KR20020082637A - Metal electrode for light emitting diodes using n-ZnO group semiconductor and manufacturing method thereof - Google Patents

Abstract

PURPOSE: A metal electrode for an LED(Light Emitting Diode) using an n-type ZnO and a method for manufacturing the same are provided to easily form an excellent ohmic contact by using transition metals having melting point of high temperature. CONSTITUTION: A light emitting diode(100) comprises an alumina(Al2O3) substrate(110), an n-type zinc oxide(ZnO) semiconductor(120) formed on the alumina substrate(110), and a metal electrode(130) formed on the ZnO semiconductor(120). The metal electrode(130) is composed of transition metals having a melting point of high temperature. Preferably, the transition metal is one selected from groups composing of Ru, Hf, Ir, Mo, Re, W, V, Pt, Pd and Ta. Also, the melting point of the transition metal is about 1500-3500°C.

Description

Metal electrode for light emitting diode using n-type zinc oxide-based semiconductor and method for manufacturing thereof {Metal electrode for light emitting diodes using n-ZnO group semiconductor and manufacturing method}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal electrode for a light emitting diode using an n-type zinc oxide-based semiconductor, and a method for manufacturing the same. In particular, a high quality ohmic contact formed at a high temperature using a metal having a high melting point is formed. The present invention relates to a metal electrode used in a light emitting diode using a zinc oxide semiconductor and a method of manufacturing the same.

Background Art Conventionally, zinc oxide-based semiconductors have been used in the field of optical devices such as transparent electrodes, window materials of solar cells, and varistors. In addition, due to the wide bandgap of zinc oxide, it has been spotlighted as a substitute material for gallium nitride (GaN) semiconductors used in optical devices such as light emitting diodes and laser diodes.

Recently, Ohota, Japan, published a paper on the fabrication of pn-type heterojunction UV Light Emitting Diode using p-SrCu ₂ O ₂ and n-ZnO in the Applied Physics Letters 77, 475, 2000. By releasing the study, research on optical devices using zinc oxide has been accelerated. In order to realize optical devices such as light emitting diodes (LEDs) and laser diodes (LDs) emitting blue / green and ultraviolet rays using these zinc oxide-based semiconductors, a high-quality ohmic between semiconductors and metals is required. A contact must be formed.

Recently, in order to overcome the deterioration of ohmic contact characteristics in n-type zinc oxide-based semiconductors, several metal electrodes have been used as a diffusion barrier to suppress outdiffusion of zinc (Zn) between the reaction layer and the injection layer. Satisfactory effects were not achieved at high temperatures above 300 ° C.

Therefore, the development of a stable ohmic contact method at a high temperature is urgently required, but studies on this are still insufficient.

Accordingly, a technical object of the present invention is to manufacture a metal electrode for a light emitting diode using an n-type zinc oxide-based semiconductor that forms an excellent ohmic contact thermally, electrically and structurally at a high temperature by using a transition metal having a high melting point. To provide a way.

1 is a schematic diagram illustrating a metal electrode used in a light emitting diode using an n-type zinc oxide-based semiconductor according to the present invention; And

2 to 5 are graphs and photographs showing the characteristics of the metal electrode according to the present invention.

A metal electrode for a light emitting diode using an n-type zinc oxide-based semiconductor according to an embodiment of the present invention for achieving the above technical problem, at least one selected from a transition metal having a melting point of 1500 ℃ to 3500 ℃ or the transition metal It is characterized by consisting of an alloy comprising a.

At this time, the transition metal may be made of Ru, Hf, Ir, Mo, Re, W, V, Pt, Pd or Ta.

According to another aspect of the present invention for achieving the above technical problem, a metal electrode for a light emitting diode using an n-type zinc oxide-based semiconductor is formed of In or an In compound.

In this case, the In compound may be made of InSn, InZn, InMg, or InGa.

In each example of the present invention for achieving the above technical problem, the metal electrode may have a thickness of 1 to 1,000 nm.

Method of manufacturing a metal electrode for a light emitting diode using an n-type zinc oxide-based semiconductor according to an embodiment of the present invention for achieving the above technical problem, selected from the transition metal having a melting point of 1500 ℃ to 3500 ℃ or the transition metal It is characterized by forming an alloy comprising at least one by evaporation or sputtering.

At this time, the transition metal may be made of Ru, Hf, Ir, Mo, Re, W, V, Pt, Pd or Ta.

According to another aspect of the present invention, there is provided a method of fabricating a metal electrode for a light emitting diode using an n-type zinc oxide-based semiconductor, comprising evaporating or spreading an In or In compound on the n-type zinc oxide-based semiconductor. It is characterized by forming by evaporation by the terring method.

In this case, the In compound may be formed of InSn, InZn, InMg, or InGa.

In each example of the present invention for achieving the technical problem may further comprise the step of heat treatment under an oxygen, nitrogen, or argon atmosphere after forming the metal electrode, the heat treatment at a temperature of 100 ℃ to 1200 ℃ It may be made for 1 second to 3 hours.

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention will be described in detail.

1 is a schematic diagram illustrating a metal electrode used in a light emitting diode using an n-type zinc oxide-based semiconductor according to the present invention.

Referring to FIG. 1, the light emitting diode 100 is formed on an n-type zinc oxide-based semiconductor 120 and an n-type zinc oxide-based semiconductor 120 formed on an aluminum oxide substrate (Al ₂ O ₃ ) 110. Melting point is made of a metal electrode 130 made of a transition metal of 1500 ~ 3500 ℃.

At this time, the metal electrode 130 has a melting point of 1500-3500 ° C. among the transition metals Ru (rusenium), Hf (hafnium), Ir (iridium), Mo (molybdenum), Re (renium), W (tungsten) , Metals such as V (vanadium), Pt (platinum), Pd (paradium) or Ta (tantalum), and alloys containing at least one selected from them. It is better to respond well. The metal electrode may be made of In or an In compound.

Hereinafter, a method of manufacturing a metal electrode for a light emitting diode using a zinc oxide semiconductor according to the present invention will be described.

Example 1

First, the n-type zinc oxide (ZnO) semiconductor formed on the substrate is surface-washed with trichloroethylene, acetone, methanol and distilled water at 50 ° C. for 5 minutes in an ultrasonic bath. The surface-washed n-type zinc oxide semiconductor was hard baked at 100 ° C. for 10 minutes to remove residual water, and then spin coated with a photoresist at 5,500 rpm on the n-type zinc oxide semiconductor. coating).

Next, the zinc oxide semiconductor coated with the photoresist is soft baked at 85 ° C. for 15 minutes, and a mask for developing the pattern is placed on the zinc oxide semiconductor. After irradiating UV light with 22.8 mW intensity on the mask for 15 seconds, the zinc oxide semiconductor is immersed for 25 seconds in a solution in which the ratio of developer and distilled water is 1: 4.

Then, the contaminated layer on the zinc oxide semiconductor is removed by immersing the patterned zinc oxide semiconductor in a solution having a HCl: H ₂ O ratio of 1: 1 for 1 minute.

Subsequently, a Ru component metal electrode is formed to a thickness of 500 kPa on the zinc oxide semiconductor by an evaporation method using an electron-beam evaporator.

Subsequently, a lift-off process is performed using acetone to produce a light emitting diode having a metal electrode with ohmic contact.

In general, the thermal electron emission (Thermionic emission) is taking place in less than the doping concentration of 10 ¹⁷ cm ^-3, thermionic field emission (Thermionic emission field) takes place in a doping concentration ^{10 17 cm -3 ~10 18 cm -3} , a field emission (Field emission) takes place at a doping concentration of 10 ¹⁸ cm ⁻³ . Therefore, at the doping concentration lower than 10 ¹⁷ cm ^-3 , the carrier flows over the contact barrier between the metal and the semiconductor.However, when the doping concentration increases and becomes more than 10 ¹⁷ cm ^-3 , regardless of the contact barrier between the metal and the semiconductor The carrier flows by tunneling. Therefore, when forming a stable ohmic contact even at high temperature with Ru metal as in Example 1, the doping concentration of the n-type zinc oxide semiconductor should be 10 ¹⁷ cm ^-3 or more.

Example 2

In order to further improve the ohmic contact of the metal electrode formed by [Example 1], the light emitting diode according to Example 1 was charged in a rapid thermal annealing (RTA), and was heated at 500 ° C. under nitrogen atmosphere at 60 ° C. Heat treatment for seconds.

Example 3

In order to further improve the ohmic contact of the metal electrode formed by [Example 1], the light emitting diode according to Example 1 was charged into a rapid heating furnace and heat-treated at 700 ° C. for 60 seconds under a nitrogen atmosphere.

Hereinafter, the ohmic contact characteristics of the embodiments according to the present invention will be described with reference to the accompanying drawings.

Figure 2 is a graph showing the specific contact resistance of the metal electrode according to the present invention, Figure 2 (1) is the case of Example 1, Figure 2 (2) is the case of Example 2, (3) is the case by Example 3.

3 is an atomic force microscope (AFM) to observe the surface state of the metal electrode according to the invention, Figure 3 (1) is the case of Example 1, Figure 3 (2) is an embodiment 2 is a case where FIG. 3 (3) shows a case by Example 3. FIG.

Comparative Example 1

2 and 3, the ohmic contact characteristics, in particular, the specific contact resistance and the surface state according to the embodiments of the present invention will be described.

Referring to Figs. 2 (1) and 3 (1), in the case of Example 1 described above, the specific contact resistance value is as low as 2.1 × 10 ⁻³ ohm-cm 2 as shown in the graph of Fig. 2 (1). The surface state of the Ru metal electrode is very flat as shown in (1) of FIG. 3, and the root mean square (RMS) roughness has a low value of 9 μs.

Referring to Figs. 2 (2) and 3 (2), in the case of Example 2 described above, 2.5 × 10 ^{−4, which} is lower than in the case of Fig. 2 (1), that is, in the case of Example 1, by heat treatment. The specific contact resistance of ohm-cm 2 was shown, and the surface state was uniform as in (2) of FIG. 3, and the RMS roughness was 11 Å, showing no significant difference from that of (1) of FIG.

Referring to Figs. 2 (3) and 3 (3), in the case of Example 3 described above, as shown in the graph of Fig. 2 (3), the specific contact resistance is much lower, such as 5 × 10 ⁻⁵ ohm-cm 2. In terms of values, the surface state also shows a flat surface as shown in Fig. 3 (3), and the RMS roughness shows a low value of 14 dB.

Therefore, the metal electrode using Ru according to an embodiment of the present invention, it is seen that the low specific contact resistance and flat surface required for manufacturing the light emitting diode is formed even in the case of rapid heat treatment as in Example 2 and Example 3 Can be.

4 is an Auger depth profile for the stability of the metal electrode using the zinc oxide semiconductor according to the present invention, Figure 1 (1) is the case of Example 1, Figure 4 (2) is This is the case according to the second embodiment, and Fig. 4 (3) is the case according to the third embodiment. The Auger Depth Analysis Table shows the external diffusion of zinc ions present in the n-type zinc oxide based semiconductor, the external diffusion of oxygen present in the n-type zinc oxide based semiconductor, and the internal diffusion of Ru ions.

Comparative Example 2

Referring to FIG. 4, the safety of the metal electrode according to each embodiment of the present invention will be described.

Referring to FIG. 4 (1), in the case of Example 1, a metal electrode in a stable state is maintained without diffusion reaction such as external diffusion of zinc ions and internal diffusion of Ru ions present in the zinc oxide semiconductor. This stable metal electrode maintains a flat metal electrode surface as shown in FIG.

Referring to Fig. 4 (2), in the case of Example 2, there is no tendency of external diffusion of zinc ions or internal diffusion of Ru ions present in the zinc oxide semiconductor. This indicates that the Ru ohmic contact can be maintained in a stable state even at a high temperature of 500 ° C.

Referring to Fig. 4 (3), it can be seen that in the case of Example 3, external diffusion of oxygen occurs from the zinc oxide semiconductor. This external diffusion of oxygen forms a RuO ₂ conductive interface through the reaction with the Ru metal electrode, which acts as a diffusion barrier to the external diffusion of zinc. In addition, oxygen external diffusion from the zinc oxide semiconductor leaves oxygen vacancies on the surface of the zinc oxide semiconductor, which acts as a dopant and increases the carrier concentration.

5 is a graph showing the results of the analysis of the glancing angle x-ray diffraction (GXRD) GXRD to see the characteristics of the metal electrode according to the present invention, 5 (1) is the case according to Example 1 5 is the case by Example 3. FIG.

Comparative Example 3

5, the components of the characteristics of the metal electrode according to the exemplary embodiments of the present invention will be compared and described.

Referring to (1) of FIG. 5, the peak intensity of only Ru metal is shown in Example 1, which indicates that the reaction between the metal electrode and the zinc oxide semiconductor did not occur at room temperature.

Referring to FIG. 5 (2), the peak intensity of the RuO ₂ crystal formed due to the external diffusion of oxygen in the case of Example 3 is shown. The RuO ₂ crystals formed by rapid thermal treatment thus serve as diffusion barriers and conductive layers.

As described in Comparative Example 1 and Comparative Example 3 described above, when the ohmic contact is formed by performing the rapid heat treatment according to the present invention, there are advantages as follows.

First, in the case of heat-treating the light emitting diode using the n-type zinc oxide-based semiconductor, it has a lower specific contact resistance than that of the non-heat treatment and keeps the surface of the metal electrode flat to form stable high quality ohmic contact.

Second, at the interface between the n-type zinc oxide-based semiconductor and the metal electrode, an oxide layer is formed by the reaction of oxygen of the n-type zinc oxide-based semiconductor with the metal at the metal electrode. The oxide layer thus formed facilitates carrier injection and serves as a metallic conductive layer. In addition, at high temperatures, zinc in the zinc oxide-based semiconductor diffuses to form zinc vacancies, where the oxide layer prevents the zinc vacancies from acting as an acceptor on the semiconductor surface. It will play the role of.

As described above, Ru has a low work function (4.71 eV) and a high melting point (2334 ° C.) to form stable ohmic contact at high temperature, and simultaneously exhibit the characteristics of the conductive layer and the diffusion barrier.

Embodiments and comparative examples of the present invention described above have been described using Ru as an example, but are not necessarily limited thereto. For example, when using V, In, InSn, InZn, InMg, InGa, etc. among In compounds or transition metals having a melting point of 1500 ° C to 3500 ° C, the conductive layer may be It is easy to form, and Ta, W and Ta-Ru easily form diffusion barriers.

The light emitting diode metal electrode using the n-type zinc oxide-based semiconductor according to the present invention has been spotlighted as the next-generation blue light emitting material by providing a basic step for commercializing high-temperature devices by maintaining a low contact resistance and a flat metal electrode surface even at high temperatures. It can be used in the development of light emitting devices and laser diodes of zinc oxide semiconductors.

In particular, since the oxide layer stable at high temperature formed by the interfacial reaction accompanying high temperature heat treatment is used as the conductive layer and the diffusion barrier, the process of additionally depositing the conductive layer or the diffusion barrier during the manufacture of the light emitting diode can be reduced. It is expected to accelerate the commercialization of semiconductors.

The present invention is not limited to the above embodiments, and it is apparent that many modifications are possible by those skilled in the art within the technical spirit of the present invention.

Claims (11)

A metal electrode for light emitting diodes using n-type zinc oxide-based semiconductors, comprising a transition metal having a melting point of 1500 ° C. to 3500 ° C. or an alloy containing at least one selected from the transition metals. The metal electrode for a light emitting diode using an n-type zinc oxide-based semiconductor according to claim 1, wherein the transition metal is Ru, Hf, Ir, Mo, Re, W, V, Pt, Pd or Ta. Light emitting diode metal electrode using an n-type zinc oxide-based semiconductor, characterized in that consisting of In or In compound. The metal electrode of claim 3, wherein the In compound is InSn, InZn, InMg, or InGa. The metal electrode for light emitting diode according to any one of claims 1 to 4, wherein the thickness is 1 to 1,000 nm. In the method of manufacturing a metal electrode for a light emitting diode using an n-type zinc oxide-based semiconductor, the metal electrode is a transition metal having a melting point of 1500 ℃ to 3500 ℃ on the n-type zinc oxide-based semiconductor or from the transition metal A method of manufacturing a metal electrode for a light emitting diode using an n-type zinc oxide-based semiconductor, characterized in that formed by depositing an alloy containing at least one selected by evaporation or spreading method. 7. The method of claim 6, wherein the transition metal is Ru, Hf, Ir, Mo, Re, W, V, Pt, Pd or Ta. . A method of manufacturing a metal electrode for a light emitting diode using an n-type zinc oxide-based semiconductor, wherein the metal electrode is formed by depositing an In or In compound on the n-type zinc oxide-based semiconductor by evaporation or sputtering. The manufacturing method of the metal electrode for light emitting diodes which uses the n-type zinc-oxide type semiconductor. 9. The method of claim 8, wherein the In compound is InSn, InZn, InMg or InGa. 9. The metal electrode for light emitting diode according to claim 6 or 8, further comprising the step of forming the metal electrode and then performing heat treatment under an oxygen, nitrogen, or argon atmosphere. Manufacturing method. The method of claim 10, wherein the heat treatment is performed at a temperature of 100 ° C. to 1200 ° C. for 1 second to 3 hours.