A light-emitting enhanced reverse polarity AlGaInP light-emitting diode and a method for preparing the same

Abstract

The invention relates to a light-enhanced reverse polarity AlGaInP light-emitting diode and a preparation method thereof, belonging to the field of optoelectronic technology. The invention optimizes and adjusts the thickness of a photoresist, the hardening temperature and the ICP etching conditions, realizes the expansion of a light-emitting area during the etching process, and realizes brightness improvement through subsequent AlGaInP coarsening. The method only requires AlGaInP coarsening and segmented etching to achieve the effects of three processes, greatly reduces the process flow, improves production efficiency and reduces costs.

Description

Technical Field

[0001] The invention relates to a light-emitting enhanced reverse-polarity AlGaInP light-emitting diode and a preparation method thereof, belonging to the technical field of optoelectronics. Background Art

[0002] As one of the most valued light source technologies, LED has the characteristics of small size on the one hand; on the other hand, it has the power-saving characteristics of low current and low voltage drive; at the same time, it also has many advantages such as strong structure, strong impact and vibration resistance, and ultra-long life. Quaternary AlGaInP is a semiconductor material with a direct wide band gap, which has been widely used in the preparation of various optoelectronic devices. Since the luminous band of AlGaInP material can cover the red to yellow-green band of visible light, the visible light emitting diodes made from it have attracted widespread attention. Light emitting diodes, especially AlGaInP (quaternary system) red high-brightness light emitting diodes, have been widely used in many aspects such as outdoor display, monitoring lighting, and car lights.

[0003] At present, for quaternary AlGaInP reverse polarity light-emitting diodes, AlGaInP roughening combined with GaP roughening, segmented etching and other processes are generally used to improve their brightness. As the demand for brightness increases, three processes need to be used at the same time to achieve it. The more processes are used, the greater the yield loss and cost increase. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention provides a method for preparing a light-enhanced reverse polarity AlGaInP light-emitting diode. The preparation method optimizes and adjusts the thickness of the photoresist, the hardening temperature and the ICP etching conditions, realizes the expansion of the light-emitting area during the etching process, and realizes the brightness improvement through the subsequent AlGaInP coarsening. The method only requires AlGaInP coarsening and segmented etching to achieve the effects of three processes, greatly reducing the process flow, improving production efficiency and reducing costs.

[0005] The technical solution of the present invention is as follows:

[0006] A light-emitting enhanced reverse polarity AlGaInP light-emitting diode comprises, from bottom to top, a permanent substrate ohmic contact electrode, a permanent substrate, a reflector, a dielectric film, a P-type ohmic contact layer, a P-GaP ohmic contact layer, a P-AlGaInP current expansion layer, a P-AlInP restriction layer, an MQW multi-quantum well layer, an N-AlInP restriction layer, an N-AlGaInP current expansion layer, an N-AlGaInP roughening layer, an N-GaAs ohmic contact layer and an N-side electrode.

[0007] A method for preparing the above-mentioned light-emitting enhanced reverse polarity AlGaInP light-emitting diode comprises the following steps:

[0008] (1) Using the MOCVD method, an N-GaAs buffer layer, an N-GalnP barrier layer, an N-GaAs ohmic contact layer, an N-AlGaInP roughening layer, an N-AlGaInP current spreading layer, an N-AlInP confinement layer, an MQW multi-quantum well layer, a P-AlInP confinement layer, a P-AlGaInP current spreading layer and a P-GaP ohmic contact layer are sequentially grown on an n-GaAs temporary substrate;

[0009] (2) depositing a dielectric layer on the P-GaP ohmic contact layer of the epitaxial wafer in step (1), and then performing photolithography, evaporation, etching, and stripping processes to form a P-type ohmic contact layer;

[0010] (3) evaporating a reflective mirror on the surface of the wafer obtained in step (2);

[0011] (4) bonding the wafer obtained in step (3) to a permanent substrate;

[0012] (5) Removing the n-GaAs temporary substrate and N-GaInP barrier layer of the wafer after bonding;

[0013] (6) Etching the N-GaAs ohmic contact layer outside the electrode area;

[0014] (7) evaporating an N-side electrode on the N-GaAs ohmic contact layer retained in step (6), and forming an ohmic contact through an alloy process;

[0015] (8) The wafer obtained in step (7) is subjected to photolithography to form a cutting pattern, and after hardening, the cutting pattern is formed by ICP etching, and the light-emitting area is expanded during the etching process;

[0016] (9) roughening the wafer obtained in step (8) with AlGaInP;

[0017] (10) thinning the permanent substrate, and then evaporating an ohmic contact metal and forming an alloy to form an ohmic contact electrode on the permanent substrate;

[0018] (11) Light-emitting diodes are obtained by laser scribing or diamond knife cutting.

[0019] Preferably, in step (2), the dielectric layer is SiO 2 Dielectric film.

[0020] Preferably, in step (3), the reflector is a gold mirror or a silver mirror.

[0021] Preferably, in step (4), the bonding method is Au-Au bonding or Au-In bonding, the bonding temperature is 200-350° C., the pressure is 200-500 kgf, and the time is 30-50 min.

[0022] Preferably, in step (5), a mixed solution of ammonia water, hydrogen peroxide and water is used to remove the temporary n-GaAs substrate of the wafer after bonding; in the mixed solution, the volume ratio of ammonia water, hydrogen peroxide and water is 1:4:5.

[0023] Preferably, in step (5), the N-GaInP barrier layer is removed by using a mixed solution of hydrochloric acid and water; in the mixed solution, the volume ratio of hydrochloric acid to water is 3:2.

[0024] Preferably, in step (7), the N-side electrode is a AuGeNiPtAu electrode, and the alloy is heated at 380° C. for 10 minutes to form an ohmic contact.

[0025] Preferably, in step (8), the thickness of the photoresist is 3.5-4.5 um, the hardening temperature is 80-100° C., and the hardening time is 10-20 min.

[0026] Further preferably, in step (8), the specific method of forming the cutting road and realizing the expansion of the light-emitting area is as follows:

[0027] First, perform the first stage of etching: adjust the first stage ICP etching parameters to RF power 350~450W, ICP power 650~750W, pressure 5.5~6.5mT, temperature 25-30℃, chlorine 55~65sccm, boron trichloride 18~22sccm, and etch for 8~10min;

[0028] Then the second stage of etching is performed: the etching temperature of the second stage is 18-22°C, and the time is 4-6 minutes;

[0029] In the first etching stage, due to the high temperature and high power, the wafer temperature exceeds the glass transition temperature of the photoresist, and the photoresist flows and expands outward. The outward expansion can be controlled by adjusting the power and temperature of the first etching stage.

[0030] Anything not described or limited in detail in the above technical solution shall be carried out with reference to the existing technology for manufacturing light emitting diodes.

[0031] The beneficial effects of the present invention are:

[0032] The present invention optimizes and adjusts the thickness of the photoresist, the hardening temperature and the ICP etching conditions, realizes the expansion of the light-emitting area during the etching process, and realizes the brightness improvement through the subsequent AlGaInP roughening. The method only needs AlGaInP roughening and segmented etching to achieve the effects of the three processes, greatly reducing the process flow, improving production efficiency and reducing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The drawings in the specification, which constitute a part of the present application, are used to provide further understanding of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute improper limitations on the present application.

[0034] Figure 1 It is a schematic structural diagram of the light-emitting enhanced reverse polarity AlGaInP light-emitting diode of the present invention;

[0035] Figure 2 Schematic diagrams of the appearance of the luminous area after roughening obtained by the process of the present invention and the existing process, wherein (a) is a picture of the luminous area after roughening obtained by the present invention, and (b) is a picture of the luminous area after roughening obtained by the existing process;

[0036] In the figure, 1. permanent substrate ohmic contact electrode, 2. permanent substrate, 3. reflector, 4. dielectric film, 5. P-type ohmic contact layer, 6. P-GaP ohmic contact layer, 7. P-AlGaInP current spreading layer, 8. P-AlInP confinement layer, 9-MQW multiple quantum well layer, 10. N-AIInP confinement layer, 11. N-AlGaInP current spreading layer, 12. N-AlGaInP roughening layer, 13. N-GaAs ohmic contact layer, 14. N-side electrode. DETAILED DESCRIPTION

[0037] In order to enable those skilled in the art to better understand the technical solutions in this specification, the technical solutions in the embodiments of the present invention are clearly and completely described, but not limited to this. Anything not fully described in the present invention shall be based on conventional techniques in the art.

[0038] Example 1

[0039] A light-emitting enhanced reverse polarity AlGaInP light-emitting diode comprises, from bottom to top, a permanent substrate ohmic contact electrode 1, a permanent substrate 2, a reflector 3, a dielectric film 4, a P-type ohmic contact layer 5, a P-GaP ohmic contact layer 6, a P-AlGaInP current spreading layer 7, a P-AlInP limiting layer 8, an MQW multi-quantum well layer 9, an N-AlInP limiting layer 10, an N-AlGaInP current spreading layer 11, an N-AlGaInP roughening layer 12, an N-GaAs ohmic contact layer 13 and an N-side electrode 14.

[0040] The preparation method comprises the following steps:

[0041] (1) Using the MOCVD method, an N-GaAs buffer layer, an N-GalnP barrier layer, an N-GaAs ohmic contact layer 13, an N-AlGaInP roughening layer 12, an N-AlGaInP current spreading layer 11, an N-AlInP confinement layer 10, an MQW multi-quantum well layer 9, a P-AlInP confinement layer 8, a P-AlGaInP current spreading layer 7 and a P-GaP ohmic contact layer 6 are sequentially grown on an n-GaAs temporary substrate;

[0042] (2) Depositing SiO on the P-GaP ohmic contact layer 6 of the epitaxial wafer in step (1) 2 The dielectric film is then processed by photolithography, evaporation, etching, and stripping to form a P-type ohmic contact layer; SiO 2 The dielectric film thickness conforms to an odd multiple of 1 / 4 wavelength;

[0043] (3) evaporating a gold reflector on the surface of the wafer obtained in step (2);

[0044] (4) performing Au-Au bonding of the wafer obtained in step (3) to a permanent substrate at a bonding temperature of 300°C, a bonding time of 45 minutes, and a bonding pressure of 400 kgf;

[0045] (5) using a mixed solution of ammonia, hydrogen peroxide and water to remove the n-GaAs temporary substrate of the wafer after bonding, wherein the volume ratio of ammonia, hydrogen peroxide and water in the mixed solution is 1:4:5; using a mixed solution of hydrochloric acid and water to remove the N-GaInP barrier layer, wherein the volume ratio of hydrochloric acid and water in the mixed solution is 3:2, exposing the N-GaAs ohmic contact layer 13;

[0046] (6) Etching away the N-GaAs ohmic contact layer 13 outside the electrode area;

[0047] (7) evaporating AuGeNiPtAu electrode on the N-GaAs ohmic contact layer 13 retained in step (6), and alloying at 380° C. for 10 minutes to form an ohmic contact;

[0048] (8) The cutting path pattern is formed by photolithography process, the photoresist thickness is 4.2um, the hardening film is 100℃, 20min, the first stage ICP etching parameters are adjusted to RF power 400W, ICP power 700W, pressure 6mT, temperature 30℃, chlorine 60sccm, boron trichloride 20sccm, etching for 9min, the second stage etching temperature is 20min, and the time is 5min. After etching, the cutting path is roughened and then the resist is removed;

[0049] (9) roughening the wafer obtained in step (8) with AlGaInP and then performing a secondary etching;

[0050] (10) Thinning the permanent substrate 2 to 160 μm, then evaporating the ohmic contact metal TiAu, and alloying at 200° C. for 10 min to form a permanent substrate ohmic contact electrode 1;

[0051] (11) Light-emitting diodes are obtained by laser scribing or diamond knife cutting.

[0052] Example 2

[0053] A method for preparing a high-brightness reverse-polarity AlGaInP light-emitting diode, the specific steps are as described in Example 1, except that in step (8), the cutting path roughening is not performed after the etching is completed.

[0054] Comparative Example 1

[0055] A method for preparing a reverse polarity AlGaInP light-emitting diode comprises conventional processes of outer expansion and roughening of a non-luminous region, roughening of a cutting path, and segmented etching.

[0056] For the products obtained in Example 1, Example 2 and Comparative Example 1, two products were taken for performance testing, and the results are shown in Table 1:

[0057] Table 1 Performance test results

[0058]

[0059] In Table 1, VF1, LOP1, and WLD1 refer to forward operating voltage, brightness, and wavelength, respectively. Compared with Comparative Example 1, Example 1 improves the brightness by 5% without increasing other process flows and costs.

[0060] Compared with comparative example 1, embodiment 2 simplifies the process and reduces the cost while maintaining the brightness.

[0061] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a light-emitting enhanced reverse polarity AlGaInP light-emitting diode, characterized in that: The light-emitting enhanced reverse polarity AlGaInP light-emitting diode comprises, from bottom to top, a permanent substrate ohmic contact electrode, a permanent substrate, a reflector, a dielectric film, a P-type ohmic contact layer, a P-GaP ohmic contact layer, a P-AlGaInP current spreading layer, a P-AlInP limiting layer, an MQW multi-quantum well layer, an N-AlInP limiting layer, an N-AlGaInP current spreading layer, an N-AlGaInP roughening layer, an N-GaAs ohmic contact layer and an N-side electrode; The method for preparing a light-emitting enhanced reverse polarity AlGaInP light-emitting diode comprises the following steps: (1) Using the MOCVD method, an N-GaAs buffer layer, an N-GalnP barrier layer, an N-GaAs ohmic contact layer, an N-AlGaInP roughening layer, an N-AlGaInP current spreading layer, an N-AlInP confinement layer, an MQW multi-quantum well layer, a P-AlInP confinement layer, a P-AlGaInP current spreading layer and a P-GaP ohmic contact layer are sequentially grown on an n-GaAs temporary substrate; (2) depositing a dielectric layer on the P-GaP ohmic contact layer of the epitaxial wafer in step (1), and then performing photolithography, evaporation, etching, and stripping processes to form a P-type ohmic contact layer; (3) evaporating a reflective mirror on the surface of the wafer obtained in step (2); (4) bonding the wafer obtained in step (3) to a permanent substrate; (5) Removing the n-GaAs temporary substrate and N-GaInP barrier layer of the wafer after bonding; (6) Etching the N-GaAs ohmic contact layer outside the electrode area; (7) evaporating an N-side electrode on the N-GaAs ohmic contact layer retained in step (6), and forming an ohmic contact through an alloy process; (8) The wafer obtained in step (7) is subjected to photolithography to form a cutting pattern, and after hardening, the cutting pattern is formed by ICP etching, and the light-emitting area is expanded during the etching process; (9) roughening the wafer obtained in step (8) with AlGaInP; (10) thinning the permanent substrate, and then evaporating an ohmic contact metal and forming an alloy to form an ohmic contact electrode on the permanent substrate; (11) Obtaining light-emitting diodes by laser scribing or diamond knife cutting; In step (8), the thickness of the photoresist is 3.5-4.5 μm, the hardening temperature is 80-100° C., and the hardening time is 10-20 min.

2. The method for preparing the light-extraction enhanced reverse polarity AlGaInP light-emitting diode according to claim 1, characterized in that: In step (2), the dielectric layer is a SiO2 dielectric film.

3. The method for preparing the light-extraction enhanced reverse polarity AlGaInP light-emitting diode according to claim 1, characterized in that: In step (3), the reflecting mirror is a gold mirror or a silver mirror.

4. The method for preparing the light-extraction enhanced reverse polarity AlGaInP light-emitting diode according to claim 1, characterized in that: In step (4), the bonding method is Au-Au bonding or Au-In bonding, the bonding temperature is 200-350°C, the pressure is 200-500kgf, and the time is 30-50min.

5. The method for preparing the light-extraction enhanced reverse polarity AlGaInP light-emitting diode according to claim 1, characterized in that: In step (5), a mixed solution of ammonia water, hydrogen peroxide and water is used to remove the temporary n-GaAs substrate of the wafer after bonding; in the mixed solution, the volume ratio of ammonia water, hydrogen peroxide and water is 1:4:

5.

6. The method for preparing the light-extraction enhanced reverse polarity AlGaInP light-emitting diode according to claim 5, characterized in that: In step (5), the N-GaInP barrier layer is removed by using a mixed solution of hydrochloric acid and water; in the mixed solution, the volume ratio of hydrochloric acid to water is 3:

2.

7. The method for preparing the light-extraction enhanced reverse polarity AlGaInP light-emitting diode according to claim 1, characterized in that: In step (7), the N-side electrode is a AuGeNiPtAu electrode, and the alloy is heated at 380°C for 10 minutes to form an ohmic contact.

8. The method for preparing the light-extraction enhanced reverse polarity AlGaInP light-emitting diode according to claim 7, characterized in that: In step (8), the specific method of forming the cutting path and realizing the expansion of the light-emitting area is as follows: First, perform the first stage of etching: adjust the first stage ICP etching parameters to RF power 350~450W, ICP power 650~750W, pressure 5.5~6.5mT, temperature 25-30℃, chlorine 55~65sccm, boron trichloride 18~22sccm, and etch for 8~10min; Then the second stage of etching is performed: the etching temperature of the second stage is 18-22°C, and the time is 4-6 minutes; In the first etching stage, due to the high temperature and high power, the wafer temperature exceeds the glass transition temperature of the photoresist, and the photoresist flows and expands outward. The outward expansion can be controlled by adjusting the power and temperature of the first etching stage.

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