CN116565103B

CN116565103B - Micro LED micro display chip and manufacturing method thereof

Info

Publication number: CN116565103B
Application number: CN202310825854.2A
Authority: CN
Inventors: 王晓楠; 顾银冬; 张盼盼; 庄永漳; 孙志鹏; 张庆
Original assignee: Laiyu Optoelectronic Technology Suzhou Co ltd
Current assignee: Laiyu Optoelectronic Technology Suzhou Co ltd
Priority date: 2023-07-06
Filing date: 2023-07-06
Publication date: 2023-09-08
Anticipated expiration: 2043-07-06
Also published as: CN116565103A

Abstract

The application discloses a micro LED micro display chip and a manufacturing method thereof, wherein the micro LED micro display chip comprises a driving substrate and a plurality of LED units, and each LED unit is independently driven; the step structure at least disconnects and electrically isolates the second doped semiconductor layers of adjacent LED units from each other; the first passivation layer covers the LED units, exposes the corresponding first contacts, and the second openings expose the second doped semiconductor layers of the corresponding LED units; and the metal reflecting cover is disconnected from each other and electrically isolated from the first passivation layer, is electrically connected with the second doping type semiconductor layer of the corresponding LED unit and is electrically connected with the corresponding first contact through the first opening. According to the application, the LED luminous angle is adjusted through the metal reflecting cover, so that the optical crosstalk between pixels is reduced; the metal reflecting cover is connected to the first contact and the second doped semiconductor layer, so that the resistance of the LED pixel can be reduced, and the overall power consumption is reduced.

Description

Micro LED micro display chip and manufacturing method thereof

Technical Field

The application belongs to the field of micro LED micro display chips, and particularly relates to a micro LED micro display chip and a manufacturing method thereof.

Background

The micro LED micro display chip is a micro LED array which is formed by integrating a plurality of single pixel elements in a high density manner, and each pixel point in the array can emit self light. The micro LED micro display chip has excellent performances of high brightness, high resolution and the like.

With the advent of micro led Display technology, miniaturization and high resolution of Display devices such as an augmented Reality (Augmented Reality, AR) Display device, a Virtual Reality (VR) Display device, a Near-Eye Display (NED), a Head Up Display (HUD) device, and the like have become possible.

However, during operation, the pixel resistance of the LED unit is high, resulting in a large overall power consumption of the micro LED micro display chip.

Disclosure of Invention

The application aims to provide a micro LED micro display chip and a preparation method thereof, which can reduce the pixel resistance of an LED unit.

Various aspects of embodiments of the application are described below.

In a first aspect, there is provided a micro led micro display chip comprising:

a drive substrate including a plurality of first contacts;

the LED units are arranged on the driving substrate in an array manner, each LED unit can be independently driven, and the first contact is positioned between the adjacent LED units; each LED unit has a step structure, and the LED unit is provided with a first doping type semiconductor layer, a second doping type semiconductor layer and an active layer positioned between the first doping type semiconductor layer and the second doping type semiconductor layer; the step structure at least disconnects and electrically isolates the second doping type semiconductor layers of adjacent LED units from each other;

A first passivation layer covering the LED units, the first passivation layer including a first opening exposing the corresponding first contact and a second opening exposing the second doped semiconductor layer of the corresponding LED unit;

a plurality of metal reflective caps covering the first passivation layer, the metal reflective caps covering the first passivation layer and surrounding the step structures corresponding to the LED units, adjacent ones of the metal reflective caps being disconnected from each other and electrically isolated;

the metal reflecting cover is electrically connected with the second doped semiconductor layer of the corresponding LED unit, and the metal reflecting cover is electrically connected with the corresponding first contact through the first opening.

In some embodiments, the metal reflective cap includes a third opening exposing the second doped semiconductor layer of the corresponding LED unit;

the micro LED micro display chip further comprises: the electrode layer is arranged on the metal reflecting cover and is used for electrically connecting the metal reflecting cover with the corresponding second doped semiconductor layer of the LED unit, the electrode layer is in contact with and is electrically connected with the second doped semiconductor layer through the second opening, and the electrode layer is in contact with and is electrically connected with the metal reflecting cover through the third opening.

In some embodiments, the micro LED micro display chip further includes a second passivation layer disposed between the metal reflective cap and the electrode layer, the second passivation layer being provided with a fourth hole exposing the second doped semiconductor layer of the corresponding LED unit.

In some embodiments, the projection of the fourth aperture in the vertical direction is not less than the projection of the third aperture in the vertical direction and exposes the third aperture.

In some embodiments, the projection of the third aperture in the vertical direction is not less than the projection of the second aperture in the vertical direction, and exposes the second aperture.

In some embodiments, the second aperture and the third aperture form a step.

In some embodiments, the second opening 1012, the third opening 1013, and the fourth opening 1014 form a step.

In some embodiments, the micro LED micro display chip further includes a bonding layer disposed between the driving substrate and the LED unit, and the bonding layer 60 is made of a metal material or a non-metal material.

In some embodiments, the metallic reflector is any one or a combination of gold, silver, aluminum, copper, titanium.

In some embodiments, the electrode layer is composed of one or more of Indium Tin Oxide (ITO), znO, AZO, ATO, FTO, snO.

In some embodiments, the first doping type semiconductor layers of adjacent LED units extend and are in contact with each other for sharing.

In a second aspect, the present application provides a method for manufacturing a micro led micro display chip, comprising:

providing a driving substrate, wherein the driving substrate comprises a driving circuit and a plurality of first contacts electrically connected with the driving circuit;

providing an LED epitaxial layer, wherein the LED epitaxial layer comprises a second doping type semiconductor layer, an active layer and a first doping type semiconductor layer; the LED epitaxial layer is arranged on the driving substrate and exposes the second doping type semiconductor layer;

etching the LED epitaxial layer downwards from the second doped semiconductor layer to form a plurality of LED units, wherein the LED units are arranged on the driving substrate in an array manner, each LED unit can be independently driven by the corresponding first contact, and the first contact is positioned between the adjacent LED units; each LED unit is provided with a step structure; the step structure at least disconnects and electrically isolates the second doping type semiconductor layers of adjacent LED units from each other;

Forming a first passivation layer, wherein the first passivation layer covers the LED unit, a first opening and a second opening are formed in the first passivation layer, the first opening exposes the corresponding first contact, and the second opening exposes the corresponding second doping type semiconductor layer of the LED unit;

forming a plurality of metal reflective caps which are disconnected from each other and electrically isolated from each other, wherein the metal reflective caps cover the first passivation layer and surround the step structures corresponding to the LED units; the metal reflecting cover is electrically connected with the second doped semiconductor layer of the corresponding LED unit, and the metal reflecting cover is electrically connected with the corresponding first contact through the first opening.

In some embodiments, the method further comprises:

forming a third opening on the metal reflective layer, the third opening exposing the second doped semiconductor layer of the corresponding LED unit (200);

and forming an electrode layer, wherein the electrode layer is arranged on the metal reflecting cover and is used for electrically connecting the metal reflecting cover with the second doped semiconductor layer of the corresponding LED unit, the electrode layer is in contact with and is electrically connected with the second doped semiconductor layer through the second opening, and the electrode layer is in contact with and is electrically connected with the metal reflecting cover through the third opening.

In some embodiments, the method further comprises: and after the metal reflecting cover is formed and before the electrode layer is formed, forming a second passivation layer on the metal reflecting cover, wherein the second passivation layer is provided with a fourth hole, and the fourth hole exposes the second doping type semiconductor layer of the corresponding LED unit.

In some embodiments, the first, second, third, and fourth openings are formed by dry etching.

In some embodiments, the second aperture, the third aperture, and the fourth aperture form a step.

In some embodiments, forming a plurality of metallic reflective caps that are disconnected from each other and electrically isolated, comprises:

forming a patterned sacrificial layer on the first passivation layer, the sacrificial layer exposing the LED unit and the first contact, and the sacrificial layer covering the second opening;

depositing a metal layer on the sacrificial layer;

and removing the sacrificial layer to form the plurality of metal reflecting covers.

depositing a metal layer on the first passivation layer;

and removing part of the metal layer by adopting an etching process so as to form the plurality of metal reflecting covers.

The beneficial technical effects obtained by the application are as follows:

according to the micro LED micro display chip provided by the application, the metal reflecting cover surrounds the step structure of the LED unit, the metal reflecting cover is electrically connected with the first contact on the driving substrate and the second doped semiconductor layer in the corresponding LED unit, the LED emits light only from the top, the LED emitting angle is adjusted through the metal reflecting cover, and the optical crosstalk between pixels is reduced. The LED pixel resistance can be reduced, and the overall power consumption of the micro LED micro display chip is reduced.

According to the micro LED micro display chip provided by the application, the projection of the third opening of the metal reflecting cover in the vertical direction is not smaller than the projection of the second opening in the vertical direction, and the second opening is exposed, so that the scattered light emitting area of the LED unit is increased, and the light emitting efficiency is improved.

According to the micro LED micro display chip provided by the application, the second opening, the third opening and the fourth opening form steps, so that the contact area between the electrode layer and the second passivation layer, the contact resistance is reduced, and the LED pixel resistance is further reduced.

According to the preparation method of the micro LED micro display chip, the LED light-emitting angle of the obtained micro LED micro display chip is adjusted through the metal reflecting cover, and optical crosstalk between pixels is reduced. The LED pixel resistance can be reduced, and the overall power consumption of the micro LED micro display chip is reduced.

Drawings

The technical solution and other advantageous effects of the present application will be made apparent by the following detailed description of the specific embodiments of the present application with reference to the accompanying drawings.

FIG. 1 is a schematic diagram of a micro LED micro display chip according to an embodiment of the present application;

FIG. 2 is a schematic diagram showing the structure of an LED unit in a micro LED micro display chip according to an embodiment of the present application;

FIG. 3 is a schematic view of an LED epitaxial layer structure according to an embodiment of the present application;

FIG. 4 is a schematic diagram showing a structure of a bonding layer formed on a driving substrate according to an embodiment of the present application;

FIG. 5 is a schematic diagram of a structure of an LED epitaxial layer structure after forming a bonding layer thereon in accordance with one embodiment of the present application;

FIG. 6 is a schematic diagram of a structure for bonding an LED epitaxial layer to a drive substrate and removing the substrate in accordance with one embodiment of the present application;

FIG. 7 is a schematic diagram showing the structure of the LED epitaxial layer thinned after the substrate is removed in accordance with one embodiment of the present application;

FIG. 8 is a schematic diagram of an embodiment of the present application for etching LED epitaxial layers to form an LED unit;

FIG. 9 is a top view of the structure of FIG. 8 etching the LED epitaxial layer to form an LED unit;

fig. 10 is a schematic view showing a structure after forming a hole groove and exposing a first contact according to an embodiment of the present application;

FIG. 11 is a top view of the structure of FIG. 10 after forming the aperture slot and exposing the first contact;

FIG. 12 is a schematic diagram of a structure after forming a first passivation layer and forming a first opening and a second opening on the first passivation layer according to an embodiment of the present application;

FIG. 13 is a top view of the structure of FIG. 12 after forming a first passivation layer and opening a first opening and a second opening in the first passivation layer;

FIG. 14 is a schematic diagram showing a structure after forming a metal reflector and forming a third opening in the metal reflector according to an embodiment of the present application;

FIG. 15 is a top view of the structure of FIG. 14 after forming a metal reflector and forming a third opening in the metal reflector;

FIG. 16 is a schematic diagram of a structure after forming a second passivation layer and forming a fourth opening in the second passivation layer according to an embodiment of the present application;

reference numerals:

10-driving substrate, 101-first contact, 20-LED epitaxial layer, 200-LED unit, 201-light exit surface, 210-first doped semiconductor layer, 220-second doped semiconductor layer, 230-active layer, 240-first passivation layer, 250-metal reflector, 260-second passivation layer, 270-electrode layer, 30-substrate, 60-bonding layer, 501-via, 1011-first opening, 1012-second opening, 1013-third opening, 1014-fourth opening, 2071-first mesa, 2072-second mesa, 2073-third mesa, 2074-fourth mesa.

Detailed Description

The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. It will be apparent that the described embodiments are only some, but not all, embodiments of the application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to fall within the scope of the application.

The disclosure of the present application provides many different embodiments or examples for implementing different structures of the application. In order to simplify the present disclosure, components and arrangements of specific examples are described herein. They are, of course, merely examples and are not intended to limit the application. Furthermore, the present application may repeat reference numerals and/or letters in the various examples, which are for the purpose of brevity and clarity, and which do not themselves indicate the relationship between the various embodiments and/or arrangements discussed. In addition, the present application provides examples of various specific processes and materials, but one of ordinary skill in the art will recognize the application of other processes and/or the use of other materials.

Generally, the terminology may be understood, at least in part, in light of the above usage of the application. For example, the term "one or more" as used herein depends at least in part on the application and may be used to describe any component, structure or feature in the singular or may be used to describe any combination of components, structures or features in the plural. Similarly, terms such as "a," "an," or "the" may also be construed to convey a singular usage or a plural usage depending, at least in part, on the application above. In addition, the term "based on …" may be understood as not necessarily intended to convey an exclusive set of factors, but rather as may be dependent, at least in part, upon the above that the application may instead allow for the presence of additional factors that are not necessarily explicitly described.

It should be readily understood that the meanings of "on …", "on …" and "on …" in the present application should be interpreted in the broadest sense such that "on …" means not only "directly on something" but also "on something" including intermediate members or layers present therebetween, and "on something" or "on something" means not only "on something" or "on something" but also "on something" without intermediate members or layers therebetween.

Furthermore, spatially relative terms, such as "under …," "under …," "lower," "above …," "upper," "lower," and the like, may be used herein for ease of description to describe one element or component's relationship to another element or component illustrated in the figures. In addition to the orientations depicted in the drawings, the spatially relative terms are intended to encompass different orientations of the device in use or operation. The device may be rotated 90 deg. in other orientations or in other orientations and the spatially relative descriptors used in the present application may be interpreted accordingly as such.

The term "layer" as used in the present application refers to a portion of material comprising regions having a certain thickness. The layers may extend over the entire underlying or overlying structure, or may have a degree less than the extent of the underlying or overlying structure. Furthermore, the layer may be a region of homogeneous or heterogeneous continuous structure having a thickness less than the thickness of the continuous structure. For example, the layer may be located between the top and bottom surfaces of the continuous structure or between any pair of horizontal planes therebetween. The layers may extend horizontally, vertically and/or along a tapered surface. The substrate may be a layer, may include one or more layers therein, and/or may have one or more layers thereon, and/or thereon. One layer may comprise multiple layers. For example, the semiconductor layer may include one or more doped or undoped semiconductor layers, and may have the same or different materials.

In the description of the present application, "micro" LEDs, "micro" devices are used to refer to descriptive dimensions of certain devices or structures according to embodiments of the present application. The size of the micro led micro display chip herein is 0.1-10 microns. However, it should be appreciated that embodiments of the present application are not necessarily limited thereto, and that certain aspects of the embodiments may be applicable to larger and possibly smaller dimensional scales.

In some embodiments, the drive substrate 10 may comprise a semiconductor material, such as silicon, silicon carbide, silicon nitride, germanium, gallium arsenide, cobalt phosphide. In some embodiments, the drive substrate 10 may be made of a non-conductive material, such as glass, plastic, or sapphire wafers.

In some embodiments, the driving substrate 10 may have a driving circuit formed therein, and the driving substrate 10 may be a CMOS (Complementary Metal Oxide Semiconductor ) back plate or a TFT glass substrate. The driving circuit supplies an electrical signal to the LED unit 200 to control brightness. In some embodiments, the driving circuit may comprise an active matrix driving circuit, wherein each individual LED unit 200 has a corresponding independent driver.

In some embodiments, the term drive substrate 10 used in the present application refers to a material to which a subsequent material layer is added. The drive substrate 10 itself may be patterned. The material added to the top of the drive substrate may be patterned or may remain unpatterned.

In some embodiments, the drive substrate 10 is bonded to the LED epitaxial layers 20 by a bonding layer 60. The functional epitaxial layer is partially patterned/etched and allows a thin continuous functional layer and bonding layer 60 to remain to avoid potential functional pixel lift-off. In addition, the manufacturing method in the application can further reduce the physical damage of the side wall of the functional pixel, reduce the damage of the quantum well structure of the light emitting area as the pixel point, and improve the optical and electrical properties of the functional pixel.

In some embodiments, the bonding layer 60 may include a conductive material, such as a metal or metal alloy. In some embodiments, the bonding layer 60 may include Au, sn, in, cu or Ti. In some embodiments, the bonding layer 60 may include a non-conductive material, such as Polyimide (PI), polydimethylsiloxane (PDMS). In some embodiments, the bonding layer 60 may include a photoresist, such as SU-8 photoresist. In some embodiments, the bonding layer 60 may be Hydrogen Silsesquioxane (HSQ) or divinyl siloxane-bis-benzocyclobutene (DVS-BCB).

However, in some embodiments, the bonding layer 60 may include one or more layers to bond the driving substrate 10 and the first doping type semiconductor layer 210. For example, the bonding layer 60 may include a single conductive layer or a non-conductive layer.

For another example, bonding layer 60 may include an adhesive material and a conductive or non-conductive layer. In some embodiments, the conductive layer may form a common electrode covering the first doping type semiconductor layer 210. In some embodiments, the conductive layer may form an ohmic contact on the first doping type semiconductor layer 210. In some embodiments, the conductive layer and the bonding layer 60 may be collectively referred to as a layer in a later operation.

It should be understood that the description of the material of the bonding layer 60 is merely illustrative and not limiting, and that one skilled in the art may vary as desired, all of which are within the scope of the present application.

The substrate 30 serves as a growth carrier for the LED epitaxial layers 20, which may be sapphire, silicon carbide, silicon, or the like.

Fig. 1 is a schematic cross-sectional view of a micro led micro display chip according to an embodiment of the present application. As shown in fig. 1, the micro led micro display chip may include a driving substrate 10, the driving substrate 10 including a plurality of first contacts 101;

A plurality of LED units 200, the LED units 200 being arranged in a row on the driving substrate 10 with first contacts 101 between adjacent LED units 200, each LED unit 200 being individually driven through a corresponding first contact 101; each of the LED units 200 has a stepped structure, and has a first doping type semiconductor layer 210, a second doping type semiconductor layer 220, and an active layer 230 therebetween; the step structure disconnects and electrically isolates at least the second doping type semiconductor layers 220 of adjacent LED units 200 from each other;

a first passivation layer 240, the first passivation layer 240 including a first opening 1011 and a second opening 1012, the first passivation layer 240 covering the LED unit 200, the first opening 1011 exposing the first contact 101, the second opening 1012 exposing the second doped semiconductor layer 220 of the corresponding LED unit;

a plurality of metal reflective caps 250, which are electrically isolated from each other, the metal reflective caps 250 covering the first passivation layer 240 and surrounding the step structures of the corresponding LED units,

the metal reflective caps 250 are electrically connected to the second doped semiconductor layers 220 of the corresponding LED units 200, and the metal reflective caps 250 are electrically connected to the corresponding first contacts 101 through the first openings 1011.

According to the micro LED micro display chip provided by the embodiment, the metal reflecting cover surrounds the step structure of the LED unit, and the metal reflecting cover is electrically connected with the first contact on the driving substrate and the second doped semiconductor layer in the corresponding LED unit, so that the resistance of an LED pixel can be reduced, and the overall power consumption of the micro LED micro display chip is reduced. The light emitted by the LED can only exit from the light emitting surface of the second doped semiconductor layer 220, and the light emitting angle of the LED is adjusted by the metal reflective cover, so as to reduce the optical crosstalk between pixels. Micro LED in some embodiments, the metal reflector 250 includes a third opening 1013, the third opening 1013 exposing the second doped semiconductor layer 220 of the corresponding LED unit 200;

The micro LED micro display chip further includes an electrode layer 270, where the electrode layer 270 is disposed on the metal reflective cap 250, and is used to electrically connect the metal reflective cap 250 with the second doped semiconductor layer 220 of the corresponding LED unit 200, and the electrode layer 270 is in contact with and electrically connected to the second doped semiconductor layer 220 through the second opening 1012, and the electrode layer 270 is in contact with and electrically connected to the metal reflective cap 250 through the third opening 1013.

The first passivation layer 240 and the metal reflective cover 250 expose the light-emitting surface 201 of the LED unit 200 through the second and third openings 1012 and 1013, respectively. The electrode layer 270 is a transparent conductive oxide having light transmitting and conductive properties.

The plurality of LED units 200 may be arranged on the driving substrate 10 in a regular or irregular manner as pixels of the micro LED micro display chip. The plurality of LED units 200 may have a plurality of LED step structures corresponding to the plurality of LED units 200 one by one, and the LED units 200 may also be referred to as micro LED units, and the size of the LED units 200 is 0.1 to 10 micrometers, preferably, the size of the LED units 200 is less than 5 micrometers.

In some embodiments, the plurality of LED step structures may be trapezoidal in configuration. The side wall of the LED step structure may be an inclined surface, and an included angle between the side wall and the top surface of the LED step structure may be an obtuse angle, so that a light condensing effect of the LED unit 200 may be improved. It should be understood that the plurality of LED mesas may also be in a columnar configuration, where the included angle between the sidewalls and the top surface of the LED mesa structure is a right angle (i.e., slanted or perpendicular).

Referring to fig. 1, the micro LED micro display chip includes a driving substrate 10 and a plurality of LED units 200, the driving substrate 10 includes a plurality of first contacts 101, the LED units 200 are disposed on the driving substrate 10, the first contacts 101 are located between adjacent LED units 200, and a bonding layer 60, a first passivation layer 240, and a metal reflective cap 250 are disposed on the LED units 200.

As shown in fig. 10, the bonding layer 60 is penetratingly provided with a plurality of hole grooves 501, and the bottoms of the hole grooves 501 expose at least the first contacts 101. Alternatively, the hole groove 501 may also expose a part of the driving substrate 10.

As shown in fig. 12, the first passivation layer 240 covers the LED unit 200, and optionally, the first passivation layer 240 also covers sidewalls of the bonding layer 60.

The first passivation layer 240 is provided with a first opening 1011 and a second opening 1012, wherein the first opening 1011 communicates with the hole 501 and exposes the first contact 101, and the second opening 1012 exposes the top light-emitting surface 201 of the LED unit 200 (e.g., the top surface of the second doped semiconductor layer 220 in fig. 1).

The first passivation layer 240 serves to protect and isolate the LED unit 200.

The first passivation layer 240 may include SiO2, a12O3, siN, or other suitable material, or the first passivation layer 240 may include polyimide, SU-8 photoresist, or other photopatternable polymer.

In some embodiments, the LED unit 200 includes a stepped structure formed by etching the LED epitaxial layer 20, the stepped structure including a first doped semiconductor layer 210, a second doped semiconductor layer 220, and an active layer 230 therebetween; the step structure disconnects and electrically isolates at least the second doping type semiconductor layers 220 of adjacent LED units 200 from each other; the light-emitting surface 201 is located on the second doped semiconductor layer 220, and the light-emitting surface 201 is located at the top of the step structure.

The first doped semiconductor layer 210 is a continuous functional layer structure, and the second doped semiconductor layer 220 is etched to form the LED unit 200.

The first doped semiconductor layer 210 extends across a plurality of LED units 200 and forms a common anode for these LED units 200, with electrical isolation between the second doped semiconductor layers 220 of different LED units 200, so that each LED unit 200 may have a cathode with a different voltage level than the other units. The active layer 230 is a multiple quantum well layer (MQW), and electrons and holes recombine in the quantum well region to generate photons, thereby realizing light emission.

In some embodiments, the first doped semiconductor layer 210 may be a P-type semiconductor layer that extends across a plurality of LED units 200 and forms a common anode of the LED units 200. In some embodiments, the first doping type semiconductor layers 210 of adjacent LED units 200 extend from each other and are in contact with each other to be common.

In some embodiments, the first doped semiconductor layer 210 and the second doped semiconductor layer 220 may include one or more layers based on IIVI materials (such as ZnSe or ZnO) or IIIV nitride materials (such as GaN, alN, inN, inGaN, gaP, alInGaP, alGaAs and alloys thereof). In some embodiments, the first doped semiconductor layer 210 is p-type gallium nitride and the second doped semiconductor layer 220 is n-type gallium nitride. As shown in fig. 1, the micro LED micro display chip further includes a metal reflective cap 250, the metal reflective cap 250 covers the first passivation layer 240, the top of the metal reflective cap 250 includes a third opening 1013, the third opening 1013 penetrates the metal reflective cap 250 to expose the second doped semiconductor layer 220 of the LED unit 200, and the metal reflective cap 250 is electrically connected to the first contact 101 through the first opening 1011 on the first passivation layer 240. The first contacts 101 are electrically connected with the corresponding LED units 200 through the metal reflective covers 250, so that the LED units 200 are individually driven through the first contacts 101.

The metallic reflector 250 is a high reflectivity material, and in some embodiments any one or a combination of gold, silver, aluminum, copper, titanium may be used, with silver having the highest emissivity in the visible band. In some embodiments, to improve the adhesion of silver, multi-metal combined electrodes of Ti/Ag, ag/Al/Ni, etc. may be utilized to achieve both low contact resistance and high reflectivity. The thickness of the metal reflective cover 250 needs to be controlled to 20 nm-200 nm.

In some embodiments, the micro LED micro display chip further includes a second passivation layer 260, the second passivation layer 260 being disposed between the metal reflective cap 250 and the electrode layer 270, and including a fourth opening 1014, the fourth opening 1014 communicating the second opening 1012 and the third opening 1013 and exposing the second doped semiconductor layer 220 of the LED unit.

The second passivation layer 260 is the same as the first passivation layer 240 and may include SiO2, a12O3, siN, or other suitable material, or the first passivation layer 240 may include polyimide, SU-8 photoresist, or other photopatternable polymer.

In some embodiments, the electrode layer 270 is in contact with and electrically connected to the second doped semiconductor layer 220 through the second opening 1012, and the electrode layer 270 is in contact with and electrically connected to the metal reflective cap 250 through the third opening 1013.

The contact surface between the electrode layer 270 and the second passivation layer 260 forms a first mesa 2701 as in fig. 2, the contact surface between the electrode layer 270 and the metal reflective cap 250 forms a second mesa 2702 as in fig. 2, the contact surface between the electrode layer 270 and the first passivation layer 240 forms a third mesa 2703 as in fig. 2, and the electrode layer 270 and the second doped semiconductor layer 220 of the LED unit 200 form a fourth mesa 2704 as shown in fig. 2. The first mesa 2701, the second mesa 2702, the third mesa 2703 and the fourth mesa 2704 form a stepped shape, which increases the contact area between the electrode layer 270 and the metal reflective cap 250, reduces the contact resistance, and reduces the LED pixel resistance.

With continued reference to fig. 2, the contact between the electrode layer 270 and the second passivation layer 260, the contact between the electrode layer 270 and the metal cap 250, and the contact between the electrode layer 270 and the first passivation layer 240 also form sidewalls, the contact area of which is related to the thickness of the first passivation layer 240, the metal cap 250, and the second passivation layer 260, and the coverage area of the tops of the adjacent structures. In particular embodiments, this may be provided as desired.

In some embodiments, the electrode layer 270 may cover only sidewalls of the first passivation layer 240, the metal reflective cap 250, and the second passivation layer 260, and the metal reflective cap 250 is electrically connected to the first contact 101 through the first opening 1011, so that the LED unit 200 is individually driven through the first contact 101.

In other embodiments, in order to increase the contact area between the electrode layer 270 and the metal reflective cap 250, a more reliable electrical connection structure is achieved, optionally the electrode layer 270 covers the top surface of the metal reflective cap 250.

The electrode layer 270 is a Transparent Conductive Oxide (TCO), and may specifically be a composite film of one or more of Indium Tin Oxide (ITO), znO, aluminum-doped AZO, ATO, FTO, snO, etc., or a composite film of one or more of Indium Zinc Oxide (IZO), indium Gallium Zinc Oxide (IGZO), and indium oxide (In 2O 3).

Fig. 3 to 16 show cross-sectional views of a micro led micro display chip at various stages in the manufacturing process.

Referring to fig. 3 and 4, an LED epitaxial layer 20 and a driving substrate 10 are provided, respectively.

The LED epitaxial layer 20 is disposed on the substrate 30, and the LED epitaxial layer 20 includes a first doping type semiconductor layer 210, a second doping type semiconductor layer 220, and an active layer 230 thereon.

A driving circuit is formed in the driving substrate 10, and is connected to the first contact 101; a bonding layer 60 is provided on the drive substrate 10.

In some embodiments, forming LED epitaxial layers 20 on substrate 30 employs MOCVD (metal organic chemical vapor deposition) technology, which is a novel vapor phase epitaxial growth technique developed on the basis of vapor phase epitaxial growth (VPE), to complete the entire epitaxial process.

Referring to fig. 5, a bonding layer 60 is disposed on the first doping type semiconductor layer 210 of the LED epitaxial layer 20.

Referring to fig. 6, the LED epitaxial layer 20 and the driving substrate 10 are bonded to form a bonding layer 60 by flipping the LED epitaxial layer 20 such that the LED epitaxial layer 20 is located on the driving substrate 10 after flipping; the bonding may be a metal bonding or an adhesive bonding, etc.; the top substrate 30 is then removed by methods including, but not limited to, laser lift-off, dry etching, wet etching, mechanical polishing, etc., and the structure of thinning the LED epitaxial layers 20 after removing the substrate 30 is shown in fig. 7.

Referring to fig. 7, the flipped LED epitaxial layers 20 are subjected to a thinning operation including dry etching, wet etching, or mechanical polishing.

Referring to fig. 8, the MESA pattern is designed according to the patterned mask, and an etching operation is performed to remove the second doping type semiconductor layer 220, and in the embodiment shown in fig. 8, the etching is performed just to the first doping type semiconductor layer 210, i.e., all of the first doping type semiconductor layer 210 remains; or in other embodiments, a portion of the first doped semiconductor layer 210 may be etched, and a portion of the first doped semiconductor layer 210 remains, forming a step structure.

In this embodiment, the MESA pattern is designed according to the patterned mask, and an etching operation is performed to remove the second doped semiconductor layer 220 to expose the first doped semiconductor layer 210, so as to form a step structure.

The stepped structure may serve as the LED units 200, with the LED units 200 being distributed in an array such that the first contact 101 is located between adjacent LED units 200.

In some embodiments, a mask arranged in an array is formed on the second doped semiconductor layer 220 by photolithography, and the mask may be photoresist, a dielectric layer, or the like; then, the region of the second doping type semiconductor layer 220 not covered by the mask is etched, and the active layer 230 is exposed; finally, removing the mask through a solvent or corrosive liquid to form the step structure.

A top view of the structure after etching the LED epitaxial layers 20 to form the LED unit is shown in fig. 9.

Referring to fig. 10 and 11, the continuous functional layer is perforated and etched to expose the bottom driving substrate 10, and the hole grooves 501 are formed in the positions of the LED units 200 corresponding to the first contacts 101, and the process of forming the hole grooves 501 is to sequentially etch the first doping type semiconductor layer 210 and the bonding layer 60 in the LED units 200 to electrically isolate between pixels, exposing the first contacts 101.

The first doping type semiconductor layer 210 and the bonding layer 60 may be formed by one-step etching using an IBE (ion beam etching) process; in some embodiments, a two-step etch may also be used, i.e., first etching first doped semiconductor layer 210 using ICP (inductively coupled plasma) and then etching bonding layer 60 using IBE process. In some embodiments, the pore channel 501 has a diameter size ranging from 2.1 to 2.5 microns, the pore channel 501 having a diameter comprising any one of 2.1 microns, 2.2 microns, 2.3 microns, 2.4 microns, and 2.5 microns.

Referring to fig. 12, a first passivation layer 240 is formed on the LED unit and opened. As shown in fig. 12, a first opening 1011 is formed on the first passivation layer 240, and the first opening 1011 communicates with the hole groove 501 and exposes the first contact 101. A second opening 1012 is also formed on the first passivation layer 240, the second opening 1012 exposing the second doping type semiconductor layer 220.

Fig. 12 illustrates that the first passivation layer 240 covers the sidewalls of the LED unit, and may cover at least the first doping type semiconductor layer 210.

If the bonding layer 60 is made of a conductive material, the first passivation layer 240 needs to cover the bonding layer 60, so that the bonding layer 60 is prevented from being exposed, and short circuit caused by contact between the bonding layer 60 and the metal reflector 250 after deposition is avoided.

A top view of the structure after forming the first passivation layer 240 and opening the first opening 1011 and the second opening 1012 on the first passivation layer 240 is shown in fig. 13.

Further, referring to fig. 14, at this time, a metal reflective cap 250 is formed on the first passivation layer 240 and is perforated, the metal reflective cap 250 may be formed by sputtering or evaporation, and then the metal reflective cap is patterned by physical or chemical etching after photolithography; alternatively, the metal reflector 250 may be formed using a lift-off process. The lift-off process is a common process in both ultraviolet lithography and electron beam lithography.

The metal reflective cover 250 is made of a material having high reflectivity, and is made of any one or a combination of a plurality of gold, silver, aluminum, copper and titanium.

The metal reflective caps 250 cover the first passivation layer 240 and enclose the step structures of the corresponding LED units 200, the metal reflective caps 250 being disconnected from each other and electrically isolated; the metal reflective caps 250 are electrically connected to the second doped semiconductor layers 220 of the corresponding LED units 200, and the metal reflective caps 250 are electrically connected to the corresponding first contacts 101 through the first openings 1011.

As shown in fig. 14, the LED units are arranged in a trapezoid, the side walls of the LED units are inclined, and the metal reflecting cover 250 needs to be attached to the trapezoid inclined side walls, so that the emission direction of light can be limited by the metal reflecting cover 250, and the crosstalk of light can be prevented.

In some embodiments, a third opening 1013 is formed on the metal reflective cover 250, the third opening 1013 exposing the light-emitting surface 201 of the LED unit 200; the metal reflective cap 250 covers a side of the first passivation layer 240, and the metal reflective cap 250 contacts the first contact 101 through the first opening 1011.

A top view of the structure after forming the metal reflector and forming the third opening in the metal reflector is shown in fig. 15.

In some embodiments, the metallic reflector 250 need only be in contact with the first contact 101 to maintain electrical connection. In other embodiments, in order to make the contact resistance as small as possible, the contact surface between the metal reflective cover 250 and the first contact 101 may be enlarged, and optionally, the metal reflective cover 250 covers the first contact 101, so that the contact resistance may be significantly reduced.

In some embodiments, the projection of the third opening 1013 in the vertical direction is not less than the projection of the second opening 1012 in the vertical direction, and the second opening 1012 is exposed. Fig. 14 illustrates an embodiment in which the projection of the third opening 1013 in the vertical direction is larger than the projection of the second opening 1012 in the vertical direction, which can ensure good coverage of the electrode layer 270 when the electrode layer 270 is subsequently formed, while the contact area increases to reduce the contact resistance.

According to the micro LED micro display chip provided by the application, the metal reflecting cover 250 is manufactured on the side wall of the LED unit, the LED can emit light only from the top, the LED light emitting angle is adjusted through the metal reflecting cover 250, and the optical crosstalk between pixels is reduced. While the metal reflective cap 250 is connected to the first contact 101 and the second doping type semiconductor layer 220 on the driving substrate 10, the LED pixel resistance can be reduced.

As shown in fig. 16, a second passivation layer 260 having a fourth opening 1014 is formed on the metal reflective cap 250. The projected area of the fourth opening 1014 in the vertical direction may be the same as the projected areas of the second and third openings 1012 and 1013 in the vertical direction. In some embodiments, the projected areas of the fourth hole 1014, the third hole 1013, and the second hole 1012 in the vertical direction may be sequentially reduced, forming a step.

In some embodiments, and/or, the projected area of the second opening 1012 in the vertical direction is greater than or equal to the projected area of the first opening 1011 in the vertical direction.

The fourth opening 1014 on the second passivation layer 260 exposes the second doping type semiconductor layer 220 and covers the entire sidewall of the LED unit, preventing the phenomenon of short circuit caused by electromigration of adjacent metal reflective caps 250 that may exist in the use process of the micro LED micro display chip, and improving the reliability of the micro LED micro display chip.

The micro LED micro display chip structure obtained by the preparation method provided by the specific embodiment is shown in figure 1.

As shown in fig. 1, an electrode layer 270 is formed on the fourth hole 1014, the third hole 1013, and the second hole 1012, and the exposed second doping type semiconductor layer 220, the electrode layer 270 is electrically connected to the first contact 101 through the metal reflective cap 250, and the driving circuit can control the voltage and current of the second doping type semiconductor layer 220 through the first contact 101. The first contacts 101 are located between adjacent LED units, and the LED units are electrically connected to the first contacts 101 such that each LED unit is individually driven.

Optionally, in some embodiments, in order to increase the scattered light emitting area of the LED unit and the contact area between the electrode layer 270 and the second passivation layer 260, the metal reflective cap 250, and the first passivation layer 240, the contact area between the electrode layer 270 and the second passivation layer 260, the metal reflective cap 250, and the first passivation layer 240 forms a stepped slope, which may reduce the contact resistance, further reducing the LED pixel resistance.

In the foregoing embodiments, the descriptions of the embodiments are emphasized, and for parts of one embodiment that are not described in detail, reference may be made to related descriptions of other embodiments. The foregoing has described the application in some detail, wherein specific examples are employed to illustrate the principles and embodiments of the application, and the above examples are provided to facilitate understanding of the technical solution and core idea of the application; those of ordinary skill in the art will appreciate that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the application.

Claims

1. A micro led micro display chip, comprising:

a drive substrate (10), the drive substrate (10) comprising a plurality of first contacts (101);

a plurality of LED units (200) arranged in an array on the driving substrate (10) and each of the LED units (200) being independently drivable, the first contacts (101) being located between adjacent LED units (200); each of the LED units (200) has a stepped structure, the LED unit (200) having a first doped semiconductor layer (210), a second doped semiconductor layer (220), and an active layer (230) therebetween; the step structure disconnects and electrically isolates at least the second doped semiconductor layers (220) of adjacent LED units (200) from each other;

-a first passivation layer (240) covering the LED unit (200), the first passivation layer (240) comprising a first opening (1011) and a second opening (1012), the first opening (1011) exposing the corresponding first contact (101), the second opening (1012) exposing the corresponding second doped semiconductor layer (220) of the LED unit (200);

-a plurality of metal reflective caps (250), said metal reflective caps (250) overlying said first passivation layer (240) and surrounding a stepped structure corresponding to said LED units (200), adjacent said metal reflective caps (250) being disconnected and electrically isolated from each other;

The metal reflecting cover (250) is electrically connected with the second doped semiconductor layer (220) of the corresponding LED unit (200), and the metal reflecting cover (250) is electrically connected with the corresponding first contact (101) through the first opening (1011).

2. The micro LED micro display chip according to claim 1, wherein the metal reflective cap (250) comprises a third opening (1013), the third opening (1013) exposing the second doped semiconductor layer (220) of the corresponding LED unit (200);

the micro LED micro display chip further comprises:

the electrode layer (270), the electrode layer (270) is disposed on the metal reflecting cover (250), and is used for electrically connecting the metal reflecting cover (250) with the second doped semiconductor layer (220) of the corresponding LED unit (200), the electrode layer (270) is in contact with and electrically connected with the second doped semiconductor layer (220) through the second opening (1012), and the electrode layer (270) is in contact with and electrically connected with the metal reflecting cover (250) through the third opening (1013).

3. The micro led micro display chip of claim 2, further comprising:

A second passivation layer (260);

the second passivation layer (260) is arranged between the metal reflecting cover (250) and the electrode layer (270), the second passivation layer (260) is provided with a fourth opening (1014), and the fourth opening (1014) exposes the second doped semiconductor layer (220) of the corresponding LED unit (200).

4. A micro led micro-display chip according to claim 3, characterized in that the projection of the fourth opening (1014) in the vertical direction is not smaller than the projection of the third opening (1013) in the vertical direction and exposes the third opening (1013).

5. The micro led micro display chip as set forth in claim 2, wherein the projection of the third opening (1013) in the vertical direction is not smaller than the projection of the second opening (1012) in the vertical direction, and the second opening (1012) is exposed.

6. The micro led micro display chip as defined in claim 5, wherein the second opening (1012) and the third opening (1013) form a step.

7. The micro led micro display chip as defined in claim 4, wherein the second opening (1012), the third opening (1013) and the fourth opening (1014) form a step.

8. The micro led micro display chip of claim 1, further comprising:

and a bonding layer (60), wherein the bonding layer (60) is arranged between the driving substrate (10) and the LED unit (200), and the bonding layer (60) is made of metal or nonmetal.

9. The micro led micro display chip according to claim 1, wherein the metal reflective cap (250) is made of any one or a combination of a plurality of gold, silver, aluminum, copper, and titanium.

10. The micro led micro display chip according to claim 2, wherein the electrode layer (270) is composed of one or more of indium tin oxide, znO, AZO, ATO, FTO, snO 2.

11. The micro LED micro display chip according to claim 1, wherein the first doping type semiconductor layers (210) of adjacent LED units (200) are extended and in contact with each other for sharing.

12. The preparation method of the micro LED micro display chip is characterized by comprising the following steps:

providing a drive substrate (10), wherein the drive substrate (10) comprises a drive circuit and a plurality of first contacts (101) electrically connected with the drive circuit;

-providing an LED epitaxial layer (20) comprising a second doped semiconductor layer (220), an active layer (230) and a first doped semiconductor layer (210), the LED epitaxial layer (20) being provided on the drive substrate (10) and exposing the second doped semiconductor layer (220);

forming a plurality of LED units (200) by etching the LED epitaxial layer (20) downwards from the second doping type semiconductor layer (220), wherein the LED units (200) are arrayed on the driving substrate (10), each LED unit (200) can be independently driven by the corresponding first contact (101), and the first contact (101) is positioned between the adjacent LED units (200); each of the LED units (200) has a stepped structure; the step structure disconnects and electrically isolates at least the second doped semiconductor layers (220) of adjacent LED units (200) from each other;

-forming a first passivation layer (240), the first passivation layer (240) covering the LED units (200), the first passivation layer (240) having a first opening (1011) and a second opening (1012) thereon, the first opening (1011) exposing the corresponding first contact (101), the second opening (1012) exposing the corresponding second doped semiconductor layer (220) of the LED units (200);

-forming a plurality of metal reflective caps (250) disconnected from each other and electrically isolated, the metal reflective caps (250) covering the first passivation layer (240) and surrounding a step structure corresponding to the LED units (200); the metal reflecting cover (250) is electrically connected with the second doped semiconductor layer (220) of the corresponding LED unit (200), and the metal reflecting cover (250) is electrically connected with the corresponding first contact (101) through the first opening (1011).

13. The method of manufacturing a micro led micro display chip according to claim 12, further comprising:

a third opening (1013) is formed on the metal reflector (250), the third opening (1013) exposing the second doped semiconductor layer (220) of the corresponding LED unit (200);

an electrode layer (270) is formed, the electrode layer (270) is disposed on the metal reflective cap (250), and is used for electrically connecting the metal reflective cap (250) with the second doped semiconductor layer (220) of the corresponding LED unit (200), the electrode layer (270) is in contact with and electrically connected with the second doped semiconductor layer (220) through the second opening (1012), and the electrode layer (270) is in contact with and electrically connected with the metal reflective cap (250) through the third opening (1013).

14. The method of manufacturing a micro led micro display chip of claim 13, further comprising:

-after forming the metal reflector (250) and before forming the electrode layer (270), forming a second passivation layer (260) on the metal reflector (250), the second passivation layer (260) being provided with a fourth opening (1014), the fourth opening (1014) exposing the second doped semiconductor layer (220) of the corresponding LED unit (200).

15. The method for manufacturing a micro LED micro display chip according to claim 12, wherein,

forming a plurality of metallic reflective caps (250) that are electrically isolated from each other and disconnected from each other, comprising:

-forming a patterned sacrificial layer on the first passivation layer (240), the sacrificial layer exposing the LED unit (200) and the first contact (101), and the sacrificial layer covering the second aperture (1012);

depositing a metal layer on the sacrificial layer;

the sacrificial layer is removed to form the plurality of metal reflective caps (250).

16. The method of manufacturing a micro led micro display chip according to claim 12, wherein forming a plurality of metal reflective caps (250) disconnected from each other and electrically isolated from each other, comprises:

Depositing a metal layer on the first passivation layer (240);

an etching process is used to remove portions of the metal layer to form the plurality of metal reflective caps (250).

17. The method for manufacturing a micro LED micro display chip according to claim 12, wherein,

the step of providing the LED epitaxial layers (20) on the drive substrate (10) comprises:

-providing a substrate (30), the LED epitaxial layers (20) being formed on the substrate (30);

bonding the LED epitaxial layers (20) to the drive substrate (10) and forming a bonding layer (60) therebetween;

-removing the substrate (30) and exposing the second doped semiconductor layer (220) of the LED epitaxial layers (20).