JP2002373527A - Transparent electrode film and sputtering target for forming this electrode film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transparent electrode film excellent in etching characteristics while maintaining good transmittance of visible light and a certain amount of resistance, and a target, which can lessen formation of nodule and unusual electric discharge in the sputtering process, which forms this transparent electrode film, and furthermore, to provide the target of the composition which can disregard pollution (contamination) from crushing media (zirconia) in the crushing process for supplying fine particles of high sintering nature on the occasion of manufacturing the target. SOLUTION: It is a transparent electrode film, which contains zirconium oxide of 5% (or more) to 10% in weight in indium oxide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transparent electrode film used for a touch panel or the like and a sputtering target for forming the electrode film.

[0002]

BACKGROUND ART ITO (indium - tin composite oxide as the main component: In ₂ O ₃ -SnO ₂₎ film is widely used as a transparent electrode (film) such as a display device around the liquid crystal display . As a method of forming the ITO film, a method generally called a physical vapor deposition method, such as a vacuum vapor deposition method or a sputtering method, is used. ing. Formation of a film by the sputtering method involves physically colliding positive ions such as Ar ions with a target placed on the cathode, releasing the material constituting the target with the collision energy, and forming the target on the facing substrate on the anode side. This is performed by laminating a film having substantially the same composition as the target material. The coating method by the sputtering method is characterized in that a thin film of angstrom unit to a thick film of several tens μm can be formed at a stable film forming rate by adjusting the processing time, the supplied power, and the like.

[0003] By the way, the most frequently used I
Although the TO-based transparent electrode film is excellent in visible light transmittance and conductivity, it mainly has the following problems. One is that the film quality is not uniform and the etching characteristics during circuit formation are poor. In recent years, in display devices and display input devices, it has been required to increase the pixel density to obtain a fine screen, and accordingly, a finer transparent electrode pattern has been required. For example, in a liquid crystal display device, there is a portion formed as a thin line having a wiring width of 20 to 50 μm, and a high etching processability is required. IXO (In ₂ O ₃ -Zn) has been proposed as an improvement over such a transparent electrode film made of ITO.
O) A film has been proposed. However, this has remarkably large etching property as compared with the ITO film, but has poor conductivity,
In addition, there is a problem that the chemical resistance or water resistance to acids and alkalis is insufficient. Further, the improved etching property is harmful, and tends to be over-etched, which is not always an appropriate material.

[0004] The second problem is that a tin-rich phase exists in a target for forming an ITO transparent electrode film. This tin-rich phase causes the generation of nodules described later. That is, when the ITO film is formed by sputtering, fine projections called nodules are generated in the erosion portion on the target surface, thereby causing abnormal discharge or splash and lowering the sputtering rate. Further, due to abnormal discharge or splash caused by the nodules, coarse particles (particles) float in the sputtering chamber, and adhere to a film formed thereby, thereby deteriorating the quality. As described above, in actual production, it is necessary to periodically remove nodules generated in the target, which significantly lowers productivity, and there is a demand for a target in which nodules are less generated.

[0005] The third problem is to reduce the number of pores in the sintered body in order to increase the density of the sintered body as much as possible. It was required to make the powder finer.
In general, fine pulverization is performed using a container having zirconia beads and an inner wall of zirconia. However, there is a problem that contamination (contamination) from such a pulverization medium, that is, zirconia is mixed into a target material. On the other hand, sintering under the pressurized state is necessary, and there is a problem that the equipment needs to be further enlarged in order to further increase the density, which can be said to be an industrially efficient method. Did not.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide a transparent electrode film having excellent etching characteristics while maintaining good visible light transmittance and a certain electric resistance. It is in. Further, the present invention provides a target capable of reducing formation of nodules and abnormal discharge in a sputtering process for forming the transparent electrode film. Further, the present invention provides a target having a composition in which contamination (contamination) from a pulverizing medium (zirconia) can be ignored in a pulverizing step for supplying a powder having a high sinterability at the time of manufacturing the target.

[0007]

The present invention provides: 5% by weight of zirconium oxide in indium oxide
1. Transparent electrode film characterized by containing (super) to 10% by weight 5% by weight of zirconium oxide in indium oxide
Provided is a sputtering target for forming a transparent electrode film characterized by containing (super) to 10% by weight. 3. 3. The sputtering target for forming a transparent electrode film according to the above item 2, wherein the zirconium phase has a diameter of 5 μm or less as observed by EPMA.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The conductivity of a transparent conductive film is generally represented by a sheet resistance (Ω / □), and usually requires a sheet resistance of about 5Ω / □, and is applied to a liquid crystal display screen as described above. In such a case, a liquid crystal screen is required to have a higher definition and a lower sheet resistance is required. The sheet resistance is represented by a value obtained by dividing the specific resistance by the thickness of the transparent conductive film. Therefore, the area conductivity of the transparent conductive film is represented by the product of the conductivity (the reciprocal of the specific resistance) and the film thickness, and this conductivity σ (Ω ⁻¹⁾
・ Cm ^-1 ) is the carrier (hole or electron) contained in the film
Charge e (coulomb) and carrier mobility μ (cm ²
/ V · sec) and the carrier concentration n (cm ⁻³ ) (σ (Ω ⁻¹ · cm ⁻¹ ) = e · μ · n). Therefore, in order to improve the conductivity of the transparent conductive film and reduce the specific resistance (also referred to as resistivity) and the sheet resistance, the carrier mobility μ (cm ² / V · sec) and the carrier concentration n (cm ⁻ Any one or both of ³ ) may be increased.

Therefore, indium oxide (In ₂ O ₃ ) is used as a dopant for increasing the carrier concentration n.
Attention was paid to zirconium oxide (ZrO ₂ ) which forms a solid solution at a high concentration (up to 5% by weight). It has been found that this zirconium oxide dopant can maintain good visible light transmittance and high conductivity as described later. Regarding this, the present inventors have already disclosed Japanese Patent Application No. 2001-02507.
8 On the other hand, from this, it can be understood that as the content of zirconium oxide (ZrO ₂ ) increases beyond 5% by weight, the specific resistance of the obtained film increases. Therefore, it was found that the adjustment of the zirconium concentration was effective in obtaining a film having a relatively high specific resistance. That is, such a film having a relatively high specific resistance is more effective as a raw material for a touch panel. The zirconium oxide dopant is not so high in acid resistance as SnO _2, which is a component of ITO, but is not as base as ZnO and has an excellent feature that an appropriate etching property can be obtained.

Further, according to the present invention, the diameter of the zirconium phase in the target can be 5 μm or less. In the target, there is a composite oxide of indium oxide and zirconium oxide or as a solid solution in indium oxide. However, zirconium oxide forms a solid solution up to a concentration of zirconium oxide up to about 5%. E without
A zirconium phase is precipitated by PMA observation. This zirconium phase is a heterogeneous phase in the target. If the zirconium phase is large, it may cause generation of nodules or arcing in long-time sputtering, and in extreme cases, the composition of the sputtered film may become non-uniform. Therefore, generation of nodules and arcing can be prevented by setting the zirconium-containing precipitation phase to 5 μm or less and uniformly dispersing the same.

Further, as described above, the factor which influences the film characteristics at the time of sputtering is the density of the target. The higher the density of the target, the more stable the sputtering characteristics and the better the film can be obtained. It is known that in order to improve the density of the target, the finer the powder before molding, the better. The above-mentioned zirconium oxide (zirconia) can be used as a dopant to be added to indium oxide, and at the same time, zirconium oxide can be used as a medium for fine pulverization, that is, pulverization using a container of zirconia beads or zirconia lining, The grinding media itself is a source of contamination (contamination source)
There is a great advantage that it does not occur. As a result, the level of pulverization can be improved, and a sputtering target with much higher purity and higher density than before can be obtained. In addition, by using such a high-density target, the generation of nodules is suppressed, the generation of particles caused by abnormal discharge or splash caused by this nodule is suppressed, and the quality of the conductive film is effectively reduced. It has the feature that it can be suppressed.

[0012]

Examples and Comparative Examples Next, examples of the present invention will be described. This embodiment is merely an example, and the present invention is not limited to this example. That is, all aspects or modifications other than the examples are included within the scope of the technical idea of the present invention.

(Examples 1 to 3) Indium oxide (In ₂
Zirconium oxide (ZrO ₂ ) powder is added to O ₃ ) powder for 6, 7,
8% by weight, and then zirconia (ZrO)
₂ ) Using balls (beads) as grinding media, mix and finely grind with an attritor, median diameter 0.8 μm
Was obtained. Examples 1, 2, and 3 were made when the amount of the zirconium oxide powder was 6, 7, and 8% by weight. This slurry was granulated to obtain a spherical granulated powder. Further, the granulated powder was press-molded, and further subjected to CIP (isotropic cold pressing). Then, this compact was sintered at a temperature of 1640 ° C. for 4 hours in an oxygen atmosphere to obtain a sintered body (hereinafter referred to as “IZO sintered body”). The sintering density reached over 99%. This sintered body was ground and cut, and processed into a sputtering target having a predetermined shape.

Next, a transparent electrode film was formed on the glass substrate by DC sputtering using the IZO sintered body target under the following conditions. Sputtering gas: Ar + O ₂ Sputtering gas pressure: 0.5 Pa Electric power: 60 W Deposition rate: about 300 ° / min The amount of nodule generated (coverage) in this case was measured, but the nodule in the IZO sintered body of this example was measured. Was 10% or less.

Further, the specific resistance (Ω · cm) of film formation and 55
The film characteristics of the transmittance% at 0 nm were examined, and the results are shown in Table 1. Table 1 shows film properties at the time of film formation at room temperature and an oxygen concentration of 1%. For comparison, an ITO film (Comparative Example 1) and an IXO film (Comparative Example 2) manufactured under the same conditions.
Table 1 shows the specific resistance (Ω · cm) and the film characteristics of the transmittance% at 550 nm. As is clear from Table 1,
The specific resistance is increased, and the transmittance is equal to the Example of the present invention and Comparative Example
It can be seen that they exhibit good visible light transmittance and high specific resistance of Examples of the present invention, almost inferior to ITO. Further, there was a certain correlation between the amount of zirconium oxide and the specific resistance of the film obtained by sputtering, and it was found that the specific resistance of the film tended to increase as the amount of zirconium oxide increased. In general, an IZO film using the IZO sintered body target of the present invention with respect to an ITO film has almost no difference in film characteristics in a state where the film is formed by raising the substrate temperature. The result was better.

[0016]

[Table 1]

Table 2 shows the measurement results of the zirconium oxide concentration and density in the targets of Examples 1 to 3 and Comparative Examples 1 and 2. As shown in Table 2, the relative densities of Examples 1 to 3 all exceeded 97%, and the relative densities improved with an increase in the zirconium oxide concentration. Although not shown in this table, zirconium oxide concentration 10 wt%
In this case, the relative density reached 98.7%. This makes it possible to form a uniform and excellent quality sputtered film. On the other hand, the densities of the targets of Comparative Examples 1 and 2 were 93% and 87%, respectively, which were lower than those of the present example and poor results were obtained. And the nodule coverage reached 70%. Furthermore, when the concentration of zirconium oxide increases,
Zirconium phase (zirconium oxide phase) without solid solution
Was observed. FIG. 1 shows an EPM of a target (Example 1) having a zirconium oxide content of 6 wt%.
A is the observation result (1000 times). In FIG. 1, fine precipitates having a zirconium phase diameter of less than 1 μm are seen. Such a precipitate does not generate nodules or arcing at the time of sputtering, and there is no possibility that the composition of the sputtered film becomes non-uniform.

In recent years, there has been a tendency to use plastic sheets and films instead of glass substrates in order to reduce the weight and cost of equipment. Since plastics have poor heat resistance,
There is a demand for film formation without heating the substrate or at a low temperature. Therefore, the transparent electrode of the present invention, which has excellent film properties at room temperature or low temperature as described above, meets this purpose and can be said to be an excellent material. In Comparative Examples 1 and 2,
When pulverization to 0.8 μm or less, which is the same as in this example, it was confirmed that the zirconia contamination was significantly increased.

[0019]

[Table 2]

Next, Table 3 shows the relationship between the substrate temperature and the etching rate for the transparent electrode films of the above embodiment and Comparative Examples 1 and 2. The etchant is HCl: H ₂ O: HNO ₃
= 1: 1: 0.08 mixed acid was used. As is clear from Table 3, when the substrate temperature is room temperature and when the substrate temperature is 200 ° C., the etching rate of IZO according to the present example is superior to Comparative Example 1 which is ITO.
In particular, when the substrate temperature is 200 ° C., the difference is remarkable.
The IXO of Comparative Example 2 had an etching property of 92
700Å / min, 90900Å / mi at 200 ° C
n is unusually high, but undesirably tends to be overetched.

[0021]

[Table 3]

[0022]

According to the present invention, a transparent electrode film having a suitable etching property is obtained while maintaining a good visible light transmittance and a certain relatively high specific resistance, and a sputtering process for forming the transparent electrode film. , Efficient production of sintered targets with high density and low nodule generation, thereby suppressing productivity and quality deterioration due to nodule generation, and ignoring contamination from grinding media It has an excellent feature that a target that can be obtained can be obtained. Further, it is excellent in film properties at room temperature or low temperature, and is particularly useful when a plastic sheet or film having poor heat resistance is used as a substrate in place of a glass substrate due to weight reduction of a liquid crystal display or the like.

[Brief description of the drawings]

FIG. 1 is a view showing a precipitate of a zirconium phase observed by EPMA.

Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat II (reference) H01L 21/285 H01L 21/285 SF term (reference) 2H092 KB05 KB14 NA29 4K029 AA09 BA45 BA50 BC09 CA05 DC05 DC09 DC34 4M104 AA10 BB36 DD39 DD40 DD42 GG20 HH20 5B087 BC33 CC11 CC16 CC36 5G307 FB01 FC09 FC10

Claims (3)

[Claims] 1. Zirconium oxide 5 in indium oxide
A transparent electrode film, which is contained in an amount of 10% by weight (excess) to 10% by weight. 2. Zirconium oxide 5 in indium oxide
A sputtering target for forming a transparent electrode film, wherein the sputtering target contains from 10% by weight (excess) to 10% by weight. 3. The sputtering target for forming a transparent electrode film according to claim 2, wherein the diameter of the zirconium phase observed by EPMA is 5 μm or less.