KR101003454B1 - Light emitting device and method for fabricating the same - Google Patents

Abstract

A semiconductor light emitting device and a method of manufacturing the same are provided. The semiconductor light emitting device according to the present invention includes a substrate, a light generating unit composed of a semiconductor on an upper surface of the substrate, a polymer layer disposed on a lower surface of the substrate, and having a plurality of grooves formed on a lower surface thereof, a plurality of beads partially inserted into the groove portions, And a metal reflective film formed along the bend of the bead. In the method of manufacturing a semiconductor light emitting device according to the present invention, a light generating portion made of a semiconductor is formed on an upper surface of a substrate, and then a plurality of beads are applied to the lower surface of the substrate. Then, a metal reflective film is formed along the bend of the bead. According to the present invention, a semiconductor light emitting device having excellent light extraction efficiency can be manufactured by a simple process, so that mass production is high and reproducibility is also high.

Description

Semiconductor light emitting device and method for manufacturing the same {Light emitting device and method for fabricating the same}

The present invention relates to a semiconductor light emitting device and a method for manufacturing the same, and more particularly, to a semiconductor light emitting device including a structure change for improving the extraction efficiency (extraction efficiency) of the semiconductor light emitting device and a method for manufacturing the same.

A semiconductor light emitting device is a device in which a material included in the device emits light. For example, a semiconductor is bonded using a diode such as a light emitting diode (LED) to convert energy from electron / hole recombination into light. There is an element that converts and emits. Such semiconductor light emitting devices are widely used as lighting, display devices, and light sources, and emit light of a desired wavelength with little power, and can suppress the emission of environmentally harmful substances such as mercury. Development is accelerating.

The LED market grew based on low-power LEDs used in portable communication devices such as mobile phones, keypads of small home appliances, and back light units of liquid crystal displays (LCDs). Recently, as the need for high-power and high-efficiency light sources used in interior lighting, exterior lighting, automotive interior and exterior, and large LCD backlight units has emerged, the LED market is shifting to high-power products, especially gallium nitride (GaN) -based LEDs. The research is focused.

In the case of GaN-based LEDs, the internal quantum efficiency is relatively excellent, and thus the light generation efficiency is high. However, the light extraction efficiency is low due to the higher refractive index (2.3 to 2.8) than the surrounding material. Therefore, in the GaN-based LED having a general structure, a large part of the light generated in the light emitting layer is not extracted to the outside of the device and disappears inside. In addition, the light that has not exited the device moves to the inside of the device and is converted into heat, resulting in a low luminous efficiency while increasing the amount of heat generated by the device to shorten the device life.

In order to overcome this disadvantage, a technique of forming irregularities on the surface of the device such as texturing or periodic patterning is formed on the surface of the substrate or optoelectronic traveling path. However, these techniques are mostly limited in reproducibility and throughput for the following reasons.

As a method of forming irregularities on the surface of the device, a method using wet etching or dry etching is currently used. Among these, wet etching is difficult to control the etching rate and has a problem of reproducibility. Normally, dry etching is performed after the formation of a pattern using photolithography. In this method, a relatively accurate pattern can be formed, but there are damage problems due to plasma and economic disadvantages. In addition, dry etching is performed even after the pattern is formed by a method using E-beam lithography. This method requires expensive equipment and has a disadvantage of difficulty in large area.

On the other hand, in addition to such wet etching and dry etching, there is also a method of improving light extraction efficiency by using a reflective film such as Ag. However, the technique of texturing to increase the efficiency of the reflective film is also performed through wet etching or dry etching, and thus has the above-mentioned problems.

Accordingly, there is a demand for a method for improving light extraction efficiency of a semiconductor light emitting device at a simpler and lower cost.

The problem to be solved by the present invention is to provide a semiconductor light emitting device that can be manufactured in a simple process, and has an excellent light extraction efficiency.

Another object of the present invention is to provide a method of manufacturing a semiconductor light emitting device that can obtain high reproducibility and mass production by a simple process.

The semiconductor light emitting device according to the present invention for solving the above problems is a substrate, a light generating portion composed of a semiconductor on the upper surface of the substrate, a polymer layer disposed on the lower surface of the substrate, a plurality of grooves formed on the lower surface, the groove portion And a plurality of beads having a portion inserted therein, and a metal reflective film formed along the bend of the beads.

Another semiconductor light emitting device according to the present invention comprises a substrate, a light generating portion composed of a semiconductor on the upper surface of the substrate, a polymer layer disposed on the lower surface of the substrate and having a plurality of groove portions formed on the lower surface thereof, and the bending of the groove portion. It includes a metal reflective film formed.

In one configuration of the method of manufacturing a semiconductor light emitting device according to the present invention for solving the above problems, a light generating portion composed of a semiconductor is formed on an upper surface of a substrate, and then a plurality of beads are applied to the lower surface of the substrate. Then, a metal reflective film is formed along the bend of the beads.

In this case, applying a plurality of beads to the lower surface of the substrate, forming a polymer layer on the lower surface of the substrate, applying the plurality of beads on the polymer layer, and glass transition of the polymer layer Heating above a glass transition temperature may include depositing a portion of the beads in the polymer layer.

In another configuration of the method for manufacturing a semiconductor light emitting device according to the present invention, a light generating unit made of a semiconductor is formed on an upper surface of a substrate, a polymer layer is formed on a lower surface of the substrate, and the plurality of beads are coated on the polymer layer. . The polymer layer is then heated above the glass transition temperature to precipitate a portion of the beads in the polymer layer. Thereafter, after removing the beads, a metal reflective film is formed along the curvature of the polymer layer from which the beads are removed.

According to the present invention, it is possible to manufacture a semiconductor light emitting device having a metal reflective film that is textured to have a curvature without applying an etching process to the substrate, so there is no problem caused by the etching process. In the present invention, since only a thin film forming process and a low temperature heat treatment process through a simple process such as spin coating are used, time and cost can be greatly reduced. In addition, texturing can be uniformly performed on a large-area substrate, which is advantageous for the large area of the semiconductor light emitting device.

Since the pattern is formed on the upper surface of the substrate by a simple process without the photolithography or electron beam lithography process for dry etching, the expensive equipment required for the photolithography or electron beam lithography process is not necessary and the time required for the photolithography or electron beam lithography process is shorter. The productivity is excellent.

In addition, it is possible to easily adjust the degree of bending of the metal reflective film by adjusting the bead size and the thickness of the polymer layer, and to prevent breakage of the metal in the metal reflective film because the textured surface is smooth.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, embodiments of the present invention may be modified in many different forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. The embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art. Accordingly, the shape of the elements in the drawings and the like are exaggerated to emphasize a clearer description.

1 is a view showing a process of performing a first embodiment of a method for manufacturing a semiconductor light emitting device according to the present invention.

Referring to FIG. 1A, a light generator 20 formed of a semiconductor is formed on an upper surface of a substrate 10. The substrate 10 may include sapphire (Al ₂ O ₃ ), gallium arsenide (GaAs), spinel (MgAl ₂ O ₄ ), indium phosphide (InP), silicon carbide (SiC), zinc oxide (ZnO), and silicon (Si ), Any one of lithium aluminum oxide (LiAlO ₂ ) and magnesium oxide (MgO) may be used, and a GaN-based buffer layer may be grown between the photo-generator 20. Sapphire substrate has a high temperature stability, but the substrate size is difficult to manufacture a large area. Silicon carbide substrates have the same crystal structure as GaN, high temperature stability, and similar lattice constants and thermal expansion coefficients to GaN, but are expensive. The silicon substrate has a difference in lattice constant from GaN of about 17% and a thermal expansion coefficient of about 35%. In consideration of these points, various substrates may be used as illustrated above to suit the characteristics of the device.

The light generating unit 20 is a semiconductor such as a laminate in which a first conductive type (for example, n-type) semiconductor layer, an active layer, and a second conductive type (p-type) semiconductor layer opposite to the first conductive type are sequentially stacked. It can be configured as. Each semiconductor layer is composed of a semiconductor such as, for example, a GaN-based semiconductor, a ZnO-based semiconductor, a GaAs-based semiconductor, a GaP-based semiconductor, and a GaAsP-based semiconductor, and can be implemented as an n-type semiconductor layer and a p-type semiconductor layer, respectively. have. The formation of the semiconductor layer may be performed using, for example, a molecular beam epitaxy (MBE) method. In addition, the semiconductor layers may be appropriately selected from the group consisting of III-V semiconductors, II-VI semiconductors, and Si. The active layer is a layer for activating light emission and is formed using a material having an energy band gap less than the energy band gap of the first conductive semiconductor layer and the second conductive semiconductor layer. For example, when the first and second conductivity-type semiconductor layers are GaN-based compound semiconductors, the active layer may be formed using an InGaN-based compound semiconductor having an energy band gap smaller than that of the GaN-based compound semiconductors. In this case, the active layer 130 may control the wavelength or the quantum efficiency by adjusting the thickness, composition, and number of wells.

In addition, although not directly illustrated in FIG. 1A, n-type electrodes and p-type electrodes for electrically connecting each semiconductor layer with an external power source may be formed. Each electrode (not shown) may be composed of a metal or a transparent electrode. For example, Ti may be configured as an n-type electrode, and Pd or Au may be configured as a p-type electrode.

Next, as shown in FIG. 1B, the polymer layer 30 is formed on the bottom surface of the substrate 10. The polymer layer 30 is made of a polymer material, and preferably, may be made of polystyrene (PS), bis-benzocyclobutene (BCB), and a combination thereof. Spin coating may be used to form the polymer layer 30 on the bottom surface of the substrate 10.

Next, as shown in FIG. 1 (c), a plurality of beads 40 are coated on the polymer layer 30. The beads 40 generally refer to spherical particles and may be applied in a single layer. The bead 40 has a lower refractive index than that of the semiconductor layer constituting the light generator 20, for example, GaN, which is lower than the semiconductor layer constituting the light generator 20 to increase light extraction efficiency. Materials having an excitation refractive index of 1.2 to 2.0 may be used.

Bead 40 may be comprised of oxide beads, polymer beads, and combinations thereof. In this case, the oxide beads are SiO ₂ , Al ₂ O ₃ , TiO ₂ , ZrO ₂ , Y ₂ O ₃ -ZrO ₂ , CuO, Cu ₂ O, Ta ₂ O ₅ , PZT (Pb (Zr, Ti) O ₃ ), One consisting of at least one selected from Nb ₂ O ₅ , Fe ₃ O ₄ , Fe ₂ O _3, and GeO ₂ may be used. At this time, the bead 40 may be used to have a diameter of 0.01 to 10 μm in order to increase the light extraction efficiency in consideration of the wavelength of light generated from the semiconductor light emitting device. In particular, SiO ₂ can be used as the bead 40, the method of producing the SiO ₂ beads are as follows.

First, tetraethyl orthosilicate (TEOS) is dissolved in anhydrous ethanol to form a first solution. And a second solution is prepared by mixing ammonia ethanol solution, deionized water (DI water) and ethanol. Ammonia acts as a catalyst. The first solution and the second solution are mixed and then stirred at a predetermined temperature for a predetermined time. The solution thus obtained is separated by SiO ₂ beads through centrifugation, washed with ethanol, and redispersed in ethanol solution to prepare SiO ₂ beads.

Bead 40 may be produced in various sizes of 0.01 to 10㎛ depending on manufacturing conditions, that is, growth time, temperature, the amount of reactants. The beads 40 thus obtained are coated on the polymer layer 30 using a method such as dip coating or spin coating.

The beads 40 used here are generally hydrophilic. Therefore, in order for the beads 40 to be coated on the polymer layer 30, the surface of the polymer layer 30 needs to be at least hydrophilic. Therefore, when the polymer layer 30 is hydrophobic, the step of hydrophilizing the surface of the polymer layer 30 is further performed by irradiating UV light or performing O ₂ plasma treatment on the polymer layer 30 before applying the beads 40. desirable. However, if the polymer layer 30 is hydrophilic, this step can be omitted.

Next, the polymer layer 30 is heated above the glass transition temperature to precipitate a portion of the beads 40 in the polymer layer 30 as shown in FIG. In this process, a plurality of grooves 35 are formed in the polymer layer 30, and a portion of the bead 40 is inserted into the grooves 35.

The degree of precipitation of the beads 40 can be changed, and in order to form a metal reflective film (see reference numeral 50 in FIG. 1 (e)) with as many bends as possible, it is preferable to deposit about half of the beads 40. The semi-spherical nano-lens shape can be made through the beads 40 thus precipitated, and the size of the lens shape can be easily adjusted by adjusting the size of the beads 40 and the thickness of the polymer layer 30. When BCB is used as the polymer layer 30, the beads 40 may be precipitated through low temperature heat treatment of about 130 to 160 ° C. to form a nanolens shape.

Then, the metal reflective film 50 is formed along the curvature of the bead 40 with reference to FIG. 1 (e) to manufacture the semiconductor light emitting device 100. For example, a metal reflective film 50 is formed by sputtering a metal such as Ag. The metal reflective film 50 is formed to a thickness such that it is conformally deposited along the bend of the bead 40. The metal reflective film 50 has a naturally curved hemispherical nanolens shape along the bend of the bead 40 to provide a three-dimensionally textured reflective surface. The metal reflective film 50 is a semiconductor light emitting device 100. It is possible to randomize the reflection angle of the photoelectron generated inside, thereby increasing the light extraction efficiency. In particular, unlike the prior art, the etching process is not required, and it is characterized by forming a textured reflective structure without a complicated process in a short time.

The semiconductor light emitting device 100 manufactured as described above is disposed on the substrate 10, the light generating unit 20 composed of semiconductors on the upper surface of the substrate 10, and a lower surface of the substrate 10, and a plurality of grooves 35 are disposed on the lower surface of the semiconductor light emitting device 100. It includes a polymer layer 30 is formed, a plurality of beads 40, a portion of which is inserted into the groove portion 35, and a metal reflective film 50 formed along the bend of the bead 40.

FIG. 2 is a SEM photograph showing a metal reflective film 50 'having a hemispherical nanolens-shaped curvature formed on a rear surface of a semiconductor light emitting device manufactured according to the first embodiment. In this case, a light generating unit including GaN / InGaN / GaN was formed on the sapphire substrate, BCB polymer layer was formed on the lower surface of the sapphire substrate, SiO ₂ beads were deposited, and Ag was deposited thereon to form a metal reflective film 50 ′. . Since the metal reflective film 50 'is formed along the smooth SiO ₂ bead surface, it can be seen that a uniformly textured surface is obtained in the metal reflective film 50' without breaking.

3 is a graph measuring the EL (electroluminescence) intensity of the semiconductor light emitting device manufactured according to the first embodiment. It can be seen that the EL intensity of the semiconductor light emitting device according to the first embodiment having the metal reflective film 50 ′ is increased from that of the comparative example and the BCB, which is not the case. You can see that.

As described above, the semiconductor light emitting device manufacturing method according to the present invention does not require an etching process, and has a semiconductor reflecting film having a bend of a hemispherical nanolens pattern using only simple processes such as spin coating, low temperature heat treatment, and metal deposition. The light emitting device can be manufactured. The metal reflective film can effectively suppress total reflection of light and increase light extraction efficiency. In addition, since the polymer layer and the plurality of beads are formed by a spin coating method, a reflective structure that is curved at a large area at a low cost for a short time can be formed. Therefore, since the semiconductor light emitting device having excellent light extraction efficiency can be manufactured by a simple process, it is high in mass production and high in reproducibility.

4 is a view showing a process of performing a second embodiment of the method for manufacturing a semiconductor light emitting device according to the present invention.

Referring to FIG. 4A, the light generating unit 120 formed of a semiconductor is formed on the top surface of the substrate 110, and then the polymer layer 130 is formed on the bottom surface of the substrate 110 as shown in FIG. 4B. ). Then, a plurality of beads 140 are coated on the polymer layer 130 as shown in Figure 4 (c). The substrate 110, the light generator 120, the polymer layer 130, and the beads 140 may be formed of the substrate 10, the light generator 20, the polymer layer 30, and the beads 40 described in the first embodiment. ), And the description is used as it is.

Next, the polymer layer 130 is heated above the glass transition temperature to deposit a portion of the bead 140 in the polymer layer 130 as shown in FIG. 4 (d). In this process, a plurality of grooves 135 are formed in the polymer layer 130, and a portion of the bead 140 is inserted into the grooves 135.

Then, the bead 140 is removed with reference to FIG. 4E to expose the groove 135. When the bead 140 is an oxide, it can be removed through an appropriate etching solution. For example, in the case of SiO ₂ beads, it can be easily removed by HF dilution. Even if the bead 140 is a polymer, it may be removed through a suitable etching solution or by heat treatment or ashing. When the bead 140 is removed in this way, the groove 135 is exposed, and the groove 135 becomes an intaglio shape as opposed to the embossed shape of the hemispherical nanolens as in the first embodiment, which is commonly referred to as a dimple. Can be.

Next, as shown in FIG. 4 (f), the metal reflective film 150 is formed along the curvature of the polymer layer 130 having the groove 135 to be manufactured as the semiconductor light emitting device 200. For example, the metal reflective film 150 is formed by covering a metal such as Ag. The metal reflective film 150 is formed to a thickness that is conformally deposited along the curvature of the groove 135. As described above, according to the present invention, unlike the conventional technology, an etching process is not required and the reflective surface, which is naturally three-dimensionally textured, can be made along the curvature of the groove 135 without a complicated process in a short time, thereby improving light extraction efficiency. have.

The semiconductor light emitting device 200 manufactured as described above is disposed on the substrate 110, the light generating unit 120 formed of a semiconductor on the upper surface of the substrate 110, and a lower surface of the substrate 110. It includes a polymer layer 130 is formed, and the metal reflective film 150 formed along the curvature of the groove 135.

FIG. 5 is a SEM photograph showing a metal reflective film 150 ′ having a dimple-shaped bend formed on a rear surface of a semiconductor light emitting device manufactured according to the second embodiment. In this case, a light generating part consisting of GaN / InGaN / GaN is formed on the sapphire substrate, BCB polymer layer is formed on the lower surface of the sapphire substrate, SiO ₂ beads are precipitated, SiO ₂ beads are removed with HF diluent, and Ag is deposited to form a metal. The reflective film 150 'was formed. Since the surface before the deposition of Ag is smooth, a uniformly textured surface is obtained in the metal reflective film 150 'without breaking.

6 is a graph measuring the EL intensity of the semiconductor light emitting device manufactured according to the second embodiment. It can be seen that the EL intensity of the semiconductor light emitting device according to the second embodiment having the metal reflective film 150 ′ is increased from that of the non-comparative example and the BCB, so that the light extraction efficiency is improved according to the present invention. You can check it.

7 is a view showing a process of performing a third embodiment of the method for manufacturing a semiconductor light emitting device according to the present invention.

Referring to FIG. 7A, after the light generating unit 320 formed of a semiconductor is formed on the upper surface of the substrate 310, a plurality of beads (see FIG. 7B) may be formed on the lower surface of the substrate 310. 340 is applied. The substrate 310, the light generator 320, and the beads 340 correspond to the substrate 10, the light generator 20, and the beads 40 described in the first embodiment, respectively.

In the first embodiment, the polymer layer 30 is formed to fix the beads 40. However, in the present embodiment, the beads 340 are formed on the bottom surface of the substrate 310 using a different method, for example, an electrical coupling using an electrolyte. It can be fixed.

Next, as shown in FIG. 7C, the metal reflective film 350 is formed along the bend of the bead 340 to be manufactured as the semiconductor light emitting device 400. For example, the metal reflective film 350 is formed by covering a metal such as Ag. The metal reflective film 350 is formed to a thickness that is conformally deposited along the bend of the bead 340. As described above, according to the present invention, a three-dimensionally textured reflective surface is naturally formed along the bend of the bead 340 without an etching process and a complicated process in a short time, unlike the conventional technology.

Although the preferred embodiments of the present invention have been shown and described above, the present invention is not limited to the specific preferred embodiments described above, and the present invention belongs to the present invention without departing from the gist of the present invention as claimed in the claims. Various modifications can be made by those skilled in the art, and such changes are within the scope of the claims.

1 is a view showing a process of performing a first embodiment of a method for manufacturing a semiconductor light emitting device according to the present invention.

FIG. 2 is a SEM photograph showing a metal reflective film having hemispherical nanolens curvatures formed on the rear surface of a semiconductor light emitting device manufactured according to the first embodiment.

3 is a graph measuring the EL intensity of the semiconductor light emitting device manufactured according to the first embodiment.

4 is a view showing a process of performing a second embodiment of the method for manufacturing a semiconductor light emitting device according to the present invention.

FIG. 5 is a SEM photograph showing a metal reflective film having a dimple-shaped curvature formed on a rear surface of a semiconductor light emitting device manufactured according to the second embodiment.

6 is a graph measuring the EL intensity of the semiconductor light emitting device manufactured according to the second embodiment.

7 is a view showing a process of performing a third embodiment of the method for manufacturing a semiconductor light emitting device according to the present invention.

<Explanation of symbols for main parts of the drawings>

10, 110, 310 ... substrate 20, 120, 320 ... light generator

30, 130 ... Polymer 35, 135 ... groove

40, 140, 340 ... Bead 50, 50 ', 150, 150', 350 ... Metal Reflective Film

100, 200, 400 ... semiconductor light emitting device

Claims (14)

Board; A light generating unit formed of a semiconductor on an upper surface of the substrate; A polymer layer disposed on a bottom surface of the substrate and having a plurality of grooves formed on a bottom surface thereof; A plurality of beads having a portion inserted into the groove portion; And And a metal reflective film formed along the bend of the bead. Board; A light generating unit formed of a semiconductor on an upper surface of the substrate; A polymer layer disposed on a bottom surface of the substrate and having a plurality of grooves formed on a bottom surface thereof; And And a metal reflective film formed along the curvature of the groove. The semiconductor light emitting device of claim 1 or 2, wherein the polymer layer is formed of at least one selected from polystyrene (PS) and bis-benzocyclobutene (BCB). The semiconductor light emitting device of claim 1, wherein the bead comprises at least one of an oxide bead and a polymer bead. The method of claim 4, wherein the oxide beads are SiO ₂ , Al ₂ O ₃ , TiO ₂ , ZrO ₂ , Y ₂ O ₃ -ZrO ₂ , CuO, Cu ₂ O, Ta ₂ O ₅ , PZT (Pb (Zr, Ti ) O ₃ ), Nb ₂ O ₅ , Fe ₃ O ₄ , Fe ₂ O ₃ And a semiconductor light emitting device comprising at least one selected from GeO ₂ . The semiconductor light emitting device of claim 1, wherein the beads have a diameter of about 0.01 μm to about 10 μm. The semiconductor light emitting device of claim 1, wherein the bead is a single layer. Forming a light generating unit formed of a semiconductor on an upper surface of the substrate; Applying a plurality of beads to a lower surface of the substrate; And And forming a metal reflective film along the bend of the bead. The method of claim 8, wherein the applying of the plurality of beads to the bottom surface of the substrate comprises: Forming a polymer layer on a lower surface of the substrate; Applying the plurality of beads on the polymer layer; And Heating the polymer layer to a glass transition temperature or higher, thereby depositing a portion of the bead on the polymer layer. Forming a light generating unit formed of a semiconductor on an upper surface of the substrate; Forming a polymer layer on a lower surface of the substrate; Applying the plurality of beads on the polymer layer; Heating the polymer layer above a glass transition temperature to precipitate a portion of the beads in the polymer layer; Removing the beads; And And forming a metal reflective film along the curvature of the polymer layer from which the beads are removed. The method of claim 9, wherein the polymer layer is made of at least one selected from polystyrene (PS) and bis-benzocyclobutene (BCB). The method according to claim 9 or 10, further comprising irradiating ultraviolet rays or performing an O ₂ plasma treatment after forming the polymer layer. The method according to any one of claims 8 to 10, wherein the bead comprises at least one of an oxide bead and a polymer bead. The method of claim 13, wherein the oxide beads are SiO ₂ , Al ₂ O ₃ , TiO ₂ , ZrO ₂ , Y ₂ O ₃ -ZrO ₂ , CuO, Cu ₂ O, Ta ₂ O ₅ , PZT (Pb (Zr, Ti (O ₃ ), Nb ₂ O ₅ , Fe ₃ O ₄ , Fe ₂ O ₃ And GeO _{2 A} method for manufacturing a semiconductor light emitting device, characterized in that consisting of one or more.

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