Packaging Structure of Deep Ultraviolet LED and Manufacturing Method Thereof

Abstract

The present invention discloses a packaging structure of a deep ultraviolet LED and a manufacturing method thereof. By means of photolithography and etching, a silicon reflective cup with an inclined surface is formed on a silicon wafer, and a deep ultraviolet reflective layer is evaporated, so as to realize the vertical reflection of the lateral light intensity of the deep ultraviolet LED, reduce the loss of the lateral light intensity of the LED chip, improve the electro-optical efficiency, reduce the thermal effect, improve the reliability of the chip, and moreover, a plurality of silicon reflective cups are arranged in an array, improving the light distribution uniformity of the integrated light source. The packaging structure of the deep ultraviolet LED provided by the present invention is reasonably designed, omits traditional structures such as dams, reduces the packaging cost, directly provides a plurality of silicon reflective cups on the silicon wafer, controls the light output angle of the deep ultraviolet LED through the inclined surface of the silicon reflective cup, has stronger and controllable directivity, effectively reduces the loss of the lateral light intensity, enhances the front light output, not only improves the electro-optical efficiency of the deep ultraviolet LED, ensures the light output consistency and the light distribution uniformity, but also has a simple and compact overall structure and is easy to package.

Description

Technical Field

[0001] The present invention relates to the technical field of LEDs, and particularly relates to a packaging structure of a deep ultraviolet LED and a manufacturing method thereof. Background Art

[0002] Traditionally, mercury lamps are used for disinfection, but mercury lamps have disadvantages such as being environmentally unfriendly, having a short lifespan, and being impractical. The development of third-generation semiconductors is expected to solve the above problems. Deep ultraviolet LEDs prepared from AlGaN materials have many advantages such as being environmentally friendly, small and portable, having low power consumption, and low voltage. The wavelength range of deep ultraviolet LEDs is 200 - 280 nm. However, due to the low quality of the deep ultraviolet LED chip material and the problem of high refractive index, the electro-optical efficiency of the chip is not high, and most are only about 2 - 4%. The AlGaN material belongs to a high refractive index material, and it is difficult to extract light from inside the material. In addition, there is strong polarization in the light-emitting quantum well. The main emitted light is the TM mode, the TE light propagates perpendicular to the chip, and the TM light propagates horizontally.

[0003] The traditional inorganic deep ultraviolet packaging structure is a dam structure. The side wall of the dam is generally perpendicular to the chip. Materials such as ceramics or copper can be used, and then quartz glass is covered on the top, and nitrogen or other inert gases are filled inside, and welding is performed in a closed environment. However, the light of the deep ultraviolet LED lamp beads packaged by this method is reflected back and forth horizontally in the dam, and the self-absorption is serious, and the light extraction due to material polarization exacerbates this problem. The ceramic substrate is used as a heat dissipation material to dissipate heat from the chip. With photolithography, laser cutting, and metal electroplating processes, dam packaging can achieve array arrangement. However, the above methods still have problems such as complex processes, low precision, high cost, inability to improve the weak vertical light extraction of the chip, and uneven light distribution of the array light source. Therefore, it is necessary to improve the existing deep ultraviolet LED packaging structure, improve the electro-optical efficiency of the deep ultraviolet LED and the precision of array packaging, and control the light-emitting angle of the chip.

[0004] The invention patent with the publication number CN110197865A and the name of "A Deep Ultraviolet LED Packaging Device with Liquid Packaging and a Preparation Method Thereof" discloses a deep ultraviolet LED packaging device with liquid packaging and a preparation method thereof. It uses a ceramic substrate and a lens to wrap silicone oil, which can well improve the refractive index difference between the semiconductor material and air. However, in this method, the silicone oil is an organic substance, which is easy to age under deep ultraviolet light irradiation, and does not control the TM light transmitted horizontally.

[0005] The invention patent with the publication number CN108389951A and the name of "A Deep Ultraviolet LED Packaging Structure and Its Manufacturing Method" discloses a deep ultraviolet LED packaging structure and its manufacturing method. It also adopts the metal and ceramic packaging form. The dam body is perpendicular to the chip. To enhance light output, the surface of the chip is subjected to patterning or an antireflection film is applied. The cover plate is prepared with antireflection layers on both the upper and lower surfaces. However, this patent still fails to effectively control the TM light in the lateral transmission. Since its dam body is vertical, the light is easily reflected back and forth in the cavity and lost. Summary of the Invention

[0006] Aiming at the problems of low light extraction efficiency, strong polarized light output, strong light output in the lateral TM mode, and weak light output in the vertical TE mode in the deep ultraviolet LED packaging structure. The object of the present invention is to provide a deep ultraviolet LED packaging structure and its manufacturing method that can enhance the light extraction efficiency, reduce the loss of lateral light intensity of the LED chip, and improve the reliability of the deep ultraviolet LED chip.

[0007] To achieve the above object, the technical solution provided by the present invention is as follows:

[0008] A manufacturing method of a deep ultraviolet LED packaging structure, characterized in that it includes the following steps:

[0009] (1) Coating photoresist on the silicon wafer;

[0010] (2) Exposing and developing the photoresist to develop the required microgroove array pattern on the photoresist;

[0011] (3) Wet etching the silicon wafer to form several microgrooves on the silicon wafer, and continuing to etch the silicon wafer until the microgrooves penetrate the bottom surface of the silicon wafer to form a silicon reflector cup; the groove walls of the microgrooves are inclined surfaces;

[0012] (4) Removing the photoresist on the silicon wafer;

[0013] (5) Providing a deep ultraviolet reflective layer on the silicon reflector cup;

[0014] (6) Bonding the silicon wafer to a ceramic substrate with metal lines. The deep ultraviolet LED chip is located at the center of the silicon reflector cup and fixed on the ceramic substrate, and is electrically connected to the metal lines on the ceramic substrate;

[0015] (7) Sealing the silicon reflector cup hermetically by bonding a high-transparency partition on the upper surface of the silicon wafer.

[0016] As a preferred embodiment of the present invention, before applying the photoresist in step (1), the silicon wafer is cleaned with acetone or / and ethanol, then rinsed thoroughly with deionized water, and then dried with nitrogen. After drying the silicon wafer, the silicon wafer is placed in an oxidation furnace for oxidation treatment to obtain a silicon oxide layer with a thickness of 5 - 200 nm on the surface of the silicon wafer.

[0017] As a preferred embodiment of the present invention, step (3) includes the following steps:

[0018] (3.1) Place the silicon wafer in an HF solution to remove the surface oxide layer;

[0019] (3.2) Place the silicon wafer in an alkaline aqueous solution for etching to form a number of microgrooves on the silicon wafer;

[0020] (3.3) Continue to etch the silicon wafer for 10 - 60 minutes until the microgrooves penetrate the bottom surface of the silicon wafer to form a silicon reflection cup; the inclination angle of the groove wall of the microgroove is 50 - 60 degrees.

[0021] As a preferred embodiment of the present invention, in step (5), a layer of Al or Ag metal reflection film or a multi-layer oxide dielectric reflection film is deposited on the surface of the silicon reflection cup by magnetron sputtering or electron beam evaporation to form the deep ultraviolet reflection layer, which has a high light reflectivity.

[0022] As a preferred embodiment of the present invention, after the silicon wafer is attached to the ceramic substrate with metal circuits, it is welded and fixed with an inorganic material.

[0023] As a preferred embodiment of the present invention, step (7) is completed in a vacuum or nitrogen environment.

[0024] A packaging structure of a deep ultraviolet LED, which includes a ceramic substrate, a silicon wafer, a deep ultraviolet LED chip, and a high-transparency separator. The ceramic substrate is provided with metal circuits. A number of silicon reflection cups vertically penetrating the silicon wafer are evenly distributed on the silicon wafer. The surface of the silicon reflection cup is provided with a deep ultraviolet reflection layer. The silicon wafer is disposed on the ceramic substrate. The deep ultraviolet LED chip is disposed on the ceramic substrate corresponding to the center position of the silicon reflection cup and is connected to the metal circuits. The high-transparency separator covers the silicon wafer and hermetically packages the silicon reflection cup.

[0025] As a preferred embodiment of the present invention, the cup wall of the silicon reflection cup is an inclined surface with an inclination angle of 50 - 60 degrees, which has a good reflection effect and improves the light extraction efficiency.

[0026] As a preferred embodiment of the present invention, the high-transparency separator is a sapphire glass plate or a quartz glass plate, which is scratch-resistant, wear-resistant, high-temperature resistant, and has high spectral transmittance, with good light transmission effect; the ceramic substrate is a aluminum nitride plate body, an alumina plate body, or a zirconia plate body, which is high-temperature resistant, stable in properties, and has good insulation.

[0027] The beneficial effects of the present invention are as follows: The manufacturing method steps of the present invention are simple and easy to implement. By means of photolithography and etching, a number of silicon reflection cups with inclined surfaces are formed on a silicon wafer, and a deep ultraviolet reflection layer is evaporated, realizing the vertical reflection of the lateral light intensity of the deep ultraviolet LED, reducing the loss of the lateral light intensity of the LED chip, improving the electro-optical efficiency, reducing the thermal effect, improving the reliability of the chip, and moreover, a number of silicon reflection cups are arranged in an array, enhancing the light distribution uniformity of the integrated light source. The packaging structure of the deep ultraviolet LED provided by the present invention is reasonably designed, omitting traditional structures such as dams, reducing the packaging cost, directly providing a plurality of silicon reflection cups on the silicon wafer, controlling the light output angle of the deep ultraviolet LED through the inclined surfaces of the silicon reflection cups, with stronger and controllable directivity, effectively reducing the loss of the lateral light intensity, enhancing the front light output, not only improving the electro-optical efficiency of the deep ultraviolet LED, ensuring the light output consistency and light distribution uniformity, but also having a simple and compact overall structure and being easy to package.

[0028] The present invention will be further described below in conjunction with the accompanying drawings and embodiments. Description of the Drawings

[0029] Figure 1 is a three-dimensional structural schematic diagram of the present invention.

[0030] Figure 2 is an exploded structural schematic diagram of the present invention.

[0031] Figure 3 is a sectional structural schematic diagram of the present invention.

[0032] Figure 4 is a flow chart of the manufacturing method of the present invention. Detailed Embodiments

[0033] Embodiment, see Figures 1 to 3, A packaging structure of a deep ultraviolet LED provided in this embodiment includes a ceramic substrate 1, a silicon wafer 2, a deep ultraviolet LED chip 3, and a high-transparency partition 4. The ceramic substrate 1 is provided with metal circuits. A plurality of silicon reflection cups 21 that vertically penetrate the silicon wafer 2 are evenly distributed on the silicon wafer 2. A deep ultraviolet reflection layer 22 is provided on the surface of the silicon reflection cup 21. The silicon wafer 2 is disposed on the ceramic substrate 1. The deep ultraviolet LED chip 3 is disposed on the ceramic substrate 1 corresponding to the center position of the silicon reflection cup 21 and is connected to the metal circuits. The high-transparency partition 4 covers the silicon wafer 2 and hermetically packages the silicon reflection cup 21. The packaging structure of the deep ultraviolet LED provided by the present invention is reasonably designed, omits traditional structures such as dams, reduces packaging costs, directly provides a plurality of silicon reflection cups 21 on the silicon wafer 2, controls the light-emitting angle of the deep ultraviolet LED through the inclined surface of the silicon reflection cup 21, has stronger and controllable directivity, effectively reduces the loss of lateral light intensity, enhances the front light emission, not only improves the electro-optical efficiency of the deep ultraviolet LED, ensures the light-emitting consistency and light distribution uniformity, but also has a simple and compact overall structure and is easy to package.

[0034] The manufacturing method for realizing the above packaging structure of the deep ultraviolet LED is specifically as follows:

[0035] (1) Taking a silicon wafer 2 with a size of 2 to 6 inches or a side length of 5 to 20 cm and a thickness of 430 to 650 μm on the (100) plane as an example; cleaning the silicon wafer 2 with acetone or ethanol, then rinsing it with deionized water 1 to 10 times, and then drying it with nitrogen. After drying the silicon wafer 2, putting the silicon wafer 2 into an oxidation furnace for oxidation treatment to obtain a silicon oxide layer with a thickness of 5 - 200 nm on the surface of the silicon wafer 2; uniformly coating a photoresist 5 on the silicon wafer 2, with a spin coating speed of 1000 - 6000 rpm. The photoresist 5 is of types such as AZ5214 or SU-8, and the coating thickness of the photoresist is preferably 1 - 5 μm;

[0036] (2) Exposing the silicon wafer 2 with the photoresist 5 uniformly coated, making the positioning edge of the silicon wafer 2 parallel to the edge of the array, and developing to obtain the required microgroove array pattern. The pattern size of each microgroove is a square with a side length of 1 - 10 mm;

[0037] (3) First placing the patterned silicon wafer 2 in an HF solution to remove the surface oxide layer, and then placing it in an alkaline aqueous solution of KOH and NaOH, with a solution ratio of 1:3 - 1:6 and a time of 10 - 60 minutes until corroding to the bottom surface of the silicon wafer 2 to obtain the silicon reflection cup 21 with an inclined surface having an inclination angle of 50 - 60 degrees;

[0038] (4) Using a stripping solution and HF acid to remove the residual photoresist and oxide layer on the silicon wafer 2 respectively. The stripping solution is acetone, and the oxide layer is removed by HF acid with a concentration of 10 - 30%;

[0039] (5)Place the silicon wafer 2 in a magnetron sputtering or electron beam evaporation device, and deposit a layer of Al or Ag metal reflective film or a multi-layer oxide dielectric reflective film on the surface of the silicon reflection cup 21 to form a deep ultraviolet reflective layer 22, so as to improve the light reflectivity;

[0040] (6)Pre-form metal circuits on the ceramic substrate 1 through photolithography and metal sputtering processes. The ceramic substrate 1 can be an aluminum nitride plate body, an alumina plate body or a zirconia plate body, which has high temperature resistance, stable properties and good insulation. Use a die bonder to install the deep ultraviolet LED chip 3 on the ceramic substrate 1, and make the deep ultraviolet LED chip 3 conduct with the metal circuit on the ceramic substrate 1; the position of the deep ultraviolet LED chip 3 corresponds to the center position of the silicon reflection cup 21. The preferred thickness of the deep ultraviolet LED chip 3 is a chip with a thickness of 200um to 1.5mm, and models of 1020, 2020, 3535mil or 4545; bond the silicon wafer 2 to the ceramic substrate 1, and use an inorganic material such as AuSn to weld and fix the silicon wafer 2 and the ceramic substrate 1. The deep ultraviolet LED chip 3 is exactly located at the center position of the silicon reflection cup 21;

[0041] (7)Cover the upper surface of the silicon wafer 2 with a high-transparency separator 4 such as a sapphire glass plate or a quartz glass plate. Place the overall structure in a vacuum chamber, for 8 - 12 minutes in a vacuum or nitrogen environment, and then sinter and solidify to achieve airtight packaging of the silicon reflection cup 21. The manufacturing method of the present invention has simple steps and is easy to implement. By photolithography and etching, a number of silicon reflection cups 21 with inclined surfaces are formed on the silicon wafer 2, and a deep ultraviolet reflective layer 22 is deposited, realizing the vertical reflection of the deep ultraviolet LED lateral light intensity, reducing the loss of the LED chip lateral light intensity, improving the electro-optical efficiency, reducing the thermal effect, improving the reliability of the chip, and moreover, a number of silicon reflection cups 21 are arranged in an array, improving the light distribution uniformity of the integrated light source.

[0042] According to the disclosure and teaching of the above specification, those skilled in the art of the present invention can also make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and changes to the present invention should also fall within the protection scope of the claims of the present invention. In addition, although some specific terms are used in this specification, these terms are only for convenience of description and do not constitute any limitation to the present invention. As described in the above embodiments of the present invention, other structures and methods obtained by using the same or similar structures are all within the protection scope of the present invention.

Claims

1. Method for manufacturing packaging structure of deep ultraviolet LED, Characterized in that: It includes the following steps: (1) Coating photoresist on a silicon wafer; (2) Exposing and developing the photoresist to develop a required microgroove array pattern on the photoresist; (3) Wet etching the silicon wafer to form a number of microgrooves on the silicon wafer, and continuing to etch the silicon wafer until the microgrooves penetrate the bottom surface of the silicon wafer to form a silicon reflector cup; the side walls of the microgrooves are inclined surfaces; (4) Removing the photoresist on the silicon wafer; (5) Providing a deep ultraviolet reflective layer on the silicon reflector cup; (6) Bonding the silicon wafer to a ceramic substrate with metal lines, the deep ultraviolet LED chip is located at the center of the silicon reflector cup and fixed on the ceramic substrate, and is electrically connected to the metal lines on the ceramic substrate; (7) Sealing the silicon reflector cup hermetically by bonding a high-transparency separator to the upper surface of the silicon wafer; Before the step (1) of coating photoresist, the silicon wafer is cleaned with acetone or / and ethanol, then rinsed with deionized water, and then dried with nitrogen; After drying the silicon wafer, the silicon wafer is put into an oxidation furnace for oxidation treatment to obtain a silicon oxide layer with a thickness of 5 - 200 nm on the surface of the silicon wafer; The step (3) includes the following steps: (3.1) Putting the silicon wafer into an HF solution to remove the surface oxide layer; (3.2) Putting the silicon wafer into an alkaline aqueous solution for etching to form a number of microgrooves on the silicon wafer; (3.3) Continuing to etch the silicon wafer for 10 - 60 minutes until the microgrooves penetrate the bottom surface of the silicon wafer to form a silicon reflector cup; the inclination angle of the side walls of the microgrooves is 50 - 60 degrees.

2. The method for manufacturing the packaging structure of the deep ultraviolet LED according to claim 1, Characterized in that: In the step (5), an Al metal reflective film, an Ag metal reflective film or an oxide dielectric reflective film is deposited on the surface of the silicon reflector cup by magnetron sputtering or electron beam evaporation to form the deep ultraviolet reflective layer.

3. The method for manufacturing the packaging structure of the deep ultraviolet LED according to claim 1, Characterized in that: In the step (6), after the silicon wafer is bonded to the ceramic substrate with metal lines, inorganic materials are used for welding and fixing.

4. The method for manufacturing the packaging structure of the deep ultraviolet LED according to claim 1, Characterized in that: The step (7) is completed in a vacuum or nitrogen environment.

5. A packaging structure of a deep ultraviolet LED manufactured by the method for manufacturing the packaging structure of a deep ultraviolet LED according to any one of claims 1 - 4, Characterized in that, It includes a ceramic substrate, a silicon wafer, a deep ultraviolet LED chip and a high-transparency separator, the ceramic substrate is provided with metal lines, a number of silicon reflector cups vertically penetrating the silicon wafer are uniformly distributed on the silicon wafer, a deep ultraviolet reflective layer is provided on the surface of the silicon reflector cup, the silicon wafer is arranged on the ceramic substrate, the deep ultraviolet LED chip is arranged on the ceramic substrate corresponding to the center position of the silicon reflector cup, and is connected to the metal lines, and the high-transparency separator covers the silicon wafer and hermetically seals the silicon reflector cup.

6. The packaging structure of the deep ultraviolet LED according to claim 5, Characterized in that: The wall of the silicon reflector cup is an inclined surface with an inclination angle of 50 to 60 degrees.

7. The packaging structure of the deep ultraviolet LED according to claim 5, characterized in that: the high-transparency partition is a sapphire glass plate or a quartz glass plate; the ceramic substrate is an aluminum nitride plate body, an aluminum oxide plate body or a zirconium oxide plate body.

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