Method and system for measuring transient temperature characteristics of resistive load samples

Abstract

The present invention discloses a method and system for measuring the transient temperature characteristics of a resistive load sample. The method comprises: keeping the light source always on, adjusting the sample to different temperatures and collecting the corresponding grayscale values, and drawing the average grayscale value-temperature curve of the corresponding areas of different materials of the sample; selecting the material with the largest absolute value of the linear fitting slope of the different average grayscale value-temperature curves, and calculating the thermal reflection calibration coefficient; applying low-frequency periodic square wave excitation to the sample to be tested, and obtaining the steady-state temperature change of the sample with a camera; finding the area with the largest steady-state temperature change of the sample, and marking it as a hot spot area; adjusting the light source intensity so that the photodetector is within the linear dynamic range; applying high-frequency periodic square wave excitation to the sample to be tested, and collecting the transient temperature change of the hot spot area of ​​the sample with a photodetector. The present invention avoids the measurement error introduced by the light source due to the pulse working mode, and improves the time resolution and measurement accuracy of the transient temperature characteristic measurement.

Description

Technical Field

[0001] The invention relates to the technical field of microelectronic temperature measurement, and in particular to a method and a system for measuring transient temperature characteristics of a resistive load sample. Background Art

[0002] Transient thermal reflection test is a transient temperature measurement technology with good time resolution. It can effectively measure the transient temperature changes caused by self-heating effect of resistive load samples such as metal resistors and microelectronic devices in the on state such as MOSFET and HEMT. Thermal reflection test is based on the principle that the reflectivity of the material surface changes approximately linearly with temperature. In transient thermal reflection test, the light source is in pulse working mode and is turned on only at the moment of interest, so that the camera only obtains the reflected light intensity information at that moment, and the temperature change of the sample to be tested is calculated by the change of reflected light intensity. The premise of this practice is to assume that the intensity and turn-on time of the light source are constant each time it is turned on. However, in actual tests, with the improvement of test time resolution, the shortening of the light source turn-on time increases the relative fluctuation amplitude of the light source intensity, introducing measurement errors; on the other hand, the shortening of the light source turn-on time leads to a decrease in the camera exposure intensity, making it difficult to obtain accurate reflected light intensity information, reducing the test accuracy.

[0003] In the prior art, in order to reduce the fluctuation of light source intensity and the influence of low camera exposure intensity in transient thermal reflection test, a method of turning on the light source multiple times in one exposure cycle of the camera is adopted. This method can improve the test accuracy to a certain extent, but it has very high requirements on the control timing of the light source, camera and sample excitation device, increases the complexity of the test method and test system, and limits the further improvement of the time resolution of transient thermal reflection test. Summary of the invention

[0004] The object of the present invention is to provide a method and system for measuring the transient temperature characteristics of a resistive load sample in view of the deficiencies of the prior art.

[0005] The objective of the present invention is achieved through the following technical solutions:

[0006] According to a first aspect of the present specification, there is provided a method for measuring transient temperature characteristics of a resistive load sample, the method comprising:

[0007] S1: Set the light source intensity to the first intensity so that the camera can obtain the sample image and keep the light source always on;

[0008] S2: By adjusting the sample to different temperatures and collecting the corresponding grayscale values, a graph of average grayscale value-temperature curves of the corresponding areas of different materials of the sample is drawn;

[0009] S3: Compare the linear fitting slopes of the average gray value-temperature curves of the corresponding areas of different materials, select the material with the largest absolute value of the slope, and calculate the thermal reflection calibration coefficient;

[0010] S4: Apply low-frequency periodic square wave excitation to the sample to be tested, and use a camera to obtain the steady-state temperature change of the sample;

[0011] S5: Find the area where the steady-state temperature of the sample changes the most, mark it as a hot spot area, and move the hot spot area to the center of the camera field of view;

[0012] S6: setting the light source intensity to a second intensity so that the photodetector is within a linear dynamic range;

[0013] S7: Apply high-frequency periodic square wave excitation to the sample to be tested, and use a photodetector to collect transient temperature changes in the hot spot area of ​​the sample.

[0014] Furthermore, in S2, the sample temperature is set to a first temperature, and a first grayscale value of the sample is collected by a camera; the sample temperature is adjusted to a second temperature, and a second grayscale value of the sample is collected by a camera; S2 is repeated to draw an average grayscale value-temperature curve of corresponding areas of different materials of the sample; wherein, room temperature < first temperature < second temperature < maximum operating temperature of the sample, and the values ​​of the first temperature and the second temperature are changed during each repetition to obtain average grayscale values ​​at different temperatures.

[0015] Furthermore, in S3, the calculation formula of the thermal reflection calibration coefficient is: , where R0 is the average gray value of the corresponding area of ​​the selected material at room temperature, and k is the linear fitting slope of the average gray value-temperature curve.

[0016] Further, in S4, the low-frequency periodic square wave excitation is a square wave with a low level of 0 V and a frequency f1≤10 Hz; the method of using a camera to obtain the steady-state temperature change of the sample is: the trigger pulse signal frequency f2 of the camera is f2=2f1, and the rising edge is aligned and phase-locked with the square wave initial excitation signal to obtain the quasi-steady-state low-temperature gray value R within the period H and the quasi-steady-state high temperature gray value R L , according to the formula Obtaining steady-state temperature changes of samples , where C TR is the thermal reflectance calibration coefficient.

[0017] Furthermore, in S4, the low-frequency periodic square wave excitation is applied as follows: in the resistor sample, the square wave excitation is applied to one end of the resistor sample, and the other end of the resistor sample is grounded; in the three-terminal microelectronic device, a voltage is first applied to the gate to turn on the device, and then the square wave excitation is applied to the drain, and the source is grounded.

[0018] Furthermore, in S5, the method for finding the area with the largest steady-state temperature change of the sample is as follows: taking the sample area that can be received by the photoelectric detector as the minimum unit, the sample surface is divided into several areas, the average value of the steady-state temperature change corresponding to each pixel point in the area is calculated, and the area with the largest average value is selected as the hot spot area.

[0019] Furthermore, S7 specifically includes the following sub-steps:

[0020] S71: Assume that the period of high-frequency periodic square wave excitation is T f , then collect n×T f The photodetector output signal of the duration, where n ≥ 10 4 ;

[0021] S72: Divide the collected photoelectric detector output signal into n segments, and superimpose the n segments of signals to obtain a time length of T f The superposition signal of

[0022] S73: performing normalization processing on the superimposed signal, and calculating the relative change ΔR of the reflectivity of the hot spot area of ​​the sample to be tested under the high-frequency periodic square wave excitation;

[0023] S74: According to the formula Calculate the transient temperature change of the hot spot area of ​​the sample to be tested , where C TR is the thermal reflectance calibration coefficient.

[0024] Further, in S73, the formula for normalizing the superimposed signal is: , where C is the superimposed signal, C min is the minimum value of the superimposed signal.

[0025] According to a second aspect of the present specification, a system for measuring transient temperature characteristics of a resistive load sample is provided, the system is used to perform the steps in the method for measuring transient temperature characteristics of a resistive load sample as described in the first aspect, the system comprising: a data processing module, an oscilloscope, a camera, a multi-channel arbitrary waveform generator, a photodetector, a constant current LED light source, a beam splitter No. 1, a beam splitter No. 2, an objective lens, a sample to be measured, and a temperature-controlled stage;

[0026] The temperature-controlled stage is used to place the sample to be tested and control the temperature of the sample to be tested;

[0027] The multi-channel arbitrary waveform generator is connected to the sample to be tested and the camera, and is used to stimulate the sample to be tested and generate a trigger pulse signal for the camera;

[0028] The constant current LED light source is used to generate illumination light, which is irradiated to the surface of the sample to be tested through the No. 2 beam splitter and the objective lens;

[0029] The beam splitter No. 1 is used to split the reflected light of the sample to be tested to the camera and the photodetector;

[0030] The camera and the photoelectric detector are used to obtain the reflected light signal of the sample to be tested;

[0031] The oscilloscope is connected to the photodetector and is used to read the output signal of the photodetector;

[0032] The data processing module is connected to the multi-channel arbitrary waveform generator, the camera and the oscilloscope, and is used to control the output waveform of the multi-channel arbitrary waveform generator, and record and process the measurement data of the camera and the oscilloscope.

[0033] Furthermore, the bandwidth of the oscilloscope should be greater than or equal to 4 GHz; the multi-channel arbitrary waveform generator should have a channel phase locking function; the photodetector is an avalanche photodiode sensitive to the visible light band; the constant current LED light source is a monochromatic LED light source in the visible light band; and the temperature-controlled stage should have an XY axis displacement function.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention adopts a constant current light source, and uses a camera and a photodetector to respectively obtain the steady-state temperature change of the sample and the transient temperature change of the hot spot area of ​​the sample, thereby avoiding the measurement error introduced by the pulse working mode of the light source, while reducing the control timing requirements, simplifying the measurement system structure, and improving the time resolution and temperature measurement accuracy of the transient thermal reflection test. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0036] Figure 1 A flow chart of a method for measuring transient temperature characteristics of a resistive load sample provided by the present invention;

[0037] Figure 2 A structural diagram of a system for measuring transient temperature characteristics of a resistive load sample provided by the present invention;

[0038] Figure 3 Control timing diagram for existing transient temperature characteristic measurement;

[0039] Figure 4 A control timing diagram for obtaining steady-state temperature changes of a sample using a camera provided in an embodiment of the present invention;

[0040] Figure 5A control timing diagram for collecting transient temperature changes in a hot spot area of ​​a sample using a photoelectric detector provided in an embodiment of the present invention;

[0041] Figure 6 A microscopic photograph of a nickel metal resistance wire sample provided in an embodiment of the present invention;

[0042] Figure 7 The average gray value-temperature curve diagram of silicon material and the linear fitting parameters provided by the embodiment of the present invention;

[0043] Figure 8 A graph showing steady-state temperature changes of a sample provided by an embodiment of the present invention;

[0044] Fig. 9 This is a graph of transient temperature changes of samples provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0045] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0046] It should be clear that the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0047] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the application. The singular forms "a", "said" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0048] refer to Figure 1 The embodiment of the present invention provides a method for measuring transient temperature characteristics of a resistive load sample, the method comprising the following steps:

[0049] S1: Set the light source intensity to the first intensity so that the camera can obtain a good sample image. After the setting is completed, the light source should remain on;

[0050] Specifically, the sample is a resistive load sample. The surface of the resistive load sample is usually composed of a variety of materials. Different materials correspond to different thermal reflection calibration coefficients. The camera can clearly distinguish the areas corresponding to different materials. After setting the light source intensity, the light source should remain always on, and the light source fluctuation depth should be less than 0.5% to ensure that the incident light intensity irradiating the sample remains unchanged. The camera can obtain the change in sample reflectivity by detecting the change in the reflected light intensity of the sample.

[0051] S2: setting the sample temperature to the first temperature, and using the camera to collect the first gray value of the sample at this time; adjusting the sample temperature to the second temperature, and using the camera to collect the second gray value of the sample at this time; repeating this step, and drawing an average gray value-temperature curve of the corresponding areas of different materials of the sample;

[0052] In this embodiment, room temperature < first temperature < second temperature < maximum operating temperature of the sample. The values ​​of the first temperature and the second temperature should be changed during each repetition to obtain the average grayscale value at different temperatures. The linear fitting correlation coefficient of the average grayscale value-temperature curve should be greater than 0.99 to ensure that a more accurate thermal reflection calibration coefficient is obtained.

[0053] S3: Compare the linear fitting slopes of the average gray value-temperature curves of the corresponding areas of different materials, select the material with the largest absolute value of the slope, and calculate the thermal reflection calibration coefficient of the material;

[0054] Specifically, the calculation formula for the thermal reflection calibration coefficient of each material of the sample is: , where R0 is the average gray value of the corresponding area of ​​the material at room temperature, and k is the linear fitting slope of the average gray value-temperature curve.

[0055] S4: Apply low-frequency periodic square wave excitation to the sample to be tested, and use a camera to obtain the steady-state temperature change of the sample;

[0056] Specifically, the low-frequency periodic square wave excitation is a square wave with a low level of 0 V and a frequency f1≤10 Hz; the low-frequency periodic square wave excitation is applied as follows: in the resistor sample, the square wave excitation should be applied to one end of the resistor sample, and the other end of the resistor sample is grounded; in three-terminal microelectronic devices such as MOSFET and HEMT, a suitable voltage should be applied to the gate to turn on the device, and then the square wave excitation should be applied to the drain, and the source should be grounded;

[0057] Apply a trigger pulse signal with a low level of 0 V, a high level of 8 V, and a rising edge of less than 5 ns to the camera. The signal frequency f2 = 2f1, and the camera trigger pulse signal should keep the rising edge aligned and phase locked with the square wave initial excitation signal to obtain the quasi-steady-state low-temperature gray value R within the period. H and the quasi-steady-state high temperature gray value R L , according to the formula Obtaining steady-state temperature changes of samples .

[0058] S5: Find the area where the sample's steady-state temperature changes the most, that is, find ΔT s The largest element of the matrix marks the sample area corresponding to this element as the hot spot area. By moving the temperature-controlled stage, the hot spot area is moved to the center of the camera's field of view;

[0059] Specifically, the method for finding the area with the largest steady-state temperature change of the sample is as follows: taking the sample area that the photoelectric detector can receive as the smallest unit, the sample surface is divided into several areas, the average steady-state temperature change corresponding to each pixel point in the area is calculated, and the area with the largest average value is selected as the hot spot area.

[0060] S6: setting the light source intensity to a second intensity so that the photodetector is within a linear dynamic range;

[0061] S7: applying high-frequency periodic square wave excitation to the sample to be tested, and using a photodetector to collect transient temperature changes in the hot spot area of ​​the sample;

[0062] In some embodiments, S7 may include:

[0063] S71: Assume that the period of high-frequency periodic square wave excitation is T f , then collect n×T f The photodetector output signal of the duration, where n ≥ 10 4 ;

[0064] S72: Divide the collected photoelectric detector output signal into n segments, and superimpose the n segments of signals to obtain a time length of T f The superposition signal of

[0065] S73: Perform normalization processing on the superimposed signal, and the following calculation formula can be used: , where ΔR is the relative change in reflectivity of the hot spot area of ​​the sample to be tested under high-frequency periodic square wave excitation, C is the superposition signal, and C min is the minimum value of the superimposed signal;

[0066] S74: According to the formula Calculate the transient temperature change of the hot spot area of ​​the sample to be tested .

[0067] Corresponding to the above method embodiment, refer to Figure 2 An embodiment of the present invention further provides a system for measuring the transient temperature characteristics of a resistive load sample, the system comprising: a data processing module 1, an oscilloscope 2, a camera 3, a multi-channel arbitrary waveform generator 4, a photodetector 5, a constant current LED light source 6, a beam splitter No. 1 7, a beam splitter No. 2 8, an objective lens 9, a sample to be measured 10 and a temperature-controlled stage 11.

[0068] The temperature-controlled stage 11 is used to place the sample 10 to be tested and control the temperature of the sample 10 to be tested; the multi-channel arbitrary waveform generator 4 is connected to the sample 10 to be tested and the camera 3, and is used to excite the sample 10 to be tested and generate a trigger pulse signal for the camera 3; the constant current LED light source 6 generates illumination light, which is irradiated to the surface of the sample 10 to be tested through the beam splitter No. 2 8 and the objective lens 9; the beam splitter No. 1 7 splits the reflected light of the sample 10 to the camera 3 and the photodetector 5; the camera 3 and the photodetector 5 are used to obtain the reflected light signal of the sample 10 to be tested; the oscilloscope 2 is connected to the photodetector 5, and is used to read the output signal of the photodetector 5; the data processing module 1 is connected to the multi-channel arbitrary waveform generator 4, the camera 3 and the oscilloscope 2, and is used to control the output waveform of the multi-channel arbitrary waveform generator 4, and record and process the measurement data of the camera 3 and the oscilloscope 2; specifically, the data processing flow of the data processing module 1 refers to the implementation steps in the above embodiment; Figure 3 Control timing diagram for existing transient temperature characteristic measurement; Figure 4 and Figure 5 They are respectively control timing diagrams for obtaining steady-state temperature changes of samples and collecting transient temperature changes of hot spot areas of samples in the present invention.

[0069] In this embodiment, the data processing module is any computer that can run LABVIEW; the bandwidth of the oscilloscope should be greater than or equal to 4 GHz, and the storage depth should be greater than or equal to 125 Mpts; the bit depth of the camera should be greater than or equal to 12 bits, and the shortest exposure time of the camera should be less than or equal to 10 μs; the multi-channel arbitrary waveform generator should have a channel phase locking function; the photodetector is an avalanche photodiode sensitive to the visible light band, with a sensitivity greater than or equal to 8 A / W in the 470nm and 530nm bands, and a bandwidth greater than or equal to 100 MHz; the constant current LED light source is an LED light source with a wavelength of 470 nm or 530 nm and a fluctuation depth of less than 0.5%; the temperature-controlled stage should have an XY-axis displacement function, a maximum temperature greater than or equal to 200°C, and a temperature control accuracy less than or equal to 0.1°C.

[0070] Furthermore, the method and system for measuring the transient temperature characteristics of a resistive load sample of the present invention are described by taking the transient temperature measurement of a nickel metal resistance wire sample as an example.

[0071] Please refer to Figure 6 , Figure 7 , Figure 8 and Fig. 9 , Figure 6 A nickel metal resistance wire sample provided by an embodiment of the present invention, Figure 7 A silicon material average gray value-temperature curve and linear fitting parameters provided by an embodiment of the present invention, Figure 8 A sample steady-state temperature change diagram provided by an embodiment of the present invention, Fig. 9A transient temperature change diagram of a sample provided in an embodiment of the present invention.

[0072] In this embodiment, the resistive load sample is Figure 6 The nickel metal resistance wire sample shown in the figure is deposited on a silicon substrate and has a size of 70 microns. The sample temperature is set to the first temperature and the second temperature by the temperature-controlled stage, and the grayscale value of the sample is obtained by the camera. It is known from the literature that the thermal reflection calibration coefficient of nickel metal under 470 nm wavelength light is extremely small, so the following is drawn: Figure 7 The average gray value-temperature curve of silicon material shown in the figure is based on the formula , calculate the thermal reflection calibration coefficient C TR =1.38e-4 K -1 . See Figure 4 A control timing diagram for obtaining a steady-state temperature change of a sample using a camera provided in an embodiment of the present invention. The multi-channel arbitrary waveform generator of this embodiment generates a low-frequency periodic square wave with a frequency of 5 Hz, a low level of 0 V, a high level of 12 V, and a duty cycle of 50% to excite the sample to be tested, and generates a trigger pulse signal of the camera with a frequency of 10 Hz. The camera trigger pulse signal should keep the rising edge aligned and phase locked with the square wave initial excitation signal to obtain the quasi-steady-state low-temperature gray value R within the period. H and the quasi-steady-state high temperature gray value R L , according to the formula Obtaining steady-state temperature changes of samples The specific sample steady-state temperature change diagram is as follows: Figure 8 As shown, since the thermal reflection calibration coefficient of nickel metal under 470 nm wavelength light is extremely small, only the temperature change of the silicon material is shown.

[0073] In this embodiment, the photodetector can receive the reflected light signal of the sample area of ​​5 μm×5 μm, so according to Figure 8 Based on the sample size data, the silicon area at the center of the sample was selected as the hot spot. Figure 5 The present invention provides a control timing diagram for collecting transient temperature changes in the hot spot area of ​​a sample using a photodetector. In this embodiment, a high-frequency periodic square wave excitation with a frequency of 1 MHz, a low level of 0 V, a high level of 12 V, and a duty cycle of 35% is applied to the sample to be tested. The photodetector is used to collect transient temperature changes in the hot spot area of ​​the sample. The output signal of the photodetector is sampled by an oscilloscope to obtain a collection signal with a duration of 1 s. The collected output signal of the photodetector is divided into 10 6 segment, 10 6 The segment signals are superimposed on each other to obtain a superimposed signal with a duration of 1 μs; the following operations are performed on the superimposed signal: , where ΔR is the relative change in reflectivity of the hot spot area of ​​the sample to be tested under high-frequency periodic square wave excitation, C is the superposition signal, and C min is the minimum value of the superimposed signal; according to the formula Calculate the transient temperature change of the hot spot area of ​​the sample to be tested, such as Fig. 9 As shown. Fig. 9 The transient temperature changes in the hot spot area of ​​the sample obtained by the test were compared with the simulation results. The temperature difference was within 1 K, demonstrating that the system has good time resolution and accuracy in measuring transient temperature characteristics.

[0074] The above description is merely a preferred embodiment of one or more embodiments of the present specification and is not intended to limit one or more embodiments of the present specification. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of one or more embodiments of the present specification shall be included in the scope of protection of one or more embodiments of the present specification.

Claims

1. A method for measuring transient temperature characteristics of a resistive load sample, characterized in that: include: S1: The light source is a constant current light source, and the light source intensity is set to the first intensity so that the camera can obtain the sample image and keep the light source always on; S2: By adjusting the sample to different temperatures and collecting the corresponding grayscale values, a graph of average grayscale value-temperature curves of the corresponding areas of different materials of the sample is drawn; S3: Compare the linear fitting slopes of the average gray value-temperature curves of the corresponding areas of different materials, select the material with the largest absolute value of the slope, and calculate the thermal reflection calibration coefficient; S4: Apply low-frequency periodic square wave excitation to the sample to be tested, and use a camera to obtain the steady-state temperature change of the sample; S5: Find the area where the steady-state temperature of the sample changes the most, mark it as a hot spot area, and move the hot spot area to the center of the camera field of view; S6: setting the light source intensity to a second intensity so that the photodetector is within a linear dynamic range; S7: Apply high-frequency periodic square wave excitation to the sample to be tested, and use a photodetector to collect transient temperature changes in the hot spot area of ​​the sample.

2. The method for measuring transient temperature characteristics of a resistive load sample according to claim 1, characterized in that: In S2, the sample temperature is set to the first temperature, and the first grayscale value of the sample is collected by a camera; the sample temperature is adjusted to the second temperature, and the second grayscale value of the sample is collected by a camera; S2 is repeated to draw an average grayscale value-temperature curve of the corresponding areas of different materials of the sample; wherein, room temperature < first temperature < second temperature < maximum operating temperature of the sample, and the values ​​of the first temperature and the second temperature are changed during each repetition to obtain the average grayscale values ​​at different temperatures.

3. The method for measuring transient temperature characteristics of a resistive load sample according to claim 1, characterized in that: In S3, the calculation formula for the thermal reflection calibration coefficient is: , where R0 is the average gray value of the corresponding area of ​​the selected material at room temperature, and k is the linear fitting slope of the average gray value-temperature curve.

4. The method for measuring transient temperature characteristics of a resistive load sample according to claim 1, characterized in that: In S4, the low-frequency periodic square wave excitation is a square wave with a low level of 0V and a frequency f1≤10 Hz; the method of using a camera to obtain the steady-state temperature change of the sample is: the trigger pulse signal frequency of the camera f2=2f1, and the rising edge is aligned and phase-locked with the square wave initial excitation signal to obtain the quasi-steady-state low-temperature gray value R within the period H and the quasi-steady-state high temperature gray value R L , according to the formula Obtaining steady-state temperature changes of samples , where C TR is the thermal reflectance calibration coefficient.

5. The method for measuring transient temperature characteristics of a resistive load sample according to claim 1, characterized in that: In S4, the low-frequency periodic square wave excitation is applied as follows: in the resistor sample, the square wave excitation is applied to one end of the resistor sample, and the other end of the resistor sample is grounded; in the three-terminal microelectronic device, a voltage is first applied to the gate to turn on the device, and then the square wave excitation is applied to the drain, and the source is grounded.

6. The method for measuring transient temperature characteristics of a resistive load sample according to claim 1, characterized in that: In S5, the method for finding the area with the largest steady-state temperature change of the sample is as follows: taking the sample area that can be received by the photoelectric detector as the minimum unit, the sample surface is divided into several areas, the average value of the steady-state temperature change corresponding to each pixel point in the area is calculated, and the area with the largest average value is selected as the hot spot area.

7. The method for measuring transient temperature characteristics of a resistive load sample according to claim 1, characterized in that: S7 specifically includes the following sub-steps: S71: Assume that the period of high-frequency periodic square wave excitation is T f , then collect n×T f The photodetector output signal of the duration, where n ≥ 10 4 ; S72: Divide the collected photoelectric detector output signal into n segments, and superimpose the n segments of signals to obtain a time length of T f The superposition signal of S73: performing normalization processing on the superimposed signal, and calculating the relative change ΔR of the reflectivity of the hot spot area of ​​the sample to be tested under the high-frequency periodic square wave excitation; S74: According to the formula Calculate the transient temperature change of the hot spot area of ​​the sample to be tested , where C TR is the thermal reflectance calibration coefficient.

8. The method for measuring transient temperature characteristics of a resistive load sample according to claim 7, characterized in that: In S73, the formula for normalizing the superimposed signal is: , where C is the superimposed signal, C min is the minimum value of the superimposed signal.

9. A system for measuring transient temperature characteristics of a resistive load sample, characterized in that: The system is used to perform the steps in the method for measuring transient temperature characteristics of a resistive load sample as described in any one of claims 1 to 8, the system comprising: a data processing module, an oscilloscope, a camera, a multi-channel arbitrary waveform generator, a photodetector, a constant current LED light source, a beam splitter No. 1, a beam splitter No. 2, an objective lens, a sample to be measured, and a temperature-controlled stage; The temperature-controlled stage is used to place the sample to be tested and control the temperature of the sample to be tested; The multi-channel arbitrary waveform generator is connected to the sample to be tested and the camera, and is used to stimulate the sample to be tested and generate a trigger pulse signal for the camera; The constant current LED light source is used to generate illumination light, which is irradiated to the surface of the sample to be tested through the No. 2 beam splitter and the objective lens; The beam splitter No. 1 is used to split the reflected light of the sample to be tested to the camera and the photodetector; The camera and the photoelectric detector are used to obtain the reflected light signal of the sample to be tested; The oscilloscope is connected to the photodetector and is used to read the output signal of the photodetector; The data processing module is connected to the multi-channel arbitrary waveform generator, the camera and the oscilloscope, and is used to control the output waveform of the multi-channel arbitrary waveform generator, and record and process the measurement data of the camera and the oscilloscope.

10. The system for measuring transient temperature characteristics of a resistive load sample according to claim 9, characterized in that: The bandwidth of the oscilloscope should be greater than or equal to 4 GHz; the multi-channel arbitrary waveform generator should have a channel phase locking function; the photodetector is an avalanche photodiode sensitive to the visible light band; the constant current LED light source is a monochromatic LED light source in the visible light band; and the temperature-controlled stage should have an XY axis displacement function.

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