Device and method for measuring thermal resistance of gallium nitride transistor based on laser thermal reflectivity

Abstract

The invention provides a gallium nitride transistor thermal resistance measuring device and method based on laser thermal reflectivity, and relates to the technical field of semiconductor device testing, and the method comprises the steps: obtaining laser reflectivity data of a gallium nitride transistor at different temperatures; calculating the distance weight of each data point of the laser reflectivity data to the target point to obtain the distance weight of each data point; performing local linear fitting based on the distance weight to obtain a current fitting value of the target point; carrying out residual calculation on all the data points based on the current fitting value of the target point to obtain robust scale estimation of the residual; updating the combined weight by using robust scale estimation of the residual error to obtain a next updating result; and when the change of the fitting value of the next updating result is smaller than a preset threshold value and any one of the maximum iterations is reached, obtaining a thermal resistance measurement result, and completing the measurement of the thermal resistance of the gallium nitride transistor. The problems that an existing heat reflection temperature measurement method is large in noise of a test result and insufficient in stability are solved.

Description

Technical Field

[0001] This invention relates to the field of semiconductor device testing technology, and in particular to a device and method for measuring the thermal resistance of gallium nitride transistors based on laser thermal reflectivity. Background Technology

[0002] Gallium nitride (GaN)-based microwave power devices have demonstrated superior performance in high-frequency, high-power applications due to their fast response, strong breakdown electric field, high RF output power, and high temperature resistance. They have become key components for microwave power amplification in radar, satellite communications, precision guidance, and electronic warfare equipment, and are a strategic development priority for many countries worldwide. However, under high-frequency, high-power operating conditions, the excessively high temperature in the active region of GaN microwave power devices becomes a critical factor restricting their reliability and stability. Therefore, measuring the surface temperature distribution of the device and detecting the thermal resistance of each material along the heat dissipation path are crucial for ensuring its reliability.

[0003] Methods that can be used to characterize the active region temperature rise characteristics of gallium nitride-based microwave power devices include infrared thermal imaging, Raman spectroscopy thermal imaging, electrical parameter methods, and thermal reflectance methods. However, these methods can only obtain the temperature distribution on the device surface or determine the temperature of the material layer along the heat source path of the device.

[0004] Traditional thermal reflection methods use charge-coupled device (CCD) cameras for data acquisition, and the minimum exposure time of the CCD camera determines the minimum time resolution of the experiment. This severely limits the time resolution of thermal reflection methods. To address this issue, some researchers have proposed a boxcar model where only one LED pulse is applied for each CCD camera exposure, shortening the CCD camera exposure time to the duration of the LED pulse and reducing the time resolution to the delay time between the excitation and the LED pulse. However, this method places high demands on the CCD camera and involves complex mechanical movements, significantly increasing costs. Other researchers have improved upon this approach by applying pulse excitation to the device during long exposures of the CCD camera. A time delay exists between the LED pulse and the device pulse excitation, and the system's time resolution is determined by this delay. This method reduces the requirements for the CCD camera, but it requires multiple heating cycles of the device. However, due to the small thickness and area of ​​the active region in typical gallium nitride (GaN) devices, the minimum thermal time constant is usually in the microsecond range, and the time to reach a stable state after packaging typically exceeds 100 seconds. Multiple cyclic heating cycles can damage the device and affect the accuracy of the experiment. In response to this situation, the industry has proposed using photodiodes for detection, but the time resolution needs to be further improved.

[0005] Existing thermal reflection temperature measurement methods suffer from high noise and insufficient stability; traditional noise reduction methods have weak adaptability and are prone to losing data details, failing to meet high-precision requirements. Summary of the Invention

[0006] To address the aforementioned shortcomings in the prior art, the gallium nitride transistor thermal resistance measurement device and method based on laser thermal reflectivity provided by this invention solves the problems of high noise and insufficient stability in the test results of existing thermal reflectivity temperature measurement methods.

[0007] To achieve the above-mentioned objectives, the technical solution adopted by the present invention is: a gallium nitride transistor thermal resistance measurement device based on laser thermal reflectivity, comprising a measurement and control module, an optical path module, and a carrier module; The support module includes a manual three-dimensional stage and a constant temperature platform set on the manual three-dimensional stage, the constant temperature platform being used to support the device under test; The measurement and control module includes a host computer, a laser driver, a photoelectric detection component, a data acquisition card, and a power supply; the host computer is electrically connected to the laser driver, the data acquisition card, and the power supply; the power supply is used to power the device under test. The optical path module includes a laser, a first optical lens, a first beam splitter, a second beam splitter, an objective lens, a focusing lens, and a CCD camera; The laser driver is electrically connected to the laser; the beam emitted by the laser is collimated by the first optical lens and then incident on the first beam splitter. The output light path of the first beam splitter is coupled to the second beam splitter; the output light path of the second beam splitter is focused onto the device under test through the objective lens; The reflected light from the device under test returns to the second beam splitter via the objective lens; The second beam splitter directs a portion of the reflected light to the CCD camera for observing the position of the light spot; and transmits or reflects another portion of the reflected light back to the first beam splitter. The first beam splitter couples the beam from the second beam splitter to the focusing lens; The outgoing light path of the focusing lens is coupled to the input terminal of the photodiode of the photodetector assembly; the output terminal of the photodetector assembly is electrically connected to the data acquisition card.

[0008] The beneficial effects of this invention are as follows: This invention utilizes a gallium nitride transistor thermal resistance measurement device based on laser thermal reflectivity to perform a gallium nitride transistor thermal resistance measurement method based on laser thermal reflectivity. By employing a photoelectric detection component, the system's temporal resolution is greatly improved. A CCD camera is introduced into the constructed optical path to fully utilize the high spatial resolution characteristics of thermal reflectivity, thereby achieving accurate measurement of the temperature rise in the active region of a gallium nitride transistor (GaN HEMT).

[0009] Furthermore, the photoelectric detection component includes: Resistors R1, R2, R3, R4, R5, R6, R7, R8, R9, and R10; a photodiode; a first operational amplifier; a second operational amplifier; a third operational amplifier; a fourth operational amplifier; and a fifth operational amplifier. The positive terminal of the photodiode is connected to the inverting input of the first operational amplifier. The negative terminal of the photodiode is connected to both the non-inverting input of the first operational amplifier and one end of resistor R2. The other end of resistor R2 is connected to both the output of the first operational amplifier and the non-inverting input of the fourth operational amplifier. The inverting input of the fourth operational amplifier is connected to one end of resistor R6 and one end of resistor R7. The output of the fourth operational amplifier is connected to the other end of resistor R7 and one end of resistor R8. Resistor R8... The other end is connected to the grounding resistor R10 and the non-inverting input of the fifth operational amplifier. The other end of the resistor R6 is connected to one end of the resistor R5 and the inverting input of the third operational amplifier. The non-inverting input of the third operational amplifier is connected to the output of the second operational amplifier and one end of the resistor R1. The other end of the resistor R1 is connected to the inverting input of the second operational amplifier. The non-inverting input of the second operational amplifier is connected to the grounding resistor R3. The output of the third operational amplifier is connected to the other end of the resistor R5 and one end of the resistor R4. The other end of the resistor R4 is connected to the inverting input of the fifth operational amplifier and one end of the resistor R9. The output of the fifth operational amplifier is connected to the other end of the resistor R9 and the positive terminal of the output of the photodetector. The negative terminal of the output of the photodetector is grounded.

[0010] This invention provides a method for measuring the thermal resistance of gallium nitride transistors based on laser thermal reflectivity, comprising: S1: Obtain laser reflectivity data of gallium nitride transistors at different temperatures; S2: Calculate the distance weight of each data point of the laser reflectivity data relative to the target point to obtain the distance weight of each data point; S3: Based on distance weights, perform local linear fitting to obtain the current fitted value of the target point; S4: Based on the current fitted value of the target point, perform residual calculation on all data points to obtain a robust scaling estimate of the residuals; S5: Use robust scaling estimation of residuals to update the combined weights and obtain the next update result; determine whether the next update result meets the preset threshold for the change of fitted value and the maximum number of iterations. If the next update result meets either the preset threshold for the change of fitted value or the maximum number of iterations, stop the iteration, obtain the thermal resistance measurement result, and complete the measurement of the thermal resistance of the gallium nitride transistor; otherwise, return the update result to S3 for iterative calculation.

[0011] This invention provides a method for measuring the thermal resistance of gallium nitride transistors based on laser thermal reflectivity. In the original structure function algorithm's input preprocessing stage, local linear fitting and row residual calculation are added, forming an integrated architecture of "noise reduction preprocessing - structure function operation". It has the following technical advantages: (1) Based on local linear fitting, the algorithm can adaptively distinguish between noise and effective features, reducing noise while preserving data details; (2) Modular design, strong portability, and high computational efficiency; (3) Adaptable to various types of noise such as Gaussian noise and impulse noise, compatible with data of different dimensions, and stable and reliable under complex working conditions.

[0012] Furthermore, the expression for the distance weight is: ; ; ; in, express relative to the distance weight of the target data point, Represents the target data point. This represents a cubic kernel function. This represents the i-th data point. This represents the local window width of the target data point. Indicates the first variable.

[0013] Furthermore, the expression for the current fitted value of the target point is: ; ; in, This represents the minimum intercept term obtained from the solution. This represents the term with the minimum slope obtained from the solution. Represents the function to be minimized. Let represent the combined weight of the target data point in the (t-1)th iteration, where i represents the data point index, n represents the number of data points, and t represents the iteration number. Represents the target data point. This represents the observation data of the i-th data point. Represents the intercept term. Represents the slope term. This represents the i-th data point. This represents the current fitted value of the target data point x.

[0014] Furthermore, the expression for the robust scaling estimate is: ; in, This represents the robust scaling estimate in the t-th iteration. Indicates the absolute deviation of the median. Let represent the residual of the i-th data point in the t-th iteration, where i represents the data point index and t represents the iteration number.

[0015] Furthermore, the expression for the next update result is: ; ; ; in, This represents the combined weight of the i-th data point in the t-th iteration. Represents the target data point. express relative to the distance weight of the target data point, Indicates a stable weighting. This represents a two-weighted function. This represents the residual of the i-th data point in the t-th iteration. This represents the robust scaling estimate in the t-th iteration. This indicates the second variable. Attached Figure Description

[0016] The present invention will be further described by way of exemplary embodiments, which will be described in detail with reference to the accompanying drawings. These embodiments are not limiting, and in these embodiments, the same reference numerals denote the same structures, wherein: Figure 1 This is a schematic diagram of a gallium nitride transistor thermal resistance measurement device based on laser thermal reflectivity, according to some embodiments of the present invention. Figure 2 This is an exemplary flowchart of a method for measuring the thermal resistance of gallium nitride transistors based on laser thermal reflectivity, according to some embodiments of the present invention. Figure 3 This is an exemplary schematic diagram of a photoelectric detection component according to some embodiments of the present invention; Figure 4 This is an exemplary schematic diagram of the temperature calibration coefficient of the acquisition voltage V according to some embodiments of the present invention; Figure 5 This is an exemplary schematic diagram of the transient temperature drop curve of the device acquired according to some embodiments of the present invention; Figure 6 This is an exemplary schematic diagram showing the measured longitudinal thermal resistance distribution of a device according to some embodiments of the present invention.

[0017] The components include: 1. Host computer; 2. Laser driver; 3. Laser; 4. First optical lens; 5. First beam splitter; 6. Second beam splitter; 7. Objective lens; 8. Device under test; 9. Temperature control platform; 10. Manual 3D stage; 11. CCD camera; 12. Focusing lens; 13. Photoelectric detection assembly; 14. Data acquisition card; 15. Power supply. Detailed Implementation

[0018] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0019] Example 1 Figure 1 This is a schematic diagram of a gallium nitride transistor thermal resistance measurement device based on laser thermal reflectivity, according to some embodiments of the present invention.

[0020] In some embodiments, the gallium nitride transistor thermal resistance measurement device based on laser thermal reflectivity may include a measurement and control module, an optical path module, and a support module; the support module includes a manual three-dimensional stage 10 and a constant temperature platform 9 disposed on the manual three-dimensional stage 10, the constant temperature platform 9 being used to support the device under test 8; the measurement and control module includes a host computer 1, a laser driver 2, a photoelectric detection component 13, a data acquisition card 14, and a power supply 15; the host computer 1 is electrically connected to the laser driver 2, the data acquisition card 14, and the power supply 15 respectively; the power supply 15 is used to supply power to the device under test 8; the optical path module includes a laser 3, a first optical lens 4, a first beam splitter 5, a second beam splitter 6, an objective lens 7, a focusing lens 12, and a CCD camera 11; the laser driver 2 and the laser driver 13 are connected to the laser driver 2, the laser driver 2, the optical path module ... The laser 3 is electrically connected; the beam emitted by the laser 3 is collimated by the first optical lens 4 and then incident on the first beam splitter 5; the outgoing light path of the first beam splitter 5 is coupled to the second beam splitter 6; the outgoing light path of the second beam splitter 6 is focused by the objective lens 7 onto the device under test 8; the reflected light from the device under test 8 returns to the second beam splitter 6 via the objective lens 7; the second beam splitter 6 splits part of the reflected light beam to the CCD camera 11 for observing the position of the light spot; and transmits or reflects another part of the reflected light back to the first beam splitter 5; the first beam splitter 5 couples the beam from the second beam splitter 6 to the focusing lens 12; the outgoing light path of the focusing lens 12 is coupled to the photodiode input terminal of the photodetector assembly 13; the output terminal of the photodetector assembly 13 is electrically connected to the data acquisition card 14.

[0021] In some embodiments, considering the reflection efficiency of gallium nitride materials to light sources of different wavelengths, using a 360nm ultraviolet laser as the probe laser can achieve the highest theoretical reflection value. This is crucial for improving the signal integrity and signal-to-noise ratio of the test system. Simultaneously, it should be ensured that the overall power of the probe laser is sufficiently low to avoid test errors caused by the device under test absorbing the probe laser. Therefore, based on the selection of the probe laser, the photodiode in the test system should also be a photodiode that is highly sensitive to 360nm ultraviolet laser wavelengths.

[0022] In some embodiments, the photodetector assembly 13 includes: resistors R1, R2, R3, R4, R5, R6, R7, R8, R9, and R10; a photodiode; a first operational amplifier; a second operational amplifier; a third operational amplifier; a fourth operational amplifier; and a fifth operational amplifier. The anode of the photodiode is connected to the inverting input of the first operational amplifier; the cathode of the photodiode is connected to the non-inverting input of the first operational amplifier and one end of resistor R2; the other end of resistor R2 is connected to the output of the first operational amplifier and the non-inverting input of the fourth operational amplifier; the inverting input of the fourth operational amplifier is connected to one end of resistor R6 and one end of resistor R7; and the output of the fourth operational amplifier is connected to the other end of resistor R7 and the other end of resistor R8. One end of the resistor R8 is connected to the grounding resistor R10 and the non-inverting input of the fifth operational amplifier. The other end of the resistor R6 is connected to one end of the resistor R5 and the inverting input of the third operational amplifier. The non-inverting input of the third operational amplifier is connected to the output of the second operational amplifier and one end of the resistor R1. The other end of the resistor R1 is connected to the inverting input of the second operational amplifier. The non-inverting input of the second operational amplifier is connected to the grounding resistor R3. The output of the third operational amplifier is connected to the other end of the resistor R5 and one end of the resistor R4. The other end of the resistor R4 is connected to the inverting input of the fifth operational amplifier and one end of the resistor R9. The output of the fifth operational amplifier is connected to the other end of the resistor R9 and the positive terminal of the output of the photodetector. The negative terminal of the output of the photodetector is grounded.

[0023] Circuit Principle: To improve the system's time resolution, this invention designs a photoelectric detection component based on the AD8033 as the detection signal acquisition and amplification system, corresponding to photoelectric detection component 13. The entire system is divided into three main modules: transimpedance amplification, reference voltage, and instrumentation amplification. The transimpedance amplification module consists of transimpedance amplifiers. Its function is to convert the photocurrent Ipd generated after the photodiode receives the reflected detection laser into a voltage value Vpd. Compared to a single sampling resistor, the transimpedance amplification circuit composed of operational amplifiers can accelerate the conversion process, thereby ensuring the signal integrity of the test system and further improving the time resolution. The reference voltage module outputs a VREF, which is composed of a voltage follower built from operational amplifiers. Its function is to ensure that the finally acquired data can be completely transmitted to the host computer without exceeding the range of the acquisition card. In addition, it helps to eliminate common-mode signals. The instrumentation amplification module outputs Vout, which is composed of an instrumentation amplifier consisting of three operational amplifiers. Compared to a differential amplifier circuit composed of a single operational amplifier, the instrumentation amplification circuit has a higher common-mode rejection ratio and can suppress common-mode noise in the signal to a greater extent, which plays a significant role in improving the system's signal-to-noise ratio.

[0024] Working Principle: The entire system consists of a 360nm ultraviolet laser (3), a laser driver (2), optical lens groups (4, 5, 6, 7, 12), a device under test (DUT) (8), a data acquisition card (14), a photodetector assembly (13), a CCD camera (11), a power supply (15), a host computer (1), a temperature-controlled platform (9), and a manual 3D stage (10). The detection optical path, composed of the laser (3), the first optical lens (4), and beam splitters (5, 6), focuses the laser onto the surface of the DUT. The reflected light is then passed through lens (12) and onto the photodetector assembly (13). Simultaneously, the CCD camera (11) obtains the specific position of the light spot on the DUT surface. The photodiode (13) converts the intensity change of the reflected light into a change in photocurrent. This small signal is then amplified by the subsequent photodetector assembly (13), and the data acquisition card (14) acquires the electrical signal. The temperature of the temperature-controlled platform (9) can be adjusted to obtain the laser reflectivity at different temperatures, thus achieving the measurement of the laser reflectivity as a function of temperature, i.e., obtaining a temperature calibration curve. The 3D platform 10 is used to adjust the position of the light spot on the surface of the device under test 8, thereby enabling the measurement of the temperature rise in the active region of the device. The power supply 15 is used to apply different bias voltages to the device under test, thereby adjusting the device's operating power. The host computer 1 controls the driving sequence of the laser driver 2, the data acquisition card 14, and the power supply 15.

[0025] After the optical path is built, temperature profile calibration is required. Place the device under test (DUT) on a constant-temperature platform and adjust the position of the probe laser to ensure its irradiation point is located in the active region of the device's main heat source. Set the constant-temperature platform temperature to T0 (which should be higher than room temperature) as the reference temperature. Once the device temperature stabilizes, obtain the output voltage V0 of the photodetector component. (See [link to photodetector component description]). Figure 3 Then the set temperatures of the constant temperature platform were changed: T1, T2, T3…T n The data acquisition card collects the output voltages V1, V2, V3…V of the photoelectric detection component at the corresponding temperature. n By performing a linear fit on the discrete points of V and T, the following can be obtained: Figure 4 The temperature calibration curve shown has the following slope. This refers to the temperature coefficient, which establishes the conversion relationship between the data acquired by the acquisition card and the device temperature; where T1 represents the first set temperature of the constant temperature platform, T2 represents the second set temperature of the constant temperature platform, T3 represents the third set temperature of the constant temperature platform, and T... n V1 represents the nth set temperature of the constant temperature platform, V2 represents the first output voltage of the photoelectric detection component, V3 represents the third output voltage of the photoelectric detection component, and V... n This represents the nth output voltage of the photoelectric detection component. It represents the ratio of two consecutive voltage changes to two consecutive consecutive temperature changes.

[0026] After obtaining the temperature calibration curve, power P is applied to the device until it reaches a thermally stable state. At this time, the output voltage of the photoelectric detection component is Vp. Then, the host computer controls the device to disconnect the power and the acquisition card starts to collect data simultaneously, so as to realize the measurement of the transient temperature drop curve of the device and obtain a curve of V(t) with respect to time t, where V(t) is the voltage collected by the acquisition card during the cooling process.

[0027] like Figure 5 The transient temperature drop curve of the device is shown. T(t)=V(t) / .

[0028] From the definition of thermal resistance, we know that the transient thermal resistance of a device is Rth = T(t) / P gives the thermal resistance along the heat dissipation path of the device, such as Figure 6 As shown in the figure. Rth1 is the thermal resistance of the chip, Rth2 is the thermal resistance of the casing, Rth3 is the thermal resistance of the PCB, and Rth4 is the thermal grease between the PCB and the constant temperature platform.

[0029] To fully utilize the high spatial resolution of thermal reflection testing methods for measuring the temperature rise of the active region of a device, this invention incorporates a CCD camera 11 into the optical path setup to accurately adjust the probe laser spot, resulting in more accurate test results. Compared to widely used electrical methods, this invention can obtain the accurate temperature of the active region of the device, rather than the average temperature of the entire channel. Compared to other thermal reflection methods, this invention combines thermal reflection with the structure function method from electrical methods, enabling the determination of the thermal resistance composition of different material layers along the heat flow path.

[0030] In some embodiments, a gallium nitride transistor thermal resistance measurement device based on laser thermal reflectivity can be used to perform a gallium nitride transistor thermal resistance measurement method based on laser thermal reflectivity, including: S1: acquiring laser reflectivity data of gallium nitride transistors at different temperatures; S2: calculating the distance weight of each data point of the laser reflectivity data relative to the target point to obtain the distance weight of each data point; S3: performing local linear fitting based on the distance weight to obtain the current fitted value of the target point; S4: calculating the residual for all data points based on the current fitted value of the target point to obtain a robust scaling estimate of the residual; S5: updating the combined weights using the robust scaling estimate of the residual to obtain the next update result; when the change in the fitted value of the next update result is less than a preset threshold or reaches the maximum number of iterations, the iteration stops, the thermal resistance measurement result is obtained, and the measurement of the thermal resistance of the gallium nitride transistor is completed; otherwise, the update result is returned to S3 for iterative calculation.

[0031] In some embodiments of the present invention, the processor utilizes a gallium nitride transistor thermal resistance measurement device based on laser thermal reflectivity to perform a gallium nitride transistor thermal resistance measurement method based on laser thermal reflectivity. By employing a photodetector component, the system's temporal resolution is significantly improved. A CCD camera is introduced into the constructed optical path to fully utilize the high spatial resolution characteristics of thermal reflectivity, thereby achieving accurate measurement of the temperature rise in the active region of GaN HEMTs.

[0032] Example 2 Figure 2 This is an exemplary flowchart illustrating a method for measuring the thermal resistance of gallium nitride transistors based on laser thermal reflectivity, according to some embodiments of the present invention. Figure 2 As shown, the process includes the following steps. In some embodiments, the process may be executed by a processor.

[0033] S1: Obtain laser reflectivity data of gallium nitride transistors at different temperatures.

[0034] The laser reflectivity data is the laser reflectivity data collected from gallium nitride transistors (GaN HEMTs) at different temperatures.

[0035] In some embodiments, the relationship between the reflectivity of a semiconductor material and temperature can be expressed as: ; in, This represents the change in the reflectivity of a material after a change in temperature. Indicates the reflectivity of a material. Indicates the material temperature. Indicates the amount of temperature change in the material. This represents the thermal reflectance coefficient of the material.

[0036] The thermal reflectance coefficient of a material is related to the material's own properties and can be considered a constant.

[0037] During the test, due to the change in the thermal reflectivity of the device surface, under the premise that the detection laser power remains constant, the photodiode photocurrent ΔI, which follows the change of ΔR, can be obtained. pd The photocurrent ΔI of the photodiode can be obtained from the formula. pd The relationship with the material temperature rise ΔT. After subsequent transimpedance amplification and instrumentation amplification modules, ΔV is finally obtained. 采集 The linear relationship between ΔT and the device surface temperature is obtained, thus enabling the acquisition of temperature changes on the device surface.

[0038] S2: Calculate the distance weight of each data point in the laser reflectivity data relative to the target point to obtain the distance weight of each data point.

[0039] Distance weight is for each data point Relative to target point Distance weights.

[0040] In some embodiments, the expression for the distance weight can be: ; ; ; in, express relative to the distance weight of the target data point, Represents the target data point. This represents a cubic kernel function. This represents the i-th data point. This represents the local window width of the target data point. Indicates the first variable.

[0041] The first variable, representing the supplementary expression for the function T, corresponds here to |xi. x| / h(x) represents whether the i-th data point exceeds the local window width h(x).

[0042] The width of a local window is usually taken as up to the first... The distance to the nearest neighbor, , This represents the smoothing parameter.

[0043] S3: Based on distance weights, perform local linear fitting to obtain the current fitted value of the target point.

[0044] In some embodiments, the expression for the current fitted value of the target point is: ; ; in, This represents the minimum intercept term obtained from the solution. This represents the term with the minimum slope obtained from the solution. Represents the function to be minimized. Let represent the combined weight of the target data point in the (t-1)th iteration, where i represents the data point index, n represents the number of data points, and t represents the iteration number. Represents the target data point. This represents the observation data of the i-th data point. Represents the intercept term. Represents the slope term. This represents the i-th data point. This represents the current fitted value of the target data point x.

[0045] S4: Based on the current fitted value of the target point, perform residual calculation on all data points to obtain a robust scaling estimate of the residuals.

[0046] Robust scaling of residuals includes parameters such as median absolute deviation.

[0047] In some embodiments, the expression for robust scaling estimation is: ; in, This represents the robust scaling estimate in the t-th iteration. Indicates the absolute deviation of the median. Let represent the residual of the i-th data point in the t-th iteration, where i represents the data point index and t represents the iteration number.

[0048] S5: Use robust scaling estimation of residuals to update the combined weights and obtain the next update result; determine whether the next update result meets the preset threshold for the change of fitted value and the maximum number of iterations. If the next update result meets either the preset threshold for the change of fitted value or the maximum number of iterations, stop the iteration, obtain the thermal resistance measurement result, and complete the measurement of the thermal resistance of the gallium nitride transistor; otherwise, return the update result to S3 for iterative calculation.

[0049] The update result is the update result of the combined weights in each iteration.

[0050] In some embodiments, the expression for the next update result is: ; ; ; ; in, This represents the combined weight of the i-th data point in the t-th iteration. Represents the target data point. express relative to the distance weight of the target data point, Indicates a stable weighting. This represents a two-weighted function. This represents the residual of the i-th data point in the t-th iteration. This represents the robust scaling estimate in the t-th iteration. This indicates the second variable.

[0051] The second variable represents a supplement to the specific expression of function B, which corresponds to the following here. , representing the standardized residual.

[0052] The thermal resistance measurement results are robust fit values ​​at all data points. This reflects the results of thermal resistance measurements of gallium nitride transistors (GaNHEMTs).

[0053] In some embodiments of the present invention, a method for measuring the thermal resistance of gallium nitride transistors based on laser thermal reflectivity is provided. In the original structure function algorithm's input preprocessing stage, local linear fitting and row residual calculation are added to form an integrated architecture of "noise reduction preprocessing - structure function operation". It has the following technical advantages: (1) Based on local linear fitting, the algorithm can adaptively distinguish between noise and effective features, reducing noise while preserving data details; (2) Modular design, strong portability, and high computational efficiency; (3) Adaptable to various types of noise such as Gaussian noise and impulse noise, compatible with data of different dimensions, and stable and reliable under complex working conditions.

[0054] It should be noted that different embodiments may produce different beneficial effects. In different embodiments, the beneficial effects may be any one or a combination of the above, or any other possible beneficial effects.

Claims

1. A gallium nitride transistor thermal resistance measurement device based on laser thermal reflectivity, characterized in that, Includes a measurement and control module, an optical path module, and a bearer module; The carrier module includes a manual three-dimensional stage (10) and a constant temperature platform (9) disposed on the manual three-dimensional stage (10), the constant temperature platform (9) being used to carry the device under test (8). The measurement and control module includes a host computer (1), a laser driver (2), a photoelectric detection component (13), a data acquisition card (14), and a power supply (15); the host computer (1) is electrically connected to the laser driver (2), the data acquisition card (14), and the power supply (15); the power supply (15) is used to supply power to the device under test (8); The optical path module includes a laser (3), a first optical lens (4), a first beam splitter (5), a second beam splitter (6), an objective lens (7), a focusing lens (12), and a CCD camera (11). The laser driver (2) is electrically connected to the laser (3); the beam emitted by the laser (3) is collimated by the first optical lens (4) and then incident on the first beam splitter (5). The outgoing light path of the first beam splitter (5) is coupled to the second beam splitter (6); the outgoing light path of the second beam splitter (6) is focused onto the device under test (8) through the objective lens (7); The reflected light from the device under test (8) returns to the second beam splitter (6) via the objective lens (7); The second beam splitter (6) splits part of the reflected light into the CCD camera (11) for observing the position of the light spot; and transmits or reflects another part of the reflected light back to the first beam splitter (5). The first beam splitter (5) couples the beam from the second beam splitter (6) to the focusing lens (12). The outgoing light path of the focusing lens (12) is coupled to the input terminal of the photodiode of the photodetector assembly (13); the output terminal of the photodetector assembly (13) is electrically connected to the data acquisition card (14).

2. The gallium nitride transistor thermal resistance measurement device based on laser thermal reflectivity according to claim 1, characterized in that, The photoelectric detection component (13) includes: Resistors R1, R2, R3, R4, R5, R6, R7, R8, R9, and R10; a photodiode; a first operational amplifier; a second operational amplifier; a third operational amplifier; a fourth operational amplifier; and a fifth operational amplifier. The positive terminal of the photodiode is connected to the inverting input of the first operational amplifier. The negative terminal of the photodiode is connected to both the non-inverting input of the first operational amplifier and one end of resistor R2. The other end of resistor R2 is connected to both the output of the first operational amplifier and the non-inverting input of the fourth operational amplifier. The inverting input of the fourth operational amplifier is connected to one end of resistor R6 and one end of resistor R7. The output of the fourth operational amplifier is connected to the other end of resistor R7 and one end of resistor R8. Resistor R8... The other end is connected to the grounding resistor R10 and the non-inverting input of the fifth operational amplifier. The other end of the resistor R6 is connected to one end of the resistor R5 and the inverting input of the third operational amplifier. The non-inverting input of the third operational amplifier is connected to the output of the second operational amplifier and one end of the resistor R1. The other end of the resistor R1 is connected to the inverting input of the second operational amplifier. The non-inverting input of the second operational amplifier is connected to the grounding resistor R3. The output of the third operational amplifier is connected to the other end of the resistor R5 and one end of the resistor R4. The other end of the resistor R4 is connected to the inverting input of the fifth operational amplifier and one end of the resistor R9. The output of the fifth operational amplifier is connected to the other end of the resistor R9 and the positive terminal of the output of the photodetector. The negative terminal of the output of the photodetector is grounded.

3. A method for measuring the thermal resistance of gallium nitride transistors based on laser thermal reflectivity, applied to the gallium nitride transistor thermal resistance measuring device based on laser thermal reflectivity as described in any one of claims 1 to 2, comprising: S1: Obtain laser reflectivity data of gallium nitride transistors at different temperatures; S2: Calculate the distance weight of each data point of the laser reflectivity data relative to the target point to obtain the distance weight of each data point; S3: Based on distance weights, perform local linear fitting to obtain the current fitted value of the target point; S4: Based on the current fitted value of the target point, perform residual calculation on all data points to obtain a robust scaling estimate of the residuals; S5: Use robust scaling estimation of residuals to update the combined weights and obtain the next update result; determine whether the next update result meets the preset threshold for the change of fitted value and the maximum number of iterations. When the next update result meets either the preset threshold for the change of fitted value or the maximum number of iterations, stop the iteration, obtain the thermal resistance measurement result, and complete the measurement of the thermal resistance of the gallium nitride transistor. Otherwise, the updated result is returned to S3 for iterative calculation.

4. The method for measuring the thermal resistance of gallium nitride transistors based on laser thermal reflectivity according to claim 3, characterized in that, The expression for the distance weight is: ； ； ； in, express relative to the distance weight of the target data point, Represents the target data point. This represents a cubic kernel function. This represents the i-th data point. This represents the local window width of the target data point. Indicates the first variable.

5. The method for measuring the thermal resistance of gallium nitride transistors based on laser thermal reflectivity according to claim 3, characterized in that, The expression for the current fitted value of the target point is: ； ； in, This represents the minimum intercept term obtained from the solution. This represents the term with the minimum slope obtained from the solution. Represents the function to be minimized. Let represent the combined weight of the target data point in the (t-1)th iteration, where i represents the data point index, n represents the number of data points, and t represents the iteration number. Represents the target data point. This represents the observation data of the i-th data point. Represents the intercept term. Represents the slope term. This represents the i-th data point. This represents the current fitted value of the target data point x.

6. The method for measuring the thermal resistance of gallium nitride transistors based on laser thermal reflectivity according to claim 3, characterized in that, The expression for the robust scaling estimate is: ； in, This represents the robust scaling estimate in the t-th iteration. Indicates the absolute deviation of the median. Let represent the residual of the i-th data point in the t-th iteration, where i represents the data point index and t represents the iteration number.

7. The method for measuring the thermal resistance of gallium nitride transistors based on laser thermal reflectivity according to claim 3, characterized in that, The expression for the next update result is: ； ； ； ； in, This represents the combined weight of the i-th data point in the t-th iteration. Represents the target data point. express relative to the distance weight of the target data point, Indicates a stable weighting. This represents a two-weighted function. This represents the residual of the i-th data point in the t-th iteration. This represents the robust scaling estimate in the t-th iteration. This indicates the second variable.

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