TWI387137B - Method for manufacturing light emitting diode structure - Google Patents

Description

Method for fabricating a light-emitting diode structure

The present invention relates to a method of fabricating a light emitting diode structure, and more particularly to a method of fabricating a light emitting diode structure by adding a cleaning etching process.

In the global awareness of environmental protection, the concept of energy saving and carbon reduction has been paid more and more attention, and the traditional lighting source has not met the demand. For example, incandescent light bulbs, although inexpensive and simple to manufacture, have large heat generation, poor luminous efficiency, short life, and are easily broken. Although fluorescent lamps save energy compared to incandescent bulbs, they have serious problems of heavy metal waste pollution. In contrast, LEDs are the most popular products in the world because of their environmental protection, low power consumption, long life and high luminous efficiency. Therefore, the process technology of the light-emitting diode has become one of the focuses of related industries.

Although the current process technology of the light-emitting diode has become more and more mature, the brightness and luminous efficiency of the light-emitting diode continue to increase. However, there is still room for improvement in the conventional light-emitting diode process. For example, a luminescent epitaxial layer is conventionally grown on a substrate by an epitaxial technique, and then the substrate is diced and cleaved to form a single dies. Wherein, the single crystal grains after the cutting may have a residue on the surface of the light-emitting diode crystal grains, thereby weakening the luminous intensity originally possessed by the light-emitting diode.

One of the objects of the present invention is to provide a method of fabricating a light emitting diode structure to solve the quality problems faced by conventional process technology.

A preferred embodiment of the present invention provides a method of fabricating a light emitting diode structure comprising the following steps. First, a substrate is provided. Next, an epitaxial layer is formed on the substrate. Subsequently, the epitaxial layer is subjected to a dicing process, and the epitaxial layer is diced into a plurality of epitaxial cells, wherein each epitaxial cell has a sidewall, and the dicing process forms a plurality of strips on the substrate when the epitaxial layer is diced Pre-cut dents. Thereafter, a cleaning etch process is performed on each epitaxial cell to clean the epitaxial cells, and a distance between the bottom of the sidewalls of each epitaxial cell and the pre-cut dent of the corresponding substrate.

The method for fabricating a light-emitting diode structure of the present invention uses a clean etching process to remove residual carbides or other impurities present in each epitaxial unit, thereby increasing the luminous intensity of the light-emitting diode. Moreover, the spacing generated by the cleaning etching process can reduce the possibility of creeping in the subsequent packaging process in the solid crystal manufacturing process. In addition, by changing the sidewalls of the epitaxial cells to the undercut sidewalls or the undercut sidewalls, the light emitted by the active layer can be effectively controlled to be emitted toward the light emitting surface of the light emitting diode, thereby increasing the light emitting diode. The light extraction efficiency further improves the luminous efficiency of the light-emitting diode.

Certain terms are used throughout the description and following claims to refer to particular elements. Those of ordinary skill in the art should understand that the manufacturer may refer to the same component by different nouns. The scope of this specification and the subsequent patent application do not use the difference of the names as the means for distinguishing the elements, but the differences in the functions of the elements as the basis for the distinction. The term "including" as used throughout the specification and subsequent claims is an open term and should be interpreted as "including but not limited to". In addition, the term "electrical connection" is used herein to include any direct and indirect electrical connection means. Therefore, if a first device is electrically connected to a second device, it means that the first device can be directly connected to the second device or indirectly connected to the second device through other devices or connection means.

Please refer to figures 1 to 6. FIG. 1 is a schematic flow chart showing the structure of the light emitting diode of the present invention, and FIGS. 2 to 6 are schematic views showing the method for fabricating the light emitting diode structure according to the first preferred embodiment of the present invention. As shown in Figures 1 and 2, step 10 provides a substrate 20. The substrate 20 may be sapphire, gallium phosphide (GaP), gallium arsenide (GaAsP), zinc selenide (ZnSe), zinc sulfide (ZnS), zinc selenide (ZnSSe) or tantalum carbide (SiC). The substrate is not limited thereto, and other suitable substrates may be selected according to the requirements of the product specifications and process conditions. In this embodiment, before the subsequent process, a plurality of microstructures 201 may be formed on the surface of the substrate 20 to enhance the light extraction rate, and the microstructure 201 may be fabricated by using a dry etching process or a wet etching process. But not limited to this.

Next, as shown in FIGS. 1 and 3, step 12 forms an epitaxial layer 21 on the substrate 20. The step of forming the epitaxial layer 21 may include the following steps, but is not limited thereto. First, an N-type doping layer 211 is formed on the substrate 20. Next, an active layer 212 is formed on the N-type doped layer 211. Subsequently, a P-type doped layer 213 is formed on the active layer 212, but it is worth noting that the number of layers of the epitaxial layer 21 is not limited thereto, and the material may be selected according to a predetermined wavelength of the light source. A material such as a binary compound, a ternary compound, or a quaternary compound. Furthermore, the method of forming the epitaxial layer 21 can be formed by a metal organic chemical vapor deposition (MOCVD) process, but not limited thereto, but may be other suitable processes, such as a liquid phase. Processes such as Liquid Phase Epitaxy (LPE), Vapor Phase Epitaxy (VPE), and Molecular Beam Epitaxy (MBE). In addition, after the epitaxial layer 21 is formed, other processes may be performed depending on the requirements of subsequent processes. For example, in this embodiment, a patterned mask can be formed to define a position where the N-type doping layer 211 of the epitaxial layer 21 is expected to be exposed, and a pattern etching process is performed to remove a portion of the active layer 212 and The P-type doped layer 213 satisfies the need for subsequent formation of an electrode on the N-type doped layer 211.

Thereafter, as shown in FIG. 3, in this embodiment, a plurality of electrodes may be formed on the epitaxial layer 21, and the plurality of electrodes may be a plurality of P-type contact electrodes 221 and a plurality of N-type contact electrodes 222. More specifically, the P-type contact electrode 221 can be electrically connected to the P-type doped layer 213 of the epitaxial unit 210, and the N-type contact electrode 222 can be electrically connected to the N-type doped layer 211 of the epitaxial unit 210. The P-type contact electrode 221 and the N-type contact electrode 222 can be used as a contact for electrically connecting each of the epitaxial units 210 to be connected to an external circuit.

Subsequently, as shown in FIG. 1 and FIG. 4, step 14 performs a dicing process on the epitaxial layer 21, and the epitaxial layer 20 is diced into a plurality of epitaxial cells 210, wherein each epitaxial cell 210 has a sidewall, and The cutting process forms a plurality of pre-cut dents 23 on the substrate 20 when the epitaxial layer 21 is cut. The depth of the pre-cut dent 23 may vary according to different embodiments, and the pre-cut dent 23 may be used as a split in the subsequent divided substrate to cause the substrate to be split along the pre-cut dent 23. In this embodiment, the cutting process may be a laser cutting process, but not limited thereto, but may be other suitable cutting processes, such as a diamond cutting process, a wheel cutting process, and the like.

Then, as shown in FIG. 1 and FIG. 5, step 16 performs a cleaning etching process on each of the epitaxial cells 210 to clean the epitaxial cells 210, and the bottoms of the sidewalls of the epitaxial cells 210 are corresponding to each other. The pre-cut indentations 23 of the substrate 20 have a spacing D therebetween. The cleaning etch process may be a wet etch process, but not limited thereto, or may be a dry etch process or other suitable etch process. In this embodiment, the cleaning etching process may be performed by using a mixture of sulfuric acid and phosphoric acid, and the ratio of the concentration of sulfuric acid to phosphoric acid in the mixed solution is preferably substantially between 2 and 4, in other words, the concentration in the mixed solution. Preferably, it is substantially sulfuric acid: phosphoric acid = 2:1 to 4:1. The cleaning process of the present invention can effectively remove residual carbides or other impurities present on each epitaxial unit 210, thereby increasing the luminous intensity of the light-emitting diode.

Furthermore, the pitch D can be generally between 1 micrometer and 50 micrometers. Moreover, the sidewall of each epitaxial cell may be an undercut sidewall, in other words, the bottom of the sidewall of each epitaxial cell 210 is closer to the inner side of the epitaxial cell than the top. Moreover, in the present embodiment, the angle A between the sidewall of each epitaxial unit 210 and the surface of the substrate 20 is preferably substantially between 30 degrees and 70 degrees, but is not limited thereto. However, the sidewall of each epitaxial unit 210 is not limited thereto, and can be controlled by process parameters to be an upright sidewall or a top cut sidewall, wherein the top cut sidewall refers to each epitaxial unit. The top of the side wall is closer to the inner side of the epitaxial unit than the bottom. Accordingly, the present invention can reduce the possibility of creeping in the subsequent packaging process in the solid-state process by the spacing D formed by the cleaning etching process. Moreover, the side wall form of each of the epitaxial units 210 can be an undercut sidewall or a top cut sidewall, which can increase the sidewall length of each epitaxial unit 210, and increase the difficulty of the subsequent process of climbing, thereby helping To reduce the possibility of climbing. In addition, by changing the sidewalls of the epitaxial cells 210 from the upright sidewalls to the undercut sidewalls or the undercut sidewalls, the light emitted by the active layer 212 can be effectively controlled to be emitted toward the light emitting surface of the LED. The light extraction efficiency of the light emitting diode is increased, thereby improving the luminous efficiency of the light emitting diode.

Next, a splitting machine can be used to perform a Breaking process on the substrate 20 in FIG. 5 to split the substrate 20 along each of the pre-cut indentations 23 into a plurality of substrate units 202. Thereafter, each of the individual light-emitting diode structures after the cleaving, as shown in FIG. 6, completes the process of fabricating the light-emitting diode structure of the first preferred embodiment.

Please refer to Figure 7 and refer to Figure 1 together. FIG. 7 is a schematic view showing a method of fabricating a light emitting diode structure according to a second preferred embodiment of the present invention. As shown in FIG. 7, the second preferred embodiment is similar to most of the processes of the first preferred embodiment. For example, as shown in FIG. 1, first, step 10 provides a substrate, and then step 12 is formed on the substrate 30. The step of forming the epitaxial layer 31 and forming the epitaxial layer 31 may include the following steps, but is not limited thereto. First, an N-type doping layer 311 is formed on the substrate 30. Next, an active layer 312 is formed on the N-type doped layer 311. Subsequently, a P-type doped layer 313 is formed on the active layer 312. Subsequently, step 14 performs a dicing process on the epitaxial layer 31, and then a cleaning etch process is performed in step 16. Finally, a cleaving process can be performed, and each individual illuminating diode structure after cleaving is as shown in FIG. Shown. In the present embodiment, by using the cleaning etching process, residual carbides or other impurities present on the epitaxial layer 31 can be effectively removed, thereby increasing the luminous intensity of the light-emitting diode. It should be noted that, as shown in FIG. 7, this embodiment is an upright side wall, but not limited thereto, and may be an undercut side wall or a top cut side wall. In order to simplify the description, only the differences between the second preferred embodiment and the first preferred embodiment will be described below, and similar parts will not be described again.

The substrate 30 of the present embodiment is not in the same position as the substrate 20 of the first preferred embodiment. The substrate 20 is not located on the light emitting surface. However, the substrate 30 is located on the light emitting surface, so that the substrate 30 is preferably transparent. The substrate of the light material may be a sapphire substrate, but not limited thereto, for example, glass, gallium phosphide (GaP), gallium arsenide (GaAsP), zinc selenide (ZnSe), and vulcanization. A substrate such as zinc (ZnS), zinc selenide sulfide (ZnSSe) or tantalum carbide (SiC).

Furthermore, as shown in FIG. 7, the present embodiment can form a reflective layer 34 on the P-type doped layer 313, so that the light emitted by the active layer 312 can change its traveling direction through the reflective layer 34. The light that originally travels toward the non-illuminating surface can be effectively reflected back to the luminous surface. The material of the reflective layer 34 is preferably a metal material or a material having both conductive and reflective functions, so as to meet the requirements of subsequent electrical connections, such as silver, aluminum, or gold, but not limit.

In addition, this embodiment may include providing a sub-mount 36, wherein the base 36 may be a carrier, but not limited thereto. Then, a plurality of conductive bumps are formed on the base 36, and the electrodes are electrically connected to the conductive bumps 321 and 322 of the base 36. More specifically, the conductive bumps 351 can be electrically connected to the P-type contact electrodes 321 , and the conductive bumps 352 can be electrically connected to the N-type contact electrodes 322 . The conductive bumps may be metal adhesives, such as gold pads, solder balls, solder paste or silver paste, but are not limited thereto. Accordingly, the second preferred embodiment can reduce the optical loss on the electrode side, and can directly contact the heat dissipation structure in the package structure directly by the conductive bumps 351 and 352, and the heat generated by the active layer 312 is conductively convex. The blocks 321 and 322 are outwardly radiated, thereby greatly improving the heat dissipation effect, and further improving the amount of light emitted by the light emitting diode.

In summary, the method for fabricating a light-emitting diode structure of the present invention can effectively remove residual carbides or other impurities present on the epitaxial layer by using a clean etching process, thereby increasing the light-emitting intensity of the light-emitting diode. At the same time, through the cleaning etching process, a gap can be formed between the sidewall of the epitaxial layer and the edge of the substrate to reduce the possibility of the subsequent packaging factory climbing the glue in the solid crystal process. Moreover, the side wall of the epitaxial layer may be an undercut sidewall, an upright sidewall, or a top sidewall, which may increase the sidewall length of the epitaxial layer and increase the difficulty of the subsequent process of climbing, thereby facilitating To reduce the possibility of climbing. In addition, by changing the sidewall of the epitaxial layer to the undercut sidewall or the undercut sidewall, the light emitted by the active layer can be effectively controlled to be emitted toward the light emitting surface of the light emitting diode, thereby increasing the light emitting diode. The light extraction efficiency improves the luminous efficiency of the light-emitting diode.

The above are only the preferred embodiments of the present invention, and all changes and modifications made to the scope of the present invention should be within the scope of the present invention.

20,30. . . Substrate

201. . . microstructure

202. . . Substrate unit

21,31. . . Epitaxial layer

210. . . Epitaxial unit

211,311. . . N-doped layer

212,312. . . Active layer

213,313. . . P-doped layer

221,321. . . P-type contact electrode

222,322. . . N-type contact electrode

twenty three. . . Pre-cut dent

34. . . Reflective layer

351,352. . . Conductive bump

36. . . Base

D. . . spacing

10,12,14,16. . . step

A. . . Angle

FIG. 1 is a schematic flow chart showing the structure of the light emitting diode of the present invention.

2 to 6 are schematic views showing a method of fabricating a light emitting diode structure according to a first preferred embodiment of the present invention.

FIG. 7 is a schematic view showing a method of fabricating a light emitting diode structure according to a second preferred embodiment of the present invention.

10,12,14,16. . . step

Claims (14)

A method for fabricating a light-emitting diode structure includes: providing a substrate; forming an epitaxial layer on the substrate; performing a cutting process on the epitaxial layer, and cutting the epitaxial layer into a plurality of epitaxial cells, wherein Each of the epitaxial cells has a sidewall, and the dicing process forms a plurality of pre-cut dents on the substrate when the epitaxial layer is diced; and performing a cleaning etching process on each of the epitaxial cells to clean And the epitaxial cells have a spacing between a bottom of the sidewall of each of the epitaxial cells and the pre-cut indentation of the corresponding substrate. The method of fabricating a light emitting diode structure according to claim 1, wherein the cleaning etching process is a wet etching process. A method of fabricating a light emitting diode structure according to claim 2, wherein the cleaning etching process is performed by using a mixture of sulfuric acid and phosphoric acid. A method of fabricating a light-emitting diode structure according to claim 3, wherein the mixture has a sulfuric acid to phosphoric acid concentration ratio substantially between 2 and 4. A method of fabricating a light emitting diode structure according to claim 1, wherein the pitch is substantially between 1 micrometer and 50 micrometers. The method of fabricating a light emitting diode structure according to claim 1, wherein the sidewall of each of the epitaxial cells is an undercut sidewall. The method of fabricating a light emitting diode structure according to claim 6, wherein an angle between the sidewall of each of the epitaxial cells and a surface of the substrate is substantially between 30 degrees and 70 degrees. The method of fabricating a light emitting diode structure according to claim 1, wherein the cutting process is a laser cutting process. The method of fabricating a light-emitting diode structure according to claim 1, further comprising performing a Breaking process on the substrate to split the substrate along each of the pre-cut dents into a plurality of substrate units. The method of fabricating a light emitting diode structure according to claim 1, wherein the step of forming the epitaxial layer comprises: forming an N-type doped layer on the substrate; forming an active layer on the N-type doped layer And forming a P-type doped layer on the active layer. The method for fabricating a light-emitting diode structure according to claim 1, further comprising forming a plurality of electrodes on the epitaxial layer such that each of the epitaxial cells has a P-type contact electrode and an N-type contact electrode. The method of fabricating a light emitting diode structure of claim 11, further comprising providing a sub-mount. The method of fabricating a light emitting diode structure according to claim 12, further comprising forming a plurality of conductive bumps on the base, and electrically connecting each of the electrodes to each of the conductive bumps of the base. The method for fabricating a light emitting diode structure according to claim 1, further comprising forming a plurality of microstructures on a surface of the substrate before forming the epitaxial layer on the substrate.