CN110108381A - LC passive wireless sensor that is a kind of while detecting temperature, humidity - Google Patents

Abstract

The invention discloses an LC passive wireless sensor for simultaneously detecting temperature and humidity, which comprises a substrate, on which a fork positive electrode, a fork negative electrode, and an inductance coil are arranged, and the substrate is connected with the fork positive electrode and the fork negative electrode. 1. There is a cavity between the inductance coils; the surface of the negative electrode of the fork is covered with a layer of sensitive medium, the positive electrode of the fork and the negative electrode of the fork form an interdigital structure, and there is an air layer between the positive electrode of the fork and the negative electrode of the fork, forming a detection Capacitance; the inductance coil is located on the periphery of the positive electrode of the fork and the negative electrode of the fork, the tail of the inductance coil is connected with the negative electrode of the fork through a lead wire, and the inductance coil and the detection capacitor constitute the LC sensor resonant circuit unit; Bottom-up oxide layer, bottom passivation layer, top passivation layer, oxide layer on the substrate. The invention can realize simultaneous detection of temperature and humidity, and has the advantages of high sensitivity, fast response, simple structure, small volume, low cost and long service life.

Description

A LC passive wireless sensor for simultaneous detection of temperature and humidity

technical field

The invention relates to an inductance-capacitor resonant circuit (Inductor-Capacitor, LC) passive wireless sensor processed based on Micro-Electro-Mechanical-System (MEMS) technology, especially a kind of sensor capable of remote temperature measurement at the same time A passive wireless sensor for two parameters, and humidity.

Background technique

The Internet of Things (IOT) is a network in which things are connected. It is a highly integrated and comprehensive application of the new generation of information technology, which is of great significance to the new round of industrial transformation and the green, intelligent and sustainable development of the economy and society. wave. Sensors are the most important part of the perception layer of the Internet of Things, and they are the entrances for data collection. Sensor performance will directly affect the accuracy of data in subsequent control systems and information systems, and determine the characteristics and overall performance indicators of the entire Internet of Things system. Moreover, the improvement of sensor performance and the increase in types also play a technical role in the application of smart equipment. and the role of scene upgrades. Passive wireless sensor research belongs to the frontier research field of sensors for Internet of Things applications. LC passive wireless sensor, that is, the sensor resonant circuit is composed of passive components, the structure is simple, the price is cheap, the working temperature is not limited in theory, and the sensor structure design is flexible, the processing materials can be diversified, and the spectrum information of the collected sensor signal It has great potential in functional design and multi-parameter design research. Temperature and humidity are two physical quantities most closely related to people's daily life, and they are also important physical quantities that need to be measured and controlled in scientific experiments and production activities. Especially with the continuous improvement of the demand for intelligence in industry, agriculture and other industries and the development of Internet of Things technology, the demand for environmental temperature and humidity detection has increased sharply. Combined with emerging technologies, independent innovation, and development of temperature and humidity sensors. Passive wireless sensors with independent intellectual property rights are imminent.

Contents of the invention

The object of the present invention is to provide an LC passive wireless sensor for simultaneously detecting temperature and humidity, so as to realize simultaneous detection of temperature and humidity.

To achieve the above object, the technical solution adopted in the present invention is:

An LC passive wireless sensor for detecting temperature and humidity at the same time, comprising a substrate, a positive electrode, a negative electrode, and an inductance coil are arranged above the substrate, and the connection between the substrate and the positive electrode, the negative electrode, and the inductance coil There is a cavity between them; the surface of the negative interdigital electrode is covered with a layer of sensitive medium, the positive interdigital electrode and the negative interdigital electrode form an interdigital structure, and there is an air layer between the positive interdigital electrode and the negative interdigital electrode to form a detection capacitance; The inductance coil is located on the periphery of the positive electrode of the fork and the negative electrode of the fork, the tail of the inductance coil is connected with the negative electrode of the fork through a lead wire, and the inductance coil and the detection capacitor form an LC sensor resonant circuit unit; Bottom-up oxide layer, bottom passivation layer, top passivation layer, oxide layer on substrate.

One end of the lead wire is located in the top passivation layer and fixed through the metal layer connection anchor area.

The lead is a polysilicon layer or an electrode metal layer.

The material of the substrate is silicon.

Both the bottom passivation layer and the top passivation layer are made of silicon nitride.

The material of the sensitive medium is graphene oxide, and the graphene oxide is obtained by selective growth, such as by CVD.

The material of the interdigitated positive electrode, the interdigitated negative electrode and the inductance coil is nickel.

The interdigitated positive electrode, the interdigitated negative electrode and the inductance coil are processed by electroplating process.

The inductance coil is a planar spiral coil.

The principle of the present invention is: the LC passive wireless sensor of the present invention includes a detection capacitor and an inductance coil, wherein the detection capacitor is a sensitive capacitor with an interdigital structure formed by positive and negative electrodes, a sensitive medium, and an air layer. The change will cause the mixed dielectric constant of the capacitor to change, and the temperature change will cause the Q value of the entire LC resonant circuit to change, that is, the changing temperature and humidity will cause the resonant frequency and the maximum impedance of the LC resonant circuit to change, and the detection of LC The resonant frequency and the maximum value of the impedance of the resonant circuit can realize the detection of the ambient temperature and humidity.

Beneficial effects: the LC passive wireless sensor of the present invention can realize simultaneous detection of temperature and humidity, and has the advantages of high sensitivity, fast response, simple structure, small volume, low cost and long life. The sensitive capacitor and inductor coils in the LC structure are MEMS structures with high aspect ratio processed by electroplating process. In terms of the processing cost of its materials, the realization of the manufacturing process, and the size of the sensitive capacitor, the sensor processed by the MEMS processing process has the advantages of low cost, mature manufacturing process, and small device size. The sensitive capacitor and inductor coil are processed by the same electroplating process, which improves the repeatability and consistency of the processing of the LC sensor. The polysilicon layer (or electrode metal layer) is used to close the loop of the inductance coil, which can simplify the steps of MEMS processing of the LC sensor. The substrate is made of silicon, and there is an air cavity between the sensitive capacitor and inductance coil and the silicon substrate. The air cavity can realize electrical isolation and thermal isolation, reduce parasitic capacitance, and reduce electromagnetic loss during the test.

Description of drawings

Fig. 1 is the sectional view of the inductance-capacitance resonant circuit type temperature and humidity sensor based on MEMS technology provided by the present invention;

Fig. 2 is the sectional view of the inductance-capacitance resonant circuit type temperature and humidity sensor based on MEMS technology provided by the present invention;

Fig. 3 is the structural representation of LC passive wireless temperature and humidity sensor system provided by the present invention;

In the figure, 1-substrate, 2-oxide layer, 3-bottom passivation layer, 4-top passivation layer, 5-metal layer connection anchor area, 6-lead, 7-inductance coil, 8-1-fork Electrode, 8-2-interdigitated negative electrode, 9-sensitive medium, 10-cavity, 11-air layer.

Detailed ways

The present invention will be further explained below in conjunction with the accompanying drawings.

As shown in Fig. 1 and Fig. 2, an LC passive wireless sensor for simultaneously detecting temperature and humidity of the present invention includes a substrate 1, which is located at the bottom of the sensor and acts as a base; Electrode 8-1, fork finger negative electrode 8-2, inductance coil 7, there is a cavity 10 between the substrate 1 and fork finger positive electrode 8-1, fork finger negative electrode 8-2, and inductance coil 7; The surface of the electrode 8-2 is covered with a layer of sensitive medium 9, the interdigitated positive electrode 8-1 and the interdigitated negative electrode 8-2 form an interdigitated structure, and there is an air layer between the interdigitated positive electrode 8-1 and the interdigitated negative electrode 8-2 11. Constitute a detection capacitor; the inductance coil 7 is a planar spiral coil, the inductance coil 7 is located on the periphery of the fork positive electrode 8-1 and the fork negative electrode 8-2, and the tail of the inductance coil 7 is connected to the fork negative electrode 8- through the lead wire 6. 2 connected, the inductance coil 7 and the detection capacitor constitute the LC sensor resonant circuit unit; the cavity 10 is surrounded by an oxide layer 2, a bottom passivation layer 3, and a top passivation layer 4, and the oxide layer 2 is located at on substrate 1.

Wherein, one end of the lead wire 6 is located in the top passivation layer 4 and fixed through the metal layer connection anchor region 5 . The lead 6 is a polysilicon layer or an electrode metal layer.

The material of the substrate 1 is silicon.

Both the bottom passivation layer 3 and the top passivation layer 4 are made of silicon nitride.

The sensitive medium 9 is made of graphene oxide. Graphene oxide is the best sensitive dielectric material for wide temperature and humidity sensing. There are a large number of oxygen-containing groups on the surface and edge of graphene oxide, which makes graphene oxide extremely hydrophilic and sensitive to moisture; the oxygen-containing functional groups also make graphene oxide lose its original conductivity. It has the characteristics of a semiconductor or an insulator; temperature changes affect the structure of the oxygen-containing functional group and the strength of the hydrogen bond, thereby affecting the temperature-sensitive characteristics.

The positive interdigitated electrode 8-1, the negative interdigitated electrode 8-2 and the inductance coil 7 are made of nickel.

The LC passive wireless sensor of the present invention is made by the following method: first, the detection capacitor and the inductance coil structure of the passive wireless temperature and humidity sensor are all processed by the MEMS on-chip metal processing technology (such as MetalMumps processing technology or self-designed metal sheet processing technology) ) in the metal structure layer; the controllable preparation of the graphene oxide layer on the interdigital negative electrode can be obtained by selective growth on the interdigital negative electrode, such as CVD growth.

In the present invention, the positive and negative electrodes, the sensitive medium layer and the air layer form an interdigitated detection capacitor, and the detection capacitor is connected in series with the inductance coil to form an LC resonant circuit. The equivalent circuit diagram is shown on the right side of FIG. 3 . When the temperature and humidity change, the impedance and capacitance reactance of the LC resonant tank will change, which will cause the amplitude Re(Z) and resonance frequency f ₀ of the spectral impedance at the detection end (as shown on the left in Figure 3) to change, thus Enables simultaneous passive wireless detection of temperature and humidity.

The above is only a preferred embodiment of the present invention, it should be pointed out that, for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, and these improvements and modifications can also be made. It should be regarded as the protection scope of the present invention.

Claims (10)

1. a kind of LC passive wireless sensor that detects temperature, humidity simultaneously, it is characterized in that: comprise substrate (1), substrate (1) top is provided with interdigital positive electrode (8-1), interdigital negative electrode (8 -2), the inductance coil (7), there is a cavity (10) between the substrate (1) and the interdigital positive electrode (8-1), the interdigital negative electrode (8-2), and the inductance coil (7); The surface of the negative interdigital electrode (8-2) is covered with a layer of sensitive medium (9), the positive interdigital electrode (8-1) and the negative interdigital electrode (8-2) form an interdigital structure, and the positive interdigital electrode (8-2) forms an interdigital structure. 1) There is an air layer (11) between the fork finger negative electrode (8-2) to form a detection capacitor; the inductance coil (7) is located between the fork finger positive electrode (8-1) and the fork finger negative electrode (8-2) ), the tail of the inductance coil (7) is connected to the fork finger negative electrode (8-2) through the lead wire (6), and the inductance coil (7) and the detection capacitor constitute the LC sensor resonant circuit unit; the cavity (10) A bottom-up oxide layer (2), a bottom passivation layer (3) and a top passivation layer (4) are arranged around the substrate, and the oxide layer (2) is located on the substrate (1). 2. The LC passive wireless sensor for simultaneously detecting temperature and humidity according to claim 1, characterized in that: one end of the lead wire (6) is located in the top passivation layer (4), and is connected to the anchor area through a metal layer (5) Fixed. 3. The LC passive wireless sensor for simultaneously detecting temperature and humidity according to claim 1 or 2, characterized in that: the lead (6) is a polysilicon layer or an electrode metal layer. 4. The LC passive wireless sensor for simultaneously detecting temperature and humidity according to claim 1, characterized in that: the material of the substrate (1) is silicon. 5. The LC passive wireless sensor for simultaneously detecting temperature and humidity according to claim 1, characterized in that: the bottom passivation layer (3) and the top passivation layer (4) are made of silicon nitride. 6. The LC passive wireless sensor for simultaneously detecting temperature and humidity according to claim 1, characterized in that: the material of the sensitive medium (9) is graphene oxide. 7. The LC passive wireless sensor for simultaneously detecting temperature and humidity according to claim 6, characterized in that: the graphene oxide is obtained by selective growth. 8. The LC passive wireless sensor for simultaneously detecting temperature and humidity according to claim 1, characterized in that: the interdigitated positive electrode (8-1), the interdigitated negative electrode (8-2) and the inductance coil (7 ) is made of nickel. 9. The LC passive wireless sensor for simultaneously detecting temperature and humidity according to claim 1, characterized in that: the interdigitated positive electrode (8-1), the interdigitated negative electrode (8-2), the inductance coil (7 ) obtained by electroplating process. 10. The LC passive wireless sensor for simultaneously detecting temperature and humidity according to claim 1, characterized in that: the inductance coil (7) is a planar spiral coil.