (6),

0.05≦In/(In+Ga+Zn)≦0.15‧‧(4)

0.15≦Ga/(In+Ga+Zn)≦0.45‧‧(5)

0.50≦Zn/(In+Ga+Zn)≦0.80‧‧(6)

More preferably, the atomic ratio of each element satisfies the following formulae (7) to (9).

0.05≦In/(In+Ga+Zn)≦0.15‧‧(7)

0.20≦Ga/(In+Ga+Zn)≦0.40‧‧(8)

0.50≦Zn/(In+Ga+Zn)≦0.70‧‧(9)

Furthermore, the oxide sintered body of the embodiment may contain unavoidable impurities derived from raw materials and the like. The unavoidable impurities in the oxide sintered body of the embodiment include Fe, Cr, Ni, Si, W, Cu, and Al, and the content of these is usually 100 ppm or less.

In addition, the single-phase crystal phase constituting the oxide sintered body of the embodiment preferably has diffraction peaks observed in the following A to P regions in the graph obtained by X-ray diffraction measurement (CuKα ray).

A. 24.5° to 26.0°

B.31.0° to 32.5°

C. 32.5° to 33.2°

D.33.2° to 34.0°

E.34.5° to 35.7°

F.35.7° to 37.0°

G.38.0° to 39.2°

H.39.2° to 40.5°

I. 43.0° to 45.0°

J.46.5° to 48.5°

K.55.5° to 57.8°

L.57.8° to 59.5°

M.59.5° to 61.5°

N.65.5° to 68.0°

O.68.0° to 69.0°

P.69.0° to 70.0°

Thereby, when the oxide sintered body is used for a sputtering target, the occurrence of abnormal discharge can be suppressed. Therefore, according to the embodiment, the generation of particles due to the abnormal discharge described above can be suppressed, so that the production yield of the TFT can be improved.

Furthermore, the oxide sintered body of the embodiment preferably has a relative density of 97.0% or more. Thereby, when the above-mentioned oxide sintered body is used as a sputtering target, the discharge state of DC sputtering can be stabilized. In addition, in the oxide sintered body of the embodiment, a relative density of 98.0% or more is more preferable, and a relative density of 99.0% or more is more preferable.

When an oxide sintered body with a relative density of 97.0% or more is used as a sputtering target, the voids in the sputtering target can be reduced, and the infiltration of gas components in the atmosphere can be easily prevented. Furthermore, in sputtering, defects such as abnormal discharge due to the above-mentioned voids and cracking of the sputtering target are less likely to occur.

Furthermore, the flexural strength of the oxide sintered body of the embodiment is preferably 40 MPa or more. Thereby, when a sputtering target is produced using the above-mentioned oxide sintered body, or when the above-mentioned sputtering target is sputtered, the breakage of the oxide sintered body can be suppressed.

Further, the flexural strength of the oxide sintered body of the embodiment is preferably 50 MPa or more, more preferably 60 MPa or more, and still more preferably 70 MPa or more. In addition, the upper limit of the flexural strength is not particularly limited, but is usually 300 MPa or less.

In addition, it is preferable that the maximum height Ry of the surface roughness of the oxide sintered body used for the sputtering target of embodiment is 15.0 micrometers or less. Thereby, when sputtering is performed using the sputtering target described above, it is possible to suppress the generation of nodules on the surface of the target.

In addition, the oxide sintered body used for the sputtering target of the embodiment preferably has a maximum height Ry of 11.0 μm or less, and more preferably 10.0 μm or less. In addition, the lower limit of the maximum height Ry is not particularly limited, but is usually 0.1 µm or more.

Furthermore, the oxide sintered body of the embodiment preferably has a specific resistance of 40 mΩ·cm or less. Thereby, when the above-mentioned oxide sintered body is used as a sputtering target, sputtering can be performed using an inexpensive DC power supply, and the film formation rate can be improved. Furthermore, the occurrence of abnormal discharge can be suppressed by this.

Further, the oxide sintered body of the embodiment preferably has a specific resistance of 35 mΩ·cm or less, and more preferably has a specific resistance of 30 mΩ·cm or less. In addition, the lower limit of the specific resistance is not particularly limited, but is usually 0.1 mΩ·cm or more.

Furthermore, in the sputtering target of the embodiment, the color difference ΔE* on the surface of the sputtering target is preferably 10 or less. Furthermore, the color difference ΔE* in the depth direction of the sputtering target is also preferably 10 or less. When this numerical value satisfies the above-mentioned conditions, it is suitable as a sputtering target because of the unbiased crystal grain size and composition.

Further, in the sputtering target of the embodiment, the color difference ΔE* of the entire surface and the depth direction is more preferably 9 or less, and the color difference ΔE* is more preferably 8 or less.

<Each production step of oxide sputtering target>

The oxide sputtering target of the embodiment can be produced, for example, by the method shown below. First, the raw material powders are mixed. The raw material powders are usually In ₂ O ₃ powder, Ga ₂ O ₃ powder and ZnO powder.

The mixing ratio of each raw material powder is appropriately determined so that the desired constituent element ratio in the oxide sintered body is obtained.

Each raw material powder is preferably dry-mixed beforehand. The dry mixing method described above is not particularly limited, and mixing can be performed using various mixers such as a container-rotating type mixer and a container-fixing type mixer. Among them, since shearing force and impact force can be applied to the raw material powder, high-speed dispersion and mixing can be performed, and mixing by, for example, a high-speed mixer manufactured by EARTHTECHNICA Co., Ltd. is preferable. By performing the dry mixing treatment in advance in this way, the raw material powders are uniformly dispersed and mixed, and it is easy to obtain a sintered body of a single-phase structure, and it is preferable that the color difference is within the aforementioned range.

As a method of producing a molded body from the mixed powder thus mixed, for example, a slip casting method, a CIP (Cold Isostatic Pressing: cold isostatic pressing method), etc. are mentioned. Next, as a specific example of the molding method, two methods will be described, respectively.

(grouting method)

The slip casting method described here is formed by preparing a slurry containing mixed powder and organic additives using a dispersion medium, injecting the slurry into a mold, and removing the dispersion medium. The organic additives that can be used here are known adhesives, dispersants, and the like.

In addition, the dispersion medium used when preparing a slurry is not specifically limited, According to the objective, it can select suitably from water, alcohol, etc.. Furthermore, the method for preparing the slurry is not particularly limited, and for example, it can be mixed with a ball mill in which the mixed powder, organic additives, and dispersion medium are fed into a pot and mixed. The slurry thus obtained is poured into a mold, the dispersion medium is removed, and a molded body is produced. The molds that can be used here are metal molds, plaster molds, resin molds that pressurize and remove the dispersion medium, and the like.

(CIP law)

In the CIP method described here, a slurry containing mixed powder and organic additives is prepared using a dispersion medium, the slurry is spray-dried, and the resulting dried powder is filled in a mold and press-molded . The organic additives that can be used here are known adhesives, dispersants, and the like.

In addition, the dispersion medium used when preparing a slurry is not specifically limited, According to the objective, it can select suitably from water, alcohol, etc.. In addition, the method for preparing the slurry is not particularly limited, and for example, the mixed powder, the organic additive, and the dispersion medium can be put into a tank and mixed with a ball mill for mixing.

The slurry thus obtained is spray-dried to prepare a dry powder with a moisture content of 1% or less, and the dry powder is filled in a mold and press-molded by the CIP method to prepare a molded body.

Next, the obtained molded body is fired to produce a sintered body. The firing furnace for producing the sintered body is not particularly limited, and a firing furnace that can be used to produce a ceramic sintered body can be used.

The firing temperature is 1350°C to 1580°C, preferably 1400°C to 1550°C, more preferably 1450°C to 1550°C. The higher the firing temperature, the more dense a sintered body can be obtained. On the other hand, from the viewpoint of suppressing enlargement of the structure of the sintered body and preventing cracking, it is preferably controlled at or below the above temperature. Furthermore, when the firing temperature is less than 1350° C., it is not preferable because it is difficult to form a single-phase crystal phase.

Next, the obtained sintered body is subjected to cutting processing. The above-mentioned cutting processing is performed using a flat grinding disc or the like. Furthermore, the maximum height Ry of the surface roughness after cutting can be appropriately controlled by selecting the grinding particle size of the whetstone used for cutting, but if the particle size of the sintered body becomes enlarged, it will be caused by the enlarged particle size. The maximum height Ry increases due to the peeling of the particles.

A sputtering target is produced by bonding the machined sintered body to a base material. The material of the substrate can be appropriately selected from stainless steel, copper, titanium and the like. As the bonding material, low melting point solder such as indium can be used.

[Example]

[Example 1]

The In ₂ O ₃ powder with an average particle size of 0.6 μm, the Ga ₂ O ₃ powder with an average particle size of 1.5 μm, and the ZnO powder with an average particle size of 0.8 μm were dry mixed with a high-speed mixer manufactured by EARTHTECHNICA Co., Ltd. Prepare mixed powder.

In addition, the average particle diameter of the raw material powder was measured using the particle size distribution measuring apparatus HRA made by Nikkiso Co., Ltd. In the above-mentioned measurement, water was used as a solvent, and the refractive index of the measurement substance was set to 2.20, and the measurement was performed. In addition, the same measurement conditions were set also about the average particle diameter of the raw material powder described below. In addition, the average particle diameter of the raw material powder is the volume cumulative particle diameter D50 of 50% by volume of the cumulative volume by the laser diffraction scattering particle size distribution measurement method.

In addition, when preparing the mixed powder described above, the atomic ratios of the metal elements contained in all the raw material powders are In/(In+Ga+Zn)=0.1, Ga/(In+Ga+Zn)=0.3, Zn/ Each raw material powder was prepared so that (In+Ga+Zn)=0.6.

Next, in the tank in which the mixed powder was prepared, 0.2 mass % of the adhesive with respect to the mixed powder, 0.6 mass % of the dispersant with respect to the mixed powder, and 20 mass % of water with respect to the mixed powder were added, and ball mill mixing was performed. And prepare the slurry.

Next, the prepared slurry was poured into a metal mold with a filter sandwiched therebetween, and drained to obtain a molded body. Next, this compact is fired to produce a sintered body. The above-mentioned firing was performed at a firing temperature of 1500°C, a firing time of 10 hours, a heating rate of 100°C/hour, and a temperature drop rate of 100°C/hour.

Next, the obtained sintered body was machined, and the sputtering target of width 210mm x length 710mm x thickness 6mm was obtained. In addition, a #170 whetstone was used in the above-mentioned cutting process.

[Examples 2 to 3]

Using the same method as Example 1, a sputtering target was obtained. In addition, in Examples 2 to 3, when preparing the mixed powder, each raw material powder was prepared so that the atomic ratio of the metal element contained in all the raw material powders would be the atomic ratio described in Table 1.

[Comparative Examples 1 to 3]

In Comparative Examples 1 to 3, when the mixed powder was prepared, the atomic ratios of the metal elements contained in all the raw material powders were In/(In+Ga+Zn)=0.1, Ga/(In+Ga+Zn) )=0.3 and Zn/(In+Ga+Zn)=0.6 to prepare each raw material powder. In addition, the baking temperature was performed so that it might become the temperature described in Table 1, and in the comparative example 2, dry mixing was not performed. Except for this, the same method as in Example 1 was used to obtain a sputtering target.

In addition, in Examples 1 to 3 and Comparative Examples 1 to 3, it was confirmed that the atomic ratio of each metal element measured when preparing each raw material powder was equivalent to the atomic ratio of each metal element in the obtained oxide sintered body. The atomic ratio of each metal element in the oxide sintered body is measured by, for example, ICP-AES (Inductively Coupled Plasma Atomic Emission Spectroscopy: Inductively Coupled Plasma Atomic Emission Spectroscopy).

Next, with respect to the sputtering targets of Examples 1 to 3 and Comparative Examples 1 to 3 obtained above, the relative density was measured. Said relative density is determined based on the Archimedes Method.

Specifically, the air mass of the sputtering target is divided by the volume (the mass of the water in the sintered body/the specific gravity of the water in the measurement temperature), and the percentage value relative to the theoretical density ρ (g/cm ³ ) is calculated. as relative density (unit: %).

In addition, the above-mentioned theoretical density ρ (g/cm ³ ) is calculated from the mass % and the density of the raw material powder used for the production of the oxide sintered body. Specifically, it is calculated by the following formula (10).

ρ={(C ₁ /100)/ρ ₁ +(C ₂ /100)/ρ ₂ +(C ₃ /100)/ρ ₃ } ^-1 ‧‧(10)

In addition, C ₁ to C ₃ and ρ ₁ to ρ ₃ in the above formula show the following values, respectively.

‧C ₁ : Mass % of In ₂ O ₃ powder used in the production of oxide sintered body

‧ρ ₁ : Density of In ₂ O ₃ (7.18g/cm ³ )

‧C ₂ : Mass % of Ga ₂ O ₃ powder used in the production of oxide sintered body

ρ ₂ : Density of Ga ₂ O ₃ (5.95g/cm ³ )

‧C ₃ : Mass % of the ZnO powder used in the production of the oxide sintered body

‧ρ ₃ : Density of ZnO (5.60g/cm ³ )

Next, with respect to the sputtering targets of Examples 1 to 3 and Comparative Examples 1 to 3 obtained above, specific resistance (volume resistance) was measured, respectively.

Specifically, Loresta (registered trademark) HP MCP-T410 (in-line 4-probe probe TYPE ESP) manufactured by Mitsubishi Chemical Co., Ltd. was used, and the probe was abutted on the surface of the processed oxide sintered body, and the AUTO RANGE mode determination. The measurement locations were 5 locations in total near the center and the four corners of the oxide sintered body, and the average value of each measured value was taken as the bulk resistance value of the sintered body.

Next, the flexural strength was measured for each of the sputtering targets of Examples 1 to 3 and Comparative Examples 1 to 3 obtained above. The flexural strength mentioned above is obtained by using a test piece (overall length 36mm, width 4.0mm, thickness 3.0mm) cut out from the oxide sintered body by wire-cut electrical discharge machining, and according to JIS-R-1601 (Precision Ceramics Flexural strength test method) The 3-point flexural strength measurement method was measured.

Here, for the above-mentioned Examples 1 to 3 and Comparative Examples 1 to 3, the atomic ratio of each element contained in the powder mixing, the presence or absence of dry mixing in the production of the oxide sintered body, the firing temperature, and the oxide sintered body The measurement results of relative density, specific resistance (volume resistance) and flexural strength are shown in Table 1.

[Table 1]

It is known that the relative densities of the oxide sintered bodies of Examples 1 to 3 are all 97.0% or more. Therefore, according to the embodiment, when the above-mentioned oxide sintered body is used as a sputtering target, the discharge state of DC sputtering can be stabilized.

Furthermore, it is known that the specific resistances of the oxide sintered bodies of Examples 1 to 3 are all 40 mΩcm or less. Therefore, according to the embodiment, when the above-described oxide sintered body is used as a sputtering target, sputtering can be performed using an inexpensive DC power source, and the film formation rate can be improved.

Furthermore, it is known that the flexural strengths of the oxide sintered bodies of Examples 1 to 3 are all 40 MPa or more. Therefore, according to the embodiment, when a sputtering target is produced using the above-mentioned oxide sintered body, or when sputtering is performed using the above-mentioned sputtering target, the breakage of the oxide sintered body can be suppressed.

Next, the surfaces of the sputtering targets of Examples 1 to 3 and Comparative Examples 1 to 3 obtained above were observed using a scanning electron microscope (SEM: Scanning Electron Microscope), and the average particle size of the crystals was measured.

Specifically, the oxide sintered body is cut, and the obtained cut surface is polished in steps with emery paper #180, #400, #800, #1000, #2000, and finally polished and finished. for mirror.

After that, the etching solution at 40°C [combines nitric acid (60 to 61% aqueous solution, manufactured by Kanto Chemical Co., Ltd.), hydrochloric acid (35.0 to 37.0% aqueous solution, manufactured by Kanto Chemical Co., Ltd.) and pure water in a volume ratio of HCl:H ₂ O: _HNO3 =1:1:0.08 ratio mixing] immersion for 2 minutes to perform etching.

Then, the surface to be presented was observed using a scanning electron microscope (SU3500, manufactured by Hitachi High-Technologies Co., Ltd.). In addition, in the measurement of the average particle size, BSE-COMP images in the range of 175 μm×250 μm in ten fields of view were randomly photographed at a magnification of 500 times, and SEM images of the tissue were obtained.

Furthermore, the particle analysis was performed using ImageJ 1.51k (http://imageJ.nih.gov/ij/), an image processing software provided by the National Institutes of Health (NIH).

First, draw along the grain boundary, and after all the drawings are completed, perform image correction (Image→Adjust→Threshold), and after image correction, remove residual noise (Process→Noise→Despecle) as necessary.

After that, particle analysis (Analyze→Analyze Particles) is performed to obtain the area of each particle, and then the diameter of the circle of equal area is calculated. The average diameter of the circles of equal area of all particles calculated in ten fields of view is taken as the average particle diameter of the present invention.

FIG. 1 and FIG. 2 are SEM images of the oxide sintered body in Example 1. FIG. In addition, in FIG. 1 and FIG. 2, the part seen to be black is a part missing by surface grinding|polishing. As shown in FIGS. 1 and 2, it can be seen that the oxide sintering system of Example 1 is constituted by a single-phase crystal phase.

Fig. 3 is an SEM image of the oxide sintered body in Comparative Example 2. In addition, in Fig. 3, the portion seen as black is a phase with little indium (In poor phase). As shown in FIG. 3, it can be seen that the oxide sintering system of Comparative Example 2 is composed of a composite phase crystal phase.

Next, with respect to the oxide sintered bodies of Examples 1 to 3 and Comparative Examples 1 to 3 obtained above, X-ray diffraction (X-Ray Diffraction: XRD) measurements were performed, respectively, and X-ray diffraction patterns were obtained.

In addition, the specific measurement conditions of the said X-ray diffraction measurement are as follows.

‧Device: SmartLab (Rigaku Co., Ltd., registered trademark)

‧Line source: CuKα rays

‧Tube voltage: 40kV

‧Tube current: 30mA

‧Scanning speed: 5deg/min

‧Step: 0.02deg

‧Scanning range: 2θ=20 degrees to 70 degrees

FIG. 4 is an X-ray diffraction diagram of the oxide sintered body in Example 1. FIG. As shown in Fig. 4, in the X-ray diffraction diagram of Example 1, diffraction peaks were observed in the following regions A to P in the range of the diffraction angle 2? of 20 to 70 degrees.

A. 24.5° to 26.0°

B.31.0° to 32.5°

C. 32.5° to 33.2°

D.33.2° to 34.0°

E.34.5° to 35.7°

F.35.7° to 37.0°

G.38.0° to 39.2°

H.39.2° to 40.5°

I. 43.0° to 45.0°

J.46.5° to 48.5°

K.55.5° to 57.8°

L.57.8° to 59.5°

M.59.5° to 61.5°

N.65.5° to 68.0°

O.68.0° to 69.0°

P.69.0° to 70.0°

As described above, the oxide sintering system of Example 1 is composed of a single-phase crystal phase, so it can be seen that the diffraction peaks observed in the above-mentioned regions A to P are caused by the single-phase crystal phase. In other words, the single-phase crystal phase constituting the oxide sintered body of Example 1 can be identified from the graph obtained by the X-ray diffraction measurement.

FIG. 5 is a diagram comparing the peak positions of the X-ray diffraction patterns of the oxide sintered body of Example 1 and the X-ray diffraction patterns of InGaZnO ₄ , In ₂ Ga ₂ ZnO ₇ and Ga ₂ ZnO ₄ .

As shown in FIG. 5, it is understood that the single-phase crystal phase constituting the oxide sintered body of Example 1 can be different from the known crystal phases (here, InGaZnO ₄ , In ₂ Ga ₂ ZnO ₇ and Ga ₂ ZnO ₄ ). Diffraction peaks were observed at the peak positions. Here, the "known crystal phase" means "the crystal phase whose peak position in the X-ray diffraction pattern is registered on the JCPDS (Joint Committee of Powder Diffraction Standards) card".

That is, it was found that the single-phase crystal phase constituting the oxide sintered body of Example 1 is a previously unknown crystal phase.

Next, with respect to the sputtering targets of Examples 1 to 3 and Comparative Examples 1 to 3 obtained above, the maximum height Ry of the surface roughness was measured, respectively. Specifically, the maximum height Ry of the sputtered surface was measured using a surface roughness measuring device (SJ-210/manufactured by Mitutoyo Co., Ltd.). Ten positions on the sputtering surface were measured, and the largest value among them was set as the maximum height Ry of the sputtering target. The measurement results are shown in Table 2.

Next, on the sputtering targets of Examples 1 to 3 and Comparative Examples 1 to 3 obtained above, the color difference ΔE* in the surface and the color difference ΔE* in the depth direction were measured, respectively. In addition, the so-called "color difference ΔE*" is an index obtained by quantifying the difference between two colors.

The maximum color difference ΔE* in the surface is measured on the surface of the machined sputtering target at intervals of 50 mm in the x-axis and y-axis directions using a color difference meter (manufactured by Konica Minolta Co., Ltd., color difference meter CP-300). , the L value, a value and b value of each point measured were evaluated in the CIE1976 space. Then, from the difference ΔL, Δa, and Δb of the L value, the a value, and the b value at two points among the measured points, the color difference ΔE* of the combination of all the two points is obtained by the following formula (11). The maximum value of the obtained multiple color differences ΔE* is set as the maximum color difference ΔE* within the surface.

ΔE*=((ΔL) ² +(Δa) ² +(Δb) ² ) ^1/2 ‧‧(11)

In addition, the maximum color difference ΔE* in the depth direction was cut by 0.5 mm at any part of the sputtering target that was machined, and each depth to the center of the sputtering target was measured using a color difference meter. The L-value, a-value and b-value of the point were evaluated in the CIE1976 space. Then, from the difference ΔL, Δa, and Δb of the L value, the a value, and the b value at two points among the measured points, the color difference ΔE* of the combination of all two points is obtained, and the maximum of the obtained plural color differences ΔE* is obtained. The value is set as the maximum color difference ΔE* in the depth direction.

Here, in order to evaluate the target from the amount of arc (abnormal discharge) generated, the sputtering targets obtained in Examples 1 to 3 and Comparative Examples 1 to 3 were bonded to copper using indium, which is a low melting point solder, as a bonding material. substrate.

Next, sputtering was performed using the sputtering targets of Examples 1 to 3 and Comparative Examples 1 to 3, and the targets were evaluated from the amount of arc (abnormal discharge) generated. The evaluation results are shown in Table 2.

(Arc Evaluation)

A: Very few.

B: Many.

C: Very much.

Here, for the above-mentioned Examples 1 to 3 and Comparative Examples 1 to 3, the atomic ratio of each element contained in the mixed powder, the crystal phase, the average particle size, and the surface roughness of the oxide sintered body used in the sputtering target were compared. Table 2 shows the measurement results of the maximum height Ry in degrees, the maximum color difference ΔE* in the in-plane direction, the maximum color difference ΔE* in the depth direction, and arc evaluation.

[Table 2]

It is known that the crystal phases of the oxide sintered bodies of Examples 1 to 3 are all composed of a single phase. Therefore, according to the embodiment, when the above-mentioned oxide sintered body is used for a sputtering target, as can be seen from the results of the arc evaluation, the sputtering can be performed stably.

In addition, it is known that the average particle size of the oxide sintered bodies of Examples 1 to 3 is 15.0 μm or less. Therefore, according to the embodiment, when the above-mentioned oxide sintered body is polished, the surface roughening can be suppressed by peeling off large crystal grains from the surface.

Furthermore, it is known that the maximum height Ry of the surface roughness of the oxide sintered bodies of the sputtering targets of Examples 1 to 3 is all 15.0 μm or less. Therefore, according to the embodiment, it is possible to suppress the generation of protrusions on the target surface during sputtering.

It is known that the sputtering targets of Examples 1 to 3 have a maximum color difference ΔE* of 10 or less in the in-plane direction and the depth direction. Therefore, according to the embodiment, since the crystal grain size and the composition are unbiased, it is suitable as a sputtering target.

The embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention. For example, the embodiment shows an example in which a plate-shaped oxide sintered body is used as a sputtering target, but the shape of the oxide sintered body is not limited to a plate shape, and may be any shape such as a cylindrical shape.

Further effects and modifications can be easily derived by those skilled in the art. Accordingly, the broader aspects of the present invention are not limited to the specific details and representative embodiments described and described above. Accordingly, various modifications are possible without departing from the spirit or scope of the broad inventive concept as defined by the appended claims and their equivalents.

Claims (11)

An oxide sintered body containing indium, gallium, and zinc in ratios satisfying the following formulae (1) to (3), the oxide sintered system being constituted by a single-phase crystal phase, and the crystal phase being formed by X-ray diffraction In the graph obtained by radiation measurement (CuKα ray), diffraction peaks are observed in the following regions from A to P; 0.01≦In/(In+Ga+Zn)<0.20‧‧(1) 0.10≦Ga/(In+ Ga+Zn)≦0.49‧‧(2) 0.50≦Zn/(In+Ga+Zn)≦0.89‧‧(3); A. 24.5° to 26.0° B. 31.0° to 32.5° C. 32.5° to 33.2 ° D. 33.2° to 34.0° E. 34.5° to 35.7° F. 35.7° to 37.0° G. 38.0° to 39.2° H. 39.2° to 40.5° I. 43.0° to 45.0° J. 46.5° to 48.5° K.55.5° to 57.8° L.57.8° to 59.5° M.59.5° to 61.5° N.65.5° to 68.0° O.68.0° to 69.0° P.69.0° to 70.0°. The oxide sintered body according to claim 1 of the claimed scope contains indium, gallium and zinc in ratios satisfying the following formulae (4) to (6); 0.05≦In/(In+Ga+Zn)≦0.15 ‧‧(4) 0.15≦Ga/(In+Ga+Zn)≦0.45‧‧(5) 0.50≦Zn/(In+Ga+Zn)≦0.80‧‧(6). The oxide sintered body as described in claim 1 or 2 of the claimed scope contains indium, gallium and zinc in ratios satisfying the following formulae (7) to (9); 0.05≦In/(In+Ga+Zn) ≦0.15‧‧(7) 0.20≦Ga/(In+Ga+Zn)≦0.40‧‧(8) 0.50≦Zn/(In+Ga+Zn)≦0.70‧‧(9). The oxide sintered body according to claim 1, wherein the average particle size of the crystal phase is 15.0 μm or less. The oxide sintered body according to claim 1 or 2, wherein the relative density is 97.0% or more. The oxide sintered body according to claim 1 or 2, wherein the flexural strength is 40 MPa or more. The oxide sintered body according to claim 1 or 2, wherein the specific resistance is 40 mΩcm or less. A sputtering target comprising the oxide sintered body described in claim 1 or claim 2. The sputtering target according to claim 8, wherein the maximum height Ry of the surface roughness is 15.0 μm or less. The sputtering target described in claim 8, wherein the color difference ΔE* 10 or less. A method for producing an oxide thin film, comprising sputtering the sputtering target described in item 8 of the patent application scope and forming a film.

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