CN114649322B - Micro LED display device and preparation method - Google Patents

Abstract

The invention discloses a Micro LED display device and a preparation method thereof, and belongs to the technical field of Micro-LED manufacturing. The Micro LED display chip comprises: a driving panel; LED units individually driven through contacts; a passivation layer on the LED unit, including a first passivation layer, a second passivation layer, and a third passivation layer; and a second light reflecting layer formed on the second passivation layer and the third passivation layer. The manufacturing method comprises providing a driving panel, and forming LED units on the driving panel; forming a passivation layer on the LED unit; forming a light reflecting layer on the passivation layer; and stripping the first reflective layer and reserving the second reflective layer. According to the invention, spontaneous radiation photons are blocked by the reflecting layer and are emitted only from the top, so that crosstalk between adjacent pixels is completely prevented, the photons reflected by the reflecting layer escape from the unique emitting window, and the light emitting power is greatly improved.

Description

Micro LED display device and preparation method

technical field

The invention belongs to the technical field of Micro-LED manufacturing, and in particular relates to a Micro LED display device and a preparation method.

Background technique

Micro LEDs are used in the micro-display industry (such as AR/VR, etc.), because the pixel pitch is very small, which will cause crosstalk problems. That is to say, when a pixel emits light, part of it leaks to adjacent pixels, resulting in Color purity decreases. At present, there are some technologies, such as resonant cavity technology, which can alleviate the problem of crosstalk to a certain extent. However, because Micro LED emits light by spontaneous radiation, not stimulated radiation like lasers, some light will still leak from the sidewall, causing crosstalk. The problem.

SUMMARY OF THE INVENTION

Purpose of the invention: The purpose of the present invention is to provide a Micro LED display device. By arranging a reflective layer on the side wall of the LED unit, the crosstalk between adjacent pixels is prevented and the light output power is improved; Preparation.

Technical solution: In order to achieve the above purpose of the invention, the preparation method of the Micro LED display device includes:

providing a drive panel including a plurality of first contacts;

an LED unit is provided, the LED unit array is arranged on the driving panel, and is driven independently by the first contact; the LED unit has a light emitting surface and a side surface connected with the light emitting surface;

A passivation layer is formed, the passivation layer is located on the LED unit, including a first passivation layer located on the light emitting surface, a second passivation layer located on the side surface and integrally connected with the first passivation layer a passivation layer and a third passivation layer located between adjacent LED units and integrally connected with the second passivation layer;

A first opening for exposing the light emitting surface is provided on the first passivation layer;

forming a sacrificial layer, the sacrificial layer is located on the first passivation layer and covers the first opening;

A reflective layer is formed, including a first reflective layer on the sacrificial layer and a second reflective layer on the second passivation layer and the third passivation layer, the first reflective layer and the first reflective layer The two light-reflecting layers are disconnected from each other; the sacrificial layer is peeled off, the second light-reflecting layer is retained, and the first passivation layer and the first opening are exposed.

In some embodiments, the step of providing the LED unit includes:

providing a substrate on which an LED epitaxial layer is provided;

bonding the driving panel and the LED epitaxial layer, and forming a bonding layer between the driving panel and the LED epitaxial layer;

The LED epitaxial layer is etched into a stepped structure, and the stepped structure includes a first doped semiconductor layer, a second doped semiconductor layer and an active layer located therebetween; the light exit surface is located on the The second doped semiconductor layer is located on the top of the step structure; the step structure at least separates and electrically isolates the second doped semiconductor layers of adjacent LED units from each other.

In some embodiments, the step structure enables the second doped semiconductor layer, the active layer, and the first doped semiconductor layer of adjacent LED units to be disconnected and electrically isolated from each other;

The material of the bonding layer is a conductive material, and the bonding layers between the adjacent LED units are disconnected from each other by etching the bonding layer;

The first contact is located under the corresponding LED unit, and the first doped semiconductor layer is electrically connected to the first contact so that the LED unit can be driven independently.

In some embodiments, the step of electrically connecting the first doped semiconductor layer with the first contact so that the LED unit can be driven independently includes:

An electrode layer is provided on the first passivation layer; the electrode layer is electrically connected to the second doped semiconductor layer of the LED unit through the first opening, and the second doped semiconductor layer of the adjacent LED unit is electrically connected The hetero-type semiconductor layer is electrically connected through the electrode layer.

In some embodiments, before the step of disposing the electrode layer on the first passivation layer, the step includes:

forming an insulating layer, the insulating layer is located on the first passivation layer and the light-reflecting layer, and then setting a second opening on the insulating layer on the first passivation layer and exposing the first opening .

In some embodiments, the insulating layer is used as an electrical isolation layer. If the reflective layer itself is not conductive, this layer can be omitted; the insulating layer material can be an organic material or an inorganic material.

In some embodiments, after the step of disposing the electrode layer on the first passivation layer, it includes:

A Bragg mirror is formed on the electrode layer.

In some embodiments, the reflectivity of the Bragg mirror is between 50%-70%. The Bragg reflector is used to improve the collimation of light. When the bottom layer of the LED unit is provided with a reflective metal, it is further ensured that the reflectivity of the Bragg reflector is smaller than that of the bottom layer of the LED unit.

In some embodiments, the step of forming the sacrificial layer includes:

forming a sacrificial coating on the first opening, the first passivation layer, the second passivation layer and the third passivation layer;

performing pattern exposure on the sacrificial coating, removing the sacrificial coating on the second passivation layer and the third passivation layer, and retaining the sacrificial coating on the first passivation layer and the first opening layer to obtain the sacrificial layer.

In some embodiments, the thickness ratio of the sacrificial coating to the reflective layer is greater than 2:1, preferably greater than or equal to 3:1, and the thickness of the sacrificial coating needs to be much thicker than that of the reflective layer to ensure The subsequently formed first light-reflecting layer and the second light-reflecting layer are discontinuous structures, so that the direct peeling of the first light-reflecting layer can be ensured without affecting the retention of the second light-reflecting layer.

In some embodiments, the sacrificial layer includes any one of photoresist, SU-8, polyimide, _SiO2 , and _SiNx . On the one hand, the material of the sacrificial layer should be convenient for direct peeling off, and on the other hand, it should also ensure that the surface of the first doped semiconductor layer of the LED unit will not be damaged during the peeling process.

In some embodiments, the electrode layer is a transparent conductive film. The transparent conductive film can be used as an ohmic contact layer and a light outlet.

In some embodiments, the reflectivity of the light-reflecting layer is greater than 80%. The reflective layer is a metal reflective layer, and the metal reflective layer can be a highly reflective metal such as Al, Ag, etc., or other non-metallic highly reflective dielectric materials.

In some embodiments, a Micro LED display device includes:

a drive panel, including a plurality of first contacts;

a plurality of LED units, the LED unit arrays are arranged on the driving panel, and are individually driven through the first contacts;

the LED unit has a light emitting surface and a side surface connected with the light emitting surface;

A passivation layer, comprising a first passivation layer located on the light-emitting surface, a second passivation layer located on the side surface and integrally connected with the first passivation layer, and a passivation layer located between adjacent LED units a third passivation layer integrally connected with the second passivation layer;

A second light-reflecting layer is located on the second passivation layer and the third passivation layer.

In some embodiments, the light-reflecting layer is formed only on the second passivation layer and the third passivation layer; the light-reflecting layer is not in contact with the first passivation layer.

In some embodiments, the active layer may be a multi-quantum well structure, which is used to confine electron and hole carriers to the quantum well region. After the electrons and holes recombine, the carriers will be emitted after radiative recombination. It emits photons and converts electrical energy into light energy.

In some embodiments, the side surface is inclined or perpendicular to the light exit surface.

In some embodiments, the first doped semiconductor layer and the second doped semiconductor layer may include II-VI based materials such as ZnSe or ZnO or III-V materials such as GaN, AlN, InN, InGaN, GaP, One or more layers of AlInGaP, AlGaAs and alloys thereof.

In some embodiments, a bonding layer is included, the bonding layer is located between the driving panel and the LED unit;

The LED unit includes a stepped structure formed by etching the LED epitaxial layer; the stepped structure includes a first doped semiconductor layer, a second doped semiconductor layer and an active layer located therebetween, and the light emitting The surface is located on the second doped semiconductor layer and at the top of the stepped structure; the stepped structure at least separates and electrically isolates the second doped semiconductor layers of adjacent LED units from each other,

In some embodiments, the step structure further disconnects and electrically isolates the first doped semiconductor layer and the active layer between adjacent LED units;

The first contact is located under the corresponding LED unit, and the first contact is electrically connected to the corresponding first doped semiconductor layer.

In some embodiments, the bonding layer is used for bonding the LED unit and the driving circuit, and the bonding method includes adhesive bonding, metal-to-metal bonding, metal-oxide bonding, wafer-to-wafer bonding, and the like.

In some embodiments, an electrode layer is included on the first passivation layer;

The electrode layer is electrically connected to the second doped semiconductor layer through the first opening, and the second doped semiconductor layer of adjacent LED units is electrically connected through the electrode layer.

In some embodiments, an insulating layer is further included, the insulating layer is located on the first passivation layer and the light-reflecting layer;

The insulating layer has second openings exposing the first openings, and the electrode layer is in contact with the insulating layer through the second openings.

In some embodiments, a Bragg mirror is further included on the electrode layer.

In some embodiments, the diameter of the second opening is not smaller than the diameter of the first opening.

In some embodiments, the driving panel is a silicon-based CMOS driving board or a thin film field effect transistor driving board.

In some embodiments, the size of the LED unit is 0.1-5 microns.

In some embodiments, the thickness of the sidewall of the passivation layer is a quarter of the emission wavelength of the LED unit, and the thickness δ of the sidewall of the passivation layer satisfies the following formula: δ=λ/(4×n);

In the formula, λ is the emission wavelength of the LED unit, and n is the refractive index of the passivation layer.

Beneficial effects: Compared with the prior art, the preparation method of the Micro LED display device of the present invention includes: providing a driving panel, the driving panel includes a plurality of first contacts; providing LED units, and the LED unit array is arranged on the driving panel , driven separately through the first contact; the LED unit includes a light-emitting surface and a side surface connected to the light-emitting surface; a passivation layer is formed, and the passivation layer is located on the LED unit, including a first passivation layer located on the light-emitting surface, located on the light-emitting surface. a second passivation layer on the side surface integrally connected with the first passivation layer and a third passivation layer located between adjacent LED units and integrally connected with the second passivation layer; provided on the first passivation layer A first opening for exposing the second doped semiconductor layer; forming a sacrificial layer, the sacrificial layer is located on the first passivation layer and covers the first opening; forming a reflective layer, including the first reflective layer on the sacrificial layer and the second reflective layer located on the second passivation layer and the third passivation layer, the first reflective layer and the second reflective layer are disconnected from each other; the sacrificial layer is peeled off, the second reflective layer is retained, and the first passivation layer is exposed and the first opening. In the preparation method of the present invention, through the process of depositing the sacrificial layer first, then depositing the reflective layer, and finally removing the sacrificial layer, the reflective layer is skillfully formed only on the side surface of the corresponding LED unit. Since the sacrificial layer has a certain thickness, the reflective layer is ensured. It is a discontinuous structure after deposition, thus ensuring that the reflective layer on the sacrificial layer can be peeled off together with the sacrificial layer. The overall process is simple, and the etching step of the reflective layer with high reflectivity is directly omitted, which greatly shortens the time. The time required to prepare the light-reflecting layer on the Micro LED display device with micro-sized structure will not cause damage to the surface of the LED unit, which improves the yield of the Micro LED display device. The present application adopts the liftoff stripping process to form the light-reflecting layer, which can reduce the cost and at the same time have the effect of blocking spontaneously radiated photons in the LED unit.

The Micro LED display device of the present invention includes: a driving panel including a plurality of first contacts; a plurality of LED units, the LED unit arrays are arranged on the driving panel and are driven individually through the first contacts; the LED units have a light emitting surface and a side surface connected with the light-emitting surface; the passivation layer includes a first passivation layer on the light-emitting surface, a second passivation layer on the side surface that is integrally connected with the first passivation layer, and a second passivation layer located between adjacent LED units. The third passivation layer is integrally connected with the second passivation layer in between; the second light-reflecting layer is located on the second passivation layer and the third passivation layer. In the Micro LED display device of the present invention, the spontaneous emission photons excited by the active layer are blocked by providing the second reflective layer. Since the second reflective layer is arranged on the side of the LED unit, the spontaneous radiation photons cannot pass from the side of the LED unit. To escape, it can only be emitted from the top, which can completely prevent the occurrence of crosstalk between adjacent pixels; the photons reflected by the second reflective layer, after multiple reflections inside the LED unit, escape through the only exit window, greatly The light output power of the Micro LED display device is improved.

The Micro LED display device of the present application also includes an insulating layer, and the insulating layer is located on the first passivation layer and the second reflective layer; on the one hand, the insulating layer can prevent the contact between the reflective layer of metal material and the electrode layer, and the electromagnetic wave On the other hand, the heat generated by the LED unit can be conducted to prolong the life of the LED unit and improve the power output.

Description of drawings

The technical solutions and other beneficial effects of the present invention will be apparent through the detailed description of the specific embodiments of the present invention with reference to the accompanying drawings.

1 shows a top view of a Micro LED display device according to some embodiments of the present application;

2 shows a schematic cross-sectional view in the direction of A-A' of a Micro LED display device according to some embodiments of the present application;

Figure 3 shows a schematic cross-sectional view in the direction A-A' of a substrate according to some embodiments of the present application;

4 shows a schematic cross-sectional view in the direction of A-A' of a drive panel according to some embodiments of the present application;

FIG. 5 shows a schematic diagram of a bonding layer structure according to some embodiments of the present application;

Figure 6 shows a schematic diagram of a bonding process according to some embodiments of the present application;

FIG. 7 shows a schematic diagram of the structure obtained after the LED epitaxial layer is bonded to the driving panel according to some embodiments of the present application;

8 shows a schematic diagram of MESA etching to form a step structure according to some embodiments of the present application;

9 shows a schematic diagram of the resulting structure after etching the bonding layer according to some embodiments of the present application;

10 shows a schematic diagram of the resulting structure after forming a passivation layer according to some embodiments of the present application;

11 shows a schematic diagram of a structure obtained by disposing a first opening according to some embodiments of the present application;

12 shows a schematic diagram of the resulting structure after forming a sacrificial coating according to some embodiments of the present application;

13 shows a schematic diagram of the resulting structure after forming a sacrificial layer according to some embodiments of the present application;

14 shows a schematic diagram of a structure obtained after forming a light-reflecting layer according to some embodiments of the present application;

15 shows a schematic diagram of the resulting structure after peeling off the sacrificial layer according to some embodiments of the present application;

16 shows a schematic diagram of the resulting structure of forming an insulating layer according to some embodiments of the present application;

17 shows a schematic diagram of a structure obtained by providing a second opening according to some embodiments of the present application;

18 shows a schematic diagram of the resulting structure of forming an electrode layer according to some embodiments of the present application;

19 shows a schematic diagram of the resulting structure of forming a Bragg mirror according to some embodiments of the present application;

Reference numerals: 100-Micro LED display device, 101-driving panel, 102-bonding layer, 103-first contact, 104-passivation layer, 105-reflective layer, 106-insulating layer, 107-electrode layer, 108-Bragg mirror, 109-LED unit, 110-second doped semiconductor layer, 111-active layer, 112-first doped semiconductor layer, 113-light exit surface, 114-side surface, 115-first Opening, 116-sacrificial layer, 117-substrate, 118-LED epitaxial layer, 119-second opening, 1041-first passivation layer, 1042-second passivation layer, 1043-third passivation layer, 1051 - first reflective layer, 1052 - second reflective layer, 1161 - sacrificial coating.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, but not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts shall fall within the protection scope of the present invention.

The present disclosure provides many different embodiments or examples for implementing different structures of the present invention. In order to simplify the present disclosure, specific example components and arrangements are described herein. Of course, they are only examples and are not intended to limit the invention. Furthermore, the present disclosure may repeat reference numerals and/or reference letters in different instances for the purpose of simplicity and clarity and not in itself indicative of a relationship between the various embodiments and/or arrangements discussed. In addition, the present disclosure 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.

In general, the terms may be understood at least in part in accordance with the usage of the present invention above. For example, as used herein, the term "one or more" may be used to describe any component, structure or feature in the singular or may be used to describe any component, structure or feature in the plural depending at least in part on the invention above. combination. Similarly, terms such as "a," "an," or "the" may also be understood to convey a singular usage or to convey a plural usage depending at least in part on the invention above. Additionally, the term "based on" may be understood as not necessarily intended to convey an exclusive set of factors, but rather, depending at least in part on the above, the invention may instead allow for the presence of additional factors that do not necessarily have to be explicitly described.

It should be readily understood that the meanings of "on", "on" and "on" in the present invention should be interpreted in the broadest sense, so that "on" does not only mean "directly on something "on", but also "on something" including intervening components or layers, and "over something" or "over something" does not only mean "on something" " or "over something", but also includes the meaning "over something" or "over something" in the absence of an intervening member or layer.

Furthermore, for ease of description, spatially relative terms such as "below", "under", "lower", "over", "upper" and the like may be used in the present invention to describe an element or component that is different from The relationship of another element or component shown in the drawings. In addition to the orientation depicted in the figures, spatially relative terms are intended to encompass different orientations of the device in use or operation. The device may be otherwise oriented, rotated 90° or at other orientations, and the spatially relative descriptors used in this disclosure may likewise be interpreted accordingly.

The term "layer" as used in the present invention refers to a portion of a material comprising a region having a thickness. A layer may extend over the entire underlying or superstructure, or may have an extent that is less than the extent of the underlying or superstructure. Furthermore, a layer may be a region of a homogeneous or heterogeneous continuous structure, the thickness of which is less than the thickness of the continuous structure. For example, a 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 on, over, and/or under it. A layer may include multiple layers. For example, the semiconductor layers may include one or more doped or undoped semiconductor layers, and may be of the same or different materials.

FIG. 1 shows a top view of the Micro LED display device 100 of some embodiments, and FIG. 2 shows a cross-sectional view of the Micro LED display device 100 in the direction A-A' in FIG. 1 . The Micro LED display device 100 includes a driving panel 101 and at least two LED units 109 . The LED units 109 are arranged in an array on the driving panel 101. The LED units 109 have a stepped structure, including a first doped semiconductor layer 112, a second doped semiconductor layer 110 and an active layer 111 located therebetween. The top surface of the structure is the light emitting surface 113, and the side surface 114 is connected to the light emitting surface 113, and the side surface 114 is formed on the second doped semiconductor layer 110; the passivation layer 104 is formed on the LED unit 109, including the first passivation layer 1041, the second passivation layer 1042 and the third passivation layer 1043, the first passivation layer 1041, the second passivation layer 1042 and the third passivation layer 1043 are integrally connected; the second reflective layer 1052 is formed on the second On the passivation layer 1042 and the third passivation layer 1043; the insulating layer 106 is formed on the second light-reflecting layer 1052; The hetero-type semiconductor layer 110 is electrically connected.

In some embodiments, the drive panel 101 may include semiconductor materials such as silicon, silicon carbide, nitride, germanium, gallium arsenide, cobalt phosphide. In some embodiments, the drive panel 101 may be made of a non-conductive material, such as glass, plastic, or a sapphire wafer. In some embodiments, the driving panel 101 may have a driving circuit formed therein, and the driving panel 101 may be a CMOS backplane or a TFT glass substrate. The drive circuit provides electrical signals to the LED unit 109 to control the brightness. In some embodiments, the driver circuit may comprise an active matrix driver circuit, wherein each individual LED unit 109 corresponds to an independent driver.

Referring to FIG. 2 , a bonding layer 102 is provided between the driving panel 101 and the LED units 109 , and the bonding layers 102 between adjacent LED units 109 are disconnected from each other, so that the bonding layers cannot pass between adjacent LED units 109 102 is electrically connected; the bonding layer 102 is an adhesive material layer formed on the driving panel 101 to bond the driving panel 101 and the LED unit 109 . In some embodiments, the bonding layer 102 may include a conductive material, such as a metal or metal alloy. In some embodiments, the bonding layer 102 may include Au, Sn, In, Cu, or Ti. In some embodiments, the bonding layer 102 may comprise a non-conductive material, such as polyimide PI, polydimethylsiloxane PDMS. In some embodiments, the bonding layer 102 may include photoresist, such as SU-8 photoresist.

In some embodiments, the stepped structure disconnects and electrically isolates the second doped semiconductor layers 110 of adjacent LED units 109 from each other, and disconnects the first doped semiconductor layers 112 between adjacent LED units 109 from each other The first contact 103 is located under the corresponding LED unit 109, and the first doped semiconductor layer 112 is electrically connected to the first contact 103 so that the LED unit 109 can be driven independently.

In some embodiments, the first doped semiconductor layer 112 may also be a continuous functional layer structure, the first contact 103 is located between adjacent LED units 109 , and the second doped semiconductor layer 110 of the LED unit 109 Electrical connection with the corresponding first contact 103 enables the LED unit 109 to be driven independently; the second doped semiconductor layer 110 is patterned, or the second doped semiconductor layer 110 is etched to form a mesa structure, Alternatively, ion implantation is performed on the second doped semiconductor layer 110 to form the LED unit 109 .

In some embodiments, an active layer 111 is formed between the first doped semiconductor layer 112 and the second doped semiconductor layer 110 of each LED unit 109 . In some embodiments, the active layer 111 is a multi-quantum well layer MQW, electrons and holes recombine in the quantum well region to generate photons, and spontaneous emission photons excited at the multi-quantum wells realize light emission.

Referring to FIG. 2 , the side surface 114 of the LED unit 109 is inclined relative to the light-emitting surface 113 , and the angle of the inclination is subject to the setting in the actual process, that is, each LED unit 109 has a trapezoidal structure and forms an array of trapezoidal LED units 109 with trapezoidal sidewalls. This helps to improve the luminous efficiency of the LED unit 109, mainly because the sidewalls of the trapezoid are able to reflect light and re-reflect it back to the sidewalls for light extraction.

In some embodiments, the first doped semiconductor layer 112 and the second doped semiconductor layer 110 may include II-VI based materials (such as ZnSe or ZnO) or III-V materials (such as GaN, AlN, InN, InGaN) , GaP, AlInGaP, AlGaAs and their alloys) one or more layers.

In some embodiments, a passivation layer 104 is provided on the LED unit 109 . The passivation layer 104 is used to protect and isolate the LED unit 109 . In some embodiments, the passivation layer 104 may include SiO ₂ , Al ₂ O ₃ , SiN, or other suitable materials. In some embodiments, passivation layer 104 includes polyimide, SU-8 photoresist, or other photo-patternable polymers.

As shown in FIG. 2 , the second light-reflecting layer 1052 is formed on the second passivation layer 1042 and the third passivation layer 1043 , which can reflect the light scattered by the active layer 111 in the LED unit 109 and exit from the light-emitting surface 113 . In some embodiments, the second reflective layer 1052 is a metal reflective layer, and the metal reflective layer includes Ag, Al, or multiple layers of metals. In some embodiments, the second light reflecting layer 1052 includes a Bragg reflecting layer. In some embodiments, the reflectivity of the second light-reflecting layer 1052 is greater than 80%.

Referring to FIG. 2 , a first opening 115 is formed on the first passivation layer 1041 exposing the second doped semiconductor layer 110 , and an electrode layer 107 is formed on the first passivation layer 1041 at the same time. The hetero-type semiconductor layer 110 is electrically connected. In some embodiments, the first opening 115 is located at the center of each LED unit 109 . In some embodiments, the electrode layer 107 may be a transparent conductive film, serving as an ohmic contact layer and a light outlet.

In some embodiments, when the multiple quantum well emits light, the light leaking from the sidewall of the functional area of the chip will be reflected back by the second light-reflecting layer 1052 , so that only the electrode layer 107 can emit light, so it will not affect the adjacent LED units 109 produce optical crosstalk.

3 to 19 show schematic diagrams of different stages in the fabrication process of the structure of the Micro LED display device 100 .

3 and 4 , a driving panel 101 is provided, a driving circuit is formed in the driving panel 101, and the driving circuit includes a first contact 103; and a substrate 117 is provided, and an LED epitaxial layer 118 is formed on the substrate 117.

In some embodiments, the driving panel 101 is a silicon-based CMOS backplane or a thin film field effect transistor. Silicon-based CMOS is a chip made of silicon. In some embodiments, the substrate 117 is a semiconductor material, such as silicon, gallium nitride, etc., or the substrate 117 is a non-conductive material, such as sapphire or glass.

Referring to FIG. 5 , a bonding layer 102 is formed on the driving panel 101 for bonding the driving panel 101 and the LED epitaxial layer 118 on the substrate 117 .

In some embodiments, the bonding layer 102 may include a conductive material, such as a metal or metal alloy. In some embodiments, the bonding layer 102 may include Au, Sn, In, Cu, or Ti. In some embodiments, the bonding layer 102 may comprise a non-conductive material, such as polyimide PI, polydimethylsiloxane PDMS. In some embodiments, the bonding layer 102 may include photoresist, such as SU-8 photoresist. In some embodiments, the bonding layer 102 is formed by deposition.

Referring to FIG. 6 , the LED epitaxial layer 118 on the substrate 117 is turned over and passed and bonded onto the driving panel 101 , and then the substrate 117 is removed from the LED epitaxial layer 118 .

In some embodiments, the bonding layer 102 may include one or more layer structures, and the bonding method is metal bonding. In some embodiments, substrate 117 removal methods include, but are not limited to, laser lift-off, dry etching, wet etching, mechanical polishing, and the like.

Referring to FIG. 7 , a thinning operation is performed on the flipped LED epitaxial layer 118 , and the thinning operation includes dry etching, wet etching or mechanical polishing.

Referring to FIG. 8 , the MESA pattern is designed according to the patterned mask, and the LED epitaxial layer 118 is etched to form the LED unit 109. The LED unit 109 is a functional step structure, and the LED epitaxial layer 118 includes a first doped semiconductor. layer 112 , the second doped semiconductor layer 110 and the active layer 111 .

In some embodiments, the first doped semiconductor layer 112 is P-type gallium nitride, the second doped semiconductor layer 110 is N-type gallium nitride, and the active layer 111 is a multiple quantum well layer. Etching includes dry or wet methods.

In some embodiments, the depth of the second doped semiconductor layer 110 is based on a predefined thickness that the first doped semiconductor layer 112 can reach, and the first doped semiconductor layer 112 remains on the driving panel 101; the step The structure at least disconnects and electrically isolates the second doped semiconductor layers 110 of adjacent LED units 109 from each other, and the stepped structure also disconnects and electrically isolates the first doped semiconductor layers 112 of adjacent LED units 109 from each other.

Referring to FIG. 9 , the bonding layer 102 cannot be electrically connected between adjacent LED units 109 by etching the bonding layer 102 .

In some embodiments, the first contact 103 is located under the corresponding LED unit 109 , and the first doped semiconductor layer 112 is electrically connected to the first contact 103 so that the LED unit 109 can be driven independently.

In some embodiments, since the first doped semiconductor layer 112 is a P-type layer, which is difficult to dope and has the characteristics of low carrier concentration, it needs to be on the first doped semiconductor layer 112 before bonding The ohmic contact layer and the reflective layer are provided, and then metal bonding is performed with the bonding layer 102 .

Referring to FIG. 10, a passivation layer 104 is formed on the LED unit 109. The passivation layer 104 includes a first passivation layer 1041, a second passivation layer 1042 and a third passivation layer 1043. The first passivation layer 1041 passes through the second passivation layer 1041. The passivation layer 1042 is connected to the third passivation layer 1043 ; the first passivation layer 1041 is formed on the second doped semiconductor layer 110 and is located on the light-emitting surface 113 of the LED unit 109 , and the second passivation layer 1042 is located on the LED unit 109 The side surfaces 114 ; the third passivation layer 1043 is formed between the adjacent LED units 109 . The passivation layer 104 can protect the LED unit 109 . In some embodiments, the passivation layer 104 is formed by chemical vapor deposition.

In some embodiments, the passivation layer 104 is an inorganic or organic dielectric material to passivate and electrically isolate the LED unit 109 .

In some embodiments, the thickness of the sidewall of the passivation layer 104 is a quarter of the emission wavelength of the LED unit 109 , and the thickness δ of the sidewall of the passivation layer 104 satisfies the following formula: δ=λ/(4×n); In the formula, λ is the emission wavelength of the LED unit 109 , and n is the refractive index of the passivation layer 104 .

In some embodiments, the sidewall of the passivation layer 104 actually refers to the thickness of the second passivation layer 1042 . When the above-mentioned thickness setting is satisfied, an ODR, ie an omnidirectional corner mirror, can be formed.

Referring to FIG. 11 , a first opening 115 is formed by etching on the first passivation layer 1041 to expose the light surface 113 .

In some embodiments, the etching process includes dry or wet etching.

Referring to FIGS. 12 and 13 , a sacrificial coating 1161 is formed on the first passivation layer 1041 , the second passivation layer 1042 and the third passivation layer 1043 where the first opening 115 is formed, and then the sacrificial coating 1161 is patterned The sacrificial coating 1161 on the second passivation layer 1042 and the third passivation layer 1043 is removed by chemical exposure, and the sacrificial coating 1161 on the first passivation layer 1041 and the first opening 115 is retained to obtain the sacrificial layer 116 .

In some embodiments, the thickness ratio of the sacrificial coating 1161 to the reflective layer 105 is 3:1, and the sacrificial layer 116 includes any one of photoresist, SU-8, polyimide, SiO ₂ and SiN _x .

Referring to FIG. 14 , a first light-reflecting layer 1051 is formed on the sacrificial layer 116, and a second light-reflecting layer 1052 is formed on the second passivation layer 1042 and the third passivation layer 1043, since the thickness of the sacrificial layer 116 is greater than that of the first passivation layer The thickness of the layer 1041 can therefore ensure that the first reflective layer 1051 and the second reflective layer 1052 are discontinuous.

In some embodiments, the first reflective layer 1051 and the second reflective layer 1052 are formed by deposition, and the first reflective layer 1051 and the second reflective layer 1052 may be highly reflective metals such as Al, Ag, or other highly reflective layers Dielectric material with reflectivity greater than 80%.

Referring to FIG. 15 , the sacrificial layer 116 is peeled off, the first reflective layer 1051 on the sacrificial layer 116 is removed, the light surface 113 is exposed, and the second reflective layer 1052 on the second passivation layer 1042 and the third passivation layer 1043 is retained .

Referring to FIGS. 16 and 17 , an insulating layer 106 is formed on the second light-reflecting layer 1052 , the first passivation layer 1041 and the first opening 115 , and then the first opening 115 is etched on the insulating layer 106 corresponding to the position of the first opening 115 . Two openings 119 expose the smooth surface 113 .

In some embodiments, the insulating layer 106 material may be an organic material or an inorganic material for electrical isolation. In some embodiments, the diameter of the second opening 119 is not smaller than the diameter of the first opening 115 to ensure that the light exit surface 113 is not blocked by the insulating layer 106 . In some embodiments, if the reflective layer 105 itself is not conductive, the insulating layer 106 may be omitted.

Referring to FIG. 18 , an electrode layer 107 is formed in the first opening 115 , the electrode layer 107 is electrically connected to the second doped semiconductor layer 110 of the LED unit 109 , and the second doped semiconductor layer 110 of the adjacent LED unit 109 is It is electrically connected through the electrode layer 107 . In some embodiments, the LED epitaxial layer 118 may further include a current spreading layer, so the electrode layer 107 and the second doped semiconductor layer 110 may also have a functional layer structure such as a current spreading layer, which can further improve the Uniform transfer performance of current. In some embodiments, the electrode layer 107 is fully coated on the LED unit 109 and then connected to the common electrode contact of the driving panel 101 together.

In some embodiments, the electrode layer 107 is made of a transparent material, such as a transparent conductive film, etc., as the ohmic contact layer and the light outlet of the LED unit 109 .

In some embodiments, in order to improve the collimation of the light, a Bragg mirror 108 may also be deposited at the light outlet. Referring to FIG. 19, the Bragg mirror 108 is located on the electrode layer 107, and the reflectivity of the Bragg mirror 108 is 50%-70%. In some embodiments, a reflective metal needs to be provided at the bottom of the LED unit 109 , and in this case, it needs to further satisfy that the reflectivity of the Bragg mirror 108 is smaller than that of the reflective metal at the bottom of the LED unit 109 .

In some embodiments, the entire surface of the Bragg mirror 108 is coated on the electrode layer 107 .

In some embodiments, when the electrode layer 107 is fully coated on the LED unit 109 and the Bragg reflector 108 is fully coated on the electrode layer 107, the electrode layer 107 and the Bragg reflector 108 are made of light-transmitting materials, such as Indium tin oxide, etc. In some embodiments, the second doped semiconductor layer 110 may be directly combined with indium tin oxide.

In some embodiments, the lift-off process of preparing the light-reflecting layer 105 by first depositing the sacrificial layer 116, then depositing the second light-reflecting layer 1052, and finally removing the sacrificial layer 116 is directly different from the existing dry etching or wet etching. etching process. The existing dry etching or wet etching is essentially the process of removing the surface material through the exposed area of the photoresist. Therefore, the reflective layer with high reflectivity needs to be etched by photolithography. In the actual operation process When the photolithography-based etching process is directly used, since the reflectivity of the reflective layer is generally at least greater than 80%, almost all of the light exposed to the photoresist that is not absorbed by the photoresist is absorbed by the reflective layer. 105 is reflected back, so that the resolution of the lithography becomes very poor, and the designed lithography pattern cannot be obtained for etching. However, after the lift-off-based lift-off technique is adopted, since the sacrificial layer 116 can be directly lifted off, there is no need to use a photolithography-based dry or wet etching process, so that the first light-reflecting layer 1051 on the sacrificial layer 116 can be removed with the sacrificial layer 116. The layer 116 is also lifted off, thereby omitting the etching step for the light-reflecting layer 105 with high reflectivity.

After the second light-reflecting layer 1052 is formed on the side of the LED unit 109, the spontaneous emission photons excited by the multiple quantum wells can be blocked by the light-reflecting layer, and cannot escape from the side of the LED unit 109, but can only be emitted by the light-emitting surface 113 at the top. Therefore, the second light-reflecting layer 1052 can completely prevent the occurrence of crosstalk between adjacent pixels; the photons reflected by the light-reflecting layer 105 will escape from the only light-emitting surface 113 after multiple reflections inside the LED unit 109, which is also greatly improved. output power.

In the above-mentioned embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference may be made to the relevant descriptions of other embodiments.

The present invention has been introduced in detail above, and specific examples are used in the present invention to illustrate the principles and implementations of the present invention. The descriptions of the above embodiments are only used to help understand the technical solutions and core ideas of the present invention; It should be understood by those of ordinary skill that the technical solutions described in the foregoing embodiments can still be modified, or some of the technical features thereof can be equivalently replaced; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the various aspects of the present invention. The scope of the technical solution of the embodiment.

Claims (18)

1. The preparation method of Micro LED display device, is characterized in that, comprises: A drive panel (101) is provided, the drive panel (101) including a plurality of first contacts (103); LED units (109) are provided, the LED units (109) are arranged in an array on the driving panel (101), and are individually driven through the corresponding first contacts (103); the LED units (109) having a light exit surface (113) and a side surface (114) connected to the light exit surface (113); A passivation layer (104) is formed, the passivation layer (104) is located on the LED unit (109), including a first passivation layer (1041) located on the light exit surface (113), located on the side surface The second passivation layer (1042) on the (114) that is integrally connected with the first passivation layer (1041) and the second passivation layer (1042) located between adjacent LED units (109) ) integrally connected third passivation layer (1043); A first opening (115) for exposing the light exit surface (113) is provided on the first passivation layer (1041); forming a sacrificial layer (116), the sacrificial layer (116) is located on the first passivation layer (1041) and covers the first opening (115); forming a light-reflecting layer (105), comprising a first light-reflecting layer (1051) on the sacrificial layer (116) and a light-reflecting layer (1051) on the second passivation layer (1042) and the third passivation layer (1043) The second reflective layer (1052), the first reflective layer (1051) and the second reflective layer (1052) are disconnected from each other; peel off the sacrificial layer (116), leaving the second reflective layer (1052) , and expose the first passivation layer (1041) and the first opening (115); The step of forming the sacrificial layer (116) includes: A sacrificial coating (1161) is formed, the sacrificial coating (1161) is located on the first opening (115), the first passivation layer (1041), the second passivation layer (1042) and the on the third passivation layer (1043); The sacrificial coating (1161) is patterned and exposed, the sacrificial coating (1161) on the second passivation layer (1042) and the third passivation layer (1043) is removed, and the first passivation is retained layer (1041) and a sacrificial coating (1161) on the first opening (115) to obtain the sacrificial layer (116); The thickness ratio of the sacrificial coating (1161) to the reflective layer (105) is greater than 2:1. 2. The method for preparing a Micro LED display device according to claim 1, wherein the step of providing an LED unit (109) comprises: providing a substrate (117) on which an LED epitaxial layer (118) is provided; bonding the driving panel (101) and the LED epitaxial layer (118), and forming a bonding layer (102) between the driving panel (101) and the LED epitaxial layer (118); removing the substrate (117); The LED epitaxial layer (118) is etched into a stepped structure, the stepped structure includes a first doped semiconductor layer (112), a second doped semiconductor layer (110) and an active semiconductor layer located therebetween layer (111); the light exit surface (113) is located on the second doped semiconductor layer (110) and is located at the top of the step structure; the step structure at least makes the first The two doped semiconductor layers (110) are disconnected and electrically isolated from each other. 3. The preparation method of the Micro LED display device according to claim 2, wherein, The stepped structure further separates and electrically isolates the first doped semiconductor layer (112) and the active layer (111) of the adjacent LED units (109) from each other; The material of the bonding layer (102) is a conductive material, and the bonding layers (102) between the adjacent LED units (109) are disconnected from each other by etching the bonding layer (102); The first contact (103) is located under the corresponding LED unit (109), and the first doped semiconductor layer (112) is electrically connected to the first contact (103) to make the LED unit (109) can be driven individually. 4. The method for manufacturing a Micro LED display device according to claim 3, wherein the first doped semiconductor layer (112) is electrically connected to the first contact (103) so that the LED is electrically connected The steps in which the unit (109) can be driven independently include: An electrode layer (107) is provided on the first passivation layer (1041); the electrode layer (107) is connected to the second doping type of the LED unit (109) through the first opening (115) The semiconductor layer (110) is electrically connected, and the second doped semiconductor layer (110) of adjacent LED units (109) is electrically connected through the electrode layer (107). 5. The method for preparing a Micro LED display device according to claim 4, wherein before the step of disposing the electrode layer (107) on the first passivation layer (1041), the method comprises: forming an insulating layer (106) on the first passivation layer (1041) and the second light-reflecting layer (1052), and then on the first passivation layer (1041) A second opening (119) is provided on the insulating layer (106) and the first opening (115) is exposed. 6. The method for preparing a Micro LED display device according to claim 4, wherein after the step of disposing an electrode layer (107) on the first passivation layer (1041), the method comprises: A Bragg mirror (108) is formed, the Bragg mirror (108) being located on the electrode layer (107). 7. The method for manufacturing a Micro LED display device according to claim 6, wherein the reflectivity of the Bragg reflector (108) is between 50% and 70%. 8. The method for preparing a Micro LED display device according to claim 1, wherein the sacrificial layer (116) comprises any of photoresist, SU-8, polyimide, SiO ₂ and SiN _x A sort of. 9 . The method for manufacturing a Micro LED display device according to claim 1 , wherein the reflectivity of the reflective layer ( 105 ) is greater than 80%. 10 . 10. A Micro LED display device, characterized in that, prepared by the method of any one of claims 1-9, the Micro LED display device comprises: a drive panel (101), comprising a plurality of first contacts (103); a plurality of LED units (109), the LED units (109) are arranged in an array on the driving panel (101), and are individually driven through the first contacts (103); The LED unit (109) has a light emitting surface (113) and a side surface (114) connected to the light emitting surface (113); A passivation layer (104), comprising a first passivation layer (1041) located on the light emitting surface (113), a first passivation layer (1041) located on the side surface (114) and integrally connected to the first passivation layer (1041) a second passivation layer (1042) and a third passivation layer (1043) located between adjacent LED units (109) and integrally connected with the second passivation layer (1042); A second light-reflecting layer (1052) is located on the second passivation layer (1042) and the third passivation layer (1043). 11. The Micro LED display device according to claim 10, characterized by comprising a bonding layer (102), wherein the bonding layer (102) is located on the driving panel (101) and the LED unit (109) between; The LED unit (109) includes a stepped structure formed by etching the LED epitaxial layer (118), the stepped structure including a first doped semiconductor layer (112), a second doped semiconductor layer (110) and a The active layer (111) between the two, the light exit surface (113) is located on the second doped semiconductor layer (110) and is located at the top of the step structure; the step structure at least makes the adjacent The second doped semiconductor layers (110) of the LED unit (109) are disconnected and electrically isolated from each other. 12 . The Micro LED display device according to claim 11 , wherein the step structure further enables the first doped semiconductor layer ( 112 ) and the active layer between adjacent LED units ( 109 ). 12 . (111) disconnected and electrically isolated from each other; The first contact (103) is located under the corresponding LED unit (109), and the first contact (103) is electrically connected to the corresponding first doped semiconductor layer (112). 13. The Micro LED display device according to claim 12, characterized by comprising an electrode layer (107), the electrode layer (107) being located on the first passivation layer (1041); The electrode layer (107) is electrically connected to the second doped semiconductor layer (110) through a first opening (115), and the second doped semiconductor layer ( 110) is electrically connected through the electrode layer (107). 14. The Micro LED display device according to claim 13, further comprising an insulating layer (106), wherein the insulating layer (106) is located between the first passivation layer (1041) and the second reflective layer layer(1052); The insulating layer (106) has a second opening (119) exposing the first opening (115), and the electrode layer (107) communicates with the insulating layer through the second opening (119) (106) CONTACT. 15. The Micro LED display device according to claim 14, further comprising a Bragg mirror (108), the Bragg mirror (108) being located on the electrode layer (107). 16. The Micro LED display device according to claim 10, wherein the driving panel (101) is a silicon-based CMOS driving board or a thin film field effect transistor driving board. 17. The Micro LED display device according to claim 10, wherein the size of the LED unit (109) is 0.1-5 microns. 18. The Micro LED display device according to claim 10, wherein the thickness δ of the sidewall of the passivation layer (104) satisfies the following formula: δ=λ/(4×n); In the formula, λ is the emission wavelength of the LED unit (109), and n is the refractive index of the passivation layer (104).

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