A hook-shaped probe and a preparation method and application thereof

Abstract

The application belongs to the technical field of precision machining, and particularly relates to a hook-shaped probe and a preparation method and application thereof. The hook-shaped probe comprises the following steps: a tungsten wire with a diameter of 60-100 microns is stretched into a conical shape by using a hot wire drawing method to obtain a conical probe rod; a smaller end of the conical probe rod is melted into a spherical shape by arc discharge; an external magnetic field in the horizontal direction is applied during the arc discharge process, and the eccentricity of the spherical shape is controlled by the Ampere force generated by the magnetic field to obtain a spoon-shaped probe; under a 10V direct current voltage, the spherical end of the spoon-shaped probe is immersed in an etching solution, and the spoon-shaped probe is periodically extracted and immersed in the alkaline solution at a uniform speed of 0.1-0.5 seconds and 1-10 microns per second to obtain a needle tip portion with a radius of curvature of 30-50 nanometers. The time for preparing a probe by using the method in the application is not more than 8 minutes, the TSV cavity detection rate is greater than 99%, and the aperture deviation is greater than or equal to 5%.

Description

Technical Field

[0001] This invention belongs to the field of precision machining technology, specifically relating to a hook-shaped probe, its preparation method, and its application. Background Technology

[0002] Through-Silicon Vias (TSVs) fabrication is a core process in advanced packaging, occurring in the later stages of chip manufacturing. Defects in TSVs can lead to entire wafer defects, thus determining the packaging quality and performance stability of 3D chips. Currently, atomic force microscopy (AFM) is commonly used to inspect TSV slices. A probe scans the sample surface, detecting the weak interactions between the probe and the sample surface atoms to obtain a three-dimensional morphological image. This highlights the crucial role of the probe in the inspection process. Due to the surge in demand for TSV inspection, and the dramatic increase in the aspect ratio of 3D packaged TSVs from 3-4:1 to 10:1, probes with hook structures and enhanced wear resistance are required due to the increased aspect ratio.

[0003] Currently, focused ion beam engraving is commonly used to fabricate hook-structured probes. However, this method is time-consuming, typically requiring over two hours to process a single probe. Furthermore, thermal damage during fabrication can lead to tip embrittlement, severely impacting the accuracy of through-silicon via (TSV) detection. Additionally, when fabricating probes with an aspect ratio of 10:1 using this method, insufficient rigidity and structural strength result in jitter and misalignment during detection. Electrochemical etching is also used to fabricate probes, but this method cannot precisely control the eccentricity of the hook structure and the radius of curvature of the tip, making it impossible to accurately measure the internal structure of TSVs during detection. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a hook-shaped probe, its preparation method, and its application.

[0005] The first aspect of this invention provides a method for preparing a hook-shaped probe for through-silicon via (TSV) detection, comprising the following steps:

[0006] A conical probe rod is obtained by drawing tungsten wire with a diameter of 60µm to 100µm into a cone shape using a hot-drawing method. Since the diameter of through-silicon vias (TSVs) is 50µm to 100µm, tungsten wire with a diameter of 60µm to 100µm is selected for drawing. Specifically, since the probe needs to meet the requirement of a length-to-diameter ratio of 20:1 for TSV detection, the diameter of the tungsten wire must be less than 60µm. Otherwise, the probe stiffness will be insufficient during the hot-drawing process, affecting the stability and accuracy of subsequent detection. Also, since the detection object is the inner wall of a TSV with a diameter of 50µm to 100µm, a probe with a diameter of less than 100µm is required. Therefore, the diameter of the selected tungsten wire cannot be greater than 100µm.

[0007] A spoon-shaped probe is obtained by melting the smaller end of a conical probe rod into a spherical shape through electric arc discharge, and applying a horizontal external magnetic field during the arc discharge process. The Ampere force generated by the magnetic field is used to control the eccentricity of the sphere. The formula for calculating the Ampere force is as follows:

[0008] F = I × ∫dl × B;

[0009] Where I is the current in A, dl is the effective length of the molten tungsten wire in the magnetic field in m, and B is the magnetic field strength in T; the current is 5A~20A, the effective length of the molten tungsten wire in the magnetic field is 10µm~100µm, and the magnetic field strength is 10mT~100mT; by controlling the current and magnetic field strength, the accuracy of the eccentricity of the sphere is controlled to ensure that the tip with a radius of curvature of 30nm~50nm is obtained after subsequent etching;

[0010] Under DC voltage, the spherical end of the spoon-shaped probe is periodically extracted and immersed in an alkaline solution at a uniform speed of 1µm / s to 10µm / s at a time interval of 0.1s to 0.5s to etch the spherical end, resulting in a tip portion with a radius of curvature of 30nm to 50nm, thus obtaining a hook-shaped probe; specifically, half of the spherical portion is immersed in the alkaline solution for etching.

[0011] This invention first obtains a conical probe rod using a hot-drawing method, then melts the smaller end of the conical probe rod into a spherical shape using an electric arc discharge. During the arc discharge process, an external horizontal magnetic field is applied, specifically the Ampere force generated by the interaction of a 5A~20A current and a 10mT~100mT magnetic field, precisely controlling the spatial position of the molten tungsten sphere to form an eccentric hook blank. The magnitude of the Ampere force is used to precisely control the eccentricity, achieving directional control of the hook structure, thereby improving the detection accuracy of through-silicon vias. Further, the radius of curvature of the probe tip is controlled through electrochemical etching. Using an alkaline solution and a 10V DC voltage, the probe is periodically lifted and immersed in the alkaline solution at a uniform speed of 1µm / s~10µm / s at 0.1s~0.5s intervals, precisely controlling the final cone angle, i.e., the sharpness, of the probe tip, resulting in a tip portion with a radius of curvature of 30nm~50nm, thus obtaining a hook-shaped probe.

[0012] In another preferred embodiment, the specific process of hot drawing the wire is as follows:

[0013] Tungsten wire is heated to a molten state under a protective atmosphere and then stretched at a stretching speed of 0.1 m / s to 1 m / s; preferably, at a stretching speed of 0.5 m / s. Specifically, the molten state refers to heating the tungsten wire to a temperature close to its melting point. The melting point of tungsten is approximately 3422°C. In practice, the portion of the tungsten wire to be stretched is typically locally heated to above 3400°C using an electric arc discharge or a high-temperature furnace, causing the tip to melt rapidly. The stretching rate is applied rapidly at the moment the tungsten wire melts to form a slender conical shape. Using a stretching speed on the order of 0.1 m / s to 1 m / s ensures that the molten tungsten is stretched thinner and longer before it solidifies. To improve the consistency of the hot-drawn wire, the process is carried out in a sealed chamber filled with the protective gas argon to prevent the tungsten from oxidizing at high temperatures.

[0014] In another preferred embodiment, the length-to-diameter ratio of the tapered probe bar is 10 to 20:1.

[0015] In another preferred embodiment, the parameters of the arc discharge are as follows:

[0016] The pulse current density is 100 A / cm 2 ~200A / cm 2 The temperature range is 8000K~10000K, and the current range is 5A~20A.

[0017] In another preferred embodiment, the alkaline solution is a NaOH solution with a concentration of 1 mol / L to 3 mol / L.

[0018] In another preferred embodiment, the DC voltage refers to a 10V DC voltage.

[0019] In another preferred embodiment, an Al2O3 protective layer is deposited on the tip surface of the hook-shaped probe.

[0020] In another preferred embodiment, the thickness of the Al2O3 protective layer is 5nm to 50nm.

[0021] The second aspect of the present invention provides a hook-shaped probe prepared by the aforementioned preparation method.

[0022] A third aspect of the present invention provides the application of the hook-shaped probe in detecting through-silicon vias.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] This invention uses tungsten wire with a diameter of 60µm to 100µm for hot drawing. After hot drawing, the tungsten wire with this diameter can maintain good rigidity and structural strength even with a length-to-diameter ratio of 10:1, avoiding bending during contact measurement in the detection process. In addition, the tungsten wire material itself has high rigidity and hardness, which can further ensure the rigidity and structural stability of the probe. After hot drawing, a horizontal external magnetic field is applied during the arc discharge process to assist in the bending and shaping of the hook. Under the conditions of current of 5A~20A and magnetic field strength of 10mT~100mT, the Ampere force generated by the magnetic field can precisely control the eccentricity of the sphere, achieving a bending angle accuracy of ±5°, thereby obtaining a probe with a hook structure. Furthermore, through electrochemical etching, under a DC voltage of 10V, the spoon-shaped probe is periodically extracted and immersed in alkaline solution at time intervals of 0.1s~0.5s and speeds of 1μm / s~10μm / s to precisely control the radius of curvature of the needle tip, improving the sharpness of the needle tip, and thus enabling precise measurement of the internal structure of through-silicon vias. The hook-shaped probe prepared by the method of the present invention not only meets the aspect ratio of 10:1, but also has high rigidity and structural strength, which can ensure the stability of the detection process and the accuracy of the detection of through silicon vias. The preparation time of a probe by the method of the present invention is no more than 8 minutes, and it has high wear resistance, TSV void detection rate >99%, and hole diameter deviation ≥5%.

[0025] The hook-shaped probe prepared by the method of the present invention has an integral structure, which can effectively improve the overall structural strength and rigidity of the probe and ensure that no deformation or wear occurs when measuring the internal dimensions of TSV with a depth-to-width ratio greater than 10:1. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the process for preparing the hook-shaped probe of the present invention.

[0027] Figure 2 This is a schematic diagram of the arc discharge process of the present invention.

[0028] Figure 3 This is a schematic diagram of the invention using a magnetic field to control the eccentricity of a sphere; wherein, (a) is a schematic diagram of the magnetic field generating device, and (b) is a schematic diagram of the Ampere force applied.

[0029] Figure 4 This is a schematic diagram of an electrochemical etching process to create a needle tip.

[0030] Figure 5 The diagram shows the distribution of measurement points inside the TSV hole and the visual guidance system; (a) is a schematic diagram of the hook-shaped probe performing detection on the worktable, and (b) is a schematic diagram of the machine vision guidance.

[0031] Figure 6This is a schematic diagram of the various parameters to be measured inside the TSV hole; where d represents the hole depth, R represents the top hole diameter, α represents the sidewall angle, R represents the roughness, and r represents the bottom hole diameter.

[0032] Figure 7 This is a photograph of the hook-shaped probe used in this invention. Detailed Implementation

[0033] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments, but this should not be construed as limiting the invention. Unless otherwise specified, the technical means used in the following embodiments are conventional means well known to those skilled in the art, and the materials, reagents, etc. used in the following embodiments are commercially available unless otherwise specified.

[0034] The tungsten wires used in the following examples were purchased from Guangming Science and Technology Research Materials Co., Ltd., with a purity of 99.99% and a Mohs hardness of 7.5.

[0035] A method for preparing a hook-shaped probe, such as Figure 1 As shown, it includes the following steps:

[0036] S1. A 60µm diameter tungsten wire rod is drawn into a conical shape with a taper of 85°~89° using an electric arc molten state. The tip of the tungsten wire rod is melted into a sphere by an electric arc discharge, and then the molten tungsten wire is drawn into a slender conical probe rod by rapidly moving the tungsten wire end along the axial direction. The parameters of the electric arc discharge are 5A~20A and the pulse current density is 100A / cm. 2 ~200A / cm 2 Temperature 8000K~10000K.

[0037] S2. An electric arc discharge is used to melt the tip of a conical probe rod into a spherical shape, and a spoon-shaped probe is obtained by controlling the eccentricity of the tungsten sphere. For example... Figure 2 As shown, a conical tungsten probe rod is used as the material, a platinum spark plug as the positive electrode, and a tungsten wire as the negative electrode. Both ends are connected in series to a high-voltage pulse power supply. The electrode material can be horizontally moved by a feeding mechanism to control the distance between the electrodes. When the smaller end of the tungsten wire approaches the spark plug, the high-voltage pulse breaks down the gas between the electrodes, generating an electric arc. The high temperature generated by the arc melts the smaller end of the tungsten wire, and the liquid tungsten condenses into a spherical shape under the action of surface tension. During the discharge process, in order to obtain a spoon-shaped probe, the center of the sphere needs to be offset from the probe rod's sub-axis by a certain distance. Figure 3 As shown, this is achieved by applying a horizontal external magnetic field. A Helmholtz coil generates a magnetic field B with variable magnetic induction intensity. After the electrodes are energized, free electrons inside the tungsten filament form a current I. Under the influence of the magnetic field, the moving charges inside are subjected to a vertical Lorentz force. This force is macroscopically manifested as an Ampere force on the tungsten sphere in the magnetic field. The formula for calculating the Ampere force is as follows:

[0038] F = I × ∫dl × B;

[0039] Where I is the current in A, l is the effective length of the molten tungsten wire in the magnetic field in m, and B is the magnetic field strength in T; where the current is 5A~20A, the effective length of the molten tungsten wire is 10µm~100µm, and the magnetic field strength is 10mT~100mT.

[0040] During this process, the tungsten sphere is subjected to Ampere force and its own gravity. Under the influence of gravity, the molten sphere tends to fall downwards and generates eccentricity. If the direction of the Ampere force is the same as that of gravity, the eccentricity will increase; conversely, the eccentricity will decrease as the Ampere force partially offsets gravity. Based on this principle, by controlling the direction and intensity of the magnetic field, the eccentricity of the sphere can be adjusted, causing the solidified sphere to deviate slightly relative to the probe axis, forming a spoon-shaped hook probe structure, where the probe tip is offset and bent relative to the probe shank.

[0041] S3. The spoon-shaped blank probe is finely etched into a needle tip using electrochemical etching. Electrochemical etching is the fastest method for preparing reliable needle tips. This invention uses electrochemical etching to etch the spoon-shaped probe. A 1-3 mol / L NaOH solution is used as the electrolyte. The anode is the spoon-shaped probe to be etched, and the cathode is a platinum wire forming an electrolytic cell. A DC voltage is applied across the electrodes. By adjusting the magnitude of the DC voltage, the etching rate of the needle tip can be controlled. Figure 4 The diagram illustrates the use of a high-displacement-resolution piezoelectric ceramic motor to periodically lift and immerse the spherical tip of a spoon-shaped probe on the anode into an alkaline solution at speeds ranging from 1 µm / s to 10 µm / s. This process controls the taper of the probe tip. Fine-tuning the lifting interval (0.1 s to 0.5 s) and the lifting speed (1 µm / s to 10 µm / s) controls the longitudinal dimension and aspect ratio of the probe tip. The tip morphology and size are continuously observed using an optical microscope. When the etching reaches the pre-designed taper and tip diameter, the power is cut off to stop the reaction, and the tungsten probe is removed for cleaning and drying. This electrochemical etching method enables the fabrication of probes with a tip curvature radius of 30 nm to 50 nm. This fabrication method balances the rigidity and spatial accessibility of the probe in high aspect ratio measurements, laying a solid foundation for subsequent ultra-high resolution sidewall scanning measurements in nanoscale coordinate measuring systems.

[0042] The following is a detailed description of a hook-shaped probe, its preparation method, and its applications.

[0043] Example 1: A method for preparing a hook-shaped probe, comprising the following steps.

[0044] S1. A tungsten wire with a diameter of 60 μm is locally heated to the part that needs to be stretched. In this embodiment, one end of the tungsten wire is heated to above 3400°C to rapidly melt the front end. The wire is then stretched at a stretching speed on the order of 0.5 m / s to obtain a tapered probe rod with a length-to-diameter ratio of 20:1 and a taper of 85°.

[0045] S2, such as Figure 2 As shown, through arc discharge, at a pulse current density of 100 A / cm 2 Under conditions of 8000K temperature and 5A current, the smaller end of the conical probe rod is melted into a spherical shape through arc discharge. During the arc discharge process, a horizontal external magnetic field is applied, and the Ampere force generated by the magnetic field is used to control the eccentricity of the sphere to be 60μm and the bending angle to be 90°±3°. After processing for 8 minutes, a spoon-shaped probe is obtained. The Ampere force is calculated using the following formula:

[0046] F = I × ∫dl × B.

[0047] Where I is the current in A, l is the effective length of the molten tungsten wire in the magnetic field in m, and B is the magnetic field strength in T; where the current is 100 A / cm², the effective length of the molten tungsten wire is 60 µm, and the magnetic field strength is 10 mT.

[0048] S3. In a 3 mol / L NaOH solution, at a DC voltage of 10 V, the spoon-shaped probe periodically extracts and immerses half of its spherical part into the NaOH solution at a time interval of 0.5 s and a speed of 10 µm / s. The spherical part is then etched to obtain a tip with a radius of curvature of 42 nm, thus obtaining a hook-shaped probe.

[0049] S4. Using atomic layer deposition (ALD), Al2O3 was deposited on the tip of the probe to obtain a 30 nm thick Al2O3 protective layer. The ALD parameters were: trimethylaluminum and O3 precursors at 100 °C, with 300 cycles of 2 s trimethylaluminum pulse followed by 30 s nitrogen purging, and then 3 s O3 pulse, to deposit a 30 nm Al2O3 coating, resulting in a hook-shaped probe. Figure 7 As shown.

[0050] Example 2: A method for preparing a hook-shaped probe, comprising the following steps.

[0051] S1. Take a tungsten wire with a diameter of 70μm and heat the part that needs to be stretched locally. In this embodiment, one end of the tungsten wire is heated to above 3400℃ to make the front end melt rapidly. Then, stretch it at a stretching speed on the order of 0.6m / s to obtain a tapered probe rod with a length-to-diameter ratio of 15:1 and a taper of 89°.

[0052] S2. Under the conditions of arc discharge with a pulse current density of 200 A / cm², a temperature of 8000 K, and a current of 20 A, the smaller end of the conical probe rod is melted into a spherical shape through arc discharge. During the arc discharge process, an external magnetic field is applied in the horizontal direction. The Ampere force generated by the magnetic field is used to control the eccentricity of the sphere to be 70 μm and the bending angle to be 90°±3°. After processing for 8 minutes, a spoon-shaped probe is obtained. The Ampere force calculation formula is as follows:

[0053] F = I × ∫dl × B.

[0054] Where I is the current in A, l is the effective length of the molten tungsten wire in the magnetic field in m, and B is the magnetic field strength in T; the current is 200 A / cm. 2 The effective length of the molten tungsten wire is 100µm, and the magnetic field strength is 100mT.

[0055] S3. In a 3 mol / L NaOH solution, at a DC voltage of 10 V, the spoon-shaped probe periodically extracts and immerses half of its spherical part into the NaOH solution at a time interval of 0.5 s and a speed of 8 µm / s. The spherical part is then etched to obtain a tip with a radius of curvature of 40 nm, thus obtaining a hook-shaped probe.

[0056] S4. Using atomic layer deposition (ALD), Al2O3 is deposited on the tip of the probe to obtain an Al2O3 protective layer with a thickness of 40 nm. The ALD parameters are: trimethylaluminum and O3 precursor at a low temperature of 100 °C, with 300 cycles of pulses of trimethylaluminum pulse for 2 s followed by nitrogen purging for 30 s, and then O3 pulse for 3 s, to deposit a 30 nm Al2O3 coating and obtain a hook-shaped probe.

[0057] Example 3: A method for preparing a hook-shaped probe, comprising the following steps.

[0058] S1. Take a tungsten wire with a diameter of 70μm and heat the part that needs to be stretched locally. In this embodiment, one end of the tungsten wire is heated to above 3400℃ to make the front end melt rapidly. Then, stretch it at a stretching speed on the order of 0.7m / s to obtain a tapered probe rod with a length-to-diameter ratio of 20:1 and a taper of 87°.

[0059] S2, such as Figure 2As shown, under the conditions of arc discharge with a pulse current density of 180 A / cm², a temperature of 9000 K, and a current of 10 A, the smaller end of the conical probe rod is melted into a spherical shape. During the arc discharge process, an external magnetic field in the horizontal direction is applied, and the Ampere force generated by the magnetic field is used to control the eccentricity of the sphere to be 70 μm and the bending angle to be 90°±3°. After processing for 8 minutes, a spoon-shaped probe is obtained. The Ampere force is calculated using the following formula:

[0060] F = I × ∫dl × B.

[0061] Where I is the current in A, l is the effective length of the molten tungsten wire in the magnetic field in m, and B is the magnetic field strength in T; the current is 180 A / cm. 2 The effective length of the molten tungsten wire is 90µm, and the magnetic field strength is 80mT.

[0062] S3. In a 3 mol / L NaOH solution, at a DC voltage of 10 V, the spoon-shaped probe periodically extracts and immerses half of its spherical part into the NaOH solution at a time interval of 0.5 s and a speed of 10 µm / s. The spherical part is then etched to obtain a tip with a radius of curvature of 40 nm, thus obtaining a hook-shaped probe.

[0063] S4. Using atomic layer deposition (ALD), Al2O3 is deposited on the tip of the probe to obtain an Al2O3 protective layer with a thickness of 40 nm. The ALD parameters are: trimethylaluminum and O3 precursor at a low temperature of 100 °C, with 300 cycles of pulses of trimethylaluminum pulse for 2 s followed by nitrogen purging for 30 s, and then O3 pulse for 3 s, to deposit a 30 nm Al2O3 coating and obtain a hook-shaped probe.

[0064] The hook-shaped probe prepared in Example 1 was used to detect through-silicon vias (TSVs). The TSV was 100 micrometers in diameter with an aspect ratio of approximately 10:1. Machine vision guidance technology was used to obtain the three-dimensional spatial position of the TSV. A schematic diagram of the machine vision guidance detection process is shown below. Figure 5 As shown in (b) of the diagram, the specific process is as follows.

[0065] Step 1: Adaptive localization.

[0066] A hook-shaped probe from a nano-coordinate measuring machine (CMM) is guided directly above the TSV (Transient Via) aperture. The CMM's motion platform then controls the probe to perform continuous measurements within the aperture. Based on the principles of CMM coordinate measurement, a local coordinate system is established within the TSV aperture. The probe first enters the bottom of the aperture and then scans from bottom to top along the aperture using a linear scanning method. An ultra-precision rotating stage ensures coverage of different radial measurement areas within the TSV. The measurement path is dynamically adjusted based on the morphological variations of the sample to minimize the force between the probe and the aperture wall, preventing probe damage due to collisions.

[0067] Step 2: Based on the actual morphology of the TSV, machine learning is used to determine the appropriate X / Y / Z displacement. During the scanning process, the probe position and its contact with the hole wall are monitored in real time to ensure accurate measurement of critical dimensions and sidewall roughness, such as... Figure 5 As shown in (a) of the diagram.

[0068] Step 3: Using the 3D coordinate data obtained from the scan, calculate five physical quantities within the TSV hole: the diameter of the top and bottom of the hole, the hole depth, the sidewall angle, and the sidewall roughness. Figure 6 As shown.

[0069] The measurement results using the above method are shown in Table 1.

[0070] Table 1 TSV Measurement Results

[0071]

[0072] As shown in Table 1, the hook-shaped probe prepared by the method of this invention can accurately measure the top and bottom diameters, depth, sidewall angles, and sidewall roughness of TSV holes. It exhibits high dimensional reproducibility, with average values ​​of 100.017µm, 89.987µm, and 100.098µm for the top, bottom, and depths, respectively, and corresponding standard deviations of only 0.042µm, 0.038µm, and 0.170µm. This indicates that the probe has minimal mechanical error during three-dimensional positioning and scanning, and can stably reproduce the hole diameter and depth. The sidewall angles show no drift; all six measurements yielded a sidewall angle of 0.26° with a standard deviation of 0, indicating that the probe does not introduce additional tilting or jitter during its movement within the hole, maintaining an ideal vertical trajectory in a hole with a depth-to-width ratio of 10:1. The roughness measurement was stable, with an average roughness of 150.85 nm, a standard deviation of 1.89 nm, and a fluctuation range of less than ±2 nm, which is much smaller than the tens of nanometer-level roughness window that is usually of concern in the process. This indicates that the contact force between the probe tip and the hole wall is consistent and the signal noise is low, which is sufficient to distinguish the subtle morphological differences of the TSV sidewall.

[0073] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for manufacturing a hook-type probe for through-silicon via inspection, characterized by, Comprising the following steps: A tungsten wire with a diameter of 60-100 microns is stretched into a conical shape by hot wire drawing to obtain a conical probe rod; The smaller end of the conical probe rod is melted into a spherical shape by arc discharge, and a horizontal external magnetic field is applied during the arc discharge process to control the eccentricity of the spherical shape by the Ampere force generated by the magnetic field to obtain a spoon-shaped probe; wherein the Ampere force calculation formula is as follows: F=I×∫dl×B; Wherein, I is the current, unit A, dl is the effective length of the molten tungsten wire in the magnetic field, unit m, B is the magnetic field strength, unit T; wherein the current is 5-20 A, the effective length of the molten tungsten wire in the magnetic field is 10-100 microns, and the magnetic field strength is 10-100 mT; Under direct current voltage, the spherical end of the spoon-shaped probe is periodically extracted and immersed in the alkali solution at a uniform speed of 1-10 microns per second with a time interval of 0.1-0.5 seconds to etch the spherical end, obtaining a needle tip part with a radius of curvature of 30-50 nm, and obtaining a hook-shaped probe.

2. The method for preparing the hook-shaped probe according to claim 1, characterized in that, The specific process of the hot wire drawing is as follows: The tungsten wire is heated and melted under a protective atmosphere, and stretched at a stretching speed of 0.1-1 m / s.

3. The method for preparing the hook-shaped probe according to claim 1, characterized in that, The aspect ratio of the conical probe rod is 10-20:

1.

4. The method for preparing the hook-shaped probe according to claim 1, characterized in that, The parameters of the arc discharge are as follows: The pulse current density is 100 A / cm 2 ~200 A / cm 2 The temperature is 8000K~10000K, and the current is 5A~20A.

5. The method for preparing the hook-shaped probe according to claim 1, characterized in that, The alkali solution is a NaOH solution with a concentration of 1-3 mol / L.

6. The method for preparing the hook-shaped probe according to claim 1, characterized in that, The direct current voltage refers to a 10V direct current voltage.

7. The method for preparing the hook-shaped probe according to claim 1, characterized in that, It also includes depositing an Al2O3 protective layer on the surface of the needle tip of the hook-shaped probe.

8. The method of claim 7, wherein the hook-shaped probe is prepared by the steps of: The thickness of the Al2O3 protective layer is 5-50 nm. ​ 9. A hook-shaped probe prepared by the preparation method of any one of claims 1-8.

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