CN112289899A - Micro LED wafer structure and preparation method thereof - Google Patents

Micro LED wafer structure and preparation method thereof Download PDF

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Publication number
CN112289899A
CN112289899A CN202011050157.7A CN202011050157A CN112289899A CN 112289899 A CN112289899 A CN 112289899A CN 202011050157 A CN202011050157 A CN 202011050157A CN 112289899 A CN112289899 A CN 112289899A
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single crystal
crystal substrate
micro led
layer
common cathode
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CN112289899B (en
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庄文荣
孙明
卢敬权
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Dongguan HCP Technology Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/005—Processes
    • H01L33/0062—Processes for devices with an active region comprising only III-V compounds
    • H01L33/0075—Processes for devices with an active region comprising only III-V compounds comprising nitride compounds
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/15—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components having potential barriers, specially adapted for light emission
    • H01L27/153—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components having potential barriers, specially adapted for light emission in a repetitive configuration, e.g. LED bars
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/36—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the electrodes
    • H01L33/38—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the electrodes with a particular shape
    • H01L33/387—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the electrodes with a particular shape with a plurality of electrode regions in direct contact with the semiconductor body and being electrically interconnected by another electrode layer
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/48—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor body packages
    • H01L33/58—Optical field-shaping elements
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2933/00—Details relating to devices covered by the group H01L33/00 but not provided for in its subgroups
    • H01L2933/0008—Processes
    • H01L2933/0016—Processes relating to electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2933/00—Details relating to devices covered by the group H01L33/00 but not provided for in its subgroups
    • H01L2933/0008—Processes
    • H01L2933/0033—Processes relating to semiconductor body packages
    • H01L2933/0058—Processes relating to semiconductor body packages relating to optical field-shaping elements

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Abstract

The invention provides a Micro LED wafer structure and a preparation method thereof, wherein the preparation method comprises the following steps: 1) providing a single crystal substrate, wherein the single crystal substrate comprises a first surface and a second surface which are opposite, and an LED structural layer is formed on the first surface of the single crystal substrate; 2) preparing a plurality of Micro LED arrays on a single crystal substrate based on the LED structure layer; 3) thinning the single crystal substrate from the second surface, and forming a lens array on the second surface by a wet etching process; 4) and forming a black matrix on the second surface of the single crystal substrate, and forming a quantum dot array in the black matrix, wherein the quantum dot array, the lens array and the Micro LED array are correspondingly arranged. The invention adopts the single crystal substrate to grow each layer of the chip, thereby greatly reducing the dislocation density. The invention forms the lens array, has the function of converging the light emitted from each chip on the wafer, can effectively reduce the crosstalk between the chips and has better contact effect between the light emitted and the quantum dots.

Description

Micro LED wafer structure and preparation method thereof
Technical Field
The invention belongs to the field of design and manufacture of semiconductor light-emitting devices, and particularly relates to a Micro LED wafer structure and a preparation method thereof.
Background
With the progress of Display technology, the market is increasingly dissatisfied with the disadvantages of low contrast, low color gamut, low response speed, etc. of Liquid Crystal Displays (LCDs), and the disadvantages of burn-in, heavy granular sensation, color cast, poor light comfort, etc. of Organic Light Emitting Displays (OLEDs). The Micro LED display technology as the next generation display technology has the advantages of high contrast, high color gamut, high response speed, ultrahigh resolution, long service life and the like, has the advantages of an LCD and an OLED, and does not have the defects. The Micro LED also has the advantages of flexible display and low energy consumption, and is known as a final display technology.
Augmented Reality (AR) and Virtual Reality (VR) technologies have been rapidly developed in recent years, and LED technologies need to be used in order to achieve better immersion and reality, but with LED scaling down, light quenching is likely to occur at the dislocation of the epitaxial layer of an LED chip, which has an important influence on the light emitting effect of the entire LED, and therefore, it is particularly necessary to reduce the dislocation density of the substrate. In the prior art, a buffer layer is generally grown under a sapphire substrate to regrow an epitaxial wafer layer of a chip, and the dislocation density is 108/cm2In the technical scheme, the single crystal GaN is used as the substrate to grow the epitaxial layer of the chip, so that the dislocation density is greatly reduced, the high-quality directional growth of each subsequent layer is ensured, the epitaxial crystal quality characteristic of the chip can be improved, and the integral light emitting effect of the whole wafer Micro-LED chip can be realized.
Moreover, Quantum Dots (QDs) have the characteristics of good photoluminescence stability, narrow half-peak width, high color gamut and the like, and the Micro-LED RGB color display is realized by exciting the QDs by using blue LEDs, so that the quantum dots are considered as an effective way for rapidly entering into productization. The QDs can be excited by blue light with shorter wavelength to generate red and green light, thereby realizing color display and reducing the difficulty of mass transfer process.
Disclosure of Invention
In view of the above disadvantages of the prior art, the present invention is to provide a Micro LED wafer structure and a method for manufacturing the same, which are used to solve the problem of large dislocation of the epitaxial layer of the LED chip in the prior art.
In order to achieve the above and other related objects, the present invention provides a method for manufacturing a Micro LED wafer structure, the method comprising: 1) providing a single crystal substrate, wherein the single crystal substrate comprises a first surface and a second surface which are opposite, and an LED structural layer is formed on the first surface of the single crystal substrate; 2) preparing a Micro LED array on the single crystal substrate based on the LED structure layer; 3) thinning the single crystal substrate from the second surface, and forming a lens array on the second surface by a wet etching process; 4) and forming a black matrix on the second surface of the single crystal substrate, and forming a quantum dot array in the black matrix, wherein the quantum dot array, the lens array and the Micro LED array are correspondingly arranged.
Optionally, in step 1), the single crystal substrate is an N-type substrate, and then a light emitting layer, an electron blocking layer, and a P-type semiconductor layer are epitaxially grown on the single crystal substrate to form the LED structure layers, wherein the LED structure layers are connected in a common-cathode manner through the single crystal substrate, and the single crystal substrate is a common-cathode path.
Optionally, in step 1), an N-type semiconductor layer, a light emitting layer, an electron blocking layer, and a P-type semiconductor layer are sequentially epitaxially grown on the single crystal substrate to form the LED structure layer, wherein the LED structure layers are connected in a common cathode manner through the N-type semiconductor layer, and the N-type semiconductor layer is a common cathode path.
Optionally, a common cathode electrode is connected between the Micro LED chips at the common cathode path; the common cathode electrode is connected with the driving circuit on one hand, and reduces voltage drop generated by a common cathode path on the other hand, so that voltages of all Micro LEDs are consistent when the Micro LEDs work.
Optionally, the common cathode electrode is in a grid shape or a dot shape, wherein the number of grids or dots is less than or equal to the number of Micro LED chips.
Optionally, the step 3) of forming the lens array on the second surface by a wet etching process includes: and carrying out wet etching on the single crystal substrate by adopting one or more of sulfuric acid, nitric acid, phosphoric acid and hydrochloric acid, wherein the etching temperature is 155-180 ℃, and the etching time is 3-10 minutes.
The invention also provides a Micro LED wafer structure, which comprises: the LED array comprises a single crystal substrate and a plurality of LED chips, wherein the single crystal substrate comprises a first surface and a second surface which are opposite, a Micro LED array is formed on the first surface of the single crystal substrate, and a lens array is formed on the second surface of the single crystal substrate; and the black matrix is formed on the second surface of the single crystal substrate, a quantum dot array is formed in the black matrix, and the quantum dot array, the lens array and the Micro LED array are correspondingly arranged.
Optionally, the single crystal substrate is an N-type substrate, the Micro LED array includes an LED structure layer, the LED structure layer includes a light emitting layer, an electron blocking layer, and a P-type semiconductor layer, wherein the LED structure layers are connected in a common cathode manner through the single crystal substrate, and the single crystal substrate is a common cathode path.
Optionally, the Micro LED array includes an LED structure layer, the LED structure layer includes an N-type semiconductor layer, a light emitting layer, an electron blocking layer, and a P-type semiconductor layer formed on the single crystal substrate, each LED structure layer realizes a common-cathode connection through the N-type semiconductor layer, and the N-type semiconductor layer is a common-cathode path.
Optionally, a common cathode electrode is connected between the Micro LED chips at the common cathode path; the common cathode electrode is connected with the driving circuit on one hand, and reduces voltage drop generated by a common cathode path on the other hand, so that voltages of all Micro LEDs are consistent when the Micro LEDs work.
Optionally, the common cathode electrode is in a grid shape or a grid shape, and the number of grids or grid points is less than or equal to the number of Micro LED chips.
As described above, the Micro LED wafer structure and the preparation method thereof of the present invention have the following beneficial effects:
the invention adopts the single crystal substrate (such as the single crystal GaN substrate) to grow each layer of the chip, thereby greatly reducing the dislocation density which can reach 105/cm2According to the method, high-quality directional growth of each subsequent layer is guaranteed, and the luminous efficiency and parameter consistency of the whole wafer Micro LED chip are improved.
According to the invention, the lens array is formed by corroding the single crystal substrate by a wet method, so that the light emitted from each Micro LED chip on the wafer is converged, the crosstalk between the Micro LED chips can be effectively reduced, and the contact effect between the light emitted and the quantum dots is better.
The whole wafer of the invention adopts a common cathode design, and all Micro LED chips share one N-type substrate or N-type semiconductor layer as a common cathode path, so that a driving circuit is simpler.
The common cathode electrode is connected with the driving circuit on one hand, and reduces the voltage drop generated by the common cathode path on the other hand, so that the voltages of all Micro LEDs are consistent when the Micro LEDs work.
Drawings
Fig. 1 to 6 are schematic views showing a structure of a Micro LED wafer according to embodiment 1 of the present invention.
Fig. 7 to 9 are schematic views illustrating a structure of a Micro LED wafer according to embodiment 2 of the present invention.
Description of the element reference numerals
10 flip-chip structure
101. 201 single crystal substrate
1011. 2011N-type semiconductor layer in single crystal substrate
102. 202N type semiconductor layer
103. 203 light emitting layer
104. 204 electron blocking layer
105. 205P-type semiconductor layer
106. 206P electrode
107. 207P external electrode
108. 208 Bragg reflector
109 second conductive layer
110N external electrode
111 lens array
112 transparent barrier layer
113 black matrix
114 quantum dot array
115 encapsulation layer
116N electrode
20 vertical structure
209 first conductive layer
Detailed Description
The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention.
As in the detailed description of the embodiments of the present invention, the cross-sectional views illustrating the device structures are not partially enlarged in general scale for convenience of illustration, and the schematic views are only examples, which should not limit the scope of the present invention. In addition, the three-dimensional dimensions of length, width and depth should be included in the actual fabrication.
For convenience in description, spatial relational terms such as "below," "beneath," "below," "under," "over," "upper," and the like may be used herein to describe one element or feature's relationship to another element or feature as illustrated in the figures. It will be understood that these terms of spatial relationship are intended to encompass other orientations of the device in use or operation in addition to the orientation depicted in the figures. Further, when a layer is referred to as being "between" two layers, it can be the only layer between the two layers, or one or more intervening layers may also be present.
In the context of this application, a structure described as having a first feature "on" a second feature may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features are formed in between the first and second features, such that the first and second features may not be in direct contact.
It should be noted that the drawings provided in the present embodiment are only for illustrating the basic idea of the present invention, and the drawings only show the components related to the present invention rather than being drawn according to the number, shape and size of the components in actual implementation, and the type, quantity and proportion of each component in actual implementation may be changed arbitrarily, and the layout of the components may be more complicated.
Example 1
As shown in fig. 1 to 6, the present embodiment provides a method for manufacturing a Micro LED wafer structure, where the method includes:
as shown in fig. 1, step 1) and step 2) are performed first, a single crystal substrate 101, 201 is provided, the single crystal substrate 101, 201 includes a first surface and a second surface opposite to each other, an LED structure layer is formed on the first surface of the single crystal substrate 101, 201, and a plurality of Micro LED arrays are prepared on the single crystal substrate 101, 201 based on the LED structure layer.
The single crystal substrates 101 and 201 may be group iii and group v compound single crystal substrates, and in this embodiment, the single crystal substrates 101 and 201 are GaN single crystal substrates. The invention adopts the single crystal substrates 101 and 201 (such as single crystal GaN substrates) to grow each layer of the chip, greatly reduces the dislocation density which can reach 105/cm2According to the method, high-quality directional growth of each subsequent layer is guaranteed, and the luminous efficiency and parameter consistency of the whole wafer Micro LED chip are improved.
As shown in fig. 3 and 5, in one embodiment, the forming of the LED structure layer on the first surface of the single crystal substrate 101, 201 includes: and epitaxially growing N-type semiconductor layers 102 and 202, light emitting layers 103 and 203, electron blocking layers 104 and 204 and P-type semiconductor layers 105 and 205 on the single crystal substrates 101 and 201 in sequence to form the LED structure layers, wherein the LED structure layers are connected in a common cathode mode through the N-type semiconductor layers 102 and 202, and the N-type semiconductor layers are in a common cathode path. The whole wafer of the invention adopts a common cathode design, all Micro LED chips share one N- type semiconductor layer 102, 202, and the single crystal substrate 101, 202 can be an undoped substrate.
As shown in fig. 3, for example, the Micro LED chip in the Micro LED array is a flip-chip structure 10, a step exposing the N-type semiconductor layer 102 is formed in the LED structure layer, a second conductive layer 109 is formed on the step, a P electrode 106 is formed on the P-type semiconductor layer 105, a bragg reflective layer 108 is formed, a through hole is formed in the bragg reflective layer 108, an N external electrode 110 and a P external electrode 107 are respectively formed in the through hole, the second conductive layer 109 is LED out to the upper side of the N-type semiconductor layer 102 through the N external electrode 110, and the P electrode 106 is LED out to the upper side of the P-type semiconductor layer 105 through the P external electrode 107.
As shown in fig. 5, for example, the Micro LED chip in the Micro LED array is a vertical structure 20, a step exposing the N-type semiconductor layer 202 is formed in the LED structure layer, a first conductive layer 209 is formed on the step, a P-electrode 206 is formed on the P-type semiconductor layer 205, a bragg reflective layer 208 is formed, a through hole is formed in the bragg reflective layer 208, a P-external electrode 207 is formed in the through hole, and the N-type semiconductor layer 202 is connected to a cathode connection point of an external driving circuit from a side edge through the first conductive layer 209.
As shown in fig. 4 and 6, in another specific implementation process, the single crystal substrate 101, 201 is doped N-type, and forming an LED structure layer on the first surface of the single crystal substrate 101, 201 includes: and epitaxially growing light-emitting layers 103 and 203, electron blocking layers 104 and 204 and P-type semiconductor layers 105 and 205 on the single crystal substrates 101 and 201 to form the LED structure layers, wherein the LED structure layers are connected in a common cathode mode through the single crystal substrates 101 and 201, and the single crystal substrates are in a common cathode path. The whole wafer is designed to be a common cathode, and all Micro LED chips share one N-type semiconductor layer, namely the N-type single crystal substrates 101 and 201, so that the epitaxial structure of the whole wafer is simpler.
As shown in fig. 4, for example, the Micro LED chip in the Micro LED array is a flip-chip structure 10, a step exposing the N-type single crystal substrate 101 is formed in the LED structure layer, a second conductive layer 109 is formed on the step, a P electrode 106 is formed on the P-type semiconductor layer 105, a bragg reflective layer 108 is formed, a through hole is formed in the bragg reflective layer 108, an N external electrode 110 and a P external electrode 107 are respectively formed in the through hole, the second conductive layer 109 is LED out to the upper side of the N-type single crystal substrate 101 through the N external electrode 110, and the P electrode 106 is LED out to the upper side of the P-type semiconductor layer 105 through the P external electrode 107.
As shown in fig. 6, for example, the Micro LED chip in the Micro LED array is a vertical structure 20, a step exposing the N-type single crystal substrate 201 is formed in the LED structure layer, a first conductive layer 209 is formed on the step, a P electrode 206 is formed on the P-type semiconductor layer 205, a bragg reflective layer 208 is then formed, a through hole is formed in the bragg reflective layer 208, a P external electrode 207 is formed in the through hole, and the N-type single crystal substrate 201 is connected to a cathode connection point of an external driving circuit from a side edge through the first conductive layer 209.
As shown in fig. 1, step 3) follows, thinning the single crystal substrate 101, 201 from the second side, and then forming a lens array 111 on the second side by a wet etching process.
For example, the single crystal substrate 101, 201 may be thinned from the second side using a chemical mechanical polishing process.
Specifically, forming the lens array 111 on the second face by a wet etching process includes: and performing wet etching on the single crystal substrates 101 and 201 by adopting one or more of sulfuric acid, nitric acid, phosphoric acid and hydrochloric acid, wherein the etching temperature is 155-180 ℃, and the etching time is 3-10 minutes. According to the invention, the lens array 111 is formed by corroding the single crystal substrates 101 and 201 by a wet method, so that the light emitted from each Micro LED chip on the wafer is converged, the crosstalk between the Micro LED chips can be effectively reduced, and the contact effect between the light emitted and the quantum dots is better.
As shown in fig. 1, step 4) is finally performed to form a black matrix 113 on the second surface of the single crystal substrate 101, 201, form a quantum dot array 114 in the black matrix 113, where the quantum dot array 114, the lens array 111 and the Micro LED array are correspondingly disposed, and then form an encapsulation layer 115 on the black matrix 113 to protect the quantum dot array 114.
Specifically, forming the black matrix 113 includes: forming a transparent isolation layer 112 on the second surface of the single crystal substrate 101, 201, then coating a black photoetching material layer on the transparent isolation layer 112, and then performing patterning processing on the black photoetching material layer by adopting a photoetching process to form the black matrix 113. Then, a quantum dot array 114 is formed in the black matrix 113 by a printing method, where the quantum dot array 114 may include red quantum dots, green quantum dots, and blue quantum dots, as shown in fig. 1; it should be noted that if the Micro LED chip is a blue chip, blue quantum dots may not be needed, as shown in fig. 2, and the manufacturing method of the quantum dot array 114 is not limited to the printing method.
Finally, it should be noted that the single crystal provided by this embodiment may be 2 inches, 4 inches, 6 inches or more, and after the above structure is formed, the wafer is cut according to the AR/VR chips of the required specification, so that a large number of AR/VR chips can be produced at one time.
As shown in fig. 1 to 6, the present embodiment further provides a Micro LED wafer structure, where the Micro LED wafer structure includes: the LED array comprises a single crystal substrate 101 and a single crystal substrate 201, wherein the single crystal substrate 101 and the single crystal substrate 201 comprise a first surface and a second surface which are opposite, a Micro LED array is formed on the first surface of the single crystal substrate 101 and 201, and a lens array 111 is formed on the second surface of the single crystal substrate 101 and 201; the black matrix 113 is formed on the second surface of the single crystal substrate 101, 201, a quantum dot array 114 is formed in the black matrix 113, and the quantum dot array 114, the lens array 111 and the Micro LED array are correspondingly arranged. According to the invention, the lens array 111 is formed by corroding the single crystal substrates 101 and 201 by a wet method, so that the light emitted from each Micro LED chip on the wafer is converged, the crosstalk between the Micro LED chips can be effectively reduced, and the contact effect between the light emitted and the quantum dots is better.
The single crystalThe substrate 101, 201 may be a group iii or group v compound single crystal substrate, and in this embodiment, the single crystal substrate 101, 201 is selected to be a GaN single crystal substrate. The invention adopts the single crystal substrates 101 and 201 (such as single crystal GaN substrates) to grow each layer of the chip, greatly reduces the dislocation density which can reach 105/cm2According to the method, high-quality directional growth of each subsequent layer is guaranteed, and the luminous efficiency and parameter consistency of the whole wafer Micro LED chip are improved.
As shown in fig. 3 and 5, in one specific implementation process, the Micro LED array includes an LED structure layer, and the LED structure layer includes N-type semiconductor layers 102 and 202, light emitting layers 103 and 203, electron blocking layers 104 and 204, and P-type semiconductor layers 105 and 205 sequentially stacked on the single crystal substrates 101 and 201 to form the LED structure layer, wherein each LED structure layer forms a common cathode through the N-type semiconductor layers 102 and 202. The whole wafer of the invention adopts a common cathode design, and all Micro LED chips share one N- type semiconductor layer 102, 202.
As shown in fig. 3, for example, the Micro LED chip in the Micro LED array is a flip-chip structure 10, a step exposing the N-type semiconductor layer 102 is formed in the LED structure layer, a second conductive layer 109 is formed on the step, a P electrode 106 is formed on the P-type semiconductor layer 105, bragg reflective layers 108 are formed on the second conductive layer 109 and the P electrode 106, through holes are formed in the bragg reflective layers 108, N external electrodes 110 and P external electrodes 107 are respectively formed in the through holes, the second conductive layer 109 is LED out to the upper side of the N-type semiconductor layer 102 through the N external electrodes 110, and the P electrode 106 is LED out to the upper side of the P-type semiconductor layer 105 through the P external electrodes 107.
As shown in fig. 5, for example, the Micro LED chip in the Micro LED array is a vertical structure 20, a step exposing the N-type semiconductor layer 202 is formed in the LED structure layer, a first conductive layer 209 is formed on the step, a P electrode 206 is formed on the P-type semiconductor layer 205, bragg reflective layers 208 are formed on the first conductive layer 209 and the P electrode 206, a through hole is formed in the bragg reflective layer 208, a P external electrode 207 is formed in the through hole, and the N-type semiconductor layer 202 is connected to a cathode connection point of an external driving circuit from a side edge through the first conductive layer 209.
As shown in fig. 4 and 6, in another specific implementation process, the Micro LED array includes an LED structure layer, and the LED structure layer includes: the LED structure layer comprises N-type doped single crystal substrates 101 and 201, light emitting layers 103 and 203, electron blocking layers 104 and 204 and P-type semiconductor layers 105 and 205 which are epitaxially grown on the single crystal substrates 101 and 201 to form the LED structure layer, wherein the LED structure layers are connected in a common cathode mode through the single crystal substrates 101 and 201, and the single crystal substrates are in a common cathode access mode. The whole wafer is designed to be a common cathode, and all Micro LED chips share one N-type semiconductor layer, namely the N-type single crystal substrates 101 and 201, so that the epitaxial structure of the whole wafer is simpler.
As shown in fig. 4, for example, the Micro LED chip in the Micro LED array is a flip-chip structure 10, a step exposing the N-type single crystal substrate 101 is formed in the LED structure layer, a second conductive layer 109 is formed on the step, a P electrode 106 is formed on the P-type semiconductor layer 105, bragg reflective layers 108 are formed on the second conductive layer 109 and the P electrode 106, through holes are formed in the bragg reflective layers 108, N external electrodes 110 and P external electrodes 107 are respectively formed in the through holes, the second conductive layer 109 is LED out to the upper side of the N-type single crystal substrate 101 through the N external electrodes 110, and the P electrode 106 is LED out to the upper side of the P-type semiconductor layer 105 through the P external electrodes 107.
As shown in fig. 6, for example, the Micro LED chip in the Micro LED array is a vertical structure 20, a step exposing the N-type single crystal substrate 201 is formed in the LED structure layer, a first conductive layer 209 is formed on the step, a P electrode 206 is formed on the P-type semiconductor layer 205, bragg reflective layers 208 are formed on the first conductive layer 209 and the P electrode 206, a through hole is formed in the bragg reflective layer 208, a P external electrode 207 is formed in the through hole, and the N-type single crystal substrate 201 is connected to a cathode connection point of an external driving circuit from a side edge through the conductive layer 209.
The quantum dot array 114 may include red, green, and blue quantum dots, as shown in fig. 1; it should be noted that if the Micro LED chip is a blue chip, blue quantum dots may not be needed, as shown in fig. 2, and the manufacturing method of the quantum dot array 114 is not limited to the printing method.
Example 2
As shown in fig. 7 to 9, the present embodiment further provides a Micro LED wafer structure and a method for manufacturing the same, the basic steps of which are similar to those of embodiment 1, wherein the difference from embodiment 1 is as follows: the Micro LED array does not need to prepare a second conducting layer 109 in the Micro LED chip, an N electrode 116 (common cathode electrode) of the Micro LED array is formed at the common cathode passage and between the Micro LED chips, the common cathode electrode is connected with a driving circuit on one hand, and the voltage drop generated by the common cathode passage on the other hand is reduced, so that the voltages of the Micro LED chips during working are consistent, and on the basis, the area of the Micro LED chips can be greatly saved, and the luminous intensity of the Micro LED chips on the unit area is greatly improved.
As an example, the common cathode electrode may be in a grid shape or a dot shape, wherein the number of grids or dots is less than or equal to the number of Micro LEDs.
As described above, the Micro LED wafer structure and the preparation method thereof of the present invention have the following beneficial effects:
the invention adopts the single crystal substrate (such as the single crystal GaN substrate) to grow each layer of the chip, thereby greatly reducing the dislocation density which can reach 105/cm2According to the method, high-quality directional growth of each subsequent layer is guaranteed, and the luminous efficiency and parameter consistency of the whole wafer Micro LED chip are improved.
According to the invention, the lens array is formed by corroding the single crystal substrate by a wet method, so that the light emitted from each Micro LED chip on the wafer is converged, the crosstalk between the Micro LED chips can be effectively reduced, and the contact effect between the light emitted and the quantum dots is better.
The whole wafer of the invention adopts a common cathode design, and all Micro LED chips share one N-type substrate or N-type semiconductor layer as a common cathode path, so that a driving circuit is simpler.
The common cathode electrode is connected with the driving circuit on one hand, and reduces the voltage drop generated by the common cathode path on the other hand, so that the voltages of all Micro LEDs are consistent when the Micro LEDs work.
Therefore, the invention effectively overcomes various defects in the prior art and has high industrial utilization value.
The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.

Claims (11)

1. A preparation method of a Micro LED wafer structure is characterized by comprising the following steps:
1) providing a single crystal substrate, wherein the single crystal substrate comprises a first surface and a second surface which are opposite, and an LED structural layer is formed on the first surface of the single crystal substrate;
2) preparing a Micro LED array on the single crystal substrate based on the LED structure layer;
3) thinning the single crystal substrate from the second surface, and forming a lens array on the second surface by a wet etching process;
4) and forming a black matrix on the second surface of the single crystal substrate, and forming a quantum dot array in the black matrix, wherein the quantum dot array, the lens array and the Micro LED array are correspondingly arranged.
2. The method for preparing a Micro LED wafer structure according to claim 1, wherein: in the step 1), the single crystal substrate is doped in an N type mode, and then a light emitting layer, an electron blocking layer and a P type semiconductor layer are epitaxially grown on the single crystal substrate to form the LED structure layers, wherein the LED structure layers are connected through a common cathode of the single crystal substrate, and the single crystal substrate is a common cathode passage.
3. The method for preparing a Micro LED wafer structure according to claim 1, wherein: step 1) epitaxially growing an N-type semiconductor layer, a light emitting layer, an electron blocking layer and a P-type semiconductor layer on the single crystal substrate in sequence to form the LED structure layers, wherein the LED structure layers are connected in a common cathode mode through the N-type semiconductor layer, and the N-type semiconductor layer is a common cathode channel.
4. The method for preparing a Micro LED wafer structure according to claim 2 or 3, wherein: a common cathode electrode is connected between the common cathode passage and the Micro LED chip; the common cathode electrode is connected with the driving circuit on one hand, and reduces voltage drop generated by a common cathode path on the other hand, so that voltages of all Micro LED chips are consistent when the Micro LED chips work.
5. The method for preparing a Micro LED wafer structure according to claim 4, wherein: the common cathode electrode is in a grid shape or a mesh shape, wherein the number of grids or mesh points is less than or equal to the number of Micro LED chips.
6. The method for preparing a Micro LED wafer structure according to claim 1, wherein: step 3) forming a lens array on the second surface by a wet etching process includes: and carrying out wet etching on the single crystal substrate by adopting one or more of sulfuric acid, nitric acid, phosphoric acid and hydrochloric acid, wherein the etching temperature is 155-180 ℃, and the etching time is 3-10 minutes.
7. A Micro LED wafer structure, comprising:
the LED array comprises a single crystal substrate and a plurality of LED chips, wherein the single crystal substrate comprises a first surface and a second surface which are opposite, a Micro LED array is formed on the first surface of the single crystal substrate, and a lens array is formed on the second surface of the single crystal substrate;
and the black matrix is formed on the second surface of the single crystal substrate, a quantum dot array is formed in the black matrix, and the quantum dot array, the lens array and the Micro LED array are correspondingly arranged.
8. The Micro LED wafer structure of claim 7, wherein: the single crystal substrate is an N-type substrate, the Micro LED array comprises an LED structure layer, the LED structure layer comprises an N-type semiconductor layer, a light emitting layer, an electron blocking layer and a P-type semiconductor layer, the LED structure layers are connected in a common cathode mode through the single crystal substrate, and the single crystal substrate is a common cathode channel.
9. The Micro LED wafer structure of claim 7, wherein: the Micro LED array comprises an LED structure layer, the LED structure layer comprises an N-type semiconductor layer, a light emitting layer, an electron blocking layer and a P-type semiconductor layer which are formed on the single crystal substrate, the LED structure layers are connected in a common cathode mode through the N-type semiconductor layer, and the N-type semiconductor layer is a common cathode channel.
10. A Micro LED wafer structure according to claim 8 or 9, wherein: a common cathode electrode is connected between the common cathode passage and the Micro LED chip; the common cathode electrode is connected with the driving circuit on one hand, and reduces voltage drop generated by a common cathode path on the other hand, so that voltages of all Micro LED chips are consistent when the Micro LED chips work.
11. The Micro LED wafer structure of claim 10, wherein: the common cathode electrode is in a grid shape or a mesh shape, wherein the number of grids or mesh points is less than or equal to the number of Micro LEDs.
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