KR20080023821A - Method for manufacturing light emitting diode - Google Patents

Abstract

A method for manufacturing an LED(Light Emitting Diode) device is provided to simplify a substrate preparation process without using a mask, and to improve efficiency and reliability of the LED device by forming an auxiliary substrate comprising a GaN rod and GaN thin film, which allows to form a GaN thin film with low defect density and high quality. A method for manufacturing an LED(Light Emitting Diode) device comprises the steps of: forming a second substrate having a first layer with a plurality of selectively grown GaN rods(310) and a second layer with a grown GaN thin film(320), on a first substrate; forming a nitride semiconductor layer comprising a first conductive semiconductor layer(330a), and active layer(330b), and a second conductive semiconductor layer(330c), on the second substrate; isolating the second substrate from the nitride semiconductor layer; and respectively forming electrodes on the first and second semiconductor layers.

Description

Method for manufacturing light emitting diode

1 is a view showing a light emitting principle of a light emitting diode,

2 is a flowchart of an embodiment of a method of manufacturing a light emitting diode according to the present invention;

3a to 3c is a view showing a process of one embodiment of a method of manufacturing a light emitting diode according to the present invention,

3D and 3E are cross-sectional views of one embodiment of a light emitting diode manufactured by the method according to FIGS. 3A-3C.

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

300: starting substrate 310: GaN pillar

320: GaN thin film 330a: n-GaN

330b: active layer 330c: p-GaN

340, 340 ': n electrode 350, 350': p electrode

The present invention relates to a method of manufacturing a light emitting diode (LED).

A light emitting diode is a device using semiconductor characteristics that emit light, and is different from a conventional light emitting device that generates light by a discharge or heating method. That is, compared with the conventional light emitting element such as a light bulb or a fluorescent lamp, the light emitting diode has characteristics such as high durability, long life, high brightness and low power consumption.

Specifically, the light emitting diode is composed of a junction between a p-type and an n-type semiconductor, and is a kind of optoelectronic device that emits energy corresponding to a bandgap of a semiconductor in the form of light when a voltage is applied and a combination of electrons and holes is applied. )to be.

As shown in FIG. 1, when a voltage is applied to the p-n junction in the forward direction, electrons of the n-type semiconductor and holes of the p-type semiconductor are respectively injected into the p-side and the n-side, and are diffused as minority carriers. The aforementioned minority carriers recombine with the majority carriers in the diffusion process, and emit light corresponding to the energy difference between the bonding electrons and the holes.

The light emitting diode having the above-described structure is manufactured by growing a nitride semiconductor on a substrate by metalorganic chemical vapor deposition (MOCVD) or the like. The manufacturing process will be described in detail. First, a buffer of about 20 to 30 nanometers is grown on a starting substrate, and n-type GaN (n-GaN) of about 2 to 4 micrometers is grown. Doped silicon (Si). Then, a light emitting active layer and P-GaN are grown in order to form a nitride semiconductor, and then selectively etched and grown on a carrier substrate and a sapphire substrate using a bonding material. In order to bond the GaN substrate, an insulating material is filled in a trench in which the nitride semiconductor is etched to form an ohmic electrode and plated with copper (Cu). Subsequently, the substrate is removed by a laser lift-off (LLO) method, a pad metal is deposited, and then each device is separated to complete each light emitting diode device.

However, the conventional method of manufacturing a light emitting diode described above has the following problems.

Gallium nitride (GaN) has a large difference in material properties such as lattice constant and thermal expansion coefficient from that of a starting substrate made of sapphire or silicon, and thus, many threading dislocations are formed in the crystal.

A method using various buffer layers has been proposed to reduce the above-mentioned penetration potential, and recently, such as selective area growth (SAG) and epitaxial lattice growth (ELO) using SiO ₂ or SiN _X masks, have been proposed. The method has been proposed. A method such as SAG or ELO is a structure in which portions with and without masks capable of inhibiting growth are selectively or repeatedly formed. It has been reported in several papers that GaN thin films grown by the above-described method such as SAG or ELO reduce defect density to 10 ⁸ cm ⁻² or less, thereby improving device characteristics.

However, since SAG or ELO requires a substrate preparation operation such as photolithography in which an oxide film is formed, the work efficiency is lowered. Therefore, a method for reducing the preparation process of the starting substrate is required.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a light emitting diode and a method for manufacturing the same, which have improved device characteristics due to reduced penetration potential.

Another object of the present invention is to provide a method of manufacturing a light emitting diode in which a preparation process of a substrate is simplified without using a mask.

In order to achieve the above object, the present invention comprises the steps of forming a second substrate on the first substrate including a first layer of GaN is selectively grown and a second layer is grown GaN thin film; And it provides a method of manufacturing a light emitting diode comprising the step of forming a nitride semiconductor layer on the second substrate.

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention that can specifically realize the above object will be described.

The same components as in the prior art are given the same names and the same reference numerals for convenience of description, and detailed description thereof will be omitted.

In the method of manufacturing a light emitting diode according to the present invention, a nano pillar is formed on a starting substrate by molecular beam epitaxy (MBE) or the like, and a chemical vapor deposition (CVD) method or a vapor phase epitaxy is formed thereon. GaN is laterally grown by a phase epitaxy (VPE) method to form a second substrate, that is, an auxiliary substrate. Then, by growing the nitride semiconductor layer on the auxiliary substrate, the effect of reducing the defect density can be obtained.

2 is a flow chart of an embodiment of a light emitting diode manufacturing method according to the present invention, Figures 3a to 3c is a view showing a process of an embodiment of a light emitting diode manufacturing method according to the present invention. Referring to Figures 2 to 3c an embodiment of a method of manufacturing a light emitting diode according to the present invention will be described.

First, prepare a starting substrate. Since nitride (GaN) semiconductors do not have homogeneous substrates, sapphire (Al ₂ O ₃ ), silicon (Si), SiC, GaN-on-sapphire, GaN-on-Si, GaN-on-SiC, etc. are used as starting substrates. do. Subsequently, an auxiliary substrate is formed on the starting substrate, and a nano pillar 310 made of GaN is formed on the starting substrate 300 as shown in FIG. 3A (S210). The nano pillars 310 form part of the auxiliary substrate and are preferably grown by the MBE method which is easy for lateral growth of GaN. That is, GaN nanopillars are formed by evaporating GaN as a raw material in an ultra-high vacuum apparatus of 10 to 11 torr or less. In addition, the GaN nano pillars preferably have a diameter of 10 to 800 nanometers, and have a height (length) of 10 nanometers to 1000 nanometers. In addition, in the MBE method, the ratio of Group 5 elements to Group 3 elements must be increased so that the GaN materials can be separated from each other to form nano pillars.

In this case, although not shown in the figure, the nano pillars 310 may be grown after growing a buffer layer of about 20-30 nanometers on the starting substrate 300. Then, the buffer layer is made _{-x- y} N layer Al _x In _y Ga ₁ is formed to a desired thickness. That is, in the related art, after forming a buffer layer and a mask material on a starting substrate, a GaN material should be selectively formed on a portion that may contribute to subsequent growth by exposing and patterning using photolithography. However, in this embodiment, by controlling the growth conditions of the GaN nano-pillar, the GaN layer is spontaneously formed, which eliminates the complicated process required for preparing a conventional starting substrate.

Subsequently, as shown in FIG. 3B, a GaN thin film 320 is formed on the GaN nano pillars 310 (S220). That is, after growing the GaN nano pillars, GaN is laterally grown by the CVD method or the VPE method by lowering the ratio of Group 5 elements to Group 3 elements, that is, lowering the ratio of N (nitrogen). That is, when plasma is formed at high frequency by applying heat or light energy to a gas containing a GaN material, the GaN material is radicalized to increase its reactivity and adsorbed onto a substrate to be deposited or from a gas mixture containing a chemical vapor of the GaN material. A method of growing on a substrate is used. Since the CVD method or the VPE method described above mainly produce lateral growth, the GaN thin film 320 is formed on the GaN nano pillars 310 as shown in FIG. 3B. The through dislocation is generally formed in a direction perpendicular to the substrate. In this embodiment, since the side growth is mainly performed from the end of the nano pillars, the through dislocations are formed by bending in the lateral direction because GaNs are isolated from each other. do. Therefore, as GaN continues to grow, the through potential decreases below 10 ⁸ cm ^{-2 at} the top of the GaN thin film.

Subsequently, as illustrated in FIG. 3C, a nitride semiconductor layer is formed on the GaN thin film 320 (S230). The nitride semiconductor layer includes an active layer having a first conductive semiconductor layer 330a and a multi quantum well structure. 330b and the second conductive semiconductor layer 330c may be included. That is, n-GaN is grown on the GaN thin film 320, and at this time, silicon (Si) may be doped as a donor. Then, the active layer 330b and p-GaN 330c that emit light are sequentially formed. In this structure, since the nitride semiconductor layer is formed on the GaN thin film 320 having a small penetration potential, it is possible to have excellent efficiency and high reliability as compared with the conventional structure. In addition, although the GaN layer is grown in this embodiment, InGaN, AlGaN, and the like may be grown.

 3D and 3E show cross-sectional views of one embodiment of a light emitting diode manufactured by the method according to FIGS. 3A-3C. FIG. 3D is an embodiment of an LED having a vertical structure, and FIG. 3E is an embodiment of an LED having a horizontal structure. In each embodiment, n-type electrodes 340 and 340 'are formed on n-GaN 330a, and p-type electrodes 350 and 350' are formed on p-GaN 330c.

In order to manufacture the LED of the above-described structure, the auxiliary substrate (second substrate) in the structure shown in Figure 3c is separated (S240). However, as shown in FIG. 3D, the GaN thin film 320 may be separated, but as shown in FIG. 3E, the GaN thin film 320 may be separated without separating the GaN pillar. At this time, the separation process of the auxiliary substrate, etc. may be performed by a laser lift off (LLO) method, etc., by separating the nitride semiconductor layer by applying the LLO method, mechanical stress that may occur during the lapping process (mechanical) stress can be reduced. In addition, the separation of the auxiliary substrate and the like may be removed by wet etching or physical impact, in addition to the LLO method. Here, since GaN pillars have a small area bonded to the GaN thin film 320, the GaN pillars may be removed by physical impact.

After separation of the GaN thin film or the GaN pillar, an n-type electrode and a P-type electrode may be formed (S250). The p-type electrode may be formed of an ohmic electrode made of indium-tin-oxide (ITO), a reflective electrode, or the like, and the n-type electrode may be formed of a metal pad or the like.

When each device is separated through a process such as selective etching before, after, or after the formation of the p-type electrode or the n-type electrode described above, each light emitting diode device is completed.

Referring to the operation of the embodiment of the light emitting diode manufacturing method according to the present invention described above are as follows.

By forming an auxiliary substrate consisting of a GaN pillar and a GaN thin film on the starting substrate, the penetration potential is formed to be bent, thereby reducing the defect density and forming a high quality GaN thin film. In addition, a light emitting diode including a double junction structure such as a GaN structure or an InGaN structure may be formed on the auxiliary substrate to improve efficiency and reliability.

The present invention is not limited to the above-described embodiments, and such modifications are included in the scope of the present invention even if modifications are possible by those skilled in the art to which the present invention pertains.

Referring to the effects of the light emitting diode and the manufacturing method according to the present invention described above are as follows.

First, the penetration potential formed inside the crystal of the nitride semiconductor layer of the light emitting diode is reduced, thereby improving device characteristics.

Second, in the process of forming the nitride semiconductor layer, a mask is not used for the starting substrate, thereby simplifying the preparation of the substrate.

Claims (8)

Forming a second substrate on the first substrate, the second substrate including a first layer on which GaN is selectively grown and a second layer on which a GaN thin film is grown; And A method of manufacturing a light emitting diode comprising a step of forming a nitride semiconductor layer on the second substrate. The method of claim 1, wherein the first layer, A method of manufacturing a light emitting diode, characterized in that a plurality of GaN pillars are grown by the MBE method in an atmosphere having a large ratio of group 5 elements to group 3 elements. The method of claim 1, wherein the plurality of GaN pillars, Method for manufacturing a light emitting diode, characterized in that each diameter is formed from 10 to 800 nanometers. The method of claim 2, wherein the plurality of GaN pillars, Method for manufacturing a light emitting diode, characterized in that each length is formed of 10 ~ 1000 nanometers. The method of claim 1, wherein the second layer, A method of manufacturing a light emitting diode, characterized in that the GaN is laterally grown in an atmosphere in which the ratio of the Group 5 element to the Group 3 element is small. The method of claim 1, wherein the nitride semiconductor layer, A method of manufacturing a light emitting diode comprising a first conductive semiconductor layer, an active layer and a second conductive semiconductor layer. The method of claim 6, Separating the second substrate from the nitride semiconductor layer; And And forming an electrode on the first conductive semiconductor layer and the second conductive semiconductor layer, respectively. The method of claim 6, Separating the second substrate from the nitride semiconductor layer; Etching a portion of the nitride semiconductor layer; And And forming electrodes on the first conductive semiconductor layer and the second conductive semiconductor layer in the same direction, respectively.

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