A method for preparing an inverted structure light-emitting diode

Abstract

The present invention relates to the technical field of light-emitting diodes, and in particular to a method for preparing an inverted structure light-emitting diode. Before ALD deposits AL2O3, N2, N2O or O3 plasma is used to clean the surface of GAN, improve the cleanliness of the GAN MESA side, eliminate residual ions and groups on the side, and then use TMAL and H2O to react and deposit a thin film, thereby improving the problem of low 1ua low current turn-on voltage; ALD deposits AL2O3, and the first 10-100 pulse cycles use TMAL and O3 as reaction sources to solve the problem of OH groups and charge residues at the interface between GAN and AL2O3. Subsequent film formation uses TMAL and H2O reaction, which not only meets the problem of low 1ua low current turn-on voltage, but also ensures production cost and efficiency; TMAL and H2O are used to react and deposit AL2O3, and the entire film layer is divided into 2-10 sections. N2 or N2O plasma is used between the two sections to clean, eliminate residual ions and charges at the AL2O3 and GAN interface, and residual ions that do not react sufficiently in the film layer, thereby improving the problem of low 1ua low current turn-on voltage.

Description

Technical Field

[0001] The present invention belongs to the technical field of light emitting diodes, and in particular relates to a method for preparing a flip-chip structure light emitting diode. Background Art

[0002] DBR flip-chip structure products use electron beam evaporated DBR as the reflective layer and insulating layer. The DBR materials are mainly SiO2 and Ti3O5. Due to the water absorption and density of the materials, DBR easily absorbs water vapor in the air, resulting in cracking and failure during long-term high temperature and high humidity aging.

[0003] To address the issue of DBRs cracking due to moisture absorption in high-temperature, high-humidity environments, the industry has introduced a composite structure combining PECVD plasma-enhanced chemical vapor deposition (PECVD) to deposit SiO2 films with ALD atomic layer deposition (ALD) to mitigate the effects of ambient moisture on the DBR film layer. ALD is a method that deposits a substance onto a substrate surface layer by layer in the form of a single atomic film. Multiple vapor-phase raw materials (precursors) are alternately exposed to the substrate surface to form the film. Unlike CVD, different precursors are not introduced into the reaction chamber simultaneously. Instead, they are introduced (pulsed) and removed (purged) in separate steps. During each pulse, the precursor molecules react autonomously on the substrate surface, and the reaction ends when no more adsorbable sites are available on the surface.

[0004] There are two schemes for ALD deposition of AL2O3: the first is the reaction of TMAL (trimethylaluminum) and H2O, two reaction sources, to generate AL2O3. This scheme has a short film production cycle and low cost, but there are -OH groups and charge residues at the contact interface between AL2O3 and GAN, resulting in a low turn-on voltage problem with a small current of 1ua on the chip; the second is the reaction of TMAL and O3 to generate AL2O3. In this scheme, there is basically no charge residue at the contact interface between AL2O3 and GAN, and there is no problem of low turn-on voltage with a small current of 1ua, but the production cycle is long and the cost is high. Summary of the Invention

[0005] In response to the problems in the background technology, the present invention has developed a method for preparing a flip-chip structure light-emitting diode, which can produce a low-cost, high-efficiency light-emitting diode with a low current turn-on voltage of 1ua and no leakage.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for preparing a flip-chip structure light-emitting diode comprises the following steps:

[0008] (1) Fabrication of epitaxy on patterned sapphire substrates, including N-GAN, quantum well, and P-GAN;

[0009] (2) Make MESA and etch out the N-type area;

[0010] (3) Making ISO to etch the middle part of the cutting path to the patterned sapphire substrate;

[0011] (4) Make a transparent conductive layer: Make a planar or graphic mesh distribution or island distribution, and make ohmic contact with P-GaN.

[0012] (5) Make metal electrode 1: divided into P region and N region, the P region is connected to the transparent conductive layer on the P-GaN, and the N region is connected to the N-GaN;

[0013] (6) Cleaning before ALD deposition: Use plasma gas to clean the GAN side exposed by MESA etching;

[0014] (7) ALD deposition of AL2O3:

[0015] 1) ALD deposition of Al2O3, the first 10-100 pulse cycles use TMAL and O3 as reaction sources, and subsequent film formation uses TMAL and H2O reaction;

[0016] 2) Using TMAL and H2O to react and deposit Al2O3, the entire film layer is divided into 2-10 sections, and plasma gas is used to clean between the two sections;

[0017] (8) PECVD deposition of SiO2;

[0018] (9) Electron beam evaporation coating DBR: Two layers with different refractive indices are deposited alternately to form a Bragg reflector layer;

[0019] (10) DBR through hole: Etch through holes through DBR, SiO2, and Al2O3 to leak out the P region and N region of metal electrode 1 respectively;

[0020] (11) Make the second metal electrode: It is divided into P region and N region. Through the connection holes made on the DBR, the P region is connected to the metal electrode-P region; the N region is connected to the metal electrode-N region.

[0021] Preferably, the transparent electrode in step (4) is made of ITO or ZnO material with a thickness of 5nm-200nm.

[0022] Preferably, in step (5), the electrode 1 comprises an adhesion layer and a structural layer, the adhesion layer is CR / NI / TI, the structural layer is AL / TI / PT / NI / AU, and the total thickness is 50nm-5000nm.

[0023] Preferably, the plasma gas in step (6) is N2O, N2 or O3, with a gas flow rate of 5-500 sccm, a power of 10-500 W, and a time of 10S-1000S.

[0024] Preferably, the plasma gas in step (7) is N2 or N2O.

[0025] Preferably, the thickness of the entire ALD layer in step (7) is 45-300 nm, which is divided into 2-10 segments, and the segmentation is uniform or the thickness of each of the first three segments is 2-15 nm, and the thickness of each of the latter segments is 10-100 nm; the segmentation with low thickness in the front segment and high thickness in the rear segment can solve the problems of residual ions and charges in the film deposition and residual ions due to insufficient reaction in the film layer, improve the insulation of the bottom layer, and avoid the current verification of the AL2O3 and GaN interface passing through, causing small current micro leakage.

[0026] Preferably, in step (8), the PECVD deposition of SiO2 has a thickness of 50-1000 nm and a temperature of 150-300°C.

[0027] Preferably, the step (9) adopts the alternate deposition of two film layers with different refractive indices, SiO2 and Ti3O5; the temperature is 150-300°C, the thickness is 1000-5000nm, and the number of film layers is 20-60.

[0028] Preferably, in step (11), the second electrode comprises an adhesion layer, a structural layer, and a eutectic layer. The adhesion layer is CR / NI / TI with a thickness of 0.5-100 nm, the structural layer is AL / TI / PT / NI / AU metal with a thickness of 1000-5000 nm, and the eutectic layer is Au, Sn, AnSn alloy, or Sn ball with a thickness of 1 μm-100 μm.

[0029] Preferably, in the step (7) ALD deposition of AL2O3, AL2O3 is replaced by HfO2. Specifically, 1) ALD deposition of HfO2 uses TDMAHf and O3 as reaction sources in the first 10-100 pulse cycles, and subsequent film formation uses TDMAHf and H2O reaction; 2) HfO2 is deposited by using TDMAHf and H2O reaction, and the entire film layer is divided into 2-10 sections, and plasma gas is used for cleaning between the two sections; the dielectric constant of AL2O3 is 9.8, and the dielectric constant of HfO2 is 18, and the latter has better insulation properties.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] (1) Before ALD deposition of AL2O3, use N2, N2O or O3 plasma to clean the GAN surface, improve the cleanliness of the GAN MESA side, eliminate the residual ions and groups on the side, and then use TMAL and H2O to react and deposit the film to improve the low turn-on voltage problem of 1ua small current;

[0032] (2) ALD deposition of AL2O3, the first 10-100 pulse cycles use TMAL and O3 as reaction sources to solve the problem of -OH groups and charge residues at the interface between GAN and AL2O3. The subsequent film formation uses TMAL and H2O reaction, which not only meets the problem of low turn-on voltage at a small current of 1ua, but also ensures production cost and efficiency;

[0033] (3) TMAL and H2O were used to react and deposit AL2O3, and the entire film layer was divided into 2-10 segments. N2 or N2O plasma was used to clean between the two segments to eliminate the residual ions and charges at the interface between AL2O3 and GAN and the residual ions in the film layer due to insufficient reaction, thereby improving the low turn-on voltage problem at a small current of 1 ua. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Schematic diagram of the DBR composite membrane structure.

[0035] Figure 2 This is a schematic diagram of the structure of one embodiment of the Al2O3 film layer. DETAILED DESCRIPTION

[0036] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, the specific implementation methods, structures, features and effects of the present invention are described in detail below in conjunction with the accompanying drawings and preferred embodiments.

[0037] Example 1: A method for preparing a flip-chip structure light-emitting diode, comprising the following steps:

[0038] 1. Epitaxy is produced on patterned sapphire substrates, including N-GAN, quantum well, and P-GAN.

[0039] 2. Make MESA and etch out the N-type area.

[0040] 3. Make ISO to etch the middle part of the cutting line to the patterned sapphire substrate.

[0041] 4. Fabrication of a transparent conductive layer: This can be made into a planar, patterned, mesh-like, or island-like distribution, creating an ohmic contact with P-GaN. The transparent electrode is made of materials such as ITO and ZnO, with a thickness of 5nm-200nm.

[0042] 5. Fabricate Metal Electrode 1: This is divided into a P region and an N region. The P region connects to the transparent conductive layer on the P-GaN, and the N region connects to the N-GaN. Electrode 1 has an adhesion layer and a structural layer. The adhesion layer is made of CR, NI, or TI, and the structural layer is made of AL, TI, PT, NI, or AU. The total thickness is 50nm-5000nm.

[0043] 6. Cleaning before ALD deposition: Use N2O, N2 or O3 plasma to clean the GAN side exposed by MESA etching, eliminate GAN side contamination and residual ions, reduce the probability of micro-leakage on the GAN side under a small current of 1ua, and reduce the problem of low start-up voltage at a small current of 1ua; the cleaning gas flow rate is 5-500sccm, the power is 10-500W, and the time is 10S-1000S.

[0044] 7. ALD deposition of AL2O3:

[0045] 1) ALD deposition of Al2O3 uses TMAL and O3 as reaction sources in the first 10-100 pulse cycles to solve the -OH group and charge residue problems at the interface between GAN and Al2O3. Subsequent film formation uses TMAL and H2O reaction, which not only meets the low turn-on voltage problem of 1uA low current, but also ensures production cost and efficiency.

[0046] 2) Use TMAL and H2O to react and deposit AL2O3, and divide the entire film into 2-10 segments. Use N2 or N2O plasma to clean between the two segments to eliminate the residual ions and charges at the interface between AL2O3 and GAN and the residual ions in the film layer due to insufficient reaction, so as to improve the low turn-on voltage problem of 1ua small current. The segments can be evenly divided, or the thickness of the first 1-3 segments can be relatively low (such as Figure 2 shown).

[0047] 8. PECVD deposition of SiO2: thickness 50-1000nm, temperature 150-300℃;

[0048] 9. Electron beam evaporation coating DBR: Two films with different refractive indices such as SiO2 and Ti3O5 can be deposited alternately to form a Bragg reflector film (such as Figure 1 as shown); temperature 150-300°C, thickness 1000-5000nm, and number of film layers 20-60.

[0049] 10. DBR through hole: Etch a through hole through the DBR, SiO2, and Al2O3 to leak out the P region and N region of the metal electrode one respectively.

[0050] 11. Make the second metal electrode: It is divided into P region and N region. Through the connection holes made on the DBR, the P region is connected to the metal electrode 1 P region; the N region is connected to the metal electrode 1 N region; the second electrode has an adhesion layer, a structural layer, and a eutectic layer. The adhesion layer is CR / NI / TI with a thickness of 0.5-100nm, the structural layer is AL / TI / PT / NI / AU and other metals with a thickness of 1000-5000nm, and the eutectic layer is Au, Sn, AnSn alloy, Sn ball with a thickness of 1um-100um.

[0051] Example 2: A method for preparing a flip-chip structure light-emitting diode, comprising the following steps:

[0052] 1. Epitaxy is produced on patterned sapphire substrates, including N-GAN, quantum well, and P-GAN.

[0053] 2. Make MESA and etch out the N-type area.

[0054] 3. Make ISO to etch the middle part of the cutting line to the patterned sapphire substrate.

[0055] 4. Fabrication of a transparent conductive layer: This can be made into a planar, patterned, mesh-like, or island-like distribution, creating an ohmic contact with P-GaN. The transparent electrode is made of materials such as ITO and ZnO, with a thickness of 5nm-200nm.

[0056] 5. Fabricate Metal Electrode 1: This is divided into a P region and an N region. The P region connects to the transparent conductive layer on the P-GaN, and the N region connects to the N-GaN. Electrode 1 has an adhesion layer and a structural layer. The adhesion layer is made of CR, NI, or TI, and the structural layer is made of AL, TI, PT, NI, or AU. The total thickness is 50nm-5000nm.

[0057] 6. Cleaning before ALD deposition: Use N2O, N2 or O3 plasma to clean the GAN side exposed by MESA etching, eliminate GAN side contamination and residual ions, reduce the probability of micro-leakage on the GAN side under a small current of 1ua, and reduce the problem of low start-up voltage at a small current of 1ua; the cleaning gas flow rate is 5-500sccm, the power is 10-500W, and the time is 10S-1000S.

[0058] 7. ALD deposition of HfO2:

[0059] 1) ALD deposition of HfO2 uses TDMAHf and O3 as reaction sources in the first 10-100 pulse cycles to solve the -OH group and charge residue problems at the interface between GAN and HfO2. Subsequent film formation uses TDMAHf and H2O reaction, which not only meets the low turn-on voltage problem of 1ua small current, but also ensures production cost and efficiency;

[0060] 2) Use TDMAHf and H2O to react and deposit HfO2, dividing the entire film layer into 2-10 segments. Use N2 or N2O plasma to clean between each segment to eliminate residual ions and charges at the interface between HfO2 and GAN, as well as residual ions from insufficient reaction in the film layer, to improve the low turn-on voltage problem at a low current of 1 ua. The segments can be evenly divided, or the thickness of the first 1-3 segments can be relatively low.

[0061] 8. PECVD deposition of SiO2: thickness 50-1000nm, temperature 150-300℃;

[0062] 9. Electron beam evaporation coating DBR: Two films with different refractive indices, such as SiO2 and Ti3O5, can be alternately deposited to form a Bragg reflector film layer; the temperature is 150-300℃, the thickness is 1000-5000nm, and the number of film layers is 20-60.

[0063] 10. DBR through hole: Etch a through hole through the DBR, SiO2, and HfO2 to leak out the P region and N region of the metal electrode one respectively.

[0064] 11. Make the second metal electrode: It is divided into P region and N region. Through the connection holes made on the DBR, the P region is connected to the metal electrode 1 P region; the N region is connected to the metal electrode 1 N region; the second electrode has an adhesion layer, a structural layer, and a eutectic layer. The adhesion layer is CR / NI / TI with a thickness of 0.5-100nm, the structural layer is AL / TI / PT / NI / AU and other metals with a thickness of 1000-5000nm, and the eutectic layer is Au, Sn, AnSn alloy, Sn ball with a thickness of 1um-100um.

[0065] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as above in terms of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can, without departing from the scope of the technical solution of the present invention, make some changes or modifications to equivalent embodiments using the technical contents disclosed above. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a flip-chip light-emitting diode, characterized in that: The following steps are involved: (1) Fabrication of epitaxy on patterned sapphire substrates, including N-GaN, quantum wells, and P-GaN; (2) Make MESA and etch out the N-type area; (3) Making ISO to etch the middle part of the cutting path to the patterned sapphire substrate; (4) Make a transparent conductive layer: Make a planar or graphic mesh distribution or island distribution, and make ohmic contact with P-GaN. (5) Make metal electrode 1: divided into P region and N region, the P region is connected to the transparent conductive layer on the P-GaN, and the N region is connected to the N-GaN; (6) Cleaning before ALD deposition: Use plasma gas to clean the GaN side exposed by MESA etching; (7) ALD deposition of Al2O3: 1) ALD deposition of Al2O3, the first 10-100 pulse cycles use TMAL and O3 as reaction sources, and subsequent film formation uses TMAL and H2O reaction; 2) Deposit Al2O3 using TMAL and H2O reaction, dividing the entire film into 2-10 sections, and using plasma gas cleaning between the two sections; (8) PECVD deposition of SiO2; (9) Electron beam evaporation coating DBR: Two layers with different refractive indices are deposited alternately to form a Bragg reflector layer; (10) DBR through hole: Etch through holes through DBR, SiO2, and Al2O3 to leak out the P region and N region of metal electrode 1 respectively; (11) Make the second metal electrode: It is divided into P region and N region. Through the connection holes made on the DBR, the P region is connected to the metal electrode-P region; the N region is connected to the metal electrode-N region.

2. The method for preparing a flip-chip structure light-emitting diode according to claim 1, wherein: The transparent electrode in step (4) is made of ITO or ZnO material with a thickness of 5nm-200nm.

3. The method for preparing a flip-chip structure light-emitting diode according to claim 1, wherein: In the step (5), the electrode 1 comprises an adhesion layer and a structural layer, wherein the adhesion layer is Cr / Ni / Ti and the structural layer is Al / Ti / Pt / Ni / Au, with a total thickness of 50 nm to 5000 nm.

4. The method for preparing a flip-chip structure light-emitting diode according to claim 1, wherein: In step (6), the plasma gas is N2O, N2 or O3, the gas flow rate is 5-500sccm, the power is 10-500W, and the time is 10S-1000S.

5. The method for preparing a flip-chip structure light-emitting diode according to claim 1, wherein: The plasma gas in step (7) is N2 or N2O.

6. The method for preparing a flip-chip structure light-emitting diode according to claim 1, wherein: The thickness of the entire ALD layer in step (7) is 45-300 nm, which is divided into 2-10 segments, and the thickness of each of the first three segments is 2-15 nm, and the thickness of each of the subsequent segments is 10-100 nm.

7. The method for preparing a flip-chip structure light-emitting diode according to claim 1, wherein: In the step (8), SiO2 is deposited by PECVD with a thickness of 50-1000 nm and a temperature of 150-300°C.

8. The method for preparing a flip-chip structure light-emitting diode according to claim 1, wherein: The step (9) uses SiO2 and Ti3O5 film layers with different refractive indices to be deposited alternately; the temperature is 150-300°C, the thickness is 1000-5000nm, and the number of film layers is 20-60.

9. The method for preparing a flip-chip structure light-emitting diode according to claim 1, wherein: In the step (11), the second electrode has an adhesion layer, a structural layer, and a eutectic layer. The adhesion layer is Cr / Ni / Ti with a thickness of 0.5-100 nm, the structural layer is Al / Ti / Pt / Ni / Au metal with a thickness of 1000-5000 nm, and the eutectic layer is Au, Sn, AnSn alloy with a thickness of 1 μm-100 μm.

10. The method for preparing a flip-chip structure light-emitting diode according to claim 1 or 6, characterized in that: In the step (7), Al2O3 in the ALD deposition of Al2O3 is replaced by HfO2. Specifically, 1) HfO2 is deposited by ALD, TDMAHf and O3 are used as reaction sources in the first 10-100 pulse cycles, and TDMAHf and H2O are used for subsequent film formation; 2) HfO2 is deposited by reacting TDMAHf and H2O, and the entire film layer is divided into 2-10 sections, and plasma gas is used for cleaning between the two sections.

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