JP2008075125A - Erbium oxide-containing oxide target - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an oxide target having high electric conductivity and free from abnormal discharge and surface blackening. <P>SOLUTION: An oxide target includes indium (In) and erbium (Er). The oxide target is characterized in including an oxide expressed as ErInO<SB>3</SB>. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

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

In the transparent conductive film containing indium 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 metal wiring of the base layer 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 and the conductive film made of indium oxide and zinc oxide are superior to the ITO film. It has been proposed (Patent Documents 1 and 2). However, since the transparent conductive film made of indium oxide and zinc oxide has a high etching rate with a weak acid, it can be etched with an etching solution for a metal thin film. Therefore, when etching a metal thin film formed on a transparent conductive film, 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 and a lanthanoid element is useful as an organic EL electrode or a transflective / semi-reflective LCD electrode (Patent Documents 3-10).
However, the oxides of lanthanoid elements are not conductive, and when these oxides are mixed with indium oxide to produce a target, insulating particles are present in the target as they are, causing abnormal discharge during sputtering. In some cases, the target surface may be blackened, resulting in a decrease 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

  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 targets (hereinafter simply referred to as targets) and the like are provided.
1. An oxide target containing indium (In) and erbium (Er), and containing an oxide represented by ErInO ₃ .
2. An oxide target containing tin (Sn) and erbium (Er), wherein the oxide target is an oxide represented by Er ₂ Sn ₂ O ₇ .
3. An oxide target containing indium (In), tin (Sn), and erbium (Er), and containing an oxide represented by Er ₂ Sn ₂ O ₇ .
4). 3. The Sn content [Sn / (total cation metal element): atomic ratio] relative to the total cation metal element is larger than the Er content [Er / (total cation metal element): atomic ratio]. The oxide target described.
5. The oxide target according to any one of 1 to 4, wherein the density is 4.5 g / cm ³ or more.

  Since the oxide target of the present invention includes an oxide having a predetermined structure containing an erbium element and is excellent in conductivity, it becomes an oxide target having no abnormal discharge. This oxide target is used as a sputtering target, an electron beam target, or an ion plating target, and becomes a raw material for forming a thin film.

A first aspect of the oxide target of the present invention is a target consisting of a sintered body of an oxide containing indium (In) and erbium (Er), which contains an oxide represented by ErInO ₃ (Hereinafter, this target is referred to as target I).
When this target I is used, the conductivity of the target is higher and the target surface is less blackened and stable without abnormal discharge during sputtering compared to the case of a target composed of In ₂ O ₃ and Er ₂ O _3. The sputtered state is maintained. Thereby, a transparent conductive film having a light transmittance equivalent to that of the ITO film and an oxide semiconductor film having a light transmittance equivalent to that of the oxide semiconductor film made of indium oxide / zinc oxide can be stably obtained.

The target I contains an oxide having a form represented by ErInO ₃ , and preferable examples of the sintered body constituting the target include the following.
(A) ErInO ₃
(B) A mixture of ErInO ₃ and In ₂ O ₃
(C) Mixture of ErInO ₃ and Er ₂ O ₃ Of these, the sintered bodies (a) and (b) are preferred. In this case, Yb ₂ O ₃ does not exist alone, and abnormal discharge during sputtering can be suppressed. Note that the structure of the oxide in the target is identified from a chart obtained by X-ray diffraction measurement. The same applies to targets II and III described later. In the case of (c), Yb ₂ O ₃ comes to exist alone and abnormal discharge may occur.

In this target, the ratio of Er in the total of Er and In (atomic ratio: Er / (Er + In)) is preferably 0.001 to 0.5, more preferably 0.01 to 0.2, and particularly preferably. Is 0.01 to 0.15. If it is less than 0.001, the effect of adding Er atoms may not be obtained. If it exceeds 0.5, Er ₂ O ₃ will be present alone, and Er ₂ O ₃ that is an insulator in the target. May be present in a granular form, and the resistance value of the target becomes too large, which may cause problems such as abnormal discharge during sputtering. Moreover, there exists a problem which the intensity | strength of target itself falls and it cracks or deform | transforms in the sintering process in a target manufacturing process.

The atomic ratio of Er and In in the target can be controlled by adjusting the mixing ratio of the indium compound and erbium compound that are raw materials before sintering. Erbium-indium compounds such as ErInO ₃ composed of an indium compound and an erbium compound corresponding to the stoichiometric ratio are generated by the mixing ratio before sintering, and the remaining indium compound exists as a crystalline substance or an amorphous substance. Estimated.

Examples of the method for producing the target I include a method of sintering a mixture of these using a compound containing an indium atom and a compound containing an erbium 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 an erbium atom include erbium oxide, erbium oxalate, and erbium nitrate. Preferred is erbium 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 3 μm or less, preferably 1 μm or less, more preferably 0.8 μm or less. If it exceeds 3 μm, for example, Er ₂ O ₃ is present as it is as insulating particles in the target, which may cause abnormal discharge. The formation of ErInO ₃ 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 _Er 2 _{O 3,} it may not produce the ErInO _3. If it exceeds 1600 ° C., In ₂ O ₃ may be sublimated or thermally decomposed to change the composition, or the produced ErInO ₃ may be decomposed.
In the present invention, the sintered body contains ErInO ₃ , but the oxide in this form can be formed by the above-described sintering. The particle size of the ErInO ₃ produced can be measured by EPMA mapping. The particle size of ErInO ₃ is 10 μm or less, preferably 5 μm or less. When ErInO ₃ particles exceeding 10 μm are present, abnormal discharge may occur due to the difference in conductivity around the particles. When the thickness is 10 μm or less, abnormal discharge is suppressed and stable sputtering can be performed.

The second aspect of the oxide target of the present invention is a target composed of an oxide sintered body containing tin (Sn) and erbium (Er), and is represented by Er ₂ Sn ₂ O ₇ (Hereinafter, this target is referred to as “target II”).
When this target II is used, a stable sputtering state is maintained without blackening of the target surface and abnormal discharge during sputtering, as compared with the case of a target made of simply SnO ₂ and Er ₂ O ₃ .

The target II contains an oxide having a form represented by Er ₂ Sn ₂ O ₇ , and preferred examples of the sintered body constituting the target include the following.
(A) Er ₂ Sn ₂ O ₇
(B) A mixture of Er ₂ Sn ₂ O ₇ and SnO ₂
(C) A mixture of Er ₂ Sn ₂ O ₇ and Er ₂ O ₃
(D) A mixture of Er ₂ Sn ₂ O ₇ , SnO ₂ and Er ₂ O ₃ Among the above, the sintered bodies (a) and (b) are preferred.

In this target, the ratio of Er in the total of Er and Sn (atomic ratio: Er / (Er + Sn)) is preferably 0.001 to 0.5, more preferably 0.01 to 0.2, particularly Preferably, it is 0.01-0.15. If it is less than 0.001, the effect of adding Er may not be obtained. If it exceeds 0.5, Er ₂ O ₃ will be present alone, and the resistance value of the target will be too large. It may cause problems such as abnormal discharge.

The atomic ratio of Er and Sn can be controlled by adjusting the mixing ratio of the tin compound and the erbium compound before sintering. Prior to sintering, an erbium-tin oxide such as Er ₂ Sn ₂ O ₇ composed of a tin compound and an erbium compound corresponding to the stoichiometric ratio is formed by mixing ratio, and the remaining tin compound is a crystalline material or amorphous It is presumed to exist as a substance.

Examples of the method for producing the target II include a method of sintering a mixture of these using a compound containing a tin atom and a compound containing an erbium atom as a raw material.
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 compound containing an erbium atom is the same as the target I described above.

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 3 μm or less, preferably 1 μm or less, more preferably 0.8 μm or less. If it exceeds 3 μm, for example, Er ₂ O ₃ is present as insulating particles in the target as it is, which may cause abnormal discharge. The formation of Er 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., the reactivity of the _Er 2 _{O 3} is _low, there may not be found the generation of Er 2 _Sn 2 _{O 7.} If it exceeds 1600 ° C., Er ₂ O ₃ may be sublimated or thermally decomposed to change the composition, or the produced Er ₂ Sn ₂ O ₇ may be decomposed.
In the present invention, the sintered body contains Er ₂ Sn ₂ O _7, oxide of this embodiment may be formed by sintering the above. The particle diameter of the produced Er ₂ Sn ₂ O ₇ can be measured by EPMA mapping. The particle size of Er ₂ Sn ₂ O ₇ is 10 μm or less, preferably 5 μm or less. When particles of Er ₂ Sn ₂ O ₇ exceeding 10 μm exist, abnormal discharge may occur due to the difference in conductivity around the particles. When the thickness is 10 μm or less, abnormal discharge is suppressed and stable sputtering can be performed.

A third aspect of the oxide target of the present invention is a target composed of an oxide sintered body containing indium (In), tin (Sn), and erbium (Er), and is Er ₂ Sn ₂ O ₇ . It is characterized by containing an oxide represented (hereinafter, this target is referred to as target III).
When this target III is used, the conductivity of the target is higher than that of a target made of simply In ₂ O ₃ , SnO ₂ and Er ₂ O _3, and there is no abnormal discharge during sputtering. There is no blackening and a stable sputtering state is maintained.

The target III contains an oxide having a form represented by Er ₂ Sn ₂ O ₇ , and preferable examples of the sintered body constituting the target include the following.
(A) A mixture of Er ₂ Sn ₂ O ₇ and In ₂ O ₃
(B) A mixture of Er ₂ Sn ₂ O ₇ , In ₂ O ₃ and SnO ₂
(C) A mixture of Er ₂ Sn ₂ O ₇ , ErInO ₃ and In ₂ O ₃
(D) A mixture of Er ₂ Sn ₂ O ₇ , ErInO ₃ and SnO ₂ Among the above, a sintered body made of (a) or (b) is preferable.

In this target, the atomic ratio of Er (Er / (Er + In + Sn)) is preferably 0.001 to 0.5, more preferably 0.01 to 0.2, and particularly preferably 0.01 to 0.15. It is. If it is less than 0.001, the effect of adding Er may not be obtained. If it exceeds 0.5, Er ₂ O ₃ will be present alone, and the resistance value of the target will be too large. It may cause problems such as abnormal discharge. In addition, the strength of the target itself may decrease, and problems such as the target breaking during sputtering may occur.

Further, the Sn content [Sn / (total cation metal): atomic ratio] relative to the total cation metal element may be larger than the Er content [Er / (total cation metal): atomic ratio] relative to the total cation metal element. preferable. That is, it is preferable to satisfy the relationship of the following formula.
Er / (total cation metal element) <Sn / (total cation metal element)
This is because Er and Sn are easy to react, so that Er ₂ Sn ₂ O ₇ is easily generated. That is, when Er is present in excess of Sn, almost all of Sn is consumed by Er, so ErInO 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 Er content is made smaller than the Sn content so as to satisfy the above formula, Er 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 / (Er + 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 0.3. .

The atomic ratio of Er, In and Sn is obtained by adjusting the mixing ratio of the indium compound, tin compound and erbium compound before sintering. Prior to sintering, an erbium-tin compound such as Er ₂ Sn ₂ O ₇ composed of a tin compound and an erbium compound corresponding to the stoichiometric ratio is formed by mixing ratio, and the remaining indium compound and tin compound are crystalline or non-crystalline. Presumed to exist as a crystalline substance.

Examples of the method for producing target III include a method of sintering a mixture of these using a compound containing indium atoms, a compound containing tin atoms, and a compound containing erbium atoms as a raw material.
Specific examples of the compound containing an indium atom, the compound containing a tin atom, and the compound containing an erbium atom are the same as those of the target I or II described above.

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., the reactivity of the _Er 2 _{O 3} is _low, there may not be found the generation of Er 2 _Sn 2 _{O 7.} If it exceeds 1600 ° C., In ₂ O ₃ may be sublimated or thermally decomposed to change the composition, or the produced Er ₂ Sn ₂ O ₇ may be decomposed.
In the present invention, the sintered body contains Er ₂ Sn ₂ O _7, oxide of this embodiment may be by sintering reaction (thermal reaction) to form.
The particle diameter of the produced Er ₂ Sn ₂ O ₇ can be measured by EPMA mapping. The particle size of Er ₂ Sn ₂ O ₇ is 10 μm or less, preferably 5 μm or less. When particles of Er ₂ Sn ₂ O ₇ exceeding 10 μm exist, abnormal discharge may occur due to the difference in conductivity around the particles. When the thickness is 10 μm or less, abnormal discharge is suppressed and stable sputtering can be performed.

In target I~III of the present invention, the density of the sintered body constituting the target is preferably 4.5 g / cm ³ or more, more preferably 4.6~7.0g / cm ^3. If the density of the sintered body is less than 4.5 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 high conductivity. Specifically, the bulk resistance can be 5 Ωcm or less. Furthermore, 1 Ωcm or less is also possible. In the present invention, in particular, in the present invention, the bulk resistance can be reduced particularly by setting the composition Er / (Er + Sn + In) <Sn / (Er + Sn + In).
In order to reduce troubles such as abnormal discharge, the bulk resistance is preferably less than 2 MΩcm.

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. When the bulk resistance of the target exceeds 1 Ωcm, if a RF magnetron sputtering method is employed, a stable sputtering state can be maintained without abnormal discharge. In addition, when the bulk resistance of the target is 1 Ωcm or less, an industrially advantageous DC magnetron sputtering method can be employed.
Thereby, a stable sputtering state is maintained without abnormal discharge, and industrially stable film formation becomes possible.

  In addition, it is known that a transparent thin film made of indium oxide and zinc oxide can be used as an oxide semiconductor when a large amount of oxygen is present during film formation by sputtering (US Publication 2005/199959). Also in the present invention, when a large amount of oxygen is present during sputtering film formation, the carrier density in the thin film can be controlled, so that it can be used as an oxide semiconductor.

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.

Example 1
450 g of indium oxide and 550 g of erbium oxide were mixed, pulverized and mixed in a wet bead mill for about 5 hours, and then dried and granulated to obtain a powder having a diameter of 0.1 to several mm.
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 of the obtained target, it was confirmed that the target was composed of an oxide containing ErInO ₃ and In ₂ O ₃ as main components.
FIG. 1 shows an X-ray chart of the target.
As a result of ICP analysis, the atomic ratio [Er / (Er + In)] was 0.47.
The dispersion state of In and Er was confirmed by in-plane elemental distribution measurement of the sintered body using EPMA (Electron Probe Micro Analyzer). As a result, the composition was substantially uniform.
Moreover, the density of the target was 4.63 g / cm ³ and the bulk resistance was 1.8 MΩcm.

Example 2
450 g of tin oxide and 550 g of erbium oxide were mixed, pulverized and mixed in a wet bead mill for about 5 hours, and dried and granulated.
Next, the obtained powder was inserted into a 10 mmφ mold, and preformed with a mold press molding machine at a pressure of 100 kg / cm ² . Next, after being consolidated by a cold isostatic press molding machine at a pressure of 4 t / cm ² , it was fired at 1350 ° C. for 10 hours to form a sintered body and processed into a target.

As a result of X-ray diffraction measurement, it was confirmed that the target thus obtained was composed of an oxide containing Er ₂ Sn ₂ O ₇ and SnO ₂ as main components.
FIG. 2 shows an X-ray chart of the target.
As a result of ICP analysis, the atomic ratio [Er / (Er + Sn)] was 0.49.
The dispersion state of Sn and Er was confirmed by measuring the element distribution in the surface of the sintered body by EPMA, but the composition was substantially uniform. Moreover, the density of the target was 4.52 g / cm ³ and the bulk resistance was 1.9 MΩcm.

Examples 3-12
Each powder of indium oxide, tin oxide and erbium oxide was mixed in the blending amounts shown in Table 1, respectively, and pulverized and mixed in a wet bead mill for about 5 hours, followed by dry granulation.
Next, the obtained powder was inserted into a 10 mmφ mold, and preformed with a mold press molding machine at a pressure of 100 kg / cm ² . Next, after being consolidated by a cold isostatic press molding machine at a pressure of 4 t / cm ² , it was fired at 1350 ° C. for 10 hours to form a sintered body and processed into a target.

As a result of X-ray diffraction measurement, it was confirmed that the target thus obtained was mainly composed of Er ₂ Sn ₂ O ₇ and In ₂ O ₃ .
The X-ray chart of the target produced in Example 3-12 is shown to FIGS. 3-12, respectively.
Table 2 shows the results of ICP analysis of the target, in-plane element distribution measurement results by EPMA, density and bulk resistance.

Comparative Example 1
100 g of indium oxide, 100 g of tin oxide and 800 g of erbium oxide were mixed, and pulverized and mixed for about 5 hours in a dry bead mill.
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 erbium oxide as a main component.
As a result of ICP analysis, the atomic ratio [Er / (Er + Sn + In)] was 0.75.
As a result of confirming the dispersion state of In, Sn, and Er by measuring the element distribution in the surface of the sintered body by EPMA, the composition was substantially non-uniform. Moreover, the bulk resistance was 2 MΩcm or more, and it was judged as an insulator.

  The target of the present invention is a transparent conductive film for various uses, such as a transparent conductive film for a liquid crystal display (LCD), a transparent conductive film for an electroluminescence (EL) display element, a transparent conductive film for a solar cell, and an oxide semiconductor film. It is suitable as a target for obtaining by a sputtering method. For example, an electrode of an organic EL element, a transparent conductive film for a semi-transmissive / semi-reflective LCD, an oxide semiconductor film for driving a liquid crystal, and an oxide semiconductor film for driving an organic EL element 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. 10 is an X-ray chart of a target manufactured in Example 11. 10 is an X-ray chart of a target manufactured in Example 12.

Claims (5)

An oxide target containing indium (In) and erbium (Er), and containing an oxide represented by ErInO ₃ . An oxide target containing tin (Sn) and erbium (Er), wherein the oxide target is an oxide represented by Er ₂ Sn ₂ O ₇ . An oxide target containing indium (In), tin (Sn), and erbium (Er), and containing an oxide represented by Er ₂ Sn ₂ O ₇ .   The Sn content [Sn / (total cation metal element): atomic ratio] with respect to the total cation metal element is larger than the Er content [Er / (total cation metal element): atomic ratio]. 3. The oxide target according to 3. The oxide target according to claim 1, wherein the density is 4.5 g / cm ³ or more.

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