Method for coarsening N-type inverted AlGaInP layer

Abstract

The invention relates to a coarsening method of an N-type inverted AlGaInP layer, and belongs to the technical field of photoelectrons. The method comprises the steps that firstly, an AuBe layer and a thin GaAs layer are fully fused and permeate into an N-type AlGaInP layer through high-temperature annealing, then an AuBe / Au / NiGeAu film and the thin GaAs layer are corroded away through normal-temperature Au corrosive liquid, metal Be and Au permeating into the N-type AlGaInP layer are corroded away through high-temperature Au corrosive liquid, fusion and permeation of the metal Au and Be are controlled through the temperature of high-temperature annealing, and the corrosion effect is controlled through the high-temperature corrosive liquid. The problem that the coarsening effect of a reversed-polarity AlGaInP quaternary LED chip is not stable is avoided, the light emitting efficiency is improved, and the quality of the chip is improved. Moreover, the conventional Au corrosive liquid is used for preparing the N-surface ohmic contact pattern and coarsening the N-type AlGaInP, the operation is simple and convenient, a more stable coarsened surface can be obtained, and the method is suitable for large-scale production.

Description

Technical Field

[0001] The invention relates to a roughening method for an N-type inverted AlGaInP layer, belonging to the technical field of optoelectronics. Background Art

[0002] Since the appearance of GaAsP red light-emitting devices in the early 1960s, new materials for light-emitting diodes have made great progress, including homojunction devices made of GaAs1-xPx, red devices doped with GaP zinc-oxygen pairs, red, orange and yellow devices doped with GaAs1-xPx nitrogen, yellow-green devices doped with GaP nitrogen, etc. In the mid-1980s, GaAlAs light-emitting diodes appeared. Since GaAlAs materials are direct-band materials and have a double heterojunction structure with high luminous efficiency, the development of LEDs has reached a new stage.

[0003] At present, flip-chip AlGaInP quaternary red LED chips are widely used in the field of high-power outdoor LED display screens. Flip-chip means replacing the substrate of the traditional quaternary red LED chip, replacing the GaAs substrate with larger light absorption with a single crystal conductive Si substrate or a sapphire substrate. After the replacement, the GaAs substrate is corroded and removed, and the corrosion barrier layer is corroded to expose the heavily doped layer. Subsequently, an Au film is evaporated on the heavily doped layer to form an ohmic contact, and then the ohmic contact layer pattern is prepared by photolithography. At present, the ohmic contact pattern is prepared by chemical etching, and the Au film etching solution has a certain corrosive effect on the N-type AlGaInP layer, resulting in fluctuations when the n-type layer is coarsened. The coarsening fluctuation will eventually affect the light output power of the flip-chip AlGaInP quaternary red LED chip. How to reduce this part of the impact and make the n-type coarsening effect of the reverse polarity quaternary LED chip more stable has become the main problem at this stage.

[0004] Chinese patent document CN104078535A discloses a method for roughening the sidewall of an inverse polarity AlGaInP-based LED, comprising the following steps: (1) using an existing photolithography process to expose and develop a mesa pattern epitaxial wafer of an inverse polarity AlGaInP-based LED, and forming a periodic edge pattern around the mesa pattern epitaxial wafer; (2) using the saturated Br 2 Deionized water is used to etch the mesa pattern epitaxial wafer developed in step (1); (3) the mesa pattern epitaxial wafer etched in step (2) is cleaned and debonded according to conventional processes to form a roughened sidewall corresponding to the shape of the periodic edge pattern. Although this method does not use ICP etching equipment and only uses conventional photolithography, chemical etching of the epitaxial layer has many uncontrollable factors such as epitaxial crystal orientation and etching rate, which is not easy to achieve in actual production and cannot be mass-produced. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention provides a method for roughening an N-type inverted AlGaInP layer, which uses conventional Au etching solution to prepare N-side ohmic contact patterns and roughen N-type AlGaInP. The operation is simple and convenient, and a more stable roughened surface can be obtained, which is suitable for large-scale production.

[0006] The technical solution of the present invention is as follows:

[0007] A method for roughening an N-type inverted AlGaInP layer, the steps are as follows:

[0008] (a) extracting the bonded AlGaInP red LED epitaxial wafer, using conventional etching methods to etch away the GaAs substrate and the epitaxially grown barrier layer GaInP, exposing the epitaxially grown thin GaAs layer and the N-type AlGaInP layer, and then, by electron beam evaporation, evaporating an AuBe / Au / NiGeAu film on the upper side of the thin GaAs layer, the AuBe / Au / NiGeAu film is a stacked structure, which is AuBe layer, Au layer and NiGeAu layer from bottom to top;

[0009] (b) annealing the evaporated AuBe / Au / NiGeAu film at high temperature so that the AuBe layer is fully integrated with the thin GaAs layer and penetrates into the N-type AlGaInP layer;

[0010] (c) coating a positive photoresist on the surface of the NiGeAu layer, forming an ohmic contact electrode pattern by photolithography, and using an Au etching solution to etch away the AuBe / Au / NiGeAu film outside the ohmic contact electrode pattern. Since the AuBe film has been fused with the thin GaAs layer, the thin GaAs layer will also be corroded;

[0011] (d) The Au etching solution is used again to etch away the metal Be and Au that have penetrated into the N-type AlGaInP layer to form an N-type AlGaInP roughened surface, and the positive photoresist is removed to obtain an N-side ohmic contact pattern and an N-type AlGaInP roughened surface.

[0012] Preferably according to the present invention, in step (a), the AuBe layer in the AuBe / Au / NiGeAu film has a thickness of 0.003-0.005 μm, the Au layer has a thickness of 0.2-0.4 μm, and the NiGeAu layer has a thickness of 0.4-0.6 μm.

[0013] Preferably according to the present invention, in step (b), the annealing temperature is 480-520° C. and the time is 15-25 minutes.

[0014] Preferably according to the present invention, in step (c), the thickness of the positive photoresist is 1.3-1.8 μm.

[0015] Preferably, according to the present invention, in step (c), the Au etching solution is prepared by using iodine, potassium iodide and pure water in a mass ratio of 2:4:20, the etching time is 3-4 minutes, and the temperature is room temperature.

[0016] Preferably, in step (d), the Au etching solution is prepared by using iodine, potassium iodide and pure water in a mass ratio of 2:4:20, the etching time is 2-3 minutes, and the temperature is 45-55°C.

[0017] The beneficial effects of the present invention are:

[0018] The present invention utilizes the characteristics of the AuBe layer, firstly performs high temperature annealing to fully fuse the AuBe layer and the thin GaAs layer and infiltrate the N-type AlGaInP layer, then uses a normal temperature Au etching solution to etch away the AuBe / Au / NiGeAu film and the thin GaAs layer, and uses a high temperature Au etching solution to etch away the metal Be and Au infiltrated in the N-type AlGaInP layer, and controls the fusion and penetration of the metal Au and Be and the corrosion effect by the high temperature etching solution through the temperature of the high temperature annealing, thereby avoiding the problem of unstable roughening effect of the reverse polarity AlGaInP quaternary LED chip, increasing the light extraction efficiency, and improving the quality of the chip. Moreover, the conventional Au etching solution is used to prepare the N-side ohmic contact pattern and roughen the N-type AlGaInP, which is simple to operate, and a more stable roughened surface can be obtained, which is suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A cross-sectional view of an N-type flip-chip AlGaInP red light chip manufactured by the present invention;

[0020] Figure 2 A cross-sectional view of the product produced in step (a) of the present invention;

[0021] Figure 3 A cross-sectional view of the product produced in step (c) of the present invention;

[0022] Among them, 1. Sapphire substrate; 2. Bonding layer; 3. N-type AlGaInP layer; 4. Thin GaAs layer; 5. AuBe / Au / NiGeAu film; 6. Positive photoresist. DETAILED DESCRIPTION

[0023] The present invention will be further described below by way of embodiments in conjunction with the accompanying drawings, but is not limited thereto.

[0024] Embodiment 1:

[0025] This embodiment provides a method for roughening an N-type inverted AlGaInP layer, the steps are as follows:

[0026] (a) The bonded AlGaInP red LED epitaxial wafer is extracted, and the GaAs substrate and the epitaxially grown barrier layer GaInP are etched away using a conventional etching method to expose the epitaxially grown thin GaAs layer 4 and the N-type AlGaInP layer 3. Then, an AuBe / Au / NiGeAu film 5 is evaporated on the upper side of the thin GaAs layer 4 by electron beam evaporation. Figure 2 As shown, the AuBe / Au / NiGeAu film is a stacked structure, which includes AuBe layer, Au layer and NiGeAu layer from bottom to top, the thickness of the AuBe layer is 0.003 μm, the thickness of the Au layer is 0.2 μm, and the thickness of the NiGeAu layer is 0.4 μm;

[0027] (b) annealing the evaporated AuBe / Au / NiGeAu film 5 at a high temperature of 480° C. for 15 minutes, so that the AuBe layer and the thin GaAs layer are fully integrated and penetrate into the N-type AlGaInP layer;

[0028] (c) A positive photoresist 6 is coated on the surface of the NiGeAu layer. The thickness of the positive photoresist is 1.3 μm. An ohmic contact electrode pattern is obtained by photolithography. The Au etching solution is used to etch away the AuBe / Au / NiGeAu film outside the ohmic contact electrode pattern. Figure 3 As shown, because the AuBe film has been fused with the thin GaAs layer, the thin GaAs layer will also be corroded. The Au etching solution is composed of iodine, potassium iodide, and pure water in a mass ratio of 2:4:20. The etching time is 3 minutes and the temperature is room temperature.

[0029] (d) Au etching solution is used again. The Au etching solution is prepared by iodine, potassium iodide and pure water in a mass ratio of 2:4:20. The etching time is 2 minutes and the temperature is 45°C. The metal Be and Au that penetrate into the N-type AlGaInP layer are etched away to form a roughened surface of the N-type AlGaInP and remove the positive photoresist. Figure 1 As shown, an N-side ohmic contact pattern and an N-type AlGaInP roughened surface are obtained.

[0030] Embodiment 2:

[0031] A roughening method for an N-type inverted AlGaInP layer as described in Example 1, except that in step (a), the thickness of the AuBe layer is 0.005 μm, the thickness of the Au layer is 0.4 μm, and the thickness of the NiGeAu layer is 0.6 μm.

[0032] In step (b), the annealing temperature is 520° C. and the time is 25 minutes.

[0033] In step (c), the thickness of the positive photoresist is 1.8 μm, and the etching time of the Au etching solution is 4 minutes.

[0034] In step (d), the Au etching solution is used for 3 minutes at a temperature of 55°C.

[0035] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for roughening an N-type inverted AlGaInP layer, characterized in that: Here are the steps: (a) extracting the bonded AlGaInP red LED epitaxial wafer, etching the GaAs substrate and the epitaxially grown barrier layer GaInP to expose the epitaxially grown thin GaAs layer and the N-type AlGaInP layer, and then evaporating the AuBe / Au / NiGeAu film on the upper side of the thin GaAs layer by electron beam evaporation. The AuBe / Au / NiGeAu film is a stacked structure, which is AuBe layer, Au layer and NiGeAu layer from bottom to top; (b) annealing the evaporated AuBe / Au / NiGeAu film at high temperature so that the AuBe layer merges with the thin GaAs layer and penetrates into the N-type AlGaInP layer; (c) coating a positive photoresist on the surface of the NiGeAu layer, forming an ohmic contact electrode pattern by photolithography, and using an Au etching solution to etch away the AuBe / Au / NiGeAu film outside the ohmic contact electrode pattern. Since the AuBe film has been fused with the thin GaAs layer, the thin GaAs layer will also be corroded; (d) The Au etching solution is used again to etch away the metal Be and Au that have penetrated into the N-type AlGaInP layer to form an N-type AlGaInP roughened surface, and the positive photoresist is removed to obtain an N-side ohmic contact pattern and an N-type AlGaInP roughened surface.

2. The roughening method of the N-type flip-chip AlGaInP layer according to claim 1, characterized in that: In step (a), the AuBe layer in the AuBe / Au / NiGeAu film has a thickness of 0.003-0.005 μm, the Au layer has a thickness of 0.2-0.4 μm, and the NiGeAu layer has a thickness of 0.4-0.6 μm.

3. The roughening method of the N-type inverted AlGaInP layer according to claim 1, characterized in that: In step (b), the annealing temperature is 480-520° C. and the time is 15-25 minutes.

4. The method for roughening an N-type flip-chip AlGaInP layer according to claim 1, characterized in that: In step (c), the thickness of the positive photoresist is 1.3-1.8 μm.

5. The roughening method of the N-type flip-chip AlGaInP layer according to claim 1, characterized in that: In step (c), the Au etching solution is prepared by using iodine, potassium iodide and pure water in a mass ratio of 2:4:20, the etching time is 3-4 minutes, and the temperature is room temperature.

6. The roughening method of the N-type flip-chip AlGaInP layer according to claim 1, characterized in that: In step (d), the Au etching solution is prepared by using iodine, potassium iodide and pure water in a mass ratio of 2:4:20, the etching time is 2-3 minutes, and the temperature is 45-55°C.

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