A method for detecting crystal dislocation based on Fenton reaction

Abstract

The present invention belongs to the field of crystal detection technology, relates to the detection of crystal dislocations, and specifically to a method for detecting crystal dislocations based on Fenton reaction. A crystal is added to a Fenton reagent for a Fenton reaction for 5 to 30 minutes, and the surface dislocations of the crystal after the Fenton reaction are detected using an electron microscope and / or an atomic force microscope; wherein, in the Fenton reagent, the mass concentration of hydrogen peroxide is 0.5 to 10%; and the mass concentration of ferrous ions in terms of ferrous sulfate is 0.05 to 5%. The present invention can oxidize crystals at room temperature, and observe oxygen dislocation pits under a microscope to detect the distribution and size of crystal dislocations. The detection method provided by the present invention can not only serve as a substitute for the CL method, but also has great advantages in detecting small-sized dislocations in crystals.

Description

Technical Field

[0001] The invention belongs to the technical field of crystal detection, relates to the detection of crystal dislocation, and specifically relates to a method for detecting crystal dislocation based on Fenton reaction. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] Gallium nitride (GaN) is a third-generation semiconductor material that has been widely used for its wide bandgap, high electron mobility, and high electron saturation velocity. Although the crystal quality of GaN single crystals has gradually improved in recent years, it still has high density dislocations (10 7 -10 9 cm −2 ), which is mainly due to the lack of high-quality bulk GaN substrates, which hinders the application of this material in high-frequency, high-efficiency electronic devices.

[0004] A lot of research has been done to observe GaN dislocations. Chinese patent CN113075177A discloses a two-photon super-resolution microscopic three-dimensional imaging device to observe GaN dislocations. It uses optical means to perform three-dimensional imaging of GaN dislocations. Although it will not damage the sample and the equipment cost is not as expensive as cathode fluorescence spectroscopy (CL), the equipment system is too complicated and requires high professionalism of the operator, which is not suitable for general use. Chinese patent CN114594119A discloses a method of etching GaN wafers at 250-400 ° C using a mixed solution of sulfuric acid solution, hydrochloric acid solution and phosphoric acid solution, and then using a scanning electron microscope to observe the etching pits to determine the dislocation density of GaN. The strong acid used not only causes serious damage to the GaN wafer, but also has adverse effects on the environment and operators. The high heating temperature makes the etching process difficult to control, and there are problems such as equipment loss, energy consumption, and safety risks. Similarly, the use of a mixed etching solution of molten potassium hydroxide and magnesium hydroxide to corrode GaN wafers at 400 ° C to 600 ° C also has the same problem.

[0005] CL is a traditional method for detecting dislocations in GaN wafers. It uses the technology of luminescence of samples under the excitation of high-energy electron beams to obtain information about the microstructure of the material by detecting light signals. However, the spatial resolution of CL imaging is limited by the size of the electron beam and the optical collection efficiency of the sample. Among them, the intensity of the luminescence signal that may be generated by small-sized dislocations is weak and insufficient to be captured by the detector. In addition, when the dislocation density is high, the signal of a single small-sized dislocation may be masked by the signals of other surrounding dislocations, resulting in the inability to distinguish them individually. Although the CL method does not cause damage to the sample itself, it is very limited in detecting small-sized GaN dislocations. Summary of the invention

[0006] In order to solve the deficiencies of the prior art, the purpose of the present invention is to provide a method for detecting crystal dislocations based on the Fenton reaction, which can oxidize crystals (especially GaN) at room temperature, observe oxygen dislocation pits through a microscope, and detect the distribution and size of dislocations in crystals (especially GaN). The detection method provided by the present invention can not only serve as a substitute for the CL method, but also has great advantages in detecting small-sized dislocations in crystals (especially GaN).

[0007] In order to achieve the above object, the technical solution of the present invention is:

[0008] A method for detecting crystal dislocation based on Fenton reaction, wherein a crystal is added to a Fenton reagent for Fenton reaction for 5 to 30 minutes, and surface dislocation of the crystal after the Fenton reaction is detected using an electron microscope and / or an atomic force microscope;

[0009] Among them, in Fenton's reagent, the mass concentration of hydrogen peroxide is 0.5~10%; the mass concentration of ferrous ion calculated as ferrous sulfate is 0.05~5%.

[0010] The Fenton reaction is a redox reaction that uses hydrogen peroxide and iron ions to produce hydroxyl radicals with extremely high oxidizing power. Since the Fenton reaction not only has a highly efficient oxidizing power (the oxidation potential of hydroxyl radicals is 2.8 V), it can oxidize crystals, and the byproducts produced during the reaction are mainly water and carbon dioxide; therefore, the Fenton reaction is generally used as an auxiliary treatment during mechanical polishing of crystals.

[0011] During the research process of the present invention, it was unexpectedly discovered that the Fenton reaction can preferentially oxidize the dislocations of the crystal. The main reason is that the existence of dislocations will lead to stress concentration inside the crystal, making the dislocation area more active than the surrounding lattice. The atomic distance at the dislocation is shorter than that in the perfect lattice, and the bonding force between atoms is weaker, so the dislocation has a higher reactivity. Therefore, the Fenton reaction will preferentially oxidize the dislocations of the crystal. The present invention can make the dislocations of the crystal at an appropriate oxidation degree by controlling the concentration of hydrogen peroxide, the concentration of ferrous ions and the Fenton reaction time. Not only can the dislocation pits with the same size as in the CL image be observed, but also the dislocations of extremely small sizes can be detected.

[0012] The beneficial effects of the present invention are:

[0013] 1. The Fenton reaction used in the present invention can not only meet the requirements of oxidizing crystals (especially GaN) at room temperature, but also has the advantages of being environmentally friendly, the equipment used is simple, and the detection cost is greatly reduced.

[0014] 2. The oxidized crystal (especially GaN) can be re-obtained with a smooth crystal (especially GaN) surface by simple chemical mechanical polishing for subsequent use. The method used in the present invention will not cause serious damage to the crystal.

[0015] 3. The present invention's method for detecting dislocations in crystals (especially GaN) based on the Fenton reaction can not only observe dislocations presented in conventional methods (CL), but also detect dislocations of smaller sizes. In addition, it has the advantages of room temperature reaction, environmental friendliness, simple equipment, low cost, and subsequent use of crystals (especially GaN). BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0017] Figure 1 is a cathode fluorescent image of the GaN wafer used in Example 1, where the scale bar is 10 μm;

[0018] Figure 2 is an AFM image of the oxidized GaN wafer in Example 1, where the scale is 2.5 μm;

[0019] Figure 3 is a SEM image of the oxidized GaN wafer in Example 1, with a scale of 1 μm;

[0020] Figure 4 is an AFM image of the oxidized GaN wafer in Example 2, where the scale is 2.5 μm;

[0021] Figure 5 is an AFM image of the oxidized GaN wafer in Example 3, with a scale of 1 μm;

[0022] Figure 6 This is an AFM image of the oxidized GaN wafer in Comparative Example 1, with a scale of 2.5 μm. DETAILED DESCRIPTION

[0023] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0024] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0025] In view of the fact that the equipment used in the prior art is complex, the cost is high, and the chemicals used are strong acids or strong bases, which have adverse effects on the environment and operators. In particular, etching of GaN wafers needs to be carried out under high temperature conditions, which is not only difficult to control the etching process but also causes damage to the equipment. In addition, there are problems of energy consumption and high cost. The present invention proposes a method for detecting crystal dislocations based on Fenton reaction.

[0026] A typical embodiment of the present invention provides a method for detecting crystal dislocation based on Fenton reaction, wherein a crystal is added to a Fenton reagent for a Fenton reaction for 5 to 30 minutes, and surface dislocations of the crystal after the Fenton reaction are detected using an electron microscope and / or an atomic force microscope;

[0027] Among them, in Fenton's reagent, the mass concentration of hydrogen peroxide is 0.5~10%; the mass concentration of ferrous ion calculated as ferrous sulfate is 0.05~5%.

[0028] The present invention utilizes the environmentally friendly Fenton reaction to oxidize crystals (especially GaN) at room temperature, which not only avoids adverse effects on the environment and operators, but is also more conducive to controlling the oxidation process of crystals (especially GaN) at room temperature, and avoids the disadvantage that the heating / cooling process is difficult to control. The strong oxidizing property of the Fenton reaction overcomes the chemical inertness of crystals (especially GaN) and effectively oxidizes crystals (especially GaN). Since the chemical activity of the dislocation region of the crystal (especially GaN) is higher, the dislocation pit can be presented through the oxidation reaction, and the dislocation distribution and size of the crystal (especially GaN) can be easily detected.

[0029] In the Fenton reaction, when the reaction time is too short or the hydrogen peroxide concentration or the ferrous ion concentration is too low, the degree of oxidation of the crystal (especially GaN) is low, and the dislocations are not oxidized into obvious pits and are difficult to observe. When the reaction time is too long or the hydrogen peroxide concentration or the ferrous ion concentration is too high, the dislocations at different positions are oxidized and connected into large-sized pits, and independent, real-sized dislocation pits cannot be detected. Therefore, the present invention adopts the above-mentioned hydrogen peroxide, ferrous ion concentration and Fenton reaction time to detect independent, real-sized dislocation pits.

[0030] In some embodiments, the crystal is GaN. GaN has high chemical bond energy, can resist many chemical corrosion and oxidation, and is difficult to process at room temperature. The present invention has found that the Fenton reaction can better process the dislocation pit of GaN dislocation.

[0031] In order to prevent the pollutants attached to the crystal surface from affecting the efficiency of the Fenton reaction, in some embodiments, the crystal is cleaned before the Fenton reaction.

[0032] Specifically, a mixture of water and an organic solvent is used for cleaning. More specifically, the organic solvent includes but is not limited to ethanol and acetone, which is conducive to cleaning pollutants on the surface of the GaN wafer, including organic matter, metal ions, etc. More specifically, the volume ratio of water to the organic solvent is 5 to 1:1, which can effectively clean the crystal.

[0033] Specifically, ultrasound is used for treatment. More specifically, the ultrasound time is 10-60 min, and the number of repetitions is 2-5 times. Prolonging the ultrasound time and increasing the number of repetitions are conducive to obtaining a clean GaN wafer surface.

[0034] Specifically, nitrogen or inert gas is used to dry the sample after cleaning to avoid other drying methods from introducing impurities, thereby affecting the accuracy of detecting dislocation pits.

[0035] In some embodiments, the electron microscope is a scanning electron microscope.

[0036] In some embodiments, the Fenton reaction is followed by cleaning and then detection is performed. Specifically, the cleaning process after the Fenton reaction is the same as the cleaning process before the Fenton reaction.

[0037] Specifically, a mixture of water and an organic solvent is used for cleaning. More specifically, the organic solvent includes but is not limited to ethanol and acetone, which is conducive to cleaning pollutants on the surface of the GaN wafer, including organic matter, metal ions, etc. More specifically, the volume ratio of water to the organic solvent is 5 to 1:1, which can effectively clean the crystal.

[0038] Specifically, ultrasound is used for treatment. More specifically, the ultrasound time is 10-60 min, and the number of repetitions is 2-5 times. Prolonging the ultrasound time and increasing the number of repetitions are conducive to obtaining a clean GaN wafer surface.

[0039] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in combination with specific embodiments and comparative examples.

[0040] Example 1

[0041] A method for detecting dislocation of a GaN wafer based on Fenton reaction comprises the following steps:

[0042] Step 1: Place the GaN wafer (0.2301 g) in a 100 mL water / ethanol mixed solution with a ratio of 3 and ultrasonicate for 20 min. Repeat 3 times and blow dry the GaN wafer surface with a nitrogen gun.

[0043] Step 2: Place the GaN wafer in a glass dish and add 3 mL of 4% hydrogen peroxide solution and 1 mL of 0.5% ferrous sulfate solution respectively. After standing for 30 minutes, take out the GaN wafer.

[0044] Step 3: Repeat step 1 and use AFM and SEM to detect the dislocation pits on the surface of the GaN wafer.

[0045] Example 2

[0046] A method for detecting dislocation of a GaN wafer based on Fenton reaction comprises the following steps:

[0047] Step 1: Place the GaN wafer (0.2331 g) in a 100 mL water / ethanol solution with a ratio of 3 and ultrasonicate for 20 min. Repeat this three times and then use a nitrogen gun to dry the GaN wafer surface.

[0048] Step 2: Place the GaN wafer in a glass dish and add 3 mL of 6% hydrogen peroxide solution and 1 mL of 1% ferrous sulfate solution respectively. After standing for 15 minutes, take out the GaN wafer.

[0049] Step 3: Repeat step 1 and use AFM and SEM to detect the dislocation pits on the surface of the GaN wafer.

[0050] Example 3

[0051] A method for detecting dislocation of a GaN wafer based on Fenton reaction comprises the following steps:

[0052] Step 1: Place the GaN wafer (0.2311 g) in a 100 mL water / ethanol solution with a ratio of 3 and ultrasonicate for 20 min. Repeat this three times and then use a nitrogen gun to dry the GaN wafer surface.

[0053] Step 2: Place the GaN wafer in a glass dish and add 3 mL of 6% hydrogen peroxide solution and 1 mL of 1% ferrous sulfate solution respectively. After standing for 5 minutes, take out the GaN wafer.

[0054] Step 3: Repeat step 1 and use AFM and SEM to detect the dislocation pits on the surface of the GaN wafer.

[0055] Comparative Example 1

[0056] A method for detecting dislocation of a GaN wafer based on Fenton reaction comprises the following steps:

[0057] Step 1: Place the GaN wafer (0.2333 g) in 100 mL of ethanol / water mixed solution and ultrasonicate for 20 min. Repeat this three times and then use a nitrogen gun to dry the surface of the GaN wafer.

[0058] Step 2: Place the GaN wafer in a glass dish and add 4 mL of 15% hydrogen peroxide solution and 2 mL of 3% ferrous sulfate solution respectively. After standing for 60 minutes, take out the GaN wafer.

[0059] Step 3: Repeat step 1 and use AFM and SEM to detect the dislocation pits on the surface of the GaN wafer.

[0060] Figure 1 is a cathode fluorescent image of the GaN wafer used in Example 1, Figure 2 is an AFM image of the oxidized GaN wafer in Example 1. In order to verify the rationality of the GaN wafer dislocation detection method based on Fenton reaction of the present invention, the dislocation distribution and size of the GaN wafer were observed by cathode fluorescence image before Fenton reaction treatment as a standard ( Figure 1 ). The dislocations in the GaN wafer are in the form of dots or dots arranged in lines, and the dislocation size is 0.1-0.4 μm. The image of the GaN wafer treated with Fenton reaction in Example 1 observed under AFM is as follows Figure 2 As shown in the figure, the morphology (dots and dots arranged in lines) and size (0.1-0.4 μm) of the dislocation pits are consistent with those of the cathode fluorescence image, proving the rationality of the GaN wafer dislocation detection method based on the Fenton reaction of the present invention. In addition, smaller dislocation pits (white circles) with a size of 0.02-0.06 μm were observed in the AFM image, which was not shown in the CL image. The relevant positions were observed by SEM ( Figure 3) also confirmed the existence of dislocations with a size of 0.03-0.08 μm. The method of the present invention can not only observe the dislocation pits that match those in CL, but also detect dislocations with smaller sizes. Figure 4 is the AFM image of the oxidized GaN wafer in Example 2, which is different from that in Example 1 ( Figure 2 ) are consistent with the results shown. Figure 5 The AFM image of the oxidized GaN wafer in Example 3 shows that the size of the dislocation pit is about 0.02 μm, which is similar to Figure 2 This is consistent with the small-sized dislocations observed in the CL image. This shows that when the oxidation time is short, small-sized dislocations are displayed, and as the oxidation degree increases, the size of the dislocation pits gradually increases until it is consistent with the CL image results.

[0061] Figure 6 This is an AFM image of the oxidized GaN wafer in Comparative Example 1. Due to the high degree of oxidation, independent dislocation pits can no longer be observed. This shows that the matching of oxidant, catalyst concentration and reaction time is crucial to the detection of GaN wafer dislocations using this method.

[0062] 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 detecting crystal dislocation based on Fenton reaction, characterized in that: The crystal is added to the Fenton reagent to perform a Fenton reaction for 5 to 30 minutes, and the surface dislocation of the crystal after the Fenton reaction is detected using an electron microscope and / or an atomic force microscope; Wherein, in the Fenton reagent, the mass concentration of hydrogen peroxide is 0.5-10%; the mass concentration of ferrous ions in terms of ferrous sulfate is 0.05-5%; the crystal is GaN; By controlling the concentration of hydrogen peroxide, the concentration of ferrous ions, and the Fenton reaction time, individual, true-sized dislocation pits can be detected.

2. The method for detecting crystal dislocation based on Fenton reaction as claimed in claim 1, characterized in that: The crystals are cleaned and then subjected to Fenton reaction.

3. The method for detecting crystal dislocation based on Fenton reaction as claimed in claim 2, characterized in that: Cleaning is done with a mixture of water and organic solvents.

4. The method for detecting crystal dislocation based on Fenton reaction as claimed in claim 3, characterized in that: The organic solvent is ethanol or acetone.

5. The method for detecting crystal dislocation based on Fenton reaction as claimed in claim 3, characterized in that: The volume ratio of water to organic solvent is 5-1:

1.

6. The method for detecting crystal dislocation based on Fenton reaction as claimed in claim 2, characterized in that: Ultrasonic treatment was used.

7. The method for detecting crystal dislocation based on Fenton reaction as claimed in claim 6, characterized in that: The ultrasonic time is 10 to 60 min, and the number of repetitions is 2 to 5 times.

8. The method for detecting crystal dislocation based on Fenton reaction as claimed in claim 2, characterized in that: After cleaning, use inert gas to blow dry; The inert gas is nitrogen.

9. The method for detecting crystal dislocation based on Fenton reaction as claimed in claim 1, characterized in that: The electron microscope is a scanning electron microscope.

10. The method for detecting crystal dislocation based on Fenton reaction according to claim 1, characterized in that: After the Fenton reaction, the sample is cleaned and then tested.

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