KR20040043245A - Structure of electrode for GaN-based semiconductor - Google Patents

Abstract

PURPOSE: A structure of GaN compound semiconductor electrode is provided to restrain the surface reaction between a GaN compound semiconductor layer and a metal layer and prevent the mutual reaction between metal layers used as electrodes by additionally forming an inter-diffusion barrier between a contact layer and an electrode layer. CONSTITUTION: A structure of GaN compound semiconductor electrode is provided with a GaN compound semiconductor layer(11), a contact layer(12) formed on the GaN compound semiconductor layer, and an inter-diffusion barrier(13) formed on the contact layer. The GaN compound semiconductor electrode structure further includes an electrode layer(14) formed on the inter-diffusion barrier. Preferably, the inter-diffusion barrier is formed on a P type GaN compound semiconductor layer. Preferably, the inter-diffusion barrier is a multilayer metal. At this time, the multilayer metal is completed by sequentially depositing a Mo/W/Mo layer.

Description

Structure of electrode for GaN-based semiconductor

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the construction of electrodes of gallium nitride (GaN) compound semiconductors. In particular, gallium nitride (GaN) compounds in which an intermediate diffusion barrier is formed between the semiconductor contact layer and the electrode layer to realize a thermally and electrically stable ohmic electrode It relates to the electrode configuration of a semiconductor.

A gallium nitride (GaN) compound semiconductor is a light emitting diode (LED) capable of realizing blue light, and its use is increasing rapidly in recent years. In order to realize more high-brightness light and stable light, many researches have been conducted on the configuration of the electrode.

1 is a diagram illustrating a laminated structure of a conventional gallium nitride (GaN) compound semiconductor.

Referring to FIG. 1, a gallium nitride (GaN) compound semiconductor (GaN) layer 1, a contact layer 2 formed on an upper surface of the gallium nitride (GaN) compound semiconductor layer, and the contact layer 2 The electrode layer 3 is further formed on the upper surface. Furthermore, the contact layer 2 is made of gold (Au) as the main component, and the electrode layer 3 is made of nickel (Ni) as the main component.

In addition, in the conventional gallium nitride (GaN) compound semiconductor, after the multilayer structure is laminated, heat treatment is generally performed to find an appropriate ohmic condition of the electrode. However, in this heat treatment step, deterioration of the electrode occurs due to mutual diffusion between unwanted components at the interface between the metal used as the electrode and the gallium nitride (GaN) compound semiconductor. In addition, such degeneration of the electrode acts as a cause of increasing the leakage current during the operation of the device for a long time has a large impact on the reliability of the semiconductor device.

Such a reaction of the metal-semiconductor interface will be described again with reference to the reaction mechanism. During the heat treatment, high heat is applied to the gallium nitride (GaN) compound semiconductor and the metal, and the heat causes a constant reaction to each other. In particular, this reaction occurs in the direction of reducing the energy of the interface energy, at which time the energy has a negative activation energy. This negative energy is also due to the difference in the different ionization energies of the metal and the semiconductor.

As a result, by reducing the difference in ionization energy between the two to absorb such negative energy, it is possible to form the electrode structure of the gallium nitride (GaN) compound semiconductor that is stable at the interface between the metal and the semiconductor.

The present invention proposes an electrode structure of a gallium nitride (GaN) compound semiconductor capable of suppressing an interfacial reaction between a gallium nitride (GaN) compound semiconductor and a metal layer in contact with the semiconductor and suppressing mutual reaction between metal layers used as electrodes. For the purpose of

In particular, an object of the present invention is to propose a configuration of an ohmic electrode in which a gallium nitride (GaN) compound semiconductor can be thermally and electrically operated stably.

BRIEF DESCRIPTION OF THE DRAWINGS The figure explaining the laminated structure of the conventional gallium nitride compound semiconductor.

2 is a view for explaining a laminated structure of a gallium nitride (GaN) compound semiconductor according to the present invention.

Figure 3 is a diagram showing the measurement of the specific contact resistance according to the passage of the heat treatment time by the C-TLM method and the comparative example of the present invention.

<Explanation of symbols for the main parts of the drawings>

1, 11: gallium nitride (GaN) compound semiconductor

2, 12: contact layer

3, 14 electrode layer

13: intermediate diffusion barrier layer

The electrode structure of the gallium nitride (GaN) compound semiconductor according to the present invention for achieving the above object is a contact layer formed on the upper side of the gallium nitride (GaN) compound semiconductor, and the intermediate diffusion barrier formed on the upper surface of the contact layer And an electrode layer formed on the upper surface of the intermediate diffusion barrier layer.

According to another aspect of the present invention, a tungsten (W) tungsten layer is used to control an interfacial reaction and ionization energy between a metal and gallium nitride semiconductor between a contact layer on an upper surface of a gallium nitride (GaN) compound semiconductor layer and an upper electrode. It consists of a single layer of Mo (molybdenum), Metal-Si (silicon), Metal-N (nitrogen), Cr (chromium), Pt (platinum), Ti (titanium), Ru (rucenium), or a combination of two or more layers. Heat-treated intermediate diffusion barrier layer is characterized in that it is further formed.

As described above, the interaction between the metal layers and the unwanted interaction between the metal layer and the semiconductor layer can be suppressed, and thus, a stable ohmic electrode of a gallium nitride (GaN) compound semiconductor can be realized.

The present invention proposes an intermediate diffusion barrier capable of selectively adjusting the interfacial reaction between a gallium nitride (GaN) compound semiconductor layer and a metal layer in contact with the gallium nitride semiconductor layer. Specifically, the reaction between the metal-Ga and the metal-N occurs at the interface between the gallium nitride (GaN) compound semiconductor layer and the metal layer, which provides an intermediate diffusion barrier that may contribute to the selective adjustment of the reaction.

For example, in the case of the p-type electrode, the reaction of Metal-Ga should occur stably and the reaction of Metal-N should be suppressed. It is to further form an intermediate diffusion barrier having a positive activation energy of the step of stopping the activation energy of.

On the other hand, there should be little reaction between the intermediate diffusion barrier and the upper electrode metal layer, so that the negative activation energy formed at the interface between the metal layer and the gallium nitride (GaN) compound semiconductor layer to be sufficiently emitted to the electrode layer.

Hereinafter, the ohmic electrode structure of the present invention will be described in detail with an example of a p-type electrode.

2 is a view for explaining a laminated structure of a gallium nitride (GaN) compound semiconductor according to the present invention.

Referring to FIG. 2, a gallium nitride (GaN) compound semiconductor layer 11, a contact layer 12, and an electrode layer 14 are included. In particular, an interfacial surface between the contact layer 12 and the electrode layer 14 is included. It can be seen that the intermediate diffusion barrier layer 13 is further formed on the substrate. The intermediate diffusion barrier layer 13 may suppress the interfacial reaction between the metal layer and the gallium nitride (GaN) compound semiconductor layer during heat treatment, and may also be negatively activated at the interface between the metal layer and the gallium nitride (GaN) compound semiconductor layer. Certain materials capable of dissipating energy to the upper electrode layer are used in single or multiple stacks.

For example, when the contact layer 12 is gold (Au) and the electrode layer 14 is nickel (Ni), the intermediate diffusion barrier layer 13 is formed of molybdenum / tungsten / molybdenum (Mo / W / Mo). It may be a stacked structure. In addition, as another metal that may exhibit the same properties, Metal-Si, Metal-N, Cr, Pt, Ti, Ru, or the like may be used. Meanwhile, the thickness of the intermediate diffusion barrier layer 13 may be formed in each layer of 1 ~ 5,000nm.

Hereinafter, specific examples and comparative examples of the present invention will be described.

The gallium nitride (GaN) compound is washed with trichloroethylene (TCE), acetone, methanol and distilled water for 5 minutes each. C-TLM (Circular-Transmission Line model) pattern is formed by photolithography. The pattern is then mounted in a metal vapor deposition chamber.

The metal evaporator may be an evaporator, a sputter, an ion beam cluster evaporator, a chemical vapor deposition (CVD), a molecular beam epitaxy (MBE), an evaporator using a magnet, or an evaporator using a laser.

After the pattern is placed on the evaporator, as a comparative example, 10 nm of gold and nickel are deposited on the upper side of the gallium nitride (GaN) compound at 10 ⁻⁶ Torr.

As an embodiment of the present invention, gold is deposited as the contact layer 12 and nickel as the electrode layer 14 on the gallium nitride (GaN) compound semiconductor layer 11, respectively. In particular, as the intermediate diffusion barrier layer 13, molybdenum / tungsten / molybdenum (Mo / W / Mo) is deposited by 10 nm each.

After deposition, heat treatment is performed to ensure that ohmic contact of the gallium nitride (GaN) semiconductor is achieved.

On the other hand, by the C-TLM method, the specific contact resistance with the passage of the heat treatment time was measured and shown as a diagram in FIG. At this time, the temperature to perform the heat treatment is an environment of 600 ℃ as a temperature for achieving ohmic contact.

Referring to FIG. 3, when the intermediate diffusion barrier layer (see 13 in FIG. 2) is not formed, thermally unstable characteristics such as the non-contact resistance value tend to increase as the heat treatment time passes (see FIG. 32). . However, when the intermediate diffusion barrier layer as in the present invention is further formed, it can be seen that the thermal stability is very excellent, such as the specific contact resistance value according to the heat treatment time is constantly measured (see FIG. 31).

Further, in the above Examples and Comparative Examples, the heat treatment was continuously performed at a temperature of 600 ° C. for 60 minutes to observe the change on the surface of the electrode using AFM (Atomic Force Microscope). This roughness affects later processes, but in the case of the present invention, it can be observed that the surface is formed very smoothly and has very good smooth surface. The above-described good surface characteristics can improve the production yield of the semiconductor device.

As described above, by providing an intermediate diffusion barrier layer between the contact layer of the semiconductor and the electrode layer, excellent thermal and electrical stability of the semiconductor can be realized.

By the electrode of the present invention, an intermediate diffusion barrier is further formed between the contact layer of the gallium nitride (GaN) compound semiconductor and the electrode layer, thereby suppressing the unsuitable interfacial reaction occurring at the interface between the metal and the semiconductor, thereby providing thermal and electrical There is an effect that can improve the characteristics, and improve the ohmic characteristics of the electrode.

Claims (6)

A contact layer formed on the upper side of the gallium nitride (GaN) compound semiconductor, An intermediate diffusion barrier layer formed on an upper surface of the contact layer; An electrode structure of a gallium nitride (GaN) compound semiconductor, characterized in that it comprises an electrode layer formed on the upper surface of the intermediate diffusion barrier layer. The method of claim 1, The intermediate diffusion barrier layer is formed on the P-type gallium nitride (GaN) compound semiconductor electrode structure of the gallium nitride (GaN) compound semiconductor. The method of claim 1, The intermediate diffusion barrier is an electrode structure of a gallium nitride (GaN) compound semiconductor, characterized in that the multi-metal layer laminated in the order of Mo (molybdenum) / W (tungsten) / Mo (bolide). The method of claim 1, The intermediate diffusion barrier layer is an electrode structure of a gallium nitride (GaN) compound semiconductor, characterized in that W (tungsten) and / or Mo (molybdenum) is deposited. W (tungsten), Mo (molybdenum), Metal-Si to control the interfacial reaction and ionization energy between the metal and gallium nitride semiconductor between the contact layer on the upper surface of the gallium nitride (GaN) compound semiconductor layer and the upper electrode The intermediate diffusion barrier layer, which is composed of a single layer of (silicon), metal-N (nitrogen), Cr (chromium), Pt (platinum), Ti (titanium), Ru (rucenium), or a combination of two or more layers, is further heat treated. An electrode structure of a gallium nitride (GaN) compound semiconductor, characterized in that formed. The method of claim 5, wherein The intermediate diffusion barrier layer is formed of one of an electron beam evaporator, a sputter, an ion beam cluster evaporator, a chemical vapor deposition (CVD), a molecular beam epitaxy (MBE), an evaporator using a magnet, and an evaporator using a laser. Electrode structure of (GaN) compound semiconductor.