KR20170005680A - Manufacturing method of light emitting device - Google Patents

Abstract

A method of manufacturing a light emitting device is disclosed. The method includes a step of forming a surface layer by performing a nitriding process on a substrate; a step of forming a buffer layer on the surface layer; and a step of forming a light emitting structure on the buffer layer. In the step of forming the surface layer, an RF voltage is applied at 30 W to 100 W in a nitrogen atmosphere. So, the light emitting device with excellent crystallinity can be provided.

Description

TECHNICAL FIELD [0001] The present invention relates to a manufacturing method of a light emitting device,

The embodiment relates to a method of manufacturing a light emitting device.

A light emitting device (LED) is a compound semiconductor device that converts electric energy into light energy. By controlling the composition ratio of the compound semiconductor, various colors can be realized.

The nitride semiconductor light emitting device has advantages of low power consumption, semi-permanent lifetime, fast response speed, safety, and environmental friendliness compared to conventional light sources such as fluorescent lamps and incandescent lamps. Accordingly, a light emitting diode backlight replacing a cold cathode fluorescent lamp (CCFL) constituting a backlight of an LCD (Liquid Crystal Display) display device, a white light emitting diode lighting device capable of replacing a fluorescent lamp or an incandescent lamp, And traffic lights.

The nitride semiconductor light emitting device forms a buffer layer to mitigate lattice mismatch between the substrate and the nitride semiconductor. However, when the crystallinity and the surface of the buffer layer are poor, there is a problem that the crystallinity and the surface of the nitride semiconductor grown thereon become poor.

The embodiment provides a light emitting device having excellent crystallinity.

The problems to be solved in the embodiments are not limited to these, and the objects and effects that can be grasped from the solution means and the embodiments of the problems described below are also included.

According to an embodiment of the present invention, there is provided a method of manufacturing a light emitting device, comprising: nitriding a substrate to form a surface layer; Forming a buffer layer on the surface layer; And forming a light emitting structure on the buffer layer, wherein forming the surface layer comprises applying an RF voltage of 30 W to 100 W in a nitrogen atmosphere.

In the step of forming the surface layer, the RF voltage may be applied at 30 W or more and 50 W or less.

In the step of forming the surface layer, the RF voltage may be applied between 40W and 50W.

In the step of forming the surface layer, the nitriding treatment time can be controlled to 30 seconds or more and 50 seconds or less.

The substrate may comprise Al.

According to the embodiment, the crystallinity of the light emitting element is improved, and the surface state can be improved.

Further, warping of the substrate can be effectively suppressed.

The various and advantageous advantages and effects of the present invention are not limited to the above description, and can be more easily understood in the course of describing a specific embodiment of the present invention.

1 is a flowchart of a method of manufacturing a light emitting device according to an embodiment of the present invention,
2 is a graph showing a change in the half width of the light emitting structure at the (002) plane according to RF power during the nitriding process,
3 is a photograph of the surface state of the light emitting structure when the RF power is controlled to 125 W,
4 is a photograph of the surface state of the light emitting structure when the RF power is controlled to 50 W,
5 is a graph showing the change in the half-width of the light emitting structure in the (102) plane according to the RF power during the nitriding process,
FIG. 6 is a graph showing a change in the bow of the substrate according to RF power during the nitridation process,
7 is a graph showing a change in the half width of the light emitting structure according to the nitriding treatment time,
8 is a graph showing a change in the amount of bow change of the substrate in accordance with the nitriding process time,
9 is a graph showing a measurement of the luminous efficiency of the light emitting device according to the nitriding time,
10 is a conceptual diagram of a light emitting device according to an embodiment of the present invention,
11 is a modification of Fig.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the embodiments of the present invention are not intended to be limited to the specific embodiments but include all modifications, equivalents, and alternatives falling within the spirit and scope of the embodiments.

Terms including ordinals, such as first, second, etc., may be used to describe various elements, but the elements are not limited to these terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the embodiments, the second component may be referred to as a first component, and similarly, the first component may also be referred to as a second component. And / or < / RTI > includes any combination of a plurality of related listed items or any of a plurality of related listed items.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the embodiments of the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the terms "comprises" or "having" and the like are used to specify that there is a feature, a number, a step, an operation, an element, a component or a combination thereof described in the specification, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

In the description of the embodiments, in the case where one element is described as being formed "on or under" another element, the upper (upper) or lower (lower) or under are all such that two elements are in direct contact with each other or one or more other elements are indirectly formed between the two elements. Also, when expressed as "on or under", it may include not only an upward direction but also a downward direction with respect to one element.

Hereinafter, embodiments will be described in detail with reference to the accompanying drawings, wherein like or corresponding elements are denoted by the same reference numerals, and redundant description thereof will be omitted.

1 is a flowchart of a method of manufacturing a light emitting device according to an embodiment of the present invention.

Referring to FIG. 1, a method of manufacturing a light emitting device according to an embodiment includes forming a surface layer by nitriding a substrate, forming a buffer layer on a surface layer, and forming a light emitting structure on the buffer layer.

Referring to FIG. 1 (a), in forming the surface layer, a surface layer 111 may be formed by nitriding a surface of the substrate 110 with a nitrogen plasma treatment.

The substrate 110 may comprise a conductive substrate or an insulating substrate. The substrate 110 may be a material suitable for semiconductor material growth or a carrier wafer. The substrate 110 may be selected from a variety of substrates including Al. In the embodiment, a sapphire (Al ₂ O ₃ ) substrate is described but not limited thereto.

The nitridation process can be performed by placing the substrate 110 in a chamber and applying a RF voltage while controlling the flow rate of the nitrogen source (N ₂ ) to 120 to 150 sccm. The nitrogen source reacts with Al of the substrate 110 by the applied voltage to form the surface layer 111 having the composition of AlN and / or AlON. The thickness of the surface layer 111 may be 1.0 Å to 10 Å, but is not limited thereto. The surface layer 111 improves the crystallinity of the buffer layer 112 and can prevent surface defects.

Referring to FIG. 1 (b), the step of forming the buffer layer may grow the AlN buffer layer 112 on the surface layer 111. The growth method can be performed by placing a nitrided substrate 110 in a chamber and applying a voltage while supplying a nitrogen source (N ₂ ) and an oxygen source (O ₂ ) in an argon atmosphere. A DC voltage of 4000 W to 6000 W is applied during growth, the flow rate of argon is 45 sccm, the flow rate of nitrogen is 120 sccm, and the flow rate of oxygen is 3 sccm.

The method of growing the buffer layer 112 is not particularly limited. Exemplary methods include PVD techniques such as sputtering, E-beam evaporation, thermal evaporation, pulsed laser deposition, and laser molecular beam epitaxy And CVD processes such as MOCVD, HVPE, ALD, PECVD, LPCVD, and APCVD can all be applied.

Referring to FIG. 1 (c), the step of forming the light emitting structure may include growing the light emitting structure 190 including the n-type semiconductor layer, the active layer, and the p-type semiconductor layer on the buffer layer 112. The method of growing the light emitting structure 190 can be applied to all of the general epitaxial growth processes. The above-described PVD and CVD processes can all be applied. Since the light emitting structure 190 grows on the AlN buffer layer 112 having high crystallinity, the crystallinity can be increased and the surface state can be improved.

FIG. 2 is a graph showing the change in the half-width of the light emitting structure at the (002) plane according to RF power during the nitriding process, FIG. 3 is a photograph of the surface state of the light emitting structure at the RF power controlled at 125 W, FIG. 5 is a graph showing the change in the half-width of the light emitting structure in the (102) plane according to the RF power during the nitriding process. FIG. 5 is a photograph of the surface state of the light emitting structure when the RF power is controlled to 50 W.

Referring to FIG. 2, when the RF power is gradually increased during the nitridation process, the half width (FWHM) gradually increases. Therefore, it can be confirmed that the crystallinity of the light emitting structure is lowered as the RF power is increased. When the RF power is 125 W, the crystallinity of the light emitting structure is lowest at about 150 arcsec. The crystallinity tends to decrease as the RF power increases at the center (C), the edge (R), and the flat point (F) of the substrate. Therefore, from the viewpoint of crystallinity, it is advantageous to control the RF power to 30 W or more and 100 W or less.

Referring to FIG. 3, it can be seen that the surface of the light emitting structure also becomes poor. This is because the RF power was too high and the surface of the substrate was damaged during the nitriding process. Therefore, it was judged that the crystallinity and surface of the buffer layer grown thereon were poor, which affected the crystallinity and surface of the light emitting structure.

On the other hand, when the RF power is controlled to 50 W, the half width is low and the crystallinity of the light emitting structure is improved. Referring to FIG. 4, it can be seen that the surface of the light emitting structure is also in a relatively smooth state.

Referring to FIG. 5, the half width of the (102) plane of the light emitting structure increases as the RF power increases, and increases sharply at 100 W (center (c) of the substrate). Therefore, it may be advantageous to control the RF power to 30 W or more and 75 W or less from the viewpoint of crystallinity in the (102) plane.

Referring to FIG. 6, it can be seen that the warpage of the substrate tends to decrease until the RF power reaches 45 W in the nitriding process, but the bow amount of the substrate increases at 55 W. The bow of the substrate can be calculated as an average value of points higher than a certain height. When controlling the RF power from 30 W to 50 W or less, the warpage of the substrate can be controlled to be 78 μm or less. Further, when the RF power is controlled to be 40 W or more and 50 W or less, warping of the substrate can be suppressed more effectively.

FIG. 7 is a graph showing a change in the half width of the light emitting structure according to the nitriding treatment time, FIG. 8 is a graph showing the bow variation of the substrate with the nitriding treatment time, Emitting efficiency of the light-emitting layer.

Referring to FIG. 7, in the (002) plane, the longer the nitriding time of the light emitting structure, the smaller the half width and the higher the crystallinity. However, as shown in FIG. 8, the longer the nitriding time, the greater the warping of the substrate. Therefore, when the nitriding treatment time is controlled to 30 seconds to 50 seconds, the warpage of the substrate can be minimized while increasing the crystallinity of the light emitting structure.

Referring to FIG. 9, it can be seen that the luminous efficiency of the light emitting device does not greatly affect the nitriding process time. This is because the crystallinity of the (102) plane contributes significantly to the luminous efficiency of the light emitting device, rather than the crystallinity of the (002) plane.

FIG. 10 is a conceptual diagram of a light emitting device according to an embodiment of the present invention, and FIG. 11 is a modification of FIG.

Referring to FIG. 10, the light emitting device according to the embodiment includes a substrate 110 having a surface layer 111, a buffer layer 112, and a light emitting structure 190.

The substrate 110 may comprise a conductive substrate or an insulating substrate. The substrate 110 may be a material suitable for semiconductor material growth or a carrier wafer. The substrate 110 may be selected from a variety of substrates including Al. In the embodiment, a sapphire (Al ₂ O ₃ ) substrate is described but not limited thereto. The substrate 110 has a surface layer 111 of AlN or AlON by nitriding treatment. The substrate 110 can be removed as needed.

The buffer layer 112 may mitigate lattice mismatch between the substrate 110 and the light emitting structure 190 provided on the substrate 110. The buffer layer 112 may be increased in crystallinity and surface defects may be lowered by the surface layer 111 of the substrate.

The buffer layer 112 may be grown as a single crystal on the substrate 110 and the buffer layer 112 grown by a single crystal may improve the crystallinity of the first semiconductor layer 130.

The light emitting structure 190 provided on the substrate 110 includes a first semiconductor layer 130, an active layer 140, and a second semiconductor layer 160. In general, the light emitting structure 190 may be divided into a plurality of parts by cutting the substrate 110.

The first semiconductor layer 130 may be a compound semiconductor such as a III-V group or a II-VI group, and the first semiconductor layer 130 may be doped with a first dopant. The first semiconductor layer 130 may be a semiconductor material having a composition formula of In _{x 1} Al _{y 1} Ga ₁ -x ₁ -y1 N (0? _{X1? 1} , 0 _{? Y1? 1} , 0? X1 + _{y1? 1} ) GaN, AlGaN, InGaN, InAlGaN, and the like. The first dopant may be an n-type dopant such as Si, Ge, Sn, Se, or Te. When the first dopant is an n-type dopant, the first semiconductor layer 130 doped with the first dopant may be an n-type semiconductor layer.

The active layer 140 is a layer where electrons (or holes) injected through the first semiconductor layer 130 and holes (or electrons) injected through the second semiconductor layer 160 meet. As the electrons and the holes are recombined, the active layer 140 transits to a low energy level and can generate light having a wavelength corresponding thereto. There is no limitation on the emission wavelength in this embodiment.

The active layer 140 may have any one of a single well structure, a multiple well structure, a single quantum well structure, a multi quantum well (MQW) structure, a quantum dot structure, Is not limited thereto.

The active layer 140 may have a structure in which a plurality of well layers 141 and barrier layers 142 are alternately arranged. The well layer 141 and the barrier layer 142 may have a composition formula of InxAlyGa1-x-yN (0? X? 1, 0? Y? 1, 0? X + y? The energy band gap of the well layer 141 may be larger than the energy band gap of the well layer 141. [

The second semiconductor layer 160 may be formed on the active layer 140 and may be formed of a compound semiconductor such as a group III-V or II-VI group. The second semiconductor layer 160 may be doped with a second dopant . A second semiconductor layer 160 is a semiconductor material having a compositional formula of _{In x5 Al y2 Ga 1 -x5- y2} N (0≤x5≤1, 0≤y2≤1, 0≤x5 + y2≤1) or AlInN, AlGaAs , GaP, GaAs, GaAsP, and AlGaInP. When the second dopant is a p-type dopant such as Mg, Zn, Ca, Sr, or Ba, the second semiconductor layer 160 doped with the second dopant may be a p-type semiconductor layer.

An electron blocking layer (EBL) 150 may be disposed between the active layer 140 and the second semiconductor layer 160. The electron blocking layer 150 blocks the flow of electrons supplied from the first semiconductor layer 130 to the second semiconductor layer 160 and increases the probability that electrons and holes recombine in the active layer 140 have. The energy band gap of the electron blocking layer 150 may be greater than the energy band gap of the active layer 140 and / or the second semiconductor layer 160.

The electron blocking layer 150 may be formed of a semiconductor material having a composition formula of In _{x 1} Al _{y 1} Ga _{1 -x 1 -y 1} N (0? _{X 1 ? 1} , 0? _{Y 1 ? 1} , 0? _{X 1 + y 1 ? 1} ) , InGaN, InAlGaN, and the like, but is not limited thereto.

The first electrode 180 may be formed on the exposed first semiconductor layer 130. Also, a second electrode 170 may be formed on the second semiconductor layer 160. The first electrode 180 and the second electrode 190 may be formed of various metals and transparent electrodes. The first electrode 180 and the second electrode 170 may be formed of a metal such as In, Co, Si, Ge, Au, Pd, Pt, Ru, Re, Mg, Zn, Hf, Ta, Rh, Ir, Cr, Mo, Nb, Al, Ni, Cu, and WTi. And may further include an ohmic electrode layer as needed.

Referring to FIG. 11, the light emitting device may have a vertical structure with the substrate removed. Thus, the buffer layer 112 can function as a light extracting layer. The buffer layer 112 may have an uneven pattern 112a. As described above, since the crystallinity of the buffer layer 112 is improved by the surface layer, the light extraction efficiency can be increased. Although not shown, the first semiconductor layer 130 and the second semiconductor layer 160 may further include electrode pads electrically connected to the first semiconductor layer 130 and the second semiconductor layer 160, respectively.

The light emitting device of the embodiment further includes optical members such as a light guide plate, a prism sheet, and a diffusion sheet, and can function as a backlight unit. Further, the light emitting element of the embodiment can be further applied to a display device, a lighting device, and a pointing device.

At this time, the display device may include a bottom cover, a reflector, a light emitting module, a light guide plate, an optical sheet, a display panel, an image signal output circuit, and a color filter. The bottom cover, the reflector, the light emitting module, the light guide plate, and the optical sheet may form a backlight unit.

The reflector is disposed on the bottom cover, and the light emitting module emits light. The light guide plate is disposed in front of the reflection plate to guide light emitted from the light emitting module forward, and the optical sheet includes a prism sheet or the like and is disposed in front of the light guide plate. The display panel is disposed in front of the optical sheet, and the image signal output circuit supplies an image signal to the display panel, and the color filter is disposed in front of the display panel.

The lighting device may include a light source module including a substrate and a light emitting device of the embodiment, a heat dissipation unit that dissipates heat of the light source module, and a power supply unit that processes or converts an electric signal provided from the outside and provides the light source module . Further, the lighting device may include a lamp, a head lamp, or a street lamp or the like.

It will be apparent to those skilled in the art that various changes, substitutions, and alterations can be made hereto without departing from the spirit and scope of the invention as defined in the appended claims. Will be apparent to those of ordinary skill in the art.

110: substrate
111: Surface layer
112: buffer layer
130: first semiconductor layer
140:
150: barrier layer
160: second semiconductor layer
190: Light emitting structure

Claims (5)

Nitriding the substrate to form a surface layer;
Forming a buffer layer on the surface layer; And
And forming a light emitting structure on the buffer layer,
The step of forming the surface layer may include:
Wherein the RF voltage is applied in a nitrogen atmosphere at 30 W or more and 100 W or less.
The method according to claim 1,
In the step of forming the surface layer,
Wherein the RF voltage is applied between 30W and 50W.
The method according to claim 1,
In the step of forming the surface layer,
Wherein the RF voltage is applied between 40W and 50W.
The method according to claim 1,
In the step of forming the surface layer,
Wherein the nitriding treatment time is controlled to be 30 seconds or more and 50 seconds or less.
The method according to claim 1,
Wherein the substrate comprises Al.

Images