CN110257782B - Cylindrical sputtering target and method for producing same - Google Patents

Cylindrical sputtering target and method for producing same Download PDF

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CN110257782B
CN110257782B CN201910536944.3A CN201910536944A CN110257782B CN 110257782 B CN110257782 B CN 110257782B CN 201910536944 A CN201910536944 A CN 201910536944A CN 110257782 B CN110257782 B CN 110257782B
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cylindrical
cylinder
sintered body
oxygen
sintering
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CN110257782A (en
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馆野谕
长田幸三
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JX Nippon Mining and Metals Corp
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    • C04B35/622—Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/64—Burning or sintering processes
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/06—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the coating material
    • C23C14/08—Oxides
    • C23C14/086—Oxides of zinc, germanium, cadmium, indium, tin, thallium or bismuth
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    • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
    • C04B35/453—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on zinc, tin, or bismuth oxides or solid solutions thereof with other oxides, e.g. zincates, stannates or bismuthates
    • C04B35/457—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on zinc, tin, or bismuth oxides or solid solutions thereof with other oxides, e.g. zincates, stannates or bismuthates based on tin oxides or stannates
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
    • C23C14/34—Sputtering
    • C23C14/3407—Cathode assembly for sputtering apparatus, e.g. Target
    • C23C14/3414—Metallurgical or chemical aspects of target preparation, e.g. casting, powder metallurgy
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    • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
    • C04B2235/02—Composition of constituents of the starting material or of secondary phases of the final product
    • C04B2235/30—Constituents and secondary phases not being of a fibrous nature
    • C04B2235/32—Metal oxides, mixed metal oxides, or oxide-forming salts thereof, e.g. carbonates, nitrates, (oxy)hydroxides, chlorides
    • C04B2235/3293—Tin oxides, stannates or oxide forming salts thereof, e.g. indium tin oxide [ITO]
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    • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
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    • C04B2235/658—Atmosphere during thermal treatment
    • C04B2235/6583—Oxygen containing atmosphere, e.g. with changing oxygen pressures
    • C—CHEMISTRY; METALLURGY
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    • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
    • C04B2235/65—Aspects relating to heat treatments of ceramic bodies such as green ceramics or pre-sintered ceramics, e.g. burning, sintering or melting processes
    • C04B2235/658—Atmosphere during thermal treatment
    • C04B2235/6586—Processes characterised by the flow of gas

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Abstract

The purpose of the present invention is to provide a cylindrical sintered body and a cylindrical sputtering target having a length in the cylindrical axis direction of 470mm or more, and methods for producing these. The method for manufacturing a cylindrical sputtering target according to an embodiment of the present invention comprises: in a method for producing a cylindrical sputtering target having a cylindrical sintered body, a cylindrical compact having a length of 600mm or more in the axial direction of the cylinder is placed on a pedestal provided with an oxygen supply port connected to a pipe for supplying oxygen, and sintering is performed while supplying oxygen to the axial direction of the cylinder from the oxygen supply port smaller than the inner circumference of the cylinder provided inside the cylinder of the cylindrical compact. In another embodiment, the pedestal may be disposed in the chamber, and a pipe for supplying oxygen may be connected to the oxygen supply port from outside the chamber.

Description

Cylindrical sputtering target and method for producing same
The present application is a divisional application of a chinese patent application having an application date of 2017, 28.02 and No. 201710112294.0, entitled "cylindrical sputtering target and method for manufacturing the same".
Technical Field
The present invention relates to a cylindrical sputtering target and a method for producing the same. In particular, the present invention relates to a method for producing a cylindrical sintered body constituting a cylindrical sputtering target.
Background
In recent years, Flat Panel Displays (FPD) and solar cells have been rapidly manufactured and their sizes have been increased. Further, as these markets expand, the demand for large glass substrates is increasing.
In particular, in a sputtering apparatus for forming a metal thin film or a metal oxide thin film on a large glass substrate, a cylindrical (also referred to as a rotary or a rotary) sputtering target is being used instead of a conventional flat plate sputtering target. Compared with a flat plate sputtering target, a cylindrical sputtering target has the advantages of high target use efficiency, less occurrence of erosion, and less generation of particles due to separation of precipitates.
As described above, a cylindrical sputtering target used in a sputtering apparatus for forming a thin film on a large glass substrate needs to have a length of 3000mm or more. It is technically impractical to manufacture and grind a cylindrical sputtering target of such a length by integral molding. Therefore, a divided sputtering target in which a plurality of cylindrical sintered bodies of several tens to several hundreds of mm are joined can be generally constituted.
Here, not only the cylindrical sintered body described above, but also the joining of ordinary sintered bodies requires an improvement in mechanical strength and an improvement in film quality of a thin film using the sintered body. When a plurality of sintered bodies are joined to a base material, the sintered bodies are arranged with a predetermined interval therebetween. This is because, when the sintered bodies are arranged without a gap and joined to the base material, the sintered bodies expand and contract due to heat during sputtering, and the sintered bodies collide with each other, thereby generating cracks or notches. On the other hand, the gaps between the sintered bodies are free of sintered bodies that would have been sputtered originally. Therefore, a problem arises in that a constituent material of the base material is sputtered, and a thin film of a desired component cannot be formed. In addition, in a divided sputtering target in which a plurality of sintered bodies are connected, the difference in relative density between adjacent sintered bodies (i.e., "inter-solid variation" in sintered body density) affects the quality of a thin film using the divided sputtering target. As described above, the shorter the connected sintered body is, the more the sputtering target is divided, and the risk of affecting the sputtering characteristics is increased.
In order to avoid the above problems as much as possible, a technique for producing a longer cylindrical sintered body that can cope with less division of the sputtering target is required. The problems in producing an elongated cylindrical sintered body are the difference in relative density in the sintered body (i.e., "in-solid variation" in density of the sintered body) and the mechanical strength. For example, patent document 1 discloses the following: in sintering an Indium Tin Oxide (ITO) target, the oxygen concentration of an ambient gas has a large influence on the quality stabilization (density and strength). Generally, a sintering furnace for ITO is supplied with oxygen from the furnace wall side.
(Prior art document)
(patent document)
Patent document 1: japanese laid-open patent publication No. 8-144056
Disclosure of Invention
However, in the case of an elongated cylindrical sintered body, oxygen deficiency occurs in the cylinder due to insufficient convection of gas in the cylinder during sintering. The technical problem of the present invention is to provide a cylindrical sintered body having a length in the cylindrical axis direction of 470mm or more, a cylindrical sputtering target, and methods for producing the same, in order to achieve a split sputtering target obtained by joining a plurality of sintered bodies to a base material, in response to a reduction in split. Another object of the present invention is to provide a cylindrical sintered body and a cylindrical sputtering target having high homogeneity in a solid and between individual bodies, and methods for producing the same.
A method for producing a cylindrical sputtering target according to an embodiment of the present invention is as follows: in a method for producing a cylindrical sputtering target having a cylindrical sintered body, a cylindrical compact having a length of 600mm or more in the axial direction of the cylinder is placed on a pedestal provided with an oxygen supply port connected to a pipe for supplying oxygen, and sintering is performed while supplying oxygen to the axial direction of the cylinder from the oxygen supply port smaller than the inner circumference of the cylinder provided inside the cylinder of the cylindrical compact.
In another embodiment, the pedestal may be disposed in the chamber, and a pipe for supplying oxygen may be connected to the oxygen supply port from outside the chamber.
In another embodiment, the sintering may be performed while supplying oxygen to the hollow portion inside the cylinder of the cylindrical molded body.
In another embodiment, the sintering may be performed while supplying oxygen from below to above in the cylindrical axis direction of the cylindrical formed body.
The cylindrical sintered body used for the cylindrical sputtering target according to one embodiment of the present invention is a cylindrical sintered body having a length of 470mm or more in the cylindrical axis direction, and the relative density difference in the cylindrical axis direction is 0.1% or less.
A cylindrical sintered body used for a cylindrical sputtering target according to one embodiment of the present invention is a cylindrical sintered body having a length of 470mm or more in the cylindrical axial direction, and the equivalent circle diameter of the area of a hole observed in the inner surface of the cylinder is 1 μm or less on average.
A cylindrical sintered body for a cylindrical sputtering target according to one embodiment of the present invention is a cylindrical sintered body having a length of 470mm or more in the cylinder axial direction, and the number of pores observed in the inner surface of the cylinder is 4.25X 10 on average-5Per mu m2The following.
In another embodiment, the holes observed in the inner surface of the cylinder may be at least five independent positions each of which is 1.176mm in the central part in the axial direction of the cylinder2The visual field of (1) observed in the eye.
According to the present invention, a cylindrical sintered body and a cylindrical sputtering target having a length in the cylindrical axis direction of 470mm or more can be provided, and methods for producing these. Further, a cylindrical sintered body and a cylindrical sputtering target having high homogeneity in a solid and between individual bodies, and methods for producing them can be provided.
Drawings
Fig. 1 is a perspective view showing an example of a cylindrical sintered body constituting a cylindrical sputtering target according to an embodiment of the present invention.
Fig. 2 is a sectional view showing an example of the structure of an assembled cylindrical sputtering target according to an embodiment of the present invention.
Fig. 3 is a process flow chart showing a method for producing a cylindrical sintered body according to an embodiment of the present invention.
Fig. 4 is a perspective view showing a step of sintering a cylindrical molded body in the method of manufacturing a cylindrical sintered body according to the embodiment of the present invention.
Fig. 5 is a cross-sectional view showing a step of sintering a cylindrical molded body in the method of manufacturing a cylindrical sintered body according to an embodiment of the present invention.
Fig. 6 is a plan view showing a step of sintering a cylindrical molded body in the method of manufacturing a cylindrical sintered body according to the embodiment of the present invention.
Fig. 7 is a plan view showing a step of sintering a cylindrical molded body in the method of manufacturing a cylindrical sintered body according to modification 1 of one embodiment of the present invention.
Fig. 8 is a cross-sectional view showing a step of sintering a cylindrical molded body in the method of manufacturing a cylindrical sintered body according to modification 2 of one embodiment of the present invention.
Fig. 9 is a diagram showing sampling positions of measurement samples in the cylindrical sintered bodies of the examples and comparative examples of the present invention in the cylindrical axis direction.
Fig. 10 is a table showing the density, the difference in solid internal density, the relative density, and the maximum difference in solid internal relative density of the cylindrical sintered bodies of the examples of the present invention and the comparative examples.
Fig. 11 is a graph showing the relationship between the length of the cylindrical sintered bodies and the minimum oxygen supply amount in examples of the present invention and comparative examples.
Fig. 12 is a table showing differences in volume resistance and solid internal volume resistance values of the cylindrical sintered bodies of examples of the present invention and comparative examples.
Fig. 13 is a diagram showing sampling positions of measurement samples on the inner surface and the outer surface of the cylinder in the cylindrical sintered bodies of the examples and comparative examples of the present invention.
Fig. 14 is an electron microscope (SEM, 1000 magnifications) photograph of the cylindrical inner surface of the cylindrical sintered bodies of the example of the present invention and the comparative example.
Fig. 15 is an electron microscope (SEM, 1000 × magnification) photograph of the outer surface of the cylinder of the cylindrical sintered body of the example of the present invention and the comparative example.
Fig. 16 is a photograph of the cylindrical inner surface of the cylindrical sintered body of the example of the present invention and the comparative example taken by an electron microscope (SEM, 5000 x or 2000 x).
Fig. 17 is an electron microscope (SEM, 5000 ×) photograph of the outer surface of the cylinder of the cylindrical sintered body of the example of the present invention and the comparative example.
Fig. 18 is a table showing the average of the equivalent circle diameters and the number of the areas of the holes on the cylindrical inner surface of the cylindrical sintered bodies in the example of the present invention and the comparative example.
(description of reference numerals)
100: a cylindrical sputtering target; 110: a cylindrical sintered body; 111: a cylindrical shaped body; 120: spacing; 130: a cylindrical base material; 140: welding flux; 150: a bottom surface; 200: sintering the pedestal; 230: an oxygen supply port; 240: piping; 260: a baffle plate; 280: an opening part; 300: chamber
Detailed Description
The cylindrical sputtering target and the method for producing the same according to the present invention will be described below with reference to the drawings. However, the cylindrical sputtering target and the method for manufacturing the same according to the present invention can be implemented in various different modes, and should not be construed as being limited to the description of the embodiments shown below. In the drawings referred to in the present embodiment, the same portions or portions having the same functions are denoted by the same reference numerals, and redundant description thereof is omitted.
< embodiment >
The structure and the outline of the structure of the cylindrical sputtering target and the cylindrical sintered body according to the embodiment of the present invention will be described with reference to fig. 1 and 2.
[ outline of cylindrical sputtering target ]
Fig. 1 is a perspective view showing an example of a cylindrical sintered body constituting a cylindrical sputtering target according to an embodiment of the present invention. As shown in fig. 1, the cylindrical sputtering target 100 has a plurality of cylindrical sintered bodies 110 having a hollow structure. The plurality of cylindrical sintered bodies 110 are arranged adjacent to each other with a constant interval. Here, in fig. 1, for convenience of explanation, the interval between adjacent cylindrical sintered bodies 110 is shown in an enlarged manner. As shown in fig. 2, a cylindrical base material 130 for holding the cylindrical sintered body 110 is introduced into the cylindrical inner hollow portion of the cylindrical sintered body 110.
The thickness of the cylindrical sintered body 110 may be 6.0mm to 20.0 mm. The length of the cylindrical sintered body 110 in the cylindrical axis direction may be 470mm to 1500 mm. The outer diameter of the cylindrical sintered body 110 may be 147mm to 175 mm. Further, the inner diameter of the cylindrical sintered body 110 may be 135mm or less. Further, the interval in the cylindrical axis direction between adjacent cylindrical sintered bodies 110 may be 0.1mm or more and 0.4mm or less.
The material of the cylindrical sintered body 110 is, for example, an ITO sintered body made of Indium, tin, and oxygen, an Indium Zinc Oxide sintered body (IZO) made of Indium, Zinc, and oxygen, an Indium Gallium Zinc Oxide sintered body (IGZO) made of Indium, Gallium, Zinc, and oxygen, a Zinc aluminum Oxide sintered body (AZO) made of Zinc, aluminum, and oxygen, Zinc Oxide (ZnO), TiO, or the like2And the like. However, the cylindrical sintered body of the cylindrical sputtering target of the present invention is not limited to the above-described components, and may be a ceramic sintered body containing oxygen.
Here, the density of the cylindrical sintered body 110 of the present embodiment may be 99.5% or more. The density of the cylindrical sintered body 110 may be more preferably 99.6% or more. Further, the difference in relative density in the cylindrical axis direction in the solid body of the cylindrical sintered body 110 may be 0.1% or less. The difference in relative density in the cylindrical axis direction of the cylindrical sintered body 110 may be more preferably 0.05% or less, and still more preferably 0.03% or less. Further, the difference in relative density between adjacent cylindrical sintered bodies 110a and 110b, that is, the difference in relative density between the solids of the cylindrical sintered bodies may preferably be 0.1% or less.
Further, the density of the sintered body is shown as a relative density. Relative density is expressed as relative density ═ 100 (%) between measured density and theoretical density. Relative density difference is expressed by relative density difference (measured density difference/theoretical density) × 100 (%) based on the difference between the measured densities and the theoretical density. The theoretical density is a value of a density calculated from theoretical densities of oxides of elements other than oxygen among the respective constituent elements of the sintered body. For example, in the case of an ITO target, indium, tin, and oxygen as the constituent elementsIndium oxide (In)2O3) And tin oxide (SnO)2) The oxides of indium and tin other than oxygen were used for the calculation of the theoretical density. Here, the elemental analysis values (at% or mass%) of indium and tin In the sintered body are converted into indium oxide (In)2O3) And tin oxide (SnO)2) The mass ratio of (a). For example, when the conversion result is that the content of indium oxide is 90% by mass and the content of tin oxide is 10% by mass of the ITO target, the theoretical density is (In)2O3Density (g/cm)3)×90+SnO2Density (g/cm)3)×10)/100(g/cm3) To calculate. In is pressed2O3Has a theoretical density of 7.18g/cm3、SnO2Has a theoretical density of 6.95g/cm3To calculate the theoretical density of 7.157g/cm3. Further, when each constituent element is Zn, ZnO oxide can be used for calculation, and when each constituent element is Ga, Ga can be used for calculation2O3The oxide of (a) was calculated. In terms of theoretical density of ZnO of 5.67g/cm3And according to Ga2O3Has a theoretical density of 5.95g/cm3To calculate. On the other hand, the measured density is a value obtained by dividing a mass by a volume. In the case of the sintered body, the volume was determined by the archimedes method and calculated. Regarding the difference in relative density in the cylindrical axis direction within the solid body of the cylindrical sintered body 110, cylindrical measurement samples of 40 to 50mm width are cut out every 150mm in the cylindrical axis direction of the cylindrical sintered body 110, and the relative density of each sample is calculated and evaluated.
As described above, by setting the length and the relative density of the cylindrical sintered body within the above ranges, the mechanical strength of the cylindrical sintered body can be improved, and when the cylindrical sintered body is used, generation of nodules or particles accompanying arcing can be suppressed, and the technical effects of reducing impurities in the thin film and increasing the film density can be obtained. Further, by setting the difference between the relative densities in the solid body and between the solid bodies of the cylindrical sintered bodies within the respective ranges described above, it is possible to suppress the distortion of the electric field in the divided sputtering target having a plurality of cylindrical sintered bodies. As a result, stable discharge characteristics can be obtained during sputtering, and a thin film having very high in-plane uniformity of film quality can be formed on a large substrate having a size exceeding one cylindrical sintered body.
The difference in the solid content of the cylindrical sintered body 110 also includes the difference between the cylindrical inner surface and the cylindrical outer surface of the cylindrical sintered body 110. The state of the cylindrical inner surface and the cylindrical outer surface of the cylindrical sintered body 110 can be evaluated by electron microscope (SEM) observation. No large difference was observed in the holes observed in the cylindrical inner surface and the outer surface in the central portion in the cylindrical axis direction of the cylindrical sintered body 110 of the present embodiment. The pores observed in the cylindrical inner and outer surfaces of the cylindrical sintered body 110 of the present embodiment have irregular particle shapes, and are observed in both grain boundaries and crystals. In other words, in the cylindrical inner surface and the cylindrical outer surface of the cylindrical sintered body 110 of the present embodiment, irregular bubble-like pores are observed in both the grain boundary and the crystal. On the other hand, in the cylindrical inner surface of the cylindrical sintered body 110 in the comparative example in which the length in the cylindrical axial direction is 470mm or more, irregular granular pores larger than those in the cylindrical outer surface in the comparative example or those in the cylindrical inner surface and the outer surface of the cylindrical sintered body 110 in the present embodiment can be observed. In other words, irregular crystal grain-like pores were observed in the cylindrical inner surface of the cylindrical sintered body 110 of the comparative example having a length of 470mm or more in the cylindrical axial direction. Such pores observed on the cylindrical inner side surface of the cylindrical sintered body 110 of the comparative example can be observed mainly at grain boundaries. The cylindrical outer surface of the cylindrical sintered body 110 of the comparative example is not greatly different from the cylindrical inner surface and the outer surface of the cylindrical sintered body 110 of the present embodiment. The shape of the pores observed in the outer surface of the cylinder of the cylindrical sintered body 110 of the comparative example was irregular particle shape smaller than the pores in the inner surface of the cylinder, and was observed in both the grain boundary and the crystal.
The shapes of the respective holes observed on the cylindrical inner surface and the cylindrical outer surface of the cylindrical sintered body 110 of the present embodiment and the comparative example are irregular. Therefore, the size of the hole can be calculated by calculating the area of one continuous hole in a plan view, and the holes can have the same surfaceThe diameter of the product circle (hereinafter referred to as the equivalent circle diameter of the area of the hole) was evaluated. The number of holes can be counted as 1 for a consecutive one on the observed face. The average equivalent circle diameter of the area of the holes observed in the cylindrical inner surface of the cylindrical sintered body 110 of the present embodiment may be 1 μm or less. More preferably, the average equivalent circle diameter of the area of the holes observed in the cylindrical inner surface of the cylindrical sintered body 110 may be 0.5 μm or less. The average number of pores observed in the cylindrical inner surface of the cylindrical sintered body 110 of the present embodiment may be 4.25 × 10-5Per mu m2The following. More preferably, the average of the number of pores observed on the cylindrical inner surface of the cylindrical sintered body 110 may be 2.125 × 10-5Per mu m2The following. The average equivalent circle diameter of the area of the hole observed in the cylindrical outer surface of the cylindrical sintered body 110 of the present embodiment may be 1 μm or less. More preferably, the average equivalent circle diameter of the area of the holes observed in the outer surface of the cylinder of the cylindrical sintered body 110 may be 0.5 μm or less. In addition, the average number of holes observed in the cylindrical outer surface of the cylindrical sintered body 110 of the present embodiment may be 4.25 × 10-5Per mu m2The following. More preferably, the average of the number of pores observed on the cylindrical outer surface of the cylindrical sintered body 110 may be 2.125 × 10-5Per mu m2The following.
In the evaluation of the state of the cylindrical inner surface and the cylindrical outer surface of the cylindrical sintered body 110, five fields of view of 980 μm × 1200 μm were observed in the central portion in the cylindrical axis direction of each sample, and the number of holes and the average value of the equivalent circle diameters of the hole areas were evaluated. The equivalent circular diameter L of the area S of the hole can be obtained by: first, the projected area S of a continuous hole is calculated, and the diameter L of a circle having the same area is calculated using the following mathematical formula:
[ mathematical formula 1]
Figure BDA0002101475200000071
There was no significant difference in crystal grains observed on the cylindrical inner surface and the outer surface of the cylindrical sintered body 110 in the central portion in the cylindrical axis direction in the present embodiment. The crystal grains observed on the cylindrical inner surface and the outer surface of the cylindrical sintered body 110 of the present embodiment grow large. On the other hand, in the comparative example in which the length in the cylindrical axial direction was 957mm or more, the crystal grains were smaller on the cylindrical inner surface than on the outer surface of the cylindrical sintered body 110, and therefore, crystal grains at the initial stage of growth were observed. In the comparative example, the crystal grains on the cylindrical inner surface of the cylindrical sintered body 110 were small and uneven at the early stage of growth, and were poor in smoothness.
As will be described in detail in the production method, the above cylindrical sintered body can be obtained by sintering a cylindrical formed body while supplying oxygen in the cylindrical axial direction.
Fig. 2 is a sectional view showing an example of the structure of an assembled cylindrical sputtering target according to the embodiment of the present invention. As shown in fig. 2, in the assembled cylindrical sputtering target 100, a cylindrical base material 130 is disposed in a hollow portion inside the cylinder of the cylindrical sintered body 110 shown in fig. 1. The cylindrical base 130 and the cylindrical sintered body 110 are brazed by a solder 140, and the adjacent cylindrical sintered bodies 110 are arranged with a space 120 therebetween.
The cylindrical base material 130 may use the following metal materials: the sputtering target material has high thermal conductivity so that heat generated by collision of electrons or ions with the target material during sputtering can be efficiently released, and has conductivity to such an extent that a bias voltage can be applied to the target material. Specifically, copper (Cu), titanium (Ti), an alloy containing them, and stainless steel (SUS) may be used.
As the cylindrical base material 130, the following materials can be used as the material of the solder 140: high thermal conductivity, electrical conductivity, and sufficient adhesion and strength to hold the cylindrical sintered body 110 by the cylindrical base material 130. However, it may be a material in which the thermal conductivity of the solder 140 is lower than that of the cylindrical base material 130. Further, a material having a conductivity of the solder 140 lower than that of the cylindrical base 130 may be used. As the solder 140, for example, indium (In), tin (Sn), and an alloy containing them can be used.
As described above, according to the sputtering target of the present embodiment, the following effects can be obtained by setting the length and the relative density of the cylindrical sintered body within the above ranges: the cylindrical sintered body has improved mechanical strength, and the thin film using the cylindrical sintered body has reduced impurities and improved film density. Further, by setting the difference between the relative densities in the solid body and between the solid bodies of the cylindrical sintered bodies within the above range, it is possible to suppress the distortion of the electric field in the divided sputtering target having a plurality of cylindrical sintered bodies. As a result, a thin film having stable discharge characteristics and very high in-plane uniformity of film quality can be formed on a large substrate having a size exceeding one cylindrical sintered body during sputtering. Further, by setting the state of the cylinder inner surface and the cylinder outer surface of the cylindrical sintered body within the above ranges, stable quality can be maintained throughout the entire target life in the divided sputtering target having the cylindrical sintered body. That is, the characteristics do not change during continuous use of the target, and nodules and particles caused by density defects can be suppressed from being generated.
[ method for producing cylindrical sintered body ]
Next, a method for producing a cylindrical sintered body of a cylindrical sputtering target according to the present invention will be described in detail with reference to fig. 3. Fig. 3 is a process flow chart showing a method for producing a cylindrical sintered body according to an embodiment of the present invention. In fig. 3, a method for producing an ITO sintered body is exemplified, but the material of the sintered body is not limited to ITO, and may be used for other metal oxide sintered bodies such as IGZO.
First, raw materials are prepared. As the raw material for mixing, for example, a metal element to be contained in an oxide, an alloy, or the like is used. The powdery raw material can be used, and can be appropriately selected depending on the target composition. For example, when ITO is used, indium oxide powder and tin oxide powder are prepared (step S301 and step S302). The purity of these raw materials is usually 2N (99% by mass) or more, preferably 3N (99.9% by mass) or more, and more preferably 4N (99.99% by mass) or more. If the purity is less than 2N, the cylindrical sintered body contains a large amount of impurities, and thus, desired physical properties (for example, a decrease in transmittance, an increase in film resistance, and generation of particles accompanying arcing if foreign matter is locally contained) cannot be obtained.
Next, these raw material powders are pulverized and mixed (step S303). The pulverization and mixing treatment of the raw material powder may be carried out by a dry method using balls or beads of zirconia, alumina, nylon resin or the like, or a wet method using a media agitation mill using the balls or beads, a media-free container rotation type, a mechanical agitation type, or a gas flow type. Here, since the wet method is generally more excellent in pulverization and mixing ability than the dry method, it is preferable to use the wet method for mixing.
The raw material components are not particularly limited, but it is desirable to appropriately adjust the raw material components according to the component ratio of the target sputtering target.
Here, when the raw material powder having a fine particle size is used, the density of the sintered body can be increased. In addition, although fine raw material powder can be obtained by strengthening the pulverization conditions, the amount of a medium (zirconia or the like) used in pulverization increases, and the impurity concentration in the product increases. In this manner, it is necessary to set the conditions for pulverization within an appropriate range while taking into consideration the balance between the densification of the sintered body and the impurity concentration in the product.
Next, the slurry of the raw material powder is dried and granulated (step S304). Here, the slurry can be rapidly dried by performing rapid drying granulation. The rapid drying granulation can be performed by using a spray dryer and adjusting the temperature and the air volume of hot air. By performing the rapid drying granulation, separation of the indium oxide powder and the tin oxide powder due to a difference in the sedimentation rate caused by a difference in the specific gravity of the raw material powder can be suppressed. By performing granulation in this manner, the ratio of the components to be blended is made uniform, and the handling property of the raw material powder is improved. In addition, pre-firing may be performed before and after granulation.
Next, the mixture obtained through the above-described mixing and granulating steps (the pre-fired mixture in the case where the pre-firing step is provided) is press-molded to form a cylindrical molded body (step S305). This step forms a sputtering target having a shape suitable for the purpose. The cylindrical molded body may have a length of 600mm or more in the cylindrical axis direction. The molding treatment may be mold forming, cast molding, injection molding, or the like, and in order to obtain a complicated shape such as a cylindrical shape, it is preferable to perform molding by Cold Isostatic Pressing (CIP) or the like. For CIP molding, a predetermined weight of raw material powder is weighed and charged into a rubber mold. At this time, the filling is performed while shaking or tapping the rubber mold, whereby unevenness or voids in the filling of the raw material powder in the mold can be eliminated. The CIP forming pressure is preferably 100MPa or more and 200MPa or less. By adjusting the molding pressure as described above, a cylindrical molded body having a relative density of 54.5% or more and 58.0% or less can be formed in the present embodiment. More preferably, by adjusting the CIP molding pressure to 150MPa or more and 180MPa or less, a cylindrical molded body having a relative density of 55.0% or more and 57.5% or less can be obtained.
Next, the cylindrical molded body obtained in the molding step is sintered (step S306). Here, a method of sintering the cylindrical molded body will be described in detail with reference to fig. 4 to 6. Fig. 4 is a perspective view showing a step of sintering a cylindrical molded body in the method of manufacturing a cylindrical sintered body according to the embodiment of the present invention. Fig. 5 is a cross-sectional view showing a step of sintering a cylindrical molded body in the method of manufacturing a cylindrical sintered body according to the embodiment of the present invention. Fig. 6 is a plan view showing a step of sintering a cylindrical molded body in the method of manufacturing a cylindrical sintered body according to the embodiment of the present invention.
First, as shown in fig. 4, the cylindrical formed body 111 obtained in the forming step of step S305 may be arranged in an upright state in which the cylindrical axis direction is substantially perpendicular to the sintering base 200 on the flat plate-like sintering base 200. However, the cylindrical formed body 111 is not limited to this as long as it can be stably arranged on the sintering base 200. For example, the cylindrical formed body 111 may be arranged in a state of being inclined with respect to the sintering base 200. Although not shown in fig. 4, when the cylindrical formed body 111 is sintered, a spacer may be disposed between the cylindrical formed body 111 and the sintering base 200. In this case, the spacer may be in contact with the bottom surface 150 in an area smaller than the bottom surface 150 of the cylindrical formed body 111. By disposing the spacers, even if the volume of the cylindrical formed body 111 is reduced in the sintering step, the friction coefficient due to the movement can be suppressed. Therefore, generation of internal stress generated in the cylindrical sintered body after sintering can be suppressed.
As shown in fig. 5 and 6, the cylindrical formed body 111 obtained in the forming step of step S305 is disposed on the sintering base 200 provided in the chamber 300. The cylindrical formed body 111 can be sintered in a state where the oxygen supply port 230 provided in the plate-like sintering base 200 is disposed at the center of the cylinder. The oxygen supply port 230 is smaller than the inner circumference of the cylindrical formed body 111 in consideration of the reduction due to the sintering process, and can supply oxygen to the cylindrical inner surface. Further, the oxygen supply port 230 is disposed from below to above in the cylindrical axial direction of the cylindrical formed body 111. The opening provided in the sintering base 200 may be only the oxygen supply port 230. One oxygen supply port 230 is directly connected to one pipe 240 for supplying oxygen. The piping 240 is connected to the oxygen supply port 230 from outside the chamber 300 via, for example, a regulator (controller), a valve, or the like. That is, oxygen supplied from the pipe 240 does not leak from other regions of the sintering bed 200, but oxygen is selectively supplied to the cylindrical inner surface from the oxygen supply port 230. By adopting such a configuration, the amount of oxygen supplied from the oxygen supply port 230 can be appropriately adjusted according to the length and thickness of the cylindrical molded body 111 in the cylindrical axial direction and the size of the cylindrical internal space. For example, the longer the length in the cylinder axis direction, the more the amount of oxygen can be supplied from the oxygen supply port 230. However, the present invention is not limited to this, and for example, when the thickness of the cylindrical formed body 111 is large, the amount of oxygen supplied from the oxygen supply port 230 may be large. For example, when the inner diameter of the cylindrical sintered body is large and the internal space of the cylinder is large, the amount of oxygen supplied from the oxygen supply port 230 may be increased.
The upper limit of the amount of oxygen supplied from the oxygen supply port 230 is not particularly limited, but may be 150L/min or less. By supplying a large amount of oxygen from one oxygen supply port 230, there is a possibility that problems such as deformation and cracking of the cylindrical sintered body during sintering, and a decrease in density of the cylindrical sintered body after sintering may occur due to the cooling effect of oxygen. Therefore, the baffle plate can be disposed in the direction of oxygen flow from the oxygen supply port 230. Oxygen supplied from the oxygen supply port 230 may be diffused in the cylindrical inner space by colliding with a baffle or the like. Further, the oxygen supplied from the oxygen supply port 230 may be supplied after preheating the piping or the like in the circulation.
When oxygen is supplied to the hollow portion inside the cylinder under the atmosphere of air, oxygen heavier than nitrogen is gradually filled from below in the axial direction of the cylinder. Therefore, oxygen can be supplied to the cylindrical inner surface of the cylindrical molded body during sintering without unevenness. When the hollow portion inside the cylinder of the cylindrical molded body is filled with oxygen, the oxygen continuously supplied flows out from above the cylindrical molded body to the outside of the cylinder through the hollow portion inside the cylinder. The oxygen flowing out flows downward through the ceiling portion of the chamber 300, and the oxygen circulating in the chamber 300 flows. Therefore, the oxygen concentration in the chamber 300 may also be uniformized. Further, oxygen may be supplied to the outside of the cylinder from the wall of the chamber 300 alone. In this case, the oxygen concentration in the cylindrical inner surface and the oxygen concentration in the outer surface of the cylindrical molded body during sintering can be made uniform by adjusting the amount of oxygen supplied to the hollow portion inside the cylinder and the amount of oxygen supplied to the outside of the cylinder.
Here, fig. 4 illustrates a method of supplying oxygen to the hollow portion inside the cylinder of the cylindrical molded body 111 from below, but the method is not limited to this method. For example, oxygen may be supplied from below or above in the axial direction of the cylinder. By supplying oxygen to the cylindrical molded body 111 in the cylindrical axial direction, the oxygen concentration in the cylindrical axial direction during sintering can be kept uniform.
In addition, fig. 4 illustrates a method of supplying oxygen from one oxygen supply port 230 disposed in the center of the cylinder of the cylindrical shaped body 111, but the method is not limited thereto. The oxygen supply port 230 is not limited to the center of the cylinder as long as oxygen can be uniformly supplied in the hollow portion inside the cylinder. The oxygen supply port 230 may be plural. In addition, oxygen may be supplied to the outside of the cylinder, not only to the inside of the cylinder. At this time, the oxygen supply ports 230 are directly connected to the pipes 240 for supplying oxygen so that the amount of oxygen can be independently controlled. Thus, the amount of oxygen supplied from each oxygen supply port 230 can be appropriately adjusted according to the length and thickness of the cylindrical molded body 111 in the axial direction of the cylinder, the size of the internal space of the cylinder, the position of the cylindrical molded body 111 with respect to the oxygen supply port 230, and the like.
In general ITO sintering, sintering under an oxygen atmosphere is essential for densification of a sintered body. Even in the sintering under an oxygen atmosphere, in the step of sintering the cylindrical molded body 111 having a length of 600mm or more, gas convection in the hollow portion inside the cylinder is insufficient, and oxygen deficiency occurs in the hollow portion inside the cylinder. The following occurs due to the lack of oxygen in the hollow inside the cylinder: deformation and cracking of the cylindrical sintered body during sintering, a decrease in density of the cylindrical sintered body after sintering, a relative density difference in the cylindrical axis direction of the cylindrical sintered body, and an increase in the size of the pores or the number of pores observed in the cylindrical inner surface of the cylindrical sintered body. In order to prevent the influence of oxygen deficiency in the inner hollow portion, in the present embodiment, as described above, when the cylindrical formed body 111 is sintered, oxygen is supplied from the oxygen supply port 230 to the cylindrical inner hollow portion of the cylindrical formed body 111, so that the cylindrical inner hollow portion of the cylindrical formed body 111 having a thickness of 600mm or more can be uniformly filled with oxygen. Further, by combining the supply of oxygen to the hollow portion inside the cylinder with the supply of oxygen to the outside of the cylinder, the oxygen concentration of the cylindrical inner surface and the outer surface of the cylindrical formed body 111 during sintering can be made uniform. As a result, deformation and cracking of the cylindrical sintered body during sintering can be prevented. In addition, the density of the cylindrical sintered body after sintering can be increased. Further, the relative density difference in the cylindrical axis direction in the solid of the cylindrical sintered body can be reduced. The size and number of apertures on the inside surface of the cylinder can be reduced.
Referring back to fig. 3, the method for producing the cylindrical sintered body will be described. The sintering of step S306 described in detail above may be performed using an electric furnace, Hot Isostatic Pressing (HIP), or microwave sintering. The sintering conditions may be appropriately selected depending on the composition of the sintered body, but for example, if it contains 10 wt.% SnO2The ITO (1) can be used in an oxygen atmosphereSintering is performed under the conditions of 500 ℃ to 1600 ℃ and 10 hours to 20 hours. In the case where the sintering temperature is less than 1500 ℃, the density of the target may decrease. On the other hand, if the temperature exceeds 1600 ℃, the electric furnace or furnace material is damaged greatly and maintenance is required at a proper time, so that the work efficiency is significantly reduced. If the sintering time is less than 10 hours, the density of the target is lowered, and if it is longer than 20 hours, the holding time in the sintering step becomes long, and the operation rate of the electric furnace is deteriorated. In addition, the consumption amount of oxygen used in the sintering process and the amount of electricity used to operate the electric furnace increase. The pressure during sintering may be atmospheric pressure, or may be reduced or increased in pressure.
Here, when sintering is performed in an electric furnace, the generation of cracks can be suppressed by adjusting the temperature increase rate and the temperature decrease rate of sintering. Specifically, the rate of temperature rise of the electric furnace at the time of sintering is preferably 300 ℃/hr or less, more preferably 180 ℃/hr or less. The cooling rate of the electric furnace during sintering is preferably 600 ℃/hr or less. In addition, the temperature increase rate or the temperature decrease rate may be adjusted in a stepwise variable manner.
The cylindrical molded article shrinks due to the sintering process, but the temperature in the furnace is made uniform until all the materials enter a temperature region where thermal shrinkage starts in common, and the temperature is maintained during the temperature rise. This eliminates temperature unevenness in the furnace, and allows all sintered bodies disposed in the furnace to contract uniformly. In addition, it is possible to obtain a stable density of the sintered body by setting appropriate conditions for the temperature and the holding time for each material. A cylindrical sintered body having a length in the cylindrical axis direction of substantially 470mm or more is obtained by sintering a cylindrical molded body having a length in the cylindrical axis direction of 600mm or more.
Next, the formed cylindrical sintered body is machined into a desired cylindrical shape by a machining device such as a surface grinder, a cylinder grinder, a lathe, a cutter, or a machining center (step S307). The machining may be performed so that the cylindrical sintered body has a shape suitable for mounting to a target device or has a desired surface roughness. Here, in order to obtain flatness to the extent that abnormal discharge does not occur after an electric field is concentrated in sputtering, it is preferable that the average roughness (Ra) of the cylindrical sintered body is 0.5 μm or less. Through the above steps, a cylindrical sintered body having high density and high homogeneity can be obtained.
Next, the machined cylindrical sintered body is bonded to the base material (step S308). In particular, in the case of a cylindrical sputtering target, a cylindrical sintered body is bonded to a cylindrical base material called a backing tube using solder as a binder. Through the above steps, a cylindrical sputtering target using the cylindrical sintered body can be obtained.
As described above, according to the method of manufacturing a cylindrical sputtering target of the embodiment, oxygen is supplied to the hollow portion inside the cylinder of the cylindrical formed body in the sintering step, whereby deformation and cracking of the cylindrical sintered body during sintering can be prevented. In addition, the density of the cylindrical sintered body after sintering can be increased. Further, the relative density difference in the cylindrical axis direction of the cylindrical sintered body after sintering can be reduced. The size of the pores observed in the cylindrical inner surface of the cylindrical sintered body after sintering can be reduced. Further, the number of holes observed in the cylindrical inner surface of the cylindrical sintered body after sintering can be reduced. Thus, a cylindrical sintered body and a cylindrical sputtering target having high homogeneity in a solid and between individual bodies can be provided.
< modification 1>
A method for sintering a cylindrical sintered body according to modification 1 of the embodiment of the present invention will be described with reference to fig. 7.
Fig. 7 is a plan view showing a step of sintering a cylindrical molded body in the method of manufacturing a cylindrical sintered body according to modification 1 of the embodiment of the present invention. In fig. 7, 16 oxygen nozzles 230 are arranged in the step of sintering the cylindrical formed body 111. At this time, the oxygen supply ports 230 are directly connected to the pipes 240 for supplying oxygen so that the amount of oxygen can be independently controlled. Accordingly, the amount of oxygen supplied from each oxygen supply port 230 can be appropriately adjusted according to the length and thickness of the cylindrical molded body 111 in the cylindrical axial direction, the size of the cylindrical internal space, the position of the oxygen supply port 230 with respect to the cylindrical molded body 111, and the like.
In fig. 7, eight pairs of oxygen outlets 230 are arranged uniformly through the wall of the cylindrical mold body 111. In other words, eight oxygen supply ports 230 are arranged along the cylindrical inner surface and the cylindrical outer surface of the cylindrical formed body 111. In fig. 7, the cylindrical compact 111 is disposed such that eight ports 230a are located inside the cylinder of the cylindrical compact 111 and eight ports 230b are located outside the cylinder of the cylindrical compact 111 (hereinafter, the ports 230a and 230b are referred to as the ports 230, unless the ports 230a and 230b are distinguished from each other). However, the number, size and arrangement of the oxygen supply ports 230 are not limited to these, as long as the cylindrical formed body 111 can be stably arranged on the sintering base 200. The oxygen supply port 230 may be disposed not only on the inner side of the cylinder of the cylindrical molded body 111 but also on the outer side of the cylinder. In other words, oxygen can be supplied not only to the inner surface of the cylinder but also to the outer surface of the cylinder.
For example, when the length of the cylindrical formed body 111 is long, the oxygen supply amount of the oxygen supply port 230a located inside the cylinder having a difference in convection can be made larger than the oxygen supply amount of the oxygen supply port 230b located outside the cylinder, whereby the oxygen concentration of the inner surface and the outer surface of the cylinder can be finally adjusted to be uniform. Further, oxygen may be supplied only from the oxygen supply port 230a located inside the cylinder. The amount of oxygen supplied to each oxygen supply port 230a may be 1/8, which is the amount of oxygen supplied when oxygen is supplied from one oxygen supply port 230 in the embodiment of the present invention. The amount of oxygen supplied to each oxygen supply port 230a may be different or different. That is, the total of the oxygen supply amounts from the plurality of oxygen supply ports 230a may be the supply amount when oxygen is supplied from one oxygen supply port 230 according to the embodiment of the present invention. Further, the total amount of oxygen supplied from the oxygen supply port 230 may be increased as the length in the cylinder axial direction is increased. However, not limited to this, for example, in the case where the thickness of the cylindrical formed body 111 is thick, the total amount of oxygen supplied from the oxygen supply port 230a may be larger. For example, when the inner diameter of the cylindrical sintered body is large and the internal space of the cylinder is large, the total amount of oxygen supplied from the oxygen supply port 230a may be increased.
The upper limit of the amount of oxygen supplied from the oxygen supply port 230 is not particularly limited, but may be 150L/min or less. The amount of oxygen supplied can be dispersed by supplying oxygen from the plurality of oxygen supply ports 230a, and the convection of gas in the hollow portion inside the cylinder can be controlled. Further, problems such as deformation and cracking of the cylindrical sintered body during sintering and a decrease in density of the cylindrical sintered body after sintering due to the cooling effect by oxygen can be suppressed. However, the oxygen supplied from the plurality of oxygen supply ports 230a may be further diffused in the cylindrical inner space through a baffle plate or the like. Further, the oxygen supplied from the oxygen supply port 230 may be supplied after preheating a pipe or the like in the circulation.
In general ITO sintering, sintering under an oxygen atmosphere is essential for densification of a sintered body. Even in the sintering under an oxygen atmosphere, in the step of sintering the cylindrical formed body 111 having a length of 600mm or more, gas convection in the hollow portion inside the cylinder is insufficient, and oxygen deficiency occurs in the cylinder. The following occurs due to the lack of oxygen in the cylinder: deformation and cracking of the cylindrical sintered body during sintering, a decrease in density of the cylindrical sintered body after sintering, a relative density difference in the cylindrical axis direction of the cylindrical sintered body, and an increase in the size of the holes or the number of holes observed in the cylindrical inner surface of the cylindrical sintered body. In order to prevent the influence of oxygen deficiency in the cylinder, in the present embodiment, the oxygen supply amount from the oxygen supply port 230a located inside the cylinder may be set to be larger than the oxygen supply amount from the oxygen supply port 230b located outside the cylinder, so that the oxygen concentration in the inner surface and the outer surface of the cylinder may be finally adjusted to be uniform. The oxygen supply amount from the oxygen supply port 230a located inside the cylinder may be further increased to finally adjust the oxygen concentration on the inner surface of the cylinder to be higher than the oxygen concentration on the outer surface of the cylinder. Further, it is also possible to adjust the oxygen supply port 230a located inside the cylinder to supply oxygen, and the oxygen supply port 230b located outside the cylinder to supply no oxygen. The oxygen supply amount can be independently controlled by directly connecting each oxygen supply port 230 to a pipe 240 for supplying oxygen. By supplying oxygen from the plurality of oxygen supply ports 230a, oxygen can be uniformly supplied to the inner surface of the cylinder. As a result, the oxygen concentration of the cylindrical inner surface and the outer surface of the cylindrical molded body during sintering can be adjusted, and deformation and cracking of the cylindrical sintered body during sintering can be prevented. In addition, the density of the cylindrical sintered body after sintering can be increased. Further, the relative density difference in the cylindrical axis direction of the cylindrical sintered body after sintering can be reduced. The equivalent circle diameter of the area of the hole observed in the cylindrical inner surface of the cylindrical sintered body after sintering can be reduced. Further, the number of holes observed in the cylindrical inner surface of the cylindrical sintered body after sintering can be reduced.
< modification 2>
A method for sintering a cylindrical sintered body according to modification 2 of the embodiment of the present invention will be described with reference to fig. 8. In this modification, the same as the embodiment of the present invention except for the baffle 260, and therefore, a detailed description thereof is omitted.
Fig. 8 is a cross-sectional view showing a step of sintering a cylindrical molded body in the method of manufacturing a cylindrical sintered body according to modification 2 of the embodiment of the present invention. In fig. 8, one oxygen supply port 230 is provided in the step of sintering the cylindrical formed body 111. The oxygen supply port 230 is directly connected to a pipe 240 for supplying oxygen, so that the amount of oxygen supplied can be independently controlled. A baffle 260 is disposed in the direction of oxygen flow from the oxygen supply port 230. In the present modification, the baffle 260 is formed in a cover shape so as to surround the oxygen supply port 230. The shutter 260 has a plurality of openings 280 in a cover-shaped side wall portion. Therefore, the oxygen supplied from oxygen supply port 230 hits the inner ceiling portion of baffle 260, and flows out from openings 280 of baffle 260 in a scattered state. In the hollow portion inside the cylindrical formed body, oxygen flowing out from the plurality of openings 280 of the baffle 260 gradually fills from below in the cylindrical axial direction and rises in the cylindrical axial direction. However, the shape of the baffle 260 is not limited to this, and the baffle 260 may be any shape as long as oxygen supplied from the oxygen supply port 230 is diffused in the cylindrical inner space. For example, when viewed from the oxygen supply direction side, the baffle 260 may overlap at least a part of the oxygen supply port 230. This has the following effects: deformation and cracking of the cylindrical sintered body during sintering, a decrease in density of the cylindrical sintered body after sintering, and the like due to a cooling effect caused by the supply of a large amount of oxygen from one oxygen supply port 230 can be suppressed.
The present invention is not limited to the above-described embodiments, and can be modified as appropriate without departing from the scope of the invention.
[ examples ]
[ production of cylindrical sintered body ]
[ example 1]
In example 1, a method for producing a cylindrical ITO target (cylindrical sintered body) will be described. First, as a raw material powder, a powder having a BET (BET equation) specific surface area of 4.0 to 6.0m is prepared24N indium oxide in a ratio of 4.0 to 5.7m in terms of BET specific surface area24N tin oxide of not more than g. Here, the BET specific surface area means a surface area calculated by a BET equation. The BET equation is a gas adsorption method in which gas molecules such as nitrogen, argon, krypton, and carbon monoxide are adsorbed to solid particles, and the specific surface area of the solid particles is measured from the amount of the adsorbed gas molecules. Here, the raw materials were weighed so that indium oxide was 90% by mass and tin oxide was 10% by mass. Next, these raw material powders were pulverized and mixed by a wet ball mill. Here, zirconia balls are used as the pulverization medium. And (4) rapidly drying and granulating the mixed slurry by using a spray dryer.
Next, the mixture obtained in the granulation step is formed into a cylindrical shape by CIP molding. The pressure at the time of CIP forming was 176 MPa.
The parameters of the cylindrical molded article of example 1 obtained by the above molding step are as follows.
Cylinder outside diameter (diameter) 194.0mm
Cylinder inner diameter (diameter) 158.7mm
Thickness of cylinder 17.65mm
Length in the cylinder axis direction of 600mm
Next, the cylindrical compact obtained by CIP was sintered in an electric furnace. The sintering conditions were as follows.
Temperature rise rate 300 ℃/hr
High temperature 1560 deg.C
High temperature hold time 20 hours (hr)
Ambient gas during sintering ═ oxygen ambient gas
Pressure at sintering equal to atmospheric pressure
Oxygen was introduced into the hollow portion inside the cylinder at 50L/min
Introduction of oxygen to the outside of the cylinder was 0L/min
The parameters of the cylindrical sintered body obtained by the above-described sintering step are as follows.
Cylinder outside diameter (diameter) 155.2mm
Inner diameter of cylinder 127.0mm
Thickness of cylinder 14.1mm
Length in the cylinder axial direction of 478mm
Density of the sintered body 7.134g/cm3
The relative density of the sintered compact was 99.68%
Volume resistance value of the sintered compact 0.11m Ω · cm
[ example 2]
In example 2, a cylindrical sintered body obtained by sintering a cylindrical formed body longer in the cylindrical axial direction than that of example 1 will be described. The molding step of the cylindrical molded article is the same as in example 1, and therefore, the description thereof is omitted.
The parameters of the cylindrical molded body of example 2 obtained by the same molding step as in example 1 are as follows.
Cylinder outside diameter (diameter) 193.8mm
Cylinder inner diameter (diameter) 158.2mm
Thickness of cylinder 17.8mm
The length in the cylinder axis direction is 1200mm
Next, the cylindrical molded body was sintered by an electric furnace. The sintering conditions in example 2 were the same as in example 1 except for the parameters for introducing oxygen into the hollow portion inside the cylindrical molded body, and therefore, the explanation thereof is omitted.
Oxygen is introduced into the hollow portion inside the cylinder at 100L/min
Introduction of oxygen to the outside of the cylinder was 0L/min
The parameters of the cylindrical sintered body obtained by the above-described sintering step are as follows.
Cylinder outside diameter (diameter) 155.0mm
Cylinder bore (diameter) 126.6mm
Thickness of cylinder 14.2mm
Length in the cylinder axis direction of 948mm
Density of sintered body 7.132g/cm3
The relative density of the sintered compact was 99.65%
Volume resistance value of the sintered compact 0.12m Ω · cm
[ example 3]
In example 3, a cylindrical sintered body obtained by sintering a cylindrical molded body longer in the cylindrical axial direction than in examples 1 and 2 will be described. The molding step of the cylindrical molded article is the same as in example 1, and therefore, the description thereof is omitted.
The parameters of the cylindrical molded article of example 3 obtained by the same molding step as in example 1 are as follows.
Cylinder outside diameter (diameter) 194.2mm
Cylinder inner diameter (diameter) 158.5mm
Thickness of cylinder 17.85mm
Length in cylinder axis direction 1755mm
Next, the cylindrical molded body was sintered by an electric furnace. The sintering conditions in example 3 were the same as in example 1 except for the parameters for oxygen introduction into the inside of the cylindrical formed body, and therefore, the explanation thereof is omitted.
Oxygen was introduced into the hollow portion inside the cylinder at 150L/min
Introduction of oxygen to the outside of the cylinder was 0L/min
The parameters of the cylindrical sintered body obtained by the above-described sintering step are as follows.
Cylinder outside diameter (diameter) 155.4mm
Cylinder bore (diameter) 126.8mm
Thickness of cylinder 14.3mm
Length in cylinder axis direction 1386mm
Density of sintered body 7.130g/cm3
The relative density of the sintered compact was 99.62%
Volume resistance value of the sintered compact 0.12m Ω · cm
Next, the comparative examples described above with respect to the cylindrical formed body and the cylindrical sintered body shown in examples 1 to 3 will be described. In the following comparative examples, a cylindrical sintered body sintered under the condition that oxygen is not introduced into the hollow portion inside the cylindrical formed body, unlike the examples, will be described. In the comparative example, instead of introducing oxygen into the hollow portion inside the cylindrical molded body, sintering was performed under the condition of introducing oxygen from the chamber wall portion to the outside of the cylindrical molded body. The molding step of the cylindrical molded article is the same as in example 1, and therefore, the description thereof is omitted.
Comparative example 1
The parameters of the cylindrical molded body of comparative example 1 obtained by the same molding step as in example 1 are as follows.
Cylinder outside diameter (diameter) 194.9mm
Inner diameter (diameter) of cylinder 159.0mm
Thickness of cylinder 17.95mm
Length in cylinder axis direction is 480mm
Next, the cylindrical molded body was sintered by an electric furnace. The sintering conditions of comparative example 1 were the same as those of example 1 except for the parameters for introducing oxygen into the cylindrical molded body, and thus the explanation thereof is omitted.
Introduction of oxygen into the hollow portion inside the cylinder was 0L/min
Introduction of oxygen to the outside of the cylinder was 100L/min
The parameters of the cylindrical sintered body obtained by the sintering step described above are as follows.
Cylinder outside diameter (diameter) 155.9mm
Inner diameter of cylinder 127.2mm
Thickness of cylinder 14.35mm
Length in the cylinder axis direction of 385mm
Density of sintered body＝7.133g/cm3
The relative density of the sintered compact was 99.66%
Volume resistance value of the sintered compact 0.11m Ω · cm
Comparative example 2
The parameters of the cylindrical molded body of comparative example 2 obtained by the same molding step as in example 1 are as follows.
Cylinder outside diameter (diameter) 193.5mm
Cylinder inner diameter (diameter) 158.2mm
Thickness of cylinder 17.65mm
Length in the cylinder axis direction of 600mm
Next, the cylindrical molded body was sintered by an electric furnace. The sintering conditions of comparative example 2 were the same as those of example 1 except for the parameters for introducing oxygen into the cylindrical molded body, and thus, the explanation thereof is omitted.
Introduction of oxygen into the hollow portion inside the cylinder was 0L/min
Introduction of oxygen to the outside of the cylinder was 100L/min
The parameters of the cylindrical sintered body obtained by the above-described sintering step are as follows.
Cylinder outside diameter (diameter) 156.7mm
Cylinder internal diameter (diameter) 128.1mm
Thickness of cylinder 14.3mm
485mm in the length of the cylinder axis
Density of the sintered body 7.041g/cm3
The relative density of the sintered compact was 98.38%
Volume resistance value of the sintered compact 0.12m Ω · cm
Comparative example 3
The parameters of the cylindrical molded body of comparative example 3 obtained by the same molding step as in example 1 are as follows.
Cylinder outside diameter (diameter) 194.1mm
Cylinder inner diameter (diameter) 158.2mm
Thickness of cylinder 17.95mm
The length in the cylinder axis direction is 1200mm
Next, the cylindrical molded body was sintered by an electric furnace. The sintering conditions of comparative example 3 were the same as those of example 1 except for the parameters for introducing oxygen into the cylindrical molded body, and thus, the explanation thereof is omitted.
Introduction of oxygen into the hollow portion inside the cylinder was 0L/min
Introduction of oxygen to the outside of the cylinder was 100L/min
The parameters of the cylindrical sintered body obtained by the above-described sintering step are as follows.
Cylinder outside diameter (diameter) 157.2mm
Cylinder internal diameter (diameter) 128.1mm
Thickness of cylinder 14.55mm
Length in cylinder axial direction of 957mm
Density of the sintered body 7.038g/cm3
The relative density of the sintered compact was 98.34%
Volume resistance value of the sintered compact 0.12m Ω · cm
In addition, comparative example 3 confirmed deformation due to sintering.
Comparative example 4
The parameters of the cylindrical molded body of comparative example 4 obtained by the same molding step as in example 1 are as follows.
Cylinder outside diameter (diameter) 194.2mm
Cylinder inner diameter (diameter) 158.4mm
Thickness of cylinder 17.9mm
Length in cylinder axis direction 1410mm
Next, the cylindrical molded body was sintered by an electric furnace. The sintering conditions of comparative example 4 were the same as in example 1 except for the parameters for oxygen introduction into the cylindrical molded body, and therefore, the explanation thereof is omitted.
Introduction of oxygen into the hollow portion inside the cylinder was 0L/min
Introduction of oxygen to the outside of the cylinder was 100L/min
The parameters of the cylindrical sintered body obtained by the above-described sintering step are as follows.
Cylinder outside diameter (diameter) 155.3mm
Inner diameter of cylinder 127.8mm
Thickness of cylinder 13.75mm
Length in the cylinder axis direction of 1145mm
Density of sintered body 7.042g/cm3
The relative density of the sintered compact was 98.39%
Volume resistance value of the sintered compact 0.12m Ω · cm
Comparative example 5
The parameters of the cylindrical molded body of comparative example 5 obtained by the same molding step as in example 1 are as follows.
Cylinder outside diameter (diameter) 193.6mm
Cylinder inner diameter (diameter) 158.3mm
Thickness of cylinder 17.65mm
Length in cylinder axis direction 1754mm
Next, the cylindrical molded body was sintered by an electric furnace. The sintering conditions of comparative example 5 were the same as in example 1 except for the parameters for oxygen introduction into the cylindrical formed body, and therefore, the explanation thereof is omitted.
Introduction of oxygen into the hollow portion inside the cylinder was 0L/min
Introduction of oxygen to the outside of the cylinder was 100L/min
The parameters of the cylindrical sintered body obtained by the above-described sintering step are as follows.
Cylinder outside diameter (diameter) 157.8mm
Cylinder internal diameter (diameter) 128.5mm
Thickness of cylinder 14.65mm
The length in the cylinder axis direction is 1394mm
Density of sintered body 7.044g/cm3
The relative density of the sintered compact was 98.42%
Volume resistance value of the sintered compact 0.12m Ω · cm
[ preparation of measurement sample ]
For the cylindrical sintered bodies of examples 1 to 3 and comparative examples 1 to 5, measurement samples for evaluating the variation in density and volume resistance in the solid body were prepared. As shown in fig. 9, the cylindrical sintered body 110 is divided into segments of 150mm each from the lower side toward the upper side in the cylindrical axis direction at the time of sintering. Cylindrical measurement samples having a width of 40 to 50mm at the center in the cylindrical axis direction were cut out from the lower side in the cylindrical axis direction as measurement samples 110-1(150mm), 110-2(300mm), and 110-3(450mm) (the names in the table to be described later).
[ evaluation of relative Density ]
The cylindrical sintered bodies of examples 1 to 3 and comparative examples 1 to 5 and the respective measurement samples were evaluated for relative density. The densities of the cylindrical sintered body and each measurement sample were measured by the archimedes method. Based on the theoretical density, the relative density and the relative density difference of the cylindrical sintered body and each measurement sample were calculated. Fig. 10 shows the densities and relative densities of the cylindrical sintered bodies of examples 1 to 3 and comparative examples 1 to 5 and the respective measurement samples, and the maximum relative density difference in the cylindrical sintered bodies.
As is clear from the results of fig. 10, the cylindrical sintered bodies of examples 1 to 3, in which oxygen was introduced into the inner hollow portion of the cylindrical formed body during sintering, had higher relative densities than the cylindrical sintered bodies of comparative examples 2 to 5, in which oxygen was not introduced into the inner hollow portion of the cylindrical formed body. In comparative example 1 in which the length in the cylindrical axis direction was 470mm or less, the relative density was improved even when oxygen was not introduced into the inner hollow portion of the cylindrical molded body. The relative density difference of each of the measurement samples of examples 1 to 3 was reduced as compared with each of the measurement samples of comparative examples 2 to 5. In comparative example 1 in which the length in the cylindrical axis direction was 470mm or less, the relative density difference was reduced even when oxygen was not introduced into the inner hollow portion of the cylindrical molded body. Further, in the sintering step, oxygen is supplied to the cylindrical inner surface of the cylindrical molded body, whereby the cylindrical molded body having a length of 1200mm or more in the axial direction of the cylinder can be prevented from deformation, cracking, or the like during sintering.
[ evaluation of minimum oxygen supply amount ]
The sintering method of the cylindrical molded bodies in the above examples and comparative examples was calculated to obtain a density of 7.130g/cm3The above minimum oxygen supply amount required for the cylindrical sintered body. Specifically, the amount of oxygen introduced into the hollow portion inside the cylinder during sintering was varied stepwise, and a cylindrical sintered body having a length in the cylinder axial direction of 390, 480, 950, 1200, or 1400mm was obtained. The density of each cylindrical sintered body was measured by the archimedes method. At a density of 7.130g/cm3In the above cylindrical sintered body, the minimum value of the amount of oxygen introduced during sintering is set as the minimum oxygen supply amount for each length in the cylindrical axis direction. Fig. 11 shows the correspondence between the minimum oxygen supply amount and the length of the cylindrical sintered body in the cylindrical axis direction.
As shown in FIG. 11, the density of 7.130g/cm was obtained until the length of the cylindrical sintered body in the cylindrical axis direction was 390mm, even if oxygen was not introduced3The above cylindrical sintered body. When a 480mm cylindrical sintered body is formed, the minimum oxygen supply amount is 5L/min or more. When a 950mm cylindrical sintered body is formed, the minimum oxygen supply amount is 20L/min or more. When a 1200mm cylindrical sintered body is formed, the minimum oxygen supply amount is 30L/min or more. When a cylindrical sintered body of 1400mm is formed, the minimum oxygen supply amount is 35L/min or more. From the results of FIG. 11, it is understood that the density of 7.130g/cm was obtained as the length in the cylinder axis direction was longer3The amount of oxygen required for the above cylindrical sintered body increases. The density was 7.130g/cm3The axial length x (mm) of the cylindrical sintered body described above is proportional to the minimum oxygen supply amount Y (L/min) supplied from the oxygen supply port 230, and can be represented by the following equation.
Y＝0.0345X－12.508
[ evaluation of volume resistance ]
The volume resistance was evaluated for the cylindrical sintered bodies and the respective measurement samples of examples 1 to 3 and comparative examples 1 to 5. The volume resistance values of the cylindrical sintered body and each measurement sample were measured on the outer surface of the cylinder by a four-probe method. Fig. 12 shows the volume resistance values of the cylindrical sintered bodies of examples 1 to 3 and comparative examples 1 to 5 and the volume resistance values of the respective measurement samples.
As is clear from the results in fig. 12, the volume resistance values of the outer surfaces of the cylinders were almost unchanged in the cylindrical sintered bodies of examples 1 to 3 and comparative examples 1 to 5 and the respective measurement samples. It is considered that since oxygen is sufficiently supplied to the outer surface of the cylinder, the volume resistance value of the outer surface of the cylinder is hardly affected in both the example in which oxygen is introduced into the hollow portion inside the cylinder of the cylindrical molded body and the comparative example in which oxygen is not introduced into the hollow portion inside the cylinder.
[ preparation of samples for Electron microscope Observation ]
Samples for observation under an electron microscope were prepared for the cylindrical sintered bodies of examples 1 and 2, and comparative examples 2 and 3. As shown in FIG. 13, in the cylindrical sintered body 110, a cylindrical sample 110-4 having a width of 10mm at the center in the cylindrical axis direction was cut out, a sample for electron microscope observation was cut out from the cylindrical inner surface 110-4a and the cylindrical outer surface 110-4b, and mirror-polished in a state of 0.5mm grinding.
[ Observation with an Electron microscope ]
The cylindrical sintered bodies of example 1 and example 2, and comparative example 2 and comparative example 3 were observed with an electron microscope (SEM) for samples for electron microscope observation of the cylindrical inner surface and the cylindrical outer surface of the cylindrical sintered bodies. Fig. 14 (inside of the cylinder) and fig. 15 (outside of the cylinder) show photographs of each sample observed with an electron microscope (SEM) at 1000 × field. Fig. 16 (inside of the cylinder) and fig. 17 (outside of the cylinder) show photographs of each sample observed with an electron microscope (SEM) at a field of view of 2000 × or 5000 × magnification. In fig. 14 to 17, samples for electron microscope observation of the cylindrical inner surface and the cylindrical outer surface of the cylindrical sintered body of (a) example 1, (b) example 2, (c) comparative example 2, and (d) comparative example 3 were observed by an electron microscope (SEM).
Portions (a) and (b) in fig. 14 are electron micrographs of the inner surface of the cylindrical sintered body in examples 1 and 2. Portions (a) and (b) in fig. 15 are electron micrographs of the outer surface of the cylindrical sintered body in examples 1 and 2. Portions (c) and (d) in fig. 14 are electron micrographs of the inner surfaces of the cylindrical sintered bodies in comparative examples 2 and 3. Portions (c) and (d) in fig. 15 are electron micrographs of the outer side surfaces of the cylindrical sintered bodies in comparative examples 2 and 3. As shown in fig. 14 and 15, in examples 1 and 2 in which oxygen was introduced into the hollow portion inside the cylinder of the cylindrical molded body during sintering, no significant difference was observed in the electron micrographs of the inner surface (portions (a) and (b) in fig. 14) and the outer surface (portions (a) and (b) in fig. 15) of the cylindrical sintered body. On the other hand, in comparative examples 2 and 3 in which oxygen was not introduced into the hollow portion inside the cylinder of the cylindrical molded body during sintering, a large number of large pores (photographs, black irregular shapes) were observed in the electron micrograph of the inner surface (parts (c) and (d) of fig. 14) of the cylindrical sintered body, as compared with the outer surface (parts (c) and (d) of fig. 15) of the cylindrical sintered body. In the cylindrical inner surfaces of the cylindrical sintered bodies of comparative examples 2 and 3, a large number of irregular granular (crystal granular) pores were observed. The pores observed in the cylindrical inner surface of the cylindrical sintered bodies in comparative examples 2 and 3 were mainly observed in the grain boundaries.
Next, in order to observe the state of the crystal grains, in the comparative example, the regions where no macropores were observed in the portions (c) and (d) of fig. 14 were observed with a visual field of 2000 times or 5000 times, in particular. Portions (a) and (b) in fig. 16 are electron micrographs of the inner surface of the cylindrical sintered body in examples 1 and 2. Portions (a) and (b) in fig. 17 are electron micrographs of the outer surface of the cylindrical sintered body in examples 1 and 2. Portions (c) and (d) in fig. 16 are electron micrographs of the inner surfaces of the cylindrical sintered bodies in comparative examples 2 and 3. Portions (c) and (d) in fig. 17 are electron micrographs of the outer side surfaces of the cylindrical sintered bodies in comparative examples 2 and 3. As shown in fig. 16 and 17, in examples 1 and 2 in which oxygen was introduced into the hollow portion inside the cylinder of the cylindrical molded body during sintering, no significant difference was observed in the electron micrographs of the inner surface (portions (a) and (b) in fig. 16) and the outer surface (portions (a) and (b) in fig. 17) of the cylindrical sintered body, and crystal grains grew greatly. In comparative example 2 in which oxygen was not introduced into the hollow portion inside the cylinder of the cylindrical molded body during sintering and the length in the cylinder axis direction was shorter than that in comparative example 3, no large difference was observed in the electron micrographs of the inner surface (portion (c) in fig. 16) and the outer surface (portion (c) in fig. 17) of the cylindrical sintered body, and crystal grains grew greatly. On the other hand, in comparative example 3 in which oxygen was not introduced into the hollow portion inside the cylinder of the cylindrical molded body at the time of sintering and the length in the cylinder axis direction was longer than that in comparative example 2, crystal grains in the initial stage of growth were observed to be small in the electron micrograph of the inner surface (portion (d) in fig. 16) of the cylindrical sintered body as compared with the outer surface (portion (d) in fig. 17) of the cylindrical sintered body. The crystal grains on the inner surface of the cylindrical sintered body in comparative example 3 were small and uneven at the early stage of growth, and were poor in smoothness.
Small and irregular particle-shaped (bubble-shaped) pores (for example, the upper left pores in fig. 17 (b)) were observed in the cylindrical inner and outer surfaces of the cylindrical sintered bodies of examples 1 and 2. Similar small and irregular particle-shaped (bubble-shaped) pores were observed in the outer cylindrical surface of the cylindrical sintered bodies of comparative examples 2 and 3. The pores observed in the cylindrical inner surface of the cylindrical sintered bodies of examples 1 and 2 and in the cylindrical outer surface of the cylindrical sintered bodies of examples 1 and 2, comparative examples 2 and 3 were observed in both the grain boundary and the crystal.
[ evaluation of holes in the inner surface of the cylindrical sintered body ]
The structures of the inner surface and the outer surface of the cylinder at the center in the cylinder axis direction of the cylindrical sintered body were observed by an electron microscope (SEM) by the above-described method for the cylindrical sintered bodies of examples 1 to 3 and comparative examples 1 to 5, and the number of holes and the equivalent circle diameter of the area of the holes were measured. For each sample, five samples for electron microscope observation were cut out in the circumferential direction from the cylindrical inner surface 110-4a of the cylindrical sample 110-4. The 980 μm × 1200 μm visual field was observed from each electron microscope observation sample, and the average value of the equivalent circle diameter of the number of holes and the area of the holes was calculated. The equivalent circle diameter L of the area S of the hole of the cylindrical sintered body is calculated by the following equation:
[ mathematical formula 1]
Figure BDA0002101475200000231
Fig. 18 shows the average value of the equivalent circle diameters of the number of holes and the area of the holes in the cylindrical inner surface of the cylindrical sintered bodies of examples 1 to 3 and comparative examples 1 to 5.
As is clear from the results of fig. 18, in the cylindrical sintered bodies of examples 1 to 3 in which oxygen was introduced into the hollow portion inside the cylinder of the cylindrical molded body during sintering, the number of holes in the inner surface of the cylinder was smaller than in the cylindrical sintered bodies of comparative examples 2 to 5 in which oxygen was not introduced into the hollow portion inside the cylinder. In comparative example 1 in which the length in the cylinder axial direction was 470mm or less, the number of holes in the cylinder inner surface was small even if oxygen was not introduced into the hollow portion inside the cylindrical molded body. The average equivalent circle diameter of the area of the pores on the cylindrical inner surface of the cylindrical sintered bodies of examples 1 to 3 was 1 μm or less. On the other hand, the average equivalent circle diameter of the area of the pores on the cylindrical inner surface of the cylindrical sintered bodies of comparative examples 2 to 5 was 4 μm or more. In comparative example 1 in which the length in the cylinder axial direction was 470mm or less, the average equivalent circle diameter of the area of the hole on the cylinder inner surface was 1 μm or less even when oxygen was not introduced into the inner hollow portion of the cylindrical molded body. Further, as shown in FIG. 18, the number of holes on the outer surface of the cylinder of the cylindrical sintered bodies of examples 1 to 3 and comparative examples 1 to 5 was 4.25X 10-5Per mu m2The average equivalent circle diameter of the area of the pores is 1 μm or less.
Examples 1 to 3 show the results of ITO, but the cylindrical molded bodies made of each component of IZO sintered body, IGZO sintered body, and AZO sintered body, each having a length in the cylindrical axial direction of 600mm or more, were similarly sintered by the manufacturing method of the present invention. In addition, the production conditions may be appropriately changed for each component within the scope of the present invention. As a result, deformation and cracking of the cylindrical sintered body during sintering can be prevented. In addition, the density of the cylindrical sintered body after sintering can be increased, and the relative density difference in the cylindrical axis direction of the cylindrical sintered body after sintering can be reduced. The equivalent circle diameter of the area of the holes observed in the cylindrical inner surface of the cylindrical sintered body after sintering can be reduced, and the number of the holes observed in the cylindrical inner surface of the cylindrical sintered body after sintering can be reduced.
The present invention is not limited to the above-described embodiments, and can be modified as appropriate without departing from the scope of the invention.

Claims (5)

1. A cylindrical sintered body characterized in that the length in the axial direction of the cylinder is 470mm or more, and the number of pores observed on the inner and outer surfaces of the cylinder is 4.25X 10 on average-5Per mu m2Hereinafter, the equivalent circle diameter of the area of the holes observed on the inner surface and the outer surface of the cylinder is 1 μm or less on average, and the relative density difference in the cylinder axial direction is less than 0.1%.
2. The cylindrical sintered body as claimed in claim 1, wherein the holes observed in the inner surface and the outer surface of the cylinder are at least five independent places in the central part in the axial direction of the cylinder, each place being 1.176mm2Is observed in the field of view of (a).
3. The cylindrical sintered body according to claim 1, wherein the equivalent circle diameter of the area of the hole observed in the inner surface and the outer surface of the cylinder is 0.5 μm or less on average in a cylindrical sintered body having a length of 470mm or more in the cylindrical axis direction.
4. The cylindrical sintered body as claimed in claim 1, wherein the relative density difference in the cylindrical axis direction is 0.05% or less.
5. A sputtering target comprising the cylindrical sintered body according to any one of claims 1 to 4 and a base material disposed in a hollow portion inside the cylinder.
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