CN114843382A

CN114843382A - Color-converted LED chip and manufacturing method thereof

Info

Publication number: CN114843382A
Application number: CN202210412743.4A
Authority: CN
Inventors: 庄文荣; 卢敬权
Original assignee: Dongguan HCP Technology Co Ltd
Current assignee: Dongguan HCP Technology Co Ltd
Priority date: 2022-04-19
Filing date: 2022-04-19
Publication date: 2022-08-02

Abstract

The present invention provides a color-converted LED chip comprising: the light-emitting epitaxial structure is provided with a plurality of first through holes and steps, and the first through holes and the steps penetrate through the P-type semiconductor layer and the light-emitting layer to a preset depth of the N-type semiconductor layer; the current expansion layer is positioned above the P-type semiconductor layer, and second through holes which are aligned with the first through holes one by one are formed on the current expansion layer; the passivation layer is arranged on the inner walls of the second through hole and the first through hole and the periphery of the opening of the second through hole, and the passivation layer and the bottom of the first through hole jointly define a cavity; the color conversion layer is positioned at the bottom of the cavity and is in contact with the N-type semiconductor layer, and the color conversion layer partially fills the cavity; and the hole transport layer fills the cavity and integrally covers the passivation layer and the current expansion layer. According to the invention, the color conversion layer and the hole transport layer are arranged in the cavity defined in the through hole, so that photoluminescence and electroluminescence of the color conversion layer can be realized simultaneously, the color conversion efficiency is improved, and the energy consumption of a chip can be reduced.

Description

Color-converted LED chip and manufacturing method thereof

Technical Field

The invention belongs to the technical field of LED manufacturing, and particularly relates to an LED chip and a manufacturing method thereof.

Background

With the increasing indoor Display application technology, currently used Display application products such as projection, DLP (Digital Light Processing), LCD (Liquid Crystal Display), PDP (Plasma Display Panel), and the like cannot completely meet the market application requirements. There are also some drawbacks in various aspects that make it impossible to break through the technological development. And the LED (Light Emitting Diode) full-color display screen overcomes the defects of the products, and becomes the first choice for indoor and outdoor large-screen display, such as occasions of command centers, outdoor advertising screens, conference centers and the like.

The LED chip has good energy-saving effect and high brightness, and is used in various industries of production and life. Generally, the LED display screen is seamlessly spliced into a large-sized display screen by a certain number of small-sized display screen modules. One of the common methods for manufacturing the small-pitch display screen module is a Chip On Board (COB). In the current process of manufacturing the small-spacing LED display screen by using a COB method, the used chip is an inverted Mini LED chip. Three kinds of Mini LED chips of red, green and blue are needed to realize full-color display. However, in the prior art, LED chips are usually made of gallium nitride-based materials, and the fabrication of blue LEDs and green LEDs using gallium nitride-based chips is a mature process, which is simple to fabricate and use, but red LEDs are quaternary LEDs, and their substrates are opaque GaAs, if it is desired to obtain flip red LEDs, it is necessary to remove the GaAs substrate after bonding a red wafer onto a sapphire substrate, the process is complicated, especially in small-pitch or micro-pitch LED display screens, the cost of flip red chips accounts for a large proportion, and the production yield of such a process is low. In addition, compared with GaN (gallium nitride) materials, the AlInGaP epitaxial layer of red light is brittle and fragile, and device failure caused by epitaxial film peeling often occurs during the use process, which results in low yield and high cost of the flip-chip red light LED, thus the application requirement cannot be met.

Therefore, it is necessary to provide a color-switchable LED chip suitable for a small-pitch or fine-pitch LED display screen to replace the existing LED chip.

Disclosure of Invention

In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a color-converted LED chip and a method for manufacturing the same, which are used to solve the problems of high manufacturing cost, low yield, and significantly reduced light-emitting efficiency and reliability caused by the reduced chip size of the red LED chip of the full-color LED display screen in the prior art, especially the red LED chip of the flip-chip structure.

To achieve the above and other related objects, the present invention provides a color-converted LED chip, comprising:

a light emitting epitaxial structure, the light emitting epitaxial structure comprising:

an N-type semiconductor layer;

the light emitting layer is positioned above the N-type semiconductor layer;

the P-type semiconductor layer is positioned above the light emitting layer;

a plurality of first through holes are formed in the light-emitting epitaxial structure; the light-emitting epitaxial structure is also provided with a step; the first through hole and the step penetrate through the P-type semiconductor layer and the light-emitting layer to a preset depth of the N-type semiconductor layer;

the current expansion layer is positioned above the P-type semiconductor layer, and second through holes which are aligned with the first through holes one by one are formed in the current expansion layer;

the passivation layer is arranged on the inner walls of the second through hole and the first through hole and the periphery of the opening of the second through hole, the passivation layer and the bottom of the first through hole jointly define a cavity, and the passivation layer is electrically insulating;

the color conversion layer is positioned at the bottom of the cavity and is in contact with the N-type semiconductor layer, and the color conversion layer partially fills the cavity;

a hole transport layer filling the cavity and entirely covering the passivation layer and the current spreading layer;

an N electrode;

and a P electrode.

Optionally, the color conversion layer comprises a quantum dot material, and the passivation layer electrically isolates the color conversion layer from the P-type semiconductor layer and the light emitting layer.

Optionally, the current spreading layer, the hole transport layer, the color conversion layer and the N-type semiconductor layer constitute a current transport path.

Optionally, the N electrode is located above the step and electrically connected to the N-type semiconductor layer, and the P electrode is located above the P-type semiconductor layer and electrically connected to the current spreading layer.

Optionally, the P-type electrode includes a P-type bottom electrode and a P-type external electrode, the P-type bottom electrode contacts with the exposed surface of the current spreading layer, the N-type electrode includes an N-type bottom electrode and an N-type external electrode, and a top surface of the N-type bottom electrode is flush with a top surface of the P-type bottom electrode.

Optionally, the LED chip further includes one or more of an insulating layer or a distributed bragg reflector or an anti-reflection layer or a light absorption layer or an ink layer, the insulating layer or the distributed bragg reflector or the anti-reflection layer or the light absorption layer or the ink layer covers the step and the front of the light emitting epitaxial structure, and by the peripheral step covers the side of the light emitting epitaxial structure, wherein the insulating layer is used for reducing leakage current on the surface of the chip, the distributed bragg reflector is used for enhancing light reflection, the anti-reflection layer is used for reducing interface reflection of light between media, and the light absorption layer or the ink layer plays a role in absorbing light.

The invention also provides a full-color LED display screen, which comprises: an LED pixel array made according to the above color converted LED chip.

The invention provides a manufacturing method of an LED chip with color conversion, which comprises the following steps:

1) providing a substrate, and forming an N-type semiconductor layer, a light emitting layer and a P-type semiconductor layer on the substrate from bottom to top to form an epitaxial stacked structure;

2) etching the epitaxial stacked structure to form a peripheral step, and defining a plurality of LED chips on the substrate;

3) forming a step exposing a part of the N-type semiconductor layer in each LED chip to separate a light-emitting epitaxial structure; simultaneously forming a plurality of first through holes penetrating to the N-type semiconductor layer;

4) forming a current extension layer on the light-emitting epitaxial structure, and patterning the current extension layer to form second through holes aligned with the first through holes one by one;

5) forming a passivation layer on the inner wall and the periphery of the opening of the second through hole and the inner wall of the first through hole to form a cavity defined by the passivation layer and the bottom of the first through hole;

6) forming a color conversion layer in the cavity;

7) forming a hole transport layer by filling the cavity with a hole transport material and entirely covering the passivation layer and the current spreading layer;

8) and respectively forming a P-type bottom electrode and an N-type bottom electrode above the P-type semiconductor layer and the N-type semiconductor layer.

Optionally, in step 6), the color conversion layer includes a quantum dot material filling the bottom of the cavity and in contact with the N-type semiconductor layer.

Optionally, in step 7), the current spreading layer, the hole transport layer, the color conversion layer, and the N-type semiconductor layer constitute a current transport path.

Optionally, the manufacturing method further comprises;

9) forming one or more of an insulating layer, a distributed Bragg reflection layer, an antireflection layer, a light absorption layer or an ink color layer on the steps, the front side of the light-emitting epitaxial structure and the side surface of the light-emitting epitaxial structure;

10) and forming a P-type external electrode and an N-type external electrode through the insulating layer or the distributed Bragg reflection layer or the antireflection layer or the light absorption layer or the ink color layer.

As described above, the color-converted LED chip and the method for manufacturing the same of the present invention have the following advantages:

according to the invention, the plurality of through holes arranged on the light-emitting epitaxial structure are utilized, the color conversion layer and the hole transport layer are arranged in the cavity defined in the through holes, the color conversion layer is positioned at the bottom of the cavity and is contacted with the N-type semiconductor layer, and the hole transport layer is positioned above the color conversion layer and fills the cavity, so that photoluminescence and electroluminescence of the color conversion layer can be realized simultaneously, the color conversion efficiency is improved, and the energy consumption of a chip can be reduced.

The manufacturing method provided by the invention has high repeatability, can effectively reduce the manufacturing cost of the red LED chip with the flip-chip structure and improve the production yield, and is applied to small-spacing or micro-spacing LED display screens.

Drawings

FIGS. 1-8 are schematic structural diagrams of steps of fabricating a color-converted LED chip according to the present invention; fig. 2B to 2C are schematic cross-sectional views along the a-plane and the B-plane of the structure obtained in step 3) of the present invention shown in fig. 2A, fig. 3B to 3C are schematic cross-sectional views along the a-plane and the B-plane of the structure obtained in step 4) of the present invention shown in fig. 3A, fig. 4B to 4C are schematic cross-sectional views along the a-plane and the B-plane of the structure obtained in step 5-1) of the present invention shown in fig. 4A, and fig. 8 is a schematic cross-sectional structure of the LED chip of the present invention.

Description of the element reference numerals

100 substrate

210 buffer layer

220 intrinsic semiconductor layer

230N type semiconductor layer

231 first through hole

232 second through hole

234 cavity

240 light emitting layer

250 electron blocking layer

260P type semiconductor layer

270 current spreading layer

280 passivation layer

291P type bottom electrode

292N type bottom electrode

293P type external electrode

294N type external electrode

300 color conversion layer

310 hole transport layer

320 insulating layer or distributed Bragg reflector or anti-reflection layer

Or light-absorbing or ink-coloured layers

235a and 235b steps

225c peripheral step

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 one

Referring to fig. 8, fig. 8 is a schematic cross-sectional structure diagram of a color-converted LED chip, where the LED chip includes a substrate 100 and a light-emitting epitaxial structure, and the light-emitting epitaxial structure is located on a front surface of the substrate 100 and includes: the light emitting diode comprises an N-type semiconductor layer 230, a light emitting layer 240, a P-type semiconductor layer 260 and a current spreading layer 270, wherein the light emitting layer 240 is positioned above the N-type semiconductor layer 230, and the P-type semiconductor layer 260 is positioned above the light emitting layer 240. The light emitting epitaxial structure is provided with a plurality of regularly arranged first through holes 231 and steps, and the first through holes 231 and the steps penetrate through the P-type semiconductor layer 260 and the light emitting layer 240 to a preset depth of the N-type semiconductor layer 230, so that the surface of the N-type semiconductor layer is exposed at the bottoms of the first through holes 231 and the steps.

Specifically, the material of the substrate 100 includes one of sapphire, silicon carbide, and silicon. In the present embodiment, the material of the substrate 100 is sapphire. As an example,

steps

235a and 235b penetrate through the P-type semiconductor layer 260 and the light emitting layer 240 and expose a portion of the surface of the N-type semiconductor layer 230, an N-mesa electrode structure (N _ mesa structure) is sandwiched between the

steps

235a and 235b, and the N _ mesa structure is consistent with the light emitting epitaxial structure 301. Or, as an alternative, the light-emitting epitaxial structure has an electrode step penetrating to the surface of the N-type semiconductor layer for disposing an N-electrode.

The LED chip further includes a current spreading layer 270, the current spreading layer 270 is located above the P-type semiconductor layer 260, and second through holes 232 aligned with the first through holes 231 one by one are formed on the current spreading layer 270. The current spreading layer 270 may be a transparent conductive layer made of, but not limited to, Indium Tin Oxide (ITO), and the thickness thereof is in a range of 10 nm to 400 nm. The current spreading layer 270 can effectively improve the uniformity of the injected current and improve the utilization efficiency of the current. The LED chip further includes a passivation layer 280, and the passivation layer 280 is disposed on the inner walls of the second through hole 232 and the first through hole 231, and the opening periphery of the second through hole 232, such that the passivation layer 280 and the bottom of the first through hole jointly define a cavity. A colored conversion layer 300 and a hole transport layer 310 are arranged in the cavity, the colored conversion layer 300 is positioned at the bottom of the cavity and is in contact with the N-type semiconductor layer 230, and the color conversion layer partially fills the cavity; the hole transport layer 310 fills the cavity and entirely covers the passivation layer 280 and the current spreading layer 270.

Specifically, the first through holes 231 are disposed to penetrate the P-type semiconductor layer 260, the light emitting layer 240 to a predetermined depth of the N-type semiconductor layer, and the second through holes 232 penetrate the current spreading layer 270 to be aligned with the first through holes one by one. In some examples, the second through-hole 232 may have a diameter not smaller than the first through-hole 231. In this embodiment, the diameter of the second via hole 232 may be equal to the diameter of the first via hole 231 in order to form a passivation layer with good step coverage.

As shown in fig. 8, the passivation layer 280 is electrically insulating as a whole to electrically isolate the color conversion layer 300 from the P-type semiconductor layer 260 and the light emitting layer 240, and the passivation layer 280 and the bottom of the first via hole together define the cavity. The color conversion layer 300 is in contact with the N-type semiconductor layer 230 at the bottom of the cavity and partially fills the cavity. The color conversion layer 300 partially fills the cavity, that is, the filling height of the color conversion layer 300 is lower than the depth of the cavity, and the color conversion layer is partially filled in the cavity penetrating through the N-type semiconductor layer 230, so that the conductive path of the LED is not blocked, and the LED normally emits blue light, and the closed space formed by the cavity is favorable for improving the reliability with quantum dots. Preferably, the color conversion layer is a quantum dot material, or a mixture of a quantum dot and a conductive adhesive, such as a core-shell quantum dot material dispersed in a conductive adhesive. Since light from the light emitting layer can excite the quantum dots to inject energy into the quantum dots, the quantum dots are used as down-conversion materials, the blue light spectrum of the GaN-based LED can be effectively absorbed, and the III-V LED light emitting device has excellent efficiency and can realize color conversion of blue light through photoluminescence. Specifically, the color conversion layer 300 may be used to convert blue light emitted from the light emitting layer 240 into light of another color, for example, when the color conversion layer 300 is a red color conversion layer, the color conversion layer 300 converts blue light emitted from the epitaxial layer into red light, and when the color conversion layer 300 is a green color conversion layer, the color conversion layer 300 converts blue light emitted from the epitaxial layer into green light.

As an example, the LED chip further includes a hole transport layer 310 over the color conversion layer 300, the hole transport layer 310 filling the cavity and entirely covering the passivation layer 280 and the current spreading layer 270, the hole transport layer 310, the color conversion layer 300 and the N-type semiconductor layer 220 constitute a current transport path. The hole transport layer 310 is arranged to reduce the potential barrier of hole injection, which is beneficial to facilitating the hole to be transported to the color conversion layer through the anode, thereby increasing the probability of positive-negative charge-carrier balance of the device and realizing the electroluminescence of the color conversion layer 300.

The LED chip further includes a P electrode and an N electrode, the N electrode is located above the step and electrically connected to the N-type semiconductor layer 230, and the P electrode is located above the P-type semiconductor layer and electrically connected to the current spreading layer 270. The LED chip further comprises one or more of an insulating layer, a distributed Bragg reflection layer, an antireflection layer, a light absorption layer or an ink layer 320, wherein the insulating layer, the distributed Bragg reflection layer, the antireflection layer, the light absorption layer or the ink layer 320 covers the steps, the front face of the light-emitting epitaxial structure and the side faces of the light-emitting epitaxial structure, the insulating layer is used for reducing leakage current on the surface of the chip, the distributed Bragg reflection layer is used for increasing light reflection from the light-emitting layer, the antireflection layer is used for absorbing light emitted by the light-emitting layer 240 and finally emitted to the antireflection layer, so that interface reflection of light between media can be reduced, and the light absorption layer or the ink layer plays a role in absorbing light, particularly absorbs blue light leaked by the light-emitting epitaxial structure. In some examples, the light absorbing layer or the ink color layer may be disposed to cover an outer portion of the distributed bragg reflector layer, so that the light absorbing layer or the ink color layer can withstand the mirror layer, further preventing blue light from leaking, and improving contrast of display.

For example, the distributed Bragg reflector layer is formed by multiple layers of SiO ₂ /Ti ₃ O ₅ And stacking the materials. In some examples, a thin silicon dioxide layer is further disposed on the bottom surface of the dbr layer to provide better insulating performance and improve adhesion of the dbr layer. The emitted blue light is emitted to the light emitting surface in a concentrated manner, so that more blue light is subjected to color conversion through the color conversion layer 300, the color conversion effect is further improved, and the blue light leakage is effectively reduced. Therefore, the technical scheme of this embodiment can realize the optical excitation and the electric excitation of quantum dot, solves the relatively poor problem of the colour conversion effect that reveals blue light when blue light LED arouses quantum dot simultaneously.

As an example, the P-electrode includes a P-type bottom electrode 291 and a P-type external electrode 293, the P-type bottom electrode 291 is in contact with an exposed surface of the current spreading layer, and the P-type external electrode 293 is connected to the P-type bottom electrode 291 through an insulating layer or a distributed bragg reflector layer or an anti-reflective layer or a light absorbing layer or an ink color layer 320; the N-electrode includes an N-type bottom electrode 292 and an N-type outer electrode 294, the N-type bottom electrode 292 is located above the surface of the N-type semiconductor layer 230 exposed by the step and surrounds the N _ mesa structure and the top thereof, and is electrically connected to the N-type semiconductor layer 230; the N-type outer electrode 294 is connected with the N-type bottom electrode 293 through the insulating layer or the distributed bragg reflector layer or the anti-reflection layer or the light absorption layer or the ink color layer 320. Preferably, the top surface of the N-type external electrode is flush with the top surface of the P-type external electrode, so that the LED chip can be conveniently packaged and connected with other circuits, and chip fracturing and extrusion cracking of an insulating material layer in the packaging process can be reduced.

As an example, the light emitting epitaxial structure includes a buffer layer 210, an intrinsic semiconductor layer 220, an N-type semiconductor layer 230, a light emitting layer 240, an electron blocking layer 250, and a P-type semiconductor layer 260. The buffer layer 210 includes one of an aluminum nitride buffer layer and a gallium nitride buffer layer, the thickness range of the buffer layer is 10-30 nm, for example, 15 nm, 20 nm, etc., the intrinsic semiconductor layer 220 includes an undoped gallium nitride layer, the N-type semiconductor layer 230 includes an N-type gallium nitride layer, the P-type semiconductor layer 260 includes a P-type gallium nitride layer, and the light emitting layer 240 includes a quantum well superlattice layer. By providing the electron blocking layer 250, electrons can be confined in the quantum well region, thereby reducing electron leakage and increasing recombination efficiency, thereby improving device performance.

The LED chip further includes a peripheral step 225c, wherein the peripheral step 225c is annular and penetrates through the P-type semiconductor layer 260, the light emitting layer 240 and the N-type semiconductor layer 230, and exposes a portion of the surface of the substrate 100. By arranging the peripheral step 225c, potential leakage channels can be effectively reduced, and the antistatic performance of the chip is improved.

Optionally, the passivation layer 280 is further disposed on the exposed surfaces of the

steps

235a and 235b and the side surface of the light emitting epitaxial structure, and is covered by the peripheral step 225 c. The passivation layer arranged on the periphery of the chip and on the inner wall of the cavity can be used for repairing chip damage caused by the step and through hole forming process.

Through implementing the technical scheme of this embodiment, the luminous epitaxial structure launches blue light, makes the peripheral colour conversion layer that sets up of it arouse the mode that carries out colour conversion, can realize the LED of other colours, can reduce ruddiness LED chip's cost effectively, can also realize quantum dot's electroluminescence in step, provides the colour conversion scheme that can improve luminous efficiency and production yield.

The embodiment further provides a full-color LED display screen, which includes the LED pixel array made of the color-converted LED chips as described above.

Example two

As shown in fig. 1 to 8, the present embodiment provides a method for manufacturing a color-converted LED chip, where the method includes the steps of:

as shown in fig. 1, step 1) is first performed to provide a substrate 100, and an epitaxial stack structure including a buffer layer 210, an intrinsic semiconductor layer 220, an N-type semiconductor layer 230, a light emitting layer 240, an electron blocking layer 250, and a P-type semiconductor layer 260 is formed on the substrate 100.

Specifically, the sapphire substrate or the silicon carbide substrate may be fed into a magnetron sputtering station, and an aluminum nitride buffer layer may be deposited on the sapphire substrate or the silicon carbide substrate, and the thickness of the aluminum nitride buffer layer may be 10 to 20 nanometers, such as 15 nanometers. The sapphire substrate or silicon carbide substrate may also be fed into a Metal Oxide Chemical Vapor Deposition (MOCVD) reaction chamber where a low temperature gallium nitride buffer layer is deposited on the sapphire substrate or silicon carbide substrate, which may have a thickness of 10-30 nm, such as 20 nm.

Then, the substrate 100 on which the buffer layer 210 is formed may be fed into an MOCVD reaction chamber, and the intrinsic semiconductor layer 220, the N-type semiconductor layer 230, the light emitting layer 240, the electron blocking layer 250, and the P-type semiconductor layer 260 may be sequentially grown thereon to form a wafer.

As shown in fig. 2A-2C, step 2) is then performed to etch the epitaxial stack structure to form a peripheral step 225C and define a plurality of LED chips on the substrate 100.

In this embodiment, as shown in fig. 2B to 2C, in step 2), an Inductively Coupled Plasma (ICP) etching process is used to etch a peripheral step 225C in the light emitting epitaxial structure, where the peripheral step 225C is annular and penetrates through the P-type semiconductor layer 260, the light emitting layer 240 and the N-type semiconductor layer 230, and exposes a portion of the surface of the substrate 100.

Continuing to refer to fig. 2B to 2C, performing step 3), forming a step exposing a part of the N-type semiconductor layer in each LED chip to separate a light emitting epitaxial structure; and a plurality of first via holes 231 penetrating to the N-type semiconductor layer 230 are simultaneously formed.

Specifically, the

steps

235a and 235b may be etched by using an Inductively Coupled Plasma (ICP) etching process to expose a portion of the N-type semiconductor layer 260, the N _ mesa structure is sandwiched between the

steps

235a and 235b, and the N _ mesa structure is consistent with the light emitting epitaxial structure.

Specifically, step 3) further comprises: defining a pattern area corresponding to the first through hole on the light-emitting epitaxial structure by utilizing a photoetching process; and etching the light emitting epitaxial structure to form a plurality of regularly arranged first through holes 231 while etching the

steps

235a and 235b by an etching process, wherein the first through holes 231 penetrate through the P-type semiconductor layer 260 and the light emitting layer 240 to reach the N-type semiconductor layer 230.

In some embodiments, step 3) may be performed after step 2); in other embodiments, step 3) may be performed before step 2).

Referring to fig. 3A to 3C, step 4) is performed, a current spreading layer 270 may be formed on the P-type semiconductor layer 260, and the current spreading layer 270 may be patterned to form second through holes 232 aligned with the first through holes 231 one by one.

For example, the current spreading layer 270 may be formed on the P-type semiconductor layer 260 by a sputter coating method, and the current spreading layer 108 may be a transparent conductive layer, which is made of a material including, but not limited to, Indium Tin Oxide (ITO) and has a thickness ranging from 10 nm to 400 nm. The current spreading layer 270 can effectively improve the uniformity of the injected current and improve the utilization efficiency of the current.

Referring to fig. 4A to 4C, step 5) is performed to form a passivation layer 280 on the inner wall and the periphery of the opening of the second via 232 and the inner wall of the first via 231, so as to form a cavity 234 defined by the passivation layer 280 and the bottom of the first via.

Specifically, the periphery of the opening and the inner wall of the second through hole, and the inner wall of the first through hole are coated with the passivation layer 280 by using an Atomic Layer Deposition (ALD) process, so that the second through hole and the inner wall of the first through hole do not form a conductive path or a leakage path.

In this embodiment, in step 5), when the passivation layer 280 is formed on the inner walls and the periphery of the openings of the plurality of second through holes 232 and the inner wall of the first through hole 231, the passivation layer is simultaneously formed on the exposed surface of the N-pad electrode structure and the side surface of the light emitting epitaxial structure, and the passivation layer is covered on the side surface of the light emitting epitaxial structure by the peripheral step 225 c. As shown in fig. 4B to 4C, by simultaneously plating the passivation layer on the periphery of the chip, damage to the chip caused by the etching process for forming the step and the first via hole can be repaired.

Referring to fig. 5, step 6) is performed to form a color conversion layer 300 in the cavity 234, wherein the color conversion layer 300 partially fills the cavity 234, i.e., the filling height of the color conversion layer 300 is lower than the depth of the cavity 234; preferably, the color conversion layer is a quantum dot material, or a mixture of quantum dots and a conductive paste, and the quantum dot film can be formed, for example, by spin-coating a core-shell quantum dot material uniformly dispersed in a conductive paste into the first through hole 232, followed by curing. The quantum dots can be excited by light from the light emitting layer to inject energy into the quantum dots, and the quantum dots are used as down-conversion materials, so that the GaN-based blue light spectrum can be effectively absorbed.

As shown in fig. 6, the process continues with step 7) to form a hole transport layer 310 by filling the cavity 234 with a hole transport material and entirely covering the passivation layer 280 and the current spreading layer 270.

Specifically, the current spreading layer 270, the hole transport layer 310, the color conversion layer 300, and the N-type semiconductor layer 230 constitute a current transport path. By way of example, the hole transport layer may be made of a conductive polymer, such as poly (3, 4-ethylenedioxythiophene): poly (styrenesulfonate) (PEDOT: PSS), by a process such as vacuum thermal evaporation coating, to reduce the hole injection barrier, facilitate hole transport through the anode to the color conversion layer, and increase the probability of positive-negative carrier balance of the device, thereby achieving electroluminescence of the color conversion layer 300.

As shown in fig. 7, step 8) is performed to form a P-type bottom electrode 291 and an N-type bottom electrode 292 above the P-type semiconductor layer 260 and the N-type semiconductor layer 240, respectively, wherein the P-type bottom electrode 291 contacts the current spreading layer 270, and the N-type bottom electrode 292 is formed on the N-mesa electrode structure.

Specifically, the N-type bottom electrode 292 may be fabricated on the exposed N-type semiconductor layer 230 of the

steps

235a and 235b by thermal evaporation or electron beam evaporation, and may have a composition of Cr/Al/Pt/Cr/Pt/Au/Ti stack; then, the P-type bottom electrode 291 is formed on the current spreading layer 270 by thermal evaporation or electron beam evaporation, and may have a composition of Cr/Al/Ti/Pt/Au/Ti stack. Finally, the top surfaces of the N-type bottom electrode 292 and the P-type bottom electrode 291 are flush by adjusting the thickness, so that the subsequent etching process for forming the electrode contact holes corresponding to the P-type external electrode and the N-type external electrode can be stopped on the same plane at the same time, the etching difficulty of the electrode contact holes is greatly reduced, and the process cost is saved.

As shown in fig. 8, the method for manufacturing the color-converted LED chip further includes: 9) forming one or more of an insulating layer, a distributed bragg reflector layer, an anti-reflection layer, a light absorption layer or an ink layer 320 on the steps, the front surface of the light emitting epitaxial structure and the side surface of the light emitting epitaxial structure; 10) a P-type external electrode 293 and an N-type external electrode 294 are formed through the insulating layer or the distributed bragg reflection layer or the anti-reflection layer or the light absorption layer or the ink layer 320.

Specifically, the dbr 320 may be formed on the

steps

235a and 235b and the front and side surfaces of the light emitting epitaxial structure by using an e-beam evaporation process, for example, and the dbr is formed by multiple layers of SiO ₂ /Ti ₃ O ₅ And stacking the materials. Alternatively, step 9) may comprise: cladding in the step with the positive of luminous epitaxial structure, and the side of luminous epitaxial structure forms light absorption layer or black layer, wherein, light absorption layer or black layer absorb by the blue light that luminous epitaxial structure leaked. In some examples, the light absorbing layer or the ink color layer may be disposed to cover an outer portion of the distributed bragg reflector layer, so that the light absorbing layer or the ink color layer can withstand the mirror layer, further preventing blue light from leaking, and improving contrast of display.

In this embodiment, the insulating layer or the distributed bragg reflector layer or the anti-reflective layer or the light absorbing layer or the ink layer 320 is covered on the side of the light emitting epitaxial structure by the peripheral step 225 c.

Specifically, the P-type external electrode 293 and the N-type external electrode 294 may be formed through the insulating layer or the distributed bragg reflector layer or the anti-reflection layer or the light absorption layer or the ink layer 320 by using an inductively coupled plasma etching (ICP) process, which may be stopped at the top surfaces of the P-type bottom electrode and the N-type bottom electrode at the same time because the top surfaces of the P-type bottom electrode and the N-type bottom electrode are flush, thereby greatly reducing process difficulty.

As an example, the P-type outer electrode 293 and the N-type outer electrode 294 may each include two portions, including a transition portion and an outer portion. The P-type external electrode 293 and the N-type external electrode 294 may be fabricated by thermal evaporation or electron beam evaporation. The material and thickness of the P-type external electrode and the N-type external electrode may be appropriately determined as necessary.

In this embodiment, the N-type external electrode 294 is flush with the top surface of the P-type external electrode 293, which facilitates the package connection of the LED chip and other circuits.

according to the invention, the light-emitting epitaxial structure is provided with the plurality of through holes penetrating to the N-type semiconductor layer, the color conversion layer and the hole transport layer are arranged in the cavity defined in the through holes, the color conversion layer is positioned at the bottom of the cavity and is contacted with the N-type semiconductor layer, and the hole transport layer is positioned above the color conversion layer and fills the cavity, so that photoluminescence and electroluminescence of the color conversion layer can be realized simultaneously, the color conversion efficiency is improved, and the energy consumption of a chip can be reduced.

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

1. A color converted LED chip, comprising:

an N-type semiconductor layer;

the light emitting layer is positioned above the N-type semiconductor layer;

the P-type semiconductor layer is positioned above the light emitting layer;

a plurality of first through holes are formed in the light-emitting epitaxial structure; the light-emitting epitaxial structure is also provided with a step; the first through hole and the step penetrate through the P-type semiconductor layer and the light emitting layer to reach a preset depth of the N-type semiconductor layer;

an N electrode;

and a P electrode.

2. The LED chip of claim 1, wherein: the color conversion layer includes a quantum dot material, and the passivation layer electrically isolates the color conversion layer from the P-type semiconductor layer and the light emitting layer.

3. The LED chip of claim 2, wherein: the current spreading layer, the hole transport layer, the color conversion layer and the N-type semiconductor layer form a current transport path.

4. The LED chip of claim 1, wherein: the N electrode is located above the step and electrically connected with the N type semiconductor layer, and the P electrode is located above the P type semiconductor layer and electrically connected with the current expansion layer.

5. The LED chip of claim 1, wherein: the P-type bottom electrode is in contact with the exposed surface of the current expansion layer, the N-type electrode comprises an N-type bottom electrode and an N-type external electrode, and the top surface of the N-type bottom electrode is flush with the top surface of the P-type bottom electrode.

6. The LED chip of claim 1, wherein the LED chip further comprises one or more of an insulating layer, a distributed bragg reflector, a reflective layer, a light absorbing layer, or an ink layer, the insulating layer, the distributed bragg reflector, the light absorbing layer, or the ink layer covers the step and the front surface of the light emitting epitaxial structure, and covers the side surface of the light emitting epitaxial structure with the peripheral step, wherein the insulating layer is used to reduce the leakage current on the chip surface, the distributed bragg reflector is used to enhance the light reflection, the anti-reflection layer is used to reduce the interface reflection of light between media, and the light absorbing layer or the ink layer plays a role of absorbing light.

7. The utility model provides a full-color LED display screen which characterized in that, full-color LED display screen includes: an array of LED pixels made of the color converted LED chips according to any one of claims 1 to 6.

8. A method of fabricating a color converted LED chip, the method comprising the steps of:

4) forming a current expansion layer on the light-emitting epitaxial structure, and patterning the current expansion layer to form second through holes which are aligned with the first through holes one by one;

6) forming a color conversion layer in the cavity;

9. The method of manufacturing according to claim 8, wherein: in step 6), the color conversion layer includes a quantum dot material, and the quantum dot material fills the bottom of the cavity and is in contact with the N-type semiconductor layer.

10. The method of manufacturing according to claim 9, wherein: in step 7), the current spreading layer, the hole transport layer, the color conversion layer, and the N-type semiconductor layer form a current transport path.

11. The method of manufacturing of claim 8, further comprising;

9) forming one or more of an insulating layer, a distributed Bragg reflection layer, an antireflection layer, a light absorption layer or an ink layer on the steps, the front side of the light-emitting epitaxial structure and the side surface of the light-emitting epitaxial structure;