A method for detecting interface defects and a method for inspecting wafers.

Abstract

This application belongs to the field of semiconductor technology and provides an interface defect detection method and a wafer inspection method. The interface defect detection method applies a horizontal static magnetic field to the power device under test, causing the spin direction of electrons in the defect energy level to change downward. After applying a radio frequency magnetic field, the spin direction of electrons in the defect energy level is reversed to upward, which prohibits the pairing behavior of electrons from the conduction band that were originally paired with the defect energy level. At this time, electrons from the conduction band will fall into the valence band and recombine with holes in the valence band to form a leakage current. Then, the interface defect density is detected by detecting the magnitude of the leakage current.

Description

Technical Field

[0001] This application belongs to the field of semiconductor technology, and in particular relates to an interface defect detection method and a wafer inspection method. Background Technology

[0002] Reliability assessment of power device performance is a crucial part of integrated circuit process development. However, reliability assessment of the gate oxide layer in power devices is a significant front-end project, primarily used to evaluate the performance of front-end dielectric materials. Many processes in integrated circuit manufacturing can affect the upper and lower interfaces of the gate oxide layer, thus influencing its TDDB (Time Dependent Dielectric Breakdown), which exhibits polarity dependence. Therefore, effectively characterizing the defect density at the upper and lower interfaces of the gate oxide layer is extremely important.

[0003] After extensive research and development, the parallel conductivity method for characterizing interface defect density is currently mainly applied to Si-based MOS devices. However, this method often has strict applicable ranges and conditions, such as requiring the device to have very low leakage current. Since AlGaN / GaN HEMTs are devices with relatively high leakage current, simply applying the above method to characterize the interface defect density of AlGaN / GaN HEMTs will obviously yield inaccurate results. Furthermore, Si and GaN materials differ significantly in their conduction band effective state density, bandgap width, and interface defect density, making the reliability of results obtained using the parallel conductivity method questionable.

[0004] It is evident that existing methods for detecting interface defects in power devices suffer from limited application scope and inaccurate detection results. Summary of the Invention

[0005] To address the aforementioned technical problems, embodiments of this application provide an interface defect detection method and a wafer inspection method, aiming to solve the problems of limited application scope and inaccurate detection results of existing power device interface defect detection methods.

[0006] This application provides an interface defect detection method applied to a power device under test (DUT), wherein the drain of the DUT is connected to a power supply, the source of the DUT is grounded, and the gate of the DUT is floating. The interface defect detection method includes:

[0007] A horizontally calm magnetic field is applied to the power device under test; wherein the horizontally calm magnetic field is used to adjust the spin direction of electrons in the defect energy level;

[0008] A radio frequency magnetic field is applied above the gate of the power device under test; wherein the radio frequency magnetic field is used to reverse the spin direction of electrons located in the defect energy level, so that electrons from the conduction band move into holes in the valence band, thereby forming a leakage current;

[0009] The leakage current of the power device under test is detected, and the interface defect density of the power device under test is determined based on the magnitude of the leakage current.

[0010] In one embodiment, the step of applying a radio frequency magnetic field over the gate of the power device under test further includes:

[0011] A radio frequency coil is disposed above the gate of the power device under test, and the radio frequency coil generates the radio frequency magnetic field when energized.

[0012] In one embodiment, the center of the radio frequency coil is located above the gate.

[0013] In one embodiment, the step of arranging an RF coil above the gate of the power device under test further includes:

[0014] A magnetic core unit is provided at the center of the radio frequency coil, and the magnetic core unit is used to increase the strength of the radio frequency magnetic field.

[0015] In one embodiment, applying a radio frequency magnetic field over the gate of the power device under test includes:

[0016] By adjusting the strength of the radio frequency magnetic field, the spin direction of electrons in the defect energy level is reversed.

[0017] In one embodiment, applying a horizontally calm magnetic field to the power device under test includes:

[0018] A first magnet and a second magnet are respectively disposed on both sides of the source and drain of the power device under test, and the first magnet and the second magnet are used to generate the horizontal calm magnetic field.

[0019] In one embodiment, the first magnet and the second magnet are arranged symmetrically.

[0020] In one embodiment, applying a horizontally calm magnetic field to the power device under test includes:

[0021] The power device under test is placed in a sealed cavity, and a first magnet and a second magnet are respectively placed on both sides of the source and drain of the power device under test.

[0022] In one embodiment, detecting the leakage current of the power device under test and determining the size of the interface defect of the power device under test based on the magnitude of the leakage current includes:

[0023] The magnitude of the leakage current is compared with a preset mapping table, and the interface defect density of the power device under test is determined based on the comparison result.

[0024] This application also provides a wafer inspection method, wherein the wafer includes a plurality of power devices and at least one power device under test, and the defect density of the power device under test is detected by the interface defect detection method described in any of the above claims.

[0025] The beneficial effects of this application embodiment compared with the prior art are as follows: by applying a horizontally calm magnetic field to the power device under test, the spin direction of electrons in the defect energy level changes, and the spin direction is vertically downward. After applying a radio frequency magnetic field, the spin direction of electrons in the defect energy level is flipped, and the direction is upward. This prohibits the pairing behavior of electrons from the conduction band that were originally paired with the defect energy level. At this time, the electrons from the conduction band that were originally paired will fall into the valence band and recombine with holes in the valence band to form a leakage current. Then, the interface defect density is detected by detecting the magnitude of the leakage current. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the steps of an interface defect detection method provided in one embodiment of this application;

[0027] Figure 2 This is a schematic diagram of the specific structure of an interface defect detection method provided in one embodiment of this application. Figure 1 ;

[0028] Figure 3 This is a schematic diagram of the specific structure of an interface defect detection method provided in one embodiment of this application. Figure 2 ;

[0029] Figure 4 This is a schematic diagram of the structure of an interface defect detection method provided in one embodiment of this application;

[0030] Figure 5 This is a top view of the structure of a radio frequency coil provided in one embodiment of this application;

[0031] Figure 6 This is a schematic diagram of the structure of a wafer inspection method provided in one embodiment of this application. Detailed Implementation

[0032] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0033] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.

[0034] It should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0035] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means one or more, unless otherwise explicitly specified.

[0036] In this specification, references to "one embodiment," "some embodiments," or simply "embodiment" mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, phrases such as "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," "in a particular embodiment," and "in a particular application," appearing in various parts of this specification, do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. Furthermore, in one or more embodiments, specific features, structures, or characteristics may be combined in any suitable manner.

[0037] Reliability assessment of power device performance is a crucial part of integrated circuit process development. However, reliability assessment of the gate oxide layer in power devices is a significant front-end project, primarily used to evaluate the performance of front-end dielectric materials. Many processes in integrated circuit manufacturing can affect the upper and lower interfaces of the gate oxide layer, thus influencing its TDDB (Time Dependent Dielectric Breakdown), which exhibits polarity dependence. Therefore, effectively characterizing the defect density at the upper and lower interfaces of the gate oxide layer is extremely important.

[0038] After extensive research and development, the parallel conductivity method for characterizing interface defect density is currently mainly applied to Si-based MOS devices. However, this method often has strict applicable ranges and conditions, such as requiring very low leakage current. Since AlGaN / GaN HEMTs are devices with high leakage current, simply applying the above method to characterize their interface defect density will obviously yield inaccurate results. Furthermore, SiC power devices have a high interface state density, which also leads to significant leakage current, making interface defect density detection particularly important. In addition, Si and GaN materials differ significantly in their conduction band effective state density, bandgap width, and interface defect density, raising doubts about the reliability of results obtained using the parallel conductivity method.

[0039] It is evident that existing methods for detecting interface defects in power devices suffer from limited application scope and inaccurate detection results.

[0040] To solve the above technical problems, refer to Figure 1 As shown, this application provides an interface defect detection method applied to a power device under test. The drain of the power device under test is connected to a power supply, the source of the power device under test is grounded, and the gate 20 of the power device under test is left floating. The interface defect detection method includes steps S100 to S300.

[0041] For details, please refer to Figure 2 , Figure 4 As shown, step S100: Apply a horizontally calm magnetic field B1 to the power device under test; wherein, the horizontally calm magnetic field B1 is used to adjust the spin direction of electrons in the defect energy level.

[0042] In this embodiment, a horizontal static magnetic field B1 is applied to the power device under test. Specifically, the channel layer 10 of the power device is generally obtained through epitaxy. However, interface defects may exist in the channel layer 10 during the epitaxial process. The channel layer 10 is the bridge that enables communication between the source and drain, so the density of interface defects directly affects the performance of the power device. Therefore, the detection of interface defects in the channel layer 10 of the power device is very important.

[0043] In this embodiment, when a horizontally calm magnetic field B1 is applied to the power device under test, or as can be understood, when a horizontally calm magnetic field B1 is applied to the channel layer 10, the electrons present in the defect energy level have disordered spin directions before the application of the horizontally calm magnetic field B1, that is, the spin directions may be in any direction. (Reference) Figure 2 As shown, when a horizontally calm magnetic field B1 is applied to the power device under test, the electrons in the defect energy level are in their lowest energy state with their spin pointing downwards. For example, Figure 2The dashed arrow segment represents the trajectory of an electron in the conduction band, and the solid arrow segment represents the corresponding electron spin direction. Figure 2 The intermediate energy level line refers to the line where electrons at the same energy level have the same energy. This can be understood as electrons in the defect energy level pointing vertically downwards (e.g., ...). Figure 2 (The arrow for the electron in the defect level points downwards), that is, perpendicular to the horizontal plane of channel layer 10. When the electron in the defect level has its spin pointing downwards, an electron from the conduction band will pair with an electron in the defect level, as shown in the reference. Figure 2 As shown, electrons from the conduction band pair with electrons in the defect energy level.

[0044] In one specific embodiment, when a horizontal static magnetic field B1 is applied to the power device under test, the direction of the horizontal static magnetic field B1 is parallel to the upper surface of the channel layer 10, that is, the direction of the horizontal static magnetic field B1 is parallel to the line connecting the source and the drain.

[0045] Step S200: Reference Figure 3 As shown, an RF magnetic field B2 is applied above the gate 20 of the power device under test; wherein, the RF magnetic field B2 is used to reverse the spin direction of electrons located in the defect energy level, so that electrons from the conduction band move into holes in the valence band, thereby forming a leakage current.

[0046] In this embodiment, a radio frequency (RF) magnetic field B2 is applied above the gate 20 of the power device under test (DUT). Specifically, the direction of the RF magnetic field B2 is perpendicular to the gate 20, that is, the direction of the RF magnetic field B2 is perpendicular to the channel layer 10, and the direction of the RF magnetic field B2 is perpendicular to the horizontal static magnetic field B1. When the RF magnetic field B2 is applied above the gate 20 of the DUT, the RF magnetic field B2 can cause the spin direction of electrons located in the defect energy level to flip. For example, refer to... Figure 2 , Figure 3 As shown, after applying a horizontal static magnetic field B1, the spin direction of electrons in the defect energy level is downward. After applying a radio frequency magnetic field B2, the spin direction of electrons in the defect energy level is reversed and becomes upward. Under the constraint of the Pauli exclusion principle, the pairing behavior of electrons that were originally paired with the defect energy level in the conduction band will be prohibited. At this time, the electrons that were originally paired from the conduction band will fall into the valence band and recombine with holes in the valence band to form a recombination current (or leakage current).

[0047] In one specific embodiment, the Pauli exclusion principle states that an atom cannot accommodate electrons in the same state of motion.

[0048] Step S300: Detect the leakage current of the power device under test, and determine the interface defect density of the power device under test based on the magnitude of the leakage current.

[0049] In this embodiment, when electrons that were originally paired from the conduction band fall into the valence band, forming a leakage current, the density of interface defects in the channel layer 10 can be detected by detecting the magnitude of the leakage current. Specifically, the interface defect density is directly proportional to the magnitude of the leakage current; that is, the greater the interface defect density, the more electrons fall into the valence band, and the greater the leakage current formed by the combination of these electrons and holes in the valence band. Therefore, the interface defect density can be detected by measuring the magnitude of the leakage current, achieving accurate detection of interface defects.

[0050] In one embodiment, the leakage current of the power device under test can be detected by a current sensor.

[0051] In one embodiment, taking SiC power devices as an example, when fabricating SiC power devices, interface defects may exist when epitaxially forming the channel layer 10 (i.e., silicon carbide layer or silicon dioxide layer). The interface between the silicon carbide layer and the silicon dioxide layer is the electronic channel of the SiC power device, which is very important to the performance of the device. Interface defect detection can ensure the stability of the power device's performance.

[0052] In one embodiment, taking a GaN power device as an example, the channel layer 10 is a gallium nitride layer. When the channel layer 10 (i.e., the gallium nitride layer) is formed epitaxially, there may be interface defects. The gallium nitride layer is also the electronic channel of the GaN power device, which is very important to the performance of the device. Interface defect detection can play a role in ensuring the stability of the power device's performance.

[0053] In one embodiment, reference Figure 4 As shown, before applying the radio frequency magnetic field B2 above the gate 20 of the power device under test, the method further includes: setting an radio frequency coil 30 above the gate 20 of the power device under test, and generating a radio frequency magnetic field B2 when the radio frequency coil 30 is energized.

[0054] In this embodiment, reference Figure 5 As shown, Figure 5 This is a top view of the RF coil 30, which is positioned above the gate 20 of the power device under test. Specifically, the RF coil 30 can be fabricated by illumination during the formation of the gate 20, with a first end M1 and a second end M2 of the RF coil 30 pre-existing. The first and second ends of the RF coil 30 are used to connect to an RF power supply, so that an RF magnetic field B2 is generated when the first end M1 and the second end M2 of the RF coil 30 are connected to the RF power supply and powered on.

[0055] In a specific application, the first end M1 and the second end M2 of the RF coil 30 can be reserved in the form of an air bridge so that the first end M1 and the second end M2 of the RF coil 30 can be used to connect to the RF power supply. The first end M1 and the second end M2 of the RF coil 30 are reserved in the form of an air bridge because the air bridge method has the advantages of low parasitic capacitance, convenient manufacturing and high reliability.

[0056] In a specific application, the method for reserving the first end M1 and the second end M2 of the RF coil 30 via an air bridge is as follows: Using a composite adhesive structure composed of photoresists of different properties, an arched sacrificial layer approximately 60% thicker than the RF coil 30 is easily fabricated through baking. This sacrificial layer provides strong protection for the metal beneath the bridge. Then, a non-toxic electroplating solution is used to thicken the air bridge. The resulting thickened air bridge has lower parasitic capacitance and higher reliability.

[0057] In one embodiment, reference Figure 4 As shown, the center of the RF coil 30 is located above the gate 20.

[0058] In this embodiment, the main function of the RF coil 30 is to reverse the spin direction of electrons located in the defect energy level. This causes electrons from the conduction band that were originally pairing with electrons in the defect energy level to stop pairing, allowing them to fall into the valence band and combine with holes, forming a leakage current. The interface defect density is then detected by measuring the magnitude of the leakage current. Because defects are generally present at the interface below the gate 20 that contacts the channel layer 10, by positioning the center of the RF coil 30 above the gate 20, the spin direction of electrons in the defect energy level can be better changed, thus allowing electrons in the conduction band to fall into the valence band more effectively, forming a leakage current. If the center of the RF coil 30 is not positioned above the gate 20, the spin direction of some electrons in the defect energy level will not change, resulting in some electrons falling into the conduction band still combining with the valence band, reducing the number of electrons falling into the valence band, decreasing the leakage current, and thus making the detection results inaccurate. Therefore, by positioning the center of the RF coil 30 above the gate 20, the detection results of interface defects can be made more accurate.

[0059] In one embodiment, an RF coil 30 is disposed above the gate 20 of the power device under test, and the embodiment further includes: a magnetic core unit disposed at the center of the RF coil 30, the magnetic core unit being used to increase the strength of the RF magnetic field B2.

[0060] In this embodiment, by setting a magnetic core unit at the center of the RF coil 30, the strength of the RF magnetic field B2 can be increased. The main function of the RF coil 30 is to generate the RF magnetic field B2, which in turn reverses the spin direction of electrons located in the defect energy level. This causes electrons from the conduction band, which were originally pairing with electrons in the defect energy level, to stop pairing, causing them to fall into the valence band and combine with holes to form a leakage current. By setting a stronger RF magnetic field B2, the spin direction of electrons in the defect energy level can be reversed more comprehensively, resulting in a more accurate detection of the leakage current and a more accurate detection of interface defects.

[0061] In one embodiment, the frequency of the radio frequency magnetic field B2 is changed by frequency sweeping, causing the spin direction of electrons located in the defect energy level to be reversed. This causes electrons from the conduction band, which were originally pairing with electrons in the defect energy level, to stop pairing. As a result, electrons from the conduction band fall into the valence band and combine with holes in the valence band, forming a leakage current.

[0062] In one specific embodiment, the material of the magnetic core unit may be iron oxide.

[0063] In one embodiment, the radio frequency coil 30 is spiral-shaped. In this embodiment, by setting the radio frequency coil 30 to a spiral shape, the radio frequency coil 30 can generate a radio frequency magnetic field B2 when energized, thereby flipping the spin direction of electrons with energy located in the defect energy level, preparing for subsequent interface defect detection.

[0064] In one specific embodiment, reference Figure 5 As shown, the RF coil 30 is a square spiral, that is, each turn of the RF coil 30 is a square.

[0065] In one embodiment, reference Figure 5 As shown, the radio frequency coil 30 includes at least two turns. Specifically, the number of turns of the radio frequency coil 30 determines the strength of the radio frequency magnetic field B2 generated by the radio frequency coil 30. By setting the radio frequency coil 30 to include at least two turns, the strength of the radio frequency magnetic field B2 can be made greater, which can better change the spin direction of electrons in the defect energy level, thereby allowing electrons in the conduction band to fall into the valence band more effectively, forming leakage current and making the detection results more accurate.

[0066] In one embodiment, the diameter of the RF coil 30 is equal to the diameter of the gate 20. In this embodiment, when the RF coil 30 is a square spiral, its diameter represents the maximum outer diameter of the RF coil 30. By setting the diameter of the RF coil 30 to be equal to the diameter of the gate 20, the RF magnetic field B2 generated by the RF coil 30 can more comprehensively enter the channel layer 10, reversing the spin direction of electrons in the defect energy level. This avoids the problem that the RF magnetic field B2 does not fully act on the electrons in the defect energy level, resulting in some electrons not reversing their spin direction and causing inaccurate detection results.

[0067] In one embodiment, the diameter of the radio frequency coil 30 is 0.1 to 0.3 μm.

[0068] In one embodiment, applying a radio frequency magnetic field B2 over the gate 20 of the power device under test includes adjusting the frequency of the radio frequency magnetic field B2 so that the spin direction of electrons in the defect energy level is reversed.

[0069] In this embodiment, after applying a horizontally calm magnetic field B1, the electrons in the defect energy level point downwards. Then, by sweeping the frequency of the radio frequency magnetic field B2, the spin direction of the electrons in the defect energy level is reversed. Under the constraint of the Pauli exclusion principle, the pairing behavior of electrons from the conduction band that were originally paired with the defect energy level is prohibited. At this time, the electrons that were originally paired from the conduction band will fall into the valence band and recombine with holes in the valence band, forming a recombination current (or leakage current). In this embodiment, by sweeping the frequency of the radio frequency magnetic field B2, the spin direction of the electrons in the defect energy level can be reversed more effectively, in preparation for subsequent leakage current detection.

[0070] In one embodiment, applying a radio frequency magnetic field B2 over the gate 20 of the power device under test includes adjusting the intensity of the radio frequency magnetic field B2 to cause the spin direction of electrons in the defect energy level to be reversed.

[0071] In this embodiment, the main function of the radio frequency coil 30 is to generate a radio frequency magnetic field B2, which in turn flips the spin direction of electrons located in the defect energy level. The stronger the radio frequency electric field, the better its effect on flipping the spin direction of electrons in the defect energy level. By adjusting the strength of the radio frequency magnetic field B2, the spin direction of electrons in the defect energy level can be flipped as much as possible. This causes electrons in the conduction band that were originally paired with electrons in the defect energy level to stop pairing and fall into the valence band, where they combine with holes to form leakage current, making the detection results more accurate.

[0072] In one embodiment, the strength of the radio frequency magnetic field B2 can be adjusted by adding a magnetic core unit of different materials to the center of the radio frequency coil 30 or by setting different numbers of turns in the radio frequency coil 30.

[0073] In one embodiment, detecting the leakage current of the power device under test and determining the interface defect size of the power device under test based on the leakage current includes: comparing the leakage current with a preset mapping table and determining the interface defect density of the power device under test based on the comparison result.

[0074] In this embodiment, after the magnitude of the leakage current is detected by the current detector, it is output to the control module. There is a mapping table in the control module that corresponds one-to-one with the leakage current. For example, if the sequence of leakage current is e1, e2, e3, e4, e5, then the corresponding sequence of interface defect density is f1, f2, f3, f4, f5. This makes each leakage current correspond to an interface defect density result, making the detection result more accurate.

[0075] In one embodiment, reference Figure 4 As shown, applying a horizontally calm magnetic field B1 to the power device under test includes: setting a first magnet 41 and a second magnet 42 on both sides of the source and drain of the power device under test, respectively, and the first magnet 41 and the second magnet 42 are used to generate a horizontally calm magnetic field B1.

[0076] In this embodiment, a first magnet 41 and a second magnet 42 are respectively provided on both sides of the source and drain of the power device under test, wherein the magnetic north pole and magnetic south pole of the first magnet 41 and the second magnet 42 are arranged opposite to each other, so that a horizontally calm magnetic field B1 is generated between the first magnet 41 and the second magnet 42. The horizontally calm magnetic field B1 adjusts the spin direction of the electrons in the defect energy level, so that the electrons in the defect energy level have a downward spin direction under the action of the externally applied horizontally calm magnetic field B1.

[0077] In one embodiment, the heights of the first magnet 41 and the second magnet 42 are equal to the height of the channel layer 10. In this embodiment, by setting the heights of the first magnet 41 and the second magnet 42 to be equal to the height of the channel layer 10, the direction of electrons in the defect energy level can be changed, and the impact on other parts of the power device can be minimized as much as possible, so as not to affect the performance of the power device and make the detection results inaccurate.

[0078] In one embodiment, the first magnet 41 and the second magnet 42 are symmetrically arranged. For example, the first magnet 41 is disposed outside the source of the power device, and the second magnet 42 is disposed outside the drain of the second magnet 42, so that the first magnet 41 and the second magnet 42 can generate a horizontally calm magnetic field B1. By symmetrically arranging the first magnet 41 and the second magnet 42, the generated horizontally calm magnetic field B1 can be made more uniform and better adjust the spin direction of the electrons.

[0079] In one embodiment, applying a horizontal static magnetic field B1 to the channel layer 10 of the power device under test includes: placing the power device under test in a sealed cavity, and respectively providing a first magnet 41 and a second magnet 42 on both sides of the source and drain of the power device under test.

[0080] In this embodiment, by placing the power device under test (DUT) within a sealed cavity, external electromagnetic interference can be reduced, leading to more accurate test results. A first magnet 41 and a second magnet 42 are respectively positioned on either side of the source and drain of the DUT. These magnets generate a horizontally calm magnetic field B1, which adjusts the spin direction of electrons in the defect energy level, ensuring the spin direction is vertically downward. A radio frequency (RF) coil 30 is integrated into the gate 20 of the DUT. When the RF coil 30 is energized, it generates an RF magnetic field B2, causing the spin direction of electrons in the defect energy level to reverse. This causes electrons from the conduction band, which were previously pairing with electrons in the defect energy level, to stop pairing and fall into the valence band, combining with holes to form a leakage current. The leakage current of the DUT is detected, and the interface defect density of the DUT is determined based on the magnitude of the leakage current. In this embodiment, by placing the power device under test inside a sealed cavity, the interference of external electromagnetic interference on the power device can be reduced, which can make the test results more accurate.

[0081] This application also provides a wafer inspection method, referring to... Figure 6 As shown, wafer 100 includes multiple power devices and at least one power device under test 200, the power device under test 200 having its defect density detected using an interface defect detection method as described above.

[0082] In this embodiment, when multiple power devices are disposed on a wafer 100, and only one power device needs to be tested, the power device to be tested is referred to as the power device under test (DUT) 200. This can be achieved by placing an RF coil 30 on the gate 20 of the DUT 200, and then placing the wafer 100 in a sealed cavity. Two magnets are disposed on opposite sides of the sealed cavity, with the wafer 100 positioned between the two magnets. The horizontal static magnetic field B1 generated by the two magnets can adjust the spin direction of electrons in the defect energy level, making the spin direction of the electrons in the defect energy level vertically downward. When the RF coil 30 is energized, an RF magnetic field B2 is generated, causing the spin direction of the electrons in the defect energy level to reverse. This causes electrons from the conduction band that were originally pairing with electrons in the defect energy level to stop pairing and fall into the valence band, combining with holes in the valence band to form a leakage current. The leakage current of the DUT 200 is then detected, and the interface defect density of the DUT 200 is determined based on the magnitude of the leakage current. In this embodiment, multiple power devices 200 under test on the wafer 100 can also be tested simultaneously, which can improve testing efficiency while ensuring testing accuracy.

[0083] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0084] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A method for detecting interface defects, applied to a power device under test, characterized in that, The drain of the power device under test is connected to a power supply, the source of the power device under test is grounded, and the gate of the power device under test is left floating. The interface defect detection method includes: A horizontally calm magnetic field is applied to the power device under test; wherein the horizontally calm magnetic field is used to adjust the spin direction of electrons in the defect energy level; A radio frequency magnetic field is applied above the gate of the power device under test; wherein the radio frequency magnetic field is used to reverse the spin direction of electrons located in the defect energy level, so that electrons from the conduction band move into holes in the valence band, thereby forming a leakage current; The leakage current of the power device under test is detected, and the interface defect density of the power device under test is determined based on the magnitude of the leakage current. The step of applying a horizontally calm magnetic field to the power device under test includes: setting a first magnet and a second magnet on both sides of the source and drain of the power device under test, respectively, wherein the first magnet and the second magnet are used to generate the horizontally calm magnetic field.

2. The interface defect detection method as described in claim 1, characterized in that, The step of applying a radio frequency magnetic field above the gate of the power device under test further includes: A radio frequency coil is disposed above the gate of the power device under test, and the radio frequency coil generates the radio frequency magnetic field when energized.

3. The interface defect detection method as described in claim 2, characterized in that, The center of the radio frequency coil is located above the gate.

4. The interface defect detection method as described in claim 2, characterized in that, The method of placing an RF coil above the gate of the power device under test further includes: A magnetic core unit is provided at the center of the radio frequency coil, and the magnetic core unit is used to increase the strength of the radio frequency magnetic field.

5. The interface defect detection method according to any one of claims 1-4, characterized in that, Applying a radio frequency magnetic field above the gate of the power device under test includes: By adjusting the strength of the radio frequency magnetic field, the spin direction of electrons in the defect energy level is reversed.

6. The interface defect detection method according to any one of claims 1-4, characterized in that, The first magnet and the second magnet are arranged symmetrically.

7. The interface defect detection method as described in claim 1, characterized in that, Applying a horizontally calm magnetic field to the power device under test includes: The power device under test is placed in a sealed cavity, and a first magnet and a second magnet are respectively placed on both sides of the source and drain of the power device under test.

8. The interface defect detection method as described in claim 1, characterized in that, The step of detecting the leakage current of the power device under test and determining the size of the interface defect of the power device under test based on the magnitude of the leakage current includes: The magnitude of the leakage current is compared with a preset mapping table, and the interface defect density of the power device under test is determined based on the comparison result.

9. A method for inspecting a wafer, characterized in that, The wafer includes multiple power devices and at least one power device under test, wherein the defect density of the power device under test is detected by the interface defect detection method as described in any one of claims 1-8.

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