JP2007211265A - Ito sintered body and ito sputtering target - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ITO sputtering target material and an ITO sputtering target capable of depositing an ITO film having excellent physical properties at low cost, and an ITO sintered body suitable for the same. <P>SOLUTION: In the ITO sintered body, the mean value of the maximum diameter of fine particles present in a mother phase of In<SB>2</SB>O<SB>3</SB>as main crystal grains is ≥0.2 μm; or the mean value of the width of the fine particle free zone from the grain boundary of the mother phase of In<SB>2</SB>O<SB>3</SB>as the main crystal grains is ≥0.3 μm; or the mean value of the maximum diameter of fine particles present in the mother phase of In<SB>2</SB>O<SB>3</SB>as the main crystal grains is ≥0.2 μm, and the mean value of the width of the fine particle free zone from the grain boundary of the mother phase of In<SB>2</SB>O<SB>3</SB>is ≥0.3 μm. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to an ITO sintered body and an ITO sputtering target. More specifically, an ITO sintered body in which fine particles of a specific size are present in the main crystal grains, In ₂ O ₃ matrix, and fine particles are present in specific areas in the In ₂ O ₃ matrix. The present invention relates to an ITO sintered body, an ITO sintered body in which fine particles of a specific size are present in a specific region in the matrix, a sputtering target material using these, and an ITO sputtering target.

  Conventionally, various studies have been made on ITO sintered bodies used as an ITO sputtering target material in order to reduce or prevent arcing and generation of particles during sputtering in order to improve the yield of film formation. For example, an attempt to prevent the occurrence of arcing by keeping the surface roughness of the ITO sputtering target within a predetermined range has been reported (see Patent Documents 1 and 2).

  Further, in recent years, in addition to the improvement of the film formation yield, improvement in the physical properties of the ITO film itself obtained by the film formation by sputtering has been demanded with the expansion of the use of the ITO film. For example, an ITO film showing a lower resistivity is desired.

  Usually, in film formation by sputtering, it is known that the resistivity of the obtained ITO film changes depending on the atmosphere during sputtering, specifically, the partial pressure of oxygen mixed in an inert gas such as argon. The oxygen partial pressure at which the resistivity of the ITO film is minimized is found, and the amount of oxygen introduced into the sputtering apparatus is controlled so that the oxygen partial pressure is controlled. If this optimum oxygen partial pressure is low, that is, if an ITO film having a lower resistivity can be formed at a low oxygen partial pressure, it is advantageous in terms of cost.

Up to now, the top data with reproducibility in ITO film is ITO film with resistivity of 7.7 × 10 ^-5 (Ω · cm) formed by Prof. Hideo Hosono et al. (See Patent Document 1 and Non-Patent Document 2). Deposition conditions; Substrate: Ultra flat YSZ (yttria stabilized zirconia) substrate, Substrate temperature: 900 ° C. Deposition method: Epitaxial growth by PLD method (Pulse Laser Deposition) There is a problem that it is not suitable for practical production and cannot be put into practical use.

By the way, when the ITO sintered body is cut horizontally in the thickness direction, the obtained cut surface is etched, and the fine structure is observed, in addition to the main crystal grains In ₂ O ₃ and the grain boundaries, In some cases, a compound phase existing in a state along the grain boundary or fine particles existing in the In ₂ O ₃ matrix may be seen. However, as far as the present inventors know, no investigation has been made on whether or not there is a relation between the microstructure of such an ITO sintered body and the film formation yield and film physical properties. .
Japanese Patent No. 2750483 Japanese Patent No. 3152108 Hiromichi Ohta, Masahiro Orita, Masahiro Hirano, Hiroaki Tanji, Hiroshi Kawazoe and Hideo Hosono, “Highly conductive conductive indium-tin-oxide thin films epitaxially grown on yttria-stabilized zirconia (100) by pulsed-laser deposition”, Appl. Phys. Lett. 76 (2000) p.2740-2742. H. OHTA, M. ORITA, M. HIRANO, and H. HOSONO, “Surface morphology and crystal quality of low resistive indium tin oxide grown on yttria-stabilized zirconia”, Journal of Applied Physics, 91 (2002) p.3547

  The present invention relates to an ITO sputtering target material and an ITO sputtering target capable of forming an ITO film having more excellent physical properties at a low cost, and in particular, an ITO sputtering target material and an ITO capable of obtaining a low resistance film under conditions suitable for industrial production. It is an object to provide a sputtering target and an ITO sintered body suitable for them.

The inventors of the present invention focused on the relationship between the fine particles in the In ₂ O ₃ matrix, which are the main crystal grains of the ITO sintered body, and the film formation yield and film physical properties. According to the ITO sintered body in which the size of the fine particles present in the In ₂ O ₃ matrix, the region where the fine particles are present, and the like are controlled, the ITO film having more excellent physical properties, particularly the low resistance ITO film As a result, it was found that an ITO sputtering target material and an ITO sputtering target capable of forming a film under conditions suitable for industrial production can be provided.

That is, the present invention relates to the following matters.
The ITO sintered body according to the present invention is characterized in that the average value of the maximum diameters of the fine particles present in the In ₂ O ₃ matrix which is the main crystal grain is 0.2 μm or more.

The ITO sintered body according to the present invention is characterized in that the average value of the width of the fine particle free zone from the grain boundary of the In ₂ O ₃ parent phase which is the main crystal grain is 0.3 μm or more.
In the ITO sintered body according to the present invention, the average value of the maximum diameters of the fine particles present in the In ₂ O ₃ matrix, which is the main crystal grain, is 0.2 μm or more, and the In ₂ O ₃ The average value of the width of the fine particle free zone from the grain boundary of the parent phase is 0.3 μm or more.

These ITO sintered bodies can be preferably used as a sputtering target material.
In addition, an ITO sputtering target according to the present invention includes the ITO sintered body and a backing plate.

  When the ITO sintered body of the present invention is used as a sputtering target, an excellent ITO film having a lower resistivity can be obtained at a low oxygen partial pressure under conditions suitable for industrial production without requiring specific conditions. This is advantageous in terms of cost.

Hereinafter, the present invention will be specifically described.
In the ITO sintered body according to the present invention, (1) the average value of the maximum diameters of the fine particles present in the In ₂ O ₃ matrix which is the main crystal grain is 0.2 μm or more, or (2) In ₂ which is the main crystal grain
The average value of the fine particle free zone width from the grain boundary of the O ₃ matrix is 0.3 μm or more, or (3) the fine particles present in the In ₂ O ₃ matrix that is the main crystal grain The average value of the maximum diameter is 0.2 μm or more, and the average value of the width of the fine particle free zone from the grain boundary of the In ₂ O ₃ matrix is 0.3 μm or more.

Here, the average value of the maximum diameters of the fine particles present in the In ₂ O ₃ matrix is a cut surface obtained by cutting the ITO sintered body horizontally in the thickness direction using a diamond cutter. Polishing step by step using Emery paper # 170, # 320, # 800, # 1500, # 2000, and finally buffing to a mirror finish, followed by etching at 40 ° C. (nitric acid (60-61% aqueous solution) , Manufactured by Kanto Chemical Co., Ltd.
Nitric acid 1.38 Deer grade 1 product number 28161-03), hydrochloric acid (35.0-37.0% aqueous solution, manufactured by Kanto Chemical Co., Ltd., hydrochloric acid deer grade 1 product number 18078-01) and water by volume ratio HCl: H ₂ O: HNO ₃ = 1: 1: 0.08) for 9 minutes to etch and etch, appear 2 μm × 2 μm area on the appearing surface (however, the grain boundary, the compound phase existing along the grain boundary, The average value of the maximum diameter of the fine particles observed in a region that does not include any of the defined free zones). The maximum diameter of the fine particles refers to the largest of the straight lines (diameters) connecting any two points on the observed cross section of the fine particles. Observation of fine particles is performed by SEM (scanning electron microscope) (magnification 30,000 times). Note that the fine particles present in the In ₂ O ₃ matrix are considered to be compounds different from In ₂ O ₃ from the SEM image, and are presumably In ₄ Sn ₃ O ₁₂ .

The fine particle free zone is a region in the In ₂ O ₃ matrix in which fine particles are not observed when SEM observation is performed at a magnification of 3,000 in the above observation method (however, in a state along the grain boundary). Does not include the region of the compound phase present). In ₂ O ₃ average of widths of micro particles free zone from the grain boundary of the matrix phase in the same conditions as in obtaining an average value of the maximum diameter of the fine particles present in the In ₂ O ₃ matrix in the above, SEM observation of the surface that appears after cutting and etching the ITO sintered body at a magnification of 3,000, and using the photographed SEM photograph, all of the cross section of the In ₂ O ₃ matrix phase grain can be observed Fine particles in the normal direction from the In ₂ O ₃ parent phase grain boundary (measured at (at the end of the photo, and those where a portion of the In ₂ O ₃ parent phase cross section is not shown) are excluded) of the distance to, the half of the sum of the shortest and longest ones and widths of micro particles free zone at the in ₂ O ₃ matrix particles, which in the number of measurement target was in ₂ O ₃ matrix grains Divided.

Below, the ITO sintered compact of said (1)-(3) which is three aspects included in this invention, and its manufacturing method are demonstrated in detail.
In the ITO sintered body of one embodiment of the present invention, (1) the average value of the maximum diameter of the fine particles present in the In ₂ O ₃ matrix which is the main crystal grain is 0.2 μm or more, preferably 0.3 μm or more. More preferably, the ITO sintered body is in the range of 0.3 to 2 μm.

In the ITO sintered body of one embodiment of the present invention, (2) the average value of the width of the fine particle free zone from the grain boundary of the In ₂ O ₃ matrix which is the main crystal grain is 0.3 μm or more, preferably It is an ITO sintered body in the range of 0.4 μm or more, more preferably 0.5 to 3 μm. When the average value of the width of the fine particle free zone is equal to or larger than the specific value, more preferably within the specific range, a region in which fine particles are not present in the main crystal grain In ₂ O ₃ matrix is widened. Therefore, the boundary with the region where the fine particles are present becomes clearer.

In the ITO sintered body of one embodiment of the present invention, (3) the average value of the maximum diameters of the fine particles present in the In ₂ O ₃ matrix which is the main crystal grain is 0.2 μm or more, preferably 0.8 μm. 3 μm or more, more preferably in the range of 0.3 to 2 μm, and the average value of the width of the fine particle free zone from the grain boundary of the In ₂ O ₃ matrix is 0.3 μm or more, preferably 0.4 μm As described above, the ITO sintered body is more preferably in the range of 0.5 to 3 μm. Thus, when fine particles of a specific size are present in a specific region in the In ₂ O ₃ matrix, both of the advantages of the ITO sintered body (1) and (2) can be obtained. Be expected. Therefore, when such an ITO sintered body is used as a sputtering target, the response to the oxygen partial pressure during film formation by sputtering becomes sharp, and an ITO film having a lower resistivity can be formed at a relatively low oxygen partial pressure. It is assumed that a film can be formed.

These ITO sintered bodies (1) to (3) can be produced by a so-called powder metallurgy method. In the powder metallurgy method, in general, a binder is added to the raw material powder as necessary, and compression molding is performed. After degreasing the obtained molded body as necessary, the molded body is fired to obtain a sintered body. In order to obtain the ITO sintered body of (1) to (3), it is necessary to perform the firing treatment among these under specific conditions.

Specifically, raw material powders such as indium oxide (In ₂ O ₃ ) and tin oxide (SnO ₂ ) are mixed in a desired ratio, a binder is added as necessary, and a compact is obtained by compression molding. The steps until the obtained molded body is degreased as necessary can be performed by commonly known means and conditions. In the present specification, ITO usually means a material obtained by adding 1 to 35% by weight of tin oxide (SnO ₂ ) to indium oxide (In ₂ O ₃ ).

Specifically, the raw material powder may be subjected to calcination and classification as necessary, and the subsequent mixing of the raw material powder can be performed by, for example, a ball mill. Thereafter, the mixed raw material powder is filled in a mold and compression-molded to produce a molded body, which may be degreased in an air atmosphere or an oxygen atmosphere, or the filtration described in JP-A-11-286002. It consists of mixed raw material powder, ion-exchanged water, and organic additives in a filter-type mold made of a water-insoluble material to obtain a compact by draining water from the ceramic raw material slurry under reduced pressure as in the conventional molding method. The slurry may be injected, and water in the slurry may be drained under reduced pressure to produce a molded body, and the molded body may be dried and degreased.

The ITO sintered body of the present invention can be obtained by firing the molded body thus obtained under specific conditions described below.
The firing treatment usually includes a heating step, a heat retention step, and a cooling step. The furnace that can be used for the firing treatment is not particularly limited as long as it has a known structure.

  In the heating step, the molded body is placed in a furnace, and the inside of the furnace is heated to 1400 to 1600 ° C, preferably 1550 to 1600 ° C, continuously or stepwise. Under the present circumstances, you may mount a molded object on a baking board as needed. From the viewpoint of production efficiency of the obtained ITO sintered body, it is preferable that the average temperature rising rate in the furnace throughout the heating process is 50 to 400 ° C./hour.

Further, from the viewpoint of improving the density of the obtained ITO sintered body, the heating step is preferably performed in an oxygen atmosphere by introducing oxygen into the furnace. The flow rate of oxygen introduced into the furnace is usually in the range of 0.1 to 500 m ³ / hour per 1 m ^{3 of} the furnace volume.

  Next, in the heat retaining step, the maximum temperature heated in the heating step is maintained for a predetermined time. The holding time is usually 2 to 30 hours considering production efficiency. In the holding step, it is preferable to introduce oxygen into the furnace under the same conditions as in the heating step.

Next, in the cooling step, the inside of the furnace is cooled continuously or stepwise to room temperature, and the molded body that has undergone the heating step and the heat retaining step is cooled. The average value of the maximum diameter of fine particles existing in the In ₂ O ₃ matrix, which is the main crystal grain of the obtained ITO sintered body, and the average width of the fine particle free zone from the grain boundary of the In ₂ O ₃ matrix From the viewpoint of controlling the value, it is desirable to adjust the rate of temperature decrease in the temperature range from the highest temperature in the heat retaining step (same as the highest temperature in the heating step) to 400 ° C. in the cooling step. The average rate of temperature drop in this temperature region is usually 30 ° C./hour or more and less than 100 ° C./hour, preferably 30 to 40 ° C./hour. When the temperature drop rate in the temperature range is within the above range, the molded body after the heating step is slowly cooled, and thus the growth of fine particles in the In ₂ O ₃ matrix is promoted and coarsened. The average value of the maximum diameter of the particles can be controlled to 0.2 μm or more, and furthermore, since the fine particles are aggregated to some extent, the average value of the width of the fine particle free zone from the grain boundary of the In ₂ O ₃ matrix is set to 0. It can be controlled to 3 μm or more.

On the other hand, the cooling rate in the temperature region from less than 400 ° C. to room temperature is not particularly limited in the cooling step. This is because, in such a temperature region, the fine particles in the In ₂ O ₃ matrix do not substantially grow. Specifically, the temperature lowering rate may be set as appropriate, and in particular, the temperature may be allowed to cool without adjusting the temperature lowering rate and then naturally cooled to room temperature.

Further, the average value of the maximum diameter of fine particles existing in the In ₂ O ₃ matrix, which is the main crystal grain of the obtained ITO sintered body, the width of the fine particle free zone from the grain boundary of the In ₂ O ₃ matrix From the viewpoint of controlling the average value, it is desirable that the cooling step be performed in an oxygen atmosphere by introducing oxygen under the same conditions as the heating step.

Although the reason is not clear, when an oxygen atmosphere perform the cooling step, In ₂ O ₃ growth of the fine particles in the matrix phase is promoted, in addition to the average value of the maximum diameter is increased, is the fine particles In ₂ It becomes easy to obtain the ITO sintered body of the present invention by aggregating and precipitating at the center of the O ₃ matrix.

The ITO sintered body thus obtained can be preferably used as a sputtering target material after being cut into a desired shape and ground, if necessary.
Furthermore, an ITO sputtering target can be obtained by joining the ITO sintered body and a backing plate that is a cooling plate.

  In this case, the backing plate may be any one that is normally used as a backing plate for a sputtering target, and examples thereof include a copper or copper alloy backing plate. Moreover, the shape may be a known one and is not particularly limited.

  Joining of the ITO sintered body and the backing plate can be appropriately performed by a known method and is not particularly limited, but from the viewpoint of cost and productivity, a method of joining via a bonding agent such as In solder is preferable. Can be mentioned. Specifically, the ITO sintered body is cut into a desired shape as necessary, and after grinding or the like as necessary, the ITO sintered body is heated to a temperature equal to or higher than the melting point of In solder, and the ITO is maintained while maintaining the temperature. Bonding can be performed by applying a molten In solder to the surface of the sintered body to be bonded to the backing plate, bonding it to the backing plate, allowing to cool while being pressurized, and cooling to room temperature.

  EXAMPLES Hereinafter, although this invention is demonstrated further more concretely based on an Example, this invention is not limited to these Examples.

[Example 1]
A degreased ITO molded body (In ₂ O ₃ : SnO ₂ (weight ratio) = 90: 10) is placed in a batch furnace in a state of being placed on a fired plate, and an oxygen gas having an oxygen concentration of 100% is allowed to flow into the furnace. (1 m ³ / h per 1 m ^{3 in the} furnace volume), the inside of the furnace was heated to 1600 ° C., kept at this temperature for 8 hours, and then cooled to room temperature to obtain an ITO sintered body.

The average heating rate of the heating process at this time is 117 ° C./hour, 1600 ° C. to 400
The average temperature drop rate of the cooling process in the temperature range of 30 ° C. was 30 ° C./hour.
The firing conditions are shown below.

Firing conditions;
Room temperature → (50 ° C./hr)→400° C. → (100 ° C./hr)→800° C. × 4 hr → (400 ° C./hr
) → 1600 ° C. × 8 hr → (−30 ° C./hr)→300° C. → cooling → room temperature (oxygen flow atmosphere throughout the whole process)

Next, the cut surface obtained by cutting the ITO sintered body with a diamond cutter horizontally in the thickness direction at a position 5 mm from the upper surface at the time of sintering was used as an emery paper # 170, # 320, # 800, Using # 1500 and # 2000, each of them is polished stepwise by rotating 90 degrees, and finally buffed to give a mirror finish. Then, an etching solution of 40 ° C. (nitric acid (60-61% aqueous solution, Kanto Chemical ( Nitric acid 1.38 Deer grade 1 product number 28161-03), hydrochloric acid (35.0-37.0% aqueous solution, manufactured by Kanto Chemical Co., Ltd., deer grade 1 product number 18078-01) and water in HCl: H by volume ratio ₂ O: HNO ₃ = 1: 1: 0.08) and soaked for 9 minutes to etch, and the exposed surface was observed with SEM at magnifications of 3,000 and 30,000 (JSM-6380A; manufactured by JEOL) and, the average value of the maximum diameter of the fine particles present in the in ₂ O ₃ matrix and in the in ₂ O ₃ matrix The average value of widths of micro particles free zone from the field were determined, respectively.

As a result, the average value of the maximum diameter of the fine particles present in the In ₂ O ₃ matrix in is 0.3 [mu] m, In ₂ O ₃ average of widths of micro particles free zone from the grain boundary of the matrix phase is 1μm Met.
The SEM image (magnification: 3,000 times) of the ITO sintered body at this time is shown in FIG. 1, and the SEM image (magnification: 30,000 times) obtained by further enlarging the fine particle group portion is shown in FIG.

FIG. 3 schematically shows a part of the structure of the ITO sintered body (however, FIG. 3 schematically shows the structure of the ITO sintered body in an exaggerated manner for the purpose of explanation). Yes, the dimensions and ratios of each component are different from the actual product). In FIG. 3, reference numeral 10 denotes an ITO sintered body as a whole. Fine particles 2 are present in the In ₂ O ₃ matrix 1 which is the main crystal of the ITO sintered body 10, and further, a grain boundary 3 The compound phase 4 exists in the state along. There is also a fine particle free zone 5 which is a region in the In ₂ O ₃ matrix 1 where no fine particles 2 are observed.

  Next, the ITO sintered body was cut out to an appropriate size and ground with a surface grinder to obtain an ITO sputtering target material having a diameter of 200 mm and a thickness of 8 mm. The obtained ITO sputtering target material was joined to a copper backing plate via In solder to produce an ITO sputtering target.

  Using this ITO sputtering target, sputtering was performed by changing the oxygen partial pressure in the sputtering apparatus under the following conditions, and a glass substrate at 100 ° C. or 250 ° C. (manufactured by Corning; Corning # 1737, 50 mm × 50 mm × 0. 8 mm), an ITO film was formed. The resistivity of the ITO film was measured by ResiTest 8308 (manufactured by Toyo Technica) based on the van der Pauw method.

As a result, the optimum oxygen partial pressure at a glass substrate temperature of 100 ° C. was 9.3 × 10 ⁻³ (Pa), and the resistivity of the ITO film at that time was 3.74 × 10 ⁻⁴ (Ω · cm). It was. The optimum oxygen partial pressure at a glass substrate temperature of 250 ° C. was 8.1 × 10 ⁻³ (Pa), and the resistivity of the ITO film at that time was 1.99 × 10 ⁻⁴ (Ω · cm). .
The results are summarized and shown in Tables 1 and 2 and FIGS.

<Sputtering conditions>
Deposition conditions:
Equipment: DC magnetron sputtering equipment, exhaust system; cryopump, rotary pump Ultimate vacuum: 3.0 × 10 ⁻⁶ Pa
Sputtering pressure: 0.4 Pa (nitrogen conversion value, Ar pressure),
Oxygen partial pressure; 4.5-13 × 10 ⁻³ Pa
Input power: 600 W (1.85 W / cm ² )
Substrate temperature: 100 ° C, 250 ° C
Film thickness: 1200mm
Glass substrate; Corning # 1737 (plate thickness 0.8mm)

[Comparative Example 1]
In accordance with the firing conditions shown below, the average temperature drop rate of the cooling process in the temperature range of 1600 ° C. to 400 ° C. is set to 175 ° C./hour, and the oxygen gas in the furnace is replaced with the atmosphere during the cooling process. An ITO sintered body was obtained in the same manner as in Example 1 except that the flow rate was 1 m ³ / h per 1 m ^{3 of the} internal volume.

Firing conditions;
Room temperature → (50 ° C./hr)→400° C. → (100 ° C./hr)→800° C. × 4 hr → (400 ° C./hr
) → 1600 ° C. × 8 hr → (−175 ° C./hr)→300° C. → cooling → room temperature The obtained ITO sintered body was treated in the same manner as in Example 1, and the surface that appeared was observed by SEM. ₂ O ₃ to obtain an average value of the average value and the in ₂ O ₃ widths of micro particles free zone from the grain boundary of the matrix phase of the maximum diameter of the fine particles present in the mother phase.

As a result, an In ₂ O ₃ average value of the maximum diameter of the fine particles present in the mother phase is 0.13μm, In ₂ O ₃ average of widths of micro particles free zone from the grain boundary of the matrix phase is 0 .2 μm. The SEM image (magnification: 3,000 times) at this time is shown in FIG. 6, and the SEM image (magnification: 30,000 times) obtained by further enlarging the fine particle group portion is shown in FIG.

  Subsequently, an ITO sputtering target having the same shape and the same size was produced in the same manner as in Example 1. An ITO film was formed under the same conditions and method as in Example 1 except that this ITO sputtering target was used, and the resistivity of this ITO film was measured.

As a result, the optimum oxygen partial pressure at a glass substrate temperature of 100 ° C. was 1.18 × 10 ⁻² (Pa), and the resistivity of the ITO film was 3.96 × 10 ⁻⁴ (Ω · cm). The optimum oxygen partial pressure at a glass substrate temperature of 250 ° C. was 1.06 × 10 ⁻² (Pa), and the resistivity of the ITO film at that time was 2.03 × 10 ⁻⁴ (Ω · cm). The results are collectively shown in Tables 1 and 2 and FIGS. 4 and 5.

  From Tables 1 and 2 and FIGS. 4 and 5, the ITO sputtering target using the ITO sintered body of Example 1 has a sharper response to the oxygen partial pressure during film formation than that of Comparative Example 1, An ITO film with low resistivity and excellent conductivity can be formed by controlling oxygen partial pressure appropriately during sputtering under conditions suitable for industrial production without setting specific film formation conditions. I understand that I can do it.

1 is a view showing an SEM image of the ITO sintered body of Example 1. FIG. 2 is a view showing an SEM image of the ITO sintered body of Example 1. FIG. FIG. 3 is a schematic view of an ITO sintered body structure. FIG. 4 is a graph showing the relationship between the resistivity of an ITO film formed on a glass substrate at 100 ° C. and the oxygen partial pressure. FIG. 5 is a graph showing the relationship between the resistivity of the ITO film formed on a glass substrate at 250 ° C. and the oxygen partial pressure. 6 is a view showing an SEM image of the ITO sintered body of Comparative Example 1. FIG. FIG. 7 is a view showing an SEM image of the ITO sintered body of Comparative Example 1.

Explanation of symbols

1: In ₂ O ₃ matrix 2: Fine particles 3: Grain boundary 4: Compound phase 5: Fine particle free zone 10: ITO sintered body

Claims (5)

An ITO (Indium-Tin-Oxide) sintered body characterized in that the average value of the maximum diameter of fine particles present in the In ₂ O ₃ matrix, which is the main crystal grain, is 0.2 μm or more. An ITO (Indium-Tin-Oxide) sintered body characterized in that the average value of the fine particle free zone width from the grain boundary of the In ₂ O ₃ matrix which is the main crystal grain is 0.3 μm or more. The average value of the maximum diameter of the fine particles existing in the In ₂ O ₃ matrix which is the main crystal grain is 0.2 μm or more, and the fine particle free zone from the grain boundary of the In ₂ O ₃ matrix An ITO (Indium-Tin-Oxide) sintered body having an average width of 0.3 μm or more.   It is a sputtering target material, The ITO sintered compact in any one of Claims 1-3 characterized by the above-mentioned.   An ITO sputtering target comprising the ITO sintered body according to any one of claims 1 to 3 and a backing plate.