Drift-free humidity sensor

Abstract

The present invention provides a drift-free humidity sensor, comprising: a first humidity sensor unit and a second humidity sensor unit, wherein the first humidity sensor unit comprises a first measuring electrode, the first measuring electrode is covered with a first humidity-sensitive material, the second humidity sensor unit comprises a second measuring electrode, the second measuring electrode is covered with a second humidity-sensitive material, and the maximum humidity drift of the first humidity sensor unit and the second humidity sensor unit are different. The humidity sensor of the present invention can effectively solve the drift problem of general capacitive humidity sensors or resistive humidity sensors; the corresponding processing methods are used for humidity-sensitive materials of different materials, and the applicability is high; and the measurement accuracy is improved through the correction algorithm.

Description

Technical Field

[0001] The present invention relates to the technical field of humidity sensors, and in particular to a drift-free humidity sensor. Background Art

[0002] Humidity sensors are widely used in indoor temperature and humidity monitoring, smart home, white appliances, security, agriculture and many other fields, playing a huge role. The implementation principles of humidity sensors include resistance, capacitance, mass weighing, dry-wet bulb, etc. Since capacitive and resistive humidity sensors are easy to be compatible with CMOS process, have good linearity, and have a wide humidity range (0-100% RH), temperature and humidity sensor chips mostly use these two implementation methods, among which capacitive is the most widely used.

[0003] However, sensors that use polymers as humidity-sensitive materials, regardless of whether they are capacitive, resistive, or pressure-sensitive, will inevitably form chemically adsorbed water vapor due to the inherent characteristics of the polymer, and it is difficult to desorb, resulting in humidity drift. Especially in high temperature and high humidity environments, the long chain space position of the polymer expands, and its humidity drift characteristics are more obvious.

[0004] In order to solve the drift characteristics of humidity sensors, US9696272B2 patent proposes a method of adjusting the sampling frequency to improve the drift characteristics; US4793175 patent proposes a solution of using inorganic substances as humidity-sensitive materials to resist drift; at the same time, there are also a large number of literatures proposing improved polymer structures to improve this problem. Summary of the invention

[0005] In view of the defects in the prior art, an object of the present invention is to provide a drift-free humidity sensor and a calibration method thereof.

[0006] A drift-free humidity sensor provided according to the present invention includes: a first humidity sensor unit, a second humidity sensor unit and an analysis and processing unit, the first humidity sensor unit includes a first measuring electrode and a first humidity-sensitive material covering the first measuring electrode, the second humidity sensor unit includes a second measuring electrode and a second humidity-sensitive material covering the second measuring electrode, the maximum humidity drift of the first humidity sensor unit and the second humidity sensor unit are different, and the analysis and processing unit corrects and outputs the measured values ​​of the first humidity sensor unit and the second humidity sensor unit.

[0007] Preferably, the first measuring electrode comprises a first measuring positive electrode and a first measuring negative electrode, and both the first measuring positive electrode and the first measuring negative electrode are provided with interdigital electrodes;

[0008] The second measuring electrode is composed of a second measuring positive electrode and a second measuring negative electrode, and both the second measuring positive electrode and the second measuring negative electrode are provided with interdigital electrodes.

[0009] The interdigitated electrodes are arranged in a staggered manner.

[0010] Preferably, the first measuring electrode and the second measuring electrode are capacitive electrodes; or, the first measuring electrode and the second measuring electrode are resistive electrodes.

[0011] Preferably, the first measuring electrode and the second measuring electrode are capacitive electrodes, a passivation layer is arranged between one side of the first measuring electrode and the first humidity-sensitive material, a dielectric layer and a substrate silicon wafer are arranged in sequence on the other side of the first measuring electrode, and the dielectric layer is filled between the first measuring electrode and the substrate silicon wafer;

[0012] A passivation layer is arranged between one side of the second measuring electrode and the second humidity sensitive material, and a dielectric layer and a substrate silicon wafer are arranged in sequence on the other two sides of the second measuring electrode, and the dielectric layer is filled between the second measuring electrode and the substrate silicon wafer.

[0013] Preferably, the first measuring electrode and the second measuring electrode are resistive electrodes, the first humidity-sensitive material is arranged on one side of the first measuring electrode, and a dielectric layer and a substrate silicon wafer are sequentially arranged on the other side of the first measuring electrode, and the dielectric layer is filled between the first measuring electrode and the substrate silicon wafer;

[0014] The second humidity-sensitive material is arranged on one side of the second measuring electrode, and a dielectric layer and a substrate silicon wafer are arranged in sequence on the other side of the second measuring electrode, and the dielectric layer is filled between the second measuring electrode and the substrate silicon wafer.

[0015] Preferably, for the capacitive electrode, the first humidity-sensitive material and the second humidity-sensitive material are photosensitive humidity-sensitive materials or non-photosensitive humidity-sensitive materials, and the processing method of the first humidity-sensitive material and the second humidity-sensitive material includes:

[0016] - If the first humidity-sensitive material and the second humidity-sensitive material are both photosensitive humidity-sensitive materials, a pattern is obtained by direct photolithography;

[0017] If one of the first moisture-sensitive material or the second moisture-sensitive material is a non-photosensitive moisture-sensitive material, the processing method includes:

[0018] Step S1.1: Spin-coating a non-photosensitive moisture-sensitive material on the passivation layer of the first measuring electrode and the second measuring electrode and curing the material, then spin-coating a photoresist on the non-photosensitive moisture-sensitive material, photolithographing a desired pattern, then processing the material by dry etching, and finally removing the photoresist to complete the processing of a moisture-sensitive material;

[0019] Step S1.2: spin coating a photosensitive humidity-sensitive material, patterning the photosensitive humidity-sensitive material by photolithography, and curing the photosensitive humidity-sensitive material to obtain another humidity-sensitive material;

[0020] - If the first moisture-sensitive material and the second moisture-sensitive material are both non-photosensitive moisture-sensitive materials, the processing method includes:

[0021] Step S2.1: Spin-coating a first moisture-sensitive material on the passivation layers of the two measuring electrodes and curing the material, wherein the thickness of the first moisture-sensitive material is more than one times the sum of the width and margin of the interdigital electrodes, and then spin-coating a photoresist on the first photosensitive moisture-sensitive material, photolithographing a desired pattern, and then processing the material by dry etching, and finally removing the photoresist to complete the processing of the first moisture-sensitive material;

[0022] Step S2.2: Spin-coat the second wet-sensitive material and solidify it, then spin-coat a photoresist on the second wet-sensitive material, and photoetch out the desired pattern, and then process it through a dry etching process to retain the second wet-sensitive material attached to the first wet-sensitive material, and finally remove the photoresist to complete the processing of the second wet-sensitive material.

[0023] Preferably, for the resistive electrode, the first humidity-sensitive material and the second humidity-sensitive material are photosensitive humidity-sensitive materials; or either one of the first humidity-sensitive material and the second humidity-sensitive material is a non-photosensitive humidity-sensitive material, and the other is a photosensitive humidity-sensitive material; the processing method of the first humidity-sensitive material and the second humidity-sensitive material includes:

[0024] - If the first humidity-sensitive material and the second humidity-sensitive material are both photosensitive humidity-sensitive materials, a pattern is obtained by direct photolithography;

[0025] - If one of the first moisture-sensitive material or the second moisture-sensitive material is a non-photosensitive moisture-sensitive material, the processing method is:

[0026] Step S3.1: Spin-coating a non-photosensitive moisture-sensitive material on the first measuring electrode and the second measuring electrode and curing the material, then spin-coating a photoresist on the non-photosensitive moisture-sensitive material, photolithographing a desired pattern, then processing the material by dry etching, and finally removing the photoresist to complete the processing of a moisture-sensitive material;

[0027] Step S3.2: spin coating a photosensitive humidity-sensitive material, patterning the photosensitive humidity-sensitive material by photolithography, and curing the photosensitive humidity-sensitive material to obtain another humidity-sensitive material;

[0028] - If the first moisture-sensitive material and the second moisture-sensitive material are both non-photosensitive moisture-sensitive materials, the processing method includes:

[0029] Step S4.1: Spin-coating a first non-photosensitive moisture-sensitive material on the first measuring electrode and the second measuring electrode and curing the material, then spin-coating a photoresist on the non-photosensitive moisture-sensitive material, photolithographing a desired pattern, and then processing the material by dry etching, and finally removing the photoresist to complete the processing of a moisture-sensitive material;

[0030] Step S4.2: Spin-coating a second non-photosensitive moisture-sensitive material, and then spin-coating a photoresist, patterning by photolithography, and then using an alkaline developer (TMAH) to corrode the second non-photosensitive material while developing the photoresist, and curing the second moisture-sensitive material after removing the photoresist to obtain another moisture-sensitive material;

[0031] Preferably, the humidity sensor adopts a differential sampling structure, wherein the first humidity sensor unit includes a first sensing subunit and a second sensing subunit, and the second humidity sensor unit includes a third sensing subunit and a fourth sensing subunit.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1. The humidity sensor of the present invention can effectively solve the drift problem of general capacitive humidity sensors or resistive humidity sensors;

[0034] 2. Use corresponding processing methods for moisture-sensitive materials of different materials, which has high applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0036] Figure 1 This is a schematic diagram of the interdigital capacitor in the humidity sensor of the present invention;

[0037] Figure 2 It is a schematic cross-sectional view of the humidity sensitive material in the humidity sensor of the present invention;

[0038] Figure 3 It is a cross-sectional view of a first humidity sensor unit of a capacitive sensor of the present invention;

[0039] Figure 4 It is a cross-sectional view of the second humidity sensor unit of the capacitive sensor of the present invention;

[0040] Figure 5 is a cross-sectional view of the first humidity sensor unit when two non-photosensitive humidity-sensitive materials are used in the present invention;

[0041] Figure 6 is a cross-sectional view of the resistive sensor of the present invention;

[0042] Figure 7This is a schematic diagram of the interdigital capacitor of the humidity sensor with a differential sampling structure of the present invention;

[0043] Figure 8 This is a flow chart of the humidity sensor calibration method of the present invention.

[0044] Description of reference numerals:

[0045] First measuring electrode 101 Second measuring electrode 102

[0046] The first positive electrode 1011 and the second positive electrode 1021

[0047] The first negative electrode 1012 and the second negative electrode 1022

[0048] First moisture-sensitive material 201 Second moisture-sensitive material 202

[0049] Passivation layer 211 Dielectric layer 213

[0050] Interdigitated electrode 212 Substrate silicon wafer 214

[0051] The first sensor subunit 111 The second sensor subunit 112

[0052] The third sensor subunit 113 and the fourth sensor subunit 114

[0053] The first subunit positive electrode 1111 The first subunit negative electrode 1112

[0054] The second subunit positive electrode 1121 The second subunit negative electrode 1122

[0055] The third subunit positive electrode 1131 The third subunit negative electrode 1132

[0056] The fourth subunit positive electrode 1141 The fourth subunit negative electrode 1142 DETAILED DESCRIPTION

[0057] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several changes and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0058] Planar humidity sensors, including capacitive humidity sensors and resistive humidity sensors, generally set up a forked structure on a silicon wafer or ASIC wafer, and then apply a layer of humidity-sensitive material on the forked electrode to detect the humidity-sensitive capacitor. The back-end circuit detection is generally divided into a single-ended structure and a differential structure. The single-ended structure samples a single electrode, and the differential structure samples two symmetrical electrodes.

[0059] The present invention discloses a non-drift humidity sensor, referring to Figure 1 and Figure 2 , including: a first humidity sensor unit, a second humidity sensor unit and an analysis and processing unit, the first humidity sensor unit includes a first measuring electrode 101, and a first humidity-sensitive material 201 covering the first measuring electrode 101, the second humidity sensor unit includes a second measuring electrode 102, and a second humidity-sensitive material 202 covering the second measuring electrode 102, the maximum humidity drift of the first humidity sensor unit and the second humidity sensor unit are different, and the analysis and processing unit corrects and outputs the measured values ​​of the first humidity sensor unit and the second humidity sensor unit.

[0060] Reference Figure 3 The first measuring electrode 101 comprises a first measuring positive electrode 1011 and a first measuring negative electrode 1012, and both the first measuring positive electrode 1011 and the first measuring negative electrode 1012 are provided with interdigital electrodes 212;

[0061] Reference Figure 4 The second measuring electrode 102 is composed of a second measuring positive electrode 1021 and a second measuring negative electrode 1022 . Both the second measuring positive electrode 1021 and the second measuring negative electrode 1022 are provided with interdigital electrodes 212 , and the interdigital electrodes 212 are arranged in a staggered manner.

[0062] The first measurement electrode 101 and the second measurement electrode 102 are capacitive electrodes; or, the first measurement electrode 101 and the second measurement electrode 102 are resistive electrodes.

[0063] The following is a detailed description of the case where capacitive electrodes are used.

[0064] A passivation layer 211 is disposed between one side of the first measuring electrode 101 and the first moisture sensitive material 201 . A dielectric layer 213 and a substrate silicon wafer 214 are sequentially disposed on the other side of the first measuring electrode 101 , and the dielectric layer 213 is filled between the first measuring electrode 101 and the substrate silicon wafer 214 .

[0065] A passivation layer 211 is disposed between one side of the second measuring electrode 102 and the second moisture sensitive material 202 , and a dielectric layer 213 and a substrate silicon wafer 214 are sequentially disposed on the other two sides of the second measuring electrode 102 , and the dielectric layer 213 is filled between the second measuring electrode 102 and the substrate silicon wafer 214 .

[0066] The first moisture-sensitive material 201 and the second moisture-sensitive material 202 are photosensitive moisture-sensitive materials or non-photosensitive moisture-sensitive materials. The processing methods of the first moisture-sensitive material 201 and the second moisture-sensitive material 202 are divided into the following situations according to different materials:

[0067] - If the first moisture-sensitive material 201 and the second moisture-sensitive material 202 are both photosensitive moisture-sensitive materials, the pattern is obtained by direct photolithography;

[0068] If one of the first moisture-sensitive material 201 or the second moisture-sensitive material 202 is a non-photosensitive moisture-sensitive material, the processing method includes:

[0069] Step S1.1: Spin-coating a non-photosensitive moisture-sensitive material on the passivation layer 211 of the first measuring electrode 101 and the second measuring electrode 102 and curing the material, then spin-coating a photoresist on the non-photosensitive moisture-sensitive material, photolithography a desired pattern, and then performing a dry etching process, and finally removing the photoresist to complete the processing of a moisture-sensitive material;

[0070] Step S1.2: spin coating a photosensitive humidity-sensitive material, patterning the photosensitive humidity-sensitive material by photolithography, and curing the photosensitive humidity-sensitive material to obtain another humidity-sensitive material;

[0071] If the first moisture-sensitive material 201 and the second moisture-sensitive material 202 are both non-photosensitive moisture-sensitive materials, the processing method includes:

[0072] Step S2.1: Spin-coat the first moisture-sensitive material 201 on the passivation layer 211 of the two measuring electrodes and cure it, then spin-coat a photoresist on the first photosensitive moisture-sensitive material, photolithograph a desired pattern, and then process it through a dry etching process, and finally remove the photoresist to complete the processing of the first moisture-sensitive material 201;

[0073] Step S2.2: Spin-coat the second wet-sensitive material 202 and cure it, then spin-coat a photoresist on the second photosensitive wet-sensitive material, and photoetch out the desired pattern, and then process it through a dry etching process to retain the second photosensitive wet-sensitive material attached to the first photosensitive wet-sensitive material, and finally remove the photoresist to complete the processing of the second wet-sensitive material 202.

[0074] When both the first wetness-sensitive material 201 and the second wetness-sensitive material 202 are non-photosensitive wetness-sensitive materials, the problem becomes complicated. The method for processing the first wetness-sensitive material 201 remains unchanged. However, if the second wetness-sensitive material 202 is processed by dry etching, then because dry etching has no selectivity for the first wetness-sensitive material 201 and the second wetness-sensitive material 202, when the second wetness-sensitive material 202 outside the second humidity sensor unit is removed, the first wetness-sensitive material 201 in the first humidity sensor unit area will also lose thickness due to over-etching. Fortunately, however, we do not necessarily need to remove the second wetness-sensitive material 202 on the first wetness-sensitive material 201. Figure 5 , that is, the second humidity-sensitive material 202 can be retained on the first sensing unit, which greatly reduces the conflict in process integration. However, this solution needs to ensure a premise that the thickness of the first humidity-sensitive material 201 is more than 1 times the sum of the aluminum strip line width and the side spacing of the interdigital electrode 212, so that the electric field lines of the capacitor will not or only a very small amount will pass through the second humidity-sensitive material 202, such as Figure 5 As shown, the crosstalk between the first moisture-sensitive material 201 and the second moisture-sensitive material 202 is reduced.

[0075] The resistive electrode will be described in detail below.

[0076] Reference Figure 6 The first moisture-sensitive material 201 is disposed on one side of the first measuring electrode 101 , and a dielectric layer 213 and a substrate silicon wafer 214 are sequentially disposed on the other side of the first measuring electrode 101 , and the dielectric layer 213 is filled between the first measuring electrode 101 and the substrate silicon wafer 214 .

[0077] The second moisture sensitive material 202 is disposed on one side of the second measuring electrode 102 , and a dielectric layer 213 and a substrate silicon wafer 214 are sequentially disposed on the other side of the second measuring electrode 102 , with the dielectric layer 213 filling between the second measuring electrode 102 and the substrate silicon wafer 214 .

[0078] The first humidity-sensitive material 201 and the second humidity-sensitive material 202 are photosensitive humidity-sensitive materials; or either one of the first humidity-sensitive material 201 and the second humidity-sensitive material 202 is a non-photosensitive humidity-sensitive material, and the other is a photosensitive humidity-sensitive material; the processing method of the first humidity-sensitive material 201 and the second humidity-sensitive material 202 includes:

[0079] - If the first moisture-sensitive material 201 and the second moisture-sensitive material 202 are both photosensitive moisture-sensitive materials, the pattern is obtained by direct photolithography;

[0080] If one of the first moisture-sensitive material 201 or the second moisture-sensitive material 202 is a non-photosensitive moisture-sensitive material, the processing method is:

[0081] Step S3.1: Spin-coating a non-photosensitive moisture-sensitive material on the first measuring electrode 101 and the second measuring electrode 102 and curing the material, then spin-coating a photoresist on the non-photosensitive moisture-sensitive material, photolithographing a desired pattern, and then processing the material by dry etching, and finally removing the photoresist to complete the processing of a moisture-sensitive material;

[0082] Step S3.2: spin coating a photosensitive humidity-sensitive material, patterning the photosensitive humidity-sensitive material by photolithography, and curing the photosensitive humidity-sensitive material to obtain another humidity-sensitive material;

[0083] If the first moisture-sensitive material 201 and the second moisture-sensitive material 202 are both non-photosensitive moisture-sensitive materials, the processing method includes:

[0084] Step S4.1: Spin-coating a first non-photosensitive moisture-sensitive material on the first measuring electrode 101 and the second measuring electrode 102 and curing the material, then spin-coating a photoresist on the non-photosensitive moisture-sensitive material, photolithographing a desired pattern, and then processing the material by dry etching, and finally removing the photoresist to complete the processing of a moisture-sensitive material;

[0085] Step S4.2: Spin-coating a second non-photosensitive moisture-sensitive material, and then spin-coating a photoresist, patterning by photolithography, and then using an alkaline developer (TMAH) to corrode the second non-photosensitive material while developing the photoresist, and curing the second moisture-sensitive material after removing the photoresist to obtain another moisture-sensitive material;

[0086] For resistive electrodes, if the first wet-sensitive material and the second wet-sensitive material are stacked and covered on the interdigital electrodes at the same time, the first wet-sensitive layer and the second wet-sensitive layer form a parallel relationship, and the measured wet-sensitive resistance will be the combined result of the first wet-sensitive material and the second wet-sensitive material, thereby affecting the result of the humidity measurement unit. Therefore, when processing the wet-sensitive material on the resistive electrode, the first wet-sensitive material and the second wet-sensitive material cannot both use non-photosensitive wet-sensitive materials. However, for capacitive electrodes, since the crossing height of the electric field lines is limited, the stacking of the first wet-sensitive material and the second wet-sensitive material is allowed to occur. At this time, the thickness of the first wet-sensitive material 201 is greater than 1 times the sum of the aluminum strip line width and the side spacing of the interdigital electrode 212.

[0087] The above is a solution for a single-ended humidity sensor. If the ASIC circuit adopts a differential sampling structure, the first humidity sensor unit and the second humidity sensor unit on the sensor device side also need to be designed in the form of a differential pair. Figure 7, including a first sensor subunit 111, a second sensor subunit 112, a third sensor subunit 113 as a third sensor unit and a fourth sensor subunit 114; wherein the first sensor subunit 111 includes a first subunit positive electrode 1111 and a first subunit negative electrode 1112; the second sensor subunit 112 includes a second subunit positive electrode 1121 and a second subunit negative electrode 1122; the third sensor subunit 113 includes a third subunit positive electrode 1131 and a third subunit negative electrode 1132; the fourth sensor subunit 114 includes a fourth subunit positive electrode 1141 and a fourth subunit negative electrode 1142. For the first humidity sensor unit and the second humidity sensor unit required by the present invention, they can be obtained by combining any two sensor subunits. However, since the actual layout requires a higher matching, generally speaking, the first humidity sensor unit is composed of the first sensor subunit 111 and the fourth sensor subunit 114, and the second humidity sensor unit is composed of the second sensor subunit 112 and the third sensor subunit 113. The subsequent application of moisture-sensitive materials is consistent with the above scheme.

[0088] The present invention discloses a drift-free humidity sensor calibration method. When the analysis and processing unit receives the results measured by the first humidity sensor unit and the second humidity sensor unit, it calculates the error between the two results and finally generates an accurate humidity value. The specific calibration process is as follows: Figure 8 , including the following steps:

[0089] Step S1: Obtain the relationship between the maximum humidity drift characteristics of the first humidity sensor unit and the second humidity sensor unit and the ambient humidity, and calculate the maximum drift difference between the first humidity sensor unit and the second humidity sensor unit.

[0090] First, through a small batch of test data, the relationship between the maximum humidity drift characteristics of the first humidity sensor unit and the second humidity sensor unit and the ambient humidity is studied respectively. The universal regression relationship can be expressed by a first-order equation about ambient humidity, as shown in Equations 1 and 2. The maximum drift can be accelerated by aging for a certain period of time, such as 85°C 85% RH test, or HAST test, so that the drift of the sensor reaches stability. Generally speaking, during the test, the humidity drift value is small at low humidity, the drift value is medium at medium humidity, and the drift value is the largest at high humidity, showing a correlation with the current test environment humidity. Some polymer materials will also show good linear drift under the full humidity range, that is, the first-order term is 0. We subtract the maximum drift value of the first humidity sensor unit and the second humidity sensor unit to obtain Equation 3 as the subsequent reference value.

[0091] RH_Drift max_A =αRH+a (1)

[0092] RH_Drift max_B=βRH+b (2)

[0093] ΔRH_Drift max =(β-α)RH+(ba) (3)

[0094] Step S2: performing regression fitting on the capacitance values ​​of the first humidity sensor unit and the second humidity sensor unit and the measured RH value to obtain a first fitting equation and a second fitting equation.

[0095] Calibrate the first humidity sensor unit and the second humidity sensor unit to establish the corresponding relationship of "ambient humidity - humidity capacitor or humidity resistor - ADC digital quantity - humidity value read". Generally speaking, the second-order fitting can meet the accuracy requirements of most sensors, as shown in equations 4 and 5; of course, according to the design capabilities of the digital circuit or the requirements of the sensor device, regression fitting such as third order or above can be used. After completing this step, the first humidity sensor unit and the second humidity sensor unit will be able to independently measure their respective humidity values.

[0096]

[0097]

[0098] Step S3: Obtain humidity values ​​of the first humidity sensor unit and the second humidity sensor unit under a certain humidity environment, calculate the actual humidity difference between the first humidity sensor unit and the second humidity sensor unit, and compare the actual humidity difference with the maximum drift difference.

[0099] When the environment is at a certain humidity RH, the first humidity sensor unit and the second humidity sensor unit will read RH respectively. A and RH B Two humidity values, at this time we get the difference between the two, as shown in formula 6:

[0100] ΔRH=RH B -RH A (6)

[0101] Step S4: Compare the actual humidity difference between the first humidity sensor unit and the second humidity sensor unit with the relationship between the maximum drift characteristic of the first humidity sensor unit and the ambient humidity, and with the relationship between the maximum drift characteristic of the second humidity sensor unit and the ambient humidity, to obtain the humidity drift amount of the first humidity sensor unit under the current humidity environment, and the humidity drift amount of the second humidity sensor unit.

[0102] By comparing Equation 6 with Equation 1 or Equation 2, we can obtain the humidity drift of sensor units A and B under the current humidity environment, as shown in Equations 7 and 8, respectively.

[0103]

[0104]

[0105] Step S5: Establish equations about the real humidity value RH according to the first fitting equation and the second fitting equation, and the humidity drift of the first humidity sensor unit and the humidity drift of the second humidity sensor unit in step S4.

[0106] According to the measured RH values ​​of equations 4 and 5 and the drift compensation values ​​of equations 7 and 8, equations about the true humidity value RH can be established, as shown in equations 9 and 10, respectively.

[0107] RH=RH A -RH_Drift A (9)

[0108] RH=RH B -RH_Drift B (10)

[0109] Step S6: According to the equation of the real humidity value RH in step S5, a second-order equation of the first humidity sensor unit with respect to RH and a second-order equation of the second humidity sensor unit with respect to RH are established.

[0110] According to equations 9 and 10, the second-order equations for RH can be obtained. Both equations can calculate the value of the true RH, as shown in equations 11 and 12. Theoretically, if the drift rates of sensor unit A and sensor unit B are similar, then the RH values ​​calculated by sensor units A and B should be equal, and any value can be taken. However, it is difficult to have such an ideal situation in reality. For example, individual differences of the same material and differences in drift rates of different materials require additional discrimination to increase the credibility of the data.

[0111] RH_real A =f A (RH A ,RH B ) (11)

[0112] RH_real B =f B (RH a ,RH B ) (12)

[0113] Step S7: weighting the difference between the second-order equation of the first humidity sensor unit with respect to RH and the second-order equation of the second humidity sensor unit with respect to RH respectively, thereby completing the calibration process.

[0114] Finally, we assign weights to the true RH values ​​obtained by sensor units A and B. When the difference between the two is less than a certain set threshold, γ and δ can be taken as 0.5. When the difference between the two exceeds the set threshold, the sensor unit with higher confidence is taken as the main sensor unit and assigned a higher weight. In this way, we can eventually obtain a humidity sensor with no drift throughout its life cycle.

[0115] RH=γRH_real A +δRH_real B (13)

[0116] In the description of the present application, it should be understood that the terms "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0117] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. In the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.

Claims

1. A drift-free humidity sensor, characterized in that: include: A first humidity sensor unit, a second humidity sensor unit and an analysis and processing unit, the first humidity sensor unit comprising a first measuring electrode (101) and a first humidity-sensitive material (201) covering the first measuring electrode (101), the second humidity sensor unit comprising a second measuring electrode (102) and a second humidity-sensitive material (202) covering the second measuring electrode (102), the first humidity sensor unit and the second humidity sensor unit having different maximum humidity drifts, and the analysis and processing unit correcting and outputting the measured values ​​of the first humidity sensor unit and the second humidity sensor unit; The drift-free humidity sensor calibration method includes: Step S1: obtaining the relationship between the maximum humidity drift characteristics of the first humidity sensor unit and the second humidity sensor unit and the ambient humidity, and calculating the maximum drift difference between the first humidity sensor unit and the second humidity sensor unit; Step S2: performing regression fitting on the capacitance values ​​of the first humidity sensor unit and the second humidity sensor unit and the measured RH value to obtain a first fitting equation and a second fitting equation; Step S3: obtaining humidity values ​​of the first humidity sensor unit and the second humidity sensor unit under a certain humidity environment, calculating an actual humidity difference between the first humidity sensor unit and the second humidity sensor unit, and comparing the actual humidity difference with the maximum drift difference; Step S4: Compare the actual humidity difference between the first humidity sensor unit and the second humidity sensor unit with the relationship between the maximum drift characteristic of the first humidity sensor unit and the ambient humidity and the relationship between the maximum drift characteristic of the second humidity sensor unit and the ambient humidity to obtain the humidity drift amount of the first humidity sensor unit and the humidity drift amount of the second humidity sensor unit under the current humidity environment; Step S5: establishing equations about the real humidity value RH according to the first fitting equation and the second fitting equation, as well as the humidity drift of the first humidity sensor unit and the humidity drift of the second humidity sensor unit in step S4; Step S6: According to the equation of the real humidity value RH in step S5, establish the second-order equation of the first humidity sensor unit with respect to RH and the second-order equation of the second humidity sensor unit with respect to RH; Step S7: weighting the difference between the second-order equation of the first humidity sensor unit with respect to RH and the second-order equation of the second humidity sensor unit with respect to RH respectively, thereby completing the calibration process.

2. The drift-free humidity sensor according to claim 1, characterized in that: The first measuring electrode (101) comprises a first measuring positive electrode (1011) and a first measuring negative electrode (1012), and both the first measuring positive electrode (1011) and the first measuring negative electrode (1012) are provided with interdigital electrodes (212); The second measuring electrode (102) is composed of a second measuring positive electrode (1021) and a second measuring negative electrode (1022), and both the second measuring positive electrode (1021) and the second measuring negative electrode (1022) are provided with interdigital electrodes (212). The interdigitated electrodes (212) are arranged in a staggered manner.

3. The drift-free humidity sensor according to claim 2, characterized in that: The first measuring electrode (101) and the second measuring electrode (102) are capacitive electrodes; or the first measuring electrode (101) and the second measuring electrode (102) are resistive electrodes.

4. The drift-free humidity sensor according to claim 3, characterized in that: The first measuring electrode (101) and the second measuring electrode (102) are capacitive electrodes, a passivation layer (211) is provided between one side of the first measuring electrode (101) and the first moisture-sensitive material (201), a dielectric layer (213) and a substrate silicon wafer (214) are provided in sequence on the other side of the first measuring electrode (101), and the dielectric layer (213) is filled between the first measuring electrode (101) and the substrate silicon wafer (214); A passivation layer (211) is provided between one side of the second measuring electrode (102) and the second moisture-sensitive material (202), and a dielectric layer (213) and a substrate silicon wafer (214) are sequentially provided on the other two sides of the second measuring electrode (102), with the dielectric layer (213) filling between the second measuring electrode (102) and the substrate silicon wafer (214).

5. The drift-free humidity sensor according to claim 3, characterized in that: The first measuring electrode (101) and the second measuring electrode (102) are resistive electrodes, the first humidity-sensitive material (201) is arranged on one side of the first measuring electrode (101), and a dielectric layer (213) and a substrate silicon wafer (214) are sequentially arranged on the other side of the first measuring electrode (101), and the dielectric layer (213) is filled between the first measuring electrode (101) and the substrate silicon wafer (214); The second moisture-sensitive material (202) is arranged on one side of the second measuring electrode (102), and a dielectric layer (213) and a substrate silicon wafer (214) are sequentially arranged on the other side of the second measuring electrode (102), with the dielectric layer (213) filling between the second measuring electrode (102) and the substrate silicon wafer (214).

6. The drift-free humidity sensor according to claim 4, characterized in that: The first humidity-sensitive material (201) and the second humidity-sensitive material (202) are photosensitive humidity-sensitive materials or non-photosensitive humidity-sensitive materials, and the processing method of the first humidity-sensitive material (201) and the second humidity-sensitive material (202) comprises: - If the first humidity-sensitive material (201) and the second humidity-sensitive material (202) are both photosensitive humidity-sensitive materials, a pattern is obtained by direct photolithography; If one of the first moisture-sensitive material (201) or the second moisture-sensitive material (202) is a non-photosensitive moisture-sensitive material, the processing method comprises: Step S1.1: Spin-coating a non-photosensitive moisture-sensitive material on the passivation layer (211) of the first measuring electrode (101) and the second measuring electrode (102) and curing the material, then spin-coating a photoresist on the non-photosensitive moisture-sensitive material, photolithography a desired pattern, then processing the material through a dry etching process, and finally removing the photoresist to complete the processing of a moisture-sensitive material; Step S1.2: spin coating a photosensitive humidity-sensitive material, patterning the photosensitive humidity-sensitive material by photolithography, and curing the photosensitive humidity-sensitive material to obtain another humidity-sensitive material; If the first humidity-sensitive material (201) and the second humidity-sensitive material (202) are both non-photosensitive humidity-sensitive materials, the processing method includes: Step S2.1: Spin coating a first moisture-sensitive material (201) on the passivation layers (211) of the two measuring electrodes and curing the material, wherein the thickness of the first moisture-sensitive material (201) is more than one times the sum of the width and margin of the interdigitated electrodes (212), then spin coating a photoresist on the first photosensitive moisture-sensitive material, photolithography a desired pattern, and then processing the material through a dry etching process, and finally removing the photoresist to complete the processing of the first moisture-sensitive material (201); Step S2.2: Spin-coat the second moisture-sensitive material (202) and cure it, then spin-coat a photoresist on the second moisture-sensitive material (202), and photoetch a desired pattern, and then perform dry etching to retain the second moisture-sensitive material (202) attached to the first moisture-sensitive material (201), and finally remove the photoresist to complete the processing of the second moisture-sensitive material (202).

7. The drift-free humidity sensor according to claim 5, characterized in that: The first humidity-sensitive material (201) and the second humidity-sensitive material (202) are photosensitive humidity-sensitive materials; or either one of the first humidity-sensitive material (201) and the second humidity-sensitive material (202) is a non-photosensitive humidity-sensitive material, and the other is a photosensitive humidity-sensitive material; The processing method of the first humidity sensitive material (201) and the second humidity sensitive material (202) comprises: - If the first humidity-sensitive material (201) and the second humidity-sensitive material (202) are both photosensitive humidity-sensitive materials, a pattern is obtained by direct photolithography; If one of the first moisture-sensitive material (201) or the second moisture-sensitive material (202) is a non-photosensitive moisture-sensitive material, the processing method is: Step S3.1: Spin-coating a non-photosensitive moisture-sensitive material on the first measuring electrode (101) and the second measuring electrode (102) and curing the material, then spin-coating a photoresist on the non-photosensitive moisture-sensitive material, photolithography a desired pattern, and then processing the material through a dry etching process, and finally removing the photoresist to complete the processing of a moisture-sensitive material; Step S3.2: spin coating a photosensitive humidity-sensitive material, patterning the photosensitive humidity-sensitive material by photolithography, and curing the photosensitive humidity-sensitive material to obtain another humidity-sensitive material; If the first humidity-sensitive material (201) and the second humidity-sensitive material (202) are both non-photosensitive humidity-sensitive materials, the processing method includes: Step S4.1: Spin coating a first non-photosensitive moisture-sensitive material on the first measuring electrode (101) and the second measuring electrode (102) and curing the material, then spin coating a photoresist on the non-photosensitive moisture-sensitive material, photolithographing a desired pattern, then processing the material through a dry etching process, and finally removing the photoresist to complete the processing of a moisture-sensitive material; Step S4.2: Spin-coat a second non-photosensitive moisture-sensitive material, then spin-coat a photoresist, pattern it by photolithography, then use an alkaline developer (TMAH) to corrode the second non-photosensitive material while developing the photoresist, remove the photoresist, and then cure the second moisture-sensitive material to obtain another moisture-sensitive material.

8. The drift-free humidity sensor according to claim 1, characterized in that: The humidity sensor adopts a differential sampling structure, wherein the first humidity sensor unit comprises a first sensing subunit (111) and a second sensing subunit (112), and the second humidity sensor unit comprises a third sensing subunit (113) and a fourth sensing subunit (114).

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