JP2014080312A - Method for producing zinc oxide-based sintered body and target - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a target for producing a high-density zinc oxide-based sintered body by suppressing volatilization of zinc and warping of the sintered body.
The method for producing a zinc oxide-based sintered body of the present invention includes the following processes A to C, and the primary firing of process B and the secondary firing of process C are performed by capsule-free hot isostatic pressing.
Process A: A raw material powder substantially consisting of zinc, titanium, carbon, and oxygen, and the proportion of titanium being 0.2% or more and 5% or less with respect to the total number of metal atoms is molded and molded. Process B: Process B: The molded body obtained in the process A is subjected to primary firing at a firing temperature of 900 to 1200 ° C. in an inert gas atmosphere at a pressure of 1 to 30 MPa, and a relative density is 92% or more and less than 98%. And a step of obtaining a primary sintered body having defects with closed pores Process C: Secondary firing of the primary sintered body obtained in the process B at 800 to 1400 ° C. in an inert gas atmosphere at a pressure of 90 MPa or more. To obtain a zinc oxide-based sintered body with a relative density of 98% or more [Selection] None

Description

  INDUSTRIAL APPLICATION This invention is useful as a target etc. which can form a zinc oxide type transparent conductive film stably by sputtering method, an ion plating method, a pulse laser deposition (PLD) method, or an electron beam (EB) vapor deposition method. The present invention relates to a method for manufacturing a zinc oxide-based sintered body and a target using the zinc oxide-based sintered body obtained by this manufacturing method.

  Transparent conductive films that have both conductivity and light transmission have been used for electrodes such as solar cells, liquid crystal display elements, and other various light receiving elements; heat ray reflective films for automobile windows and buildings; antistatic films; refrigeration It is used for a wide range of applications such as antifogging transparent heating elements in showcases. In particular, it is known that a transparent conductive film having low resistance and excellent conductivity is suitable for a solar cell, a liquid crystal display device (liquid crystal, organic electroluminescence, inorganic electroluminescence, etc.), a touch panel, and the like.

Conventionally, as a transparent conductive film, for example, an antimony-doped tin oxide (ATO) film; a tin oxide (SnO ₂ ) -based thin film such as a fluorine-doped tin oxide (FTO) film; an aluminum-doped zinc oxide (AZO) film, or a gallium-doped film Zinc oxide (ZnO) -based thin films such as zinc oxide (GZO) films; indium oxide (In ₂ O ₃ ) -based thin films such as tin-doped indium oxide (ITO) films are known. Among them, the most industrially used is an indium oxide-based transparent conductive film, and in particular, an ITO film is widely used because of its low resistance and excellent conductivity.

  Conventionally, when forming such a transparent conductive film, sputtering, ion plating, PLD, EB vapor deposition and the like are widely used industrially. The target used as a film raw material in these film formation methods is made of a solid containing a metal element constituting the film to be formed, and is a sintered body or a mixture of metal, metal oxide, metal nitride, metal carbide, etc. Body, and in some cases, a single crystal.

  For example, when an oxide film such as ITO is formed by sputtering, the target is generally an alloy target made of a metal element constituting the film (In-Sn alloy when forming an ITO film). Alternatively, an oxide target obtained by sintering or mixing an oxide containing a metal element constituting the film (in the case of forming an ITO film, a sintered body or a mixture made of In—Sn—O) is used.

When an alloy target is used, all the oxygen in the formed film is supplied from the oxygen gas in the atmosphere, so the oxygen gas amount in the atmosphere tends to fluctuate. As a result, the oxygen gas amount in the atmosphere It may be difficult to keep the film formation speed depending on the film thickness and the characteristics (specific resistance, transmittance) of the film obtained constant.
On the other hand, when an oxide target is used, part of the oxygen supplied to the film is supplied from the target itself, and only the deficiency is supplied from the oxygen gas in the atmosphere, so the amount of oxygen gas in the atmosphere This variation can be suppressed as compared with the case where an alloy target is used. As a result, it is possible to easily manufacture a transparent conductive film having a constant film thickness and a constant film characteristic.
Therefore, it has been a target for industrial use so far.

  By the way, an indium oxide-based transparent conductive film such as an ITO film is expensive because it is a rare metal because In (indium), which is an essential raw material, has a risk of resource depletion, and has toxicity and is harmful to the environment and the human body. It may have an adverse effect on it. Therefore, in recent years, an industrially versatile transparent conductive film that can be substituted for an ITO film has been demanded. Under such circumstances, a zinc oxide-based transparent conductive film that can be industrially manufactured by a sputtering method has attracted attention, and research is being conducted to improve its conductive performance.

  Specifically, Non-Patent Document 1 reports an attempt to dope various dopants into ZnO in order to increase conductivity. Among them, an AZO (aluminum-doped zinc oxide) film and a GZO (gallium-doped zinc oxide) film are practically used because they exhibit excellent conductivity. However, since AZO films and GZO films have poor chemical durability and particularly low transparency in the near infrared region, they are not suitable for solar cell applications such as applications as transparent electrodes for CIS / CIGS solar cells.

In addition, when the present inventors use low-valent titanium oxide instead of tetravalent titanium oxide (TiO ₂ (IV)) as a titanium source as a dopant, the inclusion of titanium useful for improving chemical durability. It has been found that the amount can be increased (see Patent Document 1). Furthermore, it has been found that it has low resistance and excellent near-infrared transmittance which is promising for transparent conductive films such as solar cells.
Here, the low valence titanium oxide is not only those having an integer valence of TiO (II) and Ti ₂ O ₃ (III), but also Ti ₃ O ₅ , Ti ₄ O ₇ , Ti ₆ O ₁₁ , It refers to titanium oxide represented by the general formula: TiO _2-X (X = 0.1-1) including Ti ₅ O ₉ , Ti ₈ O _{15 and the} like.

By the way, low-valent titanium oxide represented by TiO (II) is not used for general purposes unlike TiO ₂ (IV) used for photocatalysts, pigments, etc., and its use increases the cost. Therefore, there is no problem when the transparent conductive film is used for a special purpose that does not cause a problem in terms of cost. However, when the transparent conductive film is used for a general purpose, the cost may be disadvantageous. is there.
In addition to the low-valent titanium oxide already found by the present inventors as a titanium source, it is considered that titanium boride and metal titanium as described in Patent Document 2 may also exhibit the same characteristics. .

However, when titanium boride is used, boron oxide is generated during sintering. This boron oxide has a low melting point and low boiling point (melting point: about 450 ° C., boiling point: about 1860 ° C.), and at a sintering temperature (at least 1000 ° C.) necessary for obtaining a sintered body having the required minimum density, It is easy to melt and evaporate. Therefore, it becomes a sintered body having a non-uniform composition and a low density, and is inappropriate for use as a transparent conductive film forming material.
On the other hand, for titanium metal, there are no primary particles having an average particle size of 1 μm or less necessary for obtaining a uniform and high-density sintered body. That is, for commercially available metal titanium, the minimum primary particle size is about 20 μm, and it may not be possible to pulverize this to a particle size of about several μm, although it may cause a dust explosion and ignite. There is no. However, if pulverization is attempted so as to obtain a finer particle size (1 μm or less), dust explosion occurs almost certainly and ignition occurs, so primary particles having an average particle size of 1 μm or less cannot be obtained.
Furthermore, a large amount of oxygen deficiency can be introduced by introducing metal zinc or metal aluminum. However, metallic zinc (melting point: 419 ° C., boiling point: 930 ° C.) and metallic aluminum (melting point: 660 ° C., boiling point: 2060 ° C.) have low melting points and boiling points, and are easily melted and evaporated. Therefore, a porous sintered body having a low sintered density is obtained, or the molten metal flows and segregates (uneven composition).

JP 2011-190528 A JP 2009-263709 A

Monthly Display, September 1999, p10 “Trends in ZnO-based transparent conductive films”

  As a titanium source, the present inventors can significantly reduce costs compared to low-valent titanium oxide powder, have excellent storage stability, and are equivalent to a zinc oxide-based transparent conductive film formed using low-valent titanium oxide powder. It has been found that there is titanium carbide as a dopant capable of exhibiting the following characteristics (chemical durability, transmittance in the near infrared region and specific resistance).

On the other hand, in order to form the above-described zinc oxide-based transparent conductive film, an oxide target, that is, a titanium carbide-doped zinc oxide-based sintered body is used.
This titanium carbide-doped zinc oxide-based sintered body is produced by pressureless sintering, so that titanium carbide is not oxidized and becomes tetravalent titanium oxide (TiO ₂ (IV)). It is necessary to sinter in a non-oxidizing atmosphere such as an atmosphere or a reducing atmosphere.
Furthermore, the ease of volatilization of zinc differs depending on the atmosphere during sintering. For example, when zinc oxide powder is used as a raw material of the sintered body, the sintered body is oxidized in an oxidizing atmosphere such as an air atmosphere or an oxidizing atmosphere. In the production process, only the zinc oxide powder itself volatilizes, but when sintered in a non-oxidizing atmosphere, zinc oxide is reduced and becomes metal zinc that is more easily volatilized than zinc oxide. When manufacturing a sintered compact, the loss | disappearance amount of zinc increases compared with the case where it manufactures in an oxidizing atmosphere. Therefore, in order to produce a titanium carbide-doped zinc oxide-based sintered body by pressureless sintering, it is necessary to increase the amount of zinc oxide powder that is the raw material powder in advance for the target composition of the sintered body There is.

However, since it was extremely difficult to accurately calculate the amount of zinc volatilization, there was a problem that it was difficult to obtain a sintered body having the target composition.
When zinc is volatilized, there is a problem that the sintered body is warped, particularly when the size of the sintered body is large and the thickness is thin such as a disk shape or a plate shape. When cutting the sintered body with the target, if the sintered body is warped, there is a problem that workability is poor and production efficiency is lowered.

Furthermore, naturally, vacancies are likely to occur in the portion where zinc is volatilized, which leads to a decrease in the density of the sintered body. When such a low-density sintered body is used to form a film by sputtering, abnormal discharge is likely to occur. There was a problem that the film could not be formed stably. That is, suppressing the volatilization of zinc cannot be physically realized by pressureless sintering. Although there is a possibility that the volatilization of zinc can be suppressed by the pressure sintering method, in the general hot press method by the solid compression method, the raw material powder is molded and pressed and sintered. Since there is a clearance (gap) between punches, zinc volatilization cannot be avoided.
Note that a high-density sintered body has a relative density of 98% or more.

On the other hand, as one of the pressure sintering methods by the gas compression method, a gas is used as a pressure medium, and the powder to be sintered is made of a metal container (capsule so that the gas does not penetrate into the sintered body to be aimed at. The capsule HIP method is known in which a metal container is hermetically sealed and then heat treated together with the metal container under high temperature and pressure to produce a high-density sintered body.
However, in the capsule HIP method, since the powder to be sintered is hermetically sealed in a metal container, the volatilization of zinc can be suppressed to almost zero, but a metal container is used. The process of vacuum degassing the inside of the container is required, which causes the manufacturing cost to increase.

  An object of the present invention is to provide a method and a target for producing a high-density zinc oxide-based sintered body by suppressing zinc volatilization and warping of the sintered body. In particular, the present invention suppresses zinc volatilization by a capsule-free hot isostatic pressing method (HIP method) that does not use a metal container, and has a high density (relative density of 98% or more) zinc oxide-based sintering. The object is to provide a method of manufacturing a body.

  As a result of intensive studies to solve the above-mentioned problems, the present inventor has found a solution means having the following configuration and has completed the present invention.

That is, this invention consists of the following structures.
(1) A method for producing a zinc oxide-based sintered body comprising the following processes A to C, wherein the primary firing of process B and the secondary firing of process C are performed by capsule-free hot isostatic pressing.
Process A: A raw material powder substantially consisting of zinc, titanium, carbon, and oxygen, and the proportion of titanium being 0.2% or more and 5% or less with respect to the total number of metal atoms is molded and molded. Process B: Process B: The molded body obtained in the process A is subjected to primary firing at a firing temperature of 900 to 1200 ° C. in an inert gas atmosphere at a pressure of 1 to 30 MPa, and a relative density is 92% or more and less than 98%. And a step of obtaining a primary sintered body having defects with closed pores Process C: Secondary firing of the primary sintered body obtained in the process B at 800 to 1400 ° C. in an inert gas atmosphere at a pressure of 90 MPa or more. And a step of obtaining a zinc oxide-based sintered body having a relative density of 98% or more (2) including the following processes D to F, the primary firing of process E and the secondary firing of process F are capsule-free hot isostatic pressure By press Method for producing a zinc oxide-based sintered body, characterized in that the rope.
Process D: substantially consisting of at least one selected from gallium and aluminum, zinc, titanium, carbon and oxygen, and the proportion of titanium is 0.2% or more and 5% or less with respect to the total number of metal atoms, A step of forming a raw material powder by forming a raw material powder in which the ratio of the number of atoms of aluminum is 0.1 to 2.5% with respect to the total number of metal atoms. Process E: Process F in which primary firing is performed at a firing temperature of 900 to 1200 ° C. in an inert gas atmosphere of 1 to 30 MPa to obtain a primary sintered body having a relative density of 92% or more and less than 98% and defects having closed pores. : The primary sintered body obtained in the process E is subjected to secondary firing at 800 to 1400 ° C. in an inert gas atmosphere having a pressure of 90 MPa or more, and zinc oxide having a relative density of 98% or more. Obtaining a sintered body (3) the raw material powder, titanium carbide powder, method for producing a zinc oxide-based sintered body according to (1) comprising a mixed powder of zinc oxide powder.
(4) The zinc oxide-based material according to (2), wherein the raw material powder includes a mixed powder of at least one selected from gallium oxide powder, aluminum oxide powder, and aluminum carbide powder, titanium carbide powder, and zinc oxide powder. A method for producing a sintered body.
(5) A target used for film formation by a sputtering method, an ion plating method, a pulse laser deposition (PLD) method, or an electron beam (EB) vapor deposition method, which is any one of the above (1) to (4) A target obtained by processing a zinc oxide-based sintered body obtained by the production method described above.

  According to the present invention, volatilization of zinc and warpage of the sintered body are suppressed, and a high-density zinc oxide-based sintered body can be produced without substantially deviating from the target composition. By using a target obtained by processing this zinc oxide-based sintered body, it is stable with almost no abnormal discharge during film formation by sputtering, ion plating, PLD or EB vapor deposition. It is possible to form a zinc oxide-based transparent conductive film that exhibits excellent conductivity with good reproducibility. In addition, the transparent conductive film formed in this manner is extremely useful industrially because it has the advantage that it does not require toxic indium, which is a rare metal.

(Method for producing zinc oxide-based sintered body)
The production method of the present invention (hereinafter sometimes referred to as production method (a)) is a method of producing a zinc oxide-based sintered body by capsule-free hot isostatic pressing, and substantially comprises zinc and titanium. And a raw material powder (hereinafter sometimes referred to as a raw material powder (a)), which is composed of carbon and oxygen and contains titanium in a predetermined ratio, to obtain a molded body, and this molded body is placed in the HIP processing apparatus. Installed, firing temperature at which defects in the molded body become closed pores, relatively low pressure (relatively low pressure compared to normal HIP pressure) inert gas (Ar, nitrogen, etc.) that can suppress the volatilization of zinc oxide ) A primary sintered body having a relative density of 92% or more and less than 98% (usually 92% to 95%) composed of closed pores is produced by primary firing to a level at which open pores disappear in an atmosphere. Is introduced into the HIP processing equipment and deactivated By secondary sintering under high pressure gas atmosphere consisting of a gas, a method of making a relative density of 98% or more of high density of the zinc oxide-based sintered body. This method can produce a high-density sintered body that suppresses the volatilization of zinc and has almost no composition unevenness without using a metal container (capsule). The low pressure sintering (primary sintering) and the high pressure sintering (secondary sintering) may be performed by the same apparatus or may be performed by different apparatuses.

  The capsule-free hot isostatic pressing in the present invention refers to performing hot isostatic pressing (HIP) without using a capsule such as a metal container filled with raw material powder. Since the capsule-free hot isostatic press does not use a metal container, if a zinc oxide-based sintered body is produced by a capsule-free hot isostatic press, the zinc oxide-based sintered body is produced by a capsule hot isostatic press. A zinc oxide-based sintered body can be manufactured with less manufacturing cost than in the case of manufacturing.

  The raw material powder (a) consists essentially of zinc, titanium, carbon and oxygen. Here, “substantially” means that 99% or more of all atoms constituting the raw material powder are composed of zinc, titanium, carbon, and oxygen.

Furthermore, the ratio of the number of titanium atoms in the raw material powder is preferably 0.2% or more and 5% or less with respect to the total number of metal atoms, more preferably 0.3 to 4%, and still more preferably 0. .5 to 3.5%.
When the titanium carbide powder is mixed so that the ratio of the number of titanium atoms in the raw material powder is within the above range, the ratio of the number of titanium atoms is within this range without volatilizing zinc by the capsule-free HIP method. A zinc oxide-based sintered body having a composition can be produced. When the content of titanium in the zinc oxide-based sintered body is close to the upper limit in the above range (that is, close to 5%), the obtained zinc oxide-based transparent conductive film has excellent chemical durability. The refractive index is slightly higher than the case where the titanium content is close to the lower limit in the above range (that is, close to 0.2%), and the high transmittance in the near infrared region can be maintained, but the near ultraviolet region and There is a tendency for the transmittance in the visible light region to slightly decrease. There is no problem at all depending on the application, but for example, when used for a member of a solar cell such as a transparent electrode in a CIS / CIGS solar cell that requires a transmittance rather than chemical durability, the conversion efficiency of the solar cell is the content of titanium. Tends to be slightly lower than when close to the lower limit. On the other hand, when the titanium content is close to the lower limit, the refractive index of the zinc oxide-based transparent conductive film obtained is slightly lower than the case where the titanium content is close to the upper limit in a range where there is no problem. However, the transmittance in the near ultraviolet region and the visible light region can be improved while maintaining high transmittance in the near infrared region.
In this way, the titanium content can be increased or decreased depending on the use requiring chemical durability or the use requiring transmittance.
Here, the total number of metal atoms is the total number of metal atoms contained in the raw material powder, and zinc occupies about 95 to 99.8% of the total number of metal atoms. Therefore, zinc is the main component in the raw material powder.

  Examples of the powder constituting such a raw material powder include a powder containing a mixed powder of titanium carbide powder and zinc oxide powder or zinc hydroxide powder.

  As the zinc oxide powder, a powder of ZnO or the like having a wurtzite structure is usually used, and a powder obtained by firing this ZnO in advance in a reducing atmosphere and containing oxygen deficiency may be used. In addition, as a zinc oxide powder, it is good to use what has a purity of 99 weight% or more. The zinc oxide powder may have a firing history.

The average particle diameter of the zinc oxide powder is preferably 0.02 μm or more and 5 μm or less, respectively. Further, the BET specific surface area is not particularly limited.
In addition, when the particle size of the zinc oxide powder is small during the primary sintering, the specific surface area becomes large and the surface becomes active, so the primary sintering is performed at a lower sintering temperature than the primary sintering of the zinc oxide powder having a large particle size. Since sintering is possible, when the primary sintering is performed at a low firing temperature, it is preferable that the average particle diameter of the zinc oxide powder is small.

Examples of the zinc hydroxide powder include amorphous Zn (OH) ₂ powder and Zn (OH) ₂ powder having a crystal structure.

As the titanium carbide powder, for example, TiC powder is preferable.
Since TiC powder is not a metal oxide that is an unstable sub-valence in which titanium is in a low valence state, the particle itself has excellent storage stability, and the primary particle size itself is about 1 μm. Furthermore, the raw material cost of TiC itself is about 1/10 that of low-valent titanium oxide at the time of filing this application. Therefore, TiC powder that has been atomized in advance can be easily obtained and there is no need for pulverization costs. For example, the cost can be greatly reduced compared with the case of using low-valent titanium oxide powder, and the storage stability of the dopant raw material can be reduced. Excellent.

In addition, the zinc oxide-based transparent conductive film formed using titanium carbide powder as a dopant has the same characteristics (chemical durability, near infrared as the zinc oxide-based transparent conductive film formed using low-valent titanium oxide powder. Region permeability and resistivity) can be extracted. As a factor, a sintered body produced using low-valent titanium oxide powder as a dopant can stably introduce a large amount of oxygen vacancies, and even in a transparent conductive film produced using the same, A large amount of oxygen deficiency is stably introduced. Since this oxygen deficiency functions as carrier electrons, it is considered that low resistance is realized. On the other hand, when titanium carbide (TiC) powder is used, carbon is combined with the oxygen component of zinc oxide and released as CO or CO ₂ , so that a large amount of oxygen deficiency is introduced and is similar to that of low-valent titanium oxide. Estimated to be effective.

  The average particle size of each compound (powder) used as the raw material powder is preferably 5 μm or less.

  The zinc oxide-based sintered body is formed by subjecting the raw material powder containing at least the titanium carbide powder and the zinc oxide powder to uniaxial press molding or CIP molding, and setting the molded body in the HIP processing apparatus. It is manufactured by a two-step process of primary sintering and secondary sintering.

The molded body in the present invention is produced by forming a raw material powder by a molding method such as uniaxial pressing or cold isostatic pressing (CIP).
In the case of uniaxial pressing, the pressing pressure at the time of forming the raw material powder is at least 10 MPa or more and less than 50 MPa, more preferably 20 MPa or more. If it is less than 10 MPa, there is a possibility that a stable press-molded product cannot be produced. When it is 50 MPa or more, the molded body is fragile.
In the case of cold isostatic pressing (CIP), it is at least 50 MPa or more and less than 300 MPa, more preferably 100 MPa or more. If it is less than 50 MPa, there is a possibility that a stable press-molded product cannot be produced. When the pressure is 300 MPa or more, the molded body is fragile.
The shape and dimensions of the molded body are not particularly limited, and may be, for example, a cylindrical shape or a rectangular parallelepiped.

In order to make the density of the obtained molded body more uniform, before forming the raw material powder, the raw material powder may be granulated into a granulated product, and this granulated product may be molded into a molded body.
The method of making the raw material powder into a granulated product is not particularly limited. For example, after mixing the raw material powder and an aqueous solvent and sufficiently mixing the resulting slurry by wet mixing, solid-liquid separation, drying, Wet granulation; granulation by forcibly applying external force or heat to the raw material powder.

The wet mixing may be performed by, for example, a wet ball mill using a hard ZrO ₂ ball or a vibration mill, and the mixing time when using the wet ball mill or the vibration mill is preferably about 12 to 78 hours. In addition, although raw material powder may be dry-mixed as it is, wet mixing is more preferable. For solid-liquid separation / drying / granulation, known methods may be employed.
The aqueous solvent contains water as a main component and may be water alone, or may be a mixture of water and alcohol such as methanol or ethanol.
In addition, when obtaining a granulated material, what is necessary is just to granulate by a well-known method after drying, In that case, it is preferable to mix a binder with raw material powder. As the binder, for example, polyvinyl alcohol, vinyl acetate, ethyl cellulose and the like can be used.
In addition, when using a binder in order to obtain a granulated material, a debinding process is performed by degreasing before primary sintering with low-pressure HIP.

The conditions for producing the primary sintered body are 1 MPa to 30 MPa, preferably 3 MPa to 30 MPa, more preferably 4 MPa to 20 MPa in an inert gas atmosphere, and the firing temperature is 900 ° C. to 1200 ° C., preferably 950 ° C. to 1150 ° C. More preferably, it is 1000 degreeC-1100 degreeC. Under these conditions, the zinc volatilization and the warping of the sintered body can be suppressed, and the sintering of the open pores can proceed at the same level as the normal pressure, there is no open pores, and the defect is a closed pore. Thus, the relative density can be 92% or more and less than 98% (usually 92% to 95%). Sintering under these conditions is optimal for primary sintering before secondary sintering. Further, even when the pressure is in an inert gas atmosphere within the above range, if the firing temperature exceeds 1200 ° C, zinc begins to evaporate, and if the firing temperature is less than 900 ° C, sintering does not proceed sufficiently, All the open pores of the primary sintered body do not disappear, and the relative density of the obtained primary sintered body may be less than 92%.
Moreover, it is preferable that the holding | maintenance time of the conditions which produce a primary sintered compact is 1-48 hours.
In general, in a non-oxidizing atmosphere such as an inert atmosphere or a reducing atmosphere at 900 ° C. or higher and a pressure of 0.1013 MPa (normal pressure) or lower, zinc oxide is reduced to metallic zinc and volatilized in the form of metallic zinc. Therefore, the sintered body also warps due to the volatilization of zinc. On the other hand, by using a non-oxidizing atmosphere of 1 MPa to 30 MPa, the volatilization of zinc and the warpage of the sintered body can be suppressed if they are within the range of 900 ° C to 1200 ° C.
The primary sintered body thus obtained is subjected to secondary sintering, which will be described later, thereby suppressing zinc volatilization and becoming a zinc oxide-based sintered body having a relative density of 98% or more.
Examples of the inert atmosphere include nitrogen, argon, helium, vacuum, carbon dioxide, and the like.
Examples of the reducing atmosphere include hydrogen, carbon monoxide, hydrogen sulfide, sulfur dioxide, and the like.

  The primary sintered body has a relative density of 92% or more and less than 98%, and all defects are only closed pores. Since the relative density is 92% or more and less than 98%, a zinc oxide-based sintered body having a relative density of 98% or more can be obtained by secondary sintering.

Here, the relative density is obtained by multiplying the unit density of each metal oxide, which is a raw material of the sintered body, by the mixing weight ratio of each metal oxide powder, and the actual density obtained by taking the sum of the theoretical density. For example, when the sintered body is made of zinc oxide and titanium carbide, the density is obtained from the following formula.
Relative density = 100 × [(density of sintered body) / (theoretical density)]
Theoretical density = (Zinc oxide simple substance density x mixing weight ratio + Titanium carbide simple substance density x mixing weight ratio)
In addition, the density of a sintered compact can be measured with the evaluation method as described in an Example.

In the present invention, it is important that all defects of the primary sintered body are only closed pores. This is due to the following reasons.
In general, defects in a sintered body are classified into two types: open pores that communicate with the outside world and closed pores that do not communicate with the outside world. In a sintered body having open pores, volume shrinkage that crushes open pores is difficult to proceed even when a high pressure is applied. For this reason, even when capsule-free HIP sintering is performed at high pressure and high temperature, sintering that crushes open pores is difficult to proceed, and it is difficult to increase the density of the sintered body. On the other hand, when a high pressure is applied to a sintered body consisting only of closed pores, the sintered body is likely to shrink in volume by crushing the closed pores. Therefore, if capsule-free HIP sintering is performed at a high pressure and a high temperature, the sintering can be progressed to crush closed pores, and the sintered body can be densified. For this reason, before the capsule-free HIP sintering at high pressure and high temperature, the molded body is preliminarily sintered at low pressure and high temperature for a long time, that is, the sintering is performed so as to crush the open pores of the molded body. All the defects of the primary sintered body to be made are only closed pores.
In normal atmospheric pressure sintering, both the open pores and closed pores of the sample are sintered, and the reaction is crushed as the sintered density increases.

In the secondary sintering, the primary sintered body itself is sintered using an inert gas under high temperature and high pressure as a pressure medium.
The HIP treatment conditions at this time are usually carried out for 1 hour or longer under an inert gas atmosphere with a pressure of 90 MPa or higher under a firing temperature of 800 to 1400 ° C. If the HIP processing condition is this condition, the closed pores of the primary sintered body can be sintered and densified. Since the pressure in the secondary sintering is as high as 90 MPa or more, volatilization of zinc is suppressed and compositional deviation hardly occurs. The holding time is usually 1 hour or longer, but is not limited to this, and the relative density of the obtained zinc oxide-based sintered body may be 98% or higher. Nitrogen, argon, etc. can be used as the inert gas as the pressure medium.

(Manufacturing method of other zinc oxide sintered bodies)
Another method for producing a zinc oxide-based sintered body of the present invention (hereinafter sometimes referred to as production method (b)) is substantially composed of at least one selected from gallium and aluminum, zinc, titanium, carbon and oxygen. The raw material powder containing titanium in a predetermined ratio and containing gallium or aluminum in a predetermined ratio (hereinafter sometimes referred to as raw material powder (b)) is used as the raw material powder in the manufacturing method (a) described above. Other than that, a zinc oxide-based sintered body is produced in the same manner as in the production method (a) described above.

The raw material powder (b) is substantially composed of at least one selected from gallium and aluminum, zinc, titanium, carbon and oxygen. Here, “substantially” means that 99% or more of all atoms constituting the raw material powder (b) are composed of at least one selected from gallium and aluminum, zinc, titanium, carbon, and oxygen. Means.
Since the raw material powder (b) contains at least one selected from gallium and aluminum as the second dopant, the resistance of the zinc oxide-based transparent conductive film formed using the obtained zinc oxide-based sintered body is further reduced. be able to.

The ratio of the number of titanium atoms in the raw material powder (b) is preferably 0.2% or more and 5% or less with respect to the total number of metal atoms, more preferably 0.3 to 4%, and still more preferably. 0.5 to 3.6%.
When the titanium carbide powder is mixed so that the ratio of the number of titanium atoms in the raw material powder (b) is within the above range, the ratio of the number of titanium atoms is within this range without volatilizing zinc by the capsule-free HIP method. A zinc oxide-based sintered body having a composition within the above range can be produced. The ratio of the number of titanium atoms can increase or decrease the titanium content depending on the use requiring chemical durability and the use requiring transmittance, as in the case of the raw material powder (a).
Here, the total number of metal atoms is the total number of metal atoms contained in the raw material powder (b), and zinc occupies about 92.5 to 99.7% of the total number of metal atoms. Therefore, zinc is the main component in the raw material powder (b).

The ratio of the number of atoms of gallium or aluminum in the raw material powder (b) is 0.1% or more and 2.5% or less, preferably 0.5% or more and 1.9% or less with respect to the total number of metal atoms. If the ratio of the number of atoms of gallium or aluminum is less than 0.1%, the conductivity improving effect may be insufficient. On the other hand, if it exceeds 2.5%, gallium or aluminum cannot be completely substituted and dissolved in the zinc site, and is precipitated at the crystal grain boundary, which may cause a decrease in conductivity and a decrease in transmittance.
The raw material powder (b) may contain gallium and aluminum. In such a case, the ratio of the number of atoms of gallium and aluminum in the raw material powder (b) is 0.1% or more with respect to the total number of metal atoms. It may be 2.5% or less, preferably 0.5% or more and 1.9% or less.

  Examples of the powder constituting the raw material powder (b) include at least one selected from gallium oxide powder, aluminum oxide powder, and aluminum carbide powder, titanium carbide powder, and zinc oxide powder or zinc hydroxide powder. Examples include mixed powder.

Examples of the aluminum oxide powder include Al ₂ O ₃ powder, and examples of the gallium oxide powder include Ga ₂ O ₃ .
Examples of the aluminum carbide powder include Al ₄ C ₃ powder.
As the titanium carbide powder, zinc oxide powder, zinc hydroxide powder and the like, the same ones as exemplified in the production method (a) can be used.

  The average particle size of each compound (powder) used as the raw material powder (b) is preferably 5 μm or less.

(Zinc oxide sintered body)
The zinc oxide-based sintered body thus obtained has a relative density of 98% or more. For this reason, for example, when forming a film by sputtering using the sintered body, abnormal discharge hardly occurs and the film can be stably formed.

When the zinc oxide-based sintered body is manufactured by the manufacturing method (a), it is a sintered body substantially composed of zinc, titanium, carbon, and oxygen.
Further, when produced by the production method (b), it substantially comprises zinc, titanium, at least one selected from aluminum and gallium, carbon, and oxygen.
Here, “substantially” means that in the former case, 99% or more of all atoms constituting the zinc oxide sintered body are composed of zinc, titanium, carbon, and oxygen, and the latter In this case, it means that 99% or more of all atoms constituting the zinc oxide-based sintered body are composed of zinc, one of titanium, gallium and aluminum, carbon and oxygen.

  In the zinc oxide-based sintered body, it is preferable that the ratio of the number of titanium atoms is 0.2% to 5% with respect to the total number of metal atoms. If the ratio of the number of atoms of titanium is less than 0.2%, chemical durability such as chemical resistance of a film formed using the zinc oxide sintered body as a target becomes insufficient. On the other hand, if the ratio of the number of titanium atoms exceeds 5%, titanium carbide cannot be sufficiently substituted and dissolved in the zinc site, and the conductivity and transparency of the film formed using this zinc oxide-based sintered body as a target will decrease. To do. Preferably, it is an amount such that the ratio of the number of atoms of titanium is 0.3% or more and 4% or less, more preferably 0.5% or more and 3.5% or less with respect to the total number of metal atoms.

In particular, the zinc oxide-based sintered body preferably contains titanium so that Ti / (Zn + Ti) = 0.002 or more and 0.05 or less by atomic ratio.
If the value of Ti / (Zn + Ti) is smaller than 0.002, chemical durability such as chemical resistance of a film formed using this zinc oxide-based sintered body as a target becomes insufficient, and the specific resistance also increases. In addition, since the zinc titanate compound is hardly formed in the zinc oxide-based sintered body, the strength of the sintered body is lowered, and there is a possibility that it becomes difficult to process the target. On the other hand, when the value of Ti / (Zn + Ti) is a titanium content exceeding 0.05, formation of a titanium carbide crystal phase that is desired not to be contained in the zinc oxide-based sintered body can be avoided as described later. There is a risk that the conductivity and transparency of a film formed using this zinc oxide-based sintered body as a target will be reduced. Preferably, the titanium content is such that Ti / (Zn + Ti) = 0.004 to 0.04 in atomic ratio, and more preferably Ti / (Zn + Ti) = 0.005 in atomic ratio. The amount is 0.035.

In particular, when Ti / (Zn + Ti) = 0.002 or more and 0.02 or less, the chemical durability of the formed film tends to be lower than when Ti / (Zn + Ti) = 0.02 and less than 0.1. However, the chemical durability is far superior to at least the currently used AZO (aluminum-doped zinc oxide) film and GZO (gallium-doped zinc oxide) film, and it was formed by reducing the titanium content. The refractive index of the film decreases, and the transmittance particularly from the visible region to the near ultraviolet region tends to increase. When the transparency of the film in the near ultraviolet region to the visible region is improved, the conversion efficiency of a solar cell using this transparent conductive film as a member of a solar cell such as a ZnO window layer in a CIS / CIGS solar cell may be increased. it can. Furthermore, since it is difficult to sufficiently reduce the resistance of the formed film with titanium alone, it is preferable to include at least one of aluminum and gallium.
On the other hand, when Ti / (Zn + Ti) = 0.02 and 0.1 or less, the chemical durability of the formed film is extremely excellent, and it is possible to reduce the resistance only with titanium, but the resistance is further reduced. Therefore, it is preferable to include at least one of gallium and aluminum.

  The transparent conductive film formed using the zinc oxide-based sintered body produced by the production method of the present invention is superior in chemical durability and near-infrared high transmittance than the AZO film and GZO film, As described above, depending on the titanium content, high transparency in the near ultraviolet region to visible region can be emphasized, that is, whether conversion efficiency of the solar cell should be emphasized or extremely high chemical durability should be emphasized. it can.

The zinc oxide-based sintered body obtained by the production method (a) is preferably composed of a zinc oxide phase and a zinc titanate compound phase. If the zinc titanate compound phase is contained in the zinc oxide-based sintered body as described above, the strength of the sintered body itself increases. For example, even if the film is formed under severe conditions (high power, etc.) as a target. No cracks are generated.
In addition, the zinc titanate compound phase specifically includes ZnTiO ₃ and Zn ₂ TiO ₄ , those in which titanium element is dissolved in these zinc sites, those in which oxygen deficiency is introduced, Non-stoichiometric compositions with a Zn / Ti ratio slightly deviating from these compounds are also included.
In addition, the zinc oxide phase specifically includes ZnO, a solution in which a titanium element is dissolved, an oxygen deficiency introduced, or a non-stoichiometric composition due to zinc deficiency. Including things. The zinc oxide phase usually has a wurtzite structure.

The zinc oxide-based sintered body obtained by the production method (b) is a sintered body composed of a zinc oxide phase, a zinc titanate compound phase, and at least one oxide phase selected from gallium and aluminum. Preferably there is.
The at least one oxide phase selected from gallium and aluminum is at least one selected from Al ₂ O ₃ and Ga ₂ O ₃ .
The zinc titanate compound phase is specifically selected from ZnTiO ₃ , Zn ₂ TiO ₄ , at least one selected from these zinc sites and titanium sites, and from titanium element, gallium element and aluminum element. It is intended to include those in which at least one is dissolved, those into which oxygen vacancies are introduced, and those having a non-stoichiometric composition in which the Zn / Ti ratio slightly deviates from these compounds.
In addition, the zinc oxide phase specifically includes, in addition to ZnO, at least one selected from a titanium element, a gallium element, and an aluminum element at the zinc site thereof, or oxygen deficiency introduced. And those that have non-stoichiometric composition due to zinc deficiency. The zinc oxide phase usually has a wurtzite structure.

  It is preferable that the zinc oxide-based sintered body does not substantially contain a titanium carbide crystal phase. If the zinc oxide-based sintered body contains a crystal phase of titanium carbide, the resulting film may be uneven in physical properties such as specific resistance and lack uniformity. Since the value of Ti / (Zn + Ti) described above is 0.05 or less in the zinc oxide-based sintered body, usually, titanium completely reacts with zinc oxide, and the titanium oxide crystalline phase is contained in the zinc oxide-based sintered body. Is difficult to generate. The crystal phase of titanium carbide specifically includes not only TiC but also a substance in which other elements such as Zn are dissolved in these crystals.

  The zinc oxide-based sintered body preferably also contains at least one element selected from the group consisting of tin, silicon, germanium, zirconium, and hafnium (hereinafter, these may be referred to as “additive elements”). . By containing such an additive element, the specific resistance of the zinc oxide-based sintered body itself can be reduced in addition to the specific resistance of the film formed using the zinc oxide-based sintered body as a target. For example, the deposition rate during DC sputtering depends on the specific resistance of the zinc oxide-based sintered body used as the sputtering target. By reducing the specific resistance of the zinc oxide-based sintered body itself, productivity during film formation is improved. Can be made. When the additive element is contained, the total content is preferably 0.05% or less in terms of atomic ratio with respect to the total amount of all metal elements constituting the zinc oxide-based sintered body. When there is more content of an additional element than the said range, there exists a possibility that the specific resistance of the film | membrane formed using a zinc oxide type sintered compact as a target may increase.

In order to contain the additive element in the zinc oxide-based sintered body, for example, the oxide powder of the additive element may be mixed with the raw material powder described above.
The additive element may be present in the zinc oxide-based sintered body in the form of an oxide, or may be present in the form substituted (solid solution) in the zinc site of the zinc oxide phase, or titanium. It may exist in a form substituted (solid solution) with at least one selected from a titanium site and a zinc site in the zinc acid compound phase.

The zinc oxide-based sintered body may contain other elements such as indium, iridium, ruthenium, rhenium as impurities in addition to the additive elements. The total content of elements contained as impurities is preferably 0.1% or less with respect to the total amount of all metal elements constituting the zinc oxide-based sintered body in terms of atomic ratio.
In order to contain impurities in the zinc oxide-based sintered body, for example, the impurity powder may be mixed with the above-described raw material powder.

  The specific resistance of the zinc oxide-based sintered body is preferably 5 kΩ · cm or less. For example, the deposition rate during DC sputtering depends on the specific resistance of the zinc oxide-based sintered body used as a sputtering target. Therefore, when the specific resistance of the zinc oxide-based sintered body exceeds 5 kΩ · cm, the DC sputtering is stable. There is a risk that proper film formation cannot be performed. Considering the productivity at the time of film formation, the specific resistance of the zinc oxide-based sintered body is preferably as low as possible. Specifically, it should be 100 Ω · cm or less.

  Normally, when a zinc oxide-based sintered body is sintered in a reducing atmosphere, the specific resistance of the zinc oxide-based sintered body is reduced due to the introduction of oxygen deficiency, and when sintered in an oxidizing atmosphere, the specific resistance is reduced. Becomes higher.

(target)
The target of the present invention is a target used for film formation by sputtering, ion plating, PLD, or EB vapor deposition. In addition, although the solid material used in the film formation may be referred to as “tablet”, in the present invention, these are referred to as “target”.

The target of the present invention is obtained by processing the zinc oxide-based sintered body described above into a predetermined shape and a predetermined dimension.
A processing method in particular is not restrict | limited, What is necessary is just to employ | adopt a well-known method suitably. For example, after subjecting the zinc oxide-based sintered body to surface grinding or the like, the target of the present invention can be obtained by pasting the zinc oxide-based sintered body to a predetermined size and then attaching it to a support base. Further, if necessary, a plurality of zinc oxide-based sintered bodies may be divided into divided shapes to form a large-area target (composite target).

  A transparent conductive film formed using a zinc oxide-based sintered body or the target of the present invention has both reproducible and stable conductivity and chemical durability (heat resistance, moisture resistance, etc.). So, for example, transparent electrodes such as liquid crystal displays, plasma displays, inorganic EL (electroluminescence) displays, organic EL displays, and electronic paper, window electrodes of photoelectric conversion elements of solar cells, electrodes of input devices such as transparent touch panels, It is suitably used for applications such as an electromagnetic shielding film of an electromagnetic shield. Furthermore, the transparent conductive film formed using the zinc oxide-based sintered body or the target of the present invention is combined with other metal films and metal oxide films as transparent radio wave absorbers, ultraviolet absorbers, and transparent semiconductor devices. Can also be used.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited by this Example.

Example 1
Zinc oxide powder (ZnO powder; purity 99.9%, average particle size 0.05 μm, manufactured by Hakusuitec Co., Ltd.) and titanium carbide powder (TiC powder; purity 99.9%, average particle size 0.9 to 1.5 μm) , Made by Nippon Shin Metal Co., Ltd.) in a resin pot containing raw material powder containing a Zn: Ti atomic ratio of 97: 3 (ratio to the total number of titanium metal atoms: 3%). Wet mixing was performed by a ball mill mixing method. The wet mixing was performed using hard ZrO ₂ balls as balls and mixing time of 18 hours.
Next, the mixed raw material powder slurry is taken out, the balls are removed by sieving, the solvent is stripped off with an evaporator, and then dried at 100 ° C. for 3 hours with a hot air dryer and dried. Molding was performed by applying a pressure of 137 MPa with a hydraulic press, and cutting was performed to obtain a cylindrical molded body having a diameter of 80 mm and a thickness of 78 mm.

<Manufacture of zinc oxide-based sintered body>
A cylindrical molded body is installed in a HIP processing apparatus (manufactured by Kobe Steel, Ltd.), and the temperature is increased from room temperature to 950 ° C. at a temperature rising rate of 500 ° C./hour, and the temperature is 950 ° C. in an Ar atmosphere at a pressure of 10 MPa. For 24 hours, and a low-pressure HIP treatment was performed to obtain a primary sintered body. There was no volatilization of zinc during the low pressure HIP sintering, and the relative density of the primary sintered body was 92.4%. Further, when the primary sintered body was observed with an electron microscope, no obvious voids were observed and there were almost no open pore defects.
The relative density of the primary sintered body was obtained by multiplying the unit density of zinc oxide and titanium carbide by the weight ratio of mixing and taking the sum as 100% as shown in the following formula.
Relative density = 100 × [(density of sintered body) / (theoretical density)]
Theoretical density = (Zinc oxide simple substance density x mixing weight ratio + Titanium carbide simple substance density x mixing weight ratio)
The density of the sintered body was measured by the Archimedes method.

Next, a high-pressure gas (Ar gas) is introduced into the HIP processing apparatus, and the primary sintered body is held at a temperature of 1100 ° C. for 1 hour in an Ar atmosphere at a pressure of 100 MPa to perform high-pressure HIP processing and zinc oxide-based sintering. Body (1) was obtained. The relative density of the zinc oxide-based sintered body (1) after the high-pressure HIP treatment was 99.6% as determined in the same manner as the relative density of the primary sintered body. Moreover, there was no curvature in the sintered compact (1).
The presence or absence of warpage of the obtained sintered body was judged visually.

The obtained zinc oxide-based sintered body (1) was ground and then subjected to surface polishing to obtain a sintered body having a diameter of 50.8 mmφ and a thickness of 3 mm.
When this zinc oxide-based sintered body (1) was analyzed with an energy dispersive X-ray fluorescence apparatus (“EDX-700L” manufactured by Shimadzu Corporation), the atomic ratio of Zn and Ti was Zn: Ti = 97. : 3 (Ti / (Zn + Ti) = 0.03). Since the zinc oxide-based sintered body (1) has an atomic ratio of Zn and Ti that is the same as that of the raw material powder Zn: Ti = 97: 3, which is the charged composition, the volatilization of zinc is There wasn't.
When the crystal structure of this zinc oxide-based sintered body (1) was examined with an X-ray diffractometer (“RINT2000” manufactured by Rigaku Corporation), zinc oxide (ZnO) and zinc titanate (Zn ₂ TiO ₄ ) It was a mixture of crystal phases, and no titanium carbide crystal phase was present.

This zinc oxide-based sintered body (1) was bonded using indium solder using a copper plate as a backing plate to obtain a sputtering target. Using this, a transparent conductive film was formed on a transparent substrate (quartz glass substrate) by DC sputtering to obtain a transparent conductive substrate. That is, a target and a transparent base material (quartz glass substrate) are respectively installed in a sputtering apparatus (“E-200” manufactured by Canon Anelva Engineering Co., Ltd.), and Ar gas (purity 99.9995% or more, Ar pure gas) = 5N) was introduced at 12 sccm, and sputtering was performed under the conditions of a pressure of 0.5 Pa, a power of 75 W, and a substrate temperature of 250 ° C. to form a transparent conductive film having a thickness of 500 nm on the substrate.
The number of times the operation of the sputtering apparatus was stopped due to abnormal discharge generated during film formation was within 3 times per hour, and almost no abnormal discharge occurred during film formation.

  As mentioned above, since there is no volatilization of zinc, the ratio of the metal atom of the raw material powder which is a raw material of the zinc oxide sintered body (1) and the ratio of the metal atom of the obtained zinc oxide sintered body (1) Is a zinc oxide-based sintered body having no warpage and having a very high density and no warping. As a result, abnormal discharge does not occur even when sputtering is performed using a target obtained by processing the zinc oxide-based sintered body (1). The film could be formed stably.

(Example 2)
Zinc oxide powder (ZnO powder; purity 99.9%, average particle size 0.05 μm, manufactured by Hakusuitec Co., Ltd.), gallium oxide powder (Ga ₂ O ₃ powder; purity 99.9%, average particle size 1 μm or less, Sumitomo Chemical Co., Ltd.) and titanium carbide powder (TiC powder; purity 99.9%, average particle size 0.9-1.5 μm, manufactured by Nippon Shin Metal Co., Ltd.) have an atomic ratio of Zn: Ga: Ti. Resin pot containing raw material powder containing 98.2: 0.8: 1.0 (ratio of titanium to the total number of metal atoms: 1%, ratio of gallium to the total number of metal atoms: 0.8%) In the same manner as in Example 1, after wet mixing and drying, a cold isostatic press was applied by applying a pressure of 137 MPa, and a cutting process was performed to obtain a cylindrical molded body having a diameter of 80 mm and a thickness of 78 mm. Got.

<Manufacture of zinc oxide-based sintered body>
The cylindrical molded body was installed in a HIP processing apparatus (manufactured by Kobe Steel, Ltd.), and the temperature was increased from room temperature to 950 ° C. at a temperature increase rate of 500 ° C./hour, and the temperature was 950 ° C. in an Ar atmosphere of 8 MPa. Holding for 24 hours, low-pressure HIP sintering was performed to obtain a primary sintered body.
There was no volatilization of zinc during low pressure HIP sintering, and the relative density was 93.0%. Further, when the sintered body was observed with an electron microscope, no obvious voids were observed and there were almost no defects in open pores.
The relative density of the primary sintered body was obtained by multiplying the unit density of zinc oxide, titanium carbide, and gallium oxide by the weight ratio of the mixture and taking the sum as 100% as shown in the following formula.
Relative density = 100 × [(density of sintered body) / (theoretical density)]
Theoretical density = (Zinc oxide simple substance density × mixing weight ratio + Titanium carbide simple substance density × mixing weight ratio + gallium oxide simple substance density × mixing weight ratio)
The density of the sintered body was measured in the same manner as in Example 1.

  Next, the primary sintered body was subjected to high-pressure HIP treatment in the same manner as in Example 1 to obtain a zinc oxide-based sintered body (2). The relative density of the zinc oxide-based sintered body (2) after the high-pressure HIP treatment was 99.6% when determined in the same manner as the relative density of the primary sintered body. Moreover, when the curvature of the sintered body (2) was judged in the same manner as in Example 1, the sintered body (2) was not warped.

The obtained zinc oxide-based sintered body (2) was processed in the same manner as in Example 1 to obtain a sintered body having a diameter of 50.8 mmφ and a thickness of 3 mm.
When the composition and crystal structure of the zinc oxide-based sintered body (2) were analyzed in the same manner as in Example 1, the atomic ratio of Zn, Ga, and Ti was Zn: Ga: Ti = 98.2: 0. 8: 1.0. The atomic ratio of Zn, Ga, and Ti in the zinc oxide-based sintered body (2) is the charged composition. The atomic ratio of the raw material powder: Zn: Ga: Ti = 98.2: 0.8: 1.0 There was no volatilization of zinc.
The crystal structure of the zinc oxide-based sintered body (2) is a mixture of crystal phases of zinc oxide (ZnO) and zinc titanate (Zn ₂ TiO ₄ ), and there is no crystal phase of titanium carbide. There wasn't. Further, the crystal phase of gallium oxide could not be confirmed.

  The zinc oxide based sintered body (2) was bonded using indium solder using a copper plate as a backing plate to obtain a sputtering target, and a transparent conductive substrate was obtained in the same manner as in Example 1. The number of times the operation of the sputtering apparatus was stopped due to the abnormal discharge generated in 3 was within 3 times per hour, and almost no abnormal discharge occurred during the film formation.

  From the above, since there is no volatilization of zinc, the ratio of the metal atoms of the raw material powder that is the raw material of the zinc oxide-based sintered body (2) and the ratio of the metal atoms of the obtained zinc oxide-based sintered body (2) Is a zinc oxide-based sintered body with no warpage and extremely high density and without warping. As a result, abnormal discharge occurs even when sputtering is performed using a target obtained by processing the zinc oxide-based sintered body (2). The film could be formed stably.

(Example 3)
Zinc oxide powder (ZnO powder; purity 99.9%, average particle size 0.05 μm, manufactured by Hakusui Tech Co., Ltd.), aluminum oxide powder (Al ₂ O ₃ , purity 99.99%, average particle size 0.5 μm, Sumitomo Chemical Co., Ltd.) and titanium carbide powder (TiC powder; purity 99.9%, average particle size 0.9-1.5 μm, manufactured by Nippon Shin Metal Co., Ltd.) have an atomic ratio of Zn: Al: Ti Resin pot containing raw material powder containing 98.2: 0.8: 1.0 (ratio to the total number of metal atoms of titanium: 1%, ratio to the total number of metal atoms of aluminum: 0.8%) In the same manner as in Example 1, after wet mixing and drying, a cold isostatic press was applied by applying a pressure of 137 MPa, and a cutting process was performed to obtain a cylindrical molded body having a diameter of 80 mm and a thickness of 78 mm. Got.

<Manufacture of zinc oxide-based sintered body>
The cylindrical molded body was installed in a HIP processing apparatus (manufactured by Kobe Steel, Ltd.), and the temperature was increased from room temperature to 950 ° C. at a temperature increase rate of 500 ° C./hour, and the temperature was 950 ° C. in an Ar atmosphere of 8 MPa. Holding for 24 hours, low-pressure HIP sintering was performed to obtain a primary sintered body.
There was no zinc volatilization during low pressure HIP sintering and the relative density was 92.9%. Further, when the sintered body was observed with an electron microscope, no obvious voids were observed and there were almost no defects in open pores.
The relative density of the primary sintered body was obtained by multiplying the unit density of zinc oxide, titanium carbide, and aluminum oxide by the weight ratio of the mixture and taking the sum as 100% as shown in the following formula.
Relative density = 100 × [(density of sintered body) / (theoretical density)]
Theoretical density = (Zinc oxide simple substance density x mixing weight ratio + Titanium carbide simple substance density x mixing weight ratio + Aluminum oxide simple substance density x mixing weight ratio)
The density of the sintered body was measured in the same manner as in Example 1.

  Next, the primary sintered body was subjected to high-pressure HIP treatment in the same manner as in Example 1 to obtain a zinc oxide-based sintered body (3). The relative density of the zinc oxide-based sintered body (3) after the high-pressure HIP treatment was 99.6% when determined in the same manner as the relative density of the primary sintered body. Moreover, when the curvature of the sintered compact (3) was judged similarly to Example 1, there was no curvature in the sintered compact (3).

The obtained zinc oxide-based sintered body (3) was processed in the same manner as in Example 1 to obtain a sintered body having a diameter of 50.8 mmφ and a thickness of 3 mm.
When the composition and crystal structure of this zinc oxide-based sintered body (3) were analyzed in the same manner as in Example 1, the atomic ratio of Zn, Al, and Ti was Zn: Al: Ti = 98.2: 0. 8: 1.0. The atomic ratio of Zn, Al, and Ti in the zinc oxide-based sintered body (3) is the charged composition. The atomic ratio of the raw material powder Zn: Al: Ti = 98.2: 0.8: 1.0 There was no volatilization of zinc.
The crystal structure of the zinc oxide-based sintered body (3) is a mixture of crystal phases of zinc oxide (ZnO) and zinc titanate (Zn ₂ TiO ₄ ), and there is no crystal phase of titanium carbide. There wasn't. Moreover, the crystal phase of aluminum oxide could not be confirmed.

  The zinc oxide-based sintered body (3) was bonded using indium solder using a copper plate as a backing plate, and a sputtering target was obtained. In the same manner as in Example 1, a transparent conductive substrate was obtained. The number of times the operation of the sputtering apparatus was stopped due to the abnormal discharge generated in 3 was within 3 times per hour, and almost no abnormal discharge occurred during the film formation.

  As mentioned above, since there is no volatilization of zinc, the ratio of the metal atom of the raw material powder which is a raw material of the zinc oxide-based sintered body (3), and the ratio of the metal atom of the obtained zinc oxide-based sintered body (3) Is a zinc oxide-based sintered body with no warpage and extremely high density without warping. As a result, abnormal discharge does not occur even when sputtering is performed using a target obtained by processing the zinc oxide-based sintered body (3). The film could be formed stably.

(Example 4)
Zinc oxide powder (ZnO powder; purity 99.9%, average particle size 0.05 μm, manufactured by Hakusui Tech Co., Ltd.), titanium carbide powder (TiC powder; purity 99.9%, average particle size 0.9 to 1.5 μm) , Nippon Shin Metals Co., Ltd.), a raw material powder containing a Zn: Ti atomic ratio of 99.0: 1.0 (ratio with respect to the total number of metal atoms of titanium: 1%) In the same manner as in Example 1, after wet mixing and drying, a cold isostatic press was applied by applying a pressure of 137 MPa, and a cutting process was performed to obtain a cylindrical molded body having a diameter of 80 mm and a thickness of 78 mm. Got.

<Manufacture of zinc oxide-based sintered body>
The cylindrical molded body was installed in a HIP processing apparatus (manufactured by Kobe Steel, Ltd.), and the temperature was increased from room temperature to 950 ° C. at a temperature increase rate of 500 ° C./hour, and the temperature was 950 ° C. in an Ar atmosphere of 8 MPa. Holding for 24 hours, low-pressure HIP sintering was performed to obtain a primary sintered body.
There was no volatilization of zinc during low pressure HIP sintering, and the relative density was 93.3%. Further, when the sintered body was observed with an electron microscope, no obvious voids were observed and there were almost no defects in open pores.
The relative density of the primary sintered body was determined in the same manner as in Example 1.

  Next, the primary sintered body was subjected to high-pressure HIP treatment in the same manner as in Example 1 to obtain a zinc oxide-based sintered body (4). The relative density of the zinc oxide sintered body (4) after the high-pressure HIP treatment was 99.6% as determined in the same manner as the relative density of the primary sintered body. Moreover, when the curvature of the sintered body (4) was judged in the same manner as in Example 1, the sintered body (4) was not warped.

The obtained zinc oxide-based sintered body (4) was processed in the same manner as in Example 1 to obtain a sintered body having a diameter of 50.8 mmφ and a thickness of 3 mm.
The composition and crystal structure of the zinc oxide-based sintered body (4) were analyzed in the same manner as in Example 1. As a result, the atomic ratio of Zn, Al, and Ti was Zn: Ti = 99.0: 1.0. there were. Since the atomic ratio of Zn and Ti in the zinc oxide-based sintered body (4) is a prepared composition, the atomic ratio of raw material powder Zn: Ti = 99.0: 1.0 is not deviated at all. There was no volatilization of zinc.
The crystal structure of the zinc oxide-based sintered body (4) is a mixture of crystal phases of zinc oxide (ZnO) and zinc titanate (Zn ₂ TiO ₄ ), and there is no crystal phase of titanium carbide. There wasn't.

  A zinc oxide-based sintered body (4) was bonded using indium solder using a copper plate as a backing plate to obtain a sputtering target, and a transparent conductive substrate was obtained in the same manner as in Example 1. The number of times the operation of the sputtering apparatus was stopped due to the abnormal discharge generated in 3 was within 3 times per hour, and almost no abnormal discharge occurred during the film formation.

  From the above, since there is no volatilization of zinc, the ratio of the metal atoms of the raw material powder that is the raw material of the zinc oxide-based sintered body (4) and the ratio of the metal atoms of the obtained zinc oxide-based sintered body (4) Is a zinc oxide-based sintered body with no warpage and extremely high density without warping. As a result, abnormal discharge occurs even when sputtering is performed using a target obtained by processing the zinc oxide-based sintered body (4). The film could be formed stably.

(Comparative Example 1)
Zinc oxide powder (ZnO powder; purity 99.9%, average particle size 1 μm or less, manufactured by Kishida Chemical Co., Ltd.), gallium oxide powder (Ga ₂ O ₃ powder; purity 99.9%, average particle size 1 μm or less, Sumitomo Chemical Co., Ltd.) and titanium carbide powder (TiC powder; purity 99.9%, average particle size 0.9-1.5 μm, manufactured by Nippon Shin Metal Co., Ltd.) have an atomic ratio of Zn: Ga: Ti. Resin pot containing raw material powder containing 96.5: 0.5: 3.0 (ratio to the total number of metal atoms of titanium: 3%, ratio to the total number of metal atoms of gallium: 0.5%) In the same manner as in Example 2, after wet mixing and drying, pressure forming and cutting were performed to obtain a cylindrical molded body having a diameter of 80 mm and a height of 78 mm.

<Manufacture of zinc oxide-based sintered body>
A cylindrical molded body is installed in a HIP processing apparatus (manufactured by Kobe Steel, Ltd.), and the temperature is increased from room temperature to 1150 ° C. at a heating rate of 500 ° C./hour, and an Ar atmosphere at normal pressure (0.1013 MPa). The temperature was kept at 1150 ° C. for 24 hours, and primary pressure sintering was performed to obtain a primary sintered body. Further, when the warpage of the primary sintered body was judged in the same manner as in Example 1, the primary sintered body warped.
There was zinc volatilization during primary pressure primary sintering, and the relative density of the primary sintered body was determined by measuring the volume of the sintered body by length measurement and calculating the density from weight measurement. there were.
Further, when the sintered body was observed with an electron microscope, clear pores were observed and defects in open pores were found.

  Next, the primary sintered body was subjected to high-pressure HIP treatment in the same manner as in Example 1 to obtain a zinc oxide-based sintered body (C1). The relative density of the zinc oxide-based sintered body (C1) after the high-pressure HIP treatment was found to be 87.0% in the same manner as the relative density of the primary sintered body. Further, when the warpage of the sintered body (C1) was determined in the same manner as in Example 1, warpage occurred in the sintered body (C1).

The zinc oxide-based sintered body (C1) was processed in the same manner as in Example 1 to obtain a sintered body having a diameter of 50.8 mmφ and a thickness of 3 mm.
When the composition and crystal structure of the zinc oxide-based sintered body (C1) were analyzed in the same manner as in Example 1, the atomic ratio of Zn, Ga, and Ti was Zn: Ga: Ti = 95.8: 0. 7: 3.5. The atomic ratio of Zn, Ga, and Ti in the zinc oxide-based sintered body (C1) is the charged composition. The atomic ratio of the raw material powder: Zn: Ga: Ti = 96.5: 0.5: 3.0 There was a composition shift, and there was volatilization of zinc.
The crystal structure of the zinc oxide-based sintered body (C1) is a mixture of crystal phases of zinc oxide (ZnO) and zinc titanate (Zn ₂ TiO ₄ ), and there is no crystal phase of titanium carbide. It was. Further, the crystal phase of gallium oxide could not be confirmed.

  A zinc oxide-based sintered body (C1) was bonded using indium solder using a copper plate as a backing plate to obtain a sputtering target, and a transparent conductive substrate was obtained in the same manner as in Example 1. The number of times the operation of the sputtering apparatus was stopped due to the generated abnormal discharge was about 20 times or more per hour. Ar plasma was unstable during film formation, and abnormal discharge occurred frequently.

  From the above, volatilization of zinc occurs, the ratio of the metal atoms of the raw material powder that is the raw material of the zinc oxide-based sintered body (C1), and the ratio of the metal atoms of the obtained zinc oxide-based sintered body (C1) Is a zinc oxide-based sintered body having a composition deviation and a low-density warp. As a result, abnormal sputtering frequently occurs when sputtering is performed using a target obtained by processing the zinc oxide-based sintered body (C1). The film could not be stably formed.

(Comparative Example 2)
Zinc oxide powder (ZnO powder; purity 99.9%, average particle size 1 μm or less, manufactured by Kishida Chemical Co., Ltd.), aluminum carbide powder (Al ₂ O ₃ powder; purity 99.99%, average particle size 0.5 μm, Sumitomo Chemical Co., Ltd.) and titanium carbide powder (TiC powder; purity 99.9%, average particle size 0.9-1.5 μm, manufactured by Nippon Shin Metals Co., Ltd.) Zn: Al: Ti atomic ratio Is a raw material powder containing a ratio of 96.5: 0.5: 3.0 (ratio to the total number of metal atoms of titanium: 3%, ratio to the total number of metal atoms of aluminum: 0.5%) After putting into a pot and carrying out wet mixing and drying similarly to Example 2, it pressure-molded and cut and obtained the cylindrical molded object of diameter 80mm and thickness 78mm.

<Manufacture of zinc oxide-based sintered body>
The cylindrical molded body was installed in a HIP processing apparatus (manufactured by Kobe Steel, Ltd.), and the temperature was raised from room temperature to 1100 ° C. at a temperature rising rate of 100 ° C./hour, and the temperature was 1100 ° C. in an Ar atmosphere at a pressure of 100 MPa. For 1 hour, and high-pressure HIP treatment was performed to obtain a zinc oxide-based sintered body (C2). The relative density of the zinc oxide-based sintered body (C2) after the high-pressure HIP treatment was 66% when the volume of the sintered body was obtained by length measurement and the density was calculated from weight measurement. Also, there was no zinc volatilization during the high pressure HIP treatment. Further, when the warpage of the sintered body (C2) was determined in the same manner as in Example 1, the sintered body (C2) was not warped.
Further, when the zinc oxide sintered body (C2) was observed with an electron microscope, clear vacancies were observed and a large number of open pore defects were found.

The zinc oxide based sintered body (C2) was processed in the same manner as in Example 1 to obtain a sintered body having a diameter of 50.8 mmφ and a thickness of 3 mm.
When the composition and crystal structure of this zinc oxide-based sintered body (C2) were analyzed in the same manner as in Example 1, the atomic ratio of Zn, Al, and Ti was Zn: Al: Ti = 96.5: 0. 5: 3.0. The atomic ratio of Zn, Al, and Ti in the zinc oxide-based sintered body (C2) is the charged composition. The atomic ratio of the raw material powder Zn: Al: Ti = 96.5: 0.5: 3.0 There was no volatilization of zinc.
The crystal structure of the zinc oxide-based sintered body (C2) is a mixture of crystal phases of zinc oxide (ZnO) and zinc titanate (Zn ₂ TiO ₄ ), and there is no crystal phase of titanium carbide. It was. Moreover, the crystal phase of aluminum oxide could not be confirmed.

  The zinc oxide-based sintered body (C2) was bonded using indium solder using a copper plate as a backing plate to obtain a sputtering target, and a transparent conductive substrate was obtained in the same manner as in Example 1. The number of times that the operation of the sputtering apparatus was stopped due to the abnormal discharge generated in 30 minutes or more was about 30 times per hour. Ar plasma was unstable during film formation, and abnormal discharge occurred frequently.

  As mentioned above, since there is no volatilization of zinc, the ratio of the metal atom of the raw material powder which is the raw material of the zinc oxide-based sintered body (C2), and the ratio of the metal atom of the obtained zinc oxide-based sintered body (C2) There was no deviation at all, and the sintered body did not warp, but it was a low-density zinc oxide-based sintered body. As a result, a target obtained by processing the zinc oxide-based sintered body (C2) was used. When sputtering was performed, abnormal discharge occurred frequently, and a stable film could not be formed.

Claims (5)

A method for producing a zinc oxide-based sintered body comprising the following processes A to C, wherein the primary firing of process B and the secondary firing of process C are performed by capsule-free hot isostatic pressing.
Process A: A raw material powder substantially consisting of zinc, titanium, carbon, and oxygen, and the proportion of titanium being 0.2% or more and 5% or less with respect to the total number of metal atoms is molded and molded. Process B: Process B: The molded body obtained in the process A is subjected to primary firing at a firing temperature of 900 to 1200 ° C. in an inert gas atmosphere at a pressure of 1 to 30 MPa, and a relative density is 92% or more and less than 98%. And a step of obtaining a primary sintered body having defects with closed pores Process C: Secondary firing of the primary sintered body obtained in the process B at 800 to 1400 ° C. in an inert gas atmosphere at a pressure of 90 MPa or more. And obtaining a zinc oxide-based sintered body having a relative density of 98% or more A method for producing a zinc oxide-based sintered body comprising the following processes D to F, wherein the primary firing of process E and the secondary firing of process F are performed by capsule-free hot isostatic pressing.
Process D: substantially consisting of at least one selected from gallium and aluminum, zinc, titanium, carbon and oxygen, and the proportion of titanium is 0.2% or more and 5% or less with respect to the total number of metal atoms, A step of forming a raw material powder by forming a raw material powder in which the ratio of the number of atoms of aluminum is 0.1 to 2.5% with respect to the total number of metal atoms. Process E: Process F in which primary firing is performed at a firing temperature of 900 to 1200 ° C. in an inert gas atmosphere of 1 to 30 MPa to obtain a primary sintered body having a relative density of 92% or more and less than 98% and defects having closed pores. : The primary sintered body obtained in the process E is subjected to secondary firing at 800 to 1400 ° C. in an inert gas atmosphere having a pressure of 90 MPa or more, and zinc oxide having a relative density of 98% or more. Obtaining a sintered body   The said raw material powder is a manufacturing method of the zinc oxide type sintered compact of Claim 1 containing the mixed powder of titanium carbide powder and zinc oxide powder.   The zinc oxide-based sintered body according to claim 2, wherein the raw material powder includes a mixed powder of at least one selected from gallium oxide powder, aluminum oxide powder, and aluminum carbide powder, titanium carbide powder, and zinc oxide powder. Production method.   A target used for film formation by a sputtering method, an ion plating method, a pulsed laser deposition (PLD) method, or an electron beam (EB) vapor deposition method, which is obtained by the manufacturing method according to claim 1. A target obtained by processing the obtained zinc oxide-based sintered body.