JP2010230385A - Membrane-type gas sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas detection sensor which does not cause excessive generation of heat and has proper detection sensitivity. <P>SOLUTION: The holding member constituted of a plurality of beam parts within a sensor region R is provided so as to extend from a support substrate 41. A plurality of membrane heat-sensing members provided to the beam parts are provided at the positions getting out of the center region B of the sensor region R. The respective membrane heat-sensing members may by made point-symmetric, with respect to the center point C of the center region R and may be set at the positions of an equal distance from the center point C. According to this constitution, heat is not concentrated at the arrival time of gas and, if a plurality of the membrane heat-sensing members are made identical in shape and size and made identical in heat capacity, the sensitivity characteristics or the reaction speed characteristics of this membrane-type gas sensor at the time of detection of the gas is improved. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a catalytic combustion type gas sensor that detects various gas leaks, and more particularly to a thin film type gas sensor.

  Conventionally, a gas sensor has been used as a sensor for detecting a combustible gas such as hydrogen gas or methane gas. The gas sensor captures a change in the electrical signal of the detection element by an interaction caused by the arrival of gas on the detection surface of the detection element. In the following description, combustible gas is simply expressed as gas.

  Many proposals have been made regarding the configuration of the gas sensor. Among them, the catalytic combustion type gas sensor is widely known. This contact combustion type gas sensor detects the arrival of gas by causing an exothermic reaction when the gas contacts a detection element or catalyst having a detection surface.

  Such a contact combustion type gas sensor is widely used as a gas leak detection device in various devices using gas, indoors where the gas sensor is installed, and the like in home use, industrial use and the like.

  In recent years, a type called a bulk type has been widely used among catalytic combustion type gas sensors, but on the other hand, a microsensor element manufacturing that forms a thin-film heat transfer film, catalyst film, electrode, wiring, and heater on a silicon wafer. A thin-film gas sensor using a sensor chip based on MEMS (Micro Electro Mechanical Systems) using technology has also been used (for example, see Patent Document 1).

The prior art disclosed in Patent Document 1 will be described with reference to FIG. FIG. 13 is a plan view rewritten so as not to depart from the gist thereof for easy explanation.
In FIG. 13, 19 is an electrode pad, 18 is an electrical wiring, 3 is a cavity, 2 is a semiconductor substrate, 17 is a heat sensing part, and 16 is a beam part.
The semiconductor substrate 2 is processed into a frame shape, and a beam portion 16 connecting the frames is formed. When viewed from the plane, the portion without the beam portion 16 is the cavity 3. The cavity 3 is also called an air hole and is a portion through which gas passes.
The heat sensing part 17 provided on the upper part of the beam part 16 undergoes an exothermic reaction and changes its resistance value when the gas arrives.

  A thin film gas sensor is configured by the sensor chip having such a configuration and a circuit for controlling the sensor chip. In order to detect the arrival of gas, a voltage is applied between the electrode pads 19 in advance, and a change in resistance caused by heat generation of the heat sensing unit 17 due to the arrival of gas is detected.

  A sensor chip of a thin film type gas sensor is characterized in that its constituent elements can be formed by a semiconductor manufacturing technology, so that it has a higher degree of integration and higher mass productivity than a bulk type catalytic combustion type gas sensor. In addition, since the heater and the like can be formed of a metal thin film heat sensing element, the thermal response is good.

  In recent years, miniaturization of thin film gas sensors has been demanded. Since the size of the thin film gas sensor is determined by the planar area and thickness of the sensor chip, the thin film gas sensor can be made smaller as the sensor chip is smaller and thinner.

JP-A-8-247981 (page 6, FIG. 1)

  In recent years, thin-film gas sensors are required to be improved in gas sensing performance as well as to be reduced in size. In the conventional technique shown in Patent Document 1, if it is intended to meet such a requirement, the number of heat sensing parts 17 provided on the upper part of the beam part 16 may be increased. Specifically, a plurality of heat sensing parts 17 are arranged on the upper part of the beam part 16.

  With such a configuration, more heat sensing units 17 are exposed to the gas, so that a plurality of heat sensing units 17 generate heat at the same time. As a result, the amount of heat generated is increased, so that the thermal response is improved, and as a result, the sensing performance is improved.

However, it has been found that in the structure in which the plurality of heat sensing units 17 are arranged, the heat generated by the heat sensing unit 17 affects other adjacent heat sensing units 17 and may generate excessive heat. Thus, if the heat sensing parts 17 are dense, heat will be generated in that part.
Such excessive heat generation is applied as a thermal stress to the beam portion 16 provided with the heat sensing unit 17, thereby causing a problem of causing damage such as a crack in the beam portion 16 itself.

That is, in the conventional technique shown in Patent Document 1, if an attempt is made to improve the gas sensing performance, the sensor chip itself is damaged.
As shown in the prior art shown in Patent Document 1, the thin film gas sensor achieves miniaturization by using a MEMS sensor chip.
In other words, a technology that achieves both improved gas sensing performance and a smaller sensor chip has not yet been proposed.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a thin-film gas sensor that achieves both downsizing of a sensor chip and improvement of gas sensing performance.

  In order to solve the above problems, the thin film gas sensor of the present invention employs the following configuration.

  In the thin film type gas sensor including the inside of the support substrate having a frame shape as a sensor region, a holding member extending from the support substrate in the sensor region, and a plurality of thin film thermal sensors on the holding member in the sensor region, The thin-film heat sensing element is characterized in that it is arranged apart from the center point of the sensor region.

  By adopting such a configuration, the thin film heat sensing elements are not concentrated in the vicinity of the center point of the sensor region, so that the heat generated by the arrival of gas is not concentrated.

  The thin film heat sensing element may be arranged symmetrically with respect to the center point. Further, the plurality of thin film heat sensing elements may be equidistant from the center point of the sensor area.

  By adopting such a configuration, the heat generated in the thin film heat sensing element caused by the arrival of gas becomes uniform.

  In the thin film gas sensor of the present invention, it is preferable that the heat capacities of the plurality of thin film heat sensing elements are the same.

  As a result, the same heat generation characteristics can be obtained for each thin film heat sensing element, and the accuracy of the sensitivity characteristics and reaction speed characteristics for detecting the gas is improved.

  In the thin film gas sensor of the present invention, it is desirable that a plurality of thin film heat sensing elements are connected to each other through a metal thin film resistor.

  A plurality of thin film heat sensing elements can be connected in series by connecting each thin film heat sensing element via a metal thin film resistor.

  In the thin film type gas sensor of the present invention, it is desirable that the holding member is formed with a through hole avoiding the mounting portion of the thin film heat sensing element.

  By having the through-hole, gas can flow through the through-hole to the upper surface side and the back surface side of the holding member, so that the gas that has arrived at the sensor region does not stay and the gas is inadvertently held in the holding member. Stress is no longer applied.

  In the thin film gas sensor of the present invention, it is desirable that the holding member is thinner than the width of the mounting portion of the thin film heat sensing element.

  With such a configuration, the heat capacity of the holding member is reduced, and the gas detection sensitivity is improved.

  The holding member has a laminated film structure formed by laminating a plurality of thin films, and the first thin film constituting the laminated film has a beam structure having a rectangular cross section, and the second thin film constituting the laminated film. The thin film has a membrane structure, and this membrane structure may be a uniform thin film from the support substrate toward the sensor region, and may have a through hole avoiding the mounting portion of the thin film heat sensing element.

  With such a configuration, the strength of the holding member is improved. Further, since the stress characteristics of the film can be changed between the first thin film and the second thin film, the holding member can be made strong against stress.

  In addition, a plurality of holding members are provided, and the plurality of holding members have a cantilever structure in which the end portions do not overlap with the center point of the sensor region in a planar manner, and thin film heat sensing is performed on each of the plurality of holding members. A body may be provided.

  Such a configuration improves the balance as a cantilever structure.

In the thin film type gas sensor according to the present invention, the thin film heat sensing elements are appropriately separated from each other, so that the thin film heat sensing elements are not crowded, and heat generation is not concentrated.
Therefore, damage to the holding member can be prevented, and the lifetime as a sensor can be extended. In addition, since the thin film thermal detectors can be distributed and arranged in a well-balanced manner, the resistance value of the thin film thermal detectors can be set high, and the sensitivity characteristics and reaction speed characteristics during gas detection are improved. be able to.

It is the top view and end view explaining 1st Embodiment of the thin film type gas sensor of this invention. It is the elements on larger scale of the site | part of the arrow D in Fig.1 (a). It is a graph explaining the improvement of the gas detection sensitivity by this invention. It is a top view explaining the 2nd Embodiment of this invention. It is the top view and end view explaining the 3rd Embodiment of this invention. It is a top view explaining the 4th Embodiment of this invention. It is a top view explaining the 5th Embodiment of this invention. It is a top view explaining the different structure of the 5th Embodiment of this invention. It is the top view and end view explaining the 6th Embodiment of this invention. It is a top view explaining the 7th Embodiment of this invention. It is the top view and end view explaining the 8th Embodiment of this invention. It is the schematic explaining the mounting form of this invention. 2 is a plan view of a gas sensor described in Patent Document 1. FIG.

In the thin film type gas sensor of the present invention, a plurality of thin film heat sensing elements are distributed and arranged in a part slightly away from the center point of the sensor region.
Specifically, the holding member is provided in the sensor region surrounded by the inner wall of the frame-shaped support substrate. The holding member is, for example, a beam portion extending from the support substrate. The thin film heat sensing element is provided on the holding member, but it is provided so as not to overlap with the center point that is the center of the sensor region and to be separated from the center point.
By having such a structure, the thin film heat sensing element is not concentrated near the center point of the sensor region, so that heat generated by the arrival of gas is not concentrated. Therefore, it is possible to reduce the size of the thin film gas sensor and improve the gas sensing performance.

In the gas detection procedure of the thin film type gas sensor of the present invention, a current is passed through the thin film heat sensing element, and the process waits until the gas arrives in a state where the temperature has reached a predetermined temperature due to heat generated by energization. When the gas arrives and the gas comes into contact with the gas detector above the thin film heat detector, the gas detector burns, and the thin film heat detector further generates heat. As a result, the value of the current flowing through the thin film thermal sensor changes, and this is detected.
Since such a detection procedure is already known, a detailed description thereof will be omitted.

  Note that the characteristic configuration in which the thin film heat detectors are not concentrated near the center point of the sensor region can be configured with at least two thin film heat detectors, but of course, the number may be increased. Absent. One thin film heat sensing element may be provided on one holding member, and a plurality of thin film heat sensing elements may be provided on one holding member.

  By increasing the number of thin film heat detectors, the number of places where the incoming gas comes into contact increases and heat is easily generated (the resistance value is likely to change), so that the detection sensitivity is improved. Further, when all the increased thin film thermal detectors are connected in series, the resistance value becomes high, so that it becomes easier to detect a change in the resistance value due to the arrival of gas. Of course, the number of thin film heat sensing elements provided on one holding member also varies depending on the system using the thin film gas sensor of the present invention.

  In any case, regardless of the number of thin film heat detectors, the thin film heat detectors are arranged away from the center point so as not to concentrate near the center point of the sensor area, so that heat generation due to the arrival of gas is prevented. Since it is dispersed in the sensor region, there is no concentration of heat, and it is difficult to break as a thin film gas sensor, and its life is improved.

  Details of the embodiment will be described below with reference to the drawings. As already described, in the present invention, it is only necessary to have at least two thin film heat detectors. As a good example of improving detection sensitivity, an example using four thin film heat sensors; An example using eight thin film thermal detectors will be described.

[Description of First Embodiment: FIGS. 1 and 2]
A first embodiment of a thin film gas sensor of the present invention will be described with reference to FIGS. FIG. 1 is a diagram schematically showing the structure of a first embodiment of a thin film gas sensor of the present invention. FIG. 1A is a plan view thereof, and FIG. 1B is an end view schematically showing an end surface taken along a cutting line XX ′ of FIG. FIG. 2 is a partially enlarged view in which the connecting portion of the beam portion shown in FIG.

  In FIG. 1, 41 is a frame-shaped support substrate, 41c is an inner wall of the support substrate 41, 42 is an insulating film, and 42h is a through hole. 43a, 43b, 43c, 43d are beam portions. 44a, 44b, 44c, 44d are electrode pads. Reference numerals 45a, 45b, 45c, 45d, 45e, and 45f are metal thin film resistors. Reference numerals 46a, 46b, 46c and 46d are thin film heat sensing elements. Reference numeral 48 denotes a gas sensor that covers the upper part of the thin film heat sensor. The gas detector 48 functions as a catalyst. And these comprise the gas detection element 40.

A symbol R indicates a sensor region. As shown in FIG. 1, the gas detection element 40 includes a frame-shaped support substrate 41 and beam portions 43 a to 43 d inside thereof. These beam portions are provided with a thin film heat sensing element, a metal thin film resistor, and a gas sensing element.
Thus, the sensor region R is a region where a configuration for detecting gas is provided, and a portion surrounded by the four inner walls 41 c of the support substrate 41 is the sensor region R.

  The symbol C indicates the center point of the sensor region R. In FIG. 1, it is indicated by “+”. A symbol B is a central region of the sensor region R and includes a center point C. In FIG. 1, it is indicated by a circular broken line. In the example shown in FIG. 1, the central region B is also a joining portion where the beam portions 43a, 43b, 43c, and 43d join.

  In FIG. 1 and FIG. 2, a connecting portion of adjacent beam portions in the central region B is indicated by a symbol D. As shown in FIG. 2, the connection portion D has a triangular projecting portion F from a point Bcd where the beam portions contact each other.

[Description of external shape: FIGS. 1 and 2]
First, the outer shape will be described.
As shown in FIG. 1, the support substrate 41 has a frame shape in plan. The support substrate 41 is preferably made of a material having insulating properties, low thermal conductivity, and excellent heat resistance. Furthermore, considering the ease of processing, for example, silicon (Si) is suitable because a known semiconductor element manufacturing method can be applied. Of course, other materials may be used.

As shown in FIG. 1B, an insulating film 42 is formed on the surface of the support substrate 41. The insulating film 42 is made of, for example, silicon oxide (SiO ₂ ). Needless to say, silicon nitride (Si ₃ N ₄ ), aluminum oxide (Al ₂ O ₃ ), magnesium oxide (MgO), tantalum oxide (Ta ₂ O ₅ ), or the like can also be used. Moreover, it is good also as a laminated film which laminated | stacked these.

As shown in FIG. 1A, the shape of the insulating film 42 is formed so as to bridge two opposite sides of the frame shape with a predetermined width, thereby constituting beam portions 43a to 43d. . In the example illustrated in FIG. 1, the beam portions 43 a to 43 d are configured by only the insulating film 42 without the support substrate 41 on the back side. The beam portions 43a to 43d are holding members on which a thin film heat sensing element or a metal thin film resistor is mounted.

By the way, such a structure in which the beam portion is provided so as to bridge the support substrate is called a double-supported beam structure. A configuration in which the beam portion extends from the support substrate and its end portion is an open end is called a cantilever structure.
Regardless of the beam structure, it is necessary to provide strength that does not cause damage to the beam portion even when a gas arrives and a force generated by the pressure of the gas is applied to the beam portions 43a to 43d and stress is generated. is there.

When the insulating film 42 is a laminated film, the stress characteristics of the laminated film may be changed. For example, when two films are stacked, the lower film is a film having tensile stress, and the upper film is a film having compressive stress.
In this way, the stress of both films can be canceled out. Then, even if the force generated by the arrival of the gas is applied to the beam portions 43a to 43d, the stress characteristics of the insulating film 42 itself are not involved in the bending generated in the beam portion, so that the beam portion can be easily designed.

  As shown to Fig.1 (a), the area | region where the support substrate 41 was divided | segmented by the beam parts 43a-43d becomes the through-hole 42h used as the distribution | circulation part of gas. In the example shown in FIG. 1, since there are four beam portions, there are also four through holes 42h. This through hole 42h is called a so-called air hole and is a portion through which gas passes.

  By having the through hole 42h, gas flows through the through hole to the upper surface side and the back surface side of the beam portions 43a to 43d which are holding members. Then, since the gas that has arrived at the sensor region R does not stay, the gas inflow is not hindered.

  The beam portions 43 a to 43 d extending from the support substrate 41 are connected to each other in the central region B. The connecting portion D has an overhang portion F. By this overhanging portion F, the connecting portion between the beam portions has an obtuse angle instead of a right angle. Since there are four beam portions, there are also four overhanging portions F. For this reason, since the surface area of each beam portion is increased by the extent of the overhang portion F, the strength can be improved. Even if stress due to the arrival of gas is applied to the beam portion, the beam portion will not be damaged.

[Explanation of Thin Film Thermal Sensor, Metal Thin Film Resistor, and Electrode Pad: FIGS. 1 and 2]
Next, a thin film thermal sensor and a metal thin film resistor provided on the upper portions of the beam portions 43a to 43d, and electrode pads connected to these will be described.
Thin film heat detectors 46a to 46d and metal thin film resistors 45a to 45f are provided on the upper portions of the beam portions 43a to 43d which are holding members made of the insulating film 42. Electrode pads 44 a to 44 d are provided on the insulating film 42 on the support substrate 41.
The electrode pad may be provided anywhere on the upper side of the support substrate 41. However, in the example shown in FIG. 1, the electrode pad 44a is arranged at 12 o'clock in the plan view of FIG. Similarly, the electrode pad 44b is provided at 9 o'clock, the electrode pad 44c is provided at 6 o'clock, and the electrode pad 44d is provided at 3 o'clock.

  Each beam portion is provided with a thin film heat sensing element and a metal thin film resistor. A thin film heat sensing element 46a and a metal thin film resistor 45a are provided above the beam part 43a. A thin film heat sensing element 46a is connected to the electrode pad 44a on the support substrate 41 via a metal thin film resistor 45a.

Similarly, a thin film heat sensing element 46b and a metal thin film resistor 45b are provided above the beam portion 43b, and the thin film heat sensing element 46b is connected to the electrode pad 44b via the metal thin film resistor 45b. ing.
A thin film heat sensing element 46c and a metal thin film resistor 45c are provided above the beam portion 43c, and the thin film heat sensing element 46c is connected to the electrode pad 44c via the metal thin film resistor 45c.
A thin film heat sensing element 46d and a metal thin film resistor 45d are provided above the beam portion 43d, and the thin film heat sensing element 46d is connected to the electrode pad 44d via the metal thin film resistor 45d.

  The four thin film thermal detectors 46a, 46b, 46c, and 46d are arranged apart from the center point C of the sensor region R, but in the example shown in FIG. Each is provided in a position. That is, the thin film heat sensing element 46a and the thin film heat sensing element 46c are point symmetric with respect to the center point C, and the thin film heat sensing element 46b and the thin film heat sensing element 46d are point symmetric with respect to the center point C. It is also provided so as to be equidistant from the center point C.

  With such a configuration, the heat generated in the thin film heat sensing element caused by the arrival of gas becomes uniform, and heat concentrates on a specific thin film heat sensing element, thereby providing a thin film heat sensing element in which the heat is concentrated. The specific beam is not damaged by thermal stress.

  In the example shown in FIG. 1, a gas sensor 48 is provided above each thin film heat sensor. The gas sensor 48 generates heat when a gas arrives and comes into contact therewith. This is a so-called catalyst. Although depending on the material of the thin film heat sensing element, the provision of the gas sensing element 48 makes it easier to generate heat in response to the arrival of gas, so it may be used according to the specifications of the thin film gas sensor. .

Each thin film heat sensing element preferably has the same heat capacity. Specifically, when the material constituting each thin film heat sensing element is the same, the width and the film thickness may be the same.
In this way, the heat generation characteristics of each thin film heat sensing element do not vary, and the accuracy of the sensitivity characteristics and reaction speed characteristics for detecting the gas can be improved.

By the way, the reaction rate characteristic when detecting gas is the rate at which the thin film heat sensing element reaches a predetermined temperature at which it senses that the gas has arrived when the gas arrives and the thin film heat sensing element generates heat. It is shown.
Sensitivity characteristics refer to the amount of change in which the resistance value of the thin film thermal detector changes due to the arrival of gas and heat generation.
That is, as a sensor, when gas arrives, it changes quickly to a predetermined temperature, and the greater the amount of change in the resistance value, the better the sensitivity.

[Description of the shape of the thin film thermal detector: FIG. 1]
Next, the shape of the thin film heat detector will be described.
The four thin film heat detectors 46a, 46b, 46c, and 46d have a ninety-nine fold pattern shape having a plurality of folded portions. In the example shown in FIG. 1, six folding portions of one thin film heat sensing element are provided.
As described above, since it is preferable that each thin film heat sensing element has the same heat capacity, the heat capacity of each thin film heat sensing element is the same even if it has such a ninety-nine fold shape. The same shape and the same size are formed.

  By the way, there is a suitable value for the resistance value of the thin film heat detectors 46a to 46d. Of course, a higher resistance is preferable because the sensitivity characteristics and reaction rate characteristics of gas detection are improved. In order to increase the resistance value, although it becomes difficult to process, the thin film heat sensing element may be formed thin and thin.

However, if the pattern width or the like of the thin film heat sensing element is reduced, the power density is increased and the film is easily affected by electromigration.
Electromigration is a phenomenon in which metal atoms move gradually because electrons moving in an electric conductor collide with metal atoms and exchange of momentum is performed between them. For this reason, a defect occurs in a portion where the metal atom is deficient.
When electromigration occurs, the thin film heat sensing element is disconnected and the life of the gas sensor is shortened.

Under such circumstances, the resistance value of the thin-film heat sensing element has a value that achieves both sufficient sensitivity as a gas sensor and resistance to electromigration.
In view of such circumstances, the shapes of the thin film heat detectors 46a to 46d are determined. Generally, when the pattern width of the thin film heat detectors 46a to 46d is reduced, a large number of folded portions can be provided. Therefore, the overall length of the pattern can be increased and high resistance can be obtained. Therefore, in addition to the pattern width and film thickness of the thin film heat sensing element, the resistance value is determined in consideration of the number of folded portions.

The ninety-nine fold pattern shape of the thin film heat detectors 46a to 46d has a folded portion in the short direction (width direction) of the beam portions 43a to 43d in the example shown in FIG. Not what you want. Although not shown, it may have a folded portion in the longitudinal direction (length direction).
In any case, the 99-fold pattern shape can reduce the arrangement space of the thin film heat sensing element, so that the sensor region R can be reduced in size, and as a result, the thin film gas sensor itself can also be reduced in size. This also has the effect.

[Explanation of the arrangement of the thin film thermal detector: FIG. 1]
Next, the characteristics when the thin film heat sensing element is arranged in the beam portion will be described.
A central region B of the sensor region R is a joining portion where the beam portions 43a, 43b, 43c, and 43d join. This portion is not provided with the thin film heat detectors 46a to 46d. That is, each thin film heat sensing element is separated from the center point C. This is a characteristic part of the present invention. With such a configuration, it is possible to prevent excessive heat generation from concentrating on the central region B including the central point C of the sensor region R.

  In the example shown in FIG. 1, in the central region B, two thin film heat detectors are connected by metal thin film resistors, respectively. The thin film heat sensor 46a and the thin film heat sensor 46d are connected by a metal thin film resistor 45e, and the thin film heat sensor 46b and the thin film heat sensor 46c are connected by a metal thin film resistor 45f. That is, two thin film heat sensing elements are connected in series.

Note that the metal thin film resistors 45e and 45f are provided at portions away from the center point C. In this way, the four thin film heat detectors 46a, 46b, 46c, and the upper part of the four beam portions 43a, 43b, 43c, 43d without crossing the two metal thin film resistors in the central region B. 46d can be distributed in a plane.
In addition, since the overhang | projection part F is provided in the center area | region B, since the surface area becomes large by that much, a margin can be given to pattern formation of a metal thin film resistor.

[Description of insulating film constituting beam portion: FIG. 1]
Next, the characteristics of the structure of the beam portion will be described.
The beam portions 43a to 43d, which are holding members, are provided with thin film heat detectors 46a to 46d on the upper surface side, metal thin film resistors 45a to 45f connected thereto, and a gas sensor 48 on the upper portion of the thin film heat detector. , The strength required to hold the members is required. Therefore, the film thickness of the insulating film 42 constituting the beam portions 43a to 43d needs a predetermined thickness.
However, in order to improve the detection performance of the incoming gas, it is desirable to reduce the heat capacity of the portions (beam portions 43a to 43d) on which the thin film heat detectors 46a to 46d are mounted. This is because if the heat capacity is large, the heat generated by the arrival of gas is absorbed by the beam portion. In this state, the heat of the thin-film heat sensing element cannot be raised (that is, the resistance value cannot be changed), and even if gas arrives, it cannot be sensed.

  Thus, since the strength of the beam portions 43a to 43d and the performance for detecting the gas are in a trade-off relationship, the film thickness of the insulating film 42 constituting the beam portions 43a to 43d is taken into consideration. Set as appropriate. Since the heat generation temperature varies depending on the type of incoming gas, the thin film heat detector, and the material of the gas detector, the film thickness of the insulating film 42 may be set by, for example, repeating data to obtain data.

Moreover, the width | variety of the site | part which mounts the thin film heat sensors 46a-46d of the beam parts 43a-43d is also the same. If this width is wide, the strength of the beam portion is improved.
When the inventor examined, it discovered that the width | variety of the site | part which mounts the thin film heat | fever sensing bodies 46a-46d of the beam parts 43a-43d, and its film thickness should make it "film thickness <width". The reason is that the thermal conductivity is highest immediately below the portion where the thin film heat detectors 46a to 46d are mounted. Therefore, it is preferable to reduce the thickness of the insulating film 42 constituting the beam portions 43a to 43d to reduce the heat capacity and increase the width to maintain the strength.

  In the example shown in FIG. 1, for example, when the electrode pad 44a and the electrode pad 44b are electrically connected on an external substrate or the like, and a power source and an ammeter are connected between the electrode pad 44c and the electrode pad 44d, 4 Two thin film thermal detectors are connected in series, and a current can be passed through them, and the amount of current can be measured. Specifically, a voltage is applied from a power source (not shown) between the electrode pad 44c and the electrode pad 44d, and the thin film heat sensing element is energized. Thereafter, when the gas arrives, the temperature of the thin film heat sensing element rises in response to the gas, and the amount of current changes. By capturing this change in the amount of current, it is possible to know the arrival of gas.

  As already described, the gas detector 48 is provided above the thin film heat detectors 46a to 47d for the purpose of improving the detection sensitivity by quickly generating heat due to the arrival of gas. Details will be described later.

  By the way, since the thin film heat detectors 46a to 46d generate heat due to the arrival of gas, it is possible to know the arrival of the gas. Therefore, how the current flows to each thin film heat detector and the current is measured. Obviously, the present invention is not limited to the example shown in FIG.

  These thin film heat sensing elements, metal thin film resistors, and electrode pads can be made of the same metal. These are often refractory noble metals, such as platinum (Pt).

The reason for using such a refractory noble metal is temperature. That is, a gas sensor 48 is provided above the thin film heat sensor, and this gas sensor 48 functions as a catalyst, and generates heat when gas arrives, thereby improving the detection sensitivity. There is. The gas detector 48 is sintered on the thin film heat detector. However, the sintering temperature of the gas detector 48 is high, and is, for example, about 600 to 700 degrees depending on the material of the catalyst used. The temperature generated when the gas arrives is called a so-called combustion temperature, and the temperature exceeds, for example, 400 degrees.
Thus, since the thin film heat sensing element and the metal thin film resistor are exposed to a high temperature, a high melting point noble metal is used.

The thin film thermal sensors 46a to 46d, the metal thin film resistors 45a to 45f, and the electrode pads 44a to 44d are made of chromium (Cr), titanium (Ti), Alternatively, a metal film made of these alloys may be provided as an underlayer, and platinum (Pt) may be formed thereon. For example, platinum (Pt) can be formed by a known forming method such as a sputtering method.
The thin film heat sensing element, metal thin film resistor, and electrode pad are made of a material other than platinum (Pt), such as rhodium (Rd), palladium (Pd), gold (Au), or other high melting point noble metals, or these An alloy metal or the like can be used.

[Description of gas detector]
The gas sensor 48 provided on the upper surfaces of the thin film heat sensors 46a to 46d is a catalyst provided for the purpose of quickly generating heat due to the arrival of gas and improving detection sensitivity. Although not particularly limited, for example, it has a heat conductive layer made of aluminum oxide (Al 2 _{O 3),} an arrangement of repeated combustion catalyst layer on the surface of the thermally conductive layer.
The combustion catalyst layer is made of, for example, tin oxide (SnO ₂ ) as a main component, and a fine powder of platinum (Pt) and palladium (Pd) combustion catalyst is mixed with a solvent to form a slurry, which is made into a heat conductive layer. It is applied to the surface and sintered at a temperature of 600 ° C.

In the example shown in FIG. 1, the gas detector 48 is provided in the center region B of the sensor region R so as to cover the thin film heat detectors 46a to 46d in a cross shape above the beam portions 43a to 43d. However, the present invention is not limited to this. The gas detector 48 may be provided independently on the upper part of each thin film heat detector.
Of course, the gas detector 48 may not be provided depending on the resistance value of the thin film heat detectors 46a to 46d, the type of the incoming gas, and the like.

Moreover, as shown in FIG.1 (b), although the gas sensor 48 showed the example provided only in the upper surface side of the thin film heat sensors 46a-46d, of course, it is not limited to this. Since the incoming gas flows through the through-hole 42h, although not shown, it may be provided on the back surface side of the beam portions 43a to 43d as holding members. That is, the beam portions 43a to 43d may be wrapped from above and below by the gas sensor 48.
With such a structure, the surface area of the combustion catalyst layer is increased, the contact area with the gas is increased, and combustion can be performed faster. And the effect which further speeds up the reaction speed of gas detection is acquired.

[Description of Effects According to First Embodiment: FIG. 3]
The effect of the gas sensor of the present invention will be described using the graph of FIG. FIG. 3 shows a prototype of the gas sensor having the structure of the first embodiment and a gas sensor based on the technique disclosed in Patent Document 1 (referred to as a gas sensor according to the prior art). This is a comparison of gas sensitivity characteristics.

  The detection target gas uses hydrogen, the horizontal axis of the graph shown in FIG. 3 indicates the hydrogen concentration, and the vertical axis indicates the sensor output which is the output voltage of the gas sensor. The sensor output indicates a voltage output when the thin film heat sensing element generates heat due to the arrival of gas, the resistance value thereof changes, and the value of the flowing current changes accordingly.

In the graph of FIG. 3, the gas sensor according to the prior art is referred to as “conventional example” and indicated by “□”. The gas sensor having the structure of the first embodiment is “present invention” and is indicated by “♦”.
As shown in FIG. 3, the gas sensor of the present invention has a gas sensitivity characteristic that is about twice as high as that of the conventional gas sensor.

This is because the thin film heat sensing elements are not concentrated in a predetermined portion of the sensor region R but are dispersedly arranged, so that the incoming gas appropriately contacts each thin film heat sensing element.

  Table 1 below shows an example in which a combustion test of the gas detector 48 (catalyst) is performed with the gas sensor having the structure of the first embodiment and the gas sensor according to the related art, and the yield rate is compared. The combustion test can examine the influence of heat applied to the thin film heat sensing element. The non-defective product rate here is defined as a non-defective product that normally generates a sensor output when a gas detection experiment is performed as a gas sensor.

  As shown in Table 1, in the gas sensor according to the prior art, since the thin film heat sensing elements are concentrated in the center of the beam portion, excessive heat generation occurs in the portion, the beam portion is damaged, and the yield rate is reduced. . On the other hand, in the gas sensor having the structure of the first embodiment (in Table 1, expressed as the gas sensor of the present invention), since the thin film thermal detectors are distributed and arranged in a balanced manner, excessive heat generation does not occur. Since the beam does not break, the yield rate is high.

[Explanation of Second Embodiment: FIG. 4]
Next, a second embodiment will be described with reference to FIG.
FIG. 4 is a plan view schematically showing the structure of the second embodiment. In FIG. 4, for example, a configuration that is not necessary for the description, such as the gas detector 48, is omitted for easy explanation. Moreover, the same code | symbol is provided about the same structure already demonstrated, and detailed description is abbreviate | omitted.

  In FIG. 4, 54a and 54b are electrode pads. 55a, 55b, 55c, 55d, 55e, 55f, 55g, 55h, 55i are metal thin film resistors. Reference numerals 56a, 56b, 56c, 56d, 56e, 56f, 56g, and 56h denote thin film heat detectors. And these comprise the gas detection element 50.

Thin film heat detectors 56a to 56h and metal thin film resistors 55a to 55i are provided above the beam portions 43a to 43d. On the upper portion of the support substrate 41, electrode pads 54a and 54b are provided.
The electrode pads may be provided anywhere above the support substrate 41, but in the example shown in FIG. 4, the electrode pads 54a and 54b are provided in the 9 o'clock direction.

Thin film heat sensing elements 56a and 56b and metal thin film resistors 55a and 55b are provided on the beam 43b.
Similarly, thin film heat detectors 56c and 56d and a metal thin film resistor 55d are provided on the upper portion of the beam portion 43c. Thin film heat sensing elements 56e and 56f and a metal thin film resistor 55f are provided above the beam portion 43d. Thin film heat sensing elements 56g and 56h and a metal thin film resistor 55h are provided on the upper portion of the beam portion 43a.
That is, in the example shown in FIG. 4, two thin film heat detectors are mounted on one beam portion.

  Metal thin film resistors 55c, 55e, 55g, and 55i are provided in the central region B of the sensor region R (not shown in FIG. 4, but refer to FIG. 1A). These metal thin film resistors are spaced apart from the center point C of the sensor region R, and are provided at positions symmetrical with respect to the center point C. That is, the metal thin film resistor 55c and the metal thin film resistor 55g are point symmetric with respect to the center point C, and the metal thin film resistor 55e and the metal thin film resistor 55i are point symmetric with respect to the center point C. It is also provided so as to be equidistant from the center point C.

In the example shown in FIG. 4, the electrode pad 54 a and the electrode pad 54 b are connected to each metal thin film resistor via each thin film heat sensing element.
That is, tracing from the electrode pad 54a, the metal thin film resistor 55a, the thin film thermal sensor 56a, the metal thin film resistor 55i, the thin film thermal sensor 56h, the metal thin film resistor 55h, the thin film thermal sensor 56g, and the metal thin film resistor 55g. , Thin film thermal sensor 56f, metal thin film resistor 55f, thin film thermal sensor 56e, metal thin film resistor 55e, thin film thermal sensor 56d, metal thin film resistor 55d, thin film thermal sensor 56c, metal thin film resistor 55c, thin film It is connected to the electrode pad 54b through the heat sensing element 56b and the metal thin film resistor 55b.

The configuration of the gas detection element 50 shown in FIG. 4 is a circuit in which eight thin film thermal detectors 56 are connected in series. When a power source and an ammeter are connected between the electrode pad 54a and the electrode pad 54b, current can be passed through the eight thin film thermal detectors and the amount of current can be measured.
With such a configuration, connection wiring with an external device (not shown) can be reduced.

  The thin film heat detectors 56a to 56h provided on the upper portions of the beam portions 43a to 43d are adjacently arranged in parallel with the beam surface on the upper portion of one beam portion with good balance. As already described, when the thin film heat detectors are arranged close to each other, both of them are affected by excessive heat generation. In view of such a situation, both are arranged apart from each other. .

Further, the thin film heat sensing elements 56a to 56h provided on the upper portions of the beam portions 43a to 43d are respectively arranged at equal distances from the center point C and are evenly distributed, so that the overall weight balance is achieved. It has become.
By the way, the thin film heat detectors 56a and 56b are used as a first thin film heat detector group, the thin film heat detectors 56c and 56d are used as a second thin film heat detector group, and the thin film heat sensors 56e and 56f are used as a third thin film heat sensor. Assuming that the thin film heat sensing elements 56g and 56h are the fourth thin film heat sensing element group, the thin film heat sensing element groups are arranged symmetrically with respect to the center point C. become.
Furthermore, each thin film heat sensing element has the shape of a ninety-nine fold pattern having folded portions, and is formed in the same shape and the same size.

With such a configuration, a large number of thin film heat detectors can be mounted in a balanced state in a plane with a small number of beams. And the sensitivity characteristic and reaction rate characteristic of a gas detection can be improved, and the precision of the characteristic can be improved.
Moreover, since all the thin film thermal detectors can be used in series without requiring external connection, the size of the gas sensor can be reduced.

[Explanation of Third Embodiment: FIG. 5]
Next, a third embodiment will be described with reference to FIG.
FIG. 5A is a plan view thereof, and FIG. 5B is an end view schematically showing an end surface taken along a cutting line YY ′ of FIG. In FIG. 5, 69 is an interlayer insulating film. In addition, the same code | symbol is provided about the same structure already demonstrated, and detailed description is abbreviate | omitted.

  In FIG. 5, 63a, 63b, 63c and 63d are beam portions. Reference numeral 69 denotes an interlayer insulating film. Reference numeral 60 denotes a gas detection element.

The feature of the gas detection element 60 of the third embodiment shown in FIG. 5 is that the thin film heat detectors 46a to 46d are three-dimensionally arranged.
As shown in FIG. 5B, an insulating film 42 is formed on the surface of the support substrate 41, and the insulating films 42 constitute beam portions 63a and 63c. An interlayer insulating film 69 is provided on the insulating film 42, and the interlayer insulating film 69 and the insulating film 42 constitute beam portions 63b and 63d.

The interlayer insulating film 69 is provided further above the insulating film 42 provided on the surface of the frame-shaped support substrate 41. In the plan view shown in FIG. 5A, the entire surface of the support substrate 41 excluding the electrode pads 44 a to 44 d is the interlayer insulating film 69.
Therefore, all of the beam portions 63a to 63d have a laminated structure of the insulating film 42 and the interlayer insulating film 69.

  The beam portions 63a and 63c include a thin film heat sensing element and a metal thin film resistor between the insulating film 42 and the interlayer insulating film 69, and the beam portions 63b and 63d are interlayer insulating layers which are the uppermost surfaces of the beam portions. A thin film heat sensing element and a metal thin film resistor are provided on the film 69.

The thin film heat sensing element 46a and the metal thin film resistor 45a are provided on a beam portion 63a formed of the insulating film 42. Similarly, the thin film heat sensing element 46 c and the metal thin film resistor 45 c are provided on the beam portion 63 c formed by the insulating film 42.
Further, the thin film heat sensing element 46 b and the metal thin film resistor 45 b are provided on the beam portion 63 b constituted by the interlayer insulating film 69. Similarly, the thin film heat sensing element 46 d and the metal thin film resistor 45 d are provided on the beam portion 63 d constituted by the interlayer insulating film 69.

  A gas detector 48 is provided so as to cover the thin film heat detectors 45a to 45d above the beam portions 63a to 63d.

The central region B is a region in which the connection portion between the lower beam portion 63a and the beam portion 63c and the connection portion between the upper beam portion 63b and the beam portion 63d intersect each other vertically.
In the central region B, the thin film heat sensing element 46a and the thin film heat sensing element 46c are connected by a metal thin film resistor 45e at the connection portion between the lower beam part 63a and the beam part 63c. The thin film heat sensing element 46b and the thin film heat sensing element 46d are connected by a metal thin film resistor 45f at the connection portion between the upper beam part 63b and the beam part 63d.
Since there is an interlayer insulating film 69 between the metal thin film resistor 45e and the metal thin film resistor 45f, they do not come into contact with each other.

  The electrode pads 44 a to 44 d are all provided on the interlayer insulating film 69. Although not shown, a through hole is formed below the electrode pads 44a and 44c to open the interlayer insulating film 69. The electrode pad 44a and the metal thin film resistor 45a are connected to each other, and the electrode pad 44c and the metal thin film resistor are connected. The body 45c is connected.

Thus, the beam portion of the third embodiment has a laminated film structure of the insulating film 42 and the interlayer insulating film 69.
That is, the beam portions 63a and 63c are structured such that the thin film heat detectors 46a and 46c and the metal thin film resistors 45a, 45c and 45e are provided on the insulating film 42, and the interlayer insulating film 69 is provided on the thin film heat detectors 46a and 46c. Yes. In other words, the lower beam portion is provided with the thin film heat sensing element and the metal thin film resistor between the insulating film 42 and the interlayer insulating film 69.

  On the other hand, in the structure of the beam portions 63b and 63d, an interlayer insulating film 69 is provided on the insulating film 42, and thin film heat sensing elements 46b and 46d and metal thin film resistors 45b, 45d and 45f are provided on the insulating film 42. Yes. That is, in the upper beam portion, the thin film heat sensing element and the metal thin film resistor are provided on the upper portion where the insulating film 42 and the interlayer insulating film 69 are laminated.

In this way, the thin film heat detectors 46a to 46d are arranged at equal distances from the center point C and are evenly distributed, so that the overall weight balance can be achieved.
Further, the four thin film heat detectors 46a to 46d are provided at positions symmetrical with respect to the center point C, respectively. In the third embodiment shown in FIG. 5, since the thin film heat detectors 46a to 46d are three-dimensionally arranged, the thin film heat sensor 46a and the thin film heat sensor 46c are point-symmetric. The thin film heat sensor 46b and the thin film heat sensor 46d are point-symmetric.

Each thin film heat sensing element is disposed at an equal distance from the center point C, has a ninety-nine fold pattern shape having a folded portion, and is formed in the same size.
As described above, by forming the thin film heat detectors in the same shape and the same size, the heat capacity in the beam portion can be made the same, and the sensitivity characteristic and reaction rate characteristic of gas detection can be improved. In addition, the accuracy of the characteristics can be increased.

  As described above, the beam structures may be different even within the single sensor region R. Of course, it is possible to improve the accuracy of gas detection sensitivity characteristics and reaction rate characteristics by appropriately changing the resistance values of the thin film thermal detectors and metal thin film resistors provided in the respective beam portions.

The interlayer insulating film 69 can be made of the same material as the insulating film 42. For example, materials such as silicon oxide (SiO ₂ ), aluminum oxide (Al ₂ O ₃ ), silicon nitride (Si ₃ N ₄ ), magnesium oxide (MgO), and tantalum oxide (Ta ₂ O ₅ ) can be used.

  Of course, the insulating film 42 and the interlayer insulating film 69 may be composed of films of different materials. Further, the stress characteristics of the insulating film 42 and the interlayer insulating film 69 may be changed. For example, the insulating film 42 is a film having tensile stress, and the interlayer insulating film 69 is a film having compressive stress. In this way, as already explained, it is possible to cancel the stress of both films.

  Further, the insulating film 42 and the interlayer insulating film 69 can each be a laminated film. At this time, the stress characteristics of the laminated films may be changed. For example, when the insulating film 42 and the interlayer insulating film 69 are laminated by two films, the film below the insulating film 42 is a film having tensile stress, the upper film is a film having compressive stress, and the interlayer insulating film 69 is formed. The lower film is a film having tensile stress, and the upper film is a film having compressive stress. That is, films having opposite stress characteristics are provided alternately. In this way, not only the stress of both films can be canceled, but also the film stress itself can be reduced because one film thickness is reduced.

  In the central region B, the example in which the overhanging portion F illustrated in the first embodiment and the second embodiment described above is not provided is shown, but the present invention is not limited to this.

[Explanation of Fourth Embodiment: FIG. 6]
Next, a fourth embodiment will be described with reference to FIG.
FIG. 6 is a plan view schematically showing the structure of the fourth embodiment. In FIG. 6, 73a, 73b, 73c, 73d, 73e, 73f, 73g, and 73h are beam portions. 74a, 74b, 74c, 74d, 74e, 74f, 74g and 74h are electrode pads. 75a, 75b, 75c, 75d, 75e, 75f, 75g, 75h, 75i, 75j, 75k, 75l are metal thin film resistors. Reference numerals 76a, 76b, 76c, 76d, 76e, 76f, 76g, and 76h denote thin film heat detectors. Reference numeral 70 denotes a gas detection element. In addition, the same code | symbol is provided about the same structure already demonstrated, and detailed description is abbreviate | omitted.

A feature of the gas detection element 70 of the fourth embodiment shown in FIG. 6 is that a holding member is constituted by eight beams, and an interlayer insulating film 69 is formed above the insulating film 42 as in the third embodiment. And the thin film heat detectors 76a to 76h are three-dimensionally arranged.
That is, the configuration in which the thin film heat sensing element and the metal thin film resistor are provided in each beam portion and connected to each other and the thin film heat sensing elements are connected to each other by the metal thin film resistor in the central region B is basically the same. , The number is different.

  The thin film heat detectors 76b, 76d, 76f, and 76h and the metal thin film resistors 75b, 75d, 75f, and 75h are on the beam portions 73b, 73d, 73f, and 73h formed by the insulating film 42 (not shown in FIG. 6). Respectively. Similarly, the thin film thermal detectors 76a, 76c, 76e, and 76g and the metal thin film resistors 75a, 75c, 75e, and 75g are beam portions 73a, 73c, 73e, and the like, which are configured by an interlayer insulating film 69 provided on the insulating film 42. It is provided on each 73g.

Similar to the example already described, the interlayer insulating film 69 is provided further above the insulating film 42 provided on the surface of the frame-shaped support substrate 41. In the plan view shown in FIG. The entire surface except for the electrode pads 74 a to 74 h of 41 is an interlayer insulating film 69.
Therefore, the beam portions 73a to 73h all have a laminated structure of the insulating film 42 and the interlayer insulating film 69.

  The beam portions 73b, 73d, 73f, and 73h include a thin film thermal detector and a metal thin film resistor between the insulating film 42 and the interlayer insulating film 69, and the beam portions 73a, 73c, 73e, and 73g A thin film heat sensing element and a metal thin film resistor are provided on the upper part of the interlayer insulating film 69 which is the uppermost surface of the part.

  The gas detector 48 is provided so as to cover the thin film heat detectors 76a to 76h above the beam portions 73a to 73h, but is omitted in FIG. 6 for easy understanding of the drawing.

The center region B is a region where the connecting portions of the lower beam portions 73b, 73d, 73f, and 73h and the connecting portions of the upper beam portions 73a, 73c, 73e, and 73g intersect vertically.
In the central region B, the thin film heat sensing element 76b and the thin film heat sensing element 76d provided in the beam part 73b and the beam part 73d, which are the lower beam parts, are connected by the metal thin film resistor 75k. ing. Similarly, the thin film heat sensing element 76f and the thin film heat sensing element 76h provided on the beam part 73f and the beam part 73h, which are the lower beam parts, are connected by a metal thin film resistor 75l.

Further, the thin film heat sensing element 76a and the thin film heat sensing element 76g provided in the beam part 73a and the beam part 73g, which are the upper beam parts, are connected by a metal thin film resistor 75j. Similarly, the thin film heat sensing element 76c and the thin film heat sensing element 76e provided on the beam part 73c and the beam part 73e, which are the upper beam parts, are connected by a metal thin film resistor 75i.
Since there is an interlayer insulating film 69 between the metal thin film resistors 75k and 75l and the metal thin film resistors 75i and 75j, they do not come into contact with each other.

  The electrode pads 74 a to 74 h are all provided on the interlayer insulating film 69. The electrode pads may be provided anywhere on the support substrate 41, but in the example shown in FIG. 6, the electrode pads 74a, 74c, 74e, and 74g are respectively 12 o'clock direction, 9 o'clock direction, 6 o'clock direction, and 3 o'clock. The electrode pads 74b, 74d, 74f, and 74h are provided at the corners of the support substrate 41, respectively.

  Although not shown, a through hole that opens the interlayer insulating film 69 is provided below the electrode pads 74b, 74d, 74f, and 74h. The electrode pad 74b and the metal thin film resistor 75b are connected to the electrode pad 74d and the metal. The thin film resistor 75d is connected to the electrode pad 74f and the metal thin film resistor 75f, and the electrode pad 74h and the metal thin film resistor 75h are connected to each other.

  As described above, the beam portion of the fourth embodiment has a laminated film structure of the insulating film 42 and the interlayer insulating film 69 as in the third embodiment.

In the central region B, the metal thin film resistors 75k, 75l, 75i, and 75j are not provided above the center point C of the sensor region R, as in the first embodiment.
The eight thin film thermal detectors 76a to 76h are also arranged apart from the center point C of the sensor region R and provided so as to be equidistant from the center point C, as in the other embodiments. ing.

In the fourth embodiment shown in FIG. 6, the thin film thermal detectors are three-dimensionally arranged, but are provided at point-symmetrical positions with respect to the center point C, respectively.
Specifically, the thin film heat sensing element 76a and the thin film heat sensing element 76e are point symmetric, and the thin film heat sensing element 76c and the thin film heat sensing element 76g are point symmetric. Similarly, the thin film heat sensor 76b and the thin film heat sensor 76f are point symmetric, and the thin film heat sensor 76d and the thin film heat sensor 76h are point symmetric.

In this way, the thin film heat detectors 76a to 76h are arranged equidistant from the center point C and are evenly distributed, so that the overall weight balance is achieved.
Furthermore, by forming each thin film heat sensing element in the same shape and the same size, the heat capacity in the beam part can be made the same, and the sensitivity characteristic and reaction speed characteristic of gas detection can be improved. At the same time, the accuracy of the characteristics can be increased.

  4th Embodiment showed the example which provides eight beam parts. By arranging the thin film heat sensing elements in such a large number of beam portions, the heat capacity per beam portion is reduced, so that the sensitivity of the thin film heat sensing body is improved. Further, since the weight per one beam portion is reduced, the beam portion itself becomes light, and even if insufficient stress due to the arrival of gas or the like is applied, it becomes difficult to break.

In the fourth embodiment, the number of beam portions is eight, but this is an example. It can be freely selected according to the type of gas coming in, the material of the thin film thermal detector and the resistance value.
In addition, the insulating film 42 and the interlayer insulating film 69 may be made of the same material or different materials as in the third embodiment, and of course have a laminated film structure in which a plurality of films are laminated. May be.

[Explanation of Fifth Embodiment 1: FIG. 7]
Next, a fifth embodiment will be described with reference to FIG.
FIG. 7 is a plan view schematically showing the structure of the fifth embodiment. In FIG. 7, 42a is a membrane structure. 82h is a through hole provided in the membrane structure 42a. 84a and 84b are electrode pads. 85a, 85b, 85c, 85d, and 85e are metal thin film resistors. Reference numerals 86a, 86b, 86c, and 86d denote thin film heat detectors. Reference numeral 80 denotes a gas detection element. The same reference numerals are given to the same components that have already been described, and detailed description thereof is omitted.

  A feature of the gas detection element 80 of the fifth embodiment shown in FIG. 7 is that the holding member has a membrane structure. In the first to fourth embodiments already described, the insulating film 42 is provided on the support substrate 41, and the two opposing sides of the frame shape of the support substrate 41 are bridged with a predetermined width by the insulating film 42. The beam part was configured as follows. In the fifth embodiment shown in FIG. 7, the holding member is not composed of a beam portion, but is a membrane structure 42a.

  The membrane structure 42 a is configured by forming the insulating film 42 provided on the support substrate 41 with a thin film that is uniform in the direction of the sensor region R. The membrane means a “film”, and the membrane structure means the structure itself. However, in the embodiment of the present invention, the sensor region of the insulating film 42 is easy to explain. The portion R is a membrane structure 42a.

  The thin film heat sensing elements 86 a to 86 d and the metal thin film resistors 85 a to 85 e are provided on the membrane structure 42 a configured by the insulating film 42. The electrode pads 84 a and 84 b are provided on the insulating substrate 42 but on the support substrate 41. The electrode pads may be provided anywhere above the support substrate 41, but in the example shown in FIG.

  The membrane structure 42a is not particularly limited, but is a 1 μm thin film, for example. A through hole 82h is provided in a portion of the upper part of the membrane structure 42a that does not have the thin film heat sensing element and the metal thin film resistor. This through-hole 82h has a role similar to that of the through-hole 42h of the first to fourth embodiments already described, and is a portion through which gas passes.

  In the example shown in FIG. 7, the through hole 82 h has a circular shape. However, the shape is an example, and the through hole 82 h may be a polygon. Further, a polygon and a circle may be combined and can be freely changed.

The thin film heat sensing element 86a and the thin film heat sensing element 86b are connected by a metal thin film resistor 85b. Similarly, the thin film thermal sensor 86b and the thin film thermal sensor 86c are connected by a metal thin film resistor 85c, and the thin film thermal sensor 86c and the thin film thermal sensor 86d are connected by a metal thin film resistor 85d. .
The thin film heat detector 86a is connected to the electrode pad 84a by a metal thin film resistor 85a. Similarly, the thin film heat detector 86d is connected to the electrode pad 84b by a metal thin film resistor 85e.

  The gas detector 48 is provided so as to cover the thin film heat detectors 86a to 86d above the membrane structure 42a. However, in FIG. 7, the gas detector 48 is omitted for easy understanding of the drawing.

  In the example shown in FIG. 7, the thin film heat detectors 86 a to 86 d are provided so as to surround the center point C of the sensor region R. However, each thin film heat detector is disposed apart from the center point C. Each is provided at a point-symmetrical position with respect to the center point C. It is also provided so as to be equidistant from the center point C.

  In the fifth embodiment shown in FIG. 7, the thin film heat sensing element 86a and the thin film heat sensing element 86c are point symmetric, and the thin film heat sensing element 86b and the thin film heat sensing element 86d are point symmetric. .

  In the fifth embodiment shown in FIG. 7, the sensor member R surrounded by the inner wall 41c of the frame-shaped support substrate 41 becomes all the membrane structure 42a by using the membrane structure 42a as the holding member. Because of the structure, the film itself has flexibility. For this reason, even if the membrane structure 42a bends due to the flow pressure of the flowing gas, the bend can be kept small. In addition, the stress generated in the membrane structure 42a is also dispersed and reduced, thereby producing an effect of suppressing damage to the membrane structure 42a.

  In addition, if the four thin film heat detectors have an evenly distributed arrangement, and the heat capacities are the same as in the above-described embodiment, the sensitivity characteristics and reaction rate characteristics of gas detection can be enhanced and The accuracy of characteristics can be increased.

[Description of Fifth Embodiment 2: FIG. 8]
Next, another configuration of the fifth embodiment will be described with reference to FIG.
FIG. 8 is a plan view schematically showing another structure of the fifth embodiment. In the configuration shown in FIG. 8 as well, the thin film heat detectors 86a to 86d and the metal thin film resistors 85a to 85e are provided on the membrane structure 42a formed of the insulating film 42, as in the configuration shown in FIG. . However, the difference is that the thin film heat detectors 86a to 86d are distributed on the membrane structure 42a.

  In the configuration shown in FIG. 8, the thin film thermal detectors are not arranged symmetrically with respect to the center point C, and the distance from the center point C is not the same. Although the weight balance is somewhat worse for the membrane structure 42a, since it is dispersed in the sensor region R, the concentration of heat can be alleviated. As described above, the thin film heat sensing element may be arranged apart from the center point C and dispersed in the sensor region R.

[Explanation of Sixth Embodiment: FIG. 9]
Next, a sixth embodiment will be described with reference to FIG.
FIG. 9 is a plan view schematically showing the structure of the sixth embodiment. FIG. 9A is a plan view thereof, and FIG. 9B is an end view schematically showing an end surface taken along a cutting line ZZ ′ of FIG. 9A.
In FIG. 9, 99 is an insulating film. Reference numeral 99 a denotes a membrane structure constituted by the insulating film 99. 99h is a through hole provided in the membrane structure 99. Reference numeral 90 denotes a gas detection element. The same reference numerals are given to the same components that have already been described, and detailed description thereof is omitted.

  The feature of the gas detection element 90 of the sixth embodiment shown in FIG. 9 is that the holding member is a beam portion and a membrane structure. The third embodiment described with reference to FIG. 5 is combined with the fifth embodiment described with reference to FIGS. 7 and 8, and the upper portion of the lower beam portions 63 a and 63 c is arranged on the upper side. The beam portions 63b and 63d are overlapped, and a membrane structure 99a is provided below the two beam portions.

  The membrane structure 99 a is configured by forming an insulating film 99 provided on the upper portion of the support substrate 41 with a thin film that is uniform in the direction of the sensor region R. Similar to the membrane structure 42a of the fifth embodiment already described with reference to FIGS. 7 and 8, the portion of the sensor region R in the insulating film 99 is the membrane structure 99a.

Similar to the example already described, the interlayer insulating film 69 is provided further on the insulating film 42 provided on the surface of the frame-shaped support substrate 41. In the plan view shown in FIG. The entire surface except for the electrode pads 44 a to 44 d of 41 is an interlayer insulating film 69.
Accordingly, the beam portions 63a to 63d all have a laminated structure of the membrane structure 99a, the insulating film 42, and the interlayer insulating film 69.

  The beam portions 63a and 63c include a thin film thermal sensor and a metal thin film resistor between the insulating film 42 and the interlayer insulating film 69 provided on the membrane structure 99a. The beam portions 63b and 63d The thin film heat sensing element and the metal thin film resistor are provided on the upper part of the interlayer insulating film 69 which is the uppermost surface of the beam portion.

  The gas detector 48 is provided so as to cover the thin film heat detectors 46a to 46d above the membrane structure 99a. However, in FIG. 9, the gas detector 48 is omitted for easy understanding of the drawing.

Although not shown, the film thickness of the membrane structure 99a that planarly overlaps the thin film heat sensing elements 46a to 46d provided in the beam portions 63a to 63d in the central region B may be reduced or removed.
By doing so, the thickness of the lower part of the thin film heat sensing element is reduced and the heat capacity is reduced, so that the sensitivity as a sensor is improved.

  In the example shown in FIG. 9, the configuration in which the membrane structure 99a is provided below the two beam portions has been described, but the present invention is not limited to this. The membrane structure 99a may be provided above the two beam portions.

  In any configuration, if the holding member is configured by the beam portion and the membrane structure, the holding member can be hardly damaged. The material and film thickness of the insulating film 42 and the interlayer insulating film 69 constituting the two beam portions and the insulating film 99 constituting the membrane structure 99a can be appropriately selected as in the embodiment already described. . Thereby, it is possible to cancel the stress of the beam part itself, or to obtain a holding member having both strength and flexibility.

[Explanation of Seventh Embodiment: FIG. 10]
Next, a seventh embodiment will be described with reference to FIG.
FIG. 10 is a plan view schematically showing the structure of the seventh embodiment. In FIG. 10, 103a, 103b, 103c, and 103d are beam portions. 104a, 104b, 104c, 104d, 104e, 104f, 104g and 104h are electrode pads. 105a, 105b, 105c, 105d, 105e, 105f, 105g, 105h, 105i, 105j, 105k, and 105l are metal thin film resistors. Reference numerals 106a, 106b, 106c, 106d, 106e, 106f, 106g, and 106h are thin film heat detectors. Reference numeral 100 denotes a gas detection element. The same reference numerals are given to the same components that have already been described, and detailed description thereof is omitted.

The characteristic of the gas detection element 100 of 7th Embodiment shown in FIG. 10 is that the beam part which comprises a holding member has what is called a cantilever structure. That is, the insulating film 42 constituting the beam portion extends from the support substrate 41 toward the center point C, and the end thereof is an open end.
In the central region B of the sensor region R, since the beam portions are separated from each other, there is no connection portion D of the beam portion.
The electrode pads 104 a to 104 h are provided on the insulating film 42 on the support substrate 41. The electrode pads may be provided anywhere on the support substrate 41, but in the example shown in FIG. 10, the electrode pads are provided in the 12 o'clock direction, 9 o'clock direction, 6 o'clock direction, and 3 o'clock direction, respectively.

Thin film heat sensing elements 106a and 106h and metal thin film resistors 105a, 105h, and 105i are provided on the beam 103a. The thin film heat sensing element 106a and the thin film heat sensing element 106h are connected by a metal thin film resistor 105i at the end of the beam portion 103a. The thin film heat sensing element 106a is connected to the electrode pad 104a by a metal thin film resistor 105a, and the thin film heat sensing element 106h is connected to the electrode pad 104ah by a metal thin film resistor 105h.
Similarly for the other beam portions, the two thin film heat sensing elements are connected by metal thin film resistors at the ends of the beam portions, and are connected to the electrode pads, respectively.

  Note that the gas detector 48 is provided so as to cover the thin film heat detectors 106a to 106h, but is omitted in FIG. 10 for easy understanding of the drawing. Although the gas detector 48 is provided for each thin film heat detector above each beam portion, it may be provided so as to cover the upper portion of the center point C so as to bridge each beam portion.

In the example shown in FIG. 10, the thin film thermal detectors 106 a to 106 h are arranged away from the center point C of the sensor region R, as in the other embodiments. Each is provided at a point-symmetrical position with respect to the center point C, and is provided so as to be equidistant from the center point C.
By the way, the thin film heat detectors 106a and 106h are a first thin film heat sensor group, the thin film heat sensors 106b and 106c are a second thin film heat sensor group, and the thin film heat sensors 106d and 106e are a third thin film heat sensor. Assuming that the thin film heat sensing elements 106f and 106g are the fourth thin film heat sensing element group, the thin film heat sensing element groups are arranged symmetrically with respect to the center point C. become.

If the configuration shown in FIG. 10 is adopted, the beam structure is flexible, and even if pressure is generated by the arrival of gas, each beam portion can be flexed freely to receive the force. Thereby, damage to the beam portion can be prevented.
In addition, if each thin film heat sensing element has an evenly distributed arrangement and the heat capacity is the same as in the embodiment already described, the sensitivity characteristics and reaction speed characteristics of gas detection can be enhanced and The accuracy of characteristics can be increased.

In the seventh embodiment, since the beam portions 103a to 103d are composed of the insulating film 42, the strength and the like are the same, but the present invention is not limited to this. As already described, the insulating film 42 may have a laminated film structure in which a plurality of films are laminated. At this time, the strength and the degree of deflection of each beam part can be changed by changing the material and film thickness of the film of each beam part.
With such a configuration, a more suitable beam portion can be configured according to the direction, angle, speed, etc. of the incoming gas.

Although it has been described that the gas detector 48 may be provided so as to cover the upper part of the center point C so as to bridge the respective beam portions, in this configuration, the beam portions 103a to 103d are gasses. It becomes a form connected by the detection body 48. For this reason, due to the arrival of gas, it becomes difficult for each beam part to bend freely, so that it is difficult to receive the force,
By selecting the material and film thickness of the film constituting the beam part, it is possible to have flexibility as a beam structure.

[Explanation of Eighth Embodiment: FIG. 11]
Next, an eighth embodiment will be described with reference to FIG.
FIG. 11 is a plan view schematically showing the structure of the eighth embodiment. FIG. 11A is a plan view thereof, and FIG. 11B is an end view schematically showing an end face taken along a cutting line WW ′ of FIG.
In FIG. 11, reference numeral 119 denotes an insulating film. Reference numeral 119a denotes a membrane structure formed of the insulating film 119. 119h is a through hole provided in the membrane structure 119. Reference numeral 110 denotes a gas detection element. The same reference numerals are given to the same components that have already been described, and detailed description thereof is omitted.

  The feature of the gas detection element 110 of the eighth embodiment shown in FIG. 11 is that the holding member is a beam portion and a membrane structure. The seventh embodiment described with reference to FIG. 10 and the fifth embodiment described with reference to FIG. 7 and FIG. 8 are combined, and the membrane structure 119a is provided below the beam portions 103a to 103d. It is a structure to provide.

  The membrane structure 119a is configured by forming an insulating film 119 provided on the support substrate 41 with a thin film that is uniform in the direction of the sensor region R. Similar to the membrane structure 42a of the fifth embodiment described with reference to FIGS. 7 and 8, the portion of the sensor region R in the insulating film 119 is the membrane structure 119a.

  The gas detector 48 is provided so as to cover the thin film heat detectors 106a to 106h above the beam portions 103a to 103d. However, in FIG. 11, the gas detector 48 is omitted for easy viewing.

Although not shown, the film thickness of the membrane structure 119a that overlaps the thin film heat sensing elements 106a to 106h provided in the beam portions 103a to 103d in the central region B may be reduced or removed.
By doing so, the thickness of the lower part of the thin film heat sensing element is reduced and the heat capacity is reduced, so that the sensitivity as a sensor is improved.

  In the example illustrated in FIG. 11, the configuration in which the membrane structure 119a is provided below the beam portions 103a to 103d has been described. However, the configuration is not limited thereto. The membrane structure 119a may be provided above the beam portions 103a to 103d.

  Since each of the beam portions 103a to 103d can be bent similarly to the cantilever beam structure, the beam structure is more flexible. By providing the membrane structure 119a under them, strength can be obtained. Therefore, it is possible to make the holding member difficult to break.

  As described above, in the first to eighth embodiments, the configuration in which the gas detector is provided on the upper part of the thin film heat detector has been exemplified, but the present invention is not limited to this. If the thin film heat sensing element is made of a semiconductor, the gas sensing element becomes unnecessary.

[Description of Gas Sensor System: FIG. 12]
Next, a gas sensor system using the thin film gas sensor of the present invention will be described. FIG. 12 is a conceptual diagram thereof.
In FIG. 11, 1001 is a gas detection element, 1002 is a reference element, 1003 is a correction circuit, 1004 is a determination circuit, 1005 is a gas inflow direction, 1011 is a gas detector (catalyst), and 1100 is a gas sensor system.

The gas detection element 1001 is the same as the embodiment described so far. In FIG. 12, it is simplified for easy explanation. The gas detection element 1001 is provided with a gas detection body 1011 so that heat is easily generated by the arrival of gas.
The reference element 1002 has the same structure as the gas detection element 100, but does not include the gas detection body 1011.
The gas sensor system 1100 includes a gas detection element 1001 and a reference element 1002. Such a configuration is called a two-chip configuration. The gas sensor system 1100 omits parts that are not necessary for the description.

  The gas detection element 1001 is connected to the determination circuit 1004, and the reference element 1002 is connected to the determination circuit 1004 via the correction circuit 1003.

The gas sensor detects the gas by replacing the arrival of the gas with a physical quantity called a temperature change. However, since the temperature also changes depending on the surrounding environment, a single gas detection element is easily affected.
For example, when a gas sensor is installed in an environment where the ambient temperature fluctuates violently, and there is a single gas sensing element mounted on it, the change in the resistance value of the thin film thermal detector is due to the arrival of gas. It is not possible to determine whether it is due to a change in ambient temperature.

  Since the gas sensor system 1100 having a two-chip configuration includes the gas detection element 1001 and the reference element 1002, these two elements are always placed at the same environmental temperature. For example, even if the environmental temperature changes and the resistance value of the thin film heat sensing element of the gas sensing element 1001 changes, the resistance value of the thin film heat sensing element of the reference element 1002 changes in the same manner. The resistance values of the gas detection element 1001 and the reference element 1002 are compared by the determination circuit 1004. If there is no difference between the resistance values, it can be determined that no gas has arrived.

  On the other hand, when gas flows in from the inflow direction 1005, the gas detection element 1001 has the gas detection body 1011 mounted thereon, so that the resistance value of the thin film heat detection body changes. Since the reference element 1002 does not include the gas detector 1011, the resistance value does not change. That is, a difference occurs between the resistance values of the gas detection element 1001 and the reference element 1002. By detecting this difference by the determination circuit 1004, it can be determined that gas has arrived.

In other words, the gas detection element 1001 and the reference element 1002 are made to detect the arrival of gas correctly by making a difference in the degree of heat generated by the arrival of gas.
Therefore, it is sufficient that at least one gas detection element 1001 and one reference element 1002 are provided. Of course, a plurality of pairs of these gas detection elements 1001 may be provided depending on the convenience of the gas sensor system 1100. The number of reference elements 1002 may be changed.

Note that the reference element 1002 is connected to the determination circuit 1004 via the correction circuit 1003. When the gas detection element 1001 includes the gas detection body 1011, the correction circuit 1003 has a slight difference in the resistance value of the thin film thermal detection body between the gas detection element 1001 and the reference element 1002. It is provided to correct it. For example, a resistance element made of the same material as that of the thin film thermal sensor is used.
In this way, even if there is a difference in resistance between the gas detection element 1001 and the reference element 1002, the determination circuit 1004 can correctly determine.

  Further, depending on the gas sensor system 1100, the arrangement of the gas detection element 1001 and the reference element 1002 (for example, the mounting location of both elements) may not necessarily be equally affected by the environmental temperature. Even in such a case, if the correction circuit 1003 is provided, the resistance value can be corrected, and the determination circuit 1004 can correctly determine.

  Furthermore, depending on the gas sensor system 1100, the gas detection element 1001 and the reference element 1002 may be arranged apart from each other. The path through which the gas arrives is the same, but there are cases in which both are arranged apart from each other due to the structure of the apparatus. Or, in a certain gas inflow path, the gas detection element 1001 is provided on the gas inflow side, and the reference element 1002 is provided on the gas exhaust side. This may cause a difference in the ambient temperature of both elements. Even in such a case, if the correction circuit 1004 is provided, the resistance value can be corrected, and the determination circuit 1004 can correctly determine.

  In the example illustrated in FIG. 12, the correction circuit 1003 is provided between the reference element 1002 and the determination circuit 1004, but of course, the invention is not limited to this. It may be provided in between.

  In the thin film type gas sensor of the present invention, since the thin film heat sensing elements are not densely packed, heat does not concentrate even when the temperature rises due to arrival of gas, and durability of the beam portion can be improved. For this reason, it is suitable as a gas sensor operated in a relatively high temperature environment.

40, 50, 60, 70, 80, 90, 100, 110 Gas detection element 41 Support substrate 41c Inner wall 42, 99, 119 Insulating film 42a, 99a, 119a Membrane structure 42h, 82h, 99h, 119h Through-holes 43a-43d Beams 63a-63d Beams 73a-73h Beams 103a-103d Beams 44a-44d Electrode pads 54a, 54b Electrode pads 74a-74h Electrode pads 84a, 84b Electrode pads 104a-104h Electrode pads 45a-45f Metal thin film resistors 55a 55i Metal thin film resistors 75a to 75l Metal thin film resistors 85a to 85e Metal thin film resistors 105a to 105l Metal thin film resistors 46a to 46d Thin film heat detectors 56a to 56h Thin film heat detectors 76a to 76h Thin film heat detectors 86a to 86a 86d Thin Film Thermal Sensors 106a-106 Thin heat sensing body 48 gas sensing element 69 interlayer insulating film B central region C the center point F overhang portion R sensor area 1001 gas detector element 1002 Reference element 1003 correction circuit 1004 decision circuit 1005 gas inflow direction 1011 gas sensing member 1100 Gas sensor system

Claims (9)

A thin film type in which the inside of a support substrate having a frame shape is a sensor region, a holding member is provided extending from the support substrate in the sensor region, and a plurality of thin film thermal sensors are provided on the holding member in the sensor region In the gas sensor,
The thin film type heat sensor is arranged so as to be separated from a center point of the sensor region.   The thin film type gas sensor according to claim 1, wherein the thin film heat sensing element is arranged point-symmetrically with respect to the center point.   The thin film type gas sensor according to claim 1, wherein the plurality of thin film heat sensing bodies are provided at equal distances from the center point.   The thin film type gas sensor according to any one of claims 1 to 3, wherein the plurality of thin film heat sensing bodies have the same heat capacity.   The thin film type gas sensor according to any one of claims 1 to 4, wherein the plurality of thin film heat sensing elements are connected to each other through a metal thin film resistor.   6. The thin film gas sensor according to claim 1, wherein the holding member is formed with a through hole so as to avoid a mounting portion of the thin film heat sensing element.   The thin film type gas sensor according to claim 1, wherein the holding member has a thickness smaller than a width of the mounting portion of the thin film heat sensing element. The holding member has a laminated film structure in which a plurality of thin films are laminated,
The first thin film constituting the laminated film has a membrane structure,
The second thin film constituting the laminated film has a beam structure with a rectangular cross section,
The said membrane structure is a uniform thin film from the said support substrate toward the said sensor area | region, and has the said through-hole avoiding the mounting part of the said thin film heat sensing element. The thin film gas sensor according to any one of 7. A plurality of the holding members are provided,
The plurality of holding members have a cantilever structure in which end portions thereof do not overlap the center point of the sensor region in a plane,
The thin film type gas sensor according to any one of claims 1 to 7, wherein the thin film heat sensing body is provided on each of the plurality of holding members.

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