JP2003202257A - Sensor with thin film structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To appropriately prevent dust collision from breaking a membrane while preventing the characteristics of the membrane from being damaged in the case of a sensor with a thin film structure having a membrane for fluid measurement. <P>SOLUTION: The sensor with a thin film structure for fluid measurement has the membrane 20 and a reinforcing part 30 for membrane reinforcement so as to bestride an outer peripheral part of the membrane 20. The reinforcing part 30 is formed so that the reinforcement strength is larger on the downstream side than on the upstream side of a fluid flow. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film structure sensor having a membrane, and is particularly suitable for use as a sensor for measuring a fluid such as a flow sensor or a gas sensor.

[0002]

2. Description of the Related Art A thin film structure sensor has a membrane as a thin film portion formed on a substrate such as a semiconductor substrate, a sensing portion is formed on this membrane, and at the same time, the membrane ensures heat insulation and reduces heat capacity. The sensor characteristics are being improved. Such a thin film structure sensor
For example, it is applied to a flow sensor, a gas sensor, or the like.

For example, a perspective view of a flow sensor as a conventional thin film structure sensor is shown in FIG. As shown in FIG. 17, a thin film layer in which a conductor film is sandwiched between insulating films is formed on the surface of the substrate 10, and a cavity 11 is formed from the back surface side of the substrate 10 leaving the thin film layer on the cavity 11. The membrane 20 is composed of the thin film layer.

A heater 21 made of a conductor film is formed in the membrane 20, and the heater 21 is made of a conductor film on the upstream side of the fluid flow indicated by a white arrow in FIG. A temperature sensing element 22 is formed.

A fluid thermometer 23 made of a conductor film is formed on the substrate 10 upstream of the temperature measuring element 22. Further, on the substrate 10, the heater 21, the temperature measuring element 22,
And a lead portion 24 electrically connected to each of the fluid thermometers 23.

In such a flow sensor, the heater 21 is driven to a temperature higher than the fluid temperature obtained from the fluid thermometer 23. Then, the fluid is the membrane 20.
By flowing upward, the temperature of the temperature measuring element 22 changes, and the flow rate of the fluid or the like is detected from the temperature difference between the temperature measuring element 22 and the fluid thermometer 23.

[0007]

In the thin film structure sensor, however, there is a problem that the membrane is broken when foreign matter such as dust in the measurement environment collides. In order to deal with such a problem, conventionally, measures such as preventing the damage of the membrane due to dust collision by increasing the thickness of the membrane as a whole or reducing the membrane size (area) are taken.

However, such a measure has a problem that the membrane characteristics are deteriorated, that is, the heat insulation property of the membrane is deteriorated and the heat capacity is increased, and the response and sensitivity of the sensor are deteriorated. Therefore, there are limits to changing the membrane thickness and size.

On the other hand, as described in Japanese Patent No. 2633124, in order to prevent the membrane (diaphragm) from being asymmetrically deformed by a static pressure load, a thin film pattern as a reinforcing portion for reinforcing the membrane. Are symmetrically arranged so as to straddle the contour of the membrane at the outer peripheral portion of the membrane.

According to this method, since the reinforcing portion is provided not on the entire membrane but on the peripheral portion, it is possible to secure the heat insulation property and the heat capacity reduction by the membrane. However, in the membrane, the peripheral portion without the thin film pattern, the heater 21 and the temperature sensing element 2 in FIG.
Since the rigidity of the empty area where the wiring portion for fluid measurement such as 2 is not formed is still weak, the effect of preventing destruction against dust collision is small.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to appropriately prevent membrane destruction due to dust collision in a thin film structure sensor for fluid measurement having a membrane without impairing membrane characteristics. And

[0012]

In order to achieve the above object, the present inventors have examined the deformation of the membrane due to dust collision.

FIG. 18 is a diagram showing how the membrane is deformed by dust collision. As shown in FIG. 18, the measurement fluid flows in the direction of the white arrow, and dust also flies along this flow.

Then, the dust on the membrane 20 located on the downstream side of the fluid flow is higher than when the dust collides with the peripheral edge of the membrane 20 located on the upstream side of the fluid flow (see FIG. 18A). When the membrane 20 collides with the peripheral portion (see FIG. 18B), the bending of the membrane 20 is larger and the strain is also larger.

Therefore, the membrane breakage due to the dust collision is likely to occur near the peripheral portion of the membrane located on the downstream side of the fluid flow. The flow of fluid is
In the case of bidirectional, it is the flow (forward flow) that is greater in frequency and intensity. The invention of claim 1 has been made in view of this finding.

That is, the invention described in claim 1 is a thin film structure sensor for fluid measurement, which has a membrane (20) and a reinforcing portion (30) for reinforcing the membrane so as to extend over the outer peripheral edge portion of the membrane. The reinforcing portion is formed so that the reinforcing strength of the membrane is higher on the downstream side than on the upstream side of the fluid flow.

In the sensor of the present invention, as in the conventional case, since the reinforcing portion for reinforcing the membrane is arranged so as to extend over the outer peripheral portion of the membrane, deterioration of the membrane characteristics can be suppressed as much as possible. Then, the membrane peripheral portion located on the downstream side of the fluid flow is more susceptible to the pressure-bearing load due to the dust collision than the upstream membrane peripheral portion so that the membrane is not deformed or destroyed. Strength can be reinforced.

Therefore, according to the present invention, it is possible to provide a thin film structure sensor capable of appropriately preventing the membrane destruction due to the dust collision without impairing the membrane characteristics.

Here, as in the invention described in claim 2,
The wiring part (21, 2) for fluid measurement is attached to the membrane (20).
When 2) is formed, it is preferable that the reinforcing part (30) is arranged separately from the wiring part.

According to this, since the wiring portion and the reinforcing portion are separated from each other, heat transfer from the wiring portion to the reinforcing portion can be prevented, and power consumption of the sensor can be reduced.

Further, as in the invention described in claim 3, it is preferable that the reinforcing portion (30) is formed of a thin film whose internal stress is tensile. According to this, the deformation of the membrane can be suitably suppressed and the strength can be reinforced.

Further, in the invention as set forth in claim 4, there is provided a membrane (20), and a region of the membrane includes a wiring forming region in which wiring portions (21, 22) for fluid measurement are arranged and a wiring portion. In a thin film structure sensor which is divided into an unoccupied empty area, a dummy pattern (40) for reinforcing the strength of the membrane is formed in the empty area, and both ends of the dummy pattern are outer peripheral edges of the membrane. It is characterized in that it is arranged so as to straddle the section.

As in the flow sensor shown in FIG. 17 described above, the area of the membrane 20 is the wiring portion 2 for fluid measurement.
When the wiring forming area in which the wirings 1 and 22 are arranged and the vacant area in which the wiring portion is not arranged are divided, the membrane breakage is likely to occur in the vacant area where the strength is relatively weak.

On the other hand, according to the present invention, since the dummy pattern is formed in the empty area of the membrane having a relatively low strength, the strength of the empty area can be reinforced. Moreover, since both ends of the dummy pattern are arranged so as to straddle the outer peripheral edge of the membrane, the dummy pattern has a shape bridging on the membrane and is excellent in reinforcement.

Incidentally, the above-mentioned conventional patent No. 2633.
In the sensor described in Japanese Patent No. 124, although the thin film pattern that is the reinforcing portion straddles the outer peripheral edge portion of the membrane,
It is discontinuous on the membrane and does not form a bridge on the membrane. Therefore, the reinforcing property is inferior to that of the dummy pattern of the present invention.

Since this dummy pattern is patterned, it does not occupy the entire empty area even if it is formed in the empty area. Therefore, unlike the case where the reinforcing film is formed on the entire surface of the membrane, deterioration of the membrane characteristics can be suppressed as much as possible.

Therefore, according to the present invention, it is possible to provide a thin film structure sensor capable of appropriately preventing the membrane destruction due to dust collision without impairing the membrane characteristics.

Further, in the invention described in claim 5, in the sensor described in claim 4, the dummy pattern (40) is provided.
However, the downstream side of the fluid flow is formed so that the reinforcing strength of the membrane (20) is greater.

According to this, it is possible to provide a thin film structure sensor which can exert the effect of the invention of claim 1 in addition to the effect of the invention of claim 4.

The invention according to claim 6 provides a concrete means of the sensor according to claim 5, wherein a plurality of dummy patterns (40) are provided and the dummy pattern (40) is on the upstream side of the fluid flow. The feature is that it is arranged more densely on the downstream side.

According to this, since the plurality of dummy patterns are more densely arranged on the downstream side than the upstream side of the fluid flow in the empty area of the membrane, the dummy patterns on the downstream side of the upstream side of the fluid flow are denser. A dummy pattern formed so that the reinforcing strength of the membrane becomes larger can be appropriately realized.

Further, the invention according to claim 7 is characterized in that the dummy pattern (40) straddles the membrane (20) in a direction orthogonal to the direction of fluid flow.

When this type of thin film structure sensor is applied to the flow sensor represented by FIG. 17, the sensing is performed based on the temperature distribution change of the membrane along the flow direction of the fluid. If the dummy pattern straddles the membrane along the direction of fluid flow, heat transfer occurs along the direction of fluid flow through the dummy pattern, which hinders the above temperature distribution change. It will be easier.

On the other hand, according to the present invention, such a problem can be avoided and the sensor characteristics can be ensured in a good state.

Further, as in the invention described in claim 8, in the thin film structure sensor according to claim 4 or 5, the dummy pattern (40) may be a mesh pattern. The mesh pattern is effective for improving the membrane strength.

When the dummy pattern (40) is arranged separately from the wiring portions (21, 22) as in the invention described in claim 9, heat transfer from the wiring portion to the dummy pattern is performed. Can be prevented and the power consumption of the sensor can be reduced.

The reference numerals in parentheses of the above-mentioned means are examples showing the correspondence with the concrete means described in the embodiments described later.

[0038]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention shown in the drawings will be described. Although not limited, the following embodiments will be described assuming that the thin film structure sensor of the present invention is applied to a flow sensor.

The flow sensor of each embodiment has the flow sensor shown in FIG. 17 as a basic structure and is a modification of the basic structure. The same parts are designated by the same reference numerals in the drawing. . Further, in the plan view of each of the following drawings, the heater 21, the temperature sensing element 11, the reinforcing portion 30, and the dummy pattern 40 are hatched for convenience.

(First Embodiment) The essential parts of a flow sensor according to the first embodiment of the present invention are shown in FIGS. 1 to 6 are various examples showing the configuration near the membrane 20 in the flow sensor shown in FIG.

The present embodiment is a flow sensor for fluid measurement, which has a membrane 20 and a reinforcing portion 30 for reinforcing the membrane so as to straddle the outer peripheral edge portion of the membrane 20, and a fluid indicated by an outlined arrow in the figure. The reinforcing portion 30 is formed so that the reinforcing strength of the membrane 20 becomes higher on the downstream side than on the upstream side of the flow.

[First Example] FIG. 1 shows a first example of the first embodiment.
2A is a schematic cross-sectional view taken along the line AA in FIG. Further, FIG. 2B is a diagram schematically showing the state of membrane rigidity in this example, and the numbers of the heaters 21 and the temperature measuring elements 22 are simplified.

The substrate 10 is made of a semiconductor substrate such as a silicon substrate. As shown in FIG. 2A, the surface 10a of the substrate 10 has patterned conductor films 21, 22, 2 formed thereon.
A thin film layer 27 is formed by sandwiching 4 between a lower insulating film 25 and an upper insulating film 26. The thin film layer 27 on the cavity 11 formed on the back surface 10b side of the substrate 10 is configured as the membrane 20.

The lower insulating film 25 and the upper insulating film 26 are
Conductor film 2 made of silicon nitride film or silicon oxide film
1, 22, and 24 are made of a metal film such as Pt. In the conductor film, the heater 21 and the temperature measuring element 22 located on the membrane 20 are patterned in a folded shape in this example, as shown in FIG.

Further, the lead portion 24 has one end side integrally connected to the heater 21 and the temperature measuring body 22, and the other end portion is pulled out to the outside of the membrane 20 as shown in FIG. It can be electrically connected to the outside of the substrate 10 by wire bonding or the like.

Further, as shown in FIGS. 1 and 2A, the reinforcing portion 30 sandwiched between the upper and lower insulating films 25 and 26 extends over the outer peripheral edge portion of the membrane 20 located on the downstream side of the fluid flow. Is formed. The reinforcing portion 30 can be formed by a film made of the same material as the conductor films 21, 22, 24.

As shown in FIG. 2A, this reinforcing portion 30
The membrane 2 located upstream of the fluid flow by
The peripheral portion of the membrane 20 located on the downstream side of the peripheral portion of 0 is thicker. Therefore,
As shown in (b), the rigidity of the membrane 20 is higher on the downstream side than on the upstream side of the fluid flow, and the reinforcing strength by the reinforcing portion 30 is also higher.

Here, in the illustrated example, the reinforcing portion 30 is sandwiched between the upper and lower insulating films 25, 26, and the conductor films 21, 22, 2,
Although it is positioned on the same plane as 4, the lower insulating film 25 or the upper insulating film 26 may be made thicker as a part of the insulating film.

The reinforcing portion 30 is preferably formed of a thin film whose internal stress is tensile. Specifically, a polycrystalline silicon film formed by a low pressure CVD method, a silicon nitride film, or a film of Pt, Ti, TiW, Ni, Au or the like which is also used as a material for the conductor films 21, 22, 24 is used. It can be adopted as the reinforcing portion 30.

The flow sensor as shown in FIGS. 1 and 2A can be manufactured, for example, as follows. A lower insulating film 25 is formed on the surface 10a of the silicon substrate 10 by a CVD method, a sputtering method, or the like, and a conductor film is formed thereon by a vapor deposition method or the like.

Next, this conductor film is formed by photolithography,
The heater 21, the temperature measuring element 22, the fluid thermometer 23 (see FIG. 17), the lead portion 24, and the reinforcing portion 30 are simultaneously formed by patterning by making full use of etching or the like. An upper insulating film 26 is formed thereon by using the CVD method, the sputtering method, or the like. The lead portion 24 and the outside can be connected by forming a contact hole in the upper insulating film 26.

Next, anisotropic etching or the like is performed from the back surface 10b side of the substrate 10 to form the cavity 11 while leaving the thin film layer 27. Thus, the membrane 20 is formed, and the flow sensor as the first example of the first embodiment is completed.

When the reinforcing portion 30 is made of an insulating film, when the lower insulating film 25 is formed or the upper insulating film 26 is formed, the portion where the reinforcing portion 30 is to be formed is insulated. The film may be formed thicker than the surroundings.

By the way, in the flow sensor of the first example, the reinforcement portion 30 for reinforcing the membrane is arranged so as to straddle the outer peripheral edge portion of the membrane 20, as in the above-described conventional one, so that in the membrane 20. Deterioration of membrane properties such as deterioration of heat insulation and increase of heat capacity can be suppressed as much as possible.

The peripheral portion of the membrane 20 located on the downstream side of the fluid flow is closer to the upstream membrane 20.
It is possible to reinforce the strength so as to prevent the membrane 20 from being deformed or destroyed by adapting to the present situation in which the pressure receiving load due to the dust collision is more likely to be received than the peripheral portion of the.

Therefore, according to this example, it is possible to provide the flow sensor (thin film structure sensor) capable of appropriately preventing the membrane destruction due to the dust collision without impairing the membrane characteristics.

Here, wiring portions 21 and 22 for fluid measurement are formed on the membrane 20, but in this example, the reinforcing portion 30 is separated from the wiring portions 21 and 22 as shown in FIG. It is arranged. Wiring portions 21 and 22 and reinforcing portion 30
Since and are separated from each other, heat transfer from the wiring portions 21 and 22 to the reinforcing portion 30 can be prevented, and power consumption of the sensor and the like can be reduced.

Further, as described above, the reinforcing portion 30 is preferably formed of a thin film whose internal stress is tensile. According to this, as compared with the case where the reinforcing portion 30 is formed of a thin film whose internal stress is compression, the membrane 20
Can be suitably suppressed and the strength can be strengthened.

Next, the second to eighth examples of the first embodiment will be described. In each of these examples, the arrangement of the reinforcing portion 30 is modified, which is described in the first example. It can be manufactured according to the manufacturing method. Further, it goes without saying that basically the same effect as the first example is obtained.

[Second Example] FIG. 3 is a plan view showing a second example of the first embodiment. In this example, as compared with the first example shown in FIG. 1, the reinforcing portion 30 is formed so as to extend over a wider range over the outer peripheral edge portion of the membrane 20 located on the downstream side of the fluid flow. As a result, a greater rigidity improving effect than that of the first example can be obtained.

[Third Example] FIG. 4 is a plan view showing a third example of the first embodiment. In the present example, the reinforcing portion 30 is configured by making the portion of the lead portion 24 straddling the outer peripheral edge portion of the membrane wider than that of the first example shown in FIG. 1 and the second example shown in FIG. However, the outer peripheral edge portion of the membrane 20 located on the downstream side is reinforced in a wider range.

[Fourth Example] FIG. 5 is a plan view showing a fourth example of the first embodiment. This example is a modification of the third example shown in FIG. 4, and is different from the third example in that
By reducing the number of places where 0 is divided, the effect of improving rigidity is further enhanced.

[Fifth Example] FIG. 6 is a plan view showing a fifth example of the first embodiment. This example is suitable for the case where the fluid flows bidirectionally as shown by the white arrow in FIG. 6, but one flow (forward flow) is larger in frequency and strength than the other flow (backflow). Is.

In this case, the reinforcing portion 30 formed on the peripheral portion of the membrane 20 located on the downstream side of the smaller flow (flow from right to left in the figure) has a larger flow (FIG. The area is smaller than that formed on the peripheral portion of the membrane 20 located in the middle, flow from the left to the right).

In this case, the normal fluid flow, that is, the forward flow, is the larger flow (flow from left to right in the figure).
With the configuration shown in FIG. 6, the reinforcement portion 30 is formed so that the reinforcement strength of the membrane 20 is higher on the downstream side than on the upstream side in the forward flow.

Further, in the present example, the collision of the dust that comes in due to the smaller flow, that is, the reverse flow, can be sufficiently dealt with by the presence of the reinforcing portion 30, and the deformation and breakage of the membrane 20 can be prevented. It is possible.

[Sixth Example, Seventh Example, Eighth Example] FIG.
8 and 9 are plan views showing a sixth example, a seventh example, and an eighth example of the first embodiment, respectively.

In these sixth to eighth examples, as shown in each figure, by dividing the reinforcing portion 30, the heat conduction of the membrane 20 through the reinforcing portion 30 can be further suppressed and the rigidity can be reduced. It is possible to appropriately arrange the reinforcing portion 30 on the portion of the membrane 20 that needs to be improved.

In particular, in the example shown in FIGS. 7 to 9, the reinforcing portion 3
0 is divided in the direction along the flow direction of the fluid (the direction of the white arrow in the figure). In the flow sensor, sensing is performed based on the change in the temperature distribution of the membrane 20 along the flow direction of the fluid. Due to such division, the reinforcing portion 3
It is possible to suppress the heat transfer in the direction of the flow of the fluid through 0 and hardly hinder the above-mentioned temperature distribution change, so that the sensor characteristics can be ensured in a good state.

(Second Embodiment) FIGS. 10 to 16 show the main parts of a flow sensor according to a second embodiment of the present invention. 10 to 16 are various examples showing the configuration near the membrane 20 in the flow sensor shown in FIG. Hereinafter, differences from the first embodiment will be mainly described.

The present embodiment has the membrane 20, and the region of the membrane 20 has wiring portions 21 and 22 for fluid measurement.
In the flow sensor divided into a wiring formation region where the wirings are arranged and a vacant region where the wiring portions 21 and 22 are not arranged, a dummy pattern 40 for reinforcing the strength of the membrane is formed in the vacant region, This dummy pattern 40
Are arranged so that both ends thereof straddle the outer peripheral edge portion of the membrane 20, so that the dummy pattern 40 is formed on the membrane 20.
It is the one bridged above.

[First Example] FIG. 10 is a plan view showing a first example of the second embodiment. In this example, the heater 21
Is not a folded-back one, but a plurality of parallel-arranged ones.

The dummy pattern 40 can be made of the same material and method as the reinforcing portion in the first embodiment, and the conductor films 21, 22, 24 sandwiched between the upper and lower insulating films 25, 26 can be used. And a lower insulating film 25 or an upper insulating film 26.
Can be formed as an insulating film having a thickened part.

As shown in FIG. 10, the dummy pattern 40
Is formed in a vacant area of the membrane 20, and is composed of a plurality of pieces extending in parallel to the extending direction of the wiring portions 21 and 22. Then, each dummy pattern 40
Is arranged so that both ends thereof straddle the outer peripheral edge portion of the membrane 20, and thus has a form bridging on the membrane 20.

According to this example, since the dummy pattern 40 is formed in the empty region of the membrane 20 where the strength is relatively weak, the strength of this empty region can be reinforced. Moreover, since the dummy pattern 40 is bridged on the membrane 20, the dummy pattern 40 is excellent in reinforcement.

Further, as is apparent from FIG. 10, since the dummy pattern 40 is patterned and does not occupy the entire empty area, unlike the case where the reinforcing film is formed on the entire surface of the membrane, It is possible to suppress deterioration of membrane characteristics as much as possible.

Therefore, according to the present example as well, similar to the first embodiment, it is possible to provide a flow sensor (thin film structure sensor) capable of appropriately preventing membrane destruction due to dust collision without impairing the membrane characteristics. it can.

Further, as shown in FIG. 10, the dummy pattern 40 has a direction in which the heater 21 and the temperature measuring element 22 extend, that is, a direction of fluid flow indicated by a white arrow in FIG. 10 (bidirectional in this example). Are bridged in a direction orthogonal to each other across the membrane 20.

As described above, the flow sensor performs sensing based on the change in the temperature distribution of the membrane 20 along the flow direction of the fluid. If the dummy pattern straddles the membrane along the direction of fluid flow, heat transfer occurs along the direction of fluid flow through the dummy pattern, so the temperature distribution of the membrane 20 described above. It becomes easier to prevent changes.

In this respect, according to this example, the dummy pattern 4
It is possible to suppress the heat transfer in the direction of the fluid flow through 0 and hardly inhibit the temperature distribution change of the membrane 20 along the direction of the fluid flow, so that the sensor characteristics are ensured in a good state. can do.

Also in this example, since the dummy pattern 40 is arranged separately from the wiring portions 21 and 22 as in the reinforcing portion in the first embodiment, the dummy portions 40 are dummy from the wiring portions 21 and 22. Heat transfer to the pattern 40 can be prevented, and the power consumption of the sensor can be reduced.

Further, in the present example, when the heater 21, the temperature measuring element 22, and the dummy pattern 40 are simultaneously formed by patterning by etching the conductor film, the line width of these patterns 21, 22, 40 in the fluid flow direction. It is preferable that the ratio L / S of L and the interval (pattern interval) S of each line be the same. For example, L = 5 μm and S = 5 μm.

L / S of all patterns 21, 22, 40
By adjusting the above, it is possible to suppress the in-plane variation of etching and improve the in-plane variation of the resistance ratio and TCR (temperature coefficient of resistance).

[Second Example] FIG. 11 is a plan view showing a second example of the second embodiment. In this example, the dummy pattern 40 is formed such that the reinforcement strength of the membrane 20 is higher on the downstream side than on the upstream side of the fluid flow (forward flow) indicated by the white arrow in the figure.

In this example, in the plurality of dummy patterns 40 arranged at intervals, the intervals are made smaller on the downstream side than on the upstream side of the fluid flow, so that the dummy patterns 40 are It is arranged so that the downstream side is denser than the upstream side.

As a result, in addition to the effects of the second embodiment described in the first example, as in the first embodiment, the peripheral edge of the membrane located on the downstream side is more susceptible to the pressure load due to dust collision. The membrane 20 can be reinforced by adapting to the current susceptibility.

[Third Example] FIG. 12 is a plan view showing a third example of the second embodiment. Also in this example, as in the second example, the dummy pattern 40 is formed such that the reinforcement strength of the membrane 20 is greater on the downstream side than on the upstream side of the fluid flow (forward flow) indicated by the outlined arrow in the figure. It was done.

In the second example shown in FIG. 11, the distance between the dummy patterns 40 on the downstream side is narrowed between the upstream side and the downstream side with the wiring portions 21 and 22 sandwiched between them. The intervals of the dummy patterns 40 are uniform when only looking at and when only looking at the downstream side.

On the other hand, in this example, as shown in FIG. 12, the intervals of the dummy patterns 40 are gradually narrowed from the upstream side to the downstream side. Also in this example, the same effect as that of the second example of the second embodiment can be obtained.

[Fourth Example] FIG. 13 is a plan view showing a fourth example of the second embodiment. In this example, by forming the dummy pattern 40 into a mesh pattern, it is possible to further improve the membrane strength.

[Fifth Example] FIG. 14 is a plan view showing a fifth example of the second embodiment. In this example, as compared with the one shown in FIG. 10, both ends of the dummy pattern 40 extending over the outer peripheral edge of the membrane 20 are made thicker to further improve the strength.

[Sixth Example] FIG. 15 is a plan view showing a sixth example of the second embodiment. In this example, a thermometer 28 is provided in the heater 21 as compared with that shown in FIG. The thermometer 28 is for measuring the temperature of the heater 21 and feeding it back to the voltage applied to the heater 21. That is, it is possible to accurately control the temperature of the heater 21.

[Seventh Example] FIG. 16 is a plan view showing a seventh example of the second embodiment. In this example, in order to make the heater 21 thinner and to make the resistance value sufficiently smaller than that shown in FIG. 10, the resistance values are adjusted by bending the heaters 21 in parallel several times.

(Other Embodiments) The present invention can be applied to a thin film structure sensor for fluid measurement having a membrane other than the above flow sensor, for example, a gas sensor or the like.

[Brief description of drawings]

FIG. 1 is a plan view showing a main part of a flow sensor as a first example of a first embodiment of the present invention.

2A is a schematic cross-sectional view taken along the line AA in FIG. 1, and FIG. 2B is a diagram showing a state of membrane rigidity in the flow sensor shown in FIG.

FIG. 3 is a plan view showing a main part of a flow sensor as a second example of the first embodiment.

FIG. 4 is a plan view showing a main part of a flow sensor as a third example of the first embodiment.

FIG. 5 is a plan view showing a main part of a flow sensor as a fourth example of the first embodiment.

FIG. 6 is a plan view showing a main part of a flow sensor as a fifth example of the first embodiment.

FIG. 7 is a plan view showing a main part of a flow sensor as a sixth example of the first embodiment.

FIG. 8 is a plan view showing a main part of a flow sensor as a seventh example of the first embodiment.

FIG. 9 is a plan view showing a main part of a flow sensor as an eighth example of the first embodiment.

FIG. 10 is a plan view showing a main part of a flow sensor as a first example of a second embodiment of the present invention.

FIG. 11 is a plan view showing a main part of a flow sensor as a second example of the second embodiment.

FIG. 12 is a plan view showing a main part of a flow sensor as a third example of the second embodiment.

FIG. 13 is a plan view showing a main part of a flow sensor as a fourth example of the second embodiment.

FIG. 14 is a plan view showing a main part of a flow sensor as a fifth example of the second embodiment.

FIG. 15 is a plan view showing a main part of a flow sensor as a sixth example of the second embodiment.

FIG. 16 is a plan view showing a main part of a flow sensor as a seventh example of the second embodiment.

FIG. 17 is a perspective view showing a flow sensor as a conventional thin film structure sensor.

FIG. 18 is a diagram showing how the membrane is deformed by dust collision.

[Explanation of symbols]

20 ... Membrane, 21 ... Heater, 22 ... Thermometer, 30
... Reinforcement part, 40 ... Dummy pattern.

Claims (9)

[Claims] 1. A membrane (20) and a reinforcing portion (3) for reinforcing the membrane so as to extend over an outer peripheral edge portion of the membrane (20).
0) and a thin-film structure sensor for fluid measurement, wherein the reinforcing portion has a greater reinforcing strength of the membrane on the downstream side than on the upstream side of the fluid flow,
A thin film structure sensor characterized by being formed. 2. The membrane (20) is provided with wiring portions (21, 22) for measuring the fluid, and the reinforcing portion (30) is arranged separately from the wiring portion. The thin film structure sensor according to claim 1, wherein: 3. The thin film structure sensor according to claim 1, wherein the reinforcing portion (30) is formed of a thin film whose internal stress is tensile. 4. A wiring forming area having a membrane (20), wherein the area of the membrane is provided with wiring portions (21, 22) for fluid measurement and an empty area where the wiring portion is not provided. In the thin film structure sensor divided into, a dummy pattern (40) for reinforcing the strength of the membrane is formed in the empty area, and both ends of the dummy pattern straddle the outer peripheral edge of the membrane. A thin film structure sensor characterized by being arranged in the following manner. 5. The dummy pattern (40) is formed so that the reinforcement strength of the membrane (20) is higher on the downstream side than on the upstream side of the flow of the fluid. 4. The thin film structure sensor described in 4. 6. The dummy pattern (40) comprises a plurality of dummy patterns (40), wherein the downstream side of the fluid flow is more densely arranged than the upstream side of the fluid flow. Thin film structure sensor. 7. The dummy pattern (40) is formed on the membrane (2) in a direction orthogonal to a flow direction of the fluid.
0) straddling 0).
7. The thin film structure sensor according to any one of items 1 to 6. 8. The thin film structure sensor according to claim 4, wherein the dummy pattern (40) has a mesh pattern. 9. The thin film structure sensor according to claim 4, wherein the dummy pattern (40) is arranged separately from the wiring part (21, 22). .