KR20100079466A

KR20100079466A - Method for fabricating of light emitting diode

Info

Publication number: KR20100079466A
Application number: KR1020080137965A
Authority: KR
Inventors: 박성주; 조주영; 이상준; 박태영
Original assignee: 광주과학기술원
Priority date: 2008-12-31
Filing date: 2008-12-31
Publication date: 2010-07-08
Also published as: KR101108244B1

Abstract

A method of manufacturing a light emitting diode is provided. The light emitting diode manufacturing method includes forming a buffer clad layer on a substrate, forming a metal mask pattern on the buffer clad layer, growing a first conductive clad layer on the metal mask pattern, and simultaneously forming the buffer clad layer. Etching a portion in contact with a lower portion of the metal mask pattern, forming a second conductive cladding layer on the first conductive cladding layer to form the first conductive cladding layer and the second conductive cladding layer Forming a light emitting structure having a; and separating the substrate from the light emitting structure.

Description

Manufacturing method of light emitting diodes {Method for Fabricating of Light Emitting Diode}

The present invention relates to a light emitting diode, and more particularly to a method of manufacturing a light emitting diode.

Recently, in order to implement a high output light emitting diode, a vertical light emitting diode is proposed to replace a conventional horizontal light emitting diode. Vertical light emitting diodes have the advantage of increasing efficient heat dissipation and light output through separation of the substrate and light emitting diodes.

However, the substrate used in the light emitting diode is an electrically insulator, and has a problem in that mechanical and chemical processing is difficult because it has excellent hardness characteristics due to covalent bonding.

Therefore, a heterogeneous substrate was formed by forming a conductive thin film on the substrate, and the substrate and the light emitting diode were separated by removing the conductive thin film using a laser. However, the high power laser used to separate the substrate damages the light emitting diode and causes a problem such as cracking.

An object of the present invention for solving the above problems is to provide a method of manufacturing a light emitting diode that can reduce the damage of the light emitting diode.

The present invention for achieving the above object is to form a buffer clad layer on a substrate, to form a metal mask pattern on the buffer clad layer, to grow a first conductive type clad layer on the metal mask pattern Simultaneously etching a portion of the buffer clad layer in contact with the lower portion of the metal mask pattern, forming a second conductive clad layer on the first conductive clad layer to form the first conductive clad layer and the second conductive clad layer; It provides a light emitting diode manufacturing method comprising the step of forming a light emitting structure having a conductive cladding layer and separating the substrate from the light emitting structure.

The etching of the buffer clad layer may be performed by a chemical reaction between the gas used in the growth of the first conductive clad layer and the buffer clad layer. The gas may comprise hydrogen. The metal mask pattern may be formed using tungsten or molybdenum.

The light emitting diode manufacturing method may further include removing the metal mask pattern after separating the substrate from the light emitting structure.

The method of manufacturing a light emitting diode includes forming a first electrode and a second electrode electrically connected to each of the first conductive cladding layer and the second conductive cladding layer after the step of separating the substrate from the light emitting structure. It may further include.

As described above, when the substrate is separated from the light emitting structure by using the chemical reaction of the gas and the buffer clad layer used in the growth of the first conductivity type cladding layer, the damage of the light emitting diode is reduced compared to the conventional method of removing the substrate using the laser. There is an effect that can be reduced.

In addition, the first conductive cladding layer disposed on the metal mask patterns may have a very low defect density because the propagation of defects is blocked by the metal mask patterns.

With reference to the accompanying drawings, it will be described in detail a preferred embodiment of the present invention. However, this is not intended to limit the present invention to specific embodiments, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention. Hereinafter, the same reference numerals are used for the same components in the drawings, and duplicate descriptions of the same components are omitted.

1A to 1G are schematic views illustrating a method of manufacturing a light emitting diode according to an embodiment of the present invention.

Referring to FIG. 1A, a buffer clad layer 12 may be formed on a substrate 10.

The substrate 10 may be an Al ₂ O ₃ (sapphire), SiC, ZnO, Si, GaAs, LiAl ₂ O ₃ , InP, BN, AlN or GaN substrate. Preferably, the substrate 10 may be an Al ₂ O ₃ substrate.

The buffer clad layer 12 may be a SiC layer, a ZnO layer, a Si layer, a GaAs layer, an NCO layer, a BN layer, an AlN layer, or a GaN layer. Preferably, the buffer clad layer 12 may be a GaN layer. The buffer clad layer 12 may be formed using a MOCVD method, a MOVPE method, an HVPE method, or an MBE method.

Referring to FIG. 1B, a metal mask pattern 13 may be formed on the buffer clad layer 12. The metal mask pattern 13 may be a high melting point metal film. The high melting point metal film may be a metal having a melting point that does not dissolve by heat treatment performed when the first conductivity type cladding layer is described later. Specifically, the high melting point metal may be tungsten (W) or molybdenum (Mo).

The metal mask pattern 13 may be formed by forming a metal layer on the buffer clad layer 12 and then patterning the metal layer.

As a result, metal mask patterns 13 may be disposed on the buffer clad layer 12, and the buffer clad layer 12 may be exposed between the metal mask patterns 13.

The metal layer may be formed using electron beam deposition or sputtering, and the patterning may be performed using a photolithography method, a dry etching method, or a wet etching method. The metal mask pattern 13 may have a dot shape or a thin film shape.

Referring to FIG. 1C, a first conductive cladding layer 14 may be grown on the exposed buffer cladding layer 12 and the metal mask pattern 13. At the same time, a portion of the buffer cladding layer 12 that contacts the lower portion of the metal mask pattern 13 may be etched.

The first conductive cladding layer 14 may be a semiconductor layer into which first type impurities, for example, n type impurities, are implanted. The n-type semiconductor layer is a SiC layer, ZnO layer, Si layer, GaAs layer, NCO layer, BN layer, AlN layer, GaN layer, Mg _x Zn _y Cd _Z O layer (0≤x, y, z≤1) or It may be an Al _x Ga _(1-x) N (0≤x≤1) layer. Preferably, the first conductivity type cladding layer 14 may be a GaN layer or an Al _x Ga _(1-x) N (0 ≦ _x ≦ 1) layer.

The first conductive cladding layer 14 may be a horizontally grown single crystal layer formed using an epitaxial lateral overgrowth (ELO) method.

In general, defects tend to propagate more easily in the vertical direction than in the horizontal direction. However, the horizontally grown single crystal layer formed as described above, in particular, the first conductive type cladding layer 14 disposed on the metal mask patterns 13 is prevented from propagating defects by the metal mask patterns 13. It can be blocked and the density of defects can be very low.

The ELO method can be performed using MOCVD, MOVPE, LPE, MBE or HVPE techniques. When the first conductive cladding layer 14 is formed, gas may be injected into the reaction vessel. The gas may include hydrogen, specifically hydrogen, hydrogen peroxide or water vapor. In addition, the gas may further include a reaction gas for growing the first conductivity-type cladding layer 14. The reaction gas may be Al, Ga, In or N.

Heat treatment may be performed to form the first conductive cladding layer 14. The heat treatment may promote the reaction of the reaction gases to promote the formation of the first conductive clad layer 14. The heat treatment may be performed in a temperature range of 500 ℃ to 1000 ℃.

The etching of the buffer clad layer 12 may be performed by a chemical reaction between the gas used to grow the upper first clad layer and the buffer clad layer 12.

As an example, when the gas is hydrogen, the metal mask pattern 13 may serve as a catalyst for decomposing hydrogen gas into hydrogen radicals. The hydrogen radicals passing through the metal mask pattern 13 may selectively etch the buffer clad layer 12 disposed under the metal mask pattern 13. To this end, the metal mask pattern 13 may have a somewhat low density.

As a result, the buffer cladding layer 12, the metal mask pattern 13, and the first conductive cladding layer 14, which are sequentially formed on the substrate 10, may be disposed, and the buffer cladding layer 12 may be formed of the metal mask. An area under the pattern 13 may be provided with a void 15 formed by selectively etching.

Referring to FIG. 1D, an active layer 16 may be formed on the first conductive cladding layer 14. The active layer 16 may be a layer that emits light by recombination of electrons and holes between the first conductive cladding layer 14 and the second conductive cladding layer to be described later. The active layer 16 may have a quantum dot structure or a multiple quantum wells structure.

The active layer 16 may emit wavelength light corresponding to an energy gap when the electrons and holes are recombined with each other. As an example, when the energy gap is large, short wavelengths, that is, ultraviolet rays may be emitted. When the energy gap is small, long wavelengths, that is, infrared rays, may be emitted.

However, the active layer 16 may be omitted. When the active layer 16 is omitted, the first conductive cladding layer 14 and the second conductive cladding layer may generate wavelength light by p-n bonding.

Referring to FIG. 1E, the second conductive cladding layer 18 is formed on the active layer 16 to form the first conductive cladding layer 14, the active layer 16, and the second conductive cladding layer 18. The light emitting structure S may be formed. When the active layer 16 is omitted, the light emitting structure S may be provided as the first conductive cladding layer 14 and the second conductive cladding layer 18.

The second conductive cladding layer 18 may be a semiconductor layer into which a second type impurity, that is, a p type impurity is implanted. The p-type semiconductor layer is a SiC layer, ZnO layer, Si layer, GaAs layer, NCO layer, BN layer, AlN layer, GaN layer, Mg _x Zn _y Cd _Z O layer (0≤x, y, z≤1) or It may be an Al _x Ga _(1-x) N (0≤x≤1) layer.

Referring to FIG. 1F, the substrate 10 may be separated from the light emitting structure S. Referring to FIG. The substrate 10 may be easily separated by the voids 15 disposed between the metal mask pattern 13 and the buffer clad layer 12.

After separating the substrate 10 from the light emitting structure S, the residual buffer clad layer 12 existing under the light emitting structure S may be removed using an etchant. The first etchant may be KOH, NaOH, HF, HCL or H ₂ SO ₄ .

As described above, when the substrate 10 is separated from the light emitting structure S by using the chemical reaction of the gas and the buffer cladding layer 12 used in the growth of the first conductive cladding layer 14, the conventional laser Compared to the method of removing the substrate, the damage of the light emitting diode can be reduced.

After removing the substrate 10 from the light emitting structure S as described above, the metal mask pattern 13 may be removed. The metal mask pattern 13 may be removed using a second etchant.

Referring to FIG. 1G, a first electrode 22 and a second electrode 24 electrically connected to a lower portion of the first conductive cladding layer 14 and an upper portion of the second conductive cladding layer 18 are formed. can do.

The electrodes 22 and 24 may contain Al and / or Au. Specifically, the electrodes 22 and 24 may be Ti / Al or NiO / Au.

The light emitting diode manufactured as described above may have an uneven surface of the lower portion of the first conductive cladding layer 14 directly connected to the first electrode 22. The non-uniform surface can prevent the light emitted from the light emitting diode to the outside to be trapped inside the diode by total reflection, and improve the external quantum efficiency.

2 is an SEM image showing a state in which a buffer clad layer is selectively removed according to an embodiment of the present invention. The buffer clad layer and the first conductive clad layer were formed using GaN, and the metal mask pattern was formed using tungsten.

Referring to FIG. 2, the buffer cladding layer 12, the metal mask pattern 13, and the first conductive cladding layer 14 are sequentially disposed on the substrate 10, and are disposed below the metal mask pattern 13. It can be seen that part of the buffer cladding layer 12 has been selectively removed.

The void 15 formed by removing the buffer cladding layer 12 may facilitate separation of the first conductive cladding layer 14 and the substrate 10. In addition, since the metal mask pattern 13 may prevent a defect propagated vertically from the buffer clad layer 12, the defect density of the first conductive clad layer 14 may be reduced.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the present invention as defined by the following claims It can be understood that

2 is an SEM image showing a state in which a buffer clad layer is selectively removed according to an embodiment of the present invention.

10 substrate 12 buffer cladding layer

13: metal mask pattern 14: first conductive clad layer

15: void 16: active layer

18: second conductivity type clad layer 22: first electrode

24: second electrode

Claims

Forming a buffer clad layer on the substrate;

Forming a metal mask pattern on the buffer clad layer;

Growing a first conductivity type clad layer on the metal mask pattern and simultaneously etching a portion of the buffer clad layer in contact with a lower portion of the metal mask pattern;

Forming a second conductive cladding layer on the first conductive cladding layer to form a light emitting structure including the first conductive cladding layer and the second conductive cladding layer; And

And separating the substrate from the light emitting structure.

The method of claim 1,

Etching the buffer clad layer

The method of manufacturing a light emitting diode is carried out by a chemical reaction of the gas used in the growth of the first conductivity type cladding layer and the buffer cladding layer.

The method of claim 2,

The gas comprises a light emitting diode manufacturing method.

The method of claim 1,

The metal mask pattern is formed using tungsten or molybdenum.

The method of claim 1,

After separating the substrate from the light emitting structure

The method of manufacturing a light emitting diode further comprises removing the metal mask pattern.

The method of claim 1,

After separating the substrate from the light emitting structure

And forming a first electrode and a second electrode electrically connected to each of the first conductive clad layer and the second conductive clad layer.