KR102630328B1 - Humidity sensor module, humidity measuring device having the same and method of detecting humidity using the same - Google Patents

Abstract

Disclosed is a humidity sensor module, a humidity measuring device equipped with the same, and a method of measuring humidity using the same. The humidity sensor module is placed on a substrate and includes an insulating layer with a recess recessed from the upper surface, an insulating layer placed on top of the insulating layer to cover the recess, providing the recess as a sealed space cut off from the outside, and a calcium-containing thin film layer. It has a membrane that absorbs atmospheric moisture and vibrates at different resonance frequencies depending on the content of the absorbed moisture, and a lower electrode disposed below the insulating layer and an upper electrode disposed on the membrane, between the lower electrode and the upper electrode. It includes an electrode layer that serves as a capacitor for the insulating layer located thereon. The humidity measuring device detects an output signal from the humidity sensor module and uniquely obtains the humidity corresponding to the resonance frequency of the output signal based on the frequency-humidity standard. The relative humidity of the atmosphere can be detected easily and accurately.

Description

Humidity sensor module, humidity measuring device having the same, and humidity measuring method using the same {Humidity sensor module, humidity measuring device having the same and method of detecting humidity using the same}

The present invention relates to a humidity sensor module, a humidity measuring device equipped with the same, and a humidity measuring method using the same. More specifically, the present invention relates to micromachining using a capacitive micro-machined ultrasonic transducer (CMUT). This relates to an ultrasonic humidity sensor module, a humidity measuring device equipped with the same, and a humidity measuring method using the same.

Recently, as the use of microprocessing has increased in various industrial fields, various efforts have been made to simply and precisely measure the humidity of the surrounding environment where unit processes are performed.

For example, interest in microprocessed humidity sensors with improved portability, ease of use, and detection accuracy is increasing by manufacturing humidity sensor chips in large quantities from a single substrate using microprocesses such as MEMS or semiconductor manufacturing processes. .

In particular, the capacitive micro-machined ultrasound transducer (CMUT) humidity sensor, which transforms the membrane of the device into a moisture absorption layer that absorbs moisture in the air and uses it as a humidity sensor, is widely used. The CMUT humidity sensor is manufactured through the MEMS process and has a fine size and is mass-produced, so the portability and detection convenience of the humidity sensor can be improved, and measurement precision can be increased by detecting relative humidity using an electrical signal.

In particular, recently, as the need for process environments that require high precision and cleanliness, such as semiconductor manufacturing processes or precision chemical processes, has increased, the demand for high-sensitivity CMUT humidity sensors that can detect even minute changes in humidity is increasing.

Since the moisture absorption sensitivity of the CMUT humidity sensor is determined by the response sensitivity of the membrane due to changes in moisture in the atmosphere, various efforts are being made to improve the physical properties of the moisture absorption layer of the high-sensitivity CMUT humidity sensor.

For example, various CMUT humidity sensors are known in which moisture absorption sensitivity is increased by modifying or modifying the membrane of the CMUT humidity sensor using metal oxide, ceramic, carbon, or polymer. However, it does not provide sufficient moisture absorption sensitivity required for recent microprocesses where the process scale is reduced to the nanometer level, so there is a problem in that it cannot respond sensitively to changes in humidity in the process environment.

Accordingly, the demand for new CMUT humidity sensors that can increase moisture absorption sensitivity is increasing.

The present invention was proposed to improve the problems described above, and the purpose of the present invention is to provide a humidity sensor module with improved moisture absorption sensitivity by disposing a calcium-containing thin film layer on the membrane of the CMUT device.

Another object of the present invention is to provide a humidity measuring device including the humidity sensor module described above.

Another object of the present invention is to provide a method of measuring relative humidity using the humidity measuring device described above.

A humidity sensor module according to an embodiment of the present invention for achieving the above object is disposed on a substrate and has an insulating layer having a recess recessed from the upper surface, and is disposed on top of the insulating layer to cover the recess. A membrane that provides the recess as a closed space cut off from the outside and has a calcium-containing thin film layer to absorb atmospheric moisture and vibrates at different resonance frequencies depending on the content of the absorbed moisture, and a membrane disposed below the insulating layer It includes a lower electrode and an upper electrode disposed on the membrane, and an electrode layer that serves as a capacitor with the insulating layer located between the lower electrode and the upper electrode.

A humidity measuring device according to another embodiment of the present invention for achieving the above object includes an insulating layer having a recess recessed from the upper surface, and a calcium-containing layer disposed on the insulating layer and capable of absorbing moisture contained in the atmosphere. A humidity sensor module including a membrane with a thin film layer whose physical properties change depending on the amount of moisture absorption, a power source that generates membrane vibration by applying a drive signal to the humidity sensor module, and an output signal that is an electrical signal corresponding to the membrane vibration. It includes a frequency detector that detects the frequency of the drive signal resonating with the output signal as a resonant frequency, and a humidity detector that detects the relative humidity of the atmosphere corresponding to the resonant frequency.

A method for measuring humidity according to another embodiment of the present invention is disclosed to achieve the above object. First, the insulating layer, which has a thin film layer containing calcium ions and is in contact with the membrane to absorb atmospheric moisture and has a closed space, functions as a capacitor and applies an alternating current voltage to a humidity sensor module that operates as a micro-processed ultrasonic transducer. Generates membrane vibration. An alternating current output signal, which is an electrical equivalent signal related to the vibration of the membrane, is detected through an electric circuit connected to the humidity sensor module, and the frequency of the drive signal is modulated to detect the maximum effective signal of the output signal. Detect the resonance frequency. From the frequency-humidity standard, the humidity corresponding to the resonance frequency is detected as the relative humidity of the atmosphere.

According to an exemplary embodiment of the present invention, a micro-machined ultrasonic humidity sensor module, a humidity measuring device equipped with the same, and a humidity measuring method using the same are manufactured in a small size by micro-machining and can maintain linearity between frequency and humidity. A humidity measuring device can be configured using a CMUT array. The thin film layer is composed of a calcium-containing silk layer, so it responds sensitively to atmospheric humidity and has linearity between moisture absorption and relative humidity over a wide humidity range. Accordingly, the relative humidity of the atmosphere can be accurately and stably detected.

In particular, the humidity measuring device is a small device that can accurately measure relative humidity with a simple operation in places where relative humidity measurement is required. Accordingly, precise humidity can be obtained with a simple operation in places where accurate humidity measurement is required.

1 is a cross-sectional view showing a humidity sensor module according to an embodiment of the present invention.
Figure 2 is a graph showing the stress-strain relationship of the calcium silk layer according to an embodiment of the present invention.
Figure 3 is a graph showing the results of measuring the change in moisture content of the calcium silk layer at different temperatures and relative humidity.
FIG. 4 is a frequency-humidity graph showing the correlation between relative humidity and resonance frequency of the humidity sensor module shown in FIG. 1.
FIG. 5 is a schematic configuration diagram of a humidity measuring device including the humidity sensor module shown in FIG. 1 according to another embodiment of the present invention.
FIG. 6 is a configuration diagram showing the electrical connection relationship between the humidity sensor module and the frequency detector shown in FIG. 5.
Figure 7 is a schematic configuration diagram showing a humidity measuring device according to another embodiment of the present invention.
Figure 8 is a flowchart showing a method of measuring relative humidity in the air using a humidity measuring device according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings, but the present invention is not limited to the following embodiments, and those skilled in the art will understand the technicalities of the present invention. The present invention may be implemented in various other forms without departing from the spirit of the invention.

In the accompanying drawings, the dimensions of the substrate, layer (film), region, pattern, or structure are enlarged from the actual size for clarity of the present invention. In the present invention, each layer (film), region, electrode, pattern or structure is “on”, “on” or “below” the substrate, and each layer (film), region, electrode, structure or pattern is “on”, “on” or “under” the substrate. When referred to as being formed on the substrate, it means that each layer (film), region, electrode, pattern or structure is formed directly on or below the substrate, each layer (film), region, structure or pattern, or other Layers (films), other regions, other electrodes, other patterns or other structures may be additionally formed on the substrate. Additionally, when materials, layers (films), regions, electrodes, patterns or structures are referred to as “first,” “second,” “third,” and/or “preliminary,” it is not intended to define these elements. rather, it is simply to distinguish each material, layer (film), region, electrode, pattern, or structure. Accordingly, “first,” “second,” “third,” and/or “preliminary” may be used selectively or interchangeably for each layer (film), region, electrode, pattern, or structure.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings.

1 is a cross-sectional view showing a humidity sensor module according to an embodiment of the present invention. As an example, the humidity sensor module is a cross-sectional view of a CMUT humidity sensor chip manufactured through a MEMS process. However, it is obvious that if a chip can be manufactured with the same level of integration as the CMUT chip, it can also include a humidity sensor chip manufactured through various microprocesses.

Referring to FIG. 1, the humidity sensor module 500 according to an embodiment of the present invention includes a substrate 100, an insulating layer 200 disposed on the substrate 100, and a calcium-containing thin film layer that can increase moisture absorption sensitivity. It includes a disposed membrane 300 and an electrode layer 400.

In one embodiment, the substrate 100 is a structure that constitutes the base of the humidity sensor module 500, and the insulating layer 200, membrane 300, and electrode layer 400 are the substrate 100. It is placed or stacked on top.

For example, the substrate 100 is provided as a base substrate capable of performing a micro-electro mechanical system (MEMS) process for manufacturing the humidity sensor module 500 and is made of a semiconductor material such as silicon or gallium. It consists of

In particular, as will be described later, the humidity sensor module 500 is provided as a CMUT chip that detects ultrasonic waves according to charging and discharging of energy by forming a capacitor on the upper part of the substrate 100, so that the substrate 100 is connected to the lower part of the substrate 100. It can function as an electrode structure for forming a plate capacitor integrally with the lower electrode 410 disposed on. Accordingly, it is made of a semiconductor material so that the resistance to current flow of the lower electrode 410 disposed on the back of the substrate 100 can be appropriately adjusted as needed.

Alternatively, when the lower electrode 410 is located between the upper surface 101 of the substrate 100 and the insulating layer 200, the substrate 100 may have high resistance and may be made of an insulating material.

In this embodiment, the substrate 100 is made of doped silicon in which p-type impurities are added to set the resistance to less than 10 ^-3 Ωcm. However, it is obvious that the humidity sensor module 500 can be made of various semiconductor materials if it can achieve the low resistance and conductivity required for its construction by doping with the impurities.

Additionally, the substrate 100 may be provided as part of a single wafer (silicon wafer). As will be described later, the humidity sensor module 500 may be provided as a humidity sensor array including a plurality of CMUT chips manufactured by MEMS technology on the wafer. At this time, the substrate 100 may be provided as an array substrate for the humidity sensor array.

The insulating layer 200 is disposed to cover the upper surface of the substrate 100 between the lower electrode 410 and the upper electrode 420, which are spaced apart from each other along the vertical direction. The insulating layer 200 is made of an insulating material with a predetermined thickness and a constant dielectric constant, and is disposed between the lower electrode 410 and the upper electrode 420 to function as a flat capacitor (C). Accordingly, the insulating layer 200 may be made of various materials as long as it has a dielectric constant sufficient to maintain a set capacitance.

In the case of this embodiment, the insulating layer 200 is disposed on the upper surface of the substrate 100 made of silicon, so it can be made of any one of silicon oxide, silicon nitride, and silicon oxynitride, which has excellent adhesion characteristics with silicon.

In particular, as will be described later, a recess (R) is disposed on the upper surface of the insulating layer 200, which is formed as a closed space (S) by combining with the membrane 300, so that the shape of the recess (R) is It is provided with sufficient strength and rigidity to maintain. For example, the insulating layer 200 is formed as a thin film with relatively high density through a thermal growth process and may have a thickness of about 400 nm to 500 nm.

The recess (R) is recessed from the upper surface 201 of the insulating layer 200 to a certain depth (h) and serves as an enclosed space (S) defined by the membrane 300 that covers the upper surface of the insulating layer 200. do. Accordingly, the closed space (S) is limited by the insulating layer 200 and the membrane 300 and is provided as a three-dimensional space with a maximum height corresponding to the height (h) of the recess (R).

The closed space (S) accommodates the initial deformation of the membrane to expand the amplitude of vibration of the membrane 300 and increases the detection sensitivity of the ultrasonic waves. In addition, the pull-in voltage applied to the humidity sensor module 500 is determined depending on the height (h) of the recess (R). Therefore, the height (h) of the recess (R) can be appropriately set considering the appropriate detection sensitivity of ultrasonic waves and the applied pull-in voltage. For example, the height h of the recess R may be set to range from about 60% to 80% of the thickness of the insulating layer 200.

The membrane 300 is disposed on the upper surface 201 of the insulating layer 200 to cover the recess (R). Accordingly, the recess (R) is formed as a closed space (S) defined by the membrane 300 and the insulating layer 200.

At this time, the membrane 300 is provided with a thin film layer 320 capable of absorbing moisture contained in the atmosphere, and the overall physical properties of the membrane 300 change depending on the moisture content of the thin film layer 320.

For example, the membrane 300 is disposed on the insulating layer 200 and covers the recess R, and the base layer 310 is disposed to cover the base layer 310 and absorbs moisture in the atmosphere. It includes a calcium-containing thin film layer (320). In particular, the base layer 310 and the thin film layer 320 are provided as one body and have the same vibration characteristics when the membrane 300 vibrates. That is, the base layer 310 and the thin film layer 320 are integrally combined with each other to form a physically identical member and have a single vibration characteristic.

In one embodiment, the base layer 310 is made of a semiconductor material and is provided as a film that vibrates according to the charging and discharging of energy stored in the capacitor C. In particular, the base layer 310 is combined with the insulating layer 200 to cover the recess (R) to form the sealed space (S), and thus can improve sealing characteristics by combining with the insulating layer 200. It is composed of substances.

For example, the base layer 310 may be made of a silicon thin film that has excellent bonding characteristics with silicon oxide or nitride. In this embodiment, the base layer 310 is configured to have a thickness of approximately 100 nm to 500 nm.

A thin film layer 320 containing a hygroscopic material capable of absorbing moisture in the air and an upper electrode 420 for applying direct current power (DC) are disposed on the upper surface of the base layer 310.

In one embodiment, the thin film layer 320 contains calcium to absorb moisture in the air to which the membrane 300 is exposed and is provided integrally with the base layer 310. When moisture in the air is absorbed into the thin film layer 320, the physical properties or mechanical properties of the thin film layer 320 itself are changed, and the physical and mechanical properties of the membrane 300 including the thin film layer 320 are changed.

For example, the thin film layer 320 may include a silk layer to which calcium is added (hereinafter referred to as calcium silk layer). It is difficult for the pure silk layer to absorb moisture, but the calcium silk layer has the property of absorbing and retaining moisture contained in the air at room temperature.

Figure 2 is a graph showing the stress-strain relationship of the calcium silk layer according to an embodiment of the present invention. Figure 2 shows the stress-strain curve of multiple calcium silk layers with different calcium concentrations at 60% relative humidity.

As shown in Figure 2, as the concentration of calcium increases, the strain rate of the calcium silk layer increases rapidly, and when the calcium concentration is about 30% to 40%, the strain rate of the calcium silk layer increases to about 200% to 400%. do.

Accordingly, Young's Modulus of the calcium silk layer, which is the slope of the stress-strain curve, also rapidly decreases when the calcium concentration is about 30% to 40%.

In other words, since the strain rate of the calcium silk layer can sufficiently increase at the same stress, it can sufficiently absorb moisture in the atmosphere without increasing the internal stress applied to the calcium silk layer.

In addition, the content of moisture that the calcium silk layer can absorb depends only on the relative humidity in the air and is not significantly affected by temperature. As the moisture content increases, the fluidity of the calcium silk layer increases, so that the calcium silk layer and the basal layer ( 310), contact uniformity can be improved at the interface.

Figure 3 is a graph showing the results of measuring the change in moisture content of the calcium silk layer at different temperatures and relative humidity.

Referring to Figure 3, the moisture content absorbed by the calcium silk layer increases as the relative humidity of the air increases, and when the relative humidity is the same, the moisture content that the calcium silk layer can absorb is substantially the same.

In other words, it can be confirmed that the content of moisture that the calcium silk layer can absorb is most significantly affected by the concentration of moisture contained in the atmosphere, regardless of temperature.

Therefore, when the calcium silk layer is configured to have a calcium concentration of about 30% to 40%, it can have a sufficiently large strain at a substantially single internal stress, and the calcium silk layer is proportional to relative humidity regardless of temperature. May contain moisture.

In particular, the calcium silk layer is provided in the form of a thin film with a thickness of about 100 nm to 500 nm and can quickly absorb or discharge moisture depending on the relative humidity in the air. It has a sufficiently large strain under certain stress conditions and can control moisture by reacting sensitively to the relative humidity of the air, so it can have sufficiently large humidity sensitivity.

The calcium silk layer has different masses and Young's moduli depending on the concentration of calcium and the content of absorbed moisture, so when the calcium concentration is specified, the physical properties of the calcium silk layer change depending on the moisture content.

Accordingly, the physical properties of the calcium-containing thin film layer 320, which has a constant calcium concentration, change sensitively to the moisture content, and since the base layer 310 is formed integrally with the calcium-containing thin film layer 320, the membrane 300 The overall physical properties also change depending on the moisture content that the thin film layer 320 can contain.

In particular, since the moisture content that the thin film layer 320 can contain is proportional to the relative humidity of the atmosphere regardless of temperature, the physical properties of the membrane 300 also change depending on the relative humidity of the atmosphere.

By the membrane 300 disposed on the insulating layer 200, the recess R is formed as a closed space S defined by the insulating layer 200 and the membrane 300. Accordingly, the rear surface of the membrane 300 is partially exposed toward the closed space (S).

The upper electrode 420 is disposed on the base layer 310 and includes a metal layer made of a conductive metal material.

For example, the conductive metal material may include aluminum or copper and may be formed on the base layer 310 using a deposition or plating process. In particular, the upper electrode 420 is formed to have a thickness smaller than or equal to that of the thin film layer 320, so that the upper electrode 420 is buried inside the thin film layer 320 or disposed to have the same top surface as the thin film layer 320. You can.

The upper electrode 420, together with the lower electrode 410 disposed below the semiconductor substrate 100, constitutes an electrode layer 400 for charging energy to the capacitor.

The lower electrode 420 has substantially the same structure as the upper electrode 420 except that it is disposed on the back of the semiconductor substrate 100. Accordingly, the lower electrode 410 may have the same composition and the same shape as the upper electrode 420. However, it is obvious that the configuration of the lower electrode 410 is not limited to this.

In the case of this embodiment, the lower electrode 410 and the upper electrode 420 are arranged to face each other with the closed space (S) interposed therebetween. Accordingly, when direct current power is applied to the lower electrode 410 and the upper electrode 420, energy can be charged to the insulating layer 200 located between the lower electrode 410 and the upper electrode 420. there is.

The lower electrode 410 and the upper electrode 420 can be placed in various positions as long as the insulating layer 200, which functions as a capacitor, can be sufficiently charged with energy. For example, the upper electrode 420 is shifted in parallel from the top of the closed space (S) and is disposed on the upper part of the post 210 of the insulating layer 200 that defines the closed space (S). It is obvious that it is possible.

The humidity sensor module 500 is an improved membrane of a capacitive micromachined ultrasonic transducer (CMUT) with the calcium-containing thin film layer 320, and the membrane 300 is formed by moisture absorption of the calcium-containing thin film layer 320. It has substantially the same configuration as a conventional CMUT device except that the overall physical properties change. Accordingly, the humidity sensor module 500 operates in the same manner as a conventional CMUT device.

Accordingly, a driving signal having alternating current characteristics is applied to the humidity sensor module 500 to vibrate the membrane 300, and the membrane vibration can be detected as an output signal, which is an electrical signal. Afterwards, the frequency of the driving signal is modulated and the resonance frequency, which is the frequency of the driving signal resonating with the output signal, is detected. The resonance frequency may function as a physical quantity representing the physical properties of the membrane 300. Subsequently, the humidity corresponding to the resonance frequency is detected as the relative humidity in the air based on a previously set humidity-frequency criterion.

Detection of the resonance frequency and relative humidity will be described in detail with reference to FIG. 6.

In particular, the moisture absorption sensitivity of the humidity sensor module 500 can be sufficiently improved by forming the membrane 300, which includes the base layer 310 and the calcium-containing thin film layer 320, with a thickness of 1 μm or less.

Since the physical properties of the calcium-containing thin film layer 320 change depending on the content of moisture absorbed, the physical properties of the membrane 300 including the thin film layer 320 also change. That is, it is changed into a separate material with different Young's Modulus depending on the content of moisture absorbed in the thin film layer 320.

Accordingly, the membrane 300 functions as an individual material depending on the moisture content contained in the thin film layer 320, and the vibrations of the membrane 300 with different moisture contents have different resonance wave numbers.

The thin film layer 320 has a sufficient strain rate and its moisture content changes immediately depending on the relative humidity, and the change in moisture content causes a change in the physical properties of the membrane 300, so the resonance frequency of the membrane 300 and the relative humidity of the atmosphere Humidity has a certain correlation.

That is, if the resonance frequency, which is a unique physical property value of the membrane vibration, can be detected, the moisture content of the thin film layer 320 corresponding to the resonance frequency can be estimated, and the moisture content is contained in the atmosphere surrounding the membrane 300. Since it varies depending on the concentration of water vapor, the relative humidity of the atmosphere corresponding to the resonant frequency can be estimated.

FIG. 4 is a frequency-humidity graph showing the correlation between relative humidity and resonance frequency of the humidity sensor module shown in FIG. 1. The graph in FIG. 4 shows the relationship between the resonance frequency of the output voltage detected from each humidity sensor module after setting up a number of environments with known relative humidity and placing the humidity sensor module in each environment and the corresponding relative humidity. will be.

As the relative humidity increases, the resonant frequency is detected in the low-frequency region, and as the relative humidity decreases, the resonant frequency is detected in the high-frequency region. Therefore, the change in resonance frequency due to change in relative humidity is a frequency deviation based on relative humidity of 0 and is displayed as a negative value on the vertical axis of the graph.

As shown in FIG. 4, in the range of relative humidity above 40%, which is an everyday humidity area, the change in resonance frequency due to increase in relative humidity is displayed linearly with a slope corresponding to moisture absorption sensitivity, so that the resonance frequency and relative humidity are substantially It can be displayed as a one-to-one correspondence. Accordingly, if the resonance frequency of the output signal corresponding to membrane vibration is detected, the relative humidity can be uniquely detected from the linear relationship shown in FIG. 4.

In this example, the linearity has a slope of about 3.4 to 3.6. That is, when the relative humidity in the air changes by a unit humidity, the resonance frequency has the characteristic of changing by about 3.4 KHz to 3.6 KHz. Accordingly, the moisture absorption sensitivity of the humidity sensor module can be increased by reacting sufficiently sensitively to changes in humidity.

In contrast, when the calcium-containing thin film layer 320 was removed and the membrane 300 was constructed with only the base layer 310, the resonance frequency of the output signal OS was detected as a constant value regardless of changes in relative humidity. In other words, it can be confirmed that the base layer 310 alone does not perform the humidity detection function and that it functions as a humidity sensor by adding the calcium-containing thin film layer 320.

Accordingly, the humidity sensor module 500 can uniquely obtain the corresponding relative humidity by detecting the resonance frequency of the membrane 300 using the humidity-frequency graph shown in FIG. 4.

The humidity sensor module 500 as described above can precisely measure the relative humidity in the air by using the calcium-containing thin film layer 320, which has a wide range of strain at a constant internal stress and has sufficiently high moisture absorption sensitivity. In particular, the relative humidity can be uniquely detected using the detected resonance frequency by maintaining linearity between frequency and humidity in the 40% relative humidity humidity area, which is an area of daily life. Accordingly, the relative humidity in the air can be detected stably and accurately over a wide humidity range.

In addition, since the humidity sensor module can be manufactured using a CMUT device manufactured in a small size through microfabrication, portability can be significantly improved. Accordingly, in situations where precise measurement of relative humidity in the air is possible, accurate humidity can be easily obtained using the humidity sensor module.

FIG. 5 is a schematic configuration diagram of a humidity measuring device including the humidity sensor module shown in FIG. 1 according to another embodiment of the present invention.

Referring to FIG. 5, the humidity measuring device 1000 according to another embodiment of the present invention is a humidity sensor module 500 disposed on the main board 501 and detecting atmospheric humidity through a calcium-containing thin film layer 320. , a power source 600 that transmits driving power to drive the humidity sensor module 500, a frequency detector 700 that detects the resonance frequency of the output signal (OS) detected from the humidity sensor module 500, and the It may include a humidity detector 800 that detects relative humidity corresponding to the resonance frequency.

In this embodiment, the humidity sensor module 500, power source 600, frequency detector 700, and humidity detector 800 may be placed on a single main board 501 and electrically connected to each other.

For example, the main board 501 is composed of a printed circuit board with microcircuits printed therein, so devices placed on the main board 501 can be electrically connected to each other through the microcircuits. Accordingly, the humidity sensor module 500, power source 600, frequency detector 700, and humidity detector 800 can form a single humidity measurement device.

In one embodiment, the humidity sensor module 500 is provided as a capacitive micromachined ultrasonic transducer (CMUT) device having a membrane 300 composed of a calcium-containing thin film layer 320 and a base layer 310.

In this embodiment, the humidity sensor module 500 has substantially the same configuration as the humidity sensor module 500 shown in FIG. 1. Accordingly, the humidity sensor module 500 is disposed on the upper surface of the insulating layer 200 having the recessed recess (R) to cover the recess (R), so that the recess (R) is connected to the closed space (S). A membrane (300) provided with a calcium-containing thin film layer (320) to absorb moisture contained in the atmosphere, and the upper electrode (420) disposed on the lower part of the insulating layer (200) and the upper part of the membrane (300). and an electrode layer 400 that serves as a capacitor using the insulating layer 200 disposed between the lower electrodes 410.

At this time, the membrane 300 is provided as a double membrane composed of a base layer 310 that is disposed between the calcium-containing thin film layer 310 and the insulating layer 200 and defines the sealed space (S). Accordingly, by adding only the calcium-containing thin film layer 310 to a conventional CMUT device and modifying it to have a double-layer structure, a membrane 300 whose physical properties vary depending on moisture content can be easily formed.

For example, the calcium-containing thin film layer 320 may include a silk layer containing about 30 to about 40% by weight of calcium.

In FIG. 5, the same reference numerals are used for the same components as those of the humidity sensor module 500 shown in FIG. 1, and further detailed descriptions are omitted.

The humidity sensor module 500 may be provided as a CMUT device (CD) manufactured through microprocessing and may be provided as a CMUT array (CA) in which multiple CMUT devices (CDs) are integrated on a single substrate 100.

At this time, the substrate 100 is provided as a common substrate for configuring the CMUT array (CA), and the insulating layer 200 and base layer 310 are arranged separately in units of CMUT devices (CD). A calcium-containing thin film layer 320 is coated on top of the base layer 310 and then separated into units of the base layer 310, thereby forming a thin film layer 320 divided into CMUT device (CD) units. Accordingly, a plurality of humidity sensor modules 500 can be placed on a single substrate 100 by forming a CMUT humidity sensor array (CA) in which a plurality of CMUT elements (CDs) are aligned on the substrate 100. .

The upper electrode 420 of each CMUT device (CD) is connected to the connection pad 502 aligned on the main board 501 by a connection wire 503. The connection pad 502 is connected to the power source 600, the frequency detector 700, and the humidity detector 800 through circuit wiring printed on the main board 501. Each CMUT device (CD) constituting the humidity sensor module 500 is individually driven by the same power source 600 and is independently connected to the frequency detector 700 and the humidity detector 800.

Accordingly, the individual humidity sensor modules 500 constituting the humidity sensor array (CA) are driven independently to individually detect the relative humidity of the same surrounding atmosphere. By individually detecting the same relative humidity by multiple humidity sensor modules 500, the accuracy of the detected humidity can be increased.

In one embodiment, the power source 600 applies a driving signal DS to the humidity sensor module 500 to generate membrane vibration having a resonance frequency corresponding to the physical property.

In this embodiment, the power source 600 is a DC power source 610 that charges energy by applying a direct current voltage to the humidity sensor module 500 and an alternating current voltage is applied to the humidity sensor module 500 to determine the humidity. It includes an alternating current generator 620 that performs periodic charging and discharging of energy stored in the sensor module 500.

The direct current power source 610 is connected to the lower electrode 410 and the upper electrode 420 and applies a direct current voltage to the insulating layer 200, which functions as a capacitor. When a direct current voltage is applied to the electrode layer 400, the substrate 100 and the insulating layer 200 disposed between the lower electrode 410 and the upper electrode 420 function as a capacitor with a certain capacitance to store energy. It will be saved.

At this time, the energy stored in the capacitor pulls the membrane 300 covering the closed space (S) and deforms it to be concave toward the inside of the closed space (S). The membrane 300 is arranged in a concave parabolic shape in which initial stress is stored, and vibrates in response to the application of an alternating current voltage, which will be described later, while the initial stress is applied. That is, the maximum amplitude of the membrane vibration is set by the direct current voltage applied to the electrode layer 400.

As the amplitude of the membrane vibration increases, the sensitivity of the output signal (OS) detected by the frequency detector 700, which will be described later, can increase and filtering characteristics can be improved. Accordingly, the larger the direct current voltage applied to the electrode layer 400, the easier it is to remove noise from the output signal OS.

The direct current voltage can be appropriately set in a range that does not cause damage to the membrane 300 that is deformed inside the closed space (S). In this embodiment, the direct current voltage is set to have a range of about 5V to 8V. When the direct current voltage is lower than 5V, the amplitude of vibration of the membrane 300 is too small and the resonance frequency is detected in the high frequency band, making it less practical, and when the direct current voltage exceeds 8V, the energy applied to the membrane 300 is too large. The membrane 300 may collapse. Accordingly, the range of the direct current voltage is set to have a range of approximately 5V to 8V.

The AC generator 620 applies an AC voltage with a preset frequency to the humidity sensor module 500 to which the DC voltage is applied. An alternating current voltage is applied to the capacitor charged with a direct current voltage to generate electrical vibration in the insulating layer 200. Electrical vibration of the insulating layer 200 generates mechanical vibration of the membrane 300 disposed on the upper surface.

The mechanical vibration of the membrane 300 is detected as an output signal OS, which is an electrical signal, by the frequency detector 700 electrically connected to the humidity sensor module 500, as will be described later.

By applying the direct current voltage, energy is stored in the insulating layer 200, which functions as a capacitor, and by applying the alternating current voltage to the humidity sensor module 500, the stored energy is vibrated. Accordingly, the driving signal DS applied to the humidity sensor module 500 consists of a DC/AC superimposed voltage where a DC voltage and an AC voltage are superimposed.

The AC generator 620 is placed separately from the DC power source 610 on the main board 501 and can operate independently of the DC power source 610. Alternatively, the alternating current generator 620 may be provided as part of the frequency detector 700. For example, the AC generator 620 may be configured as a voltage divider provided in an oscillator that detects the output signal OS.

The power source 600 is mounted on the main board 501, and the driving signal DS is transmitted from the power source 600 to the individual CMUD through the fine circuit wiring of the main board 501 and the connection pad 502. It can be applied as a device (CD). Alternatively, the power source 600 may be configured as a power terminal supplied by an external power source. At this time, a connection terminal is provided on the main board 501 so that driving power can be transmitted to an external power source.

In one embodiment, the frequency detector 700 is electrically connected to the humidity sensor module 500 to detect the membrane vibration as an electrical signal. Accordingly, the mechanical vibration of the membrane 300 is detected as an output signal (OS), which is an electrical signal, and the frequency detector 700 is composed of a resonance circuit to automatically detect the resonance frequency of the output signal (OS). .

The frequency detector 700 is placed on the main board 501 and is electrically connected to the humidity sensor module 500 and the power source 600 through a circuit printed on the main board 501.

However, the configuration of the frequency detector 700 as described above is illustrative and is not necessarily limited thereto. For example, the frequency detector 700 may be placed externally, electrically connected to the main board 501, and detect the frequency of the output signal after receiving the output signal. At this time, the frequency detector 700 is composed of a separate structure that is portable and can be selectively connected by connecting the connection end of the humidity sensor module 500 and the connection end of the main board 501 when humidity measurement is required. there is.

FIG. 6 is a configuration diagram showing the electrical connection relationship between the humidity sensor module and the frequency detector shown in FIG. 5. In FIG. 6, the humidity sensor module 500 is shown as an equivalent circuit, and the frequency detector 700 is shown as a configuration diagram showing electrical connection with the equivalent circuit.

Referring to FIG. 6, when the driving signal DS is applied to the humidity sensor module 500 by the power source 600, the membrane 300 vibrates in response to the driving signal DS and the membrane vibrates. is detected as an output signal (OS) having a specific resonance frequency by the frequency detector 700.

For example, the equivalent circuit for the humidity sensor module 500 includes a driving section (D) connected to the power source 600 to which the driving signal (DS) is directly applied, and a driving section (D) induced by the driving signal (DS). It can be divided into an induction section (I) in which electrical energy vibrates according to the characteristics of the membrane 300 to generate ultrasonic waves.

The driving section (D) is modeled as an equivalent capacitor with an equivalent capacitance (C ₀ ) corresponding to the capacitance of the entire humidity sensor module 500 including the insulating layer 200 by the driving signal (DS). . Accordingly, periodic charging and discharging of energy is performed centering on the equivalent capacitor by the driving signal DS provided as an overlapping signal of a direct current signal and an alternating current signal, thereby performing an appropriate charge according to the physical properties of the humidity sensor module 500. An inductive alternating current signal whose energy rate is adjusted is induced and transmitted to the inductive section (I).

The induction section (I) is modeled as an LC circuit consisting of an inductor (L) and a capacitor (C) to replace the mechanical vibration of the membrane 300 with energy conversion by the induction alternating current signal. . That is, the mechanical vibration of the membrane 300 is replaced by electrical vibration in the equivalent LC circuit, and the characteristics of the membrane vibration have equivalent characteristics to the characteristics of the output signal detected in the LC circuit.

Specifically, the equivalent LC circuit constituting the induction section (I) includes the membrane capacitance (Cm) and membrane reactance (Lm), which represent the physical properties of the membrane 300, and all resistance characteristics to vibration of the humidity sensor module 500. It may have an impedance (Z) including as a circuit component.

Accordingly, the mechanical vibration of the membrane 300 caused by the induced alternating current signal is replaced by conversion between the electrostatic energy of the membrane capacitance (Cm) and the electromagnetic energy of the membrane reactance (Lm), and the cycle between electrostatic energy and electromagnetic energy The positive conversion is detected as an alternating current signal through an LC circuit with membrane capacitance (Cm) and membrane reactance (Lm).

That is, the mechanical vibration of the membrane 300 is replaced by electrical vibration, which is conversion between electrostatic energy and electromagnetic energy in the equivalent LC circuit, and the electrical vibration is converted into an output signal OS, which is an alternating current signal, by the frequency detector 700. It is detected. Membrane vibration has a resonance frequency, which is a physical property value that varies depending on the physical properties of the membrane 300. In particular, since the membrane vibration and the output signal (OS) detected in the LC circuit are equivalent to each other, the resonance frequency of the output signal (OS) resonating with the driving signal (DS) is also the physical property value of the membrane 300. It can function as

Since the physical properties of the membrane 300 are determined by relative humidity, which is the moisture content in the air, the resonance frequency of the output signal OS and the relative humidity have a high correlation.

In the case of this embodiment, as shown in FIG. 4, there is a linear correlation between relative humidity and resonance frequency, so the relative humidity in the air can be detected with high precision by detecting the resonance frequency of the output signal OS.

The frequency detector 700 that detects the resonance frequency of the output signal (OS) includes a signal detection unit 710 that detects the output signal and a resonance unit 720 that detects the resonance frequency of the output signal (OS). do.

The signal detection unit 710 is electrically connected to an individual CMUT device (CD) constituting the humidity sensor module 500 and can detect the output signal (OS). For example, the signal detection unit 710 detects an electrical signal from the humidity sensor module 500 to generate an output signal (OS), and includes an amplifier 711 to amplify the output signal (OS) and the amplified output. A plurality of filters 712 may be provided to remove noise from the signal OS.

The amplifier 711 is connected to the CMUT element (CD) to detect an electrical signal corresponding to the membrane vibration as the output signal (OS) and amplify the output signal (OS) by an amplifier circuit composed of a transistor. You can.

The membrane vibration is modeled as the electrical vibration of an equivalent LC circuit having the membrane reactance (Lm) and membrane capacitance (Cm) as described above, and the output signal (OS) can be generated as an alternating current signal of the equivalent LC circuit. .

The filter 712 includes a high-frequency filter and a low-frequency filter to remove high-frequency noise and low-frequency noise included in the output signal OS and obtain only an alternating current signal corresponding to the membrane vibration.

In this embodiment, the signal detection unit 710 may be configured as an oscillator including the amplifier 711 and the filter 712.

The resonance unit 720 receives the output signal OS detected by the signal detection unit 710 and detects a resonance frequency. In this embodiment, the resonator 720 may include a frequency counter for detecting the resonant frequency of the output signal OS. However, it is obvious that the resonator 720 is not limited to a frequency counter.

For example, the resonance unit 720 includes an arithmetic unit 721 that detects the maximum effective output of the output signal (OS), a frequency detection unit 722 that detects a resonance frequency of the output signal (OS), It includes a modulation unit 723 that modulates the frequency of the driving signal DS and a control unit 724 that controls the frequency of the driving signal DS to be modulated until the resonance frequency is detected.

For example, the operation unit 721 may receive the output signal OS from the signal detection unit 710, detect the effective output of the output signal OS, and determine whether the maximum effective output is present.

Algorithms for detecting maximum effective output can be implemented in various ways. The modulation unit 723 is forcibly driven as many times as the set initial number to generate different driving signals (DS) as many as the initial number of times, and the output of the output signal (OS) corresponding to each driving signal (DS) is detected to provide a temporary maximum effective output. It can be set to . After setting the temporary maximum effective output, the modulation unit 723 is driven as many times as the number of detections, and when an effective output exceeding the maximum effective output is detected, the detected effective output can be updated to the maximum effective output.

Alternatively, the maximum effective output that can be obtained at each humidity may be set in advance in the calculation unit. Accordingly, the modulation unit 723 may be forcibly driven so that an output signal (OS) matching the maximum effective output corresponding to each relative humidity is detected.

For example, since the output signal OS is detected as an alternating current signal of the equivalent LC circuit, the effective output may include any one of the effective voltage, active current, and active power of the output signal OS.

When the maximum effective output is detected in the operation unit 721, the frequency detection unit 722 sets the frequency of the output signal OS having the maximum effective output as the resonance frequency. Since the frequency of the output signal (OS) is the same as the frequency of the driving signal (DS), the frequency of the driving signal (DS) applied to the humidity sensor module 500 is set as the resonance frequency to generate the output signal (OS). You can.

When the operation unit 721 fails to detect the maximum effective output, the modulation unit 723 modulates the frequency of the driving signal DS and transmits the modulated frequency to the power source 600. Since the output signal OS for which the maximum effective output is not detected is a signal in which no resonance occurs, it is difficult to detect the resonance frequency of the membrane vibration. Accordingly, the frequency of the driving signal DS is modulated through the modulation unit 723 and the modulated frequency information is transmitted to the power source 600. The power source 600 generates an alternating current signal with a modulated frequency and applies it to the humidity sensor module 500.

An output signal (OS, hereinafter modulated output signal) having a modulated frequency is detected by a drive signal (DS, hereinafter referred to as modulated drive signal) having a modulated frequency, and the operation unit 721 outputs the modulated output signal (OS). Determine whether the signal has the maximum effective output.

When the operation unit 721 determines that the modulated output signal (OS) has the maximum effective output, the control unit 724 sets the frequency of the modulated output signal (OS) to the resonance frequency. The detection unit 722 is driven.

On the other hand, when the operation unit 721 determines that the effective output of the modulated output signal (OS) is not the maximum effective output, the control unit 724 controls the modulation unit 723 to generate the modulated output signal. The frequency of (OS) is modulated to a different frequency, and the modulated frequency is transmitted to the power source 600. For example, the modulation frequency modulated by the modulation unit 723 may be transmitted to the alternating current generator 620.

The control unit 724 drives the modulation unit 723 until a resonant frequency with maximum effective output is detected. Accordingly, the vibration of the membrane 300 that absorbs moisture in response to a specific relative humidity is detected by the output signal OS, and the resonance frequency of the membrane vibration is one to one with the resonance frequency of the output signal OS. It has corresponding characteristics. That is, the behavior of the output signal OS having the resonance frequency can be evaluated as a physical equivalent of the vibration of the membrane 300.

In one embodiment, the humidity detector 800 is mounted on the main board 501 and is electrically connected to the frequency detector 700 through a printed circuit of the main board 501. For example, the humidity detector 800 includes a memory that stores data related to a frequency-humidity standard, which will be described later, and a microprocessor that performs an operation to detect the relative humidity corresponding to the resonance frequency based on the frequency-humidity standard. It consists of a processor and can be mounted on the main board 501.

Accordingly, the relative humidity of the atmosphere corresponding to the resonance frequency is detected using the resonance frequency transmitted from the frequency detector 700.

For example, the humidity detector 800 includes a correlation calculation unit 810 that obtains a frequency-humidity standard, and a search frequency storage unit 820 that stores the resonance frequency transmitted from the frequency detector 700 as a humidity search target frequency. ), and a humidity calculation unit 830 that obtains the relative humidity corresponding to the search frequency according to the humidity-frequency standard.

The correlation calculation unit 810 is a reference humidity sensor module provided with a reference membrane having the same configuration as the membrane 300 in a known sample humidity environment, and obtains a reference frequency that is a resonance frequency corresponding to the resonance frequency of the reference membrane. A frequency-humidity criterion is obtained, which is the correlation between sample humidity and the reference frequency.

For example, the resonance frequency can be detected by placing the humidity measuring device 1000 inside a chamber set to a known sample humidity. At this time, the humidity measuring device 1000 is arranged to detect a resonance frequency corresponding to the sample humidity in a known sample humidity environment, so the humidity sensor module 500 included in the humidity measuring device 1000 is used to determine the sample humidity. It functions as a reference humidity sensor module for detecting a resonant frequency, and the detected resonant frequency is set as a reference frequency corresponding to the sample humidity. Accordingly, the reference humidity sensor module has substantially the same configuration as the humidity sensor module shown in FIG. 1.

By detecting the reference frequency for a number of sample humidity, a number of experimental order pairs consisting of sample humidity and reference frequency are obtained, and the experimental order pairs are processed using statistical processing techniques to generate a frequency-humidity standard, which is the correlation between frequency and humidity. You can.

For example, by performing linear regression analysis on a plurality of experimental ordered pairs of sample humidity and frequency, the reference frequency for humidity that was not actually detected can be estimated with high reliability. Accordingly, the frequency-humidity reference can be generated as a linear function with a linear relationship between frequency and humidity.

In particular, the actual ordered pair, which is the relationship between the resonance frequency and relative humidity actually detected during the operation of the humidity measuring device 1000, can be included in the experimental ordered pair to increase the size of the population to which the statistical processing technique is applied. Accordingly, the precision of the frequency-humidity standard can be increased.

The search frequency storage unit 820 stores the resonance frequency detected from the frequency detector 700 as a reference frequency for humidity detection. As will be described later, the reference frequency is provided as a dependent variable of the frequency-humidity standard, so that the humidity corresponding to the reference frequency can be uniquely obtained.

The search frequency storage unit 820 is connected to the frequency detection unit 722 and can automatically store the resonance frequency the moment the resonance frequency is detected. The search frequency storage unit 820 may be composed of various memory elements capable of storing resonance frequencies.

The humidity calculation unit 830 is connected to the search frequency storage unit 820 and the correlation calculation unit 810, and sets the reference frequency as a dependent variable of the frequency-humidity standard obtained from the correlation calculation unit 810. The humidity corresponding to can be detected. For example, when the frequency-humidity reference is obtained as a linear function, the relative humidity corresponding to the reference frequency can be obtained using the linear function.

In this example, the functional relationship obtained using statistical processing techniques is disclosed as the frequency-humidity standard, but it is not limited to this. For example, the frequency-humidity criterion may be given as a frequency-humidity table for a number of ordered pairs between relative humidity and frequency.

In this embodiment, the humidity detector 800 is disclosed on the main board 501, but it may also be provided as an individual structure outside the main board 501. For example, it may be provided as an individual calculation device that is electrically connected to the frequency detector 700 and obtains the relative humidity corresponding to the resonant frequency transmitted from the frequency detector 700 through correlation calculation. At this time, the humidity calculation device has a connection terminal that can be individually connected to the frequency detector 700 and the main board 501 and can be selectively connected to the humidity sensor module 500.

In particular, only the humidity sensor module 500 is placed on the main board 501, and the power source 600, frequency detector 700, and humidity detector 800 are used for individual integrated humidity calculation with the humidity sensor module 500. The humidity measurement device 1000 can be easily constructed by constructing it as a kit.

Figure 7 is a schematic configuration diagram showing a humidity measuring device according to another embodiment of the present invention. The modified humidity measuring device 1001 shown in FIG. 7 except that the humidity sensor module 500, power source 600, frequency detector 700, and humidity detector 800 shown in FIG. 5 are provided individually. Has substantially the same configuration as the humidity measuring device 1000 shown in FIG. 5. Accordingly, in FIG. 7, the same reference numerals are used for the same components as those in FIG. 5, and further detailed descriptions of the same components are omitted.

Referring to FIG. 7, the humidity measuring device 1001 according to another embodiment of the present invention is an output kit ( K1) and a calculation kit (K2) connected to the output kit (K1) to detect a resonance frequency corresponding to the output signal and extract the relative humidity corresponding to the resonance frequency through calculation.

The output kit (K1) is provided with a first terminal (T1) for signal transmission on the side of the main board 501, and the operation kit (K2) is connected to the first terminal (T1) to form the output kit (K1). is electrically connected to

The calculation kit (K2) is provided as a structure in which the power source 600, frequency detector 700, and humidity detector 800 are arranged on a single base (not shown) and are integrally driven by a single logic. In particular, a second connection terminal (T2) corresponding to the first terminal (T1) is provided at the outer end of the base, and the operation kit (K2) is connected to the first terminal (T1) and the second connection terminal (T2). The modified humidity measuring device 1001 can be completed by combining the output kit (K1).

When the calculation kit (K2) and the output kit (K1) are combined, a driving signal is applied to the humidity sensor module 500 by the power source 600 to start humidity measurement. When an output signal corresponding to the natural vibration of the membrane 300 is generated by the humidity sensor module 500 according to the drive signal, it is transmitted to the calculation kit (k2) and the output signal is transmitted through the frequency detector 700. The resonance frequency of is detected. The humidity detector 800 detects the current relative humidity by searching for the relative humidity corresponding to the detected resonance frequency using a frequency-humidity standard. According to the humidity measuring device according to an embodiment of the present invention, microprocessing By constructing a humidity measuring device using a CMUT array that is manufactured in a small size and can maintain linearity between frequency and humidity, the relative humidity in the air can be detected stably and accurately over a wide humidity range.

In particular, the humidity measuring device is a small device that can accurately measure relative humidity with a simple operation in places where relative humidity measurement is required. Accordingly, precise humidity can be obtained with a simple operation in places where accurate humidity measurement is required.

In addition, the manufacturing efficiency and management burden of the modified humidity sensor device 1001 can be reduced by separately manufacturing and managing the output kit (K1) in which the humidity sensor module is arranged and the operation kit (K2) for detecting humidity.

FIG. 8 is a flowchart showing a method of measuring relative humidity in the air using the humidity measuring device shown in FIG. 5 or FIG. 7 according to an embodiment of the present invention.

Referring to FIGS. 5, 7, and 8, in order to detect the relative humidity of the atmosphere with the humidity measuring device 1000 shown in FIG. 5 according to an embodiment of the present invention, a membrane having a thin film layer containing calcium ions is first installed. An alternating voltage is applied to a humidity sensor module that includes an ultrasonic transducer (step S100).

For example, an overlapping voltage of a direct current voltage and an alternating current voltage is applied to the electrode layer 400. Charge is charged to the insulating layer 200, which functions as a capacitor, by applying a direct current voltage of a certain strength from the direct current power supply 610, and charging by applying an alternating current voltage with a set frequency to the charged insulating layer 200. The accumulated charge can be periodically discharged and charged. Accordingly, the membrane 300 composed of the calcium-containing thin film layer 320 vibrates to generate membrane vibration.

Next, an alternating current output signal, which is an electrical equivalent signal related to the vibration of the membrane 300, is detected through an electric circuit connected to the humidity sensor module 500 (step S200).

For example, the frequency detector 700 including the electrode layer 400, a signal detector 710 for detecting the output signal (OS), and a resonator 720 for detecting the resonance frequency of the output signal (OS) is electrically connected. to form an electric circuit including the humidity sensor module 500 as a component.

At this time, the humidity sensor module 500 is modeled as an equivalent LC circuit having a membrane reactance (Lm) and a membrane capacitance (Cm), and the induced electromotive force induced by the driving signal (DS) moves the membrane according to the membrane vibration. Energy is periodically stored or released in the reactance (Lm) and membrane capacitance (Cm) and is detected as the output signal (OS) having alternating current characteristics. That is, the output signal OS has the same frequency as the driving signal DS and is detected as an alternating current signal whose output intensity is determined according to the characteristics of the LC equivalent circuit.

Next, the resonance frequency of the output signal is detected by modulating the frequency of the drive signal to detect the maximum effective signal of the output signal (step S300).

When the output signal (OS) is detected from the signal detector 710, the operation unit 721 determines whether the effective output of the output signal (OS) is the maximum value, and if it has the maximum effective output, the output signal (OS) Set the frequency as the resonance frequency. On the other hand, when the operation unit 721 determines that the effective output is not the maximum value, the control unit 724 drives the modulation unit 723 to modulate the frequency of the driving signal DS. Information on the test frequency, which is a modulated frequency, is transmitted to the AC generator 620 to generate a new driving signal DS having the test frequency.

A new output signal (OS) generated by a new driving signal (DS) having a test frequency is generated, and it is determined again whether the effective output has the maximum value.

The control unit 724 determines whether the effective output of the newly generated output signal (OS) is the maximum output every time the frequency of the driving signal (DS) changes and sets the frequency of the output signal (OS) having the maximum effective output. Set to resonance frequency.

Accordingly, the control unit 724 applies the driving signal DS to the humidity sensor module 500 while changing the frequency and detects the output signal OS for each driving signal DS, so that the effective output of the output signal is maximized. Repeat until .

Accordingly, when the effective output of the equivalent LC circuit is at its maximum, the frequency of the output signal OS is detected as the resonance frequency.

When the resonant frequency is detected, the relative humidity of the air is detected as the humidity corresponding to the resonant frequency according to the frequency-humidity standard (step S400).

For example, in a plurality of known sample humidity environments, a reference humidity sensor module having a reference membrane having the same configuration as the membrane 300 with a calcium-containing thin film layer 320 is used to set a reference frequency, which is the resonant frequency of the reference membrane. A frequency-humidity criterion, which is a correlation between the sample humidity and the reference frequency, is obtained, and the resonance frequency of the membrane 300 detected by the frequency detector 700 is retrieved and stored as a search frequency. Subsequently, the sample humidity corresponding to the search frequency can be calculated according to the frequency-humidity standard and determined as the relative humidity.

At this time, the frequency-humidity standard can be obtained as a linear function obtained by linear regression analysis of a plurality of ordered pairs of frequency-humidity. Therefore, the relative humidity of the atmosphere can be uniquely obtained by calculating the humidity corresponding to the resonance frequency from the linear function regarding the frequency-humidity.

According to embodiments of the present invention, the humidity sensor module, the humidity measuring device including the same, and the humidity measuring method using the same are manufactured in a small size through microfabrication and use a CMUT array that can maintain linearity between frequency and humidity. Thus, a humidity measuring device can be configured. The thin film layer is composed of a calcium-containing silk layer, so it responds sensitively to atmospheric humidity and has linearity between moisture absorption and relative humidity over a wide humidity range. Accordingly, the relative humidity of the atmosphere can be accurately and stably detected.

In particular, the humidity measuring device is a small device that can accurately measure relative humidity with a simple operation in places where relative humidity measurement is required. Accordingly, precise humidity can be obtained with a simple operation in places where accurate humidity measurement is required.

Although preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, those skilled in the art will understand the present invention without departing from the spirit and scope of the present invention as set forth in the following patent claims. You will understand that it can be modified and changed in various ways.

100: substrate 200: insulating layer
300: membrane 310: basal layer
320: Calcium-containing thin film layer 400: Electrode layer
410: lower electrode 420: upper electrode
500: Humidity sensor module 600: Power source
610: DC power 620: AC generator
700: frequency detector 710: signal detector
720: Resonator 800: Humidity detector
810: correlation association unit 820: search frequency storage unit
830: Humidity calculation unit 1000: Humidity measuring device

Claims (20)

an insulating layer disposed on a substrate and having a recess recessed from the upper surface;
It is disposed on the upper part of the insulating layer to cover the recess, provides the recess as a closed space cut off from the outside, and is provided with a calcium-containing thin film layer to absorb atmospheric moisture and have different resonance frequencies depending on the content of the absorbed moisture. Membrane vibrating with; and
A humidity sensor module comprising an electrode layer having a lower electrode disposed under the insulating layer and an upper electrode disposed on the membrane, and providing the insulating layer located between the lower electrode and the upper electrode as a capacitor. The humidity sensor module according to claim 1, wherein the membrane further includes a base layer disposed on the insulating layer below the thin film layer to provide the sealed space, and is provided as a double membrane composed of the base layer and the thin film layer. The humidity sensor module of claim 2, wherein the base layer includes any one of silicon oxide, silicon nitride, and silicon oxynitride, and the calcium-containing thin film layer includes a silk layer containing calcium at a concentration of 30-40 weight percent. The humidity sensor module of claim 2, wherein the upper electrode is disposed on the base layer and the thin film layer has a top surface that is higher than or equal to the top surface of the base layer. The method of claim 1, wherein the insulating layer disposed between the electrode layers and functioning as the capacitor and the membrane on top of the insulating layer constitute a capacitive micro-machined ultrasound transducer (CMUT) element. Humidity sensor module. The humidity sensor module of claim 1, wherein the resonance frequency has linearity with respect to the relative humidity in a range of 40% to 100%, which is the relative weight percent concentration of moisture contained in the air. The humidity sensor module of claim 6, wherein the resonance frequency has a change rate of 3.4 to 3.6 KHz (3.4 to 3.6 KHz/relative humidity (%)) for a unit change in humidity. A humidity sensor module comprising an insulating layer having a recess recessed from the upper surface and a membrane that has physical properties that change depending on the amount of moisture absorbed, including a calcium-containing thin film layer disposed on the insulating layer and capable of absorbing moisture contained in the atmosphere. ;
a power source that applies a driving signal to the humidity sensor module to generate membrane vibration having a resonance frequency corresponding to the physical property;
a frequency detector that detects an output signal, which is an electrical signal corresponding to the membrane vibration, and detects the frequency of the drive signal resonating with the output signal as the resonance frequency; and
A humidity measuring device comprising a humidity detector that detects the relative humidity of the atmosphere corresponding to the resonance frequency. The method of claim 8, wherein the humidity sensor module,
a substrate supporting the insulating layer on which the membrane is disposed; and
Including an electrode layer having a lower electrode disposed on the lower part of the substrate and an upper electrode disposed on the membrane, and providing the insulating layer located between the lower electrode and the upper electrode as a capacitor,
A humidity measuring device consisting of a capacitive micromachined ultrasonic transducer (CMUT) element that generates the membrane vibration according to the drive signal applied to the electrode layer. The method of claim 9, wherein the recess is disposed on the insulating layer to form a closed space by combining the insulating layer and the membrane, and the membrane is disposed between the calcium-containing thin film layer and the insulating layer to form the closed space. A humidity measuring device further comprising a base layer defining a double layer consisting of the base layer and the calcium-containing thin film layer. The method of claim 9, wherein a plurality of the humidity sensor modules are aligned on the substrate to form a CMUT humidity sensor array, and the relative humidity is measured simultaneously and individually from each humidity sensor module constituting the CMUT humidity sensor array. Device. The method of claim 8, wherein the frequency detector is:
A signal detection unit electrically connected to the humidity sensor module to detect the output signal; and
A humidity measuring device including a resonance unit that detects a resonance frequency between the output signal and the drive signal. The humidity measuring device of claim 12, wherein the signal detection unit includes an oscillator including an amplifier for detecting and amplifying the output signal, and a filter for removing noise from the amplified output signal. The method of claim 12, wherein the resonator unit,
an operation unit that receives the output signal from the signal detection unit, detects an effective output of the output signal, and determines whether the effective output is the maximum effective output;
a frequency detection unit that detects the frequency of the output signal having the maximum effective output as a resonance frequency;
a modulation unit that modulates the frequency of the driving signal and transmits the modulated frequency to the power source; and
Humidity measurement including a control unit that controls the frequency detection unit and the modulation unit to selectively drive the frequency detection unit and the modulation unit depending on whether the effective output is the maximum effective output to modulate the frequency of the driving signal until the resonance frequency is detected. Device. The method of claim 14, wherein the membrane vibration is modeled as an electrical vibration of an equivalent LC circuit having a membrane reactance and a membrane capacitance, and the output signal includes an alternating current signal of the equivalent LC circuit, and the effective output is the alternating current signal. A humidity measuring device that includes any one of voltage, current, and power. The method of claim 8, wherein the power source applies a direct current voltage to charge energy to the humidity sensor module and an alternating current voltage to the humidity sensor module to generate an overlap voltage by overlapping the direct current voltage and the alternating current voltage. A humidity measuring device including an alternating current generator that generates the membrane vibration. The humidity measuring device according to claim 16, wherein the alternating current generator is provided integrally with the frequency detector. The method of claim 8, wherein the humidity detector is:
A reference frequency, which is a resonance frequency corresponding to the resonance frequency of the reference membrane, is obtained with a reference humidity sensor module having a reference membrane having the same configuration as the membrane having the calcium-containing thin film layer in a plurality of known sample humidity environments, and the sample a correlation calculation unit that obtains a frequency-humidity criterion, which is a correlation between humidity and the reference frequency;
a search frequency storage unit that retrieves a resonance frequency corresponding to the resonance frequency of the membrane detected by the frequency detector and stores it as a search frequency; and
A humidity measuring device comprising a humidity calculation unit that calculates the sample humidity corresponding to the search frequency according to the frequency-humidity standard and determines the relative humidity. The humidity measuring device of claim 18, wherein the frequency-humidity reference includes a linear function obtained by statistically processing a plurality of ordered pairs regarding the reference frequency and the sample humidity. The insulating layer, which has a thin film layer containing calcium ions and is in contact with the membrane to absorb atmospheric moisture and has a closed space, functions as a capacitor and applies alternating voltage to a humidity sensor module that operates as a micro-processed ultrasonic transducer to vibrate the membrane. generate;
detecting an alternating current output signal, which is an electrical equivalent signal related to vibration of the membrane, through an electric circuit connected to the humidity sensor module;
detecting a resonance frequency of the output signal by modulating the frequency of the driving signal applied to the humidity sensor module to detect the maximum effective signal of the output signal; and
A humidity measurement method that detects the humidity corresponding to the resonance frequency as the relative humidity of the atmosphere from a frequency-humidity standard.

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