JP2009040621A - Ito sintered body and ito sputtering target - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ITO sintered body, an ITO sputtering target material and an ITO sputtering target, capable of forming an ITO film having excellent properties with improved yield, especially an ITO sputtering target material and an ITO sputtering target, for obtaining the film having low resistance and excellent amorphous stability by using an ITO sintered body having a low bulk resistance value, and to provide a method for manufacturing the ITO sintered body suitable for the ITO sputtering target material and the ITO sputtering target. <P>SOLUTION: The ITO sintered body is an ITO (Indium-Tin-Oxide) sintered body, wherein a fine particle composed of In<SB>4</SB>Sn<SB>3</SB>O<SB>12</SB>exists in an In<SB>2</SB>O<SB>3</SB>mother phase, i.e., the main crystal grain. The fine particle has a three-dimensional star shape having needle-shaped protruding sections radially from the virtual center of the particles. <P>COPYRIGHT: (C)2009,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 made of In ₄ Sn ₃ O ₁₂ having a specific shape are present in the In ₂ O ₃ matrix that is the main crystal grain, a sputtering target material using these, and The present invention relates to an ITO sputtering target.

  The ITO film is utilized as a transparent electrode for flat panel displays because of its high permeability and electrical conductivity. This ITO film is formed by sputtering an ITO sputtering target. However, with regard to the ITO sintered body used as the sputtering target material, arcing and particles during sputtering have been conventionally used in order to improve the film formation yield. Various studies have been made to reduce or prevent the occurrence of the above. 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).

  In addition, if the bulk resistance of the ITO sintered body itself is reduced, arcing generated during sputtering during film formation can be reduced and the film formation rate can be improved, so various studies have been made. (See Patent Document 3).

  On the other hand, when forming a transparent electrode, the process of etching an ITO film is required. If the ITO film obtained by sputtering the ITO sintered body is crystallized, the resistivity of the film itself can be lowered. However, in order to etch the crystallized ITO film so that no etching residue is generated. It is necessary to use a strong acid. An etching process using such a strong acid is likely to cause many problems such as disconnection of the wiring material, and an amorphous ITO film that can be easily etched without using a strong acid is desired. It was.

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, is there a conventional relationship between the composition and shape of fine particles present in such an ITO sintered body, the bulk resistance value of the ITO sintered body, and the physical properties of the formed film? No matter was taken into consideration.
Japanese Patent No. 2750483 Japanese Patent No. 3152108 JP 2007-31786 A

  The present invention uses an ITO sintered body, an ITO sputtering target material and an ITO sputtering target, particularly an ITO sintered body having a low bulk resistance value, which can form an ITO film having excellent physical properties with a further improved yield. An object of the present invention is to provide an ITO sputtering target material and an ITO sputtering target from which a film having excellent resistance and amorphous stability can be obtained, and a method for producing an ITO sintered body suitable for them.

The inventors pay attention to the presence of fine particles composed of In ₄ Sn ₃ O ₁₂ in the In ₂ O ₃ matrix, which is the main crystal grain of the ITO sintered body, and the fine particles have a specific shape. And a causal relationship between the yield and the film formation yield and the physical properties of the film formed, the shape of fine particles composed of In ₄ Sn ₃ O ₁₂ present in the In ₂ O ₃ matrix was determined. It was found that according to the controlled ITO sintered body, it is possible to provide an ITO sputtering target material and an ITO sputtering target capable of forming an ITO film having excellent physical properties with a further improved yield, and the present invention has been completed.

That is, in the ITO sintered body according to the present invention, fine particles composed of In ₄ Sn ₃ O ₁₂ are present in the main crystal grains of In ₂ O ₃ , and the fine particles are radial from the virtual center of the particles. It has a three-dimensional star shape in which needle-like projections are formed.

The ITO sintered body according to the present invention preferably has a bulk resistance value of 1.35 × 10 ⁻⁴ Ω · cm or less.
Further, the average value of the horizontal fillet diameter of the fine particles is preferably 0.25 μm or more, and the average value of the circularity coefficient of the fine particles is preferably less than 0.8.

  These ITO sintered bodies can be preferably used as a sputtering target material, and the ITO sputtering target according to the present invention is characterized by comprising the ITO sintered body and a backing plate.

  These ITO sintered bodies are molded from a mixture of indium oxide and tin oxide, and the obtained molded body is heated to a maximum sintering temperature of 1580 to 1700 ° C. to maintain the maximum sintering temperature. The secondary sintering temperature is lowered to 1400 to 1550 ° C., the holding time of the secondary sintering temperature is set to 3 to 18 hours, and then the temperature is lowered to room temperature. Including a step of forming a non-oxidizing atmosphere when the holding time of the sintering temperature has passed at least 1 to 4 hours, and lowering the temperature from the maximum sintering temperature to 400 ° C. at an average temperature reduction rate of 10 to 100 ° C./hour. It can obtain by the manufacturing method of the ITO sintered compact concerning this invention characterized by including.

In this specification, ITO (Indium-Tin-Oxide) is usually a material obtained by adding 1 to 35 wt% tin oxide (SnO ₂ ) to indium oxide (In ₂ O ₃ ). means.

In the ITO sintered body of the present invention, since the fine particles made of In ₄ Sn ₃ O ₁₂ present in the In ₂ O ₃ matrix have a specific shape, the bulk resistance value of the ITO sintered body itself is reduced. It can be kept low. For this reason, when this is used for a sputtering target, the voltage required for sputtering can be kept low, and a stable film forming process can be performed.

  Moreover, since the sputtered film obtained by using such an ITO sputtering target has a film characteristic that is excellent in amorphous stability even at high temperatures, subsequent etching processing becomes easy.

Next, the present invention will be specifically described with reference to the drawings as necessary.
In the ITO sintered body according to the present invention, fine particles composed of In ₄ Sn ₃ O ₁₂ are present in the In ₂ O ₃ matrix which is the main crystal grain. FIG. 1 is a view showing an image obtained when this ITO sintered body is set to a magnification of 3,000 times using a scanning electron microscope (SEM: JSM-6380A, manufactured by JEOL). FIG. It is shown schematically. As shown in these figures, the ITO sintered body according to the present invention has an In ₂ O ₃ parent phase 1 which is a main crystal grain, and the parent phase 1 has a fine structure composed of In ₄ Sn ₃ O _12. A plurality of particles 2 are dispersed and precipitated.

As shown in FIG. 3, the fine particles 2 are particles observed in an image obtained when the magnification is set to 30,000 using an SEM. In the ITO sintered body according to the present invention, the composition of the fine particles 2 is In ₄ Sn ₃ O ₁₂ , which uses a transmission electron microscope (FE-TEM: JEM-2100F, manufactured by JEOL Ltd.) By analyzing the fine particles 2 by the composition analysis as described below, it can be identified as In ₄ Sn ₃ O ₁₂ .

<Composition analysis of fine particles>
In the STEM image (0.5 × 0.5 μm ² field of view) of the fine particle 2 obtained by EDX attached to the FE-TEM, a plurality of arbitrary points are extracted, and the fine particle 2 is extracted based on the analysis result at each point. Elemental analysis is performed to confirm that it is composed of In, Sn, and O. Moreover, a diffraction pattern is extracted from the electron diffraction image using TEM, and it confirms that these are the diffraction patterns from the fine particle 2. FIG.

  Next, the reciprocal lattice unit including the diffraction pattern is extracted, the reciprocal lattice spacing is measured, and all crystals of In, Sn, and O are extracted from the ICDD card. Based on these results, substance identification is performed by analysis software (electron diffraction pattern analysis software, manufactured by Nippon Steel Techno Research).

The composition analysis specifies that the fine particles 2 are In ₄ Sn ₃ O ₁₂ .
In the ITO sintered body of the present invention, the fine particles 2 have a three-dimensional star shape in which needle-like protrusions are formed radially from the virtual center of the particles. Since it has a three-dimensional star shape, at least two needle-like protrusions protrude from one fine particle 2. The tips of these acicular protrusions may be sharp or rounded, and the size of each acicular protrusion existing in one fine particle 2 may not be uniform. At least 80 to 300 fine particles 2 having such a shape are confirmed in a 3 × 4 μm ² visual field when observed by SEM.

The reason why the fine particles 2 have such a shape is not clear, but it is presumed that some crystal orientation attributed to In ₄ Sn ₃ O ₁₂ has an influence. Further, since the fine particles 2 have such a shape, each needle-like protrusion can grow through a gap generated between the needle-like protrusions. Since the fine particles 2 having such a shape can be easily overlapped with each other by effectively using a limited matrix region rather than simply having a spherical shape, the mutual growth of the particles is inhibited to some extent. Therefore, the adhesion of the fine particles 2 can be improved, and it is presumed that this has some influence on the physical properties of the resulting film.

As described above, since the ITO sintered body according to the present invention has fine particles 2 made of In ₄ Sn ₃ O ₁₂ controlled in such a specific shape in the In ₂ O ₃ matrix 1, Since the bulk resistance value of the ITO sintered body can be kept low, it is possible to improve the film formation rate while suppressing the occurrence of arcing during sputtering during film formation. Furthermore, since the film obtained when such an ITO sintered body is used as a sputtering target has excellent amorphous stability even at high temperatures, the etching process speed can be improved and the pattern can be improved. It becomes easy to make the shape good. Furthermore, the amount of etching residue can be reduced.

In the ITO sintered body of the present invention, it is desirable that the fine particles 2 have an average horizontal fillet diameter of 0.25 μm or more, preferably 0.27 to 0.50 μm, more preferably 0.30 to 0. .45 μm. The horizontal fillet diameter is a value obtained by particle analysis in the above SEM observation, and the average value of the horizontal fillet diameter is a random extraction of 20 fine particles 2 within a 3 × 4 μm ² field of view when SEM observation is performed. Means the average value of horizontal fillet diameters obtained in this way.

  Specifically, the value of the horizontal ferret diameter is obtained as follows. Using particle analysis software (particle analysis Version 3.0, manufactured by Sumitomo Metal Technology Co., Ltd.), first, an SEM image of the fine particles 2 is traced and image recognition is performed by a scanner, and this image is binarized. At this time, the conversion value is set so that one pixel is displayed in units of μm. Next, by selecting the horizontal ferret diameter as a measurement item, the value of the horizontal ferret diameter (μm) calculated from the total number of pixels in the horizontal direction of the fine particles 2 can be obtained as shown in FIG.

When the fine particle 2 shows such an average value of the horizontal fillet diameter, the size of the fine particle 2 existing in the In ₂ O ₃ matrix 1 is controlled to some extent, and the fine particle 2 has a specific shape. In addition, since the adhesion between the particles is further improved, stable sputtering can be expected when sputtering is performed using the ITO sintered body as a sputtering target. Moreover, since it becomes difficult to inhibit the flow of electrons, it is possible to reduce the bulk resistance value of the obtained ITO sintered body.

In the ITO sintered body of the present invention, it is desirable that the fine particles 2 have an average circularity coefficient of less than 0.8, preferably 0.76 to 0.4, more preferably 0.73 to 0. .49. Similar to the horizontal ferret diameter, the circularity coefficient is a value obtained by particle analysis in SEM observation, and the average value of the circularity coefficient is the fine particle 2 in the 3 × 4 μm ² field of view when observed by SEM. It means the average of the circularity coefficient values obtained by extracting 20 randomly.

Specifically, the value of the circularity coefficient is obtained as follows. Similar to the horizontal ferret diameter, particle analysis software is used to first trace the SEM image of the fine particles 2 and recognize the image with a scanner, and binarize the image. At this time, the conversion value is set so that one pixel is displayed in units of μm. Next, by selecting an area as a measurement item, the particle area (μm ² ) is obtained from the total number of pixels forming the fine particles 2 as shown in FIG. Further, by selecting the peripheral length as a measurement item, the peripheral length (μm) is obtained from the total number of pixels forming the periphery of the fine particle 2 as shown in FIG. From these values of area and perimeter, the value of the circularity coefficient calculated based on the following formula (1) can be obtained.

The value of such a circularity coefficient indicates that the shape of the fine particle 2 to be measured approaches a sphere as it approximates to 1.0.
Therefore, it is shown that the average value of the circularity coefficient of the fine particles 2 in the ITO sintered body of the present invention is not close to 1.0. Also from this, the fine particles 2 have a shape far from spherical, It is proved that it has a three-dimensional star shape in which needle-like projections are formed radially from the virtual center.

The ITO sintered body according to the present invention has a bulk resistance value of 1.35 × 10 ⁻⁴ Ω · cm or less, preferably 1.30 × 10 ⁻⁴ Ω · cm or less. The lower limit value of the bulk resistance value is not particularly limited, but is usually 9 × 10 ⁻⁵ Ω · cm or more.

By showing such a bulk resistance value, when the ITO sintered body according to the present invention is used as a sputtering target, generation of arcing can be effectively suppressed and the voltage required for sputtering can be suppressed to a low level. The film forming process can be performed. As described above, such a bulk resistance value can be realized in the ITO sintered body of the present invention, in which the fine particles 2 have a three-dimensional star shape in which needle-like protrusions are formed radially from the virtual center of the particles. This is thought to be due to the fact that

It should be noted that the region within the In ₂ O ₃ matrix 1 where the fine particles 2 are not observed when SEM observation is performed at a magnification of 3,000 times (however, the region of the compound phase existing along the grain boundary is not included). Has a fine particle free zone 5. The average width of the fine particle free zone 5 from the grain boundary 3 of the In ₂ O ₃ matrix 1 is 0.3 μm or more, preferably in the range of 0.4 to 3 μm.

Here, the average value of the width of the fine particle free zone 5 from the grain boundary 3 of the In ₂ O ₃ matrix 1 is obtained by cutting the ITO sintered body horizontally in the thickness direction using a diamond cutter. The resulting cut surface is polished step by step using emery paper # 170, # 320, # 800, # 1500, # 2000, and finally buffed to give a mirror surface. 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., deer hydrochloric acid grade 1, product number 18078-01) And water are mixed for 9 minutes in a volume ratio of HCl: H ₂ O: HNO ₃ = 1: 1: 0.08) and etched, and the appearing surface is observed by SEM at a magnification of 3,000 times and photographed SEM using photographic, located on everything (end pictures a whole can be observed in the in ₂ O ₃ matrix particle cross section by the photograph, in ₂ O ₃ In which a part of the phase grains sectional Implied is the object of measuring is excluded), of the distance from In ₂ O ₃ matrix grain boundaries to the normal direction of the fine particles 2, the shortest and the longest ones 1/2 of the sum as the width of the in ₂ O ₃ matrix microparticles free zone in the particles 5, in which it was divided by the number of the in ₂ O ₃ matrix grains measured.

If the average value of the width of the fine particle free zone 5 from the grain boundary 3 of the In ₂ O ₃ matrix 1 is within the above range, the presence of the fine particles 2 in the In ₂ O ₃ matrix 1 that is the main crystal grain Since the area that is not to be widened, the boundary with the area in which the fine particles 2 are present becomes clearer, and the fine particles 2 are present in the limited area with the highest possible density. As a result, by using such an ITO sintered body as a sputtering target, it is possible to provide an excellent ITO film with little variation in physical properties.

Next, the manufacturing method of the ITO sintered body according to the present invention will be described in detail.
The ITO sintered body of the present invention can be produced by a so-called powder metallurgy method. In the powder metallurgy method, generally, a binder is added to a raw material powder if necessary, and the resulting molded body is degreased as necessary, and then the molded body is fired to obtain a sintered body. It is necessary to perform the firing process 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.

  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 a maximum sintering temperature of 1580 to 1700 ° C., preferably 1600 to 1650 ° C. continuously or stepwise. Under the present circumstances, you may mount a molded object on a baking board as needed. From the viewpoint of the production efficiency of the obtained ITO sintered body, the average heating rate in the furnace is preferably 50 to 400 ° C./hour throughout the heating process.

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.

  When the maximum sintering temperature is reached in the heating step, the maximum sintering temperature is maintained for 300 s or less, preferably 150 s or less. The lower limit of the holding time is not particularly limited, and is most preferably instantaneous. Generally, the holding time of the maximum sintering temperature is about 3 to 20 hours, but in the present invention, the density of the obtained ITO sintered body can be further increased by making the holding time of the maximum sintering temperature extremely short. It becomes possible to improve. In the holding step, it is preferable to introduce oxygen into the furnace under the same conditions as in the heating step.

  Next, the secondary sintering temperature is lowered to 1400 to 1550 ° C., preferably 1500 to 1550, and the secondary sintering temperature is maintained for 3 to 18 hours, more preferably 5 to 15 hours. At this time, when the holding time of the secondary sintering temperature has passed at least 1 to 4 hours, preferably 2 to 3 hours, the inside of the furnace is set to a non-oxidizing atmosphere. However, the time when the non-oxidizing atmosphere is set is within the holding time of the secondary sintering temperature. For example, when the holding time of the secondary sintering temperature is 3 hours, the non-oxidizing atmosphere is set when the holding time has elapsed from 1 hour to less than 3 hours.

  Here, the non-oxidizing atmosphere means an atmosphere in which the oxygen concentration in the furnace at the end of the holding time of the secondary sintering temperature is 13% or less, specifically argon, nitrogen other than oxygen, etc. An atmosphere substituted with the inert gas is mentioned, and sintering is preferably performed in this atmosphere.

Furthermore, 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. Not only the shape of the fine particles 2 present in the In ₂ O ₃ matrix 1 which is the main crystal grain of the obtained ITO sintered body, but also the average value of the horizontal ferret diameter and circularity coefficient of the particles, and In ₂ O From the viewpoint of controlling the average value of the width of the fine particle free zone 5 from the grain boundary _{3 of the} mother phase 1, the cooling rate in the temperature region from the maximum sintering temperature to 400 ° C. is adjusted in the cooling step. The average temperature decreasing rate in this temperature region is usually 10 to 100 ° C./hour, preferably 10 to 40 ° C./hour. That is, the rate of temperature decrease from the maximum sintering temperature to the maximum temperature in the heat retention step and the average temperature decrease rate in the temperature region from the maximum temperature in the heating step to 400 ° C. are within the above range. When the average temperature drop rate in the above temperature range is within the above range, the compact after the heating step is cooled slowly, facilitating the growth of fine particles 2 in the In ₂ O ₃ matrix 1 and grain growth. Because of this, the shape of the fine particles 2 can be controlled to be specific. Moreover, it becomes easy to control the average value of the horizontal ferret diameter and the circularity coefficient of the particles to a specific value. Furthermore, since the fine particles 2 are aggregated to some extent, the average value of the width of the fine particle free zone 5 from the grain boundary of the In ₂ O ₃ matrix can be controlled to 0.3 μm or more.

In the cooling step, the temperature lowering rate in the temperature region from less than 400 ° C. to room temperature is not particularly limited. This is because, in such a temperature region, the fine particles 2 in the In ₂ O ₃ matrix 1 do not substantially grow. Specifically, the temperature lowering rate may be set as appropriate. In particular, the temperature may be allowed to cool without adjusting the temperature lowering rate and may be naturally cooled to room temperature. Even in the cooling step, the non-oxidizing atmosphere introduced in the previous step is maintained. The flow rate of the inert gas 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.

The reason is not clear, but if the above cooling process is performed in an oxygen atmosphere, the average value of the horizontal fillet diameter and circularity coefficient of the particles may be out of a specific numerical range, and it becomes difficult to control the particle shape. There is a fear. In contrast, the non-oxidizing atmosphere makes it easy for the fine particles 2 to agglomerate and precipitate at the center of the In ₂ O ₃ matrix 1 and to easily obtain the ITO sintered body of the present invention. Become.

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]
Ball mill mixing was performed by adding indium oxide (In ₂ O ₃ ) powder and tin oxide (SnO ₂ ) powder at a ratio of 90:10 (weight ratio) and adding polyvinyl alcohol (PVA) as a binder. The obtained mixed powder was compression molded at a press pressure of 800 kg / cm ² and degreased in the air to obtain a molded body.

The molded body thus obtained is placed on a fired plate and placed in a batch furnace, and oxygen gas with an oxygen concentration of 100% is allowed to flow into the furnace (1 m ³ / h per 1 m ^{3 of} furnace volume). The inside of the furnace was heated to 1600 ° C., the holding time at the temperature was set to 0 s (instantaneous), and the temperature was immediately lowered to 1550 ° C. Next, after maintaining at 1550 ° C. for 2 hours, the oxygen gas in the furnace was replaced with argon, and the temperature was further maintained for 6 hours. At this time, the oxygen concentration in the furnace was 10.8%. Then, it cooled to room temperature, keeping the gas in a furnace argon, and obtained the ITO sintered compact.

The average heating rate of the heating process at this time is 117 ° C./hour, and the average cooling rate of the cooling process in the temperature region of 1600 ° C. to 1400 ° C.
The average cooling rate of the cooling process in the temperature region of 00 ° C. was 30 ° C./hour.

The firing conditions are shown below.
<< Baking conditions >>
Room temperature (oxygen atmosphere) → (50 ° C./hr)→400° C. → (100 ° C./hr)→800° C. × 4 hr → (400 ° C./hr)→1600° C. (instantaneous) → 1550 ° C. × 2 hr → (Argon atmosphere Change) → (−10 ° C./hr)→1400° C. → (−30 ° C./hr)→300° C. → cooling → room temperature Based on the four-probe method, the bulk resistivity of the obtained ITO sintered body was constant current When measured using a voltage measuring device (manufactured by Keithley; SMU236), a measurement stand (manufactured by Kyowa Riken; K-504RS) and a four-probe probe (manufactured by Kyowa Riken; K89PS150μ), 1.34 × 10 ⁻⁴ (Ω Cm).

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) did. The obtained SEM image (magnification: 3,000 times) 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.

From the obtained SEM image, an In ₂ O ₃ results an average value of widths of micro particles free zone 5 from the grain boundary of the matrix phase, In ₂ O ₃ widths of micro particles free zone from the grain boundary of the matrix phase The average value of was 1 μm.

Next, in order to analyze the fine particles 2, the fine particles 2 were observed using FE-TEM (JEM-2100F, manufactured by JEOL Ltd.). The acceleration voltage at this time was 200 kv. First, as shown in FIG. 7, six arbitrary fine particles were extracted from the STEM image (0.5 × 0.5 μm ² visual field) containing the fine particles 2. About these, the quantitative analysis was performed using EDX attached to FE-TEM. The results are shown in Table 1.

From this result, it was found that the main elements detected were In, Sn, and O, and the fine particles 2 were composed of these elements.
FIG. 8 shows a TEM image of the portion shown in FIG. 7, and FIG. 9 shows an electron diffraction image of FIG.

  From the electron diffraction image shown in FIG. 9, a diffraction pattern DF that seems to be from the fine particles 2 was extracted. A dark field image of DF is shown in FIG. This was confirmed to be a diffraction pattern from the fine particles 2.

  Furthermore, the reciprocal lattice unit including DF was extracted, and the reciprocal lattice spacing was measured. Moreover, all the crystals made of In, Sn, and O were extracted from the ICDD card. Based on these data, the substance was identified by analysis software (substance identification support system for electron diffraction patterns, manufactured by Nippon Steel Techno Research). At this time, the error of the reciprocal lattice spacing was set to 5%, and the error of the angle was set to 2 °.

As a result, the composition of the fine particles 2 was identified as In ₄ Sn ₃ O ₁₂ of the ICDD card.
Next, the sample was observed with a TEM, and it was confirmed that there are 83 or more fine particles 2 having a three-dimensional star shape in which needle-like projections are radially formed from the virtual center of the particle within a 3 × 4 μm ² visual field. It was. Furthermore, 20 of these fine particles 2 were randomly extracted, and the horizontal fillet diameter and circularity coefficient of each particle were measured using the particle analysis software. The average value of the horizontal fillet diameter and the circularity coefficient was calculated from the obtained measured values. As a result, the average value of the horizontal fillet diameter of the fine particles 2 present in the In ₂ O ₃ matrix was 0.37 μm, and the average value of the circularity coefficient was 0.6.

  Using such an ITO sputtering target, sputtering was performed under the following conditions, and an ITO film was formed on a 150 ° C. glass substrate (manufactured by Corning; Corning # 1737, 50 mm × 50 mm × 0.8 mm).

<< 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: 1.0 × 10 ⁻³ Pa
As a result of measuring the obtained film | membrane by X-ray diffraction, the peak was not observed but it was confirmed that it is amorphous.

[Reference Example 1]
An ITO molded body was produced in the same manner as in Example 1, and the obtained molded body was placed in a batch furnace in a state of being placed on a fired plate, and oxygen gas having an oxygen concentration of 100% was allowed to flow into the furnace (in the furnace 1 m ³ / h per volume of 1 m ³ ), the furnace was heated to 1600 ° C. and held at that temperature for 8 hours, and then the oxygen gas in the furnace was replaced with the atmosphere, and the atmosphere was flowing (volume in the furnace 1 m 1 m ³ / h) per ^3, cooled to room temperature to obtain an ITO sintered body.

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

<< Baking 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 entire process)
Subsequently, when the bulk resistivity of the obtained ITO sintered body was measured by the same method as in Example 1, it was 1.68 × 10 ⁻⁴ (Ω · cm).

1 is a view showing an SEM image of the ITO sintered body of Example 1. FIG. FIG. 2 is a schematic view of an ITO sintered body structure. 3 is a view showing an SEM image of the ITO sintered body of Example 1. FIG. FIG. 4 is a schematic diagram showing the principle that the horizontal Ferre diameter is obtained from the total number of pixels in the horizontal direction using the binarized SEM image of the fine particles 2. FIG. 5 is a schematic diagram showing the principle that the area of the particle is obtained from the total number of pixels forming the particle, using the SEM image of the binarized fine particle 2. FIG. 6 is a schematic diagram showing the principle that the peripheral length is obtained from the total number of pixels forming the periphery of the particle using the binarized SEM image of the fine particle 2. FIG. 7 is a STEM image containing the fine particles 2. FIG. 8 is a TEM image of the fine particles 2. FIG. 9 is an electron diffraction image of the TEM image of FIG. FIG. 10 is a dark field image of the diffraction pattern DF extracted in FIG.

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 (7)

An ITO (Indium-Tin-Oxide) sintered body in which fine particles composed of In ₄ Sn ₃ O ₁₂ are present in the main crystal grain In ₂ O ₃ matrix, and the fine particles are separated from the virtual center of the particles. An ITO sintered body having a three-dimensional star shape in which needle-like protrusions are radially formed. The ITO sintered body according to claim 1, wherein a bulk resistance value is 1.35 × 10 ⁻⁴ Ω · cm or less.   3. The ITO sintered body according to claim 1, wherein an average value of a horizontal fillet diameter of the fine particles is 0.25 μm or more.   The ITO sintered body according to any one of claims 1 to 3, wherein an average value of a circularity coefficient of the fine particles is less than 0.8.   It is a sputtering target material, The ITO sintered compact in any one of Claims 1-4 characterized by the above-mentioned.   An ITO sputtering target comprising the ITO sintered body according to claim 1 and a backing plate. In the method of manufacturing an ITO (Indium-Tin-Oxide) sintered body,
A mixture composed of indium oxide and tin oxide is molded, and the obtained molded body is heated to a maximum sintering temperature of 1580 to 1700 ° C. to keep the maximum sintering temperature at 300 s or less, and then the second A step of lowering the secondary sintering temperature to 1400 to 1550 ° C. and setting the holding time of the secondary sintering temperature to 3 to 18 hours, and then lowering the temperature to room temperature,
Including a step of setting a non-oxidizing atmosphere when the holding time of the secondary sintering temperature has passed at least 1 to 4 hours; and
The manufacturing method of the ITO sintered compact characterized by including the process of temperature-falling from this highest sintering temperature to 400 degreeC with the average temperature-fall rate of 10-100 degreeC / hour.