TWI707967B - Spattering target for transparent conductive film - Google Patents

Abstract

The spattering target for transparent conductive film of the present invention comprising an oxide sintered body, the constituent elements of the oxide sintered body are In, Sn, Si and O, the content ratio of In is 25.0 mass% or more and 82.0 mass% or less in terms of In₂O₃, the content ratio of Sn is 15.0 mass% or more and 65.0 mass% or less in terms of SnO₂, the content ratio of Si is 3.0 mass% or more and 10.0 mass% or less in terms of SiO₂. The spattering target for forming conductive film of the present invention has low resistivity and can perform DC spattering, and by spattering, a transparent conductive film having high film resistivity and high chemical resistance can be formed.

Description

Sputtering target for transparent conductive film

The present invention relates to a sputtering target for a transparent conductive film. More specifically, it relates to a sputtering target for a transparent conductive film that can perform DC sputtering and can form a transparent conductive film with high chemical resistance.

In the transparent conductive film used in the in-cell capacitive touch panel, in order to prevent low-frequency noise from hindering the operation of the display, high resistance and high transmittance are required. Because when the conductive film is low resistance, the high frequency signal used for touch sensing will be completely blocked.

The conductive film is usually formed by sputtering a sputtering target.

High-transmittance materials mainly use ITO, but because of its low resistance, ITO cannot be used as a conductive film for in-cell capacitive touch panels.

The technology for obtaining high-resistance materials is to add insulating oxide to ITO, but this is a method of adding a large amount of impurities to ITO, so the optical properties of the conductive film will be lowered, and the crystallinity of the film will collapse, so It will lower the chemical resistance of the conductive film. When the chemical resistance of the conductive film is low, it will be difficult to use it in applications where the conductive film is not dissolved by chemicals or the like, or in applications where it is used as a thin film and the etching speed is improper.

For example, Patent Document 1 discloses a of ITO as a main raw material, containing from 7.2 to 11.2 atom% of silicon, and a specific resistance of 10 ^° to 10 ³ Ω cm of a transparent conductive film. Patent Document 2 discloses a transparent conductive film having a resistivity of 0.8 to 10×10 ^-3 Ω cm obtained by sputtering a transparent conductive film composed of indium oxide, tin oxide, and silicon oxide with a sputtering target. However, any conductive film has low chemical resistance.

In addition, many high-resistance films have been proposed, but the resistance of the target used in the film formation of the film will also increase. When the resistance of the target is high, DC power supply cannot be used for sputtering, and a high-resistance film must be made with RF power supply, so the productivity is poor.

[Prior Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent No. 5855948

[Patent Document 2] Japanese Patent No. 4424889

The object of the present invention is to provide a sputtering target that can perform DC sputtering and can form a transparent conductive film with high specific resistance and high chemical resistance.

The sputtering target for a transparent conductive film of the present invention includes an oxide sintered body, the constituent elements of the oxide sintered body are In, Sn, Si, and O, and the content of In is more than 25.0% by mass in terms of In ₂ O ₃ And 82.0 mass% or less, the Sn content ratio is 15.0 mass% or more and 65.0 mass% or less in SnO ₂ conversion, and the Si content ratio is 3.0 mass% or more and less than 10.0 mass% in SiO ₂ conversion.

The aforementioned sputtering target for a transparent conductive film preferably has a specific resistance of 2×10 ² Ω cm or less.

The aforementioned sputtering target for transparent conductive film preferably has a relative density of 98.0% or more.

The constituent elements of the transparent conductive film of the present invention are In, Sn, Si and O, and the content of In is 28.0% by mass or more and 87.0% by mass in terms of In ₂ O ₃ , and the content of Sn is 12.0 by mass in terms of SnO ₂ % Or more and 63.0 mass% or less, and the Si content ratio is 1.0 mass% or more and 9.0 mass% or less in terms of SiO ₂ .

The aforementioned transparent conductive film preferably has a specific resistance of 1.0×10 ⁰ Ω cm or more, and preferably an etching rate of less than 11.0 Å/sec.

The manufacturing method of the transparent conductive film of this invention forms a film by sputtering the said sputtering target for transparent conductive films.

In the manufacturing method of the aforementioned transparent conductive film, it is preferable that the film specific resistance of the aforementioned transparent conductive film is 1.0×10 ⁰ Ω cm or more, and the etching rate is preferably less than 11.0 Å/sec.

The sputtering target for forming a conductive film of the present invention has a low specific resistance, can perform DC sputtering, and can form a transparent conductive film with high film specific resistance and high chemical resistance by sputtering. The manufacturing method of the transparent conductive film of the present invention can manufacture a transparent conductive film with high specific resistance and high chemical resistance.

The sputtering target for a transparent conductive film of the present invention includes an oxide sintered body, and the constituent elements of the oxide sintered body are In, Sn, Si, and O, and the content of In is more than 25.0 mass in terms of In ₂ O ₃ % And 82.0% by mass or less, the content of Sn is 15.0% by mass or more and 65.0% by mass in terms of SnO ₂ , and the content of Si is 3.0% by mass or more and less than 10.0% by mass in terms of SiO ₂ . Of course, a target containing an oxide sintered body like the sputtering target for transparent conductive film of the present invention contains inevitable impurities derived from raw materials, and it is also included in the sputtering target for transparent conductive film of the present invention It also contains unavoidable impurities. The content of inevitable impurities in the sputtering target for transparent conductive film of the present invention is usually 100 ppm or less.

Furthermore, in the present invention, the so-called constituent elements refer to constituent elements other than inevitable impurities in the sputtering target or transparent conductive film, and the content ratio of each constituent element means that the sputtering target or transparent conductive film as a whole The content ratio of each constituent element in.

The sputtering target for a transparent conductive film of the present invention is characterized by having a higher Sn content ratio than a normal ITO sputtering target, and the Si content is 3.0% by mass or more and less than 10.0% by SiO ₂ %.

The aforementioned oxide sintered system contains In, Sn, Si, and O as constituent elements. In the aforementioned oxide sintered body, the content ratio of In in terms of In ₂ O ₃ is more than 25.0% by mass and 82.0% by mass or less, preferably 31.0% by mass or more and 76.0% by mass or less, more preferably 31.0% by mass or more and 70.0% by mass % Or less, the Sn content is 15.0 mass% or more and 65.0 mass% or less in terms of SnO ₂ , preferably 20.0 mass% or more and 60.0 mass% or less, more preferably 25.0 mass% or more and 60.0 mass% or less, the Si content ratio Department of SiO ₂ in terms of 3.0% by mass or more and less than 10.0% by mass, preferably 9.9% by mass based more than 3.0% by mass or less, more preferably 9.0% by mass based more than 4.0% by mass or less, still more preferably 5.0 mass% or more based 9.0 Less than mass%. In addition, the composition of the sputtering target for the transparent conductive film is the same as the composition of the oxide sintered body.

The sputtering target for a transparent conductive film containing an oxide sintered body having the aforementioned composition has a low specific resistance, so that DC sputtering is possible. The specific resistance of the aforementioned sputtering target for a transparent conductive film is preferably 2.0×10 ² Ω cm or less, more preferably 1.5×10 ² Ω cm or less, and still more preferably 1.0×10 ² Ω cm or less. Generally, when the specific resistance of the target is about 10 ² Ωcm or less, DC sputtering can be performed.

The sputtering target for a transparent conductive film including an oxide sintered body having the aforementioned composition can be sputtered to form a transparent conductive film with a high film specific resistance. Therefore, when the transparent conductive film obtained from the aforementioned sputtering target for transparent conductive film is used in an in-cell capacitive touch panel, it can prevent the operation of the display from being hindered by low-frequency noise. If the aforementioned sputtering target for a transparent conductive film is used, a transparent conductive film having a film specific resistance of 1.0×10 ⁰ Ω cm or more can be obtained. The film specific resistance of the aforementioned transparent conductive film is preferably 1.1×10 ⁰ Ω cm or more, more preferably 1.2×10 ⁰ Ω cm or more. The upper limit of the film specific resistance of the aforementioned transparent conductive film is not specifically defined, but it is usually 5.0×10 ⁵ Ω cm.

The sputtering target for a transparent conductive film including the oxide sintered body having the aforementioned composition can form a transparent conductive film with high chemical resistance by sputtering. The transparent conductive film obtained from the sputtering target for the transparent conductive film is amorphous. When the transparent conductive film is amorphous, the chemical resistance is generally low. If the amorphous transparent conductive film is heat-treated to crystallize it, a transparent conductive film with high chemical resistance can be obtained, but the specific resistance of the film will decrease. The transparent conductive film obtained from the sputtering target for the transparent conductive film has the characteristics of being amorphous and having high chemical resistance. High chemical resistance can be evaluated by whether the etching rate is slow. The etching rate of the transparent conductive film obtained from the aforementioned sputtering target for transparent conductive film is preferably less than 11.0 Å/sec, more preferably 9.0 Å/sec or less, still more preferably 6.0 Å/sec or less, and even better It is less than 5.0Å/sec. The etching rate of the transparent conductive film can be etched by immersing a part of the transparent conductive film in a transparent conductive film etching solution (ITO-07N manufactured by Kanto Chemical Co., Ltd.) heated to 40°C for 6 minutes. The film thickness difference (height difference) and etching time between the places where the etching was performed and the places where the etching was not performed and the etching time were calculated.

The film specific resistance of the transparent conductive film obtained by sputtering a transparent conductive film composed of an oxide sintered body containing In, Sn and Si with a sputtering target will increase as the target has more Sn and Si The more the content, the higher it becomes. Therefore, in order to obtain a transparent conductive film with a high film specific resistance, it is only necessary to increase at least one of the Sn content and the Si content. That is, even if the Sn content is small, as long as the Si content of the corresponding component is increased, a transparent conductive film with high film specific resistance can be obtained. However, the chemical resistance of the transparent conductive film is that even if the Si content is increased, if the Sn content is small, it cannot be increased. Therefore, in order to obtain sufficient chemical resistance of the transparent conductive film, the Sn content of the aforementioned target must be 15.0% by mass or more in terms of SnO ₂ . And, Sn content of the target terms of SnO ₂ is more than 15.0% by mass, in order to obtain a very high ratio of the film resistance of the transparent conductive film, Si-based as long as the content of SiO ₂ in terms of 3.0% by mass or more, do not need to achieve 10.0% by mass. On the other hand, when the Sn content of the aforementioned target exceeds 65.0% by mass in terms of SnO ₂ , the specific resistance becomes high, and DC sputtering cannot be performed. That is, the sputtering target for a transparent conductive film of the present invention can be combined with "Sn content of 15.0% by mass to 65.0% by mass in terms of SnO ₂ " and "3.0 mass% or more in terms of SiO ₂ and less than 10.0% by mass of Si content" is used for DC sputtering, and by its combination, the high specific resistance and high chemical resistance of the transparent conductive film after film formation can be combined.

The relative density of the aforementioned sputtering target for transparent conductive film is preferably 98.0% or more, more preferably 98.5% or more, and even more preferably 99.0% or more. When the relative density is 98.0% or more, no protrusions or arcs are generated, and efficient sputtering can be performed. The upper limit of the relative density is not particularly limited, and can exceed 100%. The aforementioned relative density is a value measured according to the Archimedes method.

The aforementioned sputtering target for a transparent conductive film can be produced by, for example, the method shown below.

First, the raw material powders are mixed. The raw material powder is usually In ₂ O ₃ powder, SnO ₂ powder, and SiO ₂ powder. In ₂ O ₃ powder, SnO ₂ powder, and SiO ₂ powder are mixed so that the contents of In, Sn, and Si in the obtained sintered body fall within the aforementioned ranges. In addition, it was confirmed that the content ratios of In ₂ O ₃ powder, SnO ₂ powder, and SiO ₂ powder in the mixed powder obtained by mixing the raw material powders are the In content converted from In ₂ O ₃ in the aforementioned oxide sintered body, respectively The ratio, Sn content ratio in SnO ₂ conversion, and Si content ratio in SiO ₂ conversion are consistent.

Since the particles of each raw material powder are usually aggregated, it is preferable to pulverize and mix in advance, or to pulverize while mixing.

The method of pulverizing and mixing the raw material powder is not particularly limited. For example, the raw material powder can be placed in a mortar and pulverized or mixed by a ball mill.

The obtained mixed powder can also be directly formed into a compact and sintered thereon, but a binder can be added to the mixed powder to form a compact if necessary. The binder can be the binder used in the well-known powder metallurgy method to obtain the molded body, such as polyvinyl alcohol and acrylic emulsion binder. In addition, a dispersant may be added to the mixed powder to prepare a slurry, the slurry may be sprayed and dried to produce particles, and then the particles may be shaped.

The forming method can use the method used in the past powder metallurgy method, such as cold pressing, CIP (cold isostatic pressing) and so on.

In addition, the mixed powder may be temporarily pre-pressurized to produce a preform, and then the pulverized powder obtained by pulverization may be subjected to full pressure to produce a molded body.

In addition, a wet molding method such as a slit casting method may be used to produce a molded body.

The relative density of the formed body is usually 50 to 75%.

A sintered body can be obtained by firing the obtained molded body. The firing furnace used for firing is not particularly limited as long as the cooling rate can be controlled during cooling, and it may also be a firing furnace generally used in powder metallurgy. The firing environment is suitable for an oxygen-containing environment.

From the viewpoint of increasing the density and preventing cracking, the temperature increase rate is usually 100 to 500°C/h. The firing temperature is 1300 to 1600°C, preferably 1400 to 1600°C. When the firing temperature is within the aforementioned range, a high-density sintered body can be obtained. The holding time at the aforementioned firing temperature is usually 3 to 30 hours, preferably 5 to 20 hours. When the holding time is within the aforementioned range, it is easy to obtain a high-density sintered body.

After the above-mentioned temperature maintenance is completed, the temperature in the sintering furnace is generally lowered to be 300°C/hr or less, preferably 100°C/hr or less, and then cooled.

The sintered body obtained in this way is cut into a desired shape as required and polished, etc., thereby obtaining the aforementioned sputtering target for transparent conductive film.

The shape of the sputtering target for the transparent conductive film is flat, cylindrical, etc., and is not particularly limited.

The aforementioned sputtering target for a transparent conductive film is usually used for bonding to a substrate. The substrate is usually made of Cu, Al, Ti or stainless steel. As the bonding material, the bonding material used in the bonding of conventional ITO target materials, such as In metal, can be used. The bonding method is also the same as the bonding method of the conventional ITO target.

The transparent conductive film can be formed by sputtering the aforementioned sputtering target for the transparent conductive film. As described above, since the aforementioned sputtering target for a transparent conductive film has a low specific resistance, not only RF sputtering but also DC sputtering can be performed.

By sputtering the aforementioned sputtering target for a transparent conductive film, a transparent conductive film having In, Sn, Si, and O as constituent elements can be obtained. The Sn content ratio and the Si content ratio of the obtained transparent conductive film tend to be lower than the Sn content ratio and the Si content ratio of the aforementioned sputtering target for transparent conductive film. Therefore, in the aforementioned transparent conductive film, the content of In is 28.0% by mass or more and 87.0% by mass in terms of In ₂ O ₃ , preferably 33.0% by mass or more and 80.0% by mass or less, and the content of Sn is 12.0 in terms of SnO ₂ Mass% or more and 63.0 mass% or less, preferably 18.0 mass% or more and 58.0 mass% or less, and the Si content ratio in terms of SiO ₂ is 1.0 mass% or more and 9.0 mass% or less, preferably 2.0 mass% or more and 9.0 mass% or less. The obtained transparent conductive film is as described above, and has high specific resistance and chemical resistance. Also, as in the case of the sputtering target for the transparent conductive film, the transparent conductive film may also contain inevitable impurities. The content of unavoidable impurities in the aforementioned transparent conductive film is usually 100 ppm or less.

[Example]

The measurement methods used in the following Examples and Comparative Examples are shown below.

1. The relative density of the target

The relative density of the sputtering target for transparent conductive film is measured according to the Archimedes method. Specifically, the air mass of the target is divided by the volume (the water mass of the target/the specific gravity of the water in the measured temperature), as a percentage relative to the theoretical density ρ(g/cm ³ ) according to the following formula (X) The value is regarded as the relative density (unit: %).

ρ=((C1/100)/ρ 1+(C2/100)/ρ 2+‧‧‧+(Ci/100)/ρ i) ^-1 (X) (where C1 to Ci represent the target material respectively The content (mass%) of the constituent substances, ρ 1 to ρ i represent the density (g/cm ³ ) of each constituent substance corresponding to C1 to Ci.)

Since the materials (raw materials) used in the manufacture of the target in the following examples and comparative examples are In ₂ O ₃ , SnO ₂ , and SiO ₂ , the theoretical density can be calculated by applying the following to formula (X), for example ρ.

C1: Mass% of In ₂ O ₃ raw material used in the target

ρ 1: Density of In ₂ O ₃ (7.18g/cm ³ )

C2: The mass% of SnO ₂ raw material used in the target

ρ 2: Density of SnO ₂ (6.95g/cm ³ )

C3: Mass% of SiO ₂ raw material used in the target

ρ 3: Density of SiO ₂ (2.20g/cm ³ )

2. Specific resistance of target

The specific resistance of the sputtering target was measured in the AUTO RANGE mode using Loresta (registered trademark) HP MCP-T410 (series 4 probe TYPE ESP) manufactured by Mitsubishi Chemical Corporation, the probe was pressed against the surface of the processed sintered body.

3. Film specific resistance of transparent conductive film

The film specific resistance of the transparent conductive film was measured using a four-pointer K-705RS manufactured by Kyowa Riken Co., Ltd.

4. Etching rate of transparent conductive film

The etching rate of the transparent conductive film was etched by immersing a part of the transparent conductive film in a transparent conductive film etching solution (ITO-07N manufactured by Kanto Chemical Co., Ltd.) heated to 40°C for 6 minutes, and using KLA- The stylus-type surface profile measuring instrument P-15 manufactured by Tencor Corporation measured the height difference between the etching place and the unetched place, and calculated by dividing the height difference by the etching time.

5. The content ratio of In, Sn and Si in the transparent conductive film

The measurement uses a transparent conductive film formed on a copper foil. The content ratio of In and Sn was measured by the acid decomposition ICP-OES method using the ICP emission spectrophotometer 720 ICP-OES manufactured by Agilent Technologies, and the content ratio of Si was measured by Hitachi U-2900 spectrophotometer manufactured by Hitachi Ltd. Molybdenum blue absorptiometry (molybdenum blue absorptiometry) is used for the determination.

[Examples and Comparative Examples]

(Manufacturing of Sputtering Target)

The In ₂ O ₃ powder, SnO ₂ powder, and SiO ₂ powder were mixed at the ratio shown in Table 1 using a ball mill to prepare mixed powder.

To the aforementioned mixed powder, add 6% by mass of polyvinyl alcohol diluted to 4% by mass relative to the mixed powder, use a mortar to fully impregnate the powder with polyvinyl alcohol, and pass through a 5.5-mesh sieve. The obtained powder was pre-pressurized under the condition of 200 kg/cm ² , and then the obtained preform was crushed in a mortar. The obtained pulverized material was filled in a press mold, and molded at a press pressure of 1 t/cm ² for 60 seconds to obtain a molded body.

Place the obtained molded body in a sintering furnace, flow oxygen in the furnace at 1L/h, set the sintering environment as an oxygen flow environment, set the heating rate to 350℃/h, and sintering temperature to 1550℃. The burning time is 9h for burning temperature.

After that, it was cooled at a temperature drop rate of 100°C/h.

In the above manner, an oxide sintered body is obtained.

This oxide sintered body was cut to produce a sputtering target. The relative density and specific resistance of the sputtering target were measured by the above method. The results are shown in Table 1.

(Manufacture of transparent conductive film)

The aforementioned sputtering target was joined to a copper support plate with In solder, and sputtering was performed under the following conditions to form a transparent conductive film with a film thickness of 1000 Å on a glass substrate for measurement of specific resistance and etching rate. A transparent conductive film of 15000Å is formed on a copper foil with a thickness of 1.1mm to measure the Sn content and Si content of the transparent conductive film. In addition, in Comparative Example 5, the specific resistance of the target was high and no discharge occurred, so DC sputtering could not be performed.

Device: DC magnetron spattering device (magnetron spattering device), exhaust system refrigeration pump, rotary pump

Reaching vacuum degree: 1×10 ^-4 Pa

Sputtering pressure: 0.4Pa

Oxygen flow rate: 0 to 2.5sccm

The film specific resistance, etching rate, In content ratio, Sn content ratio, and Si content ratio of the obtained transparent conductive film were measured by the above-mentioned method. The conditions of the oxygen flow rate are suitably adjusted to obtain an amorphous transparent conductive film and the specific resistance of the film is the lowest. The results are shown in Table 1.

Claims (8)

A sputtering target for a transparent conductive film comprising an oxide sintered body, the constituent elements of the oxide sintered body are In, Sn, Si, and O, and the content of In is more than 25.0% by mass in terms of In ₂ O ₃ and 71.0% by mass or less, Sn of terms of SnO ₂ content ratio of less than 25.0% by mass 65.0% by mass or less, Si in a content ratio of SiO ₂ in terms of 4.0% by mass or more and less than 10.0% by mass. The sputtering target for a transparent conductive film as described in item 1 of the scope of the patent application has a specific resistance of 2.0×10 ² Ωcm or less. The sputtering target for transparent conductive film as described in item 1 or 2 of the scope of patent application has a relative density of 98.0% or more. A transparent conductive film whose constituent elements are In, Sn, Si and O, and the content of In is 28.0% by mass or more and 87.0% by mass in terms of In ₂ O ₃ , and the content of Sn is 12.0% by mass in terms of SnO ₂ more than 63.0% by mass or less, Si in the SiO ₂ content ratio of less than 1.0% by mass in terms of 9.0% by mass or less, the specific resistance film is not less than 1.0 × 10 ⁰ Ωcm. For the transparent conductive film described in item 4 of the scope of patent application, the etching rate is less than 11.0Å/sec. The aforementioned etching rate is from a transparent conductive film etching solution (ITO-07N manufactured by Kanto Chemical Co., Ltd.) heated to 40°C. Calculated by the etching caused. A method for manufacturing a transparent conductive film is formed by sputtering the sputtering target for a transparent conductive film described in any one of items 1 to 3 in the scope of the patent application. The method for manufacturing a transparent conductive film as described in item 6 of the scope of patent application, wherein the film specific resistance of the transparent conductive film is 1.0×10 ⁰ Ωcm or more. The method for manufacturing a transparent conductive film as described in item 6 or 7 of the scope of patent application, wherein the etching rate of the transparent conductive film is less than 11.0 Å/sec, and the etching rate is from the transparent conductive film heated to 40°C Calculator of etching by etching solution (ITO-07N manufactured by Kanto Chemical Co., Ltd.).