KR20080032121A - Sputtering target, method for manufacturing such sputtering target, and transparent conducting film - Google Patents

Abstract

Provided is a sputtering target containing zinc oxide and tin oxide or a sputtering target containing zinc oxide, tin oxide and indium oxide. A metal or an alloy is dispersed over the entire sputtering target.

Description

Sputtering target, manufacturing method thereof, and transparent conductive film {SPUTTERING TARGET, METHOD FOR MANUFACTURING SUCH SPUTTERING TARGET, AND TRANSPARENT CONDUCTING FILM}

This invention relates to a sputtering target, its manufacturing method, and a transparent conductive film. In more detail, it is related with the sputtering target etc. which do not reduce or use indium which is a scarce resource.

Liquid crystal displays (LCDs) and organic electroluminescent (EL) displays are becoming mainstream as indicators for mobile phones, portable personal digital assistants (PDAs), personal computers, laptop personal computers, and televisions from the viewpoint of display performance and energy saving. . As the transparent conductive film used in these devices, an indium tin oxide (hereinafter referred to as ITO) film is the mainstream. However, the ITO film uses indium in large quantities (usually about 90 mass%). Since indium is unstable as a scarce resource and has some toxicity, it is important to develop a transparent conductive film having a low amount of indium for further dissemination of a display device using a transparent electrode.

As a transparent conductive film which does not reduce or use indium, the transparent conductive film which has a zinc oxide-tin oxide as a main component is examined (for example, refer patent document 1).

This transparent conductive film has problems such as high resistance and large in-plane distribution of resistance, but no studies have been made to solve these problems.

As a sputtering target of ITO, the thing which can reduce resistance by making oxygen amount constant or more is disclosed (for example, refer patent document 2).

However, the oxygen content of the sputtering target which reduced indium was not examined.

Moreover, the sputtering target containing the site | part of a metal oxide and the site | part of a metal is disclosed (for example, refer patent document 3).

However, the influence on the target which cut indium was not examined. In addition, the sputtering target containing the site | part of a metal oxide and the site | part of a metal is a composite of a metal oxide target, a metal target, and a metal wire, and is high in the resistance of a target itself in order to apply to the target which reduced indium, and discharge during sputtering This was unstable, and there was a problem such as a slow sputtering speed.

Patent Document 1: Japanese Patent Application Laid-Open No. 8-171824

Patent Document 2: Japanese Patent Laid-Open No. 2000-256842

Patent Document 3: Japanese Patent Laid-Open No. 2004-030934

This invention is made | formed in view of the above-mentioned problem, and an object of this invention is to provide the sputtering target and the manufacturing method of a sputtering target from which a low conductive transparent conductive film is obtained even if indium is reduced.

MEANS TO SOLVE THE PROBLEM As a result of earnestly examining in order to overcome the said subject, the present inventors made indium by making the number of oxygen atoms in the metal atom and oxygen atom which comprise a sputtering target less than the stoichiometric amount when a metal atom comprises an oxide. Even if it cuts, it discovered that the transparent conductive film which is low resistance is obtained. In addition, the present invention has been completed by discovering that by dispersing an unoxidized metal or alloy in a sputtering target, a target having a small amount of oxygen can be stably produced and the resistance of the target can be reduced.

According to this invention, the following sputtering targets, its manufacturing method, a transparent conductive film, and a transparent electrode are provided.

1. A sputtering target comprising zinc oxide and tin oxide or zinc oxide, tin oxide and indium oxide, wherein the metal or alloy is dispersed and present throughout the sputtering target.

2. The sputtering target according to 1, which satisfies the following equations (1) and (2).

0.65≤M _Zn / (M _Zn + M _Sn ) ≤0.9

0≤M _In / (M _Zn + M _Sn + M _In ) ≤0.7

[Wherein, M _Zn , M _Sn and M _In each represent the number of atoms of Zn, Sn and In in the sputtering target]

3. The sputtering target according to 1 or 2 above, which further satisfies Equation 3 below.

M _o / (M _Zn + M _Sn × 2 + M _In × 1.5) ≤0.99

[Wherein, M _Zn , M _Sn , M _o, and M _In each represent the number of atoms of Zn, Sn, O, and In in the sputtering target]

4. Sputtering target in any one of said 1-3 containing 0.1-6 mass% of said metal or alloy.

5. The sputtering target according to any one of 1 to 4, comprising a hexagonal layered compound containing indium zinc oxide (In ₂ O ₃ (ZnO) m: m is an integer of 3 to 20).

6. The sputtering target according to any one of 1 to 5, wherein the bulk resistance is less than 100 mΩcm.

7. The sputtering target according to any one of 1 to 6, wherein the density is 5.3 to 7.2 g / cm 3.

8. The manufacturing method of the sputtering target in any one of said 1-7 containing the process of mixing the powder of metal oxide and the powder of metal.

9. The transparent conductive film manufactured using the sputtering target in any one of said 1-7.

10. The transparent electrode manufactured by etching the transparent conductive film of said 9.

By the sputtering target of this invention, even if indium is reduced, the transparent conductive film which is low resistance is obtained.

1 is a graph showing the relationship between the amount of Zn metal powder and the bulk resistance of a target.

2 is a graph showing the relationship between the amount of Zn metal powder and the specific resistance value of the transparent conductive film.

Best Mode for Carrying Out the Invention

Hereinafter, the sputtering target of this invention is demonstrated concretely.

The sputtering target of the present invention has a form in which a metal or an alloy is dispersed throughout in an oxide containing at least zinc oxide and tin oxide. Thereby, even if indium is reduced, it becomes a target from which the transparent conductive film which is low resistance is obtained. In addition, by dispersing an unoxidized metal or alloy in the sputtering target, the resistance of the target can be lowered.

As a metal or an alloy, it can use without a restriction | limiting in particular in the range which does not impair the performance of this invention. It is preferable that it is lower than the sintering temperature of a target, and a metal or alloy whose melting | fusing point is 1300 degrees C or less, preferably 1000 degrees C or less, more preferably 800 degrees C or less, still more preferably 600 degrees C or less is used. If melting | fusing point is 1300 degrees C or less, since it melts at the time of sintering and the density of a target will become high, the resistance of a target will fall easily.

It is also preferable that the metal oxide exhibit conductivity. As such, Zn, Sn, In, Ga, Ge, Cd, Nd, Sm, Ce, Eu, Ag, Au, Al, and alloys containing these as a main component can be preferably used. In particular, Zn, Sn or In is preferable. Moreover, these metal or alloy can also be used in mixture of multiple pieces.

The metal or alloy is preferably an aggregate of 500 µm or less in the target, and is preferably dispersed throughout. More preferably, it is 100 micrometers or less, More preferably, it is 10 micrometers or less, Especially preferably, it is 5 micrometers or less.

The presence of metals or alloys can be determined from the peaks of X-ray diffraction. In addition, the dispersion state can be confirmed by the presence of agglomerates or low oxygen portions of metal atoms in the surface analysis of the X-ray microanalyzer (EPMA). In addition, "disperse | distributed to the whole" means the state which can confirm one or more metal or alloy of 500 micrometers or less in arbitrary 5000 micrometer <^2> area | regions.

In addition, the form in which a metal or an alloy is disperse | distributed can be implement | achieved by the manufacturing method mentioned later.

Content of the metal or alloy occupied by a sputtering target becomes like this. Preferably it is 0.1-6 mass%, More preferably, it is 0.2-4 mass%, Especially preferably, it is 0.3-3 mass%. When the amount is less than 0.1% by mass, the effect of the present invention may not be exhibited or white spots may occur. When the amount is more than 6% by mass, oxygen may be insufficient and conversely, the resistance may increase or the transparency may decrease.

X-ray diffraction (XRD) can confirm whether the sputtering target contains an unoxidized metal or alloy.

The sputtering target of the present invention preferably satisfies the following equations (1) and (2).

<Equation 1>

0.65≤M _Zn / (M _Zn + M _Sn ) ≤0.9

<Equation 2>

0≤M _In / (M _Zn + M _Sn + M _In ) ≤0.7

[Wherein, M _Zn , M _Sn and M _In each represent the number of atoms of Zn, Sn and In in the sputtering target]

The value [M _Zn / (M _Zn + M _Sn )] in the above equation 1 defines the ratio of Zn and Sn in the sputtering target. If this value is smaller than 0.65, the amount of Sn occupied by the target increases, and SnO ₂ aggregates, and there is a possibility that it is charged at the time of film formation and causes abnormal discharge. On the other hand, when larger than 0.9, there exists a possibility that acid resistance may fall. M _Zn / (M _Zn + M _Sn ) is preferably 0.7 to 0.85, more preferably 0.7 to 0.8.

Equation 2 defines the amount of In in the sputtering target. In consideration of the object of the present invention, the amount of In used is preferably small. However, by adding In, the resistance of the target and the thin film after film formation can be reduced. M _In / (M _Zn + M _Sn + M _In ) is preferably 0.05 to 0.6, more preferably 0.1 to 0.45, still more preferably 0.15 to 0.35, particularly preferably 0.25 to 0.35.

It is preferable that the sputtering target of this invention satisfy | fills following formula (3) further.

<Equation 3>

M _o / (M _Zn + M _Sn × 2 + M _In × 1.5) ≤0.99

[Wherein, M _Zn , M _Sn , M _o, and M _In each represent the number of atoms of Zn, Sn, O, and In in the sputtering target]

Equation 3 defines the amount of oxygen atoms (O) at the sputtering target. The denominator in equation ( ₃ ) means the number of oxygen atoms when each metal atom constitutes an oxide (ZnO, SnO ₂ , In ₂ O ₃ ). If the ratio of the value of the expression (3), that is, the number of oxygen atoms contained in the sputtering target and the number of oxygen atoms when the metal atoms constitute oxides is 0.99 or less, a sputtering target from which a low-resistance transparent conductive film can be obtained without reducing or using In Becomes In addition, the value of expression (3) is preferably 0.8 to 0.98, more preferably 0.9 to 0.97. When smaller than 0.8, there exists a possibility that the electrically conductive film after film-forming may color.

By controlling the content of oxygen in the target in this way, it is possible to reduce the resistance of the sputtered thin film, but the exact reason is not clear. However, in the conventional method, it is estimated that Zn atoms, which are relatively lighter than Sn and In, are exhausted without reverse sputtering or film formation, resulting in excessive oxygen in the film.

In addition, the value of the said Formula (1)-3 can be computed from the value of the abundance of each atom obtained by carrying out compositional analysis of a sputtering target using an X-ray micro analyzer (EPMA).

As a manufacturing method of the sputtering target of this invention, there exists a method of mixing and sintering the powder of a metal or an alloy further to the mixed powder of each metal oxide, for example. By using metal powder, content of oxygen in a target can be easily controlled. In addition, since the resistance of the target itself is lowered, the sputtering speed is increased to enable stable sputtering. It is also considered that the metal powder also has a function of stabilizing oxygen defects in the film, generating a carrier, and reducing the resistance.

In addition, in order to adjust the difference of a sputtering apparatus and the difference by sputtering conditions, it can also adjust by introducing a small amount of oxidizing gas at the time of sputtering as a state of oxygen shortage at the time of sintering.

When the metal or alloy powder is mixed and sintered with the mixed powder of each metal oxide, the particle size of the powder is 500 µm or less, preferably 100 µm or less, more preferably 10 µm or less, particularly preferably 5 µm or less. . If it is larger than 500 mu m, since it is not uniformly mixed with other raw material powders, the metal or alloy may not be dispersed in the target, or the resistance of the target may be increased.

In addition, a particle diameter is the value measured by the light scattering equivalence diameter (JIS R 1629).

In the present invention, in addition to the above-described powders and metal powders of the respective metal oxides, sintering aids (yttria, magnesia, etc.), dispersing agents (ammonia polyacrylates, etc.), binders, lubricants (stear) within a range that does not impair the object of the present invention. Acid emulsions, etc.) may be added.

The sputtering target of the present invention is normally hexagonal layered compound comprising indium oxide, zinc oxide: it is preferred to include a _{(In 2 O 3 (ZnO)} m m is an integer from 3 to 20). By including these structures, the sintered density increases and the resistance of the target tends to decrease.

Such a structure can be obtained by the above-described manufacturing method. The structure is analyzed by X-ray diffraction (XRD).

It is preferable that the bulk resistance of the sputtering target of this invention is less than 0.2-100 m (ohm) cm. By satisfying this value, the discharge during sputtering is stable, and the sputtering speed also increases. More preferably, it is 0.4-20 m (ohm) cm or less, Especially preferably, it is 0.6-10 m (ohm) cm or less.

In addition, the density of the sputtering target is preferably 5.3 to 7.2 g / cm 3, more preferably 6.1 to 7.0 g / cm 3, and particularly preferably 6.4 to 6.8 g / cm 3. By satisfying this value, the discharge during sputtering is stable and the film formation speed can be improved.

The transparent conductive film of this invention is obtained by sputter-forming film-forming the sputtering target of this invention mentioned above by a conventional method. Moreover, a transparent electrode is obtained by etching this transparent conductive film with etching liquid, such as a mixed acid containing oxalic acid or phosphoric acid.

Hereinafter, the present invention will be described in more detail with reference to Examples. In addition, a particle diameter is the value measured by the laser diffraction scattering method.

<Example 1>

Zinc oxide powder (particle size of 1 μm or less), tin oxide powder (particle size of 0.4 μm or less) and metal zinc powder (particle size of 5 μm or less) were placed in a polyethylene pot at a compounding ratio shown in Table 1 below, and then dried by a dry ball mill for 72 hours. By mixing, a mixed powder was prepared.

This mixed powder was put into a metal mold | die, and it pressed at the pressure of 300 kg / cm <2>, and was made into the molded object. This compact was subjected to densification by CIP (cold isostatic press) molding at a pressure of 3 ton / cm 2. Next, this molded product was installed in a pure oxygen atmosphere sintering furnace and sintered under the following conditions.

(Sintering condition)

Sintering temperature: 1450 ° C., Heating rate: 25 ° C./hour, Sintering time: 6 hours, introduction gas of sintering furnace: oxygen, introduction gas pressure: 30 mmH ₂ O (gauge pressure), introduction gas flux: 2.6 cm / min, injection Weight / gas flow rate: 0.4 kg · min / l, gas introduction start temperature (at elevated temperature): 400 ° C, gas introduction stop temperature (at low temperature): 400 ° C.

It was 5.5 g / cm <3> when the density of the obtained sintered compact was measured by the Archimedes method.

The composition analysis of this sintered compact was performed using the X-ray micro analyzer (EPMA). As a result, the oxygen atom number ratio (O / (Zn + Sn + In)) to the total number of metal atoms was 1.18. The bulk resistance of the target measured by the four-terminal method was 80 mΩcm.

Moreover, when the target was analyzed by X-ray diffraction (XRD), the peak derived from Zn metal was confirmed.

In addition, it was confirmed by surface analysis of EPMA that metal atoms of 5 to 50 µm aggregated in the region of 5000 µm ² , and 100 or more portions of low oxygen were dispersed and present.

In addition, the measurement of EPMA and XRD was made into the following conditions.

EPMA

Device used: Shimadzu Seisakusho, electron beam micro analyzer EPMA-2300

Acceleration voltage: 15 kV, Sample current: 0.05 μm, Beam size: 1 μm, Area size: 68.4 × 68.4 μm, Step size: 0.2 μm × 0.2 μm, Measuring element: Zn, Sn, O, SBSE (reflective electron image)

XRD

Device used: Rigaku Co., Ltd., Ultima-III

X-ray: Cu-Kα ray (wavelength 1.5406 Å, monochrome with graphite monometer), measured by 2θ-θ reflection method, continuous scan (1.0 ° / min), sampling interval: 0.02 °, slit: DS, SS, 2/3 °, RS: 0.6 mm

This sintered compact was processed to the sintered compact of thickness 6mm by the wet processing method, it bonded to the backing plate made of oxygen-free copper using indium solder, and it was set as the target.

Using this target, a transparent conductive film was formed by sputtering on a glass substrate (Corning Corporation, # 7059) having a thickness of 0.7 mm. Sputtering conditions were as follows.

(Sputtering condition)

RF power: 110 W, gas pressure: 0.3 Pa, sputtering gas: Ar, 100%, film thickness: 100 nm, substrate temperature: 200 deg.

The resistivity measured by the four-terminal method of the obtained conductive film was 50 mΩ · cm. Moreover, the light transmittance at wavelength 550 nm was 90%. In addition, the transmittance | permeability was measured as the transmittance | permeability containing a glass substrate based on air.

The raw material composition, composition analysis, sputtering conditions, composition and properties of the transparent conductive film of the sputtering target are shown in Table 1 below.

<Examples 2 and 3: Comparative Examples 1 to 3>

Except having changed the composition ratio of the raw material as shown in Table 1, the target was produced like Example 1, and sputtering was formed into a film.

The results are shown in Table 1.

<Evaluation Example>

In the raw material composition of the sputtering target, the target was produced in the same manner as in Example 3 except that the amount of the Zn metal powder was changed to 0 to 4% by weight, and the amount of the ZnO powder was adjusted accordingly, and the sputtering film was formed.

About the obtained transparent conductive film, the relationship between the quantity of Zn metal powder and the bulk resistance value of a target, and the quantity of Zn metal powder, and the specific resistance value of a transparent conductive film were evaluated. Each result is shown in FIGS. 1 and 2.

The transparent conductive film formed into a film using the sputtering target of this invention can be used suitably as a transparent electrode of various display apparatuses, such as a liquid crystal display device and an EL display device.

Claims (10)

A sputtering target comprising zinc oxide and tin oxide or zinc oxide, tin oxide and indium oxide, wherein the metal or alloy is dispersed and present throughout the sputtering target. The sputtering target of claim 1, which satisfies Equations 1 and 2 below. <Equation 1> 0.65≤M _Zn / (M _Zn + M _Sn ) ≤0.9 <Equation 2> 0≤M _In / (M _Zn + M _Sn + M _In ) ≤0.7 [Wherein, M _Zn , M _Sn and M _In each represent the number of atoms of Zn, Sn and In in the sputtering target] The sputtering target according to claim 1 or 2, which further satisfies Equation 3 below. <Equation 3> M _o / (M _Zn + M _Sn × 2 + M _In × 1.5) ≤0.99 [Wherein, M _Zn , M _Sn , M _o, and M _In each represent the number of atoms of Zn, Sn, O, and In in the sputtering target] The sputtering target according to any one of claims 1 to 3, which comprises 0.1 to 6 mass% of the metal or alloy. The sputtering target according to any one of claims 1 to 4, comprising a hexagonal layered compound (In ₂ O ₃ (ZnO) m: m is an integer of 3 to 20) containing indium zinc oxide and zinc oxide. The sputtering target according to any one of claims 1 to 5, wherein the bulk resistance is less than 100 mΩcm. The sputtering target according to any one of claims 1 to 6, wherein the density is 5.3 to 7.2 g / cm 3. The manufacturing method of the sputtering target in any one of Claims 1-7 containing the process of mixing the powder of metal oxide and the powder of metal. The transparent conductive film manufactured using the sputtering target in any one of Claims 1-7. The transparent electrode manufactured by etching the transparent conductive film of Claim 9.

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