TW201935730A - Reflective anode electrode for organic EL display, thin film transistor substrate, organic electroluminescent display and sputtering target effectively supply current to the organic light emitting layer by utilizing the reflective anode electrode - Google Patents

Abstract

A reflective anode electrode for organic EL display is provided. The reflective anode electrode comprises a novel AI alloy reflective film, and can also restrain resistivity of Al alloy reflective film as low and ensure low contact resistance and high reflection rate even if the Al alloy reflective film is directly in contact with oxide conductive films, such as ITO or IZO. It comprises a lamination structure including Al-Ge based alloy film and an oxide conductive film in contact with the Al-Ge based alloy film, and a reflective anode electrode for organic EL display where a layer containing aluminum oxide as a main component is interposed at a contact interface, and Al-Ge based alloy film contains Ge in an amount of 0.1 to 2.5 atomic%, and has a Ge concentration layer and a Ge-containing precipitate are formed in the contact interface between the Al-Ge based alloy film and the oxide conductive film, wherein an average Ge concentration within 50 nm from the surface of the oxide conductive film side in the Al-Ge based alloy film is above 2 times of an average Ge concentration in the Al-Ge based alloy film, and an average diameter of the Ge containing precipitate is greater than 0.1(mu)m.

Description

Reflective anode electrode for organic EL display, thin-film transistor substrate, organic electroluminescence display, and sputtering target

The invention relates to a reflective anode electrode, a thin-film transistor substrate, an organic EL display, and a sputtering target used in an organic electroluminescence (EL) display (especially a top emission type).

Organic EL (Organic Electro-Luminescence) displays, which are one type of flat-panel display, are all solids in which organic EL elements are arranged in a matrix on a substrate such as a glass plate. Flat panel display. In an organic EL display, an anode (anode) and a cathode (cathode) are formed in stripes, and these intersecting portions correspond to pixels (organic EL elements). When the voltage of several volts (V) is applied to the organic EL element from the outside and a current flows, the organic molecule is advanced to an excited state, and when it returns to the original ground state (stable state), its excess energy is emitted as light. The luminescent color is inherent to organic materials.

Organic EL elements are self-luminous and current-driven, but there are passive and active types of driving methods. The passive type has a simple structure, but it is difficult to achieve full color. On the other hand, the active type can achieve large size and is also suitable for full color, but a thin film transistor (TFT) substrate is required in the active type. Furthermore, a TFT such as low-temperature polycrystalline Si (p-Si) or amorphous Si (a-Si) is used in the TFT substrate.

In the case of the active organic EL display, a plurality of TFTs or wiring becomes an obstacle, and the area in which the organic EL pixels can be used is reduced. If the driving circuit is complicated and the number of TFTs is increased, the influence is further increased. Recently, attention has been paid to a method in which light is not extracted from a glass substrate, but a structure (top emission) is provided to extract light from an upper surface side, thereby improving an aperture ratio.

In top emission, the anode on the lower surface uses holes to inject excellent ITO (Indium Tin Oxide). In addition, the upper surface of the cathode also requires the use of a transparent conductive film, but the ITO work function is large and is not suitable for electron injection. Furthermore, since ITO is formed by a sputtering method or an ion beam evaporation method, there is a concern that plasma ions or secondary electrons during film formation cause damage to an electron transport layer (an organic material constituting an organic EL element). Therefore, a thin Mg layer or a copper phthalocyanine layer is formed on the electron transport layer, thereby avoiding damage and improving electron injection.

The anode electrode used in such an active-matrix top-emitting organic EL display has the purpose of reflecting the light emitted from the organic EL element, and is transparent as represented by ITO or IZO (Indium Zinc Oxide) Laminated structure of oxide conductive film and reflective film (reflective anode electrode). Most of the reflective films used in the reflective anode electrode are reflective metal films such as molybdenum (Mo), chromium (Cr), aluminum (Al), or silver (Ag). For example, a reflective anode electrode in a top-emission organic EL display that has been mass-produced uses a multilayer structure of ITO and an Ag alloy film.

Taking the reflectance into consideration, Ag or an Ag-based alloy containing Ag as a host is useful because of its high reflectance. In addition, the Ag-based alloy has a unique problem of poor corrosion resistance, but the problem can be solved by coating the Ag-based alloy film with an ITO film laminated thereon. However, because of the high material cost of Ag and the difficulty in increasing the size of the sputtering target required for film formation, it is difficult to apply Ag-based alloy films to large-screen televisions for reflection of active-matrix top-emitting organic EL displays. In the film.

On the other hand, when only the reflectance is considered, Al is also good as a reflective film. For example, in Patent Document 1, an Al film or an Al-Nd film is disclosed as a reflective film, and the gist of an Al-Nd film that is excellent in reflectance is described.

However, when the Al reflective film is brought into direct contact with an oxide conductive film such as ITO or IZO, the contact resistance is high, and a sufficient current cannot be injected into the hole for the organic EL element. In order to avoid the above situation, the reflective film does not use Al but uses a high melting point metal such as Mo or Cr, or a high melting point metal such as Mo or Cr is provided between the Al reflective film and the oxide conductive film as a barrier metal. , The reflectance is greatly degraded, which causes a decrease in light emission brightness as a characteristic of the display.

Therefore, in Patent Document 2, as a reflective electrode (reflective film) capable of omitting a barrier metal, an Al-Ni alloy film containing 0.1 to 2 atomic% of Ni is proposed. According to this, it is possible to have a reflectivity as high as that of pure Al, and to achieve a low contact resistance even if the Al reflective film is brought into direct contact with an oxide conductive film such as ITO or IZO.

In addition, as in Patent Document 2, as a reflective electrode (reflective film) capable of omitting a barrier metal, Patent Document 3 proposes an Al-Ag alloy film containing 0.1 to 6 atomic% of Ag. Alternatively, Patent Document 4 proposes an Al-Ge- (Gd, La) alloy film containing 0.05 atomic% to 0.5 atomic% of Ge and a total of 0.05 atomic% to 0.45 atomic% of Gd and / or La. [Prior Art Literature] [Patent Literature]

[Patent Literature 1] Japanese Patent Laid-Open No. 2005-259695 [Patent Literature 2] Japanese Patent Laid-Open No. 2008-122941 [Patent Literature 3] Japanese Patent Laid-Open No. 2011-108459 [Patent Literature 4] Japanese Patent Special Publication No. 2008-160058

[Problems to be Solved by the Invention] In the top-emission type organic EL display, when an Al alloy is used as the anode electrode, an insulating oxide film inevitably formed on the surface of the Al alloy in an environment where oxygen is present. (A layer containing alumina as a main component), and there is a problem that it is difficult to flow a current. In this case, if a current equal to or greater than a predetermined value is to be passed, the voltage value required to pass the current becomes high. Therefore, when the same light emission intensity is maintained, there is a problem that the power consumption increases. In addition, as a characteristic required for the anode electrode, the specific resistance of the Al alloy reflection film constituting the anode electrode is low.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a reflective anode electrode for an organic EL display, which includes a novel Al alloy reflective film and allows the Al alloy reflective film to be directly connected to an oxide conductive film such as ITO or IZO. The contact can also suppress the resistivity of the Al alloy reflection film itself to be low, and can ensure low contact resistance and high reflectivity. [Technical means to solve the problem]

The reflective anode electrode for an organic EL display of the present invention that solves the problems described above has a multilayer structure including an Al-Ge-based alloy film and an oxide conductive film in contact with the Al-Ge-based alloy film, and A reflective anode electrode for an organic EL display in which a layer containing alumina as a main component is interposed between a contact interface between the Al-Ge-based alloy film and the oxide conductive film, and the Al-Ge-based alloy film is characterized in that: Containing 0.1 atomic% to 2.5 atomic% of Ge, and forming a Ge-rich layer and a Ge-containing precipitate at a contact interface between the Al-Ge-based alloy film and the oxide conductive film, the Al-Ge The average Ge concentration within 50 nm from the surface of the oxide conductive film side in the alloy-based alloy film is more than twice the average Ge concentration in the Al-Ge-based alloy film, and the Ge-containing The average diameter of the precipitates was 0.1 μm or more.

In a preferred embodiment of the present invention, the Al-Ge-based alloy film further contains 0.05 atomic% to 2.0 atomic% of Cu.

In a preferred embodiment of the present invention, the Al-Ge-based alloy film further contains a rare earth element in an amount of 0.2 atomic% to 0.5 atomic%.

In a preferred embodiment of the present invention, the oxide conductive film has a film thickness of 5 nm to 30 nm.

In a preferred embodiment of the present invention, the Al-Ge alloy film is formed by a sputtering method or a vacuum evaporation method.

In a preferred embodiment of the present invention, the Al-Ge-based alloy film is electrically connected to a source electrode and a drain electrode of a thin film transistor.

The present invention also includes a thin-film transistor substrate including a reflective anode electrode for any of the organic EL displays, or an organic EL display including the thin-film transistor substrate.

Furthermore, the present invention further includes a sputtering target which is a sputtering target for forming the Al-Ge-based alloy film described in any one of the foregoing, and contains 0.1 atomic% to 2.5 atomic% of Ge; or contains 0.1 Atom% to 2.5 atom% of Ge, and at least one of Cu atom containing 0.05 atom% to 2.0 atom% and rare earth element of 0.2 atom% to 0.5 atom%. [Effect of the invention]

According to the reflective anode electrode for an organic EL display of the present invention, an Al-Ge-based alloy film containing a predetermined amount of Ge is used as a reflective film, and Ge is formed at a contact interface between the Al-Ge-based alloy film and the oxide conductive film. The enriched layer and Ge-containing precipitates, and further, the average Ge concentration within 50 nm from the surface of the oxide conductive film side in the Al-Ge-based alloy film, and the average diameter of Ge-containing precipitates meet the prescribed requirements. Therefore, even if it is in direct contact with an oxide conductive film such as ITO or IZO, the specific resistance of the Al alloy reflective film itself can be kept low, and low contact resistance and high reflectance can be ensured. In addition, by using the reflective anode electrode of the present invention, a current can be efficiently passed through the organic light emitting layer, and light emitted from the organic light emitting layer can be efficiently reflected by the reflective film, so that an organic EL having excellent light emission brightness can be realized. monitor.

Hereinafter, the form (this embodiment) for implementing this invention is demonstrated in detail. The present invention is not limited to the embodiments described below, and can be implemented by being arbitrarily changed without departing from the gist of the present invention.

(Organic EL Display) First, the outline of an organic EL display using the reflective anode electrode of this embodiment will be described with reference to FIG. 1. Hereinafter, the Al-Ge alloy, Al-Ge-Cu alloy, Al-Ge-X alloy, and Al-Ge-Cu-X alloy (where X is Ni or a rare earth element) used in the present embodiment are summarized. The case represented by "Al-Ge alloy".

A TFT 2 and a passivation film 3 are formed on the substrate 1, and a planarization layer 4 is further formed thereon. A contact hole 5 is formed in the TFT 2, and a source electrode and a drain electrode (not shown) of the TFT 2 are electrically connected to the Al-Ge-based alloy film 6 through the contact hole 5.

The Al-Ge alloy film is preferably formed by a sputtering method. The preferable film formation conditions of a sputtering method are as follows. Substrate temperature: 25 ° C or higher and 200 ° C or lower (more preferably 150 ° C or lower) Al-Ge alloy film thickness: 50 nm or higher (more preferably 100 nm or higher) and 300 nm or lower (more preferably 200 nm or lower) )

An oxide conductive film 7 is formed directly above the Al-Ge-based alloy film 6. The Al-Ge-based alloy film 6 and the oxide conductive film 7 function as a reflective electrode of an organic EL element, are electrically connected to a source electrode and a drain electrode of the TFT 2, and function as an anode electrode. Thereby, the Al-Ge-based alloy film 6 and the oxide conductive film 7 constitute a reflective anode electrode of this embodiment.

The oxide conductive film is preferably formed by a sputtering method. The preferable film formation conditions of a sputtering method are as follows. Substrate temperature: 25 ° C or more and 150 ° C or less (more preferably 100 ° C or less) Film thickness of the oxide conductive film: 5 nm or more (more preferably 10 nm or more) and 30 nm or less (more preferably 20 nm or less)

An organic light emitting layer 8 is formed on the oxide conductive film 7, and a cathode electrode 9 is further formed thereon. In such an organic EL display, since the light emitted from the organic light emitting layer 8 is efficiently reflected by the reflective anode electrode of this embodiment, excellent light emission brightness can be realized. In addition, the higher the reflectance, the better it is. Generally, a reflectance of 75% or more, preferably 80% or more, is required.

Here, when the oxide conductive film is brought into direct contact with the Al-Ge-based alloy film as a reflective film, the following method is preferably used. After the Al-Ge-based alloy film → the oxide conductive film is formed in this order, heat treatment is performed at a temperature of 150 ° C. or higher under a vacuum or an inert gas (for example, nitrogen) environment. In addition, in this specification, a case may be referred to as "post-anneal": a reflective anode electrode (Al-Ge-based alloy film + oxide conductive film) is formed after the oxide conductive film is formed. Heat treatment.

This improves the transparency and the reflectance of the oxide conductive film, and promotes the formation of a Ge-rich layer and Ge-containing precipitates, which will be described in detail below. That is, by using the above method, it is expected that the resistivity is reduced and the reflectance is increased.

Furthermore, the environment when the oxide conductive film is brought into direct contact with the Al-Ge-based alloy film can be maintained as the environment before the contact, that is, the environment of a vacuum or an inert gas, and the film can be directly formed continuously.

(Reflective Anode Electrode) Next, a reflective anode electrode according to this embodiment will be described. The present inventors have made intensive studies in order to provide a reflective anode electrode for an organic EL display including a novel Al alloy reflective film, and even if the reflective film is made of ITO or IZO, etc. The direct contact of the oxide conductive film can also suppress the resistivity of the Al alloy reflection film itself to be low, and can ensure low contact resistance and high reflectivity.

As a result, it was found that a desired object can be achieved by using a reflective anode electrode for an organic EL display including an Al-Ge-based alloy film and an Al-Ge-based alloy film. Multilayer structure of a contacted oxide conductive film, and reflection for an organic EL display in which a layer containing alumina (Al ₂ O ₃ ) as a main component is interposed at a contact interface between the Al-Ge alloy film and the oxide conductive film Anode electrode, and the Al-Ge-based alloy film contains 0.1 atomic% to 2.5 atomic-% Ge, and a Ge-concentrated layer and a Ge-containing precipitate are formed at a contact interface between the Al-Ge-based alloy film and the oxide conductive film In the Al-Ge-based alloy film, the average Ge concentration within 50 nm from the surface of the oxide conductive film side is more than twice the average Ge concentration in the Al-Ge-based alloy film, and the precipitates containing Ge The average diameter is 0.1 μm or more.

In addition, in this specification, "the resistivity of the Al alloy reflective film itself is low" means that when the resistivity of the Al alloy reflective film itself is measured by the method described in the examples described later, the resistivity is 7.0 μΩ · cm or less.

In this specification, the term "low contact resistance" means that when the contact resistance is measured by the method described in the examples described later (10 μm square contact holes), the current is proportional to the voltage and the contact resistance is approximately Fixed (ohm).

In addition, in this specification, "high reflectance" means that when the reflectance is measured by the method described in the Example mentioned later, the reflectance at 450 nm is 75% or more.

The reason why the Al-Ge-based alloy is used to obtain good characteristics is not clear in detail. It is speculated that the reason is that Al diffusion prevention is formed at the contact interface between the Al-Ge-based alloy film and the oxide conductive film. The Ge-concentrated layer and the Ge-containing precipitates suppress the resistivity of the Al alloy reflection film itself to be low, and increase the contact resistance or decrease of the reflectance.

Here, the “Ge-rich layer” refers to a region having an average Ge concentration higher than the average Ge concentration in the Al—Ge-based alloy film. The "Ge-containing precipitate" refers to a precipitate obtained by depositing a part or all of Ge, and examples thereof include an intermetallic compound of Al and Ge.

Here, a layer (insulator layer) containing alumina as a main component is interposed at a contact interface between the Al-Ge-based alloy film and the oxide conductive film. Al is very easy to oxidize, so it is easy to bond with the oxygen in the environment to form alumina on the surface of the Al-Ge alloy film. In addition, when the Al-Ge alloy film is brought into contact with the oxide conductive film, Al self-oxidizes The conductive film takes oxygen and easily forms alumina at its interface. The layer containing the alumina as a main component is insulating, which increases contact resistance between the Al-Ge alloy film and the oxide conductive film. However, in this embodiment, in addition to this, a conductive Ge is formed. Since the concentrated layer and the precipitate containing Ge, most of the contact current flows through the Ge concentrated layer or the precipitate containing Ge. As a result, the Al-Ge-based alloy film and the oxide conductive film are electrically connected and the increase in contact resistance is suppressed. In addition, the main component refers to the most components, and usually, the content is 70% by mass or more, preferably 90% by mass or more, and more preferably 99% by mass or more.

In order to effectively suppress the increase in the contact resistance, the average Ge concentration in the Al-Ge-based alloy film within 50 nm from the surface of the oxide conductive film side is preferably in the Al-Ge-based alloy film (Al-Ge The average Ge concentration of the system-based alloy film in a portion exceeding 50 nm from the surface) is 2 times or more, more preferably 2.5 times or more, and even more preferably 3 times or more.

In addition, similarly, in order to effectively suppress the increase in the contact resistance, the average diameter of the precipitates containing Ge is preferably 0.1 μm or more, more preferably 0.15 μm or more, and still more preferably 0.2 μm or more.

The thickness of the Ge-enriched layer is preferably 5 nm or more and 100 nm or less, and more preferably 10 nm or more and 80 nm or less.

The thickness of the Ge-enriched layer, the depth from the surface of the Al-Ge-based alloy film, and the average diameter of Ge-containing precipitates can be cross-sections of the contact interface between the Al-Ge-based alloy film and the oxide conductive film. TEM (magnification: 300,000) or planar SEM (magnification: 30,000). In addition, the "average Ge concentration in the Al-Ge-based alloy film within 50 nm from the surface" or the "average Ge concentration in the Al-Ge-based alloy film" can be observed by using the cross-section TEM and using EDX ( Energy Dispersive X-ray, sigma manufactured by KEVEV, Inc. was analyzed by chemical composition analysis. TEM observation can be measured using "FE-TEM HF-2000" by Hitachi, Ltd.

It is considered that the Ge-concentrated layer and Ge-containing precipitates are deposited at the grain boundary of Al in the Al-Ge-based alloy whose solid solution limit of Ge is approximately 0 at room temperature during film formation or heat treatment steps, etc. Alternatively, it may be formed by diffusion and concentration on the aluminum surface.

For example, as described above, the Ge-enriched layer and Ge-containing precipitates are formed by sequentially forming an Al-Ge-based alloy film → an oxide conductive film, and then under a vacuum or an inert gas (such as nitrogen) environment. It is formed when a heat treatment (post annealing) is performed at a temperature of 150 ° C or higher.

In order to effectively reduce the contact resistance using the Ge-enriched layer or Ge-containing precipitates, the Ge content in the Al-Ge-based alloy film needs to be 0.1 atomic% or more. The reason is that if the Ge content is less than 0.1 atomic%, a Ge-concentrated layer or a Ge-containing precipitate that is sufficiently reduced in contact resistance with the oxide conductive film cannot be obtained, and the above-mentioned effect cannot be effectively exhibited.

On the other hand, in order to effectively use the Ge-enriched layer or Ge-containing precipitates to improve the reflectance, the Ge content in the Al—Ge-based alloy film needs to be 2.5 atomic% or less. The reason is that when the Ge content exceeds 2.5 atomic%, the resistivity of the Al alloy reflection film itself cannot be suppressed low. The reason is that the reflectance is lowered due to excessive formation of a Ge-concentrated layer or Ge-containing precipitates, and there is a concern that the above-mentioned effect cannot be effectively exerted. In addition, the reason is that convex portions (hillocks) are formed on the surface after the heat treatment, and this causes a short circuit of the device.

The Ge content is preferably 0.15 atomic% or more, more preferably 0.20 atomic% or more, preferably 1.5 atomic% or less, and still more preferably 1.0 atomic% or less. In addition, the Al-Ge-based alloy film of this embodiment contains Ge and the remainder is Al and unavoidable impurities. Specific examples of the impurity element include oxygen, nitrogen, carbon, and iron. These elements are each limited to 0.01 atomic% or less. In addition, if these elements are within the above-mentioned range, the effects of the present embodiment will not be hindered not only when they are contained as unavoidable impurities, but also when they are actively added.

The Al-Ge-based alloy film may further contain 0.05 atomic% to 2.0 atomic% of Cu. Precipitation of Cu and Ge is formed by containing a predetermined amount of Cu, and the oxide layer on the precipitate has higher conductivity than the oxide layer formed on Al, so that it is possible to suppress a decrease in reflectance and reduce contact. resistance. When the Cu content is less than 0.05 atomic%, the amount of the precipitate is insufficient and the effect cannot be effectively exhibited. In addition, when the Cu content exceeds 2.0 atomic%, the precipitate is excessively formed and reflected. The rate is reduced and the effect cannot be effectively exerted.

In addition, the Al-Ge-based alloy film may further contain a group selected from Ni and rare earth elements (La, Nd, etc.) in a total amount of 0.1 atomic% to 2.0 atomic% (hereinafter referred to as a group X). In this case, not only the heat resistance of the Al-Ge-based alloy film is improved and the formation of hillocks is effectively prevented, but also the corrosion resistance to the alkaline solution is improved. Elements belonging to the X group can be added individually or in combination of two or more.

When the content of the elements belonging to the group X (in the case of separate elements, the total amount in the case of using two or more kinds) is less than 0.1 atomic%, the effect of improving heat resistance and alkali corrosion resistance cannot be effectively exerted. Sexual enhancement effects both. From the standpoint of improving these characteristics, the more the content of the element belonging to the X group is better, but if the amount exceeds 2 atomic%, the specific resistance of the Al-Ge-based alloy film itself increases. Therefore, the content of the elements belonging to the X group is preferably 0.1 atomic% or more (more preferably 0.2 atomic% or more), and preferably 2 atomic% or less (more preferably 0.8 atomic% or less). When a rare earth element (especially La) is used as an element belonging to the group X, the content of the rare earth element is preferably 0.2 atomic% to 0.5 atomic%.

Further, in order to effectively exert the effect of using an element belonging to the X group, when the total amount of the elements is 1 atomic% or more, it is preferable that the elements exist as precipitates.

The oxide conductive film used in this embodiment is not particularly limited, and examples thereof include ordinary users such as indium tin oxide (ITO) and indium zinc oxide (IZO), and indium tin oxide is preferred.

A preferred film thickness of the oxide conductive film is 5 nm to 30 nm. If the thickness of the oxide conductive film is less than 5 nm, pinholes may be generated in the ITO film and cause black spots. On the other hand, if the thickness of the oxide conductive film exceeds 30 nm, Reflectivity decreases. A more preferable film thickness of the oxide conductive film is 5 nm or more and 20 nm or less.

Regarding the reflective anode electrode for the organic EL display of this embodiment, in addition to the low contact resistance and excellent reflectivity, the work function of the upper oxide transparent conductive film when the laminated structure with the oxide transparent conductive film is made is also controlled. It is the same degree as when a general-purpose Ag-based alloy is used, and preferably has excellent alkali corrosion resistance and heat resistance. Therefore, it is preferably applied to a thin-film transistor substrate and further to a display device (especially an organic EL display). )in.

(Sputtering Target) The Al-Ge-based alloy film is preferably formed by a sputtering method or a vacuum evaporation method, and particularly preferably a sputtering target using a sputtering method (hereinafter sometimes referred to as a “target”) To form. The reason is that according to the sputtering method, it is easier to form a thin film having excellent in-plane uniformity in composition or film thickness than a thin film formed by an ion plating method or an electron beam evaporation method.

In order to form the Al-Ge alloy film by the sputtering method, as the target, if the element (Ge, and preferably Cu, or Ni, or a rare earth element (La, Nd, etc.)) is used, Element of the X group) and an Al alloy sputtering target with the same composition as the desired Al-Ge alloy film, there is no fear of composition deviation, and an Al-Ge alloy film with a desired composition can be formed And good.

Therefore, in this embodiment, a sputtering target having the same composition as the Al-Ge-based alloy film is also included in the scope of this embodiment. In detail, the target contains 0.1 atomic% to 2.5 atomic% of Ge; or 0.1 atomic% to 2.5 atomic% of Ge, 0.05 atomic% to 2.0 atomic% of Cu, and 0.2 atomic% to 0.5 atomic% of rare earth. The remaining portion of at least one of the elements is Al and unavoidable impurities.

The shape of the target includes a shape processed into an arbitrary shape (a square plate shape, a circular plate shape, a doughnut plate shape, or the like) according to the shape or structure of the sputtering apparatus.

Examples of the method for producing the target include a method for producing an ingot containing an Al-Ge alloy by a melt casting method, a powder sintering method, or a spray forming method, or a method including A method in which a preform (an intermediate before obtaining a final dense body) of an Al-Ge-based alloy is obtained by densifying the preform by a densification method. [Example]

Hereinafter, the present invention will be described more specifically by citing examples and comparative examples. However, the present invention is not limited to these examples, and can be implemented by applying changes within a range suitable for the gist thereof. These are all included in the technical scope of the present invention. Inside.

In this embodiment, various Al alloy reflective films are used to measure the reflectance (after heat treatment), the contact resistance between the Al alloy reflective film and the oxide conductive film, the resistivity and heat resistance of the Al alloy reflective film (presence or absence of hillocks).

Specifically, an alkali-free glass plate (thickness: 0.7 mm) was used as a substrate, and an Al-Ge-based alloy film (thickness: 200 nm) was produced as a reflective film on the surface by a sputtering method. The chemical composition of the Al-Ge alloy film is shown in Table 1. In addition, the film formation conditions are set to substrate temperature: 25 ° C, pressure: 0.26 MPa, power source: DC, film formation power density: 5 W / cm ² to 20 W / cm ² . For comparison, a pure Al film (film thickness: about 100 nm) was similarly formed by a sputtering method. The chemical composition of the reflective film is identified using inductively coupled plasma (ICP) luminescence analysis.

An ITO film was formed on each of the reflective films formed in the above-described manner. Furthermore, after the ITO film was formed, a heat treatment (post-annealing) was performed at 250 ° C. for 60 minutes in a nitrogen atmosphere.

Here, when the ITO film is formed, an Al-Ge alloy film is formed, and after the atmosphere is opened, a 10 nm-thick ITO film is formed by a sputtering method to form a reflective anode electrode (reflection film + Oxide conductive film). The film formation conditions were substrate temperature: 25 ° C, pressure: 0.8 mTorr, and DC power: 150 W.

About each reflective anode electrode produced as described above, (1) the reflectance (after the heat treatment), (2) the contact resistance between the Al alloy reflective film and the oxide conductive film, and (3) the Al alloy reflective film Specific resistance and (4) heat resistance (presence or absence of Kooka) were evaluated.

(1) Reflectance (after heat treatment, 450 nm) The reflectance is the spectral reflectance of the measurement wavelength in the range of 1000 nm to 250 nm using a visible-ultraviolet spectrophotometer "V-570" manufactured by JASCO Corporation. Perform the measurement. Specifically, a value obtained by measuring the reflected light height of the sample with respect to the reflected light intensity of the reference mirror is referred to as "reflectance". The reflectance was measured for the latter of the heat treatment (post-annealing). Those having a reflectance at 450 nm of 75% or more were evaluated as good, and those having a reflectance of less than 75% were evaluated as bad.

(2) Contact resistance of Al alloy reflective film and oxide conductive film The Kelvin pattern shown in FIG. 2 was used for the evaluation of contact resistance. The Kelvin pattern is formed by forming the Al alloy reflection film, then laminating an In-Sn-O (Sn: 10 wt%) thin film (ITO film, film thickness: 10 nm) to form a wiring pattern, and then using it on its surface A plasma chemical vapor deposition (CVD) device forms a SiN film (film thickness: 200 nm) as a passivation film. The film formation conditions were substrate temperature: 280 ° C, gas ratio: SiH ₄ / NH ₃ / N ₂ = 125/6/185, pressure: 137 MPa, and RF power: 100 W. After the SiN film is patterned, a Mo film (film thickness: 100 nm) is formed on the surface by a sputtering method, and the Mo film is further patterned to obtain a Kelvin pattern in FIG. 2.

The method of measuring contact resistance is to make a Kelvin pattern (contact hole size: 10 μm square) as shown in FIG. 2 and perform a 4-terminal measurement (current is passed to an Al \ ITO-Mo alloy, and Al \ ITO-Mo is measured using another terminal) How to reduce the voltage between alloys). Specifically, I ₁ -I ₂ flows between the current I of FIG. 2 and monitor V ₁ -V between the voltage V _2, thereby _{[R = (V 1 -V 2} ) / I 2] is obtained connecting portion C's contact resistance R. A value in which the current was proportional to the voltage and the contact resistance was substantially fixed was set to “ohm” and evaluated as good (evaluation: ○). In addition, those in which the current was not proportional to the voltage were regarded as "non-ohmic" and evaluated as defective (evaluation: ×). In addition, as an example judged as “ohmic”, a graph showing the current-voltage characteristics of the reflective anode electrode of Test No. 6 of the example in FIG. 3A is shown, and as an example judged as “non-ohmic”, A graph showing the current-voltage characteristics of the reflective anode electrode of Test No. 2 of the example in FIG. 3B is shown.

(3) Resistivity of Al alloy reflective film The resistivity of the Al alloy reflective film itself was measured by a 4-terminal method using a Kelvin pattern. Those with a resistivity of 7.0 μΩ · cm or less were evaluated as good, and those with a resistivity exceeding 7.0 μΩ · cm were evaluated as bad.

(4) Heat resistance (presence or absence of hillocks) Heat resistance is judged by observing the surface of the reflective anode electrode after the heat treatment with an optical microscope (magnification: 1000 times). Specifically, those having less than 5 hillocks with a diameter of 1 μm or more in an arbitrary 140 μm × 100 μm region were judged to be “no hillocks” and evaluated as good. In addition, according to the same evaluation, a person having 5 or more hillocks was judged to have “hillocks”, and evaluated as bad.

The results are shown in Table 1.

[表 1] Table 1

In Table 1, Test No. 4 to Test No. 7 and Test No. 9 to Test No. 12 are examples, and Test No. 1 to Test No. 3 and Test No. 8 are comparative examples. In each of the examples using an Al alloy reflective film that satisfies the requirements of the present invention, good results were obtained in all the items of reflectance, contact resistance, resistivity, and heat resistance, and therefore, they were good as comprehensive evaluations (evaluation: ○) .

On the other hand, each comparative example does not satisfy certain requirements stipulated in the present invention, and does not satisfy the specific resistance of the reflective film or the performance of the contact resistance. Therefore, it is defective as a comprehensive evaluation (evaluation: ×). Specifically, for Test No. 1 to Test No. 3, the contact resistance was “evaluation ×”, and for Test No. 8, the resistivity of the reflective film was “poor”.

Next, regarding the test examples corresponding to the examples, in order to confirm that a Ge-rich layer and a precipitate containing Ge are formed at the contact interface between the Al alloy reflective film and the oxide conductive film, and to confirm the self-surface of the Al alloy reflective film The average Ge concentration within 50 nm and the average diameter of Ge-containing precipitates satisfy the requirements described above, and various analyses such as cross-section TEM and EDX analysis were performed.

As an example, an ITO film constituting an oxide conductive film (transparent conductive film) and Al-0.6Ni-0.5Cu-0.35La-1.0Ge (unit: atomic%) in Test No. 6 corresponding to the example will be shown. A cross-sectional TEM photograph (magnification: 300,000 times) of an example of a Ge-enriched layer formed at a contact interface of an alloy film (Al alloy reflective film) is shown in FIG. 4. In addition, the EDX semi-quantitative results of each point "1-1" to "1-5" in FIG. 4 (except for carbon C, the concentration of each element is at%) are shown in Table 2, and The results obtained by EDX analysis of the composition are shown in FIGS. 5A to 5E (the vertical axis in FIGS. 5A to 5E represents counts and the horizontal axis represents energy). [Table 2] Table 2 is a table showing the semi-quantitative results of Energy Dispersive X-ray (EDX) of Test No. 6 in the Examples (points indicate the points in the TEM photograph in FIG. 4).

In FIG. 4, a region from the interface between the oxide conductive film and the Al alloy reflective film to a depth of about 50 nm is a Ge-enriched layer. As shown in the results of Table 2, it was found that the Ge concentrations of points 1-1 and 1-2 belonging to the Ge-enriched layer were 2.7 at% and 3.0 at% (average of 2.85 at%). Points 1-3 to 1-5 of the area other than the thickened layer (the bulk portion of the Al alloy reflective film from the interface between the oxide conductive film and the Al alloy reflective film which is deeper than about 50 nm deep) Ge concentration ranges from 0.6 at% to 1.0 at% (average 0.8 at%). From the foregoing, it can be understood that the average Ge concentration within 50 nm from the surface of the Al alloy reflection film is more than twice the average Ge concentration in the Al alloy reflection film (2.85 / 0.8 = about 3.6 times).

Furthermore, from the results in Table 2, it can be understood that the O (oxygen) concentration at the point 1-1 near the contact interface between the oxide conductive film and the Al alloy reflection film is 41.9 at%, which is larger than the O concentration at other points. According to the above, it is suggested that a layer containing alumina as a main component at the contact interface of the Al alloy reflective film and the oxide conductive film at a few nanometers (nm) exists.

FIG. 6 is a diagram showing a result of a composition analysis in a depth direction from an oxide conductive film to an Al alloy reflection film in Test No. 6 by XPS (X-ray Photoelectron Spectroscopy) analysis. In the figure, the horizontal axis represents the sputtering depth (nm) in terms of SiO ₂ , and the vertical axis represents the atomic concentration (atomic%). The specific measurement method is as follows. First, a qualitative analysis using a wide-area wide-area photoelectron spectrum was performed using Quantera SXM, an X-ray photoelectron spectroscopic device manufactured by Physical Electronics. After that, etching was performed from the surface in the depth direction by Ar ⁺ sputtering, and the narrow-area photoelectron spectra of the constituent elements of the film and the elements detected on the outermost surface were measured at fixed depths. The composition distribution (atomic%) in the depth direction was calculated from the area-intensity ratio and the relative sensitivity coefficient of the narrow-area photoelectron spectrum obtained at each depth.

Measurement conditions · X-ray source: Al Kα (1486.6 eV) · X-ray output: 25 W · X-ray beam diameter: 100 μm · Photoelectron extraction angle: 45 ° · Device: Quantera SXM Ar ⁺ sputtering conditions · Incident energy: 1 keV • Grating: 2 mm × 2 mm • Sputtering speed: 1.83 nm / min (equivalent to SiO ₂ ) • The sputtering depth is set to the depth that is SiO ₂ equivalent.

In FIG. 6, since the In concentration is high up to a sputtering depth of about 5 nm, a region that is an oxide conductive film (ITO film) is hidden. In addition, at a sputtering depth of 5 nm to about 15 nm, the In concentration decreases, while the Al concentration increases, which is considered to be a region of a layer containing alumina as a main component. In addition, the area deeper than the sputtering depth of about 15 nm is an Al alloy reflective film, and the Ge concentration becomes higher at a sputtering depth of 15 nm to 20 nm. Therefore, the results of XPS analysis also implied that the Al alloy reflective film and the A Ge-concentrated layer and a Ge-containing precipitate are formed at the contact interface of the oxide conductive film. In addition, the sputtering depth in FIG. 6 and the actual thickness in the film direction of the laminated film of the oxide conductive film and the Al alloy reflection film are different because the sputtering depth is the SiO ₂ conversion depth and the sputtering cross section.

FIG. 7 is a plan SEM photograph (magnification: 30,000 times) showing Ge-containing precipitates formed at the contact interface between the Al-Ge-based alloy film and the oxide conductive film in Test No. 6. FIG. In addition, FIG. 7 shows the point 1-1 or the vicinity of the point 1-2 in FIG. 4. As shown in FIG. 7, Ge-containing precipitates having a diameter of 0.1 μm or more were confirmed in a region surrounded by a dotted line.

Based on the above, regarding Test No. 6, it was confirmed that a Ge-concentrated layer and a precipitate containing Ge were formed at the contact interface between the Al alloy reflective film and the oxide conductive film, and it was confirmed that the Al alloy reflective film was formed from the surface The average Ge concentration within 50 nm and the average diameter of the Ge-containing precipitates satisfy the requirements. In addition, in Examples other than Test No. 6, it was confirmed that the above requirements were satisfied in the same manner as the results of Test No. 6.

1‧‧‧ substrate

2‧‧‧TFT

3‧‧‧ passivation film

4‧‧‧ flattening layer

5‧‧‧ contact hole

6‧‧‧Al-Ge alloy film

7‧‧‧ oxide conductive film

8‧‧‧ organic light emitting layer

9‧‧‧ cathode electrode

FIG. 1 is a schematic diagram showing an organic EL display including a reflective anode electrode according to an embodiment of the present invention. FIG. 2 is a diagram showing a kelvin pattern used for measuring contact resistance between an Al alloy reflective film and an oxide conductive film. FIG. 3A is a graph showing the current-voltage characteristics of the reflective anode electrode of Test No. 6 in the example (an example in which conductivity can be ensured: Ohmic). FIG. 3B is a graph showing the current-voltage characteristics of the reflective anode electrode of Test No. 2 in the example (an example in which conduction cannot be ensured: non-ohmic). FIG. 4 shows the concentration of Ge formed at the contact interface between the ITO film constituting the oxide conductive film (transparent conductive film) and the Al-0.6Ni-0.5Cu-0.35La-1.0Ge (unit: atomic%) alloy film. A cross-section transmission electron microscope (TEM) photograph of an example of a layer (Test No. 6 of the example). FIG. 5A is a diagram showing a result obtained by performing an EDX analysis on the chemical composition of point 1-1 in FIG. 4. FIG. 5B is a diagram showing a result obtained by performing an EDX analysis on the chemical composition of points 1-2 in FIG. 4. FIG. 5C is a diagram showing a result obtained by performing EDX analysis on the chemical composition of points 1-3 in FIG. 4. FIG. 5D is a diagram showing a result obtained by performing EDX analysis on the chemical composition of points 1-4 in FIG. 4. FIG. 5E is a diagram showing a result obtained by performing EDX analysis on the chemical composition of points 1-5 in FIG. 4. FIG. 6 shows the composition analysis in the depth direction from the oxide conductive film to the Al alloy reflective film in Test No. 6 of the Example by X-ray Photoelectron Spectroscopy (XPS) analysis. Graph of the results. The horizontal axis in the figure represents the sputtering depth (nm), and the vertical axis represents the atomic concentration (atomic%). 7 is a plan scanning electron microscope (SEM) showing a Ge-containing precipitate formed at a contact interface between an Al-Ge-based alloy film and an oxide conductive film in Test No. 6 of the Example. photo.

Claims (8)

A reflective anode electrode for an organic electroluminescence display is a laminated structure including an Al-Ge-based alloy film and an oxide conductive film in contact with the Al-Ge-based alloy film. A reflective anode electrode for an organic electroluminescence display in which a layer containing alumina as a main component is interposed at a contact interface between the system-based alloy film and the oxide conductive film, and the Al-Ge-based alloy film contains 0.1 atomic% to 2.5 atomic% of Ge, and a Ge-concentrated layer and a Ge-containing precipitate are formed at a contact interface between the Al-Ge-based alloy film and the oxide conductive film, and the Al-Ge-based The average Ge concentration in the alloy film from the surface on the oxide conductive film side to 50 nm is twice or more the average Ge concentration in the Al-Ge-based alloy film, and the Ge-containing The average diameter of the objects is 0.1 μm or more. The reflective anode electrode for an organic electroluminescence display according to item 1 of the patent application scope, wherein the Al-Ge alloy film further contains 0.05 atomic% to 2.0 atomic% of Cu. The reflective anode electrode for an organic electroluminescence display according to item 1 of the scope of the patent application, wherein the Al-Ge-based alloy film further contains a rare earth element in an amount of 0.2 atomic% to 0.5 atomic%. The reflective anode electrode for an organic electroluminescence display according to item 1 of the scope of patent application, wherein the Al-Ge-based alloy film is electrically connected to a source electrode and a drain electrode of a thin film transistor. The reflective anode electrode for an organic electroluminescence display according to item 1 of the patent application scope, wherein the Al-Ge alloy film is formed by a sputtering method or a vacuum evaporation method. A thin-film transistor substrate includes: a reflective anode electrode for an organic electroluminescence display according to any one of claims 1 to 3 of a patent application scope. An organic electroluminescence display includes the thin-film transistor substrate according to item 6 of the patent application scope. A sputtering target, which is a sputtering target for forming the Al-Ge alloy film according to any one of claims 1 to 3, and is characterized in that it contains 0.1 atomic% -2.5 atomic% of Ge; or at least one of rare earth elements containing 0.1 atomic% to 2.5 atomic% of Ge, 0.05 atomic% to 2.0 atomic% of Cu, and 0.2 atomic% to 0.5 atomic% of Ge.