CN106920790A - A kind of full-color micro-display device and preparation method thereof - Google Patents

Abstract

A full-color micro-display device provided by the present invention is realized by flip-chip LED chip array and quantum dot color conversion technology. The quantum dots are excited by the flip-chip LED chip to generate the three primary colors of red, green and blue respectively, and emit three colors of red, green and blue light. A GaN-based light-emitting structure forms a pixel. The flip-chip LED chip is an LED chip based on a sapphire substrate and is flip-chip welded to a substrate with a driving circuit. Quantum dots for light color conversion are filled on the light-emitting surface of the sapphire substrate. The trenches are filled with quantum dots and covered with a protective material. The full-color micro-display device prepared by the method for preparing the full-color micro-display device provided by the present invention has the advantages of small volume, high resolution, simple color control and the like.

Description

A kind of full-color microdisplay device and preparation method thereof

technical field

The invention belongs to the field of LED flip-chip preparation technology and the application field of quantum dot technology, and specifically relates to a full-color micro-display device and a preparation method thereof.

Background technique

As micro-projectors and wearable devices gradually enter into real production and life, the application of micro-display devices is becoming more and more extensive, and the demand and requirements for micro-display devices are gradually increasing. Higher resolution, lighter weight Small systems, full-color displays, and more. Since the size of LED chips can reach the micron level, compared with other micro-display technologies such as DLP and LCoS, micro-display devices based on LED chips have the advantages of higher resolution, lighter, smaller and simpler systems, and lower energy consumption costs.

At present, the LED chip microarray mainly realizes a monochrome microdisplay device. In the research of LED monochrome microdisplays, JamesR.Bonar et al. of mLED Company have successfully prepared a 640×360 array microdisplay with a pixel size of 6μm and high contrast ratio in 2016. To achieve full-color display of LED-based microdisplay devices, there are currently two possible solutions: one is to coat phosphor film on the basis of LED monochrome microdisplay chips to excite white light, and then coat red, green and blue three-color The primary color filter film array; the second is to prepare an LED array of red, green and blue primary colors on the same substrate. The process of the first scheme is relatively simple, but the existence of the filter film reduces the effective light intensity, resulting in a large energy loss, and it is easy to cause crosstalk between pixels; the process of the second scheme is more complicated because it cannot be used on the same substrate. A quantum well structure that emits three colors of red, green and blue is grown on the bottom at one time, and because the threshold voltage of red, green and blue LEDs is different, the driving circuit becomes complicated, and it is difficult to improve the pixel resolution of the micro-display chip realized by this scheme. Therefore, how to realize a full-color micro-display and improve the resolution of the micro-display chip by using a single-color LED chip microarray is a huge challenge in the field of LED micro-display.

Quantum dots are quasi-zero-dimensional nanomaterials, which are composed of a small number of atoms, and the sizes of the three dimensions are all below 100 nanometers (nm). Some optical properties of quantum dots are very suitable for the conversion of light color. First, the emission spectrum of quantum dots can be controlled by changing the size of quantum dots. By changing the size of quantum dots and its chemical composition, the emission spectrum can be made Covering the entire visible light region; secondly, quantum dots have excellent fluorescence characteristics such as wide and continuous distribution of excitation spectrum, narrow and symmetrical emission spectrum, high photochemical stability, and long fluorescence lifetime.

Contents of the invention

The purpose of the present invention is to realize the conversion of light color on the chip level through a flip-chip LED chip preparation technology and quantum dot technology to make the size of the micro-display LED chip smaller, so as to realize a small size and high resolution LED chip. High-rate full-color microdisplay device.

In order to achieve the above object, the technical scheme adopted in the present invention is as follows:

A full-color micro-display device, comprising a substrate with a driving circuit, an arrayed LED chip flip-chip welded on the substrate with a driving circuit, and a sapphire substrate, the arrayed LED chips are arranged on the same sapphire substrate and emit the same spectrum, it is characterized in that: an isolation trench is arranged between the arrayed LED chips, an insulating layer and a light-shielding layer are arranged on the inside and two side walls of the isolation trench, and the material of the insulating layer is SiO ₂ or AlN, with a thickness of 500-2000nm; the material of the light-blocking layer is Cr/Al or Cr/Ag, with a thickness of 100-500nm; each LED chip includes three GaN-based light-emitting structures and welding electrodes, and the welding electrodes are used For connecting the GaN-based light-emitting structure and the substrate with the driving circuit, the light-emitting surface of the sapphire substrate is provided with grooves, and the positions and sizes of the grooves and the GaN-based light-emitting structure correspond one-to-one. Each LED chip The trenches corresponding to the three GaN-based light-emitting structures are filled with quantum dots used to excite red, green, and blue light, and the quantum dots are filled and covered with a layer of protective material. The invention utilizes a single-color LED chip microarray to realize full-color micro-display, and the prepared full-color micro-display device has the advantages of small volume, high resolution, simple color control, and the like.

Preferably, the groove is located directly above the GaN-based light-emitting structure, the size of the groove is 5-40 μm, and the depth of the groove is 5-20 μm.

The present invention also provides a method for preparing a full-color micro-display device, comprising the following steps:

(1) LED epitaxial wafers of GaN or AlGaN epitaxially grown on a sapphire substrate, the GaN epitaxial wafers sequentially comprising a buffer layer, an N-GaN layer, an active layer and a P-GaN layer;

(2) Continue to deposit a transparent conductive film layer as a contact layer on the P-GaN layer;

(3) Etch the N-GaN layer on the LED epitaxial wafer to form three GaN-based light-emitting structures required for each pixel;

(4) Use ICP to etch the isolation trench between pixels on the LED epitaxial wafer, that is, etch all the way to the sapphire substrate to form a display of full-color micro-display pixels;

(5) Depositing an insulating layer and a light-shielding layer in the isolation trench between pixels and on both side walls;

(6) Deposit the N electrode, the N electrode is deposited by Ti/Al/Ni/Au, with a thickness of 1-2um;

(7) Deposit the P electrode. The P electrode first deposits Al or Ag as the reflective layer structure, and then deposits Ti/Au or Ni/Au, with a deposition thickness of 1-2 μm;

(8) thinning the sapphire substrate to a thickness of 80 μm to 150 μm;

(9) etching grooves for filling quantum dots on the light-emitting surface of the sapphire substrate;

(10) Fill the three grooves of each pixel with quantum dots capable of emitting red, green and blue lights by means of drop coating or 3D printing;

(11) Cover a protective material layer on the surface of the sapphire substrate after filling the quantum dots;

(12) The LED chip is flip-chip welded to a substrate with a driving circuit, and the driving circuit on the substrate can independently control the three GaN-based light-emitting structures in each pixel.

Preferably, the shape of the three GaN-based light-emitting structures is a rectangle, and the ratio of the light-emitting area of the three GaN-based light-emitting structures to the total area of the pixel is 1:1:1.

Preferably, the shape of the pixel is rectangular, and the pixel size is 40 μm×40 μm.

Preferably, the insulating layer is made of SiO2 or AlN, with a thickness of 500-2000nm, and the light-shielding layer is made of Cr/Al or Cr/Ag metal, with a thickness of 100nm-500nm.

Preferably, the trench is formed by directly etching sapphire, or first depositing SiO2 on the sapphire and then etching it with BOE. The trench is located directly above the three GaN-based light-emitting structures in each pixel, and its shape and size are the same as those of the three GaN-based light-emitting structures. Corresponding to the base light emitting structure, the depth of the groove is 10-20 μm.

Preferably, the protective material layer is made of SiO ₂ or resin, and when the protective material layer is SiO ₂ , the thickness is 100 nm to 500 nm.

The present invention adopts the method of directly forming grooves on the sapphire substrate on the light-emitting surface of the LED chip for filling the quantum dots, so as to realize convenient and accurate control of the matching of the quantum dots in the three primary colors of red, green and blue, and let them be fixed in the corresponding positions, so that it is easy to control the light emission Depositing a light-blocking metal layer in the isolation channel between pixels also reduces the crosstalk between pixels to a certain extent. This process is easy to implement, and at the same time makes full use of the small characteristics of quantum dots, which can be realized at the chip level. Full-color, the size of the micro-display chip can be further miniaturized, and the resolution of the full-color micro-display can be guaranteed or even improved.

Description of drawings

Fig. 1 is a schematic diagram of the top view structure of the full-color micro-display pixel array of the present invention, 4 × 4 pixels, each pixel is composed of three LED units of red (R), green (G) and blue (B), and the three LED units are respectively filled with Quantum dots for exciting red, green and blue light colors;

Fig. 2 is a schematic diagram of an LED chip array used to excite quantum dots according to the present invention. It is a top view structural diagram when the electrodes face up. The three primary colors of red, green and blue of each pixel are respectively excited by three corresponding GaN-based light-emitting structures. The three GaN-based light-emitting structures have a common N pole, and there are insulating and light-blocking isolation channels between different pixels;

Fig. 3 is a schematic cross-sectional view of the full-color micro-display device of the present invention, the cross-sectional position is located at the dotted line in Fig. 2, so each pixel can only see two LED units G and B.

detailed description

The specific embodiment of the present invention will be further described below in conjunction with accompanying drawing:

As shown in Figure 1, each pixel consists of three LED units, red (R), green (G) and blue (B). The LED unit includes a GaN-based light-emitting structure and its corresponding grooves. The three grooves of each pixel It is filled with quantum dots used to excite red, green and blue light respectively.

Fig. 2 is a schematic diagram of a GaN-based light-emitting structure array for exciting red, green, and blue quantum dots, and the red, green, and blue colors of each pixel are respectively excited by three corresponding GaN-based light-emitting structures. The array of GaN-based light-emitting structures used to excite quantum dots is prepared on the same sapphire substrate and emits the same spectrum. The three GaN-based light-emitting structures for each pixel on the same sapphire substrate respectively excite quantum dots with different emission spectra to emit red light. The three primary colors of green and blue. The ratio of the light-emitting area of the three LED units to the entire pixel light-emitting area can be adjusted appropriately to adapt to the different excitation efficiencies of the different emission spectra of the quantum dots. The GaN-based light-emitting structures of the same pixel share the N pole 202, the drive circuit controls the P-electrodes 201, 203 and 204 of the three GaN-based light-emitting structures, and there are isolation channels 205 for insulation and light blocking between different pixels.

Fig. 3 is the sectional view structural representation of full-color micro-display device of the present invention, and section position is positioned at the dashed line position of Fig. A substrate with a driving circuit, welding electrodes 308, 309 and 310, a GaN-based or AlGaN-based light-emitting structure 307, a sapphire substrate 303, grooves 301 and 302 filled with quantum dots on the side of the light-emitting surface of the sapphire substrate, covering the sapphire substrate The light emitting surface of the bottom protects the protective material layer 304 of the quantum dots. The invention realizes light color conversion on the chip level to make the size of the micro-display LED chip smaller, so as to realize a small-sized and high-resolution full-color micro-display device.

Please refer to Fig. 1-Fig. 3, the present invention provides a kind of full-color micro-display device, comprises the substrate 300 with drive circuit, the array type LED chip that is flip-chip welded on the substrate 300 with drive circuit, and sapphire substrate 303, arrayed LED chips are arranged on the same sapphire substrate and emit the same spectrum, isolation channels 205 are arranged between the LED chips, and each LED chip includes three GaN-based light emitting structures 307 and welding electrodes 308, 309, 310, The welding electrodes are used to connect the GaN-based light-emitting structure 307 and the substrate 300 with the drive circuit. The light-emitting surface of the sapphire substrate 303 is provided with grooves 301, 302. The positions and sizes of the grooves 301, 302 and the GaN-based light-emitting structure 307 are the same. For one-to-one correspondence, the grooves corresponding to the three GaN-based light emitting structures 307 of each LED chip are respectively filled with quantum dots for exciting red, green and blue light, and the quantum dots are filled and covered with a protective material layer 304 . Realized by flip-chip LED chip array and quantum dot color conversion technology, the quantum dots are excited by the flip-chip LED chip to generate the three primary colors of red, green and blue respectively, and the three GaN-based light-emitting structures that emit red, green and blue light colors form a pixel. The flip-chip LED chip It is an LED chip based on a sapphire substrate and is flip-chip welded to a substrate with a driving circuit. The quantum dots used for light color conversion are filled in the grooves on the light-emitting surface of the sapphire substrate, and the quantum dots are filled and covered with protective materials. The full-color micro-display chip provided by the invention has the advantages of small chip size, high resolution, simple color control and the like.

The quantum dot absorption spectrum corresponds to the emission spectrum of the LED chip, and its emission spectrum corresponds to the three primary colors of red, green and blue. Quantum dots are preferably CdSe quantum dots, which can achieve the purpose of changing the emission spectrum by changing their size and composition.

In an embodiment of the present invention, there are isolation trenches 205 on four sides of each pixel, and the isolation trenches etch away the GaN-based light-emitting structure until the sapphire substrate. An insulating layer 305 and a light-shielding layer 306 are arranged in the isolation trench 205 between pixels and on both side walls. The material of the insulating layer is preferably SiO ₂ or AlN, and the thickness is preferably 500-2000 nm; the material of the light-shielding layer is preferably Cr/Al or Cr/Ag preferably has a thickness of 100 to 500 nm. An insulating layer is deposited on the isolation trench 205 and the four walls of each pixel, and a light-shielding metal layer structure is further deposited on the insulating layer to reduce optical crosstalk between pixels and play the role of a reflective cup. Increase and collimate the output light.

In an embodiment of the present invention, the sapphire substrate is preferably a patterned sapphire substrate.

In an embodiment of the present invention, the groove is formed by ICP etching sapphire or depositing a _SiO2 layer on the sapphire substrate and then etching. The sapphire substrate is thinned before forming the groove, and the thinned The thickness is 100 μm. The groove is located directly above the GaN-based light-emitting structure, the size of the groove is 5-40 μm, and the depth of the groove is 5-20 μm.

In an embodiment of the present invention, the protective material layer is made of SiO ₂ or organic resin.

The present invention also provides a method for preparing a full-color micro-display device, the steps are as follows:

(1) GaN or AlGaN LED epitaxial wafers are epitaxially grown on the sapphire substrate 303 , and the GaN epitaxial wafers sequentially include a buffer layer, an N-GaN layer, an active layer and a P-GaN layer.

(2) Continue to deposit a transparent conductive film layer on the P-GaN layer as a contact layer for forming good ohmic contact with both the P-GaN and the reflective layer metal. The contact layer is preferably ITO and ZnO, but not limited thereto.

(3) Etch N-GaN on the LED epitaxial wafer to form three LED chips required for each pixel. The shape of the three chips is preferably rectangular, but not limited thereto. The ratio is preferably 1:1:1, but not limited thereto.

(4) Use ICP to etch the isolation channel 205 between pixels on the LED epitaxial wafer, that is, etch all the way to the sapphire substrate to form an array of full-color micro-display pixels. The pixel shape is preferably rectangular, but not limited to rectangular, and the pixel size is preferred. 40 μm×40 μm, but not limited thereto.

(5) Deposit an insulating layer 305 and a light-shielding layer 306 in the isolation trench between pixels and on both side walls of the trench. The insulating layer is preferably SiO ₂ or AlN, with a thickness of preferably 500-2000nm. The light-shielding layer is preferably Cr/Al or Cr /Ag metal, with a thickness of 100nm to 500nm, and the light blocking layer can also be made into a reflective structure, preferably Al or Ag as the reflective layer structure, followed by deposition of Ti/Au or Ni/Au, with a thickness of 1 to 2μm. The light blocking layer can reduce the crosstalk of light between pixels to a certain extent.

(6) Deposit the N electrode 202 , the N electrode is preferably Ti/Al/Ni/Au, but not limited thereto, and the total thickness is 1-2 um.

(7) Deposit P electrodes 201, 203, and 204. The P electrodes also need to reflect light. Al or Ag is preferred as the reflective layer structure, followed by deposition of Ti/Au or Ni/Au with a thickness of 1-2 μm.

(8) The sapphire substrate of the micro-display flip-chip LED chip is thinned, and the thickness after thinning is preferably 80 μm˜150 μm.

(9) Etch grooves 301 and 302 for filling quantum dots on the light-emitting surface of the sapphire substrate, which can be formed by directly etching sapphire, or can be formed by depositing SiO2 on the sapphire first and then etched with BOE. The grooves are located in each Directly above the three LED chips in the pixel, the shape and size correspond to the three LED chips, and the groove depth is preferably 10-20 μm.

(10) Fill the three grooves of each pixel with quantum dots that can emit light of red, green and blue colors by drop coating or 3D printing.

(11) After the quantum dots are filled, the surface of the chip is covered with a protective layer. The protective layer is preferably SiO2 or resin. When SiO2 is selected, the thickness is preferably 100nm-500nm.

(12) Flip-chip welding the micro-display flip-chip LED chip to a substrate with a driving circuit, the substrate is preferably a Si substrate, but not limited thereto, and the driving circuit on the substrate can independently control three LED chips in each pixel.

It should be understood that the above specific embodiments of the present invention are only used to illustrate or explain the principles of the present invention, and not to limit the present invention. Therefore, any modification, equivalent replacement, improvement, etc. made without departing from the spirit and scope of the present invention shall fall within the protection scope of the present invention. Furthermore, it is intended that the appended claims of the present invention embrace all changes and modifications that come within the scope and metesques of the appended claims, or equivalents of such scope and metes and bounds.

Claims (9)

1. A full-color micro-display device, comprising a substrate with a drive circuit, an arrayed LED chip flip-chip welded on the substrate with a drive circuit, and a sapphire substrate, the arrayed LED chip is arranged on the same sapphire On the substrate and emit the same spectrum, it is characterized in that: an isolation trench is arranged between the arrayed LED chips, an insulating layer and a light-shielding layer are arranged on the inside and two side walls of the isolation trench, and the material of the insulating layer is It is SiO ₂ or AlN, with a thickness of 500-2000nm; the material of the light-blocking layer is Cr/Al or Cr/Ag, with a thickness of 100-500nm; each LED chip includes three GaN-based light-emitting structures and welding electrodes, and the welding The electrodes are used to connect the GaN-based light-emitting structure and the substrate with the driving circuit. The light-emitting surface of the sapphire substrate is provided with grooves, and the positions and sizes of the grooves and the GaN-based light-emitting structure correspond to each other. The grooves corresponding to the three GaN-based light-emitting structures of the LED chip are respectively filled with quantum dots used to excite red, green and blue light, and the quantum dots are filled and covered with a protective layer. 2 . The full-color micro-display device according to claim 1 , wherein the groove is located directly above the GaN-based light-emitting structure, the size of the groove is 5-40 μm, and the depth of the groove is 5-20 μm. 3. A preparation method for a full-color microdisplay device, comprising the following steps: (1) GaN or AlGaN LED epitaxial wafers are epitaxially grown on a sapphire substrate, and the GaN epitaxial wafers sequentially include a buffer layer, an N-GaN layer, an active layer and a P-GaN layer; (2) Continue to deposit a transparent conductive film layer as a contact layer on the P-GaN layer; (3) Etch the N-GaN layer on the LED epitaxial wafer to form three GaN-based light-emitting structures required for each pixel; (4) Use ICP to etch the isolation trench between pixels on the LED epitaxial wafer, that is, etch all the way to the sapphire substrate to form a display of full-color micro-display pixels; (5) Depositing an insulating layer and a light-shielding layer in the isolation trench between pixels and on both side walls; (6) Deposit the N electrode, the N electrode is deposited by Ti/Al/Ni/Au, with a thickness of 1-2um; (7) Deposit the P electrode. The P electrode first deposits Al or Ag as the reflective layer structure, and then deposits Ti/Au or Ni/Au, with a deposition thickness of 1-2 μm; (8) thinning the sapphire substrate to a thickness of 80 μm to 150 μm; (9) etching grooves for filling quantum dots on the light-emitting surface of the sapphire substrate; (10) Fill the three grooves of each pixel with quantum dots capable of emitting light of red, green and blue; (11) After the quantum dots are filled, a protective material layer is covered on the surface of the sapphire substrate. (12) The LED chip is flip-chip welded to a substrate with a driving circuit, and the driving circuit on the substrate can independently control the three GaN-based light-emitting structures in each pixel. 4. The preparation method of a full-color micro-display device according to claim 3, characterized in that: the shape of the three GaN-based light-emitting structures is a rectangle, and the ratio of the light-emitting areas of the three GaN-based light-emitting structures to the total area of the pixels 1:1:1. 5 . The method for manufacturing a full-color micro-display device according to claim 3 , wherein the shape of the pixel is rectangular, and the pixel size is 40 μm×40 μm. 6. The preparation method of a full-color micro-display device according to claim 3, characterized in that: the insulating layer adopts SiO ₂ or AlN, the thickness is 500-2000nm, and the light-shielding layer adopts Cr/Al or Cr/Ag metal , the thickness is preferably 100 to 500 nm. 7. the preparation method of full-color micro-display device according to claim 3 is characterized in that: described trench directly etches sapphire to form, or first deposits SiO _on sapphire after BOE etching forms, and described trench is located Directly above the three GaN-based light-emitting structures in each pixel, the shape and size correspond to the three GaN-based light-emitting structures, and the depth of the trench is 10-20 μm. 8 . The method for manufacturing a full-color micro-display device according to claim 3 , wherein the protective material layer is SiO ₂ with a thickness of 100 nm to 500 nm. 9. The method for preparing a full-color micro-display device according to claim 3, characterized in that: the protective material layer is resin.