Structure and manufacturing method of Micro-LED display screen
Technical Field
The invention relates to a Micro-LED display screen structure and a manufacturing method thereof, relating to the technical field of displays.
Background
Micro-LED means that a conventional LED structure is miniaturized, and various performances such as brightness, life, contrast, reaction time, power consumption, viewing angle, and the like of the Micro-LED technology are superior to those of LCD and OLED technologies, and the Micro-LED technology is self-luminous, simple in structure and extremely strong in environmental adaptability, and has been considered as a next-generation display technology by many manufacturers and starts to be actively deployed.
At present, the structure of a Micro-LED display screen mainly comprises the combination of a Micro-LED chip and a CMOS or TFT driving back plate, and the Micro-LED chip is integrated on the CMOS or TFT driving back plate in a transferring and bonding mode so as to form a complete display screen structure. However, the transfer technology of Micro-LED still has a problem to be overcome, and the bonding technology of Micro-LED needs to be improved continuously. In general, the design and fabrication of CMOS or TFT driver backplanes and the transfer and bonding of Micro-LED chips makes the development process more complex and the development cost more expensive.
In a Micro-LED display screen driven in a PM mode, a common cathode common anode metal lead needs to be additionally LED out and connected with a peripheral circuit, so that the drive control of the peripheral circuit is realized. In conventional large-size LED displays, these common-cathode common-anode metal leads can be directly fabricated on the PCB, but in Micro-LED displays, metal leads of very small width cannot be fabricated on the PCB. For solving this problem, can directly make the metal lead wire on the display screen, but this can make it occupy certain non-display area, in addition, will drive chip hot pressing also need occupy certain area on the display screen, and both can make the effective display area proportion of display screen reduce.
Disclosure of Invention
The invention aims to provide a Micro-LED display screen structure and a manufacturing method thereof, and solves the problems of transfer and bonding in the design and manufacturing process of the Micro-LED display screen.
The technical scheme of the invention is as follows: a Micro-LED display screen structure comprises a display array which is arranged on the front side of a display screen and is composed of Micro-LED chips, wherein the Micro-LED chips in each row and each column in the display array are respectively connected through metal wires, and an insulating layer is respectively arranged between the surface of the display array and the metal wires in the rows and the columns; the back surface of the display screen is provided with a driving chip, a metal bonding pad and a plurality of back surface metal wires with one ends connected with the driving chip, and each back surface metal wire is in one-to-one correspondence with the metal wires on the front surface in function; the metal wires on the front side of the display screen and the back metal wires corresponding to the back one to one are connected in a hole mode to form a passage.
Furthermore, the display array formed by the Micro-LED chips is directly etched on the substrate and directly formed.
Furthermore, the substrate is a glass substrate and can be used for epitaxial growth of the LED chip, and the substrate does not need to be peeled off after epitaxial growth and pixelation.
Furthermore, the metal wires in each row and each column on the front surface of the display screen only extend to the outermost Micro-LED chips, and an insulating layer for isolation is arranged at the overlapping position of the metal wires of the Micro-LED chips in each row and the Micro-LED chips in each column.
Furthermore, the metal lines in each row on the front surface of the display screen are common cathode metal lines, the metal lines in each column are common anode metal lines, and the insulating layer is made of SiO2An insulating layer.
Furthermore, the size of the driving chip is smaller than the area of the display array, and the driving chip is directly hot-pressed on the back surface of the glass substrate in a COG mode.
Furthermore, the via hole mode is to etch the edge of the substrate and finally form a through hole between the front side and the back side.
Further, the through hole is formed through double-sided etching and metal is filled in the through hole.
A manufacturing method of a Micro-LED display screen structure comprises the following steps:
step S1: epitaxially growing each functional layer of the LED on a glass substrate;
step S2: pixelizing the wafer with each epitaxially grown functional layer to prepare a Micro-LED array, and thinning and polishing the wafer without peeling off a glass substrate after the preparation;
step S3: etching the position of the glass substrate, which is required to be provided with the through hole, to the front side of the glass substrate, wherein the etching depth is half of the thickness of the glass substrate, an inverted frustum-shaped groove is formed, and metal is filled in the groove;
step S4: depositing a layer of SiO on the front surface of the glass substrate2Insulating layer and etchingForming ohmic contact areas of a P pole and an N pole and a through hole area;
step S5: evaporating a layer of metal on the front surface of the glass substrate, and etching a common anode metal wire by using a designed mask plate;
step S6: depositing a layer of SiO again on the front surface of the glass substrate2An insulating layer, and an N-pole ohmic contact area and a through hole area are etched;
step S7: evaporating a layer of metal on the front surface of the glass substrate, and etching a common cathode metal wire by using a designed mask plate;
step S8: on the back of the glass substrate, etching the other half depth of the substrate at the position where the through hole needs to be formed to form an inverted circular truncated cone-shaped groove, and filling metal in the groove;
step S9: evaporating a layer of metal on the back of the glass substrate, and etching back metal routing and metal Pad by using a designed mask plate;
step S10: and hot-pressing the driving chip on the back surface of the glass substrate by high-precision Bonding equipment.
Compared with the prior art, the invention has the following advantages: the structure and the manufacturing process of the Micro-LED display screen are more convenient and simpler, the technology is more mature and stable, the problems of transfer and bonding in the design and manufacturing process of the Micro-LED display screen are solved, and the problem that metal leads and a driving chip occupy redundant areas in the display screen is solved. The manufacturing of the display screen can be completed under the non-transfer and non-bonding condition, full-screen display is realized, and the development cost of the product can be greatly reduced. The invention directly manufactures the required Micro-LED display array on the substrate, directly manufactures the electrode lead wire required by driving on the basis of the Micro-LED display array, and can realize a complete display screen only by hot-pressing a driving chip. In addition, the invention has the other advantage that full-screen display of the display screen can be realized, the driving electrode leads and the driving chip are arranged on the back surface of the display screen, and the gold wire leads on the front surface and the back surface are connected in a glass drilling mode, so that the driving electrode leads and the driving chip can be prevented from occupying extra area outside the display area, and the effect of full-screen display is achieved.
Drawings
FIG. 1 is a front view of a Micro-LED display screen of the present invention;
FIG. 2 is an enlarged view of area A of FIG. 1 in accordance with the present invention;
FIG. 3 is a side view of a Micro-LED display screen of the present invention;
FIG. 4 is an enlarged view of area B of FIG. 3 in accordance with the present invention;
FIG. 5 is a top view of a Micro-LED display screen in accordance with an embodiment of the present invention;
FIG. 6 is a rear view of a Micro-LED display screen in accordance with an embodiment of the present invention;
in the figure: 1-drive chip, 2-metal pad, 3-back metal wiring, 4-glass substrate, 5-through hole, 6-common cathode metal wire, 7-common anode metal wire, 8-first SiO2Insulating layer, 9-second SiO2Insulating layer, 10-the N-pole recessed portion of the LED chip.
Detailed Description
In order to make the aforementioned features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below, but the present invention is not limited thereto.
Refer to fig. 1 to 6
A Micro-LED display screen structure comprises a display array which is arranged on the front surface of a display screen (the front surface of a glass substrate) and is composed of Micro-LED chips, wherein the Micro-LED chips in each row and each column in the display array are respectively connected through metal wires, and an insulating layer is respectively arranged between the surface of the display array and the metal wires in the rows and the columns; the back surface of the display screen is provided with a driving chip 1, a metal bonding pad 2 and a plurality of back metal wires 3 with one ends connected with the driving chip, and each back metal wire is in one-to-one correspondence with the metal wires on the front surface in function; the metal wires on the front side of the display screen and the back metal wires corresponding to the back one to one are connected in a hole mode to form a passage.
In this embodiment, the blue light Micro-LED chip is used to form the display array of the display screen, and the insulating layer is made of SiO with a thickness of 600nm2The metal wire and the back metal wiring have higher stability and conductive energyThe gold of the force acts as a wire. Each row contains 480 Micro-LED chips, each column contains 128 Micro-LED chips, and the enlarged part of the area A in FIG. 1 is a single Micro-LED chip. A first SiO layer with thickness of 600nm is deposited on the chip array of the whole display screen2An insulating layer 8 through which SiO passes2The insulating layer isolates each adjacent Micro-LED chip, and pixel short circuit between adjacent pixels is avoided.
In this embodiment, the display array formed by the Micro-LED chips is directly formed by etching on the substrate.
In this embodiment, the substrate is a glass substrate 4 and can be used for epitaxial growth of the LED chip, and the substrate does not need to be peeled off after epitaxial growth and pixelation. The glass substrate is made of sapphire (Al)2O3) The LED is used for epitaxially growing the blue LED and is used as a carrier of a metal wire, a back metal wire and a driving chip. Of course, sapphire substrates are not the only substrate material for the present invention, and other glass substrates that can be used for growing LEDs are suitable for the purposes of the present invention.
In this embodiment, the via hole mode is to etch the left edge, the right edge, and the lower edge of the substrate and finally form the through hole 5 between the front and the back, and the through hole is formed by double-sided etching and is filled with metal for connecting the front common cathode, the common anode metal line, and the back metal routing line.
In this embodiment, the metal wires in each row and each column on the front surface of the display screen only extend to the outermost Micro-LED chip, and a second SiO for isolation is disposed at the overlapping position of the metal wires of the Micro-LED chips in each row and the Micro-LED chips in each column2An insulating layer 9.
In this embodiment, the size of the driving chip is smaller than the area of the display array, and the driving chip is directly hot-pressed on the back surface of the glass substrate by a COG method. The driver chip is model number SSD1352 from Solomon Systech, and as such, this driver chip model is only one preferred option.
In this embodiment, the metal lines in each row on the front surface of the display screen are common cathode metal lines 6, and the metal lines in each column are common anode metal lines 7.
In this embodiment, the connection between the common cathode metal line 6 and the back metal trace on the back of the display screen in fig. 1 is divided into two parts, where the odd lines are connected to the back metal trace on the back of the display screen through the through holes on the right edge of the display screen, and the even lines are connected to the back metal trace on the back of the display screen through the through holes on the left edge. As can be seen visually in fig. 5. Because the metal wire has a certain resistance, the longer metal wire from the cathode of the Micro-LED to the ground end brings larger voltage drop, so that the voltage at two ends of the Micro-LED is reduced, and finally the luminous brightness of the Micro-LED is reduced. Therefore, the common cathode metal wires are distributed in a left-right interlaced mode, and the interlaced bright and dark parts are complementary, so that the overall brightness is more uniform.
In this embodiment, all the common anode metal lines 7 in fig. 1 are connected with the back metal traces on the back through the through holes on the lower edge of the display screen, and it can be seen visually from fig. 5. Second SiO2Insulating layer 9 (9 in FIG. 5 in the same layer of SiO at different heights2Insulating layers, i.e. second SiO2Insulating layer) with a thickness of 600nm for isolation at the intersections of the row and column metal lines to prevent short circuits between the cathode and anode.
In this embodiment, the Micro-LED chip structure is a normal structure, and the GaN doped layer needs to be etched back to expose the n-GaN layer, so that a groove is formed on each chip, 10 in fig. 2 corresponds to the groove region, and SiO is deposited in the groove region2An insulating layer and a common cathode metal line are shown with dotted lines. The top view of the entire display screen is shown in fig. 5. It is worth noting that the blue light Micro-LED and SiO2The insulating and gold materials are only one preferred solution provided in this example, and any other light emitting Micro-LED, insulating material suitable for semiconductor processing and conductive metal material should be considered as alternatives to the present invention.
A manufacturing method of a Micro-LED display screen structure comprises the following steps:
step S1: epitaxially growing each functional layer of the LED on a glass substrate by adopting a Metal Organic Chemical Vapor Deposition (MOCVD) method, wherein each functional layer comprises a GaN buffer layer, an n-GaN layer, an InGaN/GaN multi-quantum well layer and a p-GaN layer;
sputtering an Indium Tin Oxide (ITO) transparent conducting layer on the p-GaN layer by a magnetron sputtering method for enhancing the diffusion capability of the anode cavity;
etching away ITO of the N pole region to be exposed;
step S2: carrying out deep etching on the GaN doped layer to expose N-GaN for manufacturing N-region ohmic contact, carrying out further etching on the basis of the etched N-GaN layer until the glass substrate at the bottom is exposed, finally forming mutually independent Micro-LED pixel arrays, and carrying out thinning and polishing on the glass substrate without stripping the glass substrate after the manufacturing is finished;
step S3: etching the position of the glass substrate where the through hole needs to be formed by adopting an ICP-RIE deep etching method, wherein the etching depth is half of the thickness of the glass substrate, forming an inverted frustum-shaped groove, and filling metal in the groove;
step S4: depositing first SiO on the front surface of the glass substrate2Etching an insulating layer to form a P pole and N pole ohmic contact area and a through hole area;
step S5: evaporating a layer of metal on the front surface of the glass substrate, and etching a common anode metal wire by using a designed mask plate;
step S6: depositing second SiO on the front surface of the glass substrate2An insulating layer, and an N-pole ohmic contact area and a through hole area are etched;
step S7: evaporating a layer of metal on the front surface of the glass substrate, and etching a common cathode metal wire by using a designed mask plate;
step S8: on the back of the glass substrate, etching the other half depth of the substrate at the position where the through hole needs to be formed to form an inverted circular truncated cone-shaped groove, and filling metal in the groove;
step S9: evaporating a layer of metal on the back of the glass substrate, and etching back metal routing and metal Pad by using a designed mask plate;
step S10: and (3) hot-pressing the driving chip on the back surface of the glass substrate by adopting Lambda high-precision Bonding equipment of FineTech company to finish the manufacture of the display screen.
In this embodiment, in order to show the structure of the whole display screen, the number of the row and column Micro-LED chips is omitted in the figure and is indicated by three-point ellipses. It is worth mentioning that the schematic diagram is only for more intuitive illustration of the structure of the middle display screen according to the present invention, and therefore the geometric scale should not be taken as a strict representation of the physical dimensions.
It will be apparent to those skilled in the art that various other Micro-LED display panel structures and manufacturing methods can be devised without inventive manipulation based on the teachings of the present invention, and all changes, modifications, substitutions and alterations can be made without departing from the spirit and scope of the invention.