A method for preparing a Micro LED chip capable of controlling light emission angle

Abstract

The present invention relates to a method for preparing a Micro LED chip capable of controlling the light output angle, and belongs to the field of optoelectronic technology. The pad of the present invention is a circular ring electrode in a circular shape, and current is injected around the circular ring electrode and introduced into the MQW layer in the ring through ITO, thereby generating light. Due to the limitation of the circular electrode and the surrounding DBR layer, the light is concentrated on the circular ring for output. By changing the shape and material of the circular ring, the light output angle can be further changed. Compared with the Micro chip with front light output, the present invention further reduces the light output angle and reduces the influence of mixed light on adjacent pixels. The present invention is suitable for RGB color light-emitting chips.

Description

Technical Field

[0001] The invention relates to a method for preparing a Micro LED chip capable of controlling a light emission angle, and belongs to the technical field of optoelectronics. Background Art

[0002] Micro-displays based on micro-LED arrays have great application prospects. Compared with traditional liquid crystal displays (LCDs) and organic light-emitting displays (OLEDs), they have the advantages of high efficiency, low power consumption, ultra-high resolution, ultra-fast response speed and wide viewing angle, and are considered to be a "next-generation display technology."

[0003] The edge effect caused by LED miniaturization will reduce the brightness and luminous efficiency of the chip. The geometric structure of the chip is related to the light output angle of the pixel light source. Therefore, the chip geometry needs to be changed accordingly for different application requirements. This requires close cooperation in the upstream and downstream fields. As the chip size decreases, the density of pixel light sources increases. When the chip size is reduced to 20 microns or below, the problem of optical crosstalk between pixels cannot be ignored. It is necessary to effectively isolate the pixels from the chip structure design and packaging technology to reduce the optical crosstalk between pixels.

[0004] Chinese patent document CN217847979U discloses a MicroLED chip with a small light-emitting angle, characterized in that it includes: an epitaxial structure, the epitaxial structure includes an N-GaN layer, a multi-quantum well layer and a P-GaN layer, the multi-quantum well layer is located between the N-GaN layer and the P-GaN layer; a transparent conductive film disposed on the surface of the P-GaN layer on the side away from the multi-quantum well layer; a total reflection layer disposed on the surface of the epitaxial structure and the transparent conductive film on one side; a P-Pad layer disposed on the surface of the transparent conductive film on the side away from the P-GaN layer; an N-Pad layer disposed on the surface of one side of the N-GaN layer; and a functional layer disposed on the surface of the other side of the N-GaN layer, the functional layer being formed by alternating stacking of low-refractive index materials and high-refractive index materials. By coating the full sidewall and front surface of the MicroLED chip with a total reflection mirror, and plating the functional layer on the light-emitting surface, the functional layer and the total reflection mirror are used to realize the free control of the light-emitting angle of the MicroLED, and the process is easy to implement and the effective light efficiency is high. The functional layer of this patent is composed of 31 or 51 layers of high and low refractive index materials stacked together. It has high requirements on growth materials and growth time, and needs to control the refractive index and film thickness of each material, which is not conducive to mass production and the realization of reflection function.

[0005] Chinese patent document CN112635452A discloses a Micro-LED display device structure with controllable light emission angle, which includes a pixel structure, characterized in that the pixel structure includes an LED vertical chip array and an LED flip chip array, and the size of a single LED pixel is 30μm to 50μm. The function of controlling the light emission angle of the Micro-LED display device is achieved through the combined reflector design on the LED chip array and the periodic microstructure design of the device packaging layer, which not only improves the light utilization rate and eliminates light pollution, but also eliminates the post-reinforcement link of adding optical components to collect light, thereby achieving the advantages of lightweight and low power consumption of the device, and can meet the high reliability applications in special fields such as head-up displays. 1. A Micro-LED display device structure with controllable light emission angle, characterized by including the following two situations: (1) The pixel structure of the display device is a vertical LED chip array: the device structure is, from bottom to top, a P electrode, a current spreading layer, a reflector, a P-type GaN, a quantum hydrazine, an N-type GaN and a common N electrode, the P electrode is arranged on a substrate, and each side edge of each independent LED pixel includes one or more layers of combined reflectors; two layers of periodic microstructure encapsulation layers are arranged on the upper part of the common N electrode; (2) The pixel structure of the display device is a flip-chip LED chip array: the device structure is, from bottom to top, a P electrode, a current spreading layer, a reflector, a P-type GaN, a quantum hydrazine, an N-type GaN and a common N electrode, Reflector, P-type GaN, quantum hydrazine, N-type GaN and N electrode, the P electrode is arranged on the substrate, and each independent LED pixel includes one or more layers of combined reflectors on both sides; the upper part of the N-type GaN is provided with two layers of periodic microstructure encapsulation layer; the material of the periodic microstructure encapsulation layer is highly elastic polyacrylate resin; the thickness t of the single-layer periodic microstructure encapsulation layer is 25μm-30μm, the lower layer is horizontally serrated, the upper layer is longitudinally serrated, and the angle σ between the arrangement directions of the upper and lower microstructures is 90°; the edge angle δ of each layer of serrated microstructure is 60°-120°, and the edge spacing d is 29μm-104μm. The front of the patent is full light output, and the light output range cannot be reduced. Summary of the invention

[0006] In view of the above problems, the present invention provides a method for preparing a Micro LED chip capable of controlling the light emission angle. Compared with the traditional method of making a metal pad in the middle, the pad of the present invention is a ring-shaped ring electrode. Current is injected around the ring electrode and introduced into the MQW layer inside the ring through ITO, thereby generating light. Due to the limitation of the ring electrode and the surrounding DBR layer, the light is concentrated on the ring for emission. The light emission angle can be further changed by changing the shape and material of the ring. Compared with the Micro chip that emits light from the front, the present invention further reduces the light emission angle and reduces the influence of mixed light on adjacent pixels. The present invention is suitable for RGB color light-emitting chips.

[0007] The technical solution of the present invention is as follows:

[0008] A method for preparing a Micro LED chip capable of controlling a light output angle comprises the following steps:

[0009] (1) epitaxial growth of AlGaInP\GaN materials is performed on the substrate to form corresponding RGB luminescent materials, and the luminescent materials include an N-type layer, an MQW and a P-type layer from bottom to top;

[0010] (2) performing dry etching on the P-type layer of the light-emitting material after epitaxial growth to the upper surface of the substrate to form a plurality of independent light-emitting units;

[0011] (3) Using photolithography technology to make a mask for each independent light-emitting unit, using the mask to protect the central light-emitting area and expose the periphery and side walls of the chip;

[0012] (4) Ion implantation is performed around the light-emitting surface and on the side walls;

[0013] (5) Depositing Al2O3 by ALD or PVD to form a passivation protective layer on the sidewalls and surface;

[0014] (6) Use a degumming solution to remove the mask in the central light-emitting area;

[0015] (7) forming a DBR (Bragg reflector) on the surface of the wafer by electron beam evaporation or magnetron sputtering, wherein the DBR material is formed by alternating stacking of a low refractive index material and a high refractive index dielectric material;

[0016] (8) etching the light emitting surface by ion beam etching;

[0017] (9) making ITO on the etched light-emitting surface;

[0018] (10) Making a circular electrode on the ITO; the circular electrode pattern can be a continuous circular ring or a discontinuous circular ring during photolithography, and the number of discontinuities is set according to different requirements for the light output angle. When the light output angle needs to be increased, the complete circular ring can be divided into a plurality of sector-shaped electrodes;

[0019] (11) Use temporary bonding materials, such as PI\BCB\photoresist, to temporarily bond the wafer to a temporary substrate;

[0020] (12) peeling the epitaxial layer from the substrate by wet etching or laser stripping;

[0021] (13) depositing ITO on the N-type layer exposed after peeling;

[0022] (14) The ITO pattern is produced by double-sided exposure, and the ITO is left in the area of ​​the N-type layer corresponding to the P-side circular electrode ring, and the ITO in other areas is removed;

[0023] (15) Prepare a metal reflector on the N surface to complete the chip production.

[0024] Preferably, the width of the exposed area on all sides in step (3) is 20% of the distance from the center to the edge of the chip.

[0025] Preferably, in step (4), N ions are preferably injected, so that this part of the current does not conduct and the MQW does not emit light, which can reduce the side wall current and dangling bonds.

[0026] Preferably, in step (5), the thickness of the passivation protective layer is 10-100 nm.

[0027] Preferably, in step (7), the low refractive index material is SiO2, MgF2 or Al2O3, and the high refractive index material is TiO2 or Ti3O5.

[0028] Preferably, in step (9), the thickness of ITO is 10-100 nanometers;

[0029] Preferably, in step (10), the distance from the outer ring of the circular electrode to the edge of the chip is 10% of the distance from the center of the chip to the edge, the material of the circular electrode is a metal material with high reflectivity such as gold, silver, aluminum, etc., the height of the circular electrode is 1-10 μm, the top diameter of the circular electrode is 1-1.1 times the bottom diameter, and the bottom diameter of the circular electrode is the diameter of the DBR hole etched in step 8.

[0030] Preferably, in step (12), the wet etching solution is a mixture of ammonia water and hydrogen peroxide in a volume ratio of 3:1, or a mixture of acetic acid, phosphoric acid and hydrogen peroxide in a volume ratio of 3:1:1.

[0031] Preferably, in step (14), the thickness of ITO is 10-100 nanometers.

[0032] Preferably, the metal reflector in step (15) is made of one or a combination of several materials such as gold, silver and aluminum, and has a thickness of 1-2 microns.

[0033] The light-emitting aperture of the present invention directly determines the light-emitting area and angle. When holes with different diameters and inclinations are opened, the light-emitting angle changes accordingly. When the material of the annular electrode changes from reflective to low reflectivity, the light-emitting angle will be further reduced.

[0034] For any details not provided in the present invention, please refer to the prior art.

[0035] The beneficial effects of the present invention are:

[0036] (1) The present invention can control the light output angle and improve pixel brightness.

[0037] (2) The present invention can reduce light mixing to adjacent pixels.

[0038] (3) The preparation method of the present invention is convenient and has significant effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The drawings in the specification, which constitute a part of the present application, are used to provide further understanding of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute improper limitations on the present application.

[0040] Figure 1 A cross-sectional view of a Micro LED manufactured according to the present invention;

[0041] Figure 2 A top view of the Micro LED manufactured by the present invention;

[0042] Figure 3 A cross-sectional view of the Micro LED chip manufactured in step 2 of the present invention;

[0043] Figure 4 A cross-sectional view of the Micro LED chip manufactured in step 3 of the present invention;

[0044] Figure 5 A cross-sectional view of the Micro LED chip manufactured in step 4 of the present invention;

[0045] Figure 6 A cross-sectional view of the Micro LED chip manufactured in step 5 of the present invention;

[0046] Figure 7 A cross-sectional view of the Micro LED chip manufactured in step 6 of the present invention;

[0047] Figure 8 A cross-sectional view of the Micro LED chip manufactured in step 7 of the present invention;

[0048] Fig. 9 A cross-sectional view of the Micro LED chip manufactured in step 8 of the present invention;

[0049] Fig.10 This is a cross-sectional view of the Micro LED chip manufactured in step 9\10 of the present invention;

[0050] Fig.11 A cross-sectional view of the Micro LED chip manufactured in step 11 of the present invention;

[0051] Fig.12 A cross-sectional view of the Micro LED chip manufactured in step 12 of the present invention;

[0052] Fig.13 A cross-sectional view of the Micro LED chip manufactured in step 13 of the present invention;

[0053] Fig.14 A cross-sectional view of the Micro LED chip manufactured in step 14 of the present invention;

[0054] Fig.15 A cross-sectional view of the Micro LED chip manufactured in step 14 of the present invention;

[0055] Fig.16 Two configurations of the ring electrode, where (a) and (b) are two different forms;

[0056] Fig.17 1 and 2 are top views of the circular ring electrodes, wherein (a) is the reference circular ring electrode, (b) is the circular ring electrode 1 for increasing the light output angle, and (c) is the circular ring electrode 2 for increasing the light output angle. DETAILED DESCRIPTION

[0057] In order to enable those skilled in the art to better understand the technical solutions in this specification, the technical solutions in the embodiments of the present invention are clearly and completely described below in conjunction with the drawings in the implementation of this specification, but are not limited to this. Anything not fully described in the present invention shall be based on the conventional technology in the art.

[0058] Example 1

[0059] A method for preparing a Micro LED chip capable of controlling the light output angle, such as Figures 1 to 17 As shown, the following steps are included:

[0060] (1) epitaxial growth of GaN material is performed on a sapphire substrate to form a corresponding blue-green light emitting material, wherein the light emitting material includes an N-type layer, an MQW and a P-type layer from bottom to top;

[0061] (2) dry etching the P-type layer of the epitaxially grown light-emitting material to the upper surface of the sapphire substrate to form a plurality of independent light-emitting units;

[0062] (3) Using photolithography technology to make a mask for each independent light-emitting unit, using the mask to protect the central light-emitting area, exposing the periphery and sidewalls of the chip, and the width of the exposed area on the periphery is 20% of the distance from the center to the edge of the chip;

[0063] (4) performing ion implantation around the light-emitting surface and the sidewalls, preferably implanting N ions;

[0064] (5) using ALD or PVD to deposit Al2O3 to form a passivation protective layer on the sidewalls and surface with a thickness of 10-100 nm;

[0065] (6) Use a degumming solution to remove the mask in the central light-emitting area;

[0066] (7) forming a DBR (Bragg reflector) on the surface of the wafer by electron beam evaporation or magnetron sputtering, wherein the DBR material is formed by alternating stacking of a low refractive index material and a high refractive index dielectric material; the low refractive index material is SiO2, MgF2 or Al2O3, and the high refractive index material is TiO2 or Ti3O5;

[0067] (8) etching the light-emitting surface by ion beam etching, wherein the distance from the exposed area to the edge of the chip is 20% of the distance from the center to the edge of the chip;

[0068] (9) forming ITO on the etched light-emitting surface, wherein the thickness of the ITO is 10-100 nanometers;

[0069] (10) Making a circular electrode on the ITO; the circular electrode pattern is a continuous circular ring or a discontinuous circular ring, and the number of discontinuities is set according to different requirements for the light output angle. When the light output angle needs to be increased, the complete circular ring can be divided into multiple sector-shaped electrodes, such as Fig.17 As shown;

[0070] The distance from the outer ring of the circular electrode to the edge of the chip is 10% of the distance from the center of the chip to the edge. The material of the circular electrode is a metal material with high reflectivity such as gold, silver, and aluminum. The height of the circular electrode is 1-10μm, and the top diameter of the circular electrode is 1-1.1 times the bottom diameter. Fig.16 As shown, the bottom diameter of the annular electrode is the diameter of the DBR hole etched in step 8.

[0071] (11) Using temporary bonding materials, such as PI\BCB\photoresist, the wafer is temporarily bonded to a temporary substrate, and the thickness of the bonding layer can be 0.1 μm to 10 μm;

[0072] (12) peeling the epitaxial layer from the substrate by laser lift-off;

[0073] (13) depositing ITO on the N-type layer exposed after stripping, wherein the thickness of ITO is 10-100 nanometers;

[0074] (14) The ITO pattern is produced by double-sided exposure, and the ITO is left in the area of ​​the N-type layer corresponding to the P-side circular electrode ring, and the ITO in other areas is removed;

[0075] (15) A metal reflector is prepared on the N surface to complete chip manufacturing. The metal reflector is made of one or a combination of several materials such as gold, silver, and aluminum, and has a thickness of 1-2 microns.

[0076] Example 2

[0077] A method for preparing a Micro LED chip capable of controlling a light output angle comprises the following steps:

[0078] (1) epitaxial growth of AlGaInP material is performed on a GaAs substrate to form a corresponding red light emitting material, wherein the light emitting material includes an N-type layer, an MQW and a P-type layer from bottom to top;

[0079] (2) dry etching the P-type layer of the epitaxially grown light-emitting material to the upper surface of the GaAs substrate to form a plurality of independent light-emitting units;

[0080] (3) Using photolithography technology to make a mask for each independent light-emitting unit, using the mask to protect the central light-emitting area, exposing the periphery and sidewalls of the chip, and the width of the exposed area on the periphery is 20% of the distance from the center to the edge of the chip;

[0081] (4) performing ion implantation around the light-emitting surface and the sidewalls, preferably implanting N ions;

[0082] (5) using ALD or PVD to deposit Al2O3 to form a passivation protective layer on the sidewalls and surface with a thickness of 10-100 nm;

[0083] (6) Use a degumming solution to remove the mask in the central light-emitting area;

[0084] (7) forming a DBR (Bragg reflector) on the surface of the wafer by electron beam evaporation or magnetron sputtering, wherein the DBR material is formed by alternating stacking of a low refractive index material and a high refractive index dielectric material; the low refractive index material is SiO2, MgF2 or Al2O3, and the high refractive index material is TiO2 or Ti3O5;

[0085] (8) etching the light emitting surface by ion beam etching;

[0086] (9) forming ITO on the etched light-emitting surface, wherein the thickness of the ITO is 10-100 nanometers;

[0087] (10) Making a circular electrode on the ITO; the circular electrode pattern is a continuous circular ring or a discontinuous circular ring, and the number of discontinuities is set according to different requirements for the light output angle. When the light output angle needs to be increased, the complete circular ring can be divided into a plurality of sector-shaped electrodes;

[0088] The distance from the outer ring of the circular electrode to the edge of the chip is 10% of the distance from the center of the chip to the edge. The material of the circular electrode is a metal material with high reflectivity such as gold, silver, and aluminum. The height of the circular electrode is 1-10μm, and the top diameter of the circular electrode is 1-1.1 times the bottom diameter. The bottom diameter of the circular electrode is the diameter of the DBR hole etched in step 8.

[0089] (11) Use temporary bonding materials, such as PI\BCB\photoresist, to temporarily bond the wafer to a temporary substrate;

[0090] (12) peeling the epitaxial layer from the substrate by wet etching;

[0091] The wet etching solution is a mixture of ammonia water and hydrogen peroxide in a volume ratio of 3:1, or a mixture of acetic acid, phosphoric acid and hydrogen peroxide in a volume ratio of 3:1:1.

[0092] (13) depositing ITO on the N-type layer exposed after stripping, wherein the thickness of ITO is 10-100 nanometers;

[0093] (14) The ITO pattern is produced by double-sided exposure, and the ITO is left in the area of ​​the N-type layer corresponding to the P-side circular electrode ring, and the ITO in other areas is removed;

[0094] (15) A metal reflector is prepared on the N surface to complete chip manufacturing. The metal reflector is made of one or a combination of several materials such as gold, silver, and aluminum, and has a thickness of 1-2 microns.

[0095] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a Micro LED chip capable of controlling the light output angle, characterized in that: The steps include: (1) epitaxial growth of AlGaInP\GaN materials is performed on the substrate to form corresponding RGB luminescent materials, where the RGB luminescent materials include an N-type layer, an MQW, and a P-type layer from bottom to top; (2) performing dry etching on the P-type layer of the light-emitting material after epitaxial growth to the upper surface of the substrate to form a plurality of independent light-emitting units; (3) Using photolithography technology to make a mask for each independent light-emitting unit, using the mask to protect the central light-emitting area and expose the periphery and side walls of the chip; (4) Ion implantation is performed around the light-emitting surface and on the side walls; (5) Depositing Al2O3 by ALD or PVD to form a passivation protective layer on the sidewalls and surface; (6) Use a degumming solution to remove the mask in the central light-emitting area; (7) forming a DBR on the wafer surface by electron beam evaporation or magnetron sputtering, wherein the DBR material is formed by alternating stacking of a low refractive index material and a high refractive index dielectric material; (8) etching the light emitting surface by ion beam etching; (9) making ITO on the etched light-emitting surface; (10) Making a circular electrode on the ITO; the circular electrode pattern is a continuous circular ring or a discontinuous circular ring, and the number of discontinuities is set according to different requirements for the light output angle. When the light output angle needs to be increased, the complete circular ring is divided into a plurality of sector-shaped electrodes; (11) Using a temporary bonding material to temporarily bond the wafer to a temporary substrate, the temporary bonding material being PI, BCB or photoresist; (12) peeling the epitaxial layer from the substrate by wet etching or laser stripping; (13) depositing ITO on the N-type layer exposed after peeling; (14) The ITO pattern is produced by double-sided exposure, and the ITO is left in the area of ​​the N-type layer corresponding to the P-side circular electrode ring, and the ITO in other areas is removed; (15) Prepare a metal reflector on the N surface to complete the chip production.

2. The method for preparing a Micro LED chip capable of controlling the light emission angle according to claim 1, characterized in that: The width of the exposed area on all sides in step (3) is 20% of the distance from the center to the edge of the chip.

3. The method for preparing a Micro LED chip capable of controlling the light output angle according to claim 1, characterized in that: In step (4), N ions are injected.

4. The method for preparing a Micro LED chip capable of controlling the light emission angle according to claim 1, characterized in that: In step (5), the thickness of the passivation protection layer is 10-100 nm.

5. The method for preparing a Micro LED chip capable of controlling the light emission angle according to claim 1, characterized in that: In step (7), the low refractive index material is SiO2, MgF2 or Al2O3, and the high refractive index material is TiO2 or Ti3O5.

6. The method for preparing a Micro LED chip capable of controlling the light emission angle according to claim 1, characterized in that: In step (9), the thickness of ITO is 10-100 nanometers.

7. The method for preparing a Micro LED chip capable of controlling the light emission angle according to claim 1, characterized in that: In step (10), the distance from the outer ring of the circular electrode to the edge of the chip is 10% of the distance from the center of the chip to the edge, the material of the circular electrode is gold, silver or aluminum, the height of the circular electrode is 1-10 μm, and the top diameter of the circular electrode is 1-1.1 times the bottom diameter.

8. The method for preparing a Micro LED chip capable of controlling the light emission angle according to claim 1, characterized in that: In step (12), the wet etching solution is a mixture of ammonia water and hydrogen peroxide in a volume ratio of 3:1, or a mixture of acetic acid, phosphoric acid and hydrogen peroxide in a volume ratio of 3:1:

1.

9. The method for preparing a Micro LED chip capable of controlling the light emission angle according to claim 1, characterized in that: In step (13), the thickness of ITO is 10-100 nanometers.

10. The method for preparing a Micro LED chip capable of controlling light emission angle according to claim 1, characterized in that: The metal reflector in step (15) is made of one or a combination of several materials such as gold, silver and aluminum, and has a thickness of 1-2 microns.

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