Light emitting device

[Technical Field]

The present invention relates to a light emitting device.

[Background Art]

Recently, a light emitting diode (LED) is spotlighted as a light emitting device. Since the LED can convert electric energy into light energy with high efficiency and long life span of about 5 years or more, the LED can remarkably reduce the energy consumption and repair and maintenance cost. In this regard, the LED is spotlighted in the next-generation lighting field.

Such an LED includes a first conductive semiconductor layer, an active layer and a second conductive semiconductor layer, in which the active layer generates light according to current applied thereto through the first and second conductive semiconductor layers.

The LED may be classified into a lateral type LED and a vertical type LED.

According to the lateral type LED, a first conductivity type semiconductor layer (conductive semiconductor layer), an active layer and a second conductive semiconductor layer are formed on a growth substrate, and the second conductive semiconductor layer, the active layer and the first conductive semiconductor layer are partially removed such that a part of the first conductive semiconductor layer can be exposed to form an electrode layer. Thus, the light emitting area may be reduced so that the light efficiency may be degraded.

In addition, according to the lateral type LED, since the first conductive semiconductor layer, the active layer and the second conductive semiconductor layer are formed on the growth substrate having low thermal conductivity, the heat dissipation is not easy.

In contrast, according to the vertical type LED, a first electrode layer is formed on the first conductive semiconductor layer and a second electrode layer is formed under the second conductive semiconductor layer, so it is not necessary to remove the active layer to form the electrode layer. Thus, the light emitting area may not be reduced, so that the light efficiency may be improved as compared with that of the lateral type LED.

In addition, according to the vertical type LED, heat is transferred through the second electrode layer, so the heat dissipation is easy.

Meanwhile, the vertical type LED may employ the electroplating scheme and the wafer bonding scheme when the second electrode serving as a support substrate is formed under the second conductive semiconductor layer.

If the support substrate is manufactured through the electroplating scheme, the manufacturing process may be facilitated, but the reliability for the LED may be degraded. In addition, if the support substrate is manufactured through the wafer bonding scheme, the manufacturing process may be complicated, but the reliability for the LED may be improved. In particular, if the support substrate is manufactured through the wafer bonding scheme, since the growth substrate and the support substrate are made from heterogeneous materials, the crack or debonding may occur in the LED after the wafer has been bonded due to thermal stress caused by difference in thermal expansion coefficient.

In the vertical type LED, a first electrode layer is formed on the first conductive semiconductor layer by separating a growth substrate. However, when the growth substrate is separated by using a laser beam, an LED having a light emission area exceeding the area of the laser beam can not be manufactured.

Documents <patcit id="pcit0001" dnum="US2003141506A1"><text>US 2003/141506 A1</text></patcit>, <patcit id="pcit0002" dnum="US2007290215A1"><text>US2007/290215 A1</text></patcit>, <patcit id="pcit0003" dnum="JP2008041839A"><text>JP 2008 041839 A</text></patcit> and <patcit id="pcit0004" dnum="WO2006038665A1"><text>WO 2006/038665 A1</text></patcit> disclose relevant light emitting devices.

The embodiment provides a light emitting device having a large light emission area.

[Technical Solution]

According to the embodiment, the light emitting device includes a support substrate, a reflective ohmic contact layer on the support substrate, a functional complex layer including a process assisting region and ohmic contact regions divided by the process assisting region on the reflective ohmic contact layer, and a light emitting semiconductor layer including a second conductive semiconductor layer, an active layer, and a first conductive semiconductor layer on each ohmic contact region, as defined in appended claim 1.

[Advantageous Effects]

The embodiment can provide a light emitting device having a large light emission area.

[Description of Drawings]

<ul id="ul0001" list-style="none" compact="compact"><li><figref idref="f0001">FIG. 1</figref> is a sectional view showing the structure of a light emitting device according to a first embodiment;</li><li><figref idref="f0001 f0002 f0003 f0004 f0005 f0006 f0007 f0008 f0009 f0010 f0011">FIGS. 2 to 15</figref> are sectional views showing a method of manufacturing the light emitting device according to the first embodiment;</li><li><figref idref="f0011">FIG. 16</figref> is a view showing the structure of a light emitting device according to a comparative example not forming part of the invention; and</li><li><figref idref="f0012 f0013 f0014">FIGS. 17 to 19</figref> are the method of manufacturing the light emitting device according to the comparative example not forming part of the invention.</li></ul>

[Mode for Invention]

In the description of the embodiment, it will be understood that, when a layer (or film), a region, a pattern, or a structure is referred to as being "on" or "under" another substrate, another layer (or film), another region, another pad, or another pattern, it can be "directly" or "indirectly" on the other substrate, layer (or film), region, pad, or pattern, or one or more intervening layers may also be present. Such a position of the layer has been described with reference to the drawings.

The thickness and size of each layer shown in the drawings may be exaggerated, omitted or schematically drawn for the purpose of convenience or clarity. In addition, the size of elements does not utterly reflect an actual size.

<figref idref="f0001">FIG. 1</figref> is a view showing the structure of a light emitting device according to a first embodiment.

Referring to <figref idref="f0001">FIG. 1</figref>, the light emitting device according to the first embodiment includes a support substrate 210, a diffusion barrier layer 70 on the support substrate 210, a reflective ohmic contact layer 60 on the diffusion barrier layer 70, a functional complex layer 50 on the reflective ohmic contact layer 60, a light emitting semiconductor layer including a second conductive semiconductor layer 40, an active layer 30, and a first conductive semiconductor layer 20 on the functional complex layer 50, and a first electrode layer 900 on the light emitting semiconductor layer.

In addition, a die-bonding layer 240 may be formed under the support substrate 210, and may be firmly bonded to a printed circuit board, in which the light emitting device is installed, or a die with low resistance.

The support substrate 210 includes an electric conductive layer. The support substrate 210 may include a wafer substrate including at least one selected from the group consisting of Si, SiGe, ZnO, GaN, AlSiC, and GaAs. The support substrate 210 may include metal including at least one selected from the group consisting of Cu, Ni, Ag, Al, Nb, Ta, Ti, Au, Pd, W, and the alloy thereof, or a solid solution.

The support substrate 210 has the form of a sheet, a disk, or a foil at a thickness in the range of 10µm to 1mm. The support substrate 210 may be formed through an electro-plating scheme, a PVD (Physical Vapor Deposition) scheme or a CVD (Chemical Vapor Deposition) scheme.

In addition, first and second wafer bonding layers 80 and 230 may be interposed between the support substrate 210 and the reflective ohmic contact layer 60. The first and second wafer bonding layers 80 and 230 allow the support substrate 210 to be firmly bonded to the reflective ohmic contact layer 60.

The first and second wafer bonding layers 80 and 230 include an electric conductive layer having strong bonding strength at predetermined pressure and temperature. For example, the first and second wafer bonding layers 80 and 230 may include at least one selected from the group consisting of Au, Ag, Al, Si, Ge, W, Mo, V, Sc, Hf, Ir, Re, Co, Zr, Ru, Ta, Nb, Mn, Rh, Cu, Ni, Ti, Pd, Pt, Cr, and rare-earth metal.

In addition, a passivation layer 700 is formed at a lateral side of the light emitting semiconductor layer, and a light extracting structure 800 may be formed on the light emitting semiconductor layer.

The diffusion barrier layer 70 prevents a material constituting the first and second wafer bonding layers 80 and 230 from being diffused into the reflective ohmic contact layer 60 when the first and second wafer bonding layers 80 and 230 are bonded to each other at a temperature in the range of about 300°C to about 600°C.

The functional complex layer 50 includes a process assisting region 51, an ohmic contact region 52, and a current blocking region 53.

The ohmic contact region 52 is divided into a plurality of regions by the process assisting region 51, and the current blocking region 53 is provided in the ohmic contact region 52.

The process assisting region 51 may have the form of a lattice cell. Light emitting semiconductor layers including the second conductive semiconductor layer 40, the active layer 30, and the first conductive semiconductor layer 20 are in regions divided by the process assisting region 51.

The process assisting region 51 includes an electric insulating material or a material forming a schottky contact interface with respect to the second conductive semiconductor layer 40. If formed of an electric insulating material, the process assisting region 51 includes one selected from the group consisting of Al₂O₃, SiN, TiO₂, ZrO₂, Si₃N₄, and SiO₂.

The process assisting region 51 prevents the light emitting semiconductor layer from being damaged when a growth substrate is separated through a laser lift off scheme using a laser beam, so that the growth substrate can be separated without damage. In addition, the process assisting region 51 can prevent the performance of the light emitting device from being damaged due to etch products created in an isolation etching process to divide the light emitting semiconductor layer into a plurality of unit structures.

The process assisting region 51 may include a material having superior adhesive property with a material constituting the light emitting semiconductor layer and having low reactivity with dry etch particles used in the isolation etching process.

When the passivation layer 700 is formed, the process assisting region 51 assists the passivation layer 700 having superior quality to be formed.

The ohmic contact region 52 forms an ohmic contact interface having low interfacial contact resistance together with the second conductive semiconductor layer 40, and allows current to be smoothly applied from the outside to the light emitting semiconductor layer perpendicularly to the light emitting semiconductor layer.

The ohmic contact region 52 may include a transparentor having optically high transmittance or a reflector having a high reflective rate. For example, if the ohmic contact region 52 is the transparentor, the ohmic contact region 52 may include at least one selected from the group consisting of ITO, ZnO, IZO, and NiO-Au. If the ohmic contact region 52 is a reflector, the ohmic contact region 52 may include at least one selected from the group consisting of Ag, alloy containing Ag, solid solution containing Ag, Rh, alloy containing Rh, solid solution containing Rh, Al, alloy containing Al, and solid solution containing Rh.

The current blocking region 53 prevents current applied to the light emitting semiconductor layer from being concentrated on a portion of the light emitting semiconductor layer, so that the current can be widely spread. For example, the current blocking region 53 may include one of an electric insulating material, empty space filled with air, and a material forming a schottky contact interface with respect to the second conductive semiconductor layer 40.

Although not shown, the current blocking region 53 is divided into a plurality of regions.

The light emitting semiconductor layer including the second conductive semiconductor layer 40, the active layer 30, and the first conductive semiconductor layer 20 may include a nitride-based semiconductor material, which is a group III compound semiconductor material. For example, the first conductive semiconductor layer 20 may include a gallium nitride layer including an N type dopant such as Si, and the second conductive semiconductor layer 40 may include a P type dopant such as Mg. The active layer 30 emits light through the combination of electrons and holes. For example, the active layer 30 may include one of InGaN, AIGaN, GaN, and AlInGaN. The wavelength of light emitted from the active layer 30 varies according to the type of a material constituting the active layer 30.

Meanwhile, although not shown, an interface modification layer may be additionally interposed between the second conductive semiconductor layer 40 and the functional complex layer 50.

The interfacial modification layer may include a supperlattice structure, one of InGaN, GaN, AlInN, AIN, InN, and AIGaN doped with first conductive impurities, one of InGaN, GaN, AlInN, AIN, InN, and AIGaN doped with second conductive impurities, or one of group III nitride-based elements having a nitrogen-polar surface. In particular, the interfacial modification layer having the supperlattice structure may include a nitride or a carbon nitride including group II, III, or IV elements.

The light emitting semiconductor layer is formed on the ohmic contact region 52 divided into a plurality of regions by the process assisting region 51, and the passivation layer 700 is formed at portions of lateral and top surfaces of the light emitting semiconductor layer.

At least a portion of the passivation layer 700 is provided on the process assisting region 51. For example, the passivation layer 700 may include one of SiO₂, Al₂O₃, and Si₃N₄ which are electric insulating materials.

The passivation layer 700 allows the light emitting semiconductor layer to be supported more stably, and prevents electrical short from occurring at the light emitting semiconductor layer.

The first electrode layer 900 is formed on the first conductive semiconductor layer 20, and commonly makes contact with unit structures of the first conductive semiconductor layer 20. In addition, a portion of the first electrode layer 900 is provided in the passivation layer 700 and overlaps with the light emitting semiconductor layer perpendicularly to the light emitting semiconductor layer.

The first electrode layer 900 makes ohmic contact with the first conductive semiconductor layer 20.

The light extracting structure 800 is formed on the first conductive semiconductor layer 20 and allows light emitted from the active layer 30 to be effectively extracted to the outside. For example, the light extracting structure 800 may be formed by selectively etching the first conductive semiconductor layer 20, or may be formed in the pattern obtained by selectively etching a nitride layer which is formed on the first conductive semiconductor layer 20 and does not include impurities.

<figref idref="f0001 f0002 f0003 f0004 f0005 f0006 f0007 f0008 f0009 f0010 f0011">FIGS. 2 to 15</figref> are sectional views showing the method of manufacturing the light emitting device according to the first embodiment.

Referring to <figref idref="f0001">FIGS. 2</figref> and <figref idref="f0002">3</figref>, the light emitting semiconductor layer including the first conductive semiconductor layer 20, the active layer 30, and the second conductive semiconductor layer 40 is formed on the substrate 10. In addition, the functional complex layer 50 is formed on the second conductive semiconductor layer 40.

For example, the substrate 10 may include one of Al₂O₃, SiC, silicon Si and gallium arsenide GaAs.

Although not shown, before the first conductive semiconductor 20 is grown on the growth substrate 10, a buffer layer including at least one of InGaN, AIN, SiC, SiCN, and GaN may be formed on the growth substrate 10.

In addition, the interface modification layer may be formed between the second conductive semiconductor layer 40 and the functional complex layer 50.

The functional complex layer 50 includes the process assisting region 51, the ohmic contact region 52, and the current blocking region 53. <figref idref="f0002">FIG. 3</figref> shows a plan view of the functional complex layer 50.

The process assisting region 51 may be formed in the form of a lattice cell, and the ohmic contact region 52 is divided into a plurality of unit cell regions H by the process assisting region 51. <figref idref="f0002">FIG. 3</figref> illustrates a case in which the ohmic contact region 52 is divided into four unit cell regions H by the process assisting region 51.

The area of the unit cell region H is designed to be smaller than an area of the laser beam used when the substrate 10 is separated, and the area of the functional complex layer 50 may be designed to be larger than an area of a laser beam used when the substrate 10 is separated.

The current blocking region 53 is formed in each unit cell region H. <figref idref="f0002">FIG. 3</figref> illustrates the current blocking region 53 extending radially from the center of the ohmic contact region 52.

Referring to <figref idref="f0002">FIG. 4</figref>, the reflective ohmic contact layer 60, the diffusion barrier layer 70, and the first wafer bonding layer 80 are formed on the functional complex layer 50. Therefore, a first structure 100 shown in <figref idref="f0002">FIG. 4</figref> can be manufactured.

Referring to <figref idref="f0002">FIG. 5</figref>, a second structure 200 including the support substrate 210 provided at a top surface thereof with the second wafer bonding layer 230 and provided at a bottom surface thereof with the third wafer bonding layer 220. The third wafer bonding layer 220 may include the same material as that of the second wafer bonding layer 230.

Referring to <figref idref="f0003">FIG. 6</figref>, a third structure 300 having a sacrificial separation layer 320 and a fourth wafer bonding layer 330 is prepared on a temporary substrate 310.

The temporary substrate 310 may include a material making thermal expansion coefficient difference of 2ppm/°C or less from the growth substrate 10, or a material the same as that of the growth substrate 10. For example, the temporary substrate 310 may include one of Al₂O₃, SiC, Si, and GaAs.

The sacrificial separation layer 320 may include one of a group II-Vi compound including ZnO, a group III-V compound including GaN, ITO, PZT, and SU-8, which are subject to thermo-chemical decomposition reaction as a laser beam is irradiated thereto, or one of Al, Au, Ag, Cr, Ti, SiO₂, and SiN_x which are rapidly dissolved in a wet solution.

The fourth wafer bonding layer 330 may include the same material as that of the second wafer bonding layer 230.

Referring to <figref idref="f0003">FIG. 7</figref>, the first structure 100 shown in <figref idref="f0002">FIG. 4</figref>, the second structure 200 shown in <figref idref="f0002">FIG. 5</figref>, and the third structure 300 shown in <figref idref="f0003">FIG. 6</figref> are bonded to each other, thereby forming a complex structure.

The first wafer bonding layer 80 is bonded to the second wafer bonding layer 230, and the third wafer bonding layer 220 is bonded to the fourth wafer bonding layer 330.

The first structure 100, the second structure 200, and the third structure 300 are bonded to each other at a predetermined pressure and a predetermined temperature in the range of about 300°C to 600°C.

The third structure 300 is positioned corresponding to the first structure 100 while interposing the second structure 200 between the third structure 300 and the first structure 100, and the first structure 100 has a thermal expansion coefficient similar to that of the third structure 300. Accordingly, the cracks and debonding do not occur due to the difference in the thermal expansion coefficient when the first and second structures 100 and 200 are coupled with each other.

Referring to <figref idref="f0004">FIG. 8</figref>, the growth substrate 10 is separated from the complex structure shown in <figref idref="f0003">FIG. 7</figref>.

The growth substrate 10 may be separated by using an LLO scheme based on an eximer laser beam, or by using a dry etch scheme or a wet etch scheme.

When the eximer laser beam having a predetermined wavelength is focused on the growth substrate 10 and irradiated to the growth substrate 10, thermal energy is concentrated on the boundary surface between the substrate 10 and the first conductive semiconductor layer 20, so that the interfacial surface of the first conductive semiconductor layer 20 is thermo-chemically decomposed into into Ga and N. Accordingly, the growth substrate 10 is separated.

The used laser beam must have a size greater than a size L2 of the ohmic contact region 52 divided by the process assisting region 51.

Therefore, if the second laser beam is irradiated after the first laser beam has been irradiated, the second laser beam overlaps with the first laser beam on the process assisting region 51.

Referring to <figref idref="f0005">FIG. 9</figref>, regions L, M, and N of the light emitting semiconductor layer on the process assisting region 51 are damaged due to the overlap of the laser beams.

Referring to <figref idref="f0006">FIG. 10</figref>, the regions L, M, and N of the light emitting semiconductor layer on the process assisting region 51 are removed through a MESA etching process based on a wet etching process or a dry etching process. Accordingly, the process assisting region 51 is exposed, so that the light emitting semiconductor layer is divided into a plurality unit structures.

Referring to <figref idref="f0007">FIG. 11</figref>, the passivation layer 700 is formed on the top and lateral surfaces of the light emitting semiconductor layer. The passivation layer 700 may make contact with the process assisting region 51.

The passivation layer 700 may have a thickness in the range of about 200nm to about 1000nm.

Referring to <figref idref="f0008">FIG. 12</figref>, the passivation layer 700 formed on the light emitting semiconductor layer is partially removed, and the light extracting structure 800 is formed on the first conductive semiconductor layer 20.

The light extracting structure 800 may be formed in an irregular concave-convex pattern through a wet etching process, or may be formed in a regular concave-convex pattern through a lithography process.

Referring to <figref idref="f0009">FIG. 13</figref>, the first electrode layer 900 is formed on the first conductive semiconductor layer 20.

The first electrode layer 900 is electrically connected to the unit structures of the first conductive semiconductor layer 20, simultaneously.

At least a portion of the first electrode layer 900 overlaps with the process assisting region 51 perpendicularly to the process assisting region 51. A portion of the first electrode layer 900 is filled in the passivation layer 700.

Referring to <figref idref="f0010">FIG. 14</figref>, the temporary substrate 310 is exposed through isolation etching 1000, and a plurality of light emitting devices are formed on the temporary substrate 310.

Referring to <figref idref="f0011">FIG. 15</figref>, the temporary substrate 310 is removed through an LLO scheme, a dry etching scheme, a wet etching scheme, a CMP scheme, or a polishing scheme.

When the temporary substrate 310 is separated through the LLO scheme, the sacrificial separation layer 320 is thermo-chemically decomposed, so that the temporary substrate 310 is removed.

After removing the third wafer bonding layer 220 and the fourth wafer bonding layer 330, the die-bonding layer 240 is formed under the support substrate 210.

Accordingly, the light emitting device according to the first embodiment can be manufactured.

<figref idref="f0011">FIG. 16</figref> is a sectional view showing a light emitting device according to a comparative example not forming part of the invention.

Hereinafter, the light emitting device according to the comparative example not forming part of the invention will be described while focusing on the difference from the light emitting device according to the first embodiment in order to avoid redundancy.

Referring to <figref idref="f0011">FIG. 16</figref>, the light emitting device according to the comparative example not forming part of the invention includes the support substrate 210, the diffusion barrier layer 70 on the support substrate 210, the reflective ohmic contact layer 60 on the diffusion barrier layer 70, the functional complex layer 50 on the reflective ohmic contact layer 60, the light emitting semiconductor layer including the second conductive semiconductor layer 40, the active layer 30, and the first conductive semiconductor layer 20 on the functional complex layer 50, and the first electrode layer 900 on the light emitting semiconductor layer.

The die-bonding layer 240 may be formed under the support substrate 210.

The first and second wafer bonding layers 80 and 230 may be formed between the support substrate 210 and the reflective ohmic contact layer 60.

The passivation layer 700 may be formed on the lateral surface of the light emitting semiconductor layer, and the light extracting structure 800 may be formed on the light emitting semiconductor layer.

The functional complex layer 50 includes the process assisting region 51, the ohmic contact region 52, and the current blocking region 53.

The process assisting region 51 is formed in the vicinity of the reflective ohmic contact layer 60, the ohmic contact region 52 is surrounded by the process assisting region 51, and the current blocking region 53 is provided in the ohmic contact region 52.

Although not shown, the interface modification layer may be additionally formed between the second conductive semiconductor layer 40 and the functional complex layer 50.

The first electrode layer 900 is formed on the first conductive semiconductor layer 20. The first electrode layer 900 makes ohmic contact with the first conductive semiconductor layer 20.

The light extracting structure 800 is formed on the first conductive semiconductor layer 20, and allows the light emitted from the active layer 30 to be effectively extracted to the outside.

<figref idref="f0012 f0013 f0014">FIGS. 17 to 19</figref> are sectional views showing the method of manufacturing the light emitting device according to the comparative example not forming part of the invention.

In the method of manufacturing the light emitting device according to the comparative example not forming part of the invention, most of process steps are similar to those of the method of manufacturing the light emitting device according to the first embodiment. In particular, the method of manufacturing the light emitting device according to the first embodiment described with reference to <figref idref="f0001 f0002 f0003 f0004 f0005 f0006 f0007 f0008">FIGS. 2 to 12</figref> is identical to the method of manufacturing the light emitting device according to the comparative example not forming part of the invention.

Accordingly, the method of manufacturing the light emitting device according to the comparative example not forming part of the invention corresponding to the manufacturing method that has been described with reference to <figref idref="f0001 f0002 f0003 f0004 f0005 f0006 f0007 f0008">FIGS. 2 to 12</figref> will be omitted in order to avoid redundancy.

Referring to <figref idref="f0012">FIG. 17</figref>, the first electrode layer 900 is formed on each unit structure of the first conductive semiconductor layer 20 shown in <figref idref="f0008">FIG. 12</figref>.

Referring to <figref idref="f0013">FIG. 18</figref>, after performing the isolation etching 1000 to expose the temporary substrate 310, a plurality of light emitting devices are formed on the temporary substrate 310.

Referring to <figref idref="f0014">FIG. 19</figref>, the temporary substrate 310 is removed through the LLO scheme, the dry etching scheme, the wet etching scheme, the CMP scheme, or the polishing scheme.

When the temporary substrate 310 is separated through the LLO scheme, the sacrificial separation layer 320 is thermo-chemically decomposed, so that the temporary substrate 310 is removed.

After removing the third and fourth wafer bonding layers 220 and 330, the die-bonding layer 240 is formed under the support substrate 210.

Accordingly, the light emitting device according to the comparative example not forming part of the invention can be manufactured.

[Industrial Applicability]

The embodiment is applicable as a semiconductor device used as an electronic device or a light source.