Dual capacitance humidity sensor
By employing a dual-capacitor structure of a vertical reference capacitor and a horizontal humidity-sensitive capacitor in the humidity sensor, the problems of complex structure and susceptibility to external factors in traditional single-capacitor humidity sensors are solved, achieving high-precision and low-cost humidity measurement, which is suitable for CMOS processes.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CSMC TECH FAB2 CO LTD
- Filing Date
- 2021-09-17
- Publication Date
- 2026-07-21
Smart Images
Figure CN115825171B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of semiconductor technology, and more particularly to a dual-capacitor humidity sensor. Background Technology
[0002] Capacitive humidity sensors are sensors that measure humidity by utilizing the principle that the capacitance of a humidity-sensitive element changes with humidity. They are highly sensitive, consume little power, and have low manufacturing costs, leading to their widespread application.
[0003] There are two main types of traditional single-capacitor humidity sensors: one is the interdigitated capacitive humidity sensor, which is prone to parasitic capacitance between the electrodes and the substrate; the other is the sandwich-structure humidity sensor, which places the humidity-sensitive material between the capacitor plates as a medium. Although it has high sensitivity and low parasitic capacitance, it has a slow response speed and is not easily compatible with CMOS technology. Moreover, research has found that the capacitance of the humidity-sensitive capacitor is easily affected by factors other than humidity (such as temperature and pressure), resulting in poor accuracy of the output value of the single-capacitor humidity sensor.
[0004] To overcome the shortcomings of single-capacitor humidity sensors, dual-capacitor humidity sensors have been developed, which include a humidity-sensitive capacitor and a reference capacitor. When calculating humidity based on the humidity-sensitive capacitor, the reference capacitor helps maintain accuracy. In the fabrication of an existing dual-capacitor humidity sensor, a layer of polycrystalline silicon is first fabricated on a substrate as the lower electrode of the reference capacitor. Then, the dielectric and upper electrode of the reference capacitor are fabricated on top, and finally, the humidity-sensitive capacitor is fabricated on top. However, the structure of this dual-capacitor humidity sensor is complex, resulting in high manufacturing costs and hindering mass production. Summary of the Invention
[0005] To overcome the aforementioned problems of existing capacitive humidity sensors, this invention provides a dual-capacitor humidity sensor.
[0006] The present invention provides a dual-capacitor humidity sensor, comprising a vertical reference capacitor and a horizontal humidity-sensitive capacitor; the vertical reference capacitor uses a conductive doped substrate as the lower electrode and includes a passivation layer disposed on the upper surface of the conductive doped substrate and an upper electrode disposed on the upper surface of the passivation layer; the horizontal humidity-sensitive capacitor includes a positive electrode and a negative electrode in the same layer as the upper electrode of the vertical reference capacitor, and further includes a humidity-sensitive material located between the positive electrode and the negative electrode.
[0007] Optionally, the upper surface of the conductive doped substrate has a groove located directly below the upper electrode.
[0008] Optionally, the passivation layer fills the groove; or, the passivation layer is suspended and covers the groove.
[0009] Optionally, the positive electrode or the negative electrode is the upper electrode of the vertical reference capacitor.
[0010] Optionally, both the positive electrode and the negative electrode are interdigitated, and the interdigitated fingers of the positive electrode and the negative electrode intersect each other without touching, such that the interdigitated fingers of the positive electrode and the interdigitated fingers of the negative electrode are opposite each other and have a gap.
[0011] Optionally, the humidity-sensitive material fills the gap and buries both the interdigitated fingers of the positive electrode and the interdigitated fingers of the negative electrode within it.
[0012] Optionally, the conductive doped substrate has a plurality of said grooves, each of said grooves being located directly below the interdigitated fingers of the positive electrode or directly below the interdigitated fingers of the negative electrode.
[0013] Optionally, the horizontal humidity-sensitive capacitor has a positive terminal and a negative terminal, with the interdigitated fingers of the positive electrode all connected to the positive terminal and the interdigitated fingers of the negative electrode all connected to the negative terminal.
[0014] Optionally, the materials of the upper electrode, the positive electrode, and the negative electrode all include aluminum.
[0015] Optionally, the conductive doped substrate is a single-crystal silicon substrate with n-type ion doping or p-type ion doping.
[0016] The dual-capacitor humidity sensor provided by this invention has a vertical reference capacitor and a horizontal humidity-sensitive capacitor. The dual-capacitor structure can effectively improve the calibration accuracy of the product. Furthermore, the lower electrode of the vertical reference capacitor is a conductive doped substrate, while the upper electrode of the vertical reference capacitor is disposed on the same layer as the electrode of the horizontal humidity-sensitive capacitor. This results in small parasitic capacitance, high sensitivity, reduced manufacturing costs, good product stability, and ease of mass production. Attached Figure Description
[0017] Figure 1 This is a cross-sectional schematic diagram of a dual-capacitor humidity sensor according to an embodiment of the present invention.
[0018] Figure 2 This is a planar schematic diagram of a horizontal humidity-sensitive capacitor according to an embodiment of the present invention.
[0019] Explanation of reference numerals in the attached figures:
[0020] 100 - Dual-capacitor humidity sensor; 111 - Conductive doped substrate; 111a - Groove; 112 - Passivation layer; 110 - Vertical reference capacitor; 120 - Horizontal humidity-sensitive capacitor; 121 - Positive electrode; 123 - Negative electrode; 124 - Positive terminal; 125 - Negative terminal; 122 - Humidity-sensitive material. Detailed Implementation
[0021] The dual-capacitor humidity sensor of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The advantages and features of the present invention will become clearer from the following description. It should be understood that the accompanying drawings are in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of the present invention.
[0022] The dual-capacitor humidity sensor of this invention detects humidity in the surrounding environment through capacitance signals, and includes two capacitors, the capacitance values of which are calculated according to the following formula:
[0023]
[0024] Where C is the capacitance, ε is the dielectric constant of the dielectric material between the capacitor's plates, S is the overlap area of the capacitor's electrodes, and d is the distance between the capacitor's electrodes. It can be seen that the capacitance of a capacitor is directly proportional to the dielectric constant ε of the dielectric material between the capacitor's plates. The higher the dielectric constant of the dielectric material between the capacitor's plates, the higher the capacitance of the capacitor.
[0025] Figure 1 This is a cross-sectional schematic diagram of a dual-capacitor humidity sensor according to an embodiment of the present invention. Figure 1 As shown, the dual-capacitor humidity sensor 100 of this embodiment includes a vertical reference capacitor 110 and a horizontal humidity-sensitive capacitor 120.
[0026] The horizontal humidity-sensitive capacitor 120 is used to sense the humidity in the air surrounding the dual-capacitor humidity sensor 100 and provides a capacitance signal to characterize the humidity of the air surrounding the dual-capacitor humidity sensor 100. The two electrodes of the horizontal humidity-sensitive capacitor 120 are opposite each other and have a potential difference, with the electrode with the higher potential serving as the positive electrode 121 and the electrode with the lower potential serving as the negative electrode 123. The dielectric material disposed between the positive electrode 121 and the negative electrode 123 includes a humidity-sensitive material. After the humidity-sensitive material absorbs moisture from the air, its dielectric constant increases. When the dielectric constant of the humidity-sensitive material increases, the capacitance value of the horizontal humidity-sensitive capacitor 120 also increases. When the humidity of the air increases, the humidity-sensitive material absorbs more moisture. Therefore, by measuring the capacitance value of the horizontal humidity-sensitive capacitor 120, a measurement of the humidity in the air surrounding the dual-capacitor humidity sensor 100 can be obtained. The humidity-sensitive material may include at least one of graphene oxide, polyimide, polymethyl methacrylate, acyl cellulose, porous metal oxide (such as aluminum oxide), and porous ceramic materials, and may also include other known organic polymers and their derivatives or copolymers with other monomers, and may also include other known porous media humidity-sensitive materials.
[0027] The two opposing electrodes of the vertical reference capacitor 110 are designated as the upper electrode and the lower electrode. The dielectric material disposed between the upper and lower electrodes is not exposed to the air surrounding the dual-capacitor humidity sensor 100. Therefore, the capacitance value of the vertical reference capacitor 110 is independent of humidity and does not change with humidity. Since the capacitance value of the horizontal humidity-sensitive capacitor 120 may be affected by factors other than humidity—temperature, pressure, or other factors can all influence its capacitance value—the capacitance of the vertical reference capacitor 110 is also affected by temperature, pressure, and factors other than humidity. Therefore, if the vertical reference capacitor 110 has a capacitance value that is higher or lower than expected, the final humidity measurement can account for the possibility that the capacitance value of the horizontal humidity-sensitive capacitor 120 may be higher or lower than the value calculated solely based on humidity. Thus, the vertical reference capacitor 110 helps maintain accuracy when estimating humidity based on the horizontal humidity-sensitive capacitor 120. For example, the dual-capacitor humidity sensor 100 further includes an analog-to-digital converter (ADC) and a processor. During humidity detection, the horizontal humidity-sensitive capacitor 120 outputs an analog humidity signal characterizing the ambient air humidity through capacitance detection. The ADC converts this analog humidity signal into a digital humidity signal, and the processor calculates the humidity value based on the digital humidity signal. When calculating the humidity value, the processor references a calibration table stored in its memory, compares the value of the digital humidity signal with the values in the calibration table, and calculates, verifies, or estimates the humidity value based on the digital humidity signal and the values in the calibration table. During this process, the reference capacitance signal of the vertical reference capacitor 110 is also converted into a digital reference capacitance signal by the ADC and used when the processor calibrates the humidity measurement value characterized by the horizontal humidity-sensitive capacitor 120. The specific calibration process can employ methods disclosed in the art.
[0028] refer to Figure 1In this embodiment of the invention, the vertical reference capacitor 110 includes a conductive doped substrate 111, a passivation layer 112 disposed on the upper surface of the conductive doped substrate 111, and an upper electrode disposed on the upper surface of the passivation layer 112. The vertical reference capacitor 110 uses the conductive doped substrate 111 as its lower electrode. The horizontal humidity-sensitive capacitor 120 includes a positive electrode 121 and a negative electrode 123 in the same layer as the upper electrode of the vertical reference capacitor 110, and a humidity-sensitive material 122 located between the positive electrode 121 and the negative electrode 123. "Vertical" in the vertical reference capacitor 110 means that its upper and lower electrodes are opposite each other in the normal direction of the conductive doped substrate 111, and "horizontal" in the horizontal humidity-sensitive capacitor 120 means that its positive electrode 121 and negative electrode 123 are opposite each other in a direction parallel to the plate-like plane of the conductive doped substrate 111. It should be understood that the spatial relative terminology is intended to include different orientations in use or operation other than the orientation of the device as described in the figures. For example, if the structure in the accompanying drawings is inverted or positioned in other different ways (such as rotation), the exemplary term "on" may also include "under" and other orientational relationships.
[0029] The dual-capacitor humidity sensor 100 of this embodiment can be fabricated using CMOS technology, and a conductive doped substrate 111 commonly used in CMOS technology can be used as the lower electrode of the vertical reference capacitor 110. Optionally, the conductive doped substrate 111 is a single-crystal silicon substrate with n-type ion doping or p-type ion doping. For example, n-type dopant ions are phosphorus ions, and p-type dopant ions are boron ions. To obtain good conductivity, the n-type or p-type ion doping in the substrate is heavily doped, and the specific doping concentration can be adjusted as needed.
[0030] A passivation layer 112 is disposed on the upper surface of the conductive doped substrate 111, and the upper electrode of the vertical reference capacitor 110 is disposed on the upper surface of the passivation layer 112. That is, the passivation layer 112 is disposed in the space between the conductive doped substrate 111 and the upper electrode, thus the passivation layer 112 is the dielectric material of the vertical reference capacitor 110. The passivation layer 112 may include silicon dioxide, silicon nitride, or any other suitable dielectric material. The upper electrode of the vertical reference capacitor 110 may include a patterned conductive film, the material of which may be, for example, aluminum or any other suitable electrode material.
[0031] In this embodiment of the invention, to increase the controllability of the vertical reference capacitor 110, a groove 111a is provided on the upper surface of the conductive doped substrate 111 directly below the upper electrode of the vertical reference capacitor 110. The opening of the groove 111a faces the passivation layer 112. The change in the depth of the groove 111a is equivalent to adjusting the distance between the upper and lower electrodes of the vertical reference capacitor 110. According to the capacitance formula above, the capacitance range of the vertical reference capacitor 110 can be adjusted by increasing or decreasing the size of the groove 111a. In one embodiment, the groove 111a can be filled by the passivation layer 112 located on the upper surface of the conductive doped substrate 111. The total thickness of the passivation layer 112 can be greater than or equal to the depth of the groove 111a. The deeper the groove 111a, the greater the distance between the upper and lower electrodes, and the smaller the total capacitance value of the vertical reference capacitor 110. In another embodiment, the passivation layer 112 either does not fill the groove 111a or only fills the upper part of the groove 111a. In this case, the passivation layer 112 is equivalent to being suspended over the groove 111a. The passivation layer 112 rests on the upper surface of the conductive doped substrate 111 at the opening of the groove 111a and has continuity. The groove 111a contains air. In this way, two dielectric materials, passivation layer 112 and air, are disposed between the upper and lower electrodes of the vertical reference capacitor 110. Therefore, the total capacitance value includes two capacitance components from the passivation layer 112 and air. Since the dielectric constant of air is lower than that of the passivation layer 112, the total capacitance value of the vertical reference capacitor 110 is smaller when the groove 111a is filled with air compared to the total capacitance value obtained when the groove is not filled with air. Thus, the vertical reference capacitor 110 can achieve better controllability and can effectively improve the calibration accuracy of the dual-capacitor humidity sensor product.
[0032] In this embodiment of the invention, the upper electrode of the vertical reference capacitor 110 and the positive electrode 121 and negative electrode 123 of the horizontal humidity-sensitive capacitor 120 are made of the same material, that is, they are all disposed on the upper surface of the passivation layer 112 and can be formed by the same deposition process and patterning process, for example, both including aluminum. Specifically, in one embodiment, the upper electrode of the vertical reference capacitor 110 and the positive electrode 121 and negative electrode 123 of the horizontal humidity-sensitive capacitor 120 are disposed in separate regions and are electrically isolated from each other.
[0033] like Figure 1 As shown, in this embodiment, the positive electrode 121 or the negative electrode 123 of the horizontal humidity-sensitive capacitor 12 is used as the upper electrode of the vertical reference capacitor 110 to save area. In one embodiment, two vertical reference capacitors are provided. The lower electrodes of these two vertical reference capacitors are both conductive doped substrates 111, and the upper electrodes are the positive electrode 121 and the negative electrode 123 of the horizontal humidity-sensitive capacitor 120, respectively.
[0034] Figure 2This is a planar schematic diagram of a horizontal humidity-sensitive capacitor according to an embodiment of the present invention. (Refer to...) Figure 2 The positive electrode 121 and negative electrode 123 of the horizontal humidity-sensitive capacitor 120 are, for example, interdigitated, with the interdigitated fingers of the positive electrode 121 and the negative electrode 123 interlacing but not touching, such that the interdigitated fingers of the positive electrode 121 and the negative electrode 123 are opposite each other with a gap. The horizontal humidity-sensitive capacitor 120 may also have a positive terminal 124 and a negative terminal 125, with the interdigitated fingers of the positive electrode 121 connected to the positive terminal 124 and the interdigitated fingers of the negative electrode 123 connected to the negative terminal 125, to facilitate control of the horizontal humidity-sensitive capacitor 120. There is a gap between the interdigitated fingers of the positive electrode 121 and the interdigitated fingers of the negative electrode 123 that are opposite each other. In one embodiment, the humidity-sensitive material 122 ( Figure 2 (Not shown) The moisture-sensitive material 122 can cover the surfaces of the positive electrode 121 and the negative electrode 123, but does not fill the gap. Therefore, the moisture-sensitive material 122 together with the air constitutes the dielectric material of the horizontal moisture-sensitive capacitor 120. However, it is not limited to this. In this embodiment, only the moisture-sensitive material 122 is used as the dielectric material of the horizontal moisture-sensitive capacitor 120. The moisture-sensitive material 122 fills the gap between the interdigitated fingers of the positive electrode 121 and the interdigitated fingers of the negative electrode 123, and buries the interdigitated fingers of the positive electrode 121 and the interdigitated fingers of the negative electrode 123 within it.
[0035] Furthermore, the groove 111a disposed on the upper surface of the conductive doped substrate 111 can be formed corresponding to the positive electrode 121 and / or the negative electrode 123, which serve as the upper electrode of the vertical reference capacitor 110, to adjust the capacitance value of the vertical reference capacitor 110. That is, the upper surface of the conductive doped substrate 111 has a groove 111a located directly below the positive electrode 121 and / or the negative electrode 123. Since both the positive electrode 121 and the negative electrode 123 are interdigitated, the upper surface of the conductive doped substrate 111 further has a plurality of grooves 111a, each groove 111a located directly below the interdigitated part of the positive electrode 121 or the interdigitated part of the negative electrode 123, and having the same depth and width, for example. To avoid mutual interference of capacitance formed at the various grooves, the width of each groove 111a is preferably no greater than the width of the positive electrode 121 or negative electrode 123 directly above it. However, it is not limited to this; the width of each groove 111a may also be slightly larger than the width of the positive electrode 121 or negative electrode 123 directly above it. Here, "width" refers to the dimension parallel to the plate-like plane of the conductive doped substrate 111 and perpendicular to the length direction of the interdigitated fingers.
[0036] In the dual-capacitor humidity sensor 100 of this invention, the vertical reference capacitor 110 and the horizontal humidity-sensitive capacitor 120 are both disposed on a conductive doped substrate 111, which facilitates integration into the same die, makes testing convenient, and helps improve the calibration accuracy of the product.
[0037] The dual-capacitor humidity sensor 100 of this invention has a vertical reference capacitor 110 and a horizontal humidity-sensitive capacitor 120. The dual-capacitor structure can effectively improve the calibration accuracy of the product. Furthermore, the conductive doped substrate 111 serves as the lower electrode of the vertical reference capacitor 110, while the upper electrode of the vertical reference capacitor 110 is provided with the two electrodes of the horizontal humidity-sensitive capacitor 120 in the same layer. This results in small parasitic capacitance, high sensitivity, reduced manufacturing costs, good product stability, and ease of mass production.
[0038] The above description is merely a description of preferred embodiments of the present invention and is not intended to limit the scope of the present invention. Any person skilled in the art can make possible changes and modifications to the technical solutions of the present invention by utilizing the methods and techniques disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the protection scope of the technical solutions of the present invention.
Claims
1. A dual-capacitor humidity sensor, characterized in that, The system includes a vertical reference capacitor and a horizontal humidity-sensitive capacitor. The vertical reference capacitor uses a conductive doped substrate as its lower electrode and includes a passivation layer disposed on the upper surface of the conductive doped substrate and an upper electrode disposed on the upper surface of the passivation layer. The conductive doped substrate is a single-crystal silicon substrate with n-type ion doping or p-type ion doping. The horizontal humidity-sensitive capacitor is formed on the passivation layer and includes a positive electrode and a negative electrode in the same layer as the upper electrode of the vertical reference capacitor. It also includes a humidity-sensitive material located between the positive electrode and the negative electrode. The positive electrode or the negative electrode is the upper electrode of the vertical reference capacitor.
2. The dual-capacitor humidity sensor as described in claim 1, characterized in that, The conductive doped substrate has a groove on its upper surface located directly below the upper electrode.
3. The dual-capacitor humidity sensor as described in claim 2, characterized in that, The passivation layer fills the groove; or, the passivation layer is suspended and covers the groove.
4. The dual-capacitor humidity sensor as described in claim 1, characterized in that, Both the positive electrode and the negative electrode are interdigitated, and the interdigitated fingers of the positive electrode and the negative electrode intersect each other without touching, such that the interdigitated fingers of the positive electrode and the interdigitated fingers of the negative electrode are opposite each other and have a gap.
5. The dual-capacitor humidity sensor as described in claim 4, characterized in that, The humidity-sensitive material fills the gap and buries both the interdigitated fingers of the positive electrode and the interdigitated fingers of the negative electrode within it.
6. The dual-capacitor humidity sensor as described in claim 4, characterized in that, The conductive doped substrate has a plurality of grooves, each groove being located directly below the interdigitated fingers of the positive electrode or the interdigitated fingers of the negative electrode.
7. The dual-capacitor humidity sensor as described in claim 4, characterized in that, The horizontal humidity-sensitive capacitor has a positive terminal and a negative terminal, with the interdigitated fingers of the positive electrode all connected to the positive terminal and the interdigitated fingers of the negative electrode all connected to the negative terminal.
8. The dual-capacitor humidity sensor as described in any one of claims 1 to 7, characterized in that, Both the positive electrode and the negative electrode are made of aluminum.