TWI436056B - A composite thin film micro gas sensor - Google Patents

Description

Micro-gas sensing device for composite film

A micro-gas sensing device for a composite film, in particular, a micro-gas sensing device for a composite film that utilizes a change in resistance or capacitance to measure a change in molecular concentration of a gas to be measured.

At normal temperature and pressure, carbon monoxide is a colorless, odorless, odorless, non-irritating gas. But it is a toxic gas that can enter the body without any stimulation, and slowly cause poisoning. Its chemical structure is CO, which is an invisible killer in the environment. Since the binding force of carbon monoxide and hemoglobin is 240 times larger than that of oxygen, when carbon monoxide enters the blood circulation system, it will replace oxygen and bind to hemoglobin in a large amount, thereby inhibiting the release of oxygen in the blood, thereby causing headache, tinnitus, and vomiting. Different symptoms such as lower blood pressure. If the degree of carbon monoxide poisoning is severe but not fatal, the patient may cause dizziness, loss of memory or symptoms of visual and mental disorders during the recovery process. If the damage is severe to the brain, it will not fully recover.

Gas sensing devices are used to detect the presence and content of specific gases (such as carbon monoxide, sulfur dioxide, and ethanol) in the environment or process. However, the gas sensors used in the industry are not sensitive at room temperature and the response speed is not fast enough. A hot plate must be installed on the sensing element and heated to above 300 °C for effective use. However, this not only complicates the construction of the conventional gas sensor, but also increases the operating cost and requires operation in a high temperature and energized environment. Therefore, there are safety concerns in practical applications.

Therefore, how to design a component that is simple to prepare and can react with the gas to be detected at normal temperature, and when applied to a gas sensing device, can effectively improve sensitivity and detection efficiency, and currently exists in the industry. a huge demand and improvement between.

Because gas sensors currently have poor sensitivity, fast response time, excessive volume, high cost, and the need to work at high temperatures, there is no economic benefit in production.

Therefore, the main object of the present invention is to provide a micro gas sensing device capable of improving sensitivity, accelerating reaction time, greatly reducing volume, reducing cost, and operating at a normal temperature.

For the purpose of the above, a micro gas sensing device and a structure thereof for a composite film disclosed in the present invention can be classified into two types: a resistive type and a capacitive type.

The micro gas sensing device of the resistive composite film is used for detecting the change of the molecular concentration of the gas to be tested by using the change amount of the electric resistance, and the device comprises: a composite film for adsorbing the gas to be tested. a resistive micro gas sensor, wherein a composite film is dripped on the resistive micro gas sensor, and a resistance change of the resistive micro gas sensor is used to detect a molecular concentration change of the gas to be tested; The amplifying circuit is electrically connected to the resistive micro gas sensor to convert the resistance change of the resistive micro gas sensor into a voltage change to obtain a large variation.

The micro-gas sensing device of the capacitive composite film is used to detect the change of the molecular concentration of the gas to be tested by using the variation of the capacitance. The device comprises: a composite film, which is a molecule for adsorbing the gas to be tested. a capacitive micro gas sensor, the composite film is dripped on the capacitive micro gas sensor, and the capacitance change of the capacitive micro gas sensor is used to detect the molecular concentration change of the gas to be tested; The circuit is electrically connected to the capacitive micro gas sensor to convert the capacitance change of the capacitive micro gas sensor into a frequency signal readout.

Detailed features and implementations of the present invention are described in detail in the embodiments below.

Please refer to FIG. 1 , which is a circuit diagram of the micro gas sensing device of the resistive composite film of the present invention. The resistive composite film micro gas sensing device 1 is configured to detect the molecular concentration variation of the gas to be tested by using the change amount of the electric resistance, and the device comprises: a composite film 11 for adsorbing the gas to be tested. Molecule, the composite film 11 is a film produced by mixing cerium oxide (SnO ₂ ) and polyaniline (Polyaniline); a micro gas sensor, which is a resistive micro gas sensor 12, The composite film 11 is dropped on the resistive micro gas sensor 12, and the change in the molecular concentration of the gas to be tested is detected by the resistance change of the resistive micro gas sensor 12, and the resistive micro gas sensor is used. The 12-series is a variable resistor; a conversion circuit according to the resistive micro-gas sensor, the conversion circuit is an amplifying circuit 13, the amplifying circuit 13 is electrically connected to the resistive micro-gas sensor 12, and the resistive micro-gas sensing is performed. The change in resistance of the device 12 is converted into a voltage change to obtain a large amount of change. The amplifying circuit 13 has a first inverting amplifying circuit 131 having an operational amplifier OP1, an input resistor R1 and a feedback variable resistor Rs. The output voltage of the first inverting circuit 131 will follow The feedback of the variable resistor Rs is changed; a second inverting circuit 132 has an operational amplifier OP2, an input resistor R2 and a feedback resistor R3, and the output voltage of the second inverting circuit 132 is The differential amplifier circuit 133 has an operational amplifier OP3, two input resistors R4 and R5, a feedback resistor R6 and a grounding resistor R7. The differential amplifier circuit is used for the reference voltage of the first inverting circuit 131. 133 integrates the two output voltages of the first inverse amplification circuit 131 and the second inverse amplification circuit 132 to amplify and output.

Referring to FIG. 1 and FIG. 2, FIG. 2 is a schematic structural view of a micro gas sensing device of the resistive composite film of the present invention. The resistive composite film micro gas sensing device structure 2 is fabricated by using a standard complementary MOS process, and is disposed on an insulating substrate 21, and the bottom-up structure is: an oxide layer 22, It is located above the insulating substrate 21, and the oxide layer 22 has a slightly concave structure. The recessed portion of the concave structure is dripped with a composite film 11; a plurality of polycrystalline germanium layers 221 are located in the bottom of the concave structure of the oxide layer 22. , the arrangement is even or odd, the polysilicon layer 221 has a slightly rectangular structure; the second protective layer 23 is located on the top left and right sides of the concave structure of the oxide layer 22; and an amplifying circuit structure 24 is located in the oxidation The bottom right side of the concave structure of the layer 22, the bottom-up structure is: the two connection layers 241 are buried above the inner portion of the insulating substrate 21; the two conductive layers 242 are located above the two connection layers 241; The metal layer 243 is located above the two-conducting layer 242; and a polysilicon layer 244 is located between the two-conducting layer 242 and the two-metal layer 243.

Please refer to FIG. 3, which is a circuit diagram of the micro gas sensing device of the capacitive composite film of the present invention. The micro-gas sensing device 3 of the capacitive composite film is used to detect the change of the molecular concentration of the gas to be tested by using the variation of the capacitance. The device comprises: a composite film 31 for adsorbing the gas to be tested. Molecule, the composite film 31 is a film produced by mixing cerium oxide (SnO ₂ ) and polyaniline (Polyaniline); a micro gas sensor, which is a capacitive micro gas sensor 32, The composite film 31 is dropped on the capacitive micro gas sensor 32, and the capacitance change of the gas to be tested is detected by the capacitance change of the capacitive micro gas sensor 32, and the capacitive micro gas sensor is used. The 32-series is a variable capacitor; a conversion circuit, according to the above-mentioned capacitive gas sensor, the conversion circuit is an oscillating circuit 33, and the oscillating circuit 33 is electrically connected to the capacitive micro-gas sensor 32, and the capacitive micro-gas sensing is performed. The change in capacitance of the device 32 is converted into a frequency signal readout. The oscillating circuit 33 has five inverters Inverter1, Inverter2, Inverter3, Inverter4 and Inverter5, four capacitors C1, C2, C3 and C4 and a variable capacitor Cs.

Please refer to FIG. 3 and FIG. 4 , which are schematic structural diagrams of the micro gas sensing device of the capacitive composite film of the present invention. The micro-gas sensing device structure 4 of the capacitive composite film is fabricated by using a standard complementary MOS process, and is disposed on an insulating substrate 41. The bottom-up structure is: an oxide layer 42, It is located above the insulating substrate 41. The oxide layer 42 has a slightly concave structure. The recessed portion of the concave structure is dripped with a composite film 31. The plurality of first electrode structures 43 are located at the bottom of the concave structure of the oxide layer 42. The surface is arranged in an even or odd arrangement. The first electrode structure 43 has a rectangular structure. The plurality of second electrode structures 44 are located at the bottom surface of the concave structure of the oxide layer 42 and are arranged in an even number or An odd number arrangement, but when the plurality of first electrode structures 43 are evenly arranged, the second electrode structure 44 must be oddly arranged, interspersed between the plurality of first electrode structures 43, and vice versa, the second electrode structure 44 has a rectangular structure; a plurality of protective layers 45 are located in the plurality of first electrode structures 43 and a plurality of Above the second electrode structure 44; an oscillating circuit structure 46 is located on the right side of the concave structure of the oxide layer 42, and the bottom-up structure is: a four-connection layer 461, which is buried in the insulating substrate 21. Above the inner portion, the four connection layers 461 are arranged from left to right: a left n-type connection layer 4611, a right n-type connection layer 4612, a left p-type connection layer 4613, and a right p-type connection layer 4614; Located at the middle of the left and right n-type connection layers and the left and right p-type connection layers; a plurality of conduction layers 463 are located above the four connection layers 461 and the two polysilicon layers 462, and the right n-type connection layer 4612 and The conductive layers above the p-type connection layer 4613 are connected to each other.

The above-mentioned preferred embodiments of the present invention are disclosed above, but are not intended to limit the present invention. Any modification and refinement of those skilled in the art without departing from the spirit and scope of the present invention are the scope of protection of the present invention. Therefore, the scope of patent protection of the present invention is defined by the scope of the patent application attached to the specification.

1‧‧‧Resistive composite film micro gas sensing device

11‧‧‧Composite film

12‧‧‧Resistive micro gas sensor

13‧‧‧Amplification circuit

131‧‧‧First reverse amplification circuit

OP1‧‧‧Operational Amplifier

R1‧‧‧ input resistance

Rs‧‧‧ feedback variable resistor

132‧‧‧second reverse amplification circuit

OP2‧‧‧Operational Amplifier

R2‧‧‧ input resistance

R3‧‧‧Responsive resistor

133‧‧‧Differential Amplifying Circuit

OP3‧‧‧Operational Amplifier

R4‧‧‧ input resistance

R5‧‧‧ input resistance

R6‧‧‧Responsive resistor

R7‧‧‧ Grounding resistor

2‧‧‧Resistive composite film micro gas sensing device structure

21‧‧‧Insert substrate

22‧‧‧Oxide layer

221‧‧‧ Polycrystalline layer

23‧‧‧Protective layer

24‧‧‧Amplification circuit structure

241‧‧‧Connection layer

242‧‧‧ conduction layer

243‧‧‧metal layer

244‧‧‧Polysilicon layer

3‧‧‧Micro-gas sensing device for capacitive composite film

31‧‧‧Composite film

32‧‧‧Capacitive micro gas sensor

33‧‧‧ oscillating circuit

Inverter1‧‧‧Inverter

Inverter2‧‧‧Inverter

Inverter3‧‧‧Inverter

Inverter4‧‧‧Inverter

Inverter5‧‧‧Inverter

C1‧‧‧ capacitor

C2‧‧‧ capacitor

C3‧‧‧ capacitor

C4‧‧‧ capacitor

Cs‧‧‧Variable Capacitor

4‧‧‧Micro-gas sensing device structure of capacitive composite film

41‧‧‧Insert substrate

42‧‧‧Oxide layer

43‧‧‧First electrode structure

44‧‧‧Second electrode structure

45‧‧‧Protective layer

46‧‧‧ oscillating circuit structure

461‧‧‧Connection layer

4611‧‧‧Left n-type connection layer

4612‧‧‧Right n-type connection layer

4613‧‧‧Left p-type connection layer

4614‧‧‧Right p-type connection layer

462‧‧‧Polysilicon layer

463‧‧‧ conduction layer

1 is a circuit diagram of a micro gas sensing device of a resistive composite film of the present invention.

2 is a schematic structural view of a micro gas sensing device of the resistive composite film of the present invention.

FIG. 3 is a circuit diagram of the micro gas sensing device of the capacitive composite film of the present invention.

FIG. 4 is a schematic structural view of a micro gas sensing device of the capacitive composite film of the present invention.

1‧‧‧Resistive composite film micro gas sensing device

11‧‧‧Composite film

12‧‧‧Resistive micro gas sensor

13‧‧‧Amplification circuit

131‧‧‧First reverse amplification circuit

OP1‧‧‧Operational Amplifier

R1‧‧‧ input resistance

Rs‧‧‧ feedback variable resistor

132‧‧‧second reverse amplification circuit

OP2‧‧‧Operational Amplifier

R2‧‧‧ input resistance

R3‧‧‧Responsive resistor

133‧‧‧Differential Amplifying Circuit

OP3‧‧‧Operational Amplifier

R4‧‧‧ input resistance

R5‧‧‧ input resistance

R6‧‧‧Responsive resistor

R7‧‧‧ Grounding resistor

Claims (9)

A micro-gas sensing device for a composite film, the device comprising: a composite film, which is a film formed by mixing tin dioxide and polyaniline, is a molecule for adsorbing a gas to be tested; a micro gas sensor comprising an oxide layer disposed on an insulating substrate, the oxide layer having a concave structure, the composite film being dripped in a notch of the concave structure of the oxide layer, using the micro gas a sensor for detecting a change in the molecular concentration of the gas to be tested; a conversion circuit disposed in the oxide layer on a side of the notch of the concave structure, electrically connected to the micro gas sensor, The amount of change in the molecular concentration of the gas to be measured measured by the micro gas sensor is converted into a signal output. The micro gas sensing device of the composite film according to claim 1, wherein the micro gas sensor is a resistive micro gas sensor; the conversion circuit of the resistive micro gas sensor is an amplifying circuit Converting the molecular concentration variation of the gas to be measured measured by the micro gas sensor into a voltage signal output; the amplifying circuit has: a first inverse amplifying circuit having an operational amplifier, an input resistor, and a return a variable resistor, the output voltage of the first inverting circuit is changed according to a change of the feedback variable resistor; and a second inverting circuit having an operational amplifier, an input resistor and a feedback resistor, The output voltage of the second inverting amplifier circuit is used as a reference voltage of the first inverting amplifying circuit; a differential amplifying circuit having an operational amplifier, a two-input resistor, a feedback resistor and a grounding resistor, The differential amplifying circuit integrates and amplifies the two output voltages of the first inverse amplifying circuit and the second inverting amplifying circuit. A micro gas sensing device for a composite film according to claim 2, The resistive micro gas sensor further comprises: a plurality of polycrystalline germanium layers located in the bottom of the oxide layer; and a second protective layer located above the left and right sides of the oxide layer. The micro-gas sensing device of the composite film according to claim 1, wherein the plurality of polycrystalline germanium layers have a slightly rectangular structure. The micro gas sensing device of the composite film according to claim 1, wherein the micro gas sensor is a capacitive micro gas sensor, and the capacitive micro gas sensor is a variable capacitor; The capacitive micro gas sensor utilizes a change in capacitance to detect a change in the molecular concentration of the gas to be measured. The micro gas sensing device of the composite film according to claim 5, wherein the conversion circuit is an oscillating circuit, and the molecular concentration variation of the gas to be measured measured by the micro gas sensor is converted into a frequency. Signal output; the oscillating circuit comprises: a five-inverter, a four-capacitor and a variable capacitor. The micro-gas sensing device of the composite film according to claim 5, wherein the capacitive micro gas sensor further comprises: a plurality of first electrode structures located at a bottom surface of the oxide layer, arranged in a manner An even number or an odd number arrangement; a plurality of second electrode structures are located at the bottom surface of the oxide layer, arranged in an even or odd arrangement, interspersed between the plurality of first electrode structures; and the plurality of protective layers are located in the plural Above the first electrode structure and the plurality of second electrode structures. The micro-gas sensing device of the composite film according to claim 7, wherein the first electrode structure has a rectangular structure. The micro-gas sensing device of the composite film according to claim 7, wherein the second electrode structure has a rectangular structure.