Light emitting diode and method of manufacturing the same

Abstract

The application provides a light emitting diode and a preparation method thereof. The light emitting diode comprises a GaN layer and a transparent insulating film layer deposited on the GaN layer, the transparent insulating film layer is used for blocking current, the GaN layer comprises a flat area and a current conducting part opened on the flat area, the current conducting part comprises a platform recessed from one end of the transparent insulating film layer and a sidewall connecting the flat area and the platform, and the transparent insulating film layer is deposited on the outer ring of the platform, the sidewall and the flat area close to the sidewall. The application can effectively and uniformly diffuse current, thereby improving the brightness of the LED chip. In addition, since the current is uniformly diffused, the heat accumulation phenomenon of the chip in use is effectively improved, thereby achieving the purpose of prolonging the service life of the chip.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of LED, in particular to a light emitting diode and a preparation method thereof. BACKGROUND

[0002] Light emitting diode (LED) is a kind of semiconductor electronic component that can emit light, which attracts more and more researchers due to its small size, high brightness, low energy consumption and other characteristics, wherein, GaN-based LED has high density, low energy consumption, long service life, short response time, no radiation and other advantages, and is widely used in lighting and display fields.

[0003] The core component of LED is P-N junction, and the mainstream manufacturing method is to grow N-type and P-type semiconductor epitaxial layers on sapphire substrate, and to manufacture LED chip on the epitaxial layer. The core structure of flip-chip LED chip is current conduction layer and light reflection layer, through the design of LED chip structure, the current is combined to emit light through the conduction path, and the light is emitted from the sapphire surface through the reflection of the light reflection layer, which must design the current conduction path on the chip structure.

[0004] Among them, in order to improve the brightness of the chip, it is necessary to ensure that the area of the reflection layer is large enough, so that the conduction area of the current conduction path will be reduced. If it is set in this way, the current will be too concentrated at the opening, which will lead to large current density at the opening, uneven current distribution of the whole chip, and further cause uneven light emission of the whole chip, which will affect the brightness of the chip. SUMMARY

[0005] Therefore, the purpose of the present application is to provide a light emitting diode, a preparation method and an LED chip, which aims to solve the problem that the current distribution is uneven at the current conduction path when the opening area of the current conduction path is small, thereby affecting the light emitting brightness of the LED.

[0006] According to one of the light emitting diodes in the embodiments of the present application, the light emitting diode comprises a GaN layer and a transparent insulating film layer deposited on the GaN layer, the transparent insulating film layer is used for blocking current, the GaN layer comprises a flat area and a current conduction part opened on the flat area, the current conduction part comprises a platform recessed away from one end of the transparent insulating film layer and a side wall connecting the flat area and the platform, and the transparent insulating film layer is deposited on the outer circle of the platform, the side wall and the flat area close to the side wall.

[0007] Preferably, the light emitting diode further comprises a sapphire substrate, an insulating layer and a contact layer, the GaN layer is deposited on the sapphire substrate, the insulating layer is partially deposited on the transparent insulating film layer, and the contact layer is deposited on the current conducting part, the transparent insulating film layer and the insulating layer.

[0008] Preferably, the thickness of the transparent insulating film layer is 0.5-2 μm.

[0009] Preferably, the shape of the current conducting part is circular, square, strip or polygon, etc.

[0010] Preferably, the distance between the boundary of the transparent insulating film layer deposited on the flat area and the boundary of the platform is 3-8 μm.

[0011] Preferably, the distance between the boundary of the transparent insulating film layer deposited on the platform and the boundary of the side wall is 3-8 μm.

[0012] According to one of the embodiments of the present application, a preparation method of a light emitting diode is provided for preparing the light emitting diode as described above, and the preparation method comprises the following steps:

[0013] providing a sapphire substrate;

[0014] depositing a GaN layer on the sapphire substrate;

[0015] opening a current conducting part on a flat area of the GaN layer, the current conducting part comprising a platform recessed from one end of an initial transparent insulating film layer and a side wall connecting the flat area and the platform, depositing the initial transparent insulating film layer, and etching the initial transparent insulating film layer to obtain a transparent insulating film layer deposited only on the outer circle of the platform, the side wall and the flat area close to the side wall.

[0016] Preferably, the step of opening the current conducting part on the flat area of the GaN layer comprises the following steps:

[0017] coating a positive photoresist on the flat area of the GaN layer, then performing exposure and development to obtain a current conducting part pattern;

[0018] etching the current conducting part using ICP dry etching technology according to the current conducting part pattern, and finally removing the photoresist.

[0019] Preferably, the step of depositing an initial transparent insulating film layer, the current conducting part comprising a platform recessed away from one end of the initial transparent insulating film layer and a sidewall connecting the platform and the flat area, etching the initial transparent insulating film layer to obtain a transparent insulating film layer deposited only on the outer ring of the platform, the sidewall and the flat area close to the sidewall specifically comprises:

[0020] After depositing the initial transparent insulating film layer as a whole, a negative photoresist is coated, exposure and development are performed to obtain a first pattern;

[0021] According to the first pattern, the initial transparent insulating film layer on the flat area away from the current conducting part is etched by a wet etching technology, and the photoresist is removed to obtain a pretreatment layer;

[0022] The pretreatment layer is coated with a positive photoresist, exposure and development are performed to obtain a second pattern;

[0023] According to the second pattern, the pretreatment layer deposited in the middle region of the platform is etched by an ICP dry etching technology, and finally the photoresist is removed.

[0024] According to one of the embodiments of the present application, the LED chip comprises the light emitting diode described above.

[0025] Compared with the prior art, by providing a current conducting part on the flat area of the GaN layer, the current conducting part comprising a platform recessed away from one end of the transparent insulating film layer and a sidewall connecting the flat area and the platform, and the transparent insulating film layer is deposited only on the outer ring of the platform, the sidewall and the flat area close to the sidewall, since the conduction area of the current conducting part is relatively small, the current is easily concentrated, and the transparent insulating film layer is provided on the current conducting part, the originally concentrated current is blocked by the transparent insulating film layer, the blocked current is diffused to the surroundings, the purpose of diffusing the current is achieved, the brightness of the LED chip is improved, in addition, since the current is uniformly diffused, the heat accumulation phenomenon of the chip during use is effectively improved, and the purpose of prolonging the service life of the chip is achieved. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 FIG. 1 is a structure diagram of the light emitting diode in the first embodiment of the present application;

[0027] Figure 2 FIG. 2 is a flow chart of the preparation method of the light emitting diode in the second embodiment of the present application;

[0028] Figure 3 FIG. 3 is a structure diagram of the flip LED chip in the third embodiment of the present application;

[0029] Figure 4Fig. 1 is a schematic diagram of a structure of a flip-chip LED chip according to an embodiment of the present application.

[0030] The following detailed description will further describe the present application with reference to the above-mentioned figures. DETAILED DESCRIPTION

[0031] For the purpose of promoting an understanding of the principles of the application, reference will now be made to the embodiments illustrated in the drawings. There is shown in the drawings several embodiments of the present application. However, it should be understood that the application can be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete. It will be apparent that those skilled in the art, upon attending to the following detailed description and appropriate figures, can appreciate the various aspects of the present application.

[0032] It should be noted that when an element is referred to as being "on" another element, it can be directly on the other element or intervening elements can also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements can also be present. As used herein, the terms "vertical", "horizontal", "left", "right", and the like, are merely used for the purpose of explanation.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0034] Embodiment One

[0035] Referring to Fig. 1, a light emitting diode according to an embodiment of the present application is shown, which includes a sapphire substrate 1, a GaN layer 2 deposited on the sapphire substrate 1, and a transparent insulating film layer 3 deposited on the GaN layer 2, wherein: Figure 1

[0036] The material of the transparent insulating film layer 3 is SiO2, Si3N4, Ti3O5, or other silicon oxynitride material, which is used to block the current, and the thickness of the transparent insulating film layer 3 is 0.1-1.0 μm. For example, the thickness of the transparent insulating film layer 3 is 0.5 μm. Since the transparent insulating film layer 3 is etched into the desired shape when it is deposited on the GaN layer 2, the thickness of the transparent insulating film layer 3 on the GaN layer 2 is not uniform. For example, in some embodiments, the transparent insulating film layer 3 is made into a more convex step, which is used to form a barrier on the path where Ag can migrate, so as to effectively prevent the migration of Ag during the operation of the LED chip, thereby improving the stability and reliability of the LED chip.

[0037] ​It needs to be explained that, in the GaN layer 2 includes flat area 21 and in the flat area 21 open current conducting part 20, the current conducting part 20 is a mesa step, wherein the shape of the current conducting part 20 is circular, square, strip or polygon, etc. according to the needs of design, specific, the current conducting part 20 is a structure of low in the middle and high around, it can be understood that this structure exists inwardly recessed platform 22 and the side wall 23 connecting the flat area 21 and the platform 22, when depositing the initial transparent insulating film layer (not shown in the figure) on the GaN layer 2, the platform 22, the side wall 23 of the current conducting part 20 and the flat area 21 of the GaN layer 2 are covered by the initial transparent insulating film layer, which needs to be processed to obtain the transparent insulating film layer 3 deposited only on the outer ring of the platform 22, the side wall 23 and the flat area 21 close to the side wall 23, in addition, the distance between the boundary of the transparent insulating film layer 3 deposited on the flat area 21 and the boundary of the platform 22 is 3-8 μm, and the distance between the boundary of the transparent insulating film layer 3 deposited on the platform 22 and the boundary of the side wall 23 is 3-8 μm.

[0038] In the embodiment, the transparent insulating film layer 3 is circular ring, specifically, the cross section of the transparent insulating film layer 3 can be regarded as a trapezoidal, namely narrow at the top and wide at the bottom, further, the insulating layer (not shown in the figure) is partially deposited on the platform of the transparent insulating film layer 3, and the contact layer (not shown in the figure) is deposited in the groove structure formed by the transparent insulating film layer 3 and the current conducting part 20, covering the platform 22 of the current conducting part 20 which is not deposited with the transparent insulating film layer 3 and part of the insulating layer.

[0039] In summary, by opening the current conducting part 20 on the flat area 21 of the GaN layer 2, the current conducting part 20 includes the platform 22 recessed away from one end of the transparent insulating film layer 3 and the side wall 23 connecting the flat area 21 and the platform 22, wherein the transparent insulating film layer 3 is deposited only on the outer ring of the platform 22, the side wall 23 and the flat area 21 close to the side wall 23, which can ensure that the conduction area of the current conducting part 20 is small enough and can effectively and uniformly diffuse the current, thereby improving the brightness of the LED chip, in addition, since the current is uniformly diffused, the heat accumulation phenomenon of the chip during use is effectively improved, thereby achieving the purpose of prolonging the service life of the chip.

[0040] Embodiment two

[0041] Please refer to Figure 2 , which shows a preparation method of a light emitting diode according to the embodiment two of the present application, which is used for preparing the light emitting diode in the above embodiment one, and the method specifically comprises steps S201 to S203, wherein:

[0042] Step S201, providing a sapphire substrate required for growth and depositing a GaN layer.

[0043] Step S202, opening the current conducting part.

[0044] Wherein, the positive photoresist is coated on the flat area of the GaN layer, then exposure and development are carried out to obtain the current conducting part pattern, the shape of the current conducting part is circular, square, strip or polygon, etc., according to the current conducting part pattern, the ICP dry etching technology is used to etch the current conducting part, i.e. MESA step, and finally the photoresist is removed.

[0045] Step S203, depositing a transparent insulating film layer.

[0046] Specifically, after the etching is completed, the epitaxial wafer with the current conducting part is deposited with an initial transparent insulating film layer, the negative photoresist is coated, exposure and development are carried out to obtain the first pattern, according to the first pattern, the initial transparent insulating film layer on the flat area away from the current conducting part is etched by the wet etching technology, and the photoresist is removed to obtain a pretreatment layer, it can be understood that the shape of the pretreatment layer matches the shape of the current conducting part, and the pretreatment layer has a groove structure with a low middle and a high periphery, then the pretreatment layer is coated with a positive photoresist, exposure and development are carried out to obtain a second pattern, the purpose is to remove the pretreatment layer in the middle area of the platform in the specified current conducting part.

[0047] Further, according to the second pattern, the pretreatment layer in the middle area of the platform is etched by the ICP dry etching technology, and finally the photoresist is removed to obtain the transparent insulating film layer deposited only on the outer circle of the platform of the current conducting part, the sidewall and the GaN layer flat area close to the sidewall, the shape of the transparent insulating film layer is determined by the shape of the current conducting part, i.e. circular ring, square ring, strip ring or polygon ring, etc., this method not only saves the material of the transparent insulating film layer, but also reduces the light absorption area, so that the brightness improvement caused by the uniform current density is much larger than the brightness absorbed by the material, thereby improving the brightness of the LED chip.

[0048] Example three

[0049] The embodiment three of the present application provides a flip LED chip, please refer to Figure 3, including the epitaxial wafer in the above embodiment one, specifically, by depositing a GaN layer 302 on a sapphire substrate 301, then coating a positive photoresist on the flat area 3021 of the GaN layer 302, then performing exposure and development, to obtain a current conducting part pattern, according to the current conducting part pattern, using ICP dry etching technology, etching out the current conducting part 310, that is, the MESA step, then removing the photoresist, then depositing an initial transparent insulating film layer (not shown in the figure) on the epitaxial wafer with the current conducting part 310, and etching to obtain a transparent insulating film layer 303 deposited only on the outer circle of the current conducting part platform 308, the side wall 302 and the flat area 3021 of the GaN layer 302 close to the side wall 302.

[0050] On this basis, a negative photoresist is coated, exposure and development are performed, a design pattern is made, and then a metal reflective layer 304 is deposited by electron beam evaporation or magnetron sputtering deposition method, and stripping is performed. After the metal reflective layer 304 is made, a metal conductive layer 305 needs to be made to protect the metal of the metal reflective layer 304. Because the metal of the metal reflective layer 304 is generally selected from Ag, Al, Au and other materials with high reflectivity, Ag and Al are prone to migration under the action of electric field, which may cause chip failure. Therefore, a protective layer needs to be made for protection. Since the protective layer needs to be conductive, in this embodiment, a metal material is selected.

[0051] Specifically, the wafer with the metal reflective layer 304 is coated with a negative photoresist, then exposed and developed to form the required pattern, then metal is evaporated, and finally the unwanted metal is removed by stripping process to complete the fabrication of the metal conductive layer 305.

[0052] Further, an insulating layer 306 is deposited on the epitaxial wafer, wherein the material of the insulating layer 306 is SiO2, SiN x , and then positive photoresist coating, exposure and development are performed to make a pattern, then wet etching or ICP etching technology is used to make the required pattern, then the photoresist is removed, then negative photoresist coating, exposure and development are performed on the epitaxial wafer with the insulating layer 306, then a metal electrode 307 is prepared by electron beam evaporation or magnetron sputtering deposition method, and finally stripping is performed to obtain a flip-chip LED chip.

[0053] It should be noted that the periphery of the current conducting part 310 is wrapped by the transparent insulating film layer 303, the middle area of the current conducting part platform 308 is in contact with the metal electrode 307, specifically, the insulating layer 306, the transparent insulating film layer 303 and the current conducting part 310 form a V-shaped structure, and the metal electrode 307 covers the insulating layer 306, the transparent insulating film layer 303 and the current conducting part platform 308.

[0054] Embodiment four

[0055] The fourth embodiment of the present application provides a flip LED chip, referring to Figure 4 , which comprises the epitaxial wafer in the first embodiment, specifically, a GaN layer 402 is deposited on a sapphire substrate 401, then a positive photoresist is coated on a flat area 4021 of the GaN layer 402, and then exposure and development are performed to obtain a current conducting part pattern, according to the current conducting part pattern, ICP dry etching technology is used to etch a current conducting part 410, i.e. a MESA step, then the photoresist is removed, then a transparent conductive layer 403 is deposited on the epitaxial wafer with the current conducting part 410, and a required pattern is etched, on this basis, an initial transparent insulating film layer (not shown in the figure) is deposited and etched to obtain a transparent insulating film layer 404 deposited only on the outer circle of the current conducting part platform 407, the sidewall 408, the opening of the transparent conductive layer 403, and the flat area 4021 of the GaN layer close to the sidewall 408, then an insulating layer 405 is deposited on the epitaxial wafer, wherein the material of the insulating layer 405 is SiO2, SiN x , etc., then positive photoresist coating, exposure and development are performed to make a pattern, then wet etching or ICP etching technology is used to make a required pattern, finally the photoresist is removed, then negative photoresist coating, exposure and development are performed on the epitaxial wafer after the insulating layer 405 is made, then a metal electrode 406 is prepared by using electron beam evaporation or magnetron sputtering deposition, and finally stripping is performed to obtain a flip LED chip.

[0056] It should be noted that the four sides of the current conducting part 410 and the inner circle of the transparent conductive layer 403 are wrapped by the transparent insulating film layer 404, the middle area of the current conducting part platform 407 is in contact with the metal electrode 406, specifically, the insulating layer 405, the transparent insulating film layer 404 and the current conducting part 410 form a V-shaped structure, and the metal electrode 406 covers the insulating layer 405, the transparent insulating film layer 404 and the current conducting part platform 407.

[0057] The present application effectively homogenizes the current density of the LED chip by making a transparent insulating film layer at the sidewall position of the LED chip current conducting part, i.e. the MESA step sidewall, which improves the product brightness by more than 2%, and disperses the heat accumulation during the use of the LED chip, effectively prolonging the service life of the LED chip.

[0058] The above-described embodiments only express several embodiments of the present application, which are described in detail and specifically, but should not be understood as limiting the scope of the present application. It should be noted that for ordinary skilled persons in the art, several modifications and improvements can be made without departing from the concept of the present application, which are all within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the appended claims.

Claims

1. A light-emitting diode, characterized in that, The device includes a GaN layer and a transparent insulating film layer deposited on the GaN layer. The transparent insulating film layer is used to block current. The GaN layer includes a flat region and a current-conducting portion formed on the flat region. The current-conducting portion includes a platform recessed at one end away from the transparent insulating film layer and a sidewall connecting the flat region and the platform. The transparent insulating film layer is deposited on the outer ring of the platform, the sidewall, and the flat region near the sidewall. The light-emitting diode further includes a sapphire substrate, an insulating layer, and a contact layer. The GaN layer is deposited on the sapphire substrate. The insulating layer is partially deposited on the transparent insulating film layer. The contact layer is deposited on the current-conducting part, the transparent insulating film layer, and the insulating layer. The transparent insulating film layer has a cross-section that is narrow at the top and wide at the bottom, forming a raised step. The distance between the boundary of the transparent insulating film layer deposited on the flat area and the boundary of the platform is 3 μm to 8 μm; The distance between the boundary of the transparent insulating film layer deposited on the platform and the boundary of the sidewall is 3 μm to 8 μm.

2. The light-emitting diode according to claim 1, characterized in that, The thickness of the transparent insulating film layer is 1000Å~3000Å.

3. The light-emitting diode according to claim 1, characterized in that, The current-conducting part can be circular, square, strip-shaped, or polygonal in shape.

4. A method for fabricating a light-emitting diode, characterized in that, The method for preparing the light-emitting diode according to any one of claims 1-3 comprises: Provide a sapphire substrate; A GaN layer is deposited on the sapphire substrate; A current-conducting portion is formed on the flat region of the GaN layer, and an initial transparent insulating film layer is deposited. The current-conducting portion includes a platform recessed at one end away from the initial transparent insulating film layer and a sidewall connecting the flat region and the platform. The initial transparent insulating film layer is etched to obtain a transparent insulating film layer deposited only on the outer ring of the platform, the sidewall, and the flat region near the sidewall.

5. The method for fabricating a light-emitting diode according to claim 4, characterized in that, The step of creating a current-conducting portion on the flat region of the GaN layer includes: Positive photoresist is coated on the flat area of ​​the GaN layer, and then exposed and developed to obtain the current conduction pattern; Based on the current conduction part pattern, the current conduction part is etched using ICP dry etching technology, and finally the photoresist is removed.

6. The method for fabricating a light-emitting diode according to claim 4, characterized in that, The step of depositing an initial transparent insulating film layer, wherein the current-conducting portion includes a platform recessed at one end away from the initial transparent insulating film layer and a sidewall connecting the flat area and the platform, and etching the initial transparent insulating film layer to obtain a transparent insulating film layer deposited only on the outer ring of the platform, the sidewall, and the flat area near the sidewall specifically includes: After the initial transparent insulating film layer is deposited, a negative photoresist is coated, and then exposed and developed to obtain the first pattern. Based on the first pattern, the initial transparent insulating film layer on the flat region away from the current conduction part is etched by wet etching technology, and the photoresist is removed to obtain a pre-treatment layer. The pretreatment layer is coated with positive photoresist, exposed and developed to obtain the second pattern; Based on the second pattern, the pretreatment layer deposited in the middle region of the platform is etched using ICP dry etching technology, and finally the photoresist is removed.

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