CN114076784A

CN114076784A - Gas detection device and method for manufacturing same

Info

Publication number: CN114076784A
Application number: CN202011468411.5A
Authority: CN
Inventors: 刘宗; 王文; Y·克夫兰
Original assignee: Hong Kong University of Science and Technology
Current assignee: Hong Kong University of Science and Technology
Priority date: 2020-08-10
Filing date: 2020-12-14
Publication date: 2022-02-22

Abstract

The present invention proposes a gas detection device and a manufacturing method therefor. The gas detection device includes a plurality of detection units and interconnected control lines formed on the same substrate, the plurality of detection units are arranged in rows and columns to form an array, and each detection unit includes a micro-hot plate and associated transistors including circuit unit. Each micro-hot plate includes: a suspended membrane supported on a substrate; a heater arranged on or embedded in the suspended membrane; and a pair of measurement electrodes arranged on the heater. The interconnection control lines are arranged such that each row of detection cells shares the same selection interconnection line, each column of detection cells shares the same signal interconnection line, and the selection interconnection lines for different rows of the array are different from each other, for the array The signal interconnect lines of different columns are different from each other. Using the present invention, addressing and control of each microhotplate in an array can be achieved with reduced components and wiring, and two or more microhotplates can be manipulated independently and simultaneously.

Description

Gas detection device and method for manufacturing same

Technical Field

The present invention relates generally to the field of gas detection, and more particularly to a gas detection device including a micro-hotplate array and transistor circuitry integrated on a substrate and a method for manufacturing the same.

Background

Gas sensors for detecting the composition and component concentration of a mixed gas play an important role in industrial production and environmental monitoring. The gas sensor based on the metal oxide semiconductor functional material has the advantages of stable physical and chemical properties, simple and low-cost manufacturing process, short response and recovery time and the like. When certain metal oxide semiconductors, such as tin oxide (tetravalent) and zinc oxide (divalent), are exposed to a target gas, the gaseous species adsorbed or absorbed by the metal oxide semiconductor cause redox reactions and change the charge carrier concentration in the metal oxide semiconductor, resulting in a change in its conductivity. The magnitude of the conductivity change, i.e. the sensitivity, varies with the temperature. The optimum operating temperature for a metal oxide semiconductor gas sensitive material is typically a few hundred degrees celsius. The optimum operating temperature also varies for different combinations of gas-sensitive semiconductors and their target gases. Temperature control of metal oxide semiconductor gas sensitive materials is typically achieved by a hot plate.

A micro-hotplate is a miniature hotplate device, typically ranging in size from a few micrometers to a few millimeters. In the case of a suspended-film micro-hotplate, the active area of the micro-hotplate is typically a thin film suspended over a substrate. A gap is provided between the film and the substrate to provide thermal insulation and reduce heat conduction losses from the heated film to the substrate. The membrane is supported above the substrate by its peripheral cantilevers connected to anchor points on the substrate. Micro hotplates are typically fabricated by micro-fabrication techniques such as silicon-based micro-fabrication processes.

A micro-hotplate generally has one or more components, at least one of which is a heating element, so that an object or material placed thereon or therein can be heated and the temperature of the object or material controlled. The heating element is typically a resistive heater (also referred to as a micro-heater) based on the joule heating mechanism, i.e. it generates heat energy proportional to the product of its resistance and the square of the current flowing through it. In addition to the heating element, other components may be added, including but not limited to a thermistor, a pair of interdigitated electrodes in contact with the outside world, and the like. The thermistor is a resistor for measuring the temperature of the micro-hotplate, and the resistance thereof changes with the change of the temperature. A pair of interdigitated electrodes is typically placed on the upper surface of the micro-hotplate and coated with a layer of mos functional material to fill the gap between the two electrodes. When a gas or gas mixture is adsorbed on or absorbed by the functional material on the micro-hotplate, the electrical conductivity of the functional material (i.e. the electrical resistance between the two electrodes) changes.

The gas to be detected is usually a mixed gas. However, a single metal oxide semiconductor gas sensor typically has a low specificity, i.e. it is sensitive to multiple gas components in a mixed gas, rather than to only one of them. Therefore, a single metal oxide semiconductor gas sensor often cannot distinguish between individual components in a mixed gas and their concentrations. Therefore, it is necessary to construct an array having a plurality of metal oxide semiconductor gas sensors, each of which exhibits a different sensitivity to a different gas. Thus, by performing a collective analysis of the signals of all the sensors, information about the gas composition and the concentration of the component is extracted.

One prior art technique is an array constructed of discrete components using wire bonding. The peripheral (control and readout) circuitry and micro-hotplate are fabricated separately by micro-machining techniques and then assembled using wire-bonding. Because monolithic integration is not adopted, the scheme in the prior art has the advantages of complex processing, large volume and high cost. At the same time, the scheme has no active matrix addressing circuit, so that each micro-hotplate needs to be accessed independently. Therefore, as the number of micro-hotplates in an array increases, the number of connecting wires will increase rapidly. This implementation limits the number of micro-hotplates that can be accommodated and has the disadvantages of high cost, cumbersome assembly process, large overall system volume, etc. associated with the use of discrete components. For example, "E-Nose Sensing of Low-ppb formaldehydein Gas Mixtures at High Relative for Breath Screening of Lung Cancer? "(ACS Sensors, volume 1, phase 5, page 528-535, 2016; Available: 10.1021/acessensors.6b00008) describes an electronic nose consisting of four discrete micro-hotplates. Four micro-hotplates are suspended over a leadless chip carrier by bonding wires and assembled into an array using other bonding wires. The carrier is soldered to the printed circuit board.

A second prior art is a monolithically integrated micro-hotplate array, without active matrix addressing circuitry. In contrast to the previously mentioned arrays assembled from discrete micro-hotplate components, "micro-hotplate platforms for Chemical sensor research" (Sensors and Actuators B: Chemical, Vol.77, pp.1-2, p.579-591, 2001; Available: 10.1016/s0925-4005(01)00695-5) by S.Semick et al describe a micro-hotplate array monolithically integrated on a common substrate, connected by leads on the same substrate to a set of pads on the periphery of the substrate, and connected by wire bonds to peripheral control and readout circuitry. The monolithic integration with the micro-hotplate array on the same substrate is only the connecting wires, not the active matrix addressing circuit. As the number of micro-hotplates increases, the number of connecting lines increases rapidly. This implementation still limits the number of micro-hotplates that can be accommodated, the assembly cost is high, and the assembly process is cumbersome.

A third prior art is micro-hotplate arrays monolithically integrated with Complementary Metal Oxide Semiconductor (CMOS) circuit arrays without active matrix addressing circuitry. The prior art has attempted in the area of monolithic integration of multiple micro-hotplates and CMOS circuits.

For example, U.F., M.Graf, S.Taschini, K.Kirstein and A.Hierlemann, "A Digital CMOS Architecture for a Micro-Hotplate Array" (IEEE Journal of Solid-State Circuits, Vol.42, No. 2, p.441 and 450, 2007; Available: 10.1109/jssc.2006.938867) propose an Array comprising three Micro-hotplates, each of which integrates a Micro-heater and a Digital PID controller for temperature regulation. However, this prior art technique is not suitable for implementing arrays with a large number of micro-hotplates, since no active matrix addressing circuitry is integrated.

For another example, M.Afrid et al, "A monolithic CMOS Microhotplate-based gas sensor system" (IEEE Sensors Journal, Vol.2, No. 6, p.644 and 655, 2002; Available: 10.1109/jsen.2002.807780) proposes a system monolithically integrated with control and readout circuitry by four micro-hotplates. However, instead of using four micro-hotplates at the same time, the system uses a 2-4 decoder to select and activate one of the four micro-hotplates. This mode of operation greatly wastes the potential advantages of multiple micro-hotplate arrays.

As another example, B.Guo, A.Bermak, P.Chan, and G.Yan, "A monolithic integrated4 x 4tin oxide gas sensor array with on-chip multiplexing and differential readout circuits" (Solid-State Electronics, Vol. 51, No. 1, pp. 69-76, 2007; Available: 2006.10.015) proposes a 4 x 4 sensor array monolithically integrated with a differential readout circuit. This scheme addresses each micro-hotplate using a combination of a decoder and a multiplexing unit. However, this solution is not suitable for arrays with a large number of micro-hotplates, since it does not allow to control the temperature of each micro-hotplate independently and simultaneously, since there is no active matrix addressing circuit.

Furthermore, although the prior art incorporates varying degrees of monolithic integration of micro-hotplate-circuit technologies, the process compatibility of both micro-hotplates and conventional CMOS circuits is poor, and solving such process compatibility problems is often difficult and expensive.

Accordingly, there is a need for an improved solution.

Disclosure of Invention

It is an object of the present invention to propose a solution to solve or at least alleviate at least some of the above problems.

According to a first aspect of the present invention, there is provided a gas detection apparatus formed on the same substrate, the detection apparatus comprising:

an array of a plurality of detection cells arranged in rows and columns; and

the control lines are interconnected to each other and,

each detection unit includes:

a micro-hotplate, comprising:

a suspended membrane supported above the substrate;

a heater disposed on or embedded in the suspended membrane; and the combination of (a) and (b),

a pair of spaced apart measurement electrodes disposed above the heater, the gap between the measurement electrodes being filled with a gas sensitive material; and

a circuit unit associated with the micro-hotplate, comprising:

a heating control circuit connected to the heater, the heating control circuit having a heating control terminal and a set signal terminal, the heating control circuit being adapted to receive a heating selection signal at the heating control terminal and a temperature setting signal at the set signal terminal, and being enabled or disabled in response to the heating selection signal, wherein the heating control circuit being enabled causes the received temperature setting signal to be provided to the heater so that the heater sets the temperature of the micro-hotplate in which it is located in accordance with the temperature setting signal; and

a detection control circuit connected to the measurement electrode, the detection control circuit having a detection control terminal and a detection signal output terminal, the detection control circuit being adapted to receive a detection selection signal at the detection control terminal and to be enabled or disabled in response to the detection selection signal, wherein the detection control circuit, when enabled, provides a detection signal at the detection signal output terminal indicative of the resistance of the gas sensitive material,

wherein, for each row of detection cells, the interconnect control line comprises: a first selected interconnection line and a second selected interconnection line for sharing between the row of detecting units, the heating control terminal in each of the detecting units in the row of detecting units being connected to the first selected interconnection line, and the detecting control terminal in each of the detecting units in the row of detecting units being connected to the second selected interconnection line,

for each column of detection cells, the interconnect control line comprises: a set signal interconnection line for sharing between the columns of the detection units, the set signal terminal in each of the detection units in the columns of the detection units being connected to the set signal interconnection line,

the first selective interconnection lines for the respective rows of the array are different from each other, the second selective interconnection lines for the respective rows of the array are different from each other, and the setting signal interconnection lines for the respective columns of the array are different from each other.

According to another aspect of the present invention, there is provided a method for manufacturing the gas detection apparatus described above.

According to a solution of the invention, a plurality of micro-hotplates with addressing and control circuits therefor are integrated on the same substrate, each micro-hotplate and its associated circuit unit constituting a detection unit, a plurality of such detection units being arranged in rows and columns to form an array of detection units, each row of detection units sharing a common addressing line and each column of detection units sharing a common signal line. Thus, each micro-hotplate can be independently manipulated to be selectively enabled by addressing and control circuitry, each micro-hotplate being selectively operable independently of the other micro-hotplates to set its temperature, perform detection and provide a detection result (e.g. a signal indicative of the resistance of the gas sensitive material across the two measurement electrodes); in addition, a plurality of micro-hotplates can be operated simultaneously and each independently manipulated, and the temperature of each sensing unit located at a scanned row can be maintained while performing a line scan. With the present invention, it is possible to control a plurality of micro-hotplates independently and simultaneously, using a plurality of micro-hotplates for detection, which is advantageous to increase the specificity of detection. By using active addressing circuitry and common addressing and signal lines, the limitation on the number of micro-hotplates that can be integrated is eliminated or at least reduced.

By utilizing the invention, the problem of poor process compatibility can be solved by using an active addressing circuit which is integrated on the same substrate and consists of thin film transistors to address and control the micro-hotplate.

Drawings

Non-limiting and non-exhaustive embodiments of the present invention are described by way of example with reference to the following drawings, in which:

FIG. 1A is a schematic plan view showing a suspended membrane connected to a substrate by a cantilever according to an embodiment of the invention;

FIG. 1B schematically illustrates a cross-sectional view taken along section line AA' of FIG. 1A.

Fig. 1C is a schematic cross-sectional view showing a single micro-hotplate of a gas detection device according to an embodiment of the invention, in which two resistors, one of which functions as a heating resistor and the other of which functions as a thermistor, and a pair of interdigital electrodes are provided on a suspended membrane;

FIG. 1D is a schematic plan view showing a micro-hotplate and its vicinity, with an exposed pair of interdigitated electrodes disposed on the upper surface of the micro-hotplate, according to an embodiment of the invention;

FIG. 1E is a schematic diagram showing a cross-sectional view taken along section line CC' of FIG. 1D, showing a via connecting two conductive layers;

FIG. 1F is a schematic diagram showing a cross-sectional view taken along section line DD' of FIG. 1D, showing a via connecting two conductive layers;

FIG. 1G is a schematic cross-sectional view showing a single micro-hotplate of a gas detection device according to an embodiment of the invention, in which two resistors, one of which serves as a heating resistor and the other of which serves as a thermistor, and a pair of interdigital electrodes are provided on a suspended membrane;

figure 2A schematically illustrates a heating resistor and its associated circuitry for a single micro-hotplate according to an embodiment of the invention;

figure 2B schematically illustrates a heating resistor and its associated circuitry for a micro-hotplate in an m x n array, where m-n-2;

figure 3A schematically illustrates a thermistor and its associated circuitry for a single micro-hotplate according to an embodiment of the invention;

figure 3B schematically illustrates a thermistor and its associated circuitry for a micro-hotplate in an m x n array, where m-n-2;

figure 4A schematically illustrates a pair of interdigitated electrodes and their associated circuitry for a single micro-hotplate, in accordance with an embodiment of the present invention;

figure 4B schematically illustrates interdigitated electrodes for a micro-hotplate and their associated circuitry in an m x n array, where m is 2;

figure 5A schematically illustrates a heater resistor, a thermistor, and a pair of interdigitated electrodes and their associated circuitry on a single microhotplate according to an embodiment of the present invention;

figure 5B schematically illustrates a heater resistor, a thermistor, and a pair of interdigitated electrodes and their associated circuitry on a single microhotplate according to an embodiment of the present invention;

FIG. 6A is a schematic cross-sectional view of a single detection cell of a gas detection apparatus according to an embodiment of the invention, the detection cell comprising a micro-hotplate corresponding to the micro-hotplate shown in FIG. 1C and an associated thin film transistor;

FIG. 6B is a schematic cross-sectional view of a single detection cell of a gas detection apparatus according to an embodiment of the invention, the detection cell comprising a micro-hotplate corresponding to the micro-hotplate shown in FIG. 1G and an associated thin film transistor;

FIG. 7 is a schematic plan view showing a single detection unit of the gas detection apparatus according to an embodiment of the present invention; and

FIG. 8 is a schematic diagram illustrating an array of m n detection cells of a gas detection cell according to an embodiment of the invention.

Detailed Description

In order to make the above and other features and advantages of the present invention more apparent, the present invention will be further described with reference to the accompanying drawings and examples. It is understood that the specific embodiments described herein are for purposes of illustration only and are not intended to be limiting. Features shown in the drawings are not necessarily drawn to scale.

The features described herein may be embodied in different forms and should not be construed as limited to the examples described herein. Rather, the embodiments described herein are provided merely to illustrate some of the many possible ways of implementing the devices and/or systems described herein, which will be apparent after understanding the disclosure of the present application.

As used herein, the term "and/or" includes any one of the associated listed items and any combination of any two or more of the associated listed items.

Although terms such as "first", "second", and "third" may be used herein to describe various members, components, portions or elements, these members, components, portions or elements are not limited by these terms. Rather, these terms are only used to distinguish one element, component, portion or element from another element, component, portion or element. Thus, a first member, component, part or element referred to herein may also be termed a second member, component, part or element without departing from the teachings of the present invention.

Spatially relative terms, such as "upper," "lower," "left," "right," "above," "upper," "above," "below," "lower," and "below," may be used herein for ease of description to describe one element, component, portion or element's relationship to another element, component, portion or element as illustrated in the figures. Such spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, an element described as being "on," "over," "upper," or "above" with respect to another element, component, portion, or element would be "below," "beneath," or "beneath" the other element. Thus, the term "upper" encompasses an upper orientation and a lower orientation, depending on the spatial orientation of the device. The device may also be otherwise oriented (e.g., rotated 90 degrees or at other orientations) and the spatially relative terms used herein should be interpreted accordingly.

The terminology used herein is for the purpose of describing various embodiments only and is not intended to be limiting of the disclosure. The terms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms "comprises," "comprising," and "having" specify the presence of stated features, operations, components, elements, and/or combinations thereof, but do not preclude the presence or addition of one or more other features, operations, components, elements, and/or combinations thereof.

The general concept of the invention is as follows: providing a gas detection device integrated on a substrate comprising a plurality of detection cells arranged in rows and columns forming an array, each detection cell comprising a micro-hotplate and circuit units associated with the micro-hotplate; the interconnection control lines are arranged so that each row of the detection units shares the same selection interconnection line, each column of the detection units shares the same signal interconnection line, the selection interconnection lines for different rows of the array are different from each other, and the signal interconnection lines for different columns of the array are different from each other, so that addressing and control of each micro-hotplate in the array can be realized by reduced devices and wiring, and two or more micro-hotplates can be independently and simultaneously manipulated.

Each micro-hotplate may comprise: a suspended membrane supported over a substrate; a heater, such as a heater resistor, disposed on or embedded in the suspended membrane to set a desired operating temperature of a micro-heater in which it is located in accordance with an available temperature setting signal; a pair of spaced apart measurement electrodes, such as interdigitated electrodes, disposed over the heater for detecting the resistance of the associated gas sensitive material, thereby determining the composition and component concentration of the gas to be measured; and a temperature measuring element, such as a thermistor, optionally arranged above the heater and below the measuring electrode, for measuring the actual temperature of the micro-hotplate in which it is located.

Herein, the heater may be various forms of micro-heaters, such as heating resistors; the temperature sensing element may be a temperature sensor of various forms, such as a thermistor.

In the presence of a temperature sensing element, if the measured actual temperature of the microhotplate deviates from (e.g., is above or below) the desired operating temperature of the microhotplate, the temperature setting signal for the microhotplate may be adjusted to reduce the deviation of the actual temperature from the desired operating temperature. This can be achieved by various control means (e.g., closed loop control, PID control, etc.), which will not be described in detail herein.

The gas sensitive material associated with a pair of measurement electrodes includes the gas sensitive material filling the gap between the pair of measurement electrodes and optionally includes the gas sensitive material coated on the pair of measurement electrodes. The conductivity of the gas sensitive material changes as the contacted gas or gas mixture is absorbed or adsorbed, and thus by detecting the resistance of the gas sensitive material across the measurement electrodes, the composition and component concentration of the gas can be detected. The measurement electrodes may take a variety of possible forms, including interdigitated and non-interdigitated electrodes. For example, a gas-sensitive material may be coated on the upper surface of each micro-hotplate and the corresponding interdigital electrodes to bridge the gap between the interdigital electrodes.

The heater, the measuring electrode and optionally the temperature measuring element of each micro-hotplate may be connected to a heating control circuit, a detection control circuit and a temperature measuring control circuit, respectively, comprised by the circuit unit associated with the micro-hotplate. Each of the heating control circuit, the sensing control circuit, and the thermometry control circuit may be implemented in a variety of possible ways so long as it can be selectively activated and deactivated in response to a respective selection signal to selectively implement a respective temperature setting function, gas sensing function, or temperature measuring function in conjunction with a respective heater, measuring electrode, or thermometry element.

According to an advantageous embodiment, each detection cell comprises a micro-hotplate monolithically integrated with an active matrix circuit made of Thin Film Transistors (TFTs), each having a heating resistor, a thermistor and a pair of interdigital electrodes supported by a suspended membrane. The suspended membrane of each micro-hotplate is supported and anchored in suspension above the substrate by means of cantilevers at its edges. A circuit composed of at least two thin film transistors for selecting the micro-hotplate and controlling a current flowing through a heating resistor located on the micro-hotplate, thereby setting a temperature of the micro-hotplate; the circuit may also be referred to as a "heating control circuit". By replicating and organizing the heating control circuitry as an active matrix, the temperature of different micro-hotplates in the array of micro-hotplates can be controlled simultaneously and independently. A circuit composed of at least one thin film transistor for selecting the micro-hotplate and providing a current through a thermistor located on the micro-hotplate, thereby detecting the temperature of the micro-hotplate; the circuit may also be referred to as a "thermometry control circuit". And a circuit consisting of at least one thin film transistor for selecting the micro-hotplate and providing a current through a pair of interdigitated electrodes of the micro-hotplate, so as to measure the resistance and possible variation of the resistance of the gas-sensitive material associated with the pair of interdigitated electrodes; this circuit may also be referred to as a "detection control circuit". By replicating and organizing the detection control circuitry as an active matrix, the resistance across the interdigitated electrodes on each micro-hotplate can be independently acquired, from which the composition and component concentration of the detected gas is determined.

Consider an array of m x n micro-hotplates arranged in m rows and n columns, where m, n ≧ 1 and is an integer. If an active addressing matrix is not used, the interconnect lines for the devices of each micro-hotplate must be replicated m × n times to electrically access each micro-hotplate in the array. By using an active addressing matrix, a smaller number of transistors can be used to control access to each micro-hotplate, thereby reducing the number of interconnect lines to m + n. More generally, a complete system consists of an active matrix of detection cells and peripheral circuits outside the matrix. Each detection unit constituting the active matrix is composed of a micro-hotplate and a set of electronic devices including thin film transistors for controlling the respective micro-hotplate (for example, accessing the micro-hotplate, setting (or maintaining) the operating state of the micro-hotplate, such as the operating temperature) and other possible electronic devices such as passive devices such as capacitors; for convenience of description, the set of electronic devices may also be referred to as "circuit cells" associated with the micro-hotplate.

Typically, one of the m rows of detection cells, each comprising a micro-hotplate and its associated circuit unit, is selected at any given time to establish signal communication between the n detection cells of the row and the peripheral circuitry. At this time, the states of the sensing cells located in the other m-1 rows are not disturbed by signals from the peripheral circuits, and thus the operating states of the sensing cells are maintained. In addition to the peripheral circuits for row selection, there are additional circuits in the column direction for supplying temperature setting signals to the detection cells of the selected row and additional circuits in the column direction for acquiring detected signals (e.g., gas detection signals, temperature measurement signals) from the corresponding detection cells. The additional circuitry in the column direction is typically shared between multiple rows.

According to this advantageous embodiment, the above-mentioned problems of the prior art related to the lack of active matrix addressing circuits and poor process compatibility can be solved by replacing the conventional circuits built from CMOS technology with circuits built from thin film transistor technology using metal oxide semiconductors, polysilicon or a combination of both.

The metal oxide semiconductor used as a gas sensitive functional material of the gas sensor and the metal oxide semiconductor used for constructing the thin film transistor are not necessarily the same.

In terms of process, it is possible to first form the suspended membrane of the micro-hotplate array (which needs to be achieved using a relatively high temperature process; then monolithically integrate the devices on the suspended membrane (e.g. heater resistors, interdigital electrodes) and the devices of the circuit cells associated with the micro-hotplate (e.g. thin film transistors), which can be carried out at significantly lower temperatures without adversely affecting the formed suspended membrane.

The present invention includes two levels of integration. The first level is the monolithic integration of the micro-hotplate and the electronics of the circuit units associated with the micro-hotplate (electronics including thin film transistors), thus implementing an active matrix. The second stage involves the monolithic integration of the active matrix array with its external circuitry.

The suspended membrane may have dimensions of a few microns to a few millimeters, for example with a lateral characteristic length of between 10 and 5000 microns. Although the suspended membrane shown in this embodiment is square in shape, it may take other regular or irregular forms. The thickness of the suspended membrane may be from a few hundred nanometers to a few tens of micrometers, for example between 0.1 and 20 micrometers. The gap between the suspended membrane and the substrate may be a few hundred nanometers to a few micrometers, for example between 0.1 and 20 micrometers.

Depending on the circumstances, the suspended membrane can be constructed in various implementation methods. In one embodiment, Silicon-Migration Technology (Silicon-Migration Technology, Silicon-on) is employed. In another embodiment based on the conventional sacrificial layer method, a patterned structure layer is formed on the sacrificial layer, and when the sacrificial layer is removed, the patterned structure layer originally disposed on the sacrificial layer becomes a suspended film. For example, the top Silicon layer of a Silicon-On-Insulator (SOI) is the structural layer, while the buried Silicon oxide layer below the top Silicon layer is the sacrificial layer. In another embodiment, the deposited polysilicon layer is a sacrificial layer, and the oxide-nitride-oxide stack on the polysilicon layer constitutes a suspended membrane that acts as a suspended membrane.

As described above, the suspended membrane may have a plurality of resistors disposed thereon, including a heating resistor and a thermistor as a temperature sensor. The resistance of the resistor may be in the range of 1 milliohm to 10 kilo-ohms. In one embodiment, the heater resistors are patterned from doped polysilicon disposed on a suspended film, which need not be made of silicon. In another embodiment, the heating resistor is made of doped silicon embedded in a suspended film made of silicon, i.e. the doped silicon regions separated by pn junctions are patterned, and the dopant may be boron in an n-type silicon thin film or phosphorous in a p-type silicon thin film. In another embodiment, the resistor is patterned from a metallic conductive layer disposed on a flying film. The resistors may be of any suitable form, typically rectangular or serpentine, as desired. The resistor has an insulating layer above and/or below it, which may be made of silicon oxide, silicon nitride or a stack of both, and which may have a total thickness of between 0.01 and 10 microns, and which may have vias on it to allow electrical access between the different conductive layers.

A pair of spaced apart measurement electrodes, such as a pair of Interdigitated electrodes (IDEs), is disposed above the heater or temperature sensor. The pair of interdigital electrodes is arranged on the upper surface of the micro-hotplate. The interdigitated electrodes may be made of a stack of metal conductors, such as a noble metal, e.g. gold or platinum. The interdigital electrode is composed of two independent comb-shaped structures, and comb teeth of the interdigital electrode are mutually crossed and are in an interdigital shape and are not in direct contact. Each comb-like structure is composed of a plurality of comb teeth connected by a backbone. The number of comb teeth of the interdigital electrode may be several to several tens, and is connected to a relatively wide trunk. Electrical access to the comb is achieved through the backbone to which it is connected.

The upper surface of each micro-hotplate provided with a pair of interdigital electrodes is covered with a layer of gas-sensitive functional material so as to close the gap between the comb teeth of the pair of interdigital electrodes. When the gas or gas mixture to which the micro-hotplate is exposed is adsorbed or absorbed by the gas-sensitive functional material, the electrical conductivity of the gas-sensitive functional material changes. The gas sensitive functional material may comprise one metal oxide semiconductor or a combination of metal oxide semiconductors, such as tin oxide (tetravalent) or zinc oxide (divalent). The sensitivity of the gas sensitive functional material can be enhanced by doping, etc., for example nickel doping of tin oxide (tetravalent).

Fig. 1A schematically illustrates a plan view of a suspended membrane 103 connected to a substrate by a cantilever 104, where the size of the cantilever is defined by a release hole 105. FIG. 1B is a schematic view of a cross section along AA' of FIG. 1A, showing the suspended membrane 103 suspended over the substrate 101 with a gap 102 and a release hole 105 between the suspended membrane and the substrate.

Fig. 1C schematically shows, in cross-section, two resistors and a pair of interdigitated electrodes on the suspended membrane 103 according to a first embodiment, where one resistor is used as a heating resistor and the other resistor is used as a thermistor (i.e. a temperature sensor). A first insulating layer 106 is provided on the suspended film 103, and a first conductive layer is provided on the first insulating layer 106. The first conductive layer is patterned to form a resistor 107A, which resistor 107A may be referred to as a heating resistor or a first resistor. A second insulating layer 108 is provided on the resistor 107A. A second conductive layer is disposed on the second insulating layer 108. This second conductive layer is patterned to form a resistor 109, and the resistor 109 may be referred to as a thermistor or a second resistor. A stack of layers including insulating

layers

110 and 111 is disposed over the second conductive layer. A third conductive layer is disposed on the stack and patterned to form a pair of interdigitated electrodes 112 as described above. The interdigital electrode 112 is covered with a gas-sensitive functional material 113.

Fig. 1D schematically shows a plan view of the micro-hotplate and its vicinity, with a pair of interdigitated electrodes 112 exposed on the top surface of the micro-hotplate. A cross-sectional view along section line BB' of fig. 1D is schematically shown by fig. 1C. Fig. 1E schematically shows a cross-sectional view along section line CC' of fig. 1D, showing an embodiment of a via for connecting the second conductive layer on which the resistor 109 is located and the first conductive layer on which the resistor 107A is located, wherein the via through the insulating layer between the conductive layers is used for connecting the conductive layers at different layers. Fig. 1F schematically shows a cross-sectional view along the section line DD' of fig. 1D, showing an embodiment of a via for connecting the third conductive layer where the interdigital electrode 112 is located and the second conductive layer where the resistor 109 is located. It should be understood that in fig. 1E and 1F, the same reference numerals as those in fig. 1C refer to the same elements, and are not described again here.

Fig. 1G schematically shows a second embodiment in a cross-sectional view, which differs from fig. 1C. Instead of the resistor 107A in fig. 1C as described above, the resistor 107B in fig. 1G is made of doped silicon embedded in a thin film made of silicon. In contrast to the cross-sectional view of the embodiment shown in fig. 1C, there is no first insulating layer 106 and no first conductive layer for forming the resistor 107A in this embodiment. It should be understood that in fig. 1G, the same or similar reference numerals as those in fig. 1C refer to the same or similar elements, and are not described again here.

The operation of the heater resistor and associated heating control circuit of the gas detection device of the present invention is described below in conjunction with fig. 2A and 2B.

Fig. 2A schematically illustrates an embodiment of a circuit for controlling the current flowing through the heating resistor 201A. One end of the heating resistor 201A is connected to the drain of the driving thin film transistor 202A, and the other end is connected to a power supply voltage terminal (also referred to as a first power supply terminal) at whichCan provide a first supply voltage V_DDHeat. The source of the thin film transistor 202A is connected to a ground terminal at which a ground reference GND may be provided. The storage node 205A is connected to the gate of the thin film transistor 202A and one of the source and drain of the address thin film transistor 203A; one of the source and the drain is referred to as a storage electrode of the thin film transistor 203A. The other of the source and the drain of the thin film transistor 203A is referred to as a data electrode and serves as a setting signal terminal of the heating control circuit. The data electrode carries a voltage signal V as a temperature setting signal_DataIs connected to a set signal interconnect line (also referred to as a "data line") DLH, forming a data node 206A.

The gate of the TFT 203A and the voltage signal V are connected to the heating control terminal of the heating control circuit_SelectHIs connected to the first select interconnect line (also referred to as "scan line") SLH. The storage capacitor 204A has one terminal connected to the storage node 205A and the other terminal connected to a constant voltage node, here, a ground node GND. When the voltage signal V on the first selected interconnection line SLH_SelectHWhen switched to high, the thin film transistor 203A is turned on and V on the data node 206A_DataThe signal is transmitted to storage node 205A. When the voltage signal V_SelectHIs switched to a low level and V_DataWhen the signal is held at the data node 206A, the thin film transistor 203A is turned off and V_DataA signal is stored on the storage capacitor 204A to be supplied to the thin film transistor 202A. Stored V_DataThe signal determines the drain current I flowing through the TFT 202A_HI.e., the current flowing through the heating resistor 201A, so that the temperature of the micro-hotplate can be set.

Fig. 2B schematically illustrates an embodiment of an m × n active matrix of heating resistors and associated heating control circuits, where m-n-2. Each cell in the active matrix is made up of the circuit of fig. 2A. The gates of the address

thin film transistors

203A and 203B of the first row are both connected to the scan line SLH 1; the gates of the address thin film transistors 203C and 203D of the second row are connected to the scan line SLH 2. The data electrodes of the first column of address tfts 203A and 203C are both connected to data line DLH 1; the data electrodes of the second column of address tfts 203B and 203D are both connected to data line DLH 2. The connection of other elements is referred to the related description of fig. 2A and will not be described again here.

The active matrix operates as follows. First, a signal V_Data11And V_Data12Transmitted on data lines DLH1 and DLH2, respectively. When V of one scan line (e.g., scan line SLH1)_SelectHWhen the signal is pulled high, the corresponding first row of addressing

tfts

203A and 203B are selected and turned on. Signal V_Data11And V_Data12Are transferred to the gates of the driving

thin film transistors

202A and 202B of the corresponding row, respectively. V on the scanning line of the other row (for example, the scanning line SLH2)_SelectHThe signal remains low to keep the corresponding second row of addressing tfts 203C and 203D in the off state. Therefore, the gate voltages of the driving thin film transistors 202C and 202D of the corresponding second row are not influenced by the signal V on the data line_Data11And V_Data12The interference of (2). Then scanning V on line SLH1_SelectHThe signal is pulled low thereby turning off the addressing

tfts

203A and 203B. Signal V_Data11And V_Data12Now stored on the

storage capacitors

204A and 204B. At this time, a new set of signals V_Data21And V_Data22Can be transmitted on data lines DLH1 and DLH2, respectively. The above-described operation described with respect to the scanning line SLH1 is repeated for the scanning line SLH2, thereby converting the signal V_Data21And V_Data22Stored on

storage capacitors

204C and 204D, respectively. Thus, by the above-described operation flow, the currents I respectively flowing through the four

heating resistors

201A, 201B, 201C, 201D can be independently set_H11、I_H12、I_H21、I_H22So that the temperature of the corresponding micro-hotplate can be set.

The heating resistor in each cell of the active matrix array in fig. 2B is placed on the corresponding micro-hotplate, and the thin film transistor and the capacitor in each cell of the active matrix array are located in adjacent positions outside the corresponding micro-hotplate. As shown in fig. 1D, a single microhotplate and devices thereon can be connected to associated thin film transistors and capacitors through interconnect lines on the cantilevers that cross the boundaries of the microhotplate.

The operation of the temperature measurement control circuit of the gas detection apparatus of the present invention will be described with reference to fig. 3A and 3B.

Fig. 3A schematically illustrates an embodiment of a circuit for addressing and operating a thermistor as described above. One end of the thermistor 301A is connected to the drain of the address thin film transistor 302A, and the other end is connected to a power supply voltage terminal (also referred to as a third power supply terminal) at which a power supply voltage V can be supplied_DDTemp. The temperature signal output terminal of the thermometry control circuit, i.e., the source of the thin film transistor 302A, is connected to a temperature signal interconnection line (also referred to as "data line") DLT. The temperature measurement control terminal of the temperature measurement control circuit, namely the grid of the thin film transistor 302A, is connected to the carried voltage signal V_SelectTAnd a second select interconnect line (also referred to as a "scan line") SLT. When scanning line SLT is on V_SelectTWhen the signal is high, the thin film transistor 302A is turned on. Signal current I flowing through thermistor 301A_TThe temperature signal is transmitted to the temperature signal interconnection line DLT through a temperature signal output terminal of the temperature measurement control circuit and is detected. When V is_SelectTWhen the signal is switched to the low level, the thin film transistor 302A is turned off, and the detection is terminated.

Fig. 3B schematically illustrates an embodiment of an m × n active matrix consisting of thermistors and their associated thermometry control circuitry, where m-n-2. Each cell in the active matrix is made up of the circuit of fig. 3A. The gates of the address

thin film transistors

302A and 302B of the first row are both connected to the scan line SLT 1; the gates of the address

thin film transistors

302C and 302D of the second row are connected to the scan line SLT 2. The sources of the first column of

address tfts

302A and 302C are both connected to the data line DLT 1; the sources of the second column of addressing tfts 302B and 302D are both connected to data line DLT 2. The connection of other elements refers to the related description about fig. 3A, and is not described in detail here.

The active matrix operates as follows. V on one scan line (e.g., scan line SLT1)_SelectTWhen the signal is pulled high, the corresponding first row of addressing

tfts

302A and 302B are selected and turned on. Through a thermistor 301ACurrent signal I_T11A current signal I transmitted to the data line DLT1 through the thermistor 301B_T12Is passed to data line DLT 2. V on the scanning line of the other row (for example, the scanning line SLT2)_SelectTThe signal remains low to keep the corresponding second row of addressing tfts 302C and 302D in the off state. Therefore, the signals on data lines DLT1 and DLT2 are not disturbed by the current signals of

thermistors

301C and 301D. After detecting the current signal I_T11And I_T12Then, V on the scanning line SLH1_SelectTThe signal may be pulled low, turning off the addressing

tfts

302A and 302B. The above-described operation described with respect to the scanning line SLT1 may be repeated for the scanning line SLT2, thereby detecting the current signals I through the

thermistors

301C and 301D, respectively_T21And I_T22. Through the above-described operation flow, the currents I passing through the four

thermistors

301A, 301B, 301C, 301D, respectively, can be independently detected_T11、I_T12、I_T21、I_T22。

The thermistor in each cell of the active matrix array in fig. 3B is placed on the corresponding micro-hotplate, and the thin film transistor in each cell of the active matrix array is located in an adjacent position outside the corresponding micro-hotplate. The two devices are connected by an interconnect on the cantilever that crosses the boundary of the microhotplate.

The operation of the detection control circuit of the gas detection apparatus of the present invention is described below with reference to fig. 4A and 4B.

Fig. 4A schematically illustrates an embodiment of a circuit for addressing and operating the interdigitated electrodes as described above. A pair of interdigitated electrodes and their associated gas-sensitive material form a resistor, the two ends of which correspond to the pair of interdigitated electrodes, respectively. Here, the resistor and the corresponding interdigital electrode are denoted by reference numeral 401A for convenience. One end of the resistor 401A is connected to the drain of the address thin film transistor 402A, and the other end is connected to a power supply voltage terminal (also referred to as a second power supply terminal) at which a power supply voltage V can be supplied_DDIDE. The source of the thin film transistor 402A, which is the detection signal output terminal of the detection control circuit, is connected toTo a detection signal interconnection line (also referred to as a "data line") DLE. The gate of the thin film transistor 402A, which is the detection control terminal of the detection control circuit, is connected to the carried voltage signal V_SelectEIs also referred to as "scan line") SLE. When V on SLE_SelectEWhen the signal is high, the thin film transistor 402A is turned on. Signal current I flowing through resistor 401A_EThe detection signal is transmitted to the data line DLE via the detection signal output terminal of the detection control circuit and is detected. When V is_SelectEWhen the signal is switched to the low level, the thin film transistor 402A is turned off, and the detection is terminated.

Fig. 4B schematically illustrates an embodiment of an m × n active matrix consisting of interdigitated electrodes and their associated detection control circuits, where m ═ n ═ 2. Each cell in the active matrix is made up of the circuit of fig. 4A. The gates of addressing

tfts

402A and 402B of the first row are both connected to scan line SLE 1; the gates of the second row of addressing tfts 402C and 402D are connected to scan line SLE 2. The sources of the first column of addressing

tfts

402A and 402C are both connected to data line DLE 1; the sources of the second column of addressing tfts 402B and 402D are both connected to data line DLE 2. The connection of other elements is referred to the related description about fig. 4A, and is not described again here.

The active matrix operates as follows. When signal V on one scan line (e.g., scan line SLE1)_SelectEWhen pulled high, the corresponding first row of addressing

tfts

402A and 402B are selected and turned on. Current signal I through interdigital electrode 401A_E11A current signal I transmitted to the data line DLE1 through the interdigital electrode 401B_E12Is passed to data line DLE 2. V on scan line of other row (e.g., scan line SLE2)_SelectEThe signal remains low to keep the corresponding second row of addressing tfts 402C and 402D in the off state. Therefore, the signals on the data lines DLE1 and DLE2 are not interfered by the current signals of the

interdigital electrodes

401C and 401D. After detecting the current signal I_E11And I_E12Then, V on SLE1 is scanned_SelectEThe signal may be pulled low, turning off

thin film transistors

402A and 402B. Can be repeated for scan line SLE2The above-described operation described with respect to the scanning line SLE1 is performed to detect the current signal I passing through the

interdigital electrodes

401C and 401D, respectively_E21And I_E22. Through the above operation procedure, the currents I passing through the four pairs of

interdigital electrodes

401A, 401B, 401C, 401D, respectively, can be independently detected_E11、I_E12、I_E21、I_E22。

The interdigitated electrodes in each cell of the active matrix array of figure 4B are placed on a corresponding micro-hotplate, and the thin film transistors in each cell of the active matrix array are located in close proximity outside the corresponding micro-hotplate. The two devices are connected by an interconnect on the cantilever that crosses the boundary of the microhotplate.

Fig. 5A schematically shows an embodiment of the circuitry within one detection cell consisting of a single micro-hotplate and its associated circuit cells, comprising a heating resistor 201A, a thermistor 301A and a pair of interdigitated electrodes 401A integrated on the single hotplate. The gates of the address

thin film transistors

203A, 302A, and 402A are connected to different scan lines SLH, SLT, and SLE, respectively. Fig. 5B schematically shows another embodiment different from fig. 5A, in which the gates of the addressing

thin film transistors

302A and 402A are connected to one common scan line SLS. The connection of other elements in fig. 5A and 5B is described above with respect to fig. 2A-4B and will not be described again here.

Fig. 6A and 6B schematically show two embodiments of a cell comprising a monolithically integrated single micro-hotplate and associated thin film transistors, respectively, in cross-sectional views. As shown in fig. 6A and 6B, an initial thin film suspended over a self-formed cavity on a substrate can be constructed using silicon migration (SiMiT) techniques to form a suspended film 103. Fig. 6A corresponds to the embodiment of the microhotplate shown in fig. 1C, the first resistor 107A being provided on the first insulating layer 106 on top of the membrane 103. Fig. 6B corresponds to the embodiment of the microhotplate shown in fig. 1G, with a first resistor 107B embedded in the membrane 103. In both embodiments, the

heater resistor

107A or 107B, the thermistor 109 and the pair of interdigitated electrodes 112 are located on the membrane of the same micro-hotplate. The upper surface of the micro-hotplate can be functionalized by coating with a layer of metal oxide semiconductor material 113. The thin film transistor 600 based on the metal oxide semiconductor 601 is located outside the micro-hotplate and is monolithically integrated with the micro-hotplate (i.e. shares the same substrate). The cantilever is formed by etching an initial thin film that is suspended. The metal oxide semiconductor 601 used to construct the thin film transistor 600 and the metal oxide semiconductor 113 used as a gas sensitive functional material need not be the same. For example, the metal oxide semiconductor 601 may include, but is not limited to, one of zinc oxide, indium gallium zinc oxide, indium tin zinc oxide, and the like, or a suitable combination thereof. The metal oxide semiconductor 601 is provided between the insulating

layers

110 and 111. As shown in fig. 6A and fig. 6B, the gate 602 of the metal oxide thin film transistor 600 and the resistor 109 belong to the same conductive layer, and the source and drain 603 of the metal oxide thin film transistor 600 and the interdigital electrode 112 belong to the same conductive layer, so that the problem of poor process compatibility in the prior art can be solved. It should be understood that the same or similar reference numerals in fig. 6A and 6B as those in fig. 1C and 1G refer to the same or similar elements, which are not described again herein.

Figure 7 schematically shows in plan view the distribution of devices in a cell of an array comprising a single monolithically integrated micro-hotplate and associated thin film transistors, showing that the

thin film transistors

203A, 202A, 402A and 302A are located on the same substrate, adjacent to the associated micro-hotplate 700.

FIG. 8 schematically illustrates an array of m n detection cells of a gas detection cell according to an embodiment of the invention, showing an array of multiple detection cells arranged in rows and columns.

The respective technical features described above may be arbitrarily combined. Although not all possible combinations of features are described, any combination of features should be considered to be covered by the present specification as long as there is no contradiction between such combinations.

Finally, it should be noted that while the present invention has been described in connection with the embodiments, those skilled in the art will recognize that the foregoing description and drawings are illustrative only and not limiting, and that the foregoing embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention; the invention is not limited to the disclosed embodiments. Those skilled in the art will appreciate that various modifications and variations are possible without departing from the spirit of the invention; any modification, equivalent replacement or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A gas detection device formed on the same substrate, the detection device comprising:

an array of a plurality of detection cells arranged in rows and columns; and

the control lines are interconnected to each other and,

each detection unit includes:

a micro-hotplate, comprising:

a suspended membrane supported above the substrate;

a circuit unit associated with the micro-hotplate, comprising:

wherein, for each row of detection cells, the interconnect control line comprises: a first selected interconnection line and a second selected interconnection line for sharing between the row of detecting units, the heating control terminal in each detecting unit in the row of detecting units being connected to the first selected interconnection line, and the detecting control terminal in each detecting unit in the row of detecting units being connected to the second selected interconnection line, the interconnection control line including, for each column of detecting units: a set signal interconnection line for sharing between the columns of the detection units, the set signal terminal in each of the detection units in the columns of the detection units being connected to the set signal interconnection line,

2. The gas detection apparatus of claim 1, wherein each micro-hotplate further comprises:

a temperature measuring element arranged above the heater of the micro-hotplate and below the measuring electrode of the micro-hotplate and adapted to measure the temperature of the micro-hotplate on which it is located,

wherein the circuit unit associated with the micro-hotplate further comprises: a temperature measurement control circuit connected to the temperature measurement element, the temperature measurement control circuit having a temperature measurement control terminal and a temperature signal output terminal, the temperature measurement control circuit being adapted to receive a temperature measurement selection signal at the temperature measurement control terminal and being enabled or disabled in response to the temperature measurement selection signal, wherein the temperature measurement control circuit, when enabled, provides a temperature signal at the temperature signal output terminal indicative of the temperature of the micro-hotplate,

for each row of detection cells, the interconnect control line further comprises: a third selective interconnection line for sharing between the row of inspection units, to which the thermometric control terminal in each of the inspection units in the row of inspection units is connected, and

the third select interconnect lines for each row of the array are different from each other.

3. The gas detecting apparatus according to claim 2, wherein the second selective interconnection line and the third selective interconnection line for each row of the detecting units are the same interconnection line.

4. The gas detection apparatus according to claim 1,

for each column of detection cells, the interconnect control line comprises: a detection signal interconnection line for common use between the columns of detection units, to which the detection signal output terminal in each of the detection units in the columns of detection units is connected, and

the detection signal interconnect lines for each column of the array are different from each other.

5. The gas detection apparatus according to claim 2,

for each column of detection cells, the interconnect control line comprises: a temperature signal interconnecting line for common use between the columns of the detecting units, to which a temperature signal output terminal in each of the detecting units in the columns of the detecting units is connected, and

the temperature signal interconnect lines for each column of the array are different from each other.

6. A gas detection apparatus according to claim 1 wherein each micro-hotplate is adjacent to its associated circuit unit.

7. The gas detection apparatus according to any one of claims 1 to 6, wherein the heater includes one heating resistor, and the circuit unit includes a heating control circuit for a single detection unit including:

a first thin film transistor, a gate of which is connected to the heating control terminal in the detection cell, and one of a source and a drain of which is connected to the set signal terminal in the detection cell;

a second thin film transistor having a gate connected to the other of the source and the drain of the first thin film transistor, and one of the source and the drain of the second thin film transistor connected to a ground terminal; and

a capacitor connected between the gate of the second thin film transistor and the ground terminal,

wherein the heating resistor in the detection unit is connected between the other of the source and the drain of the second thin film transistor and the first power supply terminal.

8. The gas detection apparatus according to any one of claims 1 to 6, wherein, for a single detection unit, the circuit unit thereof includes a detection control circuit including:

a third thin film transistor having a gate connected to the sensing control terminal in the sensing unit,

wherein the measurement electrode in the detection unit is connected between one of the source and the drain of the third thin film transistor and the second power supply terminal, and the other of the source and the drain of the third thin film transistor is connected to the detection signal output terminal in the detection unit.

9. A gas detection apparatus according to any one of claim 2, claim 3, claim 5, claim 7 when dependent on claim 2, and claim 8 when dependent on claim 2, wherein the temperature measuring element comprises a thermistor, and the circuit unit of the single detection unit comprises a temperature measuring control circuit including:

a fourth thin film transistor, the grid of the fourth thin film transistor is connected to the temperature measurement control terminal in the detection unit,

wherein the thermistor in the detection unit is connected between one of the source and the drain of the fourth thin film transistor and the third power supply terminal, and the other of the source and the drain of the fourth thin film transistor is connected to the temperature signal output terminal in the detection unit.

10. The gas detection apparatus according to claim 9, wherein the thermistor and the gate of the thin film transistor are located on one conductive layer, and the measurement electrode and the source and drain of the thin film transistor are located on the other conductive layer.

11. The gas detection apparatus of claim 10, wherein one insulating layer is disposed between the one conductive layer and the heater and one insulating layer is disposed between the other conductive layer and the measurement electrode.

12. The gas detection apparatus of any of claims 1-6 and 10-11, wherein the heater is disposed over the substrate with an insulating layer disposed therebetween.

13. The gas detection apparatus of any of claims 1-6 and 10-11, wherein the suspended membrane is supported in suspension above the substrate from 0.1 to 20 microns from the substrate.

14. Method for manufacturing a gas detection device according to any of the preceding claims.