KR100955319B1 - Method of fabricating light emitting diode and light emitting diode fabricated by the same - Google Patents

Abstract

Disclosed are a light emitting diode manufacturing method and a light emitting diode manufactured thereby. In one embodiment of the method of manufacturing a light emitting diode according to the present invention, a polymer layer is formed on an upper surface of a substrate, and a plurality of beads are coated on the upper surface of the polymer layer. The polymer layer is heated above the glass transition temperature to precipitate a portion of the beads in the polymer layer. In another embodiment of the method of manufacturing a light emitting diode according to the present invention, a polymer layer is formed on an upper surface of a substrate, and a plurality of beads are coated on the upper surface of the polymer layer. Then, using the etching gas having a higher rate of etching the polymer layer than the rate of etching the beads, the top surface of the bead, the polymer layer and the substrate is dry-etched. According to the present invention, a light emitting diode having a curved pattern without an etching process or even without an etching process can be manufactured, thereby greatly reducing time and cost.

LED, external light extraction efficiency, total internal reflection, glass transition temperature, polymer

Description

Method for manufacturing light emitting diodes and light emitting diodes manufactured by the same {Method of fabricating light emitting diode and light emitting diode fabricated by the same}

The present invention relates to a light emitting diode, and more particularly, to a light emitting diode manufacturing method having excellent external light extraction efficiency and a light emitting diode manufactured thereby.

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

The biggest problem with LEDs is their low luminous efficiency. In general, the luminous efficiency is determined by the light generation efficiency (internal quantum efficiency), the efficiency emitted outside the device (external light extraction efficiency), and the efficiency with which light is switched by the phosphor. In order to increase the output power of LED, it is important to improve the active layer characteristics in terms of internal quantum efficiency, but it is very important to increase the external light extraction efficiency of the light actually generated.

The biggest obstacle to the emission of light out of the LED is the internal total reflection due to the difference in refractive index between each layer of the LED. Due to the difference in refractive index between the layers of the LED, the light exiting the interface corresponds to about 20% of the generated light. In addition, the light that has not passed through the interface moves inside the LED and is converted into heat. As a result, the luminous efficiency is low and the amount of heat generated by the device is increased, thereby shortening the life of the LED.

In order to improve the external light extraction efficiency, a method of increasing the roughness of the p-GaN surface or the n-GaN surface, a method of roughening the surface of the substrate, which is the base portion of the device, or forming a curved pattern is proposed.

FIG. 1A is a cross-sectional view of the LED 14 formed on the substrate 10 on which the pattern 12 is formed, and FIG. 1B is a view of the substrate 10 on which the pattern 12 is formed. In particular, in LEDs using heterogeneous substrates such as sapphire, forming a pattern on the substrate has an effect of improving external light extraction efficiency.

The pattern of the surface of the sapphire substrate is calculated to increase the external light extraction efficiency by 100% or more, and Korean Patent Application Nos. 2004-0021801 and 2004-0049329 refer to the shapes or patterns thereof. As a method of forming such a pattern, an etching method is currently used. In this method, the resist and the sapphire substrate are simultaneously etched by dry etching after several tens of micrometer thick films are formed to form a hemispherical pattern shape to be formed on the sapphire substrate.

The pattern formation method using such an etching is limited in the height of the pattern by the selectivity ratio between the resist and the substrate, difficult to control the etching rate, and the final uniformity due to the low uniformity of the patterning process and the dry etching process of the thick film resist There is a problem that the uniformity of the formed pattern is low. Above all, the pollution caused by dry etching is the biggest problem. The reactants such as the resist and the gas used for etching remain on the surface of the sapphire substrate due to locally generated heat during etching and are not easily removed even after the cleaning process. In addition, damage to the substrate surface is also expected by the high energy gas particles used for etching. (Silicon processing for the VLSI era, vol 1. process technology, p.574 ~ 582) When such contamination occurs, a fatal defect in the nitride epitaxial layer due to contamination when GaN epitaxial growth, the next process to be connected, is performed. This can happen. Due to the above drawbacks, very low yields are expected when fabricating devices using sapphire substrates patterned using real etching.

In the dry etching process described above, an expensive etching apparatus having a cooling function must be used for excessive heat emission generated during a forced etching of sapphire, which is difficult to etch. In order to increase the light extraction efficiency, a process of further reducing the pattern size to be etched using an expensive photo equipment such as a stepper should be used. Therefore, in order to perform the dry etching process described above, high cost is required. In addition, a process using a photo equipment such as a stepper has a disadvantage in that it is difficult to increase the process throughput due to a complicated process.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide a light emitting diode manufacturing method having excellent light extraction efficiency and a light emitting diode manufactured thereby.

Another object of the present invention is to provide a light emitting diode manufacturing method having excellent heat dissipation efficiency and a light emitting diode manufactured by the same.

In order to solve the above technical problem, a preferred embodiment of the LED manufacturing method according to the present invention comprises the steps of forming a polymer layer on the upper surface of the substrate; Applying a plurality of beads to an upper surface of the polymer layer; And heating the polymer layer above a glass transition temperature to precipitate a portion of the beads in the polymer layer.

Another preferred embodiment of the light emitting diode manufacturing method according to the present invention for solving the above technical problem is the step of forming a polymer layer on the upper surface of the substrate; Applying a plurality of beads to an upper surface of the polymer layer; And dry etching the upper surface of the bead, the polymer layer, and the substrate by using an etching gas having a higher rate at which the polymer layer is etched than a rate at which the beads are etched.

In order to solve the above other technical problem, a preferred embodiment of the light emitting diode manufacturing method according to the present invention comprises the steps of forming a polymer layer on the lower surface of the substrate; Applying a plurality of beads to a lower surface of the polymer layer; And heating the polymer layer above a glass transition temperature to precipitate a portion of the beads in the polymer layer.

Another preferred embodiment of the method of manufacturing a light emitting diode according to the present invention for solving the above technical problem is a step of forming a polymer layer on the lower surface of the substrate; Applying a plurality of beads to the lower surface of the polymer layer; And dry etching the lower surface of the bead, the polymer layer, and the substrate by using an etching gas having a higher rate at which the polymer layer is etched than a rate at which the beads are etched.

In order to solve the above technical problem, a preferred embodiment of the light emitting diode according to the present invention is a substrate; A polymer layer disposed on an upper surface of the substrate and having a plurality of grooves formed on an upper surface thereof; And a plurality of beads having a portion inserted into the groove portion.

In order to solve the above other technical problem, a preferred embodiment of the light emitting diode according to the present invention is a 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 a plurality of beads having a portion inserted into the groove portion.

According to the first embodiment of the present invention, it is possible to manufacture a light emitting diode having a bent pattern on the upper surface of the substrate without an etching process, so there is no problem in accordance with 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, the pattern can be formed uniformly even in a large area, which is advantageous for the large area of the light emitting diode.

According to the second embodiment of the present invention, a pattern may be formed on the upper surface of the substrate by a simple process without a photolithography process for dry etching. Therefore, the expensive equipment required for the photolithography process is not required, and the time required for the photolithography process is shorter, resulting in excellent productivity. In addition, the pattern can be formed uniformly even in a large area, which is advantageous for the large area of the light emitting diode.

According to the third embodiment of the present invention, a light emitting diode having a curved pattern on the lower surface of the substrate can be manufactured, and light is emitted without gathering on the lower surface of the substrate when manufacturing a light emitting diode using flip chip bonding. This reduces the chance of heat generation. In addition, since the curved pattern can be formed on the lower surface of the substrate using only a simple process such as spin coating, problems with the etching process do not occur and the time and cost can be saved.

According to the fourth embodiment of the present invention, a light emitting diode having a curved pattern on the bottom surface of the substrate can be manufactured, so that light is not collected on the bottom surface of the substrate when the light emitting diode is manufactured using flip chip bonding. This reduces the chance of heat generation. In addition, since the pattern may be formed on the bottom surface of the substrate by a simple process without a photolithography process for dry etching, productivity may be superior to that in the case of using the photolithography process as described above.

Hereinafter, a light emitting diode manufacturing method and a preferred embodiment of a light emitting diode manufactured by the same according to the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various forms, and only the present embodiments are intended to complete the disclosure of the present invention and to those skilled in the art to fully understand the scope of the invention. It is provided to inform you.

2 is a flowchart illustrating a process of performing a first embodiment of a method of manufacturing a light emitting diode according to the present invention. 3 (a) to 3 (d) are cross-sectional views illustrating a process of performing the first embodiment.

2 to 3 (d), first, as shown in FIG. 3 (b), the polymer layer 220 is formed on the upper surface of the substrate 210 (S110). The substrate 210 may include sapphire (Al ₂ O ₃ ), gallium arsenide (GaAs), spinel (MgAl ₂ O ₄ ), indium phosphide (InP), silicon carbide (SiC), silicon (Si), and lithium aluminum oxide ( The one in which gallium nitride (GaN) is deposited on LiAlO ₂ ) or magnesium oxide (MgO) may be used. 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 gallium nitride, have high temperature stability, and lattice constants and coefficients of thermal expansion are similar to gallium nitride, but they are expensive. The silicon substrate has a difference in lattice constant from gallium nitride of about 17% and a thermal expansion coefficient of about 35%. As exemplified above, various substrates can be used, and if a silicon substrate is used, it can be manufactured even in a large area of 12 inches or more, thereby reducing manufacturing costs and significantly expanding the application range of the device using the same.

The polymer layer 220 is made of a polymer material, and preferably may be made of polystyrene (PS), bis-benzocyclobutene (BCB), and a combination thereof. In order to form the polymer layer 220 on the upper surface of the substrate 210, a spin coating method may be used.

Then, the polymer layer 220 is irradiated with ultraviolet light. When the polymer layer 220 is hydrophobic, when the ultraviolet ray is irradiated onto the polymer layer 220, the polymer layer 220 is converted into hydrophilicity. Since the bead 230 to be applied on the polymer layer 220 is generally hydrophilic, UV treatment is required when the polymer layer 220 is hydrophobic. However, when the polymer layer 220 is hydrophilic, the step of irradiating ultraviolet rays to the polymer layer 220 may be omitted.

As shown in FIG. 3 (c), a plurality of beads 230 are coated on the upper surface of the polymer layer 220 (S120). Bead 230 may be used that has a refractive index of 1.2 to 2.0 to increase the external light extraction efficiency. The beads 230 may be formed of oxide beads, polymer beads, and combinations thereof. 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 One consisting of at least one selected from ₂ O ₅ , Fe ₃ O ₄ , Fe ₂ O _3, and GeO ₂ may be used. Preferably, the beads 230 are spherical, and in this case, the beads 230 may have a diameter of 0.01 to 10 μm to increase external light extraction efficiency. SiO ₂ may be used as the bead 230, and a method of manufacturing SiO ₂ beads is 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 230 may be manufactured in various sizes of 0.01 to 10㎛ depending on manufacturing conditions, that is, growth time, temperature, the amount of reactants. The beads 230 thus obtained are coated on the upper surface of the polymer layer 220 using a method such as dip coating or spin coating.

In this manner, a cross-sectional scanning electron microscopy (SEM) photograph of the SiO ₂ beads 230 formed on the BCB polymer layer 220 is illustrated in FIG. 4. In this case, a substrate 210 in which gallium nitride is deposited on sapphire is used.

Then, the polymer layer 220 is heated to a glass transition temperature or more, and a portion of the bead 230 is precipitated in the polymer layer 220 as shown in FIG. 3 (d) (S130). In order to manufacture the light emitting diodes 200 having a large number of curves, it is preferable to deposit about half of the beads 230. The light emitting diode 200 manufactured as described above has a plurality of grooves formed on an upper surface of the polymer layer 220, and a portion of the bead 230 is inserted into the grooves. When BCB is used as the polymer layer 220, a curved pattern may be formed through low temperature heat treatment of about 130 to 160 ° C. This is shown in FIG. 5.

5 is a cross-sectional scanning electron micrograph after the BCB polymer layer 220 is heated to about 130 to 160 ° C. to precipitate the SiO ₂ beads 230.

As shown in FIG. 5, when the light emitting diode manufacturing method according to the present invention is used, the light emitting diode having a hemispherical pattern can be manufactured using only a simple process such as spin coating and low temperature heat treatment. And because it is a hemispherical pattern, it can suppress total reflection of light more efficiently than other nanostructures and increase light extraction efficiency. In addition, since the polymer layer 220 and the plurality of beads 230 are formed by the same method as the spin coating, the curved pattern may be formed in a large area for a short time.

6A is a light emitting photo of a light emitting diode manufactured by a conventional method, and FIG. 6B is a light emitting photo of a light emitting diode manufactured according to the present invention. 6A and 6B are numerical values of brightness.

6A and 6B, the brightness of the light extracted from the light emitting diode manufactured by the conventional method is 118, whereas the brightness of the light extracted from the light emitting diode 200 manufactured according to the present invention is remarkably 245. You can see that it has risen. This is because a curved pattern is formed on the surface of the light emitting diode 200 to increase the external light extraction efficiency.

7 is a flowchart illustrating a process of performing a second embodiment of the method of manufacturing a light emitting diode according to the present invention. 8 (a) to 8 (d) are cross-sectional views illustrating a process of performing the second embodiment.

Referring to FIGS. 7 to 8D, first, as shown in FIG. 8B, the polymer layer 820 is formed on the upper surface of the substrate 810 (S710). As shown in FIG. 8 (c), a plurality of beads 830 are coated on the upper surface of the polymer layer 820 (S720). Steps S710 and S720 correspond to steps S110 and S120, respectively. As described above, ultraviolet rays may be irradiated onto the polymer layer 820 between steps S710 and S720.

Next, dry etching the upper surface of the bead 830, the polymer layer 820 and the substrate 810 by using an etching gas having a higher rate of etching the polymer layer 820 than the rate of etching the beads 830 ( S830). The step S830 and S820 may be performed by heating the polymer layer 820 above the glass transition temperature to precipitate a portion of the bead 830 in the polymer layer 820. This step corresponds to step S130 described with reference to FIG. 2. Even if the beads 830 are coated on the polymer layer 820, the beads 830 may not be coated so that the surface of the polymer layer 820 is not exposed. Therefore, when dry etching is performed using an etching gas having a higher rate at which the polymer layer 820 is etched than a rate at which the bead 830 is etched, a portion where the surface is exposed in the polymer layer 820 is first etched at a high speed. . When the polymer layer 820 is etched to expose the top surface of the substrate 810, the top surface of the exposed substrate 810 is also etched. In contrast, since the beads 830 are relatively slowly etched, the substrate 810 corresponding to the portion where the beads 830 are applied is not etched. Eventually, the bead 830 serves as a mask so that a portion of the substrate 810 is etched to form a pattern on the substrate.

Dry etching the upper surfaces of the beads 830, the polymer layer 820 and the substrate 810 in this manner, it is possible to manufacture a light emitting diode 800 having the irregularities as shown in Figure 8 (d). have. The irregularities formed at this time can be formed in the size of the nano-size. If the above-described method is used, the photolithography process is unnecessary. Therefore, a problem that occurs when forming a nano-sized pattern using a photolithography process does not occur. That is, it is possible to form a nano-sized pattern by a simple process without using equipment such as an expensive stepper.

9 is a view schematically showing a light emitting diode 900 manufactured by the method of the third embodiment.

Referring to FIG. 9, the third embodiment is a method of forming a pattern on a lower surface of a substrate, except that the polymer layer is formed on the lower surface of the substrate, not the upper surface of the substrate, and a plurality of beads are applied to the lower surface of the polymer layer. This is similar to the method described in FIG. When the method of the third embodiment is used, a pattern can be formed on the lower surface of the substrate by a simple process without an etching process as described above.

10 is a view schematically showing a light emitting diode 1000 manufactured by the method of the fourth embodiment.

Referring to FIG. 10, the fourth embodiment is a method of forming a pattern on a lower surface of a substrate, except that the polymer layer is formed on the lower surface of the substrate, not the upper surface of the substrate, and a plurality of beads are applied to the lower surface of the polymer layer. This is similar to the method described in FIG. When the method of the fourth embodiment is used, irregularities can be formed on the lower surface of the substrate by a simple process without the photolithography process as described above.

When the pattern is not formed on the bottom surface of the substrate and is flat, the probability of total reflection of light from the bottom surface of the substrate increases, so that light is collected on the bottom surface of the substrate, and heat is generated to adversely affect the light emitting diode performance. On the other hand, if the pattern is formed on the lower surface of the substrate as in the third and fourth embodiments, the light is emitted without being totally reflected, thereby reducing the possibility of heat generation. Therefore, when the light emitting diode is manufactured using flip chip coupling, the performance is excellent.

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.

FIG. 1A is a cross-sectional view of a light emitting diode LED formed on a patterned substrate, and FIG. 1B is a view of a substrate on which a pattern is formed.

2 is a flowchart illustrating a process of performing a first embodiment of a method of manufacturing a light emitting diode according to the present invention.

3 (a) to 3 (d) are cross-sectional views illustrating a process of performing the first embodiment.

FIG. 4 is a cross-sectional scanning electron microscopy (SEM) photograph after forming SiO ₂ particles on a bis-benzocyclobutene (BCB) polymer layer in the first embodiment.

FIG. 5 is a cross-sectional scanning electron micrograph after the BCB polymer layer is heated above the glass transition temperature to precipitate SiO ₂ particles in the first embodiment.

6A is a light emitting photo of a light emitting diode manufactured by a conventional method, and FIG. 6B is a light emitting photo of a light emitting diode manufactured according to the first embodiment.

7 is a flowchart illustrating a process of performing a second embodiment of the method of manufacturing a light emitting diode according to the present invention.

8 (a) to 8 (d) are cross-sectional views illustrating a process of performing the second embodiment.

9 is a view schematically showing a light emitting diode manufactured by the method of the third embodiment.

10 is a view schematically showing a light emitting diode manufactured by the method of the fourth embodiment.

Claims (20)

Forming a polymer layer on an upper surface of the substrate; Applying a plurality of beads to an upper surface of the polymer layer; And Heating the polymer layer above a glass transition temperature to precipitate a portion of the bead on the polymer layer. The method of claim 1, Between forming the polymer layer and applying the plurality of beads, The method of manufacturing a light emitting diode, characterized in that it further comprises; irradiating the ultraviolet ray to the polymer layer. Forming a polymer layer on an upper surface of the substrate; Applying a plurality of beads to an upper surface of the polymer layer; And And dry etching the upper surface of the bead, the polymer layer, and the substrate by using an etching gas having a higher rate at which the polymer layer is etched than a rate at which the beads are etched. . The method of claim 3, Between the step of applying the beads and the step of dry etching, And heating the polymer layer above a glass transition temperature to precipitate a portion of the bead on the polymer layer. The method of claim 3, Between forming the polymer layer and applying the beads, The method of manufacturing a light emitting diode, characterized in that it further comprises; irradiating the ultraviolet ray to the polymer layer. Forming a polymer layer on a lower surface of the substrate; Applying a plurality of beads to a lower surface of the polymer layer; And Heating the polymer layer above a glass transition temperature to precipitate a portion of the bead on the polymer layer. The method of claim 6, Between forming the polymer layer and applying the plurality of beads, The method of manufacturing a light emitting diode, characterized in that it further comprises; irradiating the ultraviolet ray to the polymer layer. Forming a polymer layer on a lower surface of the substrate; Applying a plurality of beads to the lower surface of the polymer layer; And And dry etching the lower surface of the bead, the polymer layer, and the substrate by using an etching gas having a higher rate at which the polymer layer is etched than at the rate at which the beads are etched. . The method of claim 8, Between the step of applying the beads and the step of dry etching, And heating the polymer layer above a glass transition temperature to precipitate a portion of the bead on the polymer layer. The method of claim 8, Between forming the polymer layer and applying the beads, The method of manufacturing a light emitting diode, characterized in that it further comprises; irradiating the ultraviolet ray to the polymer layer. The method according to any one of claims 1 to 10, The polymer layer is a light emitting diode manufacturing method, characterized in that consisting of at least one selected from PS (polystyrene) and BCB (bis-benzo cyclobutene). The method according to any one of claims 1 to 10, Wherein the plurality of beads comprises at least one of oxide beads and polymer beads. The method of claim 12, 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 A light emitting diode manufacturing method comprising at least one selected from ₂ O ₅ , Fe ₃ O ₄ , Fe ₂ O _3, and GeO ₂ . Board; A polymer layer disposed on an upper surface of the substrate and having a plurality of grooves formed on an upper surface thereof; And And a plurality of beads having a portion inserted into the groove portion. Board; 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 plurality of beads having a portion inserted into the groove portion. The method according to claim 14 or 15, The polymer layer is a light emitting diode, characterized in that consisting of at least one selected from PS and BCB. The method according to claim 14 or 15, The refractive index of the bead is light emitting diode, characterized in that 1.2 to 2.0. The method according to claim 14 or 15, Wherein the plurality of beads comprises at least one of oxide beads and polymer beads. The method of claim 18, 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, Nb ₂ O ₅ , Fe ₃ O ₄ , Fe A light emitting diode comprising at least one selected from ₂ O ₃ and GeO ₂ . The method according to claim 14 or 15, The diameter of the bead is light emitting diode, characterized in that 0.01 to 10 μm.

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