Thickness dependence determination method for thermal conductivity of thin film and application of thickness dependence determination method
By preparing and thinning thin film samples, and combining magnetron sputtering and time-domain thermal reflectometry, the problem of accuracy in the thickness-dependent determination of thin film thermal conductivity was solved, achieving efficient and low-cost thin film thermal conductivity determination, which is suitable for thin film material applications in complex thermal environments.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-29
- Publication Date
- 2026-03-27
AI Technical Summary
Existing technologies are insufficient to accurately determine the thickness dependence of thermal conductivity in thin film materials below the micrometer level. Traditional methods are inefficient, costly, and inconsistent, resulting in large dispersion of measurement results.
Thin film samples were prepared by physical vapor deposition or chemical vapor deposition, and the thickness was controlled by polishing. A reflective layer was deposited by magnetron sputtering, and the thermal emission signal was measured by time-domain thermal reflectometry. The relationship between the thermal conductivity of the thin film and its thickness was then fitted by a model.
It enables precise measurement of thermal conductivity of thin films ranging from hundreds of nanometers to micrometers, improves measurement efficiency, reduces costs, ensures film consistency, provides accurate film thickness-thermal conductivity function relationship, and supports the application of thin film materials in complex thermal environments.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of nanoscale thermal conductivity, specifically relating to a method for measuring the thickness dependence of thin film thermal conductivity and its application. Background Technology
[0002] With the rapid development of micro-sodium fabrication technology, thin film materials are widely used in semiconductors, energy conversion, and surface protection. As service environments become increasingly complex, thin film materials often operate under complex thermal conditions, frequently affected by thermal loads in these fields. Thermal conductivity is a core parameter for evaluating the thermal properties of thin films; however, due to factors such as size effects and interface scattering, the thermal conductivity of thin film materials typically varies significantly with thickness. Therefore, accurately determining the thickness dependence of thin film thermal conductivity is crucial for material design and application optimization.
[0003] Furthermore, most thin film materials currently have thicknesses below the micrometer level, and traditional thermal conductivity testing methods, such as laser flash powder, struggle to obtain accurate results for films below this level. Moreover, studying the thickness dependence of thermal conductivity typically requires pre-preparing a series of thin film samples of varying thicknesses. This process is not only inefficient, time-consuming, and costly, but also inevitably involves slight drifts in process parameters during long deposition periods, making it impossible to fully guarantee consistency between samples. Consequently, the functional relationship between measured thermal conductivity data and thickness exhibits significant dispersion, reducing its accuracy.
[0004] Therefore, there is an urgent need for a method that can systematically and accurately determine the thickness dependence of thin film thermal conductivity in order to support the application and development of thin film materials in complex thermal environments. Summary of the Invention
[0005] The technical problem to be solved by the present invention is to address the shortcomings of the existing technology by providing a method for measuring the thickness dependence of thin film thermal conductivity and its application. This method provides more accurate measurement of the film thickness-thermal conductivity function relationship and can measure films from hundreds of nanometers to micrometers, with a wide range of applications.
[0006] To solve the above technical problems, the following technical solution is adopted: This invention provides a method for determining the thickness dependence of thin film thermal conductivity, the specific steps of which are as follows: 1) Prepare a set of thin film samples of the same thickness on a substrate using physical vapor deposition or chemical vapor deposition, and then thin them by polishing. By controlling different polishing times, obtain 4 to 5 thin film samples with a multiple increase in thickness. 2) An Al reflective layer of the same thickness is deposited on the surface of the thin film sample obtained in step 1) by magnetron sputtering; 3) The ratio of the co-phase voltage to the out-of-phase voltage as a function of the delay time was determined using the time-domain thermal reflectance method on the thin film sample after the Al reflective layer was deposited in step 2). 4) Use the model to simulate and calculate the functional relationship described in step 3), and finally fit the thermal conductivity of the film at different thicknesses; 5) Fit the thermal conductivity obtained in step 4) to the thickness as a function.
[0007] According to the above scheme, in step 1), the thin film is prepared on the substrate by physical vapor deposition or chemical vapor deposition. By controlling the deposition process parameters, the thin film should have chemical stability and good adhesion at room temperature, and the same group of thin films should also have the same thickness.
[0008] According to the above scheme, in step 1), the substrate is stainless steel or hard alloy.
[0009] According to the above scheme, in step 1), the thinning process by polishing is specifically as follows: during the thin film polishing process, diamond polishing paste is dripped onto the contact point between the thin film surface and the polishing cloth; the thinning of the thin film is completed by controlling the polishing time; another thin film in the same group is replaced, and the above process is repeated and the polishing time is changed to prepare samples of different thicknesses.
[0010] Preferably, the polishing machine is turned on, and the film is placed horizontally on the polishing cloth, ensuring that the surface of the film is parallel to the surface of the polishing cloth.
[0011] According to the above scheme, in step 1), the polishing paste used for polishing has a particle size of 20,000 mesh or higher to ensure that the surface quality of the film after polishing meets the test requirements of the time-domain thermal reflectance method.
[0012] According to the above scheme, in step 1), there are 4 to 5 thin film samples with a thickness that increases exponentially. Between two samples with adjacent thicknesses, the thickness of the thicker sample is 1.5 to 4 times the thickness of the thinner sample.
[0013] According to the above scheme, in step 2), the thin film sample is ultrasonically cleaned before depositing the Al reflective layer.
[0014] Preferably, ultrasonic cleaning specifically involves: placing film samples of different thicknesses in anhydrous ethanol and ultrasonically cleaning for 15-30 minutes; after cleaning, using Ar gas to purge and remove the ethanol from the film surface.
[0015] According to the above scheme, in step 2), the thickness of the Al reflective layer is 50~100nm.
[0016] According to the above scheme, in step 2), depositing an Al reflective layer on the surface of the thin film sample specifically involves: suspending all cleaned thin film samples on the rotating frame of the magnetron sputtering equipment, making the thin film surface parallel to the rotation axis of the frame; placing the rotating frame with the thin film samples in the cavity of the magnetron sputtering equipment, ensuring that the frame can rotate normally in the cavity; setting the process parameters for depositing the Al reflective layer and turning on the magnetron sputtering equipment; controlling the deposition time according to the Al deposition rate to ensure that the thickness of the Al reflective layer on the surface of the thin film sample is 50~100nm.
[0017] According to the above scheme, in step 3), thermal signal measurement is performed on all thin film samples coated with Al reflective layer. Specifically, a laser beam with a repetition frequency of 80 MHz is generated by a Ti:sapphire laser, and then separated into a pump beam and a probe beam by a polarization beam splitter (PBS). The pump beam is used to heat the sample, and its modulation frequency is controlled by an electro-optic modulator (EOM) and a signal generator. Since the metal reflectivity is linearly related to temperature, the probe beam can measure the temperature change of the sample surface. By adjusting the mechanical delay, the relative time difference between the two beams reaching the sample surface can be controlled, thereby realizing the measurement of the surface temperature evolution over time. The experiment finally generates a ratio versus time curve, where the ratio is defined as the ratio of in-phase voltage to out-of-phase voltage.
[0018] According to the above scheme, in step 4), the model is:
[0019] Where r is the radial coordinate, z is the normal coordinate in the depth direction, t is time, θ is temperature, ρ is density, c is specific heat, and kr and kz are the in-plane and out-of-plane thermal conductivity, respectively.
[0020] Preferably, the thermal conductivity of films of different thicknesses can be obtained by substituting the film density, specific heat, and the ratio of in-phase voltage to out-of-phase voltage as a function of time delay into the above model.
[0021] According to the above scheme, in step 5), the relationship between the thermal conductivity and thickness of the thin film is fitted into a function using the function fitting function attached to Matlab or Origin software.
[0022] This invention provides an application of the thickness dependence measurement method for the thermal conductivity of the above-mentioned thin film. Based on the functional relationship between thermal conductivity and thickness obtained by the measurement method, the thermal conductivity of the thin film can be directly obtained from the actual measured film thickness without the need for complex thermal conductivity measurement.
[0023] The beneficial effects of this invention are as follows: This invention provides a method for determining the thickness dependence of thin film thermal conductivity. First, thin films of the same thickness are prepared in the same batch. Then, the film is thinned by grinding and polishing, significantly improving efficiency and reducing costs. This method also avoids minor drifts in process parameters during deposition at different times in multiple batches, preventing the influence of process randomness and ensuring film consistency. Combined with time-domain thermal reflectometry to determine thermal conductivity, the final fitted film thickness-thermal conductivity function relationship is more accurate and applicable to films at scales from hundreds of nanometers to micrometers. Furthermore, in practical applications, the corresponding thermal conductivity can be quickly obtained from the film thickness-thermal conductivity function relationship by simply measuring the film thickness, eliminating the need for complex thermal conductivity measurements and effectively supporting the application and development of thin film materials in complex thermal environments. Attached Figure Description
[0024] Figure 1 This is a flowchart of the method for determining the thickness dependence of the thermal conductivity of TiSiN thin films in this invention; Figure 2 These are scanning electron microscope cross-sectional and surface images of the four thinned TiSiN films obtained in Example 1. Figure 3 This is a transmission electron microscope image of the Al reflective layer deposited on the TiSiN surface in step 4 of Example 1; Figure 4 This refers to the fitting results of thermal reflection signals of TiSiN thin films with different thicknesses in step 5 of Example 1; Figure 5 This refers to the fitting result of the TiSiN film thickness-thermal conductivity function in step 7 of Example 1; Figure 6 This refers to the fitting results of thermal reflection signals of TiN thin films with different thicknesses in step 5 of Example 2; Figure 7 The result of fitting the TiN film thickness-thermal conductivity function in step 7 of Example 2 is shown. Detailed Implementation
[0025] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below using embodiments and in conjunction with the accompanying drawings.
[0026] Example 1 A method for determining the thickness dependence of thin film thermal conductivity, the flowchart of which is shown below. Figure 1 As shown, the thermal conductivity-thickness dependence of TiSiN thin films was measured, and the specific steps of the measurement method are as follows: 1) A set of TiSiN films of the same thickness were deposited using a self-made high-power pulsed magnetron sputtering system. A rectangular TiSi target (Ti:Si = 90:10, dimensions 483 mm × 81 mm) was sputtered using a high-power pulsed power supply (Truplasma, 4002 G2, Germany) to deposit the TiSiN film. Before deposition, the hard alloy substrate was ultrasonically cleaned in anhydrous ethanol for 15 minutes to remove surface impurities. The cleaned silicon substrate was mounted on a rotating support, with a target-to-substrate spacing of 100 mm. At 10... -3 Under a vacuum environment, 100 sccm of argon gas was introduced to perform glow discharge cleaning on the silicon substrate, followed by 15 minutes of etching using an AEG ion source system to enhance adhesion. The TiSiN thin film deposition process used 4 kW power, a substrate bias voltage of 100 V, a deposition temperature of 350°C, and a deposition time of 3 hours. 2) The TiSiN film prepared in step 1) was thinned using a polishing machine. The specific method is as follows: The polishing machine was turned on, and the TiSiN film was placed horizontally on the polishing cloth, ensuring that the surface of the TiSiN film was parallel to the surface of the polishing cloth. During the polishing process, diamond polishing paste with a particle size of 25,000 mesh was dripped onto the contact area between the film surface and the polishing cloth. The thinning of the film was completed by controlling the polishing time. Another film from the same group was used, and the above process was repeated with increased polishing time to prepare samples of different thicknesses. After the above thinning process, the final result was as follows: Figure 2 The four TiSiN films shown are 85nm (TiSiN-1), 330nm (TiSiN-2), 630nm (TiSiN-3), and 1090nm (TiSiN-4). 3) Perform ultrasonic cleaning on TiSiN film samples with different degrees of thinning in step 2). Specifically, place TiSiN film samples of different thicknesses in beakers containing anhydrous ethanol; place the beakers in an ultrasonic cleaner, set the cleaning time to 20 minutes and turn on the cleaner; after cleaning, use Ar gas to purge and remove the ethanol from the film surface. 4) Suspend all the cleaned TiSiN thin film samples from step 3) on the rotating frame of the magnetron sputtering equipment, ensuring the film surface is parallel to the rotation axis of the frame; place the frame with the TiSiN thin film samples inside the cavity of the magnetron sputtering equipment, ensuring the frame can rotate normally within the cavity; set the deposition temperature to 100℃ and... -3 Starting the magnetron sputtering equipment under a vacuum environment; such as... Figure 3 As shown, the thickness of the Al reflective layer on the surface of the thin film sample is approximately 65 nm. 5) Thermal signal measurements were performed on all thin film samples coated with the Al reflective layer in step 4). Specifically, a laser beam with a repetition frequency of 80 MHz was generated using a Ti:sapphire laser, and then separated into a pump beam and a probe beam using a polarization beam splitter (PBS). The pump beam was used to heat the sample, and its modulation frequency was controlled by an electro-optic modulator (EOM) and a signal generator. The pump beam frequency was adjusted to 1.82 MHz, 4.12 MHz, and 9.7 MHz using the EOM to measure the thermal properties of TiSiN-2 to TiSiN-4. Due to its extremely thin thickness, only the frequencies of 4.12 MHz and 9.7 MHz were used for TiSiN-1. Figure 4 Experimental data (hollow dots) for TiSiN-1 to TiSiN-4 and the corresponding fitted curves of the ratio of in-phase voltage to out-of-phase voltage as a function of time delay are presented, showing that the measurement results are in high agreement with theoretical predictions. By fitting the experimental curves to the following model, the target thermal properties of the samples can be accurately determined:
[0027] Where r is the radial coordinate, z is the normal coordinate in the depth direction, t is time, θ is temperature, ρ is density, c is specific heat, and kr and kz are the in-plane and out-of-plane thermal conductivity, respectively.
[0028] 6) By substituting the density, specific heat, and voltage ratio-delay time function obtained in step 5) into the above model, the thermal conductivity of films with different thicknesses can be obtained; the thermal conductivity of TiSiN films with thicknesses of 85nm, 330nm, 630nm, and 1090nm are 2.5 W / mK, 4.8 W / mK, 6.1 W / mK, and 8.1 W / mK, respectively. 7) The relationship between the thermal conductivity and thickness of the thin film was fitted into a function using the function fitting function provided in Origin software. The final fitting result is shown below. Figure 5 As shown, specifically ,in Thermal conductivity of thin films, in W / m -1 K -1 h represents the thickness, measured in nm.
[0029] Example 2 The method for determining the thickness dependence of thin film thermal conductivity is similar to that in Example 1, except that the target material is changed from TiSi to Ti, and the thin film material is changed from TiSiN to TiN; the thin film thickness is changed to 150nm, 500nm, 1000nm, and 1600nm by changing the polishing time; the thermal reflection signal fitting results are as follows. Figure 6As shown, the corresponding thermal conductivity at different thicknesses are 4.4 W / mK, 9.5 W / mK, 13.8 W / mK, and 26.4 W / mK, respectively; the thickness dependence of the thermal conductivity of the TiN thin film is as follows. Figure 7 As shown, specifically .
[0030] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.
Claims
1. A method of measuring thickness dependence of thermal conductivity of a thin film, characterized by, The specific steps are as follows: 1) A set of thin film samples with the same thickness are prepared on a substrate by physical vapor deposition or chemical vapor deposition method, and then thinned by polishing to obtain 4-5 thin film samples with thickness in multiples; 2) An Al reflective layer is deposited on the surface of the thin film sample obtained in step 1) by magnetron sputtering method; 3) The function relationship between the ratio of in-phase voltage to out-of-phase voltage and delay time of the thin film sample after depositing the Al reflective layer in step 2) is simulated by time-domain thermal reflection method; 4) The function relationship in step 3) is simulated by a model, and the thermal conductivity of the thin film at different thicknesses is finally fitted; 5) The function relationship between the thermal conductivity and the thickness obtained in step 4) is fitted.
2. The assay method according to claim 1, characterized by In step 1), the substrate is stainless steel or hard alloy.
3. The assay method according to claim 1, characterized by, In step 1), the particle size of the polishing paste used for polishing is more than 20,000 mesh.
4. The assay method according to claim 1, characterized by, In step 1), the 4-5 thin film samples with thickness in multiples, the thickness of the thick sample is 1.5-4 times the thickness of the thin sample.
5. The assay method according to claim 1, characterized by, In step 2), the thickness of the Al reflective layer is 50-100 nm.
6. The assay method according to claim 1, characterized by, In step 2), the Al reflective layer is deposited on the surface of the thin film sample, specifically: after cleaning, all the thin film samples are hung on the rotating shaft of the magnetron sputtering equipment, and the surface of the thin film is parallel to the rotating shaft; the rotating shaft with the thin film sample is placed in the cavity of the magnetron sputtering equipment to ensure that the rotating shaft can rotate normally in the cavity; set the process parameters for depositing the Al reflective layer and start the magnetron sputtering equipment; control the coating time according to the deposition rate of Al to ensure that the thickness of the Al reflective layer on the surface of the thin film sample is 50-100 nm.
7. The assay method according to claim 1, characterized by, In step 3), the thermal emission signal of all thin film samples coated with Al reflective layer is determined, specifically: a laser beam is generated by a titanium sapphire laser, and then separated into pump beam and probe beam by a polarization beam splitter; the pump beam is used to heat the sample, and the modulation frequency is controlled by an electro-optic modulator and a signal generator; since the metal reflectivity is linearly related to the temperature, the probe beam can measure the temperature change on the surface of the sample, and by adjusting the mechanical delay, the relative time difference of the two beams reaching the sample surface can be controlled, thereby realizing the measurement of the surface temperature evolution over time; the final experiment generates a curve of the ratio changing with the delay time, wherein the ratio is defined as the ratio of in-phase voltage to out-of-phase voltage.
8. The assay method of claim 1, wherein In step 4), the model is: where r is the radial coordinate, z is the normal coordinate in the depth direction, t is the time, θ is the temperature, ρ is the density, c is the specific heat, kr and kz are the in-plane and out-of-plane thermal conductivities, respectively.
9. The assay method of claim 1, wherein In step 5), the corresponding relationship between the thermal conductivity of the thin film and the thickness is fitted into a function by the function fitting function attached in Matlab or Origin software.
10. Use of the method for measuring the thickness dependence of the thermal conductivity of a thin film according to any one of claims 1 to 9, characterized in that Based on the function relationship between the thermal conductivity and the thickness obtained by the determination method, the thermal conductivity of the thin film can be directly obtained according to the actual measured thickness of the thin film.