Microstructure thermal conductivity in-situ measurement and Raman synchronous characterization device and measurement method

Abstract

According to the microstructure thermal conductivity in-situ measurement and Raman synchronous characterization device and the measurement method provided by the invention, Raman light is used as a light source, so that the thermal conductivity of a low-dimensional sample can be effectively measured, and Raman spectrum information of different positions of the sample can be obtained at the same time. The method is suitable for samples sensitive to electron beams, and the application range of the technology for measuring the thermal conductivity of the suspended low-dimensional material is greatly widened. The device can obtain Raman spectrum signals at different positions of the sample while measuring the heat conductivity of the sample, so that the crystallinity characterization of the sample structure is realized.

Description

Technical Field

[0001] The invention relates to the field of heat transfer technology, and in particular to a device and a method for in-situ measurement and Raman synchronous characterization of microstructure thermal conductivity. Background Art

[0002] Over the past century, the development of modern electronics has been significantly characterized by the miniaturization and high power density of devices, and this trend continues with the advancement of technology. High-density components generate a lot of heat when running at high speeds. If the heat cannot be dissipated in a timely and effective manner, it will seriously affect the reliability and service life of the device. As components continue to be miniaturized and the size of semiconductor devices gradually decreases, the thermal transport properties of low-dimensional materials have become a research focus. By adjusting and optimizing the design of these materials, micro-nanoelectronic devices can operate under optimal temperature conditions, thereby extending their service life and promoting the progress of the semiconductor industry.

[0003] At present, a variety of methods have been used to measure the thermal conductivity of low-dimensional materials, such as the suspended thermal bridge method, the 3ω method, the Raman method, the time-domain thermal reflection method, the T-bridge method, and the electron beam self-heating method. These methods have their own advantages and disadvantages. For example, the suspended thermal bridge method can measure the intrinsic thermal conductivity of the sample and is not affected by the substrate, but the contact thermal resistance will affect the measurement accuracy; the 3ω method is relatively simple to operate, but has certain requirements on the sample thickness; the Raman measurement error is large; the electron beam self-heating method can avoid the influence of contact thermal resistance and obtain the thermal conductivity of different positions of the sample, and its accuracy is relatively high, but it cannot be used for samples that are sensitive to electron beams.

[0004] The differences from the prior art are as follows;

[0005] Technical comparison with patent CN102944573B "Method for simultaneous measurement of laser absorptivity and thermal conductivity of a single micro-nano wire"

[0006] The temperature calibration of patent CN102944573B is obtained by measuring the offset of characteristic Raman frequency at different temperatures; the temperature calibration of this patent is obtained by using the linear dependence between the resistance of the thermal bridge device and the temperature near 300K. There is an essential difference between the two in the design concept of temperature calibration.

[0007] Patent CN102944573B changes the temperature of the substrate of the sample to be tested by a hot and cold stage, and the measured temperature range is -90℃~90℃, and the thermal properties of the nanowire as a whole are obtained. The measurement environment provided by this patent is a thermostat cooled by liquid helium, and the measured temperature range is 20K–320K, and the thermal conductivity of each point on the nanowire is measured, not the overall behavior. There is an essential difference between the two in the temperature range of measurement and application scenarios.

[0008] The fabrication of the suspended measuring device in patent CN102944573B is to prepare multiple carbon nanotubes on a silicon dioxide / silicon substrate by chemical vapor deposition, and then burn off other unselected samples; this patent uses a nanomanipulator transfer method to transfer a single nanowire to a thermal bridge device, and deposits metal in the contact area. There is an essential difference between the two in the preparation of suspended samples.

[0009] Technical comparison with patent CN113218991A "Non-contact self-heating measurement device and method for micro-nanoscale interface thermal resistance"

[0010] Patent CN113218991A uses electron beam as heat source, and heats nanowires by striking them with electron beam. The heat source of this patent is non-contact Raman light, and Raman light does not directly contact the nanowires. Some materials, such as organic metal frameworks, organic-inorganic hybrid materials, etc. are more sensitive to electron beams. Raman light can prevent the materials from being damaged during the heating process. There is an essential difference between the two in the heating method.

[0011] Patent CN113218991A uses electron beam self-heating method to measure the interface thermal resistance between two different materials by heating the sample at different positions and the temperature rise on both sides of the suspended platform; this patent uses Raman heating method to obtain the thermal conductivity of the material from the slope of the thermal resistance change and the relevant dimensions of the sample, and simultaneously uses Raman signal to characterize the crystallinity of the sample. The parameters of thermal performance measured by the two are essentially different.

[0012] Patent CN113218991A mainly measures the intrinsic interfacial thermal resistance between two materials at room temperature. This patent can further study the influence of different control methods on thermal conductivity, such as defects, stress, phase change, etc., while measuring the intrinsic thermal properties, and can use a liquid helium thermostat to perform variable temperature measurements from 20K to 320K. The application scenarios of the two are essentially different.

[0013] In summary, the existing thermal conductivity measurement methods have made some progress in measuring the thermal conductivity of low-dimensional materials, but they have their own limitations in terms of measurement accuracy, operational complexity, and scope of application. In particular, the current methods cannot simultaneously obtain the lattice structure information of the sample, and the lattice structure (such as defects, stress, phase change, etc.) has an important influence on the thermal transport characteristics. To address this problem, there is an urgent need for a new type of measurement device that can accurately measure the thermal conductivity of low-dimensional materials while also synchronously obtaining the lattice structure information of the material (such as through Raman spectroscopy analysis). This device can combine Raman light as a heat source to accurately control the heating of the sample, and use a highly sensitive sensor to measure the temperature, thereby calculating the thermal conductivity with high precision. At the same time, Raman spectroscopy can provide local lattice structure information of the sample, which can link the thermal conductivity characteristics of the material with its microstructure. This synchronous measurement device will greatly enhance the research level of the thermal properties of low-dimensional materials and provide important data support for the optimal design of micro-nano devices. Summary of the invention

[0014] In order to solve the above technical problems, the present invention proposes a device and method for in-situ measurement of microstructure thermal conductivity and synchronous Raman characterization, aiming to improve the traditional electron beam self-heating method, replacing the heating source from electron beam to Raman laser with non-contact and high-precision heating, so as to solve the problem of thermal conductivity measurement of low-dimensional material samples sensitive to electron beams, and realize in-situ characterization of Raman spectrum of samples. This invention can simultaneously meet the needs of high-precision thermal conductivity measurement and Raman spectrum analysis.

[0015] To achieve the above object, the technical solution adopted by the present invention is:

[0016] The invention discloses an in-situ measurement and Raman synchronous characterization device for microstructure thermal conductivity. The working environment of the in-situ measurement and Raman synchronous characterization device for microstructure thermal conductivity is a vacuum environment. The in-situ measurement and Raman synchronous characterization device for microstructure thermal conductivity comprises two suspended platforms, a substrate and a heat source. The two suspended platforms are arranged symmetrically on the left and right. The suspended platforms and the substrate are connected by 6 cantilever structures. The two suspended platforms are overlapped by one-dimensional nanowires. The heat source uses a Raman laser set above the one-dimensional nanowire as a heat source to heat the sample.

[0017] As a further improvement of the microstructure thermal conductivity in-situ measurement and Raman synchronous characterization device of the present invention, the suspended platform and the cantilever are both deposited with a 60nm thick platinum film for applying alternating current and measuring resistance, thereby playing the role of a thermometer.

[0018] As a further improvement of the device for in-situ measurement of microstructure thermal conductivity and synchronous Raman characterization of the present invention, the one-dimensional nanowire is transferred to the thermal bridge device by a nanomanipulator, and metal deposition is performed in the contact area between the nanowire and the electrode to ensure good thermal contact.

[0019] As a further improvement of the microstructure thermal conductivity in-situ measurement and Raman synchronous characterization device of the present invention, the vacuum environment corresponds to the internal pressure requirement of the vacuum cavity less than 10 -5 mbar to ensure measurement accuracy and environmental stability.

[0020] The measurement method of the microstructure thermal conductivity in-situ measurement and Raman synchronous characterization device described in the present invention comprises the following specific steps:

[0021] S1. The sample is heated using Raman laser. Part of the generated heat flows to the substrate through the suspended platform and cantilever on the left, and the other part flows to the substrate through the suspended platform and cantilever on the right. During this process, the temperature at both ends rises, causing the resistance to change.

[0022] S2. The heat from the heating source to the suspended platforms at both ends is equal to the heat from the suspended platforms to the substrate through the cantilever. Based on the heat flow equation, the following formula is obtained:

[0023]

[0024] Among them, ΔT1 and ΔT2 are the temperature rises of the suspended platforms on the left and right sides, x represents the relative position of the Raman laser on the nanowire, and R i (x) is the cumulative thermal resistance from the Raman laser heating point on the sample to the suspended platform on the left, R s ,R b are the total thermal resistance of the sample and the overall thermal resistance of the six cantilevers, respectively;

[0025] S3. For the same sample, R b It can be measured by the common thermal bridge method.

[0026] Combining formula (1) and (2), we get

[0027]

[0028] where α i (x)=△T1 / △T2, α0=△T 1,0 / △T 2,0 , ΔT 1,0 and ΔT 2,0 is the temperature rise caused by the Joule heat of the electrodes on the suspended platforms on both sides during the thermal bridge measurement. R is obtained through this process. i The relationship between (x) and position x;

[0029] While measuring, S4 uses CCD to collect Raman spectrum information at different positions of the sample;

[0030] S5. Measure the cross-sectional area A of the sample and calculate the thermal conductivity of the one-dimensional nanowire:

[0031]

[0032] As a further improvement of the measuring method of the present invention, the measuring process uses alternating current, and the power supply is provided by a 6221 current source meter. The measurement of the voltage signal is completed by a phase-locked amplifier, and the magnitude of the alternating current is set to 10 μA.

[0033] As a further improvement of the measurement method of the present invention, before the Raman laser measurement, the temperature coefficient of resistance on both sides is obtained by performing variable temperature measurement using the common thermal bridge method. The variable temperature measurement range is 295K to 320K, the temperature stability requirement is ±0.3K, and the data fitting method is a linear fitting.

[0034] As a further improvement to the measuring method of the present invention, during the measuring process, the sample size, ie, the cross-sectional area, is measured by a scanning electron microscope.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] The present invention provides a device and a method for in-situ measurement and Raman synchronous characterization of microstructure thermal conductivity. By using Raman light as a light source, the thermal conductivity of a low-dimensional sample can be effectively measured, and Raman spectrum information at different positions of the sample can be obtained at the same time. The method is suitable for samples that are sensitive to electron beams, greatly broadening the scope of application of thermal conductivity measurement technology for suspended low-dimensional materials. While measuring the thermal conductivity of the sample, the device can obtain Raman spectrum signals at different positions of the sample, thereby realizing the crystallinity characterization of the sample structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 Schematic diagram of the measurement device using Raman light as the heating source, showing the overall structure and key components of the device;

[0038] Figure 2 The Raman spectrum measurement results of three different measurement points of silicon nanowires are obtained by the measuring device of the present invention.

[0039] Raman spectral information at different locations is shown;

[0040] Figure 3 The schematic diagram of the measurement result of the thermal conductivity of silicon nanowires in the embodiment of the present invention shows the thermal conductivity data obtained by the measuring device of the present invention. DETAILED DESCRIPTION

[0041] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments. Figure 1 The design process of the intelligent level evaluation technical solution of the intelligent system of the present invention is as follows:

[0042] Schematic diagram of the measurement device using Raman light as a heating source Figure 1 As shown, the Raman laser generates heat as a heat source. The heat flows from the heating point to the two side platforms, causing temperature rise, and finally flows to the substrate. In terms of the preparation of the measuring device, the thermal bridge device includes two completely symmetrical left and right suspended platforms, and six cantilever structures connecting the suspended platforms and the substrate. The suspended platform and the cantilever are composed of 300nm thick silicon nitride and 60nm thick platinum. The four outer cantilevers are used to measure thermal properties, and the two inner cantilevers are used to measure electrical properties. The one-dimensional silicon nanowire is transferred from the silicon wafer to the thermal bridge device by nanomanipulator transfer technology, and platinum is deposited at both ends of the nanowire to ensure effective thermal contact between the nanowire and the thermal bridge device. The prepared measuring device includes a suspended microstructure, in which the two suspended platforms are connected by overlapping silicon nanowires, and the contact area between the sample and the suspended platform is connected by platinum metal.

[0043] First, a conventional suspended thermal bridge measurement is performed, and the temperature calibration is performed for the subsequent process. A small AC signal is applied to the left and right sides of the thermal bridge using a Keithley 6221 current source, and the change in voltage on both sides at different temperatures is measured using a lock-in amplifier to obtain the resistance value. By fitting the curve of resistance versus temperature, the resistance temperature coefficient on the left and right sides near normal temperature can be obtained for subsequent thermal conductivity measurement.

[0044] The sample is placed in a vacuum chamber and connected to an external measuring meter. The temperature in the chamber, i.e., the ambient temperature, is obtained by measuring its resistance. Next, the sample is heated by Raman laser. Part of the heat generated is transferred to the substrate through the left suspended platform and cantilever, and the other part is transferred to the substrate through the right suspended platform and cantilever. In this process, the temperature at the left and right ends gradually rises, causing the resistance to change, such as Figure 2 shown.

[0045] The heat flowing from the heating source to the suspended platform is the same as the heat flowing from the suspended platform to the substrate through the cantilever, which can be obtained

[0046]

[0047]

[0048] Among them, ΔT1 and ΔT2 are the temperature rises of the suspended platforms on the left and right sides, x represents the relative position of the Raman laser on the nanowire, and R i (x) is the cumulative thermal resistance from the Raman laser heating point on the sample to the suspended platform on the left, R s ,R b are the total thermal resistance of the sample and the overall thermal resistance of the six cantilevers, respectively.

[0049] For the same sample, R b It can be measured by the common thermal bridge method. Combining the above formulas (1) and (2), we can get

[0050]

[0051] where α i (x)=△T1 / △T2, α0=△T 1,0 / △T 2,0 , ΔT 1,0 and ΔT 2,0 is the temperature rise caused by the Joule heat of the electrodes on the suspended platforms on both sides in the thermal bridge measurement. Through the above measurement process, R i The relationship between (x) and position x is measured. During the measurement, the CCD is used to collect Raman spectrum information at different positions of the sample. The position, intensity and half-peak width of the Raman peak can be used to further analyze the lattice information at that position.

[0052] By measuring the cross-sectional area A of the sample, the thermal conductivity of the one-dimensional nanowire is obtained:

[0053]

[0054] Using Raman light as a heat source can obtain spatial distribution data of the sample's thermal resistance as a function of the heating position, which helps eliminate the influence of interface thermal resistance on the measurement results, especially for samples that are sensitive to electron beams. At the same time, Raman characterization of the sample can be performed simultaneously, making it easier to explain its microscopic phonon mechanism.

[0055] The applied AC current is 10μA. For the measurement of the ordinary thermal bridge method, the measured temperature range is 295K to 320K, the temperature gradient is 5K, and the temperature stability requirement is ±0.3K. Within the small temperature change range at room temperature, the resistance temperature coefficient is fitted using linear fitting, that is, the resistance temperature coefficient is a constant.

[0056] Among them, all measurement processes are carried out in a vacuum chamber to reduce the influence of air thermal convection, and the vacuum degree is required to be less than 10 -5 mbar. The dimensions of the samples were measured by transmission electron microscopy.

[0057] The following are the specific steps for measuring the thermal conductivity of silicon nanowires:

[0058] 1) Place the prepared silicon nanowire measuring device in a thermostat and evacuate the vacuum to less than 10 -5 mbar, and then Labview software was used to collect data and record the relationship between the resistance of the suspended platforms on the left and right sides and the temperature.

[0059] 2) Use Raman laser to scan the silicon nanowire, record the change of resistance of the suspended platform at both ends of the sample as the heating position changes, obtain the sample temperature rise data, and calculate the broken line of the thermal resistance from the Raman laser to the left end of the sample as the heating position changes by formula (3), as shown in Figure 3 shown.

[0060] 3) Synchronously, multiple positions on the silicon nanowire are selected to collect their Raman spectrum information. The Raman spectrum results are as follows: Figure 2 shown.

[0061] 4) Through data processing and measurement of sample-related dimensions, the thermal conductivity of the measured silicon nanowires was calculated to be 50.2±2.3 Wm -1 K -1 .

[0062] The above description is only a preferred embodiment of the present invention and does not constitute any other form of limitation to the present invention. Any modification or equivalent change made based on the technical essence of the present invention still falls within the scope of protection required by the present invention.

Claims

1. Microstructure thermal conductivity in-situ measurement and Raman synchronous characterization device, characterized by: The working environment of the microstructure thermal conductivity in-situ measurement and Raman synchronous characterization device is a vacuum environment. The internal pressure of the vacuum chamber is required to be less than 10 - 5 mbar The microstructure thermal conductivity in-situ measurement and Raman synchronous characterization device includes two suspended platforms, a substrate and a heat source. The two suspended platforms are arranged symmetrically on the left and right. The suspended platforms and the substrate are connected by 6 cantilever structures. The one-dimensional nanowire to be measured is overlapped between the two suspended platforms. The heat source uses a Raman laser set above the one-dimensional nanowire as a heat source to heat the sample.

2. The device for in-situ measurement of microstructure thermal conductivity and synchronous Raman characterization according to claim 1, characterized in that: A 60nm thick platinum film is deposited on both the suspended platform and the cantilever.

3. The device for in-situ measurement of microstructure thermal conductivity and synchronous Raman characterization according to claim 1, characterized in that: The one-dimensional nanowire is transferred to the thermal bridge device through a nanomanipulator, and metal deposition is performed in the contact area between the nanowire and the electrode.

4. The device for in-situ measurement of microstructure thermal conductivity and synchronous Raman characterization according to claim 1, characterized in that: The vacuum environment corresponds to a vacuum chamber with an internal pressure requirement of less than 10 -5 mbar.

5. A measurement method using the microstructure thermal conductivity in-situ measurement and Raman synchronous characterization device according to any one of claims 1 to 4, characterized in that: The specific steps are as follows: S1. The sample is heated using Raman laser. Part of the generated heat flows to the substrate through the suspended platform and cantilever on the left, and the other part flows to the substrate through the suspended platform and cantilever on the right. During this process, the temperature at both ends rises, causing the resistance to change. S2. The heat from the heating source to the suspended platforms at both ends is equal to the heat from the suspended platforms to the substrate through the cantilever. Based on the heat flow equation, the following formula is obtained: Among them, ΔT1 and ΔT2 are the temperature rises of the suspended platforms on the left and right sides, x represents the relative position of the Raman laser on the nanowire, and R i (x) is the cumulative thermal resistance from the Raman laser heating point on the sample to the suspended platform on the left, R s ,R b are the total thermal resistance of the sample and the overall thermal resistance of the six cantilevers, respectively; S3. For the same sample, R b It can be measured by the common thermal bridge method. Combining formula (1) and (2), we get where α i (x)=△T1 / △T2, α0=△T 1,0 / △T 2,0 , ΔT 1,0 and ΔT 2,0 is the temperature rise caused by the Joule heat of the electrodes on the suspended platforms on both sides during the thermal bridge measurement. R is obtained through this process. i The relationship between (x) and position x; While measuring, S4 uses CCD to collect Raman spectrum information at different positions of the sample; S5. Measure the cross-sectional area A of the sample and calculate the thermal conductivity of the one-dimensional nanowire:

6. The microstructure thermal conductivity in-situ measurement and Raman synchronous characterization device measurement method according to claim 5 is characterized by: The measurement process uses alternating current, and the power supply is provided by a 6221 current source meter. The voltage signal is measured through a phase-locked amplifier, and the size of the alternating current is set to 10μA.

7. The microstructure thermal conductivity in-situ measurement and Raman synchronous characterization device measurement method according to claim 5 is characterized by: Before Raman laser measurement, variable temperature measurement is performed by ordinary thermal bridge method to obtain the resistance temperature coefficient on both sides. The variable temperature measurement range is 295K to 320K, the temperature stability requirement is ±0.3K, and the data fitting method is a linear fit.

8. The microstructure thermal conductivity in-situ measurement and Raman synchronous characterization device measurement method according to claim 5 is characterized by: During the measurement process, the sample size, i.e. the cross-sectional area, was obtained by measuring with a scanning electron microscope.

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