CN106841319B - A kind of humidity sensor based on MEMS terminal type microwave power detector structure - Google Patents

Abstract

The invention provides a humidity sensor based on a MEMS terminal type microwave power sensor structure, characterized in that the humidity sensor comprises a terminal type microwave power sensor (1) and a humidity sensitive material polyimide (2); wherein, the terminal type microwave power sensor (1) The microwave power sensor (1) includes a first matching resistor (1a1) and a second matching resistor (1a2) connected in parallel, a coplanar waveguide signal line (1b1), and a first matching resistor (1b1) that is separated from the coplanar waveguide signal line (1b1) and is opposite to the first matching resistor. A coplanar waveguide ground wire (1b2), and a second coplanar waveguide ground wire (1b3) which is spaced apart from the coplanar waveguide signal wire (1b1) and oppositely arranged. The present invention realizes the measurement of humidity.

Description

A Humidity Sensor Based on MEMS Terminal Microwave Power Sensor Structure

technical field

The invention relates to a humidity sensor based on a MEMS terminal type microwave power sensor structure, belonging to the technical field of microelectronic devices.

Background technique

Humidity sensors are widely used in meteorological detection, agricultural production, industrial control, medical equipment and other fields. In recent years, the development of humidity sensors has increasingly tended towards miniaturization. The existing miniature humidity sensor types mainly include capacitive, resistive, piezoresistive and MEMS. Polyimide is compatible with CMOS process and has good humidity sensing properties, so it is often used as a sensitive material for humidity sensors. In recent years, my country's Internet of Things has made great progress, and sensors, as a necessary part of the Internet of Things, will also be further promoted and applied. Under such a situation, it is very meaningful to carry out the industrialization of humidity sensors. .

Therefore, the present invention is a humidity sensor based on the MEMS terminal type microwave power sensor structure. When the air humidity changes, the polyimide coated on the matching resistance of the terminal type microwave power sensor can absorb the water vapor molecules in the air. Its dielectric constant changes, so that the impedance of the coplanar waveguide terminal changes and causes mismatch, which leads to the reflection of part of the microwave power, which will change the thermoelectric potential output by the thermopile, so as to realize the measurement of humidity. In contrast, the humidity sensor based on the structure of the MEMS terminal microwave power sensor has the following main characteristics: 1. The humidity sensitive material polyimide on the matching resistance of the MEMS terminal microwave power sensor has the influence on the impedance of the coplanar waveguide terminal. The change is very sensitive, so the sensitivity can be improved; 2. The humidity sensor is a voltage output, which is easier to measure than the output of the capacitance or resistance change of the traditional humidity sensor; 3. The humidity sensor is simple in structure, small in size, and consumes Low power can meet the application requirements of high reliability, miniaturization and low power consumption; Fourth, the fabrication of the humidity sensor does not require special materials and is fully compatible with Si or GaAs processes.

Based on the humidity sensor characteristics of the above MEMS terminal type microwave power sensor structure, it can be clearly seen that the present invention improves the sensitivity compared with the traditional humidity sensor, the output measurement is simpler, and has the advantages of simple structure, small size and low power consumption. Features. The structure of the invention is compatible with Si or GaAs process, has the advantages of high repeatability, low production cost and the like, and satisfies the basic requirements of integrated circuits for devices. Therefore, the humidity sensor based on the MEMS terminal type microwave power sensor structure has good application value and broad market potential.

SUMMARY OF THE INVENTION

Technical problem: The purpose of the present invention is to provide a humidity sensor based on a MEMS terminal type microwave power sensor structure. The humidity sensor uses polyimide with good humidity sensing properties as a humidity sensitive material, and its dielectric constant changes through humidity The change of the coplanar waveguide terminal impedance, and the output thermoelectric potential through the MEMS terminal type microwave power sensor structure, so as to realize the measurement of humidity. Using this structure can achieve high sensitivity, voltage output and low power consumption, and can be compatible with Si or GaAs process, solve many problems in materials, process, reliability, repeatability and production cost, so as to realize the basic The industrial application of the humidity sensor with the MEMS terminal type microwave power sensor structure in the field of industrial automation provides support and guarantee.

Technical solution: In order to solve the above technical problems, the present invention provides a humidity sensor based on a MEMS terminal type microwave power sensor structure, the humidity sensor includes a terminal type microwave power sensor and a humidity sensitive material polyimide; wherein,

The terminal type microwave power sensor includes a first matching resistor and a second matching resistor connected in parallel, a coplanar waveguide signal line, a first coplanar waveguide ground wire that is separated from the coplanar waveguide signal line at a certain distance and opposite to the coplanar waveguide signal line, and is separated from the coplanar waveguide signal line. A second coplanar waveguide ground wire arranged opposite to a certain distance, the first coplanar waveguide ground wire and the second coplanar waveguide ground wire are respectively arranged on both sides of the coplanar waveguide signal line, and the first matching resistor is set on the coplanar waveguide signal line Between the line and the first coplanar waveguide ground line, the second matching resistor is arranged between the coplanar waveguide signal line and the second coplanar waveguide ground line, and is arranged at the opposite position of the coplanar waveguide signal line and is at a certain distance from it. Thermopile; coating a layer of moisture-sensitive material polyimide on the first matching resistor and the second matching resistor;

When the air humidity changes, the humidity-sensitive material polyimide coated on the first matching resistor and the second matching resistor of the terminal microwave power sensor absorbs the water vapor molecules in the air, and its dielectric constant changes, so that the The change in the termination impedance of the coplanar waveguide creates a mismatch, which causes a portion of the microwave power to be reflected.

Beneficial effects: the humidity sensor has a simple structure, the entire sensor is processed by microelectronics, the precision of the structure size can reach a high level, and the volume is greatly reduced, which is conducive to realizing the miniaturization of the sensor; the humidity sensitive material polyimide selected for the humidity sensor Amines are very sensitive to changes in the impedance of coplanar waveguide terminations and have high sensitivity.

In recent years, the development of humidity sensors tends to be more and more miniaturized. The present invention is a humidity sensor based on the structure of a MEMS terminal microwave power sensor. When the air humidity changes, the humidity sensor is on the matching resistance of the terminal microwave power sensor. Coating polyimide with good moisture-sensing properties as a humidity-sensitive material can change the dielectric constant by absorbing water vapor molecules in the air, resulting in a change in the impedance of the coplanar waveguide terminal and a mismatch, which makes a part of the microwave power reflected , which will change the thermoelectric potential output by the thermopile, thus realizing the measurement of humidity. The humidity sensor has high sensitivity and is easy to measure through voltage output, which greatly expands the practical applicability of the humidity sensor. At the same time, the humidity sensor based on the MEMS terminal type microwave power sensor structure has many advantages such as simple structure, small size, low power consumption and high reliability.

Description of drawings

Figure 1 is a humidity sensor based on a MEMS terminal type microwave power sensor structure.

There are: terminal microwave power sensor 1, first matching resistor 1a1, second matching resistor 1a2, coplanar waveguide signal line 1b1, first coplanar waveguide ground wire 1b2, second coplanar waveguide ground wire 1b3, thermopile 1d and moisture sensitive material polyimide 2.

Detailed ways

The present invention will be further described below with reference to the accompanying drawings.

Referring to FIG. 1, the present invention provides a humidity sensor based on a MEMS terminal type microwave power sensor structure, the humidity sensor includes a terminal type microwave power sensor 1 and a humidity sensitive material polyimide 2; wherein,

The terminal-type microwave power sensor 1 includes a first matching resistor 1a1 and a second matching resistor 1a2 connected in parallel, a coplanar waveguide signal line 1b1, a first coplanar waveguide ground wire 1b2 that is spaced from the coplanar waveguide signal line 1b1 at a certain distance and opposite to the coplanar waveguide ground wire 1b2, The second coplanar waveguide ground wire 1b3, which is at a certain distance from and opposite to the coplanar waveguide signal line 1b1, the thermopile 1d, which is arranged at the opposite position of the coplanar waveguide signal line and is at a certain distance from it, and the first coplanar waveguide ground wire 1b2 and the second coplanar waveguide ground line 1b3 are respectively arranged on both sides of the coplanar waveguide signal line 1b1, the first matching resistor 1a1 is arranged between the coplanar waveguide signal line 1b1 and the first coplanar waveguide ground line 1b2, and the second matching resistor 1a2 It is arranged between the coplanar waveguide signal line 1b1 and the second coplanar waveguide ground line 1b3; a layer of humidity sensitive material polyimide 2 is coated on the first matching resistor 1a1 and the second matching resistor 1a2;

When the air humidity changes, the humidity sensitive material polyimide 2 coated on the first matching resistor 1a1 and the second matching resistor 1a2 of the terminal microwave power sensor absorbs the water vapor molecules in the air, and its dielectric constant changes, As a result, the terminal impedance of the coplanar waveguide changes to produce a mismatch, resulting in reflection of part of the microwave power. This will change the thermoelectric potential output by the thermopile 1d, thereby realizing the measurement of humidity.

The humidity sensor based on the structure of the MEMS terminal microwave power sensor in the present invention is different from the traditional humidity sensor. The humidity sensor has the following main characteristics: 1. The humidity sensitive material polyimide on the matching resistance of the MEMS terminal microwave power sensor The amine is very sensitive to the change of the impedance of the coplanar waveguide terminal, so the sensitivity can be improved; 2. The humidity sensor is a voltage output, which is easier to measure than the output of the capacitance or resistance change of the traditional humidity sensor; 3. The structure of the humidity sensor It is simple, small in size and low in power consumption, and can meet the application requirements of high reliability, miniaturization and low power consumption; Fourth, the fabrication of the humidity sensor does not require special materials and is fully compatible with Si or GaAs processes.

The criteria for distinguishing whether it is this structure are as follows:

(a) Adopt MEMS terminal type microwave power sensor structure,

(b) Using polyimide as a humidity-sensitive material to sense humidity changes.

A structure that satisfies the above two conditions should be regarded as the humidity sensor of the structure.

The above descriptions are only the preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above-mentioned embodiments, but any equivalent modifications or changes made by those of ordinary skill in the art based on the contents disclosed in the present invention should be included in the within the scope of protection described in the claims.

Claims (1)

1. A humidity sensor based on an MEMS terminal type microwave power sensor structure is characterized by comprising a terminal type microwave power sensor (1) and a humidity sensitive material polyimide (2); the terminal type microwave power sensor (1) comprises a first matching resistor (1a1) and a second matching resistor (1a2) which are connected in parallel, a coplanar waveguide signal line (1b1), a first coplanar waveguide ground line (1b2) which is arranged opposite to the coplanar waveguide signal line (1b1) at a certain distance, a second coplanar waveguide ground line (1b3) which is arranged opposite to the coplanar waveguide signal line (1b1) at a certain distance, and a thermopile (1d) which is arranged opposite to the coplanar waveguide signal line (1b1) at a certain distance;

a first coplanar waveguide ground line (1b2) and a second coplanar waveguide ground line (1b3) are respectively arranged at two sides of the coplanar waveguide signal line (1b1), a first matching resistor (1a1) is arranged between the coplanar waveguide signal line (1b1) and the first coplanar waveguide ground line (1b2), and a second matching resistor (1a2) is arranged between the coplanar waveguide signal line (1b1) and the second coplanar waveguide ground line (1b 3); coating a layer of humidity sensitive material polyimide (2) on the first matching resistor (1a1) and the second matching resistor (1a 2);

when the humidity of air changes, the humidity sensitive material polyimide (2) coated on the first matching resistor (1a1) and the second matching resistor (1a2) of the terminal type microwave power sensor absorbs the moisture molecules in the air, and the dielectric constant of the humidity sensitive material polyimide changes, so that the terminal impedance of the coplanar waveguide changes to generate mismatch, and a part of microwave power is reflected.