JP5526905B2 - Method for producing conductive oxide sintered body - Google Patents

Description

  The present invention relates to a method for producing a conductive oxide sintered body, and more particularly to a method for producing a conductive oxide sintered body that is preferable as a target for forming an oxide semiconductor film by sputtering.

  Conventionally, an amorphous silicon film has been mainly used as a channel layer of a thin film transistor (TFT) in a liquid crystal display device, a thin film EL (electroluminescence) display device, an organic EL display device and the like.

  However, in recent years, as such a semiconductor film, an amorphous semiconductor film containing an In—Ga—Zn-based composite oxide (generally abbreviated as IGZO) as a main component is used as a carrier compared to an amorphous silicon film. Has attracted attention because of its high mobility (see, for example, Japanese Patent Application Laid-Open No. 2008-199005 of Patent Document 1). This Patent Document 1 discloses that an amorphous oxide semiconductor film is formed by a sputtering method using a target. And the target is the sintered compact of the oxide powder which shows electroconductivity.

JP 2008-199005 A

In the conventional manufacturing method of an IGZO sintered body, powders of In ₂ O ₃ , Ga ₂ O ₃ and ZnO are mixed and calcined and then pulverized, and a molded body made from the pulverized powder is sintered. doing. Alternatively, a compact is produced after mixing powders of In ₂ O ₃ , Ga ₂ O ₃ and ZnO, and the compact is sintered. In the sintering process of these manufacturing methods, In ₂ O ₃ , Ga ₂ O ₃ and ZnO are densified while reacting with each other, and a combination of four types of powders (In ₂ O ₃ and Ga ₂ O ₃ ; Ga ₂ O ₃ and ZnO; In ₂ O ₃ and ZnO; and In ₂ O ₃ , Ga ₂ O _3, and ZnO), a sintered body is formed through a complicated process. . Therefore, even if the conductive oxide is sintered under the same conditions, it is difficult to obtain a sintered body that stably includes a desired crystal phase unless the different powders are in contact with each other. It is difficult to control the type and amount of desired crystal phase contained in the body.

  Accordingly, an object of the present invention is to provide a method for producing a conductive oxide sintered body that can easily control the type and amount of crystal phases contained in the conductive oxide sintered body.

According to the present invention, a method for producing a conductive oxide sintered body including a crystal phase of In ₂ Ga ₂ ZnO ₇ and Ga ₂ ZnO ₄ is prepared by preparing a mixture of zinc oxide and gallium oxide at 800 ° C. or higher and 1300 or higher. A step of forming a Ga ₂ ZnO ₄ powder by calcining in an oxygen atmosphere or an air atmosphere at a temperature equal to or lower than ° C., and a Ga ₂ ZnO ₄ powder and a powder containing In and O for 12 hours or more Mixing or grinding and mixing in a time within a range of less than 36 hours , satisfying at least one condition of a specific surface area of 11 m ² / g to 15 m ² / g and an average particle diameter of 1.0 μm to 1.5 μm the second mixture was prepared, and a step of sintering at the second molded product of the mixture of the prepared and the temperature of 1350 ° C. or higher 1400 ° C. or less in an oxygen atmosphere or an air atmosphere the formed body It is characterized in Mukoto.

In the production method of the present invention, pre-Ga ₂ O ₃ powder by mixing a ZnO powder to form a stable Ga ₂ ZnO ₄ powder by calcining, mixing followed by adding powder containing In and oxygen Alternatively, pulverize and mix and shape and sinter the mixture. Therefore, since there is only one kind of combination of different kinds of powders during calcination and sintering, the reaction is simplified, and a desired crystal phase can be easily obtained in the sintered body.

In general, if the sintering temperature is set to a certain high temperature (generally 1500 ° C. or higher), a sintered body composed of a kind of crystal phase (for example, In ₂ Ga ₂ ZnO ₇ or InGaZnO ₄ ) can be obtained. In the production method of the present invention, a sintered body composed of a kind of crystal phase can be produced even at a relatively low sintering temperature. By reducing the sintering temperature, it is possible to suppress the growth of crystal grains constituting the sintered body and reduce the particle size. Reduction of the crystal grain size in the sintered body is desirable depending on the application in which the sintered body is used. For example, when the sintered body is used as a sputtering target, the reduction in crystal grain size can reduce the pore diameter inside the sintered body and contribute to the reduction of nodules. Note that nodules are protrusions that appear on the surface of the target during sputtering, and if this occurs, particles on the film deposited by sputtering increase and the film quality deteriorates.

As described above, according to the present invention, the method for producing a conductive oxide sintered body containing In, Ga, and Zn is prepared by preparing a mixture of zinc oxide and gallium oxide and calcining the mixture. It includes a step of forming Ga ₂ ZnO ₄ powder.

The conductive oxide sintered body containing In, Ga, and Zn is generally abbreviated as IGZO as described above. However, in the IGZO according to the present invention, additional elements other than In, Ga and Zn may be added. Examples of elements to be added include N, Al, Si, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, W, Sn, and Bi, but are not limited thereto. The additional element may be added at the time of forming the Ga ₂ ZnO ₄ powder, or may be mixed in a subsequent process.

As the crystal phase of the obtained sintered body, by changing the sintering temperature, an In ₂ O ₃ —Ga ₂ ZnO ₄ mixed phase, an In ₂ Ga ₂ ZnO ₇ —Ga ₂ ZnO ₄ mixed phase, and InGaZnO ₄ —Ga _{2 are used.} A ZnO ₄ mixed phase, an In ₂ Ga ₂ ZnO ₇ single phase, an InGaZnO ₄ single phase, an In ₂ Ga ₂ ZnO ₇ —InGaZnO ₄ mixed phase, or the like can be obtained.

In the present invention, a Ga ₂ ZnO ₄ powder obtained by calcination and a powder containing In and O are mixed or pulverized and mixed to prepare a mixture, a molded body of the mixture is produced, and the molded body is sintered. It is preferable to include the process to tie. Examples of the powder containing In and O include In ₂ O ₃ , In ₂ Zn ₄ O ₇ , and InGaO ₃ , but are not limited thereto. However, it is preferable to use In ₂ O ₃ from the viewpoint of reducing the sintering temperature.

The calcination temperature for obtaining the Ga ₂ ZnO ₄ powder is preferably 800 ° C. or higher and 1300 ° C. or lower. In the calcination of less than 800 ° C., ZnO and Ga ₂ O ₃ remaining in the calcined powder react with In ₂ O ₃ during sintering to cause non-uniformity of the sintered body and sintering. This is not preferable because the density of the sintered body is reduced due to the generation of pores due to volume shrinkage. On the other hand, calcination exceeding 1300 ° C. is not preferable because it is difficult to pulverize due to the strong setting of the calcined powder, and the activity of the powder becomes low and sintering becomes difficult.

Further, calcination to obtain a Ga ₂ ZnO ₄ powder is preferably performed in an oxygen atmosphere or an air atmosphere. Zn and Ga are in a reduced metal state and have a low vapor pressure, and ZnO has the property of being easily sublimated. If there is not enough oxygen in the calcining atmosphere, part of the metal element is reduced, and it becomes impossible to obtain a Ga ₂ ZnO ₄ powder that is easy to grind. Therefore, the calcining atmosphere is preferably an oxygen atmosphere or an air atmosphere, and the air atmosphere is more preferable from the viewpoint of obtaining a Ga ₂ ZnO ₄ powder having a small particle size.

The mixing time of the Ga ₂ ZnO ₄ powder and the powder containing In and O is preferably 12 hours or more and less than 36 hours. If the mixing time is less than 12 hours, the powder particle size is too large to obtain a dense sintered body, and the Ga ₂ ZnO ₄ powder is not sufficiently pulverized and has a non-uniform structure. Become. On the other hand, if the mixing time is 36 hours or more, impurities due to wear of the mixing apparatus and powder are mixed, which is not preferable. In addition, the powder becomes bulky and difficult to handle, and the powders are agglomerated and become inhomogeneous, which is not preferable.

The mixture of the Ga ₂ ZnO ₄ powder and the powder containing In and O has a specific surface area of 11 m ² / g to 15 m ² / g and an average particle size of 1.0 μm to 1.5 μm. It is preferable that at least one of the conditions is satisfied. When the specific surface area of the dry powder is less than 11 m ² / g and the average particle size exceeds 1.5 μm, the powder particle size is too large to obtain a dense sintered body and the Ga ₂ ZnO ₄ powder is not pulverized. This is not preferable because it becomes sufficient and the structure of the sintered body becomes uneven. On the other hand, when the specific surface area exceeds 15 m ² / g and the average particle diameter is less than 1 μm, the powder becomes bulky and difficult to handle, and the powder is agglomerated and the sintered body is non-uniform. This is not preferable.

The following oxide powders (1) to (3) were weighed and used as raw materials. The specific surface area of the powder was measured by the BET method, and the average particle size was measured by a light scattering type particle size distribution analyzer.
(1) Ga ₂ O ₃ : 1.0 mol, average particle size 0.77 μm, specific surface area 18.9 m ² / g
(2) ZnO: 1.0 mol, average particle size 0.82 μm, specific surface area 4.6 m ² / g
(3) In ₂ O ₃ : 1.0 mol, average particle size 3.45 μm, specific surface area 13.4 m ² / g
The weighed raw material (1) Ga ₂ O ₃ powder and raw material (2) ZnO powder were wet-mixed for 12 hours using a ball mill. Note that a 5 mmφ ZrO ₂ ball was used as a wet-mixing medium. Then, the mixed slurry obtained by wet mixing was naturally dried and divided into samples 1a to 1e.

Samples 1a, 1b, 1c, 1d, and 1e were calcined at temperatures of 750 ° C., 800 ° C., 950 ° C., 1300 ° C., and 1350 ° C., respectively, in an atmospheric furnace. Then, the crystal phase contained in the calcined powder was examined by X-ray diffraction. As a result, the presence of ZnO and Ga ₂ O ₃ crystals was confirmed in the powders of samples 1a and 1b calcined at 750 ° C. and 800 ° C., and in the powders of samples 1c to 1e calcined at 950 ° C. or higher. Then, the presence of Ga ₂ ZnO ₄ crystals was confirmed. In the powder calcined at a temperature lower than 800 ° C., ZnO and Ga ₂ O ₃ contained in the powder react with In ₂ O ₃ during the subsequent sintering to cause non-uniformity of the sintered body, and sintering. This is not preferable because the density of the sintered body is reduced due to the generation of pores due to volume shrinkage. In addition, a powder calcined at a temperature exceeding 1300 ° C. is not preferable because it is difficult to pulverize due to the strong setting of the powder, and it becomes difficult to sinter because the activity of the powder becomes low.

The raw material (3) In ₂ O ₃ powder was added to the obtained calcined powder and mixed for 12 hours by a ball mill. The mixed slurry thus obtained was vacuum dried at 300 ° C. after natural drying. The dried powder was molded under a pressure of 200 kg / cm ^{2 by} a hydraulic press, and further molded under a pressure of ² ton / cm ^{2 by} CIP (cold isostatic treatment). And this molded object was sintered at 1300 degreeC in the atmospheric furnace. As a result of measuring the density of the obtained sintered body by the Archimedes method, the sintered body produced from the powder of the sample 1a calcined at 750 ° C. has a relative density of 94.3%, and temporarily measured at 800 to 1300 ° C. Relative density is about 98-99% in the sintered body made from the fired sample 1b-1d powder and relative to the sintered body made from the sample 1e powder calcined at a temperature above 1300 ° C. The density was 95.2%. These results are summarized in Table 1.

Further, when the sintered body was scraped to a thickness of 1.0 mm with a surface grinder and the crystal phase analysis was performed by X-ray diffraction, the sintered body prepared from the powders of samples 1a and 1b calcined at 750 ° C. and 800 ° C. In the sintered body, the presence of ZnO, Ga ₂ ZnO ₄ and In ₂ O ₃ crystals was confirmed, and in the sintered body prepared from the powders of samples 1c to 1e calcined at 950 ° C. or higher, Ga ₂ ZnO ₄ and In _{2 were obtained.} The presence of O ₃ crystals was confirmed.

Furthermore, the grain size of the crystalline phase of the sintered body was confirmed by the contrast difference in the reflected electron image of an analytical scanning electron microscope (SEM). More specifically, the crystal phase corresponding to each contrast was identified by fluorescent X-ray analysis, and the average particle size was calculated by measuring the diameter of 20 particles for each crystal phase. As a result, in the sintered body prepared from the powder of the sample 1a calcined at 750 ° C., the ZnO particle size was 1.3 μm, the Ga ₂ ZnO ₄ particle size was 13.6 μm, and the In ₂ O ₃ particles The diameter was 10.1 μm. In the sintered body prepared from the powder of sample 1b calcined at 800 ° C., the particle size of ZnO is 0.7 μm, the particle size of Ga ₂ ZnO ₄ is 6.0 μm, and the particle size of In ₂ O ₃ is It was 1.7 μm. In the sintered body produced from the powders of samples 1c to 1d calcined at 950 to 1300 ° C., the particle size of Ga ₂ ZnO ₄ is about _{2 to 6} μm, and the particle size of In ₂ O ₃ is about 1 to 2 μm. Met. Then, in the sintered body produced from the powder of calcined sample 1e at a temperature exceeding 1300 ° _C., with a grain size of Ga 2 ZnO ₄ is 19.4Myuemu, the particle size of the _In 2 _{O 3} is at 8.3μm there were. These results are also summarized in Table 1.

Furthermore, the ratio of the crystal phase in the cross-sectional area of the sintered body was examined from observation of the reflected electron image of the analytical SEM. As a result, in the sintered body produced from the powder of sample 1a calcined at 750 ° C., ZnO: Ga ₂ ZnO ₄ : In ₂ O ₃ = 32: 18: 50, and sample 1b calcined at 800 ° C. Sintered body manufactured from the powders of samples 1c to 1e calcined at 950 to 1350 ° C. with ZnO: Ga ₂ ZnO ₄ : In ₂ O ₃ = 25: 26: 49 Oite _Ga 2 _{ZnO 4:} was _{in 2 O 3 = (47~52)} :( 48~53). These results are also summarized in Table 1.

Table 1 also shows the specific resistances of the sintered bodies made from the powders of samples 1a to 1e, and small specific resistances in the sintered bodies of samples 2b to 2d whose calcining temperature is 800 ° C. or higher and 1300 ° C. or lower. It can be seen that is preferably obtained. In addition, as can be seen from Table 1, the calcining temperature is in the range of higher than 800 ° C. and 1300 ° C. or lower, and the case where only the Ga ₂ ZnO ₄ phase is included as the crystal phase after calcination, It is preferable from the viewpoint of obtaining a high density of the body.

Also in Example 2, as in Example 1, the raw material (1) Ga ₂ O ₃ powder and the raw material (2) ZnO powder were wet-mixed by a ball mill to form a mixed slurry. This mixed slurry was naturally dried and then calcined at 950 ° C. in an atmospheric furnace. In ₂ O ₃ powder of the above raw material (3) is added to the obtained calcined powder and mixed for 6 hours, 12 hours, 24 hours, and 36 hours with a ball mill to prepare mixed slurries of samples 2a to 2d, respectively. It was.

These mixed slurries were vacuum dried at 300 ° C. after natural drying. When the particle diameters of the dry powders of Samples 2a to 2d were examined with a particle size distribution analyzer and the specific surface area was examined with a BET measuring device, the dry powder of Sample 2a mixed for 6 hours had a particle size of 5.7 μm and 8.7 m. The dry powders of Samples 2b to 2c having a specific surface area of ² / g and mixed for 12 to 24 hours have a particle size of about 1.0 to 1.5 μm and a specific surface area of about 12 to 14 m ² / g. And the dry powder of Sample 2d mixed for 36 hours had a particle size of 0.86 μm and a specific surface area of 16.3 m ² / g. These results are summarized in Table 2.

When the particle size of the dry powder exceeds 1.5 μm, the pulverization of the Ga ₂ ZnO ₄ powder is insufficient, and a dense sintered body cannot be obtained due to the influence of the powder particle size. This is not preferable because non-uniformity of the conductive oxide is generated and electric characteristics are hindered. On the other hand, when the particle size of the dry powder is less than 1 μm, impurities are mixed into the mixture due to wear of the mixing device and the powder, so that the film is formed by sputtering using a conductive oxide obtained by sintering the mixture as a target. Further, it is not preferable because it causes deterioration of electrical characteristics and transmission characteristics of the oxide semiconductor film. Further, when the particle size is less than 1 μm, the powder becomes bulky and difficult to handle, and the powder is agglomerated and the sintered body becomes non-homogeneous.

The dry powders of Samples 2a to 2d were molded under a pressure of 200 kg / cm ^{2 with} a hydraulic press, and further molded under a pressure of ² ton / cm ^{2 with} CIP. These molded bodies were sintered at 1300 ° C. in an atmospheric furnace in the same manner as in Example 1. When the density of these sintered bodies was measured by the Archimedes method, the relative density of the sintered body produced from the powder of the sample 2a mixed for 6 hours was 94.0%, and the sample 2b mixed for 12 to 24 hours The relative density of the sintered body made from the powder of ~ 2c was about 98-100%, and the relative density of the sintered body made from the powder of sample 2d mixed for 36 hours was 96.9%. These results are also summarized in Table 2.

Further, when the sintered body was scraped to a thickness of 1.0 mm with a surface grinder and the crystal phase analysis was performed by X-ray diffraction, in the sintered body prepared from any powder of samples 2a to 2d having different mixing times Also, the presence of crystals of Ga ₂ ZnO ₄ and In ₂ O ₃ was confirmed. Further, the grain size of the crystal phase of the sintered body was confirmed by the contrast difference of the reflected electron image of the analytical SEM described above. As a result, in the sintered body of Sample 2a mixed for 6 hours, the particle size of Ga ₂ ZnO ₄ was 12.9 μm and the particle size of In ₂ O ₃ was 4.6 μm. In the sintered bodies of Samples 2b to 2c mixed for 12 to 24 hours, the particle size of Ga ₂ ZnO ₄ was about 1 to ₃ μm and the particle size of In ₂ O ₃ was about 1 to 2 μm. . Furthermore, in the sintered body of the sample 2d mixed for 36 hours, the particle size of Ga ₂ ZnO ₄ was 6.4 μm, and the particle size of In ₂ O ₃ was 5.7 μm. These results are also summarized in Table 2.

  Table 2 also shows the specific resistance of the sintered bodies made from the powders of Samples 2a to 2d, and the small specific resistances in the sintered bodies of Samples 2b to 2c having a mixing time of 12 hours or more and less than 36 hours. It turns out that it is obtained preferably.

(Examples 3a to 3e)
Step 1: Grinding and mixing raw material powder Ga ₂ O ₃ powder (purity 99.99%, BET specific surface area 11 m ² / g) and ZnO powder (purity 99.99%, BET specific surface area 4 m ² / g) Was pulverized and mixed for 3 hours to prepare a Ga ₂ O ₃ —ZnO mixture as the first mixture. In this case, the molar mixing ratio is Ga ₂ O ₃ : ZnO = 1: 1. Note that water was used as a dispersion medium in the pulverization and mixing. The first mixture after pulverization and mixing was dried with a spray dryer.

Step 2: Calcination The obtained first mixture is placed in an alumina crucible and subjected to calcination for 5 hours at a temperature of 900 ° C. in an air atmosphere, thus calcination consisting of crystalline Ga ₂ ZnO _4. A powder was obtained.

Step 3: Grinding and mixing with In ₂ O ₃ powder The obtained Ga ₂ ZnO ₄ calcined powder and In ₂ O ₃ powder (purity 99.99%, BET specific surface area 5 m ² / g) And pulverized and mixed for 6 hours, thereby producing a Ga ₂ ZnO ₄ —In ₂ O ₃ mixture as the _second mixture. The molar mixing ratio at this time is Ga ₂ ZnO ₄ : In ₂ O ₃ = 1: 1. In this case, water was also used as a dispersion medium for pulverization and mixing. The second mixture after pulverization and mixing was also dried with a spray dryer.

Step 4: Molding and Sintering The resulting second mixture, Ga ₂ ZnO ₄ —In ₂ O ₃ mixed powder, is molded by pressing, further pressure-molded by CIP, and a circle having a diameter of 100 mm and a thickness of about 9 mm. A plate-like molded body was obtained. The obtained molded body was fired at a predetermined temperature for 5 hours in an oxygen atmosphere, whereby a sintered body was obtained. In addition, each sintering temperature regarding Example 3a-3e at this time is collectively shown in Table 3.

Table 3 also shows the area ratio of Ga ₂ ZnO ₄ in the cross sections of the sintered bodies of Examples 3a to 3e. The area ratio of Ga ₂ ZnO ₄ and In ₂ O ₃ occupying the cross section of the sintered body is determined by observing the SEM reflected electron image of the crystalline phase thereof, making the contrast white particles In ₂ O _{3 and} dark gray particles Was calculated by calculating the area ratio as Ga ₂ ZnO ₄ .

(Example 3f)
Also in Example 3f, Steps 1 and 2 described above are the same as in Examples 3a to 3e. However, Example 3f differs from Examples 3a-3e in that steps 3 and 4 are partially changed. That is, in Example 3f, Steps 3 and 4 described above were partially changed as Steps 3a and 4a below.

Step 3a: Grinding and mixing with In ₂ O ₃ powder and GaN powder Ga ₂ ZnO ₄ powder obtained by calcination in Step 2 and In ₂ O ₃ (purity 99.99%, BET specific surface area 5 m ² / g) The powder and GaN (purity 99.99%, BET specific surface area 2 m ² / g) were pulverized and mixed for 6 hours using a ball mill apparatus. The molar mixing ratio at this time was Ga ₂ ZnO ₄ : In ₂ O ₃ : GaN = 1: 1: 0.05. Water was used as the dispersion medium, and the mixture after pulverization and mixing was dried with a spray dryer.

Step 4a: Molding and Sintering Next, the obtained Ga ₂ ZnO ₄ —In ₂ O ₃ —GaN mixed powder is molded by pressing, further pressure-molded by CIP, and a circle having a diameter of 100 mm and a thickness of about 9 mm. A plate-like molded body was obtained. The obtained molded body was made into a sintered body by firing at 1390 ° C. for 5 hours in an N ₂ atmosphere of 1 atm. The obtained sintered body contracted to a diameter of 80 mm and a thickness of about 7 mm.

The area ratio of Ga ₂ ZnO ₄ in Example 3f was also measured in the same manner as in Examples 3a to 3e, and the results are also shown in Table 3.

(Example 3g-3s)
The sintered bodies in Examples 3g to 3s were basically manufactured in the same manner as the sintered bodies in Examples 3a to 3e, but in the pulverization and mixing of Ga ₂ ZnO ₄ powder and In ₂ O ₃ powder in Step 3 , Oxide powder containing additive elements (Al ₂ O ₃ , SiO ₂ , TiO ₂ , V ₂ O ₅ , Cr ₂ O ₃ , ZrO ₂ , Nb ₂ O ₃ , MoO ₂ , HfO ₂ , Ta ₂ O ₃ , WO ₃ , SnO ₂ , Bi ₂ O ₃ ) were added and pulverized and mixed. When the oxide of the additive element is Al ₂ O ₃ , Cr ₂ O ₃ , Nb ₂ O ₃ , Ta ₂ O ₃ , or Bi ₂ O ₃ , the molar mixing ratio is Ga ₂ ZnO ₄ : In ₂ O ₃ : The oxide of the additive element is 1: 1: (0.1 or less and 0.01 or more). When the oxide of the additive element is SiO ₂ , TiO ₂ , ZrO ₂ , MoO ₂ , HfO ₂ , WO ₃ , or SnO ₂ , the molar mixing ratio is Ga ₂ ZnO ₄ : In ₂ O ₃ : additive element. Of oxide = 1: 1: (0.2 or less and 0.02 or more). The results regarding Examples 3g to 3s as described above are also shown in Table 3.

The additive element concentration in the table was determined as the number of atoms per 1 cm ³ (atoms / cc) by analyzing a film deposited by sputtering described later by SIMS (secondary ion mass spectrometry).

(Examples 4a to 4d)
The production processes of the sintered bodies in Examples 4a to 4d were different from Examples 3a to 3e described above only in that the sintering temperature was changed. The sintering temperature and the area ratio of Ga ₂ ZnO _{4 for} the sintered bodies of Examples 4a to 4d are summarized in Table 4.

(Example 4e)
The production process of the sintered body in Example 4e was different from Example 3f described above only in that the sintering temperature was changed to 1375 ° C. The sintering temperature and the area ratio of Ga ₂ ZnO _{4 for} the sintered body of Example 4e are also shown in Table 4.

(Examples 4f to 4r)
The production processes of the sintered bodies in Examples 4f to 4r were different from those in Examples 3g to 3s described above only in that the sintering temperature was changed. The sintering temperature and the area ratio of Ga ₂ ZnO _{4 for} the sintered bodies of Examples 4f to 4r are also summarized in Table 4.

(Example 5a)
The production process of the sintered body in Example 5a was different from that in Examples 3a to 3e described above only in that the sintering temperature was changed to 1430 ° C. The sintered body obtained in Example 5a was a single phase composed only of In ₂ Ga ₂ ZnO ₇ crystals. The crystal grain size of this sintered body was 3 μm as determined from the peak half-value width of X-ray diffraction.

(Comparative Example 5a)
In Comparative Example 5a, which corresponds to a conventional method for producing a conductive oxide sintered body, the production method was slightly changed as compared with Example 5a. Specifically, it was manufactured through the following steps 1b to 3b.

Step 1b: Grinding and mixing of raw material powder In this step 1b, in comparison with Step 1 described above, In ₂ O ₃ powder (purity 99.99%, BET specific surface area 5 m ² / g) is Ga ₂ O ₃ powder and The only difference was that it was added to the ZnO powder and ground and mixed.

Step 2b: Calcination The mixed powder obtained in Step 1b was calcined under the same conditions as in Step 2 described above, whereby a calcined powder was obtained.

Step 3b: Molding and Sintering The calcined powder obtained in Step 2b was molded by uniaxial pressure molding to obtain a disk-shaped molded body having a diameter of 100 mm and a thickness of about 9 mm. This molded body was fired at 1500 ° C. for 5 hours in an oxygen atmosphere, whereby a sintered body was obtained. The sintered body obtained at this time was a single phase consisting only of In ₂ Ga ₂ ZnO ₇ crystals, and the crystal grain size was 10 μm. When the sintering temperature was changed from 1500 ° C. to 1430 ° C., an In ₂ Ga ₂ ZnO ₇ single-phase sintered body could not be obtained.

  An IGZO film was deposited by sputtering using the sintered bodies of Example 5a and Comparative Example 5a described above as targets. For this film formation, a DC (direct current) magnetron sputtering method was used. The target size was 76.2 mm in diameter and 5 mm in thickness, and a plane having a diameter of 76.2 mm was a sputter surface.

First, a synthetic quartz glass substrate of 25 mm × 25 mm × 0.6 mm was placed as a film forming substrate on a water-cooled substrate holder in the film forming chamber of the sputtering apparatus. The target was disposed to face the substrate, and the distance between the substrate and the target was 40 mm. Thereafter, the film forming chamber was evacuated to about 1 × 10 ⁻⁴ Pa, and the target was pre-sputtered. Specifically, Ar gas is introduced into the deposition chamber up to a pressure of 1 Pa with a shutter between the substrate and the target, and 30 W DC power is applied to cause sputtering discharge, thereby causing the target surface Cleaning (pre-sputtering) was performed for 10 minutes.

  Thereafter, Ar gas containing 0.5% oxygen gas at a flow rate ratio was introduced into the deposition chamber up to a sputtering pressure of 0.4 P, and an IGZO film having a thickness of 200 nm was deposited with a sputtering power of 50 W. At this time, no bias voltage was applied to the substrate holder, and it was only water-cooled. The target surface after the film formation process as described above was repeated 30 times was observed with an optical microscope with a magnification of 20, and the amount of nodules generated was measured. As a result, the target according to Comparative Example 5a had 2.4 times more nodules than the target according to Example 5a.

(Example 6a)
As Example 6a, the sintered body was manufactured three times under the conditions of the sample 2c in Example 2 described above, and the area ratio of Ga ₂ ZnO ₄ in the cross section of the obtained sintered body was measured. The results of this Example 6a are shown in Table 5.

(Example 6b)
In Example 6b, the sintered body was manufactured three times under the conditions of Example 3c in Example 3 described above, and the area ratio of Ga ₂ ZnO ₄ in the cross section of the obtained sintered body was measured. The results of Example 6b are also shown in Table 5.

(Comparative Example 6a)
As Comparative Example 6a, a sintered body was produced three times under the condition that only the sintering temperature was changed to 1400 ° C. from the condition of Comparative Example 5a described above, and Ga ₂ ZnO ₄ in the cross section of the obtained sintered body. The area ratio was measured. The results of Comparative Example 6a are also shown in Table 5.

As is clear from the results in Table 5, in Example 6a and Example 6b, the reproducibility of the area ratio of Ga ₂ ZnO ₄ is stable in the production of the sintered body multiple times, but in Comparative Example 6a, the reproducibility is stable. It turns out that it is very unstable. This means that in Examples 6a and 6b, it is easy to control the amount of the crystal phase in the sintered body, but in Comparative Example 6a, it is difficult.

  As mentioned above, according to this invention, the manufacturing method of the electroconductive oxide sintered compact which can make easy control of the kind and quantity of the crystal phase contained in an electroconductive oxide sintered compact can be provided.

Claims (1)

A method of manufacturing a conductive oxide sintered body including a crystal phase of In ₂ Ga ₂ ZnO ₇ and Ga ₂ ZnO ₄ ,
A step of forming a Ga ₂ ZnO ₄ powder by preparing a mixture of zinc oxide and gallium oxide and calcining in an oxygen atmosphere or an air atmosphere at a temperature of 800 ° C. or higher and 1300 ° C. or lower ;
The Ga ₂ ZnO ₄ powder and the powder containing In and O are mixed or pulverized and mixed for a time in a range of 12 hours to less than 36 hours, and a specific surface area of 11 m ² / g to 15 m ² / g A second mixture satisfying at least one of the average particle diameters of 1.0 μm or more and 1.5 μm or less is prepared, a molded body of the second mixture is produced, and the molded body is subjected to an oxygen atmosphere or an air atmosphere And a step of sintering at a temperature of 1350 ° C. or higher and 1400 ° C. or lower .