Humidity detection element, chip, temperature and humidity sensor and temperature and humidity calibration method

Abstract

The invention provides a humidity detection element, a chip, a temperature and humidity sensor and a temperature and humidity calibration method. Comprising a substrate, a first insulating material layer arranged on the substrate, a temperature sensing film embedded in the first insulating material layer, a metal electrode layer arranged on the first insulating material layer, a second insulating material layer arranged on the metal electrode layer and a humidity sensing film embedded in the second insulating material layer, and the humidity sensing film is exposed in air; the metal electrode layer comprises a reference capacitance electrode pair and a humidity sensing capacitance electrode pair, the reference capacitance electrode pair is located above the temperature sensing film, and the humidity sensing capacitance electrode pair is located below the humidity sensing film; the isolation groove is located between the reference capacitor electrode pair and the humidity sensing capacitor electrode pair. According to the invention, the characteristic that the humidity signal output of the sensor does not change along with the temperature is realized, the humidity curve fitting is completed with a relatively low calculation amount, and the humidity measurement precision is improved; and the requirement for a calibration system is low, and the device can be matched with a low-end single-chip microcomputer for use.

Description

Technical Field

[0001] The present invention relates to the field of semiconductors, and in particular to a humidity detection element, a chip, a temperature and humidity sensor, and a temperature and humidity calibration method. Background Art

[0002] Temperature and humidity sensors are the most common sensors in production and life. They are widely used in various fields such as food production, agricultural planting, and electronic component manufacturing. Temperature and humidity sensors based on MEMS technology usually consist of a MEMS humidity sensor chip with a single capacitor structure and an ASIC dedicated chip. MEMS capacitive thin film humidity sensor chips are widely used due to their advantages such as fast response speed, high output linearity, and low power consumption.

[0003] Since MEMS capacitive humidity sensor chips have defects such as small output signal amplitude (generally in the pF level) and temperature changes easily cause capacitance drift, the output signal of the sensor needs to be calibrated. According to the output characteristics of the humidity sensor, the traditional calibration method usually uses different calibration algorithms in different temperature ranges, that is, the least squares straight line fitting algorithm is used in the middle temperature range, and the RBP neural network compensation algorithm is used in the low and high temperature ranges; the RBP neural network compensation algorithm requires a large number of temperature and humidity data points for calibration, and the model construction is relatively complex, resulting in high calibration costs and difficult to process and implement on low-end microcontrollers.

[0004] Therefore, how to reduce the impact of temperature on humidity signals, reduce humidity measurement errors, and reduce calibration costs has become a technical problem that needs to be urgently solved by those skilled in the art.

[0005] It should be noted that the above introduction to the technical background is only for the convenience of providing a clear and complete description of the technical solutions of the present invention and for the convenience of understanding by those skilled in the art. It cannot be considered that the above technical solutions are well known to those skilled in the art simply because these solutions are described in the background technology section of the present invention. Summary of the invention

[0006] In view of the shortcomings of the prior art mentioned above, the purpose of the present invention is to provide a humidity detection element, a chip, a temperature and humidity sensor and a temperature and humidity calibration method, which are used to solve the problems in the prior art that the humidity sensor has large humidity measurement errors in low and high temperature environments; the temperature and humidity data points required for calibration are large, which is not suitable for mass production applications; the temperature parameters are involved in the fitting of the humidity curve, resulting in more coefficients and a large amount of calculation, which makes it difficult to apply to low-end single-chip microcomputer systems.

[0007] To achieve the above-mentioned object and other related objects, the present invention provides a humidity detection element, which at least comprises:

[0008] A substrate, a first insulating material layer disposed on the substrate, a temperature-sensitive film embedded in the first insulating material layer, a metal electrode layer disposed on the first insulating material layer, a second insulating material layer disposed on the metal electrode layer, and a moisture-sensitive film embedded in the second insulating material layer, wherein the moisture-sensitive film is exposed to air;

[0009] Among them, the metal electrode layer includes a reference capacitor electrode pair and a humidity sensing capacitor electrode pair, the reference capacitor electrode pair is located above the temperature sensing film, and the humidity sensing capacitor electrode pair is located below the humidity sensing film, and the positive and negative electrodes of the reference capacitor electrode pair and the humidity sensing capacitor electrode pair are respectively led out to the surface of the second insulating material layer and connected to the lead-out electrodes; the first insulating material layer, the metal electrode layer and the second insulating material layer are provided with isolation grooves, and the isolation grooves are located between the reference capacitor electrode pair and the humidity sensing capacitor electrode pair, and are used to isolate the electric fields of the reference capacitor and the humidity sensing capacitor.

[0010] Optionally, the reference capacitor electrode pair and the humidity sensing capacitor electrode pair are both interdigitated structures.

[0011] Optionally, the temperature-sensitive film and the humidity-sensitive film are both made of polyimide.

[0012] Optionally, the material of the substrate is silicon; the materials of the first insulating material layer and the second insulating material layer are both silicon dioxide; and the first insulating material layer and the second insulating material layer have the same thickness.

[0013] Optionally, the reference capacitor electrode pair and the humidity sensing capacitor electrode pair share a common negative electrode.

[0014] In order to achieve the above object and other related objects, the present invention also provides a chip, which at least includes the above humidity detection element.

[0015] To achieve the above-mentioned purpose and other related purposes, the present invention also provides a temperature and humidity sensor, which at least includes: a humidity detection circuit, a processing unit, a temperature-sensitive resistor, and the above-mentioned humidity detection element or chip;

[0016] The humidity detection circuit is connected to the positive electrode of the reference capacitor, the positive electrode of the humidity sensing capacitor and the processing unit, and controls the oscillation of the humidity sensing capacitor in the humidity detection element based on the reference oscillation number set in the processing unit; and controls the oscillation of the reference capacitor in the humidity detection element based on the oscillation time of the humidity sensing capacitor, and obtains the corresponding output oscillation number;

[0017] The temperature sensitive resistor is used to provide a temperature detection signal;

[0018] The processing unit is connected to the humidity detection circuit and the thermistor, realizes humidity calibration based on the output signal of the humidity detection circuit, and realizes temperature calibration based on the temperature detection signal on the thermistor.

[0019] Optionally, the humidity detection circuit includes a charging resistor, a first charging switch, a second charging switch, a first discharging switch, a second discharging switch, a first Schmitt trigger, a second Schmitt trigger, an AND logic unit and a selection circuit;

[0020] The two ends of the charging resistor are respectively connected to the positive electrodes of the reference capacitor and the humidity sensing capacitor;

[0021] One end of the first charging switch is connected to a preset voltage, and the other end is connected to the positive electrode of the reference capacitor; one end of the second charging switch is connected to the preset voltage, and the other end is connected to the positive electrode of the humidity sensing capacitor; the first charging switch and the second charging switch are used to provide a charging path;

[0022] The first discharge switch is connected in parallel to both ends of the reference capacitor, and the second discharge switch is connected in parallel to both ends of the humidity sensing capacitor, for providing a discharge path;

[0023] The input end of the first Schmitt trigger is connected to the positive electrode of the reference capacitor, the input end of the second Schmitt trigger is connected to the positive electrode of the humidity sensing capacitor, and the AND logic unit performs an AND operation on the output signals of the first Schmitt trigger and the second Schmitt trigger and outputs the AND operation;

[0024] The input end of the selection circuit is connected to the output end of the second Schmitt trigger, and the output end is connected to the control ends of the first discharge switch and the second discharge switch, so as to select a corresponding capacitor for oscillation.

[0025] To achieve the above purpose and other related purposes, the present invention also provides a temperature and humidity calibration method, which is implemented based on the above temperature and humidity sensor, and the temperature and humidity calibration method at least includes:

[0026] At the same temperature, n humidity calibration points are selected, and at the humidity corresponding to each humidity calibration point, the output oscillation number of the reference capacitor corresponding to the time required for the humidity sensing capacitor to oscillate the reference oscillation number is obtained, a mathematical model of the humidity value and the output oscillation number is established based on the humidity output characteristic curve, and the coefficients in the mathematical model of the humidity value and the output oscillation number are calculated based on the fitting of each output oscillation number, thereby obtaining a humidity calibration formula;

[0027] According to the output characteristics of the thermistor, m temperature calibration points are selected, the output signals of the thermistor corresponding to each temperature calibration point are obtained, a mathematical model of the temperature value and the output signal of the thermistor is established based on the temperature output characteristic curve, and the coefficients in the mathematical model of the temperature value and the output signal of the thermistor are calculated based on the fitting of each output signal of the thermistor, thereby obtaining a temperature calibration formula;

[0028] Wherein, n is a natural number greater than or equal to 2, and m is a natural number greater than or equal to 2.

[0029] Optionally, the method for obtaining the output oscillation number includes:

[0030] Performing a charge and discharge operation on the humidity sensing capacitor for a reference oscillation number, and recording the oscillation time; repeatedly performing a charge and discharge operation on the reference capacitor within the oscillation time, and recording the output oscillation number;

[0031] When the voltage across the capacitor rises to the flip level, it is determined that the charging is completed, and when the voltage across the capacitor drops to the preset level, it is determined that the discharging is completed. One charging and discharging operation is recorded as one oscillation.

[0032] Optionally, the reference oscillation number and the output oscillation number satisfy the following relationship:

[0033] Ti 总 =Ti 感湿 ·X 感湿 =Ti 参考 ·X 参考 ;

[0034] Among them, Ti 总 is the oscillation time, Ti 感湿 is the oscillation period of the humidity sensing capacitor, X 感湿 is the reference oscillation number, Ti 参考 is the oscillation period of the reference capacitor, X 参考 is the number of output oscillations.

[0035] Optionally, the mathematical model of the humidity value and the output oscillation number is a second-order mathematical model, satisfying:

[0036] H=ax 2 +bx+c;

[0037] Wherein, H is the humidity value, x is the output oscillation number, a, b, c are coefficients in the mathematical model of the humidity value and the output oscillation number, and n is a natural number greater than or equal to 3.

[0038] Optionally, the mathematical model of the temperature value and the temperature-sensitive resistor output signal is a second-order mathematical model that satisfies:

[0039] Te=dt 2+et+f;

[0040] Among them, Te is the temperature value, t is the output signal of the temperature-sensitive resistor, d, e, f are coefficients in the mathematical model of the temperature value and the output signal of the temperature-sensitive resistor, and m is a natural number greater than or equal to 3.

[0041] As described above, the humidity detection element, chip, temperature and humidity sensor and temperature and humidity calibration method of the present invention have the following beneficial effects:

[0042] 1. The humidity detection element, chip, temperature and humidity sensor and temperature and humidity calibration method of the present invention realize the characteristic that the humidity signal output of the sensor does not change with temperature through a dual capacitor structure in conjunction with a humidity detection circuit, thereby completing the temperature drift compensation of the humidity signal.

[0043] 2. The present invention calibrates humidity and temperature separately through a matching calibration algorithm, so that the temperature parameter does not participate in the fitting of the humidity curve, reduces the humidity error, and improves the measurement accuracy.

[0044] 3. The humidity detection element, chip, temperature and humidity sensor and temperature and humidity calibration method of the present invention have low calibration costs. Only one set of temperature data points and one set of humidity data points are required for calibration, which can shorten the batch calibration process.

[0045] 4. The present invention has low requirements for the calibration system. Since the temperature and humidity are calibrated separately, the amount of calculation is small and it can be used in conjunction with a low-end single-chip microcomputer; a high measurement accuracy can be achieved on a low-end single-chip microcomputer platform. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is a schematic exploded view of the structure of the humidity detection element of the present invention.

[0047] Figure 2 The diagram is a top perspective view of a humidity detection element of the present invention.

[0048] Figure 3 The AA cross-sectional view of the humidity sensing element of the present invention is shown.

[0049] Figure 4 Shown is a schematic structural diagram of the temperature and humidity sensor of the present invention.

[0050] Figure 5 Shown is a structural schematic diagram of the humidity detection circuit of the present invention.

[0051] Figure 6 It is a schematic diagram showing the equivalent structure of the humidity sensing capacitor and the reference capacitor of the present invention.

[0052] Figure 7 Shown is a schematic diagram of the capacitance change curve of a single capacitor structure.

[0053] Figure 8 It is a schematic diagram of the oscillation frequency variation curve of the dual capacitor structure of the present invention.

[0054] Fig. 9 Shown is a schematic diagram of the flow of obtaining the output oscillation number of the present invention.

[0055] Component number description

[0056] 1 Humidity detection element

[0057] 10 Base

[0058] 11. First insulating material layer

[0059] 12 temperature sensitive film

[0060] 13 Metal electrode layer

[0061] 131 Reference capacitor electrode pair

[0062] 132 Humidity sensing capacitor electrode pair

[0063] 131a Positive electrode of the reference capacitor electrode pair

[0064] 132a Positive electrode of humidity sensing capacitor electrode pair

[0065] 13b Negative electrode

[0066] 14. Second insulating material layer

[0067] 15 moisture sensitive film

[0068] 16. Lead electrode

[0069] 17 Isolation slot

[0070] 2 Humidity detection circuit

[0071] 21 The first Schmitt trigger

[0072] 22 Second Schmitt trigger

[0073] 23 AND logic unit

[0074] 24 Select Circuit

[0075] 25 Delay Circuit

[0076] 3 Processing Unit DETAILED DESCRIPTION

[0077] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0078] See also Figures 1 to 9 It should be noted that the illustrations provided in this embodiment are only used to illustrate the basic concept of the present invention in a schematic manner, and the drawings only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0079] In response to the problems of existing temperature and humidity sensors, the present invention completes the temperature drift compensation of the humidity signal through a dual capacitor structure and a humidity detection circuit, and calibrates the humidity and temperature separately through a matching calibration algorithm, thereby improving the accuracy of the sensor while reducing the amount of calculation.

[0080] like Figure 1 As shown, the present invention provides a humidity detection element 1, and the humidity detection element 1 includes:

[0081] A substrate 10, a first insulating material layer 11 arranged on the substrate 10, a temperature-sensitive film 12 embedded in the first insulating material layer 11, a metal electrode layer 13 arranged on the first insulating material layer 11, a second insulating material layer 14 arranged on the metal electrode layer 13, and a moisture-sensitive film 15 embedded in the second insulating material layer 14, wherein the moisture-sensitive film 15 is exposed to the air. Among them, the metal electrode layer 13 includes a reference capacitor electrode pair 131 and a moisture-sensing capacitor electrode pair 132, the reference capacitor electrode pair 131 is located above the temperature-sensing film 12, and the moisture-sensing capacitor electrode pair 132 is located below the moisture-sensing film 15, and the positive and negative electrodes of the reference capacitor electrode pair 131 and the moisture-sensing capacitor electrode pair 132 are respectively led to the surface of the second insulating material layer 14 and connected to the lead-out electrode 16; the first insulating material layer 11, the metal electrode layer 13 and the second insulating material layer 14 are provided with an isolation groove 17, and the isolation groove 17 is located between the reference capacitor electrode pair 131 and the moisture-sensing capacitor electrode pair 132, and is used to isolate the electric field of the reference capacitor and the moisture-sensing capacitor.

[0082] Specifically, Figure 1 to Figure 3 As shown, in this embodiment, the material of the substrate 10 is silicon (Si). In actual use, any material that can be used as a substrate is applicable and will not be described in detail here.

[0083] Specifically, Figure 1 to Figure 3 As shown, the first insulating material layer 11 is disposed on the substrate 10. In this embodiment, the material of the first insulating material layer 11 is silicon dioxide (SiO2), which can achieve an insulating effect in actual use and is suitable for materials that have an effect of preventing moisture from entering. Figure 1 and Figure 3 As shown, the first insulating material layer 11 is provided with the isolation groove 17, and the isolation groove 17 divides the first insulating material layer 11 into a first area and a second area distributed on the left and right, wherein the first area corresponds to the position of the reference capacitor electrode pair 131, and the second area corresponds to the position of the humidity sensing capacitor electrode pair 132. The temperature sensing film 12 is embedded in the first insulating material layer 11; in this embodiment, the lower end surface of the temperature sensing film 12 contacts the substrate 10, and the upper end surface contacts the reference capacitor electrode pair 131.

[0084] Specifically, Figure 1 to Figure 3 As shown, the second insulating material layer 14 is disposed on the metal electrode layer 13. In this embodiment, the material of the second insulating material layer 14 is silicon dioxide (SiO2). In actual use, any material that can achieve an insulating effect and has an effect of preventing moisture from intruding is applicable. Preferably, the second insulating material layer is made of the same material as the first insulating material layer, and the first insulating material layer and the second insulating material layer have the same thickness. Figure 1 and Figure 3 As shown, the isolation groove 17 is provided on the second insulating material layer 14, and the isolation groove 17 divides the second insulating material layer 14 into a third area and a fourth area distributed on the left and right, wherein the third area corresponds to the position of the reference capacitor electrode pair 131, and the fourth area corresponds to the position of the humidity sensing capacitor electrode pair 132. The humidity sensing film 15 is embedded in the second insulating material layer 14; in this embodiment, the lower end surface of the humidity sensing film 15 contacts the humidity sensing capacitor electrode pair 132, and the upper end surface is exposed to the air.

[0085] Specifically, Figure 1 and Figure 2As shown, the metal electrode layer 13 is provided with the isolation groove 17, and the isolation groove 17 divides the metal electrode layer 13 into the reference capacitor electrode pair 131 and the moisture-sensing capacitor electrode pair 132 distributed on the left and right. The isolation grooves on the first insulating material layer 11, the metal electrode layer 13 and the second insulating material layer 14 are aligned to form a complete isolation structure. The length of each isolation groove can be set as needed to separate the electric field of the reference capacitor from that of the moisture-sensing capacitor. In this example, the length of each isolation groove is not less than the length of the reference capacitor electrode pair 131 and the moisture-sensing capacitor electrode pair 132. Each electrode pair includes a positive electrode and a negative electrode, and each electrode is led out to the surface of the second insulating material layer 14 through a through hole on the second insulating material layer 14 and is connected to the lead-out electrode 16. In this example, the positive electrode 131a of the reference capacitor electrode pair 131 is led out separately, and the positive electrode 132a of the humidity sensing capacitor electrode pair 132 is led out separately. The reference capacitor electrode pair 131 and the humidity sensing capacitor electrode pair 132 share a negative electrode 13b and are led out together; in addition, the reference capacitor electrode pair 131 and the humidity sensing capacitor electrode pair 132 are both forked finger structures, which can increase the capacitance change and reduce the pressure on the back-end detection circuit.

[0086] like Figure 1 As shown, the substrate, the first insulating material layer, the temperature-sensitive film, the reference capacitor electrode pair and the second insulating material layer on the left side of the humidity detection element 1 constitute a reference capacitor; the substrate, the first insulating material layer, the humidity-sensitive capacitor electrode pair, the second insulating material layer and the humidity-sensitive film on the right side of the humidity detection element 1 constitute a humidity-sensitive capacitor; wherein the temperature-sensitive film is wrapped by the first insulating material layer and the second insulating material layer, and only responds to temperature changes; the humidity-sensitive film is exposed to the air, and responds to both humidity changes and temperature changes. In this embodiment, the materials of the temperature-sensitive film 12 and the humidity-sensitive film 15 are both polyimide PI (Polyimide). The principle that the dielectric constant of polyimide changes with humidity and temperature is used to establish a mapping relationship between the capacitance value of the sensor and the ambient humidity and temperature, thereby realizing humidity detection; in actual use, any material that can achieve humidity and temperature response is suitable for the present invention, and will not be described one by one here. The humidity detection element 1 of the present invention adopts a dual-capacitor structure, which can reduce or even eliminate the capacitance offset of the humidity-sensitive capacitor caused by temperature changes, improve detection accuracy, and simplify subsequent calibration algorithms.

[0087] The present invention further provides a chip, the chip at least comprising the humidity detection element 1. As an example, the humidity detection element 1 of the present invention is prepared by MEMS technology, and the specific preparation steps are not described one by one here.

[0088] like Figure 4As shown, the present invention also provides a temperature and humidity sensor, which includes: a humidity detection circuit 2, a processing unit 3, a temperature-sensitive resistor NTC and a humidity detection element 1. Preferably, the humidity detection element 1 is sealed in the same chip as a bare die with the humidity detection circuit 2 to form a humidity sensor chip. The specific structure of the humidity detection element 1 is as described above and will not be described here one by one.

[0089] like Figure 4 As shown, the humidity detection circuit 2 is connected to the positive electrode of the reference capacitor, the positive electrode of the humidity sensing capacitor and the processing unit 3, and controls the oscillation of the humidity sensing capacitor in the humidity detection element 1 based on the reference oscillation number set in the processing unit 3; it also controls the oscillation of the reference capacitor in the humidity detection element 1 based on the oscillation time of the humidity sensing capacitor, and obtains the corresponding output oscillation number.

[0090] Specifically, the humidity detection circuit 2 applies a voltage to the positive electrode of the capacitor to be oscillated, and discharges the positive electrode of the capacitor to be oscillated after charging is completed, thereby achieving an oscillation; then repeats the charging and discharging operation based on the reference oscillation times and times the oscillation time of the humidity sensing capacitor; then controls the reference capacitor to oscillate, and when the oscillation time of the reference capacitor reaches the oscillation time of the humidity sensing capacitor, stops the oscillation and obtains the corresponding output oscillation times. Figure 5As shown, in this embodiment, the humidity detection circuit 2 includes a charging resistor R, a first charging switch Q1, a second charging switch Q2, a first discharging switch Q3, a second discharging switch Q4, a first Schmitt trigger 21, a second Schmitt trigger 22, an AND logic unit 23 and a selection circuit 24. The two ends of the charging resistor R are respectively connected to the positive electrode of the reference capacitor and the positive electrode of the humidity sensing capacitor; it is used to control the current when a voltage is applied to the positive electrode of the capacitor, so as to facilitate the recording of the number of oscillations. One end of the first charging switch Q1 is connected to a preset voltage (the working voltage VDD in this embodiment), and the other end is connected to the positive electrode of the reference capacitor; one end of the second charging switch Q2 is connected to the preset voltage, and the other end is connected to the positive electrode of the humidity sensing capacitor; the first charging switch Q1 and the second charging switch Q2 are used to provide a charging path. The first discharging switch Q3 is connected in parallel to the two ends of the reference capacitor, and the second discharging switch Q4 is connected in parallel to the two ends of the humidity sensing capacitor, so as to provide a discharging path. The input end of the first Schmitt trigger 21 is connected to the positive electrode of the reference capacitor, the input end of the second Schmitt trigger 22 is connected to the positive electrode of the humidity sensing capacitor, and the AND logic unit 23 performs an AND operation on the output signals of the first Schmitt trigger 21 and the second Schmitt trigger 22 and outputs them. The input end of the selection circuit 24 is connected to the output end of the second Schmitt trigger 22, and the output end is connected to the control end of the first discharge switch Q3 and the second discharge switch Q4, and the corresponding capacitor is selected for oscillation. As another implementation, a delay circuit 25 is also provided between the output end of the second Schmitt trigger 22 and the input end of the selection circuit 24 to ensure that the next oscillation is performed after one oscillation ends.

[0091] It should be noted that any circuit that can realize the above functions is applicable to the humidity detection circuit 2 of the present invention, and the specific structure is not described here one by one.

[0092] like Figure 4 As shown, the thermistor NTC is used to provide a temperature detection signal. Temperature changes will cause changes in the resistance of the thermistor, and the current temperature can be determined by the voltage on the thermistor. In this embodiment, one end of the thermistor NTC is connected to the processing unit 3, and the other end is connected to the working voltage VDD. The signal on the thermistor NTC is measured by the internal measurement circuit of the single-chip microcomputer.

[0093] like Figure 4 As shown, the processing unit 3 is connected to the humidity detection circuit 2 and the thermistor NTC, and realizes humidity calibration based on the output signal of the humidity detection circuit 2, and realizes temperature calibration based on the temperature detection signal on the thermistor NTC.

[0094] Specifically, in this embodiment, the processing unit 3 is implemented by a single chip microcomputer. The processing unit 3 can execute a calibration algorithm based on the output oscillation number provided by the humidity detection circuit 2 to obtain a humidity calibration formula, and obtain a calibrated humidity value based on the humidity calibration formula; at the same time, the processing unit 3 also executes a calibration algorithm based on the detection signal of the thermistor NTC to obtain a temperature calibration formula, and obtains a calibrated temperature value based on the temperature calibration formula.

[0095] like Figure 1 to Figure 5 As shown, the humidity measurement method and principle of the present invention are as follows:

[0096] The definition of a capacitor oscillation is that a charge and discharge operation of a capacitor (humidity sensing capacitor or reference capacitor) through a charging resistor R is a capacitor oscillation. At the beginning of the experiment, the humidity sensing capacitor oscillates a reference number of oscillations X. 感湿 , the system records the time Ti required for oscillation 总 , oscillate the reference capacitor within the same time, and output the reference capacitor oscillation times X 参考 (ie, the output oscillation number). The reference oscillation number and the output oscillation number satisfy the following relationship:

[0097] Ti 总 =Ti 感湿 ·X 感湿 =Ti 参考 ·X 参考 (1);

[0098] Among them, Ti 感湿 is the oscillation period of the humidity sensing capacitor, Ti 参考 is the oscillation period of the reference capacitor.

[0099] An oscillation cycle consists of the charging and discharging time of the capacitor. The positive electrode of the capacitor is charged through the charging resistor R and discharged when the positive electrode of the capacitor is grounded. The capacitor charging time ti in an oscillation cycle T is 充电 and discharge time ti 放电 With input voltage V in , charging reversal voltage V out Satisfying formula (2):

[0100]

[0101] Substituting formula (2) into formula (1) yields formula (3):

[0102]

[0103] About both ends Formula (4) is obtained:

[0104]

[0105] Since the positive electrode of the capacitor is grounded and discharged, we have formula (5):

[0106]

[0107] In summary, we get formula (6):

[0108] C 感湿 ·X 感湿 =C 参考 ·X 参考 (6)

[0109] The capacitance change of the capacitive humidity sensor using polyimide and its modified substances as humidity sensing materials satisfies formula (7):

[0110] ΔC 感湿 =k·Δε (7)

[0111] In formula (7), k is a fixed coefficient. For the interdigital capacitive sensor, it is uniquely determined by the length, width, thickness, logarithm, etc. of the interdigital. ε is the relative dielectric constant of the humidity sensing material, which changes linearly with humidity.

[0112] Combining equation (6) with equation (7), we get equation (8):

[0113]

[0114] From formula (8), we can see that when the temperature remains unchanged and the humidity changes, C 参考 If ε changes, the output oscillation frequency X 参考 To determine the current humidity value.

[0115] The temperature drift compensation principle of the humidity signal of the present invention is as follows:

[0116] like Figure 6 As shown, the capacitance composition of the humidity sensing capacitor and the reference capacitor satisfies:

[0117] C 感湿 =C 感湿PI +C 感湿SiO2 +C 感湿Si +C 参考部分寄生 (9)

[0118] C 参考 =C 参考PI +C 参考SiO2 +C 参考Si +C 感湿部分寄生 (10)

[0119] Due to C 参考部分寄生 Relative to C 感湿PI , C 感湿SiO2 , C 感湿SiThe position of C is far away, and there is an isolation groove in the middle, so the electric field lines distributed here are sparse, so they can be ignored; 感湿部分寄生 Similarly, the capacitance change satisfies equations (11) and (12):

[0120] ΔC 感湿 =ΔC 感湿PI +ΔC 感湿SiO2 +ΔC 感湿Si (11)

[0121] ΔC 参考 =ΔC 参考PI +ΔC 参考SiO2 +ΔC 参考Si (12)

[0122] When the humidity remains unchanged and the temperature changes, the capacitance change satisfies formula (13):

[0123] ΔC 感湿PI =ΔC 参考PI ; ΔC 感湿SiO2 =ΔC 参考SiO2 ; ΔC 感湿Si =ΔC 参考Si (13)

[0124] In summary, we get formula (14):

[0125] ΔC 感湿 =ΔC 参考 (14)

[0126] From formula (14), we can see that when the temperature changes, the humidity sensing capacitor and the reference capacitor change synchronously. For a given reference oscillation number X 感湿 , output oscillation times X 参考 The only way to determine the temperature drift of the humidity signal is to complete the compensation. The compensation results are as follows: Figure 7 and Figure 8 As shown, it can be seen that the capacitance of the humidity sensing capacitor using a single capacitor structure has temperature drift, while the output oscillation number of the dual capacitor structure of the present invention is only related to humidity and does not have temperature drift.

[0127] The present invention also provides a temperature and humidity calibration method, which is implemented based on the temperature and humidity sensor, and the temperature and humidity calibration method includes:

[0128] At the same temperature, n humidity calibration points are selected, and at the humidity corresponding to each humidity calibration point, the output oscillation number of the reference capacitor corresponding to the time required for the humidity sensing capacitor to oscillate the reference oscillation number is obtained, a mathematical model of the humidity value and the output oscillation number is established based on the humidity output characteristic curve, and the coefficients in the mathematical model of the humidity value and the output oscillation number are calculated based on the fitting of each output oscillation number, thereby obtaining a humidity calibration formula;

[0129] According to the output characteristics of the thermistor, m temperature calibration points are selected, and the thermistor output signals corresponding to each temperature calibration point are obtained. A mathematical model of the temperature value and the thermistor output signal is established based on the temperature output characteristic curve. The coefficients in the mathematical model of the temperature value and the thermistor output signal are calculated based on the fitting of each output signal of the thermistor, and then a temperature calibration formula is obtained; wherein n is a natural number greater than or equal to 2, and m is a natural number greater than or equal to 2.

[0130] Specifically, in this embodiment, a high-precision humidity generator is provided, and a stable temperature and humidity environment is provided by the humidity generator for calibration. In actual use, any device and scenario that can provide a stable temperature and humidity environment is applicable to the present invention.

[0131] Specifically, at the same temperature T0, multiple humidity calibration points are selected; the humidity is configured to be the humidity H1 corresponding to the first humidity calibration point, and the reference oscillation number X is written to the processing unit 3. 感湿 and controls the humidity sensing capacitor oscillation X in the humidity sensing element 1 through the humidity sensing circuit 2 感湿 times, and record the oscillation time Ti 总 , and then control the reference capacitor in the humidity detection element 1 to oscillate during the oscillation time Ti 总 Internal oscillation and record the output oscillation times X 参考1 ; Then configure the humidity to the humidity H2 corresponding to the second humidity calibration point, repeat the above steps to obtain the output oscillation number X corresponding to the current humidity calibration point 参考2 ; ... and so on, the output oscillation times of all humidity calibration points are obtained, see the table below:

[0132] Ambient temperature and humidity <![CDATA[(T0,H1)]]> <![CDATA[(T0,H2)]]> <![CDATA[(T0,H3)]]> <![CDATA[(T0,H4)]]> …… <![CDATA[(T0,H n )]]> Output oscillation times <![CDATA[X 参考1 ]]> <![CDATA[X 参考2 ]]> <![CDATA[X 参考3 ]]> <![CDATA[X 参考4 ]]> …… <![CDATA[X 参考n ]]>

[0133] More specifically, the humidity sensing capacitor is charged and discharged for a reference number of oscillations, and the oscillation time is recorded; the reference capacitor is repeatedly charged and discharged within the oscillation time, and the output oscillation times are recorded; wherein, when the voltage across the capacitor rises to the flip level, charging is determined to be complete, and when the voltage across the capacitor drops to the preset level, discharging is determined to be complete, and one charge and discharge operation is recorded as one oscillation. Specifically, the flip level is greater than the preset level, and generally, the flip level is less than VDD, and the preset level is approximately 0, which can be set as needed. Fig. 9As shown, the working principle of the humidity detection circuit 2 of this embodiment is as follows: close the first charging switch Q1, the second charging switch Q2 and the first discharging switch Q3, and turn off the second discharging switch Q4. At this time, the humidity sensing capacitor starts to be charged. When the voltage across the humidity sensing capacitor rises to the flip voltage, it is determined that the charging is completed; close the second discharging switch Q4, and the humidity sensing capacitor is discharged to 0 through the second discharging switch Q4; one charge and discharge is recorded as one oscillation, and the humidity sensing capacitor stops oscillating after completing the reference oscillation number of oscillations, and the oscillation time is recorded. Then, the first discharging switch Q3 is disconnected, and the second discharging switch Q4 is closed. At this time, the reference capacitor starts to be charged, and the above charging and discharging operations are repeated. The number of oscillations of the reference capacitor within the oscillation time is recorded to obtain the output oscillation number.

[0134] According to the output characteristic curve of the humidity sensor, the mathematical model (15) is obtained:

[0135] H=ax 2 +bx+c (15)

[0136] Where H is the humidity value, x is the number of output oscillations, and a, b, and c are humidity correlation coefficients.

[0137] The n data (X 参考1 , X 参考2 , X 参考3 , X 参考4 ...X 参考n )H=ax 2 +bx+c is a mathematical model that uses the least squares second-order fitting method to calculate the coefficients a, b, and c to obtain the humidity calibration formula.

[0138] According to the output characteristics of the temperature-sensitive resistor NTC, three or more temperature calibration points are selected to obtain the following table:

[0139] Ambient temperature <![CDATA[Te1]]> <![CDATA[Te2]]> <![CDATA[Te3]]> Temperature output <![CDATA[t1]]> <![CDATA[t2]]> <![CDATA[t3]]>

[0140] According to the output characteristic curve of the temperature sensor, the mathematical model (16) is obtained:

[0141] Te=dt 2 +et+f (16)

[0142] Where Te is the temperature value, t is the temperature output of the thermistor, and d, e, and f are temperature-related coefficients. 2 +et+f is a mathematical model that uses the least squares second-order fitting method to calculate the coefficients d, e, and f to obtain the temperature calibration formula. After calculating all the coefficients (a, b, c, d, e, and f), only one set of original data (x, t) is needed to be substituted into the calibration formulas (15) and (16) to obtain the current ambient temperature and humidity values.

[0143] It should be noted that, in the present embodiment, the mathematical model (15) and the mathematical model (16) are second-order mathematical models (can also be set to a higher order), then n and m are natural numbers greater than or equal to 3, and the specific numerical values ​​are set as needed. In actual use, the mathematical models (15) and (16) can be configured as first-order mathematical models, in which case n and m are natural numbers greater than or equal to 2. The larger n and m are, the higher the accuracy of the fitting is, but the larger the amount of data is, therefore, the specific numerical values ​​of n and m can be set as needed, which will not be described one by one here. In addition, the method for calculating each coefficient is not limited to the least square method, and a suitable fitting method can be selected according to the model, which is not limited to the present embodiment.

[0144] The temperature and humidity sensor of the present invention has high humidity measurement accuracy in extreme temperature environments; only one set of temperature data points and one set of humidity data points are required for calibration, which can shorten the batch calibration process; and the temperature and humidity can be fitted using second-order or even higher-order curves respectively, with fewer calibration coefficients and lower calculation amount, to achieve higher accuracy, can be applied to low-end single-chip microcomputer systems, with low calibration cost and wide application range.

[0145] In summary, the present invention provides a humidity detection element, a chip, a temperature and humidity sensor, and a temperature and humidity calibration method. The humidity detection element includes: a substrate, a first insulating material layer arranged on the substrate, a temperature-sensitive film embedded in the first insulating material layer, a metal electrode layer arranged on the first insulating material layer, a second insulating material layer arranged on the metal electrode layer, and a humidity-sensitive film embedded in the second insulating material layer, wherein the humidity-sensitive film is exposed to the air; wherein the metal electrode layer includes a reference capacitor electrode pair and a humidity-sensitive capacitor electrode pair, wherein the reference capacitor electrode pair is located above the temperature-sensitive film, and the humidity-sensitive capacitor electrode pair is located below the humidity-sensitive film, and the positive and negative electrodes of the reference capacitor electrode pair and the humidity-sensitive capacitor electrode pair are respectively led out to the surface of the second insulating material layer and connected to the lead-out electrodes; the first insulating material layer, the metal electrode layer, and the second insulating material layer are provided with isolation grooves, wherein the isolation grooves are located between the reference capacitor electrode pair and the humidity-sensitive capacitor electrode pair, and are used to isolate the electric fields of the reference capacitor and the humidity-sensitive capacitor. The present invention realizes the characteristic that the humidity signal output of the sensor does not change with temperature through a dual capacitor structure in conjunction with a humidity detection circuit, thereby completing the temperature drift compensation of the humidity signal. The humidity and temperature are calibrated separately through a matching calibration algorithm, so that the temperature parameter does not participate in the fitting of the humidity curve, thereby improving the measurement accuracy of the humidity. In addition, the calibration system has low requirements and can be used in conjunction with a low-end single-chip microcomputer; through a set of temperature data points and a set of humidity data points, a high measurement accuracy can be achieved on a low-end single-chip microcomputer platform. Therefore, the present invention effectively overcomes various shortcomings in the prior art and has a high industrial utilization value.

[0146] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A humidity detection element, characterized in that: The humidity detection element at least comprises: A substrate, a first insulating material layer disposed on the substrate, a temperature-sensitive film embedded in the first insulating material layer, a metal electrode layer disposed on the first insulating material layer, a second insulating material layer disposed on the metal electrode layer, and a moisture-sensitive film embedded in the second insulating material layer, wherein the moisture-sensitive film is exposed to air; Among them, the metal electrode layer includes a reference capacitor electrode pair and a humidity sensing capacitor electrode pair, the reference capacitor electrode pair is located above the temperature sensing film, and the humidity sensing capacitor electrode pair is located below the humidity sensing film, and the positive and negative electrodes of the reference capacitor electrode pair and the humidity sensing capacitor electrode pair are respectively led out to the surface of the second insulating material layer and connected to the lead-out electrodes; the first insulating material layer, the metal electrode layer and the second insulating material layer are provided with isolation grooves, and the isolation grooves are located between the reference capacitor electrode pair and the humidity sensing capacitor electrode pair, and are used to isolate the electric fields of the reference capacitor and the humidity sensing capacitor.

2. The humidity detection element according to claim 1, characterized in that: The reference capacitor electrode pair and the humidity sensing capacitor electrode pair are both interdigitated structures.

3. The humidity detection element according to claim 1, characterized in that: The temperature-sensitive film and the humidity-sensitive film are both made of polyimide.

4. The humidity detection element according to claim 1, characterized in that: The material of the substrate is silicon; the materials of the first insulating material layer and the second insulating material layer are both silicon dioxide; the first insulating material layer and the second insulating material layer have the same thickness.

5. The humidity detection element according to claim 1, characterized in that: The reference capacitor electrode pair and the humidity sensing capacitor electrode pair share a negative electrode.

6. A chip, characterized in that: The chip at least includes the humidity detection element as described in any one of claims 1-5.

7. A temperature and humidity sensor, characterized in that: The temperature and humidity sensor comprises at least: a humidity detection circuit, a processing unit, a temperature-sensitive resistor, a humidity detection element according to any one of claims 1 to 5, or a chip according to claim 6; The humidity detection circuit is connected to the positive electrode of the reference capacitor, the positive electrode of the humidity sensing capacitor and the processing unit, and controls the oscillation of the humidity sensing capacitor in the humidity detection element based on the reference oscillation number set in the processing unit; and controls the oscillation of the reference capacitor in the humidity detection element based on the oscillation time of the humidity sensing capacitor, and obtains the corresponding output oscillation number; The temperature sensitive resistor is used to provide a temperature detection signal; The processing unit is connected to the humidity detection circuit and the thermistor, realizes humidity calibration based on the output signal of the humidity detection circuit, and realizes temperature calibration based on the temperature detection signal on the thermistor.

8. The temperature and humidity sensor according to claim 7, characterized in that: The humidity detection circuit includes a charging resistor, a first charging switch, a second charging switch, a first discharging switch, a second discharging switch, a first Schmitt trigger, a second Schmitt trigger, an AND logic unit and a selection circuit; The two ends of the charging resistor are respectively connected to the positive electrodes of the reference capacitor and the humidity sensing capacitor; One end of the first charging switch is connected to a preset voltage, and the other end is connected to the positive electrode of the reference capacitor; one end of the second charging switch is connected to the preset voltage, and the other end is connected to the positive electrode of the humidity sensing capacitor; the first charging switch and the second charging switch are used to provide a charging path; The first discharge switch is connected in parallel to both ends of the reference capacitor, and the second discharge switch is connected in parallel to both ends of the humidity sensing capacitor, for providing a discharge path; The input end of the first Schmitt trigger is connected to the positive electrode of the reference capacitor, the input end of the second Schmitt trigger is connected to the positive electrode of the humidity sensing capacitor, and the AND logic unit performs an AND operation on the output signals of the first Schmitt trigger and the second Schmitt trigger and outputs the AND operation; The input end of the selection circuit is connected to the output end of the second Schmitt trigger, and the output end is connected to the control ends of the first discharge switch and the second discharge switch, so as to select a corresponding capacitor for oscillation.

9. A temperature and humidity calibration method, implemented based on the temperature and humidity sensor according to any one of claims 7-8, characterized in that: The temperature and humidity calibration method at least includes: At the same temperature, n humidity calibration points are selected, and at the humidity corresponding to each humidity calibration point, the output oscillation number of the reference capacitor corresponding to the time required for the humidity sensing capacitor to oscillate the reference oscillation number is obtained, a mathematical model of the humidity value and the output oscillation number is established based on the humidity output characteristic curve, and the coefficients in the mathematical model of the humidity value and the output oscillation number are calculated based on the fitting of each output oscillation number, thereby obtaining a humidity calibration formula; According to the output characteristics of the thermistor, m temperature calibration points are selected, the output signals of the thermistor corresponding to each temperature calibration point are obtained, a mathematical model of the temperature value and the output signal of the thermistor is established based on the temperature output characteristic curve, and the coefficients in the mathematical model of the temperature value and the output signal of the thermistor are calculated based on the fitting of each output signal of the thermistor, thereby obtaining a temperature calibration formula; Wherein, n is a natural number greater than or equal to 2, and m is a natural number greater than or equal to 2.

10. The temperature and humidity calibration method according to claim 9, characterized in that: The method for obtaining the output oscillation number includes: Performing a charge and discharge operation on the humidity sensing capacitor for a reference oscillation number, and recording the oscillation time; repeatedly performing a charge and discharge operation on the reference capacitor within the oscillation time, and recording the output oscillation number; When the voltage across the capacitor rises to the flip level, it is determined that the charging is completed, and when the voltage across the capacitor drops to the preset level, it is determined that the discharging is completed. One charging and discharging operation is recorded as one oscillation.

11. The temperature and humidity calibration method according to claim 9, characterized in that: The reference oscillation number and the output oscillation number satisfy the following relationship: You 总 =You 感湿 ·X 感湿 =You 参考 ·X 参考 ; Among them, Ti 总 is the oscillation time, Ti 感湿 is the oscillation period of the humidity sensing capacitor, X 感湿 is the reference oscillation number, Ti 参考 is the oscillation period of the reference capacitor, X 参考 is the number of output oscillations.

12. The temperature and humidity calibration method according to claim 9, characterized in that: The mathematical model of humidity value and output oscillation number is a second-order mathematical model, which satisfies: H=ax 2 +bx+c; Wherein, H is the humidity value, x is the output oscillation number, a, b, c are coefficients in the mathematical model of the humidity value and the output oscillation number, and n is a natural number greater than or equal to 3.

13. The temperature and humidity calibration method according to claim 9, characterized in that: The mathematical model of the temperature value and the output signal of the temperature-sensitive resistor is a second-order mathematical model, which satisfies: Te=dt 2 +et+f; Among them, Te is the temperature value, t is the output signal of the temperature-sensitive resistor, d, e, f are coefficients in the mathematical model of the temperature value and the output signal of the temperature-sensitive resistor, and m is a natural number greater than or equal to 3.

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