CN109239137B - Miniature methane sensor and methane detection method - Google Patents
Miniature methane sensor and methane detection method Download PDFInfo
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- CN109239137B CN109239137B CN201811084814.2A CN201811084814A CN109239137B CN 109239137 B CN109239137 B CN 109239137B CN 201811084814 A CN201811084814 A CN 201811084814A CN 109239137 B CN109239137 B CN 109239137B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
- G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
- G01N27/14—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of an electrically-heated body in dependence upon change of temperature
Abstract
a miniature methane sensor and a methane detection method are suitable for methane detection and further suitable for underground methane detection of coal mines. The methane sensor comprises a heating element and one or more measuring elements, wherein the heating element is independently heated to a high-temperature working state, and the measuring element independent from the heating element directly measures voltage for detecting the concentration of the gas without applying impressed current or voltage. The methane sensor processing technology is compatible with the CMOS technology. The sensor has the advantages of simple structure, low power consumption, high sensitivity, good anti-interference performance and low cost.
Description
Technical Field
The invention relates to a miniature methane sensor and a methane detection method, in particular to a miniature methane sensor and a methane detection method suitable for underground coal mines.
Background
the inventor previously proposed a micro methane sensor based on a single heating element and a method for manufacturing the same (ZL201410605995.4), wherein a measuring element needs to apply current when in operation, and then the voltage on the measuring element can be detected to detect methane and the concentration thereof. This requires additional circuitry to provide the required current, which is complex; some power needs to be consumed to provide current excitation. Moreover, due to the difference between different measuring elements, different voltages will be generated when the same current is applied, and the consistency is poor, which is inconvenient for measurement and batch calibration. In addition, the heating element is not favorable for applying an alternating current signal, and even if the alternating current heating signal is applied, the measuring element cannot directly measure and obtain the abundant alternating current sensing signals of frequency, phase and amplitude.
Disclosure of Invention
the technical problem is as follows: the invention aims to provide a miniature methane sensor and a methane detection method, which have simple structure and good use effect and are independent of a catalyst, based on a single heating element and a measuring element which is independent of the heating element and can generate voltage and directly measure the voltage.
The technical scheme is as follows: in order to achieve the technical purpose, the miniature methane sensor comprises a support, a heating element and one or more mutually independent measuring elements;
the support comprises a substrate and an isolation silicon oxide layer arranged on the substrate, and a monocrystalline silicon layer is arranged above the isolation silicon oxide layer;
the heating element and each measuring element comprise a U-shaped cantilever and two fixed ends which are arranged on the support side by side; the fixed end of the heating element and the fixed end of the measuring element are independently arranged on the support and are not contacted with each other; the heating element and the measuring element are arranged on the support through two fixed ends respectively, two ends of a U-shaped cantilever I of the heating element and two ends of a U-shaped cantilever II of the measuring element form two-terminal devices with the two fixed ends respectively, and the U-shaped cantilever I of the heating element and the U-shaped cantilever II of the measuring element are suspended in the air; the single crystal silicon layer of the fixed end is formed by processing the single crystal silicon layer on the support and is not connected with the single crystal silicon layer of the rest part of the support outside the fixed end, a doped silicon layer is arranged in the middle of the single crystal silicon layer of the fixed end, a silicon oxide layer can be arranged on the single crystal silicon layer of the fixed end, and the electric leading-out pad metal is contacted with the doped silicon layer of the fixed end through a window of the silicon oxide layer to form ohmic contact;
the U-shaped cantilever I of the heating element is formed by a monocrystalline silicon layer, the monocrystalline silicon layer on the support is processed and connected with the monocrystalline silicon layers at the two fixed ends of the heating element, and the bonding pad metal is led out from the fixed ends to the U-shaped cantilever I;
The silicon structures of the heating element and the measuring element and the silicon structures of the measuring elements are mutually isolated, and the silicon structures of the heating element and the measuring element are also isolated from other top layer monocrystalline silicon layers on the isolation silicon oxide and are not connected; the substrate is silicon or other materials which can be processed by adopting an MEMS (micro-electromechanical system) process;
the two supporting arms of the U-shaped cantilever I of the heating element are both provided with metal layers extending out of the electric leading-out bonding pad metal, and the metal layers on the two supporting arms have the same extending length and do not exceed half of the length of the supporting arms; the widths of two supporting arms of a U-shaped cantilever I of the heating element are the same, and the widths of metal layers extending out of the electric leading-out bonding pad metal on the U-shaped cantilever I are the same and are both narrower than the widths of the supporting arms; the two parallel supporting arms of the U-shaped cantilever II have the same width; a metal layer extending out of the metal of the electric leading-out bonding pad is arranged on one supporting arm of the U-shaped cantilever II, the length of the metal layer does not exceed the length of the supporting arm, and the width of the metal layer is narrower than the width of the supporting arm;
The fixed end is formed by processing a top monocrystalline silicon layer; the top monocrystalline silicon layer is provided with a silicon oxide layer according to the requirement, when the silicon oxide layer is arranged, the silicon oxide layer is provided with electric leading-out pad metal, the electric leading-out pad metal is contacted with the lower monocrystalline silicon layer through the window of the silicon oxide layer, and when the silicon oxide layer is not arranged, the electric leading-out pad metal is directly arranged on the monocrystalline silicon layer on the fixed end; the outline area of the metal of the electrical lead-out pad is smaller than that of the fixed end.
the measuring element is vertically arranged on two sides of the heating element, the U-shaped cantilever of the measuring element is arranged on the upper side and the lower side of the two supporting arms of the heating element, the distance between the outer side of the tail end of the U-shaped cantilever of the measuring element and the outer side of the corresponding supporting arm of the heating element is 2-10 um, and the middle point of the tail end of the U-shaped cantilever of the measuring element is aligned with the end of the metal layer on the supporting arm of the heating element; one measuring element is vertically arranged or two measuring elements are respectively arranged at the upper side and the lower side, when two measuring elements with the same structure are arranged, the two measuring elements are symmetrical relative to the heating element, and the distances between the tail ends of the U-shaped cantilevers of the two measuring elements and the corresponding supporting arms of the heating element are the same;
when the measuring element is placed on the same side or the other side of the heating element, the measuring element and the heating element are aligned from top to bottom and centered along the upper central axis and the lower central axis, and the distance between the outer side of the tail end of the U-shaped cantilever of the measuring element and the outer side of the tail end of the U-shaped cantilever of the heating element is 10um to 100 um.
a methane detection method of a miniature methane sensor comprises the following steps:
the heating element is electrified with direct current or applied with direct voltage, the applied current or voltage is larger, the tail end of the U-shaped cantilever of the heating element is heated to a high temperature of more than 550 ℃, and the measuring element directly measures the voltage at two ends of the heating element without current or voltage; taking the voltage at two fixed ends of the measuring element in a normal environment without methane gas as a reference voltage; when the concentration of methane gas changes, the terminal voltage of two fixed ends of the measuring element changes; and the detection of the methane concentration is realized according to the terminal voltages of the two fixed ends of the measuring element.
a methane detection method of a miniature methane sensor comprises the following steps:
applying alternating current or voltage to the heating element to heat the end of the U-shaped cantilever of the heating element to a high temperature above 550 ℃, and directly measuring voltage signals at two ends of the measuring element without applying current or voltage to the measuring element; when the concentration of methane gas changes, the frequency, the phase and the amplitude of voltage signals at two ends of two fixed ends of the measuring element change along with the change of the concentration of methane gas, and the sensing of the concentration of methane gas is realized by detecting the change of the frequency, the phase and the amplitude of the voltage signals at the two fixed ends of the measuring element; namely, the two-end voltage signals of the two fixed ends of the measuring element without methane are used as reference signals, and the concentration of methane is obtained according to the comparison between the two-end voltage signals of the measuring element and the reference signals, namely, the methane concentration is obtained according to the frequency difference, the phase difference and the amplitude difference of the two-end voltage signals of the measuring element.
a methane detection method of a miniature methane sensor comprises the following steps:
A, B two measuring elements with the same structure are symmetrically arranged on the upper side and the lower side of the heating element respectively, direct current is applied to the heating element, A, B two measuring elements generate different voltages, different voltage differences represent different concentrations, and by taking the voltage difference value of A, B two measuring elements when methane does not exist as reference, the methane concentration is obtained according to the voltage difference value of A, B two measuring elements, and methane sensing is achieved.
a methane detection method of a miniature methane sensor comprises the following steps:
A, B two measuring elements with the same structure are symmetrically arranged on the upper side and the lower side of the heating element respectively, alternating current is applied to the heating element, the difference exists between the frequency, the phase and the amplitude of the voltage of A, B two measuring elements respectively, the difference when methane does not exist is taken as a reference, and the difference of the frequency, the phase and the amplitude of the voltage of A, B two measuring elements respectively represents different methane concentrations, so that methane sensing is realized.
a methane detection method of a miniature methane sensor comprises the following steps:
arranging a single measuring element near the heating element, wherein when currents with the same magnitude, opposite directions and the same action time and interval time are applied to the heating element in a short time, the voltages at two ends of the single measuring element are different, different voltage differences represent different concentrations, and the voltage differences are used as sensitive signals to realize methane sensing; namely, the methane concentration is obtained according to the voltage difference of the measuring element by taking the voltage difference of the measuring element when no methane exists as a reference.
has the advantages that:
1. a catalyst and a catalytic carrier are not used, and the performance of the sensor is not influenced by the catalyst due to the fact that the catalyst and the catalytic carrier are not used, so that the problems of sensitivity reduction, poisoning, activation and the like caused by the reduction of the activity of the catalyst do not exist;
2. the heating element and the measuring element are mutually independent without direct electric connection, and only one heating element needs to be heated to high temperature; the measuring element can generate and output voltage to work without additional current or voltage, and the power consumption of the sensor is reduced.
the advantages are that: the miniature methane sensor based on the single heating element can realize low methane detection without adopting a catalyst, and the miniature methane sensor has the advantages of stable performance and good long-term stability by using silicon as a heating material and a sensing material, and has the defects of poisoning resistance, carbon deposition resistance, activation resistance and the like; the power consumption of the methane sensor is mainly determined by the power consumption of the single heating element, and the measuring element does not consume the power consumption, so that the overall power consumption of the sensor is reduced. The measuring element of the methane sensor can directly generate a voltage signal without external electric excitation, and better reflects methane information.
a heating element and a measuring element of the methane sensor are mutually independent, and the measuring element detects the concentration of methane gas; the heating element and the measuring element are structurally separated, so that no electric connection exists, and the problems that heating cannot be accurately controlled and heating and measuring cannot be simultaneously carried out by using one element as the heating element and the measuring element are solved more effectively. The measuring element does not need extra current excitation, does not consume power, and solves the problem of low power consumption of methane sensing. The measuring element of the invention can directly generate voltage sensing signals, and when alternating current heating signals are applied to the heating element, the measuring element can directly generate sensing signals expressed by frequency, phase and amplitude, thereby providing abundant sensitive signals for methane sensing.
drawings
FIG. 1 is a schematic top view of a micro methane sensor according to the present invention.
FIG. 2 is a sectional view A-A of the fixed ends of the heating element and the measuring element of the present invention.
in the figure: 11-substrate, 12-isolation silicon oxide layer, 13-single crystal silicon layer, 22-bonding pad metal, 23-silicon oxide layer, 100-support, 101-heating element, 102-measuring element, 1001-fixed end, 1012-U-shaped cantilever I, 1022-U-shaped cantilever II
Detailed Description
an embodiment of the invention is further described below with reference to the accompanying drawings:
As shown in fig. 1, the micro methane sensor of the present invention comprises a support 100, a heating element 101, and one or more independent measuring elements 102;
the support 100 comprises a substrate 11 and an isolation silicon oxide layer 12 arranged on the substrate 11, wherein a monocrystalline silicon layer 13 is arranged above the isolation silicon oxide layer 12;
the heating element 101 and each measuring element 102 comprise a U-shaped cantilever arranged side by side on the support 100 and two fixed ends 1001; the fixed end 1001 of the heating element 101 and the fixed end 1001 of the measuring element 102 are independently arranged on the support 100 and are not contacted with each other; the heating element 101 and the measuring element 102 are arranged on the support 100 through two fixed ends 1001 respectively, two ends of a U-shaped cantilever I1012 of the heating element 101 and two ends of a U-shaped cantilever II 1022 of the measuring element 102 form two-terminal devices with the two fixed ends 1001 respectively, and the U-shaped cantilever I1012 of the heating element 101 and the U-shaped cantilever II 1022 of the measuring element 102 are suspended in the air; the monocrystalline silicon layer 13 of the fixing end 1001 is formed by processing the monocrystalline silicon layer 13 on the support 100 and is not connected with the monocrystalline silicon layer 13 on the rest part of the support 100 outside the fixing end, a doped silicon layer 24 is arranged in the middle of the monocrystalline silicon layer 13 of the fixing end 1001, a silicon oxide layer 23 can be arranged on the monocrystalline silicon layer 13 of the fixing end 1001, and the electric leading-out pad metal 22 is contacted with the doped silicon layer 24 of the fixing end 1001 through a window of the silicon oxide layer 23 to form ohmic contact;
The fixing end 1001 is formed by processing a top monocrystalline silicon layer 13; a silicon oxide layer 23 is arranged on the top monocrystalline silicon layer 13 according to the requirement, when the silicon oxide layer 23 is arranged, an electric leading-out bonding pad metal 22 is arranged on the silicon oxide layer 23, the electric leading-out bonding pad metal 22 is contacted with the lower monocrystalline silicon layer 13 through a window of the silicon oxide layer 23, and when the silicon oxide layer 23 is not arranged, the electric leading-out bonding pad metal 22 is directly arranged on the monocrystalline silicon layer 13 on the fixed end 1001; the outline area of the electrical lead-out pad metal 22 is smaller than that of the fixed end 1001;
the U-shaped cantilever I1012 of the heating element 101 is formed by a monocrystalline silicon layer 13, the monocrystalline silicon layer 13 on the support 100 is processed and connected with the monocrystalline silicon layers 13 of the two fixed ends 1001 of the heating element 101, and the bonding pad metal 22 is led out from the fixed ends 1001 to the U-shaped cantilever I1012;
The silicon structures of the heating element 101 and the measuring element 102 and the silicon structures of the measuring elements 102 are isolated from each other, and the silicon structures of the heating element 101 and the measuring element 102 are also isolated from and not connected with other top-layer monocrystalline silicon layers 13 on the isolating silicon oxide 12; the substrate 11 is silicon or other materials which can be processed by adopting an MEMS (micro-electromechanical system) process;
the two supporting arms of the U-shaped cantilever I1012 of the heating element 101 are both provided with metal layers extending out of the electric lead-out pad metal 22, and the metal layers on the two supporting arms have the same extension length and do not exceed half of the length of the supporting arms; the widths of the two supporting arms of the U-shaped cantilever I1012 of the heating element 101 are the same, and the widths of the metal layers extending from the electric leading-out pad metal 22 on the two supporting arms are the same and are both narrower than the widths of the supporting arms; the widths of the two parallel supporting arms of the U-shaped cantilever II 1022 are the same; and a metal layer extending from the electric lead-out pad metal 22 is arranged on one supporting arm of the U-shaped cantilever II 1022, the length of the metal layer does not exceed the length of the supporting arm, and the width of the metal layer is narrower than the width of the supporting arm.
the measuring element 102 is vertically arranged at two sides of the heating element 101, the U-shaped cantilever 1022 of the measuring element 102 is arranged at the upper and lower sides of two supporting arms of the heating element 101, the distance between the outer side of the tail end of the U-shaped cantilever 1022 of the measuring element 102 and the outer side of the corresponding supporting arm of the heating element 101 is 2um to 10um, and the middle point of the tail end of the U-shaped cantilever 1022 of the measuring element 102 is aligned with the end of the metal layer on the supporting arm of the heating element 101; one measuring element 102 is vertically arranged or one measuring element 102 is vertically arranged on each of the upper side and the lower side, when two measuring elements 102 with the same structure are arranged, the two measuring elements 102 are symmetrical relative to the heating element 101, and the distances between the tail ends of the U-shaped cantilevers 1022 of the two measuring elements 102 and the corresponding supporting arms of the heating element 101 are the same;
when the measuring element 102 is placed on the same side or the other side of the heating element 101, the measuring element 102 and the heating element 101 are aligned vertically and centrally along the upper and lower central axes, and the distance between the outer side of the end of the U-shaped cantilever 1022 of the measuring element 102 and the outer side of the end of the U-shaped cantilever 1012 of the heating element 101 is 10um to 100 um.
a methane detection method of a miniature methane sensor comprises the following five methods;
The method (I):
the heating element 101 is electrified with direct current or applied with direct voltage, the applied current or voltage is larger, the tail end of the U-shaped cantilever 1012 of the heating element 101 is heated to a high temperature of more than 550 ℃, and the measuring element 102 directly measures the voltage at the two ends without current or voltage; the voltage across two fixed ends 1001 of the measurement element 102 in a normal environment without methane gas is taken as a reference voltage; when the methane gas concentration changes, the terminal voltages at two fixed ends 1001 of the measuring element 102 change; the detection of the methane concentration is effected on the basis of the terminal voltages of the two fixed ends 1001 of the measuring element 102.
the method (II):
applying alternating current or voltage to the heating element 101 to heat the end of the U-shaped cantilever 1012 of the heating element 101 to a high temperature of 550 ℃ or higher, and directly measuring voltage signals at two ends of the measuring element 102 without applying current or voltage; when the methane gas concentration changes, the frequency, the phase and the amplitude of voltage signals at two ends of two fixed ends 1001 of the measuring element 102 change along with the change of the methane gas concentration, and the methane gas concentration is sensed by detecting the change of the frequency, the phase and the amplitude of the voltage signals at the two fixed ends 1001 of the measuring element 102; namely, the voltage signals at two ends of the two fixed ends 1001 of the measuring element 102 when no methane exists are used as reference signals, and the concentration of methane is obtained according to the comparison between the voltage signals at the two fixed ends 1001 of the measuring element 102 and the reference signals, namely, the concentration of methane is obtained according to the frequency difference, the phase difference and the amplitude difference of the voltage signals at the two fixed ends 1001 of the measuring element 102; the method comprises the steps of measuring voltage data in methane environments with various concentrations in advance, forming a database, comparing the measured voltage data in actual use to obtain current methane concentration data, or calculating the current methane concentration according to a current test value through a calibration value during calibration, a formula obtained through calibration or a fitting formula;
the method (III):
the two measuring elements 102 with the same structure are symmetrically arranged A, B on the upper side and the lower side of the heating element 101 respectively, direct current is applied to the heating element 101, A, B two measuring elements 102 generate different voltages, different voltage differences represent different concentrations, and the methane concentration is obtained according to the voltage difference of A, B two measuring elements 102 by taking the voltage difference of A, B when no methane exists as reference, so that methane sensing is realized;
the method (IV):
a, B two measuring elements 102 with the same structure are symmetrically arranged on the upper side and the lower side of the heating element 101 respectively, alternating current is applied to the heating element 101, the difference exists between the frequency, the phase and the amplitude of the voltage of A, B two measuring elements 102 respectively, the difference when methane does not exist is taken as a reference, and the difference of the frequency, the phase and the amplitude of the voltage of A, B two measuring elements 102 respectively represents different methane concentrations, so that methane sensing is realized.
The method (V):
a single measuring element 102 is arranged near the heating element 101, when currents with the same magnitude, opposite directions and the same action time and interval time are applied to the heating element 101 in a short time, the voltages at two ends of the single measuring element 102 are different correspondingly, different voltage differences represent different concentrations, and methane sensing is realized by taking the voltage differences as sensitive signals; that is, the methane concentration is obtained from the voltage difference of the measuring element 102, with the voltage difference of the measuring element 102 when there is no methane as a reference.
Claims (5)
1. a methane detection method of a miniature methane sensor uses the miniature methane sensor which comprises a support (100), a heating element (101) and one or more mutually independent measuring elements (102);
the support (100) comprises a substrate (11) and an isolation silicon oxide layer (12) arranged on the substrate (11), wherein a monocrystalline silicon layer (13) is arranged above the isolation silicon oxide layer (12);
The heating element (101) and each measuring element (102) comprise a U-shaped cantilever arranged side by side on a support (100) and two fixed ends (1001); the fixed end (1001) of the heating element (101) and the fixed end (1001) of the measuring element (102) are arranged on the support (100) independently and are not contacted with each other; the heating element (101) and the measuring element (102) are arranged on the support (100) through two fixed ends (1001) respectively, two ends of a U-shaped cantilever I (1012) of the heating element (101) and two ends of a U-shaped cantilever II (1022) of the measuring element (102) form two-terminal devices with the two fixed ends (1001) respectively, and the U-shaped cantilever I (1012) of the heating element (101) and the U-shaped cantilever II (1022) of the measuring element (102) are suspended in the air; the monocrystalline silicon layer (13) of the fixing end (1001) is formed by processing the monocrystalline silicon layer (13) on the support (100) and is not connected with the monocrystalline silicon layer (13) on the rest part of the support (100) outside the fixing end, the doped silicon layer (24) is arranged in the middle of the monocrystalline silicon layer (13) of the fixing end (1001), the monocrystalline silicon layer (13) of the fixing end (1001) can be provided with the silicon oxide layer (23), and the electric leading-out pad metal (22) is contacted with the doped silicon layer (24) of the fixing end (1001) through a window of the silicon oxide layer (23) to form ohmic contact;
the U-shaped cantilever I (1012) of the heating element (101) is formed by a monocrystalline silicon layer (13), the monocrystalline silicon layer (13) on the support (100) is processed and connected with the monocrystalline silicon layer (13) of the two fixed ends (1001) of the heating element (101), and the bonding pad metal (22) is led out from the fixed ends (1001) to the U-shaped cantilever I (1012);
the silicon structures of the heating element (101) and the measuring element (102) and the silicon structures of the measuring elements (102) are isolated from each other, and the silicon structures of the heating element (101) and the measuring element (102) are also isolated from and not connected with other top layer single crystal silicon layers (13) on the isolation silicon oxide layer (12); the substrate (11) is silicon or other materials which can be processed by adopting an MEMS (micro-electromechanical system) process;
metal layers extending out of the electric lead-out pad metal (22) are arranged on two supporting arms of a U-shaped cantilever I (1012) of the heating element (101), the extending lengths of the metal layers on the two supporting arms are the same and do not exceed half of the length of the supporting arms, the widths of the two supporting arms of the U-shaped cantilever I (1012) of the heating element (101) are the same, and the widths of the metal layers extending out of the electric lead-out pad metal (22) on the two supporting arms are the same and are both narrower than the widths of the supporting arms; the widths of the two parallel supporting arms of the U-shaped cantilever II (1022) are the same; a metal layer extending from the electric lead-out bonding pad metal (22) is arranged on one supporting arm of the U-shaped cantilever II (1022), the length of the metal layer does not exceed the length of the supporting arm, and the width of the metal layer is narrower than the width of the supporting arm;
The fixed end (1001) is formed by processing a top monocrystalline silicon layer (13); a silicon oxide layer (23) is arranged on the top monocrystalline silicon layer (13) according to the requirement, when the silicon oxide layer (23) is arranged, an electric leading-out bonding pad metal (22) is arranged on the silicon oxide layer (23), the electric leading-out bonding pad metal (22) is contacted with the lower monocrystalline silicon layer (13) through a window of the silicon oxide layer (23), and when the silicon oxide layer (23) is not arranged, the electric leading-out bonding pad metal (22) is directly arranged on the monocrystalline silicon layer (13) on the fixed end (1001); the outline area of the electric leading-out pad metal (22) is smaller than that of the fixed end (1001);
The measuring element (102) is vertically arranged on two sides of the heating element (101), U-shaped cantilevers II (1022) of the measuring element (102) are placed on the upper side and the lower side of two supporting arms of the heating element (101), the distance between the outer side of the tail end of the U-shaped cantilever II (1022) of the measuring element (102) and the outer side of the corresponding supporting arm of the heating element (101) is 2-10 um, and the middle point of the tail end of the U-shaped cantilever II (1022) of the measuring element (102) is aligned with the end of a metal layer on the supporting arm of the heating element (101);
the method is characterized by comprising the following steps:
the method comprises the steps that direct current or direct voltage is applied to a heating element (101), the applied current or voltage is large, the tail end of a U-shaped cantilever I (1012) of the heating element (101) is heated to a high temperature of above 550 ℃, and a measuring element (102) directly measures voltage at two ends of the heating element without applying current or voltage;
Taking the voltage across two fixed ends (1001) of the measuring element (102) in a normal environment without methane gas as a reference voltage; when the concentration of methane gas changes, the voltage of two fixed ends (1001) of the measuring element (102) changes; the detection of the methane concentration is achieved from the terminal voltages of the two fixed ends (1001) of the measuring element (102).
2. a methane detection method of a miniature methane sensor uses the miniature methane sensor which comprises a support (100), a heating element (101) and one or more mutually independent measuring elements (102);
the support (100) comprises a substrate (11) and an isolation silicon oxide layer (12) arranged on the substrate (11), wherein a monocrystalline silicon layer (13) is arranged above the isolation silicon oxide layer (12);
the heating element (101) and each measuring element (102) comprise a U-shaped cantilever arranged side by side on a support (100) and two fixed ends (1001); the fixed end (1001) of the heating element (101) and the fixed end (1001) of the measuring element (102) are arranged on the support (100) independently and are not contacted with each other; the heating element (101) and the measuring element (102) are arranged on the support (100) through two fixed ends (1001) respectively, two ends of a U-shaped cantilever I (1012) of the heating element (101) and two ends of a U-shaped cantilever II (1022) of the measuring element (102) form two-terminal devices with the two fixed ends (1001) respectively, and the U-shaped cantilever I (1012) of the heating element (101) and the U-shaped cantilever II (1022) of the measuring element (102) are suspended in the air; the monocrystalline silicon layer (13) of the fixing end (1001) is formed by processing the monocrystalline silicon layer (13) on the support (100) and is not connected with the monocrystalline silicon layer (13) on the rest part of the support (100) outside the fixing end, the doped silicon layer (24) is arranged in the middle of the monocrystalline silicon layer (13) of the fixing end (1001), the monocrystalline silicon layer (13) of the fixing end (1001) can be provided with the silicon oxide layer (23), and the electric leading-out pad metal (22) is contacted with the doped silicon layer (24) of the fixing end (1001) through a window of the silicon oxide layer (23) to form ohmic contact;
the U-shaped cantilever I (1012) of the heating element (101) is formed by a monocrystalline silicon layer (13), the monocrystalline silicon layer (13) on the support (100) is processed and connected with the monocrystalline silicon layer (13) of the two fixed ends (1001) of the heating element (101), and the bonding pad metal (22) is led out from the fixed ends (1001) to the U-shaped cantilever I (1012);
the silicon structures of the heating element (101) and the measuring element (102) and the silicon structures of the measuring elements (102) are isolated from each other, and the silicon structures of the heating element (101) and the measuring element (102) are also isolated from and not connected with other top layer single crystal silicon layers (13) on the isolation silicon oxide layer (12); the substrate (11) is silicon or other materials which can be processed by adopting an MEMS (micro-electromechanical system) process;
Metal layers extending out of the electric lead-out pad metal (22) are arranged on two supporting arms of a U-shaped cantilever I (1012) of the heating element (101), the extending lengths of the metal layers on the two supporting arms are the same and do not exceed half of the length of the supporting arms, the widths of the two supporting arms of the U-shaped cantilever I (1012) of the heating element (101) are the same, and the widths of the metal layers extending out of the electric lead-out pad metal (22) on the two supporting arms are the same and are both narrower than the widths of the supporting arms; the widths of the two parallel supporting arms of the U-shaped cantilever II (1022) are the same; a metal layer extending from the electric lead-out bonding pad metal (22) is arranged on one supporting arm of the U-shaped cantilever II (1022), the length of the metal layer does not exceed the length of the supporting arm, and the width of the metal layer is narrower than the width of the supporting arm;
the fixed end (1001) is formed by processing a top monocrystalline silicon layer (13); a silicon oxide layer (23) is arranged on the top monocrystalline silicon layer (13) according to the requirement, when the silicon oxide layer (23) is arranged, an electric leading-out bonding pad metal (22) is arranged on the silicon oxide layer (23), the electric leading-out bonding pad metal (22) is contacted with the lower monocrystalline silicon layer (13) through a window of the silicon oxide layer (23), and when the silicon oxide layer (23) is not arranged, the electric leading-out bonding pad metal (22) is directly arranged on the monocrystalline silicon layer (13) on the fixed end (1001); the outline area of the electric leading-out pad metal (22) is smaller than that of the fixed end (1001);
the measuring element (102) is vertically arranged on two sides of the heating element (101), U-shaped cantilevers II (1022) of the measuring element (102) are placed on the upper side and the lower side of two supporting arms of the heating element (101), the distance between the outer side of the tail end of the U-shaped cantilever II (1022) of the measuring element (102) and the outer side of the corresponding supporting arm of the heating element (101) is 2-10 um, and the middle point of the tail end of the U-shaped cantilever II (1022) of the measuring element (102) is aligned with the end of a metal layer on the supporting arm of the heating element (101);
the method is characterized in that:
the heating element (101) applies alternating current or voltage to heat the tail end of the U-shaped cantilever I (1012) of the heating element (101) to a high temperature of more than 550 ℃, and the voltage signals at two ends of the measuring element (102) are directly measured without applying current or voltage; when the concentration of methane gas changes, the frequency, the phase and the amplitude of voltage signals at two ends of two fixed ends (1001) of the measuring element (102) change along with the change, and the sensing of the concentration of methane is realized by detecting the change of the frequency, the phase and the amplitude of the voltage signals at the two fixed ends (1001) of the measuring element (102); namely, the voltage signals at two ends of two fixed ends (1001) of the measuring element (102) when no methane exists are used as reference signals, the concentration of methane is obtained according to the comparison of the voltage signals at two fixed ends (1001) of the measuring element (102) and the reference signals, namely, the methane concentration is obtained according to the frequency difference, the phase difference and the amplitude difference of the voltage signals at two fixed ends (1001) of the measuring element (102).
3. A methane detection method of a miniature methane sensor uses the miniature methane sensor which comprises a support (100), a heating element (101) and one or more mutually independent measuring elements (102);
The support (100) comprises a substrate (11) and an isolation silicon oxide layer (12) arranged on the substrate (11), wherein a monocrystalline silicon layer (13) is arranged above the isolation silicon oxide layer (12);
the heating element (101) and each measuring element (102) comprise a U-shaped cantilever arranged side by side on a support (100) and two fixed ends (1001); the fixed end (1001) of the heating element (101) and the fixed end (1001) of the measuring element (102) are arranged on the support (100) independently and are not contacted with each other; the heating element (101) and the measuring element (102) are arranged on the support (100) through two fixed ends (1001) respectively, two ends of a U-shaped cantilever I (1012) of the heating element (101) and two ends of a U-shaped cantilever II (1022) of the measuring element (102) form two-terminal devices with the two fixed ends (1001) respectively, and the U-shaped cantilever I (1012) of the heating element (101) and the U-shaped cantilever II (1022) of the measuring element (102) are suspended in the air; the monocrystalline silicon layer (13) of the fixing end (1001) is formed by processing the monocrystalline silicon layer (13) on the support (100) and is not connected with the monocrystalline silicon layer (13) on the rest part of the support (100) outside the fixing end, the doped silicon layer (24) is arranged in the middle of the monocrystalline silicon layer (13) of the fixing end (1001), the monocrystalline silicon layer (13) of the fixing end (1001) can be provided with the silicon oxide layer (23), and the electric leading-out pad metal (22) is contacted with the doped silicon layer (24) of the fixing end (1001) through a window of the silicon oxide layer (23) to form ohmic contact;
the U-shaped cantilever I (1012) of the heating element (101) is formed by a monocrystalline silicon layer (13), the monocrystalline silicon layer (13) on the support (100) is processed and connected with the monocrystalline silicon layer (13) of the two fixed ends (1001) of the heating element (101), and the bonding pad metal (22) is led out from the fixed ends (1001) to the U-shaped cantilever I (1012);
the silicon structures of the heating element (101) and the measuring element (102) and the silicon structures of the measuring elements (102) are isolated from each other, and the silicon structures of the heating element (101) and the measuring element (102) are also isolated from and not connected with other top layer single crystal silicon layers (13) on the isolation silicon oxide layer (12); the substrate (11) is silicon or other materials which can be processed by adopting an MEMS (micro-electromechanical system) process;
metal layers extending out of the electric lead-out pad metal (22) are arranged on two supporting arms of a U-shaped cantilever I (1012) of the heating element (101), the extending lengths of the metal layers on the two supporting arms are the same and do not exceed half of the length of the supporting arms, the widths of the two supporting arms of the U-shaped cantilever I (1012) of the heating element (101) are the same, and the widths of the metal layers extending out of the electric lead-out pad metal (22) on the two supporting arms are the same and are both narrower than the widths of the supporting arms; the widths of the two parallel supporting arms of the U-shaped cantilever II (1022) are the same; a metal layer extending from the electric lead-out bonding pad metal (22) is arranged on one supporting arm of the U-shaped cantilever II (1022), the length of the metal layer does not exceed the length of the supporting arm, and the width of the metal layer is narrower than the width of the supporting arm;
the fixed end (1001) is formed by processing a top monocrystalline silicon layer (13); a silicon oxide layer (23) is arranged on the top monocrystalline silicon layer (13) according to the requirement, when the silicon oxide layer (23) is arranged, an electric leading-out bonding pad metal (22) is arranged on the silicon oxide layer (23), the electric leading-out bonding pad metal (22) is contacted with the lower monocrystalline silicon layer (13) through a window of the silicon oxide layer (23), and when the silicon oxide layer (23) is not arranged, the electric leading-out bonding pad metal (22) is directly arranged on the monocrystalline silicon layer (13) on the fixed end (1001); the outline area of the electric leading-out pad metal (22) is smaller than that of the fixed end (1001);
The measuring element (102) is vertically arranged on two sides of the heating element (101), U-shaped cantilevers II (1022) of the measuring element (102) are placed on the upper side and the lower side of two supporting arms of the heating element (101), the distance between the outer side of the tail end of the U-shaped cantilever II (1022) of the measuring element (102) and the outer side of the corresponding supporting arm of the heating element (101) is 2-10 um, and the middle point of the tail end of the U-shaped cantilever II (1022) of the measuring element (102) is aligned with the end of a metal layer on the supporting arm of the heating element (101);
The method is characterized in that:
A, B two measuring elements (102) are respectively arranged on the upper side and the lower side of the heating element (101), direct current is applied to the heating element (101), A, B two measuring elements (102) generate different voltages, different voltage differences represent different concentrations, and the methane concentration is obtained according to the voltage difference of A, B two measuring elements (102) by taking the voltage difference of A, B two measuring elements (102) when no methane exists as reference, so that methane sensing is realized.
4. a methane detection method of a miniature methane sensor uses the miniature methane sensor which comprises a support (100), a heating element (101) and one or more mutually independent measuring elements (102);
the support (100) comprises a substrate (11) and an isolation silicon oxide layer (12) arranged on the substrate (11), wherein a monocrystalline silicon layer (13) is arranged above the isolation silicon oxide layer (12);
the heating element (101) and each measuring element (102) comprise a U-shaped cantilever arranged side by side on a support (100) and two fixed ends (1001); the fixed end (1001) of the heating element (101) and the fixed end (1001) of the measuring element (102) are arranged on the support (100) independently and are not contacted with each other; the heating element (101) and the measuring element (102) are arranged on the support (100) through two fixed ends (1001) respectively, two ends of a U-shaped cantilever I (1012) of the heating element (101) and two ends of a U-shaped cantilever II (1022) of the measuring element (102) form two-terminal devices with the two fixed ends (1001) respectively, and the U-shaped cantilever I (1012) of the heating element (101) and the U-shaped cantilever II (1022) of the measuring element (102) are suspended in the air; the monocrystalline silicon layer (13) of the fixing end (1001) is formed by processing the monocrystalline silicon layer (13) on the support (100) and is not connected with the monocrystalline silicon layer (13) on the rest part of the support (100) outside the fixing end, the doped silicon layer (24) is arranged in the middle of the monocrystalline silicon layer (13) of the fixing end (1001), the monocrystalline silicon layer (13) of the fixing end (1001) can be provided with the silicon oxide layer (23), and the electric leading-out pad metal (22) is contacted with the doped silicon layer (24) of the fixing end (1001) through a window of the silicon oxide layer (23) to form ohmic contact;
The U-shaped cantilever I (1012) of the heating element (101) is formed by a monocrystalline silicon layer (13), the monocrystalline silicon layer (13) on the support (100) is processed and connected with the monocrystalline silicon layer (13) of the two fixed ends (1001) of the heating element (101), and the bonding pad metal (22) is led out from the fixed ends (1001) to the U-shaped cantilever I (1012);
The silicon structures of the heating element (101) and the measuring element (102) and the silicon structures of the measuring elements (102) are isolated from each other, and the silicon structures of the heating element (101) and the measuring element (102) are also isolated from and not connected with other top layer single crystal silicon layers (13) on the isolation silicon oxide layer (12); the substrate (11) is silicon or other materials which can be processed by adopting an MEMS (micro-electromechanical system) process;
metal layers extending out of the electric lead-out pad metal (22) are arranged on two supporting arms of a U-shaped cantilever I (1012) of the heating element (101), the extending lengths of the metal layers on the two supporting arms are the same and do not exceed half of the length of the supporting arms, the widths of the two supporting arms of the U-shaped cantilever I (1012) of the heating element (101) are the same, and the widths of the metal layers extending out of the electric lead-out pad metal (22) on the two supporting arms are the same and are both narrower than the widths of the supporting arms; the widths of the two parallel supporting arms of the U-shaped cantilever II (1022) are the same; a metal layer extending from the electric lead-out bonding pad metal (22) is arranged on one supporting arm of the U-shaped cantilever II (1022), the length of the metal layer does not exceed the length of the supporting arm, and the width of the metal layer is narrower than the width of the supporting arm;
the fixed end (1001) is formed by processing a top monocrystalline silicon layer (13); a silicon oxide layer (23) is arranged on the top monocrystalline silicon layer (13) according to the requirement, when the silicon oxide layer (23) is arranged, an electric leading-out bonding pad metal (22) is arranged on the silicon oxide layer (23), the electric leading-out bonding pad metal (22) is contacted with the lower monocrystalline silicon layer (13) through a window of the silicon oxide layer (23), and when the silicon oxide layer (23) is not arranged, the electric leading-out bonding pad metal (22) is directly arranged on the monocrystalline silicon layer (13) on the fixed end (1001); the outline area of the electric leading-out pad metal (22) is smaller than that of the fixed end (1001);
the measuring element (102) is vertically arranged on two sides of the heating element (101), U-shaped cantilevers II (1022) of the measuring element (102) are placed on the upper side and the lower side of two supporting arms of the heating element (101), the distance between the outer side of the tail end of the U-shaped cantilever II (1022) of the measuring element (102) and the outer side of the corresponding supporting arm of the heating element (101) is 2-10 um, and the middle point of the tail end of the U-shaped cantilever II (1022) of the measuring element (102) is aligned with the end of a metal layer on the supporting arm of the heating element (101);
the method is characterized in that:
a, B two measuring elements (102) are respectively arranged on the upper side and the lower side of the heating element (101), alternating current is applied to the heating element (101), the difference exists between the frequency, the phase and the amplitude of the voltage of A, B two measuring elements (102), the difference when methane does not exist is taken as a reference, the difference of the frequency, the phase and the amplitude of the voltage of A, B two measuring elements (102) is respectively used for representing different methane concentrations, and therefore methane sensing is achieved.
5. A methane detection method of a miniature methane sensor uses the miniature methane sensor which comprises a support (100), a heating element (101) and one or more mutually independent measuring elements (102);
the support (100) comprises a substrate (11) and an isolation silicon oxide layer (12) arranged on the substrate (11), wherein a monocrystalline silicon layer (13) is arranged above the isolation silicon oxide layer (12);
The heating element (101) and each measuring element (102) comprise a U-shaped cantilever arranged side by side on a support (100) and two fixed ends (1001); the fixed end (1001) of the heating element (101) and the fixed end (1001) of the measuring element (102) are arranged on the support (100) independently and are not contacted with each other; the heating element (101) and the measuring element (102) are arranged on the support (100) through two fixed ends (1001) respectively, two ends of a U-shaped cantilever I (1012) of the heating element (101) and two ends of a U-shaped cantilever II (1022) of the measuring element (102) form two-terminal devices with the two fixed ends (1001) respectively, and the U-shaped cantilever I (1012) of the heating element (101) and the U-shaped cantilever II (1022) of the measuring element (102) are suspended in the air; the monocrystalline silicon layer (13) of the fixing end (1001) is formed by processing the monocrystalline silicon layer (13) on the support (100) and is not connected with the monocrystalline silicon layer (13) on the rest part of the support (100) outside the fixing end, the doped silicon layer (24) is arranged in the middle of the monocrystalline silicon layer (13) of the fixing end (1001), the monocrystalline silicon layer (13) of the fixing end (1001) can be provided with the silicon oxide layer (23), and the electric leading-out pad metal (22) is contacted with the doped silicon layer (24) of the fixing end (1001) through a window of the silicon oxide layer (23) to form ohmic contact;
the U-shaped cantilever I (1012) of the heating element (101) is formed by a monocrystalline silicon layer (13), the monocrystalline silicon layer (13) on the support (100) is processed and connected with the monocrystalline silicon layer (13) of the two fixed ends (1001) of the heating element (101), and the bonding pad metal (22) is led out from the fixed ends (1001) to the U-shaped cantilever I (1012);
The silicon structures of the heating element (101) and the measuring element (102) and the silicon structures of the measuring elements (102) are isolated from each other, and the silicon structures of the heating element (101) and the measuring element (102) are also isolated from and not connected with other top layer single crystal silicon layers (13) on the isolation silicon oxide layer (12); the substrate (11) is silicon or other materials which can be processed by adopting an MEMS (micro-electromechanical system) process;
Metal layers extending out of the electric lead-out pad metal (22) are arranged on two supporting arms of a U-shaped cantilever I (1012) of the heating element (101), the extending lengths of the metal layers on the two supporting arms are the same and do not exceed half of the length of the supporting arms, the widths of the two supporting arms of the U-shaped cantilever I (1012) of the heating element (101) are the same, and the widths of the metal layers extending out of the electric lead-out pad metal (22) on the two supporting arms are the same and are both narrower than the widths of the supporting arms; the widths of the two parallel supporting arms of the U-shaped cantilever II (1022) are the same; a metal layer extending from the electric lead-out bonding pad metal (22) is arranged on one supporting arm of the U-shaped cantilever II (1022), the length of the metal layer does not exceed the length of the supporting arm, and the width of the metal layer is narrower than the width of the supporting arm;
the fixed end (1001) is formed by processing a top monocrystalline silicon layer (13); a silicon oxide layer (23) is arranged on the top monocrystalline silicon layer (13) according to the requirement, when the silicon oxide layer (23) is arranged, an electric leading-out bonding pad metal (22) is arranged on the silicon oxide layer (23), the electric leading-out bonding pad metal (22) is contacted with the lower monocrystalline silicon layer (13) through a window of the silicon oxide layer (23), and when the silicon oxide layer (23) is not arranged, the electric leading-out bonding pad metal (22) is directly arranged on the monocrystalline silicon layer (13) on the fixed end (1001); the outline area of the electric leading-out pad metal (22) is smaller than that of the fixed end (1001);
the measuring element (102) is vertically arranged on two sides of the heating element (101), U-shaped cantilevers II (1022) of the measuring element (102) are placed on the upper side and the lower side of two supporting arms of the heating element (101), the distance between the outer side of the tail end of the U-shaped cantilever II (1022) of the measuring element (102) and the outer side of the corresponding supporting arm of the heating element (101) is 2-10 um, and the middle point of the tail end of the U-shaped cantilever II (1022) of the measuring element (102) is aligned with the end of a metal layer on the supporting arm of the heating element (101);
The method is characterized in that:
arranging a single measuring element (102) near the heating element (101), wherein when currents with the same magnitude, opposite directions and the same action time and interval time are applied to the heating element (101) in a short time, the voltages at two ends of the single measuring element (102) are different, different voltage differences represent different concentrations, and methane sensing is realized by taking the voltage differences as sensitive signals; namely, the methane concentration is obtained according to the voltage difference of the measuring element (102) by taking the voltage difference of the measuring element (102) when no methane exists as a reference.
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