CN113224212B

CN113224212B - Multicolor-stacked step-type backlight Micro-LED display device and preparation method thereof

Info

Publication number: CN113224212B
Application number: CN202110520622.7A
Authority: CN
Inventors: 刘斌; 施根俊; 陶涛; 张�荣
Original assignee: Nanjing University
Current assignee: Nanjing University
Priority date: 2021-05-13
Filing date: 2021-05-13
Publication date: 2022-10-18
Anticipated expiration: 2041-05-13
Also published as: CN113224212A

Abstract

The invention discloses a multicolor stacked step type back light emitting Micro-LED display device, which structurally comprises: a blue LED epitaxial wafer; a plurality of groups of InGaN multi-quantum well structures emitting light of different colors; forming a p-n junction above and below each multiple quantum well; the Micro-LED display device is etched into a step structure, each step emits light with different colors, an n/p type GaN electrode contact layer is formed on each step, so that two groups of multi-quantum wells adjacent to each other up and down share one n/p type GaN electrode contact layer, and a driving circuit is bonded, so that the driving circuit can realize independent control over each step. The invention selects the MBE secondary epitaxial green light and red light multi-quantum well structure on the blue light LED epitaxial wafer grown by MOCVD, and can realize RGB three-color luminescence without damaging the existing blue light LED structure. The MBE grown p-type layer also does not require a high temperature anneal activation process.

Description

Multicolor-stacked step-type backlight Micro-LED display device and preparation method thereof

Technical Field

The invention relates to a multicolor stacking step type back light emitting Micro-LED display device and a preparation method thereof, and belongs to the technical field of semiconductor materials.

Background

At present, the traditional white light LED emits light by depending on a GaN-based LED, and the fluorescent powder which deactivates green light and red light to emit light, thereby forming RGB three primary colors to emit light, and forming white light by combination. This conventional approach suffers from losses in energy exchange and inefficient green and red light emission. Patent CN108878469a proposes a mixed RGB micro-pore LED array device based on group iii nitride semiconductors/quantum dots. However, the same problem as that of the prior white light LED is that the secondary radiation luminescence is still carried out by the quantum dots, and the luminous efficiency is low. In addition, the scheme has a complex process, and the quantum dots or the fluorescent powder cannot be accurately positioned. And the fluorescent powder is mostly prepared from rare earth materials, which has great significance for national defense and military industry. The use of a large amount of phosphor for civilian LEDs would be a detriment to the national strategic resources.

And researchers have proposed a scheme of parallel light emission of a plurality of LEDs to replace the above full color light emission depending on secondary excitation radiation of fluorescent powder or quantum dots. The patent CN107833878B uses three RGB LED lighting units to realize three-color lighting according to a certain arrangement. The scheme can also display dynamic images with rich colors, high saturation and high display frequency by controlling the on and off of each group of units, and is a good solution for Micro-LED display. However, the multi-unit arrangement mode has complex process and low production efficiency, and has no good economic benefit when used for emitting light of three-color LEDs.

Currently, commercial blue LEDs are mostly grown by MOCVD. MOCVD growth is characterized by high temperature and high gas flow. In the MOCVD system, the activation degree of ammonia gas is low in a low-temperature environment, so that nitrides are difficult to effectively grow, and the crystal quality is difficult to ensure. Meanwhile, research by researchers indicates that the lower the In component In InGaN, the higher the growth temperature. The InGaN multi-quantum well of the low In composition has a short emission wavelength, and cannot realize longer wavelength emission such as yellow light and red light. Therefore, in order to realize RGB three-color light emission, a high In composition InGaN multi-quantum well must be solved. Unlike MOCVD growth system, MBE is a physical reaction in which ionized N atoms and high-temperature evaporated metal atoms are bonded to form bonds on the surface of a substrate under an ultrahigh vacuum condition. The temperature required for MBE to grow nitride does not need to be too high compared to MOCVD, and InGaN multi-quantum well growth of high In composition is more easily achieved.

Disclosure of Invention

The invention aims to provide a multicolor stacking step type back light emitting Micro-LED display device.

The purpose of the invention is realized by the following technical scheme:

the utility model provides a polychrome piles up step and carries out light-emitting Micro-LED display device, its structure includes from bottom to top in proper order:

a blue LED epitaxial wafer;

a plurality of groups of InGaN multi-quantum well structures emitting light of different colors;

the method is characterized in that: a device p-type GaN layer and/or a device n-type GaN layer are/is arranged between the blue light LED epitaxial wafer and the InGaN multi-quantum well structure, between the InGaN multi-quantum well structures and on the uppermost InGaN multi-quantum well structure, so that the n-type GaN layer and the p-type GaN layer are arranged above and below the multi-quantum well structure to inject electrons and holes;

the Micro-LED display device is etched into a step structure, an n-type GaN layer of a blue light LED epitaxial wafer is a first step, the blue light LED epitaxial wafer is a second step, each group of InGaN/GaN multi-quantum well structures on the blue light LED epitaxial wafer sequentially form the first step, each step emits light with different colors from the second step, an n/p-type GaN electron/hole injection layer is formed on each step, so that an n/p-type GaN electron/hole injection layer is shared by two groups of upper and lower adjacent multi-quantum wells, a driving circuit is bonded, and the driving circuit realizes independent light emitting control of each step.

InGaN multi-quantum well structures emitting different colors of light are commonly referred to in the art as green-emitting InGaN multi-quantum well structures and red-emitting InGaN multi-quantum well structures, but the present application is not limited to InGaN multi-quantum well structures emitting these two colors of light, and InGaN multi-quantum well structures emitting other colors of light may also be used.

Preferably, the hole concentration of the p-type GaN layer is controlled to be 1 × 10 ¹⁸ cm ^-3 ～1×10 ¹⁹ cm ^-3 (ii) a The electron concentration of the n-type GaN layer is controlled to be 1 × 10 ¹⁸ cm ^-3 ～1×10 ¹⁹ cm ^-3 。

Preferably, the Micro-LED display device sequentially includes: the LED light source comprises a blue LED epitaxial wafer, a first group of InGaN multiple quantum well structures and a device n-type GaN layer, wherein the n-type GaN layer of the blue LED epitaxial wafer is a bottom step, the second layer of step is etched to expose the p-type GaN layer of the blue LED epitaxial wafer, the top step is the device n-type GaN layer, a p-type electrode is formed on the p-type GaN layer of the blue LED epitaxial wafer, n-type electrodes are formed on the n-type GaN layer of the blue LED epitaxial wafer and the device n-type GaN layer, a driving circuit is bonded to the n-type electrode or the p-type electrode of each step, and independent light emitting control of each step is achieved.

Preferably, the Micro-LED display device sequentially includes: the LED structure comprises a blue light LED epitaxial wafer, a first n-type GaN layer of a device, a first group of InGaN multiple quantum well structures, a first p-type GaN layer of the device and a second n-type GaN layer of the device, wherein the n-type GaN layer of the blue light LED epitaxial wafer is the bottommost step, the first n-type GaN layer of the device is exposed by etching the second step, the second n-type GaN layer of the device is exposed by etching the topmost step, the second n-type GaN layer of the device is the second n-type GaN layer of the device, an n-type electrode is formed on each step, and the injection of a cavity adopts a tunnel pn junction auxiliary injection mode. A driving circuit is bonded to the n-type electrode of each step, enabling individual light emission control for each step.

Preferably, the Micro-LED display device sequentially includes: the LED light source comprises a blue LED epitaxial wafer, a first group of InGaN multi-quantum well structures, a device n-type GaN layer, a second group of InGaN multi-quantum well structures and a device p-type GaN layer, wherein the n-type GaN layer of the blue LED epitaxial wafer is a bottom step, the second layer of step is etched to expose the p-type GaN layer of the blue LED epitaxial wafer, the third layer of step is etched to expose the device n-type GaN layer, the top step is a device p-type GaN layer, p-type electrodes are formed on the p-type GaN layer of the blue LED epitaxial wafer and the device p-type GaN layer, n-type electrodes are formed on the n-type GaN layer of the blue LED epitaxial wafer and the device n-type GaN layer, a driving circuit is bonded to the n-type electrode or the p-type electrode of each step, and independent light emitting control of each step is achieved.

Preferably, the Micro-LED display device sequentially includes: the blue light LED epitaxial wafer comprises a blue light LED epitaxial wafer, a first n-type GaN layer of a device, a first InGaN multi-quantum well structure of a first group, a first p-type GaN layer of the device, a second n-type GaN layer of the device, a second InGaN multi-quantum well structure of a second group, a second p-type GaN layer of the device and a third n-type GaN layer of the device. A driving circuit is bonded to the n-type electrode of each step, enabling individual light emission control for each step.

Preferably, the cross section of the step structure is square, round, oval or polygonal,the cross sectional area of the first layer of light-emitting multiple quantum well steps is 20 × 20-30 × 30 μm ² The height is 1.0-1.5 μm; the cross sectional area of the second layer of light-emitting multi-quantum well step is 10 × 10-20 × 20 μm ² The height is 100-300 nm; the cross sectional area of the third layer of luminous multi-quantum well step is 2*2-10 x 10 mu m ² The height is 100-300 nm.

Preferably, an isolation groove is etched at a position corresponding to each step on the back of the Micro-LED display device, and the isolation groove is filled with an insulating medium.

The invention also discloses a preparation method of the multicolor stacking step type back light Micro-LED display device, which comprises the following steps:

step 1, on a blue light LED epitaxial wafer grown by MOCVD, MBE secondary epitaxy is used for growing a plurality of groups of InGaN multi-quantum well structures and device p-type GaN layers and/or device n-type GaN layer structures, so that an n-type GaN layer and a p-type GaN layer are respectively arranged on the upper and lower parts of the multi-quantum well structures to realize injection of electrons and holes, and the multi-color stacked LED epitaxial wafer is obtained.

And 2, spin-coating photoresist on the multi-color stacked LED epitaxial wafer, and developing the pattern of the first layer of step structure on the photoresist.

And 3, anisotropically etching the sample by using an ICP (inductively coupled plasma) technology to etch the n-type GaN layer of the blue LED epitaxial wafer to form a first-stage step.

And 4, preparing an n-type electrode on the first step by taking the photoresist as a mask.

And 5, ultrasonically cleaning the sample by using an acetone solution, and stripping the residual photoresist and metal.

And 6, continuously spin-coating the photoresist, and developing the pattern of the second-layer step structure on the photoresist.

And 7, anisotropically etching the sample by using an ICP (inductively coupled plasma) technology, and etching the sample to a hole injection layer of the substrate blue LED, wherein the p-type GaN layer is used as the position when a direct hole injection mode of the p-type GaN layer is selected, and the n-type GaN layer is used as the position when an auxiliary hole injection mode of the tunnel junction is selected, so that a second-stage step is formed.

And 8, preparing a p-type electrode (in a mode of direct hole injection of a p-type GaN layer) or an n-type electrode (in a mode of auxiliary hole injection of a tunnel pn junction) on the second-stage step by taking the photoresist as a mask.

And 9, repeating the steps 1 to 8, and respectively manufacturing the subsequent step structures to obtain the multicolor stacked step type Micro-LED display array chip.

And step 10, bonding electrodes of the multi-color stacked stepped Micro-LED display array and the designed Si-based CMOS driving circuits one by using a submicron bonding chip mounter to obtain a Micro-LED display array device with light emitting from the back side.

Preferably, the method further comprises the step 11: polishing and thinning the sapphire substrate surface on the back of the blue LED, then alternately growing silicon dioxide and silicon nitride on the sapphire substrate by using PECVD (plasma enhanced chemical vapor deposition), and sequentially forming a multi-component distributed Bragg reflector layer corresponding to the light-emitting wavelength of each group of multiple quantum well structures below.

Preferably, the method further comprises the steps of 12-16:

and step 12, spin-coating photoresist on the sapphire surface, and developing the step structures corresponding to the uppermost group of InGaN multiple quantum well structures onto the photoresist.

And step 13, etching a first-layer DBR step structure and an isolation groove by using RIE technology and taking the photoresist as a mask.

And step 14, continuing to grow an insulating medium by taking the photoresist as a mask and using a PECVD (plasma enhanced chemical vapor deposition) technology as a filler in the isolation groove.

And step 15, removing the residual glue and the insulating medium outside the isolation groove.

And step 16, repeating the steps 12-15, and etching the step structures of the DBRs of the other layers and the isolation groove of each light-emitting unit to finally obtain the multi-color stacked step Micro-LED display array device.

Preferably, before the step 1, the blue light LED epitaxial wafer is sequentially placed in acetone, absolute ethyl alcohol and deionized water for ultrasonic cleaning, and then dried to obtain a clean blue light LED epitaxial wafer.

Preferably, the multicolor-stacked LED epitaxial wafer in step (1) is an n-type GaN layer that sequentially grows a first group of InGaN multi-quantum well structures or an n-type GaN layer plus the first group of InGaN multi-quantum well structures on a blue LED epitaxial wafer and realizes electron injection of the first group of InGaN multi-quantum well structures, and step (9) specifically is: and naturally forming a third step by the reserved light emitting unit formed by the first group of InGaN multi-quantum well structures and the electron injection n-type GaN layer, and preparing an n-type electrode on the surface of the third step, wherein the light emitted by the first group of InGaN multi-quantum well structures is different from that of the blue LED epitaxial wafer.

Preferably, the LED epitaxial wafer stacked in multiple colors in step 1 is formed by sequentially growing a first group of InGaN multi-quantum well structures or an n-type GaN layer on a blue LED epitaxial wafer, adding the first group of InGaN multi-quantum well structures, and an n-type GaN layer for realizing electron injection of the first group of InGaN multi-quantum well structures, or forming a tunnel pn junction by using a p-type GaN layer and the n-type GaN layer, and forming a tunnel pn junction by using a second group of InGaN multi-quantum well structures and a p-type GaN layer for realizing hole injection of the second group of InGaN multi-quantum well structures, or forming a tunnel pn junction by using the p-type GaN layer and the n-type GaN layer, wherein step (9) specifically comprises: continuously spin-coating photoresist, developing the pattern of the third step structure on the photoresist, anisotropically etching the sample by using an ICP (inductively coupled plasma) technology, etching the sample to the n-type GaN layer of the second group of InGaN multi-quantum wells to form a third step, and preparing an n-type electrode on the third step by using the photoresist as a mask; and naturally forming a fourth step by the reserved second group of InGaN multi-quantum well structures, and preparing an n-type electrode or a p-type electrode on the surface of the fourth step, wherein the light emitted by the first group of InGaN multi-quantum well structures is different from the blue LED epitaxial wafer, and the light emitted by the second group of InGaN multi-quantum well structures is different from the first group of InGaN multi-quantum well structures or the blue LED epitaxial wafer. Preferably, step 1 specifically comprises: keeping the sum of the metal beam current at about 6 multiplied by 10 < -7 > Torr, the nitrogen source flow at 0.7sccm and the power at 450W, firstly growing a green light InGaN potential well layer and a GaN potential barrier layer under the condition of thermocouple temperature of 550-650 ℃, repeating 5-10 periods on the potential barrier and the potential well layer, wherein the InGaN potential well layer is 1-3 nm, the GaN potential barrier layer is 5-8 nm, forming a green light InGaN multi-quantum well structure or firstly growing an n-type GaN layer of 100-200 nm under the condition of thermocouple temperature of 750-950 ℃, forming a pn tunnel junction for assisting hole injection of the blue light InGaN multi-quantum well structure, then cooling to 550-650 ℃ to grow the green light InGaN multi-quantum well structure, and the green light multi-quantum well structure parameters are the same as the above; then, an n-type GaN layer is grown under the condition of keeping the temperature of 550-650 ℃, the thickness of the n-type GaN layer is 100-200 nm, or a p-type GaN layer with the thickness of 100-200 nm and an n-type GaN layer with the thickness of 100-200 nm are grown under the condition of 550-650 ℃, and a pn tunnel junction with the green light InGaN multiple quantum well structure and auxiliary hole injection is formed; then growing a red InGaN potential well layer and a GaN potential barrier layer under the condition that the thermocouple temperature is 450-550 ℃, repeating 5-10 periods on the potential barrier and the potential well layer, wherein the InGaN potential well layer is 1-3 nm, and the thickness of the GaN potential barrier layer is 5-8 nm to form a red InGaN multiple quantum well structure; and finally, growing a p-type GaN layer at the temperature of 450-550 ℃, wherein the thickness of the p-type GaN layer is 100-200 nm, or growing the p-type GaN layer at the temperature of 450-650 ℃ and adding an n-type GaN layer at the thickness of 100-200 nm to form the pn tunnel junction of the red light InGaN multiple quantum well structure for assisting hole injection.

The invention selects the MBE secondary epitaxy green light and red light multiple quantum well structure on the blue light LED epitaxial wafer grown by MOCVD, and can realize RGB three-color luminescence without damaging the existing blue light LED structure. Meanwhile, the tunnel junction can remarkably improve the injection efficiency of LED electron holes, so that the luminous efficiency is improved. MBE grows the LED with the multicolor stack structure, wherein a p-type layer grown by the MBE does not need high-temperature annealing activation treatment, and the InGaN multi-quantum well light-emitting structure cannot be damaged. The submicron bonding chip mounter is used for realizing back light emitting, short wavelength LEDs are prevented from exciting long wavelength LEDs to emit light, and crosstalk of light with different wavelengths in the display array unit is reduced due to the DBR and the isolation groove on the back of the device. The multicolor stacked step Micro-LED display array can control the on and off of the Micro-LED of each step in each unit through a Si-based CMOS driving circuit, and the typical pixel density is 175-3950 PPI.

Drawings

FIG. 1 is a schematic diagram of a MOCVD grown blue LED epitaxial wafer.

Fig. 2 and example 3 are schematic diagrams showing the structure of the secondary epitaxy on a blue light epitaxial wafer by MBE.

Fig. 3 and example 3 are schematic structural diagrams of a sample surface after spin coating with a photoresist.

Fig. 4 and example 3 are schematic structural views of samples after the development is completed.

Fig. 5 and example 3 are schematic diagrams showing the ICP etching to the surface of the sample completed with the n-type GaN layer.

Fig. 6 and example 3 show a schematic structural view of the first step after the residual photoresist is removed.

Fig. 7 and example 3 show a schematic structural diagram of the second step after the residual photoresist is removed.

Fig. 8 and example 3 show the structure of the third step after the residual photoresist is removed.

FIG. 9 is a schematic structural view of example 3 after a Ti/Al/Ni/Au metal contact layer is deposited by PVD.

Fig. 10 and example 3 are schematic structural diagrams after bonding the sample and the Si-based CMOS drive current.

Fig. 11 and example 2 are schematic structural views after bonding a sample to a Si-based CMOS driver circuit.

Fig. 12 is a schematic view of the structure of the sample after bonding to the Si-based CMOS driver circuit in example 1.

Fig. 13 and example 3 show a schematic structure of the DBR and the isolation trench formed on the rear surface.

Fig. 14 and example 3 are top views of an RGB display unit.

Detailed Description

The technical solution in the embodiments of the present invention is clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. The described embodiments are only some of the embodiments of the present invention, and not all of them. The following examples only show the simple structure of the two-color, three-color stacked stepped Micro-LED display array and the method for fabricating the three-color stacked stepped Micro-LED with tunnel junction to assist electron hole injection, but are not limited thereto. Other embodiments, which can be derived by one of ordinary skill in the art from the embodiments of the present invention without any creative effort, are within the scope of the present invention.

Example 1

In embodiment 1, a double-color stack stepped structure Micro-LED is prepared by performing secondary epitaxy on a green light multiple quantum well on a blue LED epitaxial wafer grown by MOCVD by using MBE and combining micromachining, and the method comprises the following steps:

step 1, selecting a high-quality blue light LED epitaxial wafer grown by MOCVD with a smooth surface as a substrate, as shown in figure 1.

Step 2, cleaning the substrate: and sequentially placing the substrate in acetone, absolute ethyl alcohol and deionized water, respectively carrying out ultrasonic cleaning for 10min, setting the ultrasonic power to be 600W, removing organic impurities on the surface and the back, and then placing the substrate in a vacuum drying oven for drying to obtain the substrate with clean surface and back.

And 3, evaporating a titanium metal heat conduction layer with the thickness of 1 mu m on the back surface of the substrate by using a PVD (physical vapor deposition) technology.

Step 4, cleaning the substrate with the titanium plated on the back: soaking the substrate in acetone, anhydrous ethanol, and deionized water for 10min by water bath method, wherein the temperature of the water bath is set to 100 deg.C.

And 5, secondarily extending an InGaN/GaN multi-quantum well structure on the substrate by using PA-MBE (plasma-assisted molecular beam epitaxy) equipment. The substrate is heated to the thermocouple temperature of 600 ℃ to carry out InGaN/GaN multiple quantum well growth, the nitrogen flow is set to be 0.7sccm in the whole epitaxial growth process, and the power of the nitrogen plasma generation device is set to be 450W. An InGaN well layer, in beam current is (5 + -0.5) x 10-7Torr, ga beam current is (8 + -0.5) x 10-8Torr. A GaN barrier layer, wherein the Ga beam current is (2.5 +/-0.5) multiplied by 10-7 Torr. The InGaN/GaN quantum well grows repeatedly for 5-10 periods.

And 6, continuing to epitaxially grow a p-type GaN layer and an n-type GaN layer by using PA-MBE (plasma-assisted molecular beam epitaxy) equipment. The substrate temperature was maintained at 600 deg.C, the nitrogen flow rate was set to 0.7sccm, and the power of the nitrogen plasma generation apparatus was set to 450W. In the n-type GaN layer, the Ga beam is (5.5 + -0.5) x 10-7Torr and the Si-doped beam is (5 + -0.5) x 10-9Torr.

And 7, obtaining the double-color stacked LED epitaxial structure after the MBE secondary epitaxy. Spin-coating photoresist on the epitaxial wafer, selecting reverse glue AZ5214, wherein the spin-coating rotation speed is 600rpm/8000rpm, the time is 10s/40s, and pre-baking for 1 minute by adopting a 90 ℃ hot plate. Since the reverse resist is used, a two-step exposure method is selected, the first pattern region is exposed for 9 seconds, followed by baking for 2 minutes at 110 ℃ and flood exposure for 12 seconds. The development is carried out for 19 seconds by adopting an alkaline positive photoresist developing solution, the deionized water is used for cleaning for 30 seconds, then the drying nitrogen is used for blow-drying, and the postbaking is carried out for 1 minute by adopting a hot plate at 100 ℃.

Step 8, designing a photoetching pattern of the blue-light step structure by adopting an ultraviolet photoetching machine, wherein the photoetching pattern comprises the following steps: the steps are 20 μm by 20 μm squares.

And 9, adopting an ICP (inductively coupled plasma) technology, introducing mixed gas of Cl2 and Ar by taking the photoresist in the undeveloped area as a mask, and anisotropically etching the sample to form a blue step structure. The etching parameters are as follows: cl2 and Ar flow rates of 48 + -12 sccm and 18 + -6 sccm, respectively, chamber gas pressure: 25 ± 5mtorr, dc bias: 600 ± 60v, rf power 250 ± 30w, icp power: 1200 +/-100W, the frequency of 13.56MHz, and the etching time is controlled to etch the n-type GaN layer of the blue LED substrate.

And step 10, evaporating Ti/Al/Ni/Au metal on the surface of the sample by using the residual photoresist as a mask by adopting a PVD (physical vapor deposition) technology to form n-type contact. The thickness of Ti/Al/Ni/Au was 30/150/50/50nm, respectively.

And 11, soaking the sample plated with the n-type metal contact in an acetone solution for about 10min, and stripping the residual photoresist together with the metal from the sample by low-power ultrasonic cleaning.

And step 12, continuously spin-coating the photoresist on the sample, selecting an inverse photoresist AZ5214, wherein the spin-coating rotation speed is 600rpm/8000rpm, the time is 10s/40s, and pre-baking for 1 minute by adopting a hot plate at 90 ℃. Since the reverse resist is used, a two-step exposure method is selected, the first pattern region is exposed for 9 seconds, followed by baking for 2 minutes at 110 ℃ and flood exposure for 12 seconds. The development is carried out for 19 seconds by adopting an alkaline positive photoresist developing solution, the deionized water is used for cleaning for 30 seconds, then the drying is carried out by drying nitrogen, and the postbaking is carried out for 1 minute by adopting a hot plate at 100 ℃.

Step 13, designing a photoetching pattern of a green light step structure by adopting an ultraviolet photoetching machine, wherein the photoetching pattern comprises the following steps: the steps are 10 μm × 10 μm squares.

And step 14, adopting an ICP (inductively coupled plasma) technology, introducing mixed gas of Cl2 and Ar by taking the photoresist in the undeveloped area as a mask, and anisotropically etching the sample to form a green step structure. The etching parameters are as follows: cl2 and Ar flow rates of 48 + -12 sccm and 18 + -6 sccm, respectively, chamber gas pressure: 25 ± 5mtorr, dc bias: 600 ± 60v, rf power 250 ± 30w, icp power: 1200 +/-100W, the frequency of 13.56MHz, and the etching time is controlled to etch the p-type GaN layer of the blue LED substrate.

And step 15, evaporating Ni/Au metal on the surface of the sample by using the residual photoresist as a mask by adopting a PVD (physical vapor deposition) technology to form a p-type contact. The Ni/Au thicknesses were 30/50nm, respectively.

And step 16, soaking the sample plated with the p-type metal contact in an acetone solution for about 10min, and stripping the residual photoresist together with the metal above by low-power ultrasonic cleaning.

And step 17, continuously spin-coating the photoresist on the sample, selecting an inverse photoresist AZ5214, wherein the spin-coating rotation speed is 600rpm/8000rpm, the time is 10s/40s, and pre-baking for 1 minute by adopting a hot plate at 90 ℃. Since a reverse glue is used, a two-step exposure method is used, the first pattern area is exposed for 9 seconds, followed by a hotplate bake at 110 ℃ for 2 minutes and a flood exposure for 12 seconds. The development is carried out for 19 seconds by adopting an alkaline positive photoresist developing solution, the deionized water is used for cleaning for 30 seconds, then the drying nitrogen is used for blow-drying, and the postbaking is carried out for 1 minute by adopting a hot plate at 100 ℃.

And step 18, evaporating Ti/Al/Ni/Au metal on the surface of the sample by using the residual photoresist as a mask by adopting a PVD (physical vapor deposition) technology to form n-type contact. The thickness of Ti/Al/Ni/Au was 30/150/50/50nm, respectively.

And step 19, soaking the sample plated with the n-type metal contact in an acetone solution for about 10min, and performing low-power ultrasonic cleaning to strip out the residual photoresist and the metal on the residual photoresist, so as to obtain the common p-type contact double-color stacked step type Micro-LED epitaxial chip.

Step 20, bonding the electrodes of the double-color stacked stepped Micro-LEDs and the corresponding Si-based CMOS driving circuits one by one through In columns by using a FINEPLACER lambda multi-purpose submicron bonding chip mounter to obtain the backside light-emitting Micro-LEDs, as shown In fig. 12.

And step 21, polishing and thinning the sapphire on the back surface of the substrate by using polishing equipment.

And step 22, growing a silicon dioxide and silicon nitride DBR (distributed Bragg Reflector) of blue light on the polished sapphire surface by using a PECVD (plasma enhanced chemical vapor deposition) technology.

And 23, spin-coating the photoresist on the DBR, selecting an inverse photoresist AZ5214, carrying out spin-coating at the rotating speed of 600rpm/8000rpm for 10s/40s, and pre-baking for 1 minute by adopting a hot plate at 90 ℃. Since the reverse resist is used, a two-step exposure method is selected, the first pattern region is exposed for 9 seconds, followed by baking for 2 minutes at 110 ℃ and flood exposure for 12 seconds. The development is carried out for 19 seconds by adopting an alkaline positive photoresist developing solution, the deionized water is used for cleaning for 30 seconds, then the drying nitrogen is used for blow-drying, and the postbaking is carried out for 1 minute by adopting a hot plate at 100 ℃.

And 24, developing the photoetching graph with the green light step structure on the photoresist by adopting an ultraviolet photoetching machine.

And step 25, etching the blue DBR step structure and the isolation groove by using RIE and taking the photoresist as a mask.

And 26, continuing to grow SiO2 by taking the photoresist as a mask and using a PECVD (plasma enhanced chemical vapor deposition) technology as a filler in the isolation groove.

Step 27, soaking in acetone solution to remove residual glue and SiO outside the isolation groove ₂ And finally obtaining the two-color stacked step Micro-LED display array.

Example 2

Embodiment 2 utilizes MBE to secondarily extend green light multiple quantum wells and red light multiple quantum wells on a blue light LED epitaxial wafer grown by MOCVD, and combines Micro-nano processing to prepare a three-color stacked step Micro-LED display array device, which comprises the following steps:

Step 2, cleaning the substrate: and sequentially placing the substrate in acetone, absolute ethyl alcohol and deionized water for ultrasonic cleaning for 10min, setting the ultrasonic power to be 600W, removing organic impurities on the surface and the back, and then placing the substrate in a vacuum drying oven for drying to obtain the substrate with clean surface and back.

And 5, secondarily extending an InGaN/GaN multi-quantum well structure on the substrate by using PA-MBE (plasma-assisted molecular beam epitaxy) equipment. The substrate is heated to 600 ℃ to carry out InGaN/GaN green light multiple quantum well growth, the nitrogen flow in the whole epitaxial growth process is set to be 0.7sccm, and the power of the nitrogen plasma generation device is set to be 450W. An InGaN well layer, in beam current is (5 + -0.5) x 10-7Torr, ga beam current is (8 + -0.5) x 10-8Torr. A GaN barrier layer, wherein the Ga beam current is (2.5 +/-0.5) multiplied by 10-7 Torr. The InGaN/GaN quantum well grows repeatedly for 5-10 periods.

And 6, continuously epitaxially growing an n-type GaN layer by using PA-MBE (plasma-assisted molecular beam epitaxy) equipment. The substrate temperature was maintained at 600 deg.C, the nitrogen flow rate was set to 0.7sccm, and the power of the nitrogen plasma generation apparatus was set to 450W. In the n-type GaN layer, the Ga beam current is (5 + -0.5) x 10-7Torr, and the Si-doped beam current is (5 + -0.5) x 10-9Torr.

And 7, continuously extending an InGaN/GaN multi-quantum well structure on the sample by using PA-MBE (plasma-assisted molecular beam epitaxy) equipment. And cooling the substrate to 500 ℃ to perform InGaN/GaN multiple quantum well growth, wherein the nitrogen flow is set to be 0.7sccm in the whole epitaxial growth process, and the power of the nitrogen plasma generation device is set to be 450W. An InGaN well layer, in beam current is (5 + -0.5) x 10-7Torr, ga beam current is (8 + -0.5) x 10-8Torr. A GaN barrier layer, wherein the Ga beam current is (2.5 +/-0.5) multiplied by 10-7 Torr. The InGaN/GaN quantum well grows repeatedly for 5-10 periods.

And 8, continuing to epitaxially grow the p-type GaN layer by using PA-MBE (plasma-assisted molecular beam epitaxy) equipment. The substrate temperature was maintained at 500 deg.C, the nitrogen flow rate was set to 0.7sccm, and the power of the nitrogen plasma generating apparatus was set to 450W. In the p-type GaN layer, the Ga beam is (5 +/-0.5) multiplied by 10-7Torr, and the Mg doped beam is (5 +/-0.5) multiplied by 10-9Torr, so that the three-color stacked LED epitaxial structure is obtained.

And 9, spin-coating a photoresist on the epitaxial wafer, selecting an inverse photoresist AZ5214, performing spin-coating at the rotation speed of 600rpm/8000rpm for 10s/40s, and performing pre-baking for 1 minute by adopting a 90 ℃ hot plate. Since the reverse resist is used, a two-step exposure method is selected, the first pattern region is exposed for 9 seconds, followed by baking for 2 minutes at 110 ℃ and flood exposure for 12 seconds. The development is carried out for 19 seconds by adopting an alkaline positive photoresist developing solution, the deionized water is used for cleaning for 30 seconds, then the drying nitrogen is used for blow-drying, and the postbaking is carried out for 1 minute by adopting a hot plate at 100 ℃.

Step 10, designing a photoetching pattern of a blue light step structure by adopting an ultraviolet photoetching machine, wherein the photoetching pattern comprises the following steps: the steps are 20 μm by 20 μm squares.

And 11, adopting an ICP (inductively coupled plasma) technology, taking the photoresist in the undeveloped area as a mask, introducing a mixed gas of Cl2 and Ar, and anisotropically etching the sample to form a blue step structure. The etching parameters are as follows: cl2 and Ar flow rates of 48 + -12 sccm and 18 + -6 sccm, respectively, chamber gas pressure: 25 ± 5mtorr, dc bias: 600 ± 60v, rf power 250 ± 30w, icp power: 1200 +/-100W, the frequency of 13.56MHz, and the etching time is controlled to etch the n-type GaN layer of the blue LED substrate.

And step 12, evaporating Ti/Al/Ni/Au metal on the surface of the sample by using the residual photoresist as a mask by adopting a PVD (physical vapor deposition) technology to form n-type contact. The thickness of Ti/Al/Ni/Au was 30/150/50/50nm, respectively.

And step 13, soaking the sample plated with the n-type metal contact in an acetone solution for about 10min, and stripping the residual photoresist together with the metal in the sample by low-power ultrasonic cleaning.

And step 14, continuously spin-coating the photoresist on the sample, selecting an inverse photoresist AZ5214, wherein the spin-coating rotation speed is 600rpm/8000rpm, the time is 10s/40s, and pre-baking for 1 minute by adopting a hot plate at 90 ℃. Since the reverse resist is used, a two-step exposure method is selected, the first pattern region is exposed for 9 seconds, followed by baking for 2 minutes at 110 ℃ and flood exposure for 12 seconds. The development is carried out for 19 seconds by adopting an alkaline positive photoresist developing solution, the deionized water is used for cleaning for 30 seconds, then the drying is carried out by drying nitrogen, and the postbaking is carried out for 1 minute by adopting a hot plate at 100 ℃.

Step 15, designing a photoetching pattern of a green light step structure by adopting an ultraviolet photoetching machine, wherein the photoetching pattern comprises the following steps: the steps are 10 μm × 10 μm squares.

And step 16, adopting an ICP (inductively coupled plasma) technology, taking the photoresist in the undeveloped area as a mask, introducing a mixed gas of Cl2 and Ar, and anisotropically etching the sample to form a green step structure. The etching parameters are as follows: cl2 and Ar flow rates of 48 + -12 sccm and 18 + -6 sccm, respectively, chamber gas pressure: 25 ± 5mtorr, dc bias: 600 ± 60v, rf power 250 ± 30w, icp power: 1200 +/-100W, the frequency of 13.56MHz, and the etching time is controlled to etch the p-type GaN layer of the blue LED substrate.

And step 17, evaporating Ni/Au metal on the surface of the sample by using the residual photoresist as a mask by adopting a PVD (physical vapor deposition) technology to form a p-type contact. The Ni/Au thicknesses were 30/50nm, respectively.

And step 18, soaking the sample plated with the p-type metal contact in an acetone solution for about 10min, and stripping the residual photoresist together with the metal above by low-power ultrasonic cleaning.

And step 19, continuously spin-coating the photoresist on the sample, selecting an inverse photoresist AZ5214, wherein the spin-coating rotation speed is 600rpm/8000rpm, the time is 10s/40s, and pre-baking for 1 minute by adopting a hot plate at 90 ℃. Since the reverse resist is used, a two-step exposure method is selected, the first pattern region is exposed for 9 seconds, followed by baking for 2 minutes at 110 ℃ and flood exposure for 12 seconds. The development is carried out for 19 seconds by adopting an alkaline positive photoresist developing solution, the deionized water is used for cleaning for 30 seconds, then the drying nitrogen is used for blow-drying, and the postbaking is carried out for 1 minute by adopting a hot plate at 100 ℃.

Step 20, designing a photoetching pattern of a red light step structure by adopting an ultraviolet photoetching machine, wherein the photoetching pattern comprises the following steps: the steps are squares of 2 μm × 2 μm.

And 21, adopting an ICP (inductively coupled plasma) technology, introducing mixed gas of Cl2 and Ar by taking the photoresist in the undeveloped area as a mask, and anisotropically etching the sample to form a red step structure. The etching parameters are as follows: cl2 and Ar flow rates of 48 + -12 sccm and 18 + -6 sccm, respectively, chamber gas pressure: 25 ± 5mtorr, dc bias: 600 ± 60v, rf power 250 ± 30w, icp power: 1200 +/-100W, the frequency of 13.56MHz, controlling the etching time and etching to the n-type GaN layer of the green LED structure.

And 22, evaporating Ti/Al/Ni/Au metal on the surface of the sample by using the residual photoresist as a mask by adopting a PVD (physical vapor deposition) technology to form an n-type contact. The thickness of Ti/Al/Ni/Au was 30/150/50/50nm, respectively.

And step 23, soaking the sample plated with the n-type metal contact in an acetone solution for about 10min, and stripping the residual photoresist together with the metal above by low-power ultrasonic cleaning.

And 24, continuously spin-coating the photoresist on the sample, selecting an inverse photoresist AZ5214, performing spin-coating at the rotation speed of 600rpm/8000rpm for 10s/40s, and performing pre-baking for 1 minute by adopting a hot plate at 90 ℃. Since the reverse resist is used, a two-step exposure method is selected, the first pattern region is exposed for 9 seconds, followed by baking for 2 minutes at 110 ℃ and flood exposure for 12 seconds. The development is carried out for 19 seconds by adopting an alkaline positive photoresist developing solution, the deionized water is used for cleaning for 30 seconds, then the drying nitrogen is used for blow-drying, and the postbaking is carried out for 1 minute by adopting a hot plate at 100 ℃.

And 25, evaporating Ni/Au metal on the surface of the sample by using the residual photoresist as a mask by adopting a PVD (physical vapor deposition) technology to form a p-type contact. The Ni/Au thicknesses were 30/50nm, respectively.

Step 26, soaking the p-type metal contact plated sample in an acetone solution for about 10min, and stripping the residual photoresist together with the above metal by low-power ultrasonic cleaning. And finally obtaining a three-color stacked stepped Micro-LED epitaxial structure.

Step 27, bonding the electrodes of the three-color stacked stepped Micro-LEDs and the corresponding Si-based CMOS driving circuits one by using a FINEPLACER lambda multi-purpose submicron bonding chip mounter, to obtain the three-color stacked stepped Micro-LEDs with back light emission, as shown in fig. 11.

And step 28, polishing and thinning the sapphire on the back surface of the substrate by using polishing equipment.

And 29, growing a silicon dioxide and silicon nitride DBR of blue light on the polished sapphire surface by using a PECVD technology.

And step 30, spin-coating the photoresist on the DBR, selecting an inverse photoresist AZ5214, wherein the spin-coating rotation speed is 600rpm/8000rpm, the time is 10s/40s, and pre-baking for 1 minute by adopting a hot plate at 90 ℃. Since a reverse glue is used, a two-step exposure method is used, the first pattern area is exposed for 9 seconds, followed by a hotplate bake at 110 ℃ for 2 minutes and a flood exposure for 12 seconds. The development is carried out for 19 seconds by adopting an alkaline positive photoresist developing solution, the deionized water is used for cleaning for 30 seconds, then the drying nitrogen is used for blow-drying, and the postbaking is carried out for 1 minute by adopting a hot plate at 100 ℃.

And 31, developing the photoetching graph with the red light step structure on the photoresist by adopting an ultraviolet photoetching machine.

And step 32, etching the blue DBR step structure and the isolation groove by using RIE and taking the photoresist as a mask.

And step 33, continuing to grow SiO2 by taking the photoresist as a mask and using a PECVD (plasma enhanced chemical vapor deposition) technology as a filler in the isolation groove.

And step 34, soaking the sample by using an acetone solution to remove residual glue and SiO2 outside the isolation groove.

And 35, repeating the steps 31 to 34, and etching a green DBR step structure and an isolation groove of each light-emitting unit to finally obtain the three-color stacked step Micro-LED display array device.

Example 3

In embodiment 3, the electrode contact layer is electrically injected using a tunnel junction structure, which optimizes the process steps.

Embodiment 3 utilizes MBE to secondarily extend green light multiple quantum wells, red light multiple quantum wells and tunnel pn junctions on a blue light LED epitaxial wafer grown by MOCVD, and combines Micro-nano processing to prepare a multicolor stacked step Micro-LED display array device with tunnel junctions assisting electron hole injection, which comprises the steps of:

step 1, as shown in fig. 1, a high-quality blue light LED epitaxial wafer grown by MOCVD with a flat surface is selected as a substrate.

And 5, secondarily extending an n-type GaN layer and an InGaN/GaN multi-quantum well structure on the substrate by using PA-MBE (plasma-assisted molecular beam epitaxy) equipment. The substrate is heated to 890 ℃ of thermocouple temperature to grow an n-type GaN layer, and a tunnel pn junction is formed with the p-type GaN layer below. The n-type GaN layer is divided into n + and n + + layers, the Ga beam in the n + layer is (5 +/-0.5) multiplied by 10-7Torr, the Si-doped beam in the n + layer is (5 +/-0.5) multiplied by 10-9Torr, the Ga beam in the n + + layer is (5 +/-0.5) multiplied by 10-7Torr, and the Si-doped beam is (8 +/-0.5) multiplied by 10-9Torr. Then cooling the substrate to 600 deg.C to grow green InGaN/GaN multi-quantum well, inGaN well layer, in beam current is (5 + -0.5) x 10-7Torr, ga beam current is (8 + -0.5) x 10-8Torr. A GaN barrier layer, wherein the Ga beam current is (2.5 +/-0.5) multiplied by 10-7 Torr. The InGaN/GaN quantum well is repeatedly grown for 10 cycles. The nitrogen flow rate was set to 0.7sccm throughout the epitaxial growth, and the power of the nitrogen plasma generation apparatus was set to 450W.

And 6, continuing to epitaxially grow a p-type GaN layer and an n-type GaN layer by using PA-MBE (plasma-assisted molecular beam epitaxy) equipment to form a tunnel pn junction. The substrate temperature was maintained at 600 deg.C, the nitrogen flow rate was set to 0.7sccm, and the power of the nitrogen plasma generation apparatus was set to 450W. The p-type GaN layer is divided into p + and p + + layers, the Ga beam in the p + layer is (5 + -0.5) multiplied by 10-7Torr, the Mg-doped beam in the p + layer is (5 + -0.5) multiplied by 10-9Torr, the Ga beam in the p + + layer is (5 + -0.5) multiplied by 10-7Torr, and the Mg-doped beam is (8 + -0.5) multiplied by 10-9Torr. The n-type GaN layer is divided into n + and n + + layers, the Ga beam in the n + layer is (5 +/-0.5) multiplied by 10-7Torr, the Si-doped beam in the n + layer is (5 +/-0.5) multiplied by 10-9Torr, the Ga beam in the n + + layer is (5 +/-0.5) multiplied by 10-7Torr, and the Si-doped beam is (8 +/-0.5) multiplied by 10-9Torr.

And 7, continuously extending the red InGaN/GaN multi-quantum well structure on the sample by using PA-MBE (plasma-assisted molecular beam epitaxy) equipment. And cooling the substrate to 500 ℃ to perform red InGaN/GaN multi-quantum well growth, wherein the nitrogen flow in the whole epitaxial growth process is set to be 0.7sccm, and the power of the nitrogen plasma generation device is set to be 450W. An InGaN well layer, in beam current is (5 + -0.5) x 10-7Torr, ga beam current is (8 + -0.5) x 10-8Torr. A GaN barrier layer, wherein the Ga beam current is (2.5 +/-0.5) multiplied by 10-7 Torr. The InGaN/GaN quantum well is repeatedly grown for 10 cycles.

And 8, continuing to epitaxially grow a p-type GaN layer and an n-type GaN layer by using PA-MBE (plasma-assisted molecular beam epitaxy) equipment to form a tunnel pn junction. The substrate temperature was maintained at 500 deg.C, the nitrogen flow rate was set to 0.7sccm, and the power of the nitrogen plasma generating apparatus was set to 450W. The p-type GaN layer is divided into p + and p + + layers, the Ga beam current in the p + layer is (5 + -0.5) multiplied by 10-7Torr, the Mg doped beam current in the p + + layer is (5 + -0.5) multiplied by 10-9Torr, the Ga beam current in the p + + layer is (5 + -0.5) multiplied by 10-7Torr, and the Mg doped beam current is (8 + -0.5) multiplied by 10-9Torr. The n-type GaN layer is divided into n + and n + + layers, the Ga beam in the n + layer is (5 + -0.5) multiplied by 10-7Torr, the Si doped beam in the n + + layer is (5 + -0.5) multiplied by 10-9Torr, the Ga beam in the n + + layer is (5 + -0.5) multiplied by 10-7Torr, and the Si doped beam is (8 + -0.5) multiplied by 10-9Torr. And obtaining the RGB three-color stacked tunnel end LED epitaxial chip after the growth is finished, as shown in figure 2.

And 9, as shown in figure 3, spin-coating a photoresist on the epitaxial wafer, selecting an inverse photoresist AZ5214, performing spin-coating at a rotation speed of 600rpm/8000rpm for 10s/40s, and pre-baking for 1 minute by using a hot plate at 90 ℃. Since the reverse resist is used, a two-step exposure method is selected, the first pattern region is exposed for 9 seconds, followed by baking for 2 minutes at 110 ℃ and flood exposure for 12 seconds. The development is carried out for 19 seconds by adopting an alkaline positive photoresist developing solution, the deionized water is used for cleaning for 30 seconds, then the drying nitrogen is used for blow-drying, and the postbaking is carried out for 1 minute by adopting a hot plate at 100 ℃.

Step 10, designing a photoetching pattern of the first layer of step structure by adopting an ultraviolet photoetching machine as follows: the steps are 20 μm by 20 μm squares. The structure after completion of development is shown in fig. 4.

And 11, adopting an ICP (inductively coupled plasma) technology, introducing mixed gas of Cl2 and Ar by taking the photoresist in the undeveloped area as a mask, and anisotropically etching the sample to form a blue step structure. The etching parameters are as follows: cl2 and Ar flow rates of 48 + -12 sccm and 18 + -6 sccm, respectively, chamber gas pressure: 25 ± 5mtorr, dc bias: 600 + -60V, RF power 250 + -30W, ICP power: 1200 +/-100W, the frequency of 13.56MHz, and the etching time is controlled, and the n-type GaN layer of the blue LED substrate is etched, as shown in figure 5.

Step 12, soaking the sample in acetone solution for about 10min, and stripping the residual photoresist with low-power ultrasonic cleaning, as shown in fig. 6.

And step 13, continuously spin-coating the photoresist on the sample, selecting an inverse photoresist AZ5214, wherein the spin-coating rotation speed is 600rpm/8000rpm, the time is 10s/40s, and pre-baking for 1 minute by adopting a hot plate at 90 ℃. Since the reverse resist is used, a two-step exposure method is selected, the first pattern region is exposed for 9 seconds, followed by baking for 2 minutes at 110 ℃ and flood exposure for 12 seconds. The development is carried out for 19 seconds by adopting an alkaline positive photoresist developing solution, the deionized water is used for cleaning for 30 seconds, then the drying nitrogen is used for blow-drying, and the postbaking is carried out for 1 minute by adopting a hot plate at 100 ℃.

Step 14, designing a photoetching pattern of a green light step structure by adopting an ultraviolet photoetching machine, wherein the photoetching pattern comprises the following steps: the steps are 10 μm × 10 μm squares.

And step 15, adopting an ICP (inductively coupled plasma) technology, taking the photoresist in the undeveloped area as a mask, introducing a mixed gas of Cl2 and Ar, and anisotropically etching the sample to form a green step structure. The etching parameters are as follows: cl2 and Ar flow rates of 48 + -12 sccm and 18 + -6 sccm, respectively, chamber gas pressure: 25 ± 5mtorr, dc bias: 600 ± 60v, rf power 250 ± 30w, icp power: 1200 +/-100W, the frequency of 13.56MHz, controlling the etching time and etching to the n-type GaN layer of the first tunnel pn junction.

Step 16, soaking the sample in acetone solution for about 10min, and stripping the residual photoresist by low-power ultrasonic cleaning, as shown in fig. 7.

And step 17, continuously spin-coating the photoresist on the sample, selecting an inverse photoresist AZ5214, wherein the spin-coating rotation speed is 600rpm/8000rpm, the time is 10s/40s, and pre-baking for 1 minute by adopting a hot plate at 90 ℃. Since the reverse resist is used, a two-step exposure method is selected, the first pattern region is exposed for 9 seconds, followed by baking for 2 minutes at 110 ℃ and flood exposure for 12 seconds. The development is carried out for 19 seconds by adopting an alkaline positive photoresist developing solution, the deionized water is used for cleaning for 30 seconds, then the drying nitrogen is used for blow-drying, and the postbaking is carried out for 1 minute by adopting a hot plate at 100 ℃.

Step 18, designing a photoetching pattern of a red light step structure by adopting an ultraviolet photoetching machine, wherein the photoetching pattern comprises the following steps: the steps are squares of 2 μm × 2 μm.

And 19, adopting an ICP (inductively coupled plasma) technology, introducing mixed gas of Cl2 and Ar by taking the photoresist in the undeveloped area as a mask, and anisotropically etching the sample to form a third-layer step structure. The etching parameters are as follows: cl2 and Ar flow rates of 48 + -12 sccm and 18 + -6 sccm, respectively, chamber gas pressure: 25 ± 5mtorr, dc bias: 600 ± 60v, rf power 250 ± 30w, icp power: 1200 +/-100W, the frequency of 13.56MHz, and the etching time is controlled, and the n-type GaN layer of the pn junction of the second tunnel is etched.

Step 20, soaking the sample in acetone solution for about 10min, and stripping the residual photoresist with low-power ultrasonic cleaning, as shown in fig. 8.

And 21, evaporating Ti/Al/Ni/Au metal on the surface of the sample by using the residual photoresist as a mask by adopting a PVD (physical vapor deposition) technology to form n-type contact. The Ti/Al/Ni/Au thicknesses were 30/150/50/50nm, respectively, as shown in FIG. 9.

Step 22, bonding the three-color stacked stepped Micro-LEDs and corresponding Si-based CMOS drive circuits one by using a FINEPLACER lambda multi-purpose submicron bonding chip mounter, and finally obtaining the Micro-LEDs with light emitting from the bottom, as shown in fig. 10.

And step 23, polishing and thinning the sapphire on the back surface of the substrate by using polishing equipment.

And 24, growing a silicon dioxide and silicon nitride DBR of blue light on the polished sapphire surface by using a PECVD technology.

And 25, spin-coating the photoresist on the DBR, selecting an inverse photoresist AZ5214, carrying out spin-coating at the rotating speed of 600rpm/8000rpm for 10s/40s, and pre-baking for 1 minute by adopting a hot plate at 90 ℃. Since the reverse resist is used, a two-step exposure method is selected, the first pattern region is exposed for 9 seconds, followed by baking for 2 minutes at 110 ℃ and flood exposure for 12 seconds. The development is carried out for 19 seconds by adopting an alkaline positive photoresist developing solution, the deionized water is used for cleaning for 30 seconds, then the drying nitrogen is used for blow-drying, and the postbaking is carried out for 1 minute by adopting a hot plate at 100 ℃.

And 26, developing the photoetching graph of the red light step structure on the photoresist by adopting an ultraviolet photoetching machine.

And 27, etching the blue DBR step structure and the isolation groove by using RIE and taking the photoresist as a mask.

And step 28, continuing to grow SiO by using the PECVD technology by taking the photoresist as a mask ₂ As a filler in the isolation trenches.

Step 29, soaking the sample in acetone solution to remove residual glue and SiO outside the isolation groove ₂ 。

And step 30, repeating the steps 25 to 29, and etching a green DBR step structure and an isolation groove of each light-emitting unit to finally obtain the three-color stacked step Micro-LED display array device, as shown in FIG. 13. A top view of the RGB display unit of the Micro-LED display array device is shown in fig. 14.

The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be regarded as equivalent replacements within the protection scope of the present invention.

Claims

1. A preparation method of a multi-color stacked step type backlight Micro-LED display device comprises the following steps:

step 1, on a blue light LED epitaxial wafer grown by MOCVD, using MBE secondary epitaxial growth to grow a plurality of InGaN multi-quantum well structures and a device p-type GaN layer and/or a device n-type GaN layer structure to ensure that an n-type GaN layer and a p-type GaN layer exist above and below the multi-quantum well structure to realize the injection of electrons and holes, and obtaining a multi-color stacked LED epitaxial wafer;

step 2, spin-coating photoresist on the multi-color stacked LED epitaxial wafer, and developing the pattern of the first layer of step structure on the photoresist;

step 3, anisotropically etching the sample by using an ICP (inductively coupled plasma) technology to etch an n-type GaN layer of the blue LED epitaxial wafer to form a first-stage step;

step 4, preparing an n-type electrode on the first layer of step by taking the photoresist as a mask;

step 5, ultrasonically cleaning the sample by using an acetone solution, and stripping residual photoresist and metal;

step 6, continuously spin-coating the photoresist, and developing the pattern of the second-layer step structure on the photoresist;

step 7, etching the sample anisotropically by using an ICP (inductively coupled plasma) technology to a hole injection layer of the substrate blue LED to form a second-stage step;

step 8, preparing a p-type electrode or an n-type electrode on the second step by taking the photoresist as a mask;

step 9, repeating the steps 2 to 8, and respectively manufacturing the subsequent step structures to obtain a multi-color stacked step type Micro-LED display array chip;

step 10, bonding electrodes of the multi-color stacked stepped Micro-LED display array and a designed Si-based CMOS driving circuit one by using a submicron bonding chip mounter to obtain a Micro-LED display array device with light emitting from the back;

step 11: polishing and thinning the sapphire substrate surface on the back of the blue LED, then alternately growing silicon dioxide and silicon nitride on the sapphire substrate by using PECVD (plasma enhanced chemical vapor deposition), and sequentially forming a multi-component distributed Bragg reflector layer corresponding to the light-emitting wavelength of each group of multiple quantum well structures below.

2. The method for manufacturing a multi-color stacked stepped back-light Micro-LED display device according to claim 1, wherein: further comprising steps 12-16:

step 12, spin-coating a photoresist on the sapphire surface, and developing the step structures corresponding to the uppermost group of InGaN multi-quantum well structures onto the photoresist;

step 13, etching a first DBR step structure and an isolation groove by using RIE technology and taking the photoresist as a mask;

step 14, continuing to grow an insulating medium by taking the photoresist as a mask and using a PECVD (plasma enhanced chemical vapor deposition) technology as a filler in the isolation groove;

step 15, removing residual glue and insulating media outside the isolation groove;

and step 16, repeating the steps 12 to 15, and engraving the step structures of the DBRs of the other layers and the isolation groove of each light-emitting unit to finally obtain the multicolor-stacked step type Micro-LED display array device.

3. The method for manufacturing a multi-color stacked stepped backlight Micro-LED display device according to claim 1, wherein: before the step 1, the blue light LED epitaxial wafer is sequentially placed in acetone, absolute ethyl alcohol and deionized water for ultrasonic cleaning, and then is dried, so that a clean blue light LED epitaxial wafer is obtained.

4. The method for manufacturing a multi-color stacked stepped backlight Micro-LED display device according to claim 1, wherein: the LED epitaxial wafer stacked in multiple colors in the step 1 is an n-type GaN layer which sequentially grows a first group of InGaN multiple quantum well structures and realizes the electron injection of the first group of InGaN multiple quantum well structures on a blue LED epitaxial wafer; or the LED epitaxial wafer stacked in multiple colors in the step 1 is formed by sequentially growing an n-type GaN layer on a blue LED epitaxial wafer and adding a first group of InGaN multiple quantum well structures, a p-type GaN layer and the n-type GaN layer to form a tunnel pn junction; the step 9 specifically comprises: and naturally forming a third step by the reserved light emitting unit formed by the first group of InGaN multi-quantum well structures and the electron injection n-type GaN layer, and preparing an n-type electrode on the surface of the third step, wherein the light emitted by the first group of InGaN multi-quantum well structures is different from that of the blue LED epitaxial wafer.

5. The method for manufacturing a multi-color stacked stepped backlight Micro-LED display device according to claim 1, wherein: the LED epitaxial wafer stacked in multiple colors in the step 1 is formed by sequentially growing a first group of InGaN multiple quantum well structures, an n-type GaN layer for realizing electron injection of the first group of InGaN multiple quantum well structures, a second group of InGaN multiple quantum well structures and a p-type GaN layer for realizing hole injection of the second group of InGaN multiple quantum wells on a blue LED epitaxial wafer; or the LED epitaxial wafer stacked in multiple colors in the step 1 is formed by sequentially growing an n-type GaN layer and a first group of InGaN multi-quantum well structures, a p-type GaN layer and the n-type GaN layer on a blue LED epitaxial wafer to form a tunnel pn junction, and forming a second group of InGaN multi-quantum well structures, a p-type GaN layer and the n-type GaN layer to form a tunnel pn junction; the step 9 specifically comprises: continuously spin-coating photoresist, developing the pattern of the third step structure on the photoresist, anisotropically etching the sample by using an ICP (inductively coupled plasma) technology, etching the sample until the sample is in contact with the n-type GaN layer below the second group of InGaN multi-quantum wells to form a third step, and preparing an n-type electrode on the third step by using the photoresist as a mask; and naturally forming a fourth step by the reserved second group of InGaN multi-quantum well structures, and preparing an n-type electrode or a p-type electrode on the surface of the fourth step, wherein the light emitted by the first group of InGaN multi-quantum well structures is different from the blue LED epitaxial wafer, and the light emitted by the second group of InGaN multi-quantum well structures is different from the first group of InGaN multi-quantum well structures or the blue LED epitaxial wafer.