Temperature sensor based on negative resistance temperature coefficient film and preparation method

Abstract

The invention provides a temperature sensor based on a negative resistance temperature coefficient film and a preparation method, and the method comprises the steps: depositing the negative resistance temperature coefficient film on a substrate as a temperature sensitive film of the sensor, and adjusting the stress level of the negative resistance temperature coefficient film, regulating and controlling the phase change degree and the conductivity of the negative resistance temperature coefficient thin film to realize regulation and control of the temperature sensing characteristic of the negative resistance temperature coefficient thin film so as to obtain a target negative resistance temperature coefficient thin film; and processing the negative resistance temperature coefficient film through an MEMS technology to obtain a target temperature sensor. By regulating the stress level in the negative resistance temperature coefficient thin film, the high-sensitivity temperature zone of the temperature sensor based on the negative resistance temperature coefficient thin film can be regulated in a range from deep hypothermia to room temperature, the temperature range of the high-sensitivity sensing temperature zone of the temperature sensor is widened, and the stability of the temperature sensor can be ensured.

Description

Technical Field

[0001] This application relates to the field of temperature sensors, and more specifically, to a temperature sensor based on a negative resistance temperature coefficient thin film and its fabrication method. Background Technology

[0002] Temperature sensors are used in a variety of applications, such as particle accelerators, space satellites, quantum devices, and photolithography equipment, covering a wide temperature range from cryogenic to room temperature. Therefore, temperature sensors with a wide temperature range offer significant advantages. Negative temperature coefficient (NTC) thin films have been shown to exhibit a negative correlation between resistance and temperature over a relatively wide temperature range, making them suitable for developing temperature sensors with broad temperature coverage. However, for applications requiring high-precision room temperature sensing, the sensitivity of NTC-based temperature sensors near room temperature remains insufficient. Therefore, it is crucial to adjust the high-sensitivity sensing temperature range of NTC-based temperature sensors to meet the high-precision sensing requirements of different temperature zones.

[0003] By controlling the conductivity of a negative temperature coefficient (NTC) thin film, the resistance-temperature characteristic curve of the film can be adjusted, thereby regulating its high-sensitivity sensing temperature range. A search reveals Chinese invention patent CN105967655A, which discloses a lithium iron-doped nickel oxide NTC thermistor material. This material adjusts the room-temperature resistance of the thermistor element by changing the content of trace dopants, thus regulating the film's resistance-temperature characteristic curve. However, adjusting the film's performance by regulating the dopant content can easily introduce excess vacancies or interstitial impurities. These defects can introduce unstable residual stress into the film, affecting the stability of the temperature sensor.

[0004] Patent application CN110132445A discloses a negative temperature coefficient resistive cryogenic temperature sensor and its fabrication method. The sensor's temperature-sensitive film is a hafnium oxynitride (HNO3) thin film. The HNO3 thin film growth process involves adjusting the flow rate of the reacting nitrogen-oxygen mixed gas to obtain different nitrogen-oxygen ratios, resulting in HNO3 films with varying properties. After obtaining the HNO3 thin film, a miniature hafnium oxynitride cryogenic sensor is fabricated using MEMS microfabrication technology. However, controlling the film's performance by adjusting its chemical composition can easily introduce vacancies or interstitial impurities, affecting the sensor's stability. Furthermore, this existing technology only regulates the film's performance by adjusting the flow rate of the nitrogen-oxygen mixed gas, resulting in a single control mechanism. Moreover, this control mechanism relies on precise gas flow control and strict vacuum management, making it difficult to guarantee consistency in mass production. Summary of the Invention

[0005] In view of one of the defects in the prior art, the purpose of this application is to provide a temperature sensor based on a negative resistance temperature coefficient thin film and its preparation method.

[0006] A first aspect of this application provides a method for fabricating a temperature sensor based on a negative resistance temperature coefficient thin film, comprising:

[0007] A negative resistance temperature coefficient thin film is deposited on a substrate as a temperature-sensitive film for a sensor. By adjusting the stress level in the negative resistance temperature coefficient thin film, the phase transition degree and conductivity of the negative resistance temperature coefficient thin film are controlled, thereby controlling the temperature sensing characteristics of the negative resistance temperature coefficient thin film and obtaining the target negative resistance temperature coefficient thin film.

[0008] The target temperature sensor is obtained by processing the negative resistance temperature coefficient thin film using MEMS technology.

[0009] Alternatively, the stress level in the negative resistance temperature coefficient film can be adjusted by adjusting the substrate type.

[0010] Optionally, adjusting the stress level in the negative resistance temperature coefficient film by adjusting the substrate type can be achieved by adjusting the substrate material or adjusting the substrate structure.

[0011] Optionally, the stress level in the negative resistance temperature coefficient film can be adjusted by adjusting the geometric parameters of the film.

[0012] Optionally, the adjustment of the stress level in the negative resistance temperature coefficient film by adjusting the geometric parameters of the film can be carried out in any of the following ways:

[0013] - Adjust the thickness of the negative resistance temperature coefficient film;

[0014] - Adjust the planar dimensions of the negative resistance temperature coefficient film.

[0015] Alternatively, the stress level in the negative resistance temperature coefficient film can be adjusted by adjusting the pressure level applied to the film.

[0016] Optionally, the negative resistance temperature coefficient film is a transition metal nitride film.

[0017] Optionally, the negative resistance temperature coefficient film is a doped transition metal nitride film, and the doped impurity ions are any one of low-valence anions, high-valence cations, and equivalent cations.

[0018] Optionally, the low-valence anion includes F - ,Br - O 2- S 2- and Se2- Any one of them, the high-valence cation includes C 4+ Si 4+ Sn 4+ and P 5+ Any one of them, the equivalent cation includes B 3+ Al 3+ and Ga 3+ Any one of them.

[0019] Optionally, the negative resistance temperature coefficient thin film is deposited by any one of physical vapor deposition, electron beam evaporation, ion beam assisted deposition, pulsed laser deposition, and chemical vapor deposition.

[0020] A second aspect of this application provides a temperature sensor based on a negative resistance temperature coefficient thin film, which is prepared using the method described above.

[0021] The method for fabricating a temperature sensor based on a negative resistance temperature coefficient film provided in this application allows for the control of the high-sensitivity temperature range of the temperature sensor from deep low temperature to room temperature by adjusting the stress level in the negative resistance temperature coefficient film. This broadens the temperature range of the high-sensitivity temperature range of the temperature sensor and ensures the stability of the temperature sensor.

[0022] Other technical effects resulting from the additional features will be further illustrated in the corresponding embodiments. Attached Figure Description

[0023] Other features, objects, and advantages of this application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0024] Figure 1 This is a flowchart illustrating a method for fabricating a temperature sensor based on a negative resistance temperature coefficient thin film according to an exemplary embodiment.

[0025] Figure 2 This is a flowchart illustrating the fabrication of a temperature sensor using MEMS technology with thin film processing, according to an exemplary embodiment.

[0026] Figure 3 This is a schematic diagram illustrating the high-sensitivity temperature range control of a temperature sensor based on a negative resistance temperature coefficient thin film, according to an exemplary embodiment.

[0027] Figure 4 The results show the stability test of a temperature sensor based on a 15nm thick zirconium oxynitride thin film over 60 minutes. Detailed Implementation

[0028] The present application will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present application, but do not limit the present application in any way. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present application, and these all fall within the protection scope of the present application. Parts not described in detail in the following embodiments can be implemented using existing technology.

[0029] Existing technologies that regulate the conductivity of negative temperature coefficient thin films by adjusting the dopant content can negatively impact the stability of temperature sensors. To address these issues, this application provides a method for fabricating a temperature sensor based on a negative temperature coefficient thin film.

[0030] Reference Figure 1 As shown, in one embodiment of this application, a method for fabricating a temperature sensor based on a negative resistance temperature coefficient thin film includes:

[0031] S1. A negative resistance temperature coefficient film is deposited on a substrate as the temperature-sensitive film of the sensor. By adjusting the stress level in the negative resistance temperature coefficient film, the phase transition degree and conductivity of the negative resistance temperature coefficient film are controlled, thereby controlling the temperature sensing characteristics of the negative resistance temperature coefficient film and obtaining the target negative resistance temperature coefficient film. The target negative resistance temperature coefficient film has a high-sensitivity sensing temperature range that meets the requirements.

[0032] S2. A negative resistance temperature coefficient thin film is fabricated using MEMS technology to obtain the target temperature sensor. The fabrication of the negative resistance temperature coefficient thin film using MEMS technology can be achieved using existing technologies.

[0033] Specifically, this application proposes introducing stress into a negative temperature coefficient (NTC) thin film to drive a phase transition in the film material. By adjusting the stress level in the film, the degree of phase transition can be controlled, thereby regulating the relative content of conductive and insulating phases and controlling the conductivity of the film material. Ultimately, this allows the resistance-temperature characteristic curve of a temperature sensor based on an NTC thin film to be shifted across different temperature ranges, achieving control over the high-sensitivity sensing temperature range of the temperature sensor. Based on this principle, this application's embodiments, by adjusting the stress level of the NTC thin film, enable the high-sensitivity temperature range of the temperature sensor based on the NTC thin film to be controlled within the range from deep cryogenic temperatures to room temperature. This breaks the limitation of traditional temperature sensors, which are only suitable for high-sensitivity sensing within a fixed temperature range, and broadens the temperature range of high-precision sensing (i.e., the temperature range of the high-sensitivity sensing range). Furthermore, the control of the film stress level can be achieved without changing the dopant content, which is beneficial to the stability of the temperature sensor.

[0034] In some specific embodiments of this application, the stress level in a negative resistance temperature coefficient thin film is adjusted by adjusting the substrate type.

[0035] In some specific embodiments of this application, the stress level in the negative resistance temperature coefficient film is adjusted by adjusting the substrate type, which is done by adjusting the substrate material or adjusting the substrate structure.

[0036] Specifically, the stress level in the negative resistance temperature coefficient film is adjusted by regulating the difference in thermal expansion coefficients between the substrate and the negative resistance temperature coefficient film through adjusting the type of substrate material.

[0037] For example, when depositing a negative temperature coefficient of resistance (NTC) film, the film is deposited on substrates of different materials such as single-crystal silicon, silicon oxide, magnesium oxide, strontium titanate, zinc oxide, glass, stainless steel with an insulating layer, and sapphire. To obtain the target temperature sensor, the substrate material should possess high thermal conductivity and insulation. When depositing the NTC film at a temperature above room temperature, stress is introduced into the film by utilizing the difference in shrinkage between the substrate and the film upon cooling to room temperature after deposition. When the coefficient of thermal expansion of the substrate is greater than that of the film, the substrate shrinks more after cooling, generating compressive stress in the film; the larger the coefficient of thermal expansion of the substrate, the greater the compressive stress in the film. When the coefficient of thermal expansion of the substrate is less than that of the film, the film shrinks more after cooling, generating tensile stress in the film; the smaller the coefficient of thermal expansion of the substrate, the greater the tensile stress in the film. By depositing NTC films on different substrate materials and testing their resistance-temperature relationship curves, the relationship between the substrate's coefficient of thermal expansion and the film's temperature sensing characteristics can be established. Based on the experimental results, a relationship was established between the thermal expansion coefficient of the substrate and the temperature sensing characteristics of the thin film. In order to obtain a negative resistance temperature coefficient thin film with the target temperature sensing characteristics, a substrate material with a specific thermal expansion coefficient was selected based on the relationship between the thermal expansion coefficient of the substrate and the temperature sensing characteristics of the thin film.

[0038] In other embodiments, substrates of other material types can also be used, as long as they have a different coefficient of thermal expansion than the negative resistance temperature coefficient film, and have high thermal conductivity and insulation to meet the requirements of film temperature sensing characteristics.

[0039] To achieve substrate structure adjustment, a groove array structure is designed and arranged on the substrate using MEMS fabrication technology before the deposition of the negative temperature coefficient of resistance (NTC) film. The grooves can be any structure, such as rectangular, cylindrical, or V-shaped, and the groove spacing is adjusted within the range of 0.2–20 μm. The NTC film is then deposited on the substrate with the groove array structure, and the stress level of the NTC film is adjusted by regulating the groove spacing. For any groove shape, the smaller the groove spacing, the greater the stress level in the NTC film. NTC films with different groove spacings are deposited on substrates with arbitrary groove shapes, and their resistance-temperature relationship curves are tested to establish the relationship between groove spacing and film temperature sensing characteristics under arbitrary groove shapes. Based on the experimental results establishing the relationship between groove spacing and film temperature sensing characteristics under arbitrary groove shapes, a specific groove spacing is selected to obtain a NTC film with target temperature sensing characteristics under arbitrary groove shapes, based on this relationship.

[0040] In some specific embodiments of this application, the stress level in the negative resistance temperature coefficient film is adjusted by adjusting the geometric parameters of the film.

[0041] In some specific embodiments of this application, the stress level in the negative resistance temperature coefficient film is adjusted by adjusting the geometric parameters of the film, using any one of the following methods: adjusting the thickness of the negative resistance temperature coefficient film, or adjusting the planar dimensions of the film.

[0042] Adjusting the thickness of a negative resistance temperature coefficient (NRTC) film involves regulating the film thickness during deposition by adjusting the deposition time, deposition power, or the argon flow rate during the deposition process, thereby adjusting the stress level within the NRTC film. For example, to adjust the NRTC film thickness, the deposition time can be adjusted within the range of 50–50000 s, the deposition power within the range of 10–500 W, or the argon flow rate within the range of 0.5–50 sccm. The thinner the NRTC film, the greater the stress level within it. By adjusting the deposition time to deposit NRTC films of different thicknesses and testing their resistance-temperature curves, the relationship between the NRTC film thickness and its temperature sensing characteristics is established. Based on this experimentally established relationship, to obtain a NRTC film with the target temperature sensing characteristics, a NRTC film of a specific thickness is deposited at a specific deposition time.

[0043] Adjusting the planar dimensions of the negative resistance temperature coefficient (NRTC) film, i.e., introducing stress by reducing the film's planar dimensions, allows for the control of stress levels. For example, after depositing the NRTC film, a MEMS fabrication process is used to pattern the film array, forming an array where the length and width of each array unit are adjusted within the range of 0.2–20 μm. Smaller lengths and widths of the NRTC film result in higher stress levels. By fabricating NRTC film arrays with different length and width combinations and testing the resistance-temperature relationship curves of the arrays, the relationship between the length and width combinations of the NRTC film array and the film's temperature sensing characteristics is established. Based on the experimentally established relationship between the length and width combinations of the NRTC film array and its temperature sensing characteristics, NRTC film arrays with specific length and width combinations are fabricated to obtain NRTC films with target temperature sensing characteristics.

[0044] In some specific embodiments of this application, the stress level in the negative resistance temperature coefficient film is adjusted by adjusting the pressure level applied to the film.

[0045] The pressure level applied to the negative temperature coefficient (NTC) film is adjusted, i.e., high pressure is applied to the film during or after NTC film deposition to introduce stress into the film. The stress level in the NTC film is adjusted by regulating the pressure level. For example, the total gas pressure is adjusted within the range of 1–1000 Pa during or after NTC film deposition. The higher the pressure level applied to the NTC film, the greater the stress level in the film. By adjusting the total gas pressure, the pressure level applied to the NTC film is regulated, and the resistance-temperature relationship curves of the film after pressurization at different pressure levels are tested to establish the relationship between the pressure level applied to the NTC film and the film's temperature sensing characteristics. Based on the experimentally established relationship between the pressure level applied to the NTC film and its temperature sensing characteristics, the NTC film is pressurized at a specific total gas pressure to obtain a NTC film with the target temperature sensing characteristics.

[0046] The resistance of a negative temperature coefficient film is negatively correlated with temperature. In some specific embodiments of this application, the negative temperature coefficient film is a transition metal nitride film. Under stress, the transition metal nitride film contains a conductive phase of transition metal nitride and an insulating phase of M3N4 with an ideal stoichiometric ratio. The stress level in the film can control the ratio of the conductive and insulating phases, thereby controlling the conductivity and temperature sensitivity of the film.

[0047] For example, transition metal nitrides include niobium nitride, chromium nitride, titanium nitride, zirconium nitride, hafnium nitride, vanadium nitride, tantalum nitride, molybdenum nitride, etc.

[0048] In some specific embodiments of this application, the negative resistance temperature coefficient thin film is a doped transition metal nitride thin film, which is a thin film doped with impurity ions in a transition metal nitride. The doped impurity ions can be any one of low-valence anions, high-valence cations, and equivalent cations. By doping, an insulating phase can be constructed in the transition metal nitride, and the stress level in the thin film can control the ratio of the conductive phase to the insulating phase in the thin film, thereby controlling the conductivity and temperature sensitivity characteristics of the thin film.

[0049] In some specific embodiments of this application, the low-valence anion includes F - ,Br - O 2- S 2- and Se 2- Any one of them, high-valence cations including C 4+ Si 4+ Sn 4+ and P 5+ Any one of them, the equivalent cation includes B 3+ Al 3+ and Ga 3+ Any one of them.

[0050] To achieve a negative temperature coefficient of resistance, considering that the transition metal nitride phase with an ideal stoichiometric ratio is a conductive phase, the impurity ions doped into the transition metal nitride should favor the construction of the insulating phase. Doping transition metal nitrides with low-valence anions and high-valence cations can generate transition metal cation vacancies, which are beneficial to the construction of the insulating phase M3N4, where M represents the transition metal element and N represents nitrogen. Furthermore, the doped low-valence anions and high-valence cations should not introduce a conductive phase after combining with transition metal cations or nitrogen ions.

[0051] It should be noted that the above-mentioned nitride phase is an insulating phase and can also be used as a dopant ion for transition metal nitrides.

[0052] In other implementations, other types of thin films may be used, as long as they can achieve the negative temperature coefficient of resistance characteristic.

[0053] In the embodiments described above, the phase transition degree and conductivity of the negative resistance temperature coefficient thin film are controlled by adjusting the relative content of the conductive and insulating phases of the film. In both transition metal nitrides and doped transition metal nitrides, the conductive phase is a transition metal nitride phase with an ideal stoichiometric ratio. In transition metal nitrides, the insulating phase is an M3N4 type phase, where M represents a transition metal element, including niobium, chromium, titanium, zirconium, hafnium, vanadium, tantalum, molybdenum, etc., and N represents nitrogen. In low-valence anion-doped transition metal nitrides, the insulating phase is a compound phase of the doped anion and transition metal cation and an M3N4 type phase. In high-valence cation-doped transition metal nitrides, the insulating phase is a nitride phase of the doped cation and an M3N4 type phase. In equivalent cation-doped transition metal nitrides, the insulating phase is a nitride phase of the doped cation.

[0054] Transition metal nitride thin films can be deposited using any of the following methods: A high-purity transition metal target (e.g., niobium, chromium, titanium, zirconium, hafnium, vanadium, tantalum, molybdenum) is added to the deposition chamber; high-purity argon and high-purity nitrogen are introduced, with high-purity argon serving as the working gas to bombard the target and generate glow discharge, and high-purity nitrogen serving as the reactant gas to provide nitrogen ions from the transition metal nitride; the substrate is heated to a specified temperature, and the transition metal nitride thin film is deposited onto the substrate under an argon and nitrogen atmosphere; or, a high-purity transition metal nitride target (e.g., niobium nitride, chromium nitride, titanium nitride, zirconium nitride, hafnium nitride, vanadium nitride, tantalum nitride, molybdenum nitride) is added to the deposition chamber; high-purity argon is introduced as the working gas to bombard the target and generate glow discharge; the substrate is heated to a specified temperature, and the transition metal nitride thin film is deposited onto the substrate under an argon atmosphere.

[0055] For example, a high-purity transition metal target with a purity of 99% to 99.999% is added to the deposition chamber. The high-purity transition metal target can be any one of niobium, chromium, titanium, zirconium, hafnium, vanadium, tantalum, or molybdenum targets. High-purity argon and high-purity nitrogen are introduced, both with a purity of 99% to 99.999% and a flow rate in the range of 0.5 to 50 sccm. The substrate is heated to a specified temperature in the range of 20 to 800°C, and a transition metal nitride film is deposited onto the substrate under an argon and nitrogen atmosphere; or... A high-purity transition metal nitride target with a purity of 99% to 99.999% is added to the deposition chamber. The high-purity transition metal nitride target can be any one of the following targets: niobium nitride, chromium nitride, titanium nitride, zirconium nitride, hafnium nitride, vanadium nitride, tantalum nitride, molybdenum nitride, etc. High-purity argon gas with a purity of 99% to 99.999% and a flow rate in the range of 0.5 to 50 sccm is introduced. The substrate is heated to a specified temperature in the range of 20 to 800°C, and a transition metal nitride film is deposited on the substrate under an argon atmosphere.

[0056] Doped transition metal nitride films are deposited using any of the following methods: Doping low-valence anions into transition metal nitrides is achieved through the following methods: A high-purity transition metal target, such as niobium, chromium, titanium, zirconium, hafnium, vanadium, tantalum, or molybdenum, is added to the deposition chamber. High-purity argon and high-purity nitrogen are introduced, with argon serving as the working gas to bombard the target and generate glow discharge, and nitrogen serving as the reactant gas to provide nitrogen ions for the doped transition metal nitrides. To facilitate adjustment of the dopant gas flow rate, any one of HF, HBr, O2, H2S, or H2Se is introduced separately as the reactant gas to provide dopant anions for the doped transition metal nitrides. The substrate is heated to a specified temperature, and the doped transition metal nitride film is deposited onto the substrate under an atmosphere of argon, nitrogen, and the dopant gas. Alternatively, a high-purity transition metal target, such as niobium, is added to the deposition chamber. The substrate is heated to a specified temperature, and a thin film of doped transition metal nitride is deposited on the substrate under an atmosphere of argon and the mixed gas. Alternatively, a high-purity target material of transition metal nitride is added to the deposition chamber, and high-purity argon is used as the working gas to bombard the target material and generate glow discharge. High ...

[0057] For example, a high-purity transition metal target with a purity of 99% to 99.999% is added to the deposition chamber. The high-purity transition metal target can be any one of niobium, chromium, titanium, zirconium, hafnium, vanadium, tantalum, or molybdenum targets. High-purity argon and high-purity nitrogen are introduced, along with any one of the doping gases selected from HF, HCl, HBr, HI, O2, H2S, and H2Se. All introduced gases have a purity of 99% to 99.999% and a flow rate in the range of 0.5 to 50 sccm. The substrate is then heated to 20–80 °C. At a specified temperature within the range of 00℃, a doped transition metal nitride film is deposited onto a substrate under an atmosphere of argon, nitrogen, and dopant gas; alternatively, a high-purity transition metal target with a purity of 99%–99.999% is added to the deposition chamber. The high-purity transition metal target can be any one of niobium, chromium, titanium, zirconium, hafnium, vanadium, tantalum, or molybdenum targets. High-purity argon gas with a purity of 99%–99.999% is introduced at a flow rate in the range of 0.5–50 sccm. HF, HBr, O2, and H2S are also introduced. A mixture of any dopant gas (H₂Se) and nitrogen, wherein the dopant gas content in the mixture ranges from 0.05% to 50%, and the flow rate of the mixture ranges from 0.5 to 50 sccm, is used. The substrate is heated to a specified temperature in the range of 20 to 800°C, and a doped transition metal nitride film is deposited on the substrate in an atmosphere of argon and the mixture; or a high-purity transition metal nitride target with a purity of 99% to 99.999% is added to the deposition chamber, wherein the high-purity transition metal nitride target is nitrogen. Using any one of the target materials such as niobium nitride, chromium nitride, titanium nitride, zirconium nitride, hafnium nitride, vanadium nitride, tantalum nitride, and molybdenum nitride, high-purity argon gas is introduced, along with any one of the doping gases HF, HBr, O2, H2S, and H2Se. The purity of the introduced gases is 99% to 99.999%, and the flow rate is in the range of 0.5 to 50 sccm. The substrate is heated to a specified temperature in the range of 20 to 800°C, and a thin film of doped transition metal nitride is deposited on the substrate under the atmosphere of argon and the doping gas.

[0058] Doping transition metal nitrides with high-valence cations or equivalent cations is achieved through the following method: A high-purity transition metal target is added to the deposition chamber. The high-purity transition metal target can be any one of niobium, chromium, titanium, zirconium, hafnium, vanadium, tantalum, or molybdenum. A high-purity target with any one of the doping elements C, Si, Sn, P, B, Al, or Ga is added to provide the dopant cations in the transition metal nitrides. High-purity argon and high-purity nitrogen are introduced, with high-purity argon serving as the working gas to bombard the target and generate glow discharge, and high-purity nitrogen serving as the reactant gas to provide nitrogen ions in the transition metal nitrides. The substrate is heated to a specified temperature, and argon... Under a gas and nitrogen atmosphere, a thin film of doped transition metal nitride is deposited onto the substrate; or, a high-purity target of transition metal nitride is added to the deposition chamber. The high-purity target of transition metal nitride is any one of the targets such as niobium nitride, chromium nitride, titanium nitride, zirconium nitride, hafnium nitride, vanadium nitride, tantalum nitride, and molybdenum nitride. A high-purity target of any one of the doping elements C, Si, Sn, P, B, Al, and Ga is added to provide doped cations in the doped transition metal nitride. High-purity argon gas is introduced as the working gas to bombard the target to generate glow discharge. The substrate is heated to a specified temperature, and the thin film of doped transition metal nitride is deposited onto the substrate under an argon atmosphere.

[0059] For example, a high-purity transition metal target with a purity of 99% to 99.999% is added to the deposition chamber. The high-purity transition metal target can be any one of niobium, chromium, titanium, zirconium, hafnium, vanadium, tantalum, or molybdenum targets. A high-purity target with a purity of 99% to 99.999% is added as a dopant element, and another high-purity target with a purity of 99% to 99.999% is added as a dopant element, and another high-purity target with a dopant element of 0.5 to 50 sccm is introduced. The substrate is heated to a specified temperature within the range of 20 to 800°C, and a doped transition metal nitride film is deposited onto the substrate under an argon and nitrogen atmosphere. Alternatively, A high-purity transition metal nitride target with a purity of 99% to 99.999% is added to the deposition chamber. The high-purity transition metal nitride target can be any one of the following targets: niobium nitride, chromium nitride, titanium nitride, zirconium nitride, hafnium nitride, vanadium nitride, tantalum nitride, molybdenum nitride, etc. A high-purity target with a purity of 99% to 99.999% is added to the chamber. High-purity argon gas with a purity of 99% to 99.999% and a flow rate in the range of 0.5 to 50 sccm is introduced. The substrate is heated to a specified temperature in the range of 20 to 800°C. The doped transition metal nitride film is deposited on the substrate under an argon atmosphere.

[0060] In other embodiments, other preparation methods can be used, as long as it is possible to dope impurity ions into the transition metal nitride.

[0061] The embodiments described above in this application obtain resistance-temperature characteristic curves of thin film samples under different stress levels, based on the samples, and determine the correspondence between the stress level in the thin film sample and the high-sensitivity sensing temperature range of the sensor. According to the temperature range requirements of the actual application of the temperature sensor device, a thin film sample with a suitable stress level is selected and prepared, and then the thin film is processed using MEMS technology to obtain the required temperature sensor.

[0062] In some specific embodiments of this application, the negative resistance temperature coefficient thin film is deposited by any one of physical vapor deposition, electron beam evaporation, ion beam assisted deposition, pulsed laser deposition, and chemical vapor deposition.

[0063] The methods described in the above embodiments of this application have a wide range of applications and are applicable to various negative temperature coefficient thin films, such as transition metal nitride thin films and transition metal nitride thin films doped with various elements. There are also many ways to control the stress level of the thin film, including controlling the stress level by adjusting the type of substrate material, controlling the stress level by adjusting the thickness of the negative temperature coefficient thin film, and controlling the stress level by adjusting the planar dimensions of the thin film. The methods are flexible and can be reasonably selected according to experimental conditions, and have strong universality.

[0064] Compared with the prior art, the embodiments of this application use stress modulation instead of chemical doping to regulate the temperature sensing characteristics of the negative resistance temperature coefficient thin film, avoiding the introduction of chemical defects in the thin film and thus improving the stability of the sensor. Secondly, the embodiments of this application utilize various methods to regulate the thin film performance, including adjusting the substrate material, substrate structure, thin film thickness, thin film planar dimensions, and the pressure level applied to the thin film. The regulation mechanisms are diverse, and the regulation process is simple and easy to control.

[0065] The temperature sensor prepared using the above method has a high-sensitivity temperature range that can be adjusted from deep low temperature to room temperature, and the stability of the temperature sensor can be guaranteed.

[0066] The preferred features in the above embodiments can be used individually in any embodiment, or in any combination thereof, provided they do not conflict with each other. Furthermore, parts not described in detail in the embodiments can be implemented using existing technologies.

[0067] Application Example 1:

[0068] Adjusting the stress level of a thin film by adjusting the substrate structure includes the following steps:

[0069] S1. Using physical vapor deposition (PVD), a high-purity zirconium target is added to the deposition chamber, and argon gas is introduced, followed by a mixture of nitrogen and O2. A zirconium oxynitride thin film is deposited under this argon and nitrogen-oxygen mixture atmosphere. The stress level of the film is controlled by adjusting the substrate structure. Specifically, the following steps are included:

[0070] S11. Use ultrasonic cleaning to remove surface impurities from the sapphire substrate; deposit a silicon oxide mask on the surface of the sapphire substrate, spin-coat photoresist on the silicon oxide mask, define the groove array pattern using photolithography, adjust the groove spacing within the range of 0.2–20 μm, then transfer the photoresist pattern to the silicon oxide mask using dry etching to obtain a patterned silicon oxide mask; then etch the sapphire substrate using dry etching to obtain a patterned sapphire substrate; finally, remove the silicon oxide mask from the surface of the sapphire substrate using wet etching to obtain a sapphire substrate with a groove array structure; after ultrasonic cleaning, the sapphire substrate with the groove array structure is dried with a nitrogen gun and baked to ensure that the substrate is clean and dry.

[0071] S12. Place the cleaned sapphire substrate with a grooved array structure into the deposition chamber, and install a zirconium target with a purity of 99%–99.999% on the target position of the physical vapor deposition equipment; evacuate the deposition chamber to 10°C. -4 ~10 -8 The ultra-high vacuum of Pa is achieved; the heating power is turned on, and the substrate temperature is raised to a specified temperature within the range of 20 to 800°C to bake the substrate surface, so that the substrate reaches the growth temperature of the thin film.

[0072] S13. Introduce sufficient high-purity argon gas (99%–99.999%) into the deposition chamber at a flow rate of 0.5–50 sccm to achieve a pressure sufficient for glow discharge of the target material. Set the zirconium target power to a specified value within the range of 10–500 W, open the zirconium target baffle, and pretreat the zirconium target surface. Introduce a nitrogen-oxygen mixture into the deposition chamber of the physical vapor deposition equipment at a flow rate of 0.5–50 sccm, with an O2 content of 0.05%–50% in the nitrogen-oxygen mixture.

[0073] S14. After the gas flow rate stabilizes, open the substrate baffle and deposit a zirconium oxynitride film on the sapphire substrate with a groove array structure.

[0074] S2. After the zirconium oxynitride thin film is deposited, the temperature sensor is fabricated using MEMS technology. The specific process flow is as follows: Figure 2 This includes the following steps:

[0075] S21. The zirconium oxynitride film deposited on the sapphire substrate with a groove array structure is ultrasonically cleaned with acetone, alcohol and water for 5 to 20 minutes each.

[0076] S22. Spin-coat photoresist onto the deposited zirconium oxynitride thin film and pattern the photoresist using ultraviolet exposure and development process.

[0077] S23. Etching zirconium oxynitride thin films using ion beam etching process;

[0078] S24. Use ultrasonic cleaning to remove residual photoresist from the thin film surface;

[0079] S25. Photoresist is spin-coated again on the surface of the zirconium oxynitride film, and the photoresist is patterned by ultraviolet exposure and development process.

[0080] S26. A chromium / gold coating is sputtered onto the patterned photoresist surface using a magnetron sputtering process;

[0081] S27. The photoresist pattern is transferred to a zirconium oxynitride film by a lift-off process to obtain the desired chromium / gold electrode pattern;

[0082] S28. Photoresist is spin-coated onto the surface of a zirconium oxynitride thin film covering chromium / gold electrodes. The photoresist is patterned using ultraviolet exposure to form a dicing pattern. The patterned zirconium oxynitride thin film is then cut into individual devices using laser cutting.

[0083] Application Example 2:

[0084] When adjusting the stress level of a thin film by adjusting the thickness of a film with a negative temperature coefficient of resistance, the following steps are included:

[0085] S1. Using physical vapor deposition (PVD), a high-purity zirconium target is added to the deposition chamber, and argon gas is introduced, followed by a mixture of nitrogen and O2. A zirconium oxynitride thin film is deposited under this argon and nitrogen-oxygen mixture atmosphere. The stress level of the film is controlled by adjusting the film thickness. Specifically, the following steps are included:

[0086] S11. Install a zirconium target with a purity of 99%–99.999% on the target position of the physical vapor deposition equipment. After ultrasonically cleaning the sapphire substrate, dry it with a nitrogen gun and bake it to ensure the substrate is clean and dry. Place the cleaned sapphire substrate in the deposition chamber. Evacuate the deposition chamber to 10... -4 ~10 -8 Ultra-high vacuum of Pa. Turn on the heating power supply and heat the substrate to a specified temperature within the range of 20 to 800°C to bake the substrate surface, so that the substrate reaches the growth temperature of the thin film.

[0087] S12. Introduce sufficient high-purity argon gas (99%–99.999%) into the deposition chamber at a flow rate of 0.5–50 sccm to achieve a pressure sufficient for glow discharge of the target material. Set the zirconium target power to a specified value within the range of 10–500 W, open the zirconium target baffle, and pretreat the zirconium target surface. Introduce a nitrogen-oxygen mixture into the deposition chamber of the physical vapor deposition equipment at a flow rate of 0.5–50 sccm, with an O2 content of 0.05%–50% in the nitrogen-oxygen mixture.

[0088] S13. Adjust the deposition time within the range of 50 to 50,000 s. After the gas flow rate stabilizes, open the substrate baffle and deposit zirconium oxynitride films of different thicknesses on the sapphire substrate.

[0089] S2. After the zirconium oxynitride thin film is deposited, the temperature sensor is fabricated using MEMS technology. The specific process includes the following steps:

[0090] S21. The deposited zirconium oxynitride film is ultrasonically cleaned with acetone, alcohol and water for 5 to 20 minutes each.

[0091] S22. Spin-coat photoresist onto the deposited zirconium oxynitride thin film surface, pattern the photoresist using ultraviolet exposure and development process, and transfer the photoresist pattern to the zirconium oxynitride thin film surface using ion beam etching process to obtain the desired pattern.

[0092] S23. Spin-coat photoresist onto the patterned zirconium oxynitride thin film surface, pattern the photoresist through ultraviolet exposure and development process, sputter a chromium / gold coating onto the patterned photoresist surface through magnetron sputtering process, and transfer the photoresist pattern to the zirconium oxynitride thin film through lift-off process to obtain the desired chromium / gold electrode pattern.

[0093] S24. Photoresist is spin-coated onto the surface of a zirconium oxynitride thin film covering patterned chromium / gold electrodes. The photoresist is then patterned using ultraviolet exposure to form a dicing pattern. The patterned zirconium oxynitride thin film is then cut into individual devices using laser cutting.

[0094] Reference Figure 3 The diagram shown illustrates the highly sensitive temperature control of the temperature sensor based on zirconium oxynitride thin films of different thicknesses prepared above. Figure 3 The results show that the resistance-temperature characteristic curve of the film can be controlled by adjusting the thickness of the film, thereby regulating the high-sensitivity sensing temperature range of the temperature sensor from deep cryogenic temperature to room temperature.

[0095] Reference Figure 4 The figure shows the stability test results of a temperature sensor based on a 15nm thick zirconium oxynitride thin film at the triple point of water for 60 minutes. The results show that the 15nm thick zirconium oxynitride thin film has a high level of stability at the triple point of water, indicating that by reducing the film thickness and adjusting the resistance-temperature characteristic curve of the film, a highly stable and highly sensitive temperature sensor with an adjustable sensing temperature range can be obtained.

[0096] This application embodiment adjusts the stress level of the zirconium oxynitride thin film by regulating the structure of the substrate and the thickness of the thin film, thereby controlling the conductivity of the thin film and achieving control over the resistance-temperature relationship curve of the MEMS temperature sensor based on the negative temperature coefficient film. This results in a temperature sensor with adjustable temperature range and high sensitivity. Specifically, by adjusting the stress level of the thin film, the phase transition degree of the film is controlled, changing the relative content of conductive and insulating phases in the film, and thus altering the conductivity of the film. This causes the resistance-temperature relationship curve of the temperature sensor based on the negative temperature coefficient film to shift within the range from deep cryogenic to room temperature, thereby achieving control over the high sensitivity temperature range from deep cryogenic to room temperature and obtaining a MEMS temperature sensor based on stress-controlled negative temperature coefficient film.

[0097] The foregoing has described some specific embodiments of this application. It should be understood that this application is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the substantive content of this application. The above-described preferred features can be used in any combination without conflict.

Claims

1. A method for fabricating a temperature sensor based on a negative resistance temperature coefficient thin film, characterized in that, include: A negative resistance temperature coefficient thin film is deposited on a substrate as a temperature-sensitive film for a sensor. By adjusting the stress level in the negative resistance temperature coefficient thin film, the phase transition degree and conductivity of the negative resistance temperature coefficient thin film are controlled, thereby controlling the temperature sensing characteristics of the negative resistance temperature coefficient thin film and obtaining the target negative resistance temperature coefficient thin film. The target temperature sensor is obtained by processing the negative resistance temperature coefficient thin film using MEMS technology.

2. The method for fabricating a temperature sensor based on a negative resistance temperature coefficient thin film according to claim 1, characterized in that, The stress level in the negative resistance temperature coefficient film can be adjusted by adjusting the substrate type.

3. The method for fabricating a temperature sensor based on a negative resistance temperature coefficient thin film according to claim 2, characterized in that, The method of adjusting the stress level in the negative resistance temperature coefficient film by adjusting the substrate type is to adjust the substrate material or the substrate structure.

4. The method for fabricating a temperature sensor based on a negative resistance temperature coefficient thin film according to claim 1, characterized in that, The stress level in the negative resistance temperature coefficient film is adjusted by regulating the geometric parameters of the film.

5. The method for fabricating a temperature sensor based on a negative resistance temperature coefficient thin film according to claim 4, characterized in that, The stress level in the negative resistance temperature coefficient film is adjusted by regulating the geometric parameters of the film, using any of the following methods: - Adjust the thickness of the negative resistance temperature coefficient film; - Adjust the planar dimensions of the negative resistance temperature coefficient film.

6. The method for fabricating a temperature sensor based on a negative resistance temperature coefficient thin film according to claim 1, characterized in that, The stress level in the negative resistance temperature coefficient film is adjusted by regulating the pressure level applied to it.

7. The method for fabricating a temperature sensor based on a negative resistance temperature coefficient thin film according to claim 1, characterized in that, The negative resistance temperature coefficient film is a transition metal nitride film.

8. The method for fabricating a temperature sensor based on a negative resistance temperature coefficient thin film according to claim 1, characterized in that, The negative resistance temperature coefficient film is a doped transition metal nitride film, and the doped impurity ions are any one of low-valence anions, high-valence cations, and equivalent cations. The low-valence anions include F. - ,Br - O 2- S 2- and Se 2- Any one of them, the high-valence cation includes C 4+ Si 4+ Sn 4+ and P 5+ Any one of them, the equivalent cation includes B 3+ Al 3+ and Ga 3+ Any one of them.

9. The method for fabricating a temperature sensor based on a negative resistance temperature coefficient thin film according to claim 1, characterized in that, The negative resistance temperature coefficient thin film is deposited by any one of physical vapor deposition, electron beam evaporation, ion beam assisted deposition, pulsed laser deposition, and chemical vapor deposition.

10. A temperature sensor based on a negative resistance temperature coefficient thin film, characterized in that, It is prepared using the method described in any one of claims 1-9.

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