A method for repairing epitaxial layer defects

Abstract

The present invention discloses a method for repairing epitaxial layer defects, relating to the field of semiconductor epitaxial technology, comprising the following steps: depositing a first metal thin layer on a defective epitaxial layer; performing an annealing process to cause metal particles in the first metal thin layer to form metal agglomerates at the defects in the epitaxial layer, and ensuring that the first metal thin layer covers the non-defective areas of the epitaxial layer to form a buffer layer; performing plasma bombardment to tightly integrate the metal particles in the metal agglomerates with the defects, and indirectly transferring the bombardment energy to the surface of the epitaxial layer through the buffer layer, thereby roughening the surface of the epitaxial layer; after the metal agglomerates and the buffer layer are bombarded by the plasma, a second metal thin layer is formed on the surface of the epitaxial layer; and removing the second metal thin layer on the surface of the epitaxial layer using a chemical solution. By repairing the defects on the surface of the epitaxial layer, the method of the present invention can effectively improve the ohmic contact of the LED chip, increase the light extraction efficiency of the chip, and enhance the brightness performance of the chip.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor epitaxy technology, and in particular to a method for repairing defects in an epitaxial layer. Background Art

[0002] The GaN substrate epitaxy for LED chips is primarily grown using the MOCVD method. This method often results in surface defects such as voids in the epitaxial layers produced. During LED chip manufacturing, these defects can further impact various chip parameters, including voltage, brightness, and IR yield. Currently, methods for addressing and improving epitaxial defects focus primarily on controlling quality and improving the structure during epitaxial growth. These methods rarely address post-epitaxial defect improvement. Furthermore, because defects during epitaxial growth are difficult to monitor, defects such as voids are difficult to avoid. Summary of the Invention

[0003] The purpose of the present invention is to overcome the shortcomings of the prior art. The present invention provides a method for repairing defects in the epitaxial layer, which does not involve controlling the epitaxial growth process. By repairing the defects on the surface of the epitaxial layer, the ohmic contact of the LED chip can be effectively improved, the light extraction efficiency of the LED chip can be improved, and the brightness performance of the LED chip can be enhanced.

[0004] The present invention provides a method for repairing defects in an epitaxial layer, comprising the following steps:

[0005] S1: depositing a first metal thin layer on the defective epitaxial layer;

[0006] S2: annealing the epitaxial layer after depositing the first metal thin layer, so that the metal particles in the first metal thin layer form metal agglomerates at the defects of the epitaxial layer, and the first metal thin layer keeps covering the non-defective areas of the epitaxial layer to form a buffer layer;

[0007] S3: Plasma bombarding the metal agglomerates and the buffer layer, so that the metal particles of the metal agglomerates are tightly embedded in the defects, and the bombardment energy is indirectly transferred to the surface of the epitaxial layer through the buffer layer, so that the surface of the epitaxial layer is roughened; after the metal agglomerates and the buffer layer are bombarded by the plasma, a second metal thin layer is formed on the surface of the epitaxial layer;

[0008] S4: removing the second metal thin layer on the surface of the epitaxial layer using a chemical solution.

[0009] Specifically, depositing the first metal thin layer on the defective epitaxial layer includes: depositing the first metal thin layer on the defective epitaxial layer by sputtering or evaporation.

[0010] Specifically, the deposition vacuum degree of the first metal thin layer is 3.0×10 -6 Below Pa, the deposition rate is The deposition thickness is

[0011] Specifically, the first metal thin layer is a Ni thin layer, or a Cr thin layer, or a Ti thin layer, or an Al thin layer.

[0012] Specifically, the annealing treatment in step S2 is performed at a temperature of 550 to 600° C. and for a time of 3 to 15 minutes.

[0013] Specifically, the atmosphere of the plasma bombardment in step S3 includes Ar or O2, the pressure is 550-650 mtorr, and the time is 200-300 s.

[0014] Specifically, the plasma bombarded by the plasma includes Ar + Ions or O2 + ion.

[0015] Specifically, the use of chemical solution to remove the second metal thin layer on the surface of the epitaxial layer in step S4 includes: soaking the epitaxial layer after plasma bombardment treatment in 50-60°C ITO etching solution for 5-10 seconds, then immediately taking it out and rinsing it with water for more than 5 minutes to remove the second metal thin layer on the surface of the epitaxial layer.

[0016] Specifically, the flushing process includes: firstly directly flushing the surface of the epitaxial layer with ultrapure water, and then immersing it in flowing ultrapure water for flushing.

[0017] Specifically, in step S2, an RTA vacuum annealing furnace is used to anneal the metal thin layer; in step S3, an Asher desmearing machine is used to perform plasma bombardment on the buffer layer.

[0018] Compared with the prior art, the present invention has the following advantages: the present invention deposits a first metal thin layer on the defective epitaxial layer, wherein the first metal thin layer is very thin, with a thickness of only It can completely cover the epitaxial layer without interface separation, and is more likely to form metal agglomerates after annealing. Moreover, the thin layer of this thickness can be quickly removed with chemical solutions later.

[0019] After annealing, the metal particles in the first metal thin layer form metal agglomerates at the defects of the epitaxial layer, and the metal agglomerates can fill the defects of the epitaxial layer. In addition, the first metal thin layer can also maintain coverage of the non-defective areas of the epitaxial layer to form a buffer layer, protecting the epitaxial layer from damage caused by direct plasma bombardment during the subsequent plasma bombardment process.

[0020] After the plasma bombardment treatment, the metal particles of the metal agglomerates are tightly integrated with the defects, thereby repairing the defects of the epitaxial layer. The bombardment energy is indirectly transferred to the surface of the epitaxial layer through the buffer layer, thereby roughening the surface of the epitaxial layer and improving the adhesion and wettability of the epitaxial layer surface. At the same time, the surface of the epitaxial layer obtains more energy and is activated.

[0021] Finally, a chemical solution is used to remove the second metal thin layer. Taking advantage of the fact that the removal rate of metal particles in the flat area is greater than the removal rate of metal particles in the defective area, the second metal thin layer on the surface of the epitaxial layer is removed, and the metal particles in the defects are retained. Finally, an epitaxial layer with repaired defects and activated surface is obtained, which can effectively improve the ohmic contact of the LED chip, improve the light output efficiency of the LED chip, and enhance the brightness performance of the LED chip. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a flow chart of a method for repairing epitaxial layer defects in an embodiment of the present invention;

[0023] Figure 2 is a schematic structural diagram of an epitaxial layer with defects in an embodiment of the present invention;

[0024] Figure 3 is a schematic diagram of the epitaxial layer structure after depositing the first metal thin layer in an embodiment of the present invention;

[0025] Figure 4 Schematic diagram of the epitaxial layer structure after annealing in an embodiment of the present invention;

[0026] Figure 5 Schematic diagram of the epitaxial layer structure during plasma bombardment treatment in an embodiment of the present invention;

[0027] Figure 6 is a schematic diagram of the epitaxial layer structure after removing the second metal thin layer in an embodiment of the present invention;

[0028] Figure 7 is a brightness-current curve diagram of a defective epitaxial layer before and after repair in an embodiment of the present invention;

[0029] Figure 8 3 is a current-voltage characteristic curve diagram of the defective epitaxial layer before and after repair in an embodiment of the present invention.

[0030] In the drawings, 100 is an epitaxial layer; 110 is a defect; 200 is a first metal thin layer; 210 is a metal particle; 220 is a metal agglomerate; and 300 is a plasma. DETAILED DESCRIPTION

[0031] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0032] refer to Figure 1 , the method for repairing epitaxial layer defects comprises the following steps:

[0033] S1, depositing a first metal thin layer on the defective epitaxial layer;

[0034] Specifically, Figure 2 The schematic diagram of the structure of the defective epitaxial layer in the embodiment of the present invention is shown. On the defective epitaxial layer 100, an electron beam evaporation machine or a magnetron sputtering vacuum coating machine is used at 3.0×10 -6 Under vacuum conditions below Pa, A layer is evaporated or sputtered at a rate of The thick first metal thin layer 200, i.e. Figure 3 The schematic diagram of the epitaxial layer structure after the first metal thin layer is deposited in the embodiment of the present invention is shown; preferably, the vacuum degree is 3.0×10 -7 Pa, the smaller the vacuum degree, the better the quality of the plated first metal thin layer 200; the thickness of the first metal thin layer 200 is controlled to be It can completely cover the surface of the epitaxial layer 100 without interface separation, and it is easier to form metal agglomerates after annealing treatment. Moreover, the thin layer of this thickness can be easily and quickly removed with chemical solutions later. The first metal thin layer 200 is a Ni thin layer, or a Cr thin layer, or a Ti thin layer, or an Al thin layer.

[0035] The working principle of the electron beam evaporation machine is to use an accelerated electron beam to strike the target material, causing the target material to heat and evaporate, and then transport the evaporated material to the substrate to be deposited to form a thin film.

[0036] The working principle of the magnetron sputtering vacuum coating machine is that under the action of the electric field, electrons collide with Ar atoms in the process of flying towards the substrate, causing them to ionize and produce Ar positive ions and new electrons; the new electrons fly towards the substrate, and the Ar positive ions are accelerated to fly towards the cathode target under the action of the electric field, and bombard the target surface with high energy, causing the target material to be sputtered. Among the sputtered particles, neutral target atoms or molecules are deposited on the substrate to form a thin film.

[0037] The above two devices can plate metals such as Ni, Cr, Ti or Al onto the epitaxial layer 100 very well, and because the thickness of the first metal thin layer 200 is controlled within Very thin, so it should be 3.0×10 -6 Under the vacuum condition of Pa, the plating rate of the first metal thin layer 200 is controlled to be In this way, the deposition thickness of the first metal thin layer 200 can be better controlled, and the first metal thin layer 200 can be made uniform and dense. If the plating rate is too high, the deposition thickness of the first metal thin layer 200 is difficult to control, and gaps are likely to appear when the metal particles 210 are gradually stacked, resulting in loose filling of the metal particles 210. During the subsequent annealing treatment, cracks are likely to appear in the first metal thin layer 200. If cracks appear, the epitaxial layer 100 cannot be protected from direct bombardment by plasma and damage.

[0038] S2, annealing the epitaxial layer after depositing the first metal thin layer;

[0039] Specifically, the epitaxial layer 100 after the first metal thin layer 200 is deposited is annealed in an RTA vacuum annealing furnace. Under a vacuum condition of 3 Torr, the epitaxial layer 100 is annealed at a high temperature of 550-600° C. for 3-15 minutes. Preferably, the treatment for 10 minutes is more effective. The epitaxial layer 100 is then taken out and naturally cooled to room temperature. The cooling time is generally 10-15 minutes. Figure 4 A schematic diagram of the epitaxial layer structure after annealing treatment in an embodiment of the present invention is shown, so that the metal particles 210 in the first metal thin layer 200 form metal agglomerates 220 at the defects 110 of the epitaxial layer 100, and the first metal thin layer 200 maintains coverage of the non-defective areas of the epitaxial layer 100 to form a buffer layer.

[0040] The first metal thin layer 200 will form nano-scale metal particles 210 when annealed at a high temperature of 550-600°C. Due to the electrostatic force and van der Waals force between the nano-scale metal particles 210, the nano-scale metal particles 210 are easily adsorbed to each other to form agglomeration. At the same time, the nano-scale metal particles 210 have very high surface energy and a large contact area, which accelerates the adsorption between the nano-scale metal particles 210 during the annealing process, which will promote the occurrence of agglomeration. Moreover, at the defects 110 of the epitaxial layer 100, since the nano-scale metal particles 210 are concentrated more, the agglomeration rate is faster, and it is easier to form metal agglomerates 220. The metal agglomerates 220 can fully fill the defects 110 on the surface of the epitaxial layer 100.

[0041] The annealing temperature, processing time, etc. will affect the integrity of the first metal thin layer 200 and its adhesion to the epitaxial layer 100. Under a vacuum condition of 3 Torr, it is treated with a high temperature of 550-600 ° C for 3-15 minutes. Preferably, the treatment effect of 10 minutes is better. Then it is taken out and naturally cooled to room temperature. While promoting the agglomeration of metal particles 210 at the defect 110, it can also keep the first metal thin layer 200 from cracking and completely cover the non-defective area of ​​the epitaxial layer 100. It is also tightly bonded to the epitaxial layer 100 and is not prone to interface separation, preparing for the subsequent plasma 300 bombardment.

[0042] S3, performing plasma bombardment on the metal agglomerates and the buffer layer;

[0043] Specifically, Figure 5 A schematic diagram of the epitaxial layer structure during plasma bombardment treatment in an embodiment of the present invention is shown. An Asher debonding machine is used in an Ar atmosphere with a purity of 99.9999% or an O2 atmosphere with a purity of 99.999%, and at a pressure of 550 to 650 mtorr, to perform plasma bombardment treatment 300 on the metal agglomerates 220 and the buffer layer for 200 to 300 seconds. This allows the metal particles 210 of the metal agglomerates 220 to be tightly integrated with the defects 110, and indirectly transfers the bombardment energy to the surface of the epitaxial layer 100 through the buffer layer, thereby roughening the surface of the epitaxial layer 100. After the metal agglomerates 220 and the buffer layer are bombarded by the plasma 300, a second metal thin layer is formed on the surface of the epitaxial layer 100. Preferably, under a pressure of 600 mtorr, the bombardment energy and bombardment rate of the plasma 300 are maintained at an optimal state, achieving the best bombardment treatment effect on the metal agglomerates 220 and the buffer layer.

[0044] Asher degumming machine ionizes Ar or O2 into Ar + Ions or O2 + ions bombard the metal agglomerates 220 and the buffer layer; the metal agglomerates 220 are + Ions or O2 + During ion bombardment, the metal particles 210 inside are strongly squeezed, so that the metal particles 210 and the defect 110 are tightly embedded into one, thereby repairing the surface of the defective epitaxial layer 100; the purity of Ar or O2 is extremely high, which can avoid ionization to produce mixed plasma that affects the bombardment effect.

[0045] During the plasma 300 bombardment process, the buffer layer protects the epitaxial layer 100 from Ar + Ions or O2 +The direct bombardment of ions causes damage and indirectly transfers energy to the surface of the epitaxial layer 100 that is tightly bonded thereto, roughening the surface of the epitaxial layer 100 and forming many fine pits, thereby increasing the roughness ratio of the surface of the epitaxial layer 100 and improving its surface adhesion and wettability. At the same time, the surface of the epitaxial layer 100 obtains more energy, destroying the original chemical bonds on its surface and creating a new reaction atmosphere. The free radicals in the plasma 300 can form a network-like cross-linked structure with these bonds, greatly activating the surface activity.

[0046] S4, removing the second metal thin layer on the surface of the epitaxial layer using a chemical solution;

[0047] Specifically, the epitaxial layer 100 after the plasma 300 bombardment treatment is immersed in an ITO etching solution at 50-60° C. for 5-10 seconds, then immediately taken out and rinsed with water for more than 5 minutes to remove the second metal thin layer on the surface of the epitaxial layer;

[0048] The ITO etching solution at 50-60°C has a strong reaction activity and can easily corrode the second metal thin layer, removing the metal particles 210 therein. The metal particles 210 on the surface of the epitaxial layer 100 will first contact the ITO etching solution over a large area and be quickly removed. The metal particles 210 in the defect 110 have a small contact area with the ITO etching solution and are removed slowly. Therefore, by controlling the immersion time in the ITO etching solution to 5-10 seconds, preferably, immersing for 10 seconds, the second metal thin layer on the surface of the epitaxial layer 100 can be removed, and the metal particles 210 in the defect 110 can be retained. The epitaxial layer 100 is then immediately taken out and rinsed with water for more than 5 minutes, preferably, for 10 minutes. When rinsing, the surface of the epitaxial layer 100 is first directly rinsed with ultrapure water, and then immersed in flowing ultrapure water for rinsing to clean the residual ITO etching solution, and finally an epitaxial layer with repaired defects and activated surface is obtained. Figure 6 A schematic diagram of the epitaxial layer structure after removing the second metal thin layer in an embodiment of the present invention is shown.

[0049] The present invention does not involve the control of epitaxial growth process, but mainly targets defects such as cavities existing after epitaxial growth of LED chips. The process is simple and easy to monitor. By depositing a layer of epitaxial layer 100 on the surface of the defective epitaxial layer 100, A thick, uniform and dense first metal thin layer 200 is then annealed to form metal agglomerates 220 at the defect 110 while maintaining coverage of other areas. The metal particles 210 are then bombarded by plasma 300 to tightly embed them into one body with the defect 110, and the energy is indirectly transferred to the surface of the epitaxial layer 100 through the buffer layer. Finally, the second metal thin layer is removed using an ITO etching solution, taking advantage of the fact that the removal rate of the metal particles 210 at the flat surface of the epitaxial layer 100 is greater than that at the defect. The metal particles 210 tightly embedded in the defect 110 are retained, and the defects on the surface of the epitaxial layer 100 are repaired. Finally, an epitaxial layer 100 with repaired defects and activated surface is obtained, which can effectively improve the ohmic contact of the LED chip, improve the light extraction efficiency of the LED chip, and enhance the brightness performance of the LED chip.

[0050] like Figure 7 As shown in the brightness-current curve, after the epitaxial layer 100 is repaired, the brightness of the LED chip is significantly improved compared to before the repair. Compared with the LED chip with the epitaxial layer 100 not treated, the brightness of the LED chip with the epitaxial layer 100 repaired is increased by 5% to 10%;

[0051] Ohmic contact means that a pure resistance is formed at the contact between metal and semiconductor, and the smaller the resistance, the better, so that when the component is operating, most of the voltage drop is in the active area rather than on the contact surface, such as Figure 8 The current-voltage characteristic curve shown in the figure, combined with Ohm's law R=U / I, shows that after the epitaxial layer 100 is repaired, the resistance of the LED chip is significantly reduced, and the improvement effect on the ohmic contact is good. Compared with the LED chip with the epitaxial layer 100 not treated, the ohmic yield of the LED chip with the epitaxial layer 100 repaired is improved by more than 5%.

[0052] The above is a detailed introduction to a method for repairing epitaxial layer defects provided by an embodiment of the present invention. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for general technical personnel in this field, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as a limitation on the present invention.

Claims

1. A method for repairing epitaxial layer defects, characterized in that: The following steps are involved: S1: depositing a first metal thin layer on the defective epitaxial layer; S2: annealing the epitaxial layer after depositing the first metal thin layer, so that the metal particles in the first metal thin layer form metal agglomerates at the defects of the epitaxial layer, and the first metal thin layer keeps covering the non-defective areas of the epitaxial layer to form a buffer layer; S3: Plasma bombarding the metal agglomerates and the buffer layer, so that the metal particles of the metal agglomerates are tightly embedded in the defects of the epitaxial layer, and the bombardment energy is indirectly transferred to the surface of the epitaxial layer through the buffer layer, so that the surface of the epitaxial layer is roughened; after the metal agglomerates and the buffer layer are bombarded by the plasma, a second metal thin layer is formed on the surface of the epitaxial layer; S4: Soak the epitaxial layer after plasma bombardment treatment in 50-60°C ITO etching solution for 5-10 seconds, then immediately take it out and rinse it with water for more than 5 minutes to remove the second metal thin layer on the surface of the epitaxial layer; the flushing process includes: first directly rinsing the surface of the epitaxial layer with ultrapure water, and then immersing the epitaxial layer in flowing ultrapure water for rinsing.

2. The method for repairing epitaxial layer defects according to claim 1, wherein: Depositing the first metal thin layer on the defective epitaxial layer includes: depositing the first metal thin layer on the defective epitaxial layer by sputtering or evaporation.

3. The method for repairing epitaxial layer defects according to claim 2, wherein: The deposition vacuum degree of the first metal thin layer is 3.0×10 -6 Below Pa, the deposition rate is The deposition thickness is 4. The method for repairing epitaxial layer defects according to claim 3, wherein: The first metal thin layer is a Ni thin layer, a Cr thin layer, a Ti thin layer, or an Al thin layer.

5. The method for repairing epitaxial layer defects according to claim 1, wherein: The annealing treatment in step S2 is performed at a temperature of 550-600° C. and for a time of 3-15 minutes.

6. The method for repairing epitaxial layer defects according to claim 1, wherein: The atmosphere of the plasma bombardment in step S3 includes Ar or O2, the pressure is 550-650 mtorr, and the time is 200-300 s.

7. The method for repairing epitaxial layer defects according to claim 6, characterized in that: The plasma bombardment includes Ar + Ions or O2 + ion.

8. The method for repairing epitaxial layer defects according to claim 1, wherein: In step S2, the metal thin layer is annealed by using an RTA vacuum annealing furnace; and in step S3, the buffer layer is plasma bombarded by using an Asher desmearing machine.

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