CN115000254A - Miniature LED display device and preparation method thereof - Google Patents
Miniature LED display device and preparation method thereof Download PDFInfo
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- CN115000254A CN115000254A CN202210777569.3A CN202210777569A CN115000254A CN 115000254 A CN115000254 A CN 115000254A CN 202210777569 A CN202210777569 A CN 202210777569A CN 115000254 A CN115000254 A CN 115000254A
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L33/005—Processes
- H01L33/0062—Processes for devices with an active region comprising only III-V compounds
- H01L33/0075—Processes for devices with an active region comprising only III-V compounds comprising nitride compounds
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
- H01L27/15—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components having potential barriers, specially adapted for light emission
- H01L27/153—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components having potential barriers, specially adapted for light emission in a repetitive configuration, e.g. LED bars
- H01L27/156—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components having potential barriers, specially adapted for light emission in a repetitive configuration, e.g. LED bars two-dimensional arrays
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L33/44—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the coatings, e.g. passivation layer or anti-reflective coating
- H01L33/46—Reflective coating, e.g. dielectric Bragg reflector
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- Computer Hardware Design (AREA)
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- Condensed Matter Physics & Semiconductors (AREA)
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Abstract
The invention discloses a micro LED display device and a preparation method thereof, wherein the preparation method comprises the following steps: after an indium tin oxide film is evaporated on the epitaxial wafer, patterning, exposing, developing and etching are carried out, and a part of the n-type gallium nitride layer is exposed, so that the epitaxial wafer forms a mesa structure and a wall structure surrounding the mesa; depositing a dielectric material on the surface of the processed epitaxial wafer to form a first passivation layer; carrying out patterning exposure and development on the surface of the first passivation layer, evaporating and plating a metal reflecting film with a preset thickness, and stripping to enable the metal reflecting film to cover the wall structure to form a metal thin film reflecting wall; depositing dielectric material again to form a second passivation layer; and carrying out patterning exposure development and etching on the second passivation layer, forming holes on the surface of the n-type gallium nitride layer and the surface of the mesa structure, and respectively evaporating an n metal electrode and a p metal electrode at the positions of the holes to obtain the micro LED display device. The scheme can improve the luminous efficiency of the micro LED display device and reduce the optical coupling crosstalk between the micro LEDs.
Description
Technical Field
The invention relates to the technical field of semiconductor devices, in particular to a micro LED display device and a preparation method thereof.
Background
The Micro-LED display technology is a display technology which takes self-luminous micrometer-scale LEDs as light-emitting pixel units and assembles the light-emitting pixel units on a driving panel to form a high-density LED array. Due to the characteristics of small size, high integration level, self-luminescence and the like of the micro-LED chip, compared with the LCD and the OLED, the micro-LED chip has greater advantages in the aspects of brightness, resolution, contrast, energy consumption, service life, response speed, thermal stability and the like, and has attracted extensive research and attention.
As the pixel size of micro-LEDs is gradually reduced and the number of arrays is increased, optical crosstalk between adjacent and nearby pixels becomes a big problem. The optical crosstalk may cause the pixels originally in the off state to be affected by the pixels in the surrounding on state and to appear non-black, thereby affecting important indexes of the micro LED display device, such as contrast, saturation, and color purity. At present, the method for realizing micro-LED full-color display mainly comprises multi-color integration of a single chip micro-LED and color conversion based on a color conversion material, but the micro-LED display array still has a few problems, no matter the micro-LED display array is displayed by self-luminescence or by the color conversion material, the micro-LED is required to have higher quantum efficiency, and meanwhile, in order to ensure the accuracy and uniformity of the displayed color, the optical coupling crosstalk among all pixel points is also required to be eliminated. For spontaneous display, in order to eliminate optical crosstalk, a black optical barrier is generally prepared between devices to reduce optical crosstalk and an optical reflective film structure is prepared to improve light extraction efficiency after the devices are prepared, and in a subsequent processing process, the devices are easily damaged due to introduction of a new process. For exciting the color conversion material, a thicker color conversion material is usually provided to absorb the excitation light as much as possible in order to improve the light emission efficiency, but this will increase the manufacturing process cost of the device and reduce the light emission efficiency of the device as a whole.
The first prior art is a chinese patent application with patent publication No. CN 108281092A. The micro-structure for improving the display light effect of the micron-sized LED is disclosed. The inverted trapezoidal liquid storage tank is prepared on the surface of the micron-sized LED, the quantum dot material is filled, and the color conversion efficiency and the light emitting efficiency in the vertical direction of the micron-sized LED are improved by reflecting light through the inverted trapezoidal liquid storage tank. The LED array substrate comprises micron-sized LED chips which are uniformly distributed on a substrate along the longitudinal direction and the transverse direction, a liquid storage tank which is arranged on the surface of the micron-sized LED chip and is in an inverted trapezoid shape, an emitting layer which is prepared on the wall of the liquid storage tank, a quantum dot color conversion material which is filled in the liquid storage tank and a Bragg reflector which is prepared on the surface of a quantum dot light emitting layer. The first prior art has the disadvantages that the process of preparing the inverted trapezoidal liquid storage tank is complex, the performance of the device is greatly influenced, the preparation cost is increased, and in addition, the method cannot control the direction of the surface vertical light rays and also causes optical crosstalk.
The second prior art is a chinese patent application with patent publication No. CN113206176A, which discloses a method for preparing micro-LED chips by selective etching. The device comprises a sapphire substrate, an n-type gallium nitride layer, a multi-quantum well layer, a p-type gallium nitride layer, a silicon dioxide insulating layer, a p electrode, a substrate, an n electrode, an ultra-black matrix shading layer, a gallium indium phosphorus nanowire array polymer film, a surface coating Ag film, a Bragg reflector and an optical filter. The second prior art has the disadvantages that the preparation process is complex, and the ultra-black matrix light shielding layer cannot completely cover the light emitting angle and cannot reduce the optical crosstalk after the light emitting color conversion.
Therefore, it is desirable to provide a method for manufacturing a micro LED display device, which can design a new device structure based on the existing micro LED device manufacturing process, effectively reduce optical coupling crosstalk, and improve the light emitting efficiency of the device, so as to solve the above problems in the prior art.
Disclosure of Invention
In view of the above, the present solution provides a micro LED display device and a method for manufacturing the same that overcomes or at least partially solves the above problems.
According to an aspect of the present invention, there is provided a method of fabricating a micro LED display device, in which first, a buffer layer, an n-type gallium nitride layer, a multi-quantum well layer, an electron blocking layer, and a p-type gallium nitride layer are epitaxially grown in this order on a substrate provided in advance to obtain an epitaxial wafer. Then, an indium tin oxide film is evaporated on the epitaxial wafer to form a first epitaxial structure so as to ensure that the electrode and the epitaxial wafer form good ohmic contact. And then, carrying out patterned exposure and development on the surface of the first epitaxial structure, and etching to expose part of the n-type gallium nitride layer to form a second epitaxial structure, wherein the second epitaxial structure comprises a mesa structure and a wall structure surrounding the mesa structure. A dielectric material can be deposited on the surface of the second epitaxial structure to serve as a first passivation layer, and a third epitaxial structure is formed; the dielectric material may protect the light emitting active region. And then, carrying out patterning exposure and development on the surface of the third epitaxial structure, evaporating a metal reflecting film with a preset thickness, and carrying out a stripping process to enable the metal reflecting film to completely cover the wall structure, thereby forming a fourth epitaxial structure. The metal film can perform wider spectral reflection, so that divergent light of adjacent or similar LED devices is projected out through the reflecting wall, the influence of each independent device is reduced, and the optical crosstalk among different pixels is greatly reduced. And then, depositing a dielectric material on the surface of the fourth epitaxial structure to serve as a second passivation layer to form a fifth epitaxial structure, and preventing the metal reflecting film from being oxidized and completely separated from the metal external electrode, thereby achieving the effects of passivation and isolation from the metal electrode. And finally, carrying out patterning exposure and development on the surface of the fifth epitaxial structure, etching to open holes on the surface of the exposed n-type gallium nitride layer and the surface of the mesa structure so as to form a sixth epitaxial structure, and respectively evaporating an n electrode and a p electrode at the positions of the open holes so as to obtain a single micro LED display device.
Optionally, in the method according to the present invention, the epitaxial wafer is cleaned before the indium tin oxide film is evaporated on the epitaxial wafer to remove residual contaminants on the surface of the epitaxial wafer, so as to avoid affecting the performance of the chip.
Alternatively, in the method according to the present invention, the step of patterning the photolithographic process may include: designing a mask plate with a specific pattern; coating photoresist on a target layer to be subjected to patterning photoetching treatment, wherein the target layer comprises any one of a first epitaxial structure and a fifth epitaxial structure; exposing and developing the photoresist on the target layer through a mask plate; etching the target layer by wet etching and/or inductively coupled plasma; and removing the photoresist on the surface of the target layer.
Optionally, in the method according to the present invention, a stripping process may be further performed on the photoresist and the evaporated metal reflective film remaining after the patterned exposure and development are performed on the surface of the third epitaxial structure, so as to obtain a metal thin film reflective wall covering the wall structure.
Alternatively, in the method according to the present invention, the shape of the wall structure is any one of a ring shape, a trapezoid shape, a square shape and a polygon shape, and the thickness and height of the wall structure and the distance between the wall structure and the mesa structure are related to the pixel size of the micro LED display device.
Alternatively, in the method according to the present invention, the substrate provided in advance may be any one of a sapphire substrate, a silicon carbide substrate, a gallium nitride substrate, and a silicon substrate.
Optionally, in the method according to the present invention, the dielectric material is any one or more of SiO2, Al2O3, Si3N4, phosphosilicate glass, and polyimide.
Optionally, in the method according to the present invention, the material of the metal reflective film includes any one of Au, Ag, Al, and Cu.
Optionally, in the method according to the present invention, the emission spectrum of the multiple quantum well layer ranges from deep ultraviolet to red light.
According to another aspect of the present invention, there is provided a micro LED display device prepared by the method as described above, which may include a substrate, a light emitting element, a reflecting element, and a metal electrode.
The substrate sequentially comprises a substrate, a buffer layer, an n-type gallium nitride layer, a first passivation layer and a second passivation layer from bottom to top; the light-emitting element is arranged on the surface of the buffer layer of the substrate and sequentially comprises an n-type gallium nitride layer, a multi-quantum well layer, an electronic barrier layer, a p-type gallium nitride layer, a mesa structure of an indium tin oxide film, a first passivation layer and a second passivation layer, wherein the first passivation layer is coated on the surface of the mesa structure, and the second passivation layer is coated on the surface of the first passivation layer; the reflecting element is arranged on the surface of the buffer layer of the substrate, surrounds the light-emitting element, and sequentially comprises an n-type gallium nitride layer, a multi-quantum well layer, an electronic barrier layer, a p-type gallium nitride layer, a mesa structure of an indium tin oxide film, a first passivation layer, a metal reflecting film and a second passivation layer from bottom to top, wherein the first passivation layer is coated on the surface of the mesa structure; the metal electrode comprises an n-type metal electrode and a p-type metal electrode, the n-type metal electrode is electrically connected with the n-type gallium nitride layer, and the p-type metal electrode is electrically connected with the indium tin oxide layer.
According to the scheme of the invention, the wall structure surrounding the light-emitting device is formed by patterning, exposing, developing and etching the epitaxial material, so that the traditional preparation process of the ultra-black matrix is replaced, the preparation flow is greatly simplified, and the preparation cost is saved; meanwhile, the metal reflecting film is evaporated on the wall structure to reflect light, so that the utilization rate of photons and the luminous efficiency of a device are improved, and the problem of optical coupling crosstalk between pixels is reduced due to the fact that the metal reflecting film reflects light.
The foregoing description is only an overview of the technical solutions of the present invention, and the embodiments of the present invention are described below in order to make the technical means of the present invention more clearly understood and to make the above and other objects, features, and advantages of the present invention more clearly understandable.
Drawings
Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. Also, like reference numerals are used to refer to like parts throughout the drawings. In the drawings:
FIG. 1 shows a schematic flow diagram of a method 100 of fabricating a micro LED display device according to one embodiment of the present invention;
fig. 2 shows a side view of the first epitaxial structure after processing in accordance with step S120 of the present invention;
fig. 3 shows a side view of the second epitaxial structure after processing in step S130 according to the present invention;
fig. 4 shows a side view of a third epitaxial structure after processing in accordance with step S140 of the present invention;
FIG. 5 shows a side view of a fourth epitaxial structure after processing in step S150 according to the present invention;
fig. 6 shows a side view of a fifth epitaxial structure after processing in accordance with step S160 of the invention;
fig. 7 shows a side view of the sixth epitaxial structure after processing in step S170 according to the present invention;
fig. 8 illustrates a schematic structural view of a micro LED display device according to an embodiment of the present invention.
Detailed Description
Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.
The problem that optical crosstalk is weakened by adding the ultra-black matrix in the existing micro LED display array is complex in preparation process and high in cost, the problem of optical crosstalk cannot be completely solved because the ultra-black matrix cannot completely cover a light-emitting angle, and the performance of a device is greatly influenced because the device is inevitably damaged after the prepared micro LED device is processed. Aiming at the defects of the prior art, the scheme provides a preparation method of a micro LED display device, and a new device structure is designed on the basis of the existing micro LED preparation process, so that the LED luminous efficiency can be improved, the optical crosstalk can be reduced, the preparation flow of the display device can be simplified, and the cost can be reduced.
One embodiment of the present invention provides a method for fabricating a micro LED display device, and fig. 1 shows a schematic flow chart of a method 100 for fabricating a micro LED display device according to one embodiment of the present invention. As shown in fig. 1, the method 100 starts with step S110 of epitaxially growing a buffer layer, an n-type gallium nitride layer, a multi-quantum well layer, an electron blocking layer, and a p-type gallium nitride layer on a substrate provided in advance to obtain an epitaxial wafer. The substrate of the epitaxial wafer mainly comprises sapphire, gallium nitride, silicon carbide, silicon and the like, different substrate materials need different LED epitaxial growth technologies, chip processing technologies and device packaging technologies, and a proper epitaxial substrate can be selected according to actual needs. In one embodiment of the present invention, an epitaxial wafer with sapphire as a substrate is selected, and the sapphire substrate is subjected to epitaxial growth of a gallium nitride buffer layer, an n-type gallium nitride layer, a multi-quantum well layer, an electron blocking layer, and a p-type gallium nitride layer in an MOCVD (metal organic chemical vapor deposition) apparatus. The light emission spectrum of the multiple quantum well layer can cover the bands from deep ultraviolet to red light, and the size and the shape of the epitaxial wafer are not limited herein.
Then, step S120 is performed to deposit an ito film on the epitaxial wafer to cover the ito film on the surface of the epitaxial wafer, so as to form a first epitaxial structure. The sapphire substrate is an insulator, so that an electrode with a vertical structure cannot be manufactured, and the indium tin oxide has the function of enabling the electrode to form good ohmic contact with an epitaxial layer. In a preferred embodiment, the epitaxial wafer can be cleaned by using a mixed solution of deionized water, hydrogen peroxide and sulfuric acid as a cleaning solution to remove residual pollutants on the surface of the epitaxial wafer, and then the epitaxial wafer is heated to a proper temperature and an indium tin oxide film is evaporated in a vacuum environment. Fig. 2 shows a side view of the first epitaxial structure after being processed according to step S120 of the present invention, and as shown in fig. 2, the bottom layer of the first epitaxial structure is a substrate and a buffer layer 01, and an n-type gallium nitride layer 02, a multi-quantum well layer 03, an electron blocking layer 04, a p-type gallium nitride layer 05 and an indium tin oxide thin film 06 are sequentially disposed above the substrate 01.
Then, step S130 is performed, a patterned exposure and development are performed on the surface of the first epitaxial structure, and etching is performed to expose a portion of the n-type gan layer, so as to form a second epitaxial structure, where the second epitaxial structure includes a mesa structure and a wall structure surrounding the mesa structure. By designing a new device structure, the light emitting part of the micro LED is surrounded by the surrounding wall structure, and the influence of light of adjacent devices is reduced. In a typical photolithography process, a photoresist is first coated on a surface of a target layer, and then exposed and developed to form a photoresist pattern. The photoresist pattern is then used to etch the target layer to form the predetermined structure, and in one embodiment of the present invention, the step of patterning the photolithography process may include: the mask plate with a specific pattern can be a fence-shaped pattern comprising an inner layer and an outer layer, so that the epitaxial wafer forms a mesa structure and a wall structure surrounding the mesa structure, the wall structure can be any one of a ring structure, a trapezoid structure, a square structure and a polygon structure, and the mesa structure can be a square structure, a circle structure, a polygon structure and the like, which is not limited herein. The thickness and the height of the wall structure and the distance between the wall structure and the table-board structure are related to the pixel size of the micro LED display device, and the thickness and the height of the wall structure and the distance between the wall structure and the table-board structure can be adjusted according to the pixel requirement of the micro LED display device to be manufactured. Coating photoresist on a target layer to be subjected to patterning photoetching treatment; exposing and developing the photoresist on the target layer through a mask plate to obtain a photoresist pattern; etching the target layer by a wet etching method and/or an inductive coupling plasma etching method; and finally, removing the photoresist on the surface of the target layer by adopting a heated acetone solution. Fig. 3 shows a side view of the second epitaxial structure after processing in step S130 according to the present invention. As shown in fig. 3, the second epitaxial structure developed and etched by the patterned exposure includes a mesa structure 07 in the middle and a wall structure 08 surrounding the mesa structure.
Next, step S140 is performed to deposit a dielectric material as a first passivation layer on the surface of the second epitaxial structure, thereby forming a third epitaxial structure. The dielectric material is used as a passivation isolation layer, a very thin and compact passivation film with good covering performance can be generated on the surface of the indium tin oxide film, and the effect of isolating corrosive media can be achieved. The dielectric material can be any one or more of SiO2, Al2O3, Si3N4, phosphorosilicate glass and polyimide. The method for depositing the dielectric material comprises any one or more of vacuum thermal evaporation, vacuum electron beam evaporation, vacuum magnetron sputtering, vacuum radio frequency sputtering, vacuum electron beam cyclotron resonance sputtering, chemical vapor deposition or atomic layer deposition. Fig. 4 shows a side view of the third epitaxial structure after processing in accordance with step S140 of the present invention. As shown in fig. 4, the first passivation layer 09 completely covers the surface of the third epitaxial structure, so that the subsequent metal reflective layer is isolated from the epitaxial layer.
And step S150, performing patterned exposure and development on the surface of the third epitaxial structure, depositing a metal reflective film with a predetermined thickness by evaporation, and performing a lift-off process to completely cover the wall structure with the metal reflective film, thereby forming a fourth epitaxial structure. The thickness, height and the distance between the metal film reflecting wall and the micro LED are all related to the size of the micro LED pixel, and can be set according to different requirements. The material of the metal reflective film includes any one of Au, Ag, Al, and Cu, and when a metal such as Al, Ag, or Au is deposited, a mirror having a high reflectance is obtained. The metal films are capable of reflection over a broad spectral region and are useful in applications where the wavelength ranges from 250 nm to over 10 μm. Since the Ag film provides the highest reflectivity between 500-800 nm, in an embodiment of the present invention, an Ag film reflective layer is deposited on the wall structure, and after the Ag reflective film is formed, the photoresist remaining after the patterned photolithography process is performed on the surface of the first passivation layer and the evaporated metal reflective film may be subjected to a lift-off process to obtain a metal film reflective wall covering the wall structure. The step of patterning the photolithography process is as described above, except that the pattern of the mask plate is different, and in the embodiment according to the present invention, the pattern of the mask plate is an outer layer pattern in a fence shape so that the metal reflective film entirely covers the wall structure of the outer layer. Fig. 5 shows a side view of a fourth epitaxial structure after processing in step S150 according to the present invention. As shown in fig. 5, the metal reflective film 010 completely covers the surface of the first passivation layer 09 of the wall structure 08 to form a metal reflective wall, so that ambient light can be reflected, thereby reducing optical crosstalk between devices.
Then, step S160 is executed, a dielectric material is deposited on the surface of the fourth epitaxial structure as a second passivation layer to form a fifth epitaxial structure, and the re-deposition of the passivation layer can generate a very thin and dense passivation film with good coverage property, usually a metal oxide, on the surface of the metal reflective film, which can play a role of dielectric isolation. The dielectric material can be any one or more of SiO2, Al2O3, Si3N4, phosphorosilicate glass and polyimide. The method for depositing the dielectric material comprises any one or more of vacuum thermal evaporation, vacuum electron beam evaporation, vacuum magnetron sputtering, vacuum radio frequency sputtering, vacuum electron beam cyclotron resonance sputtering, chemical vapor deposition or atomic layer deposition. Fig. 8 shows a side view of a fifth epitaxial structure after processing in accordance with step S160 of the present invention. As shown in fig. 6, the second passivation layer 011 completely covers the surfaces of the first passivation layer 09 and the metal reflective film 010 to isolate the subsequent electrode leads.
And finally, executing step S170, carrying out patterning exposure development on the surface of the fifth epitaxial structure, etching to open holes on the surface of the exposed n-type gallium nitride layer and the surface of the mesa structure so as to form a sixth epitaxial structure, and evaporating an n metal electrode and a p metal electrode at the positions of the open holes respectively to obtain a single micro LED display device. The steps of the patterning lithography process are as described above, and are not described herein again, except for the difference in the pattern of the mask plate. Forming openings on the surface of the indium tin oxide film of the mesa structure and the surface of the n-type gallium nitride layer between the mesa structure and the wall structure after patterning photoetching treatment, and then depositing Ti/Au on the indium tin oxide layer at the positions of the openings to prepare p electrodes; and depositing metal Ti/Au on the n-type gallium nitride layer to prepare an n electrode, thereby completing the preparation of the micro LED display device. Fig. 7 shows a side view of a sixth epitaxial structure after processing in accordance with step S170 of the present invention. As shown in fig. 7, a first opening 012, a second opening 013, and a third opening 014 are formed on the surface of the ito film 06 of the mesa structure and the surface of the n-type gan layer 02 between the mesa structure and the wall structure so as to deposit metal electrodes at the positions of the openings, and a welding point may be disposed at the openings so that the n-type electrodes are connected to the n-type gan layer through the second opening 013 and the third opening 014, and the p-type electrodes are connected to the ito layer through the first opening 012, thereby completing the fabrication of the micro LED display device.
After the preparation of the single miniature LED display device is completed, the miniature LED display array can be further prepared by methods such as a photoetching process and the like, the miniature LED display array and a driving circuit board such as a PCB and the like are subjected to lead bonding, and relevant photoelectric characteristic tests are carried out. Tests prove that the micro LED display array prepared by the invention has higher light-emitting efficiency and can effectively reduce the optical crosstalk between devices.
After the above steps, a single micro LED display device is obtained, an embodiment of the present invention further provides a micro LED display device, and fig. 8 shows a schematic structural diagram of the micro LED display device according to an embodiment of the present invention. As shown in fig. 8, the micro LED display device may include a substrate, a light emitting element, a reflective element, and a metal electrode, wherein the substrate includes, in order from bottom to top, a substrate, a buffer layer, an n-type gallium nitride layer, a first passivation layer, and a second passivation layer.
The light-emitting element is arranged on the surface of the buffer layer of the substrate and sequentially comprises an n-type gallium nitride layer, a multi-quantum well layer, an electronic barrier layer, a p-type gallium nitride layer, a table structure of an indium tin oxide film, a first passivation layer coated on the surface of the table structure and a second passivation layer coated on the surface of the first passivation layer from bottom to top. The passivation layer shown in fig. 8 includes a first passivation layer and a second passivation layer.
The reflecting element is arranged on the surface of the buffer layer of the substrate, surrounds the light-emitting element, and sequentially comprises an n-type gallium nitride layer, a multi-quantum well layer, an electronic barrier layer, a p-type gallium nitride layer, a table-board structure of an indium tin oxide film, a first passivation layer, a metal reflecting film and a second passivation layer, wherein the first passivation layer, the metal reflecting film and the second passivation layer are coated on the surface of the metal reflecting film, and the first passivation layer, the metal reflecting film and the second passivation layer are coated on the surface of the table-board structure.
The metal electrode comprises an n-type metal electrode and a p-type metal electrode, the n-type metal electrode is electrically connected with the n-type gallium nitride layer, and the p-type metal electrode is electrically connected with the indium tin oxide layer.
According to the preparation method of the micro LED device, the wall structure surrounding the light-emitting device is formed by patterning the photoetching epitaxial material to replace the traditional preparation process of the ultra-black matrix, so that the preparation flow is greatly simplified, and the preparation cost is saved; meanwhile, the metal reflection film is evaporated on the wall structure to reflect light, so that the utilization rate of photons and the luminous efficiency of a device are improved, and the problem of optical crosstalk between pixels is reduced due to the fact that the metal reflection film reflects light.
In the description provided herein, numerous specific details are set forth. It is understood, however, that embodiments of the invention may be practiced without these specific details. In some instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description.
Furthermore, those skilled in the art will appreciate that while some embodiments described herein include some features included in other embodiments, rather than other features, combinations of features of different embodiments are meant to be within the scope of the invention and form different embodiments. For example, in the following claims, any of the claimed embodiments may be used in any combination.
As used herein, unless otherwise specified the use of the ordinal adjectives "first", "second", "third", etc., to describe a common object, merely indicate that different instances of like objects are being referred to, and are not intended to imply that the objects so described must be in a given sequence, either temporally, spatially, in ranking, or in any other manner.
While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this description, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as described herein. Moreover, it should be noted that the language used in the specification has been principally selected for readability and instructional purposes, and may not have been selected to delineate or circumscribe the inventive subject matter. Accordingly, many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the appended claims. The present invention has been disclosed in an illustrative rather than a restrictive sense with respect to the scope of the invention, as defined in the appended claims.
Claims (10)
1. A preparation method of a micro LED display device is characterized by comprising the following steps:
step S110, sequentially epitaxially growing a buffer layer, an n-type gallium nitride layer, a multi-quantum well layer, an electronic barrier layer and a p-type gallium nitride layer on a pre-provided substrate to obtain an epitaxial wafer;
step S120, evaporating an indium tin oxide film on the epitaxial wafer to form a first epitaxial structure;
step S130, carrying out patterning exposure development and etching on the surface of the first epitaxial structure, exposing a part of the n-type gallium nitride layer, and forming a second epitaxial structure, wherein the second epitaxial structure comprises a mesa structure and a wall structure surrounding the mesa structure;
step S140, depositing a dielectric material on the surface of the second epitaxial structure to serve as a first passivation layer, and forming a third epitaxial structure;
step 150, performing patterned exposure and development on the surface of the third epitaxial structure, evaporating a metal reflecting film with a preset thickness, and performing a stripping process to enable the metal reflecting film to cover the wall structure to form a fourth epitaxial structure;
step S160, depositing a dielectric material on the surface of the fourth epitaxial structure to serve as a second passivation layer, and forming a fifth epitaxial structure;
step S170, performing patterned exposure and development on the surface of the fifth epitaxial structure, and performing etching, so as to open holes on the surface of the exposed n-type gallium nitride layer and the surface of the mesa structure, thereby forming a sixth epitaxial structure, and evaporating an n metal electrode and a p metal electrode at the positions of the openings, respectively, thereby obtaining a single micro LED display device.
2. The method of claim 1, wherein the step of patterning a lithographic process comprises:
manufacturing a mask plate with a specific pattern;
coating photoresist on a target layer to be subjected to patterning photoetching treatment, wherein the target layer comprises any one of a first epitaxial structure, a third epitaxial structure and a fifth epitaxial structure;
exposing and developing the photoresist on the target layer through the mask plate;
etching the target layer by wet etching and/or inductively coupled plasma; and removing the photoresist on the surface of the target layer.
3. The method of claim 1, wherein the step S150 further comprises:
and carrying out a stripping process on the photoresist and the evaporated metal reflecting film which are remained after the patterning exposure and development are carried out on the surface of the third epitaxial structure, so as to obtain the metal thin film reflecting wall covering the wall structure.
4. The method according to claim 1 or 3, wherein the shape of the wall structure is any one of a ring shape, a trapezoid shape, a square shape and a polygon shape, and the thickness and height of the wall structure and the distance between the wall structure and the mesa structure are related to the pixel size of the micro LED display device.
5. The method of claim 1, prior to the step S120, further comprising:
and cleaning the epitaxial wafer.
6. The method according to claim 1, wherein the substrate provided in advance is any one of a sapphire substrate, a silicon carbide substrate, a gallium nitride substrate, and a silicon substrate.
7. The method of claim 1, wherein the dielectric material is any one or more of SiO2, Al2O3, Si3N4, phosphosilicate glass, and polyimide.
8. The method of claim 1, wherein the material of the metal reflective film comprises any one of Au, Ag, Al, and Cu.
9. The method of claim 1 wherein the multiple quantum well layers emit light in the spectral range from deep ultraviolet to red.
10. A micro LED display device prepared according to the method of any one of claims 1 to 9, comprising: a substrate, a light emitting element, a reflective element, and a metal electrode;
the substrate sequentially comprises a substrate, a buffer layer, an n-type gallium nitride layer, a first passivation layer and a second passivation layer from bottom to top;
the light-emitting element is arranged on the surface of the buffer layer of the substrate and sequentially comprises an n-type gallium nitride layer, a multi-quantum well layer, an electronic barrier layer, a p-type gallium nitride layer, a table top structure of an indium tin oxide film, a first passivation layer coated on the surface of the table top and a second passivation layer coated on the surface of the first passivation layer from bottom to top;
the reflecting element is arranged on the surface of the buffer layer of the substrate, surrounds the light-emitting element, and sequentially comprises an n-type gallium nitride layer, a multi-quantum well layer, an electronic barrier layer, a p-type gallium nitride layer, a table-board structure of an indium tin oxide film, a first passivation layer, a metal reflecting film and a second passivation layer from bottom to top, wherein the first passivation layer, the metal reflecting film and the second passivation layer are coated on the surface of the table-board structure;
the metal electrode comprises an n-type metal electrode and a p-type metal electrode, the n-type metal electrode is electrically connected with the n-type gallium nitride layer, and the p-type metal electrode is electrically connected with the indium tin oxide layer.
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