A non-drift humidity sensor based on CMOS process

Abstract

The application discloses a CMOS process-based non-drift humidity sensor and relates to the technical field of semiconductors.The humidity sensor comprises a humidity-sensitive capacitor part, a reference capacitor part, a peripheral stress protection layer and an over-etching blocking layer.The humidity-sensitive capacitor part comprises interdigital electrodes formed by top layer metal, and the surface and gap of the humidity-sensitive capacitor part are covered with humidity-sensing material and directly exposed to air.The surface of the reference capacitor part is provided with an isolation layer.The humidity-sensitive capacitor part and the reference capacitor part have the same electrode structure and humidity-sensing material.The peripheral stress protection layer comprises a ring-shaped grounding structure formed by multiple layers of metal.The over-etching blocking layer comprises sub-top layer metal, which is distributed below the gap between the top layer metal and partially overlaps the top layer metal.The application is used to solve the problem that the humidity sensor will drift when used for a long time in a relatively harsh environment such as high temperature and high humidity.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and in particular to a drift-free humidity sensor based on CMOS technology. Background Technology

[0002] In the fields of industrial control and consumer electronics, accurate monitoring of environmental parameters is crucial for ensuring stable equipment operation, improving product performance, and guaranteeing user experience. Temperature and humidity, as two extremely important environmental parameters, are indispensable for accurate measurement in numerous application scenarios. In industrial production, precise temperature and humidity control directly impacts product quality, production efficiency, and equipment lifespan. Temperature and humidity sensor chips, as the core components for temperature and humidity monitoring, are widely used in these fields due to their advantages such as high integration, small size, high measurement accuracy, and ease of integration into various electronic systems.

[0003] Existing CMOS humidity sensors typically employ a humidity-sensitive capacitor structure, detecting humidity by coating interdigitated electrodes with moisture-sensitive materials such as polyimide. However, when these sensors operate under prolonged high-temperature and high-humidity conditions, the moisture absorbed by the underlying moisture-sensitive material is difficult to completely escape, causing irreversible drift in the capacitance value. This severely impacts measurement accuracy and long-term stability. Although differential measurement structures can partially compensate for this drift, the materials and structures of traditional reference capacitors (such as MIM capacitors or PIP capacitors) differ from those of the humidity-sensitive capacitor, making it impossible to completely eliminate drift errors caused by changes in the properties of the moisture-sensitive material. This limits the reliability of the sensor in harsh environments.

[0004] Therefore, there is an urgent need to provide a more reliable drift-free humidity sensor based on CMOS technology. Summary of the Invention

[0005] The purpose of this invention is to provide a drift-free humidity sensor based on CMOS technology, which solves the problem of humidity sensor drift when used for a long time in harsh environments such as high temperature and high humidity.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] In a first aspect, the present invention provides a drift-free humidity sensor based on CMOS technology, comprising:

[0008] Humidity-sensitive capacitor section, reference capacitor section, outer stress protection layer and over-etching barrier layer;

[0009] The humidity-sensitive capacitor portion includes interdigitated electrodes made of a top metal layer. The surface and gaps of the humidity-sensitive capacitor portion are covered with a moisture-sensitive material and are directly exposed to the air.

[0010] An isolation layer is provided on the surface of the reference capacitor portion; the reference capacitor portion and the humidity-sensitive capacitor portion have the same electrode structure and humidity-sensitive material;

[0011] The outer stress protection layer includes a ring-shaped grounding structure composed of multiple metal layers;

[0012] The overcut barrier layer includes a second-layer metal, which is distributed below the gaps in the top layer metal and partially overlaps with the top layer metal.

[0013] Optionally, the interdigitated electrodes of the humidity-sensitive capacitor portion include a first capacitor positive electrode formed by connecting equal-linewidth top metal layers and a first capacitor negative electrode formed by connecting equal-linewidth top metal layers; the moisture-sensitive material of the humidity-sensitive capacitor portion is polyimide.

[0014] Optionally, the reference capacitor portion includes a second capacitor positive electrode formed by connecting equal-linewidth top metal layers and a second capacitor negative electrode formed by connecting equal-linewidth top metal layers; the isolation layer is made of silicon nitride material.

[0015] Optionally, the outer stress protection layer includes a concentric ring structure composed of a top layer metal and a second-to-top layer metal.

[0016] Optionally, the top layer metal and the second-to-top layer metal in the concentric ring structure are arranged in a ring around the perimeter and grounded, forming a stress protection layer for the entire humidity-sensitive capacitor and the reference capacitor.

[0017] Optionally, the moisture-sensitive material in the moisture-sensitive capacitor portion is in direct contact with the air and changes linearly with the humidity in the air;

[0018] The moisture-sensitive material surface of the reference capacitor section is protected and isolated by silicon nitride, preventing direct contact with air.

[0019] Optionally, the sensor further includes a CV conversion circuit and an ADC module, with the output terminals of the humidity-sensitive capacitor and the reference capacitor connected to the CV conversion circuit;

[0020] The difference between the humidity-sensitive capacitor and the reference capacitor is converted into a voltage signal by the CV conversion circuit, and the voltage signal is quantized and output by the ADC.

[0021] Optionally, the humidity-sensitive capacitor portion and the reference capacitor portion are on the same layer, and their surfaces are both covered with the same humidity-sensitive material; the humidity drift caused by temperature changes is eliminated based on the difference between the humidity-sensitive capacitor portion and the reference capacitor portion.

[0022] Optionally, after the difference passes through the CV conversion circuit, the output voltage value is an amount that changes linearly with humidity.

[0023] Compared with existing technologies, this invention provides a drift-free humidity sensor based on CMOS technology. It includes: a humidity-sensitive capacitor portion, a reference capacitor portion, an outer stress protection layer, and an over-etching barrier layer. The humidity-sensitive capacitor portion comprises interdigitated electrodes made of a top metal layer. The surface and gaps of the humidity-sensitive capacitor portion are covered with a moisture-sensitive material and are directly exposed to air. An isolation layer is disposed on the surface of the reference capacitor portion. The reference capacitor portion and the humidity-sensitive capacitor portion have the same electrode structure and moisture-sensitive material. The outer stress protection layer comprises a ring-shaped grounding structure made of multiple metal layers. The over-etching barrier layer comprises a second-to-top metal layer, distributed below the gaps of the top metal layer and overlapping with the top metal layer. The technical solution provided by this invention, by using the same electrode structure and material for the humidity-sensitive capacitor portion and the reference capacitor portion, utilizes the lateral diffusion characteristics of moisture in the moisture-sensitive material to ensure that the moisture absorption degree of the bottom layer of the humidity-sensitive capacitor portion and the reference capacitor portion is consistent, automatically canceling drift components during differential output. The outer stress protection layer effectively prevents mechanical damage during packaging, and the over-etching barrier layer ensures circuit safety during MEMS process fabrication. The technical solution provided by this invention significantly improves the long-term stability and reliability of the sensor in high temperature and high humidity environments while maintaining the linear response of humidity measurement. Attached Figure Description

[0024] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:

[0025] Figure 1 A schematic diagram of the overall structure of a drift-free humidity sensor based on CMOS technology provided by the present invention;

[0026] Figure 2 A schematic diagram of the humidity-sensitive capacitor and reference capacitor sections of a drift-free humidity sensor based on CMOS technology provided by the present invention.

[0027] Figure 3 This is a schematic diagram of an overetch barrier layer structure for a drift-free humidity sensor based on CMOS technology, provided by the present invention.

[0028] Figure label:

[0029] 101-Humidity-sensitive capacitor section, 102-Reference capacitor section, 103-Outer stress protection layer, 104-Etching barrier layer, 1011-First capacitor positive electrode, 1012-First capacitor negative electrode, 1021-Second capacitor positive electrode, 1022-Second capacitor negative electrode. Detailed Implementation

[0030] To facilitate a clear description of the technical solutions in the embodiments of the present invention, the terms "first" and "second" are used to distinguish identical or similar items with essentially the same function and effect. For example, the first threshold and the second threshold are merely used to distinguish different thresholds and do not limit their order. Those skilled in the art will understand that the terms "first" and "second" do not limit the quantity or execution order, and that the terms "first" and "second" are not necessarily different.

[0031] It should be noted that in this invention, the terms "exemplary" or "for example" are used to indicate examples, illustrations, or descriptions. Any embodiment or design described as "exemplary" or "for example" in this invention should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of terms such as "exemplary" or "for example" is intended to present the relevant concepts in a concrete manner.

[0032] In this invention, "at least one" refers to one or more, and "more than one" refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one of a, b, or c can represent: a, b, c, a combination of a and b, a combination of a and c, a combination of b and c, or a, b, and c, where a, b, and c can be single or multiple.

[0033] Currently, there are many types of mainstream temperature and humidity sensor chips on the market, each with different working principles. However, the humidity sensing part of most of them uses a humidity-sensitive element to sense and measure the ambient humidity. The humidity-sensitive element detects the changes in its own electrical characteristics caused by changes in ambient humidity, and then converts the humidity signal into a measurable electrical signal, thereby achieving the purpose of humidity measurement. However, in practical applications, temperature and humidity sensor chips face many complex and harsh working environment challenges. Especially under high temperature and high humidity conditions, humidity sensors will inevitably experience performance degradation after long-term exposure, the most prominent problem being humidity sensor drift. This drift phenomenon manifests as a deviation between the humidity measurement value output by the sensor and the actual ambient humidity value, and this deviation gradually increases with the extension of usage time, leading to a significant reduction in the accuracy and reliability of the measurement results.

[0034] While existing temperature and humidity sensor chips employ conventional compensation and calibration methods to address drift issues during long-term use—such as integrating simple temperature compensation circuits within the sensor chip or performing periodic external calibration—these methods have significant limitations. Temperature compensation circuits often only compensate for errors caused by temperature changes, offering limited compensation for drift inherent in the humidity sensor itself due to long-term use. Furthermore, periodic external calibration not only consumes substantial manpower and resources, increasing operating costs, but also makes it difficult to guarantee the sensor's measurement accuracy throughout its entire lifespan in applications where frequent calibration is impractical, such as long-running industrial equipment or environmental monitoring stations in remote areas.

[0035] Therefore, developing a technical solution to effectively address the drift problem of temperature and humidity sensor chips during long-term use, especially in harsh environments such as high temperature and high humidity, is of significant practical importance for improving the performance stability of temperature and humidity sensor chips, extending their service life, and expanding their application range. This invention provides a drift-free humidity sensor based on CMOS technology. The following description, in conjunction with the accompanying drawings, illustrates the solution provided in the embodiments of this specification:

[0036] like Figure 1 As shown, the present invention provides a drift-free humidity sensor based on CMOS technology, which may include:

[0037] Humidity-sensitive capacitor section 101, reference capacitor section 102, outer stress protection layer 103, and over-etching barrier layer 104;

[0038] The humidity-sensitive capacitor portion 101 includes interdigitated electrodes made of top metal, and the surface and gaps of the humidity-sensitive capacitor portion 101 are covered with a moisture-sensitive material and are directly exposed to the air.

[0039] An isolation layer is provided on the surface of the reference capacitor portion 102; the reference capacitor portion 102 and the humidity-sensitive capacitor portion 101 have the same electrode structure and humidity-sensitive material.

[0040] The outer stress protection layer 103 includes a ring-shaped grounding structure composed of multiple metal layers;

[0041] The overcut barrier layer 104 includes a sub-top layer metal, which is distributed below the gaps in the top layer metal and partially overlaps with the top layer metal.

[0042] In the above structure, the humidity-sensitive capacitor part 101 can serve as the core sensing area of ​​the humidity sensor. It consists of interdigitated electrodes made of top metal, with the surface and gaps covered by a moisture-sensitive material and directly exposed to the air. It senses humidity changes by adsorbing water molecules and changing the capacitance value.

[0043] The reference capacitor section 102 has the same structure as the humidity-sensitive capacitor section 101, but its surface is covered with an isolation layer, which can shield the influence of humidity and provide a stable comparison benchmark for the humidity-sensitive capacitor section 101 to compensate for errors caused by ambient temperature or aging.

[0044] The outer stress protection layer 103 may include a ring-shaped grounding structure composed of multiple metal layers, located on the periphery, which can disperse and shield external stress or mechanical vibration to prevent them from affecting the internal structure. At the same time, grounding can reduce electromagnetic interference and ensure the stability of the humidity sensor.

[0045] The over-etching barrier layer 104 includes a second-layer metal, which is distributed below and partially overlaps with the gap of the top layer metal. In the etching process, it is used to protect the underlying structure, avoid material loss due to over-etching, and ensure the integrity of the sensor structure.

[0046] Figure 1 This invention provides a drift-free humidity sensor. By employing the same electrode structure and materials for the humidity-sensitive capacitor portion 101 and the reference capacitor portion 102, and utilizing the lateral diffusion characteristics of moisture in the humidity-sensitive material, the moisture absorption levels of the bottom layers of the humidity-sensitive capacitor portion 101 and the reference capacitor portion 102 are kept consistent, automatically canceling out drift components during differential output. An outer stress protection layer 103 effectively prevents mechanical damage during the packaging process, and an over-etching barrier layer 104 ensures circuit safety during MEMS fabrication. The technical solution provided by this invention significantly improves the long-term stability and reliability of the sensor in high-temperature and high-humidity environments while maintaining a linear response in humidity measurement.

[0047] based on Figure 1 In addition to the method described herein, this specification also provides some specific implementation methods of this method, which will be described below.

[0048] More specifically, the interdigitated electrodes of the humidity-sensitive capacitor portion 101 include a first capacitor positive electrode 1011 formed by connecting equal-linewidth top metal and a first capacitor negative electrode 1012 formed by connecting equal-linewidth top metal; the moisture-sensitive material of the humidity-sensitive capacitor portion 101 is polyimide.

[0049] from Figure 1 as well as Figure 2 As can be seen from the diagram, the humidity-sensitive capacitor 101 mainly includes a first capacitor positive electrode 1011 formed by connecting top metals of equal linewidth and a first capacitor negative electrode 1012 formed by connecting top metals of equal linewidth. The electrode surface and gaps are covered with a layer of polyimide material as a humidity-sensitive material. After the polyimide material is covered, there is no other covering on its surface, and it is directly exposed to the air, thus forming a humidity-sensitive capacitor that senses humidity.

[0050] The reference capacitor section 102 includes a second capacitor positive electrode 1021 formed by connecting top metal of equal linewidth and a second capacitor negative electrode 1022 formed by connecting top metal of equal linewidth; the isolation layer is made of silicon nitride. Specifically, the reference capacitor section 102 mainly includes a second capacitor positive electrode 1021 formed by connecting top metal of equal linewidth and a second capacitor negative electrode 1022 formed by connecting top metal of equal linewidth in a finger shape. Its electrode surface and gaps are covered with polyimide, which is the same material as the humidity-sensitive capacitor section 101, as a humidity-sensitive material. However, silicon nitride is simultaneously fabricated on its surface using MEMS technology as a protective and isolation layer, so that the humidity-sensitive material does not come into contact with air. This capacitance does not directly change with the humidity in the air, thus serving as a reference capacitor.

[0051] Since the moisture-sensitive material of the humidity-sensitive capacitor section 101 is in direct contact with the air and changes linearly with the humidity in the air, it can be used as a humidity-sensitive capacitor. The moisture-sensitive material of the reference capacitor section 102 has silicon nitride as protection and isolation on its surface, and is not in direct contact with the air. Therefore, it cannot change linearly with the humidity in the air and is close to a capacitor with a fixed capacitance value, so it can be used as a reference capacitor.

[0052] The outer stress protection layer 103 includes a concentric ring structure composed of a top layer metal and a second-to-top layer metal. Specifically, the outer stress protection layer 103 mainly includes a top layer metal and a second-to-top layer metal, and the top layer metal and the second-to-top layer metal form a ring around the periphery and are grounded, forming a stress protection layer for the entire humidity-sensitive capacitor and the reference capacitor, so as to prevent the chip from being squeezed during the packaging process and causing damage to the sensor part.

[0053] like Figure 3 As shown, the over-etching barrier layer 104 mainly includes a sub-top layer metal that is uniformly distributed below the top layer metal and overlaps with the top layer metal lines, thus serving as a barrier layer to prevent damage to the circuitry below the sensor during MEMS fabrication.

[0054] Furthermore, the sensor may also include a CV conversion circuit and an ADC module. The output terminals of the humidity-sensitive capacitor 101 and the reference capacitor 102 are connected to the CV conversion circuit. The difference between the humidity-sensitive capacitor 101 and the reference capacitor 102 is converted into a voltage signal by the CV conversion circuit, and the voltage signal is quantized and output by the ADC. More specifically, the working principle of the humidity sensor is that the difference between the humidity-sensitive capacitor and the reference capacitor is converted into a voltage signal by the CV conversion circuit, and this voltage signal is then quantized and output by the ADC. The humidity-sensitive capacitor is a capacitor that changes linearly with humidity, and the reference capacitor is a fixed capacitor. Their difference, after passing through the CV conversion circuit, results in an output voltage value that changes linearly with humidity.

[0055] In the above structure, the humidity-sensitive capacitor 101 acts as a humidity-sensitive capacitor. When its moisture-sensitive material is exposed to a high-temperature, high-humidity environment for a long time, the moisture absorbed at the bottom layer of the material is difficult to escape, causing a drift in the humidity value. If a MIM capacitor or PIP capacitor provided in the CMOS process is used as a reference capacitor, a drift that is difficult to recover will occur after differential output. Here, the capacitor shown in the reference capacitor 102 is used as a reference. Since the surfaces of the reference capacitor 102 and the humidity-sensitive capacitor 101 are covered with the same moisture-sensitive material, the moisture absorbed at the bottom layer is evenly diffused laterally to the bottom of both the reference capacitor 102 and the humidity-sensitive capacitor 101. After differential output, this drift is eliminated, and no drift will occur after prolonged exposure to a high-temperature, high-humidity environment.

[0056] To further illustrate the technical solution provided by the present invention, the following description is provided in the form of embodiments:

[0057] As an optional implementation, the humidity-sensitive capacitor portion 101 can be a CMOS process top metal forming a uniformly wide interdigitated structure, including a positive and negative capacitor electrode, with the spacing between the positive and negative electrodes adjustable according to actual application requirements. A polyimide humidity-sensitive film of a predetermined thickness is spin-coated onto the electrode surface and directly exposed to the ambient atmosphere. The reference capacitor portion 102 can employ the exact same metal layout and polyimide coating as the humidity-sensitive capacitor, but a silicon nitride protective layer is formed on its surface using plasma-enhanced chemical vapor deposition to prevent contact with the ambient atmosphere. The peripheral stress protection layer 103 consists of a double-ring structure formed by a top metal and a second-to-top metal of a predetermined width, connected and grounded through a via array. The overetch barrier layer 104 is made of the second-to-top metal in a strip-like structure, maintaining a predetermined overlap with the top metal, and is uniformly distributed below the capacitor array.

[0058] As an optional implementation, the interdigitated electrodes of the humidity-sensitive capacitor portion 101 and the reference capacitor portion 102 can be arranged in an alternating manner. The positive electrode of the capacitor is formed by connecting top metal lines of equal linewidth in parallel, and the negative electrode of the capacitor is formed by a finger-like structure of top metal lines of the same linewidth, arranged alternately with the positive electrode lines. The thickness of the moisture-sensitive material polyimide is optimized, and parameters such as the range of dielectric constant variation with humidity and the thickness of the silicon nitride isolation layer of the reference capacitor portion 102 are set. The silicon nitride isolation layer thickness of the reference capacitor portion 102 is set to effectively prevent water vapor penetration without excessively affecting the capacitance value. The width of the second-to-top metal strip of the overetch barrier layer 104 and the amount of overlap with the edge of the top metal are set to ensure that the underlying circuitry can be effectively protected within this size range during the MEMS etching process.

[0059] As an optional implementation, the sensor can integrate signal processing circuitry. The outputs of the humidity-sensitive capacitor section 101 and the reference capacitor section 102 are connected to a CV conversion circuit to convert the capacitance difference into a voltage signal. The CV conversion circuit uses a switched capacitor bank. The voltage signal is then quantized by an ADC module. The distance between the ring-shaped grounding structure of the outer stress protection layer 103 and the chip edge is set to effectively absorb mechanical stress generated during packaging. It is understood that when the sensor is operating, the humidity-sensitive capacitor value changes linearly with ambient humidity, while the reference capacitor remains relatively stable due to the protection of the silicon nitride isolation layer. The difference between the two is eliminated through differential output to remove drift errors caused by residual moisture in the underlying moisture-sensitive material.

[0060] Based on the aforementioned explanation, it can be determined that, compared with the prior art, the technical solution provided by this invention can solve the problem of humidity sensor drift caused by prolonged use in harsh environments such as high temperature and high humidity. By using the same electrode structure and materials for the humidity-sensitive capacitor portion 101 and the reference capacitor portion 102, and utilizing the lateral diffusion characteristics of moisture in the moisture-sensitive material, the moisture absorption degree of the bottom layer of the humidity-sensitive capacitor portion 101 and the reference capacitor portion 102 is kept consistent, automatically canceling the drift component during differential output. The outer stress protection layer 103 effectively prevents mechanical damage during the packaging process, and the over-etching barrier layer 104 ensures circuit safety during MEMS processing. The technical solution provided by this invention significantly improves the long-term stability and reliability of the sensor in high temperature and high humidity environments while maintaining the linear response of humidity measurement.

[0061] In this invention, humidity-sensitive materials exhibit nonlinear drift with temperature changes. The invention utilizes capacitors with identical structures and the same humidity-sensitive material (PI) as the dielectric. Subtraction is performed to eliminate humidity drift caused by temperature variations. This invention eliminates the need for high-temperature heating to remove water molecules from the PI. Existing methods, such as heating humidity-sensitive capacitors with resistance wires, result in excessive chip power consumption and inaccurate humidity and temperature readings during heating, potentially failing to completely eliminate drift. Therefore, this invention utilizes a capacitor fabricated using the interdigitated structure of the top metal layer in a CMOS process, coating the interdigitated area with a humidity-sensitive material to create both the humidity-sensitive capacitor and the reference capacitor. It primarily consists of four parts: a humidity-sensitive capacitor portion 101, a reference capacitor portion 102, an outer stress protection layer 103, and an over-etching barrier layer 104. Both the reference capacitor portion 102 and the humidity-sensitive capacitor portion 101 are on the same layer and covered with the same humidity-sensitive material, PI. Under prolonged high temperature and humidity, water molecules at the bottom of the humidity-sensitive capacitor are difficult to release, causing drift. Water molecules laterally diffusing to the reference capacitor produce the same drift effect. Subtraction between the humidity-sensitive capacitor and the reference capacitor eliminates this drift.

[0062] Although the invention has been described herein in conjunction with various embodiments, those skilled in the art will understand and implement other variations of the disclosed embodiments by reviewing the accompanying drawings, the disclosure, and the appended claims in carrying out the claimed invention. In the claims, the word "comprising" does not exclude other components or steps, and "a" or "an" does not exclude a plurality. A single processor or other unit can implement several functions listed in the claims. While different dependent claims may recite certain measures, this does not mean that these measures cannot be combined to produce good results.

[0063] Although the invention has been described in conjunction with specific features and embodiments, it is obvious that various modifications and combinations can be made therein without departing from the spirit and scope of the invention. Accordingly, this specification and drawings are merely exemplary descriptions of the invention as defined by the appended claims, and are considered to cover any and all modifications, variations, combinations, or equivalents within the scope of the invention. Clearly, those skilled in the art can make various alterations and modifications to the invention without departing from its spirit and scope. Thus, if such modifications and modifications of the invention fall within the scope of the claims and their equivalents, the invention is also intended to include such modifications and modifications.

Claims

1. A drift-free humidity sensor based on CMOS technology, characterized in that, include: Humidity-sensitive capacitor section, reference capacitor section, outer stress protection layer and over-etching barrier layer; The humidity-sensitive capacitor portion includes interdigitated electrodes made of a top metal layer. The surface and gaps of the humidity-sensitive capacitor portion are covered with a moisture-sensitive material and are directly exposed to the air. An isolation layer is provided on the surface of the reference capacitor portion; the reference capacitor portion and the humidity-sensitive capacitor portion have the same electrode structure and humidity-sensitive material; The outer stress protection layer includes a ring-shaped grounding structure composed of multiple metal layers; The overetch barrier layer includes a second-layer metal, which is distributed below the gap of the top metal and partially overlaps with the top metal; the moisture-sensitive material of the moisture-sensitive capacitor is in direct contact with the air and changes linearly with the humidity in the air; the moisture-sensitive material of the reference capacitor has silicon nitride on its surface for protection and isolation, and is not in direct contact with the air. The humidity-sensitive capacitor portion and the reference capacitor portion are on the same layer, and their surfaces are both covered with the same humidity-sensitive material. The humidity drift caused by temperature changes is eliminated by the difference between the humidity-sensitive capacitor and the reference capacitor.

2. The drift-free humidity sensor based on CMOS technology according to claim 1, characterized in that, The interdigitated electrodes of the humidity-sensitive capacitor section include a first capacitor positive electrode formed by connecting equal-linewidth top metal layers and a first capacitor negative electrode formed by connecting equal-linewidth top metal layers; the moisture-sensitive material of the humidity-sensitive capacitor section is polyimide.

3. The drift-free humidity sensor based on CMOS technology according to claim 2, characterized in that, The reference capacitor section includes a second capacitor positive electrode formed by connecting the top metal of equal linewidth and a second capacitor negative electrode formed by connecting the top metal of equal linewidth; the isolation layer is made of silicon nitride material.

4. The drift-free humidity sensor based on CMOS technology according to claim 1, characterized in that, The outer stress protection layer comprises a concentric ring structure consisting of a top layer metal and a second-to-top layer metal.

5. The drift-free humidity sensor based on CMOS technology according to claim 4, characterized in that, The top and second-top metals in the concentric ring structure form a ring around the perimeter, with the potential grounded, forming a stress protection layer for the entire humidity-sensitive capacitor and reference capacitor.

6. The drift-free humidity sensor based on CMOS technology according to claim 1, characterized in that, The sensor also includes a CV conversion circuit and an ADC module, with the outputs of the humidity-sensitive capacitor and the reference capacitor connected to the CV conversion circuit. The difference between the humidity-sensitive capacitor and the reference capacitor is converted into a voltage signal by the CV conversion circuit, and the voltage signal is quantized and output by the ADC.

7. The drift-free humidity sensor based on CMOS technology according to claim 6, characterized in that, The difference, after passing through the CV conversion circuit, outputs a voltage value that varies linearly with humidity.

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