A method for repairing gallium nitride single crystal products with local defects

Abstract

This invention discloses a method for repairing locally defective gallium nitride (GaN) single crystal substrates, belonging to the field of GaN single crystal substrate fabrication. Utilizing the principle that the localized energy of the defective region relative to the normal region reduces the free energy required for etching, the defective region is directionally etched using chemical agents or a high-temperature atmosphere. It is then re-encapsulated in a hydride vapor phase epitaxy (HVPE) machine for 0-100 μm epitaxy, healing the etched area. After polishing, the defective area is repaired, resulting in a finished single crystal. This method requires only growing 0-100 μm of the repaired single crystal surface, significantly reducing costs and improving product yield compared to regrowing a 700 μm thick single crystal.

Description

Technical Field

[0001] This invention belongs to the field of gallium nitride single crystal substrate fabrication, and specifically relates to a method for repairing gallium nitride single crystal products with local defects. Background Technology

[0002] During the preparation of gallium nitride (GaN) single crystals using the HVPE method, local dislocation anomalies are highly likely to occur in the finished single crystal due to factors such as local flow field disturbances, particle shedding, and significant differences in local 5:3 ratios. To prepare a 400 μm thick GaN single crystal using the HVPE method, at least 700 μm of material needs to be grown, followed by polishing to achieve the desired thickness. When these finished single crystals are fabricated for chip manufacturing, the blue-green lasers produced using this area exhibit significantly lower quality (output power, lifespan, etc.) compared to those from normal areas; in severe cases, they may even fail to conduct at all. Therefore, in actual production control, these locally anomalous GaN single crystals are considered scrap and cannot be used. This local anomaly leading to the scrapping of entire GaN single crystals is one of the most significant reasons for the high cost of GaN single crystals. Summary of the Invention

[0003] To address the aforementioned problems, this invention proposes a method for repairing locally defective gallium nitride (GaN) single crystal products. Utilizing the principle that the localized energy in the defective region of the GaN single crystal material, relative to the normal region, reduces the free energy required for etching, the method involves etching the defective region with a specific ratio of chemical solution or a high-temperature atmosphere, followed by re-epitaxy in a furnace, thereby eliminating the local defects.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A method for repairing gallium nitride single crystals with local defects includes the following steps: first, the gallium nitride single crystal with local defects is subjected to directional etching treatment using an etchant or a high-temperature atmosphere; then, it is put into an HVPE equipment for epitaxy to re-heal the etched area; and finally, the defective area is repaired by grinding and polishing.

[0006] The etching solution is one or more of the following: phosphoric acid, nitric acid, hydrogen peroxide, sodium hydroxide, hydrofluoric acid, sulfuric acid, hydrochloric acid, and buffer oxide etching solution.

[0007] The gas used in the high-temperature atmosphere is one or more of H2, N2, O2, HCl, Cl2 or BCl3.

[0008] The thickness of the reflowed epitaxial layer is 0-100 μm.

[0009] The etching solution is obtained by mixing phosphoric acid and hydrogen peroxide in a volume ratio of 1:1. The finished gallium nitride single crystal with local defects is placed in the etching solution and etched at 180°C for 40 minutes. The etching depth is 20-100 μm, preferably 20-40 μm.

[0010] The etching solution includes etching solution A and etching solution B. Etching solution A is obtained by mixing sulfuric acid, hydrogen peroxide and deionized water in a volume ratio of 5:1:1, and etching solution B is obtained by mixing hydrochloric acid, hydrogen peroxide and deionized water in a volume ratio of 1:1:5. The finished gallium nitride single crystal with local defects is first placed in etching solution A and etched at a temperature of 180°C for 40 minutes; then placed in etching solution B and etched at 100°C for 20 minutes. The etching depth is 20-100 μm, preferably 20-40 μm.

[0011] The high-temperature atmosphere consists of N2, HCl, and H2, with flow rates of 15000 sccm, 200 sccm, and 8000 sccm, respectively. The etching temperature is 1080℃, the pressure is 500 torr, the etching time is 30 min, and the etching depth is 30-100 μm.

[0012] The high-temperature atmosphere consists of O2, Cl2, and BCl3, with flow rates of 10 sccm, 100 sccm, and 5 sccm, respectively. The etching temperature is 100℃, the pressure is 10 torr, the etching time is 60 min, and the etching depth is 30-100 μm.

[0013] The gallium nitride single crystal obtained by the above repair method.

[0014] The beneficial effects of this invention are as follows:

[0015] By using chemical agents or high-temperature atmospheres to etch defective areas and then re-epitaxuring them in a furnace, the etching depth at the defective area can be controlled within 0-100 μm. During re-epitaxy, only the etched area needs to be filled. In other words, depending on the depth of the etching pit, this method only requires growing 0-100 μm to repair the defective single crystal surface. Compared to regrowing a 700 μm thick single crystal to prepare the finished product, this significantly reduces costs and improves product yield. Attached Figure Description

[0016] Figure 1 This is a partial view of a finished gallium nitride single crystal product.

[0017] Figure 2 This is a flowchart of a method for repairing gallium nitride single crystal products with local defects;

[0018] Figure 3 This is a diagram of the dislocation anomaly region in the gallium nitride single crystal with local defects, as shown in Example 1.

[0019] Figure 4 This is a region diagram of a locally dislocated single crystal after using the gallium nitride finished single crystal repair method for local defects in Example 1;

[0020] Figure 5 This is a diagram of the dislocation anomaly region in the gallium nitride single crystal with local defects, as shown in Example 2.

[0021] Figure 6 This is a region diagram of a locally dislocated single crystal after using the gallium nitride finished single crystal repair method for local defects in Example 2;

[0022] Figure 7 This is a diagram of the dislocation anomaly region in the gallium nitride single crystal with local defects, as shown in Example 3.

[0023] Figure 8 This is a region diagram of a locally dislocated single crystal after repair using the gallium nitride finished single crystal repair method for local defects in Example 3. Detailed Implementation

[0024] The present invention will be further described below with reference to the accompanying drawings and embodiments. It should be noted that the following detailed description is illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0025] A method for repairing localized defects in finished gallium nitride single crystals involves adding a chemical reagent or high-temperature etching step to the traditional crystal preparation process. A localized defect area of ​​the finished gallium nitride single crystal is shown in the image below. Figure 1 As shown, the repair process is as follows: Figure 2 As shown.

[0026] Example 1

[0027] A method for repairing local defects in finished gallium nitride single crystals, the specific steps of which are as follows:

[0028] (1) Screening out gallium nitride single crystal products with local dislocation defects;

[0029] (2) Mix phosphoric acid (concentration 85%-87%) and hydrogen peroxide (30%-32%) at a volume ratio of 1:1 to obtain a corrosion solution;

[0030] (3) The selected gallium nitride single crystal with local dislocation defects was placed in the above etching solution and etched at 180°C for 40 min, with an etching depth of 20-40 μm;

[0031] (4) After washing and drying the sample obtained in step (3), put it into the HVPE equipment to epitaxially grow 0-100 μm GaN. The specific epitaxial thickness is determined according to the corrosion depth. The epitaxial thickness is slightly greater than the corrosion depth. The epitaxial parameters are: temperature 1010℃, pressure 300 torr, flow rate: N2 (14000 sccm) + HCl (150 sccm) + H2 (8000 sccm) + NH3 (7500 sccm).

[0032] (5) Polish the substrate with the repaired surface obtained in step (4) to produce gallium nitride finished single crystal.

[0033] Example 2

[0034] A method for repairing local defects in finished gallium nitride single crystals, the specific steps of which are as follows:

[0035] (1) Screening out gallium nitride single crystal products with local dislocation defects;

[0036] (2) Mix sulfuric acid (concentration 95%-98%), hydrogen peroxide (30%-32%) and deionized water in a volume ratio of 5:1:1 to obtain corrosion solution A; then mix hydrochloric acid (35%-37%), hydrogen peroxide (30%-32%) and deionized water in a volume ratio of 1:1:5 to obtain corrosion solution B;

[0037] (3) First, place the selected gallium nitride single crystal with local dislocation defects into the above etching solution A and etch it at 180°C for 40 min. Then, place the etched single crystal into the etching solution B and etch it at 100°C for 20 min. The etching depth is 20-40 μm.

[0038] (4) After washing and drying the sample obtained in step (3), put it into the HVPE equipment for epitaxial growth of 0-100 μm. The specific epitaxial thickness is determined according to the corrosion depth. The thickness of the epitaxial layer is greater than the corrosion depth. The epitaxial parameters are the same as in Example 1.

[0039] (5) Polish the substrate with the repaired surface obtained in step (4) to produce a finished single crystal.

[0040] Example 3

[0041] A method for repairing local defects in finished gallium nitride single crystals, the specific steps of which are as follows:

[0042] (1) Screening out gallium nitride single crystal products with local dislocation defects;

[0043] (2) Place the single crystal selected in step (1) into a vacuum device and introduce a mixture of N2, HCl and H2 gas at flow rates of 15000 sccm, 200 sccm and 8000 sccm respectively; the temperature is 1080℃ and the pressure is maintained at 500 torr; the etching time is 30 min; the etching depth is 50 μm; after etching, the substrate is cleaned.

[0044] (3) After washing and drying the sample obtained in step (2), it is placed into the HVPE equipment for epitaxy of 60 μm. The epitaxy parameters are the same as in Example 1.

[0045] (4) The substrate with the repaired surface obtained in step (4) is polished to produce a finished single crystal.

[0046] Example 4

[0047] A method for repairing local defects in finished gallium nitride single crystals, the specific steps of which are as follows:

[0048] (1) Screening out gallium nitride single crystal products with local dislocation defects;

[0049] (2) Place the single crystal selected in step (1) into a vacuum device and introduce a mixed gas of O2, Cl2 and BCl3 at flow rates of 10 sccm, 100 sccm and 5 sccm respectively; maintain the temperature at 100℃ and the pressure at 10 torr; etch for 60 min; etch depth for 10 μm; and clean the substrate after etching.

[0050] (3) After washing and drying the sample obtained in step (2), it is placed into the HVPE equipment for epitaxial growth of 20 μm. The epitaxial parameters are the same as in Example 1.

[0051] (4) Polish the substrate with the repaired surface obtained in step (3) to produce a finished single crystal.

[0052] Figure 3 This is the dislocation anomaly region in the finished single crystal with localized defects in Example 1. Dislocations cannot be statistically counted. Figure 4 The image shows the repaired region with a dislocation size of 2.12 × 10⁻⁶. 6 / cm 2 .

[0053] Figure 5 This is the dislocation anomaly region in the finished single crystal of Example 2, where local defects exist and dislocations cannot be counted. Figure 6 The image shows the repaired region with a dislocation of 1.25 × 10⁻⁶. 6 / cm 2 .

[0054] Figure 7 This is the dislocation anomaly region in the finished single crystal of Example 2, where local defects exist and dislocations cannot be counted. Figure 8 The image shows the repaired region with a dislocation value of 1.31 × 10⁻⁶. 6 / cm 2 .

[0055] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A method of repairing a locally-defective finished gallium nitride single crystal, the method comprising: The local defect gallium nitride product single crystal is firstly treated by using a corrosion liquid or a high temperature atmosphere, then is put into a HVPE device to re-epitaxially grow and heal the corroded area, and finally the defective area is repaired after polishing and grinding. ​ The corrosion liquid is one or more of phosphoric acid, nitric acid, hydrogen peroxide, sodium hydroxide, hydrofluoric acid, sulfuric acid, hydrochloric acid and buffer oxide etching liquid. The high temperature atmosphere uses one or more of H2, N2, O2, HCl, Cl2 and BCl3. The thickness of the re-epitaxial growth is 20-100 microns.

2. The method of claim 1, wherein the local defect in the finished single crystal gallium nitride product is a dislocation. The corrosion liquid is obtained by mixing phosphoric acid and hydrogen peroxide at a volume ratio of 1:1, and the local defect gallium nitride product single crystal is placed in the corrosion liquid and corroded at 180℃ for 40 minutes, and the corrosion depth is 20-100 microns.

3. The method of claim 1, wherein the local defect in the finished single crystal gallium nitride product is a dislocation. The corrosion liquid includes corrosion liquid A and corrosion liquid B, the corrosion liquid A is obtained by mixing sulfuric acid, hydrogen peroxide and deionized water at a volume ratio of 5:1:1, and the corrosion liquid B is obtained by mixing hydrochloric acid, hydrogen peroxide and deionized water at a volume ratio of 1:1:5; the local defect gallium nitride product single crystal is firstly placed in the corrosion liquid A and corroded at 180℃ for 40 minutes, and then is placed in the corrosion liquid B and corroded at 100℃ for 20 minutes, and the corrosion depth is 20-100 microns.

4. The method of claim 1, wherein the local defect in the finished single crystal gallium nitride product is a dislocation. The high temperature atmosphere uses N2, HCl and H2, the flow rates are 15000 sccm, 200 sccm and 8000 sccm respectively, the corrosion temperature is 1080℃, the pressure is 500 torr, the corrosion time is 30 minutes, and the etching depth is 30-100 microns.

5. The method of claim 1, wherein the local defect in the finished single crystal gallium nitride product is a dislocation. The high temperature atmosphere uses O2, Cl2 and BCl3, the flow rates are 10 sccm, 100 sccm and 5 sccm respectively, the corrosion temperature is 100℃, the pressure is 10 torr, the corrosion time is 60 minutes, and the etching depth is 30-100 microns.

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