CN110546300A

CN110546300A - Sputtering target for transparent conductive film

Info

Publication number: CN110546300A
Application number: CN201880027441.7A
Authority: CN
Inventors: 矢野智泰; 儿平寿博; 立山伸一; 中村信一郎
Original assignee: MITSUI METAL MINING CO Ltd
Current assignee: MITSUI METAL MINING CO Ltd
Priority date: 2017-05-15
Filing date: 2018-03-08
Publication date: 2019-12-06
Anticipated expiration: 2038-03-08
Also published as: CN110546300B; WO2018211792A1; TW201900911A; KR20190127826A; KR102308510B1; JPWO2018211792A1; TWI707967B; JP6453528B1

Abstract

The present invention relates to a sputtering target for a transparent conductive film, which is formed from an oxide sintered body containing In, Sn, Si, and O as constituent elements, wherein the In content is more than 25.0 mass% and 82.0 mass% or less In terms of In2O3, the Sn content is 15.0 mass% or more and 65.0 mass% or less In terms of SnO2, and the Si content is 3.0 mass% or more and less than 10.0 mass% In terms of SiO 2. The sputtering target for forming a conductive film of the present invention has low resistivity, can perform DC sputtering, and can form a transparent conductive film having high film resistivity and high chemical resistance by sputtering.

Description

Sputtering target for transparent conductive film

Technical Field

The present invention relates to a sputtering target for a transparent conductive film, and more particularly, to a sputtering target for a transparent conductive film which can perform DC sputtering and can form a transparent conductive film having high chemical resistance.

Background

In the case of a transparent conductive film used In an In-cell (In-cell) type electrostatic capacitance type touch panel, high resistance and high transmittance are required In order to prevent the display from being hindered by low-frequency noise. This is because a high-frequency signal for touch sensing is blocked when the conductive film is low-resistance.

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

ITO is mainly used as a high-transmittance material, but because ITO has low resistance, it cannot be used for a conductive film of an embedded capacitive touch panel.

As a technique for obtaining a high-resistance material, there is a technique of adding an insulating oxide to ITO, but this is a method of adding a large amount of impurities to ITO, and therefore, the optical characteristics of the conductive film are lowered, and the crystallinity of the film is broken, and therefore, the chemical resistance of the conductive film is lowered. If the conductive film has low chemical resistance, it is difficult to use the conductive film in applications where the conductive film is used without being dissolved by a chemical agent or the like, and applications where a defect occurs when the etching rate is high when the conductive film is used as a thin film.

For example, patent document 1 discloses a transparent conductive film containing ITO as a main material, 7.2 to 11.2 atomic% of silicon, and having a resistivity of 100 to 103 Ω cm. Patent document 2 discloses a transparent conductive film having a resistivity of 0.8 to 10 × 10 "3 Ω cm obtained by sputtering a sputtering target for a transparent conductive film made of indium oxide, tin oxide, and silicon oxide. However, any conductive film has low chemical resistance.

In addition, although a large number of high-resistance films have been reported, the resistance of a target used for forming the film also increases. If the target resistance is high, sputtering by a DC power supply is not possible, and a film having a high resistance needs to be formed by an RF power supply, resulting in poor productivity.

Documents of the prior art

Patent document

Patent document 1: japanese patent No. 5855948

Patent document 2: japanese patent No. 4424889

Disclosure of Invention

Problems to be solved by the invention

The invention aims to provide a sputtering target which can perform DC sputtering and can form a transparent conductive film with high resistivity and high chemical resistance.

Means for solving the problems

The sputtering target for a transparent conductive film of the present invention is formed of an oxide sintered body, the constituent elements of the oxide sintered body being In, Sn, Si, and O, the In content being more than 25.0 mass% and 82.0 mass% or less In terms of In2O3, the Sn content being 15.0 mass% or more and 65.0 mass% or less In terms of SnO2, and the Si content being 3.0 mass% or more and less than 10.0 mass% In terms of SiO 2.

The sputtering target for transparent conductive films preferably has a resistivity of 2X 102. omega. cm or less.

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

The transparent conductive film of the present invention contains In, Sn, Si, and O as constituent elements, the In content ratio is 28.0 mass% or more and 87.0 mass% or less In terms of In2O3, the Sn content ratio is 12.0 mass% or more and 63.0 mass% or less In terms of SnO2, and the Si content ratio is 1.0 mass% or more and 9.0 mass% or less In terms of SiO 2.

The transparent conductive film preferably has a film resistivity of 1.0X 100. omega. cm or more, and an etching rate of less than

The method for producing a transparent conductive film of the present invention forms a film by sputtering the sputtering target for a transparent conductive film.

In the method for producing the transparent conductive film, the transparent conductive film preferably has a film resistivity of 1.0 × 100 Ω cm or more, and an etching rate of less than

Effects of the invention

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

Detailed Description

The sputtering target for a transparent conductive film of the present invention is formed of an oxide sintered body, the constituent elements of the oxide sintered body being In, Sn, Si, and O, the In content being more than 25.0 mass% and 82.0 mass% or less In terms of In2O3, the Sn content being 15.0 mass% or more and 65.0 mass% or less In terms of SnO2, and the Si content being 3.0 mass% or more and less than 10.0 mass% In terms of SiO 2. The target formed of an oxide sintered body such as the sputtering target for a transparent conductive film of the present invention may contain inevitable impurities derived from raw materials and the like, and the sputtering target for a transparent conductive film of the present invention may contain inevitable impurities. The content of inevitable impurities in the sputtering target for transparent conductive film of the present invention is usually 100ppm or less.

In the present invention, the constituent elements are constituent elements other than inevitable impurities in the sputtering target or the transparent conductive film, and the content ratio of each constituent element is a content ratio of each constituent element in the entire sputtering target or the transparent conductive film.

The sputtering target for a transparent conductive film of the present invention is characterized in that the content of Sn is higher than that of a normal ITO sputtering target, and Si is contained in an amount of 3.0 mass% or more and less than 10.0 mass% in terms of SiO 2.

The oxide sintered body contains In, Sn, Si, and O as constituent elements. In the oxide sintered body, the In content is more than 25.0 mass% and 82.0 mass% or less, preferably 31.0 mass% or more and 76.0 mass% or less, more preferably 31.0 mass% or more and 70.0 mass% or less In terms of In2O3, the Sn content is 15.0 mass% or more and 65.0 mass% or less, 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 In terms of SnO2, and the Si content is 3.0 mass% or more and less than 10.0 mass%, preferably 3.0 mass% or more and 9.9 mass% or less, more preferably 4.0 mass% or more and 9.0 mass% or less, and still more preferably 5.0 mass% or more and 9.0 mass% or less In terms of SiO 2. The composition of the sputtering target for transparent conductive film is the same as that of the oxide sintered body.

The sputtering target for a transparent conductive film formed of the oxide sintered body having the above composition has low resistivity, and thus can be DC sputtered. The resistivity of the sputtering target for a transparent conductive film is preferably 2.0 × 102 Ω cm or less, more preferably 1.5 × 102 Ω cm or less, and still more preferably 1.0 × 102 Ω cm or less. In general, DC sputtering can be performed if the target resistivity is on the order of 102 Ω cm or less.

The sputtering target for a transparent conductive film, which is formed from the oxide sintered body having the above composition, can form a transparent conductive film having a high film resistivity by sputtering. Therefore, when the transparent conductive film obtained by the sputtering target for a transparent conductive film is used for an embedded capacitive touch panel, it is possible to prevent the display operation from being hindered by low-frequency noise. By using the sputtering target for a transparent conductive film, a transparent conductive film having a film resistivity of 1.0 × 100 Ω cm or more can be obtained. The film resistivity of the transparent conductive film is preferably 1.1 × 100 Ω cm or more, and more preferably 1.2 × 100 Ω cm or more. The upper limit of the film resistivity of the transparent conductive film is not particularly limited, and is usually 5.0 × 105 Ω cm.

The sputtering target for a transparent conductive film formed from the oxide sintered body having the above composition can form a transparent conductive film having high chemical resistance by sputtering. The transparent conductive film obtained from the sputtering target for transparent conductive film is amorphous. When the transparent conductive film is amorphous, chemical resistance is generally low. When the amorphous transparent conductive film is crystallized by heat treatment, a transparent conductive film having high chemical resistance can be obtained, but the film resistivity is low. The transparent conductive film obtained from the sputtering target for transparent conductive film is amorphous and has high chemical resistance. High chemical resistance can be evaluated by slow etch rates. The etching rate of the transparent conductive film obtained from the sputtering target for a transparent conductive film is preferably less than or equal to, more preferably less than or equal to, even more preferably less than or equal to. The etching rate of the transparent conductive film can be calculated from the difference in film thickness (height difference) between the portion subjected to etching and the portion not subjected to etching and the etching time by immersing a part of the transparent conductive film in a transparent conductive film etching solution (ITO-07N manufactured by kanto chemical corporation) heated to 40 ℃ for 6 minutes.

The film resistivity of the transparent conductive film obtained by sputtering the sputtering target for the transparent conductive film formed of the oxide sintered body containing In, Sn, and Si is higher as the Sn content of the target is higher and the Si content of the target is higher. Therefore, in order to obtain a transparent conductive film having high film resistivity, at least one of the Sn content and the Si content may be increased. That is, even if the Sn content is small, if the Si content is increased accordingly, a transparent conductive film having high film resistivity can be obtained. However, with respect to the chemical resistance of the transparent conductive film, even if the Si content is increased, the Sn content does not increase as long as it is small. Therefore, in order to obtain sufficient chemical resistance of the transparent conductive film, the Sn content of the target needs to be 15.0 mass% or more in terms of SnO 2. When the Sn content of the target is 15.0 mass% or more in terms of SnO2, the Si content may be 3.0 mass% or more in terms of SiO2, and need not be 10.0 mass% in order to obtain a transparent conductive film having sufficiently high film resistivity. On the other hand, if the Sn content of the target exceeds 65.0 mass% in terms of SnO2, the resistivity becomes high, and DC sputtering cannot be performed. That is, the sputtering target for a transparent conductive film of the present invention can perform DC sputtering by combining a Sn content of 15.0 mass% or more and 65.0 mass% or less in terms of SnO2 and a Si content of 3.0 mass% or more and less than 10.0 mass% in terms of SiO2, and can achieve both high film resistivity and high chemical resistance of the formed transparent conductive film.

The relative density of the sputtering target for a transparent conductive film is preferably 98.0% or more, more preferably 98.5% or more, and still more preferably 99.0% or more. When the relative density is 98.0% or more, efficient sputtering without generating nodules and arcs can be performed. The upper limit of the relative density is not particularly limited, and may be more than 100%. The above relative density is a value measured based on the archimedes method.

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

First, raw material powders are mixed. The raw material powders are typically In2O3 powder, SnO2 powder, and SiO2 powder. The In2O3 powder, SnO2 powder, and SiO2 powder were mixed so that the contents of In, Sn, and Si In the obtained sintered body were within the above ranges, respectively. It was confirmed that the content ratios of In2O3 powder, SnO2 powder, and SiO2 powder In the mixed powder obtained by mixing the raw material powders were equal to the In content ratio In terms of In2O3, the Sn content ratio In terms of SnO2, and the Si content ratio In terms of SiO2 In the oxide sintered body.

Since each raw material powder is generally aggregated in particles, it is preferable to grind and then mix them, or grind them while mixing.

The method of pulverizing and mixing the raw material powder is not particularly limited, and for example, the raw material powder may be put in a pot and pulverized or mixed by a ball mill.

The obtained mixed powder may be directly molded to prepare a molded body and sintered, but if necessary, a binder may be added to the mixed powder to prepare a molded body. As the binder, a binder used when a molded body is obtained by a known powder metallurgy method, for example, polyvinyl alcohol, an acrylic emulsion binder, or the like can be used. Alternatively, a dispersion medium may be added to the mixed powder to prepare a slurry, and the slurry may be spray-dried to prepare particles, which may be molded.

The molding method may be a method conventionally used in powder metallurgy, for example, cold pressing or CIP (cold isostatic pressing).

Alternatively, the mixed powder may be preliminarily pressed to prepare a preform, and the pulverized powder obtained by pulverizing the preform may be pressed to prepare a compact.

The molded body may be produced by a wet molding method such as a slip casting method.

The relative density of the molded article is usually 50 to 75%.

The obtained compact is fired to obtain a sintered body. The firing furnace used for firing is not particularly limited as long as the cooling rate can be controlled during cooling, and may be one commonly used in powder metallurgy. As the firing atmosphere, an oxygen-containing atmosphere is suitable.

The temperature rise rate is usually 100 to 500 ℃/h from the viewpoint of densification and crack prevention. The firing temperature is 1300-1600 ℃, preferably 1400-1600 ℃. When the firing temperature is within the above range, a sintered body having a high density can be obtained. The holding time at the firing temperature is usually 3 to 30 hours, preferably 5 to 20 hours. If the holding time is within the above range, a sintered body having a high density can be easily obtained.

After the completion of the holding at the above temperature, the temperature in the furnace is lowered to cool the furnace at a temperature of usually 300 ℃/hr or lower, preferably 100 ℃/hr or lower.

The sintered body thus obtained is cut into a desired shape as needed, and ground or the like, whereby the sputtering target for a transparent conductive film can be obtained.

The shape of the sputtering target for a transparent conductive film is not particularly limited, and may be a flat plate shape, a cylindrical shape, or the like.

The sputtering target for transparent conductive film is generally used by bonding to a base material. The substrate is typically Cu, Al, Ti or stainless steel. As the bonding material, a bonding material used for bonding of a conventional ITO target, for example, In metal, can be used. The bonding method is also the same as the conventional method for bonding an ITO target.

The transparent conductive film can be formed by sputtering the sputtering target for transparent conductive film. As described above, since the sputtering target for a transparent conductive film has low resistivity, it can perform not only RF sputtering but also DC sputtering.

By sputtering the sputtering target for a transparent conductive film, a transparent conductive film having In, Sn, Si, and O as constituent elements can be obtained. The content ratio of Sn and the content ratio of Si in the obtained transparent conductive film tend to be lower than the content ratio of Sn and the content ratio of Si in the sputtering target for a transparent conductive film. Therefore, In the transparent conductive film, the content ratio of In is 28.0 mass% or more and 87.0 mass% or less, preferably 33.0 mass% or more and 80.0 mass% or less In terms of In2O3, the content ratio of Sn is 12.0 mass% or more and 63.0 mass% or less, preferably 18.0 mass% or more and 58.0 mass% or less In terms of SnO2, and the content ratio of Si is 1.0 mass% or more and 9.0 mass% or less, preferably 2.0 mass% or more and 9.0 mass% or less In terms of SiO 2. As described above, the obtained transparent conductive film has high film resistivity and chemical resistance. As in the case of the sputtering target for a transparent conductive film, the transparent conductive film may contain inevitable impurities. The content of inevitable impurities in the transparent conductive film is usually 100ppm or less.

Examples

The following shows the measurement methods used in the following examples and comparative examples.

1. Relative density of target

The relative density of the sputtering target for transparent conductive film was measured by the archimedes method. Specifically, the mass in the air of the target was divided by the volume (mass in water of the target/specific gravity of water at the measurement temperature), and the value of the percentage of the theoretical density ρ (g/cm3) based on the following formula (X) was defined as the relative density (unit:%).

ρ＝((C1/100)/ρ1+(C2/100)/ρ2+…+(Ci/100)/ρi) (X)

(in the formula, C1 to Ci each represents the content (mass%) of a constituent material of the target material, and ρ 1 to ρ i each represents the density (g/cm3) of the constituent material corresponding to C1 to Ci.)

In the following examples and comparative examples, the substances (raw materials) used for the production of the target are In2O3, SnO2, and SiO2, and therefore, for example, the theoretical density ρ can be calculated by applying the following parameters to the formula (X).

C1: in2O3 raw Material used In the target

ρ 1: density of In2O3 (7.18g/cm3)

C2: mass% of SnO2 raw material used in the target

ρ 2: density of SnO2 (6.95g/cm3)

C3: mass% of SiO2 raw material used in the target

ρ 3: density of SiO2 (2.20g/cm3)

2. Resistivity of the target

The resistivity of the sputtering target was measured in AUTO RANGE mode by using Loresta (registered trademark) HP MCP-T410 (TYPE ESP with in-line 4 probe) manufactured by mitsubishi chemical corporation, with a probe brought into contact with the surface of the sintered body after processing.

3. Film resistivity of transparent conductive film

The film resistivity of the transparent conductive film was measured by using a four-probe measuring apparatus K-705RS manufactured by Wai Kagaku K.K.

4. Etch rate of transparent conductive film

The etching rate of the transparent conductive film was calculated by immersing a part of the transparent conductive film in a transparent conductive film etching solution (ITO-07N manufactured by kanto chemical) heated to 40 ℃ for 6 minutes, measuring the difference in level between the portion subjected to etching and the portion not subjected to etching using a stylus-type surface shape measuring instrument P-15 manufactured by KLA-Tencor, and dividing the difference in level by the etching time.

5. Content ratio of In, Sn and Si In the transparent conductive film

For the measurement, a transparent conductive film formed on a copper foil was used. The In and Sn content ratios were measured by an acid decomposition ICP-OES method using ICP emission spectrometer 720ICP-OES manufactured by Agilent Technologies, and the Si content ratio was measured by a molybdenum blue absorptiometry using spectrophotometer U-2900 manufactured by Hitachi.

[ examples and comparative examples ]

(production of sputtering target)

In2O3 powder, SnO2 powder, and SiO2 powder were mixed at the ratios shown In table 1 using a ball mill to prepare mixed powders.

In the mixed powder, 6 mass% of polyvinyl alcohol diluted to 4 mass% was added to the mixed powder, and the polyvinyl alcohol and the powder were sufficiently fused using a mortar and passed through a 5.5 mesh sieve. The obtained powder was pre-pressed under the condition of 200kg/cm2, and the obtained preform was pulverized with a mortar. The obtained pulverized powder was charged into a mold for pressing, and molded at a pressing pressure of 1t/cm2 for 60 seconds to obtain a molded body.

The obtained molded body was placed in a firing furnace, oxygen was fluidized at 1L/h in the furnace, the firing atmosphere was an oxygen-fluidized atmosphere, the temperature rise rate was 350 ℃/h, the firing temperature was 1550 ℃, and the holding time at the firing temperature was 9 h.

Then, the mixture was cooled at a cooling rate of 100 ℃ per hour.

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

The oxide sintered body is cut to produce a sputtering target. The relative density and resistivity of the sputtering target were measured by the methods described above. The results are shown in Table 1.

(production of transparent conductive film)

The sputtering target was bonded to a copper backing plate with In solder, and sputtering was performed under the following conditions, and a transparent conductive film having a film thickness was formed on a glass substrate for measuring the specific resistance and the etching rate, and a transparent conductive film was formed on a copper foil having a thickness of 1.1mm for measuring the Sn content ratio and the Si content ratio of the transparent conductive film. In comparative example 5, since the target had a high resistivity and no discharge was generated, DC sputtering was not performed.

The device comprises the following steps: DC magnetron sputtering device, exhaust system cryopump, rotary pump

Reaching the vacuum degree: 1X 10-4Pa

Sputtering pressure: 0.4Pa

Oxygen flow rate: 0 to 2.5sccm

The film resistivity, etching rate, In content ratio, Sn content ratio, and Si content ratio of the obtained transparent conductive film were measured by the above-described methods. The oxygen flow rate is appropriately adjusted to a condition that an amorphous transparent conductive film is obtained and the resistivity of the film is the lowest. The results are shown in Table 1.

Claims

1. A sputtering target for a transparent conductive film, which is formed from an oxide sintered body containing In, Sn, Si, and O as constituent elements, wherein the In content is more than 25.0 mass% and 82.0 mass% or less In terms of In2O3, the Sn content is 15.0 mass% or more and 65.0 mass% or less In terms of SnO2, and the Si content is 3.0 mass% or more and less than 10.0 mass% In terms of SiO 2.

2. The sputtering target for a transparent conductive film according to claim 1, wherein the resistivity of the sputtering target for a transparent conductive film is 2.0 x 102 Ω cm or less.

3. The sputtering target for a transparent conductive film according to claim 1 or 2, wherein the relative density of the sputtering target for a transparent conductive film is 98.0% or more.

4. A transparent conductive film, wherein the constituent elements are In, Sn, Si and O, the content ratio of In is 28.0 mass% or more and 87.0 mass% or less In terms of In2O3, the content ratio of Sn is 12.0 mass% or more and 63.0 mass% or less In terms of SnO2, and the content ratio of Si is 1.0 mass% or more and 9.0 mass% or less In terms of SiO 2.

5. The transparent conductive film according to claim 4, wherein the film resistivity of the transparent conductive film is 1.0 x 100 Ω cm or more.

6. The transparent conductive film according to claim 4 or 5, wherein an etching rate of the transparent conductive film is less than

7. A method for producing a transparent conductive film, which comprises forming a film by sputtering the sputtering target for a transparent conductive film according to any one of claims 1 to 3.

8. The method for manufacturing a transparent conductive film according to claim 7, wherein the film resistivity of the transparent conductive film is 1.0 x 100 Ω cm or more.

9. The method for manufacturing a transparent conductive film according to claim 7 or 8, wherein an etching rate of the transparent conductive film is less than