Method of manufacturing semiconductor light emitting device

There is provided a method of manufacturing a semiconductor light emitting device, the method including: forming a light emitting structure by sequentially growing an n-type nitride semiconductor layer, an active layer, and a p-type nitride semiconductor layer on a substrate; forming a transparent electrode on the p-type nitride semiconductor layer through a sputtering process; and forming a nitrogen gas atmosphere in an interior of a reaction chamber in which the sputtering process is performed, prior to or during the sputtering process.In the case of the semiconductor light emitting device obtained according to embodiments of the invention, a deterioration phenomenon in electrode characteristics caused due to a nitrogen vacancy may be minimized in manufacturing a transparent electrode through a sputtering process to thereby allow for the provision of a transparent electrode having significantly improved electrical characteristics.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the priority of Korean Patent Application No. 10-2010-0107738 filed on Nov. 1, 2010, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of manufacturing a semiconductor light emitting device.

2. Description of the Related Art

In general, a light emitting diode (LED), a kind of semiconductor light emitting device, is a semiconductor device capable of generating light of various colors due to the recombination of electrons and holes at the junction between a p-type semiconductor and an n-type semiconductor, when current is applied thereto. Demand for this semiconductor light emitting device have been continuously increasing, since the semiconductor light emitting device has various advantages, such as a long lifespan, low power consumption, superior initial driving characteristics, high vibration resistance, and the like, as compared to a filament-based light emitting device. In particular, a group III-nitride semiconductor capable of emitting blue light having a short wavelength has recently come to prominence.

A light emitting device using the group III-nitride semiconductor may be obtained by growing a light emitting structure including n-type and p-type nitride semiconductor layers and an active layer formed therebetween on a substrate. In this case, a transparent electrode may be formed on a surface of the light emitting structure. The transparent electrode may be provided to perform an ohmic contact function or current distribution function between the semiconductor layers and the light emitting structure. The transparent electrode is required to have superior crystallinity in order to have high levels of electrical conductivity and translucency. When crystallinity is deteriorated, device characteristics may be significantly degraded, even in the case of superior light emitting structure quality. Thus, a solution capable of improving the quality of a transparent electrode used in a light emitting device in the related art is required.

SUMMARY OF THE INVENTION

An aspect of the present invention provides a semiconductor light emitting device including a transparent electrode having superior electrical functionality by minimizing a deterioration phenomenon in characteristics thereof.

According to an aspect of the present invention, there is provided a method of manufacturing a semiconductor light emitting device, the method including: forming a light emitting structure by sequentially growing an n-type nitride semiconductor layer, an active layer, and a p-type nitride semiconductor layer on a substrate; forming a transparent electrode on the p-type nitride semiconductor layer through a sputtering process; and forming a nitrogen gas atmosphere in an interior of a reaction chamber in which the sputtering process is performed, prior to or during the sputtering process. The transparent electrode may be made of a transparent conductive oxide.

The transparent electrode may be made of a transparent conductive oxide.

Nitrogen particles are emitted from the p-type nitride semiconductor layer during the sputtering process, such that a nitrogen vacancy is generated in the p-type nitride semiconductor layer. In this case, nitrogen gas in the interior of the reaction chamber fills the nitrogen vacancy.

The transparent electrode may include a part thereof formed in the nitrogen gas atmosphere and another part thereof formed in a state in which a supply of nitrogen gas is interrupted.

In the transparent electrode, after a part thereof may be formed in the nitrogen gas atmosphere, another part thereof may be formed in the state in which a supply of nitrogen gas is interrupted.

After the transparent electrode may entirely cover an upper surface of the p-type nitride semiconductor layer, the supply of nitrogen gas to the interior of the reaction chamber is interrupted.

The p-type nitride semiconductor layer may be formed of p-type GaN.

The method may further include exposing a portion of the n-type nitride semiconductor layer by removing a part of the light emitting structure; forming a first electrode on the n-type nitride semiconductor layer having the exposed portion; and forming a second electrode on the transparent electrode.

The method may further include forming a transparent electrode on the n-type nitride semiconductor layer.

The transparent electrode formed on the n-type nitride semiconductor layer may be formed through a sputtering process. After the sputtering process, an area of the n-type nitride semiconductor layer disposed under the transparent electrode may have a nitrogen vacancy concentration higher than that of other areas thereof.

The method may further include forming an n-type electrode and a p-type electrode on upper portions of the transparent electrodes formed on the n-type and p-type nitride semiconductor layers, respectively.

The n-type and p-type electrodes may be made of a material including aluminum (Al).

The n-type and p-type electrodes may be made of the same material.

The n-type and p-type electrodes may be simultaneously formed.

DETAILED DESCRIPTION OF THE INVENTION

The invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, the shapes and sizes of components are exaggerated for clarity. The same or equivalent elements are referred to by the same reference numerals throughout the specification.

FIGS. 1 through 5are process cross-sectional views schematically illustrating a method of manufacturing a semiconductor light emitting device according to an embodiment of the present invention.FIG. 6is a schematic cross-sectional view of a semiconductor light emitting device obtained by the method of manufacturing a semiconductor light emitting device according to the embodiment of the present invention. The method of manufacturing a semiconductor light emitting device according to the embodiment of the present invention will be explained as follows. First, as illustrated inFIG. 1, an n-type nitride semiconductor layer102, an active layer103, and a p-type nitride semiconductor layer104are sequentially formed on a substrate101. In this case, a structure including the n-type nitride semiconductor layer102, active layer103, and p-type nitride semiconductor layer104may be referred to as a light emitting structure.

The substrate101may be provided as a substrate for growing a semiconductor, and as the substrate101, a substrate made of an electrically insulative and conductive material, such as sapphire, SiC, MgAl2O4, MgO, LiAlO2, LiGaO2, GaN, or the like may be used. In this case, the substrate101may be made of sapphire having electrical insulating properties, and accordingly, as the substrate101having electrical insulating properties is used, an etching process for forming an electrode connected to the n-type nitride semiconductor layer102may be involved, to be described later. Sapphire, a crystal having Hexa-Rhombo R3c symmetry, has a lattice constant of 13.001 Å along a c-axis and a lattice constant of 4.758 Å along an a-axis and has a C(0001)-plane, an A(1120)-plane, an R(1102)-plane, or the like. In this case, since the C-plane may be relatively facilitated for the growth of a nitride thin film, and stable at high temperature conditions, the C-plane may be used mainly as a substrate for growing a nitride semiconductor.

The n-type nitride semiconductor layer102and the p-type nitride semiconductor layer104may be made of a nitride semiconductor doped with n-type impurities and a nitride semiconductor doped with p-type impurities, respectively. For example, each of the n-type and p-type nitride semiconductor layers102and104may be made of a material having a composition of AlxInyGa(1-x-y)N (0≦x≦1, 0≦y≦1, 0≦x+y≦1). The active layer103formed between the n-type and p-type nitride semiconductor layers102and104may emit light having a predetermined energy level due to a recombination of electrons and holes, and have a multiple quantum well (MQW) structure having an alternately stacked quantum well layer and quantum barrier layer, for example, a structure of InGaN/GaN. The n-type and p-type nitride semiconductor layers102and104, and active layer103configuring the light emitting structure may be grown through a process well-known in the related art, such as metal organic chemical vapor deposition (MOCVD), hydride vapor phase epitaxy (HVPE), molecular beam epitaxy (MBE), or the like.

Next, a transparent electrode may be formed on the p-type nitride semiconductor layer104, and a sputtering process may be used, as illustrated inFIG. 2. Sputtering refers to a method of fabricating a thin film by colliding a particle having a high energy level with a target made of a material the same as that of a desired thin film, and separating atoms and molecules therefrom. Specifically in explaining sputtering with reference to the embodiment of the present invention, the substrate101having light emitting structures102,103, and104formed thereon is disposed on a support201within a sputtering reaction chamber200, and then a sputtering gas205is introduced to the sputtering reaction chamber20. As the sputtering gas205, argon (Ar) gas known as a sputtering gas in the related art may be used. The sputtering gas205introduced to the sputtering reaction chamber200through a gas introduction unit204may be ionized due to voltage applied to the sputtering reaction chamber200, to thereby have a plasma state in which electrons, ions (for example, Ar+ions), and neutral gas are mixed. To this end, a sputtering target202may be electrically charged by a power supply unit203connected thereto, so as to be a negative terminal. In this case, although not separately illustrated, a positive terminal connected to another power supply unit may be present within the sputtering reaction chamber200, and for example, the support201may act as a positive terminal.

The ionized sputtering gas205may collide with the sputtering target202due to voltage applied to the sputtering reaction chamber200, and accordingly, a sputtered material from the sputtering target202may form a thin film on the p-type nitride semiconductor layer104. In the embodiment of the present invention, the sputtering target202may be a material for forming a transparent electrode, and as the material for forming a transparent electrode, a transparent conductive oxide, for example, ITO, CIO, ZnO, or the like may be used. The sputtering process may have advantages, in that equipment stability may be relatively high as compared to the case of using an electron bean deposition process, maintenance aspects may be advantageous, and a thickness and components of a thin film may be easily controlled. However, a transparent electrode fabricated through the sputtering process may show deteriorated electrical characteristics thereof, that is, ohmic characteristics, as compared to the case of using the electron bean deposition process. This may be understood because a nitrogen vacancy v may be generated in the p-type nitride semiconductor layer104, due to the sputtering target202, as illustrated inFIG. 3

Specifically, particles sputtered from the sputtering target202through the sputtering gas205may collide with the p-type nitride semiconductor layer104to thereby cause damage to the p-type nitride semiconductor layer104. Accordingly, a material constituting the p-type nitride semiconductor layer104may be separated to the outside. When the p-type nitride semiconductor layer104is formed of p-type GaN, nitrogen (N) particles having a particle size smaller than that of gallium particles may be more easily separated to the outside. By the separated nitrogen (N) particles, the nitrogen vacancy v may be generated in the p-type nitride semiconductor layer104, and accordingly, the amount of free electrons may be increased. Consequently, the increased free electrons may be offset with holes present in the p-type nitride semiconductor layer104, such that the amount of carriers may be reduced. The generation of the nitrogen vacancy v may be a factor leading to degradation in electrical characteristics of the p-type nitride semiconductor layer104.

In order to minimize such a defect, in the embodiment of the present invention, nitrogen gas206, as well as the sputtering gas205may be introduced to the sputtering reaction chamber200, to thereby allow the interior of the sputtering reaction chamber200to have a nitrogen gas atmosphere. The introduction of the nitrogen gas206may be performed before or during the sputtering process, and may be carried out as long as a condition, in which the interior of the sputtering reaction chamber200maintains a nitrogen gas atmosphere in the forming of the transparent electrode, is satisfied. The nitrogen gas206introduced to the sputtering reaction chamber200may fill the nitrogen vacancy v generated through the sputtering process, to thereby prevent electrical characteristics of the p-type nitride semiconductor layer104from being deteriorated.

Meanwhile, the introduction of the nitrogen gas206may be performed throughout the sputtering process; however, in some cases, the introduction of the nitrogen gas206may be performed during a portion of the sputtering process. That is, in the case of the initial sputtering process, the p-type nitride semiconductor layer104is exposed, such that the introduction of the nitrogen gas206may be required. However, when the p-type nitride semiconductor layer104is not exposed due to the formation of a transparent electrode105, as illustrated inFIG. 5, the supplying of the nitrogen gas206may be interrupted and only the sputtering gas205may be introduced. In this manner, a more efficient process may be obtained.

Next, as illustrated inFIG. 6, first and second electrodes106and107for applying an electrical signal to a semiconductor light emitting device may be formed, and accordingly, a semiconductor light emitting device100may be obtained. The embodiment of the present invention describes a method of forming the first electrode106on a surface of the n-type nitride semiconductor layer102exposed by removing a part of the light emitting structures102,103, and104and transparent electrode105after the formation of the transparent electrode105, and forming the second electrode107on the transparent electrode105; however, the order of the process may be modified. That is, prior to the formation of the transparent electrode105, the n-type nitride semiconductor layer102may be exposed by removing a part of the light emitting structures102,103, and104, the transparent electrode105may be formed, and then the first and second electrodes106and107may be formed.

FIG. 7is a schematic cross-sectional view of a semiconductor light emitting device manufactured according to another embodiment of the present invention.FIG. 8is an enlarged view of an n-type nitride semiconductor layer and n-type electrode circumferential areas fromFIG. 7. Referring toFIG. 7, a semiconductor light emitting device300may include a substrate301, an n-type nitride semiconductor layer302, an active layer303, a p-type nitride semiconductor layer304, transparent electrodes305and308, and n-type and p-type electrodes306and307. In this case, the transparent electrodes305and308may represent an n-type transparent electrode (indicated by reference numeral308) and a p-type transparent electrode (indicated by reference numeral305). Unlike the foregoing embodiment, the n-type transparent electrode308may be disposed between the n-type nitride semiconductor layer302and the n-type electrode306, and may be made of a transparent conductive oxide the same as that of the p-type transparent electrode305. In addition, the n-type transparent electrode308may also be formed through the sputtering process, and accordingly, electrical characteristics of the semiconductor light emitting device may be improved.

Specifically, similar to the case of the foregoing explanation, a part of particles constituting the n-type nitride semiconductor layer302may be separated from the n-type nitride semiconductor layer302through the sputtering process, due to re-sputtering effects. In this case, a relatively great of nitrogen (N) particles having a relatively small ion size may be separated. Accordingly, as illustrated inFIG. 8, since the nitrogen vacancy v may be generated in the n-type nitride semiconductor layer302, an area of the n-type nitride semiconductor layer302disposed under the n-type transparent electrode308may have a concentration of the nitrogen vacancy v, higher than that of the other area thereof, to thereby cause an increase in the amount of free electrons, whereby resistance in the surface of the n-type nitride semiconductor layer302may be reduced.

Meanwhile, each of the n-type and p-type electrodes306and307respectively formed on the n-type and p-type transparent electrodes308and305may be made of a material including aluminum (Al), instead of a generally used gold (Au) electrode, and accordingly, processing costs may be reduced. In addition, in the formation of an Al electrode, the n-type and p-type electrodes306and307may be simultaneously formed through a single process, and defects in the exteriors of the n-type and p-type electrodes306and307may be minimized. This will be explained with reference toFIGS. 9 through 12.

FIGS. 9 through 12are process cross-sectional views explaining an example of a method of manufacturing the semiconductor light emitting device ofFIG. 7. As illustrated inFIG. 9, in the state of forming the n-type and p-type transparent electrodes308and305, an insulating part309may be formed thereon. The insulating part309may be made of a dielectric substance, such as a silicon oxide, a silicon nitride, or the like and may function to passivate a final semiconductor light emitting device. Next, as illustrated inFIG. 10, the transparent electrodes305and308are exposed by removing a part of the insulating part309using a mask10. The transparent electrodes305and308are exposed so as to form n-type and p-type electrodes. Subsequently, as illustrated inFIG. 11, an electrode material layer311including Al may be formed, and the electrode material layer311may be formed to cover up to the mask310, with the exception of the open area of the insulating part309. In this manner, in the embodiment of the present invention, the n-type and p-type electrodes may be simultaneously formed in such a manner that they are made of the same material, for example, a material including Al, such that process convenience may be improved.

Next, as illustrated inFIG. 12, the mask310is lifted off, such that the electrode material layer311may be removed, other than portions corresponding to the n-type and p-type electrodes306and307. In the embodiment of the present invention, the n-type and p-type electrodes306and307may be made of a material including Al, as mentioned above, and a process of forming an insulating layer again after the formation of the n-type and p-type electrodes306and307or a process of etching the insulating layer so as to remove a part of the insulating layer may not required, to thereby allow for minimal damage to the n-type and p-type electrodes306and307. Therefore, a relatively inexpensive Al electrode may be realized while defects in the exterior of the electrode may be minimized.

Meanwhile, the semiconductor light emitting device manufactured through the process may be used in various fields.FIG. 13is a configuration view schematically illustrating an example of the use of the semiconductor light emitting device according to the present invention. Referring toFIG. 13, a lighting apparatus400may include alight emitting module401, a structure404having the light emitting module401disposed therein, and a power supply unit403. In the light emitting module401, at least one semiconductor light emitting device402obtained by the method according to the present invention may be disposed. In this case, the semiconductor light emitting device402may be mounted in the light emitting module401as it is, or may be provided in package form. The power supply unit403may include an interface405receiving power and a power control unit406controlling power supplied to the light emitting module401. In this case, the interface405may include a fuse blocking overcurrent and an electromagnetic wave shielding filter shielding an electromagnetic wave interference signal.

The power control unit406may include a rectifying unit converting an alternate current into a direct current, and a constant voltage control unit converting the alternate current into an appropriate voltage, when an alternate current power source is inputted thereto as a power source. When the power source is a direct current source having a voltage appropriate for the light emitting module401(for example, a battery), the rectifying unit and the constant voltage control unit may be omitted. In addition, when the light emitting module401employs a device, such as an alternate current-LED (AC-LED), the alternate current power source may be directly supplied to the light emitting module401. Also in this case, the rectifying unit or the constant voltage control unit may be omitted. Further, the power control unit406may control color temperature or the like, to thereby allow for a display of lighting according to human sensibility. In addition, the power supply unit403may include a feedback circuit device performing comparison between the amount of luminescence from the semiconductor light emitting device402and a preset amount of luminescence, and a memory device having information stored therein, such as a desired brightness or color rendering properties.

The lighting apparatus400may be used in a backlight unit used in a display device, for example, a liquid crystal display device including an image panel, an indoor lighting apparatus such as a lamp, flat panel lighting or the like, or an outdoor lighting apparatus such as a street lamp, a sign, a notice sign or the like. In addition, the lighting apparatus400may be used in a lighting device for various means of transportation, for example, automobiles, ships, air craft or the like. Further, the lighting apparatus400may be used in home appliances such as a television (TV), a refrigerator or the like, medical equipment, or the like.

As set forth above, in the semiconductor light emitting device obtained according to embodiments of the invention, a deterioration phenomenon in electrode characteristics caused due to a nitrogen vacancy may be minimized in manufacturing a transparent electrode through a sputtering process to thereby allow for the provision of a transparent electrode having significantly improved electrical characteristics. As a relatively inexpensive Al electrode may be used, defects in the exterior of the electrode may be minimized while allowing for a simplified manufacturing process. Further, an electrode structure having superior electrical characteristics may be obtained.