KR20080002200A - Manufacturing method of iii-nitride semiconductor light enitting device - Google Patents

Abstract

A method for fabricating a III-group nitride semiconductor LED(light emitting device) is provided to improve external quantum efficiency by forming fine and high-density surface gratings outside a device except a light emitting part. A second electrode is formed on a nitride semiconductor layer of a second conductivity type. A first electrode is formed, and a photoresist material is deposited in a region except a cutting region. By using an etch solution including hydrochloric acid, a wet etch process is performed on a region where the photoresist material is not deposited. The wet-etched region is dry-etched. The second electrode is made of a conductive oxide layer.

Description

Manufacturing method of group III nitride semiconductor light emitting device {MANUFACTURING METHOD OF III-NITRIDE SEMICONDUCTOR LIGHT ENITTING DEVICE}

1 is a cross-sectional view illustrating a conventional III-nitride semiconductor light emitting device;

2 and 3 are cross-sectional views showing an embodiment of a gallium nitride based light emitting diode manufactured using the present invention;

4 is a plan view showing an embodiment of a gallium nitride-based light emitting diode prepared by using the present invention,

5 is a conceptual diagram showing a process in which light generated in the case of a general light emitting diode (hexahedral structure) is extinguished inside;

6 is a conceptual diagram for the case where all generated light can escape to the outside (when the external quantum efficiency is 1) (sphere, cone),

7 is a conceptual diagram illustrating a path of light escape from a light emitting diode manufactured using the present invention;

8 is a surface micrograph of a metal oxide film after wet etching of the present invention;

9 is a SEM (Scanning Electron Microscope) photo of the surface lattice formed by the present invention,

10 is an AFM (Atomic Force Microscope) photograph of the surface grid formed by the present invention,

11 is a view comparing characteristics (luminance) of a conventional light emitting diode and a light emitting diode to which the present invention is applied.

The present invention relates to a III-nitride compound semiconductor light emitting device, and more particularly to a III-nitride semiconductor light emitting device having a high external quantum efficiency. The III-nitride semiconductor referred to in the present invention refers to Al x Ga y In 1-x -y N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, x + y ≦ 1).

In general, since the semiconductor constituting the light emitting device has a higher refractive index than the external environment (epoxy or air layer), the majority of photons generated by the combination of electrons and holes stay in the device.

In GaN-based gallium nitride-based semiconductor light emitting devices, due to the low conductivity of p-type GaN, a conductive film having a constant thickness is formed in a large area of the upper layer for efficient current diffusion. The absorption of photons by the conductive film The external quantum efficiency is much lowered.

In addition, a sapphire substrate is used in spite of high lattice mismatch because there is no substrate. Since sapphire is an electrical insulator, it is impossible to form a metal electrode on the back of the device, which is electrically connected to n-type GaN. Etching is performed to expose the n-type GaN to form a metal electrode. Due to the limitation of the device fabrication, there are many limitations in increasing the external quantum efficiency by deforming the device shape. Many technologies have been developed to overcome these limitations and increase external quantum efficiency.

In the case of III-nitride semiconductor light emitting device, the external quantum efficiency is increased. The representative techniques are flip chip technology (US Patent No. 6573537B1), and the technology of increasing the surface roughness of the p-type semiconductor layer, which is the top layer forming the nitride semiconductor light emitting device (US Patent No. 6441403B1), and the technique of forming a wave pattern on the surface of a p-type semiconductor layer (US Pat. No. 6,20,735B2).

The technique using the micro-mask effect of the etching residue (etching residue) using the characteristics of the dry etching of the pending technology is limited by the reproducibility by the atmosphere of the vacuum chamber to dry etching. In addition, the surface lattice formation method using photolithography using vertical defects of crystals (Threading Dislocation, Etch Pit, etc.) is used for the horizontal defects (Stacking Fault, etc.), when the InGaN layer forming the active layer forms a surface lattice due to the rapid etching rate. It has the disadvantage of providing another flaw on the side.

An object of the present invention is to provide a light emitting diode having a high external quantum efficiency by providing a fine high density surface lattice on the outside of the device except for the light emitting part in the gallium nitride-based light emitting diode.

According to an aspect of the present invention, there is provided a III-nitride semiconductor light emitting device comprising: a lower contact layer formed on an insulating substrate and formed of an n-type III-nitride semiconductor; An active layer formed on a predetermined region of the lower contact layer surface and formed of a III-nitride semiconductor; An upper contact layer formed on the active layer and made of a p-type III-nitride semiconductor; An n-type ohmic contact metal layer formed on a predetermined exposed surface area of the lower contact layer that is not covered by the active layer; And a transparent electrode layer formed on the upper contact layer. A surface lattice is formed on the exposed surface of the lower contact layer, which is not covered by the active layer and the n-type ohmic contact metal layer, and the surface lattice uses a mask pattern obtained by wet etching a metal or metal oxide. It characterized in that it is formed by dry etching.

The wet etching may be a solution containing HCL.

The dry etching may be to use a plasma.

The dry etching may be reactive ion etching.

The protruding portion of the surface lattice may have a conical shape. At this time, the diameter of the bottom surface of the cone and the height of the cone may be about 1 nm-10 µm, respectively.

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention will be described in detail. In the drawings, the same reference numerals as in FIG. 1 denote components that perform the same function, and a repetitive description thereof will be omitted.

The following examples are only presented to understand the content of the present invention, and those skilled in the art may make many modifications within the technical spirit of the present invention. Accordingly, the scope of the present invention should not be construed as being limited to these embodiments.

2 is a cross-sectional view illustrating a nitride semiconductor light emitting device according to an embodiment of the present invention, and FIG. 3 is one of still other embodiments of the present invention.

2 and 3, the present invention exposes the lower contact layer 31 by mesa etching the upper contact layer 35, the upper cladding layer 34, the active layer 33, and the lower cladding layer 32. After the n-type ohmic metal electrode layer 52 is formed on the lower contact layer 31, the surface lattice 54 is formed on the exposed surface of the lower contact layer 31. It is done. That is, the present invention is characterized in that the surface grid 54 is formed on the outer portion of the chip excluding the light emitting portion. 4 is a plan view according to an embodiment of the present invention.

The most preferred embodiment for forming the surface grid 54 is as follows.

(1) 1? Form a metal or metal oxide film with a thickness of ~ 1um. In this case, the metal to be formed may be one, two or more alloys of Ni, Cr, W, La, Au, Pt, Ti, Ta, Pd, Ru, V, Ir, In, Sn, Ga, Al. The metal oxide film is Ni _x O _y , Cr _x O _y , W _x O _y , La _x O _y , Ti _x O _y , Ta _x O _y , Ru _x O _y , Mg _x O _y , Ru _x O _y , V _x It may be one or two or more oxide films such as O _y , In _x O _y , Sn _x O _y , Ga _x O _y , Al _x O _y (where x and y are integers greater than or equal to 1 and less than or equal to 10). . The material used in this embodiment is ITO (Indium Tin Oxide: In _x Sn _y O _z ). The reason for using ITO material is widely used as a transparent electrode film. Therefore, by forming a metal film on the lower contact layer at the same time when forming the transparent electrode film, it is convenient because the process does not require any metal deposition or photo process. to be.

In the present embodiment, the thickness of the formed metal oxide film is 240 nm, and the heat treatment is performed at 600 ° C. for 2 minutes to form a surface as shown in FIG. 5 through wet etching, thereby performing a mask pattern during dry etching without a separate photo process. Used as At this time, the wet etching proceeds to a solution containing hydrochloric acid, and the etching conditions used in this example were performed for 30 seconds after maintaining the temperature of the solution at 45 ° C. The etching condition may be sufficiently changed by the thickness of the metal oxide film or other conditions.

(2) The gallium nitride semiconductor formed in (1) is dry etched. At this time, the dry etching usually uses a plasma, and the gas forming the plasma uses a chlorine series. The chlorine-based gas may be used by mixing one or two or more of Cl ₂ , BCl ₃ , CCl ₄ , and HCl. The etching conditions used in this embodiment are 200W when the RF power is ICP source and 45W when the RF bias is at a process pressure of Cl2 = 30sccm, 1.5mTorr, and the time is about 20 minutes. The etching conditions may have various conditions depending on the etching equipment and gas used in the process.

In the method of forming the surface lattice by the metal film or the metal oxide film, when the metal or the metal oxide film is wet-etched after the heat treatment on the surface of the gallium nitride-based semiconductor, it is selectively etched without a separate mask pattern to have a surface roughness. When dry etching, the surface lattice 54 is formed on the surface of the lower contact layer 31. In this case, the gas used is advantageous to form a surface lattice as the etching selectivity between the gallium nitride-based semiconductor and the metal increases. As the etching proceeds, the area to be etched becomes narrower and the etching mask is removed, thereby forming a conical surface grid.

The light generated in the active layer of the light emitting diode device is almost disappeared inside the device as shown in Figure 6, the external quantum efficiency is 1 structure is a sphere or a cone as shown in FIG. The ideal shape of the surface lattice is therefore a hemisphere or cone formed on the active layer. The shape of the surface grating formed by the method described above is closest to the cone as shown in FIG. FIG. 8 is a cross-sectional view illustrating the effect of a light emitting diode device in which a surface grating is formed as in FIG. 7.

When the light emitting device is completed, a cutting process of separating each device is followed to package the light emitting device. For this cutting process, a space of about 20 to 60 µm is provided between the devices, and this clearance is only for process margin for no particular reason. The present invention is to form a surface grid in such a clearance.

Although the bonding pads 53 are generally formed on the transparent electrode layer 51 as shown in FIG. 1, the bonding pads 53 may be formed to directly contact the upper contact layer 35 by removing a portion of the transparent electrode layer 51 as shown in FIG. 2. The cladding layers 32 and 34 are not necessarily present but are present to improve the performance of the device.

9 and 10 are SEM and AFM photographs of the surface lattice formed by the present invention, respectively. The surface lattice has a conical shape, the diameter of the bottom of the cone is 1 nm to 10 μm, the height is 1 nm to 10 μm, and the density is about ⁹ × 10 ⁸ holes / cm 2.

11 is an applied current-luminance graph comparing the conventional case and the present invention. In the case of the present invention there is a slight difference depending on the size and shape of the surface irregularities, but shows a brightness increase of about 30 to 50% compared to the prior art.

According to the present invention, it is possible to implement higher quantum efficiency than conventional devices. In addition, an etching process for exposing the lower contact layer, which is an essential process in the light emitting device manufacturing process, is performed. This process uses dry etching and simultaneously forms a surface lattice by etching the portions that form the surface lattice during dry etching. In addition, the metal oxide film required for the bottom contact layer for forming the surface lattice also proceeds at the same time during the formation of the transparent electrode layer, thereby eliminating the need for forming a separate surface lattice. Therefore, the process can be simplified, thereby improving productivity.

Claims (5)

Light is generated by recombination of electrons and holes between a nitride semiconductor layer having a first conductivity and a nitride semiconductor layer having a second conductivity different from the first conductivity, wherein the first electrode is formed and includes a region for cutting the light emitting device. In the method of manufacturing a group III nitride semiconductor light emitting device having an active layer is interposed, and comprising a rough surface in the region for cutting the light emitting device, A first step of forming a second electrode on the nitride semiconductor layer having a second conductivity; A second step of forming a first electrode and depositing a photosensitive material in an area except for an area for cutting; A third step of wet etching a region where the photosensitive material is not deposited; And a fourth step of dry etching the wet etched region. The method of claim 1, In the first step, the second electrode is a method of manufacturing a group III nitride semiconductor light emitting device, characterized in that formed of a conductive oxide film. The method of claim 1, In the third step, the wet etching is a method for manufacturing a group III nitride semiconductor light emitting device, characterized in that the etching solution containing hydrochloric acid. The method of claim 2, wherein the conductive oxide film includes at least one selected from the group consisting of Zn, In, Sn, Ni, Ga, Cu, La, Ag, and Al. . The method of claim 1, The method of manufacturing a group III nitride semiconductor light emitting device, characterized in that in the third step and the fourth step, the etching mask is a conductive oxide film.

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