WO2013168929A1

WO2013168929A1 - Light emitting diode having plurality of light emitting elements and method of fabricating the same

Info

Publication number: WO2013168929A1
Application number: PCT/KR2013/003827
Authority: WO
Inventors: Ye Seul Kim; Kyoung Wan Kim; Yeo Jin Yoon
Original assignee: Seoul Opto Device Co., Ltd.
Priority date: 2012-05-11
Filing date: 2013-05-03
Publication date: 2013-11-14

Abstract

Disclosed are a light emitting diode (LED) having a plurality of light emitting elements and a method of fabricating the same. The LED includes a plurality of light emitting elements arranged on a substrate, a separation groove for separating adjacent light emitting elements from each other, an insulative material filled in at least a portion of the separation groove, and a wiring for electrically connecting two adjacent light emitting elements to each other.

Description

LIGHT EMITTING DIODE HAVING PLURALITY OF LIGHT EMITTING ELEMENTS AND METHOD OF FABRICATING THE SAME

The present invention relates to a light emitting diode (LED) and a method of fabricating the same, and more particularly, to an LED having a plurality of light emitting elements on a single substrate and a method of fabricating the same.

A light emitting diode (LED) is a light emitting device that has many advantages including eco-friendliness, energy saving effect, long lifespan, and the like. However, since the LED is a DC-driven device, a converter is required so that the LED is driven by an AC power source such as a household power source. The converter has a shorter lifespan than that of the LED, and hence the lifespan of a product incorporating the converter is shortened by the lifespan of the converter. In addition, the efficiency of the product is decreased by 20 to 30% due to AC/DC conversion, and there are many problems including degradation of reliability, environmental pollution, provision of a space in the product, design limitation, and the like, which may be caused by the use of the converter. In order to solve such problems, there has been developed an LED that can be driven without using a conventional converter.

Such an LED generally includes a plurality of light emitting elements on a substrate, and the light emitting elements are electrically connected through wires to construct various circuits.

Fig. 1 is a schematic plan view illustrating an LED having a plurality of light emitting elements according to a related art. Fig. 2 is a sectional view taken along line A-A of Fig. 1.

Referring to Figs. 1 and 2, the LED includes a substrate 21, a plurality of light emitting elements 30, a transparent electrode 29, an insulation layer 31 and a wiring 33. Each of the light emitting elements 30 includes an n-type semiconductor layer 23, an active layer 25 and a p-type semiconductor layer 27.

The plurality of light emitting elements 30 are electrically separated from one other by separation grooves 30h on the substrate 21. An upper surface of the n-type semiconductor layer 23 is exposed through a contact groove 27a formed by removing the p-type semiconductor layer 27 and the active layer 25.

The wiring 33 electrically connects an n-type semiconductor layer 23 of one (first) light emitting element 30 to a p-type semiconductor layer 27 of another (second) light emitting element 30. As shown in these figures, the wiring 33 may connect the exposed upper surface of the n-type semiconductor layer 23 of the first light emitting element 30 to the transparent electrode 29 of the second light emitting element 30. The insulation layer 31 is positioned between the wiring 33 and the light emitting elements 30 to insulate the wiring 33 from side surfaces of the light emitting elements 30.

According to the related art, it is possible to provide the light emitting elements 30 connected in series by the wiring 33. Further, it is possible to provide an LED that can be driven by a high-voltage AC power source using the plurality of light emitting elements 30.

In the LED according to the related art, it is necessary to form the separation groove 30h reaching an upper surface of the substrate 21 in order to make sure the electrical separation between the light emitting elements 30. Portions of the wiring 33 are formed on the side surfaces of the light emitting elements 30 in the separation groove 30h. Since the light emitting element 30 typically has a height of about 5㎛ or more, it is difficult to form the wiring 33 on the side surface of the light emitting element 30 if the side surface of the light emitting element 30 is steep, resulting in high likelihood of disconnection of the wiring 33. In order to prevent the disconnection of the wiring 33, the side surface of the light emitting element 30 is generally formed to have a gentle slope.

However, in a case where the side surface of the light emitting element 30 is formed to have a gentle slope, the entrance of the separation groove 30h for the electrical separation between the light emitting elements 30 is relatively widened to have a width W of about 35㎛ or more, leading to reduction of the light emitting area of the LED.

An object of the present invention is to provide a light emitting diode (LED) having a plurality of light emitting elements, and particularly, to provide an LED that can ensure electrical separation between light emitting elements and increase a light emitting area while preventing a disconnection of a wiring, and a method of fabricating the same.

A light emitting diode (LED) according to an aspect of the present invention includes a substrate; a plurality of light emitting elements arranged on the substrate; a separation groove for separating adjacent light emitting elements from each other; an insulative material filled in at least a portion of the separation groove; and a wiring for electrically connecting two adjacent light emitting elements to each other. Each of the light emitting elements includes a first conductive semiconductor layer, an active layer and a second conductive semiconductor layer, and further includes a contact groove for allowing the first conductive semiconductor layer to be exposed through the second conductive semiconductor layer and the active layer. Further, the contact groove is positioned to be spaced apart from the separation groove.

Since the separation groove is filled with the insulative material, it is unnecessary to form the wiring within the separation groove. Thus, it is unnecessary to form the separation groove such that a sidewall thereof has a gentle slope, thereby decreasing the width of an entrance of the separation groove. Accordingly, the light emitting area of the LED can be increased as compared with the related art. Further, since the contact groove and the separation groove are positioned to be spaced apart from each other, it is possible to prevent the contact groove from being filled with the insulative material and to easily fill the separation groove with the insulative material.

Meanwhile, the wiring may traverse above the insulative material so as to electrically connect the first conductive semiconductor layer exposed through the contact groove of a first light emitting element to the second conductive semiconductor layer of a second light emitting element.

An upper surface of the insulative material is positioned to be higher than an upper surface of the first conductive semiconductor layer. Further, the upper surface of the insulative material may be positioned at substantially the same height as the upper surface of the second conductive semiconductor layer.

Moreover, the sidewall of the separation groove includes the first conductive semiconductor layer, the active layer and the second conductive semiconductor layer. Thus, the sidewalls on either side of the separation groove can have the same height.

The separation groove may be formed by using a dry or wet etching technique, or may be formed by means of laser processing. In a case where the separation groove is formed by means of the laser processing, the separation groove may extend to the inside of the substrate. Further, the separation groove is formed to have a width narrowed toward the substrate.

The insulative material may comprise polyimide or nanoparticles.

An air gap may be positioned between the insulative material and the substrate.

The entrance of the separation groove may have a width of 5㎛ or less, and a lower limit thereof is not particularly limited as long as the separation groove electrically separates the light emitting elements. For example, the entrance of the separation groove may have a width of 1㎛ or more. Further, the sidewall of the separation groove may be reversely inclined.

Meanwhile, the LED may further include an insulation layer covering the sidewall of the contact groove. The insulation layer is positioned between the wiring and the light emitting element so as to insulate the wiring from the light emitting element.

A portion of the insulation layer may cover the upper surface of the insulative material.

The separation groove includes an upper separation groove and a lower separation groove positioned at the bottom of the upper separation groove, and an entrance of the upper separation groove has a width wider than that of an entrance of the lower separation groove.

The upper separation groove is formed by using an etching technique, and the lower separation groove is formed by using a laser processing technique, so that the active layer can be prevented from being damaged by the laser.

A sidewall of the upper separation groove may comprise the first conductive semiconductor layer, the active layer and the second conductive semiconductor layer. Further, the sidewalls on either side of the upper separation groove may have the same height.

Meanwhile, the upper separation groove may have the same height as the contact groove. Moreover, the lower separation groove may be formed by laser processing so as to have a width narrowed toward the substrate.

The entrance of the upper separation groove may have a width of 5㎛ or less, and a lower limit thereof is not particularly limited as long as the upper separation groove electrically separates the light emitting elements. For example, the entrance of the upper separation groove may have a width of 1㎛ or more. Further, the sidewall of the upper separation groove may be reversely inclined.

A method of fabricating an LED according to another aspect of the present invention includes growing a first conductive semiconductor layer, an active layer and a second conductive semiconductor layer on a substrate; etching the second conductive semiconductor layer and the active layer to form a plurality of contact grooves for exposing the first conductive semiconductor layer therethrough; forming a separation groove so that a plurality of light emitting elements are electrically separated; filling at least a portion of the separation groove with an insulative material; and forming a wiring for electrically connecting adjacent light emitting elements to each other. Here, the separation groove and the contact groove are positioned to be spaced apart from each other.

The contact groove may be formed before the separation groove is formed, but the present invention is not limited thereto. That is, the contact groove may be formed after the separation groove is formed.

The forming the separation groove may comprise removing the first conductive semiconductor layer, the active layer and the second conductive semiconductor layer, by using an etching process or laser processing process.

The separation groove comprises an upper separation groove and a lower separation groove positioned at the bottom of the upper separation groove, and an entrance of the upper separation groove has a width wider than that of an entrance of the lower separation groove.

The upper separation groove may be formed simultaneously while the contact groove is formed. A sidewall of the upper separation groove may be inclined identically to a sidewall of the contact groove. Meanwhile, the sidewall of the upper separation groove may be inclined more gently than a sidewall of the lower separation groove.

The upper separation groove and the contact groove may be formed by using an etching technique, for example, a dry etching technique. Meanwhile, the forming the lower separation groove may include removing the first conductive semiconductor layer exposed at the bottom surface of the upper separation groove, by using a laser processing technique. Further, the forming the lower separation groove may further include removing the first conductive semiconductor layer by using the laser processing technique, and then performing a sulfuric and phosphoric acid treatment.

According to the embodiments of the present invention, a separation groove is filled with an insulative material, thereby reducing a step between light emitting elements on which a wiring is to be formed. Accordingly, a disconnection of the wiring can be prevented, and a sidewall of the separation groove is formed to be rapidly inclined, thereby decreasing the width of an entrance of the separation groove. Thus, it is possible to prevent reduction in a light emitting area which otherwise would be caused by forming the separation groove. Further, it is possible to improve light extraction efficiency, using the insulative material filled in the separation groove.

Fig. 1 is a plan view illustrating a light emitting diode (LED) according to a related art.

Fig. 2 is a sectional view taken along line A-A of Fig. 1, illustrating the LED according to the related art.

Fig. 3 is a plan view illustrating an LED according to an embodiment of the present invention.

Fig. 4 is a sectional view taken along line B-B of Fig. 3, illustrating the LED according to the embodiment of the present invention.

Figs. 5 to 20 are sectional views illustrating LEDs according to various embodiments of the present invention.

Figs. 21 to 28 are sectional views illustrating methods of fabricating LEDs according to embodiments of the present invention.

Fig. 29 is a plan view illustrating an example of an LED having four light emitting elements according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are provided only for illustrative purposes so that those skilled in the art can fully understand the spirit of the present invention. Therefore, the present invention is not limited to the following embodiments but may be implemented in other forms. In the drawings, the widths, lengths, thicknesses and the like of elements are exaggerated for convenience of illustration. Like reference numerals indicate like elements throughout the specification and drawings.

Fig. 3 is a plan view illustrating a light emitting diode (LED) according to an embodiment of the present invention, and Fig. 4 is a sectional view taken along line B-B of Fig. 3.

Referring to Figs. 3 and 4, the LED includes a substrate 51, a plurality of light emitting elements 60, a separation groove 60h, an insulative material 60i, a transparent electrode 59, an insulation layer 61 and a wiring 63. Each of the light emitting element 60 includes a first conductive semiconductor layer 53, an active layer 55 and a second conductive semiconductor layer 57.

The substrate 51 is a substrate for supporting the plurality of light emitting elements 60 and may be, but not limited to, a growth substrate, e.g., a sapphire substrate, SiC substrate, spinel substrate or the like on which gallium nitride-based semiconductor layers are grown. The first conductive semiconductor layer 53, the active layer 55 and the second conductive semiconductor layer 57 may be grown on the substrate 51 by means of a growth technique such as metal oxide chemical vapor deposition (MOCVD). Here, the first conductive semiconductor layer 53 is relatively thicker than the second conductive semiconductor layer 57. For example, the first conductive semiconductor layer 53 has a thickness of about 3㎛ or more, and the second conductive semiconductor layer 57 has a thickness of about less than 1㎛. Generally, the first conductive semiconductor layer 53 is an n-type semiconductor layer and the second conductive semiconductor layer 57 is a p-type semiconductor layer.

The plurality of light emitting elements 60 are electrically separated from one another by separation grooves 60h, and the first conductive semiconductor layer 53 of each of the light emitting elements 60 has an upper surface exposed through a contact groove 57a. The contact groove 57a exposes the first conductive semiconductor layer 53 through the second conductive semiconductor layer 57 and the active layer 55, and is spaced apart from the separation groove 60h. The contact groove 57a may be formed within the light emitting element 60 and surrounded by the second conductive semiconductor layer 57 and the active layer 55. The contact groove 57a may have an elongated rectangular shape, as shown in Fig. 3, but is not necessarily limited thereto.

The separation groove 60h is formed between the light emitting elements 60. The separation groove 60h may be also formed along the periphery of the light emitting element 60.

The separation groove 60h is formed by penetrating through the second conductive semiconductor layer 57, the active layer 55 and the first conductive semiconductor layer 53. Thus, each of sidewalls of the separation groove 60h includes the second conductive semiconductor layer 57, the active layer 55 and the first conductive semiconductor layer 53.

The sidewall of the separation groove 60h may have a relatively steep slope, and the width W of the entrance of the separation groove 60h may be less than 5㎛. Here, the separation groove 60h is formed using a dry or wet etching technique. As shown in Fig. 4, the sidewall of the contact groove 57a may be formed to have a gentler slope than that of the sidewall of the separation groove 60h.

The transparent electrode 59 is positioned on the second conductive semiconductor layer 57 of each of the light emitting elements 60 to be in ohmic-contact with the second conductive semiconductor layer 57. The transparent electrode 59 may be formed of a transparent oxide such as indium tin oxide (ITO) or a transparent metal layer such as Ni/Au.

Meanwhile, the separation groove 60h is filled with the insulative material 60i. The insulative material 60i may be polyimide. The polyimide has low thermal deformation due to excellent heat resistance, and has excellent impact resistance, dimensional stability and insulation capability. Further, the refractive index of the polyimide (about 1.7) is relatively smaller than the refractive index of GaN (about 2.45), so that the polyimide is suitable for total internal reflection of light traveling through the first conductive semiconductor layer 53.

The insulative material 60i is positioned within the separation groove 60h, and the upper surface of the insulative material 60i may be positioned to be higher than the first conductive semiconductor layer 53. Moreover, the upper surface of the insulative material 60i may be positioned to be nearly flush with the upper surface of the second conductive semiconductor layer 57.

The insulation layer 61 covers the sidewalls of the contact groove 57a, and has an opening that exposes therethrough the upper surface of the transparent electrode 59 and the upper surface of the first conductive semiconductor layer 53 exposed in the contact groove 57a. The insulation layer 61 may be formed of silicon oxide or silicon nitride, and a portion of the insulation layer 61 may cover the upper surface of the insulative material 60i.

Meanwhile, the wiring 63 electrically connects the first conductive semiconductor layer 53 of one (first) light emitting element to the second conductive semiconductor layer 57 of another (second) light emitting element. As shown in these figures, the wiring 63 can connect the first conductive semiconductor layer 53 of the first light emitting element, which is exposed in the contact groove 57a, to the transparent electrode 59 of the second light emitting element. The insulation layer 61 also prevents the wiring 63 from being electrically connected to the active layer 55 and the second conductive semiconductor layer 57 of the first light emitting element.

The wiring 63 traverses above the insulative material 60i. The wiring 63 may be insulated from the transparent electrode 59 of the first light emitting element 60 by the insulation layer 61. Meanwhile, the transparent electrode 59 of the first light emitting 60 may be omitted in a region below the wiring 63, and thus the insulation layer 61 can insulate the wiring 63 from the second conductive semiconductor layer 57. In this case, it is possible to partially remove a step formed by the transparent electrode 59 in the vicinity of the entrance of the separation groove 60h.

According to this embodiment, since it is unnecessary to form the wiring 63 in the separation groove 60h, the width W of the separation groove 60h can be further narrowed. Thus, it is possible to relieve a decrease in a light emitting area of the LED that is caused by the formation of the separation groove 60h. Further, the depth of the contact groove 57a of the light emitting element 60 is relatively smaller than the entire height of the light emitting element 60 or the depth of the separation groove 60h. Thus, the wiring 63 can be more easily formed as compared with a conventional LED, and a disconnection of the wiring 63 can be prevented.

Fig. 5 is a sectional view illustrating an LED according to another embodiment of the present invention.

Referring to Fig. 5, the LED according to this embodiment is generally similar to the LED described with reference to Fig. 4, but is different therefrom in that a separation groove 70h is formed using a laser processing technique.

That is, the separation groove 70h is formed by means of irradiation of a laser, and thus can extended into the substrate 51. Since the separation groove 70h is formed by means of the irradiation of the laser, the width of the separation groove 70h may be decreased toward the substrate 51. In a case where the separation groove 70h is formed by means of the irradiation of the laser, a phosphoric acid treatment (at 90 to 120℃, for 5 to 12 minutes) is performed to remove debris that is produced by the laser and remains on the surface of a GaN layer.

According to this embodiment, the separation groove 70h is formed using the laser processing technique, and thus the width of the separation groove 70h can be further decreased.

Fig. 6 is a sectional view illustrating an LED according to a further embodiment of the present invention.

Referring to Fig. 6, the LED according to this embodiment is generally similar to the LED described with reference to Fig. 4, but is different therefrom in that an insulative material 70i consists of nanoparticles.

That is, in this embodiment, the insulative material 70i includes nanoparticles that may be, for example, nanoscale spherical silica. By using nanoparticles having a relatively small refractive index, particularly nanoscale silica having a refractive index of about 1.46, light passing through the first conductive semiconductor layer 53 is reflected by the nanoparticles, thereby improving light extraction efficiency. Moreover, since air having a refractive index of 1 remains between the nanoparticles, the light can be further reflected.

Fig. 7 is a sectional view illustrating an LED according to a still further embodiment of the present invention.

Referring to Fig. 7, the LED according to this embodiment is generally similar to the LED described with reference to Fig. 5, but is different therefrom in that an insulative material 70i is the nanoparticles described with reference to Fig. 6.

Fig. 8 is a sectional view illustrating an LED according to a still further embodiment of the present invention.

Referring to Fig. 8, LED according to this embodiment is generally similar to the LED described with reference to Fig. 5, but is different therefrom in that an air gap 70v remains between the insulative material 60i and the substrate 51. That is, the separation groove 70h is not completely filled with the insulative material 60i but the air gap 70v is formed at a lower portion of the separation groove 70h.

Since the refractive index of the air gap 70v is 1, the air gap is more advantageous in total internal reflection than the polyimide 60i. Thus, it is possible to further improve the light extraction efficiency.

Fig. 9 is a sectional view illustrating an LED according to a still further embodiment of the present invention.

Referring to Fig. 9, the LED according to this embodiment is generally similar to the LED described with reference to Fig. 8, but is different therefrom in that nanoparticles 70i are placed instead of the air gap 70v.

That is, the nanoparticles 70i may be placed at the lower portion of the separation groove 70h, and the polyimide 60i may be positioned on the nanoparticles 70i.

Fig. 10 is a sectional view illustrating an LED according to a still further embodiment of the present invention.

Referring to Fig. 10, the LED according to this embodiment is generally similar to the LED described with reference to Fig. 4, but is different therefrom in that sidewalls of a separation groove 80h are reversely inclined.

The inclined surface of the sidewall of the separation groove 80h is controlled, so that light traveling within the first conductive semiconductor layer 53 can be easily emitted outward, thereby further improving the light extraction efficiency.

The separation groove 80h may be formed by forming the separation groove 60h of Fig. 4 and then performing a sulfuric and phosphoric acid treatment (H₂SO₄:H₃PO₄=3:1, 280℃, about 5 minutes).

Fig. 11 is a sectional view illustrating an LED according to a still further embodiment of the present invention.

Referring to Fig. 11, the LED according to this embodiment is generally similar to the LED described with reference to Fig. 5, but is different therefrom in that sidewalls of a separation groove 90h are reversely inclined.

The separation groove 90h may be formed by forming the separation groove 70h of Fig. 5 and then performing the sulfuric and phosphoric acid treatment (H₂SO₄:H₃PO₄=3:1, 280℃, about 5 minutes). Thus, a portion of the separation groove 70h extending into the substrate 51 remains.

Fig. 12 is a sectional view illustrating an LED according to a still further embodiment of the present invention.

Referring to Fig. 12, the LED according to this embodiment is generally similar to the LED described with reference to Fig. 10, but is different therefrom in that an insulative material 70i is the nanoparticles described with reference to Fig. 6.

Fig. 13 is a sectional view illustrating an LED according to a still further embodiment of the present invention.

Referring to Fig. 13, the LED according to this embodiment is generally similar to the LED described with reference to Fig. 12, but is different therefrom in that the nanoparticles 70i are placed at a lower portion of a separation groove 90h and the polyimide 60i is positioned at an upper portion of the separation groove 90h.

Fig. 14 is a sectional view illustrating an LED according to a still further embodiment of the present invention.

Referring to Fig. 14, the LED according to this embodiment is generally similar to the LED described with reference to Fig. 4, but is different therefrom in that a separation groove 160h includes an upper separation groove 160a and a lower separation groove 160b.

The upper separation groove 160a may be formed by penetrating through the second conductive semiconductor layer 57 and the active layer 55. Therefore, each of sidewalls of the upper separation groove 160a may include the second conductive semiconductor layer 57, the active layer 55 and the first conductive semiconductor layer 53. Moreover, the upper separation groove 160a may be formed by means of the same process as the contact groove 57a so as to have the same depth, and may be inclined identically to the contact groove 57a.

Meanwhile, the lower separation groove 160b is formed in the bottom surface of the upper separation groove 160a so as to be positioned beneath the upper separation groove 160a. The entrance of the lower separation groove 160b has a width narrower than that of the entrance of the upper separation groove 160a. The lower separation groove 160b is formed by penetrating through the first conductive semiconductor layer 53 and has sidewalls rapidly inclined, as compared with the upper separation groove 160a.

The width W of the entrance of the upper separation groove 160a may be less than 5㎛. Here, the upper separation groove 160a may be formed using, for example, a dry etching technique, and the lower separation groove 160b may be formed using a laser processing technique.

Further, the upper separation groove 160a is formed using the etching technique, and the lower separation groove 160b is formed using the laser processing technique, so that it is possible to prevent the active layer 55 from being damaged by a laser. Meanwhile, as the lower separation groove 160b is formed by means of irradiation of the laser, the separation groove 160h can extend into the substrate 51. The width of the lower separation groove 160b is decreased toward the substrate 51. In a case where the lower separation groove 160b is formed by means of the irradiation of the laser, a phosphoric acid treatment (90 to 120℃, 5 to 12 minutes) may be further performed so that debris remaining on the surface of the GaN layer, which is produced by the laser, may be removed. However, since the lower separation groove 160b is formed below the active layer 55, the phosphoric acid treatment may be omitted.

Fig. 15 is a sectional view illustrating an LED according to a still further embodiment of the present invention.

Referring to Fig. 15, the LED according to this embodiment is generally similar to the LED described with reference to Fig. 14, but is different therefrom in that an insulative material 70i is nanoparticles.

That is, in this embodiment, the insulative material 70i includes nanoparticles, and the nanoparticles may be, for example, nanoscale spherical silica. By using nanoparticles having a relatively small refractive index, particularly nanoscale silica having a refractive index of about 1.46, light traveling within the first conductive semiconductor layer 53 is reflected by the nanoparticles, thereby improving light extraction efficiency. Moreover, since air having a refractive index of 1 remains between the nanoparticles, the light can be further reflected.

Fig. 16 is a sectional view illustrating an LED according to a still further embodiment of the present invention.

Referring to Fig. 16, the LED according to this embodiment is generally similar to the LED described with reference to Fig. 14, but is different therefrom in that an air gap 70v remains between the insulative material 60i and the substrate 51. That is, the separation groove 160h is not completely filled with the insulative material 60i but the air gap 70v is formed at a lower portion of the separation groove 160h.

Since the refractive index of the air gap 70v is 1, the air gap is more advantageous in total internal reflection than the polyimide 60i. Thus, the light extraction efficiency can be further improved.

Fig. 17 is a sectional view illustrating an LED according to a still further embodiment of the present invention.

Referring to Fig. 17, the LED according to this embodiment is generally similar to the LED described with reference to Fig. 16, but is different therefrom in that nanoparticles 70i are placed instead of the air gap 70v.

That is, the nanoparticles 70i may be placed at the lower portion of the separation groove 160h, and the polyimide 60i may be positioned on the nanoparticles. For example, the lower separation groove 160b may be filled with the nanoparticles 70i, and the upper separation groove 160a may be filled with the polyimide 60i.

Fig. 18 is a sectional view illustrating an LED according to a still further embodiment of the present invention.

Referring to Fig. 18, the LED according to this embodiment is generally similar to the LED described with reference to Fig. 14, but is different therefrom in that the shape of a separation groove 170h is different from that of the separation groove 160h. That is, unlike the lower separation groove 160b of the separation groove 160h, a lower separation groove 160c of the separation groove 170h has sidewalls reversely inclined.

The inclined surface of the sidewall of the lower separation groove 160c is controlled, so that light traveling within the first conductive semiconductor layer 53 can be easily emitted outward, thereby further improving the light extraction efficiency.

The lower separation groove 160c may be formed by forming the lower separation groove 160b of Fig. 14 and then performing a sulfuric and phosphoric acid treatment (H₂SO₄:H₃PO₄=3:1, 280℃, about 5 minutes).

Fig. 19 is a sectional view illustrating an LED according to a still further embodiment of the present invention.

Referring to Fig. 19, the LED according to this embodiment is generally similar to the LED described with reference to Fig. 18, but is different therefrom in that an insulative material 70i is the nanoparticles as described with reference to Fig. 15.

Fig. 20 is a sectional view illustrating an LED according to a still further embodiment of the present invention.

Referring to Fig. 20, the LED according to this embodiment is generally similar to the LED described with reference to Fig. 19, but is different therefrom in that the nanoparticles 70i are placed at a lower portion of a separation groove 170h and the polyimide 60i is placed at an upper portion of the separation groove 170h. For example, the lower separation groove 160c may be filled with the nanoparticles 70i, and the upper separation groove 160a may be filled with the polyimide 60i.

Figs. 21 and 22 are sectional views illustrating a method of fabricating an LED according to an embodiment of the present invention.

Referring to Fig. 21, a first conductive semiconductor layer 53, an active layer 55 and a second conductive semiconductor layer 57 are first grown on a substrate 51. These semiconductor layers may be grown with a GaN-based compound semiconductor, using a growth technique such as MOCVD or molecular beam epitaxy (MBE). Although not shown in this figure, a buffer layer may be grown before the first conductive semiconductor layer 53 is grown.

Subsequently, the second conductive semiconductor layer 57 and the active layer 55 are etched to form a contact groove 57a for exposing the first conductive semiconductor layer 53 therethrough. The first conductive semiconductor layer 53 has an upper surface exposed by the contact groove 57a. Sidewalls of the contact groove 57a are relatively gently inclined as shown in this figure.

Referring to Fig. 22, separation grooves 60h are formed to electrically separate a plurality of light emitting elements 60 from one another. Before the separation grooves 60h are formed, a mask pattern 58 covering other regions except the regions of the separation grooves 60h may be formed. The mask pattern 58 may be formed of silicon oxide or silicon nitride.

Subsequently, regions exposed through the mask pattern 58 may be dry or wet etched to form the separation grooves 60h.

The mask pattern 58 may be removed after the separation grooves 60h are formed. Then, the insulative material (60i of Fig. 4) filled in the separation grooves 60h is formed, and a transparent electrode 59, an insulation layer 61 and a wiring are formed to fabricate the LED of Fig. 4. The insulative material 60i may be formed by spin-coating photosensitive polyimide and then exposing and developing the photosensitive polyimide to remove the polyimide in other regions except the polyimide in the separation grooves 60h. Alternatively, the insulative material 60i may be formed by coating non-photosensitive polyimide and then patterning the non-photosensitive polyimide using a photolithography (wet or dry etching) process.

The transparent electrode 59 may be pre-formed before the contact groove 57a is formed, or may be formed before the mask pattern 58 is formed or before the insulative material 60i is formed.

Meanwhile, the separation groove 60h may be filled with nanoparticles, i.e., an insulative material (70i of Fig. 6), instead of the insulative material 60i, to fabricate the LED of Fig. 6. The insulative material 70i may be formed by dispersing nanoparticles in water or another solvent and then spin-coating the resulting dispersion.

Fig. 23 is a sectional view illustrating a method of fabricating an LED according to a still further embodiment of the present invention.

Referring to Fig. 23, as described with reference to Figs. 21 and 22, the separation groove 60h is formed, and a sulfuric and phosphoric acid treatment (H₂SO₄:H₃PO₄=3:1, 280℃, about 5 minutes) is then performed before the mask pattern 58 is removed, thereby forming a separation groove 80h having sidewalls reversely inclined.

Subsequently, the mask pattern 58 is removed, an insulative material (60i of Fig. 10) filled in the separation groove 60h is formed, and the transparent electrode 59, the insulation layer 61 and the wiring 63 are formed, thereby fabricating the LED of Fig. 10.

Fig. 24 is a sectional view illustrating a method of fabricating an LED according to a still further embodiment of the present invention.

Referring to Fig. 24, the method according to this embodiment is generally similar to the method described with reference to Figs. 21 and 22, but is different therefrom in that a separation groove 70h is formed using a laser processing technique.

That is, the separation groove 70h for separating the light emitting elements 60 is formed by means of irradiation of a laser, and a phosphoric acid treatment may be performed to remove GaN damaged by the laser. The separation groove 70h extending into the substrate 51 may be formed by the laser processing.

In this embodiment, the mask pattern 58 may be pre-formed to define the entrance of the separation groove 70h before the irradiation of the laser, but the present invention is not limited thereto. For example, since a mask material may be removed by the laser, the separation groove 70h may be formed by covering the semiconductor layers, which have the contact groove 57a formed therein, with a mask material layer and directly irradiating the mask material layer with the laser.

After the separation groove 70h is formed, the mask pattern 58 is removed and an insulative material (60i of Fig. 3) filled in the separation groove 70h is formed, and the transparent electrode 59, the insulation layer 61 and the wiring 63 are formed, thereby fabricating the LED of Fig. 5. The insulative material 60i may be formed to cause an air gap (70v of Fig. 8) to remain, thereby fabricating the LED of Fig. 8. The separation groove 70h may be filled with nanoparticles (70i of Fig. 7) instead of the insulative material 60i, thereby fabricating the LED of Fig. 7. The nanoparticles and polyimide may be combined, thereby fabricating the LED of Fig. 9.

Fig. 25 is a sectional view illustrating a method of fabricating an LED according to a still further embodiment of the present invention.

Referring to Fig. 25, the method according to this embodiment further includes forming the separation groove 70h as described with reference to Fig. 24 and then performing the sulfuric and phosphoric acid treatment (H₂SO₄:H₃PO₄=3:1, 280℃, about 5 minutes) before removal of the mask pattern 58 to form a separation groove 90h having sidewalls reversely inclined.

Subsequently, the mask pattern 58 is removed, and the separation groove 90h is filled with the insulative material 60i, the insulative material 70i or a combination of the

insulative materials

60i and 70i, thereby fabricating the LED shown in Fig. 11, 12 or 13.

Figs. 26 and 27 are sectional views illustrating a method of fabricating an LED according to a still further embodiment of the present invention.

Referring to Fig. 26, in the method according to this embodiment, an upper separation groove 160a penetrating through the second conductive semiconductor layer 57 and the active layer 55 is formed during, before or after the formation of the contact groove 57a as described above with reference to Fig. 21. The upper separation groove 160a may be formed together with the contact groove 57a by means of the same process. Thus, the upper separation groove 160a and the contact groove 57a may be formed to have substantially the same depth.

Referring to Fig. 27, a lower separation groove 160b is formed in the bottom of the upper separation groove 160a to electrically separate the plurality of light emitting elements 60. Prior to the formation of the lower separation groove 160b, a mask pattern 58 covering other regions except the region of the lower separation groove 160b may be formed. The mask pattern 58 may be formed of silicon oxide or silicon nitride.

Subsequently, the regions exposed through the mask pattern 58 are dry or wet etched or removed using a laser processing technique, thereby forming the lower separation groove 160b. In addition, a phosphoric acid treatment may be performed to remove GaN damaged by the laser. The lower separation groove 160b extending into the substrate 51 may be formed by means of the laser processing technique.

In this embodiment, the mask pattern 58 may be pre-formed to define the entrance of a separation groove 160h, but the present invention is not limited thereto. For example, since a mask material may be removed by means of the laser, the lower separation groove 160b may be formed by covering the semiconductor layers, which have the contact groove 57a formed therein, with a mask material layer and directly irradiating the mask material layer with the laser.

After the formation of the lower separation groove 160b, the mask pattern 58 is removed, the insulative material (60i of Fig. 14) filled in the separation groove 160h is formed, and the transparent electrode 59, the insulation layer 61 and the wiring 63 are formed, thereby fabricating the LED of Fig. 14.

The insulative material 60i may be formed by spin-coating photosensitive polyimide and then exposing and developing the photosensitive polyimide to remove the polyimide in other regions except the polyimide in the separation grooves 160h. Alternatively, the insulative material 60i may be formed by coating non-photosensitive polyimide and then patterning the non-photosensitive polyimide using a photolithography (wet or dry etching) process.

Meanwhile, the separation groove 160h may be filled with nanoparticles, i.e., an insulative material (70i of Fig. 15), instead of the insulative material 60i, to fabricate the LED of Fig. 15. The insulative material 70i may be formed by dispersing nanoparticles in water or another solvent and then spin-coating the resulting dispersion.

The insulative material 60i may be formed so that an air gap (70v of Fig. 16) remains, thereby fabricating the LED of Fig. 16. The nanoparticles and polyimide may be combined to fabricate the LED of Fig. 17.

Fig. 28 is a sectional view illustrating a method of fabricating an LED according to a still further embodiment of the present invention.

Referring to Fig. 28, as described above with reference to Figs. 26 and 27, a separation groove 170h is formed, and a sulfuric and phosphoric acid treatment (H₂SO₄:H₃PO₄=3:1, 280℃, about 5 minutes) is then performed before a mask pattern 58 is removed, thereby forming a lower separation groove 160c having sidewalls reversely inclined.

Subsequently, the mask pattern 58 is removed, and the separation groove 170h is filled with the insulative material 60i, the insulative material 70i or a combination of the

insulative materials

60i and 70i, thereby fabricating the LED of Fig. 18, 19 or 20.

Fig. 29 is a plan view illustrating an LED having four light emitting elements according to an embodiment of the present invention.

Referring to Fig. 29, the LED includes a substrate 51, four light emitting elements 60, an insulative material 60i, an insulation layer 61, a wiring 63, a first bonding pad 100a and a second bonding pad 100b. Each of the light emitting elements 60 includes a first conductive semiconductor layer, an active layer and a second conductive semiconductor layer, as described above. Moreover, the LED may further include a transparent electrode (not shown) that is positioned on each of the light emitting elements and brought into ohmic-contact with the second conductive semiconductor layer.

Each of the light emitting elements 60 has a contact groove 57a exposing the first conductive semiconductor layer through the second conductive semiconductor layer and the active layer. The light emitting elements 60 are separated from one another by separation grooves filled with the insulative material 60i. The insulative material 60i may include polyimide, nanoparticles or a combination thereof, as described above. The insulative material 60i may surround edge regions of the light emitting diode. However, as shown in this figure, the insulative material 60i may be positioned to be confined between the light emitting elements 60.

The insulation layer 61 covers a sidewall of the contact groove 57a, and may further cover an upper portion of each of the light emitting elements 60. Further, the insulation layer 61 may cover the insulative material 60i. Meanwhile, the insulation layer has an opening through which the first conductive semiconductor layer in the contact groove 57a of each of the light emitting elements 60 is exposed, and has an opening through which the second conductive semiconductor layer or the transparent electrode on each of the light emitting elements 60 is exposed.

Meanwhile, the wiring 63 electrically connects adjacent light emitting elements 60 to each other. For example, the wiring 63, as shown in Fig. 29, may include a first electrode 63a connected to the first conductive semiconductor layer in the contact groove 57a of one light emitting element 60, a second electrode 63c connected to the second conductive semiconductor layer or transparent electrode of an adjacent light emitting element 60, and a connection portion 63b for connecting the electrodes to each other. The connection portion 63b may be insulated from the light emitting element 60 by the insulation layer 61.

As shown in Fig. 29, the four light emitting elements 60 may be connected in series to one another by three wirings 63 for connecting adjacent light emitting elements 60.

Meanwhile, the first and

second bonding pads

100a and 100b are respectively positioned at both ends of the light emitting elements connected in series to one another. The first bonding pad 100a is electrically connected to the first conductive semiconductor layer, and the second bonding pad 100b is electrically connected to the second conductive semiconductor layer.

Claims

A light emitting diode (LED), comprising:

a substrate;

a plurality of light emitting elements arranged on the substrate;

a separation groove for separating adjacent light emitting elements from each other;

an insulative material filled in at least a portion of the separation groove; and

a wiring for electrically connecting two adjacent light emitting elements to each other,

wherein each of the light emitting elements comprises a first conductive semiconductor layer, an active layer and a second conductive semiconductor layer in that order from the substrate, and further comprises a contact groove for allowing the first conductive semiconductor layer to be exposed through the second conductive semiconductor layer and the active layer, and

wherein the contact groove is positioned to be spaced apart from the separation groove.
The LED of Claim 1, wherein the wiring traverses above the insulative material so as to electrically connect the first conductive semiconductor layer exposed through the contact groove of a first light emitting element to the second conductive semiconductor layer of a second light emitting element.
The LED of Claim 1, wherein an upper surface of the insulative material is positioned to be higher than an upper surface of the first conductive semiconductor layer.
The LED of Claim 1, wherein a sidewall of the separation groove comprises the first conductive semiconductor layer, the active layer and the second conductive semiconductor layer.
The LED of Claim 1, wherein the separation groove extends to the inside of the substrate.
The LED of Claim 5, wherein the separation groove is formed to have a width narrowed toward the substrate.
The LED of Claim 1, wherein the insulative material is polyimide.
The LED of Claim 1, wherein the insulative material is nanoscale silica.
The LED of Claim 1, wherein an air gap is positioned between the insulative material and the substrate.
The LED of Claim 1, wherein the insulative material comprises nanoscale silica and polyimide placed on the silica.
The LED of Claim 1, wherein a sidewall of the separation groove is reversely inclined.
The LED of Claim 1, wherein an entrance of the separation groove has a width of 5㎛ or less.
The LED of Claim 1, further comprising an insulation layer covering a sidewall of the contact groove.
The LED of Claim 13, wherein a portion of the insulation layer covers an upper surface of the insulative material.
The LED of Claim 1, wherein the separation groove comprises an upper separation groove and a lower separation groove positioned at the bottom of the upper separation groove, and an entrance of the upper separation groove has a width wider than that of an entrance of the lower separation groove.
The LED of Claim 15, wherein a sidewall of the upper separation groove comprises the first conductive semiconductor layer, the active layer and the second conductive semiconductor layer.
The LED of Claim 15, wherein the upper separation groove has the same height as the contact groove.
The LED of Claim 17, wherein the lower separation groove is formed by means of laser processing so as to have a width narrowed toward the substrate.
The LED of Claim 15, wherein a sidewall of the lower separation groove is reversely inclined.
The LED of Claim 15, wherein an entrance of the upper separation groove has a width of 5㎛ or less.
A method of fabricating an LED, comprising:

growing a first conductive semiconductor layer, an active layer and a second conductive semiconductor layer on a substrate;

etching the second conductive semiconductor layer and the active layer to form a plurality of contact grooves for exposing the first conductive semiconductor layer therethrough;

forming a separation groove so that a plurality of light emitting elements are electrically separated;

filling at least a portion of the separation groove with an insulative material; and

forming a wiring for electrically connecting adjacent light emitting elements to each other,

wherein the separation groove and the contact groove are positioned to be spaced apart from each other.
The method of Claim 21, wherein an upper surface of the insulative material is positioned above the contact groove.
The method of Claim 21, wherein a sidewall of the contact groove is inclined more gently than a sidewall of the separation groove.
The method of Claim 21, wherein said forming the separation groove comprises removing the first conductive semiconductor layer, the active layer and the second conductive semiconductor layer, by using an etching process or laser processing process.
The method of Claim 24, wherein said forming the separation groove further comprises removing the first conductive semiconductor layer, the active layer and the second conductive semiconductor layer, by using the etching process or laser processing process, and then performing a sulfuric and phosphoric acid treatment.
The method of Claim 21, wherein the insulative material comprises polyimide or nanoscale silica.
The method of Claim 21, wherein the separation groove comprises an upper separation groove and a lower separation groove positioned at the bottom of the upper separation groove, and an entrance of the upper separation groove has a width wider than that of an entrance of the lower separation groove.
The method of Claim 27, wherein the upper separation groove is formed simultaneously while the contact groove is formed.
The method of Claim 27, wherein a sidewall of the upper separation groove is inclined more gently than a sidewall of the lower separation groove.
The method of Claim 27, wherein the upper separation groove and the contact groove are formed by using an etching technique.
The method of Claim 30, wherein said forming the lower separation groove comprises removing the first conductive semiconductor layer exposed at the bottom of the upper separation groove, by using a laser processing technique.
The method of Claim 31, wherein said forming the lower separation groove further comprises removing the first conductive semiconductor layer by using the laser processing technique, and then performing a sulfuric and phosphoric acid treatment.