Algan-based deep ultraviolet led chip preparation method and led chip

Abstract

The application provides an AlGaN-based deep ultraviolet LED chip preparation method, which comprises the following steps: providing a semi-finished LED chip with an N-type electrode, wherein the N-type electrode comprises an Al layer structure for stacking; and annealing the semi-finished LED chip to perform annealing treatment on the N-type electrode on the semi-finished LED chip; wherein the thickness of the Al layer is 30-120 nm, and the annealing temperature of the N-type electrode is 750-950 DEG C. The application solves the problem of low photoelectric conversion efficiency of the LED chip in the prior art.

Description

Technical Field

[0001] This invention relates to the field of semiconductor chip technology, and in particular to a method for fabricating an AlGaN-based deep ultraviolet LED chip and the LED chip itself. Background Technology

[0002] AlGaN is a direct bandgap semiconductor material with excellent physicochemical properties and a large bandgap. After decades of research and application exploration, AlGaN-based deep ultraviolet light-emitting diodes (DUV LEDs) have penetrated into many fields of production and daily life. Compared with traditional ultraviolet light sources, DUV LEDs have many advantages, such as energy saving, long lifespan, and mercury-free operation.

[0003] With advancements in epitaxial growth technology, the internal quantum efficiency (IQE) of AlN / AlGaN-based multiple quantum wells (MQWs) has reached as high as 60%. However, the light extract efficiency (LEE) of AlGaN-based DUV-LEDs is generally still below 8%, becoming the main reason limiting their external quantum efficiency. Lower luminous efficiency means that over 90% of electrical energy is converted into heat, leading to increased junction temperature and further reducing the chip's quantum efficiency, creating a vicious cycle that accelerates chip degradation and failure. Therefore, obtaining highly efficient and reliable AlGaN-based DUV-LEDs is currently one of the hot research topics.

[0004] In operation, AlGaN-based DUV-LED devices are prone to current congestion due to the influence of n-type AlGaN material and chip layout, resulting in uneven current injection and low injection efficiency. Defects in the N-type ohmic contact electrodes and problems in the fabrication process lead to high contact resistance, high local current density, severe local self-heating, or poor heat dissipation due to local electrode defects, and local overheating accelerates the degradation of DUV-LEDs. All these factors affect the photoelectric conversion of DUV-LEDs.

[0005] Therefore, current deep ultraviolet LED chips suffer from poor photoelectric conversion efficiency due to the large local current density caused by the high contact resistance of the N electrode, which makes current spread difficult. Summary of the Invention

[0006] Based on this, the purpose of this invention is to provide a method for fabricating AlGaN-based deep ultraviolet LED chips and the LED chip itself, aiming to solve the problem of poor photoelectric conversion efficiency in existing LED chips.

[0007] The embodiments of the present invention are implemented as follows: On one hand, this invention proposes a method for fabricating an AlGaN-based deep ultraviolet LED chip, the method comprising: A semi-finished LED chip with fabricated N-type electrodes is provided, wherein the N-type electrodes include an Al layer structure for stacking; The semi-finished LED chip is annealed to anneal the N-type electrode on the semi-finished LED chip. The Al layer has a thickness of 30nm-120nm, and the N-type electrode has an annealing temperature of 750℃-950℃.

[0008] Furthermore, in the above-mentioned method for fabricating AlGaN-based deep ultraviolet LED chips, the annealing time of the N-type electrode is 30S-60S.

[0009] Furthermore, in the above-mentioned method for fabricating AlGaN-based deep ultraviolet LED chips, the N-type electrode comprises a first metal layer, a second metal layer, a third metal layer, and a fourth metal layer stacked sequentially, wherein the second metal layer is the Al layer.

[0010] Furthermore, in the above-mentioned method for fabricating AlGaN-based deep ultraviolet LED chips, the first metal layer is a Cr layer, the third metal layer is a Ti layer, and the fourth metal layer is an Au layer.

[0011] Furthermore, in the above-mentioned method for fabricating AlGaN-based deep ultraviolet LED chips, the step of providing a semi-finished LED chip with pre-fabricated N-type electrodes includes: Provide an AlGaN-based epitaxial wafer; The epitaxial wafer was sequentially cleaned using a first and a second strong oxidizing solution, respectively. The epitaxial wafer is photolithographically etched, and then the N-type AlGaN contact layer in the AlGaN-based epitaxial wafer is exposed by ICP etching to obtain the N-type electrode deposition region. A metal stack containing the Al layer is deposited in the N-type electrode evaporation region as the N-type electrode.

[0012] Furthermore, in the above-mentioned method for preparing AlGaN-based deep ultraviolet LED chips, the first strong oxidizing solution is a mixture of hydrochloric acid and nitric acid in a predetermined ratio, and the second strong oxidizing solution is a mixture of sulfuric acid and hydrogen peroxide in a predetermined ratio.

[0013] Furthermore, in the above-mentioned method for preparing AlGaN-based deep ultraviolet LED chips, the ratio of hydrochloric acid to nitric acid is 3:1, and the ratio of sulfuric acid to hydrogen peroxide is 5:1.

[0014] Furthermore, in the above-mentioned method for fabricating AlGaN-based deep ultraviolet LED chips, the step of sequentially cleaning the epitaxial wafer with first and second strong oxidizing solutions includes: The epitaxial wafer was first cleaned using the first strong oxidizing solution at room temperature. The epitaxial wafer is then cleaned a second time using the second strong oxidizing solution at a preset temperature. The second cleaning temperature is 80℃~90℃.

[0015] Furthermore, in the above-mentioned method for fabricating AlGaN-based deep ultraviolet LED chips, the first cleaning time is twice the second cleaning time, with the first cleaning time being 40 min to 50 min and the second cleaning time being 10 min to 20 min.

[0016] In another aspect, the present invention proposes an LED chip, which is prepared by the AlGaN-based deep ultraviolet LED chip preparation method described in any of the above claims.

[0017] This invention reduces the contact barrier and improves the ohmic contact within the chip by annealing the N-type electrode. The annealing temperature is set between 750℃ and 950℃, and an Al layer is deposited within the N-type electrode with a thickness of 30nm-120nm. This avoids the surface roughness and poor morphology of the N-type contact electrode caused by excessively high annealing temperatures, which can lead to electrode protrusions, blistering, and clustering. The result is an N-type electrode with a good surface morphology and low-resistance, stable ohmic contact. This improves the problems of current diffusion and severe localized self-heating caused by localized current density in the N-type electrode, effectively enhancing the photoelectric conversion efficiency of the device. This solves the problem of low photoelectric conversion efficiency in existing LED chips. Attached Figure Description

[0018] Figure 1 This is a flowchart of a method for fabricating an AlGaN-based deep ultraviolet LED chip according to an embodiment of the present invention; The following detailed description, in conjunction with the accompanying drawings, will further illustrate the present invention. Detailed Implementation

[0019] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Several embodiments of the invention are illustrated in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

[0020] It should be noted that when a component is said to be "fixed to" another component, it can be directly on the other component or there may be an intervening component. When a component is said to be "connected to" another component, it can be directly connected to the other component or there may be an intervening component. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this document are for illustrative purposes only.

[0021] 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 invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0022] This invention addresses the problem in existing technologies where high contact resistance in LED chips leads to high local current density and severe local self-heating, resulting in low photoelectric conversion efficiency. It proposes an AlGaN-based deep ultraviolet LED chip fabrication method and an LED chip, wherein: Please see Figure 1 The diagram shows a flowchart of a method for fabricating an AlGaN-based deep ultraviolet LED chip according to an embodiment of the present invention. The method for fabricating an AlGaN-based deep ultraviolet LED chip includes steps S10 to S11.

[0023] Step S10: Provide a semi-finished LED chip with fabricated N-type electrodes, wherein the N-type electrodes include an Al layer structure for stacking.

[0024] In existing technologies, the high contact resistance of N-type electrodes and unstable ohmic contacts mainly lead to high local current density, severe local self-heating, and reduced photoelectric conversion efficiency. The present invention improves the structure and process of N-type electrodes in LED chips to effectively reduce the contact resistance of N-type electrodes and ensure stable ohmic contacts. Specifically, N-type electrodes are deposited on the surface of the epitaxial wafer. Therefore, it is necessary to first obtain a semi-finished LED chip containing N-type electrodes.

[0025] Specifically, in the embodiments of the present invention, the preparation of a semi-finished LED chip with fabricated N-type electrodes can be carried out in the following manner: Provide an AlGaN-based epitaxial wafer; The epitaxial wafer was sequentially cleaned using a first and a second strong oxidizing solution, respectively. The epitaxial wafer is photolithographically etched, and then the N-type AlGaN contact layer in the AlGaN-based epitaxial wafer is exposed by ICP etching to obtain the N-type electrode deposition region. A metal stack containing the Al layer is deposited in the N-type electrode evaporation region as the N-type electrode.

[0026] First, an AlGaN-based epitaxial structure is prepared. Specifically, a conventional AlGaN-based epitaxial wafer is grown on a sapphire substrate using an MOCVD device. Furthermore, since the conventional structure of AlGaN-based epitaxial wafers is common knowledge to those skilled in the art, it will not be described in detail here.

[0027] Furthermore, the epitaxial wafer is cleaned in preparation for etching. Specifically, the epitaxial wafer is cleaned in segments using a first and a second strong oxidizing solution. The first strong oxidizing solution is a mixture of hydrochloric acid and nitric acid in a predetermined ratio, and the second strong oxidizing solution is a mixture of sulfuric acid and hydrogen peroxide in a predetermined ratio. In the specific implementation of this embodiment, the ratio of hydrochloric acid to nitric acid is 3:1, and the ratio of sulfuric acid to hydrogen peroxide is 5:1. After cleaning with the first strong oxidizing solution at room temperature, the epitaxial wafer is cleaned again with the first strong oxidizing solution at a predetermined temperature. Specifically, the cleaning temperature for the second cleaning is 80℃~90℃, and the cleaning time for the first cleaning is twice that of the second cleaning. The first cleaning time is 40 min~50 min, and the second cleaning time is 10 min~20 min.

[0028] Furthermore, after epitaxial cleaning, photolithography is performed using positive photoresist, followed by ICP etching to expose the N-type AlGaN contact layer. Negative photoresist is then used for photolithography to expose the areas where N-type electrodes need to be deposited. Finally, electron beam evaporation is used to deposit N-type contact electrodes on the N-type AlGaN contact layer. The N-type electrode comprises a first metal layer, a second metal layer, a third metal layer, and a fourth metal layer stacked sequentially. The first metal layer is a Cr layer, the second metal layer is the Al layer, the third metal layer is a Ti layer, and the fourth metal layer is an Au layer. The thickness of the Al layer is 30 nm-120 nm, the exemplary Cr layer thickness is 2.5 nm, the Ti layer thickness is 40 nm, and the Au layer thickness is 60 Å.

[0029] Step S11: Anneal the semi-finished LED chip to anneal the N-type electrode on the semi-finished LED chip.

[0030] Specifically, the chip after the N-type electrode has been deposited is stripped to remove the adhesive. After the adhesive is removed, the chip is annealed in a rapid annealing furnace at a temperature of 750℃-950℃ for 30-60 seconds. This avoids excessively high annealing temperatures, which can lead to rough surfaces and poor morphology of the N-type contact electrode, resulting in problems such as electrode protrusion, blistering, and clustering. The final result is an N-type electrode with a good surface morphology and a low-resistance, stable ohmic contact.

[0031] On the other hand, the LED chip proposed in the embodiments of the present invention is prepared by the AlGaN-based deep ultraviolet LED chip preparation method described in any of the above claims.

[0032] In summary, the AlGaN-based deep ultraviolet LED chip fabrication method and LED chip proposed in the above embodiments of the present invention reduce the contact barrier and improve the ohmic contact within the chip by annealing the N-type electrode. The annealing temperature is set between 750℃ and 950℃, and an Al layer is deposited within the N-type electrode with a thickness of 30nm-120nm. This avoids the surface roughness and poor morphology of the N-type contact electrode caused by excessively high annealing temperatures, which can lead to problems such as electrode protrusion, blistering, and clustering. Ultimately, an N-type electrode with good surface morphology and low-resistance stable ohmic contact is obtained. This improves the problems of current diffusion and severe local self-heating caused by local current density in the N-type electrode, effectively enhancing the photoelectric conversion efficiency of the device. This solves the problem of low photoelectric conversion efficiency in existing LED chips.

[0033] In addition, LED chips obtained under different preparation conditions by the LED chip preparation method in the embodiments of the present invention and LED chips prepared in the prior art were subjected to performance tests such as dot line pattern and specific contact resistivity. The test results are shown in Table 1 below.

[0034] Table 1 As can be clearly seen from Table 1, by annealing the N-type electrode, the contact barrier is reduced, the ohmic contact within the chip is improved, and the annealing temperature is set at 750℃-950℃. An Al layer is set inside the N-type electrode, and the thickness of the Al layer is set at 30nm-120nm. This avoids the problem that excessively high annealing temperatures would cause the N-type contact electrode to have a rough surface and poor morphology, resulting in problems such as electrode protrusion, blistering, and clustering. Ultimately, an N-type electrode with good surface morphology and low-resistance stable ohmic contact is obtained. In addition, by combining Group 1, Group 2, Group 7, and Group 9, it can be clearly seen that Al layer thickness and annealing temperature both have an improving effect on surface morphology and ohmic contact stability. Furthermore, a reasonable combination of Al layer thickness and annealing temperature can effectively improve the stability of ohmic contacts, reduce contact resistance, and improve surface morphology.

[0035] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for fabricating an AlGaN-based deep ultraviolet LED chip, characterized in that, The method includes: A semi-finished LED chip with fabricated N-type electrodes is provided, wherein the N-type electrodes include an Al layer structure for stacking; The semi-finished LED chip is annealed to anneal the N-type electrode on the semi-finished LED chip. The thickness of the Al layer is 30nm-120nm, and the annealing temperature of the N-type electrode is 750℃-950℃. The annealing time for N-type electrodes is 30-60 seconds. The N-type electrode comprises a first metal layer, a second metal layer, a third metal layer, and a fourth metal layer stacked sequentially, wherein the second metal layer is the Al layer; The first metal layer is a Cr layer, the third metal layer is a Ti layer, and the fourth metal layer is an Au layer.

2. The method for fabricating an AlGaN-based deep ultraviolet LED chip according to claim 1, wherein the step of providing a semi-finished LED chip with a fabricated N-type electrode includes: Provide an AlGaN-based epitaxial wafer; The epitaxial wafer was sequentially cleaned using a first and a second strong oxidizing solution, respectively. The epitaxial wafer is photolithographically etched, and then the N-type AlGaN contact layer in the AlGaN-based epitaxial wafer is exposed by ICP etching to obtain the N-type electrode deposition region. A metal stack containing the Al layer is deposited in the N-type electrode evaporation region as the N-type electrode.

3. The method for fabricating an AlGaN-based deep ultraviolet LED chip according to claim 2, characterized in that, The first strong oxidizing solution is a mixture of hydrochloric acid and nitric acid in a predetermined ratio, and the second strong oxidizing solution is a mixture of sulfuric acid and hydrogen peroxide in a predetermined ratio.

4. The method for fabricating an AlGaN-based deep ultraviolet LED chip according to claim 3, characterized in that, The ratio of hydrochloric acid to nitric acid is 3:1, and the ratio of sulfuric acid to hydrogen peroxide is 5:

1.

5. The method for fabricating an AlGaN-based deep ultraviolet LED chip according to claim 2, characterized in that, The step of sequentially cleaning the epitaxial wafer with the first and second strong oxidizing solutions includes: The epitaxial wafer was first cleaned using the first strong oxidizing solution at room temperature. The epitaxial wafer is then cleaned a second time using the second strong oxidizing solution at a preset temperature. The second cleaning temperature is 80℃~90℃.

6. The method for fabricating an AlGaN-based deep ultraviolet LED chip according to claim 5, characterized in that, The first cleaning time is twice that of the second cleaning time, which is 40 to 50 minutes, and the second cleaning time is 10 to 20 minutes.

7. An LED chip, characterized in that, It is prepared by the AlGaN-based deep ultraviolet LED chip preparation method according to any one of claims 1 to 6.

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