A microelectromechanical system (MEMS) thermosensitive thin-film heat flux sensor designed based on the principle of Wheatstone bridge

Abstract

The present invention provides a microelectromechanical system thermosensitive thin-film type heat flux meter designed based on the principle of Wheatstone bridge. The thermosensitive thin-film type heat flux meter is made up of four parts: a silicon-based substrate, a thermosensitive thin film, a composite electrode, and a thermal resistance layer. The thermosensitive thin film is grown on the silicon-based substrate, the electrode is grown on the thermosensitive thin film, and the thermal resistance layer is grown on the thermosensitive material and the composite electrode to play a role in blocking heat flux. Under the excitation voltage, the surface of the heat flux meter is affected by the change of heat flux, specifically manifested as the different surface temperatures of the thermosensitive thin film with / without the thermal resistance layer, which further leads to different resistances of the thermosensitive thin film. Based on the principle of Wheatstone bridge, when the resistances in the bridge are different, it will cause the bridge to be unbalanced, thus generating a potential difference. Combining with Fourier's law, the temperature difference is proportional to the applied heat flux density. Therefore, the output voltage of the Wheatstone bridge measurement circuit can reflect the value of the applied heat flux density. Then, through calibration with a standard heat flux meter, the coefficient composed of the thermal conductivity coefficient and the material coefficient of the heat flux meter to be calibrated is determined, thereby completing the calibration of the microelectromechanical system thermosensitive thin-film type heat flux meter designed based on the principle of Wheatstone bridge.

Description

Technical Field

[0001] The present invention relates to a microelectromechanical system (MEMS) thin-film heat flowmeter prepared from a thermosensitive thin film and designed based on the principle of a Wheatstone bridge. Background Art

[0002] As the sensing layer in the information age, sensors are the foundation and data source in fields such as the Internet of Things, big data, intelligent manufacturing, and smart cities. Their development and application are important indicators to measure a country's informatization level. In recent years, with the continuous breakthroughs in artificial intelligence technology and the improvement of social informatization, microelectromechanical system (MEMS) intelligent sensors have gradually become the research focus in the sensor industry. A MEMS intelligent sensor is composed of a sensing unit, an information processing unit, an actuator, and a communication / interface unit. Its input signal is a physical signal, which is converted into an electrical signal by the sensor, and after signal processing (analog / digital), it acts on the outside world through the actuator. Each microsystem can communicate with other microsystems using digital or analog signals (physical quantities such as electricity, light, and magnetism). It has the advantages of miniaturization, integration, intelligence, high cost performance, batch production, high stability, and reliability.

[0003] With the development of disciplines such as carbon neutrality, energy conservation, and environmental protection, the demand for MEMS-based heat flow sensors is increasing continuously. Heat flow sensors are important sensitive components for studying heat transfer and have extensive application requirements in many industrial sectors such as metallurgy, fossil, machinery, energy, construction, refrigeration, environmental engineering, meteorological medicine, and aerospace. Traditional heat flow sensors are mostly thermopile-type heat flowmeters, and the materials are mostly platinum alloys, which are costly and need to be stable in the environment for a period of time before testing; metal sheet-type heat flowmeters have a simple principle but poor long-term stability; circular foil-type heat flowmeters have a simple structure and fast response but are easily affected by convection; calorimetric heat flowmeters have a fast response but a complex structure and high cost.

[0004] In order to improve the measurement accuracy and response speed of heat flow sensors, the present invention uses a temperature signal as the input signal source of the sensor and provides a MEMS thermosensitive thin-film heat flowmeter designed based on the principle of a Wheatstone bridge. Summary of the Invention

[0005] The object of the present invention is to provide a microelectromechanical system thermosensitive thin-film heat flux meter designed based on the principle of Wheatstone bridge. The thermosensitive thin-film heat flux meter is made of a silicon-based substrate, a thermosensitive thin film, a composite electrode, and a thermal resistance layer. The entire heat flux meter consists of four sensitive units on the silicon-based substrate, two of which are temperature-sensitive units, and the other two are temperature-sensitive units with a thermal resistance layer covering the surface. The four units are connected by a composite electrode to form a Wheatstone bridge. The thermosensitive thin film grows on the silicon-based substrate, the composite electrode grows on the thermosensitive thin film and the silicon substrate, and the thermal resistance layer grows on the thermosensitive material and the composite electrode, playing a role in blocking heat flux. This heat flux meter has good stability and short response time, and has the advantage of low cost compared with thermopile-type heat flux meters. Compared with the coefficient composed of the thermal conductivity coefficient and material coefficient of the measurement and calibration heat flux meter, which is complex and has low accuracy, it is proposed to use a standard heat flux meter to determine the coefficient composed of the thermal conductivity coefficient and material coefficient of the heat flux meter to be calibrated, so as to complete the calibration of the microelectromechanical system thermosensitive thin-film heat flux meter designed based on the principle of Wheatstone bridge.

[0006] A microelectromechanical system thermosensitive thin-film heat flux meter designed based on the principle of Wheatstone bridge according to the present invention. The thermosensitive thin-film heat flux meter is made of a silicon-based substrate (1), a thermosensitive thin film (2), a composite electrode (3), and a thermal resistance layer (4); the thermosensitive thin film (2) grows on the silicon-based substrate (1), the composite electrode (3) grows on the thermosensitive thin film (2), and the thermal resistance layer (4) grows on the thermosensitive thin film (2) and the composite electrode (3). The entire heat flux meter consists of four sensitive units A, B, C, and D on the silicon-based substrate (1), where B and C are two temperature-sensitive units, and A and D are two temperature-sensitive units with a thermal resistance layer covering the surface. The four units are connected by a composite electrode (3) to form a Wheatstone bridge. The method of covering a thin-film metal mask or coating photoresist and lithography is adopted, and the specific operation is carried out according to the following steps:

[0007] Preparation of the thin-film metal mask:

[0008] a. On the silicon-based substrate (1), cover the thin-film metal mask, and grow the thermosensitive thin film (2) by magnetron sputtering. Place the thermosensitive thin film (2) on the silicon-based substrate (1) with the grown pattern in a tube furnace for annealing. The annealing temperature is 700°C - 800°C, and keep it warm for 30 minutes to ensure that the grains of the thermosensitive thin film (2) grow evenly in crystallization.

[0009] b. Cover the thermosensitive thin film (2) of the annealed silicon-based substrate (1) with an electrode metal mask, and grow the composite electrode (3) structure by magnetron sputtering. Then place the grown thermosensitive thin film (2) in an oven for annealing. The annealing temperature is 100°C - 300°C, and the duration is 60 - 120 minutes to ensure that the grains of the composite electrode grow evenly in crystallization.

[0010] c. After annealing is completed, a thermal resistance layer (4) with a thickness of 0.05 mm - 0.2 mm is covered on two thermosensitive units at the A and D diagonals to obtain a thin-film type heat flowmeter, wherein the thermal resistance layer (4) is SiO 2 、Si 3 N 4 、AlN or Al 2 O 3 ;

[0011] d. The completed thin-film type heat flowmeter is tested in a constant temperature oil bath to obtain the temperature-resistance curve of the thermosensitive unit. Then, on the built heat flow test platform, a stable heat flow is applied, and the instantaneous output of V SIG under the excitation voltage V and the output Q of the standard heat flowmeter are recorded, and substituted into the formula Q = 2 / [(Vβ / V SIG -β) / k 1 -2βL / k 2 to calculate 1 / k 1 , L / k 2 , and the calibration of the thermosensitive thin-film type heat flowmeter is completed;

[0012] Coating and photoresist preparation:

[0013] a. A photoresist is coated on the silicon-based substrate (1). The designed structure of the thermosensitive thin film (2) is exposed and developed on the photoresist through a photomask. The thermosensitive material is grown on the photoresist using magnetron sputtering, and the photoresist is ultrasonically cleaned with acetone to obtain the pattern of the thermosensitive thin film (2) on the silicon-based substrate (1);

[0014] b. The pattern of the thermosensitive thin film (2) on the silicon-based substrate obtained in step a is annealed in a tube furnace at an annealing temperature of 750 °C - 800 °C for 30 min to ensure uniform crystal growth of the thermosensitive thin film grains;

[0015] c. A photoresist is coated on the thermosensitive thin film of the silicon-based substrate after annealing in step b. The structure of the composite electrode (3) is exposed and developed on the photoresist through a photomask. The composite electrode (3) is grown on the photoresist using magnetron sputtering, and the photoresist is ultrasonically cleaned with acetone to obtain the pattern of the composite electrode (3) on the silicon-based substrate (1) and the thermosensitive thin film (2). Then, it is placed in an oven for annealing at an annealing temperature of 100 °C - 300 °C for a duration of 60 - 120 min to ensure uniform crystal growth of the composite electrode grains;

[0016] d. After annealing is completed, a thermal resistance layer (4) is covered on two thermosensitive units at the A and D diagonals to obtain a heat flowmeter, wherein the thermal resistance layer (4) is SiO 2 、Si 3 N 4 、AlN or Al 2 O 3 ;

[0017] e. Test a single microelectromechanical system (MEMS) thermosensitive thin-film heat flowmeter in a constant-temperature oil bath to obtain the temperature-resistance curve of the thermosensitive unit. Then, on the built heat flow test platform, apply different stable heat fluxes and record the instantaneous output of V under the excitation voltage V and the output Q of the standard heat flowmeter. Substitute them into the formula Q = 2 / [(Vβ / V SIG -β) / k SIG -2βL / k 1 -2βL / k 2 to calculate 1 / k 1 , L / k 2 , and complete the calibration of the MEMS thermosensitive thin-film heat flowmeter.

[0018] The thermosensitive thin film (2) is prepared by magnetron sputtering using a transition metal oxide material and grown on the silicon-based substrate (1). The thermosensitive thin film (2) has an NTC relationship where its resistance decreases as the temperature rises.

[0019] The composite electrode (3) is prepared by magnetron sputtering on the thermosensitive thin film (2) and the silicon-based substrate (1). Ti, Cr, or Ni is selected as the electrode transition layer; one or two of Pt, Au, Al, or Ag are selected as the electrode layer.

[0020] The Wheatstone bridge is designed as two pairs of thermistors composed of four unit resistors A, B, C, and D, namely A and D, B and C.

[0021] The calibration method is to use a standard heat flowmeter to obtain the heat flow calculation coefficient to complete the calibration.

[0022] A MEMS thermosensitive thin-film heat flowmeter designed based on the Wheatstone bridge principle according to the present invention. The thermosensitive thin-film heat flowmeter includes a silicon-based substrate, a thermosensitive thin film, a composite electrode, and a thermal resistance layer. The entire heat flowmeter is composed of four sensitive units on the silicon-based substrate, where two are temperature-sensitive units and the other two are temperature-sensitive units with a thermal resistance layer covering the surface. The four units are connected by a composite electrode to form a Wheatstone bridge. The thermosensitive thin film is grown on the silicon-based substrate, the composite electrode is grown on the thermosensitive thin film and the silicon substrate, and the thermal resistance layer is grown on the thermosensitive material and the composite electrode to play a role in blocking the heat flow. Apply an excitation voltage V at both ends V + V - . When the heat flow blows onto the heat flowmeter, the surface temperature T F of the thermosensitive thin film with the thermal resistance layer is different from the surface temperature T S of the thermosensitive thin film without the thermal resistance layer, resulting in different instantaneous resistances of the thermosensitive thin films. The resistance of the thermosensitive thin film with the thermal resistance layer at that moment is R F , and the resistance of the thermosensitive thin film without the thermal resistance layer is R S , V 2 V -Different from V 1 V - The output voltage results in an unbalanced bridge, thus generating an electromotive force difference. The electromotive force difference V 1 -V 2 is the instantaneous output voltage V of the sensor SIG , according to Fourier's law, the temperature difference is proportional to the applied heat flux density T S -T F =Q / k 1 , so the measured output voltage V of the Wheatstone bridge measurement circuit SIG =(VβQ / k 1 ) / (2 + βQ / k 1 + 2βQL / k 2 ) reflects the applied heat flux density value Q = 2 / [(Vβ / V SIG -β) / k 1 - 2βL / k 2 . A standard heat flow meter can be used. The thermal conductivity and material of the same device are determined, so 1 / k 1 , L / k 2 is a constant. Take the heat flow meter to be calibrated and the standard heat flow meter. Under the same heat flow, the standard heat flow meter measures the Q of the same transient, and the heat flow meter to be measured outputs R F , R S , and calculate the constant 1 / k 1 , L / k 2 thus completing the calibration of the device.

[0023] Under the excitation voltage, the surface of the heat flow meter is affected by the change of heat flow. Specifically, the temperature of the surface of the thermosensitive film with a thermal resistance layer is different from that of the surface of the thermosensitive film without a thermal resistance layer, resulting in different resistances of the thermosensitive film, an unbalanced bridge, and thus an electromotive force difference. According to Fourier's law, the temperature difference is proportional to the applied heat flux density. Therefore, the output voltage of the Wheatstone bridge measurement circuit reflects the applied heat flux density value. Then, through calibration with a standard heat flow meter, the coefficient composed of the thermal conductivity and material coefficient of the heat flow meter to be calibrated is determined, thus completing the calibration of the microelectromechanical system thermosensitive film type heat flow meter designed based on the Wheatstone bridge principle. Brief Description of the Drawings

[0024] Figure 1 This is the relationship diagram of the temperature-resistance curve of the thermosensitive film in the microelectromechanical system thermosensitive film type heat flow meter designed based on the Wheatstone bridge principle of the present invention. It can be seen that the coverage of the thermal resistance layer does not affect the temperature measurement of the thermosensitive material, and the thermosensitive unit has good temperature-resistance consistency;

[0025] Figure 2This is a one-dimensional heat transfer schematic diagram of the microelectromechanical system (MEMS) thermosensitive thin-film heat flowmeter designed based on the Wheatstone bridge principle, where the thermal conductivity of the thermal resistance layer 4 is k 1 , and the temperature function is T 1 (x). The thermal conductivities of the composite electrode 3 and the thermosensitive thin film 2 are k 2 , and the temperature function is T 2 (x). When a heat flow with a heat flux density of Q blows, the temperature at x = -h on the surface of the thermal resistance layer 4 is T s , the temperature at x = 0 on the surfaces of the composite electrode 3 and the thermosensitive thin film 2 is T F , and the temperature at x = L on the surface of the silicon substrate 1 is T 0 ;

[0026] Figure 3 This is a schematic diagram of the device cross-sectional structure in the MEMS thermosensitive thin-film heat flowmeter designed based on the Wheatstone bridge principle of the present invention, where 1 is the silicon substrate, 2 is the thermosensitive thin film, 3 is the composite electrode, and 4 is the thermal resistance layer;

[0027] Figure 4 This is a top view schematic diagram of the device in the MEMS thermosensitive thin-film heat flowmeter designed based on the Wheatstone bridge principle of the present invention, where A and D are the thermosensitive units of the thermal resistance layer, B and C are the thermosensitive units without the thermal resistance layer, and V + V - is the end point where the excitation voltage is applied, and V 1 V 2 is the end point of the output voltage;

[0028] Figure 5 This is a schematic diagram of the circuit structure in the MEMS thermosensitive thin-film heat flowmeter designed based on the Wheatstone bridge principle of the present invention. Detailed implementation manners

[0029] To enable those skilled in the art of this technology to better understand the solution of the present invention, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts shall fall within the protection scope of the present invention.

[0030] Example 1

[0031] A microelectromechanical system (MEMS) thermosensitive thin-film heat flux meter designed based on the principle of Wheatstone bridge. The thermosensitive thin-film heat flux meter is made of a silicon-based substrate 1, a thermosensitive thin film 2, a composite electrode 3, and a thermal resistance layer 4. The thermosensitive thin film 2 is grown on the silicon-based substrate 1, the composite electrode 3 is grown on the thermosensitive thin film 2, and the thermal resistance layer 4 is grown on the thermosensitive thin film 2 and the composite electrode 3. The entire heat flux meter consists of four sensitive units A, B, C, and D on the silicon-based substrate 1. Among them, B and C are temperature-sensitive units, and A and D are temperature-sensitive units with a thermal resistance layer covering the surface. The four units are connected by a composite electrode 3 to form a Wheatstone bridge. The method of covering a thin-film metal mask is used, and the specific operation is carried out according to the following steps: Preparation of the thin-film metal mask:

[0032] a. On the silicon-based substrate 1, cover the thin-film metal mask, and grow the thermosensitive thin film 2 by magnetron sputtering. Place the thermosensitive thin film 2 of the silicon-based substrate 1 with the grown pattern in a tube furnace for annealing. The annealing temperature is 700 °C, and keep it warm for 30 min to ensure that the grains of the thermosensitive thin film 2 grow evenly in crystallization;

[0033] b. Cover the thermosensitive thin film 2 of the annealed silicon-based substrate 1 with an electrode metal mask, and magnetron sputter the composite electrode 3 structure. Then place the grown thermosensitive thin film 2 in an oven for annealing. The composite electrode 3 is prepared by magnetron sputtering on the thermosensitive thin film 2 and the silicon-based substrate 1. Ti is selected as the electrode transition layer; Pt and Au are selected as the electrode layers;

[0034] c. After annealing, cover the thermal resistance layer 4 with a thickness of 0.05 mm on the two thermosensitive units at the A and D diagonals to be SiO 2 , to obtain the thin-film heat flux meter, as shown in the schematic Figure 4 shown;

[0035] d. Test the completed thin-film heat flux meter in a constant-temperature oil bath to obtain the temperature-resistance curve of the thermosensitive unit. Then, on the built heat flux test platform, apply different stable heat fluxes, record the instantaneous output of V under the excitation voltage V SIG and the output Q of the standard heat flux meter, and substitute them into the formula Q = 2 / [(Vβ / V SIG - β) / k 1 - 2βL / k 2 , calculate to obtain 1 / k 1 , L / k 2 , to complete the calibration of the thermosensitive thin-film heat flux meter.

[0036] Example 2

[0037] The composition of this thermosensitive thin-film heat flux meter is the same as that of Example 1; the specific operation is carried out according to the following steps:

[0038] Preparation of the thin-film metal mask:

[0039] a. On the silicon-based substrate 1, a thin-film metal mask is covered, and a thermosensitive thin film 2 is grown by magnetron sputtering. The thermosensitive thin film 2 on the silicon-based substrate 1 with the grown pattern is placed in a tube furnace for annealing at an annealing temperature of 720 °C for 30 min to ensure uniform crystal growth of the grains of the thermosensitive thin film 2;

[0040] b. The thermosensitive thin film 2 on the annealed silicon-based substrate 1 is covered with an electrode metal mask, and the composite electrode 3 structure is grown by magnetron sputtering. Then, the grown thermosensitive thin film 2 is placed in an oven for annealing. The composite electrode 3 is prepared by magnetron sputtering on the thermosensitive thin film 2 and the silicon-based substrate 1. Cr is selected as the electrode transition layer; Au is selected as the electrode layer;

[0041] c. After annealing, a thermal resistance layer 4 with a thickness of 0.08 mm is covered on two thermosensitive units at the A and D diagonals, which is Si 3 N 4 , to obtain a thin-film type heat flowmeter, as shown in the schematic Figure 4 shown;

[0042] d. The completed thin-film type heat flowmeter is tested in a constant-temperature oil bath to obtain the temperature-resistance curve of the thermosensitive unit. Then, on the built heat flow test platform, different stable heat flows are applied, and the instantaneous output at the excitation voltage V and the output Q of the standard heat flowmeter are recorded, and substituted into the formula Q = 2 / [(Vβ / V SIG -β) / k SIG - 2βL / k 1 , to calculate 1 / k 2 , L / k 1 , and complete the calibration of the thermosensitive thin-film type heat flowmeter. 2

[0043] Example 3

[0044] The composition of this thermosensitive thin-film type heat flowmeter is the same as that of Example 1, and the specific operation is carried out according to the following steps:

[0045] Preparation of covering the thin-film metal mask:

[0046] a. On the silicon-based substrate 1, a thin-film metal mask is covered, and a thermosensitive thin film 2 is grown by magnetron sputtering. The thermosensitive thin film 2 on the silicon-based substrate 1 with the grown pattern is placed in a tube furnace for annealing at an annealing temperature of 750 °C for 30 min to ensure uniform crystal growth of the grains of the thermosensitive thin film 2;

[0047] b. The thermosensitive thin film 2 on the annealed silicon-based substrate 1 is covered with an electrode metal mask, and the composite electrode 3 structure is grown by magnetron sputtering. Then, the grown thermosensitive thin film 2 is placed in an oven for annealing. The composite electrode 3 is prepared by magnetron sputtering on the thermosensitive thin film 2 and the silicon-based substrate 1. Ni is selected as the electrode transition layer; Al is selected as the electrode layer;​

[0048] c. After annealing is completed, a thermal resistance layer 4 with a thickness of 0.1 mm made of AlN is covered on two thermosensitive units at the A and D diagonals to obtain a thin-film heat flowmeter, as shown in the schematic diagram; Figure 4 as shown;

[0049] d. The completed thin-film heat flowmeter is tested in a constant-temperature oil bath to obtain the temperature-resistance curve of the thermosensitive unit. Then, on the built heat flow test platform, different stable heat flows are applied, and the instantaneous output of V under the excitation voltage V and the output Q of the standard heat flowmeter are recorded. Substitute into the formula Q = 2 / [(Vβ / V SIG -β) / k SIG - 2βL / k 1 - 2βL / k 2 , and calculate to obtain 1 / k 1 , L / k 2 , and complete the calibration of the thermosensitive thin-film heat flowmeter.

[0050] Example 4

[0051] The composition of this thermosensitive thin-film heat flowmeter is the same as that of Example 1, and the specific operation is carried out according to the following steps:

[0052] Preparation of the covered thin-film metal mask:

[0053] a. On the silicon-based substrate 1, a thin-film metal mask is covered, and the thermosensitive thin film 2 is grown by magnetron sputtering. The thermosensitive thin film 2 on the silicon-based substrate 1 with the grown pattern is placed in a tube furnace for annealing. The annealing temperature is 800 °C, and the heat preservation time is 30 min to ensure uniform crystal growth of the grains of the thermosensitive thin film 2;

[0054] b. The thermosensitive thin film 2 on the annealed silicon-based substrate 1 is covered with an electrode metal mask, and the composite electrode 3 structure is grown by magnetron sputtering. Then, the grown thermosensitive thin film 2 is placed in an oven for annealing. The composite electrode 3 is prepared on the thermosensitive thin film 2 and the silicon-based substrate 1 by magnetron sputtering. Ti is selected as the electrode transition layer; Ag is selected as the electrode layer;

[0055] c. After annealing is completed, a thermal resistance layer 4 with a thickness of 0.2 mm made of Al 2 O 3 is covered on two thermosensitive units at the A and D diagonals to obtain a thin-film heat flowmeter, as shown in the schematic diagram; Figure 4 as shown;

[0056] d. The completed thin-film heat flowmeter is tested in a constant-temperature oil bath to obtain the temperature-resistance curve of the thermosensitive unit. Then, on the built heat flow test platform, different stable heat flows are applied, and the instantaneous output of V under the excitation voltage V and the output Q of the standard heat flowmeter are recorded. Substitute into the formula Q = 2 / [(Vβ / V SIG -β) / k SIG -β) / k1 -2βL / k 2 , calculate to obtain 1 / k 1 , L / k 2 , and complete the calibration of the thermosensitive thin-film heat flowmeter.

[0057] Example 5

[0058] A microelectromechanical system thermosensitive thin-film heat flowmeter designed based on the principle of Wheatstone bridge, which is made of a silicon-based substrate 1, a thermosensitive thin film 2, a composite electrode 3 and a thermal resistance layer 4; the thermosensitive thin film 2 is grown on the silicon-based substrate 1, the composite electrode 3 is grown on the thermosensitive thin film 2, and the thermal resistance layer 4 is grown on the thermosensitive thin film 2 and the composite electrode 3. The whole heat flowmeter consists of four sensitive units A, B, C and D on the silicon-based substrate 1, where B and C are temperature-sensitive units, and A and D are temperature-sensitive units with a thermal resistance layer covering the surface. The four units are connected by a composite electrode 3 to form a Wheatstone bridge. The following steps are carried out by using the method of coating photoresist and photolithography:

[0059] Preparation of coating photoresist:

[0060] a. Coat photoresist on the silicon-based substrate 1, expose and develop the designed structure of the thermosensitive thin film 2 on the photoresist through a photomask, grow the thermosensitive material on the photoresist by magnetron sputtering, and ultrasonically clean the photoresist with acetone to obtain the thermosensitive thin film 2 on the silicon-based substrate 1;

[0061] b. Anneal the pattern of the thermosensitive thin film 2 on the silicon-based substrate obtained in step a in a tube furnace at an annealing temperature of 700 °C for 30 min to ensure uniform crystal growth of the grains of the thermosensitive thin film 2. The composite electrode 3 is prepared by magnetron sputtering on the thermosensitive thin film 2 and the silicon-based substrate 1, and Ti is selected as the electrode transition layer; Pt is selected as the electrode layer;

[0062] c. Coat photoresist on the thermosensitive thin film of the silicon-based substrate after annealing in step b, expose and develop the composite electrode 3 on the photoresist through a photomask, grow the composite electrode 3 on the photoresist by magnetron sputtering, ultrasonically clean the photoresist with acetone to obtain the composite electrode 3, and then anneal it in an oven at an annealing temperature of 100 °C for 60 min to ensure uniform crystal growth of the grains of the composite electrode 3;

[0063] d. After annealing, cover the two thermosensitive units at the A and D diagonals with a thermal resistance layer 4 of appropriate thickness as SiO 2 , to obtain a heat flowmeter, and a single MEMS unit is as shown in the schematic Figure 4 as shown;

[0064] e. Test a single microelectromechanical system (MEMS) thermosensitive thin-film heat flowmeter in a constant-temperature oil bath to obtain the temperature-resistance curve of the thermosensitive unit, as shown schematically Figure 1 , and then, on the built heat flow test platform, apply different stable heat flows, record the instantaneous output of V under the excitation voltage V SIG and the output Q of the standard heat flowmeter, and substitute them into the formula Q = 2 / [(Vβ / V SIG - β) / k 1 - 2βL / k 2 to calculate 1 / k 1 , L / k 2 , and complete the calibration of the MEMS thermosensitive thin-film heat flowmeter.

[0065] Example 6

[0066] The composition of this thermosensitive thin-film heat flowmeter is based on Example 5, and the specific operation is carried out according to the following steps:

[0067] Coating and photolithography for preparation

[0068] a. Coat photoresist on the silicon-based substrate 1, expose and develop the designed structure of the thermosensitive thin film 2 through a photomask on the photoresist, grow the thermosensitive material on the photoresist by magnetron sputtering, and ultrasonically clean the photoresist with acetone to obtain the pattern of the thermosensitive thin film 2 on the silicon-based substrate 1;

[0069] b. Anneal the pattern of the thermosensitive thin film 2 on the silicon-based substrate obtained in step a in a tube furnace at an annealing temperature of 720 °C for 30 min to ensure uniform crystal grain growth of the thermosensitive thin film 2. The composite electrode 3 is prepared by magnetron sputtering on the thermosensitive thin film 2 and the silicon-based substrate 1, with Cr selected as the electrode transition layer and Au selected as the electrode layer;

[0070] c. Coat photoresist on the silicon-based substrate thermosensitive thin film after annealing in step b, expose and develop the composite electrode 3 through a photomask on the photoresist, grow the composite electrode 3 on the photoresist by magnetron sputtering, ultrasonically clean the photoresist with acetone to obtain the composite electrode 3, and then anneal it in an oven at an annealing temperature of 150 °C for 80 min to ensure uniform crystal grain growth of the composite electrode 3; d. After completion of annealing, cover the two thermosensitive units at the A and D diagonals with a heat resistance layer 4 of appropriate thickness, which is Si 3 N 4 to obtain the heat flowmeter, and a single MEMS unit is as shown schematically Figure 4 ;

[0071] e. Test a single MEMS thermosensitive thin-film heat flowmeter in a constant-temperature oil bath to obtain the temperature-resistance curve of the thermosensitive unit, as shown schematically Figure 1 , and then, on the built heat flow test platform, apply different stable heat flows, record the instantaneous output of V under the excitation voltage VSIG The instantaneous output and the standard heat flowmeter output Q are substituted into the formula Q = 2 / [(Vβ / V SIG -β) / k 1 -2βL / k 2 , and 1 / k 1 , L / k 2 are calculated to complete the calibration of the microelectromechanical system thermosensitive thin-film heat flowmeter.

[0072] Example 7

[0073] The composition of the thermosensitive thin-film heat flowmeter is based on Example 5, and the specific operation is carried out according to the following steps:

[0074] Coating and photolithography preparation

[0075] a. Coating photoresist on the silicon-based substrate 1, exposing and developing the designed thermosensitive thin-film 2 structure through a photomask on the photoresist, growing the thermosensitive material on the photoresist by magnetron sputtering, and ultrasonically cleaning the photoresist with acetone to obtain the pattern of the thermosensitive thin-film 2 on the silicon-based substrate 1;

[0076] b. Annealing the pattern of the thermosensitive thin-film 2 on the silicon-based substrate obtained in step a in a tube furnace at an annealing temperature of 760°C for 30 minutes to ensure uniform crystal growth of the grains of the thermosensitive thin-film 2. The composite electrode 3 is prepared by magnetron sputtering on the thermosensitive thin-film 2 and the silicon-based substrate 1, and Ti is selected as the electrode transition layer; Pt and Au are selected as the electrode layers;

[0077] c. Coating photoresist on the silicon-based substrate thermosensitive thin-film after annealing in step b, exposing and developing the composite electrode 3 through a photomask on the photoresist, growing the composite electrode 3 on the photoresist by magnetron sputtering, ultrasonically cleaning the photoresist with acetone to obtain the composite electrode 3, and then annealing it in an oven at an annealing temperature of 200°C for 100 minutes to ensure uniform crystal growth of the grains of the composite electrode;

[0078] d. After annealing, cover the two thermosensitive units at the A and D diagonals with a thermal resistance layer 4 of appropriate thickness, which is AlN, to obtain the heat flowmeter. A single MEMS unit is as shown in the schematic Figure 4 figure;

[0079] e. Test the single microelectromechanical system thermosensitive thin-film heat flowmeter in a constant-temperature oil bath to obtain the temperature-resistance curve of the thermosensitive unit, as shown in the schematic Figure 1 , and then, on the built heat flow test platform, apply different stable heat flows, record the instantaneous output of V SIG and the standard heat flowmeter output Q under the excitation voltage V, and substitute them into the formula Q = 2 / [(Vβ / V SIG -β) / k 1 -2βL / k 2, the value of 1 / k is calculated 1 , L / k 2 , the calibration of the microelectromechanical system (MEMS) thermosensitive thin-film heat flowmeter is completed.

[0080] Example 8

[0081] The composition of the thermosensitive thin-film heat flowmeter is based on Example 5, and the specific operations are carried out according to the following steps:

[0082] Coating and preparing photoresist

[0083] a. Coating photoresist on the silicon-based substrate 1, exposing and developing the designed structure of the thermosensitive thin film 2 through a photomask on the photoresist, growing the thermosensitive material on the photoresist by magnetron sputtering, and ultrasonically cleaning the photoresist with acetone to obtain the pattern of the thermosensitive thin film 2 on the silicon-based substrate 1;

[0084] b. Annealing the pattern of the thermosensitive thin film 2 on the silicon-based substrate obtained in step a in a tube furnace at an annealing temperature of 800 °C for 30 min to ensure uniform crystal growth of the grains of the thermosensitive thin film 2. The composite electrode 3 is prepared by magnetron sputtering on the thermosensitive thin film 2 and the silicon-based substrate 1, with Ti selected as the electrode transition layer and Ag selected as the electrode layer;

[0085] c. Coating photoresist on the silicon-based substrate thermosensitive thin film after annealing in step b, exposing and developing the composite electrode 3 through a photomask on the photoresist, growing the composite electrode 3 on the photoresist by magnetron sputtering, ultrasonically cleaning the photoresist with acetone to obtain the composite electrode 3, and then annealing it in an oven at an annealing temperature of 300 °C for 120 min to ensure uniform crystal growth of the grains of the composite electrode;

[0086] d. After completion of annealing, cover the two thermosensitive units at the A and D diagonals with a thermal resistance layer Al of appropriate thickness 2 O 3 (4) to obtain the heat flowmeter, and a single MEMS unit is as shown in the schematic Figure 4 as shown;

[0087] e. Testing the single microelectromechanical system thermosensitive thin-film heat flowmeter in a constant-temperature oil bath to obtain the temperature-resistance curve of the thermosensitive unit as shown in the schematic Figure 1 , and then on the built heat flow test platform, applying different stable heat flows, recording the instantaneous output at the excitation voltage V and the output Q of the standard heat flowmeter, substituting them into the formula Q = 2 / [(Vβ / V SIG - β) / k SIG - 2βL / k 1 - 2βL / k 2 , the value of 1 / k is calculated 1 , L / k 2, the calibration of the microelectromechanical system thermosensitive thin-film heat fluxmeter is completed.

[0088] Example 9

[0089] Combined with Figure 3 and Figure 4 , the present invention provides a thermosensitive thin-film heat fluxmeter, including a silicon-based substrate 1, a thermosensitive thin film 2, a composite electrode 3, and a thermal resistance layer 4; the entire heat fluxmeter is composed of four sensitive units A, B, C, and D on the silicon-based substrate, where B and C are temperature-sensitive units, and A and D are temperature-sensitive units with a thermal resistance layer covering the surface. The four units are connected by a composite electrode to form a Wheatstone bridge. The thermosensitive thin film 2 is prepared by magnetron sputtering using a metal oxide material with high stability and is grown on the silicon-based substrate 1. The relationship between the resistance of the thermosensitive thin film and the increase in temperature is as Figure 1 shown. The composite electrode 3 is prepared by magnetron sputtering on the thermosensitive thin film 2 and the silicon substrate 1, and has the advantages of good conductivity, ohmic contact performance, easy welding performance, firm adhesion, and low cost. The thermal resistance layer 4 is grown on the thermosensitive thin film 2 and the composite electrode 3 to play a role in blocking heat flow. The thermal resistance layer 4 is selected as SiO with a thermal conductivity of only 1.4 w / (m·K) 2 Magnetron sputtering growth;

[0090] An excitation voltage V is applied at both ends V + V - of the bridge. When heat flow blows onto the heat fluxmeter, the surface temperature T F of the thermosensitive thin film with a thermal resistance layer is different from the surface temperature T S of the thermosensitive thin film without a thermal resistance layer, resulting in different instantaneous resistances of the thermosensitive thin film. The resistance of the thermosensitive thin film with a thermal resistance layer at that moment is R F , and the resistance of the thermosensitive thin film without a thermal resistance layer is R S , V 2 V - and V 1 V - have different output voltages, causing the bridge to be unbalanced, thereby generating a potential difference. The potential difference V 1 -V 2 is the instantaneous output voltage V SIG of the sensor. According to Fourier's law, the temperature difference is proportional to the applied heat flux density T S -T F =Q / k 1 . Therefore, by measuring the output voltage V SIG =(VβQ / k 1 ) / (2+βQ / k 1 +2βQL / k 2 ) of the Wheatstone bridge measurement circuit, it reflects the applied heat flux density value Q = 2 / [(Vβ / V SIG-(β) / k 1 -2βL / k 2 , compared with the cumbersome and complex tests of the thermal resistance layer thickness and the thermal conductivity, which cannot ensure that the material thickness and thermal conductivity are exactly the same each time, a standard heat flow meter can be used. The thermal conductivity and material of the same device are determined. Thus is a constant. Take the heat flow meter to be calibrated and the standard heat flow meter. Under the same heat flow, the standard heat flow meter measures Q at the same transient, and the heat flow meter to be measured outputs R F , R S , and the calculated constant is 1 / k 1 , L / k 2 Thus, the calibration of the device is completed;

[0091] The specific formula derivation is as follows:

[0092] Initial temperature T 0 , T 0 When the resistance of the thermosensitive thin film is R 0 , under the heat flow, without the thermal resistance layers B and C, the surface temperature of the thermosensitive unit is T s , with the thermal resistance layers A and D, the surface temperature of the thermosensitive unit is T F , and T F <T S The resistance of the thermosensitive units B and C without the thermal resistance layer, that is, the resistance at T s is:

[0093]

[0094] The resistance of the thermosensitive units A and D with the thermal resistance layer, that is, the resistance at T F is

[0095]

[0096] At this time, when an excitation voltage V is applied between V + and V - , V 2 V - The output is

[0097]

[0098] V 1 V - The output is

[0099]

[0100] Then the instantaneous output of the sensor is:

[0101]

[0102] Then study one-dimensional heat transfer such as Figure 2It is shown that for T S , T F The thickness of the thermal resistance layer connecting T with the incident heat flux Q is h, the thickness of the thin film is L, the temperature of the surface of the thermal resistance layer is T S , the temperature of the surface of the thin film is T F , and the temperature of the surface of the substrate is T 0 In -h < x < 0, the temperature is T 1 (x), and the thermal conductivity is k 1 ; in 0 < x < L, the temperature is T 2 (x), and the thermal conductivity is k 2 ; the temperatures T 1 and T 2 satisfy the steady - state equation and satisfy the boundary conditions;

[0103] It is solved that

[0104]

[0105] So

[0106]

[0107]

[0108]

[0109] Substitute the result into the instantaneous output of the sensor

[0110] in

[0111] It is obtained that:

[0112]

[0113]

[0114] The relationship between the instantaneous output V of the sensor and the heat flux Q is obtained. Based on the above idea, a simple two - element heat flux meter can also be fabricated. When there is a thermal resistance layer, that is, when the thermosensitive thin film is at the temperature T SIG , the resistance is F When there is no thermal resistance layer, that is, when the thermosensitive thin film is at T , the resistance is S When it is also known that It is obtained that ​

Claims

1. A microelectromechanical system (MEMS) thermosensitive thin-film heat flux sensor designed based on the Wheatstone bridge principle, characterized in that the thermosensitive thin-film heat flux sensor is made of a silicon-based substrate (1), a thermosensitive thin film (2), a composite electrode (3), and a thermal resistance layer (4); the thermosensitive thin film (2) is grown on the silicon-based substrate (1), the composite electrode (3) is grown on the thermosensitive thin film (2), and the thermal resistance layer (4) is grown on the thermosensitive thin film (2) and the composite electrode (3). The entire heat flux sensor consists of four sensitive units A, B, C, and D on the silicon-based substrate (1). Among them, B and C are temperature-sensitive units, and A and D are temperature-sensitive units with a thermal resistance layer covering the surface. The four units are connected by a composite electrode (3) to form a Wheatstone bridge. The method of using a covering thin-film metal mask or coating photoresist and lithography is as follows: Preparation of the covering thin-film metal mask: a. On the silicon-based substrate (1), cover the thin-film metal mask, and grow the thermosensitive thin film (2) by magnetron sputtering. Place the thermosensitive thin film (2) on the silicon-based substrate (1) with the grown pattern in a tube furnace for annealing. The annealing temperature is 700°C - 800°C, and keep it warm for 30 minutes to ensure uniform grain crystallization growth of the thermosensitive thin film (2); b. Cover the thermosensitive thin film (2) of the annealed silicon-based substrate (1) with an electrode metal mask, and grow the composite electrode (3) structure by magnetron sputtering. Then place the grown thermosensitive thin film (2) in an oven for annealing. The annealing temperature is 100°C - 300°C, and the duration is 60 - 120 minutes to ensure uniform grain crystallization growth of the composite electrode; c. After annealing is completed, a thermal resistance layer (4) with a thickness of 0.05 mm - 0.2 mm is covered on the two thermosensitive units at the A and D diagonals to obtain a thin-film type heat flowmeter, wherein the thermal resistance layer (4) is SiO 2 、Si 3 N 4 、AlN or Al 2 O 3 ; d. Test the completed thin-film heat flux meter in a constant-temperature oil bath to obtain the temperature-resistance curve of the thermosensitive unit. Then, on the established heat flux test platform, apply a stable heat flux, record the instantaneous outputs of VS and G and the output Q of the standard heat flux meter under the excitation voltage V, and substitute them into the formula Q = 2 / [(Vβ / V SIG -β) / k 1 -2βL / k 2 , and calculate to obtain 1 / k 1 , L / k 2 , and complete the calibration of the thermosensitive thin-film heat flux meter, where L is the thickness of the thermosensitive thin film (2), h is the thickness of the thermal resistance layer (4), k 1 is the thermal conductivity of the thermal resistance layer (4), and k 2 is the thermal conductivity of the composite electrode (3) and the thermosensitive thin film (2); Preparation of coating photoresist: a. Coating photoresist on the silicon-based substrate (1), transfer the designed structure of the thermosensitive thin film (2) onto the photoresist through photomask exposure and development. Use magnetron sputtering to grow the thermosensitive material on the photoresist, and ultrasonically clean the photoresist with acetone to obtain the pattern of the thermosensitive thin film (2) on the silicon-based substrate (1); b. Anneal the pattern of the thermosensitive thin film (2) on the silicon-based substrate (1) obtained in step a in a tube furnace. The annealing temperature is 750°C - 800°C, and keep it warm for 30 minutes to ensure uniform grain crystallization growth of the thermosensitive thin film; c. Coating photoresist on the thermosensitive thin film of the silicon-based substrate after annealing in step b, transfer the structure of the composite electrode (3) onto the photoresist through photomask exposure and development. Use magnetron sputtering to grow the composite electrode (3) on the photoresist, and ultrasonically clean the photoresist with acetone to obtain the pattern of the composite electrode (3) on the silicon-based substrate (1) and the thermosensitive thin film (2). Then place it in an oven for annealing. The annealing temperature is 100°C - 300°C, and the duration is 60 - 120 minutes to ensure uniform grain crystallization growth of the composite electrode; d. After annealing is completed, a thermal resistance layer (4) is further covered on two thermosensitive units at the A and D diagonals to obtain a heat flow meter, wherein the thermal resistance layer (4) is SiO 2 、Si 3 N 4 、A1N or Al 2 O 3 ; e. Test a single MEMS thermistor thin film heat flow meter in a constant temperature oil bath to obtain the temperature resistance curve of the thermistor unit. Then, apply different stable heat flows on the constructed heat flow test platform and record the temperature resistance curve under the excitation voltage V. SIG The instantaneous output and the standard heat flow meter output Q are substituted into the formula Q = 2 / [(Vβ / V SIG -β) / k 1 -2βL / k 2 ], and 1 / k is calculated 1 , L / k 2 , complete the calibration of the micro-electromechanical system thermistor thin film heat flow meter, where L is the thickness of the thermistor film (2), h is the thickness of the thermal resistance layer (4), k 1 is the thermal conductivity of the thermal resistance layer (4), k 2 is the thermal conductivity of the composite electrode (3) and the thermosensitive film (2).

2. The microelectromechanical system thermosensitive thin-film heat flux sensor designed based on the Wheatstone bridge principle according to claim 1, characterized in that the thermosensitive thin film (2) is prepared by using a transition metal oxide material through magnetron sputtering and is grown on the silicon-based substrate (1). The resistance of the thermosensitive thin film (2) shows an NTC relationship where it decreases as the temperature rises.

3. The microelectromechanical system thermosensitive thin-film type heat flux meter designed based on the Wheatstone bridge principle according to claim 1, characterized in that, the composite electrode (3) is prepared on the thermosensitive thin film (2) and the silicon-based substrate (1) by magnetron sputtering, and Ti, Cr or Ni is selected as the electrode transition layer; one or two of Pt, Au, Al or Ag are selected as the electrode layer.

4. The microelectromechanical system thermosensitive thin-film type heat flux meter designed based on the Wheatstone bridge principle according to claim 1, characterized in that, the Wheatstone bridge is designed as two pairs of thermistors A and D, B and C composed of four unit resistors A, B, C, and D.

5. The microelectromechanical system thermosensitive thin-film type heat flux meter designed based on the Wheatstone bridge principle according to claim 1, characterized in that, the calibration method is to complete the calibration by obtaining the heat flux calculation coefficient using a standard heat flux meter.

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