KR20080002161A - Light emitting diode with a metal reflection layer expanded and method for manufacturing the same - Google Patents

Abstract

A flip-bonded LED(light emitting diode) with an expanded metal reflection layer is provided to improve light radiation capabilities by reflecting light even in the vicinity of an isolation region between light emitting cells without a loss/absorption. A plurality of light emitting cells(200) are separately formed on one surface of a transparent substrate(100), and include a semiconductor layer(220) of a first conductivity type, an active layer(240) defined on a partial region of the semiconductor layer of the first conductivity type, and a semiconductor layer of a second conductivity type that are sequentially formed. Step cover layers include a metal interconnection layer(420) and a metal reflection layer(450). Between adjacent light emitting cells, the semiconductor layers of the first and second conductivity types are electrically interconnected by the metal interconnection layer. The metal reflection layer is formed across the plurality of light emitting cells and an isolation region between the light emitting cells, and is insulated from the metal interconnection layer. The step cover layers include first and second transparent insulation layers(410,430). The first transparent insulation layer covers the light emitting cells to insulate the metal interconnection layer from the light emitting cells. The second transparent insulation layer is interposed between the metal interconnection layer and the metal reflection layer.

Description

LIGHT EMITTING DIODE WITH A METAL REFLECTION LAYER EXPANDED AND METHOD FOR MANUFACTURING THE SAME

1 is a cross-sectional view illustrating a flip bonded light emitting diode according to an embodiment of the present invention.

2 to 8 are views for explaining a flip bonded light emitting diode manufacturing method according to an embodiment of the present invention.

<Code Description of Main Parts of Drawing>

100: transparent substrate S: separation area

200: light emitting cell 220: first conductive semiconductor layer

240: active layer 260: P-type semiconductor layer

410: first insulating layer 420: metal wiring layer

430: second insulating layer 450: metal reflective layer.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to light emitting diodes flip bonded to a submount, and more particularly to a flip bonded light emitting diode having an extended metal reflective layer.

The light emitting diode is a photoelectric conversion semiconductor device having a structure in which an N-type semiconductor and a P-type semiconductor are bonded to each other, and are configured to emit light by recombination of electrons and holes. For example, a gallium nitride (GaN) -based light emitting diode is known as the light emitting diode. The gallium nitride-based light emitting diode includes a light emitting cell in which a first conductive semiconductor layer, an active layer (or light emitting layer), and a second conductive semiconductor layer made of GaN based on a sapphire substrate form a continuous stacked structure. At this time, when the first conductive semiconductor layer is an N-type semiconductor layer, the second conductive semiconductor layer is a P-type semiconductor layer, and conversely, when the first conductive semiconductor layer is a P-type semiconductor layer, the second conductive semiconductor layer is an N-type semiconductor. .

In general, in the light emitting cell, a portion of the second conductive semiconductor layer and an active layer below the portion is etched to expose a portion of the first conductive semiconductor layer beneath it, thereby exposing to a region of the first conductive semiconductor layer. The active layer and the second conductive semiconductor layer form a limited formation. In addition, each of the electrodes is formed in the first conductive semiconductor layer and the second conductive semiconductor layer, and among them, the electrode on the first conductive semiconductor layer, which is a main passage of light, is formed of a transparent electrode layer such as ITO, Ni / Au, or ZnO.

On the other hand, conventional light emitting diodes emit light by forward current and require supply of a direct current. Therefore, the light emitting diode as described above has a problem in that, when directly connected to an AC power source, the light emitting diode is repeatedly turned on and off according to the direction of the current, and as a result, light is not emitted and is easily damaged by the reverse current. On the other hand, a light emitting diode which can be directly connected to a high voltage AC power supply is disclosed in International Publication No. WO2004 / 023568 (A1) entitled "LIGHT-EMITTING DEVICE HAVING LIGHT-EMITTING ELEMENTS". It was disclosed by SAKAI et. Al.

In addition, according to the development of the AC light emitting diodes as described above, flip-bonded light emitting diodes in which metal layers formed in a plurality of light emitting cells are flip-bonded to submounts provided separately and light is emitted through transparent substrates positioned in opposite directions have been developed. There is a bar. The conventional flip-bonded light emitting diode has an advantage of improving heat emission performance by adopting a submount having high thermal conductivity, thereby improving light extraction efficiency.

However, the conventional flip-bonded light emitting diodes have a problem in that light emission efficiency is greatly reduced due to large light absorption and / or light loss in the separation region between the light emitting cells. This problem is due to the fact that the metal reflecting layer for reflecting light toward the transparent substrate is formed in the region of the second semiconductor layer.

Accordingly, an object of the present invention is to provide a flip-bonded light emitting diode, in which a metal reflective layer is formed over a plurality of light emitting cells and the separation region between the light emitting cells, thereby greatly reducing light loss, in particular, the light loss in the vicinity of the separation region. It is to provide a manufacturing method.

According to one aspect of the invention, there is provided a flip bonded light emitting diode that is flip bonded to a lower submount and emits light through an upper transparent substrate. According to an aspect of the present invention, a plurality of flip-bonded light emitting diodes may be formed on a surface of the transparent substrate and may be separated from each other, and the active layer and the second conductive semiconductor may be limited to one region of the first and second conductive semiconductor layers. A plurality of light emitting cells having layers in turn, a metal wiring layer electrically connecting the first conductive semiconductor layer and the second conductive semiconductor layer between adjacent light emitting cells, and the plurality of light emitting cells insulated from the metal wiring layer. And a step cover layer having a metal reflective layer formed over the light emitting cell and the separation region between the light emitting cells.

Preferably, the step cover layers include a first insulating layer formed to cover the light emitting cells to insulate the metal wiring layer from the light emitting cells, and a second insulating layer interposed between the metal wiring layer and the metal reflective layer. It includes more.

More preferably, the flip bonded light emitting diode further includes a metal bump bonded to the submount by sequentially passing through the second insulating layer and the metal reflective layer from the metal wiring layer, wherein the metal reflective layer is the metal bump. And a bump hole larger than a cross-sectional size of the metal bump so as to be electrically separated from the metal bump.

Preferably, each of the plurality of light emitting cells has an inclined surface to allow the formation of the step cover layer inclined around the separation region. The metal wiring layer is formed over the entire area of the second semiconductor layer.

In accordance with another aspect of the present invention, a method of manufacturing a flip bonded light emitting diode is disclosed. The manufacturing method includes the steps of sequentially forming a first conductive semiconductor layer, an active layer, and a second conductive semiconductor layer on one surface of the transparent substrate, wherein the second conductive semiconductor layer and the active layer are formed in one region of the first conductive semiconductor layer. Etching the active layer and the second conductive semiconductor layer, and a metal wiring layer and the metal wiring layer electrically connecting the first conductive semiconductor layer and the second conductive semiconductor layer between the light emitting cells adjacent to each other. And forming a step cover layer having the metal reflective layer formed over the plurality of light emitting cells and the isolation region between the light emitting cells while being insulated.

The forming of the step cover layers may include forming a first insulating layer to cover the light emitting cells, performing etching to expose the electrodes of the first and second conductive semiconductor layers, and Connecting the electrodes to the metal interconnection layer formed on the insulation layer, forming a second insulation layer to cover the light emitting cells in which the metal interconnection layer is formed, and a separation region between the light emitting cells; Forming the metal reflective layer along a second insulating layer, the metal reflective layer covering the light emitting cells and the separation region between the light emitting cells.

More preferably, the forming of the step cover layers further includes forming a metal bump sequentially passing through the second insulating layer and the metal reflective layer from the metal wiring layer, wherein the metal reflective layer is electrically connected to the metal bump. Bump holes larger than the cross-sectional size of the metal bumps are formed to be separated.

Preferably, in the forming of the plurality of light emitting cells, an inclined surface is formed around the separation area to allow inclined formation of the step cover layer.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Embodiments to be described below are provided as examples to sufficiently convey the spirit of the present invention to those skilled in the art. Accordingly, the present invention is not limited to the embodiments described below and may be embodied in other forms. And, in the drawings, the width, length, thickness, etc. of the components may be exaggerated for convenience. Like numbers refer to like elements throughout.

Example

1 is a cross-sectional view illustrating a flip bonded light emitting diode according to an embodiment of the present invention.

Referring to FIG. 1, a plurality of light emitting cells 200 are separated from one surface of the transparent substrate 100. The transparent substrate 100 may be, for example, a sapphire substrate. Each of the light emitting cells 200 may include a first conductive semiconductor layer 220, an active layer 240 and a second conductive semiconductor layer 260 formed on one region of the first conductive semiconductor layer 220. It is provided in order. Here, the first conductive semiconductor layer 220 and the second conductive semiconductor layer 260 may be N-type and P-type or P-type and N-type semiconductor layer, respectively, in the present embodiment, the first conductive semiconductor layer 220 ) Is formed in the N type, and the second conductive semiconductor layer 260 is formed in the P type. In addition, a buffer layer 120 is disposed between the transparent substrate 100 and the light emitting cells 200 to mitigate lattice mismatch between the lower layer of the light emitting cell 200 and the substrate 100. The buffer layer 120 is a part having a fine thickness, which is considered to be a part of the transparent substrate 100 in the following description.

In the present embodiment, the first conductive semiconductor layer 220 may be formed of N-type Al _x In _y Ga _1-xy N (0 ≦ x, y, x + y ≦ 1), and the N-type cladding layer may be formed. It may include. In addition, the second conductive semiconductor layer 260 may be formed of P-type Al _x In _y Ga _1-xy N (0 ≦ x, y, x + y ≦ 1), and may include a P-type cladding layer. . The first conductive semiconductor layer 220 may be formed by doping silicon (Si), and the second conductive semiconductor layer 260 may be formed by doping zinc (Zn) or magnesium (Mg). have. In addition, the active layer 240 is an area where electrons and holes are recombined, and includes InGaN. The emission wavelength extracted from the light emitting cell is determined according to the type of material constituting the active layer 240. The active layer 240 may be a multilayer film in which a quantum well layer and a barrier layer are repeatedly formed. The barrier layer and the well layer may be binary to quadruple compound semiconductor layers represented by general Al _x In _y Ga _1-xy N (0 ≦ x, y, x + y ≦ 1).

On the other hand, the first conductive semiconductor layer 220 and the second conductive semiconductor layer 260 is formed with a first electrode 242 and a second electrode 290 for applying AC power, respectively. The first electrode 242 is a metal pad, and the second electrode 290 in the region of the second conductive semiconductor layer 260, which is a main passage of light, is formed of a transparent electrode layer such as ITO. The first electrode 242 and the second electrode 290 of the light emitting cells 200 adjacent to each other are electrically connected to each other by a metal wiring layer 420 which is one of the step cover layers 400 described below. . The metal wiring layer 420 is provided with a plurality of bumps 53 corresponding to each of the plurality of light emitting cells 200, and the plurality of bumps 53 are different from the metal wiring layer 420. It is bonded to the bonding pads 51 of the submount 50 through the step cover layers.

The step cover layers 400 may include, for example, the first and second insulating layers 410 and 430 and the metal reflective layer 450 of a transparent insulating material, such as SiO ₂ , in addition to the metal wiring layer 420 described above. Include. In addition, the step cover layers 400 are formed to be inclined around the side, more preferably, around the side of the separation area between the light emitting cells 200, and the inclined structure forms the periphery of the separation area. The side surfaces of the light emitting cells 200 may be formed by the inclined surfaces, and the step cover layers 400 may cover the separation regions S between the light emitting cells 200 by the inclined surfaces of the light emitting cells 200. In particular, the process of forming the metal reflective layer 450 may be easily performed.

The first insulating layer 410 is formed to cover the plurality of light emitting cells 200 separated from each other, whereby the separation region S between the light emitting cells 200 is also formed by the first insulating layer ( 410). In addition, a portion corresponding to the first electrode 242 and the second electrode 290 is opened in the first insulating layer 410.

The metal wiring layer 420 is partially formed along the first insulating layer 410, and a part of the metal wiring layer 420 is formed through the openings of the first insulating layer 410 and the first electrode 242 and the second electrode 290. Connected with The metal wiring layer 420 is partially removed to prevent the first and second electrodes of the same light emitting cell from being electrically connected to each other. In addition, the metal wiring layer 420 is formed over the second conductive semiconductor layer 260 and the electrode thereon (ie, the transparent electrode layer; 290), which is then formed second semiconductor layer 260. The step cover layers of the region are prevented from being formed stepped. Although not shown, a separate reflective layer may be formed in the region of the second semiconductor layer 260 together with the metal wiring layer 420 in consideration of the reflective characteristic of the metal wiring layer 420.

The second insulating layer 430 is provided to insulate between the metal wiring layer 420 above and the metal reflective layer 450 below. The second insulating layer 430 is formed to cover the metal wiring layer 420 and the first insulating layer 410 exposed through the removed portion of the metal wiring layer 420, whereby the light emitting cells ( The separation region S between the 200 may also be covered. A portion of the second insulating layer 430 is opened to correspond to the plurality of bumps 53 described above, and the plurality of bumps 53 extend downward through the opened portion.

The metal reflective layer 450 is formed under the second insulating layer 430 along the second insulating layer 430, and is electrically insulated from the metal wiring layer 420 by the second insulating layer 430. have. The metal reflective layer 450 may cover the plurality of light emitting cells 200 and the separation region S between the light emitting cells together with the second insulating layer 430. In addition, the metal reflective layer 450 includes a plurality of bump holes 452 to allow the bumps 53 to extend. In this case, each of the bump holes 452 has a larger cross-sectional size than the bump 53 so that the bump 53 and the metal reflective layer 450 are separated without contact. As such, the metal reflective layer 450 is formed as one of the step cover layers 400 and is formed almost entirely over the plurality of light emitting cells 200 and the separation region S therebetween, Light generated at 200 may be reflected toward the transparent substrate 100 with little loss. In addition, the bumps 53 may also be made of a reflective metal material to contribute to reducing light loss together with the metal reflective layer 450.

Hereinafter, a method of manufacturing a flip bonded light emitting diode according to an exemplary embodiment of the present invention will be described with reference to FIGS. 2 to 8.

Referring to FIG. 2, the N-type first conductive semiconductor layer 220, the active layer 240, and the P-type second conductive semiconductor layer 260 are sequentially formed on the transparent substrate 100 on which the buffer layer 120 is formed. Form. The buffer layer 120 and the semiconductor layers 220, 240, and 260 may be formed using metal organic chemical vapor deposition (MOCVD), molecular beam growth (MBE), or hydride gas phase growth (HVPE). . In addition, the semiconductor layers 220, 240, and 260 may be continuously formed in the same process chamber. In addition, a second electrode 290 made of, for example, an ITO layer is formed on the second conductive semiconductor layer 260. Before the formation of the second electrode 290, a process of forming a tunnel structure having a delta topping layer of approximately 5 to 50 μs is performed to form an ohmic contact between the second electrode 290 and the second conductive semiconductor layer 260. May be In addition, the second electrode 290 may be formed after the mesa forming process described below.

Referring to FIG. 3, a plurality of light emitting cells 200 are formed on the substrate 100 by a mesa forming process. This process is performed by an etching method using exposure, and includes a plurality of light emitting cells including the first conductive semiconductor layer 220, the active layer 240, the second conductive semiconductor layer 260, and the second electrode 290. 200 is formed on the substrate 100 to be spaced apart from each other. In addition, since a portion of the second conductive semiconductor layer 260 and the active layer 240 is etched, a portion of the upper surface of the first conductive semiconductor layer 220 is exposed. In addition, the active layer 240 and the second conductive semiconductor layer 260 are limitedly formed in one region of the first conductive semiconductor layer except for the exposed region. In addition, a first electrode 242 is formed in a structure of a metal pad in an exposed region of the first conductive semiconductor layer 220. In the etching process illustrated in FIG. 3, the side surfaces of the light emitting cells 200 are formed as inclined surfaces, and the inclined surfaces are formed by the step cover layers 400 formed in the following steps. It can be easily covered to the side of each of the cells (200). Hereinafter, the steps of forming the step cover layers 400, that is, the first insulating layer 410, the metal wiring layer 420, the second insulating layer 430, and the metal reflective layer 450 in succession will be described with reference to FIGS. 4 to 4. More specifically with reference to FIG. 8.

Referring to FIG. 4, a transparent first insulating layer 410 is formed on the transparent substrate 100 having the light emitting cells 200 by a deposition method. The first insulating layer 410 covers a portion of the sidewalls and the upper surface of the light emitting cells 200 and entirely covers the separation region S between the light emitting cells 200. In FIG. 4, an opening exposing the first electrode 242 and the second electrode 290 is formed in the first insulating layer 410. This opening may be obtained by patterning etching the portion of the first insulating layer 410 to expose the first electrode 242 and the second electrode 290 after the deposition formation of the first insulating layer 410. In this case, the first insulating layer 410 is preferably formed of, for example, a silicon oxide film using chemical vapor deposition (CVD). In addition, the first insulating layer 410 may be formed to cover the separation region S and the side surface of the light emitting cell 200 more easily by side inclined surfaces of the respective light emitting cells 200.

5 and 6, a metal wiring layer 420 connecting the first electrode 242 and the second electrode 290 is formed. The metal wiring layer 420 is entirely formed along the above-described first insulating layer 410 by a deposition method or a plating method. A portion of the metal wiring layer 420 is filled in openings formed in the first insulating layer 410 to electrically connect the first electrode 242 and the second electrode 290 of the light emitting cells 200. . In order to apply AC power to the light emitting cells 200, only two electrodes of light emitting cells adjacent to each other should be electrically connected, so that a part of the metal wiring layer 420 shown in FIG. 5 is shown in FIG. 6. Removed. As a result, the electrical connection between the electrodes of the same light emitting cell is broken.

When the metal wiring layer 420 is formed, the second insulating layer 430 and the metal reflective layer 450 are formed.

As shown in FIG. 7, the second insulating layer 430 is formed to include an opening through which the bumps 53 penetrate, and the metal wiring layer 420 and the first insulating layer (except the opening). 410 is formed. Therefore, the second insulating layer 430 is formed over the region of the light emitting cells 200 and the separation region S between the light emitting cells. The metal reflective layer 450 is formed substantially along the second insulating layer 430. Accordingly, the metal reflective layer 450 may cover the areas covered by the second insulating layer 430, that is, the separation area S between the light emitting cells 200 and the light emitting cells 200. Covering the whole. In this case, a bump hole 452 through which a plurality of bumps 53 pass is formed in the metal reflective layer 450, and a plurality of bumps 53 extend through the bump holes 252, respectively. At this time, the size of the bump hole 452 is larger than the cross-sectional size of the bump 53, whereby the electrical contact between the bump 53 and the metal reflective layer 450 may be excluded.

Referring to FIG. 8, a flip bonding step of a light emitting diode to a submount 50 is shown. As shown in FIG. 8, the bumps 53 described above are oriented to face the submount 50, and the bumps 53 are bonded to the bonding pads 51 formed on the submount 50. do. By such flip bonding, as shown in FIG. 1, the light emitting diode 1 flip-bonded to the submount 50 can be manufactured.

In the light emitting diode 1 manufactured according to the present exemplary embodiment, the step cover layers 400, in particular, the metal reflective layer 450, are divided regions between the plurality of light emitting cells 200 and the light emitting cells 200. (S) is entirely covered, whereby the light generated in the light emitting cells 200 is reflected by the metal reflective layer 450 without being lost and can be emitted to the outside through the transparent substrate 100.

The flip-bonded light emitting diode according to the embodiment of the present invention can reflect light without loss / absorption even in the vicinity of the separation region between the light emitting cells, and thus has an effect of having improved light emission performance.

Claims (10)

In a flip-bonded light emitting diode that is flip-bonded to a lower submount and emits light through an upper transparent substrate, A plurality of light emitting cells which are separately formed on one surface of the transparent substrate, each having an active layer and a second conductive semiconductor layer, each of which is limited to a first conductive semiconductor layer and a region of the first conductive semiconductor layer; A metal wiring layer electrically connecting the first conductive semiconductor layer and the second conductive semiconductor layer between the light emitting cells adjacent to each other, and the plurality of light emitting cells and the isolation region between the light emitting cells while being insulated from the metal wiring layer. Step cover layers having a metal reflective layer formed thereon; Flip bonding type light emitting diode comprising a. The method according to claim 1, wherein the step cover layers, A transparent first insulating layer formed to cover the light emitting cells to insulate the metal wiring layer from the light emitting cells; A second transparent insulating layer interposed between the metal wiring layer and the metal reflective layer; Flip bonding type light emitting diode, characterized in that it further comprises.  The metal bump of claim 2, further comprising a metal bump bonded to the submount through the second insulating layer and the metal reflective layer in order from the metal wiring layer, wherein the metal reflective layer is electrically separated from the metal bump. And a bump hole larger than the cross-sectional size of the flip-bonded light emitting diode. The flip-bonded light emitting diode according to any one of claims 1 to 3, wherein each of the plurality of light emitting cells has an inclined surface to allow the step cover layer to be inclined around the separation area. The flip-bonded light emitting diode of claim 2, wherein the metal wiring layer is formed over the entire area of the second conductive semiconductor layer. Sequentially forming a first conductive semiconductor layer, an active layer, and a second conductive semiconductor layer on one surface of the transparent substrate; Etching the active layer and the second conductive semiconductor layer so that the second conductive semiconductor layer and the active layer are defined in one region of the first conductive semiconductor layer; A metal wiring layer electrically connecting the first conductive semiconductor layer and the second conductive semiconductor layer between the light emitting cells adjacent to each other, and the plurality of light emitting cells and the isolation region between the light emitting cells while being insulated from the metal wiring layer. Forming a step cover layer having a metal reflective layer formed thereon; Method for manufacturing a flip-bonded light emitting diode comprising a. The method of claim 6, wherein the forming of the step cover layers, Forming a transparent first insulating layer to cover the light emitting cells, and performing etching to expose the electrodes of the first and second conductive semiconductor layers; Connecting the electrodes to the metal wiring layer formed on the first insulating layer; Forming a transparent second insulating layer to cover the light emitting cells in which the metal wiring layer is formed and the separation region between the light emitting cells; Forming the metal reflective layer over the separation region between the light emitting cells and the light emitting cells along the second insulating layer; Method for manufacturing a flip-bonded light emitting diode comprising a.  The method of claim 7, wherein the forming of the step cover layers further comprises forming a metal bump that sequentially passes from the metal wiring layer to the second insulating layer and the metal reflective layer, wherein the metal reflective layer is electrically connected to the metal bump. And a bump hole larger than the cross-sectional size of the metal bump is formed so as to be separated. The flip bonding according to any one of claims 6 to 8, wherein in the forming of the plurality of light emitting cells, an inclined surface is formed around the separation area to allow inclined formation of the step cover layer. Method of manufacturing a light emitting diode. The method of manufacturing a flip bonded light emitting diode according to claim 7, wherein the metal wiring layer is formed over the entire area of the second semiconductor layer.

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