Tantalum nitride film, preparation method of film pressure sensing core body and film pressure sensing core body

Abstract

The invention discloses a preparation method of a tantalum nitride film and a film pressure sensing core body and the film pressure sensing core body. The preparation method of the tantalum nitride film comprises the following steps: preparing the tantalum nitride film by taking metal tantalum as a target material and adopting a sputtering deposition process; and carrying out heat treatment on the tantalum nitride film in a mixed atmosphere of nitrogen and oxygen. The preparation method of the film pressure sensing core comprises the step of preparing the tantalum nitride film. According to the invention, the tantalum nitride film with a higher strain coefficient and a lower resistance temperature system is prepared, so that the film pressure sensing core body has the characteristics of high sensitivity, small size, high measurement temperature, small influence on a pneumatic flow field, high test accuracy and the like, and the sensitivity of the core body is improved from 2mV / V to 4mV / V or above; therefore, the monitoring precision and the anti-interference performance can be optimized. Meanwhile, the preparation method has the advantages of being simple in process, convenient to operate, low in preparation cost, high in yield and the like, is suitable for large-scale preparation and is beneficial to industrial application.

Description

Technical Field

[0001] The invention belongs to the technical field of thin film pressure sensors and relates to a tantalum nitride thin film and a method for preparing a thin film pressure sensor core, and a thin film pressure sensor core. Background Art

[0002] Sensor is a very important detection device, which can convert non-electrical physical quantities (physical, biological, etc.) in various environments into electrical signals and other output signals according to a certain law. Nowadays, with the rapid development of smart homes, portable devices and the Internet of Things, sensor technology will be used more and more. It is not only an important symbol in the history of modern scientific and technological development, but also constitutes the three pillars of the modern information technology industry with communication technology and computer technology. The film material of the thin film pressure sensor greatly affects the performance of the sensor, such as the operating temperature, long-term stability and sensitivity. Therefore, the selection of the film material is very important. Among them, the functional resistor film directly constitutes a bridge circuit, and its material strain coefficient, resistivity and resistance temperature coefficient have a great influence on the performance of the thin film pressure sensor.

[0003] At present, the functional materials used to prepare thin film pressure sensors at home and abroad mainly include gold, platinum, manganese, constantan alloy (nickel copper), nickel-chromium, kama alloy (nickel-chromium-aluminum-iron), nickel-chromium-silicon, palladium-chromium and platinum-tungsten alloy, etc. Although alloys are the earliest and more mature functional resistor thin film materials studied, they have good stability and high accuracy in a wide application temperature range, but the strain coefficient is low, resulting in low sensitivity of the sensor. For example, the strain film resistor of the existing thin film pressure sensor uses nickel-chromium alloy material, and its strain coefficient k value is only about 2.0, resulting in the manufactured sensor sensitivity of only about 1.5mV / V, and the low sensitivity will seriously damage the stability, repeatability and signal-to-noise ratio of the sensor. At the same time, the matching high-power amplification circuit makes the sensor unable to meet the miniaturization requirements. In response to the above problems, technicians have proposed the research and development of a variety of strain resistor film materials. For example, nitrides (MN), oxynitrides (M-NO), carbides (MC) and carbonitrides (M-CN) of transition metals such as Zr, Hf and Ta have become candidate materials due to their high melting point, strong antioxidant ability, mature thin film deposition technology and low cost. Among them, tantalum nitride has become a strain resistor film material worthy of attention due to its excellent physical and chemical properties. However, the tantalum nitride film prepared by the existing preparation method still has defects such as low gauge coefficient and high square resistance, which makes it difficult to effectively improve the sensitivity of the thin film pressure sensor. Therefore, it is very necessary to obtain a tantalum nitride film material with a high gauge coefficient and low resistivity for the preparation of highly sensitive thin film pressure sensors, as well as to improve the stability, repeatability and signal-to-noise ratio of the sensor so that it has the reliability to serve for a long time in extreme environments. Summary of the invention

[0004] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art, provide a method for preparing a tantalum nitride film with high gauge coefficient, low square resistance and good stability, and also provide a highly sensitive thin film pressure sensor core and a method for preparing the same.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: A method for preparing a tantalum nitride film comprises the following steps: (1) Using tantalum metal as the target, tantalum nitride thin film was prepared by sputtering deposition process; (2) In a mixed atmosphere of nitrogen and oxygen, heat-treating the tantalum nitride film prepared in step (1) to complete the preparation of the tantalum nitride film.

[0006] The above preparation method is further improved, in step (2), the flow ratio of nitrogen to oxygen in the mixed atmosphere of nitrogen and oxygen is 1:0.05-0.1.

[0007] The above preparation method is further improved in that the temperature of the heat treatment is 300°C to 400°C; and the time of the heat treatment is 1h to 10h.

[0008] The above preparation method is further improved, in step (2), the composition of the tantalum nitride film is TaN 0.5 ~ 0.8 ; The square resistance of the tantalum nitride film is 5Ω / □~10Ω / □; The gauge coefficient of the tantalum nitride film is ≥4.5 when the thickness is 200nm~400nm.

[0009] The above preparation method is further improved, in step (1), the purity of the metal tantalum is 99.99%; the sputtering deposition process is an ion beam sputtering deposition process or a magnetron sputtering deposition process; the process parameters of the ion beam sputtering deposition process are: the sputtering beam current is 60mA~90mA, the cathode current is 8A~16A, the anode voltage is 40V~60V, the screen voltage is 500V~800V, the acceleration voltage is 80V~125V, and the working gas pressure is 7.0×10 -3 Pa~7.5×10 -3 Pa, the process gases are nitrogen and argon, and the flow ratio of nitrogen to argon is 1~3:2.

[0010] As a general technical concept, the present invention also provides a method for preparing a thin film pressure sensor core, comprising the following steps: S1. providing a substrate; S2, depositing a first transition layer, an insulating layer, and a second transition layer on the surface of the substrate in sequence; S3, using metal tantalum as a target material, and adopting a sputtering deposition process to prepare a tantalum nitride film on the surface of the second transition layer; S4, performing photolithography and etching on the tantalum nitride film to form strain resistor bars on the surface of the second transition layer; S5, heat-treating the substrate on which the strain resistor bars are prepared in a mixed atmosphere of nitrogen and oxygen; S6. Sequentially prepare an electrode layer and a protective layer on the heat-treated strain resistor grid to complete the preparation of the thin film pressure sensor core.

[0011] The above preparation method is further improved, in step S5, the flow ratio of nitrogen to oxygen in the mixed atmosphere of nitrogen and oxygen is 1:0.05-0.1.

[0012] The above preparation method is further improved in that the temperature of the heat treatment is 300°C to 400°C; and the time of the heat treatment is 1h to 10h.

[0013] The above preparation method is further improved, in step S5, the composition of the tantalum nitride film is TaN 0.5 ~ 0.8 ; The square resistance of the tantalum nitride film is 5Ω / □~10Ω / □; The gauge coefficient of the tantalum nitride film is ≥4.5 when the thickness is 200nm~400nm.

[0014] The above preparation method is further improved, in step S3, the purity of the metal tantalum is 99.99%; the sputtering deposition process is an ion beam sputtering deposition process or a magnetron sputtering deposition process; the process parameters of the ion beam sputtering deposition process are: the sputtering beam current is 60mA~90mA, the cathode current is 8A~16A, the anode voltage is 40V~60V, the screen voltage is 500V~800V, the acceleration voltage is 80V~125V, and the working gas pressure is 7.0×10 -3 Pa~7.5×10 -3 Pa, the process gases are nitrogen and argon, and the flow ratio of nitrogen to argon is 1~3:2.

[0015] The above preparation method is further improved in that in step S4, the tantalum nitride film is etched by an ion beam method.

[0016] The above preparation method is further improved in that step S6 further includes connecting leads to the electrode layer.

[0017] As a general technical concept, the present invention also provides a thin film pressure sensor core, wherein the thin film pressure sensor core uses the tantalum nitride film prepared by the above-mentioned preparation method as the strain resistance layer, or the thin film pressure sensor core is prepared by the above-mentioned preparation method.

[0018] The above-mentioned thin film pressure sensor core is further improved, wherein the thin film pressure sensor core comprises a substrate, on which a first transition layer, an insulating layer, a second transition layer, a strain resistor layer, an electrode layer and a protective layer are sequentially deposited.

[0019] The above-mentioned thin film pressure sensor core is further improved, wherein the substrate is an elastomer; the material of the elastomer is 17-4PH stainless steel.

[0020] The above-mentioned thin film pressure sensor core is further improved, wherein the first transition layer is a silicon nitride film; the expansion coefficient of the silicon nitride film is 2.6×10 -6 ℃ -1 .

[0021] The above-mentioned thin film pressure sensor core is further improved, wherein the insulating layer is a silicon dioxide film; the expansion coefficient of the silicon dioxide film is 0.5×10 -6 ℃ -1 .

[0022] The above-mentioned thin film pressure sensor core is further improved, wherein the second transition layer is a silicon nitride film; the expansion coefficient of the silicon nitride film is 2.6×10 -6 ℃ -1 .

[0023] The thin film pressure sensor core is further improved in that the strain resistor layer is a tantalum nitride film; the expansion coefficient of the tantalum nitride film is 6.2×10 -6 ℃ -1 .

[0024] The above-mentioned thin film pressure sensor core is further improved in that the electrode layer is a platinum thin film.

[0025] The above-mentioned thin film pressure sensor core is further improved in that the protective layer is a silicon dioxide film.

[0026] Compared with the prior art, the advantages of the present invention are: (1) In view of the shortcomings of the tantalum nitride film prepared by the existing preparation method, such as low strain coefficient and high resistance temperature coefficient, the present invention creatively provides a method for preparing a tantalum nitride film, firstly using metal tantalum as a target material and adopting a sputtering deposition process to prepare a tantalum nitride film, and then heat-treating the prepared tantalum nitride film in a mixed atmosphere of nitrogen and oxygen. During the heat treatment process, not only can the composition of the tantalum nitride strain resistor film be adjusted and thermal stress be released, but also microscopic defects such as vacancies can be healed, the crystallinity of the strain resistor can be improved, and its anti-oxidation performance can be enhanced, so that a tantalum nitride film with a high strain coefficient and a low resistance temperature coefficient can be prepared, wherein the composition of the tantalum nitride film is TaN 0.5 ~0.8 The sheet resistance is 5Ω / □~10Ω / □, and the gauge factor is ≥4.5 under the condition of thickness of 200nm~400nm. The composition of tantalum nitride film prepared by conventional method is TaN 0.5 ~ 1 , the square resistance is 5Ω / □~15Ω / □, and the gauge factor is ≥3.5 under the condition of thickness of 200nm~400nm.

[0027] (2) Aiming at the shortcomings of the tantalum nitride film prepared by the existing preparation method, such as low strain coefficient and high resistance temperature coefficient, and the resulting defects of the thin film pressure sensor core, such as poor sensitivity, large volume, low measurement temperature, great influence on the aerodynamic flow field, and poor measurement accuracy, the present invention creatively provides a method for preparing a thin film pressure sensor core, which sequentially deposits a first transition layer, an insulating layer, a second transition layer, and a tantalum nitride film on the surface of a substrate. By depositing the second transition layer between the insulating layer and the tantalum nitride film, the second transition layer can promote good adhesion between the insulating layer and the tantalum nitride film, reduce thermal stress accumulation, and because the second transition layer has good insulation properties, it can also enhance the insulation of the insulating layer. On this basis, using metal tantalum as a target, a sputtering deposition process is adopted to prepare a tantalum nitride film, and by photolithography and etching, strain resistor bars are formed. Then, the prepared tantalum nitride film is heat-treated in a mixed atmosphere of nitrogen and oxygen. During the heat treatment process, not only the nitride temperature can be adjusted, but also the temperature of the tantalum nitride film can be adjusted. Tantalum strain resistor film composition, release thermal stress, and can also heal micro defects such as vacancies, improve the crystallinity of strain resistors, and enhance their antioxidant properties, so that tantalum nitride films with high strain coefficients and low resistance temperature coefficients can be prepared. As the strain resistor of the thin film pressure sensor core, it can improve the sensitivity of the core, and then by improving the sensitivity of the core, it can also bring the following benefits: (a) The improvement of the core sensitivity can simplify the sensor compensation circuit, promote the miniaturization of the sensor, and meet the needs of the Internet of Things, the Internet of Vehicles and portable devices; (b) The improvement of the core sensitivity can increase the full-scale output, and the user can intelligently adjust and set the product range through the back-end amplifier circuit to improve the intelligence level of the sensor; (c) The improvement of the core sensitivity can make the core suitable for a wider range of ranges, improve the integration capability, reduce the production cost, and make it more competitive in the application of equipment pressure monitoring. Finally, the electrode layer and the protective layer are prepared on the strain resistor grid to complete the preparation of the thin film pressure sensor core. Compared with conventional thin film pressure sensor cores, in the present invention, by preparing a tantalum nitride film with a higher gauge factor and a lower resistance temperature coefficient, the thin film pressure sensor core prepared by the present invention has the characteristics of high sensitivity, small size, high measurement temperature, small impact on the pneumatic flow field, high test accuracy, etc., wherein the sensitivity of the core is increased from 2mV / V to more than 4mV / V, thereby optimizing its monitoring accuracy and anti-interference performance. At the same time, the preparation method of the present invention has the advantages of simple process, convenient operation, low preparation cost, high yield rate, etc., and is suitable for large-scale preparation and conducive to industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to make the purpose, technical solution and advantages of the embodiments of the present invention more clear, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0029] Figure 1 This is a flow chart of the preparation process of the thin film pressure sensor core in Example 2 of the present invention.

[0030] Figure 2a~2g Schematic diagram of the preparation process of the thin film pressure sensor core in Example 2 of the present invention.

[0031] Figure 3 Schematic diagram of the cross-sectional structure of the thin film pressure sensor core in Example 2 of the present invention.

[0032] Figure 4 Schematic diagram of the top view of the thin film pressure sensor core in Example 2 of the present invention.

[0033] Legend: 1. Substrate; 2. First transition layer; 3. Insulation layer; 4. Second transition layer; 5. Strain resistor layer; 6. Electrode layer; 7. Protective layer. DETAILED DESCRIPTION

[0034] The present invention is further described below in conjunction with the accompanying drawings and specific preferred embodiments, but the protection scope of the present invention is not limited thereby.

[0035] Embodiment 1: A method for preparing a tantalum nitride film comprises the following steps: (1) Using tantalum metal as the target, a sputtering deposition process is used to prepare tantalum nitride thin films, as follows: (1.1) A silicon nitride film, a silicon dioxide film, and a silicon nitride film are sequentially deposited on the surface of a substrate using an ion beam sputtering deposition process.

[0036] (1.2) Using 99.99% pure tantalum as the target material, a tantalum nitride film is deposited on the silicon nitride film by an ion beam sputtering deposition process. In this step, the process parameters of the ion beam sputtering deposition process are: sputtering beam current is 70±5mA, cathode current is 12±0.5A, anode voltage is 60V, screen voltage is 600V, acceleration voltage is 105V, and working gas pressure is ≤7.5×10 -3 Pa, the process gases are nitrogen and argon, the flow ratio of nitrogen to argon is 2 sccm:4 sccm, the deposition time is 1 h, and a tantalum nitride film with a thickness of 300 nm is obtained.

[0037] (1.3) A mask is deposited on the tantalum nitride film for photolithography and etching, and the tantalum nitride film is processed into strain resistor bars, wherein the etching method is ion beam etching.

[0038] (2) In a mixed atmosphere of nitrogen and oxygen, heat-treating the tantalum nitride film prepared in step (1) to complete the preparation of the tantalum nitride film.

[0039] In step (2), the flow ratio of nitrogen to oxygen in the mixed atmosphere of nitrogen and oxygen is 1:0.05, the heat treatment temperature is 300° C., and the heat treatment time is 2 h.

[0040] After testing, the composition of the tantalum nitride film obtained after heat treatment is TaN 0.68 The sheet resistance is 5.79Ω / □, and the gauge factor is 5.02 under the condition of thickness of 200nm~400nm. The composition of tantalum nitride film prepared by conventional preparation method is TaN 0.56 , the square resistance is 12Ω / □, and the gauge factor is 3.5 under the condition of thickness of 200nm~400nm. It can be seen that the tantalum nitride film prepared by the present invention has a higher gauge factor and lower square resistance, and when it is used as a strain resistor of a thin film pressure sensor core, it is beneficial to improve the sensitivity of the core.

[0041] In this embodiment, the influence of different heat treatment conditions on the gauge factor of the tantalum nitride film is also investigated, as shown in Tables 1 to 3 below.

[0042] Table 1 Effect of different nitrogen and oxygen flow ratios on the gauge factor of tantalum nitride films

[0043] In Table 1, except for the different flow ratios of nitrogen and oxygen, other conditions are the same as those in Example 1. Table 2 Effect of different heat treatment temperatures on the gauge factor of tantalum nitride films (time 2h)

[0044] In Table 2, except for the heat treatment temperature, other conditions are the same as those in Example 1.

[0045] Table 3 Effect of different heat treatment time on the gauge factor of tantalum nitride film (temperature 300℃)

[0046] In Table 3, except for the heat treatment time, other conditions are the same as those in Example 1.

[0047] It can be seen from the above results that compared with the tantalum nitride film prepared by the conventional preparation method, the composition of the tantalum nitride film prepared by the preparation method of the present invention is TaN 0.5 ~ 0.8 The sheet resistance is 5Ω / □~10Ω / □, and the gauge factor is ≥4.5 under the condition of thickness of 200nm~400nm. The composition of the tantalum nitride film prepared by the conventional method is TaN 0.5 ~ 1The square resistance is 5Ω / □~15Ω / □, and the gauge factor is ≥3.5 under the condition of a thickness of 200nm~400nm. It can be seen that the method of the present invention can prepare a tantalum nitride film with a high gauge factor and a low resistance temperature coefficient.

[0048] Example 2 A method for preparing a thin film pressure sensor core, the preparation process flow chart and the preparation process schematic diagram are as follows Figure 1 As shown in Figure 2, the following steps are included: S1. Provide a substrate, specifically: The 17-4PH stainless steel is processed into an elastomer by mechanical processing as a substrate, and then the upper surface of the elastomer is ground and polished, such as Figure 2a shown.

[0049] S2, depositing a first transition layer, an insulating layer, and a second transition layer on the surface of the substrate in sequence, specifically: The ion beam sputtering deposition process was used to deposit a silicon nitride film (100 nm thick), a silicon dioxide film (6 μm thick), and a silicon nitride film (150 nm thick) on the substrate surface in sequence. Figure 2b~2d In the present invention, by providing two transition layers between the substrate and the tantalum nitride film, the thermal expansion stress between the substrate, the insulating layer and the strained layer can be significantly reduced.

[0050] S3, using tantalum metal as a target material, a tantalum nitride film is prepared on the surface of the second transition layer by a sputtering deposition process, specifically: Using 99.99% pure tantalum as the target material, tantalum nitride film was deposited on silicon nitride film by ion beam sputtering deposition process. In this step, the process parameters of ion beam sputtering deposition process are: sputtering beam current is 70±5mA, cathode current is 12±0.5A, anode voltage is 60V, screen voltage is 600V, acceleration voltage is 105V, working gas pressure is ≤7.5×10 - 3 Pa, the process gases are nitrogen and argon, the flow ratio of nitrogen to argon is 2 sccm:4 sccm, the deposition time is 1 h, and a tantalum nitride film with a thickness of 300 nm is obtained.

[0051] S4, photolithography and etching the tantalum nitride film to form strain resistor bars on the surface of the second transition layer, specifically: A mask is deposited on the tantalum nitride film for photolithography and etching, and the tantalum nitride film is processed into strain resistor bars, wherein the etching method is ion beam etching.

[0052] S5. In a mixed atmosphere of nitrogen and oxygen, heat-treating the substrate on which the strain resistor bars are prepared is carried out, specifically: The entire component is placed in a diffusion furnace, and nitrogen and oxygen are introduced into the diffusion furnace at a flow ratio of nitrogen to oxygen of 1:0.05, so that the entire component is treated in a mixed atmosphere of nitrogen and oxygen, and the temperature is raised to 300°C for heat treatment. The heat preservation time is 2 hours, and the preparation of the strain resistor layer is completed. Figure 2e shown.

[0053] S6, sequentially preparing an electrode layer and a protective layer on the strain resistor bars after the heat treatment, specifically: Replace the mask and sequentially prepare a platinum film and a silicon dioxide film on the strain resistor layer in the corresponding area, such as Figure 2f~2g shown.

[0054] S7. Connect the electrode layer (platinum film) to the external component leads to complete the preparation of the thin film pressure sensor core.

[0055] like Figure 3 and Figure 4 As shown, the thin film pressure sensor core prepared in this embodiment includes a substrate 1, on which a first transition layer 2, an insulating layer 3, a second transition layer 4, a strain resistor layer 5, an electrode layer 6 and a protective layer 7 are sequentially deposited, wherein the substrate 1 is an elastomer, and the material of the elastomer is 17-4PH stainless steel; the first transition layer 2 is a silicon nitride film, and the expansion coefficient is 2.6×10 -6 ℃ -1 ; The insulating layer 3 is a silicon dioxide film with an expansion coefficient of 0.5×10 -6 ℃ -1 The second transition layer 4 is a silicon nitride film with an expansion coefficient of 2.6×10 -6 ℃ -1 ; The strain resistor layer 5 is a tantalum nitride film with an expansion coefficient of 6.2×10 -6 ℃ -1 ; The electrode layer 6 is a platinum film; the protective layer is a silicon dioxide film.

[0056] According to tests, the sensitivity of the thin film pressure sensor core prepared in the embodiment of the present invention is 4.5 mV / V; while the sensitivity of a conventional tantalum nitride thin film pressure sensor core is usually only 2 mV / V.

[0057] In this embodiment, the influence of different heat treatment conditions on the sensitivity of the thin film pressure sensor core is also investigated, as shown in Tables 4 to 6. According to Tables 4 to 6, the core sensitivity is correlated with the oxygen-nitrogen ratio, heat treatment temperature and heat treatment time, among which the tantalum nitride thin film core obtained under the conditions of a deposition nitrogen-oxygen ratio of 1:1.05, a heat treatment temperature of 300°C and a time of 2h has the highest sensitivity, reaching 4.5mV / V.

[0058] Table 4 Effect of different nitrogen and oxygen flow ratios on the sensitivity of the thin film pressure sensor core

[0059] In Table 4, except for the different flow ratios of nitrogen and oxygen, other conditions are the same as those in Example 2. Table 5 Effect of different heat treatment temperatures on the sensitivity of thin film pressure sensor core (time 2h)

[0060] In Table 5, except for the heat treatment temperature, other conditions are the same as those in Example 2.

[0061] Table 6 Effect of different heat treatment times on the sensitivity of thin film pressure sensor core (temperature 300℃)

[0062] In Table 6, except for the heat treatment time, other conditions are the same as those in Example 2.

[0063] It can be seen from the above results that compared with the tantalum nitride thin film pressure sensor core, the present invention improves the sensitivity of the thin film pressure sensor core from 2mV / V to more than 4mV / V by preparing a tantalum nitride thin film with a higher gauge factor and a lower resistance temperature coefficient, thereby optimizing its monitoring accuracy and anti-interference performance. At the same time, by improving the sensitivity of the core, the following benefits can be brought: (a) The improvement of the core sensitivity can simplify the sensor compensation circuit, promote the miniaturization of the sensor, and meet the requirements of the Internet of Things, the Internet of Vehicles, and portable devices; (b) The improvement of the core sensitivity can increase the full-scale output, and the user can intelligently adjust and set the product range through the back-end amplifier circuit to improve the intelligence level of the sensor; (c) The improvement of the core sensitivity can make the core suitable for a wider range, improve the integration capability, reduce the production cost, and make it more competitive in the application of equipment pressure monitoring. At the same time, the preparation method of the present invention has the advantages of simple process, convenient operation, low preparation cost, high yield rate, etc., is suitable for large-scale preparation, and is conducive to industrial application.

[0064] The above embodiments are only preferred implementations of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a tantalum nitride thin film, characterized in that: The following steps are involved: (1) Using tantalum metal as the target, tantalum nitride thin film was prepared by sputtering deposition process; (2) In a mixed atmosphere of nitrogen and oxygen, heat-treating the tantalum nitride film prepared in step (1) to complete the preparation of the tantalum nitride film.

2. The preparation method according to claim 1, characterized in that: In step (2), the flow ratio of nitrogen to oxygen in the mixed atmosphere of nitrogen and oxygen is 1:0.05-0.1; the temperature of the heat treatment is 300°C-400°C; and the time of the heat treatment is 1h-10h.

3. The preparation method according to claim 2, characterized in that: In step (2), the composition of the tantalum nitride film is TaN 0.5 ~ 0.8 ; The square resistance of the tantalum nitride film is 5Ω / □~10Ω / □; The gauge coefficient of the tantalum nitride film is ≥4.5 when the thickness is 200nm~400nm.

4. The preparation method according to any one of claims 1 to 3, characterized in that In step (1), the purity of the metal tantalum is 99.99%; the sputtering deposition process is an ion beam sputtering deposition process or a magnetron sputtering deposition process; the process parameters of the ion beam sputtering deposition process are: the sputtering beam current is 60mA~90mA, the cathode current is 8A~16A, the anode voltage is 40V~60V, the screen voltage is 500V~800V, the acceleration voltage is 80V~125V, and the working gas pressure is 7.0×10 -3 Pa~7.5×10 -3 Pa, the process gases are nitrogen and argon, and the flow ratio of nitrogen to argon is 1~3:

2.

5. A method for preparing a thin film pressure sensor core, characterized in that: The following steps are involved: S1. providing a substrate; S2, depositing a first transition layer, an insulating layer, and a second transition layer on the surface of the substrate in sequence; S3, using metal tantalum as a target material, and adopting a sputtering deposition process to prepare a tantalum nitride film on the surface of the second transition layer; S4, performing photolithography and etching on the tantalum nitride film to form strain resistor bars on the surface of the second transition layer; S5, heat-treating the substrate on which the strain resistor bars are prepared in a mixed atmosphere of nitrogen and oxygen; S6. Sequentially prepare an electrode layer and a protective layer on the heat-treated strain resistor grid to complete the preparation of the thin film pressure sensor core.

6. The preparation method according to claim 5, characterized in that: In step S5, the flow ratio of nitrogen to oxygen in the mixed atmosphere of nitrogen and oxygen is 1:0.05-0.1; the temperature of the heat treatment is 300°C-400°C; and the time of the heat treatment is 1h-10h.

7. The preparation method according to claim 6, characterized in that: In step S5, the composition of the tantalum nitride film is TaN 0.5 ~ 0.8 ; The square resistance of the tantalum nitride film is 5Ω / □~10Ω / □; The gauge coefficient of the tantalum nitride film is ≥4.5 when the thickness is 200nm~400nm.

8. The preparation method according to any one of claims 5 to 7, characterized in that In step S3, the purity of the metal tantalum is 99.99%; the sputtering deposition process is an ion beam sputtering deposition process or a magnetron sputtering deposition process; the process parameters of the ion beam sputtering deposition process are: the sputtering beam current is 60mA~90mA, the cathode current is 8A~16A, the anode voltage is 40V~60V, the screen voltage is 500V~800V, the acceleration voltage is 80V~125V, and the working gas pressure is 7.0×10 -3 Pa~7.5×10 -3 Pa, the process gas is nitrogen and argon, and the flow ratio of nitrogen to argon is 1~3:2; In step S4, the tantalum nitride film is etched by an ion beam method; Step S6 also includes connecting leads to the electrode layer.

9. A thin film pressure sensor core, characterized in that: The thin film pressure sensor core body is a tantalum nitride thin film prepared by the preparation method described in any one of claims 1 to 4 as a strain resistance layer, or the thin film pressure sensor core body is prepared by the preparation method described in any one of claims 5 to 8.

10. The thin film pressure sensor core according to claim 9, characterized in that: The thin film pressure sensor core comprises a substrate, on which a first transition layer, an insulating layer, a second transition layer, a strain resistor layer, an electrode layer and a protective layer are sequentially deposited; The substrate is an elastomer; the material of the elastomer is 17-4PH stainless steel; The first transition layer is a silicon nitride film; the expansion coefficient of the silicon nitride film is 2.6×10 -6 ℃ -1 ; The insulating layer is a silicon dioxide film; the expansion coefficient of the silicon dioxide film is 0.5×10 -6 ℃ -1 ; The second transition layer is a silicon nitride film; the expansion coefficient of the silicon nitride film is 2.6×10 -6 ℃ -1 ; The expansion coefficient of the strain resistor layer is 6.2×10 -6 ℃ -1 ; The electrode layer is a platinum film; The protective layer is a silicon dioxide film.

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