A surface roughening process for LED chips

Abstract

The invention relates to a surface roughening process for an LED chip. The process steps for the surface roughening process for an LED chip are concise, exquisite, and easy to control. Each step is carefully and meticulously performed. A GaN epitaxial wafer is first prepared, and then the GaN epitaxial wafer is roughened. Specifically, a photoresist is first coated on a portion of the GaN epitaxial wafer that needs to be retained, and then dried to form a mask layer, and then the GaN epitaxial wafer is subjected to ICP etching. A protective liquid is then coated on a portion of the GaN epitaxial wafer that needs to be retained, and then dried to form a protective layer. Subsequently, the GaN epitaxial wafer coated with the protective layer is placed in an etching solution for wet etching. The epitaxial wafer is heated to 250 degrees Celsius, and then KOH heated to a molten state is evenly applied to the surface of the GaN epitaxial wafer for dry etching. After the GaN epitaxial wafer is subjected to ICP etching, wet etching, and dry etching in sequence, a stable and dense surface microstructure is formed on its surface, thereby improving the light extraction efficiency of the LED chip.

Description

Technical Field

[0001] The invention relates to the field of LED chip processing, and in particular to a LED chip surface roughening process. Background Art

[0002] Light-emitting diodes, or LEDs for short, are a commonly used light-emitting device that emits light by releasing energy through the recombination of electrons and holes. They are widely used in the field of lighting. Light-emitting diodes can efficiently convert electrical energy into light energy and have a wide range of uses in modern society, such as lighting, flat-panel displays, and medical devices. This electronic component appeared as early as 1962. In the early days, it could only emit low-intensity red light. Later, other monochromatic versions were developed, and the light that could be emitted has spread across visible light, infrared light, and ultraviolet light, and the luminosity has also been increased to a considerable level. The uses have also changed from being used as indicator lights, display boards, etc. LEDs were originally used for indicative lighting of instruments and meters, and then expanded to traffic lights. Then to landscape lighting, automotive lighting, and mobile phone keyboards and backlight sources. Later, a new technology for micro-light-emitting diodes was developed, which greatly reduced the size of the original light-emitting diodes, and used red, blue, and green micro-light-emitting diodes that can emit light independently to form a display array for the field of display technology.

[0003] However, the LED chip is a solid-state semiconductor device. The heart of the LED is a semiconductor wafer. One end of the wafer is attached to a bracket, one end is the negative pole, and the other end is connected to the positive pole of the power supply, so that the entire wafer is encapsulated by epoxy resin. Surface roughening technology is to directly make a periodic surface microstructure on the light-emitting surface of the LED chip to change the incident light angle, thereby improving the light extraction efficiency of the chip. The traditional LED chip surface roughening process is inefficient, cumbersome, and costly. Summary of the invention

[0004] Based on this, it is necessary to provide a LED chip surface roughening process to address the technical problems of low efficiency, complicated process and high cost of the traditional LED chip surface roughening process.

[0005] A process for roughening the surface of an LED chip, the process comprising the following steps:

[0006] Preparation steps of GaN epitaxial wafer: a low-temperature GaN buffer layer, an undoped GaN layer, an N-GaN layer, a multi-quantum well light-emitting layer and a P-GaN layer are sequentially grown on a semiconductor substrate to form a GaN epitaxial wafer;

[0007] Mask layer coating step: coating the photoresist on the portion to be retained on the GaN epitaxial wafer and drying it to form a mask layer;

[0008] ICP etching step: ICP etching the GaN epitaxial wafer;

[0009] The first cleaning step of GaN epitaxial wafer: clean the GaN epitaxial wafer after ICP etching in an ultrasonic cleaner for 4 minutes and then dry it;

[0010] The first coating step of the protective layer: coating the protective liquid on the part of the GaN epitaxial wafer that needs to be retained, and forming a protective layer after drying;

[0011] Wet etching step: Place the GaN epitaxial wafer coated with a protective layer in the etching solution and soak for 80 seconds, then rinse with clean water and dry;

[0012] The second coating step of the protective layer: coating the protective liquid on the part of the GaN epitaxial wafer that needs to be retained, and forming a protective layer after drying;

[0013] Dry etching step: Heat the epitaxial wafer to 250 degrees Celsius, then evenly apply the molten KOH on the surface of the GaN epitaxial wafer, continue heating to stabilize the temperature at 220 degrees Celsius, and continue etching for 1 minute;

[0014] The second cleaning step of the GaN epitaxial wafer: After the dry-etched GaN epitaxial wafer is naturally cooled, the dry-etched GaN epitaxial wafer is cleaned in an ultrasonic cleaning machine for 4 minutes and then dried.

[0015] In one of the embodiments, in the step of preparing the GaN epitaxial wafer, the semiconductor substrate is sapphire.

[0016] In one of the embodiments, in the step of preparing the GaN epitaxial wafer, the semiconductor substrate is silicon carbide.

[0017] In one of the embodiments, in the step of preparing the GaN epitaxial wafer, a metal organic chemical vapor deposition method is adopted.

[0018] In one of the embodiments, in the ICP etching step, the etching gas is a mixture of Cl2, BCl3 and Ar2, and the volume ratio of Cl2, BCl3 and Ar2 is 70:14:16.

[0019] In one of the embodiments, in the ICP etching step, the etching power is 400 W, the RF power is 100 W, and the etching time is 8 minutes.

[0020] In one of the embodiments, in the first cleaning step of the GaN epitaxial wafer, the cleaning liquid in the ultrasonic cleaning machine is acetone.

[0021] In one of the embodiments, in the protective layer coating step, the protective solution includes the following components in parts by weight: 5 to 10 parts of nano nickel powder, 10 to 20 parts of nano silicon dioxide powder, 0.5 to 1 part of citric acid, and the remainder is anhydrous ethanol.

[0022] In one of the embodiments, in the wet etching step, the etching solution includes the following components in parts by weight: 15 to 30 parts of hydrochloric acid, 10 to 25 parts of sulfuric acid, 30 to 50 parts of hydrogen peroxide, and 5 to 10 parts of hydrofluoric acid.

[0023] In one of the embodiments, in the dry etching step, the GaN epitaxial wafer is heated by microwaves.

[0024] The above-mentioned LED chip surface roughening process steps are concise, exquisite and easy to control, and each step is careful and meticulous. First, a GaN epitaxial wafer is prepared, and then the GaN epitaxial wafer is roughened. Specifically, a photoresist is first coated on the part of the GaN epitaxial wafer that needs to be retained, and then dried to form a mask layer, and then the GaN epitaxial wafer is subjected to ICP etching. Then a protective liquid is coated on the part of the GaN epitaxial wafer that needs to be retained, and a protective layer is formed after drying. Subsequently, the GaN epitaxial wafer coated with the protective layer is placed in the etching solution for wet etching. The epitaxial wafer is heated to 250 degrees Celsius, and then KOH heated to a molten state is evenly applied to the surface of the GaN epitaxial wafer for dry etching. After the GaN epitaxial wafer is sequentially subjected to ICP etching, wet etching and dry etching, a stable and dense surface microstructure is formed on its surface, thereby improving the light extraction efficiency of the LED chip. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 FIG. 1 is a schematic diagram of a process for roughening the surface of an LED chip in one embodiment. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0027] See also Figure 1 The present invention provides a process for roughening the surface of an LED chip, the process comprising the following steps:

[0028] Step 101: GaN epitaxial wafer preparation step: a low-temperature GaN buffer layer, an undoped GaN layer, an N-GaN layer, a multi-quantum well light-emitting layer and a P-GaN layer are sequentially grown on a semiconductor substrate to form a GaN epitaxial wafer.

[0029] In this embodiment, the semiconductor substrate is sapphire. In another embodiment, the semiconductor substrate is silicon carbide. Specifically, a low-temperature GaN buffer layer, an undoped GaN layer, an N-GaN layer, a multi-quantum well light-emitting layer and a P-GaN layer are sequentially grown on the semiconductor substrate by a metal organic chemical vapor deposition method.

[0030] Specifically, a low-temperature GaN buffer layer, an undoped GaN layer, an N-GaN layer, a multi-quantum well light-emitting layer and a P-GaN layer are sequentially grown on a sapphire substrate or a silicon carbide substrate by a metal organic chemical vapor deposition method to form a GaN epitaxial wafer.

[0031] Step 102: Mask layer coating step: Coat photoresist on the portion of the GaN epitaxial wafer that needs to be retained and then dry to form a mask layer.

[0032] The photoresist includes the following components in parts by mass: 20 to 30 parts of a copolymer resin of acrylic acid and methyl methacrylate, 8 to 15 parts of trimethylolpropane acrylate triester, 20 to 40 parts of propylene glycol methyl ether acetate, 2 to 4 parts of 4,4'-diazide-2,2'-dicinnamyl acetone sulfonate, 1 to 2 parts of ammonium nitrite, and the balance is n-butyl acetate.

[0033] Specifically, the photoresist composed of the above components is coated on the part to be retained on the GaN epitaxial wafer and then dried to form a mask layer. The photoresist composed of the above components has high chemical stability and strong corrosion resistance, and can provide good protection for the GaN epitaxial wafer.

[0034] Step 103: ICP etching step: performing ICP etching on the GaN epitaxial wafer.

[0035] In this embodiment, the etching gas is a mixture of Cl2, BCl3 and Ar2, and the volume ratio of Cl2, BCl3 and Ar2 is 70:14:16. Further, in one embodiment, the etching power is 400W, the RF power is 100W, and the etching time is 8 minutes.

[0036] Specifically, the GaN epitaxial wafer coated with the mask layer is subjected to ICP etching, and the etching gas for ICP etching is a mixture of Cl2, BCl3 and Ar2. The etching power is 400W, the radio frequency power is 100W, and the etching time is 8 minutes.

[0037] Step 104: The first cleaning step of the GaN epitaxial wafer: the GaN epitaxial wafer after ICP etching is cleaned in an ultrasonic cleaning machine for 4 minutes and then dried.

[0038] The drying temperature is 50 to 60 degrees Celsius, and the drying time is 2 to 4 hours. In this embodiment, the cleaning liquid in the ultrasonic cleaning machine is acetone.

[0039] Specifically, the GaN epitaxial wafer after ICP etching is cleaned in an ultrasonic cleaning machine filled with acetone for 4 minutes, and then dried at 50 degrees Celsius to 60 degrees for 2 hours to 4 hours.

[0040] Step 105: The first coating step of the protective layer: coating the protective liquid on the portion of the GaN epitaxial wafer that needs to be retained, and forming a protective layer after drying.

[0041] In this embodiment, the protective solution includes the following components in parts by weight: 5 to 10 parts of nano nickel powder, 10 to 20 parts of nano silicon dioxide powder, 0.5 to 1 part of citric acid, and the balance is anhydrous ethanol. The protective layer formed by the protective solution composed of the above components after drying has good acid resistance and alkali resistance, and can well protect the part that needs to be retained on the GaN epitaxial wafer.

[0042] Specifically, the protective liquid is coated on the portion of the GaN epitaxial wafer that needs to be retained, and the protective layer is formed after drying. The drying temperature is 50 degrees Celsius to 60 degrees Celsius, and the drying time is 2 hours to 4 hours.

[0043] Step 106: Wet etching step: Place the GaN epitaxial wafer coated with the protective layer into the etching solution and soak for 80 seconds, then rinse with clean water and dry.

[0044] The etching solution includes the following components in mass parts: 15 to 30 parts of hydrochloric acid, 10 to 25 parts of sulfuric acid, 30 to 50 parts of hydrogen peroxide, and 5 to 10 parts of hydrofluoric acid. The mass fraction of hydrochloric acid is 37%, the mass fraction of phosphoric acid is 20%, the mass fraction of sulfuric acid is 70%, the mass fraction of hydrogen peroxide is 75%, and the mass fraction of hydrofluoric acid is 10%.

[0045] Specifically, the GaN epitaxial wafer coated with the protective layer is placed in the etching solution and immersed for 80 seconds. Further, the GaN epitaxial wafer coated with the protective layer is placed in the etching solution and shaken to improve the etching effect. After the GaN epitaxial wafer is cleaned with clean water, the GaN epitaxial wafer is dried. The drying temperature is 50 degrees Celsius to 60 degrees Celsius, and the drying time is 2 hours to 4 hours.

[0046] Step 107: Second coating step of the protective layer: coating the protective liquid on the portion of the GaN epitaxial wafer that needs to be retained, and forming a protective layer after drying.

[0047] In this embodiment, the protective solution includes the following components in parts by weight: 5 to 10 parts of nano nickel powder, 10 to 20 parts of nano silicon dioxide powder, 0.5 to 1 part of citric acid, and the balance is anhydrous ethanol. The protective layer formed by the protective solution composed of the above components after drying has good acid resistance and alkali resistance, and can well protect the part that needs to be retained on the GaN epitaxial wafer.

[0048] Specifically, the protective liquid is coated on the portion of the GaN epitaxial wafer that needs to be retained, and the protective layer is formed after drying. The drying temperature is 50 degrees Celsius to 60 degrees Celsius, and the drying time is 2 hours to 4 hours.

[0049] Step 108: Dry etching step: Heat the epitaxial wafer to 250 degrees Celsius, then evenly apply KOH heated to a molten state on the surface of the GaN epitaxial wafer, continue heating to stabilize the temperature at 220 degrees Celsius, and continue etching for 1 minute.

[0050] Among them, the GaN epitaxial wafer is heated by microwave.

[0051] Specifically, the epitaxial wafer is heated to 250 degrees Celsius by microwaves, and then KOH heated to a molten state is evenly applied to the surface of the GaN epitaxial wafer. The epitaxial wafer is further heated by microwaves to stabilize the temperature of the epitaxial wafer at 220 degrees Celsius, and the etching is continued for 1 minute.

[0052] Step 109: Second cleaning step of the GaN epitaxial wafer: After the dry-etched GaN epitaxial wafer is naturally cooled, the dry-etched GaN epitaxial wafer is cleaned in an ultrasonic cleaning machine for 4 minutes and then dried.

[0053] Among them, the cleaning liquid in the ultrasonic cleaning machine is deionized water.

[0054] Specifically, after the dry-etched GaN epitaxial wafer is naturally cooled, the dry-etched GaN epitaxial wafer is cleaned in an ultrasonic cleaner for 4 minutes to clean the KOH on the GaN epitaxial wafer, and then dried. The drying temperature is 50 degrees Celsius to 60 degrees Celsius, and the drying time is 2 hours to 4 hours.

[0055] The above-mentioned LED chip surface roughening process steps are concise, exquisite and easy to control, and each step is careful and meticulous. First, a GaN epitaxial wafer is prepared, and then the GaN epitaxial wafer is roughened. Specifically, a photoresist is first coated on the part of the GaN epitaxial wafer that needs to be retained, and then dried to form a mask layer, and then the GaN epitaxial wafer is subjected to ICP etching. Then a protective liquid is coated on the part of the GaN epitaxial wafer that needs to be retained, and a protective layer is formed after drying. Subsequently, the GaN epitaxial wafer coated with the protective layer is placed in the etching solution for wet etching. The epitaxial wafer is heated to 250 degrees Celsius, and then KOH heated to a molten state is evenly applied to the surface of the GaN epitaxial wafer for dry etching. After the GaN epitaxial wafer is sequentially subjected to ICP etching, wet etching and dry etching, a stable and dense surface microstructure is formed on its surface, thereby improving the light extraction efficiency of the LED chip.

[0056] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0057] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A process for roughening the surface of an LED chip, characterized in that: The process comprises the following steps: Preparation steps of GaN epitaxial wafer: a low-temperature GaN buffer layer, an undoped GaN layer, an N-GaN layer, a multi-quantum well light-emitting layer and a P-GaN layer are sequentially grown on a semiconductor substrate to form a GaN epitaxial wafer; Mask layer coating step: coating the photoresist on the portion to be retained on the GaN epitaxial wafer and drying it to form a mask layer; ICP etching step: ICP etching the GaN epitaxial wafer; the etching gas is a mixture of Cl2, BCl3 and Ar2, and the volume ratio of Cl2, BCl3 and Ar2 is 70:14:16; the etching power is 400W, the RF power is 100W, and the etching time is 8 minutes; The first cleaning step of GaN epitaxial wafer: clean the GaN epitaxial wafer after ICP etching in an ultrasonic cleaner for 4 minutes and then dry it; The first coating step of the protective layer: coating the protective liquid on the part of the GaN epitaxial wafer that needs to be retained, and forming a protective layer after drying; Wet etching step: Place the GaN epitaxial wafer coated with a protective layer in the etching solution and soak for 80 seconds, then rinse with clean water and dry; The second coating step of the protective layer: coating the protective liquid on the part of the GaN epitaxial wafer that needs to be retained, and forming a protective layer after drying; Dry etching step: Heat the epitaxial wafer to 250 degrees Celsius, then evenly apply the molten KOH on the surface of the GaN epitaxial wafer, continue heating to stabilize the temperature at 220 degrees Celsius, and continue etching for 1 minute; The second cleaning step of the GaN epitaxial wafer: After the dry-etched GaN epitaxial wafer is naturally cooled, the dry-etched GaN epitaxial wafer is cleaned in an ultrasonic cleaning machine for 4 minutes and then dried.

2. The process according to claim 1, characterized in that In the GaN epitaxial wafer preparation step, the semiconductor substrate is sapphire.

3. The process according to claim 1, characterized in that In the GaN epitaxial wafer preparation step, the semiconductor substrate is silicon carbide.

4. The process according to claim 1, characterized in that In the step of preparing the GaN epitaxial wafer, a metal organic chemical vapor deposition method is adopted.

5. The process according to claim 1, characterized in that In the first cleaning step of the GaN epitaxial wafer, the cleaning liquid in the ultrasonic cleaning machine is acetone.

6. The process according to claim 1, characterized in that In the protective layer coating step, the protective solution comprises the following components in parts by weight: 5 to 10 parts of nano nickel powder, 10 to 20 parts of nano silicon dioxide powder, 0.5 to 1 part of citric acid, and the balance is anhydrous ethanol.

7. The process according to claim 6, characterized in that In the wet etching step, the etching solution includes the following components in parts by mass: 15 to 30 parts of hydrochloric acid, 10 to 25 parts of sulfuric acid, 30 to 50 parts of hydrogen peroxide, and 5 to 10 parts of hydrofluoric acid.

8. The process according to claim 1, characterized in that In the dry etching step, the GaN epitaxial wafer is heated by microwaves.

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