Preparation method of AlGaInP quaternary vertical LED chip

Abstract

The invention provides a preparation method of an AlGaInP quaternary vertical LED chip, and relates to the technical field of photoelectrons. According to the preparation method, the anisotropic conductive adhesive is used as a bonding layer, the bonding layer is used as a substrate support, a transverse expansion layer of current is realized by using anisotropic conductivity, high-voltage bonding and bonding of permanent substrates such as silicon wafers and sapphire are not needed in the process mode, the process is simple and convenient, and the gear matching rate of reverse polarity chip output can be effectively improved.

Description

Technical Field

[0001] The invention relates to the field of optoelectronic technology, in particular to a method for preparing an AlGaInP quaternary vertical LED chip. Background Art

[0002] The AlGaInP material system was originally used to manufacture visible light laser diodes, and was first proposed by Japanese researchers in the mid-1980s. LED and LD devices of that period usually used Ga0.5In0.5P matched with GaAs substrate as the active light-emitting area, with a light-emitting wavelength of 650nm, and were widely used in quaternary laser pens and DVD players. Later, researchers found that the introduction of Al components in GaInP could further shorten the light-emitting wavelength, but if the Al content was too high, the luminous efficiency of the device would drop sharply, because when the Al content in GaInP exceeded 0.53, AlGaInP would become an indirect bandgap semiconductor, so AlGaInP materials are generally only used to prepare LED devices with a light-emitting wavelength of more than 570nm. In 1997, the world's first AlGaInP-based LED with a multiple quantum well (MQW) composite Bragg reflector (DBR) structure was born. LED devices designed based on this structure still occupy a large share of the low-end LED market.

[0003] Aluminum gallium indium phosphide (AlGaInP) materials are developing rapidly and are used to make high-power and high-brightness red and yellow LEDs. Although red LEDs made of AlGaInP materials have been commercialized, LEDs with quaternary alloy materials as multi-quantum well active regions have extremely high internal quantum efficiency. However, due to the limitations of the material itself and the substrate, the external quantum efficiency of traditional AlGaInP-LEDs is extremely low. An important reason for the poor light output efficiency of traditional AlGaInP-LEDs is that the substrate GaAs is a light-absorbing material, resulting in a large amount of light radiated from the active layer (MQW) to the substrate being absorbed by the GaAs substrate. Even if the industry has developed a metal omnidirectional reflector (ODR) with substrate transfer technology to replace the traditional GaAs substrate, the radiated light will still cause a fixed proportion of loss after being reflected to the active layer.

[0004] At present, reverse polarity AlGaInP quaternary LED chips are widely used in the field of high-power red light LED display screens. Reverse polarity means substrate replacement. The traditional method is to replace the GaAs substrate with large light absorption with a single crystal conductive Si substrate or sapphire substrate through high-voltage bonding, which can improve the luminous efficiency by more than 20%. However, due to the long reverse polarity process, the output matching rate of reverse polarity chips has not been high at this stage. The low output matching rate has a great impact on the production of reverse polarity chips. Summary of the invention

[0005] In response to the above problems, the present application provides a method for preparing an AlGaInP quaternary vertical LED chip, which uses anisotropic conductive adhesive as a bonding layer, does not require high-voltage bonding, does not require bonding to permanent substrates such as silicon wafers and sapphire, and has a simple process.

[0006] The technical solution adopted by the present invention to solve the technical problem is:

[0007] A method for preparing an AlGaInP quaternary vertical LED chip comprises the following steps:

[0008] S1, roughening the P-type layer of the AlGaInP system epitaxial wafer to obtain a roughened P-type layer;

[0009] S2, preparing a transparent conductive film on the roughened surface of the P-type layer;

[0010] S3, preparing anisotropic conductive adhesive on the surface of the transparent conductive film, and curing it by heating to form a supporting layer;

[0011] S4, removing the GaAs substrate layer and the N-type cutoff layer by using an etching solution to expose the N-type ohmic contact layer;

[0012] S5, etching the N-type ohmic contact layer to form an etched area and a reserved area;

[0013] S6, roughening the etched area using a roughening liquid;

[0014] S7, etching the epitaxial wafer to form cutting paths;

[0015] S8, forming an N electrode on the surface of the N ohmic contact layer;

[0016] S9, cutting is performed according to the cutting paths formed in step S7 to obtain independent chips.

[0017] Furthermore, in step S1, a mixed solution of HF, HNO3 and CH3COOH is used to roughen the P-type layer of the AlGaInP system epitaxial wafer, the temperature of the etching solution is 25-35° C., and the solution immersion time is 30-120 seconds.

[0018] Furthermore, the thickness of the transparent conductive film is 300-1200 angstroms.

[0019] Furthermore, the anisotropic conductive adhesive has a thickness of 100-200 um and is cured at a temperature of 150° C.-280° C.

[0020] Furthermore, the etching solution in step S4 is a mixture of ammonia water, hydrogen peroxide and pure water.

[0021] Furthermore, in step S5, a wet etching or dry etching process is used in combination with a photoresist mask to etch the N-type ohmic contact layer.

[0022] Furthermore, step S7 uses a wet etching or dry etching process in combination with a photoresist mask to etch the epitaxial wafer.

[0023] Furthermore, the etching area is in a long strip structure and is spaced apart from the reserved area.

[0024] Furthermore, the roughening solution in step S6 is a mixture of 96% phosphoric acid, 36.5% hydrochloric acid and pure water, and the roughening time is 30-60 seconds.

[0025] Furthermore, the cutting path only retains the support layer.

[0026] The beneficial effects of the present invention are:

[0027] The characteristic of anisotropic conductive adhesive is that the resistance characteristics of the Z-axis electrical conduction direction and the XY insulating plane have obvious differences. When the difference between the Z-axis on-resistance value and the XY plane insulation resistance value exceeds a certain ratio, it can be called good conductive anisotropy. The embodiment of the present application provides a method for preparing an AlGaInP quaternary vertical LED chip, which uses anisotropic conductive adhesive as a bonding layer. This layer serves as a substrate support and uses anisotropic conductivity to realize the lateral expansion layer of current. This process does not require high-voltage bonding, does not require permanent substrate bonding such as silicon wafers and sapphire, and has a simple process that can effectively improve the matching rate of reverse polarity chip output. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a cross-sectional view of an AlGaInP system epitaxial wafer;

[0029] Figure 2 A cross-sectional view of the reverse polarity LED quaternary chip manufactured in step S1;

[0030] Figure 3 A cross-sectional view of the reverse polarity LED quaternary chip manufactured in step S2;

[0031] Figure 4 A cross-sectional view of the reverse polarity LED quaternary chip manufactured in step S3;

[0032] Figure 5 A cross-sectional view of the reverse polarity LED quaternary chip manufactured in step S4;

[0033] Figure 6 A cross-sectional view of the reverse polarity LED quaternary chip manufactured in step S5;

[0034] Figure 7A cross-sectional view of the reverse polarity LED quaternary chip manufactured in step S6;

[0035] Figure 8 A cross-sectional view of the reverse polarity LED quaternary chip manufactured in step S7;

[0036] Fig. 9 Cross-sectional view of a single chip produced in step S8.

[0037] In the figure: 1, P-type layer; 2, GaAs substrate layer; 3, transparent conductive film; 4, anisotropic conductive adhesive; 5, N-type cutoff layer; 6, N-type ohmic contact layer; 61, etching area; 62, reserved area; 7, cutting road; 8, N electrode. DETAILED DESCRIPTION

[0038] In order to enable those skilled in the art to better understand the technical solutions in the present application, the technical solutions in the embodiments of the present application will be described in detail below in conjunction with the drawings in the embodiments of the present application, and the described embodiments are only part of the embodiments of the present application, not all of the embodiments. All other embodiments obtained by those skilled in the art without creative work on the basis of the embodiments of the present application shall belong to the protection scope of the present application.

[0039] A method for preparing an AlGaInP quaternary vertical LED chip comprises the following steps:

[0040] S1, using a mixture of HF, HNO3 and CH3COOH Figure 1 The P-type layer 1 of the AlGaInP system epitaxial wafer shown in FIG. Figure 2 The roughened P-type layer 1 is shown.

[0041] As a specific implementation manner, the volume ratio of HF, HNO3 and CH3COOH in this embodiment is 3:2:4, the temperature of the etching solution is 25-35°C, and the solution immersion time is 30-120 seconds.

[0042] S2, such as Figure 3 As shown, a transparent conductive film is prepared on the surface of the roughened P-type layer 1.

[0043] As a specific implementation, the transparent conductive film described in this embodiment is made of ITO or ZnO, and the thickness of the transparent conductive film is 300-1200 angstroms.

[0044] S3, such as Figure 4 As shown, anisotropic conductive adhesive is prepared on the surface of the transparent conductive film by scraping, spraying or dipping, and is cured by heating to form a support layer.

[0045] As a specific implementation, the anisotropic conductive adhesive in this embodiment has a thickness of 100-200 um and is cured at a temperature of 150° C.-280° C.

[0046] S4, such as Figure 5 As shown, the GaAs substrate layer 2 and the N-type cutoff layer 5 are removed by etching solution, so that the N-type ohmic contact layer 6 (heavily doped layer) is exposed.

[0047] The etching liquid is a mixture of ammonia water, hydrogen peroxide and pure water, and the volume ratio of ammonia water, hydrogen peroxide and water in the mixture is 1:2:6.

[0048] S5, such as Figure 6 As shown, the N-type ohmic contact layer 6 (heavily doped layer) is etched using a wet etching or dry etching process in conjunction with a photoresist mask to form an etched area 61 and a reserved area 62 .

[0049] As a specific implementation manner, the etching area 61 described in this embodiment is in a long strip structure and is arranged at intervals from the reserved area 62 .

[0050] S6, using a roughening solution to perform a roughening treatment on the etched area 61 obtained in step S5.

[0051] The roughening liquid is a mixture of 96% phosphoric acid, 36.5% hydrochloric acid and pure water, with a volume ratio of 1:3:5 or 2:5:10, and the roughening time is 30-60 seconds.

[0052] S7, such as Figure 7 As shown, the epitaxial wafer is etched by wet etching or dry etching process in cooperation with a photoresist mask to form a cutting path 7, and the cutting path 7 only retains the support layer.

[0053] S8, such as Figure 8 As shown, an N electrode 8 is manufactured on the surface of the N ohmic contact layer, and the N electrode 8 is in contact with at least one reserved area 62 .

[0054] S9, cutting is performed according to the cutting path 7 formed in step S7 by using laser cutting or cutting wheel cutting to obtain Fig. 9 The stand-alone chips are shown.

[0055] Other embodiments obtained by those skilled in the art by combining, splitting, reorganizing, etc. the embodiments of the present application on the basis of the embodiments provided in the present application do not exceed the protection scope of the present application.

[0056] The above specific implementation methods have detailed the purpose, technical solutions and beneficial effects of the embodiments of the present application. The above are only specific implementation methods of the embodiments of the present application and are not used to limit the protection scope of the embodiments of the present application. That is, any modifications, equivalent substitutions, improvements, etc. made on the basis of the embodiments of the present application should be included in the protection scope of the embodiments of the present application.

Claims

1. A method for preparing an AlGaInP quaternary vertical LED chip, characterized in that: The following steps are included: S1, roughening the P-type layer (1) of the AlGaInP system epitaxial wafer to obtain a roughened P-type layer (1); S2, preparing a transparent conductive film on the roughened surface of the P-type layer (1); S3, preparing anisotropic conductive adhesive on the surface of the transparent conductive film, and curing it by heating to form a supporting layer; S4, using an etching solution to remove the GaAs substrate layer (2) and the N-type cutoff layer (5), so that the N-type ohmic contact layer (6) is exposed; S5, etching the N-type ohmic contact layer (6) to form an etched area (61) and a reserved area (62); S6, roughening the etched area (61) using a roughening liquid; S7, etching the epitaxial wafer to form a cutting path (7); S8, forming an N electrode (8) on the surface of the N ohmic contact layer; S9, cutting is performed according to the cutting path (7) formed in step S7 to obtain independent chips.

2. The method for preparing an AlGaInP quaternary vertical LED chip according to claim 1, characterized in that: Step S1: The P-type layer (1) of the AlGaInP system epitaxial wafer is roughened by using a mixed solution of HF, HNO3 and CH3COOH. The temperature of the etching solution is 25-35° C. and the solution immersion time is 30-120 seconds.

3. The method for preparing an AlGaInP quaternary vertical LED chip according to claim 1, characterized in that: The thickness of the transparent conductive film is 300-1200 angstroms.

4. The method for preparing an AlGaInP quaternary vertical LED chip according to claim 1, characterized in that: The anisotropic conductive adhesive has a thickness of 100-200 um and is cured at a temperature of 150° C.-280° C.

5. The method for preparing an AlGaInP quaternary vertical LED chip according to claim 1, characterized in that: The etching solution in step S4 is a mixture of ammonia water, hydrogen peroxide and pure water.

6. The method for preparing an AlGaInP quaternary vertical LED chip according to claim 1, characterized in that: In step S5, a wet etching or dry etching process is used in combination with a photoresist mask to etch the N-type ohmic contact layer (6).

7. The method for preparing an AlGaInP quaternary vertical LED chip according to claim 1, characterized in that: In step S7, a wet etching or dry etching process is used to etch the epitaxial wafer in cooperation with a photoresist mask.

8. The method for preparing an AlGaInP quaternary vertical LED chip according to claim 1, characterized in that: The etching area (61) is in a long strip structure and is arranged at intervals from the reserved area (62).

9. The method for preparing an AlGaInP quaternary vertical LED chip according to claim 1, characterized in that: The roughening solution in step S6 is a mixture of 96% phosphoric acid, 36.5% hydrochloric acid and pure water, and the roughening time is 30-60 seconds.

10. The method for preparing an AlGaInP quaternary vertical LED chip according to claim 1, characterized in that: The cutting path (7) only retains the supporting layer.

Images