KR20180123375A - Micro LED and manufacturing method of the same - Google Patents

Abstract

According to the present invention, disclosed are a micro LED and a manufacturing method thereof. When preparing the micro LED, a transparent electrode is formed by forming a protective layer formed on an n-electrode and the micro LED with a transparent material of a resistance change material to isolate the n-electrode and a p-electrode from each other and forming a conductive filament inside the protective layer by applying a voltage higher than a threshold voltage inherent to the resistance change material to the protective layer region formed on a p-type semiconductor layer. Accordingly, the present invention can produce the LED with a lower cost and higher productivity by omitting a mask process for forming the transparent electrode in the prior art.

Description

[0001] The present invention relates to a micro-LED and a manufacturing method thereof,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a micro-electroluminescent device and a method of manufacturing the same, and more particularly, to a micro-electroluminescent device using a resistance-variable material as a transparent electrode and a method of manufacturing the same.

The external quantum efficiency (EQE) of a nitride-based LED is reduced as the current density injected increases, which is called an efficiency droop.

In recent years, in order to solve such a problem, studies on a micro LED having a pixel of less than 100 μm, which has a good current spreading effect and a current injection efficiency, have been actively studied rather than a large-area LED which is generally used.

Micro LEDs report not only efficiency degradation problems but also improved electrical and optical properties. Based on these advantages, micro LED has been applied as an alternative light source to various fields where conventional LED light sources such as illumination, display, and head-lamp are used.

In this case, the micro LED has two driving methods, that is, a unit pixel driving method and an array driving method, depending on the purpose of application. In the case of an array driving micro LED, all the pixels constituting the array are driven at one time And connects all the pixels using a p-electrode for driving.

In general, before the process of connecting all the pixels using the p-electrode is performed, the micro LED is divided into n-GaN or n-electrode portions exposed in the space between the pixel and the pixel (SiO x, SiN x) for separating the n-electrode (or n-GaN) and the p-electrode are deposited so that the p-electrode portions are not connected to each other.

Referring to FIG. 1, an overall fabrication process of an existing array-driven micro LED is briefly described. First, an n-GaN layer, an active layer (MQW), and a p-GaN layer are formed on a substrate. The MESA etching process is performed (see FIG. 1 (a)). Thereafter, ITO is deposited on the p-GaN layer by using a mask to form a transparent electrode layer (see Fig. 1 (b)), and an n-electrode is vapor-deposited between each cell by using a mask (c)). When an n-electrode is formed, a protective film is deposited between each cell using a mask to separate the n-electrode and the p-electrode from each other (see FIG. Finally, a p-electrode is deposited on the transparent electrode by using a mask (see Fig. 1 (e)).

In the conventional micro light emitting device process, five mask processes are performed. Since the mask process in the semiconductor process is complicated and takes a long time and is a very expensive process, the cost of the product increases as the number of mask processes increases , The more the mask process is reduced, the more the production cost can be reduced.

Accordingly, in order to lower the production cost of the product and improve the productivity, it is necessary to reduce the number of times of the mask process in the process of the micro LED, but in the case of the array-driven micro LED, 5 times of the mask process is reported as the minimum number of processes so far In fact.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a micro light emitting device and a method of manufacturing the same, which can reduce the manufacturing cost and productivity by minimizing the mask process.

According to another aspect of the present invention, there is provided a method of manufacturing a micro light emitting device, including: (a) sequentially forming a first semiconductor layer, an active layer, and a second semiconductor layer on a substrate; (b) sequentially etching the second semiconductor layer, the active layer, and the first semiconductor layer to expose the first semiconductor layer using a mask, thereby forming a plurality of micro light-emitting device cells on the substrate; (c) forming a first electrode between the plurality of micro-electroluminescent device cells by using a mask in a plurality of rows aligned with each other; (d) depositing a resistance-variable material of a transparent material on the substrate, forming a protective layer on the second semiconductor layer of the first electrodes and the plurality of micro-emissive element cells, Forming a transparent electrode on the second semiconductor layer of the plurality of micro-emissive element cells by applying a voltage to the layer region to form a conductive filament therein; And (e) forming a second electrode on the transparent electrode of each of the micro-electroluminescent device cells using a mask.

In the step (d), the protective layer is formed using a mask so as to form a hole exposing a part of the second semiconductor layer to the outside, and a portion of the second semiconductor layer exposed to the outside And a transparent filament may be formed by forming a conductive filament by applying a voltage higher than a threshold voltage inherent to the resistance variable material to the protective layer region formed on the second semiconductor layer.

In the step (e), the second electrode may be formed on the hole.

In the step (d), any one of the pair of probe electrodes is strongly contacted to the upper part of the protective layer, the probe electrode is made to contact the second semiconductor layer through the protective layer formed on the second semiconductor layer And the other one of the probe electrodes is brought into contact with the protective layer region formed on the second semiconductor layer, and then a voltage higher than a threshold voltage unique to the resistance change material is applied to form a conductive filament, thereby forming a transparent electrode.

In addition, in the step (e), the second electrode may be formed at a position where the protective layer is penetrated by the probe electrode and the second semiconductor layer is exposed.

According to another aspect of the present invention, there is provided a micro light emitting device comprising: a substrate; A plurality of micro light emitting device cells formed on the substrate; A first electrode formed of a plurality of rows arranged side by side between the micro-electroluminescent device cells; A protective layer formed on the first electrode and the plurality of micro light-emitting device cells by vapor deposition with transparent resistance change materials; A transparent electrode that is formed to have conductivity by forming a conductive filament within a region of the protective layer formed on the upper portion of the micro-electroluminescent device cell; And a second electrode formed on the transparent electrode, wherein the micro-electroluminescent device cells are formed by sequentially laminating a first semiconductor layer, an active layer, and a second semiconductor layer, and the micro- And the active layer are separated from each other, the first semiconductor layer is connected to each other, and the first electrode is formed on the first semiconductor layer exposed to the outside between the micro-electroluminescent device cells.

When the conductive filament is formed on the transparent electrode, a hole for contacting the probe electrode with the second semiconductor layer may be formed.

The second electrode may be formed on the transparent electrode so as to contact the transparent electrode while filling the hole.

In order to isolate the n-electrode and the p-electrode from each other, the protective layer formed on the n-electrode and the micro light-emitting device is formed of a transparent material of resistance change material, A voltage higher than a threshold voltage inherent to the resistance change material is applied to the protective layer region and a conductive filament is formed therein to form a transparent electrode.

Therefore, by omitting the mask process for forming the transparent electrode in the prior art, the present invention can produce a micro light emitting device with lower cost and higher productivity.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view showing a manufacturing process of a conventional micro-light-emitting device. FIG.
FIG. 2 is a view illustrating a process of manufacturing a micro light-emitting device according to a first embodiment of the present invention and a structure of a micro light-emitting device produced thereby.
FIG. 3 is a view illustrating a process of fabricating a micro light-emitting device according to a second embodiment of the present invention and a structure of a micro light-emitting device produced thereby.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 2 is a view illustrating a process of manufacturing a micro light-emitting device according to a first embodiment of the present invention and a structure of a micro light-emitting device produced thereby.

Referring to FIG. 2, a method of manufacturing a micro light emitting diode according to a first embodiment of the present invention will be described. First, a first semiconductor layer 220, an active layer (Multi-Quatum Well: MQW) 230 ) And a second semiconductor layer 240 are sequentially deposited on the substrate 210 and the MESA etching process is performed using the first mask to separate the plurality of micro light emitting device cells from the substrate 210 (a)). At this time, etching is performed so that the surface of the first semiconductor layer 220 is exposed, thereby separating into a plurality of micro light emitting device cells constituting the micro light emitting device. Accordingly, the first semiconductor layers 220 are connected to each other, but the active layer (MQW) 230 and the second semiconductor layer 240 are separated from each other. The separated micro-electroluminescent device cells are formed to be arranged in a line when viewed in the horizontal axis direction and the vertical axis direction.

In the preferred embodiment of the present invention, the first semiconductor layer 220 is formed of an n-GaN layer and the second semiconductor layer 240 is formed of a p- (Al) GnN layer. However, The layer 220 and the second semiconductor layer 240 may be formed of different materials.

Thereafter, a first electrode 250 (corresponding to the first semiconductor layer 220) is formed in a space between each cell on the surface of the first semiconductor layer 220 exposed to the outside by etching using a second mask electrode) (see Fig. 2 (b)). The first electrodes 250 may be formed in parallel with each other in a plurality of rows.

Next, a protective layer 260 is deposited on the entire surface of the first semiconductor layer 220, the first electrode 250 and the second semiconductor layer 240 by using a resistance change material of a transparent material 2 (c)). At this time, a hole 261 is formed on the second semiconductor layer 240 using a third mask.

Thereafter, in a first preferred embodiment of the present invention, one of the pair of probe electrodes for applying a voltage is brought into contact with the second semiconductor layer 240 through a hole 261 formed on the second semiconductor layer 240 And the other probe electrode is brought into contact with the protective layer 260 formed on the first semiconductor layer 220 and a voltage higher than a threshold voltage inherent to the resistance change material is applied to the second semiconductor layer 240, A transparent electrode 500 is formed on the second semiconductor layer 240 by forming the conductive filament 501 in a region of the protection layer 260 formed of a material having resistance change material.

The resistance change material is mainly used in the field of ReRAM (Resistive RAM). When a voltage higher than a threshold value inherent to a material is applied to a material, electro-forming (electric breakdown) The resistance state of the material which is an insulator initially changes from a high resistance state to a low resistance state, and thus the conductive material is exhibited. Thereafter, even when the voltage applied to the resistance change material is removed, the conductive filament 501 is maintained, and current flows through the conductive filament 501, so that the resistance state of the material is maintained in a low resistance state.

In the preferred embodiment of the present invention, the passivation layer 260 is formed using a transparent conductive oxide (SiO2, Ga2O3, Al2O3, ZnO, or the like) as the resistance change material. However, It is possible to apply materials other than the oxide-based materials.

Referring again to FIG. 2 (c), the probe is brought into contact with the second semiconductor layer 240 exposed through the hole 261 and the protective layer 260 over the second semiconductor layer 240 to apply a voltage The conductive filament 501 is locally formed only in the region of the protection layer 260 over the second semiconductor layer 240 and the current flows through the conductive filament 501 as shown in FIG. The resistance state is changed to the low resistance state in which the current flows. That is, the protective layer region 260b on the second semiconductor layer 240 is changed to a state in which a current can locally flow to function as the transparent electrode 500, and the conductive filament 501 is not formed Since the conductive filament 501 is not formed in the remaining protective layer region 260a, a high resistance state in which current can not flow is maintained and the transparent electrode 250 The electrically insulating state between the electrodes 500 is maintained.

2 (d), a second electrode (p-electrode) 270 is deposited on the transparent electrode 500 formed on the second semiconductor layer 240 using a fourth mask Thereby completing the micro light-emitting device. At this time, the second electrode 270 may be formed at an arbitrary position on the transparent electrode 500, and may be formed to contact the transparent electrode 500 while filling the hole 261 formed in the transparent electrode 500 .

In the case of the micro-electroluminescent device according to the first preferred embodiment of the present invention as shown in FIG. 2 (d), between the first electrode (n electrode) 250 and the second electrode (p electrode) 270 The current flowing through the second electrode 270 is injected into the second semiconductor layer through the conductive filament 501 of the transparent electrode 500 formed on the second semiconductor layer 240, Light is generated in the active layer 230 by the current injected into the semiconductor layer 240. Light generated in the active layer 230 is emitted to the outside through the transparent electrode 500 and the transparent protective layer 260.

The transparent electrode 500 (and the second electrode 270) formed on the first electrode 250 and the second semiconductor layer 240 may include a protective layer region 260a in which the conductive filament 501 is not formed, .

In other words, in order to maintain insulation between the first electrode 250 and the second electrode 270, the first and second electrodes 270 and 270 are formed on the entire surface of the micro- The conductive filament 501 is formed in the region 260b formed on the semiconductor layer 240 so that the protective layer region 260b is converted into the transparent electrode 500 to form the transparent electrode 500 can be omitted, and the production cost of the micro light emitting device can be reduced accordingly.

FIG. 3 is a view illustrating a process of fabricating a micro light-emitting device according to a second embodiment of the present invention and a structure of a micro light-emitting device produced thereby.

Referring to FIG. 3, the second preferred embodiment of the present invention reduces the entire mask process to three stages by further reducing the mask process step 1 in comparison with the first embodiment in which the four-step mask process is applied, Compared with the technology, there is an effect of further reducing the entire mask process by two steps.

A first semiconductor layer 220, an active layer (MQW) 230 and a second semiconductor layer 240 are formed on a substrate 210 in the same manner as in the first embodiment with reference to FIG. And then a mesa etching process is performed using the first mask to separate the plurality of micro light emitting device cells from the semiconductor substrate 210 (see FIG. 3A). Although the first semiconductor layer 220 is formed of an n-GaN layer and the second semiconductor layer 240 is formed of a p- (Al) GnN layer in the second preferred embodiment of the present invention, The semiconductor layer 220 and the second semiconductor layer 240 may be formed of different materials.

Then, a first electrode (n-1) corresponding to the first semiconductor layer 220 is formed on the first semiconductor layer 220 whose surface is exposed in a space between each cell on the surface of the substrate 210, Electrode) 250 (see Fig. 3 (b)).

Next, a protective layer 280 is deposited on the entire surface of the first semiconductor layer 220, the first electrode 250 and the second semiconductor layer 240 by using a resistance change material of a transparent material 3 (c)). In this case, in the case of the second embodiment, a separate hole 261 is not formed on the second semiconductor layer 240, unlike the first embodiment. Therefore, in the case of the second embodiment, there is no need to apply a separate mask for forming the hole 261 shown in Fig. 2 (c) of the first embodiment, so that one mask process Can be additionally omitted.

On the other hand, in the second embodiment, a voltage is applied to the protective layer region 280b formed of the transparent conductive resistive material on the second semiconductor layer 240 to form the conductive filament 501, thereby forming the transparent electrode 500 . In this case, in order to form the transparent electrode 500, the second embodiment is configured such that a pair of the probe electrodes are respectively contacted to the protective layer region 280b on the second semiconductor layer 240 and then a voltage is applied The conductive filament 501 can be locally formed in the protective layer region 280b.

In order to more smoothly form the conductive filament 501 in the protective layer region 280b on the second semiconductor layer 240 in the second embodiment, any one of the pair of the probe electrodes may be formed in the protective layer region 280b so that the probe electrode penetrates through the protective layer region 280b and comes into contact with the second semiconductor layer 240. In this way, in a portion of the protective layer region 260b in the first embodiment, The same effect as that of forming the first electrode 261 may be exhibited.

When the transparent electrode 500 on the second semiconductor layer 240 is formed, a third mask is formed in the same manner as in the first embodiment (FIG. 2 (d)), A second electrode (p-electrode) 270 is formed on the transparent electrode 500.

At this time, the second electrode 270 may be formed at an arbitrary position on the transparent electrode 500, and the protective layer region 280b may be penetrated by the probe electrode to a position where the second semiconductor layer 240 is exposed .

The present invention has been described with reference to the preferred embodiments. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. Therefore, the disclosed embodiments should be considered in an illustrative rather than a restrictive sense. The scope of the present invention is defined by the appended claims rather than by the foregoing description, and all differences within the scope of equivalents thereof should be construed as being included in the present invention.

210: substrate
220: first semiconductor layer
230:
240: second semiconductor layer
250: first electrode
260: protective layer
261: hole
270: second electrode
280: protective layer
500: transparent electrode
501: Conductive filament

Claims (8)

(a) sequentially forming a first semiconductor layer, an active layer, and a second semiconductor layer on a substrate;
(b) sequentially etching the second semiconductor layer, the active layer, and the first semiconductor layer to expose the first semiconductor layer using a mask, thereby forming a plurality of micro light-emitting device cells on the substrate;
(c) forming a first electrode between the plurality of micro-electroluminescent device cells by using a mask in a plurality of rows aligned with each other;
(d) depositing a resistance-variable material of a transparent material on the substrate, forming a protective layer on the second semiconductor layer of the first electrodes and the plurality of micro-emissive element cells, Forming a transparent electrode on the second semiconductor layer of the plurality of micro-emissive element cells by applying a voltage to the layer region to form a conductive filament therein; And
(e) forming a second electrode on the transparent electrode of each of the micro-electroluminescent device cells using a mask. 2. The method of claim 1, wherein step (d)
The mask is used to form the protective layer so as to form a hole exposing a part of the second semiconductor layer to the outside,
A transparent electrode is formed by forming a conductive filament by applying a voltage equal to or higher than a threshold voltage inherent to the resistance change material to a portion of the second semiconductor layer exposed to the outside and a protection layer region formed over the second semiconductor layer Wherein the light emitting layer is formed on the substrate. 3. The method of claim 2,
Wherein the second electrode is deposited on the hole in the step (e). 2. The method of claim 1, wherein step (d)
One of the pair of probe electrodes is strongly brought into contact with the upper part of the protective layer so that the probe electrode is made to contact the second semiconductor layer through the protective layer formed on the second semiconductor layer, And forming a conductive filament by applying a voltage of at least a threshold voltage inherent to the resistance variable material to form a transparent electrode. 5. The method of claim 4,
Wherein the second electrode is formed at a position where the protective layer is penetrated by the probe electrode to expose the second semiconductor layer.
Board;
A plurality of micro light emitting device cells formed on the substrate;
A first electrode formed of a plurality of rows arranged side by side between the micro-electroluminescent device cells;
A protective layer formed on the first electrode and the plurality of micro light-emitting device cells by vapor deposition with transparent resistance change materials;
A transparent electrode that is formed to have conductivity by forming a conductive filament within a region of the protective layer formed on the upper portion of the micro-electroluminescent device cell; And
And a second electrode formed on the transparent electrode,
Wherein the first semiconductor layer, the active layer, and the second semiconductor layer are sequentially stacked, wherein the second semiconductor layer and the active layer are separated from each other, and the first semiconductor layer Wherein the first electrode is formed on the first semiconductor layer exposed to the outside between the micro-electroluminescent device cells. The method according to claim 6,
Wherein the transparent electrode is formed with a hole for contacting the second semiconductor layer with the probe electrode when the conductive filament is formed. 8. The method of claim 7,
Wherein the second electrode is formed on the transparent electrode so as to contact the transparent electrode while filling the hole.

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