WO2015052927A1

WO2015052927A1 - Sputtering target and method for producing same

Info

Publication number: WO2015052927A1
Application number: PCT/JP2014/005120
Authority: WO
Inventors: 麻美西村; 正嗣大山
Original assignee: 出光興産株式会社
Priority date: 2013-10-09
Filing date: 2014-10-08
Publication date: 2015-04-16
Also published as: TW201522689A

Abstract

A sputtering target which contains a hexagonal layered compound that is mainly composed of indium oxide and zinc oxide and is represented by formula In₂O₃(ZnO)_m (wherein m is an integer of 2-7), and which also contains elemental Sn and elemental Zr. The ratio of elemental Sn relative to all metal elements in this sputtering target is more than 2,000 ppm but 20,000 ppm or less.

Description

Sputtering target and manufacturing method thereof

The present invention relates to a sputtering target suitable for manufacturing an oxide film, a manufacturing method thereof, an oxide film formed using the target, and a product using the same.

Transparent conductive films made of metal composite oxides that have both conductivity and light transmission have been used as electrodes in solar cells, liquid crystal display elements, and other various elements. It is used in a wide range of applications such as heat ray reflective films, antistatic films, and transparent heating elements for anti-fogging in refrigerated showcases. In particular, it is known that a transparent conductive film having low resistance and excellent conductivity is suitably used for solar cells, display elements such as liquid crystals, organic electroluminescence, and inorganic electroluminescence, and electronic devices such as touch panels. Yes.

Among such transparent conductive films, the most popular one is a transparent conductive film made of indium oxide-tin oxide (indium tin oxide) called ITO.
In addition, indium oxide-zinc oxide (indium zinc oxide), tin oxide with antimony added, zinc oxide with aluminum added, and the like are known. Since these are different in ease of manufacture, price, characteristics, etc., they are used as appropriate according to the application.

The indium zinc oxide film is characterized by a higher etching rate than the ITO film. However, since the indium zinc oxide target has a higher bulk resistance value than the ITO target, the discharge during sputtering may become unstable particularly in the DC magnetron sputtering process.

It is known that the bulk resistance is lowered by adding about 5% of tin oxide in the indium oxide-based sintered body, and the same effect can be obtained in the indium zinc oxide sintered body. However, adding a large amount of tin oxide in this way loses the characteristics of the indium zinc oxide transparent conductive film, and thus is not necessarily consistent with the purpose.

Therefore, in Patent Document 1, the bulk resistance value of the target is lowered with a slight addition amount of about 0.01 to 1 atomic% of an oxide of a third element having a valence of at least positive tetravalent to indium zinc oxide, Proposals have been made to stabilize the discharge of the target during sputtering and to achieve an industrially applicable etching rate with an oxalic acid etchant.

However, the target to which the third element addition amount described in the example of Patent Document 1 is added must be polished until color unevenness occurs on the target surface during the sintering process, and the color unevenness disappears. It was. As a result, the manufacturing tact time is increased and the yield is significantly reduced. On the other hand, in the target in which the third element addition amount was sequentially increased, the occurrence of color unevenness was suppressed, but a large amount of particles were observed on the film formation substrate during the sputter film formation.

In Example 1 and Example 2 of Patent Document 2, a target to which cerium oxide is added as a rare earth oxide when an indium oxide-zinc oxide target is manufactured, and in Example 3, a target to which praseodymium oxide is added, It is disclosed that it is effective in preventing color unevenness. However, these rare earth oxide-added targets can prevent color unevenness during the sintering process, but the resistance value of the formed transparent conductive film increases, and the etching performance (speed and residue) by the oxalic acid etchant also increases. Inferior. Also, the number of particles during sputter deposition increased.

International Publication Number WO2003 / 008661 JP 2001-11613 A

The present invention reduces the amount of polishing when producing a sputtering target by suppressing the occurrence of color unevenness during sintering, improves the manufacturing tact time and yield, and also suppresses the generation of particles during film formation. The purpose is to provide.

According to the present invention, the following sputtering target and manufacturing method thereof, an oxide film formed by the target, and a product using the same are provided.
1. Mainly composed of indium oxide and zinc oxide,
A hexagonal layered compound represented by In ₂ O ₃ (ZnO) _m (wherein m = 2 to 7),
Contains Sn element and Zr element,
The sputtering target whose ratio of Sn element with respect to all the metal elements is more than 2000 ppm and 20000 ppm or less.
2. 2. The sputtering target according to 1, wherein the ratio of the Zr element to the total metal elements is 50 ppm or more and 1000 ppm or less.
3. 3. The sputtering target according to 1 or 2, wherein the average crystal grain size is 2 μm to 10 μm.
4). 4. The sputtering target according to any one of 1 to 3, having a relative density of 95% or more.
5. The sputtering target according to any one of 1 to 4, which has a bulk resistance value of 50 mΩcm or less.
6). Indium raw material, zinc raw material, Sn raw material and Zr raw material are mixed and pulverized so that the ratio of Sn element to all metal elements in the sputtering target is more than 2000 ppm and 20000 ppm or less, and the ratio of Zr element is 50 ppm or more and 1000 ppm or less. The process of producing,
2. The method for producing a sputtering target according to 1, comprising a step of forming the mixture to produce a molded product, and a step of sintering the molded product at 1200 ° C. to 1600 ° C. for 1 hour to 50 hours.
7. A method for producing an oxide film formed using the sputtering target according to any one of 1 to 5.
An oxide film produced by the method described in 8.7.
9. 9. The oxide film according to 8, which is a transparent conductive film.
An electronic device using the oxide film according to 10.8 or 9.

Moreover, according to another aspect of this invention, the following sputtering targets, its manufacturing method, etc. are provided. In this embodiment, even if the sputtering target does not contain Zr as an essential component, color unevenness on the target surface is eliminated. Therefore, the cutting amount of the target surface can be reduced, the manufacturing tact time can be shortened, and the yield can be improved.
1. Mainly composed of indium oxide and zinc oxide,
A hexagonal layered compound represented by In ₂ O ₃ (ZnO) _m (wherein m = 2 to 7),
Sn content is more than 2000ppm and 20000ppm or less,
The difference Δb * between the maximum chromaticity and the minimum chromaticity on the surface or arbitrarily cut surface is 0 to 5,
A sputtering target having an average crystal grain size of 2 μm to 10 μm.
2. 2. The sputtering target according to 1, wherein the maximum chromaticity b * value on the surface or arbitrarily cut surface is 14 or less.
3. The sputtering target according to 1 or 2, excluding a sputtering target containing Sn at a content of 2100 ppm, 2700 ppm, or 3400 ppm.
4). The sputtering target according to any one of 1 to 3, having a relative density of 95% or more.
5. The sputtering target according to any one of 1 to 4, wherein the bulk resistance value is 50 mΩcm or less.
6). A step of mixing the indium raw material, the zinc raw material and the Sn raw material so that the Sn content of the sputtering target is more than 2000 ppm and not more than 20000 ppm,
Forming the mixture by molding the mixture, and sintering the molding at 1200 ° C. to 1600 ° C. for 1 hour to 50 hours, the maximum chromaticity and minimum on the surface or arbitrarily cut surface A method for producing a sputtering target, wherein the chromaticity difference Δb * value is 0 to 5, and the average crystal grain size is 2 μm to 10 μm.
The manufacturing method of the oxide film formed into a film using the sputtering target in any one of 7.1 thru | or 5.
An oxide film produced by the method described in 8.7.
9. Mainly composed of indium oxide and zinc oxide,
A hexagonal layered compound represented by In ₂ O ₃ (ZnO) _m (wherein m = 2 to 7),
Sn content is more than 2000ppm and 20000ppm or less,
The difference Δb * between the maximum chromaticity and the minimum chromaticity on an unpolished surface or an arbitrarily cut surface is 0 to 10,
An oxide sintered body having an average crystal grain size of 2 μm to 10 μm.
10. 10. The oxide sintered body according to 9, wherein the maximum chromaticity b * value on an unpolished surface or an arbitrarily cut surface is 20 or less.

According to the present invention, the ratio of the Sn element to the total metal elements is more than 2000 ppm and less than 20000 ppm (over 2000 ppm to 20000 ppm) and contains Zr, thereby suppressing the generation of color unevenness on the surface of the sintered body. In addition to improving the tact time and yield, the amount of particles during sputtering film formation can be suppressed.

A sputtering target according to an embodiment of the present invention includes indium oxide and zinc oxide as main components, and In ₂ O ₃ (ZnO) _m [wherein, m is an integer of 2 to 7. And a Sn element and a Zr element. And the ratio of Sn element with respect to all the metal elements is more than 2000 ppm and 20000 ppm or less, It is characterized by the above-mentioned.

The hexagonal layered compound contained in the sputtering target of the present invention is a compound identified by X-ray diffraction and represented as In ₂ O ₃ (ZnO) _m . M in the formula is an integer of 2 to 7, preferably 3 to 5. A compound in which m is 1 does not have a hexagonal layered structure, and a compound in which m exceeds 7 has a hexagonal layered structure, but its bulk resistance is high.

The ratio of Sn element to all metal elements contained in the sputtering target is more than 2000 ppm to 20000 ppm.
When the Sn element ratio is 2000 ppm or less, color unevenness occurs during target sintering, and the yield decreases. If it exceeds 20000 ppm, the oxide film (transparent conductive film) formed using the sputtering target may be difficult to be etched with a weak acid such as oxalic acid. The content ratio of the Sn element is preferably more than 2000 ppm to 20000 ppm, 2050 ppm to 10,000 ppm, more than 2100 ppm to 5000 ppm, or 3500 ppm to 5000 ppm.

It is preferable that the ratio of Zr element with respect to all the metal elements contained in a sputtering target is 50 ppm or more and 1000 ppm or less. If it is this range, the particle amount at the time of sputtering film-forming can be suppressed preferably, and the yield of a transparent conductive film will improve. In addition, the resistance value of the transparent conductive film formed using the sputtering target does not increase, etching with a weak acid such as oxalic acid can be performed, and no residue remains.
The ratio of the Zr element is more preferably 70 ppm to 700 ppm, and particularly preferably 100 ppm to 500 ppm.

The ratio (ppm) of Sn and Zr elements to all metal elements contained in the sputtering target can be measured by ICP emission spectroscopic analysis. Note that the proportions of the Sn and Zr elements substantially coincide with the blending proportion in the target material.

In the present invention, if the ratio of Sn element to all metal elements is increased, particles are likely to be generated during sputtering film formation. On the other hand, the generation amount of particles is suppressed by adding the Zr element. Although the mechanism of this effect is not necessarily clear, it is estimated that the addition effect of the Zr element has an effect on the ultrafine structure in the target. That is, when the addition ratio of Sn element increases, zinc oxide and tin oxide, which are target raw materials, selectively react to form a spinel phase having a high bulk resistance value. Therefore, it is considered that a micro arc is generated at the time of sputtering film formation, and the amount of particles increases.
On the other hand, it is presumed that by adding Zr element, selective reaction between zinc oxide and tin oxide is suppressed, and solid solution of Sn element into indium oxide is promoted.

By setting the ratio of the Sn element to the total metal elements within the above range, generation of the surface color unevenness layer of the sintered body is suppressed, and the amount of polishing can be reduced and the industrially applicable tact time can be secured.
On the other hand, by adding the Zr element, it is possible to suppress the amount of particles at the time of sputtering film formation, which is increased by adding the Sn element.

Furthermore, in the present invention, the bulk resistance of the sputtering target can be sufficiently lowered by setting the content ratio of the Sn element within the above range. The bulk resistance of the sputtering target of the present invention is preferably 50 mΩcm or less, 25 mΩcm or less, 10 mΩcm or less, or 5 mΩcm or less. On the other hand, when the bulk resistance of the sputtering target exceeds 50 mΩcm, it may be difficult to perform stable film formation by direct current sputtering. The lower limit is not particularly limited, but is usually about 0.1 mΩcm.

Moreover, the transparent conductive film formed using this target can be etched with a weak acid such as oxalic acid.

The average crystal grain size of the sputtering target of the present invention is preferably 2 μm to 10 μm, more preferably 2 μm to 8 μm, from the viewpoint of preventing abnormal discharge.
The average crystal grain size can be adjusted according to the conditions of the raw material and the production method. Specifically, a raw material having a small average particle diameter, for example, a raw material having a diameter of 0.01 to 10 μm, preferably 5 μm or less can be used, or the raw material can be made small by pulverization conditions. On the other hand, during sintering, the higher the sintering temperature and the longer the sintering time, the larger the average crystal grain size tends to be.

The average crystal grain size was measured by the following method.
When the shape of the sputtering target is circular, a square inscribed in the circle is divided into 16 equal areas, and at each of the 16 center points of each square, and when the shape of the sputtering target is square, each side is 4 etc. The points to be divided are determined, the opposing points are connected and divided into 16 equal areas, and the surface of each square is observed with a scanning electron microscope (SEM) in a frame with a magnification of 1000 times at 16 central points. All the particle diameters of the particles observed within the 120 × 80 μm square of the field of view were measured to obtain an average value, and the average value of the particle diameters was further determined from the average values of all 16 locations. The particle diameter was measured based on JIS R 1670 with the crystal particle diameter as the equivalent circle diameter.

The relative density of the sputtering target is preferably 95% or more, more preferably 96% or more. Since such a high-density target has high mechanical strength and excellent electrical conductivity, it is possible to further improve the stability when performing sputtering by mounting it on an RF magnetron sputtering apparatus or a DC magnetron sputtering apparatus. The relative density is a value obtained by dividing the actual density obtained by measuring the sputtering target by the Archimedes method by the theoretical density calculated from the true density and the weight ratio of the oxide of each constituent element. More specifically, the calculation was made with reference to JP-A-2002-30429.

In the sputtering target of the present invention, the atomic ratio of indium to zinc is usually In / (In + Zn) = 0.2 to 0.95, preferably In / (In + Zn) = 0.3 to 0.9. .

The sputtering target of the present invention contains indium oxide and zinc oxide as main components. Specifically, indium oxide and zinc oxide, a prescribed amount of tin oxide that suppresses the generation of the color unevenness layer, a prescribed amount of zirconium oxide that suppresses the amount of particles, and other inevitable impurities are included.

When the main component is indium oxide and zinc oxide, the total of indium oxide and zinc oxide is more than 95% by weight, 97% by weight or more, and more preferably 98% by weight or more. In addition to these metal oxides, inevitable impurities may be included within a range not impairing the effects of the present invention.

The sputtering target of the present invention includes a step of mixing and grinding an indium raw material, a zinc raw material, a tin raw material and a zirconium raw material, a step of forming a raw material mixture, a step of sintering a molded product, and annealing a sintered body as necessary. It can be manufactured through a process, a process of polishing a sintered body, and a process of cutting into a specified shape.

The raw material is not particularly limited, and a compound or metal containing In, Zn, Sn, or Zr element can be used, and preferably an oxide.
It is desirable to use raw materials such as indium oxide, zinc oxide, tin oxide, and zirconium oxide that have high purity, and the purity is 99% or more, preferably 99.9% or more, more preferably 99.99% or more. Those are preferably used. When a high-purity raw material is used, a sintered body having a dense structure is obtained, and the bulk resistance is lowered.

The raw material metal oxide preferably has an average particle size of 0.01 to 10 μm, more preferably 0.05 to 5 μm, and still more preferably 0.1 to 5 μm. When the average particle size is less than 0.01 μm, aggregation tends to occur. When the average particle size exceeds 10 μm, the mixing property becomes insufficient, and a sintered body having a dense structure may not be obtained.

Binders such as polyvinyl alcohol and vinyl acetate can be added to the raw material.
The mixing of the raw materials can be performed by a normal mixing and grinding machine such as a ball mill, a jet mill, or a bead mill.

The mixture thus obtained may be immediately molded, but may be calcined before the molding. The calcination treatment is usually carried out at 700 to 900 ° C. for 1 to 5 hours.

The mixture of raw material powders and calcined metal oxide powders are granulated to improve fluidity and filling properties in the subsequent molding process. The granulation treatment can be performed using a spray dryer or the like. The particle size of the granulated product formed by the granulation treatment is preferably 1 to 100 μm, more preferably 5 to 100 μm, still more preferably 10 to 100 μm.

Next, the raw material powder or granulated material is molded by a method such as die press molding, casting molding, injection molding or the like in the molding process. When a sintered body having a high sintering density is obtained as a sputtering target, it is preferable to perform compaction by cold isostatic pressing or the like after preforming by die pressing or the like in this molding step.

In the sintering process of the molded body, a conventional sintering method such as normal pressure sintering, hot press sintering, hot isostatic pressing sintering, or the like can be used. The sintering temperature is preferably 1200 to 1600 ° C, more preferably 1250 to 1550 ° C, still more preferably 1300 to 1500 ° C. When the sintering temperature is less than 1200 ° C., a sufficient sintering density cannot be obtained, and at a temperature exceeding 1600 ° C., the composition of the metal oxide in the sintered body varies due to sublimation of indium oxide or zinc oxide. Sometimes. The rate of temperature increase during sintering is preferably from 0.1 to 3 ° C./min from 800 ° C. to the sintering temperature.

The sintering time varies depending on the sintering temperature, but is preferably 1 to 50 hours, more preferably 2 to 30 hours, and further preferably 3 to 20 hours. The atmosphere during sintering may be air or oxygen gas, or may be a reducing gas such as hydrogen gas, methane gas or carbon monoxide gas, or an inert gas such as argon gas or nitrogen gas.

The sintered body may be annealed. In the annealing treatment, the temperature is usually maintained at 700 to 900 ° C. for 1 to 5 hours.

The color unevenness layer on the surface of the sintered oxide immediately after sintering thus obtained was measured for b * and Δb * by the method described in the examples, and the polished surface was b * ≦ 4 and Δb * ≦ 2. It was defined by the polishing depth (thickness of the color unevenness layer) when polishing until the end. The polishing depth is preferably 0 to 0.7 mm, more preferably 0 to 0.5 mm, and particularly preferably 0 to 0.3 mm.

A sputtering target can be obtained by cutting the sintered body obtained above into an appropriate shape.

A sputtering target according to another embodiment of the present invention includes indium oxide and zinc oxide, and In ₂ O ₃ (ZnO) _m [wherein, m is an integer of 2 to 7. ] The hexagonal layered compound represented by this is contained. Furthermore, Sn is contained in excess of 2000 ppm to 20000 ppm (weight conversion).

The hexagonal layered compound composed of indium oxide and zinc oxide is the same as that in the above-described embodiment.

The ratio of Sn contained in the sputtering target is more than 2000 ppm to 20000 ppm.
When the Sn ratio is 2000 ppm or less, color unevenness occurs during target sintering, and the yield decreases. Moreover, when it exceeds 20000 ppm, it may become difficult to perform the etching process by weak acids, such as an oxalic acid, in the transparent conductive film formed using the sputtering target. The content of Sn is preferably more than 2000 ppm to 20000 ppm, 2050 ppm to 10,000 ppm, more than 2100 ppm to 5000 ppm, or 3500 ppm to 5000 ppm.

By setting the Sn content in the above range, the uneven color layer on the surface of the target can be reduced during sintering, and the color does not easily differ between the inside and the surface, leading to a reduction in the cutting amount.

Furthermore, in this invention, the bulk resistance of a sputtering target can be made low enough by making the content rate of Sn into said range. The bulk resistance of the sputtering target of the present invention is preferably 50 mΩcm or less, 25 mΩcm or less, 10 mΩcm or less, or 5 mΩcm or less. On the other hand, when the bulk resistance of the sputtering target exceeds 50 mΩcm, it may be difficult to perform stable film formation by direct current sputtering.

Moreover, the transparent conductive film formed using this target can be easily etched with a weak acid such as oxalic acid.

The average crystal grain size of the sputtering target of the present invention is preferably 2 μm to 10 μm, more preferably 2 μm to 8 μm, from the viewpoint of abnormal discharge.
The average crystal grain size can be adjusted according to the conditions of the raw material and the production method. Specifically, a raw material having a small average particle diameter, for example, a raw material having a diameter of 0.01 to 10 μm, preferably 5 μm or less, more preferably 1 μm or less is used. Further, during sintering, the higher the sintering temperature and the longer the sintering time, the larger the average crystal grain size tends to be.

The relative density of the sputtering target is preferably 95% or more, more preferably 96% or more. With such a density, since the mechanical strength of the target is high and the conductivity is excellent, the stability when performing sputtering by mounting this on an RF magnetron sputtering apparatus or a DC magnetron sputtering apparatus is further increased. Can do.

Note that the average crystal grain size and the relative density are measured in the same manner as in the above-described embodiment.

The sputtering target of the present invention contains indium oxide and zinc oxide as main components. Specifically, indium oxide and zinc oxide may occupy 90% by weight, 95% by weight, 97% by weight, 98% by weight, or 98.5% by weight or more.

Alternatively, the metal element contained in the sputtering target of the present invention is substantially composed of In, Zn, and Sn, and contains inevitable impurities in addition to these metal oxides as long as the effects of the present invention are not impaired. You may go out.
In the present invention, “substantially” means that the effect as a sputtering target is caused by the oxides of In, Zn, and Sn, or 90 atomic% or more, 95 atomic% or more, 97 atoms of all metal elements of the sputtering target. % Or more, 98 atomic% or more, 99 atomic% or more, or 99.5 atomic% or more, and 100 atomic% or less means In, Zn, and Sn.

The sputtering target of the present invention is manufactured through a step of mixing an indium raw material, a zinc raw material and a Sn raw material, a step of molding the raw material mixture, a step of sintering the molded product, and a step of annealing the sintered body as necessary. can do. Specifically, it is the same as the manufacturing method of the above-described embodiment of the present invention except that the Zr element is not an essential component.

Regarding the color unevenness of the surface of the oxide sintered body or the arbitrarily cut surface in this embodiment, Δb * measured by the method described in the examples is preferably 0 to 10, more preferably 0 to 5, particularly preferably. Is 0-4. The maximum b * value of the surface of the unpolished oxide sintered body or the arbitrarily cut surface is preferably 20 or less, more preferably 19 or less, and particularly preferably 18 or less.

Regarding the color unevenness of the target surface or the arbitrarily cut surface thus obtained, Δb * measured by the method described in the examples is preferably 0 to 5, more preferably 0 to 3. Further, the maximum b * of the polished surface or the arbitrarily cut surface is preferably 14 or less, more preferably 12 or less, and particularly preferably 10 or less.

The oxide film of the present invention is obtained by forming a film by a sputtering method using the above-described sputtering target of the present invention.
The film formation by the sputtering method can be suitably performed by an RF magnetron sputtering method, a DC magnetron sputtering method, or the like, but the DC magnetron sputtering method is generally applied from the viewpoint of productivity. The film formation conditions are not particularly limited, and the film formation can be suitably performed within the normally applied condition range.

Examples 1 to 9, Comparative Examples 1 to 4
Weigh 5000 g of indium oxide powder having a specific surface area of 11 m ² / g and an average particle size of 0.98 μm, and 600 g of zinc oxide powder having the same specific surface area and average particle size, and the content in the obtained sputtering target is shown in Table 1. Tin oxide and zirconium oxide were weighed so as to have the content shown (ppm = Sn or Zr / all metal elements (In + Zn + Sn + Zr) × 10 ⁶ ), and a molding binder was added to uniformly mix and granulate.
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.

Next, the granulated product was uniformly filled into a mold, and pressure-molded at 50 MPa with a cold press machine, and then pressure-molded with a cold isostatic press machine at 200 MPa. The molded body thus obtained was sintered in a sintering furnace at 1400 ° C. (temperature increase rate from 800 ° C. to sintering temperature: 2 ° C./min) for 20 hours.

The crystal structure of the obtained sintered body was examined using an X-ray diffraction measurement apparatus (XRD). As a result, the presence of a hexagonal layered compound represented by In ₂ O ₃ (ZnO) _m (wherein m = 2 to 7) was confirmed in all Examples and Comparative Examples. 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

Furthermore, the following characteristics were measured for the obtained sintered body. The results are shown in Table 1.
(1) Chromaticity (b * value) and polishing depth Colorimetric colorimeter (Nippon Denshoku) was used to measure the chromaticity (b * value) of the oxide sintered body immediately after sintering and the surface of the oxide sintered body after polishing Measured with NR-11A). Observe the surface of the oxide sintered body and visually observe a portion with a strong yellowness (the highest value of b *: maximum b *) and a portion where the yellowness is light and dark green to blackish (the lowest value of b *) ) (Δb *). The polishing depth was determined by measuring the depth before and after polishing with calipers until b * ≦ 4 and Δb * ≦ 2 or less.

(2) Average crystal grain size (μm)
The average crystal grain size of the quadrangular sputtering target is determined by dividing each side into four equal parts, connecting the opposing points into 16 equal areas, and the surface of each quadrant at 16 central points is multiplied by 1000 times. Was observed with a scanning electron microscope (SEM). All the particle diameters of the particles observed within the 120 × 80 μm square of the field of view were measured to obtain an average value, and the average value of the particle diameters was further determined from the average values of all 16 locations. The particle diameter was measured based on JIS R 1670 with the crystal particle diameter as the equivalent circle diameter.

(3) Bulk resistance value (mΩcm)
The bulk resistance (conductivity) of the target was measured based on the four-probe method using a resistivity meter (Made by Mitsubishi Chemical Corporation, Loresta).

(4) Relative density Calculated by dividing the actual density measured by the Archimedes method of the sputtering target by the theoretical density calculated from the true density and weight ratio of the oxide of each constituent element (Japanese Patent Laid-Open No. 2002-30429) reference).

(5) Etching rate and residue A sputtering target is attached to a DC magnetron sputtering apparatus, sputter pressure is 0.3 Pa, sputter output is 100 W, Ar gas is 100%, sputtered for 10 minutes, and the entire thickness of the surface of a 100 mm □ glass substrate is obtained. A 100 nm transparent conductive film was formed.
Under the above film forming conditions, an indium zinc oxide film having a thickness of 100 nm was formed on a glass substrate, and then the resistance value of the substrate was added to a commercially available oxalic acid etching solution (ITO-06N: manufactured by Kanto Chemical Co., Ltd.) at 30 ° C. Was etched until the film reached infinity, and the etching rate was determined by dividing the initial film thickness (100 nm) by the time required to reach infinity.
Further, about five 100 mm square substrates, the substrate was immersed in an oxalic acid etching solution until the resistance value of the substrate became infinite, washed with pure water, dried, and then 10,000 times with a scanning electron microscope. And the number of residues present in the center 10 × 8 μm square of the field of view was counted. Observation was carried out at a total of five points of the intersection of the diagonal lines of each substrate and the center point of the intersection and the vertex. The number of the remaining residues was determined by an average value of five and defined as the etching residue as follows.
Etching residue evaluation criteria ○: 3 or less △; 4 or more, 7/100 or less ×; 8 or more

Etching residue usually remains in the form of particles in the space in the etching process, which may cause a short circuit. Such particle adhesion is undesirable because it significantly reduces device yield. When the number is small, it can be normalized by a repair process. However, when the number is increased, repair becomes difficult and the yield of the element is lowered.

(6) Average number of particles In the same manner as (5) above, a transparent conductive film having a thickness of 100 nm was formed, and the number of particles having a maximum diameter of 0.5 μm or more adhering to the transparent conductive film was determined as a particle counter (V -Measured by FPD inspection apparatus Capricorn manufactured by TECHNOLOGY. The film formation was repeated 5 times for one target, and the average value of the obtained numbers was defined as the average number of particles. The evaluation was as follows.
・ Evaluation criteria of particles ○: 5/100 mm □ or less △; 6/100 mm □ or more, 9/100 mm □ or less ×; 10/100 mm □ or more

Particles generated on the film formation substrate during sputter film formation may be open (disconnected) if missing in the next etching process, and may be short (short circuit) if left in the form of particles. is there. The wiring abnormality due to these particles is not preferable because it significantly reduces the yield of the element. When the number is small, it can be normalized by a repair process. However, when the number is increased, repair becomes difficult and the yield of the element is lowered.

Reference Examples 1 to 4 and Reference Comparative Examples 1 to 3
Weigh 5000 g of indium oxide powder having a specific surface area of 11 m ² / g and an average particle size of 0.98 μm, and 600 g of zinc oxide powder having the same specific surface area and average particle size, and the content in the obtained sputtering target is shown in Table 2. Tin oxide was weighed so as to have the content (Sn weight) shown, and a molding binder was added to uniformly mix and granulate.
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.

Next, this granulated product was uniformly filled in a mold and pressure-molded with a cold press machine. The molded body thus obtained was sintered in a sintering furnace at 1400 ° C. (temperature increase rate from 800 ° C. to sintering temperature: 2 ° C./min) for 20 hours.

About the obtained sintered compact, the crystal structure was investigated by XRD like Example 1. FIG. As a result, the presence of a hexagonal layered compound represented by In ₂ O ₃ (ZnO) _m (wherein m = 2 to 7) was confirmed in all examples.

Furthermore, with respect to the obtained sintered body, chromaticity (b * value), average crystal grain size and bulk resistance value were measured in the same manner as in the Examples. The results are shown in Table 2. The polishing depth is an arbitrarily polished depth.

From the above results, it was confirmed that it was necessary to add more than 2000 ppm of Sn element in order to reduce color unevenness on the target surface.
On the other hand, as the Sn element content is increased (added in a large amount), Δb * can be further reduced, but even if it exceeds 20000 ppm, a significant improvement effect of Δb * due to the increase in Sn element content is seen. Absent. As described above, when Sn element is added in an amount of more than 20000 ppm, excessive addition is not preferable because it may hinder the etching characteristics of the film obtained from the sputtering target.
From the above, it can be confirmed that it is appropriate to set the Sn element content in the range of more than 2000 ppm to 20000 ppm in order to lower the bulk resistance value, maintain the characteristics of indium zinc oxide, and reduce color unevenness. It was.
It was also confirmed that the amount of etching residue and particles during sputtering film formation can be suppressed by adding Zr.

The transparent conductive film produced using the sputtering target of the present invention can be used for solar cells, liquid crystal, organic electroluminescence, display elements such as inorganic electroluminescence, and electronic devices such as touch panels. The oxide film of the present invention can be used for a thin film transistor or the like as a semiconductor film.

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

Mainly composed of indium oxide and zinc oxide,
A hexagonal layered compound represented by In 2 O 3 (ZnO) m (wherein m = 2 to 7),
Contains Sn element and Zr element,
The sputtering target whose ratio of Sn element with respect to all the metal elements is more than 2000 ppm and 20000 ppm or less.
The sputtering target according to claim 1, wherein the ratio of the Zr element to the total metal elements is 50 ppm or more and 1000 ppm or less.
3. The sputtering target according to claim 1, wherein the average crystal grain size is 2 μm to 10 μm.
The sputtering target according to any one of claims 1 to 3, wherein the relative density is 95% or more.
The sputtering target according to any one of claims 1 to 4, wherein the bulk resistance value is 50 mΩcm or less.
Indium raw material, zinc raw material, Sn raw material and Zr raw material are mixed and pulverized so that the ratio of Sn element to all metal elements in the sputtering target is more than 2000 ppm and 20000 ppm or less, and the ratio of Zr element is 50 ppm or more and 1000 ppm or less. The process of producing,
The method for producing a sputtering target according to claim 1, comprising a step of molding the mixture to produce a molded product, and a step of sintering the molded product at 1200 ° C to 1600 ° C for 1 hour to 50 hours.
A method for producing an oxide film formed using the sputtering target according to any one of claims 1 to 5.
An oxide film produced by the method according to claim 7.
The oxide film according to claim 8, which is a transparent conductive film.
An electronic device using the oxide film according to claim 8 or 9.