Method for screening coarsening liquid in preparation process of reversed-polarity red-light LED (light-emitting diode) high-power chip

Abstract

The invention provides a coarsening liquid screening method in the preparation process of a reversed-polarity red light LED high-power chip, which comprises the following steps of: preparing 4-8 spaced patterns in the middle position of the surface of a reversed-polarity red light LED high-power epitaxial wafer, retaining a barrier layer outside the patterns, performing vapor plating electrode annealing, and then performing vapor plating on the barrier layer outside the patterns; 4-8 spaced patterns are obtained around 4-8 electrodes through conventional photoetching, then different coarsening solutions are used for coarsening, the different coarsened patterns are subjected to power-on testing, different light emitting powers are obtained, photoelectric parameters are compared, the pattern with the optimal photoelectric parameters is obtained, and therefore the optimal coarsening solution is screened out. The screened coarsening liquid can be used for preparing the reversed-polarity red-light LED high-power chips on a large scale, the obtained reversed-polarity red-light LED high-power chips are high in consistency, the yield is increased, the problem of poor parameters is avoided, the light extraction efficiency is effectively improved, and the light extraction efficiency is more stable.

Description

Technical Field

[0001] The invention relates to a method for screening a roughening liquid in a process of preparing a reverse polarity red light LED high-power chip, belonging to the technical field of optoelectronics. Background Art

[0002] The development of quaternary red LED chips dates back to 1962, when Nick Holonyak successfully developed the first red diode at General Electric. Holonyak was hailed as the "Father of the LED" for this invention, earning him the title of "Father of the LED." Initially used in indicator lights, displays, and signal lamps, red diodes gradually became one of the earliest practical types of LED technology.

[0003] Currently, reverse-polarity red LED high-power chips are widely used in high-power outdoor LED displays. Reverse polarity refers to replacing the substrate of a conventional high-power LED chip with a single-crystal conductive Si or sapphire substrate, replacing the highly light-absorbing GaAs substrate with one other than the conventional one. After the replacement, the GaAs substrate is first etched away, followed by the etching barrier layer, exposing the heavily doped layer. Subsequently, an Au film is deposited on the heavily doped layer to form an ohmic contact. The N-side ohmic contact pattern is then formed using photolithography, followed by the N-electrode. The chip surface is then roughened. This surface roughening process is performed during the fabrication of reverse-polarity red LED high-power chips primarily to improve light extraction efficiency. By roughening the chip surface, the probability of light scattering and refraction is increased, thereby reducing light loss due to total internal reflection within the chip, ultimately allowing more light to exit the chip. A flat chip surface traps some light within the chip due to total internal reflection. A roughened surface breaks this confinement, allowing more light to escape, thus improving light extraction efficiency.

[0004] Therefore, the quality of roughening plays a key role in achieving high light extraction efficiency. Because the roughening process involves etching the light-emitting surface, the choice of roughening solution and control of etching time will inevitably affect the performance of high-power, reverse-polarity red LED chips. Furthermore, roughened chips cannot be reworked. Therefore, minimizing this impact and maximizing light extraction efficiency have become key challenges.

[0005] Patent document CN110120443B provides a method for preparing a reverse-polarity AlGaInP quaternary LED chip, comprising: sequentially preparing a P-side ohmic contact layer and a current blocking layer on the P-side of a reverse-polarity AlGaInP quaternary LED epitaxial wafer; bonding the wafer to a single-crystalline conductive Si substrate or sapphire substrate; removing the GaAs substrate and blocking layer, and preparing an N-side ohmic contact electrode pattern, comprising a number of regularly distributed small units sequentially connected by linear electrode patterns; removing the linear electrode patterns connecting four small units to the electrode patterns of surrounding small units; performing point measurements on the four small units, combining several small unit electrode patterns according to customer requirements, and removing any unnecessary linear electrode patterns between the small unit electrode patterns based on the size of the combined electrode patterns, resulting in a high alignment rate. This method addresses the alignment issue of reverse-polarity quaternary LED chips, but its preparation method does not consider the roughening issue and cannot be applied to the preparation of high-power reverse-polarity red LED chips.

[0006] Patent document CN109755367B provides a roughening method for reverse polarity AlGaInP quaternary LED chips. The method involves first corroding and removing the substrate and barrier layer of the bonded AlGaInP quaternary LED chip, then vapor-depositing a GeAu film on the surface as an N-type ohmic contact electrode. A roughening protection pattern is then prepared on the surface. The N-type AlGaInP layer without roughening protection is roughened by ICP etching and wet roughening through the roughening protection pattern. This avoids the problem of unstable roughening effect of reverse polarity AlGaInP quaternary LED chips, increases light extraction efficiency, and improves chip quality. The above method addresses the problem of unstable roughening effect and proposes a roughening method. Due to the inconsistency of reverse polarity red light LED high-power epitaxial wafers, the use of this method has certain limitations and cannot be applied to reverse polarity red light LED high-power chips on a large scale.

[0007] The current roughening method involves directly roughening the surface of reverse polarity epitaxial wafers with a single roughening solution. This involves preparing a large number of reverse polarity epitaxial wafers and then using different roughening solutions to screen for the solution with the highest light extraction efficiency. This method requires extensive experimentation, is time-consuming and resource-intensive, and is inefficient. Furthermore, each experiment requires the use of a new epitaxial wafer, which is costly and results in significant material waste. Furthermore, variations in epitaxial wafer quality can occur across batches, leading to inconsistent results.

[0008] Therefore, there is an urgent need for an alternative solution that does not require a large number of epitaxial wafers, does not require a large number of experiments, is low-cost and saves materials. Summary of the Invention

[0009] In view of the shortcomings of the existing technology, the present invention provides a method for screening a roughening liquid in the process of preparing a reverse polarity red light LED high-power chip.

[0010] The present invention prepares 4-8 spaced patterns in the middle of the surface of a high-power epitaxial wafer of a reverse polarity red light LED, retains a barrier layer outside the pattern, evaporates and anneals electrodes, and obtains 4-8 spaced patterns around the 4-8 electrodes by conventional photolithography. Different roughening solutions are then used for roughening. After roughening, different patterns are subjected to power-on testing to obtain different light output powers. Photoelectric parameters are compared to obtain a pattern with optimal photoelectric parameters, thereby screening out the optimal roughening solution.

[0011] The method of the present invention eliminates the need for large numbers of epitaxial wafers and extensive experimentation, resulting in low cost and material savings. Using only one epitaxial wafer, the optimal roughening solution can be screened from 4-8 roughening solutions. The screened roughening solution can be used to mass-produce high-power reverse-polarity red LED chips. The resulting high-power reverse-polarity red LED chips exhibit high consistency, improve yield, avoid parameter problems, and effectively enhance light extraction efficiency and provide greater stability.

[0012] The present invention is achieved through the following technical solutions:

[0013] A method for screening a roughening solution in the process of preparing a reverse polarity red LED high-power chip comprises the following steps:

[0014] a) providing a reverse polarity red light LED high-power epitaxial wafer, wherein the reverse polarity red light LED high-power epitaxial wafer comprises, from bottom to top, a single crystal conductive Si substrate or a sapphire substrate, a reverse polarity red light LED epitaxial layer, an N-type AlGaInP layer, a heavily doped GaAs layer, a barrier layer, and a GaAs substrate;

[0015] b) removing the GaAs substrate of step a) to expose the barrier layer, coating the barrier layer with a layer of negative photoresist, preparing 4-8 spaced negative photoresist electrode patterns on the upper surface of the barrier layer of the reverse polarity red LED high-power epitaxial wafer, retaining the negative photoresist outside the electrode pattern, and removing the barrier layer on the negative photoresist electrode pattern;

[0016] c) evaporating a Ni / Au / Ge / Ni / Au film on the negative photoresist pattern prepared in step b), removing the negative photoresist and the Ni / Au / Ge / Ni / Au film above the negative photoresist using a blue film to leave 4-8 Ni / Au / Ge / Ni / Au electrodes, and forming good ohmic contacts between the 4-8 Ni / Au / Ge / Ni / Au electrodes and the heavily doped GaAs layer below by high temperature annealing;

[0017] d) applying a layer of positive photoresist on the reverse polarity red LED high-power epitaxial wafer prepared in step c), and forming a pattern of 4-8 intervals around the 4-8 Ni / Au / Ge / Ni / Au electrodes by conventional photolithography, removing the positive photoresist outside the Ni / Au / Ge / Ni / Au electrodes within the pattern, and retaining the positive photoresist in other areas and the 4-8 Ni / Au / Ge / Ni / Au electrodes;

[0018] e) removing the barrier layer and heavily doped GaAs layer of 4-8 patterns outside the Ni / Au / Ge / Ni / Au electrode in step d), and dripping different roughening solutions on different patterns in turn to roughen the exposed N-type AlGaInP layer. After the roughening is completed, removing the positive photoresist;

[0019] f) Power-on testing is performed on the different patterns in step e) to obtain different light output powers. By comparing the optoelectronic parameters, the optimal roughening pattern is obtained. An epitaxial wafer is prepared to screen out the optimal roughening solution. The entire reverse polarity red light LED high-power epitaxial wafer is processed according to the determined process parameters to obtain the optimal reverse polarity red light LED high-power chip.

[0020] According to the preferred embodiment of the present invention, in step b), the thickness of the negative photoresist is 2.5-4 μm.

[0021] Preferably, according to the present invention, in step b), 4-8 spaced negative photoresist electrode patterns are located in the middle of the upper surface of the barrier layer, and the negative photoresist electrode pattern closest to the edge of the epitaxial wafer is 1-3 mm away from the edge of the reverse polarity red LED high-power epitaxial wafer.

[0022] According to a preferred embodiment of the present invention, in step b), the number of spaced negative photoresist electrode patterns is 4, 6 or 8.

[0023] According to a preferred embodiment of the present invention, in step b), the spaced negative photoresist electrode patterns are circular with a diameter of 100-120 μm.

[0024] According to a preferred embodiment of the present invention, in step b), there are four spaced negative photoresist electrode patterns arranged in a square with a side length of 250-300 μm.

[0025] Preferably, according to the present invention, in step c), the thickness of the Ni / Au / Ge / Ni / Au film is 1.5-2.5um, wherein the thickness of Ni is 0.02-0.04um, the thickness of Au is 0.08-0.1um, the thickness of Ge is 0.03-0.04um, the thickness of Ni is 0.07-0.09um, and the thickness of Au is 1.3-2.3um.

[0026] According to the preferred embodiment of the present invention, in step c), the high temperature annealing temperature is 350-380° C. and the time is 10-15 minutes.

[0027] Preferably according to the present invention, in step d), the thickness of the positive photoresist is 1.5-1.8 um.

[0028] According to a preferred embodiment of the present invention, in step d), the spaced patterns are located on the periphery of the Ni / Au / Ge / Ni / Au electrode, and their shape and number match the shape of the Ni / Au / Ge / Ni / Au electrode.

[0029] According to a preferred embodiment of the present invention, in step d), there are four spaced patterns arranged in a square.

[0030] Preferably, in step e), the roughening liquids used are roughening liquid 1, roughening liquid 2, roughening liquid 3, and roughening liquid 4, respectively, and the four roughening liquids are used to roughen the pattern in step d).

[0031] According to a preferred embodiment of the present invention, the four roughening liquids are randomly matched with the four interval patterns in step d).

[0032] Further preferably, the roughening liquid 1 is a mixture of hydrochloric acid and H2O with a mass concentration of 36.5%, a volume ratio of hydrochloric acid to H2O of 1:2, and a roughening time of 60-90 seconds.

[0033] Further preferably, the roughening liquid 2 is a mixture of hydrochloric acid and H2O with a mass concentration of 36.5%, a volume ratio of hydrochloric acid to H2O of 1:1, and a roughening time of 60-90 seconds.

[0034] Further preferably, the roughening liquid 3 is a mixture of phosphoric acid with a mass concentration of 96%, hydrochloric acid with a mass concentration of 36.5% and H2O, the volume ratio of phosphoric acid, hydrochloric acid and H2O is 1:1:2, and the roughening time is 120-150 seconds.

[0035] Further preferably, the roughening liquid 4 is a mixture of 96% phosphoric acid, 36.5% hydrochloric acid, hydrogen peroxide and H2O, the volume ratio of phosphoric acid, hydrochloric acid, hydrogen peroxide and H2O is 4:4:1:8, and the roughening time is 120-150 seconds.

[0036] The technical features and advantages of the present invention are as follows:

[0037] 1. The present invention prepares 4-8 spaced patterns in the middle position of the surface of a high-power epitaxial wafer of a reverse polarity red light LED, retains the barrier layer outside the pattern, and first evaporates and anneals the electrode, and then obtains 4-8 spaced patterns around the 4-8 electrodes by conventional photolithography. Then, different roughening solutions are used for roughening. After roughening, different patterns are powered on and tested to obtain different light output powers. The photoelectric parameters are compared to obtain the pattern with the optimal photoelectric parameters, thereby screening the optimal roughening solution. The operation is simple and the optimal reverse polarity red light LED high-power chip can be obtained to the greatest extent, thereby improving the yield and avoiding the problem of poor parameters.

[0038] 2. The method of the present invention does not require a large number of epitaxial wafers or extensive experiments, is low-cost and material-efficient. Using only one epitaxial wafer, the optimal roughening solution can be screened from 4-8 roughening solutions. The screened roughening solution can be used to mass-produce high-power reverse polarity red LED chips. The resulting high-power reverse polarity red LED chips have high consistency, improved yield, avoided parameter problems, and effectively improved light extraction efficiency and stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a cross-sectional view of the reverse polarity red LED high-power epitaxial wafer produced in step a) of Example 1;

[0040] Figure 2 This is a cross-sectional view of the reverse polarity red LED high-power epitaxial wafer (top) produced in step b) of Example 1;

[0041] Figure 3 This is a cross-sectional view of the reverse polarity red LED high-power epitaxial wafer (top) produced in step c) of Example 1;

[0042] Figure 4 This is a cross-sectional view of the reverse polarity red LED high-power epitaxial wafer (top) produced in step d) of Example 1;

[0043] Figure 5 This is a cross-sectional view of the reverse polarity red LED high-power epitaxial wafer (top) produced in step e) of Example 1.

[0044] In the figure, 1. Single crystal conductive Si substrate, 2. Reverse polarity red LED epitaxial layer, 3. N-type AlGaInP layer, 4. Heavily doped GaAs layer, 5. Barrier layer, 6. GaAs substrate, 7. Negative photoresist, 8. Ni / Au / Ge / Ni / Au film, 9. Positive photoresist. DETAILED DESCRIPTION

[0045] The following is combined with Figure 1 To the attached Figure 5 The present invention is further described.

[0046] Example 1

[0047] A method for screening a roughening solution in the preparation process of a reverse polarity red LED high-power chip, comprising the following steps:

[0048] a) providing a reverse polarity red light LED high power epitaxial wafer, which comprises, from bottom to top, a single crystal conductive Si substrate or a sapphire substrate, a reverse polarity red light LED epitaxial layer, an N-type AlGaInP layer, a heavily doped GaAs layer, a barrier layer, and a GaAs substrate, with a structure as follows: Figure 1 As shown;

[0049] b) removing the GaAs substrate of the reverse polarity red LED high-power epitaxial wafer to expose the barrier layer, coating the barrier layer with a layer of negative photoresist 7 having a thickness of 3 μm, and preparing four spaced-apart negative photoresist electrode patterns at the center of the upper surface of the barrier layer. The four patterns are arranged into a square with a side length of 250 μm. The negative photoresist electrode pattern closest to the edge of the epitaxial wafer is 1 mm away from the edge of the reverse polarity red LED high-power epitaxial wafer. The negative photoresist electrode pattern is circular with a diameter of 100 μm. The negative photoresist outside the electrode pattern is retained, and the barrier layer of the negative photoresist electrode pattern is removed, as shown in FIG. Figure 2 As shown;

[0050] c) evaporating a layer of Ni / Au / Ge / Ni / Au film 8 on the negative photoresist pattern prepared in step b), wherein the thickness of the Ni / Au / Ge / Ni / Au film is 1.5 μm, wherein the thickness of Ni is 0.02 μm, the thickness of Au is 0.08 μm, the thickness of Ge is 0.03 μm, the thickness of Ni is 0.07 μm, and the thickness of Au is 1.3 μm; using a blue film to remove the negative photoresist and the NiAuGeNiAu film above the negative photoresist, leaving four Ni / Au / Ge / Ni / Au electrodes, and forming good ohmic contacts between the four Ni / Au / Ge / Ni / Au electrodes and the heavily doped GaAs layer below by high temperature annealing, the temperature of the high temperature annealing is 350° C., and the time is 10 minutes, as shown in FIG. Figure 3 As shown;

[0051] d) applying a layer of positive photoresist 9 on the reverse polarity red LED high-power epitaxial wafer prepared in step c), with a thickness of 1.5 μm, and forming four spaced patterns around the four Ni / Au / Ge / Ni / Au electrodes by conventional photolithography. The spaced patterns are located on the periphery of the Ni / Au / Ge / Ni / Au electrodes, and their shape and number match the shape of the Ni / Au / Ge / Ni / Au electrodes, and are arranged in a square.

[0052] Four patterns are obtained by conventional photolithography, and the positive photoresist outside the Ni / Au / Ge / Ni / Au electrodes in the pattern is removed, while the positive photoresist in other areas and the four Ni / Au / Ge / Ni / Au electrodes is retained, as shown in FIG. Figure 4 As shown;

[0053] e) The barrier layer and heavily doped GaAs layer outside the Ni / Au / Ge / Ni / Au electrodes of the four patterns are removed respectively, and different roughening solutions 1, 2, 3 and 4 are dripped on the four patterns in step d) respectively, and the exposed N-type AlGaInP layer is roughened. After the roughening is completed, the positive photoresist is removed. Figure 5 As shown; roughening solution 1 is hydrochloric acid with a mass concentration of 36.5%: H2O, the volume ratio is 1:2, and the roughening time is 60 seconds; roughening solution 2 is hydrochloric acid with a mass concentration of 36.5%: H2O, the volume ratio is 1:1, and the roughening time is 60 seconds; roughening solution 3 is phosphoric acid with a mass concentration of 96%: hydrochloric acid with a mass concentration of 36.5%: H2O, the volume ratio is 1:1:2, and the roughening time is 120 seconds; roughening solution 4 is phosphoric acid with a mass concentration of 96%: hydrochloric acid with a mass concentration of 36.5%: hydrogen peroxide: H2O, the volume ratio is 4:4:1:8, and the roughening time is 120 seconds; the four roughening solutions are randomly matched with the four spaced negative photoresist electrode patterns;

[0054] f) Power-on testing is performed on each of the four patterns in step e). Different light output powers are obtained due to the use of different roughening solutions. By comparing optoelectronic parameters, the optimal process parameters for this reverse polarity red LED high-power epitaxial wafer are determined. The entire reverse polarity red LED high-power epitaxial wafer is then processed according to the determined process parameters to obtain the optimal reverse polarity red LED high-power chip.

[0055] A pattern is first prepared at four locations (top, bottom, left, and right) on a high-power epitaxial wafer of a reverse-polarity red LED. The barrier layer outside the pattern is retained. The electrode is first evaporated and annealed, and four spaced patterns are obtained around the electrode by conventional photolithography. Different roughening solutions are then used for roughening. After roughening, the four patterns are powered on and tested to obtain different light output powers. The photoelectric parameters are compared to obtain the pattern with the optimal photoelectric parameters, thereby screening the optimal roughening solution. The simple operation can maximize the optimal reverse-polarity red LED high-power chip, improve the yield, and avoid parameter problems.

[0056] Example 2

[0057] The method for screening the roughening solution in the process of preparing the reverse polarity red LED high-power chip is the same as that described in Example 1, except that:

[0058] In step b), the GaAs substrate prepared in step a) is removed to expose the barrier layer, and a layer of negative photoresist 7 having a thickness of 3 μm is coated on the barrier layer. Four spaced-apart negative photoresist electrode patterns are respectively prepared at the center position of the upper surface of the barrier layer of the reverse polarity red light LED high-power epitaxial wafer. The four patterns are arranged into a square with a side length of 280 μm. The negative photoresist electrode pattern closest to the edge of the epitaxial wafer is 1 mm away from the edge of the reverse polarity red light LED high-power epitaxial wafer. The negative photoresist electrode pattern is circular with a diameter of 110 μm. The negative photoresist outside the electrode pattern is retained, and the barrier layer of the negative photoresist electrode pattern is removed.

[0059] Example 3

[0060] The method for screening the roughening solution in the process of preparing the reverse polarity red LED high-power chip is the same as that described in Example 1, except that:

[0061] In step b), the GaAs substrate of step a) is removed to expose the barrier layer, and a layer of negative photoresist 7 with a thickness of 3 μm is coated on the barrier layer. Four spaced-apart negative photoresist electrode patterns are respectively prepared at the center position of the upper surface of the barrier layer of the reverse polarity red light LED high-power epitaxial wafer. The four patterns are arranged into a square with a side length of 300 μm. The negative photoresist electrode pattern closest to the edge of the epitaxial wafer is 1 mm away from the edge of the reverse polarity red light LED high-power epitaxial wafer. The negative photoresist electrode pattern is circular with a diameter of 110 μm. The negative photoresist outside the electrode pattern is retained, and the barrier layer of the negative photoresist electrode pattern is removed.

[0062] Example 4

[0063] The method for screening the roughening solution in the process of preparing the reverse polarity red LED high-power chip is the same as that described in Example 1, except that:

[0064] Step b) removing the GaAs substrate of step a) to expose the barrier layer, coating the barrier layer with a layer of negative photoresist 7 having a thickness of 3 μm, and preparing six spaced-apart negative photoresist electrode patterns at the center of the upper surface of the barrier layer of the reverse polarity red light LED high-power epitaxial wafer. The six patterns are arranged in a rectangular shape, and the negative photoresist electrode pattern closest to the edge of the epitaxial wafer is 1.2 mm away from the edge of the reverse polarity red light LED high-power epitaxial wafer. The negative photoresist electrode pattern is circular with a diameter of 100 μm. The negative photoresist outside the electrode pattern is retained, and the barrier layer of the negative photoresist electrode pattern is removed.

[0065] Experimental Example 1

[0066] The process parameters (roughening solution) determined by the method of Example 1 were screened and determined to be used for the entire reverse polarity red LED high-power epitaxial wafer. The brightness, photoelectric conversion efficiency and yield of the obtained reverse polarity red LED high-power chip are shown in Table 1 below.

[0067] Table 1

[0068]

[0069] Comparative Example 1

[0070] Only one roughening liquid is used to perform roughening treatment directly on the surface of the reverse polarity chip epitaxial wafer. By preparing a large number of reverse polarity chip epitaxial wafers, and then roughening them with different roughening liquids, the roughening liquid with the highest light extraction efficiency is screened out.

[0071] Experimental Example 2

[0072] The method of Example 1 was compared with the method of Comparative Example 1 in terms of number of experiments, cost, time consumption, material waste, and efficiency. The results are shown in Table 2.

[0073] Table 2

[0074] Number of experiments time consuming cost efficiency Material waste Example 1 1 4h 50 yuan 30 tablets 20 hours 4 tube cores Comparative Example 1 4 16h 200 yuan 30 tablets 36 hours 3 pieces with low matching rate

[0075] As shown in Table 2, the method of the present invention does not require a large number of epitaxial wafers or extensive experimentation, is cost-effective, and conserves materials. Using only one epitaxial wafer, the optimal roughening solution can be screened from 4-8 roughening solutions. The selected roughening solution can be used to mass-produce high-power reverse-polarity red LED chips. The resulting high-power reverse-polarity red LED chips exhibit high consistency, improve yield, avoid parameter problems, and effectively enhance light extraction efficiency and provide greater stability.

Claims

1. A method for screening a roughening solution in the preparation process of a reverse polarity red LED high-power chip, comprising the following steps: a) providing a reverse polarity red light LED high-power epitaxial wafer, wherein the reverse polarity red light LED high-power epitaxial wafer comprises, from bottom to top, a single crystal conductive Si substrate or a sapphire substrate, a reverse polarity red light LED epitaxial layer, an N-type AlGaInP layer, a heavily doped GaAs layer, a barrier layer, and a GaAs substrate; b) removing the GaAs substrate of step a) to expose the barrier layer, coating the barrier layer with a layer of negative photoresist, preparing 4-8 spaced negative photoresist electrode patterns on the upper surface of the barrier layer of the reverse polarity red LED high-power epitaxial wafer, retaining the negative photoresist outside the electrode pattern, and removing the barrier layer on the negative photoresist electrode pattern; c) evaporating a Ni / Au / Ge / Ni / Au film on the negative photoresist pattern prepared in step b), removing the negative photoresist and the Ni / Au / Ge / Ni / Au film above the negative photoresist using a blue film to leave 4-8 Ni / Au / Ge / Ni / Au electrodes, and forming good ohmic contacts between the 4-8 Ni / Au / Ge / Ni / Au electrodes and the heavily doped GaAs layer below by high temperature annealing; d) applying a layer of positive photoresist on the reverse polarity red LED high-power epitaxial wafer prepared in step c), and forming a pattern of 4-8 intervals around the 4-8 Ni / Au / Ge / Ni / Au electrodes by conventional photolithography, removing the positive photoresist outside the Ni / Au / Ge / Ni / Au electrodes within the pattern, and retaining the positive photoresist in other areas and the 4-8 Ni / Au / Ge / Ni / Au electrodes; e) removing the barrier layer and heavily doped GaAs layer of 4-8 patterns outside the Ni / Au / Ge / Ni / Au electrode in step d), and dripping different roughening solutions on different patterns in turn to roughen the exposed N-type AlGaInP layer. After the roughening is completed, removing the positive photoresist; f) Power-on testing is performed on the different patterns in step e) to obtain different light output powers. By comparing the optoelectronic parameters, the optimal roughening pattern is obtained. An epitaxial wafer is prepared to screen out the optimal roughening solution. The entire reverse polarity red light LED high-power epitaxial wafer is processed according to the determined process parameters to obtain the optimal reverse polarity red light LED high-power chip.

2. The method according to claim 1, characterized in that In step b), the thickness of the negative photoresist is 2.5-4 μm.

3. The method according to claim 1, characterized in that In step b), 4-8 spaced negative photoresist electrode patterns are located in the middle of the upper surface of the barrier layer, and the negative photoresist electrode pattern closest to the edge of the epitaxial wafer is 1-3 mm away from the edge of the reverse polarity red light LED high-power epitaxial wafer.

4. The method according to claim 1, wherein b), the number of spaced negative photoresist electrode patterns is 4, 6 or 8, and the spaced negative photoresist electrode patterns are circular with a diameter of 100-120 μm; preferably, the number of spaced negative photoresist electrode patterns is 4, arranged in a square with a side length of 250-300 μm.

5. The method according to claim 1, wherein In step (c), the thickness of the Ni / Au / Ge / Ni / Au film is 1.5-2.5um, specifically Ni thickness 0.02-0.04um, Au thickness 0.08-0.1um, Ge thickness 0.03-0.04um, Ni thickness 0.07-0.09um, Au thickness 1.3-2.3um, and the high temperature annealing temperature is 350-380°C for 10-15 minutes.

6. The method according to claim 4, characterized in that In step (d), the spaced patterns are located on the periphery of the Ni / Au / Ge / Ni / Au electrode, and their shape and number match the shape of the Ni / Au / Ge / Ni / Au electrode. There are 4 spaced patterns arranged in a square.

7. The method according to claim 4, characterized in that In step (e), the roughening liquids used are roughening liquid 1, roughening liquid 2, roughening liquid 3, and roughening liquid 4, respectively. The four roughening liquids are used to roughen the pattern in step d).

8. The method according to claim 7, characterized in that The four roughening solutions are randomly matched with the four interval patterns in step d).

9. The method according to claim 7, characterized in that Roughening liquid 1 is a mixture of hydrochloric acid with a mass concentration of 36.5% and H2O, the volume ratio of hydrochloric acid to H2O is 1:2, and the roughening time is 60-90 seconds. Roughening liquid 2 is a mixture of hydrochloric acid with a mass concentration of 36.5% and H2O, the volume ratio of hydrochloric acid to H2O is 1:1, and the roughening time is 60-90 seconds.

10. The method according to claim 7, characterized in that Roughening liquid 3 is a mixture of 96% phosphoric acid, 36.5% hydrochloric acid and H2O, with a volume ratio of phosphoric acid, hydrochloric acid and H2O of 1:1:2, and the roughening time is 120-150 seconds. Roughening liquid 4 is a mixture of 96% phosphoric acid, 36.5% hydrochloric acid, hydrogen peroxide and H2O, with a volume ratio of phosphoric acid, hydrochloric acid, hydrogen peroxide and H2O of 4:4:1:8, and the roughening time is 120-150 seconds.

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