Flip LED chip and preparation method thereof

Abstract

The invention relates to the technical field of photoelectron manufacturing, and particularly discloses a flip LED chip and a preparation method thereof. The flip LED chip comprises: a substrate; the light-emitting structure comprises an N-type semiconductor layer, an active light-emitting layer, a P-type semiconductor layer and a P-type electrode which are sequentially stacked on the substrate; the light-emitting structure is provided with a conductive step exposing the N-type semiconductor layer, and the conductive step is provided with an N-type electrode; the protection structure is arranged around the light-emitting structure, and a first groove exposing the substrate is formed between the protection structure and the light-emitting structure; the reflection insulating layer covers the light emitting structure, the protection structure and the first groove; the N type bonding pad is arranged above the N type electrode and is electrically connected with the N type electrode; and the P-type bonding pad is arranged above the P-type electrode and is connected with the P-type electrode through the P-type bonding pad. According to the invention, the reliability of the flip LED chip can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of optoelectronic manufacturing, and in particular to a flip-chip LED chip and a preparation method thereof. Background Art

[0002] Flip-chip LED chips offer superior heat dissipation and luminous efficiency compared to standard upright LED chips, making them widely used in display screens, lighting, and other fields. However, when used in certain environments, flip-chip LED chips must withstand high temperatures and high humidity, placing extremely high demands on their reliability in these conditions. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a flip-chip LED chip which is resistant to high temperature and high humidity and has high reliability.

[0004] Correspondingly, the present invention also provides a method for preparing the above-mentioned flip-chip LED chip.

[0005] In order to solve the above technical problems, the present invention provides a flip-chip LED chip, which includes

[0006] substrate;

[0007] A light-emitting structure comprising an N-type semiconductor layer, an active light-emitting layer, a P-type semiconductor layer, and a P-type electrode sequentially stacked on the substrate; the light-emitting structure is provided with a conductive step exposing the N-type semiconductor layer, and the N-type electrode is provided on the conductive step;

[0008] a protective structure disposed around the light emitting structure, wherein a first groove exposing the substrate is formed between the protective structure and the light emitting structure;

[0009] a reflective insulating layer covering the light-emitting structure, the protective structure and the first groove;

[0010] An N-type pad is provided above the N-type electrode and electrically connected to the N-type electrode; and a P-type pad is provided above the P-type electrode and electrically connected to the P-type electrode.

[0011] As an improvement of the above technical solution, the width of the protection structure is 5 to 20 μm, and the width of the first groove is 2 to 10 μm.

[0012] As an improvement to the above technical solution, the protection structure includes 3 to 5 protection substructures, and a second groove exposing the substrate is provided between adjacent protection substructures;

[0013] The width of the protection substructure is 4-8 μm, and the width of the second groove is 3-5 μm.

[0014] As an improvement to the above technical solution, the widths of the plurality of protection substructures decrease from a side close to the light emitting structure to a side far away from the light emitting structure;

[0015] The widths of adjacent second grooves are the same.

[0016] As an improvement of the above technical solution, the surface and sidewall of the protection structure are provided with an insulating layer; the insulating layer is made of SiO2, SiN x , Al2O3, and its thickness is or

[0017] The surface and sidewall of the protective structure are provided with an adhesion layer and an insulation layer in sequence; the adhesion layer is made of one or more of Ti, Cr, and TiW, and its thickness is The insulating layer is made of SiO2, SiN x , Al2O3, and its thickness is

[0018] As an improvement of the above technical solution, the surface and sidewall of the protection structure are provided with an adhesion layer and an insulation layer in sequence; the adhesion layer is made of Ti and has a thickness of The insulating layer is made of SiO2 and has a thickness of

[0019] As an improvement to the above technical solution, it further includes a current blocking layer and a transparent conductive layer sequentially arranged between the P-type semiconductor layer and the P-type electrode;

[0020] The current blocking layer is made of SiO2, SiN x , Al2O3, and its thickness is

[0021]

[0022] The transparent conductive layer is made of one or more of ITO, IZO, AZO, and FTO, and its thickness is

[0023]

[0024] Correspondingly, the present invention also discloses a method for preparing a flip-chip LED chip, which is used to prepare the above-mentioned flip-chip LED chip, and comprises:

[0025] (1) forming an epitaxial layer on a substrate, wherein the epitaxial layer includes an N-type semiconductor layer, an active light-emitting layer, and a P-type semiconductor layer sequentially stacked on the substrate;

[0026] (2) etching to form a first groove exposing the substrate, wherein the first groove divides the epitaxial layer into a light-emitting area and a protective structure surrounding the light-emitting area;

[0027] (3) etching the epitaxial layer in the light-emitting region to form a conductive step exposing the N-type semiconductor layer;

[0028] (4) forming a P-type electrode on the P-type semiconductor layer in the light-emitting region and forming an N-type electrode on the conductive step to obtain a light-emitting structure;

[0029] (5) forming a reflective insulating layer; the reflective insulating layer covers the light-emitting structure, the protective structure, and the first groove;

[0030] (6) Form a P-type pad and an N-type pad.

[0031] As an improvement of the above technical solution, step (2) includes:

[0032] (2.1) etching to form a first groove exposing the substrate;

[0033] (2.2) forming an adhesion layer on the surface of the protective structure;

[0034] (2.3) An insulating layer is formed on the surface of the adhesion layer, and the insulating layer in a predetermined area on the P-type semiconductor layer on the light-emitting area is retained as a current blocking layer.

[0035] As an improvement of the above technical solution, in step (2.2), Ti is evaporated on the surface of the protective structure and then oxidized in an oxygen-containing atmosphere to obtain an adhesion layer.

[0036] The implementation of the present invention has the following beneficial effects:

[0037] A flip-chip LED chip in one embodiment of the present invention includes a substrate, a light-emitting structure, a protective structure, a reflective insulating layer, an N-type pad, and a P-type pad. The light-emitting structure includes an N-type semiconductor layer, an active light-emitting layer, a P-type semiconductor layer, an N-type electrode, and a P-type electrode. The N-type semiconductor layer, the active light-emitting layer, the P-type semiconductor layer, and the P-type electrode are sequentially stacked on the substrate. The light-emitting structure is provided with a conductive step exposing the N-type semiconductor layer, and the N-type electrode is provided on the conductive step. The protective structure is provided on the substrate and surrounds the light-emitting structure, forming a first groove exposing the substrate between the protective structure and the light-emitting structure, thereby insulating the protective structure from the light-emitting structure. Due to the provision of this protective structure, when water vapor intrudes into the flip-chip LED chip under high temperature and high humidity conditions, the protective structure and the first groove serve to prevent the spread of water vapor. That is, the water vapor first corrodes the protective structure, and then serves to protect the light-emitting structure, thereby improving the reliability of the flip-chip LED chip. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 1 is a schematic cross-sectional view of a flip-chip LED chip according to an embodiment of the present invention;

[0039] Figure 2 1 is a schematic diagram of a top view of a flip-chip LED chip according to an embodiment of the present invention;

[0040] Figure 3 is a schematic cross-sectional view of a flip-chip LED chip according to another embodiment of the present invention;

[0041] Figure 4 2 is a schematic cross-sectional view of a flip-chip LED chip according to another embodiment of the present invention;

[0042] In the figure, 1 is the substrate, 2 is the light-emitting structure, 21 is the epitaxial layer, 211 is the N-type semiconductor layer, 212 is the active light-emitting layer, and 213 is the P-type semiconductor layer. 214 is the conductive step, 22 is the N-type electrode, 23 is the P-type electrode, 24 is the isolation trench, 3 is the protection structure, 31 is the protection substructure, 32 is the second groove, 33 is the adhesion layer, 34 is the insulation layer, 4 is the first groove, 5 is the reflective insulation layer, 51 is the N-type via, 52 is the P-type via, 6 is the N-type pad, 7 is the P-type pad, 8 is the current blocking layer, and 9 is the transparent conductive layer. DETAILED DESCRIPTION

[0043] To make the objectives, technical solutions, and advantages of the present invention more apparent, the present invention will be described in further detail below with reference to the accompanying drawings. It is hereby stated that any directional terms such as "up," "down," "left," "right," "front," "back," "inside," and "outside" that appear or will appear herein are based solely on the accompanying drawings and are not intended to limit the present invention.

[0044] See also Figure 1 、 Figure 2 The present invention provides a flip-chip LED chip, which includes a substrate 1, a light-emitting structure 2, a protective structure 3, a reflective insulating layer 5, an N-type pad 6, and a P-type pad 7. The light-emitting structure 2 includes an N-type semiconductor layer 211, an active light-emitting layer 212, a P-type semiconductor layer 213, an N-type electrode 22, and a P-type electrode 23. The N-type semiconductor layer 211, the active light-emitting layer 212, the P-type semiconductor layer 213, and the P-type electrode 23 are sequentially stacked on the substrate 1. The light-emitting structure 2 is provided with a conductive step 214 exposing the N-type semiconductor layer 211, and the N-type electrode 22 is provided on the conductive step 214. The protective structure 3 is provided on the substrate 1 and surrounds the light-emitting structure 2. A first groove 4 exposing the substrate 1 is formed between the protective structure 3 and the light-emitting structure 2, that is, the protective structure 3 is insulated from the light-emitting structure 2. Through the setting of the protective structure 3, when water vapor invades the flip-chip LED chip under high temperature and high humidity conditions, the protective structure 3 and the first groove 4 play a role in blocking the spread of water vapor, that is, the water vapor first corrodes the protective structure 3, and then plays a role in protecting the light-emitting structure 2, thereby improving the reliability of the flip-chip LED chip.

[0045] The reflective insulating layer 5 covers the light-emitting structure 2, the protective structure 3, and the first groove 4. Specifically, the reflective insulating layer 5 covers the surface and sidewalls of the light-emitting structure 2, the surface and sidewalls of the protective structure 3, and the surface and sidewalls of the first groove 4. The provision of the reflective insulating layer 5 not only achieves light reflection but also effectively passivates defects on the sidewalls of the light-emitting structure 2 and the protective structure 3, further improving the reliability of the flip-chip LED chip.

[0046] N-type pad 6 is disposed above and electrically connected to N-type electrode 22. In some embodiments, N-type pad 6 is electrically connected to N-type electrode 22 via N-type via 51 disposed on reflective insulating layer 5. P-type pad 7 is disposed above and electrically connected to P-type electrode 23. In some embodiments, P-type pad 7 is electrically connected to P-type electrode 23 via P-type via 52 disposed on reflective insulating layer 5.

[0047] Specifically, the substrate 1 is a sapphire substrate, a silicon substrate, or a SiC substrate, but is not limited thereto. The N-type semiconductor layer 211 may be an N-type GaAs layer, an N-type GaN layer, or an N-type AlGaN layer, but is not limited thereto. The active light-emitting layer 212 may be an InGaN-GaN type multi-quantum well layer, an InGaN-AlGaN type multi-quantum well layer, an AlGaN-AlGaN type multi-quantum well layer, or an AlGaInP-AlGaInP type multi-quantum well layer, but is not limited thereto. The P-type semiconductor layer 213 may be a P-type GaN layer, a P-type AlGaInP layer, or a P-type AlGaN layer, but is not limited thereto. Preferably, in some embodiments, the substrate 1 is a sapphire substrate, the N-type semiconductor layer 211 is an N-type GaN layer, the active light-emitting layer 212 is an InGaN-GaN type multi-quantum well layer, and the P-type semiconductor layer 213 is a P-type GaN layer. Specifically, the thickness of the N-type semiconductor layer 211 is 1-5 μm, the thickness of the active light emitting layer 212 is 20-200 nm, and the thickness of the P-type semiconductor layer 213 is 200-500 nm.

[0048] Correspondingly, the protection structure 3 also includes an N-type semiconductor layer 211, an active light emitting layer 212, and a P-type semiconductor layer 213 stacked in sequence, and the specific materials thereof are selected as described above.

[0049] Specifically, the N-type electrode 22 and the P-type electrode 23 are both metal single-layer or laminated structures commonly used in the art, and can be made of one or more of Cr, Al, Ti, Pt, Ni, Au, Cu, and Ag, but are not limited thereto. Preferably, in some embodiments, the N-type electrode 22 and the P-type electrode 23 each include a Cr layer, an Al layer, a Ti layer, a Ni layer, an Au layer, and a Pt layer stacked in sequence, with thicknesses of 100 nm and 100 nm, respectively. and

[0050] Specifically, the reflective insulating layer 5 is a DBR layer commonly found in the art, and may be, but is not limited to, a SiO2-TiO2 DBR layer, a SiO2-Ti2O5 DBR layer, a SiO2-Ti3O5 DBR layer, or an AlGaAs / AlGaAs DBR layer. Preferably, the reflective insulating layer 5 is a SiO2-TiO2 DBR layer having 20 to 30 periods, i.e., comprising 20 to 30 pairs of SiO2-TiO2 stacks. The thickness of a single SiO2 layer is 70 to 150 nm, and the thickness of a single TiO2 layer is 50 to 100 nm.

[0051] Specifically, the N-type pad 6 and the P-type pad 7 are metal pad structures commonly used in the art, such as a stacked structure composed of one or more of Ti, Sn, Ni, Au, etc., but not limited thereto. Preferably, the N-type pad 6 and the P-type pad 7 each include a Ti layer, an Al layer, a Ti layer, a Ni layer and an Au layer stacked in sequence, with thicknesses of 100 nm and 100 nm, respectively. and

[0052] Specifically, the surface areas of the N-type pad 6 and the P-type pad 7 can be the same or different. Preferably, they are the same. The projections of the N-type pad 6 and the P-type pad 7 on the surface of the substrate 1 are both inside the first groove 4, thereby further improving the reliability of the flip-chip LED chip.

[0053] Specifically, the width of the protective structure 3, i.e., its projected width on the surface of the substrate 1, is 4 to 25 μm. If its width is less than 4 μm, it will be difficult to effectively prevent moisture from diffusing toward the light-emitting structure 2 under high temperature and high humidity conditions, making it difficult to effectively improve reliability. If its width is greater than 25 μm, it will occupy too large a light-emitting area, reducing light efficiency. Exemplarily, the width of the protective structure 3 is 7 μm, 10 μm, 13 μm, 16 μm, 19 μm, or 22 μm, but is not limited thereto. Preferably, it is 5 to 20 μm.

[0054] Specifically, the width of the first groove 4 is 2 to 15 μm. If the width is too small, it is difficult to effectively improve reliability; if the width is too large, the light efficiency is reduced. For example, the width of the first groove 4 is 3 μm, 6 μm, 9 μm, or 12 μm, but is not limited thereto. Preferably, it is 2 to 10 μm.

[0055] Preferably, in some embodiments, an isolation groove 24 is further provided on the side of the protection structure 3 away from the light emitting structure 2, the surface of which is only covered by the reflective insulating layer 5. The width of the isolation groove 24 is 2-15 μm, preferably 2-10 μm.

[0056] Preferably, in some embodiments, the surface and sidewalls of the protection structure 3 are provided with an insulating layer 34; the insulating layer 34 is made of SiO2, SiNx , Al2O3, the insulating layer 34 can slow down the corrosion of the protective structure 3 by water vapor, thereby slowing down the speed at which water vapor enters the light emitting structure 2, further improving the reliability of the flip-chip LED chip. Specifically, in this embodiment, the thickness of the insulating layer 34 is For example, or But it’s not limited to this.

[0057] More preferably, see Figure 3 In other embodiments, the surface and sidewalls of the protective structure 3 are sequentially provided with an adhesion layer 33 and an insulating layer 34; the adhesion layer 33 is made of one or more of Ti, Cr, and TiW, and the insulating layer 34 is made of SiO2, SiN x , Al2O3. The adhesion layer 33 effectively enhances the adhesion between the protective structure 3 and the insulating layer 34, significantly slowing the rate of water vapor corrosion and improving the reliability of the flip-chip LED chip. Furthermore, the provision of the adhesion layer 33 reduces the thickness of the insulating layer 34, allowing the current blocking layer 8 to be simultaneously formed on the P-type semiconductor layer 213 during the formation of the insulating layer 34, thereby improving process efficiency. It should be noted that while the current blocking layer optimizes current distribution, if its thickness is too large, it can, for example, cause fractures in the transparent conductive layer and P-type electrode at their sidewalls. Furthermore, the current blocking layer itself is a high-resistivity material, which can significantly increase the forward voltage of the flip-chip LED chip. Furthermore, if the current blocking layer is too thick, it can also affect light scattering and absorption, reducing light extraction efficiency. Therefore, the thickness of the current blocking layer must be carefully controlled and should not be excessively thick. On the other hand, the insulating layer deposited on the surface of the protective structure 3 is primarily intended to reduce the corrosion rate. Clearly, a thicker layer is more effective in resisting corrosion. This results in a performance conflict between the two. The present invention addresses this issue by introducing the adhesion layer 33. Specifically, based on this embodiment, the thickness of the adhesive layer 33 is For example, or But not limited to this. The thickness of the insulating layer 34 is For example, or But not limited to this. Further preferably, the adhesion layer 33 is made of Ti and has a thickness of The insulating layer 34 is made of SiO2 and has a thickness of

[0058] Preferably, see Figure 4In some embodiments, the protective structure 3 includes multiple protective substructures 31. Second grooves 32 exposing the substrate 1 are located between adjacent protective substructures 31. Each protective substructure 31 has a width of 4 to 8 μm, while the width of the second grooves 32 ranges from 3 to 5 μm. This embodiment further blocks the diffusion of moisture and improves reliability. More specifically, the protective structure 3 includes 3 to 5 protective substructures 31.

[0059] Specifically, the widths of the multiple protective substructures 31 may be the same or different, and the spacing between adjacent protective substructures 31 (i.e., the widths of the second grooves 32) may be the same or different. Preferably, in some embodiments, the widths of the multiple protective substructures 31 decrease from the side closest to the light-emitting structure 2 to the side further away from the light-emitting structure 2; the widths of adjacent second grooves 32 are all the same. Based on this embodiment, the reliability of the flip-chip LED chip can be further improved.

[0060] Preferably, in some embodiments, a current blocking layer 8 and a transparent conductive layer 9 are sequentially provided between the P-type semiconductor layer 213 and the P-type electrode 23. The current blocking layer 8 is made of SiO2, SiN x , Al2O3, the current blocking layer 8 can reduce the vertical transmission of current, and the transparent conductive layer 9 can increase the horizontal transmission of current. The combination of the two can optimize the current distribution, avoid local overheating, and further improve reliability. Specifically, based on this embodiment, the thickness of the current blocking layer 8 is For example, or But not limited to this. The thickness of the transparent conductive layer 9 is For example, or But it’s not limited to this.

[0061] It should be noted that the flip-chip LED chip of the present invention may also include, but is not limited to, structures such as a P-type contact layer and an electron blocking layer (not shown in the accompanying drawings) commonly found in the art. The P-type contact layer is disposed between the P-type semiconductor layer 213 and the transparent conductive layer 9 and may be, but is not limited to, a P-type InGaN layer or a P-type GaN layer. The electron blocking layer is disposed between the P-type semiconductor layer 213 and the active light-emitting layer 212 and may be, but is not limited to, a P-type AlGaN layer.

[0062] Correspondingly, the present invention also discloses a method for preparing a flip-chip LED chip, which is used to prepare the above-mentioned flip-chip LED chip, and specifically comprises the following steps:

[0063] (1) forming an epitaxial layer on a substrate;

[0064] Specifically, an N-type semiconductor layer 211, an active light-emitting layer 212, and an N-type semiconductor layer 211 are sequentially formed on the substrate 1 by MOCVD, MBE, PVD, or other methods, thereby obtaining the epitaxial layer 21. In some embodiments, the process further includes forming an electron blocking layer and a P-type contact layer.

[0065] (2) etching to form a first groove exposing the substrate;

[0066] Specifically, a mask (a photoresist layer or a SiO2 layer) can be first formed on the epitaxial layer 21, and then the P-type semiconductor layer 213, the active light-emitting layer 212, and the P-type semiconductor layer 213 in a predetermined area are removed by wet etching or dry etching to form a first groove 4 exposing the substrate 1. The first groove 4 divides the epitaxial layer 21 into a light-emitting area and a protective structure 3 surrounding the light-emitting area. Preferably, in some embodiments, a photoresist layer is first formed on the epitaxial layer 21, then exposed and developed, and then dry-etched to form the first groove 4, and finally the photoresist layer is removed.

[0067] Preferably, in some embodiments, when forming the first groove 4 , the second groove 32 may be further formed by etching, thereby obtaining a plurality of protection substructures 31 .

[0068] Preferably, in this step, an isolation groove 24 can be further etched to form the substrate 1 to separate the substrate 1 and form a single flip-chip LED chip. The isolation groove 24 is provided on the side of the protection structure 3 away from the light emitting area.

[0069] Preferably, in some embodiments, step (2) comprises:

[0070] (2.1) etching to form a first groove exposing the substrate;

[0071] (2.2) forming an adhesion layer on the surface of the protective structure;

[0072] Specifically, a photoresist layer may be formed first, and the protective structure 3 may be exposed after exposure and development. An adhesion layer 33 may then be formed on the surface of the protective structure 3 by an electron beam evaporation coating process (i.e., vapor deposition) or a PVD method. The photoresist layer and the adhesion layer 33 thereon may then be removed.

[0073] Preferably, in some embodiments, Ti is first evaporated on the surface of the adhesion layer 33, and then annealed and oxidized in an oxygen-containing atmosphere (such as O2, N2O, etc.) to form the adhesion layer 33. More preferably, the annealing and oxidation are performed in a PECVD device. Through the annealing and oxidation, the Ti surface can be fully oxidized, further optimizing the bonding between the adhesion layer 33 and the insulating layer 34.

[0074] (2.3) An insulating layer is formed on the surface of the adhesion layer, and the insulating layer in a predetermined area on the P-type semiconductor layer above the light-emitting area is retained as a current blocking layer.

[0075] Specifically, in some embodiments, a photoresist layer is first formed, and after exposure and development, the protective structure 3 with the adhesion layer 33 and the area for forming the current blocking layer 8 are exposed, and then the insulating layer 34 is formed. The insulating layer 34 can be formed by a PECVD method or a PVD method, but is not limited thereto.

[0076] In other embodiments, the insulating layer 34 is first formed, and then a photoresist layer is formed, followed by exposure and development to expose the area where the insulating layer 34 needs to be removed, and then the insulating layer 34 is removed by etching, and finally the photoresist layer is removed.

[0077] (3) etching the epitaxial layer in the light-emitting region to form a conductive step exposing the N-type semiconductor layer;

[0078] Specifically, a mask (a photoresist layer or a SiO2 layer) can be first formed on the substrate 1 obtained in step (2), and then the P-type semiconductor layer 213, the active light-emitting layer 212, and the N-type semiconductor layer 211 of a predetermined thickness in the predetermined light-emitting region are removed by wet etching or dry etching to form a conductive step 214 that exposes the N-type semiconductor layer 211, but the present invention is not limited thereto. Preferably, in some embodiments, a photoresist layer is first formed on the epitaxial layer 21, then exposed and developed, and then dry-etched to form the conductive step 214, and finally the photoresist layer is removed.

[0079] Preferably, in some embodiments, step (3) comprises:

[0080] (3.1) forming a transparent conductive layer on the epitaxial layer in the light emitting region;

[0081] Specifically, in some embodiments, a photoresist layer is first formed, and the P-type semiconductor layer 213 in the light-emitting area is exposed after exposure and development. Then, a transparent conductive layer 9 is formed by PVD or CVD, and then the photoresist layer and the transparent conductive layer 9 thereon are removed.

[0082] In other embodiments, a transparent conductive layer 9 is formed on the substrate 1 obtained in step (2), and then a photoresist layer is formed. The area where the transparent conductive layer 9 needs to be removed is exposed by exposure and development, and then the transparent conductive layer 9 in the area is corroded and removed, and finally the transparent conductive layer 9 is removed.

[0083] (3.2) Etching the epitaxial layer and the transparent conductive layer in the light-emitting area to form a conductive step exposing the N-type semiconductor layer;

[0084] Specifically, the transparent conductive layer 9 and the conductive step 214 may be formed through one photolithography-etching process or two photolithography-etching processes, but is not limited thereto.

[0085] (4) forming a P-type electrode on the P-type semiconductor layer in the light-emitting region and forming an N-type electrode on the conductive step to obtain a light-emitting structure;

[0086] Specifically, in some embodiments, a photoresist layer is first formed on the substrate 1 obtained in step (3), and a portion of the P-type semiconductor layer 213 and a portion of the conductive step 214 are exposed and developed, and then the N-type electrode 22 and the P-type electrode 23 are formed by an electron beam evaporation coating process or a PVD method, and then the photoresist layer and the metal layer thereon are removed to obtain the N-type electrode 22 and the P-type electrode 23, but the present invention is not limited thereto.

[0087] (5) forming a reflective insulating layer;

[0088] Specifically, in some embodiments, the reflective insulating layer 5 is formed by a PECVD method, a PVD method, or an electron beam evaporation coating method, but is not limited thereto.

[0089] Preferably, in some embodiments, after forming the reflective insulating layer 5 , the step of opening the reflective insulating layer 5 to form N-type through holes 51 and P-type through holes 52 is further included, which can be achieved by a photolithography and etching process, but is not limited thereto.

[0090] (6) forming a P-type pad and an N-type pad;

[0091] Specifically, in some embodiments, a photoresist layer is first formed on the substrate 1 obtained in step (5), and is exposed and developed to expose the P-type through hole 52, the N-type through hole 51, and the reflective insulating layer 5 in the preset area around the two. Then, the N-type pad 6 and the P-type pad 7 are formed by an electron beam evaporation coating process or a PVD method. Finally, the photoresist layer and the metal layer thereon are removed to obtain the N-type pad 6 and the P-type pad 7, but the present invention is not limited thereto.

[0092] The present invention will be further described below with reference to specific embodiments.

[0093] Example 1

[0094] This embodiment provides a flip-chip LED chip, which includes a substrate, a light-emitting structure, a protective structure, a reflective insulating layer, an N-type pad, and a P-type pad. The light-emitting structure includes an N-type GaN layer, an active light-emitting layer (InGaN-GaN type multi-quantum well layer), a P-type semiconductor layer (P-type GaN layer), a current blocking layer (SiO2 layer with a thickness of ), transparent conductive layer (ITO layer, thickness ), N-type electrode and P-type electrode. The N-type semiconductor layer, active light-emitting layer, P-type semiconductor layer, current blocking layer, transparent conductive layer and P-type electrode are sequentially stacked on the substrate. The light-emitting structure is provided with a conductive step exposing the N-type semiconductor layer, and the N-type electrode is provided on the conductive step. The N-type electrode and the P-type electrode each include a Cr layer, an Al layer, a Ti layer, a Ni layer, an Au layer and a Pt layer stacked in sequence, and their thicknesses are respectively and

[0095] The protective structure is provided on the substrate and surrounds the light emitting structure, and a first groove exposing the substrate is formed between the protective structure and the light emitting structure. The width of the first groove is 10 μm, and the width of the protective structure is 20 μm. The protective structure includes an N-type semiconductor layer, an active light emitting layer (InGaN-GaN type multi-quantum well layer), and a P-type semiconductor layer (P-type GaN layer) stacked in sequence. The surface and sidewalls of the protective structure are sequentially stacked with an adhesion layer (Ti layer with a thickness of ) and insulating layer (SiO2 layer, thickness An isolation groove is provided on a side of the protection structure away from the light emitting structure, and the width of the isolation groove is 10 μm.

[0096] The reflective insulating layer comprises alternating SiO2 and TiO2 layers, with a period of 22. The thickness of a single SiO2 layer is 110 nm, and the thickness of a single TiO2 layer is 60 nm. The reflective insulating layer covers the light-emitting structure, the first recess, and the sidewalls and surface of the protective structure. An N-type via is provided above the N-type electrode, penetrating the reflective insulating layer. A P-type via is provided above the P-type electrode, penetrating the reflective insulating layer.

[0097] Among them, the N-type pad and the P-type pad both include a Ti layer, an Al layer, a Ti layer, a Ni layer and an Au layer stacked in sequence, and their thicknesses are respectively and The N-type pad is arranged on the reflective insulating layer and is electrically connected to the N-type electrode through the N-type through hole. The P-type pad is arranged on the reflective insulating layer and is electrically connected to the P-type electrode through the P-type through hole.

[0098] Example 2

[0099] This embodiment provides a flip-chip LED chip, which differs from the first embodiment in that:

[0100] The protection structure includes a first protection substructure, a second protection substructure and a third protection substructure, which are evenly distributed from the side close to the light emitting structure to the side far away from the light emitting structure. A first groove is provided between the first protection substructure and the light emitting structure.

[0101] The width of the first protecting substructure is 4 μm, the width of the second protecting substructure is 6 μm, the width of the third protecting substructure is 8 μm, and the width of the second groove therebetween is 5 μm.

[0102] The rest are the same as in Example 1.

[0103] Example 3

[0104] This embodiment provides a flip-chip LED chip, which differs from the first embodiment in that:

[0105] The protective structure includes a first protective substructure, a second protective substructure, a third protective substructure, a fourth protective substructure, and a fifth protective substructure, which are evenly spaced from the side closest to the light-emitting structure to the side farther away from the light-emitting structure. A first groove with a width of 5μm is provided between the first protective substructure and the light-emitting structure, and the isolation groove is also 5μm wide.

[0106] The width of the first protection substructure is 4 μm, the width of the second protection substructure is 5 μm, the width of the third protection substructure is 6 μm, the width of the fourth protection substructure is 7 μm, the width of the fifth protection substructure is 8 μm, and the width of the second groove therebetween is 3 μm.

[0107] Example 4

[0108] This embodiment provides a flip-chip LED chip, which differs from the first embodiment in that:

[0109] The protective structure includes a first protective substructure, a second protective substructure, a third protective substructure, a fourth protective substructure, and a fifth protective substructure, which are evenly spaced from the side closest to the light-emitting structure to the side farther away from the light-emitting structure. A first groove with a width of 8μm is provided between the first protective substructure and the light-emitting structure, and the isolation groove is also 8μm wide.

[0110] The width of the first protection substructure is 4 μm, the width of the second protection substructure is 5 μm, the width of the third protection substructure is 6 μm, the width of the fourth protection substructure is 7 μm, the width of the fifth protection substructure is 8 μm, and the width of the second groove therebetween is 4 μm.

[0111] Comparative Example 1

[0112] This comparative example provides a flip-chip LED chip, which differs from Example 1 in that no protective structure is provided. The rest is the same as Example 1.

[0113] The flip-chip LED chips obtained in Examples 1 to 3 and Comparative Example 1 were tested. Specifically, an aging test was conducted at a high temperature of 85°C and a high humidity of 85%. Every 24 hours, the flip-chip LED chips were subjected to a reverse voltage test of -10V. The reverse leakage current value was recorded. When this value was greater than 0.5μA, it indicated that the chip had aged and failed. The longer the aging time, the better. The specific test results are shown in the following table:

[0114] Aging time / h Example 1 1008 Example 2 1104 Example 3 1248 Comparative Example 1 384

[0115] It can be seen from the above table that the aging time of the flip-chip LED chip of the present invention is much longer than that of the prior art (Example 1), which shows that the flip-chip LED chip structure of the present invention is highly reliable.

[0116] The above is a preferred embodiment of the invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A flip-chip LED chip, characterized in that: include substrate; A light-emitting structure comprising an N-type semiconductor layer, an active light-emitting layer, a P-type semiconductor layer, and a P-type electrode sequentially stacked on the substrate; the light-emitting structure is provided with a conductive step exposing the N-type semiconductor layer, and the N-type electrode is provided on the conductive step; a protective structure disposed around the light emitting structure, wherein a first groove exposing the substrate is formed between the protective structure and the light emitting structure; a reflective insulating layer covering the light-emitting structure, the protective structure and the first groove; an N-type pad, which is disposed above the N-type electrode and electrically connected to the N-type electrode; as well as The P-type pad is arranged above the P-type electrode and is connected to the P-type electrode.

2. The flip-chip LED chip according to claim 1, wherein: The width of the protection structure is 5 to 20 μm, and the width of the first groove is 2 to 10 μm.

3. The flip-chip LED chip according to claim 1, wherein: The protection structure includes 3 to 5 protection substructures, and a second groove exposing the substrate is provided between adjacent protection substructures; The width of the protection substructure is 4-8 μm, and the width of the second groove is 3-5 μm.

4. The flip-chip LED chip according to claim 3, wherein: The widths of the plurality of protection substructures decrease gradually from a side close to the light emitting structure to a side away from the light emitting structure; The widths of adjacent second grooves are the same.

5. The flip-chip LED chip according to claim 1, wherein: The surface and sidewall of the protection structure are provided with an insulating layer; the insulating layer is made of SiO2, SiN x , Al2O3, and its thickness is or The surface and sidewall of the protective structure are provided with an adhesion layer and an insulation layer in sequence; the adhesion layer is made of one or more of Ti, Cr, and TiW, and its thickness is The insulating layer is made of SiO2, SiN x , Al2O3, and its thickness is 6. The flip-chip LED chip according to claim 1, wherein: The surface and sidewall of the protective structure are provided with an adhesion layer and an insulation layer in sequence; the adhesion layer is made of Ti and has a thickness of The insulating layer is made of SiO2 and has a thickness of 7. The flip-chip LED chip according to claim 1, wherein: It also includes a current blocking layer and a transparent conductive layer sequentially arranged between the P-type semiconductor layer and the P-type electrode; The current blocking layer is made of SiO2, SiN x , Al2O3, and its thickness is The transparent conductive layer is made of one or more of ITO, IZO, AZO, and FTO, and its thickness is 8. A method for preparing a flip-chip LED chip, for preparing the flip-chip LED chip according to any one of claims 1 to 7, characterized in that: include: (1) forming an epitaxial layer on a substrate, wherein the epitaxial layer includes an N-type semiconductor layer, an active light-emitting layer, and a P-type semiconductor layer sequentially stacked on the substrate; (2) etching to form a first groove exposing the substrate, wherein the first groove divides the epitaxial layer into a light-emitting area and a protective structure surrounding the light-emitting area; (3) etching the epitaxial layer in the light-emitting region to form a conductive step exposing the N-type semiconductor layer; (4) forming a P-type electrode on the P-type semiconductor layer in the light-emitting region and forming an N-type electrode on the conductive step to obtain a light-emitting structure; (5) forming a reflective insulating layer; the reflective insulating layer covers the light-emitting structure, the protective structure, and the first groove; (6) Form a P-type pad and an N-type pad.

9. The method for preparing a flip-chip LED chip according to claim 8, wherein: Step (2) includes: (2.1) etching to form a first groove exposing the substrate; (2.2) forming an adhesion layer on the surface of the protective structure; (2.3) An insulating layer is formed on the surface of the adhesion layer, and the insulating layer in a predetermined area on the P-type semiconductor layer on the light-emitting area is retained as a current blocking layer.

10. The method for preparing a flip-chip LED chip according to claim 9, wherein: In step (2.2), Ti is evaporated on the surface of the protective structure and then oxidized in an oxygen-containing atmosphere to obtain an adhesion layer.

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