A GaN self-luminous lens Micro-LED and a preparation method thereof

Abstract

The application provides a GaN self-light-emitting lens Micro-LED and a preparation method thereof, wherein the structure of the self-light-emitting semiconductor layer is arranged as a microlens or a micro-lens-like structure with a light condensing effect, the whole self-light-emitting semiconductor layer is covered by a semiconductor passivation layer, a passivation layer through hole is arranged at a position corresponding to the N-type semiconductor layer on the semiconductor passivation layer, a current spreading layer is deposited on the surface of the semiconductor passivation layer, and the current spreading layer is in contact with the N-type semiconductor layer through the passivation layer through hole, specifically, the active layer for light emission is wholly arranged in the microlens, three functions of material-optoelectronic-optical are homogeneously integrated, the problem of thermal mismatch caused by the heterojunction interface is completely eliminated, and the probability of photon escape is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor technology, in particular to a GaN self-luminous lens Micro-LED and a preparation method thereof. BACKGROUND

[0002] As the core of the next generation display technology, Micro-LED displays based on III-V compound semiconductors have higher efficiency, lower energy consumption, higher brightness and longer life than liquid crystal displays. However, one of the core challenges is the light efficiency decay of micron-sized pixels (<20 μm): when the chip size is reduced, more than 80% of the light energy is trapped inside the chip due to total internal reflection.

[0003] Currently, common methods for improving the light extraction efficiency of GaN include using GaN surface roughening process, using polymer microlens, and using inorganic dielectric layer microlens. However, these methods have different drawbacks, for example, the GaN surface roughening process can cause random scattering angles, resulting in degradation of light field uniformity; traditional polymer microlenses (such as SU-8 / PDMS) can achieve high-precision light shaping control, but the fundamental defects of organic materials result in serious shortcomings: the significant difference in thermal expansion coefficient between polymer and GaN chip (GaN: 5.3×10 -6 / K, PDMS: 310×10 -6 / K) can easily cause interface peeling or lens cracking after more than 10,000 thermal cycles. Although inorganic oxide microlenses (such as SiO2 / ZrO2) formed by nanoimprinting or inkjet shaping improve thermal stability, the process involves: discrete lens manufacturing → high-precision assembly → bonding glue filling process, and the cumulative alignment deviation of multi-stage processing can cause adjacent pixel crosstalk in a Micro-LED array with micron-sized pixel spacing. SUMMARY

[0004] Therefore, the purpose of the present application is to provide a GaN self-luminous lens Micro-LED and a preparation method thereof, aiming to prepare a Micro-LED device with high brightness and narrow beam angle.

[0005] According to one of the GaN self-luminous lens Micro-LEDs in the embodiments of the present application, the GaN self-luminous lens Micro-LED comprises a driving substrate, a driving substrate metal layer, a chip bonding metal layer and a self-luminous semiconductor layer which are sequentially stacked;

[0006] The driving substrate metal layer is composed of a negative electrode metal layer and a positive electrode metal layer spaced from the negative electrode metal layer, the chip bonding metal layer and the self-luminous semiconductor layer are sequentially arranged on the positive electrode metal layer, and the self-luminous semiconductor layer comprises a P-type semiconductor layer, an active semiconductor layer and an N-type semiconductor layer which are sequentially stacked;

[0007] The structure of the self-luminous semiconductor layer is a micro-lens or micro-lens-like structure with light condensing effect, and the whole self-luminous semiconductor layer is covered by a semiconductor passivation layer, a passivation layer through hole is formed on the semiconductor passivation layer corresponding to the position of the N-type semiconductor layer, and a current spreading layer is deposited on the surface of the semiconductor passivation layer and contacts the N-type semiconductor layer through the passivation layer through hole.

[0008] Further, the bottom size of the self-luminous semiconductor layer is less than or equal to the surface size of the corresponding chip bonding metal layer.

[0009] Further, the bottom width of the self-luminous semiconductor layer is 0.1 μm to 10 μm.

[0010] Further, the material of the chip bonding metal layer is any one or a combination of several of Ni, Cr, Pt and Au.

[0011] Further, the material of the current spreading layer is any one or a combination of several of Al, Ti, Ni, Cr, Pt and Au, or the current spreading layer is a transparent material.

[0012] According to the preparation method of the GaN self-luminous lens Micro-LED in one of the embodiments of the present application, the above-mentioned GaN self-luminous lens Micro-LED is prepared, and the method comprises:

[0013] A driving substrate is provided, and a first photoetching is performed on the driving substrate to prepare a driving substrate metal layer;

[0014] An epitaxial wafer is provided, which comprises a substrate, an AlN preparation layer and an initial self-luminous semiconductor layer stacked in sequence, and an initial chip bonding metal layer is evaporated on the initial self-luminous semiconductor layer;

[0015] The initial chip bonding metal layer with the epitaxial wafer is bonded with the driving substrate metal layer;

[0016] The substrate is removed to expose the AlN preparation layer;

[0017] The AlN preparation layer is thinned to the end of the initial self-luminous semiconductor layer;

[0018] A second photoetching is performed on the initial self-luminous semiconductor layer, a patterned photoresist mask is used to etch the whole structure of the initial self-luminous semiconductor layer into a micro-lens / micro-lens-like shape, and the initial chip bonding metal layer at the interval of the driving substrate metal layer is removed;

[0019] An initial semiconductor passivation layer is prepared on the self-luminous semiconductor layer, and a third photolithography is performed to open a passivation layer via hole on the initial semiconductor passivation layer at a position corresponding to the N-type semiconductor layer;

[0020] An initial current spreading layer is prepared, and a fourth photolithography is performed to coat the semiconductor passivation layer and the passivation layer via hole.

[0021] Further, the thickness of the initial chip bonding metal layer is 10-100 nm.

[0022] Further, the step of performing the second photolithography on the initial self-luminous semiconductor layer using a patterned photoresist mask comprises:

[0023] A positive photoresist material is coated on the initial self-luminous semiconductor layer, and after photolithography, the photoresist remaining for etching the self-luminous semiconductor layer into a microlens / micro-lens-like structure covers the rest of the area without a photoresist mask.

[0024] The photoresist is heated to partially reflow to form a patterned photoresist mask.

[0025] Further, in the step of etching the initial self-luminous semiconductor layer into a microlens / micro-lens-like shape, the etching uses a gas combination of BCl3 / Cl2 / Ar, the ICP power is 200-400 W, the RF power is 100-200 W, the BCl3 / Cl2 gas ratio is controlled to be 0.2-10, the Ar gas flow is 5-100 sccm, and the etching time is 200-800 s.

[0026] Further, in the step of preparing an initial current spreading layer and performing a fourth photolithography to coat the semiconductor passivation layer and the passivation layer via hole, the material of the finally prepared current spreading layer is Cr / Au, which is prepared by electron beam evaporation, the thickness of Cr is 5-10 nm, and the thickness of Au is 10-100 nm.

[0027] The GaN self-luminous lens Micro-LED and the preparation method thereof provided in the embodiment of the application, by setting the structure of the self-luminous semiconductor layer into a microlens or micro-lens-like structure with a light collecting effect, and the whole self-luminous semiconductor layer is coated by a semiconductor passivation layer, the semiconductor passivation layer has a passivation layer via hole at a position corresponding to the N-type semiconductor layer, and the surface of the semiconductor passivation layer is deposited with a current spreading layer, the current spreading layer is in contact with the N-type semiconductor layer through the passivation layer via hole, specifically, the whole active layer for emitting light is included in the microlens to form a material-optoelectronic-optical three-function homogeneous integration, which improves the probability of photon escape and completely eliminates the problem of thermal mismatch caused by heterogeneous interfaces. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 Structure diagram of two GaN self-luminous lens Micro-LEDs;

[0029] Figure 2 Structure diagram of an epitaxial wafer and an initial chip bonding metal layer;

[0030] Figure 3 Structure diagram of an initial chip bonding metal layer with an epitaxial wafer and a driving substrate metal layer bonding;

[0031] Figure 4 Structure diagram of an epitaxial wafer and a driving substrate metal layer bonding after removing a substrate;

[0032] Figure 5 Structure diagram of an epitaxial wafer and a driving substrate metal layer bonding for thinning an AlN preparation layer;

[0033] Figure 6 Structure diagram of an initial self-luminous semiconductor layer with a mask;

[0034] Figure 7 Structure diagram of a self-luminous semiconductor layer with a mask inherited from patterning;

[0035] Figure 8 Structure diagram of a self-luminous semiconductor layer with a passivation layer via.

[0036] Explanation of the component symbols in the drawings:

[0037] Driving module 100, driving substrate 101, driving substrate metal layer 102, chip bonding metal layer 201, self-luminous semiconductor layer 202, semiconductor passivation layer 203, passivation layer via 204, current spreading layer 205, cathode metal layer 1021, anode metal layer 1022, P-type semiconductor layer 2021, active semiconductor layer 2022, N-type semiconductor layer 2023, substrate 301, AlN preparation layer 302, initial chip bonding metal layer 210, initial self-luminous semiconductor layer 220, initial P-type semiconductor layer 2201, initial active semiconductor layer 2202, initial N-type semiconductor layer 2203, patterned mask 400. DETAILED DESCRIPTION

[0038] The present application can be realized in many different ways and is not limited to the embodiments described herein. Rather, the embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the application to those skilled in the art.

[0039] It is to be understood that where an element such as a layer, region or substrate is described as being "on" another element, it can be directly on the other element or intervening elements can also be present. Where an element is described as being "connected" or "coupled" to another element, it can be directly connected or coupled or intervening elements can be present. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0041] Embodiment one

[0042] The embodiment one of the application provides a GaN self-luminous lens Micro-LED, please refer to Figure 1 , which is a structural schematic diagram of two GaN self-luminous lens Micro-LEDs, wherein the GaN self-luminous lens Micro-LED comprises a driving substrate 101, a driving substrate metal layer 102, a chip bonding metal layer 201 and a self-luminous semiconductor layer 202 which are sequentially stacked, and the driving substrate 101 and the driving substrate metal layer 102 constitute a driving module 100.

[0043] The driving substrate metal layer 102 is composed of a cathode metal layer 1021 and an anode metal layer 1022 which is spaced from the cathode metal layer 1021, the chip bonding metal layer 201 and the self-luminous semiconductor layer 202 are sequentially arranged on the anode metal layer 1022, and the self-luminous semiconductor layer 202 comprises a P-type semiconductor layer 2021, an active semiconductor layer 2022 and an N-type semiconductor layer 2023 which are sequentially stacked. It should be noted that the material of the chip bonding metal layer 201 is any one or a combination of Ni, Cr, Pt and Au, and the bottom size of the self-luminous semiconductor layer 202 is less than or equal to the surface size of the corresponding chip bonding metal layer 201, that is, the metal reflection area is greater than the light-emitting area of the self-luminous semiconductor layer 202. In addition, the material of the driving substrate metal layer 102 is a Cr / Au laminated metal, and the thickness of each layer of metal is: the thickness of Cr is 20-30 nm, and the thickness of Au is 400-1200 nm. It can be understood that in the embodiment, the area size of the driving substrate metal layer 102 is greater than or equal to the bottom area of the corresponding self-luminous semiconductor layer 202, mainly to be able to fully reflect the emitted light back, specifically, the bottom width of the self-luminous semiconductor layer 202 is 0.1-10 μm.

[0044] The self-luminous semiconductor layer 202 has a micro-lens or micro-lens-like structure with light focusing effect, and the whole self-luminous semiconductor layer 202 is covered by a semiconductor passivation layer 203, and a passivation layer through hole 204 is formed on the semiconductor passivation layer 203 corresponding to the position of the N-type semiconductor layer 2023. It can be understood that the opening position of the passivation layer through hole 204 is located on the top or side of the self-luminous semiconductor layer 202, and corresponds to part of the N-type semiconductor layer 2023, avoiding the position of the active semiconductor layer 2022. The surface of the semiconductor passivation layer 203 is deposited with a current spreading layer 205, the current spreading layer 205 is in contact with the N-type semiconductor layer 2023 through the passivation layer through hole 204, and the material of the current spreading layer 205 is any one or a combination of Al, Ti, Ni, Cr, Pt and Au, or the current spreading layer 205 is a transparent material such as ITO and conductive glass with good conductivity. In the embodiment of the present application, the finally prepared current spreading layer 205 is a Cr / Au laminated metal structure, which is prepared by electron beam evaporation, the thickness of Cr is 5-10 nm, and the thickness of Au is 10-100 nm.

[0045] In the embodiment of the present application, the whole self-luminous semiconductor layer 202 formed by etching has a hemispherical micro-lens structure, which can have certain light focusing effect in physical geometric properties. In some other embodiments of the present application, the whole structure of the self-luminous semiconductor layer 202 can also be a micro-lens or micro-lens-like structure with light focusing effect in physical geometric properties, such as ellipsoid, prism, pyramid, prism table, etc.

[0046] It should be noted that the P-type semiconductor layer 2021 in the self-luminous semiconductor layer 202 is electrically connected to the independently addressable and controllable anode metal layer 1022 through the chip bonding metal layer 201, realizing the function of single chip single control. Further, after the driving substrate 101 is powered on, the current will flow from the cathode metal layer 1021 to the N-type semiconductor layer 2023 in the structure of the self-luminous semiconductor layer 202. The N-type semiconductor layer 2023 is an N-type GaN material, and N-GaN has certain conductivity after silicon doping, which can be used as a general N electrode on one side of the self-luminous semiconductor layer 202. The current spreading layer 205 is in contact with the N-type semiconductor layer 2023 of the self-luminous semiconductor layer 202 through the passivation layer through hole 204, thereby realizing good ohmic contact.

[0047] It can be understood that when the GaN self-luminous lens Micro-LED appears in an array form, the cathode metal layer 1021 can be a common cathode annular metal layer, and the anode metal layer 1022 can be in the form of a bump array.

[0048] It should be noted that the GaN self-emitting lens in the embodiment of the present application integrates the entire active layer of light emission into the microlens, which is equivalent to placing the light source inside the lens, and the chip is the entire lens structure. Although it is different from the mainstream GaN lens structure which divides the GaN lens and the GaN chip body, and regards them as separate structures which have an up-down positional relationship in space, the GaN self-emitting lens in the present application still has all the advantages of the current GaN homogeneous lens.

[0049] The GaN-GaN homogeneous optical interface is realized, and the problems such as cracking or interface peeling of the lens caused by the large difference in expansion coefficients of the traditional heterogeneous lens (PDMS: 310x10 -6 / K), silicon oxide (0.5x10 -6 / K) and GaN (5.3x10 -6 / K), and more than 35% Fresnel reflection loss caused by the sudden change of the refractive index of the heterogeneous interface in the light extraction process of the heterogeneous lens structure are solved.

[0050] It should be further explained that the GaN self-emitting lens in the embodiment of the present application is directly etched with a microlens structure on the epitaxial light-emitting layer, which is different from the case where the GaN light-emitting area and the GaN lens are independent of each other and have a relative positional relationship. The epitaxial light-emitting layer as a light source and n-GaN, p-GaN and other structures together form a hemispherical lens structure, and are not distinguished separately.

[0051] Embodiment two

[0052] The embodiment two of the present application provides a preparation method of a GaN self-emitting lens Micro-LED, which simultaneously prepares two GaN self-emitting lens Micro-LEDs, and comprises steps S01 to S08.

[0053] Step S01, providing a driving substrate, and performing first photoetching on the driving substrate to prepare a driving substrate metal layer.

[0054] Please refer to Figure 1 , the driving substrate metal layer 102 is composed of a cathode metal layer 1021 and an independently addressable and controllable anode metal layer 1022 spaced from the cathode metal layer 1021, which is prepared on the driving substrate 101 by a conventional photoetching and stripping metal process. In the embodiment of the present application, the material of the driving substrate metal layer 102 is a Cr / Au laminated metal, and the thickness of each layer of metal is: the thickness of Cr is 10-30 nm, and the thickness of Au is 700-1000 nm.

[0055] Further, before evaporating the material of the driving substrate metal layer 102 after finishing the photoetch process, the photoetch residue which may not be developed completely in the pattern area can be removed by treating with oxygen plasma, wherein the power of the oxygen plasma is 200W~600W, and the treatment time is 3min~15min.

[0056] In step S02, an epitaxial wafer is provided, which comprises a substrate, an AlN preparation layer and an initial self-luminous semiconductor layer which are stacked in sequence, and an initial chip bonding metal layer is evaporated on the initial self-luminous semiconductor layer.

[0057] Referring to Figure 2 Fig. 3 is a structural schematic diagram of the epitaxial wafer and the initial chip bonding metal layer, wherein the substrate 301 is a Si substrate, and the initial chip bonding metal layer 210 is evaporated on the initial self-luminous semiconductor layer 220 and away from the substrate 301, wherein the initial self-luminous semiconductor layer 220 comprises an initial P-type semiconductor layer 2201, an initial active semiconductor layer 2202 and an initial N-type semiconductor layer 2203 which are arranged in sequence towards the substrate 301.

[0058] Specifically, the material of the initial chip bonding metal layer 210 is a Ni / Au laminated material, the thickness of Ni is 0.1nm~0.5nm, the thickness of Au is 10nm~30nm, and the thickness of the finally prepared initial chip bonding metal layer 210 is 10nm~100nm. The design of the initial chip bonding metal layer 210 aims to meet the requirement of bonding strength and has the light transmission property at the same time, and the thin thickness is beneficial to the etching process of removing the initial chip bonding metal layer 210 below in step S06.

[0059] In addition, after the initial chip bonding metal layer 210 is evaporated, annealing can be performed in a nitrogen atmosphere at 550℃ for 5min~10min to improve the adhesion of the initial chip bonding metal layer 210 and the epitaxial wafer.

[0060] In step S03, the initial chip bonding metal layer with the epitaxial wafer is bonded with the driving substrate metal layer.

[0061] Referring to Figure 3 Fig. 4 is a structural schematic diagram of the initial chip bonding metal layer with the epitaxial wafer and the driving substrate metal layer which are bonded, wherein the wafer bonding machine is used to bond the initial chip bonding metal layer 210 with the epitaxial wafer and the driving substrate metal layer 102, and the hot-press bonding method is used to realize the electrical connection of the two, specifically, the hot-press bonding conditions are as follows: the bonding pressure is 300kg, the bonding temperature is 350℃, and the holding time is 1800s, in addition, the bonding process is in a vacuum state all the time, and the bonding in the vacuum state is helpful to improve the wafer bonding yield.

[0062] Step S04, removing the substrate and exposing the AlN preparation layer.

[0063] Referring to Figure 4 The structure schematic diagram of the epitaxial wafer bonded with the driving substrate metal layer after removing the substrate, the specific process of removing the silicon substrate includes: thinning by using a wafer grinding machine to remove most of the silicon material, and then removing the remaining silicon material by using a plasma etching method to expose the AlN preparation layer 302. The combined gas used in the plasma dry etching is SF6 and C4F8, and the thickness of the remaining silicon substrate removed by the plasma etching method is 100 μm to 200 μm.

[0064] Step S05, thinning the AlN preparation layer to the end of the initial self-luminous semiconductor layer.

[0065] Referring to Figure 5 The structure schematic diagram of the epitaxial wafer bonded with the driving substrate metal layer after thinning the AlN preparation layer, the method of thinning the AlN preparation layer 302 is achieved by plasma etching, and the etching gas used is BCl3, and the thickness of the AlN preparation layer 302 removed by the plasma etching method is 140 nm to 280 nm.

[0066] In addition, after removing the AlN preparation layer 302 by using BCl3, the surface needs to be cleaned by using a solution of hydrochloric acid: water = 1:1 to remove the possible residual B-Ga-N polymer to prevent the impact on the subsequent process.

[0067] Step S06, implementing a second photoetching on the initial self-luminous semiconductor layer, using a patterned photoresist mask to etch the overall structure of the initial self-luminous semiconductor layer into a microlens / micro-lens-like shape, and removing the initial chip bonding metal layer at the interval of the driving substrate metal layer.

[0068] Referring to Figure 6 The structure schematic diagram of the initial self-luminous semiconductor layer with a mask, specifically, the photoresist material is coated on the initial self-luminous semiconductor layer 220, the patterned mask 400 is prepared by using photoetching and reflow, and then the initial self-luminous semiconductor layer 220 below the patterned mask 400 is etched by using a plasma etching method, so that the initial self-luminous semiconductor layer 220 after etching can inherit the topography of the patterned mask 400 to obtain the self-luminous semiconductor layer 202, as shown in Figure 7 The structure schematic diagram of the self-luminous semiconductor layer inheriting the patterned mask. Then, the initial chip bonding metal layer 210 at the interval of the driving substrate metal layer 102 is also etched clean to obtain the final cathode metal layer 1021 and the anode metal layer 1022 spaced from the cathode metal layer 1021.

[0069] It should be noted that the step of using a patterned photoresist mask includes:

[0070] A positive photoresist material 5312-20 is coated on the initial self-luminous semiconductor layer 220 at a rotation speed of 3000 rpm and a coating thickness of 0.99 μm. After photoetching, the photoresist is reserved for etching the initial self-luminous semiconductor layer 220 into a microlens / micro-lens-like structure, and the remaining area is not covered by the photoresist mask, wherein the size of the mask pattern is 1 μm to 2 μm.

[0071] The photoresist is heated and partially reflowed to form a patterned photoresist mask. It can be understood that the special shape with an arc at the top is formed by using the characteristics of photoresist thermal reflow. The reflow temperature is maintained at 240°C, and the reflow time is 40 min to 60 min.

[0072] Specifically, in the step of etching the initial self-luminous semiconductor layer 220 into a microlens / micro-lens-like shape, BCl3 / Cl2 / Ar gas combination is used for etching, the ICP power is 200 W to 400 W, the RF power is 100 W to 200 W, the BCl3 / Cl2 gas ratio is controlled to be 0.2 to 10, the Ar gas flow is 5 sccm to 100 sccm, and the etching time is 200 s to 800 s. It can be understood that the radius of curvature of the final lens is the size of the Micro-LED unit, which is 1 μm to 20 μm.

[0073] In step S07, an initial semiconductor passivation layer is prepared on the self-luminous semiconductor layer, and a third photoetching is performed, and a passivation layer via hole is formed on the initial semiconductor passivation layer corresponding to the position of the N-type semiconductor layer.

[0074] Specifically, first, an initial semiconductor passivation layer is grown by PECVD (not shown in the figure). The material of the initial semiconductor passivation layer is SiN, the growth thickness is 200 nm to 800 nm, and the growth temperature is 220°C to 300°C. Then, an etching mask for the passivation layer via hole 204 is prepared by using a photoetching process. The mask at the position of the passivation layer via hole 204 is etched by plasma etching, and finally the semiconductor passivation layer 203 is obtained, and the self-luminous semiconductor layer 202 is exposed. After etching, the overall topography is shown in Figure 8 , which is a structural diagram of a self-luminous semiconductor layer with a passivation layer via hole.

[0075] It should be noted that the initial semiconductor passivation layer can be slowly grown in PECVD, with good film quality, which can improve the density of the passivation film. The growth rate is controlled at 0.05 nm / s to 0.2 nm / s, and the size of the passivation layer via hole 204 should be controlled at 0.1 μm to 0.5 μm.

[0076] Step S08, preparing an initial current spreading layer and implementing the fourth photolithography to coat the semiconductor passivation layer and the passivation layer via hole.

[0077] The material of the finally prepared current spreading layer 205 is Cr / Au, prepared by electron beam evaporation, the thickness of Cr is 5nm-10nm, and the thickness of Au is 10nm-100nm.

[0078] In some other embodiments of the application, the material of the current spreading layer 205 can be ITO, with a thickness of 100nm-200nm, prepared by magnetron sputtering, and ITO as a transparent conductive material can avoid the problem of light blocking caused by the metal material of the current spreading layer 205.

[0079] It can be found that the GaN self-luminescent lens Micro-LED prepared in the embodiments of the application only needs four steps of photolithography, and the preparation process is extremely simple, which not only significantly reduces the problem of the superposition of the precision error of the photolithography process and the photolithography machine, but also greatly improves the preparation efficiency of the device, which is conducive to large-scale commercial application. In addition, the problem of high-precision and high-density lens transfer integration is also overcome. The GaN self-luminescent lens structure can be manufactured in situ at the wafer level through photolithography, the alignment accuracy and density of the microlens are defined by the photolithography machine, and millions of microlenses can be prepared on a single wafer at one time, and the lens yield can also be controlled according to the semiconductor manufacturing standard.

[0080] Embodiment three

[0081] The embodiment three of the application provides a preparation method of a GaN self-luminescent lens Micro-LED, which is different from the embodiment two of the application in that the material of the semiconductor passivation layer in the embodiment three of the application is a SiN / SiO2 stacked DBR structure, so that the beam angle of the entire GaN self-luminescent lens Micro-LED device is further reduced, and the luminous brightness of the GaN self-luminescent lens Micro-LED device is improved.

[0082] Specifically, the semiconductor passivation layer adopts the SiN / SiO2 stacked DBR structure grown by ALD, and the number of the SiN / SiO2 stacked layers is 10 pairs-14 pairs, and the thickness is 1um-2um.

[0083] It should be noted that the SiN / SiO2 stacked DBR structure grown by ALD has a relatively large thickness, and the conventional opening etching process is easy to cause the aperture to expand, so that the active semiconductor layer in the self-luminescent semiconductor layer is exposed, and the risk of electric leakage is increased. Therefore, in the embodiment of the application, the passivation layer via hole is prepared by etching by using the Bosch process, the etching gas is SF6, the passivation gas is CHF3, and the etching and passivation steps are alternately performed.

[0084] In summary, the GaN self-light-emitting lens Micro-LED and the preparation method thereof in the embodiment of the present application, by setting the structure of the self-light-emitting semiconductor layer into a microlens or a micro-lens-like structure with a light condensing effect, and the whole self-light-emitting semiconductor layer is covered by a semiconductor passivation layer, a passivation layer through hole is arranged at the position corresponding to the N-type semiconductor layer on the semiconductor passivation layer, and a current spreading layer is deposited on the surface of the semiconductor passivation layer and is in contact with the N-type semiconductor layer through the passivation layer through hole, specifically, the active layer for light emission is entirely included in the microlens, forming a material-optoelectronic-optical three-function homogeneous integration, which improves the probability of photon escape and completely eliminates the thermal mismatch problem caused by the heterogeneous interface.

[0085] The above-mentioned embodiments only express several embodiments of the present application, and the description is more specific and detailed, but it cannot be understood as the limitation of the patent scope of the present application. It should be pointed out that for ordinary skilled in the art, without departing from the concept of the present application, several modifications and improvements can be made, which belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A GaN self-luminous lens Micro-LED, characterized in that: It includes a driving substrate, a driving substrate metal layer, a chip bonding metal layer and a self-luminous semiconductor layer stacked in sequence; The drive substrate metal layer is composed of a cathode metal layer and an anode metal layer spaced apart from the cathode metal layer, the chip bonding metal layer and the self-luminous semiconductor layer are sequentially arranged on the anode metal layer, and the self-luminous semiconductor layer includes a P-type semiconductor layer, an active semiconductor layer, and an N-type semiconductor layer stacked in sequence; In which, the structure of the self-luminous semiconductor layer is a microlens or a microlens-like structure with a focusing effect, and the self-luminous semiconductor layer is entirely covered by a semiconductor passivation layer, a passivation layer through-hole is opened on the semiconductor passivation layer at a position corresponding to the N-type semiconductor layer, a current spreading layer is deposited on the surface of the semiconductor passivation layer, and the current spreading layer is in contact with the N-type semiconductor layer through the passivation layer through-hole.

2. The GaN self-luminous lens Micro-LED according to claim 1, characterized in that: The bottom size of the self-luminous semiconductor layer is smaller than or equal to the surface size of the corresponding chip bonding metal layer.

3. The GaN self-luminous lens Micro-LED according to claim 2, characterized in that: The bottom width of the self-luminous semiconductor layer is 0.1 μm to 10 μm.

4. The GaN self-luminous lens Micro-LED according to claim 3, characterized in that: The material of the chip bonding metal layer is any one of Ni, Cr, Pt and Au, or a combination of several of them.

5. The GaN self-luminous lens Micro-LED according to claim 1, characterized in that: The material of the current spreading layer is any one of Al, Ti, Ni, Cr, Pt, and Au, or a combination of several of them, or the current spreading layer is a transparent material.

6. A method for preparing a GaN self-luminous lens Micro-LED, characterized in that: For preparing the GaN self-luminous lens Micro-LED according to any one of claims 1 to 5, the method comprises: Providing a driving substrate, performing a first photolithography on the driving substrate to prepare a driving substrate metal layer; Providing an epitaxial wafer, the epitaxial wafer comprising a substrate, an AlN preparation layer, and an initial self-luminous semiconductor layer stacked in sequence, and evaporating an initial chip bonding metal layer onto the initial self-luminous semiconductor layer; Bonding the initial chip bonding metal layer with the epitaxial wafer to the driving substrate metal layer; removing the substrate and exposing the AlN preparation layer; Thinning the AlN preparation layer to the initial self-luminous semiconductor layer and then stopping; Performing a second photolithography on the initial self-luminous semiconductor layer, using a patterned photoresist mask to etch the entire structure of the initial self-luminous semiconductor layer into a microlens / microlens-like shape, while removing the initial chip bonding metal layer at the intervals between the drive substrate metal layers; An initial semiconductor passivation layer is prepared on the self-luminous semiconductor layer and a third photolithography is performed, and a passivation layer through hole is opened at a position on the initial semiconductor passivation layer corresponding to the N-type semiconductor layer; An initial current spreading layer is prepared and a fourth photolithography is performed to cover the semiconductor passivation layer and the passivation layer through-hole.

7. The method for preparing a GaN self-luminous lens Micro-LED according to claim 6, characterized in that: The thickness of the initial chip bonding metal layer is 10nm-100nm.

8. The method for preparing a GaN self-luminous lens Micro-LED according to claim 6, characterized in that: The step of performing a second photolithography on the initial self-luminous semiconductor layer using a patterned photoresist mask comprises: A positive photoresist material is coated on the initial self-luminous semiconductor layer, and after photolithography, the photoresist used for etching the self-luminous semiconductor layer into a microlens / microlens-like structure is retained, and the remaining area is not covered by the photoresist mask; The photoresist is heated and partially reflowed to form a patterned photoresist mask.

9. The method for preparing a GaN self-luminous lens Micro-LED according to claim 6, characterized in that: In the step of etching the overall structure of the initial self-luminous semiconductor layer into a microlens / microlens-like shape, the etching adopts a gas combination of BCl3 / Cl2 / Ar, the ICP power is 200W~400W, the RF power is 100W~200W, the BCl3 / Cl2 gas ratio is controlled to be 0.2~10, the Ar gas flow rate is 5sccm~100sccm, and the etching time is 200s~800s.

10. The method for preparing a GaN self-luminous lens Micro-LED according to claim 6, characterized in that: In the steps of preparing the initial current spreading layer and performing the fourth photolithography to cover the semiconductor passivation layer and the passivation layer through-hole, the material of the current spreading layer finally prepared is Cr / Au, which is prepared by electron beam evaporation. The thickness of Cr is 5nm~10nm, and the thickness of Au is 10nm~100nm.

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