Gallium nitride transistor detection method and device and test equipment
By measuring the input capacitance of the gallium nitride transistor under high-frequency alternating current through a digital bridge, the problem of difficulty in detecting the recessive fracture or recessive crack of the gate lead of the gallium nitride transistor is solved in the prior art, and a simple and low-cost detection method is realized.
Patent Information
- Application Number
- CN202411983955.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-31
- Publication Date
- 2025-05-13
AI Technical Summary
The prior art is difficult to detect recessive fractures or recessive cracks in the gate leads of gallium nitride transistors.
The input capacitance of the transistor to be tested is measured by a digital bridge meter under high frequency alternating current, and based on the measured input capacitance and input capacitance reference, it is determined whether there is a minor break in the gate lead.
This method can easily detect whether there is a minor break in the gallium nitride transistor, and realize the detection of hidden fracture or hidden crack problems, which is simple and low-cost.
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Figure CN119986292A_ABST
Abstract
Description
Technical Field
[0001] The present disclosure relates to the field of semiconductor testing technology, and in particular to a gallium nitride transistor detection method, device and testing equipment. Background Art
[0002] In the related art, failure analysis of GaN transistors usually uses ultrasonic scanning, X-ray machine inspection, open cover inspection, etc. to check whether the gate lead has problems such as breakage.
[0003] The above method can only detect obvious fracture problems of transistor gate leads, but is difficult to detect hidden fractures or hidden cracks. Summary of the invention
[0004] The embodiments of the present disclosure provide a gallium nitride transistor detection method, device and testing equipment, which can detect the problem of micro-breakage of gate leads. The technical solution is as follows:
[0005] In a first aspect, an embodiment of the present disclosure provides a gallium nitride transistor detection method, the method comprising:
[0006] Obtain the input capacitance of the transistor to be tested measured by the digital bridge instrument under high-frequency alternating current;
[0007] Based on the input capacitance of the transistor to be tested and the input capacitance reference, it is determined whether there is a micro-break in the gate lead of the transistor to be tested, where the micro-break refers to the presence of a crack inside the gate lead.
[0008] Optionally, the step of obtaining the input capacitance of the transistor to be tested measured by a digital bridge instrument under high-frequency alternating current includes:
[0009] When the digital bridge meter is connected to the gate and the source of the transistor to be tested respectively, the alternating current frequency of the digital bridge meter is controlled to be not less than 100 Hz;
[0010] The digital bridge instrument is controlled to measure the input capacitance of the transistor to be tested.
[0011] Optionally, the alternating current frequency of the digital bridge instrument is 1000 Hz.
[0012] Optionally, the determining whether there is a micro-break in the gate lead of the transistor to be tested based on the input capacitance and the input capacitance reference of the transistor to be tested comprises:
[0013] When the input capacitance of the transistor to be tested is not less than the input capacitance reference, determining that there is no micro-break in the gate lead of the transistor to be tested;
[0014] When the input capacitance of the transistor to be tested is less than the input capacitance reference, it is determined that a micro-break exists in the gate lead of the transistor to be tested.
[0015] Optionally, the input capacitance reference is 0.1nF to 1nF.
[0016] Optionally, the method further comprises:
[0017] Before obtaining the input capacitance of the transistor to be tested measured by the digital bridge instrument under high-frequency alternating current, a temperature cycle test is performed on the transistor to be tested.
[0018] In a second aspect, an embodiment of the present disclosure provides a gallium nitride transistor detection device, the device comprising:
[0019] An acquisition module is used to acquire the input capacitance of the transistor to be tested measured by the digital bridge instrument under high-frequency alternating current;
[0020] The determination module is used to determine whether there is a micro-break in the gate lead of the transistor to be tested based on the input capacitance and the input capacitance reference of the transistor to be tested, wherein the micro-break refers to the presence of a crack inside the gate lead.
[0021] Optionally, the acquisition module is used to:
[0022] When the digital bridge meter is connected to the gate and the source of the transistor to be tested respectively, the alternating current frequency of the digital bridge meter is controlled to be not less than 100 Hz;
[0023] The digital bridge instrument is controlled to measure the input capacitance of the transistor to be tested.
[0024] Optionally, the alternating current frequency of the digital bridge instrument is 1000 Hz.
[0025] Optionally, the determining module is used to:
[0026] When the input capacitance of the transistor to be tested is not less than the input capacitance reference, determining that there is no micro-break in the gate lead of the transistor to be tested;
[0027] When the input capacitance of the transistor to be tested is less than the input capacitance reference, it is determined that a micro-break exists in the gate lead of the transistor to be tested.
[0028] Optionally, the input capacitance reference is 0.1nF to 1nF.
[0029] Optionally, the device further comprises:
[0030] The test module is used to perform a temperature cycle test on the transistor to be tested before obtaining the input capacitance of the transistor to be tested measured by a digital bridge instrument under high-frequency alternating current.
[0031] In a third aspect, an embodiment of the present disclosure provides a testing device, comprising: a processor; and a memory configured to store processor executable instructions; wherein the processor is configured to execute the gallium nitride transistor detection method described in any one of the first aspects.
[0032] In a fourth aspect, an embodiment of the present disclosure provides a computer-readable storage medium. When instructions in the computer-readable storage medium are executed by a processor of a testing device, the testing device is able to perform the gallium nitride transistor detection method described in any one of the first aspects.
[0033] The technical solution provided by the embodiments of the present disclosure brings the following beneficial effects:
[0034] In the disclosed embodiment, the input capacitance of the transistor to be tested is measured by a digital bridge meter under high-frequency alternating current. Since high-frequency alternating current can amplify the influence of micro-breaks of the gate lead, the input capacitance of the transistor to be tested is significantly different from the input capacitance baseline of the transistor with a normal gate lead, thereby being able to detect whether the gallium nitride transistor has micro-breaks. This method can more conveniently detect the hidden fracture (or crack) problem of the transistor gate lead, is simple to implement and has low cost. BRIEF DESCRIPTION OF THE DRAWINGS
[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present disclosure. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.
[0036] Figure 1 is a flow chart of a gallium nitride transistor detection method provided by an embodiment of the present disclosure;
[0037] Figure 2 is a flow chart of a gallium nitride transistor detection method provided by an embodiment of the present disclosure;
[0038] Figure 3 It is a schematic structural diagram of a gallium nitride transistor detection device provided by an embodiment of the present disclosure;
[0039] Figure 4 It is a structural block diagram of a test device provided by an embodiment of the present disclosure. DETAILED DESCRIPTION
[0040] In order to make the objectives, technical solutions and advantages of the present disclosure more clear, the embodiments of the present disclosure will be further described in detail below with reference to the accompanying drawings.
[0041] Figure 1 is a flow chart of a gallium nitride transistor detection method provided by an embodiment of the present disclosure. Figure 1 , the method comprises the following steps:
[0042] 101: Obtain the input capacitance of the transistor under test measured by a digital bridge meter under high-frequency AC.
[0043] In the embodiment of the present disclosure, the input capacitance refers to the capacitance between the gate and the source of the transistor, that is, CISS.
[0044] In the disclosed embodiment, high-frequency alternating current refers to alternating current with a frequency higher than a threshold value, which may be 100 Hz. When the frequency of the alternating current is above 100 Hz, it can ensure the amplification effect of the impact of micro-breaks of the gate leads during testing.
[0045] For example, when the frequency of AC power is low, the input capacitance of the transistor to be tested is tested, and the difference between the test result and the input capacitance of a normal transistor is small, so it is difficult to determine whether the transistor to be tested has a micro-break.
[0046] When the frequency of the alternating current is high, the input capacitance test result of the transistor to be tested is significantly different from the input capacitance measured by a normal transistor, so it is easy to determine whether the transistor to be tested has a micro-break.
[0047] In the embodiment of the present disclosure, the gate lead refers to a lead connected to the gate of a transistor.
[0048] 102: Based on the input capacitance and input capacitance reference of the transistor to be tested, determine whether there is a micro-break in the gate lead of the transistor to be tested, where the micro-break refers to the presence of a crack inside the gate lead.
[0049] Here, the existence of cracks inside the gate lead means that the cracks are located inside the gate lead and do not extend to the surface of the gate lead, and the problem cannot be detected by ultrasonic scanning, X-ray machine inspection, or decap inspection.
[0050] Usually, if the input capacitance of the transistor to be tested is not less than the input capacitance reference, it means that the input capacitance of the transistor to be tested is normal and there is no slight break in the gate lead.
[0051] If the input capacitance of the transistor to be tested is less than the input capacitance reference, it means that the input capacitance of the transistor to be tested is abnormal and there is a slight break in the gate lead.
[0052] In an example of the present disclosure, the method is performed by a device, such as a gallium nitride transistor detection device. The device can be electrically connected to a digital bridge instrument to complete data acquisition and analysis processing to implement the above steps.
[0053] In another example of the present disclosure, the method is performed manually, and an operator manually reads the data of the digital bridge meter and performs subsequent judgment steps.
[0054] In the disclosed embodiment, the input capacitance of the transistor to be tested is measured by a digital bridge meter under high-frequency alternating current. Since high-frequency alternating current can amplify the influence of micro-breaks of the gate lead, the input capacitance of the transistor to be tested is significantly different from the input capacitance baseline of the transistor with a normal gate lead, thereby being able to detect whether the gallium nitride transistor has micro-breaks. This method can more conveniently detect the problem of hidden fractures (or cracks) in the gate lead of the transistor, is simple to implement and has low cost.
[0055] Figure 2 is a flow chart of a gallium nitride transistor detection method provided by an embodiment of the present disclosure. Figure 2 , the method comprises the following steps:
[0056] 201: Perform temperature cycle test on the transistor under test.
[0057] Among them, the temperature cycling (TC) test is a test used to evaluate the adaptability and stress screening of semiconductor devices under conditions of rapid or gradual temperature changes.
[0058] Usually, during the temperature cycle test, the transistor parameter test is performed under one temperature condition, then the temperature condition is changed to perform the cycle test, and then the transistor parameter test is performed again. The performance of the transistor is evaluated by comparing the parameter changes of the transistor before and after the temperature cycle.
[0059] Among them, the transistor parameters that can be measured in the TC test include gate-source leakage current (IGSS), threshold voltage (Vth), on-resistance (Ron), zero gate voltage drain current (IDSS), etc.
[0060] After completing the temperature cycle test, the failed transistors can be found out based on the evaluation.
[0061] For failed transistors, failure analysis is performed. In related technologies, failure analysis includes using an ultrasonic scanning microscope to check whether there is delamination in the transistor gate lead area, using an X-ray machine to check whether there are obvious signs of breakage in the transistor internal leads, and opening the cover to check and confirm whether the transistor gate lead is broken or detached.
[0062] The inventors of the disclosed embodiments discovered during the TC experiment that due to thermal expansion during temperature cycling, the gate lead was subjected to stress caused by the temperature cycle, resulting in micro-breaks inside the lead.
[0063] However, the above method is difficult to determine the problem of micro-breakage of the gate lead. Therefore, the embodiment of the present disclosure adds a failure analysis method for micro-breakage of the gate lead, namely steps 202 to 205.
[0064] 202: When the digital bridge meter is connected to the gate and the source of the transistor to be tested respectively, control the alternating current frequency of the digital bridge meter to be no less than 100 Hz.
[0065] When the frequency of the alternating current is above 100 Hz, it can ensure the amplification effect of the impact caused by the micro-break of the gate lead during the test.
[0066] In one implementation of the embodiment of the present disclosure, the alternating current frequency of the digital bridge instrument is 1000 Hz.
[0067] In this implementation, 1000Hz AC is used for testing. On the one hand, 1000Hz AC is a common frequency range of digital bridge instruments and is relatively convenient to set up. On the other hand, the frequency of the AC is not too high. Too high a frequency may cause normal leads to be magnified into defective leads, thereby affecting the accuracy of the judgment of micro-breaks in the gate leads.
[0068] In other implementations of the disclosed embodiment, the alternating current frequency of the digital bridge instrument may also be other frequencies, such as 500 Hz, 800 Hz.
[0069] Usually, the frequency of AC power can be selected within the range of 100Hz to 2000Hz. This is because when the frequency of AC power is low, the input capacitance test result obtained by testing the transistor to be tested is slightly different from the input capacitance measured by a normal transistor, making it difficult to determine whether the transistor to be tested has a micro-break. When the frequency of AC power is high, the input capacitance test result obtained by testing the transistor to be tested is significantly different from the input capacitance measured by a normal transistor, making it easy to determine whether the transistor to be tested has a micro-break. However, when the frequency of AC power is too high, normal leads will also be magnified into defective leads, thereby affecting the correctness of the judgment of micro-breaks in the gate leads. Therefore, selecting the frequency of AC power within the above frequency range can better detect micro-breaks in the gate leads.
[0070] In the embodiment of the present disclosure, the digital bridge meter is connected to the gate and source of the transistor to be tested respectively, which means: the test clips of the digital bridge meter are connected to the gate and source of the transistor respectively.
[0071] In the embodiment of the present disclosure, the digital bridge meter can be an AT826 digital bridge meter. The instrument is easy to test and simple to operate, and can meet the test requirements of the embodiment of the present disclosure. In addition, the AT826 digital bridge meter is a handheld digital bridge meter. In this case, steps 201 to 205 can be performed by the user.
[0072] In other embodiments, the digital bridge meter may also be other types of digital bridge meters, such as a digital bridge meter with data export function and controlled function. In this case, the digital bridge meter may be connected to the digital bridge meter through a test device, and steps 201 to 205 may be executed by the test device.
[0073] In the embodiments of the present disclosure, the digital bridge meter may be a product already available on the market, or a self-made circuit. As long as the digital bridge meter can achieve the effect of input capacitance testing, the embodiments of the present disclosure do not limit this.
[0074] In addition, during testing, the digital bridge instrument of the embodiment of the present disclosure can set the test speed in addition to the AC frequency.
[0075] For example, in the embodiment of the present disclosure, the test speed of the digital bridge instrument is set to high-speed testing. The high-speed testing can enhance the amplification effect of the micro-break influence, thereby enhancing the test accuracy.
[0076] Exemplarily, the high-speed test may be 4 times / second.
[0077] 203: Control the digital bridge instrument to measure the input capacitance of the transistor to be tested.
[0078] In the embodiment of the present disclosure, the input capacitance refers to the capacitance between the gate and the source of the transistor, that is, CISS.
[0079] 204: When the input capacitance of the transistor to be tested is not less than the input capacitance reference, determine that there is no micro-break in the gate lead of the transistor to be tested.
[0080] Here, the existence of cracks inside the gate lead means that the cracks are located inside the gate lead and do not extend to the surface of the gate lead, and the problem cannot be detected by ultrasonic scanning, X-ray machine inspection, or decap inspection.
[0081] Usually, if the input capacitance of the transistor to be tested is not less than the input capacitance reference, it means that the input capacitance of the transistor to be tested is normal and there is no slight break in the gate lead.
[0082] Wherein, the input capacitance reference is 0.1nF to 1nF.
[0083] Exemplarily, the input capacitance reference is 0.1 nF.
[0084] The input capacitance measured by a normal transistor is usually around 1nF, but when there is a micro-break problem in the gate line, the charge C of the transistor Cgs and Cgd will approach 0, and the input capacitance measured by the transistor is usually also around 0. Therefore, using the above input capacitance reference, it is possible to more accurately determine whether the gate lead of the transistor to be tested has a micro-break problem.
[0085] 205: When the input capacitance of the transistor to be tested is less than the input capacitance reference, determine that a micro-break exists in the gate lead of the transistor to be tested.
[0086] If the input capacitance of the transistor under test is less than the input capacitance reference, it means that the input capacitance of the transistor under test is abnormal and there is a slight break in the gate lead.
[0087] In the disclosed embodiment, the input capacitance of the transistor to be tested is measured by a digital bridge meter under high-frequency alternating current. Since high-frequency alternating current can amplify the influence of micro-breaks of the gate lead, the input capacitance of the transistor to be tested is significantly different from the input capacitance baseline of the transistor with a normal gate lead, thereby being able to detect whether the gallium nitride transistor has micro-breaks. This method can more conveniently detect the problem of hidden fractures (or cracks) in the gate lead of the transistor, is simple to implement and has low cost.
[0088] Figure 3 is a schematic diagram of the structure of a GaN transistor detection device provided by an embodiment of the present disclosure. The GaN transistor detection device can be implemented as all or part of the test equipment through software, hardware or a combination of both. Figure 3 The gallium nitride transistor detection device includes: an acquisition module 301 and a determination module 302.
[0089] Wherein, the acquisition module 301 is used to obtain the input capacitance of the transistor to be tested measured by the digital bridge instrument under high-frequency alternating current;
[0090] The determination module 302 is used to determine whether there is a micro-break in the gate lead of the transistor to be tested based on the input capacitance and the input capacitance reference of the transistor to be tested, wherein the micro-break refers to the presence of a crack inside the gate lead.
[0091] Optionally, the acquisition module 301 is used to:
[0092] When the digital bridge meter is connected to the gate and the source of the transistor to be tested respectively, the alternating current frequency of the digital bridge meter is controlled to be not less than 100 Hz;
[0093] The digital bridge instrument is controlled to measure the input capacitance of the transistor to be tested.
[0094] Optionally, the alternating current frequency of the digital bridge instrument is 1000 Hz.
[0095] Optionally, the determining module 302 is configured to:
[0096] When the input capacitance of the transistor to be tested is not less than the input capacitance reference, determining that there is no micro-break in the gate lead of the transistor to be tested;
[0097] When the input capacitance of the transistor to be tested is less than the input capacitance reference, it is determined that a micro-break exists in the gate lead of the transistor to be tested.
[0098] Optionally, the input capacitance reference is 0.1nF to 1nF.
[0099] Optionally, the device further comprises:
[0100] The testing module 303 is used to perform a temperature cycle test on the transistor to be tested before obtaining the input capacitance of the transistor to be tested measured by a digital bridge instrument under high-frequency alternating current.
[0101] In the disclosed embodiment, the input capacitance of the transistor to be tested is measured by a digital bridge meter under high-frequency alternating current. Since high-frequency alternating current can amplify the influence of micro-breaks of the gate lead, the input capacitance of the transistor to be tested is significantly different from the input capacitance baseline of the transistor with a normal gate lead, thereby being able to detect whether the gallium nitride transistor has micro-breaks. This method can more conveniently detect the problem of hidden fractures (or cracks) in the gate lead of the transistor, is simple to implement and has low cost.
[0102] It should be noted that: the GaN transistor detection device provided in the above embodiment only uses the division of the above functional modules as an example when performing GaN transistor detection. In actual applications, the above functions can be assigned to different functional modules as needed, that is, the internal structure of the device is divided into different functional modules to complete all or part of the functions described above. In addition, the GaN transistor detection device provided in the above embodiment and the GaN transistor detection method embodiment belong to the same concept, and the specific implementation process is detailed in the method embodiment, which will not be repeated here.
[0103] Figure 44 is a block diagram of a test device provided by an embodiment of the present disclosure. The test device 400 includes a central processing unit (CPU) 401, a system memory 404 including a random access memory (RAM) 402 and a read-only memory (ROM) 403, and a system bus 405 connecting the system memory 404 and the central processing unit 401. The test device 400 also includes a basic input / output system (I / O system) 406 that helps transmit information between various devices in the computer, and a large-capacity storage device 407 for storing an operating system 413, an application program 414, and other program modules 415.
[0104] The basic input / output system 406 includes a display 408 for displaying information and an input device 409 such as a mouse and a keyboard for user inputting information. The display 408 and the input device 409 are connected to the central processing unit 401 through an input / output controller 410 connected to the system bus 405. The basic input / output system 406 may also include an input / output controller 410 for receiving and processing inputs from a plurality of other devices such as a keyboard, a mouse, or an electronic stylus. Similarly, the input / output controller 410 also provides output to a display screen, a printer, or other types of output devices.
[0105] The mass storage device 407 is connected to the central processing unit 401 through a mass storage controller (not shown) connected to the system bus 405. The mass storage device 407 and its associated computer readable media provide non-volatile storage for the test device 400. That is, the mass storage device 407 may include a computer readable medium (not shown) such as a hard disk or a CD-ROM drive.
[0106] Without loss of generality, computer readable media may include computer storage media and communication media. Computer storage media include volatile and non-volatile, removable and non-removable media implemented in any method or technology for storing information such as computer readable instructions, data structures, program modules or other data. Computer storage media include RAM, ROM, EPROM, EEPROM, flash memory or other solid-state storage technologies, CD-ROM, DVD or other optical storage, cassettes, magnetic tapes, disk storage or other magnetic storage devices. Of course, those skilled in the art will appreciate that computer storage media are not limited to the above. The above-mentioned system memory 404 and mass storage device 407 can be collectively referred to as memory.
[0107] According to various embodiments of the present disclosure, the test device 400 can also be connected to a remote computer on the network through a network such as the Internet, etc. That is, the test device 400 can be connected to the network 412 through the network interface unit 411 connected to the system bus 405, or the network interface unit 411 can also be used to connect to other types of networks or remote computer systems (not shown).
[0108] The memory also includes one or more programs, one or more programs are stored in the memory, and the central processor 401 implements the one or more programs by executing the one or more programs. Figure 1 or Figure 2 The GaN transistor detection method shown.
[0109] In an exemplary embodiment, a non-transitory computer-readable storage medium including instructions is also provided, such as a memory including instructions, and the above instructions can be executed by a processor of a test device to complete the gallium nitride transistor detection method shown in various embodiments of the present disclosure. For example, the non-transitory computer-readable storage medium can be a ROM, a random access memory (RAM), a CD-ROM, a magnetic tape, a floppy disk, an optical data storage device, etc.
[0110] The above description is only an optional embodiment of the present disclosure and is not intended to limit the present disclosure. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present disclosure shall be included in the protection scope of the present disclosure.
Claims
1. A gallium nitride transistor detection method, characterized in that: The method comprises: Obtain the input capacitance of the transistor to be tested measured by the digital bridge instrument under high-frequency alternating current; Based on the input capacitance of the transistor to be tested and the input capacitance reference, it is determined whether there is a micro-break in the gate lead of the transistor to be tested, where the micro-break refers to the presence of a crack inside the gate lead.
2. The method according to claim 1, characterized in that The step of obtaining the input capacitance of the transistor to be tested measured by the digital bridge instrument under high-frequency alternating current comprises: When the digital bridge meter is connected to the gate and the source of the transistor to be tested respectively, the alternating current frequency of the digital bridge meter is controlled to be not less than 100 Hz; The digital bridge instrument is controlled to measure the input capacitance of the transistor to be tested.
3. The method according to claim 2, characterized in that The alternating current frequency of the digital bridge instrument is 1000 Hz.
4. The method according to any one of claims 1 to 3, characterized in that: The step of determining whether a gate lead of the transistor to be tested has a micro-break based on the input capacitance and the input capacitance reference of the transistor to be tested comprises: When the input capacitance of the transistor to be tested is not less than the input capacitance reference, determining that there is no micro-break in the gate lead of the transistor to be tested; When the input capacitance of the transistor to be tested is less than the input capacitance reference, it is determined that a micro-break exists in the gate lead of the transistor to be tested.
5. The method according to claim 4, characterized in that The input capacitance reference is 0.1nF to 1nF.
6. The method according to any one of claims 1 to 5, characterized in that: The method further comprises: Before obtaining the input capacitance of the transistor to be tested measured by the digital bridge instrument under high-frequency alternating current, a temperature cycle test is performed on the transistor to be tested.
7. A gallium nitride transistor detection device, characterized in that: The device comprises: An acquisition module is used to acquire the input capacitance of the transistor to be tested measured by the digital bridge instrument under high-frequency alternating current; The determination module is used to determine whether there is a micro-break in the gate lead of the transistor to be tested based on the input capacitance and the input capacitance reference of the transistor to be tested, wherein the micro-break refers to the presence of a crack inside the gate lead.
8. The device according to claim 7, characterized in that The acquisition module is used to: When the digital bridge meter is connected to the gate and the source of the transistor to be tested respectively, the alternating current frequency of the digital bridge meter is controlled to be not less than 100 Hz; The digital bridge instrument is controlled to measure the input capacitance of the transistor to be tested.
9. A testing device, characterized in that: The testing device comprises: a processor; and a memory configured to store processor-executable instructions; wherein the processor is configured to execute the method according to any one of claims 1 to 6.
10. A computer-readable storage medium, characterized in that: When the instructions in the computer-readable storage medium are executed by a processor of a test device, the test device is enabled to perform the method according to any one of claims 1 to 6.