High-precision integrated temperature and humidity sensor and construction method

Abstract

The invention discloses a high-precision integrated temperature and humidity sensor and a construction method. The sensor comprises an MEMS humidity capacitance sensor, a CMOS integrated temperature sensor, an analog-to-digital converter, a calibration configuration information storage array and a digital interface. Wherein the MEMS humidity capacitance sensor and the CMOS integrated temperature sensor are respectively connected with the analog-to-digital converter, and voltage signals of the MEMS humidity capacitance sensor and the CMOS integrated temperature sensor are converted into digital signals; the analog-to-digital converter transmits the digital signal to the calibration configuration information storage array for data processing and linearization processing, and transmits the data to the SDAamp through a digital interface; in SCL; wherein the MEMS humidity capacitance sensor comprises a capacitance pole plate, a protection ring and a heating resistor; the capacitor plates adopt an interdigital capacitor structure and have a regular octagonal part in overlook observation, and meanwhile, the upper and lower electrode plates and the polyimide PI material layer between the two electrode plates form the interdigital capacitor structure.

Description

Technical Field

[0001] The present invention relates to the technical field of multi - physical quantity integrated sensors, and particularly to a high - precision integrated temperature and humidity sensor and a construction method thereof. Background Technique

[0002] The development of the integration of MEMS sensors and CMOS dedicated circuits has made the miniaturization and low - cost mass production of multi - physical quantity test modules possible. It can be widely applied in fields such as white household appliances, intelligent production control, warehousing and logistics, aerospace, environmental monitoring, etc.

[0003] 1. MEMS humidity sensor:

[0004] Humidity sensors can be divided into three categories: electrolyte humidity sensors, semiconductor ceramic humidity sensors, and organic polymer humidity sensors. In recent years, the research on humidity sensors has mainly focused on the humidity sensing mechanism and the use of new materials and new processes to improve the humidity sensing characteristics and stability, etc.

[0005] Organic polymer humidity sensors are divided into two types according to their electrical structures: resistive polymer film humidity sensors and capacitive polymer film humidity sensors. Among them, the humidity - sensing characteristic curve of the resistive sensor has a large non - linearity, and surface contamination easily causes the resistance value of the sensor to drift, but the influence of the lead distribution is small; while the humidity - sensing characteristic curve of the capacitive sensor has good linearity, and the sensor has strong anti - pollution ability, but the parasitic capacitance of the secondary instrument interface connection has a great influence on the capacitance signal. The present invention adopts a MEMS capacitive thin - film humidity sensor.

[0006] 2. CMOS integrated temperature sensor:

[0007] In the CMOS process, bipolar transistors, metal - oxide - semiconductor transistors, and resistors are the core devices for designing temperature sensors. The present invention uses bipolar transistors to achieve temperature sensing. Summary of the Invention

[0008] A high - precision integrated temperature and humidity sensor and a construction method proposed by the present invention can solve at least one of the technical problems in the background technique.

[0009] To achieve the above object, the present invention adopts the following technical solutions:

[0010] A high - precision integrated temperature and humidity sensor, comprising: a MEMS humidity capacitance sensor, a CMOS integrated temperature sensor, an analog - to - digital converter, a calibration and calibration configuration information storage array, and a digital interface;

[0011] Among them, the MEMS humidity capacitance sensor and the CMOS integrated temperature sensor are respectively connected to the analog-to-digital converter, and the voltage signals of the MEMS humidity capacitance sensor and the CMOS integrated temperature sensor are converted into digital signals; the analog-to-digital converter transmits the digital signals to the calibration and calibration configuration information storage array for data processing and linearization processing, and transmits the data to SDA&SCL through the digital interface;

[0012] The MEMS integrated humidity sensor structure model includes a humidity capacitance plate one, a humidity capacitance plate two, and a guard ring;

[0013] Among them, the humidity capacitance plate one and the humidity capacitance plate two form a cross structure, and a polyimide PI material is filled between the plates to form an interdigital capacitance structure;

[0014] The humidity capacitance plate one has a regular octagon contour, and the humidity capacitance plate two is complementary and misaligned with it;

[0015] The guard ring has no direct electrical connection with the humidity capacitance plate one and the humidity capacitance plate two, and is separately connected to the ground GND, forming a regular octagon ring around the humidity capacitance plate two to form an electrostatic shield.

[0016] Furthermore, the MEMS integrated humidity sensor of the present invention further includes a heating resistor;

[0017] The heating resistor is connected by physical isolation and an independent circuit, and the humidity capacitance plate one, the humidity capacitance plate two and the heating resistor are arranged in layers, and thermal isolation is achieved through the insulating layer of polyimide.

[0018] Furthermore, the working method of the MEMS humidity capacitance sensor of the present invention includes:

[0019] The total humidity-sensitive interdigital capacitance consists of two parts: interdigital and coplanar. The formula for calculating the total humidity-sensitive interdigital capacitance is:

[0020] C 湿 =2·(C 叉 +C 共 )

[0021] The formula for calculating the interdigital partial capacitance is:

[0022]

[0023] Among them, L is the length of the interdigital electrode, h finger is the thickness of the interdigital electrode, ε is the relative dielectric constant, ε0 is the vacuum dielectric constant, n is the total number of interdigital electrodes, and w gap is the spacing of the interdigital electrodes;

[0024] The formula for calculating the coplanar partial capacitance is:

[0025]

[0026] Among them, L is the length of the interdigital electrode, ε is the relative permittivity, ε0 is the permittivity of vacuum, a is the distance between the interdigital electrode plates, and b is the width of the interdigital electrode plates.

[0027] Furthermore, the CMOS integrated temperature sensor of the present invention includes: a bias current generation circuit and a temperature-sensing bipolar transistor; the bias current generation circuit and the temperature-sensing bipolar transistor share the same ground and the same voltage source;

[0028] Among them, the bias current generation circuit uses the current density difference between bipolar transistors QB0 and QB1 to generate a bias voltage deltaVBE that is proportional to the absolute temperature. The bias voltage deltaVBE and the resistance value Rbias will determine a bias current Ibias. The specific relationship is as follows, where k is the Boltzmann constant, q is the electron charge, and T is the temperature:

[0029]

[0030] The temperature-sensing bipolar transistor adopts a transistor area ratio of 2:10, and respectively converts two positive-biased PN junction voltages VBE1 and VBE0 with different magnitudes through the bias current. These two voltages are respectively input to the next-stage operational amplifier for processing; the temperature relationships of the junction voltages VBE1 and VBE0 are as follows, where Is is the saturation current of the BJT.

[0031]

[0032] The above VBE1 and VBE0 are operated by the next-stage operational amplifier to synthesize a reference voltage VREF that changes with temperature and a temperature detection voltage CTAT with a negative temperature coefficient, where

[0033] VREF = VBE1 + a * (k * T / q) * ln(5)

[0034] Through the weighted operation of the operational amplifier, the coefficient a in the above formula is obtained, so that the first derivative of VREF with respect to temperature is zero, thereby obtaining a reference voltage VREF independent of temperature; at the same time, through another operational amplifier, a coefficient b is obtained, and the adjustment of this coefficient is to adapt to the input range of the ADC and reasonably reduce the resolution design requirements of the next-stage ADC.

[0035] On the other hand, a method for constructing a high-precision integrated temperature and humidity sensor. The method for constructing the capacitance structure in the humidity sensor is as follows: in the way of metal RDL secondary wiring, the bonding pads of the bottom electrode and the top electrode of the capacitor are formed.

[0036] The bottom electrode and the bonding pad form a thin metal layer by using a high-precision semiconductor planar process, including a gold layer and a titanium tungsten bonding layer.

[0037] The top electrode uses a membrane-based porous electrode, filled with an organic binder containing carbon particles, and is led out through a lap joint disc;

[0038] The top electrode completely covers the bottom electrode, and the middle gas-sensitive layer is filled with a humidity-sensitive polyimide material to form a parallel-plate capacitor.

[0039] Furthermore, the working method of the capacitance structure in the humidity sensor of the present invention includes: the upper electrode plate of the sandwich capacitance structure is strip-shaped, the whole structure is a parallel-plate capacitance structure, polyimide is used as the medium between the two metal electrode plates, through the channels left on the upper electrode plate, polyimide absorbs and releases moisture according to the content of water vapor in the air, the dielectric constant changes, and its capacitance formula is:

[0040]

[0041] where A is the area of the upper electrode plate, d is the thickness of the polyimide layer, ε r is the relative dielectric constant of polyimide after absorbing moisture, ε0 is the vacuum dielectric constant, and Cf is the fringe inductance capacitance and parasitic capacitance between the two electrode plates.

[0042] As can be seen from the above technical solutions, compared with the resistive humidity sensor, the capacitive humidity sensor of the present invention has the characteristics of low noise, strong anti-interference ability, small influence of temperature, fast response speed, small volume and low power consumption. The capacitive humidity sensor uses a humidity-sensitive material as the dielectric material of the humidity-sensitive capacitor, and the dielectric constant of the dielectric material will change when it absorbs moisture.

[0043] Common humidity-sensitive materials are metal oxides and high molecular polymers, such as porous silicon, porous silicon dioxide, porous aluminum oxide, porous silicon nitride, polystyrene, polyimide materials, etc. Among them, polyimide (Polyimide, also abbreviated as PI) has the characteristics of high mechanical strength, high elastic modulus, stable and not easily decomposed at high temperatures, good corrosion resistance, safe and non-toxic, and good linearity. At the same time, it is compatible with the standard CMOS process and is suitable for mass production.

[0044] In view of the above considerations, the present invention adopts a capacitive humidity sensor structure with polyimide (PI) as the dielectric material, using two types of interdigital structures and sandwich structures.

[0045] ② The measurement error caused by process manufacturing deviation is another major technical difficulty that needs to be solved outside the design of high-precision integrated temperature sensors.

[0046] Integrate a CMOS temperature sensor, a MEMS capacitive humidity sensor, and a dedicated measurement circuit for signal acquisition, conversion, and calibration on a single chip to achieve the integration of MEMS sensors and CMOS circuits and high-precision measurement. While achieving miniaturization, low cost, low power consumption, and high precision design, it can meet the requirements of mass production and has a wide range of application fields. Brief Description of the Drawings

[0047] Figure 1 Schematic structural diagram of the temperature and humidity sensor of the present invention;

[0048] Figure 2 Schematic structural diagram of the humidity-sensitive interdigital capacitor;

[0049] Figure 3 Top view of the humidity sensor of the present invention;

[0050] Figure 4 Simulation model of the interdigital electrode of the present invention;

[0051] Figure 5 Simulation result of the humidity-sensitive capacitor with an interdigital electrode spacing of 0.6um;

[0052] Figure 6 Simulation result of the humidity-sensitive capacitor with an interdigital electrode spacing of 0.8um;

[0053] Figure 7 Simulation result of the humidity-sensitive capacitor with an interdigital electrode spacing of 1.2um;

[0054] Figure 8 Capacitor of the humidity-sensitive sandwich structure;

[0055] Figure 9 Schematic diagram of the temperature-voltage conversion circuit; Figure 10 Schematic diagram of the humidity capacitance-voltage conversion circuit. Detailed Description of the Preferred Embodiment

[0056] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention.

[0057] As Figure 1 shown, a high-precision integrated temperature and humidity sensor described in this embodiment includes a humidity sensor, a temperature sensor, an analog-to-digital converter, a calibration and configuration information storage array, and a digital interface;

[0058] Among them, the humidity sensor and the temperature sensor are respectively connected to the analog-to-digital converter, which converts the voltage signals of the humidity sensor and the temperature sensor into digital signals. The analog-to-digital converter transmits the digital signals to the calibration and configuration information storage array for data processing and linearization processing, and transmits the data to SDA&SCL through the digital interface.

[0059] The humidity sensor is a MEMS integrated humidity sensor, and its structural model includes a humidity capacitor plate 1, a humidity capacitor plate 2, a protection ring, and a heating resistor.

[0060] Among them, as Figure 2 shown, the humidity capacitor plate 1 and the humidity capacitor plate 2 form a cross structure, and a polyimide PI material is filled between the plates to form an interdigital capacitor structure. As Figure 3-4 shown, the humidity capacitor plate 1 has a regular octagon contour, and the humidity capacitor plate 2 is complementary and misaligned with it. The protection ring has no direct electrical connection with the humidity capacitor plate 1 and the humidity capacitor plate 2, and is separately connected to the ground (GND), forming a regular octagon ring around the humidity capacitor plate 2 to form an electrostatic shield to prevent the external electric field from interfering with the electric field distribution between the capacitor plates, and at the same time absorb the leakage current (such as dielectric leakage or substrate leakage) to improve the insulation of the capacitor. The heating resistor is connected by physical isolation and an independent circuit, and the capacitor plate and the heating resistor are arranged in layers (such as the capacitor on the upper layer and the heating resistor on the lower substrate), and thermal isolation is achieved through the insulating layer of polyimide.

[0061] The solution of the CMOS integrated temperature sensor:

[0062] In the present invention, a bipolar transistor is used to implement the temperature sensor. To achieve high-precision and high-resolution temperature detection, for the measurement error caused by the BJT process deviation, the temperature sensor will introduce a chopping technique to modulate the error amount caused by the process deviation, including the mismatch of the BJT, the offset voltage VOS of the operational amplifier, and the mismatch of the bias current mirror. After orthogonal chopping modulation of the errors caused by the above mismatches, the average value is obtained after the subsequent ADC analog-to-digital conversion to reduce the mismatch error, thereby achieving the required measurement accuracy.

[0063] The implementation scheme of high-precision measurement:

[0064] In the present invention, the environmental humidity and temperature information collected by the humidity sensor and the temperature sensor are respectively converted into processable electrical signals, and after passing through small-signal analog front-end processing circuits such as various chopping circuits, switched capacitors, and capacitor array matching to improve accuracy and compatibility, the continuous voltage signal is converted into a digital signal through the ADC, and after steps such as calibration and linearization, it is output to the outside of the chip to complete the measurement of temperature and humidity.

[0065] Among them, the implementation method of the MEMS humidity capacitance sensor:

[0066] The humidity-sensitive material absorbs and releases moisture with the change of water vapor in the air, and its capacitance value changes accordingly. The present invention measures the change of humidity by measuring the change of capacitance between electrodes.

[0067] ① Interdigitated capacitor calculation

[0068] The total capacitance of the humidity-sensitive interdigitated capacitor is mainly composed of two parts: the interdigitated part and the coplanar part, and the capacitance value of the interdigitated part accounts for the main component. The calculation formula for the total capacitance of the humidity-sensitive interdigitated capacitor is:

[0069] C 湿 =2·(C 叉 +C 共 )

[0070] The calculation formula for the capacitance of the interdigitated part:

[0071]

[0072] As Figure 2 shown, where L is the length of the interdigitated electrode, h finger is the thickness of the interdigitated electrode, ε is the relative dielectric constant, ε0 is the vacuum dielectric constant, n is the total number of interdigitated electrodes, w gap is the spacing between the interdigitated electrodes.

[0073] The calculation formula for the capacitance of the coplanar part:

[0074]

[0075] Among them, L is the length of the interdigitated electrode, ε is the relative dielectric constant, ε0 is the vacuum dielectric constant, a is the spacing between the interdigitated plates, and b is the width of the interdigitated plates.

[0076] ② Interdigitated capacitor simulation

[0077] The finite element simulation analysis of the interdigitated capacitor structure is carried out using COMSOL Multiphysics software, and the simulation modeling and results are as Figures 4 to 7 shown.

[0078] Table 1 Comparison of capacitance values of interdigitated capacitors with three structural parameters

[0079]

[0080] It can be obtained from Table 1 that for the interdigitated capacitors with three structural parameters, the theoretical calculation results are close to the software simulation results. Therefore, through theoretical calculation and simulation, the capacitance value of the humidity-sensitive interdigitated capacitor is determined, so as to ensure the correctness of the capacitance value design of the humidity-sensitive capacitor and reduce the deviation between the designed value and the actual value of the humidity-sensitive capacitor.

[0081] ③ Sandwich structure design

[0082] As Figure 8 shown, for the traditional sandwich-structured capacitor, the bottom layer uses a silicon substrate with an oxide layer. The metal lower electrode of the capacitor is on top of the oxide layer of the substrate. The polyimide material is between the two electrodes. The two electrodes use copper or aluminum materials in the standard CMOS process. At the same time, the upper electrode is in a grid shape. The polyimide layer is in direct contact with the external air through the hollow channels, which is convenient for absorbing the water vapor in the air and reducing the response time. The upper electrode of the sandwich structure can also be made into a strip shape. The whole structure looks similar to a parallel-plate capacitor structure. Polyimide is used as the dielectric between the two metal electrodes. Through the channels left on the upper electrode, polyimide absorbs or releases moisture according to the content of water vapor in the air, and its dielectric constant changes. Its capacitance formula is:

[0083]

[0084] where A is the area of the upper electrode, d is the thickness of the polyimide layer, ε r is the relative dielectric constant of polyimide after absorbing moisture, ε0 is the vacuum dielectric constant, and C f is the fringe capacitance and parasitic capacitance between the two electrodes.

[0085] ④ Implementation method of the sandwich capacitor structure

[0086] In the integrated temperature, humidity and pressure sensor, on the top passivation layer of the humidity sensor interface circuit, a sandwich-structured humidity-sensitive capacitor is designed and implemented, which can reduce the transmission distance and parasitic effects between the humidity-sensitive capacitor and the processing circuit. At the same time, the humidity-sensitive capacitor does not occupy additional area, and can further realize the miniaturized design of the integrated temperature, humidity and pressure sensor.

[0087] The specific method is as follows:

[0088] In the way of metal RDL secondary wiring, form the bonding pads of the bottom electrode and the top electrode of the capacitor;

[0089] The bottom electrode and the bonding pad form a thin metal layer by using a high-precision semiconductor planar process, including a gold layer (Au) and a titanium tungsten (TiW) adhesion layer;

[0090] The top electrode uses a film-based porous electrode, fills an organic binder with platinum or carbon particles, and leads out through the bonding pad;

[0091] The top electrode completely covers the bottom electrode, and the intermediate gas-sensitive layer is filled with a humidity-sensitive polyimide material, thus forming a parallel-plate capacitor.

[0092] 2. Implementation method of the CMOS temperature integrated sensor

[0093] The temperature sensor is implemented using a bipolar transistor in the circuit. The principle is as follows:

[0094] As shown Figure 9 in the figure, the red boxed area is the bias current generation circuit. By using the current density difference between the bipolar transistors QB0 and QB1, a bias voltage deltaVBE proportional to the absolute temperature is generated. This bias voltage and Rbias will determine a bias current Ibias. The specific relationship is as follows, where k is the Boltzmann constant, q is the electron charge, and T is the temperature:

[0095]

[0096] The green boxed part is the main body of the temperature-sensing bipolar transistor. It uses a transistor area ratio of 2:10 and converts two positive-biased PN junction voltages VBE1 and VBE0 with different magnitudes through the bias current. These two voltages are respectively input to the next-stage operational amplifier for processing. The temperature relationships of the above two VBEs are as follows, where Is is the saturation current of the BJT

[0097]

[0098] The above VBE1 and VBE0 are operated by the next-stage operational amplifier to synthesize a reference voltage VREF that is almost independent of temperature change and a temperature detection voltage CTAT with a negative temperature coefficient, where

[0099] VREF = VBE1 + a * (k * T / q) * ln(5)

[0100] Through the weighted operation of the operational amplifier, the coefficient a in the above formula can be easily obtained, making the first derivative of VREF with respect to temperature zero, thereby obtaining a reference voltage VREF independent of temperature; at the same time, through another operational amplifier, a coefficient b can also be obtained. The adjustment of this coefficient is mainly to adapt to the input range of the ADC, thereby reasonably reducing the resolution design requirements of the next-stage ADC.

[0101] 3. High-precision measurement implementation method

[0102] Implementation method for high-precision measurement of temperature parameters: chopper modulation;

[0103] Adopting the chopper modulation mode, orthogonal chopper modulation is respectively performed on the offset voltage Vos and the bias current Ibias mismatch of the operational amplifier. After digitizing the error introduced by the mismatch and through sampling averaging, the error is reduced, thereby achieving accuracy improvement.

[0104] Implementation method for high-precision measurement of humidity parameters: switched capacitor and capacitor array;

[0105] Regarding the characteristic that the capacitance change amount of the humidity sensor is small in the full range, the method adopted is as Figure 10The shown switched-capacitor circuit structure and the differential detection output method can convert a small capacitance change into a voltage signal, reduce the influence of offset voltage, low-frequency noise, and parasitic factors, and improve the signal-to-noise ratio of capacitance-voltage detection and conversion.

[0106] Due to the process errors in the micro-nano manufacturing of the humidity-sensitive capacitor, and also to adapt to humidity-sensitive capacitors with different structures and capacitance values, improve the compatibility between the humidity-sensitive capacitor and the conversion circuit, and achieve the best measurement range effect. The present invention designs a reference capacitor array to obtain reference capacitor capacitance values that can fully cover the measurement range.

[0107] In summary, the present invention integrates a CMOS temperature sensor, a MEMS capacitive humidity sensor, and a dedicated measurement circuit for signal acquisition, conversion, and calibration on a single chip to achieve the integration of MEMS sensors and CMOS circuits and high-precision measurement. While achieving miniaturization, low cost, low power consumption, and high precision design, it can meet the requirements of mass production and has a wide range of application fields.

[0108] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising an..." does not exclude the existence of additional identical elements in the process, method, article or device comprising the element.

[0109] Each embodiment in this specification is described in a related manner. The same or similar parts between the embodiments can be referred to each other, and the differences between each embodiment and other embodiments are emphasized. In particular, for the system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the description of the method embodiment.

[0110] The above embodiments are only used to illustrate the technical solutions of the present invention, not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high-precision integrated temperature and humidity sensor, characterized in that Including: MEMS humidity capacitance sensor, CMOS integrated temperature sensor, analog-to-digital converter, calibration configuration information storage array, digital interface; Among them, the MEMS humidity capacitance sensor and the CMOS integrated temperature sensor are respectively connected to the analog-to-digital converter to convert the voltage signals of the MEMS humidity capacitance sensor and the CMOS integrated temperature sensor into digital signals; the analog-to-digital converter transmits the digital signals to the calibration configuration information storage array for data processing and linearization processing, and transmits the data to SDA&SCL through the digital interface; The MEMS integrated humidity sensor structure model includes a capacitor plate and a guard ring; Among them, the capacitor plate includes: humidity capacitor plate one and humidity capacitor plate two; Humidity capacitor plate one and humidity capacitor plate two form a cross structure, and a polyimide PI material is filled between the plates to form an interdigital capacitor structure; Humidity capacitor plate one has a regular octagon contour, and humidity capacitor plate two is complementary and misaligned with it; The guard ring has no direct electrical connection with humidity capacitor plate one and humidity capacitor plate two, and is separately connected to the ground GND, forming a regular octagon ring around humidity capacitor plate two to form an electrostatic shield.

2. The high-precision integrated temperature and humidity sensor according to claim 1, wherein The MEMS integrated humidity sensor also includes a heating resistor; The heating resistor is connected by physical isolation and an independent circuit, and the capacitor plate and the heating resistor are arranged in layers, and thermal isolation is achieved through the insulating layer polyimide.

3. The high-precision integrated temperature and humidity sensor according to claim 1, characterized in that, The working method of the MEMS humidity capacitance sensor includes: The total humidity-sensitive interdigital capacitance is composed of the interdigital and coplanar parts. The calculation formula for the total humidity-sensitive interdigital capacitance is: C 湿 = 2·(C 叉 + C 共 ) The calculation formula for the interdigital part capacitance: where L is the length of the interdigital electrode, h finger is the thickness of the interdigital electrode, ε is the relative permittivity, ε0 is the permittivity of free space, n is the total number of interdigital electrodes, w gap is the pitch of the interdigital electrodes; The calculation formula for the coplanar part capacitance: Among them, L is the length of the interdigital electrode, ε is the relative dielectric constant, ε0 is the vacuum dielectric constant, a is the spacing between the interdigital plates, and b is the width of the interdigital plates.

4. The high-precision integrated temperature and humidity sensor according to claim 1, wherein The CMOS integrated temperature sensor includes: a bias current generation circuit and a temperature-sensing bipolar transistor; the bias current generation circuit and the temperature-sensing bipolar transistor share the same ground and the same voltage source; Among them, the bias current generation circuit uses the current density difference between bipolar transistors QB0 and QB1 to generate a bias voltage deltaVBE that is proportional to the absolute temperature. The bias voltage deltaVBE and the resistance value Rbias will determine a bias current Ibias. The specific relationship is as follows, where k is the Boltzmann constant, q is the electron charge, and T is the temperature: The temperature-sensing bipolar transistor uses a transistor area ratio of 2:10, and respectively converts two positive-biased PN junction voltages VBE1 and VBE0 with different magnitudes through the bias current. These two voltages are respectively input to the next-stage operational amplifier for processing; the temperature relationship of the junction voltages VBE1 and VBE0 is as follows, where Is is the saturation current of the BJT, The above VBE1 and VBE0 are operated by the next-stage operational amplifier to synthesize a reference voltage VREF that changes with temperature and a temperature detection voltage CTAT with a negative temperature coefficient, where, VREF = VBE1 + a*(k*T / q)*ln(5) Through the weighted operation of the operational amplifier, the coefficient a in more than one formula is obtained, so that the first derivative of VREF with respect to temperature is zero, thereby obtaining a temperature-independent reference voltage VREF; at the same time, through another operational amplifier, a coefficient b is obtained, and the conditioning of this coefficient is to adapt to the input range of the ADC and reasonably reduce the resolution design requirements of the lower-level ADC.

5. A method for constructing a high-precision integrated temperature and humidity sensor, characterized in that The method for constructing the capacitive structure in the humidity sensor is as follows: in the way of metal RDL secondary wiring, the bonding pads of the bottom electrode and the top electrode of the capacitor are formed; The bottom electrode and the bonding pad form a thin metal layer by using a high-precision semiconductor planar process, including a gold layer and a titanium tungsten bonding layer; The top electrode adopts a film-based porous electrode, filled with an organic binder of carbon particles, and is led out through the bonding pad; The top electrode completely covers the bottom electrode, and the middle gas-sensitive layer is filled with a moisture-sensitive polyimide material to form a parallel plate capacitor.

6. The high-precision integrated temperature and humidity sensor according to claim 5, characterized in that, The working method of the capacitive structure in the humidity sensor includes: the upper electrode of the sandwich capacitive structure is strip-shaped, the whole structure is a parallel plate capacitive structure, polyimide is used as the medium between the two metal electrodes, and through the channels left on the upper electrode, polyimide absorbs and releases moisture according to the water vapor content in the air, and the dielectric constant changes. Its capacitance formula is: where A is the area of the upper plate, d is the thickness of the polyimide layer, ε r is the relative dielectric constant of the polyimide after moisture absorption, ε0 is the vacuum permittivity, and Cf is the fringe inductance capacitance and parasitic capacitance between the two plates.

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