TWI430475B - Method of manufacturing light emitting diode - Google Patents

Description

Method for manufacturing light emitting diode

The present invention relates to a method of fabricating a light-emitting diode, and more particularly to a method of fabricating a light-emitting diode that can improve light extraction efficiency.

Light Emitting Diode (LED) is mainly composed of P-type and N-type semiconductor materials, which can generate self-radiation light in the ultraviolet, visible and infrared regions. Generally, most of the visible light emitting diodes are used in the indicators or illumination of electronic equipment, and the infrared light emitting diodes are used in optical fiber communication. The light-emitting diode is often used as an indicator light, a display panel, etc. at the beginning, but is also used as illumination with the appearance of a white light-emitting diode. LEDs have many advantages such as power saving, long life, high brightness, etc. Recently, LEDs have become more and more widely used in environmental protection, energy saving and carbon saving trends, such as traffic signs, street lamps, flashlights and backlight modules for liquid crystal displays.

The conventional LED cutting technology uses a diamond drawing technique to physically cut a wafer substrate and then use a splitting machine as a segment to split the wafer into light-emitting diode grains. The more advanced cutting process uses a laser scriber for wafer dicing, which is mainly divided into general laser scribing process and stealth dicing process. The laser cutting process directly ablates the line on the wafer surface, while in the stealth laser cutting process, it penetrates the surface of the wafer, causing a stress layer inside the wafer to cause the wafer to be internally cracked.

Conventional laser scribing produces dust and laser burn marks, which easily affect the luminous efficiency of the light-emitting diode. Although the stealth laser switching process is less likely to have the problem of dust splashing, it is expensive and cannot form a chamfer on the side of the epitaxial layer to assist in light extraction.

The invention provides a method for manufacturing a light-emitting diode, which uses a laser cutting process and a side etching process to form a slope on the side of the epitaxial layer to increase the light extraction efficiency, and further utilizes the stealth laser cutting process. To cut the substrate to avoid laser burn marks and affect the luminous efficiency.

The embodiment of the invention provides a method for manufacturing a light emitting diode, comprising the steps of: providing a substrate; forming an epitaxial layer on the upper surface of the substrate; forming a plurality of light emitting diodes; and performing a laser cutting on the upper surface of the substrate a process or a dry etching process to form a trench around the LED platform; a side etching process for the LED platform; and a stealth laser cutting process on the lower surface of the substrate. The side etching process can form a bevel on the side of the epitaxial layer to increase the light extraction efficiency, and the laser cutting process can avoid the laser burnt on the side of the substrate during the cutting to affect the light extraction efficiency.

In summary, the method for manufacturing a light-emitting diode according to the present invention uses a laser cutting process, a side etching process, and a stealth laser cutting process to cut a substrate to improve the light-emitting efficiency of the light-emitting diode. The laser cutting process and the side etching process are applied on the front side of the substrate, and chamfering can be formed on the side of the epitaxial layer to increase the light output. When the substrate is cut, the invisible laser cutting process of the back surface cutting can avoid the laser burnt mark. And improve the light efficiency.

The above described features and advantages of the present invention will be more apparent from the following description.

In the following, the invention will be described in detail by the embodiments of the invention, and the same reference numerals are used in the drawings.

The embodiment of the invention is a method for manufacturing a light-emitting diode, which can be applied in a general light-emitting diode process to improve the light-emitting efficiency. In this embodiment, after forming a light-emitting diode mesa, a laser cutting process or a dry etching process is first applied to the upper surface (front surface) of the substrate to form a shallow depth trench around the LED high platform, and then utilized. A sidewall etching process forms a bevel on the side of the epitaxial layer to improve light extraction efficiency. Then, a stealth laser cutting process is performed through the back surface of the substrate to cut the wafer. The light-emitting diode crystal grains produced by the above method have an epitaxial layer having a slope formed by side etching to increase the light-emitting efficiency, and the side of the substrate is cut by stealth laser to avoid the occurrence of sintering marks, and the same can be Add light efficiency. It is worth noting that the depth of the front laser cutting is less than or equal to the thickness of the epitaxial layer, so as to avoid the occurrence of sintering marks on the side of the substrate when the laser scribing is performed, and the light is affected.

Please refer to FIG. 1A to FIG. 1G, which are schematic diagrams showing a process of an embodiment of the present invention. An epitaxial layer 105 is formed on the upper surface of the substrate 110. The epitaxial layer 105 includes a buffer layer 120, an N-type semiconductor layer 130, an active layer 140, and a P-type semiconductor layer 150, as shown in FIG. 2A. The material of the substrate 110 is, for example, sapphire, GaP, GaAs, AlGaAs, or tantalum carbide (SiC). The substrate 110 of the present embodiment is exemplified by a sapphire substrate, and the lattice direction is, for example, (0001). However, the present invention does not limit the substrate material and lattice direction used. The buffer layer 120 between the substrate 110 and the N-type semiconductor layer 130 may be aluminum gallium nitride (AlGaN), but the embodiment is not limited thereto. The epitaxial layer 105 can be formed by metal organic chemical vapor deposition (MOCVD), liquid phase epitaxy (LPE) or molecular beam epitaxy (MBE). Formed, this embodiment does not limit the epitaxial mode.

The N-type semiconductor layer 130 is, for example, germanium (Si)-doped gallium nitride (GaN), the P-type semiconductor layer 150 is, for example, magnesium (Mg)-doped gallium nitride (GaN), and the active layer 140 may be a multiple quantum. The well structure (Multiquantum Well, MQW) structure is, for example, an indium gallium nitride/gallium nitride (In _0.3 Ga _0.7 N/GaN) quantum well structure, but the embodiment is not limited thereto.

Next, after the epitaxial layer 105 is formed, the epitaxial layer 105 is etched to form a plurality of light emitting diodes (Mesa) 101, 102, as shown in FIG. 1B. The etching method is, for example, dry etching, but the embodiment is not limited thereto. The N-type semiconductor layer 130 is exposed around the light-emitting diode stages 101, 102 to vapor-deposit the metal electrodes.

Then, a trench 160 is formed around the LED emitters 101, 102 to cut the wafer into light-emitting diode dies, as shown in FIG. 1C. The trench 160 may be formed by a laser cutting process (laser line) or a dry etching process, and the embodiment does not limit the process used. It should be noted that the depth of the front laser line or dry etching may be less than or equal to the thickness of the epitaxial layer 105 to avoid laser burn marks on the side of the substrate 110, thereby affecting the light extraction efficiency. In the present embodiment, the depth of the trench 160 may be less than 10 um and will not exceed the buffer layer 120.

Next, a side etching process is performed on the sides of the light-emitting diode stages 101, 102 to produce a slope 170, as shown in FIG. 1D. An angle α formed by the inclined surface 170 and the substrate 110 of less than 90 degrees is, for example, 40 (±5) degrees or 60 (±5) degrees, but the embodiment is not limited thereto. The side etching process can be implemented using a high temperature phosphoric acid wet etching technique, but the embodiment is not limited thereto. The side etching can remove the dust generated by the laser line, and can form a slope on the side of the epitaxial layer 105 (the P-type semiconductor layer 150 and the active layer 140) to increase the light-emitting efficiency.

It should be noted that, in the side etching process, cerium oxide may be formed on the epitaxial layer 105 as an etch mask layer, and then the epitaxial layer 105 is etched by using a high temperature phosphoric acid and sulfuric acid mixture, but this embodiment does not Limit the etching solution and method used.

Then, a current blocking layer 181, a current diffusion layer 182, and conductive electrodes 183, 184 are formed on the light emitting diode platforms 101, 102, as shown in FIG. 1E. The current blocking layer 181 is, for example, cerium oxide (SiO ₂ ), and has a thickness of, for example, 0.8 to 2.4 kA (Å), but the embodiment is not limited thereto. The current diffusion layer 182 has a thickness of 1 to 3 kÅ (angstrom) and can be formed of a material having a low lateral resistance, so that current can be easily diffused to the side, and the material thereof is, for example, indium tin oxide (ITO) or aluminum zinc oxide (AZO). Tin oxide (SnO), cadmium tin oxide (CTO), antimony tin oxide (ATO), and nickel/gold (Ni/Au), etc., but the present embodiment is not limited to the above materials. The current diffusion layer 182 overlies the current blocking layer 181 to allow current to be dispersed to regions other than the current blocking layer 181 to increase light extraction efficiency. The conductive electrode 183 may be formed by vapor deposition of Cr/Pt/Au (chromium/platinum/gold) or Ni/Au (titanium/gold), and the conductive electrode 184 may be deposited by vapor deposition of Cr/Pt/Au (chromium/platinum/gold) or Ti/. Al/Pt/Au (titanium/platinum/gold) is formed, and the film thickness ranges from 15 to 22 kÅ, but the embodiment is not limited thereto. The conductive electrodes 183, 184 can be formed by a vapor-deposited low-resistance interface, which can be used as a two-way communication between the metal and the semiconductor to form an ohmic contact.

Next, a stealth laser cutting process is performed on the lower surface (bottom portion) of the substrate 110, and the cutting position 190 corresponds to the line position of the front laser cutting process, as shown in FIG. 1F. That is, the cutting position 190 corresponds to the position of the groove 160. In other words, in this embodiment, a laser cutting process and a side etching process are used on the front surface of the substrate 110 to form a slope 170 and an angle α on the sides of the LED platform 10, 102 to improve light extraction efficiency, and invisible on the back surface of the substrate 110. The laser cutting process is used to cut the wafer to avoid laser burn marks on the side of the substrate 110 and affect the light extraction efficiency.

It is worth noting that in order to avoid the burn-in process on the side of the substrate 110 in the frontal laser cutting process, the depth of the front laser cutting process is less than that of the epitaxial layer. The thickness of 105 is less than 10 um. In addition, the depth of the stealth laser cutting process is, for example, 40 um to 60 um, but the embodiment is not limited thereto.

After completing the stealth laser cutting process, the substrate 110 can form a plurality of LED cells via a breaking process, as shown in FIG. 1G. In the process of cutting the wafer, the process details such as mounting on tape, expansion and packaging are further included, and those skilled in the art should be able to infer the implementation manner through the above embodiments, and do not add Narration.

The above-mentioned light-emitting diode process in FIGS. 1A to 1G is only illustrative, and the semiconductor processes such as exposure, lithography, etching, epitaxy, and splitting included in the process details can be adjusted according to design requirements, and those skilled in the art have ordinary knowledge. The implementation details of the above embodiments are to be inferred, and are not described herein. In addition, the light-emitting diode structure in the above-mentioned FIGS. 1A to 1G can be adjusted according to design requirements, for example, a process such as Sapphire Backside Roughing (SBR) to increase luminous efficiency.

1A to 1G, a method for manufacturing a light-emitting diode can be summarized. As shown in FIG. 2, a flow chart of a method for manufacturing a light-emitting diode according to an embodiment of the present invention is shown. First, a substrate is provided (step S201), and then an epitaxial layer is formed on the upper surface of the substrate 110 (step S210). A plurality of light emitting diode platforms are then formed (step 220). Next, a laser cutting process or a dry etching process is performed on the upper surface of the substrate 110 to form trenches 160 around the light-emitting diode stages 101, 102 (step S230). Then, the light-emitting diode stages 101 and 102 are subjected to a side etching process to form a chamfer (step S240). After step S240, a stealth laser cutting process is performed on the lower surface of the substrate 110 to cut the substrate 110 (step S250). After the stealth laser cutting process is completed, the substrate 110 is subjected to a breaking process to form a plurality of light emitting diode grains (step S260).

In addition, it is worth noting that the manufacturing method of the above-mentioned light-emitting diode further includes a current blocking layer 181, a current diffusion layer (transparent electrode) 182 and a conductive electrode 184, and a device package process, etc., which has general knowledge in the technical field. The embodiments are inferred from the above embodiments, and are not described herein. Further, the manufacturing method of the present invention can be applied to light-emitting diodes of different structures, and is not limited to the above-described FIGS. 1A to 1G.

In summary, the present invention utilizes a laser cutting process and a side etching process to form a chamfer on the side of the epitaxial layer on the front side of the substrate to increase light extraction efficiency, and to perform laser scanning from the back surface of the substrate by using a stealth laser cutting process. Cut to avoid laser burn marks and affect light extraction efficiency.

Although the preferred embodiments of the present invention have been disclosed as above, the present invention is not limited to the above-described embodiments, and any one of ordinary skill in the art can make some modifications without departing from the scope of the present invention. The scope of protection of the present invention should be determined by the scope of the appended claims.

101, 102. . . Luminous diode platform

105. . . Epitaxial layer

110. . . Substrate

120. . . The buffer layer

130. . . N-type semiconductor layer

140. . . Active layer

150. . . P-type semiconductor layer

160. . . Trench

170. . . Bevel

181. . . Current blocking layer

182. . . Current diffusion layer

183, 184. . . Conductive electrode

190. . . Cutting position

α. . . Angle

S201~S260. . . step

1A-1G are schematic diagrams showing a process of an embodiment of the present invention.

2 is a flow chart showing a method of manufacturing a light-emitting diode according to an embodiment of the invention.

S201~S260. . . step

Claims (13)

A method for manufacturing a light-emitting diode, comprising: providing a substrate to form an epitaxial layer on an upper surface of the substrate; forming at least one light-emitting diode platform to perform a laser cutting process or a dry etching process on the upper surface of the substrate Forming a trench around the high-emitting diodes; performing a side etching process on the light-emitting diodes; and performing a stealth laser cutting process on the lower surface of the substrate. The method for manufacturing a light-emitting diode according to the first aspect of the invention, wherein the laser cutting process has a depth of cutting in the laser cutting process or the dry etching process in the step of performing the laser cutting process on the upper surface of the substrate Less than or equal to the thickness of the epitaxial layer. The method for fabricating a light-emitting diode according to claim 1, wherein in the step of performing the laser cutting process or the dry etching process on the upper surface of the substrate, the etching depth of the dry etching process is less than It is equal to the thickness of the epitaxial layer. The method for fabricating a light-emitting diode according to claim 1, wherein in the step of performing the side etching process, the side etching process is used to remove dust generated when the laser line is drawn. The method for fabricating a light-emitting diode according to claim 1, wherein in the step of performing the side etching process, the side etching process is formed on a side of the high-level diodes Beveled. The method of manufacturing a light-emitting diode according to claim 1, wherein the laser cutting process corresponds to a cutting position of the stealth laser cutting process. The method for producing a light-emitting diode according to claim 1, wherein the substrate is a sapphire substrate. The method for fabricating a light-emitting diode according to claim 1, wherein each of the light-emitting diodes includes at least an N-type semiconductor layer, an active layer and a P-type semiconductor layer. The method for manufacturing a light-emitting diode according to claim 1, further comprising: performing a cleaving process on the substrate to form a plurality of light-emitting diode crystal grains. The method for manufacturing a light-emitting diode according to claim 1, wherein the laser cutting process or the dry etching process has a depth of cut according to the thickness of the epitaxial layer and is less than or equal to 10 micrometers. The method of fabricating a light-emitting diode according to claim 1, wherein the depth of the stealth laser cutting process is from 40 micrometers to 60 micrometers. The method for manufacturing a light-emitting diode according to the first aspect of the invention, wherein the side etching process forms a slope on a side of the light-emitting diodes, and the slope of the light-emitting diodes is The angle between the substrates is α, and α is less than 90 degrees. The method for manufacturing a light-emitting diode according to claim 1, wherein after performing the side etching process, further comprising: forming a current blocking layer; forming a current diffusion layer; and forming a first conductive electrode And a second conductive electrode on the corresponding light-emitting diode platform.