JP5000231B2 - Gadolinium oxide-containing oxide target - Google Patents

Description

  The present invention relates to an oxide target used when forming a conductive film. More specifically, the present invention relates to an oxide target made of an oxide sintered body containing gadolinium.

In a transparent conductive film containing indium oxide as a main component, indium oxide (ITO) doped with tin is generally used. This is because a transparent conductive film excellent in conductivity can be obtained by improving the carrier concentration by doping with tin.
However, the ITO film needs to use a strong acid (for example, aqua regia) for the etching process, and when used for an electrode for a TFT liquid crystal, there is a problem that the underlying metal wiring may be corroded. is doing. Furthermore, since the ITO target used when producing the ITO film by sputtering is likely to be blackened by reduction, a change in its characteristics with time is a problem.

  A transparent conductive film having excellent etching and light transmittance as compared with the ITO film and a sputtering target suitable for obtaining the transparent conductive film, which is superior to the ITO film, and a transparent conductive film made of indium oxide and zinc oxide. It has been proposed (Patent Documents 1 and 2). These transparent conductive films made of indium oxide and zinc oxide are known to have a high etching rate with a weak acid. However, when the metal thin film formed on the transparent conductive film is etched, the transparent conductive film made of indium oxide and zinc oxide may be etched at the same time, and only the metal thin film on the transparent conductive film is selectively etched. In some cases it was inappropriate.

In addition, it has been reported that a transparent conductive film containing indium oxide and a lanthanoid element is useful as an organic EL electrode or a transflective / semi-reflective LCD electrode (Patent Documents 3-11). However, oxides of lanthanoid elements are not conductive, and when targets are prepared by mixing these oxides with indium oxide, only targets with low conductivity may be obtained. For this reason, abnormal discharge may occur during sputtering, or the target surface may become black, which may cause inconveniences such as a reduction in sputtering speed.
JP-A-6-234565 JP 7-235219 A JP 2004-68054 A JP 2004-119272 A JP 2004-139780 A JP 2004-146136 A JP 2004-158315 A JP 2004-240091 A JP 2004-294630 A JP 2004-333882 A JP 2005-314734 A

  The present invention has been made in view of the above-described problems, and an object thereof is to provide an oxide target that has high conductivity and does not cause abnormal discharge or surface blackening of the target.

According to the present invention, the following oxide target (hereinafter simply referred to as target) is provided.
1. An oxide target containing indium (In), tin (Sn) and gadolinium (Gd), characterized by containing an oxide represented by Gd ₂ Sn ₂ O ₇ and / or GdInO ₃ Oxide target.
2. 3. The oxide target according to 2, wherein the ratio [Gd / (Gd + Sn + In): atomic ratio] of Gd to the total content of In, Sn and Gd is 0.001 to 0.5.
3. The ratio of Sn [Sn / (Gd + Sn + In): atomic ratio] to the total content of In, Sn and Gd and the ratio of Gd [Gd / (Gd + Sn + In): atomic ratio] satisfy the following relational expression: The oxide target according to 1 and 2.
[Sn / (Gd + Sn + In)]> [Gd / (Gd + Sn + In)]
4). 4. The oxide target according to any one of 1 to 3, wherein the sintered density is 6.5 g / cm ³ or more.
5. Bulk resistance is 1 ohm-cm or less, The oxide target in any one of 1-4 characterized by the above-mentioned.

  Since the oxide target of the present invention includes an oxide having a predetermined structure containing a gadolinium element and has excellent conductivity, it is an oxide target without abnormal discharge. These oxide targets are used as sputtering targets, electron beam targets, or ion plating targets, and serve as raw materials for thin film formation.

The oxide target of the present invention is a target composed of an oxide sintered body containing indium (In), tin (Sn), and gadolinium (Gd), and is made of Gd ₂ Sn ₂ O ₇ and / or GdInO ₃ . It is characterized by containing the represented oxide.
When this target is used, the conductivity of the target is higher than that of a target made of simply In ₂ O ₃ , SnO ₂ and Gd ₂ O ₃ , and there is no blackening of the target surface and abnormal discharge during sputtering is also caused. And stable sputtering state is maintained.

The target of the present invention includes an oxide having a form represented by Gd ₂ Sn ₂ O ₇ and / or GdInO ₃ , and preferable examples of the oxide constituting the target include the following. It is done.
(A) A mixture of Gd ₂ Sn ₂ O ₇ and In ₂ O ₃
(B) a mixture of Gd ₂ Sn ₂ O ₇ , In ₂ O ₃ and SnO ₂
(C) A mixture of Gd ₂ Sn ₂ O ₇ , GdInO ₃ and In ₂ O ₃
(D) Gd ₂ Sn ₂ O ₇ , GdInO ₃ and SnO ₂ mixture Among the above, a sintered body made of (a), (b) or (c) is preferable.

In this target, the atomic ratio of Gd (Gd / (Gd + In + Sn)) is preferably 0.001 to 0.5, more preferably 0.01 to 0.3, and particularly preferably 0.01 to 0.25. It is. If it is less than 0.001, the effect of adding Gd may not be obtained, and if it exceeds 0.5, Gd ₂ O ₃ will be present alone, the strength of the target will be too small, and sputtering Cracks may occur due to heat stress. In addition, the strength of the target itself may decrease, and problems such as cracking may occur during the target manufacturing process.

Further, the ratio (atomic ratio) of the contents of Gd and Sn in the target preferably satisfies the relationship of the following formula.
Sn / (Gd + In + Sn)> Gd / (Gd + In + Sn)
This is because Gd and Sn are likely to react, so that Gd ₂ Sn ₂ O ₇ is easily generated. That is, when Gd is present in excess of Sn, almost all of Sn is consumed by Gd, so that GdInO ₃ is mainly generated. As a result, the amount of Sn doping into In ₂ O ₃ decreases, which may increase the bulk resistance of the target.
On the other hand, when the content of Gd is made smaller than the content of Sn so as to satisfy the above formula, Gd is consumed by Sn, but excess Sn is doped into In ₂ O ₃ . Thereby, the resistance value of the target is reduced, and a stable sputtering state can be maintained.

  The Sn content [atomic ratio: Sn / (Gd + In + Sn)] satisfies the above-described relationship and is preferably in the range of 0.03 to 0.45, particularly preferably in the range of 0.05 to 0.4. .

The atomic ratio of Gd, In and Sn is obtained by adjusting the mixing ratio of the indium compound, tin compound and gadolinium compound before sintering. Before sintering, a Gd ₂ Sn ₂ O ₇ compound composed of a tin compound and a gadolinium compound corresponding to the stoichiometric ratio is generated by a mixing ratio, and a GdInO ₃ compound composed of an indium compound and a gadolinium compound is generated, and the remaining indium compound It is presumed that tin compounds exist as crystalline substances or amorphous substances.

Examples of the method for producing the target include a method of sintering a mixture of these using a compound containing an indium atom, a compound containing a tin atom, and a compound containing a gadolinium atom as a raw material.
Examples of the compound containing indium atoms include indium oxide and indium hydroxide. Indium oxide is preferable.
Examples of the compound containing a gadolinium atom include gadolinium oxide and gadolinium hydroxide. Preferably, it is gadolinium oxide.
Examples of the compound containing a tin atom include tin oxide (stannous oxide, stannic oxide), metastannic acid, and the like. Preferably, it is tin oxide (stannic oxide).

The above starting materials are preferably pulverized and mixed with a bead mill or the like. Thereby, a raw material can be mixed uniformly and the particle size of a raw material can be made small.
The average particle size of the raw material is at most 3 μm, preferably 1 μm or less, more preferably 0.8 μm or less. If it exceeds 3 μm, for example, Gd ₂ O ₃ is present as insulating particles in the target as it is, which may cause abnormal discharge. The generation of Gd ₂ Sn ₂ O ₇ can be confirmed by X-ray diffraction.

A material powder formed into a predetermined shape is fired. Baking conditions are 1000-1600 degreeC. Preferably it is 1200-1500 degreeC, More preferably, it is 1250-1450 degreeC. Is less than 1000 ° C., less reactive of _Gd 2 _{O 3,} there are cases where Gd 2 _Sn 2 _{O 7} generated and GdInO ₃ production is not observed in the. If it exceeds 1600 ° C., the composition may change due to sublimation or thermal decomposition of In ₂ O ₃ , or the produced Gd ₂ Sn ₂ O ₇ or GdInO ₃ may be decomposed.
In the present invention, the sintered body contains Gd ₂ Sn ₂ O ₇ and / or GdInO ₃ , but this form of oxide can be formed by a sintering reaction (thermal reaction).

The target of the present invention, the density of the sintered body constituting the target is preferably 6.5 g / cm ³ or more, more preferably 6.6~7.2g / cm ^3. If the density of the sintered body is less than 6.5 g / cm ³ , the target surface may be blackened and abnormal discharge may occur.
In order to obtain a sintered body having a high density, it is preferable to form by a cold isostatic pressure (CIP) or the like in a forming step before firing, or to sinter by a hot isostatic pressure (HIP) or the like.

  The sintered body constituting the target of the present invention has little blackening during sputtering and high conductivity. Specifically, the bulk resistance of the sintered body can be 1 Ωcm or less. Furthermore, 0.1 Ωcm or less is also possible. In the present invention, in particular, the bulk resistance can be reduced by using a composition of Gd / (Gd + Sn + In) <Sn / (Gd + Sn + In).

A conductive film can be formed using the target of the present invention. As a film forming method, an RF magnetron sputtering method, a DC magnetron sputtering method, an electron beam evaporation method, an ion plating method, or the like can be used. Of these, the RF magnetron sputtering method is preferably used. Even when the target bulk resistance exceeds 1 Ωcm, if the RF magnetron sputtering method is employed, a stable sputtering state can be maintained without abnormal discharge. In the case of a low resistance where the bulk resistance of the target is 1 Ωcm or less, an industrially advantageous DC magnetron sputtering method may be employed.
Thereby, a stable sputtering state is maintained without abnormal discharge, and industrially stable film formation becomes possible.

A method for measuring the characteristics of the targets prepared in Examples and Comparative Examples is shown below.
(1) Density The density was calculated from the weight and outer dimensions of the target cut into a certain size.
(2) Atomic ratio of each element in the target The abundance of each element was measured by ICP (Inductively Coupled Plasma) measurement.
(3) Bulk resistance of target The resistivity was measured by a four-probe method using a resistivity meter (Mitsubishi Yuka, Loresta).
(4) Structure of oxide present in target The structure of the oxide was identified by analyzing the chart obtained by X-ray diffraction.

Examples 1-10
In the mixing ratio shown in Table 1, indium oxide having a purity of 99.9% or more, gadolinium oxide having a purity of 99.9% or more, and tin oxide having a purity of 99.9% or more are mixed and about 5 hours in a dry bead mill. Crushed and mixed.
Subsequently, the powder obtained above was inserted into a 10 mmφ mold, and preformed at a pressure of 100 kg / cm ^{2 with} a mold press molding machine. Next, the compact was compacted at a pressure of 4 t / cm ² using a cold isostatic press molding machine and then fired at 1350 ° C. for 10 hours to obtain a sintered body. This sintered body was processed into a target (grinding, polishing, attaching to a backing plate).

As a result of X-ray diffraction measurement, it was confirmed that the target thus obtained was composed of an oxide containing In ₂ O _3, Gd ₂ Sn ₂ O ₇ , and GdInO ₃ as main components. FIG. 1-10 shows X-ray charts of the targets manufactured in Example 1-10, respectively.
Table 2 shows the results of X-ray diffraction, ICP analysis of the target, and the in-plane element distribution measurement by EPMA (Electron Probe Micro Analyzer) to confirm the dispersion state of In and Gd, and the density and bulk resistance. Indicates.

Comparative Example 1
400 g of indium oxide and 600 g of gadolinium oxide were mixed and pulverized and mixed in a dry bead mill for about 5 hours.
Subsequently, the powder obtained above was inserted into a 10 mmφ mold, and preformed at a pressure of 100 kg / cm ^{2 with} a mold press molding machine. Next, it was consolidated at a pressure of 4 t / cm ² using a cold isostatic press molding machine, and then fired at 1350 ° C. for 10 hours.

In the sintered body taken out from the furnace, many cracks were generated and cracks were observed, and the target (grinding, polishing, pasting to backing plate) processing could not be performed.
As a result of X-ray diffraction measurement, this sintered body was confirmed to be a sintered body made of an oxide containing GdInO ₃ and Gd ₂ O ₃ as main components.
As a result of ICP analysis, the atomic ratio [Gd / (Gd + In)] was 0.56.
As a result of confirming the dispersion state of In and Gd by measuring the element distribution in the surface of the sintered body by EPMA, the composition was substantially non-uniform. Further, the bulk resistance was 2 MΩcm or more, which was almost an insulating material.

  The target of the present invention is a transparent conductive film for various uses such as a transparent conductive film for liquid crystal display devices (LCD), a transparent conductive film for electroluminescence (EL) display elements, and a transparent conductive film for solar cells. It is suitable as a target for obtaining by vapor deposition or ion plating. For example, an electrode of an organic EL element and a transparent conductive film for a semi-transmissive / semi-reflective LCD can be obtained.

2 is an X-ray chart of a target manufactured in Example 1. FIG. 3 is an X-ray chart of a target produced in Example 2. 6 is an X-ray chart of a target produced in Example 3. 6 is an X-ray chart of a target produced in Example 4. 6 is an X-ray chart of a target produced in Example 5. FIG. 10 is an X-ray chart of a target produced in Example 6. 10 is an X-ray chart of a target produced in Example 7. 10 is an X-ray chart of a target produced in Example 8. 10 is an X-ray chart of a target produced in Example 9. 10 is an X-ray chart of a target produced in Example 10.

Claims (5)

A target substantially consisting of an oxide of indium (In), tin (Sn), and gadolinium (Gd), characterized by containing an oxide represented by Gd ₂ Sn ₂ O ₇ and / or GdInO ₃ An oxide target used for sputtering, electron beam evaporation, and ion plating. 2. The sputtering and electron beam according to claim 1 , wherein the ratio [Gd / (Gd + Sn + In): atomic ratio] of Gd to the total content of In, Sn, and Gd is 0.001 to 0.5. Oxide target used for vapor deposition and ion plating. The ratio of Sn [Sn / (Gd + Sn + In): atomic ratio] to the total content of In, Sn and Gd and the ratio of Gd [Gd / (Gd + Sn + In): atomic ratio] satisfy the following relational expression: The oxide target used for sputtering, electron beam evaporation, or ion plating according to claim 1 or 2.
[Sn / (Gd + Sn + In)]> [Gd / (Gd + Sn + In)] The oxide target used for sputtering, electron beam evaporation, or ion plating according to any one of claims 1 to 3, wherein the sintered density is 6.5 g / cm ³ or more. The oxide target used for sputtering, electron beam evaporation, and ion plating according to any one of claims 1 to 4, wherein the bulk resistance is 1 Ωcm or less.

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