JP2013095657A - Oxide sintered compact and sputtering target, and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oxide sintered compact used suitably for production of an oxide semiconductor film for a display device, the oxide sintered compact being capable of stable film formation by a sputtering method, while suppressing abnormal discharge in formation of the oxide semiconductor film having high carrier mobility.SOLUTION: This oxide sintered compact is obtained by mixing and sintering zinc oxide, indium oxide, and an oxide of at least one kind of metal selected from a group consisting of Ti, Mg, Al and Nb. When the oxide sintered compact is subjected to X-ray diffraction, ZnInO(where m is an integer from 5 to 7) phase is the main phase, the ratio of crystal grains having an average particle size of ≤10 μm and a particle size of ≥30 μm is ≤15%, and the relative density is ≥85%.

Description

  The present invention relates to an oxide sintered body and a sputtering target used when a thin film transistor (TFT) oxide semiconductor thin film used in a display device such as a liquid crystal display or an organic EL display is formed by a sputtering method, and a method for manufacturing the oxide sintered body. It is about.

  Amorphous (amorphous) oxide semiconductors used for TFTs have higher carrier mobility than general-purpose amorphous silicon (a-Si), a large optical band gap, and can be formed at low temperatures. It is expected to be applied to next-generation displays that require high resolution and high-speed driving, and resin substrates with low heat resistance. As an oxide semiconductor composition suitable for these uses, for example, an In-containing amorphous oxide semiconductor [In-Ga-Zn-O, In-Zn-O, In-Sn-O (ITO), etc.] is proposed. Has been.

  In forming the oxide semiconductor (film), a sputtering method is preferably used in which a sputtering target made of the same material as the film is sputtered. In the sputtering method, prevention of abnormal discharge during sputtering and prevention of cracking of the target are important in order to stabilize the characteristics of the thin film as a product and increase the efficiency of production, and various techniques have been proposed.

  For example, Patent Document 1 proposes a technique for suppressing abnormal discharge for an ITO target by reducing the average grain size of crystal grains.

  Patent Document 2 proposes a technique for preventing cracking of the target plate during sputtering by increasing the sintering density and reducing the crystal grain size for the ITO target.

  Furthermore, in Patent Document 3, the In-Zn-O-based composite oxide is annealed in a reducing atmosphere after sintering, thereby improving the electrical conductivity of the target material, thereby preventing abnormal discharge and sputtering of the target during sputtering. Suppression techniques have been proposed.

  Along with the recent improvement in performance of display devices, there is a demand for improvement and stabilization of characteristics of oxide semiconductor thin films, and there is a demand for more efficient production of display devices. Therefore, the sputtering target used for manufacturing the oxide semiconductor film for a display device and the oxide sintered body that is a material thereof are desired to have high carrier mobility. However, productivity and manufacturing cost are considered. Then, it is also important to further suppress the abnormal discharge (arcing) in the sputtering process, and for that purpose, improvement of the target material and the oxide sintered body as the material is required.

Japanese Patent Laid-Open No. 7-243036 JP-A-5-311428 Japanese Patent No. 3746094

  This invention is made | formed in view of the said situation, The objective is the oxide sintered compact suitably used for manufacture of the oxide semiconductor film for display apparatuses, and a sputtering target, Comprising: It has high carrier mobility. An object of the present invention is to provide an oxide sintered body, a sputtering target, and a method for manufacturing the same, which can suppress abnormal discharge in the formation of an oxide semiconductor film and can be stably formed by a sputtering method.

The oxide sintered body of the present invention that can solve the above-mentioned problems includes zinc oxide; indium oxide; an oxide of at least one metal selected from the group consisting of Ti, Mg, Al, and Nb; When the oxide sintered body is subjected to X-ray diffraction, a Zn _m In ₂ O _{3 + m} (m is an integer of 5 to 7) phase is obtained. As the main phase, the average grain size of the crystal grains observed by SEM at the fracture surface of the oxide sintered body is 10 μm or less, and the ratio of crystal grains having a grain size of 30 μm or more is 15% or less, The oxide sintered body has a gist where the relative density is 85% or more.

In a preferred embodiment of the present invention, the content (atomic%) of the metal element contained in the oxide sintered body is set to [Zn], [In], [Ti], [Mg], [Al], [Al, Nb], the ratio of [In] to [Zn], [Zn] + [In] + [Ti] + [Mg] + [Al] + [Ti] + [Mg] + [Al ] + [Nb] ratios satisfy the following expressions, respectively.
0.27 ≦ [In] / [Zn] ≦ 0.45
([Ti] + [Mg] + [Al] + [Nb]) / ([Zn] + [In] + [Ti] + [Mg] + [Al] + [Nb])) ≦ 0.1

In a preferred embodiment of the present invention, the volume ratio of the Zn _m In ₂ O _{3 + m to} the total of Zn _m In ₂ O _{3 + m} , In ₂ O ₃ , and ZnO contained in the oxide sintered body Satisfy the following formulas.
Zn _m In ₂ O _{3 + m} / (Zn _m In ₂ O _{3 + m} + In ₂ O ₃ + ZnO) ≧ 0.5
(However, Zn _m In ₂ O _{3 + m} is the total of Zn ₅ In ₂ O ₈ , Zn ₆ In ₂ O ₉ , and Zn ₇ In ₂ O _10. )

  Moreover, the sputtering target of the present invention that has solved the above problems is a sputtering target obtained using the oxide sintered body according to any one of the above, and has a specific resistance of 0.1 Ω · cm or less. .

  A preferable method for producing the oxide sintered body of the present invention is to mix zinc oxide; indium oxide; and an oxide of at least one metal selected from the group consisting of Ti, Mg, Al, and Nb. After being set in a graphite mold, the temperature is raised to a sintering temperature of 1000 to 1150 ° C. at an average heating rate of 600 ° C./hr or less, and then sintered in a holding time of 0.1 to 5 hours in the temperature range. Has a summary.

  According to the present invention, there is provided an oxide sintered body and a sputtering target capable of suppressing abnormal discharge in the formation of an oxide semiconductor film having high carrier mobility and capable of stable film formation by a sputtering method, and a method for manufacturing the same. It is possible to provide.

FIG. 1 is a diagram showing a basic process for producing an oxide sintered body and a sputtering target of the present invention. FIG. 2 is a graph showing an example of a sintering process used in the production method of the present invention.

  The present inventors have made it possible to stably form a film for a long time by suppressing abnormal discharge during sputtering for an oxide sintered body containing zinc oxide and indium oxide, and have high carrier mobility. In order to provide an oxide sintered body for a sputtering target suitable for forming a physical semiconductor film, studies have been made repeatedly.

As a result, zinc oxide; indium oxide; and powders of oxides of at least one metal selected from the group consisting of Ti, Mg, Al, and Nb (hereinafter referred to as M metal) are mixed and sintered. When the oxide sintered body is obtained by X-ray diffraction, the main phase is a Zn _m In ₂ O _{3 + m} (m is an integer of 5 to 7) phase, When SEM observation was performed, it was found that the intended purpose was achieved when the average grain size and coarse crystal grains were controlled and the relative density was 85% or more.

Specifically, regarding the phase structure when the oxide sintered body is subjected to X-ray diffraction, (a) Zn and In are bonded to each other to form Zn _m In ₂ O _{3 + m} (m is an integer of 5 to 7). (B) M metal exhibits a useful effect for improving carrier mobility, and (c) SEM observation. For crystal grains, reducing the average grain size and suppressing the ratio of coarse crystal grains are effective in suppressing abnormal discharge, and (d) generating abnormal discharge during sputtering by increasing the relative density. It has been found that the suppression effect of can be further improved. (E) Then, in order to obtain an oxide sintered body having such a phase structure, it was found that the sintering should be performed under predetermined sintering conditions, and the present invention has been achieved.

First, the structure of the oxide sintered body according to the present invention will be described in detail. As described above, the oxide sintered body of the present invention is an oxide containing Zn _m In ₂ O _{3 + m} (m is an integer of 5 to 7) as a main phase when the oxide sintered body is subjected to X-ray diffraction. It is characterized by a product sintered body.

The X-ray diffraction conditions in the present invention are as follows.
Analysis device: “X-ray diffractometer RINT-1500” manufactured by Rigaku Corporation
Analysis conditions Target: Cu
Monochromatic: Uses a monochrome mate (Kα)
Target output: 40kV-200mA
(Continuous firing measurement) θ / 2θ scanning Slit: Divergence 1/2 °, Scattering 1/2 °, Received light 0.15 mm
Monochromator light receiving slit: 0.6mm
Scanning speed: 2 ° / min
Sampling width: 0.02 °
Measurement angle (2θ): 5 to 90 °

With respect to the diffraction peaks obtained by this measurement, crystal phases having a crystal structure described in ICDD (International Center for Diffraction Data) cards 20-1440, 20-1441, 06-0416, 36-1451 (respectively Zn ₅ In ₂ O ₈ , Zn ₇ In ₂ O ₁₀ , In ₂ O ₃ , and ZnO). Zn ₆ In ₂ O ₉ specifies a crystal phase having a crystal structure described in the following references (1) and (2).
References (1) M. Nakamura, N. Kimizuka and T. Mohri: J. Solid State Chem. 86 (1990) 16-40
Reference (2) M. Nakamura, N. Kimizuka, T. Mohri and M. Isobe: J. Solid State Chem. 105 (1993) 535-549

  Next, the compound that identifies the present invention detected by the X-ray diffraction will be described in detail.

(About Zn _m In ₂ O _{3 + m} compounds)
The Zn _m In ₂ O _{3 + m} compound (phase) is formed by combining zinc oxide and indium oxide constituting the oxide sintered body of the present invention. The crystal structure of this compound is a hexagonal crystal and greatly contributes to the improvement in carrier mobility of the oxide sintered body.

The Zn _m In ₂ O _{3 + m} compound is a homologous compound, and m is at least one of 5 (Zn ₅ In ₂ O ₈ ), 6 (Zn ₆ In ₂ O ₉ ), and 7 (Zn ₇ In ₂ O ₁₀ ). Or one. If m is an integer of 4 or less or an integer of 8 or more, the semiconductor characteristics of the oxide semiconductor film are deteriorated and carrier mobility is lowered, which is not desirable. Since these are crystals of complex oxides of Zn, In, and M metal, m is an integer.

In the present invention, the above Zn _m In ₂ O _{3 + m} (m = 5, 6, 7) is included as a main phase. Here, “main phase” means Zn _m In ₂ O _{3 + m} (Zn ₅ In ₂ O ₈ (m = 5), Zn ₆ In ₂ O ₉ (m = 6), Zn ₇ In ₂ O ₁₀ (m = Sum of 7) means the compound with the highest ratio among all the compounds detected by the X-ray diffraction.

In the present invention, in addition to the Zn _m In ₂ O _{3 + m} (m = 5, 6, 7) phase, In ₂ O ₃ or ZnO may be included a little. Depending on the composition ratio of Zn and In not only the _{Zn m In 2 O 3 + m} (m = 5,6,7), there is a case where In ₂ O ₃ and ZnO is detected, Ya In ₂ O ₃ This is because ZnO does not adversely affect the effects of the present invention as long as the amount is small. The Zn _m In ₂ O _{3 + m} of the present invention includes a case where M metal described later is dissolved.

  The M metal used in the present invention is an element having a strong binding property with oxygen. By dissolving the M metal, the oxygen vacancies of the Zn—In—O-based target are reduced, and the film formed by sputtering is used. Useful for improving carrier mobility. The M metal is selected from the group consisting of Ti, Mg, Al and Nb, and may be used alone or in combination of two or more. Among these, preferred M metals from the viewpoint of semiconductor characteristics are Ti, Mg, and Al.

  M metal is an element selected as an element that greatly contributes to improving the carrier mobility of an oxide sintered body composed of only zinc oxide and indium oxide. Compared with the case where no M metal is contained, carrier mobility is improved by using an oxide sintered body containing the M metal specified in the present invention, preferably in a predetermined ratio described later.

In order to exhibit the effect of improving the carrier mobility, it is desirable that at least a part (preferably most part) of the M metal is dissolved in the Zn _m In ₂ O _{3 + m} phase. As long as the effect of improving the carrier mobility of the invention is not inhibited, a part of the M metal may be present as an oxide (for example, 5% by volume or less). When In ₂ O ₃ or ZnO is included, the M metal may be present in a solid solution state in these compounds.

  In the present invention, the average grain size of crystal grains observed by a SEM (reflection electron microscope) is 10 μm or less at the fracture surface of the oxide sintered body and the sputtering target (arbitrary position of the cross section in the thickness direction, the same shall apply hereinafter). By doing so, the occurrence of abnormal discharge can be further suppressed. The average particle size is preferably 8 μm or less, more preferably 5 μm or less. On the other hand, the lower limit of the average particle diameter is not particularly limited, but the preferable lower limit of the average particle diameter is about 2 μm from the viewpoints of the refinement effect and the manufacturing cost.

  The average grain size of the crystal grains is determined by observing the structure of the fracture surface (arbitrary location) of the oxide sintered body (or sputtering target) with an SEM (magnification: 400 times), and forming a straight line with a length of 100 μm in any direction. Then, the number (N) of crystal grains included in the straight line is obtained, and the value calculated from [100 / N] is taken as the average grain size on the straight line. In the present invention, 20 straight lines are created at intervals of 20 μm or more to calculate “average particle diameter on each straight line”, and a value calculated from [total average particle diameter on each straight line / 20] is calculated. The average grain size of the crystal grains.

  Moreover, in this invention, generation | occurrence | production of abnormal discharge can be suppressed by controlling the ratio of the coarse crystal grain which exists in oxide sinter and a sputtering target. From the viewpoint of suppressing the occurrence of abnormal discharge, it is desirable to suppress the proportion of coarse crystal grains having a particle size of 30 μm or more, preferably 25 μm or more, more preferably 20 μm or more, specifically 15% or less, preferably It is desirable to control to 10% or less, more preferably 5 or less.

  The ratio of coarse crystal grains is the same as the average grain size described above, by observing with SEM, drawing a straight line having a length of 100 μm in an arbitrary direction, and coarsening the crystal grains having a length of 30 μm or more cut on this straight line. The length L (total sum of the plurality of particles: μm in the case where there are a plurality of them) is calculated, and the value calculated from [L / 100] is calculated as “on the straight line”. The ratio of coarse crystal grains (%) ”. In the present invention, 20 straight lines are created at intervals of 20 μm or more, and the ratio of coarse crystal grains on each straight line is calculated, and further calculated from [total ratio of coarse crystal grains on each straight line / 20]. The value obtained is defined as the ratio (%) of coarse crystal grains.

  Next, the content (atomic%) of the metal element contained in the oxide sintered body of the present invention will be described. When the content (atomic%) of the metal element contained in the oxide sintered body is [Zn], [In], [Ti], [Mg], [Al], and [Nb], [Zn] [In] ratio to [Zn] + [In] + [Ti] + [Mg] + [Al] + [Nb] [Ti] + [Mg] + [Al] + [Nb] A specific range is desirable from the viewpoint of obtaining the desired effect. Here, [Ti], [Mg], [Al], and [Nb] are one kind of M metal, and when each sintered body does not contain Ti, for example, [Ti] = 0 is calculated.

The ratio of [In] to [Zn] ([In] / [Zn]; hereinafter referred to as the ratio (1)) is preferably 0.27 or more, more preferably 0.28 or more, and preferably 0. .45 or less, more preferably 0.4 or less. When the ratio (1) is decreased, a complex oxide (Zn ₄ In ₂ O ₇ etc.) with [Zn _m In ₂ O _{3 + m} ] of m ≦ 4 is generated, and the resistivity is increased and carrier movement is increased. The degree decreases. On the other hand, when the ratio (1) increases, a complex oxide (Zn ₈ In ₂ O ₁₁ or the like) having [Zn _m In ₂ O _{3 + m} ] of m ≧ 8 is generated, and the carrier mobility is lowered. .

  The ratio of [Ti] + [Mg] + [Al] + [Nb] to [Zn] + [In] + [Ti] + [Mg] + [Al] + [Nb] (([Ti] + [Mg ] + [Al] + [Nb]) / ([Zn] + [In] + [Ti] + [Mg] + [Al] + [Nb]); hereinafter referred to as the ratio (2)) is preferably 0. .1 or less, more preferably 0.05 or less, and still more preferably 0.03 or less. This is because when the ratio (2) increases, the M metal generates a composite oxide with In and Zn, the semiconductor characteristics of the thin film deteriorate, and the carrier mobility decreases. In addition, although it does not specifically limit about the minimum of ratio (2), From a viewpoint of fully exhibiting the said M metal addition effect, Preferably it is 0.001 or more, More preferably, it is 0.005 or more.

Next, Zn _m In ₂ O _{3 + m} contained in the oxide sintered body (where Zn _m In ₂ O _{3 + m} is Zn ₅ In ₂ O ₈ , Zn ₆ In ₂ O ₉ , Zn ₇ In ₂ O ₁₀ ). The volume ratio of each crystal phase to the total of In ₂ O ₃ and ZnO will be described. Hereinafter, the ratio of Zn _m In ₂ O _{3 + m} to the sum of _{Zn m In 2 O 3 + m} + In 2 O 3 + ZnO is referred to as _{[Zn m In 2 O 3 +} m] ratio.

The [Zn _m In ₂ O _{3 + m} ] ratio is preferably 0.5 or more. When the [Zn _m In ₂ O _{3 + m} ] ratio is less than 0.5, abnormal discharge and cracking increase. A more preferred lower limit is 0.8 or more, and even more preferred is 0.85 or more. The lower limit may be substantially composed only of Zn _m In ₂ O _{3 + m} .

In addition to the above In ₂ O ₃ and ZnO as other crystal phases that can be included in the oxide sintered body of the present invention, oxides of M metal inevitably produced in production (for example, Zn ₂ TiO ₄ , InNbO _4, etc.) ) May be included. The ratio of the M metal oxide that is inevitably generated is preferably about 5% by volume or less, for example. These can also be measured by XRD.

  The oxide sintered body of the present invention, and further the sputtering target obtained using the oxide sintered body is characterized in that the relative density is 85% or more, preferably the specific resistance is 0.1 Ω · cm or less.

(Relative density 85% or more)
The oxide sintered body of the present invention has a very high relative density, preferably 85% or more, and more preferably 95% or more. A high relative density not only can prevent the generation of cracks and nodules during sputtering, but also provides advantages such as maintaining a stable discharge continuously to the target life.

(Specific resistance 0.1Ω ・ cm or less)
The oxide sintered body of the present invention has a small specific resistance and is 0.1 Ω · cm or less, preferably 0.01 Ω · cm or less. Thereby, the film formation in which the abnormal discharge during the sputtering is suppressed becomes possible, and the physical vapor deposition (sputtering method) using the sputtering target can be efficiently performed on the production line of the display device.

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

  The oxide sintered body of the present invention is obtained by mixing and sintering zinc oxide, indium oxide, and M metal oxide powders, and the sputtering target is obtained by processing the oxide sintered body. Can be manufactured. In FIG. 1, oxide powder obtained by (a) mixing / pulverization → (b) drying / granulation → (c) preforming → (d) degreasing → (e) hot pressing The basic process until the sputtering target is obtained by bonding the body to (f) processing → (g) is shown. Among the above steps, the present invention is characterized in that the sintering conditions ((e) hot press) are appropriately controlled as described in detail below, and the other steps are not particularly limited, and are usually used steps. Can be appropriately selected. Hereinafter, although each process is demonstrated, this invention is not the meaning limited to this.

  First, zinc oxide powder, indium oxide powder, and M metal oxide powder are mixed in a predetermined ratio, and mixed and pulverized. The purity of each raw material powder used is preferably about 99.99% or more. This is because the presence of a trace amount of impurity elements may impair the semiconductor characteristics of the oxide semiconductor film. The blending ratio of each raw material powder is preferably controlled so that the ratio is within the above-described range.

  (A) The mixing / pulverization is preferably carried out by using a pot mill and adding the raw material powder together with water. The balls and beads used in these steps are preferably made of materials such as nylon, alumina, zirconia, and the like. At this time, for the purpose of mixing uniformly, a binder or a binder may be mixed in order to ensure the ease of the subsequent molding process.

  Next, it is preferable to perform (b) drying and granulation of the mixed powder obtained in the above step using, for example, a spray dryer.

After drying and granulation, (c) preforming is performed. In the molding, the powder after drying and granulation is filled in a mold having a predetermined size, and preformed by a mold press. This pre-molding is performed for the purpose of improving the handleability when set in a predetermined mold in the hot press process. Therefore, if a pressing force of about 0.5 to 1.0 tonf / cm ² is applied to form a molded body. Good.

  In addition, when a dispersing agent and a binder are added to mixed powder, in order to remove a dispersing agent and a binder, it is desirable to heat the molded object after a preforming, and to perform (d) degreasing. The heating conditions are not particularly limited as long as the purpose of degreasing can be achieved. For example, the heating conditions may be maintained at about 500 ° C. in the atmosphere for about 5 hours.

  After degreasing, the molded body is set in a graphite mold having a desired shape, and (e) sintering is performed by hot pressing. The graphite mold is a reducing material, and since the set molded body can be sintered in a reducing atmosphere, the reduction proceeds efficiently and the specific resistance can be lowered.

In the present invention, sintering is performed at a sintering temperature of 1000 to 1150 ° C. and a holding time at the temperature of 0.1 to 5 hours (FIG. 2). When the sintering temperature is low, the crystal phase having a main phase of Zn _m In ₂ O _{3 + m} (m is an integer of 5 to 7) cannot be obtained, and an effect such as suppression of abnormal discharge cannot be obtained. Further, it cannot be sufficiently densified, and a desired relative density cannot be achieved. On the other hand, if the sintering temperature becomes too high, the crystal grains become coarse, the average grain size of the crystal grains cannot be controlled within a predetermined range, and abnormal discharge cannot be suppressed. Therefore, the sintering temperature is 1000 ° C. or higher, preferably 1020 ° C. or higher, 1150 ° C. or lower, preferably 1100 ° C. or lower.

If the holding time at the sintering temperature is too long, the crystal grains grow and become coarse, so that the average grain size and the ratio of coarse crystal grains cannot be controlled within a predetermined range. On the other hand, if the holding time is too short, the crystal phase having the main phase of Zn _m In ₂ O _{3 + m} cannot be obtained, and sufficient densification cannot be achieved. Therefore, the holding time is 0.1 hour or longer, preferably 0.5 hour or longer, and 5 hours or shorter.

  In the present invention, it is preferable that the average temperature rise rate up to the sintering temperature is 600 ° C./hr or less after preforming. When the average heating rate exceeds 600 ° C./hr, abnormal growth of crystal grains occurs, and the ratio of coarse crystal grains increases. Also, the relative density cannot be increased sufficiently. A more preferable average heating rate is 500 ° C./hr or less, and further preferably 300 ° C./hr or less. On the other hand, the lower limit of the average heating rate is not particularly limited, but is preferably 10 ° C./hr or more, more preferably 20 ° C./hr or more from the viewpoint of productivity.

The pressurizing conditions during hot pressing in the sintering step are not particularly limited, but it is desirable to apply a pressure of, for example, a surface pressure of 600 kgf / cm ² or less. If the pressure is too low, densification may not proceed sufficiently. On the other hand, if the pressure is too high, the graphite mold may be damaged, the densification promoting effect is saturated, and the press equipment must be enlarged. Preferred pressure conditions are 150 kgf / cm ² or more and 400 kgf / cm ² or less.

The sintering process is desirably performed in a reducing gas such as H ₂ , methane, and CO, and in an inert gas atmosphere such as Ar and N ₂ . Particularly in the present invention using a graphite mold, the sintering atmosphere is preferably an inert gas atmosphere in order to suppress oxidation and disappearance of graphite. The atmosphere control method is not particularly limited. For example, the atmosphere may be adjusted by introducing Ar gas or N ₂ gas into the furnace. The pressure of the atmospheric gas is preferably atmospheric pressure in order to suppress evaporation of zinc oxide having a high vapor pressure.

  After obtaining the oxide sintered body as described above, the sputtering target of the present invention is obtained by performing (f) processing → (g) bonding by a conventional method. The relative density and specific resistance of the sputtering target obtained in this way are also very good as in the case of the oxide sintered body, the preferable relative density is about 85% or more, and the preferable specific resistance is about 0. 0. 1 Ω · cm or less.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples, and may be implemented with appropriate modifications within a scope that can meet the gist of the present invention. These are all possible and are within the scope of the present invention.

  Table 2 shows zinc oxide powder (purity 99.99%), indium oxide powder (purity 99.99%), and titanium oxide, magnesium oxide, aluminum oxide, and niobium oxide powders (purity 99.99%). It mix | blended by the ratio, water and the dispersing agent (polycarboxylic acid ammonium) were added, and it mixed for 20 hours with the nylon ball mill. Next, the mixed powder obtained in the above step was dried and granulated.

After the powder thus obtained was preformed by a mold press (molding pressure: 1.0 ton / cm ² , compact size: φ110 × t13 mm, t is thickness), the temperature was raised to 500 ° C. in an air atmosphere. Warm and hold at that temperature for 5 hours to degrease. The obtained molded body was set in a graphite mold and hot pressed under the conditions (A to G) shown in Table 3. At this time, N ₂ gas was introduced into the hot press furnace and sintered in an N ₂ atmosphere. The obtained sintered body was machined and finished to φ100 × t5 mm, and bonded to a Cu backing plate to produce a sputtering target.

The sputtering target thus obtained was attached to a sputtering apparatus, and DC (direct current) magnetron sputtering was performed. The sputtering conditions were a DC sputtering power of 150 W, an Ar / 0.1 volume% O ₂ atmosphere, and a pressure of 0.8 mTorr. Further, a thin film transistor having a channel length of 10 μm and a channel width of 100 μm was formed using the thin film formed under these conditions.

(Measurement of relative density)
The relative density was determined by removing the target from the backing plate, mirror polishing after sputtering, and observing with a reflection electron microscope (SEM) and measuring the porosity. Specifically, a SEM observation (1000 times) was taken to take a photograph, and the pore occupation area ratio in a 50 μm square region was measured to obtain the porosity. 20 different visual fields were observed, and the average value was taken as the average porosity of the sample. The value obtained by subtracting the porosity from 100% was taken as the relative density (%) of the sintered body. A relative density of 85% or more was evaluated as acceptable (see “relative density (%)” in Table 4).

(Average grain size)
The average grain size of the crystal grains is the SEM (magnification: 400 times) of the structure of the fracture surface of the oxide sintered body (the oxide sintered body is cut in the thickness direction at an arbitrary position, and the arbitrary position on the cut surface). ), Draw a straight line with a length of 100 μm in an arbitrary direction, determine the number of crystal grains (N) contained in this straight line, and calculate the value calculated from [100 / N] on the straight line The average particle size was taken. Similarly, 20 straight lines are created at intervals of 20 to 30 μm, the average particle diameter on each straight line is calculated, and the value calculated from [total average particle diameter on each straight line / 20] Average particle diameter. The crystal grains were evaluated as having passed an average grain size of 10 μm or less (see “Average grain size (μm)” in Table 4).

(Ratio of coarse crystal grains)
The ratio of coarse crystal grains is the same as the average grain size described above by observing the fracture surface of the oxide sintered body by SEM, drawing a straight line having a length of 100 μm in an arbitrary direction, and the length cut on this straight line. A crystal grain having a size of 30 μm or more is defined as a coarse crystal grain, and a length L (sum of plurals if there are a plurality of the coarse crystal grains) is calculated on a straight line, and a value calculated from [L / 100] is obtained. It was set as the ratio (%) of the coarse crystal grain on the said straight line. In the present invention, 20 straight lines are created at intervals of 20 to 30 μm, and the ratio of coarse crystal grains on each straight line is calculated. Further, the total ratio of coarse crystal grains on each straight line / 20 is calculated. The calculated value was defined as the ratio (%) of coarse crystal grains. As for the ratio of coarse crystal grains, 15% or less was evaluated as acceptable (see “coarse grain ratio (%)” in Table 4).

(Crystal phase ratio)
The ratio of each crystal phase was determined by removing the target from the backing plate after sputtering, cutting out a 10 mm square test piece, and measuring the intensity of the diffraction line by X-ray diffraction.

Analysis device: “X-ray diffractometer RINT-1500” manufactured by Rigaku Corporation
Analysis conditions:
Target: Cu
Monochromatic: Uses a monochrome mate (Kα)
Target output: 40kV-200mA
(Continuous firing measurement) θ / 2θ scanning Slit: Divergence 1/2 °, Scattering 1/2 °, Received light 0.15 mm
Monochromator light receiving slit: 0.6mm
Scanning speed: 2 ° / min
Sampling width: 0.02 °
Measurement angle (2θ): 5 to 90 °

About the diffraction peak obtained by this measurement, the peak of each crystal phase shown in Table 1 was identified based on an ICDD (International Center for Diffraction Data) card, and the height of the diffraction peak was measured. Since Zn ₆ In ₂ O ₉ is not described in the ICDD card, the peak obtained by calculating the theoretical diffraction intensity by crystal structure factor calculation based on the crystal structure shown in the above references (1) and (2) and measuring it. It was determined. These peaks were selected so that the diffraction intensity of the crystal phase was sufficiently high and the overlap with the peaks of other crystal phases was as small as possible. The measured values of the peak height at the designated peak of each crystal phase are I (Zn _m In ₂ O _{3 + m} ), I (In ₂ O ₃ ), and I (ZnO), respectively (“I” is the measured value) The volume ratio of [Zn _m In ₂ O _{3 + m} ] was determined by the following equation ([Zn _m In ₂ O _{3 + m} ] phase volume ratio (%) in Table 4).
[Zn _m In ₂ O _{3 + m} ] = I (Zn _m In ₂ O _{3 + m} ) / (I (Zn _m In ₂ O _{3 + m} ) + I (In ₂ O ₃ ) + I (ZnO)) × 100

The crystal phase ratio [Zn _m In ₂ O _{3 + m} ] was evaluated as 50% or more as acceptable (see “[Zn _m In ₂ O _{3 + m} ] phase volume ratio (%)” in Table 4).

(Sputtering characteristics)
The sintered body of this research is processed into a shape with a diameter of 4 inches and a thickness of 5 mm, and bonded to a backing plate to obtain a sputtering target. The sputtering target thus obtained is attached to a sputtering apparatus, and DC (direct current) magnetron sputtering is performed. The sputtering conditions are a DC sputtering power of 150 W, an Ar / 0.1 volume% O ₂ atmosphere, and a pressure of 0.8 mTorr. At this time, the number of occurrences of arcing per 100 minutes was counted, and the number of occurrences of arcing was evaluated to be 2 or less (see “Abnormal Discharge Count” in Table 4).

(Carrier mobility)
The carrier mobility was measured by measuring the mobility of a thin film transistor having a channel length of 10 μm and a channel width of 100 μm formed using a thin film formed under the above sputtering conditions. Carrier mobility evaluated 15 cm < ² > / Vs or more as the pass (it is not described in Table 4).

  The results are shown in Table 4.

No. satisfying the preferred composition and production conditions of the present invention. Abnormal discharge was suppressed in 1-5 and 7-9. That is, when sputtering was performed, the occurrence of abnormal discharge was 2 times or less, and it was confirmed that the discharge was stably performed. In addition, the carrier mobility of the thin film obtained in this manner had a high carrier mobility of 15 cm ² / Vs or more.

On the other hand, No. which does not satisfy the preferred composition of the present invention. No. 6 is a low carrier mobility having a carrier mobility of less than 15 cm ² / Vs. About 10-13, many abnormal discharge generate | occur | produced, carrier mobility was low carrier mobility of less than 15 cm < ² > / Vs, and the desired effect was not able to be acquired.

Specifically, no. In the composition of No. 6, the ratio of In to Zn ([In] / [Zn]) was not within the scope of the present application. In the oxide sintered body, Zn _m In ₂ O _{3 + m} of m = 5, 6, 7 was not detected, but Zn ₄ In ₂ O ₇ (m = 4), Zn ₈ In ₂ O ₁₁ (m = 8) was detected. No. 6 had a low carrier mobility. In addition, No. 6, the total volume ratio of Zn ₄ In ₂ O ₇ and Zn ₈ In ₂ O ₁₁ (ratio to (Zn ₄ In ₂ O ₇ + Zn ₈ In ₂ O ₁₁ + In ₂ O ₃ + ZnO)) was 72%.

  No. No. 10 exceeded the specified rate of temperature increase of the present invention, abnormal growth of crystal grains occurred, the proportion of coarse crystal grains increased, and abnormal discharge could not be suppressed.

  No. No. 11 exceeds the specified rate of temperature increase according to the present invention, abnormal growth of crystal grains occurs, the ratio of coarse crystal grains increases, the relative density cannot be sufficiently increased, and abnormal discharge increases. became.

No. No. 12 had a low sintering temperature (holding temperature), so the relative density could not be increased, and the [Zn _m In ₂ O _{3 + m} ] phase volume ratio was low. Therefore, there were many abnormal discharges.

  No. In No. 13, since the sintering temperature (holding temperature) was high, the average grain size of the crystal grains exceeded the provisions of the present invention, and therefore abnormal discharge was frequent.

Claims (5)

An oxide sintered body obtained by mixing and sintering zinc oxide; indium oxide; and an oxide of at least one metal selected from the group consisting of Ti, Mg, Al, and Nb. ,
When the oxide sintered body is X-ray diffracted, it contains a Zn _m In ₂ O _{3 + m} (m is an integer of 5 to 7) phase as a main phase,
In the fracture surface of the oxide sintered body, the average grain size of the crystal grains observed by SEM is 10 μm or less, and the ratio of crystal grains having a grain size of 30 μm or more is 15% or less,
A relative density of the oxide sintered body is 85% or more. When the content (atomic%) of the metal element contained in the oxide sintered body is [Zn], [In], [Ti], [Mg], [Al], and [Nb], [ [In] to [Zn], [Ti] + [In] + [Ti] + [Mg] + [Al] + [Nb] to [Ti] + [Mg] + [Al] + [Nb] The oxide sintered body according to claim 1, wherein each satisfies the following formula.
0.27 ≦ [In] / [Zn] ≦ 0.45
([Ti] + [Mg] + [Al] + [Nb]) / ([Zn] + [In] + [Ti] + [Mg] + [Al] + [Nb])) ≦ 0.1 The volume ratio of the Zn _m In ₂ O _{3 + m to} the total of the Zn _m In ₂ O _{3 + m} , In ₂ O ₃ , and ZnO contained in the oxide sintered body satisfies the following formula. The oxide sintered body according to claim 1 or 2.
Zn _m In ₂ O _{3 + m} / (Zn _m In ₂ O _{3 + m} + In ₂ O ₃ + ZnO) ≧ 0.5
(However, Zn _m In ₂ O _{3 + m} is the total of Zn ₅ In ₂ O ₈ , Zn ₆ In ₂ O ₉ , and Zn ₇ In ₂ O _10. )   A sputtering target obtained using the oxide sintered body according to any one of claims 1 to 3, wherein a specific resistance is 0.1 Ω · cm or less.   It is a manufacturing method of the oxide sinter in any one of Claims 1-3, Comprising: At least 1 sort (s) selected from the group which consists of zinc oxide; Indium oxide; Ti, Mg, Al, and Nb After being mixed with a metal oxide and set in a graphite mold, the temperature was raised to a sintering temperature of 1000 to 1150 ° C. at an average temperature rising rate of 600 ° C./hr or less, and then a holding time in the temperature range was 0.1. A method for producing an oxide sintered body characterized by sintering in ~ 5 hours.

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