JP2006117462A - ZnO SINTERED COMPACT AND ITS MANUFACTURING METHOD - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique for forming a ZnO film having excellent properties as a transparent electrode by an ion-plating. <P>SOLUTION: The ZnO sintered compact that is suited for using as a source material for an ion-plating comprises a first ZnO region and a second ZnO region which have a different average degree of oxidation and a different average particle size from each other. Wherein it is preferred that the first ZnO region is a region having a higher degree of oxidation than the second ZnO region, and that the second ZnO region is a region having a color with blueness which is different from the first ZnO region. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a ZnO sintered body and a manufacturing method thereof, and more particularly to a ZnO sintered body suitable for use as a source material for ion plating and a manufacturing method thereof.

  Transparent electrodes are used in optical semiconductor devices such as solar cells and light emitting diodes, liquid crystal display devices (LCD), organic electroluminescence (EL) display devices, and the like. As the transparent electrode, indium-tin oxide (ITO) has been mainly used. In recent years, zinc oxide (ZnO) has also been used. In these oxide transparent electrode films, oxygen defects are said to generate carriers. For this reason, if the oxidation degree of the film is too high, the resistance becomes too high, and if the oxidation degree is too low, the transparency tends to deteriorate.

  The ITO film is formed by chemical vapor deposition (CVD), sputtering, ion plating, or the like. The ZnO film is formed by sputtering, ion plating or the like. Ion plating using arc discharge has little damage to the substrate due to the absence of high-speed particles like sputtering, has high reactivity due to high plasma density, and has a high deposition rate due to the use of thermal evaporation. Have

JP 2000-273617 A JP 2002-241926 A JP 2004-76025 A

  A technique for forming a ZnO film having excellent properties as a transparent electrode by ion plating has not been established yet.

  An object of the present invention is to provide a technique for forming a ZnO film having excellent properties as a transparent electrode by ion plating.

  According to one aspect of the present invention, the first ZnO region and the second ZnO region have different average oxidation degrees, and the first ZnO region and the second ZnO region have different average particle sizes. A ZnO sintered body is provided.

  According to another aspect of the present invention, (a) a step of preparing a powdery first ZnO raw material, and (b) a first part of the first ZnO raw material having a first oxygen content. (C) mixing the first ZnO raw material and the second ZnO raw material and pressing them using a mold. A step of solidifying, and (d) sintering the compacted ZnO raw material in a second atmosphere having a second oxygen content different from the first oxygen content. A manufacturing method is provided.

  A ZnO film having excellent properties as a transparent electrode can be formed by ion plating.

  First, an ion plating apparatus will be described.

  FIG. 1 is a cross-sectional view schematically showing the overall structure of an ion plating apparatus for forming a ZnO film. The ion plating apparatus includes a vacuum vessel 10 that is a film forming chamber, a plasma gun 30 that is a plasma source that supplies a plasma beam PB into the vacuum vessel 10, and a plasma beam PB that is disposed at the bottom of the vacuum vessel 10. An incident anode 50 and a transport mechanism 60 that appropriately moves a substrate holding member WH that holds a substrate W to be deposited above the anode 50 are provided.

The plasma gun 30 is a pressure gradient type plasma gun disclosed in Japanese Patent Application Laid-Open No. 9-194232 and the like, and its main body portion is attached to a cylindrical portion 12 provided on the side wall of the vacuum vessel 10. The main body portion is composed of a glass tube 32 whose one end is closed by a cathode 31. In the glass tube 32, a cylinder 33 made of molybdenum Mo is fixed to the cathode 31 and arranged concentrically. In the cylinder 33, a disk 34 made of LaB ₆ and tantalum Ta are formed. The pipe 35 is built in to constitute a hollow cathode. The first and second intermediate electrodes 41, 42 are concentric between the end of the glass tube 32 opposite to the cathode 31 and the end of the cylindrical portion 12 provided in the vacuum vessel 10. Are arranged in series. In the first intermediate electrode 41, an annular permanent magnet 44 for converging the plasma beam PB is incorporated. An electromagnetic coil 45 for converging the plasma beam PB is also built in the second intermediate electrode 42. A steering coil 47 that guides the plasma beam PB generated on the cathode 31 side and drawn to the first and second intermediate electrodes 41 and 42 into the vacuum vessel 10 is provided around the cylindrical portion 12. .

  The operation of the plasma gun 30 is controlled by a gun driving device 38. Thereby, the power supply to the cathode 31 can be turned on / off, the supply voltage to the gun, etc. can be adjusted, and the power supply to the first and second intermediate electrodes 41 and 42, the electromagnet coil 45, and the steering coil 47 can be performed. Can be adjusted. That is, the intensity and distribution state of the plasma beam PB supplied into the vacuum vessel 10 can be controlled.

  The pipe 35 arranged on the innermost side of the plasma gun 30 is for introducing a carrier gas made of an inert gas such as Ar, which is the source of the plasma beam PB, into the plasma gun 30 and thus the vacuum vessel 10. And connected to an inert gas source 90 through a flow meter 93 and a flow rate control valve 94.

  The anode 50 disposed in the lower part of the vacuum vessel 10 includes a hearth 51 as a main anode for guiding the plasma beam PB downward, and an annular auxiliary anode 52 disposed around the anode.

  The former hearth 51 is formed of a conductive material and is supported by a grounded vacuum vessel 10 via an insulator. The hearth 51 is controlled to an appropriate positive potential by the anode power supply device 80 and sucks the plasma beam PB emitted from the plasma gun 30 downward. The hearth 51 has a through-hole 51a in which a rod-shaped ZnO rod 53, which is an evaporation source (source material), is loaded at the central portion where the plasma beam PB from the plasma gun 30 is incident. The ZnO rod 53 is obtained by compressing and sintering ZnO powder as a film material by adding an additive as required. ZnO is heated and sublimated by the current from the plasma beam PB, and zinc oxide is formed on the substrate W as a transparent conductive film. The material supply device 58 provided at the lower part of the vacuum vessel 10 has a structure in which the ZnO rods 53 are successively loaded into the through holes 51a of the hearth 51 and the loaded ZnO rods 53 are gradually raised. Even if the upper end of the tube evaporates and wears, the upper end can always be protruded from the recess of the hearth 51 by a certain amount.

  The latter auxiliary anode 52 is constituted by an annular container disposed concentrically around the hearth 51. In this annular container, an annular permanent magnet 55 made of ferrite or the like and a coil 56 laminated concentrically therewith are accommodated. The permanent magnet 55 and the coil 56 are magnetic field control members, and form a cusp-like magnetic field directly above the hearth 51. Thereby, the direction of the plasma beam PB incident on the hearth 51 can be corrected.

  The coil 56 in the auxiliary anode 52 constitutes an electromagnet, which is supplied with power from the anode power supply 80 and forms an additional magnetic field that has the same orientation as the magnetic field on the center side generated by the permanent magnet 55. That is, by changing the current supplied to the coil 56, the direction of the plasma beam PB incident on the hearth 51 can be finely adjusted.

  The container of the auxiliary anode 52 is also made of a conductive material, like the hearth 51. The auxiliary anode 52 is attached to the hearth 51 via an insulator (not shown). By changing the voltage applied from the anode power supply device 80 to the auxiliary anode 52, the electric field above the hearth 51 can be complementarily controlled. That is, when the potential of the auxiliary anode 52 is made the same as that of the hearth 51, the plasma beam PB is also attracted thereto, and the supply of the plasma beam PB to the hearth 51 is reduced. On the other hand, when the potential of the auxiliary anode 52 is lowered to the same level as that of the vacuum vessel 10, the plasma beam PB is attracted to the hearth 51 and the ZnO rod 53 is heated.

  The transport mechanism 60 functions as a substrate holding means, and a plurality of rollers 62 arranged at equal intervals in the horizontal direction in the transport path 61 to support the edge of the substrate holding member WH, and these rollers 62 at an appropriate speed. And a driving device that moves the substrate holding member WH in the horizontal direction at a constant speed.

  The oxygen gas supply device 71 can supply oxygen gas to the vacuum vessel 10 as an atmospheric gas. A supply line from an oxygen gas source 71a that stores oxygen gas is connected to the vacuum vessel 10 via a flow rate control valve 71b and a flow meter 71c.

  The nitrogen gas supply device 72 can supply nitrogen gas as an atmospheric gas to the vacuum vessel 10. A supply line from a nitrogen gas source 72a that stores nitrogen gas is connected to the vacuum vessel 10 via a flow rate adjustment valve 72b and a flow meter 72c.

  The inert gas supply device 73 can supply an atmospheric gas made of an inert gas such as Ar to the vacuum vessel 10. The atmospheric gas branched from the inert gas source 90 is directly introduced into the vacuum vessel 10 through the flow rate adjustment valve 73b and the flow meter 73c of the gas supply device 73.

  The exhaust device 76 appropriately exhausts the gas in the vacuum container 10 through the exhaust valve 76a by the exhaust pump 76b. Further, the vacuum pressure measuring device 77 can measure the partial pressure of oxygen gas, Ar gas, etc. in the vacuum vessel 10.

  Hereinafter, the operation of the ion plating apparatus will be described. At the time of film formation by this film formation apparatus, glow discharge is first generated between the cathode 31 of the plasma gun 30 and the hearth 51 in the vacuum vessel 10, and the process shifts to arc discharge to generate the plasma beam PB. The plasma beam PB reaches the hearth 51 while being guided by a magnetic field determined by the steering coil 47 and the permanent magnet 55 in the auxiliary anode 52. When the current of the plasma beam PB is initially small, only the central portion of the ZnO rod 53 is heated by the current from the plasma beam PB along the magnetic field lines and becomes red hot. As the current of the plasma beam PB increases, the heating portion gradually expands, the entire upper surface of the ZnO rod 53 becomes incandescent, sublimates, and vapor of the film material is emitted therefrom. This vapor is ionized by the plasma beam PB and adheres to the surface of the substrate W with energy corresponding to the potential of the hearth 51 to form a ZnO film.

  According to the above method, since the magnetic field above the hearth 51 can be adjusted by the permanent magnet 55 and the coil 56 which are the magnetic field control members for beam correction, the flight direction of the evaporated particles evaporated from the ZnO rod 53 is controlled. And a thin film having a uniform film quality over a wide area can be obtained.

  In order to form a ZnO film exhibiting excellent characteristics as a transparent electrode, the present inventors first investigated what kind of sintered ZnO rod is preferably used. First, similarly to the sputtering target, as the ion plating raw material, a material compacted to a high density so as to be as close to the density of the bulk crystal as possible is sintered. A ZnO rod becomes very hard by sintering.

  As shown in FIG. 2A, immediately after the plasma is ignited and the arc discharge is started, the resistance of the ZnO rod R is high, and the arc plasma is incident only on the central portion of the upper surface of the rod R. Only the part is heated and becomes incandescent. As shown in FIG. 2 (B) and FIG. 2 (C), the incandescent portion gradually spreads and eventually the entire upper surface of the rod becomes incandescent. However, due to thermal expansion due to heating, the rod is chipped or cracked CR occurs. Then, the granular raw material scatters and adheres to the substrate, and the film formation target becomes a defective product. Since the cracked part is thermally separated, the subsequent film formation is also irregular.

  In order to prevent the chipping and cracking of the rod, an attempt was made to lower the relative density of the sintered body. Materials such as organic substances that evaporate by heating were mixed in the raw material. The obtained sintered body had a lower relative density, which is the relative density of the sintered body with respect to the bulk crystal density. However, it has been found that when an organic substance is mixed, carbon or the like remains and the purity of the film composition is lowered.

  Instead of mixing evaporation material, we considered mixing a material with a large volumetric shrinkage. When the powdery raw material is baked at a high temperature, it will grow in the form of granules and will not shrink in volume even if heated to a temperature below the firing temperature. It was considered that this fired raw material and unfired raw material were mixed, put into a mold, properly pressed and sintered. The unfired raw material is expected to shrink in volume and generate pores.

  In addition, when a film is formed by evaporating the oxide in a vacuum, the degree of oxidation tends to decrease due to the release of oxygen in the vacuum. Reactive (reactive) ion plating is known in which ion plating is performed in an oxygen-containing atmosphere to replenish deficient oxygen. However, it is desirable that the ZnO film as the transparent conductive film has an appropriate oxygen defect. If the degree of oxidation is high and oxygen defects are very few, the resistance of the film becomes too high.

  As a preliminary experiment, ZnO rods having different degrees of oxidation were prepared, the flow rate of oxygen flowing in the vacuum vessel was changed, and a ZnO film was formed by ion plating.

  FIG. 3A schematically shows a configuration of an ion plating apparatus used for film formation. A plasma gun 30 is provided in the vacuum vessel 10, and arc plasma is generated toward a ZnO rod (tablet) 53 that is an evaporation source housed in the crucible 51. A substrate SUB held by the substrate holder WH is disposed at a position facing the ZnO rod 53. A movable shutter SH is disposed on the front surface of the substrate SUB. The shutter SH (CL) in the closed (CL) state and the shutter SH (OP) in the open (OP) state are shown. During film formation, a controlled flow rate of oxygen is passed through the vacuum vessel 10.

  FIG. 3B shows a flowchart of the film forming process. In step S1, the target degree of vacuum is achieved, and the substrate temperature is raised to the target temperature. Thereafter, in step S2, the plasma gun is ignited. In step S3, the current value of the plasma gun is increased to the current value for film formation, and the gas pressure in the vacuum vessel is adjusted. In step S4, the temperature of the tablet is stabilized.

  In step S5, the shutter is opened and film formation is started. After the film formation time has elapsed, the shutter is closed to complete the film formation. The plasma gun is stopped in step S6, the substrate is cooled in step S7, and the substrate is taken out in step S8.

  As targets, tablets with a high degree of oxidation sintered in an atmosphere (atmosphere) with sufficient oxygen and tablets with a degree of oxidation sintered in an atmosphere with limited oxygen were used. The oxygen flow rate during film formation was changed to 0, 5, 10, 15, 20 (sccm).

  FIG. 3C shows the measurement result of the sheet resistance of the obtained ZnO film. The horizontal axis indicates the oxygen flow rate, and the vertical axis indicates the sheet resistance. At an oxygen flow rate of 10 sccm or less, the sheet resistance is in the range of 10-15 regardless of the tablet. Increasing the oxygen flow rate to greater than 10 sccm greatly increases the sheet resistance, and the sheet resistance is higher in tablets with a high degree of oxidation.

  When film formation is performed under a condition where the oxygen flow rate is large, it is not easy to make the plasma density constant in the vacuum vessel, and it is not easy to supply oxygen that is uniformly activated on the substrate surface. Furthermore, the heated ZnO rod surface reacts with oxygen and the composition changes. The film composition changes with time, and control is not easy.

  Oxygen contained in the ZnO rod itself is activated by the plasma beam PB immediately above the ZnO rod and is uniformly distributed in the formed ZnO film. However, if the entire rod has a uniform and high oxidation composition, the electrical conductivity of the ZnO rod is lowered, which is not desirable for the operation of the apparatus. Therefore, it was considered that the degree of oxidation of the above-mentioned fired raw material and the degree of oxidation of the sintered part of the unfired raw material were made different.

  As shown in FIG. 4A, ZnO powder MP as a raw material and powder DP of additives such as Ga2O3 added as necessary are weighed. When adding Ga2O3, for example, about 1 wt% to 3 wt% of Ga2O3 is added to ZnO. Group III elements can be used as additives. Since it is mixed with an oxide, it may be added in the form of a group III oxide.

  As shown in FIG. 4B, the weighed raw materials are mixed, water is added, and the mixture is pulverized and mixed in a ball mill BM using metal balls B for 3 days and 3 nights. A slurry-like mixed raw material is produced.

  As shown in FIG. 4C, the slurry S is dried to obtain a powdery raw material. This is hereinafter referred to as virgin raw material. The powder diameter of the virgin raw material was 0.2 μm to 0.6 μm.

  As shown in FIG. 4D, a part of the virgin raw material is fired at a high temperature of 800 ° C. to 1600 ° C., for example, 1500 ° C. The atmosphere was an air atmosphere in which oxygen could be sufficiently supplied. Although it is baking in powder form, the average particle size grows and becomes large. The powder grew from a powder form to a granular form, and the average particle diameter became about 2 μm to 100 μm. In addition, the sintered rod at the time of film-forming shall be heated at about 1200 degreeC.

  As shown to FIG. 4E, the obtained granular baking raw material and virgin raw material were mixed, and it put into the type | mold, and pressed and hardened moderately, and the cylindrical raw material of the mixed material R was obtained. This rod-shaped raw material is sintered at 1200 ° C. to 1400 ° C., for example, 1300 ° C., equal to or higher than the temperature at the time of film formation in a nitrogen atmosphere in which the oxygen content is limited.

  FIG. 4F is a photograph showing the appearance of the obtained ZnO cylindrical rod (tablet) for ion plating. FIG. 4G is an enlarged micrograph of the surface of the sintered rod. The granular region is yellowish granular and is considered to be a sufficiently oxidized region derived from a firing raw material fired under sufficient oxygen conditions. The raw material pre-fired at high temperature seems to remain almost intact after sintering. The region that becomes the ground is a pale region, and is considered to be a region lacking oxygen derived from sintering the virgin raw material in an atmosphere lacking oxygen. The virgin raw material is sintered in the sintering process and apparently appears to have a larger structure.

  This sintered body exhibited a conductivity of about several Ω (resistivity of several tens of Ωcm) with a tester. Since the ZnO rod is also an electrode for direct current arc discharge, there is no problem in operation if the ZnO rod has a resistivity of at least 1 × 10E6 Ωcm or less. However, the ZnO rod has a resistivity of 1 × 10E3 Ωcm or less. It is desirable to be.

  The sintered rod obtained as a result of sintering was a sintered body having a reduced relative density. It is considered that pores were generated because the volume of the virgin raw material contracted by sintering. The relative density with respect to the density of the bulk crystal was measured by changing the mixing ratio of the virgin raw material and the firing raw material and changing the sintering temperature.

  FIG. 5 is a graph showing the measurement results. When the virgin raw material was changed from 0% to 50%, the relative density gradually decreased. In particular, when the virgin raw material is mixed in an amount of more than 30%, the relative density seems to decrease greatly. It is considered that the relative density can be controlled by the firing temperature, the mixing ratio of the firing raw material and the virgin raw material, and the like.

  Note that the relative density can be achieved even if the firing process is performed in an atmosphere in which oxygen is limited at a high temperature, and then mixed with the virgin raw material, embossed, and sintered in an atmosphere having a lower oxygen content than the firing temperature. It would be possible to reduce it to a value. It is considered that the relative density can be lowered by mixing the pre-fired raw material and the unfired raw material, embossing and sintering. It is preferable that at least one of the firing step and the sintering step be performed with the oxygen supply amount limited. It is considered that regions having different degrees of oxidation can be uniformly distributed in the sintered rod by controlling the oxygen supply amounts during firing and sintering.

When ion plating was performed using these sintered rods, chipping and cracking hardly occurred at a relative density of 60% to 80%, particularly 60% to 70%, and good ion plating was possible. It was.
If the relative density is less than 60%, the mechanical strength is insufficient and inconvenience occurs during handling.
Above a relative density of 80%, cracking occurs due to thermal stress accompanying thermal shock.

  The transparency of the ZnO film was lowered when oxygen was not supplied at the time of film formation. However, when oxygen gas was supplied, the transparency was sufficiently improved, but the electrical resistance was increased.

  Oxygen was allowed to flow during film formation, the electrical resistivity was measured at the center of the obtained large area ZnO film, and the light transmittance at the center of the large area ZnO film was measured.

FIG. 6A is a graph showing the measured electrical resistivity as a function of oxygen flow rate. The oxygen flow rate was changed to 0, 5, 10, 15, 20 (sccm). The same tendency as in FIG. 3C can be seen. The resistivity was particularly low in the region where the oxygen flow rate was 10 sccm or less, and was 4 × 10 ⁻⁴ Ωcm or less.

  FIG. 6B shows the transmittance spectrum. The rising wavelength of the transmittance seems to move to the longer wavelength side as the oxygen flow rate increases. It may be preferable to set the oxygen flow rate low in order to transmit more short wavelength light. The curve with an oxygen flow rate of 0 sccm has a low transmittance of about 82% in the short wavelength region. When the oxygen flow rate is 5 sccm or more, the transmittance is improved.

  It was suggested that when a ZnO tablet produced by limiting the oxygen content during sintering to a very small amount was used, a thin film with good transparency and electrical conductivity could be obtained. Therefore, an attempt was made to limit the oxygen supply period.

  FIG. 7 is a graph showing the atmosphere during the sintering process. The sintering process was performed in an airtight container. The pressed material rod is carried in, the air in the container is exhausted, and a certain amount of oxygen is supplied at an arbitrary flow rate. After supplying oxygen, the inflow of oxygen was stopped and nitrogen was supplied at a constant flow rate to obtain an atmosphere of approximately 1 atm. For example, when baking is performed at 1300 ° C. for 1 hour, the air is exhausted by an exhaust pump before heating, and nitrogen is injected to about 0.0005 Mpa. After that, after supplying an oxygen flow rate of 1 liter / min into the furnace for a certain period of time, while supplying only a nitrogen flow rate of 1 L / min, the exhaust valve is adjusted so that the pressure in the furnace becomes 0.8 to 1.0 kPa. Adjust the heat to start heating. The oxygen supply time is 1/10 or less of the sintering period. Oxygen is supplied only for a certain period before heating, and then exhausted while continuing to supply nitrogen, thereby sufficiently reducing the oxygen content during high-temperature sintering. To do. After reaching 1300 ° C., the temperature is kept for about 1 hour and then cooled. The partial pressure of oxygen remaining in the furnace at that time is shown below.

FIG. 8 shows the oxygen concentration together with the furnace pressure and the furnace temperature when the sintering process is performed while changing the amount of initially introduced oxygen. c represents the oxygen concentration, p represents the pressure in the furnace, and t represents the temperature in the furnace. Subscript 1 indicates that the oxygen amount is 2.0 liters, 2 is 1.0 liter, 3 is 0.5 liters, and 4 is 0.1 liters. The oxygen concentration in the state of reaching 1300 ° C. is 1000 ppm or less. It may be preferred that the oxygen content during sintering is higher than 0% and lower than 1%.
In the case of using a high-precision mass flow controller, the same result will be obtained even if oxygen of 1/30 or less of the nitrogen flow rate is supplied over the entire firing period.

When a sintered rod prepared under such conditions is used, a ZnO film having a visible light transmittance of 90% (550 nm) or more and an electric resistance of 3.0 × 10 ⁻⁴ Ω · cm or less can be obtained.

  In this way, by forming a sintered rod for ion plating with a sintered body in which a plurality of materials having different characteristics are uniformly distributed, a film difficult to obtain with a sintered rod formed of a material having a single characteristic is formed. It becomes possible to film. The relative density can be adjusted by mixing and sintering the fired raw material and the unfired raw material. In particular, it is considered that the firing raw material can suppress changes in physical properties during sintering by forming it at a sufficiently oxidizing atmosphere and at a temperature higher than the temperature during sintering. It is considered that good electrical conductivity can be imparted by setting the atmosphere during sintering to a condition in which oxygen is deficient. In order to suppress changes in the characteristics of the sintered rod during film formation, it is preferable that both firing and sintering be performed at a temperature higher than the heating temperature of the sintered rod during film formation.

  A liquid crystal display device or an EL device can also be formed using a ZnO film as a transparent electrode.

  FIG. 9A shows a configuration example of a liquid crystal display device. The active matrix substrate 201 has a display area DA and a peripheral circuit area PH. In the display area DA, a scanning gate line GL, an auxiliary capacitance bus line SCL, a data line DL, and pixel electrodes formed of ZnO films at respective intersections. A pixel structure including PIX and thin film transistor TFT is formed. A gate control circuit GD and a data control circuit DD are formed in the peripheral circuit region PH. On the counter substrate 202, a color filter 203 corresponding to the pixel region and a common electrode 204 formed of a ZnO film common to all the pixels are formed. A liquid crystal layer 205 is sandwiched between the color filter substrate 202 and the active matrix substrate 201.

  FIG. 9B shows a configuration example of the organic EL panel. The active matrix substrate 201 is formed with a scanning gate wiring, a data wiring, a thin film TFT, and the like on a glass substrate as in the above embodiments. In each pixel region, the TFT source is connected to an anode 211 made of, for example, ZnO. On the anode 211, a hole transport layer 212, a light emitting layer 213, an electron transport layer 214, and a cathode 215 formed of aluminum or the like are laminated to form an organic EL element structure. The light emitted from the organic EL element is directed downward and emitted from the glass substrate of the active matrix substrate 201 to the outside. The upper part of the organic EL element is covered with a sealing material 220.

  Although the present invention has been described with reference to the embodiments, the present invention is not limited thereto. For example, the materials, thicknesses, and the like of the illustrated display device are examples and can be variously changed according to the design. Instead of the glass substrate, a transparent insulating substrate such as a quartz substrate may be used. It will be apparent to those skilled in the art that other various modifications, improvements, and combinations can be made.

It is sectional drawing which shows the structure of an ion plating apparatus. It is a general | schematic top view which shows the phenomenon when a sintered rod with a high relative density is used. It is sectional drawing, a flowchart, and a graph which show the sample formation process of a preliminary experiment, and a measurement result. It is the perspective view, sectional drawing, and photograph which show the manufacturing process of a sintered rod. It is a graph which shows the relative density of the rod which mixed and baked the baking raw material and the virgin raw material. It is a graph of the electrical resistance and transmittance | permeability of a ZnO film | membrane which provided oxygen flow rate during film-forming. It is a timing chart which shows the baking process which gives the oxygen amount limited only to the initial stage of a baking process. It is a graph which shows oxygen concentration when the oxygen amount limited only to the initial stage of a baking process is given with the furnace pressure and the furnace temperature. It is the perspective view and the top view which show the structure of a liquid crystal display device and EL device.

Explanation of symbols

MP Main powder raw material DP Additive powder raw material BM Ball mill B Ball S (High oxidation degree) area F (Low oxidation degree) area R Rod

Claims (16)

  A ZnO sintered body comprising a first ZnO region and a second ZnO region having different average degrees of oxidation, wherein the first ZnO region and the second ZnO region have different average grain sizes.   2. The ZnO sintered body according to claim 1, wherein the first ZnO region is embedded in a mottled pattern in the second ZnO region and has an average particle size larger than that of the second region.   The first ZnO region is a region having a higher degree of oxidation than the second ZnO region, and the second ZnO region is a bluish region having a color different from that of the first ZnO region. Or ZnO sintered compact of 2. The ZnO sintered body according to any one of claims 1 to 3, wherein the first and second ZnO regions are doped with a Group 3 element according to an element periodic table.   The ZnO sintered body according to claim 4, wherein the first and second ZnO regions are doped with a Ga element.   The ZnO sintered body according to any one of claims 1 to 5, wherein the sintered body including the first and second ZnO regions has a relative density of 80% or less and a resistivity of 10 kΩcm or less.   The ZnO sintered body according to any one of claims 1 to 6, wherein the ZnO sintered body has a cylindrical shape and is used for ion plating as a transparent electrode material. (A) preparing a powdery first ZnO raw material;
(B) forming a second ZnO material having an average particle size increased by firing a part of the first ZnO material in a first atmosphere having a first oxygen content;
(C) mixing the first ZnO raw material and the second ZnO raw material and pressing them using a mold;
(D) sintering the compacted ZnO raw material in a second atmosphere having a second oxygen content different from the first oxygen content;
The manufacturing method of the ZnO sintered compact containing this. The method for producing a ZnO sintered body according to claim 8, wherein in at least one of step (b) and step (d), oxygen is supplied into the firing furnace only before heating for sintering.   The method for producing a ZnO sintered body according to claim 8 or 9, wherein the firing temperature in the step (b) is higher than the sintering temperature in the step (d).   The method for producing a ZnO sintered body according to any one of claims 8 to 10, wherein the second oxygen content is lower than the first oxygen content.   The method for producing a ZnO sintered body according to claim 11, wherein the second oxygen content rate is higher than 0% and lower than 1% as an average value.   The method for producing a ZnO sintered body according to claim 11 or 12, wherein the second oxygen content rate is constituted by oxygen supplied only during a part of the sintering period.   The method for producing a ZnO sintered body according to claim 13, wherein a part of the sintering period is 1/10 or less of the sintering period.   The method for producing a ZnO sintered body according to any one of claims 11 to 14, wherein the first atmosphere is air.   A ZnO film is transparently formed on a substrate using the ZnO sintered body according to any one of claims 1 to 7 formed by the method for producing a ZnO sintered body according to any one of claims 8 to 15. A method for producing a transparent electrode formed as an electrode.

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