JP6800405B2 - Oxide sintered body, its manufacturing method and sputtering target - Google Patents

Description

The present invention relates to an oxide sintered body containing zinc, niobium, indium and oxygen as constituent elements, and a sputtering target containing the sintered body.

In recent years, a high refractive index film has been adopted for adjusting the refractive index in portable displays and building material glass.

Niobium oxide, which is generally used as a high-refractive index material, cannot obtain the conductivity of a target capable of DC discharge by the normal pressure sintering method. Therefore, the conductivity of the sintered body is enhanced by reducing the sintered body under high temperature and pressure conditions (see, for example, Patent Document 1). It has also been reported that the resistivity is lowered by adding zinc to niobium oxide (see, for example, Patent Document 2).

However, since both methods must be manufactured by the hot press method, a huge press mechanism is required to manufacture a large target, which is not a realistic process and the target size is limited to small products. There is. Further, since the hot press method is sintering in a reducing atmosphere, the amount of oxygen deficiency in the target tends to increase. In a target having a large amount of oxygen deficiency, it is necessary to introduce a larger amount of oxygen as a sputtering gas during sputtering in order to obtain high permeability, and there is also a problem that the film formation rate is lowered by the introduction of oxygen.

Further, as a high refractive index material, a composite oxide sintered body made of zinc, aluminum and titanium has also been reported (see, for example, Patent Document 3). By sputtering using such a zinc oxide-based target containing titanium, the obtained thin film has a high refractive index of 2.0 or more, and stable DC discharge performance with less arcing even in the manufacturing process can be achieved. It is supposed to show. However, since titanium has an extremely low film formation rate of less than half that of niobium, which is the same high-refractive index material, there is a problem that the productivity is low when a target containing titanium is used for sputtering.

On the other hand, thin films and sputtering targets in which niobide oxide is added to indium oxide, tin oxide, and zinc oxide (see, for example, Patent Document 4), or thin films and sputtering targets in which niobium oxide is added to indium oxide and zinc oxide have been reported. (See, for example, Patent Document 5). However, in each target, the application of the obtained thin film is a transparent conductive film, not a thin film for adjusting the refractive index. Further, since the addition was made for the purpose of solid solution, the amount of niobium added was small, and the optical characteristics were insufficient for a high refractive index film.

Further, in recent years, the adoption of a cylindrical target capable of applying a high power load has been progressing, and film formation with a high power input, which has not been assumed in the past, is becoming mainstream. Further, the sintered body obtained by mixing niobide oxide of a high refractive index material or titanium oxide and zinc oxide as described above is a composite oxide of a conductive phase mainly composed of zinc oxide and a high refractive index material and zinc oxide. DC discharge is possible with a mixed system of insulating phases, but since the conductive phase and insulating phase coexist, the sputter current concentrates on zinc oxide in the conductive phase, zinc oxide is reduced, and metallic zinc with a low melting point splashes, targeting. There was a problem that holes were formed on the surface and particles were formed.

Japanese Unexamined Patent Publication No. 2005-256175 Japanese Unexamined Patent Publication No. 2005-317093 JP-A-2009-298649 Japanese Unexamined Patent Publication No. 11-322413 Japanese Unexamined Patent Publication No. 2013-09565

An object of the present invention is to provide an oxide sintered body used for a sputtering target capable of obtaining a film having a high film formation rate and a high refractive index without splashing from the target surface even during high power film formation. Is to provide.

The present inventors have diligently studied a composite oxide sintered body prepared from ZnO and Nb ₂ O ₅ . Of the crystal phases of the composite oxide sintered body, the ZnO phase exhibits conductivity due to oxygen deficiency or solid solution substitution of a small amount of niobium, but Nb ₂ O ₅ reacts with a part of ZnO and has extremely low conductivity. ₃ Nb ₂ O ₈ phase (single phase bulk resistance: 10 ¹¹ Ω · cm or more) is formed. The present inventors have obtained sintering obtained by adding an appropriate amount of In ₂ O _3, which has a smaller reaction energy with Nb ₂ O ₅ than Zn O, and suppressing the generation of high-resistance Zn ₃ Nb ₂ O ₈ phase. By using the body as a sputtering target, the splash from the target surface during sputtering was suppressed, and excellent discharge characteristics were realized.

That is, the present invention exists in the following (1) to (9).
(1) In an oxide sintered body having zinc, niobium, indium and oxygen as constituent elements, when the contents of zinc, niobium and indium are Zn, Nb and In, respectively,
An oxide sintered body in which Nb / (Zn + Nb + In) = 0.100 or more and 0.330 or less In / Nb = 0.2 or more and 2.0 or less.
(2) The oxide sintered body according to (1) above, which has a crystal phase of InNbO ₄ .
(3) Metal elements other than Zn, Nb, and In, or oxides thereof are contained as unavoidable impurities, and the total content of these impurities in the sintered body is converted into metal elements, and Zn, Nb, and In The oxide sintered body according to (1) or (2) above, which is 0.01 or less with respect to the total of.
(4) The oxide sintered body according to any one of (1) to (3) above, wherein the ratio of the bulk density to the weighted average value of the true density of each metal element in terms of oxide is 0.99 or more.
(5) The oxide sintered body according to any one of (1) to (4) above, wherein the average particle size is 3 μm or less.
(6) The oxide sintered body according to any one of (1) to (5) above, wherein the bulk resistance value is 100 Ω · cm or less.
(7) A sputtering target using the oxide sintered body according to any one of (1) to (6) above as a target material.
(8) When zinc oxide powder, niobium oxide powder and indium oxide powder are used as raw material powders and the atomic ratios of the elements are zinc, niobium and indium, respectively, when the contents are Zn, Nb and In.
Nb / (Zn + Nb + In) = 0.100 or more, 0.330 or less In / Nb = 0.2 or more, 2.0 or less Mixing step, molding using the mixed powder obtained in the mixing step The method for producing an oxide sintered body according to any one of (1) to (6) above, which comprises a molding step and a firing step of firing the molded body obtained in the molding step.
(9) In a thin film having zinc, niobium, indium and oxygen as constituent elements, when the contents of zinc, niobium and indium are Zn, Nb and In, respectively,
Nb / (Zn + Nb + In) = 0.100 or more and 0.330 or less In / Nb = 0.2 or more and 2.0 or less.

When the oxide sintered body of the present invention is used as a sputtering target, there is no splash from the target surface even when a high power is applied, stable DC discharge is possible, a high film formation rate is obtained, and a high refractive index is obtained. Insulation film can be obtained.

Hereinafter, the present invention will be described in detail.

In the present invention, in an oxide sintered body having zinc, niobium, indium and oxygen as constituent elements, when the contents of zinc, niobium and indium are Zn, Nb and In, respectively,
Nb / (Zn + Nb + In) = 0.100 or more and 0.330 or less In / Nb = 0.2 or more and 2.0 or less. Here, each element ratio represents a molar ratio.

The Nb / (Zn + Nb + In) of the oxide sintered body of the present invention is 0.100 or more, preferably 0.120 or more, and more preferably 0.150 or more. As a result, the refractive index of the film obtained by sputtering using the sintered body is improved. The Nb / (Zn + Nb + In) of the oxide sintered body of the present invention is 0.330 or less, preferably 0.300 or less, and more preferably 0.250 or less. As a result, the bulk resistance of the oxide sintered body is lowered, and the film formation rate during sputtering is also improved.

The In / Nb of the oxide sintered body of the present invention is 0.2 or more, preferably 0.5 or more, and more preferably 1.0 or more. As a result, In ₂ O ₃ and Nb ₂ O ₅ react sufficiently to suppress the formation of the high-resistance Zn ₃ Nb ₂ O ₈ phase, and the resistance of the oxide sintered body is further reduced. On the other hand, the In / Nb of the oxide sintered body is 2.0 or less.

Sintered body of the present invention preferably has a crystal phase of InNbO _4. The crystal phase of InNbO ₄ (single-phase bulk resistance 10 ⁸ Ω · cm) has a lower resistance than the crystal phase of Zn ₃ Nb ₂ O ₈ (single-phase bulk resistance: 10 ¹¹ Ω · cm or more). Nb preferentially forms the crystal phase of InNbO ₄ , and ZnO, which is the conductive phase, can be suppressed from reacting with Nb to form a crystal phase having high resistance such as Zn ₃ Nb ₂ O ₈ , and thus the sintered body. Bulk resistance can be reduced.

It can be confirmed by X-ray diffraction measurement that it has InNbO _4- phase. In the crystal phase of InNbO ₄ , for example, the diffraction peak detected by X-ray diffraction measurement using Cu as a radiation source (hereinafter referred to as “XRD”) is JCPDS (Joint Committee for Power Diffraction Standards) card No .: 01. It can be confirmed by referring to -083-1780.

The present invention preferably is an oxide sintered body composed of zinc, niobium, indium and oxygen as constituent elements. That is, it is preferable that elements other than zinc, niobium, indium and oxygen are not contained except for unavoidable impurities described later. This can be confirmed by composition analysis when the amount of elements other than zinc, niobium, indium and oxygen is 1000 ppm or less.

The sintered body of the present invention may contain unavoidable impurities. Examples of such impurities include metal elements other than Zn, Nb, and In, or oxides thereof. The total content of these impurities in the sintered body is preferably 0.01 or less, more preferably 0.005 or less, and even more preferably 0, with respect to the total of Zn, Nb and In in terms of metal elements. It is less than .001. As a result, the conductivity of the sintered body of the present invention is further improved. Here, the ratio of impurities to the total of Zn, Nb and In is a molar ratio.

The ratio of the bulk density of the oxide sintered body of the present invention to the weighted average value of the oxide-equivalent true density of each metal element is preferably 0.99 or more, and more preferably 1.00 or more. .. As a result, when sputtering is performed using the sputtering target containing the sintered body of the present invention, arcing is less likely to occur and splash is less likely to occur. Here, it can be exemplified that the bulk density of the present application is obtained by measurement by the Archimedes method. On the other hand, the weighted average value of the true density of each metal element in terms of oxide can be calculated by the following method. For example, when the sintered body of the present application contains Zn, Nb, and In, the contents of ZnO, Nb ₂ O ₅ , and In ₂ O ₃ are first obtained from the composition ratio, and the sum thereof is used as a molecule. On the other hand, the reciprocal of the true density of each metal element is multiplied by the content, and the sum is used as the denominator. Let the above numerator / denominator be the weighted average. That is, it can be calculated by the formula (2) described later.

Here, the composition ratio of the sintered body used in the calculation of the weighted average value may be the result of composition analysis such as ICP and XRF, and the mixing step in the method for producing the sintered body of the present invention described later. The value of the mixing ratio of the oxide powder used as the raw material used in the above may be used. Further, the ratio of the densities is a value generally called a relative density, but since it exceeds 1.00, it is called a density ratio for convenience.

The oxide sintered body of the present invention preferably has an average particle size of 3 μm or less, and more preferably 2 μm or less. This further suppresses the splash from the target surface. Usually, the average particle size is 0.5 μm or more.

Here, the average particle size represents the average value of the diameters of the crystal particles in the sintered body. For example, first, the sintered body is cut to an appropriate size, and the cross section is etched if necessary. Next, an observation image of the cross section is taken with an electron microscope. As the electron microscope, a scanning electron microscope (hereinafter referred to as "SEM") or a transmission electron microscope (hereinafter referred to as "TEM") can be used. The major axis of the particles in the obtained observation image can be obtained, and the arithmetic mean thereof can be used as the average particle size.

The bulk resistance value of the oxide sintered body of the present invention is preferably 100 Ω · cm or less, and more preferably 50 Ω · cm or less. As a result, when used as a sputtering target, DC discharge can be stably performed without a decrease in the film formation rate.

Here, the bulk resistance value can be measured by, for example, a measurement method using a low current application method or a four-terminal method.

The input load to the target during sputtering is standardized by the power density (W / cm ² ) obtained by dividing the input power by the target area. While typical power density in a normal production is about 1~4W / cm ^2, very little, oxide having a high quality target material of arcing occurs even at a high power condition of more than 4W / cm ² in the present invention A sintered body is obtained. The target area is the surface area of the sintered body on the surface to be sputtered in the flat plate target, but in the cylindrical target, the area of the outer peripheral surface of the cylindrical sintered body to be sputtered is the portion where plasma is generated. It is an area, which is obtained from the shape of the magnet of the sputtering cathode, but here, for convenience, an area of 1/6 of the outer peripheral surface is used.

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

In the method for producing an oxide sintered body of the present invention, zinc oxide powder, niobium oxide powder, and indium oxide powder are used as raw material powders, and the atomic ratios of the elements are Zn, Nb, and the contents of zinc, niobium, and indium, respectively. Obtained in a mixing step and a mixing step of mixing so that Nb / (Zn + Nb + In) is 0.100 or more and 0.330 or less, and In / Nb is 0.2 or more and 2.0 or less when In. It has a molding step of molding using a mixed powder and a firing step of firing a molded body obtained in the molding step.

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

(1) Mixing Step The purity of each oxide powder of zinc oxide, niobium oxide and indium oxide powder is preferably 99.9% or more, more preferably 99.99% or more in consideration of handleability. As a result, abnormal grain growth of crystal particles in the sintered body in the firing step can be suppressed.

In this step, when the atomic ratios of the elements of zinc oxide powder, niobium oxide powder and indium oxide powder are zinc, niobium and indium, respectively, Nb / (Zn + Nb + In) is 0. Mix so that the content is 100 or more and 0.330 or less and In / Nb is 0.2 or more and 2.0 or less. The Nb / (Zn + Nb + In) of the obtained mixture is preferably 0.120 or more, more preferably 0.150 or more, and more preferably 0.250 or less.

The oxide sintered body of the present invention needs to have a small average particle size of crystal particles and a uniform sintered body structure. As a result, when sputtering is performed using a sintered body, it is possible to suppress electric field concentration on crystal particles having ZnO as the main phase, which has high conductivity. Therefore, in the mixed powder as a raw material, it is particularly important to refine the ZnO powder and uniformly mix and pulverize the Nb ₂ O ₅ powder and the In ₂ O ₃ powder. As a guideline for mixing, the amount of increase in the BET value of the mixed powder before and after mixing is preferably 2 m ² / g or more, and more preferably 3 m ² / g or more. As a result, the mixing becomes sufficient and segregation of each element can be suppressed.

Here, the BET specific surface area of the mixed powder before mixing is obtained from the mixing ratio of each raw material powder by the weighted average by the following formula. The BET value of the ZnO powder used is BZ [m ² / g], the weight ratio is WZ [wt%], the BET value of the Nb ₂ O ₅ powder is BN [m ² / g], and the weight ratio is WN [wt%]. , When the BET value of the In ₂ O ₃ powder is BI [m ² / g] and the weight ratio is WI [wt%], the weighted average of the BET values of the mixed powder is (BZ × WZ + BN × WN + BI × WI) / It is calculated by 100.

Further, the BET specific surface area after the mixed powder after mixing can be measured by a measuring method according to JIS Z 8830 (a method for measuring the specific surface area of powder (solid) by gas adsorption). Nitrogen is used as the adsorbed gas in the measurement, and the BET specific surface area can be determined by the multipoint method.

Further, in order to obtain a high-density sintered body, the BET value of the mixed powder after mixing is preferably 8 m ² / g or more, and more preferably 10 m ² / g or more. Generally, the BET value of the mixed powder is 20 m ² / g or less.

The method for crushing and mixing the powder is not particularly limited as long as it can be sufficiently crushed and mixed, but it is a dry or wet media stirring type mill using balls or beads of zirconia, alumina, nylon resin or the like. And medialess container rotary mixing, mechanical stirring mixing and other mixing methods are exemplified. Specific examples thereof include ball mills, bead mills, attritors, vibration mills, planetary mills, jet mills, V-type mixers, paddle type mixers, twin-screw planetary stirring type mixers, etc., which can be easily crushed and mixed. For this purpose, it is preferable to use a wet bead mill, which is a wet method capable of enhancing dispersibility and has a relatively high pulverization ability, for example.

When processing the powder with a wet bead mill device, it is preferable to carry out under the following conditions.

The solid content concentration in the slurry is 35 wt% or more and 65 wt% or less, more preferably 50 wt% or more and 60 wt% or less. If the solid content concentration becomes too high, the crushing ability is lowered and the desired powder physical property value cannot be obtained.

As the crushing media, zirconia beads are used in consideration of preventing impurities from being mixed into the raw material due to wear, and the bead diameter is preferably in the range of φ0.2 mm or more and 0.5 mm or less, which enhances the crushing power. The amount of beads charged into the mill is preferably in the range of 75 vol% or more and 90 vol% or less as the bead filling rate with respect to the volume of the mill.

The type of dispersant is not particularly limited, but it is important to keep the change in slurry viscosity below a certain level. Depending on the treatment batch, the slurry viscosity may increase due to some factor even under the same conditions. In this case, the amount of dispersant should be adjusted appropriately so that the slurry viscosity is always 500 mPa · s or more and 2000 mPa · s or less. This is preferable because stable powder physical properties can be obtained. The slurry temperature is also preferably controlled strictly, and the slurry temperature at the mill inlet is controlled to 12 ° C. or lower, preferably 10 ° C. or lower, more preferably 9 ° C. or lower, and the slurry temperature at the mill outlet is 18 ° C. or lower. It is preferable to manage it at all times. Normally, the slurry temperature is 5 ° C. or higher at both the mill inlet and the mill outlet.

The number of rotations of the beads shall be 6 m / sec or more and 15 m / sec or less as the peripheral speed at the outermost circumference of the bead stirring blade. If the peripheral speed is small, the crushing force is weakened, the processing time until the desired powder physical properties are reached, and the productivity is significantly inferior. On the other hand, if the peripheral speed is high, the crushing force is strengthened, but the heat generated by the crushing increases, the slurry temperature rises, and the operation becomes difficult, which is not preferable.

Based on the above conditions, adjust the operating conditions of the bead mill. Even when a raw material powder having a high specific surface area is used, it is preferable that the number of pulverization passes into the mill is at least 10 or more in consideration of the dispersibility of the raw material powder.

As for the slurry after the wet mixing treatment, the slurry can be used as it is in a wet molding method such as casting molding, but in the case of dry molding, the fluidity of the powder is high and the density of the molded body is uniform. It is desirable to use the dry granulated powder. The granulation method is not limited, but spray granulation, fluidized bed granulation, rolling granulation, stirring granulation and the like can be used. In particular, it is desirable to use spray granulation, which is easy to operate and can be processed in large quantities. In the molding process, a molding aid such as polyvinyl alcohol, acrylic polymer, methyl cellulose, waxes, and oleic acid may be added to the raw material powder.

(2) Molding Step The molding method is not particularly limited as it is possible to appropriately select a molding method capable of molding the mixed powder obtained in the mixing step into a desired shape. Examples include a press molding method, a casting molding method, and an injection molding method.

The molding pressure is not particularly limited as long as it does not cause cracks or the like in the molded body and can be handled, but it is preferable to increase the molding density as much as possible. Therefore, it is also possible to use a method such as cold hydrostatic press (CIP) molding. CIP pressure is preferably for 1 ton / cm ² or more to obtain a sufficient consolidation effect, more preferably 2 ton / cm ² or more, especially preferably not more 2 ton / cm ² or more 3 ton / cm ² or less.

(3) Firing step Next, the molded product obtained in the molding step is fired. For firing, a firing method that can obtain a high-density and uniform sintered body can be appropriately selected, and a general resistance heating type electric furnace, microwave heating furnace, or the like can be used.

As the firing conditions, for example, the firing holding temperature is preferably 1150 ° C. or higher and 1300 ° C. or lower, and the holding time is preferably 0.5 hours or longer and 10 hours or shorter, and more preferably 1 hour or longer and 5 hours or shorter. If the firing temperature is low and the holding time is short, the density of the sintered body decreases, which is not preferable. On the other hand, when the firing temperature is high and the holding time is long, crystal particles grow and cause microscopic segregation of each element, which is not preferable. When there is microscopic segregation, the electric field concentration on the conductive phase containing ZnO as the main phase becomes remarkable during sputtering, ZnO in the conductive phase is reduced to metal Zn having a low melting point, and splash is generated from the target surface. It ends up. The firing atmosphere can be either an atmospheric atmosphere or an oxygen atmosphere, which is an oxidizing atmosphere, and firing in an atmospheric atmosphere is possible without requiring special atmosphere control.

The manufacturing method of the present invention. If necessary, the following targeting steps may be included.

(4) Targeting process The sintered body obtained in the firing process can be made into a plate shape, a circular shape, a cylindrical shape, etc. by using a machining machine such as a surface grinder, a cylindrical grinder, a lathe, a cutting machine, or a machining center. Grind to the desired shape. Further, if necessary, a sputtering target using the sintered body of the present invention as a target material can be obtained by bonding the backing plate and backing tube made of oxygen-free copper, titanium, etc. with indium solder or the like. Can be done.

When the contents of zinc, niobium and indium are set to Zn, niobium and indium in a thin film having zinc, niobium, indium and oxygen as constituent elements by performing sputtering using the above-mentioned sputtering target to form a film. To,
A thin film having Nb / (Zn + Nb + In) = 0.100 or more and 0.330 or less In / Nb = 0.2 or more and 2.0 or less can be obtained. Such a thin film has a high refractive index and can be suitably used as an insulating film. The Nb / (Zn + Nb + In) of the obtained mixture is preferably 0.120 or more, more preferably 0.150 or more, and more preferably 0.250 or less.

The refractive index of the thin film of the present invention is preferably 2.00 or more, more preferably 2.05 or more. As a result, it can be suitably used as a film for adjusting the refractive index. Generally, the refractive index of the thin film of the present invention is 2.3 or less. Here, the refractive index can be measured using, for example, a spectroscopic ellipsometer.

Resistivity of the thin film of the present invention is preferably 10 ⁶ Ω · cm or more, more preferably 10 ⁸ Ω · cm or more. As a result, it can be suitably used as an insulating film.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto. In addition, each measurement in this Example was performed as follows.
(1) Density and Density Ratio of Sintered Body The density ratio of the sintered body is the bulk density (hereinafter referred to as "d ₁ ") measured by Archimedes' method in accordance with JIS R 1634 for each metal element. It was obtained by dividing by the weighted average value of the true density in terms of oxide (hereinafter referred to as "d ₂ ").

Density ratio = d ₁ / d ₂ ... (1)

For d ₂ , when Zn, Nb, and In are converted into oxides and used as ZnO, Nb ₂ O ₅ , and In ₂ O ₃ , respectively, the amounts a [g], b [g], and c [g] are obtained. ] and each of the true density ^{5.606 [g / cm 3],} 4.542 [g / cm 3], using a 7.180 [g / cm ^3], and more calculated by the following equation. Here, a, b, and c used the powder mixing ratio in the manufacturing process as a simple method.

d ₂ = (a + b + c) / ((a / 5.606) + (b / 4.542) + (c / 7.180))
・ ・ ・ Equation (2)

In an actual sintered body, it is difficult to determine the true density of the sintered body of the present application due to factors such as the presence of a composite oxide phase and the solid solution of each element. In the present application, the ratio of the bulk density to the weighted average of the oxides of each metal element is determined by the same method as the conventional relative density, but the density ratio may exceed 1.00.
(2) Average particle size The sintered body was cut, its cross section was mirror-polished, and then heat-treated to perform thermal etching. After that, the etching surface of the sintered body was observed with an SEM (product name: VE-9800, manufactured by Keyence), and from the obtained SEM observation image (magnification: × 3000 times), the particles of the sintered body cross section were measured by the diameter method. The average particle size was measured. The sample was observed at any three or more points, and 100 or more particles were measured for each.
(Thermal etching conditions)
Temperature: 900 ° C
Time: 30min
(3) Measurement of resistivity The average value of 10 samples cut out from an arbitrary part after grinding 1 mm or more from the surface of the sintered body was used as the measurement data.
Sample size: 10 mm x 20 mm x 1 mm
Measuring method: 4-terminal method Measuring device: Loresta HP MCP-T410 (manufactured by Mitsubishi Yuka)
(4) X-ray diffraction test The X-ray diffraction pattern in the range of 2θ = 20 ° or more and 70 ° or less of the mirror-polished sintered body sample was measured.
Scanning method: Step scan method (FT method)
X-ray source: CuKα
Power: 40kV, 40mA
Step width: 0.01 °
(5) BET specific surface area The BET specific surface area of the sample was determined by measurement according to JIS Z 8830. A general specific surface area measuring device (trade name: TriStar3000, manufactured by Shimadzu Corporation) was used for the measurement. As a pretreatment, the sample was held at 200 ° C. (room temperature to 90 ° C.: 5 ° C./min, 90 ° C. to 200 ° C.: 10 ° C./min) for 20 minutes. The BET specific surface area was measured for the pretreated sample. The measurement conditions are as follows.

Processing gas: Nitrogen gas Measurement method: Multi-point method (6) Sputtering evaluation After processing the obtained sintered body to 101.6 mmΦ × 6 mmt, it was bonded to an oxygen-free copper backing plate with indium solder to make a sputtering target. .. Using this target, the film formation was evaluated under the following conditions, and then the stability of DC discharge was evaluated.

The refractive index of the thin film sample obtained in the film formation evaluation was measured with a spectroscopic ellipsometer (trade name: M-2000V-Te, manufactured by JA Woollam), and a value having a wavelength of 550 nm was used. The film thickness was calculated by preparing a thin film sample formed for 30 minutes under the sputtering conditions for film formation evaluation, and measuring the film thickness with a surface shape measuring device (trade name: Dektak3030, manufactured by ULVAC).
(Sputtering conditions for film formation evaluation)
Gas: Argon + oxygen (3%)
Pressure: 0.6Pa
Power supply: DC
Input power: 200W (2.4W / cm ² )
Film thickness: 80 nm
Substrate: Non-alkali glass (EAGLE XG manufactured by Corning Inc., thickness 0.7 mm)
Substrate temperature: Room temperature (sputtering conditions for DC discharge stability evaluation)
Gas: Argon + oxygen (3%)
Pressure: 0.6Pa
Power supply: DC
Input power: 600W (7.4W / cm ² )
800W (9.9W / cm ² )
Discharge time: 30 min
Evaluation: Number of splashes on the target surface after discharge (visual)
(Example 1)
Zinc oxide powder with a BET value of 3.8 m ² / g (purity 99.9% or higher), niobium oxide powder with a BET value of 5.4 m ² / g (purity 99.9% or higher), and BET value 11.5 m ² Indium oxide powder (purity 99.9% or more) of / g was weighed so as to have a ratio of 0.207 for Nb / (Zn + Nb + In) and 1.0 for In / Nb. The weighed powder was slurried with 10 kg of pure water, and 0.1 wt% of a polyacrylate-based dispersant was added to the total amount of powder to prepare a slurry having a solid content concentration of 60%. A bead mill device with an internal volume of 2.5 L is filled with 85% of φ0.3 mm zirconia beads, and the slurry is circulated in the mill at a mill peripheral speed of 7.0 m / sec and a slurry supply amount of 2.5 L / min, and pulverized and mixed. Processing was performed. Further, the temperature of the slurry supply tank was controlled within the range of 8 ° C. or higher and 9 ° C. or lower, and the slurry outlet temperature was controlled within the range of 14 ° C. or higher and 16 ° C. or lower, and the number of circulations (passes) in the mill was 20 times. Then, the obtained slurry was spray-dried, the dried powder was passed through a 150 μm sieve, and a 120 mm × 120 mm × 8 mmt molded product was produced at a pressure of 300 kg / cm ² by a press molding method, and then ² ton / cm ² . CIP treated with pressure.

Next, this molded product was placed on an alumina setter and fired in a resistance heating type electric furnace (internal volume: 250 mm × 250 mm × 250 mm) under the following firing conditions. Table 1 shows the sputtering evaluation results of the obtained sintered body and the sputtering target.
(Baking conditions)
Baking temperature: 1250 ° C
Retention time: 3 hours Temperature rise rate: 950 ° C to 1250 ° C 300 ° C / hr
Other temperature range 100 ° C / hr
Atmosphere: Atmosphere Temperature down rate: Up to 950 ° C 100 ° C / hr
After 950 ° C, 150 ° C / hr.

(Examples 2 to 8 and Comparative Examples 1 to 3)
A sintered body was prepared by the same method as in Example 1 except that the composition was changed to the contents of Table 1 (in Examples 7 and 8, the number of passes of the bead mill was changed to 15 times and 10 times, respectively). In Comparative Examples 2 and 3, the bulk resistance of the sintered body was high and DC discharge could not be performed. The evaluation results of the obtained sintered body are shown in Table 1.

(Measurement of thin film resistivity)
The resistivity of the thin films obtained in Examples 1 to 8 was measured by a 4-terminal method using a Lenovo HP MCP-T410 (manufactured by Mitsubishi Yuka). Thin film resistance was more high-resistance film All 10 ⁸ Ω · cm.

(Reference example)
A film was formed using a reduced Nb ₂ O ₅ target (manufactured by Toshima Manufacturing Co., Ltd.) having a size of 101.6 mmΦ × 6 mmt under the same sputtering conditions as in the example. The film formation rate is 9.0 nm / min when the sputtering gas is argon + oxygen (3%), and when the transmittance of the thin film is argon + oxygen (5%) which is saturated with the oxygen gas, 7. It was 4 nm / min.

Claims (9)

In an oxide sintered body having zinc, niobium, indium and oxygen as constituent elements, when the contents of zinc, niobium and indium are Zn, Nb and In, respectively,
An oxide sintered body in which Nb / (Zn + Nb + In) = 0.100 or more and 0.330 or less In / Nb = 1.0 or more and 2.0 or less. The oxide sintered body according to claim 1, which has a crystal phase of InNbO ₄ . Metal elements other than Zn, Nb, and In, or oxides thereof are contained as unavoidable impurities, and the total content of these impurities in the sintered body is converted into a metal element to be the total of Zn, Nb, and In. The oxide sintered body according to claim 1 or 2, which is 0.01 or less. The oxide sintered body according to any one of claims 1 to 3, wherein the ratio of the bulk density to the weighted average value of the true density of each metal element in terms of oxide is 0.99 or more. The oxide sintered body according to any one of claims 1 to 4, wherein the average particle size is 3 μm or less. The oxide sintered body according to any one of claims 1 to 5, wherein the bulk resistance value is 100 Ω · cm or less. A sputtering target using the oxide sintered body according to any one of claims 1 to 6 as a target material. When zinc oxide powder, niobium oxide powder and indium oxide powder are used as raw material powders and the atomic ratios of the elements are zinc, niobium and indium contents of Zn, Nb and In, respectively.
Nb / (Zn + Nb + In) = 0.100 or more, 0.330 or less In / Nb = 1.0 or more and 2.0 or less Mixing step, molding using the mixed powder obtained in the mixing step The method for producing an oxide sintered body according to any one of claims 1 to 6, further comprising a firing step of firing the molded product obtained in the step and molding step. In a thin film having zinc, niobium, indium and oxygen as constituent elements, when the contents of zinc, niobium and indium are Zn, Nb and In, respectively,
Nb / (Zn + Nb + In) = 0.100 or more, 0.330 or less In / Nb = 1.0 or more and 2.0 or less.