Micro-LED device and preparation method thereof

Abstract

The invention discloses a Micro-LED device and a preparation method thereof. The device comprises a driving substrate with a driving circuit, Micro-LED pixel units, an N electrode and a DBR layer, wherein the Micro-LED pixel units, the N electrode and the DBR layer are located on the driving substrate and distributed in an array mode. Each Micro-LED pixel unit sequentially comprises a metal bonding layer, a P-type layer, a quantum well light-emitting layer and an N-type layer from bottom to top; the Micro-LED pixel units are bonded with the driving substrate through the metal bonding layer and are electrically connected with the driving circuit; the metal bonding layer is in ohmic contact with the P-type layer, and the N electrode is in ohmic contact with the N-type layer; the side walls of the Micro-LED pixel units are covered with the DBR layer, grooves between the Micro-LED pixel units are filled with the DBR layer, a planarization surface is formed, and the upper surface of the DBR layer is flush with the upper surfaces of the Micro-LED pixel units; the DBR layer is formed by alternately and periodically stacking high-refractive-index dielectric materials and low-refractive-index dielectric materials. The DBR layer is adopted to cover the side walls of the Micro-LED pixel units, the grooves between the Micro-LED pixel units are filled, and the planarized surfaces are formed, so that side wall passivation and side wall reflection of the Micro-LED pixel units and planarizing of the surface of a Micro-LED device can be achieved.

Description

Technical Field

[0001] This invention relates to the field of semiconductor display technology, specifically to a Micro-LED device and its fabrication method. Background Technology

[0002] The essence of Micro-LED is to miniaturize the size of traditional LEDs to the tens or even a few micrometers level. However, due to performance limitations, the thickness of the device cannot be reduced proportionally with the size, which directly leads to an increase in the aspect ratio of the pixels, thus causing a series of problems. On the one hand, the increased aspect ratio makes the preparation of the passivation layer more difficult. Since the passivation layer needs to be deposited on the entire surface first and then removed from the top surface of the pixel by photolithography, the larger the aspect ratio, the higher the requirements for photolithography precision. It not only requires high-resolution photolithography machines, but also strict control of various process parameters. On the other hand, the increased aspect ratio makes the sidewall area of ​​the device relatively larger, causing the sidewall light emission to exceed that of the front, resulting in an increased emission angle and thus reducing display performance.

[0003] Chinese patent document CN119836078A discloses a method for self-aligned trench filling and passivation of Micro-LED devices. The method involves preparing a dielectric layer on the Micro-LED device, filling trenches and covering all array units, and then progressively thinning the dielectric layer using a maskless dry etching method until the upper surface of all array units is exposed. A patterned passivation layer is formed at the trenches, avoiding the need for registration and developing processes. This process eliminates interface gaps and mesa residue problems caused by registration errors, and can form a tightly connected patterned passivation layer without shape or size constraints, increasing the etch resistance of the passivation structure and improving device manufacturing yield. However, this method only solves the problem of passivation layer preparation and does not address the issue of increasing the emission angle of Micro-LEDs. Summary of the Invention

[0004] Based on this, the present invention provides a Micro-LED device and a fabrication method, while solving the problems of passivation layer fabrication and increased emission angle caused by the increased aspect ratio of Micro-LED devices.

[0005] On one hand, the present invention provides a Micro-LED device, including a driving substrate having a driving circuit, Micro-LED pixel units arranged in an array on the driving substrate, an N electrode, and a DBR layer; The Micro-LED pixel unit comprises, from bottom to top, a metal bonding layer, a P-type layer, a quantum well light-emitting layer, and an N-type layer; the Micro-LED pixel unit is bonded to the driving substrate through the metal bonding layer and electrically connected to the driving circuit; The metal bonding layer and the P-type layer have an ohmic contact, and the N-electrode and the N-type layer have an ohmic contact. The DBR layer covers the sidewalls of the Micro-LED pixel unit, fills the trenches between the Micro-LED pixel units, and forms a planarized surface. The upper surface of the DBR layer is flush with the upper surface of the Micro-LED pixel unit. The DBR layer is composed of alternating periodic stacks of high-refractive-index and low-refractive-index dielectric materials.

[0006] The Micro-LED device provided by this invention uses a DBR layer to cover the sidewalls of the Micro-LED pixel units, filling the trenches between the Micro-LED pixel units and forming a planarized surface. This achieves sidewall passivation and sidewall reflection of the Micro-LED pixel units, resulting in a planarized surface for the Micro-LED device. Light is reflected at the sidewalls and, after multiple reflections, finally exits from the top surface. Therefore, the light reflected by the sidewalls reduces the emission angle and alleviates crosstalk, which helps improve the light extraction efficiency of the Micro-LED device and thus enhances display performance.

[0007] As an alternative to the Micro-LED device of the present invention, the alternation period between high-refractive-index dielectric material and low-refractive-index dielectric material is 5~20.

[0008] As an alternative solution for the Micro-LED device of this invention, the high refractive index dielectric material is TiO2, Al2O3, or SiN. x One or more of the following; the low refractive index medium material is SiO2.

[0009] As an alternative to the Micro-LED device of the present invention, the N electrode is an independent electrode separately disposed on each Micro-LED pixel unit, or a transparent electrode covering the entire surface.

[0010] As a preferred option among the above-mentioned alternatives, the N electrode is provided with N electrode wiring.

[0011] As a preferred embodiment of the above-mentioned optional solutions, a microlens is also provided on the Micro-LED pixel unit, the center of the microlens coincides with the center of the Micro-LED pixel unit, and the size of the microlens is larger than the size of the Micro-LED pixel unit.

[0012] On the other hand, the present invention also provides a method for fabricating a Micro-LED device, comprising the following steps: S1. A GaN-based LED epitaxial layer is grown on a substrate. The GaN-based LED epitaxial layer includes an N-type layer, a quantum well light-emitting layer, and a P-type layer from bottom to top. S2. Prepare a P-electrode metal layer on the surface of the P-type layer; S3. Fabricate a metal bump array on the surface of the driving substrate; S4. Bond the GaN-based LED epitaxial layer to the driving substrate. The bonding surface is a P-electrode metal layer and a metal bump array. S5. Remove the substrate to expose the GaN-based LED epitaxial layer; S6. Etch the GaN-based LED epitaxial layer. The GaN-based LED epitaxial layer forms an array of light-emitting mesa, which correspond to the metal bump array. S7. Etch away the P-electrode metal layer between the light-emitting mesa to form an array of Micro-LED pixel units; the Micro-LED pixel unit includes the light-emitting mesa and the P-electrode metal layer below it and the metal bump array unit. S8. A DBR layer is grown across the entire surface. The DBR layer fills the trenches between Micro-LED pixel units and completely covers the Micro-LED pixel units. The DBR layer is composed of alternating and periodically stacked high-refractive-index dielectric materials and low-refractive-index dielectric materials. S9. The DBR layer is planarized by chemical mechanical polishing until the N-type layer is exposed; S10. Prepare the N electrode to complete the fabrication of the Micro-LED device.

[0013] As an optional embodiment of the preparation method of the present invention, the method further includes the following steps: S11. Prepare microlens thin film material on the entire surface; S12. A microlens etching mask is formed by reflowing photoresist, and then the microlens thin film material prepared in S11 is etched by ICP to form an array of microlenses, each corresponding to a Micro-LED pixel unit.

[0014] The fabrication method for Micro-LED devices provided by this invention, after fabricating an array of Micro-LED pixel units, achieves the dual purpose of sidewall passivation and sidewall reflection of the Micro-LED pixel units by growing a DBR layer, thereby reducing the light emission angle and alleviating optical crosstalk. Simultaneously, the DBR layer fills the trenches between the Micro-LED pixel units, which helps to further reduce the risk of leakage. Furthermore, by chemically mechanically polishing (CMP) the DBR layer to expose the upper surface of the N-type layer, the purpose of opening the DBR layer is achieved. This not only avoids the dependence of photolithography opening processes on the precision of photolithography and etching, but also achieves surface planarization. A flat surface is beneficial for the subsequent fabrication of the N-electrode.

[0015] As an optional embodiment of the preparation method of the present invention, step S5 further includes thinning the N-type layer so that the thickness of the GaN-based LED epitaxial layer is 1µm to 1.5µm; the method for thinning the N-type layer is chemical mechanical polishing, and the polishing slurry used is an alkaline polishing slurry; or the method for thinning the N-type layer is inductively coupled plasma etching, and the etching gas is a mixture of Cl2 and BCl3.

[0016] As an optional method of the preparation method of the present invention, the method of etching the GaN-based LED epitaxial layer in step S6 is thermal phosphoric acid etching, and the light-emitting mesa formed by etching is a dodecagonal truncated structure.

[0017] Additional aspects and advantages of the invention will be set forth in part in the description which follows, some of which will become clear as the description proceeds, and others will be learned by practicing the invention. Attached Figure Description

[0018] Figure 1 This is a schematic cross-sectional view of the GaN-based LED epitaxial layer grown in an embodiment of the present invention.

[0019] Figure 2 This is a schematic cross-sectional view of the P-electrode metal layer after it has been prepared in an embodiment of the present invention.

[0020] Figure 3 This is a schematic cross-sectional view of the driving substrate in an embodiment of the present invention.

[0021] Figure 4 This is a schematic cross-sectional view of the GaN-based LED epitaxial layer bonded to the driving substrate in an embodiment of the present invention.

[0022] Figure 5 This is a schematic diagram of the cross-sectional structure after removing the substrate in an embodiment of the present invention.

[0023] Figure 6 This is a schematic cross-sectional view of the N-type layer after thinning in an embodiment of the present invention.

[0024] Figure 7 This is a schematic cross-sectional view of the GaN-based LED epitaxial layer after etching in an embodiment of the present invention.

[0025] Figure 8 This is a schematic cross-sectional view of the P-electrode metal layer after etching in an embodiment of the present invention.

[0026] Figure 9 This is a schematic cross-sectional view of the DBR passivation layer after it has been prepared in an embodiment of the present invention.

[0027] Figure 10 This is a schematic cross-sectional view of the DBR passivation layer after thinning in an embodiment of the present invention.

[0028] Figure 11 This is a schematic cross-sectional view of the Micro-LED device in Embodiment 1 of the present invention.

[0029] Figure 12 This is a cross-sectional structural diagram of the Micro-LED device in Embodiment 2 of the present invention.

[0030] Figure 13 This is a schematic cross-sectional view of the Micro-LED device in Embodiment 3 of the present invention.

[0031] Figure 14 This is a cross-sectional structural diagram of the Micro-LED device in Embodiment 4 of the present invention.

[0032] Figure 15 This is a cross-sectional structural diagram of the Micro-LED device in Embodiment 5 of the present invention.

[0033] In the figure: 1-substrate, 2-GaN-based LED epitaxial layer, 201-P-type layer, 202-quantum well light-emitting layer, 203-N-type layer; 3-P-electrode metal layer, 4-driving substrate, 401-metal bump array, 402-metal contact, 5-Micro-LED pixel unit, 6-DBR passivation layer, 7-passivation opening, 8-independent electrode, 9-microlens, 10-full-surface transparent electrode, 11-N-electrode wiring. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0035] This application provides a Micro-LED device, such as... Figure 11 , 13 As shown, it includes a driving substrate 4 with a driving circuit, Micro-LED pixel units 5 arrayed on the driving substrate 4, an N electrode, and a DBR layer 6. The Micro-LED pixel unit 5 comprises, from bottom to top, a metal bonding layer, a P-type layer 201, a quantum well light-emitting layer 202, and an N-type layer 203; the Micro-LED pixel unit 5 is bonded to the driving substrate 4 through the metal bonding layer and electrically connected to the driving circuit. The metal bonding layer has a 201-ohm contact with the P-type layer, and the N-electrode has a 203-ohm contact with the N-type layer; DBR layer 6 covers the sidewalls of Micro-LED pixel unit 5, fills the trenches between Micro-LED pixel units 5 and forms a planarized surface. The upper surface of DBR layer 6 is flush with the upper surface of Micro-LED pixel unit 5. DBR layer 6 is formed by alternating periodic stacking of high refractive index dielectric material and low refractive index dielectric material.

[0036] In some embodiments, the alternation period between high-refractive-index and low-refractive-index media is 5 to 20. An alternation period of 5 to 20 is used to achieve higher reflectivity while simultaneously achieving better trench filling.

[0037] In some embodiments, the high refractive index medium material is TiO2, Al2O3, or SiN. x One or more of the following; the low refractive index medium is SiO2. TiO2 / SiO2 has the highest refractive index contrast (approximately 1.71), exhibiting extremely high reflectivity and the widest high-reflectivity band, making it the preferred choice when pursuing the highest reflectivity and widest bandwidth. SiN x SiO2 has a moderate refractive index (approximately 1.37) contrast, excellent overall performance, low optical loss, full compatibility with CMOS processes in driving substrates, easy integration, good fabrication repeatability, and high reliability. Al2O3 / SiO2 has the lowest refractive index (approximately 1.37) contrast, but exhibits extremely low optical loss, excellent film quality, and good mechanical and chemical stability.

[0038] In some embodiments, the N electrode is an independent electrode 8 disposed separately on each Micro-LED pixel unit 5, or a fully transparent electrode 10. It should be noted that using a fully transparent electrode 10 can avoid the problem of light blocking by metal electrodes, thereby further improving the light extraction efficiency.

[0039] In some embodiments, the material of the independent electrode 8 is CrAu or AlTiAu, and the material of the full-surface transparent electrode 10 is ITO. The independent electrode 8 forms an ohmic contact and a common cathode structure with the N-type layer, making the current distribution more uniform throughout the screen; the full-surface transparent electrode 10 forms an ohmic contact and a common cathode structure with the N-type layer, but there may be a problem of current spread.

[0040] In some embodiments, the N electrode is provided with N electrode wiring 11, such as Figure 14 As shown. The N-electrode wiring 11 can effectively conduct current to each pixel of the display screen, achieving better current expansion effect. Combined with the transparent electrode 10, it can effectively avoid the problems of light blocking by metal electrodes and ITO current expansion.

[0041] In some embodiments, a microlens 9 is further provided on the Micro-LED pixel unit, such as... Figure 12 ,15 As shown, the center of microlens 9 coincides with the center of Micro-LED pixel unit 5, and the size of microlens 9 is larger than the size of Micro-LED pixel unit 5. The larger size of microlens 9 compared to Micro-LED pixel unit 5 is to achieve better light collimation.

[0042] This application also provides a method for fabricating a Micro-LED device, including the following steps, such as... Figure 1-11 As shown: S1. A GaN-based LED epitaxial layer 2 is grown on substrate 1. The GaN-based LED epitaxial layer 2 includes an N-type layer 203, a quantum well light-emitting layer 202, and a P-type layer 201 from bottom to top. It should be noted that the GaN-based epitaxial layer refers to an epitaxial layer system with gallium nitride (GaN) as the main body and containing gallium nitride materials such as InGaN and AlInGaN. S2. Prepare a P-electrode metal layer 3 on the surface of the P-type layer 201; S3. Prepare a metal bump array 401 on the surface of the driving substrate 4; S4. Bond the GaN-based LED epitaxial layer 2 to the driving substrate 4, with the bonding surface being the P-electrode metal layer 3 and the metal bump array 401. S5. Remove substrate 1 to expose GaN-based LED epitaxial layer 2; S6. Etch GaN-based LED epitaxial layer 2. The GaN-based LED epitaxial layer 2 forms an array of light-emitting mesa, which corresponds to the metal bump array 401. S7. Etch away the P-electrode metal layer 3 between the light-emitting mesa to form an array of Micro-LED pixel units 5; the Micro-LED pixel unit 5 includes the light-emitting mesa and the P-electrode metal layer 3 below it and a metal bump array unit. S8. The DBR layer 6 is grown on the entire surface. The DBR layer 6 fills the trenches between the Micro-LED pixel units 5 and completely covers the Micro-LED pixel units 5. The DBR layer 6 is formed by alternating and periodically stacking high-refractive-index dielectric materials and low-refractive-index dielectric materials. It should be noted that the thickness of each dielectric material in the DBR layer 6 is related to the wavelength of the light emitted by the Micro-LED pixel unit. The specific thickness can be obtained by calculation. S9. The DBR layer 6 is planarized by chemical mechanical polishing until the N-type layer 203 is exposed; S10. Prepare the N electrode to complete the fabrication of the Micro-LED device.

[0043] As an optional embodiment of the preparation method of the present invention, the method further includes the following steps: S11. Prepare microlens thin film material on the entire surface; S12. A hemispherical etching mask with an array distribution is formed using photolithography and photoresist thermal reflow technology. Then, the microlens thin film material prepared in S11 is etched by ICP to form an array of microlenses 9. Each microlens corresponds one-to-one with a Micro-LED pixel unit 5. The microlenses further improve the collimation of light and can improve the light extraction efficiency of Micro-LEDs, thereby increasing the overall luminous intensity of Micro-LEDs.

[0044] In some embodiments, the microlens film material is a PECVD-grown SiO2 film or spin-coated glass (SOG, QOG).

[0045] In some embodiments, step S5 further includes thinning the N-type layer 203 to make the thickness of the GaN-based LED epitaxial layer 2 between 1µm and 1.5µm; the method for thinning the N-type layer 203 is chemical mechanical polishing, using an alkaline polishing slurry; or the method for thinning the N-type layer 203 is inductively coupled plasma etching, using a mixture of Cl2 and BCl3 as the etching gas. It should be noted that thinning the GaN-based LED epitaxial layer 2 to below 1.5µm is beneficial for the subsequent fabrication of the light-emitting layer pixel separation, and the N-type layer at this point is a heavily doped layer, which can achieve N-type ohmic contacts without affecting the subsequent fabrication of the N-electrode.

[0046] In some embodiments, the abrasive particles in the alkaline polishing slurry are SiO2 particles with a particle size of less than 200 nm. The smaller the abrasive particle size, the better the polishing uniformity and the smaller the surface roughness.

[0047] In some embodiments, the method for etching the GaN-based LED epitaxial layer 2 in step S6 is thermal phosphoric acid etching, and the etched light-emitting mesa has a dodecagonal structure. The micro-LED sidewalls formed by thermal phosphoric acid etching have almost no sidewall damage caused by ICP etching, which is more conducive to the fabrication of high-efficiency micro-LED pixels.

[0048] In some embodiments, the method for etching the GaN-based LED epitaxial layer 2 in step S6 is ICP etching, the etching gas is a mixture of Cl2 and BCl3, and the etching rate is about 10 Å to 20 Å.

[0049] In some embodiments of this application, in step S7, the P-electrode metal layer 3 between the light-emitting mesa is etched away. First, IBE or ICP etching is used to etch the P-electrode metal layer 3, and then a gold etchant is used to remove residual metal. It should be noted that using a combination of dry and wet etching methods helps prevent the light-emitting mesa from detaching due to side-drilling during wet etching. Using a gold etchant after dry etching to remove residual metal prevents metal sputtering onto the GaN sidewalls during etching, thus preventing leakage channels and improving device fabrication yield.

[0050] The following are some embodiments of this application. The embodiments of the present invention will further describe in detail each technical step and process parameter in the preparation process. Example 1

[0051] This embodiment provides a method for fabricating a Micro-LED device, including the following steps: Step S1: Grow a GaN-based LED epitaxial layer 2 on substrate 1. The GaN-based LED epitaxial layer 2 includes, from bottom to top, an N-type layer 203, a quantum well light-emitting layer 202, and a P-type layer 201, as follows: Figure 1 As shown.

[0052] In this design, substrate 1 is a silicon substrate, N-type layer 203 is an N-type GaN layer, quantum well light-emitting layer 202 is an InGaN / GaN multiple quantum well, and P-type layer 201 is a P-type GaN layer. The dominant wavelength of light emitted by quantum well light-emitting layer 202 is 570nm. The thickness of substrate 1 is 1mm, the thickness of N-type layer 203 is 2~4µm, and the total thickness of GaN-based LED epitaxial layer 2 is 2.5~5.5µm.

[0053] Step S2: A P-electrode metal layer 3 is prepared on the surface of the P-type layer 201 using a metal deposition method. The material of the P-electrode metal layer 3 is CrAu. Figure 2 As shown.

[0054] Step S3: Provide a driving substrate 4, which is a CMOS driving substrate, and has metal contacts 402 on it. A metal bump array 401 is fabricated on the surface of the driving substrate 4 using a metal lift-off process. The metal bump array 401 is electrically connected to and corresponds one-to-one with the metal contacts 402, such as... Figure 3 As shown.

[0055] Step S4: The GaN-based LED epitaxial layer 2 is thermo-bonded to the driving substrate 4, with the bonding surface being the P-electrode metal layer 3 and the metal bump array 401, as shown below. Figure 4 As shown.

[0056] Step S5: Remove substrate 1 to expose GaN-based LED epitaxial layer 2, as shown below. Figure 5 As shown. The method for removing substrate 1 involves first thinning substrate 1 to 30μm-80μm using a mechanical thinning device, and then removing the thinned substrate 1 by wet etching with a mixed solution of nitric acid / hydrofluoric acid / acetic acid. In addition, the N-type layer 203 is thinned using a chemical mechanical thinning (CMP) device, so that the thickness of the GaN-based LED epitaxial layer 2 is approximately 1µm~1.5µm. Figure 6 As shown, the polishing slurry used for CMP thinning of the N-type layer 203 is an alkaline polishing slurry, and the polishing particles are SiO2 polishing particles.

[0057] Step S6: First, a specific etching mask pattern is formed on the surface of the GaN-based LED epitaxial layer 2 using photolithography. Then, the GaN-based LED epitaxial layer 2 is etched using wet etching technology, isolating the GaN-based LED epitaxial layer 2 to form an array of light-emitting mesa surfaces, which correspond to the metal bump array 401. The wet etching uses thermal phosphoric acid, and the etched light-emitting mesa surfaces have a dodecagonal frustum structure, such as... Figure 7 As shown.

[0058] Step S7: Remove the P-electrode metal layer 3 between the light-emitting mesa using a wet etching process to form an array of Micro-LED pixel units 5; the Micro-LED pixel unit 5 includes the light-emitting mesa and the P-electrode metal layer 3 below it, and a metal bump array unit, such as... Figure 8 As shown. The wet etching process uses a gold etching solution, which is a mixture of I2, KI and water.

[0059] Step S8: Grow the DBR layer 6 over the entire surface. The DBR layer 6 fills the trenches between the Micro-LED pixel units 5 and completely covers the Micro-LED pixel units 5, as shown below. Figure 9 As shown. DBR layer 6 consists of 12 pairs of SiN x It is formed by alternating growth of SiN and SiO2, with each layer of SiN... x The thickness is 71.25 nm, and the thickness of each SiO2 layer is 97.6 nm.

[0060] Step S9: Planarize the DBR layer 6 using a chemical mechanical thinning (CMP) apparatus until the N-type layer 203 is exposed, as shown. Figure 10 As shown. The polishing slurry used for CMP thinning of DBR layer 6 is an alkaline polishing slurry, and the polishing particles are SiO2 polishing particles.

[0061] Step S10: An independent electrode 8 is fabricated on the surface of the N-type layer 203 of each Micro-LED pixel unit 5, making ohmic contact with it. The material of the independent electrode 8 is AlTiAu, thus completing the fabrication of the Micro-LED device. Figure 11 As shown.

[0062] This embodiment also provides a Micro-LED device, which is prepared by the preparation method provided in this embodiment, such as... Figure 11As shown, the system includes a driving substrate 4 with a driving circuit, Micro-LED pixel units 5 arrayed on the driving substrate 4, individual electrodes 8 disposed on each Micro-LED pixel unit 5, and a DBR layer 6. The driving substrate 4 is a CMOS driving substrate, and the driving circuit includes metal contacts 402. The Micro-LED pixel unit 5, from bottom to top, comprises a metal bonding layer (formed by bonding the metal bump array unit with the P-electrode metal layer 3), a P-type layer 201, a quantum well light-emitting layer 202, and an N-type layer 203. The Micro-LED pixel unit 5 is bonded to the driving substrate 4 via the metal bonding layer and electrically connected to the driving circuit. The metal bonding layer has an ohmic contact with the P-type layer 201, and the N-electrode has an ohmic contact with the N-type layer 203. The DBR layer 6 covers the sidewalls of the Micro-LED pixel unit 5, fills the trenches between the Micro-LED pixel units 5, and forms a planarized surface. The upper surface of the DBR layer 6 is flush with the upper surface of the Micro-LED pixel unit 5. DBR layer 6 consists of 12 pairs of SiN x It is formed by periodic stacking of SiO2.

[0063] The Micro-LED device provided in this embodiment uses a DBR layer to cover the sidewalls of the Micro-LED pixel units, filling the trenches between the Micro-LED pixel units and forming a planarized surface. This not only achieves passivation of the Micro-LED pixel unit sidewalls and planarization of the Micro-LED device surface, but also enables sidewall reflection, reducing the light emission angle. In this embodiment, the light emission angle of the Micro-LED pixel units can be controlled between 70° and 90°. Example 2

[0064] The fabrication method of the Micro-LED device provided in this embodiment is basically the same as that in Embodiment 1, except that it also includes the following steps: Step S11: Prepare a layer of spin-coated glass (QOG) on the entire surface and cure at 180°C.

[0065] Step S12 involves forming an array of hemispherical etching masks using photolithography and photoresist thermal reflow techniques. Then, the microlens film material prepared in S11 is etched using ICP etching to form an array of microlenses 9. Each microlens corresponds one-to-one with a Micro-LED pixel unit 5. Figure 12 As shown.

[0066] The Micro-LED device prepared in this embodiment, such as Figure 12 As shown, by fabricating microlenses on the Micro-LED pixel unit, the light emission angle is further reduced. In this embodiment, the light emission angle is between 30° and 50°. Example 3

[0067] The fabrication method of the Micro-LED device provided in this embodiment is basically the same as that in Embodiment 1, except that the N-electrode prepared in step S10 is a fully transparent electrode 10, such as... Figure 13 As shown. The transparent electrode 10 is made of ITO. Using a transparent electrode can avoid the metal electrode blocking light and improve the light extraction rate. Example 4

[0068] The fabrication method of the Micro-LED device provided in this embodiment is basically the same as that in Embodiment 3, except that N-electrode wiring 11 is fabricated on the entire transparent electrode 10, such as... Figure 14 As shown, the N-electrode wiring 11 enables more uniform current distribution. Example 5

[0069] The fabrication method of the Micro-LED device provided in this embodiment is basically the same as that in Embodiment 4, except that a microlens 9 is fabricated on the Micro-LED pixel unit 5, such as... Figure 15 As shown.

[0070] The Micro-LED device prepared in this embodiment has a full-surface transparent electrode 10, an N-electrode wiring 11, and a microlens 9. The use of a transparent electrode can avoid the metal electrode blocking light and improve the light extraction rate. The N-electrode wiring can make the current spread more uniform, while the microlens can further reduce the light emission angle. The combination of the three can better improve the display effect.

[0071] The embodiments regarding the manufacturing method in this application only describe the manufacturing process or steps. Device structures, shapes, and materials not described herein can be referred to the above embodiments regarding Micro-LED devices, and will not be repeated here. The resulting Micro-LED devices can be further used in electronic devices, including but not limited to: augmented reality (AR) display devices, virtual reality (VR) display devices, near-eye displays (NEDs), and head-up displays (HUDs).

[0072] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0073] The present invention has been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only for the purpose of helping to understand the technical solutions and core ideas of the present invention. Those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A Micro-LED device, characterized in that: It includes a driving substrate with driving circuitry, Micro-LED pixel units arrayed on the driving substrate, an N-electrode, and a DBR layer; The Micro-LED pixel unit comprises, from bottom to top, a metal bonding layer, a P-type layer, a quantum well light-emitting layer, and an N-type layer; the Micro-LED pixel unit is bonded to the driving substrate through the metal bonding layer and electrically connected to the driving circuit; The metal bonding layer is in ohmic contact with the P-type layer, and the N-electrode is in ohmic contact with the N-type layer; The DBR layer covers the sidewalls of the Micro-LED pixel unit, fills the trenches between the Micro-LED pixel units, and forms a planarized surface. The upper surface of the DBR layer is flush with the upper surface of the Micro-LED pixel unit. The DBR layer is formed by alternating and periodically stacking high-refractive-index dielectric materials and low-refractive-index dielectric materials.

2. The Micro-LED device according to claim 1, characterized in that: The alternation period between the high-refractive-index medium material and the low-refractive-index medium material is 5 to 20.

3. The Micro-LED device according to claim 1, characterized in that: The high refractive index dielectric material is TiO2, Al2O3, or SiN. x One or more of the following; the low refractive index medium material is SiO2.

4. The Micro-LED device according to claim 1, characterized in that: The N electrode is an independent electrode located on each Micro-LED pixel unit, or a transparent electrode covering the entire surface.

5. The Micro-LED device according to claim 4, characterized in that: The N electrode has N electrode wiring.

6. The Micro-LED device according to any one of claims 1-5, characterized in that: The Micro-LED pixel unit is also provided with a microlens, the center of which coincides with the center of the Micro-LED pixel unit, and the size of the microlens is larger than the size of the Micro-LED pixel unit.

7. A method for fabricating a Micro-LED device, characterized in that, Includes the following steps: S1. A GaN-based LED epitaxial layer is grown on a substrate, wherein the GaN-based LED epitaxial layer comprises, from bottom to top, an N-type layer, a quantum well light-emitting layer, and a P-type layer; S2. Prepare a P-electrode metal layer on the surface of the P-type layer; S3. Fabricate a metal bump array on the surface of the driving substrate; S4. Bond the GaN-based LED epitaxial layer to the driving substrate. The bonding surface is a P-electrode metal layer and a metal bump array. S5. Remove the substrate to expose the GaN-based LED epitaxial layer; S6. Etch the GaN-based LED epitaxial layer, wherein the GaN-based LED epitaxial layer forms an array of light-emitting mesa, and the light-emitting mesa corresponds to the metal bump array; S7. Etch away the P-electrode metal layer between the light-emitting mesa to form an array of Micro-LED pixel units; the Micro-LED pixel unit includes the light-emitting mesa and the P-electrode metal layer below it and a metal bump array unit. S8. A DBR layer is grown across the entire surface. The DBR layer fills the trenches between Micro-LED pixel units and completely covers the Micro-LED pixel units. The DBR layer is formed by alternating and periodically stacking high-refractive-index dielectric materials and low-refractive-index dielectric materials. S9. The DBR layer is planarized by chemical mechanical polishing until the N-type layer is exposed; S10. Prepare the N electrode to complete the fabrication of the Micro-LED device.

8. The preparation method according to claim 7, characterized in that, It also includes the following steps: S11. Prepare microlens thin film material on the entire surface; S12. A hemispherical etching mask with an array distribution is formed by photolithography and photoresist thermal reflow technology, and then the microlens thin film material is etched with ICP etching technology to form microlenses with an array distribution. The microlenses correspond one-to-one with the Micro-LED pixel units.

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