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

Abstract

The invention provides a GaN self-luminous lens Micro-LED and a preparation method thereof, the structure of a self-luminous semiconductor layer is set as a micro-lens or micro-lens-like structure with a condensation effect, the self-luminous semiconductor layer is wholly coated by a semiconductor passivation layer, and a passivation layer through hole is formed in a position, corresponding to an N-type semiconductor layer, on the semiconductor passivation layer, so that the GaN self-luminous lens Micro-LED is formed. A current expansion layer is deposited on the surface of the semiconductor passivation layer, the current expansion layer is in contact with the N-type semiconductor layer through a passivation layer through hole, specifically, a luminous active layer is integrally contained in the micro-lens, material-photoelectric-optical three-function homogeneous integration is formed, the photon escape probability is improved, and meanwhile the light emitting efficiency is improved. And the problem of thermal mismatch caused by a heterogeneous interface is thoroughly eliminated.

Description

Technical Field

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

[0002] Micro-LEDs, the core of next-generation display technology, are based on III-V compound semiconductors and offer higher efficiency, lower energy consumption, higher brightness, and longer lifespans than liquid crystal displays. However, one of the core challenges is the optical degradation of micron-sized pixels (<20μm). As chip size shrinks, total internal reflection (TIR) ​​traps over 80% of light energy within the chip.

[0003] Currently, common methods for improving GaN light emission include using GaN surface roughening technology, polymer microlenses, and inorganic dielectric layer microlenses. However, these solutions all have different disadvantages. For example, the GaN surface roughening process can lead to random scattering angles, resulting in degraded light field uniformity. Traditional polymer microlenses (such as SU-8 / PDMS) can achieve high-precision light shape control, but the fundamental defects of their organic materials lead to 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 delamination or lens cracking after more than 10,000 thermal cycles. While inorganic oxide microlenses (such as SiO2 / ZrO2) formed by nanoimprinting or inkjet printing offer improved thermal stability, the manufacturing process involves discrete lens fabrication, high-precision placement, and bonding adhesive filling. Accumulated alignment deviations from these multiple processing steps can cause crosstalk between adjacent pixels in micron-level pixel pitch micro-LED arrays. Summary of the Invention

[0004] Based on this, the purpose of the present invention 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 an embodiment of the present invention, a GaN self-luminous lens Micro-LED 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.

[0006] Furthermore, 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.

[0007] Furthermore, the bottom width of the self-luminous semiconductor layer is 0.1 μm to 10 μm.

[0008] Furthermore, the material of the chip bonding metal layer is any one of Ni, Cr, Pt and Au, or a combination of several of them.

[0009] Furthermore, the material of the current spreading layer is any one of Al, Ti, Ni, Cr, Pt, and Au, or a combination of several thereof, or the current spreading layer is a transparent material. According to an embodiment of the present invention, a method for preparing a GaN self-luminous lens Micro-LED is used to prepare the above-mentioned GaN self-luminous lens Micro-LED. The method includes: 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.

[0010] Furthermore, the thickness of the initial chip bonding metal layer is 10 nm to 100 nm.

[0011] Furthermore, the step of performing a second photolithography on the initial self-luminous semiconductor layer using a patterned photoresist mask includes: 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.

[0012] Furthermore, 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.

[0013] Furthermore, in the step 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, and the thickness of Cr is 5nm~10nm, and the thickness of Au is 10nm~100nm.

[0014] A GaN self-luminous lens Micro-LED and a preparation method thereof are provided in an embodiment of the present invention. The structure of the self-luminous semiconductor layer is set to 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 contacts the N-type semiconductor layer through the passivation layer through-hole. Specifically, the light-emitting active layer is entirely incorporated into the microlens to form a homogeneous integration of material, optoelectronics, and optics. While increasing the probability of photon escape, the thermal mismatch problem caused by the heterogeneous interface is completely eliminated. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 Schematic diagram of the structure of two GaN self-luminous lens Micro-LEDs; Figure 2 It is a schematic diagram of the structure of the epitaxial wafer and the initial chip bonding metal layer; Figure 3 It is a schematic diagram of the structure of bonding the initial chip bonding metal layer with the epitaxial wafer to the driving substrate metal layer; Figure 4This is a schematic diagram of the structure of the epitaxial wafer bonded to the metal layer of the driver substrate after the substrate is removed; Figure 5 Schematic diagram of the structure for bonding the epitaxial wafer with the AlN preparation layer to the metal layer of the driving substrate; Figure 6 Schematic diagram of the structure of the initial self-luminous semiconductor layer with a mask; Figure 7 A schematic structural diagram of a self-luminous semiconductor layer inheriting a patterned mask; Figure 8 Schematic diagram of the structure of a self-luminous semiconductor layer with a passivation layer through hole.

[0016] Component symbol description in the attached figure: 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 through hole 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, and patterned mask 400. DETAILED DESCRIPTION

[0017] The present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive.

[0018] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may be an intermediate element. When an element is referred to as being "connected to" another element, it may be directly connected to the other element or there may be an intermediate element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one skilled in the art to which this invention pertains. The terms used in this specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0020] Example 1 The first embodiment of the present invention provides a GaN self-luminous lens Micro-LED, see Figure 1 , is a schematic diagram of the structure of two GaN self-luminous lens Micro-LEDs, wherein the GaN self-luminous lens Micro-LED includes a driving substrate 101, a driving substrate metal layer 102, a chip bonding metal layer 201 and a self-luminous semiconductor layer 202 stacked in sequence, and the driving substrate 101 and the driving substrate metal layer 102 constitute a driving module 100; The drive substrate metal layer 102 is composed of a cathode metal layer 1021 and an anode metal layer 1022 spaced apart from the cathode metal layer 1021. The chip bonding metal layer 201 and the self-luminous semiconductor layer 202 are sequentially disposed on the anode metal layer 1022. The self-luminous semiconductor layer 202 includes a P-type semiconductor layer 2021, an active semiconductor layer 2022, and an N-type semiconductor layer 2023 stacked in sequence. It should be noted that the chip bonding metal layer 201 is made of any one or a combination of Ni, Cr, Pt, and Au, and the bottom dimensions of the self-luminous semiconductor layer 202 are less than or equal to the corresponding surface dimensions of the chip bonding metal layer 201, ensuring that the metal reflective area is greater than the luminous area of ​​the self-luminous semiconductor layer 202. Furthermore, the drive substrate metal layer 102 is made of a Cr / Au laminated metal, with the thickness of each metal layer being 20nm to 30nm for Cr and 400nm to 1200nm for Au. It can be understood that in this embodiment, the area 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 μm to 10 μm; Among them, the structure of the self-luminous semiconductor layer 202 is a microlens or a microlens-like structure with a focusing effect, and the self-luminous semiconductor layer 202 is entirely covered by a semiconductor passivation layer 203. A passivation layer through hole 204 is opened on the semiconductor passivation layer 203 at a position corresponding to the N-type semiconductor layer 2023. It can be understood that the opening position of the passivation layer through hole 204 is located at the top or side of the self-luminous semiconductor layer 202, corresponding to the N-type semiconductor layer 2023, avoiding the position of the active semiconductor layer 2022, and the surface of the semiconductor passivation layer 203 is deposited with a current diffusion layer. The current spreading layer 205 contacts the N-type semiconductor layer 2023 through the passivation layer through-hole 204. The material of the current spreading layer 205 is any one of Al, Ti, Ni, Cr, Pt, and Au, or a combination of several thereof. Alternatively, the current spreading layer 205 is a transparent material with good conductivity, such as ITO and conductive glass. In the embodiment of the present invention, the final current spreading layer 205 is a Cr / Au laminated metal structure prepared by electron beam evaporation. The thickness of Cr is 5nm~10nm, and the thickness of Au is 10nm~100nm.

[0021] In an embodiment of the present invention, the overall shape of the self-luminous semiconductor layer 202 formed by etching is a hemispherical microlens structure, which can have a certain focusing effect in physical geometric properties. In some other embodiments of the present invention, the overall structure of the self-luminous semiconductor layer 202 can also be an ellipsoid, prism, pyramid, prism, etc., which has a microlens or microlens-like structure with a focusing effect in physical geometric properties.

[0022] 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, thereby realizing the function of single chip single control. Furthermore, after the driving substrate 101 is energized, current will flow from the cathode metal layer 1021 through 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. N-GaN has a certain conductivity after being doped with silicon and can serve as a universal N-electrode on one side of the self-luminous semiconductor layer 202. The current spreading layer 205 contacts the N-type semiconductor layer 2023 of the self-luminous semiconductor layer 202 through the passivation layer through-hole 204, thereby achieving good ohmic contact.

[0023] It is understandable that when the GaN self-luminous lens Micro-LED appears in the form of an array, the cathode electrode metal layer 1021 can be a common cathode electrode ring metal layer, and the anode electrode metal layer 1022 can be in the form of a bump array.

[0024] It should be noted that the GaN self-luminous lens in the embodiments of the present invention incorporates the entire active layer of the light-emitting element into the microlens, effectively placing the light source within the lens. The chip constitutes the entire lens structure. While different from the mainstream GaN lens structure that separates the GaN lens from the GaN chip body and treats them as separate structures positioned vertically above each other, the GaN self-luminous lens in the present invention still retains all the advantages of existing GaN homogeneous lenses.

[0025] Achieved a GaN-GaN homogeneous optical interface, solving the polymer (PDMS: 310×10 -6 / K)、Silicon oxide (0.5×10 -6 / K) and GaN (5.3×10 -6 The large difference in expansion coefficient of the lens element (K) may lead to lens cracking or interface peeling, and the sudden change in the refractive index of the heterogeneous interface during the light collection process of the heterogeneous lens structure may cause Fresnel reflection loss of more than 35%.

[0026] It should be further explained that the GaN self-luminous lens in the embodiment of the present invention is a microlens structure directly etched on the epitaxial light-emitting layer. Unlike the conventional GaN light-emitting area and GaN lens, which are independent of each other and have a relative positional relationship, the epitaxial light-emitting layer serves as a light source and together with the n-GaN, p-GaN and other structures constitute a hemispherical lens structure, which is not separately distinguished.

[0027] Example 2 A second embodiment of the present invention provides a method for preparing a GaN self-luminous lens Micro-LED. The method for preparing a GaN self-luminous lens Micro-LED simultaneously prepares two GaN self-luminous lens Micro-LEDs, including steps S01 to S08. Specifically: Step S01 : providing a driving substrate, performing a first photolithography process on the driving substrate to prepare a driving substrate metal layer.

[0028] See also 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 separated from the cathode metal layer 1021. It is prepared on the driving substrate 101 by a traditional photolithography metal stripping process. In the embodiment of the present invention, the material of the driving substrate metal layer 102 is Cr / Au laminated metal, and the thickness of each metal layer is: the thickness of Cr is 10nm~30nm, and the thickness of Au is 700nm~1000nm.

[0029] Furthermore, after the photolithography process is completed and before the driving substrate metal layer 102 material is evaporated, oxygen plasma treatment can be used to remove the photoresist residue that may not be developed cleanly in the pattern area. The oxygen plasma power is 200W~600W and the treatment time is 3min~15min.

[0030] Step S02 : providing an epitaxial wafer, wherein the epitaxial wafer comprises 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.

[0031] See also Figure 2 , 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 located above the initial self-luminous semiconductor layer 220 and away from the substrate 301 after evaporation, wherein the initial self-luminous semiconductor layer 220 includes an initial P-type semiconductor layer 2201, an initial active semiconductor layer 2202, and an initial N-type semiconductor layer 2203 arranged in sequence toward the substrate 301.

[0032] Specifically, the initial chip bonding metal layer 210 is made of a Ni / Au laminate, with Ni having a thickness of 0.1 nm to 0.5 nm and Au having a thickness of 10 nm to 30 nm. The resulting initial chip bonding metal layer 210 has a thickness of 10 nm to 100 nm. The initial chip bonding metal layer 210 is designed to meet bonding strength requirements while also being light-transmissive. Furthermore, its thinness facilitates the etching process for removing the underlying initial chip bonding metal layer 210 in step S06.

[0033] In addition, after the initial chip bonding metal layer 210 is evaporated, it may be annealed in a nitrogen atmosphere at 550° C. for 5 min to 10 min to improve the adhesion between the initial chip bonding metal layer 210 and the epitaxial wafer.

[0034] Step S03 , bonding the initial chip bonding metal layer with the epitaxial wafer to the driving substrate metal layer.

[0035] See also Figure 3 , which is a structural diagram of the bonding of the initial chip bonding metal layer with the epitaxial wafer and the driving substrate metal layer, wherein a wafer bonding machine is used to bond the initial chip bonding metal layer 210 with the epitaxial wafer to the driving substrate metal layer 102, and hot pressing bonding is used to complete the electrical connection between the two. Specifically, the hot pressing bonding conditions are: bonding pressure of 300kg, bonding temperature of 350℃, and holding time of 1800s. In addition, the entire bonding process is in a vacuum state. Bonding under a vacuum state helps to improve the bonding yield of the wafer.

[0036] Step S04: removing the substrate and exposing the AlN preparation layer.

[0037] See also Figure 4 Figure 3 is a schematic diagram of the structure of the epitaxial wafer bonded to the metal layer of the driver substrate after substrate removal. The specific process for removing the silicon substrate includes thinning using a wafer grinder to remove most of the silicon material, followed by plasma etching to remove the remaining silicon material, exposing the AlN preparation layer 302. The plasma dry etching uses a combination of SF6 and C4F8 gases, and the remaining silicon substrate removed by the plasma etching method has a thickness of 100μm to 200μm.

[0038] Step S05 , thinning the AlN preparation layer to the initial self-luminous semiconductor layer and then stopping.

[0039] See also Figure 5 , which is a structural diagram of bonding the epitaxial wafer of the thinned AlN preparation layer to the metal layer of the driving substrate, the method of thinning the AlN preparation layer 302 is achieved by plasma etching, and the specific etching gas used is BCl3. The thickness of the AlN preparation layer 302 removed by the plasma etching method is 140nm~280nm.

[0040] In addition, after removing the AlN preparation layer 302 with BCl3, the surface needs to be cleaned with a solution of hydrochloric acid: water = 1:1 to remove any remaining B-Ga-N polymer to prevent it from affecting subsequent processes.

[0041] Step S06, 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, and simultaneously removing the initial chip bonding metal layer at the intervals between the driving substrate metal layers.

[0042] See also Figure 6 , is a schematic diagram of the structure of the initial self-luminous semiconductor layer with a mask. Specifically, a photoresist material is coated on the initial self-luminous semiconductor layer 220, and a patterned mask 400 is prepared by photolithography plus reflow. Then, a plasma etching method is used to etch the initial self-luminous semiconductor layer 220 below the patterned mask 400, so that the initial self-luminous semiconductor layer 220 can inherit the morphology of the patterned mask 400 after etching, thereby obtaining a self-luminous semiconductor layer 202, as shown in FIG. Figure 7 The figure shows a schematic diagram of the structure of the self-luminous semiconductor layer that inherits the patterned mask. Etching is then continued to completely etch the initial chip bonding metal layer 210 between the drive substrate metal layer 102, resulting in the final cathode metal layer 1021 and the anode metal layer 1022 between the cathode metal layer 1021.

[0043] It should be noted that the steps of using a patterned photoresist mask include: A positive photoresist material 5312-20 is coated on the initial self-luminous semiconductor layer 220 at a rotation speed of 3000 rpm to a coating thickness of 0.99 μm. After photolithography, the photoresist used to etch the initial self-luminous semiconductor layer 220 into a microlens / microlens-like structure is retained, and the remaining area is not covered by the photoresist mask, wherein the size of the mask pattern is 1 μm to 2 μm; The photoresist is heated and partially reflowed to form a patterned photoresist mask. It can be understood that the thermal reflow characteristics of the photoresist are utilized to form a special shape with a curvature on the top. The reflow temperature is maintained at 240°C and the reflow time is 40min~60min.

[0044] Specifically, in the step of etching the initial self-luminous semiconductor layer 220 into a microlens / microlens-like shape, a BCl3 / Cl2 / Ar gas combination is used, with an ICP power of 200W to 400W, an RF power of 100W to 200W, a BCl3 / Cl2 gas ratio of 0.2 to 10, an Ar gas flow rate of 5sccm to 100sccm, and an etching time of 200s to 800s. As will be appreciated, the radius of curvature of the final lens is the same as the size of the Micro-LED unit, which is 1μm to 20μm.

[0045] Step S07 , preparing an initial semiconductor passivation layer on the self-luminous semiconductor layer and performing a third photolithography, and opening a passivation layer through hole on the initial semiconductor passivation layer at a position corresponding to the N-type semiconductor layer.

[0046] Specifically, PECVD is first used to grow an initial semiconductor passivation layer (not shown). The initial semiconductor passivation layer is made of SiN with a thickness of 200nm to 800nm ​​at a temperature of 220°C to 300°C. Subsequently, a photolithography process is used to prepare an etching mask for the passivation layer through-holes 204. The mask is then etched using plasma etching at locations where the passivation layer through-holes 204 are to be formed, ultimately obtaining a semiconductor passivation layer 203 and exposing the self-luminous semiconductor layer 202. After etching, the overall morphology obtained is as follows: Figure 8 , which is a schematic structural diagram of a self-luminous semiconductor layer with a passivation layer through hole.

[0047] It should be noted that the initial semiconductor passivation layer can be grown slowly in PECVD with good film quality, which can improve the density of the passivation film. The growth rate is controlled at 0.05nm / s~0.2nm / s, and the size of the passivation layer through hole 204 should be controlled at 0.1μm~0.5μm.

[0048] Step S08 , preparing an initial current spreading layer and performing a fourth photolithography process to cover the semiconductor passivation layer and the passivation layer through-hole.

[0049] The material of the current spreading layer 205 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.

[0050] In some other embodiments of the present invention, the material of the current spreading layer 205 can be ITO, with a thickness of 100nm~200nm, and is prepared on the entire surface by magnetron sputtering. ITO, as a transparent conductive material, can avoid the light blocking problem that may be caused by the use of metal materials in the current spreading layer 205.

[0051] It can be found that the GaN self-luminous lens Micro-LED prepared in the embodiment of the present invention only requires four steps of lithography, and the preparation process is extremely simple. It not only significantly reduces the problem of superposition of precision errors of the lithography machine due to the complexity of the lithography process, but also greatly improves the preparation efficiency of the device, which is conducive to large-scale commercial applications. In addition, the problem of high-precision and high-density lens transfer integration is overcome. The GaN self-luminous lens structure can be manufactured in situ at the wafer level through lithography. The alignment accuracy and density of the microlens are defined by the lithography machine. The preparation of millions / tens of microlenses can be completed on a single wafer at one time, and the lens yield can also be controlled according to semiconductor manufacturing standards.

[0052] Example 3 Embodiment 3 of the present invention provides a method for preparing a GaN self-luminous lens Micro-LED. The difference from Embodiment 2 of the present invention is that the material of the semiconductor passivation layer in Embodiment 3 of the present invention is a SiN / SiO2 stacked DBR structure, which further reduces the beam angle of the entire GaN self-luminous lens Micro-LED device and improves the luminous brightness of the GaN self-luminous lens Micro-LED device.

[0053] Specifically, the semiconductor passivation layer adopts a SiN / SiO2 stacked DBR structure grown by ALD, the number of stacked pairs of SiN / SiO2 is 10 to 14 pairs, and the thickness is 1 μm to 2 μm.

[0054] It should be noted that the SiN / SiO2 stacked DBR structure grown by ALD is relatively thick. The conventional hole etching process easily leads to the expansion of the aperture, exposing the active semiconductor layer in the self-luminous semiconductor layer, and increasing the risk of leakage. Therefore, in an embodiment of the present invention, the passivation layer through-hole is prepared by etching using the Bosch process, the etching gas is SF6, and the passivation gas is CHF3, and the etching and passivation steps are performed alternately.

[0055] In summary, the GaN self-luminous lens Micro-LED and its preparation method in the embodiments of the present invention are achieved by setting the structure of the self-luminous semiconductor layer into 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, and 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 contacts the N-type semiconductor layer through the passivation layer through-hole. Specifically, the light-emitting active layer is entirely incorporated into the microlens to form a homogeneous integration of material, optoelectronics, and optics. While increasing the probability of photon escape, the thermal mismatch problem caused by the heterogeneous interface is completely eliminated.

[0056] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by 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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