A method for manufacturing a micro light emitting diode

Abstract

The application provides a preparation method of a micro light emitting diode, comprising the following steps: preparing an n-GaN / multi-quantum well (MQW) / p-GaN layer on a patterned sapphire substrate; mesa patterning; mesa etching is performed to expose the n-GaN; depositing a SiO2 layer as a barrier layer; sputtering an indium tin oxide (ITO) layer on the SiO2 barrier layer; evaporating a first metal layer (FML) containing an Al / Pt / Ti multilayer film on the p and n-GaN regions; depositing an ALD Al2O3 thin layer as an internal moisture-proof layer, covering a PECVD SiO2 layer and a Bragg reflector (DBR) containing a SiO2 and Ti3O5 stack; patterning and dry etching the DBR, the SiO2 and the Al2O3 layer until the underlying FML is exposed; and depositing a Ti / Al / Ti / Au second metal layer (SML) as a p and n metal pad. The application utilizes atomic layer deposition to prepare a dense and ultrathin moisture-proof film in the mini LED, and simultaneously improves the light output.

Description

Technical Field

[0001] This invention provides a method for fabricating a miniature light-emitting diode, belonging to the field of electronic component technology. Background Technology

[0002] Mini-LED (Mini-LED) is a new type of LED technology that uses miniaturized LED elements to improve the image quality, brightness, and contrast of displays. It is suitable for various display devices such as smartphones, televisions, and computer monitors. Mini-LED emerged to address the limitations of OLED technology in terms of brightness and lifespan, and also as an improvement over the insufficient color performance of current mainstream LCD displays. Mini-LEDs consist of thousands of tiny LED elements, each only tens of micrometers in size, much smaller than traditional LEDs. This allows Mini-LEDs to incorporate more LEDs in the same area, thus improving image quality and brightness. Furthermore, Mini-LEDs employ global backlighting technology, resulting in more pronounced contrast. Mini-LED technology has a wide range of applications, especially in the high-end display device sector, where it holds great potential. It is predicted that Mini-LED displays will gradually become widespread and one of the mainstream display technologies in the coming years.

[0003] Evaluating the performance of mini-LEDs requires considering not only brightness and photoelectric characteristics, but also stable reliability, which is crucial for their continued illumination under various operating environments. Mini-LED chips are most susceptible to damage in high-temperature and high-humidity environments. The failure mechanism at high temperatures is primarily due to deformation of the internal chip structure caused by junction temperature, leading to loss of light emission. In high-humidity environments, one cause of failure is the oxidation of the LED chip's electrodes by water vapor, resulting in non-conductivity. Moisture diffusion into the LED not only reduces light output but also increases the likelihood of LED failure. Therefore, specialized data and sealing technologies are needed in LED chip design to improve reliability. Currently, the main LED packaging materials include epoxy resin, silicone, polymethyl methacrylate, polycarbonate, and UV-curable silicone-epoxy hybrids. However, these methods are mostly based on adding thick encapsulation to the outside of the device and may not be suitable for devices requiring high flexibility. Furthermore, with the increasing trend towards lightweighting and eliminating heavy encapsulation layers, it is necessary to develop thin internal moisture-proof layers for miniature LEDs using simple processes. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a method for fabricating a micro light-emitting diode, which develops an internal thin moisture-proof layer for micro LEDs through a simple process.

[0005] A method for fabricating a miniature light-emitting diode includes the following steps:

[0006] S1. Fabrication of n-GaN / multiple quantum well (MQW) / p-GaN layers on patterned sapphire substrates;

[0007] S2. Mesa patterning is performed using photolithography, followed by mesa etching using inductively coupled plasma reactive ion etching to expose n-GaN;

[0008] S3. A 230 nm thick SiO2 layer was deposited as a barrier layer using a plasma-enhanced vapor deposition (PECVD) system.

[0009] S4. Sputter an indium tin oxide (ITO) layer with a thickness of 110 nm onto the SiO2 barrier layer;

[0010] S5. First metal layer FML containing Al / Pt / Ti multilayer film is deposited in the p and n-GaN regions respectively;

[0011] S6. A thin layer of Al2O3 with a deposition thickness of only 40nm is used as an internal moisture barrier, covering a 650nm thick PECVDSiO2 layer and a Bragg reflector DBR containing SiO2 and Ti3O5 stacks.

[0012] S7. Pattern and dry etch the DBR, SiO2 and Al2O3 layers until the underlying FML is exposed;

[0013] S8. A second metal layer SML, consisting of Ti / Al / Ti / Au, is deposited as p and n metal pads. The length and width of the micro LED chip are approximately 600 μm and 200 μm, respectively.

[0014] This invention utilizes atomic layer deposition to create a dense, ultra-thin moisture-proof film inside the miniLED, while simultaneously increasing light output. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of a mini-LED device with an ultra-thin Al2O3 internal moisture-proof layer obtained in the embodiment. Detailed Implementation

[0016] The specific technical solution of the present invention is illustrated with reference to the embodiments:

[0017] A miniature light-emitting diode, with the following structure Figure 1 As shown, the specific preparation method is that the n-GaN / multiple quantum well (MQW) / p-GaN layer is prepared on a patterned sapphire substrate.

[0018] Next, mesa patterning was performed using photolithography, followed by mesa etching using inductively coupled plasma reactive ion etching to expose n-GaN. A 230 nm thick SiO2 layer was deposited as a barrier layer using a plasma-enhanced vapor deposition (PECVD) system. This is the patterning and dry etching process.

[0019] An indium tin oxide (ITO) layer with a thickness of 110 nm was sputtered onto the SiO2 barrier layer.

[0020] Then, a first metal layer containing Al / Pt / Ti multilayer films is deposited in the p and n-GaN regions, respectively. An ALD Al2O3 thin layer with a thickness of only 40 nm is deposited as an internal moisture barrier, which is covered by a 650 nm thick PECVD SiO2 layer and a Bragg reflector (DBR) containing SiO2 and Ti3O5 stacks.

[0021] Subsequently, the DBR, SiO2, and Al2O3 layers were patterned and dry-etched until the underlying FML was exposed. Finally, a Ti / Al / Ti / Au second metal layer was deposited as p and n metal pads, resulting in a micro-LED chip with a length and width of approximately 600 μm and 200 μm, respectively.

[0022] Table 1. Process parameters for atomic layer deposition of Al2O3

[0023]

[0024]

[0025] The beneficial effects of the technical solution of this invention are as follows:

[0026] 1. Improve the reliability of Mini-LED in high temperature and high humidity (85°C / 85% relative humidity) aging test. Mini-LED showed almost no degradation after 1000h aging time under constant current. The data is shown in Table 2.

[0027] Table 2. Attenuation of optical power of miniLED devices after 1000 hours of high temperature and high humidity testing.

[0028]

[0029] 2. The optical power is increased by approximately 1.9% because this layer is added inside the device structure. Its refractive index is higher than that of SiO2, so the device reflects more light at the Al2O3 and SiO2 interface, meaning that the light is reflected earlier (originally it would only be reflected at the DBR). If light is traveling towards the sidewall of the device, it may leave the sidewall before reaching the DBR. The earlier reflection can reflect this part of the light back, thereby reducing the loss of light emanating from the sidewall and increasing the amount of light emitted by the device.

Claims

1. A method for fabricating a miniature light-emitting diode, characterized in that, Includes the following steps: S1. Fabrication of n-GaN / multiple quantum well (MQW) / p-GaN layers on patterned sapphire substrates; S2. Mesa patterning is performed using photolithography, followed by mesa etching using inductively coupled plasma reactive ion etching to expose n-GaN; S3. A SiO2 layer was deposited as a barrier layer using a plasma-enhanced vapor deposition (PECVD) system; S4. Sputter an indium tin oxide (ITO) layer onto the SiO2 barrier layer; S5. First metal layer FML containing Al / Pt / Ti multilayer film is deposited in the p and n-GaN regions respectively; S6. Deposit an ALD Al2O3 thin layer as an internal moisture barrier, and cover the ALD Al2O3 thin layer with a PECVD SiO2 layer and a Bragg reflector DBR containing a SiO2 and Ti3O5 stack; S7. Pattern and dry etch the DBR, SiO2, and Al2O3 layers until the underlying FML is exposed; S8. Deposit a second metal layer SML of Ti / Al / Ti / Au as p and n metal pads.

2. The method for fabricating a miniature light-emitting diode according to claim 1, characterized in that, A 230 nm thick SiO2 layer is deposited in S3 as a barrier layer.

3. The method for fabricating a miniature light-emitting diode according to claim 1, characterized in that, An indium tin oxide (ITO) layer with a thickness of 110 nm is sputtered in S4.

4. The method for fabricating a miniature light-emitting diode according to claim 1, characterized in that, A 40 nm thick ALD Al2O3 thin layer is deposited in S6, covered by a 650 nm thick PECVD SiO2 layer.

5. The method for fabricating a miniature light-emitting diode according to claim 1, characterized in that, The resulting miniature light-emitting diode has a length of 600 µm and a width of 200 µm.

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