JP6327121B2 - Sputtering target, transparent conductive oxide thin film, and conductive film - Google Patents

Description

  The present invention relates to a sputtering target, a transparent conductive oxide thin film, and a conductive film having the transparent conductive oxide thin film.

  Since the transparent conductive oxide thin film has both light transmittance and conductivity, displays such as a liquid crystal display (LCD), a plasma display panel (PDP), and an electroluminescence panel (organic EL, inorganic EL), and a touch panel It is used as a transparent electrode for solar cells. In addition to these, they are also used for electromagnetic wave shielding films and infrared ray prevention films.

As a method of forming a transparent conductive oxide thin film, a sputtering method is frequently used. Patent Document 1 describes that a blocking film for a thin layer transistor is formed by a sputtering method using a zinc oxide (ZnO) -based sputtering target doped with gallium oxide (Ga ₂ O ₃ ). .

JP 2014-5538 A

  In recent years, with the rapid spread of smartphones and tablet terminals, devices such as displays and touch panels are required to have further improved performance. Therefore, a transparent conductive oxide thin film used in such a device is desired to have a higher level of both light transmittance and conductivity. In addition, a sufficiently high firing yield is required in the manufacturing process of the sputtering target for forming these transparent conductive oxide thin films.

  The present invention has been made in view of such a problem, and it is possible to form a transparent conductive oxide thin film having both high light transmittance and conductivity, and sputtering that can be manufactured with a high firing yield. It is an object to provide a target, a transparent conductive oxide thin film formed using the target, and a conductive film having the transparent conductive oxide thin film.

The sputtering target of the present invention includes a _Ga 2 _{O 3} of 65 to 88 mole% of ZnO and 10 to 25 mol%, further sputtering target containing at least one kind of oxides selected from MgO, CaO, BaO The total content of MgO, CaO, and BaO is 1 to 17 mol%, and particles containing Ga ₂ O ₃ as a main component, MgO, CaO, and BaO in a matrix containing ZnO as a main component. At least one oxide selected from the group consisting of particles mainly composed of Ga ₂ O ₃ and at least one selected from MgO, CaO, and BaO. The average particle diameter of particles mainly composed of oxide is 1.5 to 10 μm. The sputtering target has a sufficiently high firing yield in the manufacturing process, and the transparent conductive oxide thin film formed by sputtering using the sputtering target has both high light transmittance and conductivity.

  The present invention provides a transparent conductive oxide thin film formed by a sputtering method using the above sputtering target. Since the transparent conductive oxide thin film of the present invention has both high light transmittance and conductivity, it can be suitably used for applications such as touch panels and displays.

  Moreover, this invention provides a conductive film provided with a base material and the said transparent conductive oxide thin film formed on the base material.

  ADVANTAGE OF THE INVENTION According to this invention, the transparent conductive oxide thin film which has high light transmittance and electroconductivity can be formed into a film, The sputtering target which can be manufactured with a high baking yield, and the transparent conductive film formed using it A conductive oxide thin film and a conductive film having the transparent conductive oxide thin film can be provided.

The schematic diagram of the laminated body which concerns on this embodiment is shown.

(Sputtering target)
Sputtering target according to the present embodiment includes a _Ga 2 _{O 3} of 65 to 88 mole% of ZnO and 10 to 25 mol%, and further contained MgO, CaO, at least one oxide selected from BaO It is a sputtering target, and the total content of MgO, CaO, and BaO is 1 to 17 mol%. In a matrix mainly containing ZnO, particles containing Ga ₂ O ₃ as main components and MgO, CaO, and at least one oxide and the particles composed mainly dispersed structure selected from BaO, particles and MgO mainly composed of _Ga 2 _{O 3,} CaO, and at least one selected from BaO The average particle size of particles mainly composed of various types of oxides is 1.5 to 10 μm. In addition, a main component means that the component described as a main component occupies the maximum molar ratio in each of the said sputtering target, particle | grains, and a matrix.

The total amount of at least one kind of oxide selected from Ga ₂ O ₃ , ZnO, MgO, CaO, and BaO is preferably 95 mol% or more with respect to the total molar amount of the constituent components of the sputtering target, and is 99 mol. % Or more is more preferable.

  Moreover, the sputtering target which concerns on this embodiment can contain an unavoidable impurity particle other than the above. Inevitable impurity particles include, for example, particles containing Si, Cr, Fe, Sn, Pb, Cd, Mn, Na, Sr, and the like, and each can be allowed up to about 1000 mass ppm.

When the content of Ga ₂ O _{3 in} the particles containing Ga ₂ O ₃ as a main component is 60 mol% or more with respect to the total molar amount of the constituent components contained in the particles, the electrical resistance value of the sputtering target is Since it becomes small, it is preferable. The average particle diameter of the particles composed mainly of the _Ga 2 _{O 3,} more preferably a 3～9Myuemu. In addition, an average particle diameter can be acquired from the average value of the fixed direction tangent diameter of a cross-sectional electron micrograph, for example. Further, in various studies related to the present invention, a sputtering target having an average particle size of Ga ₂ O ₃ as a main component exceeding 10 μm was also prototyped. Yield deteriorated and could not be produced stably.

  Further, the content of ZnO in the matrix is preferably 60 mol% or more with respect to the total molar amount of the constituent components contained in the matrix, since the electric resistance value of the sputtering target becomes small.

The content of the MgO, CaO, and BaO in the particle containing as a main component at least one oxide selected from the MgO, CaO, and BaO is based on the total molar amount of the components included in the particle. The amount of 60 mol% or more is preferable because the yield of the firing step is 90% or more, and it becomes possible to stably produce. Further, the average particle diameter of particles mainly composed of at least one oxide selected from MgO, CaO, and BaO is more preferably 3 to 9 μm. In various studies relating to the present invention, a sputtering target in which the average particle size of particles mainly composed of at least one kind of oxide selected from MgO, CaO, and BaO exceeds 10 μm was also produced. When the particle size exceeded 10 μm, the yield of the firing process deteriorated and could not be stably produced.

  The shape, size, and the like of the sputtering target are not particularly limited, and can be, for example, a disk having a diameter of about 127 to 300 mm.

  The sputtering target can have an electrical resistance value (specific resistance) of 0.01 Ωcm or less. Thus, since the electrical resistance value of sputtering target itself is small, the sputtering target of this embodiment can be used for the film-forming by DC sputtering method.

The density of the sputtering target is preferably 5.41 to 5.97 gcm ³ . By setting the density of the sputtering target in such a range, the electric resistance value (specific resistance) tends to be 0.01 Ωcm or less.

(Manufacturing method of sputtering target)
An example of the manufacturing method of the sputtering target concerning this embodiment is demonstrated.

First, raw material powder having the same composition as a desired sputtering target is prepared. The raw material powder contains at least one oxide selected from Ga ₂ O ₃ powder, ZnO powder, MgO powder, CaO powder, and BaO powder.

The purity of the Ga ₂ O ₃ powder is preferably 99.9% by mass or more. It is preferable that the average particle diameter of the Ga ₂ O ₃ powder is 1 to 10 μm because the structure of the sputtering target is likely to have the above-described dispersion structure.

  The purity of the ZnO powder is preferably 99.5% by mass or more. Further, the average particle diameter of the ZnO powder is not particularly limited, but is preferably 0.1 to 10 μm because the sinterability tends to increase.

  The purity of the MgO powder, CaO powder, and BaO powder is preferably 99.9% by mass or more. Moreover, although the average particle diameter of these powders is not specifically limited, since the yield of a baking process improves that it is 0.1-10 micrometers, it is preferable.

A raw material powder is obtained by mixing the powders of the above-described components. The mixing method is not particularly limited, but it is preferable to mix in a ball mill. Mixing in the ball mill may be dry or wet. In the case of the wet type, for example, ethanol, acetone, denatured alcohol and the like can be used as the solvent. Examples of the mixer and the mixing medium in the ball mill include an alumina pot and an alumina ball, respectively. The mixing time is not particularly limited, but is preferably 12 to 30 hours because the average particle diameter of particles containing Ga ₂ O ₃ as a main component tends to be 1.5 μm to 10 μm.

Subsequently, the obtained raw material powder is hot-pressed in a vacuum atmosphere to obtain a molded body. The pressing method is not particularly limited, and may be an isotropic press or a uniaxial press. Although a press pressure is not specifically limited, either, for example, 15-49 MPa (150-500 kgf / cm < ² >) can be used. The firing temperature is preferably 900 to 1100 ° C. The stabilization time at the firing temperature is not particularly limited, but can be 1 to 5 hours.

  The sintered body obtained by firing the molded body is cut into a predetermined size, and a sputtering target is completed. The shape, size, and the like of the sputtering target are not particularly limited, and can be, for example, a disk having a diameter of about 127 to 300 mm.

(Method for producing transparent conductive oxide thin film)
Hereinafter, an example of the manufacturing method of the thin film using the sputtering target which concerns on this embodiment is demonstrated.

  First, the sputtering target is prepared. A copper cooling plate is bonded to the main surface of the sputtering target with In or the like.

  A sputtering target to which a cooling plate is attached is mounted on a sputtering apparatus and a sputtering method is performed in a sputtering gas atmosphere to form a transparent conductive oxide thin film on the substrate. The sputtering method may be either a DC sputtering method or an RF sputtering method, but the DC sputtering method is used because an inexpensive power source can be used, the film forming speed is large, the temperature rise of the substrate is small, and the like. Preferably there is. Magnetron sputtering may also be used. A rare gas such as Ar can be used as the sputtering gas.

  By forming a film as described above, a transparent conductive oxide thin film can be obtained. The transparent conductive oxide thin film according to this embodiment is excellent in light transmittance and conductivity. In addition, etching with phosphoric acid, acetic acid, nitric acid, or the like is good, and an electrode with a fine pattern can be manufactured.

  There is no restriction | limiting in particular as a refractive index of a transparent conductive oxide thin film, Although it can adjust suitably by the use of a thin film, For example, it shall be 1.8-2.0 with respect to the light of wavelength 380nm. it can. Further, the transparent conductive oxide thin film is transparent over the entire visible light region, and for example, the light transmittance can be 93% or more over a wavelength range of 380 to 800 nm. The conductivity of the transparent conductive oxide thin film can be, for example, 1E + 4 to 1E + 5Ω / □ in terms of surface resistance.

  Although the thickness of the said transparent conductive oxide thin film is not specifically limited, Although it can adjust suitably according to a use, it is preferable that it is 20-100 nm from a viewpoint which makes light transmittance and electroconductivity compatible.

  Applications of the transparent conductive oxide thin film include a resistive film for a touch panel, a transparent electrode for a display, and the like.

(Conductive film using transparent conductive oxide thin film)
The conductive film 100 shown in FIG. 1 can be produced using the transparent conductive oxide thin film. The conductive film 100 is obtained by laminating a metal oxide layer 13, an Ag alloy layer 15, and a ZnO—Ga ₂ O ₃ layer 17 in this order on a film substrate 11. The ZnO—Ga ₂ O ₃ layer 17 is the transparent conductive oxide thin film. The ZnO—Ga ₂ O ₃ layer 17 is provided with metal wiring (not shown) for wiring electrodes.

  Examples of the film substrate 11 include polyester films such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyolefin films such as polyethylene and polypropylene, polycarbonate films, acrylic films, norbornene films, polyarylate films, and polyether sulfones. A film, a diacetyl cellulose film, a triacetyl cellulose film, etc. are mentioned. Among these, organic resin films such as polyester films such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) can be mentioned. The thickness of the film base 11 is, for example, 10 to 200 μm. Since such a film base 11 is transparent and excellent in flexibility, it is useful when the laminate is also used as a touch panel, a transparent electrode such as flexible organic EL lighting, or an electromagnetic wave shield.

The metal oxide layer 13 may be formed of the transparent conductive oxide thin film, but may be a metal oxide layer other than that. The metal oxide that forms the metal oxide layer 13 is not particularly limited, but includes ZnO as a main component, In ₂ O ₃ , TiO ₂ , Al ₂ O ₃ , SiO ₂ , Ga ₂ O ₃ , GeO ₂ , SnO. A metal oxide film containing at least one of ₂ , Nb ₂ O ₃ , MgO, CaO, BaO, Sb ₂ O ₃ , Bi ₂ O ₃ and ZrO ₂ is preferable. With such a composition, DC sputtering is possible, and a highly transparent and highly corrosion-resistant metal oxide film can be obtained.

  The thickness of the metal oxide layer 13 is preferably 20 to 70 nm, for example, because it is suitable for various touch panels.

  The metal oxide layer 13 can be produced by a vacuum film formation method such as a vacuum evaporation method, a sputtering method, an ion plating method, or a CVD method. Among these, the sputtering method is preferable in that the film forming chamber can be downsized and the film forming speed is high. Examples of the sputtering method include a DC magnetron sputtering method. As the sputtering target, an oxide target, a metal, or a metalloid target can be used.

  The Ag alloy layer 15 is a layer of an alloy containing silver. The metal element other than Ag constituting the Ag alloy is at least one selected from Au, Pd, Nd, Bi, Cu, Sb, Bi, In, Sn, Ge, Nb, Ti, Ru, Al, Ga and Gd. Is mentioned. Preferred Ag alloys include Ag—Pd, Ag—Cu, Ag—Bi, Ag—Nd, Ag—In, and Ag—Nb. Such an Ag alloy may contain an additive. The content of the additive in the Ag alloy layer 15 is, for example, 0.3 to 2.5% by weight. When the content is less than 0.3% by weight, the effect of improving the corrosion resistance tends to be difficult to obtain. On the other hand, when the content exceeds 2.5% by weight, the total light transmittance tends to decrease or the resistance value tends to increase. The thickness of the metal layer 16 is, for example, 3 to 15 nm from the viewpoint of making the thickness suitable for various applications.

  The Ag alloy layer 15 can be produced by a vacuum film forming method such as a vacuum deposition method, a sputtering method, an ion plating method, or a CVD method. Among these, the sputtering method is preferable because the film forming chamber can be downsized and the film forming speed is high. Examples of the sputtering method include a DC magnetron sputtering method. As the sputtering target, an Ag alloy target having the above composition can be used.

  Since the conductive film 100 according to this embodiment has the transparent conductive oxide thin film layer formed on the metal wiring side, the Ag alloy layer 15 can be prevented from being corroded. Conductivity can be transmitted to the metal wiring, and an effect of improving the transmittance due to the optical interference effect can be obtained. Such a conductive film can be suitably used for touch panel applications. In addition, it cannot be overemphasized that the conductive film which has the said transparent conductive oxide thin film is not limited to this aspect.

As raw materials for the sputtering targets of Examples 1 to 43 and Comparative Examples 1 to 37, ZnO powder, Ga ₂ O ₃ powder and MgO powder, CaO powder, and BaO powder were prepared at the ratios shown in Table 1. The purity of the ZnO powder is 99.5%, the average particle size is 0.5 μm, the purity of the Ga ₂ O ₃ powder is 99.9%, the average particle size is 2 μm, and the purity of the MgO powder, CaO powder, and BaO powder are all The average particle size was 99.9% and 5 μm. These powders were mixed in an alumina ball mill pot using alumina balls as a medium for each of the mixing times shown in Table 1 to obtain raw material powders. Mixing was performed in a wet manner, and denatured alcohol was used as a solvent.

The obtained raw material powder was hot-press fired in a graphite mold in a vacuum atmosphere to obtain a sintered body. The hot press firing conditions were a hot press pressure of 20 MPa (200 kgf / cm ² ), a firing temperature of 1000 ° C., and a stabilization time of 120 minutes.

The obtained sintered body was cut into 200 mmφ and 6 mm thickness by a surface grinder and a cylindrical grinder to obtain a sputtering target. About the sputtering target of Example 5, the average particle diameter was acquired from the average value of the fixed direction tangent diameter of a cross-sectional electron micrograph. The matrix mainly composed of ZnO has a structure in which particles mainly composed of Ga ₂ O ₃ and particles mainly composed of MgO are dispersed. The particles composed mainly of Ga ₂ O ₃ and the MgO The average particle size of the main particles was 4 μm. Then, particles and MgO to the Ga ₂ O ₃ in the respective sputtering targets mainly in the same way, CaO, and it has acquired an average particle size of at least one oxide as a main component particles selected from BaO . The results are shown in Tables 1 and 2. Under the same firing conditions, the average particle diameter of particles mainly composed of Ga ₂ O ₃ is substantially equal to the average particle diameter of particles mainly composed of MgO or the like.

(Evaluation of sputtering target)
(1) Electric resistance value (specific resistance)
About each sputtering target obtained in Examples 1-43 and Comparative Examples 1-37, the result of having measured the electrical resistance value by the 4-probe method prescribed | regulated to JISK-7194 using a specific resistance measuring device is shown in Table 1. 2 shows.
(2) Yield of firing step For each sputtering target obtained in Examples 1 to 43 and Comparative Examples 1 to 37, a yield of 90% or more suitable for the yield of the firing step is ○, 80% to 90% Those less than% were marked with Δ, and those less than 80% were marked with x.

A transparent conductive oxide thin film was formed on a PET substrate having a thickness of 100 μm by a DC sputtering method using the sputtering targets of Examples 1 to 43 and Comparative Examples 1 to 37. The thickness of each of the formed transparent conductive oxide thin films was 70 nm. Ar and O ₂ gas were used as the sputtering gas, the sputtering pressure was 0.48 Pa, and the O ₂ gas amount was O ₂ /Ar=1.6%. The film formation power was 1.0 kW and the film formation time was adjusted.

(Evaluation of transparent conductive oxide thin film)
About the transparent conductive oxide thin film formed into a film using each sputtering target of Examples 1-43 and Comparative Examples 1-37, 4 terminal resistivity meter (brand name: Loresta GP, Mitsubishi Chemical Corporation make) was used. The surface resistance value was measured. Moreover, the refractive index and light transmittance in wavelength 380nm were measured using the spectral color difference meter (brand name: CM-5, product made from Konica Minolta). The results are shown in Tables 3 and 4, respectively.

11 ... film substrate, 13 ... metal oxide layer, 15 ... Ag alloy _{layer, 17 ... ZnO-Ga 2 O} 3 layer (transparent conductive oxide thin film), 100 ... conductive film

Claims (3)

And a 65 to 88 mole% of ZnO and 10 to 25 mol% of _Ga 2 _{O 3,} further MgO, CaO, a sputtering target containing at least one oxide selected from BaO,
The total content of MgO, CaO, and BaO is 1 to 17 mol%,
It has a structure in which particles mainly composed of Ga ₂ O ₃ and particles mainly composed of at least one oxide selected from MgO, CaO, and BaO are dispersed in a matrix mainly composed of ZnO. ,
The average particle size of the particles mainly composed of Ga ₂ O ₃ and the particles mainly composed of at least one oxide selected from MgO, CaO and BaO is 1.5 to 10 μm.
A sputtering target.   A transparent conductive oxide thin film formed by sputtering using the sputtering target according to claim 1. A substrate;
The transparent conductive oxide thin film according to claim 2 formed on the substrate,
A conductive film comprising:

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