JP2006245066A - Light emitting diode and method of manufacturing light emitting diode - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light emitting diode which can improve emission efficiency (the extraction efficiency of light), and to provide a method of manufacturing the light emitting diode. <P>SOLUTION: In the light emitting diode 1, each layer functioning as a light emission unit is laminated on a sapphire substrate 10. The end 10a of the reverse side (rear side) of a surface on which the emission unit of each side of the sapphire substrate 10 is formed is formed into an unevenly coarse surface. Therefore, light guided by the end 10a of the emitting light from the light emission unit is scattered at this end 10a, and emitted out on the sapphire substrate 10. The light emitting diode 1, for example, manufactured after a plurality of the light emission units are first formed, the sapphire substrate is divided (diced) into individual light emission units. In this case, first, the substrate is cut by a diamond scribing method, a laser scribing method, etc. , and grooves are formed, and then a polishing particle is injected to the substrate, the front surface is cut, and the coarse surface is formed on the front surface. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a light emitting diode and a method for manufacturing the light emitting diode, and more specifically to a light emitting diode having excellent luminous efficiency and a method for manufacturing the light emitting diode.

  Light emitting diodes are used in various applications because they have features such as small size, thinness, low power consumption, and long life. A light-emitting diode is a kind of semiconductor, and has a structure in which a plurality of layers are stacked on a transparent plate such as a sapphire substrate using a technique known per se, as in various semiconductor processes (for example, (See Patent Document 1).

FIG. 6 is a structural sectional view showing an example of a conventional light emitting diode.
A conventional light emitting diode 100 includes an AlN buffer layer 111 (thickness: about 200 mm), a Si-doped GaN layer 112 (thickness: about 1.2 μm), N-type GaN, and N on a transparent substrate (here, a sapphire substrate) 110. Active layer 113 (thickness: about 400 mm) made of multiple quantum wells (MQW) having a laminated structure with type InGaN, cap layer 114 (thickness: about 200 mm) made of a superlattice of AlN and P-type GaN, Mg-doped GaN layer 115 (thickness: about 0.2 μm), a Zn film 116 (thickness: several tens of millimeters), and an ITO film 117 (thickness: about 0.5 μm) are laminated. A P-type electrode 118 is formed on a part of the upper surface of the ITO film 117, and a part of the ITO film 117 is etched to expose a part of the Si-doped GaN layer 112. An N-type electrode 119 is formed on the substrate. A light emission phenomenon occurs when a voltage is applied between the P-type electrode 118 and the N-type electrode 119.

  Meanwhile, the conventional light emitting diode 100 is manufactured by forming a plurality of light emitting portions on a large-area sapphire substrate 110 and then dividing (dicing) the sapphire substrate 110 into individual light emitting portions. As a dicing method, a method called a diamond scribe method has been conventionally used. However, since diamond (industrial diamond) is used for the dicing saw, it has been a problem that the manufacturing cost is high.

Therefore, in recent years, a technique called a laser scribing method has been put into practical use. The laser scribing method is a method of irradiating a substrate with laser light and cutting the substrate with the heat thereof. Compared with the conventional diamond scribing method, a light emitting diode can be manufactured at a much lower cost.
Japanese Patent No. 3394488

  However, when the sapphire substrate 110 is diced using the laser scribing method, the sapphire substrate 110 at the portion irradiated with the laser is altered, so that the light is emitted from the residue 110a near the cut portion as shown in FIG. There is a problem that absorption occurs and the light extraction efficiency decreases.

  Further, even when the conventional diamond scribe method is used for singulation, since the cut surface is extremely sharp, as shown in FIG. There is a problem that total reflection is performed on the side surface and the bottom surface of 110, and the reflected light is absorbed by an electrode (here, N-type electrode 119) provided on the chip surface, thereby reducing the light extraction efficiency.

  This invention is made | formed in view of such a situation, and when the light emission part is formed in one surface on a transparent plate, the edge part of the other surface of a transparent plate, ie, the surface opposite to the surface in which the light emission part was formed. By adopting a structure in which the edge of the surface is roughened, the light incident on the transparent plate out of the light emitted from the light emitting portion is diffused at the edge and taken out to the outside of the transparent plate. It is an object of the present invention to provide a light emitting diode capable of improving (light extraction efficiency) and a method for manufacturing the light emitting diode.

  Further, according to the present invention, when the light emitting portion is formed on one surface of the transparent plate, the other surface of the transparent plate, that is, the surface opposite to the surface on which the light emitting portion is formed and / or the side surface of the transparent plate is roughened. By adopting such a structure, the light emitted from the light emitting part is diffused at the interface of the transparent plate (the other surface and / or side surface of the transparent plate) and taken out to the outside of the transparent plate, thereby improving the light extraction efficiency. An object of the present invention is to provide a light emitting diode and a method for manufacturing the light emitting diode.

  The light emitting diode according to the first aspect of the present invention is a light emitting diode in which a light emitting portion is formed on one surface of a transparent plate, wherein an end of the other surface of the transparent plate is roughened.

In the first invention, among the surfaces of the transparent plate, since the end of the surface opposite to the surface where the light emitting portion is formed is roughened, the light is emitted from the light emitting portion formed on the transparent plate. Of the received light, the light incident on the transparent plate is scattered at the end and emitted to the outside of the transparent plate. Thus, the light extraction efficiency can be improved by roughening the end.
In particular, when a sapphire substrate, which is a transparent substrate, is diced using a laser scribing method, the sapphire substrate is altered by laser irradiation, so that light absorption occurs in the vicinity of the cut portion, that is, the end portion to be roughened. However, there is a problem that the light extraction efficiency is lowered. However, when the surface is roughened, the altered portion is removed, and light absorption at this portion can be suppressed.

  A light emitting diode according to a second aspect of the present invention is a light emitting diode in which a light emitting part is formed on one surface of a transparent plate, wherein the other surface of the transparent plate and / or the side surface of the transparent plate is roughened. .

  In the second invention, among the respective surfaces of the transparent plate, the opposite surface (referred to as the back surface) and / or the side surface of the surface on which the light emitting part is formed are roughened, so that the transparent plate is formed on the transparent plate. Of the light emitted from the light emitting unit, the light incident on the transparent plate is scattered on the back surface and / or the side surface and emitted to the outside of the transparent plate. Thus, the light extraction efficiency can be further improved by roughening the back surface and / or the side surface.

  According to a third aspect of the present invention, there is provided a light emitting diode manufacturing method for manufacturing individual light emitting diodes by dividing the transparent plate formed with a plurality of light emitting portions into individual light emitting portions. It includes a groove forming step for forming grooves at locations to be divided, and a roughening step for roughening the surface of the grooves formed in the groove forming step.

  In the third invention, when a light emitting diode is formed by dividing a transparent plate on which a plurality of light emitting portions are formed into individual light emitting portions, first, after forming a groove at a portion to be divided on the transparent plate, The surface of the groove formed is roughened.

  According to a fourth aspect of the present invention, there is provided a light emitting diode manufacturing method for manufacturing individual light emitting diodes by dividing the transparent plate formed with a plurality of light emitting portions into individual light emitting portions. It includes a groove forming step for forming a groove at a portion to be divided, and a roughening step for roughening the surface of the transparent plate including the groove formed in the groove forming step.

  In the fourth invention, when a light emitting diode is formed by dividing a transparent plate on which a plurality of light emitting portions are formed into individual light emitting portions, first, a groove is formed in a portion to be divided of the transparent plate, and then formed. The surface of the transparent plate including the groove is roughened. Here, the surface of the transparent plate including the formed groove is the surface (front surface) of the light emitting portion, the surface opposite to the surface (back surface), and / or the side surface of each surface of the transparent plate. Yes, it is preferable to appropriately select the surface to be roughened according to the application.

  According to a fifth aspect of the present invention, there is provided the method for producing a light emitting diode according to the third or fourth aspect, wherein the groove forming step uses a diamond scribe method or a laser scribe method.

  In the fifth invention, the groove is formed at a position to be divided of the transparent plate by the diamond scribe method or the laser scribe method. The diamond scribe method or the laser scribe method is a method known per se and can stably form grooves in the transparent plate.

  According to a sixth aspect of the present invention, there is provided the method for manufacturing a light-emitting diode according to any one of the third to fifth aspects, wherein the roughening step includes cutting the surface by injecting abrasive particles onto the transparent plate. It is characterized by becoming.

  In the sixth invention, the surface of the transparent plate is cut and roughened by spraying abrasive particles onto the transparent plate. When cutting only a predetermined part on the surface of the transparent plate, the abrasive particles are jetted through a mask in which an opening pattern corresponding to the part is formed. Since the surface of the transparent plate corresponding to the opening pattern can be selectively cut, a portion to be roughened can be appropriately selected depending on the application. Also, since cutting by abrasive particle injection generally takes time, when the surface is roughened by cutting the surface, the amount of cutting is less than the amount of cutting by the groove forming step to improve manufacturing tact. It is preferable.

  According to the present invention, when the light emitting portion is formed on one surface of the transparent plate, the end of the other surface of the transparent plate, that is, the end of the surface opposite to the surface on which the light emitting portion is formed is roughened. Therefore, the light extraction efficiency can be improved by diffusing the light incident on the transparent plate out of the light emitted from the light emitting portion at the end and taking it out of the transparent plate.

  According to the present invention, when the light emitting portion is formed on one surface of the transparent plate, the side surface of the transparent plate and / or the other surface of the transparent plate, that is, the surface opposite to the surface on which the light emitting portion is formed is roughened. Because of the above structure, the light emitted from the light emitting part is diffused at the interface of the transparent plate, and taken out to the outside of the transparent plate, so that the light extraction efficiency can be improved.

  Hereinafter, the present invention will be described in detail with reference to the drawings illustrating embodiments thereof.

(Embodiment 1)
FIG. 1 is a structural sectional view showing an example of a light emitting diode according to Embodiment 1 of the present invention.

  In the light-emitting diode 1 according to Embodiment 1 of the present invention, an AlN buffer layer 11 having a thickness of approximately 200 mm is formed on a transparent substrate (here, a sapphire substrate) 10 having excellent transmittance in the visible light region. . The AlN buffer layer 11 is formed, for example, by setting the temperature of the sapphire substrate 10 to 510 ° C., using nitrogen and hydrogen as a carrier gas, and supplying ammonia and trimethylaluminum. It is assumed that the sapphire substrate 10 has been subjected to thermal cleaning (1050 ° C.) in advance.

  On the upper surface of the AlN buffer layer 11, a Si-doped GaN layer 12, which is N-type GaN, is formed with a thickness of approximately 1.2 μm. The Si-doped GaN layer 12 is formed by raising the temperature of the sapphire substrate 100 to 1000 ° C., using the same carrier gas as described above, supplying ammonia and trimethylgallium, and using silicon that functions as an N-type impurity. The

  On the upper surface of the Si-doped GaN layer 12, an active layer 13 made of multiple quantum wells (MQW), which is a stacked structure of N-type GaN and N-type InGaN, is formed with a thickness of about 400 mm. The active layer 13 can have a multiple quantum well structure by intermittently supplying trimethylindium.

  On the upper surface of the active layer 13, a cap layer 14 made of a superlattice of AlN and P-type GaN is formed with a thickness of about 200 mm. The cap layer 14 is formed by appropriately supplying a material with the temperature of the sapphire substrate 10 being 950 ° C. For example, when forming AlN, ammonia and trimethylaluminum are supplied. When forming P-type GaN, ammonia and trimethylgallium are supplied and a P-type impurity is used.

  An Mg-doped GaN layer 15 having a thickness of approximately 0.2 μm is formed on the upper surface of the cap layer 14. The Mg-doped GaN layer 15 is formed by adding magnesium as an impurity to a carrier gas.

  On the top surface of the Mg-doped GaN layer 15, a Zn film 16 having a thickness of several tens of millimeters is formed. After forming the Mg-doped GaN layer 15, the Zn film 16 has a temperature of the sapphire substrate 10 of 800 ° C., a pressure in the reduced pressure MOCVD apparatus of 6650 Pa (50 torr), and an atmosphere of a mixed gas containing hydrogen atoms such as ammonia. Then, the atmosphere in the reduced pressure MOCVD apparatus is quickly switched to nitrogen gas which is an inert gas, and nitrogen gas is used as a carrier gas and trimethyl zinc is supplied.

An ITO film 17 having a thickness of about 0.5 μm is formed on the upper surface of the Zn film 16. The ITO film 17 is formed by heating and evaporating ITO containing 10% SnO ₂ with an electron gun in a vacuum deposition apparatus at a temperature of 200 ° C. of the sapphire substrate 10.

  A P-type electrode 18 is formed on a part of the upper surface of the ITO film 17, and a part of the ITO film 17 is etched to expose a part of the Si-doped GaN layer 12. An N-type electrode 19 is formed. A light emission phenomenon occurs when a voltage is applied between the P-type electrode 18 and the N-type electrode 19.

  In the present embodiment, the end 10a on the opposite surface (back surface) to the surface on which the light emitting portion is formed is roughened in an uneven shape as shown in the enlarged end view of FIG. In Fig. 3, the uneven shape which is a feature of the present invention is exaggerated). Therefore, the light guided to the end portion 10a out of the light emitted from the light emitting portion is scattered at the end portion 10a and emitted to the outside of the sapphire substrate 10, thereby improving the light extraction efficiency. To do.

Next, a method for manufacturing the above-described light emitting diode 1 will be described. The light emitting diode 1 can be manufactured by forming a plurality of light emitting portions on a substrate and then separating them into individual light emitting portions.
FIG. 3 is an explanatory diagram for explaining the method for manufacturing the light emitting diode according to the first embodiment of the present invention. In addition, since the method of forming a several light emission part by laminating | stacking various laminates on a board | substrate is the same as the past, the description is abbreviate | omitted.

  The sapphire substrate 50 is formed with a plurality of light emitting portions 60, 60,... Formed by laminating the above-described layers using a photolithography technique known per se (FIG. 3A). A broken line in the figure is a chip dividing line (which is of course a virtual one), and a region surrounded by each dividing line indicates an individual light emitting diode, and is divided into individual pieces in the process described below.

  First, an organic film is applied to the opposite surface (back surface) of the surface on which the light emitting unit 60 is formed to form a mask 70 (FIG. 3B). The mask 70 is applied so as to cover the entire back surface of the sapphire substrate 50.

  Then, the laser beam is irradiated from the back surface of the sapphire substrate 50 while moving the laser irradiation device along the chip dividing line. Thereby, first, the mask 70 reacts with the laser beam to form a groove, and further, the sapphire substrate 50 reacts with the laser beam to change the material of the irradiated portion, and the reaction portion breaks to form the groove 50a. Is formed (FIG. 3C). The surface of the groove 50a does not have a property of transmitting light, but conversely changes to a property of absorbing light (hereinafter referred to as a residue). Although the depth of the groove 50a to be formed is not limited, for example, it is about 2/3 of the thickness of the sapphire substrate 50.

  By the way, since the emitted light from the light emitting unit 60 is absorbed by the residue, the light extraction efficiency as the light emitting diode is lowered. Therefore, the surface of the groove 50a formed in the sapphire substrate 50 is roughened. Specifically, abrasive particles such as alumina and SiC are sprayed onto the surface of the groove 50a by a sandblasting method to remove the generated residue, and the surface of the groove 50a is roughened (FIG. 3D). ). The shape of the unevenness generated on the surface of the groove 50a can be adjusted by the type of abrasive particles, the injection pressure and the injection amount of the abrasive particles, and is appropriately set so as to have a desired shape.

  When the sand blast method is used, the organic film described above functions as the mask 70, and it is possible to prevent the portions other than the grooves from being cut. As described above, when only a predetermined portion is cut, the abrasive particles are ejected through a mask in which an opening pattern corresponding to the portion is formed. Also, since cutting by injection of abrasive particles generally takes time, the necessary amount of cutting is performed in the groove forming process, and the cutting in the roughening process is performed to the extent that the residue is removed, which is necessary for manufacturing (cutting). It is preferable to shorten the time and improve the manufacturing tact.

  The mask 70 is not limited to the material as long as it has sandblast resistance. For example, a photosensitive resin film such as a dry film resist having sandblast resistance is pasted on a sapphire substrate and pasted. After forming the photosensitive resin film into a desired mask pattern by photolithography, a groove forming step by laser irradiation and a roughening step by sandblasting may be performed.

  Then, the sapphire substrate 50 is divided by applying stress to the sapphire substrate 50 on which the light emitting portions 60 and 60 adjacent to each other are formed via the groove 50a (FIG. 3E). In this way, among the surfaces of the sapphire substrate 50, the end of the surface opposite to the surface on which the light emitting unit 60 is formed can be roughened. And after dividing | segmenting into each light emitting diode, the light emitting diode 1 is manufactured by removing the mask 70 suitably.

Next, the light output of the light emitting diode 1 according to the present embodiment was evaluated.
First, the light-emitting diode 1 according to the present embodiment and a conventional light-emitting diode divided into chips only by a laser scribing method, that is, a light-emitting diode (referred to as ref1) in which the roughening step in FIG. Comparison of light output was performed. When the light output of ref1 was 1, it was confirmed that the light output of the light-emitting diode 1 was improved by 1.10 to 1.15 times. This is presumed that the light absorbed by the residue could be extracted by removing the residue generated by the laser irradiation in the roughening step. Moreover, since light absorption is suppressed, the temperature rise of light emitting diode itself is suppressed, and durability improves.

  Further, the light output of the light-emitting diode 1 according to the present embodiment and the conventional light-emitting diode (ref2) divided into chips only by the diamond scribe method was compared. When the light output of ref2 was set to 1, it was confirmed that the light output of the light-emitting diode 1 was improved by approximately 1.02. This is because, by roughening the end of each surface of the sapphire substrate opposite to the surface on which the light emitting portion is formed, light diffusion is caused at the end, and it can be taken out of the sapphire substrate. It is estimated that it was made.

  From the above-described evaluation results, it can be seen that when the laser scribing method is used as the groove forming step, it is extremely effective to improve the light extraction efficiency to remove the residue generated by the laser irradiation. Further, instead of the laser scribing method described above, a diamond scribing method that does not generate a residue may be used as the groove forming step, and even when the diamond scribing method is used, of each surface of the sapphire substrate, By roughening the end of the surface opposite to the surface on which the light emitting portion is formed, the light extraction efficiency can be improved.

(Embodiment 2)
In the first embodiment, among the surfaces of the sapphire substrate, the structure in which the end of the surface opposite to the surface on which the light emitting portion is formed is roughened, but the surface opposite to the surface on which the light emitting portion is formed. In addition, a structure in which the side surface of the sapphire substrate is roughened may be used, and this is the second embodiment.

FIG. 4 is a structural sectional view showing an example of a light emitting diode according to Embodiment 2 of the present invention.
The light emitting diode 2 according to the second embodiment of the present invention has a configuration in which the same structure as that of the first embodiment is stacked on the sapphire substrate 20. In the sapphire substrate 20, the opposite surface (back surface 20 c) and side surface 20 b of the surface on which the light emitting portion is formed are roughened in an uneven shape (in the figure, the uneven shape that is a feature of the present invention is exaggerated). is there). Since other configurations are the same as those of the first embodiment (FIG. 1), the corresponding parts are denoted by the same reference numerals, and detailed description thereof is omitted.

  Further, the light emitting diode 2 can be manufactured by combining a laser scribe method or a diamond scribe method and a sand blast method as in the first embodiment. FIG. 5 is an explanatory diagram for explaining a method of manufacturing a light emitting diode according to Embodiment 2 of the present invention.

  The sapphire substrate 50 is formed with a plurality of light emitting portions 60, 60,... Formed by laminating the above-described layers using a photolithography technique known per se (FIG. 5A). A broken line in the figure is a chip dividing line (of course, a virtual one).

  First, laser light is irradiated from the back surface of the sapphire substrate 50 while moving the laser irradiation device along the chip dividing line. As a result, the sapphire substrate 50 reacts with the laser beam to change the material of the irradiated portion, and the reaction portion is broken to form the groove 50a (FIG. 5B).

  Next, abrasive particles such as alumina and Sic are sprayed from the back surface side of the sapphire substrate 50 by sandblasting to roughen the surface of the groove 50a, that is, the side surface of the sapphire substrate 50 and the back surface of the sapphire substrate 50 ( FIG. 5 (c)). The shape of the irregularities generated on the side surface and the back surface of the sapphire substrate 50 can be adjusted according to the type of abrasive particles, the injection pressure and the injection amount of the abrasive particles, and is appropriately set so as to have a desired shape.

  Then, the sapphire substrate 50 is divided by applying stress to the sapphire substrate 50 on which the light emitting units 60 and 60 adjacent to each other are formed via the groove 50a (FIG. 5D). In this way, among the surfaces of the sapphire substrate 50, the opposite surface and the side surface of the surface on which the light emitting unit 60 is formed can be roughened.

  As in the first embodiment, the light emitting diode 2 according to the present embodiment can remove the residue generated by the laser irradiation when the laser scribing method is used as the groove forming step. Can be improved. Moreover, even when the diamond scribe method that does not generate a residue is used as the groove forming step, the surface opposite to the surface on which the light emitting portion is formed (back surface) and the side surface are roughened on each surface of the sapphire substrate. By making the surface, the light guided to the back surface and the side surface can be diffused, and the light extraction efficiency can be improved.

  In each embodiment, the sapphire substrate is divided by applying stress to the sapphire substrate. However, the cutting amount in the groove forming step or the roughening step is increased, and the groove forming step or the roughening step is performed. The sapphire substrate may be divided by.

  Moreover, although the case where dicing was performed from the back surface side of the sapphire substrate and the back surface was roughened was explained, the surface was roughened by dicing from the front surface side of the sapphire substrate, that is, the light emitting portion formation surface side. It can be applied to such cases. In that case, it is preferable to prepare a mask corresponding to the light emitting portion and to inject abrasive particles onto the surface of the sapphire substrate through the mask.

  Furthermore, although the case where a sapphire substrate is used as a transparent substrate has been described, a transparent substrate having excellent transmittance in the visible light region may be, for example, a quartz substrate, a gallium nitride substrate, etc. -The light extraction efficiency which is an effect can be improved. Further, the device structure formed on the transparent substrate is not limited.

It is a structure sectional view showing an example of a light emitting diode concerning Embodiment 1 of the present invention. It is the edge part enlarged view to which the edge part of the light emitting diode was expanded. It is explanatory drawing for demonstrating the manufacturing method of the light emitting diode which concerns on Embodiment 1 of this invention. It is structural sectional drawing which shows an example of the light emitting diode which concerns on Embodiment 2 of this invention. It is explanatory drawing for demonstrating the manufacturing method of the light emitting diode which concerns on Embodiment 2 of this invention. It is structural sectional drawing which shows an example of the conventional light emitting diode. It is explanatory drawing for demonstrating the path | route of the emitted light of the conventional light emitting diode.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 2 Light emitting diode 10, 20, 50 Sapphire substrate 11 AlN buffer layer 12 Si doped GaN layer 13 Active layer 14 Cap layer 15 Mg doped GaN layer 16 Zn film 17 ITO film 18 P-type electrode 19 N-type electrode 60 Light emitting part 70 Mask 50a Groove

Claims (6)

In the light emitting diode in which the light emitting part is formed on one surface of the transparent plate,
An end of the other surface of the transparent plate is roughened. In the light emitting diode in which the light emitting part is formed on one surface of the transparent plate,
The other surface of the said transparent plate and / or the side surface of the said transparent plate are roughened, The light emitting diode characterized by the above-mentioned. In the method for manufacturing a light emitting diode, in which each light emitting diode is manufactured by dividing the light emitting portion from a transparent plate on which a plurality of light emitting portions are formed,
A groove forming step of forming a groove in a portion to be divided of the transparent plate;
And a roughening step of roughening the surface of the groove formed in the groove forming step. In the method for manufacturing a light emitting diode, in which each light emitting diode is manufactured by dividing the light emitting portion from a transparent plate on which a plurality of light emitting portions are formed,
A groove forming step of forming a groove in a portion to be divided of the transparent plate;
And a roughening step of roughening the surface of the transparent plate including the grooves formed in the groove forming step. The groove forming step includes
The method for producing a light-emitting diode according to claim 3 or 4, wherein a diamond scribe method or a laser scribe method is used. The roughening step includes
The method for manufacturing a light-emitting diode according to any one of claims 3 to 5, wherein the surface is cut and roughened by spraying abrasive particles onto the transparent plate.

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