A GaN thermal resistance testing method based on the differential 3ω method
By using the differential 3ω method and transient electrical method, and measuring the temperature difference using two sets of comparative experiments, the error problem of the traditional 3ω method in GaN thin film thermal resistance measurement was solved, and more accurate thermal resistance testing was achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- NANJING CLP CORE VALLEY HIGH FREQUENCY DEVICE IND TECH RES INST CO LTD
- Filing Date
- 2026-04-13
- Publication Date
- 2026-06-30
AI Technical Summary
The traditional 3ω method has a large error when measuring the thermal resistance of GaN thin films, requiring the construction of a heat transfer model and the calculation results are inaccurate.
The differential 3ω method was used to measure the average temperature difference through two sets of control experiments. The transient electrical method and thermoelectric signal electrode design were used to reduce the uncertainty in determining the thermal conductivity of the thin film under test and to calculate the thermal resistance of the GaN thin film.
This reduces testing errors, improves the accuracy of GaN thin film thermal resistance measurement, and provides technical support for heteroepitaxial interface control and optimization.
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Figure CN122306875A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of GaN device development and fabrication, specifically a GaN thermal resistance testing method based on the differential 3ω method. Background Technology
[0002] The 3ω method involves fabricating a thin, elongated metal electrode on the sample surface. This electrode functions as both a heater (generating heat by applying an alternating current with frequency ω) and a temperature sensor (measuring the third harmonic voltage coupled to the electrode to determine its temperature rise). The relationship between the electrode temperature rise and the third harmonic voltage is as follows: A schematic diagram of the measuring electrodes is shown below. Figure 2 As shown, a metal strip with a geometric scale of micrometers is fabricated on the surface of the sample using semiconductor photolithography and evaporation processes, thus forming the basic test structure for testing the thermal conductivity of the material. Two pads are processed at each end of the metal strip to serve as the sensor output interface and the drive current input interface, respectively, and are connected to the external test circuit through gold wires. The thermal properties of the sample are derived by measuring the third harmonic (3ω signal) generated by the heating signal of the measuring electrode. This method is widely used for the measurement of thermal properties of bulk materials and thin films.
[0003] The traditional 3ω method obtains the thermal resistance of thin film materials through single-sample testing. This method requires not only knowledge of the substrate's thermal conductivity but also the construction of a heat transfer model to calculate the simulated substrate temperature rise, and then to calculate the film's thermal resistance. However, due to the complexity of the system, these simulations often contain biases, leading to significant errors in the calculated thermal resistance. Summary of the Invention
[0004] To address the aforementioned problems, the present invention aims to provide a GaN thermal resistance testing method based on the differential 3ω method, so as to reduce errors in the thin film thermal resistance testing process and achieve accurate measurement of the thermal resistance of the thin film of the sample under test.
[0005] The specific technical solution for achieving the objective of this invention is as follows:
[0006] A GaN thermal resistance testing method based on the differential 3ω method includes the following steps:
[0007] Step 1: Set up the control test sample;
[0008] Step 2: Set up thermoelectric signal electrodes on the control test samples respectively;
[0009] Step 3: Test the control test samples separately based on the transient electrical method parameter control method;
[0010] Step 4: Determine the thermal resistance of the GaN thin film based on the test results.
[0011] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0012] The present invention employs the differential 3ω method, using the average temperature difference measured between two sets of control experiments. One set involves the sample, and the other set is conducted on a system without the thin film being studied, thereby reducing the uncertainty in determining the thermal conductivity of the thin film under test.
[0013] This scheme, based on transient electrical methods, achieves accurate testing and characterization of the thermal resistance of GaN thin films through the design of control samples, the design and fabrication of thermoelectric signal electrodes, the parameter control and testing of transient electrical methods, and the differential calculation of GaN thin film thermal resistance. During the testing process, it was found that the measured thermal resistance is insensitive to the substrate thermal conductivity, and the contribution of any additional layer is largely eliminated by the measurement of the control sample. This reduces testing errors, improves the accuracy of test results, and provides technical support for the control and optimization of GaN material heteroepitaxial interfaces.
[0014] The present invention will be further described below with reference to specific embodiments. Attached Figure Description
[0015] Figure 1 This is a schematic diagram of the GaN thermal resistance testing method based on the differential 3ω method of the present invention.
[0016] Figure 2 This is a schematic diagram of two sets of control test samples in an embodiment of the present invention. Figure 1 .
[0017] Figure 3 This is a schematic diagram of two sets of control test samples in an embodiment of the present invention. Figure 2 . Detailed Implementation
[0018] Example
[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. The described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0020] As indicated in this application and claims, unless the context clearly indicates otherwise, the words "a," "an," "an," and / or "the" do not specifically refer to the singular and may also include the plural. Generally speaking, the terms "comprising" and "including" only indicate the inclusion of explicitly identified steps and elements, which do not constitute an exclusive list, and the method or apparatus may also include other steps or elements.
[0021] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values of the components and steps described in these embodiments do not limit the scope of this application. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following drawings denote similar items; therefore, once an item is defined in one drawing, it need not be further discussed in subsequent drawings.
[0022] Combination Figure 1 A GaN thermal resistance testing method based on the differential 3ω method includes the following steps:
[0023] Step 1: Set up the control test sample;
[0024] The first test sample includes substrate material A;
[0025] The second test sample includes substrate material A and GaN thin film material B epitaxially mounted on the substrate, wherein the thickness of GaN thin film material B is ≤2µm. Figure 2 As shown;
[0026] The substrate material A of the two sets of control test samples is the same. In this embodiment, both sets of test samples use SiC or Si substrate material.
[0027] Step 2: Set up thermoelectric signal electrodes on the control test samples respectively;
[0028] The thermoelectric signal electrode includes an effective region D and a circuit interconnection region C, wherein the circuit interconnection region C is used to externally power the effective region D;
[0029] The length of the effective region D is D l The thickness is set between 750um and 1500um, and between 50nm and 100nm; the effective region D has an epitaxial length of 150um-250um.
[0030] There are four interconnection areas C in total, each a square with a size of 200um-500um.
[0031] In this embodiment, the thermoelectric signal electrode material is Ti / Au, which is prepared on the surface of the sample under test using a Ti-Au evaporation process. The Ti thickness is 5-10 nm to improve the adhesion between the metal and the sample under test, while the Au thickness is 100-200 nm for generating and detecting the thermoelectric signal. The overall electrode design size is less than 1800 μm * 500 μm; too small a size would affect the convenience of testing, while too large a size would increase the cost of the device. The thermoelectric signal electrodes on the surfaces of the two sets of control test samples are identical in shape, material, and fabrication process.
[0032] Step 3: Test the control test samples separately based on the transient electrical method parameter control method;
[0033] When testing the control test sample based on the transient electrical method parameter control method, the test frequency is controlled between 3000Hz and 100Hz, based on the wafer functional layer structure.
[0034] The frequency test interval is controlled to be 5Hz~25Hz, and the number of test frequency points is ≥100;
[0035] The number and spacing of selected frequency points are coordinated and optimized to meet time and accuracy requirements.
[0036] The changes in frequency of the fundamental frequency and the third harmonic signal were tested separately.
[0037] In addition, the testing conditions for both control test samples remained consistent throughout the entire process.
[0038] Step 4: Determine the thermal resistance of the GaN thin film based on the test results;
[0039] In the calculation, a frequency range ≥1000Hz and a number of frequency points ≥100 were selected. The surface temperature rise of the second and first test samples was calculated using the transient electrical method formula. Then, the temperature rise of the second test sample was subtracted from the surface temperature rise of the first test sample to obtain the temperature difference between the upper and lower surfaces of the GaN thin layer. Finally, the thermal resistance of the GaN thin layer was calculated using the differential thermal resistance calculation formula.
[0040]
[0041] Where b is the electrode half-width, l is the effective electrode length, and V 3ω Where V is the third harmonic voltage, P is the heating power, α is the electrode temperature sensitivity coefficient, and V is the third harmonic voltage. ω The voltage is the fundamental frequency. The subscripts r+f and r represent samples with GaN layer and substrate, and samples with only substrate and no GaN layer, respectively.
[0042] This method removes the influence of parasitic interfacial thermal resistance, such as the thermal resistance between the metal heater and the underlying film, and the thermal resistance between the substrate and the film under test, by subtracting the temperature rise signal of the control sample from the measured temperature rise signal of the thin film sample under test. Similarly, other non-test factors that affect the results, such as buffer layers or nucleation layers, can also be subtracted from the total experimental temperature rise using similar control groups.
[0043] In this embodiment, a 10*10mm SiC wafer and a SiC-based GaN epitaxial wafer were selected as the first and second test samples.
[0044] Photolithographically evaporated electrodes were formed on the sample surface with a thickness of 100 nm (20 nm Ti, 80 nm Au), a width of 10 μm, and an effective length of 750 μm. The effective length was extended by 250 μm to form a 4-way circuit interconnection region C, which was a square with a size of 200 μm.
[0045] Subsequently, the SiC wafer and the SiC-based GaN epitaxial wafer test samples were placed on the test stage for interconnection and electrical testing and analysis were performed. The test frequency was designed to be 100 Hz~1100 Hz, and the frequency control was set with a test interval of 10 Hz and 135 test frequency points. The transient electrical method input signal voltage was adjusted to ensure that the fundamental frequency was at 400 mV to meet the high-precision acquisition of electrical signals. The test of the changes of the fundamental frequency and the third harmonic signal with frequency was started.
[0046] Finally, the surface temperature rise of the SiC-based GaN epitaxial wafer and the SiC wafer was calculated using the transient electrical method. To ensure accuracy, the frequency range was selected as 1000 Hz (100Hz-1100Hz), and 101 frequency points were selected. The thermal resistance of the GaN thin layer was calculated to be 20.18 m2K / GW using the thermal resistance calculation formula.
[0047] This differential 3ω method uses the average temperature difference measured between two sets of control experiments: one involving the sample and the other on a system without the thin film being studied, serving as a control. The differential method can extract signal changes entirely caused by the thin film under test.
[0048] Figure 3 The structure of the reference sample and the structure containing the film under test in this embodiment are particularly useful for analyzing complex systems composed of multiple films (including dielectric layers, nucleation layers, or buffer layers) because they can determine the thermal conductivity of a specific film in a multilayer structure. In such a system, the third harmonic voltage on the metal heater depends on the temperature rise caused by the entire multilayer structure. Therefore, the measured heater temperature rise is the sum of thermal oscillation contributions from different components of the entire system.
[0049] By subtracting the temperature rise signal of the control sample from the measured temperature rise signal of the test film sample, the influence of parasitic interfacial thermal resistance can be eliminated. Examples include the thermal resistance between the metal heater and the underlying film, and the thermal resistance between the substrate and the test film. Similarly, other non-tested factors affecting the results, such as buffer layers or nucleation layers, can also be subtracted from the total experimental temperature rise. For the control experiment, the heater structure deposited on the test sample and the control sample must be identical, and the input power must also be the same.
[0050] Compared to the traditional slope method, the differential 3ω method reduces the uncertainty in determining the thermal conductivity of the thin film. The measured thermal resistance is insensitive to the substrate thermal conductivity, and the contribution of any additional layer is largely eliminated by the measurement of the control sample.
[0051] This invention also provides a GaN thermal resistance testing system based on the differential 3ω method, comprising the following modules:
[0052] Control test sample module: used to set up control test samples and set thermoelectric signal electrodes on the control test samples respectively;
[0053] Test module: Used to perform separate tests on the control test samples based on the transient electrical method and parameter control method;
[0054] Thermal resistance determination module: used to determine the thermal resistance of GaN thin film based on test results.
[0055] The present invention also provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to perform the following steps:
[0056] Step 1: Set up the control test sample;
[0057] Step 2: Set up thermoelectric signal electrodes on the control test samples respectively;
[0058] Step 3: Test the control test samples separately based on the transient electrical method parameter control method;
[0059] Step 4: Determine the thermal resistance of the GaN thin film based on the test results.
[0060] The present invention also provides a computer-storable medium having a computer program stored thereon, wherein the computer program, when executed by a processor, performs the following steps:
[0061] Step 1: Set up the control test sample;
[0062] Step 2: Set up thermoelectric signal electrodes on the control test samples respectively;
[0063] Step 3: Test the control test samples separately based on the transient electrical method parameter control method;
[0064] Step 4: Determine the thermal resistance of the GaN thin film based on the test results.
[0065] The embodiments described above are merely one implementation method of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.
Claims
1. A GaN thermal resistance testing method based on the differential 3ω method, characterized in that, Includes the following steps: Step 1: Set up the control test sample; Step 2: Set up thermoelectric signal electrodes on the control test samples respectively; Step 3: Test the control test samples separately based on the transient electrical method parameter control method; Step 4: Determine the thermal resistance of the GaN thin film based on the test results.
2. The GaN thermal resistance testing method based on the differential 3ω method according to claim 1, characterized in that, The control test samples consist of two groups; The first test sample includes substrate material; The second test sample includes substrate material and GaN thin film material epitaxially grown on the substrate; The substrate materials of the two sets of control test samples are the same.
3. The GaN thermal resistance testing method based on the differential 3ω method according to claim 2, characterized in that, Step 2, which involves setting thermoelectric signal electrodes on the control test samples, specifically involves: The thermoelectric signal electrode includes an effective region and a circuit interconnection region, wherein the circuit interconnection region is used to enable external power application to the effective region; The length D of the effective region l The thickness is set between 750um~1500um, and the thickness is between 50nm~100nm; the length of the effective region is between 150um-250um.
4. The GaN thermal resistance testing method based on the differential 3ω method according to claim 3, characterized in that, The circuit interconnection area is a square with a size of 200um-500um.
5. The GaN thermal resistance testing method based on the differential method according to claim 2, characterized in that, Step 3, which involves testing the control test samples using the transient electrical parameter control method, specifically includes: When testing the control test sample based on the transient electrical method parameter control method, the test frequency is controlled between 3000 Hz and 100 Hz, based on the wafer functional layer structure. The frequency test interval is controlled to be 5Hz~25Hz, and the number of test frequency points is ≥100; The number and spacing of selected frequency points are coordinated and optimized to meet time and accuracy requirements. The changes of the fundamental frequency and the third harmonic signal with frequency were tested respectively.
6. The GaN thermal resistance testing method based on the differential 3ω method according to claim 5, characterized in that, The step 4, determining the GaN thin-film thermal resistance based on the test results, specifically involves: ； where b is the half width of the electrode, l is the effective length of the electrode, V 3ω is the third harmonic voltage, P is the heating power, a is the electrode temperature sensitivity coefficient, V ω is the fundamental harmonic voltage, the subscripts r+f, r represent the sample with GaN layer and substrate, the sample without GaN layer only with substrate.
7. A GaN thermal resistance testing system based on the differential 3ω method, characterized in that, Includes the following modules: Control test sample module: used to set up control test samples and set thermoelectric signal electrodes on the control test samples respectively; Test module: Used to perform separate tests on the control test samples based on the transient electrical method and parameter control method; Thermal resistance determination module: used to determine the thermal resistance of GaN thin film based on test results.
8. A computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the method according to any one of claims 1-6.
9. A computer-storable medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1-6.