Thin film heat flow meter of transistor structure, preparation method and measurement method

Abstract

The application discloses a transistor structure thin film heat flow meter, a preparation method and a measuring method. The transistor structure thin film heat flow meter comprises a first electrode, a thermal resistance layer, a thermoelectric material active layer, a second electrode, an insulating layer and a third electrode. The first electrode, the second electrode and the third electrode are respectively used as lead ends of the transistor structure. The thermal resistance layer is covered on the first electrode, and the first electrode and the second electrode are metal conductive layers in ohmic contact with the thermoelectric material active layer. In working, the thermal resistance layer and the second electrode are directly in contact with an external measured surface. The insulating layer is arranged between the third electrode and the thermoelectric material active layer. Compared with the existing thermopile type heat flow meter, the application can realize heat flow measurement by using a single thermoelectric thin film transistor, and the volume is smaller, and it is easier to realize integration on a chip to realize micro area heat flow measurement.

Description

Technical Field

[0001] This invention relates to the field of heat flow meter technology, specifically to a thin-film heat flow meter with a transistor structure, its preparation method, and its measurement method. Background Technology

[0002] A heat flow meter is a component that measures the magnitude of heat transfer. It is mainly used to measure the heat flow distribution of a heating element and monitor real-time changes in heat flux density. It is widely used in various fields such as construction, energy, machinery, metallurgy, aerospace, and precision instruments.

[0003] Traditional thin-film heat flow meters typically use thin-film thermocouples to measure the temperature difference across a thermal resistance layer, and calculate the heat flow at the measured interface by multiplying the thermal conductivity of the thermal resistance layer by the temperature difference. In practical measurements, to minimize the impact on heat transfer at the measurement surface, the thermal resistance layer is generally thin, resulting in a small temperature difference between the two ends. Therefore, multiple pairs of thermocouples need to be connected in series to form a thermopile, as seen in patents CN109738092A, CN115727957A, CN110836737A, and CN113091956A. These all employ a thin-film thermopile structure, resulting in a large area and volume for the heat flow meter, thus limiting further miniaturization of thin-film heat flow meters. Summary of the Invention

[0004] The purpose of this invention is to provide a transistor-structured thin-film heat flow meter, its preparation method, and its measurement method that can reduce the volume of existing thin-film heat flow meters.

[0005] First aspect: A thin-film heat flow meter with a transistor structure, wherein the transistor structure of the thin-film heat flow meter includes a first electrode, a thermal resistance layer, a thermoelectric active layer, a second electrode, an insulating layer, and a third electrode; the first electrode, the second electrode, and the third electrode respectively serve as leads of the transistor structure;

[0006] The first electrode is covered with the thermal resistance layer. The first electrode and the second electrode are metal conductive layers that are in ohmic contact with both ends of the active layer of the thermoelectric material. During operation, the thermal resistance layer and the second electrode are in direct contact with the external surface being measured.

[0007] The insulating layer is provided between the third electrode and the active layer of the thermoelectric material.

[0008] As a preferred embodiment of the present invention, the thermal resistance layer and the second electrode are located at the same physical layer height.

[0009] As a preferred embodiment of the present invention, the active layer of the thermoelectric material is a semiconductor thermoelectric material thin film with electrons or holes as charge carriers, and the thickness of the thin film is 1-200 nm.

[0010] As a preferred technical solution of the present invention, the thickness of the first electrode and the second electrode is 100-10000nm, and the formation method includes sputtering or evaporation after covering the mask, or photolithography after coating.

[0011] As a preferred embodiment of the present invention, the third electrode is made of a highly doped single-crystal Si substrate.

[0012] As a preferred technical solution of the present invention, the insulating layer is made of a highly insulating oxide and has a thickness of 100-1000 nm.

[0013] As a preferred embodiment of the present invention, the thermal resistance layer is made of a material that has insulating properties and a certain thermal resistance.

[0014] Second aspect: A method for fabricating a thin-film heat flow meter with a transistor structure, comprising the following steps:

[0015] A bismuth telluride thin film was prepared on a single-crystal silicon wafer covered with an insulating layer using a magnetron sputtering process; wherein the insulating layer is made of 300 nm silicon oxide.

[0016] After spin-coating photoresist onto the surface of the bismuth telluride thin film, it is exposed and developed using a photolithography machine or a mask, and then etched into a rectangular thermoelectric active layer using an etching machine.

[0017] After washing away the residual adhesive on the surface of the bismuth telluride thin film, Ti and Au are deposited at both ends of the active layer of the thermoelectric material using mask magnetron sputtering technology to form the first electrode and the second electrode.

[0018] A certain thickness of polyimide is sprayed onto the surface of the first electrode using a mask as a thermal resistance layer, and then the single-crystal silicon wafer is used as the third electrode to obtain a heat flow meter with a transistor structure.

[0019] Third aspect: A measurement method for a thin-film heat flow meter with a transistor structure, characterized in that it is applied to the thin-film heat flow meter with a transistor structure described in the first aspect, the measurement method comprising:

[0020] The thin-film heat flow meter is attached to the surface to be measured, so that heat flows from the surface to the heat sink through the thin-film heat flow meter.

[0021] Connect the third electrode to the first electrode to the signal generator and apply a sinusoidal AC voltage signal of a certain frequency, which is then synchronously connected to the reference signal terminal of the lock-in amplifier.

[0022] The signal to be measured between the second electrode and the first electrode is connected to the signal input terminal of the lock-in amplifier, and the corresponding amplified temperature difference signal is obtained by the lock-in amplifier. The DC signal component obtained by the lock-in amplifier after processing the reference signal and the signal to be measured is proportional to the temperature difference between the second electrode and the first electrode. The signal amplification factor depends on the amplitude of the reference signal locked by the lock-in amplifier and the integration time.

[0023] Based on the thickness, area, and thermal conductivity of the thermal resistance material, and combined with the temperature difference signal, the heat flow data of the measurement point on the tested surface is obtained.

[0024] The above technical solution has the following advantages: The thin-film heat flow meter with a transistor structure, the preparation method and the measurement method proposed in this invention construct a transistor structure by building a first electrode, a thermal resistance layer, a thermoelectric active layer, a second electrode, an insulating layer and a third electrode. Compared with the existing thermopile type heat flow meter, this invention can realize the measurement of heat flow with a single thermoelectric thin-film transistor, which is smaller in size and easier to integrate on a chip to realize the measurement of heat flow in a small area. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of a thin-film heat flow meter with a transistor structure provided in an embodiment of the present invention;

[0026] Figure 2 A flowchart illustrating a method for fabricating a thin-film heat flow meter with a transistor structure, as provided in an embodiment of the present invention;

[0027] Figure 3 This is a flowchart illustrating a measurement method for a thin-film heat flow meter with a transistor structure, provided as an embodiment of the present invention. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. 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.

[0029] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0030] Reference Figure 1As shown, a thin-film heat flow meter with a transistor structure is disclosed. The transistor structure of the thin-film heat flow meter includes a first electrode 1, a thermal resistance layer 2, a thermoelectric active layer 3, a second electrode 4, an insulating layer 5, and a third electrode 6; the first electrode 1, the second electrode 4, and the third electrode 6 respectively serve as the lead terminals of the transistor structure.

[0031] The first electrode 1 is covered with the thermal resistance layer 2. The first electrode 1 and the second electrode 4 are metal conductive layers that are ohmically in contact with both ends of the active layer 3 of the thermoelectric material, and are used to output the thermoelectric signal. During operation, the thermal resistance layer 2 and the second electrode 4 are in direct contact with the external measured surface 7.

[0032] The insulating layer 5 is provided between the third electrode 6 and the active layer 3 of the thermoelectric material.

[0033] Specifically, a transistor structure is formed by deploying the first electrode 1, the thermal resistance layer 2, the thermoelectric material active layer 3, the second electrode 4, the insulating layer 5, and the third electrode 6. During measurement, the heat flow meter is attached to the surface to be measured 7, and the back of the third electrode is the heat sink 8. Heat flows from the surface to be measured 7 to the heat sink 8 via the heat flow meter.

[0034] The thermal resistance layer 2 and the second electrode 4 are located at the same physical layer height. Since the second electrode 4 is in direct contact with the surface under test 7 and has the same temperature as the surface under test 7, the second electrode 4 measures the temperature at the upper end of the thermal resistance layer 2, and the first electrode 1 measures the temperature at the lower end of the thermal resistance layer 2. The first electrode 1 and the second electrode 4 are set separately.

[0035] The thermal resistance layer 2 is made of a material that has insulating properties and a certain thermal resistance; it covers the surface of the first electrode, and the material is preferably polyimide, but silicon dioxide, hafnium oxide, aluminum oxide, etc. can also be used, but is not limited to the listed materials.

[0036] The thickness of the first electrode 1 and the second electrode 4 is 100-10000 nm, and they are formed by sputtering or evaporation after covering a mask, or by photolithography after coating.

[0037] The third electrode 6 is made of a highly doped single-crystal Si substrate; other conductive materials can also be used as substrates.

[0038] The active layer 3 of the thermoelectric material is a semiconductor thermoelectric material thin film in which the charge carriers are electrons or holes, such as thermoelectric materials including Bi2Te3-based, PbX (X=S, Se, Te)-based, Sb2Te3, SnTe-based, PbTe-based, etc., and the thickness of the thin film is 1-200nm.

[0039] The insulating layer 5 is made of a highly insulating oxide with a thickness of 100-1000 nm. The insulating layer refers to the isolation layer between the third electrode layer and the active layer of the thermoelectric material. The material is generally a highly insulating oxide, such as silicon dioxide, hafnium oxide, aluminum oxide, etc.

[0040] A sinusoidal AC voltage signal is applied between the third electrode and the first or second electrode, and synchronously connected to the reference signal terminal of the lock-in amplifier. The signal between the second electrode and the first electrode is connected to the signal input terminal of the lock-in amplifier. The DC signal component obtained by processing the reference signal and the signal to be measured by the lock-in amplifier is proportional to the temperature difference between the second electrode and the first electrode. The signal amplification factor depends on the amplitude of the reference signal locked by the lock-in amplifier and the integration time, etc. Since the second electrode 4 is in direct contact with the surface to be measured and has the same temperature as the surface to be measured, the temperature difference between the first electrode 1 and the second electrode 4 is the temperature difference between the two ends of the thermal resistance layer 2. Based on the thickness, area and thermal conductivity of the thermal resistance material, the heat flux density at the measurement point on the surface to be measured can be obtained.

[0041] In the above embodiments, by constructing a transistor structure from the first electrode, thermal resistance layer, thermoelectric active layer, second electrode, insulating layer and third electrode, the present invention can realize the measurement of heat flow with a single thermoelectric thin film transistor compared with the existing thermopile type heat flow meter. It is smaller in size and easier to integrate on a chip to realize the measurement of tiny heat flow.

[0042] Reference Figure 2 This invention also provides a method for fabricating a thin-film heat flow meter with a transistor structure, comprising the following steps:

[0043] S101, a bismuth telluride thin film is prepared on a single-crystal silicon wafer covered with an insulating layer using a magnetron sputtering process; wherein, the insulating layer is made of 300nm silicon oxide;

[0044] S102, after spin-coating photoresist on the surface of the bismuth telluride thin film, expose and develop it using a photolithography machine or a mask, and then etch the bismuth telluride thin film into a rectangular thermoelectric active layer using an etching machine.

[0045] S103, after washing away the residual adhesive on the surface of the bismuth telluride thin film, Ti and Au are deposited at both ends of the active layer of the thermoelectric material using mask magnetron sputtering technology to form the first electrode and the second electrode; by first depositing Ti, the bonding force is enhanced, and then Au is deposited on top, which enhances conductivity and prevents oxidation.

[0046] S104, a certain thickness of polyimide is sprayed onto the surface of the first electrode using a mask as a thermal resistance layer, and then the single crystal silicon wafer is used as the third electrode to obtain a heat flow meter with a transistor structure.

[0047] This application uses the single-crystal silicon wafer as a conductive material substrate to integrate the entire transistor structure inside the chip and device. Compared with thermopile-type heat flow meters, this invention can measure heat flow with a single thermoelectric thin-film transistor, which is smaller in size and easier to integrate on the chip to achieve micro heat flow measurement. It can meet the needs of internal fixed-point heat flow monitoring, and can also achieve heat flow imaging of the measured surface by forming a sensor array.

[0048] Reference Figure 3 This invention also provides a measurement method for a thin-film heat flow meter with a transistor structure, applied to the thin-film heat flow meter with a transistor structure described above. The measurement method includes:

[0049] S201, the thin-film heat flow meter is attached to the surface to be measured, so that heat flows from the surface to the heat sink through the thin-film heat flow meter; wherein, the back of the third electrode is the heat sink;

[0050] S202, connect the third electrode to the first electrode to the signal generator, and apply a sinusoidal AC voltage signal of a certain frequency, which is then synchronously connected to the reference signal terminal of the lock-in amplifier;

[0051] S203, the signal to be measured between the second electrode and the first electrode is connected to the signal input terminal of the lock-in amplifier, and the corresponding amplified temperature difference signal is obtained by the lock-in amplifier; wherein, the DC signal component obtained by the lock-in amplifier processing the reference signal and the signal to be measured is proportional to the temperature difference between the second electrode and the first electrode, and the signal amplification factor depends on the amplitude of the reference signal locked by the lock-in amplifier and the integration time.

[0052] S204, based on the thickness, area and thermal conductivity of the thermal resistance material, and combined with the temperature difference signal, obtains the heat flow data of the measurement point on the tested surface.

[0053] It should be noted that since the second electrode is in direct contact with the surface being measured and has the same temperature as the surface, the temperature difference between the first and second electrodes is the same as the temperature difference across the thermal resistance layer. This allows for the extraction of the temperature difference signal across the thin-film transistor using a lock-in amplifier. The heat flow in the heat transfer path is then calculated using the formula Q = κ * ΔT * A / d. In this formula, κ is the thermal conductivity of the thermal resistance material, ΔT is the temperature difference between two points on the thermal resistance material, d is the distance between the two points, and A is the cross-sectional area through which the heat flow passes.

[0054] The above measurement method has the following advantages compared to existing multi-stage thermopile heat flow meters:

[0055] Firstly, the signal amplification factor of a thermopile heat flux meter is directly proportional to the number of thermocouples connected in series in the thermopile, typically on the order of tens. If a smaller heat flux is to be measured, a larger number of thermopile stages must be used, resulting in a larger volume and affecting the heat flux distribution on the measurement surface. However, lock-in amplification can generally reach over a thousand times, and the range is adjustable. The same device can achieve continuous measurement over a wide range from small to large heat fluxes. At the same time, the contact surface of a transistor heat flux meter is very small, which can reduce the impact on the heat flux distribution on the measured surface.

[0056] The technical features of the present application can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of the present application.

[0057] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; those skilled in the art should understand that modifications can be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A thin-film heat flow meter with a transistor structure, characterized in that, The transistor structure of the thin-film heat flow meter includes a first electrode, a thermal resistance layer, a thermoelectric active layer, a second electrode, an insulating layer, and a third electrode; the first electrode, the second electrode, and the third electrode respectively serve as the lead terminals of the transistor structure. The first electrode is covered with the thermal resistance layer. The first electrode and the second electrode are metal conductive layers that are ohmically in contact with both ends of the active layer of the thermoelectric material. During operation, both the thermal resistance layer and the second electrode are in direct contact with the external surface being measured. The thermal resistance layer and the second electrode are located at the same physical layer height. The insulating layer is provided between the third electrode and the active layer of the thermoelectric material.

2. The thin-film heat flow meter with a transistor structure according to claim 1, characterized in that, The active layer of the thermoelectric material is a semiconductor thermoelectric material thin film with electrons or holes as charge carriers, and the thickness of the thin film is 1-200nm.

3. A thin-film heat flow meter with a transistor structure according to claim 1, characterized in that, The thickness of the first electrode and the second electrode is 100-10000 nm, and they are formed by sputtering or evaporation after covering a mask, or by photolithography after coating.

4. A thin-film heat flow meter with a transistor structure according to claim 1, characterized in that, The third electrode is made of a highly doped single-crystal Si substrate.

5. A thin-film heat flow meter with a transistor structure according to claim 4, characterized in that, The insulating layer is made of a highly insulating oxide material with a thickness of 100-1000 nm.

6. A thin-film heat flow meter with a transistor structure according to claim 4, characterized in that, The thermal resistance layer is made of a material that has insulating properties and a certain thermal resistance.

7. A method for fabricating a thin-film heat flow meter with a transistor structure, characterized in that, This includes following these steps: A bismuth telluride thin film was prepared on a single-crystal silicon wafer covered with an insulating layer using a magnetron sputtering process; wherein the insulating layer is made of 300 nm silicon oxide. After spin-coating photoresist onto the surface of the bismuth telluride thin film, it is exposed and developed using a photolithography machine or a mask, and then etched into a rectangular thermoelectric active layer using an etching machine. After washing away the residual adhesive on the surface of the bismuth telluride thin film, Ti and Au are deposited at both ends of the active layer of the thermoelectric material using mask magnetron sputtering technology to form the first electrode and the second electrode. A certain thickness of polyimide is sprayed onto the surface of the first electrode using a mask as a thermal resistance layer, and then the single crystal silicon wafer is used as the third electrode to obtain a heat flow meter with a transistor structure. During operation, both the thermal resistance layer and the second electrode are in direct contact with the external surface being measured. The thermal resistance layer and the second electrode are located at the same physical layer height.

8. A measurement method for a thin-film heat flow meter with a transistor structure, characterized in that, The method of measuring a thin-film heat flow meter with a transistor structure as described in claim 1 includes: The thin-film heat flow meter is attached to the surface to be measured, so that heat flows from the surface to the heat sink through the thin-film heat flow meter. Connect the third electrode to the first electrode to the signal generator and apply a sinusoidal AC voltage signal of a certain frequency, which is then synchronously connected to the reference signal terminal of the lock-in amplifier. The signal to be measured between the second electrode and the first electrode is connected to the signal input terminal of the lock-in amplifier, and the corresponding amplified temperature difference signal is obtained by the lock-in amplifier. The DC signal component obtained by the lock-in amplifier after processing the reference signal and the signal to be measured is proportional to the temperature difference between the second electrode and the first electrode. The signal amplification factor depends on the amplitude of the reference signal locked by the lock-in amplifier and the integration time. Based on the thickness, area, and thermal conductivity of the thermal resistance material, and combined with the temperature difference signal, the heat flow data of the measurement point on the tested surface is obtained.

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