KR20140011854A - Multilayer transparent eletrode comprising mgzno alloy and method for preparing the same - Google Patents

Abstract

The present invention relates to a multilayer transparent electrode in which a MgZnO layer is formed on a metal layer and under the metal layer and a method for preparing the same. The multilayer transparent electrode according to the present invention is made of MgZnO, thereby being produced at lower production costs and having good flexibility. In addition, the multilayer transparent electrode of the present invention includes the MgZnO layer to have improved transmittance in near-UV while maintaining electrical properties such as sheet resistance or the like. In addition, according to the present invention, the adhesiveness of the metal layer can be improved by treating the MgZnO layer with an ion beam and the sheet resistance of the transparent electrode can be reduced by controlling the thickness of the metal layer.

Description

Multilayer transparent electrode including magnesium zinc oxide and method for preparing the same {Multilayer transparent eletrode comprising MgZnO alloy and Method for preparing the same}

The present invention relates to a multilayer transparent electrode comprising magnesium zinc oxide and a method of manufacturing the same, and more particularly, to a multilayer transparent electrode including magnesium zinc oxide formed by forming a magnesium zinc oxide layer above and below a metal layer and extending a transmission spectrum to an ultraviolet region. It relates to an electrode and a method of manufacturing the same.

Recently, due to the rapidly developing nanotechnology, information technology, and display technology, the information is entering the ubiquitous era where information can be accessed at any time and anywhere. Accordingly, the necessity of a mobile information electronic device that is portable and mobile is increasing. As an information device that realizes the ubiquitous era, the necessity of flexible information electronic devices that are free to be modified, flexible, and easy to carry is increasing.

Flexible information electronic devices such as flexible displays, flexible transistors, flexible touch panels, and flexible solar cells all use flexible transparent electrodes, represented by indium tin oxide (ITO), to control current or light. .

Currently, ITO, which is most commonly used as a transparent electrode, requires a high deposition temperature of 300 degrees or more because Sn increases the electron concentration through activation. However, in the case of flexible polymer substrates (PET, PEN, PAR, PES), it is difficult to process a temperature of 200 degrees or more, so that an ITO having an amorphous structure deposited at room temperature is deposited and used as a flexible electrode. However, amorphous ITO has a problem of exhibiting high sheet resistance at a very high defect density compared to crystalline ITO.

In the case of oxide materials such as ITO, cracks are easily formed at a thickness of 100 nm or more due to low resistance to bending or bending of the substrate, and there is a problem in manufacturing cost competitiveness due to the continuous increase in indium price, which is the main material of ITO thin film.

The present invention provides a multilayer transparent electrode having low sheet resistance even when deposited at room temperature.

The present invention is to provide a multi-layer transparent electrode which is cheaper than the ITO transparent electrode and excellent in flexible characteristics.

The present invention provides a multilayer transparent electrode capable of improving transmittance in the near-UV and blue wavelength bands.

One aspect of the invention, the lower oxide layer comprising a magnesium zinc oxide formed on the transparent substrate; A metal layer formed on the lower oxide layer; The present invention relates to a multilayer transparent electrode including an upper oxide layer including magnesium zinc oxide formed on the metal layer.

In another aspect, the present invention comprises the steps of forming a lower oxide layer comprising a magnesium zinc oxide formed on the upper surface of the transparent substrate; Forming a metal layer on the lower oxide layer; It relates to a method for manufacturing a multilayer transparent electrode comprising forming an upper oxide layer including magnesium zinc oxide on the metal layer.

The multilayer transparent electrode according to the present invention is formed of magnesium zinc oxide and has excellent manufacturing characteristics while having a low manufacturing cost. In addition, the transparent electrode of the present invention can include magnesium in the zinc oxide layer while maintaining the transmittance in the sheet resistance and visible light region and improve the transmittance in the near-UV.

In the present invention, the adhesion of the metal layer can be increased by ion beam treatment on the magnesium zinc oxide layer, and the sheet resistance can be reduced by controlling the thickness of the metal layer.

1 is a cross-sectional view showing a multilayer transparent electrode according to an embodiment of the present invention.
2 illustrates a method of forming a lower oxide layer including magnesium zinc oxide on a substrate.
Figure 3 shows the Mg content (x in the formula 1) in the magnesium zinc oxide to be formed according to the RF power ratio of MgZnO: ZnO.
Figure 4 shows the transmittance according to the wavelength of the lower MgZnO layer formed on a glass substrate with a thickness of 100nm.
5 shows the sheet resistance and carrier concentration of the multilayer transparent electrodes obtained according to the thickness of the silver layer.
6 shows an increase in transmittance with increasing Mg composition ratio in the obtained multilayer transparent electrode.
7 shows the surface roughness of the upper oxide layer according to the Mg composition.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention can be achieved by the following description with reference to the accompanying drawings. It is to be understood that the following description describes preferred embodiments of the invention, and the invention is not necessarily limited thereto. In addition, the accompanying drawings may be exaggeratedly expressed relative to the actual layer thickness (or height) or the ratio with respect to other layers in order to facilitate understanding, and the meaning thereof may be properly understood in view of the specific purpose of the related description to be described later .

The lamination structure referred to in the present specification should be understood in an exemplary sense, and the present invention is not limited to such a specific lamination structure.

As used herein, the terms "on" or "on" may be used to refer to the relative position concept, as well as where other elements or layers are directly present in the stated layer, It should be understood that the layer (interlayer) or component may be interposed or present, and also includes the case where the surface of the layer mentioned above (particularly the surface having a three-dimensional shape) is not completely covered, . Thus, unless otherwise used, the expression "directly" may be understood as a relative concept as described above. Similarly, the expression "underneath", "underneath" or "underneath" may also be understood as a relative concept of the position between a particular layer (element) and another layer (element).

1 is a cross-sectional view showing a multilayer transparent electrode according to an embodiment of the present invention. Referring to FIG. 1, the multilayer transparent electrode of the present invention includes a lower oxide layer 20, a metal layer 30, and an upper oxide layer 40 on a substrate 10.

Here, the substrate 10 is a base substrate for supporting the transparent electrode, and a transparent substrate such as a glass substrate or a sapphire substrate, which is not flexible, is used, or polyethylene naphthalate (PEN), polyethylene terephthalate (PET), or polycarbonate (PC). , Polyethylene sulfone (PES), polyimide (PI), polyarylate (PAR), polycyclic olefin (PCO), polymethyl methacrylate (PMMA), crosslinking type epoxy, crosslinking urethane film Flexible transparent substrates such as crosslinking type urethane may be used. Preferably, a flexible transparent substrate can be used as the base substrate.

The lower oxide layer 20 or the upper oxide layer 40 may be formed of magnesium zinc oxide or may be a magnesium zinc oxide (MgZnO) layer. In the present invention, the addition of other doping materials or metal components to the magnesium zinc oxide (MgZnO) layer is not excluded. For example, magnesium zinc oxide can be doped with group III elements such as Ga, Al, and In.

The magnesium zinc oxide may be represented by the following formula (1).

[Formula 1]

Mg _x Zn _{1 - x} O

X is 0.001-0.46, Preferably it is 0.01-0.3.

Magnesium zinc oxide of the formula (1) is not doped with magnesium oxide zinc, preferably, an alloy of a uniform composition of magnesium and zinc. The composition ratio of Mg in the MgZnO alloy may be in the range of 0.001 to 0.46, preferably 0.01 to 0.3 with respect to Zn. In the room temperature co-sputtering process, Mg may contain up to 46% (0.46) and have a ZnO crystal structure. When the composition of Mg exceeds 46%, phase separation may occur with ZnO (wurtzite structure) and MgO (rock salt structure). Conventionally, zinc oxide (ZnO) is doped with halogen elements, such as group III cationic metal elements such as aluminum (Al), gallium (Ga), indium (In), and boron (B), or fluorine (F). In addition, zinc oxide doped with aluminum has a difficulty in securing a large transmittance region due to increased absorption in a region similar to a bandgap of blue (450 nm) or more, that is, 3eV or more.

The MgZnO layer of the present invention can control the content of Mg to reduce the light absorption from the wavelength region of blue or more to the ultraviolet region, thereby increasing the transmittance. In general, as the Mg content increases in the MgZnO, the band gap increases.

The magnesium zinc oxide layer may have a thickness of 10 to 100nm. In the thickness range, the transmittance is excellent, and when it exceeds 100 nm, bending characteristics may be degraded.

 The metal layer includes a single element such as gold (Au), silver (Ag), copper (Cu), aluminum (Al), platinum (Pt), and the like, and an gold alloy, a silver alloy, a copper alloy ( Alloys such as Cu alloys, Al alloys, and the like may be used, and silver may be preferably used.

Since the multilayer transparent electrode of the present invention is inserted at a room temperature by inserting a very thin metal layer having a level of light transmission between the magnesium zinc oxide layers, low sheet resistance can be obtained and high transmittance can be realized through the surface plasmon phenomenon. In addition, the thickness of the upper oxide layer or the lower oxide layer can be reduced by the insertion of the metal layer.

The metal layer, in particular, the thickness of the silver (Ag) layer may be 6 ~ 20nm, preferably 8 ~ 16nm. If the thickness of the silver layer is less than 6 nm, it has an island structure and shows low electrical properties. However, if the thickness of the silver layer is more than 6 nm, the film structure has a continuous thin film structure, resulting in an increase in sheet carrier concentration. . Since the skip depth for the metal layer of light is 20 nm, it is desirable to keep it below.

In another aspect, the present invention provides a method for forming a lower oxide layer including magnesium zinc oxide on a substrate; Forming a metal layer on the lower oxide layer; It relates to a method for manufacturing a multilayer transparent electrode comprising forming an upper oxide layer including magnesium zinc oxide on the metal layer.

The upper oxide layer or the lower oxide layer may be a magnesium zinc oxide layer. The method of forming the magnesium zinc oxide layer is a sputtering method, chemical vapor deposition (CVD), thermal evaporation (thermal evaporation), ion beam (e-beam) deposition, spray pyrolysis (spray pyrosis) ), A sol-gel process and the like can be used, and preferably a sputtering method is used.

The forming of the upper oxide layer or the lower oxide layer may control the content of magnesium using a magnesium zinc oxide target and a zinc oxide target. Magnesium zinc oxide layer constituting the upper oxide layer or the lower oxide layer is the same as the formula (1) described above.

[Formula 1]

Mg _x Zn _{1 - x} O

X is 0.001-0.46, Preferably it is 0.01-0.3.

2 illustrates a method of forming a lower oxide layer including magnesium zinc oxide on a substrate. Referring to FIG. 2, a magnesium zinc oxide (MgZnO) target 110 and a zinc oxide (ZnO) target 120 to be deposited on the transparent substrate 10 are disposed in the sputter chamber, and are disposed on an upper surface of the support 200. There is a substrate 10. In the present invention, the Mg content in the magnesium zinc oxide deposited by the RF power control of each target is changed.

3 shows Mg content (x in Formula 1) in magnesium zinc oxide which is formed according to the RF power ratio of MgZnO: ZnO. In FIG. 3, the thickness of the magnesium zinc oxide layer is 100 nm. Referring to FIG. 3, it can be seen that the Mg content may be controlled using the RF power ratio (MgZnO / ZnO) in a linear relationship with the RF power ratio (MgZnO / ZnO) and Mg content.

The method includes forming a metal layer on the lower oxide layer. The metal layer may be formed using a sputtering method, chemical vapor deposition (CVD), thermal evaporation, ion beam evaporation, spray pyrosis, or the like. Can be.

The method may deposit the metal layer after performing an ion beam treatment on the upper oxide layer. As the ion beam, an electron beam, a charged particle beam, or a proton beam may be used. Argon or xenon ions can be irradiated to the metal oxide layer through an ion beam accelerator, and the energy of the ions is preferably 100 eV to 1 keV. When low energy ions enter the surface of the lower oxide layer, only mono or two layers can be selectively treated without penetrating the substrate-lower oxide layer. This ion beam treatment can remove contaminants on the surface while minimizing damage to the underlying oxide layer and increase adhesion to the metal layer.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited only to these examples.

Example  One

Argon gas was injected at 50 sccm while a glass substrate was placed in the sputter chamber to maintain the pressure in the chamber at 2.5 × 10 ⁻⁶ Torr. 50nm, Each formed at 100 nm. At this time, the substrate temperature was maintained at room temperature.

Subsequently, argon ions were irradiated to the lower metal oxide layer of 50 nm through a gridless end-hall type ion source, where ion energy was 100 eV to 1 keV. Next, the thickness of the silver layer was formed in the lower metal oxide layer at 0, 4, 8, 12, and 16 nm, respectively. The silver layer was deposited using an electron beam evaporator and the deposition rate of the silver layer was 2.6 A / s. After forming the silver layer, the upper metal oxide layer was formed to a thickness of 50 nm under the same process conditions as the lower metal oxide layer to obtain a multilayer transparent electrode.

4 shows the transmittance according to the wavelength of the lower MgZnO layer formed on a glass substrate 100nm thick, Table 1 shows the bandgap for the RF power ratio of the lower MgZnO layer.

RF power ratio (ZnO / MgZnO) 45W: 0W 45W: 25W 40W: 45W 25W: 45W Band gap 3.24 3.40 3.62 3.80

Referring to Table 1 and FIG. 4, as the power ratio for the MgZnO target increases (increasing Mg content), the bandgap also increases from 3.24 to 3.8, and accordingly, the transmission wavelength band may be expanded to Near-UV.

5 shows the sheet resistance and carrier concentration of the multilayer transparent electrodes obtained according to the thickness of the silver layer. Referring to FIG. 5, it can be seen that when the thickness of the silver layer is 8 nm or more, the continuous barrier becomes lower and the sheet resistance decreases as the potential barrier decreases, and the carrier concentration increases as the thickness of the silver layer becomes thicker.

6 shows an increase in transmittance with increasing Mg composition ratio in the obtained multilayer transparent electrode, and Table 2 shows sheet resistance, charge mobility, and transmittance (550 nm wavelength band) according to the Mg composition ratio.

Mg composition 0 0.08 0.19 0.28 Sheet resistance (Ω / sq) 6.35 6.31 7.09 6.36 Mobility (㎠ / Vs) 9.51 12.6 11 12.7 Transmittance (%) (550nm) 93.8 95.3 94.8 94.2

Referring to Table 2, the sheet resistance, mobility, and transmittance in the 550 nm wavelength band according to the Mg composition does not change significantly. Referring to FIG. 6, the transmission spectrum is expanded to Near-UV as the Mg composition ratio increases.

7 shows the surface roughness of the upper oxide layer according to the Mg composition. Referring to FIG. 7, the Rrms decreases as the Mg composition increases. It has a wurtzite structure in the case of ZnO and its surface roughness is higher than that of horizontal growth, so the surface roughness is high. However, when Mg is used, MgO having a rock slat structure is formed. have. In the case of an organic device, the smaller the surface roughness, the higher the device efficiency and stability can be.

Hereinafter, specific embodiments of the present invention have been described. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the appended claims. The scope of the present invention is defined by the appended claims rather than by the foregoing description, and all differences within the scope of equivalents thereof should be construed as being included in the present invention.

10: substrate 20: lower oxide layer
30: metal layer 40: upper oxide layer

Claims (9)

A lower oxide layer comprising magnesium zinc oxide formed on the substrate;
A metal layer formed on the lower oxide layer;
And a top oxide layer comprising magnesium zinc oxide formed on the metal layer. The multilayer transparent electrode of claim 1, wherein the magnesium zinc oxide is represented by the following Chemical Formula 1.
[Chemical Formula 1]
Mg _x Zn _{1 - x} O
Where x is from 0.001 to 0.46. The multilayer transparent electrode of claim 1, wherein the upper oxide layer or the lower oxide layer has a thickness of about 10 nm to about 100 nm. The method of claim 1, wherein the metal layer is gold (Au), silver (Ag), copper (Cu), aluminum (Al), platinum (Pt), gold alloy (Au alloy), silver alloy (Ag alloy), copper alloy (Cu alloy), a multi-layer transparent electrode, characterized in that at least one selected from the group of aluminum alloy (Al alloy). The multilayer transparent electrode of claim 1, wherein the metal layer has a thickness of 6 to 20 nm. Forming a lower oxide layer including magnesium zinc oxide on the substrate;
Forming a metal layer on the lower oxide layer;
And forming an upper oxide layer including magnesium zinc oxide on the metal layer. The method of claim 1, wherein the method comprises forming an upper oxide layer, a lower oxide layer, or a metal layer by a sputtering process. The method of claim 1, wherein the forming of the upper oxide layer or the lower oxide layer is performed by controlling magnesium content by using a magnesium zinc oxide target and a zinc oxide target. The method of claim 1, wherein the method deposits a metal layer after performing ion beam treatment on the upper oxide layer.

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