Flip light emitting diode chip

Abstract

The utility model provides a flip light-emitting diode chip. The flip light-emitting diode chip comprises a substrate, and an epitaxial layer, an electrode layer, a current expansion layer, a Bragg reflection layer and a bonding pad layer which are sequentially laminated on the substrate, wherein the bonding pad layer comprises a reflection part, an isolation part, a welding part and a protection part which are sequentially arranged on the electrode layer, the welding part comprises M first Ni metal layers and Ag metal layers which are periodically and alternately arranged, a second Ni metal layer is arranged between the welding part and the protection part, and the first Ni metal layer and the Ag metal layer are arranged along the direction from the isolation part to the welding part. The thickness ratio of the first Ni metal layer to the Ag metal layer in each period is linearly increased, and the thickness of the first Ni metal layer in each period is sequentially increased, the laminated layer of Ni metal and Ag metal is used as the welding part of the flip light emitting diode chip bonding pad, and Au metal used as the welding part in a traditional flip light emitting diode is replaced; therefore, the production and manufacturing cost of the flip-chip light-emitting diode is greatly reduced.

Description

Technical Field

[0001] The utility model belongs to the technical field of LED chips, and specifically relates to a flip-chip light emitting diode chip. Background Art

[0002] In recent years, the technology of light-emitting diode chips has developed rapidly. It has been widely used in various fields such as general lighting, special lighting, direct display screens, backlight display screens, and car lights. Flip-chip light-emitting diode chips have the advantages of resistance to large current impacts, high reliability, and high luminous efficiency.

[0003] The soldering layer (i.e., the top layer) of the pad of the existing flip-chip LED is Au metal. When the flip-chip LED chip is packaged on a PCB board, Sn metal can be printed on the PCB, and then the Au metal on the top layer of the flip-chip LED chip pad and the Sn metal on the pad are reflowed to form a eutectic, thereby soldering the flip-chip LED chip on the PCB. However, Au metal is relatively expensive, which greatly increases the production cost. Utility Model Content

[0004] In order to solve the above technical problems, the utility model provides a flip-chip light emitting diode chip, which is used to solve the technical problems raised by the above background technology.

[0005] The utility model provides the following technical solution: a flip-chip light-emitting diode chip, comprising a substrate and an epitaxial layer, an electrode layer, a current spreading layer, a Bragg reflection layer and a pad layer stacked in sequence on the substrate, wherein the Bragg reflection layer is provided with a Bragg reflection layer through hole penetrating to the electrode layer, and the pad layer contacts the electrode layer through the Bragg reflection through hole;

[0006] Among them, the pad layer includes a reflecting part, an isolating part, a welding part and a protective part which are sequentially arranged on the electrode layer, the welding part includes M first Ni metal layers and Ag metal layers which are periodically alternately arranged, and a second Ni metal layer is arranged between the welding part and the protective part. Along the direction from the isolating part to the welding part, the thickness ratio between the first Ni metal layer and the Ag metal layer in each period increases linearly and the thickness of the first Ni metal layer in each period increases sequentially.

[0007] Compared with the prior art, the beneficial effects of the present application are as follows: the present application utilizes a stack of Ni metal and Ag metal as the welding part of the flip-chip light-emitting diode chip pad, replacing the Au metal used as the welding part in the traditional flip-chip light-emitting diode, thereby greatly reducing the production cost of the flip-chip light-emitting diode.

[0008] Preferably, a period M of the alternating arrangement of the first Ni metal layer and the Ag metal layer is in the range of 5≤M≤7.

[0009] Preferably, the epitaxial layer includes an N-type semiconductor layer, an active light-emitting layer, and a P-type semiconductor layer which are sequentially stacked on the substrate.

[0010] Preferably, the electrode layer includes a P-type electrode and an N-type electrode, the P-type electrode is arranged on the P-type semiconductor layer, and the N-type electrode is arranged on the N-type semiconductor layer.

[0011] Preferably, the reflective portion is a metal Al layer.

[0012] Preferably, the isolation portion is a metal TiW layer.

[0013] Preferably, the protective layer is a rosin layer.

[0014] Preferably, a thickness ratio between the first Ni metal layer and the Ag metal layer in the same period is 5:1 to 80:1.

[0015] Preferably, the thickness of the first Ni metal layer is 50nm-400nm.

[0016] Preferably, the thickness of the second Ni metal layer is 200nm-400nm. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0018] Figure 1 A structural diagram of a flip-chip light-emitting diode chip provided by an embodiment of the utility model;

[0019] Figure 2 for Figure 1 A magnified view of the structure in Figure 2.

[0020] Description of reference numerals:

[0021] Substrate 1 Epitaxial layer 2 N-type semiconductor layer 21 Active light emitting layer 22 P-type semiconductor layer 23 N-type electrode 31 P-type electrode 32 Current spreading layer 4 Bragg reflector 5 Pad layer 6 Reflection 61 Isolation Department 62 Welding Department 63 First Ni metal layer 631 Ag metal layer 632 Second Ni metal layer 64 Protective layer 65

[0022] The embodiments of the utility model will be further described below in conjunction with the accompanying drawings. DETAILED DESCRIPTION

[0023] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the embodiments of the present invention, and should not be construed as limiting the present invention.

[0024] In the description of the embodiments of the present invention, it should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc. indicating orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0025] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present utility model, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0026] In the embodiments of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present invention can be understood according to specific circumstances.

[0027] In the embodiment of the present utility model, Figure 1 As shown, a flip-chip light-emitting diode chip comprises a substrate 1 and an epitaxial layer 2, an electrode layer, a current spreading layer 4, a Bragg reflection layer 5 and a pad layer 6 sequentially stacked on the substrate 1, wherein the Bragg reflection layer 5 is provided with a Bragg reflection layer through hole penetrating to the electrode layer, and the pad layer 6 contacts the electrode layer through the Bragg reflection through hole;

[0028] The pad layer 6 includes a reflective portion 61, an isolating portion 62, a welding portion 63 and a protective portion 65 which are sequentially arranged on the electrode layer, the welding portion 63 includes M first Ni metal layers 631 and Ag metal layers 632 which are periodically and alternately arranged, a second Ni metal layer 64 is provided between the welding portion 63 and the protective portion 65, and along the direction from the isolating portion 62 to the welding portion 63, the thickness ratio between the first Ni metal layer 631 and the Ag metal layer 632 in each period increases linearly and the thickness of the first Ni metal layer 631 in each period increases sequentially;

[0029] Specifically, the welding part 63 includes a plurality of first Ni metal layers 631 and Ag metal layers 632 that are periodically and alternately arranged, wherein the first Ni metal layer 631 of the first period is disposed on the isolation part 62, and the Ag metal layer 632 of the last period is disposed below the second Ni metal layer 64, wherein the reflection part 61 is used to cooperate with the Bragg reflection layer 5 to form a total reflection effect, reflect the light from the epitaxial layer 2 and emit it from the substrate surface, the isolation part 62 is used to isolate the metal of the reflection part 61 from the metal of the welding part 63, and prevent the metals between the reflection part 61 and the welding part 63 from migrating to each other to form a brittle intermetallic compound, and the protective layer 65 is used to protect the second Ni metal layer 64 from external pollution or oxidation;

[0030] It is understandable that the present application utilizes a stack of Ni metal and Ag metal as the welding part of the flip-chip LED chip pad. In actual circumstances, the second Ni metal layer 64 is also included in the welding part 63, so that the top metal of the welding part 63 is the Ni metal layer, which replaces the Au metal used as the welding part in the traditional flip-chip LED, thereby greatly reducing the production cost of the flip-chip LED.

[0031] In this embodiment, the period M of the alternating arrangement of the first Ni metal layer 631 and the Ag metal layer 632 is in the range of 5≤M≤7.

[0032] In this embodiment, the epitaxial layer 2 includes an N-type semiconductor layer 21 , an active light emitting layer 22 , and a P-type semiconductor layer 23 which are sequentially stacked on the substrate 1 .

[0033] In this embodiment, the electrode layer includes a P-type electrode 32 and an N-type electrode 31 , wherein the P-type electrode 32 is disposed on the P-type semiconductor layer 23 , and the N-type electrode 31 is disposed on the N-type semiconductor layer 21 ;

[0034] In the present invention, the pad layer 6 includes an N-type pad layer and a P-type pad layer, the N-type pad layer is arranged on the N-type electrode 31, and the P-type pad layer is arranged on the P-type electrode 32, and the N-type pad layer and the P-type pad layer both include a reflection part 61, an isolation part 62, a welding part 63 and a protection part 65.

[0035] In this embodiment, the reflective portion 61 is specifically a metal Al layer.

[0036] In this embodiment, the isolation portion 62 is specifically a metal TiW layer.

[0037] In this embodiment, the protective layer 65 is specifically a rosin layer, which can protect the second Ni metal layer 64 from oxidation or contamination.

[0038] In this embodiment, the thickness ratio between the first Ni metal layer 631 and the Ag metal layer 632 in the same period is 5:1 to 80:1;

[0039] Specifically, for all periods of the first Ni metal layer 631 and the Ag metal layer 632 , the thickness ratio therebetween is 5:1 to 80:1, and the thickness ratio therebetween increases linearly in a direction away from the isolation portion 62 .

[0040] In this embodiment, the thickness of the first Ni metal layer 631 is 50 nm to 400 nm.

[0041] In this embodiment, the thickness of the second Ni metal layer 64 is 200nm-400nm.

[0042] It is worth noting that, for the sake of ease of understanding, a method for preparing a flip-chip light-emitting diode chip is further introduced in this embodiment. The method is applied to the production and preparation of the above-mentioned flip-chip light-emitting diode chip, and the method comprises the following steps:

[0043] Step 1: firstly provide a substrate 1, and then sequentially deposit an N-type GaN layer 21, an active light-emitting layer 22, and a P-type GaN layer 23 on the substrate 1 by using a MOCVD process to obtain an epitaxial layer 2;

[0044] Step 2: Then, a photoresist is coated on the P-type GaN layer 23, and then the photoresist on the P-type GaN layer 23 is removed by exposure and development to expose the P-type GaN layer 23 below, and then the exposed P-type GaN layer 23 and the active light-emitting layer 22 below the P-type GaN layer 23 are removed by an inductively coupled plasma etching process until the N-type GaN layer 21 is exposed to form a conductive step of the N-type GaN layer;

[0045] Step 3: Then, photoresist is coated on the surface of the P-type GaN layer 23 and the N-type GaN layer 21, and then part of the photoresist is removed by exposure and development, and then part of the photoresist is removed by exposure and development, and then the first electrode sublayer, the second electrode sublayer, and the third electrode sublayer are sequentially evaporated by electron beam evaporation process, wherein the first electrode sublayer is a reflective layer of the electrode layer, which may be Al or Ag metal, and the second electrode sublayer is composed of three groups of Ti metal and Pt metal stacked layers to protect the Al or Ag metal of the first sublayer and prevent it from electromigration, and the third electrode sublayer is Ni metal, and the Ni metal forms an ohmic contact with the current spreading layer 4 disposed on the electrode layer, and then the metal located on the photoresist is removed by a blue film stripping process to obtain a P-type electrode 32 and an N-type electrode 31;

[0046] Step 4: Then, a photoresist is coated on the P-type electrode 32 and the N-type electrode 31, the P-type GaN layer 23 not covered by the P-type electrode 32, and the N-type GaN layer conductive step not covered by the N-type electrode 31, and then the photoresist on the P-type electrode 32 and a part of the P-type GaN layer 23 is removed by exposure and development, and then indium tin oxide is evaporated by electron beam evaporation process, and then the indium tin oxide on the photoresist is removed by blue film stripping process, and then the photoresist is removed to obtain the current spreading layer 4;

[0047] Step 5: Then, using an electron beam evaporation process, 23 groups of TiO2 and SiO2 stacked Bragg reflection layers 5 are evaporated on the current spreading layer 4 and the P-type GaN layer 23 not covered by the current spreading layer 4, the N-type electrode 31, and the N-type GaN layer conductive step not covered by the N-type electrode 31, and then a photoresist is coated on the surface of the Bragg reflection layer 5, and then the photoresist on the Bragg reflection layer 5 on the N-type electrode 31 and the photoresist on the Bragg reflection layer 5 on the current spreading layer 4 on the P-type electrode 32 are removed by exposure and development to expose the two parts of the Bragg reflection layer 5, and then the Bragg reflection layer 5 on the N-type electrode 31 is removed by an inductively coupled plasma etching process until an N-type Bragg reflection layer through hole is formed on the surface of the N-type electrode 31, and the Bragg reflection layer 5 and the current spreading layer 4 on the P-type electrode 32 are removed until the P-type electrode 32 is exposed to form a P-type Bragg reflection layer through hole, wherein the Bragg reflection through hole includes an N-type Bragg reflection layer through hole and a P-type Bragg reflection layer through hole;

[0048] Step 6: Then, a first photoresist is coated on the Bragg reflective layer 5, the N-type Bragg reflective layer through hole, and the P-type Bragg emitter layer through hole, and then a second photoresist is coated on the first photoresist, wherein the viscosity of the second photoresist is greater than that of the first photoresist, and then, exposure and development are performed to remove a portion of the first photoresist and the second photoresist to form a photoresist opening with two angles, and then, an Al metal layer, a TiW metal layer, a stack of multiple first Ni metal layers 631 and Ag metal layers 632, and a second Ni metal layer 64 are sequentially evaporated using an electron beam evaporation process;

[0049] Step 7: After evaporation, the metal on the photoresist is removed by a blue film stripping process, and then the photoresist is removed. Then, rosin is sprayed on the second Ni metal layer 64 and the uncovered Bragg reflection layer 5 as a protective layer 65 to obtain a pad layer 6, thereby completing the preparation of the flip-chip light-emitting diode chip.

[0050] In summary, the flip-chip LED chip in the above-mentioned embodiments of the present invention utilizes a stack of Ni metal and Ag metal as the welding part of the flip-chip LED chip pad, replacing the Au metal used as the welding part in the traditional flip-chip LED, thereby greatly reducing the production cost of the flip-chip LED.

[0051] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A flip-chip light emitting diode chip, characterized in that: It comprises a substrate, and an epitaxial layer, an electrode layer, a current spreading layer, a Bragg reflection layer and a pad layer stacked on the substrate in sequence, wherein the Bragg reflection layer is provided with a Bragg reflection layer through hole penetrating to the electrode layer, and the pad layer contacts the electrode layer through the Bragg reflection layer through hole; Among them, the pad layer includes a reflecting part, an isolating part, a welding part and a protective part which are sequentially arranged on the electrode layer, the welding part includes M first Ni metal layers and Ag metal layers which are periodically alternately arranged, and a second Ni metal layer is arranged between the welding part and the protective part. Along the direction from the isolating part to the welding part, the thickness ratio between the first Ni metal layer and the Ag metal layer in each period increases linearly and the thickness of the first Ni metal layer in each period increases sequentially.

2. The flip-chip light emitting diode chip according to claim 1, characterized in that: The period M of the alternating arrangement of the first Ni metal layer and the Ag metal layer is in the range of 5≤M≤7.

3. The flip-chip light emitting diode chip according to claim 1, characterized in that: The epitaxial layer includes an N-type semiconductor layer, an active light-emitting layer, and a P-type semiconductor layer which are sequentially stacked on the substrate.

4. The flip-chip light emitting diode chip according to claim 3, characterized in that: The electrode layer includes a P-type electrode and an N-type electrode. The P-type electrode is arranged on the P-type semiconductor layer, and the N-type electrode is arranged on the N-type semiconductor layer.

5. The flip-chip light emitting diode chip according to claim 1, characterized in that: The reflective portion is specifically a metal Al layer.

6. The flip-chip light emitting diode chip according to claim 1, characterized in that: The isolation portion is specifically a metal TiW layer.

7. The flip-chip light emitting diode chip according to claim 1, characterized in that: The protection part is specifically a rosin layer.

8. The flip-chip light emitting diode chip according to claim 1, characterized in that: The thickness ratio between the first Ni metal layer and the Ag metal layer in the same period is 5:1 to 80:

1.

9. The flip-chip light emitting diode chip according to claim 1, characterized in that: The thickness of the first Ni metal layer is 50 nm to 400 nm.

10. The flip-chip light emitting diode chip according to claim 1, characterized in that: The thickness of the second Ni metal layer is 200 nm to 400 nm.

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