Flexible substrate light emitting diode chip with improved heat dissipation and method of manufacturing the same

Abstract

The application discloses a flexible substrate light-emitting diode chip with improved heat dissipation and a preparation method thereof, and belongs to the field of light-emitting diode manufacturing. In the light-emitting diode chip, the polyethylene naphthalate flexible substrate comprises a flexible main body and a plurality of folding protrusions which are stacked on the flexible main body and are mutually spaced. The folding protrusions are prisms with an axis perpendicular to the surface of the flexible main body. The folding protrusions deform to release force and improve the flexibility of the light-emitting diode chip. The indium zinc oxide transparent conductive layer on the polyethylene naphthalate flexible substrate has conductive protrusions corresponding to the folding protrusions, thereby increasing the conductive effect. The Cu heat dissipation layer on the indium zinc oxide transparent conductive layer fills the concave of the pattern, thereby increasing the heat dissipation effect of the Cu heat dissipation layer. The final light-emitting diode chip has improved heat dissipation and conductive effects, and the service life of the final light-emitting diode chip is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of light-emitting diode manufacturing, in particular to a flexible substrate light-emitting diode chip with improved heat dissipation and a preparation method thereof. BACKGROUND

[0002] A light-emitting diode is a kind of semiconductor electronic component capable of emitting light. As a new type of high-efficiency, environmentally friendly and green solid-state lighting source, it is being rapidly and widely applied, such as traffic signal lights, car interior and exterior lights, urban landscape lighting, mobile phone backlights, display screens, etc. Improving the light-emitting efficiency of light-emitting diodes is the goal that light-emitting diodes are constantly pursuing.

[0003] Light-emitting diodes with vertical structure are often used for light-emitting of display screens. Light-emitting diode chips with vertical structure are the basic structure for preparing light-emitting diodes. The light-emitting diode chip with vertical structure usually includes a substrate and an n-type metal contact layer, an n-type layer, a light-emitting layer, a p-type layer and a p-type metal contact layer which are sequentially stacked on the substrate.

[0004] The substrate selected for the light-emitting diode chip is usually a sapphire substrate, a gallium arsenide substrate or a gallium nitride substrate. The sapphire substrate, the gallium arsenide substrate or the gallium nitride substrate itself is relatively rigid and has a fixed shape, which cannot meet the use requirements of some flexible displays. Even if a substrate with a certain flexibility is selected as the growth basis of the light-emitting diode epitaxial wafer, it is difficult to ensure that the epitaxial material grown on the substrate has fewer defects and good heat dissipation performance under the premise that the light-emitting diode chip for display screen has a very small volume, thereby resulting in a shorter service life of the obtained light-emitting diode chip. SUMMARY

[0005] The present application provides a flexible substrate light-emitting diode chip with improved heat dissipation and a preparation method thereof, which can improve the crystal quality and heat dissipation of the obtained light-emitting diode chip to improve the service life of the light-emitting diode chip. The technical solution is as follows:

[0006] The present application provides a flexible substrate light-emitting diode chip with improved heat dissipation, which includes a polyethylene naphthalate flexible substrate and an indium zinc oxide transparent conductive layer, a Cu heat dissipation layer, a Cr ohmic contact layer, an n-type metal contact layer, an n-type layer, a light-emitting layer, a p-type layer and a p-type metal contact layer which are sequentially stacked on the polyethylene naphthalate flexible substrate,

[0007] The polyethylene naphthalate flexible substrate comprises a flexible body and a plurality of folded protrusions which are stacked on the flexible body with mutual spacing, the folded protrusions are prisms with an axis perpendicular to the surface of the flexible body, the surface of the indium zinc oxide transparent conductive layer has conductive protrusions corresponding to the folded protrusions one by one, and the surface of the Cu heat dissipation layer away from the polyethylene naphthalate flexible substrate is a plane.

[0008] Optionally, the ratio of the thickness of the flexible body to the thickness of the folded protrusions is 2:500-1:1500.

[0009] Optionally, the thickness of the flexible body is 50-150 μm, and the thickness of the folded protrusions is 100-200 nm.

[0010] Optionally, the thickness of the indium zinc oxide transparent conductive layer is 90-300 nm.

[0011] Optionally, the minimum distance between the surface of the Cu heat dissipation layer away from the polyethylene naphthalate flexible body and the indium zinc oxide transparent conductive layer is 5-50 nm.

[0012] Optionally, the maximum thickness of the Cu heat dissipation layer is 300-600 nm.

[0013] Optionally, the area of the orthographic projection of the n-type metal contact layer on the surface of the flexible body is less than the area of the orthographic projection of the Cr ohmic contact layer on the surface of the flexible body.

[0014] The disclosure embodiment provides a preparation method of a flexible substrate light emitting diode chip with improved heat dissipation, and the preparation method comprises:

[0015] A polyethylene naphthalate flexible substrate and an epitaxial layer are provided, the polyethylene naphthalate flexible substrate comprises a flexible body and a plurality of folded protrusions which are stacked on the flexible body with mutual spacing, the folded protrusions are prisms with an axis perpendicular to the surface of the flexible body, and the epitaxial layer comprises an n-type metal contact layer, an n-type layer, a light emitting layer, a p-type layer and a p-type metal contact layer which are sequentially stacked.

[0016] An indium zinc oxide transparent conductive layer, a Cu heat dissipation layer and a Cr ohmic contact layer are sequentially deposited on the polyethylene naphthalate flexible substrate, the surface of the indium zinc oxide transparent conductive layer has conductive protrusions corresponding to the folded protrusions one by one, and the surface of the Cu heat dissipation layer away from the polyethylene naphthalate flexible substrate is a plane.

[0017] The epitaxial layer is transferred to the polyethylene naphthalate flexible substrate, and the Cr ohmic contact layer is stacked on the Cr ohmic contact layer.

[0018] Optionally, the providing a polyethylene naphthalate flexible substrate comprises:

[0019] providing a polyethylene naphthalate substrate having a first surface and a second surface parallel to each other and opposite to each other;

[0020] forming a pattern on the first surface of the polyethylene naphthalate substrate by using a photolithography process, to obtain the polyethylene naphthalate flexible substrate, wherein an exposure process in the photolithography process is performed by using a laser interference lithography machine.

[0021] Optionally, the light intensity at the outlet of the laser interference lithography machine is 0.1-0.4 mW / cm 2 , the continuous exposure time of the laser interference lithography machine is 30-50 seconds, and the total exposure energy of the laser interference lithography machine is 5-20 mJ / cm 2 .

[0022] The technical scheme provided by the embodiments of the present disclosure has the following beneficial effects:

[0023] The light-emitting diode chip comprises a polyethylene naphthalate flexible substrate and an indium zinc oxide transparent conductive layer, a Cu heat dissipation layer, a Cr ohmic contact layer, an n-type metal contact layer, an n-type layer, a light-emitting layer, a p-type layer, and a p-type metal contact layer which are sequentially stacked on the polyethylene naphthalate flexible substrate. The basic light-emitting function of the light-emitting diode chip with a vertical structure can be realized. In the light-emitting diode chip, the polyethylene naphthalate flexible substrate comprises a flexible main body and a plurality of folding protrusions which are spaced apart from each other and stacked on the flexible main body, and the folding protrusions are prisms with an axis perpendicular to the surface of the flexible main body. When the light-emitting device to which the polyethylene naphthalate flexible substrate is applied needs to be folded, the folding protrusions and the depressions between the folding protrusions can be deformed and release the acting force, so as to provide a certain tension for the whole light-emitting diode chip, improve the flexibility of the whole light-emitting diode chip, and increase the folding angle of the light-emitting device. The surface of the indium zinc oxide transparent conductive layer on the polyethylene naphthalate flexible substrate has conductive protrusions corresponding to the folding protrusions, so as to increase the conductive effect of the light-emitting diode chip while ensuring the flexibility of the light-emitting diode chip. The surface of the Cu heat dissipation layer away from the polyethylene naphthalate flexible substrate on the indium zinc oxide transparent conductive layer is a plane, and the Cu heat dissipation layer fills the depressions of the pattern, so that the Cu heat dissipation layer and the indium zinc oxide transparent conductive layer have a larger contact area, which can effectively improve the heat dissipation effect of the Cu heat dissipation layer on the whole light-emitting diode chip without increasing the thickness of the Cu heat dissipation layer. The heat dissipation effect and the conductive effect of the finally obtained light-emitting diode chip are improved, and the service life of the finally obtained light-emitting diode chip is improved. BRIEF DESCRIPTION OF DRAWINGS

[0024] To more clearly illustrate the technical solutions in the embodiments of this disclosure, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of the structure of a flexible substrate light-emitting diode chip with improved heat dissipation provided in an embodiment of this disclosure;

[0026] Figure 2 This is a schematic diagram of another flexible substrate light-emitting diode chip with improved heat dissipation provided in this embodiment of the present disclosure;

[0027] Figure 3 This is a flowchart illustrating a method for fabricating a flexible substrate light-emitting diode chip with improved heat dissipation, as provided in an embodiment of this disclosure.

[0028] Figure 4 This is a flowchart of another method for fabricating a flexible substrate light-emitting diode chip with improved heat dissipation, provided by an embodiment of this disclosure. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present disclosure will be described in further detail below with reference to the accompanying drawings.

[0030] Figure 1 This is a schematic diagram of a flexible substrate light-emitting diode chip with improved heat dissipation provided in an embodiment of this disclosure, with reference to... Figure 1 As can be seen, the present disclosure provides a flexible substrate 1 light-emitting diode chip with improved heat dissipation. The light-emitting diode chip includes a polyethylene naphthalate flexible substrate 1 and an indium zinc oxide transparent conductive layer 2, a Cu heat dissipation layer 3, a Cr ohmic contact layer 4, an n-type metal contact layer 5, an n-type layer 6, a light-emitting layer 7, a p-type layer 8, and a p-type metal contact layer 9 sequentially stacked on the polyethylene naphthalate flexible substrate 1.

[0031] The flexible polyethylene naphthalate substrate 1 includes a flexible body 101 and a plurality of folded protrusions 102 stacked on the flexible body 101 at intervals. The folded protrusions 102 are frustums with their axes perpendicular to the surface of the flexible body 101. The surface of the indium zinc oxide transparent conductive layer 2 has conductive protrusions 201 that correspond one-to-one with the folded protrusions 102. The surface of the Cu heat dissipation layer 3 away from the flexible polyethylene naphthalate substrate 1 is planar.

[0032] The light-emitting diode (LED) chip comprises a flexible polyethylene naphthalate (PEG) substrate 1 and, sequentially stacked on the PEG substrate 1, an indium zinc oxide (IZO) transparent conductive layer 2, a Cu heat dissipation layer 3, a Cr ohmic contact layer 4, an n-type metal contact layer 5, an n-type layer 6, a light-emitting layer 7, a p-type layer 8, and a p-type metal contact layer 9. This enables the basic light-emitting function of a vertically structured LED chip. In the LED chip, the PEG flexible substrate 1 includes a flexible body 101 and multiple folding protrusions 102 spaced apart and stacked on the flexible body 101. Each folding protrusion 102 is a frustum with its axis perpendicular to the surface of the flexible body 101. When the light-emitting device using the PEG flexible substrate 1 needs to be folded, the folding protrusions 102 and the recesses between them can deform and release force, providing a certain tension to the LED chip as a whole, improving the overall flexibility of the LED chip and increasing the folding angle of the light-emitting device. The surface of the indium zinc oxide transparent conductive layer 2 on the flexible polyethylene naphthalate substrate 1 has conductive protrusions 201 that correspond one-to-one with the folded protrusions 102. This increases the conductivity of the LED chip while maintaining its flexibility. The surface of the Cu heat dissipation layer 3 on the indium zinc oxide transparent conductive layer 2, away from the flexible polyethylene naphthalate substrate 1, is planar. The Cu heat dissipation layer 3 fills the depressions in the pattern, resulting in a larger contact area between the Cu heat dissipation layer 3 and the indium zinc oxide transparent conductive layer 2. This effectively improves the heat dissipation effect of the Cu heat dissipation layer 3 on the overall LED chip without increasing its thickness. This improves the heat dissipation and conductivity of the final LED chip, thus extending its lifespan.

[0033] It should be noted that the flexible body 101 and the folded protrusion 102 are essentially an integrated structure. The flexible body 101 can be a cuboid, a circular plate, or a prism-like structure (the growing surface is the top or bottom surface of the prism). The surface of the flexible body 101 is the surface on which the indium zinc oxide transparent conductive layer 2 is stacked. The indium zinc oxide transparent conductive layer 2 is stacked on the surfaces of the flexible body 101 and the folded protrusion 102.

[0034] For example, the ratio of the thickness of the flexible body 101 to the thickness of the folding protrusion 102 is 2:500 to 1:1500.

[0035] When the ratio of the thickness of the flexible body 101 to the thickness of the folded protrusion 102 is within the above range, the resulting polyethylene naphthalate flexible substrate 1 has better quality and can also ensure the flexibility of the resulting light-emitting diode chip.

[0036] Optionally, the thickness of the flexible body 101 is 50μm to 150μm, and the thickness of the folded protrusion 102 is 100nm to 200nm.

[0037] The thickness of the flexible body 101 and the thickness of the folded protrusion 102 are within the above range, which can obtain a high-quality polyethylene naphthalate flexible substrate 1. The polyethylene naphthalate flexible substrate 1 itself also has good flexibility.

[0038] Optionally, the folded protrusion 102 is a regular square frustum, the width of the folded protrusion 102 is 0.1μm to 0.3μm, and the distance between two adjacent folded protrusions 102 is 0.2μm to 0.5μm.

[0039] When the folded protrusion 102 is a regular square frustum and the width of the folded protrusion 102 and the distance between two adjacent folded protrusions 102 are within the above range, it can be ensured that the distance between adjacent folded protrusions 102 is large. While ensuring the quality of the polyethylene naphthalate flexible substrate 1 itself, the polyethylene naphthalate flexible substrate 1 can release a large amount of stress, effectively improving the flexibility of the light-emitting diode chip.

[0040] Optionally, on the cross-section obtained by cutting the light-emitting diode chip from the same plane, the shape of the interface line of the indium zinc oxide transparent conductive layer 2 near the Cu heat dissipation layer 3 is the same as the shape of the interface line of the polyethylene naphthalate flexible substrate 1 near the Cu heat dissipation layer 3.

[0041] The shape of the interface line between the indium zinc oxide transparent conductive layer 2 and the Cu heat dissipation layer 3 is the same as the shape of the interface line between the polyethylene naphthalate flexible substrate 1 and the Cu heat dissipation layer 3. This can improve the conductivity of the indium zinc oxide transparent conductive layer 2. At the same time, the structure of the indium zinc oxide transparent conductive layer 2 is similar to that of the polyethylene naphthalate flexible substrate 1, which can improve the flexibility of the indium zinc oxide transparent conductive layer 2 and further improve the flexibility of the obtained light-emitting diode chip.

[0042] It should be noted that since the shape of the interface line between the indium zinc oxide transparent conductive layer 2 and the Cu heat dissipation layer 3 is the same as the shape of the interface line between the polyethylene naphthalate flexible substrate 1 and the Cu heat dissipation layer 3, the structure and parameters of the conductive protrusion 201 on the surface of the indium zinc oxide transparent conductive layer 2 can actually refer to the structure and parameters of the folded protrusion 102 on the polyethylene naphthalate flexible substrate 1. The conductive protrusion 201 on the surface of the indium zinc oxide transparent conductive layer 2 will not be described in detail here.

[0043] For example, the thickness of the indium zinc oxide transparent conductive layer 2 is 90–300 nm.

[0044] If the thickness of the indium zinc oxide transparent conductive layer 2 is within the above range, the quality of the obtained indium zinc oxide transparent conductive layer 2 can be guaranteed to be good, and the conductivity efficiency of the obtained light-emitting diode chip can be effectively improved.

[0045] Optionally, the minimum distance between the surface of the Cu heat dissipation layer 3 away from the flexible polyethylene naphthalate body 101 and the indium zinc oxide transparent conductive layer 2 is 5 nm to 50 nm.

[0046] The minimum distance between the surface of the Cu heat dissipation layer 3 away from the flexible polynaphthalene glycol ester body 101 and the indium zinc oxide transparent conductive layer 2 is within the above range, which can ensure that the obtained Cu heat dissipation layer 3 has good quality and sufficient thickness to effectively dissipate heat, thereby improving the heat dissipation effect of the obtained light-emitting diode chip.

[0047] Optionally, the maximum thickness of the Cu heat dissipation layer 3 is 300–600 nm.

[0048] The maximum thickness of Cu heat dissipation layer 3 is within the above range, which can ensure that the quality of Cu heat dissipation layer 3 is good, and Cu heat dissipation layer 3 itself can play a good heat dissipation role.

[0049] In other implementations provided in this disclosure, the maximum thickness of the Cu heat dissipation layer 3 can also range from 200 to 900 nm. This disclosure does not impose any limitation on this.

[0050] It should be noted that the thickness and minimum distance in this disclosure refer to the thickness and minimum distance in the direction perpendicular to the surface of the flexible body 101.

[0051] Figure 2 This is a schematic diagram of another structure of a flexible substrate 1 light-emitting diode chip with improved heat dissipation provided in this disclosure embodiment, with reference to... Figure 2 As can be seen, in another implementation provided in this disclosure, the light-emitting diode chip includes a flexible polyethylene naphthalate substrate 1 and an indium zinc oxide transparent conductive layer 2, a Cu heat dissipation layer 3, a Cr ohmic contact layer 4, an Au heat dissipation layer 10, a Sn ohmic contact layer 11, an n-type metal contact layer 5, an n-type layer 6, a light-emitting layer 7, an AlGaN electron blocking layer 12, a p-type layer 8, a p-type ohmic contact layer 13, a p-type metal contact layer 9, and a passivation protection layer 14, which are sequentially stacked on the flexible polyethylene naphthalate substrate 1.

[0052] The flexible polyethylene naphthalate substrate 1 includes a flexible body 101 and a plurality of folded protrusions 102 stacked on the flexible body 101 at intervals. The folded protrusions 102 are frustums with their axes perpendicular to the surface of the flexible body 101. The surface of the indium zinc oxide transparent conductive layer 2 has conductive protrusions 201 that correspond one-to-one with the folded protrusions 102. The surface of the Cu heat dissipation layer 3 away from the flexible polyethylene naphthalate substrate 1 is planar.

[0053] Figure 2 The structure of the flexible polyethylene naphthalate substrate 1, the indium zinc oxide transparent conductive layer 2, and the Cu heat dissipation layer 3 can be referenced. Figure 1 The structures of the polyethylene naphthalate flexible substrate 1, the indium zinc oxide transparent conductive layer 2, and the Cu heat dissipation layer 3 shown are not described in detail here.

[0054] It should be noted that the Cr ohmic contact layer 4 stacked on the Cu heat dissipation layer 3 can serve as a transition layer to transition the Cu heat dissipation layer 3 to different metal materials.

[0055] Optionally, the thickness of the Cr ohmic contact layer 4 can be 9–90 nm. This ensures that the Cr ohmic contact layer 4 plays a stable transition role and also facilitates a good connection between the Cr ohmic contact layer 4 and the n-type metal contact layer 5.

[0056] For example, an Au heat dissipation layer 10 and a Sn ohmic contact layer 11 are sequentially added to the Cr ohmic contact layer 4. This facilitates extended contact with the n-type metal contact layer 5 and ensures the heat dissipation effect of the resulting LED chip.

[0057] Optionally, the thickness of the Au heat dissipation layer 10 and the thickness of the Sn ohmic contact layer 11 are both 50–200 nm. This can improve the heat dissipation effect of the obtained light-emitting diode chip.

[0058] Optionally, the area of ​​the n-type metal contact layer 5 projected onto the surface of the flexible body 101 is smaller than the area of ​​the Cr ohmic contact layer 4 projected onto the surface of the flexible body 101.

[0059] The area of ​​the n-type metal contact layer 5 projected onto the surface of the flexible body 101 is smaller than that of the Cr ohmic contact layer 4 projected onto the surface of the flexible body 101. This reduces the overall fabrication cost of the LED chip while ensuring the light extraction efficiency of the resulting LED chip, and also guarantees the flexibility of the LED chip. The exposed surface of the Cr ohmic contact layer 4 also provides space for wiring, enabling stable light emission from the LED chip.

[0060] In one implementation provided in this disclosure, the projected area of ​​all epitaxial materials stacked on the n-type metal contact layer 5 on the surface of the flexible body 101 is less than or equal to the projected area of ​​the n-type metal contact layer 5 on the surface of the flexible body 101.

[0061] For example, the n-type metal contact layer 5 includes an Au bonding sub-layer 501, a Cu heat dissipation sub-layer 502, and a Cr ohmic contact sub-layer 503 stacked sequentially. This ensures good contact and heat dissipation between the n-type metal contact layer 5 and the Sn ohmic contact layer 11, while also ensuring good ohmic contact between the n-type metal contact layer 5 and the semiconductor material of the n-type layer 6, thereby reducing the overall operating voltage required by the light-emitting diode chip.

[0062] Optionally, the n-type layer 6 may include an ALN ​​sublayer 601, a GaN buffer sublayer 602, a buffer three-dimensional sublayer 603, a GaN capping sublayer 604, a GaN undoped sublayer 605, an AlN sublayer 606, and an n-GaN sublayer 607 stacked sequentially. The overall quality of the n-type GaN layer is relatively good.

[0063] For example, the thickness of the n-type GaN layer can be 1–5 μm. The resulting n-type GaN layer has good overall quality.

[0064] In one implementation provided in this disclosure, the thickness of the n-type GaN layer can be 3 μm. This disclosure does not impose any limitation on this.

[0065] For example, the light-emitting layer 7 includes a plurality of alternately stacked InGaN well layers and GaN barrier layers, wherein the thickness of the InGaN well layers can be 2 to 5 nm and the thickness of the GaN barrier layers can be 7 to 20 nm.

[0066] For example, the overall thickness of the light-emitting layer 7 can be 50-120 nm, and the In molar content can be 12%-25%.

[0067] Optionally, the Al composition in the AlGaN electron blocking layer 12 can be 0.14–0.25%, which provides a better electron blocking effect.

[0068] Optionally, the thickness of the AlGaN electron blocking layer 12 can be 20–90 nm. The resulting AlGaN electron blocking layer 12 has good quality.

[0069] It can provide enough holes and ensure that the overall cost of the LED chip is not too high.

[0070] Optionally, the p-type layer 8 can be a p-type GaN layer. The thickness of the p-type GaN layer can be 70–300 nm, providing sufficient holes.

[0071] Optionally, the p-type metal contact layer 9 may include a Ni metal layer and an Au metal layer stacked sequentially from bottom to top. This is easy to prepare and obtain.

[0072] Optionally, the p-type ohmic contact layer 13 is made of indium tin oxide, and the thickness of the p-type ohmic contact layer 13 can be 0.5–1.5 μm. The resulting light-emitting diode chip has good quality.

[0073] For example, the passivation layer 14 is made of silicon oxide or aluminum oxide, and its thickness is 2–3 μm. The resulting light-emitting diode chip has good quality.

[0074] It should be noted that in other implementations provided in this disclosure, the light-emitting diode chip may also include other hierarchical structures, and this disclosure does not impose any restrictions on this. Furthermore, while the main material of the light-emitting diode chip provided in this disclosure is gallium nitride, in other implementations provided in this disclosure, the main material of the light-emitting diode chip may also be aluminum gallium arsenide or aluminum gallium indium phosphide, and this disclosure does not impose any restrictions on this.

[0075] Figure 3 This is a flowchart illustrating a method for fabricating a flexible substrate light-emitting diode chip with improved heat dissipation, as provided in this disclosure embodiment. Figure 3 As shown in the figure, this disclosure provides a method for fabricating a flexible substrate light-emitting diode chip with improved heat dissipation. The fabrication method includes:

[0076] S101: Provides a flexible polyethylene naphthalate substrate and an epitaxial layer. The flexible polyethylene naphthalate substrate includes a flexible body and a plurality of folded protrusions stacked on the flexible body at intervals. The folded protrusions are frustums with axes perpendicular to the surface of the flexible body. The epitaxial layer includes an n-type metal contact layer, an n-type layer, a light-emitting layer, a p-type layer and a p-type metal contact layer stacked sequentially.

[0077] S102: An indium zinc oxide transparent conductive layer, a Cu heat dissipation layer and a Cr ohmic contact layer are sequentially deposited on a polyethylene naphthalate flexible substrate. The surface of the indium zinc oxide transparent conductive layer has conductive protrusions that correspond one-to-one with the folded protrusions. The surface of the Cu heat dissipation layer away from the polyethylene naphthalate flexible substrate is planar.

[0078] S103: The epitaxial layer is transferred onto a flexible polyethylene naphthalate substrate, and an n-type metal contact layer is stacked on a Cr ohmic contact layer.

[0079] The LED chip obtained after performing step S103 can be referenced. Figure 1 The structure of the light-emitting diode chip shown is as follows: Figure 3 The technical effects of the corresponding preparation methods can be referenced. Figure 1The technical effects of the LED chip shown are not elaborated here.

[0080] Figure 4 This is a flowchart illustrating another method for fabricating a flexible substrate light-emitting diode chip with improved heat dissipation, as provided in this disclosure embodiment. Figure 4 As shown, the preparation method may include:

[0081] S201: Provide a polyethylene naphthalate substrate, the polyethylene naphthalate substrate having a first surface and a second surface that are parallel and opposite to each other; use photolithography to form a pattern on the first surface of the polyethylene naphthalate substrate to obtain a flexible polyethylene naphthalate substrate, the exposure process in the photolithography process is performed by a laser interference lithography machine.

[0082] In the process of preparing a flexible polyethylene naphthalate substrate, which includes a flexible substrate and a folded substrate, by using a photolithography process, the exposure treatment by a laser interference lithography machine can improve the surface processing accuracy of the polyethylene naphthalate substrate, which has a certain degree of elasticity and flexibility, so as to ensure the quality of the final polyethylene naphthalate flexible substrate and improve the processing quality of the final light-emitting diode chip.

[0083] It should be noted that the photolithography process includes at least adding photoresist to the substrate or epitaxial layer on which the pattern needs to be prepared, exposing and developing the photoresist, removing the softened photoresist to form a pattern on the photoresist, and etching or corroding the surface of the epitaxial layer or substrate exposed by the pattern to form a pattern on the substrate or epitaxial layer.

[0084] Optionally, the light intensity at the exit of the laser interference lithography machine is 0.1–0.4 mW / cm². 2 The continuous exposure time of a laser interference lithography machine is 30–50 seconds, and the total exposure energy is 5–20 mJ / cm². 2 .

[0085] When exposing photoresist on a flexible polyethylene naphthalate substrate using a laser interference lithography machine, the above exposure parameters can ensure effective exposure and produce a relatively accurate surface pattern. The output laser in the laser interference lithography machine can be an argon-ion continuous-wavelength steady-state laser.

[0086] It should be noted that the distance between two adjacent folded protrusions can be adjusted by changing the angle between the Loehn mirror at the front end of the laser interference lithography machine and the emitted light. The distance between adjacent folded protrusions is equal to the wavelength of the output laser from the argon ion continuous-wave steady-state laser divided by the angle between the laser incident light path and the Loehn mirror. This facilitates the adjustment of the distance between two adjacent folded protrusions.

[0087] In one implementation provided in this disclosure, the polyethylene naphthalate substrate can be cleaned before coating it with photoresist to improve the quality of the resulting flexible polyethylene naphthalate substrate.

[0088] For example, 3-phenylsalicylic acid is used to clean a polyethylene naphthalate substrate for 9–20 minutes. This ensures effective cleaning.

[0089] In one implementation provided in this disclosure, a mixture of negative photoresist and diluent is coated onto a polyethylene naphthalate substrate. This ensures adhesion between the negative photoresist and the polyethylene naphthalate substrate.

[0090] For example, the coating process includes: mixing negative photoresist and diluent at a ratio of 1:1 to 3, and then spin-coating the mixture onto the surface of a cleaned polyethylene naphthalate substrate. The spin coater rotates at 3000 to 4000 rpm. This ensures uniform photoresist coverage.

[0091] Optionally, after the photoresist is exposed and developed, the polyethylene naphthalate substrate can be heat-treated for 1-5 minutes at a temperature of 90-140°C; finally, a pattern is prepared on the surface of the polyethylene naphthalate substrate by wet etching to obtain a flexible polyethylene naphthalate substrate. This can improve the fabrication efficiency.

[0092] In other implementations provided in this disclosure, the polyethylene naphthalate substrate can also be processed using conventional photolithography processes, and this disclosure does not impose any restrictions on this.

[0093] S202: Provides an epitaxial layer comprising an n-type metal contact layer, an n-type layer, a light-emitting layer, an AlGaN electron blocking layer, a p-type layer, a p-type ohmic contact layer, a p-type metal contact layer, and a passivation protection layer stacked sequentially.

[0094] Optionally, the epitaxial layer in step S202 can be obtained through the following steps:

[0095] Growing an epitaxial layer on a sapphire substrate may include sequentially growing a buffer layer, an n-type layer, a light-emitting layer, an electron-blocking layer, a p-type layer, and a p-type ohmic contact layer on the sapphire substrate. The growth conditions for the buffer layer, n-type layer, light-emitting layer, electron-blocking layer, p-type layer, p-type ohmic contact layer, and p-type metal contact layer are as follows:

[0096] Optionally, the temperature of the reaction chamber is controlled at 450℃~500℃, and the pressure in the reaction chamber is controlled at 200 torr~500 torr to grow a three-dimensional GaN nucleation layer; then, the temperature of the reaction chamber is increased to 850℃~1100℃ to grow a GaN filling layer and an undoped GaN layer sequentially. A buffer layer of good quality is obtained.

[0097] Optionally, the growth temperature of the n-type layer can be 850℃~1100℃, and the growth pressure of the n-type layer can be 200Torr~500Torr.

[0098] Optionally, the light-emitting layer includes alternating InGaN well layers and GaN barrier layers.

[0099] Optionally, the growth temperature and pressure of the InGaN well layer are 600–700℃ and 90–300 torr, respectively, and the growth temperature and pressure of the GaN barrier layer are 600–800℃ and 90–300 torr, respectively. The resulting light-emitting layer has good quality.

[0100] Optionally, the InGaN well layer has a thickness of 2–4 nm, and the GaN barrier layer has a thickness of 5–9 nm. The resulting light-emitting layer has good quality.

[0101] For example, the growth temperature of the AlGaN electron blocking layer can be 500–900°C, and the growth pressure can be 90–300 Torr. Under these conditions, the AlGaN electron blocking layer obtained is of good quality, which is beneficial for improving the luminous efficiency of the light-emitting diode.

[0102] Optionally, the p-type layer is a p-type GaN layer, the growth temperature of the p-type GaN layer can be 800-1100℃, and the growth pressure of the p-type GaN layer can be 90-300 Torr.

[0103] For example, the growth temperature of the p-type ohmic contact layer can be 800 to 1100°C, and the growth pressure of the p-type ohmic contact layer can be 90 to 300 Torr.

[0104] Optionally, the p-type metal contact layer comprises a Ni metal layer and an Au metal layer stacked sequentially from bottom to top. The Ni metal layer and the Au metal layer can be obtained by vapor deposition.

[0105] For example, the thickness ratio of the Ni metal layer to the Au metal layer is 1:1, and the thickness of the Ni and Au metal layers is 9–20 nm. This ensures that the p-type metal contact layer has good quality and can perform its conductive function normally.

[0106] In one implementation provided in this disclosure, the epitaxial structure after the p-type metal contact layer has been grown can be cleaned before growth. Alternatively, multiple array unit patterns can be etched onto the surface of the p-type metal contact layer, facilitating subsequent dicing of the epitaxial layer to obtain multiple individual light-emitting units. This disclosure does not limit this approach.

[0107] In step S202, after the epitaxial layer is grown on the sapphire substrate, a silicon substrate with an adhesive layer coated on its surface can be provided; the epitaxial layer is flip-chip bonded to the silicon substrate, and the passivation protection layer is connected to the silicon substrate through the adhesive layer; the epitaxial layer is peeled off from the sapphire substrate; the buffer layer on the n-type GaN layer is etched to expose the surface of the n-type GaN layer; and an n-type metal contact layer is grown on the n-type layer.

[0108] With the addition of a passivation protection layer, the passivation protection layer can protect structures such as the p-type layer and ensure the quality of layers such as the n-type layer and the light-emitting layer.

[0109] S203: An indium zinc oxide transparent conductive layer, a Cu heat dissipation layer, and a Cr ohmic contact layer are sequentially deposited on a polyethylene naphthalate flexible substrate. The surface of the indium zinc oxide transparent conductive layer has conductive protrusions that correspond one-to-one with the folded protrusions. The surface of the Cu heat dissipation layer away from the polyethylene naphthalate flexible substrate is planar.

[0110] For example, the indium zinc oxide transparent conductive layer is grown using an atomic layer deposition (ALD) apparatus. This ensures the surface flatness of the resulting indium zinc oxide transparent conductive layer and guarantees that the thickness of the indium zinc oxide transparent conductive layer is substantially consistent throughout.

[0111] S204: The epitaxial layer is transferred onto a flexible polyethylene naphthalate substrate, and an n-type metal contact layer is stacked on a Cr ohmic contact layer.

[0112] Step S204 may include: using a chip bonding machine, under bonding temperatures of 200–300°C and bonding pressures of 1–3 N, transferring the epitaxial layer onto a flexible polyethylene naphthalate substrate. This results in a well-bonded epitaxial layer and a flexible polyethylene naphthalate substrate.

[0113] It should be noted that the n-type metal contact layer and the Cr ohmic contact layer provide space for wiring, and the connection between the n-type metal contact layer, the metal bonding layer and the n electrode can be achieved through wiring.

[0114] S205: Separate silicon substrate and epitaxial layer.

[0115] In step S205, a laser can be used to separate the silicon substrate from the epitaxial layer, and then the residual adhesive layer on the passivation protective layer can be removed. This ultimately yields a high-quality flexible substrate light-emitting diode chip with improved heat dissipation.

[0116] Alternatively, the adhesive layer can be removed by etching. This is easy to implement.

[0117] The structure of the LED chip after step S205 can be found in [reference needed]. Figure 2 .

[0118] It should be noted that, in the embodiments disclosed herein, a VeecoK 455i or C4 or RB MOCVD (Metal-Organic Chemical Vapor Deposition) apparatus is used to grow the epitaxial layer of the light-emitting diode. High-purity H2 (hydrogen), high-purity N2 (nitrogen), or a mixture of high-purity H2 and high-purity N2 is used as the carrier gas; high-purity NH3 is used as the N-source; trimethylgallium (TMGa) and triethylgallium (TEGa) are used as gallium sources; trimethylindium (TMIn) is used as the indium source; silane (SiH4) is used as the N-type dopant; trimethylaluminum (TMAl) is used as the aluminum source; and magnesium pyrocene (CP2Mg) is used as the P-type dopant.

[0119] The above description is not intended to limit this disclosure in any way. Although this disclosure has been disclosed above through embodiments, it is not intended to limit this disclosure. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the technical solution of this disclosure. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of this disclosure without departing from the content of the technical solution of this disclosure shall still fall within the scope of the technical solution of this disclosure.

Claims

1. A flexible substrate light-emitting diode chip with improved heat dissipation, characterized in that, The light-emitting diode chip comprises a flexible polyethylene naphthalate substrate and, sequentially stacked on the flexible polyethylene naphthalate substrate, an indium zinc oxide transparent conductive layer, a Cu heat dissipation layer, a Cr ohmic contact layer, an n-type metal contact layer, an n-type layer, a light-emitting layer, a p-type layer, and a p-type metal contact layer. The flexible polyethylene naphthalate substrate includes a flexible body and a plurality of folded protrusions stacked on the flexible body at intervals. The folded protrusions are frustums with their axes perpendicular to the surface of the flexible body. The surface of the indium zinc oxide transparent conductive layer has conductive protrusions that correspond one-to-one with the folded protrusions. The Cu heat dissipation layer fills the depressions between the conductive protrusions of the indium zinc oxide transparent conductive layer. The surface of the Cu heat dissipation layer away from the flexible polyethylene naphthalate substrate is planar.

2. The light-emitting diode chip according to claim 1, characterized in that, The ratio of the thickness of the flexible body to the thickness of the folded protrusion is 2:500 to 1:1500.

3. The light-emitting diode chip according to claim 1, characterized in that, The thickness of the flexible body is 50μm~150μm, and the thickness of the folded protrusion is 100nm~200nm.

4. The light-emitting diode chip according to any one of claims 1 to 3, characterized in that, The thickness of the indium zinc oxide transparent conductive layer is 90~300nm.

5. The light-emitting diode chip according to any one of claims 1 to 3, characterized in that, The minimum distance between the surface of the Cu heat dissipation layer away from the flexible polynaphthalene glycol substrate and the indium zinc oxide transparent conductive layer is 5 nm to 50 nm.

6. The light-emitting diode chip according to any one of claims 1 to 3, characterized in that, The maximum thickness of the Cu heat dissipation layer is 300~600nm.

7. The light-emitting diode chip according to any one of claims 1 to 3, characterized in that, The area of ​​the n-type metal contact layer projected onto the surface of the flexible body is smaller than the area of ​​the Cr ohmic contact layer projected onto the surface of the flexible body.

8. A method for fabricating a flexible substrate light-emitting diode chip with improved heat dissipation, characterized in that, The preparation method includes: A flexible polyethylene naphthalate substrate and an epitaxial layer are provided. The flexible polyethylene naphthalate substrate includes a flexible body and a plurality of folded protrusions stacked on the flexible body at intervals. The folded protrusions are frustums with axes perpendicular to the surface of the flexible body. The epitaxial layer includes an n-type metal contact layer, an n-type layer, a light-emitting layer, a p-type layer and a p-type metal contact layer stacked sequentially. An indium zinc oxide transparent conductive layer, a Cu heat dissipation layer, and a Cr ohmic contact layer are sequentially deposited on the polyethylene naphthalate flexible substrate. The surface of the indium zinc oxide transparent conductive layer has conductive protrusions that correspond one-to-one with the folded protrusions. The Cu heat dissipation layer fills the depressions between the conductive protrusions of the indium zinc oxide transparent conductive layer. The surface of the Cu heat dissipation layer away from the polyethylene naphthalate flexible substrate is planar. The epitaxial layer is transferred onto the polyethylene naphthalate flexible substrate, and the n-type metal contact layer is stacked on the Cr ohmic contact layer.

9. The method for fabricating a flexible substrate light-emitting diode chip with improved heat dissipation according to claim 8, characterized in that, The provision of a flexible polyethylene naphthalate substrate includes: A polyethylene naphthalate substrate is provided, the polyethylene naphthalate substrate having a first surface and a second surface that are parallel and opposite to each other; A pattern is formed on the first surface of the polyethylene naphthalate substrate using a photolithography process to obtain the polyethylene naphthalate flexible substrate. The exposure process in the photolithography process is performed using a laser interference lithography machine.

10. The method for fabricating a flexible substrate light-emitting diode chip with improved heat dissipation according to claim 9, characterized in that, The light intensity at the exit of the laser interference lithography machine is 0.1–0.4 mW / cm². 2 The continuous exposure time of the laser interference lithography machine is 30-50 seconds, and the total exposure energy of the laser interference lithography machine is 5-20 mJ / cm². 2 .

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