JP6340967B2 - Gas sensor - Google Patents

Description

  The present invention relates to a gas sensor that detects a temperature difference generated due to a difference in thermal conduction of a space by gas as an electrical signal. More specifically, the present invention relates to a gas sensor having a heat sensitive film and heating means on a membrane structure.

  2. Description of the Related Art Conventionally, there has been known an element capable of measuring and detecting a difference in heat conduction of a gas in space as a space temperature and detecting the gas by an electric signal corresponding to a temperature change. In such a device, the temperature change in the open space is measured with the sensing element, and the temperature change in the closed space under a certain condition is measured with the compensation element. calculate. For this purpose, for example, it has been proposed that a thermistor material using a negative resistance temperature change, a bolometer material, or a temperature measuring body using a metal such as Pt be used as a thermosensitive element by the resistance change.

  Patent Document 1 proposes a humidity sensor having a structure combined with a heating resistive film as a thermal element using a thermistor. The humidity sensor is disposed in a ceramic package, and has a structure in which one element is sealed by a lid part formed by a partition part that forms two spaces and a through hole provided on the detection element.

  Patent Document 2 discloses a structure using a can package case and a stem as a bolometric humidity sensor. A vent hole with the outside air is formed directly below the detection element on the back of the stem, and changes in the temperature of the space on the back are detected. On the other hand, the compensation element is spatially separated from the back of the detection element in the stem. to be influenced.

JP 2009-168649 A JP-T-2004-514881

  However, the following problems remain in the conventional technology. In Patent Document 1, it is difficult to reduce the size because a complicated structure is provided in order to provide a partition portion on the lid after the detection element is arranged in the ceramic package, and a ventilation hole is provided at the upper portion of the detection portion. The sensing element is easily affected by external wind and dirt.

  According to the configuration of Patent Document 2, it is difficult to reduce the size by using a can package. The vent is provided directly below the detection element and is directly affected by outside air as in Patent Document 1. In addition, when the compensation element is fixed in the stem, there is a problem of ensuring stable airtightness.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a gas sensor that detects a change in the temperature of a space, and that is small in size and is less susceptible to external influences on wind and dirt. To do.

  In order to achieve the above object, a gas sensor according to the present invention includes a first thermal element that measures the gas concentration of the outside air, a second thermal element that measures the temperature of the reference closed space atmosphere, A substrate having a second cavity, on which the first and second thermosensitive elements are formed, heating means for heating the first and second thermosensitive elements, and fixed to the substrate; And a cover provided with first and second recesses in a portion corresponding to the second thermal element, and the detection areas of the first and second thermal elements are the first and second cavities, respectively. Formed on the first heat sensitive element side of the substrate and has a vent in a portion other than the first cavity, and the first and second heat sensitive elements are the same. The vent is formed on a surface different from the surface on which the first and second heat sensitive elements are formed. A gas sensor and measuring the temperature change of the space by the incoming gas through.

  The invention according to claim 2 of the present invention is the gas sensor characterized in that two or more vent holes are formed across the detection region.

  The invention according to claim 3 of the present invention is the gas sensor characterized in that the vent is formed in a slit shape on the outer periphery of the detection region.

  The invention according to claim 4 of the present invention is the gas sensor characterized in that the space on the second heat sensitive element is an atmosphere in which the gas concentration is controlled so as to be a reference according to the object to be measured.

  The invention according to claim 5 of the present invention is the gas sensor characterized in that the heat-sensitive film is the same as the material used for the heating means.

  The invention according to claim 6 of the present invention is the gas sensor characterized in that the substrate and the cover are joined by metal, and the space between the second thermosensitive element and the cover is hermetically sealed.

  In the invention according to claim 7 of the present invention, the substrate further includes signal extraction electrodes of the first and second thermal elements, on a surface different from the first and second recess forming portions of the cover. The gas sensor further comprising an electrode, wherein the signal extraction electrode and the electrode formed on the cover are electrically connected.

  According to the first aspect of the present invention, since the element having the detection region formed into a membrane in order to reduce the heat capacity is composed of only a thin film, it may be damaged due to the influence of wind from the outside. it can. By fixing the cover and the substrate by sealing, the sensing element and the reference element package can be accurately performed without being separated into individual pieces, and air is vented from the back surface of the thermal element outside the sensing area. As a result, the influence of wind on the membrane in the detection region can be suppressed.

  According to the second aspect of the present invention, the response speed can be increased because the gas can easily enter and exit from the outside air.

  According to invention of Claim 3, since a vent hole is thermally symmetrical with respect to a detection part, the heat distribution of a detection part can be stabilized.

  According to the fourth aspect of the present invention, the gas corresponding to the application can be detected by controlling the measurement space of the reference element in an atmosphere matched to the measurement object.

  According to invention of Claim 5, a process can be simplified by forming simultaneously the taking-out electrode of a thermal element, and the heater used for a heating means.

  According to the invention of claim 6, a stable airtight level can be ensured by forming a sealed space in the second detection element with a metal having high airtightness against moisture and gas.

According to the seventh aspect of the present invention, the size of the element can be reduced by taking out the take-out electrode directly to the upper part of the cover.

It is sectional drawing of the gas sensor in 1st Embodiment. It is a top view of the thermosensitive element in 1st Embodiment. It is a top view of the 1st thermosensitive element in 1st Embodiment. It is sectional drawing of the 1st thermal element in 1st Embodiment. It is sectional drawing of the gas sensor in 2nd Embodiment. It is a top view of the thermosensitive element in 3rd Embodiment. It is a top view of the 1st thermal element in a 5th embodiment. It is sectional drawing of the 1st thermal element in 5th Embodiment.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In addition, this invention is not limited to the following embodiment. The constituent elements described below include those that can be easily assumed by those skilled in the art and those that are substantially the same. Furthermore, the constituent elements described below can be appropriately combined.

(First embodiment)
A first embodiment will be described with reference to FIGS. 1 is a cross-sectional view of a gas sensor in the first embodiment, FIG. 2 is a top view of a thermal element in the first embodiment, FIG. 3 is a top view of a thermal element 3A, and FIG. 4 is a BB cross section of the thermal element 3A. FIG. As shown in FIG. 1, the gas sensor 100 of 1st Embodiment consists of the board | substrate 1 and the cover 2 provided with the recessed part. From the first heat sensitive element 3A formed on the substrate 1 by the hollow structure on the first concave portion 4A formed on the first main surface 1A and the second concave portion 4B, and the second heat sensitive element 3B. Become. As shown in FIG. 3, the thermal element 3A is provided with a heater 14 as a heating means, and similarly, although not shown, the thermal element 3B is provided with a heater 14 as a heating means. The heat sensitive elements 3A and 3B and the heater 14 may be capable of being energized independently without being short-circuited independently, and may be arranged in parallel on a plane or may be stacked via an insulating film. As shown in the cross-sectional view of FIG. 1, the substrate 1 including the first thermosensitive element 3A has a first main surface from the second main surface 1B to a portion other than the first recess 4A formed on the first main surface 1A. The surface 1A (surface on which the thermal element is formed) has a vent hole 5, and the cover 2 is provided with a first recess 6A and a second recess 6B at a position corresponding to the detection element, The substrate 1 is connected to the first main surface 1A through a metal sealing layer 8. Note that the drawings are schematic, and for convenience of explanation, the relationship between the thickness and the planar dimensions, and the ratio of the thickness between devices are within the range where the effect of this embodiment can be obtained, and the actual sensor structure. May be different.

  In the gas sensor 100 shown in FIG. 1, the first thermal element 3A having a hollow structure serves as a detection element, and the second thermal element 3B having a hollow structure serves as a compensation element. Here, the hollow structure will be described. In the gas sensor 100, the thermal element includes a hollow structure and is formed on the substrate. A generic name of the structure having a thin film portion formed in the hollow portion on the first concave portion 4A and the second concave portion 4B of the substrate 1 is defined as a hollow structure. Furthermore, the area | region comprised with the detection element and detection material of the thin film part in a heat sensitive area | region is made into a detection area | region. The definitions of the hollow structure, the heat sensitive region, and the detection region described here are applied not only to the gas sensor 100 but also to the heat sensitive elements 3A and 3B.

  The configuration of the first thermal element 3A and the second thermal element 3B will be described with reference to FIGS. As shown in FIGS. 3 and 4, the thermal element 3 </ b> A includes an insulating film 11, a pair of extraction electrodes 12, a thermal film 13 (hereinafter referred to as a thermal film 13), a heating heater 14, an interlayer on the substrate 1. The insulating film 15 and the protective film 16 are included. Moreover, it has a pair of pad electrode 7A, 7B connected with a pair of extraction electrode 12 with which the thermal element 3A, 3B is provided. Moreover, it has a pair of extraction electrode 17 and pad electrodes 18A, 18B provided in the heater. Normally, each pad electrode 7, 18 is formed on the substrate 1.

(Description of thermal element)
A thermal element applied to the gas sensor 100 in the first embodiment shown in FIG. 1 will be described. As shown in FIG. 4, the thermal element 3 </ b> A is formed by laminating a pair of extraction electrodes 12 formed at a predetermined gap interval, and between the pair of extraction electrodes 12 and on the pair of extraction electrodes 12. And a heat sensitive film 13. Further, a heater 14 is provided on the hollow structure as a heating means. The thermal element 3 </ b> A detects a change in electrical characteristics of the thermal film 13 formed by being laminated between the pair of extraction electrodes 12 and on the pair of extraction electrodes 12. The heater 14 is drawn out to the outside of the concave portion of the substrate by wiring and is connected to the pad electrode 18. As shown in FIG. 4, the detection region 10 in the hollow structure 4 </ b> A of the concave portion is thermally insulated by the substrate 1 and air except for a thin film beam portion, and a change in heat can be detected efficiently. As shown in FIG. 3, a hollow portion formed of a thin film is a heat-sensitive region, and a portion where the heat-sensitive film 13 and the extraction electrode 12 are formed is a detection region. That is, the area where the heat sensitive film 13 exists is an effective detection area.

  As the material of the heat sensitive film 13, for example, a thermistor thin film having a negative temperature coefficient such as amorphous silicon, polysilicon, germanium, silicon carbide, composite metal oxide or the like is suitable. Alternatively, a temperature measuring body such as Pt or Ni having a certain temperature coefficient may be used. The material of the pair of extraction electrodes 12 is preferably a material having a heat resistance that can withstand the process of forming the heat-sensitive film 13 and a heat treatment process, and a relatively high melting point having an appropriate conductivity. ), Platinum (Pt), gold (Au), tungsten (W), tantalum (Ta), palladium (Pd), iridium (Ir), or an alloy containing two or more of these metals. Further, a pair of pad electrodes 7 are formed so as to be connected to each pair of extraction electrodes 12 in order to extract electric signals. When a metal temperature sensor is used, it may be formed in a wiring shape integrally with the extraction electrode. The material of the pair of pad electrodes 18 is preferably a material that can be easily electrically connected such as flip chip bonding, such as aluminum (Al), copper (Cu), gold (Au), and the like.

  The thermal film 13 used in the thermal element 2A is a thermistor thin film and has a B constant. Here, the B constant is a constant representing the magnitude of the resistance change obtained from two arbitrary temperatures of the resistance-temperature characteristics, and B is the resistance of the semiconductor R and the absolute temperature T of the semiconductor is infinite. When the value corresponding to the resistance value is R0, R = R0 * e ^ (B / T).

  The material of the heater 14 is a metal layer made of a material having a relatively high melting point and a conductive material that can withstand processes such as a heat-sensitive film forming process and a heat treatment process. For example, Mo, Pt, Au, W, Ta, Pd, Ir, or an alloy containing any two or more of these is preferable. Further, a conductive material capable of high-precision dry etching such as ion milling is preferable, and Pt or the like having higher corrosion resistance is more preferable. When using a Pt temperature sensor, the film may be formed simultaneously. In order to improve the adhesion to the insulating film 3, it is preferable to form an adhesion layer such as titanium (Ti) under the Pt.

  The substrate 1 constituting the thermal element 3A has a first main surface 1A and a second main surface 1B which is the back surface thereof, and an insulating film 11 is formed on at least the first main surface 1A. . The material of the substrate 1 is not particularly limited as long as it has an appropriate mechanical strength and is suitable for fine processing such as etching. For example, a silicon single crystal substrate, a sapphire single crystal A substrate, a ceramic substrate, a quartz substrate, a glass substrate, or the like is preferable. The insulating film 2 is not particularly limited as long as it has an appropriate mechanical strength and can be easily formed by a known thin film process. For example, a silicon oxide film, a silicon nitride film, etc. Is preferred. On the first main surface 1 </ b> A of the substrate 1, the above-described heat sensitive film 13 is formed via the insulating film 11, the heater 14, the interlayer insulating film 15, and the extraction electrode 12. Further, a protective film 16 is formed to cover the heat sensitive film 13 and shield it from the outside air. The heater 14 and the heat sensitive film 13 may be disposed in the thickness direction as long as they are electrically insulated from each other. The heater 14 may be disposed above the interlayer insulating film.

  Here, the protective film 16 only needs to cover at least the thermal element 3A. The material of the protective film 16 may be an insulating film having moderate durability, and is not particularly limited, but is preferably the same as the material of the insulating film 11. By doing in this way, since the insulating film 11 and the protective film 16 which comprise the circumference | surroundings of the thermosensitive element 3A become all the same material, it becomes preferable because it becomes more uniform temperature distribution. When the heat sensitive film 13 has sufficient corrosion resistance, the protective film 16 is not always necessary.

  The first concave portion 4A and the second concave portion 4B of the substrate are formed on the first main surface 1A, and are formed below the beam and the detection region formed of a thin film. It is desirable to form the recess after forming the vent from the second main surface 1B to the first main surface after the formation of the thermal element. The recess can be formed by removing the substrate by etching after the formation of the thermal element 3A. Alternatively, it may be formed by partially etching the lower portion of the detection region using a bonded substrate in which a recess is formed in advance, that is, a so-called SOI substrate with a cavity (Silicon on Insulator substrate).

In the vent hole 5, the substrate 1 is opened from the second main surface 1B side toward the first main surface 1A side.
The vent may be formed by opening from the second main surface 1B of the substrate by using anisotropic dry etching. The vent hole 5 is not limited to opening from the second main surface, and may be any surface other than the surface on which the thermal element is formed. For example, you may open from the side surface of a board | substrate.

(Description of gas sensor)
In the gas sensor, a cover provided with a first recess 6A, a second recess 6B, an extraction portion 18, and a sensor signal extraction terminal electrode 19 is connected to the substrate 1 on which the thermal element is formed and the position corresponding to the thermal elements 3A and 3B. It is composed by doing. The material of the cover 2 is not particularly limited as long as it has an appropriate mechanical strength and is suitable for fine processing such as etching. For example, a silicon single crystal substrate, a sapphire single crystal A substrate, a ceramic substrate, a quartz substrate, a glass substrate, or the like is preferable.

The cover 2 is provided with a first recess 6A and a second recess 6B in order to secure a space in the heat sensitive region. By forming the first recess 6A and the second recess 6B, it is possible to reduce the escape of heat from the space heated in the vicinity of the detection region by the heating means of the thermal element to the cover. The cover 2 and the thermal elements 3A and 3B are connected via the connection portion 8. For the connection, the second recess 4B of the second thermosensitive element 3B and the second recess of the cover need only be hermetically sealed, and anodic bonding, activation bonding, metal bonding, and the like are suitable. The signals of the heat sensitive elements 3A and 3B may be taken out through the lower part of the connection portion with the cover 2 on the board side, but pass through the inside of the cover board and connect the pad electrodes 7 and 18 and the cover 2 from the upper part to take out the sensor signal. It is preferable to take out to the terminal electrode 19. This makes it possible to reduce the size of the element.
The cover 2 may be connected in pieces, but it is preferable to connect the cover and the substrate on which a plurality of thermal elements are formed. Thus, the process can be performed in a lump, and the substrate and the cover, that is, the gas sensor can be separated into pieces after connection.

  With the configuration as described above, the thermal element 3A of the gas sensor 100 is directly affected by the gas entering from the outside by forming the vent 5 outside the recess 4A on the first main surface of the substrate. Therefore, it is possible to solve the problem that the detection element is directly affected by wind and dirt from the outside, which has been a problem in the prior art.

(Second Embodiment)
In the second embodiment shown in FIG. 5, in addition to the vent 5, another vent 5 </ b> B is provided. By providing a plurality of vent holes, the inflow path and the inflow amount of gas from the outside increase. The spatial temperature of the detection region can be further improved in responsiveness because the thermal change stabilizes quickly due to the inflow of gas. Note that the position of the vent 5B is a position sandwiching the first recess from the position of the vent 5. Furthermore, it is preferable that it exists in a symmetrical position with respect to a recessed part.

(Third embodiment)
In the third embodiment shown in FIG. 6, the vent 5C is formed in a slit shape on the outer periphery of the detection region. Thereby, the temperature change due to the inflow of gas is point-symmetric with respect to the center of the detection region. Since the reaction of the temperature change can be considered as an integration of the entire detection region, the temperature distribution in the detection region is improved, so that more stable measurement is possible.

(Fourth embodiment)
The fourth embodiment differs from the first embodiment in that the second sensing element is an atmosphere in which the gas concentration is controlled so that the space on the second thermosensitive element becomes a reference according to the object to be measured. Is in a low humidity state. By setting the measurement space of the second thermal element in a low humidity state, the first thermal element can detect the absolute humidity according to the amount of moisture in the space, based on the space on the second thermal element. become.

(Fifth embodiment)
In the fifth embodiment shown in FIGS. 7 and 8, the heat-sensitive material 9 of the heat-sensitive element formed on the substrate and the heater 20 used for the heating means are made of the same material. The material may be a metal layer made of a conductive material that can withstand a process such as a heat treatment process and a material having a relatively high melting point, and the resistance of the metal layer changes depending on the temperature. For example, Mo, Pt, Au, W, Ta, Pd, Ir, or an alloy containing any two or more thereof is suitable. Thereby, it becomes possible to form the structure of a heating means and a detection means simultaneously, and it becomes possible to simplify a process.

(First embodiment)
Actually, the gas sensor 100 according to the first embodiment was manufactured by the following procedure. First, a silicon substrate was prepared as the substrate 1, and a thermal oxide insulating film as an insulating film 11 was formed to 0.5 μm on the substrate surface.

  Next, an adhesion layer (not shown) made of Ti having a thickness of 5 nm is formed on the insulating film 11 on the first main surface 1A by high frequency magnetron sputtering as the heater 14 used for the first and second heating. Then, a metal layer made of Pt having a thickness of 100 nm was formed on the substantially entire surface. Note that the adhesion layer made of Ti is an adhesion layer for making the metal layer made of Pt and the insulating film 11 adhere to each other. If necessary, there is no need for an adhesion layer made of Ti.

  Thereafter, as shown in FIG. 3, after forming an etching mask having a desired shape such as a meander shape by photolithography on the formed metal film, a metal layer made of Pt not covered with the etching mask and The adhesion layer made of Ti is etched by an ion milling method. Then, the heater 14 is formed in a desired shape by removing the etching mask.

  Subsequently, when forming the thermosensitive element, an interlayer insulating film 15 for electrically insulating from the metal electrode as a heating means was formed. An SiO 2 film was formed by TEOS (Tetra-Ethyl-Ortho-Silicate) -CVD method to form an interlayer insulating film 15 having a thickness of 0.4 μm. Here, by using the same Si oxide film as the insulating film 11, it functions as a protective film firmly against thermal stress during the operation of the heater 14.

Further, as shown in FIG. 4, an adhesion layer made of Ti having a thickness of 5 nm and a metal made of Pt having a thickness of 100 nm are formed on the surface of the interlayer insulating film 15 on the first main surface 1A by high-frequency magnetron sputtering. Layers are sequentially formed to form the extraction electrode 12. The adhesion layer made of Ti is an adhesion layer for making the metal layer made of Pt and the interlayer insulating film 15 adhere to each other. Here, if necessary, the adhesion layer made of Ti may be omitted.
An etching mask having a desired shape such as a comb-teeth shape is formed on the formed extraction electrode 12 by photolithography, and then the adhesion layer and the metal layer not covered with the etching mask are etched by an ion milling method. .

Thereafter, as shown in FIG. 4, by removing the etching mask, the take-out electrode 12 in which the gap between the pair of comb-tooth electrodes of the heat-sensitive film 13 is 25 microns is formed. Note that the pair of comb electrode patterns are alternately arranged in the horizontal direction as seen in the section BB in FIG.

  Next, a MnNiCo-based composite oxide film was formed on the surface of the formed extraction electrode 12 by sputtering to form a heat sensitive film 13 that functions as a heater temperature detection film having a thickness of 0.4 μm and a resistance value of 140 kΩ. . This sputtering was performed using a multi-target sputtering apparatus under conditions of a substrate temperature of 600 ° C., an argon (Ar) pressure of 0.5 Pa, an O 2 / Ar flow rate ratio of 2%, and an input power of 400 W. Then, using the BOX baking furnace, heat processing was implemented on condition of 650 degreeC and 1 hour in air | atmosphere atmosphere.

  Subsequently, a desired etching mask was prepared by photolithography, and wet etching was performed using a ferric chloride aqueous solution to remove the MnNiCo-based composite oxide film in the non-mask region. Thereafter, the thermal mask 13 was formed by removing the etching mask.

  Next, a protective film 16 having a thickness of 0.4 μm was formed by forming a SiO 2 film by TEOS-CVD so as to cover the thermal film 13.

  Although not shown, an etching mask is created by photolithography on the protective film 16 excluding the portion where the electrode pads 7A, 7B, 18A, and 18B are disposed, and the portion where the electrode pads 7A, 7B, 18A, and 18B are disposed. An opening was formed by removing the SiO2 film, an Al metal thin film having a thickness of 1.0 micron was formed by an electron beam evaporation method, and a lift-off method was formed so as to fill the opening. Al and the mask other than the Al metal thin film were removed to form pad electrodes 7A, 7B, 18A, and 18B.

  Next, after forming an etching mask on the first main surface 1A side of the substrate 1 by photolithography, the first recess 4A and the first recesses are formed on the main surface 1A of the substrate 1 by wet etching using HF and KOH. Two recesses 4B were formed to a depth of 30 μm. After the insulating film on the substrate surface was removed by HF, the substrate 1 was partially removed by anisotropic etching using a KOH aqueous solution, leaving a detection region and a beam portion for taking out signals, thereby forming a hollow structure. Finally, the detection mask was completed on the substrate by removing the etching mask used for the cover of the necessary part.

  Finally, after forming an etching mask on the second main surface 1B of the substrate 1 by photolithography, the insulating film 11 on the second main surface 1B side is formed by reactive ion etching (RIE) using a fluoride-based gas. Removed. Thereafter, the substrate 1 was removed by RIE using a fluoride-based gas to form a vent hole 5 having a diameter of about 100 μm. In order to form the vent hole 5 by removing the substrate 1, the vent hole 5 was obtained by using a deep RIE (Deep-RIE, D-RIE) method in which etching and barrier layer formation were alternately performed. Next, an etching mask is formed on the second main surface 1B side of the substrate 1 by photolithography, and then the substrate 1 is second reactively etched by reactive ion etching such as D-RIE method using a fluoride-based gas. Deep drilling is performed perpendicular to the surface 1B, and the vent 5 is opened. The vent can be formed in a desired shape by forming a pattern before processing the shape of the etching mask. The D-RIE method uses a C4F8 gas to deposit a reaction inhibiting film (fluorocarbon-based polymer) on the side wall of the cavity, thereby mainly suppressing a chemical side etching caused by F radicals; A plasma etching process for anisotropically etching the substrate 1 substantially vertically is alternately repeated by chemical etching of the substrate 1 with F radicals using SF6 gas and physical etching of the reaction suppression film with F ions. This is a method of deeply digging the substrate 1.

  A Si substrate was used for the sensor cover 2 in the same manner as the substrate 1. In the Si used for the cover, first, holes for electrical connection are formed at points aligned in the vicinity of the pad electrode 7 of the heater and the pad electrode 18 of the thermal element formed on the substrate 1 by the DRIE method. It was formed up to 80% of the thickness of the substrate by dry etching. After forming a thin Ti layer inside the hole by sputtering, the inside of the hole was filled with Cu by plating. Thereafter, 20% of the thickness of the cover 2 was polished by CMP from the surface opposite to the surface where the holes were formed, thereby exposing the Cu embedded in the holes. Thereafter, Cu is sputtered and photolithography is performed as a connection electrode at a position facing the pad electrode of the thermosensitive element in a form electrically wired to the through electrode, and an annular connection electrode 8B for connecting the element and the cover. Formed using. Thereafter, a signal extraction terminal 20 with the outside of the sensor was formed on the back surface of the cover in the same process. Further, an etching cover was formed in a portion other than the portion corresponding to the detection region, and Si was etched by KOH, thereby forming the first recess 6A and the second recess 6B.

  The connection between the substrate 1 and the cover 2 is formed on the substrate 1 and the cover 2 by aligning at the wafer level using a double-sided wafer aligner / bonder and then pressing the substrate 1 and the cover 2 while pressing them. It was formed by performing metal diffusion of Cu between the connection electrodes 8A and 8B and between the pad electrode of the thermosensitive element and the connection electrode of the cover.

By using the above configuration, it is possible to configure a gas sensor that measures a difference in heat conduction of a gas that is small in size and hardly affected by wind and dirt from the outside.
In addition, although the cavity part formed in the board | substrate in embodiment and an Example was demonstrated as a recessed part as an example, it should just exist in the thermosensitive element vicinity, and is not limited to a recessed part.

  The present invention is mounted on industrial equipment and environmental monitoring devices, and is used for the purpose of detecting a target gas.

DESCRIPTION OF SYMBOLS 1 Board | substrate 1A 1st main surface of a board | substrate 1B 2nd main surface of a board | substrate 2 Cover 3A, 3B Thermal element 4, 4A, 4B Recessed part of the board | substrate 1, 1st recessed part, 2nd recessed part 5, Vent 6 6A, 6B Cover concave portion, third concave portion, fourth concave portion 7, 7A, 7B Thermal element pad electrode 8, 8A, 8B Connection electrode 9 Thermal material 10 Thermal area 11 Insulating film 12 Extraction electrode 13 Thermal film 14 For heating Heater 15 Interlayer insulating film 16 Protective film 17 Extraction part 18, 18A, 18B Heating heater pad electrode 19 Sensor signal extraction terminal electrode 20 Heating heater 100 Gas sensor

Claims (7)

A gas sensor that detects a gas by utilizing a temperature change caused by heat conduction of a gas in a space, and includes a first thermosensitive element that measures the ambient temperature of the outside air, and a second that measures the ambient temperature of a reference closed space. And a substrate having a first main surface on which the first and second heat sensitive elements are formed and a second main surface which is the back surface thereof . Heating means for heating the first and second thermal elements, and a cover fixed to the substrate and provided with first and second recesses in portions corresponding to the first and second thermal elements. ,
The detection regions of the first and second thermal elements are respectively formed on the first and second cavities of the substrate, are on the first thermal element side of the substrate, and There is a vent in a portion other than the first cavity, and the first and second thermal elements are formed on the same substrate, and the vent is formed from the second main surface side. The substrate is formed so as to open toward the first main surface side, and the vent hole on the first main surface side is located in the first recess of the cover, and the first and second gas sensor and measuring the temperature change of the space by the gas entering through the vent from different said second major surface and the first major surface of the heat-sensitive element is formed. 2. The gas sensor according to claim 1, wherein two or more vent holes are formed across the detection region. The gas sensor according to claim 1, wherein the vent is formed in a slit shape on an outer periphery of the detection region. The gas sensor according to any one of claims 1 to 3, wherein the space on the second thermosensitive element is an atmosphere in which a gas concentration is controlled so as to be a reference according to a measurement target. The said 1st thermosensitive element has a thermosensitive film and a heating means, The said thermosensitive film is the same as the material used for the said heating means, The any one of Claim 1 thru | or 4 characterized by the above-mentioned. Gas sensor. The gas sensor according to any one of claims 1 to 5, wherein the substrate and the cover are joined by metal, and a space joined by the second thermosensitive element and the cover is hermetically sealed. The substrate further includes signal extraction electrodes of the first and second thermal elements, and further includes an electrode on a surface different from the first and second recess forming portions of the cover, and the signal extraction electrode The gas sensor according to claim 1, wherein an electrode formed on the cover is electrically connected.

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